Heterogeneous Reaction Probabilities, Solubilities, and the Physical State of Cold Volcanic Aerosols

On 19 January 1992, heterogeneous loss of HNO$_3$, ClNO$_3$, and HCl was observed in part of the Mount Pinatubo volcanic cloud that had cooled as a result of forced ascent. Portions of the volcanic cloud froze near 191 kelvin. The reaction probability of ClNO$_3$ and the solubility of HNO$_3$ were close to laboratory measurements on liquid sulfuric acid. The magnitude of the observed loss of HCl suggests that it underwent a heterogeneous reaction. Such reactions could lead to substantial loss of HCl on background sulfuric acid particles and so be important for polar ozone loss.