Effects of moisture content and shrinkage on soil-thermal properties for peat soils in Japan

Abstract

Wetland is known as a source of atmospheric methane, typically produced by microbiological and chemical processes under anaerobic conditions. Soil temperature in the wetlands is a key factor to control the processes. Peat soils can be found in many types of wetlands. Peat soils contain high organic matter content and thus shows unique physical properties such as high total porosity and shrinkage. This study aims to study the heat transport of peat soils at variably saturated conditions and effects of volume shrinkage on thermal properties of peat soils. Study area of this research is Bibai marsh, Hokkaido in Japan. Undisturbed peat samples were obtained from two different peat profiles at different depths. In general, the thermal conductivity (TC) and the heat capacity (HC) of peat soils linearly increased with increasing volumetric water content, and simple two-phase (solid and water phases) models for TC and HC could generally express TC and HC behaviors, respectively, for most of peat soils. In addition, the observed volume-shrinkage of the peat soils under dry conditions did not affect the TC and HC behaviors for the studied samples.