Distribution and characteristics of heavy metals in soils of water-level-fluctuating zone of Pengxi River, Three Gorge Reservoir
三峡澎溪河回水区消落带岸边土壤重金属污染分布特征

The distribution and the correlation of heavy metals (Cu, Cr, Zn, As, Cd, Pb, Hg) in the surface sediment and soils of the water-level-fluctuating zone in the backwater reaches of Pengxi river were studied based on examining the heavy metal concentration and analyzing geochemical characteristics of samples. The contamination level and potential ecological risk of these elements were evaluated using the Geo-accumulation Index and Potential Ecological Risk Index. The result indicated that the average concentration of Cu, Cr, Zn, As, Cd, Pb, Hg in the soil of water-level-fluctuating zone was 28.17, 59.21, 108.98, 4.77, 2.02, 28.85, 0.52 mg·kg-1, respectively, and it was 22.32, 54.90, 98.05, 7.87, 0.77, 22.97, 0.94 mg·kg-1 in the surface sediment, respectively. Cd was highly polluted element in the Three Gorges Reservoir (TGR). Correlation analysis indicated that Cd had a significant correlation with Zn at 0.01 level, while Pb and Hg were significantly positively correlated with Cu and As in the soil of the water-level-fluctuating zone, indicating that these four heavy metals may be similar in response to external pollution. Cd was significantly correlated to Zn at 0.01 level, and so were Cr and Cu, As and Hg. Whereas Cu, Cr, Zn, and Cd were significantly positively correlated with Pb in surface sediments, indicating that these five heavy metals may have similar sources. The contamination level for the seven metals followed a descending order of Cd>Hg>Zn>Pb>Cu>As>Cr in the soil of water-level-fluctuating zone, and Hg>Cd>Zn>As>Pb>Cu>Cr in the surface sediment. Of the seven elements, Cd and Hg reached serious pollution level at some stations. The soil in the water-level-fluctuating zone can become a potential pollution source for the water column with disturbance. Therefore, close attention should be paid to the potential impact of heavy metals in this zone.