长江三角洲地区土壤重金属污染特征及潜在生态风险评价——以江苏太仓市为例

Spatial Characteristics and Potential Ecological Risk of Soil Heavy Metals Contamination in the Yangtze River Delta——A Case Study of Taicang City,Jiangsu Province

太仓市表层土壤Zn、Cu属强变异强度,呈对数正态分布;Cd、Ni、Hg、As、Cr和Pb属中等变异强度,呈正态分布。Cu、Hg、Zn、As显著高于当地背景值,以As累积指数和超背景值率最高;8种重金属除As自表层向下递增外,其余元素均为表层向下递减。土壤复合污染严重,土壤潜在生态风险达中等水平,黄泥土生态风险高于沙夹垅;重金属生态风险以印染厂最大,其次为电镀厂和养殖场,产生潜在生态风险为Hg、Cd,而As、Cu、Zn、Cr、Ni、Pb等多属轻微水平。

In this paper, soil contamination characteristics of 8 heavy metals （ Cd, Cr, Cu, Ni, Hg, Pb, Zn and As） in the topsoil （0 -20cm） from Taicang City, a typical region of the Yangtze River Delta, were analyzed, and ecological risk of soil heavy metals was evaluated by means of the potential ecological hazards index. Zn and Cu were distributed lognomally, strong in variability, while Cd, Ni, Hg, As, Cr and Pb were distributed nomally, medium in variability. The concentrations of Cu, Hg, Zn, As exceeded their background levels significantly, and As ranked first in contamination index and over limit rate. Except thatAs increased from the top down, all other soil heavy metals dropped off accordingly in the soil profile. Compound heavy metals contamination of the soil in Taicang was quite severe. The soil ecological hazard of Taicang was moderate, and the risk of well drained soil was higher than that of the sand with ridge. The soil heavy metals contamination was the most serious in the dyeing factories, followed by electric plating factories and breed factories. Hg and Cd brought the dominating potential ecological hazard, while As, Cu, Zn, Cr, Ni and Pb did slight hazard.