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Understanding peat's ability to trap methane bubbles

A paper by Nick Kettridge (McMaster University) and Andy Binley (LEC) has been identified as one of eight papers in the current AGU Journal Highlights.

Peat soils make up one third of the global soil carbon pool, and provide one of the largest natural sources of atmospheric methane. Bubbles of methane, an important greenhouse gas, are produced by the decomposition of peat underwater. The bubbles increase in size until their buoyancy exceeds the forces keeping them in place, at which point the methane bubbles move upward through the soil and are released at the surface in what is known as an ebullition event. Ebullition events may account for a large proportion of methane lost from peatlands.

To learn more about the factors contributing to the ability of peat to trap gas bubbles, Kettridge and Binley used X-ray computed tomography to produce detailed high resolution 3D images of a wide range of peat samples composed of different plant species at varying levels of decomposition. They used simulations to predict the pathways that different bubbles could take through the imaged samples and identify the potential of the peat to trap bubbles. The research shows that the ability of peat to trap gas depends on both the constituents of the peat and how these constituents are spatially arranged. Peat samples with longer structural components trapped gas more readily than those with shorter components, demonstrating the need to incorporate some representation of peat structure into models of gas bubble transport.

"Characterization of peat structure using X-ray computed tomography and its control on the ebullition of biogenic gas bubbles" VOL. 116, G01024, 11 PP., 2011 doi:10.1029/2010JG001478

Mon 09 May 2011