Articles | Volume 10, issue 23
Atmos. Chem. Phys., 10, 11753–11767, 2010
https://doi.org/10.5194/acp-10-11753-2010
Atmos. Chem. Phys., 10, 11753–11767, 2010
https://doi.org/10.5194/acp-10-11753-2010

Research article 10 Dec 2010

Research article | 10 Dec 2010

The vapor pressures and activities of dicarboxylic acids reconsidered: the impact of the physical state of the aerosol

V. Soonsin1, A. A. Zardini2, C. Marcolli1, A. Zuend3, and U. K. Krieger1 V. Soonsin et al.
  • 1Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
  • 2Department of Chemistry, University of Copenhagen, Copenhagen, Denmark
  • 3Department of Chemical Engineering, California Institute of Technology, Pasadena, California, USA

Abstract. We present vapor pressure data of the C2 to C5 dicarboxylic acids deduced from measured evaporation rates of single levitated particles as both, aqueous droplets and solid crystals. The data of aqueous solution particles over a wide concentration range allow us to directly calculate activities of the dicarboxylic acids and comparison of these activities with parameterizations reported in the literature. The data of the pure liquid state acids, i.e. the dicarboxylic acids in their supercooled melt state, exhibit no even-odd alternation in vapor pressure, while the acids in the solid form do. This observation is consistent with the known solubilities of the acids and our measured vapor pressures of the supercooled melt. Thus, the gas/particle partitioning of the different dicarboxylic acids in the atmosphere depends strongly on the physical state of the aerosol phase, the difference being largest for the even acids.

Our results show also that, in general, measurements of vapor pressures of solid dicarboxylic acids may be compromised by the presence of polymorphic forms, crystalline structures with a high defect number, and/or solvent inclusions in the solid material, yielding a higher vapor pressure than the one of the thermodynamically stable crystalline form at the same temperature.

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