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| Titel |
The effect of fatty acid surfactants on the uptake of ozone to aqueous halogenide particles |
| VerfasserIn |
A. Rouvière, M. Ammann |
| 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 ; 10, no. 23 ; Nr. 10, no. 23 (2010-12-03), S.11489-11500 |
| Datensatznummer |
250008935
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| Publikation (Nr.) |
 copernicus.org/acp-10-11489-2010.pdf |
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| Zusammenfassung |
| The reactive uptake of ozone to deliquesced potassium iodide aerosol
particles coated with linear saturated fatty acids (C9, C12,
C15, C18 and C20) was studied. The experiments were performed
in an aerosol flow tube at 293 K and atmospheric pressure. The uptake
coefficient on pure deliquesced KI aerosol was γ = (1.10±0.20)×10−2
at 72–75% relative humidity. In presence of organic coatings,
the uptake coefficient decreased significantly for long straight chain
surfactants (≥C15), while it was only slightly reduced for the
short ones (C9, C12). We linked the kinetic results to the
monolayer properties of the surfactants, and specifically to the expected
phase state of the monolayer formed (liquid expanded or liquid condensed
state). The results showed a decrease of the uptake coefficient by 30%
for C12, 85% for C15 and 50% for C18 in presence of a
monolayer of a fatty acid at the equilibrium spreading pressure at the
air/water interface. The variation among C12, C15 and C18
follows the density of the monolayer at equilibrium spreading pressure,
which is highest for the C15 fatty acid. We also investigated the
effect of organic films to mixed deliquesced aerosol composed of a variable
mixture of KI and NaCl, which allowed determining the resistance exerted to
O3 at the aqueous surface by the two longer chained surfactants
pentadecanoic acid (C15) and stearic acid (C18). For these, the
probability that a molecule hitting the surface is actually transferred to
the aqueous phase underneath was βC15=6.8×10−4 and
βC18 = 3.3×10−4, respectively. Finally, the effect of
two-component coatings, consisting of a mixture of long and short chained
surfactants, was studied qualitatively. |
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