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| Titel |
Hydroxy nitrate production in the OH-initiated oxidation of alkenes |
| VerfasserIn |
A. P. Teng, J. D. Crounse, L. Lee, J. M. St. Clair, R. C. Cohen, 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 ; 15, no. 8 ; Nr. 15, no. 8 (2015-04-28), S.4297-4316 |
| Datensatznummer |
250119666
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| Publikation (Nr.) |
 copernicus.org/acp-15-4297-2015.pdf |
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| Zusammenfassung |
| Alkenes are oxidized rapidly in the atmosphere by addition of OH and
subsequently O2 leading to the formation of β-hydroxy peroxy
radicals. These peroxy radicals react with NO to form β-hydroxy
nitrates with a branching ratio α. We quantify α for
C2–C8 alkenes at 295 K ± 3 and 993 hPa. The
branching ratio can be expressed as α = (0.045 ± 0.016) × N
− (0.11 ± 0.05) where N is the number of heavy atoms (excluding the
peroxy moiety), and listed errors are 2σ. These branching ratios are
larger than previously reported and are similar to those for peroxy radicals
formed from H abstraction from alkanes. We find the isomer distributions of
β-hydroxy nitrates formed under NO-dominated peroxy radical chemistry
to be different than the isomer distribution of hydroxy hydroperoxides
produced under HO2-dominated peroxy radical chemistry. Assuming unity
yield for the hydroperoxides implies that the branching ratio to form β-hydroxy
nitrates increases with substitution of RO2. Deuterium
substitution enhances the branching ratio to form hydroxy nitrates in both
propene and isoprene by a factor of ~ 1.5. The role of alkene chemistry
in the Houston region is re-evaluated using the RONO2 branching
ratios reported here. Small alkenes are found to play a significant role in
present-day oxidant formation more than a decade (2013) after the 2000 Texas
Air Quality Study identified these compounds as major contributors to
photochemical smog in Houston. |
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