Validation and Application of Cavity-Enhanced, Near-Infrared Tunable Diode Laser Absorption Spectrometry for Measurements of Methane Carbon Isotopes at Ambient Concentrations

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• 作者：Behzad Mortazavi ; Benjamin J. Wilson ; Feng Dong ; Manish Gupta ; Doug Baer
• 刊名：Environmental Science & Technology
• 出版年：2013
• 出版时间：October 15, 2013
• 年：2013
• 卷：47
• 期：20
• 页码：11676-11684
• 全文大小：569K
• 年卷期：v.47,no.20(October 15, 2013)
• ISSN：1520-5851

文摘

Methane is an effective greenhouse gas but has a short residence time in the atmosphere, and therefore, reductions in emissions can alleviate its greenhouse gas warming effect within a decadal time frame. Continuous and high temporal resolution measurements of methane concentrations and carbon isotopic ratios (未¹³CH₄) can inform on mechanisms of formation, provide constraints on emissions sources, and guide future mitigation efforts. We describe the development, validation, and deployment of a cavity-enhanced, near-infrared tunable diode laser absorption spectrometry system capable of quantifying 未¹³CH₄ at ambient methane concentrations. Laboratory validation and testing show that the instrument is capable of operating over a wide dynamic range of methane concentration and provides a measurement precision for 未¹³CH₄ of better than 卤0.5鈥?(1蟽) over 1000 s of data averaging at ambient methane concentrations. The analyzer is accurate to better than 卤0.5鈥? as demonstrated by measurements of characterized methane/air samples with minimal dependence (<1鈥? of measured carbon isotope ratio on methane concentration. Deployment of the instrument at a marsh over multiple days demonstrated how methane fluxes varied by an order of magnitude over 2 day deployment periods, and showed a 17 鈥?variability in 未¹³CH₄ of the emitted methane during the growing season.