Simple model of vertical dispersion of O3 in Bangkok, Thailand using regression method

Abstract

Bangkok, the capital city of Thailand, has experienced a degradation in air quality. In particular, ozone (O3) concentrations frequently exceed Thailand’s National Ambient Air Quality standards. Various policies have been developed to manage air quality at near-surface levels; however, the assessment of air quality above these levels has been neglected. Analysis of O3 concentrations and its precursors measured at various altitudes revealed that the vertical structures of the pollutants in Bangkok were stratified. While NOx concentrations decreased with height, O3 concentrations increased. These results emphasize the importance of air quality management above ground level, particularly in megacities with high-rise buildings, such as Bangkok. Assuming that the O3 formation regime over Bangkok is VOC-limited, a simple model was developed based on a linear regression method to estimate the changes in O3 concentrations with height. We found that the simple model was able to capture the variation in O3 concentrations at 30, 75, and 110 m above ground level, with an R2 of 0.48–0.65. Although the simple model had some difficulty estimating the magnitude of O3 concentrations, the estimated O3 values from the model were reasonable for capturing vertical O3 trends. Using this approach, policymakers can visualize the vertical distribution of pollutants, which will be useful in designing air quality management plans.