Application Note B-TA1091
Introduction
STA (TG-DTA) measurements were performed on soils collected from different locations to evaluate differences in their thermal behavior.
Measurement and results
Approximately 20 mg of soil collected from sandy, grassy, or farmland areas was placed in a Pt sample pan; the measurement was conducted under an air atmosphere, flow rate of 200 mL/min, at a heating rate of 10 °C/min.
Figure.1 Comparison of STA (TG-DTA) results for soil collected from sandy, grassy, or farmland areas
For soil samples collected from the grassy, or farmland areas , mass loss accompanied by an endothermic DTA peak due to dehydration was observed up to approximately 150 °C, followed by the two-step mass loss with the exothermic DTA peaks considered to be associated with the combustion of organic compounds were observed between approximately 250 °C and 650 °C.
The mass loss due to dehydration was greater for the farmland soil, whereas both samples show nearly identical mass loss associated with the combustion of organic compounds.
A similar thermal behavior was observed for the soil collected from the sandy area. However, the mass losses resulting from both dehydration and the combustion of organic compounds are smaller compared to those of soils from the grassy, or farmland areas.
The mass loss caused by dehydration reflects the moisture content of the soil and serves as an indicator of water retention capacity and drying condition. The amount of organic compounds reflects the quantity of materials such as the remains of plants, animals, and microorganisms collectively known as humus and serves as a soil indicator relevant to crop growth.
Thus, STA (TG-DTA) is a simple and effective method for evaluating moisture content and organic compounds in soils.
