Abstract:

In order to understand the pollution characteristics of heavy metals in sediments of the Lake Dishui，eighteen sediment samples were collected in December 2012 at the Dishui Lake and its surrounding areas. The concentrations of Hg, As, Cu, Cd, Pb, Zn, Cr in the sediments were analyzed and the pollution statue of heavy metals in the sediments was evaluated using geoaccumulation index and potential ecological risk index. Principal component analysis was applied to identify their sources. The results showed that the concentrations of Hg, As, Cu, Cd, Pb, Zn, Cr in sediments of the Dishui Lake were 005-028，037-593，808-2638，013-025，1136-1766，5692-9743，6730-10718 mg/kg，respectively. The As and Pb concentrations were inferior to their background values in intertidal sediments of Shanghai，but the Hg, Cd, Zn and Cr concentrations were exceeded the background values，the Cu concentrations of 50% sediment samples were exceeded the background values. Compared with domestic and international lakes，the level of heavy metals in sediments at the Dishui Lake was under Macquarie and the Dongting Lake，but corresponding to the Nansi Lake. The spatial distribution of heavy metals in sediments had certain regularity. The heavy metal concentrations in sediments from the lake were less than those from the river and estuary，which indicated the heavy metals did not have an obvious precipitating in the lake land. Pearson correlation analysis showed that TOC was the main factors influencing the spatial distribution of heavy metals in sediments，and particle size influenced the spatial distribution of Cu and Cd in sediments. The results of geoaccumulation index showed that the Dishui lake was mainly polluted by Hg, Cd, zinc and Cr，the pollution extent of Cr was partial moderate pollution，Hg, Cd and Zn were light pollution，As, Cu and Pb were unpolluted. Based on the potential ecological risk assessment results，the mean RI value can be ordered from high to low as Shanghai Maritim University > Intertidal sediments > Lake outlet > Estuary > Dishui Lake. The heavy metals in sediments of the Dishui Lake belonged to the moderate ecological risk. Hg and Cd was the main contribution of the potential ecological risk elements，accounting for 58.73% and 30.89%，respectively, while As, Cu, Pb, Zn and Cr accounted for 10.38%. The principal component analysis revealed that Hg, Cu, Cd, Pb, Zn and Cr mainly came from the anthropogenic sources，Cr was also affected by the chemical composition of the earth，but As mainly came from the initial tidal flat sediment