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| Titel |
CCN activity and volatility of β-caryophyllene secondary organic aerosol |
| VerfasserIn |
M. Frosch, M. Bilde, A. Nenes, A. P. Praplan, Z. Jurányi, J. Dommen, M. Gysel, E. Weingärtner, 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 ; 13, no. 4 ; Nr. 13, no. 4 (2013-02-27), S.2283-2297 |
| Datensatznummer |
250018437
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| Publikation (Nr.) |
 copernicus.org/acp-13-2283-2013.pdf |
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| Zusammenfassung |
In a series of smog chamber experiments, the cloud condensation nuclei (CCN)
activity of secondary organic aerosol (SOA) generated from ozonolysis of
β-caryophyllene was characterized by determining the CCN derived
hygroscopicity parameter, κCCN, from experimental data. Two
types of CCN counters, operating at different temperatures, were used. The
effect of semi-volatile organic compounds on the CCN activity of SOA was
studied using a thermodenuder.
Overall, SOA was only slightly CCN active (with κCCN in the
range 0.001–0.16), and in dark experiments with no OH scavenger present,
κCCN decreased when particles were sent through the
thermodenuder (with a temperature up to 50 °C).
SOA was generated under different experimental conditions: In some
experiments, an OH scavenger (2-butanol) was added. SOA from these
experiments was less CCN active than SOA produced in experiments without an
OH scavenger (i.e. where OH was produced during ozonolysis). In other
experiments, lights were turned on, either without or with the addition of
HONO (OH source). This led to the formation of more CCN active SOA.
SOA was aged up to 30 h through exposure to ozone and (in experiments
with no OH scavenger present) to OH. In all experiments, the derived
κCCN consistently increased with time after initial
injection of β-caryophyllene, showing that chemical ageing increases
the CCN activity of β-caryophyllene SOA. κCCN was also
observed to depend on supersaturation, which was explained either as an
evaporation artifact from semi-volatile SOA (only observed in experiments
lacking light exposure) or, alternatively, by effects related to chemical
composition depending on dry particle size.
Using the method of Threshold Droplet Growth Analysis it was also concluded
that the activation kinetics of the SOA do not differ significantly from
calibration ammonium sulphate aerosol for particles aged for several hours. |
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