Distribution characteristics of chlorinated hydrocarbons in contaminated plots of typical organic chemical plants and risk assessment based on Monte Carlo simulation

A typical organic chemical plot in the Yangtze River Delta was selected as the research object. A total of 651 soil samples and 30 groundwater samples were collected for analysis and determination. The pollution level and spatial distribution characteristics of chlorinated hydrocarbons (CAHs) in the environment were studied. The health risk probability of CAHs in soil and groundwater was analyzed using Monte Carlo simulation method. The results showed that the concentration of most CAHs was in normal distribution, and gradually decreased with the increase of depth. Trichloroethylene pollution in soil and groundwater was the most serious. The contaminant plumes were mainly concentrated in the southwest and northwest of the plot. Trichloroethylene and chloroform were the main pollutants causing health risks. The probability of a carcinogenic risk greater than 10⁻⁶ for trichloroethylene in soil was 87.2%, the probability of hazard quotient exceeding 1 was 71.76%, and the probability of chloroform hazard quotient exceeding 1 was 81.28%. The daily soil intake had the highest sensitivity to soil cancer risk (31.9%). The skin surface viscosity coefficient had the highest sensitivity to groundwater cancer risk and hazard quotient, being 16.9% and 23%, respectively. Inhaling gaseous pollutants from the underlying soil in indoor air was the main exposure pathway that caused both carcinogenic and non-carcinogenic risks in soil. Inhaling gaseous pollutants from underground was the main exposure pathway that caused both carcinogenic and non-carcinogenic risks in groundwater.