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An atmospheric photochemical source of the persistent greenhouse gas CF 4
Author(s) -
Jubb Aaron M.,
McGillen Max R.,
Portmann Robert W.,
Daniel John S.,
Burkholder James B.
Publication year - 2015
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2015gl066193
Subject(s) - photodissociation , atmosphere (unit) , atmospheric chemistry , photochemistry , greenhouse gas , chemistry , quantum yield , ozone , meteorology , physics , organic chemistry , ecology , biology , quantum mechanics , fluorescence
A previously uncharacterized atmospheric source of the persistent greenhouse gas tetrafluoromethane, CF 4 , has been identified in the UV photolysis of trifluoroacetyl fluoride, CF 3 C(O)F, which is a degradation product of several halocarbons currently present in the atmosphere. CF 4 quantum yields in the photolysis of CF 3 C(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 CF 4 budget. The atmospheric photochemical production of CF 4 from CF 3 CH 2 F (HFC‐134a), CF 3 CHFCl (HCFC‐124), and CF 3 CCl 2 F (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 CF 4 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.