INFLUENTIAL FACTORS AND OZONE FORMATION POTENTIAL OF VOLATILE ORGANIC COMPOUNDS IN SUBURBAN BANGKOK, THAILAND

Elucidation of air quality in the suburban area of Bangkok, Thailand is essential in order to achieve effective regulations and mitigation strategies. VOCs plays important role in formation of tropospheric urban ozone. Whole air canister sampling was carried out in the suburban Bangkok at Sirindhorn International Institute of Technology (SIIT) during 2008, July 2-7. Four samples per day were collected at 30 min passes 6, 12, 17, 21 hours with sampling time of 1 min. Analysis was performed using GC-FID and GC-MS. High mixing ratios of VOCs detected during the peak periods in the morning and evening are most likely due to vehicular emission. Averaged VOCs mixing ratios, revealed distinct different between mixing ratios obtained during the weekday and weekend which the latter were found to be lower. No difference was found for CFCs which the levels were also comparable to global background level reported by World Meteorological Organization. The most abundance species at SIIT were propane and toluene with averaged mixing ratios of 3100 and 2891 pptv, respectively. Ratios of benzene over toluene suggested additional concentration owing to industrial emission, of which particularly larger during the weekday. Comparison between C2Cl4 and CH3Cl mixing ratios obtained for suburban Tokyo reveal relatively higher influence of biomass burning at suburban Bangkok. In order to estimate the role of the different VOCs towards tropospheric ozone formation, ozone formation potential was calculated using maximum incremental reactivity. Toluene was found to contribute the most to O-3 production followed by ethylene, m, p-xylene, and propylene.