Size-resolved CCN distributions and activation kinetics of aged continental and marine aerosol 1Environmental Chemical Processes Laboratory, Department of Chemistry, University of Crete, Voutes, 71003, Heraklion, Greece
30 Aug 2011
2Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA
3Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
4Institute of Chemical Engineering and High Temperature Chemical Processes (ICE-HT), Foundation for Research and Technology Hellas (FORTH), Patras, 26504, Greece
5Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
Received: 15 March 2011 – Published in Atmos. Chem. Phys. Discuss.: 21 April 2011 Abstract. We present size-segregated measurements of cloud condensation nucleus (CCN)
activity of aged aerosol sampled at Finokalia, Crete, during the Finokalia
Aerosol Measurement Experiment of summer 2007 (FAME07). From analysis of the
data, hygroscopicity and activation kinetics distributions are derived. The
CCN are found to be highly hygroscopic, (expressed by a size- and time-
averaged hygroscopicity parameter κ ∼ 0.22), with the majority of
particles activating at ~0.5–0.6 % supersaturation. Air masses
originating from Central-Eastern Europe tend to be associated with higher
CCN concentrations and slightly lower hygroscopicity (κ ∼ 0.18) than for
other airmass types. The particles were always well mixed, as reflected by
the high activation ratios and narrow hygroscopicity distribution widths.
Smaller particles (~40 nm) were found to be more hygroscopic (~0.1κ units higher) than the larger ones (~100 nm). The particles with
diameters less than 80 nm exhibited a diurnal hygroscopicity cycle (with
κ peaking at ~14 h local time), consistent with photochemical aging
and volatilization of less hygroscopic material from the aerosol. Use of
bulk chemical composition and the aerosol number distribution results in
excellent CCN closure when applying Köhler theory in its simplest form.
Using asymptotic and threshold droplet growth analysis, the "aged"
organics present in the aerosol were found not to suppress or delay the
water uptake kinetics of particles in this environment.
Revised: 16 August 2011 – Accepted: 17 August 2011 – Published: 30 August 2011
Citation: Bougiatioti, A., Nenes, A., Fountoukis, C., Kalivitis, N., Pandis, S. N., and Mihalopoulos, N.: Size-resolved CCN distributions and activation kinetics of aged continental and marine aerosol, Atmos. Chem. Phys., 11, 8791-8808, doi:10.5194/acp-11-8791-2011, 2011.