Articles | Volume 15, issue 18
Atmos. Chem. Phys., 15, 10701–10721, 2015

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

Atmos. Chem. Phys., 15, 10701–10721, 2015

Research article 25 Sep 2015

Research article | 25 Sep 2015

Thermodynamics of the formation of sulfuric acid dimers in the binary (H2SO4–H2O) and ternary (H2SO4–H2O–NH3) system

A. Kürten1, S. Münch1, L. Rondo1, F. Bianchi2,3, J. Duplissy4,a, T. Jokinen5, H. Junninen5, N. Sarnela5, S. Schobesberger5,b, M. Simon1, M. Sipilä5, J. Almeida4, A. Amorim6, J. Dommen2, N. M. Donahue7, E. M. Dunne8,c, R. C. Flagan9, A. Franchin5, J. Kirkby1,4, A. Kupc10, V. Makhmutov11, T. Petäjä5, A. P. Praplan2,5,d, F. Riccobono2,e, G. Steiner5,12,f, A. Tomé6, G. Tsagkogeorgas13, P. E. Wagner10, D. Wimmer1,a, U. Baltensperger2, M. Kulmala5, D. R. Worsnop5,14, and J. Curtius1 A. Kürten et al.
  • 1Institute for Atmospheric and Environmental Sciences, Goethe University Frankfurt am Main, Frankfurt am Main, Germany
  • 2Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen, Switzerland
  • 3Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
  • 4CERN (European Organization for Nuclear Research), Geneva, Switzerland
  • 5Department of Physics, University of Helsinki, Helsinki, Finland
  • 6Laboratory for Systems, Instrumentation, and Modeling in Science and Technology for Space and the Environment (SIM), University of Lisbon and University of Beira Interior, Lisbon, Portugal
  • 7Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, USA
  • 8School of Earth and Environment, University of Leeds, Leeds, UK
  • 9Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, USA
  • 10Aerosol Physics and Environmental Physics, University of Vienna, Vienna, Austria
  • 11Solar and Cosmic Ray Research Laboratory, Lebedev Physical Institute, Moscow, Russia
  • 12Ion Physics and Applied Physics, University of Innsbruck, Innsbruck, Austria
  • 13Leibniz Institute for Tropospheric Research, Leipzig, Germany
  • 14Aerodyne Research Incorporated, Billerica, MA, USA
  • anow at: Helsinki Institute of Physics, University of Helsinki, Helsinki, Finland
  • bnow at: Department of Atmospheric Sciences, University of Washington, Seattle, USA
  • cnow at: Finnish Meteorological Institute, Kuopio, Finland
  • dnow at: Finnish Meteorological Institute, Helsinki, Finland
  • enow at: Joint Research Centre, European Commission, Ispra, Italy
  • fnow at: Faculty of Physics, University of Vienna, Vienna, Austria

Abstract. Sulfuric acid is an important gas influencing atmospheric new particle formation (NPF). Both the binary (H2SO4–H2O) system and the ternary system involving ammonia (H2SO4–H2O–NH3) may be important in the free troposphere. An essential step in the nucleation of aerosol particles from gas-phase precursors is the formation of a dimer, so an understanding of the thermodynamics of dimer formation over a wide range of atmospheric conditions is essential to describe NPF. We have used the CLOUD chamber to conduct nucleation experiments for these systems at temperatures from 208 to 248 K. Neutral monomer and dimer concentrations of sulfuric acid were measured using a chemical ionization mass spectrometer (CIMS). From these measurements, dimer evaporation rates in the binary system were derived for temperatures of 208 and 223 K. We compare these results to literature data from a previous study that was conducted at higher temperatures but is in good agreement with the present study. For the ternary system the formation of H2SO4·NH3 is very likely an essential step in the formation of sulfuric acid dimers, which were measured at 210, 223, and 248 K. We estimate the thermodynamic properties (dH and dS) of the H2SO4·NH3 cluster using a simple heuristic model and the measured data. Furthermore, we report the first measurements of large neutral sulfuric acid clusters containing as many as 10 sulfuric acid molecules for the binary system using chemical ionization–atmospheric pressure interface time-of-flight (CI-APi-TOF) mass spectrometry.

Short summary
New particle formation (NPF) is an important atmospheric process. At cold temperatures in the upper troposphere the binary (H2SO4-H2O) and ternary (H2SO4-H2O-NH3) system are thought to be important for NPF. Sulfuric acid monomer (H2SO4) and sulfuric acid dimer ((H2SO4)2) concentrations were measured between 208 and 248K for these systems and dimer evaporation rates were derived. These data will help to better understand and predict binary and ternary nucleation at low temperatures.
Final-revised paper