The effect of pore structure on ebullition from peat

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

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.

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

• Acceptance Date: Nov 26, 2015
• Online Publication Date: Jun 24, 2016
• Publication Date: 2016-06
• Deposit Date: Jun 17, 2016
• Publicly Available Date: Jun 24, 2016
• 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
• DOI: https://doi.org/10.1002/2015jg003289
• Keywords: Carbon cycling; Wetlands; Probability distributions; Heavy and fat-tailed
• Public URL: https://hull-repository.worktribe.com/output/439830
• 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