Risk Assessment Of Heavy Metal Contaminated Site In An Electroplating Plant In Dongguan

With economic development and industry adjustment,most polluting enterprises,such as electroplating industry,oil company,and chemical enterprises,have been relocated or shut down from the city center,leaving a large number of contaminated sites.Such sites have different degrees of pollution.If it is not evaluated and governed will directly or indirectly threaten human health and the ecosystem.It has become an inevitable trend to evaluate and repair the site according to the site pollution.This paper takes a plating plant in Dongguan as the research object,collects a total of 33 points of soil samples and 13 points of groundwater samples,analyzes the content characteristics of 9 heavy metal elements in the soil samples,applies a single index method,and potential ecological hazards index method to evaluate the status of soil pollution and ecological risks of contaminated sites,assess health risks,and provide a certain scientific theoretical basis for heavy metal pollution prevention in electroplating plants.The current soil quality assessment results show that Cu,Zn,Ni,Cr 4 heavy metals all have different degrees of pollution;heavy metals Cu,Zn,Ni are the main pollutants in the site,the pollution range Ni>Cu>Zn,there are heavy metal pollution at 24 points in the electroplating plant,the pollution rate is 72%,two points in the electroplating plant are polluted by four heavy metals Cu,Zn,Ni,Cr,the pollution index is the highest,the current pollution status is heavy pollution,4 of 9 heavy metals have a maximum concentration at 1.1m.According to the assessment of the groundwater environmental quality,the groundwater sampling points at the twelve sites did not meet the national Class III water standards,and the excessive levels of heavy metals at the groundwater sites may be caused by the pollution leakage of the electroplating sewage along the pipeline and the sewage treatment area.The ecological risk assessment results show that:(1)The total potential ecological hazard index RI:Eight points(accounting for 24%of the total survey points)correspond to deep soils that have strong ecological risks,of which A18-1.1(point-depth)has the highest risk value,2720.54;(2)The potential ecological risk coefficient of a single heavy metal"E_r~i":The potential ecological risk of soil heavy metals in the study area is mainly limited by Cd and Cu,and the combined potential ecological risk contribution rate of the two is 63.48%;Cu,Ni,and Cd all have strong ecological risks and account for 30%of the total survey points,of which The maximum ecological risk is 1012.50.Health risk assessment shows that Ni is the main factor causing the total carcinogenic risk of the site.When used as non-sensitive land,the non-carcinogenic risk values of heavy metals Ni and Cr at point A18 are higher than 5,and there is a high non-carcinogenic risk.There are 16 points with low-risk carcinogenic risks;11 points with non-carcinogenic risks,accounting for 48%and 33%of the total survey points,respectively.There are 4 points of heavy metal Cr that are non-carcinogenic.The above pollution points are mostly concentrated in the northern part of the site and the border zone,and the area where the sewage treatment plant and power supply house are located.According to the risk assessment results,based on the common Kriging interpolation method of Sufer software,a plan view of the repair range of heavy metal Ni was drawn,and the repair area and earthwork volume were obtained.It is recommended to use the in-situ/ex-situ solidification method for heavily contaminated soil to fundamentally solve the soil pollution problem at the site.