典型饮用水源地周边土壤环境质量及其潜在生态风险评价

受农业生产和工业活动等影响，集中式饮用水水源地周边土壤环境质量备受关注。本文以湖南省某典型集中式饮用水源为例，采用网格法和现场踏查分别在水源地一、二级保护区布设13个采样点（S1~S13）及4个底泥样点，开展了土壤及底泥样品的重金属含量监测与潜在生态风险评价。结果表明，饮用水源地周边土壤环境质量良好，土壤中重金属汞、砷、铬、铜和镍的均值都低于农用地污染风险筛选值（GB 15618—2018），而重金属镉、铅和锌均值分别为0.86 mg/kg、509.53 mg/kg和215.78 mg/kg，均超过了项目风险筛选值，其中S7和S8样点底泥的铅含量超过了项目风险管制值。单因子污染指数结果显示，土壤中镉和铅分别为中度和重度污染。内梅罗综合污染指数结果表明，11.7%的点位样品重金属为中污染，58.8%的点位样点为重污染。综合潜在生态风险指数（RI）范围为153.75~508.44，处于中等和强生态风险水平的样品比例分别为76.5%和23.5%。研究表明，该水源地周边土壤中镉和铅等重金属含量超标，综合潜在生态风险等级为中等水平，应重视该水源地周边土壤环境生态保护，避免局域土壤重金属的潜在生态风险。

Assessment of soil environmental quality and potential ecological risk in a drinking water source in Hunan Province

Due to the influence of agricultural production and industrial activities, the soil environment quality around the drinking water source has attracted more attention. In this study, the soil environment quality and sediment around a typical drinking water source in Hunan Province were studied. Thirteen sampling points and four sediment samples were set up in the first and second level water source protection areas in the drinking water source by grid method and field survey. The physical and chemical properties of soil samples were measured and heavy metals pollution status associated with potential ecological risk were evaluated. Results showed that the quality of soil surrounding the drinking water source was good. The average content of heavy metals such as Mercury (Hg), Arsenic (As), Chromium (Cr), Copper (Cu), and Nickel (Ni) in soil was reached lower than the national standard pollution risk value (GB 15618-2018). However, the average content of heavy metals such as Cadmium (Cd), Lead (Pb), and Zinc (Zn) was reached at 0.86 mg/kg, 509.5 mg/kg, and 215.8 mg/kg, respectively, which exceeded the national standard. Especially the average value of Cd and Pb were 2.71 and 6.74 times higher than the national standard value respectively. The results of single factor pollution index showed that Cd and Pb in soil were moderately and severely polluted respectively. Single factor pollution index showed that Cd and Pb were moderately and severely polluted in the sample sites, respectively. Nemerow multi-factor pollution index illustrated that 11.7% of the sample sites were moderately polluted by heavy metals and 58.8% were heavily polluted by heavy metals. The potential ecological risk index (RI) in the sample sites ranged from 153.75 to 508.44, with 76.5% at medium ecological risk level and 23.5% at strong ecological risk levels. Accordingly, the content of some heavy metals such as Cd and Pb in the soil around drinking water sources exceeded the national standard, and the potential ecological risk was moderate. Therefore, close attention should be paid to the ecological protection of soil environment around drinking water sources to avoid the potential ecological risk of heavy metals in the soil.