Historical accumulation and ecological risk assessment of heavy metals in sediments of a drinking water lake

Abstract

Heavy metal contamination in sediments is progressively being recognized as a challenging problem in large parts of the developing world, particularly in Asian countries. A drinking water lake in Yunnan-Guizhou plateau, China named Hongfeng Lake was selected as the research target. Forty surface sediment samples and 4 sediment cores were collected to reveal the accumulation of heavy metals in the sediments of the lake. The mean concentrations of Cr, Cu, Pb, Cd, As, and Hg in surface sediments were 81.67, 45.61, 29.78, 0.53, 22.71, and 0.25 mg/kg, respectively, which exceeded the background levels of sediment 1.1~3.3 times. The calculation of geoaccumulation (I_geo) and potential ecological risk (PER) index analysis were preformed, and the results showed a considerable risk for Cd and Hg on the whole. Spatially, the northern part showed a higher risk than the southern part and tributaries of the lake, and a moderate risk in the overall sediment of the lake. The historical level of heavy metals in Hongfeng Lake was traced by vertical sediments study and it was dated back approximately 35 years. The EF trends of a feature sampling site HF8 showed strong temporal variations, and peaked in the year 1995. After that, the EFs exhibited a declining trend, which reflects productive environmental protection and management by the local government. For the Hongfeng Lake, a typical lake with heavy metal-contaminated sediments, the in-situ remediation technique could be a suitable method for its remediation.