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| Titel |
A combined particle trap/HTDMA hygroscopicity study of mixed inorganic/organic aerosol particles |
| VerfasserIn |
A. A. Zardini, S. Sjogren, C. Marcolli, U. K. Krieger, M. Gysel, E. Weingärtner, U. Baltensperger, T. Peter |
| 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 ; 8, no. 18 ; Nr. 8, no. 18 (2008-09-19), S.5589-5601 |
| Datensatznummer |
250006386
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| Publikation (Nr.) |
 copernicus.org/acp-8-5589-2008.pdf |
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| Zusammenfassung |
| Atmospheric aerosols are often mixtures of inorganic and organic material.
Organics can represent a large fraction of the total aerosol mass and are
comprised of water-soluble and insoluble compounds. Increasing attention was
paid in the last decade to the capability of mixed inorganic/organic aerosol
particles to take up water (hygroscopicity). We performed hygroscopicity
measurements of internally mixed particles containing ammonium sulfate and
carboxylic acids (citric, glutaric, adipic acid) in parallel with an
electrodynamic balance (EDB) and a hygroscopicity tandem differential
mobility analyzer (HTDMA). The organic compounds were chosen to represent
three distinct physical states. During hygroscopicity cycles covering
hydration and dehydration measured by the EDB and the HTDMA, pure citric acid
remained always liquid, adipic acid remained always solid, while glutaric
acid could be either. We show that the hygroscopicity of mixtures of the
above compounds is well described by the Zdanovskii-Stokes-Robinson (ZSR)
relationship as long as the two-component particle is completely liquid in
the ammonium sulfate/glutaric acid system; deviations up to 10% in mass
growth factor (corresponding to deviations up to 3.5% in size growth factor)
are observed for the ammonium sulfate/citric acid 1:1 mixture at 80% RH. We
observe even more significant discrepancies compared to what is expected from
bulk thermodynamics when a solid component is present. We explain this in
terms of a complex morphology resulting from the crystallization process
leading to veins, pores, and grain boundaries which allow for water sorption
in excess of bulk thermodynamic predictions caused by the inverse Kelvin
effect on concave surfaces. |
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