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| Titel |
Vapor wall deposition in Teflon chambers |
| VerfasserIn |
X. Zhang, R. H. Schwantes, R. C. McVay, H. Lignell, M. M. Coggon, R. C. Flagan, J. H. Seinfeld |
| 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 ; 15, no. 8 ; Nr. 15, no. 8 (2015-04-23), S.4197-4214 |
| Datensatznummer |
250119660
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| Publikation (Nr.) |
 copernicus.org/acp-15-4197-2015.pdf |
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| Zusammenfassung |
| Teflon chambers are ubiquitous in studies of atmospheric chemistry.
Secondary organic aerosol (SOA) formation can be underestimated, owing to
deposition of SOA-forming vapors to the chamber wall. We present here an
experimental protocol and a model framework to constrain the
vapor–wall interactions in Teflon chambers. We measured the wall deposition rates of 25
oxidized organic compounds generated from the photooxidation of isoprene,
toluene, α-pinene, and dodecane in two chambers that had been
extensively used and in two new unused chambers. We found that the extent of
prior use of the chamber did not significantly affect the sorption behavior
of the Teflon films. Among the 25 compounds studied, the maximum wall
deposition rate is exhibited by the most highly oxygenated and least
volatile compounds. By optimizing the model output to the observed vapor
decay profiles, we identified that the dominant parameter governing the
extent of wall deposition of a compound is its wall accommodation
coefficient (αwi), which can be correlated
through its volatility with the number of carbons and oxygens in the
molecule. By doing so, the wall-induced deposition rate of
intermediate/semi-volatile organic vapors can be reasonably predicted based
on their molecular constituency. The extent to which vapor wall
deposition impacts measured SOA yields depends on the competition between
uptake of organic vapors by suspended particles and the chamber wall. The
timescale associated with vapor wall deposition can vary from minutes to
hours depending on the value of αw,i. For
volatile and intermediate volatility organic compounds (small
αw,i), gas-particle partitioning will dominate
wall deposition for typical particle number concentrations in chamber
experiments. For compounds characterized by relatively large αw,i, vapor transport to particles is suppressed by competition
with the chamber wall even with perfect particle accommodation. |
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