Technology Transfer EPA/625/R-93/003b
SUBSURFACE CHARACTERIZATION AND MONITORING TECHNIQUES:
A DESK REFERENCE GUIDE
Volume II: The Vadose Zone, Field Screening and Analytical Methods
Appendices C and D
May 1993
Prepared by:
Eastern Research Group
4664 N. Robs Lane
Bloomington, IN, 47408
Prepared for:
Center for Environmental Research Information
U.S. Environmental Protection Agency
26 West Martin Luther King Drive
Cincinnati, OH 45268
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Las Vegas, NV 89193-3478
Printed on Recycled Paper
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CONTENTS
VOLUME I: SOLIDS AND GROUND WATER
Introduction
Use of This Guide
Guide Organization and Format
Sources of Additional Information
References
1. Remote Sensing and Surface Geophysical Methods
1.1 Airborne Remote Sensing and Geophysics
1.1.1 Visible and Near Infrared
1.1.2 Photographic Ultraviolet
1.13 Thermal Infrared
1.1.4 Active Microwave (Radar)
1.1.5 Airborne Electromagnetics (AEM)
1.1.6 Aeromagnetks
1.2 Surface Electrical Methods
1.2.1 Electrical Resistivity (ER)
1.2.2 Self-Potential
1.2.3 Induced Polarization (IP)
1.3 Surface Electromagnetic Methods
1.3.1 Electromagnetic Induction (EMI)
1.3.2 Tune Domain Electromagnetics
13.3 Metal Detectors
13.4 Very-Low Frequency Electromagnetics (VLF)
13.S Magnelotellurics (MT)
1.4 Surface Seismic and'Acoustic Methods
1.4.1 Seismic Refraction
1.4.2 Seismic Reflection
1.43 Continuous Seismic Profiling (CSV)
1.4.4 Seismic Shear and Surface Waves
1.4.5 Acoustic Emission Monitoring
1.4.6 Sonar
1.4.7 Pulse-Echo Ultrasonics
1.5 Other Surface Geophysical Methods
1.5.1 Ground-Penetrating Radar (GPR)
13.2 Magnetometry
1.5.3 Gravimetrics
1.5.4 Radiation Detection
1.6 Near-Surface Geothermometry
1.6.1 Soil Temperature
1.6.2 Shallow Geothermal Ground-Water Detection
1.6.3 Other Thermal Properties
2. Drilling and Solids Sampling Methods
2.1 Drilling Methods
2.1.1 Hollow-Stem Auger
2.1.2 Direct Air Rotary with Rotary Bit/Downhole Hammer
2.1.3 Direct Mud Rotary
2.1.4 Cable Tool
2.1.5 Casing Advancement: Rotary Drill-Through Methods (Drill-Through Casing Driver and Dual Rotary
Advancement)
2.1.6 Casing Advancement: Reverse Circulation (Rotary, Percussion Hammer, and Hydraulic Percussion)
2.1.7 Casing Advancement: Downhole Casing Advancers (ODEX, TUBEX)
2.1.8 Jetting Methods
2.1.9 Solid Flight and Bucket Augers
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2,1.10 Rotary Diamond Drilling
2,1.11 Directional Drilling
2,1.12 Sonic Drilling
2,2 Drive Methods
22.1 Driven Wells
2.2.2 Cone Penetration
23 Hand-Held Soil Sampling Devices
23.1 Scoops, Spoons, and Shovels
23.2 Augers
233 Tubes
2.4 Power-Driven Soil Sampling Devices
2.4.1 Split and Solid Barrel
2.4.2 Rotating Core
2.43 Thin-Wall Open Tube
2.4.4 Thin-Wall Piston
2.45 Specialized Thin-Wall
25 Field Description of Soil Physical Properties
25.1 Texture
25.2 Color
253 Other Features
3. Geophysical Logging of Boririoles
3,1 Electrical Borehole Logging
3.1.1 SP Logs
3.L2 Single-Point Resistance
3.13 Fluid Conductivity
3.1.4 Resistivity Logs
3.1 J Dipmeter
3.1.6 Other Electrical Methods
32 Electromagnetic Borehole Logging
3.2.1 Induction
3.2.2 Borehole Radar
323 Dielectric
3.2.4 Other Electromagnetic Methods
33 Nuclear Borehole Logging
33.1 Natural Gamma
33.2 Gamma-Gamma
333 Neutron
33.4 Gamma-Spcctrometry
33J Neutron Activation
33.6 Neutron Lifetime
3.4 Acoustic and Seismic Logging
3.4.1 Acoustic-Velocity (Sonic)
3.4.2 Acoustic-Waveform
3,43 Acoustic Televiewer
3.4.4 Surface-Borehole Seismic Methods
3.45 Geophysical Diffraction Tomography
3.4,6 Cross-Borehole Seismic Methods
35 Miscellaneous Borehole Logging
35.1 Caliper
35.2 Temperature Log
353 Mechanical Flowmeter
35.4 Thermal Flowmeter
355 Electromagnetic (EM) Flowmeter
35.6 Single-Borehole Tracer Methods
35.7 Television/Photography
35.8 Magnetic and Gravity Logs
3.6 WeU Construction Logs
3.6.1 Casing Logging
3.6,2 Cement and Gravel Pack Logs
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3.6.3 Borehole Deviation
4. Aquifer Test Methods
4.1 Ground-Water Level/Pressure Measurement
4.1.1 Steel Tape
4.1.2 Electric Probe
4.1.3 Air line
4.1.4 Pressure Transducers
4.1.5 Audible Methods
4.1.6 Ultrasonic
4.1.7 Float Methods
4.1.8 Electromechanical
4.1.9 Artesian Aquifer Measurement
4.1.10 In Situ Piezometers
4.2 Hydraulic Conductivity (Shallow Water Table)
4.2.1 Auger Hole Method
4.2.2 Piezometer Method
4.2.3 Multiple-Hole Methods
4.3 Well Test Methods
4.3.1 Slug Tests
43.2 Pumping Tests
43 3 Packer Testing
4.4 Ground-Water Tracers
4.4.1 Ions
4.4.2 Dyes
4.4.3 Gases
4.4.4 Stable Isotopes
4.4.5 Radioactive Isotopes
4.4.6 Water Temperature
4.4.7 Particulates
4.5 Other Aquifer Characterization Methods
4.5.1 Unconfined Ground-Water Balance
4.5.2 Moisture Profiles for Specific Yield
5. Ground-Water Sampling Methods
5.1 Portable Positive Displacement Ground-Water Samplers
5.1.1 Bladder Pump
5.1.2 Gear Pump
5.13 Submersible Helical-Rotor Pump
5.1.4 Gas-Drive (Displacement) Pumps
5.1.5 Gas-Drive Piston Pump
5.1.6 Mechanical Piston Pumps
5.2 Other Portable Ground-Water Sampling Pumps
5.2.1 Suction-Lift Pumps
5.2.2 Submersible Centrifugal Pumps
5.2.3 Inertial-Ljft Pumps
5.2.4 Gas-Lift Pumps
5.2.5 Jet Pumps
5.2.6 Packer Pumps
53 Portable Grab Ground-Water Samplers
5 J.I Bailers
5.3.2 Pneumatic Depth-Specific Samplers
533 Mechanical Depth-Specific Samplers
5.4 Sampling Installations for Portable Samplers
5.4.1 Single-Riser/Limited Interval Wells
5.4.2 Single-Riser/Long-Screened Wells
5.4.3 Nested Wells/Single Borehole
5.4.4 Nested Wells/Multiple Boreholes
5.5 Portable In Situ Ground-Water Samplers/Sensors
5.5.1 Hydropunch*
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5.5,2 Other Cone Penetrometer Samplers
SJ3 Other Driven Samplers
5,5,4 Dissolved Oxygen, Eh, and pH Probes
5JJ Ion-Selective Electrodes
55.6 Fiber-Optic Chemical Sensors (FOCS)
5.6 Fixed In Situ Ground-Water Samplers
5.6,1 Multilevel Capsule Samplers
5.6.2 Multiple-Port Casings
5.7 Destructive Ground-Water Sampling Methods
5.7.1 Coring and Extraction
5.7.2 Temporary Installations
Appendix A. Design and Construction of Monitoring Wells
A.1 Well Casing Materials
A3, Well Screen Types and Materials
A3 Filter Pack
A. 4 Grouts and Seals
A5 Well Development
A.6 Well Maintenance and Rehabilitation
A.7 Well Abandonment
Appendix B, General Ground-Water Sampling Procedures
B.I Quality Assurance/Quality Control
B.2 Well Purging
B3 Sample Handling and Preservation
B.4 Decontamination
VOLUME n: THE VADOSE ZONE, FIELD SCREENING, AND ANALYTICAL METHODS
6. Vadose Zone Hydrologic Properties (I): Water State
6.1 Vadose Zone Soil Water Potential
6.1.1 Porous Cup Teosiometers
6.1.2 Thermocouple Psychrometers
6.13 Electrical Resistance Sensors
6.1.4 Electrothermal Methods
6.1 J Osmotic Tensiometers
6.1,6 Filter-Paper Method
6,1.7 Water Activity Meter
6,2 Vadose Zone Moisture Content
6.2.1 Gravimetric Methods
62.3, Nuclear Methods
6.23 Dielectric Sensors
62.4 Time Domain ReDectoraetry
6.2^ Nuclear Magnetic Resonance (NMR)
6.2.6 Electro-Optical Sensors
6.2.7 Computer Assisted Tomography (CAT)
63 Other Soil Hydrologic Properties
63.1 Soil Moislure-Polential-Conductivity Relationships
63,2 Water Sorplivity and Diflusivity
633 Available Water Capacity
7. Vadose Zone Hydrologic Properties (II): Infiltration, Conductivity, and Flux
7.1 Infiltration
7,1.1 Impoundment Methods
7.1.2 Land Surface Methods
7.1J Watershed Methods
7.1.4 Infiltration Equations
rv
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7.2 Unsaturated Hydraulic Conductivity
7.2.1 Instantaneous Profile Method
7.2.2 Draining Profile Methods
7.23 Tension Infiltrometers
7.2.4 Crust-Imposed Steady Flux
7.2.5 Sprinkler/Dripper Methods
7.2.6 Entrapped Air Method
7.2.7 Parameter Identification
7.2.8 Physical/Empirical Equations and Relationships
13 Saturated Hydraulic Conductivity (Shallow)
73.1 Cylinder Infiltrometers
73.2 Constant-Head Borehole Infiltration
73.3 Guelph Permeameter
73.4 Air-Entry Permeameter
7.3.5 Double Tube Method
73.6 Cylinder Permeameter
73.7 Infiltration Gradient Method
73.8 la Situ Monoliths
73.9 Boutwell Method
73.10 Velocity Permeameter
73.11 Percolation Test
7.4 Saturated Hydraulic Conductivity (Deep)
7.4.1 USBR Single-Well Methods
7.4.2 USBR Multiple-Well Method
7.43 Slephens-Neuman Single-Well Method
7.4.4 Air Permeability Method
7.5 Water Flux (Unsaturated Zone)
7.5.1 Water Budget Methods
7.5.2 SoilMoisture/Matric Potential Methods
7.53 Tracers
7.5.4 Soil-Viuer Flux Meters
7.5.5 Velocity Estimation
75.6 Physical and Empirical Equations
8. Vadose Zone Water Budget Characterization Methods
8.1 Water-Related Hydrometeorological Data
8.1.1 Precipitation (Nonrecording Gages)
8.1.2 Precipitation (Recording Gages)
8.13 Humidity Measurement (Psychrometers)
8.1.4 Humidity Measurement (Hygrometers)
8.2 Other HydromeUttologjcal Data
8.2.1 Air Thttmoraetry (Manual)
8.2.2 Air Tfcrmometry (Electric)
8.23 Wind Speed
8.2.4 Wind Direction
8.2J Amospheric Pressure
8.2.6 War Radiation (Pyranometers)
8.2.7 &Aai Radiation (Other Radiometers)
83 Evapotranspiration (Water Balance Methods)
83.1 Lysimtlers
8.3.2 Soil Moisture Budget
833 Water Budget Methods
83.4 Evaporation Pans
8.3.5 Evaporioieters and Atmometers
83.6 ChlorideTracer
83.7 Ground-Yater Fluctuation
83.8 Other Traspiration Methods
8.4 Evapotranspira"'0" (Micrometeorological Methods)
8.4.1 Empirical Equations
8.4.2 Physically-Based Equations (Penman and Related Methods)
8.43 Mass Transfer Methods
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8.4.4 Energy Budget Methods
8.4.5 Profile/Gradient Method
8.4.6 Eddy Correlation Method
9. Vadose Zone Soil-Solute/Gas Sampling and Monitoring Methods
9.1 Solute Movement (Indirect Methods)
9.1.1 Four Probe Electrical Resistivity
9.1.2 EC Probes
9.13 Porous Matrix Salinity Sensors
9.1.4 Electromagnetic Sensors
9.2 Direct Soil-Solute Sampling (Suction Methods)
9.2.1 Vacuum-Type Porous Cup
9.2.2 Vacuum-Pressure Type Porous Cup
923 Vacuum-Plate Samplers
9.2.4 Membrane Filter
9.25 Hollow Fiber
9.2.6 Ceramic Tube Sampler
9.2.7 Capillary Wick Sampler
93 Direct Soil-Solute Sampling (Other Methods)
93.1 Free-Drainage Samplers
93.2 Perched Water Table
933 Absorbent Methods
93.4 Solids Sampling with Soil-Water Extraction
935 Solids Sampling with Soil-Saturation Extract
93.6 Solids Sampling for Volatile and Microbial Constituents
93.7 SEAMIST
9.4 Gaseous Phase Characterization
9.4.1 Soil-Gas Sampling (Static)
9.4.2 Soil-Gas Probes
9.43 Tank/Pipeline Leak Sensors
9.4.4 Air Pressure
9.45 Gas Permeability and Diffusivtty
95 Contaminant Flux
95.1 Solute Flux Methods
953. Soil-Gas Flux
10. Chemical Field Screening and Analytical Methods
10.1 Field Measured General Chemical Parameters
10.1.1 pH/Alkalinity/Acidily
10.1.2 Redox potential (Eh)/Dissolved Oxygen
10.13 Other Parameters
10.2 Contaminant Sample Extraction Procedures
10.2.1 Gas Headspace/Vacuum Extraction
102.2 Purge and Trap Methods
1023 Solvent/Chemical Extraction/Microertraction
10.2.4 Thermal Treatment Methods
1025 Other Extraction Methods
103 Gaseous Phase Analytical Techniques
103.1 Total Organic Vapor Survey Instruments
103.2 Specific Gas/Organic Vapor Detectors
1033 Gas Chromatography (GO)
103.4 Mass Spectrometry (MS) and GC/MS
1035 Atomic Absorption Spectrometry (AAS)
103.6 Atomic Emission Spectrometry (AES)
103.7 Ion Mobility Spectrometry (IMS)
10.4 Luminescence/Spectroscopic Analytical Techniques
10.4.1 X-Ray Fluorescence (XRF)
10.42 Other Luminescence Techniques
10.43 Other Spectrometric/Spectrophotometric Techniques
10.4.4 Other Spectroscopic Techniques
VI
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105 Wet Chemistry Analytical Techniques
105.1 Colorimetric Techniques/Kits
105,2 Immunochemical Techniques
105.3 Liquid Chromatography
105.4 Electrochemical Techniques
10.6 Other Analytical Techniques
10.6.1 Radiological Techniques
10.6.2 Gravimetric/Volumetric Techniques
10.6.3 Magnetic Methods
10.6.4 Microscopic Techniques
10.65 Other Chemical Sensors
10.6.6 Other Biological Techniques
Appendix C. Guide to Major References on Subsurface Characterization, Monitoring, and Analytical Methods
Appendix D. Guide to Major Vadose Zone Models for Water Budget and Exposure Modeling
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NOTICE
This document has been reviewed in accordance with the U.S. Environmental Protection Agency's
(EPA's) peer and administrative review policies. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
This document is not intended to be a guidance or support document for a specific regulatory program.
Guidance documents are available from EPA and must be consulted to address specific regulatory issues.
ACKNOWLEDGEMENTS
This document was prepared for EPA's Center for Environmental Research Information (CERI),
Cincinnati, Ohio, and has benefitted from the input of the reviewers listed below. Every effort has been made
to provide comprehensive coverage and up-to-date information. Due to the large number of techniques and
references in this guide, errors or omission in citations might have occurred. These errors are the responsibility
of the author, who would appreciate being informed of the need for any corrections or additions at the address
indicated below.
Author:
J. Russell Boulding, Eastern Research Group, Inc. (ERG), 4664 N. Robs Lane, Bloomington, IN 47408
Project Management:
Susan Schock, EPA CERI, Cincinnati, OH
Heidi Schultz, ERG, Lexington, MA
Editing and Production:
Anne Donovan, ERG, Lexington, MA
Technical Reviewers (Chapters and appendices reviewed noted in parentheses):
Frederick Cornell, Environmental Liability Management, Princeton, NJ (10)
Lawrence Eccles, U.S. EPA, EMSL, Las Vegas, NV (9)
Lome Everett, Metcalf and Eddy, Santa Barbara, CA (6,9)
Peter Haeni, U.S. Geological Survey, Hartford, CT (1)
Jan Hendrickx, Department of Geosciences, New Mexico Tech, Socorro, NM (4,7)
Paul C. Heigold, Illinois State Geological Survey, Champaign, IL (1,3)
Beverly Herzog, Illinois State Geological Survey, Champaign, IL (4,5,6,7,9,A)
David Kaminski, QED Ground Water Specialists, Walnut Creek, CA (5)
Peter Kesri, Oak Ridge National Laboratory, Grand Junction, CO (7,8)
Jack Keeton, U.S. Army Corps of Engineers, Omaha, NE (A)
W. Scott Keys, Geokeys, Inc., Longmont, CO (Tables 3-1 and 3-2)
Eric Koglin, U.S. EPA, EMSL, Las Vegas, NV (10)
Mark Kram, NEESA, Port Hueneme, CA (10)
Robert Powell, U.S. EPA, RSKERL, Ada, OK (5,B)
Robert Puls, U.S. EPA, RSKERL, Ada, OK (5,B)
James Quinlan, Nashville, TN (4)
Charles Riggs, Sverdrup Environmental, St Louis, MO (2)
Ronald Scholia, Battelle Pacific Northwest Laboratory, Richland, WA (A,B)
Ronald Sims, Utah State University, Logan, UT (2,6,7,8,CJ>)
James Ursie, U.S. EPA, Region 5 (1,3)
Mark Vendl, U.S, EPA, Region 5 (1,3)
John Williams, U.S. Geological Survey, Albany, NY (3)
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Figures in this guide from copyrighted sources are reproduced by permission, with all rights reserved
by the copyright holder, as follows (figure numbers refer to the numbers used in this guide):
American Geophysical Union, Washington, DC (Water Resources Research): Figure 1.6.2.
American Petroleum Institute, McLean, VA: from API Publication 4367, Figures 5.1.4c, 5.2.4, 53.1, 53.2a,
533c, 5.4.1, and 5.7.2c.
American Society for Testing and Materials (AS1M), Philadelphia, PA: Figures 1.3.5,3.4.6,5,5.2a and b, 5.6.2b,
and A.1.
American Society of Agronomy/Soil Science Society of America, Madison, WI: Figures 1.6.3,4.2. Ib, 4.2.2,4.2.3,
6.1.4b, 6.1.7, 6.2.4,6.2.6,6.2.7,6J.3b, 7.1.1, 7.2.1,7.2.4,7.2.2, 7.2.3,7.2.6,73.2, 73.5,73.6,73.7,73.8,
15A, 83. Id, 83.5a, 9.1.2a, 9.1.3, 9.2.5,9.2.7,9.4.4,9.4.5a, 9.5.2, 1035,10.6.3, and 10.6.4.
American Society of Civil Engineers, New York, NY: Figures 1.4.4b and 3.4.4d.
American Water Resources Association, Bethesda, MD: Figure 93.2.
Electric Power Research Institute, Palo Alto, CA: Figures 1.2.2a and b, 1.4.6,1.5.3, LS.la, 23.2a and b, 23.3a,
2.4.1, 2.4.2,3.4.4,4.1.1,4.1.3,4.1.4,4.1.6, 4.1.7, 5.5.3, 6.2.2b, and 73.4.
*
Hsevier Science Publishers, Amsterdam, Hie Netherlands (Journal of Hydrology): Figure 93.1.
Ground Water Publishing Company (formerly Water Well Journal Publishing Company), Dublin, OH: Figures
13.1c, 13.4,1.4.2,1.4.3a, 2,1.5b, 2.2.2a, 2.4.4,3.5.7,3.6.2b, 4.4.5b, 5.2. Id, 5.2.3,5.5.1,55.2c, 7.33,9.2. Ib,
9.4.2c, 9.4.5a, A.5b, and B.2a.
Hazardous Materials Control Research Institute, Greenbelt, MD: Figures 3.4.5a-c, 10.23b, and 103.4c.
International Association of Hydrogeologists/Veiiag Heinz Heise, Hannover, Germany: Figures 3.13,3.5.1, and
3,5.3.
John Wiley & Sons, Inc., New York, NY: Figures 2.1.4,83.7, and 3.6.2a.
Johnson Filtration Systems/Wheelabrator Engineered Systems, St. Paul, MN: Figures 2.1.2a, 10.6.2, and Table
2-2.
Lewis Publishers, a subsidiary of CRC Press, Boca Raton, Florida: Figures 10.4.1b, A.2a and b, and A3.
National Ground Water Association (formerly National Water Works Association), Dublin, OH: Figures 1.4.4a,
2.1.7,2.1.12,2.2.2b, 3.2.3,3.4.5d, 3J.5,43.1b, 5.5.4, 5.5,5,S.5.6c, 7.5.1,8.1. la, 8.1.2a, 93.6,93.7,9.4.2b,
B.2, and Tables 7.1.1 and B-2.
Society of Exploration Geophysicists, Tulsa, OK (Geophysics): Figures 1.1.5, 1.2.1c, 3.1.6, and 3.2.2b.
Timco Manufacturing, Inc., Prairie du Sac, WI: Figures 1.6.1,33.2,4.1.10,5.1.1b, 5.1.3,5.1.5,5.2.6b, 5.43b and
c, 5.6.2a, 5.5.3a and b, 5.6.1a, 6.1.1,6.1.2,6.1.3,6.1.4a, 6.1.5,6.2.3,6.2.2a, 6.2.5, 9.23,9.2.4, and 93.1b.
Water Resource Publications, Highlands Ranch, CO: Figure l.l.lb.
Williams and Wilkins, Baltimore, MD (Soil Science): Figure 933.
a.
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INTRODUCTION
Many EPA programs, including those under the Resource Conservation and Recovery Act (RCRA)
and the Comprehensive Response, Compensation, and Liability Act (CERCLA), require subsurface
characterization and monitoring to detect ground-water contamination and provide data to develop plans to
prevent new contamination and remediate existing contamination. Hundreds of specific methods and techniques
exist for characterizing, sampling, and monitoring the saturated and unsaturated zones at contaminated sites.
Existing field methods are often refined and new methods are continually being developed. This guide is
designed to serve as a single, comprehensive source of information on existing and developing field methods as
of early 1993, Appendix C provides some suggestions on the best places to obtain information on new
developments that occur after this guide is completed.
USE OF THIS GUIDE
As the title "Desk Reference Guide" implies, this is not a how-to handbook for the field. Instead, the
guide provides, in a single document, enough information about specific techniques to make some judgements
concerning their potential suitability for a specific site and also gives information on where to go to find more
detailed guidance on how to use the technique. This guide can be used in two major ways:
1. Development of Site Characterization and Monitoring Plans. Each subsection listed in the table of
contents represents a one-to-two page summary of a specific technique or several related techniques.
A table at the beginning of each of the 10 major sections (summarized below), provides general
comparative information on all methods covered in the sections, and cross-references relevant methods
covered in other parts of the guide. In the summary tables, boldfacing is used to identify those
techniques that are most commonly used. These tables might also be helpful in identifying new, or less
common methods that might be of value for specific objectives or site conditions. Within a grouping
of method summary sheets, techniques are listed in approximate order of frequency of use.
2. Overview of Specific Methods. Individuals who are unfamiliar with specific methods that are being used
or proposed to be used at a hazardous waste site can find a concise description of the method, its
applications, major advantages and disadvantages in its use, and major reference sources where more
detailed information can be found about the method. To locate information on a specific method, the
table of contents should be used to identify the section in which the method is located. If the term used
to describe the method is not included in the table of contents, go to the summary table at the
beginning of the appropriate section of the guide. If the summary table does not use the term, peruse
the listing of alternative names for techniques in the individual summary sheets. For example, the
hydraulic percussion drilling method is not listed in the table of contents, but appears in summary
Table 2-1. The hollow-rod method, is listed in neither the table of contents or the summary, and
requires looking through the individual summary sheets in Section 2.1 (Drilling Methods), until Section
2.1.6 is reached, which identifies the hollow-rod method as an alternative term for hydraulic percussion.
GUIDE ORGANIZATION AND FORMAT
Site characterization, monitoring, and field screening are related activities for which there might not
be a clear dividing line. Generally, site characterization methods involve one-time field point measurements and
sampling (or continuous measurements in the case of some geophysical methods) of physical and chemical
properties of the subsurface, or multiple measurements to characterize seasonal variations at the site. Monitoring
methods, on the other hand, involve sampling or measurements at a single point or the same area over time.
Many methods can be used for both site characterization and monitoring, and site characterization activities can
continue after monitoring begins to further refine subsurface interpretations. Field screening is a form of site
characterization that involves the use of rapid, relatively low-cost field methods (typically chemical) in the field
during site characterization to assist in the selection of locations for permanent monitoring well installations or
for guiding remediation activities. Field analytical methods are distinguished from field screening methods by
having a higher degree of precision and accuracy than field screening methods. This distinction in discussed
further in the introduction to Section 10.
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This guide includes two volumes. The first volume covers solids and ground water and the second
volume covers the vadose zone. The site characterization, monitoring, and field screening methods covered in
the guide are divided into 10 major sections, which are described below. Because site characterization generally
precedes monitoring, earlier sections of the guide tend to cover site characterization methods, while later sections
cover monitoring. Finally, field screening and analytical methods are covered in Section 10.
Section 1 (Remote Sensing and Surface Geophysical Methods) covers more than 30 airborne and
surface geophysical methods that are often valuable during the initial phases of site characterization.
These methods can provide preliminary information on the subsurface to provide guidance on
placement of boreholes for direct observation of the subsurface and installation of permanent
monitoring wells. A number of these methods can also be useful for monitoring the movement of
contaminant plumes.
Section 2 (Drilling and Solids Sampling Methods) covers 20 drilling methods, and a variety of power-
driven and hand-held devices for sampling soils and geologic materials. The section also briefly
identifies important soil physical properties that are described in the field.
Section 3 (Geophysical Logging of Boreholes) covers more than 40 borehole logging and sensing
techniques for the physical and chemical characterization of the subsurface.
Section 4 (Aquifer Test Methods) covers 10 methods for measuring ground-water well levels or
pressure, pumping and slug tests, six categories of ground-water tracers, and several other techniques
for measurement of aquifer properties that might be needed for modeling ground-water flow and
contaminant transport.
Section 5 (Ground-Water Sampling Devices and Installations) covers more than 20 types of portable
ground-water sampling devices and different types of permanent well installations for portable sampling
devices. Appendix A (Design and Installation of Monitoring Wells) provides more detailed information
on such Installations. Section 5 also includes various types of portable and fixed in situ sampling devices
and installations. Genera] ground-water sampling methods are covered in Appendix B.
Section 6 (Vadose Zone Hydrologic Properties (I): Water State) covers over 20 methods for measuring
vadose zone soil water potential, moisture content, and other soil hydrologic characteristics.
Section 7 (Vadose Zone Hydrologic Properties (II): Infiltration, Conductivity, and Flux) covers four
approaches to measuring or estimating infiltration and approximately 30 methods for measuring
unsaturated and saturated hydraulic conductivity and water flux in the vadose zone.
Section 8 (Vadose Zone Water Budget Characterization Methods) covers a large number of methods
for obtaining data that might be required for water budget calculations to assess contaminant transport
in the vadose zone. This includes 37 methods for obtaining various types of hydrometeorologic data,
and 16 methods for measuring or estimating transpiration or evapotranspiration.
Section 9 (Vadose Zone Soil-Solute/Gas Sampling and Monitoring Methods) covers six indirect methods
for monitoring soil solute movement, more than 20 methods for direct sampling of soil solutions, and
a variety of methods for soil gas sampling and gaseous phase characterization in the vadose zone. The
section also summarizes a number of methods to measure or estimate soil solute and gas flux in the
vadose zone.
Section 10 (Field Screening and Analytical Methods) covers a large number of techniques and groups
of techniques for field screening and analysis: Chemical field measurement (three summary sheets),
sample extraction procedures (five summary sheets), gaseous phase analytical techniques (five summary
sheets), luminescence/spectroscopic techniques (four summary sheets); wet chemistry methods (four
summary sheets), and other techniques (five summary sheets).
XI
-------
More than 280 specific field methods are covered in this guide. The large number of methods precludes
detailed coverage of any single method, which is often available from other sources. Instead, each method has
a single-page summary in a uniform format that includes:
1. General method category title.
2. Method title.
3. Other names used to describe method.
4. Uses at contaminated sites.
5. Method^rocedure/device description.
6. Method selection considerations.
7, Frequency of use.
8. Standard Methods/Guidelines (ASTM or other sources that give detailed instruction for use of the
specific method),
9. Sources for additional information (which provides comparative information where other methods for
similar applications are available).
The frequency of use ratings are very approximate, and actual usage might vary from region to region. Similarly,
the summary tables at the beginning of each section should not be relied upon as definitive. Specific
instrumentation or variants of techniques covered in this guide might have different characteristics than indicated
in the summary tables. A specific method that has been rarely used might be suited for certain site-specific
conditions. Conversely, site-specific conditions might make a widely-used technique a poor method of choice.
When in doubt, obtaining the opinion of more than one person familiar with a particular technique is advisable.
Wherever possible, one or more figures or tables that illustrate instruments or how a method is used
are included with summary sheets. These figures and tables have the same number as the section to which they
aire related (i.e., Figure 1.1.1 and Table 1.1.1 are located after Section 1.1.1 on visible and near infrared remote
sensing). Each major section has a brief introduction that defines major concepts and provides an overview of
methods covered in the section. Summary tables and figures at the beginning of each section, and index
reference tables near the end of a section are numbered in sequence (i.e., Tables 1-1 to 1-3 provide summary
information on remote sensing and geophysical methods, and Tables 1-4 and 1-5 provide an index to references
contained at the end of the section).
SOURCES OF ADDITIONAL INFORMATION
As indicated above, two types of references are given for each method. First, if ASTM, EPA, or other
standard methods, protocols, or guidelines related to the method have been promulgated, or are being developed,
these are identified. Otherwise, references that give detailed instructions on how to use the method are cited,
if available.
Secondly, major references that provide information on the use of the method in the context of ground-
water and hazardous waste site investigations are listed. All references are in a single section. EPA documents
are indicated (with EPA and NTIS numbers). Appendix C (Guide to Major References on Subsurface
Characterization and Monitoring) provides annotated descriptions of more than 70 major books and reports and
over 80 published conference and symposium proceedings that can serve as information sources for general and
specific aspects of soil quality and ground-water field screening, characterization, and monitoring.
The following EPA documents are recommended for use as companions to this guide (all of which are
available for no cost from U.S. EPA's Center for Environmental Research Information (see Appendix C for
ordering address): Ground-Water Handbook, Volume 1: Ground Water and Contamination; Volume 2;
Methodology (U.S. EPA, 1990 and 1991 a), Site Characterization for Subsurface Remediation (U.S. EPA, 1991b),
Handbook of Suggested Practices for the Design and Installation of Ground-Water Monitoring Wells (AJler et
al., 1991), Description and Sampling of Contaminated Soils: A Field Pocket Guide (Boulding, 1991), and Use
of Airborne, Surface, and Borehole Geophysical Techniques at Contaminated Sites: A Reference Guide (U.S.
EPA, 1993). Other EPA documents that are available from NTIS and commercially published references that
can be of potential value are too numerous to be named individually here. Appendix B should provide guidance
concerning other publications that might be worth obtaining.
xu
-------
REFERENCES
Aller, L. et al. 1991. Handbook of Suggested Practices for the Design and Installation of Ground-Water
Monitoring Wells. EPA/600/4-89/Q34, 221 pp. Also published in 1989 by the National Water Well
Association, Dublin, OH in its NWWA/EPA series, 398 pp. [Nielsen and Schalla (1991) contain a more
updated version of the material in this handbook that is related to design and installation of ground-
water monitoring wells.]
Boulding, J.R. 1991. Description and Sampling of Contaminated Soils: A Field Pocket Guide. EPA/625/12-
91/002, 122 pp.
Nielsen, D.M. and R. Schalla. 1991. Design and Installation of Ground-Water Monitoring Wells. In: Practical
Handbook of Ground-Water Monitoring, D.M. Nielsen (ed.), Lewis Publishers, Chelsea, MI, pp. 239-
331.
U.S. Environmental Protection Agency (EPA). 1990. Handbook Ground Water. Volume I: Ground Water and
Contamination. EPA/625/6-90/016a, 144 pp.
U.S. Environmental Protection Agency (EPA). 1991a. Handbook Ground Water. Volume II: Methodology.
EPA/625/6-90/016b, 141 pp.
U.S. Environmental Protection Agency (EPA). 1991b. Site Characterization for Subsurface Remediation.
EPA/625/4-91/026, 259 pp.
U.S. Environmental Protection Agency (EPA). 1993. Use of Airborne, Surface, and Borehole Geophysical
Techniques at Contaminated Sites: A Reference Guide. EPA/625/R-92/007.
xiii
-------
SECTION «
VADOSE ZONE HYDROLOGIC PROPERTIES (I): WATER STATE
Water state in the subsurface is measured in terms of hydraulic head in the saturated zone (see Section
4.1) and negative pressure potential or suction in the vadose zone. Water movement in the vadose zone is
determined by the interaction of three major types of energy potentials: (1) Matric potential (the attraction of
water to solids in the subsurface, (2) osmotic potential (the attraction of solute ions to water molecules), and (3)
gravitational potential (the attraction of the force of gravity toward the earth's center). Matric and osmotic
potentials are negative and serve to inhibit the movement of water when the vadose zone is unsatu rated.
Uns at u rated flow occurs, however, whenever the force of gravity on a water molecule exceeds matric plus osmotic
potential. Water flow in the vadose zone is strongly influenced by the moisture content, with flow decreasing
as moisture content decreases.
Table 6-1 provides summary information on six major techniques for measuring soil water potential and
a dozen methods for measuring soil moisture content. The measurement of soil water potential and moisture
content in the vadose zone is intimately connected, and a specific measurement technique can be classified as
measuring potential or moisture content, depending on the perspective of the writer in the literature. Either
measurement can be used to obtain the other if a moisture characteristic curve has been developed (Section
6.3.1). Porous cup tensiometers are the most commonly used method for measuring soil water potential in the
vadose zone. The gravimetric method is most commonly used to measure moisture content from soil samples,
and the neutron probe and gamma gamma methods are most commonly used for in situ measurement of soil
moisture. The relatively recent commercial avail ability of dielectric or capacitance sensors (Section 6.2,3) is likely
to increase the use of this method, which provides accuracy similar to the neutron probe without some of the
disadvantages of nuclear methods (i.e., radioactive sources). Similarly, time domain reQectometry, a relatively
new method (Section 6.2.4), is becoming more widely used with the advent of commercially available units. All
methods for vadose zone measurement of water content or matric potential have limitations with respect to soils
contaminated with nonaqueous phase liquids, due to interference effects.
Other field-measurable hydrologic properties of the vadose zone, which might be of use in evaluating
contaminant transport include water sorptivity and diffusivity (Section 63.2) and available water capacity
(Section 63.3). Sorptivity and diSusivity are properties that are significant in evaluating infiltration of water into
the subsurface (discussed in more detail in Section 7.1). Available water capacity is a measure of the ability of
soil to store water.
6-1
-------
Table 6-1 Summaiy Information on Vadose Zone Water State Measurement and Monitoring Methods
Method
Property
Measured
Accuracy/
Range
Sections
Vadose Zone Soil Water Potential Measurement*
Porous Cup Tensiomcters
Thermocouple Psycbrometers
Water Activity Meter
Resistance Sensors
Gypsum Blocks
Fiberglass/Nylon Celts
Electrothermal Methods
Osmotic Tensiometers
Filter-Paper Method
Electro-Optical Sensors
Capillary pressure
Relative humidity
Relative humidity
Resistance
Resistance
Resistance
Heat transfer
Osmotic + pressure
potential
Water content
Optical properties
0 to -85 kPa*
0 to -80 kPa"
-200 to -8,000 kPab
-100 to -5,000 kPa"
0 to -31,600 kPa
-50 to -1,500 kPa"
0 to -30 kPafc
No limits1'
0 to -200 kPa
0 to -1,500 kPab
-10 to -100,000 kPa
0 to -2,400 kPa
Vndose Zone Soil Water Content Measurement'
6.1,1
6.1.2
6.1.2
6.1.3
6.1.3
6.13
6.1.4
6.1.5
6.1.6
6.2.6
Gravimetric
G&niiKi&*Ga2xuafk
Neutron Moisture Probe
Dielectric Sensors
Time Domain Reflcctometry
Nuclear Magnetic Resonance
Electro-Optical Sensors
CAT Scan
Thermal Infrared
Active Microwave
Four-Electrode Method
Salinity Sensors
Electromagnetic Induction
Weight *
Radiation d
Radiation d
Dielectric d
Dielectric d
Magnetic field d
Optical properties *
Radiation d
Remote sensing d
Remote sensing d
Resistivity d
Conductivity d
Conductivity d
6.2.1
6.2.2, 3.3.2
6.2.2, 3.3 3
6.2.3
6.2.4
3.2.4, 10.6.3
6.2.6
6.2.7
1.1.3
1.1.4
9.1.1
9.13
9.1.4
Boldface ** most commonly used methods.
'Moisture content can be determined from measurement of soil water potential and vice versa by the use of a moisture characteristic
curve, which relates matric potential to water content (Section 6.3.1). The pascal is the Standard International unit for measuring
pressure used by the Soil Science Society of America. Trie bar is commonly used as a pressure unit in vadose zone investigations: 1
kPa - 1 centibar.
'Indicated by Rehm et al. (1985).
Indicated by Bruce and Luxmoore (1986).
'Most methods for measuring moisture content are accurate to around 1%. Gravimetric methods and nuclear methods can be
accurate to 0.1% or less.
6-2
-------
6. VADOSE ZONE HYDROLOGIC PROPERTIES (I): WATER STATE
6,1 VADOSE ZONE SOIL WATER POTENTIAL
6.1.1 Porous Cup Tensiometers
Other Names Used to Describe Method; Capillaty potentiometer, soil hygrometer, soil moisture meter,
transiometer. Tensiometers often are described according to the type of device that is used to measure pressure:
Vacuum gauge, water manometer, mercury-water manometer, or electrical pressure transducer.
Uses at Contaminated Sites: Measuring water (matric) potential and gradients in the unsatu rated zone; irrigation
scheduling; performing root zone delineation; developing moisture characteristic curves (see Section 6.3.1); can
be used to measure and monitor changes in moisture content if matric potential-water content relationship is
known.
Method Description: Many designs for tensiometers have been developed. Most have the following basic
elements: (1) A porous tip or cup attached to a barrel or connective tube, (2) a removable air tight cap for filling
the tensiometer with water, and (3) a device to measure pressure in the water in the porous cup. The ceramic
cup (or other material, such as fritted glass) is placed in the soil, filled with water, and the unit is sealed. Pores
in the cup form a continuum with the pores in the soil, and water moves into or out of the tensiometer until
equilibrium is reached. The measured pressure corresponds to the water pressure in the soil. Figure 6.1.1 shows
three types of porous cup tensiometers. A transiometer is a type of porous cup tensiometer in which a pressure
transducer is placed inside the porous cup, rather than at the surface.
Method Selection Considerations: The useful range of tensiometers is 0 to 0.85 bars capillary pressure when the
ambient atmospheric pressure is around 76 centimeters of mercury. Advantages: (1) Provide continuous in-place
measurements of the same soil material over time; (2) are relatively inexpensive and simple; (3) transducer unit
responds fairly rapidly to water content changes and can be used for automatic data collection; and (4)
transiometers can be used to measure soil water potential in both saturated and unsaturated conditions.
Disadvantages: (1) Units fail at the air entry value of the ceramic cup, generally about -0.8 atmospheres; (2) unit
will not operate properly unless good contact is made between cup and soil; (3) are sensitive to temperature
changes; (4) water content estimates prone to error resulting from uncertainty of moisture-matric potential
relationship (hysteresis causes different curves depending on soil is wetting or drying); (5) difficult to install at
great depth in the vadose zone; (6) air in the system causes errors in measurement, and special efforts, such as
using deaired water, are required to minimize such problems; (7) lower air pressures at higher elevations reduce
the operating range; (8) operation will be affected if the surface tension characteristics of chemical liquid wastes
in the vadose zone differ from that of water; and (9) multiple calibration curves are required for soil moisture
monitoring in stratified media.
Frequency of Use; Widely used for pressure measurement; usually not recommended for water content
measurement.
Standard Methods/Guidelines: ASTM (1991), Cassel and Klute (1986).
Sources for Additional Information: Brakensiek et al. (1979), Gairon and Hadas (1973), Holmes et al. (1967),
Morrison (1983), Ream et al. (1985), Stannard (1986), Troolen et al. (1986-transiometer), Wilson (1980,1981).
See also, Table 6-2.
6-3
-------
MERCURY
MANOMETER
VACUUM
GAGE
DO
PRESSURE
TRANSDUCER
MANUAL
OBSERVATION
MANUAL
OBSERVATION
- v-
I
TO CHART RECORDER
FOR CONTINUOUS
OBSERVATION
POROUS CUP
' (2)
(3)
GROUND
"SURFACE
Figure 6.1.1 Three types of porous-cup tensiometers (Morrison, 1983, by permission).
6-4
-------
6. VADOSE ZONE HYDROLOGIC PROPERTIES (I): WATER STATE
6.1 VADOSE ZONE SOIL WATER POTENTIAL
6.1.2 Thermocouple Psychrometers
Other Names Used to Describe Method; Spanner/Peltier psychrometer, Richards-Ogata/wet-loop psyehrometer,
thermocouple hygrometer, in situ hygrometer.
Uses at Contaminated Sites: Measuring water potential (sum of osmotic and matric potential) and gradients in
the unsaturated zone; estimating water content (if moisture characteristic curve is developed, see Section 63,1);
measuring soil water flux in the vadose zone (see Section 7.5,2).
Method Description: Soil water potential is calculated based on measurement of relative humidity within the
soil voids. A basic psyehrometer unit consists of: (1) A porous bulb, with a chamber in which the relative
humidity of the soil is sampled, (2) a sensitive thermocouple, (3) a heat sink, and (4) a reference electrode. Two
major types are available, wet bulb and dew point; both types rely on cooling of the thermocouple junctions by
the Peltier effect, but differ in how temperature is controlled once the dew point of the sample is reached. With
in situ measurements of soil water potential, the thermocouple is protected by a cup-shaped device that maintains
a void in the soil. Calibration curves relating relative humidity to water potential, osmotic potential, and
temperature (if temperature in the subsurface varies) need to be developed in the laboratory. Figure 6.1.2
illustrates: (a) A basic Spanner, and (b) a modified Spanner-type psyehrometer.
Method Selection Considerations: The dew point method is more accurate than the wet bulb method. The useful
range is 10 to 70 bars capillary pressure. Advantages: (1) In situ pressure measurements are possible for very
dry soils in arid regions; (2) continuous recording of pressures is possible; (3) can be interfaced with portable
or remote data collection systems; and (4) depth is no limitation (installations have gone as deep as 300 feet).
Disadvantages: (1) Water content estimates prone to errors due to hysteresis; (2) even in very dry soils, the
relative humidity is high, making accurate calibration difficult; (3) good contact between bulb and surrounding
material might be difficult to achieve; (4) provide only point measurements; (5) accurate calibration curves for
deep regions of the vadose zone might be difficult to obtain; (6) instruments are expensive, fragile, and require
great care in installation; (7) contamination of the chamber interior or thermocouple can result in erroneous
readings; (8) interference from dissolved solutes is likely in calcium-rich waste and acid media and can cause
thermocouple wire corrosion problems; (9) perform very poorly in very wet media (water pressure > 1 bar); (10)
accuracy of near-surface measurements is adversely affected by diurnal changes in heat flux; (11) unsealed cup
units are susceptible to attack by fungi and bacteria; and (12) ceramic cup psychrometers respond slowly to rapid
changes in moisture content.
Frequency of Use: Widely used in agricultural research; sometime used at hazardous waste sites in the arid west.
Standard Methods/Guidelines: Rawlins and Campbell (1986).
Sources for Additional Information: Morrison (1983), Rehm et al. (1985), Thompson et al. (1989), Wilson
(1981). See also, Table 6-2.
6-5
-------
TYGON TUBING
JACKET
EPOXY RESIN
COPPER
LEAD WIRE
COPPER-CONSTANTAN
THERMOCOUPLE
TEFLON*, PLUG
CMROMEL-CONSTANTAN
THERMOCOUPLE
SCREEN CAGE
(a)
CHROMEL
(0 0025 cm)
SENSING
JUNCTION
TEFLON* ROD
CONST ANTAN
(26 AWG)
COPPER
(26 AWG)
REFERENCE
JUNCTION
CHROMEL
(0.0025 cm)
SENSING
JUNCTION
CONST ANTAN
(O.OOSS cm)
(b)
Figure 6.13- Thermocouple psychrometers: (a) Spanner psychrometer (Morrison, 1983, after Meyn and White, 1972,
by permission); (b) Double-loop, temperature-compensating psychrometer (Morrison, 1983, after
Meeuwig, 1972, by permission).
6-6
-------
6. VADOSE ZONE HYDROLOGIC PROPERTIES (I): WATER STATE
6.1 VADOSE ZONE SOIL WATER POTENTIAL
6.1,3 Electrical Resistance Sensors
Other Names Used to Describe Method: Four-electrode soil moisture probe, electrical resistance blocks, porous-
block method, soil moisture blocks.
Uses at Contaminated Sites: Measuring^nonitoring water potential and water content in the unsaturated zone;
monitoring of soil freezing.
Method Description: In the porous-block method, two electrodes (Figure 6.1.3a and b) are imbedded in a porous
block (nylon cloth, fiberglass, or casting plaster), or multi-electrode probes can be used (Figure 6.1.3e).
Calibration curves are first developed by placing the porous block in soil typical of the area to be measured and
resistivity is plotted against changes in matric potential. In the field, the porous blocks can be placed in a hole
and buried, or horizontally in the side of a trench, and the blocks are allowed to equilibrate with the surrounding
soil. Matric potential then can be monitored by taking resistance measurements, using the calibration curves to
convert the measurements to pressure. Water content also can be monitored either by using the procedure
described above to develop a calibration curve for water content or by using a moisture characteristic curve if
a resistance-water potential calibration curve has been developed (Section 63.1).
Method Selection Considerations: Advantages: (1) Are inexpensive and relatively easy to install; (2)
measurements can be recorded from many units over a large area using an automated recording system; and (3)
can be calibrated for either suction or water content. Disadvantages: (1) Calibration procedures can be
complicated and time consuming if accurate measurement of water potential for evaluation of hydraulic gradient
is required; (2) restricted water flow at the interface between the smooth face of a porous black creates some
problems for measurements in coarse soil material; (3) small changes in electrolyte concentration of the soil
water (which might well occur at contaminated sites) will affect resistivity readings; (4) measurements are made
in equilibrium with matric potential, so moisture content is inferred from matric potential rather than actual
moisture content; (5) gypsum sensors might dissolve in the subsurface; (6) water content estimates are prone to
error resulting from uncertainty of moisture-matric potential relationship (hysteresis causes different curves
depending on soil is wetting or drying); and (7) are rather insensitive to moisture changes in the wet range.
Frequency of Use: Commonly used for irrigation timing and other qualitative field-monitoring programs. Less
common for accurate measurement of soil hydrologic properties.
Standard Methods/Guidelines: Campbell and Gee (1986), Gardner (1986).
Sources for Additional Information: Bouyoueos (1960), Everett et al. (1983), Gairon and Hadas (1973), Holmes
et al. (1967), Morrison (1983), Rehm et al. (1985), Schmugge et al. (1980). See also, Table 6-2.
6-7
-------
ELECTRODES
POROUS MATRIX
(a)
FIBERGLASS
3 LAYERS-
MONEL
SCREEN.
(b)
5cm—)
LEADS
60 cm
T
GYPSUM
~BAYTURN
GYPSUM
STAKE
2.9 cm —1
Figure 6.1.3 Electrical resistance sensors: (a) Rectangular soil moisture block (Morrison, 1983, by permission); (b)
Fiberglass and Monel soil moisture sensor with thermistor (Morrison, 1983, after Colman and Hendrix,
1949, by permission); (c) MuKielectrode probe (Morrison, 1983, after Perrier and Marsh, 1958, by
permission).
6-8
-------
6. VADOSE ZONE HYDROLOGIC PROPERTIES (I): WATER STATE
6.1 VADOSE ZONE SOIL WATER POTENTIAL
6.1.4 Electrothermal Methods
Other Names Used to Describe Method; Thermal diffusivity, heat diffusion/dissipation sensors.
Uses at Contaminated Sites: Measuring water potential and gradients in the unsaturated zone; estimating water
content (if moisture characteristic curve is developed, see Section 63.1); measuring soil temperature.
Method Description: Similar to the resistivity method (Section 6.1.3), except that thermal diffusivity of an
implanted porous sensor, which is in equilibrium with the surrounding soil, is measured. A known amount of
heat is applied in the center of the sensor and the rate of dissipation is measured, which is a function of water
content. Major types of sensors include: (1) Porous-block type with embedded electrical elements (Figure 6.1,4a),
(2) direct-contact type with electrical elements in direct contact with the soil, and (3) modified direct-contact
probe or cell, in which the heating wire is enclosed in a protective sheath with high thermal conductivity (Figure
6.1.4b). Calibration curves of matric potential vs. temperature difference are obtained in the laboratory with soils
from the site using a pressure plate apparatus. The matric potential is related to water content by preparing a
moisture characteristic curve (Section 6J.I).
Method Selection Considerations: Useful range is 0 to 2 bars capillary pressure. Advantages: (1) Are simple;
(2) can be interfaced with data acquisition systems for remote collection of data; (3) measurements are
independent of salt content of soil; (4) calibration appears to remain constant; (5) can be used to measure soil
temperature as well as matric potential; and (6) are useful for measurement of water contents in the dry range.
Disadvantages: (1) Water content estimates subject to hysteresis; (2) calibration is required for each change in
texture; and (3) might be difficult to install at depth in the vadose zone and to maintain good contact between
the sensor and medium.
Frequency, of Use: Uncommon.
Standard Methods/Guidelines: Campbell and Gee (1986).
Sources for Additional Information; Morrison (1983), Thompson et al. (1989), Wilson (1981). See also, Table
6-2.
6-9
-------
SPAGHETTI TUBING INSULATION
4 LEAD WIRES
HEATSHRINKABLE
TUBING
HEATSHRINKABLE
TUBING
HEATSHRINKABLE
TUBING
POROUS MEDIA
(a)
ELECTRIC
WIRE STEEL WIRE
(COAXIAL) bTEEL WIHfc
STAINLESS
STEEL ARCH
ACRYLIC
^PLASTIC TUBE
CAST RESIN
HEATING
(CONSTANTAN)
WIRES AND
THERMISTOR WIRES
PLASTIC SLEEVE
GROOVE FOR
GLUING
PLASTIC CAP
STAINLESS
STEEL RING
STAINLESS STEEL
TUBE
PROTRUDING
STAINLESS STEEL
ROD
(a)
(b)
(b)
Figure 6.1.4 Electrothermal sensors: (a) Porous-block type (Morrison, 1983, after Phene et al., 1971b, by
permission); (b) Modifled direct-contact probe (Sophocleous, 1979, by permission).
6-10
-------
6. VADOSE ZONE HYDROLOGIC PROPERTIES (I): WATER STATE
6.1 VADOSE ZONE SOIL WATER POTENTIAL
6.1,5 Osmotic Tensiometers
Other Names Used to Describe Method —
Uses at Contaminated Sites: Measuring of combined osmotic and pressure potential.
Method Description: An osmotic tensiometer uses a confined solution of polyethylene glycol, rather than deaired
water, as the reference solution and a semipermeable membrane, which separates the confined solution from the
soil water (Figure 6.1.5). Small ions and molecules in the soil water are able pass through the membrane, and
once equilibrium is attained between the soil water and the reference solution, a pressure transducer measures
subsequent soil moisture-related pressure changes.
Method Selection Considerations: Advantages: Allows differentiation of osmotic and pressure components of
soil water potential if used with porous cup tensiometer. Disadvantages: (1) Are susceptible to fluid leakage and
instrument drift; (2) require long equilibration times (hours to days); and (3) are sensitive to temperature
changes.
Frequency of Use; Uncommon for reasons cited above. Thermocouple psychrometers are the preferred method
for measuring combined osmotic and pressure potential.
Standard Methods/Guidelines —
Sources for Additional Information: Bocking and Fredland (1979), Morrison (1983), Peck and Rabbidge
(1966a,b, 1969), Rehm et al. (1985).
6-11
-------
RIGID CONTAINER
SEMI-PERMEABLE
MEMBRANE
PRESSURE
TRANSDUCER
"O" RING SEALS
FITTING FOR PRESSURE RELEASE,
CALIBRATION AND ZERO
CHECK
AQUEOUS SOLUTION
POROUS CERAMIC
Figure 6.1.5 Osmotic tensiomeler (Morrison, 1983, after Peck and Rabbidge, 1966&, by permission).
6-12
-------
6. VADOSE ZONE HYDROLOGIC PROPERTIES (I): WATER STATE
6.1 VADOSE ZONE SOIL WATER POTENTIAL
6.1.6 Filter-Paper Method
Other Names Used to Describe Method --
Uses at Contaminated Sites: Measuring soil water potential and/or moisture content.
Method Description: The filter-paper method involves the collection of soil cores at different locations and/or
depths. Each soil core is placed in a sealed container in contact with filter paper, which has been pretreated with
3% pentachlorophenol dissolved in methanol to prevent microbial degradation. In the laboratory, the samples
are maintained at a constant temperature for at least 1 week to allow equilibration of moisture between the soil
and the filter paper. Gravimetric water content of the soil and filter paper is determined using the oven-drying
method (see Section 6.2.1). The matric potential then is calculated using a calibration equation (Figure 6.1.6).
Method Selection Considerations: Advantages: (1) Reasonably accurate over a wide range of matric potentials;
(2) requires minimal and inexpensive equipment; (3) cores can be used to directly measure moisture content and
to measure bulk density; and (4) simplicity allows taking a large number of measurement to characterize spatial
variability. Disadvantages: (1) Soil core collection is destructive and does not allow repeated measurements at
exactly the same location (Figure 6.2.1 in the next section shows patterns for sequential sampling, if this method
is used); and (2) different filter papers might require development of separate calibration curves.
Frequency of Use: Has commonly been used in studies of western rangeland hydrology.
Standard Methods/Guidelines: ASTM (1992b).
Sources for Additional Information: McQueen and Miller (1968a, 1968b), Sorenson et al. (1989) cite 18
references on this method.
6-13
-------
fes
UJ
O
Q.
O
DC
Calibration published by McQueen
and Miller (1968)
Revised calibration
is the coefficient of determination
1 2
WATER CONTENT OF FILTER PAPER(Wp),IN GRAMS
OF WATER PER GRAM OF PAPER
Figure 6.1.6 Calibration equations (for above and below field capacity) used to determine soil matric potential from
Dlter-papcr water content (Sorenson et al., 1989).
6-14
-------
6. VADOSE ZONE HYDROLOGIC PROPERTIES (I): WATER STATE
6.1 VADOSE ZONE SOIL WATER POTENTIAL
6.1.7 Water Activity Meter
Other Names Used to Describe Method: --
Uses at Contaminated Sites: Measuring soil water potential in very dry soils.
Method Description; A water activity meter (another term for relative humidity) can be used to measure soil
water potential in a soil using principles similar to thermocouple psychrometers (Section 6.1.2). A small amount
of soil (4 centimeters in diameter and 0.5 centimeters thick) on a slide tray is placed in a measuring chamber
(Figure 6.1.7). The sample temperature is monitored using a built-in infrared thermometer and the dew point
of the water vapor above the sample is measured using a cooled mirror. The dew point and sample temperature
are recorded on a data logger and converted to relative humidity, using an algorithm that accounts for
temperature differences between the soil sample and chamber as both are equilibrating at room temperature.
Gee et al. (1992) obtained good results with a commercially available water activity meter for measuring soil
water potential for soil textures ranging from sand to clay.
Method Selection Considerations; Advantages: (1) Provides rapid (3 to 5 minutes/sample), accurate
measurements over a wide range of soil water potentials (-4 to <-2,640 kPa); (2) allows measurement of soil
water potential in soils that are too diy from tensiometer measurements (<-85 kPa); (3) instrumentation is
relatively simple and less subject to errors than thermocouple psychrometers for measuring low potentials; and
(4) commercially available instrumentation can be readily used; Disadvantages: Requires collection of soil
samples, so limited to relatively shallow depths if time-series monitoring is desired (see 6.2.1 for possible sampling
patterns).
Frequency of Use: Only recently applied to measurement of water potential in soil samples.
Standard Methods/Guidelines: —
Sources for Additional Information: Gee et al. (1992).
6-15
-------
LIGHT
SOURCE
COOLED MIRROR
(AND THERMOPILE)
DATA
LOGGER
[CONTROLLER
SENSING
CHAMBER
SLIDE
TRAY
SOIL SAMPLE
(4 cm x 0.5 cm)
Figure 6.1.7 Schematic of a water activity (relative humidity) meter (Gee et al., 1992, by permission).
6-16
-------
6. VADOSE ZONE HYDROLOGIC PROPERTIES (I): WATER STATE
6.2 VADOSE ZONE MOISTURE CONTENT
6.2.1 Gravimetric Methods
Other Names Used to Describe Method: Oven-diying method, carbide/gas pressure method.
Uses at Contaminated Sites; Measurement of soil moisture content.
Method Description: Oven-dry method: The mass of a sample collected in the field is weighed before and after
oven drying, typically at 105°C, the difference being the water content. Other methods of drying, such as a
microwave oven and direct heating using a hotplate, stove, or blowtorch, can be used for more rapid, but less
accurate measurements in the field. Carbide method: A soil sample of known weight is placed in a container
with calcium carbide. The calcium carbide reacts with water, releasing a gas. After completion of the reaction,
the gas pressure, registered on a gage, is converted into water content on a dry weight basis. Since all gravimetric
moisture measurements require destructive sampling, the careful design of the sample collection sequence is
required to measure changes in moisture content over time (Figure 6.2.1). Other gravimetric methods: Other
techniques of drying and soil moisture extraction include: (1) Centrifugation, (2) pressure plate extraction, and
(3) desiccation. Section 93,4 further discusses these and other methods of soil water extraction from solids
samples.
Method Selection Considerations; Standard Oven-Dry Method Advantages: (1) The most accurate available
method and serves as the standard method for the calibration of all other moisture determination techniques;
(2) is simple; (3) provides a direct measurement of the mass of water. Standard Oven-Dry Method
Disadvantages: (1) Obtaining representative moisture values in a heterogeneous profile is difficult, requiring a
large number of replicate samples for each depth increment; (2) is destructive, requiring removal of samples for
laboratory analysis and thus preventing additional measurements at the same sites; (3) expensive if large numbers
of samples are required; (4) plotted vertical moisture profiles will not be accurate if water is moving rapidly
through the vadose zone, because water distribution profile is changing as samples are being taken; (5) samples
from contaminated sites might require special handling if hazardous contaminants are present; (6) not suitable
for nongranular media (i.e., fractured rock, carbonates); and (7) sample collection might be difficult in indurated
layers, such as fragipans, when soil is very dry (soil difficult to penetrate) or very wet (soil will not remain in
sampling tool), and when soils are frozen. Other Drying Methods Advantages: Generally faster than standard
oven-dry method. Other Drying Methods Disadvantages: (1) Might not be as accurate as standard oven-drying;
(2) with microwave oven, sample might explode and be lost if power level is too high; and (3) other disadvantages
are the same as for oven drying. Carbide Method Advantages: (1) Can be used in the field and is more rapid
than oven-drying; (2) initial capital investment is lower. Carbide Method Disadvantages: (1) Might not be as
accurate as standard oven-drying; and (2) other disadvantages are same as for oven drying.
Frequency of Use; Widely used. The ASTM oven-dry method is the standard by which the accuracy of other
moisture measurement methods are evaluated.
Standard Methods/Guidelines: Gardner (1986); Standard oven-dry method: ASTM (1990); Microwave oven
method: ASTM (1987); Direct heating method: ASTM (1989a); Carbide method: ASTM (1989b).
Sources for Additional Information: Everett et al. (1983), Morrison (1983), Thompson et al. (1989), Wilson
(1981). See also, Table 6-2.
6-17
-------
1
4
2
5
3
2
5
3
1
4
3
1
4
2
5
4
2
5
3
1
5
3
1
4
2
1
4
6
3
5
2
2
5
1
4
6
3
3
6
2
5
1
4
4
1
3
6
2
5
5
2
4
1
3
6
6
3
5
2
, 4
1
in
(a)
(b)
Figure 6,2.1 Arrangement of boreholes for gravimetric soil-moisture sampling: (a) Rectangular microplots; (b) along
perimeters of polygons (Brown et al., 1983)
6-18
-------
6. VADOSE ZONE HYDROLOGIC PROPERTIES (I): WATER STATE
6.2 VADOSE ZONE MOISTURE CONTENT
6.2.2 Nuclear Methods
Other Names Used to Describe Method: Neutron probe, gamma transmission/double-tube gamma method.
Uses at Contaminated Sites: Measuring and monitoring of changes in soil moisture content.
Method Description: The neutron method, which measures moisture content based on the interaction between
neutrons and hydrogen atoms in water molecules, is discussed in Section 3.3.3, and the gamma-gamma method
for measuring soil moisture is discussed in Section 3.3.2. Soil moisture using the neutron method can be
measured using either a surface neutron probe (Figure 6.2.2a) or a depth probe (see Figure 3.3.3). Near-surface
soil moisture measurements usually involve the gamma-transmission method, in which a gamma photon source
and detectors are lowered simultaneously down two parallel boreholes (Figure 6.2.2b). In boreholes, the gamma-
scattering method is used (see Figure 33.2).
Method Selection Considerations: Neutron probe: See Section 3.3.3; Double-tube gamma method: See Section
3.3.2.
Frequency of Use: Neutron probes are commonly used for monitoring of soil moisture in the near surface. The
double-tube gamma method is less common.
Standard Methods/guidelines: Neutron probe: ASTM (1988, 1992a), Gardner (1986).
Sources for Additional Information: Table 3-4 in Section 3 provides an index of over 100 references on the
neutron method and around 40 references on gamma-gamma logging methods.
6-19
-------
CABLE
TO SCALER
.SOURCE
SOIL SURFACE
DETECTORS DETECTORS
CURVE 1
CURVE 2
(a)
SYNCHRONOUS WITHDRAWAL
MECHANISM
ACCESS-
TUBE
GAMMA
DETECTOR
SHIELDED
CONTAINER
ACC6 SS
TUBE
OAMM A
SOURCE
(b)
Figure 6,2,2 Nuclear methods for soil moisture measurement: (a) Cross-section of surface neutron probe (Morrison,
1983, atter DeVries and King, 1961, by permission); (b) Double-tube gamma method for soil moisture
content determination (Ream et ai., 1985, Copyright © 1985, Electric Power Research Institute, EPRI
EA-4301, Field Measurement Methods for Hydrogeologic Investigations: A Critical Review of the Literature,
reprinted with permission).
6-20
-------
6. VADOSE ZONE HYDROLOGIC PROPERTIES (I): WATER STATE
6.2 VADOSE ZONE MOISTURE CONTENT
6.2.3 Dielectric Sensors
Other Names Used to Describe Method: Radio frequency/microwave techniques, capacitance techniques,
capacitive sensors, "fringe' capacitance, resonance capacitance, in situ permittivity meter.
Uses at Contaminated Sites: Measuring soil moisture content."
Method Description: Basic principles are similar to the induced polarization surface geophysical method (see
Section 1.2.3 for discussion of frequency domain and time domain IP methods), except that sensors are placed
below the ground surface. A variety of capacitive sensors (Figure 6.2.3a,b) have been developed that measure
the dielectric properties of soil, which are primarily related to water content. These sensors depend upon specific
electrode configurations and detailed calibration. Dielectric probes, which measure vertical soil moisture profiles
in a cased holed similar to neutron probes (Section 33.3), are a relatively recent development. Dielectric probes
have significant advantages over neutron probes and other nuclear methods for measuring soil moisture (see
below)..
Method Selection Considerations: Sensor Advantages: (1) With accurate calibration, can provide accurate values
for soil moisture; (2) can be placed at any depth for obtaining moisture profile data; (3) a wide variety of sensor
configurations, from very small to large, are possible, allowing some control over the sensor volume of influence;
and (4) capacitive sensors have high precision and the property they measure (dielectric constant) is primarily
related to water content. Sensor Disadvantages: (1) The moisture sensor must be implanted properly to
minimize disturbance to the soil; (2) long-term reliability and maintenance of the calibration is uncertain,
especially if the ionic concentration of the soil water changes; and (3) cost of readout devices and interfaces with
remote collection platforms is high. Probe Advantages: (1) Provide better resolution in measuring vertical soil
moisture profiles than neutron probes; (2) are less expensive than neutron probes and time domain reflectometry
sensors; (3) are as accurate as neutron probes without having to deal with radioactive materials; and (4) can be
used to accurately determine position of a wetting front and ground^water level in soil. Probe Disadvantages:
(1) Special care is required to make sure that there are no air gaps outside the access tube, because relatively
limited radial penetration gives more weight to measurements near the borehole compared to neutron probe;
(2) less sensitive at high moisture contents than low moisture contents; and (3) air-soil interface affects accuracy
of measurements of in the upper 20 to 50 centimeters of soil.
Frequency of Use: Numerous prototypes have been developed. Relatively recent development of commercially
available units means that this method is likely to be used more commonly in the future.
Standard Methods/Guidelines: --
Sources for Additional Information: Morrison (1983), Schmugge et al. (1980). See also, Table 6-2.
"Capacitance sensors are classified here as moisture sensors because they are most commonly calibrated to
measure soil moisture. They could just as easily be classified as a matric potential measurement technique
because they operate by moisture moving into the sensor in response to the matric potential gradient.
6-21
-------
CABLE
INSULATOR
LOWER ELECTRODE
(a)
SOLDER^
PLASTIC COUPLER
GROUNDING POST.
CONNECTOR CLIP-
LOWER CIRCUIT.
BOARD
INSULATOR -
CENTER BOLT.
"O-RING.
BOTTOMPLATE.
THREADED ROD
^^ ELECTRICAL
.CONNECTOR (BNCj
TOP PLATE
CASE
iJW --
'• \ Jrl— —•BANANA JACK
UPPER CIRCUIT
BOARD
- 5.08 cm
-PLASTIC CAP
(b)
Fieure 6^3 Capacitance sensors: (a) Capacitance probe (Morrison, 1983, after Thomas, 1966, by permission); (b)
Cylindrical sensor (Morrison, 1983, after Wobschali, 1978, by permission).
6-22
-------
6. VADOSE ZONE HYDROLOGIC PROPERTIES (I): WATER STATE
6.2 VADOSE ZONE MOISTURE CONTENT
6.2.4 Time Domain Reflectometiy
Other Names Used to Describe Method: —
Uses at Contaminated Sites: Measuring soU moisture content; estimating soil bulk electrical conductivity.
Method Description: Use of time domain reflectometry to measure soil moisture content is a relatively recent
development that shows great promise for field applications. Volumetric water content can be determined based
on measuring the travel time and the attenuation of the amplitude of an electromagnetic pulse launched along
one or more transmission lines (coaxial, two-, three-, or four-rod probes) embedded in the soil. Portable probes
can be used to make multiple near-surface measurements or in situ probes of varying length can be installed
vertically to different depths, or horizontally at different depths in the side of a trench (Figure 6.2,4). The TDR
trace can be recorded either on a photograph of the oscilloscope display or on an X-Y recorder. The measured
dielectric constant is converted to volumetric water content using an empirically derived equation that can be
applied to many soils. Electrical conductivity also can be estimated from the attenuation of the signal (Section
9.1.4).
Method Selection Considerations: Advantages: (1) With accurate calibration, can provide accurate values for
soU moisture; (2) can be placed at any depth for obtaining moisture profile data; (3) a wide variety of sensor
configurations, from very small to large, are possible, allowing some control over the sensor volume of influence;
(4) readily amenable for use with automatic data acquisition systems; and (5) available from several commercial
sources. Disadvantages: (1) The moisture sensor must be implanted properly to minimize disturbance to the soil;
(2) long-term reliability and maintenance of the calibration is uncertain, especially if the ionic concentration of
the soil water changes; and (3) cost of readout devices and interfaces with remote collection platforms is high.
Frequency of Use: Relatively new method with good potential for field applications.
Standard Methods/Guidelines: —
Sources for Additional Information: See Table 6-2.
6-23
-------
CORN
Figure 6.2,4 Diagram of vertical and horizontal TDR probe Installations for soil moisture monitoring at different
depths (Topp and Davis, 1985a, by permission).
6-24
-------
6. VADOSE ZONE HYDROLOGIC PROPERTIES (I): WATER STATE
6.2 VADOSE ZONE MOISTURE CONTENT
6.2.5 Nuclear Magnetic Resonance (NMR)
Other Names Used to Describe Method: Nuclear-magnetic logging.
Uses at Contaminated Sites: Measuring porosity, permeability, moisture content, pore-size distribution, available
water.
Method Description: A magnetic field is induced using a pulsed, direct current, polarizing field to align a
fraction of the nuclei of hydrogen atoms (protons). When the polarizing field is shut off, the probe records the
precession of the protons into the Earth's magnetic field. The proton relaxation time is short for fluids in solids
or bound to a surface, but is'much longer for fluids free to move in pore spaces. Figure 6,2.5a shows
components of a pulsed nuclear magnetic resonance sensor and Figure 6.2.5b shows a prototype unit for in situ
measurements of soil moisture. Installation involves digging a test pit to the desired depth, driving a thin-walled
plastic tube into the bottom, and excavating around the tube to a depth of about 4 centimeters. The sensor is
slipped over the tube and seated firmly and the excavation is backfilled with a coaxial cable running to the
surface, which is plugged into the instrumentation for inducing the magnetic field and measuring the response
when it shut off.
Method Selection Considerations: Advantages: (1) More precise characterization of free and bound water and
porosity than other logging methods; and (2) prototype units for in situ measurement of soil moisture have been
developed. Disadvantages: (1) Use limited to large boreholes (generally >7 inches) filled with drilling mud
(magnetite powder usually has to be added to the mud to eliminate the borehole contribution to the log); (2)
installation procedures are relatively complex for in situ units; and (3) equipment availability might be a problem.
Frequency of Use: Not widely used for petroleum applications and relatively unknown for ground-water
applications. Potentially very useful if borehole conditions are appropriate.
Standard Methods/Guidelines: —
Sources for Additional Information: NMR general: Abragam (1961), Schlichter (1963), see also, Section 10.63;
Borehole applications: See Section 3.2.4; Soil moisture applications; Morrison (1983), and references indexed
in Table 6-2.
6-25
-------
SPECIMEN C1J
NORTH
POtE
HO,
RF COIL (2J
CATHODE RAY
OSCILLOSCOPE
MAGNET (3)
(a)
STEEL PLATE MAGNET
FIBERGLASS TUBE
COPPER SHIELD
COAXIAL CABLE
(b)
Figure 6.2.5 Nuclear magnetic resonance: (a) Components of a pulsed nuclear magnetic resonance sensor and
associated instrumentation; (b) Prototype in situ nuclear magnetic resonance sensor (Morrison, 1983,
after Matzkanin and Gardner, 1974, by permission).
6-26
-------
6. VADOSE ZONE HYDROLOGIC PROPERTIES (I); WATER STATE
/
6.2 VADOSE ZONE MOISTURE CONTENT
6.2,6 Electro-Optical Sensors
Other Names Used to Describe Method: Electro-optical switch sensor, CdS photoresistor sensor.
Uses at Contaminated Sites: In situ monitoring of soil water content and/or matric potential.
Method Description: Several types of electro-optical sensors have been developed that can use changes in the
optical properties of different materials at different moisture contents to measure soil moisture and/or matric
potential. The electro-optical switch sensor involves placement of a nylon filter disk in the gap of an electro-
optical switch. (Figure 6.2.6a). An infrared light emitting diode (IR LED) sends a signal that passes through the
filter disc and is sensed by a photo diode. The sensor is calibrated by measuring the response in the soil at
known moisture content and/or matric potentials. A second type of sensor involves the placement of porous glass
or nylon disks of different pore-size grades between a CdS photoresistor cell and light emitting diode (Figure
6.2.6b). The use of different pore-size disks allows continuous measurement of electrical response over a wide
range of moisture contents. Calibration procedures are similar to those for the electro-optical switch sensor.
Method Selection Considerations: Advantages: (1) Potential for low cost and high physical stability and reliability;
(2) can be calibrated to measure both moisture content and water potential over a wide range of moisture
contents and-matric potentials (electro-optical switches are better than CdS photoresistors for direct measurement
of matric potential); and (3) electronic circuitry allows automatic data acquisition and analysis. Disadvantages:
(1) New technique with limited operational and field experience; (2) equipment is not yet readily available
(although both types of devices can be readily made using off-the-shelf materials); and (3) separate calibrations
might be required for changes in soil texture.
Frequency of Use: New technique with potential for widespread use.
Standard Methods/Guidelines: —
Sources for Additional Information: Alessia and Prunty (1986), Gary et ah (1989, 1991)
6-27
-------
Epoxy Cap
Optical
Switch
Metal Spacer
Nylon Fitter Disc
(a)
Resistance
Signal, kn
Epoxy Casing
Porous Glass Disks
(b)
Figure 62.6 Diagrams of two electro-optical soil-water sensors: (a) Electro-optical switch with nylon disk using
infrared-light transmission; (b) CdS cell (photoresistor) with layered fritted glass using visible-light
transmission (Cary et al., 1991, by permission).
6-28
-------
6. VADOSE ZONE HYDROLOGIC PROPERTIES (I): WATER STATE
6.2 VADOSE ZONE MOISTURE CONTENT
6.2.7 Computerized Axial Tomography (CAT)
Other Names Used to Describe Method: Computer assisted tomography, CAT scanning, x-ray computed
(computer) tomography, computed tomographic scanning, CT scanning, x-ray CT, gamma -ray attenuation CAT,
nuclear tomography.
Uses at Contaminated Sites: Potential for measuring spatial distribution of soil moisture, bulk density, and soil
macroporosity; detecting roots, seeds, insects.
Method Description: CAT scanning systems can use single or multiple sources of gamma radiation or x-rays.
Detectors can be on the same probe as the source, or placed in adjacent boreholes. The detectors measure the
attenuated signal, and counts in the desired energy ranges are discriminated by a single channel analyzer. Signals
are processed using tomographic theory (see also, Section 3.4.5) to allow three dimensional analysis of variations
of the parameter of interest. Figure 6.2.7 illustrates the operation of a CT scanner used for scanning soil cores
in the laboratory.
Method Selection Considerations: Relatively new method, which has shown promising results in laboratory
studies, but has not yet been tested for field applications.
Frequency of Use: Usefulness in the field not yet demonstrated.
x^
Standard Methods/Guidelines: ASTM (1991b).
Sources for Additional Information: Anderson et al. (1988), Phogat et al. (1991). /
6-29
-------
ROTATION
X-RAY
SOURCE
DETECTOR
ARRAY
ROTATION
Figure 6.2.7 Schematic of how a CT scanner measures the attenuated x-ray beams passing through a detection
aperture containing a soil core. The x-ray source and detector array rotate clockwise around the
detection zone (Anderson et al., 1988, by permission).
6-30
-------
6. VADOSE ZONE HYDROLOGIC PROPERTIES (I): WATER STATE
6.3 OTHER SOIL HYDROLOGIC PROPERTIES
6.3.1 Soil Moisture-Potential-Conduetivity Relationships
Other Names Used to Describe Method: Moisture characteristics curves: Water retention function, specific
retention, water content-matric potential relationship, capillary pressure-saturation curve, capillary-moisture
relationship.
Uses at Contaminated Sites: Estimating water content from soil water potential measurements; estimating soil
water potential from soil moisture measurements; estimating hydraulic conductivity from soil water potential or
soil moisture measurements; modeling of contaminant flow in the vadose zone.
Method Description: Soil moisture (usually represented by the symbol "6"), soil matrie potential (usually
represented with the symbol "<£"), and soil hydraulic conductivity are all intimately related. Once the relationship
between two of these properties have been established for a soil horizon, then measurement of one parameter
allows calculation of the other parameters. The soil moisture characteristic curve (see above for other terms
used to describe this relationship) is a commonly used relationship to define soil hydrologic properties. An
important property of this relationship is that it is subject to hysteresis (i.e., the relationship is different
depending on whether the soil is wetting or drying). Figure 6.3. la shows the moisture characteristic curve for
a sandy soil and illustrates the effect of hysteresis. In the field, the moisture characteristic curve is determined
by monitoring soil water content (using methods described in Section 6.2) and soil water potential (using methods
described in Section 6.1) during the wetting or drying cycle of a soil. Jury et al. (1978) provide an example of
developing a moisture characteristic curve in the field using tensiometers and neutron-probe measurements.
Shani et al. (1987) describe a reliable and quick method for estimating this relationship in the field using a
dripper method (Section 7.2.5), In a similar manner, K(0) (hydraulic conductivity as a function of moisture
content) and K($) (hydraulic conductivity as a function of soil-water potential [pressure head]) can be measured.
These relationships also are subject to hysteresis as shown in Figure 63. Ib. Estimation from other soil
properties: The hydrologic properties of soils are strongly related to physical properties, such as particle-size
distribution, porosity, and bulk density. Empirical relationships between physical and hydrologic properties can
be used to estimate soil moisture-potential relationships based on measurement of physical properties, provided
that the soils are similar to the soils from which the empirical relationships have been derived. Section 7.2.8
provides additional information on estimation of unsaturated hydraulic conductivity using physically and
empirically-based equations and relationships, many of which can be related to moisture characteristic curves.
Mualem and Friedman (1991) have developed an equation that relates soil electrical conductivity (from saturation
extract—see Section 93.5) to water content, which can be used to estimate soil water content of samples for a
wide range of coarse and stable structured soils when no other data are available. Reference index Table 9-3
(EC-Salinity Calibrations), identifies other references that discuss the relationship between moisture content and
electrical conductivity. The moisture characteristic also can be estimated from sorptivity measurements (Section
63.2).
Method Selection Considerations: The soil moisture-potential relationship is required input for many vadose
hydrologic models. Field measurement of moisture characteristic curves using conventional methods is
complicated and time-consuming, although the recently developed dripper method (Section 7.2.5) now provides
a simpler and more rapid alternative for field measurement. Laboratory measurements using undisturbed core
samples are simpler, but a large number of cores might be required to adequately characterize spatial variability.
Empirical relationships based on other soil physical properties are the simplest and least expensive method, but
probably are the least accurate method unless soil physical properties are very similar to the soils from which
the empirical relationships were derived.
Frequency of Use: Field measurement is uncommon. Usually measured in the laboratory or estimated using
empirical relationships.
Standard Methods/Guidelines: Field: Bruce and Luxmore (1986), Shani et al. (1987); Laboratory: ASTM (1968),
Mute (1986); Empirical equations/relationships: See Table 6-3.
Sources for Additional Information: See Table 6-3.
6-31
-------
-30O -200 -100
PRESSUREHEAO. h. (CM OF WATEH!
-30O -20O -100
PRESSUREHEAO, h. (CM OF WATER)
00
Figure 63.1 Relationships between soil moisture, matric potential, and hydraulic conductivity: (a) Moisture
characteristic curves for a sandy soil during wetting and drying; (b) K-matrie potential curves showing
effect of hysteresis during wetting and drying (Everett et ai. 1983, after Freeze and Cherry, 1979).
6-32
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6. VADOSE ZONE HYDROLOOIC PROPERTIES (I): WATER STATE
63 OTHER SOIL HYDROLOGIC PROPERTIES
63.2 Water Sorptivity and Diffusivity
Other Names Used to Describe Method: —
Uses at Contaminated Sites: Sorptivity: Estimating diflusivity-moisture relationship, moisture characteristic curve,
and hydraulic conductivity as a function of rnatric potential; estimating soil water distribution. Diffusivity:
Characterizing soil transmission/storage properties; calculating infiltration (some equations).
Method Description: Soil diffusivity is a single parameter of unsaturated soil that relates the hydraulic
conductivity and water storage properties of a soil and can be calculated as either a function of changes in soil
water potential or water content. Hydraulic diffusivity can be an important parameter in infiltration equations
(Section 7.1.4). Sorptivity is a measure of the capacity of a porous medium to absorb a wetting liquid. The
greater the value, the larger the volume of water that can be absorbed, and the more rapidly it will be absorbed.
Sorptivity decreases from a maximum value (dependent on the soil physical properties) to zero as water
content/matric potential increase to the point of saturation. Sorptivity is closely related to hydraulic conductivity
and soil water diffusivity, and is sometimes used to calculate diffusivity. Field Measurement of Diffusivity: Any
field method for measuring unsaturated hydraulic conductivity as a function of matric potential, which measures
changes in water content with time and changes in matric potential with time, can be used to determine diffusivity
(see Table 7-1). Field measurement of sorptivity; Green et al. (1986) describe two methods for measurement
of sorptivity: (1) Ponded infiltration: A single- or double-ring infiltrometer (see Section 73.1) is filled with water
and cumulative infiltration is measured as the head of ponded water falls with time; (2) Constant-head porous
Plate: Similar to ponded infiltration method, except that a constant-head device delivers water to the soil through
a porous plate in contact with the soil. This process results in a slight negative pressure at the bottom of the
porous plate, preventing water from entering large pores or cracks. The second method is a variant of the
tension inGltrometer (see Section 7.23). Table 7-1 identifies other methods for measuring saturated and
unsaturated hydraulic conductivity, which also can be used to measure sorptivity.
Method Selection Considerations; Sorptivity: The ponded infiltration method is simple and rapid, but works only
when there is negligible flow of water through large cracks or channels. The constant-head porous plate method
also is simple, rapid and reliable, and should be used any time flow through large pores is a concern. See also,
appropriate subsections in Section 7, as identified in Table 7-1.
Frequency of Use; Relatively uncommon in routine field applications.
Standard Methods/Guidelines: Green et al. (1986).
Sources for Additional Information: See Table 6-3 and additional references identified under tension
infilirorueters in reference index Table 7-3.
6-33
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6, VADOSE ZONE HYDROLOGIC PROPERTIES (I): WATER STATE
63 OTHER SOIL HYDROLOGIC PROPERTIES
63.3 Available Water Capacity
Other Names Used to Describe Method: Field capacity, water holding capacity.
Uses at Contaminated Sites: Evaluating water storage in the rooting zone and the movement of contaminants
from the rooting to the vadose zone in response to precipitation events.
Method Description: Available water capacity is the difference between field capacity (the amount of water
remaining in a soil 2 or 3 days after having been wetted and after free drainage is negligible) and water held in
the soil at the permanent wilting point, PWP (the point at which plants generally are unable to extract additional
water from the soil—around 15 bars suction = -1,500 kPa). This represents the amount of water that is available
to plants for growth. The field procedure involves wetting soil test plots and measuring water content using one
of the methods identified in Table 6-1 (gravimetric, neutron, or gamma-gamma are the most commonly used)
when the soil is at field capacity at different depth increments. Alternatively, natural changes in soil moisture
can be monitored over an extended period of time. Figure 6.3.3a shows that this approach can result in a range
rather than an exact percentage for field capacity. Determination of the PWP requires laboratory tests using the
Sunflower method, in which water is withheld from a dwarf sunflower growing in a sample of the depth horizon
of interest until it wilts, at which time the soil water content is determined. Alternatively, PWP can be
approximated using a pressure plate apparatus to withdraw water from a sample of the depth increment of
interest until ma trie potential is -15 bars, at which time water content is measured. Figure 6 J.3b show several
ways in which the resulting data can be plotted, and illustrates the difference that rooting depth of plants present
in a soil can make in the amount of water that is likely to be removed from the soil by evapotranspiration.
Available water capacity also can be estimated from a moisture characteristic curve (Figure 6.3,1), and from soil
texture (Figure 63.3c). The particle-size ranges of the texture classes shown 5n Figure 6.3.3c are shown in Figure
2J.1.
Method Selection Considerations: There is no good alternative to the procedure described above for accurate
measurement of in situ field capacity, although approximations using laboratory analysis of undisturbed soil cores
or eentrifugation of disturbed soil samples can be obtained.
Frequency of Use: Uncommon.
Standard Methods/Guidelines: Cassel and Nielsen (1986).
Sources for Additional Information: Richards (1965).
6-34
-------
w
trt
Field capacity
Oct. Nov. " Dec. Jan. Feb. Mar. Apr.
Month
SOIL WATER CONTENT (M/M)
0 0.2 0.4 0.6 0 0.2 0.4 0.6 0
0.60
0.50 h
0.40 r-
0.30 h
o
a.
o
0.2 0.4
0.6
PWP
Porosity
Field
capacity
Wilting"
point
0.20 h
0.10
(C)
Figure 6-3.3 Available water capacity: (a) Estimation of field capacity (28 to 30 percent) by repeated measurement
of soil moisture in situ (Dunne and Leopold, 1978, From: Water in Environmental Planning by Dunne
and Leopold, Copyright © 1978 by W.H. Freeman and Company, reprinted with permission), (b) Upper
and lower limits of available water: (A) Measured in 0.15-meter increments, (B) limits expressed for
this profile for a 0.6-meter rooting depth, (C) and for a 15-meter rooting depth,* FC = field capacity,
PWP = permanent wilting point (Cassel and Nielsen, 1986, by permission); (c) Chart for estimating
field capacity and available water capacity based on soil texture (Dunne and Leopold, 1978, From:
Water in Environmental Planning by Dunne and Leopold, Copyright © 1978 by W.H. Freeman and
Company, reprinted with permission).
-------
Table 6-2 Reference Index for Vadose Zone Soil Water Potential/Moisture Measurement and Monitoring Methods
Topic
References
Soil Water /Matric) Potential
General
Porous Cup Tensiometers
Hendrickx et al. (1990-variability), WMkinson and Mute (1962-temperature effects);
Reviews: Bouyoucos (1960), Brakensiek et al. (1979), Mullins (1991), Richards (1949)
Colman et al, (1946), Cummings and Chandler (1940), Dennehy and McMahon (1989),
Hendrickx and Nieber (1985), Huber and Dirksen (1978), Hunter and Kelley (1946),
McKim et al. (1980b), Miller (1951), Oaksford (1978-manometer), Perrier and Evans
(1961), Rehm et al. (1987), Richards (1942), Richards and Gardner (1936), Richards
and Neal (1937), Richards et a!. (1938, 1973), Rogers (1935), Sawides et al. (1977-
mercury), Thomas and Phillips (1991), Towner (1980), Wendt et al. (1978); Reviews:
Cassel and Mute (1986), Hendrickx (1990), Richards (1949), Schmugge et al. (1980),
Stannard (1986,1990); Transducer type: Anderson and Butt (1977), Bianchi (1962),
Burt (1978), Bzeftawy and Mansell (1975), Enfield and Gillaspy (1980), Fitzsirnmons
and Young (1972), Gillham et al. (1976), Mute and Peters (1962), Leonard and Low
(1962), Long (1982), Long and Huck (1980), Marthaler et al. (1983), Rice (1969),
Thiel et al. (1963), Thony and Vaehaud (1980), Watson (1965, 1967), Watson and
Jackson (1967-temperature effects), Williams (1978); Recording
Tensiometers/Automatic Data Acquisition: Anderson and Burt (1977), Bianchi and
Tovey (1968), Burt (1978), Enfield and Gillaspy (1980), Long and Huck (1980),
Lowery et al. (1986), Nyhan and Drennon (1990), Rice (1969), Walkotten (1972),
Williams (1978); Moisture Measurement: Cummings and Chandler (1940), McKim et
al. (1980b), Troolen et al. (1986); Snowpack: Colbeck (1976), Wankiewicz (1978); Wick
Tensiometen Gee and Campbell (1991)
Thermocouple Psychrometers Review: Savage and Cass (1984); Papers: Barrs and Slaytor (1965), Box (1965), Brown
(1970), Brown and Collins (1980), Brown and Johnson (1976), Campbell (1972, 1979),
Campbell et al. (1968), Chow and deVries (1973), Dalton and Rawlins (1968), Daniel
(1979), Daniel et al. (1981), Enfield and Hsieh (1972), Enfield et al. (1973), Hofflnan
et al. (1969, 1972), Hsieh and Hungate (1970), Hsieh et al. (1972), Ingvalson et al.
(1970), Jones et al. (1990), Koorevar and Janse (1972), Korven and Taylor (1959),
Lambert and van Schilfgaarde (1965), Lang and Trickett (1965), Lopushinsky (1971),
Lopushinsky and Mock (1971), Madsen et al. (1986), Meeuwig (1972), Merril and
Rawlins (1972), Merril et al. (1968), Meyn and White (1972), Monteith and Owen
(1958), Moore and Caldwell (1972), Peck (1968), Rawlins (1966), Rawlins and Dalton
(1967), Richards (1949), Richards and Caldwell (1987), Richards and Ogata (1958),
Roundy (1984), Spanner (1951), Van Heveren (1972-humidity in snow), Van Heveren
and Brown (1972), Wiebe et al. (1971, 1977), Zanstra (1976), Zollinger et al. (1966);
Texts: Brown and Van Heveren (1972), Campbell (1977), Fritschen and Gay (1979);
Measurement Interpretation: Campbell and Gardner (1971), Lang (1967); Calibration:
Brown and Collins (1980); Water Activity Meter: Gee et al. (1992)
Resistance Sensors
Anderson and Edlefsen (1942), Atchison and Butler (1951), Becker et al. (1946),
Bourget et al. (1958), Bouyoucos (1949, 1953, 1954), Bouyoucos and Mick (1940, 1947,
1948), Colman and Hendrix (1949), Croney et al. (1951), Cummings and Chandler
(1940), Daniel et al. (1992), Dennehy and McMahon (1989), El-Sarnie and Marsh
(1955), liaise and Kelley (1946), Hancox and Walker (1966), Kemper and Amemiya
(1958), Michelson and Lord (1962), Pereira (1951), Perrier and Marsh (1958), Rehm
et al. (1987), Richards and Weaver (1943), Salaruddin and Khasbardar (1967), Schlub
and Maine (1979), Slater (1942), Tanner and Hanks (1952), Williams (1980);
Automatic Data Acquisition; Armstong et al. (1985); Calibration: Atchison and Butler
(1951), Kelley (1944), Shaw and Baver (1939a); Moisture Measurement: Cummings
and Chandler (1940)
6-36
-------
Table 6-2 (conk)
Topic
References
So'il Water {Matricl Potential (cont.)
Electrothermal Methods
Aldous and Lawton (1952), Beck et al. (1971), Blackwell (1954,1956), Bloodworth and
Page (1957), Bloomer and Ward (1979), Cummings and Chandler (1940), Daniel et al.
(1992), DeVries (1952,1953), DeVries and Peck (1958a,b), Fritton et al. (1974), Fuchs
and Hada (1973), Fuchs and Tanner (1968), Gardner et al. (1991), Hooper (1952),
Hooper and Leeper (1950), Jaeger (1958), Kubo (1953), Momin (1945), Phene et al.
(1971a, 1971b, 1973), Philip (1961), Shaw and Baver (1939a,b), Slusarchuk and Fougler
(1973), Sophocleous (1979), Van Duin and DeVries (1954), Wechsler et al. (1965);
Calibration: Kelley (1944), Overgaard (1970), Shaw and Baver (1939a); Moisture
Measurement: Cummtags and Chandler (1940)
Soil Moisture Content
General
Gravimetric
Time Domain Refleetometry
Hendrickx et al. (1990-variability), Reinhart (1961-physical factors), Yates and Warriek
(1987-estimation with cokriging); Reviews: Bouyoucos (1952), Johnson (1962), McKim
et al. (1980a), Postlethwaite and Triekett (1956), Schmugge et al. (1980), Taylor
(1955), Wilson (1971)
Hawley et al. (1982), Hendrickx (1990), McKim et al. (1980b), Rehm et al. (1987),
Reynolds (1970a,b,c)
Ansoult et al. (1985), Baker and Allmaras (1990), Baker and Lascano (1989), Brisco et
al. (1992), Chudobiak et al. (1979), Cole (1977), Dalton (1989), Dalton and van
Genucthen (1986), Dalton et al. (1984), Dasberg and Dalton (1985), Dasberg and
Hopmans (1992-calibration), Davis and Annan (1977), Davis and Chudobiak (1975),
Hrick et al. (1992), Fellner-Feldegg (1969, 1972), Heimovaara et al. (1988), Hokett et
al. (1992), Hook et al. (1992), Kachonoski et al. (1990, 1992), Nadler (1991), Nadler et
al. (1991), Patterson and Smith (1981), Redman et al. (1991), Reeves and FJgezawi
(1992), Smith and Tice (1988), Stein and Kane (1983), Tektronix (1987), Topp and
Davis (1981, 1985a,b), Topp et al. (1980a,b, 1982a,b, 1984, 1988), Van Loon et al.
(1990-electrical conductivity), Yanuka et al. (1988), Zegelin et al. (1989); NAPL
Detection: Brewster et al. (1992); Leak Detection: Davis et al. (1984)
Bell et al. (1987), Birehak et al. (1974), Brisco et al. (1992), Dean et al. (1987),
DePlater (1955), Hancox and Walker (1966), Rural (1981), Rural and Matousek
(1977), Kura! et al. (1970), Layman (1979), Mack and Brach (1966), Matthews (1963),
Matzkanin et al. (1979), McKim et al. (1979, 1980b), Roth (1966), Selig and
Mansukhani (1975), Selig et al. (1975), Thomas (1966), Trader Electronic Laboratories
(1992), Walsh et al. (1979), Wobschall (1978); SoO Dielectric Properties: CMar and
Ulaby (1974), Hipp (1974), Hoekstra and Delaney (1974), Smith-Rose (1933), Wang
and Schmugge (1978), see also, references in Section 1.5.1
Nuclear Magnetic Resonance Soil Moisture: Andreyev and Martens (1960), Matzkanin and Gardner (1974), Prebble
and Currie (1970), Rollwitz (1965), Smith and Tice (1988), Tice et al. (1981), Wu
(1964); Borehole: See Section 3.2.4
Dielectric Sensors
6-37
-------
Table 6-3 Reference Index for Measurement and Estimation Soil Hydrologic Properties Other than Hydraulic
Conductivity
Topic
References
General Soil-Water
Relationships
Soil-Water Retention
Sorptivity
Difiusivity
Bouwer and Jackson (1974), OiHds (1969), Day et al. (1967), Gairon and Hadas
(1973), Hendrickx (1990), Holmes et al. (1967), Marehall (1960), Nielsen et al. (1972),
Reeve and Carter (1991), Richards (1965), Rode (1965), Wiebe et al. (1971)
Measurement: Madsen et al. (1986), Richards (1965), Su and Brooks (1980);
Equations: Bumb et al. (1991), Gillham et al. (1979), McKee and Bumb (1984); see
also, Section 7.2.8 and Table 7-5; Estimation from Other Soil Properties: Ahuja et al.
(1985), Alessi et el. (1992), Arya and Paris (1981), Bruce (1972), Brust et al. (1968),
Carsel and Parrish (1988), Clausnitzer et al. (1992), DeJong (1982), Gregson et al.
(1987), Gupta and Larson (1979), Haverkamp and Parlange (1986), Hendriekx (1990),
Hendrickx et al. (1991), McQueen and Miller (1974), Mishra and Parker (1990),
Mishra et al. (1989), Puckett et al. (1985), Rawls and Brakensiek (1985), Rawls et al.
(1982), Rogowski (1971,1972), Ross et al. (1991), Saxton et al. (1986), Schuh et al.
(1988), Topp and Zebchuek (1979), Tyler and Wheatcraft (1989), Vereecken et al.
(1992), Williams et al. (1992), Yoshida et al. (1985); Temperature Effects: Haridasan
and Jensen (1972), Nimmo and Miller (1986); Hysteresis: Nimmo (1992)
Bridge and Ross (1985), Brutsaert (1976), Chong (1983), Chong et al. (1982), Clothier
and White (1982), Dirksen (1975), Kutilek and Valentova (1986), Parlange (1971,
1975a,b), Philip (1955), Reichardt and Obardi (1974), Reynolds and Elrick (1990),
Smiles (1977), Smiles et al. (1981, 1982), Talsma (1969), Topp and Zebchuek (1979),
White (1979), White and Ferrous (1987, 1989), White et al. (1989)
Bruce and Mute (1956), Brutsaert (1976, 1979), Cassel et al. (1968), Dirksen (1975),
Gardner (1970), Gardner and Mayhugh (1958), Hillel and Gardner (1970), Jackson
(1963), Klute (1965,1972), Miller and Bresler (1977), Parlange (1975a,b), Perroux et
al. (1981), Philip (1955), Reichardt et al. (1972), Roberts (1984), Scotter and Clothier
(1983), Smiles (1977), Smiles and Harvey (1973), Weeks and Richards (1967)
6-38
-------
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Watson, K.K. and R.D. Jackson. 1967. Temperature Effects in a Tensiometer-Pressure Transducer System. Soil Sci. Soc. Am. Proc.
31:156-160.
Wechsler, A., P. Glaser, and R. McConnell. 1965. Methods of Laboratory and Field Measurements of Thermal Conductivity of
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6-55
-------
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6-56
-------
SECTION 7
VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION,
CONDUCTIVITY, AND FLUX
Characterization of water movement in the vadose zone is complicated by the fact that hydraulic
conductivity varies as a function of pressure potential and moisture content. The introduction to Section 6
discusses the types of energy potentials that affect flow of water in the vadose zone. Various terms are used to
describe hydraulic conductivity in the vadose zone:
1. Saturated hydraulic conductivity (K^) is the hydraulic conductivity at saturation with no entrapped air.
This state rarely is achieved in the vadose zone, except, perhaps, in the zone of seasonal fluctuation of
an unconfined water table.
2. Field-saturated hydraulic conductivity (K^), also called the satiated hydraulic conductivity, is the
hydraulic conductivity when entrapped air is present, which can be as much as 50 percent below the true
K,,, (Reynolds and Hrick, 1986). Methods for measuring saturated hydraulic conductivity above the
water table usually measure IQ,. Another term, K(Mt), has been proposed by Bouma (1982) for hydraulic
conductivity measurements of the soil matrix without macropore flow (see Column-Crust method,
Section 73.8 and Figure 7J.8b[c]). K(MQ will be less than K^, or K& because water flows more rapidly
in macropores than in the soil matrix. The term K,,, often is loosely used for reporting measurements
that should more accurately be termed K&.
3. Unsaturated hydraulic conductivity (K^,,,) is the hydraulic conductivity of soil at negative pressure
potentials. K(^) is the term usually used to describe the hydraulic conductivity-pressure potential
function, and K(0) to describe the hydraulic conductivity-moisture content function. Complete
characterization of K^^ requires measuring hydraulic conductivity at a range of moisture contents to
develop a K(0) curve or at a range of pressures to develop a K(<£) curve (see Section 6.4.1). These
functions are subject to hysteresis (i.e., K,,,,,,, might differ at the same water content or matric potential,
depending on whether the soil is wetting or drying [Section 6.4.1]).
Infiltration
The infiltration capacity of a soil is a critical element of water budget calculations because it affects how
much precipitation that reaches the ground surface enters the soil and how much moves off a site as surface
runoff. The infiltration rate generally is the same as the unsaturated and saturated hydraulic conductivity, except
that some processes, such as the initial moisture content (see Figure 7.1.4), crusting, or sediment clogging, might
cause different infiltrations at the ground surface compared to the subsurface with all other soil factors being
equal. Table 7-1 summarizes information on eight methods for measuring or estimating infiltration grouped into
four categories: (1) Impoundment methods, where infiltration is below a water surface (Section 7.1.1); (2) land
surface methods (Section 7.1.2), (3) watershed methods for estimating infiltration over larger areas (Section
7.1.3), and (4) infiltration equations (Section 7.1.4). In most situations infiltration can be estimated using
empirical relations or infiltration equations using other measured variables, which can be measured with an air-
entry permeameter (Section 73.4) and unsaturated hydraulic conductivity/pressure head relations (Section 63.1).
Measurement of Unsaturated Hydraulic Conductivity
Table 7-1 summarizes information on nine methods for measuring or estimating unsaturated hydraulic
conductivity from field measurements. Most of these methods can be used to develop K(^>) or K(0) relationships,
which once established, allow subsequent monitoring to focus on either changes in pressure potential or moisture
content The instantaneous profile method (Section 7.2.1) is the most commonly used method for accurate
measurement of unsaturated hydraulic conductivity in the field. Various draining profile methods (Section 7.2.2)
are simpler and less expensive to use if the simplifying assumptions apply to the site of interest. Another
common procedure is to collect undisturbed core samples and measure K^, in the laboratory (Klutc and
7-1
-------
Table 7-1 Snauiaiy Infomation on Vadose Hydraulic Conductivity Techniques*
Technique
"ij or Jv
K,^ Direction11
Other Parameters
Measured
Section
Table«
Infiltration (ice also, Sections 7.23, 7.2.5, 7.2.6, 7.3.1, 7.3.4)
Seepage Meters
Instantaneous Rate
Impoundment Water Budget
Sprinkler Infiltrometer
Infiltration Test Basins
Watershed Average
Watershed Empirical Relations
laTIllraUoa Equations
Unsaturated Hydraulic Conductivity
Instantaneous Profile
Draining Profile Methods
Tension IniHirDBMien
Crust-Imposed Steady Flux
Sprinkler/Dripper Methods
Entrapped Air Method
Parameter Identification
Empirical Equations
Column-Crust
Saturated Hydraulic Conductivity Above
Cylinder Inliltroneten
Constant Head Borehole
Infiltration
Gaelph Prr«i«uaeter
Air-Entry Penaeameter
Double Tube
Cylinder Permcameter
Infiltration Gradient
Cube
Column/Monoliths
Boutwell Method
Velocity Penneameter
Percolation Test
CP Porous Probe
Collection Lysimeter
Saturated Hydraulic Conductivity Above
USBR Single Well
USBR Multiple-Well
Stephens-Neuman Single Well
Air Permeability
Packer Tests
Saturated Undefined
Saturated Undefined
Saturated Undefined
Saturated Vertical
Saturated Undefined
Undefined Undefined
Undefined Undefined
Both Vertical
Unsaturated Vertical
Unsaturated Vertical
Both Vertical
Unsaturated Vertical
Unsaturated Vertical
Unsaturated Vertical
Both Undefined
Both Undefined
Both Vertical
Shallow Water Table"
Saturated Vertical
Saturated Horizontal
Both Vert/Hor,
Both Vertical
Saturated Vertical
Saturated Vertical
Saturated Vertical'1
Saturated Vert/Hor.
Saturated Vertical
Saturated VerUHor.
Saturated Vertical
«.* ~ *
Saturated Horizontal
Saturated Vertical
Deep Water Table"
Saturated Undefined
Saturated Horizontal
Saturated Undefined
Saturated Undefined
Saturated Vert/Hor.
I
I
I
I
I
I
I
I
D, F, K(tf>), R
D.F.K^R.S
I, D, F, K(«), R, S
I, F, K(£)
I, F, K(«), R, S
I»F
R
Varies
F, K(<6)
I,S
S
K*^9/* S
I, K(«), S
—
—
—
~
-
-
-
_
_
F
—
-
-
—
—
7.1.1
7.1.1
7.1.1
7.1.2
7.1.2
7.1.3
7.1.3
7.1.4
7.2.1
12.2
7.2.3
7.2.4
7.2.5
7.2.6
7.2.7
7.2.8
73.8
73.1
7.3.2
73.3
7.3.4
7.3.5
73.6
7.3.7
73.8
7.3.8
73.9
73.10
7.3.11
2.2.2
9.3.1
7.4.1
7.4.2
7.43
7.4.4
4.3.3
7-5
7-3
7-3
7-3
7-3
7-3
7-3
7-3
7-5
7-4
7-4
7-4
7-4
7-2, 7-4
7-2, 7-4
7-2, 7-4
7-4
7-2, 7-4
7-2, 7-4
7-4
D " diffusivity; F « Flux; I = Infiltration; K() = hydraulic conductivity-pressure head relationship; R = Retention (pressure-
moisture relationship); S = Sorptivity.
'Most methods for measuring or estimating Unsaturated hydraulic conductivity also can be used to measure water flux in the vadose
zone. Section 7.5 discusses the application of these and other methods for measuring soil water flux.
^Directional ratings are qualitative in nature. Different references might give different ratings depending on site conditions and
criteria used to define directionality.
"These methods measure field-saturated or satiated hydraulic conductivity (K^), which is lower than saturated hydraulic conductivity,
due to the presence of entrapped air.
'Differentiation of vertical and horizontal is possible when used with double tube method.
"The percolation test does not provide an accurate measure of saturated hydraulic conductivity. See Table 7-4 for sources on
information on the relationship between percolation test results and K^.
7-2
-------
Dirksen, 1986). ASTM (1990a) provides guidance on selecting field methods for measuring unsaturated hydraulic
conductivity in the vadose zone.
Measurement of Saturated Hydraulic Conductivity
Table 7-1 summarizes information on 10 methods for measuring K* above a shallow water table (Section
7.2), and 5 methods for measuring K* above a deep water table (Section 73). The cylinder or ring infiltrometer
(Section 13.1) is a widely used method that measures both infiltration and Kj, at the soil surface. Most other
shallow methods require a borehole and devices at the surface to control the flow of water into the hole to
achieve steady state infiltration before measurements are taken. The constant-head borehole infiltration or
shallow-well pump-in method (Section 13.2) and the Guelph permeameter (Section 7.3.3) probably are the most
commonly used methods for measuring K^. Most of these methods are restricted to depth of 2 meters or less,
but recently developed compact constant-head permeameter (Section 7.3.2) can be used to depths of 10 meters.
Most methods for measuring K^ above a deep water table require drilling or relatively large diameter boreholes
(at least 6 inches) and a large supply of water, which can be pumped into the borehole. ASTM (1990a) provides
guidance on selecting field methods, for measuring saturated hydraulic conductivity in the vadose zone, and Table
7-2 provides comparative information on nine methods for measuring saturated hydraulic conductivity above and
below a water table.
Measurement of Water Flux in the Vadose Zone
Various methods are available to measure or estimate the amount of water that passes through the
vadose zone and enters the ground-water system. A water budget (Section 7.5.1) uses a mass balance by
measuring inflows, outflows, and storage changes in the area of interest. More often, a simplified water budget
approach can be used, in which only changes in soil moisture or matric potential are measured (Section 7-5.2).
A variety of tracers, such as chloride and tritium, can be used to estimate the rate of recharge and water flux
(Section 75.3). Localized water flux can be measured using a soil-water flux meter (Section 7.5.4). A variety
of methods for measuring the velocity of water flow in the vadose zone are described in Section 7.5.5. Finally,
a variety of physical and empirical equations can be used in combination with the methods above, or using site-
specific data on hydraulic conductivity or soil physical characteristics, such as texture and bulk density. Tile
drains or collection lysimeters (Section 9.3.1) also can be used to measure water flux in the vadose zone,
provided the area of vertical infiltration is known and lateral ground-water flow can be excluded or quantified.
7-3
-------
Table 7-2 Operational Aspects of Nine Methods for Measuring Saturated Hydraulic Conductivity
X^V
^^^%^vx
Method
Direction Vr
Time
Costs
0°
Column method
Cube method
Drain-cube method
Air entry perm.
Cylinder perm.
Double-tube
Augerhole method
Piezometer method
Four-holes method
Source: Anioozegar and Warrick (1986), after Bouma (1983)
7-4
-------
Dirksen, 1986). ASTM (1990a) provides guidance on selecting field methods for measuring unsaturated hydraulic
conductivity in the vadose zone,
Measurement of Saturated Hydraulic Conductivity
Table 7-1 summarizes information on 10 methods for measuring K& above a shallow water table (Section
7.2), and 5 methods for measuring Kg above a deep water table (Section 73). The cylinder or ring infiltrometer
(Section 73.1) is a widely used method that measures both infiltration and Kg at the soil surface. Most other
shallow methods require a borehole and devices at the surface to control the flow of water into the hole to
achieve steady state infiltration before measurements are taken. The constant-head borehole infiltration or
shallow-well pump-in method (Section 13.2) and the Guelph permeameter (Section 7.3.3) probably are the most
commonly used methods for measuring K&. Most of these methods are restricted to depth of 2 meters or less,
but recently developed compact constant-head permeameter (Section 73.2) can be used to depths of 10 meters.
Most methods for measuring Kg above a deep water table require drilling or relatively large diameter boreholes
(at least 6 inches) and a large supply of water, which can be pumped into the borehole, ASTM (1990a) provides
guidance on selecting field methods, for measuring saturated hydraulic conductivity in the vadose zone, and Table
7-2 provides comparative information on nine methods for measuring saturated hydraulic conductivity above and
below a water table.
Measurement of Water Flux in the Vadose Zone
Various methods are available to measure or estimate the amount of water that passes through the
vadose zone and enters the ground-water system. A water budget (Section 75.1) uses a mass balance by
measuring inflows, outflows, and storage changes in the area of interest. More often, a simplified water budget
approach can be used, in which only changes in soil moisture or matrlc potential are measured (Section 7.5.2).
A variety of tracers, such as chloride and tritium, can be used to estimate the rate of recharge and water flux
(Section 7.S.3). Localized water flux can be measured using a soil-water flux meter (Section 75.4). A variety
of methods for measuring the velocity of water flow in the vadose zone are described in Section 7.5,5, Finally,
a variety of physical and empirical equations can be used in combination with the methods above, or using site-
specific data on hydraulic conductivity or soil physical characteristics, such as texture and bulk density. Tile
drains or collection lyaimeters (Section 93.1) also can be used to measure water flux in the vadose zone,
provided the area of vertical infiltration is known and lateral ground-water flow can be excluded or quantified.
7-5
-------
7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
7.1 INFILTRATION
7.1.1 Impoundment Methods
Other Names Used to Describe Method; Seepage meters (SCS, USER, Bouwer-Rice), instantaneous rate
method, water budget method,
Uses at Contaminated Sites: Measuring infiltration of surface water impoundments into the ground.
Method Description: Seepage meters are sealed infiltrometers placed in the bottom of a channel or pond that
is connected by a tube to a small reservoir of water in a container, which can be raised or lowered in relation
to the water surface of the impoundment (Figure 7.1.1). When the small reservoir is raised above the level of
the natural water surface, the rate of fall is measured, or relative changes in pressure head inside the seepage
meter and the water outside are measured. Infiltration rate can be calculated from these measurements. Types
include the SCS, U.S. Bureau of Reclamation, and Bouwer-Rice seepage meters. The instantaneous rate method
involves shutting down all inflows and discharges from a pond and observing the drop in water level. Assuming
evaporation is negligible and there is no ground-water recharge to the pond, the rate of decline in water level
is the infiltration (Wilson, 1982). The water budget method requires measurement of inflow to the pond from
all sources, precipitation, discharge, and evaporation, and the relationship between head vs. surface area. When
these parameters are known, infiltration can be solved from the water budget equation (Bouwer, 1978). Section
7.5.1 discusses the water budget method further, and Figure 7.5.1 illustrates an annual cumulative water balance
used to determine seepage from a wastewater lagoon. Other methods for characterizing interactions between
surface impoundments and ground-water systems include shoreline monitoring wells, mini-piezometers, well
points, and core samples (Wolf et al., 1991).
Method Selection Considerations: Table 7.1.1 provides some general guidelines for selecting techniques for
evaluating surface-ground water interactions. Seepage Meter Advantages: Relatively inexpensive and simple to
operate. Seepage Meter Disadvantages: (1) A large number of measurements are required to obtain average
infiltration rates, especially in unlined ponds with variable texture; (2) some underwater work is required to
install the unit, which might be hazardous to personnel in waste ponds with toxic chemical; (3) measurements
must be obtained on sides and bottoms of ponds and installation is difficult in ponds with steep-sided slopes; and
(4) cannot be used in frozen ponds. Instantaneous Rate Advantages: Simple and inexpensive way to measure
average infiltration rate. Instantaneous Rate Disadvantages: Results might be inaccurate if there is ground-water
recharge or rates of decline are slow enough for evaporation to become significant Water Budget Advantages:
Can be used in most hydrogeologic settings. Water Budget Disadvantages: (1) Time consuming and expensive;
(2) will not work where the water table is able to rise above the level of water in the pond; (3) requires accurate
estimation of evaporation, which is not easy, especially if impoundment contains chemicals that change
evaporation properties; (4) installing inflow and outflow measuring devices might be difficult at some sites; (5)
errors in measurements of any auxiliary parameter affect the accuracy of estimated infiltration; and (6)
calculation of changes in storage is difficult where water levels change slowly (can be overcome with special
techniques for very accurate measurement such as laser equipment).
Frequency of Use; Seepage meters are most commonly used. Water budget is rarely used due to complexity
and cost.
Standard Methods/Guidelines: Seepage meter: Bouwer and Rice (1963); Water budget: Bouwer (1978).
Sources for Additional Information: Seepage meter: Bouwer (1978,1986), Kraatz (1977), Wilson (1982); Other:
Everett et al. (1983), Wilson (1982), Wolf et al. (1991).
7-6
-------
Figure 744 Schematic of seepage meter in open channel with a falling-level reservoir and U-tube manometer
(Bouwer, 1986, by permission).
7-7
-------
Table 7.1.1 Guidelines for Selecting Techniques to Assess Ground-Surface Water Interactions
Use
Determination
of hydraulic
gradient
Determination
of hydraulic
conductivity
of sediments
Flux between
ground
water/surface
water systems
Determination
of long terra
interaction
of ground and
surface water
Collection of
flux samples
for field
screening
analysis
Collection of
flux samples
for lab
analysis
Estimation of
sediment
transport
properties
Shoreline
Honitoriag
Well
B, C
B, C
D
B
C
C
NA
seepage
Meter
NA
B, C
C
D
C
D
NA
Mini-
Piezometer
A
C
B, -C
C
A
C
C
(porosity
only)
Pell Point
A
A
B, C
B
A
A
C
(porosity
only)
Core
Sample
NA
C
NA
NA
NA
NA
A
NA - not applicable
A - good performance in most conditions
B - acceptable when used in conjunction w/ another technique
C - acceptable under certain conditions
D - poor choice
Source: Wolf et al. (1991), by permission
7-8
-------
7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INHLTRATION, CONDUCITVITY, AND FLUX
7.1 INHLTRATION
7,1,2 Land Surface Methods*
Other Names Used to Describe Method; Infiltration test basins, sprinkler infiltromcter, cylinder infiltromctcr.
Uses at Contaminated Sites: Measuring of ground-water recharge; determining soil infiltration capacity for land
treatment of wastewater; calculating sorptivity (sprinkler infiltrometer [see also, Section 6.4.2]).
Method Description: Infiltration test basins: Large cylinder infiltrometers (Figure 7.1.2a and b) or basins (20
feet by 20 feet) are constructed at several locations in a field and flooded with water. Measurements are similar
to cylinder infiltrometer for measuring infiltration rates. Sprinkler infiltrometer: Nozzles or drop-formers are
used to simulate the size and fall velocity of natural raindrops over a plot, which is set up so that surface runoff
can be accurately measured (see also, Section 7.2.5 and Figure 7.2.5). The difference between the amount of
water applied and the surface runoff is the infiltration rate.
Method Selection Considerations: Infiltration can be estimated using empirical relations or infiltration equations
(Section 7.1.4), using other measured variables that can be measured with an air-entry permeameter (Section
7.3.4), and from soil moisture content, if the K(<£) relationship is known (see Section 6.4,1), Infiltration test
basins are relatively simple and provide more representative measurements than cylinder infiltrometers, but are
relatively expensive, time consuming, and water availability can be a problem. Sprinkler infiltrometers are
relatively complex, expensive to operate, and are not well adapted to routine field applications. Relatively recent
developments of more portable equipment might make this a more attractive method (see Section 7,2,5).
Frequency of Use: Test basins are used primarily for the design of full-scale projects for the land treatment of
municipal wastewater. Sprinkler infiltrometers have been widely used in agricultural research, but have not been
commonly used for contaminated site characterization.
Standard Methods/Guidelines: Sprinkler infiltrometer: Peterson and Bubenzer (1986), Test basin: U.S. EPA
(1981).
Sources for Additional Information: Dunne and Leopold (1978), Thompson et al. (1989), Wilson (1982).
Sprinkler Infiltrometers: Bertrand (1965), Clothier et al. (1981b), Dunne and Leopold (1978), Grierson and
Oades (1977), Hamon (1979), Parr and Bertrand (1960), Peterson and Bubenzer (1986), Sidle (1979), Tovey and
Pair (1963), U.S. EPA (1981), Zegelin and White (1982). Peterson and Bubenzer (1986) summarize information
on over 30 rainfall simulator and sprinkler-infiltrometer studies and cite 66 references, which are not listed here
on this topic. See also, Section 7.2.5. Cylinder infiltrometers: Bureau of Reclamation (1978), Haise et al. (1956),
Hills (1971), Parr and Bertrand (1960); See also, Section 7.3.1 and Table 7-4. Test basins: Abele et al. (1980),
Nielsen et al. (1973), Parr and Bertrand (1960), U.S. Army Corps of Engineers (1980).
•See also, cylinder infiltrometers (Section 7.3.1).
7-9
-------
GROOVE CUTTING TOOL
CENTER ROD
HANDLE
•ETAL PIPE-
FOOT STOP
STEEL PLATE
7
15c«
(a)
3.0*
2 Oca AIOVC SU1FACE
A
t
15e« BELOW SURFACE
ALUI1NU1 FLASHING
figure 7.1 J! Infiltration test basin: (a) Groove preparation for flashing (berm); (b) Schematic of finished
installation (U.S. EPA, 1981, after VS. Army Corps of Engineers, 1980).
7-10
-------
7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
7.1 INMLTRATION
7.1.3 Watershed Methods
Other Names Used to Describe Method; Average infiltration method, point infiltration method, empirical
relations,
Uses at Contaminated Sites: Estimating infiltration over large areas for water budget studies.
Method Description; Average infiltration method: Infiltration is estimated by measuring the rainfall duration
and intensity from individual precipitation events, and subtracting the measured runoff. The difference between
the two values is assumed to be the infiltration. Figure 7.1.3 illustrates how infiltration capacity curves are
developed for a small watershed. Empirical relationships: Musgrave and Holtan (1964) have grouped soils into
four basic classes and summarized infiltration rates for a large number of different soil types within these classes.
The U.S. Soil Conservation Service has used this classification system to develop some empirical relationships
for estimating infiltration based on soil-vegetation types to approximate infiltration over large watershed areas
(SCS, 1975). Muggins and Monke (1966) developed an empirical infiltration equation in which infiltration is a
fUnction of soil moisture. Rankl (1990) has developed a point infiltration watershed model for estimating runoff
using infiltration estimates based on soil types and several empirical infiltration parameters.
Method Selection Considerations: Methods for estimating infiltration in watersheds generally do not have
enough accuracy for site specific applications. Empirical relationships might be useful when combined with
limited infiltrometer measurements to obtain a gross approximation of infiltration.
Frequency of Use: Uncommon, mainly because site investigations tend to cover areas that are smaller than
entire watersheds.
Standard Methods/Guidelines: —
Sources for Additional Information: Average infiltration method: Dunne and Leopold (1978); Empirical
relations: Bras (1990-Huggins-Monke and SO methods), Muggins and Monke (1966), Musgrave and Holtan
(1964), Rankl (1982, 1990), SCS (1975); Other: Parr and Bertrand (1960).
7-11
-------
2.3cm
5
1.1 cm
1.5cm
"
(a)
-
If
1
0 1 2
0.67 hr 0.4 hr
I
OS
1.5 -
1.0
0.5
(b)
0.74 cm
- 0.15cm
.2=5.
II
c~
C
(c)
,3
- -v;
i
0
2 cm/hr
""••v.. 0.9 cm/hr
1 1 !
I 2 3
Time (hours)
0.5 cm/hr
' i «~ i
4 5
Figure 7.13 Average infiltration method of computing an infiltration capacity curve for a small drainage basin
(Dunne and Leopold, 1978). Bursts of rainfall plotted in the upper diagram (a) cause separate
hydrograph rises (b). Each burst provides one point on the infiltration capacity curve (c). (From:
Water in Environmental Planning by Dunne and Leopold, Copyright © 1978 by W.H. Freeman and
Company, reprinted with permission).
7-12
-------
7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
7.1 INFILTRATION
7.1.4 Infiltration Equations
Other Names Used to Describe Method: Green-Ampt, Richards, Philip equations (numerous other solutions
and refinements have been derived from these equations); parametric infiltration equations; Horton equation;
Huggins-Monke equation (see Section 7.1.3).
Uses at Contaminated Sites: Obtaining indirect estimations of soil infiltration rates.
Method Description: An alternative to direct measurement of infiltration is to measure variables required for
analytical equations, such as the Richards', Green-Ampt, and Philip's equations. Variables typically required for
these equations include the hydraulic conductivity of the wetted zone, pressure head at the wetting front, and
sorptivity of the soil. Most of these variables can be measured in situ with an air entry pcrmcamcter (Section
73.4), from unsaturated hydraulic-conductivity/pressure head relations (Section 63.1), and from infiltroroeter
measurements (Section 7.3.1). When estimating infiltration, it also is important to take the initial water content
of the soil into account. Infiltration rates in a dry soil will be initially higher, and take a longer time to reach
saturated hydraulic conductivity than infiltration into a soil that already is relatively wet (Figure 7.1.4). The
Horton empirical equation for infiltration has been commonly used by hydrologists, but has a basic problem in
that it does not satisfy the theoretical requirement that the initial infiltration be of infinite value. It might be
suitable for describing infiltration when water is applied by rain or sprinkling for short time periods. Most
infiltration equations have been derived from the study of soil physics. The Green-Ampt equation is satisfactory
for describing infiltration into initially dry coarse-textured soils, and requires data on the hydraulic conductivity
of the wetted zone and an estimate of the critical pressure head of soil for wetting. The Philip's equation is a
two-parameter algebraic equation derived from the Richards' basic partial differentia] equation for unsaturated
flow, and requires measurement or estimation of sorptivity and an infiltration curve. Numerous solutions and
refinements of the basic Green-Ampt and Richards' equations have been developed in recent years, as well other
approaches, such as parametric infiltration equations. Each equation or model has its own assumptions and soil
moisture conditions that must be satisfied. For example, the Broadbridge-White model (Broadbridge and White,
1988) spans a wide range of known soil hydraulic properties. Table 7-5 identifies over 50 references dealing with
equations and models for infiltration and unsaturated flow in the vadose zone and this literature should be
reviewed to identity the most appropriate equation or model.
Method Selection Considerations: All infiltration equations require field measurement and characterization of
the spatial variability of the required parameters for accurate estimation of infiltration. Advantages: Might be
the best method for evaluating vertical infiltration rates of soils that contain restricting layers at some depth.
Disadvantages: If infiltrating water contains sediment or suspended solids, the reduction infiltration rate due
to the accumulation of solids on the soil surface must be estimated.
Frequency of Use: The Green-Ampt and Philip's equations are probably the most commonly used. As noted
above, numerous refinements and alternatives to these equations, which might merit consideration, have been
developed in recent years.
Standard Methods/Guidelines: -
Sources for Additional Information; Bouwer (1986), Green and Ampt (1911), Philip (1957a, 1969), Thompson,
et al. (1989). See also, references in Table 7-5 and Section 7.2.8 (Unsaturated Hydraulic Conductivity,
Physical/Empirical Equations and Relationships).
7-13
-------
Initial Water Content of A
-------
7. VADOSE ZONE HYDROLOGIC PROPERHES (II): DSMLTRATTON, CONDUCTIVITY, AND FLUX
7.2 UNSATURATED HYDRAULIC CONDUCTIVITY
7.2.1 Instantaneous Profile Method
Other Names Used to Describe Method: Unsteady drainage flux, plane of zero flux, instantaneous rate method,
hot-air method (Aiya et al., 1975, as cited by Bouma, 1982).
Uses at Contaminated Sites: Measuring unsaturated hydraulic conductivity and diffiasivity for vadose zone
contaminant transport evaluation. Also can be used for monitoring water flux (Section 7.S.2) and developing
moisture characteristic curves (Section 63.1) or K-matric potential relationships.
Method Description: A field plot (Figure 7.2.1a) or a double-ring infiltrometer is placed on a soil plot (Figure
7.2. Ib) and instrumented with a battery of tensiometers at different depths for measuring water pressures (see
Section 6.2.1) and an access tube for neutron moisture logging (see Section 33.3 and 6.3.2). The soil is wetted
to saturation throughout the study depth. Wetting is stopped and the surface covered to prevent evaporation.
Water pressure and water content are measured at intervals as the soil drains. Any combination of methods for
measuring soil water potential (see Section 6.2) and soil moisture content (see Section 63 and Table 6-1) can
be used for this method. Tensiometer/soil core method: A variant of the instantaneous profile method in which
only changes in soil water pressure are monitored in the field after the soil is wetted. Soil cores are collected
from the depth increments that tensiometers have been placed and moisture characteristic curves are measured
in the laboratory. Hydraulic conductivity at different matric potentials is calculated from the field-measured
tensiometer data and the moisture characteristic curve. The entrapped air method (Section 7.2.6) also can be
considered a variant of this method.
Method/Device Selection Considerations: Instantaneous Profile Advantages: (1) Simple and reasonably accurate
at each measuring site; and (2) suitable for stratified soils. Instantaneous Profile Disadvantages: (1) Provides
hydraulic conductivity values only for draining profiles and values will be different during wetting cycles; (2) time
consuming and relatively expensive, especially if site variability requires a large number of sites to obtain mean
values; (3) does not provide reliable data near saturation (0 to -15 centimeters) because of rapidly changing and
poorly defined pressure head gradients; (4) primarily measures vertical conductivity and will underestimate flux
if horizontal conductivity exceeds vertical conductivity; (5) interactions between wastewater and solids might affect
results (such as dispersion of clays or clogging); and (6) not suitable for percolating water with sufficient
concentration of chemical wastes (such as nonaqueous phase liquids) to change its physical properties that affect
infiltration rates. Tensiometer/Soil Core Advantages: Similar to instantaneous profile method except that field
data collection is less time consuming and expensive because only soil-water pressure is monitored.
Tensiometer/Soil Core Disadvantages: Similar to instantaneous profile method, except that use of laboratory
measurements on soil cores might not accurately reflect in situ conditions.
Frequency of Use: Probably the most commonly used field method for accurate measurement of unsaturated
hydraulic conductivity.
Standard Methods/Guidelines: ASTM (1990a), Bouma et al. (1974), Green et al. (1986).
Sources for Additional Information: Bouwer and Jackson (1974), Everett et al. (1982,1983), Hendrickx (1990),
Thompson et al. (1989), Wilson (1980). See also, Table 7-3.
7-15
-------
Outer area
Neutron probe
access tube
3,6m
(a)
To manometers
Multiple-depth
tensiomefers
0,3
Outer ring
(1.2 m dia.)
inner ring
(0.3-0,4 m dia.S
Porous cups
(b)
Figure 7.2.1 Instantaneous profile method: (a) Planar view of field plot; (b) Double-ring infiltrometer with multiple
depth tensiometers (Green et al., 198
-------
7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INHLTOATION, CONDUCIWITY, AND FLUX
7.2 UNSATURA1ED HYDRAULIC CONDUCTIVITY
7.2.2 Draining Profile Methods
Other Names Used to Describe Method: Simplified unsteady drainage flux method, unit gradient method, Theta
($) method, flux method, CGA-method, water content measurement method (flux), tensiometric simplified
functions method.
Uses at Contaminated Sites: Estimating unsatu rated hydraulic conductivity and flux of water in the vadose zone.
Method Description: Unsaturated hydraulic conductivity: A number of approaches have been developed to
simplify the instantaneous profile method so that only soil moisture content or soil water potential needs to be
monitored in the field. Procedures are similar to the instantaneous profile method in that the soil is wetted until
steady-state infiltration (field saturated) conditions are reached at the test plot or double-ring infiltrometer, at
which time wetting is stopped and the surface covered to prevent evaporation. Changes in the draining profile
are observed as a function of time either by monitoring soil water content at different depths, or by monitoring
soil matric potential at different depths. Different equations are used to calculate hydraulic conductivity as a
function of soil water content. In the theta (0) method, changes in soil water content with time at different
depths are used in the calculations. Figure 7.2.2a illustrates use of this method for a single soil horizon. In the
flux- and CGA-methods, different formulas involving changes in average water content over the depth of interest
are used. In the pressure profile method, tensiometric measurements taken over time at small depth increments
are used to calculate hydraulic conductivity as a function of soil-water suction (Figure 7,2.2b). Flux In the vadose
zone: Monitoring of changes in water content over time (neutron logging, tensiometers, resistance blocks, and
psychrometers) allows calculation of the water flux for a given depth (Wilson 1980,1982). See Section 7.5.2 for
further discussion of flux measurement using these methods,
Method Selection Considerations: Moisture Profile Advantages: (1) Simpler instrumentation allows
measurements to be made at more points than with more complex methods, allowing statistical analysis to
characterize soil variability; and (2) works well on coarse- and fine-textured homogenous materials. Moisture
Profile Disadvantages: (1) Point measurements are less accurate than instantaneous profile and crust methods;
(2) most methods assume a unit hydraulic gradient and will not work if the assumption does not apply; and (3)
separate measurements of matric potential-water content relationships are required. Pressure Profile
Advantages: (1) Simpler instrumentation allows measurements to be made at more points than with more
complex methods, allowing statistical analysis to characterize soil variability; (2) the assumption of unit hydraulic
gradient is not required; (3) measurement of matric potential^vater content relationships are not required; (4)
a one-tune measurement of the soil water content profile allows estimates of drainage fluxes and soil water
storage in the profile with time and as a function of average matric potential; and (5) works well in coarse- and
fine-textured soils and soil profiles with stratification. Pressure Profile Disadvantages: (1) Point measurements
are less accurate than instantaneous profile and crust methods; (2) reliable, frequent tensiometric data at small
time and depth intervals, especially at low suctions, are required; (3) accurate determination of the representative
field-saturated hydraulic conductivity is required; and (4) curves are somewhat less accurate for depths greater
than around 100 centimeters. General Disadvantages: (1) Generally requires uniform drainage over shallow
water tables (in deeper soils the upper profile can be draining while the lower profile is wetting, so flux will not
equal drainage); (2) chemical conditions affecting methods to measure water content changes might introduce
errors (i.e., chlorine in solution affecting neutron logging); (3) drainage in well-structured sois might occur more
rapidly than in soil blocks where water content changes are measured, resulting in underestimation of water flux;
and (4) a large number of measurements is required to characterize spatial variability.
Frequency of Use: Relatively new methods with good potential for more extensive field application due to their
relative simplicity.
Standard Methods/Guidelines: 9 and flux methods: Libardi et al. (1980); CGA-method: Chong et al. (1981);
Pressure profile: Ahuja et al. (1988). See also, Section 7.2.7 (Parameter Identification).
7-17
-------
0.3
I I
i r
2 4
Int (hourt)
(a)
10 100 10 IOO 10
SOIL-WATER SUCTION T . cm
(b)
Figure 7.2.2 Draining profile methods: (a) Theta method involves plotting the change in water content over time to
determine empirical constant beta—hydraulic conductivity at any water content can then be calculated if
steady state water content (
-------
Sources for Additional Information: Everett et al. (1983), Green et al. (1986), Hendrickx (1990), Wilson (1980,
1982). See also, Table 7-3.
7-19
-------
7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
7.2 UNSATURATED HYDRAULIC CONDUCTIVITY
7.2.3 Tension Infiltrometers
Other Names Used to Describe Method: Tension disc permeameter, suction permeameter, porous plate
infiltrometer, Guelph infiltrometer, sorptivity method.
Uses at Contaminated Sites: Measuring infiltration, sorptivity, hydraulic conductivity; characterizing macropore
soil water flow and mean pore size.
Method Description: The tension infiltrometer originally was developed to measure soil sorptivity and diffusrvity
(see Section 6.3.2), but relatively recent improvements in instrument design (Figures 7.2.3a and b) have made
this a versatile device for measuring and estimating a variety of soil hydrologic properties. Hie tension disc
permeameter has three main components: (1) A nylon membrane that rests on the ground surface, (2) a
calibrated reservoir, and (3) a bubble tower, which is used to control the starting tension in the calibrated
reservoir (Figure 7.2.3a). At the beginning of the test, the water reservoir is Ml of water, and the water level
in the bubble tower is set at a height to achieve the desired starting tension. The stopcock in the bubbler tower
is opened to start the test, allowing air to enter the reservoir as water moves through the membrane into the soil.
Multiple tests can be run in several ways by varying: (1) The starting tension, (2) the pore size of the nylon
membrane, and (3) the size of the disc-membrane. Sorptivity is calculated from the rate at which the water level
in the calibrated reservoir falls during the first 3 minutes, and hydraulic conductivity is determined when the
infiltration rate reaches a steady flux. Measurements of sorptivity and hydraulic conductivity at different starting
tensions allows development of a hydraulic conductivity-matric potential curve. The positive pressure
permeameter (Figure 7.2.3b) looks similar to the tension permeameter, but operates quite differently. The unit
is attached to a stainless steel cylinder, which is driven far enough into the ground to prevent water from leaking
around the side. The supply pressure is the distance between the air bubble exit point and the soil surface, and
can be adjusted by screws. The air entry side tube is filled with enough water to fill the space between the
central water reservoir and the soil. This water is rapidly deposited on the soil surface by opening the side tube
stopcock to start infiltration, and the rate of fall of water in the central calibrated water reservoir is measured.
Method Selection Considerations: Advantages: (1) Simpler than instantaneous profile, draining, and steady-flux
methods because knowledge of initial water potential or content is not required, which eliminates requirements
for installation of tensiometer or neutron access probes not required; (2) lower cost than more complex methods
allows more extensive characterization of spatial variability of soil hydraulic characteristics; (3) rings do not need
to be driven into the soil surface, avoiding possible disturbance of soil structure and allowing use of the method
on rocky soils; and (4) control of tension at the surface allows characterization of flow in different pore sizes.
Disadvantages: (1) Accurate measurements might be difficult in very wet and highly permeable soils; (2) methods
requiring solution of simultaneous equations might be susceptible to errors resulting from soil heterogeneity; (3)
measurements with instruments using different radii surface disks might be affected by spatial variability
associated with different soil surfaces; and (4) measurements sample a relatively shallow depth of the soil surface
(different depths can be tested by excavation, but the process become more cumbersome and time-consuming).
Frequency of Use: Tension infiltrometers have gained rapid acceptance in the last few years and are likely to
become a standard tool for in situ determination of saturated and near-saturated soil hydraulic properties near
the soil surface.
Standard Methods/Guidelines: Perroux and White (1988).
Sources for Additional Information: See Table 7-3.
7-20
-------
Spacer _. . .
i Stainless
/|~^\ steel mesh
^=-^^m^=^/ Porous
fc-fgjJKgjg _ support
V.3v Ny'on
\ screen
Membrane \ "O"ring
retaining \ seals
band \ . \
i Silicone \ \
\ (•»»'»»' \iil
X.---V
^ Supply memb
=11==
HHHHHJ-I-
^TLnr^r^/Jj^
ir^rlnjT^-
s-:-i-;-3r-
SiHxSQ:-
r^n — rr~. JsjLi
""^"-LH^^Si
ir^-in-rLr^ri
HHHHr^v
nj^nr^riXt.
--~z_-ir_-^:
rane
Intercf
calibrg
water
A
(i
JUS*
jangeable
ted
reservoir
ir inlet
I
. *} Bubble tower
at
i _-.
&
^i
1
9
y>_-
5
Air exit
[/-
h i
p J
r^j_i
=j^
'i
2
Height
Stainless adjusting
steel screw
cylinder
Air
hole
u:
-ZHHHHGI*
-3C-I---3X-
Interchangeable
calibrated
water reservoir
Side tube:
volume
equal to
volume
of water
above soil
IL
Soil surface
~-t-~
Fine s/s mesh
(a)
(b)
Figure 13.3 Disc penneameters: (a) For supplying water at pressures less than or equal to zero; (b) For supplying
water at positive pressures (Perroux and White, 1988, by permission).
-------
7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCIWITY, AND FLUX
73, UNSATURA-mD HYDRAUUC CONDUCnVTTY
7.2,4 Crust-Imposed Steady Flux
Other Names Used to Describe Method: Unit-hydraulic gradient method, crust test.
Uses at Contaminated Sites: Measuring vertical unsaturated hydraulic conductivity during wetting portion of
moisture characteristic curve.
Method Description: A pedestal soil about 25 cetimeters in diameter and 30 centimeters high is exposed by
excavation, the exterior of which is covered with aluminum foil, and a tensiometer is inserted into the pedestal
(Figure 7.2.4). Crusts with varying hydraulic conductivity by varying percentages of gypsum and sand or sand
and quick-setting hydraulic cement. Each test run uses a crust placed on the soil surface, which is then covered
by an infiltration ring with an air-tight cover, which fits tightly over the pedestal. A water source supplies water
to the infiltration ring assembly at a constant head, with the crust controlling the flow of water to the soil
pedestal to a rate below the maximum possible infiltration rates. Pressure head is monitored near the surface
and at depth to determine when steady-state unsaturated flow has been reached. Successive steady-state flow
systems, with increasing levels of saturation, are achieved by using crusts with increasingly higher permeabilities.
Multiple tests allow plotting of hydraulic conductivity as a function of pressure head.
Method Selection Considerations; Advantages: (1) Measurements and calculations are reasonably simple; (2)
a high degree of accuracy can be achieved if the crusts are carefully prepared; (3) can be used on sloping land
surfaces; and (4) measurements can be made on large undisturbed soil columns to include effects of soil structure
and other macroporosity, which might be missed by laboratory measurements of soil cores. Disadvantages: (1)
Measurements are time and labor intensive; (2) a unit hydraulic gradient must exist in a vertical direction for
measurements to be accurate (a reasonable assumption if steady-state flow is reached and the soil material is
homogeneous); (3) only records the wetting portion of the soil water retention curve (see Section 6.4.1), so the
effects of hysteresis are not determined; and (4) measurements apply to a relatively small area of soil.
Frequency of Use: Uncommon,
Standard Methods/Guidelines; ASTM (1990a), Green et al. (1986).
Sources for Additional Information: Bouma et al. (1974), Hendrickx (1990), Thompson et al. (1989), WBson
(1982). See also, Table 7-3.
7-22
-------
W A Sc RG
t / > 0.003m
Figure 7.2.4 Schematic diagram of field installation of the measurement apparatus for the crust-imposed steady flux
method: M = constant-head device, Sc = wing nut, PC = plastic cover, W = water inlet, A = air
outlet, RG = rubber gasket, C = gypsum-sand crust, Ca = tensiometer cap, Cy = metal cylinder with
sharpened edge, H = height of mercury column above mercury pool, and G = height of mercury pool
above tensiometer porous cup, P (Green et al., 1986, after Baker, 1977, by permission).
7-23
-------
7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
7.2 UNSATURATED HYDRAULIC CONDUCTTVITY
7.2.5 Sprinkler/Dripper Methods
Other Names Used to Describe Method: Sprinkler-imposed steady flux, dripper method.
Uses at Contaminated Sites; Sprinkler-impose steady flux: Measuring vertical uusaturated hydraulic conductivity
during wetting portion of moisture characteristic curve; Dripper method: Measuring of saturated hydraulic
conductivity and sorptivity and estimating hydraulic conductivity-matric potential function, K(), and matric-
potential (<£)-moisture (ff) function.
Method Description: The sprinkler-imposed steady flux method is similar in principle to the crust-imposed
steady flux method (Section 7.2.4). A sprinkler (Figure 7.2.5) is used to apply a steady rate of water to the soil
surface, which is below the rate sufficient to saturate the soil. Soil moisture content is monitored using a neutron
access tube, and matric potential is measured using tensiometers placed at different depths. Moisture content
and pressure head is measured when steady-state flow conditions are achieved. K is calculated by dividing flux
per unit area by the hydraulic gradient. Successively higher sprinkler flux rates are used to create the next
steady-state flow system. Typically, the vertical gradient is unity. The dripper method is a relatively new and
different method for measuring and estimating a variety of soil hydrologic properties. A water storage bottle
with Marriott type burette is connected to button drippers (used commercially for drip irrigation) in a cluster-like
arrangement, which allows different rates of constant discharge by plugging different numbers of drippers. The
drippers are located in the center of a level and relatively smooth plot (about 0.8 meters square). When water
flow begins, the diameters of the horizontal wetted and ponded zones are measured until a constant value is
reached (i.e., the water dripping onto the soil moves downward rather than outward on the soil surface). When
a steady state is reached, the rate of dripping is increased and the diameter measured until it stabilizes again.
Sorptivity is determined by measuring the horizontal wetting front advance from the ponded zone borders as a
function of time. The hydraulic eonduetivity-matrie-potential-water content functions are estimated from
measurements of the saturated area on the soil surface and the distance from the ponded radius to the wetting
front as a function of dripper discharge rate for several rates using equations such as Brooks-Corey (Section
7.2.8).
Method Selection Considerations: Sprinkler-Imposed Steady Flux Advantages: Measurements apply to a larger
sample area than the crust method. Sprinkler-Imposed Steady Flux Disadvantages: (1) As with the crust
method, K is determined only during wetting; (2) unlike the crust method, it works only at relatively high
moisture contents; and (3) sprinklers are relatively expensive and cumbersome to use. Dripper Method
Advantages: (1) Equipment is much simpler and more portable than conventional sprinkler devices; (2) rock
fragments in the soil do no pose a limitation (rock at the soil surface might create problems); and (3) several
hydrologic parameters are measured (infiltration, sorptivity, K^, K{], and -6 functions). Dripper Method
Disadvantages: Requires a flat, relatively dry soil.
Frequency of Use; Uncommon.
Standard Methods/Guidelines: Sprinkler-imposed steady flux: Green et al. (1986); Dripper method: Shani et
al. (1987).
Sources for Additional Information: Hendrickx (1990), Thompson et al. (1989). See also, Table 7-3 and
references in Section 7.1.2.
7-24
-------
AUXILIARY
lATi* SUPPLY
1,114 kl f«All.l»
lETTED III*
o o o o o o
o o o o o o o
o o o o o o o
1.199 L
MTEI IUPPLT
UMI
Figure 7.2.5 Layout of sprinkler inOItrometer (U.S. EPA, 1981, after Tovey and Pair, 1963).
7-25
-------
7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, (XJNDUCmTVY, AND FLUX
7.2 UNSATURATED HYDRAULIC CONDUCITVITY
7.2.6 Entrapped Air Method
Other Names Used to Describe Method: ~
Uses at Contaminated Sites: Measuring unsaturated hydraulic conductivity and flux in the vadose zone.
Method Description: This method is a variant of the instantaneous profile method (Section 7.2.1). An initially
saturated column of porous material, in the process of draining to a water table at its base, is rewet at its upper
surface at an appropriate time, causing an increase in the pore air pressure in the zone of entrapped air in the
profile between the wetting and draining fronts. When steady state is reached, soil-water pressure is measured
at different depth increments in the column to calculate pressure-head gradients along the bell-shaped water
content profile caused by the zone of entrapped air. The water content profile is measured directly, or inferred
from a separately measured moisture characteristic curve. Since the flow is steady and the flow rate is known,
hydraulic conductivity over a range of water contents can be readily calculated. Figure 7.2.6 illustrates the types
of data plots that are used in this method.
Method Selection Considerations; Advantages: (1) Instrumentation for the instantaneous profile method also
can be used for this method; and (2) total time for data collection might be somewhat shorter than for
instantaneous profile method. Disadvantages: (1) Generally does not work well in fine-grained soils; and (2)
requires more closely spaced instrumentation for moisture and matric potential measurement than a conventional
instantaneous profile method.
Frequency of Use; Uncommon. More widespread use in coarse-grained soils might be merited.
Standard Methods/Guidelines: Watson (1967).
Sources for Additional Information; Bouwer and Jackson (1974). See also, Table 7-3.
7-26
-------
WATER CONTENT (cm*/cm1)
.o op aao ay.
40
30
< 20
2
ui
X
10-
(a)
(b)
HYDRAULIC GRADIENT
ta
O.4O
B SATURATED CONDITION
WETTING CONDITION
o DRAIN1NS CONDITION
O.6 Q8 1O
HYDRAULIC CONDUCTIVITY (cm. min."*)
Figure 12.6 Entapped air method (Watson, 1967, by permission): Hydraulic head (a) and water content profiles (b)
are measured at the same time after draining soil has been rewetted and the entrapped air moved
downward into the soil. The hydraulic gradient (c) is determined from the hydraulic head profile and
conductivity values are determined by dividing the steady-state flux by the gradient, and these values
are plotted against the corresponding water content (c) to develop the K(0) relationship.
7-27
-------
7. VADQSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
12 UNSATURATED HYDRAULIC CONDUCTIVITY
7.2.7 Parameter Identification
Other Names Used to Describe Method; Parameter estimation/optimization.
Uses at Contaminated Sites; Estimating hydraulic conductivity at different water contents and other hydraulic
properties from limited data.
Method Description: Results of one field or laboratory test are used to estimate hydraulic conductivity.
Transient cumulative discharge of water from an initially saturated core (or in situ soil) are measured as a
function of time. Numerical models coupled to statistical optimization routines analyze the result of the test by
adjusting parameter values in the model until the measured response fits the model. Dane and Hruska (1983)
used parameter estimation methods to estimate unsaturated hydraulic conductivity with varying hydraulic head
using the draining profile method (see Section 7.2.2).
Method Selection Considerations; Advantage*: (1) Relatively fast and inexpensive; and (2) measuring moisture
content and hydraulic head as a function of time is not mandatory (but doing so will reduce the degree of
uncertainty). Disadvantages; Incorrect solutions can result if incorrect models for soil hydraulic properties are
used.
Frequency of Use: Relatively new method, which is being used with increasing frequency.
Standard Methods/Guidelines: —
Sources for Additional Information; Hendrickx (1990), Thompson et al. (1989). See also, Table 7-5.
7-28
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7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
7.2 UNSATURATED HYDRAULIC CONDUCTIVITY
7.2.8 Physical/Empirical Equations and Relationships
Other Names Used to Describe Method; -
Uses at Contaminated Sites: Estimating saturated and unsaturated hydraulic conductivity from other known or
estimated soil parameters.
Method Description: Numerous empirical equations have been developed for estimating unsaturated hydraulic
conductivity from other soil properties, such as: Pore-size distribution and moisture characteristic curves.
Mualcm (1986) classifies formulas into three major categories: (1) Empirical forms of K(£) and K(0)
relationships; (2) macroscopic models, which derive an analytical formula for the K(0) relationship; and (3)
statistical models, which primarily rely on the soil moisture retention curve (see Section 6.4.1) as an analogy to
the pore radii distribution function. The Childs-Collis George, Marshall, Millington-Quirk, Brooks-Corey,
Mualem, and van Genuchten equations are well-known equations based on statistical models. Table 7-5 identifies
over 30 references (Empirical Equations/Models), which cover theoretical aspects of these equations, and also
25 references, which focus on the estimation of soil hydraulic properties from soil physical properties.
Method Selection Considerations: Relatively fast; each empirical equation has its own application and limitations
based upon the assumptions of the equations. Mualem (1986) provides guidance on which methods to use based
on the type of soil data that are known or can be estimated.
Frequency of Use: Fairly Common. The Brooks-Corey (1964), Mualem (1976a), and Van Genuchten (1980)
are among the more commonly used formulas in current use.
Standard Methods/Guidelines: Mualem (1986).
Sources for Additional Information: Bouwer and Jackson (1974), Hendrickx (1990), Thompson et al. (1989).
See also, Table 7-5.
7-29
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7. VADOSE ZONK HYDROLOGIC PROPERTIES (II): INFILTRATION, CXJNDUCITVITY, AND FLUX
73 SATURATED HYDRAULIC CONDUCTIVITY (SHALLOW)
73.1 Cylinder Infiltrometers
Other Names Used to Describe Method: Open and sealed single-ring and double-ring infiltrometers.
Uses at Contaminated Sites: Measuring infiltration rates^jotential, saturated hydraulic conductivity, and
sorptivity; estimating ground-water recharge.
Method Description: An open ended cylinder (10 to 30 centimeters in diameter) is driven into the ground to
a depth ranging from 5 to SO centimeters. A shallow ponded depth (1 to 2 centimeters) is maintained in the
cylinder for a long enough time to allow steady-state (saturated-flow) infiltration to develop. The rate at which
water is added to maintain the ponded depth, or a constant head in the cylinder, is a direct measure of the
maximum infiltration rate for the soil. One or two rings (with water maintained in both the inner and outer
rings) can be used and the rings can be open or sealed (Figure 73.1a). Where infiltration rates are very slow,
as in clay soils or testing of clay liners, sealed double-rings (Figure 7.3. Ib) are recommended for measuring
infiltration rates (Sai and Anderson, 1991). Sorptivity can be determined from infiltrometer measurements by
plotting the rate of infiltration versus time during the first few minutes when flow is unsaturated (see Section
6.4.2).
Method Selection Considerations: Ring infiltrometers are the recommended method for testing the hydraulic
conductivity of compacted sols (Sai and Anderson, 1991). Advantages: (1) Are simple, inexpensive, and portable;
and (2) sealed ring infiltrometers can be used to evaluate macropore flow, but the process is more cumbersome
than using a tension infiltrometer (see Section 7.2.3). Disadvantages: (1) Tend to overestimate natural
infiltration due primarily to lateral divergence of flow with depth (especially single rings); (2) provide point
measurements only, so numerous tests are required to characterize spatial variability; (3) results might be
misleading if water used during the test is not similar to that which normally infiltrates (i.e., wastewater might
reduce infiltration by clogging compared to rainwater); and (4) shallow impeding layers might promote lateral
movement of water in preference to truly vertical flow, resulting in overestimation of intake rates over larger
areas.
Frequency of Use; Standard method for measuring compacted soils. Less commonly used to measure infiltration
potential of natural soils (see Section 7.1.1).
Standard Methods/Guidelines: Cylinder inCItrometer: Bouwer (1986); Double-ring: ASTM (1988, 1990s),
Johnson (1963); Sealed double-ring iiiCltrometer: ASTM (1990a,b), U.S. EPA (1989).
Sources for Additional Information; Thompson et al. (1989), Wilson (1982). See also, Table 7-4.
7-30
-------
V
\
Open, Single Ring
Open, Double Ring
Sealed, Single Ring
Sealed, Double Ring
(a)
Sealed Inner Ring.
Flexible Bag x
Tensionmeters
Outer Ring
H
1
£
1
^
f
y
S==jU
L
w
•=•
4 *
J L
)
I
g
y
^
\
i
Clay Liner Grout
(b)
Figure 73.1 Cylinder infiltrometers: (a) Open and sealed single- and double-ring infiltrorneters; (b) Details of
sealed double-ring inBItrometer (U.S. EPA, 1989).
7-31
-------
7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
73 SATURATED HYDRAULIC CONDUCTIVITY (SHALLOW)
73.2 Constant-Head Borehole Infiltration
Other Names Used to Describe Method; Shallow-well pump-in, constant-head infLItrometcr, borehole
permeameter, dry/inverted auger hole method, compact constant-head (CCH) permeameter.
Uses at Contaminated Sites: Mainly measuring the horizontal component of saturated hydraulic conductivity in
unsaturated soil,
Method Description; A hole is bored to the desired depth and a constant head of water is maintained in the
hole (Figure 73.2). The test also can be used with a screened well point. When water flow into the soil reaches
steady state conditions (i.e., water flow is constant to maintain constant head), the flow is measured. Hydraulic
conductivity is calculated from equations using the following measurements: (1) Steady-state injection rate, (2)
radius of the borehole, (3) height of water in the borehole, and (4) depth from the bottom of the borehole to
the top of the impermeable layer. The calculated rate is the average hydraulic conductivity for the portion of
the hole that was tested and, in a uniform soil, the measured rate of flow is dominated by the horizontal
conductivity.
Method Selection Considerations: Advantages: (1) Recently developed compact constant-head permeameter can
be used to depths up to 10 meters; (2) can be used in rocky or gravelly soil; and (3) tests a larger volume of soil
compared to the Guelph permeameter. Disadvantages: (1) Test requires presence of an impermeable layer
below the bottom of the borehole; (2) large quantities of water might be required; (3) a single test can take
several days to complete; (4) requires soil that can maintain an open borehole; (S) smearing of the auger hole
walls will result in underestimation of conductivity, and (6) measurements using water might not be applicable
for evaluating potential for moving sewage wastewater or chemical waste liquids through the soil (can be
overcome by using fluids in the test that are similar to the fluids of concern).
Frequency of Use; Commonly used method.
Standard Methods/Guidelines: Amoozegar and Warrick (1986, Section 29-3.2), ASTM (1990a).
Sources for Additional Information: Bureau of Reclamation (1978), Hendrickx (1990), Thompson et al. (1989).
See also, Table 7-4.
7-32
-------
Patm-hh
T
h,
I
,
p
'•
O
O
o
0
-\_
o
o
o
0
o
, .
2O Olifer
tank
A'f.h|.
_n_
-F
stand'*!? ' ^S>
4
4
I
d
i
*"
TT
* t*
h?
D i _i~
S
,
i
~f
s \
t H
L/ 1 '
water
^/ level
indicator
^^
siphon
tube
S
i2r»
"Patm
^•N.
N\ saturated
\^
S* soil volume
s
1
IMPERMEABLE LAYER
Figure 73.2 Diagram of constant head device and geometry of the shallow well pump-in set up (Ainoozegar and
Warrick, 1986, by permission).
7-33
-------
7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): DOTLTRAnON, CONDUCnVTTY, AND FLUX
73 SATURATED HYDRAULIC CONDUCTIVITY (SHALLOW)
73.3 Guelph Penneameter
Other Names Used to Describe Method; Constant head well permeameter.
Uses at Contaminated Sites: Measuring saturated and unsaturated hydraulic conductivity and sorptivity in
unsaturated soil,
Method Description; The Guelph Penneameter is a constant-head apparatus designed for small-diameter
boreholes (2 to 5 centimeters). A device, which controls hydraulic head and measures the injection rate, is
inserted into an uncased borehole. Constant bead is maintained until steady-state flow is achieved. The design
differs for models used in high conductivity and low conductivity porous media (Figure 73.3a and b), A vertical
profile of K can be developed by repeating the test at various depths. Measurements typically represent an
average of horizontal and vertical hydraulic conductivity.
Method Selection Considerations; Advantages: (1) Only requires one operator and is fast (usually ranges from
5 to 60 minutes); (2) relatively small volumes of water are required; (3) other parameters, such as unsaturated
hydraulic conductivity and sorptivity, can be estimated; and (4) is commercially available. Disadvantage: (1) A
limited volume of soil is tested, so replication and multiple tests are required to characterize spatial variability;
(2) requires materials that can maintain an open borehole; (3) smearing of clay on borehole walls will result in
measurements lower than the actual K; (4) rests on bottom of hole, which might impede vertical water flow,
especially in small diameter holes; (5) unsaturated hydraulic conductivity and sorptivity measurements are based
on assumptions that will have varying degrees of validity for different porous media; (6) depth limited to about
2 meters; and (7) measurements using water might not be applicable for evaluating potential for movement of
sewage wastewater or chemical waste liquids through the soil (can be overcome by using fluids in the test that
are similar to the fluids of concern).
Frequency of Use; This is a relatively new technique, which has gained rapid acceptance.
Standard Methods/Guidelines: ASTM (1990a), Reynolds and Hrick (1986).
Sources for Additional Information: Hendrickx (1990), Thompson et al. (1989). See also, Table 7-4.
7-34
-------
2
en
14
1. air-inlet tube (threaded at base)
2. threaded collar
3. removable cap
4. sliding air-tight seals
5. liquid surface in reservoir
6. measuring scale
7. reservoir tube
8. outlet tube
9. tripod assembly
10. well
11. steady liquid level in well
12. outlet port (threaded)
13. permeameter tip
14. rubber stopper
15. threaded coupling
18. pressure transducer (optional)
19. release valve
20. calibration lines
air-inlet lube (threaded at base)
threaded collar
removable cap
sliding air-tight seals
liquid surface in reservoir
measuring scale
combined reservoir and outlet tube
flexible side-tube
tripod assembly
well
steady liquid level in well
outlet port (threaded)
permeameter tip
rubber stopper
clamp
syringe
pressure transducer (optional)
calibration lines
-14
(a)
(b)
Figure 733 Schematic of Guelph permeameter: (a) Model 1 for high conductivity porous media; (b) Model 2 for
low conductivity porous media (Reynolds and Elriek, 1986, by permission).
-------
7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
73 SATURATED HYDRAULIC CONDUCTIVITY (SHALLOW)
73.4 Air-Entry Permeameter
Other Names Used to Describe Method; —
Uses at Contaminated Sites; Measuring saturated hydraulic conductivity in unsaturated soil; estimating of K(£)
and K(0) relationships.
Method Description; A cylinder 20 to 30 centimeters in diameter and over 10 centimeters long is driven about
10 centimeters into the soil. A layer of sand is placed inside the cylinder, and the cylinder is sealed with a top-
plate assembly and water is supplied to the cylinder from a reservoir (Figure 7.3.4). An air valve allows air to
escape from the cylinder until the cylinder is completely filled, at which time it is closed. When the wetting front
reaches the bottom of the cylinder below the soil surface, the supply of water is shut off and a valve attached
to a vacuum gage is opened. The time required for the wetting front can be estimated by a few trials before
the procedure is started, or alternatively, it can be detected using a fine tensiometer probe. The pressure inside
the cylinder decreases to a minimum (the alr-enby value), at which time air begins to bubble up through the soil.
At this point, the equipment is removed and the depth of wetting front is determined by digging. The air-entry
pressure can be calculated from pressure measurements and the depth of the wetting front, which can in turn
be used to calculate saturated hydraulic conductivity. Bresler et al. (1978) describe a method for estimating
unsaturated hydraulic conductivity as a function of water content and matric potential using the air-entry value
obtained using an air-entry perraeameter.
Method Selection Considerations: More sensitive to vertical than horizontal K. Advantages: (1) Is fast (around
1 hour), requires a small volume of water (around 10 liters), and is relatively simple to use; and (2) tests larger
volume of soil than the Guelph permeameter. Disadvantages: (1) Multiple tests are required to characterize
spatial variability; (2) the presence of macropores and cracks might cause problems; (3) measurements using
water might not be applicable for evaluating potential for movement of sewage wastewater or chemical waste
liquids through the soil (can be overcome by using fluids in the test that are similar to the fluids of concern); (4)
gravel within 10 to 20 centimeters of the ground surface can cause problems in placement of the cylinder. See
Table 7-2 for additional information.
Frequency of Use: Fairly widely used.
Standard Methods/Guidelines: ASTM (1990a), Bouwer (1966).
Sources for Additional Infonnation: Amoozegar and Warriek (1986), Bouma (1983), Hendrickx (1990),
Thompson et al. (1989). See also, Table 7-4.
7-36
-------
reservoir
Figure 73.4 Air entry permeameter (Thompson et al., 1989, after Bouwer, 1966, Copyright © 1989, Electric Power
Research Institute, EPRI EN-W37, Techniques to Develop Data for Hydrogeockemical Models, reprinted
with permission).
7-37
-------
7. VADOSE ZONE HYDROLOGIC PROPER1TES (II): INFILTRATION, CONDUCnVTTY, AND FLUX
73 SATURATED HYDRAULIC CONDUCTIVITY (SHALLOW)
7J.5 Double Tube Method
Other Names Used to Describe Method: —
Uses at Contaminated Sites: Measuring saturated hydraulic conductivity in unsaturated soil.
Method Description: An auger hole is dug to the desired depth and cleaned with special tools. An outer tube
is pushed into the bottom of the hole about 5 centimeters and an inner tube and a top-plate assembly are
installed in the outer tube, with the inner tube pushed about 2 centimeters into the bottom of the hole (Figure
73.5). Each tube has a standpipe above the tube for observing the water levels in each tube. Both the inner
and outer tubes are filled with water and equal head pressure is maintained in both by adjusting the water level
in the inner tube, if necessary. After saturation of the bottom of the hole is achieved (usually after 1 hour for
fine-textured soils), two sets of measurements are taken: (1) Water flow is shut off to the inner tube and the rate
of fall of water in the standpipe is measured while a constant head is maintained in the outer tube, and (2) the
water level in both tubes is brought back to the starting level, and the water level in the outer tube is controlled
so that it falls at the same rate as the inner tube. Saturated hydraulic conductivity is calculated using the two
head versus tune graphs plotted from the measurements.
Method Selection Considerations: Advantages: (1) Is commercially available; and (2) characterization of
anisotropic soils is possible when the method is combined with the infiltration gradient method (Section 7.3.7)
Disadvantages: (1) Is relatively complex and time-consuming (depending on the permeability of the soil the test
procedures takes from 2 to 6 hours to complete, and requites over 200 liters of water for each test); (2) is not
suitable for rocky soils; (3) multiple measurements are required to characterize spatial variability, (4) is less
accurate than other available methods (see Table 7-2); and (5) measurements using water might not be applicable
for evaluating potential for movement of sewage wastewater or chemical waste liquids through the soil (can be
overcome by using fluids in the test that are similar to the fluids of concern).
Frequency of Use: Fairly uncommon.
Standard Methods/Guidelines: ASTM (1990a), Amoozegar and Warrick (1986).
Sources for Additional Information: Bouma (1983), Hendrickx (1990). See also, Table 7-4.
7-38
-------
outer tube inner tube
stondplpe standpipe
v ,X
• zero mark
water
supply"
-
»
H
B
2R
I*
nut (similar to a sink
/ drain assembly)
9asket
TOP PLATE ASSEMBLY
IMPERMEABLE OR INFINITELY PERMEABLE LAYER
Figure 73.5 Diagram of equipment used for double-tube method (Amoozegar and Wai-rick, 1986, by permission).
7-39
-------
7. VADOSE ZONE HYDROLOGIC PROPER1TES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
13 SATURATED HYDRAULIC CONDUCirVITY (SHALLOW)
13.6 Cylinder Penneameter
Other Names Used to Describe Method: Penneameter, ring pertneameter.
Uses at Contammated Sites: Measuring saturated hydraulic conductivity in unsaturated soil.
Method Description: A cylinder 45 to 50 centimeters in diameter and greater than 35 centimeters long is placed
in a dug hole, which is wider than the cylinder. The cylinder is driven about 15 centimeters into the soil, and
four tensiometers are placed symmetrically around the cylinder 10 centimeters from its sides and about 23
centimeters below the bottom of the hole (Figure 73.6). The hole and inside of the cylinder are maintained at
a depth of about 15 centimeters The tensiometers are monitored until they read zero (saturation is achieved),
at which time the rate of flow of water into the soil from the cylinder is measured. Conductivity is measured
using Daisy's equation.
Method Selection Considerations: Advantages: (1) Is relatively simple; and (2) calculations are easy.
Disadvantages: (1) Is time-consuming and requires in excess of 100 liters of water; (2) is not suitable for rocky
soils; (3) measurements are not very accurate; and (4) measurements using water might not be applicable for
evaluating potential for movement of sewage wastewater or chemical waste liquids through the soil (can be
overcome by using fluids in the test that are similar to the fluids of concern). See Table 7-2 for additional
information.
Frequency of Use; Uncommon.
Standard Methods/Guidelines: Boersma (1965).
Sources for Additional Information; Bouma (1983), Bureau of Reclamation (1978), Hendrickx (1990), Roberts
(1984), U.S, EPA (1981), Winger (1960).
7-40
-------
3JL
FLOAT
REGULATOR
SOIL LEVEL
CAVITY FILLED
WITH SAND
Figure 7.3,6 Schematic diagram of equipment for the cylinder permeameter method (Boersma, 1965, bj permission).
7-41
-------
7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
13 SATURATED HYDRAULIC CONDUCTIVITY (SHALLOW)
73.7 Infiltration Gradient Method
Other Names Used to Describe Method: --
Uses at Contaminated Sites: Measuring saturated hydraulic conductivity in unsaturated soil,
Method Description; This method combines elements of the cylinder permeameter (Section 73.6) and the
double tube methods (Section 73.5). Two concentric cylinders are placed in an auger hole with small, fast-
reacting piezometer tubes placed at different depths inside the inner tube (Figure 73.7). Changes in vertical
hydraulic gradient are recorded as the hydraulic head in both tubes is kept equal and varied from 20 to over 200
centimeters When combined with the double tube method in the same hole, vertical and horizontal hydraulic
conductivity components can be separated out
Method Selection Considerations: Advantages: (1) Measures primarily vertical hydraulic conductivity; and (2)
when used with the double tube method, vertical and horizontal components of hydraulic conductivity can be
differentiated. Disadvantages: (1) Requires about 3 hours to complete and about 100 liters of water, (2) is not
suitable for stony soils; (3) measurements using water might not be applicable for evaluating potential for
movement of sewage wastewater or chemical waste liquids through the soil (can be overcome by using fluids in
the test that are similar to the fluids of concern).
Frequency of Use: Uncommon.
Standard Methods/Guidelines: Bouwer (1978).
Sources for Additional Information; Bouwer and Jackson (1974). See also, Table 7-4.
742
-------
OUTER
INNER
TUBE
_y v
SAND
TO MANOMETER OR
PRESSURE TRANSDUCER
SCREEN
Figure 73.7 Schematic of infiltration gradient technique (Bouwer and Jackson, 1974, by permission).
7-43
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7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
73 SATURATED HYDRAULIC CONDUCTIVITY (SHALLOW)
73.8 In Situ Monoliths
Other Names Used to Describe Method: Column method, cube method.
Uses at Contaminated Sites; Measuring vertical saturated hydraulic conductivity, measuring K,,, in soils with
continuous macropores (column-crust method).
Method Description: Column method: A soil column (30 centimeters in diameter and 30 centimeters thick) is
carved out in situ and encased in gypsum or resin. Water is applied to the top of the column until steady-state
infiltration is reached. Flow through the column is measured volumetrically, either by collecting outflow from
a column that has been detached from the soil, or by measuring the flow rate once steady-state infiltration has
been reached. Cube method: This is a variant of the column method, which allows measurement of both vertical
and horizontal saturated hydraulic conductivity. A cube of soil (30 centimeters by 30 centimeters by 30
centimeters) is excavated in situ and encased in gypsum. The cube is removed, and vertical hydraulic conductivity
is measured using procedures similar to the column method. Next, the open ends of the cube are sealed with
gypsum, the cube is turned sideways, and the gypsum removed from the top and bottom for a second
measurement of hydraulic conductivity (Figure 7,3.8a). Column-crust method: This combines elements of the
crust test (Section 7.2.4) with the column method in order to differentiate between the macropore and soil matrix
components of saturated flow. A column of soil is excavated in situ and tensiometers are placed in the column
before it is encased in gypsum. Macropore flow is measured by adding water until steady-state infiltration is
reached with the column detached (Figure 73.8b-A). A light crust then is placed on the column and water
applied until steady infiltration is reached at zero pressure bead (Figure 7.3.8b-C). The latter measurement
represents K*, without macropore flow. Macropore flow is the difference between the first and second
measurements. By using crusts of different thicknesses, unsaturated hydraulic conductivity can be measured with
this method as well.
Method Selection Considerations: Advantages: (1) Are relatively simple; (2) calculations are simple and accurate;
(3) cube method allows accurate measurement of vertical and horizontal saturated-hydraulic conductivity; and
(4) column-crust method allows differentiation of macropore and soil matrix saturated flow. Disadvantages: (1)
Preparation and execution are relatively time consuming; and (2) measurements using water might not be
applicable for evaluating potential for movement of sewage wastewater or chemical waste liquids through the soil
(can be overcome by using fluids in the test that are similar to the fluids of concern). See Table 7-2 for
additional information.
Frequency of Use: Uncommon.
StandardMethods/Guidelines: —
Sources for Additional Information: Bouma (1983). See also, Table 7-4.
7-44
-------
Soil
Gypsum
Cover
(a)
macropore
f
B
{HI water
% gypsum wall of column
light crust
T tensiometer
j saturated soil (h = o cm)
(b)
Figure 7.3.8 Monolith methods; (a) Gypsum covered cube of soil used to measure vertical and horizontal saturated-
hydraulic conductivity (Boiuna and Dekker, 1981, by permission); (b) Schematic representation of three
types of flux measurements using the column-crust method (Bouma, 1982, by permission).
7-45
-------
7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
7.3 SATURATED HYDRAUOC CONDUCTIVITY (SHALLOW)
73.9 Boutwell Method
Other Names Used to Describe Method: —
Uses at Contaminated Sites; Measuring vertical and horizontal components of saturated hydraulic conductivity
at the ground surface, especially clay liners.
Method Description: The Boutwell method is a two-stage falling-head borehole test used to calculate vertical
and horizontal hydraulic conductivity. In Stage I, a borehole is cased, grouted, and filled with water (Figure
73.9a). The casing and standpipc are filled with water and flow out of the bottom of the borehole is monitored
until steady-state conditions are reached. In Stage II, the hole is extended beyond the bottom of the borehole,
with the ratio of the length to diameter of the uncased zone between 1 and 1.5 (Figure 73.9a). The casing and
standpipc are reassembled and the rate of fall of water in the stand pipe is monitored until steady-state
conditions are reached again. Sai and Anderson (1991) provide the equations for calculating vertical and
horizontal hydraulic conductivity.
Method Selection Considerations; Advantages: (1) Is relatively fast, inexpensive, simple, and convenient to use;
(2) can measure very low hydraulic conductivities (1 x 10"' meters/second); (3) allows determination of vertical
and horizontal components of hydraulic conductivity. Disadvantages: (1) Measures small volume, so might miss
soil maeropores and other flaws in soil liner construction; (2) short test periods do not allow entrapped air to
dissolve; (3) method does not account for the effects of soil suction; and (4) effects of incomplete and variable
suction are not known.
Frequency of Use: Relatively new method, which has not been widely tested.
Standard Methods/Guidelines; Sai and Anderson (1991).
Sources for Additional Information; Boutwell and Derrie (1986).
7-46
-------
Stage I
Stage II
Casing
(a)
(b)
Figure 73,9 Schmatic diagram of Boiitwdl borehole permeameter: (a) Stage I; (b) Stage II (Sai and Anderson,
1991).
747
-------
7. VADOSEZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
13 SATURATED HYDRAULIC CONDUCTIVITY (SHALLOW)
73.10 Velocity Permeameter
Other Names Used to Describe Method; Velocity head permeameter, falling head perroeameter.
Uses at Contaminated Sites; Measuring vertical saturated hydraulic conductivity.
Method Description: The velocity permeameter estimates hydraulic conductivity based on the rate of fall of
water in a head tube above a soil core enclosed within a coring tube (Figure 7.3. IQa). This is a falling-head test
in which data on change of water level in the head tube is entered into small programmable calculator equipped
with a timing module. The data on varying rates of fall are used to calculate a series of hydraulic conductivity
values, which are plotted against time since the test began (Figure 7.3. lOb). The field saturated hydraulic
conductivity is the lowest value on the graph.
Method Selection Considerations; Advantages: Is a relatively simple and rapid method (about an hour),
provided the velocity of the fall of water in the head tube can be measured accurately (accuracy increases as the
ratio of the soil-core diameter to the head-tube diameter increases). Disadvantages; (1) Maintaining a seal
around the edges of the coring device might be difficult under high liquid heads; and (2) field measurements and
data reduction require a skilled operator.
Frequency of Use; Relatively new method, which has not been widely tested.
Standard Methods/Guidelines: —
Sources for Additional Information: Kanwar et a). (1987), Sai and Anderson (1991).
7-48
-------
Head Tube Scale
1.5x10"* -r-
4.2X10"6
Hole for Filling Water
- Outer Tube
Driver
Coupler
SoilCorer
Soil
(a)
Head Tube
End of Head
Tube Scale
Soil Coring Tube
Soil
Wetting Front
Time During Single Field Test
Time, mln.
Figure 73,10 Velocity permeameter. (a) Front view and operational schematic; (b) Measured hydraulic conductivity
versus time (Sai and Anderson, 1991).
7-49
-------
7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
73 SATURATED HYDRAULIC CONDUCTrVITY (SHALLOW)
73.11 Percolation Test
Other Names Used to Describe Method: Perc test, falling head test.
Hges.._aj:jCbn.tan»inated Sites: —
Method Description: This test is similar to the constant head shallow-well pump-in method, except that a
constant head is not maintained for the test. A 6-inch diameter hole is augered or dug to the depth of interest
and 2 inches of gravel are placed in the bottom to prevent scouring by water poured into the hole (Figure 7.3,11).
Water is maintained at a depth of 12 inches in the hole until the soil around the hole is saturated (generally 4
to 12 hours). The water level is adjusted to 6 inches above the gravel and the amount of fall over a 30 minute
period is measured. The water level is adjusted to 6 inches above the gravel after each measurement, and
measurements are repeated until two successive water drops do not vary by more than 1/16 inches. Results are
reported in minutes/inch or inches/hour.
Method Selection Considerations; Advantages: Is simple and easy to calculate. Disadvantages: (1) Results can
be highly variable due to soil moisture conditions at the time of the test and the individual performing the test;
and (2) when properly done, still only provides an approximate measure of saturated hydraulic conductivity.
Frequency of Use; Widely used for assessing soil suitability and design of septic tank soil absorption systems for
sewage treatment Not recommended for measuring saturated hydraulic conductivity.
Standard Methods/Guidelines: U.S. EPA (1980).
Sources for Additional Information: See Table 7-4.
7-50
-------
Thin Steel
Rod >•
Cork
Float
Yard Stick
Eyelets
Cross Arm
Support
6"-9"
Diameter
2" Layer
of Gravel
Figure 73.11 Floating indicator for percolation test (U.S. EPA, 1980).
7-51
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7, VADOSE ZONE HYDROLOOIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
7.4 SATURATED HYDRAU1JC CONDUCTIVITY (DEEP)
7,4.1 USER Single-Well Methods
Other Names Used to Describe Method; Gravity permeability tests.
Uses at Contaminated Sites: Estimating saturated hydraulic conductivity in deep boreholes in the vadose zone.
Method Description; Water is pumped into a borehole at a rate that maintains a uniform water level in a basal
test section. Saturated hydraulic conductivity is estimated from appropriate curves and equations based on: (1)
Dimensions of the hole and inlet pipes, (2) length in contact with formation, (3) height of water above the base
of the borehole, (4) depth to water table, and (5) intake rate at steady state. Method 1 (Figure 7.4.la) uses an
open borehole of 6 inches or more in diameter. The bottom of a feed pipe and observation pipe are set near
the bottom of the borehole, and the open portion of the borehole is filled with gravel pack if required to
maintain stability. Where gravel pack is required for stability, 40 feet is about the maximum depth that this test
can be economically carried out. Method 2 (Figure 7.4.Ib) uses a perforated casing for the depth of interest into
which water is pumped and an observation pipe set near the top of the perforations. The casing is sunk by
drilling, jetting or driving, whichever give the tightest fit. This method generally is less accurate than Method
1 for unconsolidated materials, but might be the only practical method for determining permeabilities in
streambeds or lakebcds below water. Method 3 uses a hardened drive shoe to drive the casing where Method
2 will not work, and is used only where Method 2 will not work because it is the least accurate of the three
methods.
Method Selection Considerations: All methods require some form of a casing advancement drilling method.
Advantages: (1) Allows estimating saturated hydraulic conductivity at great depths in the vadose zone; (2) a series
of tests as the borehole is deepened allows developing of profile of K values; and (3) can be conducted in
unconsolidated formations where packer testing (Section 4.2.3) might not be feasible. Disadvantages: (1) K^,,
tends to be underestimated because solution method assumes the flow region is entirely saturated, which is not
true; (2) expensive and time-consuming (especially in dry, coarse-grained material), so multiple tests to
adequately characterize spatial variability might be prohibitive; and (3) requires skilled personnel to conduct tests.
Method descriptions above indicate specific conditions under which the different methods are used. Packer
testing (Section 4.2.3) is probably the preferred method where boreholes are in consolidated rock.
Frequency of Use: Most likely to be used in the western United States where the saturated zone is far below
the ground surface.
Standard Methods/Guidelines: Bureau of Reclamation (1981).
Sources for Additional Information: Everett et al. (1982), Schmid (1967), Stephens and Neuman (1982a,b),
Wilson (1982), Zanger (1953).
7-52
-------
Ground I 0
surface-^
=>
o
_=•
n
4°J
0°°
1
°J>S
1?
jfOoC
1 °«
J #
i S
j ^
H
'J *
1
0°(
Iri
ZONE 1
K~ CurH
ZONE 2
20
•= K (C.+4)rTu
«x
Water
table -,
K = coefficient of permeability, feet per second under a unit gradient
Q=uniform flow into well, ftVs
r = radius of test section, ft
H = height of column of water in well, ft
A = length of test section, ft (for this method, A=H)
Cu and C, = conductivity coefficients
X = ^L{|QO) = percent of unsaturoted stratum
TU = UM-D + H = distance from water surface in well to water table, ft
U =thickness of unsaturated permeable bed, ft
D = distance from ground surface to bottom of test section, ft
1= feed pipe for pouring water into well (a 2-inch standard pipe is usually
satisfactory)
0 = observation pipe (15-inch o,d. pipe is satisfactory)
a"= surface area of test section (area of wall plus area of bottom), ft*
Limitations:
AS.IOr and
Q
:0.\Q
(a)
Ground surface
ZONE I
,_Q_
C0r«H
Base of zone I
K=?
ZONE 2
20
Water table -^
2r
K - •
ZONE 3
0
K = coefficient of permeability, feet per second under a unit gradient
Q = steady flow into well, ft'/s
H'height of water in well, ft
A = length of perforated section, ft
r, =outside radius of casing (radius of hole in consolidated material), ft
r. =effective radius of well =r,(area of perforations)/(outside area of perforated
section of cosing) ; r, * r, in consolidated material that will stand open and
is not cased
Cu and C,= conductivity coefficients
Tg'distance from water le»el in casing to water table, ft
o = surface area of test section (area of perforations plus area of bottom), ftz:
where clay seal is used at bottom, o=orea of perforations
S = thickness of saturated permeable material above on underlying relatively
impermeable stratum, ft
X = •'^•(100)= percent of unsoturated stratum
U = thickness of unsoturoted material above water table, ft
0 = distance from ground surface to hot torn of test section, ft
0 = observation pipe (I to 17-inch pipe)
Limitations: n
S>5A, AiiOr, and ^-^0.10
Notes:
In zone 3, H is the difference in elevation between the normal water table
and the water level in the well. In zones 2 and 3, if o cloy seal is placed
at the bottom of the casing, the factor 4-p is omitted from the
equations. Where the test is run with "A" as an open hole, -f- - I and
-=
Impermeable bed
(b)
Figure 7.4.1 USSR single-well hydraulic conductivity tests: (a) Method 1; (b) Method 2 (Bureau of Reclamation,
1981).
7-53
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7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
7.4 SATURATED HYDRAULIC CONDUCTIVITY (DEEP)
7.4.2 USER Multiple-Well Method
Other Names Used to Describe Method: Gravity permeability test.
Uses at Contaminated Sites: Estimating saturated hydraulic conductivity where lenses of slowly permeable
material are widespread.
Method Description: A 6-inch intake well and at least three observation wells are installed to the top of an
impermeable layer (Figure 7.4.2). Water is pumped into the central well at a steady rate and changes in water
levels in the piezometers are measured. K,,, is calculated using the appropriate curves and equations.
Method Selection Considerations: Advantages: Results can be used to estimate lateral flow rates in perched
ground-water regions. Disadvantages: (1) Is expensive and time-consuming; and (2) requires trained personnel.
Frequency of Use: Relatively uncommon.
Standard Methods/Guidelines: Bureau of Reclamation (1981-Method 4).
Sources for Additional Information; Wilson (1982).
7-54
-------
Intake well
/•Observation wells
/Observation pipe / , Ground surf ace
1 ^
VKSff
/
slyj
i
^
x
x.
JC
rl
* r*
^ '
-- yf*!
*"*- "—. _i
-»-~- :
•t
i__^y\3
— £L
f
_ 2.3Q log ?f
Top of relatively
impermeable
bed
K= coefficient of permeobility, feet per second under o unit
gradient
Q= uniform flow into intake well, ft3/s
r,,r2,andr3= distance from intake well to observation
holes, ft
h, ,h2, and h3= height of water in observation holes r, ,r2,and
r, respectively, above elevation of top of impermeable
layer , ft
H= height of column of water in intake pipe above top of
impermeable stratum, ft
U= distance from ground surface to impermeable bed, ft
Figure 7.4.2 USBR multiple-well method (Bureau of Reclamation, 1981).
7-55
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7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
7.4 SATURATED HYDRAULIC CONDUCTIVITY (DEEP)
7.4.3 Stephens-Neuman Single-Well Method
Other Names Used to Describe Method: Unsteady flow permeability test
Uses at Contaminated Sites: Estimating saturated hydraulic conductivity in the deep vadose zone.
Method Description: Water is pumped into a well drilled to the depth of interest, and changes in water level
with time ate measured and used to estimate steady-state infiltration, rather than pumping until steady-state
infiltration is achieved, as in the USBR single-well tests (Section 7,4.1). Empirical formulas based on numerical
simulations using the unsaturated characteristics of four soils allows correction for unsaturated flow conditions
during the test
Method Selection Considerations; Advantages: (1) Provides more accurate estimation of the saturated hydraulic
conductivity of unsaturated soil than the USBR single-well methods; (2) less time is required for the test because
steady-state flow conditions are not required; (3) allows estimating saturated hydraulic conductivity at great
depths in the vadose zone; (4) a series of tests as the borehole is deepened allows developing of a profile of K
values; and (5) can be conducted in unconsolidated formations where packer testing (Section 4.2.3) might not
be feasible. Disadvantages: The cost of drilling deep boreholes makes it difficult to characterize spatial variability
of hydraulic conductivity with this method. Packer testing (Section 4.2,3) probably is the preferred method where
boreholes are in consolidated rock.
Frequency of Use; Uncommon.
Standard Methods/Guidelines! Stephens and Neuman (198ft 1982c).
Sources for Additional Information: Everett et al. (1982), Wilson (1982).
7-56
-------
7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
7.4 SATURATED HYDRAULIC CONDUCTIVITY (DEEP)
7.4.4 Air Permeability Method
Other Names Used to Describe Method: --
Uses at Contaminated Sites: Estimating saturated hydraulic conductivity in the deep vadose zone.
Method Description! Air pressure changes in the subsurface in response to change in the barometric pressure
at the land surface are measured in specially constructed piezometers (Figure 7.4.4). Pressure response data
combined with information on the air-filled porosity allow calculation of air permeability. If the Klinkenberg
effect is small, hydraulic conductivity can be calculated from air permeability. Section 9.4.4 provides further
information of methods for measuring air permeability in shallow zones.
Method Selection Considerations: Advantages: Can be used to estimate hydraulic conductivity in layered
materials in the vadose zone. Disadvantages: (1) Is indirect; (2) soils must be dry, since too much soil water
inhibits air flow; (3) is expensive and time consuming; (4) is complex, requiring trained personnel; (5) in fine-
grained materials, the permeability to air is greater than the hydraulic permeability because of the Klinkenberg
effect; and (6) presence of clays with high shrink-swell make it difficult to accurately calculate hydraulic
conductivity from air permeability.
Frequency of Use: Uncommon.
Standard Methods/Guidelines; Weeks (1978).
Sources for Additional Information: Everett et al. (1982), Wilson (1982).
7-57
-------
Vented plug
(Atmospheric
pressure)
eniscus
Hose connecting manometer reservoir and tube
NOTE: All pipe fittings, valves,
and hoses are standard
1/4-inch item*
Land surface
Cement grout
1 2345 Piezometer
number (pipe)
Piezometer
Land surface
Layer
Layer
Layer
4
3
2
Layer 1
Capillary fringe
2
>
*
5
rftW
BBB
Figure 7.4.4 Schematic diagram of manifold and connections to a piezometer nest to determine air pressure at
selected depths Sn the vadose zone (adapted from Weeks, 1978).
7-58
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7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
7.5 WATER FLUX (UNSATURATED ZONE)
7.5,1 Water Budget Methods
Other Names Used to Describe Method: Water balance method, water content method.
Uses at Contaminated Sites: Estimating leachate generation by percolating water in the subsurface; estimating
solute velocity.
Method Description: Water flux: The method itself involves calculations of water flux in the subsurface based
on inflow (precipitation), outflow (runoff, evapotranspiration), and changes in storage (water content).
Parameters, which must be estimated or measured in the field, include: (1) Precipitation (Sections 8.1.1 and
8.1.2), (2) evapotranspiration (Sections 8.3 and 8.4), and (3) available water capacity (Section 63.3) or changes
in water content or soil matric potential with time (using methods described in Sections 6.2 and 6.3). Figure 7.5.1
shows a cumulative water balance used to determine seepage from a wastewater lagoon to ground water.
Simplified versions of this approach include: (1) The instantaneous profile method (Section 7.2.1); (2) Wilson
(1980) describes a variant of this method, which provides a profile-specific water budget by measuring changes
in water content at different depths by assuming all terms of the water budget calculation are zero except for flux
and soil-water storage changes (similar to draining profile method, Section 7.2.2); and (3) the Thornthwaite
method, which can be used with climatic data (monthly precipitation and temperature) and soil water holding
characteristics. Vadose-zone solute-transport models involving the soil rooting zone are based primarily on water
budget principles and allow estimation of water and contaminant flux. Velocity: Everett et al, (1983) describe
a simplified method for estimating vertical travel tune to a water table where the vadose zone is very thick.
Depth of penetration (dv2) equals depth of percolating water during a specified time period (dw), divided by the
volumetric water content at field capacity (0): dv2 = dw/5. Dividing this value into the thickness of the vadose
zone provides an estimate of how long it will take water to percolate below the rooting zone to reach the water
table if no preferential flow paths occur.
Method Selection Considerations: Advantages: (1) Provides estimates of flux for an enti re area, rather than point
estimates; and (2) relatively simple if most parameters in the water budget equation can be estimated with
acceptable accuracy or set equal to zero. Disadvantages: (1) Accurate field measurement of some parameters,
such as evapotranspiration, is difficult and field measurement of all required parameters is expensive and time
consuming; (2) errors in measurement or estimation of components (inflow and outflow, evapotranspiration,
rainfall, and ambient temperature) might accumulate in flux estimates; (3) difficult to use where water table is
high and changes in water storage are minimal; (4) contaminant chemical reactions in soil solution, which change
water transmission and water holding properties, reduce accuracy of estimates; (5) flux calculations based on soil-
water storage changes will be underestimated in highly structure soils where water flow occurs primarily in cracks
and macropores; and (6) in poorly leveled fields, water might pond in low spots, and run off rapidly in other
areas, resulting in actual local fluxes, which can vary considerably from average fluxes calculated assuming
uniform water application.
Frequency of Use: Relatively common (most vadose zone computer models use some form of water budget)
Standard Methods/Guidelines: Wagenet (1986).
Sources for Additional Information: Everett et al. (1983), Wilson (1980, 1982). See also, Table 7-6.
7-59
-------
40-
OCEAN DISCHARGE -
,' EFFLUENT
/ TO LAGOON
L SEEPAGE
FROM
LAGOON
-900
-800
700
-600
-500
400
-300
-ZOO
-100
Jan Fab Mar Apr May Jun Jul Aug Sap Oct Nov Dae
.Figure 2A - Cummulative Water Balance Plot.
OCEAN
DISCHARGE
8.67x108 gal.
61%
EVAPORATION
1.65X108 gal.
12%
u.
o
0)
z
o
PRECIPITATION
5.67X108 gal.
48%
EFFLUENT
5.94X108 gal.
52%
PACIFIC
OCEAN
WASTEWATER LAGOON
COOS
BAY
TO GROUND WATER
3.81X108 gal.
27%
Figure 7^.1 Schematic annual cumulative water balance to determine seepage from a wastewater lagoon to ground
water (Wells, 1988, by permission).
7-60
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7. VADOSE ZONE HYDROLOGIC PROPERHES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
7.5 WATER FLUX (UNSATURATED ZONE)
7.5.2 Soil Moisture/Matric Potential Methods
Other Names Used to Describe Method: Hydraulic gradient/unit hydraulic gradient methods, instantaneous
profile method (Section 7.2,1), draining profile methods (7.2.2).
Uses at Contaminated Sites; Estimating water flux in the vadose zone.
Method Description: A variety of methods are available to estimate flux in the vadose, based on measurements
of changes in soil moisture and/or matric potential with depth and over time. Depending on the specific method,
various types of calibration curves, such as matric potential versus water content and hydraulic conductivity as
a function of matric potential and/or water content, can be used. The instantaneous profile method (Section
7.2.1) and various draining profile methods (Section 7.2.2) can be used to calculate water flux. The hydraulic
gradient method uses the basic approach of the instantaneous profile method (Section 7.2.1), except that
evapotranspiration and infiltration of natural precipitation can be allowed. Hydraulic gradients in the unsaturated
zone are measured in the subsurface by installing tensiometers or psychrometers (Sections 6.2.1 and 6.2.2). For
each textural change, calibration curves are required to relate negative pressure measurement to water content
(moisture retention curves, see Section 6.4.1) and water content to unsaturated hydraulic conductivity (see
methods allowing measurement of the K(0) function in Table 7-1). The unit hydraulic gradient method is similar
to the hydraulic gradient method, except that a hydraulic gradient of 1 is assumed, requiring only one pressure
measuring unit at each depth of interest. Curves relating water content to matric potential (Section 63.1), and
water content to hydraulic conductivity, allow calculation of the amount of water flowing at the time of each
measurement, and measurements taken over time allow calculation of water flux. Alternatively, curves directly
relating hydraulic conductivity to matric potential can be used (see Table 7-1).
Method Selection Considerations: Instantaneous Profile: See Section 7.2.1. Draining Profile: See Section 7.2.2.
Hydraulic Gradient Advantages: Allows accurate measurement over a relatively large area. Hydraulic Gradient
Disadvantages: (1) Is relatively expensive to install enough units to characterize spatial variability for statistical
analysis; (2) generally is restricted to shallow depths in the vadose zone and might not be suitable for ponds or
landfills; (3) results are subject to hysteresis in the calibration curves (i.e., water content-pressure relations differ
depending on whether the soil is wetting or drying.); (4) requires obtaining calibration curves (water content
versus matric potential and hydraulic conductivity as a function of water con tent/m atric potential) for each change
in texture; (5) requires measurement units in depthwi.se increments throughout the vadose zone, and gradients
across layers might suggest vertical flow when horizontal flow is actually predominant; and (6) might not be
suitable at sites underlain by fractured media. Unit Hydraulic Gradient Advantages: Simpler and less expensive
than the unit hydraulic gradient method because fewer calibration relationships are required. Unit Hydraulic
Gradient Disadvantages: (1) A large number of units are still required to characterize spatial variability; (2) the
assumption of unit hydraulic gradients might not apply, particularly in layered media; (3) might not be suitable
for ponds or landfills; and (4) as with the hydraulic gradient method, calibration measurements are required for
each change in texture and results are subject to hysteresis in calibration curves.
Frequency of Use: Commonly used in research applications, less commonly used for monitoring flux at
contaminated sites.
Standard Methods/Guidelines: Everett et al. (1983) describe steps, equations, and sample calculations for several
draining profile and hydraulic gradient methods.
Sources for Additional Information: Bouwer and Jackson (1974), Everett et al. (1983), Wilson (1980,1982). See
also, Table 7-6.
7-61
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7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
73 WATER FLUX (UNSATURATED ZONE)
73.3 Tracers
Other Names Used to Describe Method: Chloride mass balance, bomb-pulse radionuclides (tritium, chlorine-36),
stable isotopes (deuterium and oxygen-IB), other tracers.
Uses at Contaminated Sites; Estimating flux and velocity.
Method Description: A wide variety of tracers can be used to estimate flux and velocity in the vadose zone. The
chloride mass-balance flux method is a geochemical technique in which vertical profiles of chloride concentration
are developed by analysis of soil samples. Flux is calculated based on assumed flux contributed to the soil from
precipitation. The tritium and chIoride-36 flux methods are used to identify water that has infiltrated in the last
30 to 40 years (see Section 43.5). The technique involves extracting soil water from core samples and analyzing
for tritium concentration (liquid scintillation counting technique) or extracting chloride as AgQ for analysis of
chloride-36 on using a tandem accelerator mass spectrometer. The stable Isotope flux method is a relatively new
method based on the movement of deuterium and oxygen-18 in water molecules through the vadose zone (the
same Isotopes have long been used to date ground water [see Section 43.4]). Water from soil cores is extracted
using a vacuum distillation procedure and the soil water is processed using CO2/H2O equilibration or hydrogen
reduction for analysis of stable isotope ratios on a ratio mass spectrometer. Velocity methods: A conservative
tracer (iodide, bromide) is introduced into the liquid source. Samples obtained from suction samplers and/or
free drainage samplers at successive depths are used to plot tracer breakthrough. Artificial tracers are used by
applying a known amount of a conservative tracer, such as chloride or bromide, to the ground surface and
collecting samples (from vertically spaced suction and/or free drainage samplers) at intervals to trace the speed
of flow. Analysis of changes in concentration with time also allows estimation of flux by mass balance analysis.
Method Selection Considerations: Chloride Mass-Balance Advantages: Is relatively inexpensive and easy to use.
Chloride Mass Balance Disadvantages: Is inaccurate if the following key assumptions do not apply: (1) Average
rate of chloride deposition from precipitation to the soil is constant; and (2) chloride does not move below the
root zone by preferential flow paths. Bomb-Pulse Advantages: Good method for determining whether water has
infiltrated in the last 30 to 40 years. Bomb-Pulse Disadvantages: Extraction and analytical techniques are
relatively complex and expensive and required equipment might not be readily available. Stable Isotope
Advantages: In addition to estimating recharge rate, other soil-water movement processes, such as evaporation
and liquid/vapor flux, can be estimated. Stable Isotope Disadvantages: (1) Extraction and analytical techniques
an relatively complex and expensive and required equipment might not be readily available; (2) requires
sampling to be done during a lengthy period of little or no precipitation, or infiltration into the soil from other
sources will occur (i.e., the method is restricted to arid and semi-arid areas); and (3) requires vertical movement
of soil water because significant lateral soil-water movement would invalidate assumptions used to calculate flux.
Artificial Tracer Velocity Advantages: (1) Direct and simple method; (2) reflect flow in actual pores if free-
drainage samplers are used; and (3) more accurate than methods requiring measurements of parameters in
Darcy*s equation. Artificial Tracer Velocity Disadvantages: (1) Use of nonconservative tracers (i.e., tracers that
move slower than the velocity of water) will underestimate flux/velocity; (2) use of suction samplers might alter
flow field and suction samplers cannot be used to sample soil water in very dry soil; (3) in structured media,
actual velocity might be higher than measured because of flow in cracks (can be dealt with by also using zero-
tension samplers [Section 93.1]); (4) if velocities are slow, long time periods might be required for tests; and (5)
average velocity of water-borne tracers might not be the same as average velocity of chemical liquids.
Frequency of Use: Tracer velocity: Relatively common.
Standard Methods/Guidelines; ASTM Draft Guide for Comparison of Techniques to Quantity the Soil-Moisture
Flux (in preparation).
Sources for Additional Information: Everett et al. (1983). See also, Table 7-6 and Sections 43.6 and 43.7.
7-62
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7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
7J WATER FLUX (UNSATURATED ZONE)
7.5.4 Soil-Water Flux Meters
Other Names Used to Describe Method: Soil water flowmeter, direct flow/intercepting/hydraulic-resistance type,
thermal/heat probe type.
Uses at Contaminated Sites: Measuring soil-water flux (amount of water moving through a unit cross-sectional
area of soil in a unit time period).
Method Description: Two major types of instruments have been developed for direct measurement of in situ
unsaturated soil-water flux: (1) Units that measure flow directly (intercepting meters), and (2) thermal meters,
which measure the movement of a thermal pulse in a porous cup. The intercepting-type hydraulic-resistance
meter, first developed by Gary (1968,1970) and refined by Dirksen (1972, 1974), involves intercepting part or
all of the soil-water flux and determining its magnitude by measuring the hydraulic-head loss across the inflow
and outflow portions of the meter. Tensiometers are installed nearby to monitor head loss in the undisturbed
soil and hydraulic resistance of the valve in the meter adjusted to match conditions in the soil. A recent
refinement combines features of the methods by Dirksen (1974) and by Duke and liaise (1973~see Section 9,2.6),
In this instrument, soil-water flow is intercepted by a porous plate in which the suction is automatically adjusted
to maintain the same matric potentials above the plate and in the surrounding undisturbed soil (Figure 7.5.4).
Both the hydraulic-resistance type and suction type meters require excavation of a pit and installation of the
meter in the side of the pit at the desired depth.
Method Selection Considerations: Advantages: (1) Information on hydraulic conductivity or hydraulic gradient
is not required; (2) can provide reasonable direct water flux measurements if properly used; (3) most useful for
localized and specialized studies; (4) suction-type meter overcomes most of the major disadvantages of other
types by eliminating the need for extensive laboratory or in situ calibrations, is not adversely affected by air
bubbles, and can sample flux over a larger area. Disadvantages: (1) Is relatively expensive and complex method;
(2) localized nature of measurement does not allow estimating flux over large areas unless many flux meters are
installed; (3) soil is disturbed during installation of most types and might interrupt normal soil-water flow
patterns; (4) calibration procedures are tedious, especially for multilayered media (Dirksen hydraulic-resistance
type and suction type do not require much calibration); (5) requirement for trench installation limits use to
relatively shallow depths; (6) hydraulic-resistance type meters require fairly wet soils to perform effectively and
the presence of air bubbles in soil water or in filter cloth and tubing will reduce flow into the meter; (7) most
types involve the measurement of flow in disturbed soil, and meters are especially difficult to install in layered
media without affecting flow lines; (8) most units require contact with relatively fine-grained porous media and
will not work well in coarse-grained or fractured media (not a problem with suction type); and (9) thermal meter
will give erroneous readings if chemical waste fluids have different heat conducting properties than water and
have not been thoroughly tested in the field.
Frequency of Use: Uncommon.
Standard Methods/Guidelines: Hydraulic-resistance type: Wagenet (1986); Suction type: van Grinsven et al.
(1988).
Sources for Additional Information: Bouwer and Jackson (1974), Everett et al. (1983), Wilson (1980). See also,
Table 7-6.
7-63
-------
Soil Pit
DIFFERENTIAL
PRESSURE
TRANSDUCER
FLUX
PLATE
BUFFER
CONTAINER
COLLECTING
BOTTLE
Undisturbed Soil
•Pi in disturbed soil
P1&P2at same depth
— Fluid Lines
— Power Lines
Figure 7.5.4 Schematic diagram of suction soil-water flux meter components as used in field; P,, P2, and P, are
tensiometers (van Grinsven el al., 1988, by permission).
7-64
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7, VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
7.5 WATER FLUX (UNSATLFRATED ZONE)
75.5 Velocity Estimation
Other Names Used to Describe Method; Velocity-flux/velocity-long-term infiltration calculation, velocity from
suction cups.
Uses at Contaminated Sites: Measuring or estimating velocity with which water travels in the vadose zone.
Method Description; Flux or long-term infiltration calculation: Velocity can be calculated by dividing flux values
obtained by methods described above (Sections 7S.I to 75.4), or dividing the long-term infiltration rate (as
determined using methods in Sections 7.1.1 or 7.1.4) by average water content Both methods assume that: (1)
Hydraulic gradients are unity, (2) an average water content can be determined, (3) flow is vertical, and (4) a
homogenous media exists. Indirect estimates of velocity can be obtained using suction samplers (Section 9.2),
Apparent vertical velocity is estimated by observing the time it takes a wetting front from a surface source to
reach vertically placed suction samplers, as indicated by a change from little or no soil-water retrieval during
sampling to ready collection of soil water during suction. Section 7.5.1 (flux water budget methods) describes
a simplified method for estimating velocity using water budget data, and 7.5.3 (tracers) describes use of tracers
to estimating velocity.
Method Selection Considerations: Flux/Infiltration Calculation Advantages: (1) Is simple and inexpensive when
coupled with other methods; and (2) is suitable for making a preliminary estimate of travel time of pollutants
in the vadose zone. Flux/Infiltration Calculation Disadvantages: (1) Underestimates velocity in structured media;
(2) is not valid if perching layers cause lateral flow; (3) for multi-layered media, an average moisture content
value might be difficult to obtain; (4) might be difficult to obtain equivalent water content values where liquid
wastes have different properties than water.
Frequency of Use: Flux/Infiltration calculations: Relatively common.
Standard Methods/Guidelines; Flux calculation: Bouwer (1980), Wilson (1980); Suction cup: Everett et al. (1983).
Sources for Additional Information: Wilson (1982), Everett et al. (1983); Case studies: Biggar and Nielsen
(1976), Jury and Sposito (1985).
7-65
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7. VADOSE ZONE HYDROLOGIC PROPERTIES (II): INFILTRATION, CONDUCTIVITY, AND FLUX
7.5 WATER FLUX (UNSATURATED ZONE)
75.6 Physical and Empirical Equations
Other Names Used to Describe Method: ~
Uses at Contaminated Sites; Estimating water flux in the vadose zone.
Method Description; A soil-physics based approach to quantifying soil-water flux requires measurement or
estimation of hydraulic characteristic data and the use of physically or empirically-based equations to calculate
flux. Any technique that measures hydraulic conductivity as a function of water content or matric potential (see
Section 63.1 and Section 7.2 generally) allows calculation of water flux if the appropriate parameter (water
content or matric potential) is monitored. Most of the methods in Section 75.2 (Soil Moisture/Matric Potential
Methods) use this approach in one way or another. Numerous physically- and empirically-based equations have
been developed to model infiltration and flow in the unsaturated zone. Sections 7.1.4 (Infiltration Equations)
and Section 7.2.8 (Physical/Empirical Equations and Relationships) provide an overview of these approaches.
The catalog-of-hydraulic-propertles approach involves the use of "typical" hydraulic properties associated with
physical soil properties, such as texture, porosity, and bulk density, to estimate both saturated and unsaturated
hydraulic conductivity, provided that physical characteristics of the soils of interest are similar to soils for which
data are available.
Method Selection Considerations: Physical and empirical equations: See Sections 7.1.4 and 7.2.8. Catalog-of-
hydraulic-propcrtics advantages: (1) Simple, quick, and can be used to estimate relative variations in hydraulic
conductivity caused by stratification; and (2) is good for sensitivity analysis. Catalog-of-hydraullc-propertles
disadvantages: Might be prone to large errors because of lack of comparability between soil properties and
because of spatial variability in soil properties.
Frequency of Use; Most methods for measuring soil hydraulic properties are based on, or require the use of, one
or more physical and/or empirical models. Estimation of hydraulic properties from other soil physical properties
is commonly used to obtain "ballpark" estimates of flux.
Standard Methods/Guidelines; —
Sources for Additional Information: Warrick et al. (1977). See generally, references for Sections 7.1.4,7.2.8, and
Table 7-5.
7-66
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Table 7-3 Reference Index for Measurement of Unsaturated Hydraulic Conductivity and Flux in the Vadose Zone
Topic
References
Reviews
Instantaneous Profile
Draining Profile
Tension Inffltrometers
Crust-Imposed Steady Flux
Sprinkler/Dripper Methods
Entrapped Air Method
Bouma (1977), Boutna et al. (1974), Bouwer and Jackson (1974), Dirksen (1991),
Green et al. (1986), Hendrickx (1990), Hillel and Benyamini (1974), Stephens and
Neuman (1982a), U.S. EPA (1986)
Ahuja et al, (1976), Atya et al. (1975), Baker et al. (1974), Cassel (1974), Dane
(1980), Davidson et al. (1969), Fliihler et al. (1976), Hillel and Benyamini (1974),
Hillel et al. (1972), Hsieh and Enfield (1974), Mute (1972), Nagpal and DeVries
(1976), Nielsen and Biggar (1973), Nielsen et al. (1964,1973), Ogata and
Richards (1957), Richards et al. (1956), Roberts (1984), Rose and Krishnan
(1967), Rose et al. (1965), Schuh and dine (1990), Shouse et al. (1992), Simmons
et al. (1979), Stone et al. (1973), Stoner (1985), Unlu et al. (1989, 1990), van
Bavel et al. (1968), Warrick and Amoozegar-Fard (1980), Watson (1966); In Situ
Soil Block: Cheng et al. (1975), Luxmoore et al. (1981); Tensiometers/Soij Cores:
Cassel (1971), Carvallo et al. (1976), Miller et al. (1965)
Moisture Profile: Chong et al. (1981), Dane (1980), Dane and Hruska (1983),
Libardi et al. (1980), Luxmoore et al. (1981), Sisson et al. (1980); Pressure
Profile; Ahuja et al. (1980, 1982, 1988), Schuh et al. (1984), Wall and John (1982)
Designs: Ankeny et al. (1988), Perroux and White (1988); Hydraulic Conductivity:
Ankeny et al. (1991), Baumgartner et al. (1987), Clothier and Smettem (1990),
Cook (1991), Elrick et al. (1987), Havlena and Stephens (1992), Reynolds and
Elrick (1991), Sai and Anderson (1991), Smettem and Clothier (1989), Warrick
(1992), White and Perroux (1987, 1989); Sorptivitv/Difftisivitv: Chong and Green
(1983), Clothier and Smettem (1990), Clothier and White (1981), Dirksen (1975),
Russo and Bresler (1980), Smettem and Clothier (1989), Smiles and Harvey
(1973), Walker and Chong (1986), White and Perroux (1987, 1989);
Lifiltration/Macroporositv: Ankeny et al. (1990), Clothier et ai. (1981a), Jarvis et
al. (1984), Watson and Luxmoore (1986), Wilson and Luxmoore (1988).
Anderson and Bouma (1977-laboratory), Baker (1977), Baker and Bouma (1976),
Booltinck et al. (1991), Bouma (1975), Bouma and Denning (1972), Bouma et al.
(1971), Hillel and Gardner (1969,1970), Reinds (1988-laboratory), Roberts
(1984), Spaans et al. (1990), Stoner (1985)
Sprinkler-Imposed Flux: Chong (1983-sorptrvity), Hillel and Benyamini (1974),
Hills et al. (1989), McQueen (1963), Morin et al. (1967), Rawitz et al. (1972),
Reinds (1988-laboratory), van de Pol et al. (1977), Youngs (1964-laboratory);
Dripper Infiltrometers: Bridge and Ross (1985), Shani et al (1987); Infiltration
Rates: See Section 7.1.2.
Dixon and Linden (1972), Peck (1965), Starr et al. (1978), Takagi (1960); see
also, references on effects of entrapped air on hydraulic conductivity in Table 7-4
7-67
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Table 7-4 Reference Index for Measurement of Saturated Hydraulic Conductivity in the Vadose Zone
Topic
References
Saturated Hydraulic Conductivity
(Above Shallow Water Table)
Reviews
Effect of Entrapped Air
Temperature Effects
Cylinder InfUtrometers
Constant-Head Borehole
Infiltration
Guelph Permeameter
Air-Entry Permeameter
Double Tube Method
Infiltration Gradient
Amoozegar and Warrick (1986), Boersma (1965), Bouwer and Jackson (1974),
Hamilton et al. (1981), Hendrickx (1990), Kessler and Oosterbaan (1974), Lambe
(1955), Sai and Anderson (1991), Stephens et al. (1988), Winger (1960), Youngs
(1991); Method Comparisons: Havlena and Stephens (1992), Lee et al. (1985),
Reynolds et al. (1983), Roberts (1984), Sai and Anderson (1991), U.S. EPA
(1986); Chemical Effects on Clavs: Brown (1988), Roberts (1984)
Bouwer (1966, 1978), Bouwer and Jackson (1974), Chahal (1964), Corey (1957),
Jarrett and Fritton (1978), McWhorter et al. (1973), Peck (1969), Stephens et al.
(1984)
Chahal (1964), Constants (1982), Giakoumakis and Tsakiris (1991), Haridasan
and Jensen (1972), Hopmans and Dane (1986)
Aronovici (1955), Bouwer (1963), Burgy and Luthto (1956), Dixon (1975-sealed
tafiltrometer), Havlena and Stephens (1992), Johnson (1963), Priksat et al. (1992),
Reynolds and Elrick (1990), Roberts (1984), Sai and Anderson (1991), Scotter et
al. (1982), Swartzendruber and Olsen (1961a,b); Compacted Liner Tests: Daniel
(1984,1989), Daniel and Trautwein (1986), Hsbury et al. (1988), Panno et al.
(1991), Pederson et al. (1988), Rogowski (1990), Sai and Anderson (1991), U.S.
EPA (1989), Youngs (1991)
Amoozegar (1989a,b), Banton (1993), Boersma (1965), Bouwer (1978), Elrick and
Reynolds (1992), Fritton et al. (1986), Havlena and Stephens (1992), Heinen and
Raats (1990), Kanwar et al. (1987), Philip (1985a), Picornell and Guerra (1992),
Reynolds et al. (1983, 1985), Stephens et al. (1987, 1988), Talsma (1987), Zanger
(1953)
Elrick and Reynolds (1992), Brick et al. (1987,1988), Havlena and Stephens
(1992), Heinen and Raats (1990), Jabro and Fritton (1990), Lee et al. (1985),
Logsdon et al. (1990), Reynolds and Brick (1985a, 1985b, 1986,1987), Reynolds
et al. (1983), Sai and Anderson (1991), Stephens et al. (1988), Talsma (1987),
Talsma and Hallam (1980), Wilson et al. (1989)
Aldabagh and Beer (1971), Bouma (1983), Bouwer (1966, 1978), Bresler et al.
(1978-K™"1), Havlena and Stephens (1992), Lee et al. (1985), Reynolds et al.
(1983), Roberts (1984), Russo and Bresler (1980), Sai and Anderson (1991),
Shani et al. (1987), Stephens et al. (1988), Topp and Binns (1976), U.S. EPA
(1981), Youngs (1991)
Boersma (1965), Bouma (1971, 1983), Bouma and Hole (1971), Bouwer (1961,
1962,1964a, 1978), Bouwer and Rice (1964, 1967), Brust et al. (1968), Kessler
and Oosterbaan (1974), U.S. EPA (1981)
Bouwer (1964a, 1978), Bouwer and Jackson (1974), Bouwer and Rice (1967),
Rice (1967)
7-C8
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Table 7-4 (conk)
Topic References
In Situ Monoliths Cube Method: Bouma and Dekker (1981), Roberts (1984); Column Method:
Baker and Bouma (1975), Bouma (1980), Bouma et al. (1976, 1979, 1981), Vroon
et al. (1988); Column-Crust Method: Bouma (1982); Monoliths: Jager and van der
Voort (1966), Mielke (1973), Sai and Anderson (1991), Stibbe et al, (1970),
Tzimas (1979)
Percolation Test Barbarick et al. (1976), Own (1976), Brick and Reynolds (1986), Hill (1966),
Jabro and Fritton (1990), U.S. EPA (1980), U.S. PHS (1969); Percolation Test
Relationship to Ksat: Bicki et al. (1988), Bouma (1971), Fritton et al. (1986),
Healy and Laak (1973), Jabro and Fritton (1990), Mellon (1973), Paige and
Veneman (1993), Winneberger (1974)
Saturated Hydraulic Conductivity
(Deep Water Table) See Section 7.4
7-69
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Table 7-5 Reference Index for Physical and Empirical Equations and Models of Hydraulic Properties in the
Vadosc Zone
Topic
References
Infiltration/Saturated Hydraulic
Conductivity
Infiltration Theory/Equations
Bouwer (1964b), Brandt et al. (1971), Broadbridge and White (1988), Childs
(1967), Clothier et al. (1981b), Hanks and Bowers (1962), Hanks et al. (1969),
Hogarth et al. (1989), Horton (1935,1939, 1940), Knight (1983), Knight and
Philip (1974), Kutflek (1980), Panikar and Nanjappa (1977), Parlange (1972),
Parlange and Smith (1976), Parlange et al. (1982,1985), Parr and Bertrand
(1960), Philip (1954,1957a,b, 1958a,b, 1969,1973,1975,1985b, 1989a,b), Philip
and Knight (1974), Pullan (1990), Raats (1973), Reichardt et al. (1972), Richards
(1931, 1965), Rijtema and Wassink (1969), Rubin and Steinhardt (1963), Rubin et
al. (1964), Sharma et al. (1980), Stallman (1967), Swartzendruber (1987a,b),
Swartzendruber and Qague (1989), Swartzendruber and Hogarth (1991), Talsma
and Parlange (1972), Warriek (1985), Warrick and Hussen (1993), White and
Broadbridge (1988), White and Sully (1987), White et al. (1989), Wilson and
Lutfain (1963), Wooding (1968)
Unsaturated Hydraulic Conductivity
Parameter Identification
Empirical Equations/Models
(See also, Table 6-3)
Hydraulic Properties from
Soil Physical Properties
(See also, Table 6-3)
Dane and Hruska (1983), Hornung (1983), Kool and Parker (1988), Kool et al.
(1985, 1987), Parker et al. (1985), Ravi and Jennings (1990-laboratory
measurements), Sisson et al. (1980), van Dam et al. (1992), Van Genuchten et al.
(1989), Zachmann (1981, 1982)
Empirical Equations: Bresler et al. (1978), Brooks and Corey (1964, 1966),
Gardner (1958), Laliberte et al. (1966-values for use with BC equation), Messing
(1989), Raats and Gardner (1971), Ritjema (1965), Wind (1955); Macroscopic
Models: Irmay (1954), Mualem (1978); Statistical Models: Burdine (1953), Childs
and CoUis-George (1950), Marshall (1958), Millington and Quirk (1959,1961,
1964), Mualem (1976a), Mualem and Dagan (1978), Purcell (1949), Rieu and
Sposito (1991a,b), Ross and Smettem (1993), Vachaud (1967), Van Genuchten
(1979, 1980), Weeks and Richards (1967); Use/Comparisons; Bruce (1972), Brust
et al. (1968), Brutsaert (1967), Green and Corey (1971), Jackson (1972), Jackson
et al. (1965), Kunze et al. (1968), Nielsen et al. (1960), Rogers and Mute (1971),
Roulier et al. (1972), Stockton and Warrick (1971),
Ahuja et al. (1984), Alexander and Skaggs (1987), Anderson and Bouroa (1973),
Basak (1972), Bloeman (1980), Burdine (1953), Campbell (1974), Clapp and
Hornberger (1978), Gausnitzer et al. (1992), de Jong (1982), Hanks et al. (1969),
Laliberte and Corey (1967), Marshall (1958), Mason et al. (1957), McCuen et al.
(1981), Mehuys et al. (1975), Mishra et al. (1989), Mualem (1976b), Puckett et al.
(1985), Rawls and Brakensiek (1985), Rawls et al, (1982), Reichardt et al. (1975),
Rogowski (1972), Saxton et al. (1986), Schuh et al. (1988), Tyler and Wheatcraft
(1989), Van Genuchten and Nielsen (1985), White and Perroux (1989-sorptivity),
Williams et al. (1992), Wosten and Van Genuchten (1988)
7-70
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Table 7-6 Reference Index for Water Flux Methods
Topic
References
General Reviews
Water Budget
Soil Moisture/Potential
Tracers
Soil-Water Flux Meters
Allison (1987), Gee and Hillel (1988), Roth et al. (1990), Simmons et al. (1979),
U.S. EPA (1986-vadose zone travel time), Wagenet (1986)
Fenn et al. (1975), Gee and Hillel (1988), Jensen (1974), Kmet (1982), Simmers
(1987), Sokolow and Chapman (1974), Warrick and Amoozegar-Fard (1981),
Zepp and Belz (1992); Thomthwaite Method: Dunne and Leopold (1978),
Thornethwaite and Mather (1957), Wflmott (1977); Case Studies: Aguilar and
Aldon (1991), Dreiss and Anderson (1985), Fenn et al. (1975), Forslund and
Daily (1990), Mather and Rodriguez (1978), Orr et al. (1990), Panno et al.
(1991), Young and dapp (1989)
Case Studies; Aguilar and Aldon (1991), Enfield et al. (1973), LaRue et al.
(1968), Simmons et al. (1979), van Bavel et al. (1968)
Chloride: Allison (1987), Allison and Huges (1978, 1983), Allison et al. (1985),
Johnston (1987), Knowlton et al. (1992), Scanlon (1991), Sharana and Hughes
(1985), Sukhija et al. (1988), Walker et al (1991); Tritium; Allison and Huges
(1978), &ans et al. (1976), Frissel et al. (1974), Knowlton et al. (1992), Phillips et
al. (1988); Qthen Allison et al. (1985), Frissel et al. (1974), Knowlton et al.
(1992), Sharma and Hughes (1985)
Thermal: Byrne (1971), Byrne et al. (1967,1968); Hydraulic Resistance: Gary
(1968,1970, 1971, 1973), Dirksen (1972, 1974); Suction-Hydraulic Resistance; van
Orinsven et al. (1988).
7-71
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SECTION 7 REFERENCES
Abele, G., et at. 1980. Infiltration Characteristics of Soils at Apple Valley, Minn.; Clarence Cannon Dam, Mo.; and Deer Creek
Lake, Ohio, Land Treatment Sites. CRREL Special Report 80-36, U.S. Army Cold Regions Research and Engineering
Laboratory, Hanover, NH, 52 pp. [Test basins]
Ahuja, L.R., S.A. El-Swaify, and A. Rahman. 1976. Measuring Hydrologic Properties of Soil with a Double-Ring Infiltrometer and
Multiple-Depth Tensiometers. Soil Sci. Soc. Proc. 40:494-499. [Instantaneous profile]
Ahuji, L.R., R.E. Green, S.K. Chong, and D.R. Nielsen. 1980. A Simplified Functions Approach for Determining Soil Hydraulic
Conductivities and Water Characteristics In Situ. Water Resources Research 16:947-953. [Draining pressure profile]
Ahujt, L.R., R.E. Green, S.K. Chong, and D.R. Nielsen. 1982. Reply to the Comments on "A Simplified Functions Approach for
Determining Soil Hydraulic Conductivities and Water Characteristics In Situ." Water Resources Research 18:1300-1301.
[Draining pressure profile]
Ahuja, L.R., J.W. Nancy, R.B. Green, and D.R. Nielsen. 1984. Macroporosity to Characterize Spatial Variability of Hydraulic
Conductivity and Effects of Land Management Soil Sci. Soc. Am. J. 48:499-702.
Ahuja, L.R., J.D. ROM, R.R. Bruce, and O.K. Cassel. 1988. Determining Unsaturated Hydraulic Conductivity from Tensiometric
Data Alone. Soil Sci. Soc. Am. J. 52:27-34. [Draining pressure profile]
Aguilir, R. and E.F. Aldon. 1991. Seasonal Water Flux and Potential for Leaching in a Semiarid Rangeland Soil. Ground Water
Management 5:669-683. [Water balance, soil moisture monitoring]
A!d«btgh, AS.Y, and C.E. Beer. 1971. Field Measurement of Hydraulic Conductivity Above a Water Table with Air-Entry
Permesmeter. Irani. Am. Soc. Agric, Eng. 14:29-31.
Alexander, L. and R.W. Skigg*. 1987. Predicting Unsaturated Hydraulic Conductivity from Soil Texture, J. of Irr. and Drain. Eng.
113:184-197. [Estimation from soil-water retention relationship]
Alton, G.B. 1987. A Review of Some of the Physical, Chemical and Isotopic Techniques for Estimating Groundwater Recharge.
In: Estimation of Natural Groundwater Recharge, I. Simmers (ed.), Reidel, Dordrecht, pp. 49-72. [Chloride tracer]
Allison, G.B. and M.W. Hughes, 1978. The Use of Environmental Chloride and Tritium to Estimate Total Recharge to an
Unconfirmed Aquifer. Aust, J. Soil Res. 16:181-195.
Allison, G.B. and M.W. Hughes. 1983. The Use of Natural Tracers as Indicators of Soil-Water Movement in a Temperate Semi-
Arid Region. J. Hydrology 60:157-173. [Chloride tracer]
Allison, G.B., WJ. Stone, and M.W. Hughes. 1985. Recharge in Karst and Dune Elements of a Semi-Arid Landscape as Indicated
by Natural Isotopes and Chloride. J. Hydrology 76:1-26.
American Society for Testing and Materials (ASTM). 1988. Standard Test Method for Infiltration Rate of Soils in Field Using
Double-Ring Infiltrometere, D3385-88, (Vol. 4.08), ASTM, Philadelphia, PA.
American Society for Testing and Materials (ASTM). 1990s. Guide for Comparison of Field Methods for Determining Hydraulic
Conductivity in the Vadose Zone. D5126-90, (Vol. 4.08), ASTM, Philadelphia, PA. [Saturated: single-/doubie-ruig
infiltrometer, double tube, air-entry permeameter, borehole permeameter (constant head-borehole infiltration, Guelph
permeameter), empirical; unsaturated: instantaneous profile, crust, empirical]
American Society for Testing and Materials (ASTM). 1990b. Standard Test Method for Field Measurement of Infiltration Rate
Using a Double-Ring Infiltrometer With a Sealed-Inner Ring. D5093-90, (Vol. 4.08), ASTM, Philadelphia, PA.
Amoozegar, A. 1989a. A Compact Constant-Head Permeameter for Measuring Saturated Hydraulic Conductivity In the Vadose
Zone. Soil Sci. Soc. Am. J. 55:1356-1362. (See also, errata for equations 1 and 2 in Soil Sci. Soc. Am. J. 54:216.)
Amoozegar, A. 1989b. Comparison of the Glover Solution with the Simultaneous Equations Approach for Measuring Hydraulic
Conductivity, Soil Set. Soc. Atn. J. 53:1362-1367.
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Amoozcgar, A. and A.W. Warrick. 1986. Hydraulic Conductivity of Saturated Soils: Field Methods. In: Methods of Soil Analysis,
Part 1, 2nd edition, A. Kluie (ed.), Agronomy Monograph No. 9, American Society of Agronomy, Madison, WI, pp. 735-
798.
Anderson, J.L. and J. Bouma. 1973. Relationship Between Saturated Hydraulic Conductivity and Morphometric Data of an Argillic
Horizon. Soil Sci. Soc. Am. Proc. 37:408-413.
Anderson, J.L. and J. Bouma. 1977. Water Movement Through Pedal Soils II: Unsaturated Plow. Soil Sci. Soc. Am. J, 41:419-423.
Ankeny, M.D., T.C. Kaspar, and R. Morton. 1988. Design for an Automated Tension Infiltrometer. Soil Sci. Soc. Am. J. 52:893-
896.
Ankeny, M.D., T.C. Kaspar, and R. Horton, 1990. Characterization of Tillage and Traffic Effects on an Unconfmed Infiltration
Measurement. Soil Sci. Soc. Am. J. 54:837-840. [Tension infiltrometer]
Ankeny, M.D., M. Ahmed, T.C. Kaspar, and R. Horton. 1991. Simple Field Method for Determining Unsaturated Hydraulic
Conductivity. Soil Sci. Soc. Am. J. 55:467-470. [Tension infiltrometer]
Aronovici, V.S. 1955. Model Study of Ring Infiltrometer Performance under Low Initial Soil Moisture. Soil Sci. Soc. Am. Proc.
19:1-6.
Arya, L.M., D.A. FarreU, and G.R. Blake. 1975. A Reid Study of Soil Water Depletion Patterns in the Presence of Growing
Soybean Roots, 1: Determination of Hydraulic Properties of the Soil. Soil Sci. Soc. Am. Proc. 39:424-436. [Instantaneous
profile]
Baker, F.G. 1977. Factors Influencing the Crust Test for In Situ Measurement of Hydraulic Conductivity. Soil Sci. Soc. Am. J.
41:1029-1032.
Baker, F.G. and J. Bouma. 1975. Variability of Hydraulic Conductivity in Two Subsurface Horizons in Two Silt Loam Soils. Soil
Sci. Soc. Am. J. 40:210-222. [Column method]
Baker, F.G. and J. Bouma. 1976. Variability of Hydraulic Conductivity in Two Subsurface Horizons of Two Silt Loam Soils. Soil
Sci. Soc. Am. J. 40:219-222. [Crust test]
Baker, F.G., P.L.M. Veneman, and J. Bouma. 1974. Limitations of the Instantaneous Profile Method for Field Measurement of
Unsaturated Hydraulic Conductivity. Soil Set. Soc. Am. Proc. 38:885-888.
Banton, O. 1993. Field- and Laboratory-Determined Hydraulic Conductivities Considering Anisotropy and Core Surface Area. Soil
Sci. Soc. Am. J. 47:10-15. [Constant-head permeameter]
Barbarick, K-A,, A.W. Warrick, and D.F. Foot. 1976. Percolation Tests for Septic Tank Suitability of Typical Southern Arizona
Soils. J. Soil and Water Conservation 31:110-112.
Basak, P. 1972. Soil Structure and Its Effect on Hydraulic Conductivity. Soil Science 114:417-422.
Baumgartner, N., D.E. Elrick, and K.L. Bradshaw. 1987. In-Situ Hydraulic Conductivity Measurements of Slowly Permeable
Materials Using a Modified Guelph Permeameter and the Guelph Infiltrometer. In: Proc. of the 1st Nat Outdoor Action
Conf. on Aquifer Restoration, Ground Water Monitoring and Geophysical Methods, National Water Well Association,
Dublin, OH, pp. 469-481.
Bertrand, A.R. 1965. Rate of Water Intake in the Field. In: Methods of Soil Analysis, 1st edition, C.A. Black (ed.), Agronomy
Monograph 9, American Society of Agronomy, Madison, WI, pp. 197-208. (Updated by Peterson and Bubenzer [1986].}
Bicki, TJ., T.E. Fenton, H.D. Luce, and TA. DeWitt. 1988. Comparison of Percolation Test Results and Estimated Hydraulic
Conductivities for Mollisols and Alfisols. Soil Sci. Soc. Am. J. 52:1708-1714.
Biggar, J.W. and D.R. Nielsen. 1976. Spatial Variability of the Leaching Characteristics of a Field Soil. Water Resources Research
12:78-84.
Bloemen, G.W. 1980. Calculation of Hydraulic Conductivities of Soils from Texture and Organic Matter Content. Z.
Planzenemaehr, Bodendk. 143:581-605.
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Boersma, L. 1965, field Measurement of Hydraulic Conductivity above a Water Table, In: Methods of Soil Analysis, Part 1,1st
edition, CA. Black (ed.), Soil Science Society of American, Madison, WI, pp. 234-252.
Booltink, H.W.G., J. Bouma, and D. Giraenez. 1991. Suction Crust Infiltrometer for Measuring Hydraulic Conductivity of
Unsaturated Soil Near Saturation. Soil Sci. Soc. Am. J. 55:566-568.
Bouma, J, 1971. Evaluation of the Reid Percolation Test and an Alternative Procedure to Test Soil Potential for Disposal of Septic
Tank Effluent Soil Sci. Soc. Am. Proc, 35:871-875. [Double-tube method]
Bouma, J. 1975. Unsaturated Flow Phenomena During Subsurface Disposal of Septic Tank Effluent J. Environ. Eng. Div. ASCE
191:967-983.
Bouma, J. 1977. Soil Survey and the Study of Water in Unsaturated Soil. Soil Survey Paper 13, Soil Survey Institute, Wageningen,
Netherlands.
Bouma, J. 1980. Field Measurement of Soil Hydraulic Properties Characterizing Water Movement Through Swelling Clay Soils. J.
Hydrology 45:149-158. [Column method]
Bouma, J. 1982, Measuring the Hydraulic Conductivity of Soil Horizons with Continuous Macropores. Soil Sci. Soc. An. J. 46:438-
441. [Column-crust method]
Bouma, J. 1983. Use of Soil Survey Data to Select Measurement Techniques for Hydraulic Conductivity. Agric. Water Manage.
6:177-190.
Bouma, J, and L.W. Dekker. 1981. A Method of Measuring the Vertical and Horizontal K^ of Clay Soils with Macropores. Soil
Sci. Soc, Am. J. 45:662-663. [Cube method]
Bouma, J. and J.L. Denning. 1972. Field Measurement of Unsaturated Hydraulic Conductivity by Infiltration through Gypsum
Crusts. Soil Sci. Soc. Am. Proc. 36:846-847.
Bouma, J. and F.D. Hole. 1971. Soil Structure and Hydraulic Conductivity of Adjacent Virgin and Cultivated Pedons at Two Sites:
A Typic ArgiudoU (Silt Loam) and a Typic Eutrochrept (day). Soil Sci. Soc. Am. Proc. 35:316-319. [Double tube method]
Bouma, J., D.I. Hillel, F.D. Hole, and CR. Amerraan. 1971. Field Measurement of Hydraulic Conductivity by Infiltration through
Artificial Crusts. Sol Sci. Soc. Am. Proc. 35:362-364.
Bouma, J,, F.G. Baker, and P.L.M. Veneman. 1974. Measurement of Water Movement in Soil Pedons above the Water Table.
University of Wisconsin-Extension, Geological and Natural History Survey, Information Circular No. 27.
Bouma, J., L.W. Dekker, and H.L. Verlinden. 1976. Drainage and Vertical Hydraulic Conductivity of Some Dutch "Knife" Clay Soils.
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-------
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569-7562).
7-91
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SECTION 8
VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
Water movement and transport of contaminants in the vadose zone is determined by the amount of
precipitation that enters the ground by infiltration, and the amount of water that is removed from the soil by
evaporation from bare soil or by evapotranspiration where vegetation covers the soil. This section contains
information on more than 50 techniques for measuring or estimating: (1) Hydrometeorological parameters, and
(2) evaporation and evapotranspiration for water budget calculations in the vadose zone and shallow ground-
water systems. Methods for measuring and estimating infiltration are covered in Section 7.1.
Hydrometeorological Data
Table 8-1 provides some general summary information on 38 techniques for measuring six major
hydrometeorological parameters and identifies sections of this guide were more detailed information can be
found. Precipitation is a primary input into water budget calculations, and devices for measuring precipitation
fall into two main categories; (1) Manual gages (Section 8.1.1), and (2) recording gages (Section 8.1.2).
Measurement of humidity (Sections 8.1.3 and 8.1.4) might be required during field work for protection of health
and safety and are required with most micrometeorological methods for measuring evapotranspiration (Section
8.4). Other hydrometeorological measurements might be required for monitoring weather conditions, such as
temperature (Sections 8.2.1 and 8.2.2), windspeed (Section 8.2.3), and wind direction (Section 8.2.4).
Measurement or estimation of these same parameters, as well as atmospheric pressure (Section 8.2.5) and
insolation or radiation measurement (Sections 8.2.6 and 8.2.7), might be required in order to quantify the
evapotranspiration component of water budget studies (discussed further below). Although numerous techniques
and devices have been developed for hydrometeorological measurements, most of the parameters of interest
usually can be estimated for purposes of vadose zone water budget studies by using data from nearby weather
stations or interpolations using hydrometeorological tables or maps. Consequently, only those methods relevant
to health and safety (temperature, humidity, windspeed, and direction) are likely to be used routinely during site
investigations. Table 8-1 identifies the specific hydrometeorological techniques or devices that ace most
commonly used for site investigations. ASTM (1986) provides guidance on determining the operational
comparability of meteorological measurements.
Evaporation and Evapotranspiration
Water that reaches the earth's surface can return to the atmosphere either by evaporation from free
water surfaces or bare soil, or by transpiration by plants. The term evapotranspiration (ET) specifically refers
to the combined effects of evaporation and transpiration from the land surface, but also might be used loosely
to refer to the combined effects of evaporation from water and soil surfaces and transpiration. ET is a critical
component of vadose zone water budget calculations, and is one of the most difficult of these components to
measure accurately. The numerous methods that have been developed for measuring or estimating ET can be
broadly classified as water budget or balance methods and micrometeorological methods. Table 8-1 summarizes
information on 10 water balance methods and 6 micrometeorological methods, and identifies specific applications
for each method (water evaporation, bare soil evaporation, evapotranspiration, and transpiration). Most of these
methods are too complex and time-consuming for routine site investigations.
Lysimeters (Section 8.3.1) and soil moisture monitoring (Section 8.3.2) probably are the most commonly
used methods for measuring evapotranspiration where site-specific data are required. Most vadose zone
hydrologic models use empirical equations (Section 8.4.1) and use data from nearby weather stations data and
published maps. The physically-based Penman equation (and various methods developed as refinements and
adaptations of the Penman equation) probably is the most commonly used method for estimation of evaporation
and/or evapotranspiration, where some measurements of meteorological data are feasible but the more complex
measurements and instrumentation of other ruicrometeorological methods are not feasible.
8-1
-------
Table 8-1 SMBatary Infornation on Vadose Zone Water Budget Characterization Methods
Technique
Parameters
Measured
Manual/
Automatic
Water-Related Hydrometeorolosical Measurements
Sacramento Gage
Storage Gage
Automatic Wet/Dry Collectors
Weighing Gage
Tipping Sadat Gage
Float Gage
Sling PgyduoBieter
Aspirated Psychromctcr
Thermocouple Psychrometer
Mechanical Hygrvnetera
Dew-/Frost-Point Hygrometer
Dew Cell/Probes
Electric Hygrometers
Diffusion Hygrometers
Absorption Spectra Hygrometers
Rain
Rain
Rain/Snow
Rain/Snow
Rain
Rain
Humidity
Humidity
Humidity
Humidity
Humidity
Humidity
Humidity
Humidity
Humidity
Manual
Manual
Either
Automatic
Automatic
Automatic
Manual
Either
Either
Either
Either
Automatic
Either
?
7
Other Hvdrometeoroloacal Measurements
Uqnld-ia-Glau Tbemometer
Bi-Mcial Thermometer
Bourdon Tube Thermometer
Thermocouple
Metallic Resistance Bulb
Thcrmiitor
Cup Anenoneters
Windmill Aneatoneters
Pressure Anemometers
Hot-Wire Anemometer
Acoustic Anemometer
Wind Vanes
Wind Cooes
Mercury Barometer
Altimeter
Precision Aneroid
Toennopile Fyranonetera
Bimetallic Pyranometer
Photovoltaic Pyranometer
Net Rsdiometen
Pyrheliometen
Temperature
Temperature
Temperature
Temperature
Temperature
Temperature
H windspeed
V-H windspeed
H windspeed
V-H windspeed
V-H windspeed
Direction
Direction
Air pressure
Air pressure
Air pressure
Global rad.
Global rad.
Global rad.
Net flux
Direct rad.
Manual
Either
Either
Either
Either
Either
Either
Either
Manual
Automatic
Automatic
Either
Manual
Manual
Manual
Either
Automatic
Either
Either
Either
Either
S/A/R
A
± 1 mm'
B
*
n
it
n
S/A/R
0,l/O.S/~
O.Q2/Q.1A-
?
1.0/5.0/20 to 100%
.05/0.25/-
0.5/2.0/10 to 100%
0,5/2.0/5.0 to 98%
7
?
A/R
±Q3°C/-4Q to +604
m
n
B
N
H
1.0 to 50/±0.5m/s"
n
B
It
fl
05 to 50/±5°
K
S/A
7
2 hPa/±0.2%
0.5hPa/7
A
±0.1 to 05 mW/ein2
±1.0 mW/cm2
7
t
1
Section
8.1.1
8.1.1
8.1.1
8.1,2
8.1,2
8.1.2
8.1.3
8.1.3
6.1.2
8.1.4
8.1.4
8.1.4
8.1.4
8.1.4
8,1.4
8.2.1
8.2.1
8.2.1
8,2.2
8.2.2
8.2.2
8.2.3
8.2.3
8.2,3
8.23
8.2.3
8.2.4
8.2.4
8.2,5
8.2.5
8.2.5
8.2.6
8.2.6
8.2.6
8.2,7
8.2.7
Tables
8-2
8-2
8-2
8-2
8-2
8-2
8-2
8-2
6-1,6-3
8-2
8-2
8-2
8-2
8-2
8-2
8-2
8-2
8-2
8-2
8-2
8-2
8-2
8-2
8-2
8-2
8-2
8-2
Boldface •= Most commonly used instruments/methods.
S *> Sensitivity = The smallest fraction of a division on a scale on which a reading can be made directly or by estimation; A =
Accuracy « The closeness with which an observation approaches the true value; R - Range of relative humidity that can be
measured.
'Recommended accuracy by World Meteorological Organization. Less precise measurements might be acceptable, depending on the
purpose of measurements.
*Raage and accuracy of specific thermometers can range considerably, value shown is the recommended specification in U.S. EPA
(1987b).
8-2
-------
Table 8-1 (cunt)
Technique
Parameters
Measured
Manual/
Automatic
Accuracy
Section Tables
Evapotranspiration (Water Balance Methods')
Lyshntters WE,SE,ET,T
Soil Moisture Monitoring SEJET,T
Water Budget Methods WE£E\ET,T
Evaporation Pans WE
Evaporimeter SB
Atmometers SE,T
Chloride Tracer SE,ET,T
Ground-Water Fluctuation SE.ET
Other Transpiration Methods T
Thermal Infrared WE^EJET
Evapotranspiration (Micrometeorological'i
Empirical Equation!
Physically-Baaed Equations
Mass Transfer Methods
Energy Budget Methods
Profile/Gradient Method
Eddy Correlation
WEJ3T.T
WE^BJET.T
WE^EJET
Either
Manual
Manual
Manual
Manual
Manual
Manual
Manual
Manual
Either
Manual
Either
Either
Either
Either
Either
Moderate to high*
Moderate to high*
Low to high
Moderate
High'
Moderate
Moderate
Moderate
Moderate to high*
Low to moderate
Moderate to high
Moderate to high
Moderate to high
Moderate to high
Low to moderate
High
8.3.1
83.2
83.3
83.4
83.5
8.3.5
83.6
83.7
83.8
1.13
8.4.1
8.4.2
8.43
8.4.4
8.4.5
8.4.6
8-3
8-3
8-3
8-3
8-3
8-3
8-3
1-3
8-3
8-3
8-3
8-3
8-3
8-3
Boldface = Most commonly used methods.
WE = Water evaporation; SB = Bare soil evaporation; ET = Evapotranspiration; T = transpiration.
'For high accuracy, numerous measurements at different locations might be required to adequately characterize the variability of
evapo transpiration.
8-3
-------
8. VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
8.1 WATER-RELATED HYDROMETEOROLOGICAL DATA
8.1.1 Precipitation (Nonrccording Gages)
Other Names Used to Describe Method: Standard gage, sacramento gage, conduit gage.
Uses at Contaminated Sites: Monitoring of site conditions during field work; measuring precipitation for water
budget analyse.
Device Description; Nonre cording gages require visual observation or manual measurement to record the amount
of precipitation, even though some types might involve automated handling of collected precipitation.
Sacramento gage: An 8-inch diameter receiving funnel, routes precipitation into a measuring tube with a cross-
sectional area one-tenth that of the gage. The runnel attached to the collector both directs the precipitation into
the tube and minimizes evaporation loss (Figure 8.1.1). Accumulated precipitation is measured periodically.
Snow and other forms of frozen water are melted before measurement in order to give the equivalent amount
of rainfall. The receiving cylinder can be clear with graduated markings for direct readings, or depth is measured
using a measuring stick. Storage gages are similar to funnel gages, except that the storage container is large
enough to store the seasonal catch and oil or other evaporation suppressing material is added to reduce
evaporation between measurement. Automatic wet/dry precipitation collectors are specialized nonrecording
instruments, where chemical and/or radioactive analysis of precipitation is required. The collector is built with
a sensor, which detects the onset and cessation of precipitation, and automatically releases a lid to open and
cover the collector, which prevents evaporation of the samples collected between precipitation events. Other
manual gagei: A wide variety of inexpensive gages, with various shapes for openings and graduated scales for
measuring precipitation, are available.
Device Selection Considerations; Sacramento Gage Advantages: (1) Is inexpensive and easy to use; and (2) has
no moving parts or electronic equipment to malfunction. Sacramento Gage Disadvantages: (1) Accurate
characterization of precipitation events requires measurement after each precipitation event, which is difficult
unless personnel are readily available to take readings at the required intervals; and (2) tend to underestimate
precipitation that falls as snow. Storage Gagea: Used at inaccessible sites where seasonal measurements are
adequate for data needs. Automatic Precipitation Collectors: Used to collect bulk samples of precipitation for
chemical analysis. Standard collectors require manual recording of the precipitation that is collected, but recent
advances allow both automated recording of precipitation amounts and collection of snow and rain samples for
chemical analysis (Purcell and Brown, 1991).
Frequency of Use: The Sacramento gage is the standard nonrecording gage used in the United States.
Standard Methods/Guidelines: NWS Specification No. 450.2301.
Sources for Additional Information: Brakensick et al. (1979), Brock and Nicolaidis (1984), Lockhart (1989a),
Malone (1951), National Weather Service (1972), U.S. EPA (1985), U.S. Geological Survey (1980), WMO (1971).
See also, Table 8-2, Most of the general hydrology texts listed in Table 8-3 also discuss methods for measuring
precipitation.
8-4
-------
Catch funnel
Case ^,
c
Measuring
tube —
}
\ /
-"-^
1
*—
I)
I
!-
-
1-
i-
:-
f ^
Measuring stick
Figure 8.1.1 Typical non-recording rain gage (Kazmann, 1988, by permission).
8-5
-------
8. VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
8.1 WATER-RELATED HYDROMETEOROLOGICAL DATA
8.1.2 Precipitation (Recording Gages)
Other Names Used to Describe Devices: Weighing, Fergusson, or universal gage; tipping bucket gage; float gage,
Uses at Contaminated Sites: Measuring precipitation at remote sites or where accurate characterization of the
amount and intensify of precipitation is required for water budget analysis.
Device Description; Weighing gage: A mechanical recording device is attached to a scale, which provides
continuous weight measurements of precipitation that enters a cylinder gage (Figure 8.1.2a). Changes in weight
are recorded on a chart recorder. Tipping bucket gage: A pair of small containers designed so that when a
certain amount of rainfall (typically 0.01 inches) falls in one of the containers, it tips, and moves the other
container into position to receive the next rainfall (Figure 8.1.%). When the collection container empties into
a storage container, an electrical contact is closed and the event is recorded on an electronic data logger. Float
gages are cylinder gages equipped with a float and a recording device to automate measurement (used in Great
Britain). Special features, which can be used with any gage, include: (1) Shields to improve collection efficiency
of snow, (2) heaters to melt frozen precipitation so it will not clog the collectors or funnels of the gage, and (3)
suppressants to reduce evaporation losses.
Device Selection Considerations: Weighing Gage Advantages: (1) Are very reliable; (2) equipment is readily
available; and (3) measures both rain and frozen precipitation. Weighing Gage Disadvantages: (1) Manual
reading of the chart recorder is required; (2) collection container usually must be emptied manually; and (3)
measurements of snow might not be accurate (accuracy can be increased by shielding [Simmons and Bigelow
(1990)], Tipping Bucket Gage Advantages: (1) Data are generated electronically, which facilitates data analysis,
and (2) is reliable and equipment is readily available. Tipping Bucket Gage Disadvantages: (1) Requires more
maintenance than weighing gages; (2) is not accurate for measuring snowfall; and (3) requires power source for
recording.
Frequency of Use; The weighing gage is the official precipitation measurement device of the National Weather
Service. Tipping bucket gages are both readily available and widely used.
Standard Methods/Guidelines: Weighing gage: NWS Specification No. 450.2201.
Sources for Additional Information: Brakensiek et al, (1979), Brock and Nicolaidis (1984), Lockhart (1989a),
Malone (1951), National Weather Service (1972), U.S. EPA (1985), U.S. Geological Survey (1980), WMO (1971).
See also, Table 8-2. Most of the general hydrology texts listed in Table 8-3 also discuss methods for measuring
precipitation.
8-6
-------
Catch bucket
Clock -
Record sheet
•f Cover
f Platform
Weighing
device
Pen arm
• Base
(a)
Screen or Shield
To Recording
Device
Tipping
Bucket
Collector
(b)
Figure 8,1.2 Recording rain gages: (a) Typical weighing rain gage (Kazmann, 1988, by permission); (b) Typical
tipping bucket rain gage (Dunne and Leopold, 1978, from: Water in Environmental Planning by Dunne
and Leopold, Copyright O 1978 by W.H, Freeman and Company, reprinted with permission).
8-7
-------
8. VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
8.1 WATER-RELATED HYDROMETEOROLOGICAL DATA
8.1.3 Humidity Measurement (Psychrometers)
Other Names Used to Describe Device; Sling psychrometer, dry-bulb/wet-bulb thermometer, aspirated
psychrometer, thermocouple psychrometers.
Uses at Contaminated Sites: Estimating effective air temperature when it is very hot; psychrometers are required
for several micrometeorological evapotranspiration methods (profile, eddy correlation, mass transfer).
Device Description: Psychrometers operate on the principle of reduction of temperature by evaporation.* Sling
pychrometen A dry-bulb/wet-bulb thermometer (two matched mercury-in-glass thermometers mounted on a
metal frame with the bulb of one covered by a moistened wick) is attached to a handle with a chain so that the
thermometer can swing around to equilibrate (Figure 8.1.3). Charts are used to determine relative humidity
based on the difference in temperature between the two thermometers. Readings from a static dry-bulb/wet-bulb
thermometer also can be used, but are not quite as accurate. Aspirated psychrometers are dry-bulb/wet-bulb
thermometers in which a motor-driven fan or blower draws air over the thermometers at a constant rate. As with
the sling psychrometer, humidity is determined using charts. Thermocouple psychrometers are discussed in
Section 6.1.2.
Device Selection Considerations: Sling psychrometers are accurate, readily available, and easy to use. Aspirated
psychrometers provide greater accuracy (Table 8-1), but require a power source and involve more complex
installation procedures, such as use of a radiation shield. Humidity should be monitored whenever use of
protective clothing in hot temperatures creates a possibility of heat stress.
Frequency of Use; Commonly used.
Standard Methods/Guidelines: ASTM (1982, 1984a).
Sources for Additional Information: Berry et al. (1945), Loekhart (1989a), Spilhaus and Middleton (1973), U.S.
EPA (1987a,b), U.S. Geological Survey (1980), Wexler (1965), WMO (1971). See also, Table 8-2.
•Note that the terms "psychrometer" and "hygrometer" might be used interchangeably in the published literature.
In this guide, the term psychrometer is applied to methods involving evaporation and hygrometer to any other
method of measuring humidity.
8-8
-------
Figure 8.1.3 Sling psychrometer (in motion) for obtaining wet-bulb and dry-bulb temperatures for calculating
relative humidity and dew point (Cameron et al., 1966).
8-9
-------
8. VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
8.1 WATER-RELATED HYDROMETEOROLOGICAL DATA
8.1.4 Humidity Measurement (Hygrometers)
Other Names Used to Describe Device; Mechanical hygrometer, dew-point or frost-point hygrometer, dew cell
or dew probe, electric hygrometers (resistance, capacitance, or Dunmore Cell), diffusion hygrometer, absorption
spectra hygrometers (infrared, ultraviolet, alpha radiation).
Uses at Contaminated Sites: Estimating effective air temperature when it is very hot; hygrometers required for
several micrometeorological evapotranspiration methods (profile, eddy correlation, mass transfer).
Device Description: Hygrometers* include a wide variety of instruments that measure humidity by methods other
than evaporative effects on temperature (psychrometry, previous section). Mechanical hygrometer: Operates on
a similar principle to a bi-metal thermometer (Section 8.1.1), except that materials with differing response to air
moisture (hair, wood, and natural and synthetic fibers) are used. Mechanical hygrometers usually are read
manually, but can be attached to chart recorders. Dor-point and frost-point hygrometers measure the
temperature at which dew or frost condenses from the air on a cooled surface, usually a polished mirror. The
temperature can be converted into vapor pressure from vapor-pressure formulations or tables. For relative
humidity, the dry-bulb temperature also must be measured, and measurement of atmospheric pressure is required
for calculating the mixing ratio. Dew cells operate on the principle that the equilibrium vapor pressure of a
saturated solution is a function of the temperature of the solution. The dew cell consists of a temperature sensor
surrounded by a wick impregnated with a saturated solution of a salt, such as lithium chloride. A control circuit
maintains the solution at the temperature at which the equilibrium vapor pressure of the solution is equal to the
vapor pressure of the ambient air. The output from the sensor is indicated on a dial or is recorded on a chart,
which is calibrated in terms of the dew-point temperature of the ambient air. Figure 8.1.4 illustrates a typical
dew cell sensor housing and transmitter. Electric hygrometers measure changes in resistance or capacitance of
a thin film of hygroscopic material. Most instruments consist of a sensor and a measuring circuit with the output
indicated on a meter or recorded. The response of the sensor is an empirical function of relative humidity and
temperature. Diffusion hygrometers involve the diffusion of moisture through porous membranes. Absorption-
spectra hygrometers use the absorption spectra of water vapor, in response to infrared, ultra-violet, or alpha
radiation.
Device Selection Considerations: Mechanical hygrometers are simple and inexpensive, but the least accurate of
available methods. Dew-/frost-point hygrometers are the most accurate of available methods. Dew cells are less
accurate than sling psychrometers, but can be adapted for automatic data collection. Electric hygrometers are
comparable to dew cells in terms of accuracy, allow automatic data collection, and have the added advantage
being able to measure a somewhat wider range of relative humidity. Diffusion and absorption spectra
hygrometers are very accurate but require frequent attention and are expensive to purchase and maintain.
Frequency of Use: Mechanical hygrometers are widely used when a high degree of accuracy is not required.
Diffusion and absorption spectra hygrometers are used primarily for specialized research purposes
Standard Methods/Guidelines: ASTM (1982,1983,1985b).
Sources for Additional Information: Berry et al. (1945), Lockhart (1989a), Spilhaus and Middleton (1973), U.S.
EPA (1987a,b), U.S. Geological Survey (1980), Wexler (1957, 1965), Wexler and Brombacher (1951), WMO
(1971). See also, Table 8-2.
* Note that the terms "psychrometer" and "hygrometer" might be used interchangeably in the published literature.
In this guide, the term psychrometer is applied to methods involving evaporation and hygrometer to any other
method of measuring humidity.
8-10
-------
Figure 8.1.4 A typical dew cell sensor housing and transmitter (Lockhart, 1989a).
8-11
-------
8. VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
8.2 OTHER HYDROMETEOROLOGICAL DATA
8.2.1 Air Therm ome try (Manual)
Other Names Used to Describe Device: Liquid-in-gl ass thermometer; deformation thermometers: Bi-metallic (flat
spiral, single helix, multiple helix) and filled systems/Bourdon tubes (liquid-filled, vapor-pressure systems, gas-
filled systems, mercury-in-steel).
Uses at Contaminated Sites: Measuring air temperature for calculating evaporation and relative humidity, health
and safety monitoring for potential heat or cold stress.
Device Description; Liquid-in-glass thermometer: Liquid in a sealed glass tube expands and contracts in
response to changes in temperature, and changes in the level read from a calibrated scale. The most common
Hquid-in-glass thermometer is the mercury thermometer (Figure 8.2. la), which measures to -38,9°C or -38.0°F.
Other liquids can be used if extremely low temperatures must be measured (spirit thermometers, ethyl alcohol
freezes at -117°C, and mercury-thallium thermometers record to -59°C). Deformation Thermometers: Metals
with different coefficients of expansion (bl-metalllc, Figure 8.2.1b), or filled systems in which liquid, gas, or
mercury in a sealed, coiled metal tube (Bourdon tube, Figure 8.2. Ic), expand and contract in response to
temperature changes, which are recorded by a moving pointer or pen on a calibrated scale. The accuracy of
filled-systems depends on the extent to which the differential responses of different components in the system
are compensated for. The most accurate types have full compensation, others provides for compensation of the
detecting element only. See section 8.1.4 for discussion of radiation shields for air temperature measurements.
Bi-metallic and fillcd-system thermometers can be used for continuous recording of temperature changes by
attaching them to a rotating drum recorder.
Device Selection Considerations; Unless required data can be obtained easily and cost-effectively with manual
temperature readings, these methods are not recommended. Llquid-ln-Glass Advantages; (1) Have a simple
design; (2) are easy to use; (3) are inexpensive; and (4) are accurate. Uquid-in-Glass Disadvantages: (1) Are
very fragile; (2) have a relatively long tune constant (the time required to respond to a temperature change is
relatively long). Bimetallic Advantages: Are rugged. Bimetallic Disadvantages: (1) Severe mechanical shock or
vibration can cause distortion resulting in large shifts in their calibration; (2) have time constant about the same
as liquid-in-glass thermometers; and (3) are less accurate and more expensive the liquid-in-glass thermometers.
Filled System Advantages: (1) Fundamental simplicity allows rugged construction; and (2) bulb and detection
element can be separated by some distance. Filled System Disadvantages: (1) Are sensitive to severe shock,
vibration, or other forms of mechanical abuse; and (2) capillary tube is not highly flexible or convenient to
handle.
Frequency of Use; Liquid-in-glass thermometers are commonly used for monitoring temperature conditions under
which field personnel are operating.
Standard Methods/Guidelines: ASTM (annual).
Sources for Additional Information: Brock and Nicolaidis (1984), Hardy and Fisher (1972-Chapter 1), Lockhart
(1989a), Meteorological Office (1956-Chapter 1), Spilhaus and Middleton (1973), National Weather Service
(1975-Chapter A.9), Stevens et al. (1975), Thompson et al. (1989), U.S. Geological Survey (1980), WMO (1971-
Chapter 4,1974-Chapter 4).
8-12
-------
Scale
ffllB
Capillary Tube
I
Bulb
(a)
/
Capillary
(c)
Figure 83.1 Manual thermometers: (a) LJquJd-ln-glass; (b) Deformation thermometer with helical-type bimetal
elements; (c) Deformation thermometer with Bourdon tube (Stevens et aL, 1975).
8-13
-------
8. VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
8.2 OTHER HYDROMETEOROLOGICAL DATA
8.2,2 Air Thermometiy (Electric)
Other Names Used to Describe Device: Thermocouple, wire bobbin probe, wire resistance probe, wire bobbin
bulb, wire resistance bulb, thermistor.
Uses at Contaminated Sites: Measuring temperature of air, soil, and/or water (see also, Sections 1.6 and 3.5,2).
Device Description; A thermocouple is a circuit made of two dissimilar metals (See Rgure 1.6.1). A current
is produced in the circuit when the two junctions are at different temperatures. Maintaining one junction at a
known temperature and exposing the other allows sensitive and accurate measurement of temperature, provided
that the temperature is calibrated. The two major types of electrical-resistance thermometers are: (1) Metallic
resistance thermometers, which pass an electrical current through a wire (platinum and nickel-iron being the
most commonly used wires), the resistance of which is proportional to temperature; and (2) thermistors, which
are glass insulated semiconductors with a negative coefficient of resistance such that electrical resistance varies
sharply with changes in temperature. For all types of thermometers, measurement of ambient air temperature
requires some form of shielding so that the air temperature measurements are not influenced by radiant heat.
Figure 8.2,2 provides examples of 14 types of radiation shields.
Device Selection Considerations; All electrical temperature measuring devices are well suited for electronic data
logging. Thermocouples or thermistors are the recommended method for temperature measurement when
automatic data recording is desired. Thermocouple Advantages: (1) Can be separated a considerable distance
from the measuring instrument; (2) have very rapid response time (slower in water because they have to be
cased); and (3) are relatively inexpensive. Thermocouple Disadvantages: (1) Measuring instruments used with
thermocouples are relatively expensive; and (2) insertion of electric leads of different metals between the
thermocouple and the measuring can cause errors as a result of extraneous voltages. Resistance Thermometer
Advantages: (1) Both types can be separated a considerable distance from the measuring instrument; (2) metallic
resistance thermometers are more sensitive to small temperature changes than thermocouples; and (3)
thermistors are less expensive that metallic resistance bulbs and even more sensitive. Resistance Thermometer
Disadvantages: (1) Metallic thermometers have slightly longer response time than thermocouples to changes in
temperature; and (2) thermistor's response to temperature might change with time, requiring reoalibration.
Frequency of Use: Thermistors and thermocouples are most commonly used.
Standard Methods/Guidelines: ASTM (annual).
Sources for Additional Information: Brock and Nicolaidis (1984), Hardy and Fisher (1972-Chapter 1), Lockhart
(1989a), Meteorological Office (1956-Qsapter 1), Spilhaus and Middleton (1973), National Weather Service
(1975-Chapter A.9), Stevens et al. (1975), Thompson et al. (1989), U.S. Geological Survey (1980), WMO (1971-
Chapter 4,1974-Chapter 4).
8-14
-------
AES
•• —
Stevenson S
f
cree
CCIW Parallel Pie Plate Shield
AES Parallel Plate
Teledyne Aspirated
Radiation Shield
AES Aspirated
Stevenson Screen
Israeli Thaller Shield
Jt' ^^^. /"utt.Mfc
Kahl Self-Aspirating Shield
TT
Gill Naturally
Ventilated Shield
Ciimat Motor Aspirated Shield
Modified Rames Shield
AES Marine Shield
AES Dual Aspirated Psychrometer
Curved Plate Shield
EG&G Dew Point
Hygrometer Shield
Gill Aspirated Shield
Figure 8JJ Examples of various types of radiation shields for air temperature measurements (Lockhart, 1989a,
after McKay and McTaggart-Cowan, 1977).
8-15
-------
8. VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
8.2 OTHER HYDROMETEOROLOGICAL DATA
8.2.3 Wind Speed
Other Names Used to Describe Device: Cup/bridled cup, windmill (air meter, propeller/aerovane), pressure
anemometers (hand-held/pith-ball wind meter, Dines),hot-wire anemometer, acoustic/sonic anemometer, contact
anemometer, condenser-discharge anemometer.
Uses at Contaminated Sites; Evaluating transport of atmospheric pollutants or dust from disposal sites; evaluating
evaporation rates; evaluating wind chill for field work in the winter.
Device Description; Numerous specific types of anemometers have been developed to measure wind speed. Six
major types of anemometers are described here. Cup anemometers consist of three or four cups mounted around
a vertical axis on radial arms at equal angles, which allow the anemometer to be equally responsive to wind in
any direction (Figure 8.2.3). The vertical shaft transfers the motion of the cups either to a counter or to a
generator for electronic recording. Windmill anemometers include; (1) Propeller anemometers with helicoidal
vanes, which rotate about an axis and drive a miniature generator with an electrical output that is proportional
to the wind speed, and (2) air meters with fiat vanes that records the number of linear feet (or meters) of air
that has passed the instrument during its exposure. Propeller anemometers are usually combined with a wind
vane to maintain an orientation directly into the wind, but sometimes are built with three propellers oriented at
right angles to each other to measure horizontal and vertical components separately. Manually operated
pressure anemometers consist of a thin tube open at one end. The pressure change produced by air moving
across the opening is proportional to the wind speed. In a variant of this, a pith ball rises in a graduate tube.
Hot-wire and acoustic (or sonic) anemometers are very precise instruments, which measure velocity by measuring
the change in resistance of a heated tungsten wire and accurately measuring sound velocity, respectively. A
contact anemometer actuates an electrical contact at a rate that depends on windspeed. The number of contacts
during a given time is indicated by the number of flashes of a lamp or sounds of a buzzer. A condenser-
discharge anemometer is a type of contact device with an electrical circuit that indicates average windspeed.
Device Selection Considerations: Propeller and cup anemometers are the most common types because they are
rugged, reliable, and accurate to within a few percent or less. Both are well suited for electronic data logging.
Propeller-type anemometers can measure wind speeds up to 200 miles per hour, cup-type anemometers measure
up to 100 miles per hour and can be constructed to be extremely sensitive to slight changes in speed. Pressure
anemometers are not recommended unless manual measurement is acceptable. Hot-wire and acoustic
anemometers are for specialized applications where accurate measurement of turbulence is required.
Frequency of Use: Both propeller and cup-type anemometers are widely used.
Standard Methods/Guidelines: ASTM (1985a, 1990).
Sources for Additional Information: Hardy and Fisher (1972-Chapter 3), Lockhart (1989a), Meteorological
Office (1956-Chapter 5), National Weather Service (1975-Chapter A10),Spilhaus and Middleton (1973-Chapter
6), Thompson et a], (1989), U.S. EPA (1987a,b), U.S. Geological Survey (1980). See also, Table 8-2.
8-16
-------
Figure 8.2.3 Portable hand cup anemometer for measuring windspeed (Cameron et aln 196G).
8-17
-------
8, VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
8.2 OTHER HTOROMETEOROLOGICAL DATA
8.2.4 Wind Direction
Other Names Used to Describe Method: Wind cone/sleeve/sock, vanes (flat-plate, aerodynamic-shaped, splayed,
bivanes).
Uses at Contaminated Sites: Assessing possible directions of air-borne contaminant transport and deposition.
Method Description: Wind direction can be determined visually by observing the direction of movement of any
freely moving substance or object, such as smoke or ribbons attached to poles. Wind cones are made of a
tapered fabric sleeve, which is shaped like a truncated cone and pivoted to a standard at its larger end. Various
types of wind vanes also can serve as indicators of wind direction. A flat-plate vane is mounted on a horizontal
shaft, which is attached to a vertical bearing shaft that is free to rotate (Figure 8.2.4). Aerodynamic-shaped vanes
use an airfoil section instead of a flat plate, and are usually heavier than the flat plate type. Splayed vanes have
two flat plates joined at a small angle at the end of the horizontal shaft, and react to small changes in the wind
somewhat better than flat-plate or aerodynamic vanes, Bivanes consist of two light-weight airfoil sections
mounted orthogonally on the end of a counter-balanced rod, which is free to rotate in the horizontal and vertical
planes and is used in turbulence studies to record horizontal and vertical components of wind. Wind roses can
be developed from manual recording of wind direction at specified intervals or automatic recorders attached to
wind vanes. The frequency with which the wind blows in various directions can be useful information in
designing soil sampling plans where a point source has released contaminants to the air that have been deposited
at downwind locations.
Method Selection Considerations; Some kind of wind direction indicator should be used any time site activities
could result in release of contaminants to the air.
Frequency of Use: Commonly used for health and safety purposes; less common for obtaining
hydrometeorological applications.
Standard Methods/Guidelines: ASTM (1985a).
Sources for Additional Information: Hardy and Fisher (1972-Chapter 3), Lockhart (1989a), Meteorological Office
(1956-Chapter 5), National Weather Service (1975-Cbapter A10), Spilhaus and Middleton (1973-Chapter 6),
Thompson et al. (1989), U.S. EPA (1987a,b), U.S. Geological Survey (1980). See also, Table 8-2.
8-18
-------
i
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10
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1£
10-
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1
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/
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o
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•\
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ice (50% recovery)
Thies (experimental)
697 grams
MR! 1074
656 grams
Thies
600 grams
Climatronics F460
251 grams
MSI (experimental)
191 grams
Climet
170 grams
Vaisala
92 grams
MSI (experimental)
72 grams
012 5
Distance (m) at 5 m/s
Meteorological Standards Institue
March 5,1986
figure 8.2.4 Sample of dynamic response of some wind vanes (Lockhart, 1989&).
8-19
-------
8. VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
8.2 OTHER HYDROMETEOROLOGICAL DATA
8.2.5 Atmospheric Pressure
Other Names Used to Describe Method: Mercury barometers (Fortin-type, fixed-cistern type), aneroid
barometer, altimeter.
Uses at Contaminated Sites: Interpreting ground-water level measurements; required for several methods of
measuring or estimating evapotranspiration using micrometeorological method (Section 8.4); required for
calculations involving humidity measurement (Sections 8.1.3 and 8.1.4); estimating altitude in remote locations.
Method Description: There are two major types of instruments for measuring atmospheric pressure. Mercury
barometers use changes in the level of mercury in a container to measure changes in atmospheric pressure. The
Fortln-type mercury barometer is used by the National Weather Service as the official station pressure
instrument A cistern containing mercury has a pointer made of noncorrodible materials, such as ivory or
stainless steel, projected down from the roof. The level of mercury within the cistern is raised or lowered by
turning a, thumb screw beneath the cistern, until it just touches the tip of the pointer (called the ivory point, index
point, or zero point). Pressure is read from mercury in a graduated column connected to the cistern that can
be read to a thousandth of an inch or a tenth of a millibar with a vernier on the scale. Aneroid barometers
measure pressure by the response of a capsule that is practically evacuated of gas. The response can be
measured either by deflection of a spring connected to the cell, by the change in curvature of a Bourdon tube,
or by a change in natural resonant frequency. The barometer must be temperature compensated at a given
pressure level by adjusting the residual gas in the aneroid or by a bimetallic-link arrangement. Altimeters are
aneroid barometers that have a pointer and a dial calibrated for elevation or pressure readings (Figure 8.2.5).
Precision aneroids can be of the direct-reading kind, similar to altimeters, but are designed for more accurate
measurements. A relatively recent development is the accurate digital-readout precision aneroids, which use
electronic indicators rather than mechanical linkages. Sensor types used in these instruments can be a fused
quartz Bourdon tube (quartz barometer), an aneroid capsule with which the natural frequency as related to
pressure is measured (vibrating diaphragm barometer), or the conventional aneroid capsule in which spring
deflection is measured.
Method Selection Considerations: Fortin barometers are very accurate (can be read to a thousandth of an inch),
but require permanent installation. Aneroid barometers have the main advantage of being portable.
Disadvantages include requirements for periodic calibration against mercury barometers, and the requirement
for temperature compensation.
Frequencyof Use: Not commonly used at contaminated sites.
Standard Methods/Guidelines: ASTM (1984c).
Sources for Additional Information; Brock and Nicolaidis (1984), Lockhart (1989a), U.S. Geological Survey
(1980), U.S. Weather Bureau (1963b), National Weather Service (1975-Chapter 8), WMO (1971).
8-20
-------
Figure 8.2.5 Rugged precision altimeter for measurement of elevation (Cameron et al, 1966).
8-21
-------
8. VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
8.2 OTHER HYDROMETCOROLOGICAL DATA
82.6 Solar Radiation (Pyranoroeters)
Other Names Used to Describe Methods: Thermopile, photovoltaic, bimetallic (Robitzsch-type, actinograph),
thermo-electric pyranometers, incident solar radiation meter, solarimeter.
"Uses at Contaminated Sites: Global radiation data are needed for some empirical and physically-based equations
for estimation of evaporation and evapotranspiration (Sections 8.4.1 and 8.4.2).
Device Description: A pyranometer measures global solar radiation (direct plus diffuse radiation falling on a
horizontal surface, see Figure 8.2.6a), and is the most commonly measured type of radiation. It does not
measure terrestrial or atmospheric radiation. Most pyranometers incorporate a sensor that responds to the
temperature difference caused by differential absorption of radiation of a black surface and a white surface
(Figure 8.2.6b). The most commonly used temperature sensor is a thermopile, but bimetallic sensors also can
be used. Photovoltaic pyranometers use silicon cells that respond to solar radiation by generating an electric
current, which is proportional to the amount energy hitting the cell. WMO (1971) has established criteria for
classification of pyranometers according to physical response characteristics, with 1st class being the most
sensitive and 3rd class being the least sensitive. A net pyranometer measures the net upward and downward solar
radiation flux through a horizontal surface. A spherical pyranometer measures solar radiation on a spherical
surface.
Device Selection Considerations: Thermopile Advantages: (1) A variety of instruments of this type have been
developed and are commercially available; (2) are the most accurate and responsive of available instruments
(most are 1st or 2nd class); (3) the thermopile pyranometer is the standard instrument to use if direct
measurements are required; and (4) can be readily configured for output to an electronic recording device.
Bimetallic Advantages: (1) Are simple; (2) can be attached to a chart recorder for continuous recording; and (3)
are suitable for measurements in which daily or longer interval data are acceptable. Bimetallic Disadvantages:
(1) Are relatively inaccurate (3rd class) compared to thermopile pyranometers; (2) have relatively slow response
time; and (3) require use of temperature-correction factor or some temperature compensation mechanism.
Photovoltaic Advantages: (1) Are simple and inexpensive; (2) have a nearly instantaneous response; (3) have high
current output, which can be used for automatic data recording; and (4) use can be acceptable as long as
integration periods are 1 day or longer. Photovoltaic Disadvantages: Least accurate of available methods due
to variations in sensitivity to different wavelengths.
Frequency of Use; Rare. Often estimated from nearby meteorologic station or from charts or maps.
Standard Methods/Guidelines: —
Sources for Additional Information: Brock and Nicolaidis (1984), Carter et al. (1977), Coulson (1975), Latiraer
(1972), Lockbart (1989a), Monteith (1972), Norris (1974), Selcuk and Yellott (1962), Thompson et al. (1989),
U.S. Army (1975), U.S. Geological Survey (1980), WMO (1971). See also, Table 8-2.
8-22
-------
PYRANOMETEfl
MEASURES-*"- GLOBAL • DIRECT PLUS Diffuse RADIATION ON A HORIZONTAL suRMet
DIFFUSE ' SCATTERED BEAIM SOLAR RADIATION
DIRECT = PARALLEL BEAM RADIATION FROM THS SUN
PLUS SOME
CIRCUMSOLAR • THAT PORTION OF SCATTERED SOLAR RADIATION
PARALLEL TO THE DIRECT 86AM
PVRHELIOMITER
TRACKING MOUNT KEEPS
INSTRUMENT ALIGNED
WITH THE SUN
ATMOSPHERE
TURBIDITY . A MEASURE
OF TH( CLARITY OF THE
ATMOSPHERE
HORIZON
Sensing
Element
Guard Disc
\
(a)
Precision Ground &
Polished Glass Dome
(Frequently Double!
^Leveling
111 ii !LJ Screw
It
(b)
Figure 8^.6 Measurement of solar radiation: (a) Kinds of insolation and types of measuring instruments (U.S.
Geological Survey, 1980); (b) Features of a typical pyranometcr (Carter et al., 1977).
8-23
-------
8, VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
83. OTHER HYDROMETEOROLOGICAL DATA
8.2.7 Solar Radiation (Other Radiometers)
Other Names Used to Describe Method: Net radiometer/pyrradiometer, pyrheliometer (Angstrom electrical
compensating, silver-disk, absolute, operational)
XJses at Contaminated Sites: Measuring net radiation flux for energy budget measurements of evapotranspiration
(Section 8.4.4).
Method Description: Other radiometers measure different types of radiation. Pyrradiometers measure total
radiation falling on a horizontal surface (combined solar, atmospheric and terrestrial radiation), and are similar
in design to pyranometers (Section 8.2.6). Net pyrradtometers or radiometers are designed to measure the
difference between downward and upward total radiation. Most commercially available net radiometers are made
with a small disc-shaped thermopile covered by polyethylene hemispheres. Pyrheliometers measure the intensity
of direct solar radiation and normal incidence, and are mounted in trackers that keep the devices pointed toward
the sun as the traverses from east to west (Figure 8.2.6a and 8.2.7).
Method Selection Considerations: Unlikely to be used unless an energy budget method for computing
evapotranspiration is used.
Frequency of Use: Uncommon for site characterization. Net radiometers are sometimes used in air-pollution
related programs.
Standard Methods/Guidelines: ASTM (1984b).
Sources for Additional Information; Brock and Nicolaidis (1984), Carter et al. (1977), Coulson (1975), Latimer
(1972), Lockhart (1989a), Monteith (1972), Norris (1974), Selcuk and Yellott (1962), Thompson et al. (1989),
U.S. Army (1975), U.S. Geological Survey (1980), WMO (1971). See also, Table 8-2.
8-24
-------
Pyrheh'ometer
Declination Adjustment
24 hr. Dial
Figure 8.2.7 Features of a typical pyrheHoaieter and tracking mount. (Carter et al, 1977).
8-25
-------
8. VAJDOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
83 EVAPOTRANSPIRATION (WATER BALANCE METHODS)
83.1 Lysimeters
Other Names Used to Describe Method: Pan/fiUed-in lysimeters (nonweighable, weighing, hydraulic/floating),
monolith/soil block lysimeter, monolith/soil block evapotranspirirneter, microlysimeter.
Uses at Contaminated Sites: Measuring evaporation from vegetated soil (pan lysimeter) or unvegetated soil
(microlysimeter), in order to separate out the transpiration component of evapotranspiration (ET).
Method/Device Description: A lysimeter consists of a block os soil, usually planted with some vegetation that
is enclosed in a container, which isolates the lysimeter hydrologically from its surroundings. Lysimeters used for
sampling soil solutions are discussed in Section 93.1 (Free-Drainage Samplers). There are three main types of
flllcd-in lysimeters, in which disturbed soil is used for measuring ET: (1) Nonweighing lysimeters (Figure 8.3. la);
(2) hydraulic or floating lysimeters, which rest on rubber bap or other water-filled tubing or bolsters that allow
recording of changes in pressure in response to changes in weight (Figure 83.Ib); and (3) weighing lysimeters,
in which changes in moisture contents are measured by changes in the weight of the soil block (Figure 8.3. Ic).
A typical pan lysimeter is 1 meter in diameter (range from 0.1 to 10 square meters) and range from 0,5 to 3
meters deep. Soil and vegetation representative of the area are placed in the lysimeter with the surface level the
same as the surrounding soil. Monolith lysimeters are constructed of undisturbed soil. In nonweighing
lysimeters, changes in soil moisture are determined by various soil moisture determination methods, such as
neutron-moisture logging, gamma-ray transmission, electrical resistance blocks, or tensiometers (see Section 63).
Weighing and hydraulic lysimeters measure changes in moisture content by recording changes in the total weight
of the lysimeter over time with a sensitive scale or transducer. Most lysimeters record ET over relatively large
areas. An exception is the mlcrolysimeter, where a thin-walled cylinder is pushed into the soil, the sample is
removed, sealed at the bottom, and weighed. The sample is replaced in the original hole to subject it to the same
evaporative conditions as the soil, and is removed periodically for reweighing (Figure SJ.ld).
Method Device Selection Considerations: Pan Lysimeter Advantages: (1) Probably are the most accurate of the
water balance methods; (2) allow measurement of ET from a medium or large area; and (3) cost is moderate
to low. Pan Lysimeter Disadvantages: (1) Are relatively complicated to install; and (2) must be surrounded by
a considerable area of the same vegetation to avoid horizontal diversion in energy for ET. Microlysimeter
Advantages: (1) Measure evaporation under a wide range of soil moisture conditions; and (2) are inexpensive
and easy to use. Microlysimeter Disadvantages: Have small area! coverage.
Frequency of Use: Lysimeters are a commonly used method, if field measurement of ET is required.
Standard Methods/Guidelines; Pan lysimeter: Aboukhaled et al. (1982); Microlysimeter: Boast (1986).
Sources for Additional Information: Dunne and Leopold (1978), Sharma (1985), Thompson et al. (1989), U.S.
Geological Survey (1982), Veihmeyer (1964). See also, Table 8-3.
8-26
-------
Inflow
measured
«*£»--*
iK^+r*-'
J*.' "•"•fff^'i ——-• -
!sgte
Manometer „
Spring F X'
balance V,
Drainage monitored
(C)
(a)
(d)
Figure 8J.1 Lysimetric methods:* (a) NonweigWng, drainage type; (b) Weighing float type; (c) Spring-balance
weighing type (Dunne and Leopold, 1978, firom: Water in Environmental Planning by Dunne and Leopold,
Copyright © 1978 by W.H. Freeman and Company, reprinted with permission); (d) Procedure for
microlysimeter determination of evaporation (Boast, 1986, after Boast and Robertson, 1982, by
permission).
8-27
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8. VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
8 J EVAPOTRANSPIRATION (WATER BALANCE METHODS)
83.2 Soil Moisture Budget
Other Names Used to Describe Method: —
Uses at Contaminated Sites: Measuring evapotranspiration (ET).
Method Description; Soil moisture content is measured over the entire root zone using one or more methods
described in Section 63, before and after irrigation events. Assuming that irrigation brings the soil to field
capacity, the initial moisture content after irrigation will be the available water capacity of the root zone. The
evapotranspiration rate is the difference in moisture content between the two sampling periods divided by the
time interval,
Method Selection Considerations: Advantages: Relatively simple method with the added advantage that soil
moisture monitoring is often required for other objectives (see Section 6). Disadvantages: (1) Requires uniform
soil type and texture and a water table deep enough that it does not influence the soil root zone; (2) precipitation
events will disrupt the method; and (3) calculation of ET requires adjustments (modulation) to account for the
fact that ET rates might change as soil moisture decreases.*
Frequency of Use: Probably the oldest and most commonly used method for determining ET.
Standard Methods/Guidelines: —
Sources for Additional Information: Thompson et al. (1989), U.S. Geological Survey (1982), Veihmeyer (1964).
See also, Table 8-3.
•There is not universal agreement on the need for such corrections (see, for example, Veihmeyer and
Hendrickson, 19SS), although Gray (1973) reviews some of the literature on this question and recommends that
"modulated" values of ET be used when doing soil moisture budget calculations. See also, references identified
in Table 8-3.
8-28
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8. VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
83 EVAPOTRANSPIRATION (WATER BALANCE METHODS)
8,3.3 Water Budget Methods
Other Names Used to Describe Method: River basin water balance, inflow-outflow measurement, integration
method.
Uses at Contaminated Sites: Estimating evaporation and evapotranspiration (ET).
Method Description: Inflow-outflow method: All inflows (precipitation), outflows (surface runoff, ground water
leaving basin), and changes in storage in a watershed, are measured or estimated except for ET. ET is calculated
using a water-balance equation. Figure 83.3 illustrates the components of the water balance equation. Figure
8.4.1 compares evaporation from a lake in Canada, which was computed using a water budget, to six other
methods. Integration method: Evaporation and ET for an area h calculated by the summation of the products
of ET for each crop times its area, plus the ET of natural vegetation times its areas, plus water-surface
evaporation times its surface areas, plus evaporation from bare land times its areas. This method requires
knowledge of unit ET and the areas of various classes of agricultural crops, natural vegetation, bare land, and
water surfaces. Often this can be done using sequential remote sensing data (satellite, airphotos) to identify
crop/vegetation patterns (see Raymond and Rezin, 1989, for a recent example of this approach).
Method Selection Considerations: Advantages: Water budget methods can be manageable to difficult, with
moderate to low cost. Disadvantages: (1) Small errors in measuring or estimating various components of the
water-balance equation (such as deep percolation) can cumulatively result in a large error in the calculated ET
value; (2) suitable for application to a specific site only if ET at the site can be assumed to be close to the
average ET for the watershed or area of interest; and (3) use of water budgets to calculate evaporation from
lakes is not recommended for time periods of less than 1 month in duration if the estimate is expected to be
within plus or minus 5 percent of the actual amount (Gray, 1973).
Frequency of Use: Commonly used in hydrologic studies; rarely used at the site-specific level.
Standard Methods/Guidelines: —
Sources for Additional Information: Bras (1990), Dunne and Leopold (1978), Rosenberg et ah (1983), Sharma
(1985), Thompson et al. (1989), U.S. Geological Survey (1982), Veihraeyer (1964). See also, Table 8-3.
8-29
-------
AET + OF + ASAf + LOWS + GWR
AET
Figure 833 Water balance equation and schematic diagram for a hillside or a small catchment (Dunne and
Leopold, 1978). P SB precipitation; I = interception; AET — actual evapotranspiration; OF = overland
flow; ASM — change in soil moisture; AGWS = change in ground-water storage; GWR = ground-water
outflow. Solving for ET requires measurement or estimation of other elements in the equation.
8-30
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8. VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
83 EVAPOTRANSPIRATION (WATER BALANCE METHODS)
83.4 Evaporation Pans
Other Names Used to Describe Method: Class A land pan, U.S Bureau of Plant Industry sunken pan, Colorado
sunken pan, U.S. Geological Survey floating pan, insulated evaporation pan.
Uses at Contaminated Sites: Estimating of evaporation from water impoundment surfaces; can also be used to
indirectly estimate potential evapotranspiration (ET) (Veihmeyer, 1964).
Method Description: The standard U.S. Weather Service Class A pan is built of unpointed galvanized iron. It
is 4 feet in diameter, 10 inches deeps, and mounted 12 inches above the ground on a wooden frame (Figure
8.3.4a). The rate of evaporation of water from the pan is measured. Precipitation also must be measured to
correct for additions to the pan. A pan coefficient is used (generally from .70 to .75) for large bodies of water,
to estimate actual evaporation from the water body of interest (Figure 8.4.1 illustrates the tendency of Qass-A
pans to overestimate actual evaporation). The insulated evaporation pan is constructed of fiberglass with 8
centimeters of freon-blown polyethylene (Figure 8.3.4b). The insulation reduces effects of climate and season
on variability of coefficients used to calculate actual evaporation. Other commonly used types of evaporation
pans include the U.S. Bureau of Plant Industry sunken pan, Colorado sunken pan, and U.S. Geological Survey
floating pan.
Method Selection Considerations: Advantages: (1) The Class A pan is the standard method for measuring
evaporation; (2) data on pan evaporation for the vicinity of a site in question might be published or available;
and (3) insulated pans allow use of standard coefficients. Disadvantages: (1) Several years of data are required
to characterize seasonal and annual variations in evaporation; (2) use of incorrect pan coefficient can bias results;
(3) coefficients measured using noninsulated evaporation pans can vary with location, climate, or season; (4)
cannot be used when temperature is below freezing; and (5) sunken pans are difficult to install and maintain,
they tend to collect trash, leaks are hard to detect, and it is difficult to evaluate heat loss from the pan to the
surround soil. Floating pans probably give the best estimates of lake evaporation (see Figure 8.4.1), but are not
widely used due to operational difficulties (inaccessibility and water splashing into or out of the pan).
Frequency of Use: Uncommon for site specific field measurement. Other methods usually are available for
estimating evaporation. Pan evaporation data are commonly used to estimate potential ET.
Standard Methods/Guidelines: Class A pan: National Weather Sendee (1972). Insulated pan: U.S. Geological
Survey (1982).
Sources for Additional Information: Dunne and Leopold (1978), Thompson et aL (1989), U.S. Geological Survey
(1982), Veihmeyer (1964). See also, Table 8-3.
8-31
-------
(a)
water surfa
insulatii
stilling well
\
12.7 cm white
j. pigment
gage
(b)
Figure 83.4 Evaporation Pans: (a) U.S. Weather Bureau Class A land pan (after Veihmeyer, 1964); (b) Cross
section of National Weather Service insulated evaporation pan (U.S. Geological Survey, 1982).
8-32
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8. VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
83 EVAPOTRANSHRATION (WATER BALANCE METHODS)
8.3.5 Evaporimeters and Atmometers
Other Names Used to Describe Method: First-stage evaporimeter, Piche/Bellani/Livingston/Wilde atmometer.
Uses at Contaminated Sites: Evaporimeter: Measuring evaporation from unvegetated soil; Atmometers:
Measuring latent evaporation (mainly a measure of the drying power of the air).
Method/Device Description: Evaporimeter: A fiat, soil-covered tray 0.1 meters in area is connected to a constant
suction water supply (Figure 8.3.5a). The rate of water loss from the water supply equals the evaporation rate.
Atmometer: A water-filled glass tube that has an open end through which water evaporates from a filter paper
(PIche type) or porous plate (Bellani type, Figure 83.5b). The tube supplying water is graduated to read
evaporation in millimeters. Atmometer measurements require different conversion factors related to evaporation
rate and location to estimate evaporation from water bodies.
Method Selection Considerations: Evaporimeter Advantages: Are relatively simple and easy to use. Evaporimeter
Disadvantages: (1) Only measure evaporation during the stage when evaporation equals potential evaporation;
and (2) have small area! coverage. Atmometer Advantages: (1) Are inexpensive; (2) are portable and easily
maintained and installed; (3) are representative of conditions affecting moisture loss from plants; and (4) require
a small amount of water to operate. Atmometer Disadvantages (1) Value for estimating evaporation loss from
water bodies is questionable because they are more responsive to windspeed than radiant energy; (2) observations
are difficult to interpret; (3) Class-A pans are better for estimating evaporation from lakes; and (4) cannot be
used when temperature is below freezing.
Frequency of Use: Evaporimeters: Uncommon. Generally measurement or estimates of total evapotranspiration
will meet the requirements for most water budget calculations. Atmometers commonly are used in agricultural
studies but their use has not been reported at contaminated sites.
Standard Methods/Guidelines: --
Sources for Additional Information: Evaporimeters: Adams et al. (1976), Arkin et al. (1974), Boast (1986).
Aunometars: U.S. Geological Survey (1982), Veihmeyer (1964). See also, Table 8-3.
8-33
-------
nm
mm
„ 200
1-
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u
it
ii
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H
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n 0.8
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it
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blotting "f" _ .
DOoer / 3#-pof» m«mbran«
' fllt«r, pap«r
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icratn
3.2-mm I.d.
copper tubing
DIFFERENT
PARTS OF THE
DRAWING ARE
TO DIFFERENT
SCALES
flnyl tubing
"to eon»tant-h»od watwr column
(a)
(b)
Figure 8.3.5 Evaporation measurement instruments: (a) Top view and cross section of the first-stage evaporimeter
tray (Boast, 1986, after Arkin et al, 1974, by permission); (b) Set of black-and-white Livingston
atmoraeters (after Veihmeyer, 1964).
8-34
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8, VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
83 EVAPOTRANSPIRATION (WATER BALANCE METHODS)
8.3.6 Chloride Tracer
Other Names Used to Describe Method: --
Uses at Contaminated Sites: Indirectly estimating evapotranspiration (El).
Method Description: The chloride content of precipitation and shallow ground water samples is measured at
intervals to obtain average chloride concentrations of the precipitation and ground water. Annual ET is
calculated by multiplying the ratio of chloride concentration in precipitation to chloride fa ground-water times
the long-term average precipitation.
Method Selection Considerations: The following site conditions need to apply if this method is to be used: (1)
There is a shallow water table; (2) chloride in the ground water comes only from precipitation; and (3) runoff
is negligible. Laboratory analysis of samples is required and collection of precipitation samples results in
moderate to high cost.
Frequency of Use: Uncommon.
Standard Methods/Guidelines: --
Sources for Additional Information: Sharma (1985), Thompson et al. (1989).
8-35
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8. VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
83 EVAPOTRANSPIRATION (WATER BALANCE METHODS)
83.7 Ground-Water Fluctuation
Other Names Used to Describe Method: —
Uses at Contaminated Sites: Indirectly estimating evapotranspiration (ET).
Method Description: Aquifer storage values are measured or estimated, and continuous measurement of water-
level fluctuations are continuously measured or measurements are taken at sufficiently close intervals to plot
diurnal fluctuations in ground-water level (Figure 83.7). Estimation of average ET rates requires continuing
measurements over months. A variant of this approach in Qoodplain areas is to analyze diurnal fluctuations in
stream hydrographs to estimate daily ET rates (Reigner, 1966), or based flow recession curves for monthly
estimates of ET (Langbein, 1942).
Method Selection Considerations: This method requires; (1) A shallow water-table, (2) uniform coarse or
medium soil texture that results in measurable, diurnal fluctuations in water table in response to ET, and (3)
limited precipitation unless precipitation is accurately measured as well. Where conditions are suitable, the cost
is moderate to low,
Frequency of Use; Uncommon.
Standard Methods/Guidelines; Davis and DeWiest (1966).
Sources for Additional Information; Thompson et al. (1989), U.S. Geological Survey (1982), Veihmeyer (1964).
See also, Table 8-3.
8-36
-------
3.29
3.21 II j I { i t I ! J I I I I 1 ! i t I \ I > 1J 1 I I ( I 1 i I i I 3 I 1 I \ M M t i i i
Tuesday Wednesday Thursday Friday
Xerophytes
Figure 83.7 Estimation of evapotranspiration by phreatophytes from daily water-level fluctuations in a water well
(Davis and DeWlesi, 1966, reprinted by permission of John Wiley & Sons, Inc. from Hydrogeology by
S.N. Davis and RJ.M. DeWiest, Copyright © 1966).
8-37
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8. VADQSE ZONE WATER BUDGET CHARACTERIZATION METHODS
83 EVAPOTRANSPIRATION (WATER BALANCE METHODS)
83.8 Other Transpiration Methods
Other Names Used to Describe Method; Enclosures, physico-biological methods, heat-pulse method,
radioisotopes.
Uses at Contaminated Sites: Directly or indirectly measuring the transpiration component of evapotran spiral ion
is not likely to be requited.
Method Description; The transpiration component of evapotranspiration can be measured or estimated by a
number of the methods discussed elsewhere in this section: Lysimeters (Section 83.1, considered one of the best
approach), soil moisture depletion (Section 83.2), mass transfer methods (Section 8.4.3), and energy balance
methods (Section 8.4.4). Other field methods for indirect estimation of transpiration include: (1) Enclosures,
in which changes in air moisture resulting from transpiration are measured; (2) heat-pulse methods, where plants
with woody stems are heated quickly and the rate of ascent of the heated sap is timed; and (3) injecting
radioisotopes into trees and tracing their movement through the plant (see Section 4.4.S for additional
information on radioisotope tracers). Methods for direct measurement of transpiration (such as the use of
phytometeis, photometers, porometers, thermocouple psychrometry, and corona analysis) is generally are done
in the laboratory.
Method Selection Considerations: If transpiration needs to be estimated, iysimeter or soil moisture depletion
methods probably are the best for use with water budget studies.
Frequency of Use: Rare.
Standard Methods/Guidelines: ~
Sources for Additional Information: See Table 8-3.
8-38
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8. VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
8.4 EVAPOTRANSPIRATION (MICROMETEOROLOGICAL METHODS)
8.4.1 Empirical Equations
Other Names Used to Describe Method: Equations are often identified by the names of individuals who
developed the equation.
Uses at Contaminated Sites: Estimating* evaporation and evapotranspiration (ET).
Method Description: Evapotranspiration: Numerous empirical equations have been developed that allow
estimation of potential evapotranspiration (PET) using climatic data, which can be available from nearby weather
stations or charts and maps. Once PET is known, empirical factors based primarily on the type of vegetation
are used to estimate actual evapotranspiration (AET). Three of the most commonly used empirical methods
are described here. Thornthwaite: This equation requires data on mean monthly air temperature. Latitude,
month, and average monthly daylight are required to determine adjustment factors to take into account the total
numbers of days and hours available for ET. The main advantage of this equation is that it allows general
estimates in areas where climatic records and ETdata are limited. Blaney-Criddle: This equation requires mean
monthly temperature, monthly percentage of daylight hours per year, and an empirical coefficient for the month,
which depends on the crop. A modified equation accounts for changes in the sun's zenith angle to correct for
reduced power of the sun's rays during winter, allowing use of a single empirical coefficient for crop/vegetation
type. Jensen-Haise: This equation requires mean air temperature, solar radiation, and the saturated vapor
pressures at the mean maximum and mean minimum temperature for the wannest month of the year. Numerous
other empirical equations have been developed (Table 8.4.1 shows eight of these equations), but the above
mentioned ones are the most commonly used equations. Evaporation equations: A number of empirical
equations have been developed for estimating lake evaporation. Most are based on simple aerodynamic
equations, which require measurement or estimation of: (1) Windspeed, (2) vapor pressure of saturated air at
the temperature of the water surface, (3) actual vapor pressure of air at some height above the water surface,
and (4) empirical constants appropriate to the type of water body. Table 8-3 identifies a number of references
that review and present empirical evaporation equations. Figure 8.4.1 shows calculations of evaporation from
a lake using three empirical formulas (Nordenson-Kohler-Fox, Lake Hefner "upwind formula," and Meyer
formula) with four other methods (Class-A and floating pan, water budget, energy budget, and Penman formula).
It is clear from this figure that empirical formulas can yield good results if the appropriate one is used, but can
be very far off if the wrong formula is used.
Method Selection Considerations: Evapotranspiration Equation Advantages: (1) Is best for developing monthly,
seasonal, or annual consumptive water use values; and (2) is very inexpensive if input data can be obtained from
existing meteorological records. Evapotranspiration Equation Disadvantages: (1) Calculations might not be very
accurate if site conditions are not typical of conditions upon which the equation is based (use of several equations
and comparing the results can be useful for developing an estimated range); (2) should not be used to estimate
short-term (hours to days) variations in ET because no allowance is made for variation in wind and relative
humidity; and (3) equations tend to overestimate water use during vegetation emergence and underestimate water
use for midseason, unless appropriate crop factors are used (such as Blaney-Criddle method). Thornthwaite:
Works best in the central and eastern United States for sod with high moisture content in areas with limited
advection; is inaccurate if short-term (less than one-month) data are used. Blaney-Criddle: Is widely used in the
western United States; requires empirical coefficient for crop or vegetation type (already available for many crops
and vegetation types). Jensen-Haise: Was developed for use with irrigated crops in the western United States.
Evaporation Equation Advantages: Is very simple and allow estimates from standard meteorological data.
Evaporation Equation Disadvantages: (1) Most equations of this type require measurement of the surface
temperature of the body of water, which is difficult to obtain; (2) if mean air temperature is used instead, the
failure to account for effects of adverted energy to the lake on evaporation might cause considerable error
because small errors in temperature induce large errors in the calculations; (3) measurement of wind speed and
vapor pressure must be taken at heights specified in the equation; and (4) results will be inaccurate if the
characteristics of the water body are not similar to the water body for which the empirical constants were
developed.
Frequency of Use: All equations are commonly used. See method selection considerations for geographic
limitations.
8-39
-------
Table 8,4.1 Some Empirical and Physkally-Based Evapotransplratlon Equations
Name
Hedke (Harding et a!., 1930)
I nonv.Tnhnson ( 1942Y
Blaney-Morin (1942)
Tbornthwaite and Wilm (1944)
Penman (1948)
Blaney-Criddle (1950)
Halkias-Veihmeyer-Hendrickson (1955)
Hargreaves (1956)
Date
1030
1042
1042
1044
1048
1050
1055
1056
Period
for U
Annual
Aniiunl
m inoiiths
Montlily
Daily
m months
Monthly
m months
Unit
for U
Feet
Feet
Inches
Centimeters
Millimeters
Inches
Inches
Inches
Equation
U - kll
U - 0.000 15I1//+ 0.8
m
U = A Y p/(U4-/i)
» - '•<•'(«)•
where a = 0.000000075(TB)8 - 0.0000771 (TE)J + 0.01702TjB + 0.40230
.. Alf - 0.27 E
T] =3
A - 0.27
where E = 0.35(ea - e,()(l + O.OOOSios)
H = R(l - r)(0.18 + 0.55S) - B(0.5G - 0.002erf»-«)(0.10 + O.OOS)
m m
U = k y pi = */•' where F = V pi
1 1
U = SD ,.
m
U = y 4» = mean wind velocity at 2 m above the ground in miles/day, or equal to «u (log 0.0/log h), where wi ia measured wind velocity in miles/day at height, h in ft
Source: Veihmeyer (1964)
-------
so
45
40
35
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§
u 20
15
10
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I ' LEGEND
~ — — OBSERVED FLOATING PAN
" WATER BUDGET
OBSERVED CLASS "A" PAN
NORDENSQN KOHLER AND FOX
- . — ENERGY BUDGET
" » LAKE HEFNER "UPWIND' FORMUL
MEYER FORMULA
• PENMAN FORMULA
(1) ASSUMED STABILITY PARAMETER
n =0-334
(2) MEASUREMENTS FOR RESERVOIR
STARTED APRIL 26 th.
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XPRIL MAY JUNE JULY AUG. SEPT OCT.
Figure 8.4.1 Comparison of 1961 cumulative measured and computed evaporation for Weyburn reservoir, southern
Saskatchewan, using eight methods (McKay and Stichling, 1961).
8-41
-------
Standard Methods/Guidelines: —
Sources for Additional Information: See Table 8-3.
8-42
-------
8. VADQSE ZONE WATER BUDGET CHARACTERIZATION METHODS
8.4 EVAPOTRANSPIRATION (MICROMETEOROLOGICAL METHODS)
8.4.2 Physically-Based Equations (Penman and Related Methods)
Other Names Used to Describe Method; Combination method, Penman (combination) equation. Penman-
Monteith equation.
Uses at Contaminated Sites: Indirect field method tor estimating evapotranspiration (El).
Method Description: Physically-based process equations combine energy balance (Section 8.4.4) and aerodynamic
transport of water vapor (Section 8.4.3) to calculate potential evapotranspiration (PET). Specific parameters that
must be measured in the field vary slightly, depending on the equation, but can include: Surface temperature,
surface resistance, saturation vapor pressure at mean air temperature, actual vapor pressure, mean monthly solar
radiation, and wind velocity. Although these equations are physically-based, they require the measurement or
estimation of various empirical constants. The Penman equation (Penman, 1948) was the first equation
developed using this approach, and used weekly mean climatic data in empirically derived expressions for the
energy and aerodynamic components. Figure 8.4.1 illustrates lake evaporation computed using the Penman
formula compared to six other methods. Various modifications have been suggested since then, with the
Pemnan-Monteith equation (which eliminated the need for surface temperature measurement) being the most
commonly used. The theory of a complementary relationship between actual evapotranspiration (Alii) and PET
(Bouchet, 1963) has contributed to the further development of physically-based evaporation and ET models. In
arid areas PET always exceeds AET, but as the amount of moisture available for removal from the soil increases,
AET increases and PET decreases (because moisture in the air reduces the capacity for further additions of
water vapor), until they converge on a value that is called wet environment evapotranspiration (WET). The
Morton or Complementary Relationship Areal Evapotranspiration (CRAE) model developed for calculating
WET, replaces the wind function in the Penman equation with a vapor transfer coefficient. The Bnitsaert-
Strickcr, or Advection-Aridity Evaporation model, has been developed for calculating evaporation and ET in arid
areas.
Method Selection Considerations: Penman and Related Equations Advantages: (1) Empirical constants in the
equations can be obtained from published tables and graphs, rather than being determined from additional
measurements for a specific site; and (2) work well for daily or larger periods in relatively humid areas where
horizontal heat divergence in negligible, there is a good vegetative cover, and water is not limiting. Penman and
Related Equations Disadvantages: (1) Reid measurements for a number of meteorological parameters are
required and are relatively expensive (although generally less expensive than othermicrometeorological methods);
and (2) serious discrepancies can occur in dry areas where adverted heat accounts for a significant proportion
of ET, unless locally determined empirical correction factors are developed. CRAE Model: Provides comparable
results to the Penman equation, with the advantage that wind speed measurement is not required. Advection-
Aridity Model: Works well for daily evaporation predictions. The main advantage is that it does not require
surface resistance, soil moisture content, or other land surface measures of aridity.
Frequency of Use: Equation has been widely in England and to some extent in the eastern part of the United
States. Not recommended for routine field applications and assessments.
Standard Methods/Guidelines: —
Sources for Additional Information: See Table 8-3.
8-43
-------
8. VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
8.4 EVAPOTRANSPIRATION (MICROMETEOROLOGICAL METHODS)
8.4.3 Mass Transfer Methods
Other Names Used to Describe Method: Dalton's law.
Uses at Contaminated Sites: Measuring evaporation.
Method Description; Mass transfer methods use semi-empirical equations for calculating evaporation as a
function of: (1) Windspeed, often called the wind function, (2) saturation vapor pressure calculated from the
temperature of the water surface, and (3) vapor pressure of the air. The wind function represents the combined
effect of many Variables and requires the estimation or measurement of one or more empirical constants and a
mass-transfer coefficient
Method Selection Considerations: Advantages: Once the wind function has been determined, fewer measurements
are required than for energy balance methods. Disadvantages: (1) Most accurate results require taking
measurements in the center of a water body, which is difficult; (2) requires calibration with independently
determined evaporation estimates; and (3) mass transfer methods for determining evapotranspiration (ET)
generally require very complex instrumentation and well-trained personnel.
Frequency of Use; Widely used for measuring evaporation; rarely used for ET.
Standard Methods/Guidelines; —
Sources for Additional Information; Bras (1990), Dunne and Leopold (1978), U.S. Geological Survey (1982).
See also, Table 8-3.
8-44
-------
8. VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
8.4 EVAPOTRANSPIRATION (MICROMETEOROLOGICAL METHODS)
8.4.4 Energy Budget Methods
Other Names Used to Describe Method: Energy balance/Bowen ratio method.
Uses at Contaminated Sites: Indirect field method for estimating evaporation and evapotranspiration (ET).
Method Description; The total energy available for evaporation or ET is measured. The equation for net
radiation at the earth's surface is rearranged to solve for ET. Figure 8.4.4 illustrates the various components of
the heat budget equation for a vegetated soil surface. Required field measurements include humidity (vapor
pressure) and temperature profile above the ground or water surface, net radiation (Section 8.2.7), and soil heat
flux (Section 1.6.3). Temperature gradients usually are measured using thermocouples. Humidity gradient is
measured either by using two psychrometers or hygrometers (Sections 8.1.3 and 8.1.4) positioned at different
elevations above the vegetative cover, or two tubes for collecting of samples for which moisture content is
measured.
Method Selection Considerations: ET Advantages: (1) Is accurate in high humidity environments (within 5 to
10 percent of actual); and (2) can be used on hilly as well as flat terrain and for a wide variety of vegetation
types, such as croplands and forests. ET Disadvantages: (1) Is expensive because of the large number of
parameters that must be measured; (2) is less accurate where humidity is low; (3) beat divergence, sampling
techniques, and advection can cause problems; (4) weekly instrumentation maintenance is required; (5)
measurements over months or years are required to obtain average ET values; and (6) the energy required for
photosynthesis (around 5 to 10 percent) is difficult to measure accurately, so it must be estimated. Lake
Evaporation Disadvantages: (1) Does not consider flow of heat through the bottom of the lake, which can be
significant in shallow lakes; (2) does not account for effects due to radiative difiusivity, stability of the air, and
spray; and (3) is strongly affected by the ability to evaluate the adveetive energy component.
Frequency of Use: Well accepted for research applications. Not recommended for routine field applications and
assessments.
Standard Methods/Guidelines: —
Sources for Additional Information: Bowen (1926), Bras (1990), DeVries and Afgan (1975), Dunne and Leopold
(1978), Robins (1965), Rosenberg et al. (1983), Sharma (1985), Thompson et al. (1989), U.S. Geological Survey
(1982). See also, Table 8-3.
8-45
-------
H = RN = S + ET + K + N + Storage Terms
in which H = heat budget,
Rjvf = net radiation,
S = energy to soil heat,
ET = energy used for evapotranspiration,
K - sensible heat to air, and
N = energy used by plant in photosynthesis.
NET RADIATION
CRNS
SENSIBLE
HEAT (K)
WATER VAPOUR (ET)
PLANT HEIGHT
WATER VAPOUR
SENSIBLE HEAT r~
WATER VAPOUR
STORAGE
i, TEMPERATURE CHANGE OF CROP
2, TEMPERATURE CHANGE OF MOIST AIR
3. ABSOLUTE HUMIDITY CHANGES
4. PHOTOSYNTHESIS (N!
SENSI8L£ HEAT
SOIL HEAT (S)
Figure 8.4.4 The heat budget equation and diagram of energy balance over a vegetated surface (Gray, 1973, after
King, 1961). Rw S, K, and N must be measured or estimated to solve for evapotranspiration.
8-46
-------
8. VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
8.4 EVAPOTRANSPIRATION (MXCROMETEOROLOGICAL METHODS)
8,4,5 Profile/Gradient Method
Other Names Used to Describe Method; Aerodynamic/Vapor transfer method.
Uses at Contaminated Sites: Indirect field method for estimating evapotranspiration (ET).
Method Description: The profile or gradient method relates the vertical gradients of humidity and horizontal
wind velocity to the rate of evaporation or ET from the underlying surface, Reid measurements include: (1)
The humidity gradient above the vegetative cover, and (2) wind profiles to estimate a momentum transfer
coefficient (Km). The turbulent transfer coefficient for water vapor (Ke) might need to be measured to
determine an empirical coefficient in the equation used to calculate ET to account for observed differences
between the two transfer coefficients. The Thornthwaite-Holtzmari equation is the most widely used formula
for calculating evaporation using this method,
Method Selection Considerations: Advantages: (1) Once required coefficients have been determined, only
windspeed and humidity gradient need be measured; and (2) works best in large, flat areas with uniform plant
cover. Disadvantages: (1) Requires relatively complicated humidity and wind profile measurements; (2) the
turbulent transfer coefficient for water vapor (Ke) also must be measured, unless it can be assumed to equal the
momentum transfer coefficient (Km); (3) is less suitable for areas that are aerodynamically unstable because of
rough vegetation cover or topography; and (4) is less accurate than mass transfer and energy budget methods
because calculation sensitivity of instruments is more critical for accurate results and errors are more likely from
adverse boundary conditions.
Frequency of Use: Sometimes used for short-term intensive studies, but not recommended for routine field
applications and assessments.
Standard Methods/Guidelines: —
Sources for Additional Information: Sharma (1985), Thompson et al. (1989), U.S. Geological Survey (1982),
Veihmeyer (1964). See also, Table 8-3.
8-47
-------
8. VADOSE ZONE WATER BUDGET CHARACTERIZATION METHODS
8.4 EVAPOTRANSPIRATION (MICROMETEOROLOGICAL METHODS)
8.4.6 Eddy Correlation Method
Other Names Used to Describe Method: Eddy flux method, , ;, ,
Uses at Contaminated Sites: Indirect field method for estimating evaporation and evapotranspiration (ET).
Method Description: Accurate, closely spaced instantaneous measurements of vertical wind velocity and humidity
are averaged over a period of 1/2 hour or more. Water vapor flux (ET) is calculated from an equation relating
deviations of humidity and vertical wind velocity from the mean. Extremely sensitive instrumentation, such as
a propeller anemometer or sonic anemometer, is required for vertical wind measurements. Infrared hygroraetry
or wet-bulb/dry-bulb psychrometers usually are used for humidity measurements. On sloping surfaces, three-
dimensional wind measurements are required.
Method Selection Considerations: Advantages: Is the most direct means of measuring ET; (2) is independent of
atmospheric conditions or types of underlying surfaces; (3) is accurate in low and high humidity environments,
Disadvantages; Requires expensive and delicate instrumentation.
Frequency of Use; Well accepted for short-term research applications. Not recommended for routine field
applications and assessments.
StandardMethods/Guidelines; —
Sources for Additional Information: Rosenberg et al. (1983), Sharma (1985), Thompson et al. (1989), U.S.
Geological Survey (1982). See also, Table 8-3.
8-48
-------
Table 8-2 Reference Index for Hydrometeorological Data Collection and Measurement Methods
Topic
References
Climatic Data Sources/Uses
Meteorological Tables
General References
EPA Guidance Documents
Precipitation Gages/Samplers
Precipitation Analysis
Wind Speed/Direction
Humidity
Solar Radiation
Eder et al. (1989), Hatch (1988), Whiting (1975, 1976)
Letestu (1966), List (1966)
ASTM (1986), Berry et al. (1945), Brakensiek et al. (1979), Brock and Nicolaidis
(1984), Brunt (1944), Fritschen and Gay (1979), Hardy and Fisher (1972),
Huschke (1970), Lockhart (1989a), Malone (1951), Meteorological Office (1956),
Monteith (1972), National Weather Service (1972,1975), Spilhaus and Middleton
(1973), Tanner (1963), UNESCO (1969), U.S. Army (1975), U.S. Geological
Survey (1980), U.S. Weather Bureau (1955), WMO (1971, 1973, 1974, 1975),
WMO-IASH (1965)
U.S. EPA (1985, 1987a,b)
Oilman (1964), Neff (1977), Purcell and Brown (1991), Simmons and Bigelow
(1990)
Butler (1957), DeWiest (1966), Kazmann (1988), Skeat (1969), Wisler and Brater
(1959); Frequency/Probability Maps; Thomas and Whiting (1977), U.S.
Department of Commerce (1961)
ASTM (1985a, 1990), Finkelstein et al. (1986a,b), Hayashi (1987), Lockhart
(1985a,b, 1987,1989b), Snow et al. (1989), Steams (1985), Turner (1986)
ASTM (1982,1983,1984a, 1985b), US, Weather Bureau (1963a), Weiler (1957,
1965), Wexler and Brombacher (1951)
ASTM (1984b), Carter et al. (1977), Coulson (1975), Elsasser and Culbertson
(1960-atmospheric radiation table), Gates (1962), Kennedy (1949-pyrheliometers),
Latimer (1972), Norris (1974), Selcuk and Yellott (1962), Suomi and Kuhn
(1958); Estimation methods: Anderson and Baker (1967), Koberg (1964)
8-49
-------
Table 8-3 Reference Index for Evaporation and Evapotranspiration Measurement Methods
Topic
References
Hydrology Texts Covering ET
General Reviews
ASCE (1952), Branson et al. (1981), Bras (1990), DeWiest (1966), Dunne and
Leopld (1978), Eagleson (1970), Gray (1973), Kazmann (1988), linsley et al.
(1949, 1982), Skeat (1969), Viessman et al. (1977), Wisler and Brater (1959);
Symposia; Sokolow and Chapman (1974)
Anderson et al. (1950), Barry (1973), Bennett and Dnstedt (1978), Black et al.
(1969), Brutsaert (1982), Christian et al, (1970), Griddle (1958), Doorenbos and
Pruitt (1977), Evans (1962), Gangopadhyaya et al. (1966), Hamon (1961), Hanks
and Ashcroft (1980), Hide (1954), Hillel (1982), Jensen (1974), Kittredge (1941),
Levine (1959), Lowry and Johnson (1942), Monteith (1965), Robins (1965),
Robins and Haise (1961), Rosenberg et al. (1968), Saxton and McGuiness (1982),
Sharma (1985), Stephens and Stewart (1964), Tanner (1967,1968), Thompsen et
al. (1989), Thornthwaite (1948), U.S. Geological Survey (1982), Veihmeyer
(1964), Webb (1975), WMO (1966)
Water Balance Methods (See also. Tables 4-3 and 7-6')
Lysimetric Methods
Soil Moisture Budget
Water Budget Methods
Aboukhaled et al. (1982), Harrold (1966), Kohnke et al. (1940), Pelton (1961),
Robins (1965), Tanner (1967), van Bavel (1961), Visser (1962); Nonweighable
Lysimeters: Colman and Hamilton (1947), Evans (1971), Gilbert and van Bavel
(1954), Mather (1954), Patric (1961), Robinson (1970), Stevenson and van Schaik
(1967); Weighable Lvsimeters (see also, monolith lysimeters. Table 9-4): Harrold
and Dreibelbis (1951,1958), Katul and Parlange (1992), Mustonen and
McGuinness (1968), Pruitt and Angus (1960), Ritchie and Burnett (1968),
Rosenberg et al. (1967), van Bavel and Myers (1962), van Bavel and Reginald
(1965), van Hylckama (1966, 1968), Williamson (1963), Wind Hzn (1958);
Hydraulic Lvsimeters: Black et al. (1968), Dagg (1970), DeBoodt et al. (1966),
Ekern (1967), Forsgate et al. (1965), Hanks and Shawcroft (1965); Lvsimeters
(Unspecified): Blad and Rosenberg (1974), Blaney et al. (1930), King et al.
(1956), Kittredge (1941), Makkink (1957), Martin and Rich (1948), MeGuiness
and Bordne (1972), Young and Blaney (1942); Microlysiroeters: Abramova (1968),
Al-Khafaf et al. (1978), Boast and Robertson (1982), Shawcroft and Gardner
(1983), Staple (1974), Walker (1983)
Bowman and King (1965), Bresler and Kemper (1970), DeBoodt et al. (1966),
Hillel (1971), Idso et al. (1975), Jenson (1974), Ligon (1969), Lomen and Warrick
(1978), McGowan and Williams (1980), Rose (1966), Rose and Krishnan (1967),
Slaytor (1967), Tanner (1967, 1968), van Bavel and Stirk (1967); Methods of
Modulating Potential Rates to Predict Soil Moisture Withdrawal: Holmes (1961),
Robertson and Holmes (1959), Taylor and Haddock (1956)
Eagleson (1978a,b); Evaporation: Anderson (1954), Hanks et al. (1969), Harbeck
and Kennon (1954), Horton (1943b), Langbein et al. (1951), McKay and Stichling
(1961), Winter (1981); Inflow-Outflow; Blaney et al. (1938, 1942), Jensen (1967),
Lowry and Johnson (1942), Wilcox (1960), Tin and Brook (1992);
Integration&eaf Area Index Methods: Blaney et al. (1938, 1942), Hanks (1974),
Jensen et al. (1970), Kristensen (1974), Raymond and Rezin (1989), Ritchie
(1974); Watersheds: Hewlett et al. (1969), Lee (1970), Row and Reimarm (1961),
Williams (1940); Ftoodplains; Bowie and Kam (1968), Culler (1970), Gatewood et
al. (1950), Hanson et al. (1972), Horton (1973-liteature review), Langbein (1942),
Reigner (1966), Taylor and Nickle (1933)
8-50
-------
Table 8-3 (cont.)
Topic
References
Water Balance Methods fcont.)
Pan Evaporation
Attnometers
Ground-Water Fluctuation
Transpiration
Micrometcorological Methods
General
Empirical ET Equations
ASCE (1934), Bouwer (1959), Doorenbos and Pruitt (1977), Gangopadhyaya et
al. (1966), Jensen (1974), Kohler et al. (1955), McKay and Stiehling (1961),
Mortenson and Hawthorn (1934), Mukammal (1961), Mukammal and Bruce
(1960), Nordenson and Baker (1962), Peek and Munro (1976), Pruitt (1960),
Rohwer (1931, 1934), U.S. Weather Bureau (1955), Young (1947); Modified
Energy Budget with Insulated Pan: Cummings (1940), Kohler and Parmele
(1967), U.S,Geological Survey (1982); Pan Coefficients: ASCE (1934), Ficke et al.
(1977), Hall (1934), Kohler (1954), Rohwer (1931, 1934), Somnor (1963), State of
California (1973), White (1932), Young (1947); Pan Evaporation Maps: Horton
(1943a), Kohler et al. (1959); ET Estimates from Pan Evaporation: Mortenson
and Hawthorne (1934), Pruitt (1960), Pruitt and Jensen (1955), Robertson and
Holmes (1956), StanhUl (1962), Yin and Brook (1992)
Abbe (1935), Halkias et al. (1955), Livingston (1935), Livingston and Haasis
(1929), Mukammal (1961), Mukammal and Bruce (1960), O'Connor (1955),
Somnor (1963), State of California (1973)
Blaney et al. (1933), Davis and DeWiest (1966), Gatewood et al. (1950), Troxell
(1936), Weeks and Sorey (1973), White (1932)
Cohen et al. (1981), Jarvis et al. (1981), Koch et al. (1971), Reicosky and Peters
(1977), Veihmeyer (1964). Also, U.S. Geological Survey (1982) contains ^over 50
other references on methods for measuring or estimating transpiration.
Gruff and Thompson (1967), DeVries and Afgan (1975), Ficke (1972), Halstead
and Covey (1957), Hanks and Ashcroft (1980), Harbeck (1952), Hfflel (1980,
1982), Hughes (1967), Lemon et al. (1957), Penman (1963), Penman et al. (1967),
Szeicz (1975), Tanner (1967,1968), Thorn (1975), Van Wijk and De Vries (1954);
Bare Soils; Black et al. (1969), Fuchs et al. (1969)
Reviews: Bras (1990), Griddle (1958), Cruff and Thompson (1967), Eagleson
(1970), Gray (1973), Jensen (1966a), Pierson and Jackman (1975), Pruitt and
Doorenbos (1977), Robins and Haise (1961), Shanna (1985), Tanner (1967),
Thompson et al. (1989), U.S. Geological Survey (1982), Veihmeyer (1964); -
Blaney-Morin/YModified) Blanev-Criddle: Blaney (1959), Blaney and Griddle
(1950,1962), Blaney and Morin (1942), Blaney et al. (1952), Griddle (1958), Gruff
and Thompson (1967), Dunne and Leopold (1978), Pruitt and Doorenbos (1977),
State of California (1973), Stephens and Stewart (1964), U.S. Weather Bureau
(1905), Yin and Brook (1992); Jensen-Haise: Jensen (1966b), Jensen and Haise
(1963), Jensen et al. (1970); Thomthwaite: Dunne and Leopold (1978), Pelton et
al. (1960), Stephens and Stewart (1964), Thomthwaite (1931, 1948), Thomthwaite
and Mather (1955, 1957), Thomthwaite and Wilm (1944), Yin and Brook (1992);
Others; Behnke and Maxey (1969), Benson et al. (1992), Christiansen (1968),
Christiansen and Hargreaves (1969), Gardner (1958), Halkias et al. (1955),
Harding et al. (1930), Hargreaves (1956), Hargreaves and Samani (1985),
Holdridge (1962), Kincaid et al. (1979), Lowry and Johnson (1942), Makkink
(1957), Munson (1962), Priestly and Taylor (1972), Ritchie (1972), Saxton and
McGuiness (1982), Tanner and Jury (1976)
8-51
-------
Table 8-3 (cont)
Topic
References
Empirical Evaporation
Equations
Physically-Based Equations
Mass-Transfer Methods
Energy Budget Methods
Profile/Gradient Method
Eddy Correlation
Reviews; Bras (1990), Helfrich et al, (1982), McKay and Stichling (1961),
Weisman (1975); Specific Equations: Harbeck (1962), Kohler (1954), Kohler et
al. (1955), Kuzmin (1957), Marciano and Harbeck (1954), Meyer (1915, 1942),
Rohwer (1931), Shulyakovsky (1969)
Benson et al. (1992), Bras (1990), Businger (1956), Chiew and McMahon (1991),
Cordova and Bras (1981), Crago and Brutsaert (1992), Duell (1990), Gray (1973),
Katul and Parlange (1992), Lemur and Zhang (1990), McKay and Stichling
(1961), Monteith (1963), Morton (1978, 1983, 1991), Penman (1948, 1956), Pruitt
and Doorenbos (1977), Robins (1965), Rosenberg et al. (1983), Sharma (1985),
Staple (1974), Tanner (1968), Tanner and Pelton (1960), Thompson et al. (1989),
Turner (1957), U.S. Geological Survey (1982), van Bavel (1966), Veihmeyer
(1964); Advection Aridity Evaporation Model; Brutsaert and Strieker (1979),
Lemeur and 2iang (1990), Morton (1991), Parlange and Katul (1992); Soil
Evaporation Loss Equations: Philip (1957, 1991); Lake Evaporation Equations:
Goodling et al. (1976), Weisman and Brutsaert (1973)
Evaporation: Brasklavskii and Vikulina (1954), Ficke (1972), Harbeck (1962),
Harbeck et al. (1954,1958), Hughes (1967), Jobson (1973), Marciano and
Harbeck (1954), Munn (1961), Resch and Selva (1979), Richards and Irbe (1969),
Sutton (1949), Sverdrup (1946), Thornthwaite and Holzman (1939), Turner
(1966), Wunderlfch (1972)
Evaporation: Anderson (1954), Levine (1959), McKay and Stichling (1961),
Tanner (1960); Evapotranspiration: Angus and Watts (1984), Aston and van Bavel
(1972), Black and McNaughton (1971), Blad and Rosenberg (1974, 1975),
Denmead and McDroy (1970), Dennehy and McMahon (1989), Duell (1990),
Fritschen (1965), Jackson et al. (1977), Kohler et al. (1955), Lemon (1960), Munn
(1961), Ohmura (1982), Pruitt (1963), Robins (1965), Tanner (1966, 1968, 1988),
Webb (1975)
Businger et al. (1971), Dyer (1963,1965, 1974), King (1966), Marciano and
Harbeck (1954), Pierson and Jackman (1975), Priestly (1959), Pruitt et al. (1973),
Quoin (1979), Szeicz et al. (1969), Thornthwaite and Holzman (1939, 1942);
Vapor Transfer Method: Pasquill (1949, 1950), Rider (1954, 1957), Rider and
Robinson (1951), Tanner (1960), Veihmeyer (1964)
Christian et al. (1970), Duell (1990), Dyer (1961,1968), Easterbrook (1969),
Gangopadhyaya et al. (1966), Goddard and Pruitt (1966), Goltz et al. (1970),
Hicks (1973), Hicks et al. (1973), Jobson (1973), Swinbank (1951), Swinbank and
Dyer (1967), Tanner (1966,1988)
8-52
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/• ,
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Holdridge, and pan evaporation methods]
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Youngs, E.G. 1972. Two- and Three-Dimensional Infiltration: Seepage from Irrigation Channels and Infiltrometer Rings. J.
Hydrology 15:301-315.
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SECTION 9
VADOSE ZONE SOIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
Monitoring of soil water in the vadose zone can serve as an early warning system at controlled waste
disposal sites that contaminants are entering the subsurface, and can allow actions to be taken before
contaminants reach the saturated zone. Methods for sampling and monitoring the vadose zone can be broadiy
categorized as: (1) Indirect (surface geophysical methods and probes that focus on measuring variations in soil
salinity), and (2) direct (in which soU water is collected directly in the field, or extracted from samples of soil
solids),
Indirect Soil Salinity Measurements
A variety of methods are available for locating and monitoring areas of high soil salinity. These
methods primarily have been developed for agricultural applications to identify saline soils and control irrigation
flows where soluble salts can affect crop productivity. Table 9-1 summarizes information on six indirect methods
for monitoring soil salinity. The four-probe electrical method is a direct application of the electrical resistivity
surface geophysical method (Section 1.2.1), with electrode configurations that measure near-surface resistivity.
The electromagnetic induction sensor is an instrument that is specifically designed to measure conductivity in the
near surface. The other indirect methods involve placement of probes or sensors in the subsurface. The main
advantage of indirect methods is that data can be collected quickly. The main disadvantages are: (1) Instruments
must be calibrated for each soil type by collection of samples where salinity is measured directly to obtain
quantitative measurement of soil salinity; and (2) actual chemical constituents that are contributing to soil salinity
cannot be determined. The four-probe electrical and porous matrix soD salinity sensors are the most commonly
used indirect methods.
Direct Soil Solute Sampling Methods
The U.S. Environmental Protection Agency is placing increasing emphasis on vadose zone soil solute
sampling as an early warning system to detect movement of contaminants before they reach the saturated zone
(Cullen et al., 1992; Durant et al., 1993). Three major types of soil water can be identified in the context of
sampling soil water: (1) Macropore or gravitational water, which flows through the soU relatively rapidly in
response to gravity (excess of 0,1 to 0,2 bars suction); (2) soil-pore or capillary water, which is held in the soil
at negative pressure potentials from around 0.1 to 31 bars of suction; and (3) hygroscopic water that is held at
tensions greater than 31 bars suction. Soil-pore water moves through the vadose zone, but at much slower rates
than gravitational water (see discussion of potential-conductivity relationships in Section 6.3,1), whereas
hygroscopic moves primarily in the vapor form. The term soil solute or solution sampling has been used loosely
in the literature to describe most sampling methods, whereas the term soil pore liquid is typically used in a more
restricted sense (and is so used here) to apply to sampling of capillary water. The chemistry of soil solute
sampling methods can differ significantly, depending the method used. Concentrations of inorganic species
generally increase as the matric potential increases. In general, ceramic soil suction samplers (which use suctions
up to around 0.8 bars) will collect samples that are most representative of the soil solution for the purpose of
evaluating contaminant transport.
There are a large number of specific methods by which soil water can be sampled. Suction samplers
draw water from the soil by applying a vacuum. A variety of free-drainage samples collect water percolating
through the soil by gravity flow. Other methods include: (1) Use of absorbent materials with retrieval and
extraction of water in the laboratory, (2) collection of soil solids with extraction of soil water in the laboratory
by a variety of methods, and (3) preparation of a soil saturation extract from a solids sample. Table 9-1
summarizes some information on six types of suction samplers, seven methods of collecting samples by free
drainage, and four miscellaneous methods. Table 9-1 also lists collection of soil solids for volatile constituents
and soil microorganisms in the vadose zone.
The main advantages of suction samplers is that they are relatively easy to install, and there are
essentially no limitations to the depth of sampling when a vacuum-pressure apparatus is used. The main
9-1
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Table 9-1 Summary Information on Soil Solute Monitoring and Sampling Methods
Method
Sampling
Method
Depth
Limitation
Chapter
Sections
Indirect Salinity Measurement Methods
Four Probe Electrical Resistivity Near surface 9.1.1,1.2.2
Portable EC Probe Resistivity 1.5 m 9.1.2
In Situ EC Probe Resistivity None 9.1.2
Porous Matrix Salinity Sensors Resistivity None 9.1.3
Electromagnetic Induction Sensor Conductivity 2 m 9.1.4,1.3.1
Dielectric Sensors Dielectric 2 m' 9.1.4,6.2.3
Time Domain ReOectometry Sensor Dielectric Up to 20 m 9.1.4, 6.2.4
Neutron Probe Nuclear None 33.3,6.2.2
Direct Soil Solute Sampling Methods
Vacuum-Type Porous Cup Suction 2 m 9,2.1
Vacuum-Pressure Porous Cup Suction 45 ft 9.2.2
Vacuum High-Pressure Porous Cup Suction 300 ft 9.2.2
Vacuum-Plate Sampler Suction 2 m* 9.23
Membrane Rltcr Suction 1-4 m* 9.2.4
Hollow Fiber Suction 2 m* 9.2.5
Ceramic Tube Sampler Suction 2 m' 9.2.6
Capillary Wick Sampler Capillary * 9.2.7
BAT Sampler Suction 45ft 5.5.2
Trench Lysimcter Gravity0 d 9.3.1
Caisson Lysimeter ' Gravity 3 m+ 9.3.1
Pan Lysuneter Gravity d 93.1
Glass Block Lysimeter Gravity d 93.1
Wicking Type Sampler Gravity 4 93.1
Tile Drain Outflow Gravity 50+ ft 93.1
Perched Water Table Gravity None 93.2
Nylon Sponge Absorbent Near surface 93.3
Ceramic Rod Absorbent Near surface 93.3
Solid Soil Water Extraction * None 93.4
Soil Saturation Extract Slurry None 93.5
SEAMIST Absorbent 100s ft 93.7
Methods for Sampling Sensitive Soil Constituents
Static Soil-Gas Sampling Absorbent Near Surface 9.4.1
Soil-Gas Probes Suction ' 9.4.2
Tank Leak Sensors Various Typically <2m 9.4.3
Soil Volatiles/Microorganisms Core ' 9.3.6
Boldface = Most commonly used methods.
'With vacuum sampling apparatus; greater depths would be possible using vacuum-pressure sampling system.
*Upper limit would require modification of system to use vacuum-pressure sampling apparatus.
•Sample is collected by free-drainage in all gravity samplers, but suction can be used to bring sample to the surface.
*Depth limited by the depth to which a hole or trench can be safely dug for installation of sampler in the sidewall; typically 2 meters
or less.
•Various methods can be used to extract soil water from a sample: Squeezing, displacement, displacemcni/cenlrifugaiion,
ccnirifugation, and adsorption.
'Depends on density of subsurface material and method of penetration/coring. Soil gas probes used with cone penetration rigs
(Sections 2.2.2,5.5.1, and 53.2) can penetrate 100 to 150 feet with favorable soil conditions; greater depths are possible if holes are
drilled before insertion of the soil gas probe. Coring depth limits are defined by the type of drilling/coring method used (Sections 2.3
and 2.4).
9-2
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disadvantage of suction samplers is that they might not collect representative samples. Sampling for organic
chemicals, microorganisms, volatile chemicals, and metals is especially problematic due to potential
sorption/interferences by the porous cup. Vacuum-type and vacuum-pressure type porous cup samplers are by
far the most commonly used types of suction samplers. The main advantage of free-drainage samplers is that
relatively large volumes of water, which is representative of water that is actually percolating to deeper zones,
is obtained. The main disadvantages are that installation procedures are time consuming and complex and
limited to relatively shallow depths. Trench lysimeters with pan collectors are the most commonly used free-
drainage samplers. Figure 9-la illustrates generic vadose zone monitoring installations for an existing hazardous
waste landfill and Figure 9-lb illustrates generic vadose zone monitoring installations for a new surface
impoundment. Capillary wick samplers (Section 9.2,7) are a relatively new development, which appear to have
good potential for collecting more representative samples of soil solutions than either porous cup or free-
drainage samplers in the near surface.
Gaseous Phase Characterization
Sampling of soil gases (volatile contaminants or gases such as methane and carbon dioxide, which are
indicators of increased microbial activity resulting for organic contaminants) has gained rapid acceptance as a
method for preliminary mapping of contaminant plumes in ground water, and monitoring of underground storage
tanks. Contaminant plume mapping can be done either by passive sampling, where absorbent collectors are
buried for a period of time and retrieved for laboratory analysis (Section 9.4.1), or by using soil-gas sampling
probes (Section 9.4.2), Various types of sensors can be used to detect leaks in underground storage tanks
(Section 9.4.3). Monitoring of air pressure (Section 9.4.4) and measurement of air permeability (Section 9.4.5)
might be required for modeling the transport of contaminants in the vadose zone.
Contaminant Flux
Section 9.5.1 (Solute Flux Methods) briefly describes four methods for estimating the mass transfer of
pollutants from the vadose zone to ground water, and Section 9.5.2 (Soil-Gas Rux) describes several methods
for estimating soil-gas flux to the atmosphere.
9-3
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PIBZOMETiRS
"• UNDEHGROUNO
/{ K^^x
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I MULTILEVEL
j SAMPLERS
EXPANSION AREA
RESISTIVITY.
NETWORK:
/I
"rkltallll1" / I NEU?RON PROBE
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NEST
I
-r MULT M.E
* COMPLETION
WELL
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GEOPHYSICAL
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:.',Z*- :IS^3^H':j:':^
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^.a--;:g^4s;s::-.^-.^r;-^ j..^:-,.i^,,.
(a)
WATER STAGE |—~I
Figure 9-1 Vadose a»ne monitoring systems: (a) Generic monitoring design for existing hazardous waste landfill; (b)
Water quality monitoring design for a new surface impoundment (Everett et al., 1983).
9-4
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9. VADOSE ZONE SOIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
9.1 SOLUTE MOVEMENT (INDIRECT METHODS)
9.1.1 Four Probe Electrical Resistivity
Other Names Used to Describe Method: Four electrode technique/sensors.
Uses at Contaminated Sites: Measuring in situ soil salinity in the shallow vadose zone; locating brine and chloride
plumes; estimating water content.
Method Description: A Wenner four probe electrode array (see Section 1.2.1) is used to detect areas of low
electrical resistivity (high conductivity) in the soil. For a given soil type, electrical conductivity of the bulk soil
and electrical conductivity of the saturation extract from the soil are directly related. Once a calibration curve
has been developed (requiring multiple measurements of both soil conductivity and saturation extract conductivity
at different locations in a single soil type), soil conductivity measurements can bfe related to saturation extract
conductivity, which in turn can be related to salinity (see references in Table 9-2).
Method Selection Considerations: Advantages: (1) Is a nondestructive method (once calibration constants have
been calculated); (2) readings are obtained rapidly and inexpensively; (3) is useful for detecting the presence of
shallow saline ground water; (4) horizontal variations in salinity can be easily measured by lateral transects; (5)
vertical changes in salinity can be evaluated by changing the electrode spacing; and (6) a large volume of soil can
be measured compared to other methods. Disadvantages: (1) Obtaining calibration relationships can be tedious;
(2) accuracy decreases in layered soils; (3) time-series monitoring is difficult due to the requirement of making
multiple traverses; (4) is generally limited to shallow depths; (5) does not provide data on specific pollutants; and
(6) will not detect pollutants that do not change the electrical conductivity of the subsurface. Water Content
Measurement: Moisture content can be estimated from four electrode resistivity measurements if salinity,
temperature, and bulk density can be quantified, and calibration curves are developed, however, other simpler
and more reliable methods generally are used (see Sections 6.2 and 6.3).
Frequency of Use: Commonly used for identification of saline soils in agricultural studies. DC resistivity methods
for detecting conductive contaminant plumes in the deeper subsurface are described in Section 1.2.1.
Standard Methods/Guidelines: Salinity: Rhoades and Oster (1986); Water content: Morrison (1983).
Sources for Additional Information: Everett et al. (1983). See also, Table 9-2.
9-5
-------
9. VADOSE ZONE SOIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
9.1 SOLUTE MOVEMENT (INDIRECT METHODS)
9.1.2 EC Probes
Other Names Used to Describe Method; Four-electrode salinity probe, electrical conductivity probe*, portable
salinity probe, burial type salinity probe, four-electrode conductivity cell.
Uses at Contaminated Sites: Obtaining small volume soil salinity measurements.
Method Description: A cylindrical portable probe containing electrodes at fixed spacing is attached to a rod with
a handle (Figure 9.1.2a). A hole the same diameter as the probe is augered, and resistivity is measured at
successive depths. Alternatively, a specially dedicated burial-type probe is placed permanently in the ground with
a cable running to the surface for periodic measurements (Figure 9.1.2b). Calibration of probes is similar to the
calibration method for the four probe electrical method (Section 9.1.1). The four-electrode conductivity cell is
a variant of this approach, in which and undisturbed soil core is collected using a removable lucite columnar
insert in a soil-core sampler. The lucite section is removed from the sampler and segmented to form individual
cells. Electrodes are inserted into the soil through threaded holes in the lucite cell walls and resistivity is
measured.
Method Selection Considerations: Advantages: (1) Salinity changes with depth in stratified soils can be measured;
(2) burial probe measurements can be taken at a greater depth than with four electrode method; (3) in-place
units allow easy monitoring of changes in salinity with time; (4) are well suited for mapping and diagnosis as well
as monitoring; (5) compared to salinity sensor probes, are more versatile, durable, less subject to calibration
change, and respond to changes in salinity with less time lag; and (6) can be used to measure different soil
volumes. Disadvantages: (1) Developing individual calibration relationships for each strata is time consuming
and expensive; (2) use is limited to relatively shallow depths; and (3) provide no data on specific pollutants nor
will probes detect pollutants that do not change the electrical conductivity of the subsurface.
Frequency of Use; Primarily used for land treatment areas and irrigated fields.
Standard Methods/Guidelines: Portable probe: Rhoades and van Schilfgaarde (1976), Rhoades et al. (1977);
Burial probe: Rhoades (1979).
Sources for Additional Information: Everett et al. (1983). See also, Table 9-2.
*This probe actually measures resistivity, but measurements typically are reported in its reciprocal, conductivity.
9-6
-------
(a)
CABINET BOTTOM
WITH DISPLAY
UNIT
v:;£iii£i£- PROBE SENSOR
ELECTRODES
Figure 9.1.2 Electrical conductivity probes: (a) Schematic illustrating the principle of a soil-salinity probe (Rhoades
and van Schilfgaarde, 1976, by permission); (b) Installation of in situ soil salinity sensor (Morrison,
1983).
9-7
-------
9. VADOSE ZONE SOIL-SOLUTE/GAS SAMPUNG AND MONITORING METHODS
9.1 SOLUTE MOVEMENT (INDIRECT METHODS)
9.1.3 Porous Matrix Salinity Sensors
Other Names Used to Describe Method; Ceramic salinity sensors, in situ salinity sensors.
Uses at Contaminated Sites: Monitoring soil salinity; determining dispersion coefficients from salinity gradients
and evapotranspiration; measuring water content measurement.
Method Description: Electrodes and thermistors embedded in porous ceramic are placed in the soil. Many types
of sensors have been developed. Figure 9.1.3a illustrates a cylindrical sensor, and Figure 9.1.3b a square salinity
sensor. The specific conductance is measured when the soil solution equilibrates with the ceramic. As with the
four probe electrical and EC probe, calibration curves that relate signal to salinity and/or water content must be
developed to relate conductivity readings to salinity. Temperature also must be measured and used to develop
calibration relationships.
Method Selection Considerations: Most suitable for land treatment areas and irrigated gelds. Could be installed
below ponds before they are filled with water. Advantages: (1) Are simple, easily read and sufficiently accurate
for salinity monitoring; (2) readings are taken at same depth and location each time; (3) vertical migration of
saline water can be monitored by installing units at different depths; and (4) output can be interfaced with data
acquisition systems. Disadvantages: (1) Are more subject to calibration changes than the four-electrode method;
(2) are more expensive and less durable than four-electrode method; (3) time lag in response to changing salinity
can be several days; (4) cannot be used at soil-water pressures less than about -2 bars; (5) soil disturbance during
installation can affect results (salinity readings will be lower compared to undisturbed soil if disturbed soil has
greater leaching due to increased permeability); and (6) does not provide data on specific pollutants.
Frequency of Use; Commonly used in agricultural research where continuous monitoring of soil salinity is
required.
Standard Methods/Guidelines; Rhoades and Oster (1986), Richards (1966).
Sources for Additional Information: Morrison (1983). See also, Table 9-2.
9-8
-------
PT ELECTRODE
Au ELECTRODE
SHIELDED
CABLE
EPOXY
THERMISTOR
RTV RUBBER
s*
19 mm
POROUS \
GLASS ^
'TUBE
(a)
PT-Au ELECTRODE SHIELDED
CABLE
LEAD
CONDUCTOR
1,0 cm
EPOXY
POROUS GLASS
PT-Au
ELECTRODE
THERMISTOR
„„'' GLASS OVERGLAZE
Figure 9.1.3 Soil salinity sensors: CylindrJal (a); Square (b) (Morrison, 1983, after Enfleld and Evans, 1969, by
permission).
9-9
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9. VADOSB ZONE SOIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
9.1. SOLUTE MOVEMENT (INDIRECT METHODS)
9.1.4 Electromagnetic Sensors
Other Names Used to Describe Method; Electromagnetic induction sensor, inductive electromagnetic soil
conductivity meter, soil conductivity sensor, EM soil salinity sensor, time domain reflectometry (TDR)/dielectric
sensors.
Uses at Contaminated Sites; Monitoring soil salinity.
Method Description: The EM soil salinity sensor uses the principles of electromagnetic induction (see Section
13.1) to measure electrical conductivity in the soil rooting zone (1 to 2 meters). EM instruments are designed
for measurement of conductivity of the near surface. Dielectric sensors (Section 6.2.3) and time domain
reflectotuetry (Section 6.2.4) measure the dielectric properties of the subsurface using probes that transmit and
receive electromagnetic signals.
Method Selection Considerations: EM Soil Salinity Sensor Advantages: (1) Equipment is very portable and easy
to use; (2) direct contact with the ground is not necessary; and (3) continuous measurements are possible. EM
Soil Sensor Disadvantages: Depth of penetration is limited to 1 to 2 meters. Time Domain Reflectometry has
the advantage of allowing measurement of both moisture content and electrical conductivity (see Section 63.4
for additional discussion of advantages and disadvantages).
Frequency of Use: EM soil salinity sensors are used primarily for agricultural applications for measuring salinity
of the soil rooting zone and locating saline seeps. TDR sensors are relatively new but have gained rapid
acceptance.
Standard Methods/Guidelines: —
Sources for Additional Information: Salinity sensors: See Table 9-2. TDR: Kachonoski et al. (1992); see also,
references listed in Table 63.
9-10
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9. VADOSE ZONE SOIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
9.2 DIRECT SOIL-SOLUTE SAMPLING (SUCTION METHODS)
9,2.1 Vacuum-Type Porous Cup
Other Names Used to Describe Method: Suction/soil lysimeter, tension lysimeter, soil-water extractors
Uses at Contaminated Sites: Sampling of soil pore liquids in the vadose zone to characterize contaminated sites
or provide early warning of break-through of pollutants at controlled disposal sites.
Method Description: A porous cup or plate (usually ceramic but other materials, such as alundum, fritted glass,
and nylon can be used*) is attached to a small diameter tube (usually PVC), which is placed in the soil, making
sure that there is good contact with the soil material. A one-hole rubber plug is placed in the other end of the
tube and small diameter tubing beginning at the base of the ceramic cup runs through the hole to the surface
(Figure 9.2.1a). A vacuum is applied to the small tubing and the soil solution is drawn into a small flask.
Tensiometers (Section 6.1.1) can be installed in the vicinity to determine that amount of suction that should be
applied during sampling. Figure 9.2. Ib illustrates the use of vacuum-type porous cup lysimeters in a barrel
lysimeter. A purge-and-trap device at the surface (Figure 9.2.1c) can be used for collection of volatiles from
suction samplers.
Method Selection Considerations; Advantages: (1) Allows direct sampling of soil water; (2) successive samples
can be obtained from the same depth; (3) is inexpensive and simple; and (4) can be installed below shallow
impoundments and landfills prior to construction for monitoring of seepage when the facility is operating.
Disadvantages: (1) Generally is limited to depths less than 6 feet; (2) is limited to soil water pressure less than
air entry value of the cups (-1 atmosphere or -30 kPa), so will not work in veiy dry or frozen soils; (3) small
volumes sampled might not be representative; (4) only samples pore water, water moving through cracks and
macropores might have different chemical composition (can be overcome by also using zero suction samplers
[Section 9.3.1]); (5) suction might affect soil-water flow patterns, so installation of tensiometers is required to
determine the correct vacuum to apply; (6) samples might not be representative of pore water because method
does not account for relationships between pore sequences, water quality and drainage rates; (7) contact between
cup and soils difficult to maintain in veiy coarse textured soils, such as gravels, and exposure to freeze-thaw might
break contact with soil; (8) cup might be plugged by solids or bacteria; (9) chemistry of solute might be altered
in passage through cup (sorption of metals, ammonia, chlorinated hydrocarbons); (10) PTFE cups have relatively
limited operational ranges (up to 7 centibars); (11) dead space, where fluid in the cup is not brought to the
surface, might occur if the discharge tube hangs up on the lip of the cup during installation, and some PTFE
samplers have a permanent dead space; (12) generally is not suitable for bacterial sampling due to screening and
adsorption; and (13) heavy metals might be sorbed on the porous-cup matrix.
Frequency of Use; Very common where near-surface sampling is required.
Standard Methods/Guidelines: ASTM (1992).
Sources for Additional Infoimation: See Table 9-3.
*Teflon also has been used as a material for suction lysiraeters, but is not currently recommended because of
problems with low bubbling pressure (ASTM, 1992).
9-11
-------
PLASTIC TUBE
VACUUM TEST HAND PUMP
0-18
VACUUM
COLLECTED SOIL-WATER SAMPLE
18-
24-
60 - 66'
To Sample Station
'C3 ^=
\&*
Vacuum Porous Cup SPL Samplers
(a)
SOIL SOLUTION
SAMPLER
PURGING
APPARATUS
&*
(c)
Figure 93..1 Vacuum-type porous cup lysimeters: (a) Conventional system (Everett et al, 1983); (b) A barrel
lysimeter with vacuum porous cup samplers installed within a hazardous waste land treatment facility
(Hornby et al., 1986, by permission); (c) System for sampling volatile organics in soil water (Scalf et
a]., 1981).
9-12
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9. VADOSE ZONE SOIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
9.2 DIRECT SOIL-SOLUTE SAMPLING (SUCTION METHODS)
9.2.2 Vacuum-Pressure Type Porous Cup
Other Names Used to Describe Method: Suction/soil lysimeter, high pressure-vacuum type porous cup sampler,
deep pressure vacuum lysimeter, ceramic points.
Uses at Contaminated Sites: Sampling of soil pore liquids in the vadose zone to characterize contaminated sites
or provide early warning of break-through of pollutants at controlled disposal sites.
Method Description; Vacuum-pressure type: Similar to vacuum type porous cup, except that a second line is
placed in the porous-cup-tipped tube, which ends just below the stopper. The shorter line is connected to a
pressure-vacuum source. When the unit is in place, a vacuum is applied to draw soil water into the sampler.
Then pressure is applied to push the sample into the flask. Figure 9.2.2a illustrates installation of two vacuum
pressure lysimeters in the same hole at two levels. The high pressure-vacuum type sampler is similar to the
vacuum-pressure type device, except that the sampler is divided into two chambers connected by the line with
a one-way valve (Figure 9.2.2b). When vacuum is applied, the soil solute is pulled into the upper chamber.
When pressure is applied to drive the sample into the container at the surface, the one-way valve prevents any
of the sample from being pushed out the porous cup. Nightingale et al. (1985) have developed a pressure
vacuum-type sampler suitable for both saturated and unsaturated conditions that uses a standpipe rather than
a check valve to keep the sample from being forced back into the soil when pressure is applied. With
modifications, conventional ceramic porous-cup soil-solution samplers can be used to sample volatile organic
compounds in the soil solution (Wood et al., 1981 [see Figure 9.2. lc]).
Method Selection Considerations; In most cases, ceramic vacuum-pressure lysimeters will be the method of
choice. Advantages: All the same advantages of the vacuum-type sampler (Section 9,2.1), plus: (1) Can be used
at depths below the suction lift of water (down to 50 feet for vacuum-pressure type and down to 300 feet for high
pressure-vacuum type); and (2) several units can be installed in the same borehole for sampling soil water at
different depths. Disadvantages: Same as for vacuum-type sampler (Section 9.2.1) plus: Some solution is forced
back through the walls of the cup when pressure is applied. The high pressure-vacuum type sampler overcomes
this problem.
Frequency of Use: Probably the most commonly used method for soil-solute sampling.
Standard Methods/Guidelines: ASTM (1992), Everett (1990), Rhoades and Oster (1986), U.S. EPA (1986).
Sources for Additional Information: See Table 9-3.
9-13
-------
/PRESSURE EVACUATION ACCESS
9
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|| II H
IL^ vaCUUM/PRESSUSE
^V 10TTLE
33lisi53|
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MINIMUM FOR 1
TWO LYSI METERS |
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if SILICA FLOUR
I
-VACUUM-AIR PRESSURE LINE
-UPPER CHECK VALVE
-SAMPLE DISCHARGE LINE
, UPPER CHAMBER
-LOWER CHECK VALVE
-TUBING
-LOWER CHAMBER
-SUCTION CUP
(a)
(b)
Figure 9^.2 Vacuum-pressure iysimeters: (a) Clustered vacuum-pressure suction cup lysimeters in a single borehole
(Everett et ol, 1983, after Hounslow et al, 1978); (b) High pressure-vacuum suction cup sampler
(Everett et al., 1983).
9-14
-------
9. VADOSE ZONE SOIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
9.2 DIRECT SOIL-SOLUTE SAMPLING (SUCTION METHODS)
9.2.3 Vacuum-Plate Samplers
Other Names Used to Describe Method: Alundum tension plate.
Uses at Contaminated Sites: Sampling of soil pore liquids in the vadose zone to characterize contaminated sites
or provide early warning of break-through of pollutants at controlled disposal sites.
Method Description: Principles are the same as porous cup samplers (Sections 9.2.1 and 9,2.2) except the
geometry of the porous material is different The vacuum plate consists of an Alundum or ceramic disc (range
from 43 to 25.4 centimeters in diameter) attached to an extraction vacuum extraction tube (Figure 9.2.3).
Installations reported in the literature use a vacuum sampling apparatus, but a vacuum-pressure system (Section
9,2.2) could be used as well. Installation is similar to that described in Section 93.1 for trench lysimeters.
Method Selection Considerations; Advantages and disadvantages essentially are the same as for porous cup
suction samplers (Section 9.2.1 and 9.2.2) with the added advantage that a large sample volume can be obtained
without disrupting adjacent flow pattern, and the added disadvantage that trench installation procedures are more
complicated
Frequency of Use: Uncommon.
Standard Methods/Guidelines: ASTM (1992).
Sources for Additional Information: See Table 9-3.
9-15
-------
HAND RECEIVING
PUMP T BOTTLE
ALUNDUM UFTAI "STRAP
FILTER DISK SCREEN MfTAL STRAP
CLAMP
LEACHAT6
COLLECTING
CARBOY
BUTYL RUBBER
SHEETING
R6CEIVING FLASK CONNECTOR
TENSION PLATE CONNECTOR
WELL FOR PRECLUDING
DISRUPTION OF TENSION
COLUMN DURING
DROUGHT PERIODS
Figure 93.3 Vacuum-plate lysimeter (Morrison, 1983, after Cole, 1958, by permission).
9-16
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9. VADOSE ZONE SOIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
9.2 DIRECT SOIL-SOLUTE SAMPLING (SUCTION METHODS)
9.2.4 Membrane Filter
Other Names Used to Describe Method: ~
Uses at Contaminated Sites: Sampling of soil pore liquids in the vadose zone to characterize contaminated sites
or provide early warning of break-through of pollutants at controlled disposal site.
Method Description: A membrane filter (polycarbonate or cellulose acetate) and a glass fiber prefilter are
mounted in a Swinnex-type filter holder (used for filtration of fluids delivered by a syringe [see Figure 9.2.4a]).
Installation involves digging a hole to the desired depth (up to 4 meters), and placing glass fiber collectors in the
bottom of the hole (Figure 9.2.4b). Glass fiber discs that fit within the filter holder are placed on the fiber
collectors and provide a wicking action between the collectors and the filter holder assembly (Figure 9,2.4c). The
filter holder is placed in the hole, making sure that the glass fiber prefilter in the holder is in contact with the
"wick" discs. The hole is then backfilled. The sample is drawn through a flexible tube attached to the filter
holder using suction. The prototype (Stevenson, 1978) has been used at depths to 1 meter using suction
apparatus similar to vacuum-type porous cup samplers (Section 9.2.1). Theoretically, installation could be as
deep as 4 meters using a vacuum-pressure type apparatus for fluid collection.
Method Selection Considerations: Advantages: (1) Membrane filter is better for determining phosphorus
concentrations than porous cup samplers; (2) samples are less susceptible to being drawn back into the soil when
soil-moisture tension exceeds the vacuum in the sampler; (3) can be manufactured from inexpensive, readily
available materials; (4) the wick-collector system provides contact with a relatively large soil area; and (5)
satisfactory sampling rates can be maintained even when parts of the collector sheet become blocked by fine
particles. Disadvantages: (1) Installation procedure is more complex than for porous-cup sampler; (2) under very
dry soil conditions, the membrane dries out and rapid vacuum loss occurs; (3) depending on the membrane filter
composition and manufacturer, a variety of contaminants, such as nitrogen, carbon participate matter, and
sodium, might be contributed to samples (thorough rinsing with distilled water can minimize these contributions);
and (4) clogging by biofilm growth is a problem on cellulose acetate membranes (can be controlled, in part, with
treatments of silver nitrate and sodium chloride).
Frequency of Use: Uncommon.
Standard Methods/Guidelines; ASTM (1992), Stevenson (1978).
Sources for Additional Information; See Table 9-3.
9-17
-------
FILTER/SUPPORT
BASE
MEMBRANE
FILTER
CUT-
Preparation of "Swinnex" type filter holder
(or suclion sampler.
(a)
VACUUM
INDICATOR
,SCALE MARKING
. SEALING CLAMP
SAMPLE RECEIVER
VACUUM RESERVOIR
COLLECTOR FILTER SHEET
POLYETHYLENE
SHEET
POLYETHYLENE
SHEET
Installed sampler, sample receiver, and
vacuum indicator.
GLASS FIBER
COLLECTOR"
PREFILTER
GLASS FIBER
Installation of suction sampler showing
glass fiber "wick" and "collector" arrangement.
Figure 92.4 Membrane filter sampler: (a) Preparation of Swinnex type filter holder; (b) Installation set-up; (c)
Sampler; (Morrison, 1983, after Stevenson, 1978, by permission).
9-18
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9. VADOSE ZONE SOIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
9.2 DIRECT SOIL-SOLUTE SAMPLING (SUCTION METHODS)
9.2.5 Hollow Fiber
Other Names Used to Describe Method: Cellulose-acetate hollow fiber sampler, hollow fiber filters.
Uses at Contaminated Sites: Sampling of soil pore liquids in the vadose zone to characterize contaminated sites
or provide early warning of break-through of pollutants at controlled disposal sites.
Method Description: To date, this method has been applied only to soil cores and blocks in the laboratory.
Bundles of semipermeable fibers (cellulose-acetate, or hollow fibers produced from a noncellulosic polymer
solution) are installed vertically or horizontally (Figure 9.2.5) in a soil core by inserting them down a thin
diameter (0.3 centimeter) metal tube. Once the fibers have been pushed into the core, the tube is withdrawn.
The fibers also can be placed in a perforated length of PVC tubing that is pushed into place. The hollow fibers
are attached to a vacuum pump and suction is applied (based on readings from separately installed tensiometers)
to collect the soil solution.
Method Selection Considerations; Not recommended for use in the field at this time due to lack of field testing
(Everett, 1990). Advantages: (1) The fibers used have been designed to function as molecular sieves, allowing
more precise selection of pore size (macrosolute rejection levels from 500 to 300,000 molecular weight); (2)
installing hollow fibers for solute sampling from laboratory core studies requires less disturbance than porous
ceramic cup samplers; and (3) encasing a fiber bundle within a perforated plastic tube allows installation of a
sampling unit along a long horizontal axis. Disadvantages: (1) Horizontal installation is difficult in the field; (2)
cellulose acetate fibers might screen nitrate-nitrogen, phosphorus, and potassium; (3) biological clogging of fibers
is a potential problem; (4) suitability for sampling metal and organic contaminants has not been evaluated; and
(5) has a narrow operating range (20 to 50 centibars) because large pore diameters result in low bubbling
pressure.
Frequency of Use: Uncommon.
Standard Methods/Guidelines: ~
Sources for Additional Information: See Table 9-3.
9-19
-------
LYSIMETERS
.TENSIOMETERS
Figure 9.2.5 Schematic of experimental hollow fiber sampling system (Levin and Jackson, 1977, by permission).
9-20
-------
9. VADOSE ZONE SOIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
9.2 DIRECT SOIL-SOLUTE SAMPLING (SUCTION METHODS)
9.2.6 Ceramic Tube Sampler
Other Names Used to Describe Method: Ceramic filter candle, vacuum (trough) extractor.
Uses at Contaminated Sites: Sampling soil pore liquids in the rooting zone.
Method Description: The sampling device is similar to the vacuum-type porous cup sampler, except that a porous
ceramic candle (around 12 inches long and 1 inch in diameter) is used instead of a porous cup. Installation
requires excavation of a vertical trench to below the depth of the rooting zone to provide a work area, as well
as further excavation of a horizontal cavity at the desired depth of sampling. The filter candle assembly is placed
horizontally in a galvanized sheet metal trough that has the approximate dimensions of the horizontal cavity
(Figure 9.2.6). The trough is filled with soU and the assembly is placed in the horizontal hole. Contact with the
soil above the trough is ensured by the use of an ah* pillow or mechanical jack. Sampling is accomplished by
using a separately installed tensiometer to measure soil-water tension, and using a vacuum in the system to
induce soil-water flow into the trough and candle at the same rate as the surrounding soil. A small diameter tube
attached to the other end of the filter candle and extending to the work area in the vertical trench allows
rewetting, if necessary.
Method Selection Considerations: Advantages: (1) Allows direct sampling of soil water; (2) successive samples
can be obtained from the same depth; and (3) samples both pore water and water flowing through macropores
that is intercepted by the trough. Disadvantages: The same as for vacuum-type porous cup samplers, except that
disadvantages 4 and 6 do not apply, and the added disadvantage of being more difficult to install.
Frequency of Use: Uncommon, has mainly been used for sampling of irrigation return flow.
Standard Methods/Guidelines: Duke and Haise (1973).
Sources for Additional Information: See Table 9-3.
9-21
-------
CROSS SECTION
A—A
SAMPLING
BOTTLE
ADJUSTABLE
VACUUM
SOIL
SOLUTION
DUAL CHAMBE
TRICKLE TUBING
AIR PRESSURE
DISTURBED-
SOIL
AIR PILLOW
•UNDISTURBED
SOIL
SHEET METAL
TROUGH
I m
Figure 92,6 Filter candle sampling setup (Everett et aln 1983, after Hoffman et al., 1978).
9-22
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9. VADOSE ZONE SOIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
9.2 DIRECT SOIL-SOLUTE SAMPLING (SUCTION METHODS)
9.2.7 Capillary Wick Sampler
Other Names Used to Describe Method: --
Uses at Contaminated Sites: Soil pore liquid sampling.
Method Description: Capillary wick samplers combine elements of the pan lysimeter (Section 9.3.1) and hollow
fiber samplers (Section 9.2.5). A pan with a glass cloth is inserted in the soil below the soil column to be
sampled (Figure 9.2.7). Lengths of fiberglass wick are placed in contact with the absorbent material in the pan
and suspended vertically over a sampling bottle. When wetted, the wicks apply a continuous tension to the soil
pore water equivalent to the wick length (up to -6.0 kPa). The collection chamber can be buried and samples
periodically collected through a tube to the surface using a suction sampler (Figure 9.2.7), or the collection bottle
can be accessed through a trench installation as with pan lysimeters (Figure 93. la).
Method Selection Considerations: Advantages: (1) Continuous solute samples can be obtained from unsaturated
soil without applying suction, minimizing possible affects on volatile contaminants (trench installations); and (2)
samples might be more representative of water moving through the soil than samples collected by suction
samplers or free-drainage samplers because they can collect soil water from both saturated and unsaturated
pores. Disadvantages: (1) Installation is somewhat more complex than for free drainage samplers (Section 9.3.1);
(2) solute characteristics might be altered as the solute travels up the wick; (3) is limited to relatively shallow
installations (generally 2 meters or less in undisturbed soil); and (4) only custom-built, experimental samplers
have been tested to date.
Frequency of Use: Relatively new method that has not been widely tested,
Standard Methods/Guidelines: —
Sources for Additional Information: See Table 9-3.
9-23
-------
SAMPLING TUBE TO SOIL SURFACE
6LAS3 CLOTH
30 C¥ \
3.95 CM' I
GLASS PLATE /
(0.95 era thick)
GLASS WICKS ENCLOSED IN PYREX PIPE
5 CM DIAMETER PYREX PIPE
5 L PYREX COLLECTION CHAMBER •
Figure 9.2,7 Schematic diagram of a capillary wick unsaturated zone soil pore water sampler (Holder et al., 1991, by
permission).
9-24
-------
9, VADOSE ZONE SQIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
93 DIRECT SOIL-SOLUTE SAMPLING (OTHER METHODS)
93.1 Free-Drainage Samplers
Other Names Used to Describe Method: Zero-tension samplers, tension-free lysimeter, pan lysimeter, collection
lysimeter/manifold collector, trench lysimeter, caisson lysimeter, free-drainage glass block sampler, pan-type
collectors, wicking-type sampler.
Uses at Contaminated Sites: Sampling water percolating through the vadose zone; measuring hydraulic
conductivity/solute flux.
Method Description: Free-drainage samplers, which intercept and collect water flowing in saturated pores or
fractures for delivery to a sample container, are installed in the soil, commonly at depths of interest in the side
of a trench or buried culvert. Two major types of installations are possible: (1) Open trench or caisson (Figures
9.3.1a and b respectively), in which permanent access exists and in which samples are usually collected by simple
gravity feed, and (2) buried trench, in which the access trench is backfilled after installation and samples are
brought to the surface using a suction method (Figure 9.3.1c), Various designs have been developed, including
stainless steel troughs, sand-filled funnels, and hollow glass blocks, Geotextile fabric can be used for wicking
action. In each case, gravity drainage creates a slightly positive pressure at the soil-sampler interface, allowing
the. soil water to drip into the sampler. The collection of ground-water outflow from tile drains is another way
to obtain samples that have recently moved from the vadose zone to the saturated zone. A variant in the tile
drain collection method is a collection lysimeter, also called a manifold collector, installed at the based of a
sanitary landfill to collect leachate (Figure 9.3.1d).
Method Selection Considerations: Advantages: (1) A larger volume of soil can be sampled compared to suction
samplers, and the defined surface area might allow quantitative estimates of leachate flux; (2) samples include
water moving through both large and small pores and are representative of the soil solute that is actually
percolating to greater depths without disturbing natural flow patterns; (3) have less possibility of chemical
alteration or loss of volatile compounds from the sample compared to porous-cup samplers; and (4) sampling
is continuous without the need for externally applied vacuum. Disadvantages: (1) Installation procedures are
time-consuming and complex; (2) samples will not be collected unless gravity flow is occurring; (3) installation
under impoundments generally is not feasible; (4) if collection surfaces are not installed perfectly level, a sump
or collection area can result in dead space where the soil water cannot be removed; (5) if the collection surface
is uneven, the potential exists for cross contamination from residual samples; and (6) safety considerations might
limit the depth to which trench lysiraeters can be installed. Tile Drain/Collection Lysimeter Advantages: Existing
tile drains require no installation, and manifold collectors are relatively easy to install where new landfill pits are
excavated. Tile Drain/Collection Lysimeter Disadvantages: (1) NAPLs might not appear in tile drain outflow
became they remain above the drain (light NAPLs) or might flow along the bottom of the perched water zone
(dense NAPLs); (2) is limited to shallow depth for economic reasons; and (3) the presence of air in the tile lines
might alter the chemistry of water flowing into the drain.
Frequency of Use: Relatively uncommon.
Standard Methods/Guidelines: ASTM (1992).
Sources for Additional Information: Wleklng-type sampler: Hornby et al. (1986); Trench pan lysimeter: U.S.
EPA (1986); Pan lysimeter with tension plate: Shaffer et al. (1979); Free-drainage glass-block sampler: Everett
(1990); Collection lysimeters: Sai and Anderson (1991). See also, Table 9-3.
9-25
-------
to
OS
2 «12* Siding ond
4«4" Timbers. All Wood
Tftolwi wilh Prisirwltve,
Culler Drain
Pip?
T-J:,"if "Residual Soil
rr;"" Stratified Silt,
-^-i- Cloy, ond Sond
,-, ™~— "
f-Screen an
Floor Drain
SAMPLING TUBE
.Dolomite
Bedrock
INSTALLATION TR6NCH
(BACKFILLtD AFTER IYSIM6TER INSTALLATION!
TRENCH (.VSIMET6F
OR GLASS BLOCK
SUWFACE OF
SANO BED
DOSING
WATER
10- oiAMcren
COBRU6ATED
STEEL PIPE
PVC HALF SCREEN
COLLECTOR PIPE
SAMPLE COLLECTION
(b)
(d)
20-PT LONS SECTION,
PEHTORATED PVC PIPE,
THE COLLECTOB MANIFOLD
Figure 93,1 Free-drainage sampler installations: (a) Trench lysimeter (Parizek and Lane, 1970, by permission); (b)
Caisson lysimeter (Morrison, 1983, after Aulenbach and Clesceri, 1980, by permission); (c) Pan
lysimeter installation (U.S. EPA, 1986); (d) Leachate collector installed at base of sanitary landfill
-------
9. VADOSE ZONE SOIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
9.3 DIRECT SOIL-SOLUTE SAMPLING (OTHER METHODS)
93,2 Perched Water Table
Other Names Used to Describe Method: --
Uses at Contaminated Sites; Characterizing and monitoring vadose zone soil pore liquid.
Method Description; Perched ground water is sampled as representative of water that has percolated through
the vadose zone. For shallow perched ground water, samples can be obtained by installing wells (Figure 9.3.2a),
piezometer nests (Section 5.4.3), or multilevel samplers (Section 5.6.1), or by installing a tile drainage system and
sampling at the outlet. Deeper perched ground water can be obtained by sampling cascading water in existing
wells, or by constructing special wells (Figure 9.3.2b). Wells or piezometers screened in perched aquifers are
sampled using the appropriate portable ground-water sampling device (see Section 5).
Method Selection Considerations: Advantages: (1) Larger sample volumes are obtained compared to suction and
extraction methods (particularly desirable when sampling for organics and viruses); (2) samples are more
representative than point samples obtained by suction and extraction methods, because they reflect the integrated
quality of water draining from the overlying vadose zone; (3) is cheaper than installing deep wells with batteries
of suction samplers; (4) can be located near ponds and landfills without concern about causing leaks; and (5)
nested piezometers and multilevel samplers can be used to delineate the vertical and lateral extent of plumes and
hydraulic gradients (see Sections 5,4 and 5,6). Disadvantages: (1) Perched zones must be present in the area
of concern; (2) detection of perched water deep in the subsurface can be expensive, requiring test wells or
geophysical methods; (3) some perched ground water is seasonal and might dry up (backup systems, such as
described by Nightingale et al. [1985], are recommended in this situation [see Section 9.2.2]); (4) is most suitable
for diffuse sources, such as land spreading areas or irrigated fields; and (5) multilevel sampling is restricted to
shallower depths where vacuum pumping is possible.
Frequency of Use: Commonly used, if perched water table is present.
Standard Methods/Guidelines: Sampling from cascading wells: Wilson and Schmidt (1978).
Sources for Additional Information: Everett et al. (1983), See also, Table 9-3.
9-27
-------
Ground Surface
Perched
Wafer Level.
Perching §
Layer
Water Tab!e_
Base of
Aquifer
PERCHED ZONE
AQUIFER
Perforated
Interval
Ground Surface
Perched
Vtoter Level
Perching
Layer
-w_
Wafer Table
Perforated
Interval -
Base of
Aquifer
PERCHED ZONE
Cascading Wafer
•".•*".'••/"—Zone of Cascading
r"'•'.'•/ Water in Aquifer
"X AQUIFER
(b)
Figure 9,3.2 Perched water table sampling: (a) Well in perched water table; (b) Cascading water in an idle well
(Wilson and Schmidt, 1978, by permission).
9-28
-------
9. VADOSE ZONE SOIL-SOLUTE/OAS SAMPLING AND MONITORING METHODS
9.3 DIRECT SOIL-SOLUTE SAMPLING (OTHER METHODS)
9.3.3 Absorbent Methods
Other Names Used to Describe Method: Cellulose nylon sponge, ceramic rods or points.
Uses at Contaminated Sites: Collecting of soil pore liquids in the vadose zone.
Method Description: Absorbent methods use the ability of a porous material to absorb soil pore water. Cellulose
nylon sponge: A sponge is place within a trough, which is positioned against the ceiling of a horizontal tunnel
by a series of three-lever hinges. When the sponge has absorbed a certain volume of pore water, the trough is
.withdrawn and the sponge is placed in a moisture-tight container. In the laboratory, the solution is extracted
from the sponge using rollers. Ceramic rods: Tapered ceramic rods or points (90 by 12 millimeters [Figure
93.3]) are prepared by boiling in distilled water, drying, and storage in a desiccator. In the field, the rods are-
taken out, weighed, and driven into the surface soil. After a period of time, the rods are withdrawn and weighed
to determine the volume of absorbed water. The points are leached by boiling them in a known volume of
distilled water. The solution is analyzed and the original pore water concentration determined from the ratio
of water absorbed by the ceramic to the volume of boiling water. Section 9.3.7 describes uses of absorbent
collectors with the SEAMIST system.
Method Selection Considerations; Advantages: No clear advantages over alternative methods. Disadvantages:
" (1) Require near saturated conditions; (2) procedures are relatively complex; (3) representativeness of samples
extracted from porous points is questionable.
Frequency of Use: Uncommon.
Standard Methods/Guidelines: —
Sources for Additional Information; Ceramic points: Shimshi (1966); Sponge: Tadros and McGarity (1976).
9-29
-------
Epox
-
• 5achbn
— ,». _f j<—Section of B
T^l 9 -
Figure 933 A point made from a discarded ceramic pressure plate used for collecting soil solute samples by
absorption; units in millimeters (Shiinshi, 1966, by permission).
9-30
-------
9. VADOSE ZONE SOIL-SOLUTE/OAS SAMPLING AND MONITORING METHODS
93 DIRECT SOIL-SOLUTE SAMPLING (OTHER METHODS)
9.3.4 Solids Sampling with Soil-Water Extraction
Other Names Used to Describe Method: Squeezing press, pressure extraction press/filter press, soil press.
Uses at Contaminated Sites: Soil pore water and/or solute sampling during site characterization; soil solute
monitoring where suction methods will not work.
Method Description; Soil core samples are collected and soil water is extracted in the field or (more typically)
the laboratory by one of a number of methods. Column displacement uses an immiscible fluid that displaces soil-
pore water in a soil column by gravity. Centrifugad'on uses a double bottom centrifuge to remove soil water.
The displacemcnt/centrifugation method uses a combination an immiscible fluid and a centrifuge. Soil water
also can be obtained by squeezing (Figure 93.4) or vacuum extraction. The resulting liquid is then analyzed for
constituents of interest.
Method Selection Considerations: Advantages: (1) Vertical profiles of concentrations of specific pollutants can
be obtained; (2) identification of variations of ionic concentrations in layered sequences is possible; and (3) solids
samples can be used for additional analyses, such as grain size, cation exchange capacity, etc. Disadvantages:
(1) A large number of samples is required to characterize spatial variability of soil solutes; (2) is expensive if
deep sampling is required; (3) changes in soil-water chemistry might occur during preparation and extraction;
(4) soil-water samples represent concentrations of moisture content at the time of sampling, ionic concentrations
would be different at other moisture contents; (5) is a destructive method, which precludes comparing successive
sampling results due to soil variability; (6) core holes might alter infiltration patterns and cause short-circuiting
of pollutants to greater depths; and (7) the chemistry of soil water from various extraction methods might differ
from the chemistry of soil pore liquid collected using suction and free-drainage samplers (especially if greater
pressures are used).
Frequency of Use: Sometimes used during site characterization; rarely used for monitoring because of destructive
nature of sampling.
Standard Methods/Guidelines: Squeezing: ASTM (1985).
Sources for Additional Information; See Table 9-3.
9-31
-------
"1" SCMW
PSfSSUHE INltT
MUD cw
GBADIM1ID CYUNOER
THUMB SC88VK
SUPPOUT
TOF CAP
*UIMB GASKfT
»*St CAP WITH
Flir«ATE TUBE
FIUBATE TUBE
Figure 93,4 Filter press and chamber assembly for pore water extraction (Luscynski, 1961).
9-32
-------
9. VADOSE ZONE SOIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
93 DIRECT SOIL-SOLUTE SAMPLING (OTHER METHODS)
9.3.5 Solids Sampling with Soil-Saturation Extract
Other Names Used to Describe Method; —
Uses at Contaminated Sites: Measuring water-soluble contaminants and soil minerals.
Method Description: Solids samples are collected using tube samplers or augers, and the electrical conductivity
of a saturation extract (prepared in the field or laboratory) is measured. The electrical conductivity
measurements are then interpreted in terms of salinity and other properties (Rhoades et al., 1989b,c)
Method Selection Considerations: Advantages: (1) Is a simple procedure; and (2) provides a measure of leaching
potential from a soil sample. Disadvantages: (1) A large number of samples is required to characterize spatial
variability of soil solutes; (2) is expensive if deep sampling is required; (3) changes in soil-water chemistry might
occur during preparation and extraction; (4) sample saturation extract might not be representative of actual soil
solution moving through the vadose zone; (5) is a destructive method, which precludes comparing successive
sampling results due to soil variability; (6) core holes might alter infiltration patterns and cause short-circuiting
of pollutants to greater depths; and (7) the chemistry of soil-saturation extracts will not be comparable to soil
pore liquid collected using suction and free-drainage samplers.
Frequency of Use: Commonly used in arid and semi-arid areas where soluble salt concentrations in soils are high.
Standard Methods/Guidelines: Rhoades (1982), SCS (1984, Section 8E).
Sources for Additional Information: See Table 9-3.
9-33
-------
9. VADOSE ZONE SOIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
93 DIRECT SOIL-SOLUTE SAMPLING (OTHER METHODS)
93.6 Solids Sampling for Volatile and Microbial Constituents
Other Names Used to Describe Method: —
Uses at Contaminated Sites: Collecting uncontarniriated samples for constituents that might be sensitive to
exposure to air.
Method Description: Special sampling procedures are required for sampling contaminants that can change in
concentration (degassing of volatile compounds) or chemical composition (redox-sensitive chemical species, such
as ferrous and ferric iron) when exposed to the air. Similar care is required when sampling for microbiota in
the subsurface, especially where oxygen content is low (typically in the zone of saturation). Even where exposure
to the air is not a concern for microbiological sampling (typically in the vadose zone), special care is required
to make sure that the sample has not been cross contaminated with soil microorganisms from higher soil
horizons. The basic procedure involves collection of subsamples of power-driven sample cores (Section 2.4),
using smaller diameter corers. Figure 9.3.6a shows suggested locations for microbial and volatile samples from
a core. Samples for volatiles should be quickly transferred to the sample container and sealed with no air
headspace in the container. Where cores contained anaerobic bacteria and chemical species of concern that are
in a reduced state, samples need to be extracted in an oxygen-free environment. Figure 9.3.6b shows a plexiglass
field glove box for collecting such samples. Sample containers are sterilized and filled with an inert gas such as
nitrogen. In the field, the sealed containers are placed in the field glove box, before the box is filled with
nitrogen. The core sample is pushed into the box through an iris port, and a core paring tool is used to collect
subsamples in the oxygen-free environment for placement in sample containers.
Method Selection Considerations: Required whenever accurate measurement of volatiles and microorganisms
in soil samples is necessary. The more complex glove box procedure should be used when accurate identification
of reduced metal species and/or anaerobic microorganisms is required.
Frequency of Use: Relatively uncommon. Should probably be used more commonly.
Standard Methods/Guidelines: Dunlap et al. (1977), Leach et al. (1988).
Sources for Additional Information: Beeman and Suflita (1989), Board and Lovelock (1973), Bordner et al.
(1978), Oilmore (1959), Phelps et al. (1989), Russell et al. (1992)
9-34
-------
MICRQB1AL SAMPLE
I.3X 15.2 cm
ORGANIC SAMPLE
7.6 X 10.2 cm
MICROBIAL SAMPLE
13 X 15.2 am
ORGANIC SAMPLE
76 X IO. 2 cm
(a)
Flushing Vent
Flow Regulator
and Indicator
Sample Tube
from Extruder
(b)
Figure 93,6 Solids sampling for microbiological and volatile contaminants: (a) Core subsample (Dunlap ct al.
1977); (b) Field sampling glove box (Leach ct al., 1988, by permission).
9-35
-------
9, VADOSE ZONE SOIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
93 DIRECT SOIL-SOLUTE SAMPLING (OTHER METHODS)
93.7 SEAMIST.
Other Names Used to Describe Method: —
Uses at Contaminated Sites; Sampling of soil-pore liquids and soil gases; measuring air permeability; might
eventually be adapted for ground-water sampling.
Method Description: SEAMIST (Science and Engineering Associates Membrane Instrumentation and Sampling
^Technique) is a recently developed system that involves the placement of a membrane packer in an open
borehole (Figure 93.7a-c), Soil-gas sampling ports attached to flexible tubing are attached to the membrane to
create an in situ multilevel sampling system (Figure 93.7d). Multilevel soil pore liquid sampling is accomplished
by the placement of absorbent collectors on the outside of the membrane, with leads for measuring electrical
resistance running up the inside of the membrane (Figure 93.7d). Stabilization of the resistance readings serves
as an indicator that the absorbent pad has equilibrated with the moisture content of the borehole wall. The
flexible membrane is then retrieved by a reversal of the process shown in Figure 93.7a-c, and the absorbent pads
are removed for fluid extraction in the laboratory (see Section 93.3).
Method Selection Considerations: Advantages: (1) A unit supports the hole wall against the sloughing,
eliminating the need for casing and backfilling, provided the borehole is basically stable; (2) multi-level soil-pore
liquid and gas sampling from the same borehole is possible, and the method potentially can be used with any type
of instrumentation that can be fastened to the membrane fabric; and (3) materials are relatively inexpensive,
allowing permanent installation, if desired. Disadvantages: (1) Cannot be used in unstable boreholes (i.e.,
heaving sands); and (2) k a new technique for which there has been relatively little experience or independent
testing.
Frequency of Use: New method for which there is relatively little experience. The U.S Department of Energy
is providing research and development funding for this technique.
Standard Methods/Guidelines; ~
Sources for Additional Information: Keller (1991,1992), Keller and Lowry (1990,1991), Lowry and Narbutobskih
(1991), Mallon et a!. (1992).
9-36
-------
Air Hose
Membrane
and Tether
Rolled up on
Reel
Leads for electrica
resistance measurement
(d)
Figure 93.7 The basic operation of the SEAM 1ST system: (a) Insertion of packer; (b) Emplacement of membrane;
(c) Enlarged view of bottom cmplaced membrane (Lowry and Narbutovskih, 1991, by permission); (d)
Collection of pore liquid with an absorbent pad and pore gas via an evacuated tube (Keller and Lowry,
1990).
-------
9, VADOSE ZONE SOIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
9.4 GASEOUS PHASE CHARACTERIZATION
9.4.1 Soil-Gas Sampling (Static)
Other Names Used to Describe Method: Passive sampling.
Uses at Contaminated Sites: Detecting volatile contaminants in the unsaturated zone.
Method Description: Static sampling can be done in two ways. First, an in situ adsorbent (usually an activated
charcoal rod) is buried in the soil for a few days to weeks (Figure 9.4. la and b). The adsorbent is retrieved and
analyzed for volatile organic compounds in a laboratory by mass spectrometry or gas chromatography. Second,
static grab samples are collected from containers placed in the soil surface, which collect quiescent soil-gas
samples. These samples usually are analyzed in the field using portable analytical instruments (see Sections
103.1 and 10J.2).
Method Selection Considerations: Advantages: (1) Is inexpensive and easy to install; (2) laboratory analysis
usually provides more precise measurement than field measurement of dynamic samples; (3) if sorption capacity
of the sampler is not exceeded, average flux of contaminants to the surface can be calculated; and (4) field
operations require minimal training. Disadvantages: (1) Is sensitive to exposure time and insufficient exposure
might result in a false negative and overexposure (saturation of sorbent) might mask relative difference in soil-gas
contamination at different sampling locations; (2) vertical profiles of soil-gas concentrations are more difficult
to obtain than with soil probes; (3) results using in situ absorbent samplers are not available for days to weeks
because desorption and laboratory analysis are time consuming; and (4) might not be appropriate for VOCs that
have low boiling points (<5 degrees C) or compounds that are prone to thermal decomposition during pyrolysis.
Frequency of Use; Common.
Standard Methods/Guidelines: ASTM (199la).
Sources for Additional Information: Vroblesky et al. (1992); see also, references for Section 9.4.2.
9-38
-------
*&'&&>?*.&• i.
ll
.XoJ'nJMvl'.QKXPA.^O'/-!rO..tU-p.V«i £ o
*£
•s«^
f
£
11
a 1
e sg
•B b
«
IB .b
.s s
.
i ¥
I1 *
ie 13
» S
.i 2
3
ec
9-39
-------
9. VADOSE ZONE SOIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
9.4 GASEOUS PHASE CHARACTERIZATION
9.4.2 Soil-Gas Probes
Other Names Used to Describe Method: Dynamic grab samples, headspace sampling.
Uses at Contaminated Sites; Detecting and monitoring of volatile organic contaminants in the unsaturated zone.
Method Description: Dynamic soil-gas grab samples are collected from a moving stream of soil gas, which is
pumped through a hollow probe that is driven into the soil (Figure 9.4.2a), or from permanently installed tubes
at one or more levels in the soil (see Figure 5.5.2c). The probes can be manually or pneumatically driven, or
installed in boreholes. Relatively nonvolatile NAFLs can be detected using steam injection (Figure 9.4.2b), The
samples usually are analyzed in the field using portable analytical instruments. Grab samples usually are taken
at the same depth at a number of surface locations for areal characterization of soil-gas concentrations. Where
the vadose zone is thick, or discontinuous impermeable layers exist at a site, samples can be taken at different
depths at the same location in order to define vertical changes in soil-gas concentration. An adaptation of the
method has been used to detect zone of contaminated discharge to streams using bottom sediment gas bubbles
(Figure 9.4.2e).
Method Selection Considerations: Advantages: (1) Is a nondestructive method; (2) hollow-probe samplers allow
collection of multiple samples in a relatively short period of time; (3) when combined with on-site gas
chromatography, results are available in a matter of minutes; and (4) problems associated with handling and
transporting gas samples are minimized. Disadvantages: (1) Grab-sampling results are highly depth dependent
and sampling results might be misleading if the correct depth is not sampled (based on site-specific factors, such
as moisture conditions, air-filled porosity, and depth to ground water, and compound-specific factors, such as
solubility, volatility, and degradability); (2) dynamic sampling perturbs local VOC concentrations as a result of
pumping to retrieve sample; and (3) nonvolatile contaminants, if present, will not be detected. Table 9.4.2
provides specifications for a variety of commercially available soil-gas sampling probes.
Frequency of Use; Widely used for preliminary site characterization where volatile contaminants are known or
suspected.
Standard Methods/Guidelines: ASTM (1991a). Probe and well sampling: Ford et al. (1984).
Sources for Additional Information: API (1985,1991), Devitt et al. (1987), Kerfoot (1991), Kerfoot and Barrows
(1987), Pitchford et al. (1988), Rector (1991-radon detection), Robbins (1990), Vroblesky and Lorah (1991).
9-40
-------
QT;—*•
x
i-
C-
yj
a
10 CC CLASS
SYRINGE
SYRINGE NEEDLE'
SILICONS
RUBBER TUBE
1/4 INCH TUBINQ-
SILICONS RUBBER
-TUBE CONNECTION
TO VACUUM PUMP
ADAPTER FOR SAMPLING
SOIL-GAS PROBE
(a)
5 IO
IONIZABLE GAS• CONCENTRATION (ppm-V/v)
CLEAR TUBING SLEEVE
CONNECTOR (DISPOSABLE)
•SOIL-GAS FLOW
DURING SAMPLING
_3/4 INCH
GALVANIZED PIPE
-DETACHABLE DRIVE POINT
Laboratory
for analysis
(b) (c)
Figure 9.4.2 Dynamic soil-gas sampling systems: (a) Soil vacuum withdrawal (Pitchford et al., 1988); (b) Response
of PID detector to soil-gas samples with and without steam injection (Kerfoot, 1991, by permission); (c)
Water collection system (Vroblesky and Lorah, 1991, by permission).
941
-------
Table 9.4,2 Commercial Sources for Soil-Gas Sampling Probes and Tank Leak Monitor Systems
II
§1
9 6 SOIL GAS
3 u! PROBES
MANUFACTUBEH
AGAfl
713,464-4451
ARTS MANUFACTURING 4 SUPPLY
206/228-2017. 80QB35-7330
ATLANTIC SCREEN & MANUFACTURING
302684-3197
E L E (NTERNATONAL/SOILTEST PRODUCTS
708/295-9400. 80Q323-1242
ENVIRONMENTAL INSTRUMENTS
$JO,'688-4474, 800648-9355
ENVIRONMENTAL MONrTOHING
206/488-8687, BOa'468-3106
FLUID COMPONENTS 819/744-6950. 800/854-1993
dUlO CONTROLS 205.SS1-600O. 80*462-0860
H N U SYSTEMS
817/964-6690. 800/724-5600
HIQHtANp TANK t MANUFACTURING 814/893-5701
1N-SITU 307/742-8213, 800/446-7488
INViNTRON
3I3/473-9250
KECK INSTRUMENTS S17/6S5-5616. 800VS42-S6B1
U-AK-X 2*2f822-676£ 800/336-5325
MSA. INSTRUMENT DTV.
M T S SYSTEMS, SENSOH DIV.
919,877-0100, 800/457-6620
MA6N6TEK 8 W CONTROLS 3ia'435-0700
MARLEY PUMP/RED JACKET
NEOTHONICS OF NORTH AMERICA
706. S35-0600.80CL 535-0 B06
OMNIOATA INTERNATIONAL 801/753-7760
ONg PLUS, LEAK EDGE DIV. 708/498-0955
PETROVENO
7W48S-4200
PLASTIC FUSION FABRICATORS
20$/534-0684, 800/356-1480
POU.ULEHT SYSTEMS
317/328-4020. 800,343-2128
REMEDIAL SYSTEMS
S08.S43.1512
SOLINST CANADA 416/873-2255
TELEOYNE ANALYDCAL 81&-961-9221
THERMO ENVIBONMENTAL INSTRUMENTS
SOft'S 2O-0400
TRAC6B RESEARCH 60ZB88-9400. 800.'989-9929
U.S. INDUSTRIAL PRODUCTS 213/926-9477
UNITED SENSORS S16S53-0500
UNIVERSAL SENSORS S DEVICES
81IW98-7I21, 800199-7121
VEEOERHOOT
203.«51-2700
WARflCK CONTROLS
313."S4S-2S12, 800/776^622
MAX DEPTH (FT!
ISO
00
20
ii
1
MA
MA
MA
Z
3.
ss
HS
SS
g
t—
o
L
o
u
til
a
5
50
3
MAX DEPTH (FT)
20
10
SENSOR INPUTS (NO.)
32
X
X
120
X
X
Various
X
3-8
35
X
8
X
X
X
X
X
128
X
15
32
2
X
X
X
X
16
64
16
TANK LEAK MONITOR
SYSTEMS |
ALARM TYPES
HUE
SD
HI.LO
SO
HI.LO
LE.SD
HI.LO
LE
HI.LO
LE.SD
HIAO
L1.SD
W
LE
HI.LO
LE
HIAO
LE.SD
HIAO
LE.TV
HI.LO
E.SD
SENSOB TYPES
HY.LI
CO.OT
HY.CO
HY.VA
U
FR.HY
VAAI
CO
HY.VA
U
HY.U
W,LI
HY.VA
LI.CO
HY.VA
U,CO
Y.VA
LI.CO
VAPOR SENSOR RANGE (PPM) ,
10-
2000
20+
50-
0.000
1-
0.000
20-
7SOO
0-
4000
REPORTS
AM
IR^M.DE
SR.IN
IR.LT.AM
DE.SR.IN
AM.DE
IN.LT
6V
AM
LT
AM
AM
HM.D6.SR
INAT
AUTO DIAL?
N
Y
Y
Y
N
KEY
AM ALARMS
CO COMBINATION
DE DEUVERIES
EV EVENT
FH FREON
HI HIGH
HS HARDENED STEEL
HY HYDROCARBONS
IN INVENTORY
IR INVENTORY RECONCILATION
LE LEAK
LI LIQUID
LO LOW
LT LEAK TEST RESULTS
Ol OIL THICKNESS
MA MANUAL
SD SELF DIAONOSTtC
SR SHIFT REPORT
SS STAINLESS STEEL
TV THEFT / VANDALISM
VA VAPOR
X TANK LEAK MONITORINS SYSTE
Source: Pollution Equipment News (April 1993)
9-42
-------
9. VADOSE ZONE SOIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
9,4 GASEOUS PHASE CHARACTERIZATION
9.4.3 Tank/Pipelbe Leak Sensors
Other Names Used to Describe Method: —
Uses at Contaminated Sites: Detecting leaks in underground storage tanks and pipelines.
Method Description: Numerous techniques have been developed to detect leaks in underground storage tanks
and pipelines (Figure 9.4.3). Inventory monitoring involves identification of discrepancies in tank storage
between additions and withdrawals and can be accomplished by manual tank gauging and reconciliation, statistical
reconciliation, or using automatic gauging systems. Various methods can be used for soil or ground-water release
detection: (1) Sampling of detection wells, (2) soil sampling, (3) using dyes and tracers, and (4) surface
geophysics. Vadose zone vapor detection methods include: (1) Grab sampling or soil coring, (2) surface flux
chambers (see Section 9.5.2), (3) downhole flux chambers; (4) accumulator systems, and (5) soil-gas probe testing
(Section 9.4.2). Secondary containment with interstitial monitoring provides one of the safest leak detection
methods because any releases are prevented from entering soil or ground water. Physical test methods include
visual inspection using remote cameras (see Section 3.5.7) and tightness testing of tanks and piping. Over 90 leak
detection systems are available that involve detection of organic vapors as an indication that underground storage
tanks are leaking. Vapor wells and U-tubes are commonly used. More than 200 liquid hydrocarbon and
hydrocarbon vapor detectors or sensors are available. Sensor systems can range from systems with alarms that
go off when vapors are detected to systems that monitor product flow into and out of the tank and identify
discrepancies that might be related to leakage. Table 9.4.2 provides information on a number of commercially
available tank leak monitor systems.
Method Selection Considerations: The appropriate state and/or federal regulations should be consulted to
determine the types of leak detection systems that should be used.
Frequency of Use; Standard requirement for any new installation of underground storage tanks containing
hydrocarbons and other potentially hazardous liquids.
Standard Methods/Guidelines; ASTM (1991b, 1993).
Sources for Additional Information: Boone et al. (1991), Cochran (1987), Durgin and Young (1993), Eckert and
Maresca (1992), Eklund and Crow (1987), Fromrne et al. (1991), Lyman and Noonan (1990), Maresca and
Hillger (1991), Maresca et al. (1991), Morrison and Mioduszewski (1986), Niaki and Broscius (1986), Portnoff
et al. (1991), Scheinfeld and Schwendeman (1985), Scheinfeld et al. (1986), Schwendeman and Wilcox (1987),
Starr et al. (1991b).
9-43
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1 - Groundwater Monitoring
2 • Vapor Monitoring
3 • Secondaiy Containment with Interstitial Monitoring
4 • Automatic Tank Gauging
5 - Tank Tightness Testing with Interstitial Monitoring
6 - Manual Tank Gauging
7 - Leak Detection tor Suction Piping
8 - Leak Detection tor Pressurized Piping
Figure 9.4,3 Examples of leak detection methods for tanks and piping (Floyd, 1993).
9-44
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9. VADOSE ZONE SOIL-SOLUTE/GAS SAMPIJNG AND MONITORING METHODS
9.4 GASEOUS PHASE CHARACTERIZATION
9.4,4 Air Pressure
Other Names Used to Describe Method: —
Uses at Contaminated Sites: Can be used as an indirect expression of soil structural properties because an air
pressure buildup usually affects the relative magnitude of the air permeability and hydraulic conductivity, which
are both indices of soil structure.
Method Description: Various types of manometers can be used, including: (1) Pressure transducers, (2) fluid
manometers, and (3) aneroid barometers. The manometer is attached to an air-filled access tube that is placed
in the soil (Figure 9.4.4). Changes in air pressure with time are measured in response to events like wetting of
a diy soil. Care must be taken to ensure that the access tube fits tightly in the surrounding soil.
Method Selection Considerations: Fliihler et al. (1986) consider soil-air pressure to be one of the most frequently
neglected variables in soil physics research. Air pressure measurements might have value for site
characterization, but their utility have not be evaluated in this context.
Frequency of Use: Uncommon.
Standard Methods/Guidelines: Hiihler et al. (1986).
Sources for Additional Information: —
9-45
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AIR FILLED
ACCESS -
TUBE (VA)
Manometer
WET SOIL -
CONFINED
SOIL AIR
...AIR.-J.MJj'ERV/lp.US. LAYER v
REFERENCE
PRESSURE
Figure 9.4.4 Diagram of a soil air pressure gauge (Fliihler et al., 1986, by permission).
9-46
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9. VADOSE ZONE SOIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
9.4 GASEOUS PHASE CHARACTERIZATION
9.4.5 Gas Permeability and DiSusivity
Other Names Used to Describe Method: Air permeability.
Uses at Contaminated Sites: Measuring gas permeability and diffiisivity for modeling vapor transport in the
vadose zone and designing vapor extraction remediation systems.
Method Description: The process of testing for air permeability is analogous to a multiple-well ground-water
pumping test (Section 4.3.2). A vacuum is applied to a "pumping" well, with a screened interval in the soil zone
of interest while changes in air pressure with time are monitored in pressure probes placed in the subsurface
(Figure 9.4.5a). Johnson et al. (1990) provide formulas for calculating air permeability from the measured data.
Baehr and Hull (1991) describe a more complex installation using multi-level pressure probes and two pumping
wells separated by a confining bed. Section 7.4.4 describes use of air permeability in the deep vadose zone to
estimated hydraulic conductivity. Gas diffusion is the principle mechanism for exchange of gases between the
soil and the atmosphere, and hence is of interest for evaluating the potential for movement of volatile
contaminants from the soil to the air. Gas diffusivity is measured in the field by injecting a known concentration
of the gas of interest into a sealed cylinder (Figure 9.4.5b). The air in the confined space above the soil is kept
stirred with a fan run by a hand drill, and the chamber is sampled over time to determine the change in gas
concentration. Diffiisivity is then calculated based on the decrease in concentration of the gas with time. A
prototype probe for measuring gas diflusivity in a borehole has also been developed (Figure 9.4.5c).
Method Selection Considerations: If measurement of either air permeability or gas diffiisivity is required, use
of either method is relatively straightforward. \-
Frequency of Use: Will become increasingly common, especially where vapor extraction remediation activities
are involved.
Standard Methods/Guidelines; Air permeability: ASTM Draft Standard Practice for Determining Air
Permeability in Soils (Nielsen, 1991); Corey (1986-laboratory measurement using cores); Gas diffusivity: Rolston
(1986a).
Sources for Additional Information: Baehr and Hull (1991), Bakker and Hidding (1970), Corey (1957, 1986),
Evans and Kirkham (1949), Groenewoud (1968), Grover (1955), Havlena and Stephens (1992), Izadi and
Stephenson (1992), Johnson et al. (1990), Kearl et al. (1990), Kirkham (1946), Lowry and Narbutobskih (1991),
Marrin et al. (1991), Pirkle et al. (1992), Reeve (1953), Rogers and Nielsen (1991), Springer et al. (1991),
Stonetrom and Rubin (1989), Weeks (1978), Weinig (1992); Diffusion: Jellick and Schnabel (1985), Keari et al.
(1988), Rolston et al. (1991).
9-47
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Pressure Vapor Flowmeter
Gauge
Vapor Treatment
Vapor Sampling
Port
Vapor
Flow
Pressure Sampling Probes'
(a)
Drill
(T) Co-n.d-u.-it Pipe, I 3/8"
*_ Diameter
{2) Tigre Tierra. Pnuematic
Packers
(5j Perforated Injection
;; Conduit
f l-GAS Chip
(£J Solenoid valve
(?) Liquid Product
(b)
Figure 9.4.5 Air permeability and gas diffusivHy: (a) Schematic of air permeability test system (Johnson et al, 1990,
by permission); (b) Schematic diagram of a field diffusion apparatus (Rolston et al., 1991); (c)
Illustration of equipment configuration for in situ borehole gas diffusion measurements (Kearl et al.,
1988).
9-48
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9. VADOSE ZONE SOIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
93 CONTAMINANT FLUX
95,1 Solute Flux Methods
Other Names Used to Describe Method: Various solute flux methods are available: (1) Average concentration
method, (2) approximate analytic solution method, (3) long-term flux estimation method, and (4) short-term
water and solute movement estimation method.
Uses at Contaminated Sites: Estimating the mass transfer of pollutants from the vadose zone to ground water.
Method Description: Several methods are available to calculate solute flux individual constituents or parameters
of interest. Average concentration method: Soil-water concentrations from direct samples obtained using one
of the methods described in this section for two different times are averaged. Average flux over the time period
can be calculated using estimates of water flux during the same time period (using methods described in Section
7.5). Approximate analytical solution method: This is similar to the average concentration method, except an
approximate analytic solution that considers diffusion-dispersion is used to estimate solute concentrations rather
thto measuring them directly. This method requires monitoring of soil-moisture changes with time (Section 6.3),
adding a solution to the soil with known concentration, and estimating average water flux (Section 7.5). Long
term solute flux estimation method: This is a simplified water balance method (see Section 7.5.1) requiring
sampling of soil water at selected depth intervals at two times using one of the direct soil-water sampling methods
discussed in this section. Short-term water and solute flux estimation method: This is a relatively complex
method estimating peak solute concentration in the rooting zone after infiltration and redistribution of the soil
water to field capacity.
Method Selection Considerations: These methods primarily have been developed* for agricultural applications
to calculate flux of nutrients and soluble salts in soil. The average concentration method is the simplest method,
with potential use for mass balance analysis of pollutants at contaminated sites, provided that water flux can be
estimated. The other methods require field water-budget measurements of varying complexity and are of
relatively limited applicability to contaminated sites.
Frequency 6f Use: Commonly used in agricultural applications; use at contaminated sites increasing.
Standard Methods/Guidelines; Brown et al. (1983), Wagenet (1986).
Sources for Additional Information: Parker and Van Genuchten (1984), Philip (1973), Roth et al. (1990), U.S.
EPA (1975).
9-49
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9. VADOSE ZONE SOIL-SOLUTE/GAS SAMPLING AND MONITORING METHODS
9 J CONTAMINANT FLUX
95,2 SoH-Gas Flux
Other Names Used to Describe Method: —
Uses at Contaminated Sites: Quantifying sources and sinks of gases within the soil; evaluating soil raicrobial
activity; measuring the rate of flow of gases from volatile subsurface contaminants to the surface.
Method Description: Various methods have been developed: (1) Gas samples taken at different depths and over
a period of time are collected and flux is calculated using Pick's law; (2) a closed chamber is placed over the soil
surface and the increase in concentration of gas within the chamber is measured as a function of time (Figure
9.5.2); and (3) a capped cylinder is driven into the ground surface (flow-through chamber method). Ambient
air is drawn through the chamber and concentration of the gas of interest is measured in both the input and
output streams.
Method Selection Considerations: These methods primarily have been used in research related to gases of
interest for agriculture (nitrogen and carbon dioxide).
Frequency of Use: Relatively common.
Standard Methods/Guidelines: Ball and Smith (1991), Rolston (1986b).
Sources for Additional Information: Aulach et al. (1991), Gholson et al. (1989), Loftfield et al. (1992), Matthias
et al. (1980).
9-50
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0.2m
Metol Chamber^
Foom Collar
Cham
Insulation
Vent Port
.Windbreak
Metal Bond
Figure 9.5.2 Diagram of closed chamber for directly measuring gas flux at the soil surface (Rolston, 1986b, after
Matthias et al., 1980, by permission).
9-51
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Table 9-2 Reference Index for Indirect Methods for Monitoring Solute Movement
Topic
References
Overviews
EC-Salinity Calibration
Four Electrode
EC Probes
Salinity Sensors
EMI Sensors
Everett et al. (1982, 1983), Kaufinan et al. (1981), Rhoades (1978, 1984), Rhoades
and Oster (1986), Wilson (1983), Yadav et al. (1979)
Bottraud and Rhoades (1985), Gupta and Hanks (1972), Halvorson et al. (1977),
Mute and Letey (1958), Mualem and Friedman (1991), Rhoades (1980, 1981),
Rhoades et al. (1976, 1977, 1989a-c, 1990), Sbainberg et al. (1980), van Hoom
(1980)
Austin and Rhoades (1979), Bonn et al. (1982), Cameron et al. (1981), Halvorson
and Reule (1976), Halvorson and Rhoades (1974,1976), Nadler (1981, 1991),
Nadler and Frenkel (1980), Nadler et al. (1984, 1990), Rhoades and Halvorson
(1977), Rhoades and Ingvalson (1971), Roux (1978), van Hoorn (1980); Soil
Moisture; Bunnenberg and Kuhn (1980), Edlefson and Anderson (1941), Kirkham
and Taylor (1950)
Nadler et al. (1982), Rhoades (1979), Rhoades and Halvorson (1977), Rhoades
and van Sehilfgaarde (1976), Shea and Luthin (1961)
Austin and Oster (1973), Enfield and Evans (1969), Ingvalson et al. (1970,1976),
Kemper (1959), Oster and Ingvalson (1967), Oster and Willardson (1971), Oster
et al. (1973, 1976), Reicosky et al. (1970), Rhoades (1972), Rhoades and Oster
(1986), Richards (1966), Todd and Kemper (1972), U.S. Soil Salinity Staff (1981),
Wesseling and Oster (1973), Wierenga and Patterson (1974), Wood (1978a),
Yadav et al. (1979); Temperature Correction Coefficients: Campbell et al. (1948),
Richards (1954), Richards and Campbell (1948), Whitney and Means (1897)
Cameron et al. (1981), Cook and Walker (1992), Corwin and Rhoades (1982,
1984), de Jong et al. (1979), Hendrickx et al. (1992), Kachonoski et al. (1988-soil-
water content), McBride et al. (1990), Rhoades and Corwin (1981), Rhoades and
Oster (1986), Williams and Baker (1982), Wollenhaupt et al. (1986)
9-52
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Table 9-3 Reference Index for Direct Soil-Water Sampling Methods
Topic
References
Overviews
Suction Samplers
Chemical Effects
Physical Effects
Porous Cup Cleaning
Procedures
Porous Cup (Vacuum)
Porous Cup (Vacuum-
Pressure)
Dorrance et al. (1991), Everett (1990), Everett et al. (1982, 1990), Hornby et al.
(1986), Kohnke et al. (1940), Litaor (1988), Morrison (1983), Nagpal (1982),
Rhoades and Oster (1986), Robbins and Gemmell (1985), Silkworth and Grigal
(1981), U.S. EPA (1986), Wilson (1983, 1990)
Alberts et al. (1977), Anderson (1986), Bottcher et al. (1984), Creasy and Dreiss
(1985), Dazzo and Rothwell (1974), England (1974), Grover and Lambom (1970),
Haines et al. (1982), Hansen and Harris (1975), Hornby et al. (1986), Levin and
Jackson (1977), McGuire et al. (1992), Peters and Healy (1988), Rhoades and
Bernstein (1971), Severson and Grigal (1976), Silkworth and Grigal (1981),
Stearns et al. (1980), Suarez (1987), Tasi et al. (1980), Wagner (1962), Wolff
(1967), Zabowski and Ugolini (1990)
Cochran et al. (1970), Kung and Donohue (1991), Morrison and Lowery (1990-
sampling radius), Narasimham and Dreiss (1986), Severson and Grilgal (1976),
Talsrna et al. (1979), van der Ploeg and Beese (1977), Warrick and Amoozegar-
Fard (1977)
Aulenbaeh and Clesceri (1980), Creasey and Dreiss (1988), Grover and Lamborn
(1970), Neary and Tomassini (1985)
Ahlert et al. (1976), Alberts et al. (1977), Angle et al. (1991), Ballestero et al.
(1990), Barbaricfe et al. (1979), Barbee and Brown (1986), Bell (1974), Bourgeois
and Lavkulich (1972a,b), Brooks et al. (1958), Brown (1986), Burns (1992), Chow
(1977a, 1977b-fritted glass), Debyle et al. (1988), de Jong (1976), Dugan et al.
(1975), Eleuterius (1980), Grier et al. (1977), Haines et al. (1982), Hansen and
Harris (1975), Joslin et al. (1987), Knighton and Streblow (1981), Krone et al.
(1951), Miller (1992), Nielsen and Phillips (1958-fritted glass), Quin and Forsyth
(1976), Reeves and Doering (1965), Riekerk and Morris (1983), Shuford et al.
(1977), Silkworth and Grigal (1981), Smith and Carse! (1986), Starr (1985), Starr
et al. (1991a), Suarez (1986), Tyler and Thomas (1977), Wagner (1962, 1965),
Wengel and Griffin (1971); Cup Material Comparisons: McQuire and Lowery
(1992)
Apgar and Langmuir (1971), Ball and Coley (1986), Banton et al. (1992), Biggar
and Nielsen (1976, 1978), Biggar et al. (1975), Brose et al. (1986), Everett and
McMillion (1985), Everett et al. (1984, 1988), Fenn et al. (1977), Gerhardt (1977),
Hounslow et al. (1978), Johnson and Cartwright (1980), Johnson et al. (1981),
Long (1978), Merry and Palmer (1985), Morrison (1982), Morrison and Szecsody
(1985, 1987), Morrison and Tsai (1981), Parizek and Lane (1970), Peters and
Healy (1988), Quin and Forsyth (1976-nyIon), Rehm et al. (1987), Starr et al.
(1978), Tsai et al. (1980), U.S. EPA (1986), Wood (1978b), Wood et al. (1981),
Young (1985), Yu et al. (1978), Zimmermann et al. (1978); High-Pressure
Vacuum: Bond and Rouse (1985), Wood (1973), Wood and Signer (1975)
9-53
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Table 9-3 (cent)
Topic References
Section Samplers feont.>
Vacuum Plates Chow (1977b), Cochran et a!. (1970), Cole (1958), Cole et al. (1961), Duke et al.
(1970), Haines et al. (1982), Iskandar and Nakano (1978), Neaiy and Tomassini
(1985), Tanner et al. (1954), van der Ploeg and Beese (1977)
Membrane FUter Everett (1990), Everett et al. (1982), Stevenson (1978), U.S. EPA (1986),
Wagemann and Graham (1974), WHson (1990)
Hollow Fiber Everett (1990), Jackson et al. (1976), Levin and Jackson (1977), Morrison (1982),
Silkworth and Grigal (1981), U.S. EPA (1986), Wagemann and Graham (1974)
Ceramic Filter Candle Duke and Haise (1973), Everett (1990), Hergert and Watts (1977), Hoffinan et al.
(1978), Montgomery et al. (1987), Smith and McWhorter (1977), van Shilfgaarde
(1977), U.S. Soil Salinity Laboratory Staff (1981)
Monolith Lysimeters Belford (1979), Brown (1986), Brown et al. (1974, 1985), Cameron et al. (1992),
Merek et al. (1988), Persson and Bergstrdrn (1991)
Filled-Type Lysimeters Tyler (1981), Unchurch et al. (1973)
Capillary Wick Samplers Boll et al. (1991,1992), Brown et al. (1988), Holder et al. (1991), Politeka et al.
(1992)
Other Direct Soil Water Sampling Methods
Free-Drainage Samplers Aulenbach and Clesceri (1980), Barbee and Brown (1986), Boll et al. (1991),
Fenn et al. (1977), Haines et al. (1982), Hornby et al. (1986), Jordon (1968),
Kmet and Lindorf (1983), Parizek and Lane (1970), Radulovich and Soli ins
(1987), Rehm et al, (1987), Russell and Ewel (1985), Shaffer et al. (1979), Starr
et al. (1991a), Tyler and Thomas (1977), U.S. EPA (1986), Wilson and Small
(1973); Caisson Lvsimeter: McMichael and McKee (1966), Schmidt and Clements
(1978), Schnieder and Oaksford (1986), Schneider et al. (1983); Buried Cup;
Miller (1992)
Tie-Drainage Sampling Richard and Steenhuis (1988), Starr et al. (1991a), Thomas and Barfleld (1974),
Willardson et al. (1973)
Perched Water Table Miller (1992), Starr et al. (1991a), Wilson and Schmidt (1978); Multi-Level
Samplers: Cherry and Johnson (1982), Hansen and Harris (1974, 1980), Pickens
et al. (1981), Smith at al. (1982); see also, Section 5.5.3
9-54
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Table 9-3 (cont)
Topic References
Other Direct Soil Water Sampling Methods (cont.^)
Solids Sampling (Soil-
Water Extraction) Solvent/Fluid Column Displacement: Adams (1974), Adams et al. (1980), Barrow
(1982), Batley and Giles (1979), Kittrick (1980, 1983); Double-Bottom Centrifuge;
Adams et al. (1980), Dao and Lavy (1978), Davies and Davies (1963), Edmunds
and Bath (1976), Hkhatib et al. (1986, 1987), Fenn et al. (1977), Gillman (1976),
Zabowski (1989), Zabowski and Ugolini (1990); Immiscible Fluid
Displacement/Centrifugation; Mubarak and Olsen (1976, 1977), Phillips and Bond
(1989), Whelan and Barrow (1980); Squeezing Displacement: Fenn et al. (1977),
Lusczynski (1961), Manheim (1966), Patterson et al. (1978); Vacuum
Displacement: Fenn et al. (1977), Richards (1954-pressure membrane apparatus),
Wolt and Graveel (1986); Unclassified': Behel et al. (1983), Brown (1986),
Kinniburgh and Miles (1983); Lucas and Reeves (1980), Pratt et al. (1976), Rible
et al. (1976), Wellings and Bell (1980), Yamasaki and Kishita (1972)
Solids Sampling (Soil-
Saturation Extract) Barbarick et al. (1979), Campbell et al. (1948), Moran et al. (1978), Rhoades
(1981, 1982), Rhoades and Bernstein (1971), Rhoades et al. (1989a-c), Richter
and Jury (1986), SCS (1984), Wilson (1983); Chemical Effects; Reitmeier (1946)
"It was not possible to review these references to determine what extraction method was used.
9-55
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SECTION 9 REFERENCES
Adanu, F. 1974. Soil Solution. In: The Plant Root and Its Environment, E.W. Carson (ed.), University Press, Charlottesvillc, VA,
pp. 441-481.
Adami, F., C. Burmetter, N.V. Hue, and F.L, Long. 1980. A Comparison of Column-Displacement and Centrifuge Methods for
Obtaining Soil Solutions. Soil Sci. Soc, Am. J. 44:733-735.
Ahlert, R.C, R.H. Gesumaria, and H.L. Motto. 1976. Subsurface Monitoring of Sludge Disposal Sites. In: Establishment of Water
Quality Monitoring Programs, L.G Everett and K.D. Schmidt (eds.), American Water Resources Association, St. Paul, MN,
pp. 106-121. [Vacuum porous cup]
Alberts, E.E., R.E. BurwcD, and G.E. Schuman. 1977. Soil Nitrate-Nitrogen Determined by Coring and Solution Extraction
Tedinlquei. Soil Sci. Soc. Am. J. 41:90-92. [Vacuum porous cup]
American Petroleum Institute (API). 1985. Detection of Hydrocarbons in Ground Water by Analysis of Shallow Soif Gas/Vapor.
API Publication 4394, API, Washington, DC, 80 pp.
American Petroleum Institute (API). 1991. An Evaluation of Soil Gas and Geophysical Techniques for Detection of Hydrocarbons.
API Publication No. 4509, API, Washington, DC, 110 pp.
American Society for Testing and Materials (ASTM). 1985. Standard Test Method for Pore Water Extraction and Determination of
the Soluble Salt Content of Soils by Refractometer. D4542-85, (Vol. 4.08), ASTM, Philadelphia, PA.
American Society for Testing and Materials (ASTM). 1991a. Standard Guide for Soil Gas Monitoring in the Vadose Zone. D5314-
91, (Vol. 4.08), ASTM, Philadelphia, PA.
American Society for Testing and Materials (ASTM). 1991b. Standard Guide for Using Release Detection Devices with
Underground Storage Tanks. E1430-91, (Vol. 11.04), ASTM, Philadelphia, PA.
American Society for Testing and Materials (ASTM). 1992. Standard Guide for Pore-Liquid Sampling From the Vadose Zone.
D4696-92, (Vol. 4.08), ASTM, Philadelphia, PA.
American Society for Testing and Materials (ASTM). 1993. Standard Practice for Evaluating the Performance of Release Detection
Systems for Underground Storage Tank Systems. E1526, Society Ballot, January, ASTM, Philadelphia, PA.
Anderson, L.D. 1985. Problem! Interpreting Samples Taken with Large Volume, Falling Suction Soil-Water Samplers. Ground
Wtter 24:761-769.
Angle, J.S., M.S. Mclntosh, and R.L. Hill. 1991. Tension Lysimeters for Collecting Soil Percolate. In: Groundwater Residue
Sampling, R.G. Nash and A.R. Leslie (eds.), ACS Symposium Series 465, American Chemical Society, Washington, DC,
pp. 290-299. [Vacuum-type porous cup]
Apgar, M. and D. Langmuir. 1971. Ground-Water Pollution Potential of a Landfill Above the Water Table. Ground Water 9(6):76-
96.
Aulach, M.S., J.W. Doran, and A.R. Mosier. 1991. Field Evaluation of Four Methods for Measuring Denitrification. Soil Sci. Soc.
Am. J. 55:1332-1338. [Nitrogen gas Dux measurement]
Aulenbach, D. tnd N. Cltsceri. 1980. Monitoring for Land Application of Wastewater. Water, Air, and Soil Pollution 14:81-94.
Austin, R. and J. Otter. 1973. Oscillator Circuit for Automated Salinity Sensor Measurements. Soil Sci. Soc. Am. Proc. 37:327-329.
Austin, R.S. and J.D. Rhoades. 1979. A Compact, Low-Cost Circuit for Reading Four-Electrode Salinity Sensors. Soil Sci. Soc. Am.
J. 43:808-810.
Bichr, A.L. and M.F. Hult 1991. Evaluation of Unsaturated Zone Air Permeability Through Pneumatic Tests. Water Resources
Research 27(10):2605-2617.
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Bakker, J.W. and A.P. Hidding. 1970. The Influence of Soil Structure and Air Content on Gas Diffusion in Soils. Neth. J. Agric.
Sci. 18:37-48. (Also reprinted as Tech. Bull. 71, Institute for Land and Water Management Research, Wagcningcn, The
Netherlands.)
Ball, J, and D.M. Coley. 1986. A Comparison of Vadose Monitoring Procedures. In: Proc. 6th Nat. Symp. and Exp. on Aquifer
Restoration and Ground Water Monitoring, National Water Well Association, Dublin, OH, pp. 52-61. (Vacuum pressure
porous cup]
«
Ball, B.C. and K.A. Smith. 1991. Gas Movement. In: Soil Analysis: Physical Methods, KA. Smith and C.E Mulling (eds.), Marcel
Dekker, New York, NY, pp. 511-549.
Ballestero, T.P., S.A. McHugh, and N.E. Kinner. 1990. Monitoring of Immiscible Contaminants in the Vadose Zone. In: Ground
Water and Vadose Zone Monitoring, D.M. Nielsen and A.I. Johnson (eds.), ASTM STP 1053, American Society for
Testing and Materials, Philadelphia, PA, pp. 25-33.
Banton, O., LaTrance, P., R. Martel, and J.P. Viilencuve. 1992. Planning of Soil-Pore Water Sampling Campaigns Using Pesticide
Transport Modeling. Ground Water Monitoring Review 12(3):195-202, [Pressure-vacuum porous cup]
Barbarick, K.A., B.R. Sabey, and A. Klute. 1979. Comparison of Various Methods of Sampling Soil Water for Determining Ionic
Salts, Sodium and Calcium Content in Soil Columns. Soil Sci. Soc, Am. J. 43:1053-1055.
Barbee, G.C. and K.W. Brown. 1986. Comparison Between Suction and Free-Drainage Soil Solution Samplers. Soil Science
141:149-154.
Barrow, N J. 1982. An Evaluation of the Immiscible Displacement Method for Studying the Relation Between Soil and Phosphate.
Pert. Res. 3:423-433.
Batley, G.E. and M.S. Giles. 1979. Solvent Displacement of Interstitial Waters Before Trace Metal Analysis. Water Research
13:879-886.
Beeman, R.E, and J.M. Suflita. 1989. Evaluation of Deep Subsurface Sampling Procedures Using Serendipitous Microbial
Contaminants as Tracer Organisms. Geomicrobiol. J. 7(4):223-233.
Behel, Jr., D., D.W. Nelson, and L.E. Sommers. 1983. Assessment of Heavy Metal Equilibria in Sewage Sludge-Treated Soil. J.
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Upchurch, WJ., M.Y. Cbowdhury, and C.E. Marshall. 1973. Lysimetric and Chemical Investigations of Pedological Changes, 1.
Lysimeters and Their Drainage Waters. Soil Science 116:266-281.
U.S. Environmental Protection Agency (EPA). 1975. Use of the Water Balance Method for Predicting Leachate Generation from
Solid Waste Disposal Sites. EPA/SW-168 (NTIS PB87-194643).
U.S. Environmental Protection Agency (EPA). 1986. Permit Guidance Manual on Unsaturated Zone Monitoring for Hazardous
Waste Land Treatment Units. EPA/530/SW-86/040 (NTIS PB87-215463). (This report is sometimes cited as Everett and
Wilson [1986].)
U.S. SoU Salinity Laboratory Staff. 1981. Minimizing Salt in Return Flow Through Irrigation Management EPA/600/2-82/Q73
(NTIS PB82-257445), 160 pp. (1977 interim report with same title published as EPA/60QE-77/134 {NTfS PB272-637].)
[Ceramic filter candle]
van der Ploeg, R.R. and F. Beese. 1977. Model Calculations for the Extraction of SoU Water by Ceramic Cups and Plates. Soil Sci.
Soc. Am. J. 41:466-470.
van Hoorn, J. 1980. The Calibration of Four-Electrode Soil Conductivity Measurements for Determining Soil Salinity. In: Int. Symp.
on Salt Affected Soils (Karnal, India), D. Bhumbla and J. Yadav (eds.), pp. 148-156.
van Schilfgaarde, J. 1977. Minimizing Salt in Return Flow by Improving Irrigation Efficiency. In: Proc. Nat. Conf. Irrigation Return
Flow Quality Management, J. Law, Jr. and G Skogerboe (eds.), Colorado State University, Fort Collins, CO, EPA/600/9-
77/040 (NTIS PB274-086), pp. 81-98.
Vroblesky, DA. and M.M. Lorah. 1991. Prospecting for Zones of Contaminated Ground-Water Discharge to Streams Using
Bottom-Sediment Gas Bubbles. Ground Water 29:333-340.
Vroblesky, D.A., J.F. Robertson, M. Fernandez, and CM. Aelion. 1992. The Permeable-Membrane Method of Passive Soil-Gas
Collection. Ground Water Management 11:3-16 (6th NOAC).
Wagemann, R. and B. Graham. 1974. Membrane and Glass Fiber Filter Contamination in Chemical Analysis of Fresh Water.
Water Res. 8:407-412.
Wagenet, RJ. 1986. Water and Solute Flux. In: Methods of Soil Analysis, Part 1,2nd edition, A. Klute (ed.), Agronomy
Monograph No. 9, American Society of Agronomy, Madison, WI, pp. 1055-1088.
Wagner, G.H. 1962. Use of Porous Ceramic Cups to Sample Soil Water Within the Profile, Soil Science 94:379-386.
9-71
-------
Wagner, G.H. 1965. Changes in Nitrate Nitrogen in Field Plot ProGIes as Measured by the Porous Cup Technique. Soil Science
100397-402.
Warrick, W.A. and A. Amoozegar-Fard. 1977. SOU Water Regimes Near Porous Cup Samplers. Water Resources Research 13:203-
207.
Weeks, E.P. 1978. Field Determination of Vertical Permeability to Air in the Unsaturated Zone. U.S. Geological Survey
Professional Paper 1051, 41 pp.
Weini&W.T. 1992. Monitoring the Vadose Zone During Pneumatic Pumping Tests. Ground Water Management 11:133-146 (6th
NOAC). [Air permeability]
Wellings, S.R. and J.P. Bell. 1980. Movement of Water and Nitrate in the Unsaturated Zone of Upper Chalk Near Winchester,
Hants, England. J. Hydrology 48:119-136.
Wengel, R.W. and G.F. Griffin. 1971. Remote Soil-Water Sampling Technique. Soil Sci. Sac. Am, Proc. 35:661-664.
Wesseling, J. and J. Oster. 1973. Response of Salinity Sensors to Rapidly Changing Salinity. Soil Set. Soc. Am. Proc. 37:553-557.
Whelan, B.R. and N J. Barrow. 1980. A Study of A Method for Displacing Soil Solution by Centrifuging with an Immiscible Liquid.
J. Environ. Qual. 9:315-320.
Whitney, M. and T. Means. 1897. An Electrical Method of Determining the Salt Content of Soils. U.S. Dept, of Agric., Bureau of
Soils Bull. 8:1-30.
Wiercnga, PJ. and T.C Patterson. 1974. Quality of Irrigation Return Flow in the Meslla Valley. Trans. 10th lot Congr. Soil Set.
10:216-222.
Wiilaidson, L.S., B.D. Meek, and M J. Huber. 1973. A Row Path Ground Water Sampling. Soil Sci. Soc. Am. Proc. 36:965-966.
Williams, B.G. and B.C. Baker. 1982. An Electromagnetic Induction Technique for Reconnaissance Surveys of Soil Salinity. Aust.
J. Soil Res. 20:107-118.
Wilson, L.G. 1983. Monitoring in the Vadose Zone: Part III. Ground Water Monitoring Review 3(1):155-166,
Wilson, L.G. 1990. Methods for Sampling Fluids in the Vadose Zone. In: Ground Water and Vadose Zone Monitoring, D.M.
Nielsen and A.I. Johnson (eds.), ASTM STP 10S3, American Society for Testing and Materials, Philadelphia, PA, pp. 7-24.
Wilson, L.G. and K.D. Schmidt. 1978. Monitoring Perched Groundwater in the Vadose Zone. In: Establishment of Water Quality
Monitoring Programs, L.G Everett and K.D. Schmidt (eds.), American Water Resources Association, St. Paul, MN, pp.
134-149.
Wilson, L.G. and G.G. Small. 1973. Pollution Potential of a Sanitary Landfill Near Tucson Arizona. In: Hydraulic Engineering and
the Environment, Proc. 21st Annual Hydraulics Specialty Division Conference, ASCE, New York, NY. [Free drainage
sampling]
Wolff, R.G. 1967. Weathering of Woodstock Granite Near Baltimore, Maryland. American Journal of Science 265:106-117.
WoUcnhaupt, N.C, J.L. Richardson, J.E Foss, and E.C. Doll. 1986. A Rapid Method for Estimating Weighted Soil Salinity from
Apparent Soil Electrical Conductivity Measured with an Aboveground Electromagnetic Induction Meter. Can. J. Soil Sci.
66:315-321.
Woit, J. and J.G. Graveel. 1986. Rapid Routine Method for Obtaining Soil Solution Using Vacuum Displacement Soil Sci. Soc.
Am. J. 50:602-605.
Wood, W.W. 1973. A Technique Using Porous Cups for Water Sampling at Any Depth in the Unsaturated Zone. Water Resources
Research 9(2):468-488.
Wood, J.D. 197Sa. Calibration Stability and Response Tune for Salinity Sensors. Soil Sci. Soc. Am. J. 42:248-250.
Wood, W.W. 1978b. Use of Laboratory Data to Predict Sulfate Sorption During Artificial Ground-Water Recharge. Ground Water
9-72
-------
Wood, W.W. and D.C. Signer. 1975. Geochemical Factors Affecting Artificial Recharge in the Unsaturated Zone, Trans. Am. Soc.
Agric, Bng. 18(4):677-«83.
Wood, A.L., J.T. Wilson, R.L. Cosby, A.G. Homsby, and L.B. Baskin. 1981. Apparatus and Procedure for Sampling Soil Profiles for
Volatile Organic Compounds. Soil Sci. Soc. Am. J. 45:442-444.
Yadav, B.R., N.H. Rao, K.V. Paliwal, and P.B.S. Sarroa. 19m Comparison of Different Methods for Measuring Soil Salinity Under
Field Conditions. Soil Science 127:335-339.
Yamasaki, A. and A. Kishita. 1972. Studies on Soil Solutions with Reference to Nutrient Availability. I. Effect of Various Potassium
Fertilizers on Its Behavior in the Soil Solution. Soil Sci. Plant Nutr. 18:1-6.
Young, M. 1985. Use of Suction Lysimeters for Monitoring in the Landfill Liner Zone. In: Proc. of Monitoring Hazardous Waste
Sites, Geotechnical Eng. Div. ASCE. (Vacuum-pressure porous cup]
Yu, Y., 1C Chen, R. Morrison, and J. Mang. 1978. Physical and Chemical Characterization of Dredge Material Sediments and
Leachates in Confined Land Disposal Areas. U.S. Army Corps of Engineers, Tech. Rept D-78-43, 241 pp.
Zabowski, D. 1989. Limited Release of Soluble Organics from Roots During the Centrifugal Extraction of Soil Solution. Soil Sci.
Soc. Am. J. 53:977-979.
Zabowski, D. and F.C. Ugolini. 1990. Lysimeter and Centrifuge Soil Solutions: Seasonal Differences Between Methods. Soil Sci.
Soc. Am. J. 54:1130-1135.
Zammcrmann, C.F., M.T. Price, and J.R. Montgomery. 1978. A Comparison of Ceramic and Teflon In Situ Samplers for Nutrient
Pore Water Determinations. Estuarine Coastal Mar. Sci. 7:93-97.
9-73
-------
SECTION 10
FIELD SCREENING AND ANALYTICAL METHODS
The term "field screening" has gained widespread use in recent years to describe a wide variety of
methods for chemical characterization of contaminated sites. In this guide, a distinction is made between field
screening and field analytical methods. Field screening methods provide an indication of the presence or absence
of a particular chemical or chemical class of concern, or provide an indication of whether the chemical or
chemical class of concern is above or below a predetermined threshold. Screening methods provide relative
concentrations for chemical classes, but rarely provide chemical-specific information. This definition is more
restrictive than those usually found in the literature. Field analytical methods include all chemical analysis
methods capable of providing chemical-specific quantitative data in the field or non-laboratory setting. Field
analytical techniques generally are more rapid and less expensive than similar chemical analyses performed in
laboratories with fixed facilities. Field screening and analytical techniques can be classified as portable (require
no external power source, are compact, and are rugged enough to be carried by hand into the field), fieldable
(require limited external power, are compact, and are rugged enough to be transported in a small van, pick-up,
or four-wheel drive), or mobile (are small enough to carry in a mobile laboratory, which is feasible for most
analytical instruments although power considerations can be a limitation). The standard by which the sensitivity,
precision, and accuracy of field screening techniques are measured are those obtained in fixed-base laboratories
in EPA's contract laboratory program (CUP). An intermediate option for analysis of samples is the use of a
dedicated laboratory using CLP procedures but involving more rapid turnaround time (as short as overnight) for
sample results.
Field Analysis versus CLP Analytical Laboratory
Key advantages of field analytical techniques include: (1) Results can be obtained within hours,
compared to the 20 to 40 days required for CLP laboratories, which allows for more rapid definition of the scope
of contamination and allows for optimal selection of permanent monitoring wells/locations; (2) lower cost per
sample (commonly one-tenth CLP cost) allows for more detailed characterization of contaminant distribution
and/or reduced overall costs; and (3) the techniques are best suited for preliminary site characterization,
emergency remedial actions, and monitoring of remediation activities. Some general disadvantages of field
analytical techniques include: (1) Application of analytical QA/QC procedures is more difficult in the field; (2)
generally, less sophisticated instrumentation and disadvantage #1 results in generally higher detection limits and
lower precision and accuracy compared to CLP laboratories; and (3) disadvantages #1 and #2 mean that data
are more liable to challenge by litigation.
Cost differences between field analysis and laboratory analysis are strongly dependent on the number
of samples from a site that must be analyzed, with the cost advantage tending to shift to field analysis as the
number of samples increases. For example, if less than 30 to 50 samples are required, laboratory gas
chromatograph analyses are likely to be less expensive than using portable or mobile GCs. Similarly, around 50
to 80 samples for field X-ray fluorescence analysis of metals are required to save money over conventional
laboratory XRF analyses.
Overview of Specific Techniques
Developments in miniaturization and computer processing of analytical signals and development of
innovative analytical techniques mean that almost any instrumental or analytical technique has the potential for
being used for field screening. Any attempt to publish a comprehensive compilation of techniques that have been
proposed or tested is doomed to be out-of-date before it reaches print. This section, therefore, provides a
reasonably comprehensive overview of the state-of-the-art as of early 1993. Table 10-1 provides summary
information on over 80 techniques. Techniques are grouped into the following major categories: (1) Routine
chemical field measurement techniques (Section 10.1 [chemical sensors covered in Chapter 5 also are indexed
under this section in the table]); (2) major sample extraction procedures (Section 10.2); (3) analytical techniques
that detect gases or require creation of a gaseous phase during the analytical process if the gaseous phase is not
already present (Section 10.3); (4) luminescence, spectrophotometric, and other spectroscopic techniques (Section
10-1
-------
Table 10-1 Summary Information on Sample Processing/Analytical Techniques
Technique/Instrumentation
Technology
Status*
Sample
Matrix*
Contaminant
Type"
Detection
limit*
Section/Table
Chemical Field Measurement Techniques/Sensors
ph/Alkalinity/Acidity
Eh
Dissolved Oxygen
Temperature
Electrical Conductance
Filterable Residue
Other Specific Ion Electrodes
Solid/Porous Fiber Optic
Immunochemkal Fiber Optic
Electrochemical Sensors
SAW Probes
Piezoelectric Sensors
Semiconductor Sensors
Sample Extraction Procedures
Headipace AnalysU
Vacuum Extraction
Purge and Trap
Solvent Extraction
Thermal Digestion
Thermal Extraction
Thermal Detorption
Supercritical Fluid Extract.
Membrane Extraction
Sorbcnt Extraction
GMCOUS Phase Analytical Techniques
Photo-Ionizatlon Detector
flame-Iooixation Detector
Argon-Ionization Detector
Explosimeter
Catalytic Surface Oxidation
Detector Tube*
Gai Chromatograpny (GO
Mass Spcctrometry (MS)
GQMS
Ion Trap MS
AA SpedroMetry
ICP-AES
Ion Mobility Spectrometer
Luminetctnce/Spectroscopic Techniques
X-Ray Fluorescence
UV Fluorescence
Room-Temp. Phosphoiimetry
Synchronous Luminescence
Synchronous Fluorescence
UV-Visible Spectrophotometry
Infrared Spectroscopy
I/CP
I/CP
I/CP
I/CP
I/CP
I/CM
II/CP
IV
IV
IV
IV
IV
IV
I
I/CP
I/CP
I/CP
II/CP
II/CP
III/CP
III/CP
IV
I/CP
I/CP
I/CP
HI/CP
I/CP
I/CP
I/CP
II/CP,CM
II/CF.CM
II/CM
IV
II/CM
II
II/CP
II/CP,CM
II
III
III
III
III
II
W,S
W.S
W
w
w,s
w
w
WAA
W.S.A
W.A
A
A
A,W
A
A
W
S
W.S
W,S
W.S
W.S
W
A.W
A
A
A
A
A
A
A,W
A
A
A
A.W
A.W
A
S,W
s,w
s,w
w
w
A,W
A.W.S
—
-
_
_
_
EA
voc
svo
VOC.TG
VOC.TG
VOC
voc
voc
voc
voc
SVO.VOC
EA^IM
SVO
VOQSVO
voqsvo
voc
VOQSVO
voc
voc
voc
voc
VOC.TG
VOC.TG
VOQSVO.TR
VOC^VO.TR
VOQSVO.TR
VOQSVO
EAJHM
EAflM
VOQSVO.TG
HM
VOC
voc^vo
VOQSVO
VOQSVO
VOC
M.VOQSVO
_
~
ppm
-
—
-
ppm
ppm
ppb-ppm
pbb-ppm
ppm
ppm
ppm-%
...
,.
..
-
—
-
—
-
—
-
ppb-ppm
ppb-ppm
100s ppb-ppm
%
ppm-%
high ppm
ppb-ppm
ppm
ppb
ppb-ppm
ppb-ppm
ppb-ppm
ppt-ppm
lOs-lOOs ppm
sub ppm
ppb-ppm
ppra
ppm
ppb-ppm
ppm- 1000s ppm
10.1.1, 55.4
10.1.2, 5.5.4
10.1.2, 5.5.4
10.1.3
10.1.3
10.13
5.5.5
55.6
5.5.6, 10.5.2
10.6.5
10.6.5
10.65
10.65
10.2.1
10.2.1
10.2.2
10.23
10.2.4
10.2.4
10.2.4
10.2.5
10.2.5
10.2.5
10,3.1
103.1
10.3.1
10.3.2
10.3.2
103.2
10.33/Table 10-3
10.3.4/Table 10-3
103.4/TabIe 10-3
10.3.4
1035/Table 10-3
10.3.6/Table 10-3
10.3.7
10.4.1
10.4.2/Tables 10-3, 10.4.2
10.4.2/Table 10.4.2
10.4.2
10.4.2/Table 10.4.2
10.43/Tables 10-3, 10.43
10.43/Tables 10-3, 10.4.3
10-2
-------
Table 10-1 (coot.)
Technique/Instrumentation
Technology Sample Contaminant Detection
Status* Matrix* Type' Limit4
Section/Table
Liuninescence/Snectroscopic Technique!
FTIR Spectroscopy
Scattering/Absorption Lidar
Raman Spectroscopy/SERS
Near IR Reflectance/Trans. SpecL
Wet Chemistry
Chemical Colorimetric Kits
Other Colorimetric Methods
THrimetiy
Immunoassay Colorimetric Kits
Ion Chromalography
High-Pressure Liquid Chromatography
Thin- Layer Chronatography
Coulometry
Polarography
Stripping Voltammetry
Radiological
Neutron Activation/INNA
PDCE
Radiation Detectors
X-Ray Diffraction
Gamma Spectrometiy
Other
Gravimetric
Volumetric
Nuclear Magnetic Resonance
Magnetic Susceptibility
Electron Spin Resonance
Optical Microscope
Scanning Electron Microscope
Electron Microprobe
field BioagsejMunent
Toxlcity Tests
Biomarkers
i Ccont.")
II/CP.CM
IV
II
rv
II/CP
I/CP
I/CP
II/CP
II
II/CM
II
II
II
II
II
II
I/CP
II
I/CP
I/CP
I/CP
I/CP
II
II
II/CP
II
II
II
II
III
A
A
W.S
s
w
w
w
w
w
w
w
w
w
w
s,w
s,w
A.S.W
s
s
W3
S.W.A
s,w
s
S,W,A
S
s
s
-
W.S.A
W&A
VOC
voc
VOQSVO
voc
EA.HM.SVO
TR
EA,HM,TR
svo
EA
SVO.TR
SVO
EA.TR
EA
EA
EA.TR
EAMU
R,TR
M
M
P.TDS
P
MJP
M
M
MJP
M
M
VOQHM
VOQSVOJIM
VOQSVO.HM
ppb-%
ppm
ppb-ppm
100s- 1000s ppm
ppb-lOOs ppm
ppb-lOOs ppm
ppb-lOOs ppm
ppb-ppm
ppm- 100s ppm
ppb-ppm
ppm
ppb-ppm
sub-lOOs ppm
ppt-pp»
10s ppm
10s- 100s ppm
varies
—
%
_
_
_
_
i-
-
high ppm
_
—
—
10.4.4/Tabte 10.4.4
10.4.4
10.4.4/Table 10.4.4
10.4.4/Table 10.4.4
10.5.1/Table 10-3
10^.1/Table 10-3
10.5.1
10.5.2
1043/Table 10-3
10^3/Table 10-3
1043
10^.4
10.5.4
10.5.4
10.6.1, 33,5, 33.6
10.6.1/Table 10-3
10.6.1, 33.1
10.6.1
33.2
10.6.2
10.6.2
10.6.3, 3.2.4
10.63
10.6.3
10.6.4
10.6.4
10.6.4
10.6.6
10.6.6
10.6.6
Boldface = Most commonly used/proven field techniques.
1 = Well established and routinely used field technology; II = Well established laboratory technology tor which experience in field
' applications is moderate to limited; III = Relatively well established technology for which there is limited field experience; IV =
Developing technology with potentially useful field applications. CP = Commercially available portable instruments; CF =
Commercially available fieldable instruments; CM = Commercial/custom mobile laboratories available.
VA = Air/gaseous matrix; S = Soil/solid matrix; W = Water/aqueous/liquid matrix. Volatile and semivolatiles in water and solid
samples can be extracted for analysis by gaseous phase analytical techniques. Similarly, analytes can be extracted from solids samples
for analysis using wet chemistry techniques.
TEA = Elemental/ionic analysis; HM = Metals; M = Mineralogy, P = Physical characterization; R = Radioisotopes; SVO =
Semivolatile organics; TO = Toxic gases; TDS = Total dissolved solids; TR = Tracer studies; VOC = Volatile organic compounds.
'Ranges for specific instruments and analytes might differ from range shown by orders of magnitude. In general, detection limits for
soils will be higher than for ground water.
10-3
-------
10.4); (5) wet chemistiy techniques (Section 10.5), and (6) radiological and other miscellaneous techniques
(Section 10.6).
Sonic Basic Analytical Concepts
For the nonchemist, terminology used to describe analytical techniques can be bewildering. A further
source of potential confusion is that techniques can be used for different purposes in numerous combinations
and configurations. For example, a flame ionization detector (FID) can be used by itself as a total vapor
detector, or it can be used to detect specific compounds after they have been separated by a gas chromatograph
(GC/FID). A gas chromatograph, on the other hand, can be used alone with a FID or other type of detector,
or in combination with a mass spectrometer (GC/MS). An understanding of the basic principles of operation
of major individual techniques makes it possible to have some idea of how an unfamiliar combination of
techniques functions,
A further source of possible confusion is that the different terms can be applied to the same technique.
For example, the terms fluorometry, fluorimetry, and spectrofluorometry can be used interchangeably.
Furthermore, some terms can be applied to the same technique, but are not necessarily interchangeable. For
example the term luminescence can be applied to any technique involving fluorescence, but the term fluorescence
is not applicable to all luminescence techniques (which include phosphorescence). The following discussion might
be helpful in developing an understanding of some of the basic principles involved in chemical analysis and in
sorting out the relationship between similar techniques. It might also be helpful to think of techniques in terms
of the major types of analytical signals as summarized in Table 10-2.
Chromatography refers to processes in which individual components of a mixture migrate through a
stationary medium at different rates. In analytical chemistry, chromatography refers to a diverse group of
separation methods such as gas chromatography (Section 10.3.3) and liquid chromatography (Section 10.5.3)
used to separate, isolate, and identify components of mixtures that might otherwise be resolved with great
difficulty.
A spectrum is the distribution of the phases of a radiated wave cycle or of the intensity of radiation
when some property (frequency, mass, or energy) is allowed to vary. Spectroscopy encompasses a wide range
of techniques involving optical instruments used to form and analyze spectra. Spectrometry is a spectroscopic
technique in which the instrument measures: (1) The deviation of the refracted rays, and (2) wave lengths and
angles between two faces of a prism. Spectrophotometry involves making comparisons of color intensity between
corresponding parts of different spectra, or between parts of the same spectrum. Photometry involves the
measurement of the intensity of light or the relative intensity of different lights. Luminescence involves the
emission of light at temperatures below that of incandescent bodies and includes fluorescence (emission of
radiation as a result of absorption of other radiation) and phosphorescence (light given off from slow oxidation
of phosphorus).
Table 10-3 provides information on commercial sources for four major classes of analytical instruments:
(1) Speetrophotometric instrumentation (atomic absorption, UV/visible, fluorescence, and infrared); (2)
chronaatographs (gas, ion, and liquid); (3) spectrometers (GC/MS, MS, optical emission, plasma emission, and
x-ray); and (4) colorimeters.
Sources of Additional Information
SW-846 (U.S. EPA, 1986b) is the standard reference for solid waste test methods. A field screening
methods catalog (U.S. EPA, 1988a) provides information on 26 field screening methods forwhich protocols have
been developed and is available as an expert system for use on a microcomputer. This catalog is in the process
of being updated and expanded into a format comparable to SW-846. Table 10-4, at the end of this section,
provides an index of references providing overviews of field-screening techniques and more detailed references
on sample extraction procedures. Table 10-5, also at the end of this section, provides a fairly detailed index of
more than 300 references on specific field screening and other analytical techniques contained in this section.
10-4
-------
Table 10-2 Major Analytical Signals and Methods
Signal Analytical Methods Based on Measurement of Signal
Emission of radiation Emission spectroscopy (X-ray, UV, visible, electron Auger); fluorescence and
phosphorescence spectroscopy (X-ray, UV, visible); radiochemistry
Absorption of radiation Colorimetry (visible), UV-visible/X-ray/TR spectrophotometry, photoacoustic
spectroscopy; nuclear magnetic resonance and electron spin resonance
spectroscopy
Scattering of radiation Turbidimetry, nephelometiy, Raman spectroscopy
Refraction of radiation Refractometry; interferometry; X-ray diffraction
Rotation of radiation Polarimetry; optical rotatory dispersion; circular dichroisni
Electrical potential Potentiometry, chronopotentiometry
Electrical current Polarography, amperonietry; coulometry; voltammetry
Mass-to-charge ratio Mass spectrometry
Rate of reaction Kinetic methods
Thermal properties Thermal conductivity and enthalpy methods
Mass Gravimetric analysis
Volume Volumetric analysis
Boldface = Most commonly used in field screening applications.
Source: Modified from Skoog (1985)
10-5
-------
Table 10-3 Commercial Sources for Spectropholometric Instruments, Chromatographs, Spectrometers, and Colorimeters
MANUFACTURER
ACE GLASS 800/223-4524
AIR INSTRUMENTS & MEASUREMENTS 818/813-1466, 800/969-4246
ALLTECH ASSOCIATES 708/948-8600. 800/255-8324
AMERICAN GAUGE 404/932-0550
AMERICAN ULTRAVIOLET 90a'665-2211
AMETEK, PROCESS & ANALYTICAL DIV. 302/456-4400, 800/222-6789
ANADATA 31 2/465-2688
ANALYTE 503/779-0334
ANARAD 8Q5/963-6S83
ASOMA INSTRUMENTS 512/258-6608
ASTRO INTERNATIONAL 713/332-2484
BAIRO 61 7/276-6000
BALZERS HIGH VACUUM PRODS 603/889-6888
BASELINE INDUSTRIES 303/823-6661, 800/321-4665
BOMEM INTERNATIONAL 708/350-0550, 800/888-3847
BRAINARO KIIMAN DRILL CO. 404/469-2720, 800/241-9468
BUCK SCIENTIFIC 203/853-9444, 800/562-5566
C E A INSTRUMENTS 201/967-5880
CHEMPLEX INDUSTRIES 914/337-4200
CHROMATOCHEM 406/728-5897, 800/426-7227
COLLOID ENVIRONMENTAL TECHNOLOGIES 708/392-5800
COLUMBIA SCIENTIFIC 800/531-5003
DASIBI ENVIRONMENTAL 818/247-7601
DIONEX 408/737-0700, 800/346-6390
DYNAMATJQN 313/769-0573
E M SCIENCE 609/354-9200. 800/222-0342
E S INDUSTRIES 609/983-3616, 800/356-6140
FISONS INSTRUMENTS 508/524-1000
FOXBORO 800/521 -0451
FOXBORO E M O 508/378-5558
GENERAL ANALYSIS 203/852-8999. 800/327-2460
GOW MAC INSTRUMENTS 908/560-0600
H F SCIENTIFIC 81 3/337-21 1 6
H N U SYSTEMS 617/964-6690, 800/724-5600
HACH 303/669-3050. 800/227-4224
HAMILTON 702/786-7077, 800/648-5950
HEATH CONSULTANTS 713/947-9282, 800/432-8487
HORIBA INSTRUMENTS 714/250-481 1 . 800/446-7422
HOUSTON ATLAS 713/348-1700
I C M 503/648-2014, 800/262-3668
IR ANALYTICAL 415/595-8200, 800/437-9701
INSTRUMENTS SA 908/494-8660. 800/438-7739
INTERNATIONAL LIGHT 508/465-5923
IONICS, INSTRUMENT DiV. 617/926-2500
ISCO, INSTRUMENT DIV. 402/464-0231 , 800/228-4250
L T INDUSTRIES 301/468-6777
LA JOLLA SCIENTIFIC 619/549-2818
LAMOTTE 301/778-3100. 800/344-3100
LEAP TECHNOLOGIES 919/929-8814, 800/229-8814
LEEMAN LABS 508/454-4442
MSA, INSTRUMENT DIV. 412/672-4678
M T 1 ANALYTICAL INSTRUMENTS 510/490-0900
SPECTROPHOTOMETRIC
INSTRUMENTATION
IR.UV
UV
IR
UV
AA.UV.IR
AA
FL.IR.UV
IR
SI
IR.UV.AA
FL.UV
IR.UV.FL
IR
IR
IR
SI
IR.UV
AA,FL,IR,UV
FL
IR.UV
SI
IR.SI
UV
IR.UV
CHROMATOGRAPHS
LI
IO.LI
GA
GA
GA
GA
LI
LI.IO
CH
GA
GA.LI
GA
GA.LI
GA.L1
GA
GA
GA
GA
GA.LI.IO
LI
GA
GA
GA
SPECTROMETERS
OE
GC
MS
XR
XR
SM
MS
SM
SM
XR
XR
GC,OE,PE,XR,MS
XR
XR
GC
OE
SM
MS
COLORIMETERS
CO
CO
CO
CO
CO
CO
CO
CO
10-6
-------
(eont.)
MANUFACTURER
MCNEILL INTERNATiONAL 800/626-3455
MCPHERSON INSTRUMENTS 308/263-7733, 800/255-1055
METROSONICS 716/334-7300
MIDAC 714/645^096
MILTON ROYj_ ANALYTICAL PRODUCTS 716/248-4000L800/654-9955
MILTON ROY, PROCESS & ENVIRONMENTAL INSTRUMENTS
714/974-5560
MONITEK TECHNOLOGIES 510/471-8300
NATIONAL DRAEGER 412/787-2207
O I ANALYTICAL 409/690-1711
PERKIN ELMER 203/762-1000, 800/762-4000
PHOTOVAC INTERNATIONAL 816/254-4199
PROCESS ANALYZERS 215/736-2596
QUANTUM ANALYTICS 415/570-5656, 800/992-4199
RESPONSE RENTALS 716/266-3910, 800/242-3910
S R I INSTRUMENTS 213/214-5090
SENSIDYNE 81 3/530-3602, 800/451-9444
SENTEX SYSTEMS 201/945-3694
SERVOMEX 617/769-7710, 800/862-0200
SIEMENS ENER6Y AND AUTOMATION 404/740-3931
SIERRA MONITOR 408/262-9042
SHIMADZU SCIENTIFIC 410/381-1227, 800/477-1227
SEVERS RESEARCH 303/444-2009
SPECTRA HARDWARE 412/863-7527
SPECTRA PHYSICS ANALYTICAL 408/432-3333, 800/424-7666
SPECTRACE INSTRUMENTS 415/967-6316
SPECTREX 415/365-6567
SPECTRO ANALYTICAL INSTRUMENTS 508/342-3400, 800/548-5809
SUPREX 412/826-5200
T N TECHNOLOGIES/MANNING PRODUCTS 512/388-9100, 800/736-0801
TEXMAR 513/247-7000, 800/543-4461
TELEDYNE ANALYTICAL 818/961-9221
THERMO JARRELL ASH 508/520-1880
TIMBERLINE INSTRUMENTS 303/494-4104
TREMETRICS 512/251-1555, 800/876-6711
TURNER DESIGNS 408/748-0994
TYTRONICS 617/894-0550
U V P 818/285-3123, 800/452-6788
UNOCAL UNIPURE 714/525-9225, 800/323-8647
VALCO INSTRUMENTS 713/688-9345, 800/367-8424
VARIAN ANALYTICAL INSTRUMENTS 415/945-2173, 800/926-3000
VESTEC 71 3/796-9677
VIKING INSTRUMENT CORP. 703/758-9339
WHATMAN 201 /773-5800, 800/922-0361
WYATT TECHNOLOGY 805/963-5904
SPECTROPHOTOMETRIC
INSTRUMENTATION
UV.FL
IR
IR
SI.UV
IR
UV
IR
IR,UV,M,FL
AA,FL,IR,UV
IR
IR
IR
IR
IRjyVJAA,FL
AA
IR.UV
AA
FL
SI
UV
AA.FL.UV
CHROMATOGRAPHS
GA
GA.LI
GA
CH
GA,LI,IO
GA
GA
GA
6A
GA
GA.LI.IO
GA
LI
CH
GA
CH
GA
CH
CH
GA.LI
CH
LI
LI
SPECTROMETERS
SM
GC,PE,MS
GC,NM,OE,PE,MS
SM
SM
GC.OE
PE
XR
OE
XR
OE.PE
GC
GC
GC
COLORIMETERS
CO
CO
CO
CO
CO
KEY
AA ATOMIC ABSORPTION SPECTROPHOTOMETERS
CH CHROMATOGRAPHS PRODUCED
CO COLORIMETERS PRODUCED
FL FLUORESCENCE SPECTROPHOTOMETERS
GA GAS
GC GC/MS
IO ION
IR INFRARED SPECTROPHOTOMETERS
L! LIQUID
MS MASS SPECTROMETERS
NM NMR SPECTROMETERS
OE OPTICAL EMISSION SPECTROMETERS
PE PLASMA EMISSION SPECTROMETERS
SI SPECTROPHOTOMETRIC INSTRUMENTATION PRODUCED
SM SPECTROMETERS PRODUCED
UV UV/VIS SPECTROPHOTOMETERS
XR X-RAY SPECTROMETERS
Source: Pollution Equipment News (February, 1993)
10-7
-------
10. CHEMICAL FIELD SCREENING AND ANALYTICAL METHODS
10.1 FIELD MEASURED GENERAL CHEMICAL PARAMETERS
10,1.1 pH/Alkalinity/Acidity
Other Names Used to Describe Method: —
Uses at Contaminated Sites: pH is used as an indicator during purging before ground-water sampling (see Section
C.1) and is a fundamental parameter for chemical characterization of ground water and soils. In addition pH
is used to classify corrosivity of wastes (a pH of less than or equal to 2 and greater than or equal to 12.5 is
considered hazardous). Alkalinity and acidity are indicators of the buffer capacity of a solution (the resistance
to change in pH with the addition of a strong acid or base). Alkalinity is required for chemical equilibrium
calculations related to carbonate minerals.
Method Description: The pH is the negative logarithm of the hydrogen ion activity in aqueous solutions and is
a significant water quality parameter because it affects solute concentrations perhaps more than any other single
variable. Eiectromelrtc measurement of pH involves comparison of a glass hydrogen ion electrode in the solution
of interest against a reference electrode of known potential by means of a pH meter or other potential measuring
device. Measurement of pH in soil and solids by this technique requires preparation of a saturation extract.
Colorimetric measurement involves use of reagents or litmus paper and estimation of pH by comparison of the
resulting color with color charts. Flow-through cells (see Figure 10.1.2) provide the most accurate measurement
of pH because it can be altered when samples are exposed to the atmosphere. The pH electrode and buffer
solutions must be about the same temperature as the sample. This can be accomplished by allowing sample
water to run over them or by using a portable water bath. Alkalinity and acidity are measured titrimetrically
from the initial condition by the addition of a strong base or acid to an inflection point on the titration curve or
to a fixed endpoint (titrimetry is discussed further in Section 10.5.1). In ground water, alkalinity is measured as
carbonate and bicarbonate.
Method Selection Considerations: Electrometric measurement of pH using pH electrodes and a pH meter is the
recommended technique for accurate measurement of both ground water and soil, Colorimetric techniques,
which are less precise but somewhat easier to use in the field, are satisfactory for general characterization of soils.
Field measurement of alkalinity (as carbonate and bicarbonate) is required for chemical equilibrium calculations
related to carbonate minerals because this parameter is subject to change during sample handling. The acidity
obtained from titration analysis gives a measure to total ionizable hydrogen that can be used as input to some
geoohemical computer programs.
Frequency of Use: Field measurement of the pH of ground water should be a standard procedure during
sampling. Field measurement of the pH of soil samples often is required for accurate classification of soils and
is a useful characterization technique, but is not necessarily required for soil samples collected for laboratory
analysis unless redox sensitive species are of special concern.
Standard Methods/Guidelines: See Table 10.1.1.
Sources for Additional Information: Barnes (1964), Garvis and Stuermer (1980), Hem (1985-interpretation),
Korte and Ealey (1983), Ritchey (1986), Thompson et al. (1989-Chapter 15).
10-8
-------
1
Combination Eh
Reference electrode
Nylon connection 1/2 in.
pips x 1/2In. tube (Reamed to]
fit probe)
Nylon connection
l/4in.plpe X 3/8 In.tube
-Acrylic tuba 6 1/2 In. x 2 In. O.D.
(I 3/4In. I.D.)
Plow control valve
(Plastic )s
Acrylic plug
I In.* 13/4 in.
diameter
Polyethylene tubing
3/8 In. A. 0.
—Nylon elbow 1/4 In.pipe x 3/8In. tube
(a)
WMM//W//7777r^jl
1/16 lit tuba to 1/16 in. pipe.
-1/16 in. hib« to l/!6in.pip«
lie connector
- Chamber (mods from a
thick-walled sample
bottle)
( —S«nsor gtiard
-'Q!l ring
Figure 10.13, Oxidation-reduction status: (a) Eh measuring cell; (b) Flow chamber for determination of dissolved
oxygen from a pumped well (Wood, 1976).
10-9
-------
Tabfc 10.1.1 Summary of Ground-Water and Soil Measurement* to Be Made in the Field
Propcrty/Section
Filtration
Sample
Collection
Method
Description
Reference
Wellhead Ground-Water Measurements
Temperature No
(10.1.3)
Dewar flask or
flow through
Thermometer
'Revision 1 of this method is dated November, 1990.
Source: Compiled from Boulding (1991) and Thompson et al. (1989)
USGS (1980);
EPA Method 170.1
(Kopp and McKee, 1983)
pH (10.1.1)
Carbonate/Bicarbonate
(AlkalinityXlO.1.1)
Acidity (10.1.1)
Eh (Redox Potential)
(10.1.2)
Dissolved Oxygen
(10.1.2)
No Flow through
Membrane Closed titration
vessel
Membrane Closed titration
vessel
No ' Flow through
No Flow through
Specific Conductance Membrane Flow through
(10.1.3)
Field Laboratory Ground-Water Measurements
Filterable Residue
(10.1.3)
Nitrate-Nitrite
(ScparateIyXlQ-1-3)
Sulfite (10.1.3)
Soil/Solids
SoilpH
(10.1.1)
Solid waste pH
(10.1.1)
Soil Conductivity/
Resittivity (10.1.3)
No Collect in bottle
Membrane Collect in bottle
Membrane Collect in
buffered iodine
— Grab or core
— Grab or core
— Grab or core
pH electrodes .
and meter
Potentiometric (pH
electrode) titration
with strong acid
Potentiometric (pH
electrode) titration
with strong base
Potentiometric
(ft electrode)
Potentiometric with
oxygen probe or
titrimetric
Wheatstone Bridge
conductivity meter
Gravimetric
Spectrophotometric
lodine-thiosulfate
titration
pH electrodes and
meter in saturated
paste
Wheatstone Bridge
conductivity meter
USGS (1980);
Wood (1976)
USGS (1980);
Wood (1976);
D1067-82 (ASTM, 1982)
D 1067-82 (ASTM, 1982)
D1498-76 (ASTM, 1976);
Wood (1976)
EPA Method 360.1/.2
(Kopp and McKee, 1983);
USGS(1980); Wood(1976)
USGS (1980);
Wood (1976)
EPA Method 160.1
(Kopp and McKee, 1983)
EPA Method 353.3
(Kopp and McKee, 1983)
Method M2 (Radian,
1988)
Method 8C (SCS, 1984)
D4972-89 (ASTM, 1989)
EPA Method 9045A'
(US. EPA, 1986b)
Method 8E (SCS, 1984)
10-10
-------
10, CHEMICAL FIELD SCREENING AND ANALYTICAL METHODS
10.1 FIELD MEASURED GENERAL CHEMICAL PARAMETERS
10.1.2 Redox Potential (Eh)TDissolved Oxygen
Other Names Used to Describe Method: --
Uses at Contaminated Sites; Characterizing oxidation-reduction conditions in the subsurface for evaluation of
potential for mobility of heavy metals and biodegradation of organic contaminants.
Method Description: Redox potential (Eh) is measured electrometrically using a platinum electrode and a
reference electrode to provide a reference potential and to provide an electrical connection to the solutions.
Measurement of pH and temperature also are required. Eh readings can be strongly affected by exposure to
atmospheric oxygen, consequently, flow-through cells must be used (Figure 10.1,2a). It is sometimes difficult to
obtain precise readings of Eh because redox couples might not be in mutual equilibrium. More accurate
characterization of the redox status of a sample requires analysis of the valence state of redox sensitive species
(ferrous/ferric iron, nitrate/nitrite, and sulfate/hydrogen sulfide being most important in natural systems), which
involves more complex chemical analytical procedures. Redox status of ground water and soil strongly affect the
mobility and toxicity of arsenic, chromium, and selenium. Accurate chemical analysis of valence state is required
to confirm Eh measurements. Arsenic and selenium forms usually are measured using hydride AAS (see Section
10.3.5), and chromium species can be determined colorimetrically (Hach kits for total and hexavalent chromium
recently have been developed in cooperation with EPA). Dissolved oxygen (DO) is another indicator of the
oxidation-reduction state of an aqueous solution, with low concentrations indicating reducing conditions. In the
field, DO is measured electrometrically using a membrane electrode, a reference electrode, and a meter to
measure electrode response. As with Eh, flow-through cells are used to prevent alteration of the sample by
contact with the atmosphere (Figure 10.1.2b). Dissolved oxygen also can be measured titrimetrieally using the
Modified Winkler method.
Method Selection Considerations: Along with pH, redox potential and dissolved oxygen are the most significant
parameters affecting the chemistry of ground water.
Frequency of Use: Eh and dissolved oxygen in ground-water samples are not measured as routinely as pH, but
probably should be.
Standard Methods/Guidelines: See Table 10.1.1.
Sources tor Additional Information: Garvis and Stuermer (1980), Hem (1985-interpretation), Holm et al. (1986),
Korte and Ealey (1983), Langmuir (1971), Newman and Kimball (1991-DO), Ritchey (1986), Rose and Long
(1988-DO), Thompson et al. (1989-Chapter 17).
10-11
-------
„ ,
Sampler j
Membrane
Compound!
Vapor
Sampler
Sampler Coupling
Membrane Housing
Mass Spectrometer
to Vacuum Pump
(a)
1" EXTRACTION
2nd EXTRACTION
1" SUBSTITUTION
Nth EXTRACTION
(N-l) SUBSTITUTION
(b)
Figure 10^.1 Field gas extraction techniques: (a) Vacuum extraction (Hadka and Dickinson, 1988); (b) Diagram of
multiple headspace extraction (Ho et al., 1988).
10-12
-------
10. CHEMICAL FIELD SCREENING AND ANALYTICAL METHODS
10,1 FIELD MEASURED GENERAL CHEMICAL PARAMETERS
10.1.3 Other Parameters
Other Names Used to Describe Method: Specific conductance/electrical conductivity, temperature, suspended
solids (filterable residue), sensitive chemical species (nitrate/nitrite and sulfite).
Uses at Contaminated Sites: Speciflc conductance: Monitoring of well purge water; performing qualitative
assessment of water quality; estimating total dissolved solids; detecting conductance contaminant plumes;
performing ionic tracer tests. Temperature: Monitoring of well purge water; correcting for pH and Eh
measurements; performing temperature tracer tests; monitoring air temperature. Sensitive chemical species:
Performing field measurement for evaluation of water quality. Filterable residue: Characterizing subsurface
transport of heavy metals on particles.
Method Description; Temperature measurement techniques are discussed in some detail in other sections of the
guide (Sections 1.6.1, 1.6.2, 3,5,2, 8.2.1, and 8.2,3). Temperature of ground water usually is measured with a
mercury-filled thermometer, which is placed in a sample that is continuously pumped into a dewar flask.
Pumping continues until three identical consecutive readings of temperature are obtained. Speciflc conductance
is measured using a Wheatstone bridge conductivity meter. During well purging, measurement of specific
conductance at intervals until there is no significant change between measurements serves as an indication that
stagnant water has been completely removed from the well and water quality samples can be collected. Specific
conductance typically shows a linear correlation with total dissolved solids, and consequently can be used instead
of separate measurement of TDS, provided a correlation curve for the specific area of interest has been
developed. Filterable residues are measured gravimetrically after filtering. Sensitive chemical species: The U.S.
Geological Survey (1980) recommends that certain sensitive chemical species be analyzed in the field because
of potential for alteration with holding times required for laboratory analysis. Sulfite can be analyzed using an
iodine-thiosulfate titration, and nitrate/nitrite forms of nitrogen can be analyzed colorimetrically.
Method Selection Considerations; Temperature measurement of ground-water samples is simple, inexpensive,
and a necessary complement to pH and Eh measurements. Specific conductance of ground-water samples is
simple and inexpensive and is useful for monitoring purge water and estimating total dissolved solids (TDS),
A well-designed and constructed monitoring well should produce samples with a minimum of filterable residue,
but if significant amounts are present, this measurements should probably be taken, especially if subsurface
particle transport of heavy metals is a possibility. Analysis of sensitive species should be performed when they
are considered of geochemical significance at the site.
Frequency of Use: Temperature and specific conductance of ground-water samples are standard measurements.
Use of specific conductance to estimate total dissolved solids is more commonly used for surface waters, but can
be useful for monitoring of contaminant plumes. Filterable residue and analysis of sensitive species are
performed less commonly.
Standard Methods/Guidelines: See Table 10.1.1.
Sources for Additional Information: Davis et al. (1985), Hem (1985-interpretation), Korte and Ealey (1983),
Thompson et al. (1989).
10-13
-------
10. CHEMICAL FIELD SCREENING AND ANALYTICAL METHODS
10.2 CONTAMINANT SAMPLE EXTRACTION PROCEDURES
10.2.1 Gas Headspace/Vacuum Extraction
Other Names Used to Describe Method: --
Uses at Contaminated Sites: Collecting volatile organic compounds in soil gas, soils, and ground water for
chemical analysis.
Method Description: Vacuum extraction of pore gases involves the use of a vacuum pump to pull samples of air
or soil gas directly into an analytical instrument. Figure 10.2.1a illustrates a vacuum sample probe used to obtain
soil-gas samples for analysis by a mass spectrometer (see also, Figure 10.3.3b). Alternatively, a syringe can be
used to sample the stream of gas that is created by the vacuum pump (see Figure 9.4.2a). Gas hcadspace
extraction involves the use of a dead space to collect gases that are moving through water or soil, or from a solid
or liquid phase to a gaseous phase. This can involve placement of a water or soil sample in a container that is
partly filled with air (headspace), and collecting a sample of the headspace gas (usually with a syringe) once the
vapors in the sample have equilibrated with the headspace gas. Since not all vapors are likely to degas the first
time, multiple headspace extraction is sometimes used (Figure 10,2,lb). Figure 9.4.2c illustrates a field
headspace collection device for sampling gases moving through a surface water body.
Method Selection Considerations: Advantages: Is an extremely simple procedure. Disadvantages: Might not result
in full extraction of volatiles in ground-water and soil.
Frequency of Use: Vacuum extraction of pore gases and headspace techniques are commonly used for extraction
of volatile organic compounds for analysis.
Standard Methods/Guidelines: Headspace techniques: Ford et al. (1984), U.S. EPA (1988b-FM-4 to FM-9, FM-
11); Vacuum extraction: U.S. EPA (1988b-FM-12 to FM-14, FM-16, FM-17).
Sources for Additional Information: See Table 10-4.
10-14
-------
Sampler
Membrano-
Sampler
Compound:
Vapor
.Sampler Coupling
Membrane Housing
Mass Spectrometer
us
Jill
T. -Ill
n
to Vacuum Pump
Air
-Air
1" EXTRACTION
2nd EXTRACTION
I11 SUBSTITUTION
Nth EXTRACTION
(N-l) SUBSTITUTION
Figure 10.2.1 Field gas extraction techniques: (a) Vacuum extraction (Hadka and Dickinson, 1988); (b) Diagram of
multiple headspace extraction (Ho et al., 1988).
10-15
-------
10. CHEMICAL HELD SCREENING AND ANALYTICAL METHODS
10.2 CONTAMINANT SAMPLE EXTRACTION PROCEDURES
10.2.2 Purge and Trap Methods
Other Names Used to Describe Method: P/T, purge with whole column cryotrapping (P/WCC).
Uses at Contaminated Sites: Extracting volatile organics from soil and water samples.
Method Description: Purge and trap techniques involve the forcing of a gas (usually helium) through a sample
of water or soil slurry, which entrains the volatile compounds. The entrained volatiles can be fed directly into
the analytical instrument (Figure 10.2.2a) or can be used in combination with a sorbent trap (see Section 10.2.5)
to concentrate the samples for later thermal extraction (see Section 10.2,4). Figure 10.2.2b shows a schematic
of concentrator^jurge and trap device.
Method Selection Considerations: Advantages: Provides better recovery than vacuum/headspace extraction from
water and soil samples. Disadvantages: (1) Requires somewhat more complex equipment than vacuum/headspace
extraction and also requires a purge gas; and (2) more specialized training is required compared to gas
headspace/vacuum extraction.
Frequency of Use: Commonly used for mobile laboratory analysis of volatiles in soil and ground water.
Standard Methods/Guidelines: —
Sources for Additional Information: See Table 10-4.
10-16
-------
T
HELIUM TR
PURGE
GAS
[
25 ML
VIAL
%
\
\
5A
7^
;
i
EFLON
ANSFER
\ CAPILLARY
t
*.
•t
/*
*
%
1
SPLIT fvS
VALVE V-f
SPLIT
VENT
ION
-^-JRAP
IPUMP 1
(a)
Toggle
valves
0 Bubbler
OLoadl
Load 2
Sample
out
•Traps
120 Volts AC
(b)
Figure 10,2.2 Purge and trap teclmiques; (a) Conventional (Wise et al., 1991a); (b) With concentrator (Sherman ct
al., 1988a).
10-17
-------
10. CHEMICAL FIELD SCREENING AND ANALYTICAL METHODS
10.2 CONTAMINANT SAMPLE EXTRACTION PROCEDURES
10.23 Solvent/Chemical Extraction/ Microextraction
Other Names Used to Describe Method: Soil-solvent extraction, liquid-liquid extraction, ultrasonication.
Uses at Contaminated Sites: Extracting volatile, semi-volatile, and non-volatile organic compounds from ground
water and soils.
Method Description: Solvent extraction procedures involve the use of one or more organic solvents, acids, or
other chemical substances and measures, such as filtration and centrifugation, to remove and concentrate the
analyte of interest from a soil or ground-water sample (Figure 10.2.3a). Commonly used solvents include
acetone, hexane, and methanol. Microextraction procedures require only a very small sample for extraction.
Each analyte of concern requires its own specific extraction procedure. Simplified extraction procedures can
sometimes be used for field screening purposes. Figure 10.2.3b compares a field screening and standard EPA
laboratory extraction procedures for PCBs. Ultrasonication uses ultrasonic sound waves to accelerate the
extraction of chemical species into a solvent.
Method Selection Considerations: Advantages: (1) Extraction procedures are compound specific; and (2)
simplified extraction procedures have been developed for field screening of PCBs, PAHs, phenols, and pesticides.
Disadvantages: Depending on the compounds, procedures can be complex and time-consuming.
Frequency of Use: Required for many EPA standard laboratory methods. Standard or simplified field screening
extraction procedures are being increasingly used with a variety of field screening and analytical techniques.
Standard Methods/Guidelines: ASTM (in preparation-microextraction), U.S. EPA (1988b-Soil: PCBs, pesticides;
Liquid/Liquid: Phenol; Soil or water: Total PNA).
Sources for Additional Information: See Table 10-4.
10-18
-------
Qrqtnlc
Solvent *\
100ml-
Extraction
Concentrated Sample
| 20-SOttl
Rptovap
GC-MS Control and
Data Acquisition System
EC-MS
(a)
EPA No. 3550/8060
2 gm Sampla
30 grti Sample
1.00 ml Matfianol
10 gm Sodium Sultale
LOOmiHexono
Centrifuge 5 min
Santcat8 3 min and Filter
Bepoal; Two Mora Times
Transfer
S mi Extract
*1.0 ffil Gone. Syifuric MKJ
Vortax 1 min
Pass Through Drying CoJurnn:
Socium SuffQla
QOECO AnaJyaia
Evaporate in Kudsma
Danish Conoanlrator
Solvent Exchange with
f-Octano whlEa Concentrating
wlUi Nitrogen-Evaporator
Cone. Sulfurro Acid
Vortex t mm
Canfrtfuge 10 min
Clean-up
Column
(b)
Figure 10^3 Soli extraction: (a) General schematic of organic solvent extraction from soil samples (Overton et al.,
1988b); (b) Detailed field screening and EPA 3550/8080 extraction procedures for PCBs (Moy, 1989, by
permission).
10-19
-------
10. CHEMICAL FIELD SCREENING AND ANALYTICAL METHODS
10.2 CONTAMINANT SAMPLE EXTRACTION PROCEDURES
10.2.4 Thermal Treatment Methods
Other Names Used to Describe Method: Thermal/microwave-assisted digestion, thermal extraction (Ruskan/Pyran
thermal chromatograph/Pyrocell), thermal desorption.
Uses at Contaminated Sites: Preparing soil and water samples for instruments requiring a gaseous phase for
analysis (Section 10,3); preparing soil and water samples for wet chemistry/colorimetric analysis.
Method Description: Thermal extraction techniques have in common the use of heat to prepare samples for
subsequent stages of analysis. This can be as simple as using an electric or microwave oven to dry samples
(required for soil moisture content determinations and XRF analysis in the laboratory), to highly sophisticated
instruments for vaporizing samples (such as ICP torches for atomic emission spectrometry [see Section 103.6]).
The term digestion is commonly used when heating is involved in wet chemistry analytical procedures. Figure
10.2.4a shows a thermal extraction device used with a flame ionization detector, and Figure 10.2.4b shows a
schematic of a column thermal extractor used with a mass spectrometer.
Method Selection Considerations: Most thermal treatment techniques and devices are small enough that they
can be used in mobile laboratories. Thermal digestion is required for many wet chemistry analytical procedures.
Thermal extraction/desorption can sometimes be used as an alternative to solvent extraction for analysis of non-
gaseous phase samples in analytical instruments, such as gas chromatographs and mass spectrometers, which
require a gaseous phase (see Section 10.3).
Frequency of Use: Colorimetric wet chemistry field test kits for liquids, oils, and solids (see Section 10.5.1) often
involve an initial digestion step. Use of thermal extraction procedures in conjunction with gas chromatographs
and mass spectrometers in mobile laboratories is a relatively new approach that is becoming more common.
Standard Methods/Guidelines: U.S. EPA (1988b-PAHs using GC with heated column).
Sources for Additional Information: See Table 10-4.
10-20
-------
LCCX
He
TC^MS
Quartz Analyzer
= ^ Liquid COaCooklng
Splitter Purge
Splitter Vent
Cold Trap —
-70° to 600° C -
Pyrooell —
0° to 60EfC
Sample Loader —
Helium Carrier Gas
(a)
(b)
Figure 10.2.4 Thermal extraction devices: (a) Pyrocell for FID; (b) Column thermal extractor for mass spectrometer
(Over-ton et al, 1988b).
10-21
-------
10. CHEMICAL HELD SCREENING AND ANALYTICAL METHODS
10.2 CONTAMINANT SAMPLE EXTRACTION PROCEDURES
10.2.5 Other Extraction Methods
Other Names Used to Describe Method: Membrane extraction, extraction disks, sorbent/solid phase extraction
cartridges, Tenex tubes, cyclohexyi-bonded phase extraction column, supercritical fluid/gas extraction (SFE).
Uses at Contaminated Sites: Extracting contaminants in ground water (sorbent and membrane) and air/soil gases
(sorbent).
Method Description: Sorbent extraction involves the contact of air or water through a material, such as granular
activated carbon (GAC), polyurethane, or resins, which trap organic compounds by sorption or filtration. Figure
10.2,5a illustrates the use of a polyurethane sorbent for air quality sampling. Bonded sorbents have been used
for pesticides, PAHs, and phenols. Resin cartridges can be used for concentration of VOCs obtained from purge
and trap (see Figure 10.2.2b). GAC is commonly used for passive soil sampling (see Figures 9.4.1a and b) and
sometime to extract volatiles from ground-water samples. Once the sample is collected, a thermal extraction
technique (Section 10.2.4) typically is used to extract the concentrated sample for instrumental analysis.
Membrane extraction uses extractant fluids containing organic solvents, such as hexane, flowing through a tubular
silicone rubber membrane to selectively extract and concentrate organic compounds of interest from a sample
flowing outside the tube. In the simplest application, extractant fluid flows directly to the analytical instrument
for analysis (Figure 10.2.5b). For more complex samples, additional separation steps might be required,
Supercritical fluid extraction (SFE) allows extraction of components from different matrices by means of a
supercritical fluid, such as carbon dioxide.
Method Selection Considerations: Sorbent Advantages: (1) Is a simple and inexpensive extraction technique for
gaseous and water samples; and (2) is most applicable where preconcentration or precise measurements are
required. Sorbent Disadvantages: (1) Concentrations will be underestimated if sorption is not complete or the
sorbent becomes saturated; and (2) typically requires a second extraction step for instrumental analysis.
Membrane Extraction Advantages: (1) Is a relatively simple technique; and (2) has the potential for automation
to eliminate sample handling before it goes into the instrument for analysis. Membrane Extraction
Disadvantages: (1) Is limited to aqueous samples; and (2) satisfactory extraction might be difficult with complex
samples.
Frequency of Use: Sorbents are being widely used where preconcentration of samples is required. Membrane
extraction and SFE are relatively new methods that have not been used extensively.
Standard Methods/Guidelines: Sorbent: U.S. EPA (1988b-FM-10, FM-16).
Sources for Additional Information: U.S. EPA (1988b-FM-D2, FM-D3). See also, Table 10-4.
10-22
-------
TUBING-
PARTICIPATE FILTER
(OPTIONAL)
MOISTURE TRAP
CornoNAU
PYREX TUBE
PREFILTER OR PACKING
POUtURETHANE FOAM SORBENT PLUG -
-PUMP
-TRIPOD,
ADJUSTABLE
HEIGHT
(a)
Extractant
Membrane fl
Sample
(b)
Figure 10^.5 Other extraction techniques: (a) Polyurethane sorbent plug sampling train for air quality samples
(Ford et al., 1984), (b) Membrane/flow injection system (Melcher and Morabito, 1991).
10-23
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10. CHEMICAL FIELD SCREENING AND ANALYTICAL METHODS
103 GASEOUS PHASE ANALYTICAL TECHNIQUES
103.1 Total Organic Vapor Survey Instruments
Other Names Used to Describe Method: OV detectors, photoionization detector (PID/HNU meter), flame
ionization detector (FlD/Organic vapor analyzer/OVA), argon ionization detector (AID), combustible-gas
indicator (explosimeter [EDJ/catalytic surface oxidation device),
Uses at Contaminated Sites; PID: Surveying aliphatics and aromatics; AID: Surveying aliphatics, aromatics,
halomethanes, and halethanes, PDDs, FIDs and AIDs also can be used in combination with a gas chromatograph
for detecting specific compounds (Section 10.3,3). Explosimeters are used to test manhole/sewers, pipeline leaks,
confined areas in sewage plants, and inside tanks for combustible gases.
Method Description: Photoionization detector (PID): Uses an ultraviolet lamp as an ionizing source and responds
to volatile organic compounds that have an ionization potential less than or equal to the lamp. A PID reports
concentrations as total ionizable compounds. Flame ionization detector (FID): (Uses a hydrogen flame to ionize
organic vapors entering the detector and reports concentrations of total organics as the ppm equivalent to a
calibration compound (usually methane).) Argon Ionization detector (AID): Similar to a PID, except that an
argon lamp is used. Explosimeters use a sensor (hotwire, catalytic, solid state, etc.) to produce a signal, which
is processed and displayed as the percentage of the combustible gas present to the total required to reach the
lower explosive limit (LEL) and/or the percent combustible gas by volume. Various calibration gases can be used
(butane, pentane, natural gas, and petroleum vapors), but methane is the most common.
Method Selection Considerations: Figure 10.3.1 shows sensitivity ranges for organic vapor monitoring instruments.
Total Detector Advantages: (1) Are highly portable (FID somewhat less portable than PID) and easy to use; (2)
are relatively inexpensive (around $5,000); (3) HD is sensitive to a larger number of volatile organic compounds
than PID (including low molecular weight compounds, such as methane, ethane, and certain toxic gases with high
ionization potential, such as carbon tetrachloride and HCN); (4) have very rapid response time (seconds); and
(5) AID is the most durable detector. Total Detector Disadvantages: (1) Are non-specific (they indicate if
something is present but do not identify); (2) FID is more complicated than PID and requires hydrogen gas; and
(3) AID is somewhat less sensitive than FID and PID. Explosimeters are inexpensive and portable.
Frequency of Use: PIDs and FIDs are widely used as survey instruments whenever volatile organics are
suspected, and also are commonly used in conjunction with gas chromatographs (see Section 10.3.3).
Explosimeters are commonly used where explosive gases are suspected.
Standard Methods/Guidelines: Ford et al. (1984-PED, FID, ED), U.S. EPA (1988b-Seetion 15),
Sources for Additional Information: Aller (1984-combustible gas indicator). See also, Table 10-5.
10-24
-------
SENSITIVITY RONBES FOR ORGANIC VftPOR MONITORING INSTRUMENTS
UNITS
PRINCIPAL
CONCERN
t-pTHQDS
OVOILflBLE
1
1
V
PARTS PER BILLION U0~9> ' 1 PARTS PER MILLION <10"6) 1. . PERCENT BftS «O
1 1
0. 1 1 10 208 1 20 100 2000 i 10 100
1
1
I
1
- 1
1
1
1
i
COLORIMETRIC PAPER TOPES 1
LASER / CftMERft / FTIR
OXIDflTION (£) 1 OXIDflTION (1)
(PPM RflNBE) 1 (LFL RflNGE)
1
1
1
1
OXYGEN
DEFICIENCY
( THERMflL >
CONDUCTIVITY
<— ELECTROCHEM — >
Og CELLS
Figure 103.1 Sensitivity ranges for organic vapor monitoring instruments (Moore, 1991).
-------
10. CHEMICAL HELD SCREENING AND ANALYTICAL METHODS
10.3 GASEOUS PHASE ANALYTICAL TECHNIQUES
10.3.3 Gas Chromatography (GC)
Other Names Used to Describe Method; Portable, fieldable, or mobile gas chromatograph with a: Flame
ionization detector (FID), photoionization detector (PID), argon ionization detector (AID), electron capture
detector (BCD), thermal conductivity detector (TCD), flame-photometric detector (FPD), Hall-electrolytic
conductivity detector (ELCD), ion trap detector (ITD), microwave [induced] plasma detector (M[I]PD);
GC/atomic emission spectroscopy (AES); GC/Fourier transform infrared spectroscopy (FTIR) (see section
10.4.4); GC/mass spectrometry (MS) (see Section 10.3.4).
Uses at Contaminated Sites: Portable GC: Assessing volatile organics and other gases (using headspace or purge
and trap), soil PAHs, PCP, and PCBs (using extraction techniques). GC/AES: Assessing Cl, Br, O, N, P, and S
levels.
Method Description: Gas chromatography involves the separation of gaseous constituents on a stationary phase
in a column, which is either a solid or liquid held on a solid support. Thermal desorption gas chromatographs
(TD-GC), with a unit for vaporizing samples before entering the column, are used when samples are in liquid
phases or soil. Once the analytes have been separated in the column, they are eluted one after another, and then
enter a detector attached to the column exit. Numerous types of detectors can be used with a gas chromatograph
as listed above under other names. An FID or PID (see Section 10.3.1) can be used to detect specific
compounds after they have been separated in the GC and FIDs and PIDs commonly are used in portable GCs.
The electron capture detector (BCD) is another commonly used detector. Figure 10.3.3 shows several portable
GC units. GC commonly is used as a sample preparation step for other types of instrumentation, such as the
mass spectrometer (see Section 10.3.4). Relatively new combinations that show promise for use at contaminated
sites include: (1) GC/MPD-AES, an experimental technique using GC in combination with a microwave plasma
detector (MPD) and atomic emission spectrometry (see Section 10.3.6); and (2) GC/Fourier Transform Infrared
(see Section 10.4.4).
Method Selection Considerations: GC Advantages: (1) Are fairly portable; (2) have very good specificity,
depending on detector used, with excellent ability to resolve most components in very complex mixtures; (3) have
fair sensitivity (ppb to ppm); and (4) inexpensive compared to mass spectrometer ($10,000 to $20,000 vs. $50,000
to $200,000). GC Disadvantages: (1) Are less sensitive than mass spectrometers; (2) have slower response time
than mass spectrometers (tens of minutes vs. seconds) and their calibration can be time-consuming; (3) require
a library of retention times to identify compounds and non-target compounds might be difficult to identify if
detected analytes are not in the library or the quality of the library match is too low to make positive
identification; and (4) require bottled gas. GC/FID: Universal capability in screening samples. GC/MS: Allow
better resolution of components in complex mixtures than MS alone and are most commonly used for
unequivocal identification of hazardous compounds. GC/FTIR: Allow elucidation of chemical structure and are
able to identify additional hazardous compounds not detected by GC/MS. GC/AES Advantages: (1) Allow
detection of elements that have been impossible or difficult to monitor with other GC detectors; (2) element-
specific detection can save time in sample preparation; (3) multiple element detection reduces need for GCs with
multiple detectors; (4) element ratios can reduce time for interpretation of GC/MS and GC/FTIR data for
nontarget compounds; (5) size and weight and other requirements similar to GC/MS field laboratory
instrumentation; and (6) detection limits comparable to GC/FID and GC/FPD. GC/AES Disadvantages:
Instrumentation still in developmental stages. Other Detectors: ECDs are highly sensitive to halogenated organic
molecules and can be used to analyze for PCBs in the presence of unhalogenated hydrocarbons, such as oil.
Detectors, such as NPD, ECD and ELCD (Hall detector), have lower detection limits for specific elements.
Frequency of Use: GC is the most well developed and accurate field analytical technique for organic compounds
when used with an appropriate detector. The most commonly used detectors include PID, FID, AID, ECD, Hall
detector (ELCD), and TCD.
10-27
-------
(a)
(b)
Figure 10JJ Portable gas chromatographs: (a) IINU System GC 311; (b) Photovac 10S PLUS (U.S. EPA, 1991b).
10-28
-------
Standard Methods/Guidelines: Ford et al. (1984), U.S. EPA (1987-Exhibit 7A-1, mobile lab protocol for
organics), U.S. EPA (1988b-TD/GC, GOECD, Mobile GC).
Sources for Additional Information: Davis et al. (1985), Nielsen et al. (1992), Szelewski and Wilson (1988), U.S.
EPA (1991b, 1992), Weslowski and Alwan (1991). See also, Table 10-5.
10-29
-------
10. CHEMICAL FIELD SCREENING AND ANALYTICAL METHODS
10.3 GASEOUS PHASE ANALYTICAL TECHNIQUES
10.3.4 Mass Spectrometry (MS) and GC/MS
Other Names Used to Describe Method: Fieldable/mobile mass spectrometer (MS), mobile tandem MS (MS/MS,
MINITMASS), GC/MS, GQTIMS or ITD (ion trap mass spectrometer or ion trap detector), thermal desorption
(TD) or thermal extraction (TE), GQMS.
Uses at Contaminated Sites: TD-GC/MS: Assessing VOCs (water, soil/sediment, soil gas, air), PCBs, PAHs, and
pesticides (soiWsediment); GC/ITMS: Assessing VOCs (air, water, soil) (Wise et al. [1991a] list detection limits
for 30 VOCS in air, and 21 VOCs in water).
Method Description: Mass speclrometry techniques involve conversion of compounds in a sample into charged
ionic particles that consist of the parent ion and ionic fragments of the original molecule. Distinctive mass/charge
ratios allows for identification of compounds, while the magnitude of ion currents at various mass settings is
related to concentration. Major components of a mass spectrometer include: (1) The inlet system, (2) the ion
source, (3) the electrostatic accelerating system, and (4) the detector and readout system that gives a mass
spectrum recording the numbers of different kinds of ions (Figure 10.3.4a). Mass spectrometers often are used
in conjunction with gas ehromatography (see Section 10.3.3). Figure 10.3.4 illustrates portable, fieldable, and
mobile laboratory mass spectrometers.
Method Selection Considerations: MS Advantages: (1) Have very good specificity in noncomplex matrix; (2) are
very sensitive (ppb); (3) have rapid response time (seconds); and (4) very small sample sizes (milligram to
microgram) can be used. MS Disadvantages: (1) Have poor resolution in complex mixtures (can be overcome
by using GC/MS); (2) are expensive ($50,000 to $200,000); (3) are large, heavy, and not very rugged; (4) require
high vacuum pumps and a large amount of power; (5) are complex instruments requiring long set up time; (6)
require a library of spectra; and (7) calibration procedures are more time-consuming than for GC.
Frequency of Use: Some use in mobile laboratories. Field instruments are in developmental stages.
Standard Methods/Guidelines: U.S. EPA (1988b-GC/ITMS, MS/MS).
Sources for Additional Information: Davis et al. (1985). See also, Table 10-5.
10-30
-------
(a)
(b)
Ruska
Thermal
Chromatograph
Finnigan MAT
In cos 50 Mass
Spectrometer
Data Systems
%
1
II
\-Fump
"^ Power
Conditioner
Figure 103.4 Mass spectrometers: (a) Schematic of man-portable GC/MS system: (A) Vapor inlet/transfer GC
column, (B) MSD analyzer, (C) control electronics, (D) portable 386 computer, (E) molecular drag
pump, (F) vacuum hose, (G) vacuum reservoir, (H) carrier gas, and (1) 24v DC battery (Meuzelaar et
al, 1991), (b) Fieldable mass spectrometer mounted in a 4-whoel drive vehicle (Hadka and Dickinson,
1988), (c) Mobile thermal chromatograph/mass spectrometer (Greenlaw et al^ 1989, by permission).
10-31
-------
10. CHEMICAL HELD SCREENING AND ANALYTICAL METHODS
10.3 GASEOUS PHASE ANALYTICAL TECHNIQUES
103.5 Atomic Absorption Spectrometiy (AAS)
Other Names Used to Describe Method: —
Uses at Contaminated Sites: Analyzing heavy metals, organometallic compounds, and other elements in water
and soil/solids.
Method Description: AAS involves the measurement of radiation absorbed by electrons in a vaporized liquid
sample. All AAS instruments have the following basic features (Figure 10.3,5a): (1) A light/radiant energy source
that emits resonance line radiation; (2) a sample chamber in which the sample is fed as an aerosol and vaporized;
(3) a device for selecting only one of the characteristic wavelengths (visible or ultraviolet) of the element being
determined; (4) a detector, usually a photomultiplier tube, which measures the amount of absorption; and 5) a
readout system (strip chart recorder, digital display, meter, or printer). Techniques for vaporizing the sample
include Dame (aerosol mked with fuel and oxidant gas), furnace or electrothermal (sample is deposited at room
temperature in a graphite tube and vaporized by heating), hydride generation or derivitization (elements such
as As, Se, Sb, and Sn are converted to gaseous hydrides before being vaporized in small quartz tube furnaces),
and cold vapor (for mercury only). AAS instruments can have one or two beams (Figure 10.3.5b and c), and
more sophisticated (and more expensive) instruments have more than one channel for simultaneous
determination of more than one element. Multi-element sequential AAS instruments can be programmed to
automatically determine chosen elements sequentially.
Method Selection Considerations: Advantages: (1) Simpler instruments, such as single-beam flame AAS, are
relatively inexpensive (around $6,000 in 1986); (2) operation is very simple and can be partially automated; (3)
in many determinations, standardization is easy and straightforward; and (4) have low detection limits (ppb) and
high accuracy (furnace AAS has the lowest detection limits; flame AAS is generally 10 to 100 times higher).
Disadvantages: (1) Flame AAS can only measure one element at a time and is not well suited for refractory
elements, such as boron and vanadium; (2) time required for heating cycle of furnace AAS makes it slow
compared to flame AAS; (3) sample preparation requires great care and can be time consuming; and (4) matrix
interferences might affect results for specific elements (for example Al, phosphate, and sulfate interfere with Ca
determinations), :
Frequency of Use: AAS and inductively coupled plasma atomic emission spectrometry (Section 10.3.6) are
probably the two most widely used laboratory techniques for elemental analysis of aqueous and solid samples.
Many mobile laboratories have AAS for analysts of heavy metals and hydride derivitization. AA has been used
less commonly in mobile laboratories for analysis of organometalHcs.
Standard Methods/Guidelines: U.S. EPA (1988b-FM-l), U.S. EPA (1987-protocol 7A-3).
Sources for Additional Information: Baker and Suhr (1982), Fishman and Friedman (1989), Thompson et al.
(1989).
10-32
-------
LAMP
CHOPPER FLAME
DETECTOR + AC
MONOCHROMATOR ELECTRONICS
(a)
MONOCHROMATOR
PHOTOMUL.T1PLIER
ff
BEAM
SPLITTER
PRIMARY SOURCE
(b)
PHOTOMULTIPLIER
Figure 103,5 Atomic absorption spectrometers: (a) Essential components; (b) Single-beam instrument; (c) Double-
beam instrument with background correction using a deuterium lamp (Baker and Suhr, 1982, by
permission).
10-33
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10. CHEMICAL FIELD SCREENING AND ANALYTICAL METHODS
103 GASEOUS PHASE ANALYTICAL TECHNIQUES
10.3.6 Atomic Emission Spectrometiy (AES)
Other Names Used to Describe Method: Optical emission spectrometry (OES), flame emission spectrometiy
(FES)/flame photometry.
Uses at Contaminated Sites: Analyzing heavy metals and other elements in water and soil/solids.
Method Description; AES involves the excitation of electrons in liquid samples and measurement of the radiation
emitted when they relax to an unexcited state. Each element emits radiation of a characteristic wavelength and
concentrations are proportional to the intensity. AES using a flame as an excitation source, called flame
emission spectrometry (FES) or flame photometry, has been in use since the 1860s. A variety of other excitation
sources can be used (such as direct current arc, alternating current spark, and direct current discharge plasmas),
but the most commonly used source today is the inductively coupled radiofrequency plasma (ICP) torch (Figure
103.6).
Method Seiection Considerations: Advantages: (1) A large number of elements can be measured simultaneously
(10 to 20 for FES and 20 to 35 to ICP-AES), making analysis for any one element very rapid; (2) ICP-AES linear
range for detection is greater than AAS, reducing the amount of sample handling and dilution for analysis; (3)
FESs are simple and inexpensive to operate; and (4) ICP provides a highly stable, sensitive and relatively
interference-free excitation source for solution samples, and is able to handle refractory elements that AAS and
FES cannot. Disadvantages: (1) Furnace AAS provides greater sensitivity for arsenic, lead, and selenium; and
(2) solids samples requires careful preparation of solutions for analysis.
Frequency of Use: ICP-AES and AAS (Section 10.3.5) are probably the two most widely used laboratory
techniques for elemental analysis of aqueous and solid samples,
Standard Methods/Guidelines: --
Sources for Additional Information: Baker and Suhr (1982-FES), Fishman and Friedman (1989), Soltanpour et
al. (1982-ICP-OES), Thompson et al. (1989-ICP-AES).
10-34
-------
Argon
and
sample aerosol
Optional
argon
flow
coolant flow
Figure 103.6 Plasma torch configuration for ICP-AES (Fishman and Friedman, 1989).
10-35
-------
10. CHEMICAL HELD SCREENING AND ANALYTICAL METHODS
103 GASEOUS PHASE ANALYTICAL TECHNIQUES
103.7 Ion Mobility Spectrometry (IMS)
Other Names Used to Describe Method: Plasma chromatography.
Uses at Contaminated Sites: IMS: Detecting microorganisms, anilines, nitrosoamines, organophosphorus esters,
organic sulfides and arsenicals, selected explosives, and many other organic compounds (Reategui et al. [1988]
identify more than 40 organic and inorganic compounds or groups of compounds that can be detected by IMS);
GC/IMS: Detecting alcohols, ketones, BTEX, aldehydes, haloearbons, and chlorinated aromatics.
Method Description: IMS resembles a cross between a flame ionization detector and a mass spectrometer.
Figure 10.3.7 shows the operation of an IMS cell. A sampling pump draws air though a semipermeable
membrane, which is selected to exclude or attenuate possible interferents. The sample is ionized in a reaction
region through interaction with a weak plasma of positive and negative ions produced by a radioactive source.
A shutter grid allows periodic introduction of the ions into a drift tube, where they separate based on charge,
moss, and shape, with the arrival time recorded by a detector. The identity of the molecules is determined using
a computer to match the signals to IMS signatures held in memory. If the IMS signature is known it also is
possible to program the instrument to detect specific compounds of interest.
Method Selection Considerations: IMS Advantages: (1) Combines the simplicity and sensitivity of ionization
detectors (Section 10.3.1) with the ability to distinguish specific compounds in complex matrix; (2) has very good
sensitivity (sub ppb to ppm); (3) has very fast response time (seconds); (4) is portable and rugged; and (5) is
inexpensive compared to MS and comparable in price to GC ($5,000 to $25,000). IMS Disadvantages: (1)
Provides specific identification of fewer compounds than GC or MS; (2) is better than MS at identifying certain
target compounds in a complex mixture, but GC provides better resolution in this situation; and (3) requires
a library of ion mobilities.
Frequency of Use: IMS: Recent development of portable IMS detectors might make the technique an alternative
to FID and GC
Standard Methods/Guidelines: —
Sources for Additional Information: U.S. EPA (199Ib, 1992). See also, Table 10-5.
10-36
-------
SAMPLE
IN
ELECTRIC FIELD-
!/A> jS
\ r ^» ,* " m
. */x*' * B*R
\/X B *<
! c= R»A
It. /
J C* 8* A* R*gn
n c* 8* A+ ^n
^j C* 8* A* R*p
>0 C* B* A* R*JJ
>D C* 8+ A* R*0
'D C* 8* A* R*0
D C* 8* A* R*0
jj e B* A* R»oy
SIGNAL
OUT
A
COLLECTOR
CURRENT
' /
APfRTURE COLLECTOR
GRID
10 20 30 40
MILLISECONDS
50
6O
Figure 103.7 Theory of operation of ion mobility spectrometer (Reategui et al., 1988).
10-37
-------
10. CHEMICAL FIELD SCREENING AND ANALYTICAL METHODS
10.4 LUMINESCENCE/SPECTROSCOPIC ANALYTICAL TECHNIQUES
10.4,1 X-Ray Fluorescence (XRF)
Mames Used to Describe Methods: Portable XRF, X-ray fluorescence spectroscopy/spectrometry, x-ray emission
spectrography, x-ray spectrochemical analysis.
Uses at Contaminated Sites: Detecting heavy metals and other elements in soil/solids samples. Reported
elements As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sn, and Zn.
Method Description; XRF uses primary x-rays to irradiate a solid sample, which causes elements in the sample
to emit secondary radiation of a characteristic wavelength (Figure 10.4.1a). Concentration of an element is
proportional to the intensity of the secondary radiation emission. Two basic types of detectors are used to detect
and analyze the secondary radiation. Wavelength-dispersive XRF spectrometry uses a crystal to diffract the x--
rays, as the range of angular positions are scanned using a proportional or scintillation detector (see Section 1.5.4
for description of these detectors). Energy-dispersive XRF spectrometry uses a solid-state, Si(Li) detector from
which peaks representing pulse-height distributions of the x-ray spectra can be analyzed. It is the latter type of
detector that has allowed development of field-portable instruments (Figure 10.4.1b). Figure 10.4.1c shows the
effective depth of penetration of various materials. Various terms have been used to describe this technique,
but XRF is the most commonly used term in the literature on investigation of contaminated sites.
Method Selection Considerations: Advantages: (1) Is about one-tenth the cost of conventional laboratory
analyses; (2) sample preparation is minimal compared to conventional analytical techniques; (3) allows
simultaneous determination of several elements; and (4) very portable energy-dispersive XRF instruments are
now available (Figure 10.4.1b) and more accurate wavelength-dispersive XRF instruments can be used in mobile
laboratories. Disadvantages: (1) Detection limits for portable instruments (10s to 100s ppm) typically are an
order of magnitude higher than ICP-AES; (2) laboratory use with liquid samples requires preconcentration or
precipitation, %vhich is time consuming; and (3) the relatively shallow depth of penetration of soil materials (mm)
means that collection and processing by grinding samples is generally required to obtain reproducible readings
using a portable probe.
Frequency of Use: Along with total/specific organic vapor detectors and gas chromatographs, XRF is the most
mature of the portable field screening techniques that have developed in recent years.
Standard Methods/Guidelines: Laboratory XRF: Jones (1982); Field screening: U.S. EPA (1987-Protocol 7A-4),
U.S. EPA (1988b).
Sources for Additional Information: Raab et al. (1991), Thompson et al. (1989). See also, Table 10-5.
10-38
-------
SOURCE
AMPLIFIER
MICROPROCESSOR
OUTPUT
O
o
Fe
Mn
X-RAY ENERGY
(a)
Data Transfer & Processing
Figure 10.4»1 X-ray fluorescence: (a) Schematic Indicating the field-portable XRF analytical process (Glanzman,
1988); (b) Process for real time, on-site XRF measurements, data transfer, processing and plotting
(Raab et ai., 1991, by permission).
10-39
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10. CHEMICAL HELD SCREENING AND ANALYTICAL METHODS
10.4.2 LUMINESCENCE/SPECTROSCOPIC ANALYTICAL TECHNIQUES
10.4.2 Other Luminescence Techniques
Names Used to Describe Methods: Fluorometry/fluorimetry/spectrofluorometry: UV fluorescence
spcctrophotometer; synchronous fluorescence/luminescence (SF/SL);laserfluorometry/laserinduced fluorescence
(UP); solid state fluorescence, x-ray fluorescence (Section 10.4.1); room-temperature phosphorimetry (RTF).
Uses at Contaminated Sites: UV and synchronous fluorescence: Performing semiquantitative analysis of
seraivolatile polynuclear aromatic hydrocarbons (PAHs/PNAs); field screening of BTEX. RTF: Analyzing PCBs.
Method Description: Fluoromctry is a photoluminescent technique in which the electronic state of a molecule
is elevated by absorption of electromagnetic radiation. When the molecule returns to its ground state, radiation
is emitted (typically ultraviolet or visible radiation for most fluorometric techniques) to produce a distinctive
excitation and emission spectrum. Instruments used for fluorometric analysis range from simple filter
fluorometers to very sophisticated spectrophotofluorometers. These instruments contain four principal
components: (1) A source of excitation energy (UV, laser, x-rays, etc.), (2) a sample cuvette, (3) a detector to
measure the photoluminescence, and (4) a pair of filters or monoehromators for selecting the excitation and
emission wavelengths. UV fluorescence has been used in a number of applications for field screening: (1) For
semiquantitative analysis of solvent extracted PAHs, (2) for analysis of samples using high performance liquid
chromatography (Section 10.5.3), (3) in conjunction with fiber optic sensors (Section 5.5.6), and (4) as a surface
contamination detector, in which a non-fluorescing substance sprayed on the ground surface reacts chemically
with the contaminant of interest to form a substances that fluoresces with UV excitation. Fiber optic sensors
commonly use UV fluorescence (see Section 5.5.6). Synchronous fluorescence, or luminescence, involves the
use of both emission and excitation monoehromators to record the luminescence signal, which allows greater
selectivity in the analysis of environmental samples. RTF is based on detecting the phosphorescence emitted
from organic compounds adsorbed on solid substrates at ambient temperatures (conventional phosphorimetry
requires cryogenic equipment). A recently developed test for PCBs using RTP involves a rapid extraction
procedure (1 to 3 minutes), followed by placement of a few microliters of the sample solution on a filter paper.
The sample is dried for about three minutes with a heating lamp and transferred to a spectrofluorimeter
equipped with a phosphoroscope. The presence and concentration of PCBs can be determined by the spectral
signature and intensity. Table 10.4.2 provides additional information on UV-visible luminescence, synchronous
fluorescence, room-temperature phosphorescence, and low-temperature luminescence methods.
Method Selection Considerations; Advantages: (1) Instrumentation is relatively simple and portable; and (2) UV
fluorescence can be used for rapid semiquantitative analysis of total PAHs in soil. Disadvantages: Analysis of
complex samples can be difficult due to spectral overlap of different luminescing compounds (SF can partly
overcome this).
Frequency of Use: Fluorometry in combination with fluorescent dyes probably is the most common technique
used in karst limestone tracer studies. PAH-extract/UV fluorescence has been demonstrated as a good field
screening technique for semiquantitative analysis of polynuclear aromatic compounds in soil. Synchronous
fluorescence and RTP only recently have been tested for field screening of contaminants and are still in the
developmental stages.
Standard Methods/Guidelines: U.S. EPA (1988b-total PNA with UV fluorescence).
Sources for Additional Information; Davis et al. (1985-fluorometry), Eastwood and Vo-Dinh (1991). See also,
Table 10-5.
10-40
-------
Table 10,4.2 General Characteristics of UY-Yisible Luminescence, Synchronous Fluorescence, Room Temperature
Phosphorescence, and Low Temperature Luminescence Techniques of Field Analysis (See end of Table
10.4-3 for definitions and abbreviations)
Applicability Advantages Limitations Sensitivity
Current Reid Related Lab
ApplicabSity Techniques &
Sensors
•
UV-vls LumlnoMcafico (Fiuorssconco and Phosphorescence)
Potyammatic
Compounds
fluorescent Dyes
fluoroinatne Reaction
Products
PC8s
Phenols
Pesticides ,
SGmivolats'les
NonydatBss
Petroleum Oiis
Most Sensitive Method
for Tmca and
Uitratraco Analysis
whan Applicable
Instrumantation
Readily Available
No IrttBfference by
Wafer
Few Interferences by
Nonaf&fiatics
Some Structural
Spodlicity
•Enhanced by
Special Tacetniqii&s
Very Sslectsve
'Enhgjjca&by Time
and Wavelength
Variability
Can Distinguish
Go&mairical Isomars
Limited to Compounds
with Fasrty High
Luminescence y?efe&
(Usually PACs, unless
Darivafa&d}
Relatively UnspecXc
for Strvctur&f
Momsation
(Compared to IR)
Quantttation
Complicated by
Bifterefjses in Quantum
Yields. Quenching,
Microenvirvnmonts
Limited Reference
Spectra Available
BxceHant Sensr&vity
ppb {pptfiilhn or
Less with Lasar
Excitation)
Dependant on
Quantum Yields
Portable Iftstrvmants
A
vaiiabfa
Field Dephyabla
It
f
A
jstrumgnts Avauabla
low-through Off-Water
tonrtors and HPLC
with Multichannel
Detectors
Front Surface - PTP
Synchronous F/tfom*e*jie#
Increased Specificity
for Individual PAGs
or B4C Cesses in
Complex Mixture
P&troteum Oils
Creosotes
Increased Specificity
Lass Spec ml
Overlap
Classification of PAHs
by Number of fiings
Useful tor Screening
Decrease in
Sanshiwly with
Nanwtgr Bandpm$$s
and Wavalangth Offset
Loss of v^braoonaf
Structure In So&cjmm
Need Dual Scanning
Good Sensitivity
Slightly Lower than
FluQFQSG&nce Emission
DapGndent on
Instrumental
Conditions
Luminascanca
T0Gftnk}U8$
- Fluofsscencs
• Phosphorescence
- Synchronous
~ Tims a#tt Phase
Resolution
- Polarization
-RTandLT
-3D
- Microscopy
Fiberoptic
fjuorofnsffio
Sensors
Multichannel
Detectors
- Diocte Arrays
-CCDs
Ruorescanca
Quenching or
Energy Transfer
• Indirect Ways
K> Measure Non-
itsfninsscent
Molecules
Portable instalments
under Development
field Deptoyabia
Instruments
AvaJlabfa
L T Maasurements
Ttma and Phass
Resolution
Derivative
Remote Monitor
under Development
Low Temperature Luminescence (Fiuotvsconco
Luminescent PACs
PCBs
Higher SensWwV,
Specificity than RT
wteIiS3na/fflrocS,ffl
Similar to Raman
Ouantitatiofi Over 6
Orders of Magnitude
Bl$$ngijish IsQtners
Very Selectivs
- Enhanced by Time
and Wavsl&ngtft
Variability
Cryogenic Apparatus
More Complicated
Need Skilled Operator
Less Rg&rgncB
SpeclraiData faw RT
Sorno Analyses Matrix
Dapendanf
BecoKeni Sensitivity
pp&iOfon in Optimal
Cases
Improved wifo Laser
timftad Semi-Field
DaofoyabiHty
LT Techniques
- Shpotskii Spactra
- Laser-fine
Narrowing
- Site Selection
- Matrix Isolation
Low TamparatMfes
77"K%o4 K
Source: Eastwood and Vo-Dinh (1991)
10-41
-------
10. CHEMICAL HELD SCREENING AND ANALYTICAL METHODS
10.4 LUMINESCENCE/SPECTROSCOPIC ANALYTICAL TECHNIQUES
10.43 Other Speetrometrie/Spectro-Photometric Techniques
Other Names Used to Describe Method; Ultraviolet (UV) spectroscopy, UV spectrophotometry, visible
absorption spectroscopy, spectrophotometry, IRinfrared (laserdiode) spectrometry, photoacoustic spectrometry.
Uses at Contaminated Sites: IR spectronietry: Identifying and characterizing amorphous and crystalline inorganic
or mineral phases; performing functional-group and qualitative analysis of organic compounds.
Method Description: Spectrophotemetry encompasses a number of techniques involving measurement of the
absorption spectra of narrow band-widths of radiation (visible and ultraviolet). Colorimetric techniques discussed
in Section 10.5.1 require spectrophotometric measurements, as do luminescence techniques discussed in Section
10.4.2. Infrared (IR) speetrometry involves the measurement of infrared radiation absorption bands from low-
level transitions between molecular energy levels. Different inorganic and organic functional groups have
distinctive absorption spectra that help identify mineral or chemical phases in a sample. Table 10.4.3 provides
additional information on UV-visible absorption, dispersive, and near-infrared methods.
Method Selection Considerations: Spectrophotometry: Integral to other techniques covered elsewhere. IR
Speetrometry Advantages: Most useful when used in conjunction with x-ray diffraction (XRD) because it is
capable of characterizing amorphous inorganic and mineral phases, which cannot be detected by XRD (Section
10.6.1). IR Spectrometry Disadvantages: (1) Results are primarily qualitative and require use of other techniques
for definitive identification (quantitative analysis of multicomponent systems is possible, but very difficult); and
(2) for solids samples, particle size must be less than the wavelength of the infrared radiation.
Frequency of Use; IR Spectrometry: Relatively common laboratory method for mineralogical study. Use for
characterization of soils and waste has been limited.
Standard Methods/Guidelines: White and Roth (1986-IR spectrometry).
Sources for Additional Information: Eastwood and Vo-Dinh (1991).
10-42
-------
Table 10.43 General Characteristics of UV-Visible Absorption, Dispersive Infrared, and Near Infrared Techniques for
Field Analysis
Applicability Advantages Limitations Sensitivity Cunent Field Related Lab
Applicability Techniques 4
Sensor$
UV-vIt AbaorpUon
Polyaromatic
Compounds (PACsj
Dyes
Colorimelm Reaction
Products
Mature Technique
Instrumentation
Readily Available
Good Quantitative
Accufscy for Single
Compounds and
Simple Mixtures
Few Interferences
by Nonaromatics
Spsetra/ Data
Available
Unspecilic
(Compared to IR and
Luminescence)
Extensive Sample
Preparation
Quantitation may be
Affected by Solvent,
Polarity, or Medium,
Chemical Comptexatiofi
Moderate Sensitivity
ppm • ppb in
Favorable Cases
Portable
- Hand-held Colorimeter
• Cohrimetric Kits
Field Dephyabte
Instrumentation with
Multichannel Detectors
HPLC Detectors
UV-VIS Techniques
-FT
• Derivative
LT Matrix Isolation
nefiectanca
PhQtoacoustic
Spactroscopy
Fiberoptic
Cohrimetric
Sensors
Multichannel
Detectors
- Diode Arrays
•CCDs
Infrared (Dlspwslve)
Organic and Inorganic
Determination of
Specific Functional
Groups
HigWy Specific
Structural Data on
Group Frequencies
Mature Technique
Instrumentation Widely
Available
Spectral Ubran'es
Available
Mid/low Sensitivity
Water is tnterfereni
Requires Special
Optics/Solvents
Quantiialion
Difficulties
Weak Optical
Sources and
Detectors
Less Sensitive than
UV-vis Absorbance
Much Lass Sensitive
than Fluorescence
ppthovsand to ppm
in Favorable Cases
Portable and Field
Instruments A vailable
Portable Unit with
Gas Cell
QuantitaSon of Grease
and CXI
ATR Attachments for
Solids, Oils
FTIR
GC/LC-FTIFI
Near Infrared
Single Compounds
Simple Matrices
Organics Ovdnonss
Sources and Optical
Materials Better than
M!d-IR
Optically Good Sensor
Materials
Can Distinguish Major
Components of Simple
Matrix
Fewer Interferences
than Mid-IR
Less Spectral
Structure than Md-IR
- Overtone Overlap
- Less Specificity
• Interpretation
ComplicaHxt
Not Useful for Complex
Matrices
Signal Processing and
Pattern Recognition
Required
Low Sensitivity
10- 1 ppthousand
Portable Neae-IR
Instrument with Fiber
Optic Probe
Characterization of Oil
Bulk Chemical
Analysis
Surtace/Pol/ulant
Interaction Studies
Near IR Sensors
Process Control
Definitions of portable, field dephy&ble, and semi-field deployable as used in this table are:
Portable: Field Depbyable:
Saffery powered
One person can carry
Little samp/o prep, f< 10 min.)
Instrument cost < $30,000
Analysis cost < $30
Generator powered
Compact two people can tilt (several instruments in mobOe lab)
Relatively simple sample prep. (< 1 hf.)
Instrument cost $30,000 to $ 100,000
Analysis cost $30 - $200
S&mi-ttelcS Deployable:
Can fittri mobile fab
Complex er fragile" instrument
Often considerable sample prep. (> f hr.)
Instn/merit cost > $ 100,000
Analysis cost >$200
Definitions of abbreviations as used in this table are:
ATfl
CARS
CCD
FTIR
GC
HPLC
IR
LC
LT
MRS
Attenuated Total Reflectance
Coherent Anti-Stokes Raman Specfroscopy
Chargo-Coupt&d Device
Fourier Transform-Infrared Specifoscopy
Gas Chromatography
High Performance Liquid Chromaiography
Infrared Speclroscopy
PAC
PAH
PCS
ppb/pprrt
HfP
Low Temperature
Normal Raman Spectroscopy
SFC
TLC
Mic Compounds
Palyaromatic Hydrocarbons
Polychlonnated Biphenyls
pan per billion/part per million (mg/mL, p.g/mL}
Room Temperature Phosphorescence
Surface-Enhanced Ramsn Spectfoscopy
Supercritical Fluid Chromatography
Thirj-Layef Chromatography
Source; Eastwood and Vo-Dinh (1991)
10-43
-------
10. CHEMICAL HELD SCREENING AND ANALYTICAL METHODS
10.4 LUMNESCENCE/SPECTRQSCOPIC ANALYTICAL TECHNIQUES
10.4.4 Other Spectroscopic Techniques
Other Names Used to Describe Method: Infrared (IR) spectroscopy, high resolution/long range Fourier
transform infrared (FTIR) spectroscopy; Light detection and ranging spectroscopy (LIDAR), including
differential scattering LIDAR (DISC) and differential absorption LIDAR (DIAL); IR reflectance/transmission
spectroscopy; Raman spectroscopy (RS), (surface enhanced raman scattering (SERS).
Uses at Contaminated Sites; FTIR: Remote monitoring of air contaminants.
Method Description: IR spectroscopy: A field-deployable long-path Fourier transform infrared (FTIR)
spectrometer currently is being tested by EPA, The instrument measures the absorption caused by infrared-active
molecules. Pollutant inorganic and organic gas concentrations are determined by setting up a retroflector up to
1 kilometer from the spectrometer and transmitting an infrared beam that is returned to the detector (Figure
10.4.4a). Analysis is performed by using a reference spectrum of known concentration and least square fitting
routines. The instrument measures various airborne vapors, including both organic and inorganic compounds.
Figure 10.4.4b illustrates four applications of IR spectroscopy using differential scattering and absorption LIDAR,
techniques that are being tested by the U.S. Army. RS encompasses a variety of techniques that involve detection
and analysis of the scattering of radiation. Raman techniques differs from IR spectroscopy by using visible light
to obtain structurally unique vibrational and rotational spectra. In the laboratory, RS can be used to identify
functional groups to determine mineral phases. SERS is a relatively new analytical technique in which a sorptive
surface provides a signal enhancement of up to a million times compared conventional IR spectroscopy, thus
greatly reducing the detection limit. Reflectance/transmission spectroscopy in the near and far infrared portion
of the electromagnetic spectrum has been proposed for airborne remote sensing identification of surface spills
of benzene, toluene, TCE, and gasoline, but has not been field tested. Table 10.4.4 provides additional
information about FTIR, normal RS, surface enhanced spectroscopy, and resonance raman methods.
Method Selection Considerations; Long-Path FTIR Advantages: (1) Measurements are rapid (a few minutes),
allowing temporal profiles of pollutant gas concentrations; and (2) a range of volumes can be sampled by
changing the distance between the instrument and the retroflector. Long-Path FTIR Disadvantages:
Instrumentation is still in developmental stages. RS Advantages: (1) Is the best complement to IR spectrometry
(Section 10.43) because it is able to discern vibrations from functional groups that are not discernible in the IR
spectra; (2) resolution allows observation of particles as small as 1 micron, allowing characterization of individual
particles; and (3) when combined with high pressure liquid chromotography (Section 10.5.3), can be used with
solid and liquid samples to test for nearly all substances on EPA's priority pollutant list, including semivolatiles.
RS Disadvantages: (1) Is nondefinitive and qualitative (only identifies functional groups); (2) data interpretation
is complex; and (3) instrument availability is limited.
Frequency of Use: Uncommon.
Standard Methods/Guidelines: ~
Sources for Additional Information: Eastwood and Vo-Dinh (1991), Thompson et al. (1989-IR and Raman
Spectroscopy), U.S. EPA (1991b, 1992-portable FTIR). See also, Table 10-5.
10-44
-------
(a)
AGENT VAPOR
TOPOGRAPHICAL REFLECTION , .\ . ',..'.
(VAPOR)
DIFFERENTIAL ABSORPTION AGENT VAPOR .,
(VAPOR) ' \ -.
• V *'i
NATURAL
AEROSOLS
DIFFERENTIAL SCATTERING
(AEROSOL/RAIN)
'.Vy AGENT/RAIN/
AEROSOLS
DIFFERENTIAL SCATTERING
(SURFACE CONTAMINATION)
SURFACE
CONTAMINATION
(b)
Figure 10.4.4 Several infrared spectroscopic techniques: (a) Schematic of an infrared radiation source, mirror, and
FT1R spectrometer equipped with telescopes to allow long-path analysis (Moore et al., 1991); (b) Four
applications of differential scattering and absorption Lidar (Mackay, 1991).
10-45
-------
Table 10.4.4 General Characteristics of Fourier Transform Infrared, and Raman Spectroscopic Techniques for Field
Analysis (See end of Table I0.4J for deDnitions and abbreviations)
ApfSabify Advantages UnitsH'ons Sensitivity Current Field Related Lab
Applicability Technicians t
Sensors
Mmred (Fowler Transform)
Orji/wc tnd Inorganic
Dtttmination of
Sptafie Functional
Groups
Routintly Used tor
Rftl-TmiiCCand
Vapor Anafysis
Highly Specific
Structural Data on
Group Frequencies
Instrumentation
Widely Available
Real-Tune flow
tftfoughVapar
Applications
-GC-FT1R
Spectral L&raties
Available
Lass Sensitive than
Luminescence
Requires Special
Optics/Solvents
Can Tolerate Some
Water (Background
Subtraction)
Organic* Detection
1-10 ppthausand in
Water
More Sensitive than
Dispersive IR
-Signal A veraging
pom to subppm in
Favorable Cases
field and Semi-Held
Deployatila
-With or Without GC
- Volatiles/SemivQlatiles
Adaptable to Use
with SFC
GOtC-FTW
Matrix Isolation
-LT tor Sensitivity
Microscopy
Normal Raman Spectroacopy (NRS)
Organic and tnotganie
Aqutous SotuMr.s
Kohficat Matrices
Polymtrs
Specific as IR lor
Structural la formation
Different Selection
Rules - Complements
IR
Fewer Interferences
than IR in vis or
neaf-IR Regions
Water and Siass not
Interferences
Good Optics and
Sotvents Available
Can Hafidto Unusual
Sample Shapes/Sizes
fluorescence Interfer-
ence in W-vis
Requires Laser Source
Relatively Complex
fasliwnentatioa
Requires Skilled
Operator
Not as Mature as IR
Relatively Poor Limits
of Detection
Moderate Sensitivity
1000-20ppm
Semi-field Deoloyabte
Instruments under
Development
Research in:
- Aoueous Solutions
• Biological Matrices
- Polymers
Special Raman
Techniques
-SERS
- Resonance
-CARS
- Microprobas
- Microscopy
LT Applications
Enhanc&d ffaman SfS&z&Qa
Many Polumnt*
Dtrror.tnted for
• Pyn
-------
10. CHEMICAL FIELD SCREENING AND ANALYTICAL METHODS
10.5 WET CHEMISTRY ANALYTICAL TECHNIQUES
10.5.1 Colorimetric Techniques/Kits
Other Names Used to Describe Method: Colorimetry (various field kits using colorimeters/filter
photometers/speetrophotometers [see Section 10.4.3]), titrimetry.
Uses at Contaminated Sites: Hach kits: Analyzing Al, Cd, Cr, Co, Cu, Fe, Pb, Mn, Ni, N, P, Ag, and Zn; Hanby
kits: Analyzing petroleum hydrocarbons, PAHs; Other kits: Analyzing explosive (TNT/RDX), PCBs, chlorinated
organics. Many ground-water tracers can be analyzed using eolorimetric techniques,
Method Description: Titrimetry is a wet chemistry procedure by which a solution of known concentration (a
standard solution) is added to a water sample or soil-solute extract with an unknown concentration of the analyte
of interest until the chemical reaction between the two solutions is complete (the equivalence point of titration).
Titrimetry requires an abrupt change in some property of the solution at the equivalence point, which is typically
indicated by a change in color produced by an added dye, or by monitoring changes in pH with a meter
(electrometric titrations). Colorimetry also involves mixing of reagents of known concentrations with a test
solution, but in specified amounts that result in chemical reactions in which the absorption of radiant energy
(color of the solution) is a function of the concentration of the analyte of interest. At the simplest level,
concentrations can be estimated with visual comparators. Filter photometers can be used for many routine
methods that do not involve complex spectra, and precise work is done with spectrophotometers (see Section
10.4.3). Titrjmetrie and eolorimetric techniques are well suited for development of wet chemistry field test kits,
and such kits are available commercially for many inorganic and some organic compounds. Figure 10.5.1 shows
sample instructions for chromium using a Hach test kit. HNU/Hanby test kits use reagents that can be used in
the field without use of a digester. Spectrochem has developed a kit that detects major classes of chemicals in
water (chlorinated hydrocarbons, carbamates, and organic phosphated insecticides).
Method Selection Considerations: Titrimetry and Colorimetry Advantages: (1) Procedures are relatively simple
and amenable to the development of field test kits for many analytes; (2) best suited for preliminary screening
where only a few contaminants or analytes are of concern or interest; and (3) field test kits are available for most
heavy metals. Titrimetry and Colorimetry Disadvantages: (1) Are time consuming if a large number of samples
must be analyzed; (2) each analyte of interest requires different reagents and test procedures making analysis
of multiple analytes time consuming; (3) strict QA/QC procedures are more difficult to follow in the field using
test kits; and (4) availability of eolorimetric field test kits for specific toxic organics is still relatively limited.
Frequency of Use: Colorimetric techniques are commonly used for field analysis of nutrients in soil and in
ground-water tracer studies. Use of eolorimetric field test kits for field screening of contaminants is a relatively
new and promising field screening technique.
Standard Methods/Guidelines: --
Sources for Additional Information: Davis et al. (1985-colorimetry, titrimetry), Fishman and Friedman (1989-
colorimetry, titrimetry), U.S. EPA (1987).
10-47
-------
CHROMIUM, TOTAL
I.S-Dlpbcnylcarbohydrazldc Method
Method 8023
1. Select the sample
amount from tables
below and digest
according to procedure in
Section II.
ffalet If simple omiEtf fee
attained Manly after sampling,
see Section IV for storage Md
peexrvatloti Information.
Note: This is an EPA-approved
method only if preceded by 3d
£PA-3ppi*3*c4 is/trfc aciti
digestion. The Dijiesdahl
digestion procedure Is not SPA
approved and cannot be used
far permit reporting purposes.
(See digestion Information on
page n.)
2. Use analpls volume
In the tables below that
corresponds lo the
sample amount selected
in Step I, Pipei analysis
roluine into 2 25-ml
mixing graduated
cylinder. If aliquot Is
more than 0.5 ml, pH
adjust according to the
tost step in the digestion
procedure in Section II.
Dilute to the 25-ml mark
with dcioniied water, if
necessary. Pour contents
of cylinder into a 25-ml
sample cell.
Note; For proof of accuracy,
ysff 3 8.25 mpfl chromium
standard solution (preparation
given in the Accuracy Cftfdc) in
place of the sample
9. rill a second 25-ml
sample cell with
delonlzed svater to the
25-ml mark (the reagent
blank).
4e, Add the contents of
one Chromium 1 Reagent
Powder Pillow 10 each
cell. Swirl to mix.
Expected Cone.
Chromium
(mgll)
0.05-2.0
0.20-8
0.75-33
7.5-330
75-3300
Expected Cone.
Chromium
(B;I!*W
8-330
20-820
JO-2200
350-16000
Expected Cone.
Chromium
(mg/kg)
4.0-165
10-410
25-1100
190-8200
750-3 JOOO
LIQUID SAMPLES
Sanicle
Amount
(mi)
40.0
200
10.0
5.00
1. 00
On, SAMPLES
Sample
Amount
<«)
0.25
0.20
0.15
0.10
SOLID SAMPLES
Sample
Amount
Cs>
0.500
0.100
0.300
0-200
0.100
Analysis
Volume
("0
20.0
10.0
5.00
LOG .
0.500
Analysis
Volume
(ml)
20
10
5
1
Analysis
Volume
(ml)
20.0
10.0
5.00
1.00
0.500
CHROMIUM, continued
\ \r**s^*i
^j>
5. Place cells In a
wiling water hath 2nd
H ,/-\
7?/Cfy ^^~*~~
•W
6. Remove cells from
the water bath and cool
/—
I^Z'
0
% Add conienu of one
Chromium 2 Reagent
/—-
$£'**'
0
8. Add the content* of
one Acid Reagent Powder
wail for 5 minutes. to 25 *C under lap water. Powder Pillow 10 each Pillow lo each cell. Swirl
If necessary, add cell. Swirl to mix. to mix.
Vo/ci If a precipitate forms , ,
wuicaa£v.«u*«ami delonted water to the NoKl M ,hf tmml af , WoK> »,, „„,„ „/; „« »e
Chromium 1 Hagent fooler 25-ml mark Of the sample lfcond Cluoalm 2 Keagem affected If a snail portion of
ritlcnr and mulmie heating. cc]|_ Fnwdcr Hllo* ir i second this reagent docs not dissolve.
Chromium I Reagent Powtlcr Add contents of 3 second Add
Pillow *•** added In Step 5. gesgent towdcr Mlow if a
second Chromium 1 Reagent
Pon-der Pillow was added In
Hep ;.
5:00
ZERO
9» Add contents of one
ChromaVcr 3 Chromium
Reagent Powder Pillow to
each cell. Swirl to mix,
Notet A pufple co/Of witt
develop if chfomiurn is pneseRf.
10. V&U 5 minutes for
the color to develop.
Notes D,o soi 9/ylt more tbm
20 minuses before completing
Sups II fo 12.
The
CMO fe
11. Zero insErumcnt
with reagent blank using
settings below. Read the
mg/i chromium of other
cell.
DRI3900
Program No. 13
Wavelength 540 nm
DRJ2000
Program NO. 100
Wavelength 540 nm
DRJ70Q
Module No. 55.01
Wavelength 550 nm
ft'oje: Sex SKtion I foe
information on instrument
12* Calculate the total
chromium (Cr)
concentration of the
sample using the
following formula:
tola! tig/l Cr •
B x c
WHERE
A " mgfl mad. Step 11
B • ml (g) sample amount.
Step 1
C m ml analysis volume, S&p 2
Notet For solid sniJ oli samples
ocprcsi the restiltiag
teficera*srr&3n «s fijg^g 3a
-------
10. CHEMICAL FIELD SCREENING AND ANALYTICAL METHODS
10.5 WET CHEMISTRY ANALYTICAL TECHNIQUES
10.5.2 Immunochemical Techniques
Other Names Used to Describe Method: Enzyme immunoassay (ElA), enzyme linked immunosorbent assay
(ELISA), radioimmunoassay (RIA), fluoroimmunoassay.
Uses at Contaminated Sites: EIA: Analyzing BTX (benzene, toluene, xylene), PCS, PCP (water, soil), cocaine,
heroin, and pesticides.
Method Description: EIA techniques that involve the use of antibody reagents that react with the analyte of
interest to produce reactions that can be analyzed colorimetrically are a recent development for trace organic
analysis (see Section 10.5.1 for additional discussion of methods forcoloriraetric analysis). Figure 10.5.2 shows
procedures for an EIA test for pentachlorophenol (PCP). Other types of immunoassay techniques include
radioimmunoassay and fluoroinununoassay. (See also, discussion of bioassays in Section 10.6.6.)
Method Selection Considerations: EIA Advantages: (1) Is the best suited technique for preliminary screening
where only a few contaminants or analytes are of concern or interest; (2) EIA test kits are very simple, rapid
(minutes), and inexpensive; and (3) have the potential for specific field tests for a large number of toxic organics
with very low detection limits (ppb). EIA Disadvantages: (1) Is time consuming if a large number of samples
must be analyzed; (2) each analyte of interest requires different reagents and test procedures making analysis
of multiple analytes time consuming; (3) strict QA/QC procedures are more difficult to follow in the field using
test kits; and (4) availability of kits for specific toxic organics is relatively limited at this time.
Frequency of Use: Enzyme immunoassays are a relatively new technique and have excellent potential for more
extensive use fa the future.
Standard Methods/Guidelines: —
Sources for Additional Information: U.S. EPA (1988b-immunoassays/FM-D4,1991b, 1992). See also,Table 10-5.
10-49
-------
NOTE: AH components should be at room temperature.
1. Open (oil package and remove test
module, color development tube, and
wash tube. (Just before use.)
Sample application: Remove red cap
from sample bottle and apply 10
drops (±5 drops) to the sample well of
the module.
3. Wash application: Twist tab off wash
tube and squeeze entire contents Into
sample well.
n \xw)
LJ wv 4. Color development tube application;
Hold tube upright and squeeze tube
where indicated to crush ampule
Inside. Shake vigorously for 10
seconds.
Carefully apply ONE DROP of color
development solution to sample well.
Incubate for 1-2 minutes.
Pos.
After incubation, press module closed
for 2-3 seconds. Release and open.
(Press only once.)
6. Open the module and monitor color
development. Record the result at 5
minutes.
A POSITIVE RESULT WILL SHOW A GREEN COLOR AS DARK OR DARKER
THAN THE REFERENCE COLOR.
A NEGATIVE RESULT WILL REMAIN WHITE OR BE LIGHTER THAN THE
REFERENCE COLOR.
Figure 105.2 Procedures for enzyme immunoassay test for PCPs: (A) Antibody disks, (B) redout disks, (C)
absorbent blotting reservoir, (D) crush vial containing lyophilized antibody (DuQuette ot pi,, 1991).
10-50
-------
10. CHEMICAL FIELD SCREENING AND ANALYTICAL METHODS
10,5 WET CHEMISTRY ANALYTICAL TECHNIQUES
10.5.3 Liquid Chromatography
Other Names Used to Describe Method: High pressure/performance liquid chromatography (HPLC), thin-layer
chromatography (TLC), ion (exchange) chromatography.
Uses at Contaminated Sites: HPLC: Analyzing PAHs and phenols; TLC: Analyzing nitrogen-containing aromatics;
Ion chromatography: EPA Method 300.0 (Kopp and McKee, 1983) covers the following ions: Cl, F, nitrate-N,
nitrite-N, orthophosphate-P, and sulfate; also can be used to analyze halide and fluorinated organic acid dyes
in tracer studies.
Method Description; Liquid chromatography is a type of chromatography where the mobile liquid phase
containing analytes of interest is injected into a stationary phase that is either liquid or solid. Numerous specific
techniques, such as partition, adsorption, ion exchange, paper, and TLC, have been developed. Ion
chromatography involves separation of ions (typically anions) on a column of ion exchange resin, which are
detected conductimetrically (Figure 10.5.3). A TLC technique with potential for separation of nitrogen-
containing compounds in the field has been developed. A field operable HPLC unit using UV/visible and
fluorescence detectors (see Section 10.4.2) appears to be the best field screening technique for PAHs (see
advantages below).
Method Selection Considerations; In general, liquid chromatography is able to detect more compounds than GC,
but at generally higher detection limits. Ion Chromatography Advantages: (1) Is a well established technique
for separation of both organic and inorganic species; (2) several ions can be measured in a single aqueous
sample; (3) eliminates many of the interferences associated with other techniques, and is capable differentiating
species of the same ion in some cases; and (4) sensitive and has a wider range of applicability so that accurate
measurement can be made on samples containing moderate to substantial ionic concentrations. Ion
Chromatography Disadvantages: (1) Very high concentrations of an ion relative to another ion of interest might
interfere or preclude measurement of the ion present in lower concentrations; and (2) individual measurements
have a relatively low dynamic raage, so separate dilutions might be required to bring a sample concentration into
the optimum analytical range. HPLC (for PAHs) Advantages: (1) Instrumentation requires fewer gases for field
analyses; (2) use of in-scries UVMsibie and fluorescence detectors provides real-time confirmation of target
analytes; (3) larger sample volumes can be injected compared to GC, yielding lower method quantitation limits;
and (4) provides better resolution (ppb) than GC for comparable analysis time. HPLC (for PAHs)
Disadvantages: New method for which there has been relatively little actual field experience.
Frequency of Use: Ion chromatography is commonly used for laboratory analysis of major anions. Field
application of other liquid chromatographic techniques is a new development that appears promising for specific
applications, such as detection of PAHs (HPLC) and nitrogen-containing and other polynuclear aromatic
compounds (TLC).
Standard Methods/Guidelines: --
Sources for Additional Information: Davis et al. (1985), Fisbman and Friedman (1989), Hassett (1982-high-
pressure liquid chromatography), Thompson et al. (1989-ion chromatography). See also, Table 10-5.
10-51
-------
Ion chromatography - anions
Effluent
reservoir
Pump
Injection port
Separator
column
Suppressor
column
Conductivity
detector
Waste
COa"or HCOa = X"
1
R*
R~
H*
R~ H*
R~ H*
-*-R F~*X~
" Na*+HF
-»»R" Na**MX
Recorder
Figure 10.5.3 Ion chromatography system for anions (Fishman and Friedman, 1989).
10-52
-------
10. CHEMICAL FIELD SCREENING AND ANALYTICAL METHODS
10.5 WET CHEMISTRY ANALYTICAL TECHNIQUES
10.5.4 Electrochemical Techniques
Other Names Used to Describe Method: Coulometiy, voltammetiy, polarography. Techniques covered elsewhere:
pH, Eh, DO, electrical conductance (Section 10.1); ion-selective electrodes (see Section 5.5.5);
potentiometric/amperometric/conductometric electrochemical sensors (see Section 10.6.5).
Uses at Contaminated Sites: Coulometry: Detecting ionic tracers. Voltamnietry/polarography: Determining if
trace metals, ions, and organics are in soils, waters, and sediments.
Method Description: Coulometric methods of analysis measure the quantity of electricity (in coulombs, the
amount of electricity flowing during the passage of a constant current of 1 ampere for 1 second) required to carry
out a chemical reaction. Primary coulometric analysis involves direct reactions by oxidation or reduction at the
proper electrode. Secondary coulometric analysis involves indirect reactions between the solution and a primary
reactant produced at one of the electrodes. Voltammetry is the area of electroanalytical chemistry involved in
measuring the current at an electrode as a function of potential or voltage. Numerous specific techniques have
been developed and only a very general description is provided here. Polarography is a voltammetrie method
in which a dropping mercury electrode (DME), is used for very precise control of changes in currents applied
to the electrode. Plots of current vs. potential allow identification of the analyte based on the shape of the curve
and concentration based on wave height. Stripping voltammetry is a two-step process in which electrolytic
deposition of the chemical species is followed by application of a voltage scan to cause electrolytic dissolution
(stripping) of the species back into solution at characteristic potentials.
Method Selection Considerations: Coulometric Advantages: (1) Instrumentation is relatively simple; and (2) well
suited for trace analysis of ionic tracers, such as chloride and bromide (see Section 4.3.1). Coulometric
Disadvantages: Is not well suited for analysis of complex mixtures. Polarography Advantages: (1) Instrumentation
is relatively simple; (2) depending on specific method, capable of sensitivity to sub-ppm; (3) good selectivity
allows determination of many constituents without prior chemical separation; and (4) capable of measuring large
ranges of concentration, ranging from concentrated extracts from solids to dOute natural waters. Polarography
Disadvantages: Method is not likely to be useful for field or mobile laboratory. Stripping Voltammetry
Advantages: (1) Is a relatively simple method requiring minimal sample preparation; and (2) is the most sensitive
electroanalytical technique currently available (capable of metals analyses down to ppt level). Stripping
Voltammetry Disadvantages: (1) Method is not likely to be useful for field or mobile laboratory; and (2) highest
sensitivities are difficult to achieve for routine analysis.
Frequency of Use: Measurement ofpH, Eh, and specific conductance (Section 10.1) are the most commonly used
electrochemical techniques. Polarography and stripping voltammetry are not likely to be useful in field or mobile
laboratory applications.
Standard Methods/Guidelines: —
Sources for Additional Information: Davis et al. (1985-coulometry), Fishman and Friedman (1989-
voltammetry/polarography), Street and Peterson (1982-polarography and stripping voltammetry).
10-53
-------
10. CHEMICAL FIELD SCREENING AND ANALYTICAL METHODS
10.6 OTHER ANALYTICAL TECHNIQUES
10.6.1 Radiological Techniques
Other Names Used to Describe Method: Analytical techniques: X-ray diffraction (XRD), proton induced X-ray
emission (PDCE),glancing incidence X-ray analysis (GDCA), (instrumental) neutron activation analysis([I])NAA);
Techniques covered elsewhere: Nuclear borehole techniques (Section 3.3), radioisotope single-borehole tracer
methods (3.5.4), radioisotope tracers (Section 4.4.5),X-ray fluorescence (Section 10.4.1), and electron microprobe
analysis (Section 10.6.4).
Uses at Contaminated Sites: Detecting natural radioisotopes (i.e., gamma log, Section 3.3.1); performing
elemental and mineralogical analysis (XRD, PIXE, INNA, gamma spectrometry, electron microprobe analysis,
XRF); performing tracer studies (see Sections cited above).
Method Description: XRD involves the. identification of minerals by directing a monochromatic x-ray beam at
a powdered sample and using a scintillation, proportional, or geiger counter (see above) to detect the intensities
and diffraction angles as the beam is rotated around the sample. Crystalline minerals can be identified by the
characteristic position and intensities of the diffraction peaks. PIXE analysis uses a high-speed proton beam to
displace inner-shell electrons of the sample elements. When the electrons return to their proper shells, x-rays
are emitted that have energies characteristic of the elements and proportional to their mass. Computer
processing provides data on all elements present in a given sample. In INNA, powdered samples are irradiated
for specified times and neutron fluxes, depending on the elements of interest. Gamma-ray spectra of the
irradiated samples are measured with Ge(Li) detectors coupled with multi-channel analyzers.
Method Selection Considerations: All radiological analytical methods have the disadvantage of requiring special
health and safety precautions. XRD Advantages: (1) Is a relatively simple and inexpensive bulk sample method;
(2) provides simultaneous multi-mineral characterization; and (3) is best used in conjunction with other more
quantitative species-specific chemical methods. XRD Disadvantages: (1) Estimates of mineral percentages are
only semi-quantitative; and (2) minerals present in small amounts often are difficult to discern in multicomponent
mixtures. PIXE Advantages: (1) Provides simultaneous multi-element characterization; (2) is rapid (30
minutes/sample); and (3) is good for initial screening to identify presence of elements for which more precise
analysis should be done. PIXE Disadvantages: (1) Instrumentation is expensive (but somewhat cheaper than
ICP-AES); and (2) has relatively high detection limits (10s to 100s ppm). INAA Advantages: (1) Requires less
sample preparation time compared to AAS and ICP-AES; and (2) sensitivity compares well with conventional
spectrometric techniques for many elements. INAA Disadvantages: (1) Requires nuclear reactor for irradiation
of samples; (2) sensitivity is highly dependent on the exact elements being measured and on the sample matrix;
and (3) some elements, such as lead, cannot be measured.
Frequency of Use; Analytical techniques: XRD is a widely used method for mineral identification. PIXE and
INAA are commonly used for analysis of coal fly ashes, but have received limited use for contaminated site
characterization. All three methods are primarily laboratory methods, although XRD instrumentation probably
could be used in a mobile laboratory. See neutron activation log (Section 3.3.5) and neutron-lifetime log (Section
33.6) for field applications using principles of neutron activation analysis.
Standard Methods/Guidelines: Analysis of radioactive substances: Thatcher et al. (1977); XRD of soil samples:
ASTM (1985).
Sources for Additional Information: Analytical techniques: Davis et al. (1985-gamma, beta, NAA), Helmke
(1986-neutron activation analysis), Thompson et al. (1989-INNA, PIXE, XRD), Whittig and Allardice (1986-
XRD), Wong and Carlsen (1991-tritium field screening).
10-54
-------
10. CHEMICAL FIELD SCREENING AND ANALYTICAL METHODS
10.6 OTHER ANALYTICAL TECHNIQUES
10.6.2 Gravimetric/Volumetric Techniques
Other Names Used to Describe Method: —
Uses at Contaminated Sites: Characterizing particle size distribution; measuring bulk density; measuring
dissolved/suspended solids; calculating contaminant concentrations/flux; measuring water flow during pumping
tests (Section 4.2); measuring soil gravimetric moisture (Section 6.3.1),
Method Description: Gravimetric techniques involve measuring the mass of the material of interest. For
chemical analyses, a mechanical or electronic analytical balance capable of measuring the mass of an object
within 0.1 to 0,01 mg is used. Field applications require less sensitive devices, such as a hanging spring scale with
a canvas sling or pail for weighing coarse fragments, and a scale or balance with 0.1 gram accuracy for weighing
soil samples for field tests (Boulding, 1991). Volumetric techniques involve the measurement of volume. Volume
of liquid samples for chemical analysis is easily measured by the use of graduated cylinders or sample containers
of a known volume. For borehole aquifer characterization, volume is measured using flowmeters (Section 3.5.3),
and in pumping tests, pumping rate can be determined in several ways: (1) Observing the time required to fill
a container of known volume, (2) use of commercial water meters, (3) use of a circular orifice weir (Figure
10.6.2), or (4) channeling surface flow from the pump through flumes or weirs. For gases, volume typically is
measured by using syringes of a known volume, or measuring the rate of gas flow through a tube of known
diameter. Both gravimetric and volumetric measurements are required for soil characterization because the soils
vary in bulk density (weight per unit volume), depending on the volume of pore space. There are four major
methods for measuring bulk density: (1) The core method, which involves drying and weighing of an undisturbed
core sample of known volume; (2) gamma-gamma logging (see Section 3.3.2); (3) the excavation method, which
involves excavating an amount of soil (which is dried and weighed) and measuring the volume of sand required
to fill the hole, or the volume of water required to fill a rubber-balloon; and (4) the clod method makes use of
Archimedes' principle, and involves coating a clod of known weight with a water-repellent substance and weighing
it first in air, then again while immersed in a liquid of known density.
Method Selection Considerations: A scale or balance of the required accuracy (see above) should be standard
equipment for field investigations for soil characterization. Selection of appropriate volumetric measurement
techniques for water and gases is straightforward. Bulk density is required for most vadose zone models (see
Appendix C), and allows qualitative evaluation of the potential for transport of contaminants through the vadose
zone. The core method is simple and accurate, but generally unsatisfactory in stony or very diy soils. Advantages
and disadvantages of gamma-gamma logging are covered in Section 3.3.2. The excavation method is a simple
and accurate field procedure, but lacks discrimination of localized horizons and is limited to around 12
centimeters below the surface. The clod method allows discrimination of localized horizons, but is more complex
and usually gives higher bulk density values than other methods because interclod spaces are not taken into
account. The core, excavation and clod methods can be used in the field provided an oven for drying and
accurate scales for weighing samples are available (Section 6.3.1), and have the advantage of providing moisture
content of the sample as well as bulk density,
Frequency of Use: Gravimetric and volumetric measurements are essential for the uses described above. The
core method is probably the most commonly used method for measuring bulk density, followed by gamma-gamma
logging.
Standard Methods/Guidelines: Gravimetric: Fishman and Friedman (1989). Soil bulk density: ASTM (1984-
rubber balloon method), Blake and Hartge (1986), Campbell (1991), Hint and Childs (1984).
Sources for Additional Information: Flow discharge measurement: Johnson (1964), Jorgensen (1969).
10-55
-------
1/8 - 3/8 In
Piezometer tube-
Detail of orifice plate
Gate valve
-Scale
-4ft, minimum-
*>H—24 In
Figure 10.6.2 Volumetric techniques: Construction diagram of a circular orifice weir commonly used far measuring
pumping rates of a high-capacity pump (Driscoll, 1986, by permission).
10-56
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10. CHEMICAL FIELD SCREENING AND ANALYTICAL METHODS
10.6 OTHER ANALYTICAL TECHNIQUES
10.6.3 Magnetic Methods
Other Names Used to Describe Method: Magnetic susceptibility (MGS), electron spin resonance (ESR), nuclear
magnetic resonance (NMR).
Uses at Contaminated Sites: MGS: Performing qualitative soil mineral characterization; detecting lateral changes
in soil characteristics; ESR: Characterizing clay minerals and sorption of metals; NMR: Characterizing clay
minerals and soil organic matter; borehole logging and soil moisture monitoring (see Sections 3.2,4 and 6.2.5).
Method Description: MGS is the tendency of atoms or ions in a sample to become aligned when placed in a
magnetic field, and is obtained by measuring the magnetic moment per unit volume or mass induced in a sample
by an applied magnetic field. The Gouy (Figure 10.6.3a) and Faraday (Figure 10,63b) susceptibility balances
are two commonly used types. ESR measures the electron magnetic moment in solid, water, or air samples. The
instrument consists of an electromagnet inducing a continuous magnetic field that can be varied in strength, a
resonance cavity where the sample is positioned, a microwave source, and a detector that measures the sorption
response of the sample (Figure 10.6,3c). NMR operates on the same principle as ESR, except that the nuclear
magnetic moment (carbon or proton spectra) is measured instead of the electron magnetic moment. Figure
10.6.3d shows a NMR spectrometer using a radio frequency transmitter and receiver/detector that records proton
or carbon spectra in response to variations in magnetic field. See also, section 3.2.4 for application of NMR as
a borehole logging technique and for soil moisture monitoring.
Method Selection Considerations: MGS Advantages: Instrumentation and measurement procedures are relatively
simple. MGS Disadvantages: Provides qualitative rather than quantitative information on mineralogy.
ESR/NMR Advantages; (1) Are more amenable to quantitative interpretation than MGS; and (2) are well suited
for controlled laboratory study of contaminant-soil interactions. ESR/NMR Disadvantages: (1) Are not well suited
for the chemical characterization of complex soil chemistry; and (2) instrumentation is generally too bulky for
use in mobile laboratories.
Frequency of Use: Laboratory applications for study of soil mineralogy and organic matter are relatively recent,
but are becoming more widely used. Use for contaminated site characterization has been limited.
Standard Methods/Guidelines: McBride (1986).
Sources for Additional Information: MGS: Fine et al. (1992), Mullins (1977), Williams and Cooper (1990),
Woolcock and Zafar (1992); NMR: Blearn (1991), Thorn (1987). See also, references for Section 3.2.4 and 6.2.5.
10-57
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Magnet
Pole
Balance
-Sample Tut»
Balance
y
Magnet
Pole
(a)
Detector Crystal
Attenuator
Pen
Recorder
100 kHz
Signal
Amplifier
100 kHz
Signal
Detector
Circulator (magic tee)
-•-Waveguide
Sample Cavity
/i Sample Tube
^0
WA/A
« V lW
* Electromagnet
100 kHz
Power
Amplifier
100 kHz
Oscillator
Recorder
(d)
Figure 10.63 Magnetic methods: (a) Gouy magnetic susceptibility balances; (b) Faraday magnetic susceptibility
balance; (c) Diagram of typical X-band ESR spectrometer; (d) Diagram of NMR spectrometer
(McBride, 1986, by permission).
10-58
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10. CHEMICAL FIELD SCREENING AND ANALYTICAL METHODS
10.6 OTHER ANALYTICAL TECHNIQUES
10.6.4 Microscopic Techniques
Other Names Used to Describe Method: Optical microscopy, scanning electron microscopy (SEM), electron
microprobe analysis (EMPA).
Uses at Contaminated Sites: Optical microscopy: Observating soil morphologic features; identification of coarse-
grained minerals. SEM and EMPA: Assessing morphology, composition, and identity of minerals.
Method Description: Microscopic techniques involve the visual identification and characterization of soil/solid
waste morphologic features and minerals with instruments ranging from magnification of up to 20 times, using
a simple hand lens, to magnifications of 50,000 times using an electron microscope. As magnification increases,
resolution increases, but the area viewed decreases (Figure 10.6.4a). Optical microscopy: Stereoscopic
microscopes can be used in the field for more detailed visual inspection of soil morphologic features at
magnifications of 20 to 80 times. Petrographic microscopes for mineral identification require the preparation
of thin sections by impregnating samples with epoxy resin and grinding the samples to a precise thickness. The
thin sections are examined with magnifications ranging from 50 to 400 times. Minerals are distinguished by their
color in polarized and nonpolarized light, refractive index, and crystal morphology. SEM involves the irradiation
of a sample with a focused electron beam with very short wavelengths (about 100,000 times shorter than that for
visible light) that can provide high image resolution. Secondary electrons emitted from the sample produce a
topographical image of the sample, and backscattered electrons provide some qualitative information on
elemental composition. EMPA is similar to- SEM, except that the electron beam also produces X-ray
fluorescence (see Section 10.4.1), which allows for quantitative interpretation of elemental concentration as well
as topographic images (Figure 10.6.4b).
Method Selection Considerations: Optical Microscopy Advantages; (1) Is a simple, nondestructive technique that
allows mineral identification without intermediate calculations or inferences; (2) sample preparation and
examination are relatively quick, simple, and inexpensive; and (3) use of stereoscopic microscopes in field (5 to
6 inches working distance, 20 to 80 power) allows for observation of soil features that cannot be readily seen by
eye or with a hand lens. Optical Microscopy Disadvantages: (1) Preparation of thin sections for accurate
identification of minerals is not readily done in the field; (2) accurate mineral identification requires an
experienced and skilled observer; and (3) identification of fine-grained material can be very difficult and might
require other methods, such as X-ray diffraction (Section 10.6.1). SEM Advantages: (1) Has very high resolution
(magnification from 20 to 50,000 times; and (2) can differentiate heterogeneity among fine-grained particles as
well as heterogeneity within individual particles. SEM Disadvantages: (1) Equipment is nonportable and
expensive; and (2) elemental information and topographic image interpretation is largely qualitative. EMPA
Advantages: Able to produce images that depict elemental distribution; EMPA Disadvantages: (1) Analyses are
expensive and relatively few instruments are available; (2) quantitative results for most elements are limited to
concentrations of 50 to 100 ppm; and (3) has lower resolution than SEM (up to 2500 times).
Frequency of Use: Optical microscopy and SEM are commonly used in the laboratory for mineral identification
and characterization. Hand lenses are standard equipment for observation of soils in the field; use of optical
microscopes in the field is uncommon, but more widespread use for examination of soils would be beneficial.
EMPA is most commonly used in the field of metallurgy, but could be used more widely in soil and waste studies
if limitations of expense and limited instrument availability were reduced.
Standard Methods/Guidelines: —
Sources for Additional Information: Cady et al. (1986-optical microscope), Goldstein et al. (1981), Sawhney
(1986-electron microprobe), Thompson et al. (1989-Cbapter 16).
10-59
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SCALE OF OBSERVATION
>
u_
O
Landscape
Setting
Hand
Specimen
Pedon
VISUAL
Stereo
Microscopy
X-ray
Micro-
I
Microprobe
Hand Light
tens Microscopy
Radiography|
SEM
O
CO
UJ
TEM
NlAlQSCOl
PY
SUSHICROSCOPY
(a)
OPTICAL MICROSCOPE
DEFLECTION COILS
TO ELECTRON DETECTORS
BACKSCATTERED ELECTRONS
SECONDARY ELECTRONS
EXCITED VOLUME-'
F-Y-
T
I
ELECTRON OUN
CONDENSER LENS
•1 i
ELECTRON BEAM
OBJECTIVE LENS
•TO X-RAY SPECTROMETERS
- CHARACTERISTIC X-RAYS
CONTINUOUS BACKGROUND
SECONDARY FLUORESCENCE
-X-RAY ABSORPTION
SPECIMEN CURRENT
(b)
Figure 10.6.4 Microscopy: (a) Schematic illustration of the relationship between increasing levels of resolution and
ihe area of the Geld under view (Cady ct al., 1986, by permission); (b) Schematic diagram showing
components of an electron microprobe and the signal produced from a specimen surface irradiated with
an electron beam (Sawhney, 1986, by permission).
10-60
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10. CHEMICAL FIELD SCREENING AND ANALYTICAL METHODS
10.6 OTHER ANALYTICAL TECHNIQUES
10.6.5 Other Chemical Sensors
Other Names Used to Describe Method: Electrochemical sensors (amperometric/galvanic cell sensors,
semiconductor sensors, spectroelectrochemical sensors), piezoelectric sensors (piezoelectric quartz microbalance,
surface acoustic wave [SAW] sensor).
Uses at Contaminated Sites: Field screening of contaminants in air, soil, and ground-water samples; SAW:
Screening for toxic/organophosphorus gases; Semiconductor; Screening for organochlorine; Pyrolysis-EC:
Screening for alcohols, epoxide, formaldehyde, CO, and H2S.
Method Description: Electrochemical sensors: As the name implies, these sensors measure an electrochemical
response when the sensor comes in contact with the analyte(s) of interest. Amperometric gas sensors are the
best developed sensor of this type (see Section 10.3.2). These sensors typically consist of electrodes in contact
with an electrolyte-saturated insulator. Selective membranes allow the gas of interest to enter the insulator and
redox reactions on the sensing-electrode surface generate a current that is proportional to the analyte
concentration. Figure 10.6.5 illustrates an exploded view of a typical amperometric sensor. Amperometric
sensors are capable of detecting levels as low as ppb of many organic and inorganic air pollutants. Use of
amperometric sensors for detecting contaminants in ground water is in developmental stages at this time.
Semiconductor sensors are designed to respond electrically to the substance of interest. A semiconductor sensor
designed to detect low concentrations of chlorinated and brominated organic compounds in vapor and water
(using membrane extraction [see Section 10.2.5]) has recently been tested in the laboratory. Piezoelectric
sensors: Several types of sensors using piezoelectric materials, which develop an electrical response to changes
in pressure, have been developed. Typically, oscillating crystals are used as sensitive gravimetric detectors.
Selective coatings allow specific organic solvent vapors to be sorbed on the crystal. The changed mass of the
crystal resulting from sorption changes the frequency of oscillation, which can be correlated with concentration.
SAW sensors also use piezoelectric materials and coatings that selectively sorb the vapor or gas of interest.
Changes in the mass or mechanical modulus of the surface coating are measured by the change in velocity of
electrically generated Rayleigh (surface) waves, as measured by travel time from the source of receiving
electrodes in the sensor. Concentration with SAW sensors is related to changes in velocity.
Method Selection Considerations: Amperometric Sensor Advantages: (1) Is inexpensive; (2) is simple and reliable
(no moving parts and sensor output is usually a linear function of concentration); and (3) is portable (units with
sensor, electronics, battery, and readout device can easily fit in a shirt pocket). Amperometric Sensor
Disadvantages: (1) Separate sensor required for each compound of interest; and (2) applications for ground-
water monitoring are in early developmental stages. Piezoelectric and SAW Sensor Advantages: (1) Are portable;
and (2) SAW vapor sensors have higher sensitivity than gravimetric piezoelectric sensors. Piezoelectric and SAW
Sensor Disadvantages: (1) General difficulty in developing selective coatings that are not affected by complex
mixtures; and (2) separate sensor required for each compound of interest.
Frequency of Use: Amperometric sensors: Commonly used in ambient air quality monitoring. Other sensors:
Emerging technology area.
Standard Methods/Guidelines: —
Sources for Additional Information: See Table 10-5.
10-61
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ELECTROLYTE
RESERVOIR
C/R ELECTRODES
PROTECTIVE
PERMSELECTIVE
MEMBRANE
Figure 10.6,5 Parts of a typical amperonietric sensor (Schmidt et al,, 1988).
10-62
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10. CHEMICAL FIELD SCREENING AND ANALYTICAL METHODS
10.6 OTHER ANALYTICAL TECHNIQUES
10.6.6 Other Biological Techniques
Other Names Used to Describe Method: Field: Short terra field bioassessments, biomonitoring, laser/microbe
bioassay (LMB), immunoehemieal techniques (Section 10,5.2). Laboratory: Bioassays, toxicity tests, biomarkers.
Uses at Contaminated Sites: Assessing actual or potential biological impacts of contamination at a site;
monitoring the effect of effluent on organisms; assessing the treatability of contaminated soil or ground-water
for bioremediation.
Method Description: At the simplest level, a qualitative assessment of the presence or absence of contaminants
at a site can be made by observing whether any vegetation appears to have been killed or growth inhibited by
the presence of toxic contaminants. Short-term field bioassessments: Field screening studies include collection
of small mammals, fish, benthic invertebrates, and plants for the purpose of evaluating alterations in community
structure, population dynamics, bioaccumulation of toxicants, and histopathology. The LMB system is a recently
developed technique that has potential for use in the field. Nineteen isogenic strains of Bacillus subtil is are used
to characterize and quantify the toxicants present in an aqueous solution. The response of the bacteria to toxic
substances in the solution is monitored by differential light scattering from a laser beam. The different strains
respond differently to different toxicants and a computer analyzes the measured responses to the known response
profiles to identify the type and concentration of toxicant. Figure 10.6.6 shows an example of the use of mussels
for field biomonitoring of the effects of potentially toxic effluents. A series of field cages filled with mussels are
placed along a gradient of contaminant concentrations. After a period of time (usually 7 to 30 days) the mussels
are retrieved and taken to a laboratory for further testing and analysis. Numerous laboratory methods have been
developed for biological assessment of toxicity, many of which can be run in mobile laboratories (see below).
These can be broadly classified as: (1) Toxicity tests using specific aquatic and terrestrial organisms and/or
microorganisms to measure biological response to specific contaminants or mixes of contaminants; and (2) the
analysis of biomarkers, which are molecular biological indicators that can directly link specific chemicals or
classes of chemicals to observed biological effects. The microtox bioassay, a colorimetric technique (see Section
10.5.1) that uses microorganisms, has been used to determine the appropriate range of waste application loading
for soil-based waste treatment systems (see reference in Table 10-5).
Method Selection Considerations: General Advantages: (1) Qualitative observations of inhibition of vegetative
growth can very easily be made; and (2) more sophisticated field bioassessment methods allow for correlation
of contaminant levels to actual biological impacts. General Disadvantages: (1) Field techniques have not been
widely used at contaminated sites so procedures are not well established; (2) personnel with specialized training
are required; and (3) equipment for more sophisticated techniques might not be readily available. LMB
Advantages: (1) Equipment is field portable and relatively fast (around 1 hour for a single sample); (2) can
distinguish between substances with cytotoxic and genotoxic properties; (3) potential for both high sensitivity and
high specificity for numerous toxic chemicals and chemical classes; and (4) computer processing and output
speeds up and simplifies interpretation of results. LMB Disadvantages: (1) Is a new technique that has received
limited field testing; and (2) ability to distinguish compounds in real-world complex mixtures has not yet been
demonstrated.
Frequency of Use: EPA's Environmental Research Laboratories at Duluth, Minnesota, and Narragansett, Rhode
Island, have mobile laboratories set up for ambient and effluent toxicity testing, which have been used primarily
as part of NPDES programs. Use of short-term field bioassessment methods at contaminated sites has been
fairly limited in the past, but these methods are being used with increasing frequency.
Standard Methods/Guidelines: Britton and Greeson (1989-algal growth potential bioassay), U.S. EPA (1986a)
contains recommendations for use of bioassays for evaluation of hazardous waste land treatment demonstrations.
Sources for Additional Information: U.S. EPA (1987-Section 12.6), Warren-Hicks et al. (1989). See Table 10-5
for additional references.
10-63
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Surface
Plastic Float
Polypropylene
Line
Mussel
Baskets
Anchor
(Sub-Surface)
Approx.
1 m
v ;
CEAS Station
Figure 10.6.6 Mussel field cages used to transplant mussels along transects (DiBona et al., 1989).
10-64
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Table 10-4 Reference Index for General Approaches to Field Screening/Analytical Methods and Extraction
Procedures
Topic
References
General Approaches to Reid Screening
Symposia
Review Reports/Papers
Agency Research Programs
QA/QC
Sample Extraction Procedures
Headspace Anatysis
i'
Soil Vacuum Extraction
Purge and Trap
Thermal Treatment
Soil (Micro)extraction
Other Methods
U.S. DOE (1988), U.S. EPA (1988a, 1991a)
Chudyk (1989), Coffey et al. (1988), Eastwood and Vo-Dinh (1991), Jenkins et al.
(1988, 1989), Koglin and Poziomek (1990), Montgomery et al. (1985), National
Institute for Petroleum and Energy Research (1990), Poziomek and Koglin
(1991), Remata et al. (1990), U.S. EPA (1982, 1987,1988a, 1991b)
U.S. EPA: Chapman and Fredericks (1988-FASP), Fribush and Fisk (1991),
Transue et al. (1991-FASP), Tuttle and Chapman (1989), U.S. EPA (1992);
Other; Cornell (1991-New Jersey), Frank et al. (1991-DOE), Mackay (1991-U.S.
Army), Madden and Johnson (1992-U.S. Army)
Mackiewicz (1990, 1991), Poziomek and Koglin (1991-cite 8 references from U.S,
EPA, 1991, that are not included here)
Crockett and DeHaan (1991-soil VOCs), Golding et al. (1991-VOCs in
soil/water), Hewitt et al. (1991), Ho et al. (1988), Hogan (1991), Holbrook (1987),
Pankow (1986, 1991), Roe et al. (1989), Sims et al. (1991-soil), Spittler et al.
(1988-soil, 1991-water), Stuart et al. (1991-BTEX in soil/water), Wylie (1988)
Golding et al. (1991), Spittler (1991)
Chochran and Henson (1988), Hein (1988), Liebman et al. (1991), linenberg and
Robinson (1991), Sherman et al. (1988a-coneentrator purge & trap), Turner et al.
(1991), Wise et al. (1991a), Wylie (1988); P/CCW: Pankow (1991), Pankow and
Rosen (1988)
Microwave-Assisted Digestion: Grohse et al. (1988); Thermal Desorotion: Pankow
and Isabelle (1982), Pankow and Kristensen (1983), Pankow et al. (1988),
Robbins et al. (1990), Schlesing et al. (1991), Vandegrift (1988), Wise et al.
(199 Ib); Thermal Extraction/Pvran Thermal Chromatograph: Greenlaw et al.
(1989), Henry et al. (1988), Junk et al. (1991a,b), Overton et al. (1988a,b); XRF
Sample Preparation; Bernkk et al. (1991), Harding (1991), Ramsey et al. (1991)
Semivolatile Organics: Kasper et al. (1991), Transue et al. (1991); PCB extraction:
Keller and Ganapathi (1991), Twomey et al. (1990); Tritium: Wong and Carlson
(1991)
Supercritical Fluid Extraction: Debman et al. (1991), Lopez-Avila et al. (1991),
Schulten and Schnitzer (1991), Wright and Fruchter (1992); Membrane extraction:
Melcher and Morabito (1991); Extraction Disks: Poziomek et al. (1991)
10-65
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Table 10-5 Reference Index for Screening/Analytical Methods
Topic
References
Total/Specific Vapor
Detectors
Portable Gas Chromatograph
Fkldable/Mobile Mass
Spectrometer; GC/MS
Mobile Laboratories
Ion Mobility Spectrometry
(Plasma Chromatography)
Comparisons; Clay and Spittler (1982), Gervasio and Davis (1989), Robbins et al.
(1990), Smith and Jensen (1987), Spittler (1980,1991); Erolosimeten Aller
(1984), Robbins et al. (1990); Hame lonization Detector: Gervasio and Davis
(1989), Hein (1988), Robbins et al. (1990); Organic Vapor Analyzer; Barber and
Braids (1982), Glaecum et al. (1983), Hogan (1991), Jermakian and Majika
(19,88), Robbins et al. (1989); Photoionization Detector: Brose and Gross (1988),
Gervasio and Davis (1988), Hare (1987), Robbins et al. (1990); P/T Argon
lonization Detector; Linenberg and Robinson (1991); Unspecified: Stetter et al.
(1984); Mercury Vapor Analyzer; Brass et al. (1991)
GC Comparisons/Validation: Homsher et al. (1988), Spittler (1991); Gas
Chromatographs; Baker et al. (1991-GC/FID), Berkely (1991-GC/PID),
Buehmiller (1989), Carney et al. (1991-retention indices), day and Spittler (1982),
Crockett and DeHaan (1991), Fowler and Bennett (1987), Golding et al. (1991-
GC/FBD), Hewitt et al. (1991), Ho et al. (1988), Kaelin and Prichett (1991-
GC/argon ionization detector), Keller and Ganapathi (1991), Linenberg (1988),
Moore (1991-GC/PID), Moreton et al. (1991-soil BTEX), Overton et al. (1988c),
Quimby et al. (1982-GC/OVA), Reynolds et al. (1991), Robbat and Xyrafas
(1988a), Shangraw (1988), Sherman et al. (1988b), Spittler (1980, 1984-PCBs),
Spittler et al. (1982-GC/FID), Stuart et al. (1991-GC/PID), Turner et al. (1991-
PT/GC), Wander et al. (1988), Wohltjen et al. (1991); GC/AES: Szelewski and
Wilson (1988); GC/FTIR: Gurka et al. (1986)
GC/MS: Bruell and Hoag (1984), Gurka et al. (1986), McGinnis and Hafferty
(1987-PCP), Moy (1989-PCB), Sinha (1991), Transue et al. (1991-GC/ECD,
PAHs, PCP); Mobile Mass Spectrometer; Duret et al. (1991), Hadka and
Dickinson (1988), Klainer et al. (1991), Trainor and Laukien (1988); GC/ITMS or
ITD flon Trap Mobility Spectrometrv or Ion Trap Detector): Cispar et al. (1991),
Cooks et al. (1991), Leibman et al. (1991), McClennen et al. (1991-MENIMASS),
Wise et al. (1991a, J991b); Tandem MS (MS/MS^: Wise et al. (1991a); GC/MS:
Meuzelaar et al. (1991), Robbat and Xyferas (1988b); Thermal Desorption ITMS-
MS/MS: Wise et al. (1991b), Thermal Desorption GC/MS: Robbat et al. (1991);
Semivolatile Thermal Extraction GC/MS: Henry et al. (1988), Junk et al.
(1991a,b), Overton et al. (1988d)
Ben-Hur et al. (1984-mobile MS/MS), Burger (1991), Chapman et al. (1986),
Engels et al. (1984), Franks et al. (1985), Greenlaw et al. (1989-thermal
chromatograph/MS), McGinnis and Hafferty (1987-PCP), Moy (1989-PCB), Tuttle
and Chapman (1989); Cost Analysis: Ganapathi et al. (1988); Dedicated
Laboratory: Freeman and Karmazyn (1988)
Bell and Eiceman (1991-GC/IMS), Burroughs et al. (1991), Clement et al. (1992),
Davis (1991-data analysis), Hoffland and Shoff (1991), Reategui et al. (1988),
Richter (1991), Snyder et al. (1991-microorganisms), Wise et al. (1990)
10-66
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Table 10-5 (cont.)
Topic
References
Fluorescence/Luminescence/Spectroscopic Techniques
X-Ray Fluorescence (XRF)
UV Fluorescence
Other Luminescence Methods
IR Spectroscopic Methods
Other Spectroscopy
Ashe et al. (1991), Barich et al. (1988), Bernick et al. (1991), Carlson and
Alexander (1991-QA/QC), Chappell et al. (1986), Coetzee et al. (1986-XRF, ICP-
AES), Cole et al. (1991-XRF/CLP comparison), Everitt et al. (1988), Florkowski
et al. (1971), Freiburg et al. (1987-XRF, AAS, AES), Furst et al. (1985), Gabry
(1991-XRF vs CLP), Glanzman (1988), Grupp et al. (1988), Harding (1991-
EDXRF), Harding and Walsh (1990-EDXRF), Jenkins (1984), Kendall (1991b),
Meiri et al. (1990), Perils and Chapin (1988), Piorek and Rhodes (1988-
calibration), Raab et al. (1990), Ramsey et al. (1991-EDXRF calibration),
Sackman et al. (1988), Smith and Lloyd (1986-XRF, AAS), Watson et al. (1989)
PAH Solvent Extract: Popp (1989), Saenz et al. (1991), Theis et al. (1991); With
HPLC: Mann and Vickers (1988), Riddel! et al. (1991); With Fiber Optics:
Chudyk et al. (1988), Gillispie and St. Germain (1988), Haas et al. (1988, 1991),
Kenny et al. (1988), Oeberman et al. (1991), Smith et al. (1988), Taylor et al.
(1991); UV Surface Contamination Detector: Richter (1991); Airborne:
Guermeberg (1978)
Synchronous Fluorescence: Ganimage et al. (1988, 1991);
Spectrofluorometer/Solid State Fluorescence: Poziomek et al. (1991); Room
Temperature Phosphorescence: Vo-Dinh (1984), Vo-Dinh et al. (1991)
Review; Kendall (1991a), Phelps and DeSha (1991-UDAR, FTIR); ODAR:
Mackay (1991); Mobile FUR: Fateley et al. (1990), U.S. EPA (1991a-five papers,
not indexed separately); Other Infrared: Gurka et al. (1986-GC/FTIR), Kasper et
al. (1991-soil hydrocarbons), Riehter (1991-ER laser absorption); IR
Refl ectance/Transmission: King and Clark (1988)
Ultraviolet-Visible Absorption Spectroscopy: Beemster and Schlager (1991-with
fiber optics), Schlager and Beemster (1991), Thompson (1974); UV Derivative
Spectroscopv: Hager and Jones (1990-BTEX); Surface Enhanced Raman
Spectroscopy: Carrabba et al. (1988, 1991), Ferrell et al. (1988), Smith et al.
(1988)
Wet Chemistry Analytical Techniques/Instrumentation
Immunochemical Methods
Reports/Symposia: Schnell and Chang (1990), Silverstein et al. (1992a, 1992b),
Van Emmon and Mumma (1990), Vanderlaan et al. (1991); Field Enzyme
Immunoassav Test Kits: Bushway et al. (1988), Chamerlik-Cooper et al. (1991-
PCBs), Duquette et al. (1988, 1991-PCP), Ensys Inc. (1991), Harrison and
Ferguson (1990), Ladouceur (1991), McMahon et al. (1988), Schmidt et al.
(1988), Vanderlaan et al. (1988), Van Emon et al. (1991a-pestieies, 1991b-PCP
kits); Immunochemical Fiber Optic Sensors: Bolts et al. (1988), Lin et al. (1988)
10-67
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Table 10-5 (cont)
Topic
References
Wet Chemistry Analytical Techniques/Instrumentation fcont.")
Colorimetric Chemical Field
Test Kits
Liquid Chromatography
PCB; Gabiy (1987), Woolerton et al. (1988); Qthen Hanby (1988-aromatic
compounds), Jenkins et al. (1991-explosives), Lindsay and Baedecker (1988-
aqueous sulfide), Schlesing et al. (1991-chlorinated organics), Silvestri et al.
(1981), Stamnes et al. (1991-Cr Hach kit)
Thin-Layer Chromatographv; Brumley and Brownrigg (1991-PNAs), Silvestri et al.
(1981); High Performance Liquid Chromatographv: Betowski and Jones (1989),
Ekambaram and Burch (1988-PAHs), Joseph (1992), Mann and Vickers (1988),
Pace et al. (1992), Riddell et al. (1991-PAHs)
Bioassessment Techniques
Bioassays
Bioassessments/Monitoring
Other Chemical Sensors
General
Electrochemical Sensors
Piezoelectric Sensors
Surface Acoustic Wave (SAW)
Semiconductor
Brown et al. (1984), Easterly et al. (1988), Felkner et al. (1988a,b-laserAnicrobe
bioassay); Microtox Assay: Abbott and Sims (1989-PAHs), Bulich (1979),
Matthews and Bulich (1984), Symons and Sims (1988)
Bohman et al. (1989), Charters (1988), Dermer et al. (1980-biochemical
indicators), DiBona et al. (1989), Gardner et al. (1989), Gezo and Brusick (1987),
Piekarz (1990), Steen (1987-toxieity testing), Warren-Hicks et al. (1989-field and
laboratory methods)
Adrian (1992), Edmonds (1981), Hollenberg and Sahn (1988-biosensors), Janata
and Bezegh (1988), Wohltjen (1984)
Carrabba et al. (1991-SEFOS), Penrose et al. (1991-pyrolysis-EC), Schmidt et al.
(1988)
Alder and McCallum (1983), Guilbault and Jordan (1988), Hlalvay and Guilbault
(1977), Mierzwinski and Witkiewicz (1989), Overton et al. (1988d)
Ballentine and Wohltjen (1989), Ballentine et al. (1986), Bartley (1991), Bton
and Houle (1991-SAW/GC), Jarvis et al. (1991), Nieuwenhuizen and Barendsz
(1987)
Penrose et al. (1991)
10-68
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Alter, L. 1984. Methods for Determining the Location of Abandoned Wells. EPA/600/2-83/123 (NT1S PB84-141530). (Also
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American Society for Testing and Materials (ASTM). 1984. Standard Test Method for Density and Unit Weight of Soil in Place by
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Barnes, I. 1964. Field Measurement of Alkalinity and pH. U.S. Geological Survey Water Supply Paper, 1535-H.
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Bushway, R J., J. King, B. Perkins, W.M. Pask, and B.S. Ferguson. 1988. Determination of Chlordane in Soil by Enzyme
Immunoassay. In: U.S. EPA (1988a), pp. 43*437.
Cady, J.G., L.P. Wildung, and L.R. Drees. 1986. Petrographic Microscope Techniques. In: Methods of Soil Analysis, Part 1, 2nd
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Carlson, CD. and J.R. Alexander. 1991. Data Quality Assurance/Quality Control For Field X-Ray Fluorescence Spectrometry, In:
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Carney, K.R., E.B. Overton, and R.L. Wong. 1991. Calculation and Use of Retention Indices for Identification of Volatile Organic
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377.
Chapman, G.C., P. Clay, C.K. Bradley, and S. Fredericks. 1986. Field Methods and Mobile Laboratory Scenarios for Screening and
Analysis at Hazardous Waste Sites. In: Proc. 7th Nat Conf. on Management of Uncontrolled Hazardous Waste Sites,
Hazardous Materials Control Research Institute, Silver Spring, MD, pp. 120-125.
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Materials Control Research Institute, Silver Spring, MD, pp. 115-119.
Charters, D.W. 1988. Utilization of Short-Term Bioassessments and Biomonitoring at Superfund Sites. In: Proc. U.S. EPA (1988a),
pp. 359.
Chochran, J.W. and J.M. Henson. 19S8. Analysis of Volatile Organic Chemicals in Aqueous Samples by Purge/GC with Selective
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Waste Site, Interim Report, Class A Poisons. EPA/600/X-82/014.
U.S. Environmental Protection Agency (EPA). 1986a. Permit Guidance Manual on Hazardous Waste Land Treatment
Demonstrations. EPA/530/SW-86/032 (NTIS PB86-229184). [Microtox assay]
U.S. Environmental Protection Agency (EPA). 1986b. Test Methods for Evaluating Solid Waste, 3rd edition, Vol. II: Field Manual
Physical/Chemical Methods. EPA/530/SW-846 (NTIS PB88-239223); First update, 3rd edition EPA/530/SW-846.3-1 (NTIS
PB89-148076). (Available on a subscription basis from U.S. Government Printing Office, Stock #955-001-00000-1.)
10-83
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U.S. Environmental Protection Agency (EPA). 1987. A Compendium of Superfund Field Operations Methods, Part 2. EPA/540/P-
87/001 (OSWER Directive 9355.0-14), (NTIS PB88-181557), 644 pp. [OC, total/specific organic vapor detectors]
U.S. Environmental Protection Agency (EPA). 19S8a. First International Symposium, Field Screening Methods for Hazardous
W«ite Site Investigations. EPA/600/D-89/189 (NTIS PB90-132572), 519 pp.
U.S. Environmental Protection Agency (EPA). 1988b. Field Screening Methods Catalog: User's Guide. EPA/540/2-88/005. FSMC
System Coordinator, OERR, Analytical Operations Branch (WH-S48-A), U.S. EPA, Washington, DC.
U.S. Environmental Protection Agency (EPA). 1991a. Second International Symposium, Field Screening Methods for Hazardous
Waste and Toxic Chemicals, L.R. Williams and E.N. Koglin (eds.), EPA/600/9-91/028 (NTIS PB92-125764), 892 pp.
U.S. Environmental Protection Agency (EPA). 1991b. The Superfund Innovative Technology Evaluation Program: Technology
Profiles, 4th edition. EPA/540/5-91/008. [Technology profiles on EIA, IMS, portable OC, FTIRJ
U.S. Environmental Protection Agency (EPA). 1992. The Superfund Innovative Technology Evaluation Program: Technology
Profiles, 5th edition. EPA/540/R-92/077, 388 pp. [Monitoring and measurement technology section summarizes information
on EIA, IMS, portable GC and FTIRJ
U.S. Geological Survey (USGS). 1980. Ground Water. In: National Handbook of Recommended Methods for Water Data
Acquisition, USGS Office of Water Data Coordination, Reston, VA, pp 2-1 to 2-149.
Vandegrift, S. A. 1988. Analysis of Volatile Organic Compounds in Water by Dynamic Stripping, Thermal Desorption, Cryofocusing
and Capillary Gas Chromatography. J. Chrom. Science 26(1):513-516.
Vanderlaan, M., B. Watkins, and L. Stanker. 1988. Iramunochemical QuantiGcation of Dioxins in Industrial Chemicals and Soils.
In; U.a EPA (1988a), pp, 249-250.
Vanderlaan, M., L.H, Stanker, B.E. Watkins, and D.W. Roberts (eds.). 1991. Immunoassays for Trace Chemical Analysis:
Monitoring Toxic Chemicals In Humani, Foodi and the Environment. ACS Symp. Series No. 451, American Chemical
Society, Washington, DC, 362 pp.
Van Emon, J.M. and R.O. Mumma. 1990. Immunochemlcal Methods for Environmental Analysis. ACS Symp. Series No. 442,
American Chemical Society, Washington, DC, 239 pp.
Van Emon, J.M., J.N, Seiber, and B.D. Hammock. 1991a. Immunoassay Techniques for Pesticide Analysis. In; Methods for
Pesticides and Plant Growth Regulators, Academic Press, New York, NY, pp. 217-263.
Van Emon, JJvf., R.W. Gerlach, RJ. White, and M.E. Silverstein. 1991b. U.S. EPA Evaluation of Two Pentachlorophenol
Immunoassay Systems. In: U.S. EPA (199la), pp. 815-818.
Vo-Dinh.T. 1984. Room Temperature Phosphorimetry for Chemical Analysis. Wiley, New York, NY.
Vc-Dioh, T., et al. 1991. Rapid Screening Techniques for Potychorinated Biphcnyls (PCBs) Using Room Temperature
Photphoretcence. In: U.S. EPA (1991a), pp. 819-822.
Wander, JJD., B.L. Lentz, L. Michatec, and V. Taylor. 1988. Prototype Volatile Organic Compound (VOC) Monitor. In: U.S. EPA
(1988*), pp. 319-324.
Warren-Hicks, W., BJ. Parkhurst, and S.S. Baker, Jr. (eds.). 1989. Ecological Assessment of Hazardous Waste Sites: A Held and
Laboratory Reference. EPA/600/3-89/013 (NTIS PB89-205967).
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Ion Trap and Glow Discharge Mass Spectrometry. In: U.S. EPA (1991a), pp. 273-288. [ITMS/GOMS, MS/MS]
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Wohltjen, H. 1984. Chemical Microsensors and Microinstrumentation. Analytical Chemistry 56:87A-103A.
Wohltjen, H., N.L. Jarvis, and J. Lint 1991. A New Approach for On-Site Monitoring of Organic Vapors at Low PPB Levels. In:
U.S. EPA (1991a), pp. 829-833. [Portable GC]
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(1991a), pp. 835.
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U.S. Geological Survey Techniques of Water Resources Investigations TWRI 1-D2, 24 pp.
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69:A176-A178.
Woolerton, G.R., S. Valin, and J.P. Gibeault. 1988. The Kwik-Skrene Analytical Testing System: Description of a Tool for
Remediation of PCB Spills. In: UJ. EPA (1988t), pp. 387-388. [Test kit)
Wright, B.W. and J.S. Fruchter. 1992. Supercritical Fluid Extraction for the Analysis of Contaminated Soils. EPRI TR-100754,
Electric Power Research Institute, Palo Alto, CA.
Wylie, P.L. 1988. Comparing Headspace with Purge and Trap Analysis of Volatile Priority Pollutants. Research & Technology
80(8):65-72
*ORD Publications, U.S. EPA Center for Environmental Research Information, P.O. Box 19963, Cincinnati, OH, 45268-0963 (513-
569-7562).
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APPENDIX C
GUIDE TO MAJOR REFERENCES OF SUBSURFACE CHARACTERIZATION, MONITORING,
AND ANALYTICAL METHODS
A very large technical literature has developed in the last 20 years on characterization and monitoring
of contaminated sites. This appendix provides information on major documents published by EPA, other
government organizations, universities, and commercial organizations, which provide information of one or more
aspects of vadose zone and ground-water characterization and monitoring. Most of these documents relate
wholly, or in part, to contaminated sites. Other documents that do not have this perspective are included only
if they focus primarily on field methods that can be applicable to contaminated sites.
Table C-l provides brief descriptive information on over 80 major references. These are categorized
into the following groups in the table: (1) Soils and ground water, (2) vadose zone, (3) ground water, (4) soils
and solid wastes, and (5) symposia proceedings. EPA publications that are available at no cost from the Center
for Environmental Research Information in Cincinnati are indicated with an asterisk in the reference list at the
end of this appendix. Wherever possible, the NTIS number of government publications available from the
National Technical Information Service (NTIS) is provided. (The NTIS telephone number is 800-553-6847).
Publications by the Electric Power Research Institute are available at no cost to government agencies (EPRI
Research Reports Center, P.O. Box 50490, Palo Alto, CA 94303, telephone 415-965-4081).
There is a very large literature on subsurface site characterization and monitoring techniques scattered
through various annual and intermittent conference series. The published proceedings of four regular conference
series serve as an excellent source of information on the latest developments in field characterization and
monitoring: (1) The annual National Outdoor Action Conference on Aquifer Restoration, Ground Water
Monitoring and Geophysical Methods, (2) the annual Conference on Petroleum Hydrocarbons and Organic
Chemicals in Ground Water: Prevention, Detection and Remediation, (3) the annual Conference on Hazardous
Materials Control (formerly called Superfund), and (4) the annual Conference on Hazardous Wastes and
Hazardous Materials. Proceedings of the first two series are published by the National Water Well Association
(NWWA), which changed its name to the National Ground Water Association (NGWA) in 1991 (NGWA
Bookstore, P.O. Box 182039, Columbus, OH 43218, telephone 614-761-1711), and the proceedings of the latter
two series are published by the Hazardous Materials Control Research Institute (HMCRI Publications Dept.,
9300 Columbia Rd., Silver Spring, MD 20910-1702, telephone 301-587-9390).
In addition, the Association of Ground Water Scientists and Engineers of NWWA/NGWA has
sponsored numerous conferences focussed on special topics or regional issues. Since 1990, NWWA/NGWA
conferences have been published in a subscription series titled Ground Water Management in which six coupons
are issued that can be redeemed for the publications in the series of interest to the subscription holder ($140
members/$19Z50 nonmembers, see the NGWA address above).
Table C-2 lists the titles of more than 70 published conference/series proceedings focusing on ground
water and/or contaminated sites. Many relevant papers in these proceedings are cited in earlier sections of this
guide. EPA regional offices and laboratories have many of these documents, and EPA/NTIS numbers are
indicated, where available. If a document of interest cannot be found in a nearby library, the indicated sponsor
(NWWA/NGWA or HMCRI) should be contacted concerning its availability. Out-of-print NWWA/NGWA
publications can be borrowed for a fee from the National Ground Water Information Center (6365 Riverside
Drive, Dublin, OH 43017, telephone 614-761-1711).
Table C-3 provides information on major compilations of information on analytical procedures for
constituents of geochemical interest at contaminated sites. Most of these books and reports focus on laboratory
methods and procedures, but might be useful for additional information on basic analytical methods that can be
used in mobile laboratories or adapted for more portable instrumentation.
C-l
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Table C-l M^jor Reference Sources on Subsurface Characterization and Monitoring Methods
Topic
References
Site Investigations
Hydrologic Characterization
Ecological Assessment
Specific Settings
Ground-Water Monitoring
General Procedures
Monitoring Wells
Sampling Equipment
Sampling Procedures
Costs
Specific Settings
Brakensiek et al. (1979), Brown et al. (1983), Bureau of Reclamation (1981), Dames
& Moore (1974), Driscoll (1986), Nielsen and Johnson (1990), Nielsen and Sara
(1992), Rehm et al. (1985), Thompson et al. (1989), UNESCO (1983), VS. EPA
(1991a,b), USGS (1977+), Waste Management of North America (1991), Zimmie
and Riggs (1981); see also, Tables 4-5 and 4-6
Warren-Hicks et al. (1989); see also, Table 10-5 (bioassessment techniques)
Surface Mining: Barrett et al. (1980); Hazardous Waste Sites: Cameron (1991),
Cochran and Hodge (1985), Ford and Turina (1985), Lesage and Jackson (1992),
Oudjik and Mujica (1989), Perket (1986), Slsk (1981), U.S. EPA (1987, 1989a);
RCRA FacUities: U.S. EPA (1986d, 1989b,c); Low Level Radioactive Wastes: EG&G
(1990); Remedial Operations: Ross and Keeley (1992), U.S. EPA (1988a, 1991a);
Surface Impoundments: Silka and Swearingen (1978)
Collins and Johnson (1988), Crouch et al. (1976), Devfany et al. (1990), EG&G
(1990), Everett (1980), Everett et al. (1976), Fried (1975), Gillham et al. (1983),
Keith (1992), Loftis and Ward (1979), Mooij and Rovers (1976), Morrison (1983),
Nielsen (1991), Nielsen and Johnson (1990), Nielsen and Sara (1992), Ross and
Keeley (1992), Todd et al. (1976), U.S. DOE (Various dates), U.S. EPA (1986b,
1990a,b, 1991a,b, 1993), van Duijvenbooden and van Waegeningh (1987)
Aller et al. (1991), Barcelona et al. (1983), Driscoll (1986), Howsam (1990), Korte
and Kearl (1985), Nielsen and Schalla (1991); see also, Tables 2-4 and B-2
See Tables 5-4 and 5-5
API (1987), Barcelona et al. (1983, 1985), Berg (1982), Classen (1982), Holden
(1984), Keith (1988), Korte and Kearl (1985), Nash and Leslie (1991), Rainwater and
Thatcher (I960), Scalf et al. (1981), Summers and Gherini (1987), Unwin (1982),
Wood (1976); see also, Table B-4.
Crouch et al. (1976), Everett et al. (1976), Loftis and Ward (1979)
Tinlin (1976); Solid Waste Disposal: Fenn et al. (1977), U.S. EPA (1981a,b, 19860;
RCRA Facilities: U.S. EPA (1983a,b, 1985, 1986M^A 1989e); Enhanced Oil
Recovery: Beck et al. (1981); Surface Mining; Everett (1979,1983,1985), Everett and
Hoylman (1980a,b), Williams and Schuman (1987); Oil Shale: Everett (1985),
Slawson (1979,1980a,b); Electric Utilities: GeoTrans (1989), Redwine et al. (1985);
Wastewater and Sludge Application: Ho et al. (1978); Waste Spills: Pilie et al.
(1975), Yang and Bye (1979); Qeothermal; Weiss et al. (1979)
State/Local Guidance Documents* Connecticut Environmental Protection Agency (1983), Lindorff et al. (1987), NJDEP
(1988), Santa Clara County Water District (1985), Stephens (1986)
C-2
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Table C-l (conk)
Topic
References
Microbiological Sampling
Vadose Zone Monhorin2
General
Soil Solute
Soil Gas
Soils
Field Characterization
General Sampling
Sampling for Soil Contaminants
Wastes
Sampling
Agency/Organization Index
U.S. EPA
Bitton and Gerba (1984), Board and Lovelock (1973), Bordner et al. (1978), Britton
and Greeson (1989), Costerton and Colwell (1979), Dunlap et al. (1977), Rosswall
(1973), USGS (1977+); see also, references in Section 9.3.6
Everett et al. (1983), Nielsen and Johnson (1990), Nielsen and Sara (1992), Rehm
et al. (1985), Rijtema and Wassink (1969), U.S. EPA (I986c), Wilson (1980)
Devinny et al. (1990), Morrison (1983), Nash and Leslie (1991), Nielsen (1991),
USGS (1977+); see also, Table 9-4
Devitt et al. (1987), Ford et al. (1984), Kerfoot and Barrows (1987), U.S. EPA
(1988b); see also, references for Section 9.4.2
Blume et al. (1991), Boulding (1991), Brakensiek et al. (1979), Bureau of
Reclamation (1974, 1990), Cameron (1991), Hodgson (1978), SCS (1971)
Acker (1974), Barth et al. (1989), Cameron (1966), Corps of Engineers (1972), Keith
(1992), Hodgson (1978), Hvorslev (1948, 1949), Mason (1992), McKeague (1978),
Mooij and Rovers (1976), SCS (1984), U.S. DOE (Various dates); Sediments; Barth
and Starks (1985), Edwards and Glysson (1988), Palmer (1985), Plumb (1981); see
also, Table 2-5
API (1987, 1992), Boulding (1991), Brown et al. (1991), EG&G (1990), Ford et al.
(1984), Goodwin et al. (1982), Keith (1988), Scalf et al. (1981), Schweitzer and
Santolucito (1984), U.S. EPA (1986b, 1988b, 1989c, 1991a), van Duijvenbooden and
van Waegeningh (1987)
deVera (1980), Ford et al. (1984), Keith (1988, 1992), Simmons (1991), U.S. DOE
(Various dates), U.S. EPA (1986b), Wolbach et al. (1984)
Soils and Ground Water: Aller et al. (1991), Cochran and Hodge (1985), Dunlap et
al. (1977), Everett et al. (1976), Fenn et al. (1977), Ford and Turina (1985), Ford et
al. (1984), Ross and Keeley (1992), Scalf et al. (1981), Silka and Swearingen (1978),
Sisk (1981), U.S. EPA (1986d, 1987,1989a,b,c, 1990b, 1991a); Vadose Zone: Devitt
et al. (1987), Everett et al. (1983), Kerfoot and Barrows (1987), U.S. EPA (1986c),
Wilson (1980); General Ground Water: Barcelona et al. (1985), Berg (1982), Crouch
et al. (1976), Loftis and Ward (1979), Tinlin (1976), Todd et al. (1976), U.S. EPA
(1990a, 1991a), Yang and Bye (1979); Ground-Water Guidance Documents: U.S.
EPA (1981a, 1981b, 1983a,b, 1985, 1986a,e/, 1988a, 1993); Soil and Solid/Liquid
Waste: Barth et al. (1989), Boulding (1991), Cameron (1991), deVera (1980),
Hatayarna et al. (1980), Mason (1992), Pilie et al. (1975), U.S. EPA (1986b), Yang
and Bye (1979); Energy Development Ground-Water Monitoring: Beck et al. (1981),
Everett (1979,1983), Everett and Hoylman (1980a,b); Slawson (1979,1980a,b), Weiss
et al. (1979)
C-3
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Table C-l (cont.)
Topic
References
Other Federal
Other Government
Bureau of Reclamation: Bureau of Reclamation (1974,1981,1990); Department of
Energy: EG&G (1990), U.S. DOE (Various dates); Fish and Wildlife Service: Brown
et al. (1991); Forest Service: Barrett et al. (1980); NASA: Cameron et al. (1966);
USATHAMA/Corps of Engineers: Corps of Engineers (1972), Goodwin et al. (1982),
Hvorslev (1949), Plumb (1981); USDA/SCS: Brakensiek et al. (1979), SCS (1971,
1984); U.S. Geological Survey: Classen (1982), Edwards and Glysson (1988), Guy
(1969), USGS (1977+), Wood (1976)
Canada: McKeague (1978), Mooij and Rovers (1976); States*: Barcelona et al.
(1983), Connecticut Environmental Protection Agency (1983), Lindorff et al. (1987),
NJDEP (1988), Stephens (1986)
American Chemical Society (ACS) Keith (1988,1992), Nash and Leslie (1991), Schweitzer and Santolucito (1984)
Amercian Petroleum Institute
(API)
American Society for Testing and
Materials (ASTM)
Consulting Finns
Electric Power Research Institute
(EPRI)
UNESCO
Other
API (1987, 1992), Gillham et al. (1983)
ASTM (Annual, 1992a,b); Ground-Water and Vadose Zone STPs: Collins and
Johnson (1988), Nielsen and Johnson (1990), Nielsen and Sara (1992), Zimmie and
Riggs (1980); Hazardous Waste Solid Testing Conference Series: (Papers in this
series tend to focus on laboratory methods, but also include papers on field-oriented
techniques): 1st (Conway and Mallow, 1981); 2nd (Conway and Gulledge, 1982); 3rd
(Jackson et al., 1984); 4th (Petros et al., 1985); 5th (Pericet, 1986); 6th (Lorenzen et
al., 1986)
Dames & Moore (1974), Everett (1980), GeoTrans (1989), Waste Management of
North America (1991)
Redwine et al. (1985), Rehm et al. (1985), Summers and Gherini (1987), Thompson
et al. (1989)
Brown et al. (1983); Symposia: Rijtema and Wassink (1969), UNESCO (1983)
Devinny et al. (1990), DriscoU (1986), Everett (1985), Fried (1975), Ho et al. (1978),
Holden (1984), Howsam (1990), Mute (1986), Lesage and Jackson (1992), Morrison
(1983), Nielsen (1991), Oudjik and Mujica (1989), Simmons (1991), Unwin (1982),
van Duijvenbooden and van Waegeningh (1987)
*The appropriate state regulatoiy agency should be contacted for the most current version of any guidance documents.
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