Diurnal Variation of Atmospheric Light-Absorption Characteristic of Total Suspended Particles in Bangkok

¹ Division of Environmental Design, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa 920-1192, Ishikawa, Japan
² Faculty of Geosciences and Civil Engineering, Institute of Science and Engineering, Kanazawa
³ Department of Environmental Science, Faculty of Environment, Kasetsart University, Bangkok, 10900, Thailand
⁴ Department of Environmental Technology and Management, Faculty of Environment, Kasetsart University, Bangkok, 10900, Thailand

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

In this study, the diurnal variation of light absorption characteristic of total suspended particles (TSP) collected in Bangkok, Thailand, during the haze season was investigated. Daytime and nighttime TSP samples were analyzed for carbonaceous components using thermal/optical carbon analysis and UV-vis spectrophotometry. TSP mass concentrations exhibited clear temporal variation, with higher average levels during the daytime. Carbonaceous components show distinct behaviors, with organic carbon (OC) consistently occurring at higher concentrations and exhibiting greater temporal variation than elemental carbon (EC). Light absorption at 365 nm displayed clear diurnal variation and showed a weak relationship with TSP mass concentration, characterized by considerable scatter. In contrast, clearer associations were observed between Absses and OC concentration for both water and methanol extracts, particularly during nighttime. These results indicate that variations in aerosol light absorption are more closely associated with organic carbon abundance than with total particle mass alone. Overall, the findings suggest that diurnal variability in carbonaceous aerosol properties contributes to changes in the optical behavior of urban aerosols in Bangkok.