Photochemical smog is a resultant of the reaction among

Photochemical smog is a complex mixture of pollutants formed when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in the presence of sunlight [4]. The process begins with the photolysis of nitrogen dioxide (NO2), which releases atomic oxygen that combines with molecular oxygen (O2) to form ground-level ozone (O3) [3]. Further reactions between nitrogen oxides, oxygen, and hydrocarbons (VOCs) lead to the production of secondary pollutants like peroxyacetyl nitrate (PAN) [3]. These three components—NO2, O3, and PAN—are the primary chemical constituents that characterize photochemical smog. While carbon monoxide (CO) can participate in these cycles, it is not the defining characteristic of the smog's chemical mix compared to the nitrogen-based oxidants and ozone [1]. Sunlight is the essential catalyst for these endothermic reactions, typically peaking during warm, sunny conditions [5].

Sources

1. [4] https://www.sciencedirect.com/topics/engineering/photochemical-smog
2. [3] https://www.sciencedirect.com/science/article/pii/S2352186422002784
3. [1] https://pmc.ncbi.nlm.nih.gov/articles/PMC6834528/
4. [5] https://csl.noaa.gov/assessments/ozone/1985/vol1/chapter4.pdf