沈抚灌区农田土壤重金属污染时空变化特征及生态健康风险评价

以东北典型污灌区——沈抚灌区农田土壤为研究对象,在收集整理沈抚灌区自20世纪末停灌后不同时期土壤重金属污染情况的相关文献报道后,沿灌渠主干以行政村为单位布设取样点28个,利用原子吸收分光光度法、数理统计法、空间插值法等研究了重金属元素Cd、Pb、Cu、Zn在灌区农田土壤和农作物中的污染现状及时空分布特征,并利用内梅罗污染指数法、EPA人体暴露风险评价法及潜在生态危害指数法对污灌区重金属污染土壤及农产品的潜在健康风险进行评价。结果表明:灌区土壤重金属的平均浓度为:Cd 0.60 mg·kg~(-1)、Pb 38.76 mg·kg~(-1)、Cu 22.39 mg·kg~(-1)、Zn 57.64 mg·kg~(-1),其中Cd含量超过了国家土壤环境质量二级标准;与文献报道该灌区近15年来土壤重金属污染情况相比,土壤中Cu、Zn含量明显降低,而Cd、Pb含量并无显著变化;土壤中4种重金属元素的空间分布特征各异,灌区土壤重金属综合污染水平属于轻微污染;Cd、Pb在玉米中残留浓度超过国家食品安全限值,对人摄食途径存在健康风险,尤其是Cd具有较强的潜在生态危害性。

Temporal and spatial characteristics and health risk assessments of heavy metal pollution in soils of Shenfu irrigation area

Shenfu irrigation area, a typical sewage irrigation area in Northeast China, was selected to study temporal and spatial characteristics of heavy metal(Cd, Pb, Cu, and Zn) pollution in soils and crops. Potential health risks of heavy metals in crops were also assessed. A total of 28 soil samples were collected along the main irrigation ditches according to village boundaries. Mathematical statistic method and spatial interpolation technology were used to study the spatial characteristics of heavy metals in the soils and crops. Nemero pollution index and EPA human exposure potential health risk and potential ecological risk index were used to evaluate the potential health risks of heavy metals in soils and agricultural products. Results showed that the mean concentrations of Cd, Pb, Cu, and Zn in the soil samples were 0.60, 38.76, 22.39 mg·kg^-1, and 57.64 mg·kg^-1, respectively. The concentrations of Cd exceeded the secondary grade of national soil environmental quality standard. Compared with the heavy metal concentrations in previous studies, the concentrations of Cu and Zn decreased significantly, while those of Cd and Pb had no significant changes. The spatial distribution characteristics of the heavy metals were different among Cu, Zn, Cd, and Pb. The soils in the Shenfu irrigation area was slightly polluted by heavy metals. The concentrations of Cd and Pb in corns exceeded the limits of the national food safety, indicating heavy metal risks to the human's health, especially Cd.