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| Titel |
Experimental study of the role of physicochemical surface processing on the IN ability of mineral dust particles |
| VerfasserIn |
D. Niedermeier, S. Hartmann, T. Clauss, H. Wex, A. Kiselev, R. C. Sullivan, P. J. DeMott, M. D. Petters, P. Reitz, J. Schneider, E. Mikhailov, B. Sierau, O. Stetzer, B. Reimann, U. Bundke, R. A. Shaw, A. Buchholz, T. F. Mentel, F. Stratmann |
| 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. 21 ; Nr. 11, no. 21 (2011-11-09), S.11131-11144 |
| Datensatznummer |
250010178
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| Publikation (Nr.) |
 copernicus.org/acp-11-11131-2011.pdf |
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| Zusammenfassung |
| During the measurement campaign FROST 2 (FReezing Of duST 2), the
Leipzig Aerosol Cloud Interaction Simulator (LACIS) was used to
investigate the influence of various surface modifications on the
ice nucleating ability of Arizona Test Dust (ATD) particles in the
immersion freezing mode. The dust particles were exposed to sulfuric
acid vapor, to water vapor with and without the addition of ammonia
gas, and heat using a thermodenuder operating at 250 °C.
Size selected, quasi monodisperse particles with a mobility diameter
of 300 nm were fed into LACIS and droplets grew on these particles
such that each droplet contained a single particle. Temperature
dependent frozen fractions of these droplets were determined in
a temperature range between −40 °C ≤T≤−28 °C.
The pure ATD particles nucleated ice
over a broad temperature range with their freezing behavior being
separated into two freezing branches characterized through different
slopes in the frozen fraction vs. temperature curves. Coating the
ATD particles with sulfuric acid resulted in the particles' IN
potential significantly decreasing in the first freezing branch
(T>−35 °C) and a slight increase in the second branch
(T≤−35 °C). The addition of water vapor after
the sulfuric acid coating caused the disappearance of the first
freezing branch and a strong reduction of the IN ability in the
second freezing branch. The presence of ammonia gas during water
vapor exposure had a negligible effect on the particles' IN ability
compared to the effect of water vapor. Heating in the thermodenuder
led to a decreased IN ability of the sulfuric acid coated particles
for both branches but the additional heat did not or only slightly
change the IN ability of the pure ATD and the water vapor exposed
sulfuric acid coated particles. In other words, the combination of
both sulfuric acid and water vapor being present is a main cause for
the ice active surface features of the ATD particles being
destroyed. A possible explanation could be the chemical
transformation of ice active metal silicates to metal sulfates. The
strongly enhanced reaction between sulfuric acid and dust in the
presence of water vapor and the resulting significant reductions in
IN potential are of importance for atmospheric ice cloud formation.
Our findings suggest that the IN concentration can decrease by up to
one order of magnitude for the conditions investigated. |
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