Modeling Sulfate Formation Via HOBr and Feedbacks on Reactive Halogen Budget

The radiative forcing uncertainties in climate models induced by sulfate aerosol are still large, partly due to our limited knowledge about sulfate formation mechanisms in the atmosphere. Recent studies have suggested that hypohalous acids (HOBr and HOCl) could be the main oxidants for sulfate formation in the marine boundary layer (MBL), in addition to H₂O₂. In turn, the formation of sulfate aerosol impacts the acid-catalyzed formation of reactive halogens (e.g. Br₂). Here we implement the “S(IV) + HOBr” reaction into the global chemical transport model GEOS-Chem to investigate the impacts of this reaction on the global sulfur budget and feedbacks on acid-catalyzed reactive halogen production. Preliminary results show that the addition of this reaction results in a large contribution of HOBr to sulfate formation in the MBL, and a significant change to the reactive halogen concentrations, which will have important implications for atmospheric ozone, OH and mercury budget.