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| Titel |
Aqueous phase processing of secondary organic aerosol from isoprene photooxidation |
| VerfasserIn |
Y. Liu, A. Monod, T. Tritscher, A. P. Praplan, P. F. DeCarlo, B. Temime-Roussel, E. Quivet, N. Marchand, J. Dommen, U. Baltensperger |
| 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 (2012-07-10), S.5879-5895 |
| Datensatznummer |
250011304
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| Publikation (Nr.) |
 copernicus.org/acp-12-5879-2012.pdf |
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| Zusammenfassung |
| Transport of reactive air masses into humid and wet areas is highly frequent
in the atmosphere, making the study of aqueous phase processing of secondary
organic aerosol (SOA) very relevant. We have investigated the aqueous phase
processing of SOA generated from gas-phase photooxidation of isoprene using
a smog chamber. The SOA collected on filters was extracted by water and
subsequently oxidized in the aqueous phase either by H2O2 under
dark conditions or by OH radicals in the presence of light, using a
photochemical reactor. Online and offline analytical techniques including
SMPS, HR-AMS, H-TDMA, TD-API-AMS, were employed for physical and chemical
characterization of the chamber SOA and nebulized filter extracts. After
aqueous phase processing, the particles were significantly more hygroscopic,
and HR-AMS data showed higher signal intensity at m/z 44 and a lower signal
intensity at m/z 43, thus showing the impact of aqueous phase processing on SOA
aging, in good agreement with a few previous studies. Additional offline
measurement techniques (IC-MS, APCI-MS2 and HPLC-APCI-MS) permitted the
identification and quantification of sixteen individual chemical compounds
before and after aqueous phase processing. Among these compounds, small
organic acids (including formic, glyoxylic, glycolic, butyric, oxalic and
2,3-dihydroxymethacrylic acid (i.e. 2-methylglyceric acid)) were detected,
and their concentrations significantly increased after aqueous phase
processing. In particular, the aqueous phase formation of 2-methylglyceric
acid and trihydroxy-3-methylbutanal was correlated with the consumption of
2,3-dihydroxy-2-methyl-propanal, and 2-methylbutane-1,2,3,4-tetrol,
respectively, and an aqueous phase mechanism was proposed accordingly.
Overall, the aging effect observed here was rather small compared to
previous studies, and this limited effect could possibly be explained by the
lower liquid phase OH concentrations employed here, and/or the development
of oligomers observed during aqueous phase processing. |
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