An atmospheric photochemical source of the persistent greenhouse gas CF₄

Abstract

A previously uncharacterized atmospheric source of the persistent greenhouse gas tetrafluoromethane, CF4, has been identified in the UV photolysis of trifluoroacetyl fluoride, CF3C(O)F, which is a degradation product of several halocarbons currently present in the atmosphere. CF4 quantum yields in the photolysis of CF3C(O)F were measured at 193, 214, 228, and 248 nm, wavelengths relevant to stratospheric photolysis, to be (75.3 ± 1) × 10−4, (23.7 ± 0.4) × 10−4, (6.6 ± 0.2) × 10−4, and ≤0.4 × 10−4, respectively. A 2‐D atmospheric model was used to estimate the contribution of the photochemical source to the global CF4 budget. The atmospheric photochemical production of CF4 from CF3CH2F (HFC‐134a), CF3CHFCl (HCFC‐124), and CF3CCl2F (CFC‐114a) per molecule emitted was calculated to be (1–2.5) × 10−5, 1.0 × 10−4, and 2.8 × 10−3, respectively. Although CF4 photochemical production was found to be relatively minor at the present time, the identified mechanism demonstrates that long‐lived products with potential climate impacts can be formed from the atmospheric breakdown of shorter‐lived source gases.

FC(O)C(O)F, FC(O)CF2C(O)F, and FC(O)CF2CF2C(O)F: Ultraviolet and Infrared Absorption Spectra and 248 nm Photolysis Products

“…Such a photochemical process was also observed in our study of CF 3 C(O)F photolysis where CF 4 was observed as a minor primary photolysis product. 13 The observed yield of CO in Figure 4 is significantly greater than that of CF 2 O. The difference is interpreted to be due to the 248 nm photolysis of BrC(O)F through reaction 9:…”

“…The experimental apparatus consisted of a ∼1 L cylindrical Pyrex reactor, a 15 cm long absorption cell, which was coupled to an FTIR spectrometer, and a Teflon diaphragm circulating pump. , The reaction mixture was circulated between the photolysis reactor and infrared absorption cell continuously during an experiment. The photolysis source was a KrF excimer laser and the photolysis beam passed along the length of the reactor and filled the entire volume.…”

Atmospheric abundance and global emissions of perfluorocarbons CF<sub>4</sub>, C<sub>2</sub>F<sub>6</sub> and C<sub>3</sub>F<sub>8</sub> since 1800 inferred from ice core, firn, air archive and in situ measurements

“…CF 4 (carbon tetrafluoride, is the most abundant perfluorocarbon in the atmosphere (Mühle et al, 2010). It is released predominantly from aluminium production (due to so-called "anode effects", when the feed of aluminum oxide to or within the electrolysis cell is restricted; Holiday and Henry, 1959;Tabereaux, 1994) and during semiconductor manufacture (Tsai et al, 2002;Khalil et al, 2003). There is a small natural source from rocks (fluorites and granites) released by tectonic activity and weathering (Harnisch and Eisenhauer, 1998;Deeds et al, 2008Deeds et al, , 2015Mulder et al, 2013;Schmitt et al, 2013).…”

“…There is a small natural source from rocks (fluorites and granites) released by tectonic activity and weathering (Harnisch and Eisenhauer, 1998;Deeds et al, 2008Deeds et al, , 2015Mulder et al, 2013;Schmitt et al, 2013). Other very small industrial sources of CF 4 include release during production of SF 6 and HCFC-22 (Institute for Environmental Protection and Research, 2013) and from UV photolysis of trifluoroacetyl fluoride, which is a degradation product of halocarbons such as HFC-134a, HCFC-124 and CFC-114a (Jubb et al, 2015). Another possible source of CF 4 is from the rare earth industry, particularly in China, specifically neodymium oxide electrolysis (Vogel and Friedrich, 2015).…”

“…Another possible source of CF 4 is from the rare earth industry, particularly in China, specifically neodymium oxide electrolysis (Vogel and Friedrich, 2015). However, these other sources of emissions have been negligible to date compared to the CF 4 emissions due to aluminium production and semiconductor manufacture (Harnisch and Eisenhauer, 1998;Jubb et al, 2015;Wong et al, 2015). C 2 F 6 (perfluoroethane, PFC-116) is released predominantly during aluminium production and semiconductor manufacture (Tsai et al, 2002;Fraser et al, 2013).…”