Assessment of pollution and identification of sources of heavy metals in the sediments of Changshou Lake in a branch of the Three Gorges Reservoir

To assess the heavy metal pollution in Changshou Lake, sediments were collected from nine sites at three periods (dry, normal, and wet) in 2013. The Hg, As, Cr, Cd, Pb, Cu, and Zn levels were then determined. The index of geoaccumulation (I-geo) and the sediment pollution index (SPI) were applied to the sediment assessment, and Pearson's correlation analysis and factor analysis (FA) were performed to identify common pollution sources in the basin. The results showed that heavy metals presented significant spatial variations with Cr, Cd, Pb, Cu, Zn, Hg, and As concentrations of 29.66 similar to 42.58, 0.62 similar to 0.91, 24.91 similar to 37.96, 21.18 similar to 74.91, 41.65 similar to 86.86, 0.079 similar to 0.152, and 20.17 similar to 36.88 mg kg(-1), respectively, and no obvious variations were found among the different periods. The average contents of the metals followed the order Zn>Cu>Cr>Pb>As>Cd>Hg, which showed a high pollution in the sediments collected from open water and at the river mouth. The assessment results indicated that toxic heavy metals presented obvious pollution with I-Hg of 0.64 similar to 1.36 (moderately polluted), I-Cd of 1.66 similar to 2.22 (moderately to heavily polluted), and I-As of 1.21 similar to 2.07 (moderately to heavily polluted). The heavy metal pollution states followed the order Cd>As>Hg>Cu>Pb>Zn>Cr, and the SPI showed that the sediment collected from open water area was more polluted than those obtained from the tributaries and the river mouth. Cr, Cd, Hg, Pb, Cu, As, and Zn were mainly attributed to sediment weathering with Hg, Pb, and Cu and partially due to domestic sewage from the upper reaches. These results indicate that the more attention should be paid to the inner loads of sediment in order to achieve improvements in reservoir water quality after the control of external pollution.