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| Titel |
α-pinene photooxidation under controlled chemical conditions – Part 1: Gas-phase composition in low- and high-NOx environments |
| VerfasserIn |
N. C. Eddingsaas, C. L. Loza, L. D. Yee, J. H. Seinfeld, P. O. Wennberg |
| 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. 14 ; Nr. 12, no. 14 (2012-07-25), S.6489-6504 |
| Datensatznummer |
250011339
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| Publikation (Nr.) |
 copernicus.org/acp-12-6489-2012.pdf |
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| Zusammenfassung |
| The OH oxidation of α-pinene under both low- and high-NOx
environments was studied in the Caltech atmospheric chambers. Ozone was kept
low to ensure OH was the oxidant. The initial α-pinene concentration
was 20–50 ppb to ensure that the dominant peroxy radical pathway under
low-NOx conditions is reaction with HO2, produced from reaction
of OH with H2O2, and under high-NOx conditions, reactions
with NO. Here we present the gas-phase results observed. Under low-NOx
conditions the main first generation oxidation products are a number of
α-pinene hydroxy hydroperoxides and pinonaldehyde, accounting for over
40% of the yield. In all, 65–75% of the carbon can be accounted for in
the gas phase; this excludes first-generation products that enter the
particle phase. We suggest that pinonaldehyde forms from RO2 + HO2
through an alkoxy radical channel that regenerates OH, a mechanism typically
associated with acyl peroxy radicals, not alkyl peroxy radicals. The OH
oxidation and photolysis of α-pinene hydroxy hydroperoxides leads to
further production of pinonaldehyde, resulting in total pinonaldehyde yield
from low-NOx OH oxidation of ~33%. The low-NOx
OH oxidation of pinonaldehyde produces a number of carboxylic acids and
peroxyacids known to be important secondary organic aerosol components. Under
high-NOx conditions, pinonaldehyde was also found to be the major
first-generation OH oxidation product. The high-NOx OH oxidation
of pinonaldehyde did not produce carboxylic acids and peroxyacids. A number
of organonitrates and peroxyacyl nitrates are observed and identified from
α-pinene and pinonaldehyde. |
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