基于地质统计及随机模拟技术的天津武清区土壤重金属源解析

Applications of Geostatistical Analyses and Stochastic Models to Identify Sources of Soil Heavy Metals in Wuqing District,Tianjin,China

为了解天津市武清区重金属污染状况及污染来源情况,在研究区共采集了578个表层土壤样品并分析了Cu、Zn、Pb、Cd、Hg、As(类金属)、Ni、Cr等8项重金属含量.综合应用描述性统计、主成分分析、地质统计学及随机森林回归技术对研究区表层土壤重金属含量时空变化特征及人为及自然源污染贡献性进行了探讨.结果表明,除Cr以外,研究区其余重金属平均含量均高于区域背景值,土壤As、Ni、Cr主要来自于自然源即土壤类型的差异性,Cu、Zn的变异性一是受土壤类型差异性的影响,二是受污灌的影响,Pb、Cd的变异主要受面源污染的影响,局部存在点源污染.Hg变异性主要受污灌的影响.实践证明多技术联合应用是土壤重金属来源解析的有效方法.

A survey on soil samples was conducted to study the heavy metal pollutions and their potential sources in Wuqing District,Tianjin,China. A total of 578 topsoil samples were collected and the concentrations of eight heavy metals,namely,Cd,Pb,Cu,Zn,Cr,Ni,As（ metalloid） and Hg were analyzed. A summary of descriptive statistics,principal component analysis,geostatistical analysis and stochastic forest regression models were applied to study the spatial and temporal variation and identify proportional contribution from either natural or anthropogenic sources for the eight heavy metals in topsoils of the study region. The results indicated that the average concentrations of all the heavy metals except for Cr in the topsoils exceeded their corresponding natural-background values. As,Ni and Cr were mainly contributed by natural sources（ i. e.,soil parent materials）. Cu and Zn originated from both the soil parent materials and sewage irrigation. Pb and Cd originated mainly from non-point source pollution and partially from point source. Hg originated from sewage irrigation. It was proved that combination of multi-technologies provides an effective way to delineate multiple heavy metal pollution sources.