2024 |
Aas, W., Fagerli, H., Alastuey, A., Cavalli, F., Degorska, A., Feigenspan, S., et al. (2024). Trends In Air Pollution In Europe, 2000-2019. Aerosol And Air Quality Research, 242(4).
Abstract: This Paper Encompasses An Assessment Of Air Pollution Trends In Rural Environments In Europe Over The 2000-2019 Period, Benefiting From Extensive Long-Term Observational Data From The Emep Monitoring Network And Emep Msc-W Model Computations. The Trends In Pollutant Concentrations Align With The Decreasing Emission Patterns Observed Throughout Europe. Annual Average Concentrations Of Sulfur Dioxide, Particulate Sulfate, And Sulfur Wet Deposition Have Shown Consistent Declines Of 3-4% Annually Since 2000. Similarly, Oxidized Nitrogen Species Have Markedly Decreased Across Europe, With An Annual Reduction Of 1.5-2% In Nitrogen Dioxide Concentrations, Total Nitrate In The Air, And Oxidized Nitrogen Deposition. Notably, Emission Reductions And Model Predictions Appear To Slightly Surpass The Observed Declines In Sulfur And Oxidized Nitrogen, Indicating A Potential Overestimation Of Reported Emission Reductions. Ammonia Emissions Have Decreased Less Compared To Other Pollutants Since 2000. Significant Reductions In Particulate Ammonium Have However, Been Achieved Due To The Impact Of Reductions In Sox And Nox Emissions. For Ground Level Ozone, Both The Observed And Modelled Peak Levels In Summer Show Declining Trends, Although The Observed Decline Is Smaller Than Modelled. There Have Been Substantial Annual Reductions Of 1.8% And 2.4% In The Concentrations Of Pm10 And Pm2.5, Respectively. Elemental Carbon Has Seen A Reduction Of Approximately 4.5% Per Year Since 2000. A Similar Reduction For Organic Carbon Is Only Seen In Winter When Primary Anthropogenic Sources Dominate. The Observed Improvements In European Air Quality Emphasize The Importance Of Comprehensive Legislations To Mitigate Emissions.
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Amato, F., Van Drooge, B., Jaffrezo, J., Favez, O., Colombi, C., Cuccia, E., et al. (2024). Aerosol Source Apportionment Uncertainty Linked To The Choice Of Input Chemical Components. Environment International, 1841.
Abstract: For A Positive Matrix Factorization (Pmf) Aerosol Source Apportionment (Sa) Studies There Is No Standard Procedure To Select The Most Appropriate Chemical Components To Be Included In The Input Dataset For A Given Site Typology, Nor Specific Recommendations In This Direction. However, These Choices Are Crucial For The Final Sa Outputs Not Only In Terms Of Number Of Sources Identified But Also, And Consequently, In The Source Contributions Estimates. In Fact, Pmf Tends To Reproduce Most Of Pm Mass Measured Independently And Introduced As A Total Variable In The Input Data, Regardless Of The Percentage Of Pm Mass Which Has Been Chemically Characterized, So That The Lack Of Some Specific Source Tracers (E.G. Levoglucosan) Can Potentially Affect The Results Of The Whole Source Apportionment Study. The Present Study Elaborates Further On The Same Concept, Evaluating Quantitatively The Impact Of Lacking Specific Sources' Tracers On The Whole Source Apportionment, Both In Terms Of Identified Sources And Source Contributions. This Work Aims To Provide First Recommendations On The Most Suitable And Critical Components To Be Included In Pmf Analyses In Order To Reduce Pmf Output Uncertainty As Much As Possible, And Better Represent The Most Commons Pm Sources Observed In Many Sites In Western Countries. To This Aim, We Performed Three Sensitivity Analyses On Three Different Datasets Across Eu, Including Extended Sets Of Organic Tracers, In Order To Cover Different Types Of Urban Conditions (Mediterranean, Continental, And Alpine), Source Types, And Pm Fractions. Our Findings Reveal That The Vehicle Exhaust Source Resulted To Be Less Sensitive To The Choice Of Analytes, Although Source Contributions Estimates Can Deviate Significantly Up To 44 %. On The Other Hand, For The Detection Of The Non-Exhaust One Is Clearly Necessary To Analyze Specific Inorganic Elements. The Choice Of Not Analysing Non-Polar Organics Likely Causes The Loss Of Separation Of Exhaust And Non-Exhaust Factors, Thus Obtaining A Unique Road Traffic Source, Which Provokes A Significant Bias Of Total Contribution. Levoglucosan Was, In Most Cases, Crucial To Identify Biomass Burning Contributions In Milan And In Barcelona, In Spite Of The Presence Of Pahs In Barcelona, While For The Case Of Grenoble, Even Discarding Levoglucosan, The Presence Of Pahs Allowed Identifying The Bb Factor. Modifying The Rest Of Analytes Provoke A Systematic Underestimation Of Biomass Burning Source Contributions. Sia Factors Resulted To Be Generally Overestimated With Respect To The Base Case Analysis, Also In The Case That Ions Were Not Included In The Pmf Analysis. Trace Elements Were Crucial To Identify Shipping Emissions (V And Ni) And Industrial Sources (Pb, Ni, Br, Zn, Mn, Cd And As). When Changing The Rest Of Input Variables, The Uncertainty Was Narrow For Shipping But Large For Industrial Processes. Major And Trace Elements Were Also Crucial To Identify The Mineral/Soil Factor At All Cities. Biogenic Soa And Anthropogenic Soa Factors Were Sensitive To The Presence Of Their Molecular Tracers, Since The Availability Of Oc Alone Is Unable To Separate A Soa Factor. Arabitol And Sorbitol Were Crucial To Detecting Fungal Spores While Odd Number Of Higher Alkanes (C27 To C31) For Plant Debris.
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Benning, L., Wagner, D., Larose, C., Gunde-Cimerman, N., & Haeggblom, M. (2024). Editorial: Thematic Issue On Polar And Alpine Microbiology. Fems Microbiology Ecology, 1001(4).
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Bhowmick, S., Chaudhary, A., Jishad, M., Seemanth, M., Utkarsh, Agarwal, N., et al. (2024). How Useful Are Mispointing Phase Saral/Altika Geophysical Products For Ocean Applications? Advances In Space Research, 737(1), 414–425.
Abstract: Saral/Altika, The First Microwave Altimeter Operating At Ka -Band Frequency, Recently Completed Nine Years Of Operations In Orbit. During These Years, It Has Catered To Many Applications Related To Operational Oceanography, Climate Sciences, Hydrology And Cryosphere. More Specifically, In Oceanography, Saral Has Contributed Immensely To Operational Wave And Circulation Modelling, Eddy Detection/Tracking, Ocean Current Generation And Many More. However, Since Feb 2019, Saral Has Moved From The Drifting Phase (Dp) To The Mispointing Phase (Mp) Due To The Malfunctioning Of The Star Sensor Of The Spacecraft. In This Study, We Analyse The Instrument'S Performance And Its Waveforms During Its Ongoing Mp. We Find Out That During The Mp, Significant Wave Height (Swh) Measurements Are Anomalously High Between 18 And 24 M, And Wind Speed Measurements Are Between 16 And 19 M/S. In Sea Surface Height Anomaly (Ssha), There Is A Steady Rise In Negative Values During The Mp. In The Return Waveform, -15% Degradation In Brown -Type Waveforms In The Open Ocean Region Is Noticed. These Changes Significantly Impact The Saral Applications. Two Important Applications Of Wave Forecast And Eddy Detection Are Discussed Here As Examples. Following This, We Also Recommend Using Provided Quality Flags So That The Data Can Be Further Explored For Various Ocean Applications. (C) 2023 Cospar. Published By Elsevier B.V. All Rights Reserved.
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Camman, J., Chazeau, B., Marchand, N., Durand, A., Gille, G., Lanzi, L., et al. (2024). Oxidative Potential Apportionment Of Atmospheric Pm1: A New Approach Combining High-Sensitive Online Analysers For Chemical Composition And Offline Op Measurement Technique. Atmospheric Chemistry And Physics, 242(5), 3257–3278.
Abstract: Source Apportionment Models Were Widely Used To Successfully Assign Highly Time-Resolved Aerosol Data To Specific Emissions And/Or Atmospheric Chemical Processes. These Techniques Are Necessary For Targeting The Sources Affecting Air Quality And For Designing Effective Mitigation Strategies. Moreover, Evaluation Of The Toxicity Of Airborne Particulate Matter Is Important Since The Classically Measured Particulate Matter (Pm) Concentrations Appear Insufficient For Characterizing The Impact On Human Health. Oxidative Potential (Op) Measurement Has Recently Been Developed To Quantify The Capability Of Pm To Induce An Oxidative Imbalance In The Lungs. As A Result, This Measurement Unit Could Be A Better Proxy Than Pm Mass Concentration To Represent Pm Toxicity. In The Present Study, Two Source Apportionment Analyses Were Performed Using Positive Matrix Factorization (Pmf) From Organic Aerosol (Oa) Mass Spectra Measured At A 15 Min Time Resolution Using A Time-Of-Flight Aerosol Chemical Speciation Monitor (Tof-Acsm) And From 19 Trace Elements Measured On An Hourly Basis Using An Online Metal Analyser (Xact 625I). The Field Measurements Were Carried Out In Summer 2018. While It Is Common To Perform Pmf Studies Individually On Acsms And More Recently On Xact Datasets, Here We Used A Two-Step Methodology Leading To A Complete Pm 1 Source Apportionment. The Outputs From Both Oa Pmf And Xact Pmf, The Inorganic Species Concentrations From The Acsm, And The Black Carbon (Bc) Fractions (Fossil Fuel And Wood Burning) Measured Using An Aethalometer (Ae33) Were Gathered Into A Single Dataset And Subjected To A Combined Pmf Analysis. Overall, Eight Factors Were Identified, Each Of Them Corresponding To A More Precise Source Than Performing Single Pmf Analyses. The Results Show That Besides The High Contribution Of Secondary Ammonium Sulfate (28 %) And Organic Nitrate (19 %), About 50 % Of Pm 1 Originated From Distinct Combustion Sources, Including Emissions From Traffic, Shipping, Industrial Activities, Cooking, And Biomass Burning. Simultaneously, Pm 1 Filters Were Collected During The Experimental Period On A 4 H Sampling Basis. On These Filters, Two Acellular Op Assays Were Performed (Dithiothreitol; Op Dtt And Ascorbic Acid; Op Aa ) And An Inversion Method Was Applied On Factors Issued From All Pmfs To Assess The Contribution Of The Pm Sources To The Op. This Work Highlights The Sensitivity Of Op Aa To Industrial And Dust Resuspension Sources And Those Of Op Dtt To Secondary Ammonium Sulfate, Shipping, And Biomass Burning.
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Chifflet, S., Guyomarc'H, L., Dominutti, P., Heimbürger-Boavida, L., Angeletti, B., Louvat, P., et al. (2024). Seasonal Variations Of Metals And Metalloids In Atmospheric Particulate Matter (Pm2.5) In The Urban Megacity Hanoi. Atmospheric Pollution Research, 151(1).
Abstract: Fine Particulate Matter (Pm2.5) In The Atmosphere Is Of Particular Concern Due To Its Adverse Effects On Human Health And Its Impact On Global Warming. Southeast Asia Is A Hot Spot For Fossil Fuel Combustion With Recurrent Release Of Large Plumes Spreading Over The Ocean And Neighbouring Countries. Due To The Complex Mixture Of Pm2.5, The Atmospheric Sources Contribution Related To Local And Regional Emissions In Hanoi (Northern Vietnam) Is Still Ill-Constrained. Here, We Present A Year-Round Study (November 2019 To December 2020) With Mea-Surements Of 18 Metals And Metalloids (Mm) And Lead Isotopes In The Pm2.5 Fraction To Quantify Weather-Related Atmospheric Inputs And To Assess Risk To Human Health. Anthropogenic Inputs From Fossil Fuel Combustion Accounted For About 80% In Pm2.5. We Found High Pm2.5-Bound Mm Concentrations Often Exceeding National And Global Standards With A Low Risk Of Chronic Inhalation And Carcinogenicity, Mainly Attributable To Cr. During Winter Monsoon (Northeastern Winds), Stable Weather Conditions Led To The Enrichment Of Long-Range Air Mass Transport Of Local Particulate Emissions. During The Summer Monsoon (Southeastern Winds), Warm And Moist Winds Reduced Coal Contribution In Pm2.5. Our Study Highlights The Need For A Strict Implementation Of Policies To Control Hazardous Mm Emissions By Reducing Fossil Fuel Combustion. On The One Hand, Reducing Coal-Related Activities Could Reduce Cr Emissions And Therefore Improve The Risks To Human Health. On The Other Hand, Public Policies Should Encourage Conversion To Green Transport In Order To Reduce Petrol Combustion And Thus Limit Global Warming.
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Gustin, M., Dunham-Cheatham, S., Osterwalder, S., Magand, O., & Dommergue, A. (2024). What Is The Utility Of Measuring Gaseous Hgii Dry Deposition Using Aerohead Samplers?: A Review. Science Of The Total Environment, 9079.
Abstract: The Most Efficient Way To Quantify Hgii Inputs To Ecosystems Is To Measure Wet And Dry Deposition. Wet Deposition Of Hgii Is Determined By Measuring Hg Concentrations And The Volume Of Precipitation. Dry Deposition Of Hgii Is Determined Through Direct Measurement And/Or Determined Indirectly By Measuring Air Concentrations And Using Model-Generated Deposition Velocities. Here, Data Collected Using An Aerohead Sampler Holding Cation Exchange Membranes Are Summarized, And The Utility Of This Method For Understanding Dry Deposition, And Other Measurements And Processes Is Discussed. This Analysis Includes Information From Publications, And Recent Data Collected At Guadalupe Mountains National Park, Texas, Usa, And Amsterdam Island, Southern Indian Ocean. This Method Primarily Measures Gaseous Hgii And Little Particulate-Bound Hg. The Aerohead Method Is Useful For Looking At Large-Scale Trends In Deposition, Verifying Hg Depletion Events, Calculating Dry Deposition Velocities For Compounds With Specific Chemistry, And Identification Of Sources Of Hgii. At Numerous Locations In The Western Usa, Deposition Rates Were Greater At Higher Elevations Due To Elevated Concentrations Associated With Longrange Transport Of Atmospheric Pollution. When Used In Tandem With The Reactive Mercury Active System Or A Dual-Channel System, More Accurate Deposition Velocities – That Vary As A Function Of Gom Compound Chemistry – Can Be Calculated.
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Lapere, R., Thomas, J., Favier, V., Angot, H., Asplund, J., Ekman, A., et al. (2024). Polar Aerosol Atmospheric Rivers: Detection, Characteristics, And Potential Applications. Journal Of Geophysical Research-Atmospheres, 1291(2).
Abstract: Aerosols Play A Key Role In Polar Climate, And Are Affected By Long-Range Transport From The Mid-Latitudes, Both In The Arctic And Antarctic. This Work Investigates Poleward Extreme Transport Events Of Aerosols, Referred To As Polar Aerosol Atmospheric Rivers (P-Aar), Leveraging The Concept Of Atmospheric Rivers (Ar) Which Signal Extreme Transport Of Moisture. Using Reanalysis Data, We Build A Detection Catalog Of P-Aars For Black Carbon, Dust, Sea Salt And Organic Carbon Aerosols, For The Period 1980-2022. First, We Describe The Detection Algorithm, Discuss Its Sensitivity, And Evaluate Its Validity. Then, We Present Several Extreme Transport Case Studies, In The Arctic And In The Antarctic, Illustrating The Complementarity Between Ars And P-Aars. Despite Similarities In Transport Pathways During Co-Occurring Ar/P-Aar Events, Vertical Profiles Differ Depending On The Species, And Large-Scale Transport Patterns Show That Moisture And Aerosols Do Not Necessarily Originate From The Same Areas. The Complementarity Between Ar And P-Aar Is Also Evidenced By Their Long-Term Characteristics In Terms Of Spatial Distribution, Seasonality And Trends. P-Aar Detection, As A Complement To Ar, Can Have Several Important Applications For Better Understanding Polar Climate And Its Connections To The Mid-Latitudes. The Extreme Transport Of Aerosol-Containing Air Masses, From The Mid-Latitudes To The Polar Regions, Can Be Characterized And Quantified By Leveraging Polar Aerosol Atmospheric Rivers (P-Aars). This Is Similar To The Atmospheric Rivers (Ars) Which Carry Large Amounts Of Water To The Poles And Affect The Overall Stability Of Polar Ecosystems. In This Work, We Establish A Detection Algorithm For P-Aars And Evaluate It For Different Well-Known Aerosol Intrusions Or Ar Events. The Areas Most Affected By P-Aars Are Described, Their Trends Are Investigated And We Discuss The Potential Applications Of P-Aar Detection For A Better Understanding Of Polar Climate. A Catalog Of Polar Aerosol Atmospheric Rivers (P-Aar) Is Provided For 1980-2022 By Adapting An Atmospheric River (Ar) Detection Schemeimportant P-Aar Events, Representing Rapid Poleward Transport Of Aerosol-Enriched Air Masses, Are Presentedcombining Ar And P-Aar Can Improve Our Understanding Of The Links Between Mid- And Polar-Latitudes, In The Past, Present And Future Climate
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Leriche, M., Tulet, P., Deguillaume, L., Burnet, F., Colomb, A., Borbon, A., et al. (2024). Measurement Report: Bio-Physicochemistry Of Tropical Clouds At Maïdo (Réunion, Indian Ocean): Overview Of Results From The Bio-Maïdo Campaign. Atmospheric Chemistry And Physics, 242(7), 4129–4155.
Abstract: The Bio-Maido (Bio-Physicochemistry Of Tropical Clouds At Maido: Processes And Impacts On Secondary Organic Aerosols Formation) Campaign Was Conducted From 13 March To 4 April 2019 On The Tropical Island Of Reunion. The Main Objective Of The Project Was To Improve Understanding Of Cloud Impacts On The Formation Of Secondary Organic Aerosols (Soa) From Biogenic Volatile Organic Compound (Bvoc) Precursors In A Tropical Environment. Instruments Were Deployed At Five Sites: A Receptor Site, Maido Observatory (Mo) At 2165 M A.S.L. And Four Sites Along The Slope Of The Maido Mountain. Observations Include Measurements Of Volatile Organic Compounds (Vocs) And Characterization Of The Physical, Chemical And Biological (Bacterial Diversity And Culture-Based Approaches) Properties Of Aerosols And Cloud Water. Turbulent Parameters Of The Boundary Layer, Radiative Fluxes And Emissions Fluxes Of Bvocs From The Surrounding Vegetation Were Measured To Help Interpret Observed Chemical Concentrations In The Different Phases. Dynamical Analyses Showed Two Preferred Trajectory Routes For Air Masses Arriving At Mo During The Daytime. Both Trajectories Correspond To Return Branches Of The Trade Winds Associated With Upslope Thermal Breezes, Where Air Masses Likely Encountered Cloud Processing. The Highest Mixing Ratios Of Oxygenated Vocs (Ovocs) Were Measured Above The Site Located In The Endemic Forest And The Highest Contribution Of Ovocs To Total Vocs At Mo. Chemical Compositions Of Particles During Daytime Showed Higher Concentrations Of Oxalic Acid, A Tracer Of Cloud Processing And Photochemical Aging, And A More Oxidized Organic Aerosol At Mo Than At Other Sites. Approximately 20 % Of The Dissolved Organic Compounds Were Analyzed. Additional Analyses By Ultra-High-Resolution Mass Spectrometry Will Explore The Complexity Of The Missing Cloud Organic Matter.
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Manrique, M., Consonni, V., Boubenia, S., Roussel, H., Zeghouane, M., Labau, S., et al. (2024). Enhancing The Output Voltage Of Piezoelectric Nanogenerators Based On Zno Nanowires Grown By Chemical Bath Deposition Using Compensatory Cu Doping. Energy Technology, .
Abstract: The Screening Effect In Zno Nanowires (Nws) Coming From The High Density Of Free Electrons Has Emerged As One Of The Major Issues For Their Efficient Integration Into Piezoelectric Devices. Herein, The Compensatory Cu Doping Of Zno Nws Grown By Chemical Bath Deposition In The High-Ph Region Using Cu(No3)2 And Ammonia As Chemical Additives Is Developed And The Effects Of A Postdeposition Thermal Annealing Under Oxygen Atmosphere Are Investigated. It Is Shown That The Cu Dopants Are Incorporated Into Zno Nws With An Atomic [Cu]/[Zn] Ratio In The Range Of 50-65 Ppm And Undergo A Migration Process Into Their Bulk After Thermal Annealing. Importantly, The Electrical Resistivity Of Cu-Doped Zno Nws Is Found To Increase By A Factor Of 4 Compared To Unintentionally N-Doped Zno Nws. The Increase Is Even More Pronounced After Different Thermal Annealing, Reaching A Factor Exceeding 100, Which Is Explained By The Redistribution Of Hydrogen- And Nitrogen-Related Defects Along With The Thermal Activation Of Cu Dopants. Additionally, It Is Revealed That A Rigid Piezoelectric Nanogenerator Based On A Cu-Doped Zno Nw Matrix Exhibits The Highest Output Voltage And Effective Piezoelectric Coefficient D33Eff Thanks To The Reduction Of The Screening Effect, Opening Perspectives In The Field Of Piezoelectric Devices. Cu-Doped Zno Nanowires (Nws) Grown By Chemical Bath Deposition Exhibited A Free Electron Density Decrease Of 50% As Compared To Pristine Zno Nws. Additionally, Cu-Doped Zno Nw Based Piezoelectric Nanogenerators Showed The Highest Output Voltage Along With The Effective Piezoelectric Coefficient At Different Mechanical Stress Conditions.Image (C) 2024 Wiley-Vch Gmbh
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Marsal, A., Sauvain, J., Thomas, A., Lyon-Caen, S., Borlaza, L., Philippat, C., et al. (2024). Effects Of Personal Exposure To The Oxidative Potential Of Pm<Sub>2.5</Sub> On Oxidative Stress Biomarkers In Pregnant Women. Science Of The Total Environment, 9119.
Abstract: Oxidative Stress Is A Prominent Pathway For The Health Effects Associated With Fine Particulate Matter (Pm2.5) Exposure. Oxidative Potential (Op) Of Pm Has Been Associated To Several Health Endpoints, But Studies On Its Impact On Biomarkers Of Oxidative Stress Remains Insufficient. 300 Pregnant Women From The Sepages Cohort (France) Carried Personal Pm2.5 Samplers For A Week And Op Was Measured Using Ascorbic Acid (Aa) And Dithiothreitol (Dtt) Assays, And Normalized By 1) Pm2.5 Mass (Opm) And 2) Sampled Air Volume (Opv). A Pool Of Three Urine Spots Collected On The 7Th Day Of Pm Sampling Was Analyzed For Biomarkers, Namely 8-Hydroxy-2-Deoxyguanosine (8-Ohdg), Malondialdehyde (Mda) And 8-Isoprostaglandin-F2 Alpha (8-Isopgf2 Alpha). Associations Were Investigated Using Adjusted Multiple Linear Regressions. Op Effects Were Additionally Investigated By Stratifying By Median Pm2.5 Concentration (14 Mu G M(-3)). In The Main Models, No Association Was Observed With 8-Isopgf2 Alpha, Nor Mda. An Interquartile Range (Iqr) Increase In Opmaa Exposure Was Associated With Increased 8-Ohdg (Percent Change: 6.2 %; 95 % Ci: 0.2 % To 12.6 %). In The Stratified Analysis, Exposure To Opmaa Was Associated With 8-Ohdg For Participants Exposed To Low Levels Of Pm2.5 (Percent Change: 11.4 %; 95 % Ci: 3.3 % To 20.1 %), But Not For Those Exposed To High Levels (Percent Change: -1.0 %; 95 % Ci: -10.6 % To 9.6 %). Associations For Opmdtt Also Followed A Similar Pattern (P-Values For Opmaa-Pm And Opmdtt-Pm Interaction Terms Were 0.12 And 0.11, Respectively). Overall, Our Findings Suggest That Opmaa May Be Associated With Increased Dna Oxidative Damage. This Association Was Not Observed With Pm2.5 Mass Concentration Exposure. The Effects Of Opmaa In 8-Ohdg Tended To Be Stronger At Lower (Below Median) Vs. Higher Concentrations Of Pm2.5. Further Epidemiological, Toxicological And Aerosol Research Are Needed To Further Investigate The Opmaa Effects On 8-Ohdg And The Potential Modifying Effect Of Pm Mass Concentration On This Association.
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Mayer, L., Degrendele, C., Senk, P., Kohoutek, J., Pribylová, P., Kukucka, P., et al. (2024). Widespread Pesticide Distribution In The European Atmosphere Questions Their Degradability In Air. Environmental Science & Technology, 585(7), 3342–3352.
Abstract: Risk Assessment Of Pesticide Impacts On Remote Ecosystems Makes Use Of Model-Estimated Degradation In Air. Recent Studies Suggest These Degradation Rates To Be Overestimated, Questioning Current Pesticide Regulation. Here, We Investigated The Concentrations Of 76 Pesticides In Europe At 29 Rural, Coastal, Mountain, And Polar Sites During The Agricultural Application Season. Overall, 58 Pesticides Were Observed In The European Atmosphere. Low Spatial Variation Of 7 Pesticides Suggests Continental-Scale Atmospheric Dispersal. Based On Concentrations In Free Tropospheric Air And At Arctic Sites, 22 Pesticides Were Identified To Be Prone To Long-Range Atmospheric Transport, Which Included 15 Substances Approved For Agricultural Use In Europe And 7 Banned Ones. Comparison Between Concentrations At Remote Sites And Those Found At Pesticide Source Areas Suggests Long Atmospheric Lifetimes Of Atrazine, Cyprodinil, Spiroxamine, Tebuconazole, Terbuthylazine, And Thiacloprid. In General, Our Findings Suggest That Atmospheric Transport And Persistence Of Pesticides Have Been Underestimated And That Their Risk Assessment Needs To Be Improved.
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Médieu, A., Point, D., Sonke, J., Angot, H., Allain, V., Bodin, N., et al. (2024). Stable Tuna Mercury Concentrations Since 1971 Illustrate Marine Inertia And The Need For Strong Emission Reductions Under The Minamata Convention. Environmental Science & Technology Letters, 111(3), 250–258.
Abstract: Humans Are Exposed To Toxic Methylmercury Mainly By Consuming Marine Fish. While Reducing Mercury Emissions And Releases Aims To Protect Human Health, It Is Unclear How This Affects Methylmercury Concentrations In Seawater And Marine Biota. We Compiled Existing And Newly Acquired Mercury Concentrations In Tropical Tunas From The Global Ocean To Explore Multidecadal Mercury Variability Between 1971 And 2022. We Show The Strong Inter-Annual Variability Of Tuna Mercury Concentrations At The Global Scale, After Correcting For Bioaccumulation Effects. We Found Increasing Mercury Concentrations In Skipjack In The Late 1990S In The Northwestern Pacific, Likely Resulting From Concomitant Increasing Asian Mercury Emissions. Elsewhere, Stable Long-Term Trends Of Tuna Mercury Concentrations Contrast With An Overall Decline In Global Anthropogenic Mercury Emissions And Deposition Since The 1970S. Modeling Suggests That This Limited Response Observed In Tunas Likely Reflects The Inertia Of Surface Ocean Mercury With Respect To Declining Emissions, As It Is Supplied By Legacy Mercury That Accumulated In The Subsurface Ocean Over Centuries. To Achieve Measurable Declines In Mercury Concentrations In Highly Consumed Pelagic Fish In The Near Future, Aggressive Emission Reductions And Long-Term And Continuous Mercury Monitoring In Marine Biota Are Needed.
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Moreno, C., Krejci, R., Jaffrezo, J., Uzu, G., Alastuey, A., Andrade, M., et al. (2024). Tropical Tropospheric Aerosol Sources And Chemical Composition Observed At High Altitude In The Bolivian Andes. Atmospheric Chemistry And Physics, 242(5), 2837–2860.
Abstract: The Chemical Composition Of Pm 10 And Non-Overlapping Pm 2.5 Was Studied At The Summit Of Mt. Chacaltaya (5380 M A.S.L., Lat. – 16.346950 Degrees, Long. – 68.128250 Degrees) Providing A Unique Long-Term Record Spanning From December 2011 To March 2020. The Chemical Composition Of Aerosol At The Chacaltaya Global Atmosphere Watch (Gaw) Site Is Representative Of The Regional Background, Seasonally Affected By Biomass Burning Practices And By Nearby Anthropogenic Emissions From The Metropolitan Area Of La Paz-El Alto. Concentration Levels Are Clearly Influenced By Seasons With Minima Occurring During The Wet Season (December To March) And Maxima Occurring During The Dry And Transition Seasons (April To November). Ions, Total Carbon (Ec + Oc), And Saccharide Interquartile Ranges For Concentrations Are 558-1785, 384-1120, And 4.3-25.5 Ng M – 3 For Bulk Pm 10 And 917-2308, 519-1175, And 3.9-24.1 Ng M – 3 For Pm 2.5 , Respectively, With Most Of The Aerosol Seemingly Present In The Pm 2.5 Fraction. Such Concentrations Are Overall Lower Compared To Other High-Altitude Stations Around The Globe But Higher Than Amazonian Remote Sites (Except For Oc). For Pm 10 , There Is Dominance Of Insoluble Mineral Matter (33 %-56 % Of The Mass), Organic Matter (7 %-34 %), And Secondary Inorganic Aerosol (15 %-26 %). Chemical Composition Profiles Were Identified For Different Origins: Ec, No 3 – , Nh 4 + , Glucose, And C 2 O 4 2 – For The Nearby Urban And Rural Areas; Oc, Ec, No 3 – , K + , Acetate, Formate, Levoglucosan, And Some F – And Br – For Biomass Burning; Meso 3 – , Na + , Mg 2 + , K + , And Ca 2 + For Aged Marine Emissions From The Pacific Ocean; Arabitol, Mannitol, And Glucose For Biogenic Emissions; Na + , Ca 2 + , Mg 2 + , And K + For Soil Dust; And So 4 2 – , F – , And Some Cl – For Volcanism. Regional Biomass Burning Practices Influence The Soluble Fraction Of The Aerosol Between June And November. The Organic Fraction Is Present All Year Round And Has Both Anthropogenic (Biomass Burning And Other Combustion Sources) And Natural (Primary And Secondary Biogenic Emissions) Origins, With The Oc / Ec Mass Ratio Being Practically Constant All Year Round (10.5 +/- 5.7, Iqr 8.1-13.3). Peruvian Volcanism Has Dominated The So 4 2 – Concentration Since 2014, Though It Presents Strong Temporal Variability Due To The Intermittence Of The Sources And Seasonal Changes In The Transport Patterns. These Measurements Represent Some Of The First Long-Term Observations Of Aerosol Chemical Composition At A Continental High-Altitude Site In The Tropical Southern Hemisphere.
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Pühl, M., Roiger, A., Fiehn, A., Negron, A., Kort, E., Schwietzke, S., et al. (2024). Aircraft-Based Mass Balance Estimate Of Methane Emissions From Offshore Gas Facilities In The Southern North Sea. Atmospheric Chemistry And Physics, 242(2), 1005–1024.
Abstract: Atmospheric Methane (Ch 4 ) Concentrations Have More Than Doubled Since The Beginning Of The Industrial Age, Making Ch 4 The Second Most Important Anthropogenic Greenhouse Gas After Carbon Dioxide (Co 2 ). The Oil And Gas Sector Represents One Of The Major Anthropogenic Ch 4 Emitters As It Is Estimated To Account For 22 % Of Global Anthropogenic Ch 4 Emissions. An Airborne Field Campaign Was Conducted In April-May 2019 To Study Ch 4 Emissions From Offshore Gas Facilities In The Southern North Sea With The Aim Of Deriving Emission Estimates Using A Top-Down (Measurement-Led) Approach. We Present Ch 4 Fluxes For Six Uk And Five Dutch Offshore Platforms Or Platform Complexes Using The Well-Established Mass Balance Flux Method. We Identify Specific Gas Production Emissions And Emission Processes (Venting And Fugitive Or Flaring And Combustion) Using Observations Of Co-Emitted Ethane (C 2 H 6 ) And Co 2 . We Compare Our Top-Down Estimated Fluxes With A Ship-Based Top-Down Study In The Dutch Sector And With Bottom-Up Estimates From A Globally Gridded Annual Inventory, Uk National Annual Point-Source Inventories, And Operator-Based Reporting For Individual Dutch Facilities. In This Study, We Find That All The Inventories, Except For The Operator-Based Facility-Level Reporting, Underestimate Measured Emissions, With The Largest Discrepancy Observed With The Globally Gridded Inventory. Individual Facility Reporting, As Available For Dutch Sites For The Specific Survey Date, Shows Better Agreement With Our Measurement-Based Estimates. For All The Sampled Dutch Installations Together, We Find That Our Estimated Flux Of (122.9 +/- 36.8) Kg H – 1 Deviates By A Factor Of 0.64 (0.33-12) From Reported Values (192.8 Kg H – 1 ). Comparisons With Aircraft Observations In Two Other Offshore Regions (The Norwegian Sea And The Gulf Of Mexico) Show That Measured, Absolute Facility-Level Emission Rates Agree With The General Distribution Found In Other Offshore Basins Despite Different Production Types (Oil, Gas) And Gas Production Rates, Which Vary By 2 Orders Of Magnitude. Therefore, Mitigation Is Warranted Equally Across Geographies.
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Rossi, F., Duchaine, C., Tignat-Perrier, R., Joly, M., Larose, C., Dommergue, A., et al. (2024). Temporal Variations Of Antimicrobial Resistance Genes In Aerosols: A One-Year Monitoring At The Puy De Dome Summit (Central France). Science Of The Total Environment, 9129.
Abstract: The Recent Characterization Of Antibiotic Resistance Genes (Args) In Clouds Evidenced That The Atmosphere Actively Partakes In The Global Spreading Of Antibiotic Resistance Worldwide. Indeed, The Outdoor Atmosphere Continuously Receives Large Quantities Of Particles Of Biological Origins, Emitted From Both Anthropogenic Or Natural Sources At The Near Earth'S Surface. Nonetheless, Our Understanding Of The Composition Of The Atmospheric Resistome, Especially At Mid-Altitude (I.E. Above 1000 M A.S.L.), Remains Largely Limited. The Atmosphere Is Vast And Highly Dynamic, So That The Diversity And Abundance Of Args Are Expected To Fluctuate Both Spatially And Temporally. In This Work, The Abundance And Diversity Of Args Were Assessed In Atmospheric Aerosol Samples Collected Weekly Between July 2016 And August 2017 At The Mountain Site Of Puy De Dome (1465 M A.S.L., Central France). Our Results Evidence The Presence Of 33 Different Subtypes Of Args In Atmospheric Aerosols, Out Of 34 Assessed, Whose Total Concentration Fluctuated Seasonally From 59 To 1.1 X 10(5) Copies M(-3) Of Air. These Were Heavily Dominated By Genes From The Quinolone Resistance Family, Notably The Qepa Gene Encoding Efflux Pump Mechanisms, Which Represented >95 % Of Total Args Concentration. Its Abundance Positively Correlated With That Of Bacteria Affiliated With The Genera Kineococcus, Neorhizobium, Devosia Or Massilia, Ubiquitous In Soils. This, Along With The High Abundance Of Sphingomonas Species, Points Toward A Large Contribution Of Natural Sources To The Airborne Args. Nonetheless, The Increased Contribution Of Macrolide Resistance (Notably The Erm35 Gene) During Winter Suggests A Sporadic Diffusion Of Args From Human Activities. Our Observations Depict The Atmosphere As An Important Vector Of Args From Terrestrial Sources. Therefore, Monitoring Args In Airborne Microorganisms Appears Necessary To Fully Understand The Dynamics Of Antimicrobial Resistances In The Environment And Mitigate The Threats They May Represent.
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Shangguan, Y., Zhuang, X., Querol, X., Li, B., Moreno, N., Trechera, P., et al. (2024). Physicochemical Characteristics And Oxidative Potential Of Size-Segregated Respirable Coal Mine Dust: Implications For Potentially Hazardous Agents And Health Risk Assessment. International Journal Of Coal Geology, 2822.
Abstract: The Health Risks Associated With Exposure To Respirable Dust In Coal Mines Have Been Attracted Much Attention By An Increasing Number Of Researchers. However, The Accurate Identification Of Potentially Hazardous Agents In Respirable Dusts And The Evaluation Of The Potential Health Risks Arising From It Still Remains Controversial To Varying Degrees. A Comprehensive Understanding Of The Physicochemical Properties Of Respirable Dust Is A Prerequisite And An Important Basis For Resolving This Controversy. Therefore, In This Study, The Particle Size Distribution And Morphology, Pore Structure, Mineralogical And Geochemical Patterns, And Oxidative Potential (Op) Of Respirable Coal Mine Dust Were Comprehensively Investigated. Stepwise Multiple Linear Regression Was Employed To Identify Dust Components Driving Op, Such As Anatase, Tobelite, Quartz, And Ankerite, In Respirable Coal Mine Dust, Along With Na, Ni, Se, W, And As. On This Basis, We Performed A Single-Factor Risk Prediction For Different Coal Mines By Considering Factors That May Impact Miners' Health, With The Analyses Yielding Somewhat Contradictory Results. Therefore, A Multifactor Integrated Prediction Model Is Proposed Using An Entropy-Based Technique For Order Preference By Similarity To The Ideal Solution To Categorize Coal Mines In The Study Area Into Three Risk Categories, High-, Medium-, And Low-Risk Dust Mines, Which Is Important For The Hierarchical Classification And Control Of Coal Mines And For Formulating Appropriate Dust Prevention And Control Measures.
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Spolaor, A., Scoto, F., Larose, C., Barbaro, E., Burgay, F., Bjorkman, M., et al. (2024). Climate Change Is Rapidly Deteriorating The Climatic Signal In Svalbard Glaciers. Cryosphere, 181(1), 307–320.
Abstract: The Svalbard Archipelago Is Particularly Sensitive To Climate Change Due To The Relatively Low Altitude Of Its Main Ice Fields And Its Geographical Location In The Higher North Atlantic, Where The Effect Of Arctic Amplification Is More Significant. The Largest Temperature Increases Have Been Observed During Winter, But Increasing Summer Temperatures, Above The Melting Point, Have Led To Increased Glacier Melt. Here, We Evaluate The Impact Of This Increased Melt On The Preservation Of The Oxygen Isotope ( Delta 18 O) Signal In Firn Records. Delta 18 O Is Commonly Used As A Proxy For Past Atmospheric Temperature Reconstructions, And, When Preserved, It Is A Crucial Parameter To Date And Align Ice Cores. By Comparing Four Different Firn Cores Collected In 2012, 2015, 2017 And 2019 At The Top Of The Holtedahlfonna Ice Field (1100 M A.S.L.), We Show A Progressive Deterioration Of The Isotope Signal, And We Link Its Degradation To The Increased Occurrence And Intensity Of Melt Events. Our Findings Indicate That, Starting From 2015, There Has Been An Escalation In Melting And Percolation Resulting From Changes In The Overall Atmospheric Conditions. This Has Led To The Deterioration Of The Climate Signal Preserved Within The Firn Or Ice. Our Observations Correspond With The Model'S Calculations, Demonstrating An Increase In Water Percolation Since 2014, Potentially Reaching Deeper Layers Of The Firn. Although The Delta 18 O Signal Still Reflects The Interannual Temperature Trend, More Frequent Melting Events May In The Future Affect The Interpretation Of The Isotopic Signal, Compromising The Use Of Svalbard Ice Cores. Our Findings Highlight The Impact And The Speed At Which Arctic Amplification Is Affecting Svalbard'S Cryosphere.
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Tkachenko, K., & Jacobi, H. (2024). Electrical Charging Of Snow And Ice In Polar Regions And The Potential Impact On Atmospheric Chemistry. Environmental Science-Atmospheres, 4(2), 144–163.
Abstract: Charging Of The Ice-Vapor Interface Is A Well-Studied Topic In Ice Physics And Atmospheric Electrification. However, These Effects Were Not Yet Considered To Examine Chemical Processes In Snow In Polar Regions Because Electric Potentials At Ice Surfaces Have So Far Been Considered Insufficient To Initiate Chemical Reactions And Processes. In This Review, We Analyze Literature Data To Estimate Levels Of Electrification In Snow And Other Frozen Objects That Can Be Caused By Different Processes Occurring At The Earth'S Surface. This Analysis Demonstrates That Threshold Values Of Electric Field Strength Can Be Exceeded For The Appearance Of Corona Discharges And Even For The Formation Of Rayleigh Jets Due To Combined Effects Of Different Meteorological And Physical Processes. The Accumulation Of Electrical Charges Can Lead To Different Chemical Modifications Such As Electroosmotic Phenomena Or The Accumulation Of Impurities From The Atmosphere In Growing Ice Crystals. Moreover, Highly Energetic States That Occur And Dissipate In Microseconds As “Hot Spots” Have The Potential To Initiate Free Radical Processes And Even The Production Of Charged Aerosols. The Review Also Discusses In Detail Selected Field Observations To Point Out How Processes Driven By Electrical Charging May Help To Interpret These Observations, Which Are At Least Partly Inconsistent With Our Present Understanding Of Snow And Ice Chemistry. Finally, Some Approaches Are Presented How These Effects Can Be Studied In Field And Laboratory Experiments. A Further Development Of This New Field At The Intersection Of Ice Physics And Snow Chemistry Seems Very Promising For A Better Understanding Of Relevant Chemical Processes Related To The Cryosphere. Different Processes Can Lead To High Electrical Field Strengths In Snow And Ice In Polar Regions With The Potential To Initiate Free Radical Processes And A Number Of Other Chemical Modifications.
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2023 |
Ahmed, S., Thomas, J., Angot, H., Dommergue, A., Archer, S., Bariteau, L., et al. (2023). Modelling The Coupled Mercury-Halogen-Ozone Cycle In The Central Arctic During Spring. Elementa-Science Of The Anthropocene, .
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Barten, J., Ganzeveld, L., Steeneveld, G., Blomquist, B., Angot, H., Archer, S., et al. (2023). Low Ozone Dry Deposition Rates To Sea Ice During The Mosaic Field Campaign: Implications For The Arctic Boundary Layer Ozone Budget. Elementa-Science Of The Anthropocene, .
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Borbon, A., Dominutti, P., Panopoulou, A., Gros, V., Sauvage, S., Farhat, M., et al. (2023). Ubiquity Of Anthropogenic Terpenoids In Cities Worldwide: Emission Ratios, Emission Quantification And Implications For Urban Atmospheric Chemistry. Journal Of Geophysical Research-Atmospheres, 1281(7).
Abstract: Terpenoids (Isoprene And Monoterpenes) Are Highly Reactive Volatile Organic Compounds (Vocs) Known For Decades For Their Biogenic Origin. Here, We Discuss The Nature And Magnitude Of Their Anthropogenic Emissions. We Compiled And Re-Analyzed 14 Data Sets Of In Situ Voc Observations Collected Over The Last Decade In Contrasting Urban Areas From Mid-Latitudes To Subtropical Regions. We Show The Systematic Presence Of Anthropogenic Terpenoids In Urban Ambient Air With Clear Covariations With Anthropogenic Compounds (R-2 > 0.50) Even During Mid-Latitude Winters. Despite The Emerging Importance Of Monoterpene Emissions From Consumer Products In North American Cities, There Is Some Evidence Of Monoterpene Emissions From Tailpipe Exhaust In Cities Of The Developing World. The Traffic-Related Fraction Of Monoterpenes Is Estimated And Can Account For Up To 40% Of Their Ambient Levels. The Anthropogenic Emission Ratios (Er) Of Some Terpenoids (Isoprene, A-Pinene And Limonene) Are Estimated And Spatially Compared. The Anthropogenic Emissions Of Terpenoids Are Indirectly Estimated From Those Er Combined To Regional And Global Emission Inventories (Cams-Glob-Ant_V4.2) At Urban And Country Scale Focusing On France, Lebanon, And Vietnam. Those Anthropogenic Emissions Do Not Represent More Than 3% Of Other Anthropogenic Voc Emissions. However, They Dominate By One To Three Orders Of Magnitude The Reactivity Of Other Anthropogenic Vocs Regarding No3 Oxidation And Ozonolysis. This Study Raises Two Questions Which Need Further Investigations In The Future: (A) The Significance Of Terpenoid Emissions From Traffic, Especially In Urban Areas Of The Developing World And (B) The Role Of Anthropogenic Terpenoids In Nighttime And Wintertime Atmospheric Chemistry At Mid-Latitudes.
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Borbon, A., Dominutti, P., Panopoulou, A., Gros, V., Sauvage, S., Farhat, M., et al. (2023). Ubiquity Of Anthropogenic Terpenoids In Cities Worldwide: Emission Ratios, Emission Quantification And Implications For Urban Atmospheric Chemistry. Journal Of Geophysical Research-Atmospheres, .
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Borlaza, L., Thuy, V., Grange, S., Socquet, S., Moussu, E., Mary, G., et al. (2023). Impact Of Covid-19 Lockdown On Particulate Matter Oxidative Potential At Urban Background Versus Traffic Sites. Environmental Science-Atmospheres, .
Abstract: In Europe, Covid-19 Lockdown Restrictions Were First Implemented In March 2020 To Control The Spread Of The Disease From The Sars-Cov-2 Virus. Many Studies Have Focused On The Influence Of The Applied Measures On Pollution Levels During This Period, But Very Limited Information On The Oxidative Potential (Op), An Emerging Metric Of Particulate Matter (Pm) Exposure. Furthermore, Most Previous Studies Also Commonly Used Comparative Methods With Historical Datasets, Which May Not Be Estimating The Real Pollution Levels Without The Lockdown Restrictions In Place. In This Study, The Op Of Pm Collected At Urban Background (Grenoble, France) And Traffic (Bern, Switzerland) Sites Was Assessed Using Dithiothreitol (Dtt) And Ascorbic Acid (Aa) Assays. These Measurements Were Also Compared With Pm And Black Carbon (Bc) Mass Concentrations, Including The Wood Burning And Fossil Fuel Fractions Of Bc. To Obtain A More Realistic Pollution Level, Assuming There Were No Lockdown Restrictions In Place, A Machine Learning Technique Called The Random Forest (Rf) Regression Model Was Applied To Predict A Business-As-Usual (Bau) Level For Op, Pm, And Bc In Both Sites. This Model Provided A Good Estimate Of The Bau Levels, Allowing A More Realistic Assessment Of The Pollution Changes During The Lockdown Period. The Results Indicate A Clear Decrease In Op Found In The Traffic Site, While A More Modest Change In Op Was Found At The Urban Background Site, Likely Due To Sustained Contributions From Wood Burning Sources For Residential Heating. Overall, This Study Confirms The Major Roles Of Both Of These Combustion Sources In The Op Levels In Ambient Air.
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Celli, G., Cairns, W., Scarchilli, C., Cuevas, C., Saiz-Lopez, A., Savarino, J., et al. (2023). Bromine, Iodine And Sodium Along The Eaiist Traverse: Bulk And Surface Snow Latitudinal Variability. Environmental Research, 2392.
Abstract: During The East Antarctic International Ice Sheet Traverse (Eaiist, December 2019), In An Unexplored Part Of The East Antarctic Plateau, Snow Samples Were Collected To Expand Our Knowledge Of The Latitudinal Variability Of Iodine, Bromine And Sodium As Well As Their Relation In Connection With Emission Processes And Photochemical Activation In This Unexplored Area. A Total Of 32 Surface (0-5 Cm) And 32 Bulk (Average Of 1 M Depth) Samples Were Taken And Analysed By Inductively Coupled Plasma Mass Spectrometry (Icp-Ms). Our Results Show That There Is No Relevant Latitudinal Trend For Bromine And Sodium. For Bromine They Also Show That It Has No Sig-Nificant Post-Depositional Mechanisms While Its Inland Surface Snow Concentration Is Influenced By Spring Coastal Bromine Explosions. Iodine Concentrations Are Several Orders Of Magnitude Lower Than Bromine And Sodium And They Show A Decreasing Trend In The Surface Samples Concentration Moving Southward. This Suggests That Other Processes Affect Its Accumulation In Surface Snow, Probably Related To The Radial Reduction In The Ozone Layer Moving Towards Central Antarctica. Even Though All Iodine, Bromine And Sodium Present Similar Long-Range Transport From The Dominant Coastal Antarctic Sources, The Annual Seasonal Cycle Of The Ozone Hole Over Antarctica Increases The Amount Of Uv Radiation (In The 280-320 Nm Range) Reaching The Surface, Thereby Affecting The Surface Snow Photoactivation Of Iodine. A Comparison Between The Bulk And Surface Samples Supports The Conclusion That Iodine Undergoes Spring And Summer Snow Recycling That Increases Its Atmospheric Lifetime, While It Tends To Accumulate During The Winter Months When Photochemistry Ceases.
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Dillon, K., Tignat-Perrier, R., Joly, M., Grogan, S., Larose, C., Amato, P., et al. (2023). Comparison Of Airborne Bacterial Populations Determined By Passive And Active Air Sampling At Puy De Dome, France. Aerosol And Air Quality Research, .
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Dominutti, P., Borlaza, L., Sauvain, J., Thuy, V., Houdier, S., Suarez, G., et al. (2023). Source Apportionment Of Oxidative Potential Depends On The Choice Of The Assay: Insights Into 5 Protocols Comparison And Implications For Mitigation Measures. Environmental Science-Atmospheres, 3(101), 1497–1512.
Abstract: The Oxidative Potential (Op) Of Particulate Matter (Pm) Has Recently Been Considered As A Viable Health-Based Metric Of Pm Exposure. Several Acellular Assays Have Been Developed To Assess Op, But There Is No Clear Consensus In The Methodology Or Protocols Used That Allows Inter-Comparison Between Studies. This Research Investigates Five Different Acellular Op Assays And Their Sensitivities With The Chemical Composition Of Atmospheric Particulate Matter (Pm10) And Its Emission Sources. We Revisited And Evaluated Pm10 Samples Collected Over One Year In The Urban Alpine City Of Grenoble, France. The Op Of Pm10 Was Assessed By Integrating Assays Commonly Found In The Literature, Such As Ascorbic Acid (Aa), Dithiothreitol (Dtt) And 2,7-Dichlorofluorescein (Dcfh) But Also Adding Novel And Less Explored Assays Such As Ferric-Xylenol Orange (Fox), And A Direct Ros-Quantification Through Oh. Detailed Source Apportionment Of Pm Using Positive Matrix Factorisation (Pmf) Previously Performed Was Coupled With Multiple Linear Regression (Mlr) Models To Determine The Op Contribution Of Pm10 Sources. The Results Highlight The Importance Of Seasonality In The Mass Contributions Of Each Source And Its Corresponding Influence On Op. These Seasonal Differences Helped To Identify The Specific Reactivity For Each Studied Op Assay. In Winter, A Good Agreement Was Found Between All The Op Assays With Anthropogenic Sources. However, During Warmer Months, With A Reduction In The Share Of Anthropogenic Emissions, A Higher Impact From Biogenic And Secondary Organic-Related Aerosols Has Been Found. Our Results Also Show A Dissimilar Sensitivity Of Each Op To The Pm10 Sources, Likely Associated With The Chemical Composition And Chemical Processes Involved. Thus, Our Findings Show The Importance Of Combining Various Op Assays To Capture Different Sensitivities To Redox-Active Species To Get A Clearer Picture Of The Intrinsic Capacity Of Pm Sources To Cause Damaging Oxidative Reactions In The Lung. Providing The Heterogeneity Of Sources Obtained With The Different Op Assays For A Given Ambient Pm Exposure, The Choice Of A Single Or A Combination Of Op Method(S) Must Be Rationally Evaluated As Part Of The Assessment Strategy. Such A Choice Would Offer Valuable Source-Related Information As A Powerful Tool To Better Understand The Nature And The Intensity Of Air Pollution And Envisage The Targeted Sources For Future Mitigation Policies.
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Dominutti, P., Hopkins, J., Shaw, M., Mills, G., Le, H., Huy, D., et al. (2023). Evaluating Major Anthropogenic Voc Emission Sources In Densely Populated ViETNAmese Cities. Environmental Pollution, .
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Dumont, M., Gascoin, S., Reeveillet, M., Voisin, D., Tuzet, F., Arnaud, L., et al. (2023). Spatial Variability Of Saharan Dust Deposition Revealed Through A Citizen Science Campaign. Earth System Science Data, 151(7), 3075–3094.
Abstract: Saharan Dust Outbreaks Have Profound Effects On Ecosystems, Climate, Human Health, And The Cryosphere In Europe. However, The Spatial Deposition Pattern Of Saharan Dust Is Poorly Known Due To A Sparse Network Of Ground Measurements. Following The Extreme Dust Deposition Event Of February 2021 Across Europe, A Citizen Science Campaign Was Launched To Sample Dust On Snow Over The Pyrenees And The European Alps. This Somewhat Improvised Campaign Triggered Wide Interest Since 152 Samples Were Collected From The Snow In The Pyrenees, The French Alps, And The Swiss Alps In Less Than 4 Weeks. Among The 152 Samples, 113 In Total Could Be Analysed, Corresponding To 70 Different Locations. The Analysis Of The Samples Showed A Large Variability In The Dust Properties And Amount. We Found A Decrease In The Deposited Mass And Particle Sizes With Distance From The Source Along The Transport Path. This Spatial Trend Was Also Evident In The Elemental Composition Of The Dust As The Iron Mass Fraction Decreased From 11% In The Pyrenees To 2% In The Swiss Alps. At The Local Scale, We Found A Higher Dust Mass On South-Facing Slopes, In Agreement With Estimates From High-Resolution Remote Sensing Data. This Unique Dataset, Which Resulted From The Collaboration Of Several Research Laboratories And Citizens, Is Provided As An Open Dataset To Benefit A Large Community And To Enable Further Scientific Investigations. Data Presented In This Study Are Available At Https://Doi.Org/10.5281/Zenodo.7969515 (Dumont Et Al., 2022A).
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Guilbert, A., Bernard, J., Peyre, H., Costet, N., Hough, I., Seyve, E., et al. (2023). Prenatal And Childhood Exposure To Ambient Air Pollution And Cognitive Function In School-Age Children: Examining Sensitive Windows And Sex-Specific Associations. Environmental Research, 2352.
Abstract: Background: Combined Effect Of Both Prenatal And Early Postnatal Exposure To Ambient Air Pollution On Child Cognition Has Rarely Been Investigated And Periods Of Sensitivity Are Unknown. This Study Explores The Temporal Relationship Between Pre- And Postnatal Exposure To Pm10, Pm2.5, No2 And Child Cognitive Function. Methods: Using Validated Spatiotemporally Resolved Exposure Models, Pre- And Postnatal Daily Pm2.5, Pm10 (Satellite Based, 1 Km Resolution) And No2 (Chemistry-Transport Model, 4 Km Resolution) Concentrations At The Mother'S Residence Were Estimated For 1271 Mother-Child Pairs From The French Eden And Pelagie Cohorts. Scores Representative Of Children'S General, Verbal And Non-Verbal Abilities At 5-6 Years Were Constructed Based On Subscale Scores From The Wppsi-Iii, Wisc-Iv Or Nepsy-Ii Batteries, Using Confirmatory Factor Analysis (Cfa). Associations Of Both Prenatal (First 35 Gestational Weeks) And Postnatal (60 Months After Birth) Exposure To Air Pollutants With Child Cognition Were Explored Using Distributed Lag Non-Linear Models Adjusted For Confounders. Results: Increased Maternal Exposure To Pm10, Pm2.5 And No2, During Sensitive Windows Comprised Between The 15Th And The 33Rd Gestational Weeks, Was Associated With Lower Males' General And Non-Verbal Abilities. Higher Postnatal Exposure To Pm2.5 Between The 35Th And 52Nd Month Of Life Was Associated With Lower Males' General, Verbal And Non-Verbal Abilities. Some Protective Associations Were Punctually Observed For The Very First Gestational Weeks Or Months Of Life For Both Males And Females And The Different Pollutants And Cognitive Scores. Discussion: These Results Suggest Poorer Cognitive Function At 5-6 Years Among Males Following Increased Maternal Exposure To Pm10, Pm2.5 And No2 During Mid-Pregnancy And Child Exposure To Pm2.5 Around 3-4 Years. Apparent Protective Associations Observed Are Unlikely To Be Causal And Might Be Due To Live Birth Selection Bias, Chance Finding Or Residual Confounding.
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Guilbert, A., Hough, I., Seyve, E., Rolland, M., Quentin, J., Slama, R., et al. (2023). Association Of Prenatal And Postnatal Exposures To Warm Or Cold Air Temperatures With Lung Function In Young Infants. Jama Network Open, 6(3).
Abstract: Importance Little Is Known About Long-Term Associations Of Early-Life Exposure To Extreme Temperatures With Child Health And Lung Function. Objectives To Investigate The Association Of Prenatal And Postnatal Heat Or Cold Exposure With Newborn Lung Function And Identify Windows Of Susceptibility. Design, Setting, And Participants This Population-Based Cohort Study (Sepages) Recruited Pregnant Women In France Between July 8, 2014, And July 24, 2017. Data On Temperature Exposure, Lung Function, And Covariates Were Available From 343 Mother-Child Dyads. Data Analysis Was Performed From January 1, 2021, To December 31, 2021. Exposures Mean, Sd, Minimum, And Maximum Temperatures At The Mother-Child'S Residence, Estimated Using A State-Of-The-Art Spatiotemporally Resolved Model. Main Outcomes And Measures Outcome Measures Were Tidal Breathing Analysis And Nitrogen Multiple-Breath Washout Test Measured At 2 Months Of Age. Adjusted Associations Between Both Long-Term (35 Gestational Weeks And First 4 Weeks After Delivery) And Short-Term (7 Days Before Lung Function Test) Exposure To Ambient Temperature And Newborn Lung Function Were Analyzed Using Distributed Lag Nonlinear Models. Results A Total Of 343 Mother-Child Pairs Were Included In The Analyses (Median [Iqr] Maternal Age At Conception, 32 [30.0-35.2] Years; 183 [53%] Male Newborns). A Total Of 246 Mothers And/Or Fathers (72%) Held At Least A Master'S Degree. Among The 160 Female Newborns (47%), Long-Term Heat Exposure (95Th Vs 50Th Percentile Of Mean Temperature) Was Associated With Decreased Functional Residual Capacity (-39.7 Ml; 95% Ci, -68.6 To -10.7Ml For 24 Degrees C Vs 12 Degrees C At Gestational Weeks 20-35 And Weeks 0-4 After Delivery) And Increased Respiratory Rate (28.0/Min; 95% Ci, 4.2-51.9/Min For 24 Degrees C Vs 12 Degrees C At Gestational Weeks 14-35 And Weeks 0-1 After Delivery). Long-Term Cold Exposure (5Th Vs 50Th Percentile Of Mean Temperature) Was Associated With Lower Functional Residual Capacity (-21.9 Ml; 95% Ci, -42.4 To -1.3 Ml For 1 Degrees C Vs 12 Degrees C At Gestational Weeks 15-29), Lower Tidal Volume (-23.8 Ml; 95% Ci, -43.1 To -4.4 Ml For 1 Degrees C Vs 12 Degrees C At Gestationalweeks 14-35 And Weeks 0-4 After Delivery), And Increased Respiratory Rate (45.5/Min; 95% Ci, 10.1-81.0/Min For 1 Degrees C Vs 12 Degrees C At Gestational Weeks 6-35 And Weeks 0-1 After Delivery) In Female Newborns As Well. No Consistent Association Was Observed For Male Newborns Or Short-Term Exposure To Cold Or Heat. Conclusions And Relevance In This Cohort Study, Long-Term Heat And Cold Exposure From The Second Trimester Until 4 Weeks After Birth Was Associated With Newborn Lung Volumes, Especially Among Female Newborns.
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Gupta, A., Reverdy, A., Cohard, J., Hector, B., Descloitres, M., Vandervaere, J., et al. (2023). Impact Of Distributed Meteorological Forcing On Simulated Snow Cover And Hydrological Fluxes Over A Mid-Elevation Alpine Micro-Scale Catchment. Hydrology And Earth System Sciences, 272(1), 191–212.
Abstract: From The Micro- To The Mesoscale, Water And Energy Budgets Of Mountainous Catchments Are Largely Driven By Topographic Features Such As Terrain Orientation, Slope, Steepness, And Elevation, Together With Associated Meteorological Forcings Such As Precipitation, Solar Radiation, And Wind Speed. Those Topographic Features Govern The Snow Deposition, Melting, And Transport, Which Further Impacts The Overall Water Cycle. However, This Microscale Variability Is Not Well Represented In Earth System Models Due To Coarse Resolutions. This Study Explores The Impact Of Precipitation, Shortwave Radiation, And Wind Speed On The Water Budget Distribution Over A 15.28 Ha Small, Mid-Elevation (2000-2200 M) Alpine Catchment At Col Du Lautaret (France). The Grass-Dominated Catchment Remains Covered With Snow For 5 To 6 Months Per Year. The Surface-Subsurface Coupled Distributed Hydrological Model Parflow-Clm Is Used At A Very High Resolution (10 M) To Simulate The Impacts On The Water Cycle Of Meteorological Variability At Very Small Spatial And Temporal Scales. These Include 3D Simulations Of Hydrological Fluxes With Spatially Distributed Forcing Of Precipitation, Shortwave Radiation, And Wind Speed Compared To 3D Simulations Of Hydrological Fluxes With Non-Distributed Forcing. Our Precipitation Distribution Method Encapsulates The Spatial Snow Distribution Along With Snow Transport. The Model Simulates The Dynamics And Spatial Variability Of Snow Cover Using The Common Land Model (Clm) Energy Balance Module And Under Different Combinations Of Distributed Forcing. The Resulting Subsurface And Surface Water Transfers Are Computed By The Parflow Module. Distributed Forcing Leads To Spatially Heterogeneous Snow Cover Simulation, Which Becomes Patchy At The End Of The Melt Season And Shows A Good Agreement With The Remote Sensing Images (Mean Bias Error (Mbe) = 0.22). This Asynchronous Melting Results In A Longer Melting Period Compared To The Non-Distributed Forcing, Which Does Not Generate Any Patchiness. Among The Distributed Meteorological Forcings Tested, Precipitation Distribution, Including Snow Transport, Has The Greatest Impact On Spatial Snow Cover (Mbe = 0.06) And Runoff. Shortwave Radiation Distribution Has An Important Impact, Reducing Evapotranspiration As A Function Of The Slope Orientation (Decreasing The Slope Between Observed And Simulated Evapotranspiration From 1.55 To 1.18). For The Primarily East-Facing Catchment Studied Here, Distributing Shortwave Radiation Helps Generate Realistic Timing And Spatial Heterogeneity In The Snowmelt At The Expense Of An Increase In The Mean Bias Error (From 0.06 To 0.22) For All Distributed Forcing Simulations Compared To The Simulation With Only Distributed Precipitation. Distributing Wind Speed In The Energy Balance Calculation Has A More Complex Impact On Our Catchment, As It Accelerates Snowmelt When Meteorological Conditions Are Favorable But Does Not Generate Snow Patches At The End Of Our Test Case. This Shows That Slope- And Aspect-Based Meteorological Distribution Can Improve The Spatio-Temporal Representation Of Snow Cover And Evapotranspiration In Complex Mountain Terrain.
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Gustin, M., Dunham-Cheatham, S., Allen, N., Choma, N., Johnson, W., Lopez, S., et al. (2023). Observations Of The Chemistry And Concentrations Of Reactive Hg At Locations With Different Ambient Air Chemistry. Science Of The Total Environment, 9049.
Abstract: The Hg Research Community Needs Methods To More Accurately Measure Atmospheric Hg Concentrations And Chemistry. The Reactive Mercury Active System (Rmas) Uses Cation Exchange, Nylon, And Ptfe Membranes To Determine Reactive Mercury (Rm), Gaseous Oxidized Mercury, And Particulate-Bound Mercury (Pbm) Concentrations And Chemistry. New Data For Atlanta, Georgia (Nrgt) Demonstrated That Particulate-Bound Hg Was Dominant And The Chemistry Was Primarily N And S Hg-Ii Compounds. At Great Salt Lake, Utah (Gsl), Rm Was Predominately Pbm, With N=S > Organics > Halogen > O Hg-Ii Compounds. At Guadalupe Mountains National Park, Texas (Gumo), Halogenated Compound Concentrations Were Lowest When Air Interacting With The Site Was Primarily Derived From The Midwest, And Highest When The Air Was Sourced From Mexico. At Amsterdam Island, Southern Indian Ocean, Compounds Were Primarily Halogenated With Some N, S, And Organic Hg-Ii Compounds Potentially Associated With Biological Activity. The Geos-Chem Model Was Applied To See If It Predicted Measurements At Five Field Sites. Model Values Were Higher Than Observations At Gsl, Slightly Lower At Nrgt, And Observations Were An Order Of Magnitude Higher Than Modeled Values For Gumo And Reno, Nevada. In General, Data Collected From 13 Locations Indicated That N, S, And Organic Rm Compounds Were Associated With City And Forest Locations, Halogenated Compounds Were Sourced From The Marine Boundary Layer, And O Compounds Were Associated With Long-Range Transport. Data Being Developed Currently, And In The Past, Suggest There Are Multiple Forms Of Rm That Modelers Must Consider, And Pbm Is An Important Component Of Rm.
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Heutte, B., Bergner, N., Beck, I., Angot, H., Dada, L., Quéléver, L., et al. (2023). Measurements Of Aerosol Microphysical And Chemical Properties In The Central Arctic Atmosphere During Mosaic. Scientific Data, 101(1).
Abstract: The Arctic Environment Is Transforming Rapidly Due To Climate Change. Aerosols' Abundance And Physicochemical Characteristics Play A Crucial, Yet Uncertain, Role In These Changes Due To Their Influence On The Surface Energy Budget Through Direct Interaction With Solar Radiation And Indirectly Via Cloud Formation. Importantly, Arctic Aerosol Properties Are Also Changing In Response To Climate Change. Despite Their Importance, Year-Round Measurements Of Their Characteristics Are Sparse In The Arctic And Often Confined To Lower Latitudes At Arctic Land-Based Stations And/Or Short High-Latitude Summertime Campaigns. Here, We Present Unique Aerosol Microphysics And Chemical Composition Datasets Collected During The Year-Long Multidisciplinary Drifting Observatory For The Study Of Arctic Climate (Mosaic) Expedition, In The Central Arctic. These Datasets, Which Include Aerosol Particle Number Concentrations, Size Distributions, Cloud Condensation Nuclei Concentrations, Fluorescent Aerosol Concentrations And Properties, And Aerosol Bulk Chemical Composition (Black Carbon, Sulfate, Nitrate, Ammonium, Chloride, And Organics) Will Serve To Improve Our Understanding Of High-Arctic Aerosol Processes, With Relevance Towards Improved Modelling Of The Future Arctic (And Global) Climate.
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Kleindienst, A., Zivkovic, I., Tessier, E., Koenig, A., Heimbürger-Boavida, L., Horvat, M., et al. (2023). Assessing Comparability And Uncertainty Of Analytical Methods For Methylated Mercury Species In Seawater. Analytica Chimica Acta, 12781.
Abstract: Background: The Relative Distribution And Importance Of Monomethylmercury (Mmhg) And Dimethylmercury (Dmhg) In Seawater Is Still Under Debate. A Lack Of Comparability Between Measurements At Sub-Picomolar Levels Hampered The Further Understanding Of The Biogeochemical Hg Cycle. To Overcome This, We Assessed The Relative Standard Measurement Uncertainties (U-Ex,U-R) For Direct Measurements Of Mmhg And Dmhg By Species-Specific Isotope Dilution Icp-Ms And Cryo-Focusing Gc-Icp-Ms At Femtomolar Concentrations. Furthermore, U-Ex,U-R Was Determined For The Indirect Determination Of Dmhg (Dmhgcalc = Mehg – Mmhg) And Mehg (Mehgcalc = Mmhg + Dmhg) To Compare The Two Methodologies.Results: Expanded U-Ex,U-R (Confidence Interval Of 95%) For Cryo-Focusing Gc-Icp-Ms Was 14.4 (<50 Fm) And 14.2% (>50 Fm) And For Ss-Id Gc-Icp-Ms 5.6 (<50 Fm) And 3.7% (>50 Fm). For Concentrations Above 50 Fm, U-Ex,U-R For Dmhgcalc Was Always Lower Than For Direct Measurements (14.2%). For Mehgcalc, On The Other Hand, U-Ex,U-R Was Always Higher For Concentrations Above 115 Fm (Range: 3.7-13.9%) Than For Direct Measurements (3.7%). We Evaluated The Comparability Of Directly Measured And Calculated Dmhg And Mehg Concentrations Based On Hg Speciation Measurements For Two Vertical Profiles In The Mediterranean Sea. We Show That Directly Measured And Indirectly Determined Dmhg And Mehg Concentrations Yield Comparable Results.Significance: Our Results Validate The Application Of The Indirect Method For The Determination Of Dmhg If A Direct Measurement Method With A Low U-Ex,U-R Such As Isotope Dilution Is Used For Mmhg And Mehg Measurements. The Validation Of The Indirect Measurement Approach Opens New Possibilities To Generate More Precise And Accurate Dmhg Data In The Global Ocean.
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Koenig, A., Magand, O., Rose, C., Di Muro, A., Miyazaki, Y., Colomb, A., et al. (2023). Observed In-Plume Gaseous Elemental Mercury Depletion Suggests Significant Mercury Scavenging By Volcanic Aerosols. Environmental Science-Atmospheres, .
Abstract: Terrestrial Volcanism Is Known To Emit Mercury (Hg) Into The Atmosphere. However, Despite Many Years Of Investigation, Its Net Impact On The Atmospheric Hg Budget Remains Insufficiently Constrained, In Part Because The Transformations Of Hg In Volcanic Plumes As They Age And Mix With Background Air Are Poorly Understood. Here We Report The Observation Of Complete Gaseous Elemental Mercury (Gem) Depletion Events In Dilute And Moderately Aged (& Sim;3-7 Hours) Volcanic Plumes From Piton De La Fournaise On Reunion Island. While It Has Been Suggested That Co-Emitted Bromine Could, Once Photochemically Activated, Deplete Gem In A Volcanic Plume, We Measured Low Bromine Concentrations In Both The Gas- And Particle-Phase And Observed Complete Gem Depletion Even Before Sunrise, Ruling Out A Leading Role Of Bromine Chemistry Here. Instead, We Hypothesize That The Gem Depletions Were Mainly Caused By Gas-Particle Interactions With Sulfate-Rich Volcanic Particles (Mostly Of Submicron Size), Abundantly Present In The Dilute Plume. We Consider Heterogeneous Gem Oxidation And Gem Uptake By Particles As Plausible Manifestations Of Such A Process And Derive Empirical Rate Constants. By Extrapolation, We Estimate That Volcanic Aerosols May Scavenge 210 Mg Y(-1) (67-480 Mg Y(-1)) Of Hg From The Atmosphere Globally, Acting Effectively As Atmospheric Mercury Sink. While This Estimate Is Subject To Large Uncertainties, It Highlights That Hg Transformations In Aging Volcanic Plumes Must Be Better Understood To Determine The Net Impact Of Volcanism On The Atmospheric Hg Budget And Hg Deposition Pathways.
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Koenig, A., Magand, O., Verreyken, B., Brioude, J., Amelynck, C., Schoon, N., et al. (2023). Mercury In The Free Troposphere And Bidirectional Atmosphere-Vegetation Exchanges – Insights From Maido Mountain Observatory In The Southern Hemisphere Tropics. Atmospheric Chemistry And Physics, 232(2), 1309–1328.
Abstract: Atmospheric Mercury (Hg) Observations In The Lower Free Troposphere (Lft) Can Give Important Insights Into Hg Redox Chemistry And Can Help Constrain Hg Background Concentrations On A Regional Level. Relatively Continuous Sampling Of Lft Air, Inaccessible To Most Ground-Based Stations, Can Be Achieved At Highaltitude Observatories. However, Such High-Altitude Observatories Are Rare, Especially In The Southern Hemisphere (Sh), And Atmospheric Hg In The Sh Lft Is Unconstrained. To Fill This Gap, We Continuously Measured Gaseous Elemental Mercury (Gem; Hourly) And Reactive Mercury (Rm; Integrated Over Similar To 6-14 D) For 9 Months At Maido Mountain Observatory (2160Ma.S.L.) On Remote Reunion Island (21.1 Degrees S, 55.5 Degrees E) In The Tropical Indian Ocean. Gem Exhibits A Marked Diurnal Variation Characterized By A Midday Peak (Mean: 0.95 Ngm(-3); Sd: 0.08 Ngm(-3)) And A Nighttime Low (Mean: 0.78 Ngm(-3); Sd: 0.11 Ngm(-3)). We Find That This Diurnal Variation Is Likely Driven By The Interplay Of Important Gem Photo-Reemission From The Islands' Vegetated Surfaces (I.E. Vegetation C Soil) During Daylight Hours (8-22 Ngm(-2) H(-1)), Boundary Layer Influences During The Day, And Predominant Lft Influences At Night. We Estimate Gem In The Lft Based On Nighttime Observations In Particularly Dry Air Masses And Find A Notable Seasonal Variation, With Lft Gem Being Lowest From December To March (Mean 0.66 Ngm 3; Sd: 0.07 Ngm 3) And Highest From September To November (Mean: 0.79 Ng M(-3); Sd: 0.09 Ng M(-3)). Such A Clear Gem Seasonality Contrasts With The Weak Seasonal Variation Reported For The Sh Marine Boundary Layer But Is In Line With Modeling Results, Highlighting The Added Value Of Continuous Hg Observations In The Lft. Maido Rm Is 10.6 Pg M(-3) (Sd: 5.9 Pg M(-3)) On Average, But Rm In The Cloud-Free Lft Might Be About Twice As High, As Weekly-Biweekly Sampled Rm Observations Are Likely Diluted By Low-Rm Contributions From The Boundary Layer And Clouds.
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Lapere, R., Thomas, J., Marelle, L., Ekman, A., Frey, M., Lund, M., et al. (2023). The Representation Of Sea Salt Aerosols And Their Role In Polar Climate Within Cmip6. Journal Of Geophysical Research-Atmospheres, 1281(6).
Abstract: Natural Aerosols And Their Interactions With Clouds Remain An Important Uncertainty Within Climate Models, Especially At The Poles. Here, We Study The Behavior Of Sea Salt Aerosols (Ssaer) In The Arctic And Antarctic Within 12 Climate Models From Cmip6. We Investigate The Driving Factors That Control Ssaer Abundances And Show Large Differences Based On The Choice Of The Source Function, And The Representation Of Aerosol Processes In The Atmosphere. Close To The Poles, The Cmip6 Models Do Not Match Observed Seasonal Cycles Of Surface Concentrations, Likely Due To The Absence Of Wintertime Ssaer Sources Such As Blowing Snow. Further Away From The Poles, Simulated Concentrations Have The Correct Seasonality, But Have A Positive Mean Bias Of Up To One Order Of Magnitude. Ssaer Optical Depth Is Derived From The Modis Data And Compared To Modeled Values, Revealing Good Agreement, Except For Winter Months. Better Agreement For Aerosol Optical Depth Than Surface Concentration May Indicate A Need For Improving The Vertical Distribution, The Size Distribution And/Or Hygroscopicity Of Modeled Polar Ssaer. Source Functions Used In Cmip6 Emit Very Different Numbers Of Small Ssaer, Potentially Exacerbating Cloud-Aerosol Interaction Uncertainties In These Remote Regions. For Future Climate Scenarios Ssp126 And Ssp585, We Show That Ssaer Concentrations Increase At Both Poles At The End Of The 21St Century, With More Than Two Times Mid-20Th Century Values In The Arctic. The Pre-Industrial Climate Cmip6 Experiments Suggest There Is A Large Uncertainty In The Polar Radiative Budget Due To Ssaer.Plain Language Summary Aerosols Emitted From The Ocean, Such As Sea Salt Particles (Aerosols), Are Critical For The Climate Of Polar Regions. However, There Is Still Uncertainty In Their Representation In Climate Models. The Purpose Of This Work Is To Evaluate The Representation Of Sea Salt Aerosols (Ssaer) In The Arctic And Antarctic In A Recent Model Inter-Comparison Initiative, And To Assess The Consequences For Our Understanding Of Present-Day And Future Polar Climate. We Find That The Models Disagree Between Them And With Observations From Ground Stations And From Space. This Suggests That The Formulation Of Sea Salt Emissions In Global Models Is Not Adapted For Polar Regions. With Sea Ice Retreat, Ssaer Will Most Likely Increase In The Future, Which Makes Addressing The Current Uncertainty An Important Next Step For The Scientific Community.
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Li, C., Enrico, M., Magand, O., Araujo, B., Le Roux, G., Osterwalder, S., et al. (2023). A Peat Core Hg Stable Isotope Reconstruction Of Holocene Atmospheric Hg Deposition At Amsterdam Island (37.8(O)S). Geochimica Et Cosmochimica Acta, 3413, 62–74.
Abstract: Mercury (Hg) Stable Isotopes Have Been Broadly Used To Investigate The Sources, Transformation And Deposition Of Atmospheric Hg During The Industrial Era Thanks To The Multiple Isotope Signatures Deriving From Mass-Dependent (Represented By Delta Hg-202) And Mass-Independent Fractionation (Represented By Axxxhg) In The Environment. Less Is Known About The Impact Of Past Climate Change On Atmospheric Hg Deposition And Cycling, And Whether Hg Isotopes Covary With Past Climate. Here, We Investigate Hg Concentration And Hg Isotope Signatures In A 6600-Year-Old Ombrotrophic Peat Record From Amsterdam Island (Ams, 37.8(O)S), And In Modern Ams Rainfall And Gaseous Elemental Hg (Hg-0) Samples. Results Show That Holocene Atmospheric Hg Deposition And Plant Hg Uptake Covary With Dust Deposition, And Are Both Lower Under A High Humidity Regime Associated With Enhanced Southern Westerly Winds. Modern Ams Gaseous Hg-0 And Rainfall Hgii Isotope Signatures Are Similar To Those In The Northern Hemisphere (Nh). Holocene Peat Delta Hg-199 And A200Hg Are Significantly Correlated (R2 = 0.67, P < 0.001, N = 58), Consistently Oscillating Between The Modern Hg-0 And Rainfall Hg-Ii End-Members. Peat A200Hg And Delta Hg-199 Provide Evidence Of Plant Uptake Of Hg-0 As The Dominant Pathway Of Hg Deposition To Ams Peatland, With Some Exceptions During Humid Periods. In Contrast To Nh Archives Generally Documenting A Modern Increase In Delta Hg-199, Recent Peat Layers (Post-1900Ce) From Ams Show The Lowest Delta Hg-199 In The Peat Profile (-0.42 +/- 0.27 Parts Per Thousand, 1Cs, N = 8). This Likely Reflects A Significant Change In The Post-Depositional Process On Deposited Anthropogenic Hg In 20Th Century (I.E. Dark Abiotic Reduction), Enabling More Negative Delta Hg-199 To Be Observed In Ams Peat. We Further Find That The Oscillations Of Hg Isotopes Are Consistent With Established Holocene Climate Variability From Dust Proxies. We Suggest Peat Hg Isotope Records Might Be A Valid Rainfall Indicator. (C) 2022 The Authors. Published By Elsevier Ltd.
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Magand, O., Angot, H., Bertrand, Y., Sonke, J., Laffont, L., Duperray, S., et al. (2023). Over A Decade Of Atmospheric Mercury Monitoring At Amsterdam Island In The French Southern And Antarctic Lands. Scientific Data, 101(1).
Abstract: The Minamata Convention, A Global And Legally Binding Treaty That Entered Into Force In 2017, Aims To Protect Human Health And The Environment From Harmful Mercury (Hg) Effects By Reducing Anthropogenic Hg Emissions And Environmental Levels. The Conference Of The Parties Is To Periodically Evaluate The Convention'S Effectiveness, Starting In 2023, Using Existing Monitoring Data And Observed Trends. Monitoring Atmospheric Hg Levels Has Been Proposed As A Key Indicator. However, Data Gaps Exist, Especially In The Southern Hemisphere. Here, We Present Over A Decade Of Atmospheric Hg Monitoring Data At Amsterdam Island (37.80 Degrees S, 77.55 Degrees E), In The Remote Southern Indian Ocean. Datasets Include Gaseous Elemental And Oxidised Hg Species Ambient Air Concentrations From Either Active/Continuous Or Passive/Discrete Acquisition Methods, And Annual Total Hg Wet Deposition Fluxes. These Datasets Are Made Available To The Community To Support Policy-Making And Further Scientific Advancements.
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Mallet, M., Humphries, R., Fiddes, S., Alexander, S., Altieri, K., Angot, H., et al. (2023). Untangling The Influence Of Antarctic And Southern Ocean Life On Clouds. Elementa-Science Of The Anthropocene, 111(1).
Abstract: Polar Environments Are Among The Fastest Changing Regions On The Planet. It Is A Crucial Time To Make Significant Improvements In Our Understanding Of How Ocean And Ice Biogeochemical Processes Are Linked With The Atmosphere. This Is Especially True Over Antarctica And The Southern Ocean Where Observations Are Severely Limited And The Environment Is Far From Anthropogenic Influences. In This Commentary, We Outline Major Gaps In Our Knowledge, Emerging Research Priorities, And Upcoming Opportunities And Needs. We Then Give An Overview Of The Large-Scale Measurement Campaigns Planned Across Antarctica And The Southern Ocean In The Next 5 Years That Will Address The Key Issues. Until We Do This, Climate Models Will Likely Continue To Exhibit Biases In The Simulated Energy Balance Over This Delicate Region. Addressing These Issues Will Require An International And Interdisciplinary Approach Which We Hope To Foster And Facilitate With Ongoing Community Activities And Collaborations.
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Mardoñez, V., Pandolfi, M., Borlaza, L., Jaffrezo, J., Alastuey, A., Besombes, J., et al. (2023). Source Apportionment Study On Particulate Air Pollution In Two High-Altitude Bolivian Cities: La Paz And El Alto. Atmospheric Chemistry And Physics, 232(181), 10325–10347.
Abstract: La Paz And El Alto Are Two Fast-Growing, High-Altitude Bolivian Cities Forming The Second-Largest Metropolitan Area In The Country. Located Between 3200 And 4050 M A.S.L. (Above Sea Level), These Cities Are Home To A Burgeoning Population Of Approximately 1.8 Million Residents. The Air Quality In This Conurbation Is Heavily Influenced By Urbanization; However, There Are No Comprehensive Studies Evaluating The Sources Of Air Pollution And Their Health Impacts. Despite Their Proximity, The Substantial Variation In Altitude, Topography, And Socioeconomic Activities Between La Paz And El Alto Result In Distinct Sources, Dynamics, And Transport Of Particulate Matter (Pm). In This Investigation, Pm10 Samples Were Collected At Two Urban Background Stations Located In La Paz And El Alto Between April 2016 And June 2017. The Samples Were Later Analyzed For A Wide Range Of Chemical Species Including Numerous Source Tracers (Oc, Ec, Water-Soluble Ions, Sugar Anhydrides, Sugar Alcohols, Trace Metals, And Molecular Organic Species). The United States Environmental Protection Agency (U.S. Epa) Positive Matrix Factorization (Pmf V.5.0) Receptor Model Was Employed For The Source Apportionment Of Pm10. This Is One Of The First Source Apportionment Studies In South America That Incorporates An Extensive Suite Of Organic Markers, Including Levoglucosan, Polycyclic Aromatic Hydrocarbons (Pahs), Hopanes, And Alkanes, Alongside Inorganic Species. The Multisite Pmf Resolved 11 Main Sources Of Pm. The Largest Annual Contribution To Pm10 Came From The Following Two Major Sources: The Ensemble Of The Four Vehicular Emissions Sources (Exhaust And Non-Exhaust), Accountable For 35 % And 25 % Of The Measured Pm In La Paz And El Alto, Respectively; And Dust, Which Contributed 20 % And 32 % To The Total Pm Mass. Secondary Aerosols Accounted For 22 % (24 %) In La Paz (El Alto). Agricultural Smoke Resulting From Biomass Burning In The Bolivian Lowlands And Neighboring Countries Contributed To 9 % (8 %) Of The Total Pm10 Mass Annually, Increasing To 17 % (13 %) Between August-October. Primary Biogenic Emissions Were Responsible For 13 % (7 %) Of The Measured Pm10 Mass. Additionally, A Profile Associated With Open Waste Burning Occurring From May To August Was Identified. Although This Source Contributed Only To 2 % (5 %) Of The Total Pm10 Mass, It Constitutes The Second Largest Source Of Pahs, Which Are Compounds Potentially Hazardous To Human Health. Our Analysis Additionally Resolved Two Different Traffic-Related Factors, A Lubricant Source (Not Frequently Identified), And A Non-Exhaust Emissions Source. Overall, This Study Demonstrates That Pm10 Concentrations In La Paz And El Alto Region Are Predominantly Influenced By A Limited Number Of Local Sources. In Conclusion, To Improve Air Quality In Both Cities, Efforts Should Primarily Focus On Addressing Dust, Traffic Emissions, Open Waste Burning, And Biomass Burning.
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Marsal, A., Slama, R., Lyon-Caen, S., Borlaza, L., Jaffrezo, J., Boudier, A., et al. (2023). Prenatal Exposure To Pm2.5 Oxidative Potential And Lung Function In Infants And Preschool- Age Children: A Prospective Study. Environmental Health Perspectives, 1311(1).
Abstract: Background: Fine Particulate Matter (Pm2.5) Has Been Found To Be Detrimental To Respiratory Health Of Children, But Few Studies Have Examined The Effects Of Prenatal Pm2.5 Oxidative Potential (Op) On Lung Function In Infants And Preschool Children.Objectives: We Estimated The Associations Of Personal Exposure To Pm2.5 And Op During Pregnancy On Offspring Objective Lung Function Parameters And Compared The Strengths Of Associations Between Both Exposure Metrics.Methods: We Used Data From 356 Mother-Child Pairs From The Sepages Cohort. Pm Filters Collected Twice During A Week Were Analyzed For Op, Using The Dithiothreitol (Dtt) And The Ascorbic Acid (Aa) Assays, Quantifying The Exposure Of Each Pregnant Woman. Lung Function Was Assessed With Tidal Breathing Analysis (Tbfvl) And Nitrogen Multiple-Breath Washout (N2Mbw) Test, Performed At 6 Wk, And Airwave Oscillometry (Aos) Performed At 3 Y. Associations Of Prenatal Pm2.5 Mass And Op With Lung Function Parameters Were Estimated Using Multiple Linear Regressions.Results: In Neonates, An Interquartile (Iqr) Increase In Opdttv (0.89 Nmol/Min/M3) Was Associated With A Decrease In Functional Residual Capacity (Frc) Measured Byn2Mbw [Beta = – 2.26 Ml; 95% Confidence Interval (Ci): -4.68, 0.15]. Associations With Pm2.5 Showed Similar Patterns In Comparison With Opdtt V But Of Smaller Magnitude. Lung Clearance Index (Lci) And Tbfvl Parameters Did Not Show Any Clear Association With The Exposures Considered. At 3 Y, Increased Frequency-Dependent Resistance Of The Lungs (Rrs7-19) From Aos Tended To Be Associated With Higher Opdtt V (Beta = 0.09 Hpa X S/L; 95% Ci: -0.06, 0.24) And Opaav (Iqr =1.14 Nmol/Min/M3; Beta = 0.12 Hpa X S/L; 95% Ci: -0.04, 0.27) But Not With Pm2.5 (Iqr = 6.9 Mu G/M3; Beta = 0.02 Hpa X S/L; 95% Ci: -0.13, 0.16). Results For Frc And Rrs7-19 Remained Similar In Op Models Adjusted On Pm2.5.Discussion: Prenatal Exposure To Opdtt V Was Associated With Several Offspring Lung Function Parameters Over Time, All Related To Lung Volumes. Https://Doi.Org/10.1289/Ehp11155
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Menut, L., Cholakian, A., Siour, G., Lapere, R., Pennel, R., Mailler, S., et al. (2023). Impact Of Landes Forest Fires On Air Quality In France During The 2022 Summer. Atmospheric Chemistry And Physics, , 728177–729677.
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Smith, M., Angot, H., Chamberlain, E., Droste, E., Karam, S., Muilwijk, M., et al. (2023). Thin And Transient Meltwater Layers And False Bottoms In The Arctic Sea Ice Pack-Recent Insights On These Historically Overlooked Features. Elementa-Science Of The Anthropocene, 111(1).
Abstract: The Rapid Melt Of Snow And Sea Ice During The Arctic Summer Provides A Significant Source Of Low-Salinity Meltwater To The Surface Ocean On The Local Scale. The Accumulation Of This Meltwater On, Under, And Around Sea Ice Floes Can Result In Relatively Thin Meltwater Layers In The Upper Ocean. Due To The Small-Scale Nature Of These Upper-Ocean Features, Typically On The Order Of 1 M Thick Or Less, They Are Rarely Detected By Standard Methods, But Are Nevertheless Pervasive And Critically Important In Arctic Summer. Observations During The Multidisciplinary Drifting Observatory For The Study Of Arctic Climate (Mosaic) Expedition In Summer 2020 Focused On The Evolution Of Such Layers And Made Significant Advancements In Understanding Their Role In The Coupled Arctic System. Here We Provide A Review Of Thin Meltwater Layers In The Arctic, With Emphasis On The New Findings From Mosaic. Both Prior And Recent Observational Datasets Indicate An Intermittent Yet Long-Lasting (Weeks To Months) Meltwater Layer In The Upper Ocean On The Order Of 0.1 M To 1.0 M In Thickness, With A Large Spatial Range. The Presence Of Meltwater Layers Impacts The Physical System By Reducing Bottom Ice Melt And Allowing New Ice Formation Via False Bottom Growth. Collectively, The Meltwater Layer And False Bottoms Reduce Atmosphere-Ocean Exchanges Of Momentum, Energy, And Material. The Impacts On The Coupled Arctic System Are Far-Reaching, Including Acting As A Barrier For Nutrient And Gas Exchange And Impacting Ecosystem Diversity And Productivity.
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Sonke, J., Angot, H., Zhang, Y., Poulain, A., Bjorn, E., & Schartup, A. (2023). Global Change Effects On Biogeochemical Mercury Cycling. Ambio, .
Abstract: Past And Present Anthropogenic Mercury (Hg) Release To Ecosystems Causes Neurotoxicity And Cardiovascular Disease In Humans With An Estimated Economic Cost Of $117 Billion Usd Annually. Humans Are Primarily Exposed To Hg Via The Consumption Of Contaminated Freshwater And Marine Fish. The Unep Minamata Convention On Hg Aims To Curb Hg Release To The Environment And Is Accompanied By Global Hg Monitoring Efforts To Track Its Success. The Biogeochemical Hg Cycle Is A Complex Cascade Of Release, Dispersal, Transformation And Bio-Uptake Processes That Link Hg Sources To Hg Exposure. Global Change Interacts With The Hg Cycle By Impacting The Physical, Biogeochemical And Ecological Factors That Control These Processes. In This Review We Examine How Global Change Such As Biome Shifts, Deforestation, Permafrost Thaw Or Ocean Stratification Will Alter Hg Cycling And Exposure. Based On Past Declines In Hg Release And Environmental Levels, We Expect That Future Policy Impacts Should Be Distinguishable From Global Change Effects At The Regional And Global Scales.
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T Veld, M., Pandolfi, M., Amato, F., Perez, N., Reche, C., Dominutti, P., et al. (2023). Discovering Oxidative Potential (Op) Drivers Of Atmospheric Pm10, Pm2.5, And Pm1 Simultaneously In North-Eastern Spain. Science Of The Total Environment, 8578.
Abstract: Ambient Particulate Matter (Pm) Is A Major Contributor To Air Pollution, Leading To Adverse Health Effects On The Human Population. It Has Been Suggested That The Oxidative Potential (Op, As A Tracer Of Oxidative Stress) Of Pm Is A Possible Determinant Of Its Health Impact. In This Study, Samples Of Pm10, Pm2.5, And Pm1 Were Collected Roughly Every Four Days From January 2018 Until March 2019 At A Barcelona Urban Background Site And Montseny Rural Background Site In Northeastern Spain. We Determined The Chemical Composition Of Samples, Allowing Us To Perform Source Apportionment Using Positive Matrix Factorization. The Op Of Pm Was Determined By Measuring Reactive Oxygen Species Using Dithiothreitol And Ascorbic Acid Assays. Finally, To Link The Sources With The Measured Op, Both A Pearson'S Correlation And A Multiple Linear Regression Model Were Applied To The Dataset. The Results Showed That In Barcelona, The Op Of Pm10 Was Much Higher Than Those Of Pm2.5 And Pm1, Whereas In Montseny Results For All Pm Sizes Were In The Same Range, But Significantly Lower Than In Barcelona. In Barcelona, Several Anthropogenic Sources Were The Main Drivers Of Op In Pm10 (Combustion + Road Dust + Heavy Oil + Oc-Rich) And Pm2.5 (Road Dust + Combustion). In Contrast, Pm1 -Associated Op Was Driven By Industry, With A Much Lower Contribution To Pm10 And Pm2.5 Mass. Meanwhile, Montseny Exhibited No Clear Drivers For Op Evolution, Likely Explaining The Lack Of A Significant Difference In Op Between Pm10, Pm2.5, And Pm1. Overall, This Study Indicates That Size Fraction Matters For Op, As A Function Of The Environment Typology. In An Urban Context, Op Is Driven By The Pm10 And Pm1 Size Fractions, Whereas Only The Pm1 Fraction Is Involved In Rural Environments.
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Tassone, A., Magand, O., Naccarato, A., Martino, M., Amico, D., Sprovieri, F., et al. (2023). Seven-Year Monitoring Of Mercury In Wet Precipitation And Atmosphere At The Amsterdam Island Gmos Station. Heliyon, 9(3).
Abstract: Mercury (Hg) Fate And Transport Research Requires More Effort To Obtain A Deep Knowledge Of Its Biogeochemical Cycle, Particularly In The Southern Hemisphere And Tropics That Are Still Missing Of Distributed Monitoring Sites.Continuous Monitoring Of Atmospheric Hg Concentrations And Trend Worldwide Is Relevant For The Effectiveness Evaluation Of The Minamata Convention On Mercury (Mcm) Actions. In This Context, Gaseous Elemental Mercury (Gem) And Total Mercury (Thg) In Precipitations Were Monitored From 2013 To 2019 At The Amsterdam Island Observatory (Ams -37 Degrees 48 ' S, 77 Degrees 34 ' E) To Provide Insights Into The Hg Pathway In The Remote Southern Indian Ocean, Also Considering Ancillary Dataset Of Rn-222, Co2, Co, And Ch4. Gem Average Concentration Was 1.06 +/- 0.07 Ng M- 3, With A Slight Increase During The Austral Winter Due To Both Higher Wind Speed Over The Surface Ocean And Contributions From Southern Africa. In Wet Depositions, Thg Average Concen-Tration Was 2.39 +/- 1.17 Ng L-1, Whereas The Annual Flux Averaged 2.04 +/- 0.80 Mu Gm- 2 Year -1. In General, Both Gem And Volume-Weighted Mean Concentration (Vwmc) Of Thg Did Not Show An Increasing/Decreasing Trend Over The Seven-Year Period, Suggesting A Substantial Lack Of Evolution About Emission Of Hg Reaching Ams.Air Masses Cluster Analysis And Potential Source Contribution Function Showed That Oceanic Evasion Was The Main Hg Contributor At Ams, While Further Contributions Were Attributable To Long-Range Transport Events From Southern Africa, Particularly When The Occurrence Of El Nin Similar To O Increased The Frequency Of Wildfires.
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Tham, Y., Sarnela, N., Iyer, S., Li, Q., Angot, H., Quelever, L., et al. (2023). Widespread Detection Of Chlorine Oxyacids In The Arctic Atmosphere. Nature Communications, 141(1).
Abstract: Observations Are Reported Of Hclo3 And Hclo4 In The Atmosphere And Their Widespread Occurrence Over The Pan-Arctic During Spring, Providing Further Insights Into Atmospheric Chlorine Cycling In The Polar Environment. Chlorine Radicals Are Strong Atmospheric Oxidants Known To Play An Important Role In The Depletion Of Surface Ozone And The Degradation Of Methane In The Arctic Troposphere. Initial Oxidation Processes Of Chlorine Produce Chlorine Oxides, And It Has Been Speculated That The Final Oxidation Steps Lead To The Formation Of Chloric (Hclo3) And Perchloric (Hclo4) Acids, Although These Two Species Have Not Been Detected In The Atmosphere. Here, We Present Atmospheric Observations Of Gas-Phase Hclo3 And Hclo4. Significant Levels Of Hclo3 Were Observed During Springtime At Greenland (Villum Research Station), Ny-Angstrom Lesund Research Station And Over The Central Arctic Ocean, On-Board Research Vessel Polarstern During The Multidisciplinary Drifting Observatory For The Study Of The Arctic Climate (Mosaic) Campaign, With Estimated Concentrations Up To 7 X 10(6) Molecule Cm(-3). The Increase In Hclo3, Concomitantly With That In Hclo4, Was Linked To The Increase In Bromine Levels. These Observations Indicated That Bromine Chemistry Enhances The Formation Of Oclo, Which Is Subsequently Oxidized Into Hclo3 And Hclo4 By Hydroxyl Radicals. Hclo3 And Hclo4 Are Not Photoactive And Therefore Their Loss Through Heterogeneous Uptake On Aerosol And Snow Surfaces Can Function As A Previously Missing Atmospheric Sink For Reactive Chlorine, Thereby Reducing The Chlorine-Driven Oxidation Capacity In The Arctic Boundary Layer. Our Study Reveals Additional Chlorine Species In The Atmosphere, Providing Further Insights Into Atmospheric Chlorine Cycling In The Polar Environment.
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Von Schneidemesser, E., Mcdonald, B., Van Der Gon, H., Crippa, M., Guizzardi, D., Borbon, A., et al. (2023). Comparing Urban Anthropogenic Nmvoc Measurements With Representation In Emission Inventories-A Global Perspective. Journal Of Geophysical Research-Atmospheres, .
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Willis, M., Lannuzel, D., Else, B., Angot, H., Campbell, K., Crabeck, O., et al. (2023). Polar Oceans And Sea Ice In A Changing Climate. Elementa-Science Of The Anthropocene, 111(1).
Abstract: Polar Oceans And Sea Ice Cover 15% Of The Earth'S Ocean Surface, And The Environment Is Changing Rapidly At Both Poles. Improving Knowledge On The Interactions Between The Atmospheric And Oceanic Realms In The Polar Regions, A Surface Ocean-Lower Atmosphere Study (Solas) Project Key Focus, Is Essential To Understanding The Earth System In The Context Of Climate Change. However, Our Ability To Monitor The Pace And Magnitude Of Changes In The Polar Regions And Evaluate Their Impacts For The Rest Of The Globe Is Limited By Both Remoteness And Sea-Ice Coverage. Sea Ice Not Only Supports Biological Activity And Mediates Gas And Aerosol Exchange But Can Also Hinder Some In-Situ And Remote Sensing Observations. While Satellite Remote Sensing Provides The Baseline Climate Record For Sea-Ice Properties And Extent, These Techniques Cannot Provide Key Variables Within And Below Sea Ice. Recent Robotics, Modeling, And In-Situ Measurement Advances Have Opened New Possibilities For Understanding The Ocean-Sea Ice-Atmosphere System, But Critical Knowledge Gaps Remain. Seasonal And Long-Term Observations Are Clearly Lacking Across All Variables And Phases. Observational And Modeling Efforts Across The Sea-Ice, Ocean, And Atmospheric Domains Must Be Better Linked To Achieve A System-Level Understanding Of Polar Ocean And Sea-Ice Environments. As Polar Oceans Are Warming And Sea Ice Is Becoming Thinner And More Ephemeral Than Before, Dramatic Changes Over A Suite Of Physicochemical And Biogeochemical Processes Are Expected, If Not Already Underway. These Changes In Sea-Ice And Ocean Conditions Will Affect Atmospheric Processes By Modifying The Production Of Aerosols, Aerosol Precursors, Reactive Halogens And Oxidants, And The Exchange Of Greenhouse Gases. Quantifying Which Processes Will Be Enhanced Or Reduced By Climate Change Calls For Tailored Monitoring Programs For High-Latitude Ocean Environments. Open Questions In This Coupled System Will Be Best Resolved By Leveraging Ongoing International And Multidisciplinary Programs, Such As Efforts Led By Solas, To Link Research Across The Ocean-Sea Ice-Atmosphere Interface.
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Yue, F., Angot, H., Blomquist, B., Schmale, J., Hoppe, C., Lei, R., et al. (2023). The Marginal Ice Zone As A Dominant Source Region Of Atmospheric Mercury During Central Arctic Summertime. Nature Communications, 141(1).
Abstract: Atmospheric Gaseous Elemental Mercury (Gem) Concentrations In The Arctic Exhibit A Clear Summertime Maximum, While The Origin Of This Peak Is Still A Matter Of Debate In The Community. Based On Summertime Observations During The Multidisciplinary Drifting Observatory For The Study Of Arctic Climate (Mosaic) Expedition And A Modeling Approach, We Further Investigate The Sources Of Atmospheric Hg In The Central Arctic. Simulations With A Generalized Additive Model (Gam) Show That Long-Range Transport Of Anthropogenic And Terrestrial Hg From Lower Latitudes Is A Minor Contribution (Similar To 2%), And More Than 50% Of The Explained Gem Variability Is Caused By Oceanic Evasion. A Potential Source Contribution Function (Pscf) Analysis Further Shows That Oceanic Evasion Is Not Significant Throughout The Ice-Covered Central Arctic Ocean But Mainly Occurs In The Marginal Ice Zone (Miz) Due To The Specific Environmental Conditions In That Region. Our Results Suggest That This Regional Process Could Be The Leading Contributor To The Observed Summertime Gem Maximum. In The Context Of Rapid Arctic Warming And The Observed Increase In Width Of The Miz, Oceanic Hg Evasion May Become More Significant And Strengthen The Role Of The Central Arctic Ocean As A Summertime Source Of Atmospheric Hg.
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Yue, F., Angot, H., Blomquist, B., Schmale, J., Hoppe, C., Lei, R., et al. (2023). The Marginal Ice Zone As A Dominant Source Region Of Atmospheric Mercury During Central Arctic Summertime. Nature Communications, 141(1).
Abstract: Atmospheric Gaseous Elemental Mercury (Gem) Concentrations In The Arctic Exhibit A Clear Summertime Maximum, While The Origin Of This Peak Is Still A Matter Of Debate In The Community. Based On Summertime Observations During The Multidisciplinary Drifting Observatory For The Study Of Arctic Climate (Mosaic) Expedition And A Modeling Approach, We Further Investigate The Sources Of Atmospheric Hg In The Central Arctic. Simulations With A Generalized Additive Model (Gam) Show That Long-Range Transport Of Anthropogenic And Terrestrial Hg From Lower Latitudes Is A Minor Contribution (Similar To 2%), And More Than 50% Of The Explained Gem Variability Is Caused By Oceanic Evasion. A Potential Source Contribution Function (Pscf) Analysis Further Shows That Oceanic Evasion Is Not Significant Throughout The Ice-Covered Central Arctic Ocean But Mainly Occurs In The Marginal Ice Zone (Miz) Due To The Specific Environmental Conditions In That Region. Our Results Suggest That This Regional Process Could Be The Leading Contributor To The Observed Summertime Gem Maximum. In The Context Of Rapid Arctic Warming And The Observed Increase In Width Of The Miz, Oceanic Hg Evasion May Become More Significant And Strengthen The Role Of The Central Arctic Ocean As A Summertime Source Of Atmospheric Hg.
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Zha, Q., Aliaga, D., Krejci, R., Sinclair, V., Wu, C., Ciarelli, G., et al. (2023). Oxidized Organic Molecules In The Tropical Free Troposphere Over Amazonia. National Science Review, .
Abstract: New Particle Formation (Npf) In The Tropical Free Troposphere (Ft) Is A Globally Important Source Of Cloud Condensation Nuclei, Affecting Cloud Properties And Climate. Oxidized Organic Molecules (Ooms) Produced From Biogenic Volatile Organic Compounds Are Believed To Contribute To Aerosol Formation In The Tropical Ft, But Without Direct Chemical Observations. We Performed In Situ Molecular-Level Ooms Measurements At The Bolivian Station Chacaltaya At 5240 M Above Sea Level, On The Western Edge Of Amazonia. For The First Time, We Demonstrate The Presence Of Ooms, Mainly With 4-5 Carbon Atoms, In Both Gas-Phase And Particle-Phase (In Terms Of Mass Contribution) Measurements In Tropical Ft Air From Amazonia. These Observations, Combined With Air Mass History Analyses, Indicate That The Observed Ooms Are Linked To Isoprene Emitted From The Rainforests Hundreds Of Kilometers Away. Based On Particle-Phase Measurements, We Find That These Compounds Can Contribute To Npf, At Least The Growth Of Newly Formed Nanoparticles, In The Tropical Ft On A Continental Scale. Thus, Our Study Is A Fundamental And Significant Step In Understanding The Aerosol Formation Process In The Tropical Ft. In-Situ Molecular-Level Measurements Demonstrate The Presence Of Oxidized Organic Molecules, Mainly With 4-5 Carbon Atoms, In Both Gas-Phase And Particle-Phase In Tropical Free Troposphere Air From Amazonia. These Molecules Are Linked To Isoprene Emitted From The Rainforests Hundreds Of Kilometers Away, And Can Contribute To New Particle Formation.
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Zha, Q., Huang, W., Aliaga, D., Perakyla, O., Heikkinen, L., Koenig, A., et al. (2023). Measurement Report: Molecular-Level Investigation Of Atmospheric Cluster Ions At The Tropical High-Altitude Research Station Chacaltaya (5240 M A.S.L.) In The Bolivian Andes. Atmospheric Chemistry And Physics, , 455944–457644.
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2022 |
Ahmed, S., Thomas, J. L., Tuite, K., Stutz, J., Flocke, F., Orlando, J. J., et al. (2022). The Role of Snow in Controlling Halogen Chemistry and Boundary Layer Oxidation During Arctic Spring: A 1D Modeling Case Study. Journal Of Geophysical Research-Atmospheres, 1271(5).
Abstract: Reactive chlorine and bromine species emitted from snow and aerosols can significantly alter the oxidative capacity of the polar boundary layer. However, halogen production mechanisms from snow remain highly uncertain, making it difficult for most models to include descriptions of halogen snow emissions and to understand the impact on atmospheric chemistry. We investigate the influence of Arctic halogen emissions from snow on boundary layer oxidation processes using a one-dimensional atmospheric chemistry and transport model (PACT-1D). To understand the combined impact of snow emissions and boundary layer dynamics on atmospheric chemistry, we model Cl-2 and Br-2 primary emissions from snow and include heterogeneous recycling of halogens on both snow and aerosols. We focus on a 2-day case study from the 2009 Ocean-Atmosphere-Sea Ice-Snowpack campaign at Utqia & x121;vik, Alaska. The model reproduces both the diurnal cycle and high quantity of Cl-2 observed, along with the measured concentrations of Br-2, BrO, and HOBr. Due to the combined effects of emissions, recycling, vertical mixing, and atmospheric chemistry, reactive chlorine is typically confined to the lowest 15 m of the atmosphere, while bromine can impact chemistry up to and above the surface inversion height. Upon including halogen emissions and recycling, the concentration of HOx (HOx = OH + HO2) at the surface increases by as much as a factor of 30 at mid-day. The change in HOx due to halogen chemistry, as well as chlorine atoms derived from snow emissions, significantly reduce volatile organic compound lifetimes within a shallow layer near the surface.
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Angot, H., Blomquist, B., Howard, D., Archer, S., Bariteau, L., Beck, I., et al. (2022). Year-Round Trace Gas Measurements In The Central Arctic During The Mosaic Expedition. Scientific Data, 9(1).
Abstract: Despite The Key Role Of The Arctic In The Global Earth System, Year-Round In-Situ Atmospheric Composition Observations Within The Arctic Are Sparse And Mostly Rely On Measurements At Ground-Based Coastal Stations. Measurements Of A Suite Of In-Situ Trace Gases Were Performed In The Central Arctic During The Multidisciplinary Drifting Observatory For The Study Of Arctic Climate (Mosaic) Expedition. These Observations Give A Comprehensive Picture Of Year-Round Near-Surface Atmospheric Abundances Of Key Greenhouse And Trace Gases, I.E., Carbon Dioxide, Methane, Nitrous Oxide, Ozone, Carbon Monoxide, Dimethylsulfide, Sulfur Dioxide, Elemental Mercury, And Selected Volatile Organic Compounds (Vocs). Redundancy In Certain Measurements Supported Continuity And Permitted Cross-Evaluation And Validation Of The Data. This Paper Gives An Overview Of The Trace Gas Measurements Conducted During Mosaic And Highlights The High Quality Of The Monitoring Activities. In Addition, In The Case Of Redundant Measurements, Merged Datasets Are Provided And Recommended For Further Use By The Scientific Community.
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Araujo, B., Osterwalder, S., Szponar, N., Lee, D., Petrova, M., Pernov, J., et al. (2022). Mercury Isotope Evidence For Arctic Summertime Re-Emission Of Mercury From The Cryosphere. Nature Communications, 131(1).
Abstract: During Arctic Springtime, Halogen Radicals Oxidize Atmospheric Elemental Mercury (Hg-0), Which Deposits To The Cryosphere. This Is Followed By A Summertime Atmospheric Hg-0 Peak That Is Thought To Result Mostly From Terrestrial Hg Inputs To The Arctic Ocean, Followed By Photoreduction And Emission To Air. The Large Terrestrial Hg Contribution To The Arctic Ocean And Global Atmosphere Has Raised Concern Over The Potential Release Of Permafrost Hg, Via Rivers And Coastal Erosion, With Arctic Warming. Here We Investigate Hg Isotope Variability Of Arctic Atmospheric, Marine, And Terrestrial Hg. We Observe Highly Characteristic Hg Isotope Signatures During The Summertime Peak That Reflect Re-Emission Of Hg Deposited To The Cryosphere During Spring. Air Mass Back Trajectories Support A Cryospheric Hg Emission Source But No Major Terrestrial Source. This Implies That Terrestrial Hg Inputs To The Arctic Ocean Remain In The Marine Ecosystem, Without Substantial Loss To The Global Atmosphere, But With Possible Effects On Food Webs. Arctic Warming Thaws Permafrost, Leading To Enhanced Soil Mercury Transport To The Arctic Ocean. Mercury Isotope Signatures In Arctic Rivers, Ocean And Atmosphere Suggest That Permafrost Mercury Is Buried In Marine Sediment And Not Emitted To The Global Atmosphere
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Baladima, F., Thomas, J. L., Voisin, D., Dumont, M., Junquas, C., Kumar, R., et al. (2022). Modeling An Extreme Dust Deposition Event To The French Alpine Seasonal Snowpack in April 2018: Meteorological Context and Predictions of Dust Deposition. Journal Of Geophysical Research-Atmospheres, 1271(8).
Abstract: Mineral dust is an important aerosol in the atmosphere and is known to reduce snow albedo upon deposition. Model predictions of dust deposition events in snow covered mountain regions are challenging due to the complexity of aerosol-cloud interactions and the specifics of mountain meteorological systems. We use a case study of dust deposition between 30 March and 5 April 2018 to the French alpine snowpack to study the processes that control dust deposition to the seasonal snowpack. To understand processes controlling dust transport and deposition to snow, we use a combination of in situ observations at Col du Lautaret in the French Alps, satellite remote sensing, the Copernicus Atmosphere Monitoring Service (CAMS) reanalysis global atmospheric composition, and the regional model WRF-Chem. Specifically, we investigate the role of increased model spatial resolution within WRF-Chem in capturing mountain meteorology, precipitation, and predicted dust deposition. Regional model results are also compared to the reanalysis global CAMS products including aerosols in the atmosphere and predicted dust deposition fluxes. We conclude that predicted mountain meteorology (e.g., precipitation) is better with increased model resolution (3 x 3 km resolution WRF-Chem domain). This improved meteorology has significant impacts on predicted dry and wet dust deposition to the alpine snowpack. Dry deposition is important in the western part of the French Alps at low altitudes, while wet deposition dominates over the complex higher altitude mountain terrain.
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Benavent, N., Mahajan, A., Li, Q., Cuevas, C., Schmale, J., Angot, H., et al. (2022). Substantial Contribution Of Iodine To Arctic Ozone Destruction. Nature Geoscience, .
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Bianchi, F., Sinclair, V. A., Aliaga, D., Zha, Q. Z., Scholz, W., Wu, C., et al. (2022). The Saltena Experiment Comprehensive Observations Of Aerosol Sources, Formation, and Processes in the South American Andes. Bulletin Of The American Meteorological Society, 1031(2), E212–E229.
Abstract: This paper presents an introduction to the Southern Hemisphere High Altitude Experiment on Particle Nucleation and Growth (SALTENA). This field campaign took place between December 2017 and June 2018 (wet to dry season) at Chacaltaya (CHC), a GAW (Global Atmosphere Watch) station located at 5,240 m MSL in the Bolivian Andes. Concurrent measurements were conducted at two additional sites in El Alto (4,000 m MSL) and La Paz (3,600 m MSL). The overall goal of the campaign was to identify the sources, understand the formation mechanisms and transport, and characterize the properties of aerosol at these stations. State-of-the-art instruments were brought to the station complementing the ongoing permanent GAW measurements, to allow a comprehensive description of the chemical species of anthropogenic and biogenic origin impacting the station and contributing to new particle formation. In this overview we first provide an assessment of the complex meteorology, airmass origin, and boundary layer-free troposphere interactions during the campaign using a 6-month high-resolution Weather Research and Forecasting (WRF) simulation coupled with Flexible Particle dispersion model (FLEXPART). We then show some of the research highlights from the campaign, including (i) chemical transformation processes of anthropogenic pollution while the air masses are transported to the CHC station from the metropolitan area of La Paz- El Alto, (ii) volcanic emissions as an important source of atmospheric sulfur compounds in the region, (iii) the characterization of the compounds involved in new particle formation, and (iv) the identification of long-range-transported compounds from the Pacific or the Amazon basin. We conclude the article with a presentation of future research foci. The SALTENA dataset highlights the importance of comprehensive observations in strategic high-altitude locations, especially the undersampled Southern Hemisphere.
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Borlaza, L., Uzu, G., Ouidir, M., Lyon-Caen, S., Marsal, A., Weber, S., et al. (2022). Personal Exposure To Pm2.5 Oxidative Potential And Its Association To Birth Outcomes. Journal Of Exposure Science And Environmental Epidemiology, .
Abstract: Background: Prenatal Exposure To Fine Particulate Matter (Pm2.5) Assessed Through Its Mass Concentration Has Been Associated With Foetal Growth Restriction In Studies Based On Outdoor Levels. Oxidative Potential Of Pm2.5 (Op) Is An Emerging Metric A Priori Relevant To Mechanisms Of Action Of Pm On Health, With Very Limited Evidence To Indicate Its Role On Birth Outcomes. Objectives: We Investigated The Association Of Op With Birth Outcomes And Compared It With That Of Pm2.5 Mass Concentration. Methods: 405 Pregnant Women From Sepages Cohort (Grenoble Area) Carried Pm2.5 Personal Dosimeters For One Or Two One-Week Periods. Op Was Measured Using Dithiothreitol (Dtt) And Ascorbic Acid (Aa) Assays From The Collected Filters. Associations Of Each Exposure Metric With Offspring Weight, Height, And Head Circumference At Birth Were Estimated Adjusting For Potential Confounders. Results: The Correlation Between Pm2.5 Mass Concentration And Opvdtt Was 0.7. An Interquartile Range Increase In – Was Associated With Reduced Weight (Adjusted Change, -64 G, -166 To -11, P = 0.02) And Height (-4 Mm, -6 To -1, P = 0.01) At Birth. Pm2.5 Mass Concentration Showed Similar Associations With Weight (-53 G, -99 To -8, P = 0.02) And Height (-2 Mm, -5 To 0, P = 0.05). In Birth Height Models Mutually Adjusted For The Two Exposure Metrics, The Association With Opvdtt Was Less Attenuated Than That With Mass Concentration, While For Weight Both Effect Sizes Attenuated Similarly. There Was No Clear Evidence Of Associations With Head Circumference For Any Metric, Nor For Opvaa With Any Growth Parameter. Impact: Pm2.5 Pregnancy Exposure Assessed From Personal Dosimeters Was Associated With Altered Foetal Growth. Personal Op Exposure Was Associated With Foetal Growth Restrictions, Specifically Decreased Weight And Height At Birth, Possibly To A Larger Extent Than Pm2.5 Mass Concentration Alone. These Results Support Op Assessed From Dtt As Being A Health-Relevant Metric. Larger Scale Cohort Studies Are Recommended To Support Our Findings.
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Borlaza, L. J., Weber, S., Marsal, A., Uzu, G., Jacob, V., Besombes, J. L., et al. (2022). Nine-Year Trends Of Pm10 Sources And Oxidative Potential In A Rural background site in France. Atmospheric Chemistry And Physics, 222(131), 8701–8723.
Abstract: Long-term monitoring at sites with relatively low particulate pollution could provide an opportunity to identify changes in pollutant concentration and potential effects of current air quality policies. In this study, 9-year sampling of PM10 (particles with an aerodynamic diameter below 10 μm) was performed in a rural background site in France (Observatoire Menne de l'Environnement or OPE) from 28 February 2012 to 22 December 2020. The positive matrix factorization (PMF) method was used to apportion sources of PME) based on quantified chemical constituents and specific chemical tracers analysed on collected filters. Oxidative potential (OP), an emerging health metric that measures PM capability to potentially cause anti-oxidant imbalance in the lung, was also measured using two acellular assays: dithiothreitol (DTT) and ascorbic acid (AA). The sources of OP were also estimated using multiple linear regression (MLR) analysis. In terms of mass contribution, the dominant sources are secondary aerosols (nitrate- and sulfate-rich) associated with long-range transport (LRT). However, in terms of OP contributions, the main drivers are traffic, mineral dust, and biomass burning factors. There is also some OP contribution apportioned to the sulfate- and nitrate-rich sources influenced by processes and ageing during LRT that could have encouraged mixing with other anthropogenic sources. The study indicates much lower OP values than in urban areas. A substantial decrease (58 % reduction from the year 2012 to 2020) in the mass contributions from the traffic factor was found, even though this is not clearly reflected in its OP contribution. Nevertheless, the findings in this long-term study at the OPE site could indicate effectiveness of implemented emission control policies, as also seen in other long-term studies conducted in Europe, mainly for urban areas.
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Brighty, A., Jacob, V., Uzu, G., Borlaza, L., Conil, S., Hueglin, C., et al. (2022). Cellulose In Atmospheric Particulate Matter At Rural And Urban Sites across France and Switzerland. Atmospheric Chemistry And Physics, 222(9), 6021–6043.
Abstract: The spatiotemporal variations in free-cellulose concentrations in atmospheric particles, as a proxy for plant debris, were investigated using an improved protocol with a high-performance liquid chromatography with pulsed amperometric detection (HPLC-PAD) method. Filter samples were taken from nine sites of varying characteristics across France and Switzerland, with sampling covering all seasons. Concentrations of cellulose, as well as carbonaceous aerosol and other source-specific chemical tracers (e.g. elemental carbon, EC; levoglucosan; polyols; trace metals; and glucose), were quantified. Annual mean free-cellulose concentrations within PM10 (particulate matter) ranged from 29 +/- 38 ng m(-3) at Basel (urban site) to 284 +/- 225 ng m(-3) at Payerne (rural site). Concentrations were considerably higher during episodes, with spikes exceeding 1150 and 2200 ng m(-3) at Payerne and ANDRA-OPE (Agence nationale pour la gestion des dechets radioactifs Observatoire Perenne de l'Environnement; rural site), respectively. A clear seasonality, with highest cellulose concentrations during summer and autumn, was observed at all rural and some urban sites. However, some urban locations exhibited a weakened seasonality. Contributions of cellulose carbon to total organic carbon are moderate on average (0.7 %-5.9 %) but much greater during “episodes”, reaching close to 20 % at Payerne. Cellulose concentrations correlated poorly between sites, even at ranges of about 10 km, indicating the localised nature of the sources of atmospheric plant debris. With regards to these sources, correlations between cellulose and typical biogenic chemical tracers (polyols and glucose) were moderate to strong (R-s = 0.28-0.78, p < 0.0001) across the nine sites. Seasonality was strongest at sites with stronger biogenic correlations, suggesting the main source of cellulose arises from biogenic origins. A second input to ambient plant debris concentrations was suggested via resuspension of plant matter at several urban sites, due to moderate cellulose correlations with mineral dust tracers, Ca2+, and Ti metal (R-s = 0.28-0.45, p < 0.007). No correlation was obtained with the biomass burning tracer (levoglucosan), an indication that this is not a source of atmospheric cellulose. Finally, an investigation into the interannual variability in atmospheric cellulose across the Grenoble metropole was completed. It was shown that concentrations and sources of ambient cellulose can vary considerably between years. All together, these results deeply improve our knowledge on the phenomenology of plant debris within ambient air.
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Dietz, R., Wilson, S., Loseto, L. L., Dommergue, A., Xie, Z. Q., Sonne, C., et al. (2022). Special Issue On The Amap 2021 Assessment Of Mercury In The Arctic. Science Of The Total Environment, 8438.
Abstract: This Editorial presents an overview of the Special Issue on advances in Arctic mercury (Hg) science synthesized from the 2021 assessment of the Arctic Monitoring and Assessment Programme (AMAP). Mercury continues to travel to Arctic environments and threaten wildlife and human health in this circumpolar region. Over the last decade, progress has been achieved in addressing policy-relevant uncertainties in environmental Hg contamination. This includes temporal trends of Hg, its transport to and within the Arctic, methylmercury cycling, climate change influences, biological effects of Hg on fish and wildlife, human exposure to Hg, and forecasting of Arctic responses to different future scenarios of anthropogenic Hg emissions. In addition, important contributions of Indigenous Peoples to Arctic research and monitoring of Hg are highlighted, including through projects of knowledge co-production. Finally, policy-relevant recommendations are summarized for future study of Arctic mercury. This series of scientific articles presents comprehensive information relevant to supporting effectiveness evaluation of the United Nations Minamata Convention on Mercury.
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Dominutti, P., Chevassus, E., Baray, J., Jaffrezo, J., Borbon, A., Colomb, A., et al. (2022). Evaluation Of The Sources, Precursors, And Processing Of Aerosols At A High-Altitude Tropical Site. Acs Earth And Space Chemistry, .
Abstract: This Work Presents The Results From A Set Of Aerosol- And Gas-Phase Measurements Collected During The Bio-Maido Field Campaign In Reunion Between March 8And April 5, 2019. Several Offline And Online Sampling Devices Were Installed At The Maido Observatory (Mo), A Remote High-Altitude Site In The Southern Hemisphere, Allowing The Physical And Chemical Characterization Of Atmospheric Aerosols And Gases. The Evaluation Of Short-Lived Gas-Phase Measurements Allows Us To Conclude That Air Masses Sampled During This Period Contained Little Or No Anthropogenic Influence. The Dominance Of Sulfate And Organic Species In The Submicron Fraction Of The Aerosol Is Similar To That Measured At Other Coastal Sites. Carboxylic Acids On Pm10 Showed A Significant Contribution Of Oxalic Acid, A Typical Tracer Of Aqueous Processed Air Masses, Increasing At The End Of The Campaign. This Result Agrees With The Positive Matrix Factorization Analysis Of The Submicron Organic Aerosol, Where More Oxidized Organic Aerosols (Mooas) Dominated The Organic Aerosol With An Increasing Contribution Toward The End Of The Campaign. Using A Combination Of Air Mass Trajectories (Model Predictions), It Was Possible To Assess The Impact Of Aqueous Phase Processing On The Formation Of Secondary Organic Aerosols (Soas). Our Results Show How Specific Chemical Signatures And Physical Properties Of Air Masses, Possibly Affected By Cloud Processing, Can Be Identified At Reunion. These Changes In Properties Are Represented By A Shift In Aerosol Size Distribution To Large Diameters And An Increased Contribution Of Secondary Sulfate And Organic Aerosols After Cloud Processing.
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Dominutti, P. A., Renard, P., Vaitilingom, M., Bianco, A., Baray, J. L., Borbon, A., et al. (2022). Insights into tropical cloud chemistry in Reunion (Indian Ocean): results from the BIO-MAiDO campaign. Atmospheric Chemistry And Physics, 222(1), 505–533.
Abstract: We present here the results obtained during an intensive field campaign conducted in the framework of the French “BIO-MAiDO” (Bio-physico-chemistry of tropical clouds at Maido (Reunion Island): processes and impacts on secondary organic aerosols' formation) project. This study integrates an exhaustive chemical and microphysical characterization of cloud water obtained in March-April 2019 in Reunion (Indian Ocean). Fourteen cloud samples have been collected along the slope of this mountainous island. Comprehensive chemical characterization of these samples is performed, including inorganic ions, metals, oxidants, and organic matter (organic acids, sugars, amino acids, carbonyls, and low-solubility volatile organic compounds, VOCs). Cloud water presents high molecular complexity with elevated water-soluble organic matter content partly modulated by microphysical cloud properties. As expected, our findings show the presence of compounds of marine origin in cloud water samples (e.g. chloride, sodium) demonstrating ocean-cloud exchanges. Indeed, Na+ and Cl- dominate the inorganic composition contributing to 30 % and 27 %, respectively, to the average total ion content. The strong correlations between these species (r(2) = 0.87, p value: < 0.0001) suggest similar air mass origins. However, the average molar Cl-/Na+ ratio (0.85) is lower than the sea-salt one, reflecting a chloride depletion possibly associated with strong acids such as HNO3 and H2SO4. Additionally, the non-sea-salt fraction of sulfate varies between 38 % and 91 %, indicating the presence of other sources. Also, the presence of amino acids and for the first time in cloud waters of sugars clearly indicates that biological activities contribute to the cloud water chemical composition. A significant variability between events is observed in the dissolved organic content (25.5 +/- 18.4 mgCL-1), with levels reaching up to 62 mgCL(-1). This variability was not similar for all the measured compounds, suggesting the presence of dissimilar emission sources or production mechanisms. For that, a statistical analysis is performed based on back-trajectory calculations using the CAT (Computing Atmospheric Trajectory Tool) model associated with the land cover registry. These investigations reveal that air mass origins and microphysical variables do not fully explain the variability observed in cloud chemical composition, highlighting the complexity of emission sources, multiphasic transfer, and chemical processing in clouds. Even though a minor contribution of VOCs (oxygenated and low-solubility VOCs) to the total dissolved organic carbon (DOC) (0.62 % and 0.06 %, respectively) has been observed, significant levels of biogenic VOC (20 to 180 nmolL(-1)) were detected in the aqueous phase, indicating the cloud-terrestrial vegetation exchange. Cloud scavenging of VOCs is assessed by measurements obtained in both the gas and aqueous phases and deduced experimental gas-/aqueous-phase partitioning was compared with Henry's law equilibrium to evaluate potential supersaturation or unsaturation conditions. The evaluation reveals the supersaturation of low-solubility VOCs from both natural and anthropogenic sources. Our results depict even higher supersaturation of terpenoids, evidencing a deviation from thermodynamically expected partitioning in the aqueous-phase chemistry in this highly impacted tropical area.
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Foret, G., Michoud, V., Kotthaus, S., Petit, J., Baudic, A., Siour, G., et al. (2022). The December 2016 Extreme Weather And Particulate Matter Pollution Episode In The Paris Region (France). Atmospheric Environment, 2912.
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Grange, S. K., Uzu, G., Weber, S., Jaffrezo, J. L., & Hueglin, C. (2022). Linking Switzerland'S Pm10 And Pm2.5 Oxidative Potential (Op) With emission sources. Atmospheric Chemistry And Physics, 222(101), 7029–7050.
Abstract: Particulate matter (PM) is the air pollutant that causes the greatest deleterious health effects across the world, so PM is routinely monitored within air quality networks, usually in respect to PM mass or number in different size fractions. However, such measurements do not provide information on the biological toxicity of PM. Oxidative potential (OP) is a complementary metric that aims to classify PM in respect to its oxidising ability in the lungs and is being increasingly reported due to its assumed relevance concerning human health. Between June 2018 and May 2019, an intensive filter-based PM sampling campaign was conducted across Switzerland in five locations, which involved the quantification of a large number of PM constituents and the OP for both PM10 and PM2.5. OP was quantified by three assays: ascorbic acid (AA), dithiothreitol (DTT), and dichlorofluorescein (DCFH). OPv (OP by air volume) was found to be variable over time and space: Bern-Bollwerk, an urban-traffic sampling site, had the greatest levels of OPv among the Swiss sites (especially when considering OPvAA ), with more rural locations such as Payerne experiencing a lower OPv. However, urban-background and suburban sites experienced a significant OPv enhancement, as did the rural Magadino-Cadenazzo site during wintertime because of high levels of wood smoke. The mean OP ranges for the sampling period were 0.4-4.1 nmolmin(-1)m(-3), 0.6-3.0 nmolmin(-1)m(-3), and 0.3-0.7 nmolH(2)O(2)m(-3) for OPvAA, OPDvTT, and OPvDCFH, respectively. A source allocation method using positive matrix factorisation (PMF) models indicated that although all PM10 and PM2.5 sources that were identified contributed to OPv, the anthropogenic road traffic and wood combustion sources had the greatest OPm potency (OP per PM mass) on average. A dimensionality reduction procedure coupled to multiple linear regression modelling consistently identified a handful of metals usually associated with nonexhaust emissions, namely copper, zinc, iron, tin, antimony, manganese, and cadmium, as well as three specific wood-burning-sourced organic tracers – levoglucosan, mannosan, and galactosan (or their metal substitutes: rubidium and potassium), as the most important PM components to explain and predict OPv. The combination of a metal and a wood-burning-specific tracer led to the best-performing linear models to explain OPv. Interestingly, within the non-exhaust and wood combustion emission groups, the exact choice of component was not critical; the models simply required a variable representing the emission source or process to be present. This analysis strongly suggests that anthropogenic and locally emitting road traffic and wood burning sources should be prioritised, targeted, and controlled to gain the most efficacious decrease in OPv and presumably biological harm reductions in Switzerland.
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Heredia, C., Guedron, S., Point, D., Perrot, V., Campillo, S., Verin, C., et al. (2022). Anthropogenic Eutrophication Of Lake Titicaca (Bolivia) Revealed By Carbon And Nitrogen Stable Isotopes Fingerprinting. Science Of The Total Environment, 8458.
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Hoang, C., Magand, O., Brioude, J., Dimuro, A., Brunet, C., Ah-Peng, C., et al. (2022). Probing The Limits Of Sampling Gaseous Elemental Mercury Passively In The Remote Atmosphere. Environmental Science-Atmospheres, .
Abstract: Reliably Recording Very Low Ambient Concentrations Of Gaseous Elemental Mercury (Gem) In Remote Regions Is Often Required, For Example In The Context Of Evaluating How Effective The Minamata Convention Is In Reducing Global Hg Emissions. However, Sampling Over Extended Periods Of Time At Sites That Are Difficult To Access Can Be Very Challenging. In Order To Establish What Role Inexpensive And Easy-To-Use Passive Air Samplers May Play In This Regard, We Deployed A Sampler Using A Radiello Diffusive Barrier And Activated Carbon Sorbent For Periods Of Up To Three Years And With Sampling Periods Ranging From One To Three Months In Some Of The Most Extreme, Remote And Challenging Global Environments: At Concordia Station On The Antarctic Plateau, On Amsterdam Island In The Remote Southern Indian Ocean And At Several Sites On The Tropical Island Of La Reunion. The Ability To Reliably Record The Gem Concentrations At These Sites Was Strongly Influenced By The Size Of The Sequestered Amount Of Mercury Relative To The Extent And Variability Of The Contamination Of Field Blank Samples. In Some Cases, Acceptably Low And Consistent Field Blank Contamination Could Only Be Achieved By Storing Samplers In Sealed Glass Jars During Transport And Storage. The Size Of The Sequestered Amount Is Easily Increased By Extending Deployment Times, And The Experience Of The Current Study Suggests That Deployment Periods In Excess Of Two Months Are Advisable. Sampling In Antarctica Was Compromised By The Extreme Low Temperatures, Which Caused Unknown Sampling Rates, Hoar Frost Accumulation, Material Failure And Potential Failure Of Storage Seals. While Good Agreement With Gem Concentrations Measured With An Active Sampler Was Noted On Amsterdam Island, The Passive Sampler Derived Levels At The Maido Observatory In La Reunion Were Notably Higher Than Concentrations Measured Simultaneously With A Tekran Vapour Analyzer, Which Was Possibly Related To Sampling Rates Being Temporarily Elevated At The Very Beginning Of Deployment At Low Gem Concentrations.
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Jiang, Z., Savarino, J., Alexander, B., Erbland, J., Jaffrezo, J. L., & Geng, L. (2022). Impacts Of Post-Depositional Processing On Nitrate Isotopes In The Snow and the overlying atmosphere at Summit, Greenland. Cryosphere, 161(7), 2709–2724.
Abstract: The effect of post-depositional processing on the preservation of snow nitrate isotopes at Summit, Greenland, remains a subject of debate and is relevant to the quantitative interpretation of ice-core nitrate (isotopic) records at high snow accumulation sites. Here we present the first year-round observations of atmospheric nitrate and its isotopic compositions at Summit and compare them with published surface snow and snowpack observations. The atmospheric delta N-15(NO3-) remained negative throughout the year, ranging from -3.1 parts per thousand to -47.9 parts per thousand with a mean of (-14.8 +/- 7.3)parts per thousand (n = 54), and displayed minima in spring which are distinct from the observed spring delta N-15(NO3-) maxima in snowpack. The spring average atmospheric delta N-15(NO3-) was (-17.9 +/- 8.3) parts per thousand (n = 21), significantly depleted compared to the snowpack spring average of (4.6 +/- 2.1)parts per thousand, while the surface snow delta N-15(NO3-) of (-6.8 +/- 0.5)parts per thousand was in between the atmosphere and the snowpack. The differences in atmospheric, surface snow and snowpack delta N-15(NO3-) are best explained by the photo-driven post-depositional processing of snow nitrate, with potential contributions from fractionation during nitrate deposition. In contrast to delta N-15(NO3-) the atmospheric Delta O-1(7)(NO3-) was of a similar seasonal pattern and magnitude of change to that in the snowpack, suggesting little to no changes in Delta O-1(7)(NO3-) from photolysis, consistent with previous modeling results. The atmospheric delta O-18(NO3-) varied similarly to atmospheric Delta O-1(7)(NO3-), with summer low and winter high values. However, the difference between atmospheric and snow delta O-18(NO3-) was larger than that of Delta O-17(NO3-). We found a strong correlation between atmospheric delta O-18(NO3-) and Delta O-17(NO3-) that is very similar to previous measurements for surface snow at Summit, suggesting that atmospheric delta O-18(NO3-) versus Delta O-17(NO3-) relationships were conserved during deposition. However, we found the linear relationships between delta O-18 and Delta O-17(NO3-) were significantly different for snowpack compared to atmospheric samples. This likely suggests the oxygen isotopes are also affected before preservation in the snow at Summit, but the degree of change for delta O-18(NO3-) should be larger than that of Delta O-17(NO3-). This is because photolysis is a massdependent process that would directly affect delta O-18(NO3-) in snow but not Delta O-17(NO3-) as the latter is a mass-independent signal. Although there were uncertainties associated with the complied dataset, the results suggested that post-depositional processing at Summit can induce changes in nitrate isotopes, especially delta N-15(NO3-), consistent with a previous modeling study. This reinforces the importance of understanding the effects of post-depositional processing before ice-core nitrate isotope interpretation, even for sites with relatively high snow accumulation rates.
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Koenig, A. M., Sonke, J. E., Magand, O., Andrade, M., Moreno, I., Velarde, F., et al. (2022). Evidence For Interhemispheric Mercury Exchange In The Pacific Ocean Upper Troposphere. Journal Of Geophysical Research-Atmospheres, 1271(101).
Abstract: Even though anthropogenic mercury (Hg) emissions to the atmosphere are similar to 2.5 times higher in the Northern Hemisphere (NH) than in the Southern Hemisphere (SH), atmospheric Hg concentrations in the NH are only similar to 1.5 times higher than in the SH. Global Hg models attribute this apparent discrepancy to large SH oceanic Hg emissions or to interhemispheric exchange of Hg through the atmosphere. However, no observational data set exists to serve as a benchmark to validate whether these coarse-resolution models adequately represent the complex dynamics of interhemispheric Hg exchange. During the 2015-2016 El Nino, we observed at mount Chacaltaya in the tropical Andes a similar to 50% increase in ambient Hg compared to the year before, coinciding with a shift in synoptic transport pathways. Using this event as a case study, we investigate the impact of interhemispheric exchange on atmospheric Hg in tropical South America. We use HYSPLIT to link Hg observations to long-range transport and find that the observed Hg increase relates strongly to air masses from the tropical Pacific upper troposphere (UT), a region directly impacted by interhemispheric exchange. Inclusion of the modeled seasonality of interhemispheric air mass exchange strengthens this relationship significantly. We estimate that interhemispheric exchange drives Hg seasonality in the SH tropical Pacific UT, with strongly enhanced Hg between July and October. We validate this seasonality with previously published aircraft Hg observations. Our results suggest that the transport of NH-influenced air masses to tropical South America via the Pacific UT occurs regularly but became more detectable at Chacaltaya in 2015-2016 because of a westward shift in air mass origin.
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Lanzafame, G. M., Bessagnet, B., Srivastava, D., Jaffrezo, J. L., Favez, O., Albinet, A., et al. (2022). Modelling Aerosol Molecular Markers In A 3D Air Quality Model: Focus On anthropogenic organic markers. Science Of The Total Environment, 8358.
Abstract: aerosol markers including one primary anthropogenic marker (levoglucosan) and 4 secondary anthropogenic markers (nitrophenols, nitroguaiacols, methylnitrocatechols and phthalic acid). Modelled concentrations have been compared to measurements performed at 12 locations in France for levoglucosan in winter 2014-15, and at a sub-urban station in the Paris region over the whole year 2015 for secondary molecular markers. While a good estimation of levoglucosan concentrations by the model has been obtained for a few sites, a strong underestimation was simulated for most of the stations especially for western locations due to a probable underestimation of residential wood burning emissions. The simulated ratio between wood burning organic matter and particulate phase levoglucosan is constant only at high OM values (>10 μg m-3) indicating that using marker contribution ratio may be valid only under certain conditions. Concentrations of secondary markers were well reproduced by the model for nitrophenols and nitroguaiacols but were underestimated for methylnitrocatechols and phthalic acid highlighting missing formation pathways and/or precursor emissions. By comparing modelled to measured Gas/Particle Partitioning (GPP) of markers, the simulated partitioning of Semi-Volatile Organic Compounds (SVOCs) was evaluated. Except for nitroguaiacols and nitrophenols when ideality was assumed, the GPP for all the markers was underestimated and mainly driven by the hydrophilic partitioning. SVOCs GPP, and more generally of all SVOC contributing to the formation of SOA, could therefore be significantly
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Lim, S., Lee, M., Savarino, J., & Laj, P. (2022). Oxidation Pathways And Emission Sources Of Atmospheric Particulate nitrate in Seoul: based on delta N-15 and Delta O-17 measurements. Atmospheric Chemistry And Physics, 222(8), 5099–5115.
Abstract: PM2.5 haze pollution driven by secondary inorganic NO3- has been a great concern in East Asia. It is, therefore, imperative to identify its sources and oxidation processes, for which nitrogen and oxygen stable isotopes are powerful tracers. Here, we determined the delta N-15 (NO3-) and Delta O-17 (NO3-) of PM2.5 in Seoul during the summer of 2018 and the winter of 2018-2019 and estimated quantitatively the relative contribution of oxidation pathways for particulate NO3- and investigated major NOx emission sources. In the range of PM2.5 mass concentration from 7.5 μg m(-3) (summer) to 139.0 μg m(-3) (winter), the mean delta N-15 was -0.7 parts per thousand +/- 3.3 parts per thousand and 3.8 parts per thousand +/- 3.7 parts per thousand, and the mean Delta O-17 was 23.2 parts per thousand +/- 2.2 parts per thousand and 27.7 parts per thousand +/- 2.2 parts per thousand in the summer and winter, respectively. While OH oxidation was the dominant pathway for NO3- during the summer (87 %), nighttime formation via N2O5 and NO3 was relatively more important (38 %) during the winter, when aerosol liquid water content (ALWC) and nitrogen oxidation ratio (NOR) were higher. Interestingly, the highest Delta O-17 was coupled with the lowest delta N-15 and highest NOR during the record-breaking winter PM2.5 episodes, revealing the critical role of photochemical oxidation process in severe winter haze development. For NOx sources, atmospheric delta N-15 (NOx) estimated from measured delta N-15 (NO3-) considering isotope fractionation effects indicates vehicle emissions as the most important emission source of NOx in Seoul. The contribution from biogenic soil and coal combustion was slightly increased in summer and winter, respectively. Our results built on a multiple-isotope approach provide the first explicit evidence for NO3- formation processes and major NOx emission sources in the Seoul megacity and suggest an effective mitigation measure to improve PM2.5 pollution.
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Masalaite, A., Bycenkien, S., Pauraite, J., Garbariene, I., Bozzetti, C., Besombes, J. L., et al. (2022). Seasonal Observation And Source Apportionment Of Carbonaceous Aerosol from forested rural site (Lithuania). Atmospheric Environment, 2722.
Abstract: In this work, we conducted a study of the stable carbon isotope ratios of total carbon (delta C-13(TC)) for submicron aerosol particles (< 1 μm) that were collected year round (2014) at a hemiboreal forest site in Lithuania. Higher delta C-13(TC) values characterised the seasonal variation in delta C-13(TC) during the cold season (average-26.9 +/- 0.7%o) with lower values observed during the warm season (-27.6 +/- 0.6%o). The total carbon (TC) concentration was below 8 μg/m3 during the one-year measurement period. There was one pollution event in autumn when concentrations reached up to 14.8 μg/m(3). In addition to the offline analysis of the filter samples, the online measurements of aerosol physical and chemical properties were conducted from 15 May to September 27, 2014 by operating the Aethalometer AE-31 and a quadrupole-type Aerosol Chemical Speciation Monitor (ACSM). Source apportionment was conducted by analysing the ACSM mass spectra using Positive Matrix Factorisation (PMF). Three main factors were derived, pointing to primary emissions from biomass burning along with the secondary formation of less and more oxygenated organic aerosol of biogenic origin. A comparative analysis of delta C-13(TC) with organic carbon (OC), elemental carbon (EC), and organic markers justified two dominant sources (biomass burning and fossil fuel combustion) of aerosol particles at the hemiboreal forest site during the cold season.
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Moschos, V., Dzepina, K., Bhattu, D., Lamkaddam, H., Casotto, R., Daellenbach, K. R., et al. (2022). Equal abundance of summertime natural and wintertime anthropogenic Arctic organic aerosols. Nature Geoscience, .
Abstract: Organic aerosols in the Arctic are predominantly fuelled by anthropogenic sources in winter and natural sources in summer, according to observations from eight sites across the Arctic Aerosols play an important yet uncertain role in modulating the radiation balance of the sensitive Arctic atmosphere. Organic aerosol is one of the most abundant, yet least understood, fractions of the Arctic aerosol mass. Here we use data from eight observatories that represent the entire Arctic to reveal the annual cycles in anthropogenic and biogenic sources of organic aerosol. We show that during winter, the organic aerosol in the Arctic is dominated by anthropogenic emissions, mainly from Eurasia, which consist of both direct combustion emissions and long-range transported, aged pollution. In summer, the decreasing anthropogenic pollution is replaced by natural emissions. These include marine secondary, biogenic secondary and primary biological emissions, which have the potential to be important to Arctic climate by modifying the cloud condensation nuclei properties and acting as ice-nucleating particles. Their source strength or atmospheric processing is sensitive to nutrient availability, solar radiation, temperature and snow cover. Our results provide a comprehensive understanding of the current pan-Arctic organic aerosol, which can be used to support modelling efforts that aim to quantify the climate impacts of emissions in this sensitive region.
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Moschos, V., Schmale, J., Aas, W., Becagli, S., Calzolai, G., Eleftheriadis, K., et al. (2022). Elucidating the present-day chemical composition, seasonality and source regions of climate-relevant aerosols across the Arctic land surface. Environmental Research Letters, 171(3).
Abstract: The Arctic is warming two to three times faster than the global average, and the role of aerosols is not well constrained. Aerosol number concentrations can be very low in remote environments, rendering local cloud radiative properties highly sensitive to available aerosol. The composition and sources of the climate-relevant aerosols, affecting Arctic cloud formation and altering their microphysics, remain largely elusive due to a lack of harmonized concurrent multi-component, multi-site, and multi-season observations. Here, we present a dataset on the overall chemical composition and seasonal variability of the Arctic total particulate matter (with a size cut at 10 μm, PM10, or without any size cut) at eight observatories representing all Arctic sectors. Our holistic observational approach includes the Russian Arctic, a significant emission source area with less dedicated aerosol monitoring, and extends beyond the more traditionally studied summer period and black carbon/sulfate or fine-mode pollutants. The major airborne Arctic PM components in terms of dry mass are sea salt, secondary (non-sea-salt, nss) sulfate, and organic aerosol (OA), with minor contributions from elemental carbon (EC) and ammonium. We observe substantial spatiotemporal variability in component ratios, such as EC/OA, ammonium/nss-sulfate and OA/nss-sulfate, and fractional contributions to PM. When combined with component-specific back-trajectory analysis to identify marine or terrestrial origins, as well as the companion study by Moschos et al 2022 Nat. Geosci. focusing on OA, the composition analysis provides policy-guiding observational insights into sector-based differences in natural and anthropogenic Arctic aerosol sources. In this regard, we first reveal major source regions of inner-Arctic sea salt, biogenic sulfate, and natural organics, and highlight an underappreciated wintertime source of primary carbonaceous aerosols (EC and OA) in West Siberia, potentially associated with the oil and gas sector. The presented dataset can assist in reducing uncertainties in modelling pan-Arctic aerosol-climate interactions, as the major contributors to yearly aerosol mass can be constrained. These models can then be used to predict the future evolution of individual inner-Arctic atmospheric PM components in light of current and emerging pollution mitigation measures and improved region-specific emission inventories.
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Nair, S., Kotnik, J., Gacnik, J., Zivkovic, I., Koenig, A., Mlakar, T., et al. (2022). Dispersion Of Airborne Mercury Species Emitted From The Cement Plant. Environmental Pollution, 3123.
Abstract: The Cement Industry Is The Second Largest Source Of Anthropogenic Mercury (Hg) Emissions In Europe, Accounting For 11% Of Global Anthropogenic Hg Emissions. The Main Objective Of This Study Was To Examine The Influence Of Hg Emissions From The Salonit Anhovo Cement Plant On Hg Levels Measured In The Ambient Air At Vodarna, 1 Km Downwind From The Flue Gas Chimney. The Findings Reveal That The Plant Raw Mill Operational Status Plays An Important Role In Hg Concentrations In The Flue Gas Emitted From The Plant. Emitted Total Gaseous Mercury Was, On Average, Higher (49.4 Mu G/M(3)) When Raw Mills Were In The Direct Mode (Both Raw Mills-Off) And Lower (23.4 Mu G/M(3)) In The Combined Mode (Both Raw Mills-On). The Average Hg Concentrations In Vodarna Were 3.14 Ng/M(3) For Gaseous Elemental Mercury, 53.7 Pg/M(3) For Gaseous Oxidised Mercury, And 41.9 Pg/M(3) For Particulate Bound Mercury For The Whole Measurement Period. Atmospheric Hg Speciation In Vodarna, Coupled With Plant Emissions And Wind Data, Has Revealed That The Total Gaseous Mercury Emitted From The Cement Plant Is Clearly Related To All Hg Species Measured In Vodarna. Wind Blowing From The Northeastern Quadrant (Mostly Ne, Ene) Is Responsible For The Elevated Hg Levels In Vodarna, Where Gaseous Oxidised Mercury Levels Are Highly Linked To The Cement Plant Emissions. However, Elevated Levels Of Hg Species In The Absence Of Northeastern Winds Indicate Potential Inputs From Other Unknown Local Sources As Well As Inputs From Regional And Global Transport Mechanisms.
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Nicolaus, M., Perovich, D. K., Spreen, G., Granskog, M. A., von Albedyll, L., Angelopoulos, M., et al. (2022). Overview of the MOSAiC expedition: Snow and sea ice. Elementa-Science Of The Anthropocene, 101(1).
Abstract: Year-round observations of the physical snow and ice properties and processes that govern the ice pack evolution and its interaction with the atmosphere and the ocean were conducted during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition of the research vessel Polarstern in the Arctic Ocean from October 2019 to September 2020. This work was embedded into the interdisciplinary design of the 5 MOSAiC teams, studying the atmosphere, the sea ice, the ocean, the ecosystem, and biogeochemical processes. The overall aim of the snow and sea ice observations during MOSAiC was to characterize the physical properties of the snow and ice cover comprehensively in the central Arctic over an entire annual cycle. This objective was achieved by detailed observations of physical properties and of energy and mass balance of snow and ice. By studying snow and sea ice dynamics over nested spatial scales from centimeters to tens of kilometers, the variability across scales can be considered. On-ice observations of in situ and remote sensing properties of the different surface types over all seasons will help to improve numerical process and climate models and to establish and validate novel satellite remote sensing methods; the linkages to accompanying airborne measurements, satellite observations, and results of numerical models are discussed. We found large spatial variabilities of snow metamorphism and thermal regimes impacting sea ice growth. We conclude that the highly variable snow cover needs to be considered in more detail (in observations, remote sensing, and models) to better understand snow-related feedback processes. The ice pack revealed rapid transformations and motions along the drift in all seasons. The number of coupled ice-ocean interface processes observed in detail are expected to guide upcoming research with respect to the changing Arctic sea ice.
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Noe, S. M., Tabakova, K., Mahura, A., Lappalainen, H. K., Kosmale, M., Heilimo, J., et al. (2022). Arctic Observations And Sustainable Development Goals – Contributions and examples from ERA-PLANET iCUPE data. Environmental Science & Policy, 1321, 323–336.
Abstract: Integrative and Comprehensive Understanding on Polar Environments (iCUPE) project developed 24 novel datasets utilizing in-situ observational capacities within the Arctic or remote sensing observations from ground or from space. The datasets covered atmospheric, cryospheric, marine, and terrestrial domains. This paper connects the iCUPE datasets to United Nations' Sustainable Development Goals and showcases the use of selected datasets as knowledge provision services for policy- and decision-making actions. Inclusion of indigenous and societal knowledge into the data processing pipelines enables a feedback mechanism that facilitates data driven public services.
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Prieur, C., Rabatel, A., Thomas, J., Farup, I., & Chanussot, J. (2022). Machine Learning Approaches To Automatically Detect Glacier Snow Lines On Multi-Spectral Satellite Images. Remote Sensing, 141(161).
Abstract: Documenting The Inter-Annual Variability And The Long-Term Trend Of The Glacier Snow Line Altitude Is Highly Relevant To Document The Evolution Of Glacier Mass Changes. Automatically Identifying The Snow Line On Glaciers Is Challenging; Recent Developments In Machine Learning Approaches Show Promise To Tackle This Issue. This Manuscript Presents A Proof Of Concept Of Machine Learning Approaches Applied To Multi-Spectral Images To Detect The Snow Line And Quantify Its Average Altitude. The Tested Approaches Include The Combination Of Different Image Processing And Classification Methods, And Takes Into Account Cast Shadows. The Efficiency Of These Approaches Is Evaluated On Mountain Glaciers In The European Alps By Comparing The Results With Manually Annotated Data. Solutions Provided By The Different Approaches Are Robust When Compared To The Ground Truth'S Snow Lines, With A Pearson'S Correlation Ranging From 79% To 96% Depending On The Method. However, The Tested Approaches May Fail When Snow Lines Are Not Continuous Or Exhibit A Strong Change Of Elevation. The Major Advantage Over The State Of The Art Is That The Proposed Approach Does Not Require One Calibration Per Glacier.
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Rocco, M., Baray, J. L., Colomb, A., Borbon, A., Dominutti, P., Tulet, P., et al. (2022). High Resolution Dynamical Analysis Of Volatile Organic. Compounds (Voc) Measurements During the BIO-MAIDO Field Campaign (Reunion Island, Indian Ocean). Journal Of Geophysical Research-Atmospheres, 1271(4).
Abstract: This study presents a high-resolution dynamical analysis of Volatile Organic Compound (VOC) concentrations measured from March 11 to April 4 2019 at Reunion Island during the BIO-MAIDO (Bio-physicochemistry of tropical clouds at Maido: processes and impacts on secondary organic aerosols formation) campaign. We detail the dynamical and chemical processes that govern atmospheric VOC concentrations at two targeted sites of the western slope of Reunion Island: Petite France (PF), 950 m above sea level (a.s.l.) and Maido Observatory (MO), 2150 m a.s.l. A dynamical connection between PF and MO is found during four selected days: March 28 and 31, April 1 and 3. Trajectory calculations using the coupling of Meso-Computing Advection-interpolation of atmospheric parameters and Trajectory tool (CAT) (100 m horizontal resolution of Meso-NH high-resolution non-hydrostatic model and the CAT trajectory model) Lagrangian transport model showed that air masses were dynamically linked between the two measurements sites for 19% of the time during the complete campaign. Trajectories from the Meso-CAT model combined with the Corine Land Cover-2018 register shows that backward-trajectories are frequently located above biogenic area (mixed forest, 3%-46% of total number trajectory point) and cultures area (e.g., sugar cane plantation, 1%-17%). Regarding VOCs concentrations, air masses coming from downhill MO are associated with significant measured concentrations of isoprene, isoprene oxidation products and benzene. Averaged concentration daytime ratios of isoprene and isoprene oxidation products from PF to MO are 0.73 +/- 1.01 and 0.26 +/- 0.26 respectively illustrating a loss of these VOCs due to deposition, oxidation, or possibility dilution on clouds.
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Shahne, M. Z., Arhami, M., El Haddad, I., Abbaszade, G., Schnelle-Kreis, J., Jaffrezo, J. L., et al. (2022). Particulate emissions of real-world light-duty gasoline vehicle fleet in Iran (vol 292, 118303, 2022). Environmental Pollution, 3003.
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Shangguan, Y. F., Zhuang, X. G., Querol, X., Li, B. Q., Moreno, N., Trechera, P., et al. (2022). Characterization Of Deposited Dust And Its Respirable Fractions In underground coal mines: Implications for oxidative potential-driving species and source apportionment. International Journal Of Coal Geology, 2582.
Abstract: Oxidative potential (OP) is considered to be an efficient indicator of particulate matter (PM) to induce oxidative stress in the lungs and is increasingly considered to be a relevant health metric. In this study, two complementary OP assays were deployed, including dithiothreitol (DTT) and ascorbic acid (AA) assays, to investigate the po-tential toxicity (as generators of oxidative stress) of respirable fractions (DD4, < 4 μm) of deposited dust (DD500, < 500 μm) in underground low-S and low-pyrite coal mines in Henan Province, Central China. The OPDTT of DD4 is higher than that reported for other types of atmospheric PM, whereas the OPAA of DD4 is similar and/or slightly higher. Cross-correlation and multilinear regression analyses are applied using datasets of major mineral and geochemical patterns in the DD4 samples and the respective OP values to identify the major drivers for OP in respirable coal dust. Thereafter, the patterns of DD4 are compared with those of DD500 and the parent coals to determine the sources of OP-relevant substances. OP(DTT )is mainly governed by some trace elements (Sb, As, Li, B, Sr, and Pb) and minor minerals (anatase, quartz, siderite), and their synergistic effect may be one of the reasons for the high DTT consumption. For OPAA, quartz, total clay (sum of illite, kaolinite, tobelite, and clinochlore) and Ni, Cr, Co, Si, and S, play an important role in regulating the OPAA of pyrite-free DD4 samples. These OP-relevant substances have three sources: coal dust, which has a similar composition in DD4, DD500, and the parent coal (such as siderite and its associated elements); gangue dust, which does not occur in the parent coal but is widely detected in DD4 and DD500 (such as quartz, kaolinite, and relevant elements); and cement dust (from gunite galleries), which is mainly calcite-and calcite-associated elements.
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Sharma, R., Chaudhary, A., Seemanth, M., Bhowmick, S. A., Agarwal, N., Verron, J., et al. (2022). SARAL/AltiKa data analysis for oceanographic research: Impact of drifting and post star sensor anomaly phases. Advances In Space Research, 696(6), 2349–2361.
Abstract: Y AltiKa, first ever high frequency Ka-band altimeter on board SARAL (Satellite with ARgos and ALtiKa) has gone through different phases of operations, viz. Exact Repeat Mission, (ERM, March 2013 – July 2016), Drifting phase, (DP, July 2016 – January 2018) and then to Mispointing phase, (MP, February 2018 – till date). A detailed assessment of Sea level anomaly (SLA), Significant Wave Height (SWH) and Ocean Surface Wind Speed (WS) has been carried out during these different phases with a focus on the North Indian Ocean. Crossover analysis using the Jason series of satellites available during various phases of SARAL suggest high quality of SARAL/AltiKa data during the ERM and DP with root mean square differences of the order of 0.080 m, 0.25 m and 1 m/s for SLA, SWH and WS respectively. These differences are more during MP, being 0.095 m, 0.45 m and 1.72 m/s for SLA, SWH and WS respectively. Wavenumber Power spectrum computed from the along-track AltiKa SLA reveals that slopes in the mesoscale band (70-250 km) in different phases of operations are not very different. Errors in gridded SARAL/AltiKa SLA with respect to standard AVISO product remains unchanged during DP, but degrade by nearly 9.3% in the MP as compared to ERM. To assess the effect of assimilating along track SWH and SLA from different phases, two set of wave and circulation model simulations, with and without SARAL AltiKa data assimilation, were performed. Assimilation of SWH improved the wave height simulation by similar to 12.8% during the DP and similar to 8% during ERM and MP. As regards to circulation modeling, no significant difference of assimilating SLA from different phases was observed in the mesoscale range. These results indicate the usefulness of SLA from SARAL AltiKa during DP and MP for studying the mesoscale dynamics. (C) 2021 COSPAR. Published by Elsevier B.V. All rights reserved.
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Shupe, M. D., Rex, M., Blomquist, B., Persson, P. O. G., Schmale, J., Uttal, T., et al. (2022). Overview of the MOSAiC expedition-Atmosphere INTRODUCTION. Elementa-Science Of The Anthropocene, 101(1).
Abstract: With the Arctic rapidly changing, the needs to observe, understand, and model the changes are essential. To support these needs, an annual cycle of observations of atmospheric properties, processes, and interactions were made while drifting with the sea ice across the central Arctic during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition from October 2019 to September 2020. An international team designed and implemented the comprehensive program to document and characterize all aspects of the Arctic atmospheric system in unprecedented detail, using a variety of approaches, and across multiple scales. These measurements were coordinated with other observational teams to explore crosscutting and coupled interactions with the Arctic Ocean, sea ice, and ecosystem through a variety of physical and biogeochemical processes. This overview outlines the breadth and complexity of the atmospheric research program, which was organized into 4 subgroups: atmospheric state, clouds and precipitation, gases and aerosols, and energy budgets. Atmospheric variability over the annual cycle revealed important influences from a persistent large-scale winter circulation pattern, leading to some storms with pressure and winds that were outside the interquartile range of past conditions suggested by long-term reanalysis. Similarly, the MOSAiC location was warmer and wetter in summer than the reanalysis climatology, in part due to its close proximity to the sea ice edge. The comprehensiveness of the observational program for characterizing and analyzing atmospheric phenomena is demonstrated via a winter case study examining air mass transitions and a summer case study examining vertical atmospheric evolution. Overall, the MOSAiC atmospheric program successfully met its objectives and was the most comprehensive atmospheric measurement program to date conducted over the Arctic sea ice. The obtained data will support a broad range of coupled-system scientific research and provide an important foundation for advancing multiscale modeling capabilities in the Arctic.
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Steensen, B. M., Marelle, L., Hodnebrog, O., & Myhre, G. (2022). Future urban heat island influence on precipitation. Climate Dynamics, .
Abstract: Urbanization and global warming are two of the major human impacts on the environment. The Urban Heat Island (UHI) effect can change precipitation patterns. Global warming also leads to changes in precipitation and especially an increase in intensity and frequency of extreme precipitation. With urbanization expected to grow in the future, the role of UHI in a warmer climate is an important research question. We present results from 20-year long regional convection-permitting model simulations that include the UHI effect, run for historical and future climates for two megacities, Paris and Shanghai. In the warmer future climate, urban-induced precipitation is found to decrease compared to the historical climate, for both mean and extreme precipitation, with large uncertainties due to natural variability. The mean precipitation increase due to UHI in Paris is 2.2 +/- 1.4% and 1.8 +/- 1.3% for historical and future conditions, respectively. Shanghai has slightly weaker mean precipitation change than Paris at present and no change in the future. The future reduction of the urban effect is found to be caused by a decrease in summer precipitation for both cities. Interannual variability in precipitation due to UHI is larger for Shanghai than Paris. The UHI effect on extreme precipitation is also reduced in the future climate and the area with precipitation increase is more concentrated. The general increase in extreme precipitation due to global warming, in combination with the precipitation redistribution due to UHI, underline the importance for future urban planning to mitigate damage caused by extreme precipitation events.
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Strom, J., Svensson, J., Honkanen, H., Asmi, E., Dkhar, N. B., Tayal, S., et al. (2022). Snow Albedo And Its Sensitivity To Changes In Deposited Light-Absorbing particles estimated from ambient temperature and snow depth observations at a high-altitude site in the Himalaya. Elementa-Science Of The Anthropocene, 101(1).
Abstract: Snow darkening by deposited light-absorbing particles (LAP) accelerates snowmelt and shifts the snow meltout date (MOD). Here, we present a simple approach to estimate the snow albedo variability due to LAP deposition and test this method with data for 2 seasons (February-May 2016 and December 2016-June 2017) at a high-altitude valley site in the Central Himalayas, India. We derive a parameterization for the snow albedo that only depends on the daily observations of average ambient temperature and change in snow depth, as well as an assumed average concentration of LAP in snow precipitation. Linear regression between observed and parameterized albedo for the base case assuming an equivalent elemental carbon concentration [ECeq] of 100 ng g(-1) in snow precipitation yields a slope of 0.75 and a Pearson correlation coefficient r(2) of 0.76. However, comparing the integrated amount of shortwave radiation absorbed during the winter season using observed albedo versus base case albedo resulted in rather small differences of 11% and 4% at the end of Seasons 1 and 2, respectively. The enhanced energy absorbed due to LAP at the end of the 2 seasons for the base case scenario (assuming an [ECeq] of 100 ng g(-1) in snow precipitation) was 40% and 36% compared to pristine snow. A numerical evaluation with different assumed [ECeq] in snow precipitation suggests that the relative sensitivity of snow albedo to changes in [ECeq] remains rather constant for the 2 seasons. Doubling [ECeq] augments the absorption by less than 20%, highlighting that the impact on a MOD is small even for a doubling of average LAP in snow precipitation.
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Swanson, W., Holmes, C., Simpson, W., Confer, K., Marelle, L., Thomas, J., et al. (2022). Comparison Of Model And Ground Observations Finds Snowpack And Blowing Snow Aerosols Both Contribute To Arctic Tropospheric Reactive Bromine. Atmospheric Chemistry And Physics, 222(222), 14467–14488.
Abstract: Reactive Halogens Play A Prominent Role In The Atmospheric Chemistry Of The Arctic During Springtime. Field Measurements And Modeling Studies Suggest That Halogens Are Emitted Into The Atmosphere From Snowpack And Reactions On Wind-Blown Snow-Sourced Aerosols. The Relative Importance Of Snowpack And Blowing Snow Sources Is Still Debated, Both At Local Scales And Regionally Throughout The Arctic. To Understand The Implications Of These Halogen Sources On A Pan-Arctic Scale, We Simulate Arctic Reactive Bromine Chemistry In The Atmospheric Chemical Transport Model Geos-Chem. Two Mechanisms Are Included: (1) A Blowing Snow Sea Salt Aerosol Formation Mechanism And (2) A Snowpack Mechanism Assuming Uniform Molecular Bromine Production From All Snow Surfaces. We Compare Simulations Including Neither Mechanism, Each Mechanism Individually, And Both Mechanisms To Examine Conditions Where One Process May Dominate Or The Mechanisms May Interact. We Compare The Models Using These Mechanisms To Observations Of Bromine Monoxide (Bro) Derived From Multiple-Axis Differential Optical Absorption Spectroscopy (Max-Doas) Instruments On O-Buoy Platforms On The Sea Ice And At A Coastal Site In Utqiagvik, Alaska, During Spring 2015. Model Estimations Of Hourly And Monthly Average Bro Are Improved By Assuming A Constant Yield Of 0.1 % Molecular Bromine From All Snowpack Surfaces On Ozone Deposition. The Blowing Snow Aerosol Mechanism Increases Modeled Bro By Providing More Bromide-Rich Aerosol Surface Area For Reactive Bromine Recycling. The Snowpack Mechanism Led To Increased Model Bro Across The Arctic Ocean With Maximum Production In Coastal Regions, Whereas The Blowing Snow Aerosol Mechanism Increases Bro In Specific Areas Due To High Surface Wind Speeds. Our Uniform Snowpack Source Has A Greater Impact On Bro Mixing Ratios Than The Blowing Snow Source. Model Results Best Replicate Several Features Of Bro Observations During Spring 2015 When Using Both Mechanisms In Conjunction, Adding Evidence That These Mechanisms Are Both Active During The Arctic Spring. Extending Our Transport Model Throughout The Entire Year Leads To Predictions Of Enhanced Fall Bro That Are Not Supported By Observations.
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Thera, B., Dominutti, P., Colomb, A., Michoud, V., Doussin, J. F., Beekmann, M., et al. (2022). O-3-Noy Photochemistry In Boundary Layer Polluted Plumes: Insights From the MEGAPOLI (Paris), ChArMEx/SAFMED (North West Mediterranean) and DACCIWA (southern West Africa) aircraft campaigns. Environmental Science-Atmospheres, 2(4), 659–686.
Abstract: The ozone-NOy photochemistry is explored in contrasting polluted plumes sampled with the Safire ATR 42 research aircraft during three summer field international campaigns in the megacity Paris, the North West Mediterranean basin (WMB) and southern West Africa (SWA). Various metrics derived from the photostationary steady state (PSS) and the ozone production efficiency (OPE) are calculated from airborne observations. A new metric, the oxidant production rate normalized to carbon monoxide (PROx), is introduced and quantified as a function of the processing time of the plume. In most of the polluted plumes, it is found that the Leighton ratio (phi) characterizing the equilibrium between O-3 and NOx is, on average, within the PSS range ([1 +/- 0.32]) or greater. The positive dependence of O-x to NO usually indicates a VOC-sensitive regime inside the plumes with some exceptions. In Paris, under oceanic westerly winds, and during DACCIWA, the plumes show a rural-like chemistry behaviour at moderate NOx levels (NOx-sensitive). Intense and frequent rapid changes in J(NO2), NO and NO2 explain the deviations from the PSS. The OPE for Paris plume suggests that the VOC-sensitive regime extends far beyond the urban plume. The mean ozone production is higher downwind of Paris (30 ppb h(-1) on average) compared to SWA (20 ppb h(-1)) and WMB (6 ppb h(-1)). PROx values vary between 0 (no oxidant production) and 0.27 ppb([Ox]) ppb([CO])(-1) h(-1). The determined uncertainty on the Leighton ratio value could affect the differences in the estimation of the photochemical oxidant production by PO3 and PROx. The emissions of CO along the flight path and the presence of vegetation and high humidity levels might shape the oxidant production depending on the explored environment. While limited in number, PROx values set a benchmark for future photochemical studies to compare with: Paris as representative of an anthropogenic urban plume and WMB as representative of a biogenic continental plume.
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2021 |
Aliaga, D., Sinclair, V., Andrade, M., Artaxo, P., Carbone, S., Kadantsev, E., et al. (2021). Identifying source regions of air masses sampled at the tropical high-altitude site of Chacaltaya using WRF-FLEXPART and cluster analysis. Atmospheric Chemistry And Physics, 21(21), 16453–16477.
Abstract: Observations of aerosol and trace gases in the remote troposphere are vital to quantify background concentrations and identify long-term trends in atmospheric composition on large spatial scales. Measurements made at high altitude are often used to study free-tropospheric air; however such high-altitude sites can be influenced by boundary layer air masses. Thus, accurate information on air mass origin and transport pathways to high-altitude sites is required. Here we present a new method, based on the source-receptor relationship (SRR) obtained from backwards WRF-FLEXPART simulations and a k-means clustering approach, to identify source regions of air masses arriving at measurement sites. Our method is tailored to areas of complex terrain and to stations influenced by both local and long-range sources. We have applied this method to the Chacaltaya (CHC) GAW station (5240 m a.s.l.; 16.35 degrees S, 68.13 degrees W) for the 6-month duration of the “Southern Hemisphere high-altitude experiment on particle nucleation and growth” (SALILNA) to identify where sampled air masses originate and to quantify the influence of the surface and the free troposphere. A key aspect of our method is that it is probabilistic, and for each observation time, more than one air mass (cluster) can influence the station, and the percentage influence of each air mass can be quantified. This is in contrast to binary methods, which label each observation time as influenced by either boundary layer or free-troposphere air masses. Air sampled at CHC is a mix of different provenance. We find that on average 9 % of the air, at any given observation time, has been in contact with the surface within 4 d prior to arriving at CHC. Furthermore, 24 % of the air has been located within the first 1.5 km above ground level (surface included). Consequently, 76 % of the air sampled at CHC originates from the free troposphere. However, pure free-tropospheric influences are rare, and often samples are concurrently influenced by both boundary layer and free-tropospheric air masses. A clear diurnal cycle is present, with very few air masses that have been in contact with the surface being detected at night. The 6-month analysis also shows that the most dominant air mass (cluster) originates in the Amazon and is responsible for 29 % of the sampled air. Furthermore, short-range clusters (origins within 100 km of CHC) have high temporal frequency modulated by local meteorology driven by the diurnal cycle, whereas the mid- and long-range clusters' (> 200 km) variability occurs on timescales governed by synoptic-scale dynamics. To verify the reliability of our method, in situ sulfate observations from CHC are combined with the SRR clusters to correctly identify the (pre-known) source of the sulfate: the Sabancaya volcano located 400 km north-west from the station.
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Allen, S., Allen, D., Baladima, F., Phoenix, V., Thomas, J., Le Roux, G., et al. (2021). Evidence of free tropospheric and long-range transport of microplastic at Pic du Midi Observatory. Nature Communications, 12(1).
Abstract: Microplastics are found in the environment globally, but their atmospheric transport is not well understood. Here the authors report atmospheric microplastic pollution at the Pic du Midi Observatory, suggesting free long range transport in the troposphere. The emerging threat of atmospheric microplastic pollution has prompted researchers to study areas previously considered beyond the reach of plastic. Investigating the range of atmospheric microplastic transport is key to understanding the global extent of this problem. While atmospheric microplastics have been discovered in the planetary boundary layer, their occurrence in the free troposphere is relatively unexplored. Confronting this is important because their presence in the free troposphere would facilitate transport over greater distances and thus the potential to reach more distal and remote parts of the planet. Here we show evidence of 0.09-0.66 microplastics particles/m(3) over 4 summer months from the Pic du Midi Observatory at 2877 meters above sea level. These results exhibit true free tropospheric transport of microplastic, and high altitude microplastic particles <50 μm (aerodynamic diameter). Analysis of air/particle history modelling shows intercontinental and trans-oceanic transport of microplastics illustrating the potential for global aerosol microplastic transport.
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Ballabio, C., Jiskra, M., Osterwalder, S., Borrelli, P., Montanarella, L., & Panagos, P. (2021). A spatial assessment of mercury content in the European Union topsoil. Science Of The Total Environment, 769.
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Barraza, F., Schreck, E., Uzu, G., Leveque, T., Zouiten, C., Boidot, M., et al. (2021). Beyond cadmium accumulation: Distribution of other trace elements in soils and cacao beans in Ecuador. Environmental Research, 192.
Abstract: Since cacao beans accumulate Cd in high levels and restrictions have been imposed on safe levels of chocolate consumption, concern about whether or not cacao trees store other toxic elements seems to be inevitable. Following a previous study in Ecuador examining Cd content in five cacao varieties collected in pristine areas and in places impacted by oil activities, we present here the concentrations of 11 trace elements (TEs) (As, Ba, Co, Cu, Cr, Mo, Mn, Ni, Pb, V and Zn) in soils, cacao tissues (leaves, pod husks, beans) and cocoa liquor (CL). Several TEs showed concentrations in topsoils above the Ecuadorian limits, and may have a mixed natural and anthropogenic origin. Ba and Mo concentrations in cacao tissues are slightly higher than those reported in other surveys, but this was not the case for toxic elements (As and Pb). TE contents are lower in CL, than in beans, except for Pb and Co, but no risk was identified for human health. Compared with control areas, Enrichment Factors were below 2 in impacted areas, except for Ba. Transfer factors (from soils to cacao) indicated that cacao does not accumulate TEs. A positive correlation was found between Cd and Zn in topsoils and cacao tissues for the CCN-51 variety, and between Cd and Ni for the Nacional variety. Identifying patterns of TE distribution and potential interactions in order to explain plant internal mechanisms, which is also dependent on the cacao variety, is a difficult task and needs further research.
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Berto, M., Cappelletti, D., Barbaro, E., Varin, C., Gallet, J., Markowicz, K., et al. (2021). Variability in black carbon mass concentration in surface snow at Svalbard. Atmospheric Chemistry And Physics, 21(16), 12479–12493.
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Bianchi, F., Junninen, H., Bigi, A., Sinclair, V., Dada, L., Hoyle, C., et al. (2021). Biogenic particles formed in the Himalaya as an important source of free tropospheric aerosols. Nature Geoscience, .
Abstract: Aerosols of biogenic and anthropogenic origin affect the total radiative forcing of global climate. Poor knowledge of the pre-industrial aerosol concentration and composition, in particular of particles formed directly in the atmosphere from gaseous precursors, constitutes a large uncertainty in the anthropogenic radiative forcing. Investigations of new particle formation at pre-industrial-like conditions can contribute to the reduction of this uncertainty. Here we present observations taken at the remote Nepal Climate Observatory Pyramid station at 5,079 m above sea level, a few kilometres from the summit of Everest. We show that up-valley winds funnel gaseous aerosol precursors to higher altitudes. During this transport, these are oxidized into compounds of very low volatility, which rapidly form a large number of aerosol particles. These are then transported into the free troposphere, which suggests that the whole Himalayan region may act as an 'aerosol factory' and contribute substantially to the free tropospheric aerosol population. Aerosol production in this region occurs mainly via organic precursors of biogenic origin with little evidence of the involvement of anthropogenic pollutants. This process is therefore likely to be essentially unchanged since the pre-industrial period, and may have been one of the major sources that contributes to the upper tropospheric aerosol population during that time. Newly formed biogenic particles in the Himalaya increase free-tropospheric background aerosol concentration by a factor of up to two.
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Borlaza, L., Weber, S., Uzu, G., Jacob, V., Canete, T., Micallef, S., et al. (2021). Disparities in particulate matter (PM10) origins and oxidative potential at a city scale (Grenoble, France) – Part 1: Source apportionment at three neighbouring sites. Atmospheric Chemistry And Physics, 21(7), 5415–5437.
Abstract: A fine-scale source apportionment of PM10 was conducted in three different urban sites (background, hypercenter, and peri-urban) within 15 km of the city in Grenoble, France using Positive Matrix Factorization (PMF 5.0) on measured chemical species from collected filters (24 h) from February 2017 to March 2018. To improve the PMF solution, several new organic tracers (3-MBTCA, pinic acid, phthalic acid, MSA, and cellulose) were additionally used in order to identify sources that are commonly unresolved by classic PMF methodologies. An 11-factor solution was obtained in all sites, including commonly identified sources from primary traffic (13 %), nitrate-rich (17 %), sulfate-rich (17 %), industrial (1 %), biomass burning (22 %), aged sea salt (4 %), sea/road salt (3 %), and mineral dust (7 %), and the newly found sources from primary biogenic (4 %), secondary biogenic oxidation (10 %), and MSA-rich (3 %). Generally, the chemical species exhibiting similar temporal trends and strong correlations showed uniformly distributed emission sources in the Grenoble basin. The improved PMF model was able to obtain and differentiate chemical profiles of specific sources even at high proximity of receptor locations, confirming its applicability in a fine-scale resolution. In order to test the similarities between the PMF-resolved sources, the Pearson distance and standardized identity distance (PD-SID) of the factors in each site were compared. The PD-SID metric determined whether a given source is homogeneous (i.e., with similar chemical profiles) or heterogeneous over the three sites, thereby allowing better discrimination of localized characteristics of specific sources. Overall, the addition of the new tracers allowed the identification of substantial sources (especially in the SOA fraction) that would not have been identified or possibly mixed with other factors, resulting in an enhanced resolution and sound source profile of urban air quality at a city scale.
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Cairns, W., Turetta, C., Maffezzoli, N., Magand, O., Araujo, B., Angot, H., et al. (2021). Mercury in precipitated and surface snow at Dome C and a first estimate of mercury depositional fluxes during the Austral summer on the high Antarctic plateau. Atmospheric Environment, 262.
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Evangeliou, N., Platt, S., Eckhardt, S., Myhre, C., Laj, P., Alados-Arboledas, L., et al. (2021). Changes in black carbon emissions over Europe due to COVID-19 lockdowns. Atmospheric Chemistry And Physics, 21(4), 2675–2692.
Abstract: Following the emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) responsible for COVID-19 in December 2019 in Wuhan (China) and its spread to the rest of the world, the World Health Organization declared a global pandemic in March 2020. Without effective treatment in the initial pandemic phase, social distancing and mandatory quarantines were introduced as the only available preventative measure. In contrast to the detrimental societal impacts, air quality improved in all countries in which strict lockdowns were applied, due to lower pollutant emissions. Here we investigate the effects of the COVID-19 lockdowns in Europe on ambient black carbon (BC), which affects climate and damages health, using in situ observations from 17 European stations in a Bayesian inversion framework. BC emissions declined by 23 kt in Europe (20% in Italy, 40% in Germany, 34% in Spain, 22% in France) during lockdowns compared to the same period in the previous 5 years, which is partially attributed to COVID-19 measures. BC temporal variation in the countries enduring the most drastic restrictions showed the most distinct lockdown impacts. Increased particle light absorption in the beginning of the lockdown, confirmed by assimilated satellite and remote sensing data, suggests residential combustion was the dominant BC source. Accordingly, in central and Eastern Europe, which experienced lower than average temperatures, BC was elevated compared to the previous 5 years. Nevertheless, an average decrease of 11% was seen for the whole of Europe compared to the start of the lockdown period, with the highest peaks in France (42 %), Germany (21 %), UK (13 %), Spain (11 %) and Italy (8 %). Such a decrease was not seen in the previous years, which also confirms the impact of COVID-19 on the European emissions of BC.
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Favez, O., Weber, S., Petit, J., Alleman, L., Albinet, A., Riffault, V., et al. (2021). Overview of the French Operational Network for In Situ Observation of PM Chemical Composition and Sources in Urban Environments (CARA Program). Atmosphere, 12(2).
Abstract: The CARA program has been running since 2008 by the French reference laboratory for air quality monitoring (LCSQA) and the regional monitoring networks, to gain better knowledge-at a national level-on particulate matter (PM) chemistry and its diverse origins in urban environments. It results in strong collaborations with international-level academic partners for state-of-the-art, straightforward, and robust results and methodologies within operational air quality stakeholders (and subsequently, decision makers). Here, we illustrate some of the main outputs obtained over the last decade, thanks to this program, regarding methodological aspects (both in terms of measurement techniques and data treatment procedures) as well as acquired knowledge on the predominant PM sources. Offline and online methods are used following well-suited quality assurance and quality control procedures, notably including inter-laboratory comparison exercises. Source apportionment studies are conducted using various receptor modeling approaches. Overall, the results presented herewith underline the major influences of residential wood burning (during the cold period) and road transport emissions (exhaust and non-exhaust ones, all throughout the year), as well as substantial contributions of mineral dust and primary biogenic particles (mostly during the warm period). Long-range transport phenomena, e.g., advection of secondary inorganic aerosols from the European continental sector and of Saharan dust into the French West Indies, are also discussed in this paper. Finally, we briefly address the use of stable isotope measurements (delta N-15) and of various organic molecular markers for a better understanding of the origins of ammonium and of the different organic aerosol fractions, respectively.
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Gliss, J., Mortier, A., Schulz, M., Andrews, E., Balkanski, Y., Bauer, S., et al. (2021). AeroCom phase III multi-model evaluation of the aerosol life cycle and optical properties using ground- and space-based remote sensing as well as surface in situ observations. Atmospheric Chemistry And Physics, 21(1), 87–128.
Abstract: Within the framework of the AeroCom (Aerosol Comparisons between Observations and Models) initiative, the state-of-the-art modelling of aerosol optical properties is assessed from 14 global models participating in the phase III control experiment (AP3). The models are similar to CMIP6/AerChemMIP Earth System Models (ESMs) and provide a robust multi-model ensemble. Inter-model spread of aerosol species lifetimes and emissions appears to be similar to that of mass extinction coefficients (MECs), suggesting that aerosol optical depth (AOD) uncertainties are associated with a broad spectrum of parameterised aerosol processes. Total AOD is approximately the same as in AeroCom phase I (AP1) simulations. However, we find a 50% decrease in the optical depth (OD) of black carbon (BC), attributable to a combination of decreased emissions and lifetimes. Relative contributions from sea salt (SS) and dust (DU) have shifted from being approximately equal in AP1 to SS contributing about 2/3 of the natural AOD in AP3. This shift is linked with a decrease in DU mass burden, a lower DU MEC, and a slight decrease in DU lifetime, suggesting coarser DU particle sizes in AP3 compared to AP1. Relative to observations, the AP3 ensemble median and most of the participating models underestimate all aerosol optical properties investigated, that is, total AOD as well as fine and coarse AOD (AOD(f), AOD(c)), Angstrom exponent (AE), dry surface scattering (SCdry), and absorption (AC(dry)) coefficients. Compared to AERONET, the models underestimate total AOD by ca. 21% +/- 20% (as inferred from the ensemble median and interquartile range). Against satellite data, the ensemble AOD biases range from -37% (MODIS-Terra) to -16% (MERGED-FMI, a multi-satellite AOD product), which we explain by differences between individual satellites and AERONET measurements themselves. Correlation coefficients (R) between model and observation AOD records are generally high (R > 0.75), suggesting that the models are capable of capturing spatiotemporal variations in AOD. We find a much larger underestimate in coarse AOD(c) (similar to-45% +/- 25 %) than in fine AOD(f) (similar to-15% +/- 25 %) with slightly increased inter-model spread compared to total AOD. These results indicate problems in the modelling of DU and SS. The AOD(c) bias is likely due to missing DU over continental land masses (particularly over the United States, SE Asia, and S. America), while marine AERONET sites and the AATSR SU satellite data suggest more moderate oceanic biases in AOD(c). Column AEs are underestimated by about 10% +/- 16 %. For situations in which measurements show AE > 2, models underestimate AERONET AE by ca. 35 %. In contrast, all models (but one) exhibit large overestimates in AE when coarse aerosol dominates (bias ca. +140% if observed AE < 0.5). Simulated AE does not span the observed AE variability. These results indicate that models overestimate particle size (or underestimate the fine-mode fraction) for fine-dominated aerosol and underestimate size (or overestimate the fine-mode fraction) for coarse-dominated aerosol. This must have implications for lifetime, water uptake, scattering enhancement, and the aerosol radiative effect, which we can not quantify at this moment. Comparison against Global Atmosphere Watch (GAW) in situ data results in mean bias and inter-model variations of -35% +/- 25% and -20% +/- 18% for SCdry and AC(dry), respectively. The larger underestimate of SCdry than AC(dry) suggests the models will simulate an aerosol single scattering albedo that is too low. The larger underestimate of SCdry than ambient air AOD is consistent with recent findings that models overestimate scattering enhancement due to hygroscopic growth. The broadly consistent negative bias in AOD and surface scattering suggests an underestimate of aerosol radiative effects in current global aerosol models. Considerable inter-model diversity in the simulated optical properties is often found in regions that are, unfortunately, not or only sparsely covered by ground-based observations. This includes, for instance, the Sahara, Amazonia, central Australia, and the South Pacific. This highlights the need for a better site coverage in the observations, which would enable us to better assess the models, but also the performance of satellite products in these regions. Using fine-mode AOD as a proxy for present-day aerosol forcing estimates, our results suggest that models underestimate aerosol forcing by ca. -15 %, however, with a considerably large interquartile range, suggesting a spread between -35% and +10 %.
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Grange, S., Fischer, A., Zellweger, C., Alastuey, A., Querol, X., Jaffrezo, J., et al. (2021). Switzerland's PM10 and PM2.5 environmental increments show the importance of non-exhaust emissions. Atmospheric Environment-X, 12.
Abstract: Atmospheric particulate matter (PM) is a priority pollutant for urban air pollution management because of its negative effects on human health and visibility. Emissions from road traffic have been a major focus of management over the past few decades, but non-exhaust emissions i.e., emissions from brake, tyre, road wear, and the resuspension of dust have emerged to become a major source of unregulated PM in many locations. Here, a filter-based sampling campaign was conducted between 2018 and 2019 where a large number of PM constituents were quantified for five sites in Switzerland for both PM10 and PM2.5. This had the objective of investigating urban and urban-traffic PM increments in Switzerland. The results show that PM concentrations increased as the sampling locations moved along a rural to urban-traffic gradient. However, source apportionment analysis showed that sulfate-rich, nitrate-rich, and biogenic sources were not enhanced in urban environments, but road traffic and mineral dust sources were. The total mass enhancement for PM10 and PM 2.5 were 2.4 μg m(-3) and 2.0 μg m(-3) for the urban environment while the corresponding urban-traffic enhancements were 5.7 μg m(-3) and 2.8 μg m(-3). Emissions from road traffic were estimated to contribute more than 75% to the urban increments and non-exhaust emissions contributed 48% (PM10) and 25% (PM2.5) to the total road traffic related increment at an urban background site and 62% (PM10) and 49% (PM2.5) at an urban-traffic site. Analysis of the composition of Switzerland's PM showed that elements associated with non-exhaust emissions, specifically the brake wear tracers of antimony, barium, copper, and iron were the metals with the greatest urban and urban-traffic enhancements. Critically, the urban increment of these elements was enhanced for both PM10 and PM2.5 by about the same magnitude as the urban-traffic increment (by 2-3 times), demonstrating non-exhaust emissions are encountered across urban areas, not just the urban-traffic environment. Therefore, non-exhaust emissions were an important contributor to the urban and urban-traffic PM10 and PM2.5 increments in Switzerland's urban areas. The relative contributions of non-exhaust emissions to the urban and urban-traffic increments could be expected to increase due to the introduction of further exhaust after-treatment technologies (such as gasoline particulate filters; GPFs) and the transition to a more electrified vehicle fleet. A management pivot will be required to control these non-exhaust emission pathways and although this work exclusively uses data from Switzerland, the conclusions are likely relevant to many other European urban areas.
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Koenig, A., Magand, O., Laj, P., Andrade, M., Moreno, I., Velarde, F., et al. (2021). Seasonal patterns of atmospheric mercury in tropical South America as inferred by a continuous total gaseous mercury record at Chacaltaya station (5240 m) in Bolivia. Atmospheric Chemistry And Physics, 21(5), 3447–3472.
Abstract: High-quality atmospheric mercury (Hg) data are rare for South America, especially for its tropical region. As a consequence, mercury dynamics are still highly uncertain in this region. This is a significant deficiency, as South America appears to play a major role in the global budget of this toxic pollutant. To address this issue, we performed nearly 2 years (July 2014-February 2016) of continuous high-resolution total gaseous mercury (TGM) measurements at the Chacaltaya (CHC) mountain site in the Bolivian Andes, which is subject to a diverse mix of air masses coming predominantly from the Altiplano and the Amazon rainforest. For the first 11 months of measurements, we obtained a mean TGM concentration of 0 :89 +/- 0 :01 ngm(-3), which is in good agreement with the sparse amount of data available from the continent. For the remaining 9 months, we obtained a significantly higher TGM concentration of 1 :34 +/- 0 :01 ngm(-3), a difference which we tentatively attribute to the strong El Nino event of 2015-2016. Based on HYSPLIT (Hybrid SingleParticle Lagrangian Integrated Trajectory) back trajectories and clustering techniques, we show that lower mean TGM concentrations were linked to either westerly Altiplanic air masses or those originating from the lowlands to the southeast of CHC. Elevated TGM concentrations were related to northerly air masses of Amazonian or southerly air masses of Altiplanic origin, with the former possibly linked to artisanal and small-scale gold mining (ASGM), whereas the latter might be explained by volcanic activity. We observed a marked seasonal pattern, with low TGM concentrations in the dry season (austral winter), rising concentrations during the biomass burning (BB) season, and the highest concentrations at the beginning of the wet season (austral summer). With the help of simultaneously sampled equivalent black carbon (eBC) and carbon monoxide (CO) data, we use the clearly BB-influenced signal during the BB season (August to October) to derive a mean TGM = CO emission ratio of (2.3 +/- 0.6 x 10(-7) ppbvTGM ppbv (-1)(CO), which could be used to constrain South American BB emissions. Through the link with CO2 measured in situ and remotely sensed solarinduced fluorescence (SIF) as proxies for vegetation activity, we detect signs of a vegetation sink effect in Amazonian air
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Marelle, L., Thomas, J., Ahmed, S., Tuite, K., Stutz, J., Dommergue, A., et al. (2021). Implementation and Impacts of Surface and Blowing Snow Sources of Arctic Bromine Activation Within WRF-Chem 4.1.1. Journal Of Advances In Modeling Earth Systems, 13(8).
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Massazza, G., Bacci, M., Descroix, L., Ibrahim, M., Fiorillo, E., Katiellou, G., et al. (2021). Recent Changes in Hydroclimatic Patterns over Medium Niger River Basins at the Origin of the 2020 Flood in Niamey (Niger). Water, 13(12).
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Michoud, V., Hallemans, E., Chiappini, L., Leoz-Garziandia, E., Colomb, A., Dusanter, S., et al. (2021). Molecular characterization of gaseous and particulate oxygenated compounds at a remote site in Cape Corsica in the western Mediterranean Basin. Atmospheric Chemistry And Physics, 21(10), 8067–8088.
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Noblet, C., Besombes, J., Lemire, M., Pin, M., Jaffrezo, J., Favez, O., et al. (2021). Emission factors and chemical characterization of particulate emissions from garden green waste burning. Science Of The Total Environment, 798.
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Osterwalder, S., Dunham-Cheatham, S., Araujo, B., Magand, O., Thomas, J., Baladima, F., et al. (2021). Fate of Springtime Atmospheric Reactive Mercury: Concentrations and Deposition at Zeppelin, Svalbard. Acs Earth And Space Chemistry, 5(11), 3234–3246.
Abstract: Mid-latitude atmospheric elemental mercury (Hg) emissions undergo extensive oxidation to reactive Hg (RM) compounds during Arctic polar sunrise, resulting in enhanced atmospheric deposition that impacts Arctic marine wildlife and humans. It has been difficult to estimate RM dry deposition, because RM concentrations, compounds, and their deposition velocities are ill-defined. Here, we investigate RM concentrations sampled with membrane-based methods and find these to exceed denuder-based RM detection by 5 times at the Zeppelin Observatory on Svalbard (March 26-July 24, 2019). Measured dry deposition of gaseous oxidized Hg was about half of the modeled RM deposition, demonstrating that particulate-bound Hg was an important component of dry deposition. Using thermal membrane desorption, RM chemistry was found to be dominated by Hg-Cl/Br (51%) and Hg-N (45%) compounds. Back-trajectory analysis indicated that Hg-Br/Cl compounds were predominantly advected from within the marine boundary layer (sea ice exposure), while Hg-N originated from the free troposphere. Weekly average RM compound-specific dry deposition velocities ranged from 0.12 to 0.49 cm s(-1), with a net RM dry deposition of 1.9 μg m(-2) (1.5-2.5 μg m(-2); 95% confidence interval) that exceeds the mean annual Hg wet deposition flux in Svalbard. Overall, we find that springtime atmospheric RM deposition has been underestimated in the Arctic marine environment.
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Osterwalder, S., Nerentorp, M., Zhu, W., Jiskra, M., Nilsson, E., Nilsson, M., et al. (2021). Critical Observations of Gaseous Elemental Mercury Air-Sea Exchange. Global Biogeochemical Cycles, 35(8).
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Rose, C., Coen, M., Andrews, E., Lin, Y., Bossert, I., Myhre, C., et al. (2021). Seasonality of the particle number concentration and size distribution: a global analysis retrieved from the network of Global Atmosphere Watch (GAW) near-surface observatories. Atmospheric Chemistry And Physics, 21(22), 17185–17223.
Abstract: Aerosol particles are a complex component of the atmospheric system which influence climate directly by interacting with solar radiation, and indirectly by contributing to cloud formation. The variety of their sources, as well as the multiple transformations they may undergo during their transport (including wet and dry deposition), result in significant spatial and temporal variability of their properties. Documenting this variability is essential to provide a proper representation of aerosols and cloud condensation nuclei (CCN) in climate models. Using measurements conducted in 2016 or 2017 at 62 ground-based stations around the world, this study provides the most up-to-date picture of the spatial distribution of particle number concentration (N-tot) and number size distribution (PNSD, from 39 sites). A sensitivity study was first performed to assess the impact of data availability on N-tot's annual and seasonal statistics, as well as on the analysis of its diel cycle. Thresholds of 50% and 60% were set at the seasonal and annual scale, respectively, for the study of the corresponding statistics, and a slightly higher coverage (75 %) was required to document the diel cycle. Although some observations are common to a majority of sites, the variety of environments characterizing these stations made it possible to highlight contrasting findings, which, among other factors, seem to be significantly related to the level of anthropogenic influence. The concentrations measured at polar sites are the lowest (similar to 10(2) cm(-3)) and show a clear seasonality, which is also visible in the shape of the PNSD, while diel cycles are in general less evident, due notably to the absence of a regular day-night cycle in some seasons. In contrast, the concentrations characteristic of urban environments are the highest (similar to 10(3)-10(4) cm(-3)) and do not show pronounced seasonal variations, whereas diel cycles tend to be very regular over the year at these stations. The remaining sites, including mountain and non-urban continental and coastal stations, do not exhibit as obvious common behaviour as polar and urban sites and display, on average, intermediate N-tot (similar to 10(2)-10(3) cm(-3)). Particle concentrations measured at mountain sites, however, are generally lower compared to nearby lowland sites, and tend to exhibit somewhat more pronounced seasonal variations as a likely result of the strong impact of the atmospheric boundary layer (ABL) influence in connection with the topography of the sites. ABL dynamics also likely contribute to the diel cycle of N-tot observed at these stations. Based on available PNSD measurements, CCN-sized particles (considered here as either >50 nm or >100 nm) can represent from a few percent to almost all of N-tot, corresponding to seasonal medians on the order of similar to 10 to 1000 cm(-3), with seasonal patterns and a hierarchy of the site types broadly similar to those observed for N-tot. Overall, this work illustrates the importance of in situ measurements, in particular for the study of aerosol physical properties, and thus strongly supports the development of a broad global network of near surface observatories to increase and homogenize the spatial coverage of the measurements, and guarantee as well data availability and quality. The results of this study also provide a valuable, freely available and easy to use support for model comparison and validation, with the ultimate goal of contributing to improvement of the representation of aerosol-cloud interactions in models, and, therefore, of the evaluation of the impact of aerosol particles on climate.
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Samake, A., Martins, J., Bonin, A., Uzu, G., Taberlet, P., Conil, S., et al. (2021). Variability of the Atmospheric PM10 Microbiome in Three Climatic Regions of France. Frontiers In Microbiology, 11.
Abstract: Primary Biogenic Organic Aerosols (PBOA) were recently shown to be produced by only a few types of microorganisms, emitted by the surrounding vegetation in the case of a regionally homogeneous field site. This study presents the first comprehensive description of the structure and main sources of airborne microbial communities associated with temporal trends in Sugar Compounds (SC) concentrations of PM10 in 3 sites under a climatic gradient in France. By combining sugar chemistry and DNA Metabarcoding approaches, we intended to identify PM10-associated microbial communities and their main sources at three sampling-sites in France, under different climates, during the summer of 2018. This study accounted also for the interannual variability in summer airborne microbial community structure (bacteria and fungi only) associated with PM10-SC concentrations during a 2 consecutive years' survey at one site. Our results showed that temporal changes in PM10-SC in the three sites are associated with the abundance of only a few specific taxa of airborne fungi and bacterial. These taxa differ significantly between the 3 climatic regions studied. The microbial communities structure associated with SC concentrations of PM10 during a consecutive 2-year study remained stable in the rural area. Atmospheric concentration levels of PM10-SC species varied significantly between the 3 study sites, but with no clear difference according to site typology (rural vs. urban), suggesting that SC emissions are related to regional rather than local climatic characteristics. The overall microbial beta diversity in PM10 samples is significantly different from that of the main vegetation around the urban sites studied. This indicates that the airborne microorganisms at these urban sites are not solely from the immediate surrounding vegetation, which contrasts with observations at the scale of a regionally homogeneous rural site in 2017. These results improve our understanding of the spatial behavior of tracers of PBOA emission sources, which need to be better characterized to further implement this important mass fraction of Organic Matter (OM) in Chemical Transport models (CTM).
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Serazin, G., Di Luca, A., Sen Gupta, A., Roge, M., Jourdain, N., Argueso, D., et al. (2021). East Australian Cyclones and Air-Sea Feedbacks. Journal Of Geophysical Research-Atmospheres, 126(20).
Abstract: The importance of resolving mesoscale air-sea interactions to represent cyclones impacting the East Coast of Australia, the so-called East Coast Lows (ECLs), is investigated using the Australian Regional Coupled Model based on NEMO-OASIS-WRF (NOW) at 1/4 degrees resolution. The fully coupled model is shown to be capable of reproducing correctly relevant features such as the seasonality, spatial distribution and intensity of ECLs while it partially resolves mesoscale processes, such as air-sea feedbacks over ocean eddies and fronts. The mesoscale thermal feedback (TFB) and the current feedback (CFB) are shown to influence the intensity of northern ECLs (north of 30 degrees S), with the TFB modulating the pre-storm sea surface temperature (SST) by shifting ECL locations eastwards and the CFB modulating the wind stress. By fully uncoupling the atmospheric model of NOW, the intensity of northern ECLs is increased due to the absence of the cold wake that provides a negative feedback to the cyclone. The number of ECLs might also be affected by the air-sea feedbacks but large interannual variability hampers significant results with short-term simulations. The TFB and CFB modify the climatology of SST (mean and variability) but no direct link is found between these changes and those noticed in ECL properties. These results show that the representation of ECLs, mainly north of 30 degrees S, depend on how air-sea feedbacks are simulated. This is particularly important for atmospheric downscaling of climate projections as small-scale SST interactions and the effects of ocean currents are not accounted for.
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Shangguan, Y., Zhuang, X., Querol, X., Li, B., Li, J., Moreno, N., et al. (2021). Mineralogical and geochemical variations from coal to deposited dust and toxicity of size-segregated respirable dust in a blasting mining underground coal mine in Hunan Province, South China. International Journal Of Coal Geology, 248.
Abstract: This study systematically investigates the mineralogical and geochemical variations in parent coal, coal gangue (roof, parting, and floor), deposited coal mine dust (DD), and respirable fractions of DD (RD) in an underground coal mine using the blasting mining method in China to evaluate the major sources of DD. The emission of dust in this study is affected by coal gangue sources during the mining process, which causes different geochemical patterns in the DD samples. Moreover, weathering of the cement gunite walls plays an important role in the enrichment of specific elements in the DD from air uptake and air out galleries. Furthermore, the spatial variation in RD characteristics, including mineralogy, geochemistry, and oxidative potential (OP), is discussed, with emphasis on the major health-relevant species and elements. Organic species from coal dust seem to be the essential components contributing to OP rather than metals, although some metals (e.g., Cr, Co, Ge, Se, Zn, Ba, Rb, Cs, Sn, and Pb) influence OP to some degree.
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Sierra, J., Junquas, C., Espinoza, J., Segura, H., Condom, T., Andrade, M., et al. (2021). Deforestation impacts on Amazon-Andes hydroclimatic connectivity. Climate Dynamics, .
Abstract: Amazonian deforestation has accelerated during the last decade, threatening an ecosystem where almost one third of the regional rainfall is transpired by the local rainforest. Due to precipitation recycling, the southwestern Amazon, including the Amazon-Andes transition region, is particularly sensitive to forest loss. This study evaluates the impacts of Amazonian deforestation on the hydro-climatic connectivity between the Amazon and the eastern tropical Andes during the austral summer (December-January-February) in terms of hydrological and energetic balances. Using 10-years high-resolution simulations (2001-2011) with the Weather Research and Forecasting Model, we analyze control and deforestation scenario simulations. Regionally, deforestation leads to a reduction in the surface net radiation, evaporation, moisture convergence and precipitation (similar to 20%) over the entire Amazon basin. In addition, during this season, deforestation increases the atmospheric subsidence over the southern Amazon and weakens the regional Hadley cell. Atmospheric stability increases over the western Amazon and the tropical Andes inhibiting convection in these areas. Consequently, major deforestation impacts are observed over the hydro-climate of the Amazon-Andes transition region. At local scale, nighttime precipitation decreases in Bolivian valleys (similar to 20-30%) due to a strong reduction in the humidity transport from the Amazon plains towards the Andes linked to the South American low-level jet. Over these valleys, a weakening of the daytime upslope winds is caused by local deforestation, which reduces the turbulent fluxes at lowlands. These alterations in rainfall and atmospheric circulation could impact the rich Andean ecosystems and its tropical glaciers.
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Simonin, M., Martins, J., Uzu, G., Spadini, L., Navel, A., & Richaume, A. (2021). Low mobility of CuO and TiO2 nanoparticles in agricultural soils of contrasting texture and organic matter content. Science Of The Total Environment, 783.
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Simu, S., Miyazaki, Y., Tachibana, E., Finkenzeller, H., Brioude, J., Colomb, A., et al. (2021). Origin of water-soluble organic aerosols at the Maido high-altitude observatory, Reunion Island, in the tropical Indian Ocean. Atmospheric Chemistry And Physics, 21(22), 17017–17029.
Abstract: The tropical and subtropical Indian Ocean (IO) is expected to be a significant source of water-soluble organic aerosols (WSOAs), which are important factors relevant to cloud formation of aerosol particles. Current atmospheric numerical models significantly underestimate the budget of organic aerosols and their precursors, especially over tropical oceans. This is primarily due to poor knowledge of sources and the paucity of observations of these parameters considering spatial and temporal variation over the tropical open ocean. To evaluate the contribution of sources to WSOA as well as their formation processes, submicrometer aerosol sampling was conducted at the high-altitude Maido observatory (21.1 degrees S, 55.4 degrees E; 2160ma.s.l.), located on the remote island of La Reunion in the southwest IO. The aerosol samples were continuously collected during local daytime and nighttime, which corresponded to the ambient conditions of the marine boundary layer (MBL) and free troposphere (FT), respectively, from 15 March to 24 May 2018. Chemical analysis showed that organic matter was the dominant component of submicrometer water-soluble aerosol (similar to 45 +/- 17 %) during the wet season (15 March-23 April). On the other hand, sulfate dominated (similar to 77 +/- 17 %) during the dry season (24 April-24 May), most of which was attributable to the effect of volcanic eruption. Measurements of the stable carbon isotope ratio of water-soluble organic carbon (WSOC) suggested that marine sources contributed significantly to the observed WSOC mass in both the MBL and the FT in the wet season, whereas a mixture of marine and terrestrial sources contributed to WSOC in the dry season. The distinct seasonal changes in the dominant source of WSOC were also supported by Lagrangian trajectory analysis. Positive matrix factorization analysis suggested that marine secondary organic aerosol (OA) dominantly contributed to the observed WSOC mass (similar to 70 %) during the wet season, whereas mixtures of marine and terrestrial sources contributed during the dry season in both MBL and FT. Overall, this study demonstrates that the effect of marine secondary sources is likely important up to the FT in the wet season, which may affect cloud formation as well as direct radiative forcing over oceanic regions.
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Svensson, J., Strom, J., Honkanen, H., Asmi, E., Dkhar, N., Tayal, S., et al. (2021). Deposition of light-absorbing particles in glacier snow of the Sunderdhunga Valley, the southern forefront of the central Himalayas. Atmospheric Chemistry And Physics, 21(4), 2931–2943.
Abstract: Anthropogenic activities on the Indo-Gangetic Plain emit vast amounts of light-absorbing particles (LAPs) into the atmosphere, modifying the atmospheric radiation state. With transport to the nearby Himalayas and deposition to its surfaces the particles contribute to glacier melt and snowmelt via darkening of the highly reflective snow. The central Himalayas have been identified as a region where LAPs are especially pronounced in glacier snow but still remain a region where measurements of LAPs in the snow are scarce. Here we study the deposition of LAPs in five snow pits sampled in 2016 (and one from 2015) within 1 km from each other from two glaciers in the Sunderdhunga Valley, in the state of Uttarakhand, India, in the central Himalayas. The snow pits display a distinct enriched LAP layer interleaved by younger snow above and older snow below. The LAPs exhibit a distinct vertical distribution in these different snow layers. For the analyzed elemental carbon (EC), the younger snow layers in the different pits show similarities, which can be characterized by a deposition constant of about 50 μg m(-2) mm(-1) snow water equivalent (SWE), while the old-snow layers also indicate similar values, described by a deposition constant of roughly 150 μg m(-2) mm(-1) SWE. The enriched LAP layer, contrarily, displays no similar trends between the pits. Instead, it is characterized by very high amounts of LAPs and differ in orders of magnitude for concentration between the pits. The enriched LAP layer is likely a result of strong melting that took place during the summers of 2015 and 2016, as well as possible lateral transport of LAPs. The mineral dust fractional absorption is slightly below 50% for the young- and old-snow layers, whereas it is the dominating light-absorbing constituent in the enriched LAP layer, thus, highlighting the importance of dust in the region. Our results indicate the problems with complex topography in the Himalayas but, nonetheless, can be useful in large-scale assessments of LAPs in Himalayan snow.
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Trechera, P., Moreno, T., Cordoba, P., Moreno, N., Amato, F., Cortes, J., et al. (2021). Geochemistry and oxidative potential of the respirable fraction of powdered mined Chinese coals. Science Of The Total Environment, 800.
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Tuite, K., Thomas, J., Veres, P., Roberts, J., Stevens, P., Griffith, S., et al. (2021). Quantifying Nitrous Acid Formation Mechanisms Using Measured Vertical Profiles During the CalNex 2010 Campaign and 1D Column Modeling. Journal Of Geophysical Research-Atmospheres, 126(13).
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Weber, S., Uzu, G., Favez, O., Borlaza, L., Calas, A., Salameh, D., et al. (2021). Source apportionment of atmospheric PM10 oxidative potential: synthesis of 15 year-round urban datasets in France. Atmospheric Chemistry And Physics, 21(14), 11353–11378.
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Baray, J., Deguillaume, L., Colomb, A., Sellegri, K., Freney, E., Rose, C., et al. (2020). Cezeaux-Aulnat-Opme-Puy De Dome: a multi-site for the long-term survey of the tropospheric composition and climate change. Atmospheric Measurement Techniques, 13(6), 3413–3445.
Abstract: For the last 25 years, CO-PDD (Cezeaux-Aulnat-Opme-puy de Dome) has evolved to become a full instrumented platform for atmospheric research. It has received credentials as a national observing platform in France and is internationally recognized as a global station in the GAW (Global Atmosphere Watch) network. It is a reference site of European and national research infrastructures ACTRIS (Aerosol Cloud and Trace gases Research Infrastructure) and ICOS (Integrated Carbon Observing System). The site located on top of the puy de Dome mountain (1465 m a.s.l.) is completed by additional sites located at lower altitudes and adding the vertical dimension to the atmospheric observations: Opme (660 m a.s.l.), Cezeaux (410 m), and Aulnat (330 m). The integration of different sites offers a unique combination of in situ and remote sensing measurements capturing and documenting the variability of particulate and gaseous atmospheric composition, but also the optical, biochemical, and physical properties of aerosol particles, clouds, and precipitations. Given its location far away from any major emission sources, its altitude, and the mountain orography, the puy de Dome station is ideally located to sample different air masses in the boundary layer or in the free troposphere depending on time of day and seasons. It is also an ideal place to study cloud properties with frequent presence of clouds at the top in fall and winter. As a result of the natural conditions prevailing at the site and of the very exhaustive instrumental deployment, scientific studies at the puy de Dome strongly contribute to improving knowledge in atmospheric sciences, including the characterization of trends and variability, the understanding of complex and interconnected processes (microphysical, chemical, biological, chemical and dynamical), and the provision of reference information for climate/chemistry models. In this context, CO-PDD is a pilot site to conduct instrumental development inside its wind tunnel for testing liquid and ice cloud probes in natural conditions, or in situ systems to collect aerosol and cloud. This paper reviews 25 years (1995-2020) of atmospheric observation at the station and related scientific research contributing to atmospheric and climate science.
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Barbero, A., Blouzon, C., Savarino, J., Caillon, N., Dommergue, A., & Grilli, R. (2020). A compact incoherent broadband cavity-enhanced absorption spectrometer for trace detection of nitrogen oxides, iodine oxide and glyoxal at levels below parts per billion for field applications. Atmospheric Measurement Techniques, 13(8), 4317–4331.
Abstract: We present a compact, affordable and robust instrument based on incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) for simultaneous detection of NOx, IO, CHOCHO and O-3 in the 400-475 nm wavelength region. The instrument relies on the injection of a high-power LED source in a high-finesse cavity (F similar to 33100), with the transmission signal being detected by a compact spectrometer based on a high-order diffraction grating and a charge-coupled device (CCD) camera. A minimum detectable absorption of 2.0 x 10(-10) cm(-1) was achieved within similar to 22 min of total acquisition, corresponding to a figure of merit of 1.8 x 10(-10) cm(-1) Hz(-1/2) per spectral element. Due to the multiplexing broadband feature of the setup, multi-species detection can be performed with simultaneous detection of NO2, IO, CHOCHO and O-3 achieving detection limits of 11, 0.3, 10 ppt (parts per trillion) and 47 ppb (parts per billion) (1 sigma) within 22 min of measurement, respectively (half of the time is spent on the acquisition of the reference spectrum in the absence of the absorber, and the other half is spent on the absorption spectrum). The implementation on the inlet gas line of a compact ozone generator based on electrolysis of water allows for the measurement of NOx (NO + NO2) and therefore an indirect detection of NO with detection limits for NOx and NO of 10 and 21 ppt (1 sigma), respectively. The device has been designed to fit in a 19 in., 3U (5.25 in.) rack-mount case; weighs 15 kg; and has a total electrical power consumption of < 300 W. The instrument can be employed to address different scientific objectives such as better constraining the oxidative capacity of the atmosphere, studying the chemistry of highly reactive species in atmospheric chambers as well as in the field and looking at the sources of glyoxal in the marine boundary layer to study possible implications on the formation of secondary aerosol particles.
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Barraza, F., Uzu, G., Jaffrezo, J., Schreck, E., Budzinski, H., Le Menach, K., et al. (2020). Contrasts in chemical composition and oxidative potential in PM10 near flares in oil extraction and refining areas in Ecuador. Atmospheric Environment, 223.
Abstract: For decades, oil extraction in rural sites in the North Amazon Region (NAR) in Ecuador, have generated mixtures of potentially toxic compounds, such as polycyclic aromatic hydrocarbons (PAHs) and metal(loid)s. The main national refinery and the thermal power plant located in Esmeraldas, on the North Pacific Coast (NPC), are also considered as important sources of air contamination. Particulate matter (PM10) emitted at both sites could induce the formation of reactive oxygen species (ROS) in the lungs upon inhalation and could be associated with respiratory diseases. In this study, PM10 mass composition was monitored over a two-year period in both regions: NAR (close to oil platforms and open flares) and NPC (in a public school close to the refinery). PM10 composition was assessed in terms of metal(loid)s, organic and elementary carbon (OC, EC), monosaccharides (levoglucosan, mannosan, galactosan), glucose, polyols (sorbitol, mannitol, arabitol), water soluble ions and polycyclic aromatic compounds (PAHs, oxy-PAHs and nitro-PAHs). Additionally, three complementary biochemical and acellular tests were performed to evaluate the oxidative potential (OP). Results show that the PM10 mass and elemental concentrations were higher in NPC than in NAR. Barium and Mo concentrations, commonly used in oil operations, were up to 1000-fold higher than values recorded in other regions of Ecuador. OC/EC ratios and polyols concentrations were higher in NAR than in NPC, indicating a larger biogenic contribution to the PM mass in this region. In NAR, the main sources associated with ROS burden were biogenic emissions and oil production, as indicated by positive correlations between OP, sugars, Ba, some PAHs and oxy-PAHs. On the other hand, in NPC, associations between NH4+, Ba, As and Ni imply that oil refining and industrial activities are the main contributors to the OP of PM10.
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Belis, C., Pernigotti, D., Pirovano, G., Favez, O., Jaffrezo, J., Kuenen, J., et al. (2020). Evaluation of receptor and chemical transport models for PM10 source apportionment. Atmospheric Environment-X, 5.
Abstract: In this study, the performance of two types of source apportionment models was evaluated by assessing the results provided by 40 different groups in the framework of an intercomparison organised by FAIRMODE WG3 (Forum for air quality modelling in Europe, Working Group 3). The evaluation was based on two performance indicators: z-scores and the root mean square error weighted by the reference uncertainty (RMSEu), with pre-established acceptability criteria. By involving models based on completely different and independent input data, such as receptor models (RMs) and chemical transport models (CTMs), the intercomparison provided a unique opportunity for their cross-validation. In addition, comparing the CTM chemical profiles with those measured directly at the source contributed to corroborate the consistency of the tested model results. The most commonly used RM was the US EPA- PMF version 5. RMs showed very good performance for the overall dataset (91% of z-scores accepted) while more difficulties were observed with the source contribution time series (72% of RMSEu accepted). Industrial activities proved to be the most difficult sources to be quantified by RMs, with high variability in the estimated contributions. In the CTMs, the sum of computed source contributions was lower than the measured gravimetric PM10 mass concentrations. The performance tests pointed out the differences between the two CTM approaches used for source apportionment in this study: brute force (or emission reduction impact) and tagged species methods. The sources meeting the z-score and RMSEu acceptability criteria tests were 50% and 86%, respectively. The CTM source contributions to PM10 were in the majority of cases lower than the RM averages for the corresponding source. The CTMs and RMs source contributions for the overall dataset were more comparable (83% of the z-scores accepted) than their time series (successful RMSEu in the range 25% – 34%). The comparability between CTMs and RMs varied depending on the source: traffic/exhaust and industry were the source categories with the best results in the RMSEu tests while the most critical ones were soil dust and road dust. The differences between RMs and CTMs source reconstructions confirmed the importance of cross validating the results of these two families of models.
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Bessagnet, B., Menut, L., Lapere, R., Couvidat, F., Jaffrezo, J., Mailler, S., et al. (2020). High Resolution Chemistry Transport Modeling with the On-Line CHIMERE-WRF Model over the French Alps-Analysis of a Feedback of Surface Particulate Matter Concentrations on Mountain Meteorology. Atmosphere, 11(6).
Abstract: Air pollution is of major concern throughout the world and the use of modeling tools to analyze and forecast the pollutant concentrations in complex orographic areas remains challenging. This work proposes an exhaustive framework to analyze the ability of models to simulate the air quality over the French Alps up to 1.2 km resolution over Grenoble and the Arve Valley. The on-line coupled suite of models CHIMERE-WRF is used in its recent version to analyze a 1 month episode in November-December 2013. As expected, an improved resolution increases the concentrations close to the emission areas and reduced the negative bias for Particulate Matter that is the usual weakness of air quality models. However, the nitrate concentrations seem overestimated with at the same time an overestimation of surface temperature in the morning by WRF. Different WRF settings found in the literature are tested to improve the results, particularly the ability of the meteorological model to simulate the strong thermal inversions in the morning. Wood burning is one of the main contributor of air pollution during the period ranging from 80 to 90% of the Organic Matter. The activation of the on-line coupling has a moderate impact on the background concentrations but surprisingly a change of Particulate Matter (PM) concentrations in the valley will affect more the meteorology nearby high altitude areas than in the valley. This phenomenon is the result of a chain of processes involving the radiative effects and the water vapor column gradients in complex orographic areas. At last, the model confirms that the surrounding glaciers are largely impacted by long range transport of desert dust. However, in wintertime some outbreaks of anthropogenic pollution from the valley when the synoptic situation changes can be advected up to the nearby high altitude areas, then deposited.
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Bishop, K., Shanley, J., Riscassi, A., De Wit, H., Eklof, K., Meng, B., et al. (2020). Recent advances in understanding and measurement of mercury in the environment: Terrestrial Hg cycling. Science Of The Total Environment, 721.
Abstract: This review documents recent advances in terrestrial mercury cycling. Terrestrial mercury (Hg) research has matured in some areas, and is developing rapidly in others. We summarize the state of the science circa 2010 as a starting point, and then present the advances during the last decade in three areas: land use, sulfate deposition, and climate change. The advances are presented in the framework of three Hg “gateways” to the terrestrial environment: inputs from the atmosphere, uptake in food, and run off with surface water. Among the most notable advances: The Arctic has emerged as a hotbed of Hg cycling, with high stream fluxes and large stores of Hg poised for release from permafrost with rapid high-latitude warming. The bi-directional exchange of Hg between the atmosphere and terrestrial surfaces is better understood, thanks largely to interpretation from Hg isotopes; the latest estimates place land surface Hg re-emission lower than previously thought. Artisanal gold mining is now thought responsible for over half the global stream flux of Hg. There is evidence that decreasing inputs ofHg to ecosystems may bring recovery sooner than expected, despite large ecosystem stores of legacy Hg. Freshly deposited Hg is more likely than stored Hg to methylate and be incorporated in rice. Topography and hydrological connectivity have emerged as master variables for explaining the disparate response of THg and MeHg to forest harvest and other land disturbance. These and other advances reported here are of value in evaluating the effectiveness of theMinamata Convention on reducing environmental Hg exposure to humans and wildlife. (C) 2020 The Authors. Published by Elsevier B.V.
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Bull, C., Kiss, A., Sen Gupta, A., Jourdain, N., Argueso, D., Di Luca, A., et al. (2020). Regional Versus Remote Atmosphere-Ocean Drivers of the Rapid Projected Intensification of the East Australian Current. Journal Of Geophysical Research-Oceans, 125(7).
Abstract: Like many western boundary currents, the East Australian Current (EAC) extension is projected to get stronger and warmer in the future. The CMIP5 multimodel mean (MMM) projection suggests up to 5 degrees C of warming under an RCP85 scenario by 2100. Previous studies employed Sverdrup balance to associate a trend in basin wide zonally integrated wind stress curl (resulting from the multidecadal poleward intensification in the westerly winds over the Southern Ocean) with enhanced transport in the EAC extension. Possible regional drivers are yet to be considered. Here we introduce the NEMO-OASIS-WRF coupled regional climate model as a framework to improve our understanding of CMIP5 projections. We analyze a hierarchy of simulations in which the regional atmosphere and ocean circulations are allowed to freely evolve subject to boundary conditions that represent present-day and CMIP5 RCP8.5 climate change anomalies. Evaluation of the historical simulation shows an EAC extension that is stronger than similar ocean-only models and observations. This bias is not explained by a linear response to differences in wind stress. The climate change simulations show that regional atmospheric CMIP5 MMM anomalies drive 73% of the projected 12 Sv increase in EAC extension transport whereas the remote ocean boundary conditions and regional radiative forcing (greenhouse gases within the domain) play a smaller role. The importance of regional changes in wind stress curl in driving the enhanced EAC extension is consistent with linear theory where the NEMO-OASIS-WRF response is closer to linear transport estimates compared to the CMIP5 MMM.
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Coen, M., Andrews, E., Alastuey, A., Arsov, T., Backman, J., Brem, B., et al. (2020). Multidecadal trend analysis of in situ aerosol radiative properties around the world. Atmospheric Chemistry And Physics, 20(14), 8867–8908.
Abstract: In order to assess the evolution of aerosol parameters affecting climate change, a long-term trend analysis of aerosol optical properties was performed on time series from 52 stations situated across five continents. The time series of measured scattering, backscattering and absorption coefficients as well as the derived single scattering albedo, backscattering fraction, scattering and absorption Angstrom exponents covered at least 10 years and up to 40 years for some stations. The non-parametric seasonal Mann-Kendall (MK) statistical test associated with several pre-whitening methods and with Sen's slope was used as the main trend analysis method. Comparisons with general least mean square associated with autoregressive bootstrap (GLS/ARB) and with standard least mean square analysis (LMS) enabled confirmation of the detected MK statistically significant trends and the assessment of advantages and limitations of each method. Currently, scattering and backscattering coefficient trends are mostly decreasing in Europe and North America and are not statistically significant in Asia, while polar stations exhibit a mix of increasing and decreasing trends. A few increasing trends are also found at some stations in North America and Australia. Absorption coefficient time series also exhibit primarily decreasing trends. For single scattering albedo, 52 % of the sites exhibit statistically significant positive trends, mostly in Asia, eastern/northern Europe and the Arctic, 22 % of sites exhibit statistically significant negative trends, mostly in central Europe and central North America, while the remaining 26 % of sites have trends which are not statistically significant. In addition to evaluating trends for the overall time series, the evolution of the trends in sequential 10-year segments was also analyzed. For scattering and backscattering, statistically significant increasing 10-year trends are primarily found for earlier periods (10-year trends ending in 2010-2015) for polar stations and Mauna Loa. For most of the stations, the present-day statistically significant decreasing 10-year trends of the single scattering albedo were preceded by not statistically significant and statistically significant increasing 10-year trends. The effect of air pollution abatement policies in continental North America is very obvious in the 10-year trends of the scattering coefficient – there is a shift to statistically significant negative trends in 2009-2012 for all stations in the eastern and central USA. This long-term trend analysis of aerosol radiative properties with a broad spatial coverage provides insight into potential aerosol effects on climate changes.
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Daellenbach, K., Uzu, G., Jiang, J., Cassagnes, L., Leni, Z., Vlachou, A., et al. (2020). Sources of particulate-matter air pollution and its oxidative potential in Europe. Nature, 587(7834), 414–+.
Abstract: Particulate matter is a component of ambient air pollution that has been linked to millions of annual premature deaths globally(1-3). Assessments of the chronic and acute effects of particulate matter on human health tend to be based on mass concentration, with particle size and composition also thought to play a part(4). Oxidative potential has been suggested to be one of the many possible drivers of the acute health effects of particulate matter, but the link remains uncertain(5-8). Studies investigating the particulate-matter components that manifest an oxidative activity have yielded conflicting results(7). In consequence, there is still much to be learned about the sources of particulate matter that may control the oxidative potential concentration(7). Here we use field observations and air-quality modelling to quantify the major primary and secondary sources of particulate matter and of oxidative potential in Europe. We find that secondary inorganic components, crustal material and secondary biogenic organic aerosols control the mass concentration of particulate matter. By contrast, oxidative potential concentration is associated mostly with anthropogenic sources, in particular with fine-mode secondary organic aerosols largely from residential biomass burning and coarse-mode metals from vehicular non-exhaust emissions. Our results suggest that mitigation strategies aimed at reducing the mass concentrations of particulate matter alone may not reduce the oxidative potential concentration. If the oxidative potential can be linked to major health impacts, it may be more effective to control specific sources of particulate matter rather than overall particulate mass. Observations and air-quality modelling reveal that the sources of particulate matter and oxidative potential in Europe are different, implying that reducing mass concentrations of particulate matter alone may not reduce oxidative potential.
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Esmaeilirad, S., Lai, A., Abbaszade, G., Schnelle-Kreis, J., Zimmermann, R., Uzu, G., et al. (2020). Source apportionment of fine particulate matter in a Middle Eastern Metropolis, Tehran-Iran, using PMF with organic and inorganic markers. Science Of The Total Environment, 705.
Abstract: With over 8 million inhabitants and 4 million motor vehicles on the streets, Tehran is one of the most crowded and polluted cities in the Middle East. Frequent exceedances of national daily PM2.5 limit have been reported in this city during the last decade, yet, the chemical composition and sources of fine particles are poorly determined. In the present study, 24-hour PM2.5 samples were collected at two urban sites during two separate campaigns, a one-year period from 2014 to 2015 and another three-month period at the beginning of 2017. Concentrations of organic carbon (OC), elemental carbon (EC), inorganic ions, trace metals and specific organic molecular markers were measured by chemical analysis of filter samples. The dominant mass components were organic matter (OM), sulfate and EC. With a 20% water-soluble organic carbon (WSOC) fraction, the predominance of primary anthropogenic sources (i.e. fossil fuel combustion) was anticipated. A positive matrix factorization (PMF) analysis using the ME-2 (Multilinear Engine-2) solver was then applied to this dataset. 5 factors were identified by Marker-PMF, named as traffic exhaust (TE), biomass burning (BB), industries (Ind.), nitrate-rich and sulfate-rich. Another 4 factors were identified by Metal-PMF, including, dust, vehicles (traffic nonexhaust, TNE), industries (Ind.) and heavy fuel combustion (HFC). Traffic exhaust was the dominant source with 44.5% contribution to total quantified PM2.5 mass. Sulfate-rich (24.2%) and nitrate-rich (18.4%) factors were the next major contributing sources. Dust (4.4%) and biomass burning (6.7%) also had small contributions while the total share of all other factors was < 2%. Investigating the correlations of different factors between the two sampling sites showed that traffic emissions and biomass burning were local, whereas dust, heavy fuel combustion and industrial sources were regional. Results of this study indicate that gas- and particle-phase pollutants emitted from fossil fuel combustion (mobile and stationary) are the principal origin of both primary and secondary fine aerosols in Tehran. (C) 2019 Published by Elsevier B.V.
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Farah, A., Villani, P., Rose, C., Conil, S., Langrene, L., Laj, P., et al. (2020). Characterization of Aerosol Physical and Optical Properties at the Observatoire Perenne de l'Environnement (OPE) Site. Atmosphere, 11(2).
Abstract: The Observatoire Perenne de l'Environnement (OPE) station is a rural background site located in North-Eastern France. Besides emissions from agricultural activities, the site is located far from local emissions but at an even distance from the intense emission zones of Western Germany to the north-east and the Paris area to the south-west. In the paper, we report and analyze almost six years of measurements (1 May 2012 to 31 December 2018) of the optical and physical properties of aerosol particles. Based on aerosol optical and physical measurements combined with air mass back-trajectories, we investigate the dependence of these properties on air mass type. Two distinct equivalent black carbon (EBC) sources-origins-fossil fuel (FF) and biomass burning (BB)- were identified. FF was the dominant source of EBC (>70%) but showed a very marked seasonal variation. BB fraction is found higher during the cold seasons in the order of 35% (0.1 μg m(-3)) against 17% (0.05 μg m(-3)) during the warm seasons. The highest EBC and N0.54-1.15 (particles whose diameter ranged from 0.54 to 1.15 μm) median concentrations were observed during the night time and during the cold seasons compared to the warmer seasons, indicating primary sources trapped within a thin boundary layer (BL). A different behavior is found for N10-550 (particles whose diameter ranged from 10 to 550 nm) and coarse mode particles (N1.15-4.5, i.e., particles whose diameter ranged from 1.15 to 4.5 μm) median concentrations, which were observed during the warm seasons compared to the cold seasons, indicating rather biogenic secondary sources for the smaller particles, and potentially primary biogenic sources for the coarse mode particles. The scattering and absorption coefficients and single scattering albedo (SSA) show the same seasonal variations like the ones of N0.54-1.15 concentrations, indicating that particles larger than 500 nm seemed to contribute the most to the optical properties of the aerosol.
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Laj, P., Bigi, A., Rose, C., Andrews, E., Myhre, C., Coen, M., et al. (2020). A global analysis of climate-relevant aerosol properties retrieved from the network of Global Atmosphere Watch (GAW) near-surface observatories. Atmospheric Measurement Techniques, 13(8), 4353–4392.
Abstract: Aerosol particles are essential constituents of the Earth's atmosphere, impacting the earth radiation balance directly by scattering and absorbing solar radiation, and indirectly by acting as cloud condensation nuclei. In contrast to most greenhouse gases, aerosol particles have short atmospheric residence times, resulting in a highly heterogeneous distribution in space and time. There is a clear need to document this variability at regional scale through observations involving, in particular, the in situ near-surface segment of the atmospheric observation system. This paper will provide the widest effort so far to document variability of climate-relevant in situ aerosol properties (namely wavelength dependent particle light scattering and absorption coefficients, particle number concentration and particle number size distribution) from all sites connected to the Global Atmosphere Watch network. High-quality data from almost 90 stations worldwide have been collected and controlled for quality and are reported for a reference year in 2017, providing a very extended and robust view of the variability of these variables worldwide. The range of variability observed worldwide for light scattering and absorption coefficients, single-scattering albedo, and particle number concentration are presented together with preliminary information on their long-term trends and comparison with model simulation for the different stations. The scope of the present paper is also to provide the necessary suite of information, including data provision procedures, quality control and analysis, data policy, and usage of the ground-based aerosol measurement network. It delivers to users of the World Data Centre on Aerosol, the required confidence in data products in the form of a fully characterized value chain, including uncertainty estimation and requirements for contributing to the global climate monitoring system.
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Leni, Z., Cassagnes, L., Daellenbach, K., El Haddad, I., Vlachou, A., Uzu, G., et al. (2020). Oxidative stress-induced inflammation in susceptible airways by anthropogenic aerosol. Plos One, 15(11).
Abstract: Ambient air pollution is one of the leading five health risks worldwide. One of the most harmful air pollutants is particulate matter (PM), which has different physical characteristics (particle size and number, surface area and morphology) and a highly complex and variable chemical composition. Our goal was first to comparatively assess the effects of exposure to PM regarding cytotoxicity, release of pro-inflammatory mediators and gene expression in human bronchial epithelia (HBE) reflecting normal and compromised health status. Second, we aimed at evaluating the impact of various PM components from anthropogenic and biogenic sources on the cellular responses. Air-liquid interface (ALI) cultures of fully differentiated HBE derived from normal and cystic fibrosis (CF) donor lungs were exposed at the apical cell surface to water-soluble PM filter extracts for 4 h. The particle dose deposited on cells was 0.9-2.5 and 8.8-25.4 μg per cm(2) of cell culture area for low and high PM doses, respectively. Both normal and CF HBE show a clear dose-response relationship with increasing cytotoxicity at higher PM concentrations. The concurrently enhanced release of pro-inflammatory mediators at higher PM exposure levels links cytotoxicity to inflammatory processes. Further, the PM exposure deregulates genes involved in oxidative stress and inflammatory pathways leading to an imbalance of the antioxidant system. Moreover, we identify compromised defense against PM in CF epithelia promoting exacerbation and aggravation of disease. We also demonstrate that the adverse health outcome induced by PM exposure in normal and particularly in susceptible bronchial epithelia is magnified by anthropogenic PM components. Thus, including health-relevant PM components in regulatory guidelines will result in substantial human health benefits and improve protection of the vulnerable population.
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Li, Y., Sen Gupta, A., Taschetto, A., Jourdain, N., Di Luca, A., Done, J., et al. (2020). Assessing the role of the ocean-atmosphere coupling frequency in the western Maritime Continent rainfall. Climate Dynamics, .
Abstract: High-frequency interactions between the ocean and atmosphere have the potential to affect lower frequency or mean state climate in various regions. Here we examine the importance of sub-daily air-sea interactions over the Maritime Continent region to the rectification of longer timescale variation. In order to determine the importance of these high-frequency interactions, we conducted two regional ocean-atmosphere coupled simulations over the Maritime Continent where exchanges between the oceanic and atmospheric components are performed either every hour (i.e. resolving diurnal changes) or every day. We find that coupling frequency has a significant influence on mean sea surface temperature (SST) and the mean state and diurnal cycle of rainfall over certain regions of the western Maritime Continent where air-sea interactions are strong during the Asian monsoon season, with little effect in other regions or seasons. Without sub-daily air-sea interactions, the mean SST along the southwest off Sumatra is similar to 2 degrees C warmer during the period from June to October as a result of a deepening of thermocline along the coast. This deepening is linked to anomalous downwelling equatorial eastward propagating Kelvin waves triggered by westerly anomalies in the eastern equatorial Indian Ocean. In addition, the mean rainfall in the vicinity of ocean warming increases, thereby producing an enhanced barrier layer that also provides a positive warming feedback. Although the coupling frequency has little impact on the timing of the rainfall diurnal cycle, suppression of sub-daily coupling significantly changes the diurnal rainfall amplitude causing a relative decrease (increase) in amplitude over the coast of Northwestern (Southwestern) Sumatra during the South Asian monsoon season.
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Marelle, L., Myhre, G., Steensen, B., Hodnebrog, O., Alterskjaer, K., & Sillmann, J. (2020). Urbanization in megacities increases the frequency of extreme precipitation events far more than their intensity. Environmental Research Letters, 15(12).
Abstract: More than half of the world's population lives in urban areas (UN Population Division 2018 The World's cities in 2018 (UN: New York)), which are especially vulnerable to climate extremes (Field et al 2012 Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation: Special Report of the Intergovernmental Panel on Climate Change (Cambridge: Cambridge University Press)). Urbanization itself is known to increase surface temperatures, but its quantitative effect on extreme precipitation remains very uncertain. Using decadal convection-permitting climate simulations in four midlatitude megacities (Paris, France; New York City, USA; Tokyo, Japan; Shanghai, China), we show that urbanization can strongly increase the frequency and intensity of extreme urban precipitation. Frequency increases far more than intensity, by +16% (11%-22%) (95% confidence interval) for 1 year daily extremes, and +26% (11%-41%) for 1 year hourly extremes, downwind of city centers. Intensities of the same events increase by +5% (3.2%-6.4%) (daily extremes) and +6% (3.2%-9.8%) (hourly extremes), respectively. The intensity and frequency of extremes increases more for the rarest, most extreme events considered, and there is some indication that hourly extremes increase more than daily extremes. Our simulations also show that direct urban anthropogenic emissions of heat could be an important factor driving these changes. Urbanization is expected to continue in the future, and our results indicate that these effects should be considered in urban planning decisions to make cities more resilient to extreme precipitation.
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Mortier, A., Gliss, J., Schulz, M., Aas, W., Andrews, E., Bian, H., et al. (2020). Evaluation of climate model aerosol trends with ground-based observations over the last 2 decades – an AeroCom and CMIP6 analysis. Atmospheric Chemistry And Physics, 20(21), 13355–13378.
Abstract: This study presents a multiparameter analysis of aerosol trends over the last 2 decades at regional and global scales. Regional time series have been computed for a set of nine optical, chemical-composition and mass aerosol properties by using the observations from several ground-based networks. From these regional time series the aerosol trends have been derived for the different regions of the world. Most of the properties related to aerosol loading exhibit negative trends, both at the surface and in the total atmospheric column. Significant decreases in aerosol optical depth (AOD) are found in Europe, North America, South America, North Africa and Asia, ranging from -1.2 % yr(-1) to -3.1 % yr(-1). An error and representativity analysis of the spatially and temporally limited observational data has been performed using model data subsets in order to investigate how much the observed trends represent the actual trends happening in the regions over the full study period from 2000 to 2014. This analysis reveals that significant uncertainty is associated with some of the regional trends due to time and space sampling deficiencies. The set of observed regional trends has then been used for the evaluation of 10 models (6 AeroCom phase III models and 4 CMIP6 models) and the CAMS reanalysis dataset and of their skills in reproducing the aerosol trends. Model performance is found to vary depending on the parameters and the regions of the world. The models tend to capture trends in AOD, the column Angstrom exponent, sulfate and particulate matter well (except in North Africa), but they show larger discrepancies for coarse-mode AOD. The rather good agreement of the trends, across different aerosol parameters between models and observations, when co-locating them in time and space, implies that global model trends, including those in poorly monitored regions, are likely correct. The models can help to provide a global picture of the aerosol trends by filling the gaps in regions not covered by observations. The calculation of aerosol trends at a global scale reveals a different picture from that depicted by solely relying on ground-based observations. Using a model with complete diagnostics (NorESM2), we find a global increase in AOD of about 0.2 % yr(-1) between 2000 and 2014, primarily caused by an increase in the loads of organic aerosols, sulfate and black carbon.
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Osterwalder, S., Eugster, W., Feigenwinter, I., & Jiskra, M. (2020). Eddy covariance flux measurements of gaseous elemental mercury over a grassland. Atmospheric Measurement Techniques, 13(4), 2057–2074.
Abstract: Direct measurements of the net ecosystem exchange (NEE) of gaseous elemental mercury (Hg-0) are important to improve our understanding of global Hg cycling and, ultimately, human and wildlife Hg exposure. The lack of long-term, ecosystem-scale measurements causes large uncertainties in Hg-0 flux estimates. It currently remains unclear whether terrestrial ecosystems are net sinks or sources of atmospheric Hg-0. Here, we show a detailed validation of direct Hg-0 flux measurements based on the eddy covariance technique (Eddy Mercury) using a Lumex RA-915 AM mercury monitor. The flux detection limit derived from a zero-flux experiment in the laboratory was 0.22 ng m(-2) h(-1) (maximum) with a 50% cutoff at 0.074 ng m(-2) h(-1). We present eddy covariance NEE measurements of Hg-0 over a low-Hg soil (41-75 ng Hg g(-1) in the topsoil, referring to a depth of 0-10 cm), conducted in summer 2018 at a managed grassland at the Swiss FluxNet site in Chamau, Switzerland (CH-Cha). The statistical estimate of the Hg-0 flux detection limit under outdoor conditions at the site was 5.9 ng m(-2) h(-1') (50% cutoff). We measured a net summertime emission over a period of 34 d with a median Hg-0 flux of 2.5 ng m(-2) h(-1) (with a -0.6 to 7.4 ng m(-2) h(-1) range between the 25th and 75th percentiles). We observed a distinct diel cycle with higher median daytime fluxes (8.4 ng m(-2) h(-1)) than night-time fluxes (1.0 ng m(-2) h(-1)). Drought stress during the measurement campaign in summer 2018 induced partial stomata closure of vegetation. Partial stomata closure led to a midday depression in CO2 uptake, which did not recover during the afternoon. The median CO2 flux was only 24% of the median CO2 flux measured during the same period in the previous year (2017). We suggest that partial stomata closure also dampened Hg-0 uptake by vegetation, resulting in a NEE of Hg-0 that was dominated by soil emission. Finally, we provide suggestions to further improve the precision and handling of the “Eddy Mercury” system in order to assure its suitability for long-term NEE measurements of Hg-0 over natural background surfaces with low soil Hg concentrations (< 100 ng g(-1)). With these improvements, Eddy Mercury has the potential to be integrated into global networks of micrometeorological tower sites (FluxNet) and to provide the long-term observations on terrestrial atmosphere Hg-0 exchange necessary to validate regional and global mercury models.
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Petaja, T., Duplissy, E., Tabakova, K., Schmale, J., Altstadter, B., Ancellet, G., et al. (2020). Overview: Integrative and Comprehensive Understanding on Polar Environments (iCUPE) – concept and initial results. Atmospheric Chemistry And Physics, 20(14), 8551–8592.
Abstract: The role of polar regions is increasing in terms of megatrends such as globalization, new transport routes, demography, and the use of natural resources with consequent effects on regional and transported pollutant concentrations. We set up the ERA-PLANET Strand 4 project “iCUPE – integrative and Comprehensive Understanding on Polar Environments” to provide novel insights and observational data on global grand challenges with an Arctic focus. We utilize an integrated approach combining in situ observations, satellite remote sensing Earth observations (EOs), and multi-scale modeling to synthesize data from comprehensive long-term measurements, intensive campaigns, and satellites to deliver data products, metrics, and indicators to stakeholders concerning the environmental status, availability, and extraction of natural resources in the polar areas. The iCUPE work consists of thematic state-of-the-art research and the provision of novel data in atmospheric pollution, local sources and transboundary transport, the characterization of arctic surfaces and their changes, an assessment of the concentrations and impacts of heavy metals and persistent organic pollutants and their cycling, the quantification of emissions from natural resource extraction, and the validation and optimization of satellite Earth observation (EO) data streams. In this paper we introduce the iCUPE project and summarize initial results arising out of the integration of comprehensive in situ observations, satellite remote sensing, and multi-scale modeling in the Arctic context.
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Qi, L., Vogel, A., Esmaeilirad, S., Cao, L., Zheng, J., Jaffrezo, J., et al. (2020). A 1-year characterization of organic aerosol composition and sources using an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF). Atmospheric Chemistry And Physics, 20(13), 7875–7893.
Abstract: The aerosol mass spectrometer (AMS), combined with statistical methods such as positive matrix factorization (PMF), has greatly advanced the quantification of primary organic aerosol (POA) sources and total secondary organic aerosol (SOA) mass. However, the use of thermal vaporization and electron ionization yields extensive thermal decomposition and ionization-induced fragmentation, which limit chemical information needed for SOA source apportionment. The recently developed extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) provides mass spectra of the organic aerosol fraction with a linear response to mass and no thermal decomposition or ionization-induced fragmentation. However, the costs and operational requirements of online instruments make their use impractical for long-term or spatially dense monitoring applications. This challenge was overcome for AMS measurements by measuring re-nebulized water extracts from ambient filter samples. Here, we apply the same strategy for EESI-TOF measurements of 1 year of 24 h filter samples collected approximately every fourth day throughout 2013 at an urban site. The nebulized water extracts were measured simultaneously with an AMS. The application of positive matrix factorization (PMF) to EESI-TOF spectra resolved seven factors, which describe water-soluble OA: less and more aged biomass burning aerosol (LABB(EESI) and MABB(EESI), respectively), cigarette-smoke-related organic aerosol, primary biological organic aerosol, biogenic secondary organic aerosol, and a summer mixed oxygenated organic aerosol factor. Seasonal trends and relative contributions of the EESI-TOF OA sources were compared with AMS source apportionment factors, measured water-soluble ions, cellulose, and meteorological data. Cluster analysis was utilized to identify key factor-specific ions based on PMF. Both LABB and MABB contribute strongly during winter. LABB is distinguished by very high signals from C6H10O5 (levoglucosan and isomers) and C8H12O6, whereas MABB is characterized by a large number of CxHyOz and CxHyOzN species of two distinct populations: one with low H : C and high O : C and the other with high H : C and low O : C. Two oxygenated summertime SOA sources were attributed to terpene-derived biogenic SOA, a major summertime aerosol source in central Europe. Furthermore, a primary biological organic aerosol factor was identified, which was dominated by plant-derived fatty acids and correlated with free cellulose. The cigarette-smoke-related factor contained a high contribution of nicotine and high abundance of organic nitrate ions with low m/z.
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Rigler, M., Drinovec, L., Lavric, G., Vlachou, A., Prevot, A., Jaffrezo, J., et al. (2020). The new instrument using a TC-BC (total carbon-black carbon) method for the online measurement of carbonaceous aerosols. Atmospheric Measurement Techniques, 13(8), 4333–4351.
Abstract: We present a newly developed total carbon analyzer (TCA08) and a method for online speciation of carbonaceous aerosol with a high time resolution. The total carbon content is determined by flash heating of a sample collected on a quartz-fiber filter with a time base between 20 min and 24 h. The limit of detection is approximately 0.3 ittg C, which corresponds to a concentration of 0.3 μg Cm-3 at a sample flow rate of 16.7 L min(-1) and a 1 h sampling time base. The concentration of particulate equivalent organic carbon (OC) is determined by subtracting black carbon concentration, concurrently measured optically by an Aethalometer (R) , from the total carbon concentration measured by the TCA08. The combination of the TCA08 and Aethalometer (AE33) is an easy-to-deploy and low-maintenance continuous measurement technique for the high-time-resolution determination of equivalent organic and elemental carbon (EC) in different particulate matter size fractions, which avoids pyrolytic correction and the need for high-purity compressed gases. The performance of this online method relative to the standardized off-line thermo-optical OC-EC method and respective instruments was evaluated during a winter field campaign at an urban background location in Ljubljana, Slovenia. The organic-matter-to-organic-carbon ratio obtained from the comparison with an aerosol chemical speciation monitor (ACSM) was OM/OC = 1.8, in the expected range.
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Samake, A., Bonin, A., Jaffrezo, J., Taberlet, P., Weber, S., Uzu, G., et al. (2020). High levels of primary biogenic organic aerosols are driven by only a few plant-associated microbial taxa. Atmospheric Chemistry And Physics, 20(9), 5609–5628.
Abstract: Primary biogenic organic aerosols (PBOAs) represent a major fraction of coarse organic matter (OM) in air. Despite their implication in many atmospheric processes and human health problems, we surprisingly know little about PBOA characteristics (i.e., composition, dominant sources, and contribution to airborne particles). In addition, specific primary sugar compounds (SCs) are generally used as markers of PBOAs associated with bacteria and fungi, but our knowledge of microbial communities associated with atmospheric particulate matter (PM) remains incomplete. This work aimed at providing a comprehensive understanding of the microbial fingerprints associated with SCs in PM10 (particles smaller than 10 μm) and their main sources in the surrounding environment (soils and vegetation). An intensive study was conducted on PM10 collected at a rural background site located in an agricultural area in France. We combined high-throughput sequencing of bacteria and fungi with detailed physicochemical characterizations of PM10, soil, and plant samples and monitored meteorological and agricultural activities throughout the sampling period. Results show that in summer SCs in PM10 are a major contributor of OM in air, representing 0.8 % to 13.5 % of OM mass. SC concentrations are clearly determined by the abundance of only a few specific airborne fungal and bacterial taxa. The temporal fluctuations in the abundance of only four predominant fungal genera, namely Cladosporium, Alternaria, Sporobolomyces, and Dioszegia, reflect the temporal dynamics in SC concentrations. Among bacterial taxa, the abundance of only Massilia, Pseudomonas, Frigoribacterium, and Sphingomonas is positively correlated with SC species. These microbes are significantly enhanced in leaf over soil samples. Interestingly, the overall community structure of bacteria and fungi are similar within PM10 and leaf samples and significantly distinct between PM10 and soil samples, indicating that surrounding vegetation is the major source of SC-associated microbial taxa in PM10 in this rural area of France.
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Slemr, F., Martin, L., Labuschagne, C., Mkololo, T., Angot, H., Magand, O., et al. (2020). Atmospheric mercury in the Southern Hemisphere – Part 1: Trend and inter-annual variations in atmospheric mercury at Cape Point, South Africa, in 2007-2017, and on Amsterdam Island in 2012-2017. Atmospheric Chemistry And Physics, 20(13), 7683–7692.
Abstract: The Minamata Convention on Mercury (Hg) entered into force in 2017, committing its 116 parties (as of January 2019) to curb anthropogenic emissions. Monitoring of atmospheric concentrations and trends is an important part of the effectiveness evaluation of the convention. A few years ago (in 2017) we reported an increasing trend in atmospheric Hg concentrations at the Cape Point Global Atmosphere Watch (GAW) station in South Africa (34.3535 degrees S, 18.4897 degrees E) for the 2007-2015 period. With 2 more years of measurements at Cape Point and the 2012-2017 data from Amsterdam Island (37.7983 degrees S, 77.5378 degrees E) in the remote southern Indian Ocean, a more complex picture emerges: at Cape Point the upward trend for the 2007-2017 period is still significant, but no trend or a slightly downward trend was detected for the period 2012-2017 at both Cape Point and Amsterdam Island. The upward trend at Cape Point is driven mainly by the Hg concentration minimum in 2009 and maxima in 2014 and 2012. Using ancillary data on Rn-222, CO, O-3, CO2, and CH4 from Cape Point and Amsterdam Island, the possible reasons for the trend and its change are investigated. In a companion paper this analysis is extended for the Cape Point station by calculations of source and sink regions using backward-trajectory analysis.
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Sommar, J., Osterwalder, S., & Zhu, W. (2020). Recent advances in understanding and measurement of Hg in the environment: Surface-atmosphere exchange of gaseous elemental mercury (Hg-0). Science Of The Total Environment, 721.
Abstract: The atmosphere is the major transport pathway for distribution of mercury (Hg) globally. Gaseous elemental mercury (GEM, hereafter Hg0) is the predominant form in both anthropogenic and natural emissions. Evaluation of the efficacy of reductions in emissions set by the UN's Minamata Convention (UN-MC) is critically dependent on the knowledge of the dynamics of the global Hg cycle. Of these dynamics including e.g. red-ox reactions, methylation-demethylation and dry-wet deposition, poorly constrained atmosphere-surface Hg-0 fluxes especially limit predictability of the timescales of its global biogeochemical cycle. This review focuses on Hg-0 flux field observational studies, namely the theory, applications, strengths, and limitations of the various experimental methodologies applied to gauge the exchange flux and decipher active sub-processes. We present an in-depth review, a comprehensive literature synthesis, and methodological and instrumentation advances for terrestrial and marine Hg0 flux studies in recent years. In particular, we outline the theory of a wide range of measurement techniques and detail the operational protocols. Today, the most frequently used measurement techniques to determine the net Hg-0 flux (>95% of the published flux data) are dynamic flux chambers for small-scale and micrometeorological approaches for large-scale measurements. Furthermore, top-down approaches based on Hg-0 concentration measurements have been applied as tools to better constrain Hg emissions as an independent way to e.g. challenge emission inventories. This review is an up-dated, thoroughly revised edition of Sommar et al. 2013 (DOI: 10.1080/10643389.2012.671733). To the tabulation of >100 cited flux studies 1988-2009 given in the former publication, we have here listed corresponding studies published during the last decade with a few exceptions (2008-2019). During that decade, Hg stable isotope ratios of samples involved in atmosphere-terrestrial interaction is at hand and provide in combination with concentration and/or flux measurements novel constraints to quantitatively and qualitatively assess the bi-directional Hg-0 flux. Recent efforts in the development of relaxed eddy accumulation and eddy covariance Hg-0 flux methods bear the potential to facilitate long-term, ecosystem-scale flux measurements to reduce the prevailing large uncertainties in Hg-0 flux estimates. Standardization of methods for Hg-0 flux measurements is crucial to investigate how land-use change and how climate warming impact ecosystem-specific Hg-0 sink-source characteristics and to validate frequently applied model parameterizations describing the regional and global scale Hg cycle. (C) 2020 Elsevier B.V. All rights reserved.
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Tignat-Perrier, R., Dommergue, A., Thollot, A., Magand, O., Amato, P., Joly, M., et al. (2020). Seasonal shift in airborne microbial communities. Science Of The Total Environment, 716.
Abstract: Microorganisms are ubiquitous in the atmosphere. Global investigations on the geographical and temporal distribution of airborne microbial communities are critical for identifying the sources and the factors shaping airborne communities. At mid-latitude sites, a seasonal shift in both the concentration and diversity of airborne microbial communities has been systematically observed in the planetary boundary layer. While the factors suspected of affecting this seasonal change were hypothesized (e.g., changes in the surface conditions, meteorological parameters and global air circulation), our understanding on how these factors influence the temporal variation of airborne microbial communities, especially at the microbial taxon level, remains limited. Here, we investigated the distribution of both airborne bacterial and fungal communities on a weekly basis over more than one year at the mid-latitude and continental site of puy de Dame (France; +1465 m altitude above sea level). The seasonal shift in microbial community structure was likely correlated to the seasonal changes in the characteristics of puy de DOme's landscape (croplands and natural vegetation). The airborne microbial taxa that were the most affected by seasonal changes trended differently throughout the seasons in relation with their trophic mode. In addition, the windy and variable local meteorological conditions found at puy de Mine were likely responsible for the intraseasonal variability observed in the composition of airborne microbial communities. (C) 2020 Elsevier B.V. All rights reserved.
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Tignat-Perrier, R., Dommergue, A., Thollot, A., Magand, O., Vogel, T., & Larose, C. (2020). Microbial functional signature in the atmospheric boundary layer. Biogeosciences, 17(23), 6081–6095.
Abstract: Microorganisms are ubiquitous in the atmosphere, and some airborne microbial cells were shown to be particularly resistant to atmospheric physical and chemical conditions (e.g., ultraviolet – UV – radiation, desiccation and the presence of radicals). In addition to surviving, some cultivable microorganisms of airborne origin were shown to be able to grow on atmospheric chemicals in laboratory experiments. Metagenomic investigations have been used to identify specific signatures of microbial functional potential in different ecosystems. We conducted a comparative metagenomic study on the overall microbial functional potential and specific metabolic and stress-related microbial functions of atmospheric microorganisms in order to determine whether airborne microbial communities possess an atmosphere-specific functional potential signature as compared to other ecosystems (i.e., soil, sediment, snow, feces, surface seawater etc.). In the absence of a specific atmospheric signature, the atmospheric samples collected at nine sites around the world were similar to their underlying ecosystems. In addition, atmospheric samples were characterized by a relatively high proportion of fungi. The higher proportion of sequences annotated as genes involved in stress-related functions (i.e., functions related to the response to desiccation, UV radiation, oxidative stress etc.) resulted in part from the high concentrations of fungi that might resist and survive atmospheric physical stress better than bacteria.
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Tignat-Perrier, R., Dommergue, A., Thollot, A., Magand, O., Vogel, T., & Larose, C. (2020). Microbial functional signature in the atmospheric boundary layer. Biogeosciences, 17(23), 6081–6095.
Abstract: Microorganisms are ubiquitous in the atmosphere, and some airborne microbial cells were shown to be particularly resistant to atmospheric physical and chemical conditions (e.g., ultraviolet – UV – radiation, desiccation and the presence of radicals). In addition to surviving, some cultivable microorganisms of airborne origin were shown to be able to grow on atmospheric chemicals in laboratory experiments. Metagenomic investigations have been used to identify specific signatures of microbial functional potential in different ecosystems. We conducted a comparative metagenomic study on the overall microbial functional potential and specific metabolic and stress-related microbial functions of atmospheric microorganisms in order to determine whether airborne microbial communities possess an atmosphere-specific functional potential signature as compared to other ecosystems (i.e., soil, sediment, snow, feces, surface seawater etc.). In the absence of a specific atmospheric signature, the atmospheric samples collected at nine sites around the world were similar to their underlying ecosystems. In addition, atmospheric samples were characterized by a relatively high proportion of fungi. The higher proportion of sequences annotated as genes involved in stress-related functions (i.e., functions related to the response to desiccation, UV radiation, oxidative stress etc.) resulted in part from the high concentrations of fungi that might resist and survive atmospheric physical stress better than bacteria.
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Tignat-Perrier, R., Dommergue, A., Vogel, T., & Larose, C. (2020). Microbial Ecology of the Planetary Boundary Layer. Atmosphere, 11(12).
Abstract: Aerobiology is a growing research area that covers the study of aerosols with a biological origin from the air that surrounds us to space through the different atmospheric layers. Bioaerosols have captured a growing importance in atmospheric process-related fields such as meteorology and atmospheric chemistry. The potential dissemination of pathogens and allergens through the air has raised public health concern and has highlighted the need for a better prediction of airborne microbial composition and dynamics. In this review, we focused on the sources and processes that most likely determine microbial community composition and dynamics in the air that directly surrounds us, the planetary boundary layer. Planetary boundary layer microbial communities are a mix of microbial cells that likely originate mainly from local source ecosystems (as opposed to distant sources). The adverse atmospheric conditions (i.e., UV radiation, desiccation, presence of radicals, etc.) might influence microbial survival and lead to the physical selection of the most resistant cells during aerosolization and/or aerial transport. Future work should further investigate how atmospheric chemicals and physics influence microbial survival and adaptation in order to be able to model the composition of planetary boundary layer microbial communities based on the surrounding landscapes and meteorology.
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Tuzet, F., Dumont, M., Picard, G., Lamare, M., Voisin, D., Nabat, P., et al. (2020). Quantification of the radiative impact of light-absorbing particles during two contrasted snow seasons at Col du Lautaret (2058ma.s.l., French Alps). Cryosphere, 14(12), 4553–4579.
Abstract: The presence of light-absorbing particles (LAPs) in snow leads to a decrease in short-wave albedo affecting the surface energy budget. However, the understanding of the impacts of LAPs is hampered by the lack of dedicated datasets, as well as the scarcity of models able to represent the interactions between LAPs and snow metamorphism. The present study aims to address both these limitations by introducing a survey of LAP concentrations over two snow seasons in the French Alps and an estimation of their impacts based on the Crocus snowpack model that represents the complex interplays between LAP dynamics and snow metamorphism. First, a unique dataset collected at Col du Lautaret (2058ma.s.l., above sea level, French Alps) for the two snow seasons 2016-2017 and 2017-2018 is presented. This dataset consists of spectral albedo measurements, vertical profiles of snow specific surface area (SSA), density and concentrations of different LAP species. Spectral albedos are processed to estimate SSA and LAP absorption-equivalent concentrations near the surface of the snowpack. These estimates are then compared to chemical measurements of LAP concentrations and SSA measurements. Our dataset highlights, among others, large discrepancies between two measurement techniques of black carbon (BC) concentrations in snow (namely thermal-optical and laser-induced incandescence). Second, we present ensemble snowpack simulations of the multi-physics version of the detailed snowpack model Crocus, forced with in situ meteorological data, as well as dust and BC deposition fluxes from an atmospheric model. The temporal variations of near-surface LAP concentrations and SSA are most of the time correctly simulated. The simulated seasonal radiative forcing of LAPs is 33% higher for the 2017-2018 snow season than for the 2016-2017 one, highlighting a strong variability between these two seasons. However, the shortening of the snow season caused by LAPs is similar with 10 +/- 5 and 11 +/- 1 d for the first and the second snow seasons, respectively. This counter-intuitive result is attributed to two small snowfalls at the end of the first season and highlights the importance in accounting for meteorological conditions to correctly predict the impact of LAPs. The strong variability of season shortening caused by LAPs in the multi-physics ensemble for the first season (10 +/- 5 d) also points out the sensitivity of model-based estimations of LAP impact on modelling uncertainties of other processes. Finally, the indirect impact of LAPs (i.e. the enhancement of energy absorption due to the acceleration of the metamorphism by LAPs) is negligible for the 2 years considered here, which is contrary to what was found in previous studies for other sites.
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Wohlgemuth, L., Mclagan, D., Fluckiger, B., Vienneau, D., & Osterwalder, S. (2020). Concurrently Measured Concentrations of Atmospheric Mercury in Indoor (household) and Outdoor Air of Basel, Switzerland. Environmental Science & Technology Letters, 7(4), 234–239.
Abstract: Indoor air pollution can be a major health risk because urban populations spend up to 90% of their time in closed rooms. Gaseous elemental mercury (GEM) has not been measured as routinely as other indoor air pollutants due to the high costs and limited mobility of active Hg analyzers. However, household GEM concentrations may exceed Hg air quality guidelines as a result of potential indoor GEM sources like broken Hg thermometers. Here we deploy novel low-cost mercury passive air samplers (MerPAS) in 27 households (7 days) and at 14 outdoor locations (29-31 days) in Basel, Switzerland. Average Hg concentrations ranged from 2.0 to 10.8 ng m(-3) indoors and from 1.8 to 2.5 ng m(-3) outdoors. These results reveal that households are a net source of Hg to the urban atmosphere and exceed outdoor Hg levels by a factor of 2 on average. We estimated an average weekly intake rate of 0.01 μg of Hg/kg of body weight for adult residents in Basel, which is usually lower than Hg exposure of people with dental amalgam fillings. Our campaign demonstrates that air monitoring programs can easily be complemented by straightforward Hg measurements using MerPAS.
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Wohlgemuth, L., Osterwalder, S., Joseph, C., Kahmen, A., Hoch, G., Alewell, C., et al. (2020). A bottom-up quantification of foliar mercury uptake fluxes across Europe. Biogeosciences, 17(24), 6441–6456.
Abstract: The exchange of gaseous elemental mercury, Hg(0), between the atmosphere and terrestrial surfaces remains poorly understood mainly due to difficulties in measuring net Hg(0) fluxes on the ecosystem scale. Emerging evidence suggests foliar uptake of atmospheric Hg(0) to be a major deposition pathway to terrestrial surfaces. Here, we present a bottom-up approach to calculate Hg(0) uptake fluxes to aboveground foliage by combining foliar Hg uptake rates normalized to leaf area with species-specific leaf area indices. This bottom-up approach incorporates systematic variations in crown height and needle age. We analyzed Hg content in 583 foliage samples from six tree species at 10 European forested research sites along a latitudinal gradient from Switzerland to northern Finland over the course of the 2018 growing season. Foliar Hg concentrations increased over time in all six tree species at all sites. We found that foliar Hg uptake rates normalized to leaf area were highest at the top of the tree crown. Foliar Hg uptake rates decreased with needle age of multiyear-old conifers (spruce and pine). Average species-specific foliar Hg uptake fluxes during the 2018 growing season were 18 +/- 3 μg Hg m(-2) for beech, 26 +/- 5 μg Hg m(-2) for oak, 4 +/- 1 μg Hg m(-2) for pine and 11 +/- 1 μg Hg m(-)(2) for spruce. For comparison, the average Hg(II) wet deposition flux measured at 5 of the 10 research sites during the same period was 2.3 +/- 0.3 μg Hg m(-2), which was 4 times lower than the site-averaged foliar uptake flux of 10 +/- 3 μg Hg m(-2). Scaling up site-specific foliar uptake rates to the forested area of Europe resulted in a total foliar Hg uptake flux of approximately 20 +/- 3 Mg during the 2018 growing season. Considering that the same flux applies to the global land area of temperate forests, we estimate a foliar Hg uptake flux of 108 +/- 18 Mg. Our data indicate that foliar Hg uptake is a major deposition pathway to terrestrial surfaces in Europe. The bottom-up approach provides a promising method to quantify foliar Hg uptake fluxes on an ecosystem scale.
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Xie, Z., Wang, Z., Magand, O., Thollot, A., Ebinghaus, R., Mi, W., et al. (2020). Occurrence of legacy and emerging organic contaminants in snow at Dome C in the Antarctic. Science Of The Total Environment, 741.
Abstract: Concentrations of 9 organophosphate esters (OPEs), 16 perfluoroalkylated substances (PFASs) and 17 polycyclic aromatic hydrocarbons (PAHs) were investigated in surface snow samples collected at Dome C on the Antarctic Plateau in summer 2016. Tris(1-chloro-2-propyl) phosphate (TCPP), tris-(2-chloroethyl) phosphate (TCEP) and tri-n-butylphosphate (TnBP) were the dominant compounds of OPEs, with mean concentrations of 8157 +/- 4860, 1128 +/- 928 and 1232 +/- 1147 pg/L. Perfluorooctanoic acid (PFOA, mean: 358 +/- 71 pg/L) was the dominant compound of PFASs, and following by perfluoro-n-hexanoic acid (PFHxA, mean: 222 +/- 97 pg/L), perfluoro-n-heptanoic acid (PFHpA, 183 +/- 60 pg/L) and perfluoro-n-pentanoic acid (PFPeA, 175 +/- 105 pg/L). 2-(Heptafluoropropoxy)propanoic acid (HFPO-DA, mean: 9.2 +/- 2.6 pg/L) was determined in the Antarctic for the first time. Significantly positive correlations were observed between HFPO-DA and the short-chain PFASs, implying they have similar emission sources and long-range transport potential. High levels of 2-methylnaphthalene and 1-methylnaphthalene, as well as the ratios of PAH congeners indicated PAHs were attributable mostly to combustion origin. Occurrence and profiles of the indicators of OPEs, PFASs and PAHs, as well as air mass back-trajectory analysis provided direct evidences of human activities on Concordia station and posed obvious impacts on local environments in the Antarctic. Nevertheless, the exchange processes among different environmental matrices may drive the long-range transport and redistribution of the legacy and emerging Organic contaminants from coast to inland in the Antarctic. (C) 2020 The Authors. Published by Elsevier B.V.
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Zhang, Y., Albinet, A., Petit, J., Jacob, V., Chevrier, F., Gille, G., et al. (2020). Substantial brown carbon emissions from wintertime residential wood burning over France. Science Of The Total Environment, 743.
Abstract: Brown carbon (BrC) is known to absorb light at subvisible wavelengths but its optical properties and sources arc still poorly documented, leading to large uncertainties in climate studies. Here, we show its major wintertime contribution to total aerosol absorption at 370 nm (18-42%) at 9 different French sites. Moreover, an excellent correlation with levoglucosan (r(2) = 0.9 and slope = 22.2 at 370 nm), suggesting important contribution of wood burning emissions to ambient BrC aerosols in France. At all sites, BrC peaks were mainly observed during late evening, linking to local intense residential wood burning during this time period. Furthermore, the geographic origin analysis also highlighted the high potential contribution of local and/or small-regional emissions to BrC. Focusing on the Paris region, twice higher BrC mass absorption efficiency value was obtained for less oxidized biomass burning organic aerosols (BBOA) compared to more oxidized BBOA (e.g., about 4.9 +/- 0.2 vs. 2.0 +/- 0.1 m(2) g(-1), respectively, at 370 nm). Finally, the BBOA direct radiative effect was found to be 40% higher when these two BBOA fractions are treated as light-absorbing species, compared to the non-absorbing BBOA scenario. (C) 2020 The Authors. Published by Elsevier B.V.
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2019 |
Abbatt, J., Leaitch, W., Aliabadi, A., Bertram, A., Blanchet, J., Boivin-Rioux, A., et al. (2019). Overview paper: New insights into aerosol and climate in the Arctic. Atmospheric Chemistry And Physics, 19(4), 2527–2560.
Abstract: Motivated by the need to predict how the Arctic atmosphere will change in a warming world, this article summarizes recent advances made by the research consortium NETCARE (Network on Climate and Aerosols: Addressing Key Uncertainties in Remote Canadian Environments) that contribute to our fundamental understanding of Arctic aerosol particles as they relate to climate forcing. The overall goal of NETCARE research has been to use an interdisciplinary approach encompassing extensive field observations and a range of chemical transport, earth system, and biogeochemical models. Several major findings and advances have emerged from NETCARE since its formation in 2013. (1) Unexpectedly high summertime dimethyl sulfide (DMS) levels were identified in ocean water (up to 75 nM) and the overlying atmosphere (up to 1 ppbv) in the Canadian Arctic Archipelago (CAA). Furthermore, melt ponds, which are widely prevalent, were identified as an important DMS source (with DMS concentrations of up to 6nM and a potential contribution to atmospheric DMS of 20% in the study area). (2) Evidence of widespread particle nucleation and growth in the marine boundary layer was found in the CAA in the summertime, with these events observed on 41% of days in a 2016 cruise. As well, at Alert, Nunavut, particles that are newly formed and grown under conditions of minimal anthropogenic influence during the months of July and August are estimated to contribute 20% to 80% of the 30-50 nm particle number density. DMS-oxidation-driven nucleation is facilitated by the presence of atmospheric ammonia arising from seabird-colony emissions, and potentially also from coastal regions, tundra, and biomass burning. Via accumulation of secondary organic aerosol (SOA), a significant fraction of the new particles grow to sizes that are active in cloud droplet formation. Although the gaseous precursors to Arctic marine SOA remain poorly defined, the measured levels of common continental SOA precursors (isoprene and monoterpenes) were low, whereas elevated mixing ratios of oxygenated volatile organic compounds (OVOCs) were inferred to arise via processes involving the sea surface microlayer. (3) The variability in the vertical distribution of black carbon (BC) under both springtime Arctic haze and more pristine summertime aerosol conditions was observed. Measured particle size distributions and mixing states were used to constrain, for the first time, calculations of aerosol-climate interactions under Arctic conditions. Aircraft- and ground-based measurements were used to better establish the BC source regions that supply the Arctic via long-range transport mechanisms, with evidence for a dominant springtime contribution from eastern and southern Asia to the middle troposphere, and a major contribution from northern Asia to the surface. (4) Measurements of ice nucleating particles (INPs) in the Arctic indicate that a major source of these particles is mineral dust, likely derived from local sources in the summer and long-range transport in the spring. In addition, INPs are abundant in the sea surface microlayer in the Arctic, and possibly play a role in ice nucleation in the atmosphere when mineral dust concentrations are low. (5) Amongst multiple aerosol components, BC was observed to have the smallest effective deposition velocities to high Arctic snow (0.03 cm s(-1)).
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Bonvalot, L., Tuna, T., Fagault, Y., Sylvestre, A., Mesbah, B., Wortham, H., et al. (2019). Source apportionment of carbonaceous aerosols in the vicinity of a Mediterranean industrial harbor: A coupled approach based on radiocarbon and molecular tracers. Atmospheric Environment, 212, 250–261.
Abstract: Located in the Mediterranean Basin and close to Marseille (France), Fos-sur-Mer is situated in the vicinity of industrial harbor and agricultural lands. Its location makes it prone to mixed pollution contributions, combining the influence of residential, industrial, agricultural, maritime road and traffic sources. For this study, the origins of carbonaceous particles sampled over several months are investigated by a coupled approach based on analyses of radiocarbon (C-14), elemental to total carbon ratio (EC/TC) and various molecular tracers (levoglucosan, methoxyphenols, malic and glyceric acids), giving information about their background origins. Accelerator mass spectrometry with a gas ion source give the opportunity to quantify the fossil and non-fossil fractions for each individual sample, avoiding to pool them. Analyzing C-14 in micro-samples (down to a few μg of carbon) complements the approach based on chemical tracers, which are useful to identify sources, but insufficient to quantify accurately the modern and fossil carbon fractions. The measurements in about 30 samples collected during summer and fall/winter 2013, allow the detection of a strong seasonality of the pollution: the fall/winter PM2.5 fraction concentration equals to three times the summer concentration and we observe a significant fluctuation of the relative contributions of fossil and non-fossil fractions (f(NF) is approximate to 0.83 for fall/winter samples and approximate to 0.59 for summer samples). Significant correlations between C-14, levoglucosan and different methoxyphenols, allow the identification and quantification of a major influence of biomass burning emissions during fall and winter. Biomass burning organic carbon (OCBB) and elemental carbon (ECBB) contribute to 45% and 8% of the TC, respectively, whereas their total contribution is only 3% in summer samples. Biogenic emissions from the vegetation are the main sources of carbon during summer (approximate to 57%). Significant correlations between summer OCbio and malic acid and DL glyceric acid suggest a secondary origin for this fraction. The total fossil carbon concentration (ECF and OCF) from vehicular, shipping and industrial sources is constant throughout the year, which is compatible with intense road and maritime traffics and industrial activity during both seasons. Overall, our study based on C-14 and molecular tracers illustrates the power of a coupled approach in order to both identify and quantify biomass burning, biogenic, traffic and industrial sources of carbonaceous aerosols, forming a complex mix of background PM origins in a typical industrious harbor of the Mediterranean region.
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Bourgeois, I., Clement, J., Caillon, N., & Savarino, J. (2019). Foliar uptake of atmospheric nitrate by two dominant subalpine plants: insights from in situ triple-isotope analysis. New Phytologist, 223(4), 1784–1794.
Abstract: The significance of foliar uptake of nitrogen (N) compounds in natural conditions is not well understood, despite growing evidence of its importance to plant nutrition. In subalpine meadows, N-limitation fosters the dominance of specific subalpine plant species, which in turn ensures the provision of essential ecosystems services. Understanding how these plants absorb N and from which sources is important in predicting ecological consequences of increasing N deposition. Here, we investigate the sources of N to plants from subalpine meadows with distinct land-use history in the French Alps, using the triple isotopes (Delta O-17, delta O-18, and delta N-15) of plant tissue nitrate (NO3-). We use this approach to evaluate the significance of foliar uptake of atmospheric NO3- (NO3atm-). The foliar uptake of NO3atm- accounted for 4-16% of the leaf NO3- content, and contributed more to the leaf NO3- pool after peak biomass. Additionally, the gradual N-15 enrichment of NO3- from the soil to the leaves reflected the contribution of NO3atm- assimilation to plants' metabolism. The present study confirms that foliar uptake is a potentially important pathway for NO3atm- into subalpine plants. This is of major significance as N emissions (and deposition) are predicted to increase globally in the future.
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Calas, A., Uzu, G., Besombes, J., Martins, J., Redaelli, M., Weber, S., et al. (2019). Seasonal Variations and Chemical Predictors of Oxidative Potential (OP) of Particulate Matter (PM), for Seven Urban French Sites. Atmosphere, 10(11).
Abstract: Epidemiological studies suggest that the main part of chronic effects from air pollution is likely to be linked with particulate matter (PM). Oxidative potential (OP) of PM is gaining strong interest as a promising health exposure metric. This study combined atmospheric detailed composition results obtained for seven different urban background environments over France to examine any possible common feature in OP seasonal variations obtained using two assays (acid ascorbic (AA) and dithiothreitol (DTT)) along a large set of samples (N >700). A remarkable homogeneity in annual cycles was observed with a higher OP activity in wintertime at all investigated sites. Univariate correlations were used to link the concentrations of some major chemical components of PM and their OP. Four PM components were identified as OP predictors: OC, EC, monosaccharides and Cu. These species are notably emitted by road transport and biomass burning, targeting main sources probably responsible for the measured OP activity. The results obtained confirm that the relationship between OP and atmospheric pollutants is assay- and location-dependent and, thus, the strong need for a standardized test, or set of tests, for further regulation purposes.
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Charron, A., Polo-Rehn, L., Besombes, J., Golly, B., Buisson, C., Chanut, H., et al. (2019). Identification and quantification of particulate tracers of exhaust and non-exhaust vehicle emissions. Atmospheric Chemistry And Physics, 19(7), 5187–5207.
Abstract: In order to identify and quantify key species associated with non-exhaust emissions and exhaust vehicular emissions, a large comprehensive dataset of particulate species has been obtained thanks to simultaneous near-road and urban background measurements coupled with detailed traffic counts and chassis dynamometer measurements of exhaust emissions of a few in-use vehicles well-represented in the French fleet. Elemental carbon, brake-wear metals (Cu, Fe, Sb, Sn, Mn), n-alkanes (C19-C26), light-molecular-weight polycyclic aromatic hydrocarbons (PAHs; pyrene, fluoranthene, anthracene) and two hopanes (17 alpha 21 beta norhopane and 17 alpha 21 beta hopane) are strongly associated with the road traffic. Traffic-fleet emission factors have been determined for all of them and are consistent with most recent published equivalent data. When possible, light-duty- and heavy-duty-traffic emission factors are also determined In the absence of significant non-combustion emissions, light-duty-traffic emissions are in good agreement with emissions from chassis dynamometer measurements. Since recent measurements in Europe including those from this study are consistent, ratios involving copper (Cu/Fe and Cu/Sn) could be used as brake-wear emissions tracers as long as brakes with Cu remain in use. Near the Grenoble ring road, where the traffic was largely dominated by diesel vehicles in 2011 (70 %), the OC/EC ratio estimated for traffic emissions was around 0.4. Although the use of quantitative data for source apportionment studies is not straightforward for the identified organic molecular markers, their presence seems to well-characterize fresh traffic emissions.
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Chauvigne, A., Aliaga, D., Sellegri, K., Montoux, N., Krejci, R., Mocnik, G., et al. (2019). Biomass burning and urban emission impacts in the Andes Cordillera region based on in situ measurements from the Chacaltaya observatory, Bolivia (5240 m a.s.l.). Atmospheric Chemistry And Physics, 19(23), 14805–14824.
Abstract: This study documents and analyses a 4-year continuous record of aerosol optical properties measured at the Global Atmosphere Watch (GAW) station of Chacaltaya (CHC; 5240 m a.s.l.), in Bolivia. Records of particle light scattering and particle light absorption coefficients are used to investigate how the high Andean Cordillera is affected by both long-range transport and by the fast-growing agglomeration of La Paz-El Alto, located approximately 20 km away and 1.5 km below the sampling site. The extended multiyear record allows us to study the properties of aerosol particles for different air mass types, during wet and dry seasons, also covering periods when the site was affected by biomass burning in the Bolivian lowlands and the Amazon Basin. The absorption, scattering, and extinction coefficients (median annual values of 0.74, 12.14, and 12.96 Mm(-1) respectively) show a clear seasonal variation with low values during the wet season (0.57, 7.94, and 8.68 Mm(-1) respectively) and higher values during the dry season (0.80, 11.23, and 14.51 Mm(-1) respectively). The record is driven by variability at both seasonal and diurnal scales. At a diurnal scale, all records of intensive and extensive aerosol properties show a pronounced variation (daytime maximum, night-time minimum), as a result of the dynamic and convective effects. The particle light absorption, scattering, and extinction coefficients are on average 1.94, 1.49, and 1.55 times higher respectively in the turbulent thermally driven conditions than the more stable conditions, due to more efficient transport from the boundary layer. Retrieved intensive optical properties are significantly different from one season to the other, reflecting the changing aerosol emission sources of aerosol at a larger scale. Using the wavelength dependence of aerosol particle optical properties, we discriminated between contributions from natural (mainly mineral dust) and anthropogenic (mainly biomass burning and urban transport or industries) emissions according to seasons and local circulation. The main sources influencing measurements at CHC are from the urban area of La Paz-El Alto in the Altiplano and from regional biomass burning in the Amazon Basin. Results show a 28 % to 80 % increase in the extinction coefficients during the biomass burning season with respect to the dry season, which is observed in both tropospheric dynamic conditions. From this analysis, long-term observations at CHC provide the first direct evidence of the impact of biomass burning emissions of the Amazon Basin and urban emissions from the La Paz area on atmospheric optical properties at a remote site all the way to the free troposphere.
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Crouzet, C., Wilhelm, B., Sabatier, P., Demory, F., Thouveny, N., Pignol, C., et al. (2019). Palaeomagnetism for chronologies of recent alpine lake sediments: successes and limits. Journal Of Paleolimnology, 62(3), 259–278.
Abstract: Chronologies of lake-sediment records covering the last centuries to millennia are usually based on both short-lived radionuclides and radiocarbon dating. However, beyond the range of short-lived radionuclides, age model accuracy often suffers from large radiocarbon uncertainties. For high-altitude records, this issue is even more prominent as terrestrial plant fragments for radiocarbon dating are often lacking due to the sparse vegetation in such environments. In this study, we evaluate the potential of the geomagnetic field secular variations as a complementary tool to establish more robust age-depth relationships. Our palaeomagnetic study, applied to five high-altitude lakes from the western European Alps, first shows that recent unconsolidated sediments can carry stable remanent magnetization. The analysis of the magnetic parameters indicates that low-coercivity pseudo-single domain magnetite grains carry the natural magnetization. Nevertheless, the quality of palaeomagnetic secular variation records varies from one lake to another. This quality can be illustrated through the calculation of the declination/inclination maximum angular variations and their comparison to the expected value. Compared with available models, the declination variations are usually too large and the inclination too high. We discuss the validity of palaeosecular variation (PSV) of the Earth's magnetic field regarding rock magnetism, magnetization processes and possible deformation during coring. From a magnetic point of view, the quality of data is variable, but the characteristic remanent magnetization direction is consistent at site level between neighbouring lakes and with the reference curve, suggesting that geomagnetic field secular variations are approximately recorded. Finally, we attempt to correlate the declination/inclination variations of the characteristic remanent magnetization measured in the five records to the reference geomagnetic model to provide additional chronological markers for age-depth modelling. These stratigraphic chrono-markers appear in systematic agreement with our previous chronological data and enable a reduction of dating uncertainties up to 30% when including these chrono-markers in the age-depth modelling. This agreement supports the interpretation that PSV may have been recorded more or less accurately depending on the studied lake. Therefore, coupled with a comprehensive understanding through other analysis (sedimentology, dating, geochemistry), PSV can be used to improve the age models in the more favourable cases.
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Daellenbach, K., Kourtchev, I., Vogel, A., Bruns, E., Jiang, J., Petaja, T., et al. (2019). Impact of anthropogenic and biogenic sources on the seasonal variation in the molecular composition of urban organic aerosols: a field and laboratory study using ultra-high-resolution mass spectrometry. Atmospheric Chemistry And Physics, 19(9), 5973–5991.
Abstract: This study presents the molecular composition of organic aerosol (OA) using ultra-high-resolution mass spectrometry (Orbitrap) at an urban site in Central Europe (Zurich, Switzerland). Specific source spectra were also analysed, including samples representative of woodburning emissions from Alpine valleys during wood-burning pollution episodes and smog chamber investigations of woodsmoke, as well as samples from Hyytiala, which were strongly influenced by biogenic secondary organic aerosol. While samples collected during winter in Alpine valleys have a molecular composition remarkably similar to fresh laboratory wood-burning emissions, winter samples from Zurich are influenced by more aged wood-burning emissions. In addition, other organic aerosol emissions or formation pathways seem to be important at the latter location in winter. Samples from Zurich during summer are similar to those collected in Hyytiala and are predominantly impacted by oxygenated compounds with an H/C ratio of 1.5, indicating the importance of biogenic precursors for secondary organic aerosol (SOA) formation at this location (summertime Zurich – carbon number 7.6, O : C 0.7; Hyytiala – carbon number 10.5, O : C 0.57). We could explain the strong seasonality of the molecular composition at a typical European site by primary and aged wood-burning emissions and biogenic secondary organic aerosol formation during winter and summer, respectively. Results presented here likely explain the rather constant seasonal predominance of non-fossil organic carbon at European locations.
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Dommergue, A., Amato, P., Tignat-Perrier, R., Magand, O., Thollot, A., Joly, M., et al. (2019). Methods to Investigate the Global Atmospheric Microbiome. Frontiers In Microbiology, 10.
Abstract: The interplay between microbes and atmospheric physical and chemical conditions is an open field of research that can only be fully addressed using multidisciplinary approaches. The lack of coordinated efforts to gather data at representative temporal and spatial scales limits aerobiology to help understand large scale patterns of global microbial biodiversity and its causal relationships with the environmental context. This paper presents the sampling strategy and analytical protocols developed in order to integrate different fields of research such as microbiology, -omics biology, atmospheric chemistry, physics and meteorology to characterize atmospheric microbial life. These include control of chemical and microbial contaminations from sampling to analysis and identification of experimental procedures for characterizing airborne microbial biodiversity and its functioning from the atmospheric samples collected at remote sites from low cell density environments. We used high-volume sampling strategy to address both chemical and microbial composition of the atmosphere, because it can help overcome low aerosol and microbial cell concentrations. To account for contaminations, exposed and unexposed control filters were processed along with the samples. We present a method that allows for the extraction of chemical and biological data from the same quartz filters. We tested different sampling times, extraction kits and methods to optimize DNA yield from filters. Based on our results, we recommend supplementary sterilization steps to reduce filter contamination induced by handling and transport. These include manipulation under laminar flow hoods and UV sterilization. In terms of DNA extraction, we recommend a vortex step and a heating step to reduce binding to the quartz fibers of the filters. These steps have led to a 10-fold increase in DNA yield, allowing for downstream omics analysis of air samples. Based on our results, our method can be integrated into pre-existing long-term monitoring field protocols for the atmosphere both in terms of atmospheric chemistry and biology. We recommend using standardized air volumes and to develop standard operating protocols for field users to better control the operational quality.
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Fourteau, K., Martinerie, P., Fain, X., Schaller, C., Tuckwell, R., Lowe, H., et al. (2019). Multi-tracer study of gas trapping in an East Antarctic ice core. Cryosphere, 13(12), 3383–3403.
Abstract: We study a firn and ice core drilled at the new “Lock-In” site in East Antarctica, located 136 km away from Concordia station towards Dumont d'Urville. High-resolution chemical and physical measurements were performed on the core, with a particular focus on the trapping zone of the firn where air bubbles are formed. We measured the air content in the ice, closed and open porous volumes in the firn, firn density, firn liquid conductivity, major ion concentrations, and methane concentrations in the ice. The closed and open porosity volumes of firn samples were obtained using the two independent methods of pycnometry and tomography, which yield similar results. The measured increase in the closed porosity with density is used to estimate the air content trapped in the ice with the aid of a simple gas-trapping model. Results show a discrepancy, with the model trapping too much air. Experimental errors have been considered but do not explain the discrepancy between the model and the observations. The model and data can be reconciled with the introduction of a reduced compression of the closed porosity compared to the open porosity. Yet, it is not clear if this limited compression of closed pores is the actual mechanism responsible for the low amount of air in the ice. High-resolution density measurements reveal the presence of strong layering, manifesting itself as centimeter-scale variations. Despite this heterogeneous stratification, all layers, including the ones that are especially dense or less dense compared to their surroundings, display similar pore morphology and closed porosity as a function of density. This implies that all layers close in a similar way, even though some close in advance or later compared to the bulk firn. Investigation of the chemistry data suggests that in the trapping zone, the observed stratification is partly related to the presence of chemical impurities.
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Gautier, E., Savarino, J., Hoek, J., Erbland, J., Caillon, N., Hattori, S., et al. (2019). 2600-years of stratospheric volcanism through sulfate isotopes. Nature Communications, 10.
Abstract: High quality records of stratospheric volcanic eruptions, required to model past climate variability, have been constructed by identifying synchronous (bipolar) volcanic sulfate horizons in Greenland and Antarctic ice cores. Here we present a new 2600-year chronology of stratospheric volcanic events using an independent approach that relies on isotopic signatures (Delta S-33 and in some cases Delta O-17) of ice core sulfate from five closely-located ice cores from Dome C, Antarctica. The Dome C stratospheric reconstruction provides independent validation of prior reconstructions. The isotopic approach documents several high-latitude stratospheric events that are not bipolar, but climatically-relevant, and diverges deeper in the record revealing tropospheric signals for some previously assigned bipolar events. Our record also displays a collapse of the Delta O-17 anomaly of sulfate for the largest volcanic eruptions, showing a further change in atmospheric chemistry induced by large emissions. Thus, the refinement added by considering both isotopic and bipolar correlation methods provides additional levels of insight for climate-volcano connections and improves ice core volcanic reconstructions.
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Gautier, E., Savarino, J., Hoek, J., Erbland, J., Caillon, N., Hattori, S., et al. (2019). 2600-years of stratospheric volcanism through sulfate isotopes (vol 10, 466, 2019). Nature Communications, 10.
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Geng, L., Savarino, J., Caillon, N., Gautier, E., Farquhar, J., Dottin, J., et al. (2019). Intercomparison measurements of two S-33-enriched sulfur isotope standards. Journal Of Analytical Atomic Spectrometry, 34(6), 1263–1271.
Abstract: Despite widespread applications of sulfur isotope mass-independent fractionation (MIF) signals for probing terrestrial and extra-terrestrial environments, there has been no international sulfur isotope reference material available for normalization of Delta S-33 and Delta S-36 data. International reference materials to anchor isotope values are useful for interlaboratory data comparisons and are needed to evaluate, e.g., whether issues exist associated with blanks and mass spectrometry when using different analytical approaches. We synthesized two sodium sulfate samples enriched in S-33 with different magnitudes, and termed them S-MIF-1 and S-MIF-2, respectively. The sulfur isotopic compositions of these two samples were measured in five different laboratories using two distinct techniques to place them on the V-CDT scale for delta S-34 and a provisional V-CDT scale for Delta S-33 and Delta S-36. We obtained average delta S-34 values of S-MIF-1 = 10.26 +/- 0.22 parts per thousand and S-MIF-2 = 21.53 +/- 0.26 parts per thousand (1 sigma, versus V-CDT). The average Delta S-33 and Delta S-36 values of S-MIF-1 were determined to be 9.54 +/- 0.09 parts per thousand and -0.11 +/- 0.25 parts per thousand, respectively, while the average Delta S-33 and Delta S-36 values of S-MIF-2 are 11.39 +/- 0.08 parts per thousand and -0.33 +/- 0.13 parts per thousand (1 sigma, versus V-CDT). The lack of variation among the interlaboratory isotopic values suggests sufficient homogeneity of S-MIF-1 and S-MIF-2, especially for Delta S-33. Although additional measurements may be needed to ensure the accuracy of the isotopic compositions of S-MIF-1 and S-MIF-2, they can serve as working standards for routine Delta S-33 analysis to improve data consistency, and have the potential to serve as secondary sulfur isotope reference materials to address issues such as scale contraction/expansion and for normalization and reporting of Delta S-33 and Delta S-36 between laboratories. For the same reasons as listed for sulfur isotopes, the same standards were also artificially enriched in O-17. The calibration is still in progress but first estimations gave Delta O-17 = 3.3 +/- 0.3 parts per thousand with unassigned delta O-18.
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Golly, B., Waked, A., Weber, S., Samake, A., Jacob, V., Conil, S., et al. (2019). Organic markers and OC source apportionment for seasonal variations of PM2.5 at 5 rural sites in France. Atmospheric Environment, 198, 142–157.
Abstract: The chemical characterization of PM2.5 was conducted at 5 rural background sites in France for the year 2013. Chemical analysis of daily samples every sixth day included the measurements of organic carbon (OC), elemental carbon (EC), ionic species and several specific primary and secondary organic tracers such as levoglucosan, polyols, methane sulfonic acid (MSA) and oxalate. The sampling sites were spatially distributed in order to be representative of the French atmospheric background. The results showed well identified temporal variations common to all the 5 sampling sites, covering a large fraction of France. During winter, concentrations of the biomass burning marker levoglucosan are significantly increased with high synchronous temporal pattern, indicating the strong impact of this source at a regional scale. During summer, concentrations of primary biogenic markers such as polyols (arabitol, mannitol) increase due to higher biological activities while oxalate contributions to OC also increases, attributed to ageing processes. The sources of primary organic aerosol are investigated using mono-tracer approaches based on these compounds. Results indicate that the relative contributions of wood burning to OC are very high, reaching an average value of 90% during winter for some of the rural sites. Terrestrial primary biogenic organic fraction is significant in summer and fall with a monthly contribution ranging from 4.5 to 9.5% of OC in PM2.5. A synchronous increase is also observed for secondary organic tracers (MSA, oxalic acid) during warm period confirming the influence on the large scale of these compounds that can account for 10-20% and 5-7% of the OC mass, respectively.
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Hagenmuller, P., Flin, F., Dumont, M., Tuzet, F., Peinke, I., Lapalus, P., et al. (2019). Motion of dust particles in dry snow under temperature gradient metamorphism. Cryosphere, 13(9), 2345–2359.
Abstract: The deposition of light-absorbing particles (LAPs) such as mineral dust and black carbon on snow is responsible for a highly effective climate forcing, through darkening of the snow surface and associated feedbacks. The interplay between post-depositional snow transformation (metamorphism) and the dynamics of LAPs in snow remains largely unknown. We obtained time series of X-ray tomography images of dust-contaminated samples undergoing dry snow metamorphism at around -2 degrees C. They provide the first observational evidence that temperature gradient metamorphism induces dust particle motion in snow, while no movement is observed under isothermal conditions. Under temperature gradient metamorphism, dust particles can enter the ice matrix due to sublimation-condensation processes and spread down mainly by falling into the pore space. Overall, such motions might reduce the radiative impact of dust in snow, in particular in arctic regions where temperature gradient metamorphism prevails.
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Hodnebrog, O., Marelle, L., Alterskjaer, K., Wood, R., Ludwig, R., Fischer, E., et al. (2019). Intensification of summer precipitation with shorter time-scales in Europe. Environmental Research Letters, 14(12).
Abstract: While daily extreme precipitation intensities increase with global warming on average at approximately the same rate as the availability of water vapor (-7%/ C), a debated topic is whether sub-daily extremes increase more. Modelling at convection-permitting scales has been deemed necessary to reproduce extreme summer precipitation at local scale. Here we analyze multi-model ensembles and apply a 3 km horizontal resolution model over four regions across Europe (S. Norway, Denmark, Benelux and Albania) and find very good agreement with observed daily and hourly summer precipitation extremes. Projections show that daily extreme precipitation intensifies compared to the mean in all regions and across a wide range of models and resolutions. Hourly and 10 min extremes intensify at a higher rate in nearly all regions. Unlike most recent studies, we do not find sub-daily precipitation extremes increasing much more than 7%/ C, even for sub-hourly extremes, but this maybe due to robust summer drying over large parts of Europe. However, the absolute strongest local daily precipitation event in a 20 year period will increase by 10%-20%/ C. At the same time, model projections strongly indicate that summer drying will be more pronounced for extremely dry years.
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Irish, V., Hanna, S., Willis, M., China, S., Thomas, J., Wentzell, J., et al. (2019). Ice nucleating particles in the marine boundary layer in the Canadian Arctic during summer 2014. Atmospheric Chemistry And Physics, 19(2), 1027–1039.
Abstract: Ice nucleating particles (INPs) in the Arctic can influence climate and precipitation in the region; yet our understanding of the concentrations and sources of INPs in this region remain uncertain. In the following, we (1) measured concentrations of INPs in the immersion mode in the Canadian Arctic marine boundary layer during summer 2014 on board the CCGS Amundsen, (2) determined ratios of surface areas of mineral dust aerosol to sea spray aerosol, and (3) investigated the source region of the INPs using particle dispersion modelling. Average concentrations of INPs at 15, -20, and 25 degrees C were 0.005, 0.044, and 0.154 L-1, respectively. These concentrations fall within the range of INP concentrations measured in other marine environments. For the samples investigated the ratio of mineral dust surface area to sea spray surface area ranged from 0.03 to 0.09. Based on these ratios and the ice active surface site densities of mineral dust and sea spray aerosol determined in previous laboratory studies, our results suggest that mineral dust is a more important contributor to the INP population than sea spray aerosol for the samples analysed. Based on particle dispersion modelling, the highest concentrations of INPs were often associated with lower-latitude source regions such as the Hudson Bay area, eastern Greenland, or north-western continental Canada. On the other hand, the lowest concentrations were often associated with regions further north of the sampling sites and over Baffin Bay. A weak correlation was observed between INP concentrations and the time the air mass spent over bare land, and a weak negative correlation was observed between INP concentrations and the time the air mass spent over ice and open water. These combined results suggest that mineral dust from local sources is an important contributor to the INP population in the Canadian Arctic marine boundary layer during summer 2014.
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Jacobi, H., Obleitner, F., Da Costa, S., Ginot, P., Eleftheriadis, K., Aas, W., et al. (2019). Deposition of ionic species and black carbon to the Arctic snowpack: combining snow pit observations with modeling. Atmospheric Chemistry And Physics, 19(15), 10361–10377.
Abstract: Although aerosols in the Arctic have multiple and complex impacts on the regional climate, their removal due to deposition is still not well quantified. We combined meteorological, aerosol, precipitation, and snowpack observations with simulations to derive information about the deposition of sea salt components and black carbon (BC) from November 2011 to April 2012 to the Arctic snowpack at two locations close to Ny-angstrom lesund, Svalbard. The dominating role of sea salt and the contribution of dust for the composition of atmospheric aerosols were reflected in the seasonal composition of the snowpack. The strong alignment of the concentrations of the major sea salt components in the aerosols, the precipitation, and the snowpack is linked to the importance of wet deposition for transfer from the atmosphere to the snowpack. This agreement was less strong for monthly snow budgets and deposition, indicating important relocation of the impurities inside the snowpack after deposition. Wet deposition was less important for the transfer of nitrate, non-sea-salt sulfate, and BC to the snow during the winter period. The average BC concentration in the snowpack remains small, with a limited impact on snow albedo and melting. Nevertheless, the observations also indicate an important redistribution of BC in the snowpack, leading to layers with enhanced concentrations. The complex behavior of bromide due to modifications during sea salt aerosol formation and remobilization in the atmosphere and in the snow were not resolved because of the lack of bromide measurements in aerosols and precipitation.
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Mimeau, L., Esteves, M., Zin, I., Jacobi, H., Brun, F., Wagnon, P., et al. (2019). Quantification of different flow components in a high-altitude glacierized catchment (Dudh Koshi, Himalaya): some cryospheric-related issues. Hydrology And Earth System Sciences, 23(9), 3969–3996.
Abstract: In a context of climate change and water demand growth, understanding the origin of water flows in the Himalayas is a key issue for assessing the current and future water resource availability and planning the future uses of water in downstream regions. Two of the main issues in the hydrology of high-altitude glacierized catchments are (i) the limited representation of cryospheric processes controlling the evolution of ice and snow in distributed hydrological models and (ii) the difficulty in defining and quantifying the hydrological contributions to the river outflow. This study estimates the relative contribution of rainfall, glaciers, and snowmelt to the Khumbu River streamflow (Upper Dudh Koshi, Nepal, 146 km(2), 43% glacierized, elevation range from 4260 to 8848 ma.s.l.) as well as the seasonal, daily, and sub-daily variability during the period 2012-2015 by using the DHSVM-GDM (Distributed Hydrological Soil Vegetation Model – Glaciers Dynamics Model) physically based glacio-hydrological model. The impact of different snow and glacier parameterizations was tested by modifying the snow albedo parameterization, adding an avalanche module, adding a reduction factor for the melt of debris-covered glaciers, and adding a conceptual englacial storage. The representation of snow, glacier, and hydrological processes was evaluated using three types of data (MODIS satellite images, glacier mass balances, and in situ discharge measurements). The relative flow components were estimated using two different definitions based on the water inputs and contributing areas. The simulated hydrological contributions differ not only depending on the used models and implemented processes, but also on different definitions of the estimated flow components. In the presented case study, ice melt and snowmelt contribute each more than 40% to the annual water inputs and 69% of the annual stream flow originates from glacierized areas. The analysis of the seasonal contributions highlights that ice melt and snowmelt as well as rain contribute to monsoon flows in similar proportions and that winter outflow is mainly controlled by the release from the englacial water storage. The choice of a given parametrization for snow and glacier processes, as well as their relative parameter values, has a significant impact on the simulated water balance: for instance, the different tested parameterizations led to ice melt contributions ranging from 42% to 54 %. The sensitivity of the model to the glacier inventory was also tested, demonstrating that the uncertainty related to the glacierized surface leads to an uncertainty of 20% for the simulated ice melt component.
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Orthous-Daunay, F., Wolters, C., Flandinet, L., Vuitton, V., Beck, P., Bonal, L., et al. (2019). Comparison Of Molecular Complexity Between Chondrites, Martian Meteorite And Lunar Soils. Meteoritics & Planetary Science, 54.
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Pinto, B., Maccario, L., Dommergue, A., Vogel, T., & Larose, C. (2019). Do Organic Substrates Drive Microbial Community Interactions in Arctic Snow? Frontiers In Microbiology, 10.
Abstract: The effect of nutrients on microbial interactions, including competition and collaboration, has mainly been studied in laboratories, but their potential application to complex ecosystems is unknown. Here, we examined the effect of changes in organic acids among other parameters on snow microbial communities in situ over 2 months. We compared snow bacterial communities from a low organic acid content period to that from a higher organic acid period. We hypothesized that an increase in organic acids would shift the dominant microbial interaction from collaboration to competition. To evaluate microbial interactions, we built taxonomic co-variance networks from OTUs obtained from 16S rRNA gene sequencing. In addition, we tracked marker genes of microbial cooperation (plasmid backbone genes) and competition (antibiotic resistance genes) across both sampling periods in metagenomes and metatranscriptomes. Our results showed a decrease in the average connectivity of the network during late spring compared to the early spring that we interpreted as a decrease of cooperation. This observation was strengthened by the significantly more abundant plasmid backbone genes in the metagenomes from the early spring. The modularity of the network from the late spring was also found to be higher than the one from the early spring, which is another possible indicator of increased competition. Antibiotic resistance genes were significantly more abundant in the late spring metagenomes. In addition, antibiotic resistance genes were also positively correlated to the organic acid concentration of the snow across both seasons. Snow organic acid content might be responsible for this change in bacterial interactions in the Arctic snow community.
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Samake, A., Jaffrezo, J., Favez, O., Weber, S., Jacob, V., Albinet, A., et al. (2019). Polyols and glucose particulate species as tracers of primary biogenic organic aerosols at 28 French sites. Atmospheric Chemistry And Physics, 19(5), 3357–3374.
Abstract: A growing number of studies are using specific primary sugar species, such as sugar alcohols or primary saccharides, as marker compounds to characterize and apportion primary biogenic organic aerosols (PBOAs) in the atmosphere. To better understand their annual cycles, as well as their spatiotemporal abundance in terms of concentrations and sources, we conducted a large study focusing on three major atmospheric primary sugar compounds (i.e., arabitol, mannitol, and glucose) measured in various environmental conditions for about 5300 filter samples collected at 28 sites in France. Our results show significant atmospheric concentrations of polyols (defined here as the sum of arabitol and mannitol) and glucose at each sampling location, highlighting their ubiquity. Results also confirm that polyols and glucose are mainly associated with the coarse rather than the fine aerosol mode. At nearly all sites, atmospheric concentrations of polyols and glucose display a well-marked seasonal pattern, with maximum concentrations from late spring to early autumn, followed by an abrupt decrease in late autumn, and a minimum concentration during wintertime. Such seasonal patterns support biogenic emissions associated with higher biological metabolic activities (sporulation, growth, etc.) during warmer periods. Results from a previous comprehensive study using positive matrix factorization (PMF) based on an extended aerosol chemical composition dataset of up to 130 species for 16 of the same sample series have also been used in the present work. The polyols-to-PMPBOA ratio is 0.024 +/- 0.010 on average for all sites, with no clear distinction between traffic, urban, or rural typology. Overall, even if the exact origin of the PBOA source is still under investigation, it appears to be an important source of particulate matter (PM), especially during summertime. Results also show that PBOAs are significant sources of total organic matter (OM) in PM10 (13 +/- 4% on a yearly average, and up to 40% in some environments in summer) at most of the investigated sites. The mean PBOA chemical profile is clearly dominated by contribution from OM (78 +/- 9% of the mass of the PBOA PMF on average), and only a minor contribution from the dust class (3 +/- 4 %), suggesting that ambient polyols are most likely associated with biological particle emissions (e.g., active spore discharge) rather than soil dust resuspension.
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Samake, A., Jaffrezo, J., Favez, O., Weber, S., Jacob, V., Canete, T., et al. (2019). Arabitol, mannitol, and glucose as tracers of primary biogenic organic aerosol: the influence of environmental factors on ambient air concentrations and spatial distribution over France. Atmospheric Chemistry And Physics, 19(16), 11013–11030.
Abstract: The primary sugar compounds (SCs, defined as glucose, arabitol, and mannitol) are widely recognized as suitable molecular markers to characterize and apportion primary biogenic organic aerosol emission sources. This work improves our understanding of the spatial behavior and distribution of these chemical species and evidences their major effective environmental drivers. We conducted a large study focusing on the daily (24 h) PM10 SC concentrations for 16 increasing space scale sites (local to nationwide), over at least 1 complete year. These sites are distributed in several French geographic areas of different environmental conditions. Our analyses, mainly based on the examination of the short-term evolutions of SC concentrations, clearly show distance-dependent correlations. SC concentration evolutions are highly synchronous at an urban city scale and remain well correlated throughout the same geographic regions, even if the sites are situated in different cities. However, sampling sites located in two distinct geographic areas are poorly correlated. Such a pattern indicates that the processes responsible for the evolution of the atmospheric SC concentrations present a spatial homogeneity over typical areas of at least tens of kilometers. Local phenomena, such as the resuspension of topsoil and associated microbiota, do no account for the major emissions processes of SC in urban areas not directly influenced by agricultural activities. The concentrations of SC and cellulose display remarkably synchronous temporal evolution cycles at an urban site in Grenoble, indicating a common source ascribed to vegetation. Additionally, higher concentrations of SC at another site located in a crop field region occur during each harvest periods, indicating resuspension processes of plant materials (crop detritus, leaf debris) and associated microbiota for agricultural and nearby urbanized areas. Finally, ambient air temperature, relative humidity, and vegetation density constitute the main effective drivers of SC atmospheric concentrations.
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Sellegri, K., Rose, C., Marinoni, A., Lupi, A., Wiedensohler, A., Andrade, M., et al. (2019). New Particle Formation: A Review of Ground-Based Observations at Mountain Research Stations. Atmosphere, 10(9).
Abstract: New particle formation (NPF) was predicted to contribute to a major fraction of free tropospheric particle number and cloud condensation nuclei (CCN) concentrations by global models. At high altitudes, pre-existing particle concentrations are low, leading to limited condensational sinks for nucleation precursor gases, and temperatures are cooler compared to lower altitudes, whereas radiation is higher. These factors would all be in favor of nucleation to occur with an enhanced frequency at high altitudes. In the present work, long term data from six altitude stations (and four continents) at various altitudes (from 1465 to 5240 m a.s.l) were used to derive statistically relevant NPF features (frequency, formation rates, and growth rates) and seasonal variability. The combined information together with literature data showed that the frequencies of NPF events at the two Southern hemisphere (SH) stations are some of the highest reported thus far (64% and 67%, respectively). There are indications that NPF would be favored at a preferential altitude close to the interface of the free troposphere (FT) with the planetary boundary layer (PBL) and/or at the vicinity with clouds, which otherwise inhibit the occurrence of NPF. Particle formation rates are found to be lower at high altitudes than at low altitude sites, but a higher fraction of particles are formed via the charged pathway (mainly related to positive ions) compared to boundary layer (BL) sites. Low condensational sinks (CS) are not necessarily needed at high altitudes to promote the occurrence of NPF. For stations at altitudes higher than 1000 m a.s.l., higher CSs favor NPF and are thought to be associated with precursor gases needed to initiate nucleation and early growth.
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Spolaor, A., Barbaro, E., Cappelletti, D., Turetta, C., Mazzola, M., Giardi, F., et al. (2019). Diurnal cycle of iodine, bromine, and mercury concentrations in Svalbard surface snow. Atmospheric Chemistry And Physics, 19(20), 13325–13339.
Abstract: Sunlit snow is highly photochemically active and plays a key role in the exchange of gas phase species between the cryosphere and the atmosphere. Here, we investigate the behaviour of two selected species in surface snow: mercury (Hg) and iodine (I). Hg can deposit year-round and accumulate in the snowpack. However, photo-induced re-emission of gas phase Hg from the surface has been widely reported. Iodine is active in atmospheric new particle formation, especially in the marine boundary layer, and in the destruction of atmospheric ozone. It can also undergo photochemical re-emission. Although previous studies indicate possible post-depositional processes, little is known about the diurnal behaviour of these two species and their interaction in surface snow. The mechanisms are still poorly constrained, and no field experiments have been performed in different seasons to investigate the magnitude of re-emission processes Three sampling campaigns conducted at an hourly resolution for 3 d each were carried out near Ny-Alesund (Svalbard) to study the behaviour of mercury and iodine in surface snow under different sunlight and environmental conditions (24 h darkness, 24 h sunlight and day-night cycles). Our results indicate a different behaviour of mercury and iodine in surface snow during the different campaigns. The day-night experiments demonstrate the existence of a diurnal cycle in surface snow for Hg and iodine, indicating that these species are indeed influenced by the daily solar radiation cycle. Differently, bromine did not show any diurnal cycle. The diurnal cycle also disappeared for Hg and iodine during the 24 h sunlight period and during 24 h darkness experiments supporting the idea of the occurrence (absence) of a continuous recycling or exchange at the snow-air interface. These results demonstrate that this surface snow recycling is seasonally dependent, through sunlight. They also highlight the non-negligible role that snowpack emissions have on ambient air concentrations and potentially on iodine-induced atmospheric nucleation processes.
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Svensson, J., Strom, J., & Virkkula, A. (2019). Multiple-scattering correction factor of quartz filters and the effect of filtering particles mixed in water: implications for analyses of light absorption in snow samples. Atmospheric Measurement Techniques, 12(11), 5913–5925.
Abstract: The deposition of light-absorbing aerosol (LAA) onto snow initiates processes that lead to increased snowmelt. Measurements of LAA, such as black carbon (BC) and mineral dust, have been observed globally to darken snow. Several measurement techniques of LAA in snow collect the particulates on filters for analysis. Here we investigate micro-quartz filters' optical response to BC experiments in which the particles are initially suspended in air or in a liquid. With particle soot absorption photometers (PSAPs) we observed a 20% scattering enhancement for quartz filters compared to the standard PSAP Pallflex filters. The multiple-scattering correction factor (C-ref) of the quartz filters for airborne soot aerosol is estimated to be similar to 3.4. In the next stage correction factors were determined for BC particles mixed in water and also for BC particles both mixed in water and further treated in an ultrasonic bath. Comparison of BC collected from airborne particles with BC mixed in water filters indicated a higher mass absorption cross section by approximately a factor of 2 for the liquid-based filters, which is probably due to the BC particles penetrating deeper in the filter matrix. The ultrasonic bath increased absorption still further, roughly by a factor of 1.5, compared to only mixing in water. Application of the correction functions to earlier published field data from the Himalaya and Finnish Lapland yielded mass absorption coefficient (MAC) values of similar to 7-10 m(2) g(-1) at lambda = 550 nm, which is in the range of the published MAC of airborne BC aerosol.
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Thomas, J., Stutz, J., Frey, M., Bartels-Rausch, T., Altieri, K., Baladima, F., et al. (2019). Fostering multidisciplinary research on interactions between chemistry, biology, and physics within the coupled cryosphere-atmosphere system. Elementa-Science Of The Anthropocene, 7.
Abstract: The cryosphere, which comprises a large portion of Earth's surface, is rapidly changing as a consequence of global climate change. Ice, snow, and frozen ground in the polar and alpine regions of the planet are known to directly impact atmospheric composition, which for example is observed in the large influence of ice and snow on polar boundary layer chemistry. Atmospheric inputs to the cryosphere, including aerosols, nutrients, and contaminants, are also changing in the anthropocene thus driving cryosphere-atmosphere feedbacks whose understanding is crucial for understanding future climate. Here, we present the Cryosphere and ATmospheric Chemistry initiative (CATCH) which is focused on developing new multidisciplinary research approaches studying interactions of chemistry, biology, and physics within the coupled cryosphere – atmosphere system and their sensitivity to environmental change. We identify four key science areas: (1) micro-scale processes in snow and ice, (2) the coupled cryosphere-atmosphere system, (3) cryospheric change and feedbacks, and (4) improved decisions and stakeholder engagement. To pursue these goals CATCH will foster an international, multidisciplinary research community, shed light on new research needs, support the acquisition of new knowledge, train the next generation of leading scientists, and establish interactions between the science community and society.
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Tignat-Perrier, R., Dommergue, A., Thollot, A., Keuschnig, C., Magand, O., Vogel, T., et al. (2019). Global airborne microbial communities controlled by surrounding landscapes and wind conditions. Scientific Reports, 9.
Abstract: The atmosphere is an important route for transporting and disseminating microorganisms over short and long distances. Understanding how microorganisms are distributed in the atmosphere is critical due to their role in public health, meteorology and atmospheric chemistry. In order to determine the dominant processes that structure airborne microbial communities, we investigated the diversity and abundance of both bacteria and fungi from the PM10 particle size (particulate matter of 10 micrometers or less in diameter) as well as particulate matter chemistry and local meteorological characteristics over time at nine different meteorological stations around the world. The bacterial genera Bacillus and Sphingomonas as well as the fungal species Pseudotaeniolina globaosa and Cladophialophora proteae were the most abundant taxa of the dataset, although their relative abundances varied greatly based on sampling site. Bacterial and fungal concentration was the highest at the high-altitude and semi-arid plateau of Namco (China; 3.56 X 10(6) +/- 3.01 X 10(6) cells/m(3)) and at the high-altitude and vegetated mountain peak Storm-Peak (Colorado, USA; 8.78X 10(4) +/- 6.49 X 10(4) cells/m(3)), respectively. Surrounding ecosystems, especially within a 50 km perimeter of our sampling stations, were the main contributors to the composition of airborne microbial communities. Temporal stability in the composition of airborne microbial communities was mainly explained by the diversity and evenness of the surrounding landscapes and the wind direction variability over time. Airborne microbial communities appear to be the result of large inputs from nearby sources with possible low and diluted inputs from distant sources.
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Tuzet, F., Dumont, M., Arnaud, L., Voisin, D., Lamare, M., Larue, F., et al. (2019). Influence of light-absorbing particles on snow spectral irradiance profiles. Cryosphere, 13(8), 2169–2187.
Abstract: Light-absorbing particles (LAPs) such as black carbon or mineral dust are some of the main drivers of snow radiative transfer. Small amounts of LAPs significantly increase snowpack absorption in the visible wavelengths where ice absorption is particularly weak, impacting the surface energy budget of snow-covered areas. However, linking measurements of LAP concentration in snow to their actual radiative impact is a challenging issue which is not fully resolved. In the present paper, we point out a new method based on spectral irradiance profile (SIP) measurements which makes it possible to identify the radiative impact of LAPs on visible light extinction in homogeneous layers of the snowpack. From this impact on light extinction it is possible to infer LAP concentrations present in each layer using radiative transfer theory. This study relies on a unique dataset composed of 26 spectral irradiance profile measurements in the wavelength range 350-950 nm with concomitant profile measurements of snow physical properties and LAP concentrations, collected in the Alps over two snow seasons in winter and spring conditions. For 55 homogeneous snow layers identified in our dataset, the concentrations retrieved from SIP measurements are compared to chemical measurements of LAP concentrations. A good correlation is observed for measured concentrations higher than 5 ng g(-1) (r(2) = 0.81) despite a clear positive bias. The potential causes of this bias are discussed, underlining a strong sensitivity of our method to LAP optical properties and to the relationship between snow microstructure and snow optical properties used in the theory. Additional uncertainties such as artefacts in the measurement technique for SIP and chemical contents along with LAP absorption efficiency may explain part of this bias. In addition, spectral information on LAP absorption can be retrieved from SIP measurements. We show that for layers containing a unique absorber, this absorber can be identified in some cases (e.g. mineral dust vs. black carbon). We also observe an enhancement of light absorption between 350 and 650 nm in the presence of liquid water in the snow-pack, which is discussed but not fully elucidated. A single SIP acquisition lasts approximately 1 min and is hence much faster than collecting a profile of chemical measurements. With the recent advances in modelling LAP-snow interactions, our method could become an attractive alternative to estimate vertical profiles of LAP concentrations in snow.
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Vlachou, A., Tobler, A., Lamkaddam, H., Canonaco, F., Daellenbach, K., Jaffrezo, J., et al. (2019). Development of a versatile source apportionment analysis based on positive matrix factorization: a case study of the seasonal variation of organic aerosol sources in Estonia. Atmospheric Chemistry And Physics, 19(11), 7279–7295.
Abstract: Bootstrap analysis is commonly used to capture the uncertainties of a bilinear receptor model such as the positive matrix factorization (PMF) model. This approach can estimate the factor-related uncertainties and partially assess the rotational ambiguity of the model. The selection of the environmentally plausible solutions, though, can be challenging, and a systematic approach to identify and sort the factors is needed. For this, comparison of the factors between each bootstrap run and the initial PMF output, as well as with externally determined markers, is crucial. As a result, certain solutions that exhibit suboptimal factor separation should be discarded. The retained solutions would then be used to test the robustness of the PMF output. Meanwhile, analysis of filter samples with the Aerodyne aerosol mass spectrometer and the application of PMF and bootstrap analysis on the bulk water-soluble organic aerosol mass spectra have provided insight into the source identification and their uncertainties. Here, we investigated a full yearly cycle of the sources of organic aerosol (OA) at three sites in Estonia: Tallinn (urban), Tartu (suburban) and Kohtla-Jarve (KJ; industrial). We identified six OA sources and an inorganic dust factor. The primary OA types included biomass burning, dominant in winter in Tartu and accounting for 73 % +/- 21 % of the total OA, primary biological OA which was abundant in Tartu and Tallinn in spring (21 % +/- 8 % and 11 % +/- 5 %, respectively), and two other primary OA types lower in mass. A sulfur-containing OA was related to road dust and tire abrasion which exhibited a rather stable yearly cycle, and an oil OA was connected to the oil shale industries in KJ prevailing at this site that comprises 36 % +/- 14 % of the total OA in spring. The secondary OA sources were separated based on their seasonal behavior: a winter oxygenated OA dominated in winter (36 % +/- 14 % for KJ, 25 % +/- 9 % for Tallinn and 13 % +/- 5 % for Tartu) and was correlated with benzoic and phthalic acid, implying an anthropogenic origin. A summer oxygenated OA was the main source of OA in summer at all sites (26 % +/- 5 % in KJ, 41 % +/- 7 % in Tallinn and 35 % +/- 7 % in Tartu) and exhibited high correlations with oxidation products of a-pinene-like pinic acid and 3-methyl-1, 2, 3-butanetricarboxylic acid (MBTCA), suggesting a biogenic origin.
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Weber, S., Salameh, D., Albinet, A., Alleman, L., Waked, A., Besombes, J., et al. (2019). Comparison of PM10 Sources Profiles at 15 French Sites Using a Harmonized Constrained Positive Matrix Factorization Approach. Atmosphere, 10(6).
Abstract: Receptor-oriented models, including positive matrix factorization (PMF) analyses, are now commonly used to elaborate and/or evaluate action plans to improve air quality. In this context, the SOURCES project has been set-up to gather and investigate in a harmonized way 15 datasets of chemical compounds from PM10 collected for PMF studies during a five-year period (2012-2016) in France. The present paper aims at giving an overview of the results obtained within this project, notably illustrating the behavior of key primary sources as well as focusing on their statistical robustness and representativeness. Overall, wood burning for residential heating as well as road transport were confirmed to be the two main primary sources strongly influencing PM10 loadings across the country. While wood burning profiles, as well as those dominated by secondary inorganic aerosols, present a rather good homogeneity among the sites investigated, some significant variabilities were observed for primary traffic factors, illustrating the need to better characterize the diversity of the various vehicle exhaust and non-exhaust emissions. Finally, natural sources, such as sea salts (widely observed in internal mixing with anthropogenic compounds), primary biogenic aerosols and/or terrigenous particles, were also found as non-negligible PM10 components at every investigated site.
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2018 |
Benedetti, A., Reid, J. S., Knippertz, P., Marsham, J. H., Di Giuseppe, F., Remy, S., et al. (2018). Status and future of numerical atmospheric aerosol prediction with a focus on data requirements. Atmospheric Chemistry And Physics, 18(14), 10615–10643.
Abstract: Numerical prediction of aerosol particle properties has become an important activity at many research and operational weather centers. This development is due to growing interest from a diverse set of stakeholders, such as air quality regulatory bodies, aviation and military authorities, solar energy plant managers, climate services providers, and health professionals. Owing to the complexity of atmospheric aerosol processes and their sensitivity to the underlying meteorological conditions, the prediction of aerosol particle concentrations and properties in the numerical weather prediction (NWP) framework faces a number of challenges. The modeling of numerous aerosol-related parameters increases computational expense. Errors in aerosol prediction concern all processes involved in the aerosol life cycle including (a) errors on the source terms (for both anthropogenic and natural emissions), (b) errors directly dependent on the meteorology (e.g., mixing, transport, scavenging by precipitation), and (c) errors related to aerosol chemistry (e.g., nucleation, gas-aerosol partitioning, chemical transformation and growth, hygroscopicity). Finally, there are fundamental uncertainties and significant processing overhead in the diverse observations used for verification and assimilation within these systems. Indeed, a significant component of aerosol forecast development consists in streamlining aerosol-related observations and reducing the most important errors through model development and data assimilation. Aerosol particle observations from satellite- and ground-based platforms have been crucial to guide model development of the recent years and have been made more readily available for model evaluation and assimilation. However, for the sustainability of the aerosol particle prediction activities around the globe, it is crucial that quality aerosol observations continue to be made available from different platforms (space, near surface, and aircraft) and freely shared. This paper reviews current requirements for aerosol observations in the context of the operational activities carried out at various global and regional centers. While some of the requirements are equally applicable to aerosol-climate, the focus here is on global operational prediction of aerosol properties such as mass concentrations and optical parameters. It is also recognized that the term “requirements” is loosely used here given the diversity in global aerosol observing systems and that utilized data are typically not from operational sources. M
ost operational models are based on bulk schemes that do not predict the size distribution of the aerosol particles. Others are based on a mix of “bin” and bulk schemes with limited capability of simulating the size information. However the next generation of aerosol operational models will output both mass and number density concentration to provide a more complete description of the aerosol population. A brief overview of the state of the art is provided with an introduction on the importance of aerosol prediction activities. The criteria on which the requirements for aerosol observations are based are also outlined. Assimilation and evaluation aspects are discussed from the perspective of the user requirements.
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Bourgeois, I., Savarino, J., Caillon, N., Angot, H., Barbero, A., Delbart, F., et al. (2018). Tracing the Fate of Atmospheric Nitrate in a Subalpine Watershed Using Delta O-17. Environmental Science & Technology, 52(10), 5561–5570.
Abstract: Nitrogen is an essential nutrient for life on Earth, but in excess, it can lead to environmental issues (e.g., N saturation, loss of biodiversity, acidification of lakes, etc.). Understanding the nitrogen budget (i.e., inputs and outputs) is essential to evaluate the prospective decay of the ecosystem services (e.g., freshwater quality, erosion control, loss of high patrimonial-value plant species, etc.) that subalpine headwater catchments provide, especially as these ecosystems experience high atmospheric nitrogen deposition. Here, we use a multi-isotopic tracer (Delta O-17, delta N-15 and delta O-18) of nitrate in aerosols, snow, and streams to assess the fate of atmospherically deposited nitrate in the subalpine watershed of the Lautaret Pass (French Alps). We show that atmospheric N deposition contributes significantly to stream nitrate pool year-round, either by direct inputs (up to 35%) or by in situ nitrification of atmospheric ammonium (up to 35%). Snowmelt in particular leads to high exports of atmospheric nitrate, most likely fast enough to impede assimilation by surrounding ecosystems. Yet, in a context of climate change, with shorter snow seasons, and increasing nitrogen emissions, our results hint at possibly stronger ecological consequences of nitrogen atmospheric deposition in the close future.
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Bourgeois, I., Savarino, J., Nemery, J., Caillon, N., Albertin, S., Delbart, F., et al. (2018). Atmospheric nitrate export in streams along a montane to urban gradient. Science Of The Total Environment, 633, 329–340.
Abstract: Nitrogen (N) emissions associated with urbanization exacerbate the atmospheric N influx to remote ecosystems – like mountains -, leading to well-documented detrimental effects on ecosystems (e.g., soil acidification, pollution of freshwaters). Here, the importance and fate of N deposition in a watershed was evaluated along a montane to urban gradient, using a multi-isotopic tracers approach (Delta O-17, delta N-15, delta O-18 of nitrate, delta H-2 and delta O-18 of water). In this setting, the montane streams had higher proportions of atmospheric nitrate compared to urban streams, and exported more atmospheric nitrate on a yearly basis (0.35 vs 0.10 kg-N ha(-1) yr(-1)). In urban areas, nitrate exports were driven by groundwater, whereas in the catchment head nitrate exports were dominated by surface runoff. The main sources of nitrate to the montane streams were microbial nitrification and atmospheric deposition, whereas microbial nitrification and sewage leakage contributed most to urban streams. Based on the measurement of delta N-15 and delta O-18-NO3-, biological processes such as denitrification or N assimilation were not predominant in any streams in this study. The observed low delta N-15 and delta O-18 range of terrestrial nitrate (i.e., nitrate not coming from atmospheric deposition) in surface water compared to literature suggests that atmospheric deposition may be underestimated as a direct source of N. (c) 2018 Elsevier B.V. All rights reserved.
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Calas, A., Uzu, G., Kelly, F. J., Houdier, S., Martins, J. M. F., Thomas, F., et al. (2018). Comparison between five acellular oxidative potential measurement assays performed with detailed chemistry on PM10 samples from the city of Chamonix (France). Atmospheric Chemistry And Physics, 18(11), 7863–7875.
Abstract: Many studies have demonstrated associations between exposure to ambient particulate matter (PM) and adverse health outcomes in humans that can be explained by PM capacity to induce oxidative stress in vivo. Thus, assays have been developed to quantify the oxidative potential (OP) of PM as a more refined exposure metric than PM mass alone. Only a small number of studies have compared different acellular OP measurements for a given set of ambient PM samples. Yet, fewer studies have compared different assays over a year-long period and with detailed chemical characterization of ambient PM. In this study, we report on seasonal variations of the dithiothreitol (DTT), ascorbic acid (AA), electron spin resonance (ESR) and the respiratory tract lining fluid (RTLF, composed of the reduced glutathione (GSH) and ascorbic acid (ASC)) assays over a 1-year period in which 100 samples were analyzed. A detailed PM10 characterization allowed univariate and multivariate regression analyses in order to obtain further insight into groups of chemical species that drive OP measurements. Our results show that most of the OP assays were strongly intercorrelated over the sampling year but also these correlations differed when considering specific sampling periods (cold vs. warm). All acellular assays are correlated with a significant number of chemical species when considering univariate correlations, especially for the DTT assay. Evidence is also presented of a seasonal contrast over the sampling period with significantly higher OP values during winter for the DTT, AA, GSH and ASC assays, which were assigned to biomass burning species by the multiple linear regression models. The ESR assay clearly differs from the other tests as it did not show seasonal dynamics and presented weaker correlations with other assays and chemical species.
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Carbone, F., Bruno, A. G., Naccarato, A., De Simone, F., Gencarelli, C. N., Sprovieri, F., et al. (2018). The Superstatistical Nature and Interoccurrence Time of Atmospheric Mercury Concentration Fluctuations. Journal Of Geophysical Research-Atmospheres, 123(2), 764–774.
Abstract: The probability density function (PDF) of the time intervals between subsequent extreme events in atmospheric Hg-0 concentration data series from different latitudes has been investigated. The Hg-0 dynamic possesses a long-term memory autocorrelation function. Above a fixed threshold Q in the data, the PDFs of the interoccurrence time of the Hg-0 data are well described by a Tsallis q-exponential function. This PDF behavior has been explained in the framework of superstatistics, where the competition between multiple mesoscopic processes affects the macroscopic dynamics. An extensive parameter , encompassing all possible fluctuations related to mesoscopic phenomena, has been identified. It follows a (2) distribution, indicative of the superstatistical nature of the overall process. Shuffling the data series destroys the long-term memory, the distributions become independent of Q, and the PDFs collapse on to the same exponential distribution. The possible central role of atmospheric turbulence on extreme events in the Hg-0 data is highlighted.
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Chambers, S., Preunkert, S., Weller, R., Hong, S., Humphries, R., Tositti, L., et al. (2018). Characterizing Atmospheric Transport Pathways to Antarctica and the Remote Southern Ocean Using Radon-222. Frontiers In Earth Science, 6.
Abstract: We discuss remote terrestrial influences on boundary layer air over the Southern Ocean and Antarctica, and the mechanisms by which they arise, using atmospheric radon observations as a proxy. Our primary motivation was to enhance the scientific community's ability to understand and quantify the potential effects of pollution, nutrient or pollen transport from distant land masses to these remote, sparsely instrumented regions. Seasonal radon characteristics are discussed at 6 stations (Macquarie Island, King Sejong, Neumayer, Dumont d'Urville, Jang Bogo and Dome Concordia) using 1-4 years of continuous observations. Context is provided for differences observed between these sites by Southern Ocean radon transects between 45 and 67 degrees S made by the Research Vessel Investigator. Synoptic transport of continental air within the marine boundary layer (MBL) dominated radon seasonal cycles in the mid-Southern Ocean site (Macquarie Island). MBL synoptic transport, tropospheric injection, and Antarctic outflow all contributed to the seasonal cycle at the sub-Antarctic site (King Sejong). Tropospheric subsidence and injection events delivered terrestrially influenced air to the Southern Ocean MBL in the vicinity of the circumpolar trough (or “Polar Front”). Katabatic outflow events from Antarctica were observed to modify trace gas and aerosol characteristics of the MBL 100-200 km off the coast. Radon seasonal cycles at coastal Antarctic sites were dominated by a combination of local radon sources in summer and subsidence of terrestrially influenced tropospheric air, whereas those on the Antarctic Plateau were primarily controlled by tropospheric subsidence. Separate characterization of long-term marine and katabatic flow air masses at Dumont d'Urville revealed monthly mean differences in summer of up to 5 ppbv in ozone and 0.3 ng m(-3) in gaseous elemental mercury. These differences were largely attributed to chemical processes on the Antarctic Plateau. A comparison of our observations with some Antarctic radon simulations by global climate models over the past two decades indicated that: (i) some models overestimate synoptic transport to Antarctica in the MBL, (ii) the seasonality of the Antarctic ice sheet needs to be better represented in models, (iii) coastal Antarctic radon sources need to be taken into account, and (iv) the underestimation of radon in subsiding tropospheric air needs to be investigated.
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Crumeyrolle, S., Weigel, R., Sellegri, K., Roberts, G., Gomes, L., Stohl, A., et al. (2018). Airborne investigation of the aerosols-cloud interactions in the vicinity and within a marine stratocumulus over the North Sea during EUCAARI (2008) (vol 81, pg 288, 2013). Atmospheric Environment, 183, 234–235.
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Daellenbach, K. R., El-Haddad, I., Karvonen, L., Vlachou, A., Corbin, J. C., Slowik, J. G., et al. (2018). Insights into organic-aerosol sources via a novel laser-desorption/ionization mass spectrometry technique applied to one year of PM10 samples from nine sites in central Europe. Atmospheric Chemistry And Physics, 18(3), 2155–2174.
Abstract: We assess the benefits of offline laser-desorption/ionization mass spectrometry in understanding ambient particulate matter (PM) sources. The technique was optimized for measuring PM collected on quartz-fiber filters using silver nitrate as an internal standard for m/z calibration. This is the first application of this technique to samples collected at nine sites in central Europe throughout the entire year of 2013 (819 samples). Different PM sources were identified by positive matrix factorization (PMF) including also concomitant measurements (such as NOx, levoglucosan, and temperature). By comparison to reference mass spectral signatures from laboratory wood burning experiments as well as samples from a traffic tunnel, three biomass burning factors and two traffic factors were identified. The wood burning factors could be linked to the burning conditions; the factors related to inefficient burns had a larger impact on air quality in southern Alpine valleys than in northern Switzerland. The traffic factors were identified as primary tailpipe exhaust and most possibly aged/secondary traffic emissions. The latter attribution was supported by radiocarbon analyses of both the organic and elemental carbon. Besides these sources, factors related to secondary organic aerosol were also separated. The contribution of the wood burning emissions based on LDI-PMF (laser-desorption/ionization PMF) correlates well with that based on AMS-PMF (aerosol mass spectrometer PMF) analyses, while the comparison between the two techniques for other components is more complex.
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Dall'Osto, M., Beddows, D. C. S., Asmi, A., Poulain, L., Hao, L., Freney, E., et al. (2018). Novel insights on new particle formation derived from a pan-european observing system. Scientific Reports, 8.
Abstract: The formation of new atmospheric particles involves an initial step forming stable clusters less than a nanometre in size (<similar to 1 nm), followed by growth into quasi-stable aerosol particles a few nanometres (similar to 1-10 nm) and larger (>similar to 10 nm). Although at times, the same species can be responsible for both processes, it is thought that more generally each step comprises differing chemical contributors. Here, we present a novel analysis of measurements from a unique multi-station ground-based observing system which reveals new insights into continental-scale patterns associated with new particle formation. Statistical cluster analysis of this unique 2-year multi-station dataset comprising size distribution and chemical composition reveals that across Europe, there are different major seasonal trends depending on geographical location, concomitant with diversity in nucleating species while it seems that the growth phase is dominated by organic aerosol formation. The diversity and seasonality of these events requires an advanced observing system to elucidate the key processes and species driving particle formation, along with detecting continental scale changes in aerosol formation into the future.
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Dappe, V., Uzu, G., Schreck, E., Wu, L., Li, X., Dumat, C., et al. (2018). Single-particle analysis of industrial emissions brings new insights for health risk assessment of PM. Atmospheric Pollution Research, 9(4), 697–704.
Abstract: Particulate matter (PM) emitted by human activities presents a significant risk for human health, especially through inhalation. In this work, coarse and ultrafine particles (PM10 and PM1) were collected near a lead battery recycling facility, recognized as an emission source of hazardous particles. These particles were previously found to have adverse health effects. Our multiple imaging analyses by SEM-EDX and Raman microspectrometry showed that Pb-rich particles constituted the major portion of the fine size fractions (PM1). The surface analysis of particles performed by ToF-SIMS evidenced soluble Pb-Cl rich species on the particle surface. The particle composition and chemical mixing state differed from PM at source emission. Although the annual mean lead concentration near the plant meets E.U. air quality standards, the size of the Pb-rich particles and the presence of soluble metal compounds on the particle surface may also induce harmful outcomes. The current risk assessment models only consider the total concentration of the element without dealing with speciation, morphology or surface composition of the particles. Single particle analysis could become useful in providing a more accurate assessment of human health risk and in developing more comprehensive regulations on air quality.
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Geng, L., Savarino, J., Savarino, C. A., Caillon, N., Cartigny, P., Hattori, S., et al. (2018). A simple and reliable method reducing sulfate to sulfide for multiple sulfur isotope analysis. Rapid Communications In Mass Spectrometry, 32(4), 333–341.
Abstract: RationalePrecise analysis of four sulfur isotopes of sulfate in geological and environmental samples provides the means to extract unique information in wide geological contexts. Reduction of sulfate to sulfide is the first step to access such information. The conventional reduction method suffers from a cumbersome distillation system, long reaction time and large volume of the reducing solution. We present a new and simple method enabling the process of multiple samples at one time with a much reduced volume of reducing solution. MethodsOne mL of reducing solution made of HI and NaH2PO2 was added to a septum glass tube with dry sulfate. The tube was heated at 124 degrees C and the produced H2S was purged with inert gas (He or N-2) through gas-washing tubes and then collected by NaOH solution. The collected H2S was converted into Ag2S by adding AgNO3 solution and the co-precipitated Ag2O was removed by adding a few drops of concentrated HNO3. ResultsWithin 2-3h, a 100% yield was observed for samples with 0.2-2.5mol Na2SO4. The reduction rate was much slower for BaSO4 and a complete reduction was not observed. International sulfur reference materials, NBS-127, SO-5 and SO-6, were processed with this method, and the measured against accepted S-34 values yielded a linear regression line which had a slope of 0.99 0.01 and a R-2 value of 0.998. ConclusionsThe new methodology is easy to handle and allows us to process multiple samples at a time. It has also demonstrated good reproducibility in terms of H2S yield and for further isotope analysis. It is thus a good alternative to the conventional manual method, especially when processing samples with limited amount of sulfate available.
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Houdier, S., Leveque, J., Sabatier, T., Jacob, V., & Jaffrezo, J. (2018). Aniline-based catalysts as promising tools to improve analysis of carbonyl compounds through derivatization techniques: preliminary results using dansylacetamidooxyamine derivatization and LC-fluorescence. Analytical And Bioanalytical Chemistry, 410(27), 7031–7042.
Abstract: Derivatization techniques based on alpha-effect amines and H+ catalysis are commonly used for the measurement of carbonyl compounds (CCs), whether in environmental, food, or biological samples. Here, we investigated the potential of aniline-based catalysts to improve derivatization rates of selected carbonyls by using dansylacetamidooxyamine (DNSAOA) as a reagent. Kinetic experiments were performed in aqueous solutions by varying catalyst and CC concentrations and delivered insights into the reaction mechanism. Using anilinium acetate (AnAc), rate constants varied linearly with the catalyst concentration with rate enhancements toward H+-catalyzed reactions as high as ca. 90 and 200 for acetone and benzaldehyde, respectively. Owing to contamination problems when using AnAc, anilinium chloride (AnCl) was chosen for the optimized analysis of real samples at low concentration. Rate enhancements for derivatization reaction of 4.4 (methylglyoxal), 6.0 (glyoxal), 12 (acetone), 20 (formaldehyde), and 47 (hydroxyacetaldehyde) were obtained using 0.1 M AnCl. The optimized method was successfully applied to the determination of the above compounds in natural snow and meltwater samples. Limits of detection (LODs) and limits of quantification (LOQs) were in the 2-14 and 7-41 nM range, respectively, i.e., low enough to allow for the analysis of most natural samples. Satisfactory relative recoveries (92.8 +/- 3.8-118.3 +/- 4.4%) and intra-day precision (2.7-11.3%) were achieved. Finally, we think that this approach could be applied not only to every alpha-effect nitrogen reagent-with the most evident profit of lowering derivatization times and particularly those required for low-reactive ketones-but also to the derivatization of CCs onto coated solid sorbents.
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Jiskra, M., Sonke, J. E., Obrist, D., Bieser, J., Ebinghaus, R., Myhre, C. L., et al. (2018). A vegetation control on seasonal variations in global atmospheric mercury concentrations. Nature Geoscience, 11(4), 244–+.
Abstract: Anthropogenic mercury emissions are transported through the atmosphere as gaseous elemental mercury (Hg(0)) before they are deposited to Earth's surface. Strong seasonality in atmospheric Hg(0) concentrations in the Northern Hemisphere has been explained by two factors: anthropogenic Hg(0) emissions are thought to peak in winter due to higher energy consumption, and atmospheric oxidation rates of Hg(0) are faster in summer. Oxidation-driven Hg(0) seasonality should be equally pronounced in the Southern Hemisphere, which is inconsistent with observations of constant year-round Hg(0) levels. Here, we assess the role of Hg(0) uptake by vegetation as an alternative mechanism for driving Hg(0) seasonality. We find that at terrestrial sites in the Northern Hemisphere, Hg(0) co-varies with CO2, which is known to exhibit a minimum in summer when CO2 is assimilated by vegetation. The amplitude of seasonal oscillations in the atmospheric Hg(0) concentration increases with latitude and is larger at inland terrestrial sites than coastal sites. Using satellite data, we find that the photosynthetic activity of vegetation correlates with Hg(0) levels at individual sites and across continents. We suggest that terrestrial vegetation acts as a global Hg(0) pump, which can contribute to seasonal variations of atmospheric Hg(0), and that decreasing Hg(0) levels in the Northern Hemisphere over the past 20 years can be partly attributed to increased terrestrial net primary production.
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Le Meur, E., Magand, O., Arnaud, L., Fily, M., Frezzotti, M., Cavitte, M., et al. (2018). Spatial and temporal distributions of surface mass balance between Concordia and Vostok stations, Antarctica, from combined radar and ice core data: first results and detailed error analysis. Cryosphere, 12(5), 1831–1850.
Abstract: Results from ground-penetrating radar (GPR) measurements and shallow ice cores carried out during a scientific traverse between Dome Concordia (DC) and Vostok stations are presented in order to infer both spatial and temporal characteristics of snow accumulation over the East Antarctic Plateau. Spatially continuous accumulation rates along the traverse are computed from the identification of three equally spaced radar reflections spanning about the last 600 years. Accurate dating of these internal reflection horizons (IRHs) is obtained from a depth-age relationship derived from volcanic horizons and bomb testing fallouts on a DC ice core and shows a very good consistency when tested against extra ice cores drilled along the radar profile. Accumulation rates are then inferred by accounting for density profiles down to each IRH. For the latter purpose, a careful error analysis showed that using a single and more accurate density profile along a DC core provided more reliable results than trying to include the potential spatial variability in density from extra (but less accurate) ice cores distributed along the profile. The most striking feature is an accumulation pattern that remains constant through time with persistent gradients such as a marked decrease from 26 mm w.e. yr(-1) at DC to 20 mm w.e. yr(-1) at the south-west end of the profile over the last 234 years on average (with a similar decrease from 25 to 19 mm w.e. yr(-1) over the last 592 years). As for the time dependency, despite an overall consistency with similar measurements carried out along the main East Antarctic divides, interpreting possible trends remains difficult. Indeed, error bars in our measurements are still too large to unambiguously infer an apparent time increase in accumulation rate. For the proposed absolute values, maximum margins of error are in the range 4 mm w.e. yr(-1) (last 234 years) to 2 mm w.e. yr(-1) (last 592 years), a decrease with depth mainly resulting from the time-averaging when computing accumulation rates.
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Lim, S., Lee, M., Kim, S. W., & Laj, P. (2018). Sulfate alters aerosol absorption properties in East Asian outflow. Scientific Reports, 8.
Abstract: Black carbon (BC) and brown carbon (BrC) aerosols that are released from the combustion of fossil fuels and biomass are of great concern because of their light-absorbing ability and great abundance associated with various anthropogenic sources, particularly in East Asia. However, the optical properties of ambient aerosols are dependent on the mixing state and the chemical composition of absorbing and non-absorbing aerosols. Here we examined how, in East Asian outflows, the parameters of the aerosol optical properties can be altered seasonally in conjunction with the mixing state and the chemical composition of aerosols, using 3-year aerosol measurements. Our findings highlight the important role played by sulfate in East Asia during the warm season in both enhancing single scattering albedo (SSA) and altering the absorption properties of aerosols-enhancing mass absorption cross section of BC (MAC(BC)) and reducing MAC of BrC (MAC(BrC),(370)). Therefore we suggest that in global radiative forcing models, particular attention should be paid to the consideration of the accurate treatment of the SO2 emission changes in the coming years in this region that will result from China's air quality policy.
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McGuire, A. D., Lawrence, D. M., Koven, C., Clein, J. S., Burke, E., Chen, G. S., et al. (2018). Dependence of the evolution of carbon dynamics in the northern permafrost region on the trajectory of climate change. Proceedings Of The National Academy Of Sciences Of The United States Of America, 115(15), 3882–3887.
Abstract: We conducted a model-based assessment of changes in permafrost area and carbon storage for simulations driven by RCP4.5 and RCP8.5 projections between 2010 and 2299 for the northern permafrost region. All models simulating carbon represented soil with depth, a critical structural feature needed to represent the permafrost carbon-climate feedback, but that is not a universal feature of all climate models. Between 2010 and 2299, simulations indicated losses of permafrost between 3 and 5 million km(2) for the RCP4.5 climate and between 6 and 16 million km(2) for the RCP8.5 climate. For the RCP4.5 projection, cumulative change in soil carbon varied between 66-Pg C (10(15)-g carbon) loss to 70-Pg C gain. For the RCP8.5 projection, losses in soil carbon varied between 74 and 652 Pg C (mean loss, 341 Pg C). For the RCP4.5 projection, gains in vegetation carbon were largely responsible for the overall projected net gains in ecosystem carbon by 2299 (8- to 244-Pg C gains). In contrast, for the RCP8.5 projection, gains in vegetation carbon were not great enough to compensate for the losses of carbon projected by four of the five models; changes in ecosystem carbon ranged from a 641-Pg C loss to a 167-Pg C gain (mean, 208-Pg C loss). The models indicate that substantial net losses of ecosystem carbon would not occur until after 2100. This assessment suggests that effective mitigation efforts during the remainder of this century could attenuate the negative consequences of the permafrost carbon-climate feedback.
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Pandolfi, M., Alados-Arboledas, L., Alastuey, A., Andrade, M., Angelov, C., Artinano, B., et al. (2018). A European aerosol phenomenology-6: scattering properties of atmospheric aerosol particles from 28 ACTRIS sites. Atmospheric Chemistry And Physics, 18(11), 7877–7911.
Abstract: This paper presents the light-scattering properties of atmospheric aerosol particles measured over the past decade at 28 ACTRIS observatories, which are located mainly in Europe. The data include particle light scattering (sigma(sp)) and hemispheric backscattering (sigma(bsp)) coefficients, scattering Angstrom exponent (SAE), backscatter fraction (BF) and asymmetry parameter (g). An increasing gradient of sigma(sp) is observed when moving from remote environments (arctic/mountain) to regional and to urban environments. At a regional level in Europe, sigma(sp) also increases when moving from Nordic and Baltic countries and from western Europe to central/eastern Europe, whereas no clear spatial gradient is observed for other station environments. The SAE does not show a clear gradient as a function of the placement of the station. However, a west-to-east-increasing gradient is observed for both regional and mountain placements, suggesting a lower fraction of fine-mode particle in western/south-western Europe compared to central and eastern Europe, where the fine-mode particles dominate the scattering. The g does not show any clear gradient by station placement or geographical location reflecting the complex relationship of this parameter with the physical properties of the aerosol particles. Both the station placement and the geographical location are important factors affecting the intraannual variability. At mountain sites, higher sigma(sp) and SAE values are measured in the summer due to the enhanced boundary layer influence and/or new particle-formation episodes. Conversely, the lower horizontal and vertical dispersion during winter leads to higher sigma(sp) values at all low-altitude sites in central and eastern Europe compared to summer. These sites also show SAE maxima in the summer (with corresponding g minima). At all sites, both SAE and g show a strong variation with aerosol particle loading. The lowest values of g are always observed together with low sigma(sp) values, indicating a larger contribution from particles in the smaller accumulation mode. During periods of high sigma(sp) values, the variation of g is less pronounced, whereas the SAE increases or decreases, suggesting changes mostly in the coarse aerosol particle mode rather than in the fine mode. Statistically significant decreasing trends of sigma(sp) are observed at 5 out of the 13 stations included in the trend analyses. The total reductions of sigma(sp) are consistent with those reported for PM2.5 and PM10 mass concentrations over simila
r periods across Europe.
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Salameh, D., Pey, J., Bozzetti, C., El Haddad, I., Detournay, A., Sylvestre, A., et al. (2018). Sources of PM2.5 at an urban-industrial Mediterranean city, Marseille (France): Application of the ME-2 solver to inorganic and organic markers. Atmospheric Research, 214, 263–274.
Abstract: Impacted by a complex mixture of urban, industrial, shipping and also natural emissions, Marseille, the second most populated city in France, represents a very interesting case study for the apportionment of PM(2.5 )sources in a Mediterranean urban environment. In this study, daily PM2.5 samples were collected over a one-year period (2011 -2012) at an urban background site, and were comprehensively analyzed for the determination of organic carbon (OC), elemental carbon (EC), major ions, trace elements/metals and specific organic markers. A constrained positive matrix factorization (PMF) analysis using the ME-2 (multilinear engine-2) solver was applied to this dataset. PMF results highlighted the presence of two distinct fingerprints for biomass burning (BB1 and BB2). BB1, assigned to open green waste burning peaks in fall (33%; 7.4 μg m(-3)) during land clearing periods, is characterized by a higher levoglucosan/OC ratio, while BB2, assigned to residential heating, shows the highest contribution during the cold period in winter (14%; 3.3 μg m(-3)) and it is characterized by high proportions from lignin pyrolysis products from the combustion of hardwood. Another interesting feature lies in the separation of two fossil fuel combustion processes (FF1 and FF2): FF1 likely dominated by traffic emissions, while FF2 likely linked with the harbor/industrial activities. On annual average, the major contributors to PM2.5 mass correspond to the ammonium sulfate-rich aerosol (AS-rich, 30%) and to the biomass burning emissions (BB1 + BB2, 23%). This study also outlined that during high PM pollution episodes (PM2.5 > 25 μg m(-3) ), the largest contributing sources to PM2.5 were biomass burning (33%) and FF1 (23%). Moreover, 28% of the ambient mass concentration of OC is apportioned by the AS-rich factor, which is representative of an aged secondary aerosol, reflecting thus the importance of the oxidative processes occurring in a Mediterranean environment.
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Siepka, D., Uzu, G., Stefaniak, E. A., & Sobanska, S. (2018). Combining Raman microspectrometry and chemometrics for determining quantitative molecular composition and mixing state of atmospheric aerosol particles. Microchemical Journal, 137, 119–130.
Abstract: Determining quantitative molecular composition of atmospheric particles is required for assessing their environmental and health impacts. The presented algorithm was designed to analyse numerous Raman spectra of metal rich atmospheric particles. Multivariate curve resolution-alternating least squares procedure (MCR-ALS) has been applied to resolve complex data from Raman microanalysis by means of a computer-assisted analytical procedure called Single Particle Analysis (SPA). The SPA – contrary to Raman mapping – provides data in which each single particle is assigned to a single spectrum, in the group with a statistically significant size. During the procedure, the relative contributions of individual compounds in the recorded Raman spectra have been specified. Grouping and relationship determination of the collected data have been performed by hierarchical cluster analysis (HCA) and principal component analysis (PCA). A new methodology is proposed to quantitatively determine the molecular composition and chemical mixing of single airborne particles based on the data from the automated Raman microspectrometry measurements. (C) 2017 Elsevier B.V. All rights reserved.
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Song, S., Angot, H., Selin, N., Gallee, H., Sprovieri, F., Pirrone, N., et al. (2018). Understanding mercury oxidation and air-snow exchange on the East Antarctic Plateau: a modeling study. Atmospheric Chemistry And Physics, 18(21), 15825–15840.
Abstract: Distinct diurnal and seasonal variations of mercury (Hg) have been observed in near-surface air at Concordia Station on the East Antarctic Plateau, but the processes controlling these characteristics are not well understood. Here, we use a box model to interpret the Hg-0 (gaseous elemental mercury) measurements in thes year 2013. The model includes atmospheric Hg-0 oxidation (by OH, O-3, or bromine), surface snow Hg-II (oxidized mercury) reduction, and air-snow exchange, and is driven by meteorological fields from a regional climate model. The simulations suggest that a photochemically driven mercury diurnal cycle occurs at the air-snow interface in austral summer. The fast oxidation of Hg-0 in summer may be provided by a two-step bromine-initiated scheme, which is favored by low temperature and high nitrogen oxides at Concordia. The summertime diurnal variations of Hg-0 (peaking during daytime) may be confined within several tens of meters above the snow surface and affected by changing mixed layer depths. Snow re-emission of Hg-0 is mainly driven by photoreduction of snow HgII in summer. Intermittent warming events and a hypothesized reduction of Hg-II occurring in snow in the dark may be important processes controlling the mercury variations in the non-summer period, although their relative importance is uncertain. The Br-initiated oxidation of Hg-0 is expected to be slower at Summit Station in Greenland than at Concordia (due to their difference in temperature and levels of nitrogen oxides and ozone), which may contribute to the observed differences in the summertime diurnal variations of Hg-0 between these two polar inland stations.
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Spolaor, A., Angot, H., Roman, M., Dommergue, A., Scarchilli, C., Varde, M., et al. (2018). Feedback mechanisms between snow and atmospheric mercury: Results and observations from field campaigns on the Antarctic plateau. Chemosphere, 197, 306–317.
Abstract: The Antarctic Plateau snowpack is an important environment for the mercury geochemical cycle. We have extensively characterized and compared the changes in surface snow and atmospheric mercury concentrations that occur at Dome C. Three summer sampling campaigns were conducted between 2013 and 2016. The three campaigns had different meteorological conditions that significantly affected mercury deposition processes and its abundance in surface snow. In the absence of snow deposition events, the surface mercury concentration remained stable with narrow oscillations, while an increase in precipitation results in a higher mercury variability. The Hg concentrations detected confirm that snowfall can act as a mercury atmospheric scavenger. A high temporal resolution sampling experiment showed that surface concentration changes are connected with the diurnal solar radiation cycle. Mercury in surface snow is highly dynamic and it could decrease by up to 90% within 4/6 h. A negative relationship between surface snow mercury and atmospheric concentrations has been detected suggesting a mutual dynamic exchange between these two environments. Mercury concentrations were also compared with the Br concentrations in surface and deeper snow, results suggest that Br could have an active role in Hg deposition, particularly when air masses are from coastal areas. This research presents new information on the presence of Hg in surface and deeper snow layers, improving our understanding of atmospheric Hg deposition to the snow surface and the possible role of re-emission on the atmospheric Hg concentration. (C) 2018 Elsevier Ltd. All rights reserved.
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Srivastava, D., Tomaz, S., Favez, O., Lanzafame, G. M., Golly, B., Besombes, J. L., et al. (2018). Speciation of organic fraction does matter for source apportionment. Part 1: A one-year campaign in Grenoble (France). Science Of The Total Environment, 624, 1598–1611.
Abstract: PM10 source apportionment was performed by positive matrix factorization (PMF) using specific primary and secondary organic molecular markers on samples collected over a one year period (2013) at an urban station in Grenoble (France). The results provided a 9-factor optimum solution, including sources rarely apportioned in the literature, such as two types of primary biogenic organic aerosols (fungal spores and plant debris), as well as specific biogenic and anthropogenic secondary organic aerosols (SOA). These sources were identified thanks to the use of key organic markers, namely, polyols, odd number higher alkanes, and several SOA markers related to the oxidation of isoprene, alpha-pinene, toluene and polycyclic aromatic hydrocarbons (PAHs). Primary and secondary biogenic contributions together accounted for at least 68% of the total organic carbon (OC) in the summer, while anthropogenic primary and secondary sources represented at least 71% of OC during winter-time. A very significant contribution of anthropogenic SOA was estimated in the winter during an intense PM pollution event (PM10 > 50 μg m(-3) for several days: 18% of PM10 and 42% of OC). Specific meteorological conditions with a stagnation of pollutants over 10 days and possibly Fenton-like chemistry and self-amplification cycle of SOA formation could explain such high anthropogenic SOA concentrations during this period. Finally, PMF outputs were also used to investigate the origins of humic-like substances (HuLiS), which represented 16% of OC on an annual average basis. The results indicated that HuLiS were mainly associated with biomass burning (22%), secondary inorganic (22%). mineral dust (15%) and biogenic SOA (14%) factors. This study is probably the first to state that HuLiS are significantly associated with mineral dust. (C) 2017 Elsevier B.V. All rights rights reserved.
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Vlachou, A., Daellenbach, K. R., Bozzetti, C., Chazeau, B., Salazar, G. A., Szidat, S., et al. (2018). Advanced source apportionment of carbonaceous aerosols by coupling offline AMS and radiocarbon size-segregated measurements over a nearly 2-year period. Atmospheric Chemistry And Physics, 18(9), 6187–6206.
Abstract: Carbonaceous aerosols are related to adverse human health effects. Therefore, identification of their sources and analysis of their chemical composition is important. The offline AMS (aerosol mass spectrometer) technique offers quantitative separation of organic aerosol (OA) factors which can be related to major OA sources, either primary or secondary. While primary OA can be more clearly separated into sources, secondary (SOA) source apportionment is more challenging because different sources – anthropogenic or natural, fossil or non-fossil – can yield similar highly oxygenated mass spectra. Radiocarbon measurements provide unequivocal separation between fossil and non-fossil sources of carbon. Here we coupled these two offline methods and analysed the OA and organic carbon (OC) of different size fractions (particulate matter below 10 and 2.5 μm – PM10 and PM2.5, respectively) from the Alpine valley of Magadino (Switzerland) during the years 2013 and 2014 (219 samples). The combination of the techniques gave further insight into the characteristics of secondary OC (SOC) which was rather based on the type of SOC precursor and not on the volatility or the oxidation state of OC, as typically considered. Out of the primary sources separated in this study, biomass burning OC was the dominant one in winter, with average concentrations of 5.36 +/- 2.64 μg m(-3) for PM10 and 3.83 +/- 1.81 μg m(-3) for PM2.5, indicating that wood combustion particles were predominantly generated in the fine mode. The additional information from the size-segregated measurements revealed a primary sulfur-containing factor, mainly fossil, detected in the coarse size fraction and related to non-exhaust traffic emissions with a yearly average PM10 (PM2.5) concentration of 0.20 +/- 0.24 μg m(-3) (0.05 +/- 0.04 μg m(-3)). A primary biological OC (PBOC) was also detected in the coarse mode peaking in spring and summer with a yearly average PM10 (PM2.5) concentration of 0.79 +/- 0.31 μg m(-3) (0.24 +/- 0.20 μg m(-3)). The secondary OC was separated into two oxygenated, non-fossil OC factors which were identified based on their seasonal variability (i.e. summer and winter oxygenated organic carbon, OOC and a third anthropogenic OOC factor which correlated with fossil OC mainly peaking in winter and spring, contributing on average 13% +/- 7% (10% +/- 9 %) to the total OC in PM10 (PM2.5). The winter OOC was also connected to anthropogenic sources, contributing on average 13% +/- 13% (6% +/- 6%) to the total OC in PM10 (PM2.5). The su
mmer OOC (SOOC), stemming from oxidation of biogenic emissions, was more pronounced in the fine mode, contributing on average 43% +/- 12% (75% +/- 44 %) to the total OC in PM10 (PM2.5). In total the non-fossil OC significantly dominated the fossil OC throughout all seasons, by contributing on average 75% +/- 24% to the total OC. The results also suggested that during the cold period the prevailing source was residential biomass burning while during the warm period primary biological sources and secondary organic aerosol from the oxidation of biogenic emissions became important. However, SOC was also formed by aged fossil fuel combustion emissions not only in summer but also during the rest of the year.
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Weber, S., Uzu, G., Calas, A., Chevrier, F., Besombes, J. L., Charron, A., et al. (2018). An apportionment method for the oxidative potential of atmospheric particulate matter sources: application to a one-year study in Chamonix, France. Atmospheric Chemistry And Physics, 18(13), 9617–9629.
Abstract: Inhaled aerosolized particulate matter (PM) induces cellular oxidative stress in vivo, leading to adverse health outcomes. The oxidative potential (OP) of PM appears to be a more relevant proxy of the health impact of the aerosol rather than the total mass concentration. However, the relative contributions of the aerosol sources to the OP are still poorly known. In order to better quantify the impact of different PM sources, we sampled aerosols in a French city for one year (2014, 115 samples). A coupled analysis with detailed chemical speciation (more than 100 species, including organic and carbonaceous compounds, ions, metals and aethalometer measurements) and two OP assays (ascorbic acid, AA, and dithiothreitiol, DTT) in a simulated lung fluid (SLF) were performed in these samples. We present in this study a statistical framework using a coupled approach with positive matrix factorization (PMF) and multiple linear regression to attribute a redox-activity to PM sources. Our results highlight the importance of the biomass burning and vehicular sources to explain the observed OP for both assays. In general, we see a different contribution of the sources when considering the OP AA, OP DTT or the mass of the PM10. Moreover, significant differences are observed between the DTT and AA tests which emphasized chemical specificities of the two tests and the need of a standardized approach for the future studies on epidemiology or toxicology of the PM.
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Wegmann, M., Dutra, E., Jacobi, H. W., & Zolina, O. (2018). Spring snow albedo feedback over northern Eurasia: Comparing in situ measurements with reanalysis products. Cryosphere, 12(6), 1887–1898.
Abstract: This study uses daily observations and modern reanalyses in order to evaluate reanalysis products over northern Eurasia regarding the spring snow albedo feedback (SAF) during the period from 2000 to 2013. We used the state-of-the-art reanalyses from ERA-Interim/Land and the Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA-2) as well as an experimental set-up of ERA-Interim/Land with prescribed short grass as land cover to enhance the comparability with the station data while underlining the caveats of comparing in situ observations with gridded data. Snow depth statistics derived from daily station data are well reproduced in all three reanalyses. However day-to-day albedo variability is notably higher at the stations than for any reanalysis product. The ERAInterim grass set-up shows improved performance when representing albedo variability and generates comparable estimates for the snow albedo in spring. We find that modern reanalyses show a physically consistent representation of SAF, with realistic spatial patterns and area-averaged sensitivity estimates. However, station-based SAF values are significantly higher than in the reanalyses, which is mostly driven by the stronger contrast between snow and snow-free albedo. Switching to grass-only vegetation in ERA-Interim/Land increases the SAF values up to the level of station-based estimates. We found no significant trend in the examined 14year time series of SAF, but interannual changes of about 0.5% K-1 in both station-based and reanalysis estimates were derived. This interannual variability is primarily dominated by the variability in the snowmelt sensitivity, which is correctly captured in reanalysis products. Although modern reanalyses perform well for snow variables, efforts should be made to improve the representation of dynamic albedo changes.
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Wiedensohler, A., Andrade, M., Weinhold, K., Muller, T., Birmili, W., Velarde, F., et al. (2018). Black carbon emission and transport mechanisms to the free troposphere at the La Paz/El Alto (Bolivia) metropolitan area based on the Day of Census (2012). Atmospheric Environment, 194, 158–169.
Abstract: Urban development, growing industrialization, and increasing demand for mobility have led to elevated levels of air pollution in many large cities in Latin America, where air quality standards and WHO guidelines are frequently exceeded. The conurbation of the metropolitan area of La Paz/El Alto is one of the fastest growing urban settlements in South America with the particularity of being located in a very complex terrain at a high altitude. As many large cities or metropolitan areas, the metropolitan area of La Paz/El Alto and the Altiplano region are facing air quality deterioration. Long-term measurement data of the equivalent black carbon (eBC) mass concentrations and particle number size distributions (PNSD) from the Global Atmosphere Watch Observatory Chacaltaya (CHC; 5240 m a.s.l., above sea level) indicated a systematic transport of particle matter from the metropolitan area of La Paz/El Alto to this high altitude station and subsequently to the lower free troposphere. To better understand the sources and the transport mechanisms, we conducted eBC and PNSDs measurements during an intensive campaign at two locations in the urban area of La Paz/El Alto from September to November 2012. While the airport of El Alto site (4040 m a.s.l.) can be seen as representative of the urban and Altiplano background, the road site located in Central La Paz (3590 m a.s.l.) is representative for heavy traffic-dominated conditions. Peaks of eBC mass concentrations up to 5 μg m(-3) were observed at the El Alto background site in the early morning and evening, while minimum values were detected in the early afternoon, mainly due to thermal convection and change of the planetary boundary layer height. The traffic-related eBC mass concentrations at the road site reached maximum values of 10-20 μg m(-3). A complete traffic ban on the specific Bolivian Day of Census (November 21, 2012) led to a decrease of eBC below 1 μg m(-3) at the road site for the entire day. Compared to the day before and after, particle number concentrations decreased by a factor between 5 and 25 over the particle size range from 10 to 800 nm, while the submicrometer particle mass concentration dropped by approximately 80%. These results indicate that traffic is the dominating source of BC and particulate air pollution in the metropolitan area of La Paz/El Alto. In general, the diurnal cycle of eBC mass concentration at the Chacaltaya observatory is anti-correlated to the observations at the El Alto background site. This pattern indicates that the traffic-related particulate matter, including BC, is transported to higher altitudes with the developing of the boundary layer during daytime. The metropolitan area of La Paz/El Alto seems to be a significant source for BC of the regional lower free troposphere. From there, BC can be transported over long distances and exert impact on climate and composition of remote southern hemisphere.
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Zanatta, M., Laj, P., Gysel, M., Baltensperger, U., Vratolis, S., Eleftheriadis, K., et al. (2018). Effects of mixing state on optical and radiative properties of black carbon in the European Arctic. Atmospheric Chemistry And Physics, 18(19), 14037–14057.
Abstract: Atmospheric aging promotes internal mixing of black carbon (BC), leading to an enhancement of light absorption and radiative forcing. The relationship between BC mixing state and consequent absorption enhancement was never estimated for BC found in the Arctic region. In the present work, we aim to quantify the absorption enhancement and its impact on radiative forcing as a function of microphysical properties and mixing state of BC observed in situ at the Zeppelin Arctic station (78 degrees N) in the spring of 2012 during the CLIMSLIP (Climate impacts of short-lived pollutants in the polar region) project. Single-particle soot photometer (SP2) measurements showed a mean mass concentration of refractory black carbon (rBC) of 39 ngm(-3), while the rBC mass size distribution was of lognormal shape, peaking at an rBC mass-equivalent diameter (D-rBC) of around 240 nm. On average, the number fraction of particles containing a BC core with D-rBC > 80 nm was less than 5% in the size range (overall optical particle diameter) from 150 to 500 nm. The BC cores were internally mixed with other particulate matter. The median coating thickness of BC cores with 220 nm < D-rBC < 260 nm was 52 nm, resulting in a core-shell diameter ratio of 1.4, assuming a coated sphere morphology. Combining the aerosol absorption coefficient observed with an Aethalometer and the rBC mass concentration from the SP2, a mass absorption cross section (MAC) of 9.8 m(2) g(-1) was inferred at a wavelength of 550 nm. Consistent with direct observation, a similar MAC value (8.4m(2) g(-1) at 550 nm) was obtained indirectly by using Mie theory and assuming a coated-sphere morphology with the BC mixing state constrained from the SP2 measurements. According to these calculations, the lensing effect is estimated to cause a 54% enhancement of the MAC compared to that of bare BC particles with equal BC core size distribution. Finally, the ARTDECO radiative transfer model was used to estimate the sensitivity of the radiative balance to changes in light absorption by BC as a result of a varying degree of internal mixing at constant total BC mass. The clear-sky noontime aerosol radiative forcing over a surface with an assumed wavelength-dependent albedo of 0.76-0.89 decreased, when ignoring the absorption enhancement, by -0.12 Wm(-2) compared to the base case scenario, which was constrained with mean observed aerosol properties for the Zeppelin site in Arctic spring. The exact magnitude of this forcing difference scales with environmental conditions such as the aerosol optical depth, solar zenith angle and surface albedo. Nevertheless, our investigation suggests that the absorption enhancement due to internal mixing of BC, which is a systematic effect, should be considered for quantifying the aerosol radiative forcing in the Arctic region.
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2017 |
Bozzetti, C., El Haddad, I., Salameh, D., Daellenbach, K. R., Fermo, P., Gonzalez, R., et al. (2017). Organic aerosol source apportionment by offline-AMS over a full year in Marseille. Atmospheric Chemistry And Physics, 17(13), 8247–8268.
Abstract: We investigated the seasonal trends of OA sources affecting the air quality of Marseille (France), which is the largest harbor of the Mediterranean Sea. This was achieved by measurements of nebulized filter extracts using an aerosol mass spectrometer (offline-AMS). In total 216 PM2.5 (particulate matter with an aerodynamic diameter < 2.5 μm) filter samples were collected over 1 year from August 2011 to July 2012. These filters were used to create 54 composite samples which were analyzed by offline-AMS. The same samples were also analyzed for major water-soluble ions, metals, elemental and organic carbon (EC / OC), and organic markers, including n-alkanes, hopanes, polycyclic aromatic hydrocarbons (PAHs), lignin and cellulose pyrolysis products, and nitrocatechols. The application of positive matrix factorization (PMF) to the water-soluble AMS spectra enabled the extraction of five factors, related to hydrocarbonlike OA (HOA), cooking OA (COA), biomass burning OA (BBOA), oxygenated OA (OOA), and an industry-related OA (INDOA). Seasonal trends and relative contributions of OA sources were compared with the source apportionment of OA spectra collected from the AMS field deployment at the same station but in different years and for shorter monitoring periods (February 2011 and July 2008). Online-and offline-AMS source apportionment revealed comparable seasonal contribution of the different OA sources. Results revealed that BBOA was the dominant source during winter, representing on average 48% of the OA, while during summer the main OA component was OOA (63% of OA mass on average). HOA related to traffic emissions contributed on a yearly average 17% to the OA mass, while COA was a minor source contributing 4 %. The contribution of INDOA was enhanced during winter (17% during winter and 11% during summer), consistent with an increased contribution from light alkanes, light PAHs (fluoranthene, pyrene, phenanthrene), and selenium, which is commonly considered as a unique coal combustion and coke production marker. Online-and offline-AMS source apportionments revealed evolving levoglucosan : BBOA ratios, which were higher during late autumn and March. A similar seasonality was observed in the ratios of cellulose combustion markers to lignin combustion markers, highlighting the contribution from cellulose-rich biomass combustion, possibly related to agricultural activities.
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Bozzetti, C., Sosedova, Y., Xiao, M., Daellenbach, K. R., Ulevicius, V., Dudoitis, V., et al. (2017). Argon offline-AMS source apportionment of organic aerosol over yearly cycles for an urban, rural, and marine site in northern Europe. Atmospheric Chemistry And Physics, 17(1), 117–141.
Abstract: The widespread use of Aerodyne aerosol mass spectrometers (AMS) has greatly improved real-time organic aerosol (OA) monitoring, providing mass spectra that contain sufficient information for source apportionment. However, AMS field deployments remain expensive and demanding, limiting the acquisition of long-term datasets at many sampling sites. The offline application of aerosol mass spectrometry entailing the analysis of nebulized water extracted filter samples (offline-AMS) increases the spatial coverage accessible to AMS measurements, being filters routinely collected at many stations worldwide. PM1 (particulate matter with an aerodynamic diameter <1 μm) filter samples were collected during an entire year in Lithuania at three different locations representative of three typical environments of the southeast Baltic region: Vilnius (urban background), Rugsteliskis (rural terrestrial), and Preila (rural coastal). Aqueous filter extracts were nebulized in Ar, yielding the first AMS measurements of water-soluble atmospheric organic aerosol (WSOA) without interference from air fragments. This enables direct measurement of the CO+ fragment contribution, whose intensity is typically assumed to be equal to that of CO2+. Offline-AMS spectra reveal that the water-soluble CO2+:CO+ ratio not only shows values systematically >1 but is also dependent on season, with lower values in winter than in summer. AMS WSOA spectra were analyzed using positive matrix factorization (PMF), which yielded four factors. These factors included biomass burning OA (BBOA), local OA (LOA) contributing significantly only in Vilnius, and two oxygenated OA (OOA) factors, summer OOA (S-OOA) and background OOA (B-OOA), distinguished by their seasonal variability. The contribution of traffic exhaust OA (TEOA) was not resolved by PMF due to both low concentrations and low water solubility. Therefore, the TEOA concentration was estimated using a chemical mass balance approach, based on the concentrations of hopanes, specific markers of traffic emissions. AMS-PMF source apportionment results were consistent with those obtained from PMF applied to marker concentrations (i.e., major inorganic ions, OC/EC, and organic markers including polycyclic aromatic hydrocarbons and their derivatives, hopanes, long-chain alkanes, monosaccharides, anhydrous sugars, and lignin fragmentation products). OA was the largest fraction of PM1 and was dominated by BBOA during winter with an average concentration of 2 μg m(-3) (53% of OM), while S-OOA, probably related to biogenic emissions, was the prevalent OA component during summer with an average concentration of 1.2 μg m(-3) (45% of OM). PMF ascribed a large part of the CO+ explained variability ( 97 %) to the OOA and BBOA factors. Accordingly, we discuss a new CO+ parameterization as a function of CO2+ and C2H4O2+ fragments, which were selected to describe the variability of the OOA and BBOA factors.
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Calas, A., Uzu, G., Martins, J. M. F., Voisin, D., Spadini, L., Lacroix, T., et al. (2017). The importance of simulated lung fluid (SLF) extractions for a more relevant evaluation of the oxidative potential of particulate matter. Scientific Reports, 7.
Abstract: Particulate matter (PM) induces oxidative stress in vivo, leading to adverse health effects. Oxidative potential (OP) of PM is increasingly studied as a relevant metric for health impact (instead of PM mass concentration) as much of the ambient particle mass do not contribute to PM toxicity. Several assays have been developed to quantify PM oxidative potential and a widely used one is the acellular dithiothreitol (DTT) assay. However in such assays, particles are usually extracted with methanol or Milli-Q water which is unrepresentative of physiological conditions. For this purpose, OPDTT measurements after simulated lung fluids (SLF) extraction, in order to look at the impact of simulated lung fluid constituents, were compared to Milli-Q water extraction measurements. Our major finding is a significant decrease of the OPDTT when the artificial lysosomal fluid (ALF) solution was used. Indeed, ligand compounds are present in the SLF solutions and some induce a decrease of the OP when compared to water extraction. Our results suggest that the effect of ligands and complexation in lining fluids towards PM contaminants probably has been underestimated and should be investigated further.
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Daellenbach, K. R., Stefenelli, G., Bozzetti, C., Vlachou, A., Fermo, P., Gonzalez, R., et al. (2017). Long-term chemical analysis and organic aerosol source apportionment at nine sites in central Europe: source identification and uncertainty assessment. Atmospheric Chemistry And Physics, 17(21), 13265–13282.
Abstract: Long-term monitoring of organic aerosol is important for epidemiological studies, validation of atmospheric models, and air quality management. In this study, we apply a recently developed filter-based offline methodology using an aerosol mass spectrometer (AMS) to investigate the regional and seasonal differences of contributing organic aerosol sources. We present offline AMS measurements for particulate matter smaller than 10 μm at nine stations in central Europe with different exposure characteristics for the entire year of 2013 (819 samples). The focus of this study is a detailed source apportionment analysis (using positive matrix factorization, PMF) including in-depth assessment of the related uncertainties. Primary organic aerosol (POA) is separated in three components: hydrocarbon-like OA related to traffic emissions (HOA), cooking OA (COA), and biomass burning OA (BBOA). We observe enhanced production of secondary organic aerosol (SOA) in summer, following the increase in biogenic emissions with temperature (summer oxygenated OA, SOOA). In addition, a SOA component was extracted that correlated with an anthropogenic secondary inorganic species that is dominant in winter (winter oxy-genated OA, WOOA). A factor (sulfur-containing organic, SC-OA) explaining sulfur-containing fragments (CH3SO2+),which has an event-driven temporal behaviour, was also identified. The relative yearly average factor contributions range from 4 to 14% for HOA, from 3 to 11% for COA, from 11 to 59% for BBOA, from 5 to 23% for SC-OA, from 14 to 27% forWOOA, and from 15 to 38% for SOOA. The uncertainty of the relative average factor contribution lies between 2 and 12% of OA. At the sites north of the alpine crest, the sum of HOA, COA, and BBOA (POA) contributes less to OA (POA/OA = 0.3) than at the southern alpine valley sites (0.6). BBOA is the main contributor to POA with 87% in alpine valleys and 42% north of the alpine crest. Furthermore, the influence of primary biological particles (PBOAs), not resolved by PMF, is estimated and could contribute significantly to OA in PM10.
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De Simone, F., Artaxo, P., Bencardino, M., Cinnirella, S., Carbone, F., D'Amore, F., et al. (2017). Particulate-phase mercury emissions from biomass burning and impact on resulting deposition: a modelling assessment. Atmospheric Chemistry And Physics, 17(3), 1881–1899.
Abstract: Mercury (Hg) emissions from biomass burning (BB) are an important source of atmospheric Hg and a major factor driving the interannual variation of Hg concentrations in the troposphere. The greatest fraction of Hg from BB is released in the form of elemental Hg (Hg-(g)(0)). However, little is known about the fraction of Hg bound to particulate matter (Hg-P) released from BB, and the factors controlling this fraction are also uncertain. In light of the aims of the Minamata Convention to reduce intentional Hg use and emissions from anthropogenic activities, the relative importance of Hg emissions from BB will have an increasing impact on Hg deposition fluxes. Hg speciation is one of the most important factors determining the redistribution of Hg in the atmosphere and the geographical distribution of Hg deposition. Using the latest version of the Global Fire Emissions Database (GFEDv4.1s) and the global Hg chemistry transport model, ECHMERIT, the impact of Hg speciation in BB emissions, and the factors which influence speciation, on Hg deposition have been investigated for the year 2013. The role of other uncertainties related to physical and chemical atmospheric processes involving Hg and the influence of model parametrisations were also investigated, since their interactions with Hg speciation are complex. The comparison with atmospheric Hg-P concentrations observed at two remote sites, Amsterdam Island (AMD) and Manaus (MAN), in the Amazon showed a significant improvement when considering a fraction of Hg-P from BB. The set of sensitivity runs also showed how the quantity and geographical distribution of Hg-P emitted from BB has a limited impact on a global scale, although the inclusion of increasing fractions Hg-P does limit Hg-(g)(0) availability to the global atmospheric pool. This reduces the fraction of Hg from BB which deposits to the world's oceans from 71 to 62 %. The impact locally is, however, significant on northern boreal and tropical forests, where fires are frequent, uncontrolled and lead to notable Hg inputs to local ecosystems. In the light of ongoing climatic changes this effect could be potentially be exacerbated in the future.
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Dumont, M., Arnaud, L., Picard, G., Libois, Q., Lejeune, Y., Nabat, P., et al. (2017). In situ continuous visible and near-infrared spectroscopy of an alpine snowpack. Cryosphere, 11(3), 1091–1110.
Abstract: Snow spectral albedo in the visible/near-infrared range has been continuously measured during a winter season at Col de Porte alpine site (French Alps; 45.30(circle) N, 5.77(circle) E; 1325ma.s.l.). The evolution of such alpine snowpack is complex due to intensive precipitation, rapid melt events and Saharan dust deposition outbreaks. This study highlights that the resulting intricate variations of spectral albedo can be successfully explained by variations of the following snow surface variables: specific surface area (SSA) of snow, effective light-absorbing impurities content, presence of liquid water and slope. The methodology developed in this study disentangles the effect of these variables on snow spectral albedo. The presence of liquid water at the snow surface results in a spectral shift of the albedo from which melt events can be identified with an occurrence of false detection rate lower than 3.5 %. Snow SSA mostly impacts spectral albedo in the near-infrared range. Impurity deposition mostly impacts the albedo in the visible range but this impact is very dependent on snow SSA and surface slope. Our work thus demonstrates that the SSA estimation from spectral albedo is affected by large uncertainties for a tilted snow surface and medium to high impurity contents and that the estimation of impurity content is also affected by large uncertainties, especially for low values below 50 ng g(-1) black carbon equivalent. The proposed methodology opens routes for retrieval of SSA, impurity content, melt events and surface slope from spectral albedo. However, an exhaustive accuracy assessment of the snow black properties retrieval would require more independent in situ measurements and is beyond the scope of the present study. This time series of snow spectral albedo nevertheless already provides a new insight into our understanding of the evolution of snow surface properties.
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Giorio, C., Monod, A., Bregonzio-Rozier, L., DeWitt, H. L., Cazaunau, M., Temime-Roussel, B., et al. (2017). Cloud Processing of Secondary Organic Aerosol from Isoprene and Methacrolein Photooxidation. Journal Of Physical Chemistry A, 121(40), 7641–7654.
Abstract: Aerosol-cloud interaction contributes to the largest uncertainties in the estimation and interpretation of the Earth's changing energy budget. The present study explores experimentally the impacts of water condensation-evaporation events, mimicking processes occurring, in atmospheric clouds, on the molecular composition of secondary organic aerosol (SOA) from the photooxidation of methacrolein. A range of on and off-line mass spectrometry techniques were used to obtain a detailed chemical characterization of SOA formed in control experiments in dry conditions, in triphasic experiments simulating gas-particle-cloud droplet interactions (starting from dry conditions and from 60% relative humidity (RH)), and in bulk aqueous-phase experiments. We observed that cloud events trigger fast SOA formation accompanied by evaporative losses. These evaporative losses decreased SOA concentration in the simulation chamber by 25-32% upon RH increase, while aqueous SOA was found to be metastable and slowly evaporated after cloud dissipation. In the simulation chamber, SOA composition measured with a high-resolution time-of flight aerosol mass spectrometer, did not change during cloud events compared with high RH conditions (RH > 80%). In all experiments, off-line mass spectrometry techniques emphasize the critical role of 2-methylglyceric acid as a major product of isoprene chemistry, as an important contributor to the total SOA mass (15-20%) and as a key building block of oligomers found in the particulate phase. Interestingly, the comparison between the series of oligomers obtained from experiments performed under different conditions show a markedly different reactivity. In particular, long reaction times at high RH seem to create the conditions for aqueous-phase processing to occur in a more efficient manner than during two relatively short cloud events.
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Goursaud, S., Masson-Delmotte, V., Favier, V., Preunkert, S., Fily, M., Gallee, H., et al. (2017). A 60-year ice-core record of regional climate from Adelie Land, coastal Antarctica. Cryosphere, 11(1), 343–362.
Abstract: A 22.4 m-long shallow firn core was extracted during the 2006/2007 field season from coastal Adelie Land. Annual layer counting based on subannual analyses of delta O-18 and major chemical components was combined with 5 reference years associated with nuclear tests and non-retreat of summer sea ice to build the initial ice-core chronology (19462006), stressing uncertain counting for 8 years. We focus here on the resulting delta O-18 and accumulation records. With an average value of 21.8 +/- 6.9 cmw. e. yr(-1), local accumulation shows multi-decadal variations peaking in the 1980s, but no long-term trend. Similar results are obtained for delta O-18, also characterised by a remarkably low and variable amplitude of the seasonal cycle. The ice-core records are compared with regional records of temperature, stake area accumulation measurements and variations in sea-ice extent, and outputs from two models nudged to ERA (European Re-analysis) atmospheric reanalyses: the high-resolution atmospheric general circulation model (AGCM), including stable water isotopes ECHAM5-wiso (European Centre Hamburg model), and the regional atmospheric model Modele Atmospherique Regional (AR). A significant linear correlation is identified between decadal variations in delta O-18 and regional temperature. No significant relationship appears with regional sea-ice extent. A weak and significant correlation appears with Dumont d'Urville wind speed, increasing after 1979. The model-data comparison highlights the inadequacy of ECHAM5-wiso simulations prior to 1979, possibly due to the lack of data assimilation to constrain atmospheric reanalyses. Systematic biases are identified in the ECHAM5-wiso simulation, such as an overestimation of the mean accumulation rate and its interannual variability, a strong cold bias and an underestimation of the mean delta O-18 value and its interannual variability. As a result, relationships between simulated delta O-18 and temperature are weaker than observed. Such systematic precipitation and temperature biases are not displayed by MAR, suggesting that the model resolution plays a key role along the Antarctic ice sheet coastal topography. Interannual variations in ECHAM5-wiso temperature and precipitation accurately capture signals from meteorological data and stake observations and are used to refine the initial ice-core chronology within 2 years. After this adjustment, remarkable positive (negative) delta O-18 anomalies are identified in the ice-core record and the ECHAM5-wiso simulation in 1986 and 20
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Hattori, S., Savarino, J., Kamezaki, K., Ishino, S., Dyckmans, J., Fujinawa, T., et al. (2017). Automated system measuring triple oxygen and nitrogen isotope ratios in nitrate using the bacterial method and N2O decomposition by microwave discharge (vol 30, pg 2635, 2016). Rapid Communications In Mass Spectrometry, 31(4), 396.
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Ishino, S., Hattori, S., Savarino, J., Jourdain, B., Preunkert, S., Legrand, M., et al. (2017). Seasonal variations of triple oxygen isotopic compositions of atmospheric sulfate, nitrate, and ozone at Dumont d'Urville, coastal Antarctica. Atmospheric Chemistry And Physics, 17(5), 3713–3727.
Abstract: Triple oxygen isotopic compositions (Delta O-17 = delta O-17-0.52 x delta O-18) of atmospheric sulfate (SO42-) and nitrate (NO3-) in the atmosphere reflect the relative contribution of oxidation pathways involved in their formation processes, which potentially provides information to reveal missing reactions in atmospheric chemistry models. However, there remain many theoretical assumptions for the controlling factors of Delta O-17(SO42-) and Delta O-17(NO3-) values in those model estimations. To test one of those assumption that Delta O-17 values of ozone (O-3) have a flat value and do not influence the seasonality of Delta O-17(SO42-) and Delta O-17(NO3-) values, we performed the first simultaneous measurement of Delta O-17 values of atmospheric sulfate, nitrate, and ozone collected at Dumont d'Urville (DDU) Station (66 degrees 40 ' S, 140 degrees 01 ' E) throughout 2011. Delta O-17 values of sulfate and nitrate exhibited seasonal variation characterized by minima in the austral summer and maxima in winter, within the ranges of 0.9-3.4 and 23.0-41.9 %, respectively. In contrast, Delta O-17 values of ozone showed no significant seasonal variation, with values of 26 +/- 1% throughout the year. These contrasting seasonal trends suggest that seasonality in Delta O-17(SO42-) and Delta O-17(NO3-) values is not the result of changes in Delta O-17(O-3), but of the changes in oxidation chemistry. The trends with summer minima and are caused by sunlight-driven changes in the relative contribution of O3 oxidation to the oxidation by HOx, ROx, and H2O2. In addition to that general trend, by comparing Delta O-17(SO42-) and Delta O-17(NO3-) values to ozone mixing ratios, we found that Delta O-17(SO42-) values observed in spring (September to November) were lower than in fall (March to May), while there was no significant spring and fall difference in Delta O-17(NO3-) values. The relatively lower sensitivity of Delta O-17(SO42-) values to the ozone mixing ratio in spring compared to fall is possibly explained by (i) the increased contribution of SO2 oxidations by OH and H2O2 caused by NOx emission from snowpack and/ or (ii) SO2 oxidation by hypohalous acids (HOX = HOCl + HOBr) in the aqueous phase.
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Landais, A., Casado, M., Prie, F., Magand, O., Arnaud, L., Ekaykin, A., et al. (2017). Surface studies of water isotopes in Antarctica for quantitative interpretation of deep ice core data. Comptes Rendus Geoscience, 349(4), 139–150.
Abstract: Polar ice cores are unique climate archives. Indeed, most of them have a continuous stratigraphy and present high temporal resolution of many climate variables in a single archive. While water isotopic records (delta D or delta O-18) in ice cores are often taken as references for past atmospheric temperature variations, their relationship to temperature is associated with a large uncertainty. Several reasons are invoked to explain the limitation of such an approach; in particular, post-deposition effects are important in East Antarctica because of the low accumulation rates. The strong influence of post-deposition processes highlights the need for surface polar research programs in addition to deep drilling programs. We present here new results on water isotopes from several recent surface programs, mostly over East Antarctica. Together with previously published data, the new data presented in this study have several implications for the climatic reconstructions based on ice core isotopic data: (1) The spatial relationship between surface mean temperature and mean snow isotopic composition over the first meters in depth can be explained quite straightforwardly using simple isotopic models tuned to d-excess vs. delta O-18 evolution in transects on the East Antarctic sector. The observed spatial slopes are significantly higher (similar to 0.7-0.8 parts per thousand. degrees C (1) for delta O-18 vs. temperature) than seasonal slopes inferred from precipitation data at Vostok and Dome C (0.35 to 0.46 parts per thousand. degrees C (1)). We explain these differences by changes in condensation versus surface temperature between summer and winter in the central East Antarctic plateau, where the inversion layer vanishes in summer. (2) Post-deposition effects linked to exchanges between the snow surface and the atmospheric water vapor lead to an evolution of delta O-18 in the surface snow, even in the absence of any precipitation event. This evolution preserves the positive correlation between the delta O-18 of snow and surface temperature, but is associated with a much slower delta O-18-vs-temperature slope than the slope observed in the seasonal precipitation. (3) Post-deposition effects clearly limit the archiving of high-resolution (seasonal) climatic variability in the polar snow, but we suggest that sites with an accumulation rate of the order of 40 kg.m (2).yr (1) may record a seasonal cycle at shallow depths. (C) 2017 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
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Lim, S., Fain, X., Ginot, P., Mikhalenko, V., Kutuzov, S., Paris, J. D., et al. (2017). Black carbon variability since preindustrial times in the eastern part of Europe reconstructed from Mt. Elbrus, Caucasus, ice cores. Atmospheric Chemistry And Physics, 17(5), 3489–3505.
Abstract: Black carbon (BC), emitted by fossil fuel combustion and biomass burning, is the second largest manmade contributor to global warming after carbon dioxide (Bond et al., 2013). However, limited information exists on its past emissions and atmospheric variability. In this study, we present the first high-resolution record of refractory BC (rBC, including mass concentration and size) reconstructed from ice cores drilled at a high-altitude eastern European site in Mt. Elbrus (ELB), Caucasus (5115ma. s.l.). The ELB ice core record, covering the period 1825-2013, reflects the atmospheric load of rBC particles at the ELB site transported from the European continent with a larger rBC input from sources located in the eastern part of Europe. In the first half of the 20th century, European anthropogenic emissions resulted in a 1.5-fold increase in the ice core rBC mass concentrations with respect to its level in the preindustrial era (before 1850). The summer (winter) rBC mass concentrations increased 5-fold (3.3-fold) in 1960-1980, followed by a decrease until similar to 2000. Over the last decade, the rBC signal for summertime slightly increased. We have compared the signal with the atmospheric BC load simulated using past BC emissions (ACCMIP and MACCity inventories) and taken into account the contribution of different geographical regions to rBC distribution and deposition at the ELB site. Interestingly, the observed rBC variability in the ELB ice core record since the 1960s is not in perfect agreement with the simulated atmospheric BC load. Similar features between the ice core rBC record and the best scenarios for the atmospheric BC load support anthropogenic BC increase in the 20th century being reflected in the ELB ice core record. However, the peak in BC mass concentration observed in similar to 1970 in the ice core is estimated to occur a decade later from past inventories. BC emission inventories for the period 1960s-1970s may be underestimating European anthropogenic emissions. Furthermore, for summertime snow layers of the 2000s, the slightly increasing trend of rBC deposition likely reflects recent changes in anthropogenic and biomass burning BC emissions in the eastern part of Europe. Our study highlights that the past changes in BC emissions of eastern Europe need to be considered in assessing ongoing air quality regulation.
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Rose, C., Sellegri, K., Moreno, I., Velarde, F., Ramonet, M., Weinhold, K., et al. (2017). CCN production by new particle formation in the free troposphere. Atmospheric Chemistry And Physics, 17(2), 1529–1541.
Abstract: Global models predict that new particle formation (NPF) is, in some environments, responsible for a substantial fraction of the total atmospheric particle number concentration and subsequently contributes significantly to cloud condensation nuclei (CCN) concentrations. NPF events were frequently observed at the highest atmospheric observatory in the world, on Chacaltaya (5240 m a.s.l.), Bolivia. The present study focuses on the impact of NPF on CCN population. Neutral cluster and Air Ion Spectrometer and mobility particle size spectrometer measurements were simultaneously used to follow the growth of particles from cluster sizes down to similar to 2 nm up to CCN threshold sizes set to 50, 80 and 100 nm. Using measurements performed between 1 January and 31 December 2012, we found that 61% of the 94 analysed events showed a clear particle growth and significant enhancement of the CCN-relevant particle number concentration. We evaluated the contribution of NPF, relative to the transport and growth of pre-existing particles, to CCN size. The averaged production of 50 nm particles during those events was 5072, and 1481 cm(-3) for 100 nm particles, with a larger contribution of NPF compared to transport, especially during the wet season. The data set was further segregated into boundary layer (BL) and free troposphere (FT) conditions at the site. The NPF frequency of occurrence was higher in the BL (48 %) compared to the FT (39 %). Particle condensational growth was more frequently observed for events initiated in the FT, but on average faster for those initiated in the BL, when the amount of condensable species was most probably larger. As a result, the potential to form new CCN was higher for events initiated in the BL (67% against 53% in the FT). In contrast, higher CCN number concentration increases were found when the NPF process initially occurred in the FT, under less polluted conditions. This work highlights the competition between particle growth and the removal of freshly nucleated particles by coagulation processes. The results support model predictions which suggest that NPF is an effective source of CCN in some environments, and thus may influence regional climate through cloud-related radiative processes.
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Samake, A., Uzu, G., Martins, J. M. F., Calas, A., Vince, E., Parat, S., et al. (2017). The unexpected role of bioaerosols in the Oxidative Potential of PM. Scientific Reports, 7.
Abstract: Bioaerosols represent up to 15-25% of PM by mass, but there is currently no assessment of their impact on Oxidative Potential (OP), or capacity of particulate matter (PM) to produce damaging oxidative reactions in the human lungs. Here, the OP of selected bioaerosols (bacteria cells vs fungal spores) was assessed through the cell-free DTT assay. Results show that bioaerosols induce Reactive Oxygen Species (ROS) production, varying along the microorganism type, species, and concentration. Fungal spores show up to 10 times more ROS generation than bacterial cells. At the highest concentrations, fungal spores present as much oxidative reactivity as the most redox-active airborne chemicals (Copper, Naphtoquinone). Moreover, bioaerosols substantially influence OP of ambient PM and that of its chemical constituents: in presence of A. fumigatus spores, the OP of Cu/NQ is increased by a factor of 2 to 5, whereas, 10(4) and 10(5) S. epidermidis bacterial cells. mL(-1) halves the OP of Cu/NQ. Finally, viable and gamma-rays-killed model bioaerosols present similar oxidative reactivity, suggesting a metabolism-independent cellular mechanism. These results reveal the importance of bioaerosols for PM reactivity. PM toxicity can be modified due to bioaerosols contribution or by their ability to modulate the OP of toxic chemicals present in PM.
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Schwier, A. N., Sellegri, K., Mas, S., Charriere, B., Pey, J., Rose, C., et al. (2017). Primary marine aerosol physical flux and chemical composition during a nutrient enrichment experiment in mesocosms in the Mediterranean Sea. Atmospheric Chemistry And Physics, 17(23), 14645–14660.
Abstract: While primary marine aerosol (PMA) is an important part of global aerosol total emissions, its chemical composition and physical flux as a function of the biogeo-chemical properties of the seawater still remain highly un-characterized due to the multiplicity of physical, chemical and biological parameters that are involved in the emission process. Here, two nutrient-enriched mesocosms and one control mesocosm, both filled with Mediterranean seawater, were studied over a 3-week period. PMA generated from the mesocosm waters were characterized in term of chemical composition, size distribution and size-segregated cloud condensation nuclei (CCN), as a function of the seawater chlorophyll a (Chl a) concentration, pigment composition, virus and bacteria abundances. The aerosol number size distribution flux was primarily affected by the seawater temperature and did not vary significantly from one mesocosm to the other. The aerosol number size distribution flux was primarily affected by the seawater temperature and did not vary significantly from one mesocosm to the other. Particle number and CCN aerosol fluxes increase by a factor of 2 when the temperature increases from 22 to 32 degrees C, for all particle submicron sizes. This effect, rarely observed in previous studies, could be specific to oligotrophic waters and/or to this temperature range. In all mesocosms (enriched and control mesocosms), we detected an enrichment of calcium (+ 500 %) and a deficit in chloride (36 %) in the submicron PMA mass compared to the literature inorganic composition of the seawater. There are indications that the chloride deficit and calcium enrichment are linked to biological processes, as they are found to be stronger in the enriched mesocosms. This implies a non-linear transfer function between the seawater composition and PMA composition, with complex processes taking place at the interface during the bubble bursting. We found that the artificial phytoplankton bloom did not affect the CCN activation diameter (D-p,D- 50,D- (average) = 59.85 +/- 3.52 nm and D-p,D-50,D- average = 93.42 +/- 5.14 nm for supersaturations of 0.30 and 0.15% respectively) or the organic fraction of the submicron PMA (average organic to total mass = 0.31 +/- 0.07) compared to the control mesocosm. Contrary to previous observations in natural bloom mesocosm experiments, the correlation between the particle organic fraction and the seawater Chl a was poor, indicating that Chl a is likely not a straightforward proxy for predicting, on a daily scale, PMA organi
c fraction in models for all types of sea and ocean waters. Instead, the organic fraction of the Aitken mode particles were more significantly linked to heterotrophic flagellates, viruses and dissolved organic carbon (DOC). We stress that different conclusions may be obtained in natural (non-enriched) or non-oligotrophic systems.
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Sprovieri, F., Pirrone, N., Bencardino, M., D'Amore, F., Angot, H., Barbante, C., et al. (2017). Five-year records of mercury wet deposition flux at GMOS sites in the Northern and Southern hemispheres. Atmospheric Chemistry And Physics, 17(4), 2689–2708.
Abstract: The atmospheric deposition of mercury (Hg) occurs via several mechanisms, including dry and wet scavenging by precipitation events. In an effort to understand the atmospheric cycling and seasonal depositional characteristics of Hg, wet deposition samples were collected for approximately 5 years at 17 selected GMOS monitoring sites located in the Northern and Southern hemispheres in the framework of the Global Mercury Observation System (GMOS) project. Total mercury (THg) exhibited annual and seasonal patterns in Hg wet deposition samples. Interannual differences in total wet deposition are mostly linked with precipitation volume, with the greatest deposition flux occurring in the wettest years. This data set provides a new insight into baseline concentrations of THg concentrations in precipitation worldwide, particularly in regions such as the Southern Hemisphere and tropical areas where wet deposition as well as atmospheric Hg species were not investigated before, opening the way for future and additional simultaneous measurements across the GMOS network as well as new findings in future modeling studies.
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Sylvestre, A., Mizzi, A., Mathiot, S., Masson, F., Jaffrezo, J. L., Dron, J., et al. (2017). Comprehensive chemical characterization of industrial PM2.5 from steel industry activities. Atmospheric Environment, 152, 180–190.
Abstract: Industrial sources are among the least documented PM (Particulate Matter) source in terms of chemical composition, which limits our understanding of their effective impact on ambient PM concentrations. We report 4 chemical emission profiles of PM2.5 for multiple activities located in a vast metallurgical complex. Emissions profiles were calculated as the difference of species concentrations between an upwind and a downwind site normalized by the absolute PM2.5 enrichment between both sites. We characterized the PM2.5 emissions profiles of the industrial activities related to the cast iron (complex 1) and the iron ore conversion processes (complex 2), as well as 2 storage areas: a blast furnace slag area (complex 3) and an ore terminal (complex 4). PM2.5 major fractions (Organic Carbon (OC) and Elemental Carbon (EC), major ions), organic markers as well as metals/trace elements are reported for the 4 industrial complexes. Among the trace elements, iron is the most emitted for the complex 1 (146.0 mg g(-1) of PM2.5), the complex 2 (70.07 mg g(-1)) and the complex 3 (124.4 mg g(-1)) followed by Al, Mn and Zn. A strong emission of Polycyclic Aromatic Hydrocarbons (PAH), representing 1.3% of the Organic Matter (OM), is observed for the iron ore transformation complex (complex 2) which merges the activities of coke and iron sinter production and the blast furnace processes. In addition to unsubstituted PAHs, sulfur containing PAHs (SPAHs) are also significantly emitted (between 0.011 and 0.068 mg g(-1)) by the complex 2 and could become very useful organic markers of steel industry activities. For the complexes 1 and 2 (cast iron and iron ore converters), a strong fraction of sulfate ranging from 0.284 to 0336 g g(-1)) and only partially neutralized by ammonium, is observed indicating that sulfates, if not directly emitted by the industrial activity, are formed very quickly in the plume. Emission from complex 4 (Ore terminal) are characterized by high contribution of Al (125.7 mg g(-1) of PM2.5) but also, in a lesser extent, of Fe, Mn, Ti and Zn. We also highlighted high contribution of calcium ranging from 0.123 to 0.558 g g(-1) for all of the industrial complexes under study. Since calcium is also widely used as a proxy of the dust contributions in source apportionment studies, our results suggest that this assumption should be reexamined in environments impacted by industrial emissions. (C) 2016 Elsevier Ltd. All rights reserved.
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Tomaz, S., Jaffrezo, J. L., Favez, O., Perraudin, E., Villenave, E., & Albinet, A. (2017). Sources and atmospheric chemistry of oxy- and nitro-PAHs in the ambient air of Grenoble (France). Atmospheric Environment, 161, 144–154.
Abstract: Total individual concentrations (in both gaseous and particulate phases) of 80 polycyclic aromatic compounds (PACs) including 32 nitro-PAHs, 27 oxy-PAHs (polycyclic aromatic hydrocarbons) and 21 parent PAHs have been investigated over a year in the ambient air of Grenoble (France) together with an extended aerosol chemical characterization. The results indicated that their concentrations were strongly affected by primary emissions in cold period, especially from residential heating (i.e. biomass burning). Besides, secondary processes occurred in summer but also in cold period under specific conditions such as during long thermal inversion layer periods and severe PM pollution events. Different secondary processes were involved during both PM pollution events observed in March April and in December 2013. During the first one, long range transport of air masses, nitrate chemistry and secondary nitro-PAH formation seemed linked. During the second one, the accumulation of primary pollutants over several consecutive days enhanced secondary chemical processes notably highlighted by the dramatic increase of oxy-PAH concentrations. The study of the time trends of ratios of individual nitro- or oxy-PAHs to parent PAHs, in combination with key primary or secondary aerosol species and literature data, allowed the identification of potential molecular markers of PAH oxidation. Finally, 6H-dibenzo[b,d]pyran-6-one, biphenyl-2,2'-dicarboxaldehyde and 3-nitrophenanthrene have been selected to be the best candidates as markers of PAH oxidation processes in ambient air. (C) 2017 Elsevier Ltd. All rights reserved.
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Travnikov, O., Angot, H., Artaxo, P., Bencardino, M., Bieser, J., D'Amore, F., et al. (2017). Multi-model study of mercury dispersion in the atmosphere: atmospheric processes and model evaluation. Atmospheric Chemistry And Physics, 17(8), 5271–5295.
Abstract: Current understanding of mercury (Hg) behavior in the atmosphere contains significant gaps. Some key characteristics of Hg processes, including anthropogenic and geogenic emissions, atmospheric chemistry, and air-surface exchange, are still poorly known. This study provides a complex analysis of processes governing Hg fate in the atmosphere involving both measured data from ground-based sites and simulation results from chemical transport models. A variety of long-term measurements of gaseous elemental Hg (GEM) and reactive Hg (RM) concentration as well as Hg wet deposition flux have been compiled from different global and regional monitoring networks. Four contemporary global-scale transport models for Hg were used, both in their state-of-the-art configurations and for a number of numerical experiments to evaluate particular processes. Results of the model simulations were evaluated against measurements. As follows from the analysis, the interhemispheric GEM gradient is largely formed by the prevailing spatial distribution of anthropogenic emissions in the Northern Hemisphere. The contributions of natural and secondary emissions enhance the south-to-north gradient, but their effect is less significant. Atmospheric chemistry has a limited effect on the spatial distribution and temporal variation of GEM concentration in surface air. In contrast, RM air concentration and wet deposition are largely defined by oxidation chemistry. The Br oxidation mechanism can reproduce successfully the observed seasonal variation of the RM/GEM ratio in the near-surface layer, but it predicts a wet deposition maximum in spring instead of in summer as observed at monitoring sites in North America and Europe. Model runs with OH chemistry correctly simulate both the periods of maximum and minimum values and the amplitude of observed seasonal variation but shift the maximum RM/GEM ratios from spring to summer. O-3 chemistry does not predict significant seasonal variation of Hg oxidation. Hence, the performance of the Hg oxidation mechanisms under study differs in the extent to which they can reproduce the various observed parameters. This variation implies possibility of more complex chemistry and multiple Hg oxidation pathways occurring concurrently in various parts of the atmosphere.
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Tuzet, F., Dumont, M., Lafaysse, M., Picard, G., Arnaud, L., Voisin, D., et al. (2017). A multilayer physically based snowpack model simulating direct and indirect radiative impacts of light-absorbing impurities in snow. Cryosphere, 11(6), 2633–2653.
Abstract: Light-absorbing impurities (LAIs) decrease snow albedo, increasing the amount of solar energy absorbed by the snowpack. Its most intuitive and direct impact is to accelerate snowmelt. Enhanced energy absorption in snow also modifies snow metamorphism, which can indirectly drive further variations of snow albedo in the near-infrared part of the solar spectrum because of the evolution of the near-surface snow microstructure. New capabilities have been implemented in the detailed snowpack model SURFEX/ISBACrocus (referred to as Crocus) to account for impurities' deposition and evolution within the snowpack and their direct and indirect impacts. Once deposited, the model computes impurities' mass evolution until snow melts out, accounting for scavenging by meltwater. Taking advantage of the recent inclusion of the spectral radiative transfer model TARTES (Two-stream Analytical Radiative TransfEr in Snow model) in Crocus, the model explicitly represents the radiative impacts of light-absorbing impurities in snow. The model was evaluated at the Col de Porte experimental site (French Alps) during the 2013-2014 snow season against in situ standard snow measurements and spectral albedo measurements. In situ meteorological measurements were used to drive the snowpack model, except for aerosol deposition fluxes. Black carbon (BC) and dust deposition fluxes used to drive the model were extracted from simulations of the atmospheric model ALADIN-Climate. The model simulates snowpack evolution reasonably, providing similar performances to our reference Crocus version in terms of snow depth, snow water equivalent (SWE), near-surface specific surface area (SSA) and shortwave albedo. Since the reference empirical albedo scheme was calibrated at the Col de Porte, improvements were not expected to be significant in this study. We show that the deposition fluxes from the ALADIN-Climate model provide a reasonable estimate of the amount of light-absorbing impurities deposited on the snowpack except for extreme deposition events which are greatly underestimated. For this particular season, the simulated melt-out date advances by 6 to 9 days due to the presence of light-absorbing impurities. The model makes it possible to apportion the relative importance of direct and indirect impacts of light-absorbing impurities on energy absorption in snow. For the snow season considered, the direct impact in the visible part of the solar spectrum accounts for 85% of the total impact, while the indirect impact related to accelerated snow metamorphi
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Xia, J. Y., McGuire, A. D., Lawrence, D., Burke, E., Chen, G. S., Chen, X. D., et al. (2017). Terrestrial ecosystem model performance in simulating productivity and its vulnerability to climate change in the northern permafrost region. Journal Of Geophysical Research-Biogeosciences, 122(2), 430–446.
Abstract: Realistic projection of future climate-carbon (C) cycle feedbacks requires better understanding and an improved representation of the C cycle in permafrost regions in the current generation of Earth system models. Here we evaluated 10 terrestrial ecosystem models for their estimates of net primary productivity (NPP) and responses to historical climate change in permafrost regions in the Northern Hemisphere. In comparison with the satellite estimate from the Moderate Resolution Imaging Spectroradiometer (MODIS; 246 +/- 6gCm(-2) yr (-1)), most models produced higher NPP (309 +/- 12 g Cm-2 yr(-1)) over the permafrost region during 2000-2009. By comparing the simulated gross primary productivity (GPP) with a flux tower-based database, we found that although mean GPP among the models was only overestimated by 10% over 1982-2009, there was a twofold discrepancy among models (380 to 800 g Cm-2 yr(-1)), which mainly resulted from differences in simulated maximum monthly GPP (GPP(max)). Most models overestimated C use efficiency (CUE) as compared to observations at both regional and site levels. Further analysis shows that model variability of GPP and CUE are nonlinearly correlated to variability in specific leaf area and the maximum rate of carboxylation by the enzyme Rubisco at 25 degrees C (V-cmax_(25)), respectively. Themodels also varied in their sensitivities of NPP, GPP, and CUE to historical changes in climate and atmospheric CO2 concentration. These results indicate that model predictive ability of the C cycle in permafrost regions can be improved by better representation of the processes controlling CUE and GPP(max) as well as their sensitivity to climate change.
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Alastuey, A., Querol, X., Aas, W., Lucarelli, F., Pérez, N., Moreno, T., et al. (2016). Geochemistry of PM10 over Europe during the EMEP intensive measurement periods in summer 2012 and winter 2013. Acp, 16(10), 6107–6129.
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Angot, H., Dastoor, A., De Simone, F., Gardfeldt, K., Gencarelli, C. N., Hedgecock, I. M., et al. (2016). Chemical cycling and deposition of atmospheric mercury in polar regions: review of recent measurements and comparison with models. Atmospheric Chemistry And Physics, 16(16), 10735–10763.
Abstract: Mercury (Hg) is a worldwide contaminant that can cause adverse health effects to wildlife and humans. While atmospheric modeling traces the link from emissions to deposition of Hg onto environmental surfaces, large uncertainties arise from our incomplete understanding of atmospheric processes (oxidation pathways, deposition, and re-emission). Atmospheric Hg reactivity is exacerbated in high latitudes and there is still much to be learned from polar regions in terms of atmospheric processes. This paper provides a synthesis of the atmospheric Hg monitoring data available in recent years (2011-2015) in the Arctic and in Antarctica along with a comparison of these observations with numerical simulations using four cutting-edge global models. The cycle of atmospheric Hg in the Arctic and in Antarctica presents both similarities and differences. Coastal sites in the two regions are both influenced by springtime atmospheric Hg depletion events and by summertime snowpack re-emission and oceanic evasion of Hg. The cycle of atmospheric Hg differs between the two regions primarily because of their different geography. While Arctic sites are significantly influenced by northern hemispheric Hg emissions especially in winter, coastal Antarctic sites are significantly influenced by the reactivity observed on the East Antarctic ice sheet due to katabatic winds. Based on the comparison of multi-model simulations with observations, this paper discusses whether the processes that affect atmospheric Hg seasonality and inter-annual variability are appropriately represented in the models and identifies research gaps in our understanding of the atmospheric Hg cycling in high latitudes.
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Angot, H., Dion, I., Vogel, N., Legrand, M., Magand, O., & Dommergue, A. (2016). Multi-year record of atmospheric mercury at Dumont d'Urville, East Antarctic coast: continental outflow and oceanic influences. Atmospheric Chemistry And Physics, 16(13), 8265–8279.
Abstract: Under the framework of the Global Mercury Observation System (GMOS) project, a 3.5-year record of atmospheric gaseous elemental mercury (Hg(0)) has been gathered at Dumont d'Urville (DDU, 66 degrees 40'S, 140 degrees 01'E, 43m above sea level) on the East Antarctic coast. Additionally, surface snow samples were collected in February 2009 during a traverse between Concordia Station located on the East Antarctic plateau and DDU. The record of atmospheric Hg(0) at DDU reveals particularities that are not seen at other coastal sites: a gradual decrease of concentrations over the course of winter, and a daily maximum concentration around midday in summer. Additionally, total mercury concentrations in surface snow samples were particularly elevated near DDU (up to 194.4 ng L-1) as compared to measurements at other coastal Antarctic sites. These differences can be explained by the more frequent arrival of inland air masses at DDU than at other coastal sites. This confirms the influence of processes observed on the Antarctic plateau on the cycle of atmospheric mercury at a continental scale, especially in areas subject to recurrent katabatic winds. DDU is also influenced by oceanic air masses and our data suggest that the ocean plays a dual role on Hg(0) concentrations. The open ocean may represent a source of atmospheric Hg(0) in summer whereas the sea-ice surface may provide reactive halogens in spring that can oxidize Hg(0). This paper also discusses implications for coastal Antarctic ecosystems and for the cycle of atmospheric mercury in high southern latitudes.
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Angot, H., Magand, O., Helmig, D., Ricaud, P., Quennehen, B., Gallee, H., et al. (2016). New insights into the atmospheric mercury cycling in central Antarctica and implications on a continental scale. Atmospheric Chemistry And Physics, 16(13), 8249–8264.
Abstract: Under the framework of the GMOS project (Global Mercury Observation System) atmospheric mercury monitoring has been implemented at Concordia Station on the high-altitude Antarctic plateau (75 degrees 06'S, 123 degrees 20'E, 3220m above sea level). We report here the first year-round measurements of gaseous elemental mercury (Hg(0)) in the atmosphere and in snowpack interstitial air on the East Antarctic ice sheet. This unique data set shows evidence of an intense oxidation of atmospheric Hg(0) in summer (24-hour daylight) due to the high oxidative capacity of the Antarctic plateau atmosphere in this period of the year. Summertime Hg(0) concentrations exhibited a pronounced daily cycle in ambient air with maximal concentrations around midday. Photochemical reactions and chemical exchange at the air-snow interface were prominent, highlighting the role of the snowpack on the atmospheric mercury cycle. Our observations reveal a 20 to 30% decrease of atmospheric Hg(0) concentrations from May to mid-August (winter, 24 h darkness). This phenomenon has not been reported elsewhere and possibly results from the dry deposition of Hg(0) onto the snowpack. We also reveal the occurrence of multi-day to weeklong atmospheric Hg(0) depletion events in summer, not associated with depletions of ozone, and likely due to a stagnation of air masses above the plateau triggering an accumulation of oxidants within the shallow boundary layer. Our observations suggest that the inland atmospheric reservoir is depleted in Hg(0) in summer. Due to katabatic winds flowing out from the Antarctic plateau down the steep vertical drops along the coast and according to observations at coastal Antarctic stations, the striking reactivity observed on the plateau most likely influences the cycle of atmospheric mercury on a continental scale.
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Bonvalot, L., Tuna, T., Fagault, Y., Jaffrezo, J. L., Jacob, V., Chevrier, F., et al. (2016). Estimating contributions from biomass burning, fossil fuel combustion, and biogenic carbon to carbonaceous aerosols in the Valley of Chamonix: a dual approach based on radiocarbon and levoglucosan. Atmospheric Chemistry And Physics, 16(21), 13753–13772.
Abstract: Atmospheric particulate matter (PM) affects the climate in various ways and has a negative impact on human health. In populated mountain valleys in Alpine regions, emissions from road traffic contribute to carbonaceous aerosols, but residential wood burning can be another source of PM during winter. We determine the contribution of fossil and non-fossil carbon sources by measuring radiocarbon in aerosols using the recently installed AixMICADAS facility. The accelerator mass spectrometer is coupled to an elemental analyzer (EA) by means of a gas interface system directly connected to the gas ion source. This system provides rapid and accurate radiocarbon measurements for small samples (10-100 μgC) with minimal preparation from the aerosol filters. We show how the contamination induced by the EA protocol can be quantified and corrected for. Several standards and synthetic samples are then used to demonstrate the precision and accuracy of aerosol measurements over the full range of expected C-14/C-12 ratios, ranging from modern carbon to fossil carbon depleted in C-14. Aerosols sampled in Chamonix and Passy (Arve River valley, French Alps) from November 2013 to August 2014 are analyzed for both radiocarbon (124 analyses in total) and levoglucosan, which is commonly used as a specific tracer for biomass burning. NOx concentration, which is expected to be associated with traffic emissions, is also monitored. Based on C-14 measurements, we can show that the relative fraction of non-fossil carbon is significantly higher in winter than in summer. In winter, non-fossil carbon represents about 85% of total carbon, while in summer this proportion is still 75% considering all samples. The largest total carbon and levoglucosan concentrations are observed for winter aerosols with values up to 50 and 8 μg m(-3), respectively. These levels are higher than those observed in many European cities, but are close to those for other polluted Alpine valleys. The non-fossil carbon concentrations are strongly correlated with the levoglucosan concentrations in winter samples, suggesting that almost all of the non-fossil carbon originates from wood combustion used for heating during winter. For summer samples, the joint use of C-14 and levoglucosan measurements leads to a new model to separately quantify the contributions of biomass burning and biogenic emissions in the non-fossil fraction. The comparison of the biogenic fraction with polyols (a proxy for primary soil biogenic emissions) and with the temperature suggests a major influence of the secondary biogenic aerosols. Significant correlations are found between the NOx concentration and the fossil carbon concentration for all seasons and sites, confirming the relation between road traffic emissions and fossil carbon. Overall, this dual approach combining radiocarbon and levoglucosan analyses strengthens the conclusion concerning the impact of biomass burning. Combining these geochemical data serves both to detect and quantify additional carbon sources. The Arve River valley provides the first illustration of aerosols of this model.
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Cavalli, F., Alastuey, A., Areskoug, H., Ceburnis, D., Cech, J., Genberg, J., et al. (2016). A European aerosol phenomenology-4: Harmonized concentrations of carbonaceous aerosol at 10 regional background sites across Europe. Atmospheric Environment, 144, 133–145.
Abstract: Although particulate organic and elemental carbon (OC and EC) are important constituents of the suspended atmospheric particulate matter (PM), measurements of OC and EC are much less common and More uncertain than measurements of e.g. the ionic components of PM. In the framework of atmospheric research infrastructures supported by the European Union, actions have been undertaken to determine and mitigate sampling artefacts, and assess the comparability of OC and EC data obtained in a network of 10 atmospheric observatories across Europe. Positive sampling artefacts (from 0:4 to 2.8 μg C/m(3)) and analytical discrepancies (between -50% and +40% for the EC/TC ratio) have been taken into account to generate a robust data set, from which we established the phenomenology of carbonaceous aerosols at regional background sites in Europe. Across the network, TC and EC annual average concentrations range from 0.4 to 9 μg C/m(3), and from 0.1 to 2 μg C/m(3), respectively. TC/PM10 annual mean ratios range from 0.11 at a Mediterranean site to 0.34 at the most polluted continental site, and TC/PM2.5 ratios are slightly greater at all sites (0.15-0.42). EC/TC annual mean ratios range from 0.10 to 0.22, and do not depend much on PM concentration levels, especially in winter. Seasonal variations in PM and TC concentrations, and in TC/PM and EC/TC ratios, differ across the network, which can be explained by seasonal changes in PM source contributions at some sites. (C) 2016 The Authors. Published by Elsevier Ltd.
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Dommergue, A., Martinerie, P., Courteaud, J., Witrant, E., & Etheridge, D. M. (2016). A new reconstruction of atmospheric gaseous elemental mercury trend over the last 60 years from Greenland firn records. Atmospheric Environment, 136, 156–164.
Abstract: This study presents measurements of gaseous elemental mercury (GEM) concentrations in the 80 m of firn air at the international drilling site of NEEM in Greenland (2452 m, 77 degrees 25.8 N, 51 degrees 06.4 W). Using inverse modeling, we were able to reconstruct the atmospheric GEM trend at this Arctic site over the last 60 years. We show discrepancies between this record and the previous firn record of Summit. This could be attributed to experimental biases and/or differences in air mass transport. A multisite inverse model was used to derive an atmospheric scenario reconciling the two firn records. We show that GEM seasonal variations are very limited at these high altitude sites and thus probably unaffected by spring/summer photochemistry. The firn reconstructions suggest an increase of GEM concentrations since the 1950s peaking in the late 1960s and early 1970s. A decrease is then observed with minimum GEM concentrations around 1995-2000. The reconstruction compares well with historical mercury (Hg) releases and recent simulations of atmospheric Hg. Our optimal GEM scenario does not allow to categorically conclude on recent trends for GEM concentrations over the 2000-2010 decade. (C) 2016 Elsevier Ltd. All rights reserved.
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Gabrielli, P., Barbante, C., Bertagna, G., Berto, M., Binder, D., Carton, A., et al. (2016). Age of the Mt. Ortles ice cores, the Tyrolean Iceman and glaciation of the highest summit of South Tyrol since the Northern Hemisphere Climatic Optimum. Cryosphere, 10(6), 2779–2797.
Abstract: In 2011 four ice cores were extracted from the summit of Alto dell'Ortles (3859 m), the highest glacier of South Tyrol in the Italian Alps. This drilling site is located only 37 km southwest from where the Tyrolean Iceman, similar to 5.3 kyrs old, was discovered emerging from the ablating ice field of Tisenjoch (3210 m, near the Italian-Austrian border) in 1991. The excellent preservation of this mummy suggested that the Tyrolean Iceman was continuously embedded in prehistoric ice and that additional ancient ice was likely preserved elsewhere in South Tyrol. Dating of the ice cores from Alto dell'Ortles based on Pb-210, tritium, beta activity and C-14 determinations, combined with an empirical model (COPRA), provides evidence for a chronologically ordered ice stratigraphy from the modern glacier surface down to the bottom ice layers with an age of similar to 7 kyrs, which confirms the hypothesis. Our results indicate that the drilling site has continuously been glaciated on frozen bedrock since similar to 7 kyrs BP. Absence of older ice on the highest glacier of South Tyrol is consistent with the removal of basal ice from bedrock during the Northern Hemisphere Climatic Optimum (6-9 kyrs BP), the warmest interval in the European Alps during the Holocene. Borehole inclinometric measurements of the current glacier flow combined with surface ground penetration radar (GPR) measurements indicate that, due to the sustained atmospheric warming since the 1980s, an acceleration of the glacier Alto dell'Ortles flow has just recently begun. Given the stratigraphic-chronological continuity of the Mt. Ortles cores over millennia, it can be argued that this behaviour has been unprecedented at this location since the Northern Hemisphere Climatic Optimum.
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Kim, Y., Sartelet, K., Seigneur, C., Charron, A., Besombes, J. L., Jaffrezo, J. L., et al. (2016). Effect of measurement protocol on organic aerosol measurements of exhaust emissions from gasoline and diesel vehicles. Atmospheric Environment, 140, 176–187.
Abstract: Exhaust emissions of semi-volatile organic compounds (SVOC) from passenger vehicles are usually estimated only for the particle phase via the total particulate matter measurements. However, they also need to be estimated for the gas phase, as they are semi-volatile. To better estimate SVOC emission factors of passenger vehicles, a measurement campaign using a chassis dynamometer was conducted with different instruments: (1) a constant volume sampling (CVS) system in which emissions were diluted with filtered air and sampling was performed on filters and polyurethane foams (PUF) and (2) a Dekati Fine Particle Sampler (FPS) in which emissions were diluted with purified air and sampled with on-line instruments (PTR-ToF-MS, HR-ToF-AMS, MAAP, CPC). Significant differences in the concentrations of organic carbon (OC) measured by the instruments are observed. The differences can be explained by sampling artefacts, differences between (1) the time elapsed during sampling (in the case of filter and PUF sampling) and (2) the time elapsed from emission to measurement (in the case of on-line instruments), which vary from a few seconds to 15 min, and by the different dilution factors. To relate elapsed times and measured concentrations of OC, the condensation of SVOC between the gas and particle phases is simulated with a dynamic aerosol model. The simulation results allow us to understand the relation between elapsed times and concentrations in the gas and particle phases. They indicate that the characteristic times to reach thermodynamic equilibrium between gas and particle phases may be as long as 8 min. Therefore, if the elapsed time is less than this characteristic time to reach equilibrium, gas phase SVOC are not at equilibrium with the particle phase and a larger fraction of emitted SVOC will be in the gas phase than estimated by equilibrium theory, leading to an underestimation of emitted OC if only the particle phase is considered or if the gas-phase SVOC are estimated by equilibrium theory. Current European emission inventories for passenger cars do not yet estimate gas-phase SVOC emissions, although they may represent 60% of total emitted SVOC (gas + particle phases). (C) 2016 The Authors. Published by Elsevier Ltd.
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Kupiszewski, P., Zanatta, M., Mertes, S., Vochezer, P., Lloyd, G., Schneider, J., et al. (2016). Ice residual properties in mixed-phase clouds at the high-alpine Jungfraujoch site. Journal Of Geophysical Research-Atmospheres, 121(20), 12343–12362.
Abstract: Ice residual (IR) and total aerosol properties were measured in mixed-phase clouds (MPCs) at the high-alpine Jungfraujoch research station. Black carbon (BC) content and coating thickness of BC-containing particles were determined using single-particle soot photometers. The ice activated fraction (IAF), derived from a comparison of IR and total aerosol particle size distributions, showed an enrichment of large particles in the IR, with an increase in the IAF from values on the order of 10(-4) to 10(-3) for 100nm (diameter) particles to 0.2 to 0.3 for 1m (diameter) particles. Nonetheless, due to the high number fraction of submicrometer particles with respect to total particle number, IR size distributions were still dominated by the submicrometer aerosol. A comparison of simultaneously measured number size distributions of BC-free and BC-containing IR and total aerosol particles showed depletion of BC by number in the IR, suggesting that BC does not play a significant role in ice nucleation in MPCs at the Jungfraujoch. The potential anthropogenic climate impact of BC via the glaciation effect in MPCs is therefore likely to be negligible at this site and in environments with similar meteorological conditions and a similar aerosol population. The IAF of the BC-containing particles also increased with total particle size, in a similar manner as for the BC-free particles, but on a level 1 order of magnitude lower. Furthermore, BC-containing IR were found to have a thicker coating than the BC-containing total aerosol, suggesting the importance of atmospheric aging for ice nucleation.
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Nerentorp Mastromonaco, M. G., Gardfeldt, K., Langer, S., & Dommergue, A. (2016). Seasonal Study of Mercury Species in the Antarctic Sea Ice Environment. Environmental Science & Technology, 50(23), 12705–12712.
Abstract: Limited studies have been conducted on mercury concentrations in the polar cryosphere and the factors affecting the distribution of mercury within sea ice and snow are poorly understood. Here we present the first comprehensive seasonal study of elemental and total mercury concentrations in the Antarctic sea ice environment covering data from measurements in air, sea ice, seawater, snow, frost flowers, and brine. The average concentration of total mercury in sea ice decreased from winter (9.7 ng L-1) to spring (4.7 ng L-1) while the average elemental mercury concentration increased from winter (0.07 ng L-1) to summer (0.105 ng L-1). The opposite trends suggest potential photo or dark oxidation/reduction processes within the ice and an eventual loss of mercury via brine drainage or gas evasion of elemental mercury. Our results indicate a seasonal variation of mercury species in the polar sea ice environment probably due to varying factors such as solar radiation, temperature, brine volume, and atmospheric deposition. This study shows that the sea ice environment is a significant interphase between the polar ocean and the atmosphere and should be accounted for when studying how climate change may affect the mercury cycle in polar regions.
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Nerentorp Mastromonaco, M. N., Gardfeldt, K., Jourdain, B., Abrahamsson, K., Granfors, A., Ahnoff, M., et al. (2016). Antarctic winter mercury and ozone depletion events over sea ice. Atmospheric Environment, 129, 125–132.
Abstract: During atmospheric mercury and ozone depletion events in the springtime in polar regions gaseous elemental mercury and ozone undergo rapid declines. Mercury is quicldy transformed into oxidation products, which are subsequently removed by deposition. Here we show that such events also occur during Antarctic winter over sea ice areas, leading to additional deposition of mercury. Over four months in the Weddell Sea we measured gaseous elemental, oxidized, and particulate-bound mercury, as well as ozone in the troposphere and total and elemental mercury concentrations in snow, demonstrating a series of depletion and deposition events between July and September. The winter depletions in July were characterized by stronger correlations between mercury and ozone and larger formation of particulate-bound mercury in air compared to later spring events. It appears that light at large solar zenith angles is sufficient to initiate the photolytic formation of halogen radicals. We also propose a dark mechanism that could explain observed events in air masses coming from dark regions. Br-2 that could be the main actor in dark conditions was possibly formed in high concentrations in the marine boundary layer in the dark. These high concentrations may also have caused the formation of high concentrations of CHBr3 and CH2I2 in the top layers of the Antarctic sea ice observed during winter. These new findings show that the extent of depletion events is larger than previously believed and that winter depletions result in additional deposition of mercury that could be transferred to marine and terrestrial ecosystems. (C) 2016 Elsevier Ltd. All rights reserved.
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Pearce, D. A., Alekhina, I. A., Terauds, A., Wilmotte, A., Quesada, A., Edwards, A., et al. (2016). Aerobiology Over Antarctica – A New Initiative for Atmospheric Ecology. Frontiers in Microbiology, 7, 16.
Abstract: The role of aerial dispersal in shaping patterns of biodiversity remains poorly understood, mainly due to a lack of coordinated efforts in gathering data at appropriate temporal and spatial scales. It has been long known that the rate of dispersal to an ecosystem can significantly influence ecosystem dynamics, and that aerial transport has been identified as an important source of biological input to remote locations. With the considerable effort devoted in recent decades to understanding atmospheric circulation in the south polar region, a unique opportunity has emerged to investigate the atmospheric ecology of Antarctica, from local to continental scales. This concept note identifies key questions in Antarctic microbial biogeography and the need for standardized sampling and analysis protocols to address such questions. A consortium of polar aerobiologists is established to bring together researchers with a common interest in the airborne dispersion of microbes and other propagules in the Antarctic, with opportunities for comparative studies in the Arctic.
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Quennehen, B., Raut, J. C., Law, K. S., Daskalakis, N., Ancellet, G., Clerbaux, C., et al. (2016). Multi-model evaluation of short-lived pollutant distributions over east Asia during summer 2008. Atmospheric Chemistry And Physics, 16(17), 10765–10792.
Abstract: The ability of seven state-of-the-art chemistry-aerosol models to reproduce distributions of tropospheric ozone and its precursors, as well as aerosols over eastern Asia in summer 2008, is evaluated. The study focuses on the performance of models used to assess impacts of pollutants on climate and air quality as part of the EU ECLIPSE project. Models, run using the same ECLIPSE emissions, are compared over different spatial scales to in situ surface, vertical profiles and satellite data. Several rather clear biases are found between model results and observations, including overestimation of ozone at rural locations downwind of the main emission regions in China, as well as downwind over the Pacific. Several models produce too much ozone over polluted regions, which is then transported downwind. Analysis points to different factors related to the ability of models to simulate VOC-limited regimes over polluted regions and NOx limited regimes downwind. This may also be linked to biases compared to satellite NO2, indicating overestimation of NO2 over and to the north of the northern China Plain emission region. On the other hand, model NO2 is too low to the south and west of this region and over South Korea/Japan. Overestimation of ozone is linked to systematic underestimation of CO particularly at rural sites and downwind of the main Chinese emission regions. This is likely to be due to enhanced destruction of CO by OH. Overestimation of Asian ozone and its transport downwind implies that radiative forcing from this source may be overestimated. Model-observation discrepancies over Beijing do not appear to be due to emission controls linked to the Olympic Games in summer 2008. With regard to aerosols, most models reproduce the satellite-derived AOD patterns over eastern China. Our study nevertheless reveals an overestimation of ECLIPSE model mean surface BC and sulphate aerosols in urban China in summer 2008. The effect of the short-term emission mitigation in Beijing is too weak to explain the differences between the models. Our results rather point to an overestimation of SO2 emissions, in particular, close to the surface in Chinese urban areas. However, we also identify a clear underestimation of aerosol concentrations over northern India, suggesting that the rapid recent growth of emissions in India, as well as their spatial extension, is underestimated in emission inventories. Model deficiencies in the representation of pollution accumulation due to the Indian monsoon may also be playing a role. Comparison with vertical aerosol lidar measurements highlights a general underestimation of scattering aerosols in the boundary layer associated with overestimation in the free troposphere pointing to modelled aerosol lifetimes that are too long. This is likely linked to too strong vertical transport and/or insufficient deposition efficiency during transport or export from the boundary layer, rather than chemical processing (in the case of sulphate aerosols). Underestimation of sulphate in the boundary layer implies potentially large errors in simulated aerosol-cloud interactions, via impacts on boundary-layer clouds. This evaluation has important implications for accurate assessment of air pollutants on regional air quality and global climate based on global model calculations. Ideally, models should be run at higher resolution over source regions to better simulate urban-rural pollutant gradients and/or chemical regimes, and also to better resolve pollutant processing and loss by wet deposition as well as vertical transport. Discrepancies in vertical distributions require further quantification and improvement since these are a key factor in the determination of radiative forcing from short-lived pollutants.
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Sprovieri, F., Pirrone, N., Bencardino, M., D'Amore, F., Carbone, F., Cinnirella, S., et al. (2016). Atmospheric mercury concentrations observed at ground-based monitoring sites globally distributed in the framework of the GMOS network. Atmospheric Chemistry And Physics, 16(18), 11915–11935.
Abstract: Long-term monitoring of data of ambient mercury (Hg) on a global scale to assess its emission, transport, atmospheric chemistry, and deposition processes is vital to understanding the impact of Hg pollution on the environment. The Global Mercury Observation System (GMOS) project was funded by the European Commission (http://www.gmos.eu) and started in November 2010 with the overall goal to develop a coordinated global observing system to monitor Hg on a global scale, including a large network of ground-based monitoring stations, ad hoc periodic oceanographic cruises and measurement flights in the lower and upper troposphere as well as in the lower stratosphere. To date, more than 40 ground-based monitoring sites constitute the global network covering many regions where little to no observational data were available before GMOS. This work presents atmospheric Hg concentrations recorded worldwide in the framework of the GMOS project (2010-2015), analyzing Hg measurement results in terms of temporal trends, seasonality and comparability within the network. Major findings highlighted in this paper include a clear gradient of Hg concentrations between the Northern and Southern hemispheres, confirming that the gradient observed is mostly driven by local and regional sources, which can be anthropogenic, natural or a combination of both.
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Tomaz, S., Shahpoury, P., Jaffrezo, J. L., Lammel, G., Perraudin, E., Villenave, E., et al. (2016). One-year study of polycyclic aromatic compounds at an urban site in Grenoble (France): Seasonal variations, gas/particle partitioning and cancer risk estimation. Science Of The Total Environment, 565, 1071–1083.
Abstract: 21 PAHs, 27 oxy-PAHs and 32 nitro-PAHs were measured every third day over a year in both gaseous (G) and particulate PM10 (P) phases in ambient air of Grenoble (France). Mean total concentrations (G + P) of PAHs and oxy-PAHs were in the same range and about 10 ng m(-3). Nitro-PAHs were 50 to 100 times less concentrated averaging 100 pg m(-3). Polycyclic aromatic compound (PAC) concentrations were 5 to 7 times higher in “cold” period (October to March) than in “warm” period (April to September). Seasonal variations may be explained by higher primary emissions from residential heating, especially biomass burning in “cold” season. Meteorological conditions and influence of the geomorphology around Grenoble, with the formation of thermal inversion layers leading to the stagnation of pollutants, were additional key parameters. Maximum individual PAC concentrations were observed during two PM10 pollution events in December and February-March. Chemical processes and secondary formation of oxy-and nitro-PAH were probably enhanced by the accumulation of the pollutants during these events. PAC gas/particle partitioning depended on compound molecular weight and vapour pressure. Gas/particle partitioning of oxy- and nitro-PAHs were evaluated using a multi-phase poly-parameter linear free energy relationship model. The PAC cancer risk was assessed using toxic equivalency factors available in the literature (19 PAHs, 10 nitro-PAHs and 1 oxy- PAH). Overall, particle-bound PACs contributed about 76% of the cancer risk. While PAHs accounted for most of the total PAC cancer risk, oxy- and nitro-PAHs could account for up to 24%. The risk quantification across substance classes is limited by toxicological data availability. (C) 2016 Elsevier B.V. All rights reserved.
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Tschamber, V., Trouve, G., Leyssens, G., Le-Dreff-Lorimier, C., Jaffrezo, J. L., Genevray, P., et al. (2016). Domestic Wood Heating Appliances with Environmental High Performance: Chemical Composition of Emission and Correlations between Emission Factors and Operating Conditions. Energy & Fuels, 30(9), 7241–7255.
Abstract: If the use of biomass and wood in particular replaces the fossil fuels for the heat production, this has to be made in conditions controlled to minimize the environmental and health impacts. Two recent French domestic appliances presenting high technology of adjustment of different hot air entrances (secondary and postcombustion) were tested with regard to their particulate and gaseous pollutants (total suspended particles (TSP), particulate matter with diameter below 2.5 μm (PM2.5), carbon monoxide (CO), and total hydrocarbons compounds (THC)) for different heat output and combustion phases. Characterization of particulate composition consisted of determining the total carbon (TC) fraction, and its repartition between organic (OC) and elementary (EC) carbon, polycyclic aromatic hydrocarbons (PAH), and wood tracers. Analyses of PAH in the gas phase were also performed. Differences in the proportion of EC/OC in TSP were observed during a wood load: particles are mainly constituted of organic carbon during the inflammation phase. The carbon fraction of the particles at the end of the load decreases to about 20% with approximately half of organic carbon. Levoglucosan is the major biomass tracer present in the solid phase of TSP. Light PAH are predominant in the gas phase, with the naphthalene representing 75% of the total, whereas heavy PAH with cycle numbers from 5 to 7 are mainly present in the solid phase of TSP. However, considering the toxic equivalent factor, the human health impact of adsorbed and gaseous PAH is almost the same. In these conditions, emission factors of CO and TSP were below the minimal values imposed by the highest level of the environmental French label “Flamme Verte” and future European regulations that should come into force in 2022.
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Zanatta, M., Gysel, M., Bukowiecki, N., Müller, T., Weingartner, E., Areskoug, H., et al. (2016). A European aerosol phenomenology-5: Climatology of black carbon optical properties at 9 regional background sites across Europe. Atmospheric Environment, 145, 346–364.
Abstract: A reliable assessment of the optical properties of atmospheric black carbon is of crucial importance for an accurate estimation of radiative forcing. In this study we investigated the spatio-temporal variability of the mass absorption cross-section (MAC) of atmospheric black carbon, defined as light absorption coefficient (σap) divided by elemental carbon mass concentration (mEC). σap and mEC have been monitored at supersites of the ACTRIS network for a minimum period of one year. The 9 rural background sites considered in this study cover southern Scandinavia, central Europe and the Mediterranean. σap was determined using filter based absorption photometers and mEC using a thermal-optical technique. Homogeneity of the data-set was ensured by harmonization of all involved methods and instruments during extensive intercomparison exercises at the European Center for Aerosol Calibration (ECAC). Annual mean values of σap at a wavelength of 637 nm vary between 0.66 and 1.3 Mm-1 in southern Scandinavia, 3.7-11 Mm-1 in Central Europe and the British Isles, and 2.3-2.8 Mm-1 in the Mediterranean. Annual mean values of mEC vary between 0.084 and 0.23 μg m-3 in southern Scandinavia, 0.28-1.1 in Central Europe and the British Isles, and 0.22-0.26 in the Mediterranean. Both σap and mEC in southern Scandinavia and Central Europe have a distinct seasonality with maxima during the cold season and minima during summer, whereas at the Mediterranean sites an opposite trend was observed. Annual mean MAC values were quite similar across all sites and the seasonal variability was small at most sites. Consequently, a MAC value of 10.0 m2 g-1 (geometric standard deviation = 1.33) at a wavelength of 637 nm can be considered to be representative of the mixed boundary layer at European background sites, where BC is expected to be internally mixed to a large extent. The observed spatial variability is rather small compared to the variability of values in previous literature, indicating that the harmonization efforts resulted in substantially increased precision of the reported MAC. However, absolute uncertainties of the reported MAC values remain as high as ± 30-70% due to the lack of appropriate reference methods and calibration materials. The mass ratio between elemental carbon and non-light-absorbing matter was used as a proxy for the thickness of coatings around the BC cores, in order to assess the influence of the mixing state on the MAC of BC. Indeed, the MAC was found to increase with increasing values of the coating thickness proxy. This provides evidence that coatings do increase the MAC of atmospheric BC to some extent, which is commonly referred to as lensing effect.
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2015 |
Beekmann, M., Prevot, A. S. H., Drewnick, F., Sciare, J., Pandis, S. N., van der Gon, H. A. C. D., et al. (2015). In situ, satellite measurement and model evidence on the dominant regional contribution to fine particulate matter levels in the Paris megacity. Atmospheric Chemistry And Physics, 15(16), 9577–9591.
Abstract: A detailed characterization of air quality in the megacity of Paris (France) during two 1-month intensive campaigns and from additional 1-year observations revealed that about 70% of the urban background fine particulate matter (PM) is transported on average into the megacity from upwind regions. This dominant influence of regional sources was confirmed by in situ measurements during short intensive and longer-term campaigns, aerosol optical depth (AOD) measurements from ENVISAT, and modeling results from PMCAMx and CHIMERE chemistry transport models. While advection of sulfate is well documented for other megacities, there was surprisingly high contribution from long-range transport for both nitrate and organic aerosol. The origin of organic PM was investigated by comprehensive analysis of aerosol mass spectrometer (AMS), radiocarbon and tracer measurements during two intensive campaigns. Primary fossil fuel combustion emissions constituted less than 20% in winter and 40% in summer of carbonaceous fine PM, unexpectedly small for a megacity. Cooking activities and, during winter, residential wood burning are the major primary organic PM sources. This analysis suggests that the major part of secondary organic aerosol is of modern origin, i.e., from biogenic precursors and from wood burning. Black carbon concentrations are on the lower end of values encountered in megacities worldwide, but still represent an issue for air quality. These comparatively low air pollution levels are due to a combination of low emissions per inhabitant, flat terrain, and a meteorology that is in general not conducive to local pollution build-up. This revised picture of a megacity only being partially responsible for its own average and peak PM levels has important implications for air pollution regulation policies.
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Camacho, A., Rochera, C., Hennebelle, R., Ferrari, C., & Quesada, A. (2015). Total mercury and methyl-mercury contents and accumulation in polar microbial mats. Science Of The Total Environment, 509, 145–153.
Abstract: Although polar regions are considered isolated and pristine areas, the organisms that inhabit these zones are exposed to global pollution. Heavy metals, such as mercury, are global pollutants and can reach almost any location on Earth. Mercury may come from natural, volcanic or geological sources, or result from anthropogenic sources, in particular industrial or mining activities. In this study, we have investigated one of the most prominent biological non-marine communities in both polar regions, microbial mats, in terms of their Hg and methyl-mercury (MeHg) concentrations and accumulation capacities. The main hypotheses posed argued on the importance of different factors, and to test them, we have measured Hg concentrations in microbial mats that were collected from 6 locations in different ecological situations. For this purpose, the direct anthropogenic impacts, volcanic influences, proximity to the seashore, latitudinal gradient and C contents were investigated. Our results show that, other than the direct anthropogenic influence, none of the other hypotheses alone satisfactorily explains the Hg content in microbial mats. In contrast, the MeHg contents were noticeably different between the investigated locations, with a higher proportion of MeHg on the McMurdo Ice Shelf (Antarctica) and a lower proportion on Ward Hunt Island (High Arctic). Furthermore, our results from in situ experiments indicated that the microbial mats from South Shetland Islands could quickly accumulate (48 h) Hg when Hg dissolved salts were supplied. Over short-term periods, these mats do not transform Hg into MeHg under field conditions. (C) 2014 Elsevier B.V. All rights reserved.
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DeWitt, H. L., Hellebust, S., Temime-Roussel, B., Ravier, S., Polo, L., Jacob, V., et al. (2015). Near-highway aerosol and gas-phase measurements in a high-diesel environment. Atmospheric Chemistry And Physics, 15(8), 4373–4387.
Abstract: Diesel-powered passenger cars currently outnumber gasoline-powered cars in many countries, particularly in Europe. In France, diesel cars represented 61% of light duty vehicles in 2011 and this percentage is still increasing (French Environment and Energy Management Agency, ADEME). As part of the September 2011 joint PM-DRIVE (Particulate Matter – DiRect and Indirect on-road Vehicular Emissions) and MOCOPO (Measuring and mOdeling traffic COngestion and POllution) field campaign, the concentration and high-resolution chemical composition of aerosols and volatile organic carbon species were measured adjacent to a major urban highway south of Grenoble, France. Alongside these atmospheric measurements, detailed traffic data were collected from nearby traffic cameras and loop detectors, which allowed the vehicle type, traffic concentration, and traffic speed to be quantified. Six aerosol age and source profiles were resolved using the positive matrix factorization model on real-time high-resolution aerosol mass spectra. These six aerosol source/age categories included a hydrocarbon-like organic aerosol (HOA) commonly associated with primary vehicular emissions, a nitrogen-containing aerosol with a diurnal pattern similar to that of HOA, oxidized organic aerosol (OOA), and biomass burning aerosol. While quantitatively separating the influence of diesel from that of gasoline proved impossible, a low HOA: black carbon ratio, similar to that measured in other high-diesel environments, and high levels of NOx, also indicative of diesel emissions, were observed. Although the measurement site was located next to a large source of primary emissions, which are typically found to have low oxygen incorporation, OOA was found to comprise the majority of the measured organic aerosol, and isotopic analysis showed that the measured OOA contained mainly modern carbon, not fossil-derived carbon. Thus, even in this heavily vehicular-emission-impacted environment, photochemical processes, biogenic emissions, and aerosol oxidation dominated the overall organic aerosol mass measured during most of the campaign.
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Garra, P., Maschowski, C., Liaud, C., Dieterlen, A., Trouve, G., Le Calve, S., et al. (2015). Fluorescence Microscopy Analysis of Particulate Matter from Biomass Burning: Polyaromatic Hydrocarbons as Main Contributors. Aerosol Science And Technology, 49(11), 1160–1169.
Abstract: New efficient approaches to the characterization of fly ash and particulate matter (PM) have to be developed in order to better understand their impacts on environment and health. Polycyclic aromatic hydrocarbons (PAH) contained in PM from biomass burning have been identified as genotoxic and cytotoxic, and some tools already exist to quantify their contribution to PM. Optical fluorescence microscopy is proposed as a rapid and relatively economical method to allow the quantification of PAH in different particles emitted from biomass combustion. In this study samples were collected in the flue gas of biomass-combustion facilities with nominal output ranging from 40 kW to 17.3 MW. The fly ash samples were collected with various flue gas treatment devices (multicyclone, baghouse filter, electrostatic precipitator); PM samples were fractionated from the flue gas with a DEKATI (R) DGI impactor. A method using fluorescence observations (at 470nm), white-light observations and image processing has been developed with the aim of quantifying fluorescence per sample. Organic components of PM and fly ash, such as PAH, humic-like substances (HULIS) and water-soluble organic carbon (WSOC) were also quantified. Fluorescence microscopy analysis method assessment was first realized with fly ash that was artificially coated with PAH and HULIS. Total amounts of PAH in the three size fractions of actual PM from biomass burning strongly correlated with the intensities of fluorescence. These encouraging results contribute to the development of a faster and cheaper method of quantifying particle-bound PAH.Copyright 2015 American Association for Aerosol Research
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Golly, B., Brulfert, G., Berlioux, G., Jaffrezo, J. L., & Besombes, J. L. (2015). Large chemical characterisation of PM10 emitted from graphite material production: Application in source apportionment. Science Of The Total Environment, 538, 634–643.
Abstract: This work focuses on emissions from industrial sources that are still poorly understood in Europe, especially the “carbon industry”. The study is based on two intensive sampling campaigns performed in a graphite material production plant for 2 weeks in July 2013 and November 2013 in alpine valleys. The chemical characterization of PM10 was conducted at three sampling sites (outdoor and indoor sites) located inside one industrial area, which is considered as the highest emissions source of polycyclic aromatic hydrocarbons (PAHs) in the Ante valley. The identification of specific tracers among metals and trace elements is commonly used to characterize industrial emissions. In our study, original enrichment factors relative to the “rural exposed background” have been calculated, and the metallic fraction was not affected by this industrial source. In contrast, the organic fraction of PM10 has a number of features, providing a complete organic source profile and referred to as the “carbon industry”. In particular, polycyclic aromatic sulfur heterocycles (PASH) have been largely detected from fugitive emissions with rather large concentrations. The average concentrations of benzo(b)naphtho(2,1-d)thiophene (BNT(2,1)) reached 2.35-6.56 ng.m(-3) and 60.5-376 ng.m(-3) for outdoor and indoor sites, respectively. The use of this reference profile in the chemical mass balance model (CMB) applied to samples collected in two sites near industrial areas shows that this source had an average contribution of 6% of the organic matter (OM) mass during the sampling period during the winter of 2013. (C) 2015 Elsevier B.V. All rights reserved.
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Jacobi, H. W., Lim, S., Menegoz, M., Ginot, P., Laj, P., Bonasoni, P., et al. (2015). Black carbon in snow in the upper Himalayan Khumbu Valley, Nepal: observations and modeling of the impact on snow albedo, melting, and radiative forcing. Cryosphere, 9(4), 1685–1699.
Abstract: Black carbon (BC) in snow in the Himalayas has recently attracted considerable interest due to its impact on snow albedo, snow and glacier melting, regional climate and water resources. A single particle soot photometer (SP2) instrument was used to measure refractory BC (rBC) in a series of surface snow samples collected in the upper Khumbu Valley, Nepal between November 2009 and February 2012. The obtained time series indicates annual cycles with maximum rBC concentrations before the onset of the monsoon season and fast decreases during the monsoon period. Detected concentrations ranged from a few up to 70 ppb with rather large uncertainties due to the handling of the samples. Detailed modeling of the snowpack, including the detected range and an estimated upper limit of BC concentrations, was performed to study the role of BC in the seasonal snowpack. Simulations were performed for three winter seasons with the snowpack model Crocus, including a detailed description of the radiative transfer inside the snowpack. While the standard Crocus model strongly overestimates the height and the duration of the seasonal snowpack, a better calculation of the snow albedo with the new radiative transfer scheme enhanced the representation of the snow. However, the period with snow on the ground without BC in the snow was still overestimated between 37 and 66 days, which was further diminished by 8 to 15% and more than 40% in the presence of 100 or 300 ppb of BC. Compared to snow without BC, the albedo is reduced on average by 0.027 and 0.060 in the presence of 100 and 300 ppb BC. While the impact of increasing BC in the snow on the albedo was largest for clean snow, the impact on the local radiative forcing is the opposite. Here, increasing BC caused an even larger impact at higher BC concentrations. This effect is related to an accelerated melting of the snowpack caused by a more efficient metamorphism of the snow due to an increasing size of the snow grains with increasing BC concentrations. The melting of the winter snowpack was shifted by 3 to 10 and 17 to 27 days during the three winter seasons in the presence of 100 and 300 ppb BC compared to clean snow, while the simulated annual local radiative forcing corresponds to 3 to 4.5 and 10.5 to 13.0 W m(-2). An increased sublimation or evaporation of the snow reduces the simulated radiative forcing, leading to a net forcing that is lower by 0.5 to 1.5 W m(-2), while the addition of 10 ppm dust causes an increase of the radiative forcing between 2.5 and 3 W m(-2). According to the simulations, 7.5 ppm of dust has an effect equivalent to 100 ppb of BC concerning the impact on the melting of the snowpack and the local radiative forcing.
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Lopez, M., Schmidt, M., Ramonet, M., Bonne, J. L., Colomb, A., Kazan, V., et al. (2015). Three years of semicontinuous greenhouse gas measurements at the Puy de Dome station (central France). Atmospheric Measurement Techniques, 8(9), 3941–3958.
Abstract: Three years of greenhouse gas measurements, obtained using a gas chromatograph (GC) system located at the Puy de Dome station at 1465 ma.s.l. in central France, are presented. The GC system was installed in 2010 at Puy de Dome and was designed for automatic and accurate semicontinuous measurements of atmospheric carbon dioxide, methane, nitrous oxide and sulfur hexafluoride mole fractions. We present in detail the instmmental setup and the calibration strategy, which together allow the GC to reach repeatabilities of 0.1 mmolmol-1, 1.2 nmolmol(-1), 0.3 nmolmol-1 and 0.06 μmolmol(-1) for CO2, CH4, N2O and SF6, respectively. The analysis of the 3-year atmospheric time series revealed how the planetary boundary layer height drives the mole fractions observed at a mountain site such as Puy de Dome where air masses alternate between the planetary boundary layer and the free troposphere. Accurate long-lived greenhouse gas measurements collocated with 222Rn measurements as an atmospheric tracer allowed us to determine the CO2, CH4 and N2O emissions in the catchment area of the station. The derived CO2 surface flux revealed a clear seasonal cycle, with net uptake by plant assimilation in the spring and net emission caused by the biosphere and burning of fossil fuel during the remainder of the year. We calculated a mean annual CO2 flux of 1310 680 t CO2 km(-2). The derived CH4 and N2O emissions in the station catchment area were 7.0 4.0 t CH4 km(-2) yr(-1) and 1.8 1.0 t N20 km(-2) yr(-1), respectively. Our derived annual CH4 flux is in agreement with the national French inventory, whereas our derived N2O flux is 5 times larger than the same inventory.
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Panteliadis, P., Hafkenscheid, T., Cary, B., Diapouli, E., Fischer, A., Favez, O., et al. (2015). ECOC comparison exercise with identical thermal protocols after temperature offset correction – instrument diagnostics by in-depth evaluation of operational parameters. Atmospheric Measurement Techniques, 8(2), 779–792.
Abstract: A comparison exercise on thermal-optical elemental carbon/organic carbon (ECOC) analysers was carried out among 17 European laboratories. Contrary to previous comparison exercises, the 17 participants made use of an identical instrument set-up, after correcting for temperature offsets with the application of a recently developed temperature calibration kit (Sunset Laboratory Inc, OR, US). Temperature offsets reported by participants ranged from -93 to +100 degrees C per temperature step. Five filter samples and two su-crose solutions were analysed with both the EUSAAR2 and NIOSH870 thermal protocols. z scores were calculated for total carbon (TC); nine outliers and three stragglers were identified. Three outliers and eight stragglers were found for EC. Overall, the participants provided results between the warning levels with the exception of two laboratories that showed poor performance, the causes of which were identified and corrected through the course of the comparison exercise. The TC repeatability and reproducibility (expressed as relative standard deviations) were 11 and 15% for EUSAAR2 and 9.2 and 12% for NIOSH870; the standard deviations for EC were 15 and 20% for EUSAAR2 and 20 and 26% for NIOSH870. TC was in good agreement between the two protocols, T-CNIOSH870 = 0.98 x TCEUSAAR2 (R-2 = 1.00, robust means). Transmittance (TOT) calculated EC for NIOSH870 was found to be 20% lower than for EU-SAAR2, E-CNIOSH870 = 0.80 x ECEUSAAR2 (R-2 = 0.96, robust means). The thermograms and laser signal values were compared and similar peak patterns were observed per sample and protocol for most participants. Notable deviations from the typical patterns indicated either the absence or inaccurate application of the temperature calibration procedure and/or pre-oxidation during the inert phase of the analysis. Low or zero pyrolytic organic carbon (POC), as reported by a few participants, is suggested as an indicator of an instrument-specific pre-oxidation. A sample-specific preoxidation effect was observed for filter G, for all participants and both thermal protocols, indicating the presence of oxygen donors on the suspended particulate matter. POC (TOT) levels were lower for NIOSH870 than for EUSAAR2, which is related to the heating profile differences of the two thermal protocols.
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Renard, P., Siekmann, F., Salque, G., Demelas, C., Coulomb, B., Vassalo, L., et al. (2015). Aqueous-phase oligomerization of methyl vinyl ketone through photooxidation – Part 1: Aging processes of oligomers. Atmospheric Chemistry And Physics, 15(1), 21–35.
Abstract: It has recently been established that unsaturated water-soluble organic compounds (UWSOCs) might efficiently form oligomers in polluted fogs and wet aerosol particles, even for weakly soluble ones like methyl vinyl ketone (MVK). The atmospheric relevance of these processes is explored by means of multiphase process model studies in a companion paper. In the present study, we investigate the aging of these aqueous-phase MVK oligomers formed via center dot OH oxidation, as well as their ability to form secondary organic aerosol (SOA) upon water evaporation. The comparison between aqueous-phase composition and aerosol composition after nebulization of the corresponding solutions shows similar trends for oligomer formation and aging. The measurements reveal that oligomer aging leads to the formation of organic diacids. Quantification of the SOA mass formed after nebulization is performed, and the obtained SOA mass yields seem to depend on the spectral irradiance of the light used to initiate the photochemistry. Investigating a large range of initial MVK concentrations (0.2-20 mM), the results show that their center dot OH oxidation undergoes competition between functionalization and oligomerization that is dependent on the precursor concentration. At high initial MVK concentrations (>= 2 mM), oligomerization prevails over functionalization, while at lower initial concentrations, oligomerization is not the major process, and functionalization dominates, resulting in small carbonyls, dicarbonyls and monoacids. The atmospheric implications of these processes are discussed.
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Rose, C., Sellegri, K., Velarde, F., Moreno, I., Ramonet, M., Weinhold, K., et al. (2015). Frequent nucleation events at the high altitude station of Chacaltaya (5240 m a.s.l.), Bolivia. Atmospheric Environment, 102, 18–29.
Abstract: While nucleation may represent one of the major processes responsible for the total aerosol number burden in the atmosphere, and especially at high altitude, new particle formation (NPF) events occurring in the upper part of the troposphere are poorly documented in the literature, particularly in the southern hemisphere. NPF events were detected and analyzed at the highest measurement site in the world, Chacaltaya (5240 m a.s.l.), Bolivia between January 1 and December 31 2012, using a Neutral Aerosol and Ion Spectrometer (NAIS) that detects clusters down to 0.4 nm. NPF frequency at Chacaltaya is one of the highest reported so far (63.9%) and shows a clear seasonal dependency with maximum up to 100% during the dry season. This high seasonality of the NPF events frequency was found to be likely linked to the presence of clouds in the vicinity of the station during the wet season. Multiple NPF events are seen on almost 50% of event days and can reach up to 6 events per day, increasing the potential of nucleation to be the major contributor to the particle number concentrations in the upper troposphere. Ion-induced nucleation (IIN) was 14.8% on average, which is higher than the IIN fractions reported for boundary layer stations. The median formation rate of 2 nm particles computed for first position events is increased during the dry season (1.90 cm(-3) s(-1)) compared to the wet season (1.02 cm(-3) s(-1)), showing that events are more intense, on top of being more frequent during the dry season. On the contrary, particle growth rates (GRs) are on average enhanced during the wet season, which could be explained by higher amount of biogenic volatile organic compounds transported from the Amazon rainforest. The NPF events frequency is clearly enhanced when air masses originate from the oceanic sector, with a frequency of occurrence close to 1. However, based on the particle GRs, we calculate that particles most likely nucleate after the oceanic air masses reach the land and are presumably not originating from the marine free troposphere. The high frequency of NPF events, the occurrence of multiple events per day, and the relatively high formation rates observed at Chacaltaya imply that nucleation and growth are likely to be the major mechanism feeding the upper atmosphere with aerosol particles in this part of the continent. (C) 2014 Elsevier Ltd. All rights reserved.
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Salameh, D., Detournay, A., Pey, J., Perez, N., Liguori, F., Saraga, D., et al. (2015). PM2.5 chemical composition in five European Mediterranean cities: A 1-year study. Atmospheric Research, 155, 102–117.
Abstract: The seasonal and spatial characteristics of PM2.5 and its chemical composition in the Mediterranean Basin have been studied over a 1-year period (2011-2012) in five European Mediterranean cities: Barcelona (BCN), Marseille (MRS), Genoa (GEN), Venice (VEN), and Thessaloniki (THE). During the year under study, PMuj annual mean concentration ranged from 23 to 46 μg m(-3), while the respective PM2.5 ranged from 14 to 37 μg m(-3), with the highest concentrations observed in THE and VEN. Both cities presented an elevated number of exceedances of the PM10 daily limit value, as 32% and 20% of the days exceeded 50 μg m(-3), respectively. Similarly, exceedances of the WHO guidelines for daily PM2.5 concentrations (25 μg m(-3)) were also more frequent in THE with 78% of the days during the period, followed by VEN with 39%. The lowest PM levels were measured in GEN. PM2.5 exhibited significant seasonal variability, with much higher winter concentrations for VEN and MRS, in fall for THE and in spring for BCN. PM2.5 chemical composition was markedly different even for similar PM2.5 levels. On annual average, PM2.5 was dominated by OM except in THE. OM contribution was higher in Marseille (42%), while mineral matter was the most abundant constituent in THE (32%). Moreover, PM2.5 relative mean composition during pollution episodes (PM2.5 > 25 μg m(-3)) as well as the origins of the exceedances were also investigated. Results outline mainly the effect of NO3- being the most important driver and highlight the non-negligible impact of atmospheric mixing and aging processes during pollution episodes. (C) 2014 Elsevier B.V. All rights reserved.
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Shorshani, M. F., Seigneur, C., Rehn, L. P., Chanut, H., Pellan, Y., Jaffrezo, J. L., et al. (2015). Atmospheric dispersion modeling near a roadway under calm meteorological conditions. Transportation Research Part D-Transport And Environment, 34, 137–154.
Abstract: Atmospheric pollutant dispersion near sources is typically simulated by Gaussian models because of their efficient compromise between reasonable accuracy and manageable computational time. However, the standard Gaussian dispersion formula applies downwind of a source under advective conditions with a well-defined wind direction and cannot calculate air pollutant concentrations under calm conditions with fluctuating wind direction and/or upwind of the emission source. Attempts have been made to address atmospheric dispersion under such conditions. This work evaluates the performance of standard and modified Gaussian plume models using measurements of NO2, PM10, PM2.5, five inorganic ions and seven metals conducted near a freeway in Grenoble, France, during 11-27 September 2011. The formulation for calm conditions significantly improves model performance. However, it appears that atmospheric dispersion due to vehicle-induced turbulence is still underestimated. Furthermore, model performance is poor for particulate species unless road dust resuspension by traffic is explicitly taken into account. (C) 2014 Elsevier Ltd. All rights reserved.
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Slemr, F., Angot, H., Dommergue, A., Magand, O., Barret, M., Weigelt, A., et al. (2015). Comparison of mercury concentrations measured at several sites in the Southern Hemisphere. Atmospheric Chemistry And Physics, 15(6), 3125–3133.
Abstract: Our knowledge of the distribution of mercury concentrations in air of the Southern Hemisphere was until recently based mostly on intermittent measurements made during ship cruises. In the last few years continuous mercury monitoring has commenced at several sites in the Southern Hemisphere, providing new and more refined information. In this paper we compare mercury measurements at several remote sites in the Southern Hemisphere made over a period of at least 1 year at each location. Averages of monthly medians show similar although small seasonal variations at both Cape Point and Amsterdam Island. A pronounced seasonal variation at Troll research station in Antarctica is due to frequent mercury depletion events in the austral spring. Due to large scatter and large standard deviations of monthly average median mercury concentrations at Cape Grim, no systematic seasonal variation could be found there. Nevertheless, the annual average mercury concentrations at all sites during the 2007-2013 period varied only between 0.85 and 1.05 ng m(-3). Part of this variability is likely due to systematic measurement uncertainties which we propose can be further reduced by improved calibration procedures. We conclude that mercury is much more uniformly distributed throughout the Southern Hemisphere than the distributions suggested by measurements made onboard ships. This finding implies that smaller trends can be detected in shorter time periods. We also report a change in the trend sign at Cape Point from decreasing mercury concentrations in 1996-2004 to increasing concentrations since 2007.
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Song, S., Selin, N. E., Soerensen, A. L., Angot, H., Artz, R., Brooks, S., et al. (2015). Top-down constraints on atmospheric mercury emissions and implications for global biogeochemical cycling. Atmospheric Chemistry And Physics, 15(12), 7103–7125.
Abstract: We perform global-scale inverse modeling to constrain present-day atmospheric mercury emissions and relevant physiochemical parameters in the GEOS-Chem chemical transport model. We use Bayesian inversion methods combining simulations with GEOS-Chem and ground-based Hg-0 observations from regional monitoring networks and individual sites in recent years. Using optimized emissions/parameters, GEOS-Chem better reproduces these ground-based observations and also matches regional over-water Hg-0 and wet deposition measurements. The optimized global mercury emission to the atmosphere is 5.8 Gg yr(-1). The ocean accounts for 3.2 Gg yr(-1) (55 % of the total), and the terrestrial ecosystem is neither a net source nor a net sink of Hg-0. The optimized Asian anthropogenic emission of Hg-0 (gas elemental mercury) is 650-1770 Mg yr(-1), higher than its bottom-up estimates (550-800 Mg yr(-1)). The ocean parameter inversions suggest that dark oxidation of aqueous elemental mercury is faster, and less mercury is removed from the mixed layer through particle sinking, when compared with current simulations. Parameter changes affect the simulated global ocean mercury budget, particularly mass exchange between the mixed layer and subsurface waters. Based on our inversion results, we re-evaluate the long-term global biogeochemical cycle of mercury, and show that legacy mercury becomes more likely to reside in the terrestrial ecosystem than in the ocean. We estimate that primary anthropogenic mercury contributes up to 23 % of present-day atmospheric deposition.
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Wagner, T., Harder, H., Joiner, J., Laj, P., & Richter, A. (2015). “A novel Whole Air Sample Profiler (WASP) for the quantification of volatile organic compounds in the boundary layer” published in Atmos. Meas. Tech., 6, 2703-2712, 2013. Atmospheric Measurement Techniques, 8(8), 3405–3406.
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Yttri, K. E., Schnelle-Kreis, J., Maenhaut, W., Abbaszade, G., Alves, C., Bjerke, A., et al. (2015). An intercomparison study of analytical methods used for quantification of levoglucosan in ambient aerosol filter samples. Atmospheric Measurement Techniques, 8(1), 125–147.
Abstract: The monosaccharide anhydrides (MAs) levoglucosan, galactosan and mannosan are products of incomplete combustion and pyrolysis of cellulose and hemicelluloses, and are found to be major constituents of biomass burning (BB) aerosol particles. Hence, ambient aerosol particle concentrations of levoglucosan are commonly used to study the influence of residential wood burning, agricultural waste burning and wildfire emissions on ambient air quality. A European-wide intercomparison on the analysis of the three monosaccharide anhydrides was conducted based on ambient aerosol quartz fiber filter samples collected at a Norwegian urban background site during winter. Thus, the samples' content of MAs is representative for BB particles originating from residential wood burning. The purpose of the intercomparison was to examine the comparability of the great diversity of analytical methods used for analysis of levoglucosan, mannosan and galactosan in ambient aerosol filter samples. Thirteen laboratories participated, of which three applied high-performance anion-exchange chromatography (HPAEC), four used high-performance liquid chromatography (HPLC) or ultra-performance liquid chromatography (UPLC) and six resorted to gas chromatography (GC). The analytical methods used were of such diversity that they should be considered as thirteen different analytical methods. All of the thirteen laboratories reported levels of levoglucosan, whereas nine reported data for mannosan and/or galactosan. Eight of the thirteen laboratories reported levels for all three isomers. The accuracy for levoglucosan, presented as the mean percentage error (PE) for each participating laboratory, varied from -63 to 20 %; however, for 62% of the laboratories the mean PE was within +/- 10 %, and for 85% the mean PE was within +/- 20 %. For mannosan, the corresponding range was 60 to 69 %, but as for levoglucosan, the range was substantially smaller for a subselection of the laboratories; i.e. for 33% of the laboratories the mean PE was within +/- 10 %. For galactosan, the mean PE for the participating laboratories ranged from 84 to 593 %, and as for mannosan 33% of the laboratories reported a mean PE within +/- 10 %. The variability of the various analytical methods, as defined by their minimum and maximum PE value, was typically better for levoglucosan than for mannosan and galactosan, ranging from 3.2 to 41% for levoglucosan, from 10 to 67% for mannosan and from 6 to 364% for galactosan. For the levoglucosan to mannosan ratio, which may be used to assess the relative importance of softwood versus hardwood burning, the variability only ranged from 3.5 to 24 %. To our knowledge, this is the first major intercomparison on analytical methods used to quantify monosaccharide anhydrides in ambient aerosol filter samples conducted and reported in the scientific literature. The results show that for levoglucosan the accuracy is only slightly lower than that reported for analysis of SO42- (sulfate) on filter samples, a constituent that has been analysed by numerous laboratories for several decades, typically by ion chromatography and which is considered a fairly easy constituent to measure. Hence, the results obtained for levoglucosan with respect to accuracy are encouraging and suggest that levels of levoglucosan, and to a lesser extent mannosan and galactosan, obtained by most of the analytical methods currently used to quantify monosaccharide anhydrides in ambient aerosol filter samples, are comparable. Finally, the various analytical methods used in the current study should be tested for other aerosol matrices and concentrations as well, the most obvious being summertime aerosol samples affected by wildfires and/or agricultural fires.
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2014 |
Angot, H., Barret, M., Magand, O., Ramonet, M., & Dommergue, A. (2014). A 2-year record of atmospheric mercury species at a background Southern Hemisphere station on Amsterdam Island. Atmospheric Chemistry And Physics, 14(20), 11461–11473.
Abstract: Although essential to fully understand the cycling of mercury at the global scale, mercury species records in the Southern Hemisphere are scarce. Under the framework of the Global Mercury Observation System (GMOS) project, a monitoring station has been set up on Amsterdam Island (37 degrees 48'S, 77 degrees 34'E) in the remote southern Indian Ocean. For the first time in the Southern Hemisphere, a 2-year record of gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particle-bound mercury (PBM) is presented. GEM concentrations were remarkably steady (1.03 +/- 0.08 ng m(-3)) while RGM and PBM concentrations were very low and exhibited a strong variability (mean: 0.34 pg m(-3), range: < detection limit-4.07 pg m(-3); and mean: 0.67 pg m(-3), range: < detection limit-12.67 pg m(-3), respectively). Despite the remoteness of the island, wind sector analysis, air mass back trajectories and the observation of radonic storms highlighted a long-range contribution from the southern African continent to the GEM and PBM budgets from July to September during the biomass burning season. Low concentrations of GEM were associated with southerly polar and marine air masses from the remote southern Indian Ocean. This unique data set provides new baseline GEM concentrations in the Southern Hemisphere midlatitudes while mercury speciation along with upcoming wet deposition data will help to improve our understanding of the mercury cycle in the marine boundary layer.
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Bartels-Rausch, T., Jacobi, H. W., Kahan, T. F., Thomas, J. L., Thomson, E. S., Abbatt, J. P. D., et al. (2014). A review of air-ice chemical and physical interactions (AICI): liquids, quasi-liquids, and solids in snow. Atmospheric Chemistry And Physics, 14(3), 1587–1633.
Abstract: Snow in the environment acts as a host to rich chemistry and provides a matrix for physical exchange of contaminants within the ecosystem. The goal of this review is to summarise the current state of knowledge of physical processes and chemical reactivity in surface snow with relevance to polar regions. It focuses on a description of impurities in distinct compartments present in surface snow, such as snow crystals, grain boundaries, crystal surfaces, and liquid parts. It emphasises the microscopic description of the ice surface and its link with the environment. Distinct differences between the disordered air-ice interface, often termed quasi-liquid layer, and a liquid phase are highlighted. The reactivity in these different compartments of surface snow is discussed using many experimental studies, simulations, and selected snow models from the molecular to the macro-scale. Although new experimental techniques have extended our knowledge of the surface properties of ice and their impact on some single reactions and processes, others occurring on, at or within snow grains remain unquantified. The presence of liquid or liquid-like compartments either due to the formation of brine or disorder at surfaces of snow crystals below the freezing point may strongly modify reaction rates. Therefore, future experiments should include a detailed characterisation of the surface properties of the ice matrices. A further point that remains largely unresolved is the distribution of impurities between the different domains of the condensed phase inside the snowpack, i.e. in the bulk solid, in liquid at the surface or trapped in confined pockets within or between grains, or at the surface. While surface-sensitive laboratory techniques may in the future help to resolve this point for equilibrium conditions, additional uncertainty for the environmental snowpack may be caused by the highly dynamic nature of the snowpack due to the fast metamorphism occurring under certain environmental conditions. Due to these gaps in knowledge the first snow chemistry models have attempted to reproduce certain processes like the long-term incorporation of volatile compounds in snow and firn or the release of reactive species from the snowpack. Although so far none of the models offers a coupled approach of physical and chemical processes or a detailed representation of the different compartments, they have successfully been used to reproduce some field experiments. A fully coupled snow chemistry and physics model remains to be developed.
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Beddows, D. C. S., Dall'Osto, M., Harrison, R. M., Kulmala, M., Asmi, A., Wiedensohler, A., et al. (2014). Variations in tropospheric submicron particle size distributions across the European continent 2008-2009. Atmospheric Chemistry And Physics, 14(8), 4327–4348.
Abstract: Cluster analysis of particle number size distributions from background sites across Europe is presented. This generated a total of nine clusters of particle size distributions which could be further combined into two main groups, namely: a south-to-north category (four clusters) and a west-to-east category (five clusters). The first group was identified as most frequently being detected inside and around northern Germany and neighbouring countries, showing clear evidence of local afternoon nucleation and growth events that could be linked to movement of air masses from south to north arriving ultimately at the Arctic contributing to Arctic haze. The second group of particle size spectra proved to have narrower size distributions and collectively showed a dependence of modal diameter upon the longitude of the site (west to east) at which they were most frequently detected. These clusters indicated regional nucleation (at the coastal sites) growing to larger modes further inland. The apparent growth rate of the modal diameter was around 0.6-0.9 nm h(-1). Four specific air mass back-trajectories were successively taken as case studies to examine in real time the evolution of aerosol size distributions across Europe. While aerosol growth processes can be observed as aerosol traverses Europe, the processes are often obscured by the addition of aerosol by emissions en route. This study revealed that some of the 24 stations exhibit more complex behaviour than others, especially when impacted by local sources or a variety of different air masses. Overall, the aerosol size distribution clustering analysis greatly simplifies the complex data set and allows a description of aerosol aging processes, which reflects the longer-term average development of particle number size distributions as air masses advect across Europe.
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Bourcier, L., Masson, O., Laj, P., Paulat, P., Pichon, J. - M., Chausse, P., et al. (2014). 7Be, 210Pb and 137Cs concentrations in cloud water. Journal of Environmental Radioactivity, 128, 15–19.
Abstract: Cloud water was sampled during 8 months, in 2008 and 2009, at the puy de Dome high-altitude atmospheric research station (France). The concentrations of 7Be and 210Pb, both naturally occurring radionuclides, and 137Cs of anthropogenic origin, were determined. Those values are useful for a better knowledge of the aftermath cloud deposition and more generally for wet deposition assessment of radionuclides. This is of primary interest in case of a nuclear accident, especially considering 137Cs deposition, both for high-altitude locations that are regularly embedded by clouds and also for lowlands where fog can occur. The 7Be and 210Pb average activity concentrations in cloud water found were 1.9±0.11mBqm-3 air and 140±10μBqm-3 air, respectively. For 137Cs, the average concentration was 0.14±0.02μBqm-3 air. This very low-level is representative of the long term post-accidental background level. Indeed, for the studied period, the last accidental 137Cs release was that of Chernobyl accident, in April 1986. To our knowledge this is the first data about 137Cs reference level determination in cloud water. The comparison between cloud water and rain water concentrations showed a ratio cloud/rain ranging between 3.4 and 8.1, in agreement with previous studies performed on inorganic compounds. Scavenging efficiencies of aerosols by cloud droplets were also calculated with the additional aerosol concentrations routinely measured at the station and were quite low (0.13-0.40) compared to what has previously been observed for inorganic soluble ions.
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Brocard, G., Adatte, T., Magand, O., Pfeifer, H. R., Bettini, A., Arnaud, F., et al. (2014). The recording of floods and earthquakes in Lake Chichoj, Guatemala during the twentieth century. Journal Of Paleolimnology, 52(3), 155–169.
Abstract: Laguna Chichj (Lake Chichj) is the only deep permanent lake in the central highlands of Guatemala. The lake is located in the boundary zone between the North American and Caribbean plates. The lake has been struck by devastating earthquakes and tropical cyclones in historical times. We investigated the imprint of twentieth century extreme events on the sedimentary record of this tropical lake using a bathymetric survey of the lake, coring the lake floor, and providing a chronology of sediment accumulation. The lake occupies a series of circular depressions likely formed by the rapid dissolution of a buried body of gypsum. Pb-210 and Cs-137 inventories and varve counting indicate high rates of sedimentation (1-2 cm year(-1)). The annually layered sediment is interrupted by turbidites of two types: a darker-colored turbidite, enriched in lake-derived biogenic constituents, and interpreted as a seismite, and a lighter-colored type, enriched in catchment-derived constituents, interpreted as a flood layer. Comparison of our Cs-137-determined layer ages with a catalog of twentieth century earthquakes shows that an earthquake on the Motagua fault in 1976 generated a conspicuous darker-colored turbidite and slumped deposits in separate parts of the lake. The entire earthquake inventory further reveals that mass movements in the lake are triggered at Modified Mercalli Intensities higher than V. Tropical cyclonic depressions known to have affected the lake area had limited effect on the lake, including Hurricane Mitch in 1998. One storm however produced a significantly thicker flood layer in the 1940s. This storm is reportedly the only event to have generated widespread slope failures in the lake catchment. It is thus inferred that abundant landsliding provided large amounts of concentrated sediment to the lake, through hyperpycnal flows.
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Chiappini, L., Verlhac, S., Aujay, R., Maenhaut, W., Putaud, J. P., Sciare, J., et al. (2014). Clues for a standardised thermal-optical protocol for the assessment of organic and elemental carbon within ambient air particulate matter. Atmospheric Measurement Techniques, 7(6), 1649–1661.
Abstract: Along with some research networking programmes, the European Directive 2008/50/CE requires chemical speciation of fine aerosol (PM2.5), including elemental (EC) and organic carbon (OC), at a few rural sites in European countries. Meanwhile, the thermal-optical technique is considered by the European and US networking agencies and normalisation bodies as a reference method to quantify EC-OC collected on filters. Although commonly used for many years, this technique still suffers from a lack of information on the comparability of the different analytical protocols (temperature protocols, type of optical correction) currently applied in the laboratories. To better evaluate the EC-OC data set quality and related uncertainties, the French National Reference Laboratory for Ambient Air Quality Monitoring (LCSQA) organised an EC-OC comparison exercise for French laboratories using different thermaloptical methods (five laboratories only). While there is good agreement on total carbon (TC) measurements among all participants, some differences can be observed on the EC/TC ratio, even among laboratories using the same thermal protocol. These results led to further tests on the influence of the optical correction: results obtained from different European laboratories confirmed that there were higher differences between OCTOT and OCTOR measured with NIOSH 5040 in comparison to EUSAAR-2. Also, striking differences between ECTOT/ECTOR ratios can be observed when comparing results obtained for rural and urban samples, with ECTOT being 50% lower than ECTOR at rural sites whereas it is only 20% lower at urban sites. The PM chemical composition could explain these differences but the way it influences the EC-OC measurement is not clear and needs further investigation. Meanwhile, some additional tests seem to indicate an influence of oven soiling on the EC-OC measurement data quality. This highlights the necessity to follow the laser signal decrease with time and its impact on measurements. Nevertheless, this should be confirmed by further experiments, involving more samples and various instruments, to enable statistical processing. All these results provide insights to determine the quality of EC-OC analytical methods and may contribute to the work toward establishing method standardisation.
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Cristofanelli, P., Putero, D., Adhikary, B., Landi, T. C., Marinoni, A., Duchi, R., et al. (2014). Transport of short-lived climate forcers/pollutants (SLCF/P) to the Himalayas during the South Asian summer monsoon onset. Environmental Research Letters, 9(8).
Abstract: Over the course of six years (2006-2011), equivalent black carbon (eqBC), coarse aerosol mass (PM1-10), and surface ozone (O-3), observed during the monsoon onset period at the Nepal Climate Observatory-Pyramid WMO/GAW Global Station (NCO-P, 5079 m a.s.l.), were analyzed to investigate events characterized by a significant increase in these short-lived climate forcers/pollutants (SLCF/P). These events occurred during periods characterized by low (or nearly absent) rain precipitation in the central Himalayas, and they appeared to be related to weakening stages (or 'breaking') of the South Asian summer monsoon system. As revealed by the combined analysis of atmospheric circulation, air-mass three-dimensional back trajectories, and satellite measurements of atmospheric aerosol loading, surface open fire, and tropospheric NOx, the large amount of SLCF/P reaching the NCO-P appeared to be related to natural (mineral dust) and anthropogenic emissions occurring within the PBL of central Pakistan (i.e., Thar Desert), the Northwestern Indo-Gangetic plain, and the Himalayan foothills. The systematic occurrence of these events appeared to represent the most important source of SLCF/P inputs into the central Himalayas during the summer monsoon onset period, with possible important implications for the regional climate and for hydrological cycles.
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Deguillaume, L., Charbouillot, T., Joly, M., Vaitilingom, M., Parazols, M., Marinoni, A., et al. (2014). Classification of clouds sampled at the puy de Dome (France) based on 10 yr of monitoring of their physicochemical properties. Atmospheric Chemistry And Physics, 14(3), 1485–1506.
Abstract: Long-term monitoring of the chemical composition of clouds (73 cloud events representing 199 individual samples) sampled at the puy de Dome (pdD) station (France) was performed between 2001 and 2011. Physicochemical parameters, as well as the concentrations of the major organic and inorganic constituents, were measured and analyzed by multicomponent statistical analysis. Along with the corresponding back-trajectory plots, this allowed for distinguishing four different categories of air masses reaching the summit of the pdD: polluted, continental, marine and highly marine. The statistical analysis led to the determination of criteria (concentrations of inorganic compounds, pH) that differentiate each category of air masses. Highly marine clouds exhibited high concentrations of Na+ and Cl-; the marine category presented lower concentration of ions but more elevated pH. Finally, the two remaining clusters were classified as “continental” and “polluted”; these clusters had the second-highest and highest levels of NH4+, NO3-, and SO24-, respectively. This unique data set of cloud chemical composition is then discussed as a function of this classification. Total organic carbon (TOC) is significantly higher in polluted air masses than in the other categories, which suggests additional anthropogenic sources. Concentrations of carboxylic acids and carbonyls represent around 10% of the organic matter in all categories of air masses and are studied for their relative importance. Iron concentrations are significantly higher for polluted air masses and iron is mainly present in its oxidation state (+II) in all categories of air masses. Finally, H2O2 concentrations are much more varied in marine and highly marine clouds than in polluted clouds, which are characterized by the lowest average concentration of H2O2. This data set provides concentration ranges of main inorganic and organic compounds for modeling purposes on multiphase cloud chemistry.
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Dietzel, M., Leis, A., Abdalla, R., Savarino, J., Morin, S., Bottcher, M. E., et al. (2014). O-17 excess traces atmospheric nitrate in paleo-groundwater of the Saharan desert. Biogeosciences, 11(12), 3149–3161.
Abstract: Saharan paleo-groundwater from the Hasouna area of Libya contains up to 1.8 mM of nitrate, which exceeds the World Health Organization limit for drinking water, but the origin is still disputed. Herein we show that a positive O-17 excess in NO3- (Delta O-17(NO3) = delta O-17(NO3) -0.52 delta O-18(NO3)) is preserved in the paleo-groundwater. The 17O excess provides an excellent tracer of atmospheric NO3-, which is caused by the interaction of ozone with NOx via photochemical reactions, coupled with a non-mass-dependent isotope fractionation. Our Delta(ONO3)-O-17 data from 0.4 to 5.0 parts per thousand (n = 28) indicate that up to 20 mol% of total dissolved NO3- originated from the Earth's atmosphere (x[NO3-](atm)), where the remaining NO3- refers to microbially induced nitrification in soils. High Delta O-17(NO3) values correspond to soils that are barren in dry periods, while low Delta O-17(NO3) values correspond to more fertile soils. Coupled high Delta O-17(NO3) and high x[NO3-](atm) values are caused by a sudden wash-out of accumulated disposition of atmospheric NO3- on plants, soil surfaces and in vadose zones within humid-wet cycles. The individual isotope and chemical composition of the Hasouna groundwater can be followed by a binary mixing approach using the lowest and highest mineralised groundwater as end members without considering evaporation. Using the delta S-34(SO4) and delta O-18(SO4) isotope signature of dissolved SO42-, no indication is found for a superimposition by denitrification, e. g. involving pyrite minerals within the aquifers. It is suggested that dissolved SO42- originates from the dissolution of CaSO4 minerals during groundwater evolution.
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Duchi, R., Cristofanelli, P., Marinoni, A., Bourcier, L., Laj, P., Calzolari, F., et al. (2014). Synoptic-scale dust transport events in the southern Himalaya. Aeolian Research, 13, 51–57.
Abstract: The variability of long-range dust transport events observed in the southern Himalaya and its relation with source areas have been studied thanks to five years' continuous measurements which were carried out at the “Nepal Climate Observatory-Pyramid” (NCO-P, 27 degrees 57'N, 86 degrees 8'E), the highest Northern Hemisphere GAW-WMO global station sited at 5079 m a.s.l. in the high Khumbu valley (Nepal) on the southern Himalaya. During the period March 2006-February 2011, the analyses of the aerosol particle concentrations and LAGRANTO three-dimensional backward trajectories indicated the occurrence of 275 days affected by synoptic-scale dust transport, which account for 22.2% of the investigated period. The frequency of dust transport days (DTDs) showed a clear seasonal cycle, with the highest seasonal value observed during pre-monsoon season (33.5% of the pre-monsoon's days are DTDs). Large enhancements in coarse aerosol number concentration N1-10 (average: +689%) and mass PM1-10 (average: +1086%) were observed during the dust transport events as compared to the days without dust (dust-free days, DFDs). In addition, the single scattering albedo (SSA) also showed higher values, ranging from 0.87 to 0.90, during DTDs with respect to DFDs (0.80-0.87). The predominant source of mineral dust reaching the measurement site was identified in the arid regions of the north-western Indian subcontinent (Thar desert), which accounted for 41.6% of the trajectories points associated with DTDs. Seasonal analysis also indicated that the winter season was significantly influenced by far western desert regions, such as North Africa and the Arabic Peninsula. (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).
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Ginot, P., Dumont, M., Lim, S., Patris, N., Taupin, J. D., Wagnon, P., et al. (2014). A 10 year record of black carbon and dust from a Mera Peak ice core (Nepal): variability and potential impact on melting of Himalayan glaciers. Cryosphere, 8(4), 1479–1496.
Abstract: A shallow ice core was extracted at the summit of Mera Peak at 6376ma.s.l. in the southern flank of the Nepalese Himalaya range. From this core, we reconstructed the seasonal deposition fluxes of dust and refractory black carbon (rBC) since 1999. This archive presents well preserved seasonal cycles based on a monsoonal precipitation pattern. According to the seasonal precipitation regime in which 80% of annual precipitation falls between June and September, we estimated changes in the concentrations of these aerosols in surface snow. The analyses revealed that mass fluxes are a few orders of magnitude higher for dust (10.4 +/- 2.8 gm(-2) yr(-1)) than for rBC (7.9 +/- 2.8 mgm(-2) yr(-1)). The relative lack of seasonality in the dust record may reflect a high background level of dust inputs, whether from local or regional sources. Over the 10-year record, no deposition flux trends were detected for any of the species of interest. The data were then used to simulate changes in the surface snow albedo over time and the potential melting caused by these impurities. Mean potential melting caused by dust and rBC combined was 713 kgm(-2) yr(-1), and for rBC alone, 342 kgm(-2) yr(-1) for rBC under certain assumptions. Compared to the melting rate measured using the mass and energy balance at 5360ma.s.l. on Mera Glacier between November 2009 and October 2010, i.e. 3000 kgm(-2) yr(-1) and 3690 kgm(-2) yr(-1) respectively, the impact of rBC represents less than 16% of annual potential melting while the contribution of dust and rBC combined to surface melting represents a maximum of 26 %. Over the 10-year period, rBC variability in the ice core signal primarily reflected variability of the monsoon signal rather than variations in the intensity of emissions.
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Herich, H., Gianini, M. F. D., Piot, C., Mocnik, G., Jaffrezo, J. L., Besombes, J. L., et al. (2014). Overview of the impact of wood burning emissions on carbonaceous aerosols and PM in large parts of the Alpine region. Atmospheric Environment, 89, 64–75.
Abstract: During the past years, actions implemented for the reduction of particulate matter emissions have in many European countries focused on road traffic emissions. Much less attention was paid to emissions from domestic wood combustion though the importance of residential wood burning as a source of atmospheric particulate matter (PM) in the Alpine region has been shown in many studies. Here we review the current knowledge about the contribution of wood burning emissions to ambient concentrations of elemental carbon (EC), organic carbon (OC) and PM in the Alpine region. The published results obtained by different approaches (e.g. macro-tracer method, multivariate receptor modeling, chemical mass balance modelling, and so-called Aethalometer modeling) are used in an ambient monotracer approach to estimate representative relationships between wood burning tracers (levoglucosan and mannosan) and EC, OC and PM from wood burning. The relationships found are applied to available ambient measurements of levoglucosan and mannosan at Alpine sites for estimation of the contributions of wood burning emissions to average levels of carbonaceous aerosols and PM at these sites. Our results imply that PM from wood burning alone adds often up to 50% and more of the EU daily limit value for PM10 in several alpine valleys during days in winter. Concentrations of carbonaceous aerosols in these valleys are often up to six times higher than in urban or rural sites at the foothills of the Alps. (C) 2014 Elsevier Ltd. All rights reserved.
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Holmgren, H., Sellegri, K., Hervo, M., Rose, C., Freney, E., Villani, P., et al. (2014). Hygroscopic properties and mixing state of aerosol measured at the high-altitude site Puy de Dôme (1465 m a.s.l.), France. Acp, 14(18), 9537–9554.
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Jacobi, H. W., Kleffmann, J., Villena, G., Wiesen, P., King, M., France, J., et al. (2014). Role of Nitrite in the Photochemical Formation of Radicals in the Snow. Environmental Science & Technology, 48(1), 165–172.
Abstract: Photochemical reactions in snow can have an important impact on the composition of the atmosphere over snow-covered areas as well as on the composition of the snow itself. One of the major photochemical processes is the photolysis of nitrate leading to the formation of volatile nitrogen compounds. We report nitrite concentrations determined together with nitrate and hydrogen peroxide in surface snow collected at the coastal site of Barrow, Alaska. The results demonstrate that nitrite likely plays a significant role as a precursor for reactive hydroxyl radicals as well as volatile nitrogen oxides in the snow. Pollution events leading to high concentrations of nitrous acid in the atmosphere contributed to an observed increase in nitrite in the surface snow layer during nighttime. Observed daytime nitrite concentrations are much higher than values predicted from steady-state concentrations based on photolysis of nitrate and nitrite indicating that we do not fully understand the production of nitrite and nitrous acid in snow. The discrepancy between observed and expected nitrite concentrations is probably due to a combination of factors, including an incomplete understanding of the reactive environment and chemical processes in snow, and a lack of consideration of the vertical structure of snow.
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Lim, S., Fain, X., Zanatta, M., Cozic, J., Jaffrezo, J. L., Ginot, P., et al. (2014). Refractory black carbon mass concentrations in snow and ice: method evaluation and inter-comparison with elemental carbon measurement. Atmospheric Measurement Techniques, 7(10), 3307–3324.
Abstract: Accurate measurement of black carbon (BC) mass concentrations in snow and ice is crucial for the assessment of climatic impacts. However, it is difficult to compare methods used to assess BC levels in the literature as they are not the same. The single particle soot photometer (SP2) method appears to be one of the most suitable to measure low concentrations of BC in snow and ice. In this paper, we evaluated a method for the quantification of refractory BC (rBC) in snow and ice samples coupling the SP2 with the APEX-Q nebulizer. The paper reviews all the steps of rBC determination, including SP2 calibration, correction for rBC particle aerosolization efficiency (75 +/- 7% using the APEX-Q nebulizer), and treatment of the samples. In addition, we compare the SP2 method and the thermal-optical method – Sunset organic carbon (OC) / elemental carbon (EC) aerosol analyzer with EUSAAR2 protocol – using snow and firn samples with different characteristics from the Greenland Summit, the French Alps, the Caucasus, and the Himalayas. Careful investigation was undertaken of analytical artifacts that potentially affect both methods. The SP2-based rBC quantification may be underestimated when the SP2 detection range does not cover correctly the existing size distribution of the sample. Thermal-optical EC measurements can be underestimated by low filtration efficiency of quartz fiber filter before analysis or dust properties (concentration and type), and overestimated by pyrolyzed OC artifacts during EC analysis. These results underline the need for careful assessment of the analytical technique and procedure for correct data interpretation.
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Lim, S., Lee, M., Kim, S. W., Yoon, S. C., Lee, G., & Lee, Y. J. (2014). Absorption and scattering properties of organic carbon versus sulfate dominant aerosols at Gosan climate observatory in Northeast Asia. Atmospheric Chemistry And Physics, 14(15), 7781–7793.
Abstract: Carbonaceous and soluble ionic species of PM1.0 and PM10 were measured along with the absorption and scattering properties and aerosol number size distributions at Gosan Climate Observatory (GCO) from January to September 2008. The daily averaged equivalent black carbon (EBC) measured as aerosol absorption exhibited two types of spectral dependence with a distinct maximum (peak) at either 370 nm or 880 nm, by which two subsets were extracted and classified into the respective groups (370 and 880 nm). The 370 nm group was distinguished by high organic carbon (OC) concentrations relative to elemental carbon (EC) and sulfate, but sulfate was predominant for the 880 nm group. The PM1.0 OC of the 370 nm group was mainly composed of refractory and pyrolized components that correlated well with PM1.0 EC1, referred to as char EC, which suggests bio-fuel and biomass combustion as the source of these OC fractions, particularly during winter. The scanning electron microscope (SEM) images and the number size distributions implied that aerosols of the 370 nm group were externally mixed upon transport in fast-moving air masses that passed through the Beijing area in about one day. In contrast, the aerosols of the 880 nm group were characterized by high sulfate concentrations, and seemed to be internally mixed during slow transport over the Yellow Sea region over approximately 2 to 4 days. The absorption and scattering coefficients of the 880 nm group were noticeably higher compared to those of the 370 nm group. The average absorption angstrom exponent (AAE) was estimated to be 1.29 and 1.0 for the 370 and 880 nm groups, respectively, in the range 370-950 nm. These results demonstrated that the optical properties of aerosols were intimately linked to chemical composition and mixing state, characteristics determined both by source and atmospheric aging processes. In OC dominant aerosols, absorption was enhanced in the UV region, which was possibly due to refractory and pyrolized OC compounds. Under sulfate dominant conditions, the sulfate coating on BC particles likely contributed to the absorption of the longer visible light. Consequently, single scattering albedo (SSA) was higher for the 880 nm group than for the 370 nm group, emphasizing that the relative abundances of absorbing and scattering constituents are also important in estimating the climate effect of aerosols.
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Menegoz, M., Krinner, G., Balkanski, Y., Boucher, O., Cozic, A., Lim, S., et al. (2014). Snow cover sensitivity to black carbon deposition in the Himalayas: from atmospheric and ice core measurements to regional climate simulations. Atmospheric Chemistry And Physics, 14(8), 4237–4249.
Abstract: We applied a climate-chemistry global model to evaluate the impact of black carbon (BC) deposition on the Himalayan snow cover from 1998 to 2008. Using a stretched grid with a resolution of 50 km over this complex topography, the model reproduces reasonably well the remotely sensed observations of the snow cover duration. Similar to observations, modelled atmospheric BC concentrations in the central Himalayas reach a minimum during the monsoon and a maximum during the post-and pre-monsoon periods. Comparing the simulated BC concentrations in the snow with observations is more challenging because of their high spatial variability and complex vertical distribution. We simulated spring BC concentrations in surface snow varying from tens to hundreds of μg kg(-1), higher by one to two orders of magnitude than those observed in ice cores extracted from central Himalayan glaciers at high elevations (>6000ma.s.l.), but typical for seasonal snow cover sampled in middle elevation regions (<6000ma.s.l.). In these areas, we estimate that both wet and dry BC depositions affect the Himalayan snow cover reducing its annual duration by 1 to 8 days. In our simulations, the effect of anthropogenic BC deposition on snow is quite low over the Tibetan Plateau because this area is only sparsely snow covered. However, the impact becomes larger along the entire Hindu-Kush, Karakorum and Himalayan mountain ranges. In these regions, BC in snow induces an increase of the net short-wave radiation at the surface with an annual mean of 1 to 3Wm(-2) leading to a localised warming between 0.05 and 0.3 degrees C.
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Noziere, B., Baduel, C., & Jaffrezo, J. L. (2014). The dynamic surface tension of atmospheric aerosol surfactants reveals new aspects of cloud activation. Nature Communications, 5.
Abstract: The activation of aerosol particles into cloud droplets in the Earth's atmosphere is both a key process for the climate budget and a main source of uncertainty. Its investigation is facing major experimental challenges, as no technique can measure the main driving parameters, the Raoult's term and surface tension, sigma, for sub-micron atmospheric particles. In addition, the surfactant fraction of atmospheric aerosols could not be isolated until recently. Here we present the first dynamic investigation of the total surfactant fraction of atmospheric aerosols, evidencing adsorption barriers that limit their gradient (partitioning) in particles and should enhance their cloud-forming efficiency compared with current models. The results also show that the equilibration time of surfactants in sub-micron atmospheric particles should be beyond the detection of most on-line instruments. Such instrumental and theoretical shortcomings would be consistent with atmospheric and laboratory observations and could have limited the understanding of cloud activation until now.
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Petersen, J., Wilhelm, B., Revel, M., Rolland, Y., Crouzet, C., Arnaud, F., et al. (2014). Sediments of Lake Vens (SW European Alps, France) record large-magnitude earthquake events. Journal Of Paleolimnology, 51(3), 343–355.
Abstract: We studied sediment cores from Lake Vens (2,327 m asl), in the Tin,e Valley of the SW Alps, to test the paleoseismic archive potential of the lake sediments in this particularly earthquake-sensitive area. The historical earthquake catalogue shows that moderate to strong earthquakes, with intensities of IX-X, have impacted the Southern Alps during the last millennium. Sedimentological (X-ray images, grain size distribution) and geochemical (major elements and organic matter) analyses show that Lake Vens sediments consist of a terrigenous, silty material (minerals and organic matter) sourced from the watershed and diatom frustules. A combination of X-ray images, grain-size distribution, major elements and magnetic properties shows the presence of six homogenite-type deposits interbedded in the sedimentary background. These sedimentological features are ascribed to sediment reworking and grain sorting caused by earthquake-generated seiches. The presence of microfaults that cross-cut the sediment supports the hypothesis of seismic deposits in this system. A preliminary sediment chronology is provided by Pb-210 measurement and AMS C-14 ages. According to the chronology, the most recent homogenite events are attributable to damaging historic earthquakes in AD 1887 (Ligure) and 1564 (RoquebilliSre). Hence, the Lake Vens sediment recorded large-magnitude earthquakes in the region and permits a preliminary estimate of recurrence time for such events of similar to 400 years.
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Putero, D., Cristofanelli, P., Laj, P., Marinoni, A., Villani, P., Broquet, A., et al. (2014). New atmospheric composition observations in the Karakorum region: Influence of local emissions and large-scale circulation during a summer field campaign. Atmospheric Environment, 97, 75–82.
Abstract: In this work we provide an overview of short lived climate forcers (SLCFs) and carbon dioxide variability in the Karakorum, by presenting results deriving from a field campaign carried out at Askole (3015 m a.s.l., Pakistan Northern Areas), by Baltoro glacier. By using an innovative embedded and transportable system, continuous measurements of aerosol particle number concentration (Np, 1571 +/- 2670 cm(-3)), surface ozone (O-3, 31.7 +/- 10.4 nmol/mol), carbon dioxide (CO2, 394.3 +/- 6.9 μmol/mol) and meteorological parameters have been performed from August 20th to November 10th 2012. The domestic combustion from the Askole village emerged as a possible systematic source of contamination in the valley, with short-lasting pollution events probably related to domestic cooking activities characterized by high values of Np (6066 +/- 5903 cm(-3)). By excluding these local contamination events, mountain thermal wind regime dominated the diurnal variability of Np, O-3 and CO2. In comparison to night-time, we observed higher Np (+354 cm(-3)) and O-3 (+7 nmol/mol) but lower CO2 (-8 μmol/mol) in air-masses coming from the lower valley during the central part of the day. Part of the day-to-day atmospheric composition variability can be also ascribed to synoptic circulation variability, as observed by using HYSPLIT 5-day back-trajectories. (C) 2014 The Authors. Published by Elsevier Ltd.
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Putero, D., Landi, T. C., Cristofanelli, P., Marinoni, A., Laj, P., Duchi, R., et al. (2014). Influence of open vegetation fires on black carbon and ozone variability in the southern Himalayas (NCO-P, 5079 m a.s.l.). Environmental Pollution, 184, 597–604.
Abstract: We analysed the variability of equivalent black carbon (BC) and ozone (O3) at the global WMO/GAW station Nepal Climate Observatory-Pyramid (NCO-P, 5079 m a.s.l.) in the southern Himalayas, for evaluating the possible contribution of open vegetation fires to the variability of these short-lived climate forcers/pollutants (SLCF/SLCP) in the Himalayan region. We found that 162 days (9% of the data-set) were characterised by acute pollution events with enhanced BC and O3 in respect to the climatological values. By using satellite observations (MODIS fire products and the USGS Land Use Cover Characterization) and air mass back-trajectories, we deduced that 56% of these events were likely to be affected by emissions from open fires along the Himalayas foothills, the Indian Subcontinent and the Northern Indo-Gangetic Plain. These results suggest that open fire emissions are likely to play an important role in modulating seasonal and inter-annual BC and O3 variability over south Himalayas.
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Waked, A., Favez, O., Alleman, L. Y., Piot, C., Petit, J. E., Delaunay, T., et al. (2014). Source apportionment of PM10 in a north-western Europe regional urban background site (Lens, France) using positive matrix factorization and including primary biogenic emissions. Atmospheric Chemistry And Physics, 14(7), 3325–3346.
Abstract: In this work, the source of ambient particulate matter (PM10) collected over a one-year period at an urban background site in Lens (France) was determined and investigated using a positive matrix factorization receptor model (US EPA PMF v3.0). In addition, a potential source contribution function (PSCF) was performed by means of the Hybrid Single-Particle Lagrangian Integrated Trajectory (Hysplit) v4.9 model to assess prevailing geographical origins of the identified sources. A selective iteration process was followed for the qualification of the more robust and meaningful PMF solution. Components measured and used in the PMF included inorganic and organic species: soluble ionic species, trace elements, elemental carbon (EC), sugar alcohols, sugar anhydride, and organic carbon (OC). The mean PM10 concentration measured from March 2011 to March 2012 was about 21 μg m(-3) with typically OM, nitrate and sulfate contributing to most of the mass and accounting respectively for 5.8, 4.5 and 2.3 μg m(-3) on a yearly basis. Accordingly, PMF outputs showed that the main emission sources were (in decreasing order of contribution) secondary inorganic aerosols (28% of the total PM10 mass), aged marine emissions (19 %), with probably predominant contribution of shipping activities, biomass burning (13 %), mineral dust (13 %), primary biogenic emissions (9 %), fresh sea salts (8 %), primary traffic emissions (6 %) and heavy oil combustion (4 %). Significant temporal variations were observed for most of the identified sources. In particular, biomass burning emissions were negligible in summer but responsible for about 25% of total PM10 and 50% of total OC in wintertime. Conversely, primary biogenic emissions were found to be negligible in winter but to represent about 20% of total PM10 and 40% of total OC in summer. The latter result calls for more investigations of primary biogenic aerosols using source apportionment studies, which quite usually disregard this type of source. This study further underlines the major influence of secondary processes during daily threshold exceedances. Finally, apparent discrepancies that could be generally observed between filter-based studies (such as the present one) and aerosol mass spectrometer-based PMF analyses (organic fractions) are also discussed.
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