黄河兰州城区段饮用水源地土壤重金属污染生态与健康概率风险评估

Ecological and health probabilistic risk assessment of soil heavy metal pollution in the drinking-water source in the Lanzhou urban section of the Yellow River

为探究黄河流域城市饮用水源地土壤重金属污染特征及其生态健康风险,以黄河兰州城区段饮用水源地土壤为研究对象,采集分析了39个土壤样品的pH值和As、Cd、Cr、Cu、Hg、Ni、Pb及Zn共8种重金属的含量特征,并将蒙特卡洛模拟耦合于富集因子法、改进内梅罗综合污染指数法、改进生态风险指数法和人体健康风险模型对黄河兰州城区段生活饮用水水源地的土壤重金属污染程度、生态风险及其对人类健康的潜在风险进行了全面概率评估.结果表明:1)土壤重金属含量总体低于国家风险筛选标准,其中除Ni之外,分别有87%、74%、50%、47%、45%、32%和8%的样点Hg、Cu、Pb、Cd、Zn、As和Cr的含量高于甘肃省土壤背景值.2)Hg的污染程度最高,其次是Pb、Cu、Zn、Cd、As,而Cr和Ni的污染程度相对较低.土壤重金属污染整体上为中度富集状态.3)Hg和Cd是构成水源地土壤生态风险的主要元素,其中Hg的生态风险最高,而其他元素主要处于轻微风险等级.土壤生态风险整体上为较强水平.4)土壤重金属对成人和儿童的非致癌风险较低,但在手口摄入途径下,As、Cr和Ni对两个人群均存在可接受的致癌风险,且儿童的健康风险高于成人.

To explore the characteristics of heavy metal pollution and its ecological health risks in the urban drinking water sources of the Yellow River Basin,this study focused on the soils from the drinking water source areas along the Lanzhou urban section of the Yellow River.Thirty-nine soil samples were collected and analyzed for pH values and the concentrations of eight heavy metals:As,Cd,Cr,Cu,Hg,Ni,Pb,and Zn.The Monte Carlo simulation was coupled with the enrichment factor method,the improved Nemerow integrated pollution index method,the improved ecological risk index method,and the human health risk model to comprehensively assess the probability of soil heavy metal pollution,ecological risks,and potential risks to human health in the drinking water source areas of the Lanzhou urban section of the Yellow River.The results showed that:1)The overall heavy metal content in the soil was below the national risk screening standards,except for Ni,with 87%,74%,50%,47%,45%,32%,and 8%of the sample points having Hg,Cu,Pb,Cd,Zn,As,and Cr concentrations exceeding the soil background values of Gansu Province,respectively.2)The highest pollution level was observed for Hg,followed by Pb,Cu,Zn,Cd,and As,while Cr and Ni had relatively lower pollution levels.Overall,the soil's heavy metals were in moderate enrichment.3)Hg and Cd were the main elements contributing to the ecological risks of the water source area soils.Hg posed the highest ecological risk,while other elements were mainly at a slight risk level.The overall ecological risk of the soil was at a relatively high level.4)The non-carcinogenic risks posed by soil heavy metals to adults and children were low.However,under the oral ingestion pathway,As,Cr,and Ni presented an acceptable carcinogenic risk to both populations,with children having a higher health risk than adults.