TY - JOUR

T1 - Characterization of peat structure using X-ray computed tomography and its control on the ebullition of biogenic gas bubbles

AU - Kettridge, Nicholas

AU - Binley, Andrew

N1 - Copyright 2011 by the American Geophysical Union.

PY - 2011/3/9

Y1 - 2011/3/9

N2 - The structural arrangement of peat constituents controls the hydrological and thermal properties of peat. However, the importance of these structural characteristics on other physical processes within a peatland has not been fully assessed. Here, we evaluate the importance of peat structure on its ability to entrain biogenic gas bubbles and control ebullition, an important transport mechanism for methane. X-ray computed tomography (CT) was applied to characterize the structure of a range of peats at varying levels of decomposition. The structural properties of the peat were quantified from a vector representation of the CT images, and the potential of each sample to entrain biogenic gas bubbles was quantified using a rule-based Monte Carlo model that calculates the tortuosity of bubbles pathways through the peat. Sixty-six percent of the variability in the trapping potential of the peat results from porosity variations and 34% from structural variations between samples. A metric that represents this structural control was not identified for all peat types because of difficulties adequately representing some peats as a vector network. However, for S. magellanicum peat we were able to establish that the influence of peat structure on the entrainment of gas bubbles is characterized by (L) over bar (v), the average vector length of the stems and branches. Peat characterized by longer structural components (larger (L) over bar (v)) enhances the entrainment of gas bubbles. Our findings demonstrate the need to incorporate some representation of the peat structure in numerical models of biogenic gas transport in peat.

AB - The structural arrangement of peat constituents controls the hydrological and thermal properties of peat. However, the importance of these structural characteristics on other physical processes within a peatland has not been fully assessed. Here, we evaluate the importance of peat structure on its ability to entrain biogenic gas bubbles and control ebullition, an important transport mechanism for methane. X-ray computed tomography (CT) was applied to characterize the structure of a range of peats at varying levels of decomposition. The structural properties of the peat were quantified from a vector representation of the CT images, and the potential of each sample to entrain biogenic gas bubbles was quantified using a rule-based Monte Carlo model that calculates the tortuosity of bubbles pathways through the peat. Sixty-six percent of the variability in the trapping potential of the peat results from porosity variations and 34% from structural variations between samples. A metric that represents this structural control was not identified for all peat types because of difficulties adequately representing some peats as a vector network. However, for S. magellanicum peat we were able to establish that the influence of peat structure on the entrainment of gas bubbles is characterized by (L) over bar (v), the average vector length of the stems and branches. Peat characterized by longer structural components (larger (L) over bar (v)) enhances the entrainment of gas bubbles. Our findings demonstrate the need to incorporate some representation of the peat structure in numerical models of biogenic gas transport in peat.

KW - BOG

KW - WATER

KW - HYDRAULIC CONDUCTIVITY

KW - FLOW

KW - HYDROLOGY

KW - PORE-SIZE

UR - http://www.scopus.com/inward/record.url?scp=79952754119&partnerID=8YFLogxK

U2 - 10.1029/2010JG001478

DO - 10.1029/2010JG001478

M3 - Journal article

AN - SCOPUS:79952754119

VL - 116

JO - Journal of Geophysical Research: Biogeosciences

JF - Journal of Geophysical Research: Biogeosciences

SN - 2169-8961

IS - G1

M1 - G01024

ER -