苏南某冶炼厂周边农田土壤重金属分布及风险评价

选择江苏南部冶炼厂周边污染的水稻田,采集耕层0～15cm的土壤,分析土壤中重金属Cd、Pb、Hg、As、Zn、Cu的污染程度及其空间变异特征。结果表明,土壤Cd、Pb、Cu、Zn、Hg的全量随着距污染源距离的增加而减少,呈现由东北向西南扩散的趋势,As则是由西北向东南扩散。6种重金属中Cd、Hg的污染范围相对较大,Zn的污染范围最小。DTPA浸提的6种重金属有效态含量都是距污染源距离越远而越少。采用内梅罗综合污染指数法对土壤中的重金属进行风险评价,土壤重金属的综合污染指数为39.27,污染程度已超过5级,为重度污染,其中Cd、Hg污染最为严重,含量范围分别为3.98～44.58mg·kg-1、0.36～2.01mg·kg-1,As为中度污染,Pb、Cu、Zn则为轻度污染,说明研究区域农产品安全生产存在很大的风险。

Distribution and Risk Assessment of Soil Heavy Metals Around a Smelter in South Jiangsu Province,China

Heavy metal smelting is considered as one of the most important anthropogenic metal emission sources.Heavy metal accumulated to a toxic concentration level in environment will lead to ecological damages.We assessed the characteristics of heavy metal pollution in a paddy soil surrounding smelter in southern Jiangsu.The soil was contaminated by heavy metals such as Cd,Pb,Hg,As,Zn and Cu.We collected the topsoil（0~15 cm） of the farmland.The results showed that total heavy metal contents of Cd,Pb,Cu,Zn,Hg reduced with the increasing distance from the pollution source.The concentration of Cd,Pb,Cu,Zn and Hg diminished from northeast to southwest,while As reduced from northwest to southeast.Pollution range of Cd and Hg was relatively larger than Zn.The contents of DTPA-extractable heavy metal were reduced with the increasing distance from the pollution source.The safety limits of these samples were evaluated with the standard of Nemerow pollution index.Comprehensive pollution index of heavy metal was 39.27 which exceeded 5 levels of the pollution degree.The most serious pollutants were Cd and Hg ranging from 3.98 to 44.58 mg·kg-1 and from 0.36 to 2.01 mg·kg-1,respectively.This study suggested that crop production in research area was under serious risk of heavy metal contamination.