Research On Three Dimensional Refined Risk Assessment Method Of Heavy Metals Contaminated Sites In Henan Province

With China’s emphasis on ecological and environmental protection and the adjustment of industrial structure,high pollution factories and enterprises in cities have been successively closed down or relocated.As a result,most of the remaining sites have been polluted by heavy metals to varying degrees.In order to make better use of existing land resources,it is necessary to repair and treat the urban construction land before development and utilization.Traditional health risk assessment methods mostly take block as a unit to conduct overall risk assessment on contaminated sites.The repair value is set relatively conservatively,causing problems such as excessive repair.The spatial fine distribution characteristics of heavy metal zinc are obtained by constructing three-dimensional Radial Basis Function(RBF)neural network interpolation model.The health risks caused by pollutants in different strata and areas with different concentrations to sensitive populations are carefully evaluated from the threedimensional spatial level.In this paper,the abandoned site of a hot-dip galvanizing company in Henan Province is taken as the research object.A three-dimensional refined risk assessment method is used to assess the risk of contaminated sites.It is of great significance for accurate restoration and risk control of contaminated sites.The main research results are as follows:(1)The three-dimensional RBF neural network interpolation model of soil heavy metals was constructed to accurately obtain the spatial distribution information of heavy metals in contaminated sites.Different radial basis functions were used to train the network,and the optimal radial basis functions were selected through precision comparison and analysis to predict the heavy metal content of unknown points in the plant area.The results show that the optimal radial basis function is Gaussian function,and its correlation coefficient R2 is 0.89.The error accuracy of the three radial basis functions is sorted as follows:Gaussian kernel function>abnormal S-type function>verse multi-quadratic function.(2)Based on the actual situation of Henan Province,some of the parameters in the health risk assessment model were modified locally to carry out fine risk assessment of contaminated sites.The hazard index of zinc in the first layer of the contaminated plot is 8.42×10-2<1,indicating that the non-carcinogenic risk is acceptable.The hazard index of the second layer of soil pollutant zinc is 4.94×10-2<1,which also belongs to the acceptable range.Finally,according to the soil pollution risk control standard of construction land,the areas with zinc concentration exceeding 8000mg/kg are screened for early warning.(3)The risk assessment system of heavy metals in contaminated sites in Henan Province was developed.Based on the study of the health risk assessment model of contaminated sites,the ArcGIS Engine component was used to realize the rapid and accurate risk assessment of soil heavy metals in contaminated sites.The system functions include map display,parameter modification,model setting and result output.