Abstract: To understand the present status of the heavy metal (Cr, Cu, Zn, Cd, Pb and Hg) pollution of the sediments in water supply reservoirs in Huizhou, sediment cores were sampled from three representative reservoirs. The heavy metal concentrations were analyzed by ICPMS, and the pollution status was assessed by geo-accumulation index (I_geo) and potential ecological risk index (RI). In the meantime, the possible sources of the heavy metals were analyzed by the principal component analysis (PCA). In the sediments of the three reservoirs, the test heavy metals had different vertical distribution, some had less change, the others decreased or increased with depth, and the distribution patterns differed with the reservoirs. According to the I_geo, the sediments in the reservoirs were seriously polluted by Zn and Pb (Zn: 49.98-640.29 mg·kg^-1; Pb: 21.94-300.66 mg·kg^-1), reaching slight  to high pollution, and the middle or bottom part of the sediments was slightly polluted by Cu (16.85-45.46 mg·kg^-1). On the whole, the sediments were not polluted by Cr, Cd and Hg. According to the RI and the potential ecological risk coefficient [E_r(i)], the sediments in the three reservoirs were under low potential ecological risk. Based on the PCA and relevant information, the human activities such as mining and smelting, urbanization, and agriculture and forestry had great contribution to the heavy metal pollution. The Zn and Pb pollution mainly originated from mining and smelting, Pb pollution also came from motor vehicle exhaust emission and domestic wastes, and Cu pollution mainly derived from agriculture and forestry.

Key words: heavy metal, geo-accumulation index, potential ecological risk index, sediment, reservoir.