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| Titel |
Rapid formation of isoprene photo-oxidation products observed in Amazonia |
| VerfasserIn |
T. Karl, A. Guenther, A. Turnipseed, G. Tyndall, P. Artaxo, S. Martin |
| 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. 20 ; Nr. 9, no. 20 (2009-10-19), S.7753-7767 |
| Datensatznummer |
250007690
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| Publikation (Nr.) |
 copernicus.org/acp-9-7753-2009.pdf |
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| Zusammenfassung |
| Isoprene represents the single most important reactive hydrocarbon
for atmospheric chemistry in the tropical atmosphere. It plays a central
role in global and regional atmospheric chemistry and possible climate
feedbacks. Photo-oxidation of primary hydrocarbons (e.g. isoprene) leads to
the formation of oxygenated VOCs (OVOCs). The evolution of these
intermediates affects the oxidative capacity of the atmosphere (by reacting
with OH) and can contribute to secondary aerosol formation, a poorly
understood process. An accurate and quantitative understanding of VOC
oxidation processes is needed for model simulations of regional air quality
and global climate. Based on field measurements conducted during the
Amazonian Aerosol Characterization Experiment (AMAZE-08) we show that the
production of certain OVOCs (e.g. hydroxyacetone) from isoprene
photo-oxidation in the lower atmosphere is significantly underpredicted by
standard chemistry schemes. Recently reported fast secondary production
could explain 50% of the observed discrepancy with the remaining part
possibly produced via a novel primary production channel, which has been
proposed theoretically. The observations of OVOCs are also used to test a
recently proposed HOx recycling mechanism via degradation of isoprene
peroxy radicals. If generalized our observations suggest that prompt
photochemical formation of OVOCs and other uncertainties in VOC oxidation
schemes could result in uncertainties of modelled OH reactivity, potentially
explaining a fraction of the missing OH sink over forests which has
previously been largely attributed to a missing source of primary biogenic
VOCs. |
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