Atmospheric distributions of HCFC 141b

In recent years, HCFC 141b (CH3CCl2F) has become commercially available as a replacement for CFC 11 (CCl3F) in closed‐cell foam blowing applications and as a partial replacement for CFC 113 (CCl2FCClF2) in solvent and cleaning applications. Measurements of the atmospheric distribution and rate of growth of HCFC 141b reported here provide initial data to begin evaluation of the atmospheric fate of this replacement compound. HCFC 141b measurements in March 1992 and from various periods in 1993 indicate a strong interhemispheric gradient and rapid growth in tropospheric mixing ratios during this time. Average HCFC 141b mixing ratios in April 1993 in the northern and southern hemispheres were 0.83±0.23 pptv and 0.28±0.07 pptv, respectively. HCFC 141b mixing ratios increased in the mid‐latitude northern hemisphere from 0.26 pptv in late March 1992 to 1.41 pptv in late September 1993. Southern hemisphere mixing ratios increased from approximately 0.28 pptv in April 1993 to 0.45 pptv in October 1993. Emissions estimates, based on the observations, were calculated using a two box model and for 1990–1993 were 0.5, 2.5, 7, and 15 kT, respectively.