Seasonal characterization of gaseous air pollutants in Phnom Penh, Cambodia

¹ Research and Innovation Center, Institute of Technology of Cambodia, Phnom Penh, Cambodia
² Faculty of Geosciences and Civil Engineering, Institute of Science and Engineering, Kanazawa University, Ishikawa, Japan
³ Graduate School of Integrated Science and Technology, Nagasaki University, Nagasaki, Japan

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

Abstract

Phnom Penh, the rapidly urbanized capital city of Cambodia, faces significant challenges from air pollution. Air pollutants, including gaseous compounds such as nitric oxide (NO), nitrogen dioxide (NO₂), nitrogen oxides (NO_X), ozone (O_s), and carbon monoxide (CO), impact public health and can serve as indicators of direct emission sources that may vary seasonally. This study characterized the seasonal variability of these gases over three months in the rainy (August-October, 2024) and dry (January-March, 2025) seasons in Phnom Penh. In the rainy season, NO, NO₂, and NOx exhibited higher concentration, while Os levels were elevated in dry season. These patterns suggest seasonal differences in dominant emission sources between vehicular emissions and biomass burning, as well as distinct atmospheric chemical processes. CO concentrations remained relatively stable across seasons. Meteorological factors, including precipitation and temperature, displayed limited influence on these gaseous pollutant levels, whereas wind speed showed weak correlations. Diurnal patterns revealed morning and evening peaks in NO, NO₂, NO_x, and CO associated with rush hours, while ozone peaked in the afternoon, corresponding to peak sunlight intensity.