Heat Capacity of Drained Peat Soils

Tomasz Gnatowski,Cedric Kechavarzi,Ewa Ostrowska-Ligęza,Jan Szatyłowicz,Grzegorz Kurzawski

doi:10.3390/app12031579

Tomasz Gnatowski, Cedric Kechavarzi + Show 3 more

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https://doi.org/10.3390/app12031579

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Abstract

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.

Highlights

Peat soils represent unique physical properties [1] which mainly depend on the type of the organic materials [2] and advancement of decay processes in the soil surface layers [3].The low value of the soil bulk density reflects in the high organic matter content of the peat soils
The research carried out in the study showed that the cp values determined using the modulated differential scanning calorimetry (MDSC) method were lower than those that are routinely used in estimating the volumetric heat capacity of organic soils [12]
The applicability of cp value, obtained from the MDSC method, in the mixing model for different peat deposit requires further study in steady-state conditions. It results from the low range of field moisture content changes in the field monitoring in the such type soils [35]

Summary

Introduction

Peat soils represent unique physical properties [1] which mainly depend on the type of the organic materials [2] and advancement of decay processes in the soil surface layers [3].The low value of the soil bulk density reflects in the high organic matter content (low amount of ash content) of the peat soils. The organic carbon and nitrogen contents vary in peat soils and depend on the different soil management and land use [5]. Both features representing the C:N ratio indicate the degradation of the organic matter [6]. The measured amount of the CO2 efflux in peat soils depends on soil temperature, groundwater level position [9], and soil moisture content [10]. The volumetric heat capacity (Cv ) is a complex soil property which is used in the studies of soil temperature and heat flow It includes knowledge about soil thermal status and incorporates information about soil physical properties (soil bulk density and volumetric moisture content). The cp values for soil mineral constituents are in the range of approximately 0.718 to 0.939 J g−1 K−1 [13,14,15]

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