Articles | Volume 17, issue 14
Atmos. Chem. Phys., 17, 8923–8938, 2017

Special issue: The CERN CLOUD experiment (ACP/AMT inter-journal SI)

Atmos. Chem. Phys., 17, 8923–8938, 2017

Research article 25 Jul 2017

Research article | 25 Jul 2017

Evaporation of sulfate aerosols at low relative humidity

Georgios Tsagkogeorgas1, Pontus Roldin2,3, Jonathan Duplissy2,4, Linda Rondo5, Jasmin Tröstl6, Jay G. Slowik6, Sebastian Ehrhart5,a, Alessandro Franchin2, Andreas Kürten5, Antonio Amorim7, Federico Bianchi2, Jasper Kirkby5,8, Tuukka Petäjä2, Urs Baltensperger6, Michael Boy2, Joachim Curtius5, Richard C. Flagan9, Markku Kulmala2,4, Neil M. Donahue10, and Frank Stratmann1 Georgios Tsagkogeorgas et al.
  • 1Leibniz Institute for Tropospheric Research, 04318 Leipzig, Germany
  • 2Department of Physics, University of Helsinki, P.O. Box 64, 00014 Helsinki, Finland
  • 3Division of Nuclear Physics, Lund University, P.O. Box 118, 221 00 Lund, Sweden
  • 4Helsinki Institute of Physics, University of Helsinki, P.O. Box 64, 00014 Helsinki, Finland
  • 5Institute for Atmospheric and Environmental Sciences, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany
  • 6Paul Scherrer Institute, 5232 Villigen, Switzerland
  • 7Fac. Ciencias & CENTRA, Universidade de Lisboa, Campo Grande, 1749–016 Lisbon, Portugal
  • 8CERN, 1211 Geneva, Switzerland
  • 9California Institute of Technology, Pasadena, CA 91125, USA
  • 10Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA 15213, USA
  • anow at: Atmospheric Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany

Abstract. Evaporation of sulfuric acid from particles can be important in the atmospheres of Earth and Venus. However, the equilibrium constant for the dissociation of H2SO4 to bisulfate ions, which is the one of the fundamental parameters controlling the evaporation of sulfur particles, is not well constrained. In this study we explore the volatility of sulfate particles at very low relative humidity. We measured the evaporation of sulfur particles versus temperature and relative humidity in the CLOUD chamber at CERN. We modelled the observed sulfur particle shrinkage with the ADCHAM model. Based on our model results, we conclude that the sulfur particle shrinkage is mainly governed by H2SO4 and potentially to some extent by SO3 evaporation. We found that the equilibrium constants for the dissociation of H2SO4 to HSO4(KH2SO4) and the dehydration of H2SO4 to SO3 (xKSO3) are KH2SO4 = 2–4 × 109 mol kg−1 and xKSO3 ≥  1.4  ×  1010 at 288.8 ± 5 K.

Short summary
The H2SO4 vapour pressure plays key role in Earth's and Venus' atmospheres. In regions where RH is low and stabilising bases are scarce, H2SO4 can evaporate from particles; however the H2SO4 vapour pressure at low RH is uncertain. To address this, we measured H2SO4 evaporation versus T and RH in the CLOUD chamber and constrained the equilibrium constants for dissociation and dehydration of H2SO4. This study is important for nucleation, particle growth and H2SO4 formation occurring in atmosphere.
Final-revised paper