A case study of risk assessment in contaminated site remediation in China

A field site in Nanjing, China was selected for a case study of risk assessment in contaminated site remediation. This site is about 100m long and 100m wide. A chemical plant (1999-2010) at the site manufactured optical brightener PF, 2-Amino-4-methylphenol and 2-Nitro-4-methylphenol, totally three products. Soil and groundwater samples were collected and analyzed for PPL 126 (126 pollutants in the 'Priority Pollutants List' issued by US EPA). Values of the Dutch Standards were used as the screening criteria for soil and ground water. Low levels of ethylbenezene, chlorobenzene, 1,3-dichlorobenzene and 1,4- dichlorobenzene were detected in one soil sample. Concentrations above Dutch Target Value (DTV) of benzene, toluene, ethylbenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, and/or 1,2,4-trichlorobenzene, phenol, and/or 2,4-dichlorophenol were exhibited in two groundwater samples. The ground water was especially highly impacted by bichlorobenzenes and trichlorobenzenes. The maximum concentration of impacts was 7.3 mg/L of 1,2,4-trichlorobenzene in groundwater which was 730 times higher than Dutch Intervention Values (DIV). Risk of soil and groundwater at this site was assessed according to the guidelines issued by Chinese MEP and US EPA, respectively. Finally, remedy techniques were selected according to the result of risk assessment and the characteristics of hydrogeology conditions and contaminants.