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| Titel |
Direct photolysis of carbonyl compounds dissolved in cloud and fog~droplets |
| VerfasserIn |
S. A. Epstein, E. Tapavicza, F. Furche, S. A. Nizkorodov |
| 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 ; 13, no. 18 ; Nr. 13, no. 18 (2013-09-26), S.9461-9477 |
| Datensatznummer |
250085711
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| Publikation (Nr.) |
 copernicus.org/acp-13-9461-2013.pdf |
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| Zusammenfassung |
| Gas-phase photolysis is an important tropospheric sink for many carbonyl
compounds; however the significance of direct photolysis of these compounds
dissolved in cloud and fog droplets is uncertain. We develop a theoretical
approach to assess the importance of aqueous photolysis for a series of
carbonyls that possess carboxyl and hydroxyl functional groups by comparison
with rates of other atmospheric processes. We use computationally and
experimentally derived effective Henry's law constants, hydration
equilibrium parameters, aqueous hydroxyl radical (OH) rate constants, and
optical extinction coefficients to identify types of compounds that will (or
will not) have competitive aqueous photolysis rates. We also present
molecular dynamics simulations designed to estimate gas- and aqueous-phase
extinction coefficients of unstudied atmospherically relevant compounds
found in d-limonene and isoprene secondary organic aerosol. In addition,
experiments designed to measure the photolysis rate of glyceraldehyde, an
atmospherically relevant water-soluble organic compound, reveal that aqueous
quantum yields are highly molecule-specific and cannot be extrapolated from
measurements of structurally similar compounds. We find that only two out of
the 92 carbonyl compounds investigated, pyruvic acid and acetoacetic acid,
may have aqueous photolysis rates that exceed the rate of oxidation by
dissolved OH. For almost all carbonyl compounds lacking α,β-conjugation
that were investigated, atmospheric removal by direct
photolysis in cloud and fog droplets can be neglected under typical
atmospheric conditions. |
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