矿区周边农田土壤重金属污染风险评价

Risk assessment of heavy metal pollution in farmland soil around mining area

为了系统的评价矿区周边土壤-农作物-人体系统中重金属的污染风险,为矿区生态风险的分类治理和农作物安全生产提供科学依据,选择在重庆市黔江区金洞乡主要农耕区采集表层土壤样品321件、水稻和对应根系土样品30套,分析了土壤和水稻中重金属(Cd、Hg、Pb、As和Cr)的含量、土壤中有机质和Mn的含量及土壤pH,利用潜在生态风险指数法和人体健康风险评估模型进行重金属污染风险评价.结果表明,研究区土壤中Cd和Hg均存在一定程度的超标现象,土壤重金属含量受到成土母质、矿业活动及农业活动的影响.土壤总体潜在生态风险较小,主要以轻微污染为主,Cd和Hg存在点状的很强-极强的污染点位,是主要的土壤污染因子.水稻样品存在Cd和As的超标问题,水稻重金属含量主要受到土壤中重金属的含量、土壤pH、土壤有机质含量及土壤Mn含量的影响.通过食物摄入的暴露途径存在一定程度的非致癌风险,主要的贡献因子为As和Cd.可根据重金属污染在土壤-农作物-人体系统中的不同特点,进行污染分类管理、分类治理,以达到土地安全利用的目的.

In order to systematically evaluate the pollution risk of heavy metals in the soil-crop-human system around the mining area, and to provide a scientific basis for the classification and management of ecological risks in the mining area and the safe production of crops, 321 surface soil samples and 30 sets of rice and corresponding root soil samples were collected in the main farming area of Jindong Township, Qianjiang District, Chongqing City to analyze the content of heavy metals(Cd, Hg, Pb, As and Cr) in the soil and rice, the content of organic matter and Mn in the soil, and the soil pH. By using the potential ecological risk index method and the human health risk assessment model to carry out heavy metal pollution risk assessment. The results show that both Cd and Hg in the soil of the studying area exceed the standard to a certain extent, and the content of heavy metals in the soil is affected by soil parent materials, mining activities and agricultural activities. The overall potential ecological risk of the soil is relatively small, mainly caused by slight pollution. Cd and Hg have very strong-extremely strong spot-like pollution points, which are the main soil pollution factors. Rice samples have the problem of excessive Cd and As. The content of heavy metals in rice is mainly affected by the content of heavy metals in the soil, soil pH, soil organic matter content and soil Mn content. Exposure intake through food has a certain degree of non-carcinogenic risk whose main contributing factors are As and Cd. According to the different characteristics of heavy metal pollution in the soil-crop-human body system, pollution classification management and classification treatment can be carried out to achieve the purpose of safe land use.