密云水库沉积物中重金属形态分析及风险评价

Fraction Distribution and Risk Assessment of Heavy Metal in Sediments of Miyun Reservoir

为研究北京市密云水库沉积物中重金属的总量以及形态分布特征,采用富集因子法和风险评价准则法(RAC)探讨其污染程度。结果表明,各重金属元素的平均含量均超过北京市土壤背景值,重金属元素有一定的富集。相关性分析表明,Zn、V、Cu、Mn、Pb、Ni含量之间呈显著正相关(P<0.01),说明这些元素有着相同的人为和自然污染源。形态分析表明,Cu、Ni的残渣态分别占总量的71%、72%,其次有机结合态为17%、14%;Mn残渣态为45%,铁锰氧化物结合态占22%,碳酸盐结合态为18%;其他重金属均以铁锰氧化物结合态和残渣态为主,平均含量占总量的80%以上。RAC评价结果显示,Mn(除采样点18)处于中等风险甚至高风险等级,Pb、Zn、Cu处低风险到中等风险级,Ni、V、Cr、Ti的潜在生态风险较低。研究结果将为北京市密云水库保护、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 Miyun Reservoir in Beijing were researched in this article, and the degree of pollution was analyzed by the method of Enrichment Factor and Risk Assessment Code（RAC）. The results showed that the average contents of all heavy metals were higher than the background values of Beijing soils, and heavy metals appeared certain enrichment. Correlation analysis showed that significant correlations existed among Zn, V, Cu, Mn, Pb, Ni（P〈0.01）, and it indicated that these elements have the same man-made and natural sources of pollution. The analysis of chemical speciation showed that the residual fraction for Cu and Ni accounted for 71%, 72% of the total contents, respectively. And then the organic matter fraction was 17%, 14%. The residual form for Mn accounted for 45%, Fe-Mn oxides fraction was 22%, and bound to carbonates fraction was 18%. Other heavy metals were dominated by Fe-Mn oxides fraction and residual fraction, they accounted for more than 80% of the total contents. The RAC showed that Mn（except the sampling point 18） posed a medium ecological risk or high ecological risk, and the potential ecological risk of heavy metals（Pb, Zn, Cu） was from low risk to a medium ecological risk level, whereas Ni, V, Cr and Ti posed low risk. The results of the study will provide a scientific basis for the protection of Miyun Reservoir and the estabilishment of measures for people′s health and security.