浍河祁县段底泥沉积物重金属的生物有效性及风险评价

Bioavailability and risk assessment of heavy metals in surface sediments from Qixian Section of Huihe River

为深入认识浍河祁县段底泥沉积物中重金属元素的赋存状况及生态风险,采集12个表层沉积物(0~20cm)样品,采用改进的BCR连续提取法进行元素形态和生物有效性分析,进而运用潜在生态风险指数法对其污染进行评价。结果表明,研究区河段底泥沉积物中重金属元素Zn,Pb,Ni,Cr,Cu的平均含量均高于安徽省土壤背景值,存在一定程度的累积现象;各元素含量的空间分布受煤矿开采活动影响显著,在研究区河段内沿程呈现"先升高、后降低"的变化趋势;5种重金属元素的潜在生态风险均为轻微风险等级;底泥沉积物中Zn,Ni,Cr主要以残渣态为赋存形态,Pb以可还原态为主,Cu的可还原态和可氧化态比例大致相当,且占较大比重,各元素的生物有效性从大到小依次为Pb,Cu,Zn,Ni,Cr。

To analyze the speciation and ecological risk of the heavy mentals in surface sediments from Qixian section of Huihe River, 12 surface sediments samples（0-20cm） are collected. The speciation and bioavailability of the heavy mentals are analysed by using optimized BCR sequential extraction procedure and the pollution of heavy metals is assessed using the potential ecological risk index. The result shows that the average contents of Zn, Pb, Ni, Cr, Cu in sediments from Qixian section of Huihe River are higher than background value of the local soils, indicating that the heavy metals have a certain enrichment ; The spatial distribution implied that the high values of heavy metals are significantly affected by the coal mining activities and the variation treadency of the study area increases at first and then decreases. Potential ecological risk index indicated that the degree of 5 kinds of heavy metals in the sediments from the river section represented mild ecological harm. Zn, Ni and Cr are mainly composed with residual fractions, and mass fractions of Pb existed mainly in reducible fractions, Cu is mainly constituted of reducible and oxidizable fractions. Bioavailability analysis reveals that the selected heavy metals in the sediments is in the descending order ofPb, Cu, Zn, Ni, Cr.