长沙市某集中式饮用水水源地周边土壤重金属污染特征和风险评价

以长沙某河库兼用型饮用水水源地一、二级保护区土壤为研究对象，于2018年8月采用网格布点法在一级和二级保护区分别布设3个和7个采样点，在水源地历史采样区布设5个采样点，探究土壤中Cd、Pb、Cr、Cu、Zn、Ni、Hg、As的含量分布及污染水平。结果表明：土壤中As、Cd、Cr、Cu、Hg、Ni、Pb、Zn的含量均值分别为46.56、4.90、81.87、46.64、0.19、30.11、75.11、237.93 mg/kg。重金属元素含量均值超过农用地污染风险筛选值的样品占比排序为Cd （86.7%）>Zn （60%）>As （53.3%）>Cu （6.7%）=Pb （6.7%）。土壤中As、Cd、Cr、Cu、Hg、Ni、Pb、Zn的单因子污染指数分别为1.55、16.34、0.41、0.47、0.08、0.30、0.63、0.95，主要为Cd、As污染。研究区土壤重金属综合污染指数为11.71，属重污染等级。水源地一级保护区、二级保护区、历史采样区2018年、历史采样区2014年土壤重金属综合污染指数分别为20.41、14.94、1.98、1.17。后期应加强对该饮用水水源地土壤中Cd、Pb、Cu、Zn、As的污染控制和治理。

Contamination Characteristics and Risk Assessment of Heavy Metals in Soil Around a Centralized Drinking Water Sources of Changsha City

Taking the soil in the first and second level protection areas of a drinking water source for both river and reservoir use as the research object, this study aims to explore the content distribution of Cd, Pb, Cr, Cu, Zn, Ni, Hg and the soil pollution degree. The grid layout method was adopted in August 2018 to set up 3 and 7 sampling points in the first and second level protection areas respectively, and 5 sampling points were set up at historical points of drinking water source. The results showed that the mean values of As, Cd, Cr, Cu, Hg, Ni, Pb, Zn in the soil were 46.56, 4.90, 81.87, 46.64, 0.19, 30.11, 75.11, 237.93 mg/kg, respectively. the percentage of samples with mean values of heavy metals exceeding the risk screening value for agricultural land contamination were Cd(86.7%) > Zn(60%) > As(53.3%) > Cu(6.7%)=Pb(6.7%). The single factor pollution index of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in the soil were 1.55, 16.34, 0.41, 0.47, 0.08, 0.30, 0.63 and 0.95 respectively, mainly for Cd and As pollution. The comprehensive pollution index of heavy metals of the study area was 11.71, which is a severe pollution level. The soil heavy metal comprehensive pollution indexes of the first-level protection area, the second-level protection area, the historical sampling area of drinking water source in 2018 and the historical sampling area were 20.41, 14.94, 1.98 and 1.17, respectively. Therefore, the pollution control and treatment of Cd, Pb, Cu, Zn, As in the soil of drinking water source should be strengthened in the later stage.