Study On Pollution Risk Assessment And Remediation Technology Of A Petrochemical Plant Site In Longdong Area

This thesis mainly relies on the remediation project of a petrochemical plant in Longdong area,and takes the legacy contaminated site of the petrochemical plant as the research object,carries out risk assessment of the contaminated site from four aspects of pollutant hazard identification,toxicity assessment,exposure assessment,and risk calculation and characterization,combined with the laboratory trial to screen out the isotopic chemical oxidation technology,and carries out the actual engineering remediation of the contaminated site,the results show that after remediation The results showed that the pollutant concentrations in the soil met the remediation target values after remediation.The main conclusions are as follows:（1）Through the collected site information and actual site investigation,a total of76 soil monitoring points and 17 groundwater monitoring points were deployed.The detected values of petroleum hydrocarbons,benzene and ethylbenzene in soil exceeded the risk screening values,and the exceedance rates were 8.36%,0.56%and 0.56%,respectively;the detected values of general chemical indexes such as total hardness and total dissolved solids in groundwater also exceeded the risk screening values,which may be related to the local hydrogeological background.The risk screening values were exceeded at some points.It indicates that the soil and groundwater of the legacy petrochemical site are mainly contaminated by organic substances.（2）The risk assessment shows that the contaminants of concern at the legacy site are total petroleum hydrocarbons,benzene and ethylbenzene in the soil,and total petroleum hydrocarbons,vinyl chloride,benzene,toluene,ethylbenzene and xylene in the groundwater.The exposure assessment of the contaminants of concern showed that the hazard quotients of the 12 petroleum hydrocarbon contaminated sites in soil,totaling25 samples,were greater than 1,and the maximum non-carcinogenic hazard quotient was 9.78;the highest carcinogenic risk levels of benzene and ethylbenzene were9.89×10^-4and 6.86×10^-5,respectively,and the highest non-carcinogenic hazard quotient of benzene was 22.9,while the non-carcinogenic hazard quotient of ethylbenzene was less than 1.The carcinogenic risk quotients of ethylbenzene and ethylbenzene in groundwater were less than 1.Benzene is a non-carcinogenic pollutant,and there are 3points of exceeded carcinogenic risk for benzene.（3）From the calculation results,we can see that the risk control values of petroleum hydrocarbons,benzene and ethylbenzene in soil based on human health are5420,7.84 and 31.3 mg/kg,respectively;the risk control values of groundwater pollutants of concern,benzene and ethylbenzene,are 2300 and 298 ug/L.Considering the risk control values and the screening values of the second category of sites in Table1 of the Soil Environmental Quality Soil Contamination Risk Control Standards for Construction Land,we determine that the pollutants in the soil of this site are not hazardous to human health.The target values of petroleum hydrocarbon,benzene and ethylbenzene remediation in the soil of this site are 4500,4 and 28mg/kg respectively.（4）Based on the remediation target values of petroleum hydrocarbons,benzene and ethylbenzene,we compared and analyzed the advantages and disadvantages of various remediation techniques for contaminated soil,and selected three remediation techniques,namely thermal desorption,ex-situ chemical oxidation and surfactant elution,for laboratory trial.The former can destroy the structure of pollutants by physical action such as high temperature heating,so that pollutants are removed mainly by desorption and cleavage,but the remediation cost is high and the economy is poor in the remediation of large area polluted sites;the latter can quickly degrade pollutants in soil mainly by strong oxidizing radicals generated by chemical action,without secondary pollution,and the remediation cost is low.Therefore,it was determined that the remediation of this contaminated site would be carried out by the allosteric chemical oxidation technology.（5）The actual remediation engineering practice of the contaminated site soil was carried out using the allosteric chemical oxidation remediation technology.The results showed that the highest detected concentrations of benzene,ethylbenzene and petroleum hydrocarbons were 1.71,0.0962 and 4276mg/kg respectively after remediation by the iso-chemical oxidation technology,all of which were lower than the remediation target value,and the remediation pass rate reached 100%,indicating that the iso-chemical oxidation technology has ideal remediation effect on the contaminated soil of this site.