Source Apportionment And Comprehensive Ecological Risk Assessment Of Soil Heavy Metals In A Typical Agricultural County

As an important part of terrestrial ecosystem,soil plays an irreplaceable role in human production and life.The past few decades have witnessed the rapid development of industrialization and urbanization in China,but at the same time,pollutants represented by heavy metals have entered the soil system with frequent and blind human activities.Heavy metal pollution seriously affects soil environment,ecological environment and even human health,which makes the related research widely concerned within and outside the industry.Among them,the source investigation of heavy metals can effectively promote the control and solution of pollutants from the source,and the establishment of risk assessment system can help to identify high-risk areas for priority control,these studies can provide theoretical basis for the prevention and control of pollution and risk management.Based on the current situation of soil heavy metal pollution research,this paper studied a typical agricultural area from the aspects of soil heavy metal pollution assessment,soil heavy metal source analysis and soil heavy metal ecological risk assessment.For the analysis of heavy metal sources,multivariate statistical methods,spatial interpolation analysis and positive matrix factoriza tion model(PMF)were used to achieve quantitative source analysis,and agricultural sources were considered in detail according to local conditions.In terms of ecological risk assessment,in addition to conventional risk assessment,the potential ecologi cal risk index(RI)and PMF model were combined to propose a source risk assessment model to complete the quantitative and spatial ecological risk assessment about soil heavy metals under quantified sources.In this paper,the source analysis and comprehensive ecological risk assessment of eight heavy metals-As、Cd、Cr、Cu、Hg、Ni、Pb and Zn in surface soil of a typical agricultural county in northern China were carried out.The evaluation results by descriptive statistics and enrichment coefficient evaluation showed that the average contents of As,Cd,Hg,Ni and Zn all exceed the local background value.In terms of pollution level,Cd was moderately polluted,Hg was slightly polluted,and the other 6 elements were mildly polluted--no pollution.There were four main sources of heavy metal in the study area,namely,natural source,sewage irrigation and animal husbandry,atmospheric deposition and industrial emissions,and agricultural materials.RI method showed that the total potential ecological risk grad e in the study area belonged to moderate ecological risk,and a few sampling points exhibited strong ecological risk.Among the single element risk indexes,Hg and Cd had the highest risk indexes,both of which were at moderate ecological risk and contribu te 42% and 39.9% to the total risk,respectively.The ecological risk contribution rates of four sources were in descending order: sewage irrigation and animal husbandry(35.1%)> agricultural materials(22.9 %)> atmospheric deposition and industrial emissions(22.0%)> natural source(20.0%).The first two source factors should be used as priority sources for risk control.In spatial distribution,the ecological risks under these two sources showed the lowest value in the central south area.For source of sewage irrigation and animal husbandry with relatively large spatial variation,the northwest,east and southwest corner areas belonged to high risk areas and should be listed as priority areas.In general,this study quantitatively analyzed the sources of soil heavy metals in typical agricultural areas,and comprehensively evaluated ecological risks based on this analysis.The research results were helpful to identify priority pollution sources and regions,improve the precision of pollution and risk management,and ha d reference significance for land environmental management in agricultural areas.