The Pollution Investigation And Evaluation Of A Typical Organic Contaminated Site

Soil is one of the main natural resources for human survival,but also an important part of the ecological environment.In recent years,more and more health and safety incidents caused by soil contamination make people more attention to soil problems,especially concern for soil contaminated by industrial enterprises how to use it again.Therefore,the investigation and health risk assessment of the contaminated site has great significance for the management,restoration and secondary development.This paper took a city of a gas plant which was a typical organic contaminated site as an object of study,identified its types of pollution,pollution levels and pollution distribution through preliminary and detailed investigation,and then carried out a health risk assessment to determine the target of pollutants and four kinds of exposure routes,and calculated each exposure dose and carcinogenic risk based on Risk Assessment of Contaminated Sites Technical Guidelines(HJ25.3-2014)which provided the calculation models and parameters.The main research contents and results of the paper are as follows:First,it was a preliminary investigation.Through the preliminary investigation,the study areas were divided into the key areas and the general areas.The key areas were water gas section,tar section,desulfurization section,thiamine section,crude benzene section,phenol removal section and sewage treatment station,the other for general areas.At this stage,this paper concluded that potential contaminants were the total petroleum hydrocarbons,benzene,polycyclic aromatic hydrocarbons,phenols,cyanides.Second,it was a detailed investigation.According to the results of the preliminary investigation and referring to Beijing "Site Environmental Assessment Guidelines"(DBl 1/656-2009),this paper combined the grid distribution point method and judgement point method to finalize 55 soil sampling points and 222 soil samples which were based on the hydrogeologic conditions of the site and the migration analysis results of contaminants in soil.Third,this paper got the results of site investigation in three aspects.The first aspect was the kind of pollution.The site investigation showed that PAHs and BTEX were the main pollutants including phenanthrene,fluorene,fluoranthene,acenaphthene,acenaphthylene,pyrene,naphthalene,anthracene,2-methyl naphthalene,benzene and(a)anthracene,Chrysene,benzo(a)pyrene,indeno(1,2,3-cd)pyrene,benzo(g,h,i)perylene,benzo(b)fluoranthene,benzo(k)fluoranthene,1,2,4-trimethyl benzene,ethylbenzene,o-xylene,m&p-xylene,styrene,toluene,1,3,5,n-butyl benzene,toluene,isopropyl,tert butadiene,benzene,toluene,2-chlorotoluene,4-chlorotoluene,isopropylbenzene,n-propylbenzene,also detected TPH and cyanide.The second aspect was the degree of pollution.This paper found that benzo(a)pyrene and indeno(l,2,3-cd)pyrene were excessive pollutants and their concentrations were 0.27～0.67mg/kg,0.21～0.33mg/kg respectively which showed that pollution index were 1.35 to 3.35 times and 1.05 to 1.65 times.In addition,the concentrations of other pollutants did not exceed the value of the soil evaluation criteria by comparing the monitoring data and evaluation criteria.The third aspect was the pollution distribution.Benzo(a)pyrene and indeno(l,2,3-cd)pyrene were mainly distributed in less than 2m soil of water gas section and tar section.Trends of concentration with depth were basically same.As the depth increased,the concentrations of the two pollutants gradually declined.Fourth,this paper got the results of health risk assessment.This paper identified benzo(a)pyrene and indeno(1,2,3-cd)pyrene as the target pollutants through hazard identification and determined four potential exposure routes which were oral ingestion route,inhalation of soil particles route,soil skin contact route,inhalation of gaseous pollutants from topsoil outdoor,and calculated each exposure dose and carcinogenic risk based on Risk Assessment of Contaminated Sites Technical Guidelines(HJ25.3-2014)which provided the calculation models and parameters.The carcinogenic risk of benzo(a)pyrene and indeno(1,2,3-cd)pyrene were greater than the acceptable level(10-6)in oral ingestion and soil skin contact route through the risk characterization.Although the carcinogenic risk did not exceed the acceptable level in inhalation of soil particles route,but they were still 0.27%carcinogenic contribution rate.Therefore,benzo(a)pyrene and indeno(1,2,3-cd)pyrene need conduct soil remediation.By calculating,the remediation target of benzo(a)pyrene and indeno(1,2,3-cd)pyrene in the contaminated sites were 0.0635 and 0.2 mg/kg respectively.