High O₃ episodes in Thailand's Bangkok Metropolitan Regions: sources, spatio-temporal variations and associations with O₃ precursors and meteorological factors
by Arika Bridhikitti
International Journal of Environmental Technology and Management (IJETM), Vol. 17, No. 6, 2014

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.

Online publication date: Wed, 14-Jan-2015

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