小流域矿集区土壤重金属污染评价与来源综合解析

Assessment and sources comprehensive identification of soil heavy metal pollution in small-scale drainage catchment of mining areas

涉重金属矿床(点)多分布在山区流域内,自然高背景和人为活动均会造成土壤中重金属过度富集。准确识别和定量解析土壤重金属的来源,对于针对性地制定流域环境污染与土壤重金属污染防治措施尤为重要。以矿产丰富的北山水库小流域表层土壤为对象,在重金属累积程度评价基础上,综合运用野外调查、多元统计分析、PMF模型和空间分布分析相结合的方法,来解析土壤重金属的来源种类,估算和明晰不同来源的贡献率和空间分布。结果表明:表层土壤中Cu和Cd平均含量分别是背景值的3.05、3.47倍且超过土壤风险筛选值,累积明显,有10%左右的样品点达到中度-重度富集水平;重金属来源主要有3种,自然背景源、采矿活动源和农事活动源;采矿活动源对Cu和Cd贡献率为68.92%和56.31%,自然源对它们也作出了21.05%和38.35%的贡献;自然背景对As、Cr和Ni元素的贡献显著,贡献率分别为83.13%、72.59%和78.76%;农事活动对Hg富集影响最大,贡献率达81.79%;采矿活动和自然源对Zn和Pb的贡献大体相当;综合运用多方法技术进行重金属来源分析,可提高源解析结果的可靠性和合理性。

Most of the heavy metal-related deposits are distributed in watersheds of mountainous areas,and the enrichment of soil heavy metals were affected by both natural high background and anthropogenic source in the area.It is particularly important to formulate precaution countermeasures to accurately identify and quantify the source of soil heavy metal pollution in the ore-concentrating area.This paper studies the surface soil of a small basin in Beishan Reservoir which was rich in ores.Based on the evaluation of the heavy metal accumulation degree,the pollution sources identification and their contributions to soil heavy metals were studied by multiple methods including field investigation,multivariate statistical analysis,positive matrix factorization(PMF),spatial analysis,and other methods.Conclusively,the accumulated Cu and Cd in the top soil were higher than other heavy metals,the Cu and Cd average contents were 3.05,3.47 times as high as the regional background value,and exceeded the soil risk screening values.About 10%of samples reached the level of moderate to severe enrichment.The heavy metal pollution sources in the topsoil were jointly affected by natural geological background,mining activities,and agricultural activities source.The contribution rates of mining activities to Cu and Cd are 68.92%and 56.31%,and natural geological backgrounds also contribute 21.05%and 38.35%to them.The natural source contributed most to As,Cr,and Ni,with contribution rates of 83.13%,72.59%,and 78.76%,respectively.Hg mainly comes from agricultural activities,and its contribution rate was 81.79%.Zn and Pb were affected by both material migration and natural geological background.The reliability and rationality of the analytical results for the heavy metal pollution sources can be improved by the mutual verification of the combination using different methods.