Measurement of the ambient organic aerosol volatility distribution: application during the Finokalia Aerosol Measurement Experiment (FAME-2008) 1Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
21 Dec 2010
2Department of Chemical Engineering, University of Patras, Patra, Greece
3Institute of Chemical Engineering and High Temperature Chemical Processes, ICE-HT, Patra, Greece
4Department of Physics, University of Helsinki, Helsinki, Finland
5Paul Scherrer Institute, Laboratory of Atmospheric Chemistry, 5232 Villigen, Switzerland
6University of Crete, Department of Chemistry, Heraklion, Greece
Received: 16 Jun 2010 – Published in Atmos. Chem. Phys. Discuss.: 20 Jul 2010Abstract. A variable residence time thermodenuder (TD) was combined with an Aerodyne
Aerosol Mass Spectrometer (AMS) and a Scanning Mobility Particle Sizer
(SMPS) to measure the volatility distribution of aged organic aerosol in the
Eastern Mediterranean during the Finokalia Aerosol Measurement Experiment in
May of 2008 (FAME-2008). A new method for the quantification of the organic
aerosol volatility distribution was developed combining measurements of all
three instruments together with an aerosol dynamics model.
Revised: 10 Nov 2010 – Accepted: 02 Dec 2010 – Published: 21 Dec 2010
Challenges in the interpretation of ambient thermodenuder-AMS measurements
include the potential resistances to mass transfer during particle
evaporation, the effects of particle size on the evaporated mass fraction,
the changes in the AMS collection efficiency and particle density as the
particles evaporate partially in the TD, and finally potential losses inside
the TD. Our proposed measurement and data analysis method accounts for all
of these problems combining the AMS and SMPS measurements.
The AMS collection efficiency of the aerosol that passed through the TD was
found to be approximately 10% lower than the collection efficiency of the
aerosol that passed through the bypass. The organic aerosol measured at
Finokalia is approximately 2 or more orders of magnitude less volatile than
fresh laboratory-generated monoterpene (α-pinene, β-pinene
and limonene under low NOx conditions) secondary organic aerosol. This
low volatility is consistent with its highly oxygenated AMS mass spectrum.
The results are found to be highly sensitive to the mass accommodation
coefficient of the evaporating species. This analysis is
based on the assumption that there were no significant reactions taking
place inside the thermodenuder.
Citation: Lee, B. H., Kostenidou, E., Hildebrandt, L., Riipinen, I., Engelhart, G. J., Mohr, C., DeCarlo, P. F., Mihalopoulos, N., Prevot, A. S. H., Baltensperger, U., and Pandis, S. N.: Measurement of the ambient organic aerosol volatility distribution: application during the Finokalia Aerosol Measurement Experiment (FAME-2008), Atmos. Chem. Phys., 10, 12149-12160, doi:10.5194/acp-10-12149-2010, 2010.