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| Titel |
Different photolysis kinetics at the surface of frozen freshwater vs. frozen salt solutions |
| VerfasserIn |
T. F. Kahan, N.-O. A. Kwamena, D. J. Donaldson |
| 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 ; 10, no. 22 ; Nr. 10, no. 22 (2010-11-22), S.10917-10922 |
| Datensatznummer |
250008902
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| Publikation (Nr.) |
 copernicus.org/acp-10-10917-2010.pdf |
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| Zusammenfassung |
| Reactions at air-ice interfaces can proceed at very different rates than
those in aqueous solution, due to the unique disordered region at the ice
surface known as the quasi-liquid layer (QLL) . The physical and chemical
nature of the surfacial region of ice is greatly affected by solutes such as
sodium halide salts. In this work, we studied the effects of sodium chloride
and sodium bromide on the photolysis kinetics of harmine, an aromatic
organic compound, in aqueous solution and at the surface of frozen salt
solutions above the eutectic temperature. In common with other aromatic
organic compounds we have studied, harmine photolysis is much faster on ice
surfaces than in aqueous solution, but the presence of NaCl or NaBr – which
does not affect photolysis kinetics in solution – reduces the photolysis
rate on ice. The rate decreases monotonically with increasing salt
concentration; at the concentrations found in seawater, harmine photolysis
at the surface of frozen salt solutions proceeds at the same rate as in
aqueous solution. These results suggest that the brine excluded to the
surfaces of frozen salt solutions is a true aqueous solution, and so it may
be possible to use aqueous-phase kinetics to predict photolysis rates at sea
ice surfaces. This is in marked contrast to the result at the surface of
frozen freshwater samples, where reaction kinetics are often not
well-described by aqueous-phase processes. |
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