Abstract: On the basis of investigation and analysis of heavy metals in the sediment of an urban lake in Ezhou, Hubei Province, the heavy metals in the sediment were evaluated according to geologic accumulation index and potential ecological hazard index. Results indicated that heavy metal concentration in the sediment declined from top to bottom, and the heavy metal content in the upper sediment was the highest. The west region of lake subjected to the most severe pollution of heavy metals, followed by the east region and the middle region in sequence. In terms of geological accumulation index, heavy metals in the sediment were mainly pollution-free to moderately polluted; the pollution degree of different heavy metals followed the order of Cd>Zn>Cu>Pb>Ni>Cr>Hg>As. According to the potential ecological risk index, As, Ni, Cu, Pb, Cr and Zn in the sediment posed low ecological risk, whereas Cd and Hg had potential ecological risk at different degrees, and Cd posed the highest ecological risk.

Key words: urban lake, sediment , heavy metals, index of geo-accumulation, potential ecological risk assessment