Journal of Atmospheric Chemistry

, Volume 21, Issue 2, pp 97–114 | Cite as

The oxidation of S(IV) during riming by cloud droplets

  • J. V. Iribarne
  • L. A. Barrie


Experiments have been performed to investigate whether the process of freezing during riming in clouds may induce oxidation of dissolved SO2 to SO 4 2− . The experiments were conducted in a cold room at varying temperatures between −6 and −15 °C. Solutions containing dissolved SO2 and NH4OH in various proportions, in the range of concentrations between 3×10−5 and 10−3 M, were sprayed. Rime was collected on a rotating cylinder and analyzed. Absorption of oxygen from laboratory air was prevented, except in the spray, to avoid spurious oxidation. Blank experiments were made at +3 to +6 °C. The results indicate clearly that, as the dominant cation becomes NH 4 + rather than H+, substantial oxidation of S(IV) occurs during riming. This is consistent with redox reactions taking place as a result of charge separation at the ice-water interface during freezing.

Key words

Sulphur dioxide oxidation clouds riming freezing potential 


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Copyright information

© Kluwer Academic Publishers 1995

Authors and Affiliations

  • J. V. Iribarne
    • 1
  • L. A. Barrie
    • 2
  1. 1.Department of PhysicsUniversity of TorontoTorontoCanada
  2. 2.Atmospheric Environment ServiceDownsviewCanada

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