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| Titel |
Missing peroxy radical sources within a summertime ponderosa pine forest |
| VerfasserIn |
G. M. Wolfe, C. Cantrell, S. Kim, R. L. Mauldin III, T. Karl, P. Harley, A. Turnipseed, W. Zheng, F. Flocke, E. C. Apel, R. S. Hornbrook, S. R. Hall, K. Ullmann, S. B. Henry, J. P. DiGangi, E. S. Boyle, L. Kaser, R. Schnitzhofer, A. Hansel, M. Graus, Y. Nakashima, Y. Kajii, A. Guenther, F. N. Keutsch |
| 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 ; 14, no. 9 ; Nr. 14, no. 9 (2014-05-13), S.4715-4732 |
| Datensatznummer |
250118697
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| Publikation (Nr.) |
 copernicus.org/acp-14-4715-2014.pdf |
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| Zusammenfassung |
| Organic peroxy (RO2) and hydroperoxy (HO2) radicals are key
intermediates in the photochemical processes that generate ozone, secondary
organic aerosol and reactive nitrogen reservoirs throughout the troposphere.
In regions with ample biogenic hydrocarbons, the richness and complexity of
peroxy radical chemistry presents a significant challenge to
current-generation models, especially given the scarcity of measurements in
such environments. We present peroxy radical observations acquired within a
ponderosa pine forest during the summer 2010 Bio-hydro-atmosphere
interactions of Energy, Aerosols, Carbon, H2O, Organics and Nitrogen –
Rocky Mountain Organic Carbon Study (BEACHON-ROCS). Total peroxy radical
mixing ratios reach as high as 180 pptv (parts per trillion by volume) and are among the highest yet
recorded. Using the comprehensive measurement suite to constrain a
near-explicit 0-D box model, we investigate the sources, sinks and
distribution of peroxy radicals below the forest canopy. The base chemical
mechanism underestimates total peroxy radicals by as much as a factor of 3.
Since primary reaction partners for peroxy radicals are either measured (NO)
or underpredicted (HO2 and RO2, i.e., self-reaction), missing
sources are the most likely explanation for this result. A close comparison
of model output with observations reveals at least two distinct source
signatures. The first missing source, characterized by a sharp midday
maximum and a strong dependence on solar radiation, is consistent with
photolytic production of HO2. The diel profile of the second missing
source peaks in the afternoon and suggests a process that generates RO2
independently of sun-driven photochemistry, such as ozonolysis of reactive
hydrocarbons. The maximum magnitudes of these missing sources
(~120 and 50 pptv min−1, respectively) are consistent
with previous observations alluding to unexpectedly intense oxidation within
forests. We conclude that a similar mechanism may underlie many such
observations. |
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