The heterogeneous reaction of NO3 with NaCl and KBr: A nonphotolytic source of halogen atoms

The heterogeneous reactions of NO3 on NaCl and KBr salt were studied at room temperature using a Knudsen reactor equipped with dual detection, namely Laser induced fluorescence (LIF) and mass spectrometry (MS). The uptake coefficients of NO3 were found to be gamma = (4.9+/-3).10(-2) onto NaCl and gamma = 0.16+/-0.08 onto KBr, In the case of NaCl, HCl was the sole product observed. However, there is indirect evidence that Cl atoms are the primary products. In the case of KBr we observed Br-2 and Br to be the products of reaction. A first estimation of the atmospheric relevance of these reactions indicate that under certain conditions the heterogeneous loss of NO3 on seasalt aerosols may compete with removal by homogeneous gas phase reactions.