Aerosol particle effects on the atmospheric budgets of H2O2 and HOx radicals: studies utilizing a newly-developed multiphase model

Hydrogen peroxide (H₂O₂), hydroxyl radicals (OH), hydroperoxyl (HO₂), and superoxide (O₂^-) radicals interacting with aerosol particles significantly affect the atmospheric pollutant budgets. A multiphase chemical kinetic box model (PKU-MARK), including the multiphase processes of transition metal ions (TMI) and their organic complexes (TMI-OrC), was built to numerically drive H₂O₂ chemical behaviors in the aerosol particle liquid phase using observational data obtained from a field campaign in rural China. Instead of relying on fixed uptake coefficient values, a thorough simulation of multiphase H₂O₂ chemistry was performed. In the aerosol liquid phase, light-driven TMI-OrC reactions promote OH, HO₂/O₂^-, and H₂O­₂ recycling and spontaneous regenerations. The in-situ generated aerosol H₂O₂ would offset gas-phase H₂O₂ molecular transfer into the aerosol bulk phase and promote the gas-phase level. When combined with the multiphase loss and in-situ aerosol generation involving the TMI-OrC mechanism, the HULIS-Mode significantly improves the consistency between modeled and measured gas-phase H₂O₂ levels. The aerosol liquid phase could be a pivotal potential source of aqueous H₂O­₂ and influence the multiphase budgets. Our work highlights the intricate and significant effects of aerosol TMI and TMI-OrC interactions on the multiphase partitioning of H₂O₂ when assessing atmospheric oxidant capacity.