Geochemical Characteristics And Source Apportionment Of Environmental Elements In Soils In Suburban Areas Of Beijing

With the rapid development of urbanization,the pollution degree of heavy metals in soil is deepening year by year,and the pollution area is expanding.As potential urban development region and urban agricultural development area,the environment of suburban areas is affected by industry,agriculture and even urban activities.The sources of heavy metals in suburban soil are complex,and the variability of heavy metals is high.The source apportionment of heavy metals in suburban soil has always been a difficulty in related research,and the impact of urban activities on heavy metals in suburban soil remain to be studied.To deeply understand the influence mechanism of heavy metals in suburban soil,based on a mass amount of data analysis,the distribution characteristics of As,Cd,Cr,Hg,Ni,Pb,V and Zn in the soils of Shunyi and Miyun were studied.In addition to analyzing the main influencing factors of soil heavy metals,the relative contribution of each source was quantitatively calculated.Using Sc as a reference element,the distribution of heavy metals in soil affected by human activities was analyzed,and environmental risk of heavy metals is assessed by Hakanson method.At the same time,according to the current situation of economic development,urbanization and land use in Miyun District and Shunyi District,the effects of different human activities on soil heavy metal accumulation under the background of urbanization were discussed.In this paper,the impact of human activities on the accumulation of heavy metals in soil in suburban areas was deeply analyzed,which has a certain theoretical and practical significance to guide the regional environmental pollution control.The main conclusions are as follows.1.In Shunyi district,As,Cd,Zn and Pb are relative enrichment in topsoils,whereas higher Cd,Zn,Pb and Hg occurred in subsoils.PCA and RDA demonstrated that the rock weathering was a significant source of V,Cr,Ni and As,and the local emissions and atmospheric deposition respectively contributed most of Cd,Zn and Pb,and of Hg in soils.2.Results from PMF showed that rock weathering contributed more than 70%of V,Cr,Ni and As in Shunyi,local emissions contributed 92.7-96.3%of Cd,44.4-55.4%of Zn,and 32.0-42.9%of Pb,and atmospheric source that carried urban pollutants contributed 78.7-80.2%of Hg.And for Cd,Zn,Pb,the ACR ratio more than 40%of the sampling accounted for 22.56-29.43%,8.73-17.43%and 7.47-9.99%,respectively.3.Cd,Zn and Pb were enriched in the topsoil of Miyun District,while Cd,Zn,Pb and Hg were enriched in subsoil.PCA and RDA analyses demonstrated that the elements of V,Cr,Ni and As are mainly originated from soils parent materials,and Cd,Zn,Pb are greatly influenced by the human activities,the atmospheric deposition were the dominant contributors for Hg.4.PMF results showed that the natural source of rock weathering contributed more than 75%of V,Cr,Ni and As in Miyun,the local emissions contributed 71.1-81.3%of Cd,60.3-61.8%of Zn and 64.6-68.2%of Pb in soils,and the atmospheric deposition representing urban activities amounted to 100%of Hg.And for Cd,Zn,Pb,the ACR ratio more than 40%of the sampling accounted for 22.01-29.62%,13.43-21.81%and 14.28-23.13%,respectively.5.In the case of fully investigating the distribution characteristics of soil heavy metals and the influence degree of factors on soil heavy metals in the study area,through the analysis of local soil properties and economic status,we can see that,in Shunyi District,the high contribution of local emission to Cd is caused by its high degree of industrial emission,while the development of agriculture and rural tourism in Miyun District is prosperous,and the high contribution of local emission to Zn and Pb is the result of the joint action of agriculture and tourism.