Mobility of radium and trace metals in sediments of the Winterbeek: application of sequential extraction and DGT techniques

For several decades, phosphate ores containing (226)Ra as well as several trace metals have been processed in Belgium to produce calcium phosphate for use in cattle food. The waste water is discharged in two small rivers, the Laak and the Winterbeek. In this study, the levels of (226)Ra and trace metals in surface water and sediments of the Winterbeek were investigated and the mobility of these compounds was assessed using DGT (Diffusive Gradient in Thin Films) and sequential extraction techniques. The concentrations of (226)Ra and trace metals in water and sediment indicate a decreasing trend in inputs to the Winterbeek. The mobility of (226)Ra, assessed by DGT, is related to the reductive mobilization of Fe. The sequential extraction technique shows that at some stations an important fraction of (226)Ra is found to labile sediment phases. Diffusive (226)Ra sediment fluxes, are however, relatively small and have only a minor contribution to the water column concentration of (226)Ra.