Abstract: To explore the characteristics of sediment heavy metals pollution and its history of four reservoirs in east coast of Guangdong Province, the main heavy metals Cr, Cd, Cu, Zn, Pb, and Hg in the sediments were detected, and the pollution status of surface sediments was evaluated with geo-accumulation index and Hǎkanson potential ecological risk index, respectively. The possible sources of the heavy metals were also discussed. In the surface sediments of the four reservoirs, the contents of the test heavy metals except Cd all exceeded the Class I values of the China National Standards of Soil Environmental Quality and the highest background values of heavy metals in the global sediments before industrialization, and had great variation between the reservoirs, indicating that the sediments of these reservoirs had been polluted in different degrees. Geo-accumulation index of the four reservoirs showed that the pollution degree of the heavy metals followed the order Pb>Zn>Cd>Cu>Cr>Hg, and Hǎkanson potential ecological risk index indicated that the potential ecological risk of the heavy metals followed the order Cd>Hg>Pb>Cu>Zn>Cr, of which, heavy metals Cd and Hg contributed most to the comprehensive ecological  risk index (RI). The sediment heavy metals contents had a strong correlation with human activities, and the two assessments all showed that the pollution status of Gongping Reservoir and Chisha Reservoir with stronger human activities were worse than that of Hexi Reservoir and Tangxi Reservoir with less human activities.

Key words: forest ecosystem, carbon and water interactions, water use efficiency, model, global change.