Heavy Metal Content and Pollution Assessment in Typical Check Dam Sediment in a Watershed of Loess Plateau, China

Abstract

To understand historical trends and assess the ecological risk associated with heavy metal pollution, the concentration of eight species of heavy metals (vanadium (V), chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), zinc (Zn), copper (Cu), and arsenic (As)) in typical silt dam sediments on the Loess Plateau were analyzed. The radionuclide 137Cs was used to quantify rates of erosion, deposition, and heavy metal contamination in the soils of a watershed that supplies a check dam. The sediment record revealed three time periods distinguished by trends in erosion and pollutant accumulation (1960–1967, 1968–1981, and 1985–1991). Heavy metal concentrations were highest but exhibited significant fluctuation in the first two periods (1960–1967 and 1968–1981). From 1985 to 1991, heavy metal pollution showed a downward trend and tended to be stable. The potential risks of heavy metals in silt dam sediments were explored by applying the geo-accumulation index and the potential ecological risk index. The results indicated medium risk associated with Cu and As accumulation, especially in 1963, 1971, and 1986 when the assessed values increased significantly from previous levels. Agricultural practices and high rates of slope erosion may be responsible for the enrichment of As and Cu in soil and the accompanying increase in risk. Land use optimization and the careful use of fertilizers could be used to control or intercept heavy metal pollutants in dammed lands. The results provide the basis for evaluating the current status and ecological risk of heavy metal contamination in dam sediments and for predicting possible heavy metal pollution in the future.