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| Titel |
Photochemical modeling of glyoxal at a rural site: observations and analysis from BEARPEX 2007 |
| VerfasserIn |
A. J. Huisman, J. R. Hottle, M. M. Galloway, J. P. DiGangi, K. L. Coens, W. Choi, I. C. Faloona, J. B. Gilman, W. C. Kuster, J. Gouw, N. C. Bouvier-Brown, A. H. Goldstein, B. W. LaFranchi, R. C. Cohen, G. M. Wolfe, J. A. Thornton, K. S. Docherty, D. K. Farmer, M. J. Cubison, J. L. Jimenez, J. Mao, W. H. Brune, 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 ; 11, no. 17 ; Nr. 11, no. 17 (2011-09-01), S.8883-8897 |
| Datensatznummer |
250010043
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| Publikation (Nr.) |
 copernicus.org/acp-11-8883-2011.pdf |
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| Zusammenfassung |
We present roughly one month of high time-resolution, direct, in situ
measurements of gas-phase glyoxal acquired during the BEARPEX 2007 field
campaign. The research site, located on a ponderosa pine plantation in the
Sierra Nevada mountains, is strongly influenced by biogenic volatile organic
compounds (BVOCs); thus this data adds to the few existing measurements of
glyoxal in BVOC-dominated areas. The short lifetime of glyoxal of
~1 h, the fact that glyoxal mixing ratios are much higher during high
temperature periods, and the results of a photochemical model demonstrate
that glyoxal is strongly influenced by BVOC precursors during high
temperature periods.
A zero-dimensional box model using near-explicit chemistry from the Leeds
Master Chemical Mechanism v3.1 was used to investigate the processes
controlling glyoxal chemistry during BEARPEX 2007. The model showed that MBO
is the most important glyoxal precursor (~67 %), followed by
isoprene (~26 %) and methylchavicol (~6 %), a precursor
previously not commonly considered for glyoxal production. The model
calculated a noon lifetime for glyoxal of ~0.9 h, making glyoxal well
suited as a local tracer of VOC oxidation in a forested rural environment;
however, the modeled glyoxal mixing ratios over-predicted measured glyoxal by
a factor 2 to 5. Loss of glyoxal to aerosol was not found to be significant,
likely as a result of the very dry conditions, and could not explain the
over-prediction. Although several parameters, such as an approximation for
advection, were found to improve the model measurement discrepancy, reduction
in OH was by far the most effective. Reducing model OH concentrations to half
the measured values decreased the glyoxal over-prediction from a factor of
2.4 to 1.1, as well as the overprediction of HO2 from a factor of
1.64 to 1.14. Our analysis has shown that glyoxal is particularly sensitive
to OH concentration compared to other BVOC oxidation products. This
relationship arises from (i) the predominantly secondary- or
higher-generation production of glyoxal from (mainly OH-driven, rather than
O3-driven) BVOC oxidation at this site and (ii) the relative importance of
photolysis in glyoxal loss as compared to reaction with OH. We propose that
glyoxal is a useful tracer for OH-driven BVOC oxidation chemistry. |
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