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| Titel |
The effect of photochemical ageing and initial precursor concentration on the composition and hygroscopic properties of β-caryophyllene secondary organic aerosol |
| VerfasserIn |
M. R. Alfarra, J. F. Hamilton, K. P. Wyche, N. Good, M. W. Ward, T. Carr, M. H. Barley, P. S. Monks, M. E. Jenkin, A. C. Lewis, G. B. McFiggans |
| 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. 14 ; Nr. 12, no. 14 (2012-07-24), S.6417-6436 |
| Datensatznummer |
250011335
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| Publikation (Nr.) |
 copernicus.org/acp-12-6417-2012.pdf |
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| Zusammenfassung |
| The effect of photochemical ageing and initial precursor concentration on
the composition and hygroscopic properties of secondary organic aerosol
(SOA) formed during the chamber photo-oxidation of β-caryophyllene/NOx
mixtures were investigated. Nucleation of β-caryophyllene SOA particles occurred almost immediately after oxidation
was initiated and led to the formation of fresh SOA with a relatively
simpler composition than has been reported for monoterpenes. The SOA yield
values ranged from 9.5–26.7% and 30.4–44.5% using a
differential mobility particle sizer (DMPS) and an aerosol mass spectrometer
(AMS) mass based measurements, respectively. A total of 20 compounds were
identified in the SOA by LC-MS/MS, with the most abundant compounds
identified as β-caryophyllonic acid and β-caryophyllinic
acid/β-nocaryophyllonic acid. The O:C and H:C elemental ratios of
products identified in the condensed phase ranged from 0.20 to 1.00 and 1.00
to 2.00, with average values of 0.39 and 1.58, respectively. The increase in
the O:C ratio was associated with a decrease in the saturation concentration
of the identified compounds. The compounds identified in the lower initial
concentration experiments were more oxidised compared to those that were
found to be more abundant in the higher initial concentration experiments
with average O:C ratios of 0.51 and 0.27, respectively. Photochemical ageing
led to a more complex SOA composition with a larger contribution coming from
lower molar mass, higher generation products, where both double bonds had
been oxidised. This effect was more evident in the experiments conducted
using the lower initial precursor concentration; a finding confirmed by the
temporal behaviour of key organic mass fragment measured by an Aerosol Mass
Spectrometer. Although the composition changed with both initial precursor
concentration and ageing, this had no significant measurable effect on the
hygroscopic properties of the SOA formed. The latter finding might have been
influenced by the difference in pre-treatment of the semivolatile-containing
particles prior to their measurements. |
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