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Publication - Dr Matthew Rigby

    Atmospheric histories and emissions of chlorofluorocarbons CFC-13 (CClF3), ΣCFC-114 (C2Cl2F4), and CFC-115 (C2ClF5)

    Citation

    Vollmer, MK, Young, D, Trudinger, CM, Mühle, J, Henne, S, Rigby, M, Park, S, Li, S, Guillevic, M, Mitrevski, B, Harth, CM, Miller, BR, Reimann, S, Yao, B, Steele, LP, Wyss, SA, Lunder, CR, Arduini, J, McCulloch, A, Wu, S, Rhee, TS, Wang, RHJ, Salameh, PK, Hermansen, O, Hill, M, Langenfelds, RL, Ivy, D, O'Doherty, S, Krummel, PB, Maione, M, Etheridge, DM, Zhou, L, Fraser, PJ, Prinn, RG, Weiss, RF & Simmonds, PG, 2018, ‘Atmospheric histories and emissions of chlorofluorocarbons CFC-13 (CClF3), ΣCFC-114 (C2Cl2F4), and CFC-115 (C2ClF5)’. Atmospheric Chemistry and Physics, vol 18., pp. 979-1002

    Abstract

    Based on observations of three chlorofluorocarbons, CFC-13 (chlorotrifluoromethane), CFC-114 (dichlorotetrafluoroethane) and CFC-115 (chloropentafluoroethane) in atmospheric and firn samples, we reconstruct records of their tropospheric histories spanning nearly eight decades. These compounds were measured in polar firn air samples, in ambient air archived in canisters, and in-situ at the AGAGE (Advanced Global Atmospheric Gases Experiment) network and affiliated sites. Global emissions to the atmosphere are derived from these observations using an inversion based on a 12-box atmospheric transport model. For CFC-13, we provide the first comprehensive global analysis. This compound increased monotonically from its first appearance in the atmosphere in the late 1950s to a mean global abundance of 3.18 ppt (dry air mole fraction in parts-per-trillion, pmol mol−-1) in 2016. Its growth rate has decreased since the mid 1980s but has remained at a surprisingly high level of 0.02 ppt yr−1 since the late 2000s. CFC-114 increased from its appearance in the 1950s to a maximum of 16.6 ppt in the early 2000s, and has since slightly declined to 16.3 ppt in 2016. CFC-115 increased monotonically from its first appearance in the 1960s and reached a global mean mole fraction of 8.52 ppt in 2016. Growth rates of all three compounds over the past years are significantly larger than would be expected from zero emissions. Under the assumption of unaltered lifetimes and atmospheric transport patterns, we derive global emissions from our measurements, which have remained unexpectedly high in recent years: Mean yearly emissions for the last decade (2007–2016) of CFC-13 are at 0.48 ± 0.15 kt yr−1 (> 15 % of past peak emissions), of CFC-114 at 1.90 ± 0.84 kt yr−1 (~ 10 % of peak emissions), and of CFC-115 at 0.80 ± 0.50 kt yr−1 (> 5 % of peak emissions). Mean yearly emissions of CFC-115 for 2014–2016 are 1.08 ± 0.50 kt yr−1 and have more than doubled compared to 2009. Cumulative global emissions for CFC-114 derived from observations through 2016 exceed the global cumulative production derived from reported inventory data by > 10 % while those for CFC-115 agree well. We find CFC-13 emissions from aluminum smelters and impurities of CFC-115 in the refrigerant HFC-125 (CHF2CF3) but if extrapolated to global emissions neither of them can account for the lingering global emissions determined from the atmospheric observations. We also conduct regional inversions for the years 2012–2016 for the north-east Asian area using observations from the Korean Gosan AGAGE site and find significant emissions for CFC-114 and CFC-115, suggesting that a large fraction of their global emissions currently occur in north-eastern Asia and more specifically on the Chinese mainland.

    Full details in the University publications repository