Thermophysical Properties of Histosols on Lowmoor Peat

Resumo

The temperature regime and the dependence of thermal diffusivity on the volumetric water content in high-ash drained peat soils (Sapric Drainic Histosols (Lignic)) on woody peat underlain by grass, sedge, and woody peat layer in the Yakhroma River valley (Moscow oblast) were studied in terrain and laboratory on undisturbed samples. In the laboratory, the dependences of thermal diffusivity were determined in the course of sample drying by the Kondrat’ev method (a steady-state radial heat flow); whereas the terrain dynamic data on the daily temperature variations were used to solve the inverse problem by the heat wave method. The dependences obtained by laboratory and field methods showed a dome-like shape, the maxima of which were close (at the volumetric water content equal to 57–60%), but the thermal diffusivity obtained from the terrain data was 1.2 times lower at the maximum point. Considering the further use of dependences in predictive mathematical models, approximation of the curves by the method of Chang and Horton made it possible to evaluate the accuracy of the approximation parameters and to compare them. According to the laboratory method, the approximation errors grew reliably with an increase in the measured thermal diffusivity, which points to a systematic error in the laboratory measurement of the latter as dependent on the water content; this effect was not registered in the field method. The systematic errors in laboratory studies must be associated with shrinkage and vapor transfer.