Heavy metal pollutions in the farmland are regarded as serious threats to rural environment in China. Human activities, such as intensive livestock, sewage irrigation, large amounts of agrochemicals input and the rapid urbanization are proved to be the main sources of the heavy metals in farmland. The study area is located in middle and lower reaches of the Yangtze River in Anhui Province, China. The concentrations of Cr, Pb, As, Hg and Cd in the topsoil(0~20 cm)of the farmland in the district were analyzed, and the potential ecological risks of these heavy metals were assessed. It turned out that the average content of Cd, Pb, Cr, As and Hg in soils were 0.302, 61.17, 87.13, 12.89 mg·kg-1 and 0.139 mg·kg-1 respectively. According to the second grade in Chinese Standard of the Soil Environment Quality(GB 15618—1995), Cd was the only element that exceeded the limit. However, all the elements were beyond the scope comparing with the background values of the elements in the local soils. Besides, the proportions of samples beyond the standard of limit of the heavy metal elements in soils were as follow respectively:Cd(85.43%), Hg(76.38%), Pb(59.30%), As(26.63%)and Cr(19.60%). The results showed that the pollution rank were Cd>Hg>Pb>As>Cr and the potential ecological risk index of heavy metals in the research area were Hg>Cd>As>Pb>Cr with Hg and Cd took the dominant position. The comprehensive potential ecological risk indexes of the research area were from 83.83 to 6987.87 with the average value of 250.76 and high risk level for 13.57% of the samples, which should be paid attention by relevant government agencies.%以安徽省沿江某县农田土壤为研究对象,通过野外调查采集土壤样品199个,分析了土壤中主要重金属元素含量,采用地积累指数法和Hakanson潜在生态风险指数法,并与GIS相结合评价了研究区农田土壤重金属潜在生态风险.结果表明:Cd、Pb、Cr、As、Hg等5种重金属元素的平均值分别为0.302、61.17、87.13、12.89 mg·kg-1以及0.139 mg·kg-1,相较于《土壤环境质量标准》的二级标准只有Cd的平均值略超标;相较于当地土壤元素背景值则全部元素都超出范围;研究区土壤各种重金属元素出现污染的点位占比分别为:Cd 85.43%、Hg 76.38%、Pb 59.30%、As 26.63%以及Cr 19.60%.污染程度由强到弱依次为Cd>Hg>Pb>As>Cr;研究区各种重金属潜在生态风险指数由高到低分别为:Hg>Cd>As>Pb>Cr,其中Hg和Cd占主导地位;研究区综合潜在生态风险指数介于83.83~6987.87之间,平均值为250.76,有13.57%的点位处于强或以上风险,应该引起相关部门的重视.
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