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

Abstract

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 (•Br-2) 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 •Br-2 to Br2, Using this reaction in a simple aerosol model reveals that the hydroxyl radical-induced oxidation of particulate bromide, followed by reaction of •Br-2 with HO2•, could be an important source of Br2 in the MBL. Copyright 2003 by the American Geophysical Union.