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| Titel |
Inorganic salts interact with oxalic acid in submicron particles to form material with low hygroscopicity and volatility |
| VerfasserIn |
G. Drozd, J. Woo, S. A. K. Häkkinen, A. Nenes, V. F. McNeill |
| 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. 10 ; Nr. 14, no. 10 (2014-05-27), S.5205-5215 |
| Datensatznummer |
250118738
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| Publikation (Nr.) |
 copernicus.org/acp-14-5205-2014.pdf |
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| Zusammenfassung |
| Volatility and hygroscopicity are two key properties of organic aerosol
components, and both are strongly related to chemical identity. While the
hygroscopicities of pure salts, di-carboxylic acids (DCA), and DCA salts are
known, the hygroscopicity of internal mixtures of these components, as they
are typically found in the atmosphere, has not been fully characterized. Here
we show that inorganic–organic component interactions typically not
considered in atmospheric models can lead to very strongly bound
metal–organic complexes and greatly affect aerosol volatility and
hygroscopicity; in particular, the bi-dentate binding of DCA to soluble
inorganic ions. We have studied the volatility of pure, dry organic salt
particles and the hygroscopicity of internal mixtures of oxalic acid (OxA,
the dominant DCA in the atmosphere) and a number of salts, both mono- and
di-valent. The formation of very low volatility organic salts was confirmed,
with minimal evaporation of oxalate salt particles below 75 °C.
Dramatic increases in the cloud condensation nuclei (CCN) activation diameter for particles with di-valent
salts (e.g., CaCl2) and relatively small particle volume fractions of OxA
indicate that standard volume additivity rules for hygroscopicity do not
apply. Thus small organic compounds with high O : C ratios are capable of
forming low-volatility and very low hygroscopicity particles. Given current
knowledge of the formation mechanisms of OxA and M–Ox salts, surface
enrichment of insoluble M–Ox salts is expected. The resulting formation of an
insoluble coating of metal-oxalate salts can explain low-particle
hygroscopicities. The formation of particles with a hard coating could offer
an alternative explanation for observations of glass-like particles without
the need for a phase transition. |
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