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Heterogeneous reactions of N 2 O 5 with H 2 O and HCl on ice surfaces: Implications for Antarctic ozone depletion
Author(s) -
Leu MingTaun
Publication year - 1988
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl015i008p00851
Subject(s) - ozone depletion , ozone , trace gas , chemistry , nitric acid , stratosphere , quadrupole mass analyzer , nitrogen dioxide , chemical reaction , catalysis , atmospheric chemistry , analytical chemistry (journal) , mass spectrometry , inorganic chemistry , atmospheric sciences , environmental chemistry , organic chemistry , chromatography , geology
Laboratory studies of heterogeneous reactions of N 2 O 5 with H 2 O and HCl on ice surfaces have been performed in a fast flow reactor. A differentially pumped quadrupole mass spectrometer with an electron impact ionizer was used as a detector for the trace gas analysis. The reaction probability (or the heterogeneous reaction rate) of N 2 O 5 on water ice was measured to be 0.028 (±0.011) at 195 K, while nitric acid was the sole product in the condensed phase. This reaction may effectively provide a sink for odd nitrogen species during the polar winter. In the presence of HCl with mole fractions between 0.015 and 0.04 in ice, the measured reaction probability of N 2 O 5 was enhanced by about a factor of 2 at 195 K while nitryl chloride (ClNO 2 ) or chlorine nitrite (ClONO) was found to be the major product in the gas phase. The quoted error bar represents the statistical error only. ClNO 2 or ClONO can be readily photolyzed in the austral spring to form active chlorine which removes stratospheric ozone through several catalytic cycles. Another reaction product was nitric acid which remained in the solid phase. Since the polar stratospheric clouds are thought to consist of ice particles or possibly mixtures of HCl‐ice on the surface, the large reaction probabilities measured in this work suggest that these reactions should be a major factor in producing the observed springtime ozone depletion in the Antarctic stratosphere. Finally, a new ozone destruction mechanism based on surface recombination of ClO radicals is also proposed.