Concentrations and risk assessment of chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), lead (Pb), cadmium (Cd) and mercury (Hg) were investigated in 106 samples of surface sediments from the East Lake, China in this study. The mean concentration of Zn was highest among the eight heavy metals (225 mg kg(-1)), followed by As (191 mg kg(-1)), Cr (145 mg kg(-1)), Cu (55 mg kg(-1)), Ni (27.1 mg kg(-1)), Pb (7.93 mg kg(-1)), Cd (0.94 mg kg(-1)) and Hg (0.21 mg kg(-1)). Niuchao Hu was less polluted by heavy metals compare to the other four lakelets of the East Lake. The correlations among these heavy metals and the results of principal component analysis indicated that the distribution of Cd, Pb and Hg was related to anthropogenic activities, whereas Cu, As and Cr were affected by the parent rocks. Zinc and Ni were influenced both by anthropogenic activities and parent rocks. Based on the Sediment Quality Guidelines, the results of toxicity assessment indicated that adverse effects caused by Cr and As would be expected frequently. Nickel, Zn, Cd and Hg may cause adverse effects occasionally and Cu and Pb may cause toxicity infrequently. Arsenic was found to have the highest acute toxicity by toxic units (TUs), followed by Cr, Ni, Zn, Hg, Cu, Cd and Pb. The potential ecological risk index analysis indicated that As, Cd and Hg had considerable or high ecological risk, whereas Cr, Ni, Cu, Zn and Pb had low ecological risk. The potential ecological risk index (RI) of the heavy metals in the surface sediments of East Lake was 483, indicating considerable ecological risk. Close attention should be paid to pollution of the heavy metals in East Lake, China.
