江苏省某镇土壤重金属污染评价

为了解江苏省某镇表层土壤重金属污染特征，采集并测定了190个土壤样品的As、Cd、Hg和Pb 4种重金属含量，分析土壤重金属的分布特征，综合运用内梅罗综合污染指数法和污染负荷指数法两种评价方法对土壤重金属污染状况进行评价。结果表明：该镇表层土壤中As、Cd和Pb含量平均值高于土壤背景值，Hg与之相反。4种重金属都是主要受到点源污染的影响，其中As的高含量区主要分布在镇的正西边，Cd和Pb的高含量区主要分布在镇的中心区域，Hg的高含量区主要分布在东部以及东北区域。经内梅罗综合污染指数法评价，安全、警戒线、轻污染、中污染和重污染样点的比例分别为5.79%、32.11%、52.11%、4.74%和5.26%。经污染负荷指数法评价，无污染、轻度污染、中度污染和重度污染样点的比例分别为73.69%、25.26%、1.05%和0%。在内梅罗综合污染指数法和污染负荷指数法评价的结果中，有55.26%的样点评价结果相同，而44.74%的样点不同，但都显示出污染程度从镇中心向四周逐渐降低的变化态势。

Evaluation of soil heavy metals pollution in a town,Jiangsu Province

An investigation was carried out to assess heavy metal contamination in the soils of a local town in Jiangsu province. Specifically, based on the concentration of As, Cd, Hg, and Pb in 190 topsoil samples, the distribution features of heavy metals in the soils were analyzed and the pollution status was assessed synthetically by applying the Nemerow integrated pollution index and the pollution load index. In the topsoil, the average concentrations of As, Cd, and Pb were higher than the background values for soil, but concentrations of Hg were lower than background values. The distributions of the four types of heavy metals were indicative of point source pollution. The areas with high concentrations of As were mainly distributed in the western part of the town, while the areas with high concentrations of Cd and Pb were mainly distributed in the center of the town. The areas with high concentrations of Hg were mainly distributed in the eastern and northeastern parts of the town. The Nemerow integrated pollution index results showed that the categories for non-pollution levels, dangerous levels, slight pollution levels, moderate pollution levels, and high pollution levels accounted for 5.79%, 32.11%, 52.11%, 4.74%, and 5.26% of the study region, respectively. Moreover, the pollution load index results showed that the categories for non-pollution levels, slight pollution levels, moderate pollution levels, and high pollution levels accounted for 73.69%, 25.26%, 1.05%, and 0% of the study region, respectively. In terms of correspondence in the evaluation results for the two methods, 55.26% of the samples were classified similarly and 44.74% of the samples were classified differently. However, both evaluation methods clearly indicated that pollution levels gradually decrease as one moves from the center of the town to the edges.