DIELECTRIC PROPERTIES OF CONTAMINATED SOIL BY SALT CRYSTALS

Abstract

Dielectric permittivity is a physical property that reflects the electric polarizability of a medium. This property is highly sensitive to the components of the studied material. It can be affected by varying the water content and the salinity of the sample. In this work, an impedance analyzer and a capacitive cell have been used to measure the complex permittivity of different samples composed of a mixture of salt crystals and soil for a frequency range between 100-10⁷ Hz and for various proportions of salt crystals in each sample. Experimental results for permittivity spectra exhibit frequency dispersion and dielectric relaxation phenomena for all samples. The relaxation occurs in the range of frequency from 1 kHz to 100 kHz. The real and imaginary parts of the permittivity are strongly correlated with the salt crystal volume fraction at 1 kHz. However, the sensitivity at 100 kHz decreases, especially for the imaginary part. Three composite dielectric mixing models (alpha models) fitting the relationship between the permittivity and the salt crystal content are evaluated with the experimental dataset. The results indicate a good estimation of the real and imaginary parts of the complex permittivity using the complex refractive index model (CRIM). However, the experimental results are misestimated by the "parallel" and "series" models. Experimental results are better fitted at 1 kHz.