Abstract

Aims: The study were evaluated for the presence of the ambient air volatile organic compounds (VOCs) (benzene, toluene, ethylbenzene and xylene [BTEX] and carbonyl compounds [CCs]) at the university, roadside and residential areas in order to assess the applicability for prediction of ozone formation in ambient air of these in urban area, Bangkok, Thailand. Methods: The ambient air VOCs levels were evaluated by the gas chromatography/flame ionization detector for BTEX analysis and the high-performance liquid chromatography/UV-visible detector for CCs analysis. Results: The comparison of VOCs levels in those areas showed that the roadside area had the highest VOCs levels (of toluene and benzene levels), while the residential area had the lowest of benzene level. However, the benzene levels of all studied-areas were higher than ambient air quality standard. The contributions of hydrocarbons to local ozone formation potential were evaluated in terms of maximum incremental reactivity. Our results showed that the largest contributors to ozone production in Bangkok were toluene and formaldehyde (possibly from the emission of biofuel motor vehicle exhaustion). The roadside area also had the highest ozone formation potential. The aromatic hydrocarbon was the major contribution to anthropogenic emissions of VOCs. However, anthropogenic emissions and photochemistry are mainly transported VOCs to ozone formation. Conclusion: There was the highest VOCs level at roadside area and also was the largest amount of ozone level from chemical reactions. Therefore, it is a need for more research and the environmental protection policy because it may have serious health risk from these pollutants in these areas.

Key words: Ambient Air, Volatile organic compounds, Ozone formation, Urban areas