北京市密云区农业土壤重金属元素地球化学特征及生态风险评价

摘要

在北京市密云区西南部农业区系统地采集了1 065件表层土壤样品,对其中Ni、V、Cr、As、Cd、Pb、Zn、Hg 8种重金属元素的含量开展了测试分析.采用多元统计分析法及空间分析法,阐明了这些重金属元素的地球平均化学分布特征,并探讨了其可能的主要来源.结果表明,8种重金属元素主要分为3类:第一类为Ni、V、Cr、As,其含量低于北京地区背景值,其分布主要受成土母质等自然因素的影响;第二类为Cd、Pb、Zn,其平均含量高于背景值,且居民区含量最高.除继承成土母质外,此类元素的分布特征受人为活动影响较大,其中Cd受人为活动影响的程度明显高于Pb和Zn;第三类为Hg,推断大气沉降为影响Hg分布的主要因素.主要采用Hakanson法评价了土壤中重金属的生态风险,结果表明该地区潜在生态危害指数较低.%One thousand and sixty-five surface soil samples were systematically collected at the agricultural area in the southwest of Miyun District of Beijing,and the concentration of 8 heavy metals in the samples were analyzed,such as Ni,V,Cr,As,Cd,Pb,Zn and Hg.By the methods of multivariate statistical analysis and spatial analysis,the geochemical distributions of 8 heavy metals were stated and the main sources for them were also determined.The results show that 8 heavy metals can be classified into three groups.The first group includes Ni,V,Cr and As.The mean concentration of them was found being lower than the background values in Beijing,and the spatial distribution of them was determined being dominantly influenced by the soil parent materials.The second group includes Cd,Pb and Zn.The mean concentration of them generally exceeded the background value in Beijing,and highest values were observed in the residential area.Besides of the origination from the soil parent materials,the spatial distribution of them was determined being greatly influenced by the human activities,in which Cd underwent greater influence than Pb and Zn.The third group only includes Hg,and atmospheric deposition was proposed to be the main influence factor for its distribution.Ecological risks of 8 heavy metals were mainly assessed by Hakanson method,and the indexes of the potential ecological risk for them are relatively low in the study area.