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| Titel |
Long-term field performance of a tunable diode laser absorption spectrometer for analysis of carbon isotopes of CO2 in forest air |
| VerfasserIn |
S. M. Schaeffer, J. B. Miller, B. H. Vaughn, J. W. C. White, D. R. Bowling |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 8, no. 17 ; Nr. 8, no. 17 (2008-09-05), S.5263-5277 |
| Datensatznummer |
250006363
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| Publikation (Nr.) |
 copernicus.org/acp-8-5263-2008.pdf |
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| Zusammenfassung |
| Tunable diode laser absorption spectrometry (TDLAS) is gaining in popularity
for measuring the mole fraction [CO2] and stable isotopic composition
(δ13C) of carbon dioxide (CO2) in air in studies of
biosphere-atmosphere gas exchange. Here we present a detailed examination of
the performance of a commercially-available TDLAS located in a high-altitude
subalpine coniferous forest (the Niwot Ridge AmeriFlux site), providing the
first multi-year analysis of TDLAS instrument performance for measuring
CO2 isotopes in the field. Air was sampled from five to nine vertical
locations in and above the forest canopy every ten minutes for 2.4 years. A
variety of methods were used to assess instrument performance. Measurement
of two compressed air cylinders that were in place over the entire study
establish the long-term field precision of 0.2 μmol mol−1 for
[CO2] and 0.35‰ for δ13C, but after fixing several
problems the isotope precision improved to 0.2\permil (over the last several
months). The TDLAS provided detail on variability of δ13C of
atmospheric CO2 that was not represented in weekly flask samples, as
well as information regarding the influence of large-scale (regional)
seasonal cycle and local forest processes on [CO2] and δ13C
of CO2. There were also clear growing season and winter
differences in the relative contributions of photosynthesis and respiration
on the [CO2] and δ13C of forest air. |
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