Emission characteristics, risk assessment and scale effective control of VOCs from automobile repair industry in Beijing.

Automobile repair is regarded as a typical domestic source of VOCs in China characterized by numerous sites, wide dispersion and intermittent VOCs emissions. It is of great importance to study and control VOCs from such activities. In this research, emission characteristics, risk assessment and scale effective control of VOCs from automobile repair in Beijing were studied. Results showed that coating spraying and baking were the main processes of VOCs and the major species determined were mostly oxygen-containing VOCs and aromatic hydrocarbons in the case of solvent-based coating usage. Meanwhile, alkanes were determined and accounted for 40 % of total VOCs emissions during the water-based coating spraying and baking. Generally, the total determined VOCs during the automobile repair processes were 1.06-1.27 mg/m and 2.93-53.46 mg/m for the usage of water-based and solvent-based paint, respectively. Health risk assessments indicated that the residents in the region about 30 m high within a radius of 20 m around the automobile repair plants might suffer from both serious non-carcinogenic and carcinogenic risk threats in the case of solvent-based coating usage in that the values of total hazard index (HI) represented by dichloropropane and acrolein were higher than 1 and the value of lifetime cancer risk (LCR) represented by dichloroethane was higher than 10. Besides, those in the region about 30 m high and within a wider radius of 340 m might suffer from carcinogenic risk threat with a certain probability (LCR > 10) no matter either solvent-based or water-based coatings were used. As for the scale control of VOCs from automobile repair, independent adsorption by activated carbon combined with mobile regeneration by catalytic combustion was also proposed as an efficient way.