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| Titel |
Cloud condensation nuclei activity and droplet activation kinetics of wet processed regional dust samples and minerals |
| VerfasserIn |
P. Kumar, I. N. Sokolik, 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 ; 11, no. 16 ; Nr. 11, no. 16 (2011-08-25), S.8661-8676 |
| Datensatznummer |
250010028
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| Publikation (Nr.) |
 copernicus.org/acp-11-8661-2011.pdf |
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| Zusammenfassung |
This study reports laboratory measurements of particle size distributions,
cloud condensation nuclei (CCN) activity, and droplet activation kinetics of
wet generated aerosols from clays, calcite, quartz, and desert soil samples
from Northern Africa, East Asia/China, and Northern America. The dependence
of critical supersaturation, sc, on particle dry diameter, Ddry, is
used to characterize particle-water interactions and assess the ability of
Frenkel-Halsey-Hill adsorption activation theory (FHH-AT) and Köhler
theory (KT) to describe the CCN activity of the considered samples. Wet
generated regional dust samples produce unimodal size distributions with
particle sizes as small as 40 nm, CCN activation consistent with KT, and
exhibit hygroscopicity similar to inorganic salts. Wet generated clays and
minerals produce a bimodal size distribution; the CCN activity of the
smaller mode is consistent with KT, while the larger mode is less
hydrophilic, follows activation by FHH-AT, and displays almost identical CCN
activity to dry generated dust. Ion Chromatography (IC) analysis performed
on regional dust samples indicates a soluble fraction that cannot explain
the CCN activity of dry or wet generated dust. A mass balance and
hygroscopicity closure suggests that the small amount of ions (from low solubility compounds like calcite) present in the dry dust dissolve in the
aqueous suspension during the wet generation process and give rise to the
observed small hygroscopic mode. Overall these results identify an artifact
that may question the atmospheric relevance of dust CCN activity studies
using the wet generation method.
Based on the method of threshold droplet growth analysis, wet generated mineral aerosols
display similar activation kinetics compared to ammonium sulfate calibration
aerosol. Finally, a unified CCN activity framework that accounts for
concurrent effects of solute and adsorption is developed to describe the CCN
activity of aged or hygroscopic dusts. |
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