矿区耕地土壤重金属污染评价模型与实例研究

为对湘南某矿区耕地土壤重金属污染情况作出客观实际的评价,将层次分析理论用于环境评价领域,引入重金属毒性响应系数和重金属在粮食中限量值双重准则,以确定重金属元素之间的权重,并结合加权平均法建立综合评价模型.同时,结合GIS对耕地土壤重金属空间分布、重金属富集特征及综合污染情况进行分析.对该矿区4种重金属Pb、Cd、Cu和Zn的综合污染评价结果表明,该矿区耕地土壤重金属综合污染情况严重,综合污染指数变化范围为1.25～427,属重度污染.因子分析结果表明,4种重金属的来源具有一定相似性,主要来源于矿区有色金属采选冶炼活动.空间分析表明,4种重金属的含量及综合污染的空间分布特征呈明显富集.该评价模型可用于对矿区耕地土壤重金属污染评价的研究,为土壤重金属污染评价提供了新的思路.

Assessment model of heavy metal pollution for arable soils and a case study in a mining area

To assess pollution status of heavy metals in arable soils in a mining area in southern Hunan, the hierarchy analysis process was used for environmental assessment systems. Double standards of toxic response coefficients and limited values of crops for heavy metals were introduced to determine the weights among different heavy metals, and a comprehensive assessment model was built by combing the method of weighting mean. The pollution status of heavy metals in arable soils in this area was analysed using this model considering spatial distribution of soil heavy metals, accumulation characteristics of heavy metal in crops, and comprehensive pollution analysis based on GIS. The result of assessment on 4 elements of heavy metal (Pb, Cd, Cu, Zn) in the mining area showed that the comprehesive pollution of heavy metals in arable soils in the mining area was serious, and the range of comprehensive pollution index varied in 1.25~427, which belonged to heavy pollution. The factor analysis suggested that the sources of all 4 heavy metals were similar, and came mainly from smelting activities in the mining area of nonferrous metals. The spatial analysis indicated that the contents of 4 heavy metals and comprehensive pollution character of spatial distribution were accumulated obviously. This comprehensive assessment model could be used in the assessment study of heavy metal pollution in arable soils in a mining area, which offered a new idea for assessment of soil heavy metal pollution.