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| Titel |
Global atmospheric budget of acetaldehyde: 3-D model analysis and constraints from in-situ and satellite observations |
| VerfasserIn |
D. B. Millet, A. Guenther, D. A. Siegel, N. B. Nelson, H. B. Singh, J. A. Gouw, C. Warneke, J. Williams, G. Eerdekens, V. Sinha, T. Karl, F. Flocke, E. Apel, D. D. Riemer, P. I. Palmer, M. Barkley |
| 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 ; 10, no. 7 ; Nr. 10, no. 7 (2010-04-12), S.3405-3425 |
| Datensatznummer |
250008339
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| Publikation (Nr.) |
 copernicus.org/acp-10-3405-2010.pdf |
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| Zusammenfassung |
| We construct a global atmospheric budget for acetaldehyde using a 3-D model
of atmospheric chemistry (GEOS-Chem), and use an ensemble of observations to
evaluate present understanding of its sources and sinks. Hydrocarbon
oxidation provides the largest acetaldehyde source in the model (128 Tg a−1,
a factor of 4 greater than the previous estimate), with alkanes,
alkenes, and ethanol the main precursors. There is also a minor source from
isoprene oxidation. We use an updated chemical mechanism for GEOS-Chem, and
photochemical acetaldehyde yields are consistent with the Master Chemical
Mechanism. We present a new approach to quantifying the acetaldehyde air-sea
flux based on the global distribution of light absorption due to colored
dissolved organic matter (CDOM) derived from satellite ocean color
observations. The resulting net ocean emission is 57 Tg a−1, the second
largest global source of acetaldehyde. A key uncertainty is the acetaldehyde
turnover time in the ocean mixed layer, with quantitative model evaluation
over the ocean complicated by known measurement artifacts in clean air.
Simulated concentrations in surface air over the ocean generally agree well
with aircraft measurements, though the model tends to overestimate the
vertical gradient. PAN:NOx ratios are well-simulated in the marine
boundary layer, providing some support for the modeled ocean source. We
introduce the Model of Emissions of Gases and Aerosols from Nature
(MEGANv2.1) for acetaldehyde and ethanol and use it to quantify their net
flux from living terrestrial plants. Including emissions from decaying
plants the total direct acetaldehyde source from the land biosphere is 23 Tg a−1.
Other terrestrial acetaldehyde sources include biomass burning
(3 Tg a−1) and anthropogenic emissions (2 Tg a−1). Simulated
concentrations in the continental boundary layer are generally unbiased and
capture the spatial gradients seen in observations over North America,
Europe, and tropical South America. However, the model underestimates
acetaldehyde levels in urban outflow, suggesting a missing source in
polluted air. Ubiquitous high measured concentrations in the free
troposphere are not captured by the model, and based on present
understanding are not consistent with concurrent measurements of PAN and
NOx: we find no compelling evidence for a widespread missing
acetaldehyde source in the free troposphere. We estimate the current US
source of ethanol and acetaldehyde (primary + secondary) at 1.3 Tg a−1
and 7.8 Tg a−1, approximately 60{%} and 480% of the corresponding
increases expected for a national transition from gasoline to ethanol fuel. |
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