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| Titel |
Density changes of aerosol particles as a result of chemical reaction |
| VerfasserIn |
Y. Katrib, S. T. Martin, Y. Rudich, P. Davidovits, J. T. Jayne, D. R. Worsnop |
| 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 ; 5, no. 1 ; Nr. 5, no. 1 (2005-02-03), S.275-291 |
| Datensatznummer |
250002222
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| Publikation (Nr.) |
 copernicus.org/acp-5-275-2005.pdf |
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| Zusammenfassung |
| This paper introduces the capability to study simultaneously changes in the
density, the chemical composition, the mobility diameter, the aerodynamic
diameter, and the layer thickness of multi-layered aerosol particles as they
are being altered by heterogeneous chemical reactions. A
vaporization-condensation method is used to generate aerosol particles
composed of oleic acid outer layers of 2 to 30nm on 101-nm polystyrene
latex cores. The layer density is modified by reaction of oleic acid with
ozone for variable exposure times. For increasing ozone exposure, the
mobility diameter decreases while the vacuum aerodynamic diameter increases,
which, for spherical particles, implies that particle density increases. The
aerosol particles are confirmed as spherical based upon the small divergence
of the particle beam in the aerosol mass spectrometer. The particle and
layer densities are calculated by two independent methods, namely one based
on the measured aerodynamic and mobility diameters and the other based on
the measured mobility diameter and particle mass. The uncertainty estimates
for density calculated by the second method are two to three times greater
than those of the first method. Both methods indicate that the layer density
increases from 0.89 to 1.12g·cm-3 with increasing ozone
exposure. Aerosol mass spectrometry shows that, concomitant with the
increase in the layer density, the oxygen content of the reacted layer
increases. Even after all of the oleic acid has reacted, the layer density
and the oxygen content continue to increase slowly with prolonged ozone
exposure, a finding which indicates continued chemical reactions of the
organic products either with ozone or with themselves. The results of this
paper provide new insights into the complex changes occurring for
atmospheric particles during the aging processes caused by gas-phase
oxidants. |
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