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| Titel |
Volatility and hygroscopicity of aging secondary organic aerosol in a smog chamber |
| VerfasserIn |
T. Tritscher, J. Dommen, P. F. DeCarlo, M. Gysel, P. B. Barmet, A. P. Praplan, E. Weingärtner, A. S. H. Prévôt, I. Riipinen, N. M. Donahue, 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 ; 11, no. 22 ; Nr. 11, no. 22 (2011-11-18), S.11477-11496 |
| Datensatznummer |
250010200
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| Publikation (Nr.) |
 copernicus.org/acp-11-11477-2011.pdf |
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| Zusammenfassung |
The evolution of secondary organic aerosols (SOA) during (photo-)chemical
aging processes was investigated in a smog chamber. Fresh SOA from ozonolysis
of 10 to 40 ppb α-pinene was formed followed by aging with OH
radicals. The particles' volatility and hygroscopicity (expressed as volume
fraction remaining (VFR) and hygroscopicity parameter κ) were measured
in parallel with a volatility and hygroscopicity tandem differential mobility
analyzer (V/H-TDMA). An aerosol mass spectrometer (AMS) was used for the
chemical characterization of the aerosol. These measurements were used as
sensitive parameters to reveal the mechanisms possibly responsible for the
changes in the SOA composition during aging. A change of VFR and/or κ
during processing of atmospheric aerosols may occur either by addition of SOA
mass (by condensation) or by a change of SOA composition leading to different
aerosol properties. The latter may occur either by heterogeneous reactions on
the surface of the SOA particles, by condensed phase reactions like
oligomerization or by an evaporation – gas-phase oxidation – recondensation
cycle. The condensation mechanism showed to be dominant when there is a
substantial change in the aerosol mass by addition of new molecules to the
aerosol phase with time. Experiments could be divided into four periods based
on the temporal evolution (qualitative changes) of VFR, κ and
organic mass: O3 induced condensation, ripening, and OH induced
chemical aging first with substantial mass gain and then without significant
mass gain.
During the O3 induced condensation the particles' volatility decreased
(increasing VFR) while the hygroscopicity increased. Thereafter, in the
course of ripening volatility continued to decrease, but hygroscopicity
stayed roughly constant. After exposing the SOA to OH radicals an OH induced
chemical aging with substantial mass gain started resulting in the production
of at least 50 % more SOA mass. This new SOA mass was highly volatile and
oxidized. This period was then followed by further OH induced chemical aging
without significant mass gain leading to a decrease of volatility while
hygroscopicity and SOA mass stayed roughly constant. |
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