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Dynamics of methane ebullition from a peat monolith revealed from a dynamic flux chamber system
Author(s) -
Yu Zhongjie,
Slater Lee D.,
Schäfer Karina V. R.,
Reeve Andrew S.,
Varner Ruth K.
Publication year - 2014
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1002/2014jg002654
Subject(s) - monolith , methane , peat , flux (metallurgy) , dynamics (music) , environmental science , chemistry , physics , ecology , catalysis , organic chemistry , biology , biochemistry , acoustics
Abstract Methane (CH 4 ) ebullition in northern peatlands is poorly quantified in part due to its high spatiotemporal variability. In this study, a dynamic flux chamber (DFC) system was used to continuously measure CH 4 fluxes from a monolith of near‐surface Sphagnum peat at the laboratory scale to understand the complex behavior of CH 4 ebullition. Coincident transmission ground penetrating radar measurements of gas content were also acquired at three depths within the monolith. A graphical method was developed to separate diffusion, steady ebullition, and episodic ebullition fluxes from the total CH 4 flux recorded and to identify the timing and CH 4 content of individual ebullition events. The results show that the application of the DFC had minimal disturbance on air‐peat CH 4 exchange and estimated ebullition fluxes were not sensitive to the uncertainties associated with the graphical model. Steady and episodic ebullition fluxes were estimated to be averagely 36 ± 24% and 38 ± 24% of the total fluxes over the study period, respectively. The coupling between episodic CH 4 ebullition and gas content within the three layers supports the existence of a threshold gas content regulating CH 4 ebullition. However, the threshold at which active ebullition commenced varied between peat layers with a larger threshold (0.14 m 3 m −3 ) observed in the deeper layers, suggesting that the peat physical structure controls gas bubble dynamics in peat. Temperature variation (23°C to 27°C) was likely only responsible for small episodic ebullition events from the upper peat layer, while large ebullition events from the deeper layers were most likely triggered by drops in atmospheric pressure.