In:
Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 19, No. 6 ( 2019-03-20), p. 3481-3492
Abstract:
Abstract. The first atmospheric observations of octafluorooxolane
(octafluorotetrahydrofuran, c-C4F8O), a persistent greenhouse gas, are
reported. In addition, a complementary laboratory study of its most likely atmospheric
loss processes, its infrared absorption spectrum, and global warming potential (GWP) are
reported. First atmospheric measurements of c-C4F8O are provided from the
Cape Grim Air Archive (41∘ S, Tasmania, Australia, 1978–present), supplemented
by two firn air samples from Antarctica, in situ measurements of ambient air at
Aspendale, Victoria (38∘ S), and a few archived air samples from the Northern
Hemisphere. The atmospheric abundance in the Southern Hemisphere has monotonically grown
over the past decades and leveled at 74 ppq (parts per quadrillion, femtomole per mole
in dry air) by 2015–2018. The growth rate of c-C4F8O has decreased from a
maximum in 2004 of 4.0 to 〈0.25 ppq yr−1 in 2017 and 2018. Using a 12-box
atmospheric transport model, globally averaged yearly emissions and abundances of
c-C4F8O are calculated for 1951–2018. Emissions, which we speculate to
derive predominantly from usage of c-C4F8O as a solvent in the
semiconductor industry, peaked at 0.15 (±0.04, 2σ) kt yr−1 in 2004 and
have since declined to 〈0.015 kt yr−1 in 2017 and 2018. Cumulative emissions
over the full range of our record amount to 2.8 (2.4–3.3) kt, which correspond to 34 Mt
of CO2-equivalent emissions. Infrared and ultraviolet absorption spectra for
c-C4F8O as well as the reactive channel rate coefficient for the
O(1D) + c-C4F8O reaction were determined from laboratory
studies. On the basis of these experiments, a radiative efficiency of
0.430 W m−2 ppb−1 (parts per billion, nanomol mol−1) was determined,
which is one of the largest found for synthetic greenhouse gases. The global annually
averaged atmospheric lifetime, including mesospheric loss, is estimated to be
〉3000 years. GWPs of 8975, 12 000, and 16 000 are estimated for the 20-, 100-, and
500-year time horizons, respectively.
Type of Medium:
Online Resource
ISSN:
1680-7324
DOI:
10.5194/acp-19-3481-2019
DOI:
10.5194/acp-19-3481-2019-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2019
detail.hit.zdb_id:
2092549-9
detail.hit.zdb_id:
2069847-1
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