Research On The Release Characteristics, Diffusion Law And Health Risk Assessment Of VOCs In The Process Of Remediation Of A Chemical Polluted Site

Some VOCs are harmful to human health and ecological environment,which emission from the remediation process of chemical contaminated sites.The studies of VOCs emission characteristics,diffusion laws and health risk are helpful for the secondary air pollution prevention,and can provide scientific and effective controlling measures.Air samples were collected during the remediation processes of a chemical contaminated site in Nanjing,using Summa canisters,enriched by cryofocus and analyzed by gas chromatography/mass spectrometry.Firstly,VOCs concentration and pollution characteristics were analyzed during the process of soil excavating,ex-situ chemical oxidation and ex-situ thermal desorption,respectively.Principal component analysis and cluster analysis were used to find the VOCs sources.Secondly,VOCs diffusion laws were studied by PID and CFD.Finally,the VOCs respiratory pathways risk was assessed by USEPA health risk assessment methods.The results showed that:(1)32 VOCs were detected during the soil excavating stage,the concentration of VOCs varied from 86.21?g/m~3 to 4099.38?g/m~3.12 VOCs were detected during the ex-situ chemical oxidation process,the concentration of TVOC varied from 147.17?g/m~3 to 254.32?g/m~3.26VOCs were detected during the ex-situ thermal desorption process,the TVOC concentration was 74.63?g/m~3.Acetone and propene were the characteristic compounds.(2)The ambient VOCs were mainly from the production process of nitro chlorobenzene,organic solvents using and tail gas in the production process.(3)The terrain and wind speed play important roles in VOCs diffusion.The VOCs maximum vertical diffusion distance was 111.5 m.500 m within the downwind site direction from the emission point was the risk prevention area.(4)The health risk was detected during remediation process and risk value showed as:soil excavating stage>ex-situ thermal desorption stage>ex-situ chemical oxidation stage.Bromomethane,benzene,chlorobenzene,cyclohexane,1,2-dichloroethane and 1,3-butadiene led to the non-carcinogenic risk.1,3-butadiene led to the carcinogenic risk.