密云水库入库河流沉积物中重金属形态分析及风险评价

Fraction distribution and risk assessment of heavy metals in sediments of inflow rivers of Miyun Reservoir

研究了北京市密云水库入库河流潮白河水系沉积物中重金属的总量及形态分布特征,采用风险评价准则法(RAC)和Tucker3模型探讨沉积物中重金属的潜在危害性.结果表明,Hg、Cd、Cr、Cu、V、Zn的平均含量均超过北京市土壤背景值,呈现一定的富集.形态分析表明,Cu的残渣态含量占总量的72%,其次为有机结合态,占22%;Mn的残渣态含量占总量的62%,铁锰氧化物结合态占23%,碳酸盐结合态占10%;Ni的残渣态含量占总量的73%,铁锰氧化物结合态占13%,有机结合态占11%;Pb、Cd、V、Zn均以铁锰氧化物结合态和残渣态为主,含量占总量的90%以上.Ti、Cr则以残渣态为主要形态.RAC评价结果显示,Cr、V、Ti对环境无风险,Ni处于无风险到低风险级,Cu处于低风险级,Cd、Pb、Mn处于低风险到中等风险级.研究结果将为北京市水源保护、人体健康安全保护措施的制定提供科学依据.

Contents and spatial distribution of heavy metals in the sediments of Chao River and Bai River in the upstream of Miyun Reservoir in Beijing were investigated in this article, and the degree of pollution was analyzed by the method of Risk assessment code （RAC） and Tucker3 model. The results showed that the average contents of heavy metals （Hg, Cd, Cr, Cu, V and Zn） were higher than the background values of Beijing soils, indicating enrichment of heavy metals. The analysis of chemical speciation showed that the residual fraction of Cu accounted for 72% of the total contents, and the organic matter fraction was 22%. The residual form for Mn accounted for 62%, Fe-Mn oxides 23%, and carbonates 10%. The residual form for Ni accounted for 73%, Fe-Mn oxides 13%, and organic matter 11%. Pb, Cd, V and Zn were dominated by Fe-Mn oxides and residual fraction, accounting for more than 90% of the total contents. Ti and Cr were dominated by the residual states. The RAC showed that Cr, V and Ti posed no risk, and Ni was between no-risk and low-risk level. Cu had a low potential ecological risk, whereas the potential ecological risk of Cd, Pb and Mn was between low-to medium-ecological risk level. The results of the study provided a scientific basis for the protection of Beijing water source and for the establishment of control measures for the sake of people＇s health and security.