Characterisation of ambient benzene, toluene, ethylbenzene and m-, p- and o-xylene in an urban traffic area in Bangkok, Thailand

Ambient Volatile Organic Compounds (VOCs) were examined in a heavy traffic urban area in Bangkok, Thailand, on focusing monoaromatic compounds of benzene, toluene, ethylbenzene, m-, p- and o-xylene (BTEX). Passive samplers were used to measure ambient BTEX concentrations in the environment close to very congested roads. Prior to the measurement, the validity of passive sampler performance was investigated to be acceptable for actual use. The monitoring was made five times on weekly basis in April-June in 2003. It was observed that averages of BTEX concentrations were as follows: 12.7 mu g m(-3) for benzene, 72.8 mu g m(-3) for toluene, 6.0 mu g m(-3) for ethylbenzene, 25.7 mu g m(-3) for m-, p-xylene and 13.6 mu g m(-3) for o-xylene. They are considered to be at very high concentration levels compared to other countries. Their distributions seemed to be in the form of logarithmic normal distribution. On the other hand, cluster analysis suggested that ambient BTEX in this study were derived from automobile exhaust gases.