某铅锌尾矿库周边农田土壤重金属污染状况及风险评价

Pollution and risk assessment of heavy metals in agricultural soils around a Pb-Zn tailing pond

为研究广东省某铅锌尾矿库周边农田土壤重金属污染状况及评价重金属污染对农田土壤的风险,测试分析了土壤中重金属元素Pb、Zn、Cu、Cr、Cd、Ni和As的含量,并采用内梅罗综合污染指数法、潜在生态危害指数法和模糊综合评价法3种评价方法对土壤重金属污染进行风险评价。结果表明,稻田土壤中的重金属含量高于蔬菜地土壤,部分土壤样品中的Pb、Zn、Cu、Cd、Ni、As含量已超过土壤环境质量标准二级标准值,Cr含量均未超标,重金属超标率顺序为:Cd>Zn>As>Pb>Ni>Cu。相关性分析表明农田土壤中各重金属含量之间都有极显著的相关性,主成分分析表明Pb、Zn、Cu、Cd、As是当地农田土壤环境质量的主要影响因子。3种评价方法的结果存在差异,内梅罗综合污染指数法和模糊综合评价法的结果显示农田土壤重金属污染处于重度污染程度;而潜在生态危害指数法评价结果表明土壤重金属污染处于中等潜在生态危害程度。根据分析和评价结果认为农田土壤受到多种重金属的复合污染,其中Cd污染最严重,重金属对农田存在某种程度的风险,评价方法各有其侧重点,人们在评价重金属污染土壤时要根据评价目的选择合适的评价方法。

In order to study the heavy metal pollution of agricultural soils surrounding a Pb-Zn tailing pond in Guangdong Province and evaluate the risk of heavy metals to the agricultural soils, the contents of Pb, Zn, Cu, Cr, Cd, Ni, and As in the soils were analyzed. The risk of heavy metals to the agricultural soils was assessed via three methods:the Nemerow index method, potential ecological risk index method,and fuzzy comprehensive evaluation method. Results showed that the contents of heavy metals in paddy soils were higher than those in vegetable plantation soils. The contents of Pb, Zn, Cu, Cd, Ni, and As in some soil samples were higher than the criteria of environmental quality standards for agricultural soils, whereas the Cr contents were lower than the critical level. The exceeded rate decreased in the order of Cd>Zn>As>Pb>Ni>Cu. Correlation analysis showed that extremely significant correlations existed among heavy metal contents in the soils, and principal component analysis showed that Pb, Zn, Cu, Cd, and As were dominant factors of soil environmental quality in the study areas.Based on the three evaluation methods, we concluded that the results of the Nemerow index method and fuzzy comprehensive evaluation method showed that the soils were in the degree of heavy pollution, whereas the potential ecological risk index showed that the soils were classified as moderate potential ecological risk. According to the analysis of contents and risk assessment of heavy metals in contaminated soil, the farmland soil was contaminated by a variety of heavy metals, with Cd pollution the most serious. There was some degree of heavy metal risk to the farmland soil. Each evaluation method has its advantages. The appropriate method for evaluating heavy metal pollution of soil should be carefully chosen based on the evaluation purpose.