Distribution characteristics and contamination assessment of heavy metals in surface sediments of Chaohu Lake, China
巢湖表层沉积物中重金属的分布特征及其污染评价

Surface sediment samples were taken from Chaohu Lake and different fractions of eight heavy metals (Cr, Co, Ni, Cu, Cd, Zn, V and Pb) were studied using BCR (European Communities Bureau of Reference) sequential extraction procedure. The pollution levels of eight heavy metals were evaluated by the potential ecological risk index (RI) and geoaccumulation index (Igeo). The heavy metal distribution of surface sediment indicated a higher degree of contamination in the east and west regions of the lake than that in the middle region. The residual fraction was the main contribution for Cr, Co, Ni, V and Cu in the sediments and the soluble fraction was the dominant for Zn and Cd, while Pb was found mainly in the reducible fraction. Meanwhile, Co and Cu were composed of the soluble and reducible fractions indicating potential hazard to aquatic organisms. The results of correlations analysis showed that Cr, Cu, Pb, Ni, Zn and Cd have the similar origin and distribution.However, Co and V possessed the alike geochemical source and their origins likely were different from the other six heavy metals. Potential ecological risk index of eight heavy metals investigated were the rank order: Cd> Pb> Co> Cu> Ni> Zn> V> Cr. Cd had high potential ecological risk and contributed most to potential ecological index compared with the other heavy metals. Based on the geoaccumulation index of heavy metals, the degree of heavy metal pollution decreased in the order of Cd > Zn> Pb> Co> Cu> V> Ni> Cr. The Igeo values suggested the unpolluted for Cr, unpolluted to moderately polluted for Co, Cu, V, and Ni, moderately polluted for Zn and Pb and moderately to heavily polluted for Cd.