| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
USDA-ARS, National Soil Tilth Lab., 2150 Pammel Dr., Ames, IA 50011
* Corresponding author (logsdon{at}nstl.gov)
In soil science, single frequency permittivity measurements are used to determine soil water content, and single frequency bulk electrical conductivity is used to determine soil salinity. The accuracy of these measurements may be influenced by complex interactions between frequency, temperature, and water that is tightly bound to clay surfaces. The purpose of this study is to determine the effect of temperature, saturating cation, water content, smectite properties, and frequency on electrical properties of humidified clays by analyzing three different activation energies for dipole rotations, which are calculated from the temperature dependence of electrical properties. Four reference smectites saturated with K, Na, Ca, and Mg and equilibrated at relative humidities ranging from 56 to 99% were investigated over a frequency range from 3 x 105 to 1 x 109 Hz. Two of the three activation energies were found to decrease slightly as water content increased. Higher activation energies were found for smectites saturated with Mg and K and lower values for smectites saturated with Na and Ca. Trends for type of clay were variable but appeared to be influenced by both the total water content and the distribution of water between the interlayers and the external surfaces of the smectite quasi-crystals. Changes in quasi-crystal orientation induced by thermal cycling were also found to influence the activation energies. The results indicate complex frequency and temperature dependent interactions impact electrical properties of the clays. We conclude that no simple equation will correct for temperature and clay content effects on single frequency measurements of permittivity or bulk electrical conductivity.
Abbreviations: RH, relative humidities • TDR, time domain reflectometry
This article has been cited by other articles:
|
|
 |
|
  D. A. Robinson, C. S. Campbell, J. W. Hopmans, B. K. Hornbuckle, S. B. Jones, R. Knight, F. Ogden, J. Selker, and O. Wendroth Soil Moisture Measurement for Ecological and Hydrological Watershed-Scale Observatories: A Review Vadose Zone J., February 25, 2008; 7(1): 358 - 389. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Langlois and D. G. Barber Passive microwave remote sensing of seasonal snow-covered sea ice Progress in Physical Geography, December 1, 2007; 31(6): 539 - 573. [Abstract] [PDF]
|
|
|
|
|
|
M. Schwank, T. R. Green, C. Matzler, H. Benedickter, and H. Fluhler Laboratory Characterization of a Commercial Capacitance Sensor for Estimating Permittivity and Inferring Soil Water Content Vadose Zone J., August 24, 2006; 5(3): 1048 - 1064. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. G. Hunt, S. D. Logsdon, and D. A. Laird Percolation Treatment of Charge Transfer in Humidified Smectite Clays Soil Sci. Soc. Am. J., December 2, 2005; 70(1): 14 - 23. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Logsdon Time Domain Reflectometry Range of Accuracy for High Surface Area Soils Vadose Zone J., November 11, 2005; 4(4): 1011 - 1019. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. B. Jones, J. M. Blonquist Jr., D. A. Robinson, V. P. Rasmussen, and D. Or Standardizing Characterization of Electromagnetic Water Content Sensors: Part 1. Methodology Vadose Zone J., November 11, 2005; 4(4): 1048 - 1058. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. D. Logsdon Soil Dielectric Spectra from Vector Network Analyzer Data Soil Sci. Soc. Am. J., June 2, 2005; 69(4): 983 - 989. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| The SCI Journals | Agronomy Journal | Crop Science | |||
| Vadose Zone Journal | Journal of Plant Registrations | ||||
| Journal of Natural Resources and Life Sciences Education |
Journal of Environmental Quality |
||||
