- Scientists at the Max Planck Institute for Chemistry
in Mainz, from the School of Environmental Science at University of East
Anglia/ UK, Ford Motor Company/USA, University of Reading/UK, University
of Frankfurt and British Antarctic Survey, Natural Environment Research
Council in Cambridge/UK have detected a previously unreported compound
in the atmosphere, trifluoromethyl sulphur pentaflouride (SF5CF3). The
increase of this peculiar gas in the atmosphere is coupled with the increase
of the very inert gas sulfur hexaflouride (SF6), suggesting a common source
(Science, 28 July 2000).
- There is no doubt that the new gas SF5CF3 is made by
industry, or is produced during certain process involving industrial gases,
but its exact source remains a mystery. The scientists speculate that SF5CF3,
which is closely chemically related to SF6, originates as a breakdown product
of SF6 in high voltage equipment. SF6 is used in electrical switches to
suppress sparks, in protecting metals during a melting process, in tennis
balls, car tires and even at one stage in running shoes. Due to its good
insulation properties it was also used as a noise barrier in double glazed
window panes. However, SF6 is a strong greenhouse gas and the molecule
is very resistant against attack in the atmosphere. The natural self-cleansing
property of the atmosphere is insufficient to deal with such super molecules.
Therefore, it has a long lifetime, and being a strong greenhouse gas, its
production is now restricted under the Kyoto Protocol.
- The new molecule SF5CF3 is even a stronger greenhouse
gas. Measurements of its infrared absorption cross-section revealed the
largest radiative forcing, on a per molecule basis, of any gas found in
the atmosphere to date (0.57 W/m2 ppb). Together with the fact that also
this gas has a long lifetime - somewhere between several hundred and a
few thousand years - there is good reason to know more about this gas,
and to try to stop its increase in the atmosphere.
- How do we know the atmospheric increase of this gas?
The Max Planck Institute for Chemistry in Mainz has participated in expeditions
in Antarctica to extract air samples from the thick firn layers (snow).
These layers can be up to 100 meter thick and contain old air, sometimes
reaching to the beginning of the last century. This air has been extensively
analyzed in our institute and in Norwich, England. The new gas was discovered
at extremely low concentrations. At the surface the concentration is the
same as in the air at the moment, and amounts to about 0.1 ppt (parts per
trillion; one ppt is one part in 1012). At 100 meter depth in the snow
its concentration was close to the detection level of 0.01 ppt. This shows
the grown of the gas during the second half of the last century. Because
the increase of the new gas is very much like that of SF6, we suspect a
link between the two gases.
- This discovery once again shows that we have to be careful
with our atmosphere, and that research is much needed indeed. Without even
knowing it, we have been releasing a very potent greenhouse gas for almost
50 years. We have to find the source of this gas and to try to stop its
increase. Even though the concentrations are very small, and its implication
in climate change is for practical reasons no grave concern, this type
of global pollution is unwanted, and most likely unnecessary.
- Editor's Note: The original news release can be found
at http://www.mpg.de/news00/news19_00.htm Note: This story has been adapted
from a news release issued by Max Planck Society for journalists and other
members of the public. If you wish to quote from any part of this story,
please credit Max Planck Society as the original source. You may also wish
to include the following link in any citation: http://www.sciencedaily.com/releases/2000/07/000728081713.htm
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