Interactions of phosphorus with sediments in the River Swale, Yorkshire, UK

The ultimate fate of inorganic phosphorus in natural waters is to a large d egree determined by interactions with sediments. The interactions in river bed sediments have been investigated by a combination of methods using surf ace sediments, <2 mm in diameter, collected from a 55 km stretch of the Riv er Swale in Yorkshire, UK. The sediments were analysed by digestion (Fe, Ca and P), clay mineralogy and their equilibrium phosphate concentration. All the equilibrium phosphate concentrations were below 2 mu mol dm(-3), which is much less than the concentration in the overlying water and indicates a net uptake of phosphorus by the sediments. Experiments in a fluvarium chan nel with a coarse sediment also showed that the release and uptake of solub le phosphorus was towards a steady-state concentration in the overlying sol ution, consistent with measurements of the equilibrium phosphate concentrat ion. A kinetic model describing the net uptake of soluble reactive phosphor us by river sediments was applied to chemical data collected during an inte nsive monitoring exercise in the catchment. Copyright (C) 1999 John Wiley & Sons, Ltd.