Source Apportionment And Risk Scenario Simulation Of Heavy Metal Pollution In Regional Soil

The extensive pattern of economic growth has an inestimable negative impact on the ecological environment,leading the problem of soil pollution becoming more and more prominent.Because of its latent and hidden nature,soil heavy metal pollution often lags behind the discovery of other pollution problems.Furthermore,Due to the special physical and chemical properties and toxic characteristics of heavy metal elements,once soil heavy metal pollution actually breaks out,it will cause great damage both to the ecological environment and human health.In order to improve the effectiveness and scientific rationality of prevention and control of heavy metal pollution in regional soil,understanding the current situation of pollution,identifying pollution sources and clarifying future pollution risks are the basic guarantee for steadily promoting the improvement of governance.The eastern coastal areas of China takes the leading position in urbanization and industrialization,however,the soil there has been seriously affected by heavy metal pollution.In this paper,an industrial developed city in the above region is taken as the study area,with statistical analysis,spatial analysis,source apportionment and scenario simulation used as research methods.Basing on the soil surface heavy metal data which at the number of2051 in the study area,the grade evaluation,distribution characteristics,source apportionment and scenario simulation of heavy metal pollution are carried out to explore the soil pollution status,pollution sources and future pollution risk probability,so as to put forward policy suggestions for regional soil heavy metal pollution control.The main research conclusions are as follows:1.Referring to the soil background values in the study area,Hg,Cr,Cd,Pb,Cu,Zn and Ni all exceeded the standard in varying degrees,with the exceeding degrees of Hg and Cd were the highest,with the average values being 3.37 times and 2.86 times of the soil background values in Zhejiang Province.Single factor index method and potential ecological risk index method were used to evaluate each type of heavy metal.The results showed that the pollution risk levels of Hg,Cd and Cu were relatively high.The study area is in a mild to moderate pollution level as a whole,and heavy metal pollution in some regions is relatively serious.The results of Nemerow index method show that the soil in the study area is in a safe level as a whole,while the pollution load index and potential ecological risk index indicate that it is in a medium pollution state.The main heavy metal pollution elements in the study area are Hg,Cd and Cu,and their distributions are mainly non-point source pollution areas in the central urban area and surrounding areas,and point source pollution areas in the north and south of the study area.2.Two receptor models were used to identify and determine the sources and contributions of soil heavy metal pollution in the study area.The PMF Probabilistic Matrix Factorization)model identified six factors,which is the same as UNMIX model’s result of amount.But the source identification and source contribution results of the two models are not completely consistent.After comparison,it is concluded that Hg,Ni pollution and Cr enrichment in the study area are related to the industrial pollutant discharge sources of enterprises or factories,Cd pollution is related to traffic emission sources,Cu and Zn pollution is related to the multiple sources mixed with industrial pollution of electronic enterprises,traffic emissions soil parent materials,Pb pollution is related to soil acidity and alkalinity and industrial emission sources,and As enrichment is related to soil parent materials and agricultural inputs.Soil heavy metal pollution or enrichment in the study area is mainly from human sources,supplemented by natural factors.3.Setting the optimistic scenario and non-mutation scenario,the cumulative model and time model were used to predict the soil heavy metal concentrations in2020 and 2030 in the study area,and the results were presented in the form of pollution risk probability that exceeds certain specified threshold.Scenario simulation results show that the central district is a high-risk probability area of Hg pollution and Cu pollution,so as Cd pollution distributed disorderly in the study area.The distribution of Pb and Zn pollution also showed the characteristics of disorder and dispersion,but it was mainly in the point distribution of medium and low risk probability.The medium and low risk probability areas of Ni pollution were mainly concentrated in the western and southern areas of the study area.4.The following policy suggestions are put forward for the treatment of soil heavy metal pollution in the study area: weaving the soil pollution dynamic monitoring network densely to accurately distinguish pollution control space;strictly control the source of pollutants,minimizing the exogenous pollution;carry out comprehensive remediation of soil heavy metal pollution to form a smart governance with public participation.Further policy recommendations on soil heavy metal pollution control were also put forward for industrialized developed cities such as the study area,the aspects are as follows: comprehensive governance at the regional scale;institutional mechanism under multi-integration;technological Innovation under sustainable development.