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The effect of pore structure on ebullition from peat

Ramirez, Jorge A.; Baird, Andy J.; Coulthard, Tom J.

Authors

Jorge A. Ramirez

Andy J. Baird

Abstract

The controls on methane (CH₄) bubbling (ebullition) from peatlands are uncertain, but evidence suggests that physical factors related to gas transport and storage within the peat matrix are important. Variability in peat pore size and the permeability of layers within peat can produce ebullition that ranges from steady to erratic in time, and can affect the degree to which CH₄ bubbles bypass consumption by methanotrophic bacteria and enter the atmosphere. Here we investigate the role of peat structure on ebullition in structurally different peats using a physical model that replicates bubble production using air injection into peat. We find that the frequency distributions of number of ebullition events per time and the magnitude of bubble loss from the physical model were similar in shape to ebullition from peatlands and incubated peats. This indicates that the physical model could be a valid proxy for naturally occurring ebullition from peat. For the first time, data on bubble sizes from peat were collected to conceptualize ebullition, and we find that peat structure affects bubble sizes. Using a new method to measure peat macro structure, we collected evidence that supports the hypothesis that structural differences in peat determine if bubble release is steady or erratic and extreme. Collected pore size data suggests that erratic ebullition occurs when large amounts of gas stored at depth easily move through shallower layers of open peat. In contrast, steady ebullition occurs when dense shallower layers of peat regulate the flow of gas emitted from peat.

Publication Date 2016-06
Journal Journal of geophysical research. Biogeosciences
Print ISSN 2169-8953
Electronic ISSN 2169-8961
Publisher American Geophysical Union
Peer Reviewed Peer Reviewed
Volume 121
Issue 6
Pages 1646-1656
Institution Citation Ramirez, J. A., Baird, A. J., & Coulthard, T. J. (2016). The effect of pore structure on ebullition from peat. Journal of Geophysical Research: Biogeosciences, 121(6), 1646-1656. https://doi.org/10.1002/2015jg003289
DOI https://doi.org/10.1002/2015jg003289
Keywords Carbon cycling; Wetlands; Probability distributions; Heavy and fat-tailed
Publisher URL http://onlinelibrary.wiley.com/doi/10.1002/2015JG003289/full
Additional Information Authors' accepted manuscript of article published in Journal of geophysical research. Biogeosciences, 2016, v.121, issue 6

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