Source Apportionment Of Soil Heavy Metals In A Regional-scale Typical Industrial Area

Understanding the status of heavy metal pollution in soil and exploring its pollution sources are the key links in soil pollution prevention and control.Especially in industrial agglomeration areas,the severity of heavy metal pollution and the complexity of pollution sources make it more difficult.In this paper,five heavy metals(Cd,Hg,As,Pb,Cr)in the surface soil of typical industrial areas in Chenzhou City,Hunan Province were taken as the research objects.The pollution characteristics and causes were analyzed through the combined application of a variety of technologies.The main research results are as follows:(1)The mean values of the five heavy metals in soil of the study area were higher than the background values of soil environment in Hunan Province,indicating that the five heavy metals were enriched to different degrees.The Pearson correlation coefficient between Cd,Pb and As were large,which indicated the homology among these three heavy metals.The geo-accumulation index of the five heavy metals in descending order was Cd > Hg > Pb > As > Cr.The pollution of Cd was most serious and reached moderate pollution.Hg,As and Pb were slightly polluted,while Cr was almost not polluted.(2)The spatial correlation of heavy metals Cd,Pb and Hg in study area was poor,indicating that the spatial variability was strong.The spatial distribution of As and Cr had moderate correlation.The contents of Cd and Hg in study area were higher in the southwest and lower in the northeast.The content of As in study area was higher in southeast and lower in northwest.The contents of Pb and Cr in study area had no obvious trend in the east-west direction,but were higher in south and lower in north.The high value areas of Cd and Pb contents were mainly distributed in the middle of Suxian District and the south of Guiyang County.The high value areas of Hg content were mainly distributed in Jiahe County and a small part of western Guiyang County The high value areas of As content were mainly distributed in the middle of Suxian District,the south and north of Guiyang County,and the south of Zixing City.Cr content distribution was dispersed,and there was no obvious high value aggregation.(3)The mining industry in study area had the most significant effect on the contents of Cd,Pb and As,with the contribution rates of 87.7%,88.5% and 62.5%,respectively.Agricultural activities had the most significant effect on Hg content,with the contribution rate of 66%.Soil parent materials had the most significant effect on Cr content,with the contribution rate of 90.75%.The key influence areas of mining on As were mainly distributed in the middle of Suxian District,the south and north of Guiyang County,and the south of Zixing City.The key influence areas of mining on Cd and Pb were mainly distributed in the middle of Suxian District and the south of Guiyang County.The key influence areas of agricultural sources on Hg were mainly distributed in Jiahe County.After partition processing,the primary source of the same element was different in different regions.Compared with non-zoned treatment,zoned treatment highlighted the importance of agricultural activities on Cd accumulation,soil organic matter and altitude on Hg accumulation,soil parent material and sewage irrigation on As accumulation,and transportation sources on Pb accumulation.Therefore,at the regional scale,not only the main sources affecting the heavy metal content can be identified,but also the secondary sources in the local area can be identified by zoning processing,so as to more clearly clarify the multiple sources of heavy metals in the complex environmental system.(4)In the study area,the ecological risk degree of Cd was highest,reaching high potential ecological risk,Hg was medium to high potential ecological risk,As,Pb,Cr were all low potential ecological risk.The compound ecological damage of the five heavy metals was of high ecological risk level.The distribution of the potential ecological risk index of heavy metals had a strong spatial correlation with the main anthropogenic pollution sources.The high Cd and Hg ecological risks caused by the mining industry were distributed in the south of Guiyang County and the middle of Suxian District.The high Hg ecological risk areas caused by agricultural sources were distributed in Jiahe County and the middle of Guiyang County.The high As ecological risk areas caused by the mining industry were distributed in central Suxian District,southern and northern parts of Guiyang County,and southern parts of Zixing City.