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| Titel |
A new analyzer to measure the abundance of 14N15N16O and 15N14N16O relative to 14N14N16O to help elucidate microbial N2O dynamics in terrestrial ecosystems. |
| VerfasserIn |
Eric Crosson, David Balslev-Clausen, John Dore |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250050922
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| Zusammenfassung |
| Nitrous oxide (N2O) is an atmospheric trace gas that contributes to global warming and stratospheric ozone depletion. The major sources from terrestrial ecosystems are the microbial processes of nitrification and denitrification occurring in soils. Isotopomer ratios of N2O, i.e., the abundances of 14N15N16O and 15N14N16O relative to 14N14N16O, are promising for elucidation of N2O biogeochemistry(1). Although isotopic signatures of inorganic N species tend to be variable because of the high turnover of N in terrestrial ecosystems, variations in their 15N isotopic and isotopomeric ratios can provide important information about ecosystem functions without disturbing the environment through the addition of inhibitors and tracer-labeled compounds(2). For example, nitrogen isotopic site preference (the difference between the isotope ratios of the central and terminal nitrogen atoms) can be useful to distinguish between N2O produced via hydroxylamine oxidation versus nitrite reduction.
Picarro, Inc. has developed a Cavity Ring-Down Spectroscopy (CRDS) based analyzer, able to measure the abundance of 14N15N16O and 15N14N16O relative to 14N14N16O in N2O. The analyzer is easy to use and makes continuous measurements in real time. Unlike with mass spectrometry, the 14N15N16O and 15N14N16O configurations can be clearly distinguished using optical absorption spectroscopy via CRDS. This unique capability is possible because, in optical absorption spectroscopy, the wavelength location of the 14N15N16O and 15N14N16O isotopomers are defined by the molecular mass AND the molecular configuration. In isotopic ratio mass spectrometry (IRMS), the charge to mass ratio must be different in order to discriminate different molecules. Therefore distinguishing isotopomers using IRMS requires additional analyses of N2O mass fragments generated by the ion source.
In this work, measurements of 14N15N16O and 15N14N16O relative to 14N14N16O in N2O taken from soil gas flux chambers will be shown. This work is a first step in proving the viability of this new technology in terrestrial ecosystem applications.
(1) K. Koba,*, K. Osaka, Y. Tobari, S. Toyoda, N. Ohte, M. Katsuyama, N. Suzuki, M. Itoh, H. Yamagishi, M. Kawasaki, S.J. Kim, N. Yoshida, T. Nakajima (2009) Biogeochemistry of nitrous oxide in groundwater in a forested ecosystem elucidated by nitrous oxide. Geochimica et Cosmochimica Acta 73 (2009) 3115–3133.
(2) Ostrom N. E., Hedin L. O., von Fischer J. C. and Robertson G. P.(2002) Nitrogen transformations and NO3- removal at a soil–stream interface: a stable isotope approach. Ecol. Appl. 12(4), 1027–1043. |
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