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- Title
Evaluation of a cavity ring-down spectrometer for in situ observations of <sup>13</sup>CO<sub>2</sub>.
- Authors
Vogel, F. R.; Huang, L.; Ernst, D.; Giroux, L.; Racki, S.; Worthy, D. E. J.
- Abstract
With the emergence of wide-spread application of new optical techniques to monitor δ13C in atmospheric CO2 there is a growing need to ensure well-calibrated measurements. We characterized one commonly available instrument, a cavity ring-down spectrometer (CRDS) system used for continuous in situ monitoring of atmospheric 13CO2. We found no dependency of δ13C on the CO2 concentration in the range of 303-437 ppm. We designed a calibration scheme according to the diagnosed instrumental drifts and established a quality assurance protocol. We find that the repeatability (1-σ) of measurements is 0.25 ‰ for 10 min and 0.15 ‰ for 20 min integrated averages, respectively. Due to a spectral overlap, our instrument displays a cross-sensitivity to CH4 of 0.42±0.024 ‰ ppm-1. Our ongoing target measurements yield standard deviations of δ13C from 0.22 ‰ to 0.28 ‰ for 10 min averages. We furthermore estimate the reproducibility of our system for ambient air samples from weekly measurements of a long-term target gas to be 0.18 ‰. We find only a minuscule offset of 0.002±0.025 ‰ between the CRDS and Environment Canada's isotope ratio mass spectrometer (IRMS) results for four target gases used over the course of one year.
- Subjects
CALIBRATION gases; CARBON dioxide; PROTOCOL engineering; STANDARD deviations; MASS spectrometers; ACIDIFICATION
- Publication
Atmospheric Measurement Techniques, 2013, Vol 6, Issue 2, p301
- ISSN
1867-1381
- Publication type
Article
- DOI
10.5194/amt-6-301-2013