黄石典型城市小型浅水湖泊沉积物重金属污染特征及潜在生态风险评价

Pollution Characteristics and Potential Ecological Risk Assessment of Heavy Metals in Sediments from a Small and Shallow Urban Lake in Huangshi City

采集青山湖(4号湖)18个样点共计50个沉积物样品,分析了Cu、Pb、Cr、Cd、Ni、Hg、As和Zn等8种重金属的分布特征,并采用内梅罗综合污染指数法、地累积指数法和潜在生态危害指数法进行生态风险评价.结果显示,除Hg和Ni外,其它重金属的平均含量均超出湖北省A层土壤元素背景值以及全国土壤环境质量标准(GB 15618-1995)的限值,以Cd污染最严重,其次依次为Cu、Zn、Pb、As等;且每种重金属空间分布的差异性不大.内梅罗综合污染指数评价显示,青山湖沉积物大部分重金属指标处于V级严重污染状态,污染程度由高至低依次为:Cd>Cu>Pb>Zn>As>Cr>Ni;地累积指数评价表明,沉积物重金属污染程度由高至低依次为:Cd>Cu>Zn>Pb>As>Cr>Ni;潜在生态危害指数评价表明,青山湖所有样点重金属均表现出很强的潜在生态风险,风险由强到弱依次为:Cd>Cu>Pb>As>Zn>Ni>Cr,其中Cd的生态风险贡献率达90.25%.研究表明,青山湖沉积物重金属污染严重,其中Cd为最主要的污染元素,潜在生态风险极高,其次为Cu、Pb、Zn、As.

A total of 50 sediment samples from 18 sampling sites in Qingshan Lake(No.4 Lake)was sampled.The pollution characteristics of 8 heavy metals including Cu,Pb,Cr,Cd,Ni,Hg,As and Zn were analyzed,and the potential ecological risk of heavy metals were evaluated by the nemerow comprehensive pollution index,geo-accumulation index and potential ecological risk index.Results showed that,except Hg and Ni,the average concentrations of other measured heavy metals in the surface sediments exceeded both the environment background values of soil element in A layer of Hubei Province and the limiting values of the national environmental quality standard for soils(GB 15618-1995).Cd was the most severely contaminated element,followed successively by Cu,Zn,Pb and As.The spatial distribution of each heavy metal showed little difference.The nemerow comprehensive pollution index indicated severe contamination status(Grade V)of most of the heavy metals in the sediments,with the contamination degrees following the order of Cd>Cu>Pb>Zn>As>Cr>Ni.According to the geo-accumulation index,the contamination degrees followed the order of Cd>Cu>Zn>Pb>As>Cr>Ni.The potential ecological risk index suggested all the sampling sites showed strong potential ecological risk and the risk grades were as follows:Cd>Cu>Pb>As>Zn>Ni>Cr.The present study indicated that the sediments in Qingshan Lake were severely contaminated by heavy metals,and Cd was the most contaminated element with very high potential ecological risk,followed successively by Cu,Pb,Zn and As.