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| Titel |
Reversible adsorption of hydrogen chloride to ice surfaces |
| VerfasserIn |
Stefan Zimmermann, Matthias Kippenberger, John Crowley |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250110186
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| Publikation (Nr.) |
 EGU/EGU2015-10163.pdf |
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| Zusammenfassung |
| Hydrogen chloride is the most important reservoir of gaseous, reactive chlorine in the
atmosphere. Although several laboratory investigations of the interaction of HCl with ice
surfaces have been conducted, there is still great uncertainty associated with the adsorption
isotherms of HCl on ice, which is largely a consequence of most previous studies being
unable to work at concentrations relevant for the atmosphere and to explore the non-saturated
part of the isotherm at sub-monolayer coverage.
We have conducted experiments on HCl uptake on ice surfaces at temperatures between
190 and 220ÂK, using a coated wall flow tube. HCl at concentrations as low as 2 x 109
molecule cm3 (~10-8 Torr) was detected using a chemical-ionization, quadrupole mass
spectrometer.
The equilibrium surface coverage of HCl on ice could be interpreted using the
Langmuir-model to derive partition coefficients (KLang). We find that the dissociative
Langmuir isotherm describes our data significantly better than the non-dissociative type.
Surprisingly, and in contrast to the behavior of the majority of traces-gases which adsorb
reversibly on ice surfaces, the partition-coefficients we derive for HCl do not show a
systematic dependence on temperature, precluding the simple derivation of an adsorption
enthalpy and indicating the presence of more complex adsorption and desorption
mechanisms for strong acids ionizing on the surface compared to H-bonded trace gases. |
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