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United States Department of Agriculture

Agricultural Research Service

Title: Complex Dielectric Spectra of Soil As Influenced by Hydrophobicity

Author
item Logsdon, Sally

Submitted to: Pacific Division American Association for the Advancement of Science
Publication Type: Abstract Only
Publication Acceptance Date: June 16, 2004
Publication Date: June 16, 2004
Citation: Logsdon, S.D. 2004. Complex dielectric spectra of soil as influenced by hydrophobicity [abstract]. Pacific Division American Association for the Advancement of Science. 23(1):61.

Technical Abstract: The apparent dielectric and bulk electrical conductivity have traditionally been measured at one frequency and related to water content or salinity. Inconsistencies suggest other soil properties are measured. The purpose of this study was to measure soil electrical properties across a range of frequencies, and to relate the spectra to soil properties. We measured the reflection scattering parameter for six soils packed into two sizes of truncated coaxial chambers. The soils ranged from kaolinitic to smectitic, and were each measured at four water contents. The frequencies ranged from 300 kHz to 3 GHz. The scattering parameter was converted to complex electrical properties: permittivity, electrical conductivity, and resistivity. The smaller chamber had larger permittivity values at lower frequencies. The direct current (d.c.) electrical conductivity fitted from the electrical conductivity spectra was correlated 1:1 with that fitted from resistivity spectra, but the fitted relaxation frequency and exponent did not agree between the electrical conductivity and resistivity spectra. Multiple relaxations were required to fit the complex permittivity spectra, and the fitted parameters did not agree with those from the electrical conductivity or resistivity spectra. Also fitting the complex permittivity spectra resulted in non-unique parameters. Most of the dielectric dispersion occurred at frequencies less than 30 MHz, and dielectric dispersion was greatest for the calcareous soil and high for the smectitic soils. Study is ongoing to determine the physical and chemical significance of the spectra.

Last Modified: 4/18/2014
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