Dielectric Behavior of Sodic Solonchak at 1.41 GHz in the South of Western Siberia

Saline soils, characterized by low biological productivity, bring the threat to food security in many countries of the world. An urgent task is to develop and improve methods of remote microwave sensing of saline soils. The accuracy and reliability of microwave methods are achieved by studying the behavior of dielectric properties of saline soils under variations of their physical and chemical parameters. This paper presents the results of the study of moisture and temperature influence on the dielectric properties of sodic solonchak. Samples of saline soil were taken from the surface of sodic solonchak on the Kulunda steppe, in the south of Western Siberia. The dielectric properties of saline soils were measured at a frequency of 1.41 GHz. From the results of chemical and granulometric analyses, it follows that solonchak contains bound water adsorbed by the surface of soil particles, crystallization water stored in crystalline hydrates of mineral salts, and soil solution (SS) of mineral salts. A refractive model is used to describe the dependence of refractive index and absorption factor on moisture. Based on this model, the dielectric properties of different phases of water present in sodic solonchak are estimated. The simulation of the temperature dependence of refractive index and absorption factor for two different values of moisture is carried out. By using the model as the base, the dependences of solonchak emissivity on temperature conforming to the experimental data are established. The results obtained can be used in the development of algorithms to increase the accuracy of remote microwave sensing of saline soils, consideration of solonchak influence on microwave radiation of the underlying surface, the interpretation of satellite data of microwave sensing.