| With the development of China's industrialization,the problem of heavy metal pollution in urban soils has become increasingly serious,affecting the growth of plants and human health.The production activities of industrial enterprises are one of the main sources of heavy metals in urban soils.Therefore,the spatial distribution of soil heavy metals is studied on the scale of industrial enterprises.To analyze the pollution situation,and then put forward pollution control and risk management and control strategies,which can improve the management level of the soil environment and is of great significance for the sustainable use of soil resources.Due to the nature of the soil,the accumulation of pollutants in the soil will continue to spread to the surrounding and underground,so it is also important to understand the distribution of pollutants in the three-dimensional space of the soil.In order to reveal the influence of the enterprise on the environmental quality of the soil in the production process,this article takes the site of an alloy manufacturing enterprise as a research area,and selects the characteristic pollutants soil heavy metals Co,Cu,Pb,Zn,and Ni as The research object uses geostatistical methods to analyze the two-dimensional and three-dimensional spatial variability structure and distribution of heavy metals in the soil,and evaluates the pollution status of heavy metals.The main conclusions are as follows:1.The statistical results of the heavy metal content of the soil in the study area show that the statistical characteristics and coefficients of variation of the heavy metal content in the three layers of soil are obviously different.The heavy metals Co,Cu,Pb,and Zn in the first layer of soil are normally distributed.After the Cox transformation,the distribution is normal,and the degree of variation is Ni,Cu,Zn,Pb,Co in order from large to small.The Cu content in the second layer of soil showed a normal distribution,and Co,Pb,Zn,and Ni showed a normal distribution after Box-Cox transformation.The degree of variation of heavy metal content in the soil was Pb,Ni,Cu,Zn,Co.The content of Co,Cu,Pb and Ni in the third layer of soil showed a normal distribution,and Zn showed a normal distribution after Box-Cox transformation.The degree of variation was Zn,Cu,Ni,Pb and Co in order from large to small.From the perspective of the change of soil heavy metal content in the vertical direction,as the depth increases,the soil heavy metal content shows a decreasing trend.2.The two-dimensional spatial structure of heavy metals in soil shows that the impact of production activities of enterprises on the spatial differentiation of heavy metals Co is mainly concentrated in the first layer,and some of the influencing factors of spatial differentiation of heavy metals Co in the first layer of soil come from the production activities of enterprises.The spatial differentiation of heavy metal Cu in the soil is also caused by human factors such as production activities of the enterprise.The spatial differentiation of Cu in the second layer of soil is affected by both random factors and structural factors.The spatial autocorrelation of the third layer of soil is strongly affected mainly by The influence of structural factors.The spatial variability of soil heavy metal Pb in the first layer of soil is caused by the combination of random variation and structural variation,and the spatial correlation is strong.The structural factors of the spatial variability of the second and third layers of soil are dominant,and the spatial autocorrelation is strong.The influence of spatial differentiation of heavy metals Pb is mainly concentrated on the surface layer.The heavy metal Zn in the soil is less subject to human interference in the three-layer soil,and its spatial variability is mainly determined by the nature of the soil.The spatial autocorrelation of heavy metals Ni in the soil is weak in the first layer of soil,and the spatial autocorrelation of the third layer of soil is strong.The effects of human activities on the spatial differentiation of heavy metals Ni are mainly concentrated in the surface soil.The enterprise is mainly engaged in the surfacing welding of special alloys and the production of cobalt-based and nickel-based high-alloy precision castings and forging materials.The random variation of Ni element in the first layer of soil is related to the production activities of the enterprise.The existence of copper and lead alloy products in the scrap metal yard is the main reason for the random variation of soil Cu and Pb.3.The spatial distribution results of heavy metal content in the three-layer soil show.In the first layer of soil,the content of heavy metals Co was distributed in a strip shape,and the high value area was located in the west of the northern part of the study area.The soil heavy metals Cu,Pb,Ni element high value area is more consistent in the study area,located in the north part of the middle of the study area,distributed in an "island" shape,the source of the three heavy metals may be the production activities of the enterprise,the soil Ni content exceeds the soil The background value area is concentrated and the density is high.The soil heavy metal Zn high-value area is located in the southwest of the middle of the study area,showing an "island" distribution.The concentrations of heavy metals Co,Cu,Pb,Zn,and Ni in the second layer of soil are lower than the Shanghai soil background values.The contents of heavy metals Co,Cu,and Ni are distributed in a strip shape,and the distribution is relatively uniform,and the contents of heavy metals Pb and Zn are islands.The high-value soil heavy metal Pb area is located in the north part of the middle of the study area,and the high-value soil heavy metal Zn area is located in the southwest part of the middle of the study area.The contents of heavy metals Co,Cu,Pb,Zn,Ni in the third layer of soil are relatively low,and the distribution is relatively uniform.The overall distribution of low-value areas is wide.The local area content is relatively higher than the surrounding areas,but far lower than Shanghai Soil background value.From the overall distribution position and change trend of the heavy metal content in the three layers of soil,as the depth increases,the concentration of heavy metals in the soil decreases continuously.The heavy metals in the soil are enriched in the surface soil,and migrate,diffuse,and infiltrate through various pollution pathways.4.The analysis results of the three-dimensional spatial structure of soil heavy metals show that the variation function of the soil heavy metals Cu,Pb and Ni in the direction of the main axis(south-north)conforms to the spherical model,the soil heavy metals Co and Zn conform to the Gaussian model,and the soil heavy metals Cu,Pb and Zn have more Strong spatial autocorrelation.Spatial variability is a combination of random variation and structural variation.Soil heavy metals Co and Ni have strong spatial autocorrelation.Spatial variation is dominated by structural variation;heavy metals Cu,Pb in the secondary axis(east-west)direction The variation functions of Ni and Ni conform to the spherical model,and the heavy metals Co and Zn of the soil conform to the Gaussian model.The heavy metals Cu,Pb and Ni of the soil have strong spatial autocorrelation.The spatial variation is caused by the combination of random variation and structural variation.The heavy metals Co and Zn of the soil Spatial autocorrelation is strong,and spatial variation is mainly structure variation.From the perspective of the spatial structure of soil heavy metals in the vertical direction,the variation functions of soil heavy metals Cu,Pb,Ni conform to the spherical model,the soil heavy metals Co and Zn conform to the Gaussian model,and the soil heavy metals Co,Cu,Pb,Zn,Ni have a strong space Autocorrelation,spatial variation is dominated by structural variation.In the vertical direction,spatial variation is dominated by structural variation,while in the horizontal direction,random factors and structural factors work together,indicating that human production activities have a greater influence on the spatial distribution characteristics of soil heavy metals in the horizontal direction.Increased,the impact of human activities weakened,the random factors affecting the spatial distribution characteristics of heavy metals weakened,and structural factors increased.5.The three-dimensional spatial distribution of heavy metals in the soil shows that the high-value soil heavy metal Co content area is located in the west of the northern part of the study area,and the overall content is evenly distributed and the concentration is not high.The high-value areas of heavy metal Cu in the soil are mainly concentrated in the northwest direction in the middle of the study area,and the high-value areas are relatively large.The distribution of heavy metal Pb elements in the soil is relatively uniform,the content is low,there is no obvious high value area,and the area area with relatively high concentration is relatively small.The high-value areas of soil heavy metal Zn are distributed in the southwest of the study area,and the high-value areas are more concentrated.The heavy metal Ni element in the soil has a significant high value area in the study area,concentrated in the northwest of the middle of the study area,and the concentration is significantly higher than the surrounding soil.By comparing the production distribution pattern of factories and enterprises in areas with high heavy metal content and research areas,it can be seen that the areas with relatively low heavy metal concentrations are mostly vacant land and office buildings,and the areas with high concentrations are mainly distributed in the factory's production workshops and scrap metal yards.In the long-term production process of the enterprise,the concentration of heavy metals may be higher than the surrounding soil due to factors such as raw material stacking,welding dust deposition,improper disposal of solid waste,and rainwater scouring and the nature of the underlying surface.The soil heavy metal high value area in the study area is mainly located in the middle,northwest and central southwest of the study area.The low value area is mainly located in the east and southeast areas of the study area,and the high value area in the vertical direction of heavy metals is located in the surface soil and is composed of the surface core The migration and diffusion of the high-value area to the surrounding and underground indicates that the source of heavy metals may be related to the daily production and human activities of the enterprise.6.The single-factor index method of pollution assessment in the study area showed that in the first layer of soil,there was a certain degree of accumulation of heavy metals in the soil.The samples of heavy metals Co,Cu,Pb,Zn,and Ni that were slightly polluted accounted for 41%,32%,39%,16%,16%,the proportion of light pollution is 2%,18%,2%,2%,11%,Pb and Ni,which accounted for the heavy pollution,accounted for the sample 2% and 5% of the total,Ni is seriously polluted,accounting for 5% of the total sample.The proportions of the five heavy metals in the second layer of soil that are slightly polluted are 20%,8%,5%,2%,and 5%.The heavy metals that are slightly polluted are Cu,Zn,and Ni,accounting for 2% of the total sample.,2%,5%,with heavy pollution Pb,accounting for 2% of the total sample.In the third layer of soil,the five heavy metals Co,Cu,Pb,Zn,and Ni are in a pollution-free state.In general,the order of heavy metal pollution in soil is Ni> Cu> Pb> Co> Zn.Most of the five soil heavy metal samples are in a non-polluted or slightly polluted state,and some samples are heavily polluted.From the perspective of the depth of pollution,under the influence of the daily production and human activities of the enterprise,the pollution is mainly concentrated in the surface soil of the study area.The pollution status of soil heavy metals is basically consistent with the results of spatial variation of heavy metals.In the production activities of enterprises,the pollution of heavy metals Ni,Cu and Pb in the soil is relatively serious,the spatial autocorrelation is weak,the soil Zn pollution is light,and the spatial autocorrelation is strong.7.The evaluation result of Nemero's comprehensive pollution index shows that the proportion of heavy metal soil pollution in the first layer of soil is 27.27%,and there is no heavy pollution.The second layer of soil is lightly polluted,accounting for 6.82%,without heavy pollution and heavy pollution.The condition of the third layer of soil is clean and free of pollution.The soil in the study area has a large proportion of uncontaminated heavy soil.Some sample sites are in a lightly polluted state,and a few are heavily polluted.It shows that the overall pollution status of the study area is relatively light,but there are relatively heavy pollution status in some areas. |
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