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| Titel |
Potential for long-term, high-frequency, high-precision methane isotope measurements to improve UK emissions estimates |
| VerfasserIn |
Chris Rennick, Francesco Bausi, Tim Arnold |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250151244
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| Publikation (Nr.) |
 EGU/EGU2017-15807.pdf |
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| Zusammenfassung |
| On the global scale methane (CH4) concentrations have more than doubled over the last 150
years, and the contribution to the enhanced greenhouse effect is almost half of that due to the
increase in carbon dioxide (CO2) over the same period. Microbial, fossil fuel, biomass
burning and landfill are dominant methane sources with differing annual variabilities;
however, in the UK for example, mixing ratio measurements from a tall tower network
and regional scale inversion modelling have thus far been unable to disaggregate
emissions from specific source categories with any significant certainty. Measurement of
the methane isotopologue ratios will provide the additional information needed
for more robust sector attribution, which will be important for directing policy
action
Here we explore the potential for isotope ratio measurements to improve the
interpretation of atmospheric mixing ratios beyond calculation of total UK emissions, and
describe current analytical work at the National Physical Laboratory that will realise
deployment of such measurements. We simulate isotopic variations at the four UK
greenhouse gas tall tower network sites to understand where deployment of the first isotope
analyser would be best situated. We calculate the levels of precision needed in both δ-13C and
δ-D in order to detect particular scenarios of emissions.
Spectroscopic measurement in the infrared by quantum cascade laser (QCL)
absorption is a well-established technique to quantify the mixing ratios of trace
species in atmospheric samples and, as has been demonstrated in 2016, if coupled to
a suitable preconcentrator then high-precision measurements are possible. The
current preconcentration system under development at NPL is designed to make
the highest precision measurements yet of the standard isotope ratios via a new
large-volume cryogenic trap design and controlled thermal desorption into a QCL
spectrometer.
Finally we explore the potential for the measurement of clumped isotopes at high
frequency and precision. The doubly-substituted 13CH3D isotopologue is a tracer for
methane formed at geological temperatures, and will provide additional information for
identification of these sources. |
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