2021 |
Archundia, D., Martins, J., Lehembre, F., Morel, M., & Duwig, C. (2021). Sulfamethoxazole biodegradation and impacts on soil microbial communities in a Bolivian arid high altitude catchment. Chemosphere, 284.
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Bahar, T., Oxarango, L., Castebrunet, H., Rossier, Y., & Mermillod-Blondin, F. (2021). 3D modelling of solute transport and mixing during managed aquifer recharge with an infiltration basin. Journal Of Contaminant Hydrology, 237.
Abstract: Artificial basins are used to recharge groundwater by many municipalities to improve the sustainability of storm water management. Despite its increasing operational implementation, artificial recharge still raises numerous questions related to its impact on groundwater quality. In this paper, a 3D numerical model of MAR basin/ aquifer system was implemented in order to simulate the fate of water and pollutants. It was used to illustrate the complex distribution in time and space of a tracer contaminant injected in the basin. The model was based on a well instrumented storm water infiltration basin located in Chassieu (Lyon area, France). The well-known Richards model was used to simulate the water flow in the saturated and unsaturated zone of the study site. The transfer of solutes in the basin/aquifer system was modelled by the advection-dispersion-equation (ADE). The model was calibrated during a rain event using hydraulic head and electric conductivity data from a set of piezometers located around the basin. The flow model was validated on a one month period of basin operation presenting several rain events. The model was then used to simulate the fate of a solute pollutant considered as a tracer during a high intensity rain event. This simplified test case illustrated the mechanism of capillary trapping in the vadose zone and the effect of sampling point location on concentration measurements. Three main results were obtained: (1) capillary trapping promoted a retention of up to 20% of the injected tracer in the vadose zone, (2) 0 to 24% of the injected solute concentration could be recovered depending on the piezometer location, (3) the averaged concentration decreased by 50% if the measuring device is lowered by 5 m under the water table. These results were strongly site and event dependant but observed trends should be considered while discussing punctual water quality measurements used to monitor MAR systems. It also allowed to suggest some guidelines for sampling point positioning.
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Braunig, J., Baduel, C., Barnes, C., & Mueller, J. (2021). Sorbent assisted immobilisation of perfluoroalkyl acids in soils & ndash; effect on leaching and bioavailability. Journal Of Hazardous Materials, 412.
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.
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Camenen, B., Gratiot, N., Cohard, J., Gard, F., Tran, V., Nguyen, A., et al. (2021). Monitoring discharge in a tidal river using water level observations: Application to the Saigon River, Vietnam. Science Of The Total Environment, 761.
Abstract: The hydrological dynamics of the Saigon River is ruled by a complex combination of factors, which need to be disentangled to prevent and limit risks of flooding and salt intrusion. In particular, the Saigon water discharge is highly influenced by tidal cycles with a relatively low net discharge. This study proposes a low-cost technique to estimate river discharge at high frequency (every 10 min in this study). It is based on a stage-fall-discharge (SFD) rating curve adapted from the general Manning Strickler law, and calibrated thanks to two ADCP campaigns. Two pressure sensors were placed at different locations of the river in September 2016: one at the centre of Ho Chi Minh City and one in Phu Cuong, 40 km upstream approximately. The instantaneous water discharge data were used to evaluate the net residual discharge and to highlight seasonal and inter-annual trends. Both water level and water discharge show a seasonal behaviour. Rainfall, including during the Usagi typhoon that hit the megalopolis in November 2018, has no clear and direct impact on water level and water discharge due to the delta flat morphology and complex response between main channel and side channel network and ground water in this estuarine system under tidal influence. However, we found some evidences of interactions between precipitation, groundwater, the river network and possibly coastal waters. This paper can be seen as a proof of concept to (1) present a low-cost discharge method that can be applied to other tidal rivers, and (2) demonstrate how the high-frequency discharge data obtained with this method can be used to evaluate discharge dynamics in tidal river systems. (C) 2020 Elsevier B.V. All rights reserved.
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Daher, H., Arbic, B., Williams, J., Ansong, J., Boggs, D., Muller, M., et al. (2021). Long-Term Earth-Moon Evolution With High-Level Orbit and Ocean Tide Models. Journal Of Geophysical Research-Planets, 126(12).
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.
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Du Roscoat, S., Ivankovic, T., Lenoir, N., Dekic, S., Martins, J., & Geindreau, C. (2021). First visualisation of bacterial biofilms in 3D porous media with neutron microtomography without contrast agent. Journal Of Microscopy, .
Abstract: Characterising bacterial biofilm growth in porous media is important for developing reliable numerical models of biofouling in industrial biofilters. One of the promising imaging methods to do that has been a recent successful application of X-ray microtomography. However, this technique requires a contrast agent (1-chloronaphtalene, for example) to distinguish biofilm from the liquid phase, which raises concern about biofilm disruption and impaired image interpretation. To overcome these drawbacks, we tested a new approach based on neutron tomography (NT), which does not need a contrast agent, by imaging two types of porous media (polytetrafluoroethylene – PTFE – and clay beads of various diameters) in glass or PTFE tubes in which bacterial biofilms were grown for 7 days and by comparing these images with the ones obtained with X-ray microtomography. NT images showed that the biofilm formed preferentially around the beads and at bead/bead interface. Visual comparison of both imaging techniques showed consistent biofilm spatial distributions and that the contrasting agent did not significantly disrupt the biofilm. NT images, on the other hand, were still too noisy to allow quantitative measurements. Therefore, X-ray microtomography (provided it uses non-disruptive contrast agents) seems to provide more reliable microstructural descriptors.
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Ezersky, M., Eppelbaum, L., Legchenko, A., Al-Zoubi, A., & Abueladas, A. (2021). Salt layer characteristics in the Ghor Al-Haditha area, Jordan: comprehensive combined reprocessing of geophysical data. Environmental Earth Sciences, 80(4).
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.
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Favez, O., Weber, S., Petit, J., Alleman, L., Albinet, A., Riffault, V., et al. (2021). Overview of the French Operational Network for In Situ Observation of PM Chemical Composition and Sources in Urban Environments (CARA Program). Atmosphere, 12(2).
Abstract: The CARA program has been running since 2008 by the French reference laboratory for air quality monitoring (LCSQA) and the regional monitoring networks, to gain better knowledge-at a national level-on particulate matter (PM) chemistry and its diverse origins in urban environments. It results in strong collaborations with international-level academic partners for state-of-the-art, straightforward, and robust results and methodologies within operational air quality stakeholders (and subsequently, decision makers). Here, we illustrate some of the main outputs obtained over the last decade, thanks to this program, regarding methodological aspects (both in terms of measurement techniques and data treatment procedures) as well as acquired knowledge on the predominant PM sources. Offline and online methods are used following well-suited quality assurance and quality control procedures, notably including inter-laboratory comparison exercises. Source apportionment studies are conducted using various receptor modeling approaches. Overall, the results presented herewith underline the major influences of residential wood burning (during the cold period) and road transport emissions (exhaust and non-exhaust ones, all throughout the year), as well as substantial contributions of mineral dust and primary biogenic particles (mostly during the warm period). Long-range transport phenomena, e.g., advection of secondary inorganic aerosols from the European continental sector and of Saharan dust into the French West Indies, are also discussed in this paper. Finally, we briefly address the use of stable isotope measurements (delta N-15) and of various organic molecular markers for a better understanding of the origins of ammonium and of the different organic aerosol fractions, respectively.
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Gonzalez, J., Comte, J., Legchenko, A., Ofterdinger, U., & Healy, D. (2021). Quantification of groundwater storage heterogeneity in weathered/fractured basement rock aquifers using electrical resistivity tomography: Sensitivity and uncertainty associated with petrophysical modelling. Journal Of Hydrology, 593.
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.
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Haalck, I., Loffler, P., Baduel, C., Wiberg, K., Ahrens, L., & Lai, F. (2021). Mining chemical information in Swedish wastewaters for simultaneous assessment of population consumption, treatment efficiency and environmental discharge of illicit drugs. Scientific Reports, 11(1).
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Hugoni, M., Nunan, N., Thioulouse, J., Dubost, A., Abrouk, D., Martins, J., et al. (2021). Small-Scale Variability in Bacterial Community Structure in Different Soil Types. Microbial Ecology, .
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.
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Legout, C., Freche, G., Biron, R., Esteves, M., Navratil, O., Nord, G., et al. (2021). A critical zone observatory dedicated to suspended sediment transport: The meso-scale Galabre catchment (southern French Alps). Hydrological Processes, 35(3).
Abstract: The 20 km(2) Galabre catchment belongs to the French network of critical zone observatories (OZCAR; Gaillardet et al., Vadose Zone Journal, 2018, 17(1), 1-24). It is representative of the sedimentary lithology and meteorological forcing found in Mediterranean and mountainous areas. Due to the presence of highly erodible and sloping badlands on various lithologies, the site was instrumented in 2007 to understand the dynamics of suspended sediments (SS) in such areas. Two meteorological stations including measurements of air temperature, wind speed and direction, air moisture, rainfall intensity, raindrop size and velocity distribution were installed both in the upper and lower part of the catchment. At the catchment outlet, a gauging station records the water level, temperature and turbidity (10 min time-step). Stream water samples are collected automatically to estimate SS concentration-turbidity relationships, allowing quantification of SS fluxes with known uncertainty. The sediment samples are further characterized by measuring their particle size distributions and by applying a low-cost sediment fingerprinting approach using spectrocolorimetric tracers. Thus, the contributions of badlands located on different lithologies to total SS flux are quantified at a high temporal resolution, providing the opportunity to better analyse the links between meteorological forcing variability and watershed hydrosedimentary response. The set of measurements was extended to the dissolved phase in 2017. Both stream water electrical conductivity and major ion concentrations are measured each week and every 3 h during storm events. This extension of measurements to the dissolved phase will allow progress in understanding both the origin of the water during the events and the partitioning between particulate and dissolved fluxes of solutes in the critical zone. All data sets are available at .
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Martinez-Carvajal, G., Oxarango, L., Adrien, J., Molle, P., & Forquet, N. (2021). Structural Changes in French VF Treatment Wetland Porous Media during the Rest Period: An Ex Situ Study Using X-ray Tomography. Water, 13(3).
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.
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Misset, C., Recking, A., Legout, C., Bakker, M., Gimbert, F., Geay, T., et al. (2021). Using Continuous Turbidity and Seismic Measurements to Unravel Sediment Provenance and Interaction Between Suspended and Bedload Transport in an Alpine Catchment. Geophysical Research Letters, 48(4).
Abstract: Fine sediment transport results from the complexity of the interactions between the different modes of transport and the variety of possible sediment sources, from the river bed stocks remobilization to hillslopes erosion. From a 2-year period in an Alpine catchment, we show how the combined use of continuous turbidity and seismic measurements can help to address these issues. In the studied catchment, the signals are more strongly correlated during the high flows of the snowmelt period than during the summer period when the river bed is stable and the hillslopes are no longer protected by a snow cover during storms. This sheds light on the seasonal control exerted by the river bed mobility and the snow cover on suspended sediment dynamics in mountainous catchments. It also questions the potential shift of this dynamics from river bed to hillslope dominated in a context of global warming.
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Misset, C., Recking, A., Legout, C., Viana-Bandeira, B., & Poirel, A. (2021). Assessment of fine sediment river bed stocks in seven Alpine catchments. Catena, 196.
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.
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Nakhle, P., Ribolzi, O., Boithias, L., Rattanavong, S., Auda, Y., Sayavong, S., et al. (2021). Effects of hydrological regime and land use on in-stream Escherichia coli concentration in the Mekong basin, Lao PDR. Scientific Reports, 11(1).
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Nguyen, A., Nemery, J., Gratiot, N., Garnier, J., Dao, T., Thieu, V., et al. (2021). Biogeochemical functioning of an urbanized tropical estuary: Implementing the generic C-GEM (reactive transport) model. Science Of The Total Environment, 784.
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Nguyen, T., Bui, X., Ngo, H., Nguyen, T., Nguyen, K., Nguyen, H., et al. (2021). Nutrient recovery and microalgae biomass production from urine by membrane photobioreactor at low biomass retention times. Science Of The Total Environment, 785.
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Ortega-Ramirez, M., & Oxarango, L. (2021). Effect of X-ray μCT Resolution on the Computation of Permeability and Dispersion Coefficient for Granular Soils. Transport In Porous Media, .
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.
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Samake, A., Martins, J., Bonin, A., Uzu, G., Taberlet, P., Conil, S., et al. (2021). Variability of the Atmospheric PM10 Microbiome in Three Climatic Regions of France. Frontiers In Microbiology, 11.
Abstract: Primary Biogenic Organic Aerosols (PBOA) were recently shown to be produced by only a few types of microorganisms, emitted by the surrounding vegetation in the case of a regionally homogeneous field site. This study presents the first comprehensive description of the structure and main sources of airborne microbial communities associated with temporal trends in Sugar Compounds (SC) concentrations of PM10 in 3 sites under a climatic gradient in France. By combining sugar chemistry and DNA Metabarcoding approaches, we intended to identify PM10-associated microbial communities and their main sources at three sampling-sites in France, under different climates, during the summer of 2018. This study accounted also for the interannual variability in summer airborne microbial community structure (bacteria and fungi only) associated with PM10-SC concentrations during a 2 consecutive years' survey at one site. Our results showed that temporal changes in PM10-SC in the three sites are associated with the abundance of only a few specific taxa of airborne fungi and bacterial. These taxa differ significantly between the 3 climatic regions studied. The microbial communities structure associated with SC concentrations of PM10 during a consecutive 2-year study remained stable in the rural area. Atmospheric concentration levels of PM10-SC species varied significantly between the 3 study sites, but with no clear difference according to site typology (rural vs. urban), suggesting that SC emissions are related to regional rather than local climatic characteristics. The overall microbial beta diversity in PM10 samples is significantly different from that of the main vegetation around the urban sites studied. This indicates that the airborne microorganisms at these urban sites are not solely from the immediate surrounding vegetation, which contrasts with observations at the scale of a regionally homogeneous rural site in 2017. These results improve our understanding of the spatial behavior of tracers of PBOA emission sources, which need to be better characterized to further implement this important mass fraction of Organic Matter (OM) in Chemical Transport models (CTM).
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Sellier, V., Navratil, O., Laceby, J., Legout, C., Foucher, A., Allenbach, M., et al. (2021). Combining colour parameters and geochemical tracers to improve sediment source discrimination in a mining catchment (New Caledonia, South Pacific Islands). Soil, 7(2), 743–766.
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.
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Simonin, M., Martins, J., Uzu, G., Spadini, L., Navel, A., & Richaume, A. (2021). Low mobility of CuO and TiO2 nanoparticles in agricultural soils of contrasting texture and organic matter content. Science Of The Total Environment, 783.
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Thollet, F., Rousseau, C., Camenen, B., Boubkraoui, S., Branger, F., Lauters, F., et al. (2021). Long term high frequency sediment observatory in an alpine catchment: The Arc-Isere rivers, France. Hydrological Processes, 35(2).
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.
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Troger, R., Ren, H., Yin, D., Postigo, C., Nguyen, P., Baduel, C., et al. (2021). What 's in the water? – Target and suspect screening of contaminants of emerging concern in raw water and drinking water from Europe and Asia. Water Research, 198.
Abstract: There is growing worry that drinking water can be affected by contaminants of emerging concern (CECs), potentially threatening human health. In this study, a wide range of CECs ( n = 177), including pharmaceuticals, pesticides, perfluoroalkyl substances (PFASs) and other compounds, were analysed in raw water and in drinking water collected from drinking water treatment plants (DWTPs) in Europe and Asia ( n = 13). The impact of human activities was reflected in large numbers of compounds detected ( n = 115) and high variation in concentrations in the raw water (range 15-7995 ng L & minus;1 for E177 CECs). The variation was less pronounced in drinking water, with total concentration ranging from 35 to 919 ng L & minus;1 . Treatment efficiency was on average 65 +/- 28%, with wide variation between different DWTPs. The DWTP with the highest ECEC concentrations in raw water had the most efficient treatment procedure (average treatment efficiency 89%), whereas the DWTP with the lowest E177 CEC concentration in the raw water had the lowest average treatment efficiency (2.3%). Suspect screening was performed for 500 compounds ranked high as chemicals of concern for drinking water, using a prioritisation tool (SusTool). Overall, 208 features of interest were discovered and three were confirmed with reference standards. There was co-variation between removal efficiency in DWTPs for the target compounds and the suspected features detected using suspect screening, implying that removal of known contaminants can be used to predict overall removal of potential CECs for drinking water production. Our results can be of high value for DWTPs around the globe in their planning for future treatment strategies to meet the increasing concern about human ex-posure to unknown CECs present in their drinking water. (c) 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
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Uber, M., Nord, G., Legout, C., & Cea, L. (2021). How do modeling choices and erosion zone locations impact the representation of connectivity and the dynamics of suspended sediments in a multi-source soil erosion model? Earth Surface Dynamics, 9(1), 123–144.
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.
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2020 |
Aires, F., Venot, J., Massuel, S., Gratiot, N., Pham-Duc, B., & Prigent, C. (2020). Surface Water Evolution (2001-2017) at the Cambodia/Vietnam Border in the Upper Mekong Delta Using Satellite MODIS Observations. Remote Sensing, 12(5).
Abstract: Studying the spatial and temporal distribution of surface water resources is critical, especially in highly populated areas and in regions under climate change pressure. There is an increasing number of satellite Earth observations that can provide information to monitor surface water at global scale. However, mapping surface waters at local and regional scales is still a challenge for numerous reasons (insufficient spatial resolution, vegetation or cloud opacity, limited time-frequency or time-record, information content of the instrument, lack in global retrieval method, interpretability of results, etc.). In this paper, we use 17 years of the MODIS (MODerate-resolution Imaging Spectro-radiometer) observations at a 8-day resolution. This satellite dataset is combined with ground expertise to analyse the evolution of surface waters at the Cambodia/Vietnam border in the Upper Mekong Delta. The trends and evolution of surface waters are very significant and contrasted, illustrating the impact of agriculture practices and dykes construction. In most of the study area in Cambodia. surface water areas show a decreasing trend but with a strong inter-annual variability. In specific areas, an increase of the wet surfaces is even observed. Ground expertise and historical knowledge of the development of the territory enable to link the decrease to ongoing excavation of drainage canals and the increase of deforestation and land reclamation, exposing flooded surfaces previously hidden by vegetation cover. By contrast, in Vietnam, the decreasing trend in wet surfaces is very clear and can be explained by the development of dykes dating back to the 1990s with an acceleration in the late 2000s as part of a national strategy of agriculture intensification. This study shows that coupling satellite data with ground-expertise allows to monitor surface waters at mesoscale (<100 x 100 km(2)), demonstrating the potential of interdisciplinary approaches for water ressource management and planning.
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Antoine, G., Camenen, B., Jodeau, M., Nemery, J., & Esteves, M. (2020). Downstream erosion and deposition dynamics of fine suspended sediments due to dam flushing. Journal Of Hydrology, 585.
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.
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Attard, G., Bayer, P., Rossier, Y., Blum, P., & Eisenlohr, L. (2020). A novel concept for managing thermal interference between geothermal systems in cities. Renewable Energy, 145, 914–924.
Abstract: The growing interest in shallow geothermal resources leads to dense installation areas, where interference and decrease in efficiency might occur. To optimize geothermal use in cities which prevents interference between neighbouring and future installations, we present a novel concept relying on the definition of thermal protection perimeters (TPP) around geothermal installations. These perimeters are determined by quantifying the thermal probability of capture around closed- and open-loop geothermal systems. Then, the maximal acceptable power that can be exploited in the vicinity of the installations can be continuously mapped. Existing analytical heat transport models are adapted to calculate these thermal capture probabilities. Two applications are illustrated in Lyon (France). The first application shows that adapted analytical models can help to manage multiple geothermal installations already in place in sectors of few square kilometres. In the second application, a numerical deterministic model is used to determine the TPP of one open-loop system at a local scale. The numerical approach applied for this case allows to account for flow disturbances caused by underground constructions, and thus offers a refined representativeness of the probability of capture. The presented methodology facilitates compatibility assessments between existing and planned new geothermal installations, which is otherwise not feasible by only mapping thermal plumes caused by existing installations, as done in common practice. (C) 2019 Elsevier Ltd. All rights reserved.
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Aviles, G., Descloitres, M., Duwig, C., Rossier, Y., Spadini, L., Legchenko, A., et al. (2020). Insight into the Katari-Lago Menor Basin aquifer, Lake Titicaca-Bolivia, inferred from geophysical (TDEM), hydrogeological and geochemical data. Journal Of South American Earth Sciences, 99.
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.
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Bakker, M., Gimbert, F., Geay, T., Misset, C., Zanker, S., & Recking, A. (2020). Field Application and Validation of a Seismic Bedload Transport Model. Journal Of Geophysical Research-Earth Surface, 125(5).
Abstract: Bedload transport drives morphological changes in gravel-bed streams and sediment transfer in catchments. The large impact forces associated with bedload motion and its highly dynamic spatiotemporal nature make it difficult to monitor bedload transport in the field. In this study, we revise a physically-based model of bedload-induced seismic ground motion proposed by Tsai et al. (2012, ) and apply it to invert bedload flux from seismic measurements alongside an Alpine stream. First, we constrain the seismic response of a braided river reach with a simple active experiment using a series of large-rock impacts. This allows the characterization of surface wave propagation and attenuation with distance from the impact source. Second, we distinguish bedload-generated ground vibrations from those caused by turbulent flow using frequency-based scaling relationships between seismic power and discharge. Finally, absolute bedload transport rates are quantified from seismic measurements using inverse modeling based on a simplified formulation of bedload particle motion. The results are verified with a large data set of bedload samples, demonstrating that seismic measurements can provide an indirect measure for bedload flux with uncertainties within a factor of 5(+/- 1) for instantaneous measurements (between 0.01 and 1 kg/m/s). Larger deviations may be caused by uncertainties in the contribution of turbulent flow effects, particle impact velocity, and especially particle size that may vary with sediment supply and flow conditions. When constraining these uncertainties, instream sediment transport measurements are no longer necessarily required and seismic monitoring may provide an accurate and continuous means to investigate bedload dynamics in gravel-bed streams.
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Barraza, F., Uzu, G., Jaffrezo, J., Schreck, E., Budzinski, H., Le Menach, K., et al. (2020). Contrasts in chemical composition and oxidative potential in PM10 near flares in oil extraction and refining areas in Ecuador. Atmospheric Environment, 223.
Abstract: For decades, oil extraction in rural sites in the North Amazon Region (NAR) in Ecuador, have generated mixtures of potentially toxic compounds, such as polycyclic aromatic hydrocarbons (PAHs) and metal(loid)s. The main national refinery and the thermal power plant located in Esmeraldas, on the North Pacific Coast (NPC), are also considered as important sources of air contamination. Particulate matter (PM10) emitted at both sites could induce the formation of reactive oxygen species (ROS) in the lungs upon inhalation and could be associated with respiratory diseases. In this study, PM10 mass composition was monitored over a two-year period in both regions: NAR (close to oil platforms and open flares) and NPC (in a public school close to the refinery). PM10 composition was assessed in terms of metal(loid)s, organic and elementary carbon (OC, EC), monosaccharides (levoglucosan, mannosan, galactosan), glucose, polyols (sorbitol, mannitol, arabitol), water soluble ions and polycyclic aromatic compounds (PAHs, oxy-PAHs and nitro-PAHs). Additionally, three complementary biochemical and acellular tests were performed to evaluate the oxidative potential (OP). Results show that the PM10 mass and elemental concentrations were higher in NPC than in NAR. Barium and Mo concentrations, commonly used in oil operations, were up to 1000-fold higher than values recorded in other regions of Ecuador. OC/EC ratios and polyols concentrations were higher in NAR than in NPC, indicating a larger biogenic contribution to the PM mass in this region. In NAR, the main sources associated with ROS burden were biogenic emissions and oil production, as indicated by positive correlations between OP, sugars, Ba, some PAHs and oxy-PAHs. On the other hand, in NPC, associations between NH4+, Ba, As and Ni imply that oil refining and industrial activities are the main contributors to the OP of PM10.
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Le, H., Gratiot, N., Santini, W., Ribolzi, O., Tran, D., Meriaux, X., et al. (2020). Suspended sediment properties in the Lower Mekong River, from fluvial to estuarine environments. Estuarine Coastal And Shelf Science, 233.
Abstract: The Mekong river is one of the largest rivers in the world, which flows through six countries of Southeast Asia (China, Myanmar, Laos, Thailand, Cambodia and Vietnam). Its hydro-sedimentary regime is changing rapidly, as a consequence of a regional shift of land use (agriculture, road, etc.), damming, sand mining and climate changes, among others. This study assesses the behavior of particles transported in suspension in the Lower Mekong River (LMR), along approximately 1700 km from fluvial to estuarine environments. Suspended sediment properties were estimated, simultaneously with hydrodynamic conditions, during three field campaigns. In addition, further investigations were performed in the laboratory to assess the structures of particles (flocculated or not), their capacity to flocculate (and the impacts on siltation), under a wide range of sediment concentration (20-30,000 mg.L-1). This study confirms that suspended sediment transported in the LMR are predominantly (75% by volume) flocculi (or freshly eroded soils aggregates), with median aggregated particle size in the range 10-20 μm and median settling velocity of the order of 0.01-0.1 μm s(-1). These flocculi are robust under the hydrodynamic conditions (turbulence and suspended sediment concentration – SSC) existing in the LMR. Laboratory investigations reveal the existence of a threshold sediment concentration (400 mg.L-1), beyond which flocculation and sedimentation increase of orders of magnitudes. Thus, concentration that exceeds this threshold might promote the formation of so-called fluid mud layers. Because of the nonlinear response of flocculation and sedimentation with SSC and considering the ongoing changes at a regional scale in the LMR, higher occurrence of fluid mud layers in the fluvial upstream waterbodies might be anticipated, and a lower occurrence in estuaries and alongshore where the concentration decrease. The geomorphology could be impacted, with an over-siltation in dams and an exacerbated erosion of the muddy-mangrove coast.
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Le, H., Lambrechts, J., Ortleb, S., Gratiot, N., Deleersnijder, E., & Soares-Frazao, S. (2020). An implicit wetting-drying algorithm for the discontinuous Galerkin method: application to the Tonle Sap, Mekong River Basin. Environmental Fluid Mechanics, 20(4), 923–951.
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.
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Legchenko, A., Baltassat, J., Duwig, C., Boucher, M., Girard, J., Soruco, A., et al. (2020). Time-lapse magnetic resonance sounding measurements for numerical modeling of water flow in variably saturated media. Journal Of Applied Geophysics, 175.
Abstract: We presented an innovative hydrogeophysical approach that allows numerical modeling of water flow in a variably saturated media. In our model, we approximated the subsurface by horizontally stratified porous media. The model output was a time varying water content profile. Then, we compared the water content provided by the model with the water content measurements carried out using the time-lapse Magnetic Resonance Sounding (MRS) method. Each MRS sounding provided a water content profile in the unsaturated zone down to twenty meters. The time shift between the profiles corresponded to the time lapse between individual MRS soundings. We minimized the discrepancy between the observed and the modeled MRS signals by varying hydraulic parameters of soil layers in the water flow model. For measuring and processing MRS data, we used NUMIS MRS instrument and SAMOVAR software. We carried out water flow modeling with HYDRUS-1D software. This paper reports our results and summarizes the limitations of the MRS method applied to water content measurements in the unsaturated zone. (C) 2020 Elsevier B.V. All rights reserved.
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Lima, I., Ramos, O., Munoz, M., Aguirre, J., Duwig, C., Maity, J., et al. (2020). Spatial dependency of arsenic, antimony, boron and other trace elements in the shallow groundwater systems of the Lower Katari Basin, Bolivian Altiplano. Science Of The Total Environment, 719.
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.
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Martinez-Carvajal, G., Oxarango, L., Clement, R., Molle, P., & Forquet, N. (2020). Assessment of spatial representativity of X-ray tomography to study Vertical Flow Treatment wetlands. Science Of The Total Environment, 713.
Abstract: French Vertical Flow (VF) treatment wetlands receive raw wastewater and provide simultaneous sludge and wastewater treatment. For proper sludge handling, the treatment wetland must be designed adequately and specific operational conditions must be maintained. When these conditions are not met, accumulation of biosolids may lead to clogging. Filtration in French VF Treatment wetlands is governed by mechanisms at the pore-scale. They must be better understood to predict reliably biosolid accumulation. X-ray Computed Tomography (Xray-CT) is a promising technique to characterize in detail the morphology of the filtering media in treatment wetlands. In order to set a solid basis for the use of Xray-CT, the spatial representativity of measurements must be assessed. This issue is addressed in this study by successively analyzing spatial properties at the filter scale using Frequency Domain Electromagnetic Measurements (FDEMs), and at the pore scale using Xray-CT. A map of the electric conductivity at the surface of a French VF Treatment wetland is obtained by FDEM that indicates a homogeneous distribution of biosolids to which electrical conductivity is highly correlated. Different morphological properties were computed from Xray-CT after phase segmentation: phase volume fraction profiles, Specific Surface Area profiles and pore size distributions. Samples show several similarities of pore scale properties obtained by Xray-CT independently of the sampling region and especially the same vertical gradients. FDEM measurements and Xray-CT analysis are in agreement to indicate a good influent distribution at the surface of a full-scale mature French VF Treatment wetland. A criterion to define the limits of the deposit layer and gravel layer is introduced. This division allows to compare layers independently. Finally, a 2D-REV analysis suggests that the selected sample diameter of 5 cm is large enough to be representative of the heterogeneous distribution of phases at the pore-scale as long as no Phragmites are present. (C) 2020 Elsevier B.V. All rights reserved.
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Mazzilli, N., Chalikakis, K., Carriere, S., & Legchenko, A. (2020). Surface Nuclear Magnetic Resonance Monitoring Reveals Karst Unsaturated Zone Recharge Dynamics during a Rain Event. Water, 12(11).
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.
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Miller, O., Solomon, D., Miege, C., Koenig, L., Forster, R., Schmerr, N., et al. (2020). Hydrology of a Perennial Firn Aquifer in Southeast Greenland: An Overview Driven by Field Data. Water Resources Research, 56(8).
Abstract: Firn aquifers have been discovered across regions of the Greenland ice sheet with high snow accumulation and melt rates, but the processes and rates that sustain these aquifers have not been fully quantified or supported by field data. A quantitative description of the hydrology of a firn aquifer upslope from Helheim Glacier that integrates field measurements is presented to constrain melt and recharge rates and timing, temporal variations in temperature and water levels, and liquid-water residence time. Field measurements include weather data, firn temperatures, water levels, geochemical tracers, and airborne radar data. Field measurements show that once the firn column is temperate (0 degrees C), meltwater from the surface infiltrates to the water table in less than 2 days and raises the water table. Average recharge is 22 cm/year (lower 95% confidence interval is 13 cm/year and upper 95% confidence interval is 33 cm/year). Meltwater within the recently formed aquifer, which flows laterally downslope and likely discharges into crevasses, has a mean residence time of similar to 6.5 years. Airborne radar data suggest that the aquifer in the study area continues to expand inland, presumably from Arctic warming. These comprehensive field measurements and integrated description of aquifer hydrology provide a comprehensive, quantitative framework for modeling fluid flow through firn, and understanding existing and yet undiscovered firn aquifers, and may help researchers evaluate the role of firn aquifers in climate change impacts.
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Misset, C., Recking, A., Legout, C., Bakker, M., Bodereau, N., Borgniet, L., et al. (2020). Combining multi-physical measurements to quantify bedload transport and morphodynamics interactions in an Alpine braiding river reach. Geomorphology, 351.
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.
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Nguyen, T., N?Mery, J., Gratiot, N., Garnier, J., Strady, E., Nguyen, D., et al. (2020). Nutrient budgets in the Saigon-Dongnai River basin: Past to future inputs from the developing Ho Chi Minh megacity (Vietnam). River Research And Applications, 36(6), 974–990.
Abstract: Ho Chi Minh City (HCMC, Vietnam) is one of the fastest growing megacities in the world. In this paper, we attempt to analyse the dynamics of nutrients, suspended sediments, and water discharges in its aquatic systems today and in the future. The work is based on nine sampling sites along the Saigon River and one on the Dongnai River to identify the reference water status upstream from the urban area and the increase in fluxes that occur within the city and its surroundings. For the first time, the calculated fluxes allow drawing up sediment and nutrient budgets at the basin scale and the quantification of total nutrient loading to the estuarine and coastal zones (2012-2016 period). Based on both national Vietnamese and supplementary monitoring programs, we estimated the water, total suspended sediment, and nutrients (Total N, Total P, and dissolved silica: DSi) fluxes at 137 m(3)year(-1), 3,292 x 10(3)tonSS year(-1), 5,323 tonN year(-1), 450 tonP year(-1), and 2,734 tonSi year(-1)for the Saigon River and 1,693 m(3)year(-1), 1,175 x 10(3)tonSS year(-1), 31,030 tonN year(-1), 1,653 tonP year(-1), and 31,138 tonSi year(-1)for the Dongnai River, respectively. Nutrient fluxes provide an indicator of coastal eutrophication potential (indicator of coastal eutrophication potential), using nutrient stoichiometry ratios. Despite an excess of nitrogen and phosphorus over silica, estuarine waters downstream of the megacity are not heavily impacted by HCMC. Finally, we analysed scenarios of future trends (2025-2050) for the nutrient inputs on the basis of expected population growth in HCMC and improvement of wastewater treatment capacity. We observed that without the construction of a large number of additional wastewater treatment plants, the eutrophication problem is likely to worsen. The results are discussed in the context of the wastewater management policy.
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Noncent, D., Strady, E., Nemery, J., Thanh-Nho, N., Denis, H., Mourier, B., et al. (2020). Sedimentological and geochemical data in bed sediments from a tropical river-estuary system impacted by a developing megacity, Ho Chi Minh City-Vietnam. Data In Brief, 31.
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.
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Nord, G., Michielin, Y., Biron, R., Esteves, M., Freche, G., Geay, T., et al. (2020). An autonomous low-power instrument platform for monitoring water and solid discharges in mesoscale rivers. Geoscientific Instrumentation Methods And Data Systems, 9(1), 41–67.
Abstract: We present the development of the River Platform for Monitoring Erosion (RIPLE) designed for monitoring at high temporal frequency (similar to 10 min) of water discharge, solid fluxes (bedload and suspended load) and properties of fine particles (settling velocity) in mesoscale rivers, i.e. which drain mesoscale catchments (approximate to 10-10(3) km(2)). This platform responds to a request to continuously measure these variables in rivers using a single, centralized device, and to do this in the most direct way possible. The platform integrates the following instruments: (i) for water discharge, water level radar, and surface velocity radar, digital cameras and an echo sounder; (ii) for fine sediment load, turbidimeters and automatic samplers including the SCAF (a sediment settling velocity characterization device); (iii) for bedload, a hydrophone; and (iv) for water quality, a conductivity probe and water sampling. As far as water discharge monitoring is concerned, priority has been given to non-intrusive instruments to improve the robustness of the system. All the instruments are driven by a data logger (Campbell (R) CR6), which locally stores the data and then uploads them to a remote server every hour during the day using a 3G modem. SMS (Short Message Service) alerts can be sent depending on scheduled conditions (e.g. low battery voltage, water level threshold, all samples of the automatic sampler collected). The platform has been designed to be as autonomous as possible: it is powered by a battery that is supplied by a solar panel. Limiting the power consumption of the platform was one of the main technical challenges because of the quantity of instruments integrated. A simple 100W solar panel is sufficient to power the entire platform, even during winter or low insulation conditions. A user-friendly interface has been developed, enabling to visualize the data collected by the platform from an internet connection. It is also possible to remotely configure the platform within this interface, e.g. to modify water sampling thresholds or alert thresholds. Finally, the platform is relatively easy to move from one site to another, because its installation requires little civil engineering. To date, RIPLE has been tested on two rivers of the Alps in France: the Romanche river in Bourg d'Oisans from September 2016 to July 2018 and the Galabre river in La Robine sur Galabre since October 2018, demonstrating the proper functioning of the platform.
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Rauly, D., Vindret, M., Chamberod, E., Martins, J., & Xavier, P. (2020). Distribution of AC Electric Field-Induced Transmembrane Voltage in Escherichia coli Cell Wall Layers. Bioelectromagnetics, 41(4), 279–288.
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.
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Saito, T., Spadini, L., Saito, H., Martins, J., Oxarango, L., Takemura, T., et al. (2020). Characterization and comparison of groundwater quality and redox conditions in the Arakawa Lowland and Musashino Upland, southern Kanto Plain of the Tokyo Metropolitan area, Japan. Science Of The Total Environment, 722.
Abstract: Groundwater is essential for the Earth biosphere but is often contaminated by harmful chemical compounds due to both anthropogenic and natural causes. A key factor controlling the fate of harmful chemicals in groundwater is the reduction/oxidation (redox) conditions. The formation factors for the groundwater redox conditions are insufficiently understood. In this study, long-term groundwater quality beneath one of the world megacities was monitored and evaluated. We measured and compared hydrogeochemical conditions including groundwater quality (35 chemical parameters) and redox conditions of five aquifers in the Arakawa Lowland and Musashino Upland, southern Kanto Plain of the TokyoMetropolitan area, Japan. Monitoring results suggested the following: The main origin of groundwater is precipitation in both the Lowland and Upland areas. The three aquifers in the Arakawa Lowland are likely fully separated, with one unconfined and two confined aquifers under iron reducing and methanogenic conditions, respectively. Oppositely, in the Musashino Upland, the water masses in the two aquifers are likely partly connected, under aerobic conditions, and undergoing the same groundwater recharge and flow processes under similar hydrogeological conditions. The different groundwater redox conditions observed are likely caused by the very different groundwater residence times for the Arakawa Lowland and Musashino Upland. (C) 2020 Elsevier B.V. All rights reserved.
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Samake, A., Bonin, A., Jaffrezo, J., Taberlet, P., Weber, S., Uzu, G., et al. (2020). High levels of primary biogenic organic aerosols are driven by only a few plant-associated microbial taxa. Atmospheric Chemistry And Physics, 20(9), 5609–5628.
Abstract: Primary biogenic organic aerosols (PBOAs) represent a major fraction of coarse organic matter (OM) in air. Despite their implication in many atmospheric processes and human health problems, we surprisingly know little about PBOA characteristics (i.e., composition, dominant sources, and contribution to airborne particles). In addition, specific primary sugar compounds (SCs) are generally used as markers of PBOAs associated with bacteria and fungi, but our knowledge of microbial communities associated with atmospheric particulate matter (PM) remains incomplete. This work aimed at providing a comprehensive understanding of the microbial fingerprints associated with SCs in PM10 (particles smaller than 10 μm) and their main sources in the surrounding environment (soils and vegetation). An intensive study was conducted on PM10 collected at a rural background site located in an agricultural area in France. We combined high-throughput sequencing of bacteria and fungi with detailed physicochemical characterizations of PM10, soil, and plant samples and monitored meteorological and agricultural activities throughout the sampling period. Results show that in summer SCs in PM10 are a major contributor of OM in air, representing 0.8 % to 13.5 % of OM mass. SC concentrations are clearly determined by the abundance of only a few specific airborne fungal and bacterial taxa. The temporal fluctuations in the abundance of only four predominant fungal genera, namely Cladosporium, Alternaria, Sporobolomyces, and Dioszegia, reflect the temporal dynamics in SC concentrations. Among bacterial taxa, the abundance of only Massilia, Pseudomonas, Frigoribacterium, and Sphingomonas is positively correlated with SC species. These microbes are significantly enhanced in leaf over soil samples. Interestingly, the overall community structure of bacteria and fungi are similar within PM10 and leaf samples and significantly distinct between PM10 and soil samples, indicating that surrounding vegetation is the major source of SC-associated microbial taxa in PM10 in this rural area of France.
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Valente, M., Reichert, J., Legout, C., Tiecher, T., Cavalcante, R., & Evrard, O. (2020). Quantification of sediment source contributions in two paired catchments of the Brazilian Pampa using conventional and alternative fingerprinting approaches. Hydrological Processes, .
Abstract: The knowledge of the contribution of sediment sources to river networks is a prerequisite to understand the impact of land use change on sediment yield. We calculated the relative contributions of sediment sources in two paired catchments, one with commercial eucalyptus plantations (0.83 km(2)) and the other with grassland used for livestock farming (1.10 km(2)), located in the Brazilian Pampa biome, using different combinations of conventional [geochemical (G), radionuclide (R) and stable isotopes and organic matter properties (S)] and alternative tracer properties [spectrocolorimetric visible-based-colour parameters (V)]. Potential sediment sources evaluated were stream channel, natural grassland and oat pasture fields in the grassland catchment, and stream channel, unpaved roads and eucalyptus plantation in the eucalyptus catchment. The results show that the best combination of tracers to discriminate the potential sources was using GSRV tracers in the grassland catchment, and using GSRV, GSV and GS tracers in the eucalyptus catchment. In all these cases, samples were 100% correctly classified in their respective groups. Considering the best tracers results (GSRV) in both catchments, the sediment source contributions estimated in the catchment with eucalyptus plantations was 63, 30 and 7% for stream channel, eucalyptus stands and unpaved roads, respectively. In the grassland catchment, the source contributions to sediment were 84, 14 and 2% for natural grassland, stream channel and oats pasture fields, respectively. The combination of these source apportionment results with the annual sediment loads monitored during a 3-year period demonstrates that commercial eucalyptus plantations supplied approximately 10 times less sediment (0.1 ton ha(-1) year(-1)) than the traditional land uses in this region, that is, 1.0 ton ha(-1) year(-1) from grassland and 0.3 ton ha(-1) year(-1) from oats pasture fields. These results demonstrate the potential of combining conventional and alternative approaches to trace sediment sources originating from different land uses in this region. Furthermore, they show that well-managed forest plantations may be less sensitive to erosion than grassland used for intensive livestock farming, which should be taken into account to promote the sustainable use of land in this region of South America.
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Archundia, D., Duwig, C., Spadini, L., Morel, M., Prado, B., Perez, M., et al. (2019). Assessment of the Sulfamethoxazole mobility in natural soils and of the risk of contamination of water resources at the catchment scale. Environment International, 130.
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.
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Azhar, M., Chang, X., Debes, J., Delmas, P., Duwig, C., Dal Ferro, N., et al. (2019). Advantages of multi-region kriging over bi-region techniques for computed tomography-scan segmentation. Soil Research, 57(6), 521–534.
Abstract: Quantifying the structure of soil is essential for developing effective soil management for farming and environmental conservation efforts. One approach to quantify soil structure is to scan intact soil cores by X-ray computed tomography (CT), which allows using computer vision algorithms to identify internal components within the soil. One commonly used approach is the colour-based segmentation of CT-scan soil images into two regions – matter and void – for the purpose of determining the soil porosity. A key problem with this approach is that soil CT images tend to be rather complicated, and thus this type of bi-region segmentation is a non-trivial problem, with algorithms following this type of bi-region approach typically performing unreliability across a variety of image sets. In this work, a technique is proposed that identifies an optimal number of regions present in the soil, rather than just two. It is claimed that this more sophisticated representation of soil structure leads to a more accurate representation than traditional bi-region segmentation; however, it is reducible to a bi-region segmentation yielding the required estimation of porosity with more accuracy and robustness than traditional methods. It is also proposed that segmentation is performed using a multi-region kriging algorithm, which establishes relationships between distance and regions that allows the segmentation to overcome many of the artefacts and noise issues associated with CT scanning. Our experiments focused on layer-by-layer segmentation and results demonstrated that the proposed approach produced segmentations consistent across a variety of scanned cores and were visually more correct than current state-of-the-art bi-region techniques.
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Babut, M., Mourier, B., Desmet, M., Simonnet-Laprade, C., Labadie, P., Budzinski, H., et al. (2019). Where has the pollution gone? A survey of organic contaminants in Ho Chi Minh city / Saigon River (Vietnam) bed sediments. Chemosphere, 217, 261–269.
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.
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Baduel, C., Lai, F., Van Nuijs, A., & Covaci, A. (2019). Suspect and Nontargeted Strategies to Investigate in Vitro Human Biotransformation Products of Emerging Environmental Contaminants: The Benzotriazoles. Environmental Science & Technology, 53(17), 10462–10469.
Abstract: Benzotriazole derivatives (BTRs) are high production volume chemicals involved in a wide range of applications and consumer products resulting in their ubiquitous presence in environmental matrices. Yet, the human exposure assessment to these chemicals is limited since it is based only on the analysis of parent compounds in biological matrices. The objective of this study was to investigate the in vitro human biotransformation for three widely used BTRs and to stepwise examine the role of Phase I and II enzymes (cytochrome P450 (CYP), uridine glucuronic acid transferase (UGT), and sulfotransferase (SULT)) in their biotransformation. Extracts with generated biotransformation products (bioTPs) were analyzed using liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry (LC-QTOF-MS), followed by their identification based on a workflow combining suspect and nontargeted strategies. Ten bioTPs were identified for 1H-benzotriazole, 14 for tolyltriazole, and 14 for 5-chloro-1-H-benzotriazole. Most of the proposed bioTPs were identified and structurally elucidated for the first time. Based on these findings, possible bioTPs and metabolic transformation pathways were subsequently predicted for other structurally close BTR derivatives. Our findings provide new identified in vitro biotransformation products for future biomonitoring studies and emphasize that it is important to investigate the biotransformation pathway to assess overall exposure to xenobiotics.
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Besset, M., Gratiot, N., Anthony, E., Bouchette, F., Goichot, M., & Marchesiello, P. (2019). Mangroves and shoreline erosion in the Mekong River delta, Viet Nam. Estuarine Coastal And Shelf Science, 226.
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.
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Brunier, G., Anthony, E., Gratiot, N., & Gardel, A. (2019). Exceptional rates and mechanisms of muddy shoreline retreat following mangrove removal. Earth Surface Processes And Landforms, 44(8), 1559–1571.
Abstract: Probably the largest regular shoreline fluctuations on Earth occur along the 1500 km-long wave-exposed Guianas coast of South America between the mouths of the Amazon and Orinoco Rivers, the world's longest muddy coast. The Guianas coast is influenced by a succession of mud banks migrating northwestward from the Amazon. Migrating mud banks dissipate waves, partially weld onshore, and lead to coastal progradation, aided by large-scale colonization by mangroves, whereas mangrove-colonized areas between banks (inter-bank areas) are exposed to strong wave action and undergo erosion. On large tracts of this coast, urbanization and farming have led to fragmentation and removal of mangroves, resulting in aggravated shoreline retreat. To highlight this situation, we determined, in a setting where mangroves and backshore freshwater marshes have been converted into rice polders in French Guiana, shoreline change over 38 years (1976-2014) from satellite images and aerial orthophotographs. We also conducted four field experiments between October 2013 and October 2014, comprising topographic and hydrodynamic measurements, to determine mechanisms of retreat. The polder showed persistent retreat, at peak rates of up to -200 m/yr, and no recovery over the 38-year period of monitored change. Notwithstanding high erosion rates, mangrove shorelines show strong resilience, with recovery characterized by massive accretion. Retreat of the polder results in a steep wave-reworked shoreface with a lowered capacity for bank welding onshore and mangrove establishment. Persistent polder erosion is accompanied by the formation of a sandy chenier that retreats landwards at rates largely exceeding those in inter-bank situations. These results show that anthropogenic mangrove removal can durably modify the morphodynamics of muddy shorefaces. This limits the capacity for shoreline recovery and mangrove re-establishment even when there is no sustained long-term deficit in mud supply, as in the case of the Amazon-influenced Guianas coast. (c) 2019 John Wiley & Sons, Ltd.
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Calas, A., Uzu, G., Besombes, J., Martins, J., Redaelli, M., Weber, S., et al. (2019). Seasonal Variations and Chemical Predictors of Oxidative Potential (OP) of Particulate Matter (PM), for Seven Urban French Sites. Atmosphere, 10(11).
Abstract: Epidemiological studies suggest that the main part of chronic effects from air pollution is likely to be linked with particulate matter (PM). Oxidative potential (OP) of PM is gaining strong interest as a promising health exposure metric. This study combined atmospheric detailed composition results obtained for seven different urban background environments over France to examine any possible common feature in OP seasonal variations obtained using two assays (acid ascorbic (AA) and dithiothreitol (DTT)) along a large set of samples (N >700). A remarkable homogeneity in annual cycles was observed with a higher OP activity in wintertime at all investigated sites. Univariate correlations were used to link the concentrations of some major chemical components of PM and their OP. Four PM components were identified as OP predictors: OC, EC, monosaccharides and Cu. These species are notably emitted by road transport and biomass burning, targeting main sources probably responsible for the measured OP activity. The results obtained confirm that the relationship between OP and atmospheric pollutants is assay- and location-dependent and, thus, the strong need for a standardized test, or set of tests, for further regulation purposes.
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Duwig, C., Muller, K., Morari, F., & Delmas, P. (2019). Linking Soil Structure to Soil Functions Foreword. Soil Research, 57(6), I-III.
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Duwig, C., Prado, B., Tinet, A., Delmas, P., Dal Ferro, N., Vandervaere, J., et al. (2019). Impacts of land use on hydrodynamic properties and pore architecture of volcanic soils from the Mexican Highlands. Soil Research, 57(6), 629–641.
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.
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Esteves, M., Legout, C., Navratil, O., & Evrard, O. (2019). Medium term high frequency observation of discharges and suspended sediment in a Mediterranean mountainous catchment. Journal Of Hydrology, 568, 562–574.
Abstract: In mountainous catchments, soil erosion and sediment transport are highly variable throughout time and their quantification remains a major challenge for the scientific community. Understanding the temporal patterns and the main controls of sediment yields in these environments requires a long term monitoring of rainfall, runoff and sediment flux. This paper analyses this type of data collected during 7 years (2007-2014), at the outlet of the Galabre River, a 20 km(2) watershed, in south eastern France, representative of meso-scale Mediterranean mountainous catchments. This study is based on a hybrid approach using continuous turbidity records and automated total suspended solid sampling to quantify the instantaneous suspended sediment concentrations (SSC), sediment fluxes, event loads and yields. The total suspended sediment yield was 4661 Mg km(-2) and was observed during flood events. The two crucial periods for suspended sediment transport at the outlet were June and November/December (63% of the total). The analysis of suspended sediment transport dynamics observed during 236 flood events highlighted their intermittency and did not show any clear relationship between rainfall, discharge and SSC. The most efficient floods were characterised by counter-clockwise hysteresis relationships between SSC and discharges. The floods with complex hysteresis were the more productive in the long term, during this measuring period exceeding a decade. Nevertheless, the current research outlines the need to obtain medium-term (five years) continuous time series to assess the range of variations of suspended sediment fluxes and to outline clearly the seasonality of suspended sediment yields. Results suggest the occurrence of a temporal dis-connectivity in meso-scale catchments over short time-scales between the meteorological forcing and the sediment yields estimated at the outlet. These findings have important methodological impacts for modelling and operational implications for watershed management.
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Marchesiello, P., Nguyen, N., Gratiot, N., Loisel, H., Anthony, E., Dinh, C., et al. (2019). Erosion of the coastal Mekong delta: Assessing natural against man induced processes. Continental Shelf Research, 181, 72–89.
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.
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Martinez-Carvajal, G., Oxarango, L., Adrien, J., Molle, P., & Forquet, N. (2019). Assessment of X-ray Computed Tomography to characterize filtering media from Vertical Flow Treatment Wetlands at the pore scale. Science Of The Total Environment, 658, 178–188.
Abstract: Computed Tomography is a non-destructive technique often used in earth sciences for the description of porous media at the pore scale. This paper shows the feasibility of this technique to obtain 3D descriptions of filtering media in Vertical Flow Treatment Wetlands (VFTW). Three different samples from two full-scale VFTW were scanned. The samples vary in moisture content and gravel size distribution. The 3D images show three characteristic phases of unsaturated media: voids, fouling material and gravel. The gray contrast level is good enough to perform phase segmentation successfully using region growing algorithms. In this study the results from segmentation arc used (i) to compute profiles of phase volume fraction and specific surface at high resolution, (ii) to observe 3D distribution of elements, (iii) and to draw the void's skeleton and to perform a percolation pathway study. This method highlights the presence of a transition zone between the deposit cake and the dense gravel layer. In this zone, mechanical interactions between gravels and filtered solids tend to promote a heterogeneous layer of gravel, fouling material and open porosity. The presence of isolated gravels in the deposit layer is clearly evidenced. The effect of drying to enhance the contrast between phases has been analyzed for one sample by a direct comparison of images obtained before and after drying. The resulting opening of the void phase tends to increase significantly the void-fouling material specific surface and the number and size of percolating pathways computed as the skeleton of the void phase. Finally, a first analysis of filtration processes is proposed. It consists in analyzing the percolation pathways for a class of void size by applying the distance map and skeleton concepts to the void phase. (C) 2018 Elsevier B.V. All rights reserved.
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Mimeau, L., Esteves, M., Zin, I., Jacobi, H., Brun, F., Wagnon, P., et al. (2019). Quantification of different flow components in a high-altitude glacierized catchment (Dudh Koshi, Himalaya): some cryospheric-related issues. Hydrology And Earth System Sciences, 23(9), 3969–3996.
Abstract: In a context of climate change and water demand growth, understanding the origin of water flows in the Himalayas is a key issue for assessing the current and future water resource availability and planning the future uses of water in downstream regions. Two of the main issues in the hydrology of high-altitude glacierized catchments are (i) the limited representation of cryospheric processes controlling the evolution of ice and snow in distributed hydrological models and (ii) the difficulty in defining and quantifying the hydrological contributions to the river outflow. This study estimates the relative contribution of rainfall, glaciers, and snowmelt to the Khumbu River streamflow (Upper Dudh Koshi, Nepal, 146 km(2), 43% glacierized, elevation range from 4260 to 8848 ma.s.l.) as well as the seasonal, daily, and sub-daily variability during the period 2012-2015 by using the DHSVM-GDM (Distributed Hydrological Soil Vegetation Model – Glaciers Dynamics Model) physically based glacio-hydrological model. The impact of different snow and glacier parameterizations was tested by modifying the snow albedo parameterization, adding an avalanche module, adding a reduction factor for the melt of debris-covered glaciers, and adding a conceptual englacial storage. The representation of snow, glacier, and hydrological processes was evaluated using three types of data (MODIS satellite images, glacier mass balances, and in situ discharge measurements). The relative flow components were estimated using two different definitions based on the water inputs and contributing areas. The simulated hydrological contributions differ not only depending on the used models and implemented processes, but also on different definitions of the estimated flow components. In the presented case study, ice melt and snowmelt contribute each more than 40% to the annual water inputs and 69% of the annual stream flow originates from glacierized areas. The analysis of the seasonal contributions highlights that ice melt and snowmelt as well as rain contribute to monsoon flows in similar proportions and that winter outflow is mainly controlled by the release from the englacial water storage. The choice of a given parametrization for snow and glacier processes, as well as their relative parameter values, has a significant impact on the simulated water balance: for instance, the different tested parameterizations led to ice melt contributions ranging from 42% to 54 %. The sensitivity of the model to the glacier inventory was also tested, demonstrating that the uncertainty related to the glacierized surface leads to an uncertainty of 20% for the simulated ice melt component.
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Misset, C., Recking, A., Legout, C., Poirel, A., Cazilhac, M., Esteves, M., et al. (2019). An attempt to link suspended load hysteresis patterns and sediment sources configuration in alpine catchments. Journal Of Hydrology, 576, 72–84.
Abstract: A large part of total solid flux is transported as suspension in mountainous rivers. It is crucial for water resource management and for environmental issues to be able to model and to understand these fluxes. However, suspended load is known to be highly variable in time and space, as fine sediments can originate from various erosion processes and from various sources. Among the different methodologies available for analyzing the suspended sediment flux dynamics, hysteretic loops in discharge and suspended load signals are commonly used to assess sediment sources and production processes. However, the shape of these loops is often analyzed qualitatively for a single or a small number of catchments. Hence it is still unclear how the geomorphological catchment properties influence the variability of the flow rate – suspended sediment concentration relationship through the hysteresis effects. This is particularly true in mountainous catchments where important sources of fine sediments may originate from the river bed in addition to hillslopes. In this study we analyzed quantitatively ten long-term series of high-frequency observations of suspended sediment load measured in contrasted alpine catchments. Hysteresis effects were analyzed in a high number of automated sampled events and the dominant response for each catchment was sought. This was done by using a normalized hysteresis index developed by Lloyd et al. (2016), which we weighted by the mass transported during each event. The various catchments were characterized with a normalized geomorphological index expressing the relative importance of sediment sources originating from the river bed or from eroded areas as a function of the distance to the outlet of the catchment. The dominant hysteresis response of the ten alpine catchments studied was found to be greatly linked to their geomorphological index. These results suggest that the sediment source configuration upstream of a measuring station drives hysteresis effects and thus the variability of the flow rate-suspended sediment concentration relationship.
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Misset, C., Recking, A., Legout, C., Valsangkar, N., Bodereau, N., Zanker, S., et al. (2019). The Dynamics of Suspended Sediment in a Typical Alpine Alluvial River Reach: Insight From a Seasonal Survey. Water Resources Research, 55(12), 10918–10934.
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.
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Misset, C., Recking, A., Navratil, O., Legout, C., Poirel, A., Cazilhac, M., et al. (2019). Quantifying bed-related suspended load in gravel bed rivers through an analysis of the bedload-suspended load relationship. Earth Surface Processes And Landforms, 44(9), 1722–1733.
Abstract: Suspended load transport can strongly impact ecosystems, dam filling and water resources. However, contrary to bedload, the use of physically based predicting equations is very challenging because of the complexity of interactions between suspended load and the river system. Through the analysis of extensive data sets, we investigated extent to which one or several river bed or flow parameters could be used as a proxy for quantifying suspended fluxes in gravel bed rivers. For this purpose, we gathered in the literature nearly 2400 instantaneous field measurements collected in 56 gravel bed rivers. Among all standard dimensionless parameters tested, the strongest correlation was observed between the suspended sediment concentration and the dimensionless bedload rate. An empirical relation between these two parameters was calibrated. Used with a reach average bedload transport formula, the approach allowed to successfully reproduce suspended fluxes measured during major flood events in seven gravel bed alpine rivers, morphodynamically active and distant from hillslope sources. These results are discussed in light of the complexity of the processes potentially influencing suspended load in a mountainous context. The approach proposed in this paper will never replace direct field measurements, which can be considered the only confident method to assess sediment fluxes in alpine streams; however, it can increment existing panel tools that help river managers to estimate even rough but not unrealistic suspended fluxes when measurements are totally absent. (c) 2019 John Wiley & Sons, Ltd.
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Muller, K., Duwig, C., Tinet, A., Strozzi, A., Spadini, L., Morel, M., et al. (2019). Orchard management and preferential flow in Andosols – comparing two kiwifruit orchards in New Zealand. Soil Research, 57(6), 615–628.
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.
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Nguyen, T., Marchand, C., Strady, E., Nguyen, H., & Nhu-Trang, T. (2019). Bioaccumulation of some trace elements in tropical mangrove plants and snails (Can Gio, Vietnam). Environmental Pollution, 248, 635–645.
Abstract: Mangrove sediments can store high amount of pollutants that can be more or less bioavailable depending on environmental conditions. When in available forms, these elements can be subject to an uptake by mangrove biota, and can thus become a problem for human health. The main objective of this study was to assess the distribution of some trace elements (Fe, Mn, Co, Ni, Cr, As, and Cu) in tissues of different plants and snails in a tropical mangrove (Can Gio mangrove Biosphere Reserve) developing downstream a megacity (Ho Chi Minh City, Vietnam). In addition, we were interested in the relationships between mangrove habitats, sediment quality and bioaccumulation in the different tissues studied. Roots and leaves of main mangrove trees (Avicennia alba and Rhizophora apiculata) were collected, as well as different snail species: Chicoreus capucinus, Littoraria melanostoma, Cerithidea obtusa, Nerita articulata. Trace elements concentrations in the different tissues were determined by ICP-MS after digestion with concentrated HNO3 and H2O2. Concentrations differed between stands and tissues, showing the influence of sediment geochemistry, species specific requirements, and eventually adaptation abilities. Regarding plants tissues, the formation of iron plaque on roots may play a key role in preventing Fe and As translocation to the aerial parts of the mangrove trees. Mn presented higher concentrations in the leaves than in the roots, possibly because of physiological requirements. Non-essential elements (Ni, Cr and Co) showed low bioconcentration factors (BCF) in both roots and leaves, probably resulting from their low bioavailability in sediments. Regarding snails, essential elements (Fe, Mn, and Cu) were the dominant ones in their tissues. Most of snails were “macroconcentrators” for Cu, with BCF values reaching up to 42.8 for Cerithidea obtusa. We suggest that high quantity of As in all snails may result from its high bioavailability and from their ability to metabolize As. (C) 2019 Elsevier Ltd. All rights reserved.
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Nguyen, T., Nemery, J., Gratiot, N., Garnier, J., Strady, E., Tran, V., et al. (2019). Phosphorus adsorption/desorption processes in the tropical Saigon River estuary (Southern Vietnam) impacted by a megacity. Estuarine Coastal And Shelf Science, 227.
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.
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Nguyen, T., Nemery, J., Gratiot, N., Strady, E., Tran, V., Nguyen, A., et al. (2019). Nutrient dynamics and eutrophication assessment in the tropical river system of Saigon – Dongnai (southern Vietnam). Science Of The Total Environment, 653, 370–383.
Abstract: Saigon-Dongnai Rivers in Southern Vietnam is a complex lowland hydrological network of tributaries that is strongly influenced by the tidal cycles. The increasing economic, industrial and domestic developments in and around Ho ChiMinh City (HCMC) have led to serious impacts on water quality due to lack of appropriate wastewaters treatment. Drinkingwater production is impacted and the large aquaculture production areas may also be affected. We analyzed spatial and seasonal variability of nutrient concentrations (Phosphorus, Nitrogen and Silica) and eutrophication indicators (Organic Carbon, Chlorophyll-a and Dissolved Oxygen) based on bi-monthly monitoring during two hydrological cycles (July 2015-December 2017). Four monitoring sites were selected to assess the impact of HCMC: two upstream stations on the Saigon River and Dongnai River branches to provide the reference water quality status before reaching the urbanized area of HCMC; one monitoring station in the city center to highlight Saigon River water quality within the heart of the megacity; the fourth station downstream of the confluence to evaluate the impact of HCMC on the estuarine waters. This study points to excess nutrients in HCMC's water body with concentrations of NH4+ and PO43- averaging to 0.7 +/- 0.6 mgN L-1 and 0.07 +/- 0.06 mgP L-1, respectively in mean over the monitored period and rising up to 3 mgN L-1 and 0.2 mgP L-1, in extreme conditions. During the dry season, we evidenced that untreated domestic discharges leads to degradation of the Saigon River's water quality with extreme values of algal biomass (up 150 μChl-a L-1) and hypoxic conditions occurring episodically (DO < 2 mg L`(-1)) in the heart of the megacity. Until now, eutrophication in the urban center has had no clear effect downstream because eutrophicwater mass from the Saigon River is efficiently mixed with the Dongnai River and sea water masses during the successive semi-diurnal tidal cycles. (c) 2018 Elsevier B.V. All rights reserved.
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Park, J., Batalla, R., Birgand, F., Esteves, M., Gentile, F., Harrington, J., et al. (2019). Influences of Catchment and River Channel Characteristics on the Magnitude and Dynamics of Storage and Re-Suspension of Fine Sediments in River Beds. Water, 11(5).
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.
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Pham, H., & Dias, D. (2019). 3D Numerical Modeling of a Piled Embankment under Cyclic Loading. International Journal Of Geomechanics, 19(4).
Abstract: Embankments over pile-reinforced soft soil (called piled embankments) are known as one of the interesting techniques for soft soil improvement. They have been broadly applied in infrastructure projects thanks to their advantages, such as the decrease in settlement, the reduction in construction time, and the reasonable cost. The shearing and the soil-arching mechanisms within embankments result in an increase of the stress acting on the pile head and a reduction of the soft soil pressure. They can reduce the total and differential settlements. Numerous studies were carried out to better understand the behavior of this technique. However, most of the research focused on static loadings, and few studies concerning the cyclic loading were conducted. The aim of this study was to investigate the behavior of a piled embankment subjected to different traffic cyclic loadings. A three-dimensional numerical modeling using the finite-element method (FEM) was conducted with the use of Abaqus. An advanced constitutive soil model based on the hypoplasticity concept was used for granular soil and compared with the conventional one (a linear elastic-perfectly plastic model with the Mohr-Coulomb failure criterion) for aspects of static and cyclic loading. A high number of load cycles applied to a piled embankment was also considered in the study. The numerical results show that the hypoplastic model is better than the linear elastic-perfectly plastic model to deal with the soil-arching decrease and cumulative settlements under cyclic loading. In addition, the influence of the number of traffic load cycles, the vehicle speed, and the embankment height on the arching effect and the cumulative settlements is presented.
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Pham, H., Briancon, L., Dias, D., & Racinais, J. (2019). Investigation of behavior of footings over rigid inclusion-reinforced soft soil: experimental and numerical approaches. Canadian Geotechnical Journal, 56(12), 1940–1952.
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.
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Ramirez, M., Oxarango, L., & Strozzi, A. (2019). Effect of X-ray CT resolution on the quality of permeability computation for granular soils: definition of a criterion based on morphological properties. Soil Research, 57(6), 589–600.
Abstract: In this study, the quality of soil permeability estimation based on computational fluid dynamics is discussed. Two types of three-dimensional geometries were considered: an image of Fontainebleau sand obtained from X-ray computed micro-tomography and a virtual pack of spheres. Numerical methods such as finite difference or lattice Boltzmann can conveniently use the image voxels as computational mesh elements. In this framework, the image resolution is directly associated with quality of the numerical computation. A higher resolution should promote both a better morphological description and discretisation. However, increasing the resolution may prevent the studied volume from being representative. Here, each sample was scaled and analysed at five resolutions. The dependence of soil properties with respect to the image resolution is discussed. As resolution decreased, the permeability and specific surface values tended to diverge from the reference value. This deterioration could be attributed to the shift of the pore size distribution towards badly resolved pores in the voxelised geometry. As long as granular soils are investigated, the volume fraction of pores smaller than six voxels in diameter should not exceed 50% to ensure the validity of permeability computation. In addition, based on an analysis of flow distribution, the volume fraction of pores smaller than four voxels should not exceed 25% in order to limit the flow rate occurring in badly discretised pores under 10%. For the Fontainebleau sand and virtual pack of spheres, the maximum voxel size meeting this criterion corresponded to 1/14 and 1/20 of the mean grain size respectively.
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Samake, A., Jaffrezo, J., Favez, O., Weber, S., Jacob, V., Albinet, A., et al. (2019). Polyols and glucose particulate species as tracers of primary biogenic organic aerosols at 28 French sites. Atmospheric Chemistry And Physics, 19(5), 3357–3374.
Abstract: A growing number of studies are using specific primary sugar species, such as sugar alcohols or primary saccharides, as marker compounds to characterize and apportion primary biogenic organic aerosols (PBOAs) in the atmosphere. To better understand their annual cycles, as well as their spatiotemporal abundance in terms of concentrations and sources, we conducted a large study focusing on three major atmospheric primary sugar compounds (i.e., arabitol, mannitol, and glucose) measured in various environmental conditions for about 5300 filter samples collected at 28 sites in France. Our results show significant atmospheric concentrations of polyols (defined here as the sum of arabitol and mannitol) and glucose at each sampling location, highlighting their ubiquity. Results also confirm that polyols and glucose are mainly associated with the coarse rather than the fine aerosol mode. At nearly all sites, atmospheric concentrations of polyols and glucose display a well-marked seasonal pattern, with maximum concentrations from late spring to early autumn, followed by an abrupt decrease in late autumn, and a minimum concentration during wintertime. Such seasonal patterns support biogenic emissions associated with higher biological metabolic activities (sporulation, growth, etc.) during warmer periods. Results from a previous comprehensive study using positive matrix factorization (PMF) based on an extended aerosol chemical composition dataset of up to 130 species for 16 of the same sample series have also been used in the present work. The polyols-to-PMPBOA ratio is 0.024 +/- 0.010 on average for all sites, with no clear distinction between traffic, urban, or rural typology. Overall, even if the exact origin of the PBOA source is still under investigation, it appears to be an important source of particulate matter (PM), especially during summertime. Results also show that PBOAs are significant sources of total organic matter (OM) in PM10 (13 +/- 4% on a yearly average, and up to 40% in some environments in summer) at most of the investigated sites. The mean PBOA chemical profile is clearly dominated by contribution from OM (78 +/- 9% of the mass of the PBOA PMF on average), and only a minor contribution from the dust class (3 +/- 4 %), suggesting that ambient polyols are most likely associated with biological particle emissions (e.g., active spore discharge) rather than soil dust resuspension.
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Samake, A., Jaffrezo, J., Favez, O., Weber, S., Jacob, V., Canete, T., et al. (2019). Arabitol, mannitol, and glucose as tracers of primary biogenic organic aerosol: the influence of environmental factors on ambient air concentrations and spatial distribution over France. Atmospheric Chemistry And Physics, 19(16), 11013–11030.
Abstract: The primary sugar compounds (SCs, defined as glucose, arabitol, and mannitol) are widely recognized as suitable molecular markers to characterize and apportion primary biogenic organic aerosol emission sources. This work improves our understanding of the spatial behavior and distribution of these chemical species and evidences their major effective environmental drivers. We conducted a large study focusing on the daily (24 h) PM10 SC concentrations for 16 increasing space scale sites (local to nationwide), over at least 1 complete year. These sites are distributed in several French geographic areas of different environmental conditions. Our analyses, mainly based on the examination of the short-term evolutions of SC concentrations, clearly show distance-dependent correlations. SC concentration evolutions are highly synchronous at an urban city scale and remain well correlated throughout the same geographic regions, even if the sites are situated in different cities. However, sampling sites located in two distinct geographic areas are poorly correlated. Such a pattern indicates that the processes responsible for the evolution of the atmospheric SC concentrations present a spatial homogeneity over typical areas of at least tens of kilometers. Local phenomena, such as the resuspension of topsoil and associated microbiota, do no account for the major emissions processes of SC in urban areas not directly influenced by agricultural activities. The concentrations of SC and cellulose display remarkably synchronous temporal evolution cycles at an urban site in Grenoble, indicating a common source ascribed to vegetation. Additionally, higher concentrations of SC at another site located in a crop field region occur during each harvest periods, indicating resuspension processes of plant materials (crop detritus, leaf debris) and associated microbiota for agricultural and nearby urbanized areas. Finally, ambient air temperature, relative humidity, and vegetation density constitute the main effective drivers of SC atmospheric concentrations.
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Sarret, G., Guedron, S., Acha, D., Bureau, S., Arnaud-Godet, F., Tisserand, D., et al. (2019). Extreme Arsenic Bioaccumulation Factor Variability in Lake Titicaca, Bolivia. Scientific Reports, 9.
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.
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Shiota, E., Mukunoki, T., Oxarango, L., Tinet, A., & Golfier, F. (2019). Micro- and macro-scale water retention properties of granular soils: contribution of the X-Ray CT-based voxel percolation method. Soil Research, 57(6), 575–588.
Abstract: Water retention in granular soils is a key mechanism for understanding transport processes in the vadose zone for various applications from agronomy to hydrological and environmental sciences. The macroscopic pattern of water entrapment is mainly driven by the pore-scale morphology and capillary and gravity forces. In the present study, the drainage water retention curve (WRC) was measured for three different granular materials using a miniaturised hanging column apparatus. The samples were scanned using X-ray micro-computed tomography during the experiment. A segmentation procedure was applied to identify air, water and solid phases in 3D at the pore-scale. A representative elementary volume analysis based on volume and surface properties validated the experimental setup size. A morphological approach, the voxel percolation method (VPM) was used to model the drainage experiment under the assumption of capillary-dominated quasi-static flow. At the macro-scale, the VPM showed a good capability to predict the WRC when compared with direct experimental measurements. An in-depth comparison with image data also revealed a satisfactory agreement concerning both the average volumetric distributions and the pore-scale local topology. Image voxelisation and the quasi-static assumption of VPM are likely to explain minor discrepancies observed at low suctions and for coarser materials.
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Thanh-Nho, N., Mrchand, C., Strady, E., Vinh, T., & Nhu-Trang, T. (2019). Metals geochemistry and ecological risk assessment in a tropical mangrove (Can Gio, Vietnam). Chemosphere, 219, 365–382.
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.
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Uber, M., Legout, C., Nord, G., Crouzet, C., Demory, F., & Poulenard, J. (2019). Comparing alternative tracing measurements and mixing models to fingerprint suspended sediment sources in a mesoscale Mediterranean catchment. Journal Of Soils And Sediments, 19(9), 3255–3273.
Abstract: Purpose Knowledge of suspended sediment provenance in mesoscale catchments is important for applying erosion control measures and best management practices as well as for understanding the processes controlling sediment transport in the critical zone. As suspended sediment fluxes are highly variable in time, particularly given the variability of soil and rainfall properties in mesoscale catchments, knowledge of sediment provenance at high temporal resolution is crucial. Materials and methods Suspended sediment fluxes were analyzed at the outlet of a 42-km(2) Mediterranean catchment belonging to the French critical zone observatory network (OZCAR). Spatial origins of the suspended sediments were analyzed at high temporal resolution using low-cost analytical approaches (color tracers, X-ray fluorescence, and magnetic susceptibility). As the measurements of magnetic susceptibility provide only one variable, they were used for cross-validation of the results obtained with the two alternative tracing methods. The comparison of the tracer sets and three mixing models (non-negative least squares, Bayesian mixing model SIMMR, and partial least squares regression) allowed us to estimate different sources of errors inherent in sediment fingerprinting studies and to assess the challenges and opportunities of using these fingerprinting methods. Results and discussion All tracer sets and mixing models could identify marly badlands as the main source of suspended sediments. However, the percentage of source contributions varied between the 11 flood events in the catchment. The mean contribution of the badlands varied between 74 and 84%; the topsoils on sedimentary geology ranged from 12 to 29% and the basaltic topsoils from 1 to 8%. While for some events the contribution remained constant, others showed a high within-event variability of the sediment provenance. Considerable differences in the predicted contributions were observed when different tracer sets (mean RMSE 19.9%) or mixing models (mean RMSE 10.1%) were used. Our result shows that the choice of the tracer set was more important than the choice of the mixing model. Conclusions These results highlighted the importance of using multi-tracer multi-model approaches for sediment fingerprinting in order to obtain reliable estimates of source contributions. As a given fingerprinting approach might be more sensitive to one type of error, i.e., source variability, particle size selectivity, multi-tracer ensemble predictions allow to detect and quantify these potential biases. High sampling resolution realized with low-cost methods is important to reveal within- and between-event dynamics of sediment fluxes and to obtain reliable information of main contributing sources.
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Vijayasarathy, S., Baduel, C., Hof, C., Bell, I., Ramos, M., Ramos, M., et al. (2019). Multi-residue screening of non-polar hazardous chemicals in green turtle blood from different foraging regions of the Great Barrier Reef. Science Of The Total Environment, 652, 862–868.
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.
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Alcayaga, H. A., Mao, L. C., & Belleudy, P. (2018). Predicting the geomorphological responses of gravel-bed rivers to flow and sediment source perturbations at the watershed scale: an application in an Alpine watershed. Earth Surface Processes And Landforms, 43(4), 894–908.
Abstract: Predicting morphological channel changes using physically-based models requires extended data for the description of the river channel and for hydrological and sedimentological inputs. At the watershed scale, these data are usually scarce, and such a refined modeling is typically difficult to build. A simpler modeling of the morphological impacts due to the changes in the principal drivers that control channel shape and dynamics is more adaptable. In this study we focused on the morphological responses of gravel-bed rivers to flow and sediment source perturbation at watershed scale. The aim is to develop and test a tool capable of semi-quantitatively predicting the morphological river response at the watershed scale due to a set of spatially distributed perturbations. The model considers flow regime (Q) and sediment supply (S) as the two main factors controlling the fluvial morphology in alluvial rivers. Two indicators have been proposed to evaluate the alteration on Q and S, and they are illustrated as vectors on each reach of the river network. The magnitude of the vectors corresponds to the intensity of the perturbation and its direction represents the changing trend that nine selected morphological variables (bed elevation, slope, width, depth, wetted area, width to depth ratio, d50, terrace formation, and colonization of vegetation) are likely to follow from an initial state. The trends or trajectories of changes were assessed based on empirical relations, case studies, and conceptual models. This method was applied to the Isere watershed (5700 km(2)) at Grenoble (France), a river that hosts large and complex hydropower plant systems constructed during 50s -70s. The predictions over 23 river reaches and eight variables were evaluated in the range where the model was capable of predicting the morphological evolution of the river system. Its performance was verified and in the majority of the cases the results were coherent with field surveys and previous observations. The results indicate that this is a complex problem which needs more careful consideration of constraints that are difficult to assess, such as simultaneous and different sources of perturbations, hypotheses of initial dynamic equilibrium, and sediment supply quantification. Copyright (c) 2017 John Wiley & Sons, Ltd.
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Amponsah, W., Ayral, P., Boudevillain, B., Bouvier, C., Braud, I., Brunet, P., et al. (2018). Integrated high-resolution dataset of high-intensity European and Mediterranean flash floods. Earth System Science Data, 10(4), 1783–1794.
Abstract: This paper describes an integrated, high-resolution dataset of hydro-meteorological variables (rainfall and discharge) concerning a number of high-intensity flash floods that occurred in Europe and in the Mediterranean region from 1991 to 2015. This type of dataset is rare in the scientific literature because flash floods are typically poorly observed hydrological extremes. Valuable features of the dataset (hereinafter referred to as the EuroMedeFF database) include (i) its coverage of varied hydro-climatic regions, ranging from Continental Europe through the Mediterranean to Arid climates, (ii) the high space-time resolution radar rainfall estimates, and (iii) the dense spatial sampling of the flood response, by observed hydrographs and/or flood peak estimates from post-flood surveys. Flash floods included in the database are selected based on the limited upstream catchment areas (up to 3000 km(2)), the limited storm durations (up to 2 days), and the unit peak flood magnitude. The EuroMedeFF database comprises 49 events that occurred in France, Israel, Italy, Romania, Germany and Slovenia, and constitutes a sample of rainfall and flood discharge extremes in different climates. The dataset may be of help to hydrologists as well as other scientific communities because it offers benchmark data for the identification and analysis of the hydro-meteorological causative processes, evaluation of flash flood hydrological models and for hydro-meteorological forecast systems. The dataset also provides a template for the analysis of the space-time variability of flash flood triggering rainfall fields and of the effects of their estimation on the flood response modelling.
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Archundia, D., Boithias, L., Duwig, C., Morel, M. C., Aviles, G. F., & Martins, J. M. F. (2018). Environmental fate and ecotoxicological risk of the antibiotic sulfamethoxazole across the Katari catchment (Bolivian Altiplano): Application of the GREAT-ER model. Science Of The Total Environment, 622, 1046–1055.
Abstract: Antibiotics are emergent contaminants that can induce adverse effects in terrestrial and aquatic organisms. The surface water compartment is of particular concern as it receives direct waste water discharge. Modeling is highlighted as an essential tool to understand the fate and behavior of these compounds and to assess their eco-toxicological risk. This study aims at testing the ability of the GREAT-ER model in simulating sulfamethoxazole (SMX) concentrations in the surface waters of the arid high-altitude Katari catchment (Bolivian Altiplano), assessing the sensitivity of the parameters considered, and evaluating the ecotoxicological risk posed. The model predicted the general spatial pattern of SMX concentrations. No contaminant abatement was observed during the wet season, supporting the idea that non-point sources, such as runoff and remobilization processes, play an important role during that season. During the dry season, the abatement capacity was 91%, suggesting that natural attenuation, particularly photodegradation, is high during low flow. Pharmaceutical consumption was the parameter that influenced the environmental concentrations the most. The ratio of Predicted Environmental Concentrations to predicted no-effect concentrations varied between 0.14 and 26.6 for the wet season and between 0.14 and 7.6 for the dry season depending on the river stretch. (c) 2017 Elsevier B.V. All rights reserved.
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Barraza, F., Maurice, L., Uzu, G., Becerra, S., Lopez, F., Ochoa-Herrera, V., et al. (2018). Distribution, contents and health risk assessment of metal(loid)s in small-scale farms in the Ecuadorian Amazon: An insight into impacts of oil activities. Science Of The Total Environment, 622, 106–120.
Abstract: In the last 50 years, oil extraction activities in the Northeast Amazonian Region (NAR) of Ecuador impacted ecosystems and may still affect the local population health. To our knowledge, no previous studies have determined the concentrations of metal(loid)s in the oil Ecuadorian Amazon environment. A total of 15 small farms, located in the Orellana and Sucumbios provinces, were sampled in order to determine the concentrations of As, Ba, Co, Cu, Cd, Cr, Mn, Mo, Ni, Pb, V and Zn in soils, crops, drinking water and air (PM10). Among non-essential metal(loid) s, Ba concentrations in soils exceeded the Ecuadorian limits of 200 mg kg(-1) in 53% of the sampling sites. In crops, Cd concentrations in cacao and Pb in manioc exceeded the FAO/WHO recommendations. In drinking water and PM10, regulated metal(loid) s did not exceed the international thresholds. Nevertheless metals such as Ba and Mo showed the highest annual mean concentrations in PM10 in both sampling sites. Natural (bedrock, volcanic ashes) and anthropogenic (oil activities, agrochemical products) sources could explain the high content of some meta(loid) s in the environment. According to the hazard quotient and cancer risk indexes, crops and water ingestion represent 71% and 88% of the exposure pathways for non-carcinogenic elements in adults and children respectively while inhalation is the main exposure pathways for carcinogenic elements for the whole population. Both indexes were 2 to 13 times higher than the US EPA recommended values. However, estimates of exposure pathways should be considered taking into account the risk perception of residents: they may be overestimated for people who are able to change their dietary and/or agricultural practices to limit their exposure, or underestimated in the case of persons who are socio-economically vulnerable and who cannot leave the impacted areas. (c) 2017 Elsevier B.V. All rights reserved.
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Bievre, G., Oxarango, L., Gunther, T., Goutaland, D., & Massardi, M. (2018). Improvement of 2D ERT measurements conducted along a small earth-filled dyke using 3D topographic data and 3D computation of geometric factors. Journal Of Applied Geophysics, 153, 100–112.
Abstract: In the framework of earth-filled dykes characterization and monitoring, Electrical Resistivity Tomography (ERT) turns out to be a commonly used method. 2D sections are generally acquired along the dyke crest thus putting forward the question of 3D artefacts in the inversion process. This paper proposes a methodology based on 3D direct numerical simulations of the ERT acquisition using a realistic topography of the study site. It allows computing ad hoc geometrical factors which can be used for the inversion of experimental ERT data. The method is first evaluated on a set of synthetic dyke configurations. Then, it is applied to experimental static and time-lapse ERT data set acquired before and after repair works carried out on a leaking zone of an earth-filled canal dyke in the centre of France. The computed geometric factors are lower than the analytic geometric factors in a range between -8% and -18% for measurements conducted on the crest of the dyke. They exhibit a maximum under-estimation for intermediate electrode spacings in the Wenner and Schlumberger configurations. In the same way, for measurements conducted on the mid-slope of the dyke, the computed geometric factors are higher for short electrode spacings (+18%) and lower for lower for large electrode spacings (-8%). The 2D inversion of the synthetic data with these computed geometric factors provides a significant improvement of the agreement with the original resistivity. Two experimental profiles conducted on the same portion of the dyke but at different elevations also reveal a better agreement using this methodology. The comparison with apparent resistivity from EM31 profiling along the stretch of the dyke also supports this evidence. In the same way, some spurious effects which affected the time-lapse data were removed and improved the global readability of the time-lapse resistivity sections. The benefit on the structural interpretation of ERT images remains moderate but allows a better delineation of the repair work location. Therefore, and even if the 2D assumption cannot be considered valid in such a context, the proposed methodology could be applied easily to any dyke or strongly 3D-shaped structure using a realistic topographic model. It appears suitable for practical application. (C) 2018 Elsevier B.V. All rights reserved.
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Bourgeois, I., Savarino, J., Nemery, J., Caillon, N., Albertin, S., Delbart, F., et al. (2018). Atmospheric nitrate export in streams along a montane to urban gradient. Science Of The Total Environment, 633, 329–340.
Abstract: Nitrogen (N) emissions associated with urbanization exacerbate the atmospheric N influx to remote ecosystems – like mountains -, leading to well-documented detrimental effects on ecosystems (e.g., soil acidification, pollution of freshwaters). Here, the importance and fate of N deposition in a watershed was evaluated along a montane to urban gradient, using a multi-isotopic tracers approach (Delta O-17, delta N-15, delta O-18 of nitrate, delta H-2 and delta O-18 of water). In this setting, the montane streams had higher proportions of atmospheric nitrate compared to urban streams, and exported more atmospheric nitrate on a yearly basis (0.35 vs 0.10 kg-N ha(-1) yr(-1)). In urban areas, nitrate exports were driven by groundwater, whereas in the catchment head nitrate exports were dominated by surface runoff. The main sources of nitrate to the montane streams were microbial nitrification and atmospheric deposition, whereas microbial nitrification and sewage leakage contributed most to urban streams. Based on the measurement of delta N-15 and delta O-18-NO3-, biological processes such as denitrification or N assimilation were not predominant in any streams in this study. The observed low delta N-15 and delta O-18 range of terrestrial nitrate (i.e., nitrate not coming from atmospheric deposition) in surface water compared to literature suggests that atmospheric deposition may be underestimated as a direct source of N. (c) 2018 Elsevier B.V. All rights reserved.
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Braunig, J., Baduel, C., Barnes, C., & Mueller, J. (2018). Leaching and bioavailability of selected perfluoroalkyl acids (PFAAs) from soil contaminated by firefighting activities. Science Of The Total Environment, 646, 471–479.
Abstract: Historical usage of aqueous film-forming foam (AFFF) at firefighting training grounds (FTGs) is a potential source of perfluoroalkyl acids (PFAAs) to the surrounding environment. In this study the leaching of PFAAs from field contaminated soil and their uptake into biota was investigated. Soil was sampled from FTGs at two airports and the total as well as the leachable concentration of 12 PFAAs was determined. A greenhouse study was carried out to investigate the uptake of PFAAs from soils into earthworms (Eisenia fetida) and wheat grass (Elymus scaber). Perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonate (PFHxS) were the most dominant PFAAs in all soils samples, with concentrations of PFOS reaching 13,400 ng/g. Leachable concentrations of PFOS and PFHxS reached up to 550 μg/L and 22 μg/L, respectively. In earthworms concentrations of PFOS reached 65,100 ng/g after a 28-day exposure period, while in wheat grass the highest concentration was measured for uptake of PFHxS (2,800 ng/g) after a 10-week growth-period. Bioaccumulation factors (BAFs) for earthworms ranged from 0.1 for perfluorohexanoic acid (PFHxA) to 23 for perfluorododecanoic acid (PFDoA) and initially showed a decreasing trend with increasing perfluoroalkyl chain length, followed by an increase with increasing perfluoroalkyl chain length for perfluoroalkyl carboxylic acids (PFCAs). In wheat grass the highest BAF was found for perfluorobutanoic acid (BAF=70), while the lowest was observed for perfluorononanoic acid (BAF=0.06). BAFs in wheat grass decreased with increasing perfluoroalkyl chain length for both PFCAs and perfluoroalkyl sulfonic acids (PFSAs). The results show that PFAAs readily leach from impacted soils and are bioaccumulated into earthworms and plants in an analyte dependent way. This shows considerable potential for PFAAs to move away from the original source either by leaching or uptake into ecological receptors, which may be a potential entry route into the terrestrial foodweb. (C) 2018 Elsevier B.V. All rights reserved.
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Calas, A., Uzu, G., Kelly, F. J., Houdier, S., Martins, J. M. F., Thomas, F., et al. (2018). Comparison between five acellular oxidative potential measurement assays performed with detailed chemistry on PM10 samples from the city of Chamonix (France). Atmospheric Chemistry And Physics, 18(11), 7863–7875.
Abstract: Many studies have demonstrated associations between exposure to ambient particulate matter (PM) and adverse health outcomes in humans that can be explained by PM capacity to induce oxidative stress in vivo. Thus, assays have been developed to quantify the oxidative potential (OP) of PM as a more refined exposure metric than PM mass alone. Only a small number of studies have compared different acellular OP measurements for a given set of ambient PM samples. Yet, fewer studies have compared different assays over a year-long period and with detailed chemical characterization of ambient PM. In this study, we report on seasonal variations of the dithiothreitol (DTT), ascorbic acid (AA), electron spin resonance (ESR) and the respiratory tract lining fluid (RTLF, composed of the reduced glutathione (GSH) and ascorbic acid (ASC)) assays over a 1-year period in which 100 samples were analyzed. A detailed PM10 characterization allowed univariate and multivariate regression analyses in order to obtain further insight into groups of chemical species that drive OP measurements. Our results show that most of the OP assays were strongly intercorrelated over the sampling year but also these correlations differed when considering specific sampling periods (cold vs. warm). All acellular assays are correlated with a significant number of chemical species when considering univariate correlations, especially for the DTT assay. Evidence is also presented of a seasonal contrast over the sampling period with significantly higher OP values during winter for the DTT, AA, GSH and ASC assays, which were assigned to biomass burning species by the multiple linear regression models. The ESR assay clearly differs from the other tests as it did not show seasonal dynamics and presented weaker correlations with other assays and chemical species.
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Divya, P. V., Viswanadham, B. V. S., & Gourc, J. P. (2018). Hydraulic conductivity behaviour of soil blended with geofiber inclusions. Geotextiles And Geomembranes, 46(2), 121–130.
Abstract: Efficiency of fiber reinforcements to ensure the sealing efficiency of the landfill cap soil barriers so as to isolate the waste from the environment was demonstrated in the present study. Evaluation of hydraulic conductivity of soil barrier materials with different types of fibers, fiber dosage and fiber lengths are very important to ensure the sealing efficiency of the fiber reinforced soil barriers. An attempt was made to evaluate the hydraulic conductivity of the soil barrier material at a known effective stress using a flexible wall permeameter. Soil samples of 100 mm diameter and 100 mm height were prepared and tested in the present study. In all the cases, the hydraulic conductivity test phase was started after the completion of initialisation, saturation and isotropic consolidation phases of the soil samples. In the present study, seventeen (17) hydraulic conductivity tests were conducted on two different soil types for studying the influence of fiber content, fiber length and fiber type on the hydraulic conductivity of fiber reinforced soil. The fiber content, f used were 0.25%, 0.50% and 0.75% and the fiber lengths, l were 30 mm, 60 mm and 90 mm. Two types of fibers namely polyester (PET) fibers and polypropylene tape (PP-T) fibers were used for hydraulic conductivity tests. The repeatability of test results was also demonstrated. As the fiber content and fiber length were increased, initially there was a marginal decrease in hydraulic conductivity of the soil and thereafter marginally increased. Short fibers and low fiber contents were found to have greater influence in reducing the hydraulic conductivity of the soil and the variation was found to depend on the soil type also. Even with long fibers, the hydraulic conductivity of selected barrier material remained within the permissible limit required for a barrier material. The hydraulic conductivity of PP-T fiber reinforced soil is more, compared to hydraulic conductivity of PET fiber reinforced soil at all the fiber contents varied in the present study. The use of Scanning Electron Microscopy (SEM) is also attempted for the interpretation of the results.
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Gaillardet, J., Braud, I., Hankard, F., Anquetin, S., Bour, O., Dorfliger, N., et al. (2018). OZCAR: The French Network of Critical Zone Observatories. Vadose Zone Journal, 17(1).
Abstract: The French critical zone initiative, called OZCAR (Observatoires de la Zone Critique-Application et Recherche or Critical Zone Observatories-Application and Research) is a National Research Infrastructure (RI). OZCAR-RI is a network of instrumented sites, bringing together 21 pre-existing research observatories monitoring different compartments of the zone situated between “the rock and the sky,” the Earth's skin or critical zone (CZ), over the long term. These observatories are regionally based and have specific initial scientific questions, monitoring strategies, databases, and modeling activities. The diversity of OZCAR-RI observatories and sites is well representative of the heterogeneity of the CZ and of the scientific communities studying it. Despite this diversity, all OZCAR-RI sites share a main overarching mandate, which is to monitor, understand, and predict (“earthcast”) the fluxes of water and matter of the Earth's near surface and how they will change in response to the “new climatic regime.” The vision for OZCAR strategic development aims at designing an open infrastructure, building a national CZ community able to share a systemic representation of the CZ, and educating a new generation of scientists more apt to tackle the wicked problem of the Anthropocene. OZCAR articulates around: (i) a set of common scientific questions and cross-cutting scientific activities using the wealth of OZCAR-RI observatories, (ii) an ambitious instrumental development program, and (iii) a better interaction between data and models to integrate the different time and spatial scales. Internationally, OZCAR-RI aims at strengthening the CZ community by providing a model of organization for pre-existing observatories and by offering CZ instrumented sites. OZCAR is one of two French mirrors of the European Strategy Forum on Research Infrastructure (eLTER-ESFRI) project.
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Garnier, J., Ramarson, A., Thieu, V., Nemery, J., Thery, S., Billen, G., et al. (2018). How can water quality be improved when the urban waste water directive has been fulfilled? A case study of the Lot river (France). Environmental Science And Pollution Research, 25(12), 11924–11939.
Abstract: The Lot river, a major tributary of the downstream Garonne river, the largest river on the Northern side of the Pyrenees Mountains, was intensively studied in the 1970s. A pioneering program called “Lot RiviSre Claire” provided a diagnosis of water quality at the scale of the whole watershed and proposed an ambitious program to manage nutrient pollution and eutrophication largely caused by urban wastewater releases. Later on, the implementation of European directives from 1991 to 2000 resulted in the nearly complete treatment of point sources of pollution in spite of a doubling of the basin's population. At the outlet of the Lot river, ammonium and phosphate contamination which respectively peaked to 1 mg N-NH4 L-1 and 0.3 mg P-PO4 L-1 in the 1980s returned to much lower levels in recent years (0.06 mg N-NH4 L-1 and 0.02 mg P-PO4 L-1), a reduction by a factor 15. However, during this time, nitrate contamination has regularly increased since the 1980s, from 0.5 to 1.2 mg N-NO3 L-1 in average, owing to the intensification of agriculture and livestock farming. Application of the Riverstrahler model allowed us to simulate the water quality of the Lot drainage network for the 2002-2014 period. We showed that, with respect to algal requirements, phosphorus and silica are well balanced, but nitrogen remains largely in excess over phosphorus and silica. This imbalance can be problematic for the ecological status of the water bodies. Using the model, for simulating various scenarios of watershed management, we showed that improvement of urban wastewater treatment would not result in any significant change in the river's water quality. Even though arable land occupies a rather limited fraction of the watershed area, only the adoption of better farming practices or more radical changes in the agro-food system could reverse the trend of increasing nitrate contamination.
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He, C., Wang, X., Tang, S., Thai, P., Li, Z., Baduel, C., et al. (2018). Concentrations of Organophosphate Esters and Their Specific Metabolites in Food in Southeast Queensland, Australia: Is Dietary Exposure an Important Pathway of Organophosphate Esters and Their Metabolites? Environmental Science & Technology, 52(21), 12765–12773.
Abstract: There were several studies that measured organophosphate esters (OPEs) in foods to assess the dietary intake of OPEs but none has measured OPE metabolites (mOPEs) in the same samples. In this study, we measured the concentrations of OPEs and mOPEs in 87 food samples and in five tap water samples collected in Queensland, Australia belonging to eight food groups. Tris(2-chloroisopropyl) phosphate (TCIPP) (detection frequency (DF), 77%) and tributyl phosphate (TBP) (DF, 71%), were the most frequently detected OPEs, while dibutyl phosphate (DBP) (DF, 84%) and diphenyl phosphate (DPhP) (DF, 86%) were the most frequently detected mOPEs. Vegetables had the highest concentrations of both Sigma 9OPEs and Sigma(11)mOPEs, with the mean concentrations of 2.6 and 17 ng/g wet weight. Compared with dust ingestion and inhalation, dietary intake was the most important exposure pathway for tris(2-chloroethyl) phosphate (TCEP) (4.1 ng/kg bw/day), TCIPP (25 ng/kg bw/day), and TBP (6.7 ng/kg bw/day), accounting for >75% of total intake. Furthermore, we found that the intakes of some mOPEs, that is, bis(1,3-dichloroisopropyl) phosphate (BDCIPP) and DPhP from diet were typically higher than that of their parent OPEs. Such high levels of mOPE intakes could interfere with the utilization of mOPEs as biomarkers for assessing OPE exposure and warrant further investigation.
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Hoang, H. T. T., Duong, T. T., Nguyen, K. T., Le, Q. T. P., Luu, M. T. N., Trinh, D. A., et al. (2018). Impact of anthropogenic activities on water quality and plankton communities in the Day River (Red River Delta, Vietnam). Environmental Monitoring And Assessment, 190(2).
Abstract: Plankton are a major component of food web structure in aquatic ecosystems. Their distribution and community structure are driven by the combination and interactions between physical, chemical, and biological factors within the environment. In the present study, water quality and the community structure of phytoplankton and zooplankton were monthly investigated from January to December 2015 at 11 sampling sites along the gradient course of the Day River (Red River Delta, northern Vietnam). The study demonstrated that the Day River was eutrophic with the average values of total phosphorus concentration 0.17 mg/L, total nitrogen concentration 1.98 mg/L, and Chl a 54 μg/L. Microscopic plankton analysis showed that phytoplankton comprised 87 species belonging to seven groups in which Chlorophyceae, Bacillariophyceae, and Cyanobacteria accounted for the most important constituents of the river's phytoplankton assemblage. A total 53 zooplankton species belonging to three main groups including Copepoda, Cladocera, and Rotatoria were identified. Plankton biomass values were greatest in rainy season (3002.10-3 cell/L for phytoplankton and 12.573 individuals/m(3) for zooplankton). Using principal correspondence and Pearson correlation analyses, it was found that the Day River was divided into three main site groups based on water quality and characteristics of plankton community. Temperature and nutrients (total phosphorus and total nitrogen) are key factors regulating plankton abundance and distribution in the Day River.
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Lahens, L., Strady, E., Kieu-Le, T. C., Dris, R., Boukerma, K., Rinnert, E., et al. (2018). Macroplastic and microplastic contamination assessment of a tropical river (Saigon River, Vietnam) transversed by a developing megacity. Environmental Pollution, 236, 661–671.
Abstract: Both macroplastic and microplastic contamination levels were assessed for the first time in a tropical river estuary system, i.e. the Saigon River, that traverses a developing South East Asian megacity, i.e. Ho Chi Minh City, Vietnam. The analysis of floating debris collected daily on the Nhieu Loc – Thi Nghe canal by the municipal waste management service shows that the plastic mass percentage represents 11-43%, and the land-based plastic debris entering the river was estimated from 0.96 to 19.91 g inhabitant(-1) d(-1), namely 350 to 7270 g inhabitant(-1) yr(-1). Microplastics were assessed in the Saigon River and in four urban canals by sampling bulk water for anthropogenic fiber analysis and 300 gm mesh size plankton net exposition for fragment analysis. Fibers and fragments are highly concentrated in this system, respectively 172,000 to 519,000 items m(-3) and 10 to 223 items(-3). They were found in various colors and shapes with smallest size and surface classes being predominant. The macroplastics and fragments were mainly made of polyethylene and polypropylene while the anthropogenic fibers were mainly made of polyester. The relation between macroplastic and microplastic concentrations, waste management, population density and water treatment are further discussed. (C) 2018 Elsevier Ltd. All rights reserved.
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Legout, C., Droppo, I. G., Coutaz, J., Bel, C., & Jodeau, M. (2018). Assessment of erosion and settling properties of fine sediments stored in cobble bed rivers: the Arc and Isere alpine rivers before and after reservoir flushing. Earth Surface Processes And Landforms, 43(6), 1295–1309.
Abstract: Cohesive sediment dynamics in mountainous rivers is poorly understood even though these rivers are the main providers of fine particles to the oceans. Complex interactions exist between the coarse matrix of cobble bed rivers and fine sediments. Given that fine sediment load in such environments can be very high due to intense natural rainfall or snowmelt events and to man-induced reservoir or dam flushing, a better understanding of the deposition and sedimentation processes is needed in order to reduce ecohydrological downstream impacts. We tested a field-based approach on the Arc and Isere alpine rivers combining measurements of erosion and settling properties of river bed deposits before and after a dam flushing, with the U-GEMS (Gust Erosion Microcosm System) and SCAF (System Characterizing Aggregates and Flocs), respectively. These measurements highlight that critical shears, rates of erosion, settling velocities and propensity of particles to flocculate are highly variable in time and space. This is reflective of the heterogeneity of the hydrodynamic conditions during particle settling, local bed roughness, and nature and size of particles. Generally the deposits were found to be stable relative to what is measured in lowland rivers. It was, however, not possible to make a conclusive assessment of the extent to which the dynamics of deposits after reservoir flushing were different from those settled after natural events. The absence of any relationships between erosion and deposition variables, making it impossible to predict one from another, underlined the need to measure all of them to have a full assessment of the fine sediment dynamics and to obtain representative input variables for numerical models. While the SCAF was found to be effective, an alternative to the U-GEMS device will have to be found for the erodibility assessment in cobble bed rivers, in order to make more rapid measurements at higher shears. Copyright (C) 2017 John Wiley & Sons, Ltd.
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Petrut, T., Geay, T., Gervaise, C., Belleudy, P., & Zanker, S. (2018). Passive acoustic measurement of bedload grain size distribution using self-generated noise. Hydrology And Earth System Sciences, 22(1), 767–787.
Abstract: Monitoring sediment transport processes in rivers is of particular interest to engineers and scientists to assess the stability of rivers and hydraulic structures. Various methods for sediment transport process description were proposed using conventional or surrogate measurement techniques. This paper addresses the topic of the passive acoustic monitoring of bedload transport in rivers and especially the estimation of the bedload grain size distribution from self-generated noise. It discusses the feasibility of linking the acoustic signal spectrum shape to bedload grain sizes involved in elastic impacts with the river bed treated as a massive slab. Bedload grain size distribution is estimated by a regularized algebraic inversion scheme fed with the power spectrum density of river noise estimated from one hydrophone. The inversion methodology relies upon a physical model that predicts the acoustic field generated by the collision between rigid bodies. Here we proposed an analytic model of the acoustic energy spectrum generated by the impacts between a sphere and a slab. The proposed model computes the power spectral density of bedload noise using a linear system of analytic energy spectra weighted by the grain size distribution. The algebraic system of equations is then solved by least square optimization and solution regularization methods. The result of inversion leads directly to the estimation of the bedload grain size distribution. The inversion method was applied to real acoustic data from passive acoustics experiments realized on the Isere River, in France. The inversion of in situ measured spectra reveals good estimations of grain size distribution, fairly close to what was estimated by physical sampling instruments. These results illustrate the potential of the hydrophone technique to be used as a standalone method that could ensure high spatial and temporal resolution measurements for sediment transport in rivers.
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Pham, H., Dias, D., Miranda, T., Cristelo, N., & Araujo, N. (2018). 3D Numerical Modeling of Foundation Solutions for Wind Turbines. International Journal Of Geomechanics, 18(12).
Abstract: With the current tendency to gradually increase the contribution of renewable energy to achieve significant proportions of the entire production, the wind farm construction rate is actually high. Because the location of the wind turbines (WTs) is dictated by factors usually independent of the foundation soil conditions, which are mostly based on energy production and consumption efficiency (e.g., average wind speeds, possibility of connecting to existing electrical networks, approval of authorities and local population, etc.), it is not uncommon for the construction sites to be unfavorable in terms of geotechnical demands. In these circumstances, the choice of the optimal foundation system is an important aspect in the design phase of a WT. The aim of this paper is to analyze, using three-dimensional (3D) numerical models and the suitability of currently available foundation solutions (based on a shallow foundation on the natural or improved ground), and compare the overall behavior with solutions based on rigid inclusions (RIs). The parametric study developed was based on a real soil profile, and all the foundation solutions are analyzed for realistic static WT loads. The assessment of the efficiency of each foundation system, as well as the subsequent comparative analysis, was performed in terms of the surface settlement on the foundation soil and the axial force and bending moment on the vertical reinforcements. (C) 2018 American Society of Civil Engineers.
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Serlet, A. J., Gurnell, A. M., Zolezzi, G., Wharton, G., Belleudy, P., & Jourdain, C. (2018). Biomorphodynamics of alternate bars in a channelized, regulated river: An integrated historical and modelling analysis. Earth Surface Processes And Landforms, 43(9), 1739–1756.
Abstract: The development of alternate bars in channelized rivers can be explained theoretically as an instability of the riverbed when the active channel width to depth ratio exceeds a threshold. However, the development of a vegetation cover on the alternate bars of some channelized rivers and its interactions with bar morphology have not been investigated in detail. Our study focused on the co-evolution of alternate bars and vegetation along a 33km reach of the Isere River, France. We analysed historical information to investigate the development of alternate bars and their colonization by vegetation within a straightened, embanked river subject to flow regulation, sediment mining, and vegetation management. Over an 80year period, bar density decreased, bar length increased, and bar mobility slowed. Vegetation encroachment across bar surfaces accompanied these temporal changes and, once established, vegetation cover persisted, shifting the overall system from an unvegetated to a vegetated dynamic equilibrium state. The unvegetated morphodynamics of the impressively regular sequence of alternate bars that developed in the Isere following channelization is consistent with previous theoretical morphodynamic work. However, the apparent triggering dynamics of vegetation colonization needs to be investigated, based on complex biophysical instability processes. If instability related to vegetation colonization is confirmed, further work needs to focus on the relevance of initial conditions for this instability, and on related feedback effects such as how the morphodynamics of bare-sediment alternate bars may have affected vegetation development and, in turn, how vegetation has created a new dynamic equilibrium state. Copyright (c) 2018 John Wiley & Sons, Ltd.
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Simonin, M., Cantarel, A., Crouzet, A., Gervaix, J., Martins, J., & Richaume, A. (2018). Negative Effects of Copper Oxide Nanoparticles on Carbon and Nitrogen Cycle Microbial Activities in Contrasting Agricultural Soils and in Presence of Plants. Frontiers In Microbiology, 9, 3102.
Abstract: Metal-oxide nanoparticles (NPs) such as copper oxide (CuO) NPs offer promising perspectives for the development of novel agro-chemical formulations of pesticides and fertilizers. However, their potential impact on agro-ecosystem functioning still remains to be investigated. Here, we assessed the impact of CuO-NPs (0.1, 1, and 100 mg/kg dry soil) on soil microbial activities involved in the carbon and nitrogen cycles in five contrasting agricultural soils in a microcosm experiment over 90 days. Additionally, in a pot experiment, we evaluated the influence of plant presence on the toxicity of CuO-NPs on soil microbial activities. CuO-NPs caused significant reductions of the three microbial activities measured (denitrification, nitrification, and soil respiration) at 100 mg/kg dry soil, but the low concentrations (0.1 and 1 mg/kg) had limited effects. We observed that denitrification was the most sensitive microbial activity to CuO-NPs in most soil types, while soil respiration and nitrification were mainly impacted in coarse soils with low organic matter content. Additionally, large decreases in heterotrophic microbial activities were observed in soils planted with wheat, even at 1 mg/kg for soil substrate-induced respiration, indicating that plant presence did not mitigate or compensate CuO-NP toxicity for microorganisms. These two experiments show that CuO-NPs can have detrimental effects on microbial activities in soils with contrasting physicochemical properties and previously exposed to various agricultural practices. Moreover, we observed that the negative effects of CuO-NPs increased over time, indicating that short-term studies (hours, days) may underestimate the risks posed by these contaminants in soils.
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Spadini, L., Navel, A., Martins, J., Vince, E., & Lamy, I. (2018). Soil aggregates: a scale to investigate the densities of metal and proton reactive sites of organic matter and clay phases in soil. European Journal Of Soil Science, 69(5), 953–961.
Abstract: Determining site density of reactive sites of metals in the main soil phases remains a challenging task. This study aimed to show that densities of reactive sites in soil may be assessed by a fractionation procedure based on soil being spatially organized as aggregates. The method is described with copper as a model trace element and a common silty loam soil after applying a low energy fractionation method to maintain the integrity of soil aggregates. The reactivity of five soil size fractions (>250, 250-63, 63-20, 20-2 and <2m) to protons and copper was quantified by acid-base titrations. The total proton sorption capacities were assigned to the total concentration of copper reactive sites and fitted to a linear combination of the relevant reactivity data of each phase, namely the total contents of organic carbon, copper and acid-extractable aluminium. Acid-base reactivity was linearly related to the distribution of copper, and differences between fractions were used to reconstruct the distribution of acid-base and copper-complexing sites among the clay, organic and weakly reactive residual phases. In accordance with our hypothesis that key reactive phases are mainly organic materials and clays, we used this procedure to determine the site densities of (i) two size classes of particulate organic matter, (ii) strongly reactive organic matter (e.g. soil humic and fulvic acids) and (iii) clay. The site densities and the distributions of copper obtained were used to validate our conceptual model for predicting global soil reactivity to metals. Highlights Precise site densities of key soil reactive phases are often lacking in transfer modelling We applied specific experimental methods of aggregate analysis and partial leaching of Al phases Site densities of the various types of organic matter were assessed using variably amended soils Soil aggregate analysis is powerful for determining base parameters in element transfer modelling
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Tano, B. F. G., Stoltz, G., Coulibaly, S. S., Bruhier, J., Dias, D., Olivier, F., et al. (2018). Large-scale tests to assess the efficiency of a geosynthetic reinforcement over a cavity. Geosynthetics International, 25(2), 242–258.
Abstract: This report presents a new large-scale test apparatus (LSTA) developed to assess the efficiency of a geosynthetic reinforcement for the limitation of deformations of a geosynthetic lining system (GLS) over a 0.5 m wide cavity. Two experiments were conducted. The first one involved a geosynthetic clay liner, a nonwoven needle-punched geotextile and a high-density polyethylene geomembrane. For the second experiment, a 50 kN/m polyvinyl alcohol geogrid was imbedded within the sand layer below the geosynthetic clay liner to provide reinforcement above the cavity. An overburden pressure varying from 10 to 100 kPa was applied to the top of the GLS. Strain gauges were used to measure the strain within the geogrid and the geomembrane. The results proved that the 50 kN/m geogrid reinforcement beneath the geomembrane reduced the maximum strain within the geomembrane, compared to the case where the geomembrane was unreinforced, by 25% on average. The results showed that the overall strain within the geomembrane was 31% to 42% less than that of the geogrid above the cavity. Finally, the results showed that the spatial distribution of the strain within the geomembrane and that of the geogrid differed because of a conical shape of the collapsed zone.
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Thanh-Nho, N., Strady, E., Nhu-Trang, T. T., David, F., & Marchand, C. (2018). Trace metals partitioning between particulate and dissolved phases along a tropical mangrove estuary (Can Gio, Vietnam). Chemosphere, 196, 311–322.
Abstract: Mangroves can be considered as biogeochemical reactors along (sub)tropical coastlines, acting both as sinks or sources for trace metals depending on environmental factors, In this study, we characterized the role of a mangrove estuary, developing downstream a densely populated megacity (Ho Chi Minh City, Vietnam), on the fate and partitioning of trace metals. Surface water and suspended particulate matter were collected at four sites along the estuarine salinity gradient during 24 h cycling in dry and rainy seasons. Salinity, pH, DO, TSS, POC, DOC, dissolved and particulate Fe, Mn, Cr, As, Cu, Ni, Co and Pb were measured. TSS was the main trace metals carrier during their transit in the estuary. However, TSS variations did not explain the whole variability of metals distribution. Mn, Cr and As were highly reactive metals while the other metals (Fe, Ni, Cu, Co and Pb) presented stable log K-D values along the estuary. Organic matter dynamic appeared to play a key role in metals fractioning. Its decomposition during water transit in the estuary induced metal desorption, especially for Cr and As. Conversely, dissolved Mn concentrations decreased along the estuary, which was suggested to result from Mn oxidative precipitation onto solid phase due to oxidation and pH changes. Extra sources as pore-water release, runoff from adjacent soils, or aquaculture effluents were suggested to be involved in trace metal dynamic in this estuary. In addition, the monsoon increased metal loads, notably dissolved and particulate Fe, Cr, Ni and Pb. (C) 2018 Elsevier Ltd. All rights reserved.
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Uber, M., Vandervaere, J., Zin, I., Braud, I., Heistermann, M., Legout, C., et al. (2018). How does initial soil moisture influence the hydrological response? A case study from southern France. Hydrology And Earth System Sciences, 22(12), 6127–6146.
Abstract: The Cevennes-Vivarais region in southern France is prone to heavy rainfall that can lead to flash floods which are one of the most hazardous natural risks in Europe. The results of numerous studies show that besides rainfall and physical catchment characteristics the catchment's initial soil moisture also impacts the hydrological response to rain events. The aim of this paper is to analyze the relationship between catchment mean initial soil moisture (theta) over bar (ini) and the hydrological response that is quantified using the event-based runoff coefficient phi(ev) in the two nested catchments of the Gazel (3.4 km(2)) and the Claduegne (43 km(2)). Thus, the objectives are twofold: (1) obtaining meaningful estimates of soil moisture at catchment scale from a dense network of in situ measurements and (2) using this estimate of (theta) over bar (ini) to analyze its relation with phi(ev) calculated for many runoff events. A sampling setup including 45 permanently installed frequency domain reflectancy probes that continuously measure soil moisture at three depths is applied. Additionally, on-alert surface measurements at approximate to 10 locations in each one of 11 plots are conducted. Thus, catchment mean soil moisture can be confidently assessed with a standard error of the mean of <= 1.7 vol% over a wide range of soil moisture conditions. The phi(ev) is calculated from high-resolution discharge and precipitation data for several rain events with a cumulative precipitation P-cum ranging from less than 5mm to more than 80 mm. Because of the high uncertainty of phi(ev) associated with the hydrograph separation method, phi(ev) is calculated with several methods, including graphical methods, digital filters and a tracer-based method. The results indicate that the hydrological response depends on (theta) over bar (ini): during dry conditions phi(ev) is consistently below 0.1, even for events with high and intense precipitation. Above a threshold of (theta) over bar (ini) = 34 vol % phi(ev) can reach values up to 0.99 but there is a high scatter. Some variability can be explained with a weak correlation of phi(ev) with P-cum and rain intensity, but a considerable part of the variability remains unexplained. It is concluded that threshold-based methods can be helpful to prevent overestimation of the hydrological response during dry catchment conditions. The impact of soil moisture on the hydrological response during wet catchment conditions, however, is still insufficiently understood and cannot be generalized based on the present results.
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Vachaud, G., Quertamp, F., Phan, T. S. H., Tran Ngoc, T. D., Nguyen, T., Luu, X. L., et al. (2018). Flood-related risks in Ho Chi Minh City and ways of mitigation. Journal of Hydrology, .
Abstract: With an ever-growing population of around 10 million inhabitants (officially 7.9 in 2013), Ho Chi Minh City (HCMC) is set to become one of the largest cities in South East Asia and already occupies a major economic role in the area. To accommodate the increasing population, the megacity now stretches out in an urban continuum covering more than 800 square kilometers and is currently growing at a rate of 3.2% per year. If the neighboring provinces around HCMC are included, the total population reaches nearly 18 million people. This paper attempts to describe the interplay between HCMC and flood-related risks and offer some guidelines to deal with inundations. The potential risks of flooding by rain, tsunami and/or dam failure upstream of the city are evaluated and contextualized within the perspective of climate and human-induced environmental changes. The region is highly vulnerable to the combined effects of subsidence and rising sea levels and has already led to serious flooding that may extend spatially before the end of the century. We propose possible preventative solutions to urban flooding using a multi-pronged approach to issues regarding urban development and suggest a redevelopment strategy for major infrastructure projects.
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Van Emmerik, T., Kieu-Le, T., Loozen, M., Van Oeveren, K., Strady, E., Bui, X., et al. (2018). A Methodology to Characterize Riverine Macroplastic Emission Into the Ocean. Frontiers In Marine Science, 5.
Abstract: Land-based macroplastic is considered one of the major sources of marine plastic debris. However, estimations of plastic emission from rivers into the oceans remain scarce and uncertain, mainly due to a severe lack of standardized observations. To properly assess global plastic fluxes, detailed information on spatiotemporal variation in river plastic quantities and composition are urgently needed. In this paper, we present a new methodology to characterize riverine macroplastic dynamics. The proposed methodology was applied to estimate the plastic emission from the Saigon River, Vietnam. During a 2-week period, hourly cross-sectional profiles of plastic transport were made across the river width. Simultaneously, sub-hourly samples were taken to determine the weight, size and composition of riverine macroplastics (>5 cm). Finally, extrapolation of the observations based on available hydrological data yielded new estimates of daily, monthly and annual macroplastic emission into the ocean. Our results suggest that plastic emissions from the Saigon River are up to four times higher than previously estimated. Importantly, our flexible methodology can be adapted to local hydrological circumstances and data availability, thus enabling a consistent characterization of macroplastic dynamics in rivers worldwide. Such data will provide crucial knowledge for the optimization of future mediation and recycling efforts.
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Weber, S., Uzu, G., Calas, A., Chevrier, F., Besombes, J. L., Charron, A., et al. (2018). An apportionment method for the oxidative potential of atmospheric particulate matter sources: application to a one-year study in Chamonix, France. Atmospheric Chemistry And Physics, 18(13), 9617–9629.
Abstract: Inhaled aerosolized particulate matter (PM) induces cellular oxidative stress in vivo, leading to adverse health outcomes. The oxidative potential (OP) of PM appears to be a more relevant proxy of the health impact of the aerosol rather than the total mass concentration. However, the relative contributions of the aerosol sources to the OP are still poorly known. In order to better quantify the impact of different PM sources, we sampled aerosols in a French city for one year (2014, 115 samples). A coupled analysis with detailed chemical speciation (more than 100 species, including organic and carbonaceous compounds, ions, metals and aethalometer measurements) and two OP assays (ascorbic acid, AA, and dithiothreitiol, DTT) in a simulated lung fluid (SLF) were performed in these samples. We present in this study a statistical framework using a coupled approach with positive matrix factorization (PMF) and multiple linear regression to attribute a redox-activity to PM sources. Our results highlight the importance of the biomass burning and vehicular sources to explain the observed OP for both assays. In general, we see a different contribution of the sources when considering the OP AA, OP DTT or the mass of the PM10. Moreover, significant differences are observed between the DTT and AA tests which emphasized chemical specificities of the two tests and the need of a standardized approach for the future studies on epidemiology or toxicology of the PM.
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Zaharia, L., Ioana-Toroimac, G., Morosanu, G. A., Galie, A. C., Moldoveanu, M., Canjevac, I., et al. (2018). Review of national methodologies for rivers' hydromorphological assessment: A comparative approach in France, Romania, and Croatia. Journal Of Environmental Management, 217, 735–746.
Abstract: Conducting hydromorphological assessments for evaluating the ecological status of rivers is a key requirement of the Directive 2000/60/EC (Water Framework Directive – WFD) within European Union (EU) Member States. This paper aims at understanding how this requirement was implemented, through an original comparative review of methodologies for rivers' hydromorphological assessment in three EU Member States, which joined the EU at different times, and with many differences in terms of hydro graphic features, socio-economic and water management systems: France, Romania, and Croatia. More precisely, the paper aims at identifying and understanding the main principles guiding the hydro morphological assessment methodologies, elements and data used, giving an overview of the results of hydromorphological river status assessment, and concluding on the stage of hydromorphological assessment implementation. France developed numerous methodologies for physical habitat survey since the 1990s and it is currently conducting a rigorous hydromorphological field survey, but it does not yet have any national methodology for rivers' hydromorphological status assessment, nevertheless foreseen for the next cycle of the WFD. Besides, Romania and Croatia have already started the assessment of the hydromorphological status of rivers within the two cycles of the River Basin Management Plans and are making efforts to improve the hydromorphological monitoring activity. The methods generally differ in indicators, data used, and spatial scale of analysis, which makes it difficult to compare the results of the assessments. Despite a common water policy, the methodological dissimilarities seem to be rather usual between EU Member States. Therefore, the standardization of methodologies appears to be necessary, but the current results could be useful for setting priorities for river restoration and for achieving a better status at a national scale. (C) 2018 Elsevier Ltd. All rights reserved.
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Archundia, D., Duwig, C., Lehembre, F., Chiron, S., Morel, M. C., Prado, B., et al. (2017). Antibiotic pollution in the Katari subcatchment of the Titicaca Lake: Major transformation products and occurrence of resistance genes. Science Of The Total Environment, 576, 671–682.
Abstract: An increasing number of studies pointed out the ubiquitous presence of medical residues in surface and ground water as well as in soil compartments. Not only antibiotics can be found in the environment but also their transformation products about which little information is generally available. The development of bacterial resistance to antibiotics is particularly worrying as it can lead to sanitary and health problems. Studies about the dissemination of antibiotics and associated resistances in the Bolivian Altiplano are scarce. We provide baseline information on the occurrence of Sulfamethoxazole (SMX) and Trimethoprim (TMP) antibiotics as well as on the most common human SMX transformation products (TP) and on the occurrence of sulfonamide resistance genes. The studied water and soil compartments presented high levels of antibiotic pollution. This situation was shown to be mainly linked with uncontrolled discharges of treated and untreated wastewaters, resulting on the presence of antibiotics in the Titicaca Lake. SMXTPs were detected in surface waters and on soil sampled next to the wastewater treatment plant (WWTP). SMX resistance genes sull and sulll were widely detected in the basin hydrological network, even in areas unpolluted with antibiotics. Mechanisms of co-selection of antibiotic-and metal-resistance may be involved in the prevalence of ARG's in pristine areas with no anthropogenic activity and free of antibiotic pollution. (C) 2016 Elsevier B.V. All rights reserved.
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Archundia, D., Duwig, C., Spadini, L., Uzu, G., Guedron, S., Morel, M. C., et al. (2017). How Uncontrolled Urban Expansion Increases the Contamination of the Titicaca Lake Basin (El Alto, La Paz, Bolivia). Water Air And Soil Pollution, 228(1).
Abstract: Cities in developing countries encounter rapid waves of social transformation and economic development where the environment is mostly a neglected aspect. The Katari watershed encompasses mining areas, El Alto city (one of the fastest growing urban areas in South America and the biggest in the Altiplano) as well as agricultural areas. Its outlet is Cohana Bay, one of the most polluted areas of Lake Titicaca. Here we propose an integrative approach (hydrological, physicochemical, chemical and bacterial data) to understand the pollution problem of this developing area, in which a variety of anthropogenic activities takes place. Both mining and urban areas appear to be sources of metal pollution. Nutrient and bacterial contaminations are mainly related to urban and industrial discharges. These situations have impacts in the basin from the mining area down to Cohana Bay of Lake Titicaca. Pollutant concentration patterns are highly influenced by seasonal hydrology variations. The poor quality of surface waters in the basin represents a risk for human and animal populations, as well as for the quality of aquifers located underneath El Alto city.
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Attard, G., Rossier, Y., & Eisenlohr, L. (2017). Underground structures increasing the intrinsic vulnerability of urban groundwater: Sensitivity analysis and development of an empirical law based on a groundwater age modelling approach. Journal Of Hydrology, 552, 460–473.
Abstract: In a previous paper published in Journal of Hydrology, it was shown that underground structures are responsible for a mixing process between shallow and deep groundwater that can favour the spreading of urban contamination. In this paper, the impact of underground structures on the intrinsic vulnerability of urban aquifers was investigated. A sensitivity analysis was performed using a 2D deterministic modelling approach based on the reservoir theory generalized to hydrodispersive systems to better understand this mixing phenomenon and the mixing affected zone (MAZ) caused by underground structures. It was shown that the maximal extent of the MAZ caused by an underground structure is reached approximately 20 years after construction. Consequently, underground structures represent a long-term threat for deep aquifer reservoirs. Regarding the construction process, draining operations have a major impact and favour large-scale mixing between shallow and deep groundwater. Consequently, dewatering should be reduced and enclosed as much as possible. The role played by underground structures' dimensions was assessed. The obstruction of the first aquifer layer caused by construction has the greatest influence on the MAZ. The cumulative impact of several underground structures was assessed. It was shown that the total MAZ area increases linearly with underground structures' density. The role played by materials' properties and hydraulic gradient were assessed. Hydraulic conductivity, anisotropy and porosity have the strongest influence on the development of MAZ. Finally, an empirical law was derived to estimate the MAZ caused by an underground structure in a bi-layered aquifer under unconfined conditions. This empirical law, based on the results of the sensitivity analysis developed in this paper, allows for the estimation of MAZ dimensions under known material properties and underground structure dimensions. This empirical law can help urban planners assess the area of influence of underground structures and protect urban strategic reservoirs. (C) 2017 Elsevier B.V. All rights reserved.
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Attard, G., Rossier, Y., Winiarski, T., & Eisenlohr, L. (2017). Urban underground development confronted by the challenges of groundwater resources: Guidelines dedicated to the construction of underground structures in urban aquifers. Land Use Policy, 64, 461–469.
Abstract: Urban subsoil provides space, groundwater, geothermal energy and geomaterials, and the importance underlying the management of this strategic space is well-known. In the context of vertical urban growth, groundwater management is a crucial issue. In particular, operational tools dedicated to urban planners are needed in urban areas prone to conflicts over use in order to aid the decision-making process. The aim of this paper is to propose guidelines dedicated to urban underground development in view to incorporating groundwater resource management. These guidelines are supported by analyses of the scientific literature dealing with: (1) the impacts caused by underground structures on urban groundwater, and (2) the quantitative overview of urban groundwater resources at the operational level in terms of quantity, quality and temperature. Finally, perspectives are discussed regarding the research work needed to ensure better management of urban groundwater resources confronted by underground development. (C) 2017 Elsevier Ltd. All rights reserved.
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Barraza, F., Schreck, E., Leveque, T., Uzu, G., Lopez, F., Ruales, J., et al. (2017). Cadmium bioaccumulation and gastric bioaccessibility in cacao: A field study in areas impacted by oil activities in Ecuador. Environmental Pollution, 229, 950–963.
Abstract: Cacao from South America is especially used to produce premium quality chocolate. Although the European Food Safety Authority has not established a limit for cadmium (Cd) in chocolate raw material, recent studies demonstrate that Cd concentrations in cacao beans can reach levels higher than the legal limits for dark chocolate (0.8 mg kg(-1), effective January 1st, 2019). Despite the fact that the presence of Cd in agricultural soils is related to contamination by fertilizers, other potential sources must be considered in Ecuador. This field study was conducted to investigate Cd content in soils and cacao cultivated on Ecuadorian farms in areas impacted by oil activities. Soils, cacao leaves, and pod husks were collected from 31 farms in the northern Amazon and Pacific coastal regions exposed to oil production and refining and compared to two control areas. Human gastric bioaccessibility was determined in raw cacao beans and cacao liquor samples in order to assess potential health risks involved. Our results show that topsoils (0-20 cm) have higher Cd concentrations than deeper layers, exceeding the Ecuadorian legislation limit in 39% of the sampling sites. Cacao leaves accumulate more Cd than pod husks or beans but, nevertheless, 50% of the sampled beans have Cd contents above 0.8 mg kg-1. Root-to-cacao transfer seems to be the main pathway of Cd uptake, which is not only regulated by physico-chemical soil properties but also agricultural practices. Additionally, natural Cd enrichment by volcanic inputs must not be neglected. Finally, Cd in cacao trees cannot be considered as a tracer of oil activities. Assuming that total Cd content and its bioaccessible fraction (up to 90%) in cacao beans and liquor is directly linked to those in chocolate, the health risk associated with Cd exposure varies from low to moderate. (C) 2017 Elsevier Ltd. All rights reserved.
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Bievre, G., Lacroix, P., Oxarango, L., Goutaland, D., Monnot, G., & Fargier, Y. (2017). Integration of geotechnical and geophysical techniques for the characterization of a small earth-filled canal dyke and the localization of water leakage. Journal Of Applied Geophysics, 139, 1–15.
Abstract: This paper investigates the combined use of extensive geotechnical, hydrogeological and geophysical techniques to assess a small earth dyke with a permanent hydraulic head, namely a canal embankment. The experimental site was chosen because of known issues regarding internal erosion and piping phenomena. Two leakages were visually located following the emptying of the canal prior to remediation works. The results showed a good agreement between the geophysical imaging techniques (Electrical Resistivity Tomography, P- and SH-waves Tomography) and the geotechnical data to detect the depth to the bedrock and its lateral variations. It appeared that surface waves might not be fully adapted for dyke investigation because of the particular geometry of the studied dyke, non-respectful of the 10 assumption, and which induced depth and velocity discrepancies retrieved from Rayleigh and Love waves inversion. The use of these classical prospecting techniques however did not allow to directly locate the two leakages within the studied earth dyke. The analysis of ambient vibration time series with a modified beam-forming algorithm allowed to localize the most energetic water flow prior to remediation works. It was not possible to detect the leakage after remediation works, suggesting that they efficiently contributed to significantly reduce the water flow. The second leakage was not detected probably because of a non-turbulent water flow, generating few energetic vibrations. (C) 2017 Elsevier B.V. All rights reserved.
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Brienza, M., Duwig, C., Perez, S., & Chiron, S. (2017). 4-nitroso-sulfamethoxazole generation in soil under denitrifying conditions: Field observations versus laboratory results. Journal Of Hazardous Materials, 334, 185–192.
Abstract: The formation of 4-nitroso-sulfamethoxazole and 4-nitro-SMX, two transformation products (TPs) of sulfamethoxazole (SMX) was investigated under batch soil slurry experiments and in a field study. Due to their low occurrence levels (ng/L) in environmental waters, a suitable analytical method based on liquid chromatography – high resolution – mass spectrometry was developed. Consequently, field observations revealed, for the first time, the occurrence of 4-nitroso-SMX in groundwater at concentrations as high as 18 ng/L.Nitric oxide (NO center dot) steady-state concentrations were determined in soil slurry experiments because this reactive specie accounted for the formation of 4-nitroso-SMX and 4-nitro-SMX. Measurements revealed that environmental SMX concentrations (0.2-2 μg/L) at neutral pH induced the accumulation of nitric oxide. Under acidic conditions (pH< 6), nitrous acid (HONO) was the major source of nitric oxide while under neutral/basic conditions nitric oxide release was related to the inhibition of denitrification processes. Under laboratory experiments, SMX nitration reaction appeared to be an irreversible transformation pathway, while 4-nitroso-SMX was slowly transformed over time. The occurrence of 4-nitroso-SMX conditions was therefore unexpected in the field study but could be due to its continuous input from soil and/or its relative persistence under anoxic conditions. A mechanism for 4-nitroso-SMX formation was proposed involving a nitrosative desamination pathway through a phenyl radical. (C) 2017 Elsevier B.V. All rights reserved.
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Calas, A., Uzu, G., Martins, J. M. F., Voisin, D., Spadini, L., Lacroix, T., et al. (2017). The importance of simulated lung fluid (SLF) extractions for a more relevant evaluation of the oxidative potential of particulate matter. Scientific Reports, 7.
Abstract: Particulate matter (PM) induces oxidative stress in vivo, leading to adverse health effects. Oxidative potential (OP) of PM is increasingly studied as a relevant metric for health impact (instead of PM mass concentration) as much of the ambient particle mass do not contribute to PM toxicity. Several assays have been developed to quantify PM oxidative potential and a widely used one is the acellular dithiothreitol (DTT) assay. However in such assays, particles are usually extracted with methanol or Milli-Q water which is unrepresentative of physiological conditions. For this purpose, OPDTT measurements after simulated lung fluids (SLF) extraction, in order to look at the impact of simulated lung fluid constituents, were compared to Milli-Q water extraction measurements. Our major finding is a significant decrease of the OPDTT when the artificial lysosomal fluid (ALF) solution was used. Indeed, ligand compounds are present in the SLF solutions and some induce a decrease of the OP when compared to water extraction. Our results suggest that the effect of ligands and complexation in lining fluids towards PM contaminants probably has been underestimated and should be investigated further.
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D'Amboise, C. J. L., Muller, K., Oxarango, L., Morin, S., & Schuler, T. V. (2017). Implementation of a physically based water percolation routine in the Crocus/SURFEX (V7.3) snowpack model. Geoscientific Model Development, 10(9), 3547–3566.
Abstract: We present a new water percolation routine added to the one-dimensional snowpack model Crocus as an alternative to the empirical bucket routine. This routine solves the Richards equation, which describes flow of water through unsaturated porous snow governed by capillary suction, gravity and hydraulic conductivity of the snow layers. We tested the Richards routine on two data sets, one recorded from an automatic weather station over the winter of 2013-2014 at Filefjell, Norway, and the other an idealized synthetic data set. Model results using the Richards routine generally lead to higher water contents in the snow layers. Snow layers often reached a point at which the ice crystals' surface area is completely covered by a thin film of water (the transition between pendular and funicular regimes), at which feedback from the snow metamorphism and compaction routines are expected to be nonlinear. With the synthetic simulation 18% of snow layers obtained a saturation of > 10% and 0.57% of layers reached saturation of > 15 %. The Richards routine had a maximum liquid water content of 173.6 kg m(-3) whereas the bucket routine had a maximum of 42.1 kg m(-3). We found that wet-snow processes, such as wet-snow metamorphism and wet-snow compaction rates, are not accurately represented at higher water contents. These routines feed back on the Richards routines, which rely heavily on grain size and snow density. The parameter sets for the water retention curve and hydraulic conductivity of snow layers, which are used in the Richards routine, do not represent all the snow types that can be found in a natural snowpack. We show that the new routine has been implemented in the Crocus model, but due to feedback amplification and parameter uncertainties, meaningful applicability is limited. Updating or adapting other routines in Crocus, specifically the snow compaction routine and the grain metamorphism routine, is needed before Crocus can accurately simulate the snowpack using the Richards routine.
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Divya, P. V., Viswanadham, B. V. S., & Gourc, J. P. (2017). Centrifuge model study on the performance of fiber reinforced clay-based landfill covers subjected to flexural distress. Applied Clay Science, 142, 173–184.
Abstract: The influence of discrete and randomly distributed polyester (PET) fibers in improving the crack resistance and water-tightness of clay barriers was studied by conducting a series of centrifuge model tests at 40 gravities using a large beam centrifuge available at Indian Institute of Technology Bombay. Model clay barriers with and without fibers were subjected to flexural distress by inducing differential settlements using a settlement simulator. Two types of clay barriers were prepared by using two different types of soil, namely bentonite amended silty soil (Soil A) and kaolin clay-sand mixture (Soil B). Digital image cross-correlation (DIC) technique was used for analyzing the images captured by a digital photo camera and a charged couple device (CCD) camera, mounted along with the model. Unreinforced soil barriers (URSB) were found to lose their water-tightness and integrity at relatively lower distortion levels compared to identical fiber reinforced soil barriers (FRSB). Also, the performance of URSB and FRSB was found to be superior for Soil A compared to Soil B. The capability of PET fibers on preservation of existing unreinforced soil barriers was also demonstrated. The strain at crack initiation, epsilon(c), for FRSB is 2.90 and 2.36 times higher than identical URSB for Soil A and Soil B, respectively. Similarly, the strain at the onset of water breakthrough, epsilon(b), for FRSB is 2.14 and 2.79 times higher than identical URSB for Soil A and Soil B, respectively. There is a significant influence of fiber inclusion in retarding the crack initiation and water breakthrough at the onset of flexural distress for both the soil types. Thus, FRSB can withstand more distortion and strain while maintaining the integrity of the clay barrier. This observed behaviour of restraining cracks and improved performance of FRSB is primarily due to the reinforcement effect achieved due to soil-fiber interactions. (C) 2016 Elsevier B.V. All rights reserved.
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Divya, P. V., Viswanadham, B. V. S., & Gourc, J. P. (2017). Centrifuge Modeling and Digital Image Cross-Correlation Analysis of Geofiber-Reinforced Clay-Based Landfill Covers. Journal Of Geotechnical And Geoenvironmental Engineering, 143(1).
Abstract: The influence of discrete and randomly distributed fibers (DRDF) on the improvement of the resistance to cracking of clay-based landfill covers was studied by conducting a series of centrifuge model tests. A motor-based differential settlement simulator (MDSS) was used to induce differential settlements to the soil layers during centrifuge tests performed at 40g using the 4.5 m radius beam centrifuge at Indian Institute of Technology Bombay. A digital image cross-correlation (DIC) technique was used to capture deformations of the model barriers and to obtain strain field distributions. Thickness of the unreinforced barriers (URSB) and fiber-reinforced barriers (FRSB) were varied as 15 mm (similar to 0.6 m in the field) and 25 mm (1.0 m). Fiber lengths were varied as 30, 60, and 90 mm. The strain at water breakthrough of 15 mm (0.6 m) and 25 mm (1 m) FRSB were respectively 1.9 and 2.2 times higher compared to identical URSBs. A relatively crack-free surface was observed for FRSB with longer fibers even after subjected to differential settlement of 1 m. (C) 2016 American Society of Civil Engineers.
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Fichez, R., Archundia, D., Grenz, C., Douillet, P., Mendieta, F. G., Moreno, M. O., et al. (2017). Global climate change and local watershed management as potential drivers of salinity variation in a tropical coastal lagoon (Laguna de Terminos, Mexico). Aquatic Sciences, 79(2), 219–230.
Abstract: The wide range of ecological goods and services provided by tropical coastal lagoons and wetlands are under considerable pressure due to the synergistic effects of local anthropogenic impact and global climate change. In transitional waters, salinity is a key driver of ecological processes mostly depending on the balance between marine and river inputs, a balance that can be significantly modified by climate change and by anthropogenic alteration of the watershed. Mesoamerica being considered as a climate change hot-spot and as an ecoregion strongly vulnerable to global change, our study aimed at analyzing the relationship between salinity, river runoff, and rainfall variability in a tropical coastal lagoon and to assess the respective influence of climate change and watershed management. The study focusing on the large and shallow coastal lagoon of Laguna de Terminos in south eastern Mexico established: (1) the variability in salinity distribution along the yearly cycle and the occurrence of a high salinity anomaly period during the wet season of 2009; (2) the relationship between lagoon waters salinity and river inputs further underlying the anomalous situation encountered in 2009; (3) a long term increase in river discharge during the past 60 years, indicating potential salinity decrease in the lagoon during that same period; (4) an absence of any change in rainfall linking the increase in runoff to watershed management rather than long term trend in climate change. Additionally, the specific context of the 2009-2010 Central-Equatorial Pacific El Nio is underlined and the potential relationship between river discharge and ENSO is discussed. Those results should be of significant practical value to decision-makers who are often keen to point the finger at global climate change when local environmental management is also and sometime most significantly responsible.
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Geay, T., Belleudy, P., Laronne, J. B., Camenen, B., & Gervaise, C. (2017). Spectral variations of underwater river sounds. Earth Surface Processes And Landforms, 42(14), 2447–2456.
Abstract: Passive acoustic monitoring of the self-generated noise of particle impacts has been shown to be correlated to bedload flux and bedload size. However, few studies have concentrated on the role of acoustic wave propagation in a river. For the first time, the river environment is modeled as a Pekeris waveguide, where a wave number integration technique is used to predict the transformation of sounds through their propagation paths. Focusing on the distance of a hydrophone from the channel bed and cutting off the low frequencies produced by impacts between gravel particles, we demonstrate that acoustic propagation modifies the spectral content of bedload-generated sound. Acoustic signals analyzed with the proposed model are interpreted by comparison to Helley-Smith bedload data obtained during flood conditions on the large gravel-bedded Arc-en-Maurienne River, France. This study shows that careful attention to acoustic propagation effects is required when estimating bedload grain size distribution with hydrophones in rivers, especially for rivers with slopes higher than 1%. Bedload monitoring with a hydrophone is particularly appropriate for large gravel-bed rivers – especially so during large floods, when in situ sampling is difficult or impractical and the impact of acoustic propagation is weaker relative to the self-generated noise of bedload impacts. Copyright (c) 2017 John Wiley & Sons, Ltd.
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Gratiot, N., Bildstein, A., Anh, T. T., Thoss, H., Denis, H., Michallet, H., et al. (2017). Sediment flocculation in the Mekong River estuary, Vietnam, an important driver of geomorphological changes. Comptes Rendus Geoscience, 349(6-7), 260–268.
Abstract: Over the past several decades, major hydro-sedimentary changes have occurred in both continental and coastal regions of the Mekong Delta, and this has severely impacted coastal erosion. A good characterization of floc properties and of their changes over time is necessary to gain comprehensive understanding and modelling of hydrodynamics and of the associated geomorphological changes. This paper quantifies the influence of sediment concentration, turbulence and differential particle settling on flocculation through field and laboratory investigations of the Mekong estuary. For concentrations lower than 200 mg.L-1, the particles do not exhibit a dynamic response to their environment, while for higher concentrations (up to 3-4 g.L-1), particle size and settling velocity increased by more than one order of magnitude. Flocculation by differential settling has not been sufficiently investigated yet, but this study reveals it as a predominant factor for siltation in quiescent environments such as the ones existing in the inner mangrove fringe. Such results are important to provide realistic simulations of the coastal evolution. (C) 2017 Academie des sciences. Published by Elsevier Masson SAS.
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Guedron, S., Point, D., Acha, D., Bouchet, S., Baya, P. A., Tessier, E., et al. (2017). Mercury contamination level and speciation inventory in Lakes Titicaca & Uru-Uru (Bolivia): Current status and future trends. Environmental Pollution, 231, 262–270.
Abstract: Aquatic ecosystems of the Bolivian Altiplano (similar to 3800 m a.s.l.) are characterized by extreme hydro-climatic constrains (e.g., high UV-radiations and low oxygen) and are under the pressure of increasing anthropogenic activities, unregulated mining, agricultural and urban development. We report here a complete inventory of mercury (Hg) levels and speciation in the water column, atmosphere, sediment and key sentinel organisms (i.e., plankton, fish and birds) of two endorheic Lakes of the same watershed differing with respect to their size, eutrophication and contamination levels. Total Hg (THg) and mono-methylmercury (MMHg) concentrations in filtered water and sediment of Lake Titicaca are in the lowest range of reported levels in other large lakes worldwide. Downstream, Hg levels are 3-10 times higher in the shallow eutrophic Lake Uru-Uru than in Lake Titicaca due to high Hg inputs from the surrounding mining region. High percentages of MMHg were found in the filtered and unfiltered water rising up from <1 to similar to 50% THg from the oligoihetero-trophic Lake Titicaca to the eutrophic Lake Uru-Uru. Such high % MMHg is explained by a high in situ MMHg production in relation to the sulfate rich substrate, the low oxygen levels of the water column, and the stabilization of MMHg due to abundant ligands present in these alkaline waters. Differences in MMHg concentrations in water and sediments compartments between Lake Titicaca and Uru-Uru were found to mirror the offset in MMHg levels that also exist in their respective food webs. This suggests that in situ MMHg baseline production is likely the main factor controlling MMHg levels in fish species consumed by the local population. Finally, the increase of anthropogenic pressure in Lake Titicaca may probably enhance eutrophication processes which favor MMHg production and thus accumulation in water and biota. (C) 2017 Elsevier Ltd. All rights reserved.
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Ioana-Toroimac, G., Zaharia, L., Minea, G., & Morosanu, G. A. (2017). Using a multi-criteria analysis to identify rivers with hydromorphological restoration priority: Braided rivers in the south-eastern Subcarpathians (Romania). Science Of The Total Environment, 599, 700–709.
Abstract: In order to systematically plan river restoration actions at a regional scale, this paper develops a multi-criteria analysis that classifies rivers, based on their priority for hydromorphological restoration. This priority is defined by severe human pressures within the erodible corridor of the river, drastic alteration of the stream channel, and low intensity of river pattern functioning. Based on relevant indicators for three groups of features (human pressures, channel changes, and river functionality), a Hydromorphological Restoration Priority Index (HRPI) was designed. The high values (>66%) of HRPI reflect an urgent need for hydromorphological restoration while low values (<33%) reveal a less immediate necessity for restoration. The proposed methodology was applied on braided sectors of rivers crossing the south-eastern (Curvature) Subcarpathians (Romania). The values of the total HRPI ranged between 21% (Zabrdut River) and almost 44% (Prahova River). According to our results, most of the analyzed sectors have a low need for hydromorphological restoration of the braided pattern, while some have a moderate necessity for restoration. Whereas the Prahova River has the highest HRPI, it should be given priority for restoration at a regional scale, which corresponds to the objectives of River Basin Management Plans for the interval beyond 2021. (C) 2017 Elsevier B.V. All rights reserved.
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Jourdain, C., Belleudy, P., Tal, M., & Malavoi, J. R. (2017). The role of hydrology on vegetation removal in a heavily managed gravel bed river: the Isere, Combe de Savoie, France. Geomorphologie-Relief Processus Environnement, 23(3), 203–217.
Abstract: The impacts of frequent or moderate floods (return interval <1 year to 10 years) on vegetated macroform turnover in river beds are interesting from a management perspective: artificial floods are an option often considered for managing vegetation in rivers. However their effects are not well documented. In this context, our study was aimed at characterizing the impact of high flow events of different magnitudes on sediment and vegetation dynamics in a heavily managed gravel bed river, from aerial photos and hydrological time series. Specifically, our aims were: (i) to characterize the evolution of vegetation surfaces at the reach scale and over decadal time scales, (ii) to analyze the link between different descriptors of the hydrological time series and vegetation removal, and (iii) to outline the main mechanisms of vegetation removal at these scales. Our study was conducted on the Isere River, a heavily managed gravel bed river flowing in the French Alps for the period 1996-2015. The hydrological parameters which best explained vegetation removal on the Isere bed were the volumes of water flowing between 350 m(3).s(-1) (return interval <1 year) and 600 m(3).s(-1) (return interval of approximately 5 years). Most vegetation removal was due to lateral erosion of the upstream end of the bars. The areas of vegetation removal were modest compared to those of newly established vegetation: 3.4% of vegetated area on average was removed annually, while vegetation cover increased by 6.2%. These results suggest that on this reach, artificial floods could potentially invigorate sediment dynamics and vegetation renewal, but are unlikely to be sufficient to maintain the bed free of vegetation.
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Loizeau, S., Rossier, Y., Gaudet, J. P., Refloch, A., Besnard, K., Angulo-Jaramillo, R., et al. (2017). Water infiltration in an aquifer recharge basin affected by temperature and air entrapment. Journal Of Hydrology And Hydromechanics, 65(3), 222–233.
Abstract: Artificial basins are used to recharge groundwater and protect water pumping fields. In these basins, infiltration rates are monitored to detect any decrease in water infiltration in relation with clogging. However, miss-estimations of infiltration rate may result from neglecting the effects of water temperature change and air-entrapment. This study aims to investigate the effect of temperature and air entrapment on water infiltration at the basin scale by conducting successive infiltration cycles in an experimental basin of 11869 m(2) in a pumping field at Crepieux-Charmy (Lyon, France). A first experiment, conducted in summer 2011, showed a strong increase in infiltration rate; which was linked to a potential increase in ground water temperature or a potential dissolution of air entrapped at the beginning of the infiltration. A second experiment was conducted in summer, to inject cold water instead of warm water, and also revealed an increase in infiltration rate. This increase was linked to air dissolution in the soil. A final experiment was conducted in spring with no temperature contrast and no entrapped air (soil initially water-saturated), revealing a constant infiltration rate. Modeling and analysis of experiments revealed that air entrapment and cold water temperature in the soil could substantially reduce infiltration rate over the first infiltration cycles, with respective effects of similar magnitude. Clearly, both water temperature change and air entrapment must be considered for an accurate assessment of the infiltration rate in basins.
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Nord, G., Boudevillain, B., Berne, A., Branger, F., Braud, I., Dramais, G., et al. (2017). A high space-time resolution dataset linking meteorological forcing and hydro-sedimentary response in a mesoscale Mediterranean catchment (Auzon) of the Ardeche region, France. Earth System Science Data, 9(1).
Abstract: A comprehensive hydrometeorological dataset is presented spanning the period 1 January 201131 December 2014 to improve the understanding of the hydrological processes leading to flash floods and the relation between rainfall, runoff, erosion and sediment transport in a mesoscale catchment (Auzon, 116 km(2)) of the Mediterranean region. Badlands are present in the Auzon catchment and well connected to high-gradient channels of bedrock rivers which promotes the transfer of suspended solids downstream. The number of observed variables, the various sensors involved (both in situ and remote) and the space-time resolution (similar to km(2), similar to min) of this comprehensive dataset make it a unique contribution to research communities focused on hydrometeorology, surface hydrology and erosion. Given that rainfall is highly variable in space and time in this region, the observation system enables assessment of the hydrological response to rainfall fields. Indeed, (i) rainfall data are provided by rain gauges (both a research network of 21 rain gauges with a 5 min time step and an operational network of 10 rain gauges with a 5 min or 1 h time step), S-band Doppler dual-polarization radars (1 km(2), 5 min resolution), disdrometers (16 sensors working at 30 s or 1 min time step) and Micro Rain Radars (5 sensors, 100m height resolution). Additionally, during the special observation period (SOP-1) of the HyMeX (Hydrological Cycle in the Mediterranean Experiment) project, two X-band radars provided precipitation measurements at very fine spatial and temporal scales (1 ha, 5 min). (ii) Other meteorological data are taken from the operational surface weather observation stations of Meteo-France (including 2m air temperature, atmospheric pressure, 2 m relative humidity, 10m wind speed and direction, global radiation) at the hourly time resolution (six stations in the region of interest). (iii) The monitoring of surface hydrology and suspended sediment is multi-scale and based on nested catchments. Three hydrometric stations estimate water discharge at a 2-10 min time resolution. Two of these stations also measure additional physico-chemical variables (turbidity, temperature, conductivity) and water samples are collected automatically during floods, allowing further geochemical characterization of water and suspended solids. Two experimental plots monitor overland flow and erosion at 1 min time resolution on a hillslope with vineyard. A network of 11 sensors installed in the intermittent hydrographic network continuously me
asures water level and water temperature in headwater subcatchments (from 0.17 to 116 km(2)) at a time resolution of 2-5 min. A network of soil moisture sensors enables the continuous measurement of soil volumetric water content at 20 min time resolution at 9 sites. Additionally, concomitant observations (soil moisture measurements and stream gauging) were performed during floods between 2012 and 2014. Finally, this dataset is considered appropriate for understanding the rainfall variability in time and space at fine scales, improving areal rainfall estimations and progressing in distributed hydrological and erosion modelling.
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Refloch, A., Gaudet, J. P., Oxarango, L., & Rossier, Y. (2017). Estimation of saturated hydraulic conductivity from ring infiltrometer test taking into account the surface moisture stain extension. Journal Of Hydrology And Hydromechanics, 65(3), 321–324.
Abstract: A large single-ring infiltrometer test was performed in order to characterize the saturated hydraulic conductivity below an infiltration basin in the well field of Lyon (France). Two kinds of data are recorded during the experiment: the volume of water infiltrated over time and the extension of the moisture stain around the ring. Then numerical analysis was performed to determine the saturated hydraulic conductivity of the soil by calibration. Considering an isotropic hydraulic conductivity, the saturated hydraulic conductivity of the alluvial deposits is estimated at 3.8 10(-6) m s(-1). However, with this assumption, we are not able to represent accurately the extension of the moisture stain around the ring. When anisotropy of hydraulic conductivity is introduced, experimental data and simulation results are in good agreement, both for the volume of water infiltrated over time and the extension of the moisture stain. The vertical saturated hydraulic conductivity in the anisotropic configuration is 4.75 times smaller than in the isotropic configuration (8.0 10(-7) m s(-1)), and the horizontal saturated hydraulic conductivity is 125 times higher than the vertical saturated hydraulic conductivity (1.0 10(-4) m s(-1)).
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Samake, A., Uzu, G., Martins, J. M. F., Calas, A., Vince, E., Parat, S., et al. (2017). The unexpected role of bioaerosols in the Oxidative Potential of PM. Scientific Reports, 7.
Abstract: Bioaerosols represent up to 15-25% of PM by mass, but there is currently no assessment of their impact on Oxidative Potential (OP), or capacity of particulate matter (PM) to produce damaging oxidative reactions in the human lungs. Here, the OP of selected bioaerosols (bacteria cells vs fungal spores) was assessed through the cell-free DTT assay. Results show that bioaerosols induce Reactive Oxygen Species (ROS) production, varying along the microorganism type, species, and concentration. Fungal spores show up to 10 times more ROS generation than bacterial cells. At the highest concentrations, fungal spores present as much oxidative reactivity as the most redox-active airborne chemicals (Copper, Naphtoquinone). Moreover, bioaerosols substantially influence OP of ambient PM and that of its chemical constituents: in presence of A. fumigatus spores, the OP of Cu/NQ is increased by a factor of 2 to 5, whereas, 10(4) and 10(5) S. epidermidis bacterial cells. mL(-1) halves the OP of Cu/NQ. Finally, viable and gamma-rays-killed model bioaerosols present similar oxidative reactivity, suggesting a metabolism-independent cellular mechanism. These results reveal the importance of bioaerosols for PM reactivity. PM toxicity can be modified due to bioaerosols contribution or by their ability to modulate the OP of toxic chemicals present in PM.
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Simonin, M., Martins, J. M. F., Le Roux, X., Uzu, G., Calas, A., & Richaume, A. (2017). Toxicity of TiO2 nanoparticles on soil nitrification at environmentally relevant concentrations: Lack of classical dose-response relationships. Nanotoxicology, 11(2), 247–255.
Abstract: Titanium-dioxide nanoparticles (TiO2-NPs) are increasingly released in agricultural soils through, e.g. biosolids, irrigation or nanoagrochemicals. Soils are submitted to a wide range of concentrations of TiO2-NPs depending on the type of exposure. However, most studies have assessed the effects of unrealistically high concentrations, and the dose-response relationships are not well characterized for soil microbial communities. Here, using soil microcosms, we assessed the impact of TiO2-NPs at concentrations ranging from 0.05 to 500mg kg(-1)dry-soil, on the activity and abundance of ammonia-oxidizing archaea (AOA) and bacteria (AOB), and nitrite-oxidizing bacteria (Nitrobacter and Nitrospira). In addition, aggregation and oxidative potential of TiO2-NPs were measured in the spiking suspensions, as they can be important drivers of TiO2-NPs toxicity. After 90days of exposure, non-classical dose-response relationships were observed for nitrifier abundance or activity, making threshold concentrations impossible to compute. Indeed, AOA abundance was reduced by 40% by TiO2-NPs whatever the concentration, while Nitrospira was never affected. Moreover, AOB and Nitrobacter abundances were decreased mainly at intermediate concentrations nitrification was reduced by 25% at the lowest (0.05mgkg(-1)) and the highest (100 and 500mgkg(-1)) TiO2-NPs concentrations. Path analyses indicated that TiO2-NPs affected nitrification through an effect on the specific activity of nitrifiers, in addition to indirect effects on nitrifier abundances. Altogether these results point out the need to include very low concentrations of NPs in soil toxicological studies, and the lack of relevance of classical dose-response tests and ecotoxicological dose metrics (EC50, IC50...) for TiO2-NPs impact on soil microorganisms.
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Slimani, R., Oxarango, L., Sbartai, B., Tinet, A. J., Olivier, F., & Dias, D. (2017). Leachate flow around a well in MSW landfill: Analysis of field tests using Richards model. Waste Management, 63, 122–130.
Abstract: During the lifespan of a Municipal Solid Waste landfill, its leachate drainage system may get clogged. Then, as a consequence of rainfall, leachate generation and possibly leachate injection, the moisture content in the landfill increases to the point that a leachate mound could be created. Therefore, pumping the leachate becomes a necessary solution. This paper presents an original analysis of leachate pumping and injection in an instrumented well. The water table level around the well is monitored by nine piezometers which allow the leachate flow behaviour to be captured. A numerical model based on Richards equation and an exponential relationship between saturated hydraulic conductivity and depth is used to analyze the landfill response to pumping and injection. Decreasing permeability with depth appears to have a major influence on the behaviour of the leachate flow. It could have a drastic negative impact on the pumping efficiency with a maximum quasi-stationary pumping rate limited to approximately 1 m(3)/11 for the tested well and the radius of influence is less than 20 m. The numerical model provides a reasonable description of both pumping and injection tests. However, an anomalous behaviour observed at the transition between pumping and recovery phases is observed. This could be due to a limitation of the Richards model in that it neglects the gas phase behaviour and other double porosity heterogeneous effects. (C) 2016 Elsevier Ltd. All rights reserved.
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Strady, E., Dang, V. B. H., Nemery, J., Guedron, S., Dinh, Q. T., Denis, H., et al. (2017). Baseline seasonal investigation of nutrients and trace metals in surface waters and sediments along the Saigon River basin impacted by the megacity of Ho Chi Minh (Vietnam). Environmental Science And Pollution Research, 24(4), 3226–3243.
Abstract: The Saigon River, Southern Vietnam, crosses one of the most dynamic developing Megacity in Southeast Asia: Ho Chi Minh City (HCMC). The increased economic, industrial, and domestic developments may affect the environmental quality of water and halicutic resources. In this study, we evaluated the seasonal (dry and wet seasons) biogeochemical state of the Saigon River during two snapshot campaigns conducted along the river basin upstream from HCMC; the Saigon River was characterized by slightly acidic (pH 5.7-7.7) and oxygen-depleted water (dissolved oxygen (DO), 0.36-5.18 mg l(-1)). Nutrients (N-NH4 = 0.01-2.41, N-NO3 = 0.14-2.72, and P-PO4 = similar to 0-0.42 mg l(-1)), DOC (2.2-8.0 mg l(-1)), POC, and trace metal(oid) (As, Cd, Cr, Cu, Zn, and Hg) concentrations were low showing a good quality of the upstream river. In the urban center area, DO dropped to 0.03 mg l(-1) accompanied with a rise of nutrient concentrations (e.g., N-NH4, up to 17.7 mg l(-1)) likely originating from wastewater discharges. Trace metal concentrations also rose sharply (e.g., Cr and Hg rose up to 10-fold higher) in both water and sediments but remained under the World Health Organization (WHO) and Vietnamese concentration guidelines. In the downstream estuarine area, the intrusion of marine waters diluted water flowing from HCMC, leading water quality to return close to the state observed upstream from HCMC. In general, levels of nutrient and metal contaminations along the Saigon River during both seasons appear moderate regarding to Vietnamese and WHO guidelines although the urban area is highlighted as the major contributor for metal(oid) emissions. Finally, we showed that apart from wastewater and industrial discharges that affect the river quality, metal(oid) partitioning between solid and solution is controlled by the change in water geochemistry along the continuum during both seasons, such as DO (e.g., for As and Cr) and pH (e.g., for Pb) which drives their sorption/dissolution dynamics.
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Strady, E., Dinh, Q. T., Nemery, J., Nguyen, T. N., Guedron, S., Nguyen, N. S., et al. (2017). Spatial variation and risk assessment of trace metals in water and sediment of the Mekong Delta. Chemosphere, 179, 367–378.
Abstract: The Mekong Delta, is home to 17 million inhabitants and faces numerous challenges relating to climate change, environmental degradation and water issues. In this study, we assess trace metals concentrations (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Mo, Cd, Hg, Pb) in the water, suspended particulate matter and surface sediments of the Tien River, the Northern branch of the Mekong Delta, during both dry and rainy seasons. Metal concentrations in the dissolved and suspended particle phases remain in the low concentration range of the main Asian Tropical River. During transportation in the riverine part, we evidenced that V, Cr, Co, As and Pb are dominant in the particulate phase while Mo, Ni and Cu dominate in the dissolved fraction. In the salinity gradient, dissolved U, V, Mo exhibit conservative behaviour while Ni, Cu, As, Co and Cd showed additive behaviour suggesting desorption processes. In the surface sediment, metal concentrations are controlled by the particle-size, POC contents and Fe, Al and Mn – oxy(hydr)oxides. Calculated Enrichment Factor and Geoaccumulation Index evidenced As enrichment while the calculated mean effect range median quotients evidenced a low to medium ecotoxicological potential effects range in the surface sediments. (C) 2017 Elsevier Ltd. All rights reserved.
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Tano, B. F. G., Dias, D., Stoltz, G., Touze-Foltz, N., & Olivier, F. (2017). Numerical modelling to identify key factors controlling interface behaviour of geosynthetic lining systems. Geosynthetics International, 24(2), 167–183.
Abstract: Geosynthetics have been extensively used in landfills as a lining system to prevent leachate infiltration into groundwater. In piggy-back landfill expansion (PBLE), consisting of building a new landfill over an existing one, a lining system is implemented between the old and new waste. In this context, interface failure (stability) and deformation (integrity) of the lining system should be considered for the design. Such stability and integrity mainly depend on the PBLE geometry and the mechanical properties of the geosynthetics. Comprehensive numerical modelling simulations were performed to show how these factors influence the shear stresses, shear displacements, translational stability and the axial strains/ forces within the various geosynthetics. The numerical modelling was conducted using the finite difference code FLAC 2D, focusing on a typical PBLE and considering geosynthetic interface strain softening, the nonlinear stiffness of geosynthetics, and the differentiation between the compressive and tensile behaviours of geosynthetics. The simulations showed that the lateral length of the PBLE, the type of geomembrane (textured or smooth) and the level of the leachate table in new waste are the factors that most influenced the mechanical behaviour of the lining system and its stability. Finally, a parameter called the stability ratio was proposed as a complement to the traditional factor of safety, to analyse the progressive slippage along the geosynthetic interfaces. The numerical results indicated that interface failure concurrently begins at the rightmost part of the lower flat area of the PBLE and near the corner of the inner slope before spreading out to the left as backfilling progresses.
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Tano, B. F. G., Stoltz, G., Touze-Foltz, N., Dias, D., & Olivier, F. (2017). A numerical modelling technique for geosynthetics validated on a cavity model test. Geotextiles And Geomembranes, 45(4), 339–349.
Abstract: Numerical modelling approaches can aid in designing geotechnical constructions involving geosynthetics. However, the reliability of numerical results depends on how the model is developed, the constitutive model, and the set of parameters used. By comparing the numerical results with experiment, the present work verifies a numerical modelling technique developed to model multilayered geosynthetic lining systems for landfills. The numerical modelling technique involves strain softening at interfaces and allows the axial stiffness of the geosynthetics to evolve as a function of strain. This work focuses on a two-dimensional finite-difference model, which is used to simulate three types of experimental tests: conventional uniaxial tensile tests, direct shear tests, and a large-scale test that was used to assess the overall mechanical behaviour of a reinforced geosynthetic system that spanned over a cavity. This reinforced geosynthetic system consisted of a 50 kNim polyvinyl alcohol geogrid reinforcement embedded in a layer of sand, a geosynthetic clay liner, a high-density polyethylene geomembrane, and a non-woven needle-punched geotextile. The uniaxial tensile tests, direct shear tests, and the large-scale test were numerically modelled and the numerical results were compared with experimental results. The results of the numerical modelling technique presented very closely match the results of the three experimental tests, which indicates that the numerical model correctly predicted the measured data. (C) 2017 Elsevier Ltd. All rights reserved.
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Xavier, P., Rauly, D., Chamberod, E., & Martins, J. M. F. (2017). Theoretical Evidence of Maximum Intracellular Currents Versus Frequency in an Escherichia coli Cell Submitted to AC Voltage. Bioelectromagnetics, 38(3), 213–219.
Abstract: In this work, the problem of intracellular currents in longilinear bacteria, such as Escherichia coli, suspended in a physiological medium and submitted to a harmonic voltage (AC), is analyzed using the Finite-Element-based software COMSOL Multiphysics. Bacterium was modeled as a cylindrical capsule, ended by semi-spheres and surrounded by a dielectric cell wall. An equivalent single-layer cell wall was defined, starting from the well-recognized three-shell modeling approach. The bacterium was considered immersed in a physiological medium, which was also taken into account in the modeling. A new complex transconductance was thus introduced, relating the complex ratio between current inside the bacterium and voltage applied between two parallel equipotential planes, separated by a realistic distance. When voltage was applied longitudinally relative to the bacterium main axis, numerical results in terms of frequency response in the 1-20 MHz range for E. coli cells revealed that transconductance magnitude exhibited a maximum at a frequency depending on the cell wall capacitance. This occurred in spite of the purely passive character of the model and could be explained by an equivalent electrical network giving very similar results and showing special conditions for lateral paths of the currents through the cell wall. It is shown that the main contribution to this behavior is due to the conductive part of the current. (C) 2016 Wiley Periodicals, Inc.
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Arshad, M., Merlina, G., Uzu, G., Sobanska, S., Sarret, G., Dumat, C., et al. (2016). Phytoavailability of lead altered by two Pelargonium cultivars grown on contrasting lead-spiked soils. Journal Of Soils And Sediments, 16(2), 581–591.
Abstract: This study assesses the potential of two contrasted fragrant Pelargonium cultivars to induce pH and dissolved organic carbon (DOC) changes in the soil solution, Pb speciation, and their subsequent effects on rhizosphere phytoavailable Pb. Rooted plantlets were grown in special devices, floating on aerated nutrient solution in PVC tanks. This setup allows roots to be physically separated, through a mesh, from a 3-mm soil matrix layer that can be considered as rhizosphere soil. Two contrasted soils, each spiked with Pb-rich particles, emitted from a battery recycling industry, were used at total burdens of 500 and 1500 mg Pb kg(-1) in addition to a control unspiked soil. Soil solution pH, phytoavailable Pb, DOC, Pb adsorption, precipitation on roots, and Pb phases in soil and plant were investigated. Attar of Roses (Attar) cultivar acidified its rhizosphere by 0.4 pH units in both spiked soils. Concolor Lace (Concolor) was unable to change soil solution pH on soil-1 and increased it by 0.7 units on soil 2. Concentrations of Pb in soil solution from Attar plants were always higher than those of Concolor ones. DOC contents of both unspiked soil-1 and soil-2 without plants were not significantly different. In the case of spiked samples, DOC contents in the rhizosphere soil were increased by three and two times for Attar and Concolor, respectively, compared to the unspiked soil without plant. Both cultivars were able to increase DOC contents, independent of soil type and level of contamination. Accumulation of Pb in shoots and roots was higher in Attar as compared to Concolor due to enhanced available Pb as a result of pH and DOC modifications of the rhizosphere soil. Significant amounts of Pb were adsorbed on roots of both cultivars. X-ray elemental analysis of precipitates on roots revealed the association of Pb with P in cylinder-like structures. Extended X-ray absorption fine structure (EXAFS) spectroscopy revealed that Pb was present, to a major extent in the inorganic form, mainly as PbSO4 in the soil, whereas it was complexed with organic species within plant tissues. The conversion of Pb into organic species could decrease toxicity, may enhance plant tolerance, and could increase translocation. Plant-induced changes were responsible for the modification of lead phases within the soil. Immobile forms present in the source leaded particles as well as in the soils were converted into soluble species, ultimately improving the phytoavailable or soil solubilized Pb.
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Attard, G., Rossier, Y., & Eisenlohr, L. (2016). Urban groundwater age modeling under unconfined condition – Impact of underground structures on groundwater age: Evidence of a piston effect. Journal Of Hydrology, 535, 652–661.
Abstract: In this paper, underground structures are shown to have a major influence on the groundwater mean age distribution described as a dispersive piston effect. Urban underground development does not occur without impacts on subsoil resources. In particular, groundwater resources can be vulnerable and generate disturbances when this space is exploited. Groundwater age spatial distribution data are fundamental for resource management as it can provide operational sustainability indicators. However, the application of groundwater age modeling is neglected regarding the potential effect of underground structures in urban areas. A three dimensional modeling approach was conducted to quantify the impact of two underground structures: (1) an impervious structure and (2) a draining structure. Both structures are shown to cause significant mixing processes occurring between shallow and deeper aquifers. The design technique used for draining structures is shown to have the greatest impact, generating a decrease in mean age of more than 80% under the structure. Groundwater age modeling is shown to be relevant for highlighting the role played by underground structures in advective-dispersive flows in urban areas. (C) 2016 Elsevier B.V. All rights reserved.
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Attard, G., Rossier, Y., Winiarski, T., Cuvillier, L., & Eisenlohr, L. (2016). Deterministic modelling of the cumulative impacts of underground structures on urban groundwater flow and the definition of a potential state of urban groundwater flow: example of Lyon, France. Hydrogeology Journal, 24(5), 1213–1229.
Abstract: Underground structures have been shown to have a great influence on subsoil resources in urban aquifers. A methodology to assess the actual and the potential state of the groundwater flow in an urban area is proposed. The study develops a three-dimensional modeling approach to understand the cumulative impacts of underground infrastructures on urban groundwater flow, using a case in the city of Lyon (France). All known underground structures were integrated in the numerical model. Several simulations were run: the actual state of groundwater flow, the potential state of groundwater flow (without underground structures), an intermediate state (without impervious structures), and a transient simulation of the actual state of groundwater flow. The results show that underground structures fragment groundwater flow systems leading to a modification of the aquifer regime. For the case studied, the flow systems are shown to be stable over time with a transient simulation. Structures with drainage systems are shown to have a major impact on flow systems. The barrier effect of impervious structures was negligible because of the small hydraulic gradient of the area. The study demonstrates that the definition of a potential urban groundwater flow and the depiction of urban flow systems, which involves understanding the impact of underground structures, are important issues with respect to urban underground planning.
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Attard, G., Rossier, Y., Winiarski, T., & Eisenlohr, L. (2016). Deterministic modeling of the impact of underground structures on urban groundwater temperature. Science Of The Total Environment, 572, 986–994.
Abstract: Underground structures have a major influence on groundwater temperature and have a major contribution on the anthropogenic heat fluxes into urban aquifers. Groundwater temperature is crucial for resource management as it can provide operational sustainability indicators for groundwater quality and geothermal energy. Here, a three dimensional heat transport modeling approach was conducted to quantify the thermally affected zone (TAZ, i.e. increase in temperature of more than +0.5 degrees C) caused by two common underground structures: (1) an impervious structure and (2) a draining structure. These design techniques consist in (1) ballasting the underground structure in order to resist hydrostatic pressure, or (2) draining the groundwater under the structure in order to remove the hydrostatic pressure. The volume of the TAZ caused by these underground structures was shown to range from 14 to 20 times the volume of the underground structure. Additionally, the cumulative impact of underground structures was assessed under average thermal conditions at the scale of the greater Lyon area (France). The heat island effect caused by underground structures was highlighted in the business center of the city. Increase in temperature of more than +4.5 degrees C were locally put in evidence. The annual heat flow from underground structures to the urban aquifer was computed deterministically and represents 4.5 GW.h. Considering these impacts, the TAZ of deep underground structures should be taken into account in the geothermal potential mapping. Finally, the amount of heat energy provided should be used as an indicator of heating potential in these areas. (C) 2016 Elsevier B.V. All rights reserved.
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Attard, G., Winiarski, T., Rossier, Y., & Eisenlohr, L. (2016). Review: Impact of underground structures on the flow of urban groundwater. Hydrogeology Journal, 24(1), 5–19.
Abstract: Property economics favours the vertical development of cities but flow of groundwater can be affected by the use of underground space in them. This review article presents the state of the art regarding the impact of disturbances caused by underground structures (tunnels, basements of buildings, deep foundations, etc.) on the groundwater flow in urban aquifers. The structures built in the underground levels of urban areas are presented and organised in terms of their impact on flow: obstacle to the flow or disturbance of the groundwater budget of the flow system. These two types of disturbance are described in relation to the structure area and the urban area. The work reviewed shows, on one hand, the individual impacts of different urban underground structures, and on the other, their cumulative impacts on flow, using real case studies. Lastly, the works are placed in perspective regarding the integration of underground structures with the aim of operational management of an urban aquifer. The literature presents deterministic numerical modelling as a tool capable of contributing to this aim, in that it helps to quantify the effect of an underground infrastructure project on groundwater flow, which is crucial for decision-making processes. It can also be an operational decision-aid tool for choosing construction techniques or for formulating strategies to manage the water resource.
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Audebert, M., Oxarango, L., Duquennoi, C., Touze-Foltz, N., Forquet, N., & Clement, R. (2016). Understanding leachate flow in municipal solid waste landfills by combining time-lapse ERT and subsurface flow modelling – Part II: Constraint methodology of hydrodynamic models. Waste Management, 55, 176–190.
Abstract: Leachate recirculation is a key process in the operation of municipal solid waste landfills as bioreactors. To ensure optimal water content distribution, bioreactor operators need tools to design leachate injection systems. Prediction of leachate flow by subsurface flow modelling could provide useful information for the design of such systems. However, hydrodynamic models require additional data to constrain them and to assess hydrodynamic parameters. Electrical resistivity tomography (ERT) is a suitable method to study leachate infiltration at the landfill scale. It can provide spatially distributed information which is useful for constraining hydrodynamic models. However, this geophysical method does not allow ERT users to directly measure water content in waste. The MICS (multiple inversions and clustering strategy) methodology was proposed to delineate the infiltration area precisely during time-lapse ERT survey in order to avoid the use of empirical petrophysical relationships, which are not adapted to a heterogeneous medium such as waste. The infiltration shapes and hydrodynamic information extracted with MICS were used to constrain hydrodynamic models in assessing parameters. The constraint methodology developed in this paper was tested on two hydrodynamic models: an equilibrium model where, flow within the waste medium is estimated using a single continuum approach and a non-equilibrium model where flow is estimated using a dual continuum approach. The latter represents leachate flows into fractures. Finally, this methodology provides insight to identify the advantages and limitations of hydrodynamic models. Furthermore, we suggest an explanation for the large volume detected by MICS when a small volume of leachate is injected. (C) 2016 Elsevier Ltd. All rights reserved.
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Bannour, H., Touze-Foltz, N., & Pierson, P. (2016). Transient hydraulic behavior of two GMBs-GCLs composite liners. Geotextiles And Geomembranes, 44(1), 51–58.
Abstract: In general, interface transmissivity is obtained based on measurements of the steady-state flow in composite geomembranes (GMBs) – geosynthetic clay liners (GCLs). However, transient flow rate has not been studied prior to this study. It has been already noticed that its consideration can lead to an important increase in predicted effluent volumes penetrating the liner, the subgrade soil and the ground water. The goal of the study presented herein is to study the transient state by quantifing the reduction in flow rate with time for two different composite liners. In these composite liners, a needle-punched GCL was combined to a high-density polyethylene GMB. The first GCL contained granular sodium bentonite and the second GCL contained powdered sodium bentonite. While the GCLs hydrated their water content and deformation were quantified. To this aim, various tests were conducted over various periods of time, corresponding to different flow rate values through the composite liner. Relationships between the flow rate and water uptake of the GCL on one side and swell on the other side are given for both GCLs. The results show that the mass per unit area in addition to the granulometric distribution of bentonite in GCL specimens may affect the hydration process and the flow rate evolution through composite liners. In addition, For both GCLs, the deformation follows the same trend of evolution with water content. (C) 2015 Elsevier Ltd. All rights reserved.
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Boudevillain, B., Delrieu, G., Wijbrans, A., & Confoland, A. (2016). A high-resolution rainfall re-analysis based on radar-raingauge merging in the Cevennes-Vivarais region, France. Journal Of Hydrology, 541, 14–23.
Abstract: This work aims at providing quantitative precipitation estimates (QPEs) for the Cevennes-Vivarais region, France, over temporal (1-6 h) and spatial (1-300 km(2)) scales relevant for flash-flood prediction in that region. A systematic implementation of three estimation methods (radar QPE, hourly raingauge Ordinary Kriging – OK – and merging of radar and raingauge data through ICriging with External Drift – KED) proves the ICED method to systematically outperform the concurrent approaches for the 131 main rain events selected during the period 2007-2014. Error models, assuming the standard deviation of the QPE error to be a bi-linear function of the rain rate and the kriging normalized estimation standard deviation, are parameterized for the KED and OK QPEs for the considered temporal and spatial scales. The error models are shown to depend on the type of rain event (Cevennes rain events, localized convection, widespread rainfall) and physical parameters such as the 0 degrees C isotherm altitude and the rain intermittency. The added-value of the radar network in terms of QPE with respect to the hourly raingauge network is larger for localized convection rain events as well as for the smallest space-time scales which are those of interest for flash-flood prediction in the region. (C) 2016 Elsevier B.V. All rights reserved.
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Causse, B., Spadini, L., Sarret, G., Faure, A., Travelet, C., Madern, D., et al. (2016). Xanthan Exopolysaccharide: Cu2+ Complexes Affected from the pH-Dependent Conformational State; Implications for Environmentally Relevant Biopolymers. Environmental Science & Technology, 50(7), 3477–3485.
Abstract: The conformational impact of environmental biopolymers on metal sorption was studied through Cu sorption on xanthan. The apparent Cu2+ complexation constant (logK; Cu2+ + L- <-> CuL+) decreased from 2.9 +/- 0.1 at pH 3.5 to 2.5 +/- 0.1 at pH 5.5 (ionic strength I = 0.1). This behavior is in apparent contradiction with basic thermodynamics, as usually the higher the pH the more cations bind. Our combined titration, circular dichroism and dynamic light scattering study indicated that the change observed in Cu bond strength relates to a conformational change of the structure of xanthan, which generates more chelating sites at pH 3.5 than at pH 5.5. This hypothesis was validated by the fact that the Cu sorption constants on xanthan were always higher than those measured on a mixture of pyruvic and glucuronic acids (logK = 2.2), which are the two constitutive ligands present in the xanthan monomer. This study shows the role of the structural conformation of natural biopolymers in metal bond strength. This finding may help to better predict the fate of Cu and other metals in acidic environmental settings such as aquatic media affected by acid mine drainage, as well as peats and acidic soils, and to better define optimal conditions for bioremediation processes.
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Cea, L., Legout, C., Grangeon, T., & Nord, G. (2016). Impact of model simplifications on soil erosion predictions: application of the GLUE methodology to a distributed event-based model at the hillslope scale. Hydrological Processes, 30(7), 1096–1113.
Abstract: In this paper, we analyse how the performance and calibration of a distributed event-based soil erosion model at the hillslope scale is affected by different simplifications on the parameterizations used to compute the production of suspended sediment by rainfall and runoff. Six modelling scenarios of different complexity are used to evaluate the temporal variability of the sedimentograph at the outlet of a 60m long cultivated hillslope. The six scenarios are calibrated within the generalized likelihood uncertainty estimation framework in order to account for parameter uncertainty, and their performance is evaluated against experimental data registered during five storm events. The Nash-Sutcliffe efficiency, percent bias and coverage performance ratios show that the sedimentary response of the hillslope in terms of mass flux of eroded soil can be efficiently captured by a model structure including only two soil erodibility parameters, which control the rainfall and runoff production of suspended sediment. Increasing the number of parameters makes the calibration process more complex without increasing in a noticeable manner the predictive capability of the model. Copyright (c) 2015 John Wiley & Sons, Ltd.
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Chiron, S., & Duwig, C. (2016). Biotic nitrosation of diclofenac in a soil aquifer system (Katari watershed, Bolivia). Science Of The Total Environment, 565, 473–480.
Abstract: Up till now, the diclofenac (DCF) transformation into its nitrogen-derivatives, N-nitroso-DCF (NO-DCF) and 5-nitro-DCF (NO2-DCF), has been mainly investigated in waste water treatment plant under nitrification or denitrification processes. This work reports, for the first time, an additional DCF microbial mediated nitrosation pathway of DCF in soil under strictly anoxic conditions probably involving codenitrification processes and fungal activities. This transformation pathway was investigated by using field observations data at a soil aquifer system (Katari watershed, Bolivia) and by carrying out soil slurry batch experiments. It was also observed for diphenylamine (DPA). Field measurements revealed the occurrence of NO-DCF, NO2-DCF and NO-DPA in groundwater samples at concentration levels in the 6-68 s/L range. These concentration levels are more significant than those previously reported in waste water treatment plant effluents taking into account dilution processes in soil. Interestingly, the p-benzoquinone imine of 5-OH-DCF was also found to be rather stable in surface water. In laboratory batch experiments under strictly anoxic conditions, the transformation of DCF and DPA into their corresponding N-nitroso derivatives was well correlated to denitrification processes. It was also observed that NO-DCF evolved into NO2-DCF while NO-DPA was stable. In vitro experiments showed that the Fisher-Hepp rearrangement could not account for NO2-DCF formation. One possible mechanism might be that NO-DCF underwent spontaneous NO loss to give the resulting intermediates diphenylaminyl radical or nitrenium cation which might evolve into NO2-DCF in presence of NO2 radical or nitrite ion, respectively. (C) 2016 Elsevier B.V. All rights reserved.
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Erktan, A., Cecillon, L., Graf, F., Roumet, C., Legout, C., & Rey, F. (2016). Increase in soil aggregate stability along a Mediterranean successional gradient in severely eroded gully bed ecosystems: combined effects of soil, root traits and plant community characteristics. Plant And Soil, 398(1-2), 121–137.
Abstract: Our objectives were to evaluate changes in soil aggregate stability along a successional gradient, located in severely eroded Mediterranean gully bed ecosystems and to identify predictors of soil aggregate stability variations among several soil, root traits and plant community characteristics. We selected 75 plots in gully beds, representing five successional stages that differ in plant community composition, dominated by herbs, shrubs or trees according to successional stage. In each plot, we measured soil aggregate stability, basic soil characteristics, root traits and plant diversity indices. Soil aggregate stability increased along the successional gradient, being thrice higher in tree-dominated communities as compared to grass-dominated communities. This increase was mainly driven by soil organic carbon (SOC) accumulation. In early successional stages showing low SOC (below 24 g.kg(-1) or 12 g.kg(-1) in some cases), fine sand content and the percentage of fine roots acted as co-drivers enhancing soil aggregate stability while silt content decreased it. Plant succession in severely eroded Mediterranean gully bed ecosystems is accompanied by a strong stabilization of soil aggregates, mainly driven by SOC accumulation and for early successional stages, by soil granulometry and root traits as co-drivers. Stimulating succession thus appears as a promising restoration strategy for severely eroded ecosystems.
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Erktan, A., Legout, C., De Danieli, S., Daumergue, N., & Cecillon, L. (2016). Comparison of infrared spectroscopy and laser granulometry as alternative methods to estimate soil aggregate stability in Mediterranean badlands. Geoderma, 271, 225–233.
Abstract: Soil aggregate stability is a key indicator of soil resistance to erosion, but its measurement remains fastidious for large scale uses. Alternative time and cost-effective methods are thus needed. Our objective was to assess and compare the efficiency of laser granulometry (LG) and soil mid- and near-infrared spectroscopy (MIR/NIR) as alternative methods to assess soil aggregate stability in Mediterranean badland soils. A collection of 75 badland soil samples was used, showing wide variations in soil aggregate stability. Three different categories of measurements were performed: (i) the aggregate breakdown kinetics of the [<1 mm] size fraction under stirring and sonication, tracked by repeated particle size distribution measurements, using LG, (ii) mid-(diffuse-MIR-DR and attenuate transmitted reflectance MIR-ATR) and near-(NIR-DR) infrared spectra of the fine soil fraction [<2 mm] and (iii) the soil aggregate [3-5 mm] stability, using the standardized method (ISO/FDIS 10930, 2012). Partial least squares regression models were used to predict soil aggregate stability using LG data and infrared spectra. Results showed that NIR-DR and MIR-ATR data provided the best prediction model for soil aggregate stability values (RPD = 2.61 & 2.74; R-2 = 0.85 & 810.87), followed by MIR-DR data (RPD = 2.24; R-2 = 0.89) and finally LG data (RPD = 2.12; R-2 = 0.80). For a quantitative use of the models to assign soil samples to standardized soil aggregate stability classes (ISO/FDIS 10930, 2012), infrared spectra also provided the best accuracy, with a misclassification rate below 30% for NIR-DR and MIR-ATR models, while it reached 43% with the LG-based model. The combination of IR and LG data did not yield a better prediction model for soil aggregate stability values and classes, Infrared-based method also provided best results in terms of time-saving strategy, reducing the measurement time to 8 min only. To conclude, infrared spectra (NIR-DR and MIR-ATR) outperformed LG-data to predict soil aggregate stability. Further development of this technique would require calibrating a set of soil-type specific prediction models for a wide range of soil types. (C) 2016 Elsevier B.V. All rights reserved.
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Goix, S., Uzu, G., Oliva, P., Barraza, F., Calas, A., Castet, S., et al. (2016). Metal concentration and bioaccessibility in different particle sizes of dust and aerosols to refine metal exposure assessment. Journal Of Hazardous Materials, 317, 552–562.
Abstract: Refined exposure assessments were realized for children, 7-9 yrs, in the mining/smelting city of Oruro, Bolivia. Aerosols (PM>2.5, PM1-2.5, PM0.4-1 and PM0.5) and dust (separated in different particle size fractions: 2000-200 μm, 200-50 μm, 50-20 μm, 20-2 μm and <2 μm) were sampled on football fields highly frequented by children in both the mining and smelting areas. Trace element concentrations (Ag, As, Cd, Cu, Pb, Sb, Sn and Zn) in each size fraction of dust and aerosols, lung bioaccessibility of metals in aerosols, and gastric bioaccessibility of metals in dust were measured. Exposure was assessed considering actual external exposure (i.e. exposure pathways: metals inhaled and ingested) and simulated internal exposure (i.e., complex estimation using gastric and lung bioaccessibility, deposition and clearance of particles in lungs). Significant differences between external and simulated internal exposure were attributed to dissemblances in gastric and lung bioaccessibilities, as well as metal distribution within particle size range, revealing the importance of both parameters in exposure assessment. (C) 2016 Elsevier B.V. All rights reserved.
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Gratiot, N., & Anthony, E. J. (2016). Role of flocculation and settling processes in development of the mangrove-colonized, Amazon-influenced mud-bank coast of South America. Marine Geology, 373, 1–10.
Abstract: The Guianas coast downdrift (northwestward) of the Amazon River mouth is characterized by the periodic migration of mud banks that originate from the Amazon. The characteristic sizes of these banks as well as their rates of alongshore migration have been estimated from remote sensing. However, the physical mechanisms leading to their displacement are not yet fully understood. The present work is aimed at investigating a number of micro-scale processes involved in the coastal and estuarine dynamics of fine sediments, and expected to occur during the migration of mud banks. The relative magnitudes of flocculation, hindered settling and consolidation have been determined. Sampling of coastal mud was carried out during a field survey in 2001 that focussed on the fluid mud layer in the leading edge of a mud bank in French Guiana. Settling column experiments were conducted under quiescent conditions for various mean sediment concentrations in the range of 2.5-110 g.l(-1), which is typical of mud bank concentrations. The time dependent vertical profiles of suspended sediment concentration were monitored using an optical settling tank equipped with 32 pre-calibrated optical sensors. The corresponding settling velocities were deduced from the equation of the conservation of mass. The results show that the timescales of hindered settling and consolidation processes are much larger than the timescales of mixing mechanisms such as tides or propagating waves. The individual floc settling velocities are too small to counterbalance the turbulent mixing induced by breaking waves. Hindered settling, favoured by wave action and by the high background suspended sediment concentrations, is thus an overarching process in wave-driven mud bank migration. This pervasive hindered settling regime is characteristic of the wave-exposed outer and leading edges of mud banks where active mobilization of mud assures mud bank migration. As a result, consolidation is theoretically precluded. The experiments pointed out, however, that additional flocculation and differential settling should enhance sedimentation during slack water and under low wave conditions. We deduce from this that enhanced settling in the inner,subtidal-intertidal, parts of leading edges of banks during such conditions is important in the temporary sedimentation that generates gel-like fluid mud patches and mud bars. These low-energy inner, leading parts of banks form an accreted substrate colonized by mangroves, which further contribute to enhanced settling and rapid sedimentation. (C) 2015 Elsevier B.V. All rights reserved.
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Ivankovic, T., du Roscoat, S. R., Geindreau, C., Sechet, P., Huang, Z. J., & Martins, J. M. F. (2016). Development and evaluation of an experimental protocol for 3-D visualization and characterization of the structure of bacterial biofilms in porous media using laboratory X-ray tomography. Biofouling, 32(10), 1235–1244.
Abstract: The development of a reliable model allowing accurate predictions of biofilm growth in porous media relies on a good knowledge of the temporal evolution of biofilm structure within the porous network. Since little is known about the real 3-D structure of biofilms in porous media, this work was aimed at developing a new experimental protocol to visualize the 3-D microstructure of the inside of a porous medium using laboratory X-ray microtomography. A reliable and reproducible methodology is proposed for (1) growing a biofilm inside a porous medium, and (2) X-ray tomography-based characterization of the temporal development of the biofilm at the inlet of the biofilter. The statistical analysis proposed here also validates the results presented in the literature based on a biofilm structure single measurement.
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Morri, M., Soualmia, A., & Belleudy, P. (2016). Mean Velocity Predictions in Vegetated Flows. Journal Of Applied Fluid Mechanics, 9(3), 1273–1283.
Abstract: Vegetation plays an important role in influencing the hydrodynamic behavior, ecological equilibrium and environmental characteristics of water bodies. Several previous models have been developed, to predict hydraulic conditions in vegetated rivers, but only few are actually used in practice. In This paper six analytic model derived for submerged vegetation are compared and evaluate: Klopstra et al. (1997); Stone and Shen (2002); Van velzen (2003); Baptist et al. (2007); Huthoff et al. (2007) and Yang and Choi (2010). The evaluation of the flow formulas is based on the comparison with experimental data from literature using the criteria of deviation. Most descriptors show a good performance for predicting the mean velocity for rigid vegetation. However, the flow formulas proposed by Klopstra et al. (1997) and Huthoff et al. (2007) show the best fit to experimental data. Only for experiments with law density, these models indicate an underestimation. Velocity predicted for flexible vegetation by the six models is less accurate than the prediction in the case of rigid vegetation.
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Nemery, J., & Garnier, J. (2016). BIOGEOCHEMISTRY The fate of phosphorus. Nature Geoscience, 9(5), 343–344.
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Nemery, J., Gratiot, N., Doan, P. T. K., Duvert, C., Alvarado-Villanueva, R., & Duwig, C. (2016). Carbon, nitrogen, phosphorus, and sediment sources and retention in a small eutrophic tropical reservoir. Aquatic Sciences, 78(1), 171–189.
Abstract: Rapid urbanization and the absence of efficient water management policies are increasingly degrading the water quality of tropical reservoirs in developing countries. The small tropical reservoir of Cointzio, located in the Trans-Mexican Volcanic Belt, is a warm monomictic water body (surface area = 6 km(2) with short water residence time < 1 year) that is strategic to the drinking water supply of the city of Morelia and to downstream irrigation during the dry season (6 months of the year). The reservoir faces two threats: (a) reduced water storage capacity due to sediment accumulation and (b) eutrophication caused by excess nutrients that likely come from untreated wastewaters in the upstream watershed. Intensive field measurements of water and sediment were conducted in 2009 to characterize the trophic status of the reservoir and to estimate nitrogen (N) and phosphorus (P) sources, total suspended sediment (TSS) (N), (P), and carbon (C) loads, and their accumulation or removal in the reservoir. We found that point sources represent the majority of N and P inputs to the reservoir. The trophic status is clearly eutrophic given the high chlorophyll a peaks (up to 70 A μg L-1) and a long period of anoxia (from May to October). Most of the TSS, C, N, and P were conveyed to the reservoir between June and October during the wet season. The TSS yield from the watershed was estimated at 35 +/- A 19 t km(-2) year(-1), of which more than 90 % was trapped in the reservoir (sediment accumulation rate = 7800 +/- A 2100 g m(-2) of reservoir year(-1)). The export load of C, N, and P downstream at the reservoir outlet was reduced by 31, 46 and 30 % respectively in comparison to the load at the reservoir inlet. This study reveals the effect of climatic seasonality on inputs to tropical reservoirs and accumulation; it also highlights the need to both reduce nutrient input to combat eutrophication and mitigate erosion to maintain the water storage capacity of the reservoir over the long term.
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Prado, B., Strozzi, A. G., Huerta, E., Duwig, C., Zamora, O., Delmas, P., et al. (2016). 2,4-D mobility in clay soils: Impact of macrofauna abundance on soil porosity. Geoderma, 279, 87–96.
Abstract: Pesticides in agriculture are commonly used to meet the growing food demand; however they compromise the quality of water and soil. The pesticide 2,4-D is one of the most widely used herbicides in the world, it belongs to the group of synthetic herbicides that control broadleaf weeds. In this paper the risk of groundwater contamination by 24-D and its major metabolite, 2,4-DCP, is studied in a context of high density of soil worms. We compared the adsorption, desorption, degradation and displacement of 2,4-D in soils from Tabasco Region having different properties: clay, organic matter, iron and aluminum oxides contents. In addition to the classical soil physicochemical characterizations, a 3D analysis of the soil structure and porosity was performed by analyzing images acquired by Computed Tomography. The objective was to evaluate the effect of soil properties and macroporosity produced by the macrofauna activity on solute movement. All the four soils studied sorbed the herbicides, more importantly 2,4-DCP, the metabolite, than 2,4-D itself. The distribution coefficients for 2,4-D sorption were linear and varied between 1 and 4 while those for 2,4-DCP were above 10. The contents of iron and aluminum have an important role in the adsorption of these two compounds. In aerobic conditions, the herbicides half-life was about 2 days. Water movement occurred in physical equilibrium in three of the four soils; soil dispersivity ranged from 1.2 to 7 cm, clay content being the main factor. After 20 to 60 days depending on the soil, no 2,4-D leaching was observed through the soil columns, except for one soil were there was preferential flow. Earthworms burrows were exhibited and quantified in the soils samples through the analysis of Computer Tomography (CT) images, they appeared as small, snail-shaped, rounded volume of 3 to 7 mm radius with a higher density with respect to the surrounding soil. They were extracted from the original data using a combination of image, processing and mathematical morphology operators. Based on the results obtained, it can be concluded that preferential flow caused by both high clay content and the presence of macrofauna pores significantly reduces the buffering capacity of the soil, increasing the risk of contamination by herbicides of the underlying aquifer. (C) 2016 Elsevier B.V. All rights reserved.
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Schreck, E., Sarret, G., Oliva, P., Calas, A., Sobanska, S., Guedron, S., et al. (2016). Is Tillandsia capillaris an efficient bioindicator of atmospheric metal and metalloid deposition? Insights from five months of monitoring in an urban mining area. Ecological Indicators, 67, 227–237.
Abstract: Atmospheric pollution in megacities has a major impact on human health and environmental quality. Air quality bioindicators may have some advantages over standard devices such as impactors or filters. In this study we evaluated the reliability of Tillandsia sp. versus passive filters for monitoring the atmospheric deposition of metal(loid)s in an area affected by anthropogenic activities. We aimed to gain insight into the composition and origin of atmospheric particles and their fate after deposition on the plant. Three zones with different contamination levels were monitored for five months in 2012. For the highly contaminated area, a linear increase in metalloid) accumulation was found in passive filters, whereas for transplanted Tillandsia capillaris the increase was almost linear for As, Cd, Hg, and Sn, but not for Ag, Pb, Sb, and Zn. For the moderately contaminated zone, the results showed that the exposure time was not sufficient for metal(loid) concentrations to increase in either the plants or filters. However, natural specimens provided some indications of the levels of metal contamination. Metal particles were observed on the plant surface and also in the central disc underneath tillandsia trichomes, suggesting that this is a possible pathway for metals to enter the plant. X-ray absorption spectroscopy demonstrated chemical transformation for Pb and As, both in filters and plants. For Pb, sorbed Pb and/or cell wall complexes were identified in the plants. No As-III-S species, indicative of As detoxification, were identified in the plant. Arsenic was oxidized from As-III to As-V in both plants and filters. Thus, in the present study, passive filters proved more reliable than T. capillaris transplants, although natural specimens provided some insights into local contamination. Particulate contaminants underwent chemical transformation after being trapped in the plant, but there was no clear evidence of internalization and detoxification. (C) 2016 Elsevier Ltd. All rights reserved.
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Simonin, M., Martins, J. M. F., Uzu, G., Vince, E., & Richaume, A. (2016). Combined Study of Titanium Dioxide Nanoparticle Transport and Toxicity on Microbial Nitrifying Communities under Single and Repeated Exposures in Soil Columns. Environmental Science & Technology, 50(19), 10693–10699.
Abstract: Soils are exposed to nanoparticles (NPs) as a result of their increasing use in many commercial products. Adverse effects of NPs on soil microorganisms have, been reported in several ecotoxicological studies using microcosms. Although repeated exposures are more likely to occur in soils, most of these previous studies were performed as a single exposure to NPs. Contrary to single, contamination, the study of multiple NP contaminations in soils requires the use of specialized setups. Using a soil column experiment, we compared the influence of single and repeated exposures (one, two, or three exposures that resulted in the same final concentration applied) on the transport of titanium dioxide (TiO2) NPs through soil and the effect of these different exposure scenarios on the abundance and activity of soil nitrifying microbial communities after a 2 month incubation. The transport of TiO2 NPs was very limited under both single and repeated exposures and was highest for the lowest concentration injected during the first application. Significant decreases in nitrification-activity and ammonia-oxidizing archaea and bacteria populations were observed only for the repeated exposure scenario (three TiO2 NP contaminations). These results suggest that, under repeated exposures, the transport of TiO2 NPs to deep soil layers and groundwater is limited and that a chronic contamination is more harmful for the soil microbiological functioning than a single exposure.
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Simonin, M., Richaume, A., Guyonnet, J. P., Dubost, A., Martins, J. M. F., & Pommier, T. (2016). Titanium dioxide nanoparticles strongly impact soil microbial function by affecting archaeal nitrifiers. Scientific Reports, 6.
Abstract: Soils are facing new environmental stressors, such as titanium dioxide nanoparticles (TiO2-NPs). While these emerging pollutants are increasingly released into most ecosystems, including agricultural fields, their potential impacts on soil and its function remain to be investigated. Here we report the response of the microbial community of an agricultural soil exposed over 90 days to TiO2-NPs (1 and 500 mg kg(-1) dry soil). To assess their impact on soil function, we focused on the nitrogen cycle and measured nitrification and denitrification enzymatic activities and by quantifying specific representative genes (amoA for ammonia-oxidizers, nirK and nirS for denitrifiers). Additionally, diversity shifts were examined in bacteria, archaea, and the ammonia-oxidizing clades of each domain. With strong negative impacts on nitrification enzyme activities and the abundances of ammonia-oxidizing microorganism, TiO2-NPs triggered cascading negative effects on denitrification enzyme activity and a deep modification of the bacterial community structure after just 90 days of exposure to even the lowest, realistic concentration of NPs. These results appeal further research to assess how these emerging pollutants modify the soil health and broader ecosystem function.
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Tano, B. F. G., Dias, D., Fowmes, G. J., Olivier, F., Stoltz, G., & Touze-Foltz, N. (2016). Numerical modeling of the nonlinear mechanical behavior of multilayer geosynthetic system for piggyback landfill expansions. Geotextiles And Geomembranes, 44(6), 782–798.
Abstract: This study examines the extent to which the results of numerical calculations can be influenced both by the differing compressive and tensile behavior of multiple geosynthetics GSYs and by the assumption of strain softening at interfaces between GSYs. Several numerical models are implemented using the finite difference code FLAC 2D on a typical piggyback landfill expansion (PBLE) that involves four GSYs and six interfaces. The present work applies comprehensive, state-of-the-art numerical modeling to study the interactions, between multiple layers of GSYs. It also investigates the nonlinear axial stiffness of GSYs through a series of uniaxial tensile tests. The numerical results,show that, if the GSY axial compressive and tensile characteristics are the same, then tensile force is minimized, which induces significant compressive force in the GSYs. The results also indicate that neglecting strain softening at the interface between GSYs affects interface shear stresses, displacements of GSYs at the interface, and the GSY force distribution, potentially rendering the model unrealistic. Including strain softening, however, allows the assessment (location) of unstable areas along the interface where large displacements occur. (C) 2016 Elsevier Ltd. All rights reserved.
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Veylon, G., Stoltz, G., Meriaux, P., Faure, Y. H., & Touze-Foltz, N. (2016). Performance of geotextile filters after 18 years' service in drainage trenches. Geotextiles And Geomembranes, 44(4), 515–533.
Abstract: This study evaluates the long-term performance of two types of geotextiles that were used for 18 years in drainage trenches to stabilize slopes in the French Alps. The flow rate analysis of each trench enabled estimating an average permittivity at trench scale of between 10(-5) and 10(-6) s(-1). After exhuming the geotextiles, their hydraulic and mechanical properties were assessed. The hydraulic tests performed on geotextiles alone gave permittivities greater than 10(-3) s(-1). Gradient ratio tests were performed on undisturbed soil/geotextile/drainage specimens and gave results in the order of 10(-8) s(-1). The aged specimens were examined using scanning electron microscopy. Quantifying the overall performance of the geotextile filter is complicated because of the brittleness of the calcite crust and the subsequent difficulty of characterizing undisturbed interfaces. Various possible explanatory mechanisms involved in the deterioration of trench performance were reviewed: filter cake blinding, internal clogging and downstream chemical clogging. Existing analytical models were used in order to predict the loss of hydraulic performance due to each of these clogging mechanisms. By comparing the measured permittivities to the calculated permittivities, we demonstrated that chemical clogging due to calcite precipitation on the downstream face of the geotextiles was probably the preponderant mechanism responsible for the poorer performance of geotextile filters at trench scale. (C) 2016 Elsevier Ltd. All rights reserved.
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Wendling, V., Legout, C., Gratiot, N., Michallet, H., & Grangeon, T. (2016). Dynamics of soil aggregate size in turbulent flow: Respective effect of soil type and suspended concentration. Catena, 141, 66–72.
Abstract: The fate of eroded soil particles impacts soil loss, river engineering and aquatic ecosystems. However, little is known about soil aggregate dynamics within the flow just after their detachment from the soil matrix. The relationship between particle size and turbulence has already been studied but few studies analysed the associated effect of particle concentration. The disaggregation/flocculation of three soils, two badland materials and a well developed calcareous brown soil, was studied by using a grid-stirred tank. An isotropic and homogeneous turbulence was generated to focus on the effects of suspended concentration on particle sizes. Increasing the suspended concentration in the range 1-10 g L-1 leads to a decrease of the proportion of the medium size particles and of an increase of the proportion of the smallest particles, as a consequence to enhanced abrasion. The soil aggregates with the largest organic content had the highest strength but were still subject to disaggregation within the turbulent flow, the resulting particle size depending on the suspended concentration. This study demonstrates that soil aggregate characteristics are influenced by concentration, this behaviour being dependent upon the soil type. (C) 2016 Elsevier B.V. All rights reserved.
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Yousefi, S., Pourghasemi, H. R., Hooke, J., Navratil, O., & Kidova, A. (2016). Changes in morphometric meander parameters identified on the Karoon River, Iran, using remote sensing data. Geomorphology, 271, 55–64.
Abstract: River meander dynamics and mobility are important indicators of environmental change related to climate changes and anthropogenic activities at local and river basin scales. The aim of the present study is to identify morphological changes of the Maroon River in Iran using high accuracy maps and Landsat satellite images by analyses during the time period 1989-2008. In this study, 20 meandering reaches were analyzed over a 128-km-long river reach located in the middle part of the Karoon River, Iran. Morphometric indicators such as: river width (W), meander neck length (L), axis length (A), radius of curvature (R), water flow length (S), and sinuosity of meander (C) were extracted for the identified meanders. The results of a paired t-test showed that river width (W) and meander neck length (L) have significantly changed during the study period (1989-2008), with an increase of +3.5 m for Wand a decrease of 274 m for L Spearman correlation analysis has shown that meander parameter changes are highly correlated to each other. The parameters that do not have significant correlation together are C with W and L, Wand L, and L with S and A. During the period of the study, the flow length and river sinuosity decreased for the whole river reach, by 4.77 km and 0.11, respectively. Analysis of land use/land cover categories (1989 and 2008) using the support vector machine (SVM) and kernel function method served as one of the tools for interpretation of the meander parameter changes. These changes can be attributed not only to LU/LC (riparian vegetation to agriculture area ratio) but also to dam construction in the upstream part of the river that leads to major hydrological regime and sediment transfer alteration. Sediment extraction may also be an important factor. (C) 2016 Elsevier B.V. All rights reserved.
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