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| Titel |
A novel method of carbon dioxide clumped isotope analysis with tunable infra-red laser direct absorption spectroscopy |
| VerfasserIn |
Ivan Prokhorov, Tobias Kluge, Christof Janssen |
| 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 |
250124487
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| Publikation (Nr.) |
 EGU/EGU2016-3931.pdf |
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| Zusammenfassung |
| Precise clumped isotopes analysis of carbon dioxide opens up new horizons of atmospheric
and biogeochemical research. Recent advances in laser and spectroscopic techniques provides
us necessary instrumentation to access extremely low sub-permill variations of
multiply-substituted isotopologues.
We present an advanced analysis method of carbon dioxide clumped isotopes using direct
absorption spectroscopy. Our assessments predict the ultimate precision of the new
method on the sub-permill level comparable to state of the art mass spectrometry.
Among the most auspicious intrinsic properties of this method we highlight genuine
Δ16O13C18O and Δ16O13C18O measurements without isobaric interference, measurement
cycle duration of several minutes versus hours for mass spectrometric analysis,
reduced sample size of ∼ 10 μmol and high flexibility, allowing us to perform in-situ
measurements.
The pilot version of the instrument is being developed in an international collaboration
framework between Heidelberg University, Germany and Pierre and Marie Curie University,
Paris, France. It employs two continuous interband quantum cascade lasers tuned at
4.439 μm and 4.329 μm to measure doubly ( 16O13C18O, 16O13C17O) and singly (
16O12C16O, 16O13C16O, 16O12C17O, 16O12C18O) substituted isotopologues,
respectively.
Two identical Herriot cells are filled with dry pure CO2 sample and reference gas at
working pressure of 1 − 10 mbar. Cells provide optical path lengths of ∼ 17 m for the laser
tuned at doubly substituted isotopologues lines and use a single pass for the laser tuned at the
stronger lines of singly substituted isotopologues. Light outside of the gas cells is coupled
into optical fiber to avoid absorption by ambient air CO2. Simulations predict sub-permill
precision at working pressure of 1 mbar and room temperature stabilised at the ±10 mK
level.
Our prime target is to apply the proposed method for continuous in-situ analysis of CO2.
We are foreseeing potential applications to the following environmental issues: assessments
of distinct sources of atmospheric CO2, temperature reconstructions from terrestrial and
marine archives, extra-terrestrial atmosphere studies, etc. |
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