The Study of Energetic Status of Bound Water Using Dielectric Methods

The main goal of this work is to estimate energy status of water (its mobility) in both unfrozen and frozen soil and ground on the basis of their dielectric properties. We studied the relationships between complex (E), real (E') and imaginary (E") components of dielectric permittivity and (1) volumetric water content (W) within the range of hydroscopic water to total water content, and (2) temperature (T) in the range --16 to + 2oC (for melting samples). Investigation was conducted for Soddy Podzolic, Gray Forest, and Chernozemic soils as well as the samples of bentonite, kaolin, and quartz sand. Energy status of water was determined on the basis of soil-hydrological constants and water soil potential. Dielectric properties were measured in both time and frequency domains. We used a time domain reflectometer (TDR) (pulse rising times < 100 ps), and a capacitive sensor (at 50 MHz). For both methods, slope angle of the curves of E, E' and E'' versus W changes as water status changes. It is dependent on both mineralogy of these samples and method used. Unlike TDR, the capacitive sensor (Hydra Soil Moisture Probe, Vitel Inc) was sensitive to change in water mobility at lower water content. The shape of curves of E' and E'' versus T reflects a gradual increase of water mobility as T increases, and they are different for samples having different mineralogy. We hope that a more detailed investigation of the relationships obtained will allow us to develop a technique for the determination of energy status of water in the wet soil and grounds on the basis of their dielectric characteristics. This work was support by Russian Foundation for Basic Research grants 03-04-49325 and 04-05-79077.