BrCl production in NaBr/NaCl/HNO3/O-3 solutions representative of sea-saltaerosols in the marine boundary layer

Atomic bromine and chlorine liberated from seasalt aerosol is thought to pl ay an important role in chemistry of the marine boundary layer. Despite num erous modeling studies, no prior experimental investigations pf the oxidati on of halide species contained in simulated, or actual, sea-salt solutions have been performed. We present laboratory data that examines chemistry in NaBr/NaCl/KNO3/O-3 solutions at 290 K. Ozonation experiments were performed by flowing atone in air through a nitric acid/salt solution and monitoring pH with time using an ion-sensitive electrode. The rate of oxidation was o bserved to be first order in ozone concentration and to have a non-first or der bromide concentration dependence. Ion chromatography was used to measur e both bromide disappearance as well as oxidation products formed during th e course of the reactions studied. Our measurements of the oxidation rate v ersus ion concentration indicate that the high ionic strength present in se a-salt aerosol will possess unique kinetics different from dilute solution behavior. In addition, our results are consistent with the reaction sequenc e O-3 + H+ + Br- --> O-2 + HOBr and HOBr + Cl- + H+ --> BrCl + H2O. These o bservations support the HOBr mediated Cl- oxidation process proposed previo usly (Vogt et al., 1996).