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| Titel |
Relating CCN activity, volatility, and droplet growth kinetics of β-caryophyllene secondary organic aerosol |
| VerfasserIn |
A. Asa-Awuku, G. J. Engelhart, B. H. Lee, S. N. Pandis, A. Nenes |
| 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 ; 9, no. 3 ; Nr. 9, no. 3 (2009-02-02), S.795-812 |
| Datensatznummer |
250006811
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| Publikation (Nr.) |
 copernicus.org/acp-9-795-2009.pdf |
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| Zusammenfassung |
| This study investigates the droplet formation characteristics of
secondary organic aerosol (SOA) formed during the ozonolysis of
sesquiterpene β-caryophyllene (with and without hydroxyl
radicals present). Emphasis is placed on understanding the role of
semi-volatile material on Cloud Condensation Nucleus (CCN) activity
and droplet growth kinetics. Aging of β-caryophyllene SOA
significantly affects all CCN-relevant properties measured
throughout the experiments. Using a thermodenuder and two CCN
instruments, we find that CCN activity is a strong function of
temperature (activation diameter at ~0.6% supersaturation: 100±10 nm at
20°C and 130±10 nm at 35°C), suggesting that the
hygroscopic fraction of the SOA is volatile. The water-soluble
organic carbon (WSOC) is extracted from the SOA and characterized
with Köhler Theory Analysis (KTA); the results suggest that the WSOC
is composed of low molecular weight (<200 g mol−1) slightly
surface-active material that constitute 5–15% of the SOA mass.
These properties are similar to the water-soluble fraction of
monoterpene SOA, suggesting that predictive understanding of SOA CCN
activity requires knowledge of the WSOC fraction but not its exact
speciation. Droplet growth kinetics of the CCN are found to be
strongly anticorrelated with WSOC fraction, suggesting that the
insoluble material in the SOA forms a kinetic barrier that delays
droplet growth. Overall, volatilization effects can increase activation
diameters by 30%, and depress droplet growth rate by a factor of two;
these results may have important implications for the droplet formation characteristics of SOA,
and the atmospheric relevance of CCN measurements carried out at temperatures different
from ambient. |
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