Heterogeneous reactions of Cl 2 with sea salts at ambient temperature: Implications for halogen exchange in the atmosphere

Laboratory measurements of heterogeneous reactions of Cl 2 (g) on solid sea salts at ambient temperature and low relative humidity have been carried out using a Knudsen cell reactor. Synthetic sea salt and commercial natural sea salt are used to represent sea salt particles. The uptake probabilities for synthetic sea salt (γ = (2.2 ± 0.3) × 10 −2 ) and for natural salt (γ = (3.1 ± 1.1) × 10 −2 ) have been obtained and Br 2 is observed as the predominant product. The heterogeneous reactions of Cl 2 with solid pure NaBr and KBr: 1/2Cl 2 (g) + MBr(s) → MCl(s) + 1/2Br 2 (g) (M = Na, K), have been investigated. These results show that synthetic and natural salts have a similar extent of reactivity compared with solid pure bromides in spite of their small Br fraction. These reactions are expected to be an important Cl 2 sink and Br 2 source in the marine boundary layer.