Thermal analysis of organic matter in cryogenic soils (Central Siberian Plateau)

Abstract

The thermal degradation of organic matter was studied in cryogenic soils with methods of thermal analysis: differential scanning calorimetry and thermogravimetry (DSC and TG, respectively). The DSC curves of most of the samples within the temperature range from 221–247°C to 600°C were characterized by the presence of one wide exothermic peak (at 311–373°C) with a shoulder (or without it) on the descending branch at a temperature of about 400°C. This was connected mostly with the destruction of thermolabile compounds (oligo- and polysaccharides) and with the oxidation of low-aromatic complexes of plant residues and humus substances. Two exothermic peaks at 337–373°C and 448–492°C were found for some samples from the organic horizons. The high-temperature peaks were caused by the thermal destruction of lignin. The fraction of the thermolabile organic matter of the soil (237–261…331–377°C) reached 59–73% in the organic and 52–59% in the organomineral and mineral horizons.