Title: High O3 episodes in Thailand's Bangkok Metropolitan Regions: sources, spatio-temporal variations and associations with O3 precursors and meteorological factors

Authors: Arika Bridhikitti

Addresses: Faculty of Environment and Resource Studies, Mahasarakham University, Kantarawichai, Maha Sarakham, 44150, Thailand

Abstract: High ozone levels were often observed from December to April at suburban stations in the Bangkok Metropolitan Region (BMR). Wind direction analyses show significant roles of air masses from outside BMR on elevating the BMR O3 levels. These air masses include biomass burning smoke from the northwestern BMR and sea spray from the Gulf of Thailand mixing with industrial emissions from the southern BMR. Seasonal O3 profiles corresponded with NO2 and CO trends and diurnal O3 corresponded with solar radiation. Diurnal peaks of NO2 and CO were results of traffic emissions during traffic rush hours, whereas nighttime NO2 peaks, for northern BMR, attributed to NO-O3 reactions. Both NO2 and CO at 7:00-9:00 highly correlated with the O3 in the following afternoon. Principal component analysis (PCA) and an analysis of non-methane hydrocarbons-to-NO2 ratio suggest the NO2-limited O3 formation in the BMR suburb. The PCA also suggests a negative response of wind speeds on the afternoon O3 formation, whereas roles of ambient temperature on the O3 were seasonally different.

Keywords: Bangkok Metropolitan Region; BMR; biomass burnings; NOx titration; photochemistry; principal component analysis; PCA; traffic emissions; urban pollution; air pollution; ozone pollution; Thailand; vehicle emissions; sea spray; industrial emissions; wind speed; ambient temperature.

DOI: 10.1504/IJETM.2014.066521

International Journal of Environmental Technology and Management, 2014 Vol.17 No.6, pp.521 - 537

Received: 21 Apr 2014
Accepted: 16 Jul 2014

Published online: 14 Jan 2015 *

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