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| Titel |
Frontiers of QC Laser spectroscopy for high precision isotope ratio analysis of greenhouse gases |
| VerfasserIn |
Lukas Emmenegger, Joachim Mohn, Eliza Harris, Simon Eyer, Erkan Ibraim, Béla Tuzson |
| 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 |
250122477
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| Publikation (Nr.) |
 EGU/EGU2016-1522.pdf |
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| Zusammenfassung |
| An important milestone for laser spectroscopy was achieved when isotope ratios of greenhouse gases were reported at precision levels that allow addressing research questions in environmental sciences. Real-time data with high temporal resolution at moderate cost and instrument size make the optical approach highly attractive, complementary to the well-established isotope-ratio mass-spectrometry (IRMS) method. Especially appealing, in comparison to IRMS, is the inherent specificity to structural isomers having the same molecular mass.
Direct absorption in the MIR in single or dual QCL configuration has proven highly reliable for the sta-ble isotopes of CO$_{2}$, N$_{2}$O and CH$_{4}$. The longest time series of real-time measurements is currently available for $\delta^{13}$C and $\delta^{18}$O in CO$_{2}$ at the high-alpine station Jung-fraujoch. At this well-equipped site, QCL based direct absorption spectroscopy (QCLAS) measurements are ongoing since 2008 $^{1,2}$.
Applications of QCLAS for N$_{2}$O and CH$_{4}$ stable isotopes are considerably more challenging because of the lower atmospheric mixing ratios, especially for the less abundant species, such as N$_{2}$^{18}$O and CH$_{3}$D. For high precision (\textless 0.1 \permil) measurements in ambient air, QCLAS may be combined with a fully automated preconcentration unit yielding an up to 500 times concentration increase and the capability to separate the target gas from spectral interferants by se-quential desorption $^{3}$.
Here, we review our recent developments on high precision isotope ratio analysis of greenhouse gases, with special focus on the isotopic species of N$_{2}$O and CH$_{4}$. Furthermore, we show environ-mental applications illustrating the highly valuable information that isotope ratios of atmospheric trace gases can carry. For example, the intramolecular distribution of $^{15}$N in N$_{2}$O gives important information on the geochemical cycle of N$_{2}$O$^{4-6}$, while the analysis of $\delta^{13}$C and $\delta $D in CH$_{4}$ may be applied to disentangle microbial, fossil and landfill sources $^{7}$.
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1 Sturm, P., Tuzson, B., Henne, S. {\&} Emmenegger, L. Tracking isotopic signatures of CO$_{2}$ at the high altitude site Jungfraujoch with laser spectroscopy: Analytical improvements and representative re-sults. \textit{Atmospheric Measurement Techniques} \textbf{6}, 1659-1671 (2013).
2 Tuzson, B.\textit{ et al.} Continuous isotopic composition measurements of tropospheric CO$_{2}$ at Jungfraujoch (3580 m a.s.l.), Switzerland: real-time observation of regional pollution events. \textit{Atmospheric Chemistry and Physics} \textbf{11}, 1685-1696 (2011).
3 Mohn, J.\textit{ et al.} A liquid nitrogen-free preconcentration unit for measurements of ambient N$_{2}$O isotopomers by QCLAS. \textit{Atmospheric Measurement Techniques} \textbf{3}, 609-618 (2010).
4 Wolf, B.\textit{ et al.} First on-line isotopic characterization of N$_{2}$O above intensively managed grassland. \textit{Biogeosciences} \textbf{12}, 2517-1960 (2015).
5 Harris, E.\textit{ et al.} Nitrous oxide and methane emissions and nitrous oxide isotopic composition from waste incineration in Switzerland. \textit{Waste Management} \textbf{35}, 135-140 (2015).
6 Harris, E.\textit{ et al.} Isotopic evidence for nitrous oxide production pathways in a partial nitritation-anammox reactor. \textit{Water Research} \textbf{83}, 258-270 (2015).
7 Eyer, S.\textit{ et al.} Real-time analysis of $\delta^{13}$C- and $\delta $D-CH$_{4}$ in ambient air with laser spectroscopy: method development and first intercomparison results. \textit{Atmos. Meas. Tech. Discuss.} \textbf{8}, 8925-8970 (2015). |
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