Heavy metals and arsenic in alluvial sediments of the Grote Beek river (N Belgium) :contribution of natural and antropogenic sources

Wastewater discharge from the processing of phosphate ores has contributed to pollution by heavy metal and As in soils adjoining the Grote Beek river. Overbank deposition of polluted river sediments during inundation of the floodplain and the disposal of dredged sediments brought about a severe pollution of the peat soils with Cd, As, Zn, Ni, Cr, Ba and Cu, 3km from the effluent ejecting point. Moreover, anomalous enrichments of As occur as a result of the presence of glauconite. The pollution of flooding zones, especially of As and Cd, is extended to more than 50m from the river channel. Porewater from soils near the river displays high concentrations of Zn, Ni, Cu, Cd, Ba and Cl. In contrast, the sandy soils 10km downstream are hardly influenced by polluted sediments. However, elevated Asconcentrations in subsoil may have a diagenetic origin. In sediments disposed by overbank flooding, Cr, Cu and Zn were primarily associated with the fine grained fraction, while As is bounded to Fe-(hydr)oxides. Ca-carbonate seems to contribute to the binding of heavy metals in dredged sediments. ispartof: Aardkundige Mededelingen (Proceedings of the first Geologica Belgica International Meeting, Leuven, 11-15 September 2002) vol:12 pages:227-230 status: published