Multigas Leakage Correction in Static Environmental Chambers Using Sulfur Hexafluoride and Raman Spectroscopy

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• 作者：Tobias Jochum ; Joseph C. von Fischer ; Susan Trumbore ; J眉rgen Popp ; Torsten Frosch
• 刊名：Analytical Chemistry
• 出版年：2015
• 出版时间：November 3, 2015
• 年：2015
• 卷：87
• 期：21
• 页码：11137-11142
• 全文大小：322K
• ISSN：1520-6882

文摘

In static environmental chamber experiments, the precision of gas flux measurements can be significantly improved by a thorough gas leakage correction to avoid under- or overestimation of biological activity such as respiration or photosynthesis. Especially in the case of small biological net gas exchange rates or gas accumulation phases during long environmental monitoring experiments, gas leakage fluxes could distort the analysis of the biogenic gas kinetics. Here we propose and demonstrate a general protocol for online correction of diffusion-driven gas leakage in plant chambers by simultaneous quantification of the inert tracer sulfur hexafluoride (SF₆) and the investigated biogenic gases using enhanced Raman spectroscopy. By quantifying the leakage rates of carbon dioxide (CO₂), methane (CH₄), and hydrogen (H₂) simultaneously with SF₆ in the test chamber, their effective diffusivity ratios of approximately 1.60, 1.96, and 5.65 were determined, each related to SF₆. Because our experiments suggest that the effective diffusivity ratios are reproducible for an individual static environmental chamber, even under varying concentration gradients and slight changes of the chamber sealing, an experimental method to quantify gas leakage fluxes by using effective diffusivity ratios and SF₆ leakage fluxes is proposed. The method is demonstrated by quantifying the CO₂ net exchange rate of a plant鈥搒oil ecosystem (Mirabilis jalapa). By knowing the effective chamber diffusivity ratio CO₂/SF₆ and the measured SF₆ leakage rate during the experiment, the leakage contribution to the total CO₂ exchange rate could be calculated and the biological net CO₂ concentration change within the chamber atmosphere determined.