NIR-diode laser spectroscopy for isotope-selective sensing of soil-respired carbon dioxide

  • The performance of a home-built tunable diode laser (TDL) spectrometer has been optimized regarding multi-line detection of carbon dioxide in natural gases. In the regime of the (30<SUP>0</SUP>1)<SUB>III</SUB> ← (000) band of <SUP>12</SUP>CO<SUB>2</SUB> around 1.6 μm, the dominating isotope species <SUP>12</SUP>CO<SUB>2</SUB>, <SUP>13</SUP>CO<SUB>2</SUB>, and <SUP>12</SUP>C<SUP>18</SUP>O<SUP>16</SUP>O were detected simultaneously. In contrast to most established techniques, selective measurements are performed without any sample preparation. This is possible since the CO<SUB>2</SUB> detection is free of interference from water, ubiquitous in natural gases. Detection limits in the range of a few ppmv were obtained for each species utilizing wavelength modulation (WM) spectroscopy with balanced detection in a long-path absorption cell set-up. Linear calibration plots cover a dynamic range of four orders of magnitude, allowing for quantitative CO<SUB>2</SUB> detection in various samples, like soil and breath gas. High isotopic resolutionThe performance of a home-built tunable diode laser (TDL) spectrometer has been optimized regarding multi-line detection of carbon dioxide in natural gases. In the regime of the (30<SUP>0</SUP>1)<SUB>III</SUB> ← (000) band of <SUP>12</SUP>CO<SUB>2</SUB> around 1.6 μm, the dominating isotope species <SUP>12</SUP>CO<SUB>2</SUB>, <SUP>13</SUP>CO<SUB>2</SUB>, and <SUP>12</SUP>C<SUP>18</SUP>O<SUP>16</SUP>O were detected simultaneously. In contrast to most established techniques, selective measurements are performed without any sample preparation. This is possible since the CO<SUB>2</SUB> detection is free of interference from water, ubiquitous in natural gases. Detection limits in the range of a few ppmv were obtained for each species utilizing wavelength modulation (WM) spectroscopy with balanced detection in a long-path absorption cell set-up. Linear calibration plots cover a dynamic range of four orders of magnitude, allowing for quantitative CO<SUB>2</SUB> detection in various samples, like soil and breath gas. High isotopic resolution enables the excellent selectivity, sensitivity, and stability of the chosen analytical concept. The obtained isotopic resolution of typically ± 1.0 ‰ and ± 1.5 ‰ (for 3 vol. % and 0.7 vol. % of CO<SUB>2</SUB>, respectively) offers a promising analytical tool for isotope-ratio determination of carbon dioxide in soil gas. Preliminary experiments on soil respiration for the first time combine the on-line quantification of the overall carbon dioxide content with an optode sensor and isotopic determination (TDL system) of natural gas species.show moreshow less

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Metadaten
Author:Gerald Hörner, Steffen Lau, Hans-Gerd Löhmannsröben
URN:urn:nbn:de:kobv:517-opus-10148
Series (Serial Number):Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe, ISSN 1866-8372 (paper 021)
Document Type:Postprint
Language:English
Date of Publication (online):2006/11/01
Year of Completion:2004
Publishing Institution:Universität Potsdam
Release Date:2006/11/01
Tag:Bodengas; Diodenlaserspektroskopie
carbon dioxide; isotope ratios; soil gas; tunable diode laser (TDL)
GND Keyword:Isotopenverhältnis; Kohlendioxid
Source:Proc. SPIE Vol. 5544 (2004), pp. 47 - 54
RVK - Regensburg Classification:VE 9908
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Chemie
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 54 Chemie / 540 Chemie und zugeordnete Wissenschaften
Collections:Universität Potsdam / Aufsätze (Pre- und Postprints) / Mathematisch-Naturwissenschaftliche Fakultät / Institut für Chemie / Physikalische Chemie
Notes extern:
© 2004 Society of Photo-Optical Instrumentation Engineers

This paper was published in:
Remote Sensing and Modeling of Ecosystems for Sustainability / Wei Gao, David R. Shaw (eds.), Proceedings of SPIE, Vol. 5544 (2004), pp. 47-54
ISBN: 0-8194-5482-6
DOI:10.1117/12.559551

It is made available as an electronic reprint with permission of SPIE. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purpose, or modification of the content of the paper are prohibited.