Zinc behavior in river materials through the double spectroscopic and isotopic tools

International audienceActually, the fate of the metal rich sediments and the dynamics of their re-mobilization need to be better understood for a better management of water resources. Widely used in industry and urban areas, Zn is ubiquitous in continental waterbodies, with contents ranging from few dozens to several thousand ppm in sediments and suspended particulate matter (SPM). In a double context of metal contamination and global climate change, we aim to identify the resuspended contaminated sediments via several markers, including Zn speciation and Zn isotopic fingerprinting.Sediments and SPM were collected in different rivers of the Moselle watershed, France, including rivers previously impacted by steelmaking activities (the Orne and Fensch Rivers). River SPM were collected during low an high water discharges and with intensive sampling during several flood events. Besides chemical composition and mineralogy, Zn speciation in river materials was unraveled using TEM and X-ray absorption spectroscopy at the Zn K-edge. Contaminated sediments were characterized by the predominance of Zn-sulfides, while SPM and recent sediments display Zn mainly bound to clay minerals and to a lesser extent to iron oxyhydroxides and carbonates. Concerning isotopic signature, δ66ZnIRMM-3702 values ranged from -0.12 to 1.36 ‰ and from -0.12 to -0.05 ‰ for sediments and SPM, respectively. The combination of spectroscopic and isotopic tools provided insights about sources and resuspension processes during flood events