Project Number: 3625-11120-002-05
Project Type: Specific C/A

Start Date: May 07, 2004
End Date: Dec 31, 2004

Objective:
The overall objective of this cooperative research project is to develop an analysis of complex relative permittivity and electrical conductivity that will explain the discrepancies in field determination of water and salt content from relative permittivity and elctrical conductivity. The specific objective of this project will mechanistically determine the frequency-dependent conduction within the clay minerals as controlled by the distribution of clay mineral sizes, types, hydrations, and ionic contents; and compare the theory with measured spectra.

Approach:
First the activation energies will be developed based on characteristics of different hydrated smectite minerals. Characteristics include anisotrophy due to large lateral dimensions (a and b) compared with vertical dimension (d-spacing) for different relative humidities, surface charge density, percent of charge in tetrahedral locations, saturating cation. Then the theoretical activation energy profiles will be used to generate distributions of dipolar relaxation times. Realistic distributions of mineral sizes and related hydrations and ionic contents will be applied. Finally the theoretical analysis will be compared with data. If the analysis proves successful, the theory will be used to explain field dielectric measurments by TDR and capacitance probes.

Project Team

Logsdon, Sally Allen Hunt - Assistant Professor 515-294-8265

Related National Programs

Soil Resource Management (202)   Global Change (204)