Influence of ponds on hazardous metal distribution in sediments at a catchment scale (agricultural critical zone, S-W France)

Eight potentially toxic trace elements were investigated together with the physicochemical characteristics of sediments collected upstream, downstream, and from various ponds three adjacent carbonated agricultural catchments in southwestern France. Geochemical indices local references multivariate data analysis revealed a significant enrichment Cd, followed by Ni Cu sediments, originating practices, especially upper sensitive to erosion processes. Five other PTEs (As, Pb, Co, Cr, Zn) mostly originated weathering process molasse. Clay minerals and/or iron oxides main controlling factors for most PTEs. In ponds, Cd was regulated Ca co-precipitation favoured long hydraulic retention time increased pH, whereas it controlled silicates stream sediments. Copper, highly extractable metals, suggesting risk hazardous environment. Multivariate that several environmental affected spatial variation PTE concentrations as well trapping role (texture, slope, soil erosion, pond size position, discharge, time) this area intensive practices. Our conclusions are useful management context increasing water demand climate warming.