United States
Environmental Protection
Agency
Office of
Radiation Programs
Washington DC 20460
EPA 520/1-83-003
March 1983
&EPA
Quantitative Mineral Assessment
and Radionuclide Retention Potential
of Atlantic 3800-Meter Nuclear Waste
Dumpsite Sediments
Biogenous Materials
LEGEND
Contemporary
Sediment
A Slump from
Canyon Wall
Terrigenous
Materials
Clay
Minerals
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EPA REVIEW NOTICE
This report has been reviewed by the Office of Radiation Programs,
U.S. Environmental Protection Agency (EPA), and approved for publication.
Approval does not signify that the contents necessarily reflect the views
and policies of the EPA. Neither the United States nor the EPA makes any
warranty, expressed or implied, or assumes any legal liability or
responsibility for any information, apparatus, product, or process
disclosed or represents that its use would not infringe privately owned
rights.
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Quantitative Mineral Assessment
and Radionuclide Retention Potential
of Atlantic 3800-Meter
Nuclear Waste Dumpsite Sediments
by
James Neiheisel
March 1983
U.S. Environmental Protection Agency
Office of Radiation Programs
Washington, D.C. 20460
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FOREWORD
The Environmental Protection Agency (EPA) was given a Congressional
mandate to develop criteria, standards, and regulations governing the
ocean disposal of all forms of wastes pursuant to Public Law 92-532, the
Marine Protection, Research, and Sanctuaries Act of 1972. Within this
Congressional mandate, EPA has initiated a specific program to develop
regulations and criteria to control the ocean disposal of radioactive
wastes.
The EPA Office of Radiation Programs (ORP) initiated feasibility
studies to determine whether current technologies could be applied toward
determining the fate of radioactive wastes dumped in the past. After
successfully locating radioactive waste containers in three of the primary
radioactive waste disposal sites used by the United States in the past,
ORP developed an intensive program of dumpsite characterization studies to
investigate: (1) the biological, chemical, and physical parameters,
(2) the presence and distribution of radionuclides within these sites, and
(3) the performance of past packaging techniques and materials.
During the 1978 survey of the Atlantic 3800-meter radioactive waste
disposal site, sediments from this waste disposal site were collected with
a Soutar box corer to characterize the sediment geochemical properties and
to obtain information regarding the capabilities of sediment to act as a
natural barrier in the retention of radionuclides from the low-level
radioactive waste. Under Interagency Agreement Number EPA-79-D-H0706, the
U.S. Army Corps of Engineers, South Atlantic Division Laboratory, has
assisted the EPA Office of Radiation Programs in analyzing the sediment
samples using quantitative measurement techniques applicable to the
precise requirements of this survey. This report presents the results of
the laboratory analyses performed and considers the radionuclide retention
potential of the sediment.
The Agency invites all readers of this report to send any comments or
suggestions to Mr. David E. Janes, Director, Analysis and Support Division,
Office of Radiation Programs (ANR-461), Washington, D.C. 20460.
Glen L. Sjoblom, Dijrector
Office of Radiation Programs
111
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ACKNOWLEDGMENTS
The author wishes to thank Robert S. Dyer of the Office of Radiation
Programs, U.S. Environmental Protection Agency, for critical review of
this report and for the many helpful suggestions and discussions during
the course of this work.
The assistance of the U.S. Army Corps of Engineers, South Atlantic
Division Laboratory, personnel in performing the numerous tasks associated
with physical tests and x-ray diffractogram preparation is acknowledged
with thanks. Appreciation is especially extended to Mr. Ray Willingham
for his technical assistance in areas of petrographic and x-ray
diffraction testing.
The author also wishes to thank Dr. Kevin Beck of the Georgia
Institute of Technology for cation exchange capacity measurements and a
verification check on a clay mineralogy sample. Appreciation is also
extended to John Brown of the Georgia Institute of Technology, Engineering
Experiment Station, for the Scanning Electron Micrographs.
The critical review and comments provided by Dr. Charles E. Weaver of
Georgia Institute of Technology are gratefully acknowledged and
appreciated.
The assistance of Ms. Mary Anne Culliton for editorial review and
Ms. Sharon Scott and Ms. Marianne Bender of this office for typing is
gratefully acknowledged and appreciated. Appreciation is also extended to
Ms. Barbara Doyle for the drafting of charts and figures.
IV
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CONTENTS
Foreword ill
Acknowledgments iv
List of Tables vii
List of Figures viii
Summary ix
Introduction 1
Site Description 2
Field and Laboratory Methods 4
Sediment Sampling 4
Method of Analysis 4
Quantitative Mineral Analysis 5
Sediment Texture and Physical Properties 8
Sediment Composition 10
Introduction 10
Biogenous Materials 14
Terrigenous Materials 20
Clay Minerals 20
Chemical and Structural Configuration of Clay Minerals 22
General Considerations 22
Kaolinite 22
Illite 22
Montmorillonite 22
Chlorite 24
Size Considerations 24
Cation Exchange Capacity of Clay Minerals 24
Waste Form and Background Considerations 27
Waste Form 27
Natural Background Radiation 27
v
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CONTENTS (continued)
Distribution Coefficient (Kd) of Radionuclides 29
General 29
Factors Affecting Kd Values 29
Potential Radionuclide Retention 32
Introduction 32
Tritium, Carbon-14, and Iodine-129 32
Cesium-137 and Strontium-90 32
Cobalt-60 and Nickel-63 33
Technetium-99 33
Uranium-238 35
Transuranic Elements 35
Comparison with World Ocean Clay Suites 37
Conclusions and Recommendations 40
Conclusions 40
Recommendations 41
References 42
vi
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LIST OF TABLES
Page
Table 1.
Table 2.
Table 3.
Table 4.
Table 5,
Texture and Physical Properties of Sediment Samples
from the 3800-Meter Atlantic Nuclear Waste Disposal Site
Mineral Suite of Sand-Silt-Clay Size Fractions and
Average Sediment Composition from the 3800-Meter
Atlantic Nuclear Waste Disposal Site
Average Bulk Composition and Clay Mineral-Suite of
Sediment from the 3800-Meter Atlantic Site ....
Transparent Heavy-Mineral Suite of Sand-Size Sediment
from the 3800-Meter Atlantic Nuclear Waste Disposal Site
and Vicinity
Factors Affecting Sorption of Radionuclides of
Importance in Low-Level Radioactive Waste
11
12
19
30
vii
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LIST OF FIGURES
Page
Figure 1. Location of the Atlantic 3800-Meter Radioactive Waste
Dumpsite and Soutar Box Core Sediment Sample Locations . . 3
Figure 2. Percentage of Sand, Silt, and Clay in the Atlantic
3800-Meter Site Bottom Sediments 6
Figure 3. Percentage of Terrigenous, Biogenous, and Clay Minerals
in the 3800-Meter Site Bottom Sediments 13
Figure 4. Relative Mineral Distribution for Sand, Silt, and
Clay-Size Fractions of Contemporary Sediment from the
3800-Meter Atlantic Nuclear Waste Dumpsite 15
Figure 5. Sand Fraction of Sediment from the 3800-Meter Atlantic Site
Showing Typical Calcareous Foraminifera of Contemporary
Sediment (Top) and Sediment with Arenaceous Tubular Tests
of Foraminifera from Canyon Slump Claystone (Bottom) ... 16
Figure 6. Scanning Electron Micrograph (9500X) of Coccoliths
in Silt Fraction of Field Sample Number 8 at 3800-Meter
Atlantic Nuclear Waste Site 17
Figure 7. Scanning Electron Micrograph (2400X) of Radiolarian
in Silt Fraction of Field Sample Number 8 at the
3800-Meter Atlantic Nuclear Waste Site 18
Figure 8. Clay Mineralogy of the 3800-Meter Site Sediment Samples
and Probable Originating Source 21
Figure 9. Diagrammatic Sketch of Clay Minerals of the 3800-Meter
Atlantic Nuclear Waste Dumpsite 23
Figure 10. Relative Size of Clay Minerals as They Occur in Nature
and General Relationship to Adsorption 25
Figure 11. Distribution Coefficient (Kd) for Strontium and Cesium
on Minerals Typical of the 3800-Meter Atlantic Nuclear
Waste Dumpsite 34
Figure 12. Generalized Distribution of Clay-Mineral Suites in
Sediments of the World Ocean 38
viii
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SUMMARY
In June 1978, seven box core sediment samples were obtained from the
abandoned 3800-meter Atlantic low-level radioactive waste dumpsite. This
site is located approximately 320 km east of the New York coast in the
main axis of the Hudson submarine canyon. The sediments were charac-
terized for assessment of their potential to act as a natural barrier to
the migration of radionuclides.
An important first step in the sediment characterization is
delineation of the highly sorptive materials which are concentrated in the
fine fractions. A quantitative, state-of-the-art method was employed to
obtain an accurate assessment of the sorptive minerals. This method
combines the following: (1) textural grain-size accumulation curve;
(2) separate mineral evaluation of sand, silt, and clay-size fractions to
provide greater accuracy with x-ray diffraction; and (3) calculation of
average composition of minerals by the sum of the weighted average on
respective size fractions. The clay minerals, comprised of predominantly
illite and lesser amounts of chlorite, kaolinite, and montmorillonite are
the principal sorptive minerals of the 3800-meter site sediment. Two
samples, containing divergent physical characteristics and montmorillonite
as the dominant clay mineral, are believed to be slump block, Tertiary
age, sedimentary units from the canyon wall.
An approximation of potential radionuclide retention that might be
expected from the 3800-meter sediment can be calculated for cationic
radionuclide species in which the sorption distribution coefficient (Kd)
is known. Measured Kd values are known for cesium and strontium on pure
mineral phases of quartz, feldspar, mica, illite, kaolinite, and
montmorillonite, and approximations are made for chlorite and calcite.
Calculations made using these data for the 3800-meter sediments
approximate a Kd of 460 ml/g for cesium and 30 ml/g for strontium.
Sufficient data are not available for other radionuclides of interest.
However, approximations are made from similar Kd calculations with other
ocean sediments that closely match the environmental conditions (pH, Eh)
and chemical factors in the Atlantic 3800-meter nuclear waste dumpsite.
IX
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INTRODUCTION
The U.S. Environmental Protection Agency (EPA), in carrying out
Public Law 92-532, the Marine Protection Research and Sanctuaries Act, is
investigating abandoned nuclear waste dumpsites located in the Pacific and
Atlantic Oceans off the continental United States. The Atlantic 3800-meter
dumpsite, located approximately 320 km off the New York coast, was studied
in the summer of 1978. Sediment samples were recovered to characterize
the ability of the sediment to act as a natural barrier for the retention
of radionuclides. To assess this capability, quantitative techniques were
employed for precision in reporting the amount of sorptive minerals in the
sediment.
Korte, et al. (1976), have investigated the-relative mobility of
heavy metals and trace elements in soils. They conclude that determining
the percent clay in the soil is the most useful means of predicting
whether a soil will retain a particular element. Onishi, et al. (1981),
and other investigators, reporting on the mobility of radionuclides in
soil and ocean sediment, have also cited the importance of clay minerals,
as well as chemical factors, as they affect the retention of radionuclides.
The purpose of this paper is to present a quantitative mineral
evaluation technique to delineate the precise amount of the highly
sorptive clay minerals, as well as the lesser sorptive materials, in the
sediment of the 3800-meter Atlantic nuclear waste dumpsite and to evaluate
the potential of these clay minerals for retention of specific radio-
nuclides found in low-level radioactive waste.
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SITE DESCRIPTION
The 3800-meter Atlantic nuclear waste site is located approximately
320 kilometers off the New York coast and comprises an area of about
256 square kilometers (Figure 1). The area is centered at 37°50'N and
70°35'w. From 1957 to 1959, in excess of 14,500 drums of low-level
radioactive waste were dumped at this site (Dyer, 1976). This amounts to
approximately 40 percent of all waste dumped in the Atlantic (Holcomb,
1982). In 1962, the United States ceased ocean disposal practices, and
low-level radioactive waste is disposed of in shallow land burial sites on
the continent.
The 3800-meter site is physiographically part of the lower
continental rise in the region of the main axis of the Hudson Canyon
(Figure 1). During the 1978 site survey of this area, the submersible,
DSRV Alvin, was used to recover waste drums and to investigate the
physiographic and sediment conditions at the site. Hanselman and Ryan
(1983), from observations made aboard the DSRV Alvin, describe the canyon
floor as gently sloping and about one kilometer wide covered with
fine-grained sediment and local claystone slump blocks of various sizes
and shapes. Adjacent canyon walls rise from the canyon floor along
sloping-to-vertical surfaces to heights up to 200 meters in relief;
channel thalwegs in contact with channel walls apparently provide the
cutting mechanism that activates slumps or gravity slides (Hanselman and
Ryan, 1983).
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76°W
70°40'W
70°20'W
I 4000
LEGEND
CONTOURS IN METERS
SAMPLE LOCATIONS
h- 38° 00' N
- 3?o 50'N
- 37<> 40'N
- 37<> 30'N
-3800 Meter Site
Scale in Miles
0 20 40 60 80 100 120
76°W
70°
0 100 200
Scale in Kilometers
Depths in Fathoms
Figure 1. Location of the Atlantic 3800 m radioactive waste dumpsite
and Soutar boxcore sediment sample locations.
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FIELD AND LABORATORY METHODS
Sediment Sampling
In June 1978 the sediment samples from the 3800-meter site were
obtained by using the Soutar Box Corer from the SS Advance II. The bottom
sediment locations are depicted in Figure 1. Geographic coordinates of
the sample locations obtained by Loran navigational fix are listed as
follows:
Field Location 2 37° 50.83' N 70° 35.50' W
Field Location 3 37° 49.30' N 70° 36.71' W
Field Location 4 37° 45.03' N 70° 35.75' W
Field Location 5 37° 46.75' N 70° 34.01' W
Field Location 6 37° 54.65' N 70° 32.69' W
Field Location 7 37° 48.10' N 70° 37.11' W
Field Location 8 37° 49.79' N 70° 36.13' W
Field Location 15 37o 43.8!' N 7Qo 32.38' W
Plexiglass tube sub-cores were obtained as relatively undisturbed
samples from the large-volume Soutar Box Corer as soon as the sample
arrived on deck. The samples were visually inspected, and those selected
for sediment and physical property analysis were frozen in dry ice to
prevent physical or chemical change. Samples, numbered 5 and 7, appeared
more consolidated and desiccated with numerous bore holes from organisms
than the typical, plastic, less consolidated samples.
The frozen sediment samples were analyzed by the South Atlantic
Division Laboratory for physical, textural, and mineral properties.
Scanning electron micrograph (SEM) and cation exchange capacity (CEC)
sediment test samples were also delivered in frozen condition to the
Georgia Institute of Technology for analysis.
Method of Analysis
The sediments were examined for physical, chemical, and mineralogical
properties with special methodology employed to characterize selected
phases of the sediment for radionuclide retention. Radionuclide retention
factors will be described in detail in a later section.
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The cation exchange capacity was determined by a method similar to
that of Zaytseva, as described by Sayles and Mangelsdorf (1977). The
samples were squeezed into a stainless steel device, and the pore water
was collected and analyzed for Na+, K+, Mg++, and Ca++; the remaining
partially dewatered cake was split into two parts. One part was used for
determining the residual water content (110°C drying), and the other was
leached of residual seawater and exchange cations, using a succession of
washes (80 percent methanol, IN NH^Cl adjusted to pH 8 with NIfyOH).
The exchange cations were calculated by subtracting the seawater
contribution from the total leach solution. This procedure thus
circumvented the exchange cation-seawater reequilibrium (Donnan effect)
that occurs during the washing step which precedes the exchange in the
more traditional approach. The pH adjustment and the use of methanol
minimized the solution of CaCOg during leaching.
The grain-size analysis, bulk specific gravity, porosity, and
Atterberg Limits tests were performed in accordance with standard soil
testing procedures described by the U.S. Army Corps of Engineers (1970) in
EM-110-2-1906. In preparing the grain-size accumulation curve by the
sieve-hydrometer method, the clay-size- fraction is reported as that
material less than 2 micron size; the division between silt and sand-size
material occurs at the 50 micron size. Sediment' texture description is
based on the percentages of sand, silt, and clay-size fractions in
accordance with the nomenclature of Shepard (1954); this is depicted in
the ternary plot of Figure 2. In determining porosity, it was assumed
that no compaction occurred and that the sample volume, upon receipt in
the laboratory, was the same as the volume of the in situ sediment sample;
as such, the value obtained is considered reasonably accurate.
Quantitative Mineral Analysis
Several quantitative or semiquantitative techniques to identify clay
minerals have been described by Johns, et al. (1954), Schultz (1960),
Brindley (1961), Griffin and Goldberg (1963), Biscaye (1965), Neiheisel
and Weaver (1967), Devine (1972), and others. These methods and the
variables involved have also been evaluated by Gibbs (1968), Pierce and
Siegel (1969), and others. An understanding of the capabilities and
limitations of each of these methods enables one to design a method
applicable to the need. In this context, the method used in this
investigation builds upon established concepts, but its application
provides greater accuracy in the semiquantitative to quantitative results
derived.
The method employs separate x-ray diffraction analysis of
representative portions of both the silt and clay-size fractions to
eliminate some of the phases. With fewer phases, there is greater
accuracy in the analysis of the clay minerals for reasons inherent in the
x-ray diffraction procedure. The powder press mounting technique,
endorsed by Gibbs (1965), is used to eliminate errors due to segregation.
The resulting diffractograms are superior to those which combine the silt
and clay-size fractions, commonly referred to as "fines" by some
investigators; this is especially true where several phases are involved.
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Legend
- 3800 Meter Site
Field Location 7
Field Location 5
Field Location 3
Field Location 15
Field Location 8
Figure 2. Percentage of sand, silt, and clay in the Atlantic 3800 meter site bottom sediments.
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Fast x-ray diffraction scans and diagnostic tests (glycolation and
heat treatments at 300° c and 500° C) identify the clay-mineral suite
present by standard methods before determining the percent of clay minerals
from powder pre°ss samples. The more difficult separation of kaolinite and
chlorite is performed by the slow scan method after Biscaye (1964); the
peak height intensity of the kaolinite peak at 3.58A and the chlorite peak
at 3.54A are proportioned to determine their quantity represented in the
7.2A peak. The clay minerals in the clay-size fraction are then calculated
by the peak area method (Biscaye, 1965) or the peak height intensity method
on the diffractograms generated from the powder press mounted sample. The
calcite may be determined independently of the clay minerals on a separate
sample by the dilute acid leach (1:4 HC1) method.
The x-ray diffractograms of silt-size sediment contain predominantly
quartz, feldspar, and calcite, and minor aggregations of clay minerals.
While there are no quantitative methods to evaluate the percentages of
these minerals, reasonably accurate percentage evaluations exist in the
following:
(1) Determination of carbonate (calcite) by dilute acid leach
(1:4 HC1) of a separate representative sample.
(2) After a first estimate of quartz, feldspar, and minor other
minerals by peak intensity estimates, prepare laboratory mixtures
to duplicate the diffractogram such as described by Buck (1972).
The "best fit" matching diffractogram defines the percentages of
the admixture.
Again, precision is gained by eliminating the conflicting phases such as
occur if all size fractions were pulverized into one sample; a separate
silt-size diffractogram provides this advantage.
The sand-size fraction is analyzed by standard petrographic techniques
using at least a statistical 300 grain count. The calcite (biogenous)
fraction can be separated from the insoluble terrigenous fraction by dilute
acid (1:4 HC1) separation techniques.
The percentages of mineral composition are recorded for the sand,
silt, and clay-size fractions, and these are multiplied by the weighted
fractions of the grain-size accumulation curve. The sum of the various
components from each of the respective size fractions represents the
calculated percentages of each material in the total sample. The materials
may now be grouped into categories of low, medium, and high sorptive
materials.
The quantitative mineral method identifies the percentages of minerals
in relation to their radionuclide retention potential. This method
combines the following: (1) textural grain-size accumulation curve;
(2) separate mineral evaluation of sand, silt, and clay-size fractions to
provide fewest phases for greatest accuracy with x-ray diffraction; and
(3) calculation of average composition of minerals by the sum of the
weighted average on respective size fractions. The grouping of sorptive
minerals will be described in later sections.
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SEDIMENT TEXTURE AND PHYSICAL PROPERTIES
Sediment samples of the 3800-meter Atlantic waste dumpsite consist of
olive grey to brown-colored fine-grained, clayey silt comprising the
canyon floor and compact silty-clay and clays tone samples, possibly
derived from canyon or slump blocks from the canyon wall. This sediment
description is based on the percentages of sand, silt, and clay-size
fractions (Figure 2). The weight percent of the respective size fractions
is obtained from the grain-size accumulation curve. As shown in Table 1,
a comparison of the average texture between the top and bottom portions of
the cores show that it is relatively uniform throughout the entire
vertical length of each core. This is also reflected in the phi units for
the median and standard deviation of the sediment samples (Table 1).
Field samples 5 and especially 7, of probable canyon wall origin, show the
most deviation from the standard (Table 1).
The bulk density and porosity were measured on five of the more
typical sediment samples (Table 1). The bulk density ranges between
1.38 g/cm3 and 1.55 g/cm^ and the porosity between 0.67 and 0.76.
These parameters are used along with the distribution coefficient (Kd) of
a radionuclide of interest to determine the retardation factor of a
radionuclide in sediment, as will be considered in a later section.
The Atterberg Limits are relatively inexpensive parameters to reflect
upon the uniformity of the sediment properties. They are useful in
describing quantitatively the effect of varying water content on the
consistency of fine-grained sediments. The boundaries are defined by the
water content which produces a specified consistency. The liquid limit
(LL) defines the water content at which" the sediment closes with standard
mechanical manipulation, and the plastic limit (PL) is the water content
at which the sediment begins to crumble or break apart. The difference
between the plastic and liquid limits, termed the plasticity index (PI),
represents the range in water contents through which the sediment is in a
plastic state and is inversely proportional to the ease with which water
passes through the sediment. The liquid limit is especially diagnostic in
that the clayey-silt sediments have a relatively narrow range between 72
and 88, whereas the two silty-clay sediments, samples 5 and 7 (probably
canyon wall materials), have values of 94 and 100 (Table 1). This
correlation is as significant for mineral composition as it is for
texture, as will be shown in a later section.
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Table 1. Texture and Physical Properties of Sediment Samples
from the 3800 Meter Atlantic Nuclear Waste Disposal Site
Sample
No-
2
3
3
4
4
VO
5
6
6
7
8
8
15
15
Depth
(cm)
10-20
0-26
26-40
0-26
26-40
0-13
0-26
26-40
0-18
0-26
26-40
0-26
26-40
Percent Dry Weight
Sand Silt Clay
3
3
3
3
4
4
8
7
2
5
5
2
2
48
50
50
49
49
48
51
52
36
50
52
52
53
49
47
47
48
47
48
41
41
62
45
43
46
45
Phi
Median
8.9
8.8
8.6
8.5
8.7
8.8
8.2
8.3
9.2
8.2
8.3
8.8
8.5
Units Bulk Density
Std. Dev. g/cm3
3.6
3.3 1.55
3.7
3.5 1.50
3.3
2.8
3.1 1.38
3.9
2.2
3.2 1.39
3.1
3.6 1.44
3.5
Atterberg
Porosity Limits
LL PL PI
82
0.67 85
86
0.69 83
88
94
0.70 78
72
100
0.76 85
85
0.71 81
78
44
37
45
43
36
40
36
36
41
34
34
41
37
38
48
41
40
52
54
42
36
59
51
51
40
41
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SEDIMENT COMPOSITION
Introduction
The sediment composition in this investigation was determined by a
methodology designed for specific assessment of the highly sorptive
minerals capable of radionuclide retention. The methodology builds upon
established practices, but is more refined in (1) determination of mineral
composition on separate sand, silt, and clay-size fractions for greater
accuracy in the fewer phases involved, (2) requirement of a texture
grain-size accumulation curve to calculate the weighted average of mineral
species within each size fraction, and (3) calculation of the percent of
each mineral species in the total sample. The most highly sorbent
minerals are the clay minerals which occur in the smaller grain-size
fractions, and the least sorbent phases occur in the larger grain-size
materials. The biogenous materials occupy a position somewhere between
these extremes as will be considered in more detail in a later section.
Mineral composition of the various size fractions and the calculated
amount in the total sample are listed in Table 2. The weight percent of
sand, silt, and clay-size fractions used to calculate the weighted average
shown in column D of Table 2 are listed in Table 1. Each of the percen-
tages of respective materials for the sand-size fraction (column A),
silt-size fraction (column B), and clay-size fraction (column C) listed in
Table 2 may also be used to reflect on the differences between the older
slump material from the canyon wall and contemporary sediment. For
example, note the high representation of quartz in the sand-size fraction
of field sample 5 (40%) and field sample 7 (27%) as compared to the quartz
in the sand-size of the other field samples (3 to 14%); in these same
samples, note the relatively low carbonate content of the sand-size of
field samples 5 and 7 (10%) as compared to 80 to 94% carbonate in the
other field samples. These and other comparisons of physical and chemical
factors enable deduction of slump materials from the contemporary
sediments of the Hudson canyon floor. Mineral composition of individual
clay mineral species is listed in Table 3. Mineral groupings, applicable
to radionuclide retention, are also listed in Table 3 as terrigenous,
biogenous, and clay minerals; these are depicted in the ternary plot of
Figure 3. Each of these groupings will be considered in the following
sections.
10
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Table 2. Mineral Suite of Sand-Silt-Clay Size Fractions and Average
Sediment Composition from the 3800 Meter Atlantic Nuclear Waste Disposal Site
Sample Depth Lab. Carbonate Quartz Feldspar Mica Clay Minerals Misc.
No. (cm) No. ABCD ABCDABCDABCDABCDABC
2
3
3
4
4
5
6
6
7
8
8
15
15
0-20
0-26
26-40
0-26
26-40
0-13
0-26
26-40
0-18
0-26
26-40
0-26
26-40
102
74-75
76
77-78
79
80
81-82
83
84
85-86
87
88-89
90
94 36 44 42
80 31 46 40
80 39 41 40
91 29 45 39
95 37 47 44
10 30 25 27
90 37 46 45
84 37 40 42
10 8 21 16
80 43 39 44
80 47 36 42
80 40 48 43
85 35 35 37
3 35 17
12 44 22
12 30 15
5 36 18
4 35 17
40 40 -- 21
6 45 23
10 39 21
27 60 22
13 37 17
12 38 16
14 36 19
10 35 17
1 12 6
4 14 7
4 15 8
2 7 4
1 10 5
8 12 6
3 8 4
4 8 4
8 10 4
4 8 4
5 6-3
4 9 5
3 11 6
1 11 5
27 4
2 10 5
1 18 -- 9
TR 13 7
2 12 6
18 4
1 11 -- 6
5 17 6
17 4
16-3
1 10 5
2 18 9
5 55 29
3 54 27
5 59 30
7 55 30
4 53 27
3 80 40
2 55 24
5 60 27
5 79 52
4 61 30
3 65 35
4 52 28
5 65 31
1 1 TR
2 1 TR
2 1 TR
1 1 TR
TR TR TR
40 TR TR
TR TR TR
1 TR TR
50 TR TR
2 1 TR
2 1 TR
1 1 TR
1 1 TR
Notes: 1 A = Sand-Size Fraction; B = Silt-Size Fraction; C = Clay-Size Fraction; D = Weighted Average
2 Clay minerals are illite, kaolinite, chlorite, montmorillonite and minor other (See Table 4).
3 Miscellaneous includes heavy minerals, pyrite.giauconite.radiolarians, diatoms, and minor other;
Field samples 5 and 7 contain appreciable pyrite in miscellaneous fraction.
TR present only in trace amounts.
-------
Table 3. Average Bulk Composition and Clay Mineral Suite of
Sediment from 3800-Meter Atlantic Site
Average Bulk Composition
Clay Mineral Fraction
Field
Sample
Number
3
4
5
6
7
8
15
Biogenous
Materials
40
42
27
43
16
43
40
Terrigenous
Materials
31
29
33
32
32
24
31
Clay
Minerals
29
29
40
25
52
23
29
Illite
53
51
30
47
5
53
53
Kaolinite
19
24
10
13
9
10
18
Chlorite
10
10
10
7
3
10
8
Montmor-
illonite
18
15
50
33
83
27
21
Notes: 1. Average bulk composition materials are depicted in triangular plot of Figure 3.
2. Average clay minerals are depicted in triangular plot of Figure 7.
-------
Biogenous Materials
Terrigenous
Materials
LEGEND
- 3800 Meter Site
Clay
Minerals
Figure 3. Percentage of terrigenous, biogenous, and clay minerals
in the 3800 meter site bottom sediments.
13
-------
Biogenous Materials
Biogenous materials, originating from hard parts (calcareous,
siliceous) secreted by microorganisms, comprise 40 to 43 percent of the
contemporary sediment and 16 to 27 percent of the canyon wall slump
material analyzed (Figure 3). The biogenous material is comprised
predominantly of calcareous foraminifera and coccoliths and very minor
siliceous radiolarian and diatom tests. The textural relationship of the
various biogenous groups is depicted in Figure 4. As a result of
foraminifera abundance in the larger size fractions and coccoliths in the
fines, calcite is similar in distribution on all size fractions, with the
greatest abundance in the sand-size, as depicted in Figure 4.
The calcareous foraminifera comprise from 80 to 94 percent of the
sand-size fraction which constitutes 2 to 7 percent of the contemporary
sediment. The foraminifera of the contemporary sediment are calcareous
and comprised predominantly of Globigerina (Figure 5), whereas arenaceous
tubular foraminifera occur in relative abundance in the slump block
material comprising samples 5 and 7 (Figure 5). Some of the tubules
contain appreciable pyrite replacement which oxidizes readily to red iron
oxide when exposed to the atmosphere. The striking difference in faunal
biogenic material in field samples 5 and 7 compared to contemporary
sediment is highly significant when combined with clay mineral composition
and other physical parameters in relating this material to a slump source
from the canyon wall.
The calcareous coccoliths range from middle silt-size into clay-size
as depicted in Figure 4. The scanning electron micrograph of Figure 6
illustrates the morphology of typical coccoliths in the silt-size
fraction. The coccoliths comprise the major portion of the total
carbonate reported for the average sample (Table 2); calcareous
foraminifera dominate the sand-size and upper-silt size materials
(Table 4), but the weight percent as regards total sample is less.
Siliceous radiolarian and diatom tests are restricted to the sand and
upper-silt size sediment and occur in very subordinate amounts (generally
less than one percent) in these sediment fractions (Figure 4). A scanning
electron micrograph of a radiolarian from field sample number 8 is
depicted in Figure 7.
The general increase of biogenous materials in a seaward direction
from the upper to the lower continental slope is apparent if one compares
the average 30 percent reported by Neiheisel (1979) for the 2800-meter
site with the 42 percent at the 3800-meter site. This also corroborates
the observations of Turekian (1971) regarding the general gradual decrease
in calcium carbonate with increasing depth until about 4,500 meters; at
4,500 meters, the calcium carbonate goes into solution..
14
-------
TEXTURE - MINERAL DISTRIBUTION - 3800 METER SITE
500
v>
o
3E
V)
O
tr
u
100
10
2
N
u
I 1
BIOGENOUS MATERIALS
TERRIGENOUS MATERIALS
CLAY MINERAL SUITE
LEGEND
RELATIVE PERCENT WITHIN SAND,
SILT, AND CLAY SIZE FRACTIONS
M
t/i
o
50
I
100
= E
V)
u
1
Figure 4. Relative mineral distribution for sand, silt, and clay-size fractions of contemporary
sediment from the 3800 meter Atlantic nuclear waste dumpsite.
-------
FIELD LOCATION 4
FIELD LOCATION 7
Figure 5. Photomicrograph (10x) of sand fraction from 3800 meter Atlantic site
showing typical calcareous foraminifera of contemporary sediment (top)
and sediment with arenaceous tubular tests of foraminifera from canyon
slump claystone (bottom).
16
-------
Figure 6. Scanning electron micrograph (9500 X) of coccoliths in silt fraction
of field sample number 8 at 3800 meter Atlantic nuclear waste site.
17
-------
Figure 7. Scanning electron micrograph (2400 X) of radiolarian in silt fraction
of field sample number 8 at the 3800 meter Atlantic nuclear waste site.
18
-------
Table 4. Transparent Heavy-Mineral Suite of Sand-Size Sediment
from the 3800-Meter Atlantic Nuclear Waste Disposal Site and Vicinity
Sample Number
Lab No.
Amphibole/Pyroxene
Garnet
Staurolite
Epidote Group
Zircon
Sillimanite
Kyanite
Rutile
Tourmaline
Monazite
Other (apatite, etc.)
2
102
42
29
5
7
4
5
2
TR
4
1
1
3
74-76
Percent
56
10
2
10
7
6
TR
1
6
1
1
4
77-79
5
80
Transparent
52
18
3
10
5
2
2
1
4
1
1
43
20
3
12
5
8
2
TR
5
1
1
6
81-83
7
84
Heavy-Mineral
31
30
6
9
7
8
2
1
4
1
1
38
18
3
14
5
14
4
TR
2
1
1
8
85-87
Fraction
52
14
2
9
7
6
2
1
5
1
1
15
88-90
55
10
2
18
5
3
1
1
3
1
1
19
-------
Terrigenous Materials
Terrigenous material, as used in the sediment grouping, includes all
other materials except the biogenous materials and the clay mineral
species. The terrigenous materials comprise from 24 to 33 percent of the
sediment (Table 3). These materials, in order of abundance, are quartz,
feldspar, mica (biotite, muscovite, and chlorite), and less than one
percent consists of minor detrital heavy minerals and glauconite. The
terrigenous materials are shown to occur most abundantly in the silt-size
fraction and to a lesser degree in the sand-size fraction (Figure 4).
Most of this material probably originates from the continental shelf area
off the New York Bight and is funneled down the Hudson Canyon by turbidity
currents, while another minor contributing source is probably from
southerly flowing countour currents (Keller and Shepard, 1978).
Clay Minerals
The clay minerals comprise 23 to 29 percent of the contemporary
sediment and 40 to 50 percent of the canyon slump material. The clay
minerals and the calcareous coccoliths constitute the major materials of
the clay-size fraction (Figure 4). Some aggregates of clay particles also
occur in the silt-size fraction (Table 2). The proportional amount of
clay mineral species is depicted graphically in the ternary plot of
Figure 8 and listed for individual species in Table 3.
The clay-mineral suite of the contemporary sediment consists of
illite (51-53 percent), kaolinite (10-24 percent), chlorite (7-10 percent),
montmorillonite (15-27 percent), and other minerals in very minor amounts
(Table 3). In the ternary diagram of clay minerals shown in Figure 8, the
kaolinite and chlorite are combined since these two clay minerals are
generally similar in sorptive properties and are the most difficult to
separate on x-ray diffractograms. The clay-mineral suite of the probable
Tertiary age canyon wall sediment, consisting predominantly of
montmorillonite, is observed to be markedly divergent on the ternary
diagram of Figure 8.
The distribution of the clay minerals and the characterized
clay-mineral suite for the lower portion of the continental rise
containing the 3800-meter site is in general agreement with the broader
projections suggested by Hathaway (1972). The montmorillonite-rich,
clay-mineral suite of the canyon wall slump material is also in proportions
that correlate with Tertiary sediments of probable Miocene age from the
formations comprising the canyon wall. The amount of montmorillonite
reported in the sediment of the 2800-meter site situated on the upper
continental rise between the Hudson and Wilmington Submarine Canyons
(Neiheisel, 1979) is considerably less than that comprising the
contemporary sediment of the 3800-meter site. This suggests that a
significant portion of the montmorillonite found in the contemporary
sediment may be derived from erosion of the canyon wall. The high illite,
chlorite, and kaolinite appear more related to the clay-mineral suite of
the glacial sediments which cover the adjacent continental shelf area.
20
-------
Kaolinite & Chlorite
LEGEND
Contemporary
Sediment
A Slump from
Canyon Wall
Illite
Montmorillonite
Figure 8. Clay mineralogy of the 3800 meter site sediment samples and probable originating source.
21
-------
CHEMICAL AND STRUCTURAL CONFIGURATION OF CLAY MINERALS
General Considerations
In order to consider some of the physicochemical relations associated
with the relatively high radionuclide retention by clay minerals, it is
necessary to have a general concept of the chemical and structural makeup
of the clay-mineral suite of the 3800-meter site. The following informa-
tion is presented for those readers having little familiarity with clay
minerals.
The clay minerals are comprised of thin sheet-like structures as
depicted in Figure 9. The tetrahedral layer is comprised of units of
silica tetrahedrons, with each unit consisting of one silicon atom
equidistant from four oxygen or hydroxyl atoms. The tetrahedral layer,
made up of these units, are arranged in a sheet-like hexagonal network
(Figure 9). The octahedral layer consists of units made up of an
aluminum, iron, or magnesium atom equidistant from six oxygen or hydroxyl
atoms. As depicted in Figure 9, the units form sheet-like layers by
sharing of oxygen atoms between adjacent octahedrons.
Kaolinite
The varieties of clay minerals are a result of the number of
tetrahedral and octahedral layers and associated cations. As
diagrammatically shown in Figure 9, kaolinite is made up of one
tetrahedral sheet and one octahedral sheet; the thickness of the
structural unit is seven angstrom units (Figure 9).
Illite
Illite consists of one octahedral sheet between two tetrahedral
sheets with the entire structural unit ten angstroms thick (Figure 9).
The potassium ion (K+), fixed to the illite, does not add much thickness
to the illite because it fits into the hexagonal hole in the top of the
tetrahedral layer; this will be an important consideration in a later
section regarding radionuclide retention potential.
Montmorillonite
^The montmorillonite clay has a similar structural layering as illite,
but in addition has one to two layers of water between tetrahedral sheets,
with thickness depending on the variety of cationic species in the water
interlayer (Figure 9). With the cation interlayer comprised predominantly
22
-------
T
KAOLINITE
) -
c
CHLORITE
MONTMORILLONITE
EXPLANATION
= TETRAHEDRAL LAYER
= OCTAHEDRAL LAYER
KEY.
OXYGEN OR HYDROXYL
O ALUMINUM, IRON
OR MAGNESIUM
SILICON
Figure 9. Diagrammatic sketch of clay minerals of the 3800 meter Atlantic nuclear waste dumpsite.
23
-------
of Na+, the thickness of montmorillonite is 12 angstrom units. With Ca++
predominant in the interlayer, the structural thickness is 14 angstrom
units thick (Figure 9). In ocean sediment, montmorillonite occurs with
multiple layers. Ethylene glycol used in laboratory tests also swells the
interlayer to a maximum structural thickness of 17.5 angstrom units for
montmorillonite. Because of the interlayer accumulation of cations (H+,
Mg-H-, Ca++, Na+, K+) and other factors of instability, montmorillonite has
a higher cation exchange capacity and sorption potential for radionuclides
than any of the other clay species.
Chlorite
The chlorite clay structure consists of two tetrahedral layers
alternating with two octahedral layers (Figure 9). The structural
thickness of chlorite is 14 angstrom units thick and matches that of the
more common montmorillonite. However, the ability of ethylene glycol to
displace the water layer in montmorillonite and increase the interlayer
thickness to 17.5 angstrom units while the chlorite structure remains
fixed at 14 angstrom units facilitates identification by x-ray diffraction
analysis. Some chlorite varieties contain Mg++ and others Fe++ in the
octahedral layer, which also affects the behavior of this mineral in
relation to solubility and heat treatments. The magnesium chlorite is
generally more stable than the iron chlorite varieties.
Size Considerations
The clay minerals in ocean sediments range in size from 2 microns to
less than 0.1 microns in diameter. Average diameters in decreasing size
for three common clay mineral varieties are depicted in Figure 10;
kaolinite averages 1 micron diameter, illite averages 0.3 microns
diameter, and montmorillonite 0.1 microns diameter (Krone, 1972). Clay
minerals also occur in silt-size as aggregated particles in the ocean
sediment; however, their presence is relatively minor in this size
fraction (Figure 4 and Table 2). In general, the sorption potential of
the clay minerals increases with increasing surface area, i.e., with
decreasing diameters. The increased sorption with decreasing diameters is
probably more related to the mineral structures and ionic bonding than any
other factor.
Cation Exchange Capacity of Clay Minerals
In an important study of the behavior of trace element movement in
soils, Korte, et al. (1976), concluded that knowledge of cation exchange
capacity (CEC) does not improve the ability to predict the movement of
ions through the natural soils. They state that the percentage of clay in
the soil stands out as the most useful means of predicting whether a soil
will retain a particular element. Surface area and the percentage of free
iron oxides provide the next best correlation after the clay fraction.
24
-------
.t
a.
cc
s
CO
TJ
CO
111
cc
O
z
111
cc
UJ
O
cc
CO
O
z
CO
HI
cc
O
z
0.1 U+l I
, , * -0011-1
(4-0.1 Jl+l
c. MONTMORILLONITE
b. ILLITE
0.3
1H
0.1 [I
a. KAOLINITE
Figure 10. Relative size of clay minerals as they occur in nature
and general relationships to adsorption.
-------
Radionuclides probably behave somewhat similar to some of the trace
elements studied by Korte, et al. (1976), but the chemical environment in
the marine sediments differs in that there is less divergence in pH but a
marked change in Eh (redox) from oxidizing to reducing conditions over a
few feet of sediment depth. The percentage of the element Mn in marine
sediments is as important as the percentage of free iron oxides is to the
soils. The role of cation exchange is probably similar in being of
generally less significance in predicting radionuclide behavior than the
determination of sorptive minerals and other chemical factors.
The cation exchange capacity, however, may be used as a correlation
to clay mineral composition. The CEC is expressed in milliequivalents
per 100 grams, and the general range of CEC for the clay minerals
reported by several investigators for estuarine and marine sediments are:
kaolinite 3-15; chlorite 10-40; illite 10-40; montmorillonite 80-150. The
cation exchange capacity for sediment samples at the 3800-meter Atlantic
site varies between 30.0 and 35.1 meq/100 g for the contemporary samples
and 43.8 meq/100 g for sample number 7. The higher cation exchange
capacity correlates with the higher montmorillonite clay occurrence in
this sample.
26
-------
WASTE FORM AND BACKGROUND CONSIDERATIONS
Waste Form
A waste form is a monolithic free-standing solid resulting from the
incorporation of the low-level radioactive waste (LLW) into a matrix
material which, in this case for the 3800-meter dumpsite, was concrete
(Columbo, et al., 1982). The low-level radioactive waste discharged to
the 3800-meter site contained both naturally occurring and man-made
radionuclides. Many of the radionuclides in the waste form are
short-lived and are not of long-term radiological concern. Three criteria
used to identify radionuclides of concern are (1) half-life more than
five years, (2) presence in comparatively significant quantities, and
(3) biological toxicity (Wild, et al., 1981). Radioisotopes that meet one
or more of these criteria are tritium, carbon-14, cobalt-60, nickel-59 and
63, strontium-90, niobium-94, technetium-99, iodine-129, cesium-135 and
137, uranium-235 and 238, neptunium-237, plutonium-238, 239, 240, and 241,
americium-241 and 243, and curium-243 and 244 (Wild, et al., 1981). These
radioisotopes will be considered in relation to factors affecting sorption
by the sediment in a later section.
Natural Background Radiation
If one conducts an investigation to determine the radionuclides
released from radioactive waste and retained by the sediment, it is
necessary to first obtain background data. Sediment samples, free of
waste release, must be analyzed for (1) the presence of naturally
occurring radionuclides, and (2) elements that are isotopes of the
radionuclides of interest. Since site specific samples are measured in
the laboratory, it is necessary to determine the "blank." Gillham, et al.
(1980), has shown that retardation of Cs-137 in hydrologic systems can be
governed by the concentration of natural exchangeable cesium that occurs
in the system, and that in order for laboratory distribution coefficient
(Kd) values to provide an accurate representation of the field retardation
potential, the total exchangeable cesium concentration in the batch test
must duplicate the field condition. Nonradioactive isotopes of
radionuclides of interest must therefore be determined in the site
specific sediments for an accurate assessment of the distribution
coefficient.
27
-------
At the 3800-meter site, the natural background radiation can be
estimated by use of the quantitative mineral evaluation. As Joseph,
et al. (1971), and other investigators point out, the source of
radioactivity in ocean sediment is primarily from the radioactive
materials occurring in .the minerals of the sediment. Cosmic rays and
radioactivity from atmospheric testing programs, however, while of lesser
significance, are also part of the background radiation.
The naturally occurring radionuclide responsible for the major
portion of the background radiation is undoubtedly potassium-40. The K-40
occurs in the following minerals at the 3800-meter waste site: K-feldspar,
muscovite (mica), illite, montmorillonite, glauconite, and hornblende.
Since K-feldspar comprises the major portion of the feldspar listed in
Table 2, this source averages about 3 percent of the sediment. Illite
clay mineral comprises approximately one-sixth of the sediment by volume
and represents the largest source of K-40. Muscovite (least abundant of
the mica group) approximates one percent of the total sediment. Both
glauconite and hornblende occur in trace amounts (less than 0.5 percent)
in the sediment. Thus, at least one-fifth of the total sediment by volume
at the 3800-meter site contains K-40 as a primary constituent of the
minerals comprising the sediment.
The minerals, zircon and monazite, reported in fractional amounts of
the heavy-mineral suite (Table 4) contain naturally occurring radio-
nuclides of uranium and thorium. These minerals, of terrigenous origin,
are found only in the upper silt and sand-size fractions. Their amount as
regards total sample is estimated at a fraction of one percent (trace
'amounts). Zircon contains both uranium and thorium which replace
zirconium in the mineral structure (Berry and Mason, 1959). Monazite
contains thorium in variable amounts in the range between 2 and 40 percent
of the mineral composition (Berry and Mason, 1959). The amount of
radiation from these two minerals is estimated at probably less than
10 percent of the background radiation in the sediment. The major
radiation source is the potassium-40 as previously stated.
28
-------
DISTRIBUTION COEFFICIENT (Kd) OF RADIONUCLIDES
General
The ocean sediments have the capacity to sorb radionuclides from the
leachate derived from the waste form with the amount dependent on the
mineral composition and chemical factors of the sediment environment. The
clay minerals are the most effective materials in the sediment for
sorption of most radionuclides; however, it will be shown that other
chemical factors may also control sorption.
A measure of sorptive behavior of a radionuclide under a specific set
of conditions can be expressed as a distribution coefficient (Kd). The Kd
is defined as the ratio of specific activity in the sediment phase to that
in the liquid phase for the radionuclide of interest (Pietrzak, et al.,
1981).
_ sediment activity/weight of sediment
liquid activity/volume of liquid
The distribution coefficients (Kd) of radionuclides obtained from
laboratory measurements are the most accepted means of quantifying the
radionuclide retention in a geologic media (Gillham, et al., 1980). While
more than 5,000 experiments exist on measured Kd values for various
radionuclides of the continents, few Kd measurements exist for ocean
sediment. Those that have been reported for specific radionuclides in
ocean sediment will be considered in a later section.
Factors Affecting Kd Values
In addition to the percent clay mineral fraction present in the
sediment, several other factors inherent with the sediment and water
phases of the ocean environment affect the Kd values of radionuclides.
These factors include type and quantity of sorptive minerals, pH, Eh
(oxidizing-reduction potential), surface area, complexing ligands and
organics, amorphous oxides, cation exchange capacity, and competing ions.
Onishi, et al. (1981), has reviewed a number of elements and the probable
factors most strongly affecting their sorption in geologic media. Some of
these factors are listed in Table 5 for the various radionuclides
considered of importance in low level radioactive waste. These factors
are presented in a general manner here and will be related to specific
radionuclides in a later section. The method of determining type and
quantity of sorptive minerals has been presented in earlier sections.
29
-------
Table 5. Factors Affecting Sorption of Radionuclides of Importance
in Low-Level Radioactive Waste
(Modified after Onishi, et al., 1981)
Element
H3
14
C
129
I
*Tc"
Sr90
137
Cs1
Co60
Ni63
*U238
*Np
239
*Pu
241
A * ' *
Am
Cm243
_pj_ Eh
_ .
X
X
X X
X X
X X
X
X X
X
X
Sorptive Competing
CEC2 Minerals Ions
__
-
_ _ _
XX X
XX
- X
- X
- X
_
XX
XX X
- X
Inorganic
Ligands
.
X
X
-
X
X
X
X
X
Complex Ions
Organic
Constituents
.
X
X
X
X
X
-
X
-
X
~
Colloid3
Formation Probable Sorption Mechanisms
- None
- None
None
- Unknown
Ion Exchange
Ion Exchange
X Ibn Exchange, 2PPT,
X Ion Exchange, PPT,
PPT, Ion Exchange
X Unknown (PPT)
X Ion Exchange, PPT
Ion Exchange, PPT
X PPT
2OX
OX
* Most dependent on oxidation-reduction condition.
Notes
'Radionuclides listed are present in significant quantifies in LLW and have a half-life greater than
5 years (after Wild, et al., 1981).
2CEC = Cation Exchange Capacity; PPT = precipitation; OX = oxide.
3The controlling sorption mechanism for colloid is precipitation.
-------
The pH and Eh of the in situ ocean sediment are important factors
regarding the stability of a radionuclide. The pH is important in
controlling the solubility of many of the radionuclides, but this factor
is less variable in the marine sediments than the continental deposits.
The Eh is more variable in changing from an oxidizing environment in the
first several centimeters of sediment to reducing below that depth for
many parts of the ocean (Talbert, 1982). The pH and Eh were measured on a
sediment from a depth of 2500 meters at a site located on the upper
continental rise off the coast of Maine. These measurements by Schmidt
(1979) indicated that the sediments were well oxygenated throughout the
first 0.6 meters of the sediment, after which reducing conditions occur
through depth. Similar conditions probably prevail at the 3800-meter
Atlantic site. As indicated in Table 5, the radionuclides most strongly
affected by the Eh are Tc, Np, U, and Pu which are rendered immobile in
the reducing environment but have little retention in the oxidizing
environment. Nickel and cobalt tend to be affected by Eh in their
relationship to the presence of Mn and Fe, respectively; both Mn and Fe
precipitate as hydrous oxides in oxygenated conditions and coprecipitate
the Co and Ni. Jenne (1976) cites convincing evidence in which electron
probe measurements of oceanic manganese nodules show nickel occurring in
manganese bands and cobalt predominantly in iron rich areas. Schmidt
(1979) reports manganese from the 2500-meter Atlantic site as the most
mobile of the metals in the deep-sea sediments, with Mn precipitating near
the surface due to oxidation following diffusive transport from deeper
layers. Phase diagrams have also been assembled which are used to depict
the mineral or solid phase form which will most likely prevail under a set
of pH and Eh conditions; such stability field diagrams, however, should be
used with caution since they contain many limitations.
The factors listed in Table 5 will be used as a guide in the
discussion of the probable mechanisms affecting sorption. This list,
modified after Onishi, et al. (1981), examines all the factors reported
for each element, and a deduction is made as regards the probable
principal sorption mechanism. A sorption sensitivity to cation exchange
capacity, competing ions, and pH may indicate an ion exchange sorption
mechanism such as shown for strontium (Table 5). Precipitation is
probably the control mechanism for nickel and cobalt as coprecipitates
with Mn and Fe oxides. Neptunium and plutonium in reducing conditions and
curium may also be controlled by precipitation (Table 5). If the Eh
environment allows it, Pu(IV) can be oxidized to Pu(V) or (VI), with
precipitation or much lower plutonium sorption values resulting;
additional investigation is required to determine if neptunium can be
reduced to much less soluble Np(IV) forms by reducing sediments or if
curium precipitation is the sorption control mechanism (Onishi, et al.,
1981). The probable Kd that might be predicted for the 3800-meter site
sediment will be based on the quantitative mineralogy and the chemical
factors which affect the sorption mechanisms.
31
-------
POTENTIAL RADIONUCLIDE RETENTION
Introduction
The potential radionuclide retention by the sediment of the 3800-meter
site will be assessed for the radionuclides of concern in the low-level
radioactive waste. The prediction is based on the concept of a diffusion
release to a physical setting experiencing minimal sediment transport. The
pH and Eh of the sediment in the absence of measured values will be
considered to be similar to that existing on the adjacent continental rise
at 2500-meter depth described by Schmidt (1979).
The sediment can only be an effective barrier if the drums containing
the waste are surrounded by sediment. Leakage from any exposed area of the
drum would "short circuit" the sediment trap by moving directly into the
water column. Bioturbation could also "short circuit" radionuclide
retention. This assessment of radionuclide retention considers the drum
surrounded by sediment with no "short circuit" mechanisms in operation.
Only the radionuclides considered important by virtue of greater than
five-year half-life, abundance, and toxic nature are considered in this
assessment.
Tritium, Carbon-14, and Iodine-129
Most investigators agree that tritium substitutes readily for the
hydrogen in water and is not sorbed to any significant degree by sediment.
The distribution coefficient (Kd) for tritium at the 3800-meter site would
thus be close to zero. Any release of carbon-14 to the sediment would
likewise result in transfer to the interstitial water system to form, most
probably, a bicarbonate ion. The Kd for C-14 would probably be zero.
Iodine-129 would also have minimal retention (probably zero), although
under other circumstances it could combine with organic matter (Table 5).
Cesium-137 and Strontium-90
A considerable range of Kd values over orders of magnitude have been
reported by numerous investigators for both cesium and strontium. The
average Kd reported for cesium and strontium in saltwater is, respectively,
300 and 50 (Onishi, et al., 1981). Considering the fact that the most
likely control mechanism affecting sorption may be ion exchange, the
quantity and type of sorptive minerals could be profitably used to provide
an approximation of the distribution coefficient of both Cs and Sr at the
3800-meter site.
32
-------
The distribution coefficients (Kd) of cesium and strontium have been
determined for pure mineral phases (Ames and Rai, 1979). Most of the Kd
values for the common terrigenous minerals of sand and silt-size are on the
order of 0-15, whereas clay minerals range from 15-4900 (Figure 11). In
the absence of measured Kd values on pure phases of marine calcareous
biogenous materials, the values reported for the Yucca Flat limestone by
Norke and Fenske (1970) are used: a Kd of 0.2 for strontium and 13.5 for
cesium thus approximates the biogenous carbonate fraction of the 3800-meter
site. The Kd of chlorite is also considered to be similar to kaolinite for
the purposes of this assessment of Cs and Sr retention.
The potential Kd values for strontium-90 and cesium-137 in the
3800-meter site contemporary sediment samples are calculated by multiplying
the mineral percentages listed in Tables 2 and 3 by the Kd value of
individual minerals in Figure 11. The resultant calculated values predict
the following Kd for the contemporary sediment of the 3800-meter site:
Kd (ml/g)
Strontium-90 30
Cesium-137 460
These values compare favorably with average measured values from
saltwater sediments reported by Onishi, et al. (1981), who has reported an
average Kd of 50 for strontium and a Kd value of 300 for cesium.
Cobalt-60 and Nickel-63
The principal sorption mechanism of cobalt 'and nickel in the marine
sediments is the coprecipitation of these radionuclides with hydrous oxides
of manganese and iron under controlling conditions of pH and Eh (Jenne,
1968). The average Kd of cobalt in the ocean sediment is listed by Onishi,
et al. (1981), as 10,000 with the Atlantic Ocean values generally similar
to those of the world oceans. The Kd values of nickel are not reported for
ocean sediment; however, values for continental soils rich in montmoril-
lonite and a generally alkaline pH have a Kd range between 1300-3000, and
kaolinite-rich soils of acidic pH (6.0) have a Kd range between 130 and 330
(Swanson, 1982). An estimated Kd for nickel at the 3800-meter site might
be 1000, whereas cobalt might approximate a Kd of 10,000.
Technetium-99
The average Kd for measurements of technetium-99 in oxidizing
conditions in ocean sediments is zero (Onishi, et al., 1981). In soils
with high organic matter and reducing conditions, Kd values as high as 900
have been reported. At the 3800-meter site, the Eh could be the main
controlling factor, in which case this measurement should be made. At the
expected depth of a drum in the sediments, it is probable that the Kd of
technetium will be zero.
33
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Typical Kd values of Sr and Cs on Pure Mineral Phases
TEXTURE
SAND-
SIZE
SILT-
SIZE
CLAY-
SIZE
MINERALS
CALCITE (FORAMINIFERA)
QUARTZ
FELDSPAR
MICA
/FORAMINIFERA\
CALCITE V &COCCOLITHS /
QUARTZ
FELDSPAR
MICA
CALCITE (COCCOLITHS)
KAOLINITE
ILLITE
MONTMORILLONITE
(1) DISTRIBUTION COEFFICIENT (Kd)
Sr
unknown
0-5
9
5
unknown
0-5
9
5
unknown
15
100
150
Cs
unknown
0
9
5-15
unknown
0
9
5-15
unknown
45
400
4900
(1). Kd values after Ames and Rai (1978).
Figure 11. Distribution coefficients (Kd) for strontium and cesium on minerals
typical of the 3800 meter Atlantic nuclear waste dumpsite.
34
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Uranium-238
The Kd of uranium is controlled by the pH, Eh, inorganic ligands
(carbonate), and organic constituents (Table 5); both precipitation in the
reducing environment and ion exchange are probable sorption mechanisms.
The average Kd reported for uranium in ocean sediment by Onishi, et al.
(1981), is 500. In the presence of complexing anions such as carbonate,
uranium tends to form soluble complexes.
The probable Kd that might be expected in the sediment at the
3800-meter Atlantic waste site is suggested as 500. This value is
expected to be nearer to the average for ocean sediment since carbonate is
the common constituent in most biogenous deep ocean sediments. The
extreme values Kd up to 10,000 probably occur in highly organic, strongly
reducing, or carbonate-free sediment.
Transuranic Elements
The important transuranic elements in the waste form are
neptunium-239, plutonium-239, americium-241, and curium-243. The average
Kd reported by Onishi, et al. (1981), for these radionuclides in ocean
sediments are: Np - no data; Pu - 50,000; Am - 10,000; Cm - no data.
While little data exists on neptunium for ocean sediment, the Kd
numbers are very low for oxygenated sediments on the continent. However,
it is recognized that neptunium is rendered immobile in reducing
environments with precipitation as the probable sorption mechanism
(Table 5). Since the upper several centimeters of the 3800-meter site
sediment are oxidizing, the Kd suggested might be on the order of 5.
The sorption of plutonium-239 on ocean sediment is affected by a
number of factors, including sorptive minerals, Eh, pH, cation exchange,
inorganic ligands, and organics, with ion exchange and/or precipitation
the most probable sorption mechanism (Table 5). Strongest sorption occurs
in the pH range of 4 to 8. Average Kd for plutonium in ocean sediment is
50,000 (Onishi, et al., 1981). Plutonium varies over two orders of
magnitude depending on the oxidation state. The Kd for plutonium
suggested for the 3800-meter Atlantic site is 50,000.
The factors affecting americium-241 sorption are sorptive minerals,
pH, competing ions, cation exchange, and inorganic ligands, with ion
exchange and/or precipitation the probable sorption mechanism (Table 5).
The average americium Kd reported by Onishi, et al. (1981), for the marine
environment is 10,000, with pH especially an important mechanism in marine
environments. The Kd of americium is greater in freshwater than marine
waters since the sorption of this radionuclide decreases with an increase
in concentration of competing ions (Onishi, et al., 1981). The Kd for
americium suggested for the 3800-meter Atlantic site is the marine
environment value of 10,000.
35
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Although little data are available for curium-243, it is believed
that the principal sorption mechanism is by precipitation controlled
largely by pH and inorganic ligands (Table 5). Iron and manganese oxides
are believed to act as scavengers for curium (Onishi, et al., 1981). A
highly speculative Kd of 1000 is suggested for the 3800-meter Atlantic
site based on some limited observations of continental deposits reporting
an average Kd of 5000 (Onishi, et al., 1981).
36
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COMPARISON WITH WORLD OCEAN CLAY SUITES
The clay-mineral suite of the North Atlantic Ocean to as far south as
35° N latitude has been characterized by Hathaway (1972) and others as
an illite-chlorite suite (Figure 12). The illite at the 3800-meter site
is the dominant clay mineral, and the ratio of kaolinite to chlorite is in
general agreement with that mapped by Biscaye (1965). Montmorillonite is
subordinate to illite in all of the contemporary sediment samples but
slightly higher than that reported by Neiheisel (1979) for the upper
continental rise or by Hathaway (1972) for the lower continental rise in
this portion of the ocean. The slightly larger montmorillonite values are
probably due to scour of the montmorillonite-rich portions of the Tertiary
canyon wall effected by turbidity currents down the Hudson Canyon.
Except for the montmorillonite-kaolinite clay-mineral suite
comprising the sediment of the southwest portion of the North Atlantic
Ocean, the middle latitudes and equatorial Atlantic are dominated by
kaolinite (Figure 12). The typical weathering in humid, tropical climates
produces the kaolinite which is transported as detritus by winds and major
discharge by rivers from the adjacent South American and African
continents. The kaolinite is unique to the Atlantic Ocean because of the
comparitively small size of the ocean basin in relation to the world
ocean, the lack of trenches or volcanic activity on its margins, and the
predominance of equatorial drainage from the continents to this basin of
deposition. The lack of trenches, in particular, enable kaolinite to be
transported to the ocean basins.
The sediment of the Pacific Ocean is dominated by a montmorillonite-
suite in the middle latitudes and equatorial regions and illite-chlorite
in the high latitudes (Figure 12). In addition, much of the Pacific Ocean
sediment in the middle latitudes contains an abundance of zeolite minerals
(Turekian, 1972) which have high sorption properties like the clay
minerals. Both the montmorillonite and zeolites are presumed to be
derived indigenously from the abundance of volcanic ash generated along
the margins of the ocean basin and intrabasin locations. The illite,
predominant in the clay-mineral suite of the high latitudes, is mainly
detrital matter carried by winds and rivers (Figure 12). Chlorite occurs
in fair abundance in the clay-mineral suite of the high latitudes where it
can be preserved (Millot, 1979).
37
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00
EXPLANATION
PREDOMINANT CLAY MINERALS
MONTMORILLONITE
KAOLINITE
rnrm ILLITE
ILLITE
&
CHLORITE
ILLITE
&
MONTMORILLONITE
^x'KAO UNITE x^x
MONTMORILLONITE
ILLITE-CHLORITE
ILLITE-CHLORITE
ILLITE-CHLORITE
Figure 12. Generalized distribution of clay - mineral suites in the world ocean.
-------
The Pacific Ocean sediments, by comparison with the Atlantic Ocean
sediments, contain a higher order of sorptive minerals in the clay-mineral
suite and, in addition, contain appreciable zeolites which also have high
sorptive properties. The Pacific Ocean sediment could be expected to
contain potentially greater radionuclide retention on this basis if other
chemical factors are comparable. The few distribution coefficient
measurements made in the world oceans have been summarized by Onishi, et
al. (1981); to date, they show that Kd values of radionudides range over
orders of magnitude with most similarity in similar ocean basins. With
site specific investigations similar to this investigation for detailed
mineralogy and also including measurements of chemical factors, it is
forseeable that predictions of radionuclide retention will be more
meaningful.
39
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CONCLUSIONS AND RECOMMENDATONS
Conclusions
The sediments of the abandoned 3800-meter Atlantic nuclear waste
dumpsite are relatively uniform in textural, physical, and mineralogical
composition. However, two samples differ markedly in the clay-mineral
suite and physical properties indicating that they may be slump block
material from the canyon walls. The contemporary sediment averages
42 percent biogenous materials, 29 percent terrigenous materials, and
29 percent clay minerals, while the Tertiary canyon wall material averages
21 percent biogenous material, 33 percent terrigenous material, and
37 percent clay minerals. The most diagnostic difference is the
predominance of montmorillonite (50-83 percent) in the clay-mineral suite
of the older Tertiary sediment versus an average of 24 percent in the
contemporary sediment clay-mineral suite. There is also a noticeable
difference in percent quartz in the sand-size fraction and the amount and
type of biogenous material. Pyrite also occurs in the older, dessicated
slump material, and the liquid limit (LL) ranges between 94 and 100 as
compared with a range between 72 and 88 in the contemporary sediment.
Any assessment of the potential for the sediment to act as a barrier
to radionuclide migration should consider the dynamics of sediment
deposition, extent of burial of waste drums into the sediment, and
potential "short circuits" of sorbed radionuclides to the surface of the
sediment by bioturbation or other mechanisms. This assessment, for
generic purposes, considers an ideal case in which the waste drums are
buried in sediment and the radionuclides are retained in the sediment
should radionuclide release occur from the waste form in the drums. In
such an assessment, the percent of sorptive minerals constitutes the
primary consideration along with chemical factors which affect the
sorption mechanism of radionuclides in the sediment.
An important first step in the sediment characterization is
delineation of the highly sorptive materials which are concentrated
in the fines. A quantitative method was employed which consists of:
(1) compiling a texture grain-size accumulation curve; (2) separate
mineral evaluations of sand, silt, and clay-size fractions; and
(3) calculation of the percent of each mineral in the total sample. With
the percent of sorptive minerals known and the retention of a radionuclide
known as a distribution coefficient (Kd) for the pure mineral phase, the
radionuclide retention can be calculated for the sediment. The sorption
40
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mechanism for some radionuclides may be affected by the concentration and
oxidation state of the radionuclide, presence of amorphous Fe and Mn
oxides, presence of organics or ligands, the pH and Eh of the pore water,
and other factors. These must be known for a total assessment of all
radionuclides of concern.
The fact that the sorption mechanisms of cesium and strontium are
governed primarily by ion exchange, and the percent of each mineral in the
sediment is known as well as the Kd for the pure mineral phase, makes
calculation of their potential retention feasible. The Kd values
obtained (Sr = 30 and Cs = 460) are nearer average values for the few Kd
measurements made on ocean sediments; values differ by orders of magnitude
in world ocean sediments.
Recommendations
It is recommended that site specific sediment samples be collected at
existing and/or potential dumpsites and tested in the laboratory for the
texture and quantitative mineral evaluation, as well as the sorption
distribution coefficient (Kd) for each radionuclide of concern. The pH
and Eh of the sediment should be determined as soon as the sediment is
received aboard the survey ship since these are important factors
affecting the sorption mechanism. Other laboratory measurements which
should be made for assessment of sorption mechanisms of radionuclides
include: quantity of Fe and Mn oxides, organic matter, quantity of
ligands, measurements of naturally occurring radionuclides, and elements
that have radioactive isotopes.
A predictive methodology for radionuclide retention in ocean sediment
combines measurement of sorptive minerals, chemical factors, and the
distribution coefficients (Kd) of radionuclides. With a sufficient number
of measurements, a nomograph may be constructed' that will provide an
assessment of the Kd of radionuclides of interest.
41
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RE FE FENCES
AMES, L.L., and RAI, D. 1979, Radionuclide interactions with soil and
rock media, EPA 520/6-78-007, v. 1, p. 253.
BERRY, L.G., and MASON, B. 1959, Mineralogy, W.H. Freeman and Company,
San Francisco, CA, p. 630.
BISCAYE, P.E. 1964, Distinction between kaolinite and chlorite in recent
sediments by x-ray diffraction, Amer. Mineralogist, v. 49, p. 1281-1289.
BISCAYE, P.E. 1965, Mineralogy and sedimentation of recent deep-sea clay
in the Atlantic Ocean and adjacent seas and oceans, Geol. Soc. Amer.
Bull., v. 76, p. 803-832.
BRINDLEY, G.W. 1961, Quantitative analysis of clay mixtures, p. 489-516,
in Brown, George, ed., X-ray identification and crystal structures of clay
minerals: Mineralogical Society, London, p. 544.
BUCK, A.D. 1972, Quantitative mineralogical analysis by x-ray
diffraction, U.S. Army Corps of Engineers, Waterways Experiment Station,
Miscellaneous Paper C-72-2, p. 25.
COLUMBO, P., FUHRMANN, M., NEILSON, R.M., and SAILOR, V.L. 1982,
Development of a working set of waste package performance criteria for
deepsea disposal of low-level radioactive waste, U.S. Environmental
Protection Agency, Office of Radiation Programs, Report No. 520/1-82-007,
p. 10.
DEVINE, S.B., FERRELL, R.E., JR., and BILLINGS, G.K. 1972, A quantitative
x-ray diffraction technique applied to fine-grained sediments of the deep
Gulf of Mexico, Jour. Sed. Petrology, v. 42, n. 2, pp. 468-475.
DYER, R. S. 1976, Environmental surveys of two deep-sea radioactive waste
disposal sites using submersibles, Proceeding of the International Atomic
Energy Agency, Vienna, Austria, pp. 317-338.
GIBBS, R.J. 1965, Error due to segregation in quantitative clay mineral
x-ray diffraction mounting techniques, Amer. Mineralogist, v. 50,
pp. 741-751.
GIBBS, R.J. 1968, Clay mineral mounting techniques for x-ray diffraction
analysis, Jour. Sed. Petrology, v. 38, pp. 242-243.
42
-------
GILLHAM, R.W., CHERRY, J.A., and LINDSAY, L.E. 1980, Cesium distribution
coefficients in unconsolidated geological materials, Health Physics,
v. 39, pp. 637-649.
GRIFFIN, J.J., and GOLDBERG, E.D. 1963, Clay-mineral distribution in the
Pacific Ocean, pp. 728-741, in Hill, M.N., ed., The Seas: Ideas and
Observations, v. 3, John Wiley and Sons, p. 963.
HANSELMAN, D.H., and RYAN, W.B.F. 1983, Atlantic 3800-meter radioactive
waste disposal site survey - sedimentary micromorphologic and geophysical
analyses, U.S. Environmental Protection Agency, Report under contract
number 68-01-4836 (in press).
HATHAWAY, J.C. 1972, Regional clay mineral facies in estuaries and
continental margin of the United States east coast, in Geological Society
of American Memoir 133, B. Nelson, Editor, pp. 293-316.
HEATH, R.C. 1977, Barriers to radionuclide waste migration, Oceanus,
v. 20, pp. 26-30.
HOLCOMB, W.F. 1982, A history of ocean disposal of packaged low-level
radioactive waste, Nuclear Safety, v. 23, pp. 183-197.
JENNE, E.A. 1968, Controls of Mn, Fe, Co, Ni, Cu, and Zn concentrations
in soils and water: The significant role of hydrous Mn and Fe oxides,
pp. 337-387, in Trace Inorganics in Water, R.A. Baker, Editor, American
Chemical Society, Advances in Chemistry Series 73, p. 387.
JOHNS, W.D., GRIM, R.E., and BRADLEY, W.F. 1954, Quantitative estimations
of clay minerals by diffraction methods, Jour. Sed Petrology, v. 24,
pp. 242-251.
JOSEPH, A.B., GUSTAFSON, P.F., RUSSELL, I.R., SCHUERT, E.A.,
VOLCHOK, H.L., and TAMPLIN, A. 1971, Sources of radioactivity and their
characteristics, in Radioactivity in the Marine Environment, National
Academy of Sciences, pp. 6-41.
KELLER, G., and SHEPARD, F.P. 1978, Currents and sedimentation processes
in submarine canyons off the northeast United States, in: D.J. Stanley
and G. Kelling (Editors), Sedimentation in submarine canyons, fans, and
trenches. Dowden, Hutchinson and Ross, Stroudsburg, Pa., pp. 15-32.
KORTE, N.E., SKOPP, J., FULLER, W.H., NIEBLA, E.E., and ALESII, B.A.
1976, Trace element movement in soils: Influence of soil physical and
chemical properties, Soil Science, v. 122, pp. 350-359.
KRONE, R.B. 1963, A study of Theological properties of estuarine
sediments, U.S. Army Corps of Engineers, Committee on Tidal Hydraulics,
Tech. Bull. No. 7, p. 41.
43
-------
MILLOT, G. 1979, Clay, Scientific American, v. 240, n. 4, pp. 108-119.
NEIHEISEL, J. 1979, Sediment characteristics of the 2800-meter Atlantic
nuclear waste disposal site: Radionuclide retention potential,
U.S. Environmental Protection Agency, Technical Note ORP/TAD-79-10, p. 29.
NEIHEISEL, J. and WEAVER, C.E. 1967, Transport and deposition of clay
minerals in southeastern United States, Jour. Sed. Petrology, v. 37,
pp. 1084-1116.
NORKE, W.E., and FENSKE, P.R. 1970, Radioactivity in water - Project
Rulison, NVD-1229-131.
ONISHI, Y., SERNE, R.J., ARNOLD, E.M., COWAN, C.E., and THOMPSON, F.L.
1981, Critical review: radionuclide transport, sediment transport, and
water quality mathematical modeling; and radionuclide adsorption/desorption
mechanisms, Battelle Pacific Northwest Laboratory, PNL-2901, p. 339.
PIERCE, J.W., and SIEGEL. 1969, Quantification in clay mineral studies of
sediments in sedimentary rocks, Jour. Sed. Petrology, v. 39, pp. 187-193.
PIETRZAK, R.F., CZYSCINSKI, K.S., and WEISS, A.J. 1981, Sorption
measurements performed under site-specific conditions - Maxey Flats,
Kentucky, and West Valley, New York, disposal sites: Nuclear and Chemical
Waste Management, v. 2, pp. 279-285. t>
F r
RELYEA, J.F., SERNE, R.'j". , and RAI, D. 1980, Methods for determining
radionuclide retardation factors: status report, Battelle Pacific
Northwest Laboratory, PNL-3349, p. 80.
SAYLES, F.L., and Mangelsdorf, D.C. 1977, The equilibrium of clay
minerals with seawater: exchange reactions, Geochem., Cosmochim. Acta, v.
41, pp. 951-960.
SCHMIDT, R.L. 1979, The chemistry of water and sediment from the benthic
boundary layer at a site in the Northwest Atlantic Ocean, Battelle Pacific
Northwest Laboratory, PNL-2842, UC 11, p. 23.
SCHULTZ, L.G. 1960, Quantitative x-ray determinations of some aluminous
clay minerals in rocks, pp. 216-224 in Swineford, Ada, ed., Proc. Seventh
National Conference on Clays and Clay Minerals.
SHEPARD, F.P. 1954, Nomenclature based on sand-silt-clay ratios: Jour.
Sed. Petrology, v. 24, pp. 151-158.
SWANSON, J.L. 1982, Effect of organic complexants on the mobility of
nickel and cobalt in soils: Status Report, Battelle Pacific Northwest
Laboratory, PNL-4389.
44
-------
TALBERT, D.M. 1982, Oceanographic studies to support the assessment of
submarine disposal at sea: Vol. 1, Sandia National Laboratories,
SAND 82-1005/1, p. 50.
TUEEKIAN, K.K. 1971, Oceans: Prentice Hall, Inc., Englewood Cliffs,
New Jersey, p. 120.
U.S. ARMY CORPS OF ENGINEERS. 1970, Laboratory soils testing,
EM-110-2-1906, Appendix II, Washington, D.C.
WILD, R.E., OZTUNALI, O.I., CLANCY, J.J., PITT, C.J., and PICAZO, E.D.
1981, Data base for radioactive waste management, U.S. Nuclear Regulatory
Commission, NUREG/CR-1759, Vol. 2.
45
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA 520/1-83-003
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Quantitative Mineral Assessment and Radionuclide
Retention Potential of Atlantic 3800-Meter Nuclear
Waste Dumpsite Sediments
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
James Neiheisel
8. PERFORMING ORGANIZATION REPORT NO.
EPA 520/1-83-003
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Office of Radiation Programs
U.S. Environmental Protection Agency
401 M Street, SW
Washington, DC 20460
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
IAG Number EPA-79-D-H0706
12. SPONSORING AGENCY NAME AND ADDRESS
Office of Radiation Programs
U.S. Environmental Protection Agency
401 M Street, SW
Washington, DC 20460
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Seven box core sediment samples were obtained from the 3800-meter low-level
radioactive waste dumpsite located 320 km off the New York coast in the main axis
of the Hudson canyon. Sorptive minerals in the sediment were calculated from the
texture grain-size curve and separate mineral evaluations of the sand, silt, and
clay-size fractions. Two of the sediment samples, having marked differences in
physical properties and mineralogy, are believed to be slump material from the
Tertiary age canyon wall.
The contemporary sediment averages 42% biogenous calcite, 29% terrigenous
materials, and 29% clay minerals. Clay mineral fractional composition averages
52% illite, 9% chlorite, 16% kaolinite, and 23% montmorillonite.
Calculations made from percentages of individual minerals and the distribution
coefficients (Kd) of Sr and Cs on measured pure mineral phases suggests a potential
Kd of 30 for Sr and 460 for Cs. The sorption mechanism of some of the other radio-
nuclides are strongly influenced by pH, Eh (redox potential), presence of Fe and Mn,
organics, and ligands. These factors should be known in addition to percentages of
sorptive minerals for assessment of sediment retention potential of sediments for
radionuclides of concern in the low-level waste form.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COS AT I Field/Group
Ocean Dumping
Sediment Characterization
Sorptive Minerals
Clay Minerals
Radionuclide Retention Potential
18. DISTRIBUTION STATEMENT
Unlimited Release
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (Ray. 4-77)
PREVIOUS EDITION IS OBSOLETE
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