Archie McCulloch، نويسنده , , Pauline M. Midgley، نويسنده , , Paul Ashford، نويسنده ,
Two of the gases, CFC-12 (dichlorodifluoromethane, CF2Cl2) and HCFC-22 (chlorodifluoromethane, CHClF2) have long histories of emission from refrigeration and other uses. Production and sales records show the expected fall in the amounts of CFC-12 used in refrigeration after the Montreal Protocol came into effect but this does not seem to have been accompanied by significant substitution by HCFC-22, demand for which appears governed by organic growth. HFC-134a (1,1,1,2-tetrafluoroethane, CH2FCF3) is a relative newcomer that has partially substituted for CFC-12.
After developing a single data set for the global use of each substance in refrigeration, foam blowing and aerosol propulsion, and other promptly emissive uses, annual releases of the compounds were estimated by applying emission functions derived from surveying both the producers of the chemicals and the principal industrial users.
For CFC-12 and HFC-134a, atmospheric concentrations calculated from the emissions estimated here are in good agreement with observations, verifying that the emission functions adequately describe the relationship between the quantities in use, the atmospheric lifetimes of 100 and 14.6 years, respectively, and the extent of release into the atmosphere. The agreement between observation and calculation is poorer for HCFC-22, if its atmospheric lifetime is 12 years, but becomes much closer with a lifetime of 10 years.
An 80% reduction in CFC requirement has been substituted only to the extent of 25% by HFC-134a. This is consistent with improved technology to curtail leakage and so enable lower system charges that, in turn, translate into less demand. For the same reason, the refrigeration emission function for HFC-134a over the period 1990–2000 was not significantly different from that of CFC-12. The lower absolute rate of leakage and lower absolute charge sizes combining to maintain a similar relative rate of loss.
Dichlorodifluoromethane , Tetrafluoroethane , Montreal Protocol , Atmospheric concentration , Chlorodifluoromethane , Atmospheric lifetime