AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Quantitative Particle Sizing in the Cluster-particle Transition Region during new Particle Formation
DOMINIK STOLZENBURG, Katrianne Lehtipalo, Robert Wagner, Paul M. Winkler, University of Vienna
Abstract Number: 168 Working Group: Aerosol Physics
Abstract New particle formation and subsequent nanoparticle growth is frequently observed in the atmosphere (Kulmala et al. (2004), J. Aerosol Sci. 35, 143-176). The dynamics of the aerosol population determines the impact of new particle formation on the global budget of cloud condensation nuclei (Weber et al. (1997), J. Geophys. Res. 102, 4375). However, high particle losses and low detection efficiencies have limited the precision of size-distribution measurements in the critical sub-10nm range.
Here we present the first results from a newly developed Differential Mobility Analyser – train (DMA-train) operating six DMAs together with six ultrafine nanoparticle detectors in parallel. The DMA-train was used to track new particle formation events in the CLOUD chamber at CERN (Duplissy et al. (2016). J. Geophys. Res. Atmos., 121, and references therein) during a 12-week intensive campaign in fall 2015. While a particle size magnifier operated in scanning-mode (Airmodus A11) was used to measure the very initial growth, and a fast-scanning nanoSMPS (TSI 3938) monitored the size-distributions from about 5 nm onwards, a gap was left in the crucial 2-5nm size range, where clusters become aerosol particles. Intercomparison of the three instruments shows, that the DMA-train perfectly fills the gap, due to its excellent counting statistics achieved by measuring fixed particle sizes in distinct channels.
With this unprecedented array of instruments, the quantification of both neutral and charged particle growth from 1 to 60 nm in the presence of highly oxidised biogenic vapours, sulphuric acid and ammonia becomes possible. We will present the most detailed and precise particle growth rate measurements so far obtained in CLOUD. We are now at a stage where we can perform quantitative growth law-analysis (Rao and McMurry (1989), Aerosol Sci. Tech. 11:2, 120-132) and compare nanoparticle evolution to model simulations over the full size range.