Hydrogen peroxide serves as pivotal fountainhead for aerosol aqueous sulfate formation from a global perspective.

Traditional atmospheric chemistry posits that sulfur dioxide (SO ₂ ) can be oxidized to sulfate (SO ₄ ^2- ) through aqueous-phase reactions in clouds and gas-phase oxidation. Despite adequate knowledge of traditional mechanisms, several studies have highlighted the potential for SO ₂ oxidation within aerosol water. Given the widespread presence of tropospheric aerosols, SO ₄ ^2- production through aqueous-phase oxidation in aerosol water could have a pervasive global impact. Here, we quantify the potential contributions of aerosol aqueous pathways to global sulfate formation based on the GEOS-Chem simulations and subsequent theoretical calculations. Hydrogen peroxide (H ₂ O ₂ ) oxidation significantly influences continental regions both horizontally and vertically. Over the past two decades, shifts in the formation pathways within typical cities reveal an intriguing trend: despite reductions in SO ₂ emissions, the increased atmospheric oxidation capacities, like rising H ₂ O ₂ levels, prevent a steady decline in SO ₄ ^2- concentrations. Abating oxidants would facilitate the benefit of SO ₂ reduction and the positive feedback in sulfate mitigation.
(© 2024. The Author(s).)