张家口市万全区某种植区土壤重金属污染评价与来源分析

Evaluation and Source Analysis of Soil Heavy Metal Pollution in a Planting Area in Wanquan District,Zhangjiakou City

以张家口市万全区某蔬菜种植区土壤为研究对象,采集132件表层和80件深层土壤样品,测试分析As、Cd、Cr、Hg、Cu、Ni、Pb和Zn等8种重金属元素含量以及Cr和Ni赋存形态.综合应用地统计学分析和PMF受体模型,并结合3种重金属污染评价方法,摸清了研究区土壤重金属空间分布特征、重金属污染程度和垂向上Cr和Ni赋存形态的分布情况,探析了土壤重金属污染源和贡献率.结果表明,表层土壤重金属Cd和Pb含量平均值均高于河北省土壤背景值,表层土壤Cr、Ni、Cu,Cd、Pb和Zn空间分布特征存在相似性.地累积指数法表明研究区以无污染为主,分布少量轻污染点位,以Cd污染点居多;富集因子法表明研究区主要以无-弱污染为主,各元素均存在中污染情况,背景区显著污染元素为As、Pb和Hg,重点区中显著污染元素为Cd;潜在生态风险指数法表明研究区以轻污染为主,局部分布“中”和“强”风险点,背景区Hg存在“很强”风险点,重点区Cd存在“很强”风险点.这3种评价结果表明背景区以Cd和Hg污染为主,而重点区则以Cd污染为主.垂向土壤赋存形态研究表明Cr以残渣态(F4)为主,可氧化态(F3)为辅,垂向以表聚型为主,以弱迁移型为辅,而Ni以残渣态(F4)为主,以可还原态(F2)为辅,垂向以强迁移型为主,以弱迁移型为辅.表层土壤重金属来源共分3类,Cr、Cu和Ni主要来自自然地质背景源,贡献率分别为66.9%、66.9%和76.1%;As、Cd、Pb和Zn主要来自人为活动源,贡献率分别为77.38%、59.2%、83.5%和59.5%;Hg主要来自大气干湿沉降,贡献率为87.8%.

Taking the soil of a vegetable planting area in Wanquan District of Zhangjiakou City as the research object,132 surface and 80 deep soil samples were collected to test and analyze the contents of eight heavy metals such as As,Cd,Cr,Hg,Cu,Ni,Pb,and Zn and the occurrence forms of Cr and Ni.By applying geostatistical analysis and the PMF receptor model and combining three heavy metal pollution evaluation methods,the spatial distribution characteristics of soil heavy metals in the study area,the degree of heavy metal pollution,and the distribution of Cr and Ni fugitive forms in the vertical layer were clarified,and the sources and contribution rates of soil heavy metal pollution were analyzed.The results showed that the average contents of Cd and Pb in surface soils were higher than the background values of soils in Hebei Province,and the spatial distribution characteristics of Cr,Ni,Cu,Cd,Pb,and Zn in surface soils were similar.The ground accumulation index method showed that the study area was mainly free of pollution,with a small number of lightly polluted sites,and most of them were polluted with Cd.The enrichment factor method showed that the study area was mainly free-weakly polluted,with medium pollution of all elements;the significantly polluted elements in the background area were As,Pb,and Hg,and the significantly polluted element in the key area was Cd.The potential ecological risk index method showed that the study area was mainly lightly polluted,with local distribution.The potential ecological risk index method showed that the study area was mainly lightly polluted,with a local distribution of"medium"and"strong"risk points,with"very strong"risk points for Hg in the background area and"very strong"risk points for Cd in the focus area.These three evaluation results indicated that the background area was dominated by Cd and Hg pollution,whereas the focus area was dominated by Cd pollution.The study on the fugitive morphology of vertical soil showed that Cr was dominated by the residue state(F4)and supplemented by the oxidizable state(F3),and the vertical direction was dominated by the surface aggregation type and supplemented by the weak migration type.Ni was dominated by the residue state(F4)and supplemented by the reducible state(F2),and the vertical direction was dominated by the strong migration type and supplemented by the weak migration type.The sources of heavy metals in the surface soil were divided into three categories;Cr,Cu,and Ni were mainly from natural geological background sources.The contributions of Cr,Cu,and Ni were 66.9%,66.9%,and 76.1%,respectively.As,Cd,Pb,and Zn were mainly from anthropogenic sources,with contributions of 77.38%,59.2%,83.5%,and 59.5%,respectively.Hg was mainly from dry and wet atmospheric deposition,with a contribution of 87.8%.