煤矿区周边农田土壤重金属积累特征及生态风险评价

Accumulation Characteristics of Heavy Metals in Agricultural Soil around the Mining Area and Ecological Risk Assessment

为揭示开采活动对周边农田土壤重金属性质的影响,以贵州省织金县煤矿区废弃地周边农田土壤为研究对象,分别对距离矿区50 m、100 m、400 m的农田区A1、A2、A3表层土壤进行取样调查,分析了土样重金属含量及其分布特征,利用因子分析法对土壤重金属污染来源进行分析,分别采用内梅罗综合指数法、潜在生态危害指数法对其污染程度和生态风险进行评价。结果表明,农田区A1、A2、A3样点重金属含量均高于对照点,且距离矿区越近,农田土壤重金属积累越严重。因子分析结果表明,Cd、Cu、Ni、Zn主要来源于煤炭开采过程中的三废排放,Cr和Pb可能来源于成土母质,Hg、As可能来源于采矿产生的粉尘和当地煤炭燃烧产生的降尘。内梅罗综合指数评价结果表明,Hg、Cd、Cu、Cr是土壤重金属污染的主要因子,农田区A1、A2、A3的综合污染程度达到重污染水平的样点比例分别为66.7%、52.6%、6.2%;潜在生态危害指数评价结果表明,Cd、Hg是土壤重金属最主要的潜在生态风险因子,农田区A1、A2分别有50%、21.1%的样点处于强生态危害水平,内梅罗综合污染指数和潜在生态风险指数均表现为距离矿区越近,土壤重金属污染越严重,潜在生态风险越强。

To reveal the influence of mining activity on heavy metal properties in agricultural soil around mining areas,this article investigated the accumulation characteristics of heavy metals in the topsoil of A1, A2 and A3 farmland,respectively, at 50 m, 100 m, 400 m distance from the abandoned mining area in Zhijin County, Guizhou Province.The research was conducted by analyzing the concentrations and source of heavy metals by factor analysis and the pollution degree and ecological risk were evaluated by using Nemerow index and the potential ecological risk index,respectively. The results demonstrated that the content of heavy metals in A1, A2 and A3 was higher than that in control and the heavy metal accumulation was more serious in farmland topsoil at closer distance to the mining area.Factor analysis results showed that the contamination of Cd, Cu, Ni, and Zn was mainly from the three wastes（waste gas, waste water, waste residue） during mining and that of Cr and Pb mainly from soil parent material. The contamination of Hg and As might be caused by the mining dust and coal burning. The assessment result of Nemerow index indicated that Hg, Cd, Cu and Cr were the main sources of heavy metal pollution, which accounted for 66.7%,52.6%, and 6.2% of the total pollution in A1, A2, and A3, respectively, in agricultural soil around the mining area. Cd and Hg were the principal factors of the potential ecological risk of soil around mining area. And 50% and 21.1% of the sampling sites were at the strong ecological risk level in A1 and A2, respectively. Nemerow index and the potential ecological risk index all showed that the nearer mining area, the more seriously pollution and the more strong potential ecological risk level.