Influence of Sediment Characteristics on Heavy Metal Fraction Distribution in the Water-Level Fluctuation Zone of the Three Gorges Reservoir Area, China

Abstract

The concentrations and fractions of heavy metal in sediments at different altitudes in the water-level fluctuation zone (WLFZ) of the Three Gorges Reservoir (TGR) were determined. The Pearson correlation analysis was used to determine the differences between heavy metal fractions and physicochemical properties. The results showed that Cr and Cu were mainly horizontally and vertically distributed in the residual (RE) fractions with the highest stability and relatively low ecological risk. Pb and Zn were mainly in the Fe-Mn oxide-bound (Fe-Mn) fractions, which can be reduced to a bioavailable state when the redox potential decreased or the oxygen was severely depleted in the aquatic environment. There were significant differences in the heavy metal fractions and risks in sediment in the three different altitudes of the TGR. The physicochemical characteristics of the sediment indicated that the sediments in the low altitude area had rough forms and large pores. In addition, heavy metals at low altitudes were likely to be released into the water during antiseasonal water storage, causing secondary pollution, which greatly increased the mobility of heavy metals and ecological risks to the environment.