ACTIVATION OF STRATOSPHERIC CHLORINE BY REACTIONS IN LIQUID SULFURIC-ACID

Active chlorine release on H2SO4 aerosol particles via the reaction of HOCl and HCl in solution is discussed. Based on current laboratory da ta, the process is shown to have an appreciable rate at temperatures b elow about 195 K, when the aerosol particles become sufficiently dilut e to allow both HCl dissolution and fast ClONO2 hydrolysis. Evolution of part-per-billion concentrations of Cl2, could be significant in cas es in which volcanically enhanced aerosol remains liquid until the fro st point (almost-equal-to 190 K) as observed on several occasions in t he Arctic stratosphere.