The formation of secondary organic aerosol (SOA) from the photooxidation of three monoalkylbenzenes (toluene, ethylbenzene, and n-propylbenzene) has been simulated using the SOA model under varying environments (temperature, humidity, sunlight, NO_x levels, electrolytic inorganic seed – acidity and water content, and aging). The model demonstrates that the effect of an electrolytic aqueous phase on SOA formation is more critical than that of NO_x levels under SO₂-rich polluted urban environments.