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| Titel |
Viscosity controls humidity dependence of N2O5 uptake to citric acid aerosol |
| VerfasserIn |
G. Grzinic, T. Bartels-Rausch, T. Berkemeier, A. Türler, 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 ; 15, no. 23 ; Nr. 15, no. 23 (2015-12-09), S.13615-13625 |
| Datensatznummer |
250120214
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| Publikation (Nr.) |
 copernicus.org/acp-15-13615-2015.pdf |
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| Zusammenfassung |
| The heterogeneous loss of dinitrogen pentoxide (N2O5) to aerosol
particles has a significant impact on the night-time nitrogen oxide cycle
and therefore the oxidative capacity in the troposphere. Using a 13N
short-lived radioactive tracer method, we studied the uptake kinetics of
N2O5 on citric acid aerosol particles as a function of relative
humidity (RH). The results show that citric acid exhibits lower reactivity
than similar dicarboxylic and polycarboxylic acids, with uptake coefficients between
∼ 3 × 10-4–∼ 3 × 10-3 depending on
humidity (17–70 % RH). At RH above 50 %, the magnitude and the humidity
dependence can be best explained by the viscosity of citric acid as compared
to aqueous solutions of simpler organic and inorganic solutes and the
variation of viscosity with RH and, hence, diffusivity in the organic
matrix. Since the diffusion rates of N2O5 in highly concentrated
citric acid solutions are not well established, we present four different
parameterizations of N2O5 diffusivity based on the available
literature data or estimates for viscosity and diffusivity of H2O.
Above 50 % RH, uptake is consistent with the reacto-diffusive kinetic
regime whereas below 50 % RH, the uptake coefficient is higher than
expected from hydrolysis of N2O5 within the bulk of the particles,
and the uptake kinetics is most likely limited by loss on the surface only.
This study demonstrates the impact of viscosity in highly oxidized and
highly functionalized secondary organic aerosol material on the
heterogeneous chemistry of N2O5 and may explain some of the
unexpectedly low loss rates to aerosol derived from field studies. |
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