Distribution, Bioavailability and Ecological Risk of Heavy Metals in Surface Sediments from the Wujiang River Basin, Southwest of China

Abstract

Chemical speciation of Cu, Zn, Mn, Pb, Cd, As, and Hg in surface sediments from the Wujiang River Basin was analyzed by using modified BCR sequential extraction procedure. The results indicated that the mean total concentrations of all heavy metals except As were higher than their background values. Cu, Zn, Pb, As, and Hg mostly exist in a residual fraction. The Mn and Cd were dominated by the reducible fraction and exchangeable fraction, respectively. According to the risk assessment code (RAC) classification, Cu, Zn, Pb, As, and Hg posed a relatively low risk in this study area, while Mn and Cd posed a high risk in most sampling sites. The I geo classification manifested that Cd has the highest environmental risk and the pollution levels of heavy metals in the surface sediments were generally in the sequence of Cd>Zn>Cu>Pb>Hg>Mn>As. The potential ecological risk index (PERI) was classified as considerable risk in two sampling sites and moderate risk in ten sampling sites. It should pay much attention to the ecological risk of heavy metals from the Wujiang River Basin which will influence the Yangtze River ecosystem eventually.