Research On Spatial Distribution And Diffusion Characteristics Of Soil Heavy Metal Pollutants Based On Geostatistics

Soil plays an important role in ecosystem.It provides living space for various creatures and has a profound influence on the mode and direction of human society’s development.But with the improvement of industrialization,although people enjoy the convenience of economic development,they bear the risk of soil pollution.Soil pollution has the characteristics of multisource,persistence and difficult controlling,especially the soil contaminated by heavy metals,which has a great threat to the surrounding ecological environment.It is especially obvious in the disused plant site.With the upgrading and adjustment of urban structure,a large number of disused plant sites will be replaced by other construction land.In order to change the function of these disused land smoothly,it is necessary to research the heavy metals in the soil of these area in case these soils which contaminated heavy metal cause more harm to human and our environment.This paper takes a retired site in Wenling City as the research object,using the system placement method to set up 22 sampling points in the site and collected 183 soil samples to analyze the contents of 7 heavy metal elements(As、Cr、Cu、Mn、Ni、Pb and Zn)in soil.The distribution of heavy metals in three-dimensional space is analyzed by using the geological model of the plant area and the three-dimensional model based on geostatistical Kriging interpolation method;The sources of 7 heavy metals were analyzed by correlation analysis and main component analysis;At the same time,the pollution grade and risk of heavy metals in the retired plant area are evaluated by various pollution assessment methods;Finally,by considering the borehole data and the occurrence forms of heavy metals,the migration trend of heavy metals in soil can be qualitative analyzed.The results of soil heavy metal pollution assessment and descriptive statistical analysis show that the soil in the plant is in a state of mild pollution.By fitting various metals through half-variance function,As and Pb are better suited for exponential models,effect of spherical model for metal Zn is better,the other four metals were more suitable by Gaussian model.Combined with the results of heavy metal source analysis and 3D Spatial Distribution Model,Cr、Cu、Ni、Pb and Zn are derived from the production process of the electroplating industry,and the regions with higher concentrations is mainly distributed in the plant waste treatment facilities and the location of production workshop A;Mn comes from the process of soil formation,and the regions with higher concentrations is mainly distributed in the east and south of the factory area;As are influenced by human activity and the parent material,the spatial distribution has both characters of the above two types of metals.Combined with the stratigraphic model,with the depth of the formation increasing,the range of As、Cr、Cu、Ni、Pb and Zn above the background concentrations decreases gradually,while the area that Mn higher than the background concentrations are gradually increased.The exchangeable state is the main form of heavy metal migration in this plant area,which can move with the flow of groundwater,showing the trend of migration from the high concentrations area of the northern surface to the deep soil in the south.