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| Titel |
Methane Fingerprinting: Isotopic Methane and Ethane-to-Methane Ratio Analysis Using a Cavity Ring-Down Spectrometer |
| VerfasserIn |
Nabil Saad, Derek Fleck, John Hoffnagle |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250130379
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| Publikation (Nr.) |
 EGU/EGU2016-10628.pdf |
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| Zusammenfassung |
| Emissions of Natural gas, and methane (CH4) specifically, have come under increased
scrutiny by virtue of methane’s 28-36x greenhouse warming potential compared to carbon
dioxide (CO2) while accounting for 10% of the total greenhouse gas emissions in the US.
Large uncontrolled leaks, such as the recent Aliso Canyon leak, originating from
uncapped wells, coal mines and storage facilities have increased the total global
contribution of methane missions even further. Determining the specific fingerprint of
methane sources, by quantifying δ13C values and C2:C1 ratios, provides the means to
understand methane producing processes and allows for sources of methane to be
mapped and classified through these processes; i.e. biogenic vs. thermogenic, wet vs
dry.
In this study we present a fully developed Cavity Ring-Down Spectrometer (CRDS) that
precisely measures 12CH4 concentration and its 13CH4 isotope concentration, yielding δ13C
measurements, C2H6 concentration, along with CO2 and H2O. This provides real-time
continuous measurements without an upfront separation requirement or multiple analyses to
derive the origin of the gas samples. The highly sensitive analyzer allows for measurements
of scarce molecules down to sub-ppb 1-σ precision in 5 minutes of measurement: with
CH4 <0.1ppb, δ13C <1‰ C2H6 <1ppb and CO2 <1ppm. To complement this work,
we provide the analysis of different methane sources providing a 2-dimensional
mapping of methane sources as functions of δ13C and C2:C1 ratios, which can
be thought of as a modified Bernard Plot. This dual ratio mapping can be used
to discriminate between naturally occurring biogenic methane sources, naturally
occurring enriched thermogenic sources, and natural gas distribution sources. This also
shows future promise in aiding gas and oil exploration, in distinguishing oil vs
coal gases, as well as a valuable tool in the development of methane sequestration. |
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