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 comme rcial natural sea salt are used to represent sea salt particles. The u ptake probabilities for synthetic sea salt (gamma = (2.2 +/- 0.3) x 10 (-2)) and for natural: salt (gamma = (3.1 +/- 1.1) x 10(-2)) have been obtained and Br-2 is observed as the predominant product. The heterog eneous reactions of Cl-2 with solid pure NaBr and KBr: 1/2Cl(2)(g) + M Br(s) --> MCl(s) + 1/2Br(2)(g) (M = Na, K), have been investigated. Th ese results show that synthetic and natural salts have a similar exten t of reactivity compared with solid pure bromides in spite of their sm all Br fraction. These reactions are expected to be an important Cl-2 sink and Br-2 source in the marine boundary layer.