| In 2018,Ministry of Ecology and Environment of the People's Republic of China promulgated the“Soil environmental quality Risk control standard for soil contamination of development land”?GB36600-2018?,in which the concepts of screening value and control value were put forward for the first time according to land types,and it showed that"the contaminant content in construction land soil is equal to or lower than the risk screening value,the risk of soil pollution can generally be ignored".The content of pollutants in soil is higher than the value of risk control,there are generally unacceptable risks to human health,risk control or remediation measures should be taken.At the same time,the standard stipulates that the target value of soil remediation for contaminated sites of construction land shall be determined mainly according to the standards of“Technical guidelines for risk assessment of contaminated sites”and“Technical guidelines for site soil remediation”and related technical requirements,but shall not be higher than the control value.Therefore,the risk control value based on health risk assessment results is an important basis for selecting the target value of soil remediation in contaminated sites.For a large number of contaminated sites with volatile organic compounds left over from petroleum,chemical and pesticide industries in China,the carcinogenic pathways of pollutants mainly include oral intake,skin contact,inhalation of soil particulate matter,outdoor steam invasion?inhalation of external surface and underlying soil gaseous pollutants?and indoor steam invasion?inhalation of indoor gaseous pollution from underlying soil?.Research shows that the health risk of this type of polluted site is mainly caused by the carcinogenic effect caused by indoor steam intrusion exposure.At present,the J&E model in the”Technical guidelines for risk assessment of contaminated sites”issued by the Ministry of Ecology and Environment of the People's Republic of China in 2014 is mainly used to assess the exposure of indoor steam intrusion pathways.J&E model is suitable for living with lawns and gardens in European and American countries.At present,China's residential land is generally high-rise residential areas,so the bottom of the lowest living room is usually underground garage,which is not directly connected with the underground garage.The direct application of this model will lead to a larger result of carcinogenic risk assessment,so that the calculation of carcinogenic risk control value will be too small.Based on previous studies,the model was modified,and the risk control value,screening value and control value before and after the model modification were compared and analyzed,and the appropriate repair target was selected.Because volatile organic pollutants are divided into semi-volatile organic compounds?SVOCs?and volatile organic compounds?VOCs?.Therefore,this paper chooses the pollution sites with SVOCs and VOCs as the main pollutants as the research objects,carries on the health risk assessment of the main pollutants in the sites,and makes a comparative study on the assessment results of indoor steam intrusion and the contribution rate of carcinogenic risk of J&E model and modified model.The carcinogenic risk control values before and after the model correction were compared with the screening values and control values in?GB36600-2018?.The main achievements and conclusions are as follows:?1?The main pollutant in site A was benzo?a?pyrene,which belongs to SVOC.Before the J&E model was revised,the total carcinogenic risk of benzo?a?pyrene was9.66*10-5,close to 1*x 10-4.The risk of carcinogenesis mainly came from oral intake and exposure to indoor vapor intrusion,accounting for 47.8%and 39.3%respectively.After model modification,the total carcinogenic risk of benzo?a?pyrene was 2.69*10-5,and the contribution rate of carcinogenic risk by oral exposure increased from 47.8%to 85%,while the carcinogenic risk of indoor steam intrusion exposure decreased from3.8*10-5 to 3.44*10-19.?2?Site B mainly assesses the pollutants as benzene,which belongs to VOCs.After indoor steam intrusion exposure model,the total carcinogenic risk of benzene changed from 7.96*10-5 to 2.51*10-7.The carcinogenic risk of benzene before model modification mainly came from the exposure pathway of indoor steam intrusion,and the contribution rate reached 99.68%.After modification,the carcinogenic risk of indoor steam intrusion exposure pathway decreases from 7.94*10-5 to 5.34*10-23.?3?The carcinogenic risk control values of site A benzo?a?pyrene model before and after modification were 0.048 mg/kg and 0.087 mg/kg,respectively,which were still far less than the screening value of the first kind of land.The main reason is that the carcinogenic slope factor?SFo?of benzo?a?pyrene ingested orally is larger,and the main carcinogenic exposure way is through oral intake.The volume of remediation needed for site A was 20952 m3,and the cost of remediation was 16.8 million yuan.?4?The carcinogenic risk control values of B-benzene in site before and after model modification were 0.05 mg/kg and 9.26 mg/kg.After model modification,the carcinogenic risk control values of B-benzene in site were less than those of land use control values of type I.It showed that the revised risk control value was in good agreement with the?GB36600-2018?.Before and after the model modification,the amount of remediation needed for site B benzene contaminated area was 1784.80 m3and 21692 m3,respectively.The amount of remediation needed after the model modification was about 12.2%of that before the model modification.The cost of repair before and after model modification is about 166 million yuan and 26 million yuan. |
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