Publications

Abstract: Various Pharmaceuticals Are Essential For Livestock Farming, But Some Are Highly Toxic To Aquatic Life If They Reach Surface Water Bodies. Mediterranean Climate Is Characterized By Dry Summers Followed By Intense Autumn Storms. We Studied The Effect Of These Climatic Conditions On The Risk Of Pharmaceutical Residues Transfer To Streams At The Catchment-Scale. Pharmaceutical Products Routinely Used In The Study Area, As Well As Their Application Frequency And Season, Were Identified Through Interviews With Farmers. As A Proof A Concept, Three Veterinary Pharmaceuticals (Fenbendazole (Fbz), Mebendazole (Mbz) And Ivermectin (Ivm)) Were Chosen As Model Chemicals Based On Their Relatively High Usage, Their Specificity To Represent Different Types Of Livestock (Swine, Sheep And Cattle), And Their Ability To Be Analyzed Using The Same Analytical Method. Stream Water Was Analyzed During Low Flow Periods And At High Frequency (Up To 2 H(-1)) During Flood Events. The Selected Veterinary Pharmaceuticals Were Not Detected During Low Flow, But Fbz And Mbz Reached High Concentrations For Short Periods During Floods. Due To The Event-Driven Nature Of Their Transfer, A Significant Load Of Veterinary Pharmaceuticals Can Reach The River And Cause Temporary But Significant Degradation Of Water Quality (E.G. For Fbz, The Water Concentration Reached Up To 355 Times The Predicted No Effect Concentration (Pnec)). This Indicates That Special Care Should Be Taken To Avoid Keeping Freshly Treated Livestock On Pastures That May Become Hydrologically Connected Under Wet Conditions. In Addition, It Suggests That Low-Frequency Monitoring Is Not Sufficient To Detect Those High Concentration Levels That Exist During Very Short Periods.

Abstract: Pesticides Use Raises Concerns Regarding Environmental Sustainability, As Pesticides Are Closely Linked To The Decline Of Biodiversity And Adverse Human Health Outcomes. This Study Proposed A Holistic Approach For Assessing The Potential Risks Posed By Pesticides For Human Health And The Environment In The Eastern Region Of Michoacan, Where Extensive Agricultural Lands, Especially Corn And Avocado Fields, Surround The Monarch Butterfly Biosphere Reserve. We Used A Combination Of Qualitative (Semi -Structured Interviews) And Quantitative (Chemical Analysis) Data. Fifty-Five Interviews With Smallholder Farmers Allowed Us To Identify Pesticide Types, Quantities, Frequencies, And Application Methods. A Robust And Precise Analytical Method Based On Solid -Phase Extraction And Lc-Ms/Ms Was Developed And Validated To Quantify 21 Different Pesticides In 16 Water Samples (Rivers, Wells, Runoff Areas). We Assessed Environmental And Human Health Risks Based On The Pesticides Detected In The Water Samples And Reported In The Interviews. The Interviews Revealed The Use Of 28 Active Ingredients, Including Glyphosate (29 % Of Respondents), Imidacloprid (27 %), And Benomyl (24 %). The Pesticide Analysis Showed The Presence Of 13 Different Pesticides And Degradation Products In The Water Samples. The Highest Concentrations Were Found For Imidacloprid (1195 Ngl-1) And Carbendazim (A Degradation Product Of Benomyl; 932 Ngl-1), Along With The Metabolite Of Pyrethroid Insecticides, 3-Pba (494 Ngl-1). The Risk Assessment Indicates That Among The Most Used Pesticides, The Fungicide Benomyl And Carbendazim Pose The Highest Risk To Human Health And Aquatic Ecosystems, Respectively. This Study Unveils Novel Insights On Agricultural Practices For The Avocado, A Globally Consumed Crop That Is Undergoing Rapid Production Expansion. It Calls For The Harmonisation Of Crop Protection With Environmental Responsibility, Safeguarding The Health Of The People Involved And The Surrounding Ecosystems.

Abstract: During Major Floods, Rivers Erode Their Banks And Thus Recruit Large Wood Pieces From The Riparian Zones. There Is Still A Lack Of Knowledge About The Transport Of Large Wood, The Volumes Involved And The Flux Distribution, I.E. The Large Wood Connectivity At Catchment Scale. During Storm Alex (October 2020), The French Roya Catchment (394 Km2) Experienced A Paroxysmal Morphogenic Flood Involving Massive Bank Erosion. The Riparian Vegetation Was Largely Recruited, With Large Wood Contributing To Logjams And Bridge Destruction. This Paper Presents A Methodology For Volumetric Assessment Of The Large Wood Fluxes Involved. Simple Approaches Are Used To (I) Quantify The Inputs From Stand Density Data From The National Forest Inventory And From Source Areas Based On Diachronic Analysis Of Active Channels Highlighting The Erosion Of 87 Ha Of Wooded Areas; And (Ii) Quantify The Volumes Deposited Via An Exhaustive Manual Digitisation Of 16,846 Pieces Of Large Wood Deposited On 59 Km Of Channels On The Roya And Its Tributaries. This Catchment-Scale, Large Wood Connectivity Analysis Shows That The Flood Recruited And Transported Downstream A Volume Of Around 14,000 M3 Of Large Wood (Uncertainty Range: 7000-29,500 M3). Drone Observations Of The Roya River Mouth In Italy And Satellite Images Showing A Raft Of Driftwood, Several Km Long, Drifting Off The Roya River Mouth In The Aftermath Of The Flood Corroborate Our Findings.

Abstract: Fine Sediment Stored In The Gravel Bed Is An Important Component Of River Systems. Current Field Protocols Usually Allow Evaluation Of The Silt-Clay Fraction Of Fine Sediment Stocks Only And Neglect The Sand Fraction. This Study Proposes A New Protocol To Quantify Fine Sediment Stocks, Including The Sand Fraction Inside The Gravel Bed Matrix. Fine Sediment Stocks Were Sampled Within Patches Of 0.30 M X 0.30 M On The Dry Gravel Bed Surface, Separating The Surface Layer And The Subsurface Layer. The Grain-Size Distribution Of The Samples Was Obtained By Field Sieving (10 Mm, 2 Mm, 500 Mu M And 100 Mu M) Over A Bucket, Using A Known Volume Of Water. The Mass Of The Fraction Below 100 Mu M Was Measured Based On The Concentration Within The Bucket. The Local Stocks Were Then Integrated Over The Whole River Reach By Assigning Local Stocks To Facies, In Which Fine Sediment Stocks Were Assumed To Be Homogeneously Distributed. The Methodology Was Applied To A 1 Km Long Reach Of The River Galabre (Southern French Alps), Characterized By Significant Fine Sediment Stocks And Upstream Sediment Input. Results From Local Measurements Show A Large Amount Of Sand In Both Surface And Subsurface Layers. The Quantity Of Sand Can Reach Up To Three Times The Quantity Of Silt-Clay. An Estimation Of Porosity Showed That Fine Material May Play An Important Role In Structuring The Bed, Since Porosity Increases With Increasing Fine Sediment Content. The Potential Fine Sediment Stock That Can Be Resuspended Due To Channel Migration Is Found To Be Of The Same Order Of Magnitude As The Sediment Budget Estimated From The Measured Flux In The Upstream Hydrometric Station Of The Studied Reach.

Abstract: Lakes And Reservoirs Are A Significant Source Of Atmospheric Methane (Ch4), With Emissions Comparable To The Largest Global Ch4 Emitters. Understanding The Processes Leading To Such Significant Emissions From Aquatic Systems Is Therefore Of Primary Importance For Producing Accurate Projections Of Emissions In A Changing Climate. In This Work, We Present The First Deployment Of A Novel Membrane Inlet Laser Spectrometer (Mils) For Fast Simultaneous Detection Of Dissolved Ch4, Ethane (C2H6) And The Stable Carbon Isotope Of Methane (Delta 13Ch4). During A 1-Day Field Campaign, We Performed 2D Mapping Of Surface Water Of Lake Aiguebelette (France). Average Dissolved Ch4 Concentrations And Delta 13Ch4 Were 391.9 +/- 156.3 Nmol L-1 And -67.3 +/- 3.4 Parts Per Thousand In The Littoral Area And 169.8 +/- 26.6 Nmol L-1 And -61.5 +/- 3.6 Parts Per Thousand In The Pelagic Area. The Dissolved Ch4 Concentration In The Pelagic Zone Was 50 Times Larger Than The Concentration Expected At Equilibrium With The Atmosphere, Confirming An Oversaturation Of Dissolved Ch4 In Surface Waters Over Shallow And Deep Areas. The Results Suggest The Presence Of Ch4 Sources Less Enriched In 13C In The Littoral Zone (Presumably The Littoral Sediments). The Ch4 Pool Became More Enriched In 13C With Distance From Shore, Suggesting That Oxidation Prevailed Over Epilimnetic Ch4 Production And It Was Further Confirmed By An Isotopic Mass Balance Technique With The High-Resolution Data. This New In Situ Fast Response Sensor Allows One To Obtain Unique High-Resolution And High-Spatial Coverage Data Sets Within A Limited Amount Of Survey Time. This Tool Will Be Useful In The Future For Studying Processes Governing Ch4 Dynamics In Aquatic Systems. High-Resolution Mapping Of Surface Methane And Its Isotopic Signature Enables Accurate Characterization Of Aquatic Systems And Discrimination Of Biochemical Processes At Work. At Lake Aiguebelette, This New In Situ Tool Allowed Us To Conclude That Methane Present At The Surface Comes Mainly From Shallow Littoral Areas, Where Sediments, Which Are A Source Of Methane, Are Closer To The Surface. During Lateral Transport Of Water Masses From The Littoral Zone, The Change In Isotopic Signature Reveals That Methane Oxidation Prevails Over Local In Situ Production. Comparison With Previous Studies Validates The Importance Of High-Resolution Measurements (Particularly To Capture The High Variability In The Littoral Zone) And Showed That Smaller Lakes Experience Stronger Methane Isotopic Signature Changes For A Given Methane Concentration Variation. This Can Be Explained By The Fact That The Smaller Lake Has A Larger Littoral-To-Total Surface Area. This New Tool Will Be Useful In The Nearby Future To Study The Processes Governing Ch4 Dynamics In Aquatic Systems. Fast In Situ Measurements Of Dissolved Methane And Its Stable Carbon Isotopehigh-Spatial Resolution Mapping Of Dissolved Methane And Its Stable Carbon Isotopeimproved Production/Oxidation Process Identification Over Discrete Sampling

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.

Abstract: The Mekong Delta Has The World'S Third-Largest Surface Area. It Plays An Indisputable Role In The Economy And Livelihoods Of Vietnam And Cambodia, With Repercussions At Regional And Global Scales. During Recent Decades, The Vietnamese Part Of The Mekong Delta Underwent Profound Human Interventions (Construction Of Dykes And Multi-Channel Networks), Which Modified The Hydrodynamic Regime, Especially Cycles Of Field Submersion. In This Study, We First Applied A Full 2D Numerical Hydraulic Model, Telemac-2D, To Examine The Effects Of The Complex Channel And River Networks On The Spatial And Temporal Distribution Of The Flow In The 40,000 Km2 Of The Vietnamese Mekong Delta. Then, Two Scenarios Of Relative Sea-Level Rise In 2050 And 2100 Were Implemented To Simulate The Future Patterns Of Water Fluxes In The Delta. The Results Show That Dykes And Multi-Channel Networks Would Reduce The Inundation Area By 36% And Lessen The Peak Water Level By 15% And The Discharge Over The Floodplains By 24%. Despite This Protection, Under A Relative Sea-Level Rise Of 30 Cm And 100 Cm, The Maximum Flooded Area Could Occupy About 69% And 85% Of The Whole Delta In 2050 And 2100, Respectively.

Abstract: Soon After Their First Deployment In Rivers In The Early 2000S, Rfid Tags Rapidly Became The Reference Technology For Bedload Tracing In Rivers. We Can Estimate From The Literature That During The Last 20 Years, More Than 30,000 Rfid Tracers Have Been Injected In Gravel-Bed Rivers All Around The World To Study Bedload Transport. Many Field Experiments Have Been Reported In A Great Diversity Of Fluvial Environments, Complemented By Many Laboratory Experiments And Methodological Developments. This Paper Proposes A Review Of These Works, Notably Based On The Compilation Of More Than 350 Rfid Surveys, Complemented By 97 Magnetic Surveys, For A Total Of 125 Study Sites. The Meta-Analysis Of This Database Shows That Rfid Tracers Have Improved Our Understanding Of Sediment Transport In Fluvial Environments With Rapid Bedload Dispersion. It Is Also Shown That Central Positions Of Tracer Plumes Are Moving Faster Over Time Than Tracer Leading Fronts, As Attested By A General Relation Between Maximum And Mean Distances Of Transport. The Most Recent Methodological Developments Based On The Use Of Active Uhf Rfid Tags Show That It Is Now Possible To Conduct Efficient Bedload Tracing Experiments Not Only In Small Streams, But Also In Large Gravel-Bed Rivers Or Very Active Braided Channels. Other Addressed Topics Include Rfid Deployment And Survey In River Channels, Controlling Factors Of Tracer Mobility (Flow Conditions, Grain-Size And Shape, Channel Morphology), Bedload Monitoring Approaches Using Rfid Tracers, And Applications Of Rfid Tracers For Evaluating Human Effects On Bedload Transport. Key Challenges Of Bedload Tracing With Rfid Tags Are Also Proposed. A Review Of Field And Laboratory Radio Frequency Identification (Rfid) Bedload Tracing Experiments Is Proposed, Including A Meta-Analysis Of Data Coming From 459 Tracer Surveys For A Total Of 125 Study Sites. Rfid Tracers Open New Avenues For Exploring Fluvial Environments Prone To Rapid Bedload Dispersion. The Most Recent Methodological Developments Based On Active Ultra-High Frequency Rfid Tags Show That It Is Now Possible To Conduct Efficient Bedload Tracing Experiments Not Only In Small Streams But Also In Large Gravel-Bed Rivers Or Active Braided Channels.Image

Abstract: A hydrogeochemical and stable isotopic (delta(15) N-NO3 and delta O-18(NO3)) multitracer approach was combined with previous geological and hydrogeological knowledge in a groundwater-dominated basin, located within the semiarid region of the Bolivian Altiplano (SE of Lake Titicaca). Major natural processes and anthropogenic impacts controlling water chemistry and isotopic compositions of groundwater were identified and corresponding aquifer impacted zones determined. The main natural processes are, by following water flowlines, (1) silicate weathering in the piedmont subsystem (similar to 4,600-3,910 m asl, Ca(Mg)HCO3 facies), (2) Na-Ca exchange within glacial-fluvial deposits overlying paleolacustrine deposits (similar to 3,910 to 3,860 m asl, Na-HCO3 facies), and (3) evaporite dissolution in the confined zone of the lacustrine plain (similar to 3,860-3,810 m asl, Na-Cl-SO4 facies). The highest contributions of anthropogenic nitrate in groundwater have been observed at 3,960-3,860 m asl in the piedmont subsystem and were isotopically associated with leaching from areas influenced by manure piles, synthetic N fertilizers, and sewage collector pipes. In this subsystem, natural water-rock interactions could be deciphered with minimal anthropogenic impact, allowing nitrate sources to be clearly identified. Denitrification, occurring in the topographic lows of the piedmont subsystem, was identified as the main natural attenuation process. The multitracer approach provided a consistent understanding of the major processes that take place along the groundwater flow system and confirmed the significant role of anthropogenic nitrate. This aquifer system thus represents an ideal model of the region's hydrochemical evolution along the gravity-driven flow caused by natural water-rock interaction processes and the influence of anthropogenic contamination.

Abstract: Rainfall is a key driver of geomorphological processes ranging from impacting drops that lead to the small-scale dislodgement of soil particles to large-scale morphogenic floods and rainfall-induced hillslope processes. Although rainfall has been identified in seismic records, the associated power spectral density and its quantitative relation to the underlying physical processes have not yet been studied. Here, we analyze nearly 2 years of combined seismic and optical disdrometer measurements, where the latter enables the drop-based quantification of rainfall physical properties. Our measurements confirm the broadband observation of ground velocity power spectral density due to rainfall, allowing the seismic identification of rainfall at intensities as low as 1 mm/h. Seismic power, P, shows a power-law scaling with rainfall intensity, I, and kinetic energy, E: P proportional to I-2.1 and P proportional to E-1.6. The observed scaling relations are consistent between the three monitored sites although there are absolute differences in seismic power of about 1 order of magnitude, which are likely due to variability in landcover and subsurface seismic properties. With a physical model, we demonstrate that the observed power-law relations are set by an underlying linear relation between seismic power and rainfall impulse power, and that the associated exponent values of I and E are due to the covariance of the raindrop size distribution with the total number of drops. The largest raindrop fractions, whose relative contribution increases with rainfall intensity, dominate the seismic signal where, in our case, 90% of the seismic power is attributed to drops larger than 3 mm. Using our model, we estimate the contributing area of rainfall to seismic observations to be within a radial distance of -5-25 m. The spatially integrated nature of the seismic measurements and their sensitivity to large raindrops, which control the disaggregation and the mobilization of soil particles, make seismic records well-suited for the investigation of soil erosion processes. More generally, our work provides a basis for the temporally-resolved seismic quantification of rainfall that drives the dynamics of various hydro-geomorphological processes.

Abstract: Plasticizers such as di(2-ethylhexyl) phthalate (DEHP) and tris (2-butoxyethyl) phosphate (TBOEP) are manufactured chemicals produced in high volumes. These chemicals are frequently detected in the aquatic environment and cause toxic effects on organisms. In this study, we assessed the chronic impacts of DEHP and TBOEP, respectively, at the concentration of 100 μL-1 dissolved in the artificial medium (M4/4) and Mekong River water on life history traits of a tropical micro-crustacean, Ceriodaphnia cornuta, for 14 days. DEHP and TBOEP substantially reduced the survival of C. cornuta. In M4/4 medium, both plasticizers strongly enhanced reproduction but did not influence the growth of C. cornuta. Mekong River water, plasticizers-exposed C. cornuta produced less neonates than those in the control. The detrimental impacts of DEHP and TBOEP on the fitness of C. cornuta were much stronger in natural river water than in M4/4. Our results suggest that plasticizers can cause adverse effects on tropical freshwater cladocerans, particularly in natural water. These results are of a deep concern, as national and international regulatory guidelines which are based on ecotoxicological tests using standard media may not fully capture these effects.

Abstract: Water-Resource Management Has Become A Major Global Issue In A World Threatened By Climate Change. High-Resolution Geophysical Methods May Be Of Valuable Help In Monitoring The Water Masses, Both In Space And Time. Passive Seismic Interferometry Takes Advantage Of Ambient Seismic Noise To Recover The Variations In Seismic Wave Velocity Induced By Changes In Groundwater. We Present Hereafter The Time And Space Monitoring Of An Hydraulic Dome Artificially Formed To Prevent Biological And Chemical Pollutants From Entering The Exploitation Field Of Crepieux-Charmy (Lyon, France). We Use A Dense Seismic Network To Passively Monitor The Water Table Changes Induced By Infilling Of An Infiltration Basin At The Water Supply Facility For The Two Million Inhabitants Of The Lyon Metropolis (France). We Assess The Hourly Seismic Velocity Variations Over 19 Days, During Which Two Filling And Drainage Cycles Were Performed. The Use Of A Dense Three-Component Seismic Network Allows Fine Characterization Of The Seismic Wavefield, And Offers The Possibility To Include The Analysis Of 4,851 Raypaths In A Robust Inversion Algorithm Based On Ray Theory. The Velocity Variations Are Mapped With High Resolution. They Are Directly Related To The Water Table Variations And To Residual Water Saturation Changes Within The Unsaturated Zone. This Seismic Experiment Highlights The Three-Dimensional (3D) Implementation And Evolution Of A Hydraulic Dome Under The Infiltration Basin. This Dynamic Information Helps In The Understanding And Modeling Of Water Flows Between The Water Table And A River, Which Represents A Fundamental Issue For Discussions On The Effectiveness Of The Barrier.

Abstract: An experimental study was performed to investigate the effects of an acid solution on the mechanical strength and the microstructure of biocemented sand. The tests were performed on small triaxial samples extracted from a large-scale model. An acid solution composed of hydrochloric acid and Tris buffer with an initial pH of 6.6 was injected in the triaxial apparatus in different amounts. The changes of the physical and mechanical properties of the sample were studied afterwards. Triaxial drained tests with constant confining pressures were performed on the chemically treated samples in order to determine the remaining strength of the samples. Moreover, several scanning electron microscope (SEM) and X-ray microtomography observations were performed on small subsamples in order to identify the changes in the microstructure due to the chemical dissolution. The experimental results point out that the strength of the treated specimens decreases dramatically compared with that of the initial untreated specimens. Typically, a 50% strength reduction has been found for 10% of total calcite dissolution. Furthermore, the microstructural observations have shown uniform calcite dissolution at the pore scale (no preferential locations). The calcite crystal structures were damaged randomly by the chemical solution. A reduction of the spatial densities and sizes of these crystals were found from SEM and X-ray microtomography observations. Overall, no hysteretic effects were observed on the mechanical (strength) and microstructural (contact surface area) properties between the biocementation and dissolution paths.

Abstract: Water stable isotope analysis using Cavity Ring-Down Spectroscopy (CRDS) has a strong between-sample memory effect. The classic approach to correct this memory effect is to inject the sample at least 6 times and ignore the first two to three injections. The average of the remaining injections is then used as measured value. This is in many cases insufficient to completely compensate the memory effect. We propose a simple approach to correct this memory effect by predicting the asymptote of consecutive repeated injections instead of averaging over them. The asymptote is predicted by fitting a y = a/x + b relation to the sample repetitions and keeping b as measured value. This allows to save analysis time by doing less injections while gaining precision. We provide a Python program applying this method and describe the steps necessary to implement this method in any other programming language. We also show validation data comparing this method to the classical method of averaging over the last couple of injections. The validation suggests a gain in time of a factor two while gaining in precision at the same time. The method does not have any specific requirements for the order of analysis and can therefore also be applied to an existing set of analyzes in retrospect. We fit a simple y = a/x + b relation to the sample repetitions of Picarro L2130-i isotopic water analyzer, in order to keep the asymptote (b) as measured value instead of using the average over the last couple of measurements. This allows a higher precision in the measured value with less repetitions of the injection saving precious time during analysis. We provide a sample code using Python, but generally this method is easy to implement in any automated data treatment protocol. (C) 2022 The Author(s). Published by Elsevier B.V.

Abstract: Purposegravel-Bed Rivers Can Store Significant Amounts Of Fine Sediments, In The Gravel Matrix Or At The Bar Surface. The Contribution Of The Latter To Suspended Sediment Fluxes Depends On Their Erodibility Which Is Highly Variable Spatially. The Sensitivity Induced By This Spatial Variability On Outputs Of A 2D Hydro-Sedimentary Numerical Model Was Investigated And Recommendations For In Situ Erodibility Measurement Strategy Were Provided.Methodsthe Spatial Variability Of Fine Sediment Erodibility Was Determined Using The Cohesive Strength Meter (Csm) Device In A 1-Km-Long River Reach Of The Galabre River In The Southern French Alps. A 2D Hydro-Sedimentary Numerical Model Was Built On The Monitored Reach Displaying Three Deposit Zones With Distinct Erodibility Values. The Sensitivity Of The Modeled Eroded Masses To Sediment Erodibility Variability Was Assessed Through Ten Distinct Sediment Erodibility Settings And Three Schematic Flood Events, Based On The In Situ Monitoring Of The River.Results And Discussionthe Spatial Variability Of Fine Sediment Deposit Erodibility Was Significant. Marginal Deposits Were More Resistant Than Superficial Or Water-Saturated Ones. The Sensitivity Of The Modeled Eroded Mass To Erodibility Parameters Was Different Depending On The Set Of Measurements Used. When Considering The Entire Dataset, Which Exhaustively Characterizes The Fine Sediment Deposits, The Numerical Sensitivity Was Relatively Low. On The Other Hand, When A Partial Set Of Measurements Outside The Quartiles Was Considered, The Sensitivity Was More Significant Leading To Large Differences In Eroded Masses Between Spatially Distributed And Spatially Averaged Settings. Using Bootstrap Sampling, We Recommended Making 15 To 20 Measurements In Marginal And Superficial Zones To Adequately Capture The Distribution Of Erodibility.Conclusionsthis Work Provided Insight On The Spatial Variability Of Erodibility And The Sensitivity Induced In 2D Numerical Modeling Of Fine Sediments. The Proposed Methodology Could Be Applied To Other Environments (E.G., Reservoirs, Estuaries, Or Lowland Rivers) In Order To Adapt The Monitoring And Numerical Modeling Strategies.

Abstract: Introductionmicro-Scale Analysis Of Microbes In Soil Is Essential To The Overall Understanding Of Microbial Organization, Interactions, And Ecosystem Functioning. Soil Fractionation According To Its Aggregated Structure Has Been Used To Access Microbial Habitats. While Bacterial Communities Have Been Extensively Described, Little Is Known About The Fungal Communities At Scales Relevant To Microbial Interactions. Methodswe Applied A Gentle Soil Fractionation Method To Preserve Stable Aggregated Structures Within The Range Of Micro-Aggregates And Studied Fungal And Bacterial Communities As Well As Nitrogen Cycling Potentials In The Pristine Rothamsted Park Grass Soil (Bulk Soil) As Well As In Its Particle Size Fractions (Psfs; >250 Mu M, 250-63 Mu M, 63-20 Mu M, 20-2 Mu M, <2 Mu M, And Supernatant). Resultsoverall Bacterial And Fungal Community Structures Changed In Psfs Below 20 Mu M. The Relative Abundance Of Basidiomycota Decreased With Decreasing Particle Size Over The Entire Measure Range, While Ascomycota Showed An Increase And Mucoromycota Became More Prominent In Particles Below 20 Mu M. Bacterial Diversity Was Found Highest In The < 2 Mu M Fraction, But Only A Few Taxa Were Washed-Off During The Procedure And Found In Supernatant Samples. These Taxa Have Been Associated With Exopolysaccharide Production And Biofilm Formation (E.G., Pseudomonas, Massilia, Mucilaginibacter, Edaphobaculum, Duganella, Janthinobacterium, And Variovorax). The Potential For Nitrogen Reduction Was Found Elevated In Bigger Aggregates. Discussionthe Observed Changes Below 20 Mu M Particle Are In Line With Scales Where Microbes Operate And Interact, Highlighting The Potential To Focus On Little Researched Sub-Fractions Of Micro-Aggregates. The Applied Method Shows Potential For Use In Studies Focusing On The Role Of Microbial Biofilms In Soil And Might Also Be Adapted To Research Various Other Soil Microbial Functions. Technical Advances In Combination With Micro-Sampling Methods In Soil Promise Valuable Output In Soil Studies When Particles Below 20 Mu M Are Included.

Abstract: Estuaries are considered as important sources of the global emission of greenhouse gases (GHGs). Urbanized estuaries often experience eutrophication under strong anthropogenic activities. Eutrophication can enhance phytoplankton abundance, leading to carbon dioxide (CO2) consumption in the water column. Only a few studies have evaluated the relationship between GHGs and eutrophication in estuaries. In this study, we assessed the concentrations and fluxes of CO2, methane (CH4) and nitrous oxide (N2O) in combination with a suite of biogeochemical variables in four sampling campaigns over two years in a highly urbanized tropical estuary in Southeast Asia (the Saigon River Estuary, Vietnam). The impact of eutrophication on GHGs was evaluated through several statistical methods and interpreted by biological processes. The average concentrations of CO2, CH4 and N2O at the Saigon River in 2019-2020 were 3174 +/- 1725 μgC-CO2 L-1, 5.9 +/- 16.8 μgC-CH4 L-1 and 3.0 +/- 4.8 μgN-N2O L-1, respectively. Their concentrations were 13-18 times, 52-332 times, and 9-37 times higher than the global mean concentrations of GHGs, respectively. While CO2 concentration had no clear seasonal pattern, N2O and CH(4 )concentrations significantly differed between the dry and the rainy seasons. The increase in eutrophication status along the dense urban area was linearly correlated with the increase in GHGs concentrations. The presence of both nitrification and denitrification resulted in elevated N2O concentrations in this urban area of the estuary. The high concentration of CO2 was contributed by the high concentration of organic carbon and mineralization process. GHGs fluxes at the Saigon River Estuary were comparable to other urbanized estuaries regardless of climatic condition. Control of eutrophication in urbanized estuaries through the implantation of efficient wastewater treatment facilities will be an effective solution in mitigating the global warming potential caused by estuarine emissions.

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.

Abstract: Contamination of soils and groundwater with perfluoroalkyl acids (PFAAs) is widespread due to their use in aqueous film-forming foams (AFFF). In this study the effectiveness of RemBind?, a sorbent containing activated carbon and aluminium oxyhydroxides was tested, as a tool to reduce the leaching and bioavailability of 12 PFAAs in soils, by amending contaminated soils with 5?30% (by weight) of the sorbents. Batch tests were used to determine the leaching of PFAAs. Their bioavailability to earthworms and wheat grass was assessed in greenhouse microcosms. Leaching and bioavailability of PFOS was reduced by up to 99.9%, at most sorbent application rates. Lowest reduction of leaching was found for shorter perfluoroalkyl chain length chemicals. The specific formulation of RemBind?, which is available in a basic and superior formulation, as well as the application rate were parameters for increasing effectiveness of the treatment. Furthermore, differences in leaching as well as bioavailability were seen depending on the perfluoroalkyl chain length. A preliminary assessment of the long-term stability of the treatment, assessed after a three-year curing period, suggested that the sorbent continued to be effective in reducing PFAAs in leachates, thus showing the potential of this sorbent to hinder further environmental contamination.

Abstract: Tides and Earth-Moon system evolution are coupled over geological time. Tidal energy dissipation on Earth slows Earth ' s rotation rate, increases obliquity, lunar orbit semi-major axis and eccentricity, and decreases lunar inclination. Tidal and core-mantle boundary dissipation within the Moon decrease inclination, eccentricity and semi-major axis. Here we integrate the Earth-Moon system backwards for 4.5 Ga with orbital dynamics and explicit ocean tide models that are “high-level” (i.e., not idealized). To account for uncertain plate tectonic histories, we employ Monte Carlo simulations, with tidal energy dissipation rates (normalized relative to astronomical forcing parameters) randomly selected from ocean tide simulations with modern ocean basin geometry and with 55, 116, and 252 Ma reconstructed basin paleogeometries. The normalized dissipation rates depend upon basin geometry and Earth ' s rotation rate. Faster Earth rotation generally yields lower normalized dissipation rates. The Monte Carlo results provide a spread of possible early values for the Earth-Moon system parameters. Of consequence for ocean circulation and climate, absolute (un-normalized) ocean tidal energy dissipation rates on the early Earth may have exceeded today ' s rate due to a closer Moon. Prior to similar to 3 Ga, evolution of inclination and eccentricity is dominated by tidal and core-mantle boundary dissipation within the Moon, which yield high lunar orbit inclinations in the early Earth-Moon system. A drawback for our results is that the semi-major axis does not collapse to near-zero values at 4.5 Ga, as indicated by most lunar formation models. Additional processes, missing from our current efforts, are discussed as topics for future investigation.

Abstract: The presence of buried salt layer in the Ghor Al-Haditha area is discussed concerning sinkhole hazard. Numerous geophysical methods such as seismic refraction (SRFR), reflection (SRFL), seismic tomography, multichannel analysis of surface waves (MASW) were developed earlier for the salt layer identification. Geophysical criteria of salt parameters (such as longitudinal V-p and shear V-s wave velocities) were established to identify salt layers. This paper presents new geophysical results proving the salt extension in the Dead Sea (DS) coastal area in its eastern shore potentially representing a sinkhole hazard. The reprocessing technique of MASW data using the synthetic modeling enabled us to detect salt layer characteristics such as depth to its top, the thickness of the layer, and its V-s velocity. It was established that a salt layer with 7-10 m thick is located at a depth of 37-41 m and is characterized by shear-wave velocity (V-s) of 850-1200 m/s. Similar results were obtained by the Transient Electromagnetic (TEM) resistivity method, which detected a comparatively resistive salt layer at a background of very low resistivity. The resolution of the TEM method allows detecting a salt layer of 3 m thick and more at a depth of 39-40 m. Seismic refraction data processing has shown the presence of a salt layer with a velocity of more than 2900 m/s at approximately or the same depths. Analysis of seismic tomography data also confirms the parameters of the discovered target. Analysis of results of geophysical studies in the western and eastern DS shores, comparison of geological conditions in shores, and sinkhole development, enabled us to conclude with a high probability that salt layers exist in both shores and sinkhole development is determined here by similar mechanisms.

Abstract: Quantifying groundwater storage in weathered/fractured basement rock aquifers can be challenging owing to both their high degree of heterogeneity and their overall low storage capacity. Therefore, in these aquifers, the use of direct borehole hydraulic data is usually insufficient. Here we assessed the popular method of electrical resistivity tomography (ERT), combined with borehole data and including associated uncertainties, to resolve the spatial variability of groundwater storage properties at high resolution within a fractured mica schist aquifer in Ireland. Porosity distributions across both the saturated and unsaturated zones were calculated from two-dimensional (2D) ERT resistivities using two standard petrophysical models, Archie and Waxman & Smits (WS), the latter accounting for the influence of clay minerals on resistivity data. Our results demonstrated the importance of the hydrogeological conceptual constraints provided by ERT when parametrizing the 2D petrophysical models from borehole point data. They also confirmed the importance of accounting for clay minerals (the products of bedrock weathering processes) in the WS model, whereas predictions from Archie's model produced unrealistically high porosity values of over an order of magnitude higher than the WS model. The WS model predicted porosities decreasing exponentially with depth, with values ranging from a few % in the shallowest, most-weathered part of the bedrock (upper 5 m on average) and deep fractured zones (to about 20 m deep), to <1% in the underlying fissured aquifer, and possibly down another order of magnitude in the deep massive bedrock. WS-derived porosities were in agreement with independent vertical water content profiles derived from magnetic resonance sounding (MRS), as well as point storativity values estimated from borehole hydraulic testing at the study site, with particularly good matches in the upper weathered/fractured bedrock and deeply weathered/fractured zones associated with regional faults. Detailed comparison suggested that WS provides an upper-bound estimate of groundwater storage in this environment. In the deep massive, un-weathered, and poorly fractured bedrock, however, discrepancies between groundwater storage estimate obtained from the three methods (ERT, MRS, and hydraulic) prevented reliable storage quantification, owing to the methods' inherent technical limitations in such low porosity rocks. Our results demonstrated the suitability of resistivity tomography to quantify groundwater storage heterogeneity in weathered/fractured basement rock aquifers at high resolution and with reasonable overall uncertainty given the relative high uncertainties in petrophysical parameters at the kilometric scale. The results are promising for better characterization of groundwater storage variations in these hydrogeological systems, which are crucial to predict their response to climate variability and human exploitation.

Abstract: Microbial spatial distribution has mostly been studied at field to global scales (i.e., ecosystem scales). However, the spatial organization at small scales (i.e., centimeter to millimeter scales), which can help improve our understanding of the impacts of spatial communities structure on microbial functioning, has received comparatively little attention. Previous work has shown that small-scale spatial structure exists in soil microbial communities, but these studies have not compared soils from geographically distant locations, nor have they utilized community ecology approaches, such as the core and satellite hypothesis and/or abundance-occupancy relationships, often used in macro-ecology, to improve the description of the spatial organization of communities. In the present work, we focused on bacterial diversity (i.e., 16S rRNA gene sequencing) occurring in micro-samples from a variety of locations with different pedo-climatic histories (i.e., from semi-arid, alpine, and temperate climates) and physicochemical properties. The forms of ecological spatial relationships in bacterial communities (i.e., occupancy-frequency and abundance-occupancy) and taxa distributions (i.e., habitat generalists and specialists) were investigated. The results showed that bacterial composition differed in the four soils at the small scale. Moreover, one soil presented a satellite mode distribution, whereas the three others presented bimodal distributions. Interestingly, numerous core taxa were present in the four soils among which 8 OTUs were common to the four sites. These results confirm that analyses of the small-scale spatial distribution are necessary to understand consequent functional processes taking place in soils, affecting thus ecosystem functioning.

Abstract: Clogging constitutes a major operational issue for treatment wetlands. The rest period is a key feature of French Vertical Flow (VF) treatment wetlands and serves to mitigate clogging. An ex-situ drying experiment was performed to mimic the rest period and record structural changes in the porous media using X-ray Computed Tomography (CT). Samples containing the deposit and gravel layers of a first stage French VF treatment wetland were extracted and left to dry in a control environment. Based on CT scans, three phases were identified (voids, biosolids, and gravels). The impact of the rest period was assessed by means of different pore-scale variables. Ultimately, the volume of biosolids had reduced to 58% of its initial value, the deposit layer thickness dropped to 68% of its initial value, and the void/biosolid specific surface area ratio increased from a minimum value of 1.1 to a maximum of 4.2. Cracks greater than 3 mm developed at the uppermost part of the deposit layer, while, in the gravel layer, the rise in void volume corresponds to pores smaller than 2 mm in diameter. Lastly, the air-filled microporosity is estimated to have increased by 0.11 v/v.

Abstract: While the finest fraction of suspension has long been considered to have limited interactions with the river bed, several recent studies based on flume and field observations raise questions about this hypothesis which is fundamental for suspended load modeling and river management. In this study, we report a large field campaign in which we quantify the river bed stocks of fine particles in 7 contrasted Alpine catchments. Using a simple protocol, we performed more than 300 riverbed measurements of the local surface and subsurface stocks. Results indicate that even when the river bed surface contains no fine particles, significant quantities can be found in the subsurface layer which is in most cases the layer having the higher stocks. We also observed that stocks highly depend on the facies considered suggesting that storage processes are strongly driven by the local hydraulics and river bed characteristics. By integrating these local stocks at the catchment scale, we estimated that they could represent more than 50% of the mean annual suspended load in catchments having large alluvial braided sections. On the opposite, these stocks could be as small as 1% in highly eroded head water catchments. This suggests that the bed of large alluvial Alpine rivers can be considered as a significant source of fine particles. These observations were confirmed by using a simplified vertical scouring model to estimate conditions for these stocks to be released in the flow. However, the use of this model suggests that other bed reworking processes (channel widening and migration) have to be considered. Finally, these observations suggest that interactions between particles transported as suspension and gravel beds are far from being negligible processes in catchments having large alluvial sections typically found in Alpine environments.

Abstract: X-ray micro-computed tomography (mu CT) can produce realistic 3D-images of the pore structure of a material. Extracting its geometry enables the computation of effective properties of the material-such as the permeability (k) and the hydrodynamic dispersion coefficient (D-h)-, through the solutions of the Stokes equation (SE) and Advection-Diffusion equation (ADE), respectively. In this study, the effect of the image resolution on these properties is discussed. For such purpose, four different resolutions are evaluated for both a real sample of Fontainebleau sand and a numerically generated sample created by degrading the Fontainebleau image with highest resolution. The SE was computed using the commercial software GeoDict. To solve the ADE, a Finite Volume software was developed which includes a high order total variation diminishing scheme for advection. The analysis of dispersion was based on numerical breakthrough curves. Our model was tested in a large range of Peclet numbers (Pe) and travel distances, accurately describing the transition between diffusion and advection dominated regimes of dispersion. The D-h exhibits a linear increase with travel distance for Pe > 10. This classical effect increases with increasing Pe. The percentage change on k and D-h increases with decreasing resolution in agreement with the corresponding behavior of porosity, specific surface and pore size distributions. The images directly scaled with the μCT showed more discrepancy than the numerically scaled images. The criteria to estimate the quality of permeability from the pore size distribution proposed on our previous study remains valid. The D-h is less sensitive to resolution than k.

Abstract: Tracing the origin of sediment is needed to improve our knowledge of hydro-sedimentary dynamics at the catchment scale. Several fingerprinting approaches have been developed to provide this crucial information. In particular, spectroscopy provides a rapid, inexpensive and non-destructive alternative technique to the conventional analysis of the geochemical properties. Here, we investigated the performance of four multi-proxy approaches based on (1) colour parameters, (2) geochemical properties, (3) colour parameters coupled with geochemical properties and (4) the entire visible spectrum to discriminate sediment source contributions in a mining catchment of New Caledonia. This French archipelago located in the south-west Pacific Ocean is the world's sixth largest producer of nickel. Open-cast nickel mining increases soil degradation and the downstream transfer of sediments in river systems, leading to the river system siltation. The sediment sources considered in the current research were therefore sediment eroded from mining sub-catchments and non-mining sub-catchments. To this end, sediment deposited during two cyclonic events (i.e. 2015 and 2017) was collected following a tributary design approach in one of the first areas exploited for nickel mining on the archipelago, the Thio River catchment (397 km(2)). Source (n = 24) and river sediment (n = 19) samples were analysed by X-ray fluorescence and spectroscopy in the visible spectra (i.e. 365-735 nm). The results demonstrated that the individual sediment tracing methods based on spectroscopy measurements (i.e. (1) and (4)) were not able to discriminate sources. In contrast, the geochemical approach (2) did discriminate sources, with 83.1% of variance in sources explained. However, it is the inclusion of colour properties in addition to geochemical parameters (3) which provides the strongest discrimination between sources, with 92.6% of source variance explained. For each of these approaches ((2) and (3)), the associated fingerprinting properties were used in an optimized mixing model. The predictive performance of the models was validated through tests with artificial mixture samples, i.e. where the proportions of the sources were known beforehand. Although with a slightly lower discrimination potential, the “geochemistry” model (2) provided similar predictions of sediment contributions to those obtained with the coupled “colour + geochemistry” model (3). Indeed, the geochemistry model (2) showed that mining tributary contributions dominated the sediments inputs, with a mean contribution of 68 +/- 25% for the 2015 flood event, whereas the colour + geochemistry model (3) estimated that the mining tributaries contributed 65 +/- 27 %. In a similar way, the contributions of mining tributaries were evaluated to 83 +/- 8% by the geochemistry model (2) versus 88 +/- 8% by the colour C geochemistry model (3) for the 2017 flood event. Therefore, the use of these approaches based on geochemical properties only (2) or of those coupled to colour parameters (3) was shown to improve source discrimination and to reduce uncertainties associated with sediment source apportionment. These techniques could be extended to other mining catchments of New Caledonia but also to other similar nickel mining areas around the world.

Abstract: We present a dataset on to the Arc-Isere long-term environmental research observatory, which is part of the Rhone Basin Long Term Environmental Research Observatory. This alpine catchment located in the French Alps is characterized by high Suspended Particulate Matter (SPM) in anthropogenized valleys. Suspended Sediment Concentrations (SSC) naturally observed in the river are very high, ranging from a few tens of milligrams per litre at low flow to tens of grams per litre during major natural hydrological events (floods, debris flows) or river dam hydraulic flushes. One research objective related to this site is to better understanding the SSC dynamics along the river using a system of nested catchments (Arvan, Arc, and Isere) in order to assess both temporal and spatial dynamics. The data allow the quantification of fine sediment yields and also the evaluation of possible morphological changes due to fine sediment deposition or resuspension. Additionally, the observatory database support studies on contaminants (either dissolved or particulate contaminants). Our monitoring includes six stations with high frequency (2-30 min) streamflow, SSC measurement using turbidity sensors, and associated automatic sampling. Discharge is measured via water level measurements and a rating curve. The oldest station (Grenoble-campus) started recording discharge and concentration data from April 2006 while others stations were built between 2009 and 2011. Data are available in an online data website called 'Base de Donnees des Observatoires en Hydrologie' (Hydrological observatory database, ) with a DOI reference for the dataset. The hydrological and sediment transport time series are stored, managed and made available to a wide community with unfettered access in order to be used at their full extent. This database is used as a data exchange tool for both scientists and operational end-users and there is an associated online tool to compute integrated fluxes.

Abstract: Soil erosion and suspended sediment transport understanding is an important issue in terms of soil and water resources management in the critical zone. In mesoscale watersheds (> 10 km(2)) the spatial distribution of potential sediment sources within the catchment associated with rainfall dynamics is considered to be the main factor in the observed suspended sediment flux variability within and between runoff events. Given the high spatial heterogeneity that can exist for such scales of interest, distributed physically based models of soil erosion and sediment transport are powerful tools to distinguish the specific effect of structural and functional connectivity on suspended sediment flux dynamics. As the spatial discretization of a model and its parameterization can crucially influence how the structural connectivity of the catchment is represented in the model, this study analyzed the impact of modeling choices in terms of the contributing drainage area (CDA) threshold to define the river network and of Manning's roughness parameter (n) on the sediment flux variability at the outlet of two geomorphologically distinct watersheds. While the modeled liquid and solid discharges were found to be sensitive to these choices, the patterns of the modeled source contributions remained relatively similar when the CDA threshold was restricted to the range of 15 to 50 ha, with n restricted to the range 0.4-0.8 on the hill-slopes and to 0.025-0.075 in the river. The comparison of the two catchments showed that the actual location of sediment sources was more important than the choices made during discretization and parameterization of the model. Among the various structural connectivity indicators used to describe the geological sources, the mean distance to the stream was the most relevant proxy for the temporal characteristics of the modeled sedigraphs.

Abstract: Fine sediment dynamics downstream dams is a key issue when dealing with environmental impact of hydraulic flushing. This paper presents an analysis of six field campaigns carried out during dam flushing events (in June 2006, 2007, 2009, 2010, 2011, and 2012) in the Arc- Isere river system in the Northern French Alps. Suspended sediment concentrations (SSC) and discharges were evaluated using direct measurements or/and 1D hydraulic modelling at up to 14 locations along the 120 kilometres-long river channel. The total suspended sediment flux (SSF) is analysed along the Arc and Isere rivers for each Arc dam flushing event. Uncertainties were quantified based on a propagation method of both measurement and modelling errors. The resulting confidence interval provides elements of discussion on the significance of the sediment mass balance between two consecutive measurement sites. Whereas the discharge time-series of each flushing event is roughly the same, the quantity of fine sediments removed from the reservoirs varied from 10,000 tons in 2007 to 40,000 tons in 2006. Also, a significant erosion is observed in the river system for some events (20,000 tons in 2007) while the SSF barely varied for other events (in 2009 and 2011). This detailed data set allows to identify specific locations in the river network where deposition or erosion occurred. This dynamics is closely related to both the hydrology in the upper Isere River and the morphology of the Arc and Isere rivers, which have been affected by the 2008 and 2010 floods.

Abstract: The increasing demand for water and irrigation in the semi-arid Bolivian Altiplano requires a better knowledge of the available resources, particularly groundwater. The aim of this study is to provide a first insight into the hydrogeological structure (0-200 m deep) and groundwater dynamics of the Katari-Lago Menor Basin aquifer located between the Eastern Cordillera and Lake Titicaca, Bolivia. This aquifer is studied using geophysical data (a total of 187 Time Domain Electromagnetic (TDEM) soundings), piezometric data (97 groundwater level measurements) and geochemical data (52 groundwater samples), combined with geological, lithological and topographical information. The results allowed identifying stratigraphic models consistent with the Quaternary sediments being hydraulically connected and behaving as a single regional basin-aquifer. This basin-aquifer is delimited by the most ancient lake invasions towards the southern, western and northern sides and by the lower limit of rock glaciers towards the eastern side. A large portion of the aquifer presents an unconfined behaviour varying from 50 to 150 m while the confined portion varies from 100 to 150 m. Groundwater flow within the Katari and Lago Menor Basin aquifer is composed of several interconnected groundwater flow systems. The main groundwater flow system starts in the high mountain ranges of the Eastern Cordillera, follows the topographic Piedmont gradient (NE to SW) and discharges in a series of wetlands. This multidisciplinary approach proved to be an appropriate method to derive a consistent picture of the hydrogeological functioning of the Katari-Lago Menor Basin aquifer.

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.

Abstract: The accurate simulation of wetting-drying processes in floodplains and coastal zones is a challenge for hydrodynamic modelling, especially for long time simulations. Indeed, dedicated numerical procedures are generally time-consuming, instabilities can occur at the wet/dry front, rapid transition of wet/dry interface and mass conservation are not always ensured. We present the extension of an existing wetting-drying algorithm in two space dimensions and its application to a real case. The wetting-drying algorithm is implemented in Second-generation Louvain-la-Neuve Ice-ocean Model (), a discontinuous Galerkin finite element model solving the shallow water equations in a fully implicit way. This algorithm consists in applying a threshold value of fluid depth for a thin layer and a blending parameter in order to guarantee positive values of the water depth, while preserving local mass conservation and the well balanced property at wet/dry interfaces. The technique is first validated against standard analytical test cases (Balzano 1, Balzano 3 and Thacker test cases) and is subsquently applied in a realistic domain, the Tonle Sap Lake in the Mekong River Basin, where the water level can vary by about 10 m between the dry and the wet season.

Abstract: Spatial patterns, cluster or dispersion trends are statistically different from random patterns of trace elements (TEs), which are essential to recognize, e.g., how they are distributed and change their behavior in different environmental processes and/or in the polluted/contaminated areas caused by urban and industrial pollutant located in upstream basins and/or by different natural geological conditions. The present study focused on a statistical approach to obtain the spatial variability of TEs (As, B and Sb) in shallow groundwater (GW) in a high-altitude arid region (Lower Katari Basin, Bolivian Altiplano), using multivariate analysis (PCA and HCA), geochemical modeling (PHREEQC, MINTEQ) and spatial analyses (Moran's 1 and LISA), considering the community supply wells. The results indicate that despite of the outliers there is a good autocorrelation in all cases, since Moran's I values are positive. The global spatial dependence analysis indicated a positive and statistically significant spatial autocorrelation (SA) for all cases and TEs are not randomly distributed at 99% confidence level. The results of hydrochemical modeling suggested the precipitation and stability of Fe (III) phases such as goethite. The re-adsorption of As and Sb on the mineral surface in the aquifer could be limiting the concentrations of both metalloids in southern regions. Spatial autocorrelation was positive (High-High) in northwestern (arsenic), southeastern (boron) and northeastern (antimony) region. The results reflected that the As and Sb are the main pollutants linked to the natural geological conditions, but B is a main pollutant due to the anthropogenic activities. Furthermore, >50% shallow groundwater exceeded the WHO limit and NB-512 guideline values for Sb (87%), B (56%) and As (50%); therefore the spatial distribution and concentrations of these TEs in GW raise a significant concern about drinking water quality in the study area. (C) 2020 Elsevier B.V. All rights reserved.

Abstract: Understanding karst unsaturated zone (UZ) recharge dynamics is crucial for achieving sustainable management of karst hydrosystems. In this paper, we provide the first report of the application of surface nuclear magnetic resonance (SNMR) monitoring of a karst UZ during a typical Mediterranean rain event. This 79 days' SNMR monitoring is a part of a more than 2 years of SNMR monitoring at the Low Noise Underground Laboratory (LSBB) experimental site located within the Fontaine de Vaucluse karst hydrosystem (southeastern France). We present eight SNMR soundings conducted before and after the rain event that accumulated 168 mm in 5 days. The obtained results demonstrate the applicability and the efficiency of SNMR for investigating infiltration dynamics in karst UZs at the time scale of a few days. We present the SNMR amplitudes that highlight strong signal variations related to water dynamics in the karst UZ. Infiltrated water cause increased SNMR signal during 5 days after the rain event. A significant draining process of the medium starts 15 days after the main event. Finally, after 42 days, the SNMR signal returns close to the initial state.

Abstract: Understanding the interactions between bedload transport and morpholdynamics in braided streams has important applications in river management and restoration. Direct field measurements addressing this question are however scarce as they are often challenging to perform. Here, we report an extensive two-month field campaign in an Alpine braided reach (La Severaisse river, French Alps) that experienced predictable daily peak discharge (48 events observed) generating significant bedload transport and morphological changes during the melting season. We monitored these processes using a wide range of direct and indirect techniques (bedload sampling, continuous seismic measurements, pebbles tracking, topographic surveys, remote sensing using ground control cameras and drone flights). Doing so, surrogate measurements allowed to extend temporally discrete manual bedload sampling, and to extend spatially local riverbed cross section measurements. These measurements provide unique complementary constraints on the targeted physics, at various spatial and temporal scales which enabled us to draw robust conclusions. Data showed a progressive decrease in bedload transport for a given flow rate along the two months period. Simultaneously, river morphology in the braided sections changed from an incised to a more distributed configuration which led to a decrease of local maxima in dimensionless shear stresses in the braided reach for similar flow conditions. This control of bedload transport by maximum local shear stresses was in line with tracked pebble surveys indicating that coarse bedload particles were mostly transported in the main active channel. At the reach scale, this transport was found to be more efficient in laterally confined sections than in braided ones which has important implications in terms of bedload estimation in alternative confined and braided (unconfined) rivers. Finally, this study highlight the interest to combine a large variety of traditional and innovative measurements techniques to better understand complex sediment transport processes in the field. (C) 2019 Elsevier B.V. All rights reserved.

Abstract: Sedimentological and geochemical data were obtained for bed sediments from a tropical estuary environment in Vietnam in October 2014, January 2016, and November 2016. The data include grain-size distribution, percentage of clay, silt and sand, percentage of organic matter, concentration of total particulate phosphorus (TPP), concentration of particulate inorganic phosphorus (PIP), concentration of particulate organic phosphorus (POP), percentage of total nitrogen (TN), percentage of total carbon (TC), trace metals concentrations (V, Cr, Co, Ni, Cu, Zn, As, Mo, Cd, Pb) and major elements (Al, Fe, Mn). Geochemical indexes (Enrichment factor EF and Geo-accumulation Index I-geo) and sediment quality guideline (mean Effect Range Median quotients) were calculated. (C) 2020 The Author(s). Published by Elsevier Inc.

Abstract: On the basis of Gram-negative bacterium Escherichia coli models previously published in the literature, the transmembrane voltage induced by the application of an alternating current (AC) electric field on a bacterial suspension is calculated using COMSOL Multiphysics software, in the range 1-20 MHz, for longitudinal and transverse field orientations. The voltages developed on each of the three layers of the cell wall are then calculated using an electrical equivalent circuit. This study shows that the overall voltage on the cell wall, whose order of magnitude is a few tens of μV, is mainly distributed on inner and outer layers, while a near-zero voltage is found on the periplasm, due to its much higher electrical conductivity compared with the other layers. Although the outer membrane electrical conductivity taken in the model is a thousand times higher than that of the inner membrane, the voltage there is about half of that on the inner membrane, due to capacitive effects. It follows that the expression of protein complexes anchored in the inner membrane could potentially be disrupted, inducing in particular a possible perturbation of biological processes related to cellular respiration and proton cycle, and leading to growth inhibition as a consequence. Protein complexes anchored in the outer membrane or constituting a bridge between the three layers of the cell wall, such as some porins, may also undergo the same action, which would add another growth inhibition factor, as a result of deficiency in porin filtration function when the external environment contains biocides. Bioelectromagnetics. 2020;41:279-288 (c) 2020 Bioelectromagnetics Society.

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.

Abstract: Sulfamethoxazole (SMX) is one of the antibiotics most commonly detected in aquatic and terrestrial environments and is still widely used, especially in low income countries. SMX is assumed to be highly mobile in soils due to its intrinsic molecular properties. Ten soils with contrasting properties and representative of the catchment soil types and land uses were collected throughout the watershed, which undergoes very rapid urban development. SMX displacement experiments were carried out in repacked columns of the 10 soils to explore SMX reactive transfer (mobility and reactivity) in order to assess the contamination risk of water resources in the context of the Bolivian Altiplano. Relevant sorption processes were identified by modelling (HYDRUS-1D) considering different sorption concepts. SMX mobility was best simulated when considering irreversible sorption as well as instantaneous and rate-limited reversible sorption, depending on the soil type. SMX mobility appeared lower in soils located upstream of the watershed (organic and acidic soils – Regosol) in relation with a higher adsorption capacity compared to the soils located downstream (lower organic carbon content – Cambisol). By combining soil column experiments and soil profiles description, this study suggests that SMX can be classified as a moderately to highly mobile compound in the studied watershed, depending principally on soil properties such as pH and OC. Potential risks of surface and groundwater pollution by SMX were thus identified in the lower part of the studied catchment, threatening Lake Titicaca water quality.

Abstract: A wide range of persistent organic chemicals, including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), some insecticides, as well as polybrominated diphenyl ethers (PBDEs) and some perfluoroalkyl substances (PFASs) were analyzed in 17 bed sediments collected along the Saigon River and at adjacent canal mouths from upstream to downstream in Ho Chi Minh City (Vietnam). Concentrations were rather low for PAHs, as well as for legacy PCBs and dichloro-diphenyl-trichlorethane and metabolites (DDTs), or below detection limits for several PFASs and all PBDEs measured. Several insecticides (chlorpyrifos-ethyl, and the pyrethroids cypermethrin and lambda-cyhalothrin) displayed rather high concentrations at a few sites within the city. There was no distinct upstream – downstream trend for PAHs, (DDTs) or PCBs. Although adjacent canal sediments tended to be more contaminated than Saigon River sediments, the differences were not significant. Emissions are almost certainly substantial for PAHs, and probably also for other contaminants such as PBDEs and some PFASs. During the dry season, contaminants are presumably stored in the city, either in canals or on urban surfaces. Heavy rainfall during the monsoon period carries away contaminated particle flows into the canals and then the Saigon River. The strong tidal influence in the river channel hinders the accumulation of contaminated particles. Contaminated deposits should accordingly be investigated further downstream in depositional environments, such as the mangrove. (C) 2018 Elsevier Ltd. All rights reserved.

Abstract: The question of the rampant erosion of the shorelines rimming the Mekong River delta has assumed increasing importance over the last few years. Among issues pertinent to this question is how it is related to mangroves. Using high-resolution satellite images, we compared the width of the mangrove belt fringing the shoreline in 2012 to shoreline change (advance, retreat) between 2003 and 2012 for 3687 cross-shore transects, spaced 100 m apart, and thus covering nearly 370 km of delta shoreline bearing mangroves. The results show no significant relationships. We infer from this that, once erosion sets in following sustained deficient mud supply to the coast, the rate of shoreline change is independent of the width of the mangrove belt. Numerous studies have shown that: (1) mangroves promote coastal accretion where fine-grained sediment supply is adequate, (2) a large and healthy belt of fringing mangroves can efficiently protect a shoreline by inducing more efficient dissipation of wave energy than a narrower fringe, and (3) mangrove removal contributes to the aggravation of ongoing shoreline erosion. We fully concur, but draw attention to the fact that mangroves cannot accomplish their land-building and coastal protection roles under conditions of a failing sediment supply and prevailing erosion. Ignoring these overarching conditions implies that high expectations from mangroves in protecting and/or stabilizing the Mekong delta shoreline, and eroding shorelines elsewhere, will meet with disappointment. Among these false expectations are: (1) a large and healthy mangrove fringe is sufficient to stabilize the (eroding) shoreline, (2) a reduction in the width of a large mangrove fringe to the benefit of other activities, such as shrimp-farming, is not deleterious to the shoreline position, and (3) the effects of human-induced reductions in sediment supply to the coast can be offset by a large belt of fringing mangroves.

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.

Abstract: Volcanic soils are important resources because of their unique mineralogical and physical characteristics, and allophanic Andosols represent some of the world's most fertile soils. However, their unique properties can be lost when cultivated. Most soils in the Central Valley, Mexico, are derived from volcanic materials. This valley encompasses one of the largest water supply systems in the world by volume, but is affected by soil degradation and deforestation. Sustainably managing volcanic soils requires understanding how land use affects their hydrodynamic properties. Gas adsorption and mercury intrusion porosimetry, water retention curves, tension infiltrometry and X-ray tomography were used to describe pore structure characteristics. Two volcanic soils (one Andosol and one derived from indurated tuff – Tepetates), three land uses (maize monoculture, maize-wheat rotation and fallow) and two horizons (Ap and A2 for maize monoculture and maize-wheat rotation) were studied. Tillage affected topsoil by increasing the sand fraction by 38% and decreasing total porosity and macroporosity by 23% and 40% respectively. Macropore size was reduced and the number of isolated macropores was higher in the tilled layer under maize, compared with untilled subsoil. The plot under maize-wheat rotation had lower allophane content, and saturated hydraulic conductivity was reduced by nearly an order of magnitude and water retention by half, compared with maize and fallow plots. Compared with Andosols, Tepetates showed differences in mineralogical composition with lower contents of amorphous compounds and in its porous network characteristics with twice the total and percolating macroporosity compared with the maize plot. Its high content of organic carbon (3.5%) seemed beneficial for its hydrodynamic properties. Sustainable agricultural management of these volcanic soils requires reducing mechanised tillage, avoiding periods when soil is bare, not applying maize-wheat rotation and applying maize-fallow rotation allowing natural vegetation growth.

Abstract: The Lower Mekong Delta Coastal Zone (LMDCZ) is emblematic of the coastal erosion problem facing many tropical deltas. Over the last 3500 years, large river sediment fluxes expanded the delta seaward, and waves and currents formed the Ca Mau Peninsula to the southwest. Since the middle of the 20th century, the LMDCZ is affected by various human activities that include reduction of river fluxes due to damming and sand mining, land subsidence due to groundwater extraction, and reduction of protective coastal mangroves in favor of agriculture and aquaculture. Coastal erosion is observed along many sections of the delta, with a rate of up to 50 m per year in some areas. However, the role of human activities remains difficult to assess because of its complexity. The present modeling study is designed to sort out the contribution of natural hydrodynamic redistribution of sediments from man-induced erosion. The modeling system used is based on CROCO, forced by global reanalyses at the boundaries and at the surface, including wave statistics (required by the sediment transport model). Tides and realistic river forcing are also included. Calibration and validation relies on a combination of in situ and remotely-sensed observations, and laboratory experiments. Once validated, coastal dynamics are investigated by performing sensitivity experiments for both the hydro- and sediment dynamics. The results suggest that while wind is the main factor driving the coastal currents, the sediment dynamics is essentially the result of re-suspension due to wave-induced bed shear stress. The suspended sediments are then redistributed by coastal currents that are not limited to the nearshore zone. Strong seasonality of the process is observed with the northeast winter monsoon being the season of strongest re-suspension and sediment redistribution. The annual sediment budget is characterized by important local disequilibrium, with alongshore patterns that are in agreement with the observed shoreline evolution. The effect of a decrease in river sediment supply is difficult to evaluate because the estuarine zone is still in accretion, apart from the particular case of Go Cong shores. Far from the estuarine zone, subsidence is an additional strong candidate to explain erosion in areas that should naturally be accreting. Synthesizing these results, the study proposes a first attempt at a “taxonomy and geography” of processes along the coastal Mekong delta that can explain the recent observations of shoreline changes and help design protection measures.

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.

Abstract: The transport of suspended sediment is associated with important social, economic, and environmental issues. It is still unclear, however, how suspended sediments eroded on hillslopes are transferred downstream through the river system. In this study, we aimed to investigate this process by applying a sediment budget approach to a typical 3.5-km-long Alpine braided reach. Using high-frequency suspended load measurements combined with Monte Carlo simulations for uncertainty propagation, we observed a significant buffering behavior of the reach studied. Thirty-two of the 48 events observed during the 2-month campaign showed significant differences between upstream and downstream mass transported as suspension, despite the reach studied was short compared to the upstream drainage area (130 km(2)). These differences at the event scale varied widely within an envelope comprised between a net erosion equivalent to 74% of upstream suspended mass and a net deposition equivalent to 71%. Budgets were found to be controlled at a nearly instantaneous time scale by the liquid discharges and the suspended sediment concentrations in an opposite way: for low upstream concentrations, net erosion increased when the discharges increased, while above a certain concentration, net deposition increased when the concentrations increased. Moreover, coarse particles mobility in the reach (characterized via bedload transport measurements) appeared to have a strong influence on the availability of suspended particles as both quantities evolved concomitantly through time. These observations have important implications for our understanding and modeling of the transfer of suspended particles in gravel bedded streams.

Abstract: Sustainable horticulture depends on the integrity of soil functions, which directly depend on soil architecture affecting aggregation, root growth, as well as liquid and gas permeability. We hypothesised that changes in soil architecture resulting from feedback mechanisms between management, soil organic carbon contents (SOC), biota and vegetation can be captured with X-ray computed tomography (CT), and that these affect the soil filtering function, which thus, can be manipulated through orchard management. We compared the transport of copper, a widely used fungicide, through intact soil cores from vine rows of kiwifruit orchards under organic and integrated management. We first derived 3D-macropore characteristics from CT-images, followed by leaching a pulse of copper and a tracer through the same cores. The organic orchard soil had a significantly higher SOC content than the integrated orchard soil, and this was positively correlated with total porosity. Macropores (>92 μm) were larger with a higher connectivity, but significantly fewer in the organic than the integrated orchard soil. This resulted in a lower macroporosity and a better copper filtering capacity of the organic than the integrated orchard soil. Copper distribution was reasonably predicted when combining SOC contents, pH and macropore characteristics. Significant relationships between soil parameters and indicators of the strength of preferential flow verified that CT-derived macropore characteristics can be used to predict functional solute transport parameters. The relevance of our results and relationships observed between macropore characteristics, functional indicators of preferential flow and the fate of copper needs verification with samples representing more soils and sites.

Abstract: The Saigon River flows through one of the most rapidly growing megacities of Southeast Asia, Ho Chi Minh City (HCMC, > 8.4 million inhabitants). This tidal river is characterized by a tropical monsoon climate, alternating a wet and a dry season. In the last few decades, increased economic and urban developments of HCMC have led to harmful impacts on the water quality of this tidal river, with severe eutrophication events. This situation results from the conjunction of contrasting hydrological seasons and the lack of upgraded sanitation infrastructures: indeed, less than 10% of the domestic wastewater is collected and treated before being discharged directly into urban canals or rivers. This study focuses on P dynamics because this is considered the key nutrient factor controlling freshwater eutrophication. Based on field measurements and original laboratory experiments, we assessed the P levels in the river water and sediments, and investigated P adsorption/desorption capacity onto suspended sediment (SS) within the salinity gradient observed. Field surveys showed a clear impact of the HCMC megacity on the total P content in SS, which increased threefold at HCMC Center, as compared with the upstream values (0.3-0.8 gP kg(-1)). Downstream, in the mixed estuarine area, the Total P was lower than 0.5 gP kg(-1). Laboratory experiments were carried out to characterize the influence of SS concentrations (SS = [0.25-0.9] g L-1 ), salinity (S = [2.6-9.3]) and turbulence (G = [22-44] s(-1)) on the sorption capacity of P onto sediment. The size of sediment particles and their propensity to flocculate were also originally measured with a recently developed instrument: the System for the Characterization of Aggregates and Flocs (SCAF (R)). Under the experimental conditions considered, SS concentrations had the greatest effect on the adsorption of P onto sediment, e.g., P adsorption capacity increased when SS concentrations rose. In contrast, salinity and turbulence had a smaller effect on the adsorption properties of sediments. Among these observed variables, the SS concentration was shown to be the main driver for adsorption capacity of P onto SS within the salinity gradient. We discuss the implication of these findings on understanding P dynamics within a highly urbanized, tropical estuary.

Abstract: Fine particles or sediments are one of the important variables that should be considered for the proper management of water quality and aquatic ecosystems. In the present study, the effect of catchment characteristics on the performance of an already developed model for the estimation of fine sediments dynamics between the water column and sediment bed was tested, using 13 catchments distributed worldwide. The model was calibrated to determine two optimal model parameters. The first is the filtration parameter, which represents the filtration of fine sediments through pores of the stream bed during the recession period of a flood event. The second parameter is the bed erosion parameter that represents the active layer, directly related to the re-suspension of fine sediments during a flood event. A dependency of the filtration parameter with the catchment area was observed in catchments smaller than 100 km(2), whereas no particular relationship was observed for larger catchments (>100 km(2)). In contrast, the bed erosion parameter does not show a noticeable dependency with the area or other environmental characteristics. The model estimated the mass of fine sediments released from the sediment bed to the water column during flood events in the 13 catchments within 23% bias.

Abstract: The aim of this study is to investigate the behavior of a footing lying directly upon a rigid inclusion-reinforced soft soil. Both experimental and numerical approaches were conducted. The studied cases include single rigid inclusion tests, a footing over nonrigid inclusion-reinforced soil, and a footing over rigid inclusion-reinforced soil. The vertical loading tests on single rigid inclusions and the footing over unreinforced soil showed the behavior of the multi-layered soil, thus allowing for the determination of soil parameters for the numerical analyses. The tests on the footing over reinforced soil were, furthermore, carried out with different loading cases (centered and eccentric vertical loads and horizontal loads). Special attention was paid to the influence of the complex loading cases on the footing over a reinforced soil system by the measurement of the inclusion head pressure, the vertical and lateral footing settlements, and the lateral inclusion displacements. The measured pressure on the inclusion seemed to increase linearly with the vertical loading on the footing. A good agreement between the numerical analysis results and measurement data has been found for the loading phases while underprediction appears for a few loading cycles, probably due to the simplified soil constitutive model adopted.

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.

Abstract: Latin America, like other areas in the world, is faced with the problem of high arsenic (As) background in surface and groundwater, with impacts on human health. We studied As biogeochemical cycling by periphyton in Lake Titicaca and the mine-impacted Lake Uru Uru. As concentration was measured in water, sediment, totora plants (Schoenoplectus californicus) and periphyton growing on stems, and As speciation was determined by X-ray absorption spectroscopy in bulk and EDTA-extracted periphyton. Dissolved arsenic was between 5.0 and 15 μg L-1 in Lake Titicaca and reached 78.5 μg L-1 in Lake Uru Uru. As accumulation in periphyton was highly variable. We report the highest As bioaccumulation factors ever measured (BAFs(periphyton) up to 245,000) in one zone of Lake Titicaca, with As present as As(V) and monomethyl-As (MMA(V)). Non-accumulating periphyton found in the other sites presented BAFsperiphyton between 1281 and 11,962, with As present as As(III), As(V) and arsenosugars. DNA analysis evidenced several taxa possibly related to this phenomenon. Further screening of bacterial and algal isolates would be necessary to identify the organism(s) responsible for As hyperaccumulation. Impacts on the ecosystem and human health appear limited, but such organisms or consortia would be of great interest for the treatment of As contaminated water.

Abstract: Mangrove sediments act as natural biogeochemical reactors, modifying metals partitioning after their deposition. The objectives of the present study were: to determine distribution and partitioning of metals (Fe, Mn, Ni, Cr, Cu, Co and As) in sediments and pore-waters of Can Gio Mangrove; and to assess their ecological risks based on Risk Assessment Code. Three cores were collected within a mudflat, beneath Avicennia alba and Rhizophora apiculata stands. We suggest that most metals had a natural origin, being deposited in the mangrove mainly as oxyhydroxides derived from the upstream lateritic soils. This hypothesis could be supported by the high proportion of metals in the residual fraction (mean values (%): 71.9, 30.7, 80.7, 80.9, 67.9, 53.4 and 66.5 for Fe, Mn, Ni, Cr, Cu, Co, and As respectively, in the mudflat). The enrichment of mangrove-derived organic matter from the mudflat to the Rhizophora stand (i.e. up to 4.6% of TOC) played a key role in controlling metals partitioning. We suggest that dissolution of Fe and Mn oxyhydroxides in reducing condition during decomposition of organic matter may be a major source of dissolved metals in pore-waters. Only Mn exhibited a potential high risk to the ecosystem. Most metals stocks in the sediments were higher in the Avicennia stand than the Rhizophora stand, possibly because of enhanced dissolution of metal bearing phases beneath later one. In a context of enhanced mangrove forests destruction, this study provides insights on the effects of perturbation and oxidation of sediments on metal release to the environment. (C) 2018 Elsevier Ltd. All rights reserved.

Abstract: Green turtles spend a large part of their lifecycle foraging in nearshore seagrass habitats, which are often in close proximity to sources of anthropogenic contaminants. As most biomonitoring studies focus on a limited number of targeted chemical groups, this study was designed to screen for a wider range of hazardous chemicals that may not have been considered in prior studies. Whole blood of sub-adult green turtles (Chelonia mydas) were sampled from three different locations, a remote, offshore 'control' site; and two coastal 'case' sites influenced by urban and agricultural activities on the Great Barrier Reef in North Queensland, Australia. In order to screen blood samples for chemicals across a wide range of K-OW's, a modified QuEChER's extraction method was used. The samples were analysed using a multi-residue gas chromatography with tandem mass spectrometry system (GC-MS/MS method that allowed simultaneous quantification of polychlorinated biphenyls (PCBs), polychlorinated diphenyl ethers (PBDES), organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs). While PBDEs, PCBs and OCPS were below the limits of quantification, PAHs were detected in all turtle blood samples. However, PAH levels were relatively low(maximum Sigma PAH = 13 ng/mL ww) and comparable to or less than those reported from other green turtles globally. The present study provides the first baseline PAH levels in blood samples from green turtles from nearshore and offshore locations in the Southern Hemisphere. (C) 2018 Elsevier B.V. All rights reserved.