PB85-124899
Review of In-Place Treatment Techniques for Contaminated Surface Soils
Volume 2: Background Information for In Situ Treatment
Utah State University
Logan, Utah
Nov 84
U.S. DEPARTMENT OF COMMERCE
National Technical Information Service
NT1S
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PROPERTY OF THE
U.S. Environmental Protection Agency OFFICE °Fsuf$fjfU
Region 5, Library (PL-12J) cPA-540/2-84-003b
77 West Jackson Boulevard, 12th Floor November
Chicago, IL 60504-3590 -
REVIEW OF IN-PLACE TREATMENT TECHNIQUES
FOR CONTAMINATED SURFACE SOILS
Volume 2: Background Information for In Situ Treatment
by
Ronald C. Sims, Darwin L. Sorensen, Judith L. Sims,
Joan E. McLean, Ramzi Mahmood, and R. Ryan Dupont
Utah State University
Logan, Utah 84322'
and
Kathleen Wagner
JRB Associates
McLean, Virginia 22102
Contract No. 68-03-3113
Project Officer
Naomi Barkley
Solid and Hazardous Waste Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
REPRODUCED BY
NATIONAL TECHNICAL
INFORMATION SERVICE
US DEPAR'MiNl OF COMMfRCE
SPfWGfiElD VS. 22161
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THCHNICAL REPORT DATA
'P'.ssst rtsd Instrjcr.cns on she rtvtne sefare zomt
i. 3S=ORT NO. 2.
EPA-540/2-84-003b
*. TfTLS ANO SUSTITi.£
REVIEW OF IN-PLACE TREATMENT TECHNIQUES FOR
CONTAMINATED SURFACE SOILS - VOLUME 2: BACKGROUND
INFORMATION FOR IN-SITU TREATMENT
7. AUTHORIS)
Ronald Sims
9. ?£ai=Ofl.V)ING ORGANISATION NAME ANO AOORS53
Utah Water Research Laboratory
Utah State University
Loqan, Utah ' 84322
12. SPONSORING AGENCY NAME ANO ADDRESS
Municipal Environmental Research Laboratory—Gin. , OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. SUPPLEMENTARY NOTES
Naomi P. Barkley 513/684-7875
we::n%i
2. 3£C:?>eN-r 3 -iCC333'G OeSCfllPTOflS
18. 01STRI3UTIOM STATSMe.NT
RELEASE TO PUBLIC
b.lO6NT1PlSaS/CPSN SNO6O TS3MS
19. SECURITY CLASS tnia Xeporn
UNCLASSIFIED
20. sscoRiTY CLASS , r;»i pu?«/
UNCLASSIFIED
C. COSAT' - t c C.C'-r
21. .NO. :- -Z^'
389
:; a<^ics
f PA form 2220-1 iR«». 4-77) f*eviou> «ac now 11 3 aiOu£-E
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DISCLAIMER
The information in this document has been funded wholly or in part by the
United States Environmental Protection Agency under Contract No. 68-03-3133
(Task 41) to JRB Associates with a subcontract to the Utah Water Research
Laboratory, and Contract No. 68-01-6160 (Work Order 12) to Arthur D. Little,
Inc. It has been subject to the Agency's peer and administrative review
and has been approved for publication. The contents reflect the views and
policies of the Agency. Mention of trade names or commercial products does
not constitute endorsement or recommendation for use.
n
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FOREWORD
The U.S. Environmental Protection Agency was created because of in-
creasing public and government concern about the dangers of pollution to the
health and welfare of the American people. Noxious air, foul water, and
spoiled land are tragic testimonies to the deterioration of our natural
environment. The complexity of that environment and the interplay of its
components require a concentrated and integrated attack on the problem.
Research and development constitute that necessary first step in problem
solution, and they involve defining the problem, measuring its impact, and
searching for solutions. The Municipal Environmental Research Laboratory
develops new and improved technology and systems to prevent, treat, and manage
wastewater and solid and hazardous waste pollutant discharges from municipal
and community sources, to preserve and treat public drinking water supplies,
and to minimize the adverse economic, social, health, and aesthetic effects of
pollution. This publication is one of the products of that research and is a
most vital communications link between the researcher and the user community.
Contaminated soils present one of the most significant problems of
uncontrolled hazardous waste sites. This report presents a review of avail-
able information on in-place treatment techniques applicable to remediation of
hazardous waste-contaminated surface soils.
Francis T. Mayo
Director
Municipal Environmental Research Laboratory
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ABSTRACT
This second volume of a two volume manual on in-place treatment of
hazardous waste contaminated soil supports the treatment methodology described
in Volume 1 (EPA-540/2-84-0032). The information presented on monitoring
to determine treatment effectiveness, characterization and evaluation of
the behavior and fate of hazardous constituents in soil/waste systems, and
properties (including adsorption, degradation, and volatilization parameters)
for various compounds is intended to help the manual user in making more
complex decisions and in selecting analyses concerning site, soil, and waste
interactions.
This report was submitted in partial fulfillment of Contract No. 68-03-
3113 by Utah State University under the sponsorship of the U.S. Environmental
Protection Agency. The report covers the period December 1982 to December
1984 and work was completed as of January 1984.
IV
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CONTENTS
FOREWORD
ACKNOWLEDGMENTS
ABSTRACT
LIST OF FIGURES
LIST OF TABLES
SECTION 1 - INTRODUCTION
SECTION 2 - MONITORING
Introduction
Statistical Considerations
Soils Sampling in the Treatment Zone and in the
Underlying Unsaturated Zone
Soil Pore Liquid Sampling in The Unsaturated Zone
Water Samples from the Saturated Zone
Runoff Water Monitoring
Air Monitoring
References
SECTION 3 - CHARACTERIZATION AND EVALUATION OF FUNDAMENTAL
PROCESSES IN SOIL/WASTE SYSTEMS
Site and Soil Factors Related to In Situ Treatment
Introduction
Site Characterization Related to Off-site
Migration
Site Characteristics with Regard to In Situ
Treatment Techniques
Site Characterization Related to Physical
Execution of In Situ Treatment Technology
Sources of Information
Waste Characterization Related to In Situ Soil Treatment
Introduction
Definition of Hazard and Degree of Hazard
Preliminary Waste Identification
2
2
3
5
6
7
10
11
13
13
13
15
61
61
62
63
63
64
68
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CONTENTS (Continued)
Chemical Analysis of the Wastes 69
Waste Characteristics Related to Soil Treatment 70
Statistical Considerations 73
Immobilization of Chemical Constituents as Related to
In Situ Treatment 73
Inorganics 73
Fate of Metals in Soils 78
Solution Chemistry 80
Solid Phase Formation 81
Heavy Metal Complexation in Soil Solution 82
Computer Simulation of the Soil Solution 87
Solid-aqueous Interface Exchange (Outer
Sphere Complexes) - 88
Specific Adsorption (Inner Sphere Complexes) 89
Factors Affecting Sorption 89
Oxidation-reduction 95
Soil Sorption - Organics 107
Ionic Compounds 112
Nonionic Compounds 119
Quantitative Description of Adsorption 125
Factors Affecting Sorption 134
Soil Microbiological Factors Related to In Situ
Treatment 138
The Soil Microbial Ecosystem 138
Biogeochemistry of Toxic Metals and Metalloids 144
Decomposition of Xenobiotic Organic Compounds 148
Quantitative Description of Organic Decomposition 157
Initial Concentration 160
Temperature 160
Moisture Content 166
Chemical Reactions in the Soil Matrix 167
Introduction 167
Effects of Waste Type on Soil Properties 168
Desorption 175
Soil Catalysis 178
Polymerization 180
VI
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CONTENTS (Continued)
Modeling the Behavior of Waste Constituents in
Soil Systems 180
Transport Models 180
Limitations 187
Atmospheric Aspects of In Situ Treatment:
Volatilization and Photodegradation 190
Volatilization of Organics 190
Factors Controlling Contaminant Volatilization 202
Compound Photoreactivity 204
References 212
Appendix A. Parameters for Assessing Soil/Waste
Interaction 246
Appendix B. Glossary 358
Copyright Notice 365
VI 1
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FIGURES
Page
Processes influencing the migration of hazardous con-
stituents in the terrestrial environment 14
3-2 USDA soil textural classification 26
3-3 A hypothetical soil profile illustrating the common soil
horizons 31
3-4 Diagrammatic definition and location of various types of
soil structure 35
3-5 Weathering pathways which take place under moderately acid
conditions common in humid temperature regions 38
3-6 General relationship between particle size and kinds of
minerals present 39
3-7 (a) Single silica tetrahedron, (b) Sheet structure of
silica tetrahedrons arranged in a hexagonal network 40
3-8 (a) Single octahedral unit, (b) Sheet structure of
octahedral units 40
3-9 Sketch showing an edge view of the crystal structure of
a 1:1 and a 2:1 type clay mineral 41
3-10 Relationships in mineral soils between pH and the activity
of microorganisms and the availability of plant nutrients 46
3-11 Soil-water characteristic curves for several soils 50
3-12 Typical water-holding capacities of different textured soils 51
3-13 Frequency of occurrence of inorganic constituents in soil
at FIT sites 77
3-14 Principal controls on free trace metal concentrations in
soil solutions 80
3-15 The solubility of various lead oxides, carbonates, and
sulfates when S0|- and Cl~ are 10"3 M and C02 is 0.003
atm or as specified 83
vm
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LIST OF FIGURES (Continued)
Page
3-16 The solubility diagram for Pb in Nibley clay loam soil 83
3-17 The solubility diagram for Cd in Nibley clay loam soil 84
3-18 Breakthrough curves for Cd as affected by Cl~ and CIC^' ions 85
3-19 Breakthrough curves for Cu as affected by Cl~ and C104" ions 86
3-20 Breakthrough curves for Ni as affected by Cl~ and C104" ions 86
3-21 Solubility of CuO as a function of log H+ (25°C., I = 0,
log PC02 = -3-52) 87
3-22 The pH-dependent speciation of Cd in: (a) the absence of
organic ligands Ox°, and (b) the presence of 3.5 x 10~4
M Ox - 92
3-23 Cadmium binding as a function of pH 93
3-24 Cu2+ adsorption isotherms on Lansing and Mardin A horizon
soils in the absence and presence of 0.01M CaCl2 94
3-25 Langmuir adsorption isotherm for Cu2+ adsorption on the
Lansing A soil 96
3-26 Typical adsorption isotherm for metals and soil 96
3-27 Nickel sorption by Glendale soil, 0.01N CaCL2 97
3-28 Zero point of charge (pzc) on an iron hydrous oxide 101
3-29 Eh-pH diagram of Cr species in water at 25°C calculated 102
3-30 Sorption of Cr(VI) on NaOH-extracted soil 102
3-31 Concentration of Cr(III) in 24-hour equilibrium solutions
as a function of pH (HCl-CaC03) and presence of Marlow
Ap soil 103
3-32 The amount of As(V) removed from DuPage leachate solutions
by kaolinite and montmori1lonite at 25°C plotted as a
function of pH 105
3-33 Diagram showing distribution of forms of As(V) 105
3-34 The amount of As(III) removed from DuPage leachate solutions
by kaolinite and montmorilloriite at 25°C plotted as a
function of pH 107
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LIST OF FIGURES (Continued)
Page
Stable fields of selenium 108
The amount of Se(IV) removed from DuPage leachate solutions
by kaolinite and montmorillonite at 25°C, plotted as a
function of pH 109
3-37 Solubility diagram for the ferric selenites, and the
solubility data obtained from 1:10 soil-O.OlM Ca (1^3)2
extracts of several soils 110
3-38 Effect of pH on adsorption of four related s-triazines
on (top) Na-montmori 11 on ite and (bottom) soil organic
matter 115
3-39 Classification of adsorption isotherms 128
3-40 Isotherms for adsorption of several cationic pesticides
on (top) Na-montmori llonite, (center) Na-kaol in ite,
(bottom) soil organic matter 128
3-41 Extent of sorption as a function of soil moisture 9 and kj 131
3-42 Linear transforms of adsorption isotherms 134
3-43 Errors introduced by the assumption that adsorption
desorption isotherms are singular when they are
nonsingular 138
3-44 Evolution of C02 from Core Creek soil suspensions
amended with [^Cjmalathion 152
3-45 Evolution CQ,, from tobacco field soil suspensions 152
3-46 Schematic description of "two compartment" model 160
3-47 Disappearance of total chemical for different sizes of
bound residue reservoir, i.e., k^ (binding)/k_i
(unbinding) = R 161
3-48 Rates of transformation of PNA compounds in soil as a
function of initial soil concentration 162
3-49 Effect of climatic conditions at major refinery locations
on the annual pattern of oil decomposition 167
3-50 Influence of exchangeable sodium percentage on the
hydraulic conductivity of a clay loam 172
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LIST OF FIGURES (Continued)
Page
Desorption of fensulfothion from four soils 177
Desorption of fensulfothion sulfide from four soils 178
Soil-water characteristic relating the volumetric water
content 0 to the matric potential 4>m 182
3-54 Frequency distribution of values of the pore-water
velocity for a class length of 10 cm day~l 182
3-55 Frequency distribution of values of the apparent diffusion
coefficient D for a class length of 20 cm? dayl 182
3-56 Calculated relative effluent concentrations for a
nonadsorbed solute 189
3-57 Fraction of contaminant remaining versus dimensionless
time 198
XI
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TABLES
Table Page
2-1 Requirements of a Complete Monitoring Program 3
2-2 Equipment for Field Collection of Soil Samples 4
2-3 Soil-Pore Liquid Sampling Devices 6
2-4 Groundwater Sampling Methods 7
2-5 Cost Estimates for Various Monitoring Techniques and
Construction Methods in the Zone of" Saturation 8
3-1 Landforms and Topography of Hazardous Waste Sites as
Related to Potential for Migration of Hazardous
Constituents 16
3-2 Site and Soil Characteristics Identified as Important
in In Situ Treatment 19
3-3 Major Divisions, Soil Type Symbols, and the Descriptions
for the Unified Soil Classification System (USCS) 20
3-4 Descriptions of Soils in the Highest (Most General)
Categories of the Present USDA Classification System 22
3-5 Orders in the Present USDA Soil Classification System and
Approximate Equivalents in the 1938 USDA System 25
3-6 U.S. Department of Agriculture (USDA) and Unified Soil
Classification System (USCS) Particle Sizes 26
3-7 Corresponding USCS and USDA Soil Classifications 27
3-8 Corresponding USDA and USCS Soil Classifications 28
3-9 Information That Can Be Inferred from the USDA Soil
Classification System, Using the Order Mollisol as
an Example 30
3-10 Suitability of Various Textured Soils for Land Treatment
of Hazardous Industrial Wastes 34
xi
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LIST OF TABLES (Continued)
Table
3-11 Average Mineralogical Composition of Igneous and
Sedimentary Rocks 37
3-12 The Size, Number, and Surface Area of Soil Particles 38
3-13 Summary of Characteristics of Soil Colloids 42
3-13a Oxygen-Containing Functional Groups in Humic Substances 44
3-14 Succession of Events Related to the Redox Potential
Which Can Occur in Waterlogged Soils, or Poorly
Drained Soils Receiving Excessive Loadings of
Organic Chemical Wastes or Crop Residues 47
3-15 Essential Elements for Biological Growth 48
3-16 Permeability Values for Soils Classified in the Unified
Soil Classification System 53
3-17 Factors Affecting Erosion of Soil by Wind 57
3-18 Important Receiver Characteristics 60
3-19 Maximum Concentration of Contaminants for Characteristic
of EP Toxicity 65
3-20 Method for Determination of Microbial Toxicity of a
Waste/Soil Mixture 68
3-21 Types of GC Detectors 70
3-22 Methods for Analyzing Waste Constituents Important to
In Situ Treatment 71
3-23 Soil-Based Waste Characterization 74
3-24 Basic Statistical Terminology Applicable to Sampling
Plans for Solid Wastes 75
3-25 List of Inorganic Priority Pollutants 77
3-26 Percent Occurrence of Inorganics in Soils--Superfund
and Nonsuperfund sites 78
3-27 Content of Various Elements in Soils (Lindsay 1979)
and in Fit Sites 79
XT 1
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LIST OF TABLES (Continued)
Table Page
3-28 Industrial Use of Selected Metals 79
3-29 Some Probable Bivalent Metal Complexes with Inorganic
Ligands in Soil Solutions 85
3-30 Estimated Values of Log ciq and Log c<2 88
3-31 Stability Constants for Cl Complexes to Ni(II), Cu(II),
and Cd(II) 91
3-32 Overall Stability Constants of Cd Complexes 92
3-33 Effect of pH on Probable Solution Percent Composition
of Different Ion Species 94
3-34 Calculated Langmuir Parameters from Soil Adsorption
of Cu2+ and Cd?+ 97
3-35 Freundlich Parameters and Correlation Coefficients for
Sorption of Ni in 0.01N CaCl2 by 12 Soils 99
3-36 Freundlich Parameters for Sorption of Ni in Different
Ca Solutions by Four Soils 99
3-37 Freundlich Parameters for Sorption of Zn in 0.01N CaCl2
by the Soils Studied 100
3-38 Percent of Applied Hg Evolved from Soils Within 144
Hours 104
3-39 Properties of Basic Pesticides 113
3-40 Properties of Cationic Pesticides 117
3-41 Properties of Acidic Pesticides 118
3-42 Selected Properties of Some Nonionic Pesticides 120
3-43 Equilibrium and Nonequilibrium Models 126
3-4/l Koc Relationships with Solubility and Octanol-Water
Partition Coefficient 133
3-45 Selected Physical Properties of Soil Constituents 136
3-46 Persistence of Polynuclear Aromatic Hydrocarbons in
Natural Waters 153
xiv
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LIST OF TABLES (Continued)
Table Page
3-47 Pesticides Included as Constituents of Hazardous Waste 154
3-48 Kinetic Parameters Describing Rates of Degradation of
Aromatic Compounds 163
3-49 Industrial Categories Generating Acidic Waste Constituents 169
3-50 Effect of Organic Acids on Clay Solubility 170
3-51 Classification of Salt-Affected Soils 171
3-52 Critical SAR Values for Soil 172
3-53 Response of Soil Microbial Populations to Application of
Solvents 172
3-54 Dielectric Constants, Densities and Water Solubilities
of Various Halogenated and Nonhalogenated Solvents 174
3-55 Effect of Organic Solvent in Clay Permeability 174
3-56 Sorption of Halogenated Organics on Soil and Clay 175
3-57 Adsorption of Surfactants on Montmorillonite 176
3-58 Properties of Soil Adsorbents 177
3-59 Boundary Conditions for the Transport Equation 183
3-60 Representative Values of Hydraulic Parameters 189
3-61 Hazardous Chemical Vapors Detected at Uncontrolled
Hazardous Waste Sites 191
3-62 Pesticide Photochemical Reactions in the Vapor-Phase 208
3-63 Rate Constants for the Hydroxide Radical Reaction in
Air with Various Organic Substances, KQH° in Units of
/Mole-Sec 210
xv
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SECTION 1
INTRODUCTION
To support the methodology presented in Volume 1 monitoring information
and data on the behavior and fate of hazardous constituents in soil systems
are presented here in Volume 2 of the Manual. This additional information is
intended to provide the manual user with more information and background
material for making more complex decisions and analyses concerning site,
soil, and waste interactions than can be presented in Volume 1.
Section 2, "Monitoring," includes a discussion of the factors required
for a comprehensive and effective monitoring program including soil care,
soil pore liquid, unsaturated zone, groundwater and atmosphere sampling. A
monitoring program is necessary to assure that the objectives of the in-place
treatment program are being met.
Section 3, "Characterization and Evaluation of Fundamental Processes
in Soil/Waste Systems," presents information on the behavior and fate of
hazardous constituents in soil systems. The information presented served
as a basis for selecting treatment techniques and developing the methodology
for in-place treatment. Elements of soil/waste systems considered included
site and soil factors important in influencing in-place treatment, soil
mobilization processes for leaching and volatilization control, biodegradation
processes and transformation processes. A brief discussion addressing the
modeling of waste constituents in soil systems is presented.
The Appendix provides compound properties and adsorption, degradation
and volatilization parameters for various chemical compounds. A glossary
of terms is also included.
The information in Volume 2 represents an effort to present the manual
user with the most current information and research activities that directly
or indirectly influence the in-place processes and treatment techniques.
The topics addressed present areas of critical concern and provide fundamental
principles for characterizing the basic processes in soil/waste systems.
Since most in-place treatment techniques have not been thoroughly tested, the
information in Volume 2 will provide the background or framework for planning
and interpreting in-place treatment techniques specifically addressed in
Volume 1.
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SECTION 2
MONITORING
INTRODUCTION
During the execution of an in situ remedial action, the primary ob-
jectives are to prevent off-site migration of hazardous constituents via
migration to ground or surface waters or transmission through the atmosphere,
as well as to render the wastes nonhazardous through degradation, detoxifica-
tion, or immobilization. To assure that these objectives are being met, a
monitoring program must be established.
Specific objectives of a monitoring program are to: (K. W. Brown and
Associates 1980, U. S. Environmental Protection Agency 1983):
1. Assure that the hazardous or toxic constituents of the waste are
being degraded, detoxicated, or inactivated as planned.
2. Monitor degradation rates of degradable constituents.
3. Assure that waste constituents are not entering runoff or leachate
water and leaving the area in unacceptable concentrations.
4. Determine whether adjustments in treatment management are needed
to maintain the treatment process (e.g., Is soil pH within desirable range?
Are adequate nutrients available for biological degradation of organic con-
stituents? Does soil moisture require adjustment? Are additional chemical
amendments needed to complete chemical treatment of the wastes?).
A complete monitoring program would include the media listed in Table
2-1. The waste constituents to be monitored in the various media are those
determined to be hazardous in the initial site/waste characterization study as
well as expected important degradation or transformation products. Nonhazard-
ous constituents and/or their transformation/degradation products and soil
properties which might affect treatment processes should also be monitored.
The monitoring program may include substances which are required for treat-
ment, whether native to the soil or added as a treatment agent.
STATISTICAL CONSIDERATIONS
A limitation in field sampling is the large number of samples required to
ensure that tne measured mean value of a particular parameter is within a
given range of a true value (Wilson 1980). This limitation is due to the
natural spatial variability of soil properties. It is therefore necessary to
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TABLE 2-1. REQUIREMENTS OF A COMPLETE MONITORING PROGRAM
(ADAPTED FROM U.S. ENVIRONMENTAL PROTECTION AGENCY 1983)
Media to be Monitored Purpose
Soil in the treatment zone Determine extent of degradation, trans-
formation, and immobilization pH and
nutrient status, and any other factors or
substances affecting treatment execution
and effectiveness.
Soil cores (unsaturated zone) Determine slow movement of hazardous
constituents.
Soil-pore liquid in the Determine highly mobile constituents.
unsaturated zone
Groundwater Determine mobile constituents.
Runoff water Determine -migration off-site of soluble,
suspended, or adsorbed constituents.
Air Determine personnel and population
health hazards.
take a significant number of replicate samples which are representative of the
area being sampled. Realistic, unbiased data are required so that valid
comparisons can be made between the values of monitored parameters and back-
ground values.
The hazardous waste site should be divided into uniform areas for sampl-
ing purposes. These areas may be according to soil series or to phases based
on surface texture within a series. If known "hot spots" of wastes or signi-
ficant differences in types of wastes occur at the site, these areas should
also be monitored separately. For each medium sampled, appropriate background
sampling sites should be monitored.
Guidelines for statistical sampling procedures within the selected
areas are given in Hazardous Waste Land Treatment (U. S. Environmental
Protection Agency 1983) arid Test Methods for Evaluating Solid Waste (U.S.
Environmental Protection Agency 1982c).Professionals who may be consulted
for assistance may include certified professional soil scientists, statisti-
cians, and environmental analytical chemists.
SOILS SAMPLING IN THE TREATMENT ZONE AND IN
THE UNDERLYING UNSATURATED ZONE
Soil cores and borings are used to measure the vertical movement of
waste constituents as well as to determine the progression of treatment
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in the soil treatment zone. Soil core sampling in the treatment zone is
used as a management tool. The extent of treatment (i.e., degradation,
transformation, and/or immobilization) of the hazardous constituents can
be monitored as well as factors which may affect the execution of the treat-
ment, such as nutrients and pH. Soil core sampling below the treatment zone
is used to determine whether significant concentrations of hazardous constitu-
ents are moving below the treatment zone. If unacceptable leaching of con-
taminants is occurring, contingency plans should provide means to prevent
groundwater contamination, such as the use of a grout bottom seal.
Soil sampling methods used by soil scientists and irrigation and drainage
engineers to evaluate physical properties of soils are also suitable for
determining chemical constituents in the upper layers of soils (Wilson 1980).
Several types of equipment which have been used are listed in Table 2-2. The
split spoon sampler is a barrel-type auger, with one side which pivots on a
hinge. A tube-type sampler consists of a tube bevelled and sharpened on one
end to aid insertion in the soil. A drive hammer is used to force the tube to
the desired depth, and an intact soil core is removed from the tube.
Wilson (1980) identified several problems associated with the use of
soil samplers. With augers and tube-type samplers, dry soil may fall out
of the unit when it is withdrawn from the soil, which requires the use of
a core catcher. Also, if a soil is wet, chemical interactions occurring
between the soil water and metal parts of the sampler may introduce metal
contamination into the sample. Contamination is an especially important
problem in the case of organic chemicals and microorganisms. Techniques
for microbial sampling have been described by Bordner, Winter, and Scarpino
(1978) and for organic and microbial sampling by Dunlap et al. (1977). One of
the most promising methods appears to be the use of a combination auger/dry
tube corer technique. A hole is augered to the top of the desired sampling
depth; then the soil is sampled with a core sampler forced into the sampling
region. Wilson (1980) suggests that a lucite plastic insert in the dry tube
coring barrel would minimize contamination with metals.
TABLE 2-2. EQUIPMENT FOR FIELD COLLECTION OF SOIL SAMPLES
(WILSON 1980)
Hand-driven Equipment Power-driven Equipment
Screw-type auger Continuous flight power auger
Post-hole auger (hollow-stemmed)
Barrel auger Core sampler
Dutch auger Bucket auger
Split-spoon sampler Cable-tool drill rig
Tube-type sampler Rotary drill rig
Auger/dry-tube corer
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Soil samples from lower soil depths are more easily obtained by the use
of powered coring or drilling equipment. The U.S. Environmental Protection
Agency (1983) suggest^, that even for samples at shallower depths, powered
equipment may be less ctly due to clean, minimally disturbed samples for
analysis.
Several types of p .--driven sampling units are listed in Table 2-2.
Coring type machines are generally more desirable than drilling rigs since the
addition of water during the drilling operation, to remove cuttings and in
some cases mud to hold open the hole, may change the soil water chemistry and
may result in sample contamination. Air rotary drilling rigs, which use air
to bring cuttings to the surface, do not have the problem of contamination.
Spiral type augers, unless hollow-stemmed (which allows for the insert of a
core sampler), are not recommended because of difficulty in determining the
depth the sample was taken (Wilson 1980).
After soil core sampling, holes should be backfilled with native soil
(compacted to field bulk density), clay slurry, or other suitable materials in
order to prevent the channelling of hazardous constituents down the holes
U.S. Environmental Protection Agency 1983).
Procedures for handling, preserving, and shipping soil solids samples may
be found in Test Methods for Evaluating Solid Waste (U.S. Environmental
Protection Agency 1982c).
SOIL PORE LIQUID SAMPLING IN
THE UNSATURATED ZONE
Water added to a site by precipitation or irrigation while percolating
through the treatment zone may rapidly transport some mobile hazardous con-
stituents or transformation products through the unsaturated zone to the
groundwater (U.S. Environmental Protection Agency 1983). The purpose of
soil-pore liquid monitoring is to detect these rapid pulses of contaminants.
Heavy precipitation, snow melt, and irrigation events are often responsible
for such pulses, and sampling periods should be scheduled to correspond to
such events. Soil texture and structure and other soil properties, as they
affect infiltration and percolation rates, also determine to what extent
precipitation events cause rapid water movement in a particular soil and can
be used as predictive tools to schedule sampling events.
Soil pore liquid sampling may also indicate the amount of materials
leaching to the groundwater. Samples of groundwater do not provide this
information due to the diluting effect of the groundwater. In addition,
analysis of the soil pore liquid can provide an early warning signal that
remedial action is required for the management of the treatment process.
Since water in the unsaturated zone is held under negative pressure
(suction), wells and open cavities cannot be used to collect the flowing
water. Therefore samplers in the unsaturated zone are called suction sampling
devices. A summary of various types of suction samplers are presented in
Table 2-3. The reader is referred to Wilson (1980) for a comprehensive
discussion of these samplers.
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TABLE 2-3. SOIL-PORE LIQUID SAMPLING DEVICES (WILSON 1980;
Sampl ing devices
A. Ceramic-type samplers
1. Suction cup
a. Vacuum-operated soil-water samplers
b. Vacuum-pressure samplers
c. Vacuum-pressure samplers with check valves
2. Filter candle
B. Cellulose-acetate hollow fiber samplers
C. Membrane filter samplers
WATER SAMPLES FROM THE SATURATED ZONE
(i.e., groundwater)
Groundwater sampling will indicate whether hazardous waste constitu-
ents have indeed migrated to the groundwater and may present a public health
hazard, depending on the hydrogeological characteristics and uses of the
groundwater system. If contamination has occurred and is deemed unacceptable,
provisions must be made to recover and treat or otherwise handle the contami-
nated groundwater.
Sophisticated groundwater sampling equipment and procedures are not
desirable for monitoring programs (U. S. Army Corps of Engineers 1982).
Rather, to ensure long-term, efficient operation of the monitoring system, the
devices should be simple, rugged, foolproof, and operable by trained, but not
necessarily educationally skilled personnel (Vanhoff, Weyer, and Whitaker
1979). In Table 2-4, a list of saturated zone sampling methods and sample
extraction techniques are given. Again, the reader is referred to Wilson
(1980) for a discussion of these methods. In addition, the U. S. Environ-
mental Protection Agency (1983) has suggested the following documents as
sources of information on groundwater monitoring:
1. Manual of Ground-Water Sample Procedures (Scalf et al. 1981):
2. Ground-Water Manual (U.S. Department of the Interior, Bureau of
Reclamation 1977);
3. Procedures Manual for Ground-Water Monitoring at Solid Waste Disposal
Facilities (U.S. Environmental Protection Agency 1977);
-------
CUSTOMER MEMO
Dear Colleague,
In this issue, Digest focuses its attention on scientific and technical information from
abroad.
NTIS has just concluded an agreement with the Japan Information Center of Science
and Technology (JICST) to make available, in English, a catalog listing some 16,000
science and technology research projects currently ongoing in Japan. The sponsoring
institutions and researchers' names are provided to give interested individuals an
opportunity to communicate directly with their Japanese counterparts. In addition, NTIS
has just negotiated to distribute a quarterly JICST bulletin which summarizes (abstracts)
the results of Japanese electronics research. The ad on page 10 lists reports from JICST on
renewable energy resources.
Featured inside are foreign technology reports acquired by NTIS' Office of
International Affairs. These items, arranged by subject category, illustrate the wide range
of research available as the result of an extensive foreign acquisition program.
For more information on the above products and reports, please write to Mr. David
Shonyo, Director, Office of International Affairs, Springfield, VA 22161.
The HOTLINE section, on page 15, features reports from the International Food Policy
Research Institute (IFPRI).
Trade Press reports, including one published by the International Trade Administration,
are described on page 9.
An ad on The Role of Metrics in U.S. Exports appears on page 11.
Other sections and ads in Digest cover various products and reports. For example,
Database News, on page 17, announces the availability of new data files from the Energy
Information Administration (El A) as well as updates to others previously highlighted.
Also, new data files from the National Center for Health Statistics (NCHS) and the
Defense Logistics Supply Center (DLSC) are listed. Six new titles of data files available
on floppy diskettes are also cited.
If you have any questions or recommendations about Digest, please let me know.
Sincerely,
Lois Grooms
Editor
-------
The following listing of current and recent research from
worldwide sources reflects the growing stream of foreign
technology flowing to NTIS. These reports are the positive
results produced by an aggressive NTIS Foreign Technol-
ogy Acquisition Program administered by the NTIS Office
of International Affairs. This program is designed to be
responsive to the information needs of U.S. industry by
acquiring targeted foreign technology. Telephone David
Shonyo, (703) 487-4822, if you have any questions.
Aeronautics
Deregulation of Air Transport: A Perspective on the
Experience in the United States.
Civil Aviation Authority, London (England). 1984. 69pp.
PB84-230630/CAO PC$11.50/MF$11.50
Methodology of Runway Capacity Assessment — A
Summary Paper.
Civil Aviation Authority, London (England). 1983. 23pp.
PB84-204403/CAO PC$9.50/MF$9.50
Evaluation of a Mobile Aerodynamic Test Facility for Hang
Glider Wings.
Cranfield Inst. of Tech. (England). Nov. '83, 125pp.
PB84-170315/CAO PC$15.50/MF$15.50
Biological & Medical Sciences
Health and Safety in the Plastics and Rubber Industries 2,
Conference Held at University of York on April 16-17,
1984.
Plastics and Rubber Inst., London (England). 1984. 179pp.
PB84-232768/CAO PC$21.50/MF$21.50
Technological Forecasting for Downstream Processing in
Biotechnology. Phase I. Intermediate Forecast Report.
Commission of the European Communities, Luxembourg.
1982. 87pp.
PB83-200576/CAO PC$13.50/MF$13.50
Technological Forecasting for Downstream Processing in
Biotechnology. Phase II. Process and Unit Operation
Needs. FAST Series No. 7.
Commission of the European Communities, Luxembourg.
1983. 121pp.
PB84-214980/CAO PC$15.50/MF$15.50
Safety Aspects of Storage, Handling and Use of Chlorine
and Sulphur Dioxide.
National Joint Health and Safety Committee for the Water
Service, London (England). Apr. '82, 54pp.
PB84-167907/C AO PC$ 11.50/MF$ 11.50
Guidelines for Recording Industrial Hygiene Data.
CONCAWE, The Hague (Netherlands). 1983. 27pp.
PB84-128842/CAO PC$11.50/MF$11.50
International Symposium on Protection Against Chemical
Warfare Agents Held at Stockholm, Sweden on June 6-9,
1983.
Foersvarets Forskningsanstalt, Umea (Sweden). Aug. '83,
123pp.
PB84-109586/CAO PC$15.50/MF$6.50
Science and Technology for Aquaculture Development
National Board for Science and Technology, Dublin
(Ireland). 1982. 177pp.
PB84-109222/CAO PC$23.50/MF$23.50
Civil Engineering
Aerobic Thermophilic Digestion of Sludge Using Air —
Full Scale Operation.
Electricity Council Research Centre, Capenhurst (England).
Mar. '84, 33pp.
PB84-202019/CAO PC$11.50/MF$11.50
Sludge Treatment Plant for Waterworks.
Water Research Centre, Stevenage (England). 1983. 83pp.
PB84-201771/CAO PC$19.50/MF$19.50
How to Design Sewage Sludge Pumping Systems.
Water Research Centre, Stevenage (England). 1983. 90pp.
PB84-201755/CAO PC$19.50/MF$19.50
Polyelectrolyte Users' Manual.
Water Research Centre, Stevenage (England). 1983. 58pp.
PB84-201748/CAO PC$17.50/MF$17.50
Quantification of Sewage Odours.
Queensland Univ., Brisbane (Australia). Jan. '83, 45pp.
PB84-116169/CAO PC$11.50/MFS6.50
Communications Technology
Implementation Strategies for Digital Signal Processing
Systems.
Helsinki Univ. of Technology, Espoo (Finland). Mar. '84,
90pp.
PB84-214303/CAO PC$13.50/MF$6.50
Formalism for the Design and Evaluation of Parallel Signal
Processing Systems.
Helsinki Univ. of Technology, Espoo (Finland). Apr. '84,
165pp.
PB84-214253/CAO PC$19.50/MF$6.50
DFSP: A Data Flow Signal Processor.
Helsinki Univ. of Technology, Espoo (Finland). Jun. '83,
51pp.
PB84-112135/CAO PC$11.50/MF$6.50
Network Reliability — A Brief Introduction.
Norges Tekniske Hoegskole, Trondheim (Norway). Jan
'83, 25pp.
PB84-109792/C AO PC$9.50/MF$9.50
Computers
Proteus Distributed Database System.
Kent Univ., Canterbury (England). 1984. 23pp.
PB84-234350/CAO PC$9.50/MF$9.50
Real-Time Languages for Process Control.
Warren Spring Lab., Stevenage (England). 1984. 90pp.
PB84-234319/CAO PC$15.50/MF$15.50
Uniform User Interface for Modular Pascal Operating
Systems.
Groningen Rijksuniversiteit (Netherlands). Apr. '84,
124pp.
PB84-215896/CAO PC$15.50/MF$6.50
Large-Dictionary, On-Line Recognition of Spoken Words.
Helsinki Univ. of Technology, Espoo (Finland). 1983.
68pp.
PB84-214246/CAO PC$11.50/MF$6.50
LispKit Manual. Volume 1.
Oxford Univ. (England). 1983. 129pp.
PB84-204874/CAO PC$17.50/MF$17.50
-------
LispKit Manual. Volume 2. (Sources).
Oxford Univ. (England). 1983. 140pp.
PB 84-204882/C AO PCS 17.50/MF$ 17.50
Interfacing UNIX to Data Communications Networks.
Newcastle upon Tyne Univ. (England). 1983. 41pp.
PB84-205996/CAO PC$11.50/MF$11.50
Practical Fault Tolerant Software for Asynchronous Sys-
tems.
Newcastle upon Tyne Univ. (England). 1983. 10pp.
PB84-205970/CAO PC$9.50/MF$9.50
IBM to Cambridge Ring Interface.
Science and Engineering Research Council, Chilton
(England). 1984. 49pp.
PB84-205228/CAO PC$11.50/MF$11.50
Notes on Communicating Sequential Processes.
Oxford Univ. (England). 1983. 157pp.
PB 84-204817/C AO PC$ 19.50/MF$ 19.50
Converting to ADA Packages.
National Physical Lab., Teddington (England). 1984. 23pp.
PB84-203892/CAO PC$9.50/MF$9.50
Guidelines for the Design of Large Modular Scientific
Libraries in Ada.
National Physical Lab., Teddington (England). 1984.
154pp.
PB84-203808/CAO PC$19.50/MF$19.50
Abstract Machine Support for Purely Functional Operating
Systems.
Oxford Univ. (England). 1983. 46pp.
PB84-202316/CAO PC$11.50/MF$11.50
Colour Order Systems for Computer Graphics. I. Trans-
formation of NCS Data into CIELAB Colour Space.
Foersvarets Forskningsanstalt, Stockholm (Sweden). Jan.
'84, 93pp.
PB84-179688/CAO PC$13.50/MF$6.50
Personal Computers in Japan: The Most Up-to-Date
Information on Japanese Computer Industries.
PB Co. Ltd., Tokyo (Japan). Dec. '83, 127pp.
PB84-176510/CAO PC$25/MF$25
Annotated Bibliography of Recent Publications on Data
Security and Cryptography (6th).
National Physical Lab., Teddington (England). 1983. 33pp.
PB84-169168/CAO PC$11.50/MF$11.50
Newcastle Connection or UNIXes of the World Unite.
Newcastle upon Tyne Univ. (England). 1982. 24pp.
PB84-160571/CAO PC$9.50/MF$9.50
Programs for Handling RC-Coded Images.
Foersvarets Forskningsanstalt, Stockholm (Sweden). Dec.
'83, 47pp.
PB84-158260/CAO PC$11.50/MF$6.50
Computer Communications Projects.
Leeds Univ. (England). Dec. '81, 27pp.
PB84-145200/CAO PC$11.50/MF$11.50
Networking Standards: A Comparison.
Leeds Univ. (England). 1983. 35pp.
PB84-144385/CAO PC$11.50/MF$11.50
Distributed Secure System.
Newcastle upon Tyne Univ. (England). 1982. 50pp.
PB84-141126/CAO PCS 11.50/MF$11.50
Unknotting Fortran.
Kent Univ., Canterbury (England). Oct. '83, 14pp.
PB84-139047/CAO PC$9.50/MF$9.50
Verification of Secure Systems.
Newcastle upon Tyne Univ. (England). 1982. 76pp.
PB84-138718/CAO PC$13.50/MF$13.50
Construction Engineering & Materials
Comparative Evaluation of Insulating Sealed Glass Units.
Ontario Ministry of Municipal Affairs and Housing,
Toronto (Canada). Jan. '84, 79pp.
PB84-210582/CAO PC$13.50/MF$6.50
CIRIA (Construction Industry Research and Information
Association) Guide to Concrete Construction in the Gulf
Region.
Construction Industry Research and Information Associa-
tion, London (England). 1984. 108pp.
PB84-203504/CAO PC$112.50/MF$112.50
Site Investigation Manual.
Construction Industry Research and Information Associa-
tion, London (England). 1983. 148pp.
PB84-203488/CAO PC$27/MF$27
Use of Waste Materials from Coal Combustion in Road
Construction.
Statens Vaeg- och Trafikinstitut, Linkoeping (Sweden).
1984. 311pp.
PB84-172006/CAO PC$34.50/MF$34.50
Development and Use of Composite Fibrous Materials and
Structures: A Construction Survey.
Sydney Univ. (Australia). Feb. '83, 32pp.
PB84-170513/CAO PC$11.50/MF$6.50
High Performance Roofing Systems (Conference, 1 March
1984).
Plastics and Rubber Inst., London (England). Mar. '84,
98pp.
PB84-178243/CAO PC$13.50/MF$13.50
Preliminary Investigation of Test Methods for the Assess-
ment of Strength of in Situ Concrete.
Cement and Concrete Association, Slough (England).
1982. 40pp.
PB84-162031/CAO PC$11.50/MF$11.50
Fire and Plastics in Buildings.
National Building Research Inst., Pretoria (South Africa).
1982. 18pp.
PB84-126648/CAO PC$9.50/MF$6.50
Make Your Home a Quiet Refuge.
National Building Research Inst., Pretoria (South Africa).
1982. 14pp.
PB84-126291/CAO PC$9.50/MF$6.50
Waffle Shells for Roof and Floor.
Structural Engineering Research Centre, Madras (India).
Oct. '81, 65pp.
PB84-125814/CAO PC$13.50/MF$13.50
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Earth Sciences
RTRSOC (Real Time Reporting System on Oceanic
Conditions) Concept of Space Station Missions.
RTRSOC Concept Study Group, Tokyo (Japan). 1984.
304pp.
PB84-238807/CAO PC$25/MF$25
Applications of Remote Sensing Techniques to Oceanog-
raphy and Sea Ice.
Foersvarets Forskningsanstalt, Stockholm (Sweden). Apr.
'84, 16pp.
PB84-231208/CAO PC$9.50/MF$6.50
Algorithm to Compute the Geoid Surface.
Institute of Oceanographic Sciences, Birkenhead (Eng-
land). 1983. 22pp.
PB84-204288/CAO PC$9.50/MF$9.50
Contour-To-Grid Transformation: Development of a
Method for Generation of a Sparse Grid Structure Out of
Terrain Elevation Contours.
Foersvarets Forskningsanstalt, Stockholm (Sweden). Dec.
'83, 35pp.
PB84-158237/CAO PC$11.50/MF$6.50
Rock Dynamics.
Stiftelsen Svensk Detonikforskning, Stockholm (Sweden).
1983. 21pp.
PB84-127042/CAO PC$9.50/MF$6.50
Electronics
Modelling the MOSFET Using ASTAP (Advanced Statis-
tical Analysis Program).
Science and Engineering Research Council, Chilton
(England). 1984. 51pp.
PB84-204478/C AO PC$ 11.50/MF$ 11.50
Digital Filters and Reverberation Time Measurement.
Bradford Univ. (England). Jul. '83, 83pp.
PB84-163104/CAO PC$13.50/MF$13.50
Computer-Aided Design of Microstrip Hybrid Signal
Dividers.
Bradford Univ. (England). Jul. '83, 31pp.
PB84-163096/CAO PC$11.50/MF$11.50
Characterization of Microstrip Fixtures, a Broad Band
Model for a Microstrip Connector.
Foersvarets Forskningsanstalt, Stockholm (Sweden). Sep.
'83, 47pp.
PB84-130095/CAO PC$11.50/MF$6.50
Impedance Loaded Circular Wire Loop as Receiving
Antenna.
Technische Nogeschool, Delft (Netherlands). Aug. '83,
82pp.
PB84-115500/CAO PC$13.50/MF$6.50
Energy & Fuels
Catalytic Coal Gasification.
International Energy Agency Coal Research, London
(England). 1984. 60pp.
PB84-233238/CAO PC$18/MF$18
International Meeting on Lithium Batteries (2nd) Held at
Paris on April 25-27, 1984.
Centre de Documentation de I'Armement, Paris (France).
Apr. '84, 125pp.
PB 84-222702/C AO PC$ 1 5 . 50/MFS 15.50
Consequences of Limiting Benzene Content of Motor
Gasoline.
CONCAWE, The Hague (Netherlands). 1983. 19pp.
PB84-170240/CAO PC$9.50/MF$6.50
Symposium on Nuclear Heat for High Temperature Fossil
Fuel Processing Held at London, England on 28 April 1981 .
Institute of Energy, London (England). 1981. 82pp.
PB84-167261/CAO PC$19.50/MF$19.50
Survey of the Technological Requirements for High-
Temperature Materials R and D (Research and Develop-
ment). Section 1: Diesel Engines.
Commission of the European Communities, Luxembourg.
1983. 72pp.
PB84- 164524/CAO PC$1 1 .50/MF$1 1 .50
Symposium on Nuclear Heat for High Temperature Fossil
Fuel Processing Held at London, England on 28 April 1981 .
Institute of Energy, London (England). 1981. 82pp.
PB 84- 1 6726 1 /CAO PC$ 1 9 . 50/MF$ 1 9 . 50
Hydrogen Safety Manual.
Commission of the European Communities, Luxembourg.
1983. 520pp.
PB84- 1 63468/CAO PC$43 . 50/MFS43 . 50
Precautionary Advice on the Handling of Motor Gasolines.
CONCAWE, The Hague (Netherlands). 1983. 19pp.
PB84- 15897 1/CAO PC$9.50/MF$6.50
Combustion of Coal Liquid Mixtures.
International Energy Agency Coal
(England). 1983. 54pp.
PB84-138981/CAO PC$18/MF$18
Research, London
Characteristics of Petroleum and Its Behaviour at Sea.
CONCAWE, The Hague (Netherlands). 1983. 56pp.
PB84-132711/CAO PCS11.50/MFS6.50
Waste Utilisation Technologies.
National Board for Science and Technology, Dublin
(Ireland). 1981. 35pp.
PB 84- 1 08976/C AO PCS 1 1 . 50/MF$ 1 1 . 50
Environment
Influence of Wind on the Dust Emission from a Municipal
Refuse Incinerator.
Sheffield Univ. (England). Nov. '82, 18pp.
PB84-233592/CAO PC$9.50/MF$9.50
Wind Tunnel Modelling of Buoyant Plumes.
Oxford Univ. (England). Jan. '84, 252pp.
PB84-203413/C AO PC$28.50/MF$28.50
Field Guide to Inland Oil Spill Clean-Up Techniques.
CONCAWE, The Hague (Netherlands). 1983. 104pp.
PB84-174085/CAO PC$15.50/MF$6.50
Acid Rain and Forest Decline in West Germany.
Forestry Commission, Edenburgh (Scotland). 1983. 17pp.
PB84-162239/CAO PC$9.50/MF$9.50
-------
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HERSHEY CONTRIBUTION TO COMPUTER TYPESETTING TECHNIQUES
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NUTRIENT DATABASE FOR STANDARD REFERENCE
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Industrial Engineering & Manufacturing Technologies
Gas Metal Arc-Narrow Gap Welding.
Valtion Teknillinen Tutkimuskeskus, Espoo (Finland).
1984. 30pp.
PB84-214212/CAO PC$11.50/MF$6.50
Computer Aided Fault Tree Synthesis.
Commission of the European Communities, Luxembourg.
1983. 52pp.
PB84-211689/CAO PC$11.50/MF$11.50
Bridging the CAD-CAM (Computer Aided Design-
Computer Aided Manufacture) Gap for Casting Design —
An Opportunity for the Development of Expert Systems.
University of Wales Inst. of Science and Technology,
Cardiff. 1984. 6pp.
PB84-168178/CAO PC$9.50/MF$9.50
Flexible Manufacturing Systems — Some Guidelines for
the Non-Specialist.
University of Wales Inst. of Science and Technology,
Cardiff. 1984. 8pp.
PB84-167451/CAO PC$9.50/MF$9.50
Study on Evaluation of Print Quality.
Mitsubishi Heavy Industries Ltd., Tokyo (Japan). Nov.
'83, 13pp.
PB84-132026/CAO PC$9.50/MF$6.50
Mini-Seminar on Quality Assurance.
Council for Scientific and Industrial Research, Pretoria
(South Africa). Nov. '82, 66pp.
PB84-125640/CAO PC$11.50/MF$6.50
Analysing Products with Respect to Flexible Assembly
Automation.
Norges Tekniske Hoegskole, Trondheim (Norway). May
'83, llpp.
PB84-109966/CAO PC$9.50/MF$9.50
Role of the Chip-Tool Interface in Machining.
Cambridge Univ. (England). 1982. 13pp.
PB84-107267/CAO PC$9.50/MF$9.50
Important: Please order all reports bv complete Order
Number; e.g., PB85-000000/CAO. See
Order page for order instructions and
options.
A $3 handling charge will apply to all
orders, except subscriptions, standing
orders, and Rush Handling items.
Marine Engineering
Study on Motions of High Speed Planing Boats with
Controllable Flaps in Regular Waves.
Technische Hogeschool. Delft (Netherlands). Apr. '84,
66pp.
PB84-216761/CAO PC$11.50/MF$6.50
Calculation of Sailing Yacht Resistance.
Technische Hogeschool, Delft (Netherlands). Dec. '83,
60pp.
PB84-184266/CAO PC$11.50/MF$6.50
Estimating the Flexibility of Offshore Pile Groups.
Sydney Univ. (Australia). Jan. '83, 28pp.
PB84-116938/CAO PC$11.50/MF$6.50
Development of Hull Forms for RO-RO (Roll-on/Roll-off)
Ships and Ferries.
Statens Skeppsprovningsanstalt, Goeteborg (Sweden).
1983. 34pp.
PB84-107572/CAO PC$11.50/MF$6.50
Materials (Metallic)
Creep Damage Mechanics and Micro mechanisms.
National Physical Lab., Teddington (England). 1984. 32pp.
PB84-236314/CAO PC$11.50/MF$11.50
Special Steels and Systems for Corrosion Prevention in
Reinforced Concrete.
Concrete Society, London (England). 1983. 118pp.
PB84-233915/C AO PC$ 15.50/MF$ 15.50
Fatigue Crack Growth and Fracture Resistance of Steels in
High-Pressure Hydrogen Environments.
Commission of the European Communities, Luxembourg.
1983. 67pp.
PB84-213230/CAO PC$11.50/MF$ 11.50
Development of a Ni-Base Heat Resistant Alloy (TOMIL-
LOY) for Gas Turbine Combustor.
Mitsubishi Heavy Industries Ltd., Tokyo (Japan). 1984.
13pp.
PB84-170265/CAO PC$9.50/MF$6.50
Swedish Symposium on Non-Metallic Inclusions in Steel
Held on 27-29 April, 1981.
Swedish Inst. for Metals Research, Stockholm. 1981.
467pp.
PB83-131292/CAO PC$34/MF$4.5()
Materials (Non-Metallic)
Fibre Reinforced Composites '84 — International Confer-
ence Held at the University of Liverpool on April 3-5,
1984.
Plastics and Rubber Inst., London (England). Apr. '84,
414pp.
PB84-236355/C AO PC$40.50/MFS40.50
Non-Linear Data Fitting for the Analysis of Creep Rupture
Data on GRP Materials in Aggressive Environments.
National Physical Lab., Teddington (England). 1984. 24pp.
PB84-236280/CAO PC$9.50/MF$9.50
Research on the Applications of and Material Resources for
Fine Ceramics.
Research Inst. for Natural Resources, Tokyo (Japan). Jul.
'84, 125pp.
PB84-220045/CAO PC$17.50/MF$6.50
Survey of the Technological Requirements for High
Temperature Materials R and D. Section 2: Composites.
Commission of the European Communities, Luxembourg.
1982. 31pp.
PB84-215136/CAO PC$9.50/MF$9.50
Polymers in Cables. Conference Held at Mere Golf and
Conference Centre, Knutsford, Cheshire on May 18-19,
1983.
Plastics and Rubber Inst., London (England). 1983. 245pp.
PB84-203793/CAO PC$25.50/MF$25.50
Fatigue Damage: Mechanics of Carbon-Fibre Reinforced
Laminates.
-------
Cambridge Univ. (England). Dec. '83, 66pp.
PB84-170133/CAO PC$13.50/MF$13.50
GC-MS Studies on the Pyrolysis of Wood and Lignin.
Helsinki Univ. (Finland). 1982. 10pp.
PB84-157726/CAO PC$9.50/MF$6.50
Fatigue in Polymers: International Conference Held at the
Forum Hotel, London on 29-30 June, 1983.
Plastics and Rubber Inst., London (England). 1983. 175pp.
PB84-142199/CAO PC$19.50/MF$19.50
Polypropylene Fibres and Textiles: International Confer-
ence (3rd) Held at University of York on 4-6 October,
1983.
Plastics and Rubber Inst., London (England). 1983. 424pp.
PB84-142207/CAO PC$37.50/MFS37.50
Polyethylenes 1933-83: Golden Jubilee Conference Held at
Royal Lancaster Hotel, London on 8-10 June, 1983.
Plastics and Rubber Inst., London (England). 1983. 443pp.
PB 84- 142223/C AO PC$37.50/MFS37.50
Energy Conservation — the Use of Foamed and Expanded
Plastics: Conference Held on 6 December 1983.
Plastics and Rubber Inst., London (England). 1983. 71pp.
PB84-142215/CAO PC$11.50/MF$11.50
Carbon Fibre Reinforced Polysulphone for Orthopaedic
Surgical Implants: Proposed Paper for International Confer-
ence on Biomedical Polymers Held at Durham 12-14, July
1982.
National Mechanical Engineering Research Inst., Pretoria
(South Africa). 1983. 17pp.
PB84-124304/CAO PC$9.50/MF$6.50
Resin Development in Advanced Composites.
Foersvarets Forskningsanstalt, Stockholm (Sweden). Sep.
'83, 62pp.
PB84-113539/CAO PC$11.50/MF$6.50
Repair of Ballistically Impacted Carbon Fibre Reinforced
(CFR) Laminates.
Cranfield Inst. of Tech. (England). Nov. '82, 23pp.
PB84-108612/CAO PC$9.50/MF$9.50
Failure Criteria for Timber Subjected to Complex Stress
States Due to Short Term Loading.
Timber Research and Development Association, High
Wycombe (England). Jan. '82, 30pp.
PB84-107721/CAO PC$11.50/MFSl 1.50
Dry Wear of Carbon-Graphite Materials Running Against
316 Stainless Steel.
Cambridge Univ. (England). 1982. 60pp.
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Mathematics & Statistics
CONTROL: A Suite of Interactive Transfer-Function
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Oxford Univ. (England). 1984. 41pp.
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Adaptive Algorithms for Estimating Eigenvectors of
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Helsinki Univ. of Technology, Espoo (Finland). 1983.
25pp.
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New Approach to Failure Detection in Large Scale
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University of Manchester Inst. of Science and Technology
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Analogy and Mathematical Reasoning: A Survey.
Leeds Univ. (England). May '83, 62pp.
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HP67 and HP97 Calculator Programs for Elementary
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Oxford Univ. (England). 1982. 120pp.
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Multigrid Methods: Development of Fast Solvers.
Technische Hogeschool, Delft (Netherlands). 1983. 26pp.
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Recursive Estimation of Eigenvectors of Correlation
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Database Packages for Microcomputers Reviewed: Com-
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Sussex Univ., Brighton (England). 1983. 29pp.
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Robots and People.
Univ. of Manchester Inst. of Science and Technology
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Non-Use of Library-Information Resources at the Work-
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Outline of a Study on the Relationship between Technical
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Mismatch between Machine Representations and Human
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Commission of the European Communities, Luxembourg.
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Effects of Microelectronics on Employment.
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Designing Automated Systems — Need Skill Be Lost.
Univ. of Manchester Inst. of Science and Technology
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Structural Engineering
Behaviour of a Lined Circular Tunnel in Viscoelastic
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7
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Catalog of Government Patents
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Robot Manipulators: Program Control.
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-------
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Social Indicators for Planning and Evaluation.
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Nutrition Education for the Elderly. Volume 1. Final
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Irrigation with Reclaimed Municipal Wastewater — A
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California State Water Resources Control Board, Sac-
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Foreign Agricultural Trade of the United States (FATUS),
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Technology Assessment of Biological Nitrogen Fixation in
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Communication
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Toward the Prevention of Alcohol Problems:
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Technical Digest — Symposium on Optical Fiber
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10
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THE ROLE OF
METRICS
IN US. EXPORTS
A MAJOR NEW REPORT FROM THE U.S. DEPARTMENT OF COMMERCE
• To what extent is it necessary for
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in metric to maintain or penetrate
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Computers
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National Bureau of Standards, Gaithersburg, MD. Jun '84,
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Microcomputers in Transportation: Addressing
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Energy
Research and Development Activities in Geothermal
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Sandia National Labs., Albuquerque, NM. 1984, 5pp.
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Technology of High-Level Nuclear Waste Disposal:
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Interagency Advanced Power Group Project Briefs by
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Heating and Climatisation: Review of Research, 1983.
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DOE (Department of Energy) Patents Available for
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Department of Energy, Oak Ridge, TN. Jun '82, 280pp.
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Air Infiltration and Heat Exchange.
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Electrotechnology
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Robotic Technology: An Assessment and Forecast.
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Computational Mechanics: A Perspective on Problems and
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National Research Council, Washington, DC. Oct '84,
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Robotic Safety.
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Factors Affecting the Competitive Position of Natural Gas
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Materials
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EPA (Environmental Protection Agency) Method Study 28,
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Environmental
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Capital and O and M (Operation'Maintenance) Cost
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Construction Grants — 1985: Municipal Wastewater
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12
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Irrigation with Reclaimed Municipal Wastewater — A
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Voluntary Standards-Setting for Drinking Water Chemi-
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Nationwide Urban Runoff Program, Washington, DC. Area
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Water Distribution System as a Potential Source of
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Adjustment of Incidence Rates for Migration in Indirect
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California Univ., Berkeley. Nov '84, 80pp.
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Health Assessment Document for Carbon Tetrachloride.
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Asbestiform Fibers: Nonoccupational Health Risks.
National Research Council, Washington, DC. Feb '84,
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Evaluation of the Asbestos-in-Schools Identification and
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Asbestos in Buildings: A National Survey of Asbestos-
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Overview of Major Wetland Functions and Values.
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Value Engineering for Wastewater Treatment Works.
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Chemical Substances Information Network (CSIN): An
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Indoor Air Quality: 20 Existing Homes.
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National Marine Pollution Program: Catalog of Federal
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National Marine Pollution Program Office, Rockville, MD.
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National Marine Pollution Program: Catalog of Federal
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Potential Office Hazards and Controls.
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Meeting Food Needs in the Developing World: The
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Recent and Prospective Developments in Food Consump-
tion: Some Policy Issues.
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Food Needs of Developing Countries: Projections of
Production and Consumption to 1990.
PB85-167377/CAO Price: MF$4.50
Food Security: An Insurance Approach.
PB85-167492/CAO Price: MF$4.50
Impact of Subsidized Rice on Food Consumption and
Nutrition in Kerala.
PB85-167484/CAO Price: MF$4.50
Intersectoral Factor Mobility and Agricultural Growth.
PB85-167468/CAO Price: MF$4.50
Public Distribution of Foodgrains in Kerala — Income
Distribution Implications and Effectiveness.
PB85-167427/CAO Price: MF$4.50
Foodgrain Supply, Distribution, and Consumption Policies
within a Dual Pricing Mechanism: A Case Study of
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Brazil's Minimum Price Policy and the Agricultural Sector
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Rapid Food Production Growth in Selected Developing
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1961-76.
PB85-167443/CAO Price: MF$4.50
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PB85-167450/CAO Price: MF$4.50
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PB85-167658/CAO Price: MFS4.50
Developed-Country Agricultural Policies and Developing-
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PB85-167641/CAO Price: MF$4.50
Food Production in the People's Republic of China.
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Agricultural Research Policy in Nigeria.
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The Economics of the International Stockholding of Wheat.
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A Comparative Study of FAO and USDA Data on
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PB85-166718/CAO Price: MFS4.50
Impact of Irrigation and Labor Availability on Multiple
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PB85-166734/CAO Price: MF$4.50
Agricultural Protection in OECD Countries: Its Cost to
Less-Developed Countries.
PB85-166726/CAO Price: MF$4.50
Estimates of Soviet Grain Imports in 1980-85: Alternative
Approaches.
PB85-166742/CAO Price: MF$4.50
Government Expenditures on Agriculture in Latin America.
PB85-166387/CAO Price: MF$4.50
The Effects of Exchange Rates and Commercial Policy on
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Instability in Indian Agriculture in the Context of the New
Technology.
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Food Security in the Sahel: Variable Import Levy, Grain
Reserves, and Foreign Exchange Assistance.
PB85-166361/CAO Price: MF$4.50
Agricultural Price Policies Under Complex Socioeconomic
and Natural Constraints: The Case of Bangladesh.
PB85-165199/CAO Price: MFS4.50
Growth and Equity: Policies and Implementation in Indian
Agriculture.
PB85-165264/CAO Price: MF$4.50
15
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Government Policy and Food Imports: The Case of Wheat
in Egypt.
PB85-165256/CAO Price: MFS4.50
Instability in Indian Foodgrain Production.
PB85-167393/CAO Price: MF$4.50
Sustaining Rapid Growth in India's Fertilizer Consumption:
A Perspective Based on Composition of Use.
PB85-165249/CAO Price: MF$4.50
Food Consumption Parameters for Brazil and Their
Application to Food Policy.
PB85-165231/CAO Price: MF$4.50
Agriculture Growth and Industrial Performance in India.
PB85-165223/CAO Price: MF$4.50
Egypt's Food Subsidy and Rationing System: A Descrip-
tion.
PB85-165215/CAO Price: MF$4.50
Policy Options for the Grain Economy of the European
Community: Implications for Developing Countries.
PB85-165207/CAO Price: MF$4.50
Agriculture and Economic Growth in an Open Economy:
The Case of Argentina.
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Service Provision and Rural Development in India: A Study
of Miryalguda Taluka.
PB85-166239/CAO Price: MFS4.50
Policy Modeling of a Dual Grain Market: The Case of
Wheat in India.
PB85-166247/CAO Price: MF$4.50
The World Rice Market: Structure, Conduct, and Perform-
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PB85-166254/CAO Price: MFS4.50
Food Subsidies in Egypt: Their Impact on Foreign
Exchange and Trade.
PB85-166262/CAO Price: MFS4.50
Rural Growth Linkages: Household Expenditure Patterns in
Malaysia and Nigeria.
PB85-166270/CAO Price: MF$4.50
The Effects of Food Price and Subsidy Policies on Egyptian
Agriculture.
PB85-166296/CAO Price: MFS4.50
Closing the Cereals Gap with Trade and Food Aid.
PB85-166288/CAO Price: MFS4.50
Constraints on Kenya's Food and Beverage Exports.
PB85-166213/CAO Price: MFS4.50
The Effects of the Egyptian Food Ration and Subsidy
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PB85-166205/CAO Price: MFS4.50
The Effects on Income Distribution and Nutrition of
Alternative Rice Price Policies in Thailand.
PB85-166221/CAO Price: MF$4.50
Evolving Food Gaps in the Middle East/North Africa:
Prospects and Policy Implications.
PB85-167476/CAO Price: MFS4.50
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TABLE 2-4. GROUNDWATER SAMPLING METHODS (WILSON 1980)
Sampling devices
Tile 1ines
Collection pans and manifolds
Wells
Piezometers
Multilevel samplers
Groundwater profile samplers
Sample extraction methods
Hand bailers
Air-lift and gas-lift pumps
Suction lift pumps
Piston pumps
Centrifugal pumps
Submersible pumps
4. Ground-water Monitoring Systems, Technical Resource Document (U.S.
Environmental Protection Agency, in preparation); and
5. Ground-water Monitoring Guidance for Owners and Operators of Interim
Status Facilities (U.S. Environmental Protection Agency 1982b).
Cost estimates prepared by the U.S. Environmental Protection Agency (1982) for
several types of monitoring techniques are presented in Table 2-5.
Caution should be exercised in the choice of well casing material.
The selection of casing depends on the constituents being monitored. Steel
casing may contribute such contaminants as zinc and iron; therefore the use of
PVC, fiberglass, or teflon is recommended. Wilson (1980) discusses the
controversy of whether PVC is appropriate for sampling of organic pollutants.
Dunlap et al. (1977) feel that PVC adsorbs organic constituents as well as
contributes such contaminants as phthalic acid esters to samples. However,
Geraghty and Miller, Inc. (1977) indicate that PVC does not leak organic
compounds and is more inert than steel casing, which develops an iron oxide
coating which has an unpredictable and changeable adsorptive capacity. With
PVC, once the adsorption sites are saturated, the concentration of organics in
the water remain in equilibrium with the adsorbed organics. For microbial
sampling, Wilson (1980) suggests the use of PVC pipe, because metal constitu-
ents in steel wells could inhibit microbial growth.
RUNOFF WATER MONITORING
To ensure the health and safety of off-site populations, runoff water, if
any occurs, should be monitored for hazardous constituents or byproducts. If
7
-------
TABLE 2-5. COST ESTIMATES FOR VARIOUS MONITORING TECHNIQUES AND CONSTRUCTION METHODS
IN THE ZONE OF SATURATION (U.S. ENVIRONMENTAL PROTECTION AGENCY 1982)
Monitoring technique & Price per installation well diameter
construction method 51 .mm (2-inch) 102mm (4-inch) 152mm (6-inch)
Screened over a single interval (plastic screen
and casing)
1. Entire aquifer $1,600-$3,700 $2,300-$4,500 $6,400-$7,500
2. Top 3 meters (10 feet) of aquifer 600- 1,050 700- 1,150
3. Top 1.5 meters (5 feet) of aquifer with drive 100- 200
point
Piezometers (plastic screen & casing)
1. Entire aquifer screened
a. Cement grout 2,100- 4,700 2,800- 5,500 6,900- 8,500
b. Bentonite seal 1,850- 4,150 2,350- 4,950 6,650- 7,950
2. Top 3 meters (10 feet) of aquifer screened
a. Cement grout 1,150- 2,050 1,200- 2,150
b. Bentonite seal 900- 1,500 950- 1,600
Well clusters
1. Jet-percussion
a. Five-well cluster, each well with a 2,500- 3,800
6-meter (20-foot) long plastic screen
b. Five-well cluster, each well with only 1,700- 2,300
a 1.5 meter (5-foot) long plastic screen
2. Augers
a. Five-well cluster, each well with a 6- 4,600- 5,300
meter (20-foot) long stainless steel
wire-wrapped screen
b. Five-well cluster, each well with only 1,800- 2,600
a 1.5 meter (5-foot) long gauze wrapped
drive points
3. Cable tool
a. Five-well cluster, each well with a 6- - - 9,850-14,150
meter (20-foot) long stainless steel,
wire-wrapped screen
-------
TABLE 2-5. CONTINUED
Monitoring technique & Price per installation well diameter
construction method 51 mm (2-inch)102mm (4-inch)152mm (6-inch)
4. Hydraulic rotary
a. Five-well cluster, each well with a - 9,050-14,900 13,800-19,400
6 meter (20-foot) long plastic screen
casing grounded in place
b. Five-well cluster, completed in a single 4,240- 5,800 8,250-11,000
large-diameter borehole 4.5 meter (15-
foot) long plastic screens, 1.5-meter
(5-foot) seal between screens
5. Single well/multiple sampling point - - 3,000- 4,700
a. 33.5-meters (110-foot) deep well with
1-foot long screens separated by 1.2
meters (4-feet) of casing starting
at 3 meters (10-feet) below ground
surface
Sampling during drilling - 3,000- 4,700 3,300- 5,200
Note: Cost estimates are for an aquifer composed of unconsolidated sand with a depth to water of 3
meters (10 feet) and a total saturated thickness of 30 meters (100 feet). Cost estimates are
based on rates prevailing in the Northeast in Autumn, 1975. Actual costs will be lower and higher
depending upon conditions in other areas. Therefore, while the costs presented will become out-
dated with time, the relative cost relationships among the monitoring techniques should remain
fairly constant.
-------
significant concentrations are found, provisions should be available for
collecting, storing, treating, and/or recycling the water through the site.
AIR MONITORING
Air monitoring at hazardous waste sites is essential for the protection
of health and safety of the remedial action team due to the volatile nature of
many hazardous compounds anticipated at hazardous waste sites. An adequate
air monitoring program allows the evaluation of the relative importance of
vapor transport from the site, provides a means for evaluating the effective-
ness of vapor suppression techniques, permits the identification of volatile
daughter products from the various treatment techniques utilized, and is a
requirement if vapor phase photolysis is used as a treatment alternative.
In addition to personal monitoring equipment, a perimeter sampling
network should be established to detect off-site migration of gaseous and/or
particulate emissions. Upwind and downwind sampling sites should also be used
to determine background air quality as well as the extent of off-site contami-
nation, if any. A large number of sources are available concerning the
development of air sampling networks from both the USEPA and professional
organizations such as the Air Pollution Control Association, and these enti-
ties should be contacted for specifics.
Both high-efficiency particle filter samplers and gas/vapor samplers
should be used for contaminant collection (Cheremisinoff et al. 1982).
Solid sorbent traps have become the standard sampling medium for volatile
organic air pollutants (Seiber and Woodrow 1983) and are suggested for mate-
rials with boiling points greater than 100°C (Cheremisinoff et al. 1982).
Continuous air monitoring during normal working hours, suggested for
industrial and hazardous waste impoundments (Cheremisinoff et al. 1982), would
be a minimum requirement at hazardous waste sites with potentially significant
vapor phase hazards. Sites with known significant vapor phase hazard would
require continuous air monitoring until hazard mitigation is complete.
Cheremisinoff et al. (1982) indicate that a minimum air monitoring
program should include the following analyses:
1. Organic compounds with boiling points greater than 300"C, from
particulate filter samplers.
2. Total Chromatographable Organic (TCO) analysis for compounds with
boiling points from 100 to 300°C from solid sorbent samplers.
3. Mass Spec analysis for inorganic/element determinations of materials
collected on particulate filter samplers.
4. Analysis for specific compounds of concern based on specific site
information via acceptable EPA or NIOSH standard procedures.
Specific constitutent analysis would be a requirement for treatment
effective evaluation and would indicate parent compound destruction and
10
-------
reaction product formation during implementation of on-site hazard mitiga-
tion procedures.
REFERENCES
Bordner, R., J. Winter, and P. Scarpino. 1978. Microbiological methods
for monitoring the environment. EPA-600/8-78-017. U.S. Environmental
Protection Agency, Washington, D.C.
Brown, K. W. and Associates, Inc. 1980. Hazardous waste land treatment.
SW-874 (Draft) U.S. Environmental Protection Agency, Cincinnati, OH.
Cheremisinoff, N. P., P. N. Cheremisinoff, F. Ellerbush, and A. J Perna.
1982. Industrial and hazardous waste impoundments. Ann Arbor Science
Publishing, Inc., Ann Arbor, MI.
Dunlap, W. J., J. F. McNabb, M. R. Scalf, and R. L. Cosby. 1977. Sampling
for organic chemicals and microorganisms in the subsurface. EPA-600/2-
77-176. U.S. Environmental Protection Agency, Washington, D.C.
Geraghty and Miller, Inc. 1977. The prevalence of subsurface migration
of hazardous chemical substances at selected industrial waste land
disposal sites. EPA/530/SW-634, U.S. Environmental Protection Agency,
Washington, D.C.
Scalf, M. R., J. F. McNabb, W. J. Dunlap, R. J. Cosby and J. Fryberger.
1981. Manual of ground-water sampling procedures. National Water
Well Association., Worthington, OH. 93 p.
Seiber, J. N., and J. E. Woodrow. 1983. Methods for studying pesticide
atmospheric dispersal and fate at treated areas. Pesticide Reviews
85:217-229.
U.S. Army Corps of Engineers. 1982. Preliminary guidelines for selection and
design of remedial systems for uncontrolled hazardous waste sites. EM
1110-2-(Draft). Department of the Army, Corps of Engineers, Washington,
D.C.
U.S. Department of the Interior, Bureau of Reclamation. 1977. Ground-
water manual. U.S. Government Printing, Washington, D.C.
U.S. Environmental Protection Agency. 1977. Procedures manual for ground-
water monitoring at solid waste disposal facilities. SW-616. U.S.
Environmental Protection Agency, Washington, D.C.
U.S. Environmental Protection Agency. 1982a. Handbook for remedial action at
waste disposal sites. EPA-625/6-82-006. U.S. Environmental Protection
Agency, Cincinnati, OH.
U.S. Environmental Protection Agency. 1982b. Ground-water monitoring guidance
for owners and operators of interium status facilities. SW-963. U.S.
Environmental Protection Agency, Washington, D.C.
11
-------
U.S. Environmental Protection Agency. 1982c. Test methods for evaluating
solid waste. SW-846. U.S. Environmental Protection agency, Washing-
ton, D.C.
U.S. Environmental Proection Agency. 1983. Hazardous waste land treatment.
SW-874, U.S. Environmental Protection Agency, Cincinnati, OH.
Vanhoff, J. A., K. U. Weyer, and S. H. Whitaker. 1979. Discussion of "A
multilevel device for ground-water sampling and piezometric monitoring
by J. F. Pickens, J. A. Cherry, G. E. Grisak, W. F. Merritt, and B.
A. Rizto." Groundwater 17(4):391-393.
Wilson, L. G. 1980. Monitoring in the vadose zone: A review of technical
elements and methods. EPA-600/7-80-134, U.S. Environmental Protection
Agency, Las Vegas, NV.
12
-------
SECTION 3
CHARACTERIZATION AND EVALUATION OF FUNDAMENTAL
PROCESSES IN SOIL/WASTE SYSTEMS
SITE AND SOIL FACTORS RELATED TO IN SITU TREATMENT
Introduction
Identification of site characteristics is necessary before the initiation
of in situ remedial actions for treatment of hazardous waste contaminated
soils for three reasons. First, residual hazardous constituents are of public
health concern because of their ultimate abil'ity to contaminate the atmo-
sphere, through volatilization or resuspension, and the hydrosphere, through
leaching and runoff (Dawson and Brown 1981). Thus to protect the public
health, both route characteristics by which the contaminant migrates off-site,
and off-site receiver characteristics must be considered. Route characteris-
tics determine the potential for contamination, while receiver characteristics
and the corresponding degree of public health hazard indicate the time frame
in which the remedial action must be performed. Site characterization also
may serve to elucidate aspects of site modification or management to improve
protection of human health.
In determining the public health hazard potential, both site and waste
characteristics must be integrated. For example, if site characteristics
indicate an immediate public health hazard due to high potential for off-site
migration of an extremely hazardous chemical, an expensive but rapidly acting
chemical in situ treatment technique may be more appropriate than a slower
acting, less expensive technique utilizing natural soil processes.
Figure 3-1 depicts transport, decomposition, and immobilization processes
influencing the migration of hazardous constituents in the environment.
Hazardous compounds can be dispersed through the atmosphere via airborne
particles or as gases. Human exposure occurs directly through dermal contact
and inhalation of particles or gas or indirectly through deposition on crops
or bioaccumulation in grazing game and agricultural animals, either or both of
which may be ingested by humans. Hazardous compounds may reach surface waters
in runoff, either dissolved or suspended in water or adsorbed to eroding soil
particles. Movement through the soil may occur as liquid or gas or dissolved
in soil water both in lateral and vertical directions to ground and surface
waters. Human contact occurs through ingestion of the contaminated water.
For purposes of this manual, detoxification by plants or removal in vegetation
are not considered as means of in situ treatment.
13
-------
Detoxification
Removal in
Vegetation
Decomposition
o^^/Sorption7
• 0
o ) Biological
\Precipitaton Degradation
Capillary
Flow
Groundwater
Figure 3-1. Processes influencing the migration of hazardous constituents in the terrestrial environ-
ment (adapted from Weber et al. 1973).
-------
Decomposition and transformation of compounds may occur by biological
processes, by chemical means (e.g. oxidation, reduction, hydrolysis) or
by photodecomposition at the soil surface. Degradation refers to changes
from hazardous to less hazardous or innocuous substances, while transforma-
tion refers to changes from hazardous to less toxic or innocuous substances.
Compounds may be also immobilized by adsorption to soil particles, which may
either be organic materials, such as humus or inorganic materials, such as the
clays montmorillonite, vermiculite, or the hydrous oxides.
Secondly, the site must be evaluated in terms of its potential for
decreasing the degree of hazardous of contaminants by degradation, trans-
formation and immobilization. This aspect of site characterization focuses on
soil physical, chemical, and biological properties and on climatological
variables. The choice of a particular in situ treatment technology or train
of treatments and its (their) effectiveness is often highly dependent on
site/soil characteristics as well as on waste characteristics.
The third aspect of site characterization concerns the actual physical
execution of the treatment techniques. Trafficability of the site (steep
slopes, excessively wet conditions, soils high in sticky, plastic clays, etc.)
may affect the choice of an appropriate treatment or the manner in which the
in situ treatment is conducted, or may even preclude the use of any in situ
treatment method. Appropriate site modifications and management options to
enhance treatment are dependent upon the existing site conditions.
In many instances, data needs for off-site migration potential, treatment
choice and effectiveness, and treatment execution may overlap, but the use of
particular types of data should be kept in mind while investigating and
characterizing a site. This will ensure that data are collected in an inte-
grated manner and that necessary data are collected. At sites where previous
remedial actions have removed acute hazards but contaminated soils with low
levels of hazardous constituents remain, a preliminary assessment of available
information may indicate that existing data are sufficient and few or no new
characterization efforts are required.
Site Characterization Related to Off-site Migration
Site characteristics that relate to potential for off-site migration
of hazardous compounds include a) site location and topography; b) soil
properties; c) geological factors; d) hydrogeological factors; and 3) cli-
matological factors.
Site Location and Topography--
Potential for contaminant migration due to soil permeability, depth
to groundwater, credibility, and flooding potential can sometimes be predicted
by knowledge of the type of landform on which the hazardous waste site is
located (Table 3-1). The type of landform may also indicate possible site
modifications necessary to minimize migration (Phung et al. 1978). For
example, on upland crests and valley side landforms, surface water is limited
to incident precipitation and controllable off-site runoff. These landforms
may require the diversion of surface waters to reduce the amount of water
entering and infiltrating the site. However, upland crests or valley sides
15
-------
TABLE 3-1. LANDFORMS AND TOPOGRAPHY OF HAZARDOUS WASTE SITES AS RELATED TO
POTENTIAL FOR MIGRATION OF HAZARDOUS CONSTITUENTS
(ADAPTED FROM RYAN AND LOEHR 1981)
Landscape Position:
Topography
Outwash plains: near level
broad tracts gently
sloping from origin
Terraces: flat areas with
stair-stepped develop-
ment, commonly between
river and upland:
glacial
marine
lake
Lake beds: broad,
exceptionally f1 at
Till plains: young-broad,
gently roll ing
old-broad, level
areas
Alluvial fans: smooth
moderate slopes,
transitional area
between highlands
and lowlands
Playas: broad, exceptionally
flat surfaces
Loess: undulating topography
with smoothly rounded
convex hills
Moraine
Migration Potential
GroundwaterErosion
Eskers: long, low, narrow
steep-sided ridges
Kames: low, long, steep-
sided ridges
high permeability
high permeability
steep
slopes
steep
slopes
potential high water-
table, especi al ly on
fringe
high permeability
high to moderate
permeability
low permeabi1ity
low permeability
high watertable
high watertable
moderately deep
watertable
high permeability
potential high water-
table at bottom of
fan
low permeabi1ity
moderate
permeabi1ity
highly heterogeneous -
moderate
slopes
high erosion
potential
more investigation
required
16
-------
TABLE 3-1. (continued)
Landscape Position: Migration Potential
Topography Groundwater Erosion
Floodplain flooding
Delta flooding
Beach ridges high groundwater
Coastal plains highly heterogeneous - more investigation
required
Tidal flat flooding
Sand dunes wind
erosion
potential
may pose a high hazard to groundwater since they are often in groundwater
recharge areas.
Upland flat areas with fine-grained soils of low permeability pose
less risk of high groundwater and erosion and have greater attenuation
capacities than terrace landforms. Terrace landforms are often underlain
by highly permeable coarse-grained soils, sometimes at shallow depths.
Contamination from these sites may occur at nearby surface expressions of
underlying groundwater. The probability of groundwater intersecting a
terrace site increases as the site position approaches either the valley
wall or the level of the modern floodplain.
Warner (1976) describes four site conditions where pollution poten-
tial is especially high. They are as follows:
1. Sloping sites with relatively impermeable bedrock (e.g. shale,
dense limestone, crystalline igneous rock) 0.6 m or less from the surface
--high potential for erosion, seepage and overland flow of contaminated
effluent.
2. Sites located in karst topography, with clayey residual soils
overlying limestone or dolomite with fracture and solution porosity and
permeability - high potential for contamination of groundwater, for though
infiltration into soil itself is slow, liquids can rapidly enter bedrock where
soil is absent, creating sinkholes and paths for direct flow into groundwater
systems.
17
-------
3. Sites with little topographic relief where groundwater table is
at or very near the surface (e.g. old lake beds, floodplains) - high ground-
water pollution potential.
4. Sites with fractured bedrock and a shallow soil depth (e.g. in
granitic areas) - high groundwater pollution potential.
Soil Characteristics--
Important soil hydraulic, physical, and chemical properties that affect
the migration through the vadose zone of hazardous constituents to groundwater
or off-site in runoff must also be characterized. The vadose zone is the
region extending from the ground surface to the upper surface of the principal
water-bearing formation (Everett et al. 1982). In this zone, water in pore
spaces primarily coexists with air, though saturated regions may occur.
Perched water tables may develop at interfaces of layers with greatly differ-
ent textures. Prolonged infiltration may also result in saturated conditions.
The vadose zone usually consists of topsoils, which are weathered geological
materials usually 3 to 6 feet deep, arranged in more or less well-developed
profiles. Water movement in the topsoil is usually unsaturated, with soil
water at less-than atmospheric pressure. Weathered topsoil materials gradu-
ally merge with underlying earth materials, which may include residual or
transported clays or sands. The topsoil differs from the material lying below
it in that it is more weathered, contains organic matter and the biological
life associated with organic matter, and is the zone of plant-root growth.
The entire vadose zone may be hundreds of feet thick and the travel time of
pollutants hundreds or thousands of years, while other regions may be under-
lain by shallow potable aquifers which are especially susceptible to contami-
nation due to short travel times and reduced potential for pollutant attenu-
ation.
Those soil characteristics that affect water movement, i.e. infiltra-
tion and permeability, and those factors that affect contaminant mobility
are the most important. It must be noted, however, that certain waste
characteristics may affect natural infiltration and permeability of the
soil and such interactions must be considered (see section 4). The site/soil
properties that should be characterized are given in Table 3-2. If such a
complete soil description can be obtained, predictions for potential migration
can be fairly accurately defined.
Soil Classification--
There are three systems under which soils are most likely to have
been classified in the United States (Fuller 1978): the Unified Soil Classi-
fication System (USCS), the 1938 U. S. Department of Agriculture System (USDA)
and the present (I960, 1968) U. S. Department of Agriculture System.
The USCS was developed to describe engineering properties of soils.
(Fuller 1978). Classification of soil types are based on particle (grain)
sizes and response to physical manipulation at various water contents. An
abbreviated description of the system (not including information on manipu-
lation (liquid limit and plasticity index)) is given in Table 3-3 (Fuller
1978).
18
-------
TABLE 3-2. SITE AND SOIL CHARACTERISTICS IDENTIFIED AS IMPORTANT IN IN SITU
TREATMENT
Site location/topography and slope
Soil type, and extent
Soil profile properties
boundary characteristics
depth
texture*
amount and type of coarse fragments
structure*
color
degree of mottling
bulk density*
clay content
type of clay
cation exchange capacity*
organic matter content*
pH*
Eh*
aeration status*
Hydraulic properties and conditions
soil water characteristic curve
field capacity/permanent wilting point
water holding capacity*
permeability* (under saturated and a range of unsaturated conditions)
infiltration rates*
depth to impermeable layer or bedrock
depth to groundwater,* including seasonal variations
flooding frequency
runoff potential*
Geological and hydrogeological factors
subsurface geological features
groundwater flow patterns and characteristics
Meteorological and climatological data
wind velocity and direction
temperature
precipitation
water budget
*Factors that may be managed to enhance soil treatment.
19
-------
TABLE 3-3. MAJOR DIVISIONS, SOIL TYPE SYMBOLS, AND TYPE DESCRIPTIONS FOR
THE UNIFIED SOIL CLASSIFICATION SYSTEM (USCS)(FULLER 1978)
Major Divisions
Symbol
Description
Coarse-grained soils
00
r—
•r—
O
CO
CU
01
1
CU
c
•r-
U-
co CU
•t— N
i — 00
ro
•i- CU
i- >
ra oo
O CM
4- .
•— 0
ro Z
C
d ra
ra -C
i-
ai cu
i. 01
o s-
00 O)
•i— NJ
i — CO
•t- CU
i. >
CU CU
+J •<-
ra 00
O
4- O
O CM
4- .
r— O
ro Z
S-
cu ai
0 ^
E
10
to
'cu
ra
S-
CD
CO
C
ro
OO
13
C
ro
oo
00
ro
CO
•M
OO
r- CU
4- § §£
°ti"
cu r- J s. >
i- ro £ CL> CU
s: c a, t- oo
•^ o "> o
C C N
"^ O co O
u -i- z:
0) --^
C i — I — O 00
ro CU +J c CU
CU > •!-> C
i — ra -i— i- T-
0 S- r— 0 4-
tnl^ — • — -
to i
•— -c co cu cu -— -
cu -*-> cu s- i — oo
> .f— c O--Q CD
ra S -i- CL ro C
cu
C (/) i — O - — .
ro T: -t-> c oo
OJ C +J O)
0 00 i— 0 -I-
- — 4-
oo ^: co cu cu •— -
T3 4-> CU S- i — 00
C •!- SZ Q.J2 CU
ra S •>— Q- ro C
OO U_ ro -i— T-
- — 04-
+J C
CO •!— 4->
ro co O
i — T3 to LO
O -i- CU
a-1"
•i— CO
_J T-
•r- S_
E CU 0
oo -i— +J in
ra cu c
r— -a s- ro
_j
Highly Organic Soils
GW
GP
GM
GC
sw
SP
SM
sc
ML
CL
OL
MH
CH
OH
p
Well graded gravels, gravel-sand
mixtures, little or no fines.
Poorly graded gravels or gravel -
sand mixtures, little or no fines.
Silty gravels, gravel -sand-si 1 1
mixture.
Clayey gravels, gravel -sand-clay
mixtures.
Well graded sands, gravelly sands,
little or no fines.
Poorly graded sands or gravelly
sands, little or no fines.
Silty sands, sand-silt mixtures.
Clayey sands, sand-clay mixtures.
Inorganic silts & very fine sands,
silty or clayey fine sands or
clayey silts with slight
_plasticity.
Inorganic clays of low to medium
plasticity, gravelly clays, sandy
clays, silty clays, lean clays.
Organic silts and organic silty
clays of low plasticity.
Inorganic silts, micaceous or
diatomaceous fine sandy or silty
soils, elastic silts.
Inorganic clays of high plasticity
fat clays.
Organic clays of medium to high
plasticity, organic silts.
Peat & other highly organic soils.
Notes: ML includes rock flour. The No. 4 sieve opening is 4.76 mm
(0.187 in.); the No. 200 sieve opening is 0.074 mm (0.0029 in.)
20
-------
The USDA system was developed for agricultural and other land management
uses and is based on both chemical and physical properties of the soil. The
first system (1938-1960) was based on soil genesis, i.e., how soils formed or
were thought to have formed, while the present system is based on quantita-
tively measurable properties of soils as they exist in the field. The present
system is being constantly refined but is in general use by U. S. soil scien-
tists. The highest level of the present USDA system is described in Table
3-4, and the approximate equivalents in the 1938 USDA system are shown in
Table 3-5.
Fuller (1978) developed a comparison of the USDA classification and
the USCS. The part of the USDA system that can be compared most directly
in the USCS system is soil texture and associated modifiers (e.g. gravelly,
mucky). The size ranges for the USDA and the USCS particle designations
are shown in Table 3-6. The two systems are not directly comparable. The
soil texture designation in the USDA system is based only on the amounts
of sand-silt-and clay-sized particles in the soil (Figure 3-2). In the
USCS, the soil type is determined both on the amounts of certain sizes of
soil particles and on the response of the soil to physical manipulation
at varying water contents. Correlations of USDA soil textures and USCS
soil types are presented in Tables 3-7 and 3-8. Correlations between USCS
soil types and other parts of the USDA system would not be possible. Texture
is a major criterion in the USCS but only a minor criterion in the USDA
system. A soil of a given texture can be classified into only a limited
number of the 15 USCS soil types. However, in the USDA system, soils of the
same texture may be found in many of the 10 orders and 43 suborders of the
system because of differences in their chemical properties or the climatic
areas in which they are located.
The complete USDA soil classification system follows the pattern of
(Anderson 1977):
1. orders
2. suborders
3. great groups
4. subgroups
5. family
6. series
7. types
Each level is a subdivision of the preceding classification level. The
orders are based on soil morphology and development similarity. Suborders
emphasize genetic homogeneity. Great groups are based on similarity in
diagnostic surface and subsurface horizons. A subgroup is based on general
similarities of profiles of soils located within a large area. Families are
based on properties important to the growth of plants, such as texture,
mineral composition, and soil temperature. A soil series is composed of soils
with similar but not identical profiles but with different surface layer
textures. A soil type consists of soils with similar surface texture, and may
be divided into phases based on some prominent deviation (e.g. slope, stoni-
ness, erosion, or soluble salt content).
21
-------
TABLE 3-4. DESCRIPTIONS OF SOILS IN THE HIGHEST (MOST GENERAL;
CATEGORIES OF THE PRESENT USDA CLASSIFICATION SYSTEM
(FULLER 1978)
ORDER
DESCRIPTION
Alfisols Alfisols have a clayey subsoil horizon and moderate to high
base (cation) saturation. Water is held above the wilting
point during at least three of the warm months of the year.
Alfisols are higher in hydroxy-oxides (sesquioxides) than most
soils, as the name implies, and therefore may have a fragipan,
duripan, sodium horizon, petrocalcic (lime), and plinthite
(iron oxides or sesquioxides) or other similar features which
separate them from other soils. Where the temperature is
moderate to cool, Alfisols form a belt between the Mollisols
of the grasslands, and Spodosols and Inceptisols of very humid
climates. In warmer climates, Alfisols form a belt between
Aridisols of arid regions and Inceptisols, Ultisols, and
Oxisols of warmer climates. Leaching of bases from the soil
may occur almost every year or may be infrequent.
Aridisols Aridisols occur in arid climates. They do not have water
available to mesophytic plants for long periods as do the Alfi-
sols. Water is held at less than 15 bars or it is salty. A few
Aridisols occur in semiarid climates because they take up
water slowly and most of the rainfall runs off.
Aridisols have one or more pedogenic horizons that may have
formed in the present dry environment or that may be relics of a
former pluvial period. The pedogenic horizon may be the result
of translocation and accumulation of salts, lime, or silicate
clays or of cementation by carbonates or silica. The pH usually
is neutral alkaline, sometimes highly alkaline.
Entisols Entisols do not have horizon or profile development, or at least
no evidence of such. In many of the soils time has been too
short for distinct horizons to differentiate. Other Entisols
are on soil slopes too steep for water to pentrate well or where
erosion rate exceeds development rate, still others are on flood
or glacial outwash plains which continuously accumulate new
alluvium. Some are wind-moved sand. Not all Entisols are
young. Some are actually very old, consisting mostly of quartz
sand which weathers very slowly. Such materials as organic
matter, lime, gypsum, iron oxides, and clays do not accumulate
or at least only to a very small extent.
Histosols Most Histosols are saturated or nearly saturated with water most
of the year. They are high in organic matter and represent what
is often described as mucks, peat bogs, high moors, or raised
peats.
22
-------
TABLE 3-4. (CONTINUED)
ORDER
DESCRIPTION
Inceptisols By USDA definition (1968), in part at least, "Inceptisols are
soils of humid regions that have altered horizons which have
lost bases or iron and aluminum but retain some weatherable
minerals. They do not have an illuvial horizon enriched
either with silicate clay that contains aluminum or with an
amorphous mixture of aluminum and organic matter." This is a
difficult soil order to visualize from the description. It
represents more what other soils are not than what they are.
Inceptisols develop mainly in the more clayey parent materials,
in contrast to Spodosols, which develop in materials which have
little clay.
Mollisols Very dark colored soils, rich in bases and naturally covered by
grass (steppe land) are called Mollisols. Many soils of this
order accumulate lime and/or sodium, and clay. Mollisols occupy
extensive subhumid to semi arid areas of the grass plains in
the USA. They are located generally between the Aridisols of
arid climates and the Spodosols or Alfisols of humid climates.
These soils are highly productive, constituting rich crop land
in the breadbasket areas of central and west central U.S.
Areas of Mollisols appear in nearly every state. Luxuriant,
perennial grass seems to be essential to their formation. Where
waste waters and leachates are applied to the surface, the high
soil organic matter plays an important part in mobility of
trace and heavy elements. Where leachate and aqueous wastes
pass through subsoils only, 1irne and bases influence mobility
in addition to the effect of clay minerals.
Oxisols Those soils which once were called red and yellow laterites are
now named Oxisols. Reddish, yellowish, or grayish soils of
tropical and subtropical climates that form on mostly gentle
slopes on surfaces of great age are Oxisols. They are mix-
tures of quartz, kaolin, free oxides and organic matter. The
boundaries of horizons blend into each other so gradually they
are generally arbitrary. Weathering has proceeded to great
depths. Water moves through these soils rapidly. Because of
the high oxide (primarily iron) content that coats particles and
forms granular particulates, these soils attenuate the trace and
heavy metals very well. Oxisols occur in Hawaii.
Spodosols Two well defined and obvious-to-the-eye horizons distinguish
Spodosols. Just below the surface layer of forest litter and
partly decomposed dark organic matter is a bleached layer of
uncoated quartz sand. The second layer, just below, usually
is coffee color. Organic matter and iron complexes accumulate
to give the dark brown color. However, this spodic is one in
which amorphous mixtures of organic matter and aluminum may also
occur with or without iron.
23
-------
TABLE 3-4. (CONTINUED).
ORDER
DESCRIPTION
Spodosols generally are coarse textured, containing only small
quantities of clay, if any, and usually permit rapid water
movement. These soils occur under high rainfall conditions and
coniferous forest, though sometimes hardwoods are present.
Attenuation is poor despite the spodic horizon where aluminum,
and often iron, complexes with organic matter. Usually the iron
and aluminum content is low, though, even when a fragipan (soft
when wet, brittle when dry) is present. The textures are mostly
sandy, sandy-skeletal, coarse loam, loamy-skeletal, and coarse-
si Ity. New England, New York, Northern lake states, and Alaska
are most noted for spodic (Podzolic) soils.
Ultisols The concept of Ultisols is that of soils of mid-to-low latitudes
that have a horizon that contains-an appreciable amount of
translocated silicate clay but few bases. Highly humid condi-
tions sometime during the year cause water to move through
them. Ultisols are most commonly found in warm-humid climates
that have a seasonal deficit of rain and on older surfaces.
They develop from a wide variety of parent materials. Kaolin,
gibbsite, and aluminum-interlaid clays are common in the soil
clay fraction. They usually form under coniferous and hardwood-
forest vegetation in the United States.
Vertisols Vertisols are clayey soils which crack severely when dry and
have high bulk densities between the cracks. The clay minerals
are dominated by montmorillonite. Most are found under warm
climatic conditions, i.e., thermic or warmer. In arid regions
they form in closed depressions or playas. Vertisols often are
referred to as churning soils because during swelling, pressure
is exerted, causing them to heave and recycle the soil.
24
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TABLE 3-5. ORDERS IN THE PRESENT USDA SOIL CLASSIFICATION
SYSTEM AND APPROXIMATE EQUIVALENTS IN THE
1938 USDA system (Fuller 1978)
Present Order^
Approximate Equivalentsb
1. Entisols
2. Vertisols
3. Inceptisols
4. Aridisols
5. Mo Hi so Is
6. Spodosols
7. Alfisols
8. Ultisols
9. Oxisols
10. Histosols
Azonal soils, and some Low-Humic Gley soils
Grumusols
Ando, Sol Brun Acide, some Brown Forest, Low-Humic
Gley, and Humic Gley soils
Desert, Reddish Desert, Sierozem, Solonchak, some
Brown and Reddish Brown soils, and associated
Solonetz
Chestnut, Chernozem, Brunizem (Prairie), Rendzinas,
some Brown, Brown Forest, and associated Solonetz and
Humic Gley soils
Podzols, Brown Podzolic soils, and Groundwater
Podzols
Gray-Brown Podzolic, Gray Wooded soils, Non-calcic
Brown soils, Degraded Chernozem, and associated
Planosols and some Half-bog soils
Red-yellow Podzolic soils, Reddish-brown Lateritic
soils of the U.S., and associated Planosols and
Half-bog soils
Laterite soils, Latosols
Bog soils
aPresent (1960, 1968) USDA comprehensive soil classification.
bOld (1938) USDA soil classification.
-------
TABLE 3-6. U.S. DEPARTMENT OF AGRICULTURE (USDA) AND UNIFIED SOIL
CLASSIFICATION SYSTEM (USCS) PARTICLE SIZES (FULLER 1978)
USDA
Particle
Cobbles
Gravel
Coarse gravel
Fine gravel
Sand
Very coarse sand
Coarse sand
Medium sand
Fine sand
Very fine sand
Silt
Clay
Size Range (mm)
76.2-254
2.0-76.2
12.7-76.2
2.0-12.7
0.05-2.0
1.0-2.0
0.5-1.0
0.25-0.5
0.1-0.25
0.05-0.1
0.002-0.05
<0.002
USCS
Particle
Cobbles
Gravel
Coarse gravel
Fine gravel
Sand
Very coarse sand
Coarse sand
Medium sand
Fine sand
Very fine sand
Finest
(Silt and clay)
Size Range (mm)
>76.2
4.76-76.2
19.1-76.2
4.76-19.1
0.074-4.76
2.0-4.76
0.42-2.0
0.074-0.42
<0.074
aUSCS silt and clay designations are determined by response of the soil to
manipulation at various water contents rather than by measurement of size.
Figure 3-2. USDA soil textural classification (Fuller 1978).
d Irom
has available ccpy.
-------
TABLE 3-7. CORRESPONDING USCS AND USDA SOIL
CLASSIFICATIONS (FULLER 1978)
Unified Soil Corresponding United States
Classification Department of Agriculture
System (USCS) (USDA) Soil Textures
Soil Types
1. GW Same as GP--gradation of gravel sizes not a criteria.
2. GP Gravel, very gravelly3 sand less than 5% by weight silt
and clay.
3. GM Very gravelly3 sandy loam, very gravelly3 loamy sand
very gravelly3 silt loam, and very gravelly3 loamb.
4. GC Very gravelly clay loam, very gravelly sandy clay loam,
very gravelly silty clay loam, very gravelly silty clay,
very gravelly clayb.
5. SW Same—gradation of sand size not a criteria.
6. SP Coarse to fine sand; gravelly sandc (less than 20% very
fine sand).
7. SM Loamy sands and sandy loams (with coarse to fine sand),
very fine sand; gravelly loamy sandc and gravelly sandy
loamc.
8. SC Sandy clay loams and sandy clays (with coarse to fine
sands); gravelly sandy clay loams and gravelly sandy
claysc.
9. ML Silt, silt loam, loam very fine sandy loamd.
10. CL Silty clay loam, clay loam, sandy clays with <50% sandd.
11. OL Mucky silt loam, mucky loam, mucky silty clay loam, mucky
clay loam.
12. MH Highly micaceous or diatomaceous silts, silt loams --
highly elastic.
13. CH Silty clay and clayd.
14. OH Mucky silty clay.
15. PT Muck and peats.
aAlso includes cobbly, channery, and shaly.
t>Also includes all of textures with gravelly modifiers where >l/2 of total
held on No. 200 sieve is of gravel size.
^Gravelly textures included if > 1/2 of total held on No. 200 sieve
is of gravel size.
dAlso includes all of these textures with gravelly modifiers where >l/2 of
the total soil passes the No. 200 sieve.
27
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TABLE 3-8. CORRESPONDING USDA AND USCS SOIL
CLASSIFICATIONS (FULLER 1978)
United States Department of Agriculture
(USDA) Soil Textures
Corresponding Unified
Soil Classification System
(USCS) Soil Types
1. Gravel, very gravelly loamy sand
2. Sand, coarse sand, fine sand
3. Loamy gravel, very gravelly sandy
loam, very gravelly loam
4. Loamy sand, gravelly loamy sand,
very fine sand
5. Gravelly loam, gravelly sandy clay
loam
6. Sandy loam, fine sandy loam, loamy
very fine sand, gravelly sandy loam
7. Silt loam, very fine sandy clay loam
8. Loam, sandy clay loam
9. Silty clay loam, clay loam
10. Sandy clay, gravelly clay loam,
gravelly clay
11. Very gravelly clay loam, very gravelly
sandy clay loam, very gravelly silty
clay loam, very gravelly silty clay
and clay
12. Silty clay, clay
13. Muck and peat
GP, GH, GM
SP, SW
GM
SM
GM, GC
SM
ML
ML, SC
CL
SC, GC
GC
CH
PT
28
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Identification of kinds of soils at a site in terms of the higher
categories of the classification system can provide information that is
relevant to identifyinq pollutant attenuation and migration. The names
of soils from the order to subgroup level are composed of a series of forma-
tive elements, which can be used to predict many soil properties relevant to
in situ teatment of wastes. Table 3-9 illustrates the kinds of information
that can be inferred from soil names using the order Mollisol as an example.
The reader is referred to Soil Taxonomy (Soil Survey Staff 1975) for a com-
prehensive description of the USDA soil classification system.
SI ope--
The type and degree of slope indicates surface drainage problems.
Concave slopes cause surface runoff to converge while convex slopes disperse
runoff (U.S. Environmental Protection Agency 1980).
Soil Profile Properties--
In climates where there is sufficient rainfall, soils become highly
organized into layers (horizons). A soil profile is a vertical cross-section
of the soil, made up of several horizons, each having its own distinctive
characteristics. Descriptions of soil profile characteristics made in the
field are especially valuable, because predictions about waste management can
be made more accurately.
Soil Horizons--
Soil horizons are designated A, B, and C to represent the surface
soil, subsoil, and substratum, respectively. The A and B horizons are
formed by weathering and other soil-forming processes. The C horizon is
usually the parent material or undifferentiated geological deposits from
which the A and B horizons developed and is unaltered by soil forming pro-
cesses (e.g. sediment from ancient sea and lake beds, loess blown from
dry floodplains, rocks and rock powder released from melting glaciers,
alluvium from flooding streams). Not all soils have all three horizons,
while many soils show variations within each master horizon. A hypothetical
soil profile with all the common soil horizons is illustrated in Figure 3-3.
Each horizon can have significantly different characteristics such as depth,
texture, structure, bulk density and chemical properties which will result in
differing drainage and pollutant attenuative characteristics.
Boundary Characteristics--
Boundary characteristics, especially abrupt changes in texture and
structure (e.g. clay or sand layers, hard pans) can adversely affect vertical
percolation of water. Horizontal flow may result from textural discontinui-
ties, thus resulting in contamination of adjacent areas.
Depth--
The depth of the soil profile is important for attenuation of hazardous
constituents moving through the soil zone, with greater depths beinq more
desirable. K.W. Brown and Associates, Inc. (1980) suggest a depth of three
times the depth of incorporation of a hazardous waste or 1.4 meters, whichever
is greater, as appropriate for treatment of hazardous wastes. Federal regu-
lations for the land treatment of hazardous wastes also require 1.4 m (Federal
Register 1982). In general, the greater the depth of the soil profile, the
29
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TABLE 3-9. INFORMATION THAT CAN BE INFERRED FROM THE USDA SOIL CLASSIFICATION
SYSTEM, USING THE ORDER MOLLISOL AS AN EXAMPLE. (FORMA-
ELEMENTS FOR THE CLASSIFICATION LEVEL ARE UNDERLINED)
(ADAPTED FROM AGRICULTURAL RESEARCH SERVICE 1974)
Soil Classification Example
Level
Information Relevant to In Situ
Treatment
Order
Suborder
Great Group
Subgroup
Mo11iso 1 Fertile, high in organic matter
Boro11 Long cold, winters; soils frozen for
extended periods; only short time periods
that soil is warm enough for biological
activity
Aquoll Naturally wet; often develops in low
places where water collects and stands
Xerol1 Dry for extended periods in summer;
in most, moisture moves through soil in
underlying layers in winter
Calcixeroll Strong concentration of calcium carbonate
or gypsum at some depth above 60 inches;
calcareous in all parts above that depth
unless texture is sandy
Argixerol1 Horizon of clay accumulation in subsoil;
most with horizon of carbonate accumula-
tion below that
Aquic Moderately shallow groundwater at some
Argixeroll times of the year unless artificially
drained
Lithic Hard rock at shallow depths
Argixerol1
Vertic Fine-textured soils with deep, wide
Argixeroll cracks at some period in most years
Typic Lacking features or combination of
Argixeroll features specified for other subgroups
30
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Corrccsee of organic matter on
unoio«*ed soils. Usually aosent from
S31 "3 developed unaer crass
vegetation.
iave' in wn;i
mstts- is -ecocnizatsie
The cominant features of A horizcns
are one or more of the following:
(1) an accumulation of organic matter,
formsd at or adjacent to tne surface
of tne mineral portion of the soil;
(2) a loss of clay, hydrous oxides of
iron or aluminum, or both, with
resultant concentration of resistant
minerals of sand or silt size. 7?ie
maximum biological activity in the
mineral portion of the soil occurs
in tne A horizon.
The oominant features are one or more
of the following: (1) an accumulation
of silicate clay, organic matter, or
hyarous oxides of iron or aluminum;
(2) a residual concentration of
sesouioxioes or silicate clays; (3)
coatings of sesQuioxides to give
conspicuously darks', Stronger, or
redder colors; (<) an alteration of
material from its original condition
that OD!iterates original rock
structure, forms silicate clays,
liberates oxides and forms granular,
b'locxv or prismatic structure.
Underlying consolidated becrock,
which is not necessarily the parent
material.
*•»
X.
'
I
r
\
1
\
V
f
V.
02
A1
A2
A3
B1
B2
B3
C
R
O-gamc layer in WHICH r*cst slant 0'
animal matter csnnot oe recosmzea.
Characte-ized 5y an accumulafon c-
organic matter mixed wi tn tne mmeral
matter anc coatinc trie mineral
particles, darkening the color of tne
soil mass.
Characterized by loss of clay, iron, or
aluminum, with resultant concentration
of Quartz or othe" resistant minerals
in sano and silt sizes. This horizon
is generally lignte^ in color anc1
lower in content of organic Tatter than
tne AT horizon.
Transitional to E, but rr.ore like A
than B. Sometimes assent.
Transitional to B, but more like 5
than A. Sometimes aosect.
Part of the B horizon in which the "3"
properties are without clesrly expressed
subordinate characteristics indicitinc
that the horizon is transitional to an
adjacent overlyino A or adjacent
underlying C or R.
A zone of transition between S and
C or P..
Nume-ous modified layers recoomisd
by use of cnaractenstic suffixes.
Figure 3-3. A hypothetical soil profile illustrating the common soil horizons
(Otis 1983). Used by permission, see Copyright Notice.
31
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greater the protection against migration of hazardous constituents to ground-
water and greater the soils attenuation properties.
Soil Texture--
Soil texture is a description of the particle size distribution of
various soil separates (particles less than 2 mm). The USDA soil texture
system was shown in Figure 3-2, while a comparison of the USDA system and
USCS system was shown in Table 3-8. K. W. Brown and Associates Inc. (1980)
described soil characteristics important to hazardous waste treatment based on
soil texture in the following manner:
The sand and gravel particles are normally thought of as the
coarse separates, and soils dominated by these coarse separates
are usually of an open character, have low water-holding capacity,
possess good drainage, high permeability and aeration, and are
generally in a loose friable condition. In contrast to the coarse
separates, the silt and clay particles are considered the fine
separates. Silt particles are micro-sand particles predominantly
composed of quartz and have some plasticity, cohesion, and adsorp-
tion. A high percentage of silt is undesirable and leads to physi-
cal problems such as soil crusting. Clay particles are very small,
less than 0.002 mm in diameter, and therefore have a very high
surface area. Clays are commonly flat or plate-like, highly plas-
tic, cohesive, and have a very high adsorptive capacity for water,
ions and gases. In general soils high in silt and clay are called
fine textured soils and are very plastic, cohesive, high in water
holding capacity, and have very slow water and air permeabilities.
Each type of soil, fine or coarse, has various advantages and
disadvantages for use in a waste disposal system. Coarse textured
soils will remain oxidized while fine soils may often become reduced
due to wetness. The oxidation state will play an important role in
how quickly, by what pathway, and in what form various waste con-
stituents will be degraded. Ammonia, for example, will be rapidly
converted to nitrate in an oxidized coarse soil and, due to the
potential for rapid water infiltration, may leach to the groundwater
supply. Oxidation also affects the degradation of organics by
regulating which and how many microbes can exist. Therefore, a
given hydrocarbon will degrade via one pathway at a rapid rate when
well oxidized, a slower rate when less well oxidized, and via a
second pathway and rate when under reduced conditions. This is
exemplified by the data of Gibson and Yeh (1973) who show that under
aerobic conditions the primary pathway for hydrocarbon degradation
is oxidation to form epoxides while under anaerobic conditions
organic materials are mainly fermented into organic acids such
as methanol. The high adsorptive capacity of the fine textured
soils may, however, be very useful in holding various ions, such as
heavy metals, in an immobile form and preventing their movement to
water supplies or other undesirable areas.... In general, it can be
suggested tnat hazardous waste land treatment facilities not be
established on extremely deep sandy soils due to the potential for
leaching to groundwater. Similarly, silt/ soils having a severe
problem with crusting should not be selected dje to the extreme
32
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potential for runoff. In general, the loam, silt loam, clay loam,
sandy clay loam, silty clay loam, silty clay, and sandy clay soils
are best suited for land treatment of hazardous wastes.
A summary of the advantages of each type of soil texture in the USDA
system is given in Table 3-10.
Soil Structure--
Soil structure refers to the aggregation of primary soil particles
(sand, silt, and clay) into compound particles or clusters of primary parti-
cles, which are called peds. The aggregates, separated by surfaces of weak-
ness or open planar voids, are often seen as cracks in the soil. The struc-
tures of the different horizons of a soil profile are essential characteris-
tics of the soil profile just as are texture or chemical composition. Seven
basic structure types are defined by the shape and arrangement of peds. These
are illustrated in Figure 3-4. Soils may also have no structure: coarse
textured soils with no texture are called single grain while fine textured
soils are called massive (soil material clings together in large uniform
masses). Aggregate formation is thought to result from the cementing action
of soil colloidal matter (clay minerals, colloidal oxides of iron and manga-
nese, and colloidal organic matter). Aggregation may vary in stability,
changing in response to moisture content, chemical composition of the soil
solution, biological activity, and management practices. Soils high in
shrink/swell clays show particularly dramatic structural changes in response
to changes in water content.
Structure may modify the influence of texture in regard to moisture
and air relationships. Interpedal voids are often large and continuous com-
pared to voids between the primary particles within the peds. For example,
a soil with a high content of plastic clays would exhibit limited permeability
if it did not have a well-developed structure which facilitates water and air
movement. Aggregates in coarse textured soils stabilize the surface and
increase water retention in the soil.
The type of structure determines the dominant direction of the pores
and thus the direction of water movement. Platy structures restrict vertical
percolation, prismatic and columnar enhance vertical percolation, and blocky
and granular enhance percolation both vertically and horizontally (Otis 1983).
Structural units that can withstand moderate handling without disintegrating
will provide better hydraulic properties.
Color--
Color and color patterns in soil are good indicators of drainage char-
acteristics of soil. Soil colors can be described in general terms (e.g.
brown, gray, yellow, etc.) or by the Munsell color system, which characterizes
a color in terms of hue, value, and chroma.
Uniform red, yellow, or brown colors indicate that a soil is well-
drained and seldomly or never saturated with water. Gray or blue colors
indicate that the soil is saturated continuously or for extended periods.
Soils with spots or streaks of red, yellow, or black in a gray matrix ("mot-
tled") are usually periodically saturated with water.
33
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TABLE 3-10. SUITABILITY OF VARIOUS TEXTURED SOILS FOR LAND
TREATMENT OF HAZARDOUS INDUSTRIAL WASTES (K. W. BROWN AND
ASSOCIATES 1980)
Texture
Advantages
Disadvantages
Sand
Loamy sand
Loam
Silt loam
Silt
Silty clay
loam
Silty clay
Clay loam
Clav
Sandy clay
Sandy clay
loam
Very rapid infiltration
Usually oxidized & dry
Low runoff potential
High infiltration
Low to medium runoff
Moderate infiltration
Fair oxidation
Moderate runoff potential
Generally accessible
Good CEC
Moderate infiltration
Fair oxidation
Moderate runoff potential
Generally accessible
Good CEC
Low infiltration
Fair to poor oxidation
Good CEC
Good available water
Medium-low percolation
Fair structure
High CEC
Good to high available
water
Medium-low percolation
Good structure
Med-poor aeration
High CEC
High available water
Low percolation
High CEC
High available water
Med-low percolation
Mea-high CEC
Med-high available water
Good aeration
Very low CEC
Very high hydraulic
conductivity rate
Low available water
Little soil structure
Low CEC
Moderate to high hydraulic
conductivity rate
Low to medium available water
Fair structure
Some crusting
Fair to poor structure
High crusting potential
Poor structure
High runoff
Med-low infiltration
Some crusting potential
Moderate runoff
Often wet
Fair oxidation
Med-low infiltration
Mod-high runoff
Often wet
Low infiltration
Often massive structure
High runoff
Sometimes low aeration
Fair structure
Moderate-high runoff
Medium infiltration
34
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Structure
Type
Aggregate Description
Diagrammatic
Aggregate
Common
Horizon
Location
Grangular Relatively nonporous, small and
spheroidal peds; not fined to
adjoining aggregates
Crumb Relatively porous, small and
spheroidal peds; not fined to
adjoining aggregates
Platy Aggregates are platelike. Plates
often overlap and impair
permeability
Biocky Blocklike peds bounded by
other aggregates whose sharp
angular faces form the cast for
the ped. The aggregates often
break into smaller biocky
peds
Subangular Blocklike peds bounded by
biocky other aggregates whose
rounded subangular faces
form the cast for the ped
Co
A horizon
A horizon
A2 horizon
in forest
and
claypan
soils
Bt horizon
Bt horizon
Prismatic Columnlike peds without
rounded caps. Other prismatic
aggregates form the cast for
the ped. Some prismatic
aggregates break into smaller
biocky peds
Bt horizon
Columnar Columnlike peds with rounded
caps bounded laterally by
other columnar aggregates that
form the cast for the peds
Bt horizon
Figure 3-4. Diagrammatic definition and location of various types of soil
structure (Foth 1978). Used by permission, see Copyright Notice.
-------
Mottles--
Mottles result from chemical and biochemical reactions when saturated
conditions, organic matter, and temperatures above 4°C occur together in the
soil. Bacteria utilizing organic matter deplete oxygen present in the soil.
Other bacteria continue the organic decomposition using oxidized iron and
manganese compounds instead of oxygen in their metabolism. The insoluble iron
and manganese are reduced to soluble forms, causing the soil to lose its red,
yellow, and brown color and turning it gray. When the soil drains, the
soluble iron and manganese are carried with the water to the larger pores in
the soil. When they, contact air-filled pores, they are reoxidized, -Forming
insoluble compounds that accumulate as red, yellow or black spots near pore
surfaces. The soil from which the compounds were removed remain gray (Otis
1983).
Bulk Density--
Bulk density is the mass of dry soil per unit bulk volume. As the
density of a soil increases, the volume of pore space decreases. Density
and pore space relationships determine the ease and amount of air and water
stored in and moving through pore spaces. Of soils with the same texture,
those with higher bulk densities are more dense -with less pore volume and thus
less permeable. Good structure and lower bulk densities promote good aeration
and drainage. Soil bulk densities usually increase with depth due to less
organic manner, less aggregation, and compression from the weight of the
overlying soil (K.W. Brown and Associates, Inc. 1980). Sandy soils, with
particles lying close together, exhibit hiqh bulk densities, ranging from 1.2
to 1.8 g/cm^. Finer textured soils with usually higher organic matter
contents and more structure have more pore space and lower bulk densities,
generally ranging from 1.0 to 1.6 g/cm^ (Brady 1974).
Type and Amount of Soil Colloids--
Clays and organic matter—The colloidal fraction of a soil is of primary
importance in the sorptionand immobilization of hazardous organic and in-
organic compounds. The colloidal fraction, composed of organic and inorganic
particles with a maximum size of 0.001 mm, is the most chemically active
portion of a soil. These particles are characterized by a large exposed
surface or interface, a capacity to adsorb and hold solids, qases, ions, and
polar compounds, and a tendency to hasten or retard chemical reactions by
catalytic action (Anderson 1977). Of the mineral, inorganic portion of soils,
only the clay particles are colloidal in size and even some clay particles are
too large to be classified as colloidal. However, recognizing the exceptions,
the term clay is used for the inorganic colloidal portion of soils. The
organic colloidal fraction is composed of amorphous humus, derived from
organic materials during their breakdown by microoganisms.
Inorganic soil colloids—The formation of soil inorganic colloids results
from the weathering of minerals, which in mixtures form the rocks of the
earth. Since oxygen and silicon make up about 75 percent of the earth's crust
on a weight basis, most minerals are primary or secondary silicates. The
average mineralogical composition of igneous and sedimentary rocks is shown
in Table 3-11.
Weathering is basically a combination of destruction arid synthesis
(Brady 1974). Both mechanical factors (e.g. strains from temperature changes,
36
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TABLE 3-11. AVERAGE MINERALOGICAl COMPOSITION OF IGNEOUS AND
SEDIMENTARY ROCKS (FOTH 1978)
Used by permission, see Copyright Notice
Mineral
Constituent
Feldspars
Amphiboles and
pyroxenes
Quartz
Micas
Titanium minerals
Apatite
Clay
Limonite
Carbonates
Other minerals
Origin
Primary
Primary
Primary
Primary
Primary
Primary or
secondary
Secondary
Secondary
Secondary
~
Igneous
Rock,
%
59.5
16.8
12.0
3.8
1.5
0.6
-
-
- -
5.8
Shale,
%
30.0
-
22.3
-
-
-
25.0
5.6
5.7
11.4
Sand-
stone,
%
11.5
a
66.8
a
a
a
6.6
1.8
11.1
2.2
aPresent in small amounts.
pressures of freezing water, erosive action of water, wind, and ice and
exfoliation) and chemical processes (e.g. hydration hydrolysis oxidation,
solution, and carbonation) act in the process of weathering. Rocks are broken
into smaller rocks and eventually into their individual minerals, many of
which are primary silicates (i.e. silicate minerals not altered chemically
because of deposition and crystallization from molten lava). At the same
time, the rock fragments and minerals are changed to new secondary minerals
either by minor alterations or complete chemical changes. These changes are
accompanied by a continued decrease in particle size, increase in specific
surface area (area per unit weight) and by the release of soluble constitu-
ents, most of which may be lost in drainage. An illustration of the weather-
ing process is shown in Figure 3-5. The size, number, and surface area of
soil particles from very coarse sand to clay are shown in Table 3-12.
The minerals which are synthesized are primarily layer silicate clays and
very resistant end products, usually iron and aluminum oxides. Soils are
predominately composed of these synthesized secondary minerals and very
resistant primary minerals such as quartz. The sand and coarse silt fractions
of soils are composed mainly of quartz and generally quite inactive chemically
(Figure 3-6). Primary silicates such as the feldspars, amphiboles, and micas
are present in sands but decrease in amount in silts. Secondary silicates
dominate the clay fraction, while oxides of iron and aluminum are important in
the fine silt and coarse clay fractions. The silicate clays are characteristic
of temperate regions while the hydrous oxides are characteristic of the tropic
37
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RO
llGN
SEDIME
V.ETAM
-=-
:KS
EOUS.
NTARY.
ORPHIC)
Decomposition
VERY SLOWLY
* WEATHERED MINERALS 1
lea.QUWt; mu^ov.l.l Con,,nu«1 d,s.nleor.lK>r, RESISTA-.-
(accreas« in sue) le g ausn;
SLOWLY 1
_^J MINERALS
— _., !C.°™OSlTIOn *" ^ ie g . ^il.caieci
EASILY WEATHERED rfcrwall,;ation
^ MINERALS 1
otivinc. cdlcitel
RESISTANT
Qecomoosiiion DECAY PR'1^
(cnem-cal re.c.,or>sl '\ ' \ •% "" F'.'.*'/^"'''
^^ N. V,
\ \ SOLUBLE
N^ Solunor, N^ MATERIALS
Figure 3-5. Weathering pathways which take place under moderately acid condi-
tions common in humid temperature regions. (Major paths of
weathering are indicated by the heavier arrows, minor pathways by
broken lines.) (Brady 1974). Used by permission, see Copyright
Notice.
TABLE 3-12. THE SIZE, NUMBER, AND SURFACE AREA OF SOIL PARTICLES
(FOTH 1978)
Used by permission, see Copyright Notice
Particle type
Very coarse sand
Coarse sand
Medium sand
Fine sand
Very fine sand
Silt
Clay
Diameter
(mm)
2.00-1.00
1.00-0.50
0.50-0.25
0.25-0.10
0.10-0.05
0.05-0.002
below 0.002
Number of
particles/ga
90
720
5,700
46,000
722,000
5,776,000
90,260,853,000
Surface area
(sq cm/g)
11
23
45
91
227
454
8,000,000
^Assumed to have spherical shapes, based on maximum diameter of the particle
type.
38
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jSecondary silicate!
".:: .-Xv/Xv/XvlvXC- X-'-Xv>\\ 1 minerals [
SAND
SILT
CLAY
Figure 3-6. General relationship between particle size
present (Brady 1974). Used by permission,
and kinds of minerals
see Copyright Notice.
and semitropics,
silicate clays.
though they do occur in temperate regions intermixed with
The layer silicates have a planar geometry, very large specific surface
areas, and very high residual negative charge densities which are neutralized
by a large external swarm of cations, thus resulting in a capacity for strong
adsorption of and catalytic action towards hazardous compounds (Ahlrichs
1972).
Two basic sheet-like molecules make up the structure of silicate clays.
A tetrahedral sheet is composed of series of tetrahedrons with four oxygen
atoms surrounding a central cation, which is usually silicon (Si+4), but may
be aluminum (Al+o), in a close-packed arrangement (Figure 3-7). An octahedral
sheet is composed of a series of octahedrons with six oxygen atoms forming the
corners around a large cation, which is usually Al+3, but may be magnesium
(Mg+2) or iron (Fe+2 or Fe+3). The sheets are formed by the sharing of corner
oxygens (Figure 3-8).
The sheets may be joined in one of two ways, 1:1 or 2:1 arrangements.
In 1:1 arrangements, one tetrahedral layer is connected to one octahedral
layer by sharing of a common oxygen. Repeats of this 1:1 unit produces
the clay kaolinite. The 2:1 arrangement has single tetranedral layers joined
to each side of the octahedral layer by sharing of oxygen atoms. This 2:1
unit produces the basic layer of the clays montmorillonite, chlorite, vermi-
culite, and micas. The 1:1 and 2:1 units are shown in Figure 3-9.
Some 2:1 clays exhibit a very high negative charge due to substitution
of low valency for high valency cations within normally neutral crystals.
During formation, ions of similar radi, such as Al+3 for some Si+4 in the
tetrahedral layer and Mg+2 or Fe+2 for Al+3 or Fe+3 in the octahedral layer,
may be substituted. The lower valency of the substituting cation results in a
residual negative charge, which must be balanced by a cation external to the
39
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(a)
O and O Oxygens
• Silicons
(b)
Mgure 3-7. (a) Single silica tetrahedron. (b) Sheet structure of silica
tetrahedrons arranged in a hexagonal network (Foth 1974). Used
by permission, see Copyright Notice.
Aluminums, magnesiums, etc.
igure 3-8. (a) Single octahedral unit. (b) Sheet structure of octahedral
units (Foth 1974). Used by permission , see Copyright Notice.
:1 unit either on its edge or in the interlayer surface. Cation exchange
opacity is an expression of the number of cation adsorption sites per unit
eight of soil. It is defined as the sum total of exchangeable cations
isorbed, expressed in mi 11iequivalents per 100 grams of oven dry soil.
of silicate clays but most are variations of a few
is the most common 1:1 type clay. The 1:1 units are
jnded together by hydrogen bonding between hydroxyl groups. There is no
iterlayer surface area and kaolinite aces not swell with the addition of
There are a number
ijor types. Kaolinite
here is also little substitution within the tetrahedral or
;yers so the charge deficit
id sorptive capacity.
is low. Thus kaolinite has quite low
octahedral
reactivity
Montmoril lonite is a common 2:1 type clay which has a negative charge of
) to 120 mill iequivalents per 100 grams of soil and swells and shrinks as
.ter moves freely between the weakly bonded 2:1 units. Water is attracted
the oxygen surface of the clay and to the neutralizing cations in the
4C
-------
7.2 A
AU
c-Axis
a %
b-Axis •
nH20
x+y M
Water
+
Exchangeable
Cations
(0)6
2:1
9.6 A
c-
(O).(OH^
•b-Axis-
Figure 3-9. Sketch showing an edge view of the crystal structure of a 1:1 and
a 2:1 type clay mineral (Ahlrichs 1972). Used by permission, see
Copyright Notice.
interlayers. The swelling caused by the water exposes the large surface area
and the large charge deficit of montmorillonite.
Illite or hydrous mica possesses the same 2:1 structure as montmorillon-
ite but differs in that adjacent 2:1 units are tightly bonded by a potassium
bridge. Illite therefore does not swell in water, and most of its charge is
neutralized by potassium. II lite is expected to exhibit minimal interaction
with hazardous organic compounds added to the soil (Ahlrichs 1972).
Vermiculite is similar to illite, except that potassium is not present,
and the charge deficit is somewhat lower in the crystal. Vermiculite usually
has hydrated Mg+2 or calcium (Ca+2) in the interlayers neutralizing the
charge. A summary of the overall characteristics of these common clay
minerals is given in Table 3-13.
The hydrous oxide clays are oxides containing associated water molecules.
They are formed by intense weathering, where silicon has been removed from the
silicate clays, leaving iron and aluminum hydroxides in a highly colloidal
41
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2LE 3-13. SUMMARY OF CHARACTERISTICS OF SOUL COLLOIDS (COOK AND PACE 1973)
Used by permission, see Copyright Notice
'.si a Tit.
!', lorn te Irvsta'line. None
ciate like
""-KIL ;i'_ c ,
DC'1'- .
arainee
--tially- Verrciculite Crystalline, Mg(hjG)6 .. lio A! - s, L0(> ^ M
cancing platelike tetra'ieoral) i,:,-;nerr u^
CandGd
Illite Crystalline, k. 0.1-2.0 15-40 A1 - Si Lo» Lo.
Dlatelike I tetranetfral! T^f
Canada
orous A12CJ3 > M?Q (OTr,rr>ious N.A. colloidal nh- ae- H N.A. Hion Fe Ai
'.aes Fe?03 » H2° Crystal line pendent Dissociation Southeast C.S., contain-
"roPlCi ' inc
"•i np^a 15
worDtioui. N.A. coiloioal ph- -CGOf- LO» o* ', vine Pijr-
UrQan'c oep't -u- .can ooorl'v oramec , smr.ai
structure (t'OO-M /P) lose area;"
Dy burn-
-ate. Their important sites for adsorption are -OH and -OH2 on the outer
-rfaces, which may become charged in the presence of excess H+ or OH- ions.
~^e pH values at which the charge on the ions changes ranges from 7.5 to 9
•- the iron and aluminum oxides. Below these values, the compounds are
:3itively charged, thus providing adsorption capacity for anions.
The surface geometry of the silicate clays is important in the attenua-
•?n of hazardous compounds. The interlayer surfaces provide most of their
^sorptive surface area (Ahlrichs 1972). The source of the charge deficit in
clay has been suggested as important in determining the bonding action
itween layers and consequently the amount of swelling. Marshall (1964)
-ggests that tetrahedral sources of charge deficit give greater bonding
-orgies than octahedral sources since the distance from the cause of charge
3,-iciency is closer to the planar surface in the tetrahedra.
The size of the crystal c-axis spacing (see Figure 3-9) may determine
•••ch compounds enter the interlayer of a clay. For example, montmoril lon-
"= will allow almost any size molecule or compound to enter if there is
• attraction for it. When neutralized with sodium (Na+) or other similar
—ovalent ions as the exchangeable cations, these clays are especially free
•tiling. Less swelling is exhibited with multivalent ions. The interlayer
.-faces of vermiculite, with a more restrained swelling potential then
:-*morillonite, are small enough to prevent the entrance of many compounds.
42
-------
The importance of the spatial geometry of negative charge sites in
clays was demonstrated by Weed and Weber (1968), using two divalent cationic
organic compounds,. The average distance between charge sites in a montmoril-
lonite is 11-12 A, while in micas it is 6-8 A. Diquat, with charge sites 3-4
A apart on ring nitrogen groups, preferentially sorbed to the higher charge
density (closer spacing) of the micas.- In paraquat, the charge sites were 7-8
A apart on the ring nitrogen groups, and paraquat was sorbed preferentially by
montmorillonite, with its lower charge density.
Anion exchange on colloidal clay minerals also occurs but apparently
to a much lesser extent in most soils than that of cation exchange. Anions
may replace the hydroxyl groups in the clays, and as these groups are more
numerous in kaolinte than in other silicate clays, kaolinite is considered to
be primarily responsible for anion exchange in temperature or arid region
soils. Aluminum and iron oxides become protonated in the acid environments
which are normal for highly weathered tropical soils and thus are also impor-
tant in anion exchange reactions, as discussed previously.
Organic colloids--Soil contains many organic compounds in various stages
of decomposition.Soil organic matter is derived from: 1) plant material;
2) animal matter; 3) microorganisms, both living and dead; 4) synthesized and
secreted products of living plants and microorganisms; and 5) decomposition
products of organic debris (Anderson 1977).
Schnitzer (1978) estimated that 65 to 75 percent of the organic matter
in mineral soils consists of humic materials, i.e., humic acid (HA), fulvic
acid (FA), and humin. They are amorphous, dark-colored, hydrophilic, acidic,
partly aromatic, chemically complex organic substances ranging in molecular
weight from hundreds to several thousand, with very large surface areas
(500 - 800 m2/g) and high cation exchange capacities. The remainder of
the organic matter is composed primarily of polysaccharides and protein-
like substances (Flaig et al. 1975). These include substances with still
recognizable physical and chemical characteristics, such as carbohydrates,
proteins, peptides, amino acids, fats, waxes, alkanes and low molecular
weight organic acids (Schnitzer 1982). They are readily decomposed by
microorganisms and have a short lifetime in the soil. Schnitzer (1982)
identified the following important characteristics of all humic materials:
1. Ability to form water-soluble and water-insoluble complexes with
metal ions and hydrous oxides.
2. Ability to interact with minerals and a wide variety of organic
compounds, including alkanes, fatty acids, dialkyl phthalates,
pesticides, herbicides, carbohydrates, amino acids, peptides, and
proteins.
The formation of water soluble complex of FA with metals and toxic organics
can increase the concentrations of these constituents in soil solutions
and natural waters to levels much greater than their calculated solubilities.
The oxygen-containing functional groups are important for the reactions
of humic materials with metals, minerals, and organic compounds. Humic matter
is somewhat organophilic, which is very important for adsorption of some
43
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hazardous nonionic organic molecules. A summary of types of functional groups
and distribution in humic materials is presented in Table 3-13a. The func-
tional groups contribute to a high cation exchange capacity (200-400 milli-
equivalents/100 g), thus acting similarly to clays in preventing cations from
leaching. A summary of characteristics of soil humus is previously included
in Table 3-6.
Humus increases the water holding capacity of a soil, since it swells
when wet and can adsorb two to six times its own weight in water. However, it
does rewet slowly if thoroughly dried.
Humus and other organic matter, because of their chemical composition,
can add to the nutrient status of the soil, thus increasing microbial activity
which may be responsible for attenuation of hazardous soil contaminants.
Nitrogen, phosphorus, and some of the minor nutrients, such as sulfur, zinc,
and boron all can be contributed by organic matter.
The amount of nitrogen in decomposing organic matter relative to the
amount of carbon is especially important, for insufficient nitrogen may limit
the rate of degradation. Organic matter with a low nitrogen content (or wide
C:N ratio) is often associated with a slow rate of decomposition. Materials
which contain more than 1.5 to 1.7 percent nitrogen probably do not need
additional fertilizer or soil nitrogen to meet the requirements of micro-
organisms during decomposition. This corresponds to a threshold carbon:nitro-
gen ratio of 25 to 30 (Taylor et al. 1980). However, carbon:nitrogen ratios
should be used with caution, for the ratio does not indicate the availability
of the carbon or nitrogen to microorganisms.
In summary, humified soil organic matter, because of its surface area,
surface properties, and functional groups, can serve as a buffer, an ion ex-
changer, a surfactant, a chelating agent, and a general sorbent, all of which
are important in the attenuation of hazardous compounds in soils (Ahlrichs
1972).
TABLE 3-13a. OXYGEN-CONTAINING FUNCTIONAL GROUPS IN HUMIC SUB-
STANCES (SCHNITZER 1975).
meq/g
Type of
Material
HA
Humi n
FA
C02H
4.4
3.1
8.1
Phenolic
OH
3.3
2.2
3.9
Alcohol ic
OH
1.9
N.D.a
4.0
Ketonic
C=0
1.2
3.1
1.4
Quinonoid
C=0
1.0
2.0
0.6
Methoxyl
0.3
0.4
0.4
aN.D. = not determined.
44
-------
Soil pH--Soil pH determines in part the degree of surface charge on
colloidal-sized soil particles. At high pH values, negatively charged sur-
faces develop, while at low pH values, positively charged surfaces occur. The
tendency for adsorption of anions or cations is thus dependent on the pH
of the soil water in the vadose zone.
Soil pH also has major effects on biological activity in the soil.
Some organisms have small tolerances to variations in pH while others can
tolerate a wide pH range. The optimum pH range for rapid decomposition
of most wastes and residues is 6.5 to 8.5. Bacteria and actinomycetes
have pH optima near neutrality and do not compete effectively with fungi
under acidic conditions (Taylor et al. 1980). Soil pH also affects the
availability of nutrients, as shown in Figure 3-10.
There are several sources of hydrogen (H+) and hydroxyl (OH-) ions in
soil solutions. The hydrolysis of exchangeable bases (Ca+2, Mg+2, Na+, and
K+) which dissociate from cation exchange surfaces contribute OH- ions.
Exchangeable hydrogen (H+) which has dissociated contributes H+. Exchangeable
H+ is the principal source of H+ until the pH of the soil goes below 6, when
aluminum in the octahedral sheet of clays becomes unstable and is adsorbed as
exchangeable Al. Upon hydrolysis, each Al ion becomes the source of three H+
ions.
The pH of a calcareous (containing CaC03) soil or a calcareous soil
horizon ranges from 7 to a maximum of 8.3. A calcareous soil horizon may
greatly affect migration of hazardous compounds by an abrupt change in soil pH
which may affect solubility or ionization states of the compounds.
A soil high in sodium (sodic soil) has an even higher pH than a cal-
careous soil, due to the hydrolysis of sodium carbonate and the formation of a
strong base, sodium hydroxide. When the cation exchange capacity is 15
percent or more saturated with sodium, or a significant amount of sodium
carbonate exists in the soil, the pH values range from 8.5 to 10.
Saline soils are high in soluble salts. Plant growth may be impaired due
to the osmotic pressure of the soil solution restricting water uptake. Saline
soils tend to have a pH at or near 7 due to hydrolysis of soluble salts
(Foth 1978). The pH of soils can be adjusted by several means. Sulfur
compounds can be used to lower pH or liming compounds can be used to raise
pH.
Oxidation-reduction potential--In conjunction with measurement of pH in
the soil solution, a measurement of the oxidation-reduction potential or Eh of
the soil solution will add valuable information. Eh is an expression of the
electron density of a system. As a system becomes reduced, there is a corre-
sponding increase in electron density, resulting in a progressively increased
negative potential (Taylor et al. 1980). With Eh and pH known, Eh-pH diagrams
can be constructed showing stability fields for major dissolved species and
solid phases. These diagrams can be useful in understanding the occurrence
and mobility of hazardous compounds in soils (Everett et al. 1982).
The maximum rate of decomposition of degradable hazardous compounds
is correlated with a continuous supply of oxygen. Excessive levels of
45
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Figure 3-10.
Relationships in mineral soils between pH and the activity of
microorganisms and the availability of plant nutrients (Brady
1974). Used by permission, see Copyright Notice.
degradable materials may lead to depletion of 03 in soil and anaerobio-
sis, which slows the rate and extent of decomposition and may produce some
reduced compounds which are odorous and toxic to microgranisms and plants.
Table 3-14 shows the succession of microbial events relative to soil redox
potential.
The degradative pathways for some hazardous compound may involve some
critically reductive steps. An important initial step in the degradation of
DDT is a reductive one, which requires anaerobiosis (Guenzi and Beard 1967).
Farr and Smith (1973, 1976) have shown that toxaphene and trifluralin degrade
more rapidly under anaerobic conditions. Thus an engineering management tool
to maximize detoxification and degradation of some compounds may be tne
alternation of aerobic/anaerobic conditions (Guentner 1975) by adjusting Eh
46
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TABLE 3-14. SUCCESSION OF EVENTS RELATED TO THE REDOX POTENTIAL WHICH
CAN OCCUR IN WATERLOGGED SOILS, OR POORLY DRAINED SOILS .RECEIVING
EXCESSIVE LOADINGS OF ORGANIC CHEMICAL WASTES OR CROP RESIDUES
(TAKAI AND KAMURA 1966)
Used by permission, see Copyright Notice
.£=•
-J
Period
of
Incubation
Early
Later
State
of
Reduction
First
Stage
Second
Stage
System
Disappearance of 02
Disappearance of N03-
Formation of Mn2+
Formation of Fe2+
Formation of $2-
Formation of H£
Formation of CH4
Redox
Potential
(Millivolts)
+600 to +400
+500 to +300
+400 to +200
+300 to +100
0 to -150
-150 to -220
-150 to -220
Nature
of
Microbial
Metabolism
Aerobes
Facultative
anaerobes
Obligate
anaerobes
Formation
of
Organic
Acids
None
Some accumulation
after addition of
organic matter
Rapid accumula-
tion
Rapid decrease
-------
through flooding or cultivation. Anaerobic conditions may be maintained by
keeping the soil saturated with water and limiting aeration. Regular culti-
vation of soil can be used to maintain aerobic conditions.
Nutrient status—The biological degradation of hazardous compounds
requires the presence of nutrients for optimum biological growth (Table 3-15).
Three of the major nutrients, nitrogen, phosphorus, and potassium, can be
supplied,in common inorganic fertilizers. Calcium deficiencies usually occur
only in acid soils and can be corrected by liming. If the soil is deficient
in magnesium, the use of dolomitic lime is advised. A high level of exchange-
able bases (calcium, magnesium, sodium, and potassium) on the surface exchange
sites of the soil is also desirable for good microbial activity and to prevent
excessively acid conditions.
Though sulfur levels in soils are usually sufficient, sulfur is also
added as a constituent of most inorganic fertilizers. Micronutrients also
occur in adequate amounts in most soils. At hazardous waste sites, the
primary danger may be in overloading of the soil with one of these elements
TABLE 3-15. ESSENTIAL ELEMENTS FOR BIOLOGICAL GROWTH (BASED ON REQUIREMENTS
FOR PLANT GROWTH) (TISDALE AND NELSON 1975)
Used by permission, see Copyright Notice
Elements
Minor nutrients:
Iron
Manganese
Boron
Molybdenum
Copper
Zinc
Chlorine
Sodium
Cobalt
Vanadium
Silicon
Source
Major nutrients: Carbon "^
Hydrogen >
Oxygen )
Nitrogen "^
PhosphorusV
Potassium f
Sulfur J
Calcium >
Maqnesium J
Air
and
Water
Soil, inorganic
fertil izers,
or in waste
Soil liming
materials, or in
waste
Soil, soil
amendments,
in waste
or
43
-------
which may have been in the waste, thus causing toxicity and leaching problems.
The pH of the soil is also important, for it determines for some of the
elements their solubilities and availabilities and thus toxicity and leaching
potential (Figure 3-10) (K. W. Brown and Associates 1980).
Hydraulic Properties of the Soil Profile--
Soil/water relationships and associated soil hydraulic properties affect
both the movement of hazardous compounds through the soil and the soil pro-
cesses acting within the soil profile to effect attenuation of waste com-
pounds. Biodegradation of waste chemicals requires water for microbial growth
and for diffusion of nutrients and by-products during the breakdown process.
Soil hydraulic properties are those properties whose measurement involves the
flow or retention of water within the soil profile (U.S. EPA 1977).
The total volume of a soil consists of about 50 percent pore space and 50
percent solid matter. Water entering the soil fills the pore spaces until
they are all full. The water then continues to move down into the subsoil,
displacing air as it travels; this flow, when the soil is at its maximum
retentive capacity, is said to be saturated. After water input to the soil
ceases, the water drains from the pores, and the soil becomes unsaturated.
Water in the soil below the saturation level is held in the soil against the
force of gravity. The forces that hold the water in the soil result from the
surface tension of water, the cohesion of water molecules, the adhesion
of water molecules to soil surfaces, and other electrical forces at the
molecular level. The terms soil water pressure potential or matric potential
are used to describe the energy required to remove water from an unsaturated
soil. This energy may be expressed as a potential, (e.g., erg/g), as pressure
(e.g., dyne/cm2 or bar), or as pressure head (e.g., cm). All of these terms
are negative quantities, since water is held in the soil pores at less than
atmospheric pressure. Soil tension and suction are also used to describe the
energy of soil water retention, but are reported as positive quantities and
are not precise in regard to units.
The force by which water is held in the soil pores is approximately
inversely proportional to the pore diameter. As water evaporates or drains,
the larger, or macropores, drain first, while the smaller, or micropores, are
still filled with water. Therefore, as soil water content decreases, the
absolute value of the matric potential increases. A graphical representation
of such a relationship is known as a soil moisture characteristic curve and is
illustrated in Figure 3-11 for several different soil textures. The shape of
the soil water characteristic curve is strongly dependent on soil texture and
structure. Soils witn primarily large pores", such as sands, lose nearly all
their water at a very small (absolute value) matric potential. However, soils
with a mixture of pore sizes, such as loamy soils, hold more water at satura-
tion due to a greater porosity and lose water more slowly as the absolute
value of the matric potential increases.
The terms field capacity and permanent wilting point are qualitative
descriptions of soil water content. Field capacity refers to the percent-
age of water remaining in a soil after having been saturated and after free
gravitational drainage has ceased. Gravitational water movement is signifi-
cant in migration due to leaching of hazardous compounds ana nutrients for use
49
-------
SOIL WATER CONTENT 9m
(MASS OF WATER/MASS OF DRY SOIL)
01
02
0 3
F 1 ( LO C» '» C I TT
(0.3 03')
- I 600
Figure 3-11. Soil-water characteristic curves for several soils (Taylor and
Ashcroft 1972). Used by permission, see Copyright Notice.
in microbial degradation of the compounds. Also, if water does not drain
quickly from the soil, it may have a harmful effect on microbial activity due
to poor aeration. It may also affect solubility of compounds due to an
alteration in oxidation-reduction potential. Field capacity of a particular
soil is not a unique value but represents a range of water contents. In
sands, moisture content at field capacity corresponds to matric potentials in
the range of -0.10 to -0.15 bar, while in medium to fine-textured, potentials
range from -0.3 to -0.5 bar, with -0.3 bar most commonly used.
Drainage does not cease at field capacity but continues at a reduced
rate aue to movement of water through micropores by capillarity. Adhesive
attraction between the water and the walls of the micropores causes water
to move through the pores, pulling along other water due to the cohesive
attraction between water molecules. Capillary water can move in any direction
in the soil, following micropore channels.
When moisture in a soil is no longer in adequate supply to meet the
demands of plants growing in the soil, ana plants wilt and remain wilted, the
moisture content is said to be at the permanent wilting point. This moisture
content occurs in most soils when the matric potential is in the range of -15
bars. The amount of water held in a soil between field capacity arid the
permanent wilting point is known as available water. This is the water
available for plants and for soil microbial and chemical reactions. Informa-
tion on optimal and marginal water potentials for growth, reproduction, and
50
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survival of individual species of microorganisms in soils is limited (Taylor
et al . 1980). Bacterial activity is highest in wet conditions, but noticeably
decreases by about -3 bars (Clark 1967). Some fungi can grow and survive in
soils under dry conditions. Fungal growth is often decreased in wet soils,
suggesting that bacteria may be antagonistic to fungi under these conditions.
At low potentials, bacteria are less active, thus allowing fungal growth (Cook
and Papendick 1970).
As seen in Figure 3-12, though fine-textured soils have the maximum
total water-holding capacity, medium textured soils have the maximum available
water due to favorable pore size distribution. Even at the permanent wilting
point, soil contains a considerable amount of water, though it is unavailable
for use. This water, which is bound tightly to individual soil particles, is
known as hygroscopic water.
Permeability describes the ease with which liquids pass through the
soil. Knowledge of permeability is necessary to predict the rate of movement
of hazardous compounds through a soil profile.
Water moves through soils according to Darcy's Law:
q = K dH/dL " (3-1)
q = flux of water per unit cross sectional area (cm/h)
K = permeability of hydraulic conductivity (cm/h)
dH/dL = total head (or hydraulic) gradient (m/m)
The total head is the sum of the soil water pressure head (h) and the head due
to gravity (z), or H = h + z. The path length of water is L.
The hydraulic conductivity constant K is not a true constant but changes
rapidly as a function of water content. Even under conditions of constant
water content, K may change due to swelling of clay particles or changes in
the chemical nature of the soil water. Due to their negatively charged
where
Sand Sandy Loam
loam
Clay
loam
Clay
Figure 3-12. Typical water-holding capacities of different textured soils
(Fcth 1978). Used by permission, see Copyright Notice.
51
-------
nature, soil clay particles tend to repel each other and remain dispersed,
resulting in low permeability. Positively charged cations in the soil water
neutralize the negative charges and allow the soil particles to come close
enough together so that floccul ation can occur, which increases soil pore size
and permeability. Thus a water low in salts may result in permeability
problems.
However, sodium in its hydrated state is much larger than the other
common cations and tends to keep clay particles dispersed. If sufficient
salt is present, the layer of sodium ions will be suppressed so the clay
particles can flocculate. However, the required salt concentration may
be so high as to restrict microbial activity and degradative processes in
the soil. The sodium adsorption ratio (SAR) is used as a measurement of
the degree to which sodium will be adsorbed by soils from a solution in
equilibrium with the soil. Specifically:
SAR = a
Ca * + MgV2
where the ionic concentrations are expressed in mi lliequivalents per liter.
As a general rule, an SAR of 15 or greater is considered unacceptable.
However, there is a difference depending on the dominant clay type. With
kaolinate, the SAR may be as high as 20 before serious swelling problems
occur. However, with soils in which montmoril lonite is dominant, SAR values
of 8-10 may cause serious swelling problems (Ferguson 1976).
Other chemicals, especially organic compounds, may also alter soil
permeability. Potential for such alteration should be investigated in order
to predict and minimize leaching of the compound, if it is hazardous itself,
or to determine if it would increase the leaching of associated hazardous
compounds.
Soil permeability is primarily determined by soil texture, with coarser
materials usually having higher conductivities. However, soil structure may
also be important by increasing macropore space in a finer-textured soil. A
listing of permeability values for soils classified by the USCS is shown in
Table 3-16.
Hydraulic conductivity decreases greatly as water content decreases
below saturation. In sandy soils, though permeability is much higher at
saturation than in loamy soils, permeability decreases more rapidly as the
matric potential becomes more negative, eventually becoming lower than in
medium textured soils.
Drainability is a term used to describe the relative rapidity and extent
of removal of water from a soil profile. Drair.ability is dependent upon the
permeability (i.e., K, the hydraulic conductivity) and groundwater relation-
ships that are controlled by soil properties and the position of the site on
the lancscape (i.e., the hydraulic gradient, dH/dL). A well-drained soil (e.g.
a loamy soil) is one in which water is removed readily but not rapidly; a
52
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TABLE 3-16. PERMEABILITY VALUES FOR SOILS CLASSIFIED IN THE
UNIFIED SOIL CLASSIFICATION SYSTEM (YANG AND BYE 1979)
Earth Material Category Unified Soil Permeability
Classification Range (cm/sec)
System Designation
Gravel GW, GP
Medium to Coarse Sand SW, SP Permeable
Fine to Very Fine Sand SW, SP >10-4 cm/sec
Sand with <15% Clay, Silt GM, SM, SC Semi-permeable
Sand with >15% but £50% Clay GM, SM, ML 10-2 to 10-6 cm/sec
Clay with <50% Sand OL, MH Relatively impermeable
Clay CL, CH, OH <10-6 cm/sec
poorly drained soil (e.g., a poorly structured fine soil) remains waterlogged
for extended periods of time, resulting in reducing conditions and insuffi-
cient oxygen for biological activity; an excessively drained soil (e.g. a
sandy soil) is one in which water is removed so completely that droughty
conditions occur.
For in situ treatment of hazardous waste contaminated soils, the most
desirable soil would be one in which permeability was only large enough to
maximize soil attenuation processes (e.g. adequate aeration for aerobic
microbial degradation) while still minimizing leaching (assume lower perme-
abilities protect against leaching).
Infiltration rate refers to the rate at which water enters the soil from
the surface. When the soil profile is saturated, the infiltration rate
is equal to the saturated hydraulic conductivity. However, when the soil
initially is relatively dry, the infiltration rate is higher as water enters
large pores and cracks. The infiltration rate is reduced rapidly to a near
steady-state value as the large pores fill and clay particles swell. Infil-
tration rates are affected by soil texture and structure, ionic composition of
the applied liquid, condition of the soil surface, and type of vegetation.
Another soil characteristic important in terms of potential migration
of hazardous compounds is the depth to an impermeable layer, bedrock, or
groundwater (including seasonal variations). The depth affects the drain-
ability of the soil and the effective depth for pollutant attenuation. It
may also indicate whether leaching to groundwater poses an acute hazard.
Ryan and Loehr (1981) reported that with depths of less than 1.5 m,
horizontal flow predominates and the saturated hydraulic conductivity can be
assumed to be equal to the permeability of the saturated horizon with the
53
-------
highest permeability. The hydraulic gradient is assumed to be equal to the
slope of the limiting layer and can be approximated by the slope of the soil
surface. When the depth to an impermeable layer, bedrock, or groundwater is
greater than 1.5 m, vertical flow is predominant. The saturated hydraulic
conductivity of the soil can be assumed to be equal to the permeability of the
most limiting horizon, and the hydraulic gradient is assumed to be one.
An assessment of the flooding frequency of the site should be made
to determine potential for off-site migration in floodwaters. Only slight
hazards exist if the soil is usually not flooded any part of the year, moder-
ate hazards if occasional flooding occurs (10-50 percent chance of flooding
once every two years) and severe hazards if frequent flooding occurs (greater
than 50% chance of flooding every two years) (Ryan and Loehr 1981).
Potential for off-site migration in runoff can be predicted by site/
soil characteristics and waste characteristics. Various runoff models have
been developed and can be used as predictive tools. (See Huber and Heaney
(1981) and Foster (1981) for reviews of available models.) If the situation
warrants, precautionary methods to reduce erosion should be included as an
important and necessary part of an in situ remedial treatment plan.
Runoff is the portion of precipitation that appears in surface waters.
Technically runoff not only includes surface and subsurface runoff but also
movement of water vertically to groundwater and then lateral movement of the
groundwater to surface receiving waters (baseflow). Surface runoff is water
that travels over the ground surface to reach a lake or stream (overland
flow). Subsurface runoff is water that has infiltrated the surface soil and
moved laterally through the vadoze zone to the receiving water as shallow flow
above the groundwater (interflow). Because the pathway that water takes to the
receiving water determines what type and how much of a chemical is transported
to that water, the three types of runoff need to be estimated separately to
assess potential problems. Surface runoff may carry chemicals in solution, in
suspension, or adsorbed to suspended soil particles. Subsurface runoff and
groundwater carry primarily soluble chemicals not strongly adsorbed to soil
particles.
Steenhuis and Walter (1979) describe a method of categorizing pollutants
with regard to potential losses in soil and water according to their relative
concentrations in water and on soil particles as indicated by adsorption-
desorption isotherms. An adsorption partition coefficient, ks, for a given
solution concentration is a calculated as the ratio of amount adsorbed to that
in solution:
ks =
concentration of substance adsorbed to soil particles (ppm; mg/kg)
concentration of substance in solution (ppm; mg/1)
Group I pollutants are those with ks values approximately equal to 1000.
These include the strongly adsorbed and solid phase pollutants. The loss of
tnese pollutants in baseflow and interflow is small. Their losses in overland
flow are high ana are related to the amount of sediment in the soil and the
54
-------
amount of substance in the soil. Organic matter, which may be an important
sorbent of hazardous compounds, is more easily eroded than most mineral
particles and tends to remain in suspension because of its low density. Silt
and clay are also more credible than sand and are usually higher in organic
matter content, which may be adsorbed on the clay particles. Clay is also an
important sorbent of hazardous compounds. Therefore, an "enriching process"
occurs in overland runoff in which the concentration of a hazardous compound
in an eroded sediment may be much higher than in the original soil. Loss of
Group I pollutants can be decreased by erosion control practices which
minimize sediment detachment and transport.
Group II pollutants, with ks values of about 5, include the moderately
adsorbed pollutants (e.g. most pesticides). Their loss in overland flow has
been shown to be related to the amount of runoff water and not to the amount
of soil loss. Erosion control practices which prevent sediment detachment and
transport are not as effective as practices which reduce the total amount of
runoff volume. Transport of adsorbed substances by water passing through the
soil matrix is much slower than transport by surface flow. An equilibrium
exists between substances dissolved in the soil water and those adsorbed to
the soil. The greatest pollution of sub-surface flow water comes from those
substances which are weakly adsorbed or those slow to degrade.
The Group III pollutants have ks values of about 0 to 0.5 and are non-
adsorbed or soluble pollutants. Their primary pathway of loss is through
interflow and baseflow. Losses in surface runoff are small and therefore are
not greatly affected by practices to reduce runoff. In fact, reduced runoff
might increase subsurface flow and thus increase their losses to interflow and
groundwater.
Moderately and weakly adsorbed substances usually migrate fairly rapidly
after application to the soil with initial precipitation events. Strongly
adsorbed substances, depending on their recalcitrance, may pose hazards for
years due to movement in overland flow.
The control of runoff can be accomplished by several means (Steenhuis
and Walter 1979). Decreasing runoff velocity will reduce both surface runoff
volume and sediment loss. More water remains on the soil for a longer period
of time, thus permitting increased infiltration. Runoff velocity may be
reduced in several ways: 1) by forcing water to move laterally rather than
straight down slopes; 2) by reducing the slope of the land through land-
forming; or 3) by increasing the roughness of the soil surface to dissipate
the kinetic energy of the water.
An increase in surface storage will remove trapped water from total
surface runoff volume, thereby resulting in decreased runoff velocity and a
reduced sediment carrying capacity. Surface storage can be increased by
various engineering and agricultural practices (e.g., creation of ridges of
soil or vegetation) which allow water to pool. Moisture storage capacity in
the soil itself can be increased by addition of organic matter or by draining
or evaporating moisture already in the scil profile.
Infiltration governs the amount of water that will enter a soil. Thus
engineering and agronomic practices that affect the physical, chemical,
55
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and biological soil characteristics may alter infiltration rates. Changes in
bulk density, porosity, and percent of water-stable aggregates all affect a
soil's capacity for infiltration and its erodibility. Infiltration rates can
be increased by lower bulk densities and higher porosity or by an increase in
the number of macropores connecting to the soil surface.
Frozen soil often has a lower infiltration rate than unfrozen soil,
especially if the soil was frozen when moist. Since frost usually penetrates
deeper if soil is bare than if it is snow covered, practices that prevent snow
from blowing away may lessen frost penetration. However, the additional snow
may increase surface runoff. Snowmelt occurring in the spring, often on
frozen ground, can carry a higher contaminant load than rainfall runoff that
has infiltrated the ground. Also the time frames in which rainfall runoff
and snow melt runoff occur are different. Rainfall runoff occurs when the
infiltration capacity of the soil is exceeded by the rate of precipitation.
The infiltration capacity may be exceeded by the intensity of the rainfall
event and/or its duration. Spring snowmelt occurs over a period of time
interrupted periodically by subfreezing weather and continuing until all the
snow melts.
Runoff can also be controlled by reduction of the splash-energy of
falling rain. Raindrop impact on bare soil may break soil aggregates to
component particles. These smaller particles may be carried by water into
larger pores, thus forming a thin surface layer with low hydraulic con-
ductivity. Dissipating raindrop energy by use of a plant canopy or mulch or
promoting aggregate stability with organic matter addition may greatly reduce
this surface sealing effect.
Off-site Migration in Air--
Soil properties that affect off-site migration of hazardous compounds
via air transmission also need to be characterized. Again, the degree of
migration in air is an interaction between soil/site characteristics and
waste characteristics.
Important soil properties that determine the extent and rate of volatili-
zation of hazardous compounds are those related to soil permeability and soil
moisture. The total porosity of the soil, the distribution of macro and
micropores, and the tortuosity of the soil pores should be characterized. The
range of air-filled porosities exhibited by the soils under moisture regimes
encountered at the contaminated site also should be investigated, for wetter
soils are less permeable to gases than dry soils. At lower moisture contents,
there is also an increase in sorption of compounds. Volatilization of com-
pounds from soils is more completely discussed in section 6.
wind erosion, unlike water erosion, is not divided into types but varies
only by degree. The major factors affecting erosion by wind are climate,
soil, and vegetation. Specific factors are shown in Table 3-17. A wind
erosion model has been developed by Chepil and Woodruff (1963) to predict soil
loss from wind erosion.
Geological and Hydrogeological Factors--
In addition to soil characteristics, geological information in the form
of subsurface geological characteristics and nydrcgeological factors are
56
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TABLE 3-17. FACTORS AFFECTING EROSION OF SOIL BY WIND (SCHWAB ET AL. 1966)
Used by permission, see Copyright Notice
Climatic Variables Soil Factors Vegetative Factors
Precipitation Texture Height and density of
Temperature Structure cover
Wind Particle density Type of vegetation
Humidity Bulk density Seasonal distribution
Viscosity of air Organic matter
Density of air Moisture content
Surface roughness
important in determining potential for offsite migration via transmission by
water to ground or surface receiving waters. The nature of groundwater flow
systems within the subsurface structure is an -important factor which deter-
mines the impact hazardous wastes may have on the environment.
The geological framework of the site consists of the rocks or sediments
in the formations beneath the site. Information is required on the extent,
composition, stratification, and thickness of the layers. For example,
sedimentary layers (e.g., limestones, sandstones, and shales) tend to channel
flows along bedding planes. Thus, flow directions may be determined by
dips in the strata. In humid climates, solution channels may form in lime-
stones, which may allow very rapid transport of pollutants over long distances
with little attenuation. Fracture zones that occur in igneous and meta-
morphic bedrock (e.g. granites, diorite, marble, quartzite, slate, gneiss, and
schist), may also permit rapid transport of polluted groundwater (Blackman et
al. 1980). The most favorable areas would be those covered by thick deposits
of unconsolidated low permeability materials overlying shales or undisturbed
fine-grained sedimentary bedrock formations which have no major structural
variations or fractures affecting formation stability (Corbin 1980). Large
thicknesses of unconsolidated materials allow opportunities for natural
attenuation while providing a protective barrier to any usable aquifer
system.
Hydrogeological factors relating to groundwater are also required to
assess potential for pollution from hazardous waste contaminated soils.
For groundwater in unconsolidated formations, less hazard exists if there
is no connection with surficial or buried drift aquifers, especially if
the hazardous waste site is overlain with lower permeable materials to
bedrock. For groundwater in bedrock formations, more favorable conditions
to minimize pollution potential from hazardous waste sites exist if the
site is away from any recharge areas to major freshwater aquifers or there is
no direct connection to a usable bedrock aquifer (Corbin 1980). Confined
groundwater, which is isolated from the surface by a relatively impermeable
bed consisting of clay, shale, or dense limestone, is not easily contaminated,
nor is it affected much by local sources of recharge (Warner 1976).
57
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Knowledge of the nature of groundwater flow patterns is also critical.
Localized, rather than regional, groundwater flow patterns, preferably with
known discharge points and a large distance to the water table are the most
favorable conditions. Information required to assess hazard might include:
1. Elevations of water table and potentiometic surface (groundwater
gradients).
2. Fluctuations of groundwater levels due to natural inputs and outputs
of water.
3. Drawdowns of groundwater levels from wells (cones of depression
caused by pumping can alter groundwater levels from those that would naturally
exist).
4. Effects on groundwater flow patterns from changes in surface water
flows or levels.
5. Hydraulic characteristics of the aquifer including transmissivity,
specific yield, and specific retention.
Specific yield and specific retention are measures of the amount of ground-
water an aquifer will yield upon pumping. Specific yield is the amount of
water that will drain by gravity from a saturated aquifer divided by the bulk
volume of the aquifer. Specific retention is equal to the porosity minus the
specific yield under saturated conditions. Transmissivity is the rate at
which water is transmitted through a unit width of the aquifer under a unit
hydraulic gradient. It is equal to the permeability multiplied by the aquifer
thickness (U. S. Environmental Protection Agency 1977).
Meteorological and Climatological Data--
Meteorological and climatological data are required to assess the public
health hazard from migration of hazardous compounds to receiving ground and
surface waters and via air transmission. These factors also impact upon the
attenuation of hazardous compounds in the soil environment.
The dispersion characteristics of the area are an important component
of the air migration potential. Greater dispersion associated with open
lands is more favorable than areas with channel type dispersion, such as
in valley and depressional areas. Determination of prevailing wind directions
and wind velocities will give an indication of the direction and extent of
migration.
Temperature of both the air and soil affect the rate of biological and
chemical attenuation processes in the soil, the volatilization of compounds,
and the soil moisture budget. In general, temperature is difficult to control
in a field situation, but may be affected by the use of mulches of natural or
artificial materials and soil moisture control.
Most soil microorganisms are mesophiles, i.e. they exhibit maximum
growth and activity in the 20 to 35"C temperature range. Soils also contain
some microorganisms which grow best at temperatures below 20°C (psychropiles)
58
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and some which exhibit maximum growth rates between 50 to 60°C (thermophiles).
In general, organic matter decomposition increases with increasing tempera-
ture. The influence of temperature on microorganism activity should be
considered to estimate the time for site recovery.
Soil temperature data are not as extensive as air temperature data.
K. W. Brown and Associates, Inc. (1980) discuss a method for predicting
annual soil temperature cycles developed by Fluker (1958). They also present
isotherm maps of soil temperature data at the 4-inch depth for the spring of
1979 in the United States.
The preparation of a water budget for the contaminated hazardous waste site
will aid in indicating leaching potential and predicting the type and extent
of attenuation processes that will act upon the waste (biodegradation, sorp-
tion, etc.). Inputs to the site include precipitation and any added water
that may be necessary for execution of the appropriate in situ treatment
technique. Factors which may limit required water addition must also be
considered, such as the total amount of precipitation relative to evapo-
transpiration, the distribution of precipitation during the year, and changes
in precipitation from year to year. Outputs include evaporation, transpira-
tion, percolation to the groundwater, and subsurface and surface runoff.
Precipitation data may be based on real measured rainfall events or on
frequency analyses, (e.g. amount of precipitation expected in a 10-year,
24-hour storm, 25-year, 1-hour storm, etc.). Of importance is the total
rainfall a site receives as well as the intensity, duration, and frequency of
single precipitation events.
Evaporation is the transfer of liquid water into the atmosphere. Factors
affecting the rate of evaporation are the nature of the evaporating surface
and the vapor pressure differences as affected by temperature, wind, atmo-
spheric pressure, quality of water, and available energy (Schwab et al. 1966).
In saturated soils, evaporation is expected to be the same as from open
freewater surfaces. However, in unsaturated soils, below field capacity,
evaporation is very low, as soil moisture movement is slow when the soil is
relatively dry.
Transpiration is the process by which water vapor passes into the atmo-
sphere through the tissues of living plants. Loss of soil moisture by tran-
spiration is often a substantial portion of the total water available during a
growing season. Transpiration is dependent on the moisture available, the
kind and density of plant growth, the amount of sunshine, and soil fertility
and structure.
The measurement of evaporation and transpiration is usually combined
and referred to as evapotranspiration. Evapotranspiration can either be
measured directly or predicted using various models (e.g. see Schwab et
al. 1966 for a discussion of methods).
The Receiver System--
The receiver system around the hazardous waste contaminated site may
be an important site charactertistic, which, when evaluated in conjunction
59
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with waste characteristics, may determine precautions necessary to prevent
migration of hazardous constituents and also may dictate the remedial action
appropriate for the specific site/soil/waste situation. For example, a
contaminated site located in a sparsely populated arid region over a deep
unusable aquifer may not require the use of a quick-acting remedial in situ
treatment technique. However, a site in an urban area, with high rainfall and
soils of high erosion potential, overlying a heavily used aquifer, may require
the choice of an in situ treatment technique with little or no secondary
health impacts and which can treat the wastes in a shorter span of time.
The characteristics listed in Table 3-18 can be used to give an assess-
ment of hazard potential. Information from organized hazard ranking systems,
such as the Mitre Hazard Ranking System Model, the LeGrand Model, the Surface
Impoundment Assessment Model, the EPA Solid and Hazardous Waste Research
Division Model, and the Rating Metholodogy Model (Caldwell et al. 1981) may be
available or be used to obtain an indication of the urgency of clean-up and
required precautionary methods.
TABLE 3-18. IMPORTANT RECEIVER CHARACTERISTICS
Migration to Groundwater
Groundwater use - present and potential
Groundwater quality-usability of aquifer
Distance to nearest downgradient well-treatment of water from the well
Population served
Discharges to surface waters - uses of surface waters
Recharge zone for freshwater aquifer
Migration in Runoff to Surface Waters
Surface water use - drinking, recreation, fishing, irrigation, livestock
watering
Population served
Distance to a sensitive environment - floodplain, wetlands, etc.
Migration via Air Transmission
Distance to nearest human population
Population within 1 mile radius
Population downwind from site
Land use - crops, forestry products, livestock, urban, schools, parks,
playgrounds, industrial, residential, etc.
Distance to a sensitive environment
60
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Site Characteristics with Regard
to In Situ Treatment Techniques"
Soil and site characteristics necessary for the choice and design of
in situ treatment techniques overlap significantly with the data required
to assess the potential for off-site migration of hazardous compounds from
contaminated sites. Many of the natural attenuation processes which determine
migration potential may be used as in situ techniques but under engineering
management control and monitoring. Therefore, the characteristics listed in
Table 3-2 are also relevant for choosing appropriate treatments for degrading,
transforming, or immobilizing hazardous compounds. Those characteristics
which are subject to some degree of engineering control are indicated in Table
3-2. The remainder of this chapter is devoted to the discussion of soil
attenuation processes related to hazardous waste treatment. In Section 2 of
this manual, various treatment processes based on soil attenuation properties
are discussed.
Site Characterization Related to Physical
Execution of In Situ Treatment Technology
Site requirements for the physical execution of an in situ treatment
technique may be a determining factor in whether the technique may actually be
utilized at a particular site or what precautions or operational controls
need to be incorporated into the execution plan.
The trafficability of the soil under different climatological and soil
moisture conditions needs to be assessed. There may be restrictions on the
type of equipment that can be used and times when the equipment can be used
(e.g., presence of boulders, steep slopes, excessively wet conditions in
clayey soils).
Trafficability refers to the capability of a soil to permit the movement
of a vehicle over the land surface (Reeve and Fausey 1974). In military
operations, trafficability is defined as whether or not vehicles of various
kinds can pass over a given terrain without regard for the final condition of
the soil. However, in agriculture, the primary concern is for successfully
performing given operations on the land without damaging the soil. Such
damage might include decreased permeability to air and water, altered thermal
relations, and resistance to root penetration. Generally, trafficabi1ity
means being able to perform required operations in such a way as to create a
desired soil condition or to get an operation completed expediently. Opera-
tions that require manipulation (tillage) require a different interpretation
of trafficabi lity than do operations in which soil is used as a surface on
which to operate (non-tillage).
The U. S. Army Engineer Waterways Experiment Station (1956) identified
four soil characteristics that relate to trafficability of soils: 1) bearing
capacity, 2) traction capacity, 3) siipperiness, and 4) stickiness. Any one or
a combination of these may cause vehicle immobilization.
The traf f icabi lity of a soil is considered adequate for a vehicle if
it has sufficient bearing capacity to support the vehicle and sufficient
61
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traction to develop the forward thrust necessary to overcome the rolling
resistance. Bearing and traction capacities are related to soil strength
or shear resistance. Soil strength can be determined by laboratory tests
(direct shear, triaxial shear, and unconfined compression) or by a field
test using a cone penetrometer.
Slipperiness is the condition of deficient traction capacity in a thin
surface layer of soil which is otherwise trafficable. When soils adhere and
build up on the running gears of a vehicle, increasing rolling resistance and
making steering difficult, the condition is called sticky. Soil stickiness
and slipperiness usually occur on soils high in clay. When the soil surface
is cooler than the underlying soil, moisture migrates from the lower layers to
the surface. If the evaporative demand is not great, the moisture accumu-
lates at the surface and causes decreased traction. This condition is not a
problem which can be alleviated by drainage, but by water management. It is
especially a problem in seasons when the radiant energy input is low.
Damage to the soil by vehicular traffic usually results from compressing
and puddling the soil. To avoid such damage, the soil must be manipulated or
traversed when the soil is below some critical moisture level, which is
dependent on the type of soil. Wet soils are easily compacted by both tillage
and nontillage operations. Clay soils are especially a problem, since they
hold a large amount of water that must be removed by internal drainage or
evaporation before tillage is possible.
Soil compaction can be reduced in several ways. Reducing the load
intensity on a soil or reducing the number of trips over a soil can be accom-
plished by changing machinery configurations or tractor tire designs. Sub-
surface and surface drainage systems can also be used to reduce soil moisture
content.
Other site conditions which may affect trafficability include slopes and
the presence of large coarse fragments, such as boulders. Reeve and Fausey
(1974) present a review of methods regarding the determination of soil traf-
ficability using predictive equations and empirical rating systems.
If the treatment itself requires a certain site condition, modifications
must be made, if possible, to achieve that condition. An assessment must be
made to determine if required modifications are feasible at that particular
site. For example, the initial steps in biodegradation of a chlorinated
organic compound may require anaerobic conditions followed by aerobic condi-
tion. Thus the site/soil infiltration, permeability, and drainability
characteristics all determine whether anaerobic/aerobic conditions can be
achieved.
Sources of Information
Many hazardous waste sites for which in situ treatment may prove to
be an appropriate remedial response may have been subjected to earlier
acute emergency response cleanup actions or preliminary investigations to
determine the necessity of remedial action, such as a Superfund site. There-
fore, there may be significant existing data on site and soil characteristics.
62
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The necessary data required to assess the choice and execution of an appro-
priate treatment or series of treatments has been discussed generally in this
section and will be discussed in greater detail in the following sections
relating to soil attenuation processes. Existing data should be assessed
to determine adequacy for meeting information requirements and to design
any subsequent data collection activities. If data are sufficient, no new
characterization efforts are needed. If further data collection is needed,
trained soil scientists, geotechnical engineers, geologists, and other persons
trained in appropriate disciplines should be hired to generate the required
information.
Some sources of existing information include the following:
1. Government investigative reports (e.g., Field Investigation Team
(FIT) reports, Hazard Assessment Reports (Mitre Model)
2. Engineering data from other public or private agencies or firms
(e.g., university geology departments, state water resource agencies, state
geological surveys, city water departments)
3. County soils maps (general background i-nformation--on-site investiga-
tion also required)
4. Aerial photographs
5. Water well borings logs
6. Geotechnical reports from nearby facilities
It is expected that data related to potential migration from the site
(route characteristics) and potential public health hazards (waste and re-
ceiver characteristics) will have been generated for many sites where in situ
treatment is being considered. Most new data collection efforts will be
expected to emphasize information required for the choice and execution of
appropriate successful in situ treatment technology, i.e., the information
will center around soil characterization. Therefore, persons knowledgeable
in soil science should be utilized for sampling and analysis of soil samples
and for the interpretation of sample results.
WASTE CHARACTERIZATION RELATED TO IN SITU SOIL TREATMENT
Introduction
The hazardous-waste contaminated site must be thoroughly characterized
in terms of waste characteristics in order to assess the degrees of hazard to
both on-site workers and to off-site populations and to determine applicable
and appropriate types of in situ treatment technology. Together with knowl-
edge of soil and S'lte characteristics, knowledge of waste characteristics
will enable the selection of a particular treatment technique specifically
designed for the site/soil/waste situation or will indicate whether in situ
treatment is not appropriate for the specific situation.
63
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Since the wastes at a contaminated site do not exist separately from
the soil, measurement of waste types, amounts, and distributions must be
assessed as part of the soil, soil pore liquid, groundwater, or surface or
subsurface runoff. Thus analysis techniques will usually include both
extraction procedures to separate waste constituents from the environmental
matrix as well as chemical analyses of the constituents. It is not practical
to use identification based on observable characteristics, such as odor,
color, reaction, etc. In general, analysis of substances classified as
hazardous requires more sophisticated methods and instrumentation than
traditional waste parameters in pollution control, such as chemical oxygen
demand, nitrogen forms, phosphorus, etc.
Definition of Hazard and Degree of Hazard
A waste stream is characterized as hazardous if it is defined as hazard-
ous, or if it contains substances which are defined as hazardous (40 CFR 261),
or if it exhibits one or more of the characteristics of hazardous waste:
ignitability, corrosivity, reactivity, or toxicity.
Ignitability refers to wastes that either present fire hazards during
routine storage, transportation, or disposal or are capable of severely
exacerbating a fire once started. Corrosivity identifies wastes which have
the ability to mobilize toxic metals when discharged to a land environment,
corrode handling, storage, and management equipment, or destroy human or
animal tissue in the event of inadvertent contact. Reactivity refers to
wastes which have any of the following properties: ~TJreadily undergo
violent chemical change; 2) react violently or form potentially explosive
mixtures with water; 3) generate toxic fumes when mixed with water or, in
the case of cyanide or sulfide-bearing wastes, when exposed to mild acidic
or basic conditions; 4) explode when subjected to a strong initiating force;
5) explode at normal temperatures and pressures; or 6) fit within the Depart-
ment of Transportation's list of forbidden explosives (49 CFR 173.53), or
Class B explosives (49 CFR 173.88).
Toxicity, as used in defining a hazardous waste, refers to a reading
of toxicity in the Extraction Procedure (EP) Toxicity Test. The EP is
designed to simulate leaching of waste in a sanitary landfill. It is a
laboratory test in which a representative sample of a waste is extracted
with distilled water with pH maintained at 5 by acetic acid. The EP extract
is analyzed to determine if threshold levels for eight metals, four pesti-
cides, and two herbicides (Table 3.19) have been exceeded. If the EP extract
contains one or more of the substances in amounts equal to or exceeding the
specified levels, the waste is classified as hazardous according to the
Extraction Procedure Toxicity Test.
Definitions of methods to determine these characteristics are presented
in Test Methods for Evaluating Solid Waste: Physical/Chemical Methods (U.S.
EnvironmentalProtectionAgency1982b).In a contaminated environmental
sample, it may be difficult to determine if the waste substances exhibit
these hazardous characteristics. Chemical identification may be the only way
to determine which waste constituents are undesirable and thus require in
situ treatment.
54
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TABLE 3-19. MAXIMUM CONCENTRATION OF CONTAMINANTS FOR CHARACTERISTIC
OF EP TOXICITY (U.S. ENVIRONMENTAL PROTECTION AGENCY 1982b)
EPA Maxiumum
Hazardous Waste Concentration
Number Contaminant (mg/1)
D004
D005
D006
0007
D008
0009
D010
D011
D012
D013
D014
D015
U016
D017
Arsenic
Barium
Cadmium
Chromium
Lead
Mercury
Selenium
Si Tver
Endrin (1,2,3,4,10,10-Hexachloro-l
7-epoxy-l,4,4a,5,6,7,8,8a-octahydro-l
4-endo, endo-5,8-dimethanonaph-
thalene)
Lindane (1,2,3,4,5,6-
Hexachlorocyclohexane, gamma isomer)
Methoxychlor (l,l,l-Trichloro-2,2-bis
(p-methoxyphenyl jethane)
Toxaphene (CiQHioCis, Technical
chlorinated camphene, 67-69%
chlorine)
2,4-D (2,4-Dichlorophenoxyacetic acid)
2,4,5-TP (Silvex) (2,4,5-
5.0
100.0
1.0
5.0
5.0
0.2
1.0
5.0
0.02
0.4
10.0
0.5
10.0
1.0
Trichlorophenoxypropionic acid)
-------
Other waste characteristics are important in determining degree of
hazard, though not legally defined as such. These include various types
of human toxic effects, animal toxic effects, persistence/biodegradabi1ity,
infectiousness, volatility (affecting migration via atmospheric route),
and solubility (affecting migration via water routes) (U. S. Environmental
Protection Agency 1982b). These must also be assessed in order to select an
appropriate treatment technology which is effective and ensures safety for
both on-site workers and off-site populations.
Toxicity information is available from many different sources. The
following is a partial listing of reference publications and systems which
may be consulted for human and/or ecological toxicity data and chemical
hazards:
1. Chemical Hazards Response Information System (CHRIS), U.S. Coast
Guard, consists of four handbooks (A Condensed Guide to Chemical Hazards,
Hazardous Chemical Data Manual, Hazard Assessment Handbook, and Response
Methods Handbook), data bases for regional contingency planning, and the
Hazard Assessment Computer System.
2. Oil and Hazardous Materials Technical A-ssistance Data System
(OHM-TADS) is an automated information retrieval file designed to facilitate
the rapid retrieval of information on approximately 1000 chemicals. In-
cludes information on physical, chemical, biological, toxicological, air,
land, and water effects and commercial data.
3. Chemical Transportation Emergency Center (CHEMTREC) serves as
clearinghouse by providing an emergency 24-hour telephone number for chemical
emergencies. Provides warnings and limited guidance on hazards of spills,
fire, or exposure, and contacts shipper of the chemical.
4. TOXLINE (Toxicity Information On-Line), National Library of Medi-
cine, is a computerized data resource for health and toxicological effects
information.
5. NIH/EPA Chemical Information System (CIS), Interactive Sciences
Corporation, Washington, D.C, contains information on toxicological, analyti-
cal, and physical properties of chemical substances.
6. Organic Chemical Producers Data Base, EPA/ORD Cincinnati Research
Laboratory, contains data on physical/chemical properties, manufacturing
processes, uses, and by-products.
7. Karnofsky, B., J. King, P. Thielmann, K. Gleason, and M. Baer.
1981. Chemical information resources handbook: Toxics integration informa-
tion series. EPA-560/TIIS-81-001. Office of Pesticides and Toxic Sub-
stances, Washington, D.C. This publication describes chemical information
resources dealing with chemical toxicology, environmental effects, spill
responses, disposal methods, ambient air and water concentrations, control
technologies, and existing regulations.
8. Sax, Irving N. 1975. Dangerous properties of industrial materials.
Van Nostrand Reinhold Co., New York, NY.
66
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9. National Fire Protection Association. Hazardous chemicals data.
Boston, MA.
10. Milson, M. et al. (Eds.). 1976. The Merck Index, 9th Ed. Merck
and Co., Inc. Rahway, NJ.
11. Chemical Manufacturers Association. Chemical safety data sheets.
(SD-l-SD-96). CMA, Washington, D.C.
12. Fawcell, H. H., and W. S. Woods (Eds.). 1981. Safety and health in
chemical operations. 2nd ed., Wiley-Interscience, New York, NY.
13. Bretherick, L. 1979. Handbook of reactive chemical hazards.
Butterworths, Boston, MA.
14, National Institute for Occupational Safety and Health (NIOSH).
Registry of Toxic Effects of Chemical Subtances. Annual publication.
U.S. Government Printing Office, Washington, D.C.
15. Survey of Compounds Which have been Tested for Carcinogenic Activi-
ty. U.S. Government Printing Office, Washington, D.C. Seven-volume series.
16. American Industrial Hygiene Association. Hygienic guide series.
Detroit, MI.
17. Patty, F. A. Industrial hygiene and toxicology. Wiley Inter-
science, New York, NY.
18. National Institute for Occupational Safety and Health. NIOSH/
OSHA pocket guide to chemical hazards. Publ. No. 78-210, NIOSH, Washington
D.C.
A comprehensive list of biological test systems which may be used
to detect genetic toxicity of hazardous wastes is presented in Hazardous
Waste Land Treatment (U.S. Environmental Protection Agency 1983).
Toxicity of waste constituents to soil microorganisms is especially
of concern because of the effects on biological in situ treatment processes.
Acute microbial toxicity can be evaluated using a pour plate method which
enumerates total viable heterotrophic and hydrocarbon-utilizing microorgan-
isms. A overview of this method, which involves a series of soil/waste
dilutions in phosphate buffer, is presented in Table 3-20.
Another method is currently being tested by the U.S. Environmental
Protection Agency (1983) for evaluation of acute microbial toxicity in
hazardous waste land treatment systems. The Beckman Microtox"1 measures
the light output of a suspension of marine luminescent bacteria before
and after a sample is added. A reduction in light output signifies the
presence of toxicants in the waste sample (Beckman Instruments, Inc. 1982).
Soil respirometry (monitoring CO? evolution from soil/waste samples) may
also be used to determine effects of the complex waste in the soil system on
67
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TABLE 3-20. METHOD FOR DETERMINATION OF MICROBIAL TOXICITY OF A WASTE/SOIL
MIXTURE (U.S. ENVIRONMENTAL PROTECTION 1983)
Microorganism Type of Media
to be Enumerated for Enumeration
Total viable Soil extract agar, with
heterotrophs amphoteracin B.
Soil fungi Potato dextrose agar or_
soil extract agar with rose
bengal and streptomycin.
Hydrocarbon - Soil extract agar, with
utilizing bacteria carbon source replaced with
and fungi silica gel oil. (Prepared
by mixing fumed silica gel
with waste.)
microbial activity. In addition to monitoring toxicity, the technique can
also be used to study the effects of various soil treatments and amendments
on degradation of organic compounds (e.g., levels and timing of nutrient
additions, temperatures, etc.). A description of the technique is presented
in Hazardous Waste Land Treatment (U.S. Environmental Protection Agency
1983).
Preliminary Waste Identification
At a contaminated site, it may be possible to obtain a preliminary
assessment of expected waste constituents if the industrial source or sources
of the wastes stored at the site are known. Unique hazardous waste streams
are produced from a number of industries, including textiles, paper, leather
products, primary metals, etc. (U.S. Environmental Protection Agency 1983).
The draft edition of Hazardous Waste Land Treatment (K. W. Brown and Asso-
ciates, Inc. 1980) contains a section dealing with hazardous wastes by
specific industry. An update of this section is currently being prepared by
K. W. Brown and Associates, Inc.
Several hazardous waste generating activities are not specific to a
particular industry but are used in many industries to perform certain
processes. Examples of these activities include painting, electroplating,
and cleaning, which produce paint residues, metals and cyanide, and solvents,
respectively (U.S. Environmental Protection Agency 1983). Therefore, the
presence of specific hazardous substances may be predicted if the industry
or industrial process responsible for the wastes is known. Knowledge of the
68
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feedstocks used and expected industrial products and by-products will indicate
what substances may be present. Chemical analyses are still required, how-
ever, to confirm the presence and the degree of contamination.
Another source of information on waste constituents at a site may be
preliminary site assessments, such as those performed by Field Investigation
Teams (FIT) for the U. S. Environmental Agency. From such reports, informa-
tion on type and amount of constituents in soil, groundwater, and surface
water samples may be available.
Chemical Analysis of the Wastes
In order to effectively design an in situ treatment technology, the
types and amounts, and distribution of wastes present must be accurately
known. Knowledge of waste source will only give an estimate of specific
substances that may be present. Reactions between different wastes and in
the soil matrix may have created new hazardous substances which must also
be treated. In addition to the hazardous components of the wastes which
require treatment (i.e., by degradation, transformation, or immobilization),
other waste substances which may impact on the effectiveness of the treatment
process or have adverse effects on the soil system must also be characterized.
Treatment effectiveness and completeness also can only be determined by
knowledge of the waste constituents originally present at the site.
Identification of hazardous constituents in wastes is usually accom-
plished by instrumental methods rather than the standard types of analyses
commonly used for pollution analysis. Instrumental methods require more
costly equipment, a well-equipped analytical laboratory, and trained, skilled
personnel.
The instrumental methods used for analysis are:
1. Gas chromatography (GC)
2. High-performance liquid chromatography (HPLC)
3. Gas chromatography/mass spectrometry (GC/MS)
4. Atomic absorption spectrometer (AAS)
5. Inductively-coupled, argon-plasma spectrophotometry (ICAP)
GC and HPLC are used to quantitatively determine contamination levels of
known specific organic materials. Concentration levels in the parts per
billion range (ppb) can be determined. They are not suitable for qualitative
analysis of unknown substances. Different GC detectors are available for
analysis of different classes of organic compounds (Table 3-21).
GC/MS is primarily used for qualitative analysis but recent improvements
permit quantitative measurements as well. A large number of substances can be
simultaneously analyzed at ppb or sub-ppb levels.
69
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TABLE 3-21. TYPES OF GC DETECTORS (U.S. ENVIRONMENTAL PROTECTION AGENCY 1983)
Type of Detector
Type of Compounds Detected
Flame ionization detector
Flame photometric detector
Electron capture detector
Nitrogen-phosphorus detector
Hydrocarbons
Sulfur and/or phosphorus
containing compounds
Halogenated hydrocarbons
and phthalates
Nitrogen and/or phosphorus
containing compounds
AAS and ICAP are used for quantitative determination of metals in the
parts per million (ppm) or ppb range. AAS can quantify amounts of individual
metals, while ICAP can quantify amounts of several dozen metals simultaneous-
ly.
Tables summarizing U.S. Environmental Protection Agency-approved analyti-
cal procedures for 16 classes of organic chemicals and approved analytical
procedures for 80 hazardous materials are given in EPA Field Guide for Scien-
tific Support Activities Associated with Superfund Emergency Response '("U.S.
Environmental Protection Agency 1982a).
The U.S. Environmental Protection Agency (1983) has defined waste
characteristics important for hazardous waste land treatment in terms of
determination of hazardous constituents of the wastes and constituents
which may affect the soil as an effective treatment medium. These char-
acteristics are presented in Table 3-22. The reader is referred to the
referenced document for a thorough discussion of the significance of the
various constituents.
Waste Characteristics Related
to Soil Treatment"
Wastes identified at uncontrolled soil contaminated sites must also be
characterized with respect to properties that affect the behavior and fate
of chemicals in soil systems. Knowledge of properties that affect the
behavior and fate of chemicals also directly affect pathways of treatment,
or assimilation, of waste constituents in soil systems. Pathways of treat-
ment include 1) degradation, 2) transformation, and/or 3) immobilization of
chemical constituents in a soil treatment zone, with subsequent protection of
groundwater, surface water, and atmosphere.
Degradation and transformation reactions include chemical and biologi-
cal reactions which breakdown waste constituents resulting in nontoxic
70
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TABLE 3-22. METHODS FOR ANALYZING WASTE CONSTITUENTS IMPORTANT TO IN SITU
TREATMENT (ADAPTED FROM U.S. ENVIRONMENTAL
PROTECTION AGENCY 1983)
Element/Compound/
Property
Possible Analysis
Method(s)
Reference(s)
Inorganic chemicals/
properties
Metals
Halides
(bromine,
chlorine, and
fluorine)
Nitrogen forms
Electrical
conductivity
PH
Titratable acids
and bases
Organic chemicals
Total organic
carbon
Volatile organic
compounds
Sample digestion
followed by atomic
absorption spectro-
photometry or_ in-
ductively coupled arc
spectrometry
Various methods
Various methods
Saturation extracts and
other aqueous extracts
Colorimetric or poten-
tiometric
Aqueous waste suspen-
sions
Dry or wet combustion
with C02 determina-
ations; dichromate
oxidation techniques
Purge and trap or
head space deter-
minations: analysis
with GC or GC-MS
U.S. EPA 1982b
U.S. EPA 1979
Page et al. 1982
Adriano and Doner 1982
U.S. EPA 1982b
U.S. EPA 1979
Bremner and Mulvaney
1982
Stevenson 1982
Keeney and Nelson 1982
U.S. EPA 1982b
U.S. EPA 1979
Rhoades 1982
McLean 1982
U.S. EPA 1979
U.S. EPA 1982b
McLean 1982
U.S. EPA 1979
Nelson and Sommers
1982
U.S. EPA 1982b
71
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TABLE 3-22. CONTINUED.
Element/Compound/
Property
Possible Analysis
Method(s)
Reference(s)
Extract able
organics
organic acids
(e.g., carboxylic
acids, quaiacols,
and phenols)
organic bases
(e.g., alkyl,
aromatic, and
aza-heterocyclic
amines)
neutrals (e.g.,
aliphatic and
aromatic hydro-
carbons, and
oxygenated and
chlorinated
hydrocarbons)
Water solubles
Residual solids (e.g.,
inorganics and rela-
tively nondegradable
forms of carbon such
as coke, charcoal,
and graphite)
Liquid/liquid acid/
base extraction
method:
Analysis with GC
with capillary or
packed columns
Analysis with GC
with capillary or
packed columns
Analysis with GC
or HPLC
U.S. EPA 1983
Variable; further
study needed
Evaporation of water
from aqueous fraction
of acid-base extrac-
tion procedure
U.S. EPA 1983
U.S. EPA 1983
U.S. EPA 1983
U.S. EPA 1983
products. Immobilization reactions include adsorption and chemical reactions
which result in accumulation and termination of constituent mobility in the
soil treatment zone. Since many organic compounds and organo-metal1ic
complexes exhibit simultaneous decomposition and migration, the relative
rates of degradation and mobilization must be considered.
Characterization of chemical contaminants with respect to soil treat-
ment pathways (degradation, transformation, and immobilization) provides
the basis for establishing qualitative and calculational procedures for
determining soil assimilative capacities for hazardous waste constituents
or classes of constituents.
72
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Utilizing this approach for hazardous waste contaminated soils manage-
ment, all constituents and constituent classes identified as associated
with a specific uncontrolled site can be classified functionally into three
pathways by which soil treatment occurs. This approach also provides end-
points for field verification of treatment effectiveness and protection
of groundwater, surface water, and atmosphere.
Specific parameters important for determining the behavior and fate,
and therefore treatment pathways, for waste constituents in soil are listed
in Table 3-23. For each chemical, or chemical class, the information re-
quired can be summarized as: 1) characteristics related to potential leach-
ing, e.g., water solubility, octanol/water partition coefficient, solid
sorption coefficient; 2) characteristics related to potential volatilization,
e.g., vapor pressure, relative volatilization index; 3) characteristics
related to potential decomposition, e.g., half-life, degradation rate bio-
degradability index; and 4) characteristics related to chemical reactivity
e.g., oxidation, reduction, hydrolysis potential. Interfacing these "soil-
based behavorial characteristics" with specific site and soil properties
allows a determination of the potential for: 1) soil treatment and 2) offsite
contamination. This information, then, provides a rational basis for selec-
tion of treatment techniques that augment natural soil processes to accomplish
complete treatment of the waste.
Statistical Considerations
A sampling and analysis plan for characterization of wastes at a hazard-
ous waste contaminated site must be based on fundamental statistical concepts
such that the uncertainty of general conclusions based on partial knowledge
can be evaluated. Table 3-24 presents basic statistical terminology asso-
ciated with a sampling/analysis strategy. The primary objectives of such a
strategy are to collect samples that will allow sufficiently accurate (close-
ness of a sample to its true value) and precise (closeness of repeated sample
values) measurements of the chemical properties of the wastes. A complete
discussion of a statistical strategy to determine if chemical contaminants
are present at hazardous levels is presented in Test Methods for Evaluating
Solid Waste: Physical/Chemical Methods (U.S. Environmental Protection Agency
1982b).
IMMOBILIZATION OF CHEMICAL CONSTITUENTS AS
RELATED TO IN SITU TREATMENT
Inorganics
Rather than discuss all possible inorganic pollutants, this section
will be limited to those inorganics which have been the subject of concern
resulting from their toxicity and those that, because of their use in indus-
trial processes, are likely to be involved in an accidental spill. The
listing of inorganic priority pollutants as defined by the U.S. EPA (1976), is
given in Table 3-25. Figure 3-13 illustrates the frequency of occurrence of
inorganics in soils found at Superfund and non-Superfund sites (F.I.T. Re-
ports). Table 3-26 lists the percent occurrence for each element. The
concentration range of inorganics found at Superfund plus non-Superfund sites,
73
-------
-------
TABLE 3-24. BASIC STATISTICAL TERMINOLOGY APPLICABLE TO SAMPLING PLANS FOR
SOLID WASTES (U.S. EPA 1982b)
Terminology Symbol
• Variable (e.g., barium X
or endrin)
• Individual measurement X.
of variabl e
• Mean of all possible y
measurements of variable
(population mean)
• Mean of measurements x
generated by sample
(sample mean)
Mathematical equation
N
Z X.
1=1 n
, with N = number
(Equa-
tion)
(1)
H N of possible
measurements
Simple random sampling and
systematic
n
. ,V'
x n
random sampl ing
, with n = number of
sample measurements
(2a)
• Variance of sample
Stratified random sampling
x =
Z W.x.
k=l
with x^ = stratum
mean and W^ =
fraction of popu-
lation represented
by Stratum k (number
of strata [k] ranges
from 1 to r)
Simple random sampling and
systematic random sampling
t- - (Z X.) Vn
i _• _i i
Stratified random sampling
(2b)
(3a)
= Z W, s. , with s, = stratum
k=l variance and W^ =
fraction of popu-
lation represented
by Stratum k
(number of strata
[k] ranges from
1 to r)
(3b)
75
-------
TABLE 3-24. CONTINUED
Terminology
Symbol
Mathematical equation
(Equa
tion)
Standard deviation of
sample
Standard error
(also standard error
of mean and standard
deviation of mean)
of sample
Confidence interval
for ya
sx
CI
Regulatory threshold3
Appropriate number of
samples to collect from
a solid waste (financial
constraints not considered)
Degrees of freedom
Square root transformation
Arcs in transformation
RT
CI = x _+ t 2Q s- , with t 2Q
obtained
from Table 2
in this sec-
tion for
appropriate
degrees of
freedom
Defined by EPA (e.g., 100 ppm
for barium in elutriate of EP
toxicity test)
n =
with A = RT - x
df
df = n - 1
T/2
(4)
(5)
(6)
(7)
/ X.
Arcsin /p; if necessary, refer
to any text on basic
statistics; measure-
ments must be con-
verted to percentages
(P)
(8)
(9)
(10)
(ID
The upper limit of the CI for u is compared to the applicable regulatory
threshold (RT) to determine if a solid waste contains the variable (chemical
contaminant) of concern at a hazardous level. The contaminant of concern is
not considered to be present in the waste at a hazardous level if the upper
limit of the CI is less than the applicable RT. Otherwise, the opposite con-
clusion is reached.
76
-------
TABLE 3-25. LIST OF INORGANIC PRIORITY POLLUTANTS (U.S. EPA 1976
Antimony
Arsenic
Asbestos
Beryl 1i urn
Cadmium
Chromium
Copper
Cyanide
Lead
Mercury
Nickel
Se1 en i urn
Si Tver
Thai 1 ium
Zinc
ALUMINUM
ANTIMONY
A r CCMT r
rtLoLlNl U
BARIUM
QCDVI 1 T! IM
BtKYLLlUn
BORON
r A PlM T 1 IM
LAUMiUrl
IHKUMIUM
COBALT
pnnn CO
LUrrhK
FLUORINE
LEAD
MAGNESIUM
MA MP A MCC """
MANbANLbc
MCDTf ID V
ntKuUKi
MOLYBDENUM
M T CVC\
ni LIxLL
SELENIUM
C T 1 I/ CD
MLv tK
THALLIUM
TUNCSTEN
VANADIUM
77 fjr
Li IHU
- +
— +
-- +
- -- _ * — - -f-
-f
-r
+
4-- -_ — -4.
• r
- +
H +
+
•f
•> +
' i ,,,,,,•..
10 20 30 40
Number of si tes
50
60
70
Figure 3-13. Frequency of occurrence of inorganic constituents in soil at FIT
sites.
-------
TABLE 3-26. PERCENT OCCURRENCE OF INORGANICS IN SOILS—SUPERFUND AND NON-
SUPERFUND SITES (TOTAL NUMBER OF SITES=436)
Pb
As
Cr
Zn
Cd
Cu
15
11
11
9
8
7
Hg
Ni
Ag
Be
Se
6
5
2
2
1
Al
Sb
Ba
B
Co
F
1
1
1
1
1
1
Mo
Tl
W
V
1
1
1
1
along with the content of these elements in uncontaminated soils, is listed
in Table 3-27. Barium, boron, cobalt, and vanadium concentrations at these
polluted sites were within background levels.
Considering inorganics relative toxicity (Table 3-25) and their concen-
trations and frequency of occurrence in present disposal sites, the following
discussion on the behavior of inorganics in soils will be limited to: As, Be,
Cd, Cr, Cu, Pb, Hg, Ni, Se, Ag, and Zn. Common industrial use of these
elements is listed in Table 3-28.
All the elements under consideration are metals. Arsenic, selenium,
and chromium are the only metals listed that can exist as anions in nature.
Because of their anionic nature, their behavior in soil will differ from the
other heavy metals. A discussion of their unique behavior will follow a
general overview of the fate of metals in soils.
Fate of Metals in Soils
The fate of metals added to soil will be controlled by a complex and
dynamic system of physical, chemical and biological reactions. Metals, unlike
many hazardous organic constituents, cannot be readily degraded or detoxified.
Toxic metals represent a long term threat in the soil environment. This
threat can be reduced considerably if the heavy metals can be permanently
immobilized by either chemical or physical methods.
The heavy metal-soil interaction is such that an accumulation of metals
normally occurs on the soil surface and downward transport does not occur to
any great extent unless the buffer capacity of the soil is overcome. Soils
can be regarded as having a finite loading, or buffer capacity for metals.
This capacity is intimately related to the solution and surface chemistry of
the soil matrix with reference to the heavy metal in question. Because of the
wide range of soil characteristics and various forms by which heavy metals can
be added to soil, heavy metal contamination presents a major problem which is
highly site-specific.
A schematic diagram illustrating the multiphase equilibria which must be
considered when defining the soil solution is shown in Figure 3-14. As Figure
3-14 indicates, at any given time, heavy metal concentrations in the soil
78
-------
TABLE 3-27. CONTENT OF VARIOUS ELEMENTS IN SOILS (LINDSAY 1979) AND IN FIT
SITES
Element
Sb
As
Ba
Be
B
Cd
Cr
Cu
Co
Pb
Hg
Mo
N1
Se
Ag
W
V
Zn
F
Tl
Common Range
for Soils (ppm)
2-10
1-50
100-3,000
0.1-40
2-100
0.01-0.70
1-1,000
2-100
1-40
2-200
0.01-0.3
0.2-5
5-500
0.1-2
0.01-5
NG
20-500
10-300
10-4,000
NG
Average for
Soils (ppm)
5
430
6
10
0.06
100
30
8
10
0.03
2
40
0.3
0.05
NG
100
50
200
0.1
Range found
in FIT sites (ppm)
15d
0.02-11,700
0.02-0.2
2-38
0.3a
0.3-118,300
0.04-136,000
2.2-186,300
2.6^
0.16-466,000
0.04-83,200
322^
0.4-8,800
0.9-1.3
1.2-18
b
0.04-2
0.03-38,000
110,000a
b
aOne site reporting concentration
sites reporting concentration
TABLE 3-28. INDUSTRIAL USE OF SELECTED METALS
As
Be
Cd
Cr
Cu
Pb
Hg
Ni
Se
Ag
Zn
Pesticides, pigments, glass, textiles, wood preservatives, fireworks,
printing, tanning, antifouling paints, enamels, ceramics, lubricating
oil, alloys, oil cloth, linoleum, semiconductors, photoconductors.
Rocket fuel, alloys, ceramics
Electroplating, pigments, alloys, enamels, batteries, rubber, plastics,
fungicides, motor oil, textiles
Pigments, chrome tanning, electroplating, chrome-plating, corrosion
inhibitor, varnishes, dye fixers, photography emulsion, defolient
Brass, dyes, wire, fungicides, alloys, plating, pipes, roofing, paints
glass, insecticides, gasoline additive, ammunition,
bronze, pigments
fungicides, pharmaceutical, plastics, paper pro-
electrical apparatus manufacturing
pigments, cosmetics, batteries, electroplating,
Batteries, paints
solder, brass and
Paints, catalysis
ducts, batteries,
Steel and alloys,
electrical contacts, gasoline, spark plugs, paints, laquers, cellulose
compounds
Glass, photocopy, pigments, electrical industry, paints and inks,
cosmetics, paint remover
Photography, electroplating, mirror manufacturing
Alloys, metal coating, inks, copying paper, cosmetics, paints, rubber
and linoleum, glass
79
-------
FREE METAL
CONCENTRATION
IN SOIL SOLUTION
Figure 3-14.
Principal controls on free
solutions (Mattigod et al
Copyright Notice.
trace metal concentrations in soil
. 1981). Used by permission, see
aqueous phase are governed by a number of interrelated processes, e.g.,
inorganic and organic complexation, acid-base reactions, redox, precipitation/
dissolution, and interfacial interaction. The ability to predict the con-
centration of a given heavy metal in the soil solution depends, to a large
degree, on the accuracy with which the multiphase equilibria can be calcu-
lated.
In terms of industrial spills involving heavy metals, an obvious strategy
is to apply a treatment(s) which will minimize the concentration of heavy
metal(s) in the soil solution. Ideally the treatment will reduce the metal's
aqueous concentration to essentially zero, thus resulting in a leakage (leach-
ing) rate from the site to a biologically insignificant level.
The soil chemistry of heavy metals in soils can be divided for con-
venience into two interdependent but separate categories: 1) solution
chemistry and 2) interfacial chemistry. Both are important in defining
the status of heavy metals in soils. However, since one of the critical
parameters in evaluating detoxification procedures will be the concentra-
tion of a given metal in solution, the topic of soil solution chemistry
will be addressed first. The following brief discussion will be directed
toward the general principles which will affect the
tation of the solid phase since solid phase formation
from solution is a primary objective of treatment.
Solution Chemistry
di ssolution/precipi-
to scavenge metals
The kinetic aspects of dissolution and precipitation reactions involving
heavy metals in the soil matrix suffer from the lack of published data. Thus
80
-------
the kinetic component, which in many cases can be critical to decontamination
procedures, cannot be assessed easily. The currently acceptable alternative
is to assume localized equilibrium occurs in the soil profile (Stumm and
Morgan 1981) and then establish the boundary conditions toward which the
system is moving. The application of equilibrium thermodynamics to the
natural soil system will not only allow one to predict if a given treatment
reaction is possible, but it will also provide a prediction of the solution
concentration when equilibrium is attained. This approach relies heavily on
the accuracy of thermodynamic data that can be found in the literature.
Solid Phase Formation
Consider the dissolution/precipitation of a generic solid phase compound
containing a heavy metal cation Me and ligand L in an aqueous solution
MejLk = j Mez+ + k l_z- (3-3)
where j and k are stoichiometric numbers which numerically represent the
valence Z of L and Me, respectively. Assuming constant pressure and tempera-
ture and ignoring the charge designation of the ions, the solubility equilib-
rium constant Kso is
Kso = (Me)J(L)k (3-4)
where ( ) represent activities and the pure solid phase MejLk 1S considered
to be at unit activity. The value of Kso is related to the Gibbs free energy
of dissolution by
AG = RT In Q/KSO (3-5)
Where Q, the reaction quotient, has the exact form as Kso (see Equation
3-4) but represents the actual ion activity product IAP of Mez+ and Lz~
species in solution. When Q = Kso the system is at equilibrium and AGO;
if Q/KSO > 0> tne solution is oversaturated and precipitation will occur,
i.e.,AG > 0 and Equation 3-3 will proceed in the reverse direction; if
Q/KSO < 1 tne solution is undersaturated and dissolution occurs, i.e., AG <
0 and Equation 3-3 proceeds as written.
The concept of ionic activity is important in the development of any
model of the effect of treatment on heavy metal equilibria. The relationship
between the molar concentration of the ith specie mj in solution and its
activity is
i"i = ai/mj (3-6)
where rj is the activity coefficient which has the property that lim ri = l
as m-j -* 0. Since natural systems are not infinitely dilute, r-j cannot be
assigned a value of unity. The calculation of ri for an ionic specie of
valence Zj is given by the Davies equation (Davies 1962)
-log ri = A Zi? [(/T/1+7T) - 0.31] (3-7)
81
-------
where I = 1/2 E m-j Z and is summed over all charged species in solution
i
and A is the Debye-Huckel constant which has an approximate value of 0.5 in an
aqueous solution of a mixed electrolyte (Stumm and Morgan 1981). Equation 3-7
can be used for solution concentrations of I <_0.5 ML'l.
Equation 3-4 can now be written
KSO = CKSO rJ rk (3-8)
where cK$o = m^' ^» the 1on Product in terms of molar concentration. Using
the Davies equation and rearranging, Equation 3-8 can be written
P' = O + 1ML~1) the possibility exists that the
value of r-j may become greater than 1 and the solubility of the solid phase
may decrease in the presence of an inert electrolyte (Stumm and Morgan 1981).
The use of solubility diagrams is a convenient technique of showing
how the solubility of heavy metals compounds varies with pH and at the same
time it allows some prediction as to what solid phase regulates heavy metal
activity in the soil solution. An example is the solubility diagram for lead
in soils (Lindsay 1979) which shows the relative solubilities of lead sili-
cate, phosphate, and carbonate as predicted in pure water in equilibrium with
atmospheric C02- This is shown in Figure 3-15 which also incorporates the
solubility isotherm for tricalcium phosphate (TCP), dicalcium phosphate
dihydrate (OCPD), and hydroxyapatite (HA). The solubility data presented
supports the idea that soil phosphorus may be a factor in regulating Pb2+
ion activity as originally suggested by Nriagu (1974).
Santill an-Medrano and Jurinak (1975) obtained experimental data from soil
column studies using both Pb and Cd . The data in Figure 3-16 show that in the
calcareous Nibley soil: 1) the solubility of Pb decreases with increasing
soil pH, which is the usual trend for most heavy metals, 2) Pb phosphate
compounds could be regulating the activity of Pb++ ion in solution, and
3) mix compound precipitation cannot be precluded between pH 7.5-8.0 because
of the convergence of the solubility isotherms for PbC03, Pb(OH)2, Pb3(P04)2,
and Pb5(PC>4)3 Cl. Similar comments can be made for the solubility of Cd in
Nibley soil (Figure 3-17) with the additional comment that the solubility of
Cd is considerably higher than Pb at any pH and at the high pH values the soil
solution is undersaturated with respect to the compounds considered.
Heavy Metal Complexation in Soil Solution
Heavy metal ions form many soluble complexes with both organic and
inorganic ligands. The effect of complexation is to increase the solubility
82
-------
Figure 3-15. The solubility of vairous lead oxides, carbonates, and sulfates
when S0|~ and CT are 10~3 M and CC>2 is 0.003 atm or as
specified (Lindsay 1979). Used by permission, see Copyright
Notice.
Figure 3-16. The solubility diagram for Pb in Nibley clay loam soil (San-
til 1an-Medrano and Jurinak 1975). Used by permission, see Copy-
right Notice.
83
-------
u
a
a.
10
6.0
6.5
7.0
7.5
PH
8.0
8.5
9.0
Figure 3-17.
The solubility diagram for Cd in Nibley clay loam soil (San-
til 1an-Medrano and Jurinak 1975). Used by permission, see
Copyright Notice.
of the solid phase of which the complex ions are constituent. At any time,
the total concentration of metal Mej in the soil solution is the sum of the
free ion concentration [Me^"1"] and the concentrations of all organic and
inorganic metal complexes. A general expression considering complex formation
with any type of ligand L or its protinated form HXL plus hydroxo complexes
is given (Stumm and Morgan 1981)
Mej =
Z[Mem Hk Ln (OH),-]
where m, n, i or K >_ 0.
complex designation.
In Equation 3-10 ion pairs are included in the
The dominant complex specie in the soil solution can be significant when
dealing with the transport of heavy metal through the matrix. The factors
involved are: 1) the free metal concentration, 2) the dominant complex
specie, and 3) the charge on the complexes. Inorganic complexes which can be
expected to be formed with bivalent metals are given in Table 3-29.
Doner (1978), using soil columns, studied Cd, Cu, and Ni transport
as affected by Cl~ and C104~ ions. This study clearly showed the effect
of the chloride complex on heavy metal movement in soils. The breakthrough
curves for the three metals are shown in Figures 3-18, 3-19, and 3-20. The
mobilities were found to be in order with the dissociation constants of the
chloro-complexes of the metal ions, i.e., Cd > Cu > Ni.
An example of how complexation affects solubility is shown in Figure 3-21
where the solubility of CuO is plotted as a function of (H+). The observed
solubility, in the pH range of most natural systems, is attributed to the
Cu2+ ion and the two carbonate complexes.
84
-------
TABLE 3-29. SOME PROBABLE BIVALENT METAL COMPLEXES WITH INORGANIC
LIGANDS IN SOIL SOLUTIONS (FROM MATTIGOD ET AL. 1981)
Used by permission, see Copyright Notice.
OH
MOH+
M(OH)2°
M(OH)3~
M(OH)42-
CL
MCL+
MCL2°
MCL3-
MCL42-
S04
MHS04+
MS040
M(S04)22-
C03
MHC03+
M(HC03)2°
MC03°
M(C03)22-
P04
MH2P04+
MHP040
MP04"
o
o
I Or
0.8
06
0.4
0.2
NoCI04
/i*0!M
000009M
100 200 300 0 100
PORE VOLUME NUMBER
200
Figure 3-18. Breakthrough curves for Cd as affected by Cl~ and C104- ions
(Doner 1978). Used by permission, see Copyright Notice.
85
-------
o
*
o
10
06
06
04
0.2
NaCls
i J
100 200 300 0 100 200
PORE VOLUME NUMBER
300
Figure 3-19. Breakthrough curves for Cu as affected by Cl" and C104" ions
(Doner 1978). Used by permission, see Copyright Notice.
o
o
1.0
0.8
06
04
0.2
0 100 200 300 0 100 200
PORE VOLUME NUMBER
Figure 3-20. Breakthrough curves for Ni as affected by Cl~ ar.d C104~ ions
(Doner 1978). Used by permission, see Copyright Notice.
86
-------
Or-
Figure 3-21.
-log{H*}
Solubility of CuO as a function of log {H+} (25°C., I = 0, log
PC02 = -3-52) (Schindler 1967). Used by permission, see Copy-
Right Notice.
Organic complexation of heavy metals in soil is not as well defined
as inorganic complexation because of the difficulties of identifying the
organic ligands. The recent disposal technique of land application of sewage
sludge has fostered considerable interest in heavy metal complexation by
fulvic acid extracted from sludge (Sposito et al . 1977, 1979, 1981; Behel et
al. 1983, and Baham and Sposito 1983).
Sposito and co-workers have developed an interesting conceptual fulvic
acid model to interpret potentiometric titration data involving heavy metals.
In brief, a fulvic acid extract is treated as an assembly of hypothetical
macro molecules (similar to protein molecules). This system has been deter-
mined to contain four classes of acidic functional groups which can react with
heavy metals through proton exchange (Sposito and Holtzclaw 1977). Of these
four groups, only two appear to be important in complexing the metals studied.
Table 3-30 gives experimental and estimated values of cKi for i = 1, 2.
These studies were conducted in an ionic medium of 0.1M KC104- KI and
l<2 refer to the stability constants of the two functional groups of the
fulvic acid model. It is of interest to note tnat log CK
to the log K values for metal complexes with alphatic acids such
acetic (Martell and Smith 1977).
are comparable
as citric and
Computer Simulation of the Soil Solution
The multiphase eauilibria and the myriad of potential interactions
involving heavy metals make the soil solution a prime candidate for computer
simulation, however, because of the limitations in analytical techniques, the
87
-------
TABLE 3-30. ESTIMATED VALUES OF LOG CKX AND LOG
(MODIFIED FROM SPOSITO ET AL. 1981)
Used by permission, see Copright Notice
Metal cation logcKi 1ogcl<2
Mg2+ 2.71
Ca2+ (3.12)a
Mn2+ 3.93
Fe2+ 3.96
Ni2+ 3.81
Cu2+ (3.88)
Zn2+ 3.54
Cd2+ (3.04)
Pb2+ (4.22)
0.69
1.23
2.23
2.28
2.08
(2.11)
1.74
(2.27)
(2.62)
aParentheses denote measured values.
complete validation of the free ion and metal complex concentrations predicted
is difficult.
An excellent example of an equilibrium model which has been used exten-
sively in soil chemistry is GEOCHEM. This model (Mattigod and Sposito 1979)
was developed from the program REDEQL2 (McDuff and Morel 1974). GEOCHEM
expands REDEQL2 to account for ion exchange and expands the base for equilib-
rium constants particularly with regards to inorganic and organic metal
complexes.
Sol id-aqueous Interface Exchange
(Outer Sphere Complexes)"
As cations, metals are capable of participating in cation exchange
reactions on negatively charged surfaces of layer silicates (clays), oxides,
and organic matter. Negatively charged mineral surfaces arise from either
substitution of structural cations by ions of lower charge (permanent negative
charge) or by dissociation of hydrogen ions of surface edges (pH-dependent
charge). The negative charge of organic matter is totally pH dependent and
arises from the dissociation of functional groups. Cations are held loosely
in the vicinity of these negative charged sites by electrostatic forces.
88
-------
These sites are "non-specific" (outer sphere complexes) and cations held at
these sites can be displaced by other cations.
Specific Adsorption (Inner Sphere Complexes)
Specific adsorption forming inner sphere complexes at the interface
is distinguished from the exchangeable state in terms of the increase in
binding energy between the metal and the surface. Metals specifically
adsorbed are apparently held by electrical forces as well as by additional
forces including covalent bonding, Van der Waals forces, and steric fit
at the site. The term specific implies that other metal cations do not
effectively compete for the surface site occupied by the specifically adsorbed
metal cation. This is the practical distinction between the non specific
exchangeable and specifically adsorbed states.
Specific adsorption is the most important interfacial mechanism con-
trolling soil-water concentration of a particular metal ion at low concentra-
tions. As more of this metal ion is added, a specific adsorption capacity or
limit is apparently reached and additional metal ions enter less energetically
bound exchange positions. Specifically adsorbed metals are relatively im-
mobile and unaffected by moderate concentrations of "macro" salt cations,
i.e., Ca, Mg, Na and K. Metals held by exchange mechanisms will, however, be
subject to exchange and subsequent leaching as "macro" cation concentrations
increase.
The sorption capacity (exchange and adsorption) of a soil is determined
by the number and kinds of sites available. Sorption of metals has been
correlated with such soil properties as clay content, soil organic matter, Fe
and Mn oxides and calcium carbonate, all of which contribute to the soils
cation adsorption potential. Sorption processes are affected by these various
soil factors, by the form of the metal added, and by the nature of the solvent
introduced along with the metal. The result of these interactions may in-
crease or decrease the movement of heavy metals with the soil water.
Factors Affecting Sorption
Effect of An ions--
Metal cations will form ion-pairs, complexes and chelates with inorganic
and organic anions. Anionic ligands form metal associations that have a lower
positive charge than the "free" metal cation. The resulting association may
be uncharged or it may have a net negative charge. Benjamin and Leckie (1982)
stated that the interaction between metal ions and complexing ligands may
result in either a complex that is weakly sorbed to sorbent surfaces or in a
complex that is sorb more strongly than the "free" metal ion. In general, the
decrease in positive charge on the complexed metal reduces sorption to a
negatively charged surface. One noted exception is the preferential sorption
of hydrolyzed metals (MeOH+) versus the "free" bivalent metal (James and
Healy 1972).
Within normal concentration of electrolytes in soil solution, Elrashidi
and O'Connor (1982) found no measurable changes in Zn sorption by soils due
to complex formation of Zn with Cl", NC'32", or SO^- ions. Under these
89
-------
conditions, anion complex formation did not compete with the highly selective
sorption sites for Zn. The highest anion concentration studied was 0.1 ML~1.
Doner (1978) using 0.1 to 0.5 M NaCl leaching solutions, concluded
that the increased mobility, relative to NaC104 leachate, of Ni, Cu, and
Cd through a soil column was due to complex formation of the metals with
Cl~. The mobility of Cd increased more than that of Ni and Cu, Ni being the
least mobile. These observed mobilities are in the same order as that of the
stability constants of the chloride complexes of these metals (Table 3-31).
Complex ion formations may be represented by the equation:
Me2+ + nCT = MeCln2-n (3-11)
where n is the number of Cl~ ions complexed with the metal ion, Me2+. The
stability constant, K, is defined as:
K = (MeC1n(2-n)/(Me2+) (CT)n (3-12)
where ( ) denotes activity. The larger the log K value, the more stable
the complex. Doner et al. (1982), using geothermal brine solutions, again
found increased mobility of Cu, Pb, Zn, and Cd due to complex formation with
Cl~. Mercuric-chloride complexes are not as strongly adsorbed as the Cl~
free species (Kinniburgh and Jackson 1978). The effect is pH-dependent, with
the greatest complexing of Cl~ and Hg(II) at low pH (4.5). These authors
caution against generalization regarding Cl~ inhibitory effect on sorption
of other metal complexes.
Complex formation between metals and organic ligands may also affect
metal sorption and hence mobility. This complexation may be of particular
importance when organic waste is involved at the same spill site. Bowman
et al. (1981) demonstrated drastic reduction in Ni sorption in the presence of
EDTA, a synthetic chelating agent. Elrashidi and O'Connor (1982) likewise
found that EDTA and DTPA can compete effectively with the soil sorbing sites
for Zn. Both papers emphasize the great potential for leaching of metals in
the presence of organic ligands.
Application of organic matter to soils, e.g. sludge, may, in some cases,
increase the mobility of metals if this material contains significant levels
of dissolved organic matter. The fulvic acid fraction of sludges has been
shown to complex metals (Sposito et al . 1979; Sposito et al. 1981; Boyd et al.
1979; Sposito et al. 1982). Fulvic acid is soluble between pH 1 to 11 (Holtz-
claw et al. 1976). Baham's et al. (1978) study illustrated the relative order
of affinity of fulvic acid fraction of sludge for metals: Cu >_ Fe > Zn >^ Ni >
Cd. Stability constants of metal organic complexes may govern their relative
mobilities. Increased mobility of metals in a sandy soil and a sandy loam
soil with the addition of sludge was also observed by Gerritse et al . (1982).
The authors attributed this increase not only to complexation by dissolved
organic compounds, but also to high ionic strength of the soil solution.
Khan et al. (1982) showed that the mobility of metals through soil followed
the order: Cu > Ni > Pb > Ag > Cd. The high mobility of Cu and Ni was
attributed to their high complexing nature with soluble soil organic matter.
Overcash and Pal (1979) reported that the order metal-chelate stabilities is
Hg > Cu > Ni > Pb > Co > Zn > Cd.
90
-------
TABLE 3-31. STABILITY CONSTANTS FOR Cl COMPLEXES TO Ni(II), Cu(II),
AND Cd(II). FROM MATTIGOD ET AL. (1981)
Used by permission, see Copyright Notice
Metal Stability constant, log
Ni(II) -0.43
Cu(II) 0.40
Cd(II) 1.98
The extent of complexation between a metal and soluble organic matter,
and hence mobility, depends on the competition between metal-binding surface
sites and the organic ligand for the metal. Metals with a high affinity for
organic chelates, such as Cu and Ni, will readily be complexed by the organic
matter and will be subject to leaching. Metals such as Cd and Zn that do not
form highly stable complexes with organic matter will be less affected by its
presence in the soil solution. Elliott and Denneny (1982) stated that soil
metal binding sites should outcompete organic ligands for Cd if the log
stability constant for the metal-organic complex is less than six (Table
3-32). Their study showed that only NTA and EDTA. reduced Cd sorption by
soil .
Effect of pH on Sorption--
Most fuctional groups of chelates, as well as most complex and ion-pair
formers are weak acids, thus the stability of the metal complex is pH depen-
dent with little association in acid media. The degree of association in-
reases with pH to a maximum often determined by some competing alternative
reaction such as precipitation. Elliott and Denneny's (1982) study illus-
trated this effect of soil solution pH on organic ligands. As soil solution
became increasing acidic, the influence of the organic ligands (Ox°) on
metal sorption diminished (Figure 3-22) due to a decreasing ability of the
ligands to bind the metal relative to H+. As the pH increases, the concen-
tration of metal-ligand complex again decreases due to the hydrolysis of Cd
(CdOH+, CdOH2°) at pH>8.
pH also directly effects sorption (McBride and Blasiak 1979, Kuo and
Baker 1980, Harter 1983). Many sorption sites in soil are pH dependent
so that as the pH decreases, the number of possible negatively charged sites
diminishes. In acid media, metals face competition for available permanent
charged sites by H+ and Al3+. Figure 3-23 shows the impact of soil pH on
Cd sorption by three soils. As is true for all cationic metals, Cd sorption
increased with pH.
Cavallaro and McBride (1980) found that soils of higher pH retain more
Cd and Cu. Copper sorption showed a stronger pH dependence than Cd. This
finding is consistent with the hypothesis that hydrolysis of Cu at pH 6
increases its retention by soil. Cadmium does not hydrolyze until pH 8 (see
91
-------
VD
ro
to
c
-5
n>
co
i
ro
ro
c:3 -^^
rD 3 ua ro
fs f^ f\J
Q. 3 -O
cr Q. 3:
'•< c w i
t/) tJ-
~o _*, o n>
rD 3 x ~o
(/) ""j ._! ^
o Jja1
ro"1
- ft)
rt-
l^i
;5 cr 1 —.
^TJ ^
,+ V n <^
n
ro
f^> —*
o ..
*-—^ ~^l
-^ CO cu
c?"1"^
rT X ~*"
CX
0
ro
ft)
3
o
ro x o
3 • -h
c<
o
I-1 O ~S
uj ro ia
CO r+ CU
ro ro 3
— -$_..
i n
Cn
01
1-
OJ
o
PERCENT TOTAL SOLUBLE CftDMIUM
cri CD Q _ (y -^ ^
80
T
o
Q
CU
3 f~t~
n ro
cn
' — - C
0 0
a."
r~
3 CU
CX
^~"*' C— it
r~ a
13 in
,—~s <-+•
O CD
CX CX
— o
CU
f. 3
3-
fD — *•
T O
ro 3
i— o'
— '• in
in r-t-
r+ ro
ro 10
c-t-
— ' 3"
_j.
U3 O
Cu -h
3
CX 0
. .
O
ro
cn
2
*.
(-t-
3-
f-f-
;3~
ro
o
<
— i.
rt>
l/>
m
c
CU
rf
O
m -z. o 3> o
a x n a:
— t > ro i i
3= co i
i
i—1 t— •
^O O CO H- > CO
ro co -P» o> oo
cn cn i-*
cn ro UD
• • •
ro ~^i cn
-C» cn ro
ro co
•^4 -^4
CO O
CO
•
CO
cn
I
— ••
ua
Cu
CX
»—»
7s
ro
p3^
CO
x*^
-f^k
Q
Id
O
-h
ro
-Q
c:
—i.
^-*
— i.
cr
-s
~i.
s
n
o
13
(/I
<-*•
Cu
rt
CU
C
in
ro
CX
cr
"O
ro
i
-*•
1/1
_ i.
0
13
^
in
ro
ro
o
o
"O
<^-
>
IQ'
^"
r-*-
~^
O
<"••
n
ro
— 1
DO
r~
m
CO
t
CO
ro
O
«=^
'-£
t~
oo
— 1
ro
t — *
* —
• — i
-H
-<
0
0
C? *£
rn oo
-^ — I
—2 3^
m ^
z -H
-< 00
V-> O
1-O "n.
O3
ro o
CL
c~>
CD
-o
I
m
X
rn
CO
^
o
3
rn
r~
i
o
-H
-H
3=
z:
-------
.6
o>
o> ,
E •'
I'4
2.3
O
ffi
2x I0"3 M CaCI2
• Soil 3- silt loam, pH 5.2
a Soil 4-silt loam, pH 4.4
A Soil 5- sandy, pH 4.5
5.0 5.2 5.4 5.6 5.8 6.0 6.2 6.4 6.6 6.8 7.0 7.2 7.4
Figure 3-23.
Cadmium binding as a function of pH (Tirsch et al. 1979). Used
by permission, see Copyright Notice.
Note: The sandy textured soil, #5, sorbed the least Cd over
this pH range. Differences in sorption of Cd between soils 3
and 4 may be due to the higher oraanic matter content in soil
4.
Figure 3-22). Table 3-33 shows the predicted percent distribution of metal
species with pH (Harter 1983). The increasing importance of the hydrolyzed
metal species with pH should effect metal sorption.
Jenne (1968) stated that hydrous oxides of Fe and Mn play a principal
role in the retention of metals in soils. Solubility of Fe and Mn oxides
is pH-related. Below pH 6, the oxides of Fe and Mn dissolve releasing
sorbed metals ions to solution (Essen and El Bassam 1981).
Effect of Other Cations Present in Solution--
For specific adsorption sites, heavy metals are preferentially adsorbed
over alkaline metals (Na, K, Ca, Mg) (Milberg et al . 1978; Kinniburgh and
Jackson 1982). However, when specific adsorptions sites become saturated,
exchange reactions dominate and competition for these sites with soil "macro"
cations become important. Cavallaro and McBride (1978) found that sorption of
Cu and Cd decreased in the presence of 0.01M CaCl2. They attributed this
decrease, not to complexation with Cl, but to competition with Ca for sorption
sites (Figure 3-24). Cadmium sorption (not shown) was more affected by the
presence Ca than was Cu. The mobility of Cd may be greatly increased due to
such competitions. Likewise, Harter (1979) indicated the Ca in solution had
a greater affect on Pb sorption than on Cu.
-------
TABLE 3-33. EFFECT OF pH ON PROBABLE SOLUTION PERCENT COMPOSITION
OF DIFFERENT ION SPECIES3 (FROM HARTER 1983)
Used by permission, see Copyright Notice
PH
5
Pb2-
PbOH"
Pb(OH)20
CU2-
CuOH-
Cu(OH)20
CuCOpO
Zn2-
ZnOH-
Zn[OH)2°
Ni2"
NiOH-
100
100
100
100
100
100
100
100
98
2
96
2
2
98
2
100
83
17
1
33
7
56
4
83
17
100
33
66
1
1
92
6
31
64
5
99
1
-ihe solution is assumed to be in equilibrium with atmospheric C02
and it is further assumed that anions other than OH~, HC03", and
C03=, are not present in large enough quantities to make a contribu-
tion to solution complexes of these metals.
2.0-
10-
•s,
.2
o Lansing A (neutral soil pH)
D Lansing A in .01 M CaCI2
i Mardin A .. (acid soil pH)
• Mardin A in .01 M CaCI;,
;gure 3-24. Cu^+ adsorption isotherms on Lansing and Mardin A horizon soils;
in the absence and presence of 0.01M CaClz (Cavallaro and
McBride 1978). (Note: under the same conditions the neutral
Lansing A soil sorbed more Cu+2 than the acid Mardin A soil.)
Used by permission, see Copyright Notice.
94
-------
"'x id at ion-reduction
The metals under discussion at the present time, Cd, Zn, Pb, Ni, and
lu, normally have one oxidation state in the soil environment and are not
:irectly affected by changes in the oxidation-reduction (redox) potential
in soils. The redox potential does affect the solid phase of soils, in
oarticular Fe and Mn oxides. Under reduced conditions Fe and Mn oxides
are solubilized, releasing associated heavy metals. Sims and Patrick (1978),
nowever, found that Zn and Cu did not remain in solution but became associated
with exchange and organic sorption sites. The solubility and decomposition of
organic matter is also affected by soil redox.
Mercury, As, Se and Cr all have multiple oxidation states in soils.
Their reaction in soil is directly dependent on the redox potential of
-he soil. (This subject will be discussed in greater detail in a later
section.)
Adsorption Isotherms--
Langmuir and Freundlich equations have become popular as a means of
describing solid-solution reactions in soils. The Langmuir expression pro-
vides a theoretical adsorption maximum and a coefficient which is theoretical-
ly related to bonding energy. The linearized form of the Langmuir equation:
1
x/m (x/m)max (x/m)max b
(3-13)
Miere C is. the concentration or activity of the free metal in solution, x/m
is the quantity (meq/100 g) of the metal ion adsorbed by the soil, (x/m)max
is the maximum adsorption capacity of the soil, and b is the coefficient
-elated to bonding energy. When —— is plotted as a function of C, the slope
A / lit
vi 11 be the reciprocal of the adsorption capacity, (x/m)max, and the intercept
vi 11 be-;—r-r r-. A typical linear Langmuir adsorption isotherm is given in
\ x/m)max o
rigure 3-25.
The Freundlich expression is essentially empirical but has the virtue of
oeing of appropriate form to fit the graphical shape (Figure 3-26) of many
-netal sorption data. The linearized form of the Freundlich isotherm equation
's:
log (x/m) = 1/nlog C + log K ' (3-14)
vnere x/m and C have defined previously and 1/n and K are constants fitted
•rom the experimental data. A typical Freundlich adsorption isotherm is given
:n Figure 3-27. The two sections of this plot, the linear form of the Freund-
"ich equation followed by the curvilinear section, has been interpreted to
•'ndicate two different mechanisms of retention of Ni by this soil.
Cavallaro and McBride (1978) used the Langmuir expression to describe
sorption of Cu and Cd by two soils. Table 3-24 gives values for the Tiaximum
95
-------
8 10
(M)
Figure 3-25. Langmuir adsorption isotherm for Cu^"1" adsorption on the Lansing
A soil (Cavallaro and McBride 1978). Used by permission, see
Copyright Notice.
o>
EQUILIBRIUM SOLUTION CONCENTRATION
meq/l
Figure 3-26. Typical adsorption isotherm fcr metals and soil
96
-------
s
^
X
-2
GLENOAtE CLAY
-4 -3 -2-10 I
LOG ACTIVITY (PPM)
Figure 3-27. Nickel sorption by Glendale soil, 0.01N CaCL2.
TABLE 3-34. CALCULATED LANGMUIR PARAMETERS FROM SOIL ADSORPTION
OF Cu2+ AND Cd2+ (FROM CAVALLARO AND MCBRIDE 1978)
Used by permission, see Copyright Notice
(x/m)max(meq/100 9)
Lansing A-Cu2+
Lansing A-Cd2+
Lansing C-Cd2+
Mardin A-Cu2+
Mardin A-Cd2+
No
Salt
5.6 + 0.4
4.0 +_ 0.5
4.1 +_ 0.8
2.3 + 0.2
1.1 T 0.1
0.01 M
CaCl2
2.2 + 0.2
0.2 + 0.05
1.2 +_ 0.1
0.6 + 0.1
070
bxlO-5 (M-l) r2
No
Salt
15.6
1.7
1.3
1.5
1.9
0.01 M
CaCl2
3.2
^0.2
2.3
0.5
a
No
Salt
0.99
0.97
0.95
0.99
0.99
0.01 M
CaCl2
0.99
a
0.99
0.94
a
aAdsorption was too low to permit calculation.
97
-------
adsorption capacity ((x/m)max) and for the "bonding constant" (b). The
authors determined that the sorption maximum for Cu2+ was slightly less than
the CEC of the Lansing A soil (neutral soil pH), while the maximum Cu^+
adsorbed by Mardin soil (acid soil pH) was less than half the soil's CEC.
This indicates that Cu was not held as strongly on the Mardin soil. The
adsorption maximum for Cd was less than Cu. The bonding constant (b) re-
flected the weaker retention of Cd relative to Cu in the Lansing A soil,
although this effect is not consistent for Mardin A soil. The presence of
0.01M CaCl2 lowered the values of (x/m)max and b by introducing Ca^+ ions
competition for exchange sites.
Bowman et al. (1981), using K values derived from the Freundlich equa-
tion, compared the sorbing tendencies of 11 soils for Ni (Table 3-35). The
Tuff sample (unweathered rock) showed much lower affinity for Ni than did the
soils studied. Table 3-36 (Bowman et al. 1981) illustrates that the effect of
Ca concentration and the effect of anions, Cl~ and C104" on the sorption
resulted in a lowering of sorption. Sorption in the non-complexing per-
chlorate (C104-) system was greater than in the 0.1N CaCl2 system, but was
much less than that in the 0.01N CaCl2 system. The authors concluded that
Ca competition for sorbing sites, rather than Cl~ complex formation, played
the greater role in reducing Ni sorption.
Elrashidi and O'Connor (1982) compared the affinity of Zn on nine soils
(Table 3-37) using Freundlich parameters. The authors also used these param-
eters in a correlation of sorption affinity with various soil properties.
Clay percent, CEC, and specific surface were all found to be significantly
correlated to Zn sorption.
From the above examples it is evident that the mathematical form of
the Langmuir and Freundlich isotherm expressions, have proven valuable in
interpreting metal behavior in soils. At present, however, the applica-
bility of adsorption isotherm equations to the interpretation of soil chemical
phenomena is a subject of controversy. For further discussion of this con-
troversy see Elprince and Sposito (1981); Griffin and Au 1977; Veith and
Sposito 1977; and Sposito (1979).
The preceding discussion dealt with the general behavior of divalent
heavy metals in the soil environment. Although principles of sorption,
precipitation, etc., are applicable to the fate of all ions in soil, some
specific aspects of the chemistry of As, Se, Hg, Cr, Ag, and Be must be
discussed individually.
Anions in the Soil Environment--
Of the metals under consideration in this text, arsenic, selenium
and chromium, in one of its oxidation states, exists as anions in soils.
Like cationic metals, these anions will participate in precipitation and
sorption reactions.
Soil particles, though predominantly negatively charged, may also
carry some positive charges. The oxide surfaces, notably iron and aluminum
hydrous-oxides, can generate a significant number of positive charges as the
pH decreases. For example, at pH 8-8.5 the positive and negative changes on
98
-------
TABLE 3-35. FREUNDLICH PARAMETERS AND CORRELATION COEFFICIENTS FOR SORPTION
OF Ni IN 0.01N CaC12 BY 12 SOILS. DATA FOR INITIAL
NI CONCENTRATIONS OF 100 AND 1,000 ppm OMITTED (FROM
BOWMAN ET AL. 1981)
Used by permission, see Copyright Notice
Soil
1/n
Car jo
Puye
Tuff
Chem Bottom
R-28
R-30
Glendale
Reagen
Palouse
Doak
Harvey
Lea
262
74.0
8.23
517
534
380
650
541
396
199
233
441
0.95
0.87
0.92
1.18
1.02
1.01
1.03
1.02
0.96
0.99
0.97
0.97
0.999
0.993
0.997
0.999
1.000
0.999
0.998
0.999
0.999
0.999
0.997
0.998
TABLE 3-36. FREUNDLICH PARAMETERS FOR SORPTION OF Ni IN DIFFERENT Ca SOLU-
TIONS BY FOUR SOILS. DATA FOR INITIAL Ni
CONCENTRATIONS OF 100 AND 1,000 ppm
OMITTED (FROM BOWMAN ET AL. 1981)
Used by permission, see Copyright Notice
Matrix
Soil
Carjo
Glendale
Doak
Tuff
0.01N
K
262
650
199
8.23
uc,2
1/n
0.95
1.03
0.99
0.92
0.1
K
43.8
534
78.2
3.45
CaCl2
1/n
0.91
0.95
0.81
0.87
0.1N
K
70.2
691
98.6
5.05
Ca(C104)2
1/n
0.94
0.98
0.85
0.87
99
-------
TABLE 3-37. FREUNDLICH PARAMETERS FOR SORPTION OF ZN IN 0.01N CACL2 BY
THE SOILS STUDIED* (FROM ELRASHIDI AND
O'CONNOR (1982))
Used by permission, see Copyright Notice
Freundlich parameters
Soil
Part lb
Part 2b
1/n
1/n
Car jo silt loam
Puye sandy loam
Tuff loamy sand
Chem B sand
R28 sand
Gl end ale clay
Reagan clay loam
Lea sandy loam
Harvey sandy loam
134
61.0
29.2
1434
829
2732
808
1318
557
0.84
0.88
0.84
1.04
0.91
0.94
0.97
1.03
0.97
92.8
29.9
17.2
108
102
469
302
293
189
0.47
0.52
0.45
0.42
0.44
0.44
0.53
0.46
0.41
Correlation coefficients for all Freundlich adsorption equations are
> 0.98.
bParts 1 and 2 refer to linear isotherms at low and high Zn solution
concentrations, respectively.
the surface of goethite (FeOOH) are balanced and the surface exhibits no net
charge. This pH region is known as the zero point of charge (pzc). At pHs
above the pzc the goethite surface will have a net negative charge and at pHs
below the pzc the surface will have a net positive charge (Figure 3-28).
Oxides can differ widely in their pzc.
It has also been suggested (Van Olphen 1963) that broken bonds at the
edges of the particles of clay minerals, particularly of kaolin types, may
carry localized positive charges. This might be expected, particularly at low
pH values.
Clay minerals and oxides exert a strong preference for some an ions
in comparison to other anions, indicating the existence of chemical bonds
between the solid surface and the specific anion. Phosphate has been the
most extensively studied anion that exhibits this specific sorption phenomena.
Phosphate ions are bonded strongly, or "fixed," by clay minerals and oxides.
The sorption capacity for phosphate and other anions is, however, very small
relative to cation sorption capacity of soils.
Chromium—Chromium
-3+
forms, the Cr-
exists in four possible forms in soils--trivalent
cation and the CrO?" anion and hexavalent forms,
100
-------
Fe—OHr
71
Fe—OHt*
-71
surface acid side of p.z.c.
_Fe—OH"
p.z.c.
—Fe—OH:'
/Fe-OH-
alkaline side of p.z.c.
Figure 3-28.
Zero point of charge (pzc) on an iron hydrous oxide (Greenland
and Hayes 1981). Used by permission, see copyright notice.
and
potential
. Figure 3-29 illustrates the relationships between pH and redox
and speciation of chromium in water.
Hexavalent chromium is the major chromium species used in industry.
Forms of Cr(VI) in soils are as chromate ions CrO^-, predominant at pH 6,
and as dichromate ions C^Oy2", predominant at pH 2-6 (Figure 3-29). The
dichromate ions possess a greater health hazard than chromate ions. Both
Cr(VI) ions are more toxic than Cr(III) ions.
Because of Cr(VI) anionic nature, its association with soil surface
is limited to positively charged exchange sites, the number of which decreases
with increasing soil pH (Figure 3-30, Bloomfield and Pruden 1980: James and
Bartlett 1983). No precipitates of any hexavalent compounds of chromium were
observed in the pH range 1.0 to 9.0 (Griffin and Shimp 1978). Thus Cr(VI) is
highly mobile in soil.
Chromium (III) is considered the stable form of chromium in soil. The
predominant cationic form of Cr(III) in aqueous solution is [Cr(H20)s]3+.
Increasing pH results in the formation of hydroxy species such as Cr(OH)2+,
Cr(OH)2+, ... Cr6(OH)126+. All species of Cr(III) are readily sorbed by
soils. In a study of the relative mobility of metals in soils of pH 5,
Cr(III) was found to be the least mobile (Griffin and Shimp 1978). Hydroxy
species of Cr(III) precipitate at pH 4.5. Complete precipitation of the
hydroxy species occurs at pH 5.5 (Figure 3-31).
At most soils' pH and redox, Cr(VI) is reduced to Cr(III). Soil organic
matter and reduced Fe can serve as electron donors in the reduction of Cr(VI)
(Article and Fuller 1979). Bartlett and James (1979), however, demonstrated
that under conditions prevalent in many soils, Cr(III) can be oxidized. The
presence of oxidized Mn, which serves as an electron acceptor, was determined
as an important factor in this reaction.
Industrial use of chromium also includes organic complexed
Organically compl exed Cr(III) may remain mob-He in soil (James and
1983). In addition to decreased Cr(III) sorption, added organic
Cr(III).
Bartlett
matter may
101
-------
14
11'
1.0
06
0.6
04
0.2
00
-02
-Q4
-0.6
H,0
10 I? 14
'gure 3-29. Eh-pH diagram of Cr species in water at 25°C calculated (Bart-
lett and Kimble 1976a). Used by permission, see Copyright
Notice.
UJ
Q.
20 i
15 -
£C o
o 10
co o>
— O
> 2
o
V
E
5 -
0 -
sorption
02 A 6 8
SORPTION pH
i
10
gure 3-30. Sorption of Cr(VI) on NaOH-extracted soil. (Modified from
Bloomfield and Pruden 1980.)
102
-------
\
23456
pH
Figure 3-31. Concentration of Cr(III) in 24-hour equilibrium solutions as a
function of pH (HCl-CaC03) and presence of Marlow Ap soil.
Initial concentration was 5 ymole CrCl3/ml (Bartlett and Kimble
1976a). Used by permission, see Copyright Notice.
also facilitate the oxidation of Cr(III) to Cr(VI). Under different condi-
tions, this organic matter may facilitate the reduction of Cr(VI) (James and
Bartlett 1983).
Mercury--The distribution of mercury species in soils, elemental mercury
(Hg°), mercurous ions (Hg22+) and mercuric ions (Hg2+), is dependent on soil
pH and redox. Cationic mercury forms may be sorbed earily onto soil constitu-
ents. Divalent mercury is rapidly and strongly complexed by covalent bonding
to organic matter and inorganic particles. Walters and Wolery (1974) stated
that as much as 62 percent of the mercury in surface soils was bound to these
particles. Mercuric ions are also bound to exchange sites of clays and
hydrous oxides of iron and manganese. Sorption is pH dependent, increasing
with increasing pH.
Mercurous and mercuric mercury are also immobilized by precipitation
with phosphate, carbonate, and sulfide. Precipitates of Hg(OH)2> HgS04,
HgNOs, and Hg( 1^3)4 are insoluble at high pH. Insoluble HgS and HgCl3 occur
at all pH ranges. Divalent mercury will also form complexes with soluble
organic matter, chlorides, and hydroxides which may contribute to its mobil-
ity.
The major loss of mercury from soils is through volatilization. Griffin
and Shimp (1978) estimated that the removal of Hg from a leachate was not due
to sorption by clay, but are due to volatilization and/or precipitation. This
removal of mercury increased with pH. Rogers (1979) also found large amounts
of mercury volatilized from soils. Amounts of mercury volatilized appeared to
be affected by the solubility of the mercury compound added to soil (Table
3-38). Volatilization was also found to be inversely related to soil sorption
capacity, thus losses followed sand > loam > clay (Table 3-38).
Under mildly reducing conditions, both organically bound mercury and
inorganic mercury compounds may be degraded to the elemental form of mercury,
HgG. Mercury metal can readily be converted to methyl or ethyl mercury by
microbial transformation. These are the most toxic forms of mercury. Both
103
-------
TABLE 3-38. PERCENT OF APPLIED Hg EVOLVED FROM SOILS WITHIN 144
HOURS (ROGERS 1979).
Used by permission, see Copyright Notice
% Hg Evolved
Hg Compound Sand Soil Loam Clay
HgO-2
Hg(N03)2
Hg(C2H302)2
HgO
HgS
38.3
36.5
26.4
19.6
0.2
32.9
24.1
30.5
15.0
0.3
14.2
13.4
12.1
6.4
0.2
methyl and ethyl mercury are volatile and soluble in water. The formation of
methyl mercury occurs primarily under acid conditions, while dimethyl mercury
is produced at near neutral pH.
Arsenic--In the soil environment, arsenic exists as either arsenate,
As(V) or as arsenite, As(III). Arsenite is the more toxic form of arsenic.
The behavior of arsenate in soil has been assumed to be analogous to
that of phosphate, because of their chemical similarity. Like phosphate,
arsenate is fixed to soils and is thus relatively immobile. Iron, Al, and Ca
influences this fixation by forming insoluble precipitates with arsenate.
Texture is often related to As(V) fixation. The reason for this relationship
is that both reactive Fe and Al usually vary directly with clay content of the
soil. Woolson et al . (1971) stated that arsenate may be leached from soil if
the level of reactive Fe, Al, and Ca in soil are low. The solubility product
for FeAs04 is reported as 5.7xlO~21, whereas for Ca3(As04)2 it is 6.8x10"^.
The presence of Fe in soils is therefore most effective in controlling arsen-
ates1 mobility. Arsenite compounds are reported to be 4-10 times more soluble
than arsenate compounds.
Griffin and Shimp (1978), in a sorption study of arsenate by kaolinite
and montmorillonite, found maximum sorption of As(V) to occur at pH 5 (Figure
3-32). In comparing these sorption curves with the distribution diagram of
As(V) (Figure 3-33), they concluded that H2As04" ion was the principal As(V)
ion being sorbed by the clays. The non-sorption of HAs042- Was apparently
due to repulsion of the ion from the clay surface resulting in decreased
sorption of As(V) above pH 5.
104
-------
< 200 ->
ril /* \v
100-
0
(
/.v \ \
***>" /"^X \
?o.s /i \ \
'/ft/ \ v
/ / • ; ^»
2/.1 lio.a \
•
\
3246802468 1C
pH
Figure 3-32. The amount of As(V) removed from DuPage leachate solutions by
kaolinite and montmorillonite at 25"C plotted as a function of
pH. Initial solution concentrations of As(V) are given in ppm.
Each data point was obtained by using either 4 g of kaolinite or
1 g of montmorillonite in a total solution volume of 52.5 ml
(Griffin and Shimp 1978).
A AsOZ)
pH
Figure 3-33. Diagram showing distribution of forms of As(V) (Griffin and
Shimp 1978).
105
-------
The sorption of As(III) is also strongly pH-dependent. Figure 3-34
shows increased sorption with pH in the pH range 3-9 (Griffin and Shimp
1978). These authors concluded that this increased sorption with pH was
due to an increase in concentration of monovalent As(III) species with pH.
Under anaerobic conditions-, arsenate may be reduced to arsenite. The
reduced form of arsenic is more subject to leaching because of its increased
solubility. Arsenite may also be volatilized from soils. High organic
matter, warm temperatures, adequate moisture, and other conditions con-
ducive to microbial activity drive the reaction sequence toward methylation
and volatilization which reduces arsenic residues in soil (Woolson 1977).
Wool son's (1977) study showed that only 1-2 percent of the arsenate applied at
a rate of 10 ppm was volatilized as arsine (AsH3) in 160 days.
Selenium—Forms and concentrations of selenium in soil solution are
governed by various physical and chemical factors expressed in terms of pH,
dissolution constants, solubility products, and redox potential. Figure
3-35 illustrates a phase diagram for selenium. Selenate, Se(VI) is the
predominant form of selenium in calcareous soils and selenite, Se(IV), is
the predominant form in acid soils.
Selenite can be bound to sesquioxides, especially to Fe oxides. Griffin
and Shimp (1978) found maximum sorption of selenite on montmori11inite and
kaolinite to occur at pH 2-3 (Figure 3-36).
Selenium is least soluble under acid conditions. Precipitates of selen-
ite by ferric hydroxide in acid soils is presumed to be the factor in reducing
selenium's mobility. In the solubility diagram (Figure 3-37, Geering et al.
1968), selenous acid potential (pH + pHSeO^) is plotted against the ferric
hydroxide potential (pH-l/3pFe). The solid line represents an estimated,
average formation potential for the compounds Fe2(Se03)3 and Fe2(OH)4Se03.
For the soils used in this study, all fall along the Fe(OH)3 line and below
the ferric selenite lines, indicating that crystalline ferric selenites are
not governing the observed selenium solubility in these soils. Selenite
probably forms sorption complexes with ferric oxides in soils rather than
crystalline ferric selenite.
In contrast to selenite, selenate, Se(VI), is highly mobile in soils.
Selenate dominates under alkaline conditions. Unlike most metals, selenium is
more mobile at higher pHs.
Under reduced conditions, selenium is converted to elemental form
(Figure 3-35). This conversion can provide an effective mechanism for
attenuation since mobile selenate occurs only under well aerated, alkaline
conditions.
Si 1ver--SiIver is very strongly sorbed by clay and organic matter.
Precipitate of silver, AqCl, Ag2S04, and Ag2C03, are highly insoluble. Silver
is highly immobile in the soil environment. Published data concerning the
interaction of Ag with soil are rare.
Beryl 1ium--Although beryllium is considered the most toxic metal in the
environment, few studies have been done on the chemistry of beryllium in
106
-------
Montmor li lonite
;oo-
Figure 3-34. The amount of As(III) removed from DuPage leachate solutions by
kaolinite and montmorillom'te at 25°C plotted as a function of
pH. Numbers give the initial solution concentration of As(III)
in ppm. Each data point was obtained by using 4 g of clay in a
total solution volume of 52.5 ml (Griffin and Shimp 1978).
soil. Berillium is known to be strongly adsorbed at exchange sites and
is readily precipitated by liming. Beryllium is an alkaline earth metal
(the same group as Ca and Mg) and presumably its activity in soils would
be controlled by the same solution chemistry as other metals. Generaliza-
tions are, however, impossible.
SOIL SORPTION - ORGANICS
Soil sorption is perhaps the most important soil-waste process affecting
the toxic and recalcitrant fractions of hazardous waste. The influence of
soil sorption on the extent and rate of leaching, and also on biological
decomposition of these fractions must be understood and described in order to
effectively use the sorption reaction as a treatment process. Understanding
the effect of different solid surfaces on hazardous waste constituents pro-
vides a mechanism for rationally selecting additional sorbents for use in
augmenting the natural ability of a soil system for immobilizing hazardous
chemicals. Also, understanding the relationship between soil water content
and extent of sorption of hazardous chemicals provides the hazardous waste
manager with a process for controlling the potential release and migration of
constituents through leaching. Thus, this section of the manual describes the
factors involved in soil sorption of chemical constituents and the basic
parameters influencing the sorption process that may be used in treatment
processes for immobilizing specific hazardous waste fractions.
Soil sorption is a physical/chemical process which involves the increase
of solute at tne soil water interface. The terms sorption and adsorption will
-------
+ 1.2
+ 1.0
+ 0.8
+ 0.6
+ 0.4
> +0.2
-C
LU
0
-0.2
-0.4
-0.6
ASSUMED BOUNDARY
OF NORMAL
SURFACE CONDITIONS
I I
I I
6 e
PH
10
12 14
Figure 3-35. Stable fields of selenium (Brown and Associates, Inc. 1980)
108
-------
02«6802468IO
Figure 3-36. The amount of Se(IV) removed from DuPage leachate solutions by
kaolinite and montmorillonite at 25"C, plotted as a function of
pH. Numbers are the initial solution concentration of Se(IV) in
ppm. Each data point was obtained by using either 5 g of
kaolinite or 1 g of montmorillonite in a total solution volume
of 52.5 ml (Griffin and Shimp 1978).
109
-------
12 —
13 L-
00
1...
O 5
L. _
I O
pH-
20
Figure 3-37. Solubility diagram for the ferric selenites, and the solubility
data obtained from 1:10 soil-O.OlM Ca (N03)2 extracts of several
soils (Geering et al. 1968). Used by permission, see Copyright
Notice.
Reproduced from
best available copy,
110
-------
be used interchangeably to include both adsorption and absorption, unless
otherwise stated. Sorption represents an important soil mechanism for removal
of pollutants from the soil solution. The pollutants are "immobilized" by the
soil, hence preventing polluted groundwater. In this section adsorption and
factors affecting adsorption that may be used for controlling, managing, and
treating hazardous constituents are discussed. Thorough descriptions of
adsorption can be found in comprehensive reviews by Davies and Rideal (1963),
Kipling (1965), Ekwall et al. (1963), Bailey and White (1970), and Hamaker
and Thompson (1972).
Sorption can be "specific" or "nonspecific." Specific sorption occurs
when specific sites on the surface exert forces on a particular unit of a
molecule at a certain configuration, for example, adsorption of fluoride anion
on geothite (Bohn et al . 1979). Nonspecific sorption is more general, and it
precedes the specific sorption due to lower heat of adsorption. The major
forces that make sorption possible are: 1) Van der Waals-London forces, 2)
hydrophobic bonding, 3) hydrogen bonding, 4) charge transfer, 5) ligand
exchange, and 6) chemisorption.
Van der Waals-London forces are weak electrostatic forces which are
caused by uneven distribution of electrons of molecules due to the circulation
in their orbits. This motion causes an instantaneous dipole which results in
attraction. Van der Waals forces are weak forces; however, they are additive
forces. Van der Waals forces become significant for large molecules when they
interact with the soil surface at a few sites. Van der Waals bonding is
important for organic molecules.
Hydrophobic bonding is actually a partitioning between a polar solvent
(e.g. water) and a nonpolar adsorbent surface (e.g. soil humus). Hydrophobic
bonding is a phenomenon related to entropy at low temperatures (Hamaker and
Thompson 1972). The entropy is decreased as a result of hydrophobic compound
dissolution in water. Hence, the molecules tend to leave water to increase
the entropy and accumulate on hydrophobic regions of the adsorbent (organic
matter of the soil). At higher temperatures, the enthalpy of transfer of
molecules from adsorbent surface to the water increases which leads to the
unfavorable condition where the molecule reenters the soil water. Hydrophobic
bonding was used to explain the high correlation observed between the soil
adsorption coefficients normalized for percent organic carbon (Koc), and
octanol/water partition coefficient (Kow) for nonionic and polar organic
compounds (Karickhoff et al. 1979, Karickhoff 1981, and Chiou et al. 1983).
This correlation will be discussed in detail.
Hydrogen bonding is a special case of charge transfer. The hydrogen
bond is a weak electrostatic bond and occurs between hydrogen and two atoms of
high electronegativity (e.g., F, 0, and N). Energy of adsorption in hydrogen
bonding ranges from 0.5 - 15 kcal/mole. Hydrogen bonding becomes more signif-
icant with larger molecules, as in the case of Van der Waals bonding. Hydro-
gen bonding has been suggested for the adsorption of s-triazine herbicide
molecules (Hamaker and Thompson 1972).
Charge transfer is a partial overlap of molecular orbitals of two
molecules in an electron donor-acceptor system. Charge transfer complexes
111
-------
are formed between bonds or lone pairs of electrons. Charge transfer adsorp-
tion is an important mechanism in adsorption of organics (Hamaker and Thompson
1972).
Ligand exchange is a replacement of one or more ligands by an adsorbent
molecule. This replacement occurs only if an adsorbent molecule is a stronger
chelating agent than the ligand. For example, bipyridines and organophos-
phates can be adsorbed by ligand exchange (Hamaker and Thompson 1972).
Ion exchange is a process in which a cation is taken from a solution
to replace another cation adsorbed on the soil surface. Cation exchange
involves Coloumbic forces which reach up to 50 kcal/mole. Many organic
molecules will be exchanged upon protonation in soil including alcohols,
amines, and carbonyl groups. After protonation these molecules can be
adsorbed on clay surfaces (Hamaker and Thompson 1972).
Chemisorption is an exothermic process with an energy range of 30-190
kcal/mole (Merrill et al. 1982). Usually, chemisorption involves a chemical
bonding between adsorbent and adsorbate. In short-term sorption studies (<12
hours) the occurrence of chemisorption is low. However, chemisorption might
be very important in the long-term immobilization of organic constituents and
in influencing their fate in soil systems (Osgerby 1970).
The sorption behavior of organic compounds can be simplified by catego-
rizing organics into functional classes (Weber 1972). The two major classes
are: 1) ionic and 2) nonionic compounds.
Ionic Compounds
Organic ionic compounds consist of basic, cationic and acidic compounds.
Organic basic compounds represent organic constituents that are capable of
accepting a proton to become an ionized cation. Properties of basic pesti-
cides, taken from Weber (1972), are shown in Table 3-39. Three mechanisms
that function in adsorption of basic compounds by soil organic matter include:
1) ion exchange, depending on protonation, 2) hydrogen bonding, and 3) hydro-
phobic bonding, which is greatest at higher pH values when the molecules are
not protonated. Acidic groups of soil organic matter have an average pKa
value of approximately 5.5 (Hayes 1970). Some acidic functional groups of
fractions of soil organic matter have pKa values less than three (fulvic
acid) and 3.4 to 3.6 (humic acids) (Gamble 1970 and Gilmour and Coleman 1971).
Adsorption of s-triazine molecules to soil organic matter is attributed to the
complexing of the s-triazine molecule by ionizable H+ ions on functional
groups of organic colloids and to adsorption of protonated species by ion
exchange (Weber et al. 1969). Factors shown to influence the adsorption
of the s-triazine class of organic bases in soil systems include: 1) molecu-
lar structure, basicity, and solubility; 2) type of clay mineral; 3) acidity;
4) type and concentration of ions in solution and on clay surface; and 5)
temperature.
Talibudeen (1955) reported that organic nitrogen bases react direc-
tly with H-montmorillonite through a cation-exchange mechanism which is
pH dependent. Strong bases were adsorbed more strongly than weak bases.
112
-------
TABLE 3-39. PROPERTIES OF BASIC PESTICIDES (WEBER 1972)
Used by permission, see Copyright Notice
Common
Name or
Designation
Atrazine
Propazine
Simazine
SD-15418
Ametryne
Prometryne
Desmetryne
Terbutryne
Atratone
Prometone
Hydroxy
Propazine
Menazon
Amitrole
Trade
Name
AAtrex
•
Milogard
Princep
Bladex
Evik
Caparol
Semeron
Igran
Gesatamin
Pramitol
"Degradation
product"
Saphos
Amino Triazole
Chemical
Name
2-chloro-4-ethylamino-6-iso-
propyl-amino-s-triazine
2-chloro-4,6-bi si sopropyl -ami no-
s-triazine
2-chloro-4,6-bi si sopropyl ami no-
s-triazine
2-chloro-4-(l-cyano-l-methyl-
ethyl amino)-6-ethyl amino-s-
triazine
2-methyl thio-4-ethyl amino-6-
isopropylamino-s-triazine
2-methyl th i o-4 , 6-b i s i sopropyl -
amino-s-triazine
2-methyl thi o-4n-methyl ami no-6-
i sopropyl amino-s-triazine
2-methyl thi o-4-ethyl ami no-6-
tert-butyl amino-s-triazine
2-methoxy-4-ethyl ami no-6-
i sopropyl amino-s-triazine
2-methoxy-4,6-bi si sopropyl amino-
s-triazine
2-hydroxy-4,6-bisisopropl amino-
s-triazine
S-(4,6-diamino-s-triazin-2-
ylmethyl )-0,0-dimethylphos-
phorodithioate
3-amino-s-triazole
pKa
1.68
1.85
1.65
1.1
3.93
4.05
4.0
4.07
4.20
4.28
5.20
3.8
4.17
Water
Solubility
20-25"C,ppm
pH3 pH/
31 35
4.8 4.8
5.8 5.0
160
404 194
206 40
501
58
1900 1600
1000 677
326 41
250
280,000
Vapor
Pressure
mm Hg 20°C
(xlO-6)
0.3
0.029
0.0061
0.01 (830°
0.84
1.0
1.0
0.96
2.9
2.3
-------
He suggested that the basic property of organic bases was the most important
property influencing their adsorption. Frissel (1961) also reported the
pH-dependency of organic bases (s-triazine herbicides) on adsorption and
concluded that triazines are adsorbed as neutral molecules in neutral and
basic environments and as positively charged ions in acidic solutions. Weber
(1966) demonstrated that maximum adsorption of 13 s-traizines on Na-montmoril-
lonite clay occurred in the vicinity of the pKa of each s-triazine (Figure
3-38). The more basic compounds were adsorbed in greater amounts than less
basic compounds. H- and Al-montmorillonite may be acidic enough to hydrolyze
atrazine to hydroxyatrazine (Weber 1970). Generally, adsorption of s-tria-
zines increases as acidity, organic matter, and clay content of soils increase
(Lavy 1968).
The mechanism of adsorption of basic compounds to soil systems can be
illustrated using the s-triazine class of organic bases as a model. The
following processes, taken from Weber (1970), will be considered:
R + H+ « RH+ (3-15)
R + X-mont = RX-mont (3-16)
RH+ + X-mont = RH-mont + X+ (3-17)
H+ + RH-mont = H=mont + RH+ (3-18)
H+ + X-mont = H-mont + X+ (3-19)
R + H-mont = RH-mont (3-20)
where R = triazine compound; RH+ = triazine cation; X-mont = montmorillonite
with X = exchangeable cations Na, Li, l/2Ca, l/2Mg, etc.; H-mont = hydro-
gen (aluminum) montmoril lonite; and H+ = hydrogen ion, as the hydrated H20
species.
Equation 3-15 is related to the basicity of the compound, indicated by
the equilibrium constant Ka, given by:
pKa = log [(RH+)/(R)] + PH (3-21)
As indicated previously, maximum adsorption occurs at a pH equal to the
pKa of the compound.
Equations 3-16 and 3-17 represent adsorption of netural and cationic
s-triazines by montmorillonite. Equations 3-17, 3-18, and 3-19 indicate
competition of s-tria-zine molecules with other cations for soil sites.
Equation 3-20 indicates s-triazine adsorption through direct complexation
with hydrogen ions on H-montmorillonite.
The effects of pH on organic base adsorption is illustrated as follows,
and is taken from Weber (1970). As the pH is decreased, the s-triazine
molecules become protonated (Equation 3-15), and these cations are adsorbed by
clay minerals such as montmorillonite in exchange for X (Equation 3-17). The
114
-------
n>
CO
I
CO
CO
AMOUNT OF ORGANIC COMPOUND ADSORBED-(|imol*/l)
o o o o o
o o o o o
O
o
_-; — •• -t> o
^ — . fO
- — r>
• o «•*"
t/> Cu
CT" ^
3 3 U
T3 0»
fft CT Ql
1 *"*" ^~ t»
—5 TO ^ ^ *
5 -< o
E -a °
±' 3 !l P "
g O-o 5
• 3 "°
in 0- 0 5 *
ns o ~*> 5
!-»•-+> * -1
0 o °
S — •"*
TJ ._ j • '
_». 2 fO
ua ai __i
Saft
O fD
Z 3 CL
0 «-•• -
f-f- ;j (/> °
^' o '
n ;i rt-
fD ^ 1
• .j>
— ' N
O -•.
3 3
-4. m
rt «"
1 1 1 1 1 1 r
-•«•> "°\ *^^
N.x. o. N
\*% ^ v
- '•? °X <
- t\ fS V1
'X * I \ I \
** \S O\ 4
•' • I*N^ • ol "3
9 ** •t^® i ri /^ *
2 < O
I "I «/ /'•
1 * xCf ^*
• 1 rf°' >» '
• /o •
p » X»
/ s '
/09% /
/' /
'/• -S>~1
?//* Ss' '
/./
F •
n
O
•
»
° -
HERBICIDE ADSORBED (M molt /g)
CT
-S -
-------
result is an increase in adsorption. Addition of acid also causes some of the
X cations on the clay to be replaced by hydrogen (Equation 3-19) and the
resulting H-montmorillonite may absorb neutral R molecules (Equation 3-20).
When the pH equals approximately the pKa, adsorption reaches a maximum. As
pH is increased further, adsorption is decreased. The decrease in adsorption
is attributed to competition from the H+ ions (Equation 3-18). It is also
known (Weber 1970) that salts such as barium chloride (O.lm) cause "large
decreases in adsorption of these basic molecules because Equation 3-17 is
driven to the left, releasing the s-triazine cations to the solution.
Adsorption of s-triazine bases has also been reported to be relatively
independent of soil pH. The s-triazine molecules atrazine, propazine, prome-
tone, and prometryne were found to adsorb to 30 soils varying in pH from 4.9
to 7.6 according to the linear Freundlich isotherm:
Y = Kd C (3-22)
For soils containing greater than 5 percent carbon, adsorption was independent
of clay content and directly dependent on soil organic matter. Aqueous
solubility did not influence sorption. Thus, adsorption of basic compounds
may also be due to a partitioning out of aqueous solution onto nonpolar
hydrophobic surfaces, in addition to specific charge related sorption sites
(Walker and Crawford 1968).
Desorption of s-triazine molecules from soil minerals and soil organic
matter occurs relatively easily in the presence of distilled water. Strong
bonding of these organic bases to soil components is not indicated.
Cationic compounds generally are characterized by high-water solubility
and by strong adsorption to clay fractions of soils. Examples of strongly
adsorbed cations include the compounds paraquat and diquat. The mechanism of
adsorption involves cation exchange. That is, a positively charged cation
associated with a clay mineral is displaced by the positively charged organic
cation. Cation properties are shown in Table 3-40 for several compounds.
Acidic compounds (anionic compounds) contain functional groups which
may ionize to produce organic anions. The tendency to ionize is described
by the dissociation constant, Ka:
RCOOH = RCOO- + H+ (3-23)
pKa = PH - log [(RCOO-)/(RCOOH)] (3-24)
where RCOOH is the undissociated molecule and RCOO- is the anion species.
Properties of acidic compounds are shown in Table 3-41. Weak acids, with
relatively higher dissociation constants than strong acids, are in the free
acid form at pH values below their pKa values and are adsorbed to a much
greater extent than in dissociated (anion) form. Due to the net negative
charge associated with clay minerals, there is a net repulsion between the
negatively charged organic anion and soil fractions including minerals and
organic matter. However, Harter and Ahlrichs (1967) demonstrated that the pH
of water at the clay surface is lower than in an aqueous soil bulk solution.
116
-------
TABLE 3-40. PROPERTIES OF CATIONIC PESTICIDES (WEBER 1972)
Used by permission, see Copyright Notice
Common
Name or
Designation
Diquat
Paraquat
Chlormequat
Morfamquat
Methyl ene blue
Phosphon
Hyamine
Phenacridane
chloride
Et. Pyr. Br.
Pyr. Pyr. Cl.
Trade
Name
Ortho diquat
Ortho paraquat
Cycocel
Ceroxone
Phosfon
Hyamine 10-X
Acrizane
Chemical
Name
6,7-dihydrodipyrido[l,2-a:2',l'-
c]pyrazidiinium dibromide
1,1 '-dimethyl -4, 4 '-bypyridinium
dichloride
(2-chl oroethyl ) -tr imethyl -
ammonium chloride
l,l-bis(3,5-dimethylmorpholino-
carbonylmethyl )-4,4' -bipyridyl ium
dichloride
3, 7-bis (dimethyl ami no )-phenazathionium
chloride
tributyl-2,4-dichlorobenzyl phos-
phonium chloride
di-isobutyl cresoxyethoxy-ethyl dimethyl -
benzyl ammonium chloride, mono-
hydrate
9-(p-n-hexyloxyphenyl)-10-methyl-
acridinium chloride
1-ethylpyridinium bromide
N-(4-pyridyl )-pyridinium chloride
Molecular
Weight
344
257
374
398
480
406
188
193
Water
Solubility
20eC,%
70
70
74
4
high
high
high
high
high
-------
TABLE 3-41. PROPERTIES OF ACIDIC PESTICIDES (WEBER 1972)
Used by permission, see Copyright Notice
CO
Common
Name or
Designation
2,4-D
2,4,5-T
MCPA
MCPB
Silvex
Chlorainben
Dicamba
Tricamba
2,3,6-TBA
TIBA
Fenac
Benzadox
Picloram
Endothall
N apt a lam
Dalapon
TCA
UMSA
MH
Dinoseb
DNOC
loxynil
Bromoxynil
Trade
Name
Weedone 638
Brush Killer
Methoxone
Thistrol
Kuron
Ami ben
Banvel D
Banvel T
Benzac
Floraltone
Fenac
Topicide
Tordon
Endothall
Alanap
Dowpon
TCA
Alar
MH-30
Premerge
Sinox
Certrol
Brominil
Chemical
Name
2,4-dichlorophenoxyacetic acid
2,4,5-trichlorophenoxyacetic acid
(4-chloro-o-tolyloxy)acetic acid
4-(4-chloro-o-tolyloxy)butyric
acid
2-(2,4,5-trichlorophenoxy)pro- *
pionic acid
3-amino-2,5-dichlorobenzoic acid
3,6-dichloro-o-anisic acid
3,5,6-trichloro-o-anisic acid •»•
2,3,6-trichlorobenzoic acid •»•
2,3,5-triiodobenzoic acid *
2,3,6-trichlorophenylacetic acid
Benzamidooxyacetic acid ^
4-amino-3,5,6-trichloropicolinic
acid
7-oxabicyclo[2.2.1]heptane-2,3- %
dicarboxylic acid
N-1-naphthylphthalmic acid *»•
2,2-dichloropropionic acid
trichloroacetic acid
N-dimethylamino succinamic acid ^
l,2-dihydro-3,6-pyridazinedione **•
2-sec-butyl-4,6-dinitrophenol
4,6-dinitro-o-cresol
4-hydroxy-3,5-diiodobenzonitrile
3,5-dibromo-4-hydroxybenzonitrile
pKa
2.80
2.84
3.11
4.80
3.0
3.40
1.93
1.5
1.5
1.5
3.70
4.7
1.90
4.0
4.0
1.84
0;63
4:0
4.0
4.40
4.35
3.96
4.08
Water
Solubility
20-25eC,ppm
650
238
550
44
140
700
4500
si. sol.
8400
si. sol.
si. sol .
19,000
430
10,000
200
450,000
1,300,000
si. sol.
6000
52
130
1.8
130
Vapor
Pressure
mm Hg 35°C
(xlO-6)
low
very low
negligible
0.62
negligible
low
0
0
"• 0
>1.0
1.0-52.0
negligible
negligible
-------
With suspension pH values of 6, 5, 4 and 3, it was estimated that the pH at
the clay surface was approximately 4.5, 4.0, 3.2 and 2.5 respectively. Water,
therefore, is more acidic at clay surfaces than in the bulk solution. This
phenomenon may play a role in the adsorption of acidic compounds so that the
extent of adsorption to clay surface is higher than is expected from the pH of
the bulk solution.
However, anion adsorption can occur in soil systems to other soil
components. The reaction of an organic anion with iron and aluminum oxides
can be illustrated as follows:
Anion- + A1(OH)3+ = A-A1(OH)3 (3-25)
Arsenates and phosphates can also react as follows:
CH3-As-OHOO- + Fe(OH)2+ = CH3-As-OHOQ- — Fe(OH)2 (3-26)
Therefore, adsorption of organic anions does occur, and usually does not
involve ion exchange, as with organic cations such as paraquat and diquat.
Acidic organic molecules, including pesticides, ionize in soil solution
to form anionic species. The pH at which ionization occurs depends upon the
pKa value for each organic acid. Under normal pH values for soil solutions,
the anionic forms predominate. Since soil inorganic and organic fractions are
generally negatively charged at normal pH values for soil, organic acids tend
to be relatively mobile. Thus, highly water soluble, acidic organic molecules
comprise one of the most mobile classes of organic chemicals in soil systems.
Nonionic Compounds
According to Weber (1972), nonionic pesticides consist of the following
families of compounds: 1) chlorinated hydrocarbon; 2) organophosphates; 3)
substituted anilines; 4) phenyl carbamates; 5) phenylureas; 6) substituted
anilides; 7) phenylamides; 8) thio carbamates, carbotioates, and acetamides;
9) Benzonitrites; and 10) esters. Nonionic compounds do not ionize signifi-
cantly in aqueous or soil systems. These families of compounds are highly
variable in their properties, not only among the ten families of compounds
mentioned, but also among the individual compounds within each family of
compounds (Table 3-42).
The nonionic nonpolar compounds in general adsorb at the hydrophobic
regions of the soil. In other words, organic carbon content of soil is a
very important factor in adsorption of nonionic nonpolar compounds (Lichten-
stein et al. 1960; Gr.aham-Bryce 1967; Kay and Elrick 1967; Lambert 1967;
Whitney 1967; Harris et al. 1969; Shin et al. 1970; Peterson et al. 1971;
Felsot and Dahm 1979; Karickhoff et al. 1979; Wahid and Sethunathan 1978,
1979, 1980; Kozak and Weber 1983; Nkedi-Kizza et al. 1983). For polar com-
pounds, adsorption occurs in competition with water molecules on adsorbent
surface (Guenzi and Bread 1967). The adsorption is negatively correlated to
the solubility of compounds, while desorption was proportional to the solubil-
ity (Sharom et al. 1980).
119
-------
TABLE 3-42. SELECTED PROPERTIES OF SOME NONIONIC PESTICIDES (WEBER 1972)
Used by permission, see Copyright Notice
ro
o
Common
Name or
Designation
Trade
Name
Chemical Water
Name Solubility
20-25°C,ppm
Vapor
Pressure Parachor
mm Hg 20-25
°C (xlO-6)
Organophosphates
Dimetnoate
Methyl
parathion
Phorate
Demeton
Parathion
Disulfoton
Dursban
Diazinon
Malathion
Carbophe-
nothion
Ethion
Schraden
Cygon
Metron
Thimet
Systox
Phoskil
Disyston
Dursban
Diazol
Cythion
Trithion
Nialate
OMPA
0, 0-d imethyl -S-(N-methyl carba-
moyl -methyl) -phosphorodithio-
ate
0,0-dimethyl -0-p-nitrophenyl
phosphorothioate
0,0-diethyl-S-(ethylthio)-methyl
phosphorodithioate
0,0-diethyl-0(and S)-[2-ethyl-
thio)-ethyl ]phosphorothioates
0,0-diethyl -0-p-nitrophenyl
phosphorothioate
0,0-diethyl -S-[2-(ethylthio)-
ethyl] phosphorodithioate
0,0-diethyl-0-(3,5,6-trichloro-
2-pyridyl) phosphorothioate
0,0-diethyl -0-(2-i sopropyl -6-
methyl-4-pyrimidinyl ) phos-
phorothioate
0,0-dimethyl-S-(l,2-dicarbethoxy-
ethyl) phosphorodithioate
0, 0-di ethyl -S-(p-chl orophenylthi o-
methyl ) phosphorodithioate
0,0,0 ' ,0 ' -tetraethyl -S ,S ' -methyl -
ene biophosphorodithioate
Octamethyl pyrophosphorami de
20,000
50
80-85
100
24
60-66
2
40
145
1-2
1
misible
100
2300
1000
37.8
300
18.7
140
40
1000
484
529
573
553-583
609
613
659
693
699
707
815
689
-------
TABLE 3-42. (CONTINUED)
Common
Name or
Designation
Trade
Name
Chemical Water
Name Solubility
20-25°C,ppm
vapor
Pressure
mm Hg 20-25
°C (xlO-6)
Parachor
Chlorinated hydrocarbons
DDT
Methoxychlor
Endrin
Dieldrin
Aldrin
Toxaphene
Lindane
Chlordane
Heptachlor
Substituted anil
Nitralin
Benefin
Triflural in
Gesapon
Mar late
Endrin
Octalox
Drinox
Phenacide
Gamexane
Octa-Klor
Drinox
H-34
ines
Planavin
Balan
Treflan
l,l,l-trichlor-2,2-bis(p-chloro- 0.001-0.04
phenyl)-ethane
2, 2-bis(p-methoxyphenyl )-!,!, 1- 0.1-0.25
trichloroethane
l,2,3,4,10,10-hexachloro-6,7- 0.23
epoxy-l,4-4a,5,6,7,8,8a-octa-
hydro-l,4-endo-endo-5,8-di-
methanonaphthalene
l,2,3,4,10,10-hexachloro-6,7-epoxy- 0.1-0.25
l,4-4a,5,6,7,8,8a-octahydro-l,4-
endo-exo-5,8-dimethanonaphtha-
lene
l,2,3,4,10,10-hexachloro-l,4,4a,5, 0.01-0.2
8,8a-hexahydro-l,4,-endo-exo-5,8-
dimethanonaphthalene
mixture made by chlorinating cam- 0.4
phene to 69% chlorine
l,2,3,5,6,7,8,8-octachloro-2,3,3a, very low
4,7-7a-hexahydro-4,7-methanoin-
dene
l,4,5,6,7,8,8a-heptachloro-3a,4,7a- very low
tetrahydro-4,7-methanoindene
4-(methylsulfonyl)-2,6-dinitro-N, 0.6
N-dipropyl aniline
N-butyl-N-ethyl- , , -trifluro- 0.5
2,6-dinitro-p-toluidine
, , -trifluro-2,6-dinitro-N,N- 0.05
0.15
0.20
0.18
6.0
1.0
9.4-45.0
10.0
300
1.0
38.9
114
658
699
494
494
493
mixture
478
647
596
768
671
671
di propyl-p-toluidine
-------
TABLE 3-42. (CONTINUED)
ro
ro
Common
Name or
Designation
Phenylcarbamates
Propham
Dichlormate
Chlorpropham
Carbaryl
Barban
Terbutol
Acetamide
CDAA
Benzonitrile
Dichlobenil
Esters
Methyl ester
of chlor-
amben
Isopropyl
ester of
2,4-D
DC PA
Phenyl ureas
Fenuron
Monuron
Monolinuron
Trade
Name
(and carbanilates)
Chem-hoe
Rowmate
Chloro I PC
Sevin
Carbyne
Azak
Randox
Casoron
Ami ben methyl -
ester
2,4-D ester
Dacthal
Dybar
Telvan
Aresin
Chemical
Name
isopropyl carbanilate
3,4-dichlorobenzyl methylcarba-
mate
isopropyl m-chl orocarbani late
1-naphthyl -N -methyl carbamate
4-chl oro-2-butynyl -m-chl oro-
carbani late
2,6-di-tert-butyl-p-tolyl
methyl carbamate
2-chloro-N,N-diallylacetamide
2,6-dichlorobenzonitrile
methyl ester of 3-amino-2,5-
dichlorobenzoic acid
isopropyl ester of 2,4-di-
chloro-phenoxyacetic acid
tetrachloroterephthalic acid,
dimethyl ester
1,1 -dimethyl -3-phenyl urea
3-(p-chlorophenyl )-l,l-dimethyl -
urea
3-(p-chlorophenyl )-l-methoxy-l-
methylurea
Water
Solubility
20-25°C,ppm
250-254
170
88-102
40-99
11-12
6-7
20,000
18-25
120
0.5
2900-3850
230
580
vapor
Pressure Parachor
mm Hg 20-25
°C (xlO-6)
426
466
10 466
453
522
706
9.4-9.6 408
0.5 334
426
10-15 533
<10 580
399
0.5 439
150 459
-------
TABLE 3-42. (CONTINUED)
ro
co
Common
Name or
Designation
Fluometuron
Metobromuron
Diuron
Linuron
C-6313
Norea
Siduron
Neburon
Fluorodifen
Chloroxuron
Substituted ani
Propachlor
Propanil
Alachlor
Dicryl
Solan
Trade
Name
Cotoran
Patoran
Karmex
Lorox
Maloran
Herban
Tupersan
Kloben
Preforan
Tenoran
lides
Ramrod
Rogue
Lasso
Dicryl
Solan
Chemical Water
Name Solubil
20-25'C,
l,l-dimethyl-3-( , , -trifluro-
m-tolyl)-urea
3- ( p-bromophenyl ) - 1 -methoxy- 1 -
methyl urea
3-(3,4-dichlorophenyl)-l,l-di-
methylurea
3-(3,4-dichlorophenyl)-l-methoxy-l-
methylurea
3-(4-bromo-3-chlorophenyl )-l-
methoxy-1-methyl urea
3-(hexahydro-4,7-methanoindan-5-yl)-
1,1-dimethylurea
l-(2-methylcyclohexyl)-3-phenyl-
urea
l-butyl-3-(3,4-dichlorophenyl)-l-
methylurea
p-nitrophenyl- , , -trifluro-2-
nitro-p-tolyl ether
ity
ppm
90
330
42
75
50
150
18
4.8
<2.0
3-[p-(p'-chlorophenoxy)phenyl]- 2.7-3.7
1,1-dimethylurea
2-chlor-N-i sopropyl acetani 1 ide
3', 4' (-dichloropropionanilide
2-chlor-2',6'-diethyl-N-(methoxy-
methyl) acetani 1 ide
3 ' , 4 ' -di chl oro-2-methyl acryl an i 1 i de
N-(3-chloro-4-methylphenyl)-2-
methyl-pentan amide
700
500
148
8-9
8-9
vapor
Pressure
mm Hg 20-25
°C (xlO-6)
0.5
3.0
15
0.4
0.07
0.02
Parachor
470
473
479
499
513
539
569
599
592
634
HOC
486
446
626
474
566
-------
TABLE 3-42. (CONTINUED)
Common
Name or
Designation
Phenyl amide
Diphenamide
Thiocarbamates
EPTC
CDEC
Pebulate
Vernolate
Cycloate
Butyl ate
Carbothioate
Molinate
Trade
Name
Enide
Eptam
Vegadex
Til lam
Vernam
Ro-Neet
Sutan
Ordram
Chemical Water
Name Solubility
20-25°C,Ppm
N,N-dimethyl-2,2-diphenylacetamide
S-ethyl dipropylthiocarbamate
2-chloroallyl diethyl-dithio-
carbamate
S-propyl butyl ethyl thiocarbamate
S-propyl dipropylthiocarbamate
S-ethyl -N -ethyl thi ocyc 1 ohex ane-
carbamate
S-ethyl diisobutylthiocarbamate
S-ethyl hexahydro-1-H-azepine-
260
370-375
92
90-92
90-109
85-90
45
800-912
Vapor
Pressure
mm Hg 20-25
°C (xlO-6)
20-34
2.2
4.3-4.8
5.4-10.4
2.0-6.2
13
5.6
Parachor
581
482
500
522
522
532
562
455
1-carbothioate
-------
Weber (1972) discusses each family of compounds in detail. Chlorinated
hydrocarbons are insoluble in water (< 1 ppm) except for lindane. DDT is the
most studied compound in this family; it is the least soluble, and it is
highly immobile in soils (Weed and Weber 1974, Grau and Peterle 1979). DDT is
also very persistent in soils (half-life is 10-20 years). The other compounds
are less persistent than DDT, but still relatively immobile (Harris et al.
1969).
Organophosphates are more soluble and more volatile (higher vapor
pressure) than chlorinated hydrocarbon. These compounds are more degradable
than chlorinated hydrocarbons. The mobility of organophosphate is directly
related to solubility (King and McCarty 1968, Fuhremann and Lichtenstein
1980). Organophosphate still is considered to be immobile in soil systems
(Harris 1967, Jenkins et al. 1978).
Quantitative Description of Adsorption
Adsorption can be described in two ways: 1) adsorption equilibrium,
and 2) adsorption kinetics. The first approach is based on the assump-
tion that the adsorption process is instantaneous, i.e., equilibrium is
achieved in relatively very short times. The second approach is based on
the assumption that adsorption is a time dependent process. The quanti-
tative description of adsorption, when coupled with a transport equation, is
important in assessing the fate of pollutants in soil systems as discussed
previously. Travis and Etnier (1981) have reviewed available adsorption
models, which are summarized in Table 3-43. Some of the models will be
described in this section.
Adsorption Equilibrium--
Equilibrium adsorption is described by an adsorption isotherm, which
is the relationship between the amount of solute adsorbed and the equilib-
rium concentration of solute in the soil solution. Isotherms can be divided
into four general types according to Giles et al. (1960) and are presented in
Figure 3-39. The L-type curve, also known as a Langmuir type curve, occurs
when there is no strong competition from the solvent for sorption sited on the
adsorbent surface. The S-type curve shows an initial slow rate of adsorption
at low concentration. The rate of adsorption increases as the concentration
increases. The C-curve is applicable where constant partitioning occurs
between solution and adsorbent phases. Finally, the H-curve is applicable
where there is a very high affinity of the adsorbate for the adsorbent.
Chemisorption, for example, usually produces an H-curve adsorption isotherm.
H-type isotherm has been observed for diquat (6, 7-dihydrobipyrid) (1.2-a:2-,
1-c) pyrazidinium dibromide) and paraquat (1,1- dimethyl-4, 4-bipyridinium
dichloride) on Na-montmorillonite and Na-kaolinite clays and for promotone
on H-montmorillonite (Weed and Weber 1974). Examples of H-isotherms for
some pesticides obtained from Weber (1972) are shown in Figure 3-40.
Specific adsorption isotherms that are used to describe immobiliza-
tion of organic constituents in soils include the following: 1) Langmuir
isotherm, 2) Freundlich isotherm, and 3) Brunauer, Emmet and Teller (BET)
isotherm.
125
-------
TABLE 3-43. EQUILIBRIUM AND NONEQUILIBRIUM MODELS (TRAVIS AND ETNIER 1981)
Used by permission, see Copyright Notice
1.0 Equilibrium sorption models
1.1 Langmuir isotherm
K, K7 C
S = T
+ K2 C
1.2 Freundlich isotherm
S = KCN (nonlinear)
S = KdC (linear)
1.3 BET isotherm
s , BQ°
(Cs - C) [1 + (B - 1)(C/CS71
1.4 University phosphate adsorption
S = ac + X0 C ^ Cc
S = ac + KCN C <_ Cc
where Cc = (X0/K)1/N
1.5 Langmuir two surface isotherm
kl bl C k2 b2 C
O — "^^^^T it f\ * W . * f+
1.6 Competitive Langmuir
(Ci/C2)/S = (b2/ki bi) + (Ci/b2 C2)
2.0 Nonequilibrium sorption models
2.1 Reversible linear
2.2 Reversible nonlinear
= _ c . k S
dt p L K2
126
-------
TABLE 3-43. CONTINUED.
2.3 Kinetic product model
dS _ rb d
dt ' a C S
2.4 Bilinear adsorption model
|| - kxC(b - s) - k2s
2.5 Mass transfer model
|| = K(C - C*)
2.6 Elovich model
|| = Aj_ exp(-B2 a)
q = fraction of adsorption sites in soil matrix covered by
solute
2.7 Fava and Eyring model
= Zktf) sinh(b<{>)
S(0) and S(°°) are the initial amount sorbed and amount
sorbed at equilibrium respectively.
2.8 Two site kinetic model
SI
f denotes fraction of sorption sites occupied which are
type 1.
127
-------
V
O
in
E
<
H
Equilibrium Solution Concentration
Figure 3-39. Classification of adsorption isotherms (Giles et al. 1960,
by permission, see Copyright Notice.
Used
10O
CT
8
80
60
4O'
20
E
< 0
*" ""* • Diq & Paraq
^ o Hyamme
' J.-"^ * Me Bt
' „• "" 7? ° * Pnen Cl
f^ -*"~ O Pnospnon
^ • Pyr Pyr Cl
o Et Pyr 8r
34567
turn Concentration (X10 )
O1
o
o
V
E
I
a
i.
o
wi
•o
<
c
o
E
<
5O
40
3O
20
10
i
0
-Hyamme
| -Pnen Cl
_---'D * rMe B>
,- 'f^-—^~A~~ " "~ * r-Pnospnon
'//^ \ r-^'Q ^ Paraq
'/ O— m lP_ | i-Pyr Pvr Cl
3 «^ — — • •* "— <^^ t Py r 8 r
x'" — - -•""• ~~~ "~~ ^^»>
2 3 < 5 6 7 8
Molar Equilibrium Concentration (X10~*)
10
Equilibrium C oneentration (X10 )
Figure 3-40. Isotherms for adsorption of several cationic pesticides on (top)
Na-montmorillonite, (center) Na-kaolinite, (bottom) soil organic
matter (Weber 1972). Used by permission, see Copyright Notice.
128
-------
1) langmuir isotherm: originally this isotherm was developed for
adsorption of gases by solids. The derivation was based on three assump-
tions: 1) constant energy of adsorption, i.e., independent of the extent of
surface covered, 2) no interaction between adsorbed molecules, and 3) only a
monolayer adsorption is formed on the solid surface. The Langmuir adsorption
equation may be expressed as:
K- K9 C
where S is the amount of adsorbed solute per unit mass adsorbent, Kj repre-
sents the maximum amount of solute that can be adsorbed by the soil matrix,
l<2 is a measure of the bond strength holding the sorbed solute on soil
surface, and C is the equilibrium concentration in the soil solution. The
Langmuir isotherm has been used extensively (e.g., Cavallaro and McBride 1978)
for organic and inorganic constituents.
2) Freundlich isotherm: The Freundlich isotherm is expressed as:
S = KCN (3-28)
where K and N are constants. This isotherm was an empirical formulation
which was used to describe gas adsorption on solid phase. However, the
Freundlich isotherm was derived by Halsey and Taylor (1947) based on the
assumption that the heat of adsorption is a logarithmic function of the
surface covered. The Freundlich isotherm has two important properties.
The first is that the Freundlich isotherm is a very flexible equation. Con-
sidering the flexibility of two parameters, the isotherm can fit a wide range
of data. The second property is that the Freundlich isotherm does not have
a maximum limit for the amount of substance sorbed. Due to the flexibility of
this Freundlich isotherm it is used extensively and has been proposed to be
used with a transport equation to describ the movement of synthetic organic
chemicals (pesticides) in soils (e.g., Van Genuchten et al . 1974).
The linear isotherm is an important isotherm which- can be obtained from
the Freundlich isotherm when N = 1. The linear isotherm has been used for low
concentration of pesticides because of the available analytical solutions
when coupled with a transport equation (Kay and Elrick 1967, Green et al .
1972, Davidson et al . 1968, Davidson and Chang 1972, Hugenberger et al . 1972,
and Davidson and McDougal 1973). The linear isotherm may be expressed as:
S = kdC (3-29)
where Kd is called the distribution coefficient. This isotherm can also be
obtained from the Langmuir isotherm (Equation 3-15) if it is assumed that
K2C«1, in which case Kd = KjKj.
Under normal soil moisture conditions, with sorption constants greater
than one (e.g., usually for nonionic compounds), most of the chemical is
present in the soil system in an adsorbed state. The percent sorbed can be
expressed in terms of K
-------
where 9 = soil moisture content (weight basis, assuming density of water as
1.0 g/cc). Figure 3.41 illustrates the extent of sorption (percent sorbed)
as a function of distribution coefficient K^ for different values of 0.
Hamaker and Thompson (1972) point out that this explains the observation that
chemicals tend to resist leaching and remain in the upper soil layers longer
than would be expected based on chemical solubilities.
These observations have important implications with respect to management/
treatment of hazardous waste contaminated soil. Careful control of soil water
content will determine, to a large extent, the relative immobilization of a
given set of chemical constituents identified at a remedial site. Optimiza-
tion of cost effective and efficient treatment may require a compromise
between optimum soil moisture content for biodegradation versus adsorption.
Implications for specific treatment methods are discussed in detail in Chapter
2, Volume I.
The K or Kj value is dependent on the type of soil, even for the same
chemical. Koc, the normalized coefficient of adsorption with respect to
organic carbon content (OC), is defined as:
x 100 for linear isotherm (3.31)
KOC = K/OC% x 100 for nonlinear Freundlich isotherm (3.32)
The Koc parameter is less variable than the original coefficient of adsorption
and is nearly independent of soil type (Hamaker and Thompson 1972, Rao and
Davidson 1980, Kenaga and Goring 1980, and Karickhoff 1981). Thus the impli-
cit assumption is that the organic matter content plays the most important
role in adsorption of organics by soils. If this assumption is not true, the
KQC will be dependent on the mineral content of soils as well. Also, the
argument does not hold for soils with very low and very high organic carbon
contents (Hamaker and Thompson 1972, Rao and Jessup '1982). Koc values for a
multitude of organic compounds are listed in several publications (Hamaker and
Thompson 1972, Kenaga and Goring 1980, and Karickhoff 1981). Recently it has
been reported that Koc is also independent of soil fractions i.e., particle
size separates (Karickhoff et al. 1979, Rao et al. 1982, and Nkedi-Kizza
et al. 1983).
Due to the large number of toxic organic substances contaminating soil
systems, it is impractical to measure adsorption constants for all substances.
Hence, indirect measurement of adsorption constants by relating them to
properties of the specific compound appears to be efficient and economical .
Lambert (1967) has derived a relationship between adsorption by soil and
chemical structure of certain classes of chemicals. The relationship is based
on extrathermodynamic linear free energy approximations and uses "parachor"
(p) as a measure of the molar volume (V™) and surface tension (r) of the
chemical under investigation: p = Vmr^/^. Two assumptions were made in
this model: 1) the soil organic matter is the dominant sorbing medium, and 2)
130
-------
Q
LU
QQ
-------
the adsorbate molecule is an uncharged molecule. Because of difficulties in
measuring parachor for pesticides, this concept has not been thoroughly
investigated (Rao and Davidson 1980). Recently there have been some attempts
to correlate Koc with solubility and octanol-water partition coefficient
(Kow) if a compound (Karickhoff et al . 1979; Karickhoff 1981; Kenaga and
Goring 1980; Schwarzenbach and We stall 1981; Chiou et al . 1982). Briggs
(1981) has demonstrated both theoretical and experimental justification for
such relationships. Table 3-44 summarizes these relationships.
As shown by the equations in Table 3-44, Koc values are correlated
with octanol-water partition coefficients (Kow). The Kow values were general-
ly measured by direct liquid-liquid partitioning. However, recently Veith et
al . (1979) and Ellgehausen et al. (1981) have used the retention time of
constituents in high performance liquid chromatography (HPLC) for estimating
Kow. Veith et al . (1979) obtained a calibration curve using a mixture of
standard chemicals. The average variation of the calculated K0w's f°r 18
other chemicals was 22.5 percent, which is comparable to other methods of
estimating Kow. Laboratory measurement of Kow is often highly variable
(Mingelgrin and Gerstl 1983, and Baes and Sharp 1983).
Sabljic and Protic (1982) have used molecular connectivity indices to
predict Koc. Molecular connectivity indices are numerical characteristics
of a molecule depending on the number and types of atoms and bonds and the
adjacent environment. Polycyclic aromatic hydrocarbon data was used in this
study, which was developed by Karickhoff et al . (1979).
3. Brunauer, Emmet, and Teller (BET) adsorption isotherm: The BET
adsorption theory is actually an extension of Langmuir monol ayer adsorption
theory. The BET model assumes that the Langmuir equation applies to each
layer adsorbed. Also, it assumes that the first layer need not be completed
before another layer can start. The BET equation may be expressed as:
BCQ°
S =
(cs - e) LI + (B-l)(c - cs)J
where cs is the saturation concentration of the solute, c is the concentra-
tion of the solute in liquid phase, Q° is the number of moles adsorbed per
unit weight of adsorbent in forming a complete surface layer, qe is the
number of moles of solutes adsorbed per unit weight at concentration c, and B
is a constant. The BET isotherm has been used for adsorption of pesticides
(Jurinak 1957).
The isotherms discussed above can be presented graphically as straight
lines using convenient transformations (Figure 3-42). More models are avail-
able and are listed in Table 3-43.
Nonequilibrium Adsorption--
The summary of kinetics models available are shown in Table 3-43. A
detailed discussion of the kinetic equations is given by Hamaker and Thompson
(1972) and Travis and Etnier (1981). The relevant kinetic models will be
discussed in conjunction with transport models in another section of this
report.
132
-------
TABLE 3-44. Koc RELATIONSHIPS WITH SOLUBILITY AND OCTANOL-WATER PARTITION
COEFFICIENT
1. Karickhoff et al. (1979), for the polycyclic aromatic class of
chemicals
log Koc = 1.0 log kow - 0.21 (1.1)
log Koc =-0.54 log Xsol + 0.44 (1.2)
where Xsoj is water solubility expressed as a mole fraction
2. Karickhoff (1981) obtained from data for five polycyclic hydrophobic
compounds (benzene, hapthalene, phenonthrene, anthracene, and pyrene)
log Koc = -0.921 log Xsoi - 0.00953 (MP-25) - 1.045 (2.1)
log Koc = -0.594 log Xsol - 0.197 (2.2)
log Koc = 0.987 log Kow - 0.336 (2.3)
where MP is melting point ("C), if liquid at 25°C MP = 25
3. Chiou et al. (1979)
log KOM = 4.04 - 0.557 log WS (3.1)
where WS is solubility in ^mole/1
4. Chiou et al. (1982)
log KoM = -0.813 log (SV) - 0.993 (4.1)
log KoM = lfl.729 log (S) (4.2)
where S is solubility in mole/1 and 17 is the molar volume (I/mole).
5. Kenaga and Goring (1980)
log Koc = 3-64 - °-55 1o9 ws (5.1)
where WS is the solubility in mg/1
6. Schwarzenbach and Westall (1981)
log Koc = 0.72 log Kow + 0.49 (6.1)
133
-------
1/S
l/ C
logS
flog K
log C
a. Langmuir b. Freundlich
Figure 3-42. Linear transforms of adsorption isotherms.
c. BET
Factors Affecting Sorption
It was stated previously that adsorption is a complex process involving
the interaction of a solvent, solute, and adsorbent system. Hence, it is
expected that the properties of the solvent, solute, and asorbent will in-
fluence the adsorption process. Bailey and White (1970, and Hamaker and
Thompson (1972) have discussed in detail the various factors that influence
adsorption. In this section the factors important for predicting sorption of
hazardous constituents on soil are highlighted.
Characteristics of the adsorbate that affect adsorption are: 1) chemical
character, 2) dissociation constant, 3) water solubility, 4) charge distribu-
tion of organic cation, 5) molecular size, 6) polarity, and 7) polarizability.
These factors relate specifically to the following aspects of sorption:
1. Th'e mechanism by which the adsorbate will be adsorbed (e.g., hydrogen
bonding vs. ion exchange).
2. The effect of pH on adsorption and reversibility of of adsorption.
3. Location of adsorption, in other words exterior surface vs. inter-
layer surface of clay mineral.
4. Orientation of molecule with respect to adsorbent surface.
Characteristics of a chemical such as parachor, solubility, and connectivity
index have been used as mentioned previously to determine adsorption constants
(Lambert 1967, Karickhoff et al. 1979, Chiou et al. 1979, Karickhoff 1981,
Chiou et al. 1982, and Sabljic and Protic 1982).
The physicochemical characteristics of adsorbents that affect adsorption
are mainly related to surface characteristics. That is the surface area,
134
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shape, and charge (magnitude and distribution) of the adsorbent surface.
The colloidal part of soil is important due to its high surface area. The
colloidal part consists of clay minerals, organic matter and hydrated metal
oxides.
Clay minerals are minerals with sheet silicate structures. A layer
silicate may be a combination of two types of structural units. The first
unit is a tetrahedral sheet which is an Si'4+ atom joined with four oxygen
atoms forming a tetrahedron. The second structural unit is an octahedral
sheet with an Al3+ (typically) in octahedral coordination with six oxygen
atoms or hydroxyl anions. The relative proportions of the two sheets de-
scribes the clay type. A 1:1 clay (e.g., kaolinite) has low specific area and
low cation exchange capacity (CEC). The adsorption in 1:1 clay occurs only on
the external surface area. A 2:1 expanding clay (e.g., montmorillonite and
vermiculite) has high specific area and high CEC. Adsorption may occur
between the layers as well as on the external surface. The organic molecule
should have some polarity in order to penetrate the basal plane (between the
layers). Organic molecules adsorbed between the layers might not be available
for biodegradation (Weber and Scott 1966). Other 2:1 clays that are not
expandable due to strong bonds between the layers (e.g., illite and chlorite),
have lower specific area and lower CEC. Table 3-45 has a summary of proper-
ties of different clay minerals obtained from Bailey and White (1970). Clay
minerals have a net negative charge which is the result of isomorphic substi-
tution (Bonn et al. 1979). The charge induced by isomorphic substitution is a
permanent charge and is independent of pH. The magnitude and location of
this charge is important in attracting cations to clay surface.
Soil organic matter (OM) is a complex mixture of organic compounds in
soil. Qualitatively OM consists of two fractions, humic and nonhumic. Humic
organic matter is the transformed (microbiologically or chemically) component
of plants, animals, and microorganisms. Humic organic matter is divided into
three components: 1) fulvic acid, 2) humic acid, and 3) humins. These are
similar in structure but rather different in molecular weight and functional
groups. Nonhumic organic matter is represented by the unaltered remains of
plants, animals, and microorganisms such as cellulose, starch, proteins,
chitin, and fats (Bohn et al. 1979, Morrill et al. 1982). Soil OM generally
has high CEC, however, the CEC is pH dependent (Bohn et al. 1979). Many
reseachers consider soil OM the most important parameter for pesticide adsorp-
tion (Sheets et al . 1962, Roberts and Wilson 1965, Hamaker et al. 1966, Savage
and Wauchope 1974, and Nkedi-Kizza et al. 1983). Also it has been reported
that desorption of organic compounds from soil OM is slower than that from
clay minerals (McGlamery and Slife 1966; Helling et al . 1971; Jamet and
Piedallu 1975). Desorption is not complete if soil is allowed to dry after
adsorption (Hamaker and Thompson 1972). Walker and Crawford (1968) showed an
absolute increase in adsorption of four triazine herbicides when straw was
added to soil. Their study was performed on 36 different soils. Also, they
found a high correlation between adsorption and present organic carbon for
soils with percent OC>5. Thus the implications of enhanced adsorption of
hazardous constituents by adding a source of organic matter to the soil such
as straw is important in terms of "immobilizing" the contaminants of the
soil .
135
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TABLE 3-45. SELECTED PHYSICAL PROPERTIES OF SOIL CONSTITUENTS
(BAILEY AND WHITE 1970)
Used by permission, see Copyright Notice
Physical Property
Soil constituent Cation exchangeSurface area
capacity (sq. m/g)
(meq/100 g)
Organic matter
Vermicul ite
Montmorillonite
Dioctahedral vermiculite
11 lite
Chlorite
Kaolin ite
Oxides and hydroxides
200 to 400
100 to 150
80 to 150
10 to 150
10 to 40
10 to 40
3 to 15
2 to 6
500 to 800
600 to 800
600 to 800
50 to 800
65 to 100
- . 25 to 40
7 to 30
100 to 800
Amorphous minerals are non-crystalline metal oxides and hydroxides
(mainly Al and Fe). These minerals represent the transition stage between
unweathered parent materials and well crystallized secondary soil minerals.
The CEC of amorphous mineral is pH dependent. The charge for freshly de-
posited mineral is positive which becomes negative with aging. The positive
charge plays an important role in anion adsorption (Bohn et al. 1979).
Nonsingularity of Adsorption-Desorption--
The adsorption isotherms described are obtained by implicitly assuming
that the adsorption is a reversible process. However, in some cases adsorp-
tion is not reversible. That is, the desorption path will be different from
that of the adsorption path. Nonsingularity (hysteresis) is defined when
there is a residual retained on soil at a given equilibrium concentrate when
desorption occurs (Rao and Davidson 1980). Desorption has been observed
frequently (Hornsby and Davidson 1973, Swanson and Dutt 1973, Farmer and Aochi
1974, Savage and Wauchope 1974). Hornsby and Davidson (1973) found that the
desorption distribution coefficient is a function of the amount adsorbed prior
to desorption. Desorption generally follows the Freundlich isotherm equation
but with a different coefficient. The desorption exponent (Na) was equal to
the adsorption coefficient divided by 2.3 (Swanson and Dutt 1973). Rao and
Davidson (1980) gave three reasons for non-singularity: 1) artifacts created
due to some aspects of the desorption method used, 2) failure to establish
complete equilibrium during the adsorption phase, and 3) chemical and/or
biological transformations of pesticides during the experiment. Koskinen et
al . (1979) have studied the desorption of 2,4,5-T. They noticed that non-
singularity increases as the equilibrium time allowed for adsorption in-
creases. Also, they found that when concentrations were corrected for bio-
degradation, which they monitored by C02 emission, the hysteresis (reaction
136
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direction dependence) was decreased considerably. Shalom et al . (1980),
studied desorption of 12 insecticides, and found desorption was proportional
to the solubility of the compound. They also noticed that insecticides
desorbed in decreasing order from sand, sandy loam, and sediments, while the
relative order of desorption of the 12 insecticides remained the same in each
so i 1.
Rao and Davidson (1980) have shown the variation of error in estimating
adsorbed material when desorption is neglected and the following argument is
taken from them. As indicated previously, both adsorption and desorption
phases follow Freundlich isotherm but with different coefficients:
Sa = Ka CNa (3-34)
Sd = Kd CNd (3-35)
where subscripts a, d denote adsorption and desorption respectively. Since
the degree of non-singularity is dependent on the maximum amount adsorbed
(5^,) before desorption (e.g., Van Genuchten et al. 1974), therefore:
Kd = K^ Sm"B (3-36)
where 3 = Nd/Na. Since Sm can be expressed using Equation 3-35 as:
Sm = KaCma (3-37)
substituting Sp, from Equation 3-37 into Equation 3-36 we get:
N -N
Kd = Ka Cm (3-38)
Substitution of Equation 3-38 into Equation 3-35 for Kd yields:
Sd = Ka Cma" Vd (3.39)
Calculating the ratio Sd/Sa by dividing Equation 3-39 by Equation 3-35:
S, N -N. N.-N
_£ _ ir a dwr d Cv
S2 ' (Cm )(C ) (3-40)
Using Na = 2-3Nd (Swanson and Dutt 1973), and assuming that the largest
Cm = 10 mg/1, Equation 3-40 is simplified to
fd . (100.5652 Na)-(c-0.5652 Na) (3_41)
This equation is plotted for different Na values in Figure 3-43. From
Figure 3-43 it is apparent that the error in estimating the adsorbed amount
becomes larger as the concentration decreases, and as adsorption becomes
a linear function, i.e., as Na approaches 1.
137
-------
20
10
0.1
SOLUTION
1.O
CON C
10..0
Figure 3-43. Errors introduced by the assumption that adsorption-desorption
isotherms are singular when they are nonsingular (Rao and
Davidson 1980). Used by permission, see Copyright Notice.
The information presented here concerning processes and factors in-
fluencing adsorption of solute species by soil systems can be used to assess
the relative mobility and potential for immobilization in a specific waste-
soil system and aid in determining specific in situ treatment schemes. Ex-
amples and methodologies concerning the use of such information are presented
in the modeling section of this chapter and in Volume I of this manual.
SOIL MICROBIOLOGICAL FACTORS RELATED TO IN SITU TREATMENT
The Soil Microbial Ecosystem
Physical and Chemical Properties--
The soil environment is one of heterogeneity with scales of particulate
size ranging from meters to nanometers. The environment having direct effect
on the biological activity of a single bacterium or yeast, or microcolony of
bacteria in the soil -is probably no larger than a cubic millimeter. The
hyphae of filamentous fungi may, however, interact with a range of soil
microenvironments extending over a much larger volume. Variations in water
availability, soil atmosphere composition, inorganic and organic nutrient
availability, soil texture, and soil structure all make up the environment of
soil microbes and affect their metabolism and growth. In a practical sense,
we are forced to deal with management of the soil microbial environment on a
relatively large scale, relying on the average condition at microsites in the
138
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soil to be conducive to the microbial function we are trying to encourage. We
are, however, more likely to be successful in our approach if we keep in mind
the nature of the soil microbial environment and the microsites of which it
is made. It is, of course, beyond the scope of this manual to deal extensive-
ly with soil microbiology or microbial ecology. Good textbooks are available
(Alexander 1977, Atlas and Bartha 1981) if more complete information on these
topics is needed. Gray (1978) has discussed microbial aspects of the soil
relating to pesticide transformations. We will also briefly review principles
of soil microbiology which pertain to the broader topic of toxic and hazardous
waste transformations, with emphasis on environmental factors and microbial
populations or microbial community structure which might be manipulated to
accomplish treatment of contaminated soil.
Soil microbes are greatly affected by soil water. Water is of course,
necessary for microbial life and the water potential against which micro-
organisms must extract water from the soil regulates their activity. The Soil
Science Society of America (1981) has published proceedings of a symposium on
the relation of soil .w.ater potential to soil microbiology. Many micro-
organisms are capable of metabolic activity at water potentials lower than -15
bar. The lower limit for all bacterial activity is probably abouth -80 bar,
but some organisms cease activities at -5 bar. Fungi appear to be more
tolerant of low soil water potential, than are the bacteria (Gray 1978, Harris
1981), and microbial decomposition of organic materials in dryer soils is
probably due primarily to fungi. When the soil becomes too dry many micro-
organism form spores, cysts, or other resistant forms, while many others are
killed by desiccation. Soil water also serves as the transport medium
through which many nutrients diffuse to the microbial cell, and through which
waste products are removed. The decomposition of pesticides and other xeno-
biotic organic compounds as well as natural organic matter in the soil depends
on soil water potential and its influence on microbial activity (Sommers
1981).
The degree to which the soil pore space is filled with water also affects
the exchange of gasses through the soil. Microbial respiration, plant root
respiration, and the respiration of other organisms removes oxygen from the
soil atmosphere and enriches it with carbon dioxide. Gasses diffuse into the
soil from the air above it, and gasses in the soil atmosphere diffuse into the
air, but the oxygen concentration in ordinary soil may be only half that in
air while carbon dioxide concentrations may be many times that of air (Brady
1974). Even so, a large fraction of the microbial population within the soil
depends on oxygen as the terminal election acceptor in metabolism. Bacteria
of the genus Pseudpmonas, members of which are often linked to the transforma-
tion of xenobiotic compounds in the soil, are of this type, i.e. strict
aerobs. When soil pores become filled with water, the diffusion of gasses
through the soil is severely restricted, oxygen is consumed faster than it can
be replaced, and the soil becomes anaerobic. This loss of oxygen as a meta-
bolic electron acceptor induces a drastic change in the make up of the soil
microflora. Facultative anaerobic organisms, organisms which use alternative
election acceptors such as nitrate (denitrifiers) or sulfate (sulfate re-
ducers), and strict anaerobic organisms become the dominant species. General-
ly, microbial metabolism shifts from oxidative to fermentative, and becomes
less efficient in terms of biosynthetic energy production. Soil structure
139
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and/or texture primarily determine the size of soil pores, and hence the water
content at which gas diffusion is significantly limited in a given soil, and
the rate at which anaerobiosis sets in.
Soil texture and clay mineralogy are also important factors in soil
microbial ecology (Stotzky 1972, 1980). Clays with a 1:1 crystal lattice
(e.g. kaolinite) are non-swelling and have lower cation exchange capacity,
while 1:2 crystal lattice clays (e.g. montmorillonite) swell enormously
trapping water and perhaps other compounds between the lattices. The high
cation exchange of clays like montmorillonite greatly increases the buffer
capacity at microsites within the soil, reducing the impact of protons re-
leased into the environment as a product of microbial metabolism. Differ-
ential sorption of organic compounds and inorganic ions, including hazardous
waste components by different clays, also affects the availability of sub-
strates and micronutrients to microogranisms. Stotzky (1980) has investigated
the biodegradabilty of proteins, peptides, and amino acids adsorbed by mont-
morillonite clay and found that they were much less susceptible to degradation
by microorganisms- readily able to use them in solution. However, since all
clay in soil is apparently not complexed with organic matter, some mechanism
(mechanical, chemical, or biological) must remove or prevent complexing of
clay with organic matter in situ. Perhaps organics in situ are not bound
directly to the clay but to polymeric hydous oxides of Fe, Al, and Mn asso-
ciated with the clay. Fluctuations in soil (microsite) pH would disrupt these
inorganic polymers, releasing the organic matter to solution. It could then
either be degraded or rebind to soil clays (Stotzky 1980).
Soil organic matter is extremely important to the microbial ecology and
activity of the soil. Its high cation exchange capacity and high density of
reactive functional groups play important roles in the retention of bacteria
in the soil as well as binding both organic and inorganic compounds which may
be added to the soil. These adsorbed or chemically bound compounds or ions
may be available for microbial attack and transformation. This microbial
activity may detach-the compound or its metabolite from the soil organic
matter, increasing its mobility in the soil (Bartha 1980). Although generally
considered to be recalcitrant, soil organic matter is in a state of flux.
Mineralization of soil organic matter may provide important source nutrients
to the soil from organically bound nitrogen, phosphorus, and sulfur (Woodman-
see et al. 1978).
Due to their high surface to volume ratio, soil microogranisms are
well adapted to take up inorganic nutrients from the soil. If biodegrad-
able organic materials are added to the soil so as to raise the carbon to
nitrogen (C:N) ratio higher than about 20:1, mineral nitrogen in the soil will
be immobilized into microbial biomass, and the decomposition process will be
slowed considerably. -Similar immobilization of phosphorous can occur when
carbon is in excess (Alexander 1977). If during the treatment of hazardous
waste contaminated soils, the soil must be managed to decompose organic
matter, nitrogen and phosphorus may be required to bring the C:N:P ratio to
approximately 120:10:1, the approximate ratio found in bacterial biomass
(Alexander 1977, Kowalenko 1978).
140
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Soils contaminated by waste materials may contain elevated concentrations
of salts. In addition, treatment approaches such as the use of fertilizers or
chemical agents, may add salinity to the soil. Increased salinity increases
the osmotic potential of the soil water, and soil microbes may be restricted
in their activity due to osmotic stress. Monitoring of soil salinity prior to
and during treatment is important to the success of any biological treatment
process.
The soil reaction, or pH, affects the activity of soil microbes. Fungi
are typically more tolerant of acidic soil conditions (below pH 5) than are
bacteria in aqueous media, but the differences are less clear in soil where
the buffer capacity of clay and humic materials affect the concentration of
protons at microsites. (Gray 1978). Soils may need to be limed to raise pH
or treated with sulfur or other acid forming materials to lower pH so that the
soil pH ranges between 5.5 and 8.5 to encourage microbial activity. Phos-
phorus solubility is maximized at pH 6.5; this may be the ideal soil pH.
Adsorption of organic molecules on negatively charged clay colloids
strongly depends on the solution pH. Critical pH values are dependent on
the pKa of the adsorbate and the magnitude of charge on the adsorbent.
Adsorption of pesticides of widely varying molecular structure on clays
increases as pH decreases (Frissel and Bolt 1962, Harris and Warren 1964,
Talbert and Fletchall 1965). The pH effect is apparently less important
for peat and some other organic soils which suggests that a different
sorptive mechanism is occurring for those types of soils.
The Bacteria—
The metabolic diversity of the procaryotic organisms in the soil focuses
a great deal of attention on them when biodegration of xenobiotic or hazardous
materials is of concern. In general, bacteria may be classified metabolically
as heterotrophic; that is, they derive their energy and carbon for survival
and growth from the decomposition of organic materials, or as autotrophic,
meaning that they fix the carbon they need for growth from carbon dioxide and
(usually) obtain their energy from light (photosynthetic) or the oxidation of
inorganic compounds (1ithotrophic). The heterotrophic bacteria are most
important in the transformation of organic hazardous compunds, and soil
treatment schemes may be directed toward enhancing their activity. However
the availabilty of nutrients (especially nitrogen) to the heterotrophic
microorganisms of the soil may depend on the transformation of inorganic
materials by 1ithotrophic organisms (Focht and Verstraete 1977, Painter
1977). Transformations of toxic metals or metabloids and their compounds may
directly or indirectly involve the activities of 1ithotrophic or photo-
synthetic bacteria.
The Fungi —
The fungi are eucaryotic microorganisms which lack photosynthetic
apparatus and depend on heterotrophic metabolism. They may be either filamen-
tous or uncellular (yeasts or amoeboid), while some types aggregate to form
macroscopic forms such as a plasmodium or fruit-bodies (mushrooms). Fungi
constitute a large fraction of microbial biomass in soil, especially in acidic
soil, and their enzymatic activity is important to most decomposition pro-
cesses. When levels of available substrate are low or water availability is
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low, a major portion of the fungal biomass in soil is either dormant or dead.
Fungal spores or other resistant structures can survive in soil under adverse
conditions for long periods of time, and then quickly germinate and grow when
conditions become favorable. Clay mineralogy, temperature, and other soil
environmental conditions affect the speciation and diversity of fungi in the
soil. Most filamentous fungi are aerobic, and yeasts are often facultatively
anaerobic. Most fungi are mesophilic, and even thermophilic fungi do not grow
above about 65°C. Many fungi grow at temperatures below 10°C.
Algae--
The soil surface usually contains appreciable populations of eucaryotic
algae and cyanobacteria. Since the zone of light penetration into the soil is
severely restricted, the algal biomass in soil is usually low. Algae may be
important, however, in enhancing photodecomposition of hazardous organic
compounds at the soil surface.
Higher Life Forms--
The soil also contains many other higher organisms which graze the
bacterial or fungal populations, or feed on detrital matter and its associated
microflora. Protozoa, nematodes, insects, and worms are important in this
regard. These organisms affect the decomposition process by controlling
bacterial or fungal population size through grazing (Bryant et al . 1982), by
harboring microbes within their intestinal tract which may decompose a
compound of interest, by comminuting plant materials (insects), or by mixing
the soil and contributing to its aeration.
Microbial Interactions—
Interactions between microorganisms in the soil are complex, and un-
doubtedly play an important role in the activity of microorganisms important
to the transformation or decomposition of hazardous waste compounds. Some of
these interactions have already been suggested in earlier discussion. Com-
petition for growth requirements among microorganisms is intense. Many
microorganisms are metabolically specialized (e.g., the autotrophic nitri-
fiers) and are less reliant on preformed organic substrates and/or growth
factors. However the nutritional requirements of many soil microbes overlap
to some degree, and those organisms which are to survive in the soil must be
able to effectively compete with their neighbors for these required nutrients.
To increase their opportunities for survival in the competitive soil
environment, many microorganisms have aquired antagonistic abilities with
which they may limit the growth of other microorganisms. The antibiotics
produced by soil microorganisms are probably the best known microbial antago-
nistic agents, but other kinds of inhibitors, including acids, bases and other
inorgranic compounds are used (Alexander 1971, Atlas and Bartha 1981).
Suppressive influences .are often expressed between microorganisms and higher
life forms in the soil as well (Rice 1974).
Soil microbes may also be closely associated with one another physically
and/or metabolically. True mutualistic or symbiotic relationships exist,
where the organisms relationships are necessary to their survival in the
niche they occupy. Less restrictive relationships are perhaps more common.
It is not uncommon for the degradation of a xenobiotic compound to involve
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sequential metabolism by two or more microorganisms (Beam and Perry 1974); a
relationship which may benefit only one partner (commensalism) or both (proto-
cooperation or synergism) (Atlas and Bartha 1981).
Life on the Verge of Starvation—
Readily assimilable substrates are short lived in most soil environments.
The majority of time, carbon and energy supplies are limited and microbial
growth rates are restricted. Soil organic matter, including many hazardous
waste components, is recalcitrant to microbial attack and supplies carbon and
energy slowly to the soil microbial ecosystem. Organisms able to survive in
such a growth limited environment must have evolved strategies which compen-
sate for this state of affairs. Two major kinds of survival strategies are
apparent in the microbial ecosystem. Winogradsky (1949) observed, in about
1924, that soil harbored a population of bacteria which increased their
numbers rapidly when a readily "fermentable" substrate was introduced to the
soil. These "zymogenous" organisms would dominate the population until the
added substrate was depleted, and then would die away. Another population of
"autochthonous" bacteria grew much more slowly, and their population did not
change significantly when a fermentable substrate was added. Population
ecologists often classify organisms which depend on high growth rates for
competitive advantage as "r" strategists. This type of organism would
correspond to Winogradsky1s zymogenous bacteria. Organisms which reproduce
more slowly and have many competitive adaptations are classified as "k"
strategists, implying that their growth is related to the carrying capacity of
the ecosystem. These organisms correspond to Winogradsky's autochthonous
bacteria (Atlas and Bartha 1981).
The inoculation of hazardous waste contaminated soils with microorganisms
selected for their ability to degrade or transform hazardous materials is a
very attractive treatment concept. However, the treatment manager must be
aware that the restrictive environment and complex ecology of the soil micro-
bial system may limit the ability of introduced microbes to become self-
perpetuating and perform their specialized functions for more than a short
period of time. Reinoculation may need to be repeated several times before
satisfactory levels of treatment are achieved. Liang et al. (1982) conducted
experiments on the survival of antibiotic resistant microorganisms after
inoculation into sterile and nonsterile water, sewage, and soil. They suggest
that microorganisms which are tolerant of multiple kinds of stresses (e.g.,
abiotic stress, starvation, and antagonism) have a higher potential for
survival in the soil after genetic manipulation (engineering) in the labora-
tory, than do microorganisms with less tolerance versatility. Much of the
current genetic engineering work directed at producing bacteria capable of
complete degradation of xenobiotic compounds is being done with bacteria
(e.g., Pseudomonas) which are zymogenous (Chakrabarty 1982). It is en-
couraging that some recent isolations of xenobiotic degrading bacteria have
turned out to be Arthrobacter spp. These organisms were isolated using
chemostat technique!whichallow time for more slow growing, autotrophic
bacteria to become dominant and their degradative ability to be recognized
(Stanlake and Finn 1982). Recently reported experiments have shown the
potential for use of these more autochthonous bacteria to treat hazardous
waste contaminated soils (Edgehill and Finn 1983).
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Biogeochemistry of Toxic Metals and Metalloids
Arsenic, barium, cadmium, chromium, lead, mercury, nickel, selenium,
silver, thallium, and vanadium and/or one or more of their compounds are
listed as hazardous waste constituents by the U. S. Environmental Protec-
tion Agency (40 CFR 261). The toxic nature of these elements or their
compounds adversly affects some fraction of the microbial population when the
soil is contaminated, while other organisms or groups of organisms may be able
oxidize, reduce, methyl ate, demethylate or otherwise transform these elements
so that their solubility, sorption, or volatility in the soil is greatly
affected.
Arsenic--
Since arsenic exists in the -3, +3, or +5 valence states it is subject to
oxidation and reduction by microbial activity. The positive trivalent state
is generally the most toxic (Zajic 1969). There is no evidence that organisms
which oxidize arsenite to arsenate use the energy available from the reaction
for growth. Apparently, the oxidation is done by heterotrophic organisms.
Many heterotrophs can also reduce arsenate (Alexander 1977, Zajic 1969).
Arsenic can be lost from soils as volatile arsine or as methylarsines.
Cheng and Focht (1979) studied the volatilization of arsenicals from flooded
soils amended with glucose and urea in aerobic flasks. They found that soil
treated with arsenate or arsenite gave off arsine, while soil amended with
disodium methylarsonate gave off arsine and monomethylarsine, and soil
amended with dimethyl arson ate (cacodylic adic) yielded arsine and dimethyl-
arsine. No evidence was found for methyl ation of any of the arsenical sub-
strates in the three soils tested. Apparently, demethylation was more impor-
tant under these conditions. Other studies (Cox and Alexander 1973, Woolson
and Kearney 1973, Kaufman 1974, and Woolson 1977) have found methyl ation of
arsenical s as an important process in soils, and have also found that tri-
methylarsine is an important gaseous product. These results suggest that
soils contaminated with arsenic must be managed to minimize volatilization
through microbial reduction. Hassler (1982) found that essentially only
soluble arsenic was volatile in soil and processed oil shale.
Barium—
Although barium is distributed in biological systems in comparable
amounts with strontium, very little is known about its interactions with
soil microorganisms (Zajic 1969).
Cadmium—
The growth of soil bacteria is retarded by cadmium, and the community
structure is affected. Cells of Escherichia coli exposed to Cd suffer
single stranded breakage in their deoxyribonucleic acid (Mitra and Bernstein
1978). In experiments with bacteria isolated from Cd contaminated soils in
Great Britain, Shearer and Olson (1983) found that the bacteria would grow in
media containing lOppm Cd (regardless of chemical species tested), but that
growth rate was inversely proportional to Cd concentration (0, 0.1 and 10 ppm)
in a defined growth medium. Chemical species of Cd tested were toxic to the
bacteria in the order: Cd2* > Cd aspartate > Cd3 (PO/{)2 > Cd3 (PO^s. Tripp
et al. (1983) isolated 50 strains of bacteria on media containing 0, 10, and
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100 ppm Cd from six sewage sludge amended sites in England. Gram negative
bacteria were most common on the 100 ppm medium, and the number of genera of
bacteria decreased with increasing Cd concentration. The number of genera
isolated on cadmium medium was significantly lower from sites not contaminated
with cadmium than from contaminated sites. Apparently, the bacterial popula-
tion had adapted to the heavy metal contamination. Khazael and Mitra (1981)
found that cells of E. coli which were adapted to growth in 0.34 ppm Cd in a
minimal salts medium produced a Cd binding high-molecular-weight cytoplasmic
component which may sequester Cd2+ in the cells and allow normal metabolic
function. It is not clear if this mode of adaptation to Cd in the environment
is common to other microorganisms.
Chaney et al. (1978) studied respiration rates of black oak forest soil
and litter which had been both "naturally" and experimentally contaminated
with Cd and Zn. After 23 days incubation, soil and litter microcosms treated
with 10 ppm Cd and no zinc had significantly lower respiration rates than the
control. The most severely reduced respiration rate occurred when 10 ppm Cd
plus 1000 ppm Zn was applied. But even this highest combined treatment rate
was not significantly lower than the control. Apparently the litter-soil
system used in this study was quite resilient to contamination by these
metals.
The soil microflora may have significant impact on Cd availability. Work
by Kurek et al. (1982) has shown that soil microbial biomass may contribute
significantly to the soil Cd binding capacity. Dead bacterial cells sorbed
more Cd from liquid medium than did live cells.
Since cadmium exists in nature only in the valence state of +2, microbial
oxidation or reduction of this element is unlikely.
Chromium—
Although chromium has common valence states of +2, +3, and +6, and
should be amenable to oxidation or reduction by microbes, no information
is available on the biochemical transformation of chromium (Zajic 1969).
Hexavalent chromium has been shown to be toxic and mutagenic to Salmonella
typhimurium, while trivalent chromium was neither toxic or mutagenic in
the same tests (Petrilli and De Flora 1977). Ross et al. (1981) tested
the toxicity of Cr+6 and Cr+3 to liquid cultures of soil bacteria and con-
cluded that Cr+6 was more toxic than Cr"1"^ and that gram negative bacteria
were more sensitive to Cr+6 than were gram positive bacteria. When they
treated a loam and fine sandy loam soil with Cr+3 or Cr+6 under laboratory
conditions, they observed decreased soil respiration (C02 evolution) in both
treatments. Small amounts of extractable Cr+6 were observed within 6 days
of treatment with 100 ppm Cr+3, but no Cr+6 could be extracted from this
treatment after 13 days incubation. Extractable levels of Cr+6 decreased to
less than 5 ppm after 13 days incubation of the soils treated with 100 ppm
Cr+6 but no increase in soil respiration was observed in any of Cr+6 or
Cr+3 soils in up to 22 days incubation. Apparently, it should not be assumed
that Cr*3 is harmless to the soil microflora. Working with laboratory media
alone, Babich et al. (1982) demonstrated that Cr+6 was significantly more
toxic than Cr+3 in terms of spore germination, growth, and sporulation
to six species of soil fungi. However, at 100 ppm (the lowest treatment
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reported) of either Cr+3 or Cr"1"^ the mycelial growth rate of Penicilium
vermiculatum was not significantly different from the control culture.
Lead-
Inorganic lead has been shown to be toxic to a broad range of micro-
organisms including cyanobacteria, marine algae, fungi, and protozoa. Lead
and its compounds have also been shown to affect microbial activities in soil,
including inhibition of nitrogen mineralization, stimulation of nitrification,
and the synthesis of soil enzymes. Species diversity of microbes in lead
contaminated soils has also been found to be lower. Babich and Stotzky
(1979) found different sensitivities to lead among eight species of fungi.
Rhizoctonia soloni ceased growth at 500 yg Pb/ml of medium, while Aspergillus
niger was~not appreciably inhibited by 1000 yg Pb/ml of medium. In the same
study, Ph, phosphate and carbonate ions, clay minerals, particulate humic
acid, and soluble organics affected the toxicity of lead. Low pH of 5 or 6
increased the toxicity of lead, probably through the increased dominance of
Pb2+ ion, while higher pH and the other abiotic factors tested reduced
toxicity. Apparently, hydroxylated, sorbed, or complexed forms of Pb are less
toxic to fungi, and probably to other soil microorganisms.
Mercury--
Microbiological processes are responsible for the oxidation, reduction,
methylation, and demethylation of mercury. Mercurial pesticides, phenyl-
mercury acetate (PMA), ethyl mercuric phosphate, and methyl mercuric chloride
are all biodegradable (Kaufman 1974). Metallic mercury is often the reduced
product of the decomposition of such compounds (Alexander 1977). Monomethyl
or dimethyl mercury may also be formed biologically in the soil from Hg2+ or
from organomercurials. Landa (1978) monitored 203ng ioss from five Montana
soils of varying texture and classification which were ammended with Ippm Hg
as 203ngN03, and incubated for 7 weeks at room temperature at 1/3-bar moisture
content. Mercury loss ranged from 5 to 30 percent with the higher initial
rates of loss observed in soil ammended with glucose. Losses of Hg from
autoclaved, but not necessarily sterile, soil of each type was much lower.
After 2-24 days, depending on treatment and soil, very little if any Hg loss
was observed. Inoculation of the autoclaved soils or reamendment of the
treated soil after 38 days did not initiate further Hg loss. Apparently,
the remaining Hg was stabilized in the soil and unavailable for microbial
processing. Shariat et al. (1979) screened 40 common soil bacteria for their
ability to tolerate and degrade methylmercury chloride. Twenty-seven (67.5
percent) could tolerate CHsHgCl at 0.37 to 2.5 mg/1, and 21 (52.5 percent)
could degrade it. The disappearance of CH3HgCl from the medium was accom-
panied by a loss of total Hg, probably to volatilization of Hg" produced from
reduction of CH3HgCl. Mason et al. (1979) investigated the kinetics of
methylmercury chloride degradation by the bacteria Enterobacter aerogenes and
Serratia marcesens. They found that the initial rate depended on C^HgCl
concentration and pH, "and that the kinetic pattern was characteristic of
enzymatic reactions. £_._ aerogenes exhibited uniform kinetics over the pH
range tested, while S. marcescens had the highest rate of degradation at pH 8.
Calli'ster and Winfrey (1983) found that both aerobic and anaerobic hetero-
trophic bacteria were resistant to 14 ppm Hg2+. Mercury methylation was
highest in anaerobicalIv incubated surface sediments. Nearly all (99 percent)
of the Hg added as 203ng (N03)2 bound to the sediment within one hour, but
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more than 7 percent of the added Hg was methylated during a 7-day incubation.
This suggests that bound inorganic mercury was available for methylation. The
processes of mercury methylation and demethylation have usually been ascribed
to different bacteria strains. However, Pan-Hou et al. (1980) found that a
strain of the mercury methylating, anaerobic bacterium Clostridium cochlearium
1-2 acquired the ability to decompose methyl mercury and other organomercur-
ials. Apparently this ability was coded for on transferable genetic material,
probably a plasmid. Silver and Kinscherf (1982) have recently reviewed the
genetics and biochemistry of microbial transformations of mercury and its
compounds. They point out that mercury resistance is an inducible trait of
organisms possessing this ability, and that the genetic material coding for
this ability is transposable.
Nickel--
Nitrification, carbon mineralization, and the activities of acid and
alkaline phosphatase and arylsulfatase are all inhibited in soil by nickel.
Babich and Stotzky (1982, 1983a, 1983b) have studied the toxicity of nickel to
microorganisms in pure culture and in soil. In pH 4.9 soil without montmoril-
lonite clay minerals, incipient Ni toxicity to fungi ranged from 50 ppm for
Aspergillus clavatus to 750 ppm for Tri'choderma viride. Only one species of
fungus (Gliocladium sp.) showed any growth at 1000 ppm Ni. Addition of
kaolinite or montmorillonite clay reduced the toxicity of Ni to fungi with
montmorillonite being most effective. Increasing the pH to approximately 7.0
also reduced toxicity. At 1000 ppm Ni, adjusting the soil pH to approximately
7.0 with CaC03 essential ly doubled the fungal growth rate. Incipient de-
creases in survival of unicellular microbes in the same pH 4.9, Ni treated
soil began at 250 ppm for Agrobacterium radiobacter, B acill us megateriurm
(both bacteria), Cryptococcus terreus and Torulopsis glabrata (both yeasts).
Proteus vulgaris, Baci 11u~cereus"lboth bacteria), Nocardia rhodocnrous
Tanactinomycete), Cryrtoco'ccus terrus, Rhodotorula rubra,and ToruTopsis
ajabrata (all yeasts) were viable after 7 days exposureTcTlOOO ppm Ni in the
pH 4.9 soil. In a pH 7.7 soil, 1000 ppm Ni did not affect the viability of
the six bacteria and yeasts tested. The pH 7.7 soil also contained some
montmorillonite clay, and significantly higher amounts of magnesium than the
pH 4.9 soil. Apparently, alkaline pH, type and amount of clay minerals, and
other ions (e.g., Mg) greatly affect the microbial toxicity of nickel. Babich
and Statzky (I983b) have also reported that Mg2+ or Zn2+ cations, and S2~
and P04~ am'ons also reduce Ni toxicity. However, K+, Na+, Ca2+, Fe3+,
amino acids, tryptone, casamino acids, yeast extract, and chelating agents
(citrate, EDTA, DPA, NTA) did not reduce Ni toxicity.
Selenium--
The soil microflora, as a whole, are capable of several transforma-
tions of selenium. Since organic selenium compounds do not accumulate in
the soil in areas where organic selenium compounds, including volatile di-
methylselenide, are common in plant tissue, these compounds must be mineral-
ized and the selenium released as selenite and/or selenate. Apparently, the
oxidation of elemental selenium in soil is at least partly mediated by micro-
organisms, but the mechanisms and organisms participating in the process have
yet to be discovered. The reduction of selenite and selenate by soil micro-
organisms is a relatively common attribute, but bacteria do not seem to
use selenate or selenite as metabolic electron acceptors. Selenium may be
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methylated to dimethylselenide by a variety of soil fungi and bacteria, and
rates of methylation are greatly accelerated when a readily available carbon
source, such as glucose, is added to the soil (Alexander 1977).
Silver—
The bacteriocidal property of silver is well known (Chambers et al. 1962,
Woodward 1963). Sokol and Klein (1975) and Klein and Molise (1975) studied
the effects of silver from cloud seeding agents on soil and sediment microbial
activity. In laboratory culture, silver ions from AgN03 or ^rom saturated Agl
exhibited about the same level of toxicity to Arthrobacter sp. Anaerobic
cellulose degradation was inhibited in muds amended with 100 ppm Agl, and
apparently, organic matter decomposition was inhibited in soil contaminated
with Agl from a cloud seeding devise. Silver concentration in these contami-
nated forest soils reached nearly 1500 ppm (organic matter free basis). From
this and studies in a semiarid grassland soil, these investigators concluded
that the threshold level of impact of silver to soil decomposer activity
was 1-2 ppm Ag. Approximately 11 percent of the bacteria in the grassland
soil which was not treated with Ag could reduce Ag+ ions to metalic silver.
Experimental plots treated with approximately 100 ppm Ag to a depth of 2 cm
had significantly higher numbers (22 percent of total) of Ag+ reducers.
Vanadium—
Ammonium vanadate and vanadium pentoxide may be components of hazardous
waste (40 CFR 261). Vanadate may be reduced by microorganisms under appro-
priate conditions to vanadium oxide. Ferric ion produced by the oxidation of
Fe2+ by the Thiobacilli has been shown to oxidize V+3 to V+5. Vanadium is
chelated by EDTA and presumably by humic acids and other natural ligands
(Zajic 1969).
Decomposition of Xenobiotic Organic Compounds
The Role of Microorganisms--
Most of the compounds that can render a waste hazardous are organic, and
many of these hazardous organic compounds are synthetic and without close
structural analogs in nature. The molecular structure of some of these
compounds was purposefully designed to resist microbial attack and hence
prolong the persistence of the compound in the environment. However, many of
these compounds are susceptible to some kind of transformation or complete
mineralization by microorganisms in the environment. Where biodegradation is
possible, augmentation of the soil microbiota with cultured organisms and/or
manipulation of the soil environment through chemical or physical means to
optimize the desired activity may accelerate the biotransformation or mineral-
ization process. Alexander (1981) has pointed out that few abiotic processes
completely mineralize complex organic compounds in nature and complete degra-
dation of these compounds depends on microbial activity. However, physical/
chemical transformation processes may act synergistically with biochemical
decomposition in the decomposition of compounds of environmental concern.
For example, simultaneous photo and microbial decomposition of 2,4,5-tri-
chloroanaline in river water was nearly twice as fast as photodegradation
alone, and more than 10 times as fast as microbial mineralization in the dark
(H.-M. Hwang and R. E. Hodson, personal communication, May 1983, University of
Georgia, Athens).
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Genetic Engineering—
The resistance of many organic chemicals to degradation in the environ-
ment has prompted a search for techniques to improve the capabilities of
microorganisms in degrading these compounds. The use of genetic manipulation
of microorganisms to enhance the production of biological materials of commer-
cial importance has made significant advancements in recent years (Hopwood
1981), and many of the principles used can be and have been employed to
improve the degradative capabilities of microorganisms. Many degradative
capabilities in bacteria are encoded on extrachromosomal elements called
plasmids. Under appropriate conditions, plasmids can be transferred from one
organism to another, and once inside the cell can impart the plasmid coded
trait to the new host. Using plasmid manipulation techniques it has been
possible to "engineer" organisms that have extended degradative capability,
i.e., organisms that can degrade more than one xenobiotic substrate or that
can completely mineralize highly recalcitrant molecules such as 2,4,5-tri-
chlorophenoxyacetic acid (2,4,5-T) (Kamp and Chakrabarty 1979, Chakrabarty
1980, Chatterjee et al. 1981, Johnston and Robinson 1982, Pierce 1982).
Continuing efforts to genetically manipulate microorganisms to be able to
degrade recalcitrant hazardous compounds hold out great hope for future
treatment of contaminated soil and other environments.
Concerns have been expressed over the ability of genetically engineered
microorganisms to survive and function in the complex soil or aquatic environ-
ment (Stotsky and Krasovsky 1981). Since the permutations of interactions of
factors in the environment which influence microbial activity and growth in
the soil are essentially unlimited, it is difficult to predict the fate of
organisms with new or extra genetic material (Stotsky and Krasovsky 1981).
Unless the new genetic information increases an organism's ability to detoxify
its environment, or increases its ability to use a broader substrate range,
maintaining the genetic material would seem energetically disadvantageous for
the organism, and the organism or its new genes would be selected against.
However, Liang et al. (1982) have suggested that mutant organisms that toler-
ate abiotic stresses, resist starvation, and can coexist with antagonists may
persist in the environment for extended periods. Kilbane et al. (1983)
observed that a genetically engineered Pseudpmonas cepacia, which could use
2,4,5-T as its sole source of carbon, maintained high populations in soil as
long as appreciable amounts of 2,4,5-T were present, but decreased to un-
measurable levels when 2,4,5-T was exhausted from the soil.
There is some indirect evidence that plasmid born genes may be trans-
ferred among bacteria in the soil, and it has been suggested that some degra-
dative plasmids have evolved through the natural combinations of plasmid DNA
from different organisms (Pemberton et al. 1979, Chatterjee et al. 1981). No
information is available on the ability of introduced microbes to transfer
genes to indigenous organisms in natural habitats (Stotsky and Krasovsky
1981).
Effect of Structure--
Many factors, some of them only poorly understood, determine the degrad-
ability of an organic compound. Molecular structure and degree of substitu-
tion may be important. Apparently, for polychlorinated biphenyls (PCBs)
recalcitrance is related to the degree of chlorination and the position of the
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chlorine moieties on the ring structure of the molecule (Furukawa 1982). The
number of fused rings in polynuclear aromatics (PNAs) is important in deter-
mining the rate of their decomposition (Sims and Overcash 1983). Paris et
al. (1983) found an inverse relationship and a high correlation between
microbial transformation rates and van der Waal's radius of 8 phenols and
suggest that this molecular property may be useful in predicting degradability
of xenobiotics. More basically, the biodegradability of complex organic
molecules depends on the existence or inducibility of enzymes in the microbial
population which are capable of catalyzing the reactions needed. Alexander
(1981) has compiled lists of type reactions for transformation of chemicals of
environmental concern, but points out that the list is far from complete,, and
that more research is needed to provide this kind of information.
Cometabolism--
Xenobiotic organic compounds are usually transformed or degraded by
microorganisms in either a metabolic sequence which provides energy and
nutrients (i.e., C, N, P, etc.) for growth or maintenance of the organism,
or by a biochemically mediated reaction which provides neither energy or
nutrients to the cell. The first process usually results in the complete
biqdegradation of the organic molecule to mineral products (C02, ^0, NHL,
P0.~, etc.) and is called mineralization. The second process usually results
in only a minor transformation of the organic molecule and is called co-
metabolism or cooxidation (Alexander 1973, 1977, 1982). Two or more sub-
strates are required for cometabolism; one is the nongrowth substrate which is
neither essential for, nor sufficient to, support replication of the micro-
organism (Hulbert and Krawiec 1977, Perry 1979), while the other compound(s)
does support growth. The nongrowth substrate is only incompletely oxidized
(or otherwise transformed) by the microorganism involved, although other
microorganisms sometimes can utilize by-products of the cometabolic process
(de Klerk and van der Linden 1974, Perry 1979).
It is generally recognized that cometabolism results when a non-specific
enzyme attacks a recalcitrant molecule resulting in metabolism of the compound
(Horvath and Alexander 1970, de Klerk and van der Linden 1974). This could be
called a "metabolic mishap" since the organism supplying the enzyme gains no
benefit from the metabolic transformation. The enzyme is made by the micro-
organism to metabolize some other organic compound in the environment which,
when fully metabolized, could provide energy to the microorganisms (Perry
1979, McKenna 1977). Oxygenases are often involved in cometabolism because
they can be induced by, and can attack, a large set of substrates (Perry 1979,
McKenna 1977).
Cometabolism may be a prerequisite for the mineralization of many recal-
citrant molecules in the environment. For example, de Klerk and van der
Linden (1974) found the oxidation of cyclohexane to involve two distinct
steps. First, the conversion of cyclohexane to cyclohexanol by a Pseudomonad
bacterium which was using n-heptane as its energy source. Second, cyclo-
hexanol was readily utilized by a second strain of Pseudomonad. Beam and
Perry (1973, 1974) reported the same general results for the oxidation of
unsubstituted cycloparaffinic hydrocarbons. Over 100 strains of bacteria were
tested and none could use the hydrocarbons as their sole carbon and energy
source. However, many strains could partially oxidize the hydrocarbons when a
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suitable energy source was present (e.g., n-alkane). The cycloalkanones
resulting from the partial oxidation were readily oxidized and used as an
energy source by other strains of bacteria (Beam and Perry 1974). Unsubsti-
tuted cycloparaffinic hydrocarbons are readily mineralized in natural soil
systems, presumably by a process including cometabolism (Beam and Perry 1973,
1974).
Cometabolism probably occurs frequently in natural soil systems since
numerous genera of bacteria, fungi, and actinomycetes have been shown to
participate in the process (Horvath and Alexander 1970, Alexander 1977).
Compounds incompletely degraded by cometabolism are diverse and include
saturated hydrocarbons, halogenated hydrocarbons, numerous pesticides, and
single ringed polycyclic aromatic hydrocarbons (Horvath 1972, Raymond et al.
1969, Horvath and Alexander 1970, Alexander 1977, Merkel and Perry 1977,
McKenna 1977, Perry 1979, Sims and Overcash 1983). Since cometabolism is a
generally occurring process and has the potential for transforming very
refractory compounds to compounds which are more easily degraded, it may be
important in the biodegradation of complex organics in hazardous waste con-
taminated soils. Treatment to encourage cometabolism may include adding a
more easily degraded compound which is a chemical analog to the hazardous
compound that must be decomposed in the soil. Figures 3-44 and 3-45 illus-
trate the effect of several different growth substrates on the rate at which
C02 was released from malathion. Other growth substrates, including glu-
cose, glycerol, and glycerophosphate, did not have an appreciable effect on
the rate of [^C] carbon dioxide evolved from malathion (Merkel and Perry
1977). Table 3.46 shows the relative effects of naphthalene and phenanthrene
as growth substrates for the cometabolism of four polynuclear aromatic hydro-
carbons in water (McKenna 1977). Sims and Overcash (1981) showed that the
rate of cometabolism of benz(a)pyrene was significantly increased when the
soil was enriched with phenanthrene as an analog.
Degradation of Organic Pesticides--
Seventy of the organic based compounds listed by the U.S. EPA as con-
stituents of hazardous waste have been or are used as pesticides. These
compounds are listed by broad classes of compounds in Table 3.47. Insecti-
cides, acaricides, rodenticides, and herbicides are all represented. Concern
over the environmental fate and public health effects of pesticides has
focused a great deal of research on the biodecomposition or transformation of
many of these compounds, and much can be learned about hazardous organic
compound degradation from these studies. Here we will concentrate on the
classes and specific pesticide compounds included as constituents of hazardous
waste.
Decomposition of the chlorinated hydrocarbon pesticides has been the
frequent topic of research. The litersture pertaining to this topic has
been reviewed by Kaufman (1974), and Matsumura and Benezet (1978). Reduc-
tive dechlorination under anaerobic conditions and cometabolism seem to be
central mechanistic principles for these compounds (Horowitz et al. 1983,
Sulflita et al. 1983). However, greater metabolic diversity of microorganisms
degrading these compounds is being discovered (Stanlake and Finn 1982, Edge-
hill and Finn 1983, Nielson et al. 1983), and the importance of sequential
metabolism by microbial consortia is being recognized. For example, a strain
151
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50 IOO ISO 200 250
INCUBATION TIME (HRS )
Figure 3-44. Evolution of ^C02 from Core Creek soil suspensions amended with
[l4C]malathion. (0.1 yCi of [14C]malathion added to each flask
at beginning of the experiment. NO IND = no inducer added;
^17:1 = 1-heptadecene; C]j = n-tridecane; C]_3:i = 1-tridecene.
Control was 1 g of soil/50 ml of basal medium autoclaved for 50
min on three consecutive days.) (From Merkel and Perry 1977.)
Used by permission, see Copyright Notice.
17 I
iO 100 ISO 200 250
INCUBATION TIME IMPS )
Figure 3-45. Evolution 14C02 from tobacco field soil suspensions. Conditions
same as Figure 3-44 with CTJ « n-heptadecane also added (from
Merkel and Perry 1977). Used by permission see Copyright
Notice.
152
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TABLE 3-46. PERSISTENCE OF POLYNUCLEAR AROMATIC HYDROCARBONS IN
NATURAL WATERS (FROM McKENNA 1977)
Used by permission, see Copyright Notice
Non-Growth
Substrate
Growth
Substrate
Amount Non-Growth
Substrate Remaining
After Four Weeks
Pyrerte
3,4-Benzpyrene
1,2-Benzanthracene
1,3,5,6-Dibenzanthracene
Naphthalene
Phenanthrene
Naphthalene
Phenanthrene
Naphthalene
Phenanthrene
Naphthalene
Phenanthrene
36.7%
47.2
83.5
38.3
58.3
33.8
92.7
32.9
of Hydrogenomonas in consortium with the fungus Fusarium can mineralize DDM
(bis-(p-chlorophenyl)methane), a metabolite of DDT (Focht 1972). Chlorinated
hydrocarbon pesticides tend to be persistent in soil, but several of them are
short lived. Hexachlorocyclohexane (Lindane) for example disappears from soil
quite rapidly through a combination of chemical and biological degradation
mechanisms. The persistence of chlorinated hydrocarbons and their metabolic
products in soil may be affected by their incorporation into soil organic
matter (Bartha 1980, Bollag and Liu 1983). Some chlorinated hydrocarbon
pesticides have been shown to be toxic to soil microbial activity (Chendrayan
and Sethunathan 1980, Subba-Rao and Alexander 1980, Tarn and Trevors 1981,
Trevors 1982).
The microbial degradation of organophosphate pesticides has been reviewed
by Kaufman (1974), Matsunura and Benezet (1978), and Munnecke et al. (1982).
Organophosphate pesticides exhibit relatively low persistence in soil, and
this property influences their widespread use despite their mammalian toxicity
(Hsu and Bartha 1979). Microbial decomposition is the major degradative route
for organophosphorus insecticides (Miles et al . 1979). Decomposition usually
proceeds through oxidative pathways, but reductive mechanisms have been
reported (i.e., parathion aminoparathion) (Matsumura and Benezet 1978).
Hsu and Bartha (1979) point out that microbial metabolism of diazinon and
parathion appears to be cometabolic at least in the first step. The enriched
environment of the plant rhicosphere apparently stimulates microbial activity
and accelerates microbial mineralization of organophosphate insecticides (Hsu
and Bartha 1979, Reddy and Sethunathan 1983). The diffusion of parathion
through the soil is appreciably restricted by microbial activity after a lag
153
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TABLE 3-47. PESTICIDES INCLUDED AS CONSTITUENTS OF HAZARDOUS WASTE (40 CFR
261)
Chlorinated Hydrocarbons
Aldrin
Chlordane
Chlorbenzilate
ODD
DDE
DDT
1,2-Dichlorobenzene
1,4-Dichlorobenzene
1,2-Dichloroethane
Dichloromethane
1,2-Dich1oropropane
1,3-Dichloropropene
Dieldrin
Endosulfan
Endrin (and metabolites)
Heptachlor (oxidation product-
Heptachorepoxide)
Hexachlorbenzene
Hexachlorocyclohexane (Lindane)
Hexachloroethane
Hexachlophene
Methoxychlor
Pentachloronitrobenzene (PCNB)
Pentachlorophenol (PCP)
1,2,4-Trichlorobenzene
1,1,1-Trichloroethane
Trichloroethylene
Trichlorophenol
Toxaphene
Organophosphates
0,0-Diethyl S- 2-(ethylthiolethyl phosphorodithioate
(Disulfoton)
0,0-Diethyl 0-2-pyrazinyl phosphorothioate (Zinophos)
Methyl parathion
Parathion
Phosphorodithioric acid (Phorate)
Phosphorothioric acid (Famphur)
Tetraethylpyrophosphate (TEPP)
Thiocarbamates
Dial late (Avadex)
Dithiocarbamates
Ethylenebisdithiocarbamic acid, salts and esters (Nabam,
Maneb, Zineb)
Phenoxyalkanoates
2,4-Dichlorophenoxyacetic acid (2,4-D)
2,4,5-Trichlorophenoxyacetic acid (2,4,5-T)
2,4,5-Trichlorophenoxypropionic acid (Silvex)
Aldehydes
Acrolein (Aqualin)
Formaldehyde
154
-------
TABLE 3-47. CONTINUED
Alkyl halides
Bromomethane
1.2-Dibromomethane
Tetrachloromethane
Cyclic ketones
Kepone
Maleic hydrazide
Dinitrophenols
2-sec-Butyl-4,6-Dinitrophenol (Dinoseb)
2-Cyclohexyl-4,6-Dinitrophenol (DN-111)
4,6-Dinitro-o-cresol (DNOC)
2,4-Dinitrophenol
Miscellaneous
Acrylonitrile (Acn'tet)
Ally! alcohol
4-Aminopyridine
Amitrole
Aramite
Bis (2-chloroethyl) ether
Carbon Disulfide
Creosote
Cyclophosphamide (Endoxin)
Decamox
Dimethoate
Dimethyl phthalate
Diphenylamide
Ethylene oxide
Fluoroacetamide
Napthalene
l-Naphthyl-2-thiourea (Antu)
Nicotine
Pronamide (Kerb)
Strychnine
Warfarin
155
-------
period or period of adaptation of the microbial population (Gerstl et al.
1979). Phorate has been shown to be inhibitory to nitrification in soil
for up to 4 weeks, after which activity returned. In the same study, soil
respiration (03 consumption) increased when phorate was added (Tu 1980).
Forrest et al. (1981) found that soil that had been adapted to diazinon
through several annual treatments degraded diazinon rapidly. Successive
treatments of the soil with diazinon further increased degradative ability.
Freezing and thawing the soil did not adversely affect its degradation abili-
ty. A Flavobacterium isolated from the soil hydrolysed both parathion and
diazinon.
Kaufman (1974), Matsumura and Benezet (1978), and Munnecke et al.
(1982) have reviewed the microbial decomposition of carbamate pesticides.
The only carbamate pesticides listed as hazardous waste constituents are
members of the thiocarbamate and dithiocarbamate subgroups. The thiocarba-
mate dial late is an herbicide which controls growth by interfering with
cell division. The half-life of dial late in soil has been reported in
one study as 12 days (Banting 1967) and 4 weeks in another (Anderson and
Domsch 1976). Mineralization of l^C-labeled diallate nas been observed
and a fungus (Tridioderma harzianium) isolated which can use diallate as
a carbon source. Other fungi could transform diallate cometabolical1y
(Anderson and Domsch 1976).
The salts and esters of ethylene bisdithrocarbamic acid, which includes
the fungicides nabam, maneb, and zineb are the only dithiocarbamates included
as constituent compounds of hazardous waste (40 CFR 261). These compounds
degrade primarily by chemical means, although limited microbial degradation
has been observed. One decomposition product is ethylenethiourea (ETU), a
known carcinogen. Apparently, ETU degrades rapidly with ethyleneurea as an
intermediate to other compounds including C02 (Kaufman 1974).
Phenoxyalkonate herbicide degradation by microbes has been reviewed
by Kaufman (1974) Cripps and Roberts (1978), and Munnecke et al. (1982).
Recent concern over the mutagenicity of these compounds and the dioxin
contamination of 2,4,5-T has prompted a renewed interest in the degrada-
tion of these compounds. Many strains of bacteria and fungi can degrade
these herbicides. Complete mineralization of 2,4-D by soil microorganisms
has been demonstrated, but 2,4,5-T is more resistant to degradation. Until
recently, cometabolism has been the only degradative mechanism described.
Recently, reductive dehalogenation of 2,4,5-T to 2,4-D by microbial activity
in anaerobic environments has been described (Horowitz et al. 1983, Sulflita
et al. 1983). Kilbane et al. (1982) have produced, through "plasmid assisted
molecular breeding" (genetic engineering) a strain of Pseudomonas cepacia
which will grow on 2,4,5-T as a sole carbon source. This organism has been
used to detoxify 2,4,5-T in contaminated soil (Kilbane et al. 1983).
Degradation of Polychlorinated Biphenyls (PCBs)--
The fate of PCBs in soil-pi ant systems has been reviewed recently by
Pal et al. (1980). They conclude that all isomers of mono- and di-chloro-
biphenyls are degraded by various aerobic soil microbes, but that a few tri-
and tetrachlorinated PCBs are more resistant. Only a few species with five or
six chlorines are known to biodegrade. Biodegradation of the more highly
156
-------
chlorinated PCBs has not been studied. Furukawa (1982) has also reviewed the
microbial degradation of PCBs. This review points out that the position of
chlorine atoms on the PCB molecule is important to degradabil ity as well as
the number of chlorines. Transformations of highly chlorinated PCBS are
probably cometabolic, but the mixed microbial population of the soil may
perform extensive decomposition. Apparently, highly chlorinated PCBs are
quite photolabile, and Furukawa (1982) suggests that if photolysis and micro-
bial degradation of PCBs were combined more efficient and rapid decomposition
of PCBs might be expected. Liu (1982) also concluded from fermentor studies
with a PCB degrading Pseudomonas sp. that the position of chlorine substitu-
tion on the biphenyl molecule helps determine a PCB isomer's biodegradability,
and that higher chlorinated PCB formulations was much slower. A genetically
engineered pseudomonad, with the capability to completely degrade mono- or
dichlorobenzoates, and an Acinetobacter sp. or Arthrobacter sp. capable of
growing on 4-chlorobiphenyl, in combined culture were able to utilize more
than 98 percent of mono- and dichlorobiphenyls, with liberation of equivalent
amounts of chloride ions (Furukawa and Chakabarty 1982).
Degradation of Aromatic Hydrocarbons--
Sims and Overcash (1983) have recently reviewed the microbial decomposi-
tion of polynuclear aromatic compounds (PNAs) in the soil environment. The
toxicity of PNAs to microorganisms is related to their water solubility.
Cometabolism appears to be the biotransformation process for PNAs with more
than three rings, and acclimation of soils to PNAs enhances their ability to
degrade these compounds.
Degradation of Phthalic Acid Esters--
A broad spectrum of soil bacteria and fungi have been shown to degrade
phthalic acid esters (PAEs). Mixed populations of microorganisms degrade PAEs
more rapidly than pure cultures (Overcash et al. 1982).
Degradation of Substituted Benzenes--
The microbial decomposition of chlorophenols and phenol in soil has
been studied by Baker and Mayfield (1980). They found that phenol, £,
and £-chlorophenol, 2,4- and 2,6-dichlorphenol, and 2,4,6-trichlorophenol
were rapidly degraded in aerobically incubated soil, but m-chlorophenol,
3,4-dichlorophenol, 2,4,5-trichlorophenol and pentachlorophenoF were degraded
very slowly under aerobic conditions. None of the compounds tested were
degraded in anaerobic soil. Sulflita et al. (1982) have demonstrated the
potential for dehalogenation of haloaromatic substances by anaerobic microbial
communities using halogenated benzoates.
QUANTITATIVE DESCRIPTION OF
ORGANIC DECOMPOSITION
Microorganisms are highly effective in removing certain hazardous
organic constituents from soil systems. Principles of biological degradation
of organic substances derived from the study of decomposition in aqueous
systems provide the starting point for predicting attenuation in soil systems.
These principles also provide the fundamentals for explaining the effects of
toxic constituents and solid surfaces on quantitative decomposition in soil
systems. Organic chemical decomposition in soil systems is a very complex
157
-------
process which depends upon organic substance properties, soil properties, and
environmental factors (Hamaker 1972, Goring et al. 1975). The addition of
exogenous toxic organic wastes to soil systems greatly increases the com-
plexity of soil metabolic processes. This is partly because organisms are
exposed to at least three different types of chemicals: 1) readily consumable
substrates, 2) toxic constituents which may inhibit metabolic processes,
and 3) non-readily consumable organics which may not be toxic, but which
do not serve as sources of carbon and energy for cellular metabolism (co-
metabolites). The effects of these functional classes of organics on the rate
and extent of metabolism of each class and the effects of solid surfaces
within the soil system is very complex and very difficult to describe quanti-
tatively. Nevertheless, studies concerning herbicide and insecticide degrada-
tion in soil systems have provided a quantitative basis for extrapolating from
aqueous system fundamentals to soil systems which can be utilized as a tool
for describing the biodegradation of hazardous waste constituents.
In addition to biological decomposition, the degradation of a chemical or
class of chemicals in soil can also be influenced by chemical degradation,
volatilization, photodecomposition, and plant uptake and metabolism. The
latter process will not be addressed in this manual.
The goal in this section is to describe models for evaluating and
predicting the disappearance of certain compounds or classes of compounds
in soils with time. Mathematically, the rate of decomposition represents
a sink term in organic transport models which are needed to predict potential
groundwater contamination with respect to magnitude and type of contamination
and the time factor for contamination (rate of transport). Thus, a descrip-
tion of quantitative organic chemical decomposition in soil systems is neces-
sary to determine potential contamination of groundwater, and to determine the
chemicals or classes of chemicals that require management, through control of
mass transport, and treatment for destruction.
Useful degradation rate models of organics in soils have been described
by Hamaker (1966, 1972) and Goring et al. (1975), and Rao and Jessup (1982).
Two basic models which may be used to model the fate of toxic organic sub-
stances in soil systems were described by Hamaker (1972). The "power rate
model" can be expressed as:
dc/dt = -KCN (3-42)
where, C is the concentration remaining in soil solution at time t, k is
a rate constant, and N is the order of reaction. The second model, the
"hyperbolic rate model" can be expressed as:
dc/dt = - KI C/K2 + C (3-43)
where, KI, K£ are constants. The constant K represents the maximum rate
of degradation that is approached as the concentration increases.
The "power rate model" is applicable to chemical reactions in homoge-
nous solutions and reaction occurs in proportion to the concentration in
solution. The "hyperbolic rate model," which is similar to Michaelis-Menten
158
-------
enzyme kinetics, simulates a catalytic process. That is, degradation is cata-
lyzed by either microorganisms, adsorption, or complex formation with soils.
A first order rate model can be obtained from both models. When N =
1 in Equation 3-42, the rate law becomes:
dc/dt = - KC ............ (3-44)
Also, when K2»C, Equation 3-43 reduces to Equation 3-44 with K = «i/l<2.
The first order rate model is widely used in modeling degradation of organic
compounds in soil systems (Goring et al . 1975) because of its simplicity. The
first order rate model when coupled with a transport equation, provides a
simple model with an analytical solution for transport of pollutants in soil
systems. Analytical solutions are generally preferred over numerical solu-
tions that require computing facilities and large amounts of computer time.
Also, the half-life of a pollutant, a concept associated with the first order
rate, is independent of the initial pollutant concentration. The degradation
rate constant in Equation 3-44 actually represents a lumped parameter for
several complicated processes responsible for dissipation of organics taking
place in soil. Rao and Jessup (1982) recently pointed out that it is satis-
factory to assume a constant value for "global" degradation rate coefficients.
However, the degradation rate could be represented as a function of soil
temperature and soil -water potential, two very important parameters in-
fluencing the rate of degradation in soil systems (Walker 1976a, b).
Effect of sorption on the rate and extent of biodegradation is difficult
to assess for the wide range of organics and complex mixtures involved.
Hamaker and Goring (1976) developed a model for decomposition of pesticides to
explain the low degradation rates at low residual concentrations observed in
experiments that were monitored for relatively long periods. The model
organic constituent (pesticide) is assumed to be divided into available and
unavailable fractions. The available fraction is considered to be mobile,
labile, and is subject to degradation and movement. The unavailable fraction
is characterized as immobile and non-labile with no degradation allowed.
However, a first order transfer rate is allowed to describe movement to and
from the unavailable fraction. The decomposition is also assumed to be first
order (Figure 3-46). The fresh chemical in soil is assumed to be available
initially, but as time proceeds, the unavailable fraction increases. Hence,
based on this model, it is expected that desorption will be more difficult for
aged samples, as observed by Saha et al . (1969).
The "two compartment" model is formulated as follows:
dc/dt = - (K + K!) Ci + K.iC2 (3-45)
dc/dt = KiCi - K.!C2 (3-46)
where Cj and ^2 are concentrations in the available and unavailable fractions,
respectively; K is the first order decomposition rate constant; and KI and
K_i are first order transfer rate constants between the two fractions (Figure
3-46). Solution of the two equations and an estimation of parameters are
presented by Hamaker and Goring (1976).
159
-------
av a i 1 ab 1 e
K
-^•decompos it ion
1 *-l
unavailable
Figure 3-46.
Schematic description of "two compartment" model (after Hamaker
and Goring 1976). Used by permission, see Copyright Notice.
The ratio (K]/K_i) is a measure of the equilibrium between the sorbed
(unavailable) and desorbed (available) fractions. It has an effect in the
overall degradation rate (Figure 3-47). The degradation rate deviation
from first order increases as the ratio K]/K_i increases, i.e., the rate of
degradation decreases as the residual concentration decreases (Figure 3-47).
The rate law models discussed thus far do not consider the effect of
environmental factors on the degradation rate. Three of these factors
will be discussed, including: 1) initial concentration of the chemical,
2) temperature, and 3) moisture content. These factors have been reviewed by
Hamaker (1972) and recently by Hurle and Walker (1980).
Initial Concentration
Hamaker (1972) presented data showing that the 50 percent disappearance
time (DT-50%) increases as the initial concentration increases, i.e., the
persistence increases as the initial concentration increases. Walker (1976a)
has also observed the same phenomenon. The reduced rate is explained either
by the limited active sites available (Hance and McKone 1971), or by a toxic
effect on microorganisms or enzyme inhibition (Hurle and Walker 1980).
Sims and Overcash (1983) compiled data from the literature and conducted
experiments at North Carolina State University concerning polynuclear aromatic
hydrocarbon (PNAs) initial degradation rates and initial concentrations
(Figure 3-48). The data indicate an increasing trend of initial rate of
degradation as the initial concentration increases.
to 2C"C temperature, using Arrhenius equation, with
No apparent toxic effects of PNA on microbial
concentrations studied.
Temperature
The data were norma'ized
G = 1.013 (Table 3-48).
activity were evident at the
Generally, an increase in temperature increases the rate of degradation
of organic compounds in soil. This phenomenon is attributed to a decrease in
160
-------
100
k (decomp.) = 0.0152
(ti/2decomp- = 45-
0\R= 0.51
1/2—>106
300 350
Figure 3-47.
Disappearance of total chemical for different sizes of bound
residue reservoir, i.e., k^ (binding)/k_i (unbinding) = R
(Hamaker and Goring 1976). Used by permission, see Copyright
Notice.
161
-------
Reoroduced from
best available copy.
•X
o2
o1 J *
3 -,
CT
0
o ..
Ct
O
LU
O
U_
O
UJ
cr:
TO'2 J
- 10'3 =
10-5
ACENAPHTHENE
ACFNAPHTHYLENE
ACRID1NE
ANTHRACENE
BENZ (B)ANTHRACENE
BENZO (b)FLUORANTHENE
BENZO (k)FLUORANTHENE
BENZO (a)PYRENE
CHRYSENE
- DIBENZ (a.J)ACR1DINE
- DIBENZ Ca.h)ANTHRACENE
- D1BENZOFURAN
— D1BENZOTH10PHENE
- FLUORENE
— FLUORANTHENE
- NAPHTHALENE
— PHENANTHRENE
— PYRENE
10"1 10° 101 102 103 104 TO5
INITIAL CONCENTRATION (ug/g-dry wt.)
Figure 3-48. Rates of transformation of PNA compounds in soil as a function
of initial soil concentration.
162
-------
TABLE 3-48. KINETIC PARAMETERS DESCRIBING RATES OF DEGRADATION OF AROMATIC COMPOUNDS
IN SOIL SYSTEM (SIMS AND OVERCASH 1983)
en
CO
PNA
Initial Con-
centration
(n9/g soil)
k
(dayl)
Rate of
transformation
(yg/g-day)
t1/2a
(dayl)
Reference
Pyrocatechol
Phenol
Phenol
Fluorene
Kluorene
Indole
Indole
Naphthol
Naphthalene
Naphthalene
Naphthalene
1,4-Naphthoquinone
Acenaphthene
Acenaphthene
Anthracene
Anthracene
Anthracene
Anthracene
Anthracene
Anthracene
Anthracene
Phenanthrene
Phenanthrene
Carbazole
Carbazole
Acridine
Acridine
Benz(a)anthracene
Benz(a)anthracene
Benz(a)anthracene
500
500
500
0.9
500
500
500
500
7.0
7.0
25,000
500
500
5
3.4
13.7
10.3
11.4
40.0
36.4
25,000
2.1
25,000
500
5
500
5
0.12
0.12
3.5
3.47
0.693
0.315
0.018
0.347
0.693
0.315
0.770
5.78
0.005
0.173
0.578
0.173
2.81
0.21
0.004
0.005
0.006
0.005
0.005
0.198
0.027
0.277
0.067
0.231
0.075
0.281
0.04fa
0.0001
0.007
1,735
364.
157.
0.
173.
364.
157.
385
40.
0.
4,331
288.
86.
22.
0.
0.
0,
0.
0.
0.
4,950
0.
6,930
33
1.
37.
1.
0.
0.
0.
5
5
016
3
5
5
4
035
8
6
6
714
054
050
073
208
196
056
16
67
16
005
00001
024
0.2
1.0
2.2
39
2
1.0
2.2
0.9
0.12
125
4
1.2
4
0.3
3.3
175
143
108
138
129
3.5
26
2.5
10.5
3
9.2
3
15.2
6250
102
m
m
1
m
m
m
1
m
m
1
h
m
m
m
1
m
m
m
m
m
h
m
h
m
m
m
m
1
m
m
Medvedev & Davidov (1972)
Medvedev & Davidov (1972)
Medvedev & Davidov (1972)
Groenewegen & Stolp (1976)
Medvedev & Davidov (1972)
Medvedev & Davidov (1972)
Medvedev & Davidov (1972)
Medvedev & Davidov (1972)
Herbes & Schwall (1978)
Herbes & Schwall (1978)
Sisler & Zobell (1947)
Medvedev & Davidov (1972)
Medvedev & Davidov (1972)
Medvedev & Davidov (1972)
Gardner et al. (1979)
Gardner et al. (1979)
Gardner et al. (1979)
Gardner et al. (1979)
Gardner et al. (1979)
Gardner et al. (1979)
Sisler & Zobell (1947)
Groenewegen & Stolp (1976)
Sisler & Zobell (1947)
Medvedev & Davidov (1972)
Medvedev & Davidov (1972)
Medvedev & Davidov (1972)
Medvedev & Davidov (1972)
Herbes & Schwall (1978)
Herbes & Schwall (1978)
Groenewegen & Stolp (1976)
-------
TABLE 3-48. (CONTINUED)
PNA
Benz( a) anthracene
Benz( a) anthracene
Benz(a)anthracene
Benz(a)anthracene
Benz(a)anthracene ,
Benz( a) anthracene
Benz( a) anthracene
F luoranthene
Fluoranthene
Fluoranthene
Fluoranthene
Fluoranthene
Fluoranthene
Fluoranthene
Pyrene
Pyrene
Pyrene
Chrysene
Chrysene
Chrysene
Benz(a)pyrene
Benz(a)pyrene
Benz(a)pyrene
Benz(a)pyrene
Benz(a)pyrene
Benz(a)pyrene
Benz(a)pyrene
Benz(a)pyrene
Benz(a)pyrene
Benz(a)pyrene
Initial Con-
centration
(yg/g soil)
20.8
25.8
17.2
22.1
42.6
72.8
25,000
3.9
18.8
23.0
16.5
20.9
44.5
72.8
3.1
500
5
4.4
500
5
0.048
0.01
3.4
9.5
12.3
7.6
18.5
17.0
32.6
1.0
(day-1)
0.003
0.005
0.008
0.006
0.003
0.004
0.173
0.016
0.004
0.007
0.005
0.006
0.004
0.005
0.020
0.067
0.231
0
0.067
0.126
0.014
0.001
0.012
0.002
0.005
0.003
0.023
0.002
0.004
0.347
Rate of
transformation
(yg/g-day)
0.062
0.134
0.060
0.130
0.118
0.257
4,331
0.061
0.072
0.152
0.080
0.125
0.176
0.379
0.061
33
1.16
0
33
0.63
0.007
0.00001
0.041
0.022
0.058
0.020
0.312
0.028
0.129
0.347
(day!)
231
133
199
118
252
196
4
44
182
105
143
109
175
133
35
10.5
3
-
10.5
5.5
50
694
57
294
147
264
30
420
175
2
i
m
m
m
m
m
m
h
m
m
m
m
m
m
m
m
m
m
m
m
1
1
m
m
m
m
m
m
m
h
Reference
Gardner et al. (1979)
Gardner et al . (1979)
Gardner et al. (1979)
Gardner et al . (1979)
Gardner et al. (1979)
Gardner et al . (1979)
Sisler & Zobell (1947)
Groenewegen & Stolp (1976)
Gardner et al. (1979)
Gardner et al. (1979)
Gardner et al. (1979)
Gardner et al. (1979)
Gardner et al. (1979)
Gardner et al. (1979)
Groenewegen & Stolp (1976)
Medvedev & Davidov (1972)
Medvedev & Davidov (1972)
Groenewegen & Stolp (1976)
Medvedev & Davidov (1972)
Medvedev & Davidov (1972)
Herbes & Schwall (1978)
Herbes 8< Schwall (1978)
Groenewegen & Stolp (1976)
Gardner et al . (1979)
Gardner et al . (1979)
Gardner et al. (1979)
Gardner et al . (1979)
Gardner et al . (1979)
Gardner et al. (1979)
Shabad et al. (1971)
-------
TABLE 3-48. (CONTINUED)
Initial Con-
PNA centration
(yg/g soil)
Benz(a)pyrene
Benz(a)pyrene
Benz(a)pyrene
Benz(a)pyrene
Benz(a)pyrene
Benz(a)pyrene
Benz(a)pyrene
Benz(a)pyrene
Benz(a)pyrene
Benz(a)pyrene
Benz(a)pyrene
Benz(a)pyrene
Di benz( a, h) anthracene
Dibenz( a, h) anthracene
0.515
0.00135
0.0094
0.545
28.5
29.2
9,100
19.5
19.5
19.5
130.6
130.6
9,700
25,000
(day-1)
0.347
0.139
0.002
0.011
0.019
0
0.018
0.099
0.139
0.231
0.173
0.116
0.033
0.039
Rate of
transformation
(yg/g-day)
0.179
0.0002
0.00002
0.006
0.533
0
161.7
1.93
2.70
4.50
22.63
15.08
320.1
962.5
<&
2
5
406
66
37
-
39
7
5
3
4
6
21
18
s)
h
h
1
1
1
h
h
h
h
h
h
h
h
Reference
Shabad et al. (1971)
Shabad et al . (1971)
Shabad et al . (1971)
Shabad et al. (1971)
Shabad et al . (1971)
Shabad et al . (1971)
Lijinsky & Quastel (1956)
Poglazova et al. (1967b)
Poglazova et al . (1967b)
Poglazova et al. (1967b)
Poglazova et al . (1967b)
Poglazova et al. (1967b)
Lijinsky & Quastel (1956)
Sisler & Zobell (1947)
= low temperature range (< 15"C), m = medium temperature range (15-25"C), and h = high tempera-
ture range (> 25°C).
-------
adsorption with increasing temperature which makes more organics available, or
to an increase in biological activity, or both. The second factor has an
optimum temperature beyond which biological activity decreases.
The effect of temperature can be described quantitatively by the change
in the degradation constant which can be determined using the Arrhenius
equation:
K = A0e-(Ea/T) (3-47)
where A0 is a constant, R is the gas constant, T is the absolute temperature,
and Ea is the activation energy. Equation 3-47 implies that the rate law is
known. Usually, the rate law is assumed to be first order (e.g., Walker
1978). The half-lives at different temperatures can be estimated by:
log[t1/2(T1)] - log[t1/2(T2)] = Ea/4.575 (1/Ti - 1/T2) (3-48)
where ti/2(T]J and tj/2(T2) are the half-lives at absolute temperatures
TI and T2.
Temperature effect on degradation rate is important in terms of assess-
ment of the seasonal and geographical variation of degradation rates. Knowl-
edge of temperature effects allows an estimation of assimilative capacities
for organic wastes in soil systems for different regions of the United States.
The effect of controlling soil temperature on the rate of degradation of
organics can also be quantified and evaluated. Overcash and Pal (1979)
quantified the seasonal and geographical variation of oil waste decomposition
(Figure 3-49). The annual rate of degradation is higher in high temperature
regions than in low temperature regions. Field measurements also show in-
creased disappearance rates with seasonal high temperatures (Walker 1970,
Schweizer 1976).
Moisture Content
Hamaker (1972) presented data for several pesticides indicating an
increase in the degradation rate with increasing soil moisture content.
It was observed that the degradation rate increased as the moisture content
increased up to field capacity (Walker, 1976 a,b,c; 1978). Hamaker (1972)
suggested the following empirical equation to quantitatively describe the
rate dependence on moisture content for organic constituents in soil systems:
rate = r + KWn (3-49)
where W is the moisture content less than saturation, n is a constant less
than one, K is a constant, and r is the rate of degradation when N = 0. Note
that when using Equation 3-49, it is assumed all other factors are constant.
Harris et al. (1969) conducted field measurements of persistence of
atrazine and chlorfenanc at 12 locations. For both chemicals there was
more persistence in cooler northern and drier western states than in the
semi-tropical southern states.
166
-------
0.6
; 5
0 7
3 3
t i
Figure 3-49.
Effect of climatic conditions at major refinery locations on the
annual pattern of oil decomposition (Overcash and Pal 1979).
Used by permission, see Copyright Notice.
The quantitative approach to determining organic constituent degrada-
tion is utilized in Volume I of the manual. The models presented provide a
rational framework for determining relative degradation rates of constituents
in a soil system as a function of temperature and soil moisture. When models
for degradation are combined with simple transport models, the dynamic profile
in a soil system can be determined and used to identify those constituents
that require treatment first. Thus a prioritization of treatment steps and
processes can be developed based on the fate of contaminants, specifically
with respect to the potential danger to public health.
CHEMICAL REACTIONS IN THE SOIL MATRIX
Introduction
For a site characterized by large quantities of hazardous waste con-
taminated soils, consideration of in situ treatment requires certain informa-
tion related specifically to chemical reactions in the soil-waste matrix.
These chemical reactions can be classified into two functional groups for
simplicity: 1) chemical reactions involving the soil medium, and 2) chemical
reactions involving chemicals in the soil or soil solution. The latter group
of reactions may occur among chemicals already present at the site, or may
occur as a result of addition of a treatment reagent to the soil-waste matrix.
For in situ treatment it is anticipated that all immediate chemical reactions
that affect public health (explosion, heat generation, flammability, etc.)
will have occurred prior to site assessment for treatment. Therefore chemical
reactions as a result of addition of treatment agent will be emphasized.
167
-------
This section is concerned with the first group of chemical reactions
identified above, i.e., chemical reactions involving the soil medium. The
effects of gross chemical structure of inorganic and organic chemicals added
to soil systems are considered, including acids, bases, salts, nonionic
organics, surfactants, and aqueous-solvent mixtures. Effects on soil include:
1) dissolution, 2) permeability 3) sorption, 4) polymerization, and 5) micro-
bial activity. These effects on soil relate specifically to soil treatment
process, i e., immobilization and degradation/transformation.
Reactions among chemicals in the soil or soil solution are considered
with respect to health hazard (heat generation, fire, explosion, formation
of toxic fumes, formation of flammable gases, solubilization of substances,
and volatilization of toxic substances) in Volume I for specific waste
constituent-treatment agent combinations.
Effects of Waste Type on Soil Properties
Acidic Wastes--
Table 3-49 summarizes several industrial categories that generate
acidic waste constituents. Organic acids in soil systems are very likely
to undergo biodecomposition with evolution of C02, stimulation of microbial
populations, and consumption of 02 resources. If there are carbonates in
the system, such as in calcareous and sodic soils, C02 may evolve through
reactions of the acid with carbonate and bicarbonate species (Pal et al.
1977). Under acidic conditions in soils, soubilities of complexed cations
such as Cu and Zn increase, and Fe, Mn, and Cu are easily reduced to more
soluble forms. Acidic wastes may also be used as treatment process for
saline-sodic soils.
The decrease in soil pH due to the presence of hazardous acidic wastes
will also change the microorganism distribution within the soil systems.
Under acidic conditions (pH < 7) fungi predominate and thrive in soil systems.
Biochemical reactions resulting from fungal metabolism of certain hazardous
chemicals may make soil pH an important determinant, not only of the type of
microorganism, but also of the metabolic pathway of degradation.
Hydrocarbon-utilizing organisms possess a class of enzymes, known as
oxygenases, which incorporates atmospheric oxygen into the inert ring-struc-
ture as the initial step in aromatic hydrocarbon transformation and degrada-
tion. The substrate specificities of bacterial hydroxylation mechanisms,
however, may differ from those of microsomal enzyme systems present in fungal
tissues. Fungal systems may transform aromatic hydrocarbons by means of
monooxygenases into arene oxides, the mutagenic form of PNAs (Cerniglia et al.
1979), while bacterial systems carry out the dioxygenation of the aromatic
nucleus to form a cis-glycol as the first stable intermediate, not the arene
oxide.
These differences in the mechanism of aromatic hydrocarbon metabolism by
microogranisms have important implications for engineering techniques for
controlling and possibly detoxifying PNAs in hazardous waste contaminated
soils. Because of the major differences with respect to microbial oxidation
of aromatic hydrocarbons between bacteria and fungi, it may be especially
168
-------
TABLE 3-49. INDUSTRIAL CATEGORIES GENERATING ACIDIC WASTE CONSTITUENTS
(PAL ET AL. 1977)
Used by permission, see Copyright Notice
Organic
Inorganic
Winery Still age (3.5-5)
Paper and Pulp (4-6)
Organic Acid Manufacture (3-6)
Leather Processing (5-6)
Mineral Acid Manufacturing (3-4)
Dredge Mines (2-4)
Coal Processing (3-5)
Steel Cleaning (3-5)
Metal Plating (2-4)
Petrochemical Manufacturing (4-6)
important in soil systems to encourage bacterial growth and competition vis-
a-vis fungi. Since soil pH has a significant effect on the soil bacterial/
fungal proportions, pH may be an important engineering tool to direct the
pathway of PNA degradation.
Dissolution of clay minerals in the presence of organic acids has also
been observed. Those elements comprising the framework cations of clay
minerals, i.e., silicon, aluminum, magnesium, and iron, greatly increased in
solutions phases containing organic acids (Huang and Keller 1971). The
organic acids studied included aspartic, citric, salicyclic, taratric, and
tannic. The most rapid rate of dissolution occurs during the first 24 hours
of exposure of clay minerals to organic acids. After 45 days of exposure, the
solution concentration reaches a constant value.
The ability of organic acids to solubilize soil minerals has also been
observed with humic and fulvic acid fractions. Fulvic acids (FA) and low-
molecular weight humic acids (HA) can attack and degrade soil minerals to form
water-soluble and water-insoluble metal complexes, depending on how much
metal per unit weight of HA or FA is dissoved. The ability of these organic
acid fractions to dissolve clay minerals is believed to be due to their
ability to complex di- and trivalent metal ions. Fulvic acid can dissolve a
proportion of the dominant cation in the clay, forming a soluble complex and
replacing the removed cation with H+. If this process continues the FA will
degrade the clay structure (Schnitzer and Kodama 1977).
Table 3-50 presents results summarizing the increase in solubility of
framework cations of clay minerals, including kaolinite, illite, and mont-
morillonite in the presence of the organic acids listed previously. Aluminum
dissolution from clay minerals reached 60 ppm with illite. This concentration
is very high compared to less than 1 ppm solubility typical in aqueous solu-
tions. Iron disolution was observed to be similar to aluminum in ratios and
concentrations. In strongly complexing acids, silica solubility rose by
a factor of 2 to 6 for the kaolinites, and by larger factors for the 2:1
169
-------
TABLE 3-50. EFFECT OF ORGANIC ACIDS ON CLAY SOLUBILITY (HUANG AND KELLER 1971
Element Increase in solubility (factor) over water
KaloniteIlliteMontmorillonite
Si 2-6
AT 10-50
Fe 10-50
15-30
10-100
10-100
12-25
10-50
10-50
layer clays. Aspartic acid was especially active in dissolving calcium and
magnesium. Clay mineral framework cation concentrations are much lower in the
presence of water.
Implications of these observations include: 1) susceptibility of weather-
ing of silicate minerals in water is not followed in reactions with organic
acids; 2) dissolution of clay minerals by organic acid constitutents of
hazardous wastes may directly impact mass transport and permeability aspects
of the soil-waste matrix; 3) toxic metal ions at hazardous wastes sites may
also become mobile through chelation with natural and exogenous organic acid
fractions.
Basic Wastes--
Basic waste addition to acidic soil has been reported to increase the
pH of the surface layer (4" -18") but not the subsoil (Brown 1975). Basic
wastes would be expected to react with acidic groups of the soil system to
neutralize the buffer capacity of the soil, and increase the exchangeable
sodium percentage (ESP), percent base saturation, and soil pH. Basic waste
added to soil may result in physical damage to the soil system with resultant
low permeability, decreased hydraulic conductivity, and high runoff potential.
However, organic bases added to soil systems may increase soil buffer capacity
and exchange capacity as the bases are degraded. Generally an increase in
soil pH is associated with an increase in cation exchange capacity, which
increases the buffering action of a soil (Pal et al. 1977).
Salts--
Salt affected soils may be classified based on chemical conditions
of the soil-waste system identified in Table 3-51.
Soils contaminated by salty wastes become friable, flocculated, and
permeable with a high osmotic concentration of the soil solution. With sodium
as the dominant ion, and the SAR of the waste above 30, sodium dominates on
the exchange sites. Subsequent leaching of salts by precipitation results in
dispersed, deflocculated, and impermeable soils. In the absence of salts,
170
-------
TABLE 3-51. CLASSIFICATION OF SALT-AFFECTED SOILS
Soil Group
Sal ine
Saline-sodic
Sodic
EC of saturation
extract
(mmhos/cm at 25" C)
>4
>4
<4
ESP
(X)
<15
XL 5
XL 5
pH
<8.5
=8.5
>8.5
sodium soils become extremely dispersed and impermeable to water. The effect
of sodium on hydraulic conductivity is indicated in Figure 3-50.
In regions of base unsaturated soils (Southeastern U. S.), addition of
salt wastes may improve base saturation, decrease exchange acidity, and
increase nutrient supply (Pal et al. 1977). Sodic soils, however, can only
be treated in place by chemical treatment with calcium salts (gypsum) and
leaching of excessive sodium with solutions low in sodium and high in other
salts (Ca and Mg). Critical SAR values for soil are listed in Table 3-52.
Overcash and Pal (1979) point out that treatment of a soil that has been
salt-damaged is a difficult and slow process. If the damage is restricted to
the shallow soil surface layer, restoration is easier since amendments can be
mechanically incorporated into the soil. Restoration may be accomplished
within months. However, if structure deterioration has progressed to the
upper B horizon, calcium salts must be leached into the B horizon zone through
the severely restrictive deflocculated zone. This process for soil restora-
tion may require several years.
Solvents--
Very little information has been generated concerning the behavior
and effects of the solvent class of organic constituents on terrestrial
systems and on transport through terrestrial systems. However, assessment
of hazardous waste sites has identified numerous organic solvents present
in soil as well as groundwater samples.
Volatile solvents are known to exert an initial soil sterilization
effect on soil systems as the critical dose level is achieved. Soil recovery
is indicated by an increase in soil microbial activity and degradation of the
solvent. Solvents of low volatility produce very little soil sterilization
when applied in moderate to high levels. Table 3-53 lists solvents, the
critical soil levels for soil microbial populations, and the time period for
recovery at the critical dose.
Solvents also have an effect on the physical properties of soil. Several
studies have indicated that organic solvents, in general, will react with clay
171
-------
20
3O
4O
EXCHANGEABLE- SODIUM
-PERCENTAGE
Figure 3-50. Influence of exchangeable sodium percentage on the hydraulic
conductivity of a clay loam (Overcash and Pal 1979). Used by
permission, see Copyright Notice.
TABLE 3-52. CRITICAL SAR VALUES FOR SOIL (OVERCASH AND PAL 1979)
Used by permission, see Copyright Notice
Soil
SAR
Swelling clay (bentonite)
Nonswelling clay
Pure sand
Loam or finer textures
(>10% clay)
8-10
20
750
5-15
TABLE 3-53. RESPONSE OF SOIL MICROBIAL POPULATIONS TO APPLICATION OF
SOLVENTS (OVERCASH AND PAL 1979)
Used by permission, see Copyright Notice
Solvent
Cyclohexane
Hexane
Heptane
Pentane
Formaldehyde
Chloroform
Ether
Acetone
Pyridine
Critical soil
level (ppm)
840
430
10,000
7,200
150-300
590
7,400
58,000
7,900
Time period for recovery
at critical dose
(days)
within 37 days
within 19 days
within 24-63 days
within 30-53 days
within 22 days
within 12 days
within 14 days
within 12 days
within 16-30 days
172
-------
minerals in soil systems resulting in an increase in permeability of the clay
fraction (Buchanan 1964, White 1976, Anderson 1981, Anderson and Brown 1981,
Schram 1981, Anderson et al. 1982, Brown and Anderson 1983, and Brown et al.
1983). A change in permeability is related to a change in the relative volume
that a given clay occupies as a function of the adsorbing liquid. A solvent
property that can be used to describe the magnitude of the result of the
clay-solvent interaction, or change in permeability, is the dielectric con-
stant of a liquid. A clay surface in contact with a high dielectric constant
liquid undergoes swelling. Conversely, a low dielectric constant liquid in
contact with a clay surface will cause very little swelling. In the situation
where a soil system containing a high dielectric constuant fluid (e.g., water)
receives a concentrated waste containing a low dielectric constant liquid
(solvent), an increase in soil permeability may be anticipated as the relative
clay-liquid volume decreases.
Table 3-54 contains dielectric constants for several solvents identified
at hazardous waste sites. It is also apparent that organic solvents generally
become less water soluble with decreasing dielectric constant.
The effect of specific solvents on soil permeability is summarized
in Table 3-55 (Anderson and Brown 1981). General classes of organics,
including acidic, basic, neutral polar, and neutral nonpolar are included.
From Table 3-55 it is evident that most solvent organics increase permeability
of clay minerals in soil systems.
While a decrease in water solubility is generally associated with an
increase in sorption for the solvents listed, this is not true for several
solvents, including carbon tetrachloride, ethylene dibromide, and trichloro-
ethylene (Rogers and McFarlane 1981). These chlorinated hydrocarbons had
relatively low adsorption in batch isotherm tests to several surfaces, in-
cluding two silty clay loam soils, aluminum-saturated montmorillonite, and
calcium-saturated montmorillonite. Experimental results are indicated in
Table 3-56. For these chemicals the K values indicate that only minimal
sorption would occur in soil or clay. The sorption of chemials did not exceed
6 percent, except for 10 percent sorption of TCE by Al-mortmorillonite. It is
important to point out that the elevated volatility of these solvents may
result in atmospheric mass transfer as the primary pathway in the soil-
atmospheric system.
Surfactants--
Surfactants are organic molecules widely used in industry for cleaning
purposes. Cationic surfactants are usually quaternary ammonium salts, while
nonionic surfactants are characterized by polymers of oxyethylene (Cj^O)
with both polymer ends attached to alcohol and are nondissociated in water.
Anionic surfactants comprise the largest class of detergents (80-85 percent)
and consist of a sodium cation and the active organic anionic surfactant
(Overcash and Pal 1979). The anion part is usually a sulfate or sulfonate.
Application of surfactants to the soil will affect physical and biologi-
cal properties. For a total soil concentration of approximately 100 ppm, no
substantial adverse microbial response has been noted. A large amount of
information exists concerning field movement of surfactants to subsurface
173
-------
TABLE 3-54. DIELECTRIC CONSTANTS, DENSITIES AND WATER SOLUBILITIES OF VARIOUS
HALOGENATED AND NONHALOGENATED SOLVENTS (ANDERSON ET AL. 1983, MELLAN 1977)
Name
Water
Methanol
Ethanol
Benzyl Chloride
Acetone
1-Propanol
1-Butanol
1-Pentanol
Pyr id i ne
Phenol
Dichloromethane
1-Bromopropane
1-Chloropropane
1,1,1-Trichl oroethane
Aniline
Chloroform
Bromoform
1, 1,2-Trichloroethyl ene
Toluene
Benzene
Carbon tetrachloride
Cyclohexane
Hexane
Dielectric
Constant
78.5
32.7
24.6
23.0
20.7
20.3
17.5
13.5
12.4
9.8
8.9
8.1
7.7
7.5
6.9
4.8
4.4
3.4
2.4
2.3
2.2
2.0
1.9
Density
(g cm-3)
1.00
0.79
0.79
1.10
0.79
0.80
0.81
0.81
0.97
1.05
1.31
1.34
0.89
1.34
1.02
1.48
2.89
1.48
0.87
0.88
1.60
0.78
0.65
Water Solubility
(a 25°C
_
Miscible
Miscible
Moderately Miscible
Mi scible
Miscible
Miscible
Miscible
Miscible
Miscible
1.32%
NA
NA
Slightly Soluble
Soluble
0.82%
0.10%
0.10%
Slightly Soluble
Slightly Soluble
0.08%
45 ppm
NA
NA - not available.
TABLE 3-55. EFFECT OF ORGANIC SOLVENT IN CLAY PERMEABILITY (ANDERSON AND
BROWN 1981)
Chemical
Class
Acid
Base
Neutral
Polar
Neutral
Nonpolar
Solvent
Acetic acid
Aniline
Acetone
Ethyl ene Glycol
Xylene
Heptane
Effect on
Permeabil ity
decrease
increase
increase
increase
increase
increase
Comment
dissolution of clay
100 fold for Lufkin3
10 fold for H.B.a
1000 fold for Lufkin
50 fold for H.B.
100 fold for Lufkin
4 fold for H. B.
1000 fold for Lufkin
100 fold for H.B.
similar to Xylene
aSmectite clay.
174
-------
TABLE 3-56. SORPTION OF HALOGENATED OR6ANICS ON SOIL AND CLAY (ROGERS AND
MCFARLANE 1981)
Adsorbent
Clay Organic
(%) carbon
Freundlich constants
EDBb
Silty clay
loam
Silty clay
loam
Al -saturated
montmorillonite
Ca-saturated
31
34
100
100
(*)
2.6
1.8
0
0
K
0.62
1.18
1.75
NSd
1/n
1.08
1.04
0.88
NS
K
1.31
1.49
0.47
0.05
1/n
0.93
0.92
1.04
1.03
K
3.89
1.57
6.96
NS
1/n
0.82
0.93
0.92
NS
montmorillonite
aCT = carbon tetrachloride.
bEDB = ethylene dibromide.
CTCE = trichloroethylene.
dNS = Not sufficiently sorbed to determine constants.
waters (Sebastiani et al. 1971). These situations involve very concentrated
solutions in land fill operations. Overcash and Pal (1979) point out that the
adsorption process for surfactants in most soils cannot be considered instan-
taneous, but rather occurs at a finite rate. Therefore saturated flow condi-
tions should be avoided. Table 3-57 lists results of the adsorption of a
cationic and a nonionic surfactant by montmorillonite clay as a function of
surfactant concentration.
While surfactants may be toxic to soil microoganisms at high concentra-
tions (> 10,000 ppm), the most severe effects of surfactants in soil systems
would most likely involve mass transport of toxic and hazardous constituents
through soil systems. Very little information is available concerning actual
mass transport of toxic substances in soil systems due to surfactant addition.
Desorption
A very important area where initial soil-waste interactions may affect
subsequent constitutent mobility is desorption. Desorption of chemicals from
soil systems may result from precipitation events following a contamination
event, or may occur as a result of addition of amendments for land treatment.
The chemical matrix of the waste appears to have an important effect on the
subsequent behavior of waste constituents in soil systems.
175
-------
TABLE 3-57. ADSORPTION OF SURFACTANTS ON MONTMORILLONITE (HOWER 1970)
Used by permission, see Copyright Notice
Surfactant Surfactant adsorbed (mg/g montmorilignite)
Added
mg/g montmorillonite Cationic Nonionic
100
200
400
600
1,000
1,500
97
188
351
451
510
528
99
192
321
412
512
540
Three matrices were utilized by Bowman and Sans (1982) to place pesti-
cides on soils. The pesticide matrices included: 1) aqueous solutions,
2) hexane-acetone (95:S volume/volume) solvent, and 3) pure acetone. Two
levels of spiking were used with the hexane-acetone solvent, one at 5.0 ug/g
(low spike) and one at the level obtained with aqueous equilibrium isotherm
studies. With the acetone matrix, spiking was done at the level indicated by
the aqueous equilibrium isotherm method. Four desorption cycles were used
with two pesticides of different water solubilities, fensulfothion (water
solubility = 2000 mg/1) and its related sulfide (f. sulfide) (water solubility
= 1.7 mg/1). Three mineral soils and a muck soil were used to determine the
influence of organic matter on desorption (Table 3-58).
Figures 3-51 and 3-52 illustrate desorption of the pesticides as func-
tions of application matrix and soil type. For both pesticides desorption was
greater for solvent applied pesticide (hexane-acetone, and acetone) than
for aqueous applied pesticide in the mineral soils. Also an obvious effect of
solvent matrix on desorption is evident for f. sulfide. Less f. sulfide was
desorbed in the acetone treated soil than in the hexaneacetone (high spike)
treated soil. This was not observed for fensulfothion. Thus the type of
solvent also appears to play an important role in desorption behavior of
organic wastes.
The muck soil did not show differences in desorption to the extent
exhibited by the mineral soils. This was true for both pesticides studied.
However, while the maximum desorption of f. sulfide was 10 percent after four
desorption cycles (of the high spike hexane-acetone method), 60 to 70 percent
fensulfothion was desorbed from the muck soil. Desorption was also consis-
tently greater for fensulfothion from the mineral soils. This would be
expected for the more water soluble fensulfothion.
Thus the chemical matrix in which organic constituents are dissolved
may have a very important effect on the subsequent mobilization of the
176
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TABLE 3-58. PROPERTIES OF SOIL ADSORBENTS (BOWMAN AND SANS 1982)
Used by permission, see Copyright Notice
Adsorbent
Sand
TTTT
Organic
Matter
Sandy
Creek sediment
Sandy loam
Muck soil
91.5
71
77
52
1.5
22
15
34
7
7
8
14
0.7
2.3
3.9
36.7
6.9
6.5
6.9
6.3
Bondhead
Sandy
Loam
0 1
Oesorption Cycle
Figure 3-51.
Desorption of fensulfothion from four soils. ( ) Low spike;
( ) high-spike acetone; (—) high-spike hexane; ( ) equilib-
rium (Bowman and Sans 1982). Used by permission, see Copyright
Notice.
177
-------
I
100
80
60
40
20
Q
Big Creek
Sediment
15005=304
Muck
SoTI
. LS00.*142
34Qi
Desorption Cycle
Figure 3-52 Desorption of fensulfothion sulfide from four soils. ( ) Low
spike; ( ) high-spike acetone; (—) high-spike hexane; ( )
equilibrium (Bowman and Sans 1982). Used by permission., see
Copyright Notice.
constituents. For typical mineral soils, which are likely to be typical
of hazardous waste sites, insecticides adsorbed from aqueous solutions
would be desorbed to a lesser extent than insecticides adsorbed from organic
solvents. Also, less water soluble constitutents may desorb to a less extent
than more water soluble constituents.
The work of Brown et al. (1983)
direct application to hazardous waste
results in clay shrinkage,
chemicals will be reduced.
result. If the application
event or amendment addition,
anticipated. Also, the mass
and Bowman and Sans (1982) may have
sites. If solvent-action generally
the number of sites available for sorption of
Less total sorption may be anticipated as a
of an aqueous solution follows, as with a rain
rapid desorption of poorly sorbed chemicals is
transport of chemicals in the soil solution is
excerbated due to the increased permeability of the soil as a result of soil
shrinkage. Thus the effects of solvents in hazardous waste contaminated soils
may include two factors: 1) decrease in total sorption to soils, and 2)
increase in leaching potential through changes in soil structure.
Soil Catalysis
Many chemical reactions that occur in soil systems may occur independent-
ly of the soil, or may be soil-catalyzed. For example, there is a rapid
178
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release from soil of toxic methyl isothiocyanate after application of dazomet
or metham to moist soil. Catalysis of dazomet by clay surfaces resulted in
the formation of isothiocyanate within 15-20 minutes of application to soil
compost (Brady 1971). The reaction generally increases with decrease in soil
moisture. This is due to the increased availability of 63 in soil with
decreasing moisture content, and the 02 dependence of the reaction:
metham » methylisothiocyanate
02
The ability of clays to catalyze chemical reactions is attributed to
their strongly acidic nature. Heptachlor is rapidly degraded in the presence
of the acid clay attapulgite (pKa < 1). Significant decomposition of several
substances, including: 1) chlordane, 2) toxaphene, 3) heptachlor, 4) DDT, 5)
dieldrin, and 6) endrin can be achieved with kaolinite and attapulgite
(Fawkes et al. 1960). The chemical 2, 3-dichloropropene has been shown to be
hydrolyzed up to three times faster in moist soil than in solution.
Hydrolysis reactions are important for attenuation of chemicals in soils.
Sorption-catalyzed reactions are especially important for two classes of
chemicals, the chloro-s-triazines, and the organophosphates. Hydrolysis of
atrazine, simazine, and propazine to their hydroxy derivatives in soils
incubated at 30"C for 8 weeks was reported by Harris (1967).
The mechanism of chemical degradation of atrazine and other chloro-s-
triazines is believed to be explained by the reaction of triazines with
carboxyl groups (COOH) associated with soil organic matter. Sorption of
triazines occurs between protonated carboxyl groups and triazine ring N
atoms. Hydrogen bonding of the ring N and a soil organic matter carboxyl
group causes electron withdrawal, in addition to that caused by electro-
negative chlorine and nitrogen atoms, from the electron deficient carbon
atom enabling soil water to replace the chlorine groups.
Chemical degradation of organophosphates involves primarily soil-sorp-
tion-catalyzed hydrolysis of ester linkages. Although hydrolysis leads to
degradation, the hydrolysis products may exhibit pesticidal properties (Cowart
et al. 1971). The most important factors controlling rate and product forma-
tion include pH (Faust and Suffet 1966) and sorption. Degradation of diazinon,
ciodrin, and malathion occur by chemical hydrolysis. While malathion degrada-
tion may be chemical or biological, chemical hydrolysis is complete before the
biological lag phase is complete (Konrad et al. 1969). Hydrolysis in soil
systems is sorption catalyzed. Specifically, sorption of organophosphate
insecticides through complexation by soil-bound cations is the suggested
mechanism for sorption-catalyzed hydrolysis.
Malathion degradation half-lives were 6-8 hr in soil systems at pH 7.
First order kinetics of degradation were observed. Results of Hindin (1963)
suggest that in alkaline soils (pH 8), hydrolysis of malathion may be base
rather than sorption catalyzed.
It has been suggested that the extent of sorption-catalyzed hydrolysis
of chemicals may be related to susceptiblity to undergo acidic or basic
hydrolysis in soil-free systems (Guenzi 1971).
179
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Polymerization
Organic compounds added to soil systems often react with soil oragnic
matter to form complexes. The covalent binding of the pesticide class of
organic chmicals to soil humic material is discussed by Bartha (1980). For
example, 3, 4-dichloroanil ine, a principal residue of several phenyl amide
herbicides, exhibited a half-life in soil at 500 ppm as the humic acid-
dichloroaniline (HA-DCA) complex of 693 days. The addition of aniline at 1000
ppm to the HA-OCA containing soil decreased the half- life, based on first
order kinetics, to 178 days (You et al . 1982). Incorporation of substituted
aniline compounds into soil humic material may occur through the attachment of
substituted anilines to the quinoidal subunits of soil humus (You et al . 1982,
Hsu and Bartha 1976, and Parris 1980). Thus although the recalcitrance of
compounds may increase in the soil system through polymerization reactions,
addition of analogs to the system may significantly reduce the half-life of
constituents and increase degradation. Results of chemical incorporation
of constituents into soil humic material through polymerization and sub-
sequent effects on biodegradation are sometimes confused with the effects
of physical sorption of chemical constituents on biodegradation rate and
extent.
MODELING THE BEHAVIOR OF WASTE
CONSTITUENTS IN SOIL SYSTEMS
Transport Models
Transport models are important prediction tools for assessing the
fate of organics in the soil environment and the potential for groundwater
pollution. Transport models in principle consist of two parts: 1) a water
flow model, and 2) a solute transport model (Selim and Iskandar 1981, Rao and
Jessup 1982). In this section one dimensional transport models will be
described and plant uptake will be assumed to be zero. The water flow model
may be expressed as:
f • -it (-«Q) $> (3-so)
where 0 is the volumetric water-soil content, K is the hydraulic conduc-
tivity, x is the soil depth, and H is the hydraulic head. Equation 3-50
can also be expressed as:
by substituting H = h + x, where h is the pressure head and D(Q) is the soil
water diffusivity, and a(Q ) = -k(6)^i. The term $§ is found from the soil-
water characteristic, which is a functional relationship between soil water
content (e) and the pressure head (h). However, the soil-water characteristic
is not a unique relationship, and it exhibits hysteresis (Nielsen et al .
1981a). That is, the response is different depending on whether the soil is
180
-------
in a wetting or drying cycle (Figure 3-53). The solute transport model can be
derived for a "representative elementary value" (REV) of a porous medium. In
this REV level it is assumed that the variability in medium properties is
minimal (Bear 1972). The solute transport for REV is formulated as
where Dn is the hydrodynamic dispersion coefficient, c is the solution con-
centration of solute, S is the amount of solute adsorbed per unit weight of
soil, and Qi represents source and sink terms. Sink terms include degradation
(chemical and/or microbial), volatilization, decay, and any other removal
mechanisms. The models for describing degradation and volatilization are
discussed in other sections of this report. The hydrodynamic dispersion
coefficient is composed of two components: 1) mechanical dispersion and 2)
molecular diffusion. Mechanical dispersion is caused by: 1) velocity dis-
tribution within each pore, i.e., the velocity of fluid is zero at the soil
particle surface and increases away from the particle surface, 2) velocity
change due to pore size change, and 3) continuous fluctuation in velocity
direction with respect to the mean direction of flow. Molecular diffusion is
caused by the concentration gradient, i.e., Pick's law (the concentrations
tend to diffuse from high to low concentration regions) (Fried 1977). The
hydrodynamic dispersion coefficient is the sum of the mechanical dispersion
and molecular diffusion (Dm) (Fried and Combarnous 1971):
Dx = avn + Dm (3-53)
where the second term is the mechanical dispersion, v is interstitial velocity
(Darcy's flux divided by the water content), and a and n are constants. When
the soil is unsaturated a, n, and Dm are functions of soil-water content (Yule
and Gardner 1978, Kirda et al . 1973). For saturated conditions n is assumed
to be 1, and a is defined as dispersivity (Freeze and Cherry 1979). Hydro-
dynamic dispersion relationships with interstitial velocity were discussed by
Fried and Combarnous (1971), Fried (1977), Biggar and Nielsen (1980), Nielsen
et al . (1981b), and Gelham and Cherry. (1982). It should be recognized that
the hydrodynamic dispersion coefficient and the interstitial velocity are
highly variable in the field (Nielsen et al . 1981b). Figures 3-54 and 3-55
show the skewed distribution of the interstitial velocity and the hydrodynamic
dispersion coefficient for 360 field observations (Biggar and Nielsen 1976).
The practical significance will be discussed later in this section.
The solution of the solute transport equation is possible if the spatial
and temporal distribution of water content (0) and interstitial velocity (v)
are known with appropriate boundary conditions (Table 3-59). Under transient
flow conditions the distribution of 0 and v can be determined. Finite differ-
ence methods have been used for solving transport equations under unsaturated
conditions (Bresler and Hanks 1969, Bresler 1973, Kirda et al . 1973, Wood and
Davidson 1975, Tilloston et al . 1980). Selim (1978) has used a finite differ-
ence method for multilayered soil under unsaturated flow conditions with
reactive solutes. Gureghian et al . (1979) have also solved the transport
equation under transient unsaturated flow conditions for a layered soil.
181
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MATRIC POTENTIAL
Figure 3-53.
Soil-water characteristic relating the volumetric water content
0 to the matric potential tym. Hysteresis properties are illus-
strated by the directional arrows (Nielsen et al. 1981a). Used
by permission, see Copyright Notice.
120-
ode * 4.3 cm day"
median2 20.3
mean =44.2
v (cm day"' )
Figure 3-54. Frequency distribution of values of the pore-water velocity for
a class length of 10. cm day1 (Nielsen et al. 1981b). Used by
permission, see Copyright Notice.
IOO 200"
D (cm1 day")
400
Figure 3-55. Frequency distribution of values of the apparent diffusion co-
efficient D for a class length of 20 cm? day! (Nielsen et al.
1981b), Used by permission, see Copyright Notice.
182
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TABLE 3-59. BOUNDARY CONDITIONS FOR THE TRANSPORT EQUATION
1.0 Water Flow Boundary Conditions:
1.1 Soil surface boundary condition
1.1.1 Water head boundary condition
h = ho(t) at z = 0
1.1.2 Water flux boundary condition
q(t> = -D(0) || - K(9) at z=0
where q(t) = water flux - it can be either constant or time
dependent.
1.2 Bottom boundary condition
1.2.1 Impervious barrier
The flux is zero at the impermeable surface
(e.g. heavy clays)
-D(0) |2 + K(0) =0 at Z = L
oZ
1.2.2 Soil profile extends to a great depth (semi-infinite medium)
This boundary condition can be used in a well drained soil
1.2.3 Groundwater table
G=0s Z = L t > 0
h = 0 Z = L t 7 0
Qs = saturation water content
2.0 Mass Transport Boundary Conditions
2.1 Application of waste
vC = -0 D |£ + vc Z = 0 t < T
S dZ
where Cs = concentration of applied wastewater
v = flux of wastewater application (cm hr-1)
T = duration of application
The same boundary condition can be used for a rainfall event
2.2 Boundary condition at the bottom of soil profile
= 0 Z = L t > 0
183
-------
Finite element methods have also been used for the transport eauation (e.g.
Duguid and Reeves 1974, Segol 1977). Sykes et -al . (1982) have used Galerkin-
finite element methods to solve the transport equation under steady state flow
conditions. Adsorption was neglected and Michael is-Menten kinetics (hyper-
bolic rate law) were used to model the biodegradation of organics in leachate
from a landfill. Recently Van Genuchten (1982) has compared different numeri-
cal schemes that can be used in solving one dimensional saturated-unsaturated
flow and solute transport equations.
Under steady state flow conditions Equation 3-52 becomes:
3c _ n 3 c 3c p 3S . _„.
•ft' Dh^T ' V^T' 9 3t <3-54)
assuming a constant dispersion coefficient, and neglecting source and sink
terms. Equation 3-54 can be solved if an appropriate relationship between S
and c is defined in addition to appropriate boundary and initial conditions.
Two types of adsorption equations are used in conjunction with the transport
equation: 1) the equilibrium equation and 2) the nonequil ibrium equation (Rao
and Jessup 1982). Equilibrium equations are simply one of the adsorption
isotherms described previously in this report. The rationale in using adsorp-
tion isotherm in the transport equation is that, in most cases, adsorption
reaches equilibrium instantaneously. In other words, the sorption rate is
very high compared to the pore water velocity. The Freundlich isotherm has
been most often used with the transport equation. When the Freundlich iso-
therm is assumed for adsorption Equation 3-54 becomes:
R=D^-v (3-55)
where R is the retardation factor, which is defined as
R = ! + - (3-56)
The retardation factor represents the ratio between average pore water
velocity and average pollutant front velocity. R becomes independent of
concentration when N=l, i.e., when the isotherm is linear. The use of
a linear isotherm with the transport equation gives rise to an analytic
solution of the transport equation (Lapidus and Amundson 1952). The linear
isotherms have been used with the transport equation very frequently (Kay and
Elrick 1967, Davidson et al . 1968, Davidson and Chang 1972, Davidson and
McDougal 1973). Van Genuchten and Alves (1981) have compiled analytical
solutions for the diffusive convective transport equation with linear iso-
therms for different combinations of boundary conditions.
The assumption of a linear isotherm appears to be reasonable at low
concentration ranges for organic constituents in soil systems. However, at
high concentration ranges, i.e., close to solubility limits (such conditions
184
-------
may exist at hazardous waste sites), the exponent N of the Freundlich isotherm
is usually less than one (Hamaker and Thompson 1972, Davidson et al. 1980b,
Rao and Davidson 1980). In fact the assumption of a linear isotherm at high
concentration seems to underestimate the Teachable concentration, which may
have dangerous consequences with respect to management of hazardous wastes
sites (Davidson et al. 1978, Rao and Davidson 1979, Davidson et al. 1980b,c).
Also, deviations between calculated and observed breakthrough curves (BTC's)
often occur when linear isotherms are used. Van Genuchten and Wierenga
(I976a) listed the experimental conditions under which asymmetry (tailing) is
observed in BTC: 1) unsaturated flow, 2) aggregated media, and 3) pore-water
velocity. The inadequate prediction of transport with equilibrium models led
some investigators to use a kinetic (nonequilibrium) adsorption equation. Two
approaches were used in developing nonequilibrium models: 1) the use of
chemical-process models and 2) the use of physical-process models. In the
chemical-process models the assumption is that adsorption is a time dependent
reaction and that sorption equilibrium is not attained instantaneously.
Travis and Etnier (1981) have reviewed adsorption kinetic models (see Table
3-29) In the second approach the assumption is that sorption is instantaneous.
However, the rate of sorption is controlled by the rate of diffusion of the
solute to the soil surface (Rao et al. 1980, Rao and Jessup 1982).
Chemical-process models can be divided into: 1) one-site models and 2)
two-site models. In one-site models the sorption is assumed to be uniform
throughout the soil surface. Lapidus and Amundson (1952) have presented an
analytical solution for a transport equation with first order reversible
kinetic adsorption. Oddson et al. (1970) have also presented an analytical
solution for a transport equation with first order kinetic adsorption.
However, the authors neglected the diffusion term in the transport equation.
Lindstrom and Boersma (1978) presented an analytical solution for their model,
developed earlier (Lindstrom and Boersma 1971), coupled with first order
kinetic sorption. Hornsby and Davidson (1973) and Hansel! et al. (1977) have
also used the kinetic model that was developed by Lindstrom and Boersma
(1973). The one-site kinetic models showed much improvement of results
compared with equilibrium adsorption models. However, the improvements were
only limited to low pore-water velocities (Davidson and McDougal 1973, Hornsby
and Davidson 1973, Van Genuchten et al. 1974). In two-site models the
sorption sites are divided into two types. The first site type is where
sorption occurs instantaneously; with the second type of site the sorption
is time dependent (Cameron and Klute 1977). The advantage of a two-site
model over a one-site model is that two-site model can better simulate BTCs
obtained from miscible displacement studies (Rao and Jessup 1982). The
adsorption rate is defined as:
3t - (3-57)
and
3S2 N
-5T ' °<[K2CN ' S?3 (3-58)
185
-------
where the subscripts 1 and 2 denote the sites type 1 and type 2, respec-
tively. The total amount adsorbed, S, is
S = Si + S2 (3-59)
The rate of change of S is found by substituting Equations 3-57 and 3-58 into
the rate of change of Equation 3-59. The expression can be simplified
further by setting N=l, and assuming that F is the fraction of sorption
site 1 of the total sorption sites. The rate of amount sorbed becomes:
- F)K C - S2] (3-60)
The dimensionless form of the transport equation is (Van Genuchten 1981):
ov*i <3L~ -I 3 Ci oL,
~aT + (RT " V TT = "P
•"i C7W* i O U^
n - j. f n D \ - — _ ±_ / *3 £1 \
Ki at \KT *i ' ar ~ "D 5 2T U-oi;
az*
where the transformed dimensionless variables are defined as:
Ri = 1+£r '• RT = 1+f (3-62)
T = vt/L ; Z = x/L (3-63)
w - kL/v (3-64)
C- C1 S2- (1 - F)KC1
Cl = CQ - C. ; C2 = (1 - F)K(CQ - C^) (3-65)
T is dimensionless time, L is column length, P is Peclet number (a measure of
convection relative to dispersion); Cj and G£ are dimensionless concentra-
tions; and Ci and C0 are the initial and applied solution concentrations,
respectively. Van Genuchten and Cleary (1979) and Rao et al . 1982 have stated
that for w >_ 5 equilibrium conditions can be assumed.
In physical process models the liquid phase in the porous medium is
divided into "mobile" and "immobile" regions. Convective-dispersive solute
transport occurs only in the mobile region. Adsorption is assumed to occur
instantaneously. However, the sorption rate is controlled by the rate of
transfer between the mobile and immobile regions. The rate of transfer
between the two regions is driven by the difference in the concentrations (Van
Genuchten and Wierenga 1976, 1977). This model is formulated as follows:
9Cim
at
*\
- P n m
CmDm , 2
3x
V 0 - m
m m ox
(3-66)
III III ,, C. Ill III C'A
186
-------
[0 + (l-f)pk] -—• = a(C - C. ) (3-67)
m o L in i ni
where subscripts m and im denote the variables for mobile and immobile
regions, respectively, and f is the fraction of sorption sites in contact
with the mobile region. The dimensionless form of Equations 3-66 and 3-67
are:
^f* ^ \ ^C"
D m /D n \ im. _ 1 01 01 (3-68)
Ri Tf + (RT " Ri) ~FT ' P ^72 3Z u ba;
where the transformed dimensionless variables are defined as follows:
T = vmt 4>/L ; z = x/L (3-70)
QS = (Qm +OiJ ; * = (V®s) - (3-71)
I • (* + ) ; RT = (i - F) (3-72)
P = (VnL/Dm) (3-73)
(3-74)
r _ r
°im wi ,, 7C-N
; C2 = -r — TTT (3-75)
^o Li
$ represents the fraction of moisture content in the mobile region. Although
the chemical process model and physical process model are conceptually differ-
ent, mathematically they are equivalent for given boundary and initial condi-
tions. The validity of any of these models can be proven experimentally if
independent measurements of the parameters of the models are available.
Unfortunately this is not usually the case. Nonlinear least squares have
been used to optimize the parameter values in order to make the difference
between the model and observed points minimum. Rao et al . (1980b) used the
analytic expression developed to calculate the transfer coefficient as an
independent measure of the parameter. The results showed good agreement with
the BTC's observed for-38ci- and 3^0 over a wide range of pore-water veloci-
ties. Based on theoretical and experimental analysis, Rao et al . (1980a) have
found that the transfer coefficient is a function of system variables.
Limitations
The parameters for the models described above were estimated using
nonlinear least squares. The parameters were optimized so that the difference
187
-------
between observed data and computed data is minimum. Hence, the validity of
the models is questionable since there is no independent measurements of
parameters for the models. In addition to the unavailability of independent
parameter estimates, the field applicability of these models is further
limited by the heteorogeneity of most soils. As demonstrated in Figures 3-54
and 3-55 pore water velocities and diffusion coefficients in field measure-
ments are highly variable. The pore water velocity and the diffusion coeffi-
cient field measurements were shown to be log normally distributed (Biggar and
Nielsen 1976, Van De Pol et al. 1977). These uncertainties in the parameters
will be reflected in decreased accuracy of predictions. Dagan and Bresler
(1979), using mixed stochastic and deterministic differential equations,
attributed the variability of concentration profile in the field mainly to the
uncertainty of hydraulic properties of the porous medium. In their analysis
they neglected molecular diffusion and any interaction between the solute
and soil. Recently, Amoozegar-Fard et al. (1982) used a Monte Carlo simula-
tion and generated 2000 values of C/C0 using the solute transport equa-
tion. They assumed normal distribution for In D, In v, and the water filled
porosity, and no solute interaction with the soil. The results showed wide
differences between solute profiles when deterministic values of v and D were
used. The variability of D was much less important than the variability of v.
Therefore, according to the above discussions, conceptual models have
been developed but not much attention is paid to parameter evaluation.
Davidson et al. (1980) have shown that differences between the physical
nonequilibrium model Equations 3-68 and 3-69, and the analytic solution of
Equation 3-55 for nonreacting solutes is negligible (Figure 3-56). Hence,
the simple model is preferred over the more complicated in many situations.
For the purpose of site assessment for in situ treatment, a simple model
has been selected. The model chosen is described in detail by Enfield et
al. (1982). The model includes a first order degradation term and assumes
a linear adsorption isotherm. The model is a one dimensional advective-
dispersive transport model with a linear adsorption isotherm, and a first
order degradation rate. This model can be expressed as follows:
!l = °h§-»-i-kic (3-76'
where KI is the first order degradation rate constant and the rest of the
terms are as defined previously. Steady state unsaturated flow condition was
assumed in this model. The water content is estimated such that mass conser-
vation holds. Assuming a unit hydraulic gradient, the water recharge rate
(Darcy's flux) is equal to the hydraulic conductivity. The hydraulic conduc-
tivity is related to water content by the following empirical equation devel-
oped by Clapp and Hornberger (1978):
k * (9/0s)2b+3 (3-77)
where k is the hydraulic conductivity, Qs is the saturation water content,
0 is the water content, and b is a constant. Clapp and Hornberger (1978) have
estimated ©s and b for a range of soil textures (Table 3-60). Hence, Equation
3-77 can be used to estimate the water content, knowing 0S, b and the recharge
188
-------
u
u
1.0
.0.8
U
z
O 0.6
U
UJ 0.4
< 0.2
_J
U
cr o
NONADSORBED
Q = 10 cm/day
AGGREGATE MODEL
6 =0.26;9 = 0.14,P=9.6
M A
DISPERSION MODEL
= 0-4, P=1.3
234567
PORE VOLUMES, V/V.
8
Figure 3-56. Calculated relative effluent concentrations for a nonadsorbed
solute. Solid line obtained using analytic solution of Equa-
tions 3-68, 3-69; dashed line obtained with analytic solution
of Equation 3-55 (Davidson et al. 1980). Used by permission,
see Copyright Notice.
TABLE 3-60. REPRESENTATIVE VALUES OF HYDRAULIC PARAMETERS
(STANDARD DEVIATION IN PARENTHESES) (CLAPP AND
HORNBERGER 1978)
Used by permission, see Copyright Notice.
Soil texture
Sand
Loamy sand
Sandy loam
Silt loam
Loam
Sandy clay loam
Silty clay loam
Clay loam '
Sandy clay
Silty clay
Clay
No. of
soils
13
30
204
384
125
80 -
147
262
19
441
140
b
4.05 (1.78)
4.38 (1.47)
4.90 (1.75)
5.30 (1.87)
5.39 (1.87)
7.12 (2.43)
7.75 (2.77)
8.52 (3.44)
10.4 (1.64)
10.4 (4.45)
11.4 (3.70)
s
cm
12.1 (14.3)
9.0 (12.4)
21.8 (31.0)
78.6 (51.2)
47.8 (51.2)
29.9 (37.8)
35.6 (37.8)
63.0 (51.0)
15.3 (17.3)
49.0 (62.1)
40.5 (39.7)
s
cm-Vcm^
0.395 (0.056)
0.410 (0.068)
0.435 (0.086)
0.485 (0.059)
0.451 (0.078)
0.420 (0.059)
0.477 (0.057)
0.476 (0.053)
0.426 (0.057)
0.492 (0.064)
0.482 (0.050)
189
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rate. The model will be useful, not in terms of the absolute estimate, but
rather for establishing priorities with respect to chemicals and chemical
classes that require treatment. An example of the application of the model
and data requirements are presented in Volume I of this report.
ATMOSPHERIC ASPECTS OF IN SITU TREATMENT:
VOLATILIZATION AND PHOTODE6RADATION
Volatilization of Qrganics
The primary emphasis in monitoring at sites of hazardous waste contami-
nated soils has been related to the impact of these contaminants on the water
environment. Studies have concentrated on the movement of metals, salts and
hazardous organic compounds under uncontrolled hazardous waste sites and
through soil systems via groundwater and leachates. Information obtained from
ambient air measurements of the Love Canal area and from the Hudson River
Basin indicate that significant concentrations of toxic materials can be
released from landfills and dump sites, often much greater than emissions via
water transport (Shen and Tofflemire 1980). A number of hazardous compounds,
ranging from benzene to vanadium pentoxide, have been identified at un-
controlled hazardous waste sites in varying concentrations as shown in Table
3-61, indicating that air releases of many hazardous compounds from these
waste sites may be significant.
Volatilization of Organic Contaminants--
Although a paucity of information exists relating to the modeling of
organic contaminant emissions from hazardous waste disposal sites, much
information exists concerning the volatilization of organics, primarily
pesticides, from soil surfaces. General definitions of volatilization
include the loss of chemicals from surfaces in the vapor phase, indicating
that volatilization requires the vaporization and movement of chemicals
from a surface into the atmosphere above the surface. The rate of contaminant
volatilization is a complex function of the properties of the contaminant and
its surrounding environment. The driving force for volatilization is derived
from the vaporized chemical in the soil pore spaces, and the volatilization
rate of the material will be affected greatly by the adsorption onto soil
particles and the absorption or solubility of the compound within the soil
organic matter and within the soil water.
For organics in soil systems Spencer and Cliath (1977) indicate that
the factors affecting volatilization include:
1. Contaminant vapor pressure
2. Contaminant concentration
3. Soil/chemical adsorption reactions
4. Contaminant solubility in soil water
5. Contaminant solubility in soil organic matter
190
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TABLE 3-61. HAZARDOUS CHEMICAL VAPORS DETECTED AT UNCONTROLLED HAZARDOUS
WASTE SITES
Chemical Number of Sites
Benzene 5
Hexane 1
Toluene 6
Dichloroethane 1
Acetone 1
Tetrach1oroethylene 1
Xylene 3
Methane 6
Vinyl chloride monomer 3
PCB 3
Other VHO's and VNHO's 2
Dioxin 1
Ozone 1
lonizable vapors 1
Vanadium pentoxide 1
TCE 1
THC 1
Methyl fur an 1
Benzaldehyde 1
Bis(2-chloroethyl) ether 1
Thorium 1
Radium 1
Methylene chloride 1
Trichloro ethane 1
Phenol 2
191
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6. Soil temperature, water content, organic content, porosity, and bulk
density
The major contaminant property affecting volatilization is its vapor pressure,
while the major environmental factors affecting the contaminant's vapor
pressure are the soil/water and air/water partition coefficients that exist
for the various soil/water/air environments within the soil system. Addi-
tional complexity results if the contaminant is added along with an additional
adsorbing fluid such as oil in refinery wastes, where partitioning of the
contaminant between the oil/soil, oil/ water, and oil/air phases would also be
expected to affect the volatilization or vapor pressure of the volatile
compounds.
Equilibrium Chemical Partitioning--
The tendency of a compound to migrate from one environmental medium
to another is a function of the driving force to reach equilibrium between
media, and is related to the compound's chemical potential energy or its
fugacity. MacKay (1979) originally proposed the fugacity approach for com-
pound partitioning as an indication of the potential fate of compounds re-
leased in multicomponent environments. Further development of the equilibrium
partition approach has been presented by McCall et al . (1983) for estimations
of chemical partitioning based on the:
1. Sol, sermon constant - Koc - •"•
2. Water/air partition constant - KW = -^ - = 16 Q4 p^- =fj
air
3. Bioconceatration factor - BCF .
.
where
T = temperature, "K
Cajr, = concentration of the chemical in the air and water,
^water
respectively, mg/1
WS = water solubility, mg/1
P = vapor pressure of pure chemical (mm Hg)
M = chemical molecular weight, and
H = Henry's law constant
Correlations between partitioning coefficients have been presented
by a number of authors and have been tabulated in Table according to
chemical class. These correlation equations are valid for nonionic compounds
192
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and describe partition coefficients in terms of a compound's vapor pressure,
water solubility, and melting point. Knowing the comoound's partitioning
among the various media allows the estimation of its equilibrium distribution
throughout the environment, and indicates the relative importance of each
medium as the contaminant concentration moves toward an equilibrium level.
A compound's potential for volatilization from aqueous solution is
indicated by its air to water partition coefficient, 1/KW = H. From the
expression for Kw given above, volatility is seen to increase as water
solubility decreases or vapor pressure increases. Volatilization from soils
is also affected by soil sorption allowing an expression for volatiliza-
tion from wet soils to be developed through a modification of the water
volatilization term (Swann et al. 1983):
Volatility rate «-jr4— (3-78)
w oc
PM
(WS)TK '(3--79)
An analysis of a compound's physical properties in the above manner will
indicate its potential for volatility as compared to other compounds of
interest. McCall et al . (1983) showed that tetrachlorobiphenyl (Kw = 2;
Koc = 32,500; P = 4.9xlO~4 mm Hg) has a large tendency to volatilize from
aqueous solutions due to its low Kw value, even with a vapor pressure five
orders of magnitude less than 1,3-dichloropropene (Kw = 18, Koc = 68, P =
25 mm Hg), yet its volatilization from soils is less than that of 1,3-di-
chloropropene because of tetrachlorobiphenyl's large Koc value.
Because of the importance of partition coefficients in estimating con-
taminant movement, and the large number of compounds of concern, efforts have
been made to estimate partition coefficient values based on rapidly determin-
able surrogate parameters. Swann et al. (1983) have presented equations
relating various partition coefficients to retention times obtained by reverse
phase high-performance liquid chromotagraphy (RP-HPLC). A Waters Associates
HPLC system was utilized with an 85:15 v/v mobile phase of methanol-water
pumped at room temperature at 1.0 ml/min. Expressions for the various parti-
tion coefficients of interest based on RP-HPLC retention time (Rt) and com-
pound melting point (MP) were as follows:
In Koc = 3.446 In Rt + 1.029 (3-80)
In Kow = 5.505 In Rt - 3.780 (3-81)-
In BCF * 5.147 In "Rt - 6.977 (3-82)
In WS = 7.618 In Rt - 0.01 (MP-25) + 18.328 (3-83)
Correlation coefficients for the above equations ranged from 0.95 to 0.98,
indicating that a rapid estimation of compound partitioning is possible based
on RP-HPLC data. The equations were presented for nine pesticides; benzene;
193
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bromobenzene; bibenzyl; biphenyl; 2,2',4,5,5'-PCB; and anthracene and cannot
be considered general purpose relationships. They do suggest, however, the
validity of using RP-HPLC retention for partition coefficient estimates if
correlation equations for a specific compound class are developed using a
particular RP-HPLC operation.
Dynamic Vapor Movement Models--
Evaluation of chemical characteristics using equilibrium concepts as
described above indicate gross chemical movement potential but do not provide
information concerning the rate of movement toward equilibrium nor the vari-
ation of rates with time. Analysis of contaminant vapor movement using
diffusion concepts provides this time variant analysis for movement through
soil systems.
Volatilization from an Adsorbing Surface--
Adsorption of a compound onto an adsorbing surface reduces its chemical
activity, or fugacity, resulting in a reduction in its vapor pressure (Spencer
and Cliath 1977). This reduction in vapor pressure decreases significantly
the vaporization rate of the compound. This fact invalidates volatilization
equations based on compound aqueous vapor pressure measurements and on the
rate of volatilization of a model compound assuming nonadsorbing surface
volatilization as presented by Hartley (1969):
P (M )*
Fh =~ ^ ' Fa (3-84)
b P (M ) 2 a
a v a'
where
F = vapor flux rate
P = vapor pressure
M = molecular weight
a,b = model compound and volatilizing compound, respectively
A relationship similar to Equation 3-84 could be used to estimate
volatilization from soil systems if vapor pressure measurements of the
compound in the soil are determined. Spencer and Cliath (1969, 1983) describe
a modification to a gas saturation method they have developed which utilizes a
pesticide-treated soil, in place of a pesticide treated quartz sand, in a test
saturator along with a humidity control device for maintenance of soil mois-
ture content during testing. Diffusion time variation information for the
volatilizing compound can then be obtained from Equation 3-84 if diffusion
variation of the model compound is known.
Further complications result when the compound is soil incorporated.
Under soil incorporation conditions, volatilization of the compound in-
volves the desorption of the compound from liauid layers that coat the soil
particles, diffusion through the air filled pore spaces within the soil column
194
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to the air/soil interface, followed finally by the diffusion from the soil
surface to the overlying atmosphere (Thibodeaux 1979). Vaporization under
soil incorporation conditions occurs at a much slower rate as compared to
vaporization from soil surfaces due to reductions in the vapor pressure of the
compound and the slow rate of diffusion through the soil column to the air/
soil interface. As volatilization occurs, a concentration gradient develops
between equilibrium and actual concentration levels in all phases resulting
in a driving force for continued diffusion. The rate of diffusion declines
with time, however, as the concentration gradient is reduced due to an ever
increasing diffusion path length to the air/soil surface (Hamaker 1972).
Simplification of this complex problem, by assuming a compound concentration
at the soil surface equal to zero and a soil column of infinite depth, has
resulted in relationships for mass flux rate with time based on Pick's second
law of diffusion in the general form as presented by Mayer et al . (1974):
-
(n ot)"2
(3-85)
where
F = component mass flux rate through the soil surface
Ds = soil diffusion coefficient
CAO = initial component concentration
t = time
Contaminant Advection —
An additional source of contaminant volatilization from soil systems
is an advection process, labeled the "wick effect" by Hartley (1969), that
describes the net contaminant transport via a large upward diffusion of water
toward the soil surface due to evaporation of water from soil surfaces. The
impact of this advection term will vary from compound to compound and is a
function of the compound's soil adsorption characteristics, water solubility,
and partition coefficients in the air, soil, and water phases. A simple
relationship for this flux term was presented by Spencer and Cliath (1973):
F = Fw x c (3-86)
where
Fw = water mass flux rate
c = component concentration in soil water
A complete accounting for the mass flux of a volatile component from a soil
system can then be written using the summation of Equations 3-85 and 3-86 to
account for flux due to diffusion and due to mass transport via advection with
evaporated soil moisture.
195
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Vapor Transport from Hazardous Waste Sites--
The models developed as described above are limited in that they lack the
ability to include intimate soil and waste interactions as occurs in hazardous
waste sites where drums of chemicals leak into soil systems and around soil
particles. To accurately model volatile organic emissions from hazardous
waste sites, both the soil pore diffusion and soil surface diffusion phenome-
non must be considered, and means must be provided to predict diffusion as a
function of soil and diffusion length characteristics.
Modeling of the evaporation and diffusion of chemicals within the
pore spaces of soil systems using the concept of a "dried-out" zone was
presented by Thibodeaux (1979) to describe soil contamination from liquid
spills. In his model, soil contamination to a soil depth of h was assumed,
with compound evaporation from soil surfaces, vapor diffusion into soil air
spaces, and movement of the vapor up and out of the air/soil interface. A
"dried-out" zone develops at the air/soil surface which is relatively free of
adsorbed contaminant but through which vapors from the lower level must
travel. With time, this "dried-out" zone increases in depth, correspondingly
reducing the contaminated zone to an ever decreasing thickness, y. The soil
column is assumed to be isothermal, capillary action is considered minimal,
and soil adsorption of vapor through the dried-out zone along with biodegrada-
tion are also considered negligible.
Vapor diffusion through soil pores in the "dried-out" zone is considered
limiting, resulting in the following expression for compound mass flux rate
from the contaminated zone through the dry surface zone:
(3-87)
where
D/\ = component diffusion coefficient in soil air spaces
h = initial depth of soil contamination
y = variable thickness of soil contamination after onset of diffusion
C/\* = equilibrium concentration of component in pore spaces at the
evaporating plane
CA.J = concentration of the compound at the air/soil interface
The time for all of the liquid to vaporize from the contaminated zone was
given as:
h m.
t= - * - (3_88)
196
-------
where
A = surface area of contaminated region
t = time for all liquid to vaporize.
m^ = mass of component originally in the contaminated zone
Upon complete vaporization within the contaminated zone, diffusion can be
modeled as the diffusion of a chemical from vapor filled pore spaces that
are saturated to a depth of h. Analysis of the multicomponent continuity
equation with appropriate boundary conditions results in an expression for
the average concentration in the contaminated zone at time t (Thibodeaux
1979):
IT n=0'(2n+l)'
exp
DA(2n+l)Vt
(3-89)
where
C/\ = average compound concentration in the pore spaces, and other terms
are as defined above.
Thibodeaux (1979) presented, a graphical representation of the fraction of
chemical remaining, F/\ = C/\/C/\*, versus dimensionless time, log (O^t/h^)
(Figure 3-57), allowing the determination of compound lifetime for pore
diffusion. Total decontamination time is thus the sum of results from
Equation 3-88 for vaporization time and Equation 3-89 for vapor diffusion
time.
Refinement of the "dried-out" zone approach to air emissions from land-
farming of petroleum wastes has been carried out by Thibodeaux and Hwang
(1982) and represents the state-of-the-art description for the volatilization
of organics from land treatment operations. This model is applicable to the
estimation of air emissions from hazardous waste sites with slight modifica-
tions as discussed below. The model as developed assumes an isothermal soil
column, no capillary action through the soil layer, no adsorption in the soil
pore space, and no biodegradation of applied organics within the soil column.
The description of vapor movement through the soil/waste matrix is valid for
surface or subsurface waste applications through the use of surface injection
depth, hs, and depth of penetration or plow slice depth, hp. As applied
to hazardous waste sites, hs=0 and hp are equated to the estimated or measured
depth of the contaminated soil layer. Under steady-state conditions, the time
for the intial mass applied to completely volatilize is determined through the
analysis of the component vaporization rate, assuming a diffusion length
197
-------
log (l»4jf'V I
Figure 3-57. Fraction of contaminant remaining versus dimensionless time
from Thibodeaux 1979). Used by permission, see Copyright
Notice.
varying from the surface -i-nc-orporation depth, hs, at time t=0 to a value of
the penetration depth, hp, at complete volatilization. The average diffusion
length is:
h -h h +h
13-90)
the flux rate into the pore spaces from Fick's first law becomes:
A "
(3-91)
Equating F to its principal components and solving for the lifetime of the
diffusion reaction assuming a mass concentration at the air/soil interface
equal to 0 yields an expression for the lifetime, t, of the applied component:
"
t =
2 A DA CA
(3-92)
where
CA = component concentration within the pore air spaces
MA = total mass component volatilized
A = applied surface area or area of soil contamination
It should be recognized that M/\/A represents the waste application rate
on the landfarming area if all mass is volatilized. In waste spills analysis,
198
-------
M/\ represents the estimated mass of component A originally in the contami-
nated zone, again assuming all mass is volatilized.
Through mass balance relationships the mass flux rate of component A
through the wet zone-dry zone interface with appropriate boundary conditions
can be presented as:
D. C.
A A I-
MA
where
t = time after waste application
The component pore-space air concentration is related to the component
concentration within the applied oil by equating the rate of transport through
the oil phase to that through the dry soil column. The transfer rate equality
takes the form:
where
as = interfacial area per unit volume of soil
D0 = component diffusion in the oil phase
Z0 = oil -layer diffusion length
C-JQ = component concentration on the oil side of the air/oil interface
y = average thickness of the wet zone
The concentration of the component in the air and oil phases within the
soil pore space is related by Henry's law constant to yield:
CA = HCCL (3-95)
where
HC = Henry's law constant in molar concentration form
Substitution of Equation 3-94 into Equation 3-95 allows for the expression of
the concentration of the component in the soil vapor phase in terms of its
initial concentration within the oil as:
-------
Hc
1 - „ / °AZ° \
c kas ^v^l
Cio
(3-95;
The expression y(hp-y) indicates the impact of a lengthening dry zone
and is expressed as:
y(hp - y) =
- 2h
(3-97)
resulting in
CA =
H
/ 5 DAZ. \
1 + H A °
C ^ 2 , , 2v
\ D a ( h +h h -2h ) I
\os p ps s /
Cio
(3-98)
The relative importance of the oil layer diffusion rate is highly
dependent upon the oil-layer diffusion length, Z0, and the interfacial area,
as, which should be intimately tied to the waste application rate and the
nature of the soil in the soil system. Thibodeaux and Hwang (1982) presented
equations for Z0 and as for oil/soil interactions that result in either "film"
forms or "lump" forms within the soil column. Oil interactions resulting in a
thin coating around hypothetical spherical soil particles results in "film"
forms with the following characteristics:
2 -
«
(3-99)
as =
(3-100)
where
dp = particle diameter
Pp = soil particle density
P = oil density
f = fraction of oil in film form
20C
-------
Soil aggregation results in the clumping of soil particles and causes the
entrapment of oil or contaminant "lumps" within tne soil particle aggregate.
Diffusion film thickness and interfacial area expressions for soil clumps
assuming an orthogonal arrangement of particles surrounding an oil "lump"
yield:
Z- (3-101)
(3-102)
The fraction of pore spaces that is air filled is assumed to be 50 percent,
yielding an estimated f value of 0.5.
With a thin oil diffusion length, on the order of soil particle size
thickness, Equation 3-96 simplifies to:
CA = Hc Cio (3-103)
Transport between the oil and air pore spaces is at equilibrium under these
conditions and diffusion in the air spaces limits the overall mass transfer
rate from the landf arming area.
The diffusivity of the component in the air filled pore spaces is
related to that in air by taking into account the reduction in molecular
diffusion in a soil medium due to cross-sectional area occupied by soil
particles (porosity correction) and to twists and turns in the diffusion path
due to irregularities of the pore spaces within the soil column (tortuosity
correction). Mathematically this correction takes the form:
(3-104)
rv i
where
D/\. = component diffusion in air
« - son porosity - 1 -
T = soil tortuosity
With the use of Equations 3-92, 3-93, 3-98, 3-99, 3-102, and 3-104, the
time for decontamination and the rate of organic emissions from hazardous
waste sites can be determined using the Thibodeaux-Hwang model, once the
following parameters are measured: soil parameters including bulk density,
particle diameter and particle density; compound parameters including air
and oil molecular diffusivity and Henry's law constant; and operational
201
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parameters including surface injection and penetration or plow splice depth,
surface area of application, mass application, and time.
This model represents the state-of-the-art for landfarm air emission
rate (AERR) modeling and for a general case of soil contamination from
spills or leaking drums, volatilization from contaminated soil without
the oil film diffusion term can be modeled utilizing partitioning coeffi-
cients described earlier. The partitioning between soil organic carbon
and soil water would be controlled by Koc and between the soil water and
the soil air pore spaces by Kw. Assuming equilibrium conditions occur between
phases before volatilization begins results in an expression for soil air pore
concentration:
CA = CW/KW . (3-105)
where
Cw = the component concentration on the water side of the air/water
interface
Following the development of an expression for C/\ as carried out above
assuming the rate of diffusion through that the water phase and dry soil
column can be equated and the water film diffusion length is small yields
the following equation:
CA = Ciw/Kw (3-106)
where
C-jw = the initial component concentration measured in the soil water
C-jw will represent the measured value established based both on partitioning
between the soil/water and water/air phases if equilibrium conditions are
reached.
In the development of the above models, the air/soil surface concen-
tration of the contaminant was assumed to be equal to zero due to surface
air transport of vaporized components away from the site. Movement in both
the vertical direction, due to vertical turbulent diffusion as modeled by
the Thornthwaite-Holzman equation (Thibodeaux 1979), and the horizontal
direction due to advection, result in contaminant transport away from the
diffusing surface. The integration of surface flux r^te models for transport
through soil systems, with surface transport models, enables the evaluation of
the impact of micrometeorological conditions on the emission and transport of
toxic organics from hazardous waste sites and allows an evaluation to be made
of ambient air quality level impacts from hazardous w.v.e sites.
Factors Controlling Contaminant Volatilization
In reviewing the models presented for prediction of contaminant volatili-
zation from soil systems, the following soil and contaminant characteristics
can be identified as significantly impacting compound volatibi1ity:
202
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1. Soil moisture content, for compounds with low K0- and Kw. values
when soil moisture content is low, causing an increase in cif*jsion due to
water competition for soil adsorption sites (Hamaker 1972, Spencer and Cliath
1977, Thibodeaux 1979). The moael parameter reflecting this effect would be
Henry's law constant, Hc, which varies with vapor pressure from tne rela-
tionship:
Hc - H Cg ()
where
Hc = Henry's law constant in molar concentration terms
H = Henry's law constant in partial pressure/molar concentration
terms
P = total pressure
Cg = molar gas density = P°/RT
Po = component partial pressure
R = gas 1 aw constant
T = absolute temperature
An increase in component partial pressure would increase Cg, which in turn
increases Hc, which in turn increases C/\, resulting in an expected increase
in the mass flux rate F until greater than one monolayer exists. With greater
than a single water monolayer within the soil (high moisture content), reduced
porosity affects becomes controlling.
2. Temperature, causing an increase in vaoor pressure, water advection
rates, soil/water/air partition coefficients, and biodegradation rates (Ha-
maker 1972, Thibodeaux 1979).
3. Soil organic content, causing the partitioning between the soil/vapor
phase and a reduction in compound diffusion coefficient due to a reduction in
its vapor pressure (Hamaker 1972, Thibodeaux 1979).
4. Surface air flow rate, causing an enhancement of flux rates due to
maintenance of minimal organic and water vapor concentrations above the air/
soil interface, maintaining the driving force for diffusion. This effect is
reported to be of major concern for surface applied wastes due to the pore
diffusion limitations that exist for volatilization from subsurface applica-
tions (Spencer and Cliath 1977, Thibodeaux 1979).
5. Biodegradabil ity, causing the removal of the compound via uptake
and metabolism thus reducing its volatility. Degradation products have
been reported to be more volatile than parent compounds however (Spencer
203
-------
and Cliath 1977), and may potentially cause an increase in component flux
rates.
Other contaminant characteristics such as Kow, Koc, Kw, BCF, MP, and
vapor pressure affect volatility due to their interaction with soil/ water
conditions within the environment and are not generally controllable. Their
relationship with one another for a given compound will indicate the potential
effect of organic amendment addition and water addition on volatility, how-
ever, and can serve as tools for contaminant management as will be discussed
in the treatment section of this report.
Compound Photoreactivity
Photooxidation is the use of incident solar radiation to carry out
photoreaction processes. It utilizes cost-free solar energy as the driving
force for reaction but suffers from the variable supply of incident solar
energy and the attenuation of UV light as it travels through the atmosphere.
Photodegradation of organic compounds may occur by two processes: direct
photodegradation and sensitized photooxidation. In the direct photoreaction
process, each particle of light, or quanta, excites one substrate molecule.
Although many organic compounds absorb light, their adsorption is primarily in
the ultraviolet region, rendering direct photodegradation an inefficient
treatment process (Thorington 1980).
In the sensitized photooxidation process, sensitizing molecules absorb
light in the visible region where there is a wealth of energy reaching the
earth's surface. The electronically excited sensitizing molecule, or triplet
sensitizer, then returns to ground state by transferring its excess energy to
molecular oxygen, resulting in the formation of singlet oxygen. Sensitized
rates of photolysis are often orders of magnitude greater than those of direct
photolysis (Acher and Saltzman 1980) and are also characteristically photo-
oxidations, whereas direct photolysis may proceed by a variety of mechanisms
including isomerism, dehalogenation and dissociation.
Singlet oxygen is a highly reactive species of oxygen with a lifetime of
3 psec (Kearns 1971). It readily attacks organic substrates, yielding
oxidized photoproducts. Spikes and Straight (1967) stated that many classes
of organic molecules are susceptible to sensitized photooxidation. Among
these are alcohols, nitrogen heterocycles, organic acids, phenols, and poly-
cyclic aromatic hydrocarbons. Sargent and Sanks (1974) concluded that: many
compounds found in industrial wastes, such as phenols, cresols, trinitro-
toluene, and unsaturated nitriles should also be susceptible to photooxida-
tion.
The rate of photolysis is influenced by a number of factors including
the intensity and wavelength distribution of light reaching the reaction
media, their diurnal and seasonal variations, the absorption spectra of the
contaminant or photosensitizer, the concentration of reacting compounds,
and the energy yield produced during photon absorption. Additionally, the
nature of the media in which the reaction takes place and the interactions
204
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between the contaminant and its surroundings nas a Tiajor effect on pncto-
cnemical reactions as will be discussed briefly below.
Photolysis in Soils--
The evaluation of pesticide reactivity has been of primary concern to
past investigators due to the loss of effectiveness of pesticides unaergoing
photooxidation, and both direct and sensitized photolysis have been observed
for pesticides in aqueous, soil, and vapor phases (Miller and Zepp 1983).
Although the occurrence of the soil photoreaction of adsorbed chemicals has
been identified, the importance of this reaction as compared to aqueous or
vapor photoactivity and the reaction pathways through which the reactions
occur, have not been identified to date. General soil characteristics in-
cluding soil particle size, organic content, mineral composition, light
absorption characteristics, and moisture content have been identified as
affecting the nature of photodecomposition products and the rate and extent
of the photoreaction of some pesticides (Miller and Zepp 1983).
The relative importance of the photooxidation reaction of a chemical
on or within a soil will depend to a large extent upon its partitioning
between the air/water/soil media within the soil system. The soil/air
distribution coefficient, K$/\, can be calculation from other constants as
follows (Lemaire et al . 1982):
where
'-soil = concentration of chemical in wet soil on a dry basis, ug/g
Ca-jr = concentration of chemical in air, ug/cm^)
r = weight of soil /unit weight of water
KQ = soil/water adsorption coefficient, vg/g
Once partitioning is determined, determination of the importance of volatili-
zation or mobility to the groundwater may be made. Soil photodecomposition
will be of concern if the model compound remains relatively stationary within
the contaminated soil. Soil strongly absorbs incident light energy and
continuous soil turn over may be necessary to expose adsorbed chemicals to
solar radiation.
Soil organic content would be exoected to affect the partitioning of
chemicals between the soil organic material and the soil water. Partition-
ing within soil organic matter reduces the availability of the compound
for photodecomposition reactions as shown by the reduction in the photo-
conversion of parathion to paraoxon as the organic matter in soil increased
from 0.1 percent to 4.2 percent (Spencer et al . 1980). Additional soil
characteristics such as transition metal content (Nilles and Zabik 1975) and
soil pigment content (Hautala 1973) have also been indicated as affecting the
photochemical reactions taking place within a soil system.
205
-------
Moisture content is an additional parameter affecting the relative
distribution of a compound within the soil/water/air matrix within a soil
system and would be expected to affect contaminant photolysis accordingly.
Burkhard and Guth (1979) reported that photolysis rates of profenfos and
diazinon increased slightly as dry soils were amended to 12 percent moisture
content. Hautala (1978) found a significant decrease in the photolysis of
carboyl in wet soils as compared to dry soils, while the photolysis of para-
thion was independent of moisture content.
Photoreactions of halogenated aromatic compounds have also recently
been of interest because of a 2,3,7,8-tetrachlorodibenz-p-dioxin (TCDD)
release near Seveso, Italy, in 1976 (Choudhry and Hutzinger 1982). Photolysis
of TCDD on soil surfaces was reported by Crosby et al . (1971) in the presence
of suitable hydrogen sources in the form of polar solvents, and Plimmer and
Klingeble (1973) indicated that methanol used as a solvent for TCDD photo-
oxidation experimentation also acted as a hydrogen donor in the photolysis
reaction. Investigations of the use of alternative hydrogen donors for in
situ treatment of contaminated surfaces in the Seveso area was reported by
Wipf et al. (1978). Solutions of 80 percent olive oil and 20 percent cyclo-
hexane at 350 1/ha and 40 percent aqueous emulsion with 4 percent biodegrad-
able emulsifying agent at 400 1/ha were found to produce a thin film on
vegetation and other smooth surfaces to provide a maximum reaction surface for
TCDD photolysis. Under laboratory conditions, the oil and emulsion solutions
reduced the half life of TCDD by a factor of 25 when irradiated with light of
approximate solar wave-length distribution. Liberti et al . (1978) reported
that a 1:1 solution of ethyl oleate and xyl ene used as hydrogen donors also
resulted in comiplete TCDD degradation on building surfaces in approximately 1
hour at 2m W/cm^ and 72 hours at 20 yW/cm^ light intensity.
Despite the isolated observations of soil photodecomposition, little
substantive information exists to allow accurate predictions of the importance
of soil surfaces on general chemical photodecomposition. As Helling et al.
(1971) indicated in 1971 and Miller and Zepp (1983) repeated 12 years later,
the effects of soil sensitization, reaction quenching, radical formation, and
light screening and the soil characteristics such as particle size, organic
content, and temperature which alter these effects remain poorly understood.
A great deal of additional basic data is needed if soil photolysis rate and
magnitude predictions are to be possible in the future.
Photolysis in Air—
Because of the relatively high volatility of pesticides and their trans-
port by the air medium, vapor phase photochemistry of these compounds has been
studied extensively. Reviews of general photooxidation mechanisms for pesti-
cides have been presented (Crosby 1971, Plimmer 1971) and indicate that
oxidation is the most widespread reaction mechanism of pesticides under normal
environmental conditions. Vapor phase studies have been hampered, however, by
a lack of general experimental protocol for reactor design, reaction kinetics,
light source selections, and photoproduct collection and analysis.
Seiber et al. (1975) described methods for evaluating vapor phase photo-
decomposition of trifluralin on a lab and field scale, identifying four
photodecomposition products of the parent compound. The decomposition
206
-------
products were also found within the soil matrix, preventing an absolute
identification of them as vapor phase products or volatilized soil phase
products. Definite vapor phase production of photodegradation products of DDT
(Crosby and Moilanen 1977), and trifluralin and parathion (Woodrow et al .
1978) have been observed in the laboratory. Woodrow et al . (1983) have
recently reviewed pesticide vapor-phase photochemistry and presented informa-
tion concerning observed photochemical vapor phase reactions under laboratory
and field conditions for a number of additional pesticides as shown in Table
3-62. Some compounds require ozone, an hydroxyl radical, or hydrocarbon free
radicals to photoreact while others display a reaction rate enhancement
in the presence of an oxidant (Table 3-62). Pesticides not amenable to
photodecomposition included toxaphene, methyl bromide, and sulfuryl fluoride
(Vikane).
Polynuclear aromatic hydrocarbons (PNA) are known to readily decompose in
the air medium upon reaction with ozone, NOX and SOX (NAS 1972). PNAs are
not readily volatile as a class due to their partitioning into the soil
medium, making vapor phase photodecomposition of these materials in soils
under ambient conditions an insignificant pathway for their degradation.
Information regarding the photooxidation of other organic compounds
within the vapor phase is generally lacking but information from the pesticide
investigations indicates that major photoreactions within the atmosphere are
secondary reactions, i.e., reaction of the model compound with photochemical ly
produced reactive species such as radicals, ozone, singlet oxygen, etc. The
major secondary reactions that occur are those between these organic vapors
and the OH radical or ozone, of which the OH radical is the photoactive
species of greatest reactivity (Laniaire et al . 1982). The international
standard hydroxide radical environmental concentration of 4x10^ molecules/cm^
(Lamaire et al . 1982) provides a basis for estimating lifetimes of compounds
within the atmosphere if reaction rates of the compound, or its homologs, with
the hydroxide radical are known.
The half life of the chemical in air may be determined as follows:
1. The reaction rate expression takes the form
dC/dt = -kohKOH-lenv [C] (3-109)
where
dC/dt = rate of compound decomposition, mole/sec
= bimolecular hydroxide radical rate constant, I/mole-sec
[°H"]env = environmental hydroxide radical concentration, 4xl05
molecules/cm3 = 6645xlO~19 moles/cm3
[C] = component concentration, mole/cm3
Integration of Equation 3-109 yields:
207
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TABLE 3-62. PESTICIDE PHOTOCHEMICAL REACTIONS IN THE VAPOR-PHASE
(SUMMARY) (WOODROW ET AL. 1983)
Used by permission, see Copyright Notice
Chemical
Trifluralin
Parathion
Folex
DEF
Molinate
Chloropicrin
Aldrin
Dieldrin
DDT
DDE
Telone
Tetrachloro-
ethylene
Reaction observed in
lab field
yes yes
yes yes
yes
yes no
yes no
yes yes
yes
yes
yes
yes
yes
yes
Effect of
oxidant Major pathway
rate enhanced -NR2 -»• -NH
/ R
rate enhanced P -*S •* P -*0
P(III) * P(V)0
required P(SR)0 -» P(OH)0
required -CH2N- ->- -C(0)-N-
^ N-C(0)-S-J N-H
C13C-N02 ->• C1-C(0)-C1
Xc = cx^>'-xc"
•*• photodieldrin
^CH-CC13->=CC12
>=CC12 -^C=0
required ^Tc=CHCl •* ^CH-
C(0)-C1
^C^CL.^CCl-
C(0)-C1+C1-C(0)-C1
208
-------
In C/C0 = -k0H-[OH']env t (3-110)
2. Component half life occurs when c/c0 = 1/2 therefore
In 1/2 = -0.693 = -koH°[OH°]env ti/2 (3-111)
ti/2 = 0.693/(kOH'[OH0]env) (3-112)
Table 3-63 contains a number of kgn0 values for various compounds in air as
presented by Lamaire et al . (1982) and Cupitt (1980). Additional krj^0 values
will be required to allow the evaluation of atmospheric residence time of the
full range of materials anticipated to be generated from hazardous waste
si tes .
Biological Interactions--
Biological interactions in terms of enhancement of volatility of biologi-
cal metabolic end products, and the impacts of photodecomposition products on
biological activity become important in the evaluation of the significance and
applicability of vapor phase reactions for the treatment of materials at
hazardous waste sites.
The major evaluation of photodecomposition products has been related to
atmospheric reaction of ozone, NOX and SOX with the numerous hydrocarbons
found in urban air. These analyses are concerned with the impact of the
oxidizer/hydrocarbon reactions on photochemical smog production (National
Academy of Sciences 1976). Of concern, from a hazard mitigation standpoint,
is the production of hazardous compounds as photodecomposition products of
parent compounds of less hazard. Such occurrences have been documented, e.g.,
aldrin photooxidation to the more toxic doeldrin and paraoxon formation from
parathion (Crosby 1971) along with the detection of phosgene from the photo-
oxidation of chloropicrin, and the formation of PCBs from the photoreaction
of DOT (Woodrow et al . 1983), and the potential for such occurrences with
additional parent compounds would be expected to be high. Full evaluation of
the potential for hazardous photodecomposition product formation is not
possible at this time due to a lack of general information related to the
nature of photodecomposition products formed, and further research is needed
in this area.
Studies of the enhancement of compound volatility due to biological
activity are few and a general lack of information exists. Studies concerning
the enhanced volatility of mercury from soils due to biological activity have
recently been reported (Landa 1978, Rogers and McFarlane 1979) and only
through more research related to microbial degradation/vapor phase interaction
will an understanding of this process be obtained.
The use of photochemical reactions for the enhancement of compound
biodegradation is an additional area of interest for hazard mitigation from
hazardous waste sites. The major photolysis process in the vapor phase is one
of compound oxidation and it would be expected to aid in microbial degradation
through the oxidation of resistant complex structures (Crosby 1971, Sims and
Overcash 1983). Information regarding this aspect of the vapor phase photo-
lysis process is also lacking and research related to aqueous phase photolysis
microbial degradation enhancement presently underway (Oupont and Sims 1983)
may shed light upon its usefulness as a treatment option in soil systems.
209
-------
TABLE 3-63. RATE CONSTANTS FOR THE HYDROXIDE RADICAL REACTION IN AIR WITH
VARIOUS ORGANIC SUBSTANCES, Kni,0 IN UNITS OF /MOLE-SEC
(ADOPTED FROM LEMAIRE ET ALVH(1980) AND CUPITT (1980))
Substance log kQ 0
air
Acetaldehyde 9.98
Acrolein 10.42
Acrylonitrile 9.08
Ally! chloride 10.23
Benzene 8.95
Benzyl chloride 9.26
Bis(chloromethyl)ether 9.38
Carbon tetrachloride <5.78
Chlorobenzene 8.38
Chloroform 7.78
Chloromethyl methyl ether 9.26
Chloroprene 10.44
o-,m-,p-cresol* 10.52
p-cresol 10.49
Dichlorobromobenzene* 8.26
Diethyl ether 9.73
Dimethyl nitrosarnine 10.37
Dioxane 9.26
Epichlorohydrin 9.08
1,2-epoxybutane 9.16
Epoxypropane 8.89
Ethanol 9.28
Ethyl acetate 9.06
Ethyl propionate 9.03
Ethylene dibromide 8.18
Ethylene dichloride 3.12
Ethylene oxide 9.08
Formaldehyde 9.78
Hexachlorocyclopentadiene 10.55
Maelic annydride 10.56
Methanol 5.78
Methyl acetate 3.04
Methyl chloroform 6.36
Methyl ethyl ketone .-.32
Methylene chloride 7.93
Methyl iodide 6.38
Methyl propionate 8.23
Nitrobenzene 7.56
Nitromethane 8.81
2-nitropropane 10.52
n-nitrosodiethylamine 10.19
Nitroscetpylurea 9.89
210
-------
TABLE 3-63. CONTINUED
Substance log k
ai
n-propylacetate 9.41
Perch!oroethylene 8.01
Phenol 10.01
Phosgene nonreactive
Polychlorinated biphenyls <8.78
Propanol 9.51
Propylene oxide 8.89
Tetrahydrofuran 9.95
Toluene 9.52, 9.56
Trichloroethylene 9.12
Vinylidene chloride 9.38
o-,m-,p-xylene* 9.98
211
-------
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2-15
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APPENDIX A
PARAMETERS FOR ASSESSING SOIL/WASTE INTERACTION
Compound Name: Acenaphthene
Compound Properties: Structure
M.W. 154.2 Water solubility 3.47 mg/1
M.P. 96.2 Log Kow 4.33
B.P. Chemical class
Sp. gr. Chemical reactivity
Vapor pressure 2.0xlO"2 torr (20°C)
Adsorption in Soils
Adsorption Parameters Soil Properties
Percent (%)
Vir
_pH CEC QC Sand SiltClay
Degradation in Soils
Degradation Parameters _ _ Soil Properties __
Mo is-
Initial Temp, ture Percent (%)
KS n cone. °C _ pH CEC PC Sand S i 1 1 ~CTay
"OTTTS 500
0.3 2.81 5 15-25
Volatilization in Soils
Volatilization Parameters _ Soil Properties __
Moisture Bulk Temp.
QC (%) _ Density °C Porosity
246
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Compound Name:
Aldicarb [2-methyl-2-(methylthio)-propion aldehyde
0-(methylcarbamoyl)oxime]
Compound Properties:
M.W. 162.2
M.P.
B.P.
Sp. gr.
Vapor pressure
Structure
Water solubility
Low K
QW
Chemcial
Chemical
class
reactivity
40000
0.85
ppm
Adsorption in Soils
Adsorption Parameters
K N Kor
0.17
0.20
0.62
0.88
3.47
0.93
0.95
0.86
0.85
0.89
33
18,
23
23
18.9
Soil Properties
Percent (%)
PH
7.30
6.83
5.00
7.30
6.98
CEC
5.71
6.10
21.02
37.84
77.34
OC
0.51
1.07
2.64
3.80
18.36
Sand
77
83
37
21
42
Silt
15
9
42
55
39
Clay
8
8
21
24
19
Degradation in Soils
Degradation Parameters
Soil Properties
tl/2
0
0
0
0
<0
Ks n
.00273
.0087
.0420
.0322
.0032
Mois-
Initial Temp, ture
cone. °C 0
PH
5.
7.
7.
7.
4
8
5
5
CEC
0
1
0
0
OC
.58
.16
.15
.15
Percent (%)
Sand Silt
Clay
Volatilization in Soils
Volatilization Parameters
KwKQ
OC (%)
Soil Properties
MoistureBulkTemp.
0
Density °C
Porosity
247
-------
Compound Name: Aldrin [l,2,3,4,10,10-Hexachloro-l,4,4a,5,8,8a-hexachloro-l,4-
endoexo-5, 8-dimethanonaphthalene]
Compound Properties:
M.W. 364.9
M.P. 104
B.P.
Sp. gr.
Vapor pressure 2.3lxl-~-> torr
(20°C)
Structure
Water solubility 0.025 ppm
Log Kow -0.14
Chemical class
Chemical reactivity
Adsorption in Soi1s
Adsorption Parameters
K N K,
nr
0.7783 253d
Soil Properties
CEC
Percent (%)
SandSTTt
Clay
Deqradation in Soils
Degradation Parameters
Soil Properties
tl/2
0.0149
0.0165
0.0061
0.0096
0.0038
Mois-
Initial Temp, ture
cone. °C 0
Percent (%)
pH CEC QC Sand' Silt Clay
7.8 0.93
8.6 0.15
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
PC (%) e Density °C Porosity
aThese are average values from three soils.
248
-------
Compound Name: 2-Ammoanthracene
Compound Properties:
Structure
M.W. 193.2 Water solubility
M.P. Log Kow
8. P. Chemical class
Sp. gr . Chemical reactivity
Vapor pressure
Adsorption in
Adsorption Parameters
1.3 yg/1
4.13
Soils
Soil Properties
Percent (%)
K N
321.6
329.2
304.1
259.5
79.0
103.7
145.1
191.9
283.0
458.7
531.9
502.1
875.2
688.7
Knr
26580
15904
13338
36039
52659
94276
30225
41248
42878
35287
28292
30069
36772
48537
pH
7.79
7.74
7.83
8.32
8.34a
4.54a
7.79
7.76
5.503
7.60
7.55
6.70
7.75
CEC
3.72
23.72
19.00
33.01
3.72
12.40
18.86
11.30
15.43
8.50
8.33
8.53
31.15
20.86
Degradation in
Degradation
Parameters
Initial Temp.
t!/? K,
n cone
°C
Mois-
ture
0
OC
1.21
2.07
7.28
0.72
0.15
0.11
0.48
0.95
0.66
1.30
1.88
1.67
2.38
1.48
Soils
Soil
pH
Sand
67.5
3.0
33.6
0.2
82.4
7.1
2.1
15.6
34.6
0.0
50.2
26.1
17.3
1.6
Properties
CEC OC
Silt
13.9
41.8
35.4
31.2
10.7
75.6
34.4
48.7
25.8
71.4
42.7
52.7
13.6
55.4
Percent (
Sand Si
Clay
18.6
55.2
31.0
68.6
6.8
17.4
61.6
35.7
39.5
28.6
7.1
21.2
69.1
42.9
X)
It Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
OC (%) 6 Density °C Porosity
aSoils; all others are sediments.
249
-------
Compound Name: 6-aminochrysene
Compound Properties:
Structure
M.W.
M.P.
B.P.
Sp. gr
Vapor
243.2
210-211'C
pressure
Water solubility 0.155
Log Kow 4.99
Chemical class
Chemical reactivity
Adsorption in Soils
ug/i
Adsorption Parameters
K
nr
1688.8
143427
150519
174232
149817
382185
624022
192553
136025
215835
67070
139149
87363
164844
114108
Soil Properties
PH
CEC
Percent (%)
OC
Sand
Silt
Clay
Degradation in Soils
Degradation Parameters
Soil Properties
Mois-
Initial Temp, ture
cone. °C 0
pH
CEC
Percent (%)
OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
QC (%)
Soil Properties
Moisture Bulk Temp.
Density
Porosity
250
-------
Compound Name: Anthracene
Compound Properties:
M.W. 178.2 Water solubility 0.075 mg/1 (15°C)
M.P. 216°C Log Kow 4.45
B.P. 342°C Chemical class
Sp. gr. Chemical reactivity
Vapor pressure 196xlQ-4 torr (20°C)
Adsorption in Soils
Structure
Adsorption Parameters
K N K,
Soil Properties
or.
PH
CEC
Percent (%)
OC
Sand
Silt
Clay
Degradation in Soils
Degradation Parameters
tl/2
175
143
108
138
129
3.5
42
36
45
43
39
43
Volati
oir
0.004
0.005
0.006
0.005
0.005
0.198
0.017
0.019
0.015
0.016
0.018
0.016
1 ization
Initial
n cone.
3.4
13.7
10.3
11.4
40.0
36.4
25000
41
0.41
47
0.49
62
0.60
Vol
Parameters
Soil Properties
Mois-
Temp. ture Percent (%)
"C G pH CEC OC Sand Silt Clay
<15
15-25
15-25
15-25
15-25
15-25
>25
at il ization in Soils
Soil Properties
OC (%)
Moisture
9
Bulk
Density
Temp.
°C
Porosity
251
-------
Compound Name: Anthracene-9-Carboxylic acid
Compound Properties:
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
222.2
Structure
Water solubility 85 pg/1
Log Kow 3.11
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
K
N
K,
27
49
96
47
84
82
nr
10.03
2,
1
13
6
5
9
66
78
27
45
59
88
7.50
463
265
349
760
1227
2564
2090
280
270
1021
343
335
415
507
Soil Properties
pH
CEC
Percent (%)
ocr
Sand
STTt
Clay
Degradation in Soils
Degradation Parameters
Soil Properties
Mois-
Initial Temp, ture
cone. "C 6
pH
CEC
Percent (%)
OC
Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
MoistureBulk
OC (%) 9 Density
Temp.
°C
Porosity
252
-------
Compound Name: Atrazine [2-chloro-4-ethylamino-6-isopropylamino-l,3,5-
triazine]
Compound Properties:
M.W.
M.P.
B.P.
Sp. gr.
215.7
173-175°C
Vapor pressure 1.4xlO"6 mm Hg (30°C)
Water solubility 70 mg/1 (20°C
33 mg/1 (278C)
Log Kow 2.68
Chemical class
Chemical reactivity
Structure
Adsorption in Soils
Adsorption Parameters
Soil Properties
Percent (%)
K
6 .03
0.89
0.62
0.62
0.21
2.61
1.2
0.4
0.7
0.8
1.6
1.2
1.9
1.5
2.5
1.5
1.5
1.1
2.0
1.1
2.9
2.8
1.8
3.5
4.1
3.7
2.9
9.5
10.3
10.6
11.8
13.8
12.3
17.4
N Knr
0.73 155.8
1.04 98.9
0.79 110.7
0.93 124.0
1 80.8
0.85 174
1200
100
140
89
178
100
146
100
167
100
94
69
118
78
107
90
53
92
89
57
37
101
104
84
87
99
87
113
PH
7.3
5.6
5.6
7.4
6.5
6.8
7.0
6.6
6.2
4.9
5.7
5.9
6.1
5.8
6.7
6.2
5.8
6.9
6.4
6.7
6.6
6.5
6.9
6.5
5.7
7.6
7.2
6.8
5.3
7.1
7.1
6.9
6.5
6.5
CEC
54.7
6.8
5.2
35.8
5.1
20.0
25.4
10.2
10.6
11.0
9.2
12.4
14.0
11.0
30.1
13.9
10.3
20.2
21.5
22.3
24.8
25.9
29.2
26.9
27.4
25.7
42.0
44.6
51.3
37.6
11.2
50.4
61.3
82.1
OC Sand
3.87 18.4
0.90 65.8
0.56 93.8
0.50 56.7
0.26* 77
1.503 16
0.1
0.4
0.5
0.9
0.9
1.2
1.3
1.5
1.5
1.5
1.6
1.6
1.7
1.8
2.7
3.1
3.4
3.8
4.6
6.5
7.8
9.4
9.9
12.6
13.6
14.0
14.1
15.4
Silt Clay
45.3 38.3
19.5 14.7
3.0 3.2
16.4 22.9
18 5
68 16
42.8
8.2
15.8
13.9
20.3
28.5
10.3
17.9
27.8
33.5
21.0
22.0
35.2
37.1
61.6
63.4
31.9
25.9
30.2
28.1
33.8
20.1
29.5
28.4
8.1
17.6
51.2
28.7
^Reported as OM.
253
-------
Compound Name: Atrazine (continued)
Compound Properties:
M.W. 215.7 Water solubility 33 mg/1 (27'C)
M.P. 173-175°C Log Kow 2.68
B.P. Chemical class
Sp. gr. Chemical reactivity
Vapor pressure 1.4xlO'6 mm Hg (30°C)
Adsorption in Soils
Structure
Adsorption Parameters
K N
187
117
115
119
134
108
97
So i1 Properties
pH
b. 5
5.9
6.8
6.9
6.8
5.6
6.7
6.9
CEC
84.3
92.3
94.2
83.1
106.7
126.9
131.1
123.1
OC
lb.8
18.6
18.9
20.0
22.9
23.6
25.9
27.1
Percent (%)
Sand Silt Clay
19.4
31.4
11.2
12.8
7.3
32.1
24.9
18.8
Degradation in Soils
Degradation Parameters
Soil Properties
*1Z2L J<
0.5l31
0.0063
0.0064
0.0133
0.0149
Mois-
Initial Temp, ture
cone. °C 0
6.5
6.5
6.8
6.4
CEC
Percent (%)
OC
CT5F
1.16
Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
OC (%)
Soil Properties
Moisture
G
"BuTF
Density
Temp.
°C
Porosity
254
-------
Compound Name: Benefin [N-butyl-N-ethyl-a, a, crtrifluoro-2, 6-dinitro-N,
N-dipropyl-p-toluidine]
Compound Properties:
M.W. 335.3
M.P.
B.P.
Sp. gr.
Vapor pressure
Structure
Water solubility
Log Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
K N Knr
Soil Properties
pH CEC OC
Percent (%)
Sand Silt Clay
Degradation in Soils
Degradation Parameters
tl/2 Ks
1/ba
663
168a
543
Initial Temp.
n cone. °C
30
15
30
Soil Properties
Mois-
ture
0 pH
7
6
6
Percent (%)
.6"
.6
.6
.6
CEC
~TT
11
19
19
74
.4
.4
.4
OC
o!g
1.2
1.2
Sand
3& 5"4
2b 64
8b 35
8b 35
Silt
20
45
45
Clay
14
20
20
Volatilization in Soils
Volatilization Parameters
Soil Properties
MoistureBulkTemp.
OC (_%) e Density "C Porosity
Reported in months.
Reported as OM.
255
-------
Compound Name: 1,2-benzanthracene (benz(a)anthracine)
Compound Properties:
Structure
M.W. 228.2 Water solubility
M.P. 162°C Log Kow
B.P. Chemical class
Sp. gr. Chemical reactivity
Vapor pressure 5.0x10-9 torr (20°C)
Adsorption in Soils
0.014 mg/1
5.61
Adsorption Parameters
K N Knr
Soil Properties
pH
CEC
Percent (%)
OC
Sand
Silt
Clay
Degradation in Soils
Degradation
"Hi" 0.816
134 0.005
41 0.017
142 0.005
41 0.017
154 0.005
Parameters
Initial Temp.
n cone. °C
7
0.07
8.2
0.1
9.7
0.15
Soi
Mois-
ture
e PH
6.1
6.1
6.1
6.1
6.1
6.1
1 Properties
Percent (%)
CEC OC Sand Silt
0.75
0.75
0.75
0.75
0.75
0.75
Clay
Volatilization in Soils
Volatilization Parameters
KW ^w^D ^C (*)
Soi
Mo isture
0
1 Properties
Bulk
Density
Temp.
°C
Porosity
256
-------
Compound Name: Benzene
Compound Properties:
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
78.1
Structure
Water solubility
Log Kow
Chemical class
Chemical reactivity
Adsorption in Soils
1.8 g/1
2.13
Adsorption Parameters
Soil Properties
Percent (%)
K
2 .43
1.8*
30. 9a
4.43
0.35
N
0.89
0.94
1.08
0.99
Degradation
Kor pH CEC
92 5.6
100 7.8
4.2
6.6
31.4
Degradat
Parameters
Initial Temp.
17
29
80
80
14
ion in
Mois-
ture
OC
2.6
1.8
0
0
1.10
Soils
Soil
Sand
1
15
9
Propert
Silt
68
51
68
ies
Percent (
Clay
31
34
loot"
100C
21
%)
*U2_ -1
cone. "C 9
PH
CEC
OC
Sand Silt Cla\
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
OC (%) Q Density _'C Porosity
Reported in terms of ng to convert to g multiply by (10~3)
t>Al -Montmori llonite
cCa-Montmorillonite
257
-------
Compound Name: Benzo(b)fluoranthene
Compound Properties:
M.W. 252.3 Water solubility
M.P. 167 Log Kow
B.P. Chemical class
Sp. gr. Chemical reactivity
Vapor pressure 5.0x10'7 torr (20°C)
Adsorption in Soils
0.0012 mg/1
6.57
Structure
Adsorption Parameters
K N K
Soil Properties
PH
CEC
Percent (%)
OC
Sand
Silt
Clay
Degradation in Soils
Degradation Parameters
Soil Properties
Mois-
^&-
98
85
123
73
130
Volati
0.010
0.007
0.008
0.006
0.010
0.006
1 izat ion
Initial Temp, ture
n cone. °C 0
33
0.33
46
0.57
53
0.8
Vol atil izat ion
Parameters
pH
6.1
6.1
6.1
6.1
6.1
in Soi
Percent (%)
CEC OC Sand Silt Clay
O./b
0.75
0.75
0.75
0.75
0.75
Is
Soil Properties
Moisture BulK Temp.
OC (_%) 9 Density °C Porosity
258
-------
Compound Name: Benzo(k)fluoranthene
Compound Properties:
M.W. 252.3 Water solubility
M.P. 217 Log Kow
B.P. Chemical class
Sp. gr. Chemical reactivity
Vapor pressure 5.0x10-7 torr (20°C)
Adsorption in Soils
Structure
0.00055
6.84
Adsorption Parameters
Soil Properties
K
N
lxnr
pH
CEC
Percent (%)
Sand
Silt
Clay
Degradation in
Degradation
TUO" 0.^07
89 0.008
87 0.008
94 0.007
100 0.007
87 0.008
Parameters
Initial
n cone.
1.7
0.1
2.6
0.15
2.7
0.17
Temp.
'C
Mo i s -
ture
0
Soils
Soi
pH
FTT
6.1
6.1
6.1
6.1
6.1
1 Properties
Percent (%)
CEC OC Sand Silt Clay
0.75
0.75
0.75
0.75
0.75
0.75
Volatilization in Soils
Volatilization Parameters
k" Y \(
OC (%)
Soil Properties
Moisture Bulk Temp.
G Density °C
Porosity
259
-------
Compound Name: 1,12-benzoperylene
Compound Properties:
276.3
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
Structure
Water solubility
Log Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters Soil Properties
Percent (%)
K N Koc PH CEC OC
Sand Silt Clay
Degradation in Soils
Degradation Parameters
Soil Properties
MOIS-
Initial Temp, ture
cone. °C 9
pH
CEC
Percent (%)
OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
MoistureBulk Temp.
OC (%) 9 Density °C Porosity
260
-------
Compound Name: Benzo(a)pyrene [3,4-benzopyrene]
Compound Properties:
M.W. 252.3 Water solubility
M.P. 179 Log Kow
B.P. Chemical class
Sp. gr. . Chemical reactivity
Vapor pressure 6.85x10" 7 torr (20°C)
Adsorption in Soils
Structure
0.0038 mg/1
6.04
Adsorption Parameters Soil Properties
K
N Koc pH CEC OC
Percent (%)
Sand Silt Clay
Degradation in Soils
Degradation Parameters
^£g-
694
57
294
147
264
30
420
175
2
2
5
406
66
37
Ks n
0.014
0.001
0.012
0.002
0.005
0.003
0.023
0.002
0.004
0.347
0.347
0.139
0.002
0.011
0.019
Initial
cone.
0.048
0.01
3.4
9.5
12.3
7.6
18.5
17.0
32.6
1.0
0.515
1.00135
0.0094
0.545
28.5
Soil Properties
Temp.
°C
~25
>25
>25
Mois-
ture
0 pH
"57T
6.1
6.1
6.1
6.1
6.1
Percent (%)
CEC OC Sand Silt Clay
0.75
0.75
0.75
0.75
0.75
0.75
Volatilization in Soils
Volatilization Parameters
OC (%)
Soil
Moisture
Properties
"EUTS
Density
Temp.
C
Porosity
261
-------
Compound Name: Benzo(a)pyrene [3,4-benzopyrene] (continued)
Compound Properties:
Structure
M.W. 252.3 Water solubility
M.P. 179 Log KQW
B.P. Chemical class
Sp. gr. Chemical reactivity
Vapor pressure 6.85x10-7 torr (20°C)
Adsorption in Soils
0.0038 mg/1
6.04
Adsorption Parameters
K N K,
Soil Properties
or
PH
CEC
Percent (%)
OC
Sand
Silt
Clay
Degradation in Soils
Degradation Parameters
tl/2
39
7
5
3
4
6
92
79
100
83
92
120
0
0.018
0.099
0.139
0.231
.173
,116
0.008
0.009
0.007
0.008
0.008
0.006
0.
0.
Initial
cone.
29.2
910.0
19.5
19.5
19.5
130.6
130.6
36
0.36
55
0.41
69
Soil Properties
Temp.
'C
>25
>25
>25
>25
>25
>25
Mois-
ture
0
6.1
6.1
6.1
6.1
6.1
CEC
Volatilization in Soils
0.75
0.75
0.75
0.75
0.75
Percent (%)
OC Sand Silt Clay
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
OC (%) 9 Density °C Porosity
262
-------
Compound Name: Bromoform
Compound Properties:
M.W. 252.8
M.P. 8.3°C
B.P.
Sp. gr.
Vapor pressure 5.6 mm (25°C)
Structure
Water solubility 3190 mg/1 30°C
Log Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
K N KQC
Soil Properties
PH
CEC
Percent (%)
OC
Sand
Silt
Clay
Degradation in Soils
Degradation Parameters
tl/2
Mois-
Initial Temp, ture
cone. °C 0
Soil Properties
pH
CEC
Percent (%)
OC
Sand Silt Cla\
Volatilization in Soils
Volatilization Parameters
QC (%)
Soil Properties
MoistureBulk
Density
Temp.
C
Porosity
263
-------
Compound Name: Bromomethane
Compound Properties:
Structure
M.W. 94.95
M.P. -93°C
B.P.
Sp. gr.
Vapor pressure
Adsorption Parameters
K N Kor
Water solubility 900 mg/1 (20°C)
Log Kow 1.19
Chemical class
Chemical reactivity
Adsorption in Soils
Soil Properties
Percent (%)
pH CEC OC Sand Silt
Clay
Degradation in Soils
Degradation Parameters
SoilProperties
tl/2
Mo i s -
Initial Temp, ture
cone. °C Q
CEC
Percent (%)
OC Sand SiltClay
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
OC (%) 0 Density °C Porosity
264
-------
Compound Name:
Carbofuron [2,3-dihydro-2, 2-dimethylbenzofuron-7-yl
methyl carbonate]
Compound Properties:
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
219.2
Structure
Water solubi1ity
Log Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
N
14.7
61.6
51.9
36
39
29
.5
.7
.6
1.08
0.98
1.07
0.88
52.0
210
93
324
39
Soil Properties
Percent (%)
pH
6.1
6.6
6.8
7.0
CEC
1.7
7.5
34.4
24.8
27.7
55.5
72.4
OC
0.4
1.2
2.7
3.1
3.5
7.8
16.8
43.7
1.62
1.45
0.41
Sand
52
71
45
91.5
Silt
34
22
30
1.5
Clay
14
7
14
7
Degradation in Soils
Degradation Parameters
Soil Properties
0.0/68
0.0079
Initial
cone.
Temp.
°C
Mois-
ture
0
ElL
8.5
CEC
Percent (%)
OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
So i1 Properties
"Bulk
Moisture
OC (%) 0 Dens it
Temp.
8C
Porosity
265
-------
Compound Name: Carbon tetrachloride (tetra chloromethane)
Compound Properties:
M.W. 153.8
M.P. -23°C
B.P.
Sp. gr.
Vapor pressure 99 mm (20°C)
Water solubility 1160 mg/1 (25'C)
800 mg/1 (20°C)
Log Kow 2.73
Chemical class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters
<
Soil Properties
PH
CEC
Percent (%)
OC
Sand
Silt
Clay
Degradation in Soils
Degradation Parameters
Soil Properties
Mois-
Initial Temp, ture
cone. "C 0
CEC
Percent (%)
OC
Sand Silt Cla\
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
OC (%) 0 Density °C Porosity
266
-------
Compound Name: C6A-15646 [3-(3-chloro-4-methy1phenyl)-l,l-dimethylurea]
Compound Properties:
M.W. 212.7
M.P.
B.P.
Sp. gr.
Vapor pressure
Structure
Water solubility 70 g/1
Log Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
K N Koc
.18
.49
.89
.61
.80
4.61
4.07
16.13
2,
2.
2,
3.
6,
0.79
0.81
0.88
0.81
0.90
0.89
0.86
0.74
150
146
203
148
249
246
333
346
pH
8
7.9
7.6
7.7
5.1
7.8
4.6
Soil Properties
Texture
S
S
S
S
S cl
S
S
S
0.06
0.58
0.81
0.87
0.93
1.10
0.70
2.67
Percent (%)
Sand
STU
Clay
9.8
15.0
13.0
6.8
31.5
10.6
18.3
4.5
Degradation in Soils
Degradation Parameters
Soil Properties
M/?
Initial
cone.
Temp.
°C
Mois-
ture
G
PH
CEC
Percent (%)
OCSand SiltClay
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
OC (%) Q Density "C Porosity
267
-------
Compound Name: Chlorobenzene
Compound Properties:
Structure
M.W. 112.6
M.P. -45°C
B.P. 131-132*C
Sp. gr.
Vapor pressure
Adsorption Parameters
K N Knr
0.91 - 82.7
Water solubility
Log Kow
Chemical class
Chemical
Adsorption
pH CEC
14
react iv
i n Soil
Soil
OC
1.10
490 mg/1 (20-25°C)
2.84
ity
s
Properties
Percent (%)
Sand Silt
9 6.8
Clay
21
Degradation in Soils
Degradation Parameters
tl/2
Soil Properties
Mois-
Initial Temp, ture
cone. "C 0
pH
CEC
Percent (%)
OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
QC (%) e Density "C Porosity
268
-------
Compound Name: Chlorobromiiron [3-(4-bromo-3-ch1orophenyl 0-1-methoxy-l-
methylurea]
Compound Properties:
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
293.5
Structure
Water solubility 50 ug/1
Log Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
K
6.
7.
.98
.98
14.10
19.10
28.10
39.80
128.00
N
0.70
0.67
0.59
0.80
0.80
0.63
0.50
1533
684
561
772
1186
1502
3262
2758
Soil Properties
pH
8.5
8.5
7.9
7.6
7.7
5.1
7.8
4.6
Texture
S
S
S
S
S cl
S
S
S
oc
0.06
0.58
0.81
0.87
0.93
1.10
0.70
2.67
Percent (%)
Sand Silt Clay
9.8
15.0
13.0
6.8
31.5
10.6
18.3
4.5
Degradation in Soils
Degradation Parameters
Initial
n cone.
Soil Properties
Temp.
°C
Mois-
ture
G
CEC
Percent (%)
OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
OC (%)
Soil Properties
Moisture^
9
~5UTF
Density
Temp.
°C
Porosity
269
-------
Compound Name: Chloroethane (gas)
Compound Properties:
M.W. 64.5
M.P. -138.3°C
B.P.
Sp. gr.
Vapor pressure 457 mm (0"C)
700 mm (10°C)
1000 mm (20°C)
1.7 atm (30°C)
Water solubility 3330 mg/1 (0*C)
740 mg/1 (20"C)
Log Kow 1.43
Chemical class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters Soil Properties
Percent (%)
K N Knr pH CEC OC
Sand Silt Clay
Degradation in Soils
Degradation Parameters
Soil Properties
Mois-
Initial Temp, ture
cone. °C 0
pH
CEC
Percent (%)
OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
OC (%) Q Density "C Porosity
270
-------
Compound Name: Chloroethene [Vinylchloride] (gas)
Compound Properties:
Structure
M.W. 62.5
M.P. -153/-160°C
B.P.
Sp. gr.
Vapor pressure 240 mm (-40°C)
580 mm (-20'C)
2660 mm (25°C)
Water solubility 1.1 mg/1 (25°C)
Log Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
K N IW
Soil Properties
pH
CEC
Percent (%)
Sand
Silt
Clay
Degradation in Soils
Degradation Parameters
Soil Properties
Mois-
Initial Temp, ture
cone. "C 9 pH
CEC
Percent (%)
PC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
PC (%) 6 Density °C Porosity
271
-------
Compound Name: Chloroform [trichloromethane]
Compound Properties:
M.W. 119.4
M.P. -64°C
B.P.
Sp. gr.
Vapor pressure 160 mm (20°C)
Water solubility 8000 mg/1 (20°C)
9300 mg/1 (25eC)
10000 mg/1 (158C)
Log Kow 1.96
Chemical class
Chemical reactivity
Structure
Adsorption in Soils
Adsorption Parameters Soil Properties
Percent (%)
K N Knr pH CEC OC
Sand Silt Clay
Degradation in Soils
Degradation Parameters
Soil Properties
Mois-
Initial Temp, ture
cone. "C 0
PH
CEC
Percent (%)
OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
OC (%) e Density "C Porosity
272
-------
Compound Name: Chloromethane (gas)
Compound Properties:
M.W. 51
M.P. -97.7°C
B.P.
Sp.gr.
Vapor pressure 5.0 atm (20°C)
6.7 atm (30°C)
Relative vapor
density 1.8 (air = 1)
Water solubility 4000 cm3/!
Log Kow 0.91
Chemical class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters
K N K,
DC,
PH
CEC
Soil Properties
Percent (%)
OC
Sand
Silt
Clay
Degradation in Soils
Degradation Parameters
Mois-
Initial Temp, ture
M/2
cone.
0
Soil Properties
CEC
Percent (%)
OC Sand Silt Cla\
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
QC (%) 0 Density 8C Porosity
273
-------
Compound Name:
Chlorpyrifos [0,0-diethyl 0-3,5,6-trichloro-2-pyridyl
phosphorothioate]
Compound Properties:
M.W. 350.6
M.P.
B.P.
Sp. gr.
Vapor pressure
Water solubility 1.12
Log Kow 5.11
Chemical class
Chemical reactivity
Adsorption in Soils
ppm
Structure
Adsorption Parameters
Soil Properties
Percent (%)
K
N
24.51 0.86
36.84
147.24
388.95
7095
103.3
101.7
13.4
0
0
0
1
0
0
0
.77
.91
.98
.09
.98
.99
.98
KOC
4806
3443
5577
10236
16236
6377
7014
3268
pH CEC
6.
5.
7.
6.
6.
6.
7.
3 5
83 6
00 21
30 37
1
6
8
0
.71
.10
.02
.84
Degradation
Degradat
ion
Parameters
In it
ial
ti/2 Kg n cone.
120
120
1
0.
1
Temp.
'C
20
20
Mo is
ture
9
OC
0.51
1.07
2.64
3.80
43.7
1.62
1.45
0.41
in So i 1 s
Soi
-
pH
6.2
6.2
Sand
77
83
37
21
52
71
56
91.5
1 Properties
CEC OC
20 1.74
20 1.74
Silt
15
9
42
55
34
22
30
1.5
Percent (
Sand Si
Clay
8
8
21
24
14
7
14
7
%)
It
Clay
51
-
-
51
Volatilization Parameters
Volatilization in Soils __
Soil Properties
MoistureBulKTemp.
OC (%) 9 Density °C Porosity
274
-------
Compound Name: Chrysene [1,2 benzophenanthrene]
Compound Properties:
M.W. 228.2 ' Water solubility 0.002 mg/1
M.P. 254°C Log Kow 5.61
B.P. 448"C Chemical class
Sp. gr. Chemical reactivity
Vapor pressure 6.3xlQ-7 torr (20"C)
Adsorption in Soils
Adsorption Parameters
K N Knr
Soil Properties
Structure
PH
CEC
Percent (%)
OC
Sand
Silt
Clay
Degradation in Soils
Degradation Parameters
tl/2
10.5
5.5
Ks n
0.067
0.126
Initial
cone.
4.4
500
5
Mo i s -
Temp, ture
°C 0
15-25
15-25
Soil Properties
Percent (%)
pH CEC OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
OC (%) 0 Density °C Porosity
275
-------
Compound Name: Cyanazine [2-[[4-Chloro-6-(ethylamino)-5-triazine-2-ylJamino]-
2-methyl propionitrile]
Compound Properties:
M.W. 206.2'
M.P.
B.P.
Sp. gr.
Vapor pressure
Water solubility
Log Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters
Soil Properties
Percent (%)
K
4.6
3.4
N
0.96
0.86
K0(-
368
453
pH CEC
6^7 8.'2
OC
1.25
0.75
Sand
11
90
Silt
63
8
Clay
26
5
Degradation in Soils
Degradation Parameters
Mois-
Initial Temp, ture
cone. °C 0
Soil Properties
CEC
Percent (%)
OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
MoistureBulk Temp.
OC (%) 0 Density °C Porosity
276
-------
Compound Name: 2,4-0 [2,4-Dichlorophenoxy acetic acid]
Compound Properties:
Structure
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
221.0
135-138°C
160"C
Water solubility 900 mg/1 (25°C)
Log KQW 2.81
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
K,
oc
1.30
0.78
0.47
0.13
0.31
0.36
0.09
1.90
0.21
1.00
0.98
1.01
1.00
0.97
1.01
0.79
0.90
0.86
21.4
10.8
12.
5.
13.
14.
8.
109
45.7
Soil Properties
pH
CEC
"OT
Percent (%)
Silt
Sand
5.9
7.7
6.5
7.7
08
20
75
41
36
48
47,
45,
53,
7.5
5.9
7.7
19.0
31.1
1.03
1.74
0.46
5.3
69.3
69.0
81.6
12
39
33.2
41.2
27.5
25.3
12.3
16.0
10.4
61
30
Degradation in Soils
Clay
20.
13.
19.
69
18.
15.0
8.0
27
31
Degradation Parameters
Soil Properties
tl/2
Ks n
0.1733
>0.0768
0.1386
0.1733
0.2731
Initial
cone.
Mois-
Temp. ture
°C 0
pH CEC
Percent (%)
10
OC
"2723
1.91
1.62
1.86
Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
K,,
OC (%)
Moisture
0
Soil Properties
Bulk
Density
Temp.
°C
Porosity
277
-------
Compound Name: 2,4-D amine
Compound Properties:
M.W. 236.1
M.P. 85-87°C
B.P.
Sp. gr.
Vapor pressure lx!0~y mm Hg
9 28°C
Structure
Water solubility 3xl06 mg/1 @ 20°C
Log Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
K
0.65
0.76
gr
119.4
72.2
135.7
Soil Properties
PH
5.6
9.6
CEC
54.7
6.8
5.6
Percent (%)
OC
3.87
0.90
0.56
Sand
18.4
65.8
93.8
Silt
45.3
19.5
3.0
Clay
38.3
14.7
3.2
Degradation in Soils
Degradation Parameters
Soil Properties
tl/2 J
-------
Compound Name: Dialifor
Compound Properties:
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
Water solubility
Log Kow
Chemical class
Chemical reactivity
Structure
Adsorption in Soils
Adsorption Parameters
K N K
nr
Soil Properties
PH
CEC
Percent (%}
Sand
TTTt
Clay'
Degradation in Soils
Degradation Parameters
Soil Properties
tl/2
140"
150
Mois-
Initial Temp, ture
cone. "C 0
PH
CEC
Percent (%)
Sand Silt Clay
1
0.1
Volatilization in Soils
Volatilization Parameters
Soi1 Properties
Moisture Bulk Temp.
PC (%) 0 Density °C Porosity
279
-------
Compound Name: 1,2,5,6-dibenzanthracene [dibenz[a,b]anthrancene]
Compound Properties:
M.W. 278.4
M.P. 262"C
B.P.
Sp. gr.
Vapor pressure Ixl0~iu torr
(20°C)
Water solubility 0.5 ug/1
Log Kow 5.97
Chemical class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters
K N KQC
Soil Properties
pH
CEC
Percent (%)
OC
Sand
Silt
Clay
Degradation in Soils
Degradation Parameters
Soil Properties
Mois-
t]/2
21
18
130
183
99
141
119
190
Vol ati
I/
0.033
0.039
0.005
0.004
0.007
0.005
0.007
0.004
1 ization
Initial Temp, ture
n cone. °C 0
97000 >25
25000 >25
57
57
93
4.54
147
3.46
Vol atil ization
Parameters
pH
6.1
6.1
6.1
6.1
6.1
6.1
in Soi
Percent (%)
CEC OC Sand Silt Clay
0.75
0.75
0.75
0.75
0.75
0.75
Is
Soil Properties
Moisture Bulk Temp.
OC (%) 9 Density °C Porosity
280
-------
Compound Name: 1,2,5,6-dibenzantnracene
Compound Properties:
278.3
Structure
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
Water solubility 249 g/1
Log Kow 6.50
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters Soil Properties
K N
20461
34929
18361
18882
1759
2506
14497
25302
20192
7345
55697
39809
19254
39840
Degradation
ti/? K,
Percent (%)
Knr pH CEC OC Sand Silt Clay
1690971
1687404
805292
2622453
1172847
2277875
3020262
2663317
3059425
565014
2962603
2383765
808991
2691870
Degradation in Soils
Parameters Soil Properties
Mo i s -
Initial Temp, ture Percent (%)
n cone. °C 0 pH CEC OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk
OC (%) y Density
Temp.
°C
Porosity
281
-------
Compound Name: Dibenzothiophene
Compound Propert i es :
Structure
184.27
99-100°C
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
Water solubility 1.47
Log Kow 4.38
Chemical class
Chemical reactivity
Adsorption in Soils
ppm
Adsorption Parameters
Soil Properties
K
117.5
180.6
167.1
60.8
9.4
5.8
49.7
179.9
65.1
101.4
276.0
176.3
338.6
134.5
N
-
-
-
-
-
-
-
_
_
_
-
.
_
-
Kgr
9/11
8725
7329
8444
6267
5273
10354
18937
9864
7800
14681
10557
16328
9088
PH
6 .35
7.79
7.44
7.83
8.32
8.34
4.54
7.79
7.76
5.50
7.60
7.55
6.70
7.75
CEC
3.72
23.72
19.00
33.01
3.72
12.40
18.86
11.30
15.43
8.50
8.33
8.53
31.15
20.86
Degradation in
Degradation
*fr
24
U.U29
0.029
Parameters
In it
ial Temp
n cone. °C
69
0.
57
Mois-
ture
0
OC
1.21
2.07
2.28
0.72
0.15
0.11
0.48
0.95
0.66
1.30
1.88
1.67
2.38
1.48
Soils
Soi
pH
S7T
6.1
Percent (%)
Sand Silt Clay
18.6
55.2
31.0
68.6
6.8
17.4
63.6
35.7
39.5
28.6
7.1
21.2
69.1
42.9
1 Properties
Percent (%)
CEC OC Sand Silt Clay
O./b
0.75
Volatilization in Soils
Volatilization Parameters
Soil Properties
OC (%)
Moisture
9
Bulk
Density
Temp.
•c
Porosity
282
-------
Compound Name: 1,2-bibromo, 3-chloropropane
Compound Properties:
236.3
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
Water solubility
Log Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters
K N Koc
Soil Properties
Percent (%)
pH CEC OC Sand Silt Clay
Degradation in Soils
Degradation Parameters
Soil Properties
Mois-
Initial Temp, ture
cone. "C 0 pH
CEC
Percent (%)
OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
MoistureBulk
OC (%) 9 Density
Temp.
°C Porosity
283
-------
Compound Name: Dibromomethane [methylene bromide]
Compound Properties:
M.W. 173.9
M.P. -52.8°C
B.P.
Sp. gr.
Vapor pressure 340 mm (20°C)
Water solubility 3218 mg/1 (20aC)
5033 mg/1 (30°C)
Low Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters
K N KQC
Soil Properties
pH
CEC
Percent (%)
OC
Sand
Silt
Clay
Degradation in Soils
Degradation Parameters
Soil Properties
Mois-
Initial Temp, ture
cone. °C Q
pH
CEC
Percent (%)
Sand STlt Claj
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
QC (%) G Density °C Porosity
284
-------
Compound Name: Dicamba [3,6-dichloro-2-methoxybenzoic acid]
Compound Properties:
221.0
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
Structure
Water solubility 4470 mg/1
Low Kow -1.69
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
Soil Properties
Percent (%)
K N Knr
0.11 0.72
0.00
0.00
0.00
0.00
PH
6.5
7.7
7.8
7.5
CEC OF
6.08
3.75
2.41
2.36
1.03
Sand
47.5
53.3
5.3
69.3
81.6
Silt
33.2
27.5
25.3
12.3
10.4
Clay
20.3
19.2
69.5
18.5
8.0
Degradation in Soils
Degradation Parameters
Soil Properties
tl/2
Ks
0.2140
0.2140
0.0486
0.0982
0.0217
0.0407
0.0267
Initial
cone.
Temp.
°C
Mois-
ture
5%
10%
25%
35%
7.5
7.5
5.2
7.7
7.7
Percent (%)
pH CEC PC Sand Silt Clay
1.86
1.86
6.79
2.43
2.43
1.91
1.62
2.20
Volatilization in Soils
Volatilization Parameters
Soil Properties
QC (%)
Mo isture
0
Bulk
Density
Temp.
°C
Porosity
285
-------
Compound Name: Dicapthon [0-(2-chloro-4-nitropheny1) 0,0-dimethyl-
phosphorothioate]
Compound Properties:
Structure
M.W. 297.7
M.P. 53°C
B.P.
Sp. gr.
Vapor pressure
Adsorption
K
Parameters
N Knr
Water solubility
Low Kow
Chemical class
Chemical react ivi
Adsorption in Soils
Soil
pH CEC OC
ty
Properties
Percent (%)
Sand Silt Clay
Degradation in Soils
Degradation Parameters
Soil Properties
43
Mois-
Initial Temp, ture
cone. °C e
071
pH
CEC
Percent (%)
OCSandSiltCla\
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
OC (%) 9 Density °C Porosity
286
-------
Compound Name: 1,2-dichlorobenzene
Compound Properties:
147.0
M.W.
M.P.
B.P. 180.5°C
Sp. gr.
Vapor pressure
Water solubility 150 mg/1
Log Kow 3.38
Chemical class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters
Soil Properties
Percent (%)
K N Knr
3.54 - 321.6
PH
CEC
14
OC
1.10
Sand
9
Silt
68
Clay
21
Degradation in Soils
Degradation Parameters
Soil Properties
Mois-
Initial Temp, ture
cone. °C 0 pH
CEC
Percent (%)
OC Sand Silt Clas
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
OC (%) 6 Density °C Porosity
287
-------
Compound Name: 1,3-dichlorobenzene
Compound Properties:
147.0
M.W.
M.P.
B.P. 173°C
Sp. gr.
Vapor pressure
Water solubility 134 mg/1
Log Kow 3.38
Chemical class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters
K N Knr pH CEC
3.23 - 293.3 14
Soil Properties
Percent (%)
OC
1.1
Sand
9
Silt
68
Clay
21
Degradation in Soils
Degradation Parameters
Soil Properties
Mois-
Initial Temp, ture
cone. °C 0
CEC
Percent (%)
OC Sand Silt Cla\
Volatilization in Soils
Volatilization Parameters
So i1 Properties
TToisture Bulk Temp.
OC (%} Q Density °C Porosity
288
-------
Compound Name: 1,4-dichlorobenzene
Compound Properties:
M.W. 147.0
M.P. 53.5°C
B.P. 174.1°C
Sp. gr.
Vapor pressure
Water solubility 137 mg/1
Log Kow 3.39
Chemical class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters
Soi
1 Properties
Percent (%)
-j
K
.01
N Kn
273
r pH CEC
.8
14
OC
1.
1
Sand
9
Silt Cl
ay
68 21
Degradation in Soils
Degradation Parameters
Soil Properties
tl/2
Initial
cone.
Temp.
Mois-
ture
e
pH
CEC
Percent (%)
OC Sand Silt Cla\
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture bulk Temp.
OC (%) 6 Density °C Porosity
>89
-------
Compound Name: l,4-Dichloro-2-butene
Compound Properties:
M.W.
M.P. 3.5°C
B.P.
Sp. gr.
Vapor pressure
Water solubility
Low Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters Soil Properties
Percent (%)
K N Knr pH CEC OC
Sand Silt Clay
Degradation in Soils
Degradation Parameters
Soil Properties
MblS-
Initial Temp, ture
cone. °C 0
PH
CEC
Percent
OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
MoistureBulkTemp.
OC (%) 9 Density °C Porosity
290
-------
Compound Name: Dichlorodifluoromethane (gas)
Compound Properties:
M.W. 120.9
M.P. -111°C
B.P.
Sp. gr.
Vapor pressure
Structure
Water solubility 280 mg/1 (25°C)
Low Kow 2.16
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters Soil Properties
K
N Koc pH CEC OC
Percent (%)
Sand Silt Clay
Degradation in Soils
Degradation Parameters
MX?
Soil Properties
Mois-
Initial Temp, ture
cone. °C 9
PH
CEC
Percent
bandSTTt CTaj
Volatilization in Soils
Volatilization Parameters
Soil Properties
MoistureBulk
OC (%) 0 Density
Temp.
°C
Porosity
291
-------
Compound Name: 1-1-Dichloroethane
Compound Properties:
99.0
-97.4°C
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
70 mm (0°C)
180 mm (20'C)
234 mm (25'C)
270 mm (30°C)
Water solubility
Low Kow
Chemical class
Chemical reactivity
5500 mg/1
1.79
Adsorption in Soils
Structure
;20°C)
Adsorption Parameters
K N i>nr
Soil Properties
PH
CEC
Percent (%)
OC
Sand
Silt
Clay
Degradation in Soils
Degradation Parameters
MX?
Soil Properties
Mois-
Initial Temp, ture
cone. °C 0
pH
CEC
Percent (%)
OC Sand S iIt Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
OC (%) 9 Density JC Porosity
292
-------
Compound Name: 1-2-Dichloroethane
Compound Properties:
99
-35.4°C
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
40 mm (10'C)
61 mm (20°C)
105 mm (30°C)
Water solubility 8690 mg/1 (20°C;
9200 mg/1 (O'C)
Low Kow 1.48
Chemical class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters
K N Knr
Soil Properties
pH CEC OC
Percent (%)
Sand Silt Clay
Degradation in Soils
Degradation Parameters
Soil Properties
Mois-
Initial Temp, ture
cone. °C 9
pH
CEC
Percent (%)
OCSand Silt Clay
Volatilization in Soils
Volatilization Parameters
QC (%)
Soil Properties
Moisture
9
"SUIT
Density
Temp.
°C
Porosity
293
-------
Compound Name: 1,2 Dichloropropane
Compound Properties:
Structure
M.W. 113 Water solubility 2700 mg/1 (20°C)
M.P. -100/-80°C Low Kow
B.P. Chemical class
Sp. gr. Chemical reactivity
Vapor pressure 42 mm (20°C)
50 mm (25'C)
66 mm (30°C)
Adsorption in Soils
Adsorption Parameters Soil Properties
Percent (%)
K N Kor pH CEC OC
Sand Silt Clay
Degradation in Soils
Degradation Parameters
Soil Properties
Mois-
Initial Temp, ture
cone. °C 0 pH
CEC
Percent (%)
OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
Soi1 Properties
Moisture Bulk Temp.
OC (%) G Density "C Porosity
294
-------
Compound Name: 1,3 Dichloropropane
Compound Properties:
113
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
Water solubility
Low Kow 2.00
Chemical class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters
K N Knr
Soil Properties
pH CEC OC
Percent (%)
Sand Silt Clay
Degradation in Soils
Degradation Parameters
Mois-
Initial Temp, ture
cone. °C 0
Soil Properties
PH
CEC
Percent (%)
bandSiltCTa\
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
OC (%) e Density °C Porosity
295
-------
Compound Name: Dieldrin [1,2,3,4,10,10-hexachloro-b, 7-epoxy-l,4,4a,5,6,7,3,
8a-ortanydro-exo-l,4-endo-5,8-dimethanonaphthalene]
Compound Properties:
M.W. 380.9
M.P. 176-177'C
B.P.
Sp. gr.
Vapor pressure 1.78x10'' torr
' 25*C
Structure
Water solubility
Low Kow 2.00
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
Soil Properties
Percent (%)
K
39
147
265
198
260
297
1507
13937
117
66
17.8
N Koc
9750
12250
9815
6387
7429
3960
8970
1.08 31892
0.91 7222
0.89 4552
0.88 4341
pH
6.1
6.6
6.8
7.0
CEC
1.7
7.5
34.4
24.8
27.7
55.5
72.4
Degradation
OC Sand
0.4
1.2
2.7
3.1
3.5
7.5
16.8
43.7 52
1.62 71
1.45 56
0.41 91.5
in So i 1 s
Silt
34
22
30
1.5
Clay
14
7
14
7
Degradation Parameters
Soil Properties
tl/?
0.0002
0.0001
Mo i s -
Initial Temp, ture
cone. *C 0 pH CEC
778-
7.8
Volatilization in Soils
Percent (%)
OC Sand Silt Clay
T573S ~~
0.29
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
OC (%} e Density "C Porosity
296
-------
Compound Name: 7,12-dimethylbenz(a)anthracene
Compound Properties:
Structure
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
256.3
122-123°C
Water solubility 24.4 yg/1
Low Kow 5.98
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters Soil Properties
K N
2371
2646
5210
1346
611
1028
562
3742
1895
1617
5576
2679
6777
3740
Degradation
tl/2 K5
Percent (%)
Kor pH CEC OC Sand Silt Clay
195998
127812
228499
186986
407496
934225
117161
393907
287196
124347
296580
160391
284743
252735
Degradation in Soils
Parameters Soil Properties
Mois-
Initial Temp, ture Percent (%)
n cone. "C 0 pH CEC OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
MoistureBulk
_OC (%) Q Density
Temp.
Porosity
297
-------
Compound Name: 2,6-dinitro-N(3-pentyl )-a,ct,ct-trif"luoro-p-toluidine
Compound Properties: Structure
391.4
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
Water solubility
Low Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters Soil Properties
K
N Knr pH CEC OC
Percent (%)
Sand Silt Clay
Degradation in Soils
Degradation Parameters
ti/o Ks
168"
603
1083
423
Volatil ization
Mo i s -
Initial Temp, ture
n cone. °C 0
15
30
15
30
Volati 1 ization
Parameters
Soil Properties
Percent (%)
pH
7.6
7.6
6.6
6.6
in Soi
CEC
11.
19.
19.
is
Soil
OC Sand
4
4
4
4
0.93U
0.93b
1.28b
1.28b
64
64
35
35
Silt
20
20
45
45
Clay
14
14
20
20
Properties
Reported in months.
bReported as OM.
Moisture Bulk Temp.
QC (%) e Density °C Porosity
298
-------
Compound Name: Oiuron [3-(3,4-dichlorophenyl)-l, 1-dimethylurea]
Compound Properties:
Structure
M.W. 233.1
M.P. 158-159°C
B.P.
Sp. gr.
Vapor pressure
Adsorption Parameters
K N Koc
14.3 0.77 1144
6.5 0.74 867
Water solubility
Low Kow
Chemical
Chemical
Adsorption
pH CEC
6.7 2U .
6.7 8.2
class
react ivi
in Soils
Soil
OC
7 1.25^
0.75a
42 (25'C)
ty
Properties
Percent (%)
Sand Silt
11 63
90 5
Clay
26
5
Degradation in Soils
Degradation Parameters
So i1 Properties
0.0064
0.0072
Mois-
Initial Temp, ture
cone. °C 0
pH
O'
6.4
CEC
Percent (%)
OC Sand Silt Cla\
Volatilization in Soils
Volatilization Parameters
Soil Properties
MoistureBulkTemp.
OC (%) 0 Density "C Porosity
299
-------
Compound Name: Ethyl benzene
Compound Properties:
Adsorption Parameters
K N K,
TT
nr
165
pH
CEC
14
Soil Properties
OC
1.10
Percent
Structure
M.W. 106.2
M.P. -94.97°C
B.P. 136*C
Sp. gr.
Vapor pressure 7 mm
12 mm
(20'C)
(30°C)
Water solubility 140 mg/1
152 mg/1
206 mg/1
Low Kow 3.15
Chemical class
Chemical reactivity
Adsorption in Soils
(15°C)
(20°C)
(30°C)
Sand
Silt
68
Clay
21
Degradation in Soils
Degradation Parameters
Soil Properties
tl/2
Initial
cone.
Temp.
Mois-
ture
0
pH
CEC
Percent (%)
OC Sand Silt
Volatilization in Soils
Volatilization Parameters
Soil Properties
OC (%)
Moisture
G
Bulk
Density
Temp.
"C
Porosity
300
-------
Compound Name: Fluometuron [1,1-Dimethyl-3- , , -trifluoro-m-tolyl)urea]
Compound Properties: Structure
232.2
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
0.4
0.98 40.4
Water solubility 79.4 mg/1
Low Kow 3.44
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
Soil Properties
Percent (%)
K
0.90 '
0.80
N
_a
KOC
120
107
pH CEC OC
/.I U./b
7.1 0.75
Sand
25
25
Silt
43
43
Clay
32
32
6.6
9.2
0.99
46
37.6
16.4
Degradation in Soils
Degradation Parameters
Soil Properties
MoTs-
Initial Temp, ture
cone. °C 0 pH
CEC
Percent (%)
OC Sand Silt Cla\
Volatilization in Soils
Volatilization Parameters
aN is assumed to be one.
Soil Properties
Moisture Bulk Temp.
OC:_(%_) e Density "C Porosity
301
-------
Compound Name: Fluoranthene
Compound Properties:
M.W. 202.2
M.P. Ill
B.P.
Sp. gr.
Vapor pressure 6.0x10-° (20"C)
Water solubility 0.26 mg/1
Low Kow 5.33
Chemical class
Chemical reactivity
Adsorption In Soils
Structure
Adsorption Parameters
K N K
Soil Properties
Percent (%}
nr
CEC
Sand
Silt
Clay
Degradation in Soils
Degradation Parameters
Soil Properties
tl/2
44
182
105
143
109
175
133
Kc; n
0.016
0.004
0.007
0.005
0.006
0.004
0.005
Initial
cone.
3.9
18.8
23.0
16.5
20.9
44.5
72.8
Mois-
Temp. ture Percent (%)
•C 0 pH CEC OC Sand Silt Clay
15-25
15-25
15-25
15-25
15-25
15-25
Volatilization in Soils
Volatilization Parameters
Soil Properties
MoistureSulkTemp.
OC (%) 9 Density °C Porosity
302
-------
Compound Name: Fonofos [0-Ethyl S-phenyl ethylphosphonodithioate]
Compound Properties: Structure
230.3
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
Water solubility
Low Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters Soil Properties
Percent (%)
K N Knr pH CEC OC
Sand Silt Clay
Degradation in Soils
Degradation Parameters
46
Soil Properties
Mois-
Initial Temp, ture
cone. °C 0
CEC
8.2
Percent (%)
OC Sand Silt Clay
ITS' ~ZTT ~5D~ ~3TT
2.0 30 20 50
Volatilization in Soils
Volatilization Parameters
Moisture
QC (%) 9 Density
SoJJ Properties
BulkTemp.
°C
Porosity
303
-------
Compound Name: HCB [Hexachlorobenzene]
Compound Properties:
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
248.8
230 °C
323-326°C
Structure
Water solubility
Low Kow 4.13
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
K
4193
276
136
N
0.99
0.93
5835
11525
Soil Properties
Percent (%)
PH
?!l
4.5
CEC
72.4
18.1
13.1
OC
16.81
4.73
1.18
Sand
15. 7
6.1
1.1
Silt
50.8
61.4
64.3
Clay
33.5
32.5
34.6
Degradation in Soils
Degradation Parameters
Soil Properties
Ks
MoTs-
Initial Temp, ture
cone. *C 0
Percent (%)
PH
CEC
OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk
OC (%) 9 Density
•c
Porosity
304
-------
Compound Name: HCH [Hexachlorocyclohexane]
Compound Properties:
Structure
M.W. 290.8
M.P. 157-158'C (a)
309°C (B)
112. 5°C (Y)
B.P.
Sp. gr.
Vapor pressure
2.15x10-5 torr (a)
2.0x10-7 torr (8)
0.14 mm Hg (y)
Water solubility 1
0.
Low Kow 4
O i
3,
Chemical class
Chemical reactivity
(40°C)
Adsorption in Soils
Adsorption Parameters
.63 ppm @ 25°C (a.)
,70 ppm 9 25°C (g)
.14 (Lindane)
,81 (a)
.81 (6)
Soil Properties
Percent (%)
K
"28 . 18
52.48
70.79
501.20
5.13
39.81
79.43
158.50
8.91
25.12
31.62
446.70
295
7.91
45.1
665
13.1
10.2
6.9
N
1.60
1.26
0.94
1.16
0.82
1.20
0.80
0.80
0.90
0.80
0.80
1.10
0.92
0.80
O.S4
0.98
0.96
0.97
0.99
Kqc
640b
3143
2212
3510
1166
2384
2482
1110
2025
1504
988
3128
1635
2274
1313
1522
809
703
1679
pH
b.ZU
6.30
5.20
3.30
6.20
6.30
5.20
3.30
6.20
6.30
5.20
3.30
6.1
6.6
6.8
7.0
CEC
ia.o
42.8
19.2
28.9
18.6
42.8
19.2
28.9
18.6
42.8
19.2
28.9
18
0.35
3.5
OC
0.44
1.67
3.20
14.28
0.44
1.67
3.20
14.28
0.44
1.67
3.20
14.28
43.7
1.62
1.45
91.5
Sand
/y.b
69.6
45.6
63.6
79.6
69.6
45.6
63.6
79.6
69.6
45.6
63.6
52
71
56
91.5
Silt
4.8
6-8
7.8
6.8
4.8
6.8
7.8
6.8
4.8
6.8
7.8
6.8
34
22
30
1.5
Clay
ib.b
23-6
45.6
29.6
15.6
23.6
45.6
29.6
15.6
23.6
45.6
29.6
14
7
14
7
305
-------
Compound Name: HCH [Hexachlorocyclohexane] (Continued)
Degradation in Soils
Degradation Parameters
Soil Properties
tl/2
Mo i s -
Initial Temp, ture Percent (%)
Ks n cone. "C 0 pH CEC OC Sand Silt Clay
U.UU22 /.8 U.bb
0.0026 7.8 0.29
0.0011
0.0014
0.0048
0.0147
0.0264
0.0074
0.0263
0.0264
0.0139
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk
OC (%) 9 Density
Temp.
°C
Porosity
306
-------
Compound Name: Hexachlorocyclopentadiene
Compound Properties:
Structure
M.W.
M.P.
B.P.
Sp. gr.
272.8
9/10'C
Vapor pressure 0.08 mm (25
Adsorpt
K
1 mm (78-79
ion Parameters
Nv
OC
Water solubility
Low Kow
*C) Chemical class
*C) Chemical reactivi
Adsorption in Soils
Soil
pH CEC OC
0.8 ppm
1.8 ppm
2.0 ppm
ty
Properties
Percent (%}
Sand Silt Clay
Degradation in Soils
Degradation Parameters
Soil Properties
Ks
Mois-
Initial Temp, ture
cone. °C 0
CEC
Percent (%)
OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
Soi1 Properties
KW
KwKD
Moisture Bulk
CC (%) S Density
Temp.
Porosity
307
-------
Compound Name: Hexachloroethane
Compound Properties: Structure
M.W. 236.76 Water solubility 50 mg/1 (22°C)
M.P. 187°C Low Kow
B.P. Chemical class
Sp. gr. Chemical reactivity
Vapor pressure 0.4 mm (20°C)
0.8 mm (30*C)
Adsorption in Soils
Adsorption Parameters Soil Properties
Percent (%7
K N KQC pH CEC OC Sand Silt Clay
Degradation in Soils
Degradation Parameters Soil Properties
Mois-
Initial Temp, ture Percent (%)
Ks n cone. °C 9 pH CEC OC Sand Silt Cla}
Volatilization in Soils
Volatilization Parameters Soil Properties
Moisture Bulk Temp.
OC (%) G Density °C Porosity
308
-------
Compound Name: Idomethane
Compound Properties:
M.W. 142
M.P. -66.1 °C
8.P.
Sp. gr.
Vapor pressure 400 mm (25°C)
Structure
Water solubility 14 g/1 (20°C)
Low Kow 1.69
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
K N Koc
Soil Properties
PH
CEC
Percent (%)
OC
Sand
Silt
Clay
Degradation in Soils
Degradation Parameters
Soil Properties
H/2
Mois-
Initial Temp, ture
cone. °C 0
pH
CEC
Percent (%)
OC Sand Silt Cla\
Volatilization in Soils
Volatilization Parameters
OC (%)
Soil Properties
Moisture
0
"BuTF
Density
Temp.
°C
Porosity
309
-------
Compound Name: Indeno(l,2,3-Cd)-pyrene
Compound Properties:
M.W. 289.3
M.P. 163
6.P.
Sp. gr.
Vapor pressure 1.0x10-10
torr (20°C)
Water solubility 0.062 mg/1
Low Kow 7.66
Chemical class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters
_J< N Koc
pH
CEC
Soil Properties
Percent (17
OC
Sand
Silt
Clay
Degradation in Soils
Degradation Parameters
Mois-
Initial Temp, ture
cone. °C Q
Soil Properties
pH
Percent (%)
CEC OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
KwKD
Soil Properties
Moisture Bulk Temp.
OC (%) e Density °C Porosity
110
-------
Compound Name: Linuron[3-(3-4-dichlorophenyl)-l-methoxy-l-methylurea]
Compound Properties: Structure
249.1
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
Water solubility 75 ug/1
Low Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
K
30
80
90
50
93
18.20
12.80
23.10
J_
0.84
0.85
0.79
0.73
0.94
0.82
0.77
0.86
Koc
1916
470
345
655
492
913
1049
497
Soil Properties
PH
8.5
8.5
7.9
7.6
7.7
5.1
7.8
4.6
Texture
S
S
S
S
S cl
S
S
S
Percent (%)
OC Sand Silt
0.06
0.58
0.81
0.87
0.93
1.10
0.70
2.67
Clay
4.8
15.0
13.0
6.8
31.5
10.5
18.3
4.5
Degradation in Soi 1 s
Degradation Parameters
Soil Properties
M01S-
Initial Temp, ture
cone. °C e
PH
0.0047
CEC
Percent (%)
OC Sand Silt Cla\
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture
OC (%)
0
"BUTF
Density
Temp.
°C
Porosity
311
-------
Compound Name: Malathion [0,0-dimethyl S-(l,2-di)(ethoxycarbonyl)ethy)-
phosphorodithioate]
Compound Properties:
Structure
M.W. 330.4
M.P. 2.9°C
B.P. 156-157°C
Sp. gr.
Vapor pressure
Adsorption
K 1
Parameters
1 Knr
Water solubility
Low Kow
Chemical class
Chemical react ivi
Adsorption in Soils
Soil
pH Texture OC
145 mg/1
ty
Properties
Percent (%)
Sand Silt
Clay
Degradation in Soils
Degradation Parameters
Soil Properties
Mois-
tl/2
Volati
Initial Temp, ture
KS n cone. °C 0
2.9173
2.4618
1.2681
0.4152
1.9832
1.9026
Volati 1 izat ion
1 izat ion Parameters
pH
7.2
6.4
3.8
5.3
7.4
7.2
in Soi
Percent (%)
CEC OC Sand Silt Clay
0.64
1.80
2.73
Is
Soil Properties
Moisture Bulk
QC (%) 0 Density
Temp.
•c
Porosity
312
-------
Compound Name: MCPA [4-chloro-2-methy1phenoxyacitic acidjarbonyl)ethy)-
phosphorodithioate]
Compound Properties:
Structure
M.W. 200.6
M.P. 120"C
8. P.
Sp. gr.
Vapor pressure
Adsorption Parameters
K N Kor
Water solubility 890 mg/1
Low Kow -1.41
Chemical class
Chemical reactivity
Adsorption in Soils
Soil Properties
Percent (%)
pH Texture OC Sand Silt Clay
Degradation in Soils
Degradation Parameters
Soil Properties
Mois-
Initial Temp, ture
cone. 'C 0 pH
~
CEC
Percent (%)
OC Sand Silt Clay
3072 3275 TO"
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture
QC (%)
"EuTF
Density
Temp.
°C
Porosity
313
-------
Compound Name: Methoxychlor [l,l,l-Trichloro-2, 2-bis(p-methoxypheny1)-
ethane]
Compound Properties:
M.W. 345.65
M.P. 89°C
B.P.
Sp. gr.
Vapor pressure
Structure
Water solubility 0.12 mg/1
Low Kow 4.30
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
Soil Properties
Percent (%)
J<_
53
2600
1800
1400
1100
8.3
2200
1700
2300
2400
95
2500
2000
2100
N
lac_
41000
80000
91000
100000
92000
9700
80000
73000
80000
73000
17000
86000
100000
93000
pH
Texture
OC
0.13
3.27
1.98
1.34
1.20
0.086
2.78
2.34
2.84
3.29
0.57
2.92
1.92
1.99
Degradation in Soils
Sand
Silt
Clay
Degradation Parameters
Soil Properties
Initial Temp.
ti/2 KS n cone. "C
0.0046
0.0033
Mois-
ture
9 pH CEC
4.8
6.5
Percent (%)
OC Sand
0.58
1.16
Silt Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
OC (%)
Moisture
0
Bulk
Density
Temp.
•c
Porosity
314
-------
Compound Name: 3-Methylcholanthrene
Compound Properties:
Structure
M.W.
M.P.
8. P.
Sp. gr.
Vapor pressure
268.3 Water solubility 3.23 pg/1
179-180'C Low Kow 6.42
280°C Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters Soil Properties
K N
15140
30085
8273
15820
2257
2694
30627
23080
20642
16231
24506
20972
17127
37364
Degradation
H/2 KS
Percent (%)
Knr pH CEC OC Sand Silt Clay
1251210
1453404
362845
2197250
1504538
2449190
6380703
2429456
3127521
1248534
1303532
1255821
719633
2524581
Degradation in Soils
Parameters Soil Properties
Mois-
Initial Temp, ture Percent (%)
n cone. *C G pH CEC OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
KwKp
Soil Properties
MoistureBulkTemp.
OC (%) 9 Density "C Porosity
215
-------
Compound Name: Methyl parathion [0-0-dimethy1-0-p-nitrophenyl phosphoro-
thioate]
Compound Properties:
Structure
263.2
35-36'C
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
9.5xlO-6 mm
Hg (20°C)
Water solubility 55-60
Low Kow 1.91
Chemical class
Chemical reactivity
Adsorption in Soils
mg/1 (258C;
Adsorption Parameters
13.39
3.95
2.72
3.57
0.75
0.85
0.86
0.61
346.0
438.6
486.4
714.5
Soil Properties
Percent (%)
PH
7.3
5.6
5.6
7.4
CEC
54.7
6.8
5.2
35.8
OC
3.87
0.90
0.56
0.50
Sand
18.4
65.8
93.8
50.7
Silt
45.3
19.5
3.0
16.4
Clay
38.3
14.7
3.2
22.9
Degradation in Soils
Degradation Parameters
In itial
n cone.
Soil Properties
Temp.
•c
Mois-
ture
0
Percent (%}
PH
CEC
OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
K
•w
KWKD
Soil Properties
MoistureBulkTemp.
OC (%) 6 Density "C Porosity
316
-------
Compound Name: Metobromuron [3-(p-bromophenyl )-l-methoxy-l-methylurea]
Compound Properties: Structure
259.1
M.W.
M.P.
8.P.
Sp. gr.
Vapor pressure
Water solubility 350 ug/1
Low Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
K N Kor
52
09
20
95
4.54
,18
,12
10.20
0.58
0.78
0.82
0.82
0.85
0.80
0.82
0.81
2100
204
154
134
281
330
501
219
Soil Properties
pH
8.5
8.5
7.9
7.6
7.7
5.1
7.8
4.6
Texture
S
S
S
S
S cl
S
S
S
Percent (%)
OC Sand Silt
0.06
0.58
0.81
0.87
0.93
1.10
0.70
2.67
Clay
9.8
15.0
13.0
6.8
31.5
10.6
18.3
4.5
Degradation in Soils
Degradation Parameters
Soil Properties
tl/2
Mois-
Initial Temp, ture
cone. *C 0
pH
CEC
Percent (%)
OCSandSiltClay
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
OC (%) 0 Density "C Porosity
317
-------
Compound Name: Mono!inuron [3-(p-chlorophenyl)-l-methoxy-l-methylurea]
Compound Properties: Structure
M.W. 214.6
M.P.
B.P.
Sp. gr.
Vapor pressure
Water solubility 580 yg/1
Low Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
K N Knr
43
28
20
90
3.41
4.19
6.35
12.70
0.50
0.86
0.60
0.81
0.91
0.82
0.87
0.90
2025
321
225
334
211
224
520
273
Soil Properties
PH
8.5
8.5
7.9
7.6
7.7
5.1
7.8
4.6
Texture
S
S
S
S
S cl
S
S
S
Percent (%)
OC Sand Silt
0.06
0.58
0.81
0.87
0.93
1.10
0.70
2.67
Clay
9.8
15.0
13.0
6.8
31.5
10.6
18.3
4.5
Degradation in
Degradation
tl/2
Ks
Parameters
n
Initial
cone.
Temp.
•c
Mois-
ture
0
Soils
Soil
PH
Properties
CEC
OC
Percent
Sand
(X)
Silt
Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
OC (%) 6 Density "C Porosity
318
-------
Compound Name: Naphthalene
Compound Properties:
M.W. 128.2
M.P. 80.2'C
B.P.
Sp. gr.
Vapor pressure 4.92x10-2 torr
(20'C)
Water solubility 30 mg/1
Low Kow 3.37
Chemical class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters
K N Knr
1300
Soil Properties
PH
CEC
Percent (%)
OC
Sand
Silt
Clay
Degradation in Soils
Dearadation Parameters
0.12
125
4
KS n
5.78
0.005
0.173
Initial
cone.
7.0
7.0
25000
Soil Properties
Mots-
Temp, ture Percent (%)
°C 0 pH CEC OC Sand Silt Clay
15-25
>25
Volatilization in Soils
Volatilization Parameters
Soil Properties
MoistureSulkTemp.
OC (%) 0 Density "C Porosity
319
-------
Compound Name: Parathion [0,0-Diethyl 0-(p-nitrophenyl) phosphorothioate]
Compound Properties: Structure
M.W. 291.3
M.P. 6°C
B.P. 37S°C
Sp. gr.
Vapor pressure
3.78x10-5 torr
(20'C)
Water solubility 6.54 ppm
24 ppm (25'C)
Low Kow 3.40
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
Soil Properties
Percent (%)
K
4.61
8.98
29.16
32.13
201.47
7.67
12.30
38.02
125.90
213.80
457.10
349
18.9
16.3
5.2
N
0.83
0.83
0.88
0.80
0.81
1.04
1.05
1.11
1.05
1.03
1.02
0.95
0.99
1.01
0.98
KOC
904
839
1105
845
1097
1743
1309
2277
3934
4792
3200
799
1166
1124
1264
PH
7.30
6.83
5.00
7.30
6.98
6.2
6.25
6.30
5.20
3.50
3.30
6.1
6.6
6.8
7.0
CEC
5.71
6.10
21.02
37.84
77.34
18.6
26.6
42.8
19.2
21.2
28.9
OC
0.51
1.07
2.64
3.80
18.36
0.44
0.94
1.67
3.20
4.76
14.28
43.7
1.62
1.45
0.41
Sand
77
83
37
21
42
79.6
75.9
69.6
45.6
53.6
63.6
52
71
56
91.5
Silt
15
9
42
55
39
48
3.4
6.8
7.8
12.8
6.8
34
22
30
1.5
Clay
8
8
21
24
19
15.6
20.7
23.6
45.6
33.6
29.6
14
-t
I
14
7
Degradation in Soils
Degradation Parameters
Soil Properties
tl/2 KS
180
110
Mois-
Initial Temp, ture
cone. *C 0
Percent (%)
1 20
0.1 20
Volatilization in Soils
Volatilization Parameters
Soil Properties
MoistureBulk Temp.
OC (%) 9 Density "C Porosity
320
-------
Compound Name: PBBs [polybrominated biphenyls]
Compound Properties:
Structure
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
Water solubility
Low Kow
Chemical
Chemical
Adsorption
Adsorption Parameters
K N
36ia 1.99
1443 1.89
883 1.77
KOC
2142
3044
7458
PH
7.2
7.1
CEC
72.4
18.1
4.50 13.1
class
react ivi
in Soils
Soil
OC
16.81
4.73
1.18
ty
Properties
Percent (%)
Sand Silt
15.7 50.8
6.1 61.4
1.1 64 . 3
Clay
33.5
32.5
34.6
Degradation in Soils
Degradation Parameters
Soil Properties
tl/2
Initial
cone.
Temp.
'C
Mois-
ture
e
PH
CEC
Percent (%)
OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
^Reported in
Soil Properties
Mo isture
OC (%)
0
"WTF
Density
Temp.
°C
Porosity
321
-------
Compound Name: Pentachloroethane
Compound Properties:
Structure
M.W.
M.P.
B.P.
Sp. gr
Vapor
202.3
-29°C
.
pressure 3.4 mm
6 mm
Adsorption Parameters
K
N KOC
Water solubility
Low Kow
Chemical class
Chemical reactivity
(20°C)
(30'C)
Adsorption in Soils
Soil Properties
Percent (%)
pH CEC OC Sand Silt Clay
Degradation in Soils
Degradation Parameters
Soil Properties
tl/2
Mois-
Initial Temp, ture
cone. "C G
PH
CEC
Percent (%)
OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
MoistureBulkTemp.
OC (%) 3 Density *C Porosity
322
-------
Compound Name: Phenanthrene
Compound Properties:
M.W. 178.2
M.P. 100'C
B.P. 340°C
Sp. gr.
Vapor pressure 6.8xlO"4 torr
(20°C)
Water solubility 1.6 mg/1
Low Kow 4.46
Chemical class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters
K N Koc
23000
Soil Properties
PH
CEC
Percent (%)
OC
Sand
Silt
Clay
Degradation in Soils
Degradation Parameters
ti/2 Ks n
26 0.027
35 0.198
Initial
cone.
2.1
25000
Temp.
•c
15-25
>25
Soil Properties
Mois-
ture Percent (%)
0 pH CEC OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
KWKD
Soil Properties
MoistureBulkTemp.
OC (%) e Density °C Porosity
323
-------
Compound Name: Phorate [0,0-Diethyl S-[(ethy1thio)methy1 phosphorodithioate;
di ethyl s-( ethyl thiomethyl )phosphorothiol athionate]
Compound Properties:
Structure
M.W. 260.4
M.P. <-15°C
B.P. 75-78°C
Sp. gr.
Vapor pressure 8.4xl0'4 torr
(20'C)
Water solubility 20 ppm
50 ppm
Low Kow 3.33
Chemical class
Chemical reactivity
@ room temp
Adsorption in Soils
Adsorption Parameters
K N Kn/~
2.14
4.86
8.63
13.73
74.79
0.94
0.91
0.92
0.88
1.01
419.6
454.2
326.9
361.3
407.4
Soil Properties
Percent (%)
PH
7.3
6.83
5.00
7.30
6.98
CEC
5.71
6.10
21.02
37.84
77.34
OC
0.51
1.07
2.64
3.80
18.36
Sand
77
83
37
21
42
Silt
15
9
42
55
39
Clay
8
8
21
24
19
Degradation in Soils
Degradation Parameters
tl/2
18
14
Initial
cone.
Soil Properties
Mois-
Temp. ture
•C 9 pH CEC
7.1
8.0
Percent (%)
OC Sand Silt Clay
1.5a 20 50 30
2.0a 30 20 50
Volatilization in Soils
Volatilization Parameters
Soil Properties
KwKp OC
Reported as OM (OC = OM/1.724).
Mo i s ture Bulk Temp.
B Density *C Porosity
324
-------
Compound Name: Phosmet
Compound Properties:
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
Water solubility
Low Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters
K N Koc
Soil Properties
Percent (%)
pH CEC OC Sand Silt Clay
Degradation in Soils
Degradation
H
12
60
51
Ks
-
Parameters
n
-
Initial
cone.
1
0.1
Temp.
•c
Mois-
ture
8
Soil Properties
Percent (%)
pH CEC
OC
Sand Si
It
Clay
Volatilization in Soils
Volatilization Parameters
KW KWKD
Soil Properties
Moisture Bulk Temp.
QC (%) e Density "C Porosity
325
-------
Compound Name: Picloram [4-Amino-3,5,6-trichloro-picolinic acid]
Compound Propert1es:
M.W. 241.5
M.P.
B.P.
Sp. gr.
Vapor pressure
— oLrucuure
Water solubility 426 mg/1
Low Kow 3.47
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
K
0.6843
0.6643
0.6393
0.6143
0.5293
0.4993
0.2973
0.3143
0.2973
0.043
0.976b
0.533b
0.310b
0.409b
O.llSb
0.070b
0.75
0.49
0.31
0.23
0.24
.0
0.24
0.09
N *
0.841
0.850
0.861
0.822
0.840
0.841
0.886
0.815
0.835
0.92
0.849
0.816
0.829
0.743
0.838
0.596
-
-
_
-
^oc pH
5.60
5.60
5.60
5.68
5.68
5.68
7.40
7.40
7.40
7.14
5.60
5.68
6.97
7.40
6.40
7.14
7.9
6.5
7.9
8.1
8.2
8.0
8.1
6.9
CEC
20
20
20
19
19
19
41
41
41
8
20
19
14
41
12
8
Soil Properties
Percent (%)
OC Sdnd c •» i •*• ^ i .» .,
2.44
2.44
2.44
2.09
2.09
2.09
1.39
1.39
1.39
0.54
2.44
2.09
1.39
1.39
0.93
0.54
7.20
6.08
3.75
14.72
2.48
2.41
2.36
1.03
Jill, i, | ay
18
1 0
io
10
97
97
27
33
33
8
18
27
83
33
9
8
n s
20.3
19.2
57.3
15.0
69.5
18 "5
8.0
3These constants are determined at 1:5 soil/solution ratio.
°These constants are determined at 1:2 soil/solution ratio.
326
-------
Compound Name: Picloram [4-Amino-3,5,6-tri'ch1oro-picol inic acid]
(continued)
Degradation in Soils
Degradation Parameters Soil Properties
tl/2
Ks n
0.0025
0.0044
0.0050
0.0354
0.0258
0.0268
0.0269
0.0048
Mois-
Initial Temp, ture
cone. *C 3 pH
4.8
6.3
5.5
5.8
5.8
Percent (%}
CEC OC Sand Silt Clay
1.68
1.10
0.99
1.10
1.10
1.62
Volatilization in Soils
Volatilization Parameters Soil Properties
Moisture Bulk Temp.
Kw KwKp OC (%) 9 Density °C Porosity
327
-------
Compound Name:. Prometone [2-methoxy-4,6-bis(isopropylamino)-l,3,5-triazine]
Compound Properties: Structure
M.W. 225.3
M.P.
PKl = 4.3
8. P.
Sp. gr.
Adsorption Parameters
. * N Koc
1.4
0.4
0.5
1.1
0.9
1.3
1.5
1.4
0.7
1.6
1.4
1.5
1.8
1.3
2.1
2.3
1.6
2.7
2.7
2.7
2.4
5.4
7.9
6.7
7.4
9.8
9.5
11.3
11.9
13.1
14.4
18.5
17.2
25.6
21.7
16.7
Vapor pressure
Water solubility 750 ppm
pH
7.0
6.6
6.2
4.9
5.7
5.9
6.1
5.8
6.7
6.2
5.8
6.9
6.4
6.7
6.6
6.5
6.9
6.3
5.7
7.6
7.2
6.8
5.3
7.1
7.1
6.9
6.5
6.5
6.5
5.9
6.8
6.9
6.8
5.6
6.7
6.9
Low KQW
Chemical
Chemical
Adsorption
CEC
25.4
10.2
10.6
11.0
9.2
12.4
14.0
11.0
30.1
13.9
10.3
20.2
21.5
22.3
24.8
25.9
29.2
26.9
27.4
25.7
42.0
44.6
51.3
37.6
li.2
50.4
61.3
82.1
84.3
92.3
94.2
85.1
106.7
120.9
131.1
123.1
1.94
class
reactivity
in Soils
Soil Properties
Percent (%)
OC Sand Silt
0.1
0.4
0.5
0.9
0.9
1.2
1.3
1.5
1.5
1.5
1.0
1.6
1.7
1.8
2.7
3.1
3.4
3.8
4.6
6.5
7.8
9.4
9.9
12.6
13.6
14.0
14.1
15.4
15.8
16.6
18.9
20.0
22.9
23.6
25.9
27.1
Clay
42.8
8.2
15.8
13.9
20.3
28.5
19.3
17.9
27.8
33.5
21.0
22.0
35.2
37.1
61.6
63.4
31.9
25.9
30.2
28.1
53.8
20.1
29.5
28.4
8.1
17.6
31.2
28.7
19.4
31.4
11.2
12.8
7.3
32.1
24.9
18.8
328
-------
Compound Name: Prometone [2-methoxy-4,6-bis(isopropylamino)-l,3,5-triazine]
(continued)
Degradation in Soils
Degradation Parameters Soil Properties
Mo is-
Initial Temp, ture Percent (%)
tj/2 Ks n cone. *C 9 pH CEC PC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters Soil Properties
MoistureBulkTemp.
Kw KwKp PC (%) 6 Density °C Porosity
329
-------
Compound Name: Prometryne [2-methlthio-4,6-bis(isopropylamino)-l,3,5-triazine]
Compound Properties: Structure
M.W. 241.3
M.P. 118-120'C
PKi = 4.05
B.P.
Sp. gr.
Adsorption Parameters
K N Knc
3.3
1.8
3.1
4.7
6.2
3.8
3.6
6.2
8.2
3.8
4.8
5.8
5.4
5.4
6.2
6.5
8.2
10.2
9.8
12.2
14.2
28.3
39.7
33.1
34.7
56.4
49.2
44.9
47.5
54.9
53.3
63.8
75.1
77.6
106.6
83.8
Vapor pressure
Water solubility 48 ppm
PH
7.0
6.6
6.2
4.9
5.7
5.9
6.1
5.8
6.7
6.2
5.8
6.9
6.4
6.7
6.6
6.5
6.9
6.3
5.7
7.6
7.2
6.8
5.3
7.1
7.1
6.9
6.5
6.5
6.5
5.9
6.8
6.9
6.8
5.6
6.7
6.9
Low Kow
Chemical
Chemical
Adsorption
CEC
25.4
10.2
10.6
11.0
9.2
12.4
14.0
11.0
30.1
13.9
10.3
20.2
21.5
22.3
24.8
25.9
29.2
26.9
27.4
25.7
42.0
44.6
51.3
37.6
11.2
50. *
61.3
82.1
84.3
92.3
94.2
85.1
106.7
120.9
131.1
123.1
class
reactivity
in Soils
Soil Properties
Percent (%)
OC Sand Silt
0.1
0.4
0.5
0.9
0.9
1.2
1.3
1.5
1.5
1.5
1.0
1.6
1.7
1.8
2.7
3.1
3.4
3.8
4.6
6.5
7.8
9.4
9.9
12.6
13.6
14.0
14.1
15.4
15.8
16.6
18.9
20.0
22.9
23.6
25.9
27.1
Clay
42.8
8.2
15.3
13.9
20.3
28.5
19.3
17.9
27.3
33.5
21.0
22.0
35.2
37.1
61.6
63.4
31.9
25.9
30.2
28.1
53.8
20.1
29.5
28.4
8.1
17.6
31.2
28.7
19.4
31.4
11.2
12.8
7.3
32.1
24.9
18.8
330
-------
Compound Name: Prometryne [2-methlthio-4,6-bis(isopropylamino)-l,3,5-triazine]
(continued)
Degradation in Soils
Degradation Parameters Soil Properties
Mois-
Initial Temp, ture Percent (%)
tj/2 Ks n. cone. 'C 9 pH CEC QC Sand Silt Clay
0.0238 - 7.0 1.16 18
Volatilization in Soils
Volatilization Parameters Soil Properties
Moisture Bulk Temp.
Kw KwKp PC (%) 0 Density °C Porosity
^Reported as OM (OC = OM/1.724).
331
-------
Compound Name: Propazine [2-chloro-4,6-bis(isopropylamino)-l,3,5-triazinej
Compound Properties: Structure
M.W. 229.7
M.P.
8. P.
Sp. gr.
Vapor pressure
Adsorption Parameters
K N Koc
1.1
0.5
0.9
1.4
1.4
2.3
2.4
1.5
2.7
1.2
2.0
2.1
2.6
3.0
3.9
3.9
3.5
4.3
4.7
5.7
4.9
12.9
16.2
16.5
19.0
20.5
18.0
24.3
21.4
27.4
34.0
31.6
42.8
45.7
42.5
40.0
Water solubility 8.6 ppm (20°C)
pH
7.0
6.6
6.2
4.9
5.7
5.9
6.1
5.8
6.7
6.2
5.8
6.9
6.4
6.7
6.6
6.5
6.9
6.3
5.7
7.6
7.2
6.8
5.3
7.1
7.1
6.9
6.5
6.5
6.5
5.9
6.8
6.9
6.8
5.6
6.7
6.9
Low Kow
Chemical
Chemical
Adsorption
CEC
25.4
10.2
10.6
11.0
9.2
12.4
14.0
11.0
30.1
13.9
10.3
20.2
21.5
22.3
24.8
25.9
29.2
26.9
27.4
25.7
42.0
44.6
51.3
37.6
11.2
50.4
61.3
82.1
84.3
92.3
94.2
83.1
106.7
126.9
131.1
123.1
class
reactivity
in Soils
Soil Properties
Percent (%)
OC Sand Silt
0.1
0.4
0.5
0.9
0.9
1.2
1.3
1.5
1.5
1.5
1.6
1.6
1.7
1.8
2.7
3.1
3.4
3.8
4.6
6.5
7.8
9.4
9.9
12.6
13.6
14.0
14.1
15.4
15.8
16.6
18.9
20.0
22.9
23.6
25.9
27.1
Clay
20.3
28.5
19.3
17.9
27.3
33.5
21.0
22.0
35.2
37.1
61.6 -
63.4
31.9
25.9
30.2
28.1
53.8
20.1
29.5
28.4
8.1
17.6
31.2
28.7
19.4
31.4
11.2
12.8
7.3
32.1
24.9
18.8
332
-------
Compound Name: Propazine [2-ch1oro-4,6-bis(isoprop.ylamino)-l,3,5-triazine]
(continued)
Degradation in Soils
Degradation Parameters Soil Properties
Moi-s_
Initial Temp, ture Percent (%)
ti/2 Ks _n cone. *C 0 pH CEC PC Sand Silt C1 ay
0.0108 4.8 0.58
0.0056 6.5 1.16
Volatilization in Soils
Volatilization Parameters Soil Properties
MoistureBulkTemp.
PC (%) 8 Density °C Porosity
333
-------
Compound Name: Pyrene (benzo(def)phenanthrene)
Compound Properties:
Structure
M.W. 202.24
M.P. 156*C
B.P.
Sp. gr.
Vapor pressure
6.85x10-7
(3 20°C
Adsorption Parameters
K N
42
3000
2500
1500
1400
994
2100
3000
3600
3800
68
3200
2300
2500
760
1065
1155
614
101
71
277
783
504
723
1119
806
1043
994
KOC
32000
92000
130000
110000
120000
11000
76000
130000
120000
120000
12000
110000
120000
110000
62860
51469
50650
32256
67467
64706
57763
82421
76316
59546
59515
48236
43807
67189
Water solubility 0.14 mg/1
Low Kow 4.88
Chemical class
Chemical reactivity
torr
Adsorption in Soils
Soil Properties
Percent (%)
pH CEC OC Sand Silt Clay
0.13
3.27
1.98
1.34
1.20
0.086
2.78
2.34
2.89
3.29
0.57
2.92
1.99
2.26
334
-------
Compound Name: Pyrene (benzo(def)phenanthrene) (continued)
Degradation in Soils
Degradation Parameters Soil Properties
MoTs^
Initial Temp, ture Percent (%)
tj/2 Ks n cone. *C 9 pH CEC PC Sand Silt Clay
35 0.020 - 3.1
10.5 0.067 - 500
3 0.231 - 5
Volatilization in Soils
Volatilization Parameters Soil Properties
MoistureBulkTemp.
QC (%) e Density "C Porosity
335
-------
Compound Name: Silvex [2,(2,4,5-Trichlorophenoxy)propionic acid]
Compound Properties:
M.W. 269.5
M.P. 181.6'C
8.P.
Sp. gr.
Vapor pressure
Structure
Water solubility
Low Kow
Chemical class
Chemical reactivity
Adsorption in Soils
140 mg/1 (25"C)
Adsorption Parameters
Soil Properties
Percent (%)
K
42.1
34.2
162
N
0.639
0.987
1.05
KOC
2786
4682
440
PH
6.09
6.07
6.25
CEC
39.6
34.5
42.0
OC
1.51
0.73
36.8
Sand
4.0
6.5
8.3
Silt
79.6
81.5
80.2
Clay
16.4
12.0
11.5
Degradation in Soils
Degradation Parameters
0.0330
0.0495
0.0462
cone.
Soil Properties
Temp.
°C
Mois-
ture
0 pH
Percent (%}
CEC OC Sand Silt
1.91
1.62
2.20
Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
OC (%) Q Density "C Porosity
336
-------
Compound Name: Tebuthiuron [l-(5-tert-butyl-l,3,4-thiodiazo1-2-yl)-l,3-
dimethylurea]
Compound Properties:
M.W. 216.3
M.P.
B.P.
Sp. gr.
Vapor pressure
Structure
Water solubility 2500 ppm (25°C)
Low Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
Soil Properties
Percent (%)
K
2.4
1.2
0.5
0.1
N Knr
_a
PH
6.3
6.1
6.1
6.7
CEC
9.2
13.3
6.7
0.6
OC
2.55b
2.49b
O.Slb
0.17b
Sand
30
57
58
95
Silt
52.2
30.5
33.8
3
Clay
17.8
12.5
8.2
2
Degradation in Soils
Degradation Parameters ^
Mois-
Initial Temp, ture
Soil Properties
tl/2
cone.
•c
0
CEC
Percent (%)
OC
Sand Silt Cla\
Volatilization in Soils
Volatilization Parameters
aAssumed to be 1.
Reported as OM.
OC (%}
Soil Properties
MoistureBulkTemp.
e
Density *C
Porosity
337
-------
Compound Name: Terbacil [3-tert-butyl-5 chloro-6 methyluraci1]
Compound Properties:
M.W. 216.7
M.P. 175-177'C
B.P.
Sp. gr.
Vapor pressure 4.8x10-' mm
Hg (29.5'C)
Water solubility 710 mg/1 (25°C)
Low Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters
_K_
2.46
0.38
0.12
0.38
_N_
0.88
0.99
0.88
0.93
63.6
42.2
21.4
76.0
Soil Properties
Percent (%)
PH
7.3
5.6
5.6
7.4
CEC
54.7
6.8
5.2
35.8
OC
3.87
0.90
0.56
0.50
Sand
18.4
65.8
93.8
50.7
Silt
45.3
19.5
3.0
16.4
Clay
38.3
14.7
3.2
22.9
Degradation in Soils
Degradation Parameters
Soil Properties
tl/2
Mois-
Initial Temp, ture
cone. "C 0
Percent
PH
CEC
OC Sand Silt
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture
OC (%)
0
Bulk
Density
Temp.
"C
Porosity
333
-------
Compound Name:
Terbufos [0,0-diethyl S-[(l,l-dimethylethylthio)methyl]
phosphorodith ioate]
Compound Properties:
M.W. 262.4
M.P.
B.P.
Sp. gr.
Vapor pressure
Structure
Water solubility 5.07
Low Kow 3.68
Chemical class
Chemical reactivity
Adsorption in Soils
ppm
Adsorption Parameters
3.14
10.58
7.90
20.55
50.79
0.95
0.94
0.96
0.97
0.97
616
989
299
541
277
Soil Properties
Percent (%)
pH
7.3
6.83
5.00
7.30
6.98
CEC
5.71
6.10
21.02
37.84
71.34
OC
0.51
1.07
2.64
3.80
18.36
Sand
77
83
37
21
42
Silt
15
9
42
55
39
Clay
8
8
21
24
19
Degradation in
Degradation
n/2 KS
12
11
Parameters
Initial Temp.
n cone. °C
Mois-
ture
e
Soils
Soi
pH
7.1
8.0
1 Properties
Percent (%)
CEC OC Sand Silt
1.5 20 50
2.0 30 20
Clay
30
50
Volatilization in Soils
Volatilization Parameters
QC (%)
Soil Properties
MoistureSulkTemp.
_ _ 0 Density °C
Poros ity
339
-------
Compound Name: 1,1,1,2-Tetrachloroethane
Compound Properties:
167.9
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
Water solubility
Low Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters
K N Koc
Soil Properties
pH CEC OC
Percent (%)
Sand Silt Clay
Degradation in Soils
Degradation Parameters
Soil Properties
M/2
Mo is-
Initial Temp, ture
cone. °C 0
pH
CEC
Percent (%)
Sand_ Silt Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Sulk
OC (%) 9 Density
Temp.
Porosity
340
-------
Compound Name: 1,1,2,2-Tetrachloroethane
Compound Properties:
Structure
M.W. 167.9
M.P. -42.5/43.8'C
B.P.
Sp. gr.
Vapor pressure 5 mm (20°C)
8.5 mm (30'C)
Water solubility 2900 mg/1 (20'C)
Low Kow
Chemical class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
K N Koc
Soil Properties
PH
CEC
Percent (%}
OC
Sand
Silt
Clay
Dearadation in Soils
Degradation Parameters
Soil Properties
Mois-
Initial Temp, ture
cone. *C 9 pH
CEC
OC
Percent (%)
Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
BUTI<
Moisture
OC (%) 9 Density
Temp.
•c
Porosity
341
-------
Compound Name: Tetrachloroethylene
Compound Properties:
Structure
M.W. 165.8
M.P. -22.7'
B.P.
Sp. gr.
Vapor pressure
Water solubility 150 mg/1 (25°C)
C Low Kow 2.60
Chemical class
Chemical reactivity
14 mm (20'C)
24 mm (30'C)
45 mm (40'C)
Adsorption in Soils
Adsorption Parameters Soil Properties
K N
Percent (%)
Knr pH CEC OC Sand Silt Clay
Degradation in Soils
Degradation Parameters
Soil Properties
tl/2
Mois-
Initial Temp, ture
cone. *C 9
pH
CEC
Percent (%)
OC Sand Silt Cla\
Volatilization in Soils
Volatilization Parameters
Soil Properties
Mo i sture Bulk Temp.
QC (%) 6 Density "C Porosity
342
-------
Compound Name: Toluene (methylbenzene)
Compound Properties:
Structure
92.1
-95.1*C
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
Water solubility
10 mm (6.4'C)
22 mm (20"C)
40 mm (31.8'C)
Low- Kow
Chemical
Chemical
class
reactivity
470 mg/1 (16°C)
515 mg/1 (20°C)
2.60
Adsorption in Soils
Adsorption Parameters
Soil Properties
Percent w
K
3.52
2.69
0.90
N
1.008
1.002
0.996
Knr
37.4
46.4
155.2
pH CEC
5.4
5.1
4.3
OC Sand
9.40
5.80
0.58
Silt Clay
Degradation in Soils
Degradation Parameters
Soil Properties
M01S-
Initial Temp, ture
cone. °C 0
Percent (%)
CEC
OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
OC (%} Q Density *C Porosity
343
-------
Compound Name: 1,2,4-trichlorobenzene
Compound Properties:
M.W. 181.4
M.P. 17°C
B.P. 213°C
Sp. gr.
Vapor pressure
Water solubility 49 mg/1
Low Kgw 4.02
Chemcial class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters
K N Kor
9.52 - 865.7
pH CEC
14
Soil Properties
Percent (%)
OC Sand Silt
1.1 9 68
Clay
21
Degradation in Soils
Degradation Parameters
Soil Properties
tl/2
Initial
cone.
Temp.
Mois-
ture
0
Percent (%)
PH
CEC OC Sand Silt Cla\
Volatilization in Soils
Volatilization Parameters
Soil Properties
OC (%)
Moisture
0
Bulk
Density
Temp.
'C
Porosity
344
-------
Compound Name: 1,1,1-trichloroethane
Compound Properties:
Structure
M.W. 133.4
M.P. -32'C
B.P.
Sp. gr.
Vapor pressure 100 mm (20°C)
155 mm (30°C)
Water solubility 4400 mg/1 (20"C)
Low Kow 2.49
Chemcial class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
K N K
Soil Properties
PH
CEC
Percent (%)
OC
Sand
Silt
Clay
Degradation in Soils
Degradation Parameters
Mois-
Initial Temp, ture
cone. *C 0
Soil Properties
CEC
Percent (%)
OC Sand Silt Clav
Volatilization in Soils
Vo1 ati1izat ion Parameters
KwKQ
QC (%)
Soil Properties
Moisture
0
"BuTlT
Density
Temp.
Porosity
345
-------
Compound Name: 1,1,2-trichloroethane
Compound Properties:
M.W. 133.4
M.P. -357-36.7°C
B.P.
Sp. gr.
Vapor pressure 19 mm (20°C)
32 mm (30°C)
40 mm (35*C)
Structure
Water solubility 4500 mg/1 (20°C)
Low KQW
Chemcial class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
Soil Properties
PH
CEC
Percent (%)
OC
Sand
Silt
Clay
Degradation in Soils
Degradation Parameters
Soil Properties
Mois-
Initial Temp, ture
cone. °C 0
PH
CEC
Percent (%)
OC
Sand Silt Cl_ay
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
OC (%) 9 Density "C Porosity
3*6
-------
Compound Name: Trichloroethylene
Compound Properties:
M.W. 131.5
M.P. -87°C
B.P.
Sp. gr.
Vapor pressure 20 mm (O'C)
60 mm (20'C)
95 mm (30'C)
Structure
Water solubility 1.10 mg/1 (25°C)
Low KQW 2.29
Chemcial class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
K N Koc
Soil Properties
PH
CEC
Percent (%}
OC
Sand
Silt
Clay
Degradation in Soils
Degradation Parameters
Soil Properties
tl/2
Mois-
Initial Temp, ture
cone. °C Q
PH
CEC
Percent (%)
QC Sand SjM1 Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
MoistureBulk
OC (%)
9
Density
Temp.
•c
Porosity
347
-------
Compound Name: Trichloromethane
Compound Properties: Structure
M.W. 137.4 Water solubility 1100 mg/1 (25°C)
M.P. -lll'C Low Kgw 2.53
B.P. Chemcial class
Sp. gr. Chemical reactivity
Vapor pressure 0.904 atm (20°C)
1.29 atm (30*C)
Adsorption in Soils
Adsorption Parameters Soil Properties
Percent~T%T
J< N KQC pH CEC QC Sand Silt Clay
Degradation in Soils
Degradation Parameters Soil Properties
Mois-
Initial Temp, ture Percent (%)
Ks n cone. *C 0 pH CEC OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters Soil Properties
MoistureBulkTempT
OC (%) G Density "C Porosity
348
-------
Compound Name: Trifluraline [a,a,a-trif1uoro-2,6-dinitro-N, N-dipropyl-p-
toluidine]
Compound Properties:
Structure
M.W. 335.3 Water solubility :
M.P. 48.5-49°C Low Kow
B.P. 139-140°C Chemcial class
Sp. gr. Chemical reactivity
Vapor pressure 1.99x10-4 mm
Hg (29.5"C)
Adsorption in Soils
Adsorption Parameters
1 mg/1 (27°C)
Soil Properties
Percent (%)
K
2.73
0.46
0.24
1.60
N
1.15
1.05
1.06
1.18
KOC
75.7
50.7
43.2
177.8
pH
7.3
5.6
5.6
7.4
CEC
54.7
0.90
0.56
0.50
OC
3.87
0.90
0.56
0.50
Sand
18.4
65.8
93.8
50.7
Silt
45.3
19.5
3.0
16.4
Clay
38.3
14.7
3.2
22.9
Degradation Parameters
Degradation
in Soils
Soil Properties
Mois-
Initial Temp, ture
ti/2 Ks n cone
375a
90a
2733
75a
Volatilization Parameters
- Kw KwKp
•C 0
15
30
15
30
Volatil ization
pH CEC
OC
7.6 11.4 0.93b
7.6 11.4 0.93t>
6.6 19.4 ,
6.6 19.4 .
in Soils
L.28&
L.28b
Soil Propert
OC (%)
Moisture Bui
c
9 Density
Percent (%)
Sand
64
64
35
35
ies
Temp.
•c
Silt Clay
20
20
45
45
Poros
14
14
20
20
ity
Reported in months.
^Reported as OM.
349
-------
Compound Name: Carbaryl [N-methyl-a-napthylurethene]
Compound Properties:
M.W. 201.2
M.P.
B.P.
Sp. gr.
Vapor pressure
Water solubility
Low KQW
Chemcial class
Chemical reactivity
Adsorption in Soils
Degradation in Soils
Structure
Adsorption
K
4.87x10-6
2.41x10-6
8.98x10-4
8.42xlO-4
109
4.3
2.9
3.4
Parameters
N
0.438
0.432
0.933
0.893
0.97
0.96
0.98
1.08
Kfir
2.85x10-4
1.41x10-4
0.37
0.35
249
265
200
829
8.1
8.1
7.95
7.95
6.1
6.6
6.8
7.0
Soil Properties
CEC
32.0
32.0
11.6
11.6
OC
1.71
1.71
0.24
0.24
43.7
1.62
1.45
0.41
Percent
Sand
51.5
51.5
51.6
51.6
52
71
56
91.5
(%)
Silt
25.3
25.3
21.6
21.6
34
22
30
1.5
Clay
23.2
23.2
27.0
27.0
14
7
14
7
Degradation Parameters
Soil Properties
tl/2
Mois-
Initial Temp, ture
cone. °C 0
pH
CEC
Percent (%)
OC Sand Silt Cla\
Volatilization in Soils
Volatilization Parameters
Soil Properties
OC (%)
Mo i s ture
9
Bulk
Density
Tern p .
"C
Porosity
350
-------
Compound Name: Chlordane
Compound Properties:
M.W. 409.8
M.P. 103-108.8°C
B.P.
Sp.gr.
Vapor pressure 1x10-= torr
Structure
Water solubility 0.056-1.85 ppm
Low Kow 2.78
Chemcial class
Chemical reactivity
Adsorption in Soils
Adsorption Parameters
K N W
Soil Properties
PH
CEC
Percent (%)
OC
Sand
Silt
Clay
Degradation in Soils
Degradation Parameters
Soil Properties
0.00072
0.0020
Mois-
Initial Temp, ture
cone. °C 9
pH
CEC
Percent (%}
OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
MoistureBulkTemp.
OC (%) 0 Density °C Porosity
351
-------
Compound Name:
Diazinon [0,0-diethyl 0-(2-isopropyl-4-methyl-6-pyrimidyl
phosphorothioate]
Compound Properties:
M.W. 304.4
M.P.
B.P. 83-84°C
Sp. gr.
Vapor pressure 4.1xlO~4 (2
1.1x10-3 W
Water solubility 40 ppm
Low KQW
Chemcial class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters
1\ IN i^nf*
325
20.1
5.2
6.7
1.00
1.07
0.99
1.08
744
1240
359
1630
Soil Properties
Percent (%)
pH CEC
6.1
6.6
6.8
7.0
OC
43.7
1.62
1.45
0.41
Sand
52
71
56
91.5
Silt
34
22
30
15
Clay
14
7
14
7
Degradation in Soils
Degradation Parameters
So i1 Properties
tl/2
Ks n
0.0151
0.0067
0.0242
0.0239
0.0239
0.0248
0.0189
0.0260
0.0166
0.0171
Initial
cone.
Temp.
•c
25
15
Mois-
ture
9 PH
6.7
6.7
4.3
4.8
6.5
6.5
4.0
5.4
5.6
5.4
Percent (%)
CEC OC Sand Silt Clay
1.80
1.80
1.80
0.58
1.16
1.16
1.22
1.74
4.18
23.2
Volatilization in Soils
Volatilization Parameters
Soil
OC (*)
Moisture
0
Properties
"BUTE
Density
Temp.
°C
Porosity
352
-------
Compound Name:
Endrin [l,2,3,4,10,10-hexach1oro-6,7-epoxy-l,4,4a,5,6,7,8,8a-
octahydroexo-5,8-dimethanonaphthalene]
Compound Properties:
Structure
M.W.
M.P.
B.P.
Sp. gr
Vapor
376.9
200 °C
184'C
.
pressure
•c
2x10-7 torr
9 25°C
Water solubility 200
Low Kow 5.6
Chemcial class
Chemical reactivity
Adsorption in Soils
ppb °25'C
(calculated)
Adsorption Parameters
K N Knr
11115
222.5
660.5
90.4
1.08 25435
0.99 13735
1.12 45572
1.03 22049
Soil Properties
Percent (%)
pH CEC
6.1
6.6
6.8
7.0
OC
43.7
1.62
1.45
0.41
Sand
52
71
56
91.5
Silt
34
22
30
1.5
Clay
14
7
14
7
Degradation in Soils
Degradation
HZ2 KS_
Parameters Soil Properties
Mois-
Initial Temp, ture Percent (%)
n cone. *C 0 pH CEC OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
Soil Properties
MoistureBulkTemp.
OC (%) Q Density "C Porosity
353
-------
Compound Name: Mevinphos
Compound Properties:
M.W. 208.1
M.P.
B.P.
Sp. gr.
Vapor pressure
Water solubility
Low K,
•Qw,
Chemcial class
Chemical reactivity
Adsorption in Soils
Structure
Adsorption Parameters
Soil Properties
Percent (%)
K
8.8
N KQC
0.95 20.1
PH
6.1
CEC OC
43.7
Sand
52
Silt
34
Clay
14
Degradation in Soils
Degradation Parameters
Soil Properties
MOIS-
Initial Temp, ture
cone. "C 0
Percent (%)
pH
"
CEC
OC Sand Silt Clay
TJ7Z3"
Volatilization in Soils
Volatilization Parameters
Soil Properties
Moisture Bulk Temp.
QC (%) 6 Density °C Porosity
354
-------
Compound Nane: a-napthol (1-hydroxynapthalene, 1-napthol
Compound Properties:
Structure
M.W.
M.P.
8.P.
Sp. gr.
Vapor pressure
144.2
96.1'C
184'C
1 mm (94'C)
10 mm (142°C)
100 mm (206°C)
Water solubility
Low Kgw
Chemcial class
Chemical reactivity
866 mg/1
2.85
Adsorption in Soils
Adsorption Parameters
Soil Properties
N
Koc
257.4
76.5
933.3
18.2
821.5
243.4
24.7
761.1
489.
650.
100.
52.
295
163.9
76.7
243.4
.7
.6
.4
.1
0.441
0.550
0.310
0.609
0.222
0.357
0.563
0.318
0.283
0.313
0.501
0.642
0.387
0.442
0.549
0.357
12435
3355
129625
12133
746818
8007
5146b
80116
74197
50046t>
5340
3120
12395
11074
8522b
20116
PH
7.79
2.74
7.83
8.32
8.34
6.90
4.54
7.79
7.76
5.50
7.60
7.55
6.70
7.75
6.40
6.35
CEC
24
19
33
4
12
12
19
11
15
9
8
9
31
21
3
4
OC
2.07
2.28
0.72
0.15
0.11
3.04
0.48
0.95
0.66
1.30
1.88
1.67
2.38
1.48
0.90
1.21
Percent (%}
Sand Silt Clay
55.2
31.0
68.6
6.8
17.4
52.6
63.6
35.7
39.5
28.6
7.1
21.2
69.1
42.9
22.5
18.6
Degradation in Soils
Degradation Parameters
tl/2
Mois-
Initial Temp, ture
cone. °C n
Soil Properties
Percent (%)
pH CEC OC Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
OC (%)
Soil Properties
Moisture
0
"TOTF
Density
aOriginally reported in umole instead of
s and the others are sediments.
Temp.
*C
Porosity
355
-------
Compound Name: PCBs [polychlon'nated biphenyl]
Compound Properties:
M.W.
M.P.
B.P.
Sp. gr.
Vapor pressure
Structure
Water solubility
Low Kow 3.47
Chemcial class
Chemical reactivity
Adsorption in Soils
3.54
Adsorption Parameters
Soil Properties
Percent (%)
K N
1300
1290
1370
620
1250
1090
1210
540
1180
990
580
420
1270
1080
650
510
Degradation
Koc
54167
92143
171250
155000
42083
77857
151250
135000
49167
70714
72500
105000
52917
77143
81250
127500
Parameters
pH CEC
6.3
6.1
6.4
6.5
6.3
6.1
6.4
6.5
6.3
6.1
6.4
6.5
6.3
6.1
6.4
6.5
Degradation in
Mois-
OC
2.4
1.4
0.8
0.4
2.4
1.4
0.8
0.4
2.4
1.4
0.8
0.4
2.4
1.4
0.8
0.4
Soils
Soil
Sand
55.0
56.0
-
93.0
55.0
56.0
-
93.0
55.0
56.0
-
93.0
55.0
56.0
_
93.0
Properties
Initial Temp, ture
M/2 KS
n cone
•c e
pH
CEC OC
Silt Clay
45 <1.0
44 <1.0
-
6.0 2.0
45 <1.0
44 <1.0
-
6.0 2.0
45 <1.0
44 <1.0
-
6.0 2.0
45 <1.0
44 <1.0
_
6.0 2.0
Percent (%)
Sand Silt Clay
Volatilization in Soils
Volatilization Parameters
KwKp
Soil Properties
Moisture Bulk
OC (%) 0 Density
Temp.
°C
Porosity
356
-------
Compound Name: 2,4,5-T [2,4,5 tricholorophenoxy acetic acid]
Compound Properties:
M.W. 225.5
M.P. 153°C
B.P.
Sp. gr.
Vapor pressure
Water solubility
Low Kow
Chemcial class
Chemical reactivity
Adsorption in Soils
228 ppm (25°C)
0.60
Structure
Adsorption Parameters
Soil Properties
Percent (%)
K
5.023
0.74a
N
0.81
0.85
Kor pH CEC OC Sand Silt
167
92.5
5.9
7.7
3.0
0.8
61
31
Clay
27
30
Degradation in Soils
Degradation Parameters
0.0289
0.0330
0.0330
0.0495
0.0414
Soil Properties
Mois-
Initial Temp, ture
cone. "C 0
PH
5.5
5.8
CEC
Percent (%)
OC Sand Silt Cla\
1.91
1.64
2.20
0.99
1.10
Volatilization in Soils
Volatilization Parameters
if tr if
OC (%)
Soil Properties
Moisture Bulk Temp.
0 Density °C
Porosity
Reported in terms umoles.
357
-------
APPENDIX B
GLOSSARY
Aggregated media
Aliphatic compounds
Alkali earth metals
Alkali metals
An ions
•
Aromatic compounds
Autochthonous microorganisms
Autotrophic bacteria
Breakthrough curves (BTC)
Media with two
and micropores.
Organic compounds
groups are linked
carbon chain.
sets of pores, macropore
in which the characteristic
in a straight or branched
CA
CAR
The elements of group II of the periodic
table, including beryllium, magnesium, and
calcium.
The elements of group I of the periodic table
including sodium and potassium.
Atoms or molecules that are negatively charged.
Organic compounds in which characteristic
groups are linked to a particular six-member
carbon ring which contains three double bonds.
That part of soil microbial community which is
capable of utilizing the refractory humic sub-
stances. The characteristic of these organisms
is slow and constant activity.
Bacteria that fix the carbon they need for
growth from carbon dioxide and (usually) obtain
their energy from light (photosynthetic) or the
oxidation of inorganic compounds (litho-
trophic).
A curve of C/C0 vs. V/V0 where:
C = concentration of column effluent
C0 = concentration of column influent
V = cumulative outflow volume
V0 = total water volume in soil column
Constituent attenuation achieved.
Constituent attenuation required at the site.
358
-------
CASSACI
Cations
CEC
Chelate
CIS
Cometabolism (cooxidation)
Complex ions
Critical Depth
Desorption
Direct photodegradation
EH
Equilibrium
ESP
ET
Exchange (outer sphere
complex)
Constituent attenuation achieved based on
assimilation capacity for degradation (SSAC)
treatment for immobilization.
Atoms or molecules that are positively charged.
Cation exchange capacity, usually is expressed
in mill iequivalents of cations per 100 grams
of soil.
A 1igand which contains two donor atoms so
arranged that both coordinate simultaneously to
the same central elements.
Constituent level in the contaminated soil.
Metabolism by microorganism of a compound
that the cell is unable to use as a source of
energy or an essential nutrient.
Designates all ions other than monoatomic ones.
End of microbially active zone, depth of
groundwater, or end of soil zone.
The reverse process of sorption, i.e., solute
concentration decrease at the soil water
interface.
The excitation of substrate molecules directly
via absorption of light particles or quanta.
Loss of absorbed energy by the substrate
molecules is via photodegradation reaction of
dissociation, dehalogenation, isomerization,
oxidation or other deactivation routes.
Excavation and hauling of contamined soils.
A state in which a chemical reaction and its
reverse reaction are taking place at equal
rates, so that the concentration of reacting
constituents is constant.
Exchangeable sodium ratio
E3P= [Na+](me/l)
concentration of total cations (me/1)
xlOO
Exogeneous treatment for constituent attenua-
tion.
Ions held loosely in the vicinity of a charged
surface site by electrostatic forces.
359
-------
Pick's Law
Fugacity
Heavy metals
Heterocyclic compounds
Heterotrophic bacteria
Hydrolysis
Hydrophobia bonding
Hysteresis (nonsingularity)
Immobilization
Ion pairs
Ionic strength
The concentrations tend to diffuse from high
to low concentration regions. Mathematically
Pick's Law is:
J = 0(3c/5x)
where J = mass flux
0 = constant (diffusion constant)
x = space coordinate
c = concentration
A compound's chemical potential energy or
"escaping tendency" expressed in units of
pressure. Fugacity concepts allow a steady-
state equilibrium estimation of compound
partitioning in mul ticomponent environments.
Defined as metals that precipitated in acid
solution by hydrogen sulfide (Cd, Cr, Cu,
Hg, Mn, Ni, Pb, and Zn).
Compounds that have ring structure in which one
member is an element other than carbon.
Bacteria that derive their energy and carbon
for survival and growth from decomposition of
organic materials.
Reaction of an ion with water to form a weak
acid or base.
Partitioning between a polar solvent (e.g.,
water) and a nonpolar adsorbent surface (e.g.,
soil humus).
Retention of a residual on soil at a given
equilibrium concentration, when desorption
occurs.
Irreversible sorption of pollutants thus pre-
venting leaching.
Short range interactions between closely adja-
cent ions usually in pairs (e.g., CdC03° ,
and CaS0°).
Total electrolyte content of a solution.
360
-------
Koc Normalized Freundlich adsorption constant with
respect to organic carbon content of soil. Koc
is defined as:
Koc = (K/oc%) x 100 or
KOC = (Kd/oc%) x 100
where K is nonlinear Freundlich adsorption
isotherm (N^l), K
-------
KWK,
oc
LC
LD
Ligands
LR
Macro cation
MEGs
Mole
Mutualistic (symbiotic)
conditions
Oxidation
Oxidizing agent
Permanent surface charge
Photodegradation
Polymerization
Recalcitrant compounds
Redox
Redox potential
Parameter used interchangeably with KwK,j to
described the relative volatility rate of a
compound. A large KWKOC or KwK
-------
Reducing agent
Reduction
Retardation factor (R)
Sensitized photooxidation
Sensitizing compounds
Singlet oxygen
SAR
Solubility constant
Sorption
Sorption isotherm
A substance that does the reduction.
A process in which the oxidation state of
a substance is decreased due to gain of elec-
trons.
The ratio between average pore water velocity
and average pollutant front velocity.
The transfer of absorbed light energy from
sensitizing compounds to molecular oxygen to
form a highly reactive singlet oxygen species,
followed by the oxidation of substrate molecule
by singlet oxygen.
Organic compounds which absorb light in the
visible region and transfer this absorbed
energy to other molecules as they return to a
low energy or ground state. Energy transfer to
molecular oxygen yields reactive singlet
oxygen. Examples of sensitizers include
riboflavin and methylene blue.
A highly reactive species of
life time of 3 y sec which is
the transfer of energy from
compound to molecular oxygen.
Sodium adsorption ratio.
oxygen with a
formed through
a sensitizing
SSAC
The product of the concentration of the ions
of a substance in a saturated solution of the
substance.
A physical/chemical process in which the
increase of solute concentration evolves at
the soil water interface. Sorption term is
used without distinguishing whether the process
is exchange, hydrophobic bonding, adsorption,
etc.
A functional relation between the amount
adsorbed per unit weight of soil (S) and
the equilibrium solution phase concentration
(C). As an example, Freundlich isotherm which
is expressed as:
S = K CN
where K and N are constants.
Site/soil assimilative or attenuation capacity.
363
-------
SSACD Assimilative capacity for degradation rate
(biodegradation and photodegradation) per
unit soil weight.
SSWI Site/soil/waste interaction.
Stoichiometric Pertaining to weight relations in a chemical
reaction.
ti/2 Half-life time, the time needed for 50% of
the initial concentration to degrade. Usually,
the concept of ty2 is associated with first
order degradation rate, in which case the ti/2
is independent of the initial concentration.
However, the ^\f2 can De generalized as for
other rate orders, which is not independent at'
the initial concentration. ^1/2 is a simple
tool for comparing degradation potential of
different compounds.
364
-------
COPYRIGHT NOTICE
Figure 3-4
Table 3-11
Figure 3-5
Table 3-12
Figure 3-6
Figure 3-7
Figure 3-8
Figure 3-9
Table 3-13
Table 3-13a
From Fundamentals of Soil Science by
EditiolT Copyright 1978 by John Wi ley
NY. Used by permission of the publisher.
From Fundamentals of Soil Science by
Editio"rTCopyright 1978 by John Wi 1 ey
NY. Used by permission of the publisher.
H. D. Foth. Sixth
and Sons, New York,
H. 0. Foth. Sixth
and Sons, New York,
From The Nature and Properties of Soils by N. C. Brady.
'. Copyr ight 1974 by Macmillan Publishing
York, NY. Used by permission of the pub-
Eighth Edition,
Co., Inc., New
lisher.
From Fundamentals of Soil Science by
Edition.
NY. Used
From The
Copyright
NY. Used
Copyright 1978 by
by permission of the
Nature and Propert
John Wiley
publisher.
ies of Soi
1974 by Macmillan Publishing
by permission of the
publisher.
and
Is
Co. ,
Sons,
by N.
Inc. ,
New
York,
C. Brady.
New
York,
From Fundamentals of Soil Science by
EditioTu Copyright 1978 by John Wi ley
NY. Used by permission of the publisher.
From Fundamentals of Soil Science by
Ed i t io~FT Copyright 1978 by John B"i 1 ey
NY. Used by permission of the publisher.
H. D. Foth. Sixth
and Sons, New York,
H. D. Foth. Sixth
and Sons, New York,
From "The Soil Environment" by J. L. Ahlrichs, p. 3-26 in
Organic Chemicals in the Soil Environment edited by C.A.I,
Goring and J.vTHamaker.Copyright 1972 by Marcel Dekker,
Inc., New York, NY. Used by permission of the publisher.
From Concepts in Soil Science by M. G. Cook and G. M. Pace.
Copyright 1978 by North Carolina State University, Raleigh,
NC. Used by permission of the publisher.
From "Chemical, Spectroscopic, and Thermal Methods for the
Classification and Characterization of Humic Substances"
by M. Schnitzer, p. 293-310 in Humic Substances, Their Struc-
ture and
H.
L.
Go
Function
Iterman.
in the
Copyr
Biosphere
Tght
1975
ed i ted by
by Center
D.
for
Povoledo and
Agricultural
365
-------
Figure 3-10
Table 3-14
Table 3-15
Figure 3-11
Figure 3-12
Table 3-17
Figure 3-14
Figure 3-15
Figure 3-16
Figure 3-17
Table 3-29
Publishing and Documentation,
of the publisher.
Wageningen. Used by permission
From The Nature and Properties of Soils by N. C. Brady.
Eighth Edition.
Inc., New York,
Copyright 1974 by Macmi1 Ian Publishing Co.,
NY. Used by permission of the puolisher.
From "The Mechanism of Reduction in Waterlogged Paddy Soil"
by Y. Takai and T. Kamura. Folia Microbiol. (Prague) 11:
135-145, 1966. Used by permission of Folia Microbiologica.
From Soil
W. L.
Inc., New
Fertility
Nelson.
Copyright 1975
York, NY. Used by
and Fertilizers by S. L. Tisdale and
by Macmillan Publishing Co.,
permission of the publisher.
From Physical Edaphology by S. A. Taylor and G. L. Ashcroft.
Copyright 1972 by W. H. Freeman and Co., San Francisco, CA.
Used by permission of the publisher.
From Fundamentals of Soil Science by
Edition.
NY. Used
Copyright 1978
by permission of
by~John Wiley
the publisher.
H. D. Foth. Sixth
and Sons, New York,
From Soil and Hater Conservation Engineering by G. 0. Schwab,
R. K. Frevert, T. W. Edminster, and K. K. Barnes. Second
Edition. Copyright 1966 by John Wiley and Sons, Inc., New
York, NY. Used by permission of the publisher.
From "Factors Affecting the Solubility of Trace Metals in
Soils" by S. W. Mattigod, G. Sposito, and A. L. Page in
Chemistry in the_Soj_1 Envi ronment. ASA Special Publication
7RT,r98l. Used by pe>mi ssion of the American Society of
Agronomy.
Equilibria in Soi 1 s
1979 by John" Wiley""and
permission of the publisher.
From Chemical
right
by W. L. Lindsay. Copy-
"Sons, New York, NY. Used by
From "The Chemistry of Lead and Cadmium in Soil: Solid Phase
Formation" by J. Santil lan-Medrano and J. J. Jurinak. Soil
Sci. Soc. Am. Proc. 29:851-856, 1975. Used by permission of
the Soil Science Society of America.
From "The Chemistry of Lead and Cadmium in Soil: Solid Phase
Formation" by J. Santillan-Medrano and J. J. Jurinak. Soil
Sci. Soc. Am. Proc. 29:851-856, 1975. Used by permission of
the Soil Science Society of America.
From "Factors Affecting the Solubility of Trace Metals in
Soils" by S. W. Mattigod, G. Sposito, and A. L. Page in Chem-
istry in the Soil Environment. ASA Special Publication40,
1981.Used by permission of the American Society of Agronomy.
366
-------
Figure 3-18
Figure 3-19
Figure 3-20
Figure 3-21
Table 3-30
Table 3-31
Table 3-32
Figure 3-22
Figure 3-23
From "Chloride as a Factor in Mobilities of Ni(II), Cu(II),
and Cd(II) in Soil" by H. E. Doner. Soil Sci. Soc. Am. J.
42:882-885, 1978. Used by permission of the SoilScience
Society of America.
From "Chloride as a Factor in Mobilities of Ni(II),
and Cd(II) in Soil" by H. E. Doner. Soil Sci. Soc
42:882-885, 1978. Used by permission
Society of America.
Cu(II),
. Am. J.
of the Soil Science
From "Chloride as a Factor in Mobilities of Ni(II), Cu(II),
and Cd(II) in Soil" by H. E. Doner. So i 1 Sci. Soc. Am. J.
42:882-885, 1978. Used by permission of the SoilScience
Society of America.
From "Heterogeneous Equilibria Involving Oxides, Hydroxides,
Carbonates and Hydroxide Carbonates" by P. W. Schindler in
Equilibrium Concepts in Natural Water Systems edited by R. F.
Gould.Adv. in Chem. Ser. No. 67.Copyright 1967 by American
Chemical Society, Washington, DC. Used by permission of the
American Chemical Society.
From "Trace Metal Complexation by Fluvic Acid Extracted from
Sewage Sludge: I. Determination of Stability Constants and
Linear Correlation Analysis" by G. Sposito, K. M. Holzclaw,
and C. S. LeVesque-Madore. Soil Sci. Soc. Am. J. 45:465-468,
1981. Used by permission of the Soil Science Society of
America.
From "Factors Affecting the Solubility of Trace Metals in
Soils" by S. W. Mattigod, G. Sposito, and A. L. Page in
Chemistry in the Soil Environment. ASA Special Publication
7U^1981.Used by permission of the American Society of
Agronomy.
From "Soil Adsorption of Cadmium from Solutions Containing
Organic Ligands" by H. A. Elliott and C. M. Denneny. _J_i
Environ. Qual. 11:658,663, 1982. Used by permission of the
Journal of Environmental Quality.
From "Soil Adsorption of Cadmium from Solutions Containing
Organic Ligands" by H. A. Elliott and C. M. Denneny. J_._
Environ. Qua!. 11:658-663, 1982. Used by permission of the
Journal of Environmental Quality.
From "Copper and Cadmium Reactions with Soils in Land Appli-
cations" by F. S. Tirsch, J. H. Baker, and F. A. Diglano.
J. Water Pollution Control Fed. 51:2649-2660, 1979. Used by
Control Federa-
permission
tion.
of the Journalof Water Pollution
367
-------
Table 3-33 From "Effect of Soil pH on Adsorption of Lead, Copper, Zinc
and Nickel" by R. D. Harter. Soil Sci. Soc. Am. J. 47:47-51,
1983. Used by permission of the Soil Science Society of
America.
Figure 3-24 From "Copper and Cadmium Adsorption Characteristics of Se-
lected Acid and Calcareous Soils" by N. Cavallaro and M. B.
McBride. Soil Sci. Soc. Am. J. 42:550-556, 1978. Used by
permission of the Soil Science Society of America.
Figure 3-25 From "Copper and Cadmium Adsorption Characteristics of Se-
lected Acid and Calcareous Soils" by N. Cavallaro and M. B.
McBride. Soil Sci. Soc. Am. J. 42:550-556, 1978. Used by
permission of the Soil Science Society of America.
Table 3-34 From "Copper and Cadmium Adsorption Characteristics of Se-
lected Acid and Calcareous Soils" by N. Cavallaro and M. B.
McBride. Soil Sci. Soc. Am. J. 42:550-556, 1978. Used by
permission of the Soil Science Society of America.
Table 3-35 From "Soil Sorption of Nickel: Influence of Solution Compo-
sition" by R. S. Bowman, M. E. Essington, and G. A. O'Connor.
Soil Sci. Soc. Am. J. 45:860-865, 1981. Used by permission
of the Soil Science Society of America.
Table 3-36 From "Soil Sorption of Nickel: Influence of Solution Compo-
sition" by R. S. Bowman, M. E.-Essington, and G. A. O'Connor.
Soil Sci. Soc. Am. J. 45:860-865, 1981. Used by permission
of the Soil Science Society of America.
Table 3-37 From "Influence of Solution Composition on Sorption of Zinc
by Soil" by M. A. Elrashidi and G. A. O'Connor. Soil Sci.
Soc. Am. J. 46:1153-1158, 1982. Used by permission of the
Soil Science Society of America.
Figure 3-28 From "The Chemistry of Soil Processes" by D. J. Greenland
and M. H. B. Hayes. John Wiley and Sons, Chichester, England,
1981. Used by permission of the publisher.
Figure 3-29 From "Behavior of Chromium in Soils: I. Trivalent Forms,
II. Hexavalent Forms" by R. S. Bartlett and J. M. Kimble.
J. Environ. Qual. 5:379-386, 1976. Used by permission of
the Journal of Environmental Quality.
Figure 3-31 From "Behavior of Chromium in Soils: I. Trivalent Forms,
II. Hexavalent Forms" by R. S. Bartlett and J. M. Kimble.
J. Environ. Qual. 5:379-386, 1976. Used by permission of
the Journal of Environmental Quality.
Table 3-38 From "Volatility of Mercury from Soils Amended with Various
Mercury Compounds" by J. D. Rogers. Soil Sci. Soc. Am. J.
43:289-291, 1979. Used by permission of the Soil Science
Society of America.
268
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Figure 3-37 From "Solubility and Redox Criteria for the Possible Forms
of Selenium in Soils" by H. R. Geering, E. E. Cory, L. H. P.
Jones, and W. H. Alloway. Soil Sci. Soc. Am. Proc. 32:35-40,
1968. Used by permission of the Soil Science Society of
America.
Table 3-39 From "Interaction of Organic Pesticides with Particular Matter
in Aquatic and Soil Systems" by J. 8. Weber in Fate of Organic
Pesticides in the Aquatic Environment edited by R. F!Gould.
Copyright 1972 by American Chemical Society, Washington, DC.
Used by permission of the American Chemical Society. Used by
permission of the author.
Figure 3-38 From "Interaction of Organic Pesticides with Particular Matter
in Aquatic and Soil Systems" by J. B. Weber in Fate of Organic
Pesticides in the Aquatic Environment edited by R.F!Gould.
Copyright 1972 by ^American Chemical Society, Washington, DC.
Used by permission of the American Chemical Society. Used by
permission of the author.
Table 3-40 From "Interaction of Organic Pesticides with Particular Matter
in Aquatic and Soil Systems" by 0. B. Weber in Fate of Organic
Pesticides in the Aquatic Environment edited by R.F!Gould.
Copyright 1972 by~ Amerfcan Chemical Society, Washington, OC.
Used by permission of the American Chemical Society. Used by
permission of the author.
Table 3-41 From "Interaction of Organic Pesticides with Particular Matter
in Aquatic and Soil Systems" by J. B. Weber in Fate of Organic
Pesticides in the Aquatic Environment edited by R. F. Gould.
Copyright 1972 by American Chemical Society, Washington, DC.
Used by permission of the American Chemical Society. Used by
permission of the author.
Table 3-42 From "Interaction of Organic Pesticides with Particular Matter
in Aquatic and Soil Systems" by J. B. Weber in Fate of Organic
Pesticides in the Aquatic Environment edited by~~R~;F. Gould.
Copyright 1972 by American Chemical Society, Washington, DC.
Used by permission of the American Chemical Society. Used by
permission of the author.
Table 3-43 From "A Survey of Sorption Relationships for Reactive Solutes
in Soils" by C. C. Travis and E. K. Etnier. J. Environ. Qua!.
10:8-17, 1981. Used by permission of the Journal of Environ-
mental Qua!ity.
Figure 3-39 From "Studies in Adsorption. Part XI. A System of Classifi-
cation of Solution Adsorption Isotherms and Its Use in Diag-
nosis of Adsorption Mechanisms and in Measurement of Specific
Surface Areas of Solids" by H. Giles, T, H. MacEwan, S. N.
Nakhaw, and D. Smith. J. Chem. Soc. 111:3973-3993, 1960.
Used by permission of the Royal Society of Chemistry, London,
England.
369
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Figure 3-40 From "Interaction of Organic Pesticides with Particular Matter
in Aquatic and Soil Systems" by J. B. Weber in Fate of Organic
Pesticides in the Aquatic Environment edited by R.F. Gould.
Copyright1972 by American Chemical Society, Washington, DC.
Used by permission of the American Chemical Society. Used by
permission of the author.
Table 3-45 From "Factors Influencing the Adsorption, Desorption, and
Movement of Pesticides in Soils" by G. W. Bailey and J. L.
White. Residue Reviews 32:29-93. Copyright 1970 by Springer-
Verlag New .York, Inc. Used by permission of the publisher.
Figure 3-43 From "Estimation of Pesticide Retention and Transformation
Parameters Required in Non-Point Source Pollution Models" by
P. S. C. Rao and J. M. Davidson in Environmental Impact of
Nonpoint Source Pollution edited by M. R. Overcash and J. M.
Davidson.Copyright19150 by Ann Arbor Science Pub., Inc.,
Ann Arbor, MI. Used by permission of the publisher.
Figure 3-44 From "Increased Cooxidative Biodegradation of Malathion in
Soil via Cosubstrate Enrichment" by G. J. Merkel and J. J.
Perry. J. Agr. Food Chem. 25:1011-1012, 1977. Used by
permission of the American Chemical Society.
Figure 3-45 From "Increased Cooxidative Biodegradation of Malathion in
Soil via Cosubstrate Enrichment" by G. J. Merkel and J. J.
Perry. J. Agr. Food Chem. 25:1011-1012, 1977. Used by
permission of the American Chemical Society.
Table 3-46 From "Biodegradation of Polynuclear Aromatic Hydrocarbon Pol-
lutants by Soil and Water Microorganisms" by E. J. McKenna.
Presented at the 70th Annual Meeting of the Am. Inst. Chem.
Eng., New York, NY. Used by permission of the American In-
stitute of Chemical Engineers.
Figure 3-46 From "Turnover of Pesticide Residues in Soil" by J. W. Hamaker
and C. A. I. Goring in Bound and Conjugate Pesticide Residues
edited by D. 0. Kaufman et al . ACS Symposium Series 29.
Copyright 1976 by American Chemical Society, Washington, DC.
Used by permission of the American Chemical Society.
Figure 3-47 From "Turnover of Pesticide Residues in Soil" by J. W. Hamaker
and C. A. I. Goring in Bound and Conjugate Pesticide Residues
edited by D. D. Kaufman et al . ACS Symposium Series 29.
Copyright 1976 by American Chemical Society, Washington, DC.
Used by permission of the American Chemical Society.
Figure 3-49 From Design of Land Treatment Systems for Industrial Wastes -
Theory and Practice by M. R. Qvercash and D. Pal . Copyright
1979 by Ann Arbor Science Pub., Inc., Ann Arbor, MI. Used by
permission of the publisher.
370
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Table 3-49 From "Land Disposal of Acidic Basic and Salty Wastes from
Industries" by D. Pal, M. R. Overcash, and P. W. Westerman.
Manuscript originally printed in the Proceedings of the
National Conference on Treatment and Disposal of Industrial
Wastewaters and Residues^ 1977. Avai1ab1e from Hazardous
MaterialsControlResearch Institute, 9300 Columbia Blvd.,
Silver Spring, MD 20910. Used by permission of the Hazardous
Materials Control Research Institute.
Table 3-50 From "Dissolution of Clay Minerals in Dilute Organic Acids
at Room Temperature" by W. H. Huang and W. D. Keller. The
Am. Mineralogist 56:1082-1095. Copyright 1971 by the MlrP
eralogicalSociety of America. Used by permission of the
Mineralogical Society of America.
Figure 3-50 From Design of Land Treatment Systems for Industrial Wastes -
Theory and Practice by M. R. Overcash and D. Pal . Copyright
1979 by Ann Arbor Science Pub., Inc., Ann Arbor, MI. Used
by permission of the publisher.
Table 3-52 From Design of Land Treatment Systems for Industrial Wastes -
Theory and Practice by M. R. Overcash and D. Pal . Copyright
1979 by Ann Arbor Science Pub., Inc., Ann Arbor, MI. Used
by permission of the publisher.
Table 3-53 From Design of Land Treatment Systems for Industrial Wastes -
Theory and Practice by M. R. Overcash and D. Pal.Copyright
1979 by Ann Arbor Science Pub., Inc., Ann Arbor, MI. Used
by permission of the publisher.
Table 3-.S7 From "Adsorption of Surfactants on Montmoril lonite" by W. F.
Hower. Clays and Clay Minerals 18:97-105, 1970. Used by
permission of the Clay Minerals Society.
Table 3-58 From "Influence of Methods of Pesticide Application on Sub-
sequent Desorption from Soils" by B. T. Bowman and W. W.
Sans. J. Agr. Food Chem. 30:147-150. Copyright 1982 by
American Chemical Society, Washington, DC. Used by permis-
sion of the American Chemical Society.
Figure 3-51 From "Influence of Methods of Pesticide Application on Sub-
sequent Desorption from Soils" by B. T. Bowman and W. W.
Sans. J. Agr. Food Chem. 30:147-150. Copyright 1982 by
American ChemicalSociety, Washington, DC. Used by permis-
sion of the American Chemical Society.
Figure 3-52 From "Influence of Methods of Pesticide Application on Sub-
sequent Desorption from Soils" by B. T. Bowman and W. W.
Sans. J. Agr. Food CheriK 30:147-150. Copyright 1982 by
American ChemicalSociety, Washington, DC. Used by permis-
sion of the American Chemical Society.
371
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Figure 3-53 From "Mechanisms of Solute Transport in Soils" by D. R.
Nielsen, J. W. Biggar, and C. S. Simons in Model ing Waste-
water Renovation Land Treatment edited by I. FTIskandar.
Copyright 1981 by Wi ley-Interscience, New York, NY. Used by
permission of the publisher.
Figure 3-54 From "Soil Hydraulic Properties, Spatial Variability, and
Soil-Water Movement" by 0. R. Nielsen, J. Matthey, and J. W.
Biggar in Modeling Wastewater Renovation Land Treatment edited
by I. K. Iskandar.Copyright 1981 by Wiley-Interscience, New
York, NY. Used by permission of the publisher.
Figure 3-55 From "Soil Hydraulic Properties, Spatial Variability, and
Soil-Water Movement" by D. R. Nielsen, J. Matthey, and J. W.
Biggar in Modeling Wastewater Renovation Land Treatment edited
by I. K. Iskandar.Copyright 1981 by Wiley-Interscience, New
York, NY. Used by permission of the publisher.
Figure 3-56 From "Evaluation of Conceptual Process Models for Solute Be-
havior in Soil-Water Systems" by M. M. Davidson, P. S. C. Rao,
R. E. Green, and H. M. Selim in Agrochemicals in Soils edited
by A. Banin and U. Kafkafi. Copyright 1980 by Pergamon Press,
London. Used by permission of the publisher.
Table 3-60 From "Empirical Equations for. Some Soil Hydraulic Properties"
by R. B. Clapp and 6. M. Hornberger. Water Resour. Res. 14:
601-604. Copyright 1978 by American* Geophysical Union.Used
by permission of the American Geophysical Union.
Figure 3-57 From Chemodynamics, Environmental Movement of Chemicals in
Air, Water and Soil by C T. Thibodeaux. Copyright 1979 by
John Wiley and Sons, New York, NY. Used by permission of the
publisher.
Table 3-62 From "Vapor-Phase Photochemistry of Pesticides" by J. E.
Woodrow, D. G. Crosby, and J. N. Seiber. Residue Reviews
85:111-125. Copyright 1983 by Springer-Verlag New York, Inc.
Used by permission of the publisher.
372
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