太原市污灌区土壤重金属污染现状评价

Access of Heavy Metals Pollution of the Sewage Irrigation Region in Taiyuan,China

对太原市污灌区土壤重金属分布特征进行了分析评价,结果表明重金属Pb、Zn、Cu、Ni、Mn、Cr、As、Hg、Cd含量均值均未超过土壤环境质量标准(GB15618—1995),但其平均值均显著高于太原市土壤背景值。各重金属间的相关分析表明,Pb、Zn、Cu、Ni、Mn、Cr、As、Cd之间呈极显著相关,说明这8种元素污染源可能相同。Hg是本区表层土壤重金属污染的主要因子,重金属元素的污染程度依次为Hg>Cd>Pb>As>Cu>Zn>Cr>Mn>Ni。土壤重金属单项污染指数均值均大于1,综合污染指数为2.81,总体上,污染水平为中度及其以上。各种重金属单因子污染指数和综合指数在研究区有相似的空间分布格局,总体分布趋势为东南部小店地区和中南部晋源区相对较高,南部清徐县相对较小;通过因子分析并结合污灌区污染源调查,表明Hg除受污水灌溉的影响外,燃煤释放的Hg可能是重要来源之一,Cd、Zn、Pb和Cu可能来自污水灌溉和大气沉降,以污水灌溉的贡献为主,Ni、Mn、As、Cr来自污水灌溉。Hg、Cd是太原市污灌区土壤中需要优先控制的重金属。

Distribution characteristics of soil heavy metals in the sewage irrigation area in Taiyuan were investigated and analyzed.The results showed that concentrations of nine heavy metals（Pb,Zn,Cu,Ni,Mn,Cr,As,Hg and Cd） detected in the studied soils did not exceed the National Standard for Soil Environment Quality（GB 15618—1995）,but they were higher than background values of Taiyuan soil.According to the correlation analysis of various heavy metals,there was a remarkable correlation among Pb,Zn,Cu,Ni,Mn,Cr,As and Cd,which suggested they might have the same origin.Hg was considered as a dominant element causing soil heavy metal pollution in the area.The order of typical heavy metal pollution extent was HgCdPbAsCuZnCrMnNi.The mean value of single-factor indices of soil heavy metals in all soil samples has exceeded 1.Comprehensive pollution index of soil heavy metal was 2.81,the level of pollution was moderately pollution.The single-factor polluted index and the synthesis polluted index had similar spatial distribution pattern which revealed high concentration in the southeast and south-central parts of the region.Furthermore,measures,including factor analysis and in situ investigation,were taken to identify the main sources of heavy metals contamination,and it showed that Hg contamination resulted from anthropogenic effect as well as deposition of coal combustion.Cd,Zn,Pb,and Cu contamination were mainly from sewage irrigation,and atmosphere deposition also makes certain contribution.Ni,Mn,As and Cr contamination were attributed to sewage irrigation.Hg and Cd,which were the priority pollutants,should be frequently monitored and closely regulated in the sewage-irrigated soils in Taiyuan city.