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| Titel |
Reactive processing of formaldehyde and acetaldehyde in aqueous aerosol mimics: surface tension depression and secondary organic products |
| VerfasserIn |
Z. Li, A. N. Schwier, N. Sareen, 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 ; 11, no. 22 ; Nr. 11, no. 22 (2011-11-22), S.11617-11629 |
| Datensatznummer |
250010209
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| Publikation (Nr.) |
 copernicus.org/acp-11-11617-2011.pdf |
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| Zusammenfassung |
| The reactive uptake of carbonyl-containing volatile organic compounds
(cVOCs) by aqueous atmospheric aerosols is a likely source of particulate
organic material. The aqueous-phase secondary organic products of some cVOCs
are surface-active. Therefore, cVOC uptake can lead to organic film
formation at the gas-aerosol interface and changes in aerosol surface
tension. We examined the chemical reactions of two abundant cVOCs,
formaldehyde and acetaldehyde, in water and aqueous ammonium sulfate (AS)
solutions mimicking tropospheric aerosols. Secondary organic products were
identified using Aerosol Chemical Ionization Mass Spectrometry
(Aerosol-CIMS), and changes in surface tension were monitored using pendant
drop tensiometry. Hemiacetal oligomers and aldol condensation products were
identified using Aerosol-CIMS. Acetaldehyde depresses surface tension to
65(±2) dyn cm−1 in pure water (a 10% surface tension reduction
from that of pure water) and 62(±1) dyn cm−1 in AS solutions (a
20.6% reduction from that of a 3.1 M AS solution). Surface tension
depression by formaldehyde in pure water is negligible; in AS solutions, a
9% reduction in surface tension is observed. Mixtures of these species
were also studied in combination with methylglyoxal in order to evaluate the
influence of cross-reactions on surface tension depression and product
formation in these systems. We find that surface tension depression in the
solutions containing mixed cVOCs exceeds that predicted by an additive model
based on the single-species isotherms. |
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