SPECIAL SECTION - ADVANCES IN MEASUREMENT AND MONITORING METHODS:

Ty P. A. Ferré and Gerard J. Kluitenberg

Advances in Measurement and Monitoring Methods: Preface from the Guest Editors
Vadose Zone J 2003 2: 443. [Full Text] [PDF]  

D. A. Robinson, S. B. Jones, J. M. Wraith, D. Or, and S. P. Friedman

A Review of Advances in Dielectric and Electrical Conductivity Measurement in Soils Using Time Domain Reflectometry
Time domain reflectometry has become a standard method of estimating soil water content and soil bulk electrical conductivity in both laboratory and field applications. Topics covered in this review include general theory of operation, waveform analysis, signal propagation in layered and dispersive media, and probe design and construction.
Vadose Zone J 2003 2: 444-475. [Abstract] [Full Text] [Figures Only] [PDF]  

J. A. Huisman, S. S. Hubbard, J. D. Redman, and A. P. Annan

Measuring Soil Water Content with Ground Penetrating Radar: A Review
This comprehensive review distinguishes four methodologies for measuring soil water content with ground penetrating radar: reflected wave velocity, ground wave velocity, transmitted wave velocity between boreholes, and surface reflection coefficient. The basic principles underlying each of these methods are reviewed, and the quality of data acquired from each is illustrated with field examples. The review also evaluates the potential and the limitations of each of the methods and outlines future research needs.
Vadose Zone J 2003 2: 476-491. [Abstract] [Full Text] [Figures Only] [PDF]  

G. Clarke Topp, J. Les Davis, and A. Peter Annan

The Early Development of TDR for Soil Measurements
The early development of time domain reflectometry (TDR) for measuring water content in soils began somewhat by chance, but supportive relationships quickly developed among the authors to sustain the research and development program through the early difficult stages. By 1987, TDR in soil had "come of age" with the presentation of five TDR papers at the Utah State University Centennial Symposium.
Vadose Zone J 2003 2: 492-499. [Abstract] [Full Text] [Figures Only] [PDF]  

Guy Serbin and Dani Or

Near-Surface Soil Water Content Measurements Using Horn Antenna Radar: Methodology and Overview
Ground penetrating radar with a suspended 1-GHz horn antenna was used for continual measurement of water content over bare and vegetated soils using surface reflection (SR) and signal propagation time (PT). We measured marked differences in water content dynamics for different soil textures, including the influence of soil temperature on SR diurnal variations. Wheat canopy development caused a decrease in SR-measured water content but did not affect PT. Key features of wheat canopy structure were deduced from radar reflections.
Vadose Zone J 2003 2: 500-510. [Abstract] [Full Text] [Figures Only] [PDF]  

T. P. A. Ferré, G. von Glinski, and L. A. Ferré

Monitoring the Maximum Depth of Drainage in Response to Pumping Using Borehole Ground Penetrating Radar
Borehole ground penetrating radar (BPGR) may allow us to monitor water content rapidly to great depths with high spatial resolution over large sample volumes and with minimal need for medium-specific calibration. We demonstrate that BGPR can be used to monitor water content with a vertical sampling interval that is smaller than the antenna length. However, while there is good agreement between the patterns of maximum depth of drainage and water table depth during pumping and recovery, the maximum depth of drainage, referenced to the middle of the BGPR antennae, is consistently 50 cm deeper than the water table.
Vadose Zone J 2003 2: 511-518. [Abstract] [Full Text] [Figures Only] [PDF]  

J. A. Huisman, J. J. J. C. Snepvangers, W. Bouten, and G. B. M. Heuvelink

Monitoring Temporal Development of Spatial Soil Water Content Variation: Comparison of Ground Penetrating Radar and Time Domain Reflectometry
The capabilities of ground penetrating radar (GPR) and time domain reflectometry (TDR) to assess the temporal evolution of surface volumetric water content spatial variation are compared. The results show that the larger number of GPR measurements that can be acquired in the same time span resulted in more reliable estimates of spatial variation, both in terms of variogram model parameters and water content maps. It was concluded that GPR is an attractive alternative to other measurement techniques for monitoring spatial and temporal water content variation at the field scale.
Vadose Zone J 2003 2: 519-529. [Abstract] [Full Text] [Figures Only] [PDF]  

R. C. Schwartz and S. R. Evett

Conjunctive Use of Tension Infiltrometry and Time-Domain Reflectometry for Inverse Estimation of Soil Hydraulic Properties
Outflow from a tension disc infiltrometer, TDR measurements of soil water content with probes inserted diagonally from the soil surface, and a branch of the water characteristic curve were simultaneously utilized to inversely estimate hydraulic parameters of a repacked soil. The procedure permitted concurrent estimation of at least four hydraulic parameters and simulation of transient water contents. Parameter uniqueness was improved by use of volume averaged TDR water contents in optimizations.
Vadose Zone J 2003 2: 530-538. [Abstract] [Full Text] [Figures Only] [PDF]  

Anju Gaur, Robert Horton, Dan B. Jaynes, Jaehoon Lee, and Salem A. Al-Jabri

Using Surface Time Domain Reflectometry Measurements to Estimate Subsurface Chemical Movement
Surface soil solute transport properties measured with a time domain reflectometry (TDR) technique were used to predict subsurface leaching in a greenhouse soil pit. The centers of mass of measured and predicted chemical distributions were 13.8 and 13.5 cm, respectively. The TDR technique has potential for use in fields where surface and subsurface conditions are similar.
Vadose Zone J 2003 2: 539-543. [Abstract] [Full Text] [Figures Only] [PDF]  

Tusheng Ren, Tyson E. Ochsner, and Robert Horton

Development of Thermo-Time Domain Reflectometry for Vadose Zone Measurements
Heat pulse and time domain reflectometry technologies have been combined to produce a thermo-TDR sensor capable of measuring soil thermal and electrical properties. The thermo-TDR sensor performed well in determining soil water content, temperature, electrical conductivity, thermal conductivity, heat capacity, air-filled porosity, and degree of saturation. Further developments are needed in order for it to make accurate determinations of soil bulk density.
Vadose Zone J 2003 2: 544-551. [Abstract] [Full Text] [Figures Only] [PDF]  

J. L. Heitman, J. M. Basinger, G. J. Kluitenberg, J. M. Ham, J. M. Frank, and P. L. Barnes

Field Evaluation of the Dual-Probe Heat-Pulse Method for Measuring Soil Water Content
In a field evaluation of the dual-probe heat-pulse method, measurements of water content taken near the soil surface were found to have substantial offset error in addition to slight bias. Offset error was reduced considerably by using the heat-pulse sensors to measure change in water content and coupling the results with an independent (gravimetric) measurement of water content. Using a published calibration relationship to eliminate bias reduced the offset error.
Vadose Zone J 2003 2: 552-560. [Abstract] [Full Text] [Figures Only] [PDF]  

Y. Mori, J. W. Hopmans, A. P. Mortensen, and G. J. Kluitenberg

Multi-Functional Heat Pulse Probe for the Simultaneous Measurement of Soil Water Content, Solute Concentration, and Heat Transport Parameters
A multi-functional heat pulse probe (MFHPP), consisting of a single central heater, four thermistors, and four electrodes (Wenner array), was developed. Tests with the MFHPP were performed on Tottori Dune sand for which the soil water content and bulk soil thermal properties were determined. Simultaneously, the bulk soil electrical conductivity was measured using the Wenner array, from which soil solution concentration can be obtained after calibration. With the MFHPP it was possible to estimate soil water fluxes at rates larger than 0.7 m/d.
Vadose Zone J 2003 2: 561-571. [Abstract] [Full Text] [Figures Only] [PDF]  

Tyson E. Ochsner, Robert Horton, and Tusheng Ren

Use of the Dual-Probe Heat-Pulse Technique to Monitor Soil Water Content in the Vadose Zone
Soil water content in a soybean field was monitored using dual-probe heat-pulse (DPHP) sensors to evaluate the effectiveness of the DPHP technique. A simple in situ calibration of the sensors reduced the difference between water content estimated by the sensors and that estimated by soil sampling and reduced the average standard deviation of water content estimates between sensors. The results demonstrate that the DPHP technique can be used to accurately monitor soil water content in the vadose zone.
Vadose Zone J 2003 2: 572-579. [Abstract] [Full Text] [Figures Only] [PDF]  

T. J. Sauer, D. W. Meek, T. E. Ochsner, A. R. Harris, and R. Horton

Errors in Heat Flux Measurement by Flux Plates of Contrasting Design and Thermal Conductivity
Controlled laboratory experiments and a field study were used to evaluate the accuracy of six soil heat flux plate designs. Plate estimates of soil heat flux were consistently in error by 10 to 70%, and a proposed procedure for correction did not always reduce the errors to acceptable levels. Significant theoretical development and auxiliary measurements will be required to improve the correction procedure, suggesting that research initiatives would be better directed to developing soil heat flux sensors that avoid the errors inherent in flux plate measurements.
Vadose Zone J 2003 2: 580-588. [Abstract] [Full Text] [Figures Only] [PDF]  

Douglas R. Cobos and John M. Baker

In Situ Measurement of Soil Heat Flux with the Gradient Method
Tri-needle probes were used to measure soil heat flux with the gradient technique where the heat flux is equal to the product of the temperature gradient and the soil thermal conductivity measured with a transient heated needle technique. Laboratory investigations indicated that the tri-needle probes are more accurate than commonly used heat flux plates in coarse media, but spatial effects in the field confounded meaningful comparison. The application of the gradient technique using tri-needle probes appears to be a viable alternative to the heat flux plate technique.
Vadose Zone J 2003 2: 589-594. [Abstract] [Full Text] [Figures Only] [PDF]  

Charles E. Dowman, V, Ty P.A. Ferré, John P. Hoffmann, Dale F. Rucker, and James B. Callegary

Quantifying Ephemeral Streambed Infiltration from Downhole Temperature Measurements Collected Before and After Streamflow
A constant flux infiltration experiment was conducted to determine whether downhole temperature measurements, made within cased boreholes located within ephemeral streambeds, can be used to estimate streambed infiltration flux. Numerical sensitivity analyses showed that the temperature profile was most sensitive to infiltrating water temperature, the infiltration flux, and the specific heat capacity of dry soil, thereby providing the opportunity to numerically invert temperature measurements to infer water flux.
Vadose Zone J 2003 2: 595-601. [Abstract] [Full Text] [Figures Only] [PDF]  

Scott B. Jones, Dani Or, and Gail E. Bingham

Gas Diffusion Measurement and Modeling in Coarse-Textured Porous Media
Hydrostatically induced variations in water content produce severe limitations for the use of conventional gas diffusion measurement methods for coarse-textured and aggregated porous media. To overcome this problem, a fully automated dual-chamber cell was developed using a thin profile design to provide gas diffusion measurements in a closed chamber system. Diffusion coefficients were measured in 0.25- to 2-mm aggregated porous medium at fixed points along both wetting and draining water retention curves, showing good correlation with two widely used gas diffusion models.
Vadose Zone J 2003 2: 602-610. [Abstract] [Full Text] [Figures Only] [PDF]  

Marc Jalbert and Jacob H. Dane

A Handheld Device for Intrusive and Nonintrusive Field Measurements of Air Permeability
We developed a rugged handheld device to measure air permeability in the field using either of two interchangeable probes, a contact probe or an insertion probe. The entire device, excluding the probes, consists of a power supply, voltage regulators, an air pump, a pressure transducer, and a voltmeter; is contained in a 25 by 19 by 8 cm rectangular box; and weighs approximately 1700 g. Values obtained with the probe were found to compare favorably with other published data and results obtained in the laboratory.
Vadose Zone J 2003 2: 611-617. [Abstract] [Full Text] [Figures Only] [PDF]  

Bo V. Iversen, Per Moldrup, Per Schjønning, and Ole H. Jacobsen

Field Application of a Portable Air Permeameter to Characterize Spatial Variability in Air and Water Permeability
This study involved the testing of a portable insertion-type air permeameter as a tool for rapid quantification of the spatial variability of saturated hydraulic conductivity in field conditions. Results showed the existence of a linear log-log relationship between air permeability measured at near field capacity and measured saturated hydraulic conductivity. Prediction of saturated hydraulic conductivity with this log-log relationship was found to be far superior to predictions based on pedotransfer functions using soil texture alone.
Vadose Zone J 2003 2: 618-626. [Abstract] [Full Text] [Figures Only] [PDF]  

Glendon W. Gee, Z. Fred Zhang, and Andy L. Ward

A Modified Vadose Zone Fluxmeter with Solution Collection Capability
A water fluxmeter with divergence control, developed in previous work, was modified to measure solute concentrations and thereby facilitate the estimation of solute flux. The accuracy of the modified fluxmeter was proved by measuring water flow and solute fluxes simultaneously in experiments on coarse and fine sands in a laboratory setting. At low flow (621 mm/yr), the dispersion coefficient for nitrate in the coarse sand was about 40% lower than in the fine sand material.
Vadose Zone J 2003 2: 627-632. [Abstract] [Full Text] [Figures Only] [PDF]  

G. C. Topp, D. R. Lapen, M. J. Edwards, and G. D. Young

Laboratory Calibration, In-Field Validation and Use of a Soil Penetrometer Measuring Cone Resistance and Water Content
Relationships between cone penetrometer resistance (PR) and water content (WC) were developed for conventional tilled and no-till fields where PR and WC data were collected concurrently and coincidentally along 300-m plots. WC measurements were collected with time domain transmissiometry, while a piezoelectric force sensor was used to measure PR. Calibration in the laboratory along with validations in the field were used to assure the quality of the acquired data. The PR vs. WC relationships developed for depths below cultivation were similar to that for the 0.10-m depth in the no-till plot and were not impacted by tillage, traffic, and cropping treatments.
Vadose Zone J 2003 2: 633-641. [Abstract] [Full Text] [Figures Only] [PDF]  

S. R. Evett, J. A. Tolk, and T. A. Howell

A Depth Control Stand for Improved Accuracy with the Neutron Probe
A neutron moisture meter stand was designed to fit over access tubes, providing a constant elevation difference between the meter body and soil surface, thus ensuring that the probe is placed at the same depth(s) for each access tube and for each reading date. The stand also elevates the meter sufficiently above the soil surface to avoid errors in standard counts due to surface moisture changes. Improved calibration and reading accuracies for near-surface water content estimates were achieved, with less operator exposure to repetitive strain injuries and without additional exposure to radiation.
Vadose Zone J 2003 2: 642-649. [Abstract] [Full Text] [Figures Only] [PDF]  

Bobbie McMichael and Robert J. Lascano

Laboratory Evaluation of a Commercial Dielectric Soil Water Sensor
Two soil series and a potting material were used to evaluate a commercial soil moisture sensor over a range of moisture contents and temperatures. The sensors were found to be sensitive to changes in soil temperature in the range of 15.9 to 39.1 degrees Celsius and to produce different response curves depending on the soil type. The results thus point to a need for calibration of the sensors for each soil type encountered.
Vadose Zone J 2003 2: 650-654. [Abstract] [Full Text] [Figures Only] [PDF]  

REVIEWS AND ANALYSES:

A. T. Corey and B. W. Auvermann

Transport by Advection and Diffusion Revisited
Diffusion and advection are defined to correspond with associated resistance functions. The paper shows that diffusion as usually defined (as a flux relative to the mean flux) cannot be evaluated with a constitutive equation. Both diffusion and advection are shown to contribute independently to the net transport of a solution constituent.
Vadose Zone J 2003 2: 655-663. [Abstract] [Full Text] [Figures Only] [PDF]  

ORIGINAL RESEARCH PAPERS:

M. N. Pace, M. A. Mayes, P. M. Jardine, T. L. Mehlhorn, J. M. Zachara, and B. N. Bjornstad

Quantifying the Effects of Small-Scale Heterogeneities on Flow and Transport in Undisturbed Cores from the Hanford Formation
Multiple-tracer technique and undisturbed core technology were used to quantify hydrologic processes controlling the fate and transport of contaminants in the Hanford formation. Separation of multiple nonreactive tracers, early breakthrough of tracers, and a change in breakthrough curve symmetry indicated that preferential flow, media bypass, and the formation of immobile water regimes influence transport at various water contents. Our results demonstrate that original sedimentary depositional processes may be important in governing contaminant transport in porous media.
Vadose Zone J 2003 2: 664-676. [Abstract] [Full Text] [Figures Only] [PDF]  

Bernard T. Nolan, Arthur L. Baehr, and Leon J. Kauffman

Spatial Variability of Groundwater Recharge and its Effect on Shallow Groundwater Quality in Southern New Jersey
To assess aquifer vulnerability in southern New Jersey, point estimates of groundwater recharge were made at 48 locations using pedotransfer functions based on measured sediment properties. It was found that the estimated recharge is significantly related to soil texture and drainage characteristic. Nitrate concentration and percentage detection of atrazine in samples of shallow groundwater were higher for low recharge sites than for high recharge sites in developed areas, indicating possible dilution by infiltrating water.
Vadose Zone J 2003 2: 677-691. [Abstract] [Full Text] [Figures Only] [PDF]  

Guohui Wang, Sayonara Brederode F. Reckhorn, and Peter Grathwohl

Volatile Organic Compounds Volatilization from Multicomponent Organic Liquids and Diffusion in Unsaturated Porous Media
Volatilization of organic compounds from multicomponent organic liquids and their transport in the unsaturated zone are modeled based on the combination of Fick's Second Law and Raoult's Law. The model predicts the diffusion process and the aging of the organic mixtures very well.
Vadose Zone J 2003 2: 692-701. [Abstract] [Full Text] [Figures Only] [PDF]  

J. M. Hutchison, J. C. Seaman, S. A. Aburime, and D. E. Radcliffe

Chromate Transport and Retention in Variably Saturated Soil Columns
Chromate and tritium migration through the vadose zone was evaluated using vacuum and centrifuge techniques to obtain a steady state unsaturated flow. Tritium breakthrough curves indicated that mobile water was >90% regardless of saturation level, with dispersivity increasing nonlinearly with decreasing water content. Despite the difference in solute residence time, the average apparent distribution coefficient of all Cr(VI) leaching experiments was very similar to the distribution coefficient derived from batch equilibrations.
Vadose Zone J 2003 2: 702-714. [Abstract] [Full Text] [Figures Only] [PDF]  

M. Saleem Akhtar, Tammo S. Steenhuis, Brian K. Richards, and Murray B. McBride

Chloride and Lithium Transport in Large Arrays of Undisturbed Silt Loam and Sandy Loam Soil Columns
We measured the variability of transport among 90 undisturbed soil columns. Significant preferential flow effects were evident as lithium and chloride rapidly appeared in the outflow. Preferential flow model parameters determined from the chloride tracer were normally distributed, but lognormally distributed for the lithium tracer. Probabilistic approaches can be used to determine the number of columns in an experimental set required to assure a meaningful range of transport velocities will likely be represented.
Vadose Zone J 2003 2: 715-727. [Abstract] [Full Text] [Figures Only] [PDF]  

Fábio Prata, Arquimedes Lavorenti, Jan Vanderborght, Peter Burauel, and Harry Vereecken

Miscible Displacement, Sorption and Desorption of Atrazine in a Brazilian Oxisol
The (de)sorption, leaching and decay of atrazine in a Brazilian Oxisol were investigated using batch sorption and column scale leaching experiments. "Irreversible" sorption of atrazine was observed in the leaching experiment but not in the batch experiment. The atrazine breakthrough and the atrazine remaining in the column and bound to irreversible sorption sites were successfully modeled using a three-site chemical nonequilibrium model in which irreversible sorption was described as a first-order rate decay process.
Vadose Zone J 2003 2: 728-738. [Abstract] [Full Text] [Figures Only] [PDF]  

Aijie Cheng, Yakov Krasnov, and Shmulik P. Friedman

A Single Source–Cylindrical Soil Domain Model for Studying Simultaneous Controlled-Release and Mixing Processes
A physically based model that conceptualizes the three-dimensional, axisymmetric problem of diffusion controlled release of an agrochemical from a spherical capsule and convective-dispersive vertical transport of the released chemical is presented. The governing equations are solved with a finite element numerical method. An analysis based on dimensionless variables is presented to quantify the sensitivity of release rate to the factors of capsule membrane conductance, capsule radius, capsule chemical concentration, water flux, and the longitudinal and transverse dispersivities.
Vadose Zone J 2003 2: 739-750. [Abstract] [Full Text] [Figures Only] [PDF]  

L. M. Dudley and U. Shani

Modeling Plant Response to Drought and Salt Stress: Reformulation of the Root-Sink Term
Plant response functions to matric and osmotic stresses, commonly used in hydrochemical models, are formulated following a potential flow or a transpiration apportioning approach. An alternative formulation was proposed that used potential flow for response to matric stress and transpiration apportioning for response to osmotic stress. The proposed formulation better predicted yield, from a field experiment of melon response to water and salt, than a formulation based exclusively on either a potential flow approach or a transpiration apportioning approach.
Vadose Zone J 2003 2: 751-758. [Abstract] [Full Text] [Figures Only] [PDF]  

A. G. Hunt and G. W. Gee

Wet-End Deviations from Scaling of the Water Retention Characteristics of Fractal Porous Media
A previous investigation demonstrated that dry-end deviations from fractal scaling of the water retention of USDOE Hanford site soils set on at a moisture content closely related to the moisture content at which solute diffusion vanishes. This result was interpreted in terms of a minimum water content for percolation of filled capillaries. We now find that wet-end deviations from fractal scaling set on at approximately the same air content, inviting an explanation in terms of air percolation, at least in these relatively coarse soils.
Vadose Zone J 2003 2: 759-765. [Abstract] [Full Text] [Figures Only] [PDF]  

BOOK REVIEWS:

Roger Beckie

Groundwater Science.
Vadose Zone J 2003 2: 766. [Full Text] [PDF]  

Thomas J. Rice

Soil Genesis and Classification, Fifth Edition.
Vadose Zone J 2003 2: 767. [Full Text] [PDF]  

Blake Ketchum

Soil Classification: A Global Desk Reference.
Vadose Zone J 2003 2: 768. [Full Text] [PDF]  

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