Dissertation
Measurement of forest ecosystem-atmosphere exchange of 813 C-CO2 using Fourier transform infrared spectroscopy and disjunct eddy covariance
Washington State University
Doctor of Philosophy (PhD), Washington State University
05/2010
DOI:
https://doi.org/10.7273/000006047
Abstract
The measurement of the stable isotopic content and isotopic flux of atmospheric carbon dioxide is important for understanding the carbon budget on ecosystem, regional, and global spatial scales. Conventional measurements of the isotopic composition of atmospheric CO2 involve laboratory mass spectrometry analysis of grab samples from the field, which limits the location, collection frequency and throughput of samples. More technologically advanced methods (e.g. tunable diode laser spectroscopy) suffer from interferences with other chemical species. We have developed a new measurement method based on Fourier-transform infrared spectroscopy (FTIR) and disjunct eddy covariance (DEC) for fast, continuous, real-time measurement of the carbon isotopic composition of atmospheric CO2. Molecular absorption is measured in the 2100 to 2500 cm-1 spectral region of the 13CO2 and 12CO2 vibration-rotation bands with concentrations of both isotopologues used to determine [delta]13C. We demonstrate the capability of this new technique in a managed poplar forest near Boardman, Oregon with measurements during the summers of 2005 and 2006 from a 22-meter tower in a 16-m forest canopy. Long-term calibration using reference gas cylinders yielded field accuracy and precision for the forest measurements of 0.5 and 0.8 , respectively, for the 45-second cycle time between samples. The signature of ecosystem respiration derived from the nighttime vertical profile measurements of CO2 - [delta]13C was 26.6 , about 2 more enriched than the isotopic composition of measured bulk leaf samples from the forest. Ecosystem respired CO2 was ~1.6 more enriched than soil-respired CO2. A comparison of the FTIR DEC total CO2 fluxes against standard eddy covariance measurements showed excellent (10%) agreement. FTIR DEC measurement of the CO2 isoflux enabled the estimation of the mean carbon isotope ratio of the photosynthetic flux ([delta]P). The average [delta]P (-24.9 ) was 13C enriched compared with the isotopic composition of bulk leaf samples. These results are consistent with observations using conventional methods. The FTIR DEC technique can simultaneously measure several important trace gases, which will make it a powerful tool for application in forest, agricultural and urban ecosystems.
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Details
- Title
- Measurement of forest ecosystem-atmosphere exchange of 813 C-CO2 using Fourier transform infrared spectroscopy and disjunct eddy covariance
- Creators
- Maria Obiminda L. Cambaliza
- Contributors
- George H. Mount (Chair)Brian K Lamb (Committee Member) - Washington State University, Department of Civil and Environmental EngineeringHalvor H Westberg (Committee Member)John D MARSHALL (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Civil and Environmental Engineering
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 153
- Identifiers
- 99901055024201842
- Language
- English
- Resource Type
- Dissertation