武穴市大法寺镇农田重金属含量特征及生态风险评价

Characteristics of Heavy Metal Content and Ecological Risk Assessment in Farmland of Dafa Si Town,Wuxue City

以大法寺镇268个耕地地块为研究对象,人工采集土壤样品139个,采用相关性分析、潜在生态风险指数法和正定矩阵分解模型(positive matrix factorization,PMF)等方法分析了土壤重金属Cu、Zn、Pu、Cd、Cr、Ni、Hg、As的含量分布特征和污染水平。结果表明:Cd、Ni、Pb、Zn、As的含量均高于湖北省土壤背景值,分别为湖北省土壤背景值的2.23、1.71、1.23、1.15、1.14倍,其中,Cd超标倍数最大,应当引起重视;潜在生态风险指数法评价结果显示,研究区约有97%的土壤样品处于轻微生态风险等级及中度生态风险等级;通过正定矩阵分解模型和主成分分析解析出3个污染因子,分别为农业源与自然源的复合源,工业源、大气沉降源,而农业源与工业源是研究区的主要污染源。

The 286 croplands were selected as the subject in this study.139 surface soil samples were collected from this agricultural area.The distribution characteristics and pollution levels of heavy metals,namely Cu,Zn,Pu,Cd,Cr,Ni,Hg and As,in the soil were analyzed by correlation analysis,the potential ecological risk index and positive matrix factorizing model.The results showed that the mean values of Cd,Ni,Pb,Zn and As in the agricultural area were exceeded the mean soil background values in Hubei Province by 2.23,1.71,1.23,1.15 and 1.14 times,respectively,among which Cd exceeded the standard by the largest factor and should be taken seriously.About 97% of sampling sites in the study area were in the mild ecological risk level and the moderate ecological risk level.Three pollution factors,including agricultural and natural combined pollution source,the industrial source and the atmospheric deposition,were analyzed by the positive matrix factorizing model(PMF),of which agricultural and industrial sources were the main sources of heavy metals in the agricultural area.