Heterogeneous reactions with NaCl in the El Chichon volcanic aerosols

Previous investigations of the effects of the 1982 eruption of the El Chichon volcano could not explain all the observations of changes in O 3 , HCl, NO and NO 2 simultaneously without proposing unproven chemical reactions. Since reactions between solid NaCl and gaseous ClNO 3 and N 2 O 5 rapidly produce photochemically active chlorine species and solid NaNO 3 in laboratory experiments, we suggest that these reactions could have occurred with the NaCl observed to be present in the El Chichon sulfuric acid aerosols. As a consequence, we predict that HCl should increase substantially, while NO x should decrease, in agreement with the measurements after the eruption. Ozone should only be slightly affected by these reactions. Reactions between solid NaCl and the acids H 2 SO 4 and HNO 3 might prove to be important, but we lack sufficient evidence regarding their efficiency and the presence of HNO 3 in the aerosols to be more conclusive.