Experimental Studies of Ozone Depletion by Chlorofluorocarbons (CFC's), Bromofluorocarbons (BFC's), Hydrochlorofluorocarbons (HCFC's), and CH3Br Using a 6-m3 Photochemical Chamber

Article abstract of DOI:10.1246/bcsj.69.535

Ozone destruction by CFC's (CFCl₃ and CF₂Cl₂), BFC's (CF₃Br and C₂F₄Br₂), HCFC's (CH₃CCl₂F, CF₃CHCl₂, and CF₃CHFCl), and CH₃Br was demonstrated using a 6-m³ evacuable photochemical chamber equipped with UV-enhanced Xe arc lamps. The decay of ozone by a catalytic cycle involving Cl or Br atoms released from the photolysis of halocarbons by UV light was evident, although the chain length was far less than that in the real stratosphere: It was about 8 for CFCl₃ and 40 for CF₃Br. The rates of ozone decomposition were faster in the BFC's than in the CFC's. According to a box-model simulation, in the CFCl₃ system 90% of the catalytic cycle proceeds from reactions of Cl+O₃→ClO+O₂ and ClO+O→Cl+O₂. On the other hand, in the CF₃Br system 90% of the catalytic cycle is governed by the following reactions: Br+O₃→BrO+O₂ and BrO+BrO→₂Br+O₂. The HCFC's and CH₃Br can destroy the ozone with sufficient potential as CFC's and BFC's when they enter the stratosphere.