Investigation of pm2.5 dispersion in Din Daeng district, Bangkok using computational fluid dynamics modeling

Din Daeng is a small and densely populated district of Bangkok with two major expressways in the area. PM2.5 concentrations in Din Daeng district often exceed both daily and annual standards of the National Ambient Air Quality Standards. Computational Fluid Dynamics (CFD) was applied to investigate the effects of the metropolitan characteristics and traffic volumes on the dispersion of PM2.5 in Din Daeng district. The turbulent flow was analyzed using the Standard k-ε model. There are two scenarios in this simulation study. One is to investigate the consequences of having the expressways and their resulting PM2.5 emissions. The other is to examine the influence of the COVID-19 pandemic and the city lockdown which affected the traffic volumes. The presence of the expressways in Din Daeng district was demonstrated to enhance PM2.5 concentrations. The presence of the expressway increased the concentration of PM2.5 by approximately 3.4 times compared to the case of no expressways. The COVID-19 pandemic seemed to have an impact on the concentration of PM2.5 during the city lockdown. During the city lockdown, the concentration of PM2.5 was reduced by approximately 63% compared to the normal period.