密云水库上游某铁矿区土壤重金属含量及形态研究

Studies on the distribution and chemical speciation of heavy metals in a iron mine soil of the upstream area of Miyun Reservoir,Beijing

应用富集因子法（EF）和风险评估编码方法（RAC）对北京市密云水库上游某铁矿矿区及其周边土壤中重金属的分布状况和潜在生态风险进行了研究.结果表明,各重金属元素含量除As外,其余均明显高于北京市土壤重金属背景值,矿区的选冶活动已经对下游的水体和土壤环境造成一定的影响.富集因子法评价表明Cd、Pb、Cr富集较为严重,达到显著污染水平.形态分析表明,残渣态是重金属元素的主要存在形态,Cd元素可交换态所占比例（2.88%~21.15%）最高,RAC评价结果显示Cd基本处于中等风险水平,Pb为无风险,风险等级由强至弱的顺序为：Cd〉Mn〉Zn〉Cu〉Co〉Cr〉Pb.

The distribution characteristics and potential ecological risk of heavy metals in a iron mine soil of the upstream area of Miyun Reservoir, Beijing were investigated by the enrichment factor and risk assessment code （RAC）. The results showed that, the metal concentrations in the iron mine soil samples exceeded the background levels in Beijing, with As, as an exceptions; the ore dressing and smelting activities in this iron mine had definitely impacted the downstream water and the soil environment. The enrichment factor suggested that the enrichment of Cd, Pb, and Cr were very serious, which posed a remarkable pollution level. Furthermore, the analysis of chemical speciation indicated that heavy metals appeared mainly associated with the residual fraction in the soil, and the exchangeable fractions of Cd was the highest （2.88%-21.15%） among these elements. The RAC showed that Cd posed a medium ecological risk, whereas Pb posed no risk. The degrees of ecological risk descended in the order Cd〉Mn〉Zn〉Cu〉Co〉Cr〉Pb.