HR: 1340h
AN: A23B-0950    [Abstracts]
TI: Enhanced HBr uptake on ice in the lower stratosphere
AU: * Robinson, J
EM: jeanne.robinson@lanl.gov
AF: Los Alamos National Laboratory, C-PCS, J567, Los Alamos, NM 87544 United States
AU: Henson, B F
EM: henson@lanl.gov
AF: Los Alamos National Laboratory, C-PCS, J567, Los Alamos, NM 87544 United States
AB: We have recently reported measurements of HCl adsorption on ice and nitric acid trihydrate indicating very low levels of HCl uptake on these surfaces at the conditions of the lower stratosphere [J. Chem. Phys. 121, 8486 (2004)]. These data enabled the construction of a detailed model of uptake based on the thermodynamics of the HCl/H2O binary system. Although the fact of heterogeneous chlorine activation is well established, these data raise questions regarding the detailed mechanism by which this is achieved. In this paper we propose a model of HBr uptake on ice under stratospheric conditions analogous to that previously presented for HCl. This model indicates that, even at the very low Br mixing ratio in the stratosphere, high levels of HBr may exist on the ice surface at equilibrium. Chlorine activation would then proceed via surface reactions which yield the BrCl product. Such a mechanism would explain Chlorine activation in the absence of HCl adsorption, and may contribute to the explanation of the low predictions of midlatitude ozone depletion.
DE: 0317 Chemical kinetic and photochemical properties
DE: 0340 Middle atmosphere: composition and chemistry
DE: 0341 Middle atmosphere: constituent transport and chemistry (3334)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005