Ternary Solutions under Stratospheric Conditions

The reaction probabilities of NzO~ and C10N02 with HZO on liquid sulfuric acid surfaces have been reexamined to survey the effect of HNO~ on these two hydrolysis rates, using a fast flow reactor coupled to a chemical ionimtion mass spectrometer. The. measurements were cankd out by maintaining constant H20 and HNO~ partial pressures and by varying temperatures between 227 and 195 K in order to mimic compositions representat ive of stratospheric aerosols. For experiments excluding HNOJ, the reaction probability of NZ05 hydrolysis was found to be near 0.1, independent of temperature and H$Od content, This is in agreement with results previously measured under similar conditions. In the presence of gaseous HNOJ at stratospheric concentrations, the reaction probability y was observed to decrease from about 0.09 at 218 K to about 0.02-0.03 at 195 K for P}lzo = 3.8x1041.Ox 10-3 Torr, showing that incorporation of HNO~ into liquid sulfuric acid greatly retarded the NzO~ hydrolysis. The CIONOZ reaction with HZO on liquid sulfuric acid, on the other hand, did not appmr to be affected by the presence of HNO~. (Submitted to GRL, Dec. 15, 1994)