Effect of biogenic gas bubbles on water flow through poorly decomposed blanket peat

A laboratory investigation was used to determine whether biogenic gas bubbles accumulate and block water-conducting pores below the water table in poorly decomposed Sphagnum peat. We found that biogenic gas bubbles did accumulate under realistic incubation temperatures. At the end of incubations at 10.5°C, volumetric water contents in two peat samples decreased to between 0.8 and 0.85 (porosity of the samples ranged from 0.96 to 0.97), indicating that the peat was considerably undersaturated with respect to water. Methane was found to be an important constituent of the gas bubbles. The presence of gas bubbles appeared to have a major effect on hydraulic conductivity (K). In control incubations, prior to which the peat had been irradiated and dosed with a biocide, biogenic gas bubbles did not accumulate, and K was 5–8 times higher than at the end of the microbially active incubations. Our results suggest that biogenic gas bubbles have a potentially significant effect on seepage in peat soils.

[1]  D. Siegel,et al.  Chemical dilation and the dual porosity of humified bog peat , 1997 .

[2]  Fred Murphy,et al.  Air Encapsulation During Infiltration , 1988 .

[3]  J. Bubier.  The Relationship of Vegetation to Methane Emission and Hydrochemical Gradients in Northern Peatlands , 1995 .

[4]  S. P. Mathur,et al.  An ombrotrophic bog as a methane reservoir , 1989 .

[5]  N. Dise,et al.  Environmental Factors Controlling Methane Emissions from Peatlands in Northern Minnesota , 1993 .

[6]  J. Chanton,et al.  Temporal variations in dissolved methane deep in the Lake Agassiz Peatlands, Minnesota , 1995 .

[7]  Tim R. Moore,et al.  Methane flux: Water table relations in northern wetlands , 1993 .

[8]  S. Zinder,et al.  Decrease of the hydraulic conductivity of sand columns by Methanosarcina barkeri , 1994, World journal of microbiology & biotechnology.

[9]  M. J. Fayer,et al.  Air encapsulation. I: Measurement in a field soil , 1986 .

[10]  D. Keeney,et al.  Gas Production in Sediments of Lake Mendota, Wisconsin 1 , 1972 .

[11]  Boris Faybishenko,et al.  Hydraulic Behavior of Quasi‐Saturated Soils in the Presence of Entrapped Air: Laboratory Experiments , 1995 .

[12]  T. Moore,et al.  Low boreal wetlands as a source of atmospheric methane , 1992 .

[13]  S. P. Mathur,et al.  A field study of the effect of depth on methane production in peatland waters: equipment and preliminary results , 1988 .

[14]  H. Ingram,et al.  Non-Darcian transmission of water in certain humified peats , 1985 .

[15]  S. P. Mathur,et al.  EFFECT OF IN‐SITU GAS ACCUMULATION ON THE HYDRAULIC CONDUCTIVITY OF PEAT , 1992 .

[16]  Jeffrey R. White,et al.  A process-based model to derive methane emissions from natural wetlands , 1996 .