Health Risk Assessment Of Heavy Metals In An Electroplating Plot In Suzhou

With the rapid development of human society and economy,people are increasingly aware of the importance of a healthy living environment.Enterprises with high risk of environmental pollution such as metal processing and electroplating use heavy metals such as zinc,nickel,chromium and other compounds in the production process,which can easily cause pollution to the surrounding soil and groundwater environment of the plot.Therefore,determining the pollution degree of the plot and evaluating the health risk of the plot has become a research hotspot at present.This paper takes an electroplating plot in Suzhou as the research object,using Single pollution index method,Nemerow index method and index of geoaccumulation method to evaluate the pollution degree of 8 heavy metals in soil samples[As,Cd,Pb,Cu,Ni,Zn,Hg and Cr（Ⅵ）]is based on the health risk model and Kriging interpolation method to study the three-dimensional spatial distribution of the health risk of heavy metals in the soil.And use MINTEQ software to simulate and optimize the concentration of heavy metal-nickel form in the soil for health risk analysis.The main research contents and results are as follows:（1）Through detection and analysis,the content of Ni and Cr（VI）in 0.5m,1.5m and 3.0m sampling layers exceeded the standard,and the exceeding points were all located in the fourth workshop of the electroplating plant,indicating that Ni and Cr（VI）in heavy metal layer accumulated in 0-3.0m soil depth.The coefficient of variation of the average contents of eight heavy metals in each layer of soil:Cr（VI）>Ni>200%>Zn>Cd>100%>Hg>As>Pb>Cu>36%,which belongs to high variation and is multi-point or non-point source pollution.（2）According to the analysis of SPSS software and the principal component analysis of heavy metals in each layer of soil,two principal components are proposed.The first principal component is Hg and Cd,which indicates that Hg and Cd are affected by the same pollution source and come from natural sources;the second principal component includes Pb,Cr（VI）,Ni and Cu,which is mainly affected by the combined source of natural and man-made sources.（3）From the single factor index and Nemero comprehensive pollution index,the surface soil was not polluted by Cu,Zn,Pb,Cd and Hg,but was polluted by Ni and Cr（VI）,and Ni was the main pollutant.Ni and Cr（Ⅵ）in the soil in the 0.5m,1.5m,3.0m,4.5m sampling layers all caused different degrees of pollution to the soil,especially the depth of 0-3.0m.（4）According to the results of Igeo,the soil at the depth of 0-4.5m is mainly polluted by heavy metals Ni and Zn,and the pollution is the most serious in the topsoil,with Ni reaching a moderate pollution level and Zn is close to moderate pollution.（5）Based on the health risk model and Kriging interpolation method,the soil heavy metal health risk distribution map was drawn,and the results showed that the carcinogenic risk of surface soil Ni（sampling points No.6 and No.10 to No.13）>10^-6,at sampling point 12 the carcinogenic risk of Cr（Ⅵ）>10^-6.The non-carcinogenic risk of some Ni sampling points is higher than the limit,so Ni and Cr（Ⅵ）are considered to be the main pollutants in the surface soil of the plot,and these points are located in the fourth workshop of the electroplating plant（rack nickel,chromium）.From the perspective of the spatial distribution of health risks,in the 1.5m and 3.0m areas,the carcinogenic risk of Cr（Ⅵ）at point 13 is more than 10^-6;At a depth of 1.5m,the non-carcinogenic risk of Ni and Cr（Ⅵ）at sampling point 13 and Ni at sampling point6 at 4.5m depth were both>1.Ni and Cr（Ⅵ）exhibit the pollution characteristics of point source diffusion.Among them,the pollution in the fourth workshop is the most significant.The farther away from the fourth workshop（contaminated area）,the lower the pollution degree;From the longitudinal point of view,both Ni and Cr（Ⅵ）migrate from the surface layer to the deep soil.（6）After carrying out heavy metal form simulation and concentration data correction,it is found that the dominant Ni form is Ni（OH）₂、Ni（OH）₃^-、Ni²⁺、Ni Cl⁺、Ni CO₃、Ni F⁺、Ni HCO₃⁺、Ni OH⁺、Ni SO₄.After the health risk assessment,it was found that the carcinogenic and non-carcinogenic at some points of the form Ni²⁺and Ni CO₃ exceeded the acceptable threshold,which would cause harm to the human body and should not be ignored;Other forms of carcinogenic and non-carcinogenic risks are very small and will not cause harm to the human body.This shows that it is necessary to study the health risks of heavy metal forms.In summary,the soil of the electroplating plot has been polluted by heavy metals Ni and Cr（Ⅵ）,mainly from human sources during industrial operations during the operation of the electroplating plant,and the pollutants are mainly distributed in the soil at a depth of 0-3.0m;The health risk of the heavy metals Ni and Cr（Ⅵ）in the soil of the fourth workshop of the plot is greater than the acceptable level,indicating that they are heavy metals that cause health hazards to the human body.The three-dimensional spatial distribution map is conducive to clearly showing the distribution of heavy metal pollution risks at various depths in the soil.It is expected to provide technical support for the subsequent restoration of the land.Analyzing the health risk assessment of the heavy metal Ni form in the plot,it can be seen that not all heavy metal forms pose a health risk to humans.It is expected to provide a theoretical basis for the quantitative assessment of land remediation in the future.