Downstream changes in the transport and storage of sediment-associated contaminants P, Cr and PCBs/ in agricultural and industrialized drainage basins

Samples of suspended, floodplain and channel bed sediment have been used to examine downstream changes in sediment-associated contaminant transport and storage in contrasting rivers in Yorkshire, UK. The concentrations of phosphorus, chromium and selected PCBs associated with sediment in the River Aire and its main tributary, the River Calder, which drain an urbanized and industrialized catchment, are considerably higher than those in the relatively unpolluted River Swale, which drains an agricultural catchment. Concentrations of sediment-associated contaminants in the AirerCalder system increase downstream, reflecting the location of urban and industrial areas in the middle and lower reaches, and the location of point source inputs, such as sewage treatment works. The contaminant concentrations associated with floodplain and channel bed sediment in the Rivers Aire and Calder are high, particularly in the lower reaches. This, combined with measurements of sediment storage on the floodplain and channel bed, indicate that significant storage of sediment-associated contaminants occurs in the Rivers Aire and Calder.