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| Titel |
Organic acids as cloud condensation nuclei: Laboratory studies of highly soluble and insoluble species |
| VerfasserIn |
P. Pradeep Kumar, K. Broekhuizen, J. P. D. Abbatt |
| 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 ; 3, no. 3 ; Nr. 3, no. 3 (2003-05-19), S.509-520 |
| Datensatznummer |
250001028
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| Publikation (Nr.) |
 copernicus.org/acp-3-509-2003.pdf |
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| Zusammenfassung |
| The ability of sub-micron-sized organic acid particles to act as cloud condensation nuclei
(CCN) has been examined at room temperature using a newly constructed continuous-flow, thermal-gradient
diffusion chamber (TGDC). The organic acids studied were: oxalic, malonic, glutaric, oleic and
stearic. The CCN properties of the highly soluble acids - oxalic, malonic and glutaric
- match very closely Köhler theory predictions which assume full dissolution of the dry particle and a surface
tension of the growing droplet equal to that of water. In particular, for supersaturations between 0.3
and 0.6, agreement between the dry particle diameter which gives 50% activation and that calculated
from Köhler theory is to within 3nm on average. In the course of the experiments, considerable
instability of glutaric acid particles was observed as a function of time and there is evidence that they
fragment to some degree to smaller particles. Stearic acid and oleic acid, which are both highly
insoluble in water, did not activate at supersaturations of 0.6% with dry diameters up to
140nm. Finally, to validate the performance of the TGDC, we present results for the activation of ammonium
sulfate particles that demonstrate good agreement with Köhler theory if solution non-ideality is
considered. Our findings support earlier studies in the literature that showed highly soluble organics to
be CCN active but insoluble species to be largely inactive. |
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