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| Titel |
Single-particle characterization of ice-nucleating particles and ice particle residuals sampled by three different techniques |
| VerfasserIn |
A. Worringen, K. Kandler, N. Benker, T. Dirsch, S. Mertes, L. Schenk, U. Kästner, F. Frank, B. Nillius, U. Bundke, D. Rose, J. Curtius, P. Kupiszewski, E. Weingärtner, P. Vochezer, J. Schneider, S. Schmidt, S. Weinbruch, M. Ebert |
| 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. 8 ; Nr. 15, no. 8 (2015-04-22), S.4161-4178 |
| Datensatznummer |
250119658
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| Publikation (Nr.) |
 copernicus.org/acp-15-4161-2015.pdf |
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| Zusammenfassung |
| In the present work, three different techniques to separate ice-nucleating
particles (INPs) as well as ice particle residuals (IPRs) from non-ice-active
particles are compared. The Ice Selective Inlet (ISI) and the Ice Counterflow
Virtual Impactor (Ice-CVI) sample ice particles from mixed-phase clouds and
allow after evaporation in the instrument for the analysis of the residuals.
The Fast Ice Nucleus Chamber (FINCH) coupled with the Ice Nuclei Pumped
Counterflow Virtual Impactor (IN-PCVI) provides ice-activating conditions to
aerosol particles and extracts the activated particles for analysis. The
instruments were run during a joint field campaign which took place in
January and February 2013 at the High Alpine Research Station Jungfraujoch
(Switzerland). INPs and IPRs were analyzed offline by scanning electron
microscopy and energy-dispersive X-ray microanalysis to determine their size,
chemical composition and mixing state. Online analysis of the size and
chemical composition of INP activated in FINCH was performed by laser
ablation mass spectrometry. With all three INP/IPR separation techniques high
abundances (median 20–70%) of instrumental contamination artifacts were
observed (ISI: Si-O spheres, probably calibration aerosol; Ice-CVI: Al-O
particles; FINCH + IN-PCVI: steel particles). After removal of the
instrumental contamination particles, silicates, Ca-rich particles,
carbonaceous material and metal oxides were the major INP/IPR particle types
obtained by all three techniques. In addition, considerable amounts (median
abundance mostly a few percent) of soluble material (e.g., sea salt,
sulfates) were observed. As these soluble particles are often not expected to
act as INP/IPR, we consider them as potential measurement artifacts. Minor
types of INP/IPR include soot and Pb-bearing particles. The Pb-bearing
particles are mainly present as an internal mixture with other particle
types. Most samples showed a maximum of the INP/IPR size distribution at
200–400 nm in geometric diameter. In a few cases, a second supermicron
maximum was identified. Soot/carbonaceous material and metal oxides were
present mainly in the sub-micrometer range. Silicates and Ca-rich particles
were mainly found with diameters above 1 μm (using ISI and FINCH),
in contrast to the Ice-CVI which also sampled many submicron particles of
both groups. Due to changing meteorological conditions, the INP/IPR
composition was highly variable if different samples were compared. Thus, the
observed discrepancies between the different separation techniques may partly
result from the non-parallel sampling. The differences of the particle group
relative number abundance as well as the mixing state of INP/IPR clearly
demonstrate the need of further studies to better understand the influence of
the separation techniques on the INP/IPR chemical composition. Also, it must
be concluded that the abundance of contamination artifacts in the separated
INP and IPR is generally large and should be corrected for, emphasizing the
need for the accompanying chemical measurements. Thus, further work is needed
to allow for routine operation of the three separation techniques
investigated. |
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