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| Titel |
Fast photolysis of carbonyl nitrates from isoprene |
| VerfasserIn |
Jean-Francois Müller, Jozef Peeters, Trisevgeni Stavrakou |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250088794
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| Publikation (Nr.) |
 EGU/EGU2014-2947.pdf |
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| Zusammenfassung |
| We show that photolysis is, by far, the major atmospheric sink of isoprene-derived
carbonyl nitrates. Empirical evidence from published laboratory studies on the
absorption cross sections and photolysis rates of α-nitrooxy ketones suggests that the
presence of the nitrate group (i) greatly enhances the absorption cross sections, and (ii)
facilitates dissociation to a point that the photolysis quantum yield is close to unity, with
O–NO2 dissociation as the likely major channel. On this basis, we provide new
recommendations for estimating the cross sections and photolysis rates of carbonyl
nitrates. The newly estimated photorates are validated using a chemical box model
against measured temporal profiles of carbonyl nitrates in an isoprene oxidation
experiment by Paulot etal. (2009). The comparisons for ethanal nitrate and for
the sum of methacrolein- and methylvinylketone nitrates strongly supports our
assumptions of large cross section enhancements and a near-unit quantum yield for these
compounds. These findings have significant atmospheric implications, as carbonyl nitrates
constitute an important component of the total organic nitrate pool over vegetated
areas: the photorates of key carbonyl nitrates from isoprene are estimated to be
typically between ~3 and 20 times higher than their sink due to reaction with OH in
relevant atmospheric conditions. Moreover, since the reaction is expected to release
NO2, photolysis is especially effective in depleting the total organic nitrate pool. |
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