A lumped bubble capacitance model controlled by matrix structure to describe layered biogenic gas bubble storage in shallow subtropical peat

Chen, Xi and Comas, Xavier and Binley, Andrew Mark and Slater, Lee (2018) A lumped bubble capacitance model controlled by matrix structure to describe layered biogenic gas bubble storage in shallow subtropical peat. Water Resources Research, 54 (8). pp. 5487-5503. ISSN 0043-1397

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Abstract

Methane (CH4) accumulates in the gaseous phase in peat soils, being released to the atmosphere at rates higher than those for diffusion and plant‐mediated pathways. An understanding of the mechanisms regulating gas bubble storage in peat remains incomplete. We developed a layered capacitance model to compare the bubble storage ability of peat over different depths. A peat monolith (0.395 m × 0.243 m × 0.247 m) was collected from the U.S. Everglades and kept submerged for 102 days from a condition of minimum bubble storage to bubble saturation. Time‐lapse electromagnetic wave velocity and power spectrum data were used to estimate changes in both gas content and relative average dimensions of stored bubbles with depth. Bubble capacitance, defined as the increase in volumetric gas content (m3 m−3) divided by the corresponding pressure (Pa), ranges from 3.3 × 10−4 to 6.8 × 10−4 m3 m−3 Pa−1, with a maximum at 5.5 cm depth Bubbles in this hotspot were larger relative to those in deeper layers, while the decomposition degree of the upper layers was generally smaller than that of the lower layers. X‐ray computed tomography on peat sections identified a specific depth with a low void ratio, and likely regulating bubble storage. Our results suggest that bubble capacitance is related to (1) the difference in size between bubbles and peat pores, and (2) the void ratio. Our work suggests that changes in bubble size associated with variations in water level driven by climate change will modify bubble storage in peat soils.

Item Type:
Journal Article
Journal or Publication Title:
Water Resources Research
Additional Information:
An edited version of this paper was published by AGU. Copyright 2018 American Geophysical Union. Chen, X., Comas, X., Binley, A., & Slater, L. (2018). A lumped bubble capacitance model controlled by matrix structure to describe layered biogenic gas bubble storage in shallow subtropical peat. Water Resources Research, 54. https://doi.org/10.1029/2018WR022573 To view the published open abstract, go to http://dx.doi.org and enter the DOI.
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/2300/2312
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ID Code:
126957
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Deposited On:
17 Aug 2018 09:22
Refereed?:
Yes
Published?:
Published
Last Modified:
29 Sep 2020 04:24