Recent laboratory data concerning the reactions of HCl and HOx on/in sulfuric acid aerosol (Hanson et al., 1994) N2O5 and ClONO2 hydrolysis on the frozen aerosol (Hanson and Ravishankara, 1993a) and the temperature dependence of the HNO3 absorption cross section (Burkholder et al., 1993) indicate that a reevaluation of the role of heterogeneous reactions in the chemical balance of the stratosphere is required. A chemical module prepared for a three-dimensional (3-D) global chemistry transport model (CTM) and a general circulation model (GCM) has been used to carry out a sensitivity study of the effects of heterogeneous reactions on/in the sulfate aerosol and on the polar stratospheric cloud (PSC) particles. We present here results for the latitudes 60¿S, 70¿S and 75¿S at the 50-mbar level.

Our findings indicate that (1) the new values of the HNO3 cross sections result in lower mixing ratios for NOx and make ozone more vulnerable to catalytic destruction by ClOx; (2) the effect of the heterogeneous reactions OH+HNO3(a)→H2O+NO3 and HO2+HO2(a)→H2O2+O2 are small in comprison with the same gas phase reactions and play a negligible role for the ozone balance; (3) the HCl reactions in the sulfuric acid aerosol at 60¿S and 70¿S increase the chlorine activation up to 0.53 parts per billion by volume (ppbv) and 0.72 ppbv, respectively, for liquid aerosol and up to 0.87 ppbv for frozen aerosol at 70¿S for volcanic conditions and this results in considerable ozone depletion at these latitudes; (4) studying the ozone ''hole'' phenomenon, we have considered the different initial ratios of ClONO2/HCl, of N2O5, galactic cosmic rays (GCRs), and longer lifetimes for the PSC. We have speculated an existence of the reaction N2O5+HCl(a)→ClNO2+HNO3. ¿ American Geophysical Union 1994