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| Titel |
Cloud condensation nucleus activity comparison of dry- and wet-generated mineral dust aerosol: the significance of soluble material |
| VerfasserIn |
S. Garimella, Y.-W. Huang, J. S. Seewald, D. J. Cziczo |
| 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 ; 14, no. 12 ; Nr. 14, no. 12 (2014-06-18), S.6003-6019 |
| Datensatznummer |
250118816
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| Publikation (Nr.) |
 copernicus.org/acp-14-6003-2014.pdf |
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| Zusammenfassung |
| This study examines the interaction of clay mineral particles and water vapor
for determining the conditions required for cloud droplet formation. Droplet
formation conditions are investigated for two common clay minerals, illite
and sodium-rich montmorillonite, and an industrially derived sample, Arizona
Test Dust. Using wet and dry particle generation coupled to a differential
mobility analyzer (DMA) and cloud condensation nuclei counter, the critical
activation of the clay mineral particles as cloud condensation nuclei is
characterized. Electron microscopy (EM) is used in order to determine non-sphericity
in particle shape. It is also used in order to determine particle surface area and
account for transmission of multiply charged particles by the DMA. Single
particle mass spectrometry and ion chromatography are used to investigate
soluble material in wet-generated samples and demonstrate that wet and dry
generation yield compositionally different particles. Activation results are
analyzed in the context of both κ-Köhler theory (κ-KT) and
Frenkel–Halsey–Hill (FHH) adsorption activation theory. This study has
two main results: (1) κ-KT is the suitable framework to describe clay
mineral nucleation activity. Apparent differences in κ with respect to
size arise from an artifact introduced by improper size-selection
methodology. For dust particles with mobility sizes larger than ~300 nm, i.e., ones that are within an atmospherically relevant size range,
both κ-KT and FHH theory yield similar critical supersaturations.
However, the former requires a single hygroscopicity parameter instead of the
two adjustable parameters required by the latter. For dry-generated
particles, the size dependence of κ is likely an artifact of the shape
of the size distribution: there is a sharp drop-off in particle concentration
at ~300 nm, and a large fraction of particles classified with
a mobility diameter less than ~300 nm are actually multiply
charged, resulting in a much lower critical supersaturation for droplet
activation than expected. For wet-generated particles, deviation from
κ-KT is likely a result of the dissolution and redistribution of
soluble material. (2) Wet generation is found to be unsuitable for simulating
the lofting of fresh dry dust because it changes the size-dependent critical
supersaturations by fractionating and re-partitioning soluble material. |
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