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| Titel |
Temperature dependent halogen activation by N2O5 reactions on halide-doped ice surfaces |
| VerfasserIn |
F. D. Lopez-Hilfiker, K. Constantin, J. P. Kercher, J. A. Thornton |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 11 ; Nr. 12, no. 11 (2012-06-15), S.5237-5247 |
| Datensatznummer |
250011239
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| Publikation (Nr.) |
 copernicus.org/acp-12-5237-2012.pdf |
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| Zusammenfassung |
| We examined the reaction of N2O5 on frozen halide salt solutions
as a function of temperature and composition using a coated wall flow tube
technique coupled to a chemical ionization mass spectrometer (CIMS). The
molar yield of photo-labile halogen compounds was near unity for almost all
conditions studied, with the observed reaction products being nitryl
chloride (ClNO2) and/or molecular bromine (Br2). The relative
yield of ClNO2 and Br2 depended on the ratio of bromide to
chloride ions in the solutions used to form the ice. At a bromide to
chloride ion molar ratio greater than 1/30 in the starting solution,
Br2 was the dominant product otherwise ClNO2 was primarily
produced on these near pH-neutral brines. We demonstrate that the
competition between chlorine and bromine activation is a function of the
ice/brine temperature presumably due to the preferential precipitation of
NaCl hydrates from the brine below 250 K. Our results provide new
experimental confirmation that the chemical environment of the brine layer
changes with temperature and that these changes can directly affect
multiphase chemistry. These findings have implications for modeling
air-snow-ice interactions in polar regions and likely in polluted
mid-latitude regions during winter as well. |
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