Heterogeneous Interconversion Reactions of BrNO2, ClNO2, Br2, and Cl2

The heterogeneous reactions leading to formation and loss of BrNO 2 on salt solutions as a model substrate for atmospheric sea salt aerosol are investigated. Further to the reaction of ClNO 2 with bromide solutions, the reaction of Br 2 with nitrite solution was found to be a convenient method for the synthesis of BrNO 2 . We measured the temperature-dependent lifetime of BrNO 2 in a quartz cell and obtained the activation energy E A = 89 ± 9 kJ/mol for the unimolecular decay at atmospheric pressure. The reactive uptake of BrNO 2 and ClNO 2 on water and aqueous solutions was determined using a wetted-wall flow tube technique. We observed the reactions Br 2 + NO 2 - ↔ BrNO 2 + Br -, Cl 2 + NO 2 - → ClNO 2 + Cl -, and the net reaction ClNO 2 + Br - ↔ BrNO 2 + Cl - . BrNO 2 and ClNO 2 both react with NO 2 - to release NO 2 into the gas phase. Observed concentration profiles in the gas phase and in solution can be described qualitatively by a numerical model of the diffusion and reaction processes in the experimental setup.