Abstract: Based on the investigating for the concentrations and vertical profiles of four heavy metals (Cu, Pb, Cr and Cd) in the sediments collected from the Dishui Lake and its diversion channels, ecological risk assessments were performed using the methods of land accumulation index and potential ecological risk index. Furthermore, the bioaccumulation characteristics and dietary risk resulted by consumption of the freshwater fish in the lake were analyzed. Finally, the sources of heavy metals in sediments were identified using multiple regression and principal component analysis. The results show that the concentrations of Cu and Cd in the surface sediments of the Dishui Lake area and the diversion channel were 1.3 time and 13.0 times higher than the background value of heavy metal Cu and Cd in Shanghai tidal flat, respectively. Among the concentrations of heavy metals in the lake sediments worldwide, the concentrations of Dishui Lake were at a low level. The results also show that the concentrations of heavy metals declined with increasing of depth vertically. Cd was found the main contributor to the heavy metal pollution in the sediments of the Dishui Lake. Although heavy metals in organisms did not pose significant food risks, attention should be paid to Cu and Cd due to their high bioaccumulation potentials. Finally, based on the source identification, Cu, Pb and Cr were mainly from similar origins of traffic activities, while Cd was primarily from agricultural activities.

Key words: sediment, heavy metal, vertical distribution characteristics, the Dishui Lake