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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 21 | Copyright
Atmos. Chem. Phys., 18, 15903-15919, 2018
https://doi.org/10.5194/acp-18-15903-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 07 Nov 2018

Research article | 07 Nov 2018

The influence of HCl on the evaporation rates of H2O over water ice in the range 188 to 210 K at small average concentrations

Christophe Delval1,2,a and Michel J. Rossi1,3 Christophe Delval and Michel J. Rossi
  • 1Laboratory of Air and Soil Pollution Studies (LPAS), ENAC Faculty, Swiss Federal Institute of Technology (EPFL), 1015 Lausanne, Switzerland
  • 2Atmospheric Particle Research Laboratory (APRL), ENAC Faculty, Swiss Federal Institute of Technology (EPFL), 1015 Lausanne, Switzerland
  • 3Laboratory of Atmospheric Chemistry (LAC), Paul Scherrer Institute (PSI), 5232 Villigen-PSI, Switzerland
  • apresent address: Patent Examiner – Directorate 1657, Dir. 1.6.5.7, European Patent Office, Patentlaan 3-9, 2288 EE Rijswijk, the Netherlands

Abstract. The evaporation flux Jev(H2O) of H2O from HCl-doped typically 1.5µm or so thick vapor-deposited ice films has been measured in a combined quartz crystal microbalance (QCMB)–residual gas mass spectrometry (MS) experiment. Jev(H2O) has been found to show complex behavior and to be a function of the average mole fraction χHCl of HCl in the ice film ranging from 6×1014 to 3×1017moleculecm−2s−1 at 174–210K for initial values χ0HCl ranging from 5×10−5 to 3×10−3 at the start of the evaporation. The dose of HCl on ice was in the range of 1 to 40 formal monolayers and the H2O vapor pressure was independent of χHCl within the measured range and equal to that of pure ice down to 80nm thickness. The dependence of Jev(H2O) with increasing average χHCl was correlated with (a) the evaporation range rb∕e parameter, that is, the ratio of Jev(H2O) just before HCl doping of the pure ice film and Jev(H2O) after observable HCl desorption towards the end of film evaporation, and (b) the remaining thickness dD below which Jev(H2O) decreases to less than 85% of pure ice. The dependence of Jev(H2O) with increasing average χHCl from HCl-doped ice films suggests two limiting data sets, one associated with the occurrence of a two-phase pure ice/crystalline HCl hydrate binary phase (set A) and the other with a single-phase amorphous HCl∕H2O binary mixture (set B). The measured values of Jev(H2O) may lead to significant evaporative lifetime extensions of HCl-contaminated ice cloud particles under atmospheric conditions, regardless of whether the structure corresponds to an amorphous or crystalline state of the HCl∕H2O aggregate.

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Evaporation rates of H2O and HCl were observed from a thin film condensate at low temperature at an average HCl mole fraction of 10(−5)–10(−3) in order to probe the evaporative lifetime of ice particles of the upper troposphere and lower stratosphere. The results show a decrease in the H2O evaporation rate with increasing mass loss of the condensate under conditions where the saturation vapor pressure corresponded to pure ice. This supports gas–surface reactions of HCl-doped ice particles.
Evaporation rates of H2O and HCl were observed from a thin film condensate at low temperature at...
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