Droplet activation, separation, and compositional analysis: laboratory studies and atmospheric measurements [Discussion paper]

Droplets produced in a cloud condensation nucleus chamber as a function of supersaturation have been separated from unactivated aerosol particles using counterflow virtual impaction. Residual material after droplets were
Droplets produced in a cloud condensation nucleus chamber 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 and the Particle Analysis by Laser Mass Spectrometry 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 (ammonium sulfate) but not the other (polystyrene latex spheres). The mass spectrum observed after separation indicated only the former, validating separation of droplets from unactivated particles. Results from atmospheric measurements using this technique indicate that aerosol particles often activate predominantly as a function of particle size. Chemical composition is not irrelevant, however, and we observed enhancement of sulfate in droplet residuals using single particle analysis.
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Author:Naruki Hiranuma, Monika Kohn, Mikhail S. Pekour, Danny A. Nelson, John E. Shilling, Daniel J. Cziczo
URN:urn:nbn:de:hebis:30:3-234765
DOI:http://dx.doi.org/10.5194/amtd-4-691-2011
ISSN:1867-8610
Parent Title (English):Atmospheric measurement techniques discussions
Publisher:Copernicus
Place of publication:Katlenburg-Lindau
Document Type:Article
Language:English
Date of Publication (online):2011/01/24
Date of first Publication:2011/01/24
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2011/12/04
Volume:4
Pagenumber:12
First Page:691
Last Page:713
HeBIS PPN:286873559
Institutes:Geowissenschaften
Dewey Decimal Classification:550 Geowissenschaften
Sammlungen:Universitätspublikationen
Licence (German):License LogoCreative Commons - Namensnennung 3.0

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