International audience | The tropical climate and human pressures (mining industry, forest fires) cause significant sediment inputs into the New Caledonia lagoon and are a major cause of degradation of the fringing reefs. The erosion process is spatially characterized on the west coast of New Caledonia to assess potential sediment inputs in the marine area. This paper describes the methodologies that are used to map soil sensitivity to erosion using remote sensing and a geographic information system tool. A cognitive approach, multi-criteria evaluation model and Universal Soil Loss Equation are implemented. This article compares the relevance of each model in order to spatialize and quantify potential erosion at catchment basin scale. These types of studies provide valuable results for focusing on areas subject to erosion and serve as a decision-making tool for the minimization of lagoon vulnerability to the natural and human dynamics on the level of the catchment basins.

[Departement_IRSTEA]EEE [TR1_IRSTEA]E33-Maîtrise et gestion des déchets | International audience | It is well-known that heavy metals brought by intensive pig slurry applications accumulate in the soil ; because of their potential impact on the environment, studying their behaviour is of utmost interest. The Solepur process has been developed in Brittany (France) where pig farming causes serious environmental problems ; it enables the soil to be used as a treatment medium to process pig slurry. Numerous pig slurry applications were performed from 1991 to 1995 on an experimental hydrologically-isolated field specially equipped to recover all the leachate. These applications approximately corresponded to the amount which might have been spread over one century. The Solepur process can be considered as a simulation model for what happens to metals in pig slurry under normal field conditions over a long period of time. This work measured the concentrations of Cu, Zn, Mn, Co, Fe, Cd in pig slurry, in soil and in drainage water, and the results are discussed. Total concentrations and specification data within the three different compartments were analysed and showed that Cu and Zn accumulate in the surface layer, whereas other metals, such as Mn and Co, dissolve and are washed away in the leachate. The increase in the bioavailability and toxicity of these metals as well as their impact on the environment are discussed. | Il est bien connu que les métaux-lourds apportés par des épandages intensifs de lisier de porc s'accumulent dans le sol ; l'étude de leur comportement est donc de la plus haute importance étant donné leur impact potentiel sur l'environnement. Le procédé Solépur a été développé en Bretagne (France), où l'élevage porcin engendre de sérieux problèmes environnementaux ; ce procédé utilise le sol comme un intermédiaire épuratif dans le traitement du lisier de porc. Des épandages répétés de lisier, correspondant approximativement à un siècle d'épandage, ont été réalisés de 1991 à 1995 sur un champ expérimental isolé et équipé de façon à récolter totalement l'eau de drainage. Cette étude est consacrée à la mesure des concentrations de Cu, Zn, Mn, Co, Fe et Cd dans le lisier de porc, le sol et l'eau de drainage. Les concentrations totales et celles résultant de la spéciation chimique sont analysées dans ces trois compartiments et permettent de montrer que certains métaux (Cu et Zn) s'accumulent dans la couche de surface, alors que d'autres (Co et Mn) sont lessivés. L'accroissement de leur toxicité et de leur biodisponibilité ainsi que leur impact sur l'environnement sont également discutés.

International audience | Shredder organisms play a key role in rivers by feeding and fragmenting coarse organic matter that will then beexploited by other consumers. The effects of microplastics (MPs) on Gammarus sp., an ubiquitous genus offreshwater amphipods, and its shredding activity have been broadly investigated. However, the potentialbehavioral and physiological effects of different sizes of MPs on Gammarus sp. remain overlooked despite therecognized influence of MP size on MP toxicity. This study investigated the effects of a 28-day exposure to fourdifferent concentrations of two size fractions of PVC-microplastics (PVC-MPs), on Gammarus fossarum mortalityrate, feeding rate, assimilation efficiency, and expression of proteins involved in key processes. Increased mortalitywas observed for all treatments exposed to PVC-MPs, with higher mortality in the presence of smaller PVC-MPs at the highest concentration. No protein biomarker modulation was observed in presence of PVC-MPs,suggesting that no metabolic stress but direct physical damages of PVC-MPs might have led to the observedmortalities. No difference was observed for feeding rates, but a higher assimilation efficiency was measured forindividuals exposed to PVC-MPs, regardless of the concentration. This could be due to energy reallocation towardsdefense mechanisms or indicate a potential shift in digestive microbiota. This study highlighted thetoxicity of PVC-MPs, particularly of smaller sizes and even at relatively low concentration, for Gammarus fossarum.PVC-MP pollution may therefore alter the functional integrity of river ecosystems by reducing theabundance of shredder organisms and, subsequently, the process of leaf litter decomposition.

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International audience | Fine particulate matter (PM2.5) in the atmosphere is of particular concern due to its adverse effects on human health and its impact on global warming. southeast Asia is a hot spot for fossil fuel combustion with recurrent release of large plumes spreading over the ocean and neighbouring countries. Due to the complex mixture of PM2.5, the atmospheric sources contribution related to local and regional emissions in Hanoi (northern Vietnam) is still ill-constrained. Here, we present a year-round study (November 2019 to December 2020) with measurements of 18 metals and metalloids (MM) and lead isotopes in the PM2.5 fraction to quantify weather-related atmospheric inputs and to assess risk to human health. Anthropogenic inputs from fossil fuel combustion accounted for about 80% in PM2.5. We found high PM2.5-bound MM concentrations often exceeding national and global standards with a low risk of chronic inhalation and carcinogenicity, mainly attributable to Cr. During winter monsoon (northeastern winds), stable weather conditions led to the enrichment of long-range air mass transport of local particulate emissions. During the summer monsoon (southeastern winds), warm and moist winds reduced coal contribution in PM2.5. Our study highlights the need for a strict implementation of policies to control hazardous MM emissions by reducing fossil fuel combustion. On the one hand, reducing coal-related activities could reduce Cr emissions and therefore improve the risks to human health. On the other hand, public policies should encourage conversion to green transport in order to reduce petrol combustion and thus limit global warming.

International audience | <div><p>Aerated compost teas (ACTs) are rich in soluble humic substances (SHS) that have high affinity for metals, notably Cu. Using a batch experiment, we measured the extent to which two ACTs altered Cu dynamics in vineyard topsoils one day and 21 days after their addition. Soils were extracted with 0.01 M KCl, and total Cu concentration, free Cu ion fraction and size distribution of Cu ligands were measured in the extraction solution to assess the impact of ACT on the mobility of Cu. Diffusive gradient in thin film (DGT) measurements were carried out to assess the effect of ACT on Cu bioavailability, and the dissociation rate of Cu-SHS complexes was measured. The results revealed that ACT increased the mobility of Cu from a factor 1.2 to 5.8 depending on the soil, the ACT and the incubation time. Cu mobilization was associated with an increase in absorbance at 254 nm and a decrease in the free Cu ion fraction in the KCl extract. Associated with the strong agreement between the size distribution of SHS and that of Cu ligands in the KCl extract of soils treated with ACT, these results showed that Cu was mobilized through complexation by the SHS present in ACTs. A fraction of the SHS supplied with ACTs sorbed onto the soil constituents, notably in calcareous soils where this fraction reached 86% for ACT B. Between 15% and 50% of the SHS remaining in solution degraded between day one and day 21 under the presumed action of microflora. This explains why the Cu mobilization efficiency of ACTs was on average lower in calcareous soils than in non-calcareous soils, and decreased with time. Lastly, ACT increased the bioavailability of Cu in soils from a factor 1.3 to 4.2, due to the relatively high dissociation rate of Cu-SHS complexes.</p></div>

International audience | Wetlands are among the most threatened ecosystems on the planet and pollution is a major factor causing the decline of wetland biodiversity. Despite the increasing use of pesticides, their fate and effects on freshwater reptiles remain largely unknown. We studied the European pond turtle (Emys orbicularis), a long-lived species at risk with a high exposure potential to pesticides. Between 2018 and 2020, we measured 29 pesticides and metabolites in 408 blood samples of turtles from two populations in the Camargue wetland (France). We were able to quantify 24 compounds and at least one pesticide or one degradation product in 62.5% of samples. Pesticide occurrences and concentrations were low, except for a herbicide widely used in rice cultivation and locally detected in water: bentazone that reached high blood concentrations in E. orbicularis. The occurrence and the concentration of pesticides in E. orbicularis blood depended mainly on the site and the sampling date in relation to pesticide application. Individual characteristics (sex, age, body condition) did not explain the occurrence or the concentration of pesticides found in turtle blood. Assessing the exposure of aquatic wildlife to a cocktail of currently-used pesticides is a first and crucial step before studying their effects at the individual and population levels.

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