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| Titel |
Volatility of secondary organic aerosol during OH radical induced ageing |
| VerfasserIn |
K. Salo, M. Hallquist, A. M. Jönsson, H. Saathoff, K.-H. Naumann, C. Spindler, R. Tillmann, H. Fuchs, B. Bohn, F. Rubach, Th. F. Mentel, L. Müller, M. Reinnig, T. Hoffmann, N. M. Donahue |
| 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. 21 ; Nr. 11, no. 21 (2011-11-09), S.11055-11067 |
| Datensatznummer |
250010175
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| Publikation (Nr.) |
 copernicus.org/acp-11-11055-2011.pdf |
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| Zusammenfassung |
| The aim of this study was to investigate oxidation of SOA formed from
ozonolysis of α-pinene and limonene by hydroxyl radicals. This paper
focuses on changes of particle volatility, using a Volatility Tandem DMA
(VTDMA) set-up, in order to explain and elucidate the mechanism behind
atmospheric ageing of the organic aerosol. The experiments were conducted at
the AIDA chamber facility of Karlsruhe Institute of Technology (KIT) in
Karlsruhe and at the SAPHIR chamber of Forchungzentrum Jülich (FZJ) in
Jülich. A fresh SOA was produced from ozonolysis of α-pinene or
limonene and then aged by enhanced OH exposure. As an OH radical source in
the AIDA-chamber the ozonolysis of tetramethylethylene (TME) was used while
in the SAPHIR-chamber the OH was produced by natural light photochemistry. A
general feature is that SOA produced from ozonolysis of α-pinene and
limonene initially was rather volatile and becomes less volatile with time
in the ozonolysis part of the experiment. Inducing OH chemistry or adding a
new portion of precursors made the SOA more volatile due to addition of new
semi-volatile material to the aged aerosol. The effect of OH chemistry was
less pronounced in high concentration and low temperature experiments when
lower relative amounts of semi-volatile material were available in the gas
phase. Conclusions drawn from the changes in volatility were confirmed by
comparison with the measured and modelled chemical composition of the
aerosol phase. Three quantified products from the α-pinene
oxidation; pinonic acid, pinic acid and methylbutanetricarboxylic acid
(MBTCA) were used to probe the processes influencing aerosol volatility. A
major conclusion from the work is that the OH induced ageing can be
attributed to gas phase oxidation of products produced in the primary SOA
formation process and that there was no indication on significant bulk or
surface reactions. The presented results, thus, strongly emphasise the
importance of gas phase oxidation of semi- or intermediate-volatile organic
compounds (SVOC and IVOC) for atmospheric aerosol ageing. |
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