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Göran Frank

Director of graduate studies

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The size dependent composition of fog droplets


  • Paolo Laj
  • Sandro Fuzzi
  • Alberto Lazzari
  • Loretta Ricci
  • Giordano Orsi
  • Axel Berner
  • Ulrike Dusek
  • Dieter Schell
  • Armin Günther
  • Manfred Wendisch
  • Wolfram Wobrock
  • Göran Frank
  • Bengt G. Martinsson
  • Risto Hillamo

Summary, in English

The size dependency of fog droplet concentration and composition was studied using newly developed droplet impactors during the CHEMDROP campaign in the Po Valley (Italy). A strong size dependency of solute concentrations was measured during several fog episodes. The ionic strength of the droplet solutions varies as a function of droplet diameter, showing maximum values in the 9-19 μm diameter range. The solute concentration varies up to a factor of 10 among droplets of different diameter. Similarly, differences of up to 2 pH units are found among droplets of different diameter. The solute dependency of aerosol and droplets species from 0.1 μm to 50 μm is investigated. The monomodal behaviour of the solute concentration in droplets can be explained by both diffusional condensation of the aerosols serving as cloud condensation nuclei (CCN) and the air/liquid transfer of volatile species, in particular for HNO3 and NH3. The distribution of sulphur species is also size-dependent and is directly linked to the pH variations across the droplet spectrum, resulting in HMSA formation in small droplets and S(IV) oxidation large droplets.


  • Nuclear physics

Publishing year







Contributions to Atmospheric Physics





Document type

Journal article


Deutsche Meteorologische Gesellschaft / Friedr. Vieweg & Sohn Verlagsgesellschaft mbh


  • Ecology




  • ISSN: 0005-8173