Atmospheric trace gases such as ozone (Osub3/sub), carbon monoxide (CO), and nitrogen oxides (NO and NOsub2/sub, collectively termed NOsubx/sub) play a central role in tropospheric photochemistry and strongly influence air quality, climate forcing, and ecosystem health. This manuscript explores the current understanding of the sources, chemical transformation pathways, and environmental impacts of these trace gases by integrating from observational studies and atmospheric modeling research. The literature was compiled through a structured review of peer-reviewed research published in science journals, with emphasis on recent advances in photochemical mechanisms, boundary layer dynamics and regional air pollution processes. Particular attention is given to nonlinear Osub3/sub formation regimes, radical chemistry involving volatile organic compounds (VOCs), and the interactions between trace gases and climate processes. This manuscript highlights how the balance between NOsubx/sub and VOC emissions determines Osub3/sub production efficiency in different atmospheric environments, ranging from NOsubx/sub limited rural regions to VOC limited urban areas. Regional perspectives from South Asia illustrate how rapid urbanization, biomass burning, and meteorological variability influence trace gas distributions. The analysis identifies major knowledge gaps related to radical chemistry uncertainties, climate–chemistry feedback mechanisms, and the integration of observational networks with chemical transport models. Improved monitoring strategies and advanced modeling approaches are essential for developing effective air quality management policies and understanding the evolving role of trace gases in the Earth’s climate system.
A et al. (2026) studied this question.