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| Titel |
Airborne observations of total RONO2: new constraints on the yield and lifetime of isoprene nitrates |
| VerfasserIn |
A. E. Perring, T. H. Bertram, P. J. Wooldridge, A. Fried, B. G. Heikes, J. Dibb, J. D. Crounse, P. O. Wennberg, N. J. Blake, D. R. Blake, W. H. Brune, H. B. Singh, R. C. Cohen |
| 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 ; 9, no. 4 ; Nr. 9, no. 4 (2009-02-23), S.1451-1463 |
| Datensatznummer |
250006937
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| Publikation (Nr.) |
 copernicus.org/acp-9-1451-2009.pdf |
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| Zusammenfassung |
| Formation of isoprene nitrates (INs) is an important free radical chain
termination step ending production of ozone and possibly affecting formation
of secondary organic aerosol. Isoprene nitrates also represent a potentially
large, unmeasured contribution to OH reactivity and are a major pathway for
the removal of nitrogen oxides from the atmosphere. Current assessments
indicate that formation rates of isoprene nitrates are uncertain to a factor
of 2–3 and the subsequent fate of isoprene nitrates remains largely
unconstrained by laboratory, field or modeling studies. Measurements of
total alkyl and multifunctional nitrates (ΣANs), NO2, total
peroxy nitrates (ΣPNs), HNO3, CH2O, isoprene and other VOC
were obtained from the NASA DC-8 aircraft during summer 2004 over the
continental US during the INTEX-NA campaign. These observations represent
the first characterization of ΣANs over a wide range of land surface
types and in the lower free troposphere. ΣANs were a significant,
12–20%, fraction of NOy throughout the experimental domain and
ΣANs were more abundant when isoprene was high. We use the observed
hydrocarbon species to calculate the relative contributions of ΣAN
precursors to their production. These calculations indicate that isoprene
represents at least three quarters of the ΣAN source in the
summertime continental boundary layer of the US. An observed correlation
between ΣANs and CH2O is used to place constraints on nitrate
yields from isoprene oxidation, atmospheric lifetimes of the resulting
nitrates and recycling efficiencies of nitrates during subsequent oxidation.
We find reasonable fits to the data using sets of production rates,
lifetimes and recycling efficiencies of INs as follows (4.4%, 16 h,
97%), (8%, 2.5 h, 79%) and (12%, 95 min, 67%). The analysis
indicates that the lifetime of ΣANs as a pool of compounds is
considerably longer than the lifetime of the individual isoprene nitrates to
reaction with OH, implying that the organic nitrate functionality is at
least partially maintained through a second oxidation cycle. |
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