TY  - JOUR
A1  - Hiranuma, Naruki
A1  - Kohn, Monika
A1  - Pekour, Mikhail S.
A1  - Nelson, Danny A.
A1  - Shilling, John E.
A1  - Cziczo, Daniel J.
T1  - Droplet activation, separation, and compositional analysis: laboratory studies and atmospheric measurements [Discussion paper]
T2  - Atmospheric measurement techniques discussions
N2  - 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.
Y1  - 2011
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/23476
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-234765
SN  - 1867-8610
VL  - 4
SP  - 691
EP  - 713
PB  - Copernicus
CY  - Katlenburg-Lindau
ER  -