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| Titel |
Reversible and irreversible processing of biogenic olefins on acidic aerosols |
| VerfasserIn |
J. Liggio, S.-M. Li |
| 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 ; 8, no. 7 ; Nr. 8, no. 7 (2008-04-09), S.2039-2055 |
| Datensatznummer |
250006034
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| Publikation (Nr.) |
 copernicus.org/acp-8-2039-2008.pdf |
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| Zusammenfassung |
| Recent evidence has suggested that heterogeneous chemistry of oxygenated
hydrocarbons, primarily carbonyls, plays a role in the formation of
secondary organic aerosol (SOA); however, evidence is emerging that direct
uptake of alkenes on acidic aerosols does occur and can contribute to SOA
formation. In the present study, significant uptake of monoterpenes,
oxygenated monoterpenes and sesquiterpenes to acidic sulfate aerosols is
found under various conditions in a reaction chamber. Proton transfer mass
spectrometry is used to quantify the organic gases, while an aerosol mass
spectrometer is used to quantify the organic mass uptake and obtain
structural information for heterogeneous products. Aerosol mass spectra are
consistent with several mechanisms including acid catalyzed olefin
hydration, cationic polymerization and organic ether formation, while
measurable decreases in the sulfate mass on a per particle basis suggest
that the formation of organosulfate compounds is also likely. A portion of
the heterogeneous reactions appears to be reversible, consistent with
reversible olefin hydration reactions. A slow increase in the organic mass
after a fast initial uptake is attributed to irreversible reactions,
consistent with polymerization and organosulfate formation. Uptake
coefficients (γ) were estimated for a fast initial uptake governed
by the mass accommodation coefficient (α) and ranged from 1×10-6-2.5×10-2. Uptake coefficients for a subsequent
slower reactive uptake ranged from 1×10-7-1×10-4. These processes may potentially lead to a considerable amount of
SOA from the various biogenic hydrocarbons under acidic conditions, which
can be highly significant for freshly nucleated aerosols, particularly given
the large array of atmospheric olefins. |
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