Quote:1989). At least two factors reduce the impact of HCl, chlorine appears to be preferentially released during low-levels of volcanic activity and thus may be limited to the troposphere, where it can be scrubbed by rain. Hydrogen chloride may also condense in the rising volcanic plume, again to be scrubbed out by rain or ice. Lack of HCl in ice cores with high amounts of H2SO4 (from large eruptions) may indicate ambient stratospheric conditions are extremely efficient at removing HCl. Thus, most HCl never has the opportunity to react with ozone. No increase in stratospheric chlorine was observed during the 1991 eruption of Mt. Pinatubo.