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© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 30 Apr 2019

Research article | 30 Apr 2019

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This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Atmospheric Chemistry and Physics (ACP) and is expected to appear here in due course.

Perfluorocyclobutane (PFC-318, c-C4F8) in the global atmosphere

Jens Mühle1, Cathy M. Trudinger2, Matthew Rigby3, Luke M. Western3, Martin K. Vollmer4, Sunyoung Park5, Alistair J. Manning6, Daniel Say3, Anita Ganesan7, L. Paul Steele2, Diane J. Ivy8, Tim Arnold9,10, Shanlan Li5, Andreas Stohl11, Christina M. Harth1, Peter K. Salameh1, Archie McCulloch3, Simon O'Doherty3, Mi-Kyung Park5, Chun Ok Jo5, Dickon Young3, Kieran M. Stanley3, Paul B. Krummel2, Blagoj Mitrevski2, Ove Hermansen11, Chris Lunder11, Nikolaos Evangeliou11, Bo Yao12, Jooil Kim1, Benjamin Hmiel13, Christo Buizert14, Vasilii V. Petrenko13, Jgor Arduini15,16, Michela Maione15,16, David M. Etheridge2, Eleni Michalopoulou3, Mike Czerniak17, Jeffrey P. Severinghaus1, Stefan Reimann4, Peter G. Simmonds3, Paul J. Fraser2, Ronald G. Prinn8, and Ray F. Weiss1 Jens Mühle et al.
  • 1Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
  • 2Climate Science Centre, CSIRO Oceans and Atmosphere, Aspendale, Victoria, Australia
  • 3School of Chemistry, University of Bristol, Bristol, UK
  • 4Laboratory for Air Pollution and Environmental Technology, Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
  • 5KNU, Kyungpook Institute of Oceanography, College of Natural Sciences, Kyungpook National University, South Korea
  • 6Met Office Hadley Centre, Exeter, UK
  • 7School of Geographical Sciences, University of Bristol, Bristol, UK
  • 8Center for Global Change Science, Massachusetts Institute of Technology, Cambridge, MA, USA
  • 9National Physical Laboratory, Teddington, Middlesex, UK
  • 10School of GeoSciences, University of Edinburgh, Edinburgh, UK
  • 11NILU, Norwegian Institute for Air Research, Kjeller, Norway
  • 12Meteorological Observation Centre (MOC), China Meteorological Administration (CMA), Beijing, China
  • 13Department of Earth & Environmental Sciences, University of Rochester, Rochester, NY, USA
  • 14College of College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
  • 15Department of Pure and Applied Sciences, University of Urbino, Urbino, Italy
  • 16ISAC-CNR, Bologna, Italy
  • 17Edwards LTD, Burgess Hill, West Sussex, UK

Abstract. We reconstruct atmospheric abundances of the potent greenhouse gas c-C4F8 (perfluorocyclobutane, perfluorocarbon PFC-318) from measurements of in situ, archived, firn, and aircraft air samples with precisions of ~ 1–2 % reported on the SIO-14 gravimetric calibration scale. Combined with inverse methods, we found near zero atmospheric abundances from the early 1900s to the early 1960s, after which they rose sharply, reaching 1.66 ppt (parts per trillion dry-air mole fraction) in 2017. Global c-C4F8 emissions rose from near zero in the 1960s to ~ 1.2 Gg yr−1 in the late 1970s to late 1980s, then declined to ~ 0.8 Gg yr−1 in the mid-1990s to early 2000s, followed by a rise since the early 2000s to ~ 2.2 Gg yr−1 in 2017. These emissions are significantly larger than inventory based emission estimates. Estimated emissions from eastern Asia rose from 0.36 Gg yr−1 in 2010 to 0.73 Gg yr−1 in 2016 and 2017, 31 % of global emissions, mostly from eastern China. We estimate emissions of 0.14 Gg yr−1 from Northern and Central India in 2016 and find evidence for significant emissions from Russia. In contrast, recent emissions from North Western Europe and Australia are estimated to be small (≤ 1 % each). We conclude that emissions from China, India and Russia are likely related to production of polytetrafluoroethylene (PTFE, “Teflon”) and other fluoropolymers that are based on the pyrolysis of hydrochlorofluorocarbon HCFC-22 (CHClF2) in which c-C4F8 is a known by-product. The semiconductor sector, where c-C4F8 is used, is estimated to be a small source. Without an obvious correlation with population density, incineration of waste containing fluoropolymers is probably a minor source, and we find no evidence of emissions from electrolytic production of aluminum in Australia. While many possible emissive uses of c-C4F8 are known, the start of significant emissions may well be related to the advent of commercial PTFE production in 1947. Process controls or abatement to reduce c-C4F8 by-product were probably not in place in the early decades, explaining the increase in emissions. With the advent of by-product reporting requirements to the United Nations Framework Convention on Climate Change (UNFCCC) in the 1990s, concern about climate change and product stewardship, abatement, and perhaps the collection of c-C4F8 by-product for use in the semiconductor industry where it can be easily abated, it is conceivable that emissions in developed countries were stabilized and then reduced, explaining the observed emission reduction in the 1980s and 1990s. Concurrently, production of PTFE in China began to increase rapidly. Without emission reduction requirements, it is plausible that global emissions today are dominated by China and other developing countries, in agreement with our analysis. We predict that c-C4F8 emissions will continue to rise and that c-C4F8 will become the second most important emitted PFC in terms of CO2-equivalent emissions within a year or two. The 2017 radiative forcing of c-C4F8 (0.52 mW m−2) is small but emissions of c-C4F8 and other PFCs, due to their very long atmospheric lifetimes, essentially permanently alter Earth's radiative budget and should be reduced. Significant emissions outside of the investigated regions clearly show that observational capabilities and reporting requirements need to be improved to understand global and country scale emissions of PFCs and other synthetic greenhouse gases and ozone depleting substances.

Jens Mühle et al.
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Interactive discussion
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Jens Mühle et al.
Jens Mühle et al.
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Short summary
We discuss atmospheric concentrations and emissions of the strong greenhouse gas perfluorocyclobutane. A large fraction of recent emissions stem from China, India, and Russia, probably as a by-product from the production of Teflon and other fluoropolymers. Most historic emissions likely stem from developed countries. Total emissions are higher than what is being reported. Clearly, more measurements and better reporting are needed to understand emissions of this and other greenhouse gases.
We discuss atmospheric concentrations and emissions of the strong greenhouse gas...