Atmospheric Chemistry and Physics Discussions
ACPD 12, 4447–4476, 2012
Phase state of SOA
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Atmos. Chem. Phys. Discuss., 12, 4447–4476, 2012 www.atmos-chem-phys-discuss.net/12/4447/2012/ doi:10.5194/acpd-12-4447-2012 © Author(s) 2012. CC Attribution 3.0 License.
E. Saukko et al.
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Department of Physics, Tampere University of Technology, Tampere, Finland Chemistry Department, Boston College, Chestnut Hill, MA, USA 3 Aerodyne Research Inc., Billerica, MA, USA 4 Faculty of Chemistry, Bielefeld University, Bielefeld, Germany 5 Finnish Meteorological Institute, Helsinki, Finland 6 Department of Applied Physics, University of Eastern Finland, Kuopio, Finland 7 Division of Atmospheric Sciences, Department of Physics, University of Helsinki, Helsinki, Finland * ´ now at: Faculty of Mathematics, Astronomy and Physics, National University of Cordoba, ´ Cordoba, Argentina 2
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E. Saukko , A. T. Lambe , P. Massoli , Koop, T. , J. P. Wright , 2 4,* 2,3 5,6 D. R. Croasdale , D. A. Pedernera , T. B. Onasch , A. Laaksonen , 2 3,7 1,** P. Davidovits , D. R. Worsnop , and A. Virtanen
Discussion Paper
Humidity-dependent phase state of SOA particles from biogenic and anthropogenic precursors
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now at: Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
Received: 22 December 2011 – Accepted: 28 January 2012 – Published: 8 February 2012 Correspondence to: A. Virtanen (
[email protected])
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ACPD 12, 4447–4476, 2012
Phase state of SOA
| E. Saukko et al. Discussion Paper
Published by Copernicus Publications on behalf of the European Geosciences Union.
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Phase state of SOA
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12, 4447–4476, 2012
E. Saukko et al. Discussion Paper
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ACPD
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The physical phase state (solid, semi-solid, or liquid) of secondary organic aerosol (SOA) particles has important implications for a number of atmospheric processes. We report the phase state of SOA particles spanning a wide range of oxygen to carbon ratios (O/C), used here as a surrogate for SOA oxidation level, produced in a flow tube reactor by photo-oxidation of various atmospherically relevant surrogate anthropogenic and biogenic volatile organic compounds (VOCs). The phase state of laboratory-generated SOA was determined by the particle bounce behavior after inertial impaction on a polished steel substrate. The measured bounce fraction was evaluated as a function of relative humidity and SOA oxidation level (O/C) measured by an Aerodyne high resolution time of flight aerosol mass spectrometer (HR-ToF AMS). The main findings of the study are: (1) Biogenic and anthropogenic SOA particles are found to be solid or semi-solid until a relative humidity of at least 50 % RH at impaction is reached. (2) Long-chain alkanes produce liquid SOA particles when generated at low oxidation level of O/C
