Abstract: The first observations of the feedstocks, CFC-216ba (1,2-dichlorohexafluoropropane) and CFC-216ca (1,3-dichlorohexafluoropropane), as well as the CFC substitute HCFC-225ca (3,3-dichloro-1,1,1,2,2-pentafluoropropane), are reported in air samples collected between 1978 and 2012 at Cape Grim, Tasmania. Present day (2012) mixing ratios are 37.8 ± 0.08 ppq (parts per quadrillion; 1015) and 20.2 ± 0.3 ppq for CFC-216ba and CFC-216ca, respectively. The abundance of CFC-216ba has been approximately constant for the past 20 years, whilst that of CFC-216ca is increasing, at a current rate of 0.2 ppq/year. Upper tropospheric air samples collected in 2013 suggest a further continuation of this trend. Inferred annual emissions peaked 421 at 0.18 Gg/year (CFC-216ba) and 0.05 Gg/year (CFC-216ca) in the mid-1980s and then decreased sharply as expected from the Montreal Protocol phase-out schedule for CFCs. The atmospheric trend of CFC-216ca and CFC-216ba translates into continuing emissions of around 0.01 Gg/year in 2011, indicating that significant banks still exist or that they are still being used. HCFC-225ca was not detected in air samples collected before 1992. The highest mixing ratio of 52 ± 1 ppq was observed in 2001. Increasing annual emissions were found in the 1990s (i.e., when HCFC-225ca was being introduced as a replacement for CFCs). Emissions peaked around 1999 at about 1.51 Gg/year. In accordance with the Montreal Protocol, restrictions on HCFC consumption and the short lifetime of HCFC-225ca, mixing ratios declined after 2001 to 23.3 ± 0.7 ppq by 2012.
Keywords: CFC-216ba; CFC-216ca; HCFC-225ca; Montreal Protocol; ozone depletion; ODP; lifetime; fractional release; emission
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Kloss, C.; Newland, M.J.; Oram, D.E.; Fraser, P.J.; Brenninkmeijer, C.A.M.; Röckmann, T.; Laube, J.C. Atmospheric Abundances, Trends and Emissions of CFC-216ba, CFC-216ca and HCFC-225ca. Atmosphere 2014, 5, 420-434.
Kloss C, Newland MJ, Oram DE, Fraser PJ, Brenninkmeijer CAM, Röckmann T, Laube JC. Atmospheric Abundances, Trends and Emissions of CFC-216ba, CFC-216ca and HCFC-225ca. Atmosphere. 2014; 5(2):420-434.
Kloss, Corinna; Newland, Mike J.; Oram, David E.; Fraser, Paul J.; Brenninkmeijer, Carl A.M.; Röckmann, Thomas; Laube, Johannes C. 2014. "Atmospheric Abundances, Trends and Emissions of CFC-216ba, CFC-216ca and HCFC-225ca." Atmosphere 5, no. 2: 420-434.