咸阳城区表层土壤重金属污染特征及生态健康风险评价

Heavy Metal Pollution Characteristics and Ecological Health Risk Assessment of Surface Soil in Xianyang City

在咸阳市区采集表层土壤样品60个,包括交通主干道路两侧、城市公园、住宅小区、工矿企业周边区域4类典型功能区。采用原子吸收分光光度法测定土壤样品中Cr(铬)、Cu(铜)、Ni(镍)、Pb(铅)、Zn(锌)5种重金属的含量,运用污染指数评价法、潜在生态风险指数法对土壤重金属的污染现状及风险进行评价。结果表明:(1)咸阳市土壤中Cr、Cu、Ni、Pb、Zn 5种重金属的平均含量分别为65.11、26.91、29.81、38.26、90.94mg/kg,均超过陕西省土壤重金属元素背景值;不同城市功能区土壤重金属含量水平具有明显的差异。(2)从土壤重金属单因子污染指数来看,除重金属Pb在城市公园为中度污染外,其余元素在不同功能区及整个咸阳市均为轻度污染;从土壤重金属综合污染指数来看,不论是咸阳市还是不同功能区,其土壤环境质量等级均属于轻污染。(3)不论是综合潜在生态风险还是单个重金属元素潜在生态风险,咸阳市及不同功能区都属于低生态风险水平,且重金属Pb对综合潜在生态风险的贡献率最大(37.56%)。(4)5种重金属(Cr、Cu、Ni、Pb、Zn)对儿童和成人的非致癌风险均很小;人体(儿童和成人)暴露土壤中,Ni的综合致癌风险在可接受范围内,但明显高于下限值,而Cr的综合致癌风险则是显著的;人体(儿童和成人)暴露土壤重金属而产生的非致癌风险和致癌风险的主要途径是直接摄入和皮肤接触。

A total of 60 surface soil samples were collected in Xianyang City,including four typical functional areas on both sides of main traffic roads,urban parks,residential areas,and surrounding areas of industrial and mining enterprises.The contents of Cr,Cu,Ni,Pb,Zn in soil samples were determined by atomic absorption spectrophotometry.The pollution status and risk of heavy metals in soil were evaluated by pollution index and potential ecological risk index.The results showed that:(1)The average contents of Cr,Cu,Ni,Pb and Zn in Xianyang were 65.11,26.91,29.81,38.26 and 90.94mg/kg,respectively,which were higher than the background values of heavy metal elements in Shaanxi Province;and the contents of heavy metals in different urban functional areas were significantly different.(2)According to the single factor pollution index of soil heavy metals,except for the moderate pollution of heavy metal Pb in urban parks,the other elements are slightly polluted in different functional areas and the whole city of Xianyang;according to the comprehensive pollution index of soil heavy metals,no matter in Xianyang or in different functional areas,the soil environmental quality level is mild pollution.(3)No matter comprehensive potential ecological risk or single heavy metal element potential ecological risk,Xianyang city and different functional areas all belong to low ecological risk level,and the heavy metal Pb contribute the most to comprehensive potential ecological risk(37.56%).(4)The non-carcinogenic risk from five heavy metals(Cr,Cu,Ni,Pb,Zn)to children and adults is very little.When human(children and adults)exposes to soil,the comprehensive carcinogenic risk of Ni is within the acceptable range.Though the risk is significantly higher than the lower limit,the comprehensive carcinogenic risk of Cr is obvious.The main non-carcinogenic and carcinogenic risks associated with heavy metal exposure to soil in humans(children and adults)are through direct ingestion and skin contact.