Abstract:

Heavy metal pollution is one of the major problems in aquatic sediment. Studies on the sources and chemical speciation of heavy metals in aquatic sediment can provide a theoretical basis for the remediation of heavy metal pollution in aquatic sediment. BCR three stage sequential extraction procedure was applied to examine the chemical speciation of As and 7 heavy metals (Cd,Co,CrM,Cu,Ni,Pb and Zn) in sediments of Poyang Lake, and the potential ecological risks of As and these 7 heavy metals were assessed based on the risk assessment cod (RAC) criteria, which is based on the percentage of metal present in acid soluble fraction. The average total concentrations of As, Cd, Co, Cr, Cu, Ni, Pb, and Zn in sediment of Poyang Lake were 1574 mg/kg, 052 mg/kg, 1557 mg/kg, 6903 mg/kg, 3092 mg/kg, 2474 mg/kg, 6717 mg/kg, 8028 mg/kg, respectively, and the concentrations of all the trace elements were higher than their background values of soil in Jiangxi Province. The major speciation of As, Co, Cr, Cu, Ni and Zn in sediment of Poyang Lake was residual fraction (6160%-8518%). While Pb showed the highest percentages in the residual fraction (5097%) and FeMn oxide fractions (4102%), and the percentage of extractable Pb form was 4903%, implying that the potential risk of secondary release of Pb in Poyang Lake was high. Cd was mostly concentrated in acid extractable fraction (4160%) and FeMn oxide fraction (2719%), and the extractable Cd (F1+F2+F3) was as high as 7749%, indicating that Cd posed a high risk to local environments. According to the Risk Assessment Code (RAC), major portion of Cd was contained in acid extractable fraction (4160%), suggesting that the potential ecological risk of Cd in Poyang Lake was high, and more attention should be paid to the Cd pollution in Poyang Lake. Cr in acid soluble fraction at all the sampling sites was less than 1% of the total content and therefore came under the no risk category. Speciation pattern of As, Ni, and Pb showed low risk to aquatic environment health in Poyang Lake, and Cu, Co, and Zn showed low to medium risk to the environment. The extractable contents (F1+F2+F3) of As, Cd, Co, Cr, Cu, Ni, Pb, and Zn in sediment of Poyang Lake were 366 mg/kg, 042 mg/kg, 603 mg/kg, 824 mg/kg, 1200 mg/kg, 3205 mg/kg, and 2749 mg/kg, respectively, and their spatial variability coefficients were 2514%, 8453%, 4240%, 3421%, 13422%, 5078%, 3742%, and 5504%, respectively, suggesting that spatial distributions of Cd, Cu, Ni, and Zn in sediment of Poyang Lake are inhomogeneous