Droplet activation, separation, and compositional analysis: laboratory studies and atmospheric measurements

Droplets produced in a cloud condensation nuclei chamber (CCNC) as a function of supersaturation have been separated from unactivated aerosol particles using counterflow virtual impaction. Residual material after droplet
Droplets produced in a cloud condensation nuclei chamber (CCNC) as a function of supersaturation have been separated from unactivated aerosol particles using counterflow virtual impaction. Residual material after droplets were evaporated was chemically analyzed with an Aerodyne Aerosol Mass Spectrometer (AMS) and the Particle Analysis by Laser Mass Spectrometry (PALMS) instrument. Experiments were initially conducted to verify activation conditions for monodisperse ammonium sulfate particles and to determine the resulting droplet size distribution as a function of supersaturation. Based on the observed droplet size, the counterflow virtual impactor cut-size was set to differentiate droplets from unactivated interstitial particles. Validation experiments were then performed to verify that only droplets with sufficient size passed through the counterflow virtual impactor for subsequent analysis. A two-component external mixture of monodisperse particles was also exposed to a supersaturation which would activate one of the types (hygroscopic salts) but not the other (polystyrene latex spheres or adipic acid). The mass spectrum observed after separation indicated only the former, validating separation of droplets from unactivated particles. Results from ambient measurements using this technique and AMS analysis were inconclusive, showing little chemical differentiation between ambient aerosol and activated droplet residuals, largely due to low signal levels. When employing as single particle mass spectrometer for compositional analysis, however, we observed enhancement of sulfate in droplet residuals.
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Metadaten
Author:Naruki Hiranuma, Monika Kohn, Mikhail S. Pekour, Danny A. Nelson, John E. Shilling, Daniel J. Cziczo
URN:urn:nbn:de:hebis:30:3-234745
DOI:http://dx.doi.org/10.5194/amt-4-2333-2011
ISSN:1867-8548
ISSN:1867-1381
Parent Title (English):Atmospheric measurement techniques
Publisher:Copernicus
Place of publication:Katlenburg-Lindau
Document Type:Article
Language:English
Date of Publication (online):2011/10/26
Date of first Publication:2011/10/26
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2011/12/04
Volume:4
Issue:10
Pagenumber:11
First Page:2333
Last Page:2343
Note:
© Author(s) 2011. This work is distributed under the Creative Commons Attribution 3.0 License.
HeBIS PPN:286867060
Institutes:Geowissenschaften
Dewey Decimal Classification:550 Geowissenschaften
Sammlungen:Universitätspublikationen
Licence (German):License LogoCreative Commons - Namensnennung 3.0

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