One conceivable mechanism of UV-light induced SO ₂ Oxidation to H ₂SO ₄

The electron-excited chemistry of sulfur dioxide oxidation induced by UV irradiation of air with trace O ₃ and SO ₂ is considered. The importance of this mechanism is evaluated based on recent laboratory experiments on SO ₂ oxidation in a laminar tube with air induced by UV irradiation. Results show that under respective conditions the route of SO ₂ oxidation involving electron excited oxygen molecules may present an additional source of gaseous H ₂SO ₄ production to known OH-radical mechanism.