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| Titel |
Acetaldehyde in the Alaskan subarctic snowpack |
| VerfasserIn |
F. Domine, S. Houdier, A.-S. Taillandier, W. R. Simpson |
| 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. 3 ; Nr. 10, no. 3 (2010-02-01), S.919-929 |
| Datensatznummer |
250008021
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| Publikation (Nr.) |
 copernicus.org/acp-10-919-2010.pdf |
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| Zusammenfassung |
| Acetaldehyde is a reactive intermediate in hydrocarbon oxidation. It is both
emitted and taken up by snowpacks and photochemical and physical processes
are probably involved. Understanding the reactivity of acetaldehyde in snow
and its processes of physical and chemical exchanges requires the knowledge
of its incorporation mechanism in snow crystals. We have performed a
season-long study of the evolution of acetaldehyde concentrations in the
subarctic snowpack near Fairbanks (65° N), central Alaska, which is
subjected to a vigorous metamorphism due to persistent elevated temperature
gradients in the snowpack, between 20 and 200° C m−1. The snowpack
therefore almost entirely transforms into depth hoar. We have also analyzed
acetaldehyde in a manipulated snowpack where temperature gradients were
suppressed. Snow crystals there transformed much more slowly and their
original shapes remained recognizable for months. The specific surface area
of snow layers in both types of snowpacks was also measured. We deduce that
acetaldehyde is not adsorbed onto the surface of snow crystals and that most
of the acetaldehyde is probably not dissolved in the ice lattice of the snow
crystals. We propose that most of the acetaldehyde measured is either
trapped or dissolved within organic aerosol particles trapped in snow, or
that acetaldehyde is formed by the hydrolysis of organic precursors
contained in organic aerosols trapped in the snow, when the snow is melted
for analysis. These precursors are probably aldehyde polymers formed within
the aerosol particles by acid catalysis, but might also be biological
molecules. In a laboratory experiment, acetaldehyde-di-n-hexyl acetal,
representing a potential acetaldehyde precursor, was subjected to our
analytical procedure and reacted to form acetaldehyde. This confirms our
suggestion that acetaldehyde detected in snow could be produced during the melting of
snow for analysis. |
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