Assessment of gaseous criteria pollutants in the Bangkok Metropolitan Region, Thailand

Uttamang, Pornpan; Aneja, Viney P.; Hanna, Adel F.

The analysis of gaseous criteria pollutants in the Bangkok Metropolitan Region (BMR), Thailand, from 2010 to 2014 reveals that while the hourly concentrations of CO, inline-formulaSO2 and inline-formulaNO2 were mostly within the National Ambient Air Quality Standards (NAAQs) of Thailand, the hourly concentrations of inline-formulaO3 frequently exceeded the standard. The results reveal that the problem of high inline-formulaO3 concentration continuously persisted in this area. The inline-formulaO3 photolytic rate constant (inline-formulaj1) for BMR calculated based on assuming a photostationary state ranged from 0.008 to 0.013 sinline-formula−1, which is similar to the calculated inline-formulaj1 using the NCAR TUV model (inline-formula0.021±0.0024 sinline-formula−1). Interconversion between inline-formulaO3, NO and inline-formulaNO2 indicates that crossover points between the species occur when the concentration of inline-formulaNOx (inline-formula= NO inline-formula+ NOinline-formula2) is inline-formula∼60 ppb. Under a low-inline-formulaNOx regime ([inline-formulaNOx] < 60 ppb), inline-formulaO3 is the dominant species, while, under a high-inline-formulaNOx regime ([inline-formulaNOx] > 60 ppb), NO dominates. Linear regression analysis between the concentrations of inline-formulaOx (inline-formula=inline-formulaO3inline-formula+inline-formulaNO2) and inline-formulaNOx provides the role of local and regional contributions to inline-formulaOx. During inline-formulaO3 episodes ([inline-formulaO3]inline-formulahourly > 100 ppb), the values of the local and regional contributions were nearly double of those during non-episodes. Ratio analysis suggests that the major contributors of primary pollutants over BMR are mobile sources. The air quality index (AQI) for BMR was predominantly good to moderate; however, unhealthy inline-formulaO3 categories were observed during episode conditions in the region.

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Uttamang, Pornpan / Aneja, Viney P. / Hanna, Adel F.: Assessment of gaseous criteria pollutants in the Bangkok Metropolitan Region, Thailand. 2018. Copernicus Publications.

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