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CATEGORIES:Centre for Atmospheric Science seminars\, Chemistr
y Dept.
SUMMARY:Isotope fractionation in nitrous oxide and CFC-12
reflects stratospheric chemistry and transport rat
es - Dr Jan Kaiser\, University of East Anglia
DTSTART;TZID=Europe/London:20120309T141500
DTEND;TZID=Europe/London:20120309T153000
UID:TALK36309AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/36309
DESCRIPTION:Nitrous oxide (N2O) and dichlorodifluor
omethane (CFC-12) are the third- and fourth-most i
mportant anthropogenic greenhouse gases. Both have
long atmospheric lifetimes of about 100 years and
are only destroyed in the stratosphere. There\, t
hey are the most important ozone-depleting gases i
n terms of abundance (CFC-12) and emissions (N2O).\n\nNovel mass-spectrometric techniques
have been developed over the last decade\, which
allow the detailed study of individual isotopologu
es and isotopomers of these gases. Strong enrichme
nts in the heavier isotopic variants were found in
stratospheric balloon and aircraft\, tightly rela
ted to the degree of photochemical decomposition a
nd the age of air. Kinetic measurements in the lab
oratory have provided a good understanding of the
wavelength- and temperature-dependent isotopic fra
ctionation.\n\nThe comparison between field observ
ations and laboratory measurements provides insigh
ts into the rates of stratospheric transport and c
hemistry as well as the relative contributions of
individual sink reactions (photolysis and photo-ox
idation). The increase of the apparent isotopic fr
actionation with altitude and its decrease towards
the poles reflects the interplay between chemistr
y\, mixing and transport in different regions of t
he stratosphere.
LOCATION:Unilever Lecture Theatre\, Department of Chemistry
CONTACT:Dr Alex Archibald
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