武汉市土壤重金属空间分布特征及污染评价

Spatial distribution and pollution assessment of soil heavy metals in Wuhan urban

以武汉市主城区为研究区域,分析表层土壤中5种重金属（Pb、Zn、Cu、Cr和As）元素的含量水平及累积状况.采用单因子污染指数法、内梅罗综合污染指数法和潜在生态危害指数法评价武汉市主城区表层土壤中重金属的污染程度及生态危害等级,同时运用ArcGIS空间插值并绘制出5种重金属元素的空间分布图.结果表明研究区内Pb、Zn、Cu、Cr、As的平均含量均高于湖北省背景值,各元素的超标率分别为38.9%、62.2%、85.5%、83.3%、98.9%,As、Zn、Cu、Cr的累积较为明显;Zn变异系数最大,表现出强变异,Cu、Cr、As为弱变异,空间分布均一.单因子污染指数评价表明,各元素的污染指数有一定的差异,大小顺序为：Pb（0.12）〈Cu（0.45）〈Zn（0.55）〈Cr（0.59）〈As（0.77）,表明As的污染较其他元素严重.内梅罗综合污染指数评价表明,主城区的综合污染指数（PN）为0.77,属轻度污染;各行政区的污染差异不大,PN 的取值为0.64-0.84.潜在生态危害指数表明,各元素的单项生态因子（Eir）都小于40,每个区的综合生态危害指数（RI）均小于135,表明各行政区土壤中重金属的潜在生态危害都属于轻度生态危害.ArcGIS插值空间分析表明,Zn的分布差异最大,Cu、Cr、As的分布差异较小且比较均一,研究区的重金属污染以As、Zn为主.

The contents and accumulation status of heavy metals of the surface soil in Wuhan urban including Pb,Zn,Cu,Cr and As were analyzed.The soil pollution states and the rank of potential ecological hazards of heavy metals were evaluated with single factor index,Nemerow index and potential ecological risk(RI)of the surface soil.The spatial distribution of all elements was studied with the spatial interpolation in ArcGIS.The results showed that the concentrations of heavy metals including Pb,Zn,Cu,Cr and As were higher than the background value of Hubei Province,with the exceeding rate in the order of 38.9%,62.2%,85.5%,83.3%,98.9%,indicating that As,Zn,Cu and Cr were the main pollution elements.The highest of coefficient of variation(CV)was Zn,expressing the strong variation.The low variation of Cu,Cr and As was uniformed at spatial distribution.The results of single factor index showed that elements were in the order of Pb(0.12)< Cu(0.45)<Zn(0.55)<Cr(0.59)<As(0.77),indicating that pollution of As was higher than that of other elements.The Nemerow index showed that the PN of the studied area was 0.77.There was little difference in every region with PNvalue ranged from 0.64 to 0.84.The potential ecological risk index were Eirsmaller than 40.RI was smaller than 135,indicating that all regions were low potential ecological risk.The results of spatial interpolation showed that Zn,Cu,Cr had diverse distribution.As was relatively uniformed,the main pollutants of studied area were As and Zn.