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| Titel |
Mechanisms leading to oligomers and SOA through aqueous photooxidation: insights from OH radical oxidation of acetic acid and methylglyoxal |
| VerfasserIn |
Y. Tan, Y. B. Lim, K. E. Altieri, S. P. Seitzinger, B. J. Turpin |
| 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. 2 ; Nr. 12, no. 2 (2012-01-18), S.801-813 |
| Datensatznummer |
250010531
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| Publikation (Nr.) |
 copernicus.org/acp-12-801-2012.pdf |
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| Zusammenfassung |
| Previous experiments have demonstrated that the aqueous OH radical oxidation
of methylglyoxal produces low volatility products including pyruvate,
oxalate and oligomers. These products are found predominantly in the
particle phase in the atmosphere, suggesting that methylglyoxal is a
precursor of secondary organic aerosol (SOA). Acetic acid plays a central
role in the aqueous oxidation of methylglyoxal and it is a ubiquitous
product of gas phase photochemistry, making it a potential "aqueous" SOA
precursor in its own right. However, the fate of acetic acid upon
aqueous-phase oxidation is not well understood. In this research, acetic
acid (20 μM–10 mM) was oxidized by OH radicals, and pyruvic acid and
methylglyoxal experimental samples were analyzed using new analytical
methods, in order to better understand the formation of SOA from acetic acid
and methylglyoxal. Glyoxylic, glycolic, and oxalic acids formed from acetic
acid and OH radicals. In contrast to the aqueous OH radical oxidation of
methylglyoxal, the aqueous OH radical oxidation of acetic acid did not
produce succinic acid and oligomers. This suggests that the
methylgloxal-derived oligomers do not form through the acid catalyzed
esterification pathway proposed previously. Using results from these
experiments, radical mechanisms responsible for oligomer formation from
methylglyoxal oxidation in clouds and wet aerosols are proposed. The
importance of acetic acid/acetate as an SOA precursor is also discussed. We
hypothesize that this and similar chemistry is central to the daytime
formation of oligomers in wet aerosols. |
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