NDLI: Maxwell–Wagner Relaxation in Two Desert Soils at Medium and High Water Contents: Interpretation From Modeling of Time Domain Reflectometry Data

Content Provider	IEEE Xplore Digital Library
Author	Arcone, S.A. Grant, S.A. Boitnott, G.E.
Copyright Year	2008
Abstract	Maxwell-Wagner relaxations (MWRs) are generally between 1 and 20 MHz in fine grain soils at volumetric water contents less than 10%. Isolated water inclusions appear to cause MWR. We used time domain reflectometry to measure complex permittivity from 6 kHz to 6 GHz of two, quartz-rich desert soils to test if MWR occur at a limited number of higher water contents because inclusion concentration should then decrease. One soil had lesser calcite; the other lesser gypsum. Water contents ranged from 6.2% to 33.8%. Unwanted electrode polarization (EP) dominates the real part of permittivity below 1 MHz. We interpreted MWR from complex refractive index models (CRIMs) that summed expressions for EP, Debye-type MWR, free water relaxation (FWR), and air volume. Broadband MWRs centered from 1 to 36 MHz exist up to 17% volumetric water contents and up to 196 MHz in the quartz-gypsum soil at saturation, with small to significant Cole-Cole factors that suggest a range of relaxation processes, and attenuation rates that increase to nearly 100 dBm^-1 as frequency increased across the 100-1000 MHz GPR bandwidth. The Cole-Cole factor generally decreased with increasing relaxation frequency, while inclusion conductivity, derived from relaxation frequency, generally increased with increasing bulk conductivity and water content. These results suggest inclusion concentration and a spectrum of their conductivity values decreased, while ionic mobility increased. At saturation, the quartz-calcite soil provided an unexpected low relaxation frequency of 1.28 MHz, possibly caused by inclusions retained within calcite growths upon quartz grains, and within minor amount of smectite.
Starting Page	201
Ending Page	211
Page Count	11
File Size	2690323
File Format	PDF
ISSN	19391404
Volume Number	9
Issue Number	1
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2016-01-01
Publisher Place	U.S.A.
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Soil Conductivity Soil measurements Permittivity Minerals Data models Atmospheric modeling soils Dielectric permittivity electrode polarization (EP) induced polarization (IP) Maxwell–Wagner
Content Type	Text
Resource Type	Article
Subject	Atmospheric Science Computers in Earth Sciences

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