ACPD

Atmospheric Chemistry and Physics Discussions

ACPD

1680-7375

Copernicus GmbH

Göttingen, Germany

10.5194/acpd-3-2179-2003

The rate of water vapor evaporation from ice substrates in the presence of HCl and HBr: Implications for the lifetime of atmospheric ice particles

Delval

¹ Fluckiger

¹ Rossi

M. J.

Laboratory of Air and Soil Pollution Studies (LPAS), Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland

08 05 2003

3 3 2179 2218

This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

This article is available from http://www.atmos-chem-phys-discuss.net/3/2179/2003/acpd-3-2179-2003.html

The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/3/2179/2003/acpd-3-2179-2003.pdf

Using a multidiagnostic approach the rate Rev or flux Jevof evaporation of H2O and its condensation, kcond, on a 1mm thick ice film have been studied in the temperature range 190 to 240 K as well as in the presence of small amounts of HCl and HBr that left the vapor pressure of H2O on ice unchanged. The resulting Arrhenius expressions with RT in kcal mol-1 for pure ice are Jev=1.6×1028+/−1·exp({−10.3+\−1.2}/{RT}) [molec cm−2 s−1], kcond=1.7×10−2+\-1×exp({+1.6+\−1.5}/{RT}) [s−1], in the presence of an HCl mole fraction in the range 3.2×10−5-6.4×10−3: Jev=6.4×1026+/−1×exp({−9.7+/−1.2}/{RT}) [molec cm−2 s−1], kcond=2.8×10−2+/-1×exp({+1.5+/−1.6}/{RT}) [s−1], and an HBr mole fraction smaller than 6.4×10−3:Jev=7.4×1025+/−1×exp({−9.1+/−1.2}/{RT}) [molec cm−2 s−1], kcond=7.1×10−5+\−1×exp({+2.6+/−1.5}/{RT}) [s−1]}. The small negative activation energy for H2O condensation on ice points to a precursor mechanism. The corresponding enthalpy of sublimation is DHsubl=Eev-Econd=11.9+/−2.7 kcal mol−1, DHsubl=11.2+/−2.8 kcal mol−1, and DHsubl=11.7+/−2.8 kcal mol−1 whose values are identical within experimental uncertainty to the accepted literature value of 12.3 kcal mol−1. Interferometric data at 633 nm and FTIR absorption spectra in transmission support the kinetic results. The data are consistent with a significant lifetime enhancement for HCl- and HBr-contaminated ice particles by a factor of 3–6 and 10–20, respectively, for submonolayer coverages of HX.