天水市蔬菜大棚土壤重金属污染特征及生态风险评价

Heavy Metal Pollution Characteristics and Assessment of Ecological Risk for Vegetable Greenhouse Soils in Tianshui City

[目的]对甘肃省天水市蔬菜大棚土壤重金属污染程度和生态风险进行评价,为该地区设施农产品安全生产提供科学依据。[方法]以天水市大棚蔬菜主产区21个乡镇的362个土壤样品为研究对象,用电感耦合等离子体质谱仪(ICP-MS)测定As,Ni,Cu,Zn,Cd,Pb,Hg含量,采用内梅罗综合污染指数和潜在生态风险指数对蔬菜大棚土壤重金属环境质量和潜在生态风险进行评价;利用相关分析和主成分分析对土壤重金属的可能来源进行探讨。[结果]①7种元素平均含量均未超出《土壤环境质量农用地土壤污染风险管控标准(试行)》(GB15618-2018)的土壤风险筛选值;但与甘肃省土壤背景值相比,Cu,Zn,Cd,Pb和Hg积累普遍,分别是背景值的1.9,1.4,3.1,1.3,5.2倍;②内梅罗综合污染指数平均值为0.508,9.9%的点位出现了轻度和中度污染;多金属潜在生态风险指数的平均值为289,Hg对潜在生态风险指数的贡献率为61.3%;③7种元素被识别出3个主成分。[结论]蔬菜大棚土壤重金属90%以上点位处于安全水平,潜在生态风险为轻微—中度等级,Hg是最大的潜在风险因子。重金属轻度、中度污染和潜在生态风险强、极强的点位较为集中的分布在耕作年限高、人口密集的城镇和交通沿线。

[Objectives]The degree of heavy metal pollution and ecological risks in the soil of vegetable greenhouses in Tianshui City,Gansu Province was evaluated in order to provide a scientific basis for the safe production of agricultural products in that area.[Methods]362 soil samples were obtained from 21 villages and towns in the main greenhouse vegetable production areas of Tianshui City.We used ICP-MS to determine the contents of As,Ni,Cu,Zn,Cd,Pb,and Hg,and employed the Nemerow comprehensive pollution index and potential ecological risk index to evaluate the environmental quality and potential ecological risks of heavy metals in vegetable greenhouse soil.We used correlation analysis and principal component analysis to explore the sources of soil heavy metals.[Results]①The average contents of As,Ni,Cu,Zn,Cd,Pb,and Hg did not exceed the soil risk screening value of the“Soil Environmental Quality Control Standard for Soil Pollution Risk of Agricultural Land(Trial)”(GB15618-2018).However,compared with the soil background values in Gansu Province,Cu,Zn,Cd,Pb,and Hg had generally accumulated,and were 1.9,1.4,3.1,1.3,and 5.2 times of the background values,respectively;②The average value of the Nemero composite pollution index was 0.508,and 9.9%of the points showed light and moderate pollution.The average value of the polymetallic potential ecological risk index was 289,and the contribution rate of Hg to the potential ecological risk index was 61.3%;③Three principal components of the seven elements were identified.[Conclusion]More than 90%of heavy metals in vegetable greenhouse soil samples were at a safe level,and the potential ecological risk was mild to moderate,with Hg being the largest potential risk factor.Sites with light and moderate pollution and sites with strong and very strong potential ecological risks were concentrated in cities and towns with intensive farming and along densely populated areas and traffic lines.