拉萨市城区土壤重金属分布特征及生态风险评价

Distribution characteristics and ecological risk assessment of heavy metals in soil of Lhasa City

  • 摘要: 为了解拉萨市土壤重金属污染情况和空间分布特征,对其主城区20个表层土壤样品中8种重金属浓度进行测定,利用内梅罗综合污染指数法和潜在生态风险指数(RI)法对其环境质量和生态风险进行评价。结果表明:土壤中的Cu、Zn、Cr、Ni、Pb、Cd、As、Hg浓度均值分别是拉萨市土壤背景值的0.92、1.02、0.85、0.83、0.73、0.83、1.28、0.8倍,但均符合GB 15618—1995《土壤环境质量标准》二级标准,其中Zn、As超标率较高,分别为45%、95%;重金属元素空间分布呈现一定规律,大部分元素呈点状格局,其中Ni分布均匀,其他元素均有高值区出现,重金属累积状态与人为活动轨迹相似;除Zn和As的单项污染指数为轻度污染外,其他元素均为无污染,内梅罗综合污染指数均值为1.24,属于轻度污染;RI均值为85.96,为低生态风险,Hg和Cd为主要风险因子。拉萨市土壤中Cu、Zn、Pb和Cd的累积以自然源为主,部分受到交通运输活动的影响;As的累积主要源于较高的自然背景值,Hg的累积受到自然源和工业源共同影响,Ni和Cr的累积受自然因子控制。

     

    Abstract: In order to study the pollution and spatial distribution characteristics of soil heavy metals in Lhasa, the contents of 8 heavy metals in 20 surface soil samples in the main urban area were analyzed and determined. And the Nemerow comprehensive pollution index and potential ecological hazard index were used to evaluate the environmental quality and ecology risk. The research results showed that the average values of Cu, Zn, Cr, Ni, Pb, Cd, As, and Hg in the soil are 0.92, 1.02, 0.85, 0.83, 0.73, 0.83, 1.28, and 0.8 times of the Lhasa background values, All of them meet the grade Ⅱ standard of National Soil Environmental Quality Standard (GB 15618-1995), among which Zn and As have a higher rate of exceeding the standard, 45% and 95% respectively. From the spatial distribution map of heavy metals, the distribution of elements presents a certain pattern, which mostly presents a dot pattern. Among them, Ni was evenly distributed, and other elements have high value areas. The accumulation status of heavy metals in the study area was similar to the track of human activities. Except for the single pollution index of Zn and As, which was slight pollution, all other elements are non-pollution. The average value of Nemerow comprehensive pollution index was 1.24, which belongs to slight pollution; The mean value of RI was 85.96, which was low ecological hazard, and Hg and Cd were the main risk factors. The accumulation of Cu, Zn, Pb, and Cd were mainly from natural sources, partly affected by transportation activities; the accumulation of As were mainly due to the high natural background value; the accumulation of Hg was affected by both natural sources and industrial sources; the accumulation of Ni and Cr were controlled by natural factors.

     

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