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| Titel |
DOAS measurements of formaldehyde and glyoxal above a south-east Asian tropical rainforest |
| VerfasserIn |
S. M. MacDonald, H. Oetjen, A. S. Mahajan, L. K. Whalley, P. M. Edwards, D. E. Heard, C. E. Jones, J. M. C. Plane |
| 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. 13 ; Nr. 12, no. 13 (2012-07-12), S.5949-5962 |
| Datensatznummer |
250011308
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| Publikation (Nr.) |
 copernicus.org/acp-12-5949-2012.pdf |
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| Zusammenfassung |
| Tropical rainforests act as a huge contributor to the global emissions of
biogenic volatile organic compounds (BVOCs). Measurements of their oxidation
products, such as formaldehyde (HCHO) and glyoxal (CHOCHO), provide useful
indicators of fast photochemistry occurring in the lower troposphere.
However, measurements of these species in tropical forest locations are
extremely limited. To redress this, HCHO and CHOCHO were measured using the
long-path (LP) and multi-axis (MAX) differential optical absorption
spectroscopy (DOAS) techniques above the rainforest canopy in Borneo during
two campaigns in spring and summer 2008, as part of the Oxidant and Particle
Photochemical Processes above a south-east Asian tropical rainforest (OP3)
project. The results were compared with concurrent measurements of hydroxyl
radical (OH), isoprene (C5H8) (which was the dominant organic
species emitted in this forest environment), and various meteorological
parameters. Formaldehyde was observed at a maximum concentration of 4.5 ppb
and glyoxal at a maximum of 1.6 ppb, significantly higher than previous
measurements in rural locations. A 1-D chemistry model was then used to
assess the diurnal evolution of formaldehyde and glyoxal throughout the
boundary layer. The results, which compare well with the LP-DOAS and
MAX-DOAS observations, suggest that the majority of the glyoxal and
formaldehyde is confined to the first 500 m of the boundary layer, and that
the measured ratio of these species is reproduced using currently accepted
product yields for the oxidation of isoprene by OH. An important conclusion
is that the measured levels of glyoxal are consistent with the surprisingly
high concentrations of OH measured in this environment. |
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