Determining the relationship between the dielectric properties and the basic physical and chemical parameters of the air-dry soil

Measurements of the electric conductivity, σ, and relative dielectric permittivity, εr, were conducted (0.1Hz –15 MHz) on 40 air-dried soil samples that were subsequently analyzed for pH, total organic matter in soil (ΔM/m1), P2O5, , Fe2O3 and heavy metal concentrations (Pb, Cd, Cr, Ni, Cu и Zn). The pH of soil samples varied between pH 5.25 and pH 7.73 (mean pH 6.71), the ΔM/m1 varied between 1,49 % and 9.96 % (mean 4.56 %). The mean content of Fe2O3 was 44352.5 mg/kg, which was 114 fold higher than the mean concentration of the heavy metals (Pb, Cd, Cr, Ni, Cu и Zn). The mean content of P2O5 was 0.26% . We found a linear relation between σ (1 MHz) and the indicated physicochemical parameters; P2O5 (coefficient of correlation, r = 0.637), рН (R = 0.530 ) , Fe2O3 concentration (r = 0.450), content of ΔM/m1 (r = 0.545) and heavy metal concentration (r = 0.460). Similar relationships and correlation coefficients were found between εr (10 kHz) and the same physicochemical parameters. As the latter represent general biogeochemical parameters, our findings suggest that dielectric spectroscopy may provide useful approach to probing soil geochemistry, iron cycling and anaerobic microbial activity. Furthermore, our results yield insights into the impact of various physicochemical parameters on the induced polarization of soils.