新疆焉耆盆地农田土壤重金属污染及健康风险评价

为研究新疆焉耆盆地绿洲农田土壤重金属的污染及潜在健康风险,选取194个样点采集土壤样品,测定As、Cd、Cr、Cu、Ni、Pb和Zn共7种重金属元素含量。利用地质累积指数(I_(geo))评价农田土壤污染水平,采用US EPA健康风险评价模型,对农田土壤重金属污染的潜在健康风险进行评估。结果表明,研究区农田土壤7种重金属平均含量均未超出《食用农产品产地环境质量评价标准》中的限值,但Cd、Cr、Ni、Pb和Zn含量平均值分别超出新疆灌耕土背景值的1.67、1.41、1.30、3.01和6.78倍。农田土壤中Zn呈现轻度污染,Cd与Pb呈现轻微污染,As、Cr、Cu与Ni呈现无污染态势。健康风险评估结果表明,经手-口摄入是研究区农田土壤重金属日均暴露量及健康风险主要途径。农田土壤7种重金属通过3种暴露途径的非致癌风险商(HQ)与非致癌风险指数(HI),单项致癌风险指数(CR)与总致癌风险指数(TCR)均小于安全阈值,属于可接受风险水平。研究区农田土壤重金属对儿童的非致癌风险低于成人,致癌风险高于成人。研究区农田土壤中As与Pb是最主要的非致癌风险因子,As是最主要的致癌风险因子,研究区农田土壤中As对人体的健康风险应当引起重视。

Assessment of Heavy Metals Pollution and Its Health Risk of Farmland Soils of Yanqi Basin in Xinjiang Province

With the purpose of the heavy metal contamination and its health risk assessment of farmland soils in Yanqi basin, Xinjiang, the contents of seven heavy metal elements (As, Cd, Cr, Cu, Ni, Pb and Zn) collected from 194 soil sampling sites were determined by standard methods. The contamination level of heavy metals of farmland soils were analyzed based on geo-accumulation Index (Igeo), and the risks to human health was assessed using the US EPA Health Risk Assessment Model. Results indicated that, the average contents of seven metal elements not exceeded the Chinese Farmland Environmental Quality Evaluation Standards for Edible Agricultural Products, but the average contents of Cd, Cr, Ni, Pb and Zn exceeded by 1.67, 1.41, 1.30, 3.01 and 6.78 times of the background values for irrigation soils in Xinjiang, respectively. The average contents of Zn in farmland soils fell into light contamination level while Cd and Pb fell into slight contamination level, and As, Cr, Cu and Ni fell into no contamination level. The results of EPA health risk assessment indicated that the hand-mouth ingest intake were the dominant pathway of the average daily exposure and health risks for both adults and children. The non-carcinogenic risk quotient (HQ) and non-carcinogenic risk index (HI), individual carcinogenic health risk index (CR) and total carcinogenic health risk index (TCR) calculated by three exposure pathways of seven metal elements were lower than their threshold values, which within the limits of the acceptable risk level. The non-carcinogenic risks of heavy metals in farmland soils for children were lower then for adults, whereas the carcinogenic risks of for children were higher then for adults. As and Pb were the main non-carcinogenic risk factors and As was the main carcinogenic risk factor. Great attentions should be paid to the contamination risks of As in farmland soils of the study area.