| There are some problems about the risk assessment model in the technical guidelines of pollution site risk assessment.?1?Due to the complexity and spatial heterogeneity of the soil environment,pollutant concentrations are fuzzy,and?2?the differences between different individuals and cities,such as population density,lifestyle and natural conditions,lead to uncertainty of exposure parameters in the assessment model.There are some deficiencies in the health risk assessment using deterministic methods,so a method of health risk assessment for heavy metals in soil is proposed to solve the uncertainty problem in model parameters.Trigonometric fuzzy number is an effective method to quantify the parameter uncertainty in health risk assessment.It uses the stochastic theory to simplify the calculation and obtain the health risk range of each pollutant under different probability levels.Combined with GIS to predict the spatial distribution of human health risk in soil,determine the non-carcinogenic and carcinogenic high-risk areas in the study area,and finally obtain the priority control of heavy metals and the priority control area.It is important to study the spatial distribution of heavy metals in soil for the identification of hot spots and the assessment of potential sources of pollutants.Taking a regional soil environment of Dahua Group as an example to verify the applicability and feasibility of the method,the results show that:?1?Combined with GIS and Pearson correlation analysis,factor analysis and cluster analysis in multivariate statistical analysis to identify the sources of heavy metals in soil,the results show that the study area is mainly divided into two groups:the first group is lead,cadmium and mercury,which comes from traffic and transportation emissions,improper storage of raw materials in early chemical plants,and improper treatment of wastewater and slag produced in production and transportation,mainly distributed in the south of A4 and northwest of A5.The second group is arsenic,nickel and copper.The industrial pollution from reclamation materials and chemical plants is mainly distributed in the northern part of A4block.?2?The results show that the non-carcinogenic risk of six heavy metals decrease in the order of As>1>Pb>Cd>Ni>Cu>Hg,and the non-carcinogenic risk is 8.28,exceeding the risk threshold of 1.The average total carcinogenic risks for adults and children are 3.01×10-5 and4.80×10-5,respectively,both exceeding 1×10-6,indicating that all residents in the study area have potential carcinogenic risks.Calculated by the random-fuzzy coupled health risk assessment model,the total non-carcinogenic risk value range is[0.93,62.50],and the average HI value is 8.31,which is slightly higher than the average value of the deterministic health risk model.T The range of total carcinogenic risk in children and adults is[2.43×10-6,4.32×10-4],[1.60×10-6,1.61×10-4],respectively.The cumulative carcinogenic risk exceeds the target risk value,and t and belongs to the four grades of mild,moderate,moderate and high risk,which indicates that the level of carcinogenic risk is ambiguous and affects the final judgment of decision makers.The contribution rate of exposure risk shows that the exposure pathway is in the order of oral intake>skin contact>respiratory inhalation,and the possibility of oral intake route is 16.22%beyond the acceptable threshold,so the risk caused by oral intake pathway cannot be ignored.Sensitivity analysis shows that CAs,DAIRA s,BWAs are the key factors influencing the non-carcinogenic risk and carcinogenic risk of children and adults.The results of this study will improve managers reduce potential health risks and provide new insights to solve uncertainties in soil management.?3?Kriging interpolation is used to plot the spatial distribution of heavy metal health risks.The results show that HI is more than 1 in the study area,indicating that the site has a high impact on children's non-carcinogenic health risks.The high HI value sites are mainly distributed in the north of A4 and the middle and south of A5.The entire study area exceed1×10-6,of which 2.98%is low-medium risk and 45.45%is medium risk,51.57%of the area is more than 1×10-4,which belongs to the medium-high risk area,and the distribution is similar to the area of the second group?As-Ni-Cu?pollution sources.Arsenic is the most important element affecting health risk.Therefore,arsenic is set as the priority control metal,and the severe risk area is designated as the priority control area. |
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