Evaluation on Potential Ecological Risk of Heavy Metal Pollution in Sediment of Urban Sewage River

Taking an urban sewage river in north China as study object, total concentrations and concentrations of different chemical forms of heavy metals in surface sediment samples are determined. The relative enrichment factors and the potential ecological risk index, Hakanson index, are taken to study the pollution status of heavy metals in sediments and assess the potential ecological risk. The results show that Cd and Cu are more enriched while Zn, Pb and Cr are less enriched. The ecological risk of heavy metals in sediments of the sewage river is at a high level, dominated by the considerable ecological risk of Cd and Cu. The five metals of Cd, Cu, Pb, Zn and Cr at ecological risk levels are in the descending order. The main chemical forms of different heavy metals are not the same. Zn is concentrated in carbonate associated form, Cd is concentrated in exchangeable and carbonate associated forms, while Pb, Cu and Cr is concentrated in residual form.