Contamination Assessment and Source Identification of Heavy Metals in River Sediments in Nantong, Eastern China

Heavy metal pollution in river sediments caused by industrialization and urbanization is a pressing environmental issue around the world. This issue is more serious in the rapidly industrializing countries like China. In this study, the contamination and sources of nine metals (Al, As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) in 134 river sediments in Nantong, Eastern China have been analyzed using various statistical and spatial analysis techniques. Contamination level assessments using enrichment factor (EF), geo-accumulation index (I-geo), and ecological risk index (RI) revealed that rivers suffer severe heavy metal pollutions, especially for Pb and Zn. Four main potential sources of the metals were identified using principal component analysis (PCA) and cluster analysis (CA). They are: (1) industrial sources contributing As, Cr, Pb, Zn, and partly Cu, (2) parent materials contributing Al, Ni, and partly Cu, (3) municipal and domestic wastes associated with Hg, and (4) excessive fertilizer application responsible for Cd. The potential sources were further verified by comparing their spatial distributions and the locations of the actual local sources using GIS (Geographic Information System)-based spatial analysis. The results are useful for environmental protection agencies to target corresponding pollution sources for the contaminations of specific heavy metals.