Temperature and Mineralogy Dependable Model for Microwave Dielectric Spectra of Moist Soils

In this paper, a physically based dielectric model in microwave band for moist soils is developed to account for both the temperature and granulometric mineralogy of the soil. The generalized refractive mixing dielectric model (GRMDM) previously developed by V. L. Mironov et al. was used as a mean to determine the spectroscopic parameters for 5 soils which complex dielectric constant spectra were measured and presented in Technical Report EL-95-34, December 1995 by J. O. Curtis et al. The measurement results used covered the temperatures of 10, 20, 30, and 40◦C, gravimetric clay contents from 0 to 0.76 g/g, and frequencies from 0.3 to 26.5GHz. Relating to each individual soil, such GRMDM spectroscopic parameters as dielectric constants in low frequency limit, relaxation times, and ohmic conductivities, pertaining to both bound and unbound soil water, were fitted as functions of temperature with the ClausiussMossotii, Debye and linear equations, respectively. As a result, a set of physical parameters for a temperature dependable generalized refractive mixing dielectric model (TD GRMDM), consisting of the volumetric expansion coefficients, activation energies, enthropies of activation and others, were obtained. Finally, the parameters of the TD GRMDM as functions of gravimetric clay content were fitted to yield the closing set of polinomial formulas, which, in conjunction with the TD GRMDM, represent a temperature and mineralogy dependable soil dielectric model (TMD SDM). Thus developed, the TMD SDM provides for predictions of the complex dielectric constant of moist soils as a function of moisture, wave frequency, temperature and gravimetric clay content. Further the TMD SDM prediction error was estimated with the use of the ndependent dielectric data.