Heat Capacity of Drained Peat Soils

Soil-specific heat capacity (cp) and volumetric heat capacity (Cv) are recognized as a fundamental soil property essential for the accurate prediction of soil temperature and heat flow. This study presents the analysis of these thermal properties for drained peat soils in Poland. The objectives of this study were to (i) measure and develop a method for determining cp, (ii) analyze the (Cv) data for undisturbed soil samples from surface layers, and (iii) test the applicability of the cp value for calculating Cv of drained peat soils using the mixing model concept. The cp value was measured under laboratory conditions using a modulated differential scanning calorimetry (MDSC) for 18 soil layers sampled in six degraded peat soil profiles. The Cv was estimated for undisturbed triplicate soil samples from the 22 depths (66 samples) by using a dual-needle probe. The cp data for the organic soils were linearly temperature-dependent (MDSC) for the temperature range considered (−20–30 °C). The overall average cp value was equal to 1.202 J g−1 K−1 at a temperature of 0 °C. An increment in temperature of 1 °C corresponded to an increase in cp of 0.0043 J g−1 K−1 on average. Nevertheless, the lowest cp value was obtained for moss samples whereas the highest value represents alder peats. The Cv data measured using the heat thermal probe (HTP) method changed linearly with changes in the soil moisture content (θv) of the moorsh soils. The volumetric heat capacity calculated using the mixing model was comparable to the mean of measured values obtained on the triplicate samples.