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| Titel |
Irreversible loss of ice nucleation active sites in mineral dust particles caused by sulphuric acid condensation |
| VerfasserIn |
R. C. Sullivan, M. D. Petters, P. J. DeMott, S. M. Kreidenweis, H. Wex, D. Niedermeier, S. Hartmann, T. Clauss, F. Stratmann, P. Reitz, J. Schneider, B. Sierau |
| 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.11471-11487 |
| Datensatznummer |
250008934
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| Publikation (Nr.) |
 copernicus.org/acp-10-11471-2010.pdf |
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| Zusammenfassung |
| During the FROST-2 (FReezing Of duST) measurement campaign conducted at the
Leipzig Aerosol Cloud Interaction Simulator (LACIS), we investigated changes
in the ice nucleation properties of 300 nm Arizona Test Dust mineral
particles following thermochemical processing by varying amounts and
combinations of exposure to sulphuric acid vapour, ammonia gas, water
vapour, and heat. The processed particles' heterogeneous ice nucleation
properties were determined in both the water subsaturated and supersaturated
humidity regimes at −30 °C and −25 °C using Colorado State
University's continuous flow diffusion chamber. The amount of sulphuric acid
coating material was estimated by an aerosol mass spectrometer and from
CCN-derived hygroscopicity measurements. The condensation of sulphuric acid
decreased the dust particles' ice nucleation ability in proportion to the
amount of sulphuric acid added. Heating the coated particles in a
thermodenuder at 250 °C – intended to evaporate the sulphuric acid
coating – reduced their freezing ability even further. We attribute this
behaviour to accelerated acid digestion of ice active surface sites by heat.
Exposing sulphuric acid coated dust to ammonia gas produced particles with
similarly poor freezing potential; however a portion of their ice nucleation
ability could be restored after heating in the thermodenuder. In no case did
any combination of thermochemical treatments increase the ice nucleation
ability of the coated mineral dust particles compared to unprocessed dust.
These first measurements of the effect of identical chemical processing of
dust particles on their ice nucleation ability under both water subsaturated
and mixed-phase supersaturated cloud conditions revealed that ice nucleation
was more sensitive to all coating treatments in the water subsaturated
regime. The results clearly indicate irreversible impairment of ice
nucleation activity in both regimes after condensation of concentrated
sulphuric acid. This implies that the sulphuric acid coating caused
permanent chemical and/or physical modification of the ice active surface
sites; the possible dissolution of the coating during droplet activation did
not restore all immersion/condensation-freezing ability. |
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