A study on PM2.5 concentration in Bangkok, Thailand: A case study of Bang Na Station

In contemporary times, air pollution has emerged as a pressing concern in major metropolises worldwide. Particulate matter, particularly PM2.5, has been identified as a key contributor to elevated pollution levels. While previous studies in Thailand have primarily focused on PM2.5 in agricultural, forestry, and industrial regions, they often examine its relationship with precursor gases (e.g., SO2, NOx, VOCs, and NH3) and hotspots. However, research pertaining to the capital city, Bangkok, remains limited due to its complex source composition and unnatural urban structure, leading to unique airborne conditions. This study seeks to explore the interplay between PM2.5, precursor gases, and meteorological factors in Bangkok. To assess the influence of precursor gases and meteorological variables on PM2.5 concentrations, correlation analysis and regression techniques were applied to monitoring data obtained from relevant government agencies. Notably, PM2.5 exhibited strong correlations with precursor gases, especially NO2 (correlation coefficient, R, ranging from 0.11 to 0.87), while SO2 showed more variable correlations (R ranging from -0.45 to 0.85). Furthermore, meteorological factors exhibited significant but slightly weaker correlations with PM2.5 compared to SO2 and NO2. This suggests that NO2 plays a dominant role in driving the secondary formation of PM2.5 in the Bang Na area. Regression analysis confirmed the strong association of NO2, SO2, and relative humidity with PM2.5, while other meteorological parameters displayed less significance, even the planetary boundary layer. Contrary to previous studies that primarily rely on real-time monitoring for short durations and emphasize potential pollution sources, our research underscores the pivotal role of precursor gases, particularly under high relative humidity conditions. To elucidate the secondary formation of PM2.5 from precursor gases within urban settings, future studies should encompass longer-term real-time monitoring of both precursor gases and meteorological variables, especially in urban areas