铅锌矿区周边耕地土壤团聚体重金属污染状况及风险评估

为了解铅锌矿区耕地土壤团聚体污染状况,以贵州省都匀范家河铅锌矿区周围耕地土壤为研究对象,研究土壤团聚体中镉(Cd)、铅(Pb)、锌(Zn)3种重金属垂直分布特征和赋存形态。采用三步连续提取法(BCR)对污染土壤团聚体中3种重金属进行赋存形态分析,利用分布因子法(DFx)和地质累积指数法(Igeo)评估其环境风险。结果表明:土壤样品中重金属Cd、Pb和Zn的平均质量分数分别为23.25、518.40、3471.83 mg·kg^-1,已分别达到贵州土壤背景值的35.23、36.35、14.73倍,且3种重金属在土壤团聚体中的含量与其主要赋存形态特征均存在明显差异。研究区域剖面土壤中各粒径Cd主要以残渣态和可还原提取态的形式存在,各粒径Pb主要以残渣态和可氧化提取态的形式存在,80%及以上各粒径Zn为残渣态,综合得出研究区域土壤中重金属潜在影响程度为Cd>Pb>Zn。分布因子法结果表明:在0-100 cm剖面深度,Cd主要富集在0.25-1 mm的颗粒中,Pb主要富集在1-2 mm的颗粒中,Zn主要富集在0.053-2 mm的颗粒中;地质积累指数法结果显示,各粒径颗粒中Cd、Zn的污染水平主要为重污染,Pb主要为偏重污染。研究矿区周围耕地土壤已受到严重的重金属污染,应采取有效措施进行修复治理。该文为范家河铅锌矿区环境风险评价提供基础,旨在为矿区环境管理提供数据支撑。

Contamination Status and Risk Assessment of Heavy Metals in Soil Aggregates of Pb-Zn Mining Area

The purpose of this study was to investigate the contamination status of soil aggregates around the Pb-Zn mining area.The vertical distribution and speciation characteristics of cadmium(Cd),lead(Pb)and zinc(Zn)in soil aggregates were studied in the Fanjiahe Pb-Zn mining area of Duyun,city of Guizhou province.The speciation of three kinds of heavy metal in the contaminated soil aggregates form mining area were analyzed using the modified Community Bureau of Reference(BCR)sequential extraction procedure,and the environmental risk was assessed using both distribution factor method(DFx)and geological accumulation index method(Igeo).The results showed that the average content of Cd,Pb and Zn in soil samples was 23.25,518.40,and 3471.83 mg·kg^-1,respectively,which had exceeded 35.23,36.35,and 14.73 times of background values in the Guizhou soil.The contents and main speciation characteristics of three heavy metals in soil aggregates are significantly different.In the soil of the study area,Cd in different particles were dominated by residual fractions and reducible fractions,and Pb in different particles were dominated by residual fractions and oxidizable fractions.Zn(>80%)were in residue fraction.It is concluded that the potential impact of heavy metals in the soil in the study area was Cd>Pb>Zn.The depth of the soil profile is 0?100 cm,results of the DFx indicate that,Cd is mainly concentrated in the particles of 0.25-1 mm,Pb is mainly enriched in the particles of 1?2 mm,and Zn is mainly enriched in the particles of 0.053-2 mm.Results of Igeo showed that the pollution levels of Cd and Zn in the particles were in heavy pollution status,and Pb was in heavy pollution tendency.The soil in the mining area has been seriously polluted by heavy metals,and measures should be taken for remidiation.This paper provides a basis for environmental risk assessment in the Fanjiahe Pb-Zn mining area,which aims to provide data support for environmental management of the mining area.