[Spatio-temporal Variations, Contamination and Potential Ecological Risk of Heavy Metals in the Sediments of Chenghai Lake].

Heavy metals pollution in the sediments is one of the main factors impacting the water quality and ecosystem health. In this study, concentrations of ten metals in nine sediment cores from the Chenghai Lake were determined. Chronology of a typical core (CH2012) was constructed by the Pb and Cs dating method. The spatio-temporal variations in concentrations and contamination characteristics of As, Cd, Cu, Hg, Ni, Pb, and Zn were evaluated. The potential eco-risks of heavy metals in the surface sediments were studied by combining the ecological risk index and sediment quality guidelines (SQGs) assessment as well as their pollution levels (enrichment factors, EF). The metal concentrations in each sediment core showed little vertical change with coefficients of variation of less than 0.20, except for Cd, whose coefficient of variation was 0.59. Spatially, the average concentrations of each metal showed minor difference among the cores, with ratios ranging from 1.2 to 1.8, suggesting similar sedimentary characteristics of metals in the whole lake. Cd and Pb were influenced by anthropogenic contamination that has started in the mid-1980s. The pollution level of Cd decreased in the past decade and still belongs to the moderate pollution degree, whereas the pollution level of Pb increased continually and could be classified as the weak pollution degree. The Hg contamination began in the late 1990s, with EFs ranging from 0.9 to 1.6, belonging to the weak pollution degree. The As, Cu, and Zn pollution occurred mainly near the surface sediments with weak pollution degrees. Spatially, there were no obvious trends in pollution levels of the metals. The heavy metals pollution is mainly influenced by atmospheric deposition that originates from non-ferrous metal smelting emissions, as well as agricultural and domestic discharges. As, Cu, Ni, Pb, and Zn in the surface sediments have low potential ecological risks, whereas Hg and Cd may pose middle-high potential risks.