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| Titel |
Ammonium nitrate evaporation and nitric acid condensation in DMT CCN counters |
| VerfasserIn |
S. Romakkaniemi, A. Jaatinen, A. Laaksonen, A. Nenes, T. Raatikainen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 7, no. 5 ; Nr. 7, no. 5 (2014-05-20), S.1377-1384 |
| Datensatznummer |
250115762
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| Publikation (Nr.) |
 copernicus.org/amt-7-1377-2014.pdf |
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| Zusammenfassung |
The effect of inorganic semivolatile aerosol compounds on the cloud
condensation nucleus (CCN) activity of aerosol particles was studied by
using a computational model for a DMT-CCN counter, a cloud parcel model for
condensation kinetics and experiments to quantify the modelled results.
Concentrations of water vapour and semivolatiles as well as aerosol
trajectories in the CCN column were calculated by a computational fluid
dynamics model. These trajectories and vapour concentrations were then used
as an input for the cloud parcel model to simulate mass transfer kinetics of
water and semivolatiles between aerosol particles and the gas phase.
Two different questions were studied: (1) how big a fraction of
semivolatiles is evaporated from particles after entering but before
particle activation in the DMT-CCN counter? (2) How much can the CCN activity
be increased due to condensation of semivolatiles prior to the maximum
water supersaturation in the case of high semivolatile concentration in the
gas phase?
Both experimental and modelling results show that the evaporation of ammonia
and nitric acid from ammonium nitrate particles causes a 10 to 15 nm
decrease to the critical particle size in supersaturations between 0.1%
and 0.7%. On the other hand, the modelling results also show that
condensation of nitric acid or similar vapour can increase the CCN activity
of nonvolatile aerosol particles, but a very high gas phase concentration
(as compared to typical ambient conditions) would be needed. Overall, it is
more likely that the CCN activity of semivolatile aerosol is underestimated
than overestimated in the measurements conducted in ambient conditions. |
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