Integrated biogeochemical, geographical and hydrological approaches to track sources of contaminants in mixed land-use watersheds – CHYPSTER

The presence of numerous chemical and microbiological contaminants in aquatic ecosystems, including toxic (e.g. endocrine disruptors) and/or persistent contaminants can lead to a significant degradation of the ecological status of natural waters and increase human and animal exposures to these contaminants through drinking water, crop irrigation or recreational uses; they may also trigger a rise of antimicrobial resistance (AMR) genes and bacterial pathogens in hydrosystems. Mesoscale watersheds (~10-1000 km²) with mixed land-use and heterogeneous geologies are particularly sensitive to such contaminations. In the near future, increasing surface artificialization as well as climate change could result in critical degradation of water quality in these watersheds. The identification of contaminant sources in mesoscale watersheds, including non-point sources, the estimation of their contributions to watershed outlets, and the prediction of water quality in a context of climate change and land-use trajectory are key issues for the development of action plans to reduce contamination of freshwater ecosystems and protect their ecological state.
This CHYPSTER project aims to define a new interdisciplinary approach to identify the sources of anthropogenic contaminants and predict future water quality trajectories based on hydrological processes, changes in land-use and anthropogenic activities, and climate change. This approach will be applied on two mesoscale watersheds (the Claduègne and Yzeron sites that belong to the national research infrastructure OZCAR) by combining diagnosis of land cover and uses of chemicals, biogeochemical fingerprinting, and distributed hydrological modelling. Methodological expertise in spatial analysis, combining geomatics and survey, will be mobilized in order to identify potential sources of contaminants and their location. Advanced passive sampling, and target and non-target analytical tools, both chemical and microbiological, will be deployed to obtain specific datasets on contaminant sources and allow building-up new biogeochemical fingerprints that will be combined with flow contributions estimated by the hydrological model for hydrological events. The use of the validated hydrological model on scenarios of climate change and territories trajectories evaluated with local socio-economic actors will allow to make predictions on the surface water chemical and microbiological qualities at the outlet of watersheds.
This project will bring new knowledge on the characterization of chemical cocktails and microbial contamination (AMR and pathogen–related genes, source-specific keystone taxa) of freshwater ecosystems. The results will facilitate the location, identification and quantification of the main sources of contaminants (including Contaminants of Emerging Concerns [CECs]) along with land-use in catchments of mixed land-use (multiple sources) and mesoscale, in order to define and then initiate relevant actions (e.g. management of storm water outfalls and retention basins for the urban part, buffer zones in agricultural areas) to reduce contaminant pressure onto hydrosystems and the related hazards and ecological impacts. The projections of future river hydrology and water quality according to land-use and land cover change scenarios will also give keys for water and soils management at the catchment scale, in order to reduce contaminations. This project will also contribute to the development of innovative tools and markers for the monitoring of water quality that will be transferable to other research laboratories including private ones. Interestingly, the use of passive samplers termed germcatchers will allow to infer the relationships between chemical pollutants and bacterial taxa developing as biofilms in river systems. These data will thus bring novel insights on resistomes emerging in the environment, and the associated AMR gene recruitments or bacterial taxa enrichments.