Heterogeneous reactions of chlorine compounds

Conclusions: Although the present experiments have not been performed under stratospheric conditions, the results imply that HCl can be oxidized by O3 in the dark to photochemically active Cl2 in the presence of aerosol surfaces. The activity of various types of aerosol must be checked, before an estimate of the stratospheric relevance can be given. A strong influence of aerosols is expected for tropospheric chemistry with a source of atomic Cl exceeding the well-known source of the gas phase reaction of OH with HCl by far. Molecular chlorine is identified as the main photolytic precursor of atomic Cl in the absence of NOx. It appears that O3 can oxidize surface-adsorbed HCl or Cl- more rapidly than known from the aqueous phase. Furthermore, HCl is oxidized extremely rapidly in the presence of semiconducting mineral aerosols by photocatalytic action to form Cl2 and other photolytic precursors of atomic Cl. (Abstract truncated