Reactivity of BrNO2 and ClNO2 with solid alkali salt substrates

The reactions of BrNO2 and ClNO2 with bromide have been studied in a Knudsen-cell reactor in order to better understand the elementary reactions of these potentially important tropospheric species in the presence of solid sea-salt aerosol. BrNO2 efficiently reacts with bromide to produce molecular bromine (gamma > 0.3). To better understand the fate of BrNO2 in the Knudsen-cell reactor, we have developed a BrNO2 source based on the reaction of molecular bromine with solid KNO2. We have determined that the lifetime of BrNO2 under our experimental conditions is on the order of 10 s and is Limited by heterogeneous decomposition reactions. The interaction of BrNO2 with KBr, KCl, and KNO2 was studied using the external BrNO2 source. ClNO2 can be converted to BrNO2 in the presence of solid bromide, characterized by an uptake probability of gamma = 1.3 x 10(-4), in good agreement with results obtained for several substrate presentations such as salt powder, grain, and single crystals. We compared these results with previous work and briefly discuss atmospheric implications.