V.L. Mironov – Dr.Sc.(Phys.-Math.), Corresponding Member of RAS, Main Research Scientist,  Kirensky Institute of Physics (Krasnoyarsk)

E-mail: rsdvm@ksc.krasn.ru

Yu.I. Lukin – Junior Research Scientist, 

Kirensky Institute of Physics (Krasnoyarsk)

E-mail: rsdlu@ksc.krasn.ru

In the problems of radiophysical remote sensing of soils, associated with determining such parameters such as temperature and moisture of soils, it is required the use of a model of the complex dielectric permittivity (CDP) of soils, which connects the soil parameters with the CDP value. At the same time, soils with a high clay content are of particular interest. Clay soils have a high content of bound water, which absorbs on the surface of the particles due to electrostatic forces. The presence of bound water significantly affects the physical properties of the soil. It is known that the freezing point of bound water is below the freezing point of bulk water outside clay, even at −30°C, some amount of unfrozen bound water remains, which affects the plastic properties of the soil. The dielectric properties of bound water also differ from the properties of bulk water outside the soil. Thus, the creation of a CDP model of clay soils is an urgent task.

In the current work, the multi-relaxation model of the CDP of bentonite clay, taking into account effect of Maxwell–Wagner relaxation at the low frequencies and dipole orientational relaxation of water molecules in the SHF range, has been suggested. The developing of the model proposed based on the measured spectra of the real and imaginary parts of the CDP of bentonite clay samples in the range of electromagnetic field frequency from 15 MHz to 15 GHz, in the range of gravimetric moisture from dry state to 1 g/g and in the temperature range from 25 to −30°C during freezing process. Using the regression analysis method, the optimal number of relaxations in each type of water in bentonite was found to describe the CDP spectrum in the frequency range under consideration. The parameters, which are the characteristics of the spectrum of the CDP of each type of water in bentonite, were found. A model of ionic conductivity has been developed to take this parameter into account in the СDP model.

The results obtained can be used in the developing of the CDP models of soils containing bound water, which in turn can be used in the methods of remote sensing of the Earth's surface.

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