北京市得田沟金矿和崎峰茶金矿周边土壤重金属形态分析和潜在风险评价

Fraction Distribution and Risk Assessment of Heavy Metals in Soils Around the Gold Mine of Detiangou-Qifengcha,Beijing City,China

对密云水库上游已关闭的得田沟金矿和崎峰茶金矿周边土壤中重金属的总量和形态分布进行分析,并通过富集因子法和风险评价编码法(RAC)对其污染状况进行了评价。结果表明,除As和Pb外的重金属平均含量都高于北京市土壤背景值,重金属的空间分布具有一定的差异性。土壤中Pb的铁锰氧化物结合态占总量的50%,其次为残渣态占33%;Cu的残渣态为72%,其次有机结合态为21%;Zn和Mn均以铁锰氧化物结合态和残渣态为主,分别占总量的93%和87%,其他重金属元素则以残渣态为主要形态。大多数重金属含量和可提取态含量的最大值都出现在堆积过尾矿石处(Z8、Z9和Z10),污染程度较重。基于总量的富集因子结果表明,研究区内Cr有显著污染,Hg、Cu、Cd和Ni为中度污染,其他元素轻微污染或无污染;基于形态的RAC表明该地区重金属元素具有较低的风险水平。

Contents and species of heavy metals in the soils around the closed gold mines of Detiangou-Qifengcha in the upstream of Miyun Reservoir were determined to evaluate the level of contamination by the enrichment factor and risk assessment code（RAC）.The results showed that the contents of all heavy metals（except of As and Pb）were higher than the background values of Beijing soils,and the spatial distributions of heavy metals were of some differences.Pb mainly existed in Fe-Mn oxides fraction,it accounted for more than 50% of total contents,and the residual form was 33% as followed.Cu was mostly presented in residual state and it was about 72%,and the second was organic matter fraction,it accounted for 21%.Zn and Mn were dominated by Fe-Mn oxides fraction and residual fraction,they accounted for more than 93% and 87%,respectively.However,other heavy metals were dominated by the residual states.The maximal total concentrations and extractable values of most heavy metals were found in around the stacked tailings,so the soils were suffered pollution from stacked tailings.The enrichment factors indicated that Cr was moderately severe pollution,Hg,Cu,Cd and Ni were moderate pollution,and other heavy metals were no pollution or minor pollution.RAC showed heavy metals in this area were lower risk.