text: In the gas phase sulfur dioxide is oxidized by reaction with the hydroxyl radical via an intermolecular reaction:
  :SO + OH· → HOSO·
  which is followed by:
  :HOSO· + O → HO· + SO
  In the presence of water, sulfur trioxide (SO) is converted rapidly to sulfuric acid:
  :SO (g) + HO (l) → HSO (aq)
  Nitrogen dioxide reacts with OH to form nitric acid:
  :NO + OH· → HNO