Distribution and Trend of Chlorodifluoromethane (HCFC-22) in the Atmosphere
Atmospheric concentration of HCFC-22 in the Northern and Southern Hemispheres over the past 15 years was measured by using an oxygen sensitized ECD (electron capture detector). The global concentration increased by about 5.2 ± 0.4 pptv (pptv = 10−12 v/v) per year for the period 1980–1988, and about 10.3 ± 0.2 pptv per year for the period 1988–1994. The observed result until 1988 was consistent with the mixing ratios calculated by 2-box model based on the statistical figures of production and emission with 14.0 ± 1.5 years lifetime. However, the observed data suggest that the statistical figures of HCFC-22 emission have been underestimated since 1988.