Hydroperoxyl radical (HO2•) oxidizes dibromide radical anion (•Br2−) to bromine (Br2) in aqueous solution: Implications for the formation of Br2 in the marine boundary layer

The release of photoactive halogen species such as Br2 from sea‐salt particles, snowpack, and sea‐ice can have significant effects on chemistry in the marine boundary layer (MBL). Although the reaction of hydroperoxyl radical (HO2•) with dibromide radical anion (•Br2−) might be a key step in the formation and release of Br2, there is currently no consensus on whether this reaction produces bromide (Br−) or molecular bromine (Br2). To address this question, we measured the formation of gaseous and aqueous oxidized bromide (primarily Br2) in illuminated bromide solutions as a function of pH. Results from these two sets of experimental data are best explained by kinetic models where HO2• oxidizes •Br2− to Br2. Using this reaction in a simple aerosol model reveals that the hydroxyl radical‐induced oxidation of particulate bromide, followed by reaction of •Br2− with HO2•, could be an important source of Br2 in the MBL.