Lessons from a national scale study in France: Trace metals measured in freshwater by diffusive gradient in thin film

The last past decades of research have shown that the passive sampling technique DGT (Diffusive gradient in thin film)(Zhang and Davison, 1995) is a robust tool to monitor trace metals in freshwater. The progress made in... [ view full abstract ]

The last past decades of research have shown that the passive sampling technique DGT (Diffusive gradient in thin film)(Zhang and Davison, 1995) is a robust tool to monitor trace metals in freshwater. The progress made in understanding the use of DGT allow us to produce reliable measurement of metals and to extend the use of DGT at a scale larger than a few close sampling sites. We propose to present how a field study including more than 100 sites all over France has been implemented and what are the first results and lessons from this study regarding the spatial and environmental distribution of metals.
DGT were deployed during one week at each site. Grab sampling of total and filtered metals were taken at the beginning and the end of the deployment. Physicochemical parameters (temperature, pH, conductivity, anions and cations, DOC) were also measured. In parallel, gammarids were transplanted to measure bioaccumulated metals. The whole set of measurements constitute a rich dataset including large and small rivers, and reference as well as impacted sites. The results first allowed us to draw a map the metallic contamination at the national scale. Then multivariate analyses were conducted to assess the explanatory variables of the distribution: geochemical patterns, anthropogenic stresses, and abiotic factors like organic matter or temperature. The advantages to use passive samplers like DGT to assess trace metal contamination and the ability of the DGT to meet regulatory monitoring expectations will be discussed, as well as implication for environmental management.