Evaluation of Sediment-associated Heavy Metal Pollution in Chaohu Lake, Eastern China

Abstract

Heavy metal pollution in lacustrine sediments is a worldwide environmental issue. In the present study, eight heavy metals including Zn, Pb, Co, Cr, Cd, Mn, As and Cu in sediment cores collected from Chaohu Lake, Eastern China were determined, and potential sources and risks of selected heavy metals were evaluated using multivariate statistical techniques and pollution indices. Results show that all sampling areas were extremely contaminated by Cd, and were not significantly affected by Mn. High accumulation of Zn, Pb and Cu in urban area related sites implies they were generally derived from urban sources including municipal and industrial sewage. Whereas high concentrations of As and Cd, and Co in rural locations possibly suggests agricultural sources. Possible decreasing trends for most elements in the sediment cores indicate the reduction of total input amounts which would be attributed to the increasing operation of wastewater treatment plants in the urban areas. Different intercorrelations between each two elements for four sampling sites reflect the different input sources. Cluster analysis also indicates the residual elements in sediment cores of Chaohu Lake were generally from natural materials for Mn, from urban origins for Cu, Zn and Pb, and from agricultural activities for the remaining elements. The results from both contamination factors and geo-accumulation index (I_geo) suggest sediments were not polluted by Mn, extremely contaminated by Cd, and slightly to moderately impacted by the remaining elements. But all samples were examined with significant metal pollution given their pollution level index values higher than 1.0.