Health Risk Assessment of a Brownfield Contaminated by Volatile Chlorinated Hydrocarbons and Study on Screening of Remediation Technique
|School||Nanjing Agricultural College|
|Keywords||Volatile Chlorinated Hydrocarbons Health Risk Assessment Brownfield Remediation Technology Analytical Hierarchy Process|
The characteristics of volatile chlorinated hydrocarbons such as volatile, poisonous, concealment, cumulative and diversity do serious harm and influence with human health and environment and today already become a new global environmental problem. In recent years, many factories produced volatile chlorinated hydrocarbons are about to closed or switched to other products, as a result of high speed of social and economic growth, industry structure optimization and industry layout and adjustment. However, because of old production facility, less advanced production process, crude workshop, leakage and pollutants emission during the manufacture, large areas of soils and groundwater nearby become contaminated sites that contain high level of volatile chlorinated hydrocarbons waste. According to health risk assessment and remediation technology selection on volatile chlorinated hydrocarbons contaminated soils and groundwater, this research aims to provide technical guidance and techniques in reserve to health risk assessment and pollution control on contaminated sites, which can also be a reference to environmental harmless management to contaminated sites.This research studied on volatile chlorinated hydrocarbons contaminated sites, which is a typical kind of contaminated site in China. Among many health risk assessment models, Among many risk assessment models, there are three models were widely used and highly recommended, which are RBCA model developed by ASTM, CLEA model developed by environmental EA and DEFRA, and CSOIL mode developed by RIVM. In this research, we carried out a comparative research of these three models, taken an abandoned pesticide factory and an abandoned resin factory in Changzhou for example, calculated exposed density, exposure dose rate, health risk and the scope need to repair of each exposure.Through spot sampling survey and analysis, chlordane and 1,2-dichloroethane were proposed as indicator chemicals of this site for the purposes of this risk assessment, chlordane and 1,2-dichloroethane in soil and shallow groundwater had high spatial variability. Soil pollution of chlordane and 1,2-dichloroethane was serious around the original workshops. The pollutants had significantly horizontal migration and the spread of contamination was related with the wind direction. Chlordane and 1,2-dichloroethane existed obvious vertical migration with water leaching and would be carried away into the deeper soil. The contamination of chlordane and 1,2-dichloroethane was mainly in surface soil. Shallow groundwater and surface water around the site were contaminated. The concentration distribution of chlordane and 1,2-dichloroethane in shallow groundwater was similar to that in surface soil, which had high concentration in the downstream of production workshop and rapidly reduced in the downstream to the polluted center area.The evaluation results showed that no matter what kind of model to calculate was used, the risk through mouth is the largest in all the exposure pathways caused by soil pollution, accounted for more than 70% of the proportion. Because the volatile of 1,2-dichloroethane is larger than chlordane, during the exposure pathways caused by soil the contribution of 1, 2-dichloroethane through breathing intake way is larger than chlordane. Csoil model is more targeted with health risk assessment through the comparation of the three evaluation models of the sites contaminated by volatile chlorinated hydrocarbons or the sites which groundwater was contaminated.In order to reuse the abandoned contaminated sites and considering the requirements of risk management and safety, this paper used site cleanup based on risk management strategy, calculated the repair range through American 9 area primary repair target (PRGs), British soil guideline values (SGVS), and Netherland intervention values, this paper took site cleanup strategy to calculate the remediation range of the pesticide factory and resin factory. The results showed that the scope according to United States primary repair target calculated is the smallest, according to soil guideline values of British is the largest.Because volatile chlorinated hydrocarbons contaminated soil remediation technology is diversity and has both advantages and disadvantages, there are too many factors would affect scheme selection, including technology, environment, economy and society. Considering above various aspects, Analytical Hierarchy Process as a multiple criteria decision-making tool was firstly applied in order to screen the optimal remediation technique. Introduced system engineering method into decision-making process of environmental engineering and established a volatile chlorinated hydrocarbons contaminated soil remediation technology selecting index system. An integrated evaluation system was constructed with four levels and nineteen indexes. Ten experts with professional backgrounds were asked to fill in the comparison matrices in order to reduce bias in the evaluation. The final result indicated that the technique of heat treatment method could be adopted as an optimum alternative for remediation on the site contaminated by chlordane, the technique of steam leaching formulation could be adopted as an optimum alternative for remediation on the site contaminated by 1,2-dichloroethane.