汤峪水源水库沉积物中重金属形态分布特征及潜在生态风险评价

The speciation of heavy metals in the sediment of the Tangyu Reservoir and assessments of the potential ecological risk

汤峪水库是西安市的重要供水水源地,为了解重金属污染状况,对汤峪水库沉积物中重金属Cd、Zn、Cr、Ni、Cu和Pb的形态分布特征和潜在生态风险进行了研究.结果表明:汤峪水库沉积物中重金属含量均低于中国水库底泥重金属含量背景值.沉积物中Cd的单项潜在生态风险系数远大于其他重金属,达32.40,因此Cd是汤峪水库沉积物中重金属的潜在生态风险的主要贡献者.沉积物中Pb主要以可还原态形式存在,Cd的赋存形态除残渣态外,主要以更易从沉积物孔隙水向上覆水体释放的水溶态、可交换态形式存在.氧化还原条件对沉积物中Cr,Cd和Pb的形态分布有较为显著的影响,好氧条件下沉积物中Cr,Cd和Pb的具有潜在环境效应的各形态含量占总量的比例均发生不同程度的下降趋势,而厌氧条件下,沉积物中重金属的环境地球化学行为得到了进一步的活化.

The Tangyu Reservoir is the main drink water source for Xi′an city.The research on the pollution characteristics and the assessments of the potential ecological risk of the heavy metals（Cd,Zn,Cr,Ni,Cu and Pb） in the superficial sediment seems necessary.The results showed that the concentrations of the six heavy metals are lower than that of the background values in lake sediment in China. The speciation of the heavy metals in the superficial sediment were investigated by the BCR sequential extraction. The potential ecological risk index（） of Cd in the superficial sediment is higher than other heavy metals. The sequential extraction experiment showed that the main speciation of Pb in sediment was the reducible fraction. In addition to the residue fraction,Cd existed in the sediment mainly as the form of dissolvable and exchangeable fraction which could be more easily transferred from the sediment to the overlying water. The study of the influence of the redox condition on the heavy metal speciation shows that the environmental behavior of Cd,Cr and Pb was strengthened,while it was opposite to that in the reduced condition.