Dielectric properties, soil

The dielectric properties of soil determine the amount of RF power that can be dissipated in the soil. These properties are the relative dielectric constant (e ) and the loss-tangent. The loss-tangent, tan 6, is defined as o/oieQe where a is the apparent conductivity, w is the frequency of the applied electric field, radians/sec, and is the permittivity of free space which equals 8.85 X 10 Farads/meter. All the dielectric properties are a function of soil temperature, the frequency of the applied field, and the composition of the soil. 

Adsorption of enteric viruses on mineral surfaces in soil and aquatic environments is well recognized as an important mechanism controlling virus dissemination in natural systems. The adsorption of poliovirus type 1, strain LSc2ab, on oxide surfaces was studied from the standpoint of equilibrium thermodynamics. Mass-action free energies are found to agree with potentials evaluated from the DLVO-Lifshitz theory of colloid stability, the sum of electrodynamic van der Waals potentials and electrostatic double-layer interactions. The effects of pH and ionic strength as well as electrokinetic and dielectric properties of system components are developed from the model in the context of virus adsorption in extra-host systems. 

The third exanqile for polycyclic aromatic compoimds of environmental concern is the polychlorinated biphenyls (PCBs). The vast majority of PCBs in the environment are derived from commercial mixtures iAroclors), which contain 60 to 80 different congeners. These mixtures have found widespread industrial use in the past, owing to their physical and chemical stability and their dielectric properties. Inadequate waste disposal has led to their release into the environment, and they have been routinely detected in soil and water samples since the early 1960s. 

Trademarked Kalene, this material is a depolymerized virgin butyl rubber, which is similar to butyl LM rubber. The properties are similar to those of conventional butyl rubber such as the lowest vapor transmission rate of any elastomer, resistance to degradation in high-humidity, high-temperature environments (very Uttle change after 120°C steam for 1(X)0 h), excellent electrical properties (volume resistivity of 5.5 X 10 ohm-cm and a dielectric constant of 3.1), resistance to soil bacteria, excellent weathering, and resistance to chemicals and oxidation. 

Application of the model to clay-solution aggregates showed that the radiofrequency dispersions of these systems at 10-50 MHz are fairly well described by the model. These dispersions were found to depend on the clay type (kaolinite, illite, montmorillonite), degree of consolidation, and soil fabric these properties are reflected in the values of the geometrical parameters and of the dielectric constant of the solid which fit the dispersion curves best. 

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