Uranium and tritium as natural tracers in the Floridan aquifer

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Title:
Uranium and tritium as natural tracers in the Floridan aquifer
Series Title:
Florida Water Resources Research Center Publication Number 14
Physical Description:
Book
Creator:
Osmond, J. K.
Buie, B. F.
Rydell, H. S.
Kaufman, M. I.
Wallick, E. I.
Publisher:
University of Florida
Place of Publication:
Gainesville, Fla.
Publication Date:

Notes

Abstract:
Naturally occurring radioisotopes serve as hydrologic tracers in the study of ground water movement and aquifer recharge. A benzene synthesis method of tritium analysis involving no isotopic enrichment has been developed which permits analysis of samples at a level of 10 or more tritium units (10+ H-3 per 10 18 H-l). In the North Florida study area sharp boundaries separate young and old waters in the aquifer according to their tritium content. Uranium in ground water exhibits extreme variability in isotopic distribution and the combination of isotopic ratio (U-234/U-238) and total uranium concentration (0.0X to X parts per billion) serves as the tag with which to trace aquifer water. The sources of water flowing from Wakulla Springs and Silver Springs is calculated quantitatively; the results agree well with conclusions based on standard hydrologic methods of analysis. Uranium analysis requires one to four gallons of water per sample, and involves isotopic spiking with U-232, iron hydroxide co-precipitation, ion exchange separation, electrodeposition, vacuum counting, and alpha pulse height analysis.

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URANIUM AND TRITIUM AS NATURAL TRACERS IN THE FLORIDAN AQUIFER


by


J. K. OSMOND and B. F. BUIE
-(Principal Investi-gators)-

and

H. S. RYDELL, M. I. KAUFMAN, and E. I. WALLICK



PUBLICATION NO. 14

FLORIDA WATER RESOURCES RESEARCH CENTER






RESEARCH PROJECT TECHNICAL COMPLETION REPORT

OWRR Project Number A-011-FLA

Annual Allotment Agreement Numbers
14-01-0001-1628 (1969)
14-31-0001-3009 (1970)
14-31-0001-3209 (1971)

Report Submitted: August, 1971





The work upon which this report is based was supported in
part by funds provided by the United States Department
of the Interior, Office of Water Resources
Research as Authorized under the Water
Resources Act of 1964.










TABLE OF CONTENTS
Page
LIST OF TABLES --------------------------------------- iv

LIST OF FIGURES ----------------------------------------- v

ABSTRACT ------------------------------------------------ 1

1. INTRODUCTION ---------------------------------------- 2

2. URANIUM ISOTOPES IN NATURE: BACKGROUND AND
ANALYTICAL PROCEDURE ---------------------------- 4
Previous Studies --------------------------------- 4
Decay Scheme and U-234 Fractionation Mechanism ---- 5
Methods and Procedures ------ --------------------- 8

3. URANIUM ISOTOPES AS 1_ .-ID TO HYDROLOGIC STUDY OF
THE FLORIDAN AQUIFER ------------------------------ 10
Purpose and Significance --------------------------- 10
Results and Discussion ---------------------------- 10
Conclusions ------------------------------------- 26

4. URANIUM ISOTOPES AS QUANTITATIVE INDICATORS OF
GROUND WATER SOURCES ---------------------------- 27

The Isotope Dilution Approach to Hydrologic
Problems -------------------------------------- 27

A. Wakulla Springs --------------------------- 27
B. Silver Springs ---------------------------- 30

5. TRITIUM ANALYSIS: A MODIFICATION OF THE BENZENE
SYNTHESIS METHOD ---------------------------------- 39
Introduction ------------------------------------- 39
Theory ------------------------------------------- 39
Operational Procedure ----------------------------- 40
Fractionation Effect ------------------ 42
Discussion ---------------------------------------- 42
Conclusion ----------------------------- --- 44

6. TRITIUM HYDROLOGY OF THE TALLAHASSEE, FLORIDA AREA -- 45
Field Methods and Procedures ---------------------- 45
Sample Locations and Analytical Results ----------- 45
Discussion of Results ---------------------------- 52

APPENDIX A: DETAILED METHODS AND ANALYTICAL PROCEDURES
FOR URANIUM ANALYSES ---------- ---------------------- 55
Water Samples ------------------------------------- 55
Ion Exchange ------------------------------------- 56
Electrodeposition --------------------------------- 57
Counting ------------------------------------------ 57
General Remarks ----------------------------------- 58









Page
APPENDIX B: TREATMENT OF URANIUM DATA ----------------- 59
Sources of Error ----------------------------------- 59
Systematic Errors ------------------------------- 59
Random Errors ---------------------------------- 59
Data Handling ------------------------------------ 60
Fortran IV Computer Program ----------------------- 61

APPENDIX C: REPORTS AND PUBLICATIONS ------------------ 62

LITERATURE CITED --------------------------------------- 63















































iii










LIST OF TABLES


Page
Table 1 Uranium concentrations and isotopic activity
ratios of natural waters of Florida -------- 11

Table 2 Location and description of water samples ---- 13

Table 3 Additions of uranium and water between aquifer
sampling points --------------------------- 31

Table 4 Uranium concentrations and uranium isotopic
activity ratios: Silver Springs Region ---- 32

Table 5 Mixing proportions -------------------------- 36

Table 6 Source of-Silver Springs water: hydrologic
vs isotopic calculations ------------------- 37

Table 7 Interlaboratory checks ----------------------- 43

Table 8 Tritium concentration of selected waters with
pertinent sampling information ------------ 47










LIST OF FIGURES


Page


Figure 1



Figure-2



Figure 3



Figure 4




Figure 5



Figure 6


Figure 7



Figure 8


Figure 9


Figure 10


Figure 11


Figure 12


Decay scheme of the natural U-238 series
showing isotopes of interest, half-life,
mode and energy of decay-----------------

Alpha-particle spectrum of uranium isotopes;
alpha energy in million electron volts
(MeV)----------------------------------

Location of sampling sites and potentio-
metric surface of the Floridan aquifer in
North Florida ----------------------------

Geologic section and distribution of the
U-234/U-238 activity ratios and uranium
content in micrograms per liter in the
waters of North Florida -------------------

Areal distribution of the U-234/U-238
activity ratios of waters from the
Floridan aquifer in North Florida --------

Regional structure and physiographic map of
North Florida depicting recharge areas ----

Relation between the U-234/U-238 activity
ratio and uranium content in the waters of
North Florida----------------------------

Composite hydrologic map and diagrammatic
geologic cross section --------------------

Ocala Area: Inferred ground water flow
directions ------------------------------

Activity ratio vs. reciprocal of concentra-
tion diagram of Ocala area samples --------

Diagrammatic sketch of benzene synthesis
system -----------------------------------

Map of Tallahassee and surrounding area
showing tritium content of Floridan
aquifer well water------------------------











ABSTRACT


URANIUM AND TRITIUM AS NATURAL TRACERS IN THE FLORIDAN AQUIFER


Naturally occurring radioisotopes serve as hydrologic
tracers in the study of ground water movement and aquifer
recharge.

A benzene synthesis method of tritium analysis involving
no isotopic enrichment has been developed which permits
analysis of samples at a level of 10 or more tritium units
(10+ H-3 per 1018 H-l). In the North Florida study area sharp
boundaries separate young and old waters in the aquifer accord-
ing to their tritium content.

Uranium in ground water exhibits extreme variability in
isotopic distribution and the combination of isotopic ratio
(U-234/U-238) and total uranium concentration (0.0X to X parts
per billion) serves as the tag with which to trace aquifer
water. The sources of water flowing from Wakulla Springs and
Silver Springs is calculated quantitatively; the results agree
well with conclusions based on standard hydrologic methods of
analysis. Uranium analysis requires one to four gallons of
water per sample, and involves isotopic spiking with U-232,
iron hydroxide co-precipitation, ion exchange separation,
electrodeposition, vacuum counting, and alpha pulse height
analysis.
















Osmond, J. K., B. F. Buie,
H. S. Rydell, M. I. Kaufman, and E. I. Wallick
URANIUM AND TRITIUM AS NATURAL TRACERS IN THE FLORIDAN AQUIFER
Completion Report to the Office of Water Resources Research,
Department of the Interior, August, 1971, Washington, D.C. 20240.
KEYWORDS: tritium*, uranium isotopes*, ground water recharge*,
aquifers*, tracers, ground water movement, springs.










1. INTRODUCTION


The use of naturally occurring radioisotopes to study
the movement of ground water has been the subject of study
by researchers at the Florida State University Department
of Geology for several years. From April 1, 1966 to June 30,
1971 this research has been supported by the U.S. Department
of-Interior Office-ef Water Resources Research under its
Title I program (A-005-FLA and A-011-FLA).

This report covers the activity from July 1, 1968 through
June 30, 1971 (A-011-FLA). Some of the work described herein,
especially that concerned with analytical techniques, had its
inception under the previous grant (A-005-FLA). Conversely,
some of the sub-projects begun under A-011-FLA are not
complete. Work on these will continue and separate reports
will be issued. One of these, a-PhD Dissertation by L. I.
Briel, will require several months of analysis and data
reduction before completion. It will be concerned with the
application of uranium isotopes to analysis of the sources
and mixing patterns of the Santa Fe River System of north
central Florida. The second, an MS Thesis by Ivan Wilson,
will Te completed soon. It deals with the application of-
non-isotopically enriched tritium analyses to the study of
the Floridan Aquifer of north central Florida, between
Tallahassee and Lake City. The following quotation from a
preliminary report by Wilson illustrates the direction of
this research:

"In the eastern part of the study area the Floridan
aquifer receives little or no local recharge during
below normal rainfall periods. Some recharge in the
upper portions of the Floridan aquifer occurs where
the overlying Hawthorn Formation thins. Where the
Hawthorn thickens or a well taps a deeper portion of
the Floridan aquifer no local recharge was indicated.
The Floridan aquifer is nearer the surface in the
central part of the study area, west of Live Oak,
Suwannee County. Here the low tritium content of the
shallow wells and a sinkhole indicate that the aquifer
is discharging during the drier periods. The western
part of the study area appears to have a greater local
recharge. A possible flow direction to the southwest
in Madison and Jefferson Counties is indicated by the
decrease in the tritium content down the piezometric
gradient. Local recharge over the entire area can
not be entirely ruled out since the overall low
tritium content may be a reflection of the dry period."

Because of the interesting possibilities of the uranium
isotopic approach to ground water studies, as developed under
the Office of Water Resources Research Title I funding,
continued support has recently been granted under the OWRR










Title II program, so that some of the approaches herein
described will receive continued attention and development.

Most of the data and conclusions of this report have
been published elsewhere and a list of publications and
theses supported entirely or in part by A-011-FLA is appended.
Those researchers, students, and technicians, other than the
authors of this report, who have participated in the research
program-are acknowledged in the separate publications, and
are listed in the annual reports to the Office of Water
Resources Research.










2. URANIUM ISOTOPES IN NATURE: BACKGROUND AND ANALYTICAL
PROCEDURE


Previous Studies


In closed geologic systems older than about 106 years,
U-234 is in equilibrium with its parent U-238 (U-234/U-238
alpha activity ratio = 1.00). At secular equilibrium, by
definition: N1X1 = N2X2 = A; and AU23 /AU238 = 1.00, where
Ni and N2 = number of atoms of U-238 and U-234 respectively,
X1 and X2 = decay constant of U-238 and U-234 respectively,
and A = alpha activity. In open systems such as those exposed
to weathering and ground-water circulation, separation of these
two isotopes can occur, giving rise to a state of radioactive
disequilibrium.

An increased interest in radioactive disequilibrium within
the natural U-238 series in hydrologic systems has developed
in recent years, especially with respect to geochemical, geo-
chronological and hydrogeological studies. Rosholt (1958)
suggested that radioactive disequilibrium studies could aid in
understanding the natural migration of uranium and its decay
products and also provide an insight into the geological and
geochemical history of deposits. Until recently, the magnitude
and frequency of disequilibria have been generally under-
estimated. The fractionation of U-234 with respect to its
radiogenic parent U-238 was first discovered in 1953 by Russian
investigators working with ground waters and secondary minerals
(Cherdyntsev, et al, 1955).

Detailed studies in both the United States and Russia of
natural waters, carbonates, sandstones, uranium ore deposits,
soils, secondary minerals and peats have confirmed and extended
these initial observations and have shown that preferential
leaching of U-234 from a variety of rock types occurs, that
differing isotopic ratios are characteristic of various source
areas, and that for most natural waters, a relative enrichment
of U-234 over U-238 is observed (Chalov, 1959; Isabaev, et al,
1960; Thurber, 1962; Cherdyntsev, et al, 1963; Rosholt, et al,
1963, 1965, 1966; Dooley et al, 1966).

The greatest deviations from equilibrium of the isotopes
of the radioelements are observed in natural waters. The large
reservoir of uranium, the oceans, reflects the magnitude of
isotopic disequilibrium of uranium in nature (U-234/U-238
activity ratio = 1.14) (Thurber, 1962; Koide and Goldberg,
1965). Successful applications of U-234/U-238 activity ratios
to Pleistocene geochronology have been made (Chalov, et al,
1964). By noting that U-234/U-238 activity ratios in natural
waters draining specific source areas remained constant with
time, in spite of considerable change in uranium content,










discharge, and salinity, Chalov, et al (1964) were able to
utilize the isotopic ratios to arrive at absolute age deter-
minations of closed drainage basins.


Decay Scheme and U-234 Fractionation Mechanism

The decay scheme of the natural U-238 series is shown
in part in Figure 1. The two isotopes, U-234 and U-238, are
separated in the decay chain by two short-lived daughter
nuclides, Th-234 and Pa-234. It has been suggested that the
physicochemical reason for the U-234 fractionation is a change
in the valence electron configuration from the U-238 parent
to the radiogenically produced U-234 daughter for a time long
enough to permit fractionation (Cherdyntsev, et al, 1955;
Chalov, 1959; Rosholt, et al, 1963).

Possible mechanisms for the U-234 fractionation have
been presented by Rosholt, et al (1963) and Dooley, et al
(1966). In the three-step decay of U-238 to U-234, chemical
bonds holding the decaying tetravalent U-238 are broken by the
nuclear recoil from the decay. As a result of the U-238 alpha
decay and Th-234 and Pa-234 beta decay, the daughter atom
(U-234) is both displaced within the crystal structure and
stripped of some of its electrons thus attaining an excited
electronic state. According to Dooley, et al (1966, p. 1373),

"At the time of decay and recoil the transformed
nucleus is stripped of some of its electrons and momen-
tarily is in a chemically uncombined state as a charged
particle within the mineral lattice, or within a micro-
fissure perhaps beyond the crystal boundary or in
solution. Chemical recombining of U-234, except in a
highly reducing environment, probably favors the
electron-deficient hexavalent or oxidized state either
as UO ++ in a compound, or as an ion in solution."

Thus, as noted by Rosholt, et al (1963), U-234 would
differ from much of the U-238 in oxidation state, in location
in interstitial spaces (unstable site?), and in type of
chemical bonds, and is therefore potentially more mobile than
its parent U-238.

Chalov and Merkulova (1966), in studying comparative
oxidation rates of U-234 and U-238, concluded that on the
natural dissolution of uranium from minerals a partial
separation of U-234 and U-238 may occur as a result of the
greater ease of oxidation of U-234 atoms. They also considered
radioactive recoil to be of great importance. In addition,
according to Rosholt, et al (1965), the differing chemical
affinities between uranium and the intermediate daughter
products may result in differential migration of the Th-234
and Pa-234 with respect to U-238.




























ALPHA
(4.77, 4.72 MEV)


Pc 234

LIFE =
1.18 rain.


U 238

2 LIFE :
4.51 x 10 yrs.






ALPHA
(4.19 MEV)


Th 230

' LIFE=
7.6 x104 yrs.


Th 234

2 LIFE
24.1 doys


140


142
NUMBER


143 144
OF NEUTRONS


Figure 1. Decay scheme of the natural U-238 series showing isotopes of interest,
half-life, mode and energy of decay.


92 -


91-


90 -


146


(N)


_ __ _


_ I -1 -- I -----LL-~


(0.19, 0.10 MEV)










It is pertinent to note that the transition from the
+4 to the +6 state has an oxidation potential within the
normal range for geologic environments:


U+4 + 2H20 -+ UO2 2 + 4H+ + 2e-; Eo = +0.33 volt

so compounds of both valences would be expected in nature
(Krauskopf, 1967, p. 527). Thus the oxidation potential of
the environment, in addition to the electronic effects of
decay, may be a major control on the separation of uranium
isotopes, once decay and recoil of the daughter isotope into
solution occurs. It has been observed (Rosholt, et al, 1965)
that slightly oxidizing environments appear to result in
large magnitudes of isotopic disequilibrium, whereas in
reducing environments U-234 does not appear to be prefer-
entially leached. Both U-238 and U-234 are leached in more
equal proportions from an environment having a strong oxidizing
potential.

The leaching solutions preferentially pick up the oxidized
U-234 as the stable divalent uranyl ion UO +. The greater
solubility of uranyl compounds hexavalentt uranium) relative
to those of tetravalent uranium has been documented (Adams,
et al, 1959). Although noting that in aqueous solutions the
uranyl ion forms a somewhat soluble series of hydroxides or
hydrates (U02(OH)2, HU04-, UO-2), Krauskopf (1967, p. 527,
528) reported that the solubilities of the latter two ions
became appreciable only in strongly alkaline solutions. In
solutions containing carbonate ion, the solubility of compounds
of hexavalent uranium is greatly increased by the formation of
carbonate complexes such as the uranyl dicarbonate and uranyl
tri-carbonate anionic species, hence carbonate-bearing solutions
are excellent solvents for uranium (Scott and Barker, 1958;
Garrels and Christ, 1965, p. 253; Krauskopf, 1967, p. 528).
The solubility of uranyl compounds is strongly pH dependent,
thus the pH of the environment plays a major role in the
mobility of uranium. Serebryakova (1964), utilizing physico-
chemical methods, determined that in oxygenated ground waters
uranium is present as anionic complexes such as (U02(C03)2(H20)2)
(86%) and (U02(CO3)3) -4 (12%), consistent with earlier results.
No colloidal uranium was detected.

Dooley, et al (1966), in studying U-234 fractionation in
sandstone-type uranium ore deposits, noted that greater U-234
deficiencies and range of disequilibrium in ore samples appeared
to be related to zones of higher permeability and greater
circulation of ground water. A water saturated, slightly
oxidizing, environment appears to be the primary medium for
continuous fractionation and differential solution of uranium
isotopes; consequently, the hydrologic system exerts a major
control on the patterns of environmental disequilibrium.










Methods and Procedures


Sampling sites, consisting of wells, springs, streams, and
lakes were selected so as to adequately represent the regional
geohydrologic environment within the study area. Determinations
were made of the total uranium content and of the U-234/U-238
activity ratios, using the analytical procedures of isotope
dilution and alpha-particle spectrometry.

In brief, the field sampling and analytical procedures
were as follows:

Samples were collected from each source in duplicate to
serve as a check on analytical variability. The radioactive
isotope U-232, which served as the isotopic yield tracer, and
sufficient nitric acid to attain a pH of 1.0 were added in the
field. The recovery procedure for uranium consisted of co-
precipitation with ferric hydroxide, and purification using
solvent extraction and ion-exchange. Following ion-exchange,
the uranium samples were plated onto stainless steel planchets
by electrodeposition for isotopic analysis using a high resolu-
tion solid state alpha-particle spectrometer. Figure 2
illustrates a typical alpha-particle spectrum of uranium
isotopes.

Blank solutions were run through the entire chemical
separation and electrodeposition procedure and analyzed on the
alpha spectrometer. These blanks provided a correction factor
for background as well as for any contaminants which may have
been introduced during the chemical processing. Chemical
yields ranged from 15 percent to greater than 50 percent. The
above methods and procedures resulted in determinations of
uranium isotopes in trace amounts of less than .04 micrograms
per liter and of U-234/U-238 activity ratios to within .003.
Average errors for uranium content and activity ratio at the
0.95 confidence level were 5 and 3 percent, respectively,
for water with a uranium content greater than 0.1 micrograms
per liter.

For a more complete description of technique, see the
discussion under "Detailed Methods and Analytical Procedures"
in Appendix A.













WAKULLA S-i;.'
Collected 9-21-66


3681


U 234
(4.7 MEV)

S3050


NUMBER


Alpha-particle spectrum of uranium
electron volts (MeV).


isotopes; alpha energy in million


S0OO0


U238
(4.2 MEV)


U232
(5.3 MEV)


3329


CHANNEL


Figure 2.


~"""~"""""-"""`""""~'~ ~R~--- -~---------- ~--------------------- --------










3. URANIUM ISOTOPES AS AN AID TO HYDROLOGIC STUDY OF THE
FLORIDAN AQUIFER


Purpose and Significance

One of the purposes of this study is to investigate
uranium isotope disequilibrium conditions within the Floridan
aquifer and related natural watersof north Florida with a
view towards evaluating the potential applicability of uranium
isotope studies to hydrology. By studying the occurrence,
distribution, and environmental disequilibrium patterns of
naturally occurring uranium isotopes in selected Florida
waters, it may be possible to determine the suitability of
these isotopes as natural tracers or as other aids to
hydrologic investigations, and to determine whether variations
in radioisotope ratios and concentrations in natural waters
can be used to indicate sources and/or history of waters from
various parts of the geohydrologic environment. An analysis
of the relations between the isotopic distribution patterns
and the hydrologic-flow system may permit interpretation in
terms of regional permeability characteristics, ground-water
circulation, and areas of extensive Pleistocene leaching within
the Floridan aquifer.

Furthermore, although detailed discussions are beyond the
scope of this investigation, in order to utilize uranium
isotopes in geochemical and geochronological studies, an
extensive knowledge of the fundamental physicochemical behavior
of the U-234 daughter product in relation to parent U-238 in
hydrologic environments, as well as an understanding of the
hydrologic-flow system, is needed (Rosholt, et al, 1966;
Thurber, 1962). As pointed out by Osmond (1947), a more com-
prehensive study of the heavy radioelements in the waters of
Florida may lead to new concepts in the mobility of these
elements. In addition, a knowledge of the isotopic distribu-
tion patterns may contribute to a better understanding of the
hydrogeochemistry of uranium in natural aqueous systems.


Results and Discussion

The results of the analyses (Table 1) show that in natural
waters within the study area (refer to Table 2) both the
U-234/U-238 activity ratio and the uranium content are quite
variable, indicative of extensive disequilibrium within the
hydrogeologic environment. The errors given are based on
counting statistics of samples and do not include consideration
of systematic errors. The artesian Floridan aquifer, part of
the main Tertiary limestone aquifer system in the southeastern
United States, is the major source of ground water and the most









Table 1


URANIUM CONCENTRATIONS AND ISOTOPIC ACTIVITY RATIOS
OF NATURAL WATERS OF FLORIDA


Uranium Content in
Parts Per Billion


FAW
FAW
FAW
FAW
FAW
FAW
FAW
FAW
FAW

FAW
FAW
PAW
FAW
FAW
PAW
FAW
FAW
PAW
FAW
PAW
FAW
FAW
FAW
PAW
FAW
PAW
FAW
FAW
PAW
PAW
FAW
FAW
PAW
FAW
FAW
FAW
FAW
FAW
PAW
FAW
PAW
FAW
FAW
FAW


010
011
012
013
014
015
020
021
023
024
025
026
027
029
030
033
034
035
036
039
040
041
042
043
044
045
046
049
050
051
052
053
054
056
057
060
061
063
065
066
067
068
069
070
071


U-234/U-238
Activity Ratio


0 -363
0.080
0.019
0.016
0.662
0.013
0.514
0.584
0.154
0.036
0.007
0.209
0.038
18,484
1.968
0.608
2.631
0.604
25.912
0.050
0.135
1.552
0.079
0.691
0.014
0.134
11.015
0.488
0.008
0.340
1.140
0.481
0.191
2.673
0.687
0.696
0.532
3.422
0.008
0.314
0.600
0.386
2.649
0.082
0.042


0. 0 28
0.013
0.006
0.005
0.080
0.009
0.021
0.024
0.008
0.005
0.002
0.010
0.003
0.954
0.104
0.029
0.101
0.027
1.450
0.007
0.009
0.081
0.007
0.037
0.004
0.100
0.661
0.027
0.003
0.017
0.059
0.027
0.056
0.151
0.042
0.050
0.030
0.166
0.004
0.025
0.037
0.026
0.189
0.007
0.005


Sample
Number


2.116
0.999
3.327
4.070
1.145
1.580
0.953
0.878
1.021
1.230
1.468
1.012
1.121
0.523
0.941
0.854
0.686
0.852
0.503
1.588
0.841
1.073
2.938
0.687
1.343
0.803
0.925
0.899
1.972
0.963
1.021
1.002
1.001
0.710
0.836
0.762
0.896
1.116
0.618
0.935
0.840
0.928
1.019
3.710
1.034


0.138
0.213
1.149
1.301
0.124
1.343
0.020
0.020
0.053
0.207
0.572
0.045
0.108
0.006
0.019
0.028
0.007
0.025
0.005
0.264
0.063
0.022
0.237
0.023
0.455
0.724
0.010
0.032
0.896
0.032
0.024
0.037
0.275
0.029
0.044
0.033
0.030
0.012
0.613
0.059
0.031
0.046
0.023
0.297
0.149










Table 1 Continued


Uranium Content in
Parts Per Billion


1.343
0.276
0.674
0.119
0.858
0.376
0.628
0.702


0.083
0.020
0.046
0.018
0.052
0.024
0.040
0.046


U-234/U-238
Activity Ratio


0.971
1.062
0.824
1.041
0.892
1.002
1.096
0.904


0.026
0.062
0.033
0.160
0.028
0.045
0.039
0.034


Sample
Number


FAW
FAW
FAW
FAW
FAW
FAW
FAW
FAW


072
073
074
075
076
077
078
079












Table 2


LOCATION AND DESCRIPTION OF WATER SAMPLES


Sample
Number


Location


FAW 010 T33S; R22E; Sec. 22
Hillsborough County

FAW 011 T31S; R23E; Sec. 23
Polk County

FAW 012 T31S; R23E; Sec. 25
Polk County

SFAW 013 T34S; R25E; Sec. 3
Hardee County


FAW 014


T30S; R25E; Sec. 5
Polk County


FAW 015 T28S; R26E; Sec. 21
Polk County

FAW 020 T1N; R1E; Sec. 30
Leon County

FAW 021 T3S; R1W; Sec. 11
Wakulla County

FAW 023 T1S; R1E; Sec. 6
Leon County


Description

L. Taylor Well; well depth 11 ft.,
csg. 11 ft., sample slightly rusty

R. Marsee Well; well depth 120 ft.,
csg. 80 ft.

American Cyanamid Co. Well; well
depth 950 ft.,csg. 337ft.

City of Wauchula Municipal Well;
well depth 1,103 ft., csg. 404 ft.

Bartow City Well Number 10; well
depth 663 ft., csg. 59 ft.,
possibly some fine pebble phosphate
in sample

Winter Haven City Well Number 2;
well depth 816 ft., csg. 138 ft.

Tallahassee City Well Number 6;
well depth 414 ft., csg. 170 ft.

Wakulla Spring, southwest of
Woodville; discharge 560 cfs.

Unnamed spring in Myers Park,
Tallahassee; flow issuing from
hillslope above clay layer


Date
Sampled


6-21-66


6-21-66


6-21-66


6-21-66


6-21-66


6-21-66


9-21-66


9-22-66


11-16-66


Aquifer or
Source


Water Table

Hawthorn
Formation

Floridan
Aquifer

Floridan
Aquifer


Floridan
Aquifer

Floridan
Aquifer

Floridan
Aquifer

Floridan
Aquifer


Hawthorn
Formation













Table 2 Continued


Location

TIS; R5E; Sec. 15
Jefferson County


FAW 025 T2N; R1W; Sec.
Leon County

FAW 026 T5N; R9W; Sec.
Jackson County

FAW 027 T3N; R5W; Sec.
Gadsden County

FAW 029 T2S; RlE; Sec.
Leon County

FAW 030 T2S; R1E; Sec.
Leon County


Description

Beasleys Creek, nr. Lamont; brown
color due to organic


33 Lake Jackson, nr. Tallahassee


33 Blue Springs, nr. Marianna


14 Glen Julia Springs, nr. Mt.
Pleasant

8 City of Woodville Municipal Well;
well depth 183 ft., csg. 32 ft.


Well at Ice House in Woodville;
well depth 21 ft., csgi. 15 ft.


Date
Sampled


11-17-66

11-18-66|


11-26-66



11-26-66


Aquifer or
Source


Surface
Water

Surface
Water


Floridan
Aquifer

Water Table
Aquifer


Floridan
1-27-67 Aquifer

Floridan
1-28-67 Aquifer


FAW 033


T3S; R1W; Sec.
Wakulla County


11 Wakulla Spring, southwest of
Woodville; discharge 255 cfs., clear,
unfiltered


4-8-67


Floridan
Aquifer


FAW 034 TIS; RIE; Sec. 19 Well at Big Bend Truck Center South
Leon County of Tallahassee; well depth 100 ft.,
csg. 70 ft.

FAW 035 T3S; R1W; Sec. 11 Wakulla Spring, southwest of
Woodville; discharge 255 cfs.; clear


FAW 036


T2S; R1E; Sec.
Leon County


8 City of Woodville Municipal Well;
well depth 183 ft., csg. 32 ft.


Floridan
4-10-67 Aquifer


4-8-67


4-8-67


Floridan
Aquifer

Floridan
Aquifer


Sample
Number

FAW 024












Table 2 Continued


Sample
Number


Location


FAW 039 T38S; R38E; Sec. 1
Martin County


FAW 040


FAW 041


U1 FAW


T30S; R23E; Sec. 13
Polk County



T30S; R24E; Sec. 35


042 T31S; R25E; Sec. 30
Polk County


FAW 043 T30S; R21E; Sec. 17
Hillsborough County


FAW 044


T30S; R23E; Sec. 12
Polk County


FAW 045 T28S; R25E; Sec. 12
Polk County


FAW 046



FAW 049


T30S; R24E; Sec. 25
Polk County


T2S; R2E; Sec. 9
Leon County


Description

R. Carlton flowing artesian well;
well depth 835 ft., csg. 373 ft,

Well at Kingsford Plant Inter-
national Minerals & Chem. Corp.
shallow well removing water from
phosphate deposit

C. W. Shepard Well; well depth 50
ft., csg. 20 ft.

A. L. McClellan Well; well depth
165 ft., csg. 42 ft.

Lithia Springs, southwest of Plant
City

City of Mulberry Municipal Well;
well depth 833 ft., csg. 330 ft.


Eagle Lake, nr. Winter Haven


Seepage from mine face at Noralyn
Plant International Minerals & Chem.
Corp.

Horn Springs, east of Woodville


Date
Sampled


Aquifer or
Source


Floridan
5-24-67 Aquifer


5-23-67 Water Table


5-23-67 Water Table

Hawthorn
5-23-67 Formation

Floridan
5-22-67 Aquifer

Floridan
5-22-67 Aquifer

5-22-67 Surface
Water


Bone Valley
5-23-67 Formation

7-16-67 Floridan
Aquifer












Table 2 Continued


Date
Description Sampled


Location


Aquifer or
Source


FAW 050 TlS; R4W; Sec. 11
Leon County

FAW 051 T2N; R5E; Sec. 19
Jefferson County

FAW 052 T3N; R2W; Sec. 26


FAW 053 TIN; R1W; Sec. 2
Leon County


FAW 054


TIN; R2W; Sec. 23
Leon-Gadsden Line


FAW 056 TlS; R1E; Sec. 19
Leon County


FAW 057 T3S; R1W; Sec. 11
Wakulla County

FAW 060 T2S; R1W; Sec. 17
Leon County

FAW 061 T2S; R1E; Sec. 10
Leon County


FAW 063


T3N; R4W; Sec. 32
Gadsden County


Flowing Well at Elk Horn Fish Camp;
well depth 136 ft., csg. 127 ft.

City of Monticello Municipal Well;
well depth 350 ft., csg. 155 ft.

City of Havana Municipal Well; well
depth 692 ft., csg. 418 ft.

R. O. Vernon Well, nr. Lake Jackson;
well depth 236 ft., csg. 171 ft.


Ochlockonee River


Well at Big Bend Truck Center, south
of Tallahassee; well depth 100 ft.,
csg. 70 ft.

Wakulla Spring, southwest of Woodville;
discharge 1100 cfs; brbwn color


Dismal Sink


Osgood Sink, 2 miles east of Rhodes
Cemetery, Woodville

Well At Spring Hill Elementary
School, Gretna


Hawthorn
7-16-67 Formation

Floridan
7-19-67 Aquifer

Floridan
7-19-67 Aquifer

Floridan
7-21-67 Aquifer

7-21-67 Surface
Water


Floridan
8-17-67 Aquifer


8-18-67


Floridan
Aquifer


2-27-68 Floridan
Aquifer

Floridan
2-27-68 Aquifer

Floridan
2-29-68 Aquifer


Sample
Number












Table 2 Continued


Date
Location Description Sampled


TlS; R4W; Sec. 11
Leon County

TIS; R2W; Sec. 11
Leon County


FAW 067 T1S; R1W; Sec. 31
Leon County


FAW 068


FAW 069


TIN; R1E; Sec. 23
Leon County

TIS; R2E; Sec. 3
Leon County


FAW 070 T2N; R3W; Sec. 24
Gadsden County

FAW 071 TIN; R3W; Sec. 14
Gadsden County

FAW 072 TIN; R1W; Sec. 29
Leon County

FAW 073 T2S; R2E; Sec. 29
Leon County


FAW 074 T2S; R1W; Sec. 28
Wakulla County


Sample
Number

FAW 065


FAW 066


8-6-68


8-6-68


8-6-68


8-6-68


8-6-68


8-6-68


8-8-68


8-8-68


Aquifer or
Source


Hawthorn
Formation

Floridan
Aquifer

Floridan
Aquifer

Floridan
Aquifer

Hawthorn
Formation

Floridan
Aquifer

Hawthorn
Formation

Floridan
Aquifer


Flowing Well at Elk Horn Fish Camp;
well depth 136 ft., csg 127 ft.

Well at Silver Lake, Southwest of
Tallahassee, depth unknown

Well at Lost Lake; well depth 154
ft., csg. 100 ft.

J. Sessions Well, east of Tallahassee;
well depth 155 ft., csg. 85 ft.

Well at Hollis Motor Court, Chaires;
well depth 120 ft., csg. 64 ft.

Well at Hay-a-Tampa Cigar Co.; well
depth 411 ft., csg. 261 ft.

E. Tennell Well, nr. Midway; well
depth 10 ft., csg. 10 ft.

Well at Floridan Company, Tallahassee;
well depth 170 ft., csg. 105 ft.

Well at Natural Bridge Monument,
southeast of Woodville; well depth
175 ft.

River Sink Spring, Southwest of
Woodville


Floridan
8-10-68 Aquifer

Floridan
8-9-68 Aquifer












Table 2 Continued


Date
Location Description Sampled


Aquifer or
Source


FAW 075 T3S; R2W; Sec. 26
Wakulla County


FAW 076


T2S; R1W; Sec. 22
Wakulla County


Lost Creek, nr. Arran


M. L. Huntley Well, southwest of
Woodville; well depth 43 ft.


8-9-68



8-9-68


Surface
Water

Floridan
Aquifer


FAW 077 T1N; R1W; Sec.
Leon County

FAW 078 TIN; R1E; Sec.
Leon County


FAW 079


TlS; R1W; Sec. 4
Leon County


5 Well nr. Lake Jackson; well depth
194 ft., csg. 140 ft.

5 Well at Maclay Gardens, north of
Tallahassee; depth unknown


Tallahassee City Well at Ridgeway
& Arnold Sts.; well depth 254 ft.,
csg. 156 ft.


Floridan
8-15-68 Aquifer

Floridan
8-15-68 Aquifer


Floridan
8-15-68 Aquifer


Sample
Number










important hydrologic unit within the study area (Hendry and
Sproul, 1966; Stringfield, 1966). The generalized potentio-
metric surface is shown in Figure 3 (Healy, 1962) with the
direction of ground-water movement being southeasterly to
southerly along section A-A'.

The cross-sectional distribution of the uranium content
and the U-234/U-238 activity ratios is given in Figure 4.
The data show that surface waters and ground waters above the
Hawthorn Formation have a relatively low uranium content and
a high U-234/U-238 activity ratio. Water from the Hawthorn,
which contains phosphatic material and clays, has a slightly
increased uranium content. The artesian waters from the
underlying Floridan aquifer exhibit the highest and most
variable uranium content, probably due to a variable uranium
distribution within the sediments (Kaufman, 1968). U-234/U-238
activity ratios approaching equilibrium occur in waters from
the Hawthorn Formation and from the Floridan aquifer where it is
overlain by thick younger deposits. Waters from the Floridan
aquifer exhibiting activity ratios less than unity (234U/238U =
0.50 to 0.90) underlie the Woodville Karst Plain.

Figures 5 and 6 portray the areal distribution of the
U-234/U-238 activity ratios of water in the Floridan aquifer
and the regional structural and physiographic setting within
the report area. The data indicate definitive distribution
patterns, the most notable being a deficiency of U-234 in the
waters underlying the Woodville Karst Plain and the southern
and eastern parts of the sinkhole-riddled Tallahassee Hills
(area B, Figure 5). Activity ratios near equilibrium underlie
the Gulf Trough, the Marianna Lowlands, and the northwestern
part of the Tallahassee Hills (areas A and C, Figure 5).
Consequently, a close interrelation between uranium isotope
disequilibrium and the hydrogeologic framework is suggested.

Within area B (Figure 5) the karstic topography results
in a well-developed subterranean drainage system, including
several first-magnitude springs (Figure 6), suggestive of
high permeability and active circulation. Sellards (1917)
concluded that a structural ridge (upthrown fault block?)
existed within this area which elevated the limestone nearer
the surface. This resulted in a thin, easily breached over-
burden, and permitted increased ground-water circulation with
concomitant increased solution and development of secondary
permeability. Hydrologic data, including large seasonal fluc-
tuations of Wakulla Spring discharge correlative with local
precipitation suggest the occurrence of extensive local
recharge (Kaufman, 1968).

To account for the low activity ratios observed in these
waters, it is hypothesized that during periods of lowered
Pleistocene sea levels, extensive leaching within the Floridan













F U,

- ,


Figure 3. Location of sampling sites and potentiometric surface of the Floridan
aquifer in North Florida.













NORTH -
A



200

LOWLA



100 C


1.021/



0





-100


-200
GEOLO
SEVER


Figure 4.


NORTHWEST







NDS L


uwonnee Ls.


GULF TROUGH


TALLAHASSEE HILLS

Miccosukee Formation 1.23/
I /0.04


II00
II.4


Ochlockonee
Fnrult


0.95/


I1TH SOUTHEAST
A'



WOODVILLE KARST
PLAIN


.Hawthorn Formation


Pleistocene








I I
I I


Suwannee Limestone O.-5 9
II


0


1- -100


-200


motion


'3.42 II /0.51
II "!
II ? II
11 ______|1____
DIAGRAMMATIC I -----I ----
iGIC SECTION ADAPTED FROM II .
HENDRY AND SPROUL II
(VERT. EXAG., NOT TO SCALE) 1.0/ Crystal River For

II
11 1


Geologic. section and distribution of the U-234/U-238 activity ratios (upper number)
and uranium content in micrograms per liter (lower number) in the waters of
North Florida.


~1--- 1111_~1~----11 11111--.----- _1..*-~ ~--IIX-~~-~~ -I.


~II ~-~----_I__.--~------_II~_ ___ -- ---_I I_ _~-~---I^--- _. I


0.88y
/0.58

































-N-




0 1
I


C
//
I, -
1.01

/ ----- --.02
-/---..=

I i/ 0.95
,/ 00.69
A 0.90
I 0.50 B
0.88




EXPLANATION

^/ / Control point
Number is U234/U238
0 20 30 miles activity ratio of water
= I from the Floridan aquifer

A Area of low permeability, poor
circulation little leaching.
B Area of high permeability, rapid
circulation, extensive leaching.
C Area of good permeability and
circulation, little leaching.
Divide separating area A, B and C.


Figure 5. Areal distribution of the U-234/U-238 activity ratios
of waters from the Floridan aquifer in North
Florida.


L___I____I_____II_____~LI-l.^l~_~lll~- ---~- IIIII~III... --sl--CI --__~.~-_~--_1II1~-~-------X--_ ~---X
















7,~a


/u/
x BARWICK ARCH


0 O 20 30 miles


After Sever
r, d


_100- Shows thickness of Pliocene,
ISOPACH Pleistocene, and Holocene deposits
combined; Interval 50 feet.

Korst topography, Floridan aquifer
S at or near land surface, both
recharge and discharge occur.

S Sinkholes breaching Hawthorn or
iL -ii younger deposits, *--:;' area.


C First Magnitude Spring


Figure 6. Regional structure and physiographic map of North
Florida depicting recharge areas.


:l__~_m~_________l_____I____~ ~










aquifer occurred, associated with an active ground-water flow
system and favorable environmental oxidation potentials.
This resulted in preferential leaching of U-234, leaving
behind rocks deficient in U-234 with respect to U-238. The
physicochemical processes responsible for the low activity
ratios, utilizing geochemical and paleohydrologic models has
been evaluated by Rydell (1969).

An apparent relation between the magnitude of the U-234
deficiency and the uranium content is indicated for most of
the waters sampled (Figure 7). The increased U-234 deficiency
may define areas of greater ground-water circulation and
solution during Pleistocene time with concurrent development
of secondary aquifer permeability and preferential leaching of
U-234. Waters with a higher uranium content may define zones
of greater leaching of uranium. Thus, points falling on or
near the plotted line in Figure 7 suggest the waters are part
of an active flow system. As one moves up the curve, the
higher uranium content and increased magnitude of the U-234
deficiency indicate progressively greater permeability and
ground-water circulation. This concept is consistent with the
results of Dooley et al (1966) who noted that greater U-234
deficiencies and range of disequilibrium in sandstone-type
uranium ore deposits appear to be related to zones of higher
permeability and greater circulation of ground water.

Area A (Figure 5) coincides with the Gulf Trough (Figure
6), a northeast-southwest trending downfaulted syncline
containing thick Hawthorn and post-Miocene deposits (Sever,
1964, 1966; Hendry and Sproul, 1966). Drainage is for the
most part by surface streams, flowing over poorly drained
materials of low permeability. Hendry and Sproul (1966) report
that limestone cores from within the trough show little
evidence of solution or development of secondary permeability.
This, plus the low yield of wells in the area, suggests a
limited ground-water circulation system, negligible recharge,
and no significant Pleistocene leaching of the sediments.

Data presented by Wait (1960) suggest the influence of
structural features upon the hydrologic system and ground-
water quality in southwestern Georgia. Water from wells
located within the Gulf Trough, adjacent to the Ochlockonee
Fault, trending northeast-southwest is poorer in quality (high
dissolved solids and sulfate) and higher in temperature than
water from wells located away from these structural features.
These physical and chemical differences suggest low aquifer
permeability and restricted circulation. Olds (1961) concluded
that the Ochlockonee Fault may restrict the flow of artesian
water, a conclusion supported by the later results of Hendry
and Sproul (1966) and Kaufman (1968).















S / 6036

7 7

AREA
o034 B /
7 / /


027


S24

24 /


0.5


0.6


0,7


0.8


I ~ I I III


0.01


URANIUM


0.1
CO;iT I -11


I I I I I 1111


IN MICROGRAMS


I I I I I II1


1.0
PER


10.0


LITER ( pg/1)


/ 057/


/ 044 021
051 t 020'

026 0052

\ AREA
\ ^ S o0


>-
> 0.9


l.2h


SURFACE
WATERS

'1Z


025
r--' I


3


.i 0.95 error


Figure 7. Relation between the U-234/U-238 activity ratio and uranium content in the
waters of North Florida.


I I I I


1~1__ ~11^1_1111_1^1~ _^_~sl _1 1~1~--11~_1~ 1___~ .1_11 ~~~11~-~1_ 11 __ I~-----~


I _IJ ~_UI I I I I I I I I --


A^ 06 __










Artesian waters from within area A depart considerably
from the plotted line in Figure 7, indicating waters that
are not part of the active hydraulic flow system, consistent
with the concept of low permeability and restricted circula-
tion in this region.

Area C is interpreted as one of active circulation and
high permeability today with little preferential leaching of
U-234 during the Pleistocene. The region may have been shielded
somewhat from the Pleistocene circulation, solution and leaching
by its thick cover of overlying sediments and/or environmental
oxidation potentials may not have been favorable.


Conclusions

Artesian waters deficient in U-234 are associated with a
karst terrane an area of extensive recharge, high permea-
bility and active ground-water circulation. The magnitude of
the U-234 deficiency appears to be related to the degree of
circulation, leaching, and permeability, as well as the
oxidation potential of the environment and infiltrating waters.
Artesian waters with U-234/U-238 ratios at, or slightly greater
than, equilibrium are associated with a downfaulted syncline -
an area of negligible recharge, low permeability and little
ground-water circulation, with limited preferential leaching of
U-234 during the Pleistocene. The data suggest that waters
within the faulted syncline are isolated from Pleistocene
and present-day active hydraulic flow systems.

As the activity ratios should reflect ratios in the source
materials, the U-234 deficient waters sampled from the karst
terrane appear to reflect a different source or history than
waters updip to the northwest. The Gulf Trough and Ochlockonee
Fault act as a hydraulic barrier that prevents any significant
southeastward flow of groundwater.










4. URANIUM ISOTOPES AS QUANTITATIVE INDICATORS OF GROUND
WATER SOURCES


The Isotope Dilution Approach to Hydrologic Problems

Investigation of the distribution and environmental
disequilibrium patterns of naturally occurring uranium
isotopes (U-2-34 and U-238) in waters of the Floridan aquifer
(Table 1) suggests that variations in isotopic activity ratios
and concentrations can be used to quantitatively evaluate
mixing proportions of waters from differing sources.

Quantitative evaluation of mixing proportions may be
achieved by treating the uranium disequilibrium of ground
waters as a natural experiment in isotope dilution analysis
(Osmond, et al, 1968).


A. Wakulla Springs

This approach may be illustrated by an example from the
Tallahassee area-where the karstic nature of the-topography
results in a well-developed subterranean drainage system and,
toward the south, several first magnitude springs. Wakulla
Spring, one of the largest in Florida, has an average discharge
of 10.3 cubic meters (365 cubic feet) per second (U. S.
Geologic Survey, 1966). Hydrologic data, including large
seasonal fluctuations of spring discharge correlative with
local precipitation, suggest that a large portion of the water
is derived from local recharge in the karst area (Kaufman,
1968). An alternative, in part, is that the source is to the
north, with flow down the gradient of the piezometric surface.

Natural waters may be considered an isotope dilution
system inasmuch as variations in the U-234/U-238 activity
ratio can occur only at the time uranium is added to the
system through leaching of enclosing rock or by mixing with
other uranium-bearing waters; once uranium is in solution, the
activity ratio is unaffected by dilution, precipitation, or
changes in chemical state.

If an amount of water #1 is mixed with water #2 (each with
its dissolved uranium) to produce a mixture, water #3, the
following relationships hold;

(1) VI + V2 = V3
(2) MI + M2 = M3
(3) MIAI + M2A2 = M3A3
(4) Mi = CIVI










Where V is volume in liters; M is the amount of uranium in
micrograms; C is concentration in pg/l; and A is the activity
ratio, U-234/U-238. From these relationships, and letting VI
be unity, the following two equations are derived:

A -A
(5) M2 = C1 A
A3 A2

C + M
(6) V2 -= 2
C3

These expressions can be used in two ways: (1) in the
calculation of the relative mixing volumes of two waters when
C and A values for the two source waters (#1 and #2) and the
resultant mixed water (#3) have been determined, and (2) in
deducing the amount of uranium and water (#2) that have been
added-to an initial water (#1) to produce a resultant water
(#3). In the latter case, there are three unknowns, M2, A2,
and V2, in the two equations (5) and (6), and one of these
variables must be estimated.

As an example in which three waters are analyzed, we
might ask: What vol.i-i- of water-like that from Horn Spring
(#2) must be mixed with a unit volume of water like that from
Big Bend (#1) to produce water like that flowing from Wakulla
Spring (#3) (Figure 8). Using equations (5) and (6), M2 is
8.4 and V2 is 17.4. Consequently, for every liter of Big Bend
water, 17.4 liters of Horn Spring water would be required to
yield 18.4 liters of Wakulla Spring water. As a check on the
uranium balance, we can compute the necessary C2 of Horn Spring
water, obtaining 0.48 pg/l, almost precisely the value measured.

There are probably numerous hydrologic situations in which
"closed system" assumptions can be made, the C and A values of
three waters determined, and the mixing volumes calculated with
confidence and accuracy. Requirements include: sufficient
uranium (0.1 yg/l or more), diverse activity ratios, and a
reasonable understanding of the hydrologic system--of which the
latter probably contributes the greatest error to this approach.

Isotope dilution analysis cannot of course, define a
mixing model; it does, however, set limits on possible models
and develops the implications of these.

As an example of the second approach, again referring to
Figure 8, successive aquifer points are compared and the addi-
tions of uranium and water between points deduced. This is
useful because the aquifer system here is quite "open" in that
rainwater is infiltrating from the surface and uranium is
being leached from the aquifer rock. In this case, the observed
variations in activity ratio of waters within the aquifer are




























































Figure 8. Composite hydrologic map and diagrammatic geologic cross
section. Geol -i_ modified from Hendry and Sproul (1966).
Composite pci-'.- -- the inferred hydrologic flow system.
Each box represents a sampling site 1. .i.g activity
ratio above and uranium concentration in pg/1 below.
The numbers within the arrows refer to inferred activity
ratio of the uranium added to the water (leached from
the rock) between sampling sites. All A and C values
correspond to those used in Table 3.

29










systematic enough to permit "most probable" A2 values to be
assigned and thus M2 and V2 values to be calculated.

In estimating the A2 value, the activity ratio, of the
uranium leached between sampling points #1 and #3, the
following aspects were considered: (1) aquifer waters here
show a generally decreasing activity ratio for their dissolved
uranium in the down-dip direction relative to the piezometric
surface, (2) surface waters generally have activity ratios
greater than 1.00, in agreement with the commonly observed
isotope fractionation 1.- leaching, (3) A2 A3 must have the
same sign as A3 Ai, and (4) whenever C3 is significantly
greater than C1, A2 A3 must be small. As a result of these
considerations, all A2 values were selected such that the
range of A2 A3 was .02 to .10, except for Tallahassee to
Big Bend, where it was .01 to .06. Infiltrating waters were
assumed to be contributing only small amounts of uranium; the
activity ratio of these waters is indicated as being 0.90+
in Figure 8.

The results of these successive interval calculations
based on the values of Tables 2 and 3 are shown in Table 4,
in which the relative volumes, as well as the computed amounts
of uranium which are added between Havana, Tallahassee, Big
Bend, and Wakulla Spring, are also computed for comparison.

Since each V2 is defined relative to each initial V1,
the total volume increment to the final water can be deter-
mined (last column of Table 4). Calculation shows that of
the hypothesized sources for Wakulla Spring the more local
sources predominate, and no more than about 8% could be
contributed from as far away as Havana.


B. Silver Springs

The proposed Cross-Florida Barge Canal has precipitated
considerable interest in the geohydrology of the Floridan
aquifer in the area of Ocala and Silver Springs. Faulkner
in a U.S.G.S. open file report (1970) summarizes the under-
ground water flow pattern in this region, and has calculated
the probable sources of water for the major effluence of the
area, Silver Springs.

As a test of the utility of the uranium isotope technique
for calculating water sources and mixing proportions, we
chose this well documented system for sampling and analysis.
We will accept Faulkner's conclusions as correct, and compare
with them the isotopic results derived more or less independently
of hydrologic data.









Table 3


Results of Analysis


Aquifer
Interval
(see Fig. 1)


H to T
T to B
B to W
T to W


Al
ratio

1.02
0.95
0.69
0.95


(iig/
liter)


1.14
0.51
2.63
0.51


A3
ratio

0.95
0.69
0.85
0.85


CG
(lg/
liter)


0.51
2.63
0.60
0.60


Deduced Values
A2
A2 ratio
ratio range


0.90
0.65
0.90
0.80


0.85-0.93
0.63-0.68
0.87-0.95
0.75-0.83


Aquifer
Interval
(see Fig. 1)


Computed Values
V2 C2 AM
M2 V2 range (pg/ (per-
(fg) (liter) (liter) liter) cent)


AV Contrib.
(per- to Wakulla
cent) (percent)


H to T
T to B
B to W
T to W


1.60
3.31
8.42
1.02


4.37
0.45
17.4
1.55


2.8-9.1
<0.1-4.2
10.0-38.
0.7-4.1


0.37
7.35
.48
.66


140
650
320
200


440
45
1740
155


Additions of uranium and water between aquifer sampling points. The
first row refers to the aquifer between Havana and Tallahassee, Florida-,
in which Ai and C1 are the activity ratio and concentration respectively,
of the aquifer water at Havana, and A3 and C3 are the corresponding
values at Tallahassee; A2 is the estimated range of possible values for
the activity ratio of uranium added between these two points. Values
for M2 V2 and C2 are calculated from Eqs. 5 and 6; M2 is the amount of
uranium added, V2 is the volume of water added (the range of possible
V2 values is given, corresponding to the listed A2 ranges), and C2 is
the resulting concentration of uranium if M2 and V2 describes a mixing
water. The quantities AM and AV refer to the proportions M2/CI and
V2/V1, respectively. The last column follows from the various V2
values calculated with respect to the flow model (Fig. 1).









Table 4


URANIUM CONCENTRATIONS AND URANIUM ISOTOPIC ACTIVITY RATIOS:
SILVER SPRINGS REGION


Location or U-234
Well No. U cone., ppb U-238

SCE 124 1-.27 .04 0.84 .03
CE 47S 1.60 .02 0.96 .02
CE 48 0.57 .02 0.56 .02
CE 79 0.21 + .03 1.09 .06
CE 39 0.13 .03 0.95 .10
CE 81 0.88 .04 0.94 .04
CE 33 0.47 .05 0.98 + .07
BELLE VIEW 4.04 .03 0.56 .02
ORANGE LAKE 0.66 .12 1.04 .04
CE 30A 0 71 + .03 1 .-47 .06
SCE 172 0.31 .04 1.05 .04
SCE 132 0.16 .02 1.42 .04
SCE 156 0.24 .03 1.27 .05
SCE 153 0.61 .03 1.26 .08
OCALA #3 1.08 .10 0.94 .02
OCALA:
LIBBY MCNEIL 0.13 .02 2.43 .04
CE 42 0.01 .02 ----
LAKE WEIR 0.01 .02 --- --
CE 61 0.10 .02 0.98 .04
CE 51 0.01 .02 ----+ --
CE 55 0.01 .02 -- +
CE 53 2.98 .26 0.85 .02
CE 131A 0.10 .04 1.19 .06
SALT SPRINGS 0.37 .03 1.30 .04
SILVER SPRINGS 0.71 .04 1.03 .02










The uranium data are listed in Table 4, and the sample
sites are shown in Figure 9. The analytic data are also
plotted on a graph of activity ratio versus reciprocal of
concentration in Figure 10. (Several sample sites listed in
Table 4 are not plotted in Figures 9 and 10. These samples
contain too little uranium to analyze reliably, or were too
far from the focus of the study area, or for other reasons
were not considered to be important sources for Silver Springs
water.)

The type of plot used (Figure 10) reveals unique and
useful properties of the data. For example, the combining
of two waters will produce a resulting water mixture whose
activity ratio and reciprocal of concentration must fall on
a straight line joining the plotted points of the two sources.
The proportions of the two sources is a simple function (not
linear) of the position of the resultant point on this line.
This is, in effect, a-graph of the mixing equations reported
by Osmond, et al (1965) and discussed in an earlier portion
of this chapter. In practice, one plots the possible sources
to see if they do in fact, form a straight line relative to
the resultant water, and if so, the equation is used to
calculate the mixing proportions.

A simple extension of this procedure shows that a unique
mixing proportions solution results when three possible
sources are considered, provided that the plot of the resultant
mixture falls within the triangle formed by the three plotted
sources. For more than three sources, solutions are possible
whenever the resultant water plots within the polygon formed
by joining the proposed plotted sources. In the latter case
however, a unique solution generally does not result; a certain
range of possible mixing proportions can be calculated.

A straight-forward procedure for solving a complex source
system, as in the case of Silver Springs, would be to select
three proximal sources for the final resultant water (Silver
Springs), and then select three sources for each of the proximal
sources, etc., ultimately arriving at mixing proportions
distributed among a number of primary sources.

Table 5 shows the results of a partial and tentative
calculation of assignable proportions for sources for Silver
Springs water. The resulting flow net is shown by arrows on
the map of Figure 9, and also on the diagram of Figure 10.
For this very rudimentary application of the isotopic analysis,
the only selection rules for possible sources were: among
the nearest (radially oriented) possible sources for a
resultant water, choose three which plot as a relatively
compact triangle and thus yield a unique mixing solution. On
the diagrams, the dotted lines show inferred but not calculated
contributions; except for one or two wells, these are excluded
from the calculations summarized in Table 6.










030A 172 132




156 /

Q-1 SILVER /
1530 SPRINGS
412O 0A 47 S
OCALAQO- f\ 48
048


33
07
-1 \

CROSS FLORIDA BARGE
(PROPOSED)


5 MILES


,"


OCALA


IEW


MIXING PROPORTIONS
NOT CALCULATED


AREA


INFERRED GROUND WATER
FLOW DIRECTIONS


Ocala Area: Inferred ground water flow directions. Numbered circles are sampled well localities
which satisfy the selection rules for the mixing calculations. Pattern of arrows from number
to number matches that of Figure 10. In this diagram, geographic locations of sample points is
only approximate.


053


/


/
/
/


MIXING PROPORTIONS
CALCULATED


Figure 9.


w















1.401


1,20


1.00


O30A
O132


153 1J56
O O
-



SILVER 79
0-3 SPRINGS z ___-
R kO 172
4 /7 033

53//
47SO /- ----30


0 1240- -



-~---> MIXING PROPORTION
CALCULATED
-\ -MIXING PROPORTION
OBV 048 NOT CALCULATED


0.0


2,0


3,0


4.0


5.0


6.0


S

3


8.0


U CONC,, PPB
Figure 10. Activity ratio vs. reciprocal of concentration diagram of Ocala area samples. Numbered
circles are plots of : :.1--:: which satisfy the selection rules for the mixing calculations.
Pattern of arrows from number to number matches that of Figure 9. This type of diagram
permits immediate recognition of possible solutions to the mixing formula; however,
exact mixing proportions must be calculated.


0

<:
cr
>-

I-
I-
<:I


0,80


0,60


_ __ __










Table 5


Resulting Mixture
As In ----

A. SILVER SPRINGS



B. SCE 156


C. SCE 124



D. SILVER SPRINGS


MIXING PROPORTIONS


Possible Sources
As In ----


SCE
SCE
SCE

CE
SCE
SCE


Proportions of
Sources


124
153
156


30A
172
132


CE 47S
BELLEVIEW
CE 81

PRIMARY SOURCES
SCE 153
CE 30A
SCE 172
SCE 132
CE 47S
CE 81
BELLEVIEW


45%
29%
26%

6%
33%
61%

16%
8%
76%


29%
2%
9%
16%
7%
33%
4%









Table 6

SOURCE OF SILVER SPRINGS WATER:
HYDROLOGIC vs ISOTOPIC CALCULATIONS


Source Zones
(Faulkner)

1-5

8-10

14-17


Representative
Sources
(This Report)

33,81,BV

0-3

30A,132,172,153


Percent Contribution
to Silver Springs
(Faulkner) (This Report)

27% 37% 28


5% 4


45%


51%


22-25


47S


All others


7% 5


23%


*As calculated
*Corrected for 23% "others"










Table 6 compares the results of this calculation with
that of Faulkner. The wells which were computed to be
'primary sources' according to the selection rules are grouped
according to the corresponding radial geographic zones of
Faulkner, and the percent contributions of source zones
compared. As initially calculated the isotopically computed
sources necessarily add up to 100%. However because the data
points are limited and the calculation only partially
completed, the figures are arbitrarily reduced by- 23%-in the
last column to allow for the source zones of Faulkner.

The resulting percent contributions as computed here
show a truly remarkable agreement with those of Faulkner, in
fact, the agreement must be in part fortuitous. Among the
factors which might have adversely affected the comparisons,
but did not or else did so in a compensating way are;
appreciable infiltration of ground water near the spring,
appreciable solution of uranium-within the aquifer flow system,
seasonal variations in well sample uranium or in hydrologic
flow pattern, strong depth dependence of flow pattern, etc.
It should be noted that a more sophisticated treatment of the
procedures would allow the computation of increments of surface
recharge by low activity water (points at the extreme right of
the ratio-concentration diagram) and also increments of newly
dissolved uranium within the aquifer (points at extreme left
in the diagram).

The point to be emphasized is that the isotopic flow
pattern was deduced from a relatively small number of data
points, whose geographic position was the only hydrologic factor
considered. Even if other systems should prove to be less
favorable with respect to uranium geochemistry, e.g., low
uranium concentration or small isotopic variability, it seems
that a combination of uranium-isotopic and standard hydraulic
analyses would be a very useful approach to ground water
studies.










5. TRITIUM ANALYSIS: A MODIFICATION OF THE BENZENE SYNTHESIS
METHOD


Introduction

Tritium is produced naturally in the upper atmosphere by
interaction of cosmic ray produced thermal neutrons with
nitrogen and oxygen. It-is formed artificially-in nuclear
fusion reactions, and since 1954, when the first major thermo-
nuclear device was detonated in the Pacific, thermonuclear
test explosions have produced worldwide pulses of tritium.
These rapid increases in the abundance of the sole radioactive
isotope of hydrogen that occur in nature, coupled with the
fact that tritium is an actual part of the water molecule,
make tritium an important hydrologic tracer.

Th- method herein described was initially developed by
Tamers et al (1961). Tamers and Bibron (1963) and Tamers
(1964) developed the technique somewhat further. The method
is closely related to a popular means of radiocarbon analysis
described by Noakes et al (1965). The modification of the
benzene synthesis method for tritium analysis described in this
paper simplifies the procedure further and has been shown to
produce results that agree very satisfactorily with data from
other laboratories. The method should prove valuable to the
hydrologist who wishes to perform his own tritium analyses,
and is particularly suitable for a limited production volume.


Theory

The water sample containing tritium as a contaminant is
converted into acetylene by hydrolysis of calcium carbide.
The tritiated acetylene is then trimerized to benzene using
an extremely efficient vanadium catalyst (Noakes et al, 1965).
A constant isotope effect lowers the tritium activity per
gram hydrogen of the benzene to about 80% of that in the
water sample. Hence a constant portion of the tritium,
originally in the water sample, now satisfies the carbon bonds
of the benzene molecules in the synthetic benzene. The
benzene is of high purity and is an excellent counting liquid
when mixed with the primary fluor PPO. The tritium beta
radiation is then counted in a liquid scintillation counter.
Pertinent chemical equations in the procedure are:

CaC2 + 2H20 --> Ca(OH)2 + C2H2 (1)


3C2H2 C6He (2)

vanadium catalyst at 25 in. vacuum










Operational Procedure


A schematic diagram of the benzene synthesis apparatus
is shown in Figure 11. On the left is the acetylene generator
G and a 50 ml burette that permits the drop-by-drop addition
of the water sample to the calcium carbide contained in a 3 1
flask. The entire system was evacuated, flushed with argon,
then evacuated again to 30 inches vacuum. The 3 1 flask is
partially immersed in an ice water slush to remove heat from
the flask during the exothermic hydrolysis and to condense
any steam that may form. In addition, the slush maintains a
constant temperature, which stabilizes the reaction chemically
and isotopically. Spattering is avoided by introducing the
water below the level of the carbide, and excessive absorption
of water by the residue is prevented by using a large excess
of CaC2 and slowly adding the water. In this procedure, 120
grams of carbide is reacted with 50 ml of sample water, which
is the volume that empirically produces 17 1 of C2H2 (STP).
The use of an auxiliary tank storage volume of 17 1 is not
arbitrary but reflects the volume of acetylene necessary to
yield 17 ml of benzene with a conversion efficiency of 75%.
Typical efficiencies are usually in excess of 90%, however.

Adjacent to the acetylene generator, two purification
columns (PI and P2) are connected in series. The first
contains powdered calcium carbide and is water cooled. This
column is used to convert any water vapor evolved in the
generator to C2H2. The next column contains, in the upper
position, reagent grade PbCl2, which extracts sulfides, and
in the lower position, P205, which removes traces of water
and ammonia. The acetylene is passed through trap A, which
is cooled by a dry ice alcohol slush bath to remove gases that
are condensible above -78C. The purified acetylene is finally
collected in a liquid nitrogen cooled trap (trap B).

The acetylene to benzene conversion is a one-step
catalytic reaction. The frozen acetylene is permitted to
sublime at room temperature from the cold trap (B) through
the storage tanks (S) onto the evacuated catalyst column(CC).
The column contains 375 grams of vanadium activated silica
alumina catalyst (available through John E. Noakes, Oak Ridge
Institute for Nuclear Studies, Oak Ridge, Tennessee). The
catalyst has been baked under vacuum at 3800C for 3 hours to
remove associated water, which inhibits the reaction. The
catalyst is allowed to cool before mounting on the system
and is cooled with ice water during the conversion reaction.
Cooling is of paramount importance for high yields because it
prevents both vapor blocks and surface area contamination of
the catalyst pellets. In addition, cooling prevents appreciable
pyrolysis of acetylene and benzene into more polymerized hydro-
carbons. Upon completion of the reaction (45 minutes to 1 hour),




















--VAC.


CC


Figure 11.


Diagrammatic sketch of benzene synthesis system.
purification columns. A,B,C: cold traps. S:


G: acetylene generator. P1,P2:
storage tanks. CC: catalyst column.


PI a P2










a heating jacket is applied to the catalyst column, raising
the temperature of the column to 1000C, and the benzene is drawn
off under vacuum into a dry ice alcohol slush cooled trap (C).

A 15 ml aliquot of the synthetic benzene is placed in a
20 ml nylon counting vial (obtained from Nuclear Chicago, 333
E. Howard Ave., Des Plaines, Illinois 60018) and 60 mg of the
primary fluor, PPO, is added. Sample preparation takes place
in a-photographic darkroom under red light. This procedure
eliminates phosphorescence in the vial and its contents,
thereby providing minimal background fluctuation during the
counting period. The tritium beta radiation is counted to the
desired error, and the sample count is preceded and succeeded
by efficiency and background counts. In this way, any possible
counter fluctuations are closely monitored. An external
standard (137Cs) is employed to check for sample quenching;
however, no quenching has been observed to date.


Fractionation Effect

Reproducibility of fractionation effects for hydrogen
isotopes is the keystone of the benzene synthesis method of
tritium analysis.

Tritiated water analyzed by Ostlund at the Marine Institute
of the University of Miami was processed by the benzene syn-
thesis method at full strength, as well as at half and quarter
strength dilutions. The mean fractionation effect for tritium
equals 19.3% 0.2%.

Several interlaboratory cross checks were performed with
the cooperation of Ostlund at Miami and the U.S. Geological
Survey Tritium and Radiocarbon Counting Laboratory in
Washington, D.C. Results of the comparison checks are shown
in Table 7. Agreement is surprisingly good; the two data sets
agree within one sigma error in most cases. The errors
associated with our answers are large, mainly because of the
high background count rate of our liquid scintillation counter.
Additional lead shielding might be helpful. The lower detection
limit of the system is about 10 TU (10 tritium atoms per 1018
protium atoms) presuming absolute counter stability.


Discussion

Overall, several factors have proved important in the
determination of tritium by this method:










Table 7

Ii-TR L, LABORATORY CHECKS

Known
Description TU

groundwater* 70.5 3.9

groundwater* 13.2 .08

rainwater 31. 1.2

rainwater 40.9 2.0

rainwater 31.6 1.4

rainwater 54.3 2.6


Measured
TU

71.2 5.5

15.4 11.

27.7 8.4

43.9 8.5

30.9 6.7

51.1 10.


* Collected and analyzed by the U.S. Geological Survey,
Tritium and Radiocarbon Counting Laboratory,
Washington, D.-C.
Collected and analyzed by Ostlund at the University of
Miami.


No.

1

2

3

4

5

6










1. The stability of counter background and counting
efficiency is of prime concern since counting times are long
when the sample is of low specific activity, i.e., 48 hours.
Most of the modern liquid scintillation counters that employ
ambient temperature photomultiplier tubes meet this require-
ment within acceptable limits.

2. The choice of a calcium carbide that is low in
sulfides is imperative since excess sulfides quench the
catalyst and benzene counting liquid and contribute heavily
to the loss of sample hydrogen as H2S. Carbide of low sulfide
content may be purchased from Research Inorganic Chemical
Company of Sun Valley, California. This carbide is 'dead'
with respect to 1 C. Spillover of radiocarbon beta activity
into the tritium counting channel would result in variable
count rates that are difficult to correct because of the low
specific activities involved.

3. Successful use of the catalyst is dependent upon
complete removal of associated water. The catalyst will
maintain its own vacuum during the conversion. Generally,
the lower the pressure, the higher the benzene yield.


Conclusion

The distinct advantages of this modification to the
benzene synthesis method for tritium analysis are three.

1. Samples may be prepared easily by the isotope hydro-
logist and/or his technician.

2. In its present form, without enrichment, the system
is suitable for groundwater studies where large volume sample
processing is not required.

3. Results compare favorably with those from other
laboratories.









6. TRITIUM HYDROLOGY OF THE TALLAHASSEE, FLORIDA AREA


Field Methods and Procedures

Samples of ground and surface waters in Leon, northern
Wakulla, and eastern Gadsden counties were taken over a two
year period. Sampling sites consisted of wells, both table
and artesian, Wakulla Spring, the St. Marks River, and Lakes
lamonia and Jackson. The sample sites were chosen to represent,
broadly, the local geohydrologic environment. Determination
of sample tritium concentration was done in part at Miami
Institute of Marine Sciences, in part, by Isotopes, Inc.,
Westwood, New Jersey and, in part, at the Florida State Univer-
sity using the newly developed benzene synthesis-liquid
scintillation counting method described in the previous section.


Sample Locations and Analytical Results

A sample location map is shown in Figure 12. The specific
location and description of each sample point is presented in
Table 8. Many of the groundwater samples were drawn from the
Floridan aquifer. The Floridan aquifer is-composed of marine
limestones and dolomites which range from Eocene through Miocene
in age. The formations function as a unit because their porosity
and permeability are similarly developed. The formations which
make up the Floridan aquifer in the Tallahassee area are the
Upper Eocene Crystal River formation, the Oligocene Suwannee
limestone, and the lower Miocene St. Marks formation (Hendry
and Sproul, 1966). The Floridan aquifer is overlain by
surficial sands, silts, and clays of the Miocene Hawthorn forma-
tion. The overlying veneer of sediments is of highly variable
thickness. Additional information on the hydrology and the
geology of the study area may be obtained from Sellards (1917),
Moore (1955), Gremillion (1965), Hendry and Sproul (1966),
Stringfield (1966), and Sever (1966).

In conducting a study where natural rainout tritium is to
be used as a tag for water, which is the case with the present
problem, several questions must be answered:

1. What are the input activities of tritium from precipita-
tion and what have they been in the past?

2. What are the tritium activities at present in the
ground waters of the study area?

3. What were the natural groundwater tritium activities?

(Stewart and Farnsworth, 1968)


















2.2 57.8
0 / 38.4
0.0 150.1
SP 25.2 172 48.9

GADSDEN / LN
LEON

1t 94.5
'' 6.1
--J* 114.2'
5 43.0
10 10
73.8
10 S I
54.2
_129.9
89.3 \-I
*I


WAKULLA


33.6


Figure 12.


Map of Tallahassee and surrounding
of Floridan aquifer well water.
(left) and fast (right) recharge


area showing tritium content
Dashed line separates slow
regimes.


111____ ~_ ~II ~












Table 8


TRITIUM CONCENTRATION OF SELECTED WATERS
WITH PERTINENT SAMPLING INFORMATION


Date of
Collection


1-27-67


10-15-67




10-22-67



10-20-67



10-20-67


11-16-68


Sampling Location
and Details


Sample
Number

LG-01


Date of
Analysis


T.U.


6.1 00.5*


13.9 01.0*



2.2 00.3*



43.0 31.0*




54.2 03.7*


#6 Municipal Well at Lafayette Park,
Tallahassee, Fla., Wln. IN-IE, 30cc,
depth 413 ft., cased to 170 ft. open
only to Suwannee L.S. at 170 ft.

Lake Jackson nr. Capital Circle Trk.
Rt., Wln. 1N-1W-566 Depth 194 ft. cased
to 140 ft., open only to Suwannee L.S.,
140 ft.

N.W. Lk. lamonia Shore, Leon Co., Win.
3N-lE-Zod, depth 268 ft., cased to 260
ft., open only to Suwannee L.S. at 260 ft.

Jctn. U.S. 319 & S-261 at Big Bend Trk.,
Rt. Wln. 1S-1E-19C, depth 10p ft., cased
to 70 ft., open only to St. Marks

Wdvlle. Mncpl. Well, Win. 2S-lE-8dd,
depth 183 ft., cased to 32 ft., open to
St. Marks & Suwannee L.S. at 15 ft. and
110 ft. respectively

Well at Chaires Gen. Str., No well info.
available


114.2 09.2*** 1-23-69


LG-02




LG-03



LG-04



LG-05


LG-06


9-20-67


1-03-68



1-03-68



1-03-68




1-03-68












Table 8 Continued


Date of
Collection


Sample
Number

LG-007



LG-008


LG-009


LG-010




LG-011



LG-012


11-16-68



10-25-68


11-15-68



11-15-68


11-15-68


11-15-68




11-15-68



11-15-68


T.U.


Sampling Location
and Details

Well at Sunny Hill Farm, Win., 3N-2E
14-d, depth 148 ft., cased to 103 ft.,
open only to Suwannee at 103 ft.

Well S. of lamonia, Win., 3N-ZE-nc,
depth 33 ft., Shallow well

Well on the N.W. Shore Lk. Mice.,
Shallow well, no info. available

Well at Gen. Str. Town of Mice., Win.,
2N-3E-8bb, depth 235 ft., open to
Hawthorn at 65, St. Marks at 105,
Suwannee 185 ft.

Well at Felkel 2N-2E-3cb, depth 179 ft.,
50 ft. to Hawthorn, 80 ft. to St. Marks,
110 ft. to Suwannee

Well near Gardner 1N-2E-15 ca, depth
220 ft., cased to 177 ft., open to
Suwannee L.S. at 185 ft.

1.75 mi. E. Corey on 261A Win., IS-ZE-
29cb, depth? 70 ft. to St. Marks, 75
ft. to Suwannee L.S.

Well Lk. McBride Elem. School, 3 mi.
E. of U.S. 319 Rd., connecting
Brdfdvlle and Cntrvlle, no info.
available


<10


Date of
Analysis



1-28-69


1-31-69


2-03-69




2-06-69



2-09-69



2-13-69


2-16-69


26.2 11.2*** 2-20-69


38.5 08.4***


57.8 05.8***


151.0 08.8***




48.9 08.4***



17.2 13.4***



94.0 13.8***


LG-013



LG-014















Date of
Collection

11-17-68




11-17-68


11-16-68


11-16-68



11-17-68





10-10-67

10-10-67

8-19-68


8-06-68


Table 8 Continued


Sampling Location
and Details


Sample
Number

LG-015




LG-016


LG-017


T.U.


<10.Q0 ***


<10.00 ***




129.0 09.3***


Well at Confdrt. Inn Spr. Bib
Ochlockonee, Wln., 1N-2W-23 da., depth
254 ft., cased to 84 ft., open to St.
Marks at 40 ft.

Well 1 mi. N.W. Int. 261 with 151 Wln.,
IN-lE-16d., depth? No info. available

Well at Nat. Bridge nr. Wdvl. Wln.,
2S-2E-29 da., depth 175 ft., cased to 163
ft., 5 ft. to St. Marks. 36 ft. to
Suwannee L.S.

Well nr. Bradford Brook on Rt. 61 S., Wln.
lS, 1W-26cb, depth 220 ft., cased to 140
ft., open to Suwannee L.S. at 140 ft.

Well at WFSU transmitter Sta. in
Apalachiocola Nat'l. Forest, Wln.,
1S-4W-35aa, depth 230 ft., cased to 132
ft., open to Jcsn. Blf. at 50 ft. and
Hawthn. at 61 ft.

Surface sample of Lk. Jsckn. wtr.

Surface sample of Lk. Iamonia wtr.

Sample of St. Marks Rvr. wtr. at Natrl.
Bridge, near Woodville

Rainwater collected on FSU Campus during
afternoon thunderstorm


Date of
Analysis


2-22-69


2-26-69




3-01-69


3-04-69





3-07-69

1-03-68

1-03-68


11-19-68


13.4 06.3*** 8-13-68


73.8 10.8***





<10.00 ***

115.0 08.0*

113.0 08.0*


21.2 03.8***


LG-018



LG-019





LS-001

LS-002

LS-003


LP-01















Date of
Collection

10-20-67



1-27-67


10-10-67


Sample
Number

WG-01



WS-01


WS-02


WS-03


WS-04

GG-01



GG-02


Table 8 Continued


Sampling Location
and Details


Wakulla Co., 4 mi. N. of Wakulla Spring
on Rt. 61, depth 43.5 ft., open entirely
to St. Marks

Wakulla Spring surface wtr., sample taken
from pier

Wakulla Spring surface wtr., taken over
cave

Wakulla Spring as above at 50 ft. depth
using Van Dorn Bottle

As above, but at 85 ft. depth

Havana Municpl. Well, located at
T3N-R2W-SEC26, Gadsden Co., depth 692
ft., cased to 418 ft.

Sprnfld. Elem. Schl., nr. Quincy,
Gadsden Co., located at T2N-R4W-SEC5ab,
depth 467 ft., cased to 318 ft.


T.U.



89.3 06.3*


36.5 01.5*


31.3 02.1*


32.8 02.2*

33.7 + 02.3*



00.0 + 00.18**



00.0 + 00.18**


Date of
Analysis



1-03-68


9-20-67


1-03-68


1-03-68

1-03-68



3-22-68



3-22-68


* Analysis performed by I
** Analysis performed by H
** Analysis by E. I. Walli


isotopes, Inc.
. G. Ostlund at Miami Marine Institute
ck using benzene method


10-10-67


10-10-67

2-15-68



2-15-68









To document tritium input to surface and ground waters,
the United States Geological Survey established a network in
1958 for collecting and testing rainwater samples for tritium
activity. One such station, operated by the Survey is at
Ocala, Florida, approximately 170 miles southeast of Tallahassee.
Although the Ocala station is the closest to the study area,
the following argument must be understood if the significance
of these data are to be evaluated.

It has been observed that rain sampling stations near the
oceans which receive their precipitation from oceanic air
masses have rain which is low in tritium due to great oceanic
dilution effects. In contrast, precipitation at continental
stations is rather high in tritium. The maximum tritium rainout
occurred in the summer of 1963 after a series of nuclear tests
that winter. The tritium rainout has declined each subsequent
year as an exponential function. Data for the Ocala station
alone was obtained from the U.S.G.S. office there and graphed.
The months of greatest tritium rainout are June and July.
This is so because the greatest amount of precipitation falls
at Ocala when meteorological conditions favor greatest tritium
concentration in precipitation.

The third requirement for tritium study is a knowledge of
the tritium background against which tritium levels may-be
compared. In the Tallahassee area, we may safely assume that
there is negligible tritium background for several reasons:

1. Tritium levels before 1952 ranged from 2 to 10 T.U.
and, because Tallahassee receives most of its precipitation
from maritime air masses, these levels would have been fairly
low initially.

2. In addition, the effects of time and dilution would
have reduced tritium levels even further.

3. Although waters in the eastern portion of the study
area are generously tagged with tritium, those in the west are
virtually background.

Figure 12 is a map which indicates the areal distribution
of tritium concentration in the waters of the Tallahassee area.
The errors associated with the tritium determinations are to
be found in Table 8, and are based on the 0.95 confidence level
i.e., 2 significance level. The 0.95 error cited is dependent
only on counting statistics and does not consider any
systematic error.

These data show that waters in western Leon and eastern
Leon and northern Wakulla counties have a relatively high
tritium content. The tritium concentration of surface and
shallow ground waters lying above the Hawthorn formation









aquiclude was much higher than that of the deeper artesian
waters of the Floridan aquifer. The range of tritium concen-
trations is from 0.0 .18 T.U. to 151.0 8.8 T.U.


Discussion of Results

Several important factors which influence the tritium
concentration of groundwater at an observation point are:

1. Tritium input levels are affected by the time,
intensity and tritium concentration of precipitation and the
distance this precipitation must travel to reach the recharge
area;

2. Evapotranspiration of precipitation;

3. Rates of diffusion and hydrodynamic dispersion.

(Stewart and Farnsworth, 1968)

With reference to 1. above, it is important to realize
that heavy precipitation resulting in high total tritium rain-
out, rather than high concentration-alone, is of more-signifi-
cance hydrologically.

Evaporation and transpiration may cause the tritium input
to differ from the input expected when only the tritium concen-
tration of precipitation from the principal recharge area is
considered. In the Tallahassee area, evapotranspiration rates
are high owing to the large areal extent of several lake basins,
dense foliage, warm climate and good ventilation.

The third factor, mentioned above, is associated with
mixing and dispersion. Should permeabilities be anisotropic,
and flow patterns complex, then tritium concentrations in
groundwater may not closely resemble tritium rainout.

Keeping these factors in mind, we shall draw some conclu-
sions about the geohydrology of the Tallahassee area in light
of the tritium in precipitation from Ocala, and tritium
determinations in local ground and surface waters.

The most prominent observation of the study is the apparent
absence of tritium in groundwaters sampled in western Leon and
Gadsden Counties. Evidently, no local recharge occurs here as
suggested by the very low tritium levels. Also, because fairly
high and very low activity waters are juxtaposed, no significant
lateral communication takes place in an east-west direction.
High tritium concentrations in groundwaters of eastern Leon and
Wakulla counties indicate rapid recharge.









Tritium concentrations fall below about 151 T.U. in waters
of the eastern sector, and the observed range is equivalent to
that found in recent rainfall. A tentative age for waters in
the shallow aquifer is between zero and two years old based on
the fact that tritium levels in rain began to fall within the
observed range only as early as August, 1967. Tritium concen-
tration of rainwater preceding this date are much higher due
to the nuclear tests of winter, 1963.

Generally then, waters of the western sector of the study
area are devoid of tritium suggesting an origin as rain prior
to 1952, year of the first fusion bomb test. Tritium levels
in the shallow groundwaters of eastern Leon and northern
Wakulla Counties are very young waters with an origin as rain
within the last two years.

Some observations have been made on a more intensive level.
In northern Leon County, there is an increase of tritium
activity toward the east, suggesting that recharge increases in
the direction of Lake Miccosukee.

Water leaving the Floridan aquifer at Wakulla Spring, the
principal discharge point for the study area, had a tritium
content of 33.6 T.U. when sampled during the "dry season"
during January, 1968. A tritium -content 89.3 T.U. was observed
in a shallow water well some four miles up-gradient from the
spring. Tritium in rainout at Ocala during this time ranged
from 20-30 T.U. Tritium content of water of the No. 6 municipal
well in Tallahassee, sampled in January, 1967, was 6.1 0.5 T.U.
Tritium levels in rain at this time, were 50-70 T.U. The
relative stability of the tritium content of Wakulla Springs
water from the "dry season" in 1967, to that of 1968, is
certainly worthy of note. It is reasonable that very low
tritium concentration is attributed to the deeper waters of the
Floridan aquifer which travel south to Wakulla Spring. The 6.1
T.U. Tallahassee water, the 13.9 1.0 T.U. Lake Jackson well
water, and the 2.2 0.3 T.U. Lake lamonia well water are indica-
tive of low tritium in deep artesian waters. The reader is
referred to Table 8 for the depths of these wells and other
particulars. The low tritium deep waters apparently mix with
the younger tritium rich waters of the shallow aquifer to yield
water of an intermediate tritium concentration. This water is
discharged at Wakulla Spring, and at numerous other springs
and streams.

Given: T.U. Deep Water = 6.1 T.U.
T.U. Shallow H20 = 84.2 T.U.
T.U. Spring H20 = 33.6 T.U.

Let: x = the fraction of water of tritium content
6.1 T.U.
y = the fraction of water of tritium content
84.2 T.U.









then, x + y = 1
6.1x + 84.2y = 33.6
6.1x + 84.2(1-x) = 33.6
x = .65
y = .35

A rather rough estimate of mixing coefficients for water of
Wakulla Spring during the dry season is, then, 65% deep water
and 35% shallow groundwaters.









APPENDIX A:


DETAILED METHODS AND ANALYTICAL PROCEDURES FOR URANIUM ANALYSES


Water Samples

1. Water samples of 14-21 liters were collected in dupli-
cate from each source in one-gallon bottles (alternating a
bottle of "A", then a bottle of "B", etc.). In collecting,
the samples were passed through a 37 micron sieve to remove any
coarse particulate matter that might influence results.

Duplication is necessary to guard against the possibi-
lity of laboratory contamination (i.e., the "A" and "B" fractions
must be in agreement or they both are suspect). The alternation
of collection of "A" and "B" fractions is thought to aid in
achieving agreement between "A" and "B" fractions in that it
reduces the possibility of one fraction being disproportionately
influenced by factors such as drawdown in a small well.

2. Prior to water collection, tracer-carrier solutions
are prepared in the laboratory so that a predetermined amount
of U-232 spike and iron carrier may be equilibrated with each
bottle of sample at the time of collection.

The tracer-carrier solution consists of:

A) U-232 spike of known specific activity and in an
amount approximately equal to the expected natural
uranium activity of the sample. U-232 is a non-
naturally occurring nuclide which was provided
under a loan agreement by the U.S. Atomic Energy
facility at Oak Ridge.

B) Fe+. carrier (13 mg Fe+++ per liter of sample in
the form of Fe(NOs)3-9H20).

C) 25 ml 16 N HN03 (sufficient to cause a pH of 1
or less in 3.5 liters of sample).

3. Samples are placed in a water bath and taken to boiling
temperature for one hour to aid in removing dissolved gases,
especially C02, which in subsequent chemical processing could
possibly form sufficient (NH4)2C03 to act as a holdback carrier
by completing with U to form highly soluble carbonate-uranyl
complexes.

4. While still hot, the sample is stirred; and the U is
almost quantitatively coprecipitated with ferric hydroxide
formed by the addition of sufficient NH40H to attain a pH of 9.









The high temperature of the solution aids in the coagulation
of the gelatinous ferric hydroxide precipitate.

5. The precipitate is allowed to settle overnight and
is then decanted, centrifuged, dissolved in HC1, evaporated,
and redissolved in 8N HC1. It was found that one-gallon
disposable plastic bottles, such as milk is sold in, were
well suited to heating in the water bath and facilitated
decanting by puncturing the bottle well above the precipitate
level.

6. The large amount of iron contained in the 8N HC1
solution is mostly removed by solvent extraction with an equal
volume of isopropyl ether equilibrated for 30 seconds in a
separatory funnel.

7. The sample is heated to remove traces of ether and
then is evaporated with 5 drops of HC104 to remove any remaining
organic.

8. The sample is redissolved in 1ON HC1 for ion exchange.


Ion Exchange

1. The resin used is Dowex 1-X8, 100-200 mesh, ionic
form Cl", an anion exchange resin.

2. The ion exchange columns consist of a resin bed of
approximately 1 cm x 14 cm topped by a 50 ml reservoir and
constricted and plugged at the bottom with glass wool.

3. The resin is pretreated in the column by washing the
resin with acids in the reverse order that the acids are used
in the exchange process.

4. Add the sample to the column in 10N HC1; after the
sample has passed through the column, the column is washed
with 20 ml 10N HC1.

5. Elute uranium from column with 30 ml 0.1N HC1,
evaporate with drops HC104, and redissolve sample in 7N HNO3.

6. To a pretreated new column, add the sample in 7N HNO3;
after the sample has passed through the column, the column is
washed with 20 ml 7N HNO3.

7. Elute uranium from column with 30 ml 0.1N HC1 and
evaporate with 5 drops HC104 for electrodeposition.










FLOW CHART


First Column
Stepl & 2

Step 3 & 4 Step 5

Th Ra Ac U ::

Ca etc. Second Column

Step 6 Step 7

Fe U




Electrodeposition

I1. The sample is dissolved in 5 ml 2M NH44C1 (pH 2.5),
in a deposition cell consisting of a 1.5 cm chimney and 3 cm
stainless steel planchet, and deposited for 30 minutes at 12
volts and 1 amp.

2. While the current is still flowing, a few drops of
concentrated NH40H are added and the solution discarded.

3. The cell is disassembled and the planchet heated over
a burner to volatilize any NH4Cl, harden the uranium deposit,
and provide a thin source for alpha particle spectrometry.

Counting

The planchets are counted in a vacuum chamber with a
Technical Measurements Corporation Diffused Passivated
Detector, 50 KEv resolution and 300 mm active area. This is
coupled to a 100-channel TMC pulse height analyzer with a
scale expander which facilitates excellent resolution of the
alpha particle spectrum.

Three peaks of greatest interest are U-238 4.2 Mev,
U-234 4.75 Mev, and U-232 5.3 Mev. However, peaks such
as U-235 4.35 Mev, differing in energy by 0.15 Mev from
the nearest principal peak, may be resolved.









General Remarks


The average chemical yield of uranium for water samples
was 35%, for rocks 38%.

With each series of samples, a duplicate set of blanks
were run using the same amount of reagents and tracers from
the same batch as used in processing the samples. These
blanks are necessary to provide a correction factor for back-
ground as well as any contaminants introduced in the chemical
processing.









APPENDIX B:


TREATMENT OF URANIUM DATA


Sources of Error

Systematic Errors

Systematic errors arising from malfunctioning of counting
equipment are difficult to detect in low-level radioactive
determination. The only practical way of ascertaining that
the counting equipment is giving a statistically valid response
is by periodic counting of calibration standards and by
multiple counting of samples and inspection of the data for an
unwarranted variation. In this respect, the counting equipment
used was found to be very reliable and little rejection of
data due to this type of error was necessary.

A second source of systematic error is in calibration of
the U-232 spike. To reduce this error to a minimum, the U-232
spike used was calibrated against a uranyl nitrate solution
whose activity was calculated from gravimetric and volumetric
determinations as well as determined by counting. As an
additional check, the U-232 spike was calibrated in a 2r
windowless proportional counter against a uranium oxide standard
of 2% accuracy prepared by the National Bureau of Standards.


Random Errors

The possible sources of random errors are:

1. Contaminants introduced in the sampling procedure.

2. Contamination from chemical reagents and glassware
used.

3. Failure to achieve equilibration of spike with
sample.

4. Variations in counter background.

5. Statistical counting errors.

Analyzing samples in duplicate, along with appropriate
blanks, greatly reduces the possibility of the first three
types of error going undetected and provides a basis for
rejection or correction of the results. Background variations
were found to be negligible, and only a slight increase in
background with time was noted. Of the various random errors,
the only one that can be expressed quantitatively is the









counting error arising from the random nature of the radio-
active disintegration process.


Data Handling

1. The recorded spectra, including the three uranium
peaks U-238, U-234, U-232, were inspected for inconsistencies
and gr:-ihically checked for peak energy and linearity.

2. The three peaks of interest were integrated by
addition of the counts in a six-channel envelope.

3. Data was spot-checked graphically with the charts
given by Jarrett (1946) to see if variations were within the
limits expected from statistical variations.

4. Six-channel envelopes corresponding to uranium peak
energies were determined for the blank and background spectra.

5. Data were transferred to computer cards for calculation
of results.

The equation used -todetermine the error or a counting
rate determination is that given by Jarrett (1946):

Y = K (Ns/Ts + Nb/Tb)1/2

Where Ns = count rate of sample

Nb = count rate of background

Ts = time of sample count

Tb = time of background count

K = 1.96 factor for the 0.05 level of confidence.

The calculated error for each sample is that propagated
through multiplication and division, where the fractional
error of a product or quotient is equal to the square root
of the sum of the squares of the individual fractional error,
for z = xy:


z 2 + 2/2
7 (XI









Fortran IV Computer Program

A Fortran IV computer program was used to treat the raw
data. The program performs the stripping of the blank and
background contributions from the sample and calculates the
desired uranium concentrations, activity ratios and errors.
For purposes of calculation, the following errors are assigned:
weight or volume 2%, spike 2%, 44.6 dph/pg U-238 2%. In
addition, K is given as 1.96 so that all calculated-errors
represent the 0.05 level of significance.









APPENDIX C:


REPORTS AND PUBLICATIONS. Research on naturally occurring
radioisotopes in the Floridan aquifer supported by Office of
Water Resources Research Title I Grants A-005-FLA and A-O11-FLA.

Rydell, H. S. and M. I. Kaufman
Isotopic uranium studies of the Floridan Aquifer and
related natural waters (abstract). Program, Geological
Society of America S.E. Sectici !Ie-ting, Tallahassee,
Florida. Pages 52-53. 1967. A-005-FLA.

Kaufman, M. I., H. S. Rydell and J. K. Osmond
U-234/U-238 Disequilibrium as an aid to hydrologic study
of the Floridan Aquifer (abstract). Transactions,
American Geophysical Union, Vol. 49, No. 1. Page 165.
1968. A-005-FLA.

Kaufman, M. I.
Uranium isotope investigation of the Floridan Aquifer
and related natural waters of North Florida. M.S.
Thesis. Florida State University. 1968. A-005-FLA.

Wallick, Edward I.
Tritium hydrology of the Tallahassee, Florida area with
analysis by liquid scintillation counting without
isotopic enrichment. M.S. Thesis. Florida State
University. 1969. A-011-FLA.

Osmond, J. K., H. S. Rydell and M. I. Kaufman
Uranium disequilibrium in groundwater: An isotope
dilution approach in hydrologic investigations. Science,
Volume 162. Pages 997-999. 1968. A-O11-FLA.

Rydell, H. S.
The implications of uranium isotope distributions
associated with the Floridan aquifer of North Florida.
Ph.D. dissertation. Florida State University,
Tallahassee, Florida. 1969. A-O11-FLA.

Kaufman, M. I., H. S. Rydell and J. K. Osmond
U-234/U-238 Disequilibrium as an aid to hydrologic study
of the Floridan aquifer. Journal of Hydrology, Volume 9,
Number 4. Pages 374-386. 1969. A-O11-FLA.

Wallick, Edward I. and George A. Knauer
A modification of the benzene synthesis method for
tritium analysis. Water Resources Research, Volume 6.
Pages 986-988. 1970. A-011-FLA.









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18, 74 p.




Full Text

PAGE 1

URANIUM AND TRITIUM AS NATURAL TRACERS IN THE FLORIDAN AQUIFER by J. K. OSMOND and B. F. BUIE and H. S. RYDELL, M. I. KAUFMAN,; and E. I. WALLICK PUBLICATION NO. 14 FLORIDA WATER RESOURCES RESEARCH CENTER RESEARCH PROJECT TECHNICAL COMPLETION REPORT OWRR Project Number A-Oll-FLA Annual Allotment Agreement Numbers 14-01-0001-1628 (1969) 14-31-DOOl-3009 (1970) 14-31-0001-3209 (1971) Report Submitted: August, 1971 The work upon which this report is based was supported in part by funds provided by the United States Department of the Interior, Office of Water Resources Research as Authorized under the Water Resources Act of 1964.

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TABLE OF CONTENTS Page LIST OF TABLES ------------------------------------------iv LIST OF FIGURES v ABSTRACT ------------------------------------------------1 1. INTRODUCTION 2 2. URANIUM ISOTOPES IN NATURE: BACKGROUND AND ANALYTICAL PROCEDURE -----------------------------4 Previous Studies ----------------------------------4 Decay Scheme and U-234 Fractionation Mechanism ----5 Methods and Procedures ----------------------------8 3. URANIUM ISOTOPES AS AN AID TO HYDROLOGIC STUDY OF THE FLORIDAN AQUIFER -----------------------------10 Purpose and Significance -------------------------Results and Discussion ----------------------------Conclusions 10 10 26 4. URANIUM ISOTOPES AS QUANTITATIVE INDICATORS OF 5. GROUND WATER SOURCES ------------------------------27 The Isotope Dilution Approach to Hydrologic Problems ----------------------------------------27 A. Wakulla Springs -----------------------------27 B. Silver Springs -----------------------------30 TRITIUM ANALYSIS: A MODIFICATION OF THE BENZENE SYNTHESIS METHOD Introduction --------------------------------------Theory --------------------------------------------Operational Procedure ----------------------------Fractionation Effect ------------------------------Discussion Conclusion ----------------------------------------39 39 39 40 42 42 44 6. TRITIUM HYDROLOGY OF THE TALLAHASSEE, FLORIDA AREA --45 Field Methods and Procedures ----------------------45 Sample Locations and Analytical Results -----------45 Discussion of Results ----------------------------52 APPENDIX A: DETAILED METHODS AND ANALYTICAL PROCEDURES FOR URANIUM ANALYSES 55 Water Samples -------------------------------------55 Ion Exchange --------------------------------------56 Electrodeposition ---------------------------------57 Counting ------------------------------------------57 General Remarks -----------------------------------58 ii

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Page APPENDIX B: TREATMENT OF URANIUM DATA ------------------59 Sources of Error ----------------------------------59 Systematic Errors -------------------------------59 Random Errors -----------------------------------59 Data Handling ------------------------------------60 Fortran IV Computer Program -----------------------61 APPENDIXC: REPORTS AND PUBLICATIONS -------------------62 LITERATURE CITED ----------------------------------------63 -----iii

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Table 1 Table 2 Table 3 Table 4 Table 5 -Tab-Ie 6 Table 7 Table 8 LIST OF TABLES Uranium concentrations and isotopic activity ratios of natural waters of Florida --------Location and description of water samples -----------------Additions of uranium and water between aquifer sampling points ----------------------------Uranium concentrations and uranium isotopic activity ratios: Silver Springs Region ---Page 11 13 31 32 Mixing proportions ---------------------------36 -S otl-r ee Elf---S i I-vepSpr i-B&-w at e r:---1:l-;7-drol,ogi c----vs isotopic calculations -------------------37 Interlaboratory checks -----------------------43 Tritium concentration of selected waters with ------p-e r-t-rhe n-e-s-am:pTtn-g-trrformati-on.... ----.---=--... ....--4-7'--iv

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Figure I LIST OF FIGURES Decay scheme of the natural U-238 series showing isotopes of interest} half-life, mode and energy of decay -----------------Page 6 -Alpha .... particle spectrum uranium is_otopes; alpha energy in million electron volts Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 (MeV) ------------------------------------9 Location of sampling sites and potentiometric surface of the Floridan aquifer in North Florida -----------------------------20 Geologic section and distribution of the U-234/U-238 activity ratios content in micrograms per liter in the waters of North Florida -------------------21 Areal distribution of the U-234/U-238 activity ratios of waters from the Floridan aquifer in North Florida --------22. Regional structure and physiographic map of North Florida depicting recharge areas 23 Relation between the U-234/U-238 activity ratio and uranium content in the waters of North Florida -----------------------------25 Composite hydrologic map and diagrammatic geologic cross section --------------------29 Ocala Area: Inferred ground water flow directions --------------------------------34 Figure 10 Activity ratio vs. reciprocal of concentra-tion diagram of Ocala area samples --------35 Figure 11 Diagrammatic sketch of benzene synthesis system ------------------------------------41 Figure 12 Map of Tallahassee and surrounding area showing tritium content of Floridan aquifer well water ------------------------46 v

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ABSTRACT URANIUM AND TRITIUM AS NATURAL TRACERS IN THE FLORIDAN AQUIFER Naturally occurring radioisotopes serve as hydrologic tracers in the study of ground water movement and aquifer rec-harge. A benzene synthesis method of tritium analysis involving no isotopic enrichment has been developed which permits analysis of samples at a level of 10 or more tritium units (10+ H-3 per 1018 H-l). In the North Florida study area sharp boundaries separate young and old waters in the aquifer according to their tritium content. Uranium in ground water exhibits extreme variability in isotopic distribution and the combination of isotopic ratio (U-234/U-238) and total uranium concentration (O.OX to X parts per billion) serves as the tag with which to trace aquifer water. The sources of water flowing from Wakulla Springs and Silver Springs is calculated quantitatively; the results agree well with concluslons basedon standard hydrologic metnodsoY analysis. Uranium analysis requires one to four gallons of water per sample, and involves isotopic spiking with U-232, iron hydroxide co-precipitation, ion exchange separation, electrodeposition, vacuum counting, and alpha pulse height analysis. Osmond, J. K., B. F. Buie, H. S. Rydell, M. I. Kaufman, and E. I. Wallick URANIUM AND TRITIUM AS NATURAL TRACERS IN THE FLORIDAN AQUIFER Completion Report to the Office of Water Resources Research, Department of the Interior, August, 1971, Washington, D.C. 20240. KEYWORDS: tritium*, uranium isotopes*, ground water recharge*, aquifers*, tracers, ground water movement, springs. 1

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1. INTRODUCTION The use of naturally occurring radioisotopes to study the movement of ground water has been the subject of study by researchers at the Florida State University Department of Geology for several years. From April 1, 1966 to June 30, 1971 this research has been supported by the U.S. Department --------c-f--I-n-t-e-r-ie-r-8-f-f-i-ee---e-f'-Wa-t-e-F---Rs t_8...... ______ ___ Title I program (A-005-FLA and A-OII-FLA). This report covers the activity from July 1, 1968 through June 30, 1971 (A-OII-FLA). Some of the work described herein, especially that concerned with analytical techniques, had its inception under the previous grant (A-005-FLA). Conversely, some of the sub-projects begun under A-OII-FLA are not complete. Work on these will continue and separate reports wi-l----e--i-ss"bl-ed .OJ:'l----Q-:f th-se, a-PhD-Disse.rtation byL_. __ L._ Briel, will require several months of analysis and data reduction before completion. It will be concerned with the application of uranium isotopes to analysis of the sources and mixing patterns of the Santa Fe River System of north central Florida .. The second, an MS Thesis by Ivan Wilson, wJ.:TT-oe completeasooTI. rt--deal-s-wtth-the---appl-ic-a-t-1-en-ef-.--------non-isotopically enriched tritium analyses to the study of the Floridan Aquifer of north central Florida, between Tallahassee and Lake City. The following quotation from a preliminary report by Wilson illustrates the direction of this research: "In the eastern part of the study area the Floridan aquifer receives little or no local recharge during below normal rainfall periods. Some recharge in the upper portions of the Floridan aquifer occurs where the overlying Hawthorn Formation thins. Where the Hawthorn thickens or a well taps a deeper portion of the Floridan aquifer no local recharge was indicated. The Floridan aquifer is nearer the surface in the central part of the study area, west of Live Oak, Suwannee County. Here the low tritium content of the shallow wells and a sinkhole indicate that the aquifer is discharging during the drier periods. The western part of the study area appears to have a greater local recharge. A possible flow direction to the southwest in Madison and Jefferson Counties is indicated by the decrease in the tritium content down the piezometric gradient. Local recharge over the entire area can not be entirely ruled out since the overall low tritium content may be a reflection of the dry period." Because of the interesting possibilities of the uranium isotopic approach to ground water studies, as developed under the Office of Water Resources Research Title I funding, continued support has recently been granted under the OWRR 2

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Title II program, so that some of the approaches herein described will receive continued attention and development. Most of the data and conclusions of this report have been published elsewhere and a list of publications and theses supported entirely or in part by A-Oll-FLA is appended. Those researchers, students, and technicians, other than the authors of this report, who have participated in the research --_. __ are listed in the annual reports to the Office of Water Resources Research. 3

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2. URANIUM ISOTOPES IN NATURE: BACKGROUND AND ANALYTICAL PROCEDURE Previous Studies In closed geologic systems older than about 106 years, -------U=2-34-is in equilihrJum with its parent U-238 (U-234/u-238 ratio = 1.00). At secular equilibrium, by deflnltlon: NIAI = N2A2 = A; and = 1.00, where NI and N2 = number of atoms of U-238 and U-234 respectively, Al and AZ = decai constant of U-238 and U-234 respectively, and A = alpha activity. In open systems such as those exposed to weathering and ground-water circulation, separation of these two isotopes can occur, giving rise to a state of radioactive disequilibrium. An increased interest in radioactive disequilibrium wIth-in the natural U-238 series in hydrologic systems has developed in recent years, especially with respect to geochemical, geochronological and hydrogeological studies. Rosholt (1958) suggested that radioactive disequilibrium studies could aid in undeT'S-t-a-nci-1:-ng-t-he-rta-t-ura-l-mig-r atproducts and also provide an insight into the geological and geochemical history of deposits. Until recently, the magnitude and frequency of disequilibria have been generally underestimated. The fractionation of U-234 with respect to its radiogenic parent U-238 was first discovered in 1953 by Russian investigators working with ground waters and secondary minerals (Cherdyntsev, et aI, 1955). Detailed studies in both the United States and Russia of natural waters, carbonates, sandstones, uranium ore deposits, soils, secondary minerals and peats have confirmed and extended these initial observations and have shown that preferential leaching of U-234 from a variety of rock types occurs, that differing isotopic ratios are characteristic of various source areas, and that for most natural waters, a relative enrichment of U-234 over U-238 is observed (Chalov, 1959; Isabaev, et aI, 1960; Thurber, 1962; Cherdyntsev, et aI, 1963; Rosholt, et aI, 1963, 1965, 1966; Dooley et aI, 195b)--. --The greatest deviations from equilibrium of the isotopes of the radioelements are observed in natural waters. The large reservoir of uranium, the oceans, reflects the magnitude of isotopic disequilibrium of uranium in nature (U-234/U-238 activity ratio = 1.14) (Thurber, 1962; Koide and Goldberg, 1965). Successful applications of U-234/U-238 activity ratios to Pleistocene geochronology have been made (Chalov, et aI, 1964). By noting that U-234/U-238 activity ratios in:natural waters draining specific source areas remained constant with time, in spite of considerable change in uranium content, 4

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discharge, and salinity, Chalov, et al (1964) were able to utilize the isotopic ratios to arriveat absolute age determinations of closed drainage basins. Decay Scheme and U-234 Fractionation Mechanism The decay scheme of the natural U-238 series is shown in part in-Figure 1-.-Thet-wo isot()peS, U-234 and U"'-238, are separated in the decay chain by two short-lived daughter nuclides, Th-234 and Pa-234. It has been suggested that the physicochemical reason for the U-234 fractionation is a change in the valence electron configuration from the U-238 parent to the radiogenically produced U-234 daughter for a time long enough to permit fractionation (Cherdyntsev, et aI, 1955; Chalov, 1959; Rosholt, et aI, 1963). ---Possible mechanisms for the U--234 fract-ionationhave been presented by Rosholt, et al (1963) and Dooley, et al (1966). In the three-step decay of U-238 to U-234, chemical bonds holding the decaying tetravalent U-238 are broken by the nuclear recoil from the decay. As a result of the U-238 alpha -decay and Th-234 and Pa-23-4_beta de_cay, thB_ daughter atom (U-234) is both displaced within the crystal structure and stripped of some of its electrons thus attaining an excited electronic state. According to Dooley, et al (1966, p. 1373), "At the time of decay and recoil the transformed nucleus is stripped of some of its electrons and momentarily is in a chemically uncombined state as a charged particle within the mineral lattice, or within a microfissure perhaps beyond the crystal boundary or in solution. Chemical recombining of U-234, except in a highly reducing environment, probably favors the electron-deficient hexavalent or oxidized state either as UO 2 ++ in a compound, or as an ion in s oluti on. !I Thus, as noted by Rosholt, et al (1963), U-234 would differ from much of the U-238 in-oxidation state, in location in interstitial spaces (unstable site?), and in type of chemical bonds, and is therefore potentially more mobile than its parent U-238. Chalov and Merkulova (1966), in studying comparative oxidation rates of U-234 and U-238, concluded that on the natural dissolution of uranium from minerals a partial separation of U-234 and U-238 may occur as a result of the greater ease of oxidation of U-234 atoms. They also considered radioactive recoil to be of great importance. In addition, according to Rosholt, et al (1965), the differing chemical affinities between uranium-and the intermediate daughter products may result in differential migration of the Th-234 and Pa-234 with respect to U-238. 5

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92 No.1 (/') z 0 .-0 a:: t:l. 0\ 91 lL 0 a:: w CD :E :::::> z Th 230 LIFE II: 7.6x104 yn. 140 U 234 LIFE II: yra. (2.31 MEV) ALPHA (4.77,4.72 MEV) (0.19, 142 NUMBER Po 234 LIiF II Lli M. Tn 234 JiLIiFII 24.1 ..,. 143 144 OF NEUTRON S ( N) ALPHA (4.19 MtV) Figure 1. Decay scheme of the natural U-238 series showing isotopes of interest, half-life, mode and energy of decay. U 238 >t UF' II 4.S! X 10' ,.... 146

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-------------------.., It is pertinent to note that the transition from the +4 to the +6 state has an oxidation potential within the normal range for geologic environments: so compounds of both valences would be expected in nature (Krauskopf, 1967, p. 527). Thus the oxidation potential of the environment, in addition to the electronic effects of decay, may be a major control on the separation of uranium isotopes, once decay and recoil of the daughter isotope into solution occurs. It has been observed (Rosholt, et al, 1965) that slightly oxidizing environments appear to large magnitudes of isotopic disequilibrium, whereas in reducing environments U-234 does not appear to be preferentially leached. Both U-238 and U-234 are leached in more equal proportions from an environment having a strong oxidizing potential. The leaching solutions preferentially up the oxidized U-234 as the stable divalent uranyl ion U02 +. The greater solubility of uranyl compounds (hexavalent uranium) relative to those of tetravalent uranium has been documented (Adams, et al, 1959). Although noting that in aqueous solutions the uranyl ion forms a somewhat soluble series of hydroxides or hydrates (U0 2(OH)2, HU04-, UO2), Krauskopf (1967, p. 527, 528) reported that the solubilities of the latter two ions became appreciable only in strongly alkaline solutions. In solutions containing carbonate ion, the solubility of compounds of hexavalent uranium is greatly increased by the formation of carbonate complexes such as the uranyl dicarbonate and uranyl tri-carbonate anionic species, hence carbonate-bearing solutions are excellent solvents for uranium (Scott and Barker, 1958; Garrels and Christ, 1965, p. 253; Krauskopf, 1967, p. 528). The solubility of uranyl compounds is strongly pH dependent, thus the pH of the environment plays a major role in the mobility of uranium. Serebryakova (1964), utilizing physicochemical methods, determined that in oxygenated ground waters uranium is present as anionic complexes such as (U02(C03)2(H20)2)-2 (86%) and (U0 2(C03)3D-4 (12%), consistent with earlier results. No colloidal uranium was detected. Dooley, et al (1966), in studying U-234 fractionation in sandstone-type-uranium ore deposits, noted that greater U-234 deficiencies and range of disequilibrium in ore samples appeared to be related to zones of higher permeability and greater circulation of ground water. A water saturated, slightly oxidizing, environment appears to be the primary medium for continuous fractionation and differential solution of uranium isotopes; consequently, the hydrologic system exerts a major control on the patterns of environmental disequilibrium. 7

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Methods and Procedures Sampling sites, consisting of wells, springs, streams, and lakes were selected so as to adequately represent the regional geohydrologic environment within the study area. Determinations were made of the total uranium content and of the U-234/U-238 activity ratios, using the analytical procedures of isotope dilution and alpha-particle spectrometry. In brief, the field sampling and analytical procedures were as follows: Samples were collected from each source in duplicate to serve as a check on analytical variability. The radioactive isotope U-232, which served as the isotopic yield tracer, and sufficient nitric acid to attain a pH of 1.0 were added in the field. The recovery procedure for uranium consisted of coprecipitation with ferric hydroxide, and purification using solvent extraction and ion-exchange. Following ion-exchange, the uranium samples were plated onto stainless steel planchets by electrodeposition for isotopic analysis using a high resolution solid state alpha-particle spectrometer. Figure 2 illustrates a typical alpha-particle spectrum of uranium isotopes. Blank solutions were run through the entire chemical separation and electrodeposition procedure and analyzed on the alpha spectrometer. These blanks provided a correction factor for background as well as for any contaminants which may have been introduced during the chemical processing. Chemical yields ranged from 15 percent to greater than 50 percent. The above methods and procedures resulted in determinations of uranium isotopes in trace amounts of less than .04 micrograms per liter and of U-234/U-238 activity ratios to within .003. Average errors for uranium content and activity ratio at the 0.95 confidence level were and percent, respectively, for water with a uranium content greater than 0.1 micrograms per liter. For a more complete description of technique, see the discussion under "Detailed Methods and Analytical Procedures" in Appendix A. 8

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en w I-::> z I{) en N \.0 ........ en I-Z ::> 0 u 1100 1000 900 600 500 400 300 200 100 10 20 U238 (4.2 MEV) 3681 30 40 U234 (4.7 MEV) 3050 50 CHANNEL NUMBER 60 U232 (5.3 MEV) 3329 70 WAKULLA SPRING Collected 9-2166 80 90 Figure 2. Alpha-particle spectrum of uranium isotopes; alpha energy in million electron volts (MeV).

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3. URANIUM ISOTOPES AS AN AID TO HYDROLOGIC STUDY OF THE FLORIDAN AQUIFER Purpose and Significance One of the purposes of this study is to investigate uranium isotope disequilibrium conditions within the Floridan --e r ana re lat e a---Yra-t-ur al w at ers------of'--n-or-t-rl-Floritl-a-w-i-t-h-a-------view towards evaluating the potential applicability of uranium isotope studies to hydrology. By studying the occurrence, distribution, and environmental disequilibrium patterns of naturally occurring uranium isotopes in selected Florida waters, it may be possible to determine the suitability of these isotopes as natural tracers or as other aids to hydrologic investigations, and to determine whether variations in radioisotope ratios and concentrations in natural waters carr-b euse dto-i ndic ate--s-aurc e8--and/or-his tory f-wat er-s-from .. various parts of the geohydrologic environment. An analysis of the relations between the isotopic distribution patterns and the hydrologic-flow system may permit interpretation in terms of regional permeability characteristics, ground-water ______ .Ql r c ula t i __ 9L e 0 within the Floridan aquifer. Furthermore, although detailed discussions are beyond the scope of this investigation, in order to utilize uranium isotopes in geochemical and geochronological studies, an extensive knowledge of the fundamental physicochemical behavior of the U-234 daughter product in relation to parent U-238 in hydrologic environments, as well as an understanding of the hydrologic-flow system, is needed (Rosholt, et al, 1966; Thurber, 1962). As pointed out by Osmond (19b4); a more comprehensive study of the heavy radioelements in the waters of Florida may lead to new concepts in the mobility of these elements. In addition, a knowledge of the isotopic distribution patterns may contribute to a better understanding of the hydrogeochemistry of uranium in natural aqueous systems. Results and Discussion The results of the analyses (Table 1) show that in natural waters within the study area (refer to Table 2) both the U-234/U-238 activity ratio and the uranium content are quite variable, indicative of extensive disequilibrium within the hydrogeologic environment. The errors given are based on counting statistics of samples and do not include consideration of systematic errors. The artesian Floridan aquifer, part of the main Tertiary limestone aquifer system in the southeastern United States, is the major source of ground water and the most 10

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Table 1 URANIUM CONCENTRATIONS AND ISOTOPIC ACTIVITY RATIOS OF NATURAL WATERS OF FLORIDA Sample Number FA-W-OTO-FAW 011 FAW 012 FAW 013 FAW 014 FAW 015 FAW 020 FAW 021 FAW 023 FAW-FAW 025 FAW 026 FAW 027 FAW 029 Uranium Content in Parts Per Billion U-234/U-238 Activity Ratio 0.080 0.013 0.999 0.213 0.019 + 0.006 3.327 1.149 0.016 0.005 4.070 1.301 0.662 0.080 1.145 0.124 0.013 0.009 1.580 1.343 0.514 0.021 0.953 0.020 0.584 0.024 0.878 0.020 0.154 0.008 1.021 0.053 o .UJbT 0 0-0-5 0.007 0.002 1.468 0.572 0.209 0.010 1.012 0.045 0.038 0.003 1.121 0.108 18.484 0.954 0.523 0.006 __ F FAW 033 FAW 034 FAW 035 FAW 036 FAW 039 FAW 040 FAW 041 FAW 042 FAW 043 FAW 044 FAW 045 FAW 046 FAW 049 FAW 050 FAW 051 FAW 052 FAW 053 FAW 054 FAW 056 FAW 057 FAW 060 FAW 061 FAW 063 FAW 065 FAW 066 FAW 067 FAW 068 FAW 069 FAW 070 FAW 071 __ 0--,-1 ___ ____ O. 0 19 ____ .608 0.029 0.854 0.028 2.631 0.101 0.686 0.007 0.604 0.027 0.852 0.025 25.912 1.450 0.503 0.005 0.050 0.007 1.588 0.264 0.135 0.009 0.841 0.063 1.552 0.081 1.073 0.022 0.079 0.007 2.938 0.237 0.691 0.037 0.687 0.023 0.014 0.004 1.343 0.455 0.134 0.100 0.803 0.724 11.015 0.661 0.925 0.010 0.488 0.027 0.899 0.032 0.008 0.003 1.972 0.896 0.340 0.017 0.963 0.032 1.140 0.059 1.021 0.024 0.481 0.027 1.002 0.037 0.191 0.056 1.001 0.275 2.673 0.151 0.710 0.029 0.687 0.042 0.836 0.044 0.696 0.050 0.762 0.033 0.532 0.030 0.896 0.030 3.422 0.166 1.116 0.012 0.008 0.004 0.618 0.613 0.314 0.025 0.935 0.059 0.600 0.037 0.840 0.031 0.386 0.026 0.928 0.046 2.649 0.189 1.019 0.023 0.082 0.007 3.710 0.297 0.042 0.005 1.034 0.149 11

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Sample Number FAW FAW FAW FAW FAW FAW FAW FAW 072 073 Q74 075 076 077 078 079 Table 1 -Continued Uranium Content in Parts Per Billion 1.343 0.083 0.276 0.020 0.674 0.046 119--:1:0 :-0 i80.858 0.052 0.376 0.024 0.628 0.040 0.702 0.046 12 U-234/U-238 Activity Ratio 0.971 0.026 1.062 0.062 0.824 0.033 -------------l.--cfIfi-f--0-. 160-----0.892 0.028 1.002 0.045 1.096 0.039 0.904 0.034

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Table 2 LOCATION AND DESCRIPTION OF WATER SAMPLES I Sample Date Aquifer or Number Location Description Sampled Source FAW 010 T33S; R22E; Sec. 22 L. Taylor Well; well depth 11 ft., Hillsborough County csg. 11 ft., sample slightly rusty 6-21-66 Water Table FAW 011 T31S; R23E; Sec. 23 R. I Marsee Well; well depth 120 ft., Hawthorn Polk County csg. 80 ft. 6-21-66 Formation I I FAW 012 T31S; R23E; Sec. 25 American Cyanamid Co. Well; well Floridan Polk County depth 950 ft., csg. 337 ft, 6-21-66 Aquifer I--' w FAW 013 T34s; R25E; Sec. 3 City of Wauchula Municipal Well; Floridan Hardee County well depth 1,103 ft., csg. 404 ft. 6-21-66 Aquifer FAW 014 T30S; R25E; Sec. 5 Bartow City Well Number 10; well Polk County depth 663 ft., csg. 591ft., possibly some fine pebble phosphate Floridan in sample 6-21-66 I Aquifer FAW 015 T28S; R26E; Sec. 21 Winter Haven City Well Number 2; Floridan Polk County well depth 816 ft., csg. 138 ft. 6-21-66 Aquifer FAW 020 TIN; RIE; Sec. 30 Tallahassee City Well Number 6; Floridan Leon County well depth 414 ft., csg. 170 ft. 9-21-66 i Aquifer FAW 021 T3S; RIW; Sec. 11 Wakulla Spring, of Floridan Wakulla County Woodville; discharge 560 cfs. 9-22-66 Aquifer FAW 023 TIS; RIE; Sec. 6 Unnamed spring in Myers Park, I Leon County Tallahassee; flow issuing from Hawthorn hills lope above clay layer 11-16-66 Formation

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Table 2 Continued Sample Date Aquifer or Number Location Description Sampled Source FAW 024 TIS; R5E; Sec. 15 Beasleys Creek, nr. Lamont; brown Surface Jefferson County color due to organics 11-17-66 Water FAW 025 T2N; RIW; Sec. 33 Lake Jackson, nr. Tallahassee 11-18-66 Surface Leon County Water FAW 026 T5N; R9W; Sec. 33 Blue Springs, nr. Marianna 11-26-66 I Floridan Jackson County Aquifer FAW 027 T3N; R5W; Sec. 14 Glen Julia Springs, Mt. Water Table f-' Gadsden County Pleasant 11-26-66' Aquifer -l= FAW 029 T2S; RIE; Sec. 8 City of Woodville Municipal Well; I Floridan Leon County well depth 183 ft., csg. 32 ft. 1-27-67 Aquifer 8 I FAW 030 T2S; RIE; Sec. Well at Ice House in Wbodville; Floridan Leon County well depth 21 ft., csg" 15 ft. 1-28-67 Aquifer FAW 033 T3S; RIW; Sec. 11 Wakulla Spring, southwest of Wakulla County Woodville; discharge 255 cfs. clear, : Floridan unfiltered I 4-8-67 Aquifer FAW 034 TIS; RIE; Sec. 19 Well at Big Bend Truck Center South Leon County of Tallahassee; well 100 ft., Floridan csg. 70 ft. 4-10-67 Aquifer FAW 035 T3S; RIW; Sec. 11 Wakulla Spring, southwest of Floridan Woodville; discharge 255 cfs.; clear 4-8-67 I Aquifer FAW 036 T2S; RIE; Sec. 8 City of Woodville Municipal Well; Floridan Leon County well depth 183 ft" cSig 32 ft. 4-8-67 : Aquifer

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Sample Number FAW 039 FAW 040 FAW 041 FAW 042 FAW 043 FAW 044 FAW 045 FAW 046 FAW 049 Location T38S; R38E; Sec. 1 Martin County T30S; R23E; Sec. 13 Polk County T30S; R24E; Sec. 35 T31S; R25E; Sec. 30 Polk County T30S; R21E; Sec. 17 Hillsborough County T30S; R23E; Sec. 12 Polk County T28S; R25E; Sec. 12 Polk County T30S; R24E; Sec. 25 Polk County T2S; R2E; Sec. 9 Leon County Table 2 -Contihued I Descriptipn R. Carlton flowing artesian well; well depth 835 ft., csg. 373 ft. Well at Kingsford International Minerals & Chern. Corp. shallow well removing water from phosphate deposit C. W. Shepard Well; well depth 50 ft ., c s g. 20ft. A. L. McClellan Well; well depth 165 csg. 42 ft. I Lithia Springs, southwest of Plant City City of Mulberry Municipal Well; well depth 833 ft., csg. 330 ft. Eagle Lake, nr. Winter Haven Seepage from mine face at Noralyn Plant International Mirterals & Chern. Corp. Horn Springs, east of Woodville Date Sampled 5-24-67 5-23-67 5-23-61 5-23-67 5-22-67 5-22-61 5-22-61 5-23-61 I 7-16-67 Aquifer or Source Floridan Aquifer Water Table Water Table Hawthorn Formation Floridan Aquifer Floridan Aquifer Surface Water Bone Valley Formation Floridan Aquifer

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I-' 0\ Sample Number FAW 050 FAW 051 FAW 052 FAW 053 FAW 054 FAW 056 FAW 057 FAW 060 FAW 061 FAW 063 Location TIS; R4w; Sec. 11 Leon County T2N; R5E; Sec. 19 Jefferson County T3N; R2W; Sec. 26 TIN; RIW; Sec. 2 Leon County TIN; R2W; Sec. 23 Leon-Gadsden Line TIS; RIE; Sec. 19 Leon County T3S; RIW; Sec. 11 Wakulla County T2S; RIW; Sec. 17 Leon County T2S; RIE; Sec. 10 Leon County T3N; R4w; Sec. 32 Gadsden County I Table 2 Conti+ued I Descriptin Flowing Well at Elk well depth 136 ft., csg. Fish 127 ft.! I I J of Monticello Mun:f-cipal City well depth 350 ft., cSf. 155 ft.1 I City of Havana Municip$.l Well; Wjell depth 692 ft., csg. 41? ft. I R. O. Vernon Well, nr'iLake well depth 236 ft., csg. 171 ft.i Ochlockonee River I csg. 70 ft. south flt. Wakulla Spring, of Woodville; dis charge 1100 c fs; brpwn color I Dismal Sink Osgood Sink, 2 miles of Rhddes Cemetery, Woodville Well At Spring Hill School, Gretna I Date Sampled 7-16-67! I 7-19-671 I i I I i I 2-27-68 I i 2-29-6a Aquifer or Source Hawthorn Formation Floridan Aquifer Floridan Aquifer Floridan Aquifer Surface Water Floridan Aquifer Floridan Aquifer Floridan Aquifer Floridan Aquifer Floridan Aquifer

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I-' -..:) Sample Number FAW 065 FAW 066 FAW 067 FAW 068 FAW 069 FAW 070 FAW 071 FAW 072 FAW 073 FAW 074 Location TIS; R4W; Sec. 11 Leon County TIS; R2W; Sec. 11 Leon County TIS; RIW; Sec. 31 Leon County TIN; RIE; Sec. 23 Leon County TIS; R2E; Sec. 3 Leon County T2N; R3W; Sec. 24 Gadsden County TIN; R3W; Sec. 14 Gadsden County TIN; RIW; Sec. 29 Leon County T2S; R2E; Sec. 29 Leon County T2S; RIW; Sec. 28 Wakulla County Table 2 Contipued Descriptipn I Flowing Well at Elk Fish well depth 136 ft., csg 127 ft. i Well at Silver Lake, Siouthwest CDf Tallahassee, depth unkfown Well at Lost Lake; weIll depth 154 I I ft ., c s g. 100 ft. I I J. Sessions Well, easti of Tallafuassee; well depth 155 ft., 85 ft.: I Well at Hollis Motor Chaires; well depth 120 ft., cslg. 64 ft. i i Well at Hav-a-Tampa Cilgar Co.; "o/ell depth 411 ft., csg. 261 ft. ; I I i i E. Tennell Well, nr. well depth 10 ft., csg. 10 ift. I i Well at Floridan Company, well depth 170 ft., 105 Well at Natural Monument I, southeast of well depth 175 ft. River Sink Spring, of! Woodville Date Sampled 8-6-68 8-6-68 8-6-68 8-6-68 8-6-68 8-6-68; 8-8-68 8-8-681 i 8-10-68 8-9-68 Aquifer or Source Hawthorn Formation Floridan Aquifer Floridan Aquifer Floridan Aquifer Hawthorn Formation Floridan Aquifer Hawthorn Formation Floridan Aquifer Floridan Aquifer Floridan Aquifer

PAGE 23

i-' CD Sample Number FAW 075 FAW 076 FAW 077 FAW 078 FAW 079 Location T3S; R2W; Sec. 26 Wakulla County T2S; RIW; Sec. 22 Wakulla County TIN; RIW; Sec. 5 Leon County TIN; RIE; Sec. 5 Leon County TIS; RIW; Sec. 4 Leon County Table 2 -Continued I Description Lost nr. Arran M. L. Huntley Well, southwest of Woodville; well depth !43 ft. Well nr. Lake Jackson; well depth 194 ft., csg. 140 ft. Well at Maclay Gardens" north of Tallahassee; depth unKnown Tallahassee City Well lat Ridgeway & Arnold Sts.; well depth 254 ft., csg. 156 ft. Date Sampled 8-9-68' 8-15-6$ 8-15-6$ 8-15-68 Aquifer or Source Surface Water Floridan Aquifer Floridan Aquifer Floridan Aquifer Floridan Aquifer

PAGE 24

important hydrologic unit within the study area (Hendry and Sproul, 1966; Stringfield, 1966). The generalized potentiometric surface is shown in Figure 3 (Healy, 1962) with the direction of ground-water movement being southeasterly to southerly along section A-A'. The cross-sectional distribution of the uranium content _________ and the U-234/U-238 activity ratios is given in Figure 4. The data-show th-cit-sur facevrate-rs-ana.-g-round-waters--ab-uve-th-e-----Hawthorn Formation have a relatively low uranium content and a high U-234/U-238 activity ratio. Water from the Hawthorn, which contains phosphatic material and clays, has a slightly increased uranium content. The artesian waters from the underlying Floridan aquifer exhibit the highest and most variable uranium content, probably due to a variable uranium distribution within the sediments (Kaufman, 1968). U-234/u-238 activity ratios approaching equilibrium occur in waters from tE-e-Hawtfi-orri-Formation-and from the F1C)r1dan-aqui-rer-where i-t1:s overlain by thick younger deposits. Waters from the Floridan aquifer exhibiting activity ratios less than unity (Z34U/238U = 0.50 to 0.90) underlie the Woodville Karst Plain. __ n u----_Eigur.e.s_S-.and6 _up ori:;ray. __ areal distribution of the U-234/U-238 acti vi ty ratios of waterln-the--Florldan aquifer and the regional structural and physiographic setting within the report area. The data indicate definitive distribution patterns, the most notable being a deficiency of U-234 in the waters underlying the Woodville Karst Plain and the southern and eastern parts of the sinkhole-riddled Tallahassee Hills (area B, Figure 5). Activity ratios near equilibrium underlie the Gulf Trough, the Marianna Lowlands, and the northwestern part of the Tallahassee Hills (areas A and C, Figure 5). Consequently, a close interrelation between uranium isotope disequilibrium and the hydrogeologic framework is suggested. Within area B (Figure 5) the karstic topography results in a well-developed subterranean drainage system, including several first-magnitude springs (Figure 6), suggestive of high permeability and active circulation. Sellards (1917) concluded that a structural ridge (upthrown fault block?) existed within this area which elevated the limestone nearer the surface. This resulted in a thin, easily breached overburden, and permitted increased ground-water circulation with concomitant increased solution and development of secondary permeability. Hydrologic data, including large seasonal fluctuations of Wakulla Spring discharge correlative with local precipitation suggest the occurrence of extensive local recharge (Kaufman, 1968). To account for the low activity ratios observed in these waters, it is hypothesized that during periods of lowered Pleistocene sea levels, extensive leaching within the Floridan 19

PAGE 25

I\.) o o I I EXPLANATION. Contour represents the altitude of -30--the potentiometric surface, in feet .53 .27 A--A' above mean sea leve', July tMI. Contour interval / 10 feet. Da-.ct where inferred. Floridan aquifer sampling site with identification number. Surface or shallow water sampling site with identification number. Location of section, figure 4. Figure 3. Location of sampling sites and potentiometric surface of the Floridan aquifer in North Florida.

PAGE 26

f\.) I-' NORTH NORTHWEST A 200 MARIANNA LOWLANDS 1.% \ -.... '\ .21 '0 Suwannee Ls. -100 GULF TROUGH TALLAHASSEE HILLS II II ? II II 1.00/ II 1>.48 II II II (I Suwannee II II 1.12/ I l' Co-. Foult iii 70.51 I tl "I I SOUTH SOUTHEAST A' 200 WOODVILLE KARST Limestone PLAIN Formation II II :: 100 o II I I 0.5
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I\) I\) --\ ----" C I // '/ .01 X / ,,' "----------1-----:::--,," 1.02. I C ......... ;0.96 112 I 1.00_ ....... A I ._-I ..... 0.95 Ii' .0.69 90 O. I .50 8 I \ 0 \ -N Contro,f I"01Rt Nlilmlaer is U234!U238 activity ratio of water from the Floridan aeruifer A Area of low permeability, poor ci!f.u"atiOl'l, little leaching. B Area ,of hig!h permeability, rapid ci,rcufation, extensive leaching. C Area of good permeability and circulation, little leaching. Divide sepOratmg area A, Bond C. Figure 5. Areal distribution of the U-234/U-238 activity ratios of waters from the Floridan aquifer in North Florida.

PAGE 28

-----------------------------------------------------------------------------------, o 10 20 30 miles iii I After Sever Stringfield OCHLOCKONEE FAULT EXPLANATION -100Shows thickness of Pliocene I I SOPACH Pleistocene I and Holocene deposits combined i Interval 50 feet. Karst topography I Floridan aquifer at or near land surface I both recharge and discharge occur. Sinkholes breaching Hawthorn or younger deposits I recharge area. First Magnitude Spring -Figure 6. Regional structure and physiographic map of North Florida depicting recharge areas. 23

PAGE 29

aquifer occurred, associated with an active ground-water flow system and favorable environmental oxidation potentials. This resulted in preferential leaching of D-234, leaving behind rocks deficient in D-234 with respect to D-238. The physicochemical processes responsible for the low activity ratios, utilizing geochemical and paleohydrologic models has been evaluated by Rydell (1969). An apparent relation between the magnitude of the D-234 deficiency and the uranium content is indicated for most of the waters sampled (Figure 7). The increased D-234 deficiency may define areas of greater ground-water circulation and solution during Pleistocene time with concurrent development of secondary aquifer permeability and preferential leaching of D-234. Waters with a higher uranium content may define zones of greater leaching of uranium. Thus, points falling on or near the plotted line in Figure 7 suggest the waters are part of an active flow system. As one moves up the curve, the higher uranium content and increased magnitude of the D-234 deficiency indicate progressively greater permeability and ground-water circulation. This concept is consistent with the results of Dooley et al (1966) who noted that greater D-234 deficiencies and range-of disequilibrium in sandstone-type uranium ore deposits appear to be related to zones of higher permeability and greater circulation of ground water. Area A (Figure 5) coincides with the Gulf Trough (Figure 6), a northeast-southwest trending downfaulted syncline containing thick Hawthorn and post-Miocene deposits (Sever, 1964, 1966; Hendry and Sproul, 1966). Drainage is for the most part by surface streams, flowing over poorly drained materials of low permeability. Hendry and Sproul (1966) report that limestone cores from within the trough show little evidence of solution or development of secondary permeability. This, plus the low yield of wells in the area, suggests a limited ground-water circulation system, negligible recharge, and no significant Pleistocene leaching of the sediments. Data presented by Wait (1960) suggest the influence of structural features upon the hydrologic system and groundwater quality in southwestern Georgia. Water from wells located within the Gulf Trough, adjacent to the Ochlockonee Fault, trending northeast-southwest is poorer in quality (high dissolved solids and sulfate) and higher in temperature than water from wells located away from these structural features. These physical and chemical differences suggest low aquifer permeability and restricted circulation. Olds (1961) concluded that the Ochlockonee Fault may restrict the flow of artesian water, a conclusion supported by the later results of Hendry and Sproul (1966) and Kaufman (1968). 24

PAGE 30

i\.) \Jl 0.5 0.6 o 0.7 a:: 0.8 >-I> 0.9 lU CO 1.0 r0 N :::> 1.1 ........ "" L2L1 SURFACE !'0 N WATERS :::> 1.311/ 1.4H 025 0.01 URANIUM /->, /./ // / .036 /" /,'// // / ,/ ,/" AREA / ,/,/ /034V ,/ / t B / // ,/ / /,// /03.J,OS/-,./ // 051 / 10445,I: ,/"/ 0231 r.xf 020 __ YI02: --027 / I !OS2 -, ./" I \ \ ./" / "AREA) / ,__ A t 063 24 / --_./ f 0.95 error / / / 0.1 1.0 CONTENT IN MICROGRAMS PER LITER ()Jg/l ) Figure 7. Relation between the U-234/U-238 activity ratio and uranium content in the waters of North Florida.

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Artesian waters from within area A depart considerably from the plotted line in Figure 7, indicating waters that are not part of the active hydraulic flow system, consistent with the concept of low permeability and restricted circulation in this region. Area C is interpreted as one of active circulation and high permeability today with little preferential leaching of during the -1?leistocene.The region may have been shielcied somewhat from the Pleistocene circulation, solution and leaching by its thick cover of overlying sediments and/or environmental oxidation potentials may not have been favorable. Conclusions Artesian waters deficient in U-234 are associated with a Karst terrane ariarea ofe:x:tensiVe recharge, high permea bility and active ground-water circulation. The magnitude of the U-234 deficiency appears to be related to the degree of circulation, leaching, and permeability, as well as the oxidation potential of the environment and infiltrating waters. Artesian_waters witb U-23!/U=-238 ratiQs at ___ oJ' sligh"tly greater than, equilibrium are associated with a downfaulted syncline an area of negligible recharge, low permeability and little ground-water circulation, with limited preferential leaching of U-234 during the Pleistocene. The data suggest that waters within the faulted syncline are isolated from Pleistocene and present-day active hydraulic flow systems. As the activity ratios should reflect ratios in the source materials, the U-234 deficient waters sampled from the karst terrane appear to reflect a different source or history than waters updip to the northwest. The Gulf Trough and Ochlockonee Fault act as a hydraulic barrier that prevents any significant southeastward flow of groundwater. 26

PAGE 32

4. URANIUM ISOTOPES AS QUANTITATIVE INDICATORS OF GROUND WATER SOURCES The Isotope Dilution Approach to Hydrologic Problems Investigation of the distribution and environmental disequilibrium patterns of naturally occurring uranium iscrt-crp-es-tlj -n-1:j.-arrd lj 2:58 )-in-wat-ers--o:r---"th-e-?lori-aan aqu-rfer----(Table 1) suggests that variations in isotopic activity ratios and concentrations can be used to quantitatively evaluate mixing proportions of waters from differing sources. Quantitative evaluation of mixing proportions may be achieved by treating the uranium disequilibrium of ground waters as a natural experiment in isotope dilution analysis (Osmond, et aI, 1968). A. Wakulla Springs This approach may be illustrated by an example from the --''a-l1-ah-a&s-ee-a-pe-a---wRe-pe--t-he--ka-p-&-t4-e-fJ.-a-t-'l::I:Pe results in a well-developed subterranean drainage system and, toward the south, several first magnitude springs. Wakulla Spring, one of the largest in Florida, has an average discharge of 10.3 cubic meters (365 cubic feet) per second (U. S. Geologic Survey, 1966). Hydrologic data, including large seasonal fluctuations of spring discharge correlative with local precipitation, suggest that a large portion of the water is derived from local recharge in the karst area (Kaufman, 1968). An alternative, in part, is that the source is to the north, with flow down the gradient of the piezometric surface. Natural waters may be considered an isotope dilution system inasmuch as variations in the U-234/U-238 activity ratio can occur only at the time uranium is added to the system through leaching of enclosing rock or by mixing with other uranium-bearing waters; once uranium is in solution, the activity ratio is unaffected by dilution, precipitation, or changes in chemical state. If an amount of water #1 is mixed with water #2 (each with its dissolved uranium) to produce a mixture, water #3, the following relationships hold; (1) VI + V 2 = V3 (2) MI + M2 = M3 (3) MIAI + M2A2 = M3A 3 (4) MI = C1V I 27

PAGE 33

Where V is volume in liters; M is the amount of uranium in micrograms; C is concentration in and A is the activity ratio, U-234/U-238. From these relationships, and letting VI be unity, the following two equations are derived: A A ( 5 ) M2 = C1 1 3 A3 -A2 C1 + (6 ) V2 = 2 1 C3 These expressions can be used in two ways: (1) in the calculation of the relative mixing volumes of two waters when C and A values for the two source waters (#1 and #2) and the resultant mixed water (#3) have been determined, and (2) in deducing the amount of uranium and water (#2) that have been added to an initial water (#1) to produce a resultant water (#3). In the latter case, there are three unknowns, M 2 A 2 and V2 in the two equations (5) and (6), and one of these variables must be estimated. As an example in which three waters are analyzed, we might as-k:-Vlhat volume of water like that from Horn-Spring(#2) must be mixed with a unit volume of water like that from Big Bend (#1) to produce water like that flowing from Wakulla Spring (#3) (Figure 8). Using equations (5) and (6), M2 is 8.4 and V2 is 17.4. Consequently, for every liter of Big Bend water, 17.4 liters of Horn Spring water would be required to yield 18.4 liters of Wakulla Spring water. As a check on the uranium balance, we can compute the necessary C 2 of Horn Spring water, obtaining 0.48 almost precisely the value measured. There are probably numerous hydrologic situations in which Ilclosed system" assumptions can be made, the C and A values of three waters determined, and the mixing volumes calculated with confidence and accuracy. Requirements include: sufficient uranium (0.1 or more), diverse activity ratios, and a reasonable understanding of the hydrologic system--of which the latter probably contributes the greatest error to this approach. Isotope dilution analysis cannot of course, define a mixing model; it does, however, set limits on possible models and develops the implications of these. As an example of the second approach, again referring to Figure 8, successive aquifer points are compared and the addi tions of uranium and water between points deduced. This is useful because the aquifer system here is quite flopen" in that rainwater is infiltrating from the surface and uranium is being leached from the aquifer rock. In this case, the observed variations in activity ratio of waters within the aquifer are 28

PAGE 34

A '2.\ (LAKE\O ........... .JACKSON) ':-.'-/ /8 '! ,"-(BIG BEND) (HORN /. / I ;'t SPRING) 9 /( /SPRING) 6/, 11 _-=::52. -==4.0-=:::5S? KM Sampling sites and piezometric surface of the Floridan aquifer in meters above mean sea level (7/61) Contour interval 3 meters. Well Spr.ing a Lake A-A' Denotes line of section. HORN SPRING A' !? j Inferred hydrologic flow system (vertically exaggerated, ngf to scale). Geology modified from Hendry and Sproul Number within Upper number arrow is deduced leaching ratio, A2 within box is measured U 234/ U 238 Activity Ratio, (Ali Lower number is measured uranium concentration in ),Ig/I, (C). Figure 8. Corrposi te hydrologic map and diagrammatic geologic cross section. Geology modified from Hendry and Sproul (1966). Composite portrays the 'inferred-hydrologic flow system. -Each box represents a sampling site show:i:ng activity ratio above and uranium conc.entrati-on in J-lg/l below --'Ihenunbers-within the arrows refer to inferred activity ratio of the uranium added to the water (leached from the rock): betweensarrpling sites. All A and C values correspond to those used ln Table 3. 29

PAGE 35

systematic enough to permit "most probable" A2 values to be assigned and thus 002 and V2 values to be calculated. In estimating the A2 value, the activity ratio, of the uranium leached between sampling points #1 and #3, the following aspects were considered: (1) aquifer waters here show a generally decreasing activity ratio for their dissolved uranium in the down-dip direction relative to the piezometric surface, (22 surface waters_ generally haveaQti vi tY_Y'atios greater than 1.00, in agreement with the commonly observed isotope fractionation by leaching, (3) A2 -A3 must have the same sign as A3 AI, and (4) whenever C3 is significantly greater than CI, A2 -A3 must be small. As a result of these considerations, all A2 values were selected such that the range of A2 -A3 was .02 to .10, except for Tallahassee to Big Bend, where it was .01 to .06. Infiltrating waters were assumed to be contributing only small amounts of uranium; the activity ratio of these waters is being 0.90+ in Figure 8. The results of these successive interval calculations based on the values of Tables 2 and 3 are shown in Table 4, in which the relative volumes, as well as the computed amounts of uranium which are added between-Havana, 'l'al-lahas s ee ,Big Bend, and Wakulla Spring, are also computed for comparison. Since each V 2 is defined relative to each initial VI, the total volume increment to the final water can be determined (last column of Table 4). Calculation shows that of the hypothesized sources for Wakulla Spring the more local sources predominate, and no more than about 8% could be contributed from as far away as Havana. B. Silver Springs The proposed Cross-Florida Barge Canal has precipitated considerable interest in the geohydrology of the Floridan aquifer in the area of Ocala and Silver Springs. Faulkner in a U.S.G.S. open file report (1970) summarizes the underground water flow pattern in this region, and has calculated the probable sources of water for the major effluence of the area, Silver Springs. As a test of the utility of the uranium isotope technique for calculating water sources and mixing proportions, we chose this well documented system for sampling and analYSis. We will accept Faulkner'S conclusions as correct, and compare with them the isotopic results derived more or less independently of hydrologic data. 30

PAGE 36

Table 3 Results of' Analysis Cs Aquifer Interval (see Fig. 1) CI (llg/ Titer) As (llg/ ratio Titer) H to T 1.02 1.14 0.95 T to B 0.95 0.51 0.69 B to W 0.69 2.63 0.85 -------------------T--0--W--------------0 95---tr.-51--Cr:-S-5--0.51 2.63 0.60 0-'-60-----Computed Values Aquifer V 2 C 2 L1M Interval M2 V2 range (llg/ (per-(see Fig. 1) (liter) (liter) liter) cent) H to T 1.60 4.37 2.8-9.1 0.37 140 T to B o .lf5-1: 35---050 B to W 8.42 17.4 10.0-38. .48 320 T to W 1. 02 1. 55 0.7-4.1 .66 200 Deduced Values A2 ratio range 0.90 0.85-0.93 0.65 0.63-0.68 0.90 0.87-0.95 ---O:mr----o--:-T 5 0-:-8 3 L1V Contrib. (per-to Wakulla cent) (percent) 440 8 -----45 ---3-2--1740 60 155 Additions of uranium and water between aquifer sampling points. The in which Al and Cl are the activity ratio and concentration respectively, of the aquifer water at Havana, and As and Cs are the corresponding values at Tallahassee; A2 is the estimated range of possible values for the activity ratio of uranium added between these two points. Values for M2 V2 and C2 are calculated from Eqs. 5 and 6; M2 is the amount of uranium added, V2 is the volume of water added (the range of possible V2 values is given, corresponding to the listed A2 ranges), and C 2 is the resulting concentration of uranium if M2 and V2 describes a mixing water. The quantities L1M and L1V refer to the proportions M2/CI and V 2/VI respectively. The last column follows from the various V2 values calculated with respect to the flow model (Fig. 1). 31

PAGE 37

Table 4 URANIUM CONCENTRATIONS AND URANIUM ISOTOPIC ACTIVITY RATIOS: SILVER SPRINGS REGION Location or U-234 Well No. U cone., P2b U-238 -----------------------::lCE--j:24-----1-;27 ---;-0-4-0-;-84--1---:--0-3---------------------------CE 47S 1.60 .02 0.96 .02 CE 48 0.57 .02 0.56 .02 CE 79 0.21 .03 1. 09 .06 CE 39 0.13 .03 0.95 .10 CE 81 0.88 .04 0.94 .04 CE 33 0.47 .05 0.98 .07 BELLE VIEW 4.04 .03 0.56 .02 ORANGE LAKE 0.66 .12 1.04 .04 eE 30-A: 0--;'71--06-SCE 172 0.31 .04 1.05 .04 SCE 132 0.16 .02 1.42 .04 SCE 156 0.24 .03 1.27 .05 SCE 153 0.61 .03 1. 26 .08 OCALA #3 1. 08 .10 O. 4 .02 ---------------------OCALA: LIBBY MCNEIL 0.13 .02 2.43 .04 CE 42 0.01 .02 LAKE WEIR 0.01 .02 CE 61 0.10 .02 0.98 .04 CE 51 0.01 .02 CE 55 0.01 .02 CE 53 2.98 .26 0.85 .02 CE 131A 0.10 .04 1.19 .06 SALT SPRINGS 0.37 .03 1. 30 .04 SILVER SPRINGS 0.71 .04 1. 03 .02 32

PAGE 38

The uranium data are listed in and the sample sites are shown in Figure 9. The analytic data are also plotted on a graph of activity versus reciprocal of concentration in Figure 10, (Several sample sites listed in Table 4 are not plotted in Figures 9 and 10. These samples contain too little uranium to analyze or were too far from the focus of the study or for other reasons were not considered to be important sources for Silver Springs -water.) -The type of plot used (Figure 10) reveals unique and useful properties of the data. For example, the combining of two waters will produce a resulting water mixture whose activity ratio and reciprocal of concentration must fallon a straight line joining the plotted pOints of the two sources. The proportions of the two sources is a simple function (not linear) of the position of the resultant point on this line. This is, in effeet,a graph0f the mixing equations-reported by Osmond, et al (1965) and discussed in an earlier portion of this In practice, one plots the possible sources to see if they do in fact, form a straight line relative to the resultant water, and if so, the equation is used to calculate the mixing proportions. A simple extension of this procedure shows that a unique mixing proportions solution results when three possible sources are conSidered, provided that the plot of the resultant mixture falls within the triangle formed by the three plotted sources. For more than three sources, solutions are possible whenever the resultant water plots within the polygon formed by joining the proposed plotted sources. In the latter case however, a unique solution generally does not result; a certain range of possible mixing proportions can be calculated. A straight-forward procedure for solving a complex source system, as in the case of Silver Springs, would be to select three proximal sources for the final resultant water (Silver Springs), and then select three sources for each of the proximal sources, etc., ultimately arriving at mixing proportions distributed among a number of primary sources. Table 5 shows the results of a partial and tentative calculation of assignable proportions for sources for Silver Springs water. The resulting flow net is shown by arrows on the map of Figure 9, and also on the diagram of Figure 10, For this very rudimentary application of the isotopic analysis, the only selection rules for possible sources were: among the nearest (radially oriented) possible sources for a resultant water, choose three which plot as a relatively compact triangle and thus yield a unique mixing solution. On the diagrams, the dotted lines show inferred but not calculated contributions; except for one or two wells, these are excluded from the calculations summarized in Table 6. 33

PAGE 39

W ../:=" 172 132 / 0i //053 ;/ // II / I ,-, // / 0156: / / / / / 1530-: OSILVER II SPRINGS OCALAO//""'''" / \ I \ \ 79948 \ 01 \/ /039 / \ \ I / /' 4'.i081 5 MILES / 33 / O .,// /" V ---/ -----1 ----i CROSS BARGE o BELLEVIEW __ .. MIXING PROPORTIONS CALCULATED Figure 9. (PROPOSED) OCALA AREA I N FER RED G Rio U N D W ATE R FLOW DIR&CTIONS ___ MIXI NG PROPORTIONS NOT CALCULATED i I I Ocala Inferred water fflow directions. Numbered circles are sampled well localities whicp. satisfy the rules Ifor the mixing calculations. Pattern of arrows from number to nUmber matches that of Figure ]0. In this diagram, geographic locations of sample points is only I approximate.

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0 1-00 '0 O::N I >-:::> 1-, w IJl -'\j >1'0 I-N o:!J lAO 1,20 1,00 0,80 0,60 o 30A 0132 153 1 SILVER 0-3 / 79 // 0172 4750 / _______ 033 -----o ------\ _-------------------. _--0 \ 39 \ \ \ OBV \ \ 048 MIXING PROPORTIONS CALCULATED ___ MI XI NG PR9pORTIONS NOT CALCULATED 0,0 1.0 2,0 3,0 4.0 5,0 6.0 7,0 8.0 U CONC" PPB Figure 10. Acti vi ty ratio vs. reciprocal of concentration diagram of Ocala area samples. Nunibered circles are plots of samples which satisfy the selection rules for the mlxing calculations. Pattern of arrow::: from nuniber to nuniber matches that of Figure 9. This type of diagram permits immediate recognition of possible solutions to the mixing formula; however, exact mixing proportions mus t be calculated.

PAGE 41

Resulting Mixture As In ----B. SCE 156 C. SCE 124 D. SILVER SPRINGS Table 5 MIXING PROPORTIONS Possible Sources As In __ aQL124 SCE 153 SCE 156 CE 30A SCE 172 SCE 132 CE 47S BELLEVIEW CE BT PRIMARY SOURCES Proportions of Sources ____ 42% __ ___ __ 29% 26% 6% 33% 61% 16% 8% ---76% SCE 153 29% CE 30A 2% S-C-E--l-'i'-b-2 SCE 132 16% CE 47S 7% CE 81 33% BELLEVIEW 4%

PAGE 42

Table 6 SOURCE OF SILVER SPRINGS WATER: HYDROLOGIC vs ISOTOPIC CALCULATIONS Representative Percent Contribution Source Zones Sources to Silver Springs (Faulkner) (This Report) (Faulkner) (This Report) -* -** 1-5 27% 37% 28 8-10 0-3 4% 5% 4 14-17 30A,132,172,153 45% 51% 49 22-25 47S 1% 7% 5 All others ------23% 23 *As calculated **Corrected for 23% rrothers!! 37

PAGE 43

Table 6 compares the results of this calculation with that of Faulkner. The wells which were computed to be 'primary sources' according to the .selection rules are grouped according to the corresporiding radial geographic zones of Faulkner, and the percent contributions of source zones compared. As initially calculated the isotopically computed sources necessarily add up to 100%. However because the data points are limited and the calculation only partially c-omp-l--ete-d-,-the-i'igtlre sare-a-rbi-t-ra-ri-1-y-. pe4 ue-e-El-li.y-&3-%--i-l'l-th@--....... ---------last column to allow for the source zones of Faulkner. The resulting percent contributions as computed here show a truly remarkable agreement with those of Faulkner, in fact, the agreement must be in part fortuitous. Among the factors which might have adversely affected the comparisons, but did not or else did so in a compensating way are; appreciable infiltration of ground water near the spring, ap p-re-c iable-8-0-1 u t-ion-o-f1:1:I' an-i urn-wi -thin-t-he-aq-u-ife p.-f'lGwsy st-@m ,-seasonal variations in well sample uranium or in hydrologic flow pattern, strong depth dependence of flow pattern, etc. It should be noted that a more sophisticated treatment of the procedures would allow the computation of increments of surface recharge by low activity water (points at the extreme right of -the ratio-concentra'Glon a-iagram) and also lncrements or---n-ewJ::-Y----.. .. .. ---dissolved uranium within the aquifer (points at extreme left in the diagram). The point to be emphasized is that the isotopic flow pattern was deduced from a relatively small number of data points, whose geographic position was the only hydrologic factor considered. Even if other systems should prove to be less favorable with respect to uranium geochemistry, e. g'., low uranium concentration or small isotopic variability, it seems that a combination of uranium-isotopic and standard hydraulic analyses would be a very useful approach to ground water studies. 38

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5. TRITIUM ANALYSIS: A MODIFICATION OF THE BENZENE SYNTHESIS METHOD Introduction Tritium is produced naturally in the upper atmosphere by interaction of cosmic ray produced thermal neutrons with -_. I-t-TS-forme-d--artt-i'i-ci-a-El::y -::i:-n--n-tl-e3.-ear--fusion and since 1954, when first major thermonuclear device was detonated in the Pacific, thermonuclear test explosions have produced worldwide pulses of tritium. These rapid increases in the abundance of the sole radioactive isotope of hydrogen that occur in nature, coupled with the fact that tritium is an actual part of the water molecule, make tritium an important hydrologic tracer. The-m-ethodhere-i n-d-esc-rib-ed--w as irri-t-i-al lydevele>ped b-y -Tamers et al (1961). Tamers and Bibron (1963) and Tamers (1964) developed the technique somewhat further. The method is closely related to a popular means of radiocarbon analysis described by Noakes (1965). The modification of the benzene synthesis methoa-for tritium analysis described in this paper simplifies the procedure --further and has been shown produce results that agree very satisfactorily with data from other laboratories. The method should prove valuable to the hydrologist who wishes to perform his own tritium analyses, and is particularly suitable for a limited production volume. Theory The water sample containing tritium as a contaminant is converted into acetylene by hydrolysis of calcium carbide. The tritiated acetylene is then trimerized to benzene using an extremely efficient vanadium catalyst (Noakes et al, 1965). A constant isotope effect lowers the tritium activitY-per gram hydrogen of the benzene to about 80% of that in the water sample. Hence a constant portion of the tritium, originally in the water sample, now satisfies the carbon bonds of the benzene molecules in the synthetic benzene. The benzene is of high purity and is an excellent counting liquid when mixed with the primary fluor PPO. The tritium beta radiation is then counted in a liquid scintillation counter. Pertinent chemical equations in the procedure are: --------------------+) C6H6 (2) vanadium catalyst at 25 in. vacuum 39

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Procedure A schematic diagram of the benzene synthesis apparatus is shown in Figure 11. On the left is the acetylene generator G and a 50 ml burette that permits the drop-by-drop addition of the water sample to the calcium contained in a 3 1 flask. The entire system was evacuated, flushed with argon, then eyacuatedagain to_30inches vacuum. The 3 1 flask is partially immersed in an ice water slush to remove heat from the flask during the exothermic hydrolysis and to condense any steam that may form. In addition, the slush maintains a constant temperature, which stabilizes the reaction chemically and isotopically. Spattering is avoided by introducing the water below the level of the carbide, and excessive absorption of water by the residue is prevented by using a large excess of CaC2 and slowly adding the water. In this procedure, 120 grams of carbide is reacted with 50 ml of sample water, which is the volume that empirically produces 17 1 of C2H2 (STP). The use of an auxiliary tank storage volume of 17 1 is not arbitrary but reflects the volume of acetylene necessary to yield 17 ml of benzene with a conversion efficiency of 75%. Typical efficiencies are usually in excess of 90%, however. Adjacent to the acetylene generator, two purification columns (PI and P2) are connected in series. The first contains powdered calcium carbide and is water cooled. This column is used to convert any water vapor evolved in the generator to C2H2 The next column contains, in the upper position, reagent grade PbC12 which extracts sulfides, and in the lower position, P20S which removes traces of water and ammonia. The acetylene is passed through trap A, which is cooled by a dry ice alcohol slush bath to remove gases that are condensible above -78C. The purified acetylene is finally collected in a liquid nitrogen cooled trap (trap B). The acetylene to benzene conversion is a one-step catalytic reaction. The frozen acetylene is permitted to sublime at room temperature from the cold trap (B) through the storage tanks (S) onto the evacuated catalyst column(CC). The column contains 375 grams of vanadium activated silica alumina catalyst (available through John E. Noakes, Oak Ridge Institute for Nuclear Studies, Oak Ridge, Tennessee). The catalyst has been baked under vacuum at 380C for 3 hours to remove associated water, which inhibits the reaction. The catalyst is allowed to cool before mounting on the system and is cooled with ice water during the conversion reaction. Cooling is of paramount importance for high yields because it prevents both vapor blocks and surface area contamination of the catalyst pellets. In addition, cooling prevents appreciable pyrolysis of acetylene and benzene into more polymerized hydrocarbons. Upon completion of the reaction (45 minutes to 1 hour), 40

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-l= I-' Pl8P2 B A G Figure 11. Diagrammatic sketch of benzene synthesis purification columns. A,B,C: cold traps. p: s <:::HJ 1 )\ cc G: acetylene generator'Pl'P2: storage tanks. CC: cata+yst column.

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a heating jacket is applied to the catalyst column, raising the temperature of the column to 100C, and the benzene is drawn off under vacuum into a dry ice alcohol slush cooled trap (C). A 15 ml aliquot of the synthetic benzene is placed in a 20 ml nylon counting vial (obtained from Nuclear Chicago, 333 E. Howard Ave., Des Plaines, Illinois 60018) and 60 rug of the primary fluor, PPO, is added. Sample preparation takes place in-a photographiGd-a-rkroom under light-.-'I'his pro"cedure eliminates phosphorescence in the vial and its contents, thereby providing minimal background fluctuation during the counting period. The tritium beta radiation is counted to the desired error, and the sample count is preceded and succeeded by efficiency and background counts. In this way, any possible counter fluctuations are closely monitored. An external standard (137CS) is employed to check for sample quenching; however, no quenching has been observed to date. Fractionation Effect Reproducibility of fractionation effects for hydrogen isntopes is the keystone QLthe benzene synthesis method of tritium analysis. Tritiated water analyzed by Ostlund at the Marine Institute of the University of Miami was processed by the benzene synthesis method at full strength, as well as at half and quarter strength dilutions. The mean fractionation effect for tritium equals 19.3% .2%. Several interlaboratory cross checks were performed with the cooperation of Ostlund at Miami and the U.S. Geological Survey Tritium and Radiocarbon Counting Laboratory in Washington, D.C. Results of the comparison checks are shown in Table 7. Agreement is surprisingly good; the two data sets agree within one sigma error in most cases. The errors associated with our answers are large, mainly because of the high background count rate of our liquid scintillation counter. Additional lead shielding might be helpful. The lower detection limit of the system is about 10 TU (10 tritium atoms per 1018 protium atoms) presuming absolute counter stability, Discussion Overall, several factors have proved important in the determination of tritium by this method: 42

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-------------------------Table 7 INTERLABORATORY CHECKS Known Measured No. Description TU TU 1 groundwater* 70.5 3.9 71.2 5.5 -------------------------------------------------------------------2 groundwater* 13.2 15.4 11. 3 rainwater 31. 1.2 27.7 8.4 4 rainwater 40.9 2.0 43.9 8.5 5 rainwater 31.6 1.4 30.9 6.7 6 rainwater 54.3 2.6 51.1 10. Collected and analyzed by the U.S. Geological Survey, Tritium and Radiocarbon Counting Laboratory, ---Collected and analyzed by Ostlund at the University of Miami. 43

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1. The stability of counter background and counting efficiency is of prime concern since counting are long when the sample is of low i.e., 48 hours. Most of the modern liquid scintillation counters that employ ambient temperature phOtomultiplier tubes meet this requirement within acceptable limits. 2. The choice of a calcium carbide that is low in s-u-J:-fides h;-imperati ve siflce-exces's--8ulfidesEi1:iench t-he catalyst and benzene counting liquid and contribute heavily to the loss of sample hydrogen as H2S. Carbide of low sulfide content may be purchased from Research Inorganic Chemical Company of Sun Valley, California. This carbide is 'dead' with respect to 140 Spillover of radiocarbon beta activity into the tritium counting channel would result in variable count rates that are difficult to correct because of the low specific activities involved. 3. Successful use of the catalyst is dependent upon complete removal of associated water. The catalyst will maintain its own vacuum during the conversion. Generally, the lower the pressure, the higher the benzene yield. Conclusion The distinct advantages of this modification to the benzene synthesis method for tritium analysis are three. 1. Samples may be prepared easily by the isotope hydrologist and/or his technician. 2. In its present form, without enrichment, the system is suitable for groundwater studies where large volume sample processing is not required. 3. Results compare favorably with those from other laboratories. 44

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6. TRITIUM HYDROLOGY OF THE FLORIDA AREA Field Methods and Procedures Samples of ground and surface waters in Leon, northern Wakulla, and eastern Gadsden counties were taken over a two year period. Sampling sites consisted of wells, both table and artesian, Wakulla Spring, the St. Marks River, and Lakes Iamonia and JacKson. The sample sites were chosen to represent, broadly, the local geohydrologic environment. Determination of sample tritium concentration was done in part at Miami Institute of Marine Sciences, in part, by Isotopes, Inc., Westwood, New Jersey and, in part, at the Florida State University using the newly developed benzene synthesis-liquid scintillation counting method described in the previous section. Sample Locations and Analytical Results A sample location map is shown in Figure 12. The specific location and description of each sample point is presented in Table 8. Many of the groundwater samples were drawn from the FToridan aquifer The Floridan-aquifer -is composed of marine limestones and dolomites which range from Eocene through Miocene in age. The formations function as a unit because their porosity and permeability are similarly developed. The formations which make up the Floridan aquifer in the Tallahassee area are the Upper Eocene Crystal River formation, the Oligocene Suwannee limestone, and the lower Miocene St. Marks formation (Hendry and Sproul, 1966). The Floridan aquifer is overlain by surficial sands, silts, and clays of the Miocene Hawthorn formation. The overlying veneer of sediments is of highly variable thickness. Additional information on the hydrology and the geology of the study area may be obtained from Sellards (1917), Moore (1955), Gremillion (1965), Hendry and Sproul (1966), Stringfield (1966), and Sever (1966). In conducting a study where natural rainout tritium is to be used as a tag for which is the case with the present several questions must be answered: 1. What are the input activities of tritium from precipitation and what have they been in the past? 2. What are the tritium activities at present in the ground waters of the study area? 3. What were the natural groundwater tritium activities? (Stewart and Farnsworth, 1968) 45

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-1= 0\ -..-_ 1 ..... -,---.. ) ctf I 57.8----r---0.0 / 38A \ I \ .,3 125. 2 48 9 \) 172' (. I /. LEO 0.0 GADSDEN I 150.1' \ \ 1 N 1----__ 10\ I ,_ 94.5 J / __ .) 61 I / .. / f" : 114.2( / 10 43.0 I ( : I L 10 73.8 1 0 I __ I ____ 1 .. ___ I 893 --,. 129.9 I WAKULLA .' '-, :____ 1 I J 33.6 I I I Figure 12. Map of Tallahassee and surrounding area showing tritium content of Floridan aquifer well water. Dashed line separates slow (left) and fast (right) recharge regimes.

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---.;] Sample Number LG-Ol LG-02 LG-03 LG-04 LG-05 LG-06 Date of Collection 1-27-67 10-15-67 10-22-67 10-20-67 10-20-67 11-16-68 Table 8 TRITIUM CONCENTRATION OF WATERS WITH PERTINENT SAMPLING INFORMATION Sampling Locatioi and Details i #6 Municipal Well at Park, Tallahassee, Fla., Wln. IN-IE, 30cc, depth 413 ft., cased to 170 rt. open only to Suwannee L.S. at 170i ft. I Lake Jackson nr. Capital Trk. Rt., Wln. IN-1W-566 Depth 19f ft. cased to 140 ft., open only to 140 ft. N.W. Lk. Iamonia Shore, Leoni Co., Wln. 3N-1E-Zod, depth 268 ft., caFed to 260 ft., open only to Suwannee L,. S. at 260 ft. Jctn. U.s. 319 & s-261 at Bend Trk., Rt. Wln. lS-lE-19C, depth lOp ft., cased to 70 ft., open only to St. rarks Wdvlle. Mncpl. Well, Wln. 2SrlE-8dd, depth 183 ft., cased to 32 ff., open to St. Marks & Suwannee L.S. atl15 ft. and 110 ft. respectively i Well at Chaires Gen. Str., Nb well info. available T.U. 6.1 QO.5* 13.9 q1.0* 2.2 QO.3* i 43.0 31.0* 54.2 q3.7* 114.2 09.2*** Date of Analysis 9-20-67 1-03-68 1-03-68 1-03-68 1-03-68 1-23-69

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-l= OJ Sample Number LG-007 LG-008 LG-009 LG-OIO LG-Oll LG-012 LG-013 LG-014 Date of Collection 11-15-68 11-15-68 11-15-68 11-15-68 11-15-68 11-15-68 11-16-68 10-25-68 I Table 8 Continred Sampling Locatior and Details Well at Sunny Hill Farm, wlnl., 3N-2E h 148 ft., cased to 1 open only to Suwannee at 103[ft. Well S. of Iamonia, WIn., 3N ZE-nc, depth 33 ft., Shallow well Well on the N. W. Shore Lk. MliCC., Shallow well, no info. available Well at Gen. Str. Town of Mice., WIn., 2N-3E-8bb, depth 235 ft., open to Hawthorn at 65, St. Marks at 105, Suwannee 185 ft. Well at Felkel 2N-2E-3cb, 179 ft., 50 ft. to Hawthorn, 80 ft. tjO St. Marks, 110 ft. to Suwannee i Well near Gardner IN-2E-15 1a, depth 220 ft., cased to 177 ft., o)pen to Suwannee L.S. at 185 ft. I 1.75 mi. E. Corey on 261A 29 cb, depth? 70 ft. to St. jMarks, 75 ft. to Suwannee L.S. Well Lk. McBride Elem. 3 mi. E. of U.S. 319 Rd., connect'ng Brdfdvlle and Cntrvlle, no available I I I T.U.! 38.5 08.4*** I 57.8 Q5.8*** 151.0 q8.8*** 48.9 G8.4*** 17.2 +3.4*** 94.0 13.8*** I <10 ** 26.2 11.2*** Date of Analysis 1-28-69 1-31-69 2-03-69 2-06-69 2-09-69 2-13-69 2-16-69 2-20-69

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+=\D Sample Number LG-015 LG-016 LG-017 LG-018 LG-019 LS-OOI LS-002 LS-003 LP-Ol Date of Collection 11-17-68 11-17-68 11-16-68 11-16-68 11-17-68 10-10-67 10-10-67 8-19-68 8-06-68 Table 8 -Continued Sampling Location and Details I Well at Confdrt. Inn Spr. BIb Ochlockonee, WIn., IN-2W-23 da., depth 254 ft., cased to 84 ft., op'en to St. Marks at 40 ft. I WeIll mi. N.W. Int. 261 wit!h 151 WIn., IN-IE-16d., depth? No info. available Well at Nat. Bridge nr. Wdvl. WIn., 2S-2E-29 da., depth 175 ft., cased to 163 ft ., 5 ft. t 0 St. Mark s. 36 ,ft. to Suwannee L.S. I Well nr. Bradford Brook on Rt. 61 S., WIn. IS, lW-26cb, depth 220 ft., cased to 140 ft., open to Suwannee L.S. at 140 ft. Well at WFSU transmitter Sta. in Apalachiocola Nat'l. Forest, WIn., Is-4W-35aa, depth 230 ft., cased to 132 ft., open to Jcsn. Blf. at 50 ft. and Hawthn. at 61 ft. Surface sample of Lk. Jsckn'i wtr. Surface sample of Lk. Iamonia wtr. Sample of St. Marks Rvr. wtr. at Natrl. Bridge, near Woodville Rainwater collected on FSU Campus during afternoon thunderstorm T.V. <10.00 *** <10.00 *** 129.0 09.3*** 73.8 10.8*** <10.00 *** 115.0 08.0* 113.0 08.0* 21.2 03.8*** 13.4 06.3*** Date of Analysis 2-22-69 2-26-69 3-01-69 3-04-69 3-07-69 1-03-68 1-03-68 11-19-68 8-13-68

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Vl 0 Sample Number WG-Ol WS-Ol WS-02 WS-03 ws-04 GG-Ol GG-02 Date of Collection 10-20-67 1-27-67 10-10-67 10-10-67 10-10-67 2-15-68 2-15-68 Table 8 Continued Sampling Location and Details Wakulla Co., 4 mi. N. of Wakulla Spring on Rt. 61, depth 43.5 ft., open entirely to St. Marks Wakulla Spring surface wtr., sample taken from pier ; Wakulla Spring surface wtr." taken over cave Wakulla Spring as above at 5,0 ft. depth using Van Dorn Bottle I I As above, but at 85 ft. Havana Municpl. Well, at T3N-R2W-SEC26, Gadsden Co., depth 692 ft., cased to 418 ft. I Sprnfld. Elem. Schl., nr. Quincy, Gadsden Co., located at T2N-R4W-SEC5ab, depth 467 ft., cased to 318 ft. Analysis performed by Isotopes, Inc. ** Analysis performed by H. G. Ostlund at Miami Marine Institute *** Analysis by E. I. Wallick using benzene method T.U. 89.3 06.3* 36.5 01.5* 31.3 02.1* 32.8 02.2* 33.7 Q2.3* 00.0 00.18** 00.0 00.18** Date of Analysis 1-03-68 9-20-67 1-03-68 1-03-68 1-03-68 3-22-68 3-22-68

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To document tritium input to surface and ground waters, the United States Geological Survey established a network in 1958 for collecting and testing rainwater samples for tritium activity. One such station, operated by the Survey is at Ocala, Florida, approximately 170 miles southeast of Tallahassee. Although the Ocala station is the closest to the study area, the following argument must be understood if the significance of these data are to be evaluated. It has been 08served that rain sampling stations_near the oceans which receive their precipitation from oceanic air masses have rain which is low in tritium due to great oceanic dilution effects. In contrast, precipitation at continental stations is rather high in tritium. The maximum tritium rainout occurred in the summer of 1963 after a series of nuclear tests that winter. The tritium rainout has declined each subsequent year as an exponential function. Data for the Ocala station alone was obtained from the U.S.G.S. office there and graphed. The months of greatest tritium rainout are June and July. This is so because the greatest amount of precipitation falls at Ocala when meteorological conditions favor greatest tritium concentration in precipitation. The third requirement for tritium study is a knowledge of the tritium background-against which tritium levels may becompared. In the Tallahassee area, we may safely assume that there is negligible tritium background for several reasons: 1. Tritium levels before 1952 ranged from 2 to 10 T.U. and, because Tallahassee receives most of its precipitation from maritime air masses, these levels would have been fairly low initially. 2. In addition, the effects of time and dilution would have reduced tritium levels even further. 3. Although waters in the eastern portion of the study area are generously tagged with tritium, those in the west are virtually background. Figure 12 is a map which indicates the areal distribution of tritium concentration in the waters of the Tallahassee area. The errors associated with the tritium determinations are to be found in Table 8, and are based on the 0.95 confidence level i.e., 2 significance level. The 0.95 error cited is dependent only on counting statistics and does not consider any systematic error. These data show that waters in western Leon and eastern Leon and northern Wakulla counties have a relatively high tritium content. The tritium concentration of surface and shallow ground waters lying above the Hawthorn formation 51

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aquiclude was much higher than that of the deeper artesian waters of the Floridan aquifer. The range of tritium concentrations is from a.a .18 T.U. to 151.a 8.8 T.U. Discussion of Results Several important factors which influence the tritium concentration ofgr()u:t1.dwater at an observation point are: 1. Tritium input levels are affected by the time, intensity and tritium concentration of precipitation and the distance this precipitation must travel to reach the recharge area; 2. Evapotranspiration of precipitation; 3. Rates of diffusion and hydrodynamic dispersion. (Stewart and Farnsworth, 1968) With reference to 1. above, it is important to realize that heavy precipitation resulting in high total tritium rain --out-, rather than high concent-r-a-T:tnn-a-lnn-e, is cance hydrologically. Evaporation and transpiration may cause the tritium input to differ from the input expected when only the tritium concentration of precipitation from the principal recharge area is considered. In the Tallahassee area, evapotranspiration rates are high owing to the large areal extent of several lake basins, dense foliage, warm climate and good ventilation. The third factor, mentioned above, is associated with mixing and dispersion. Should permeabilities be anisotropic, and flow patterns complex, then tritium concentrations in groundwater may not closely resemble tritium rainout. Keeping these factors in mind, we shall draw some conclusions about the geohydrology of the Tallahassee area in light of the tritium in precipitation from Ocala, and tritium determinations in local ground and surface waters. The most prominent observation of the study is the apparent absence of tritium in groundwaters sampled in western Leon and Gadsden Counties. Evidently, no local recharge occurs here as suggested by the very low tritium levels. Also, because fairly high and very low activity waters are juxtaposed, no significant lateral communication takes place in an east-west direction. High tritium concentrations in groundwaters of eastern Leon and Wakulla counties indicate rapid recharge. 52

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Tritium concentrations fall below about 151 T.U. in waters of the eastern sector, and the observed range is equivalent to that found in recent rainfall. A tentative age for waters in the shallow aquifer is between zero and two years old based on the fact that tritium levels in rain began to fall within the observed range only as early as August, 1967. Tritium concentration of rainwater preceding this date are much higher due to the nuclear tests of winter, 1963. Genera-lly"th@n, waters of the western sector Qf thest:u.dy area are devoid of tritium suggesting an origin as rain prior to 1952, year of the first fusion bomb test. Tritium levels in the shallow groundwaters of eastern Leon and northern Wakulla Counties are very young waters with an origin as rain within the last two years. Some observations have been made on a more intensive level. In northern Leon County, there is an increase of tritium activity toward the east, suggesting that recharge increases in the direction of Lake Miccosukee. Water leaving the Floridan aquifer at Wakulla Spring, the principal discharge point for the study area, had a tritium content of 33.6 T.U. when sampled during the "dry season" d ur i ng January, in a shallow water well some four miles up-gradient from the spring. Tritium in rainout at Ocala during this time ranged from 20-30 T.U. Tritium content of water of the No.6 municipal well in Tallahassee, sampled in January, 1967, was 6.1 .5 T.U. Tritium levels in rain at this time, were 50-70 T.U. The relative stability of the tritium content of Wakulla Springs water from the "dry season" in 1967, to that of 1968, is certainly worthy of note. It is reasonable that very low tritium concentration is attributed to the deeper waters of the Floridan aquifer which travel south to Wakulla Spring. The 6.1 T.U. Tallahassee water, the 13.9 .0 T.U. Lake Jackson well water, and the 2.2 .3 T.U. Lake Iamonia well water are indicative of low tritium in deep artesian waters. The reader is referred to Table 8 for the depths of these wells and other particulars. The low tritium deep waters apparently mix with the younger tritium rich waters of the shallow aquifer to yield water of an intermediate tritium concentration. This water is discharged at Wakulla Spring, and at numerous other springs and streams. Given: T.U. Deep Water = 6.1 T.U. T.U. Shallow H2O = 84.2 T.U. T.U. Spring H2O = 33.6 T.U. Let: x = the fraction of water of tritium content 6.1 T.U. y = the fraction of water of tritium content 84.2 T.U. 53

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then, x + y = 1 6.1x + 84.2y = 33.6 6.1x + 84.2(1-x) = 33.6 x = .65 y = .35 A rather rough estimate of mixing coefficients for water of Wakulla Spring during the dry season is, then, 65% deep water and 35% shallow groundwaters. 54

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APPENDIX A: DETAILED METHODS AND ANALYTICAL PROCEDURES FOR URANIUM ANALYSES Water Samples 1. Water samples of 14-21 liters were collected in duplicate from each source in one-gallon bottles (alternating a ee-tte ef' "A",-then a bettIe ef"E-", etc.-). In cGleet-i-ng, the samples were passed through a 37 micron sieve to remove any coarse particulate matter that might influence results. Duplication is necessary to guard against the possibility of laboratory contamination (i.e., the "A" and "B" fractions must be in agreement or they both are suspect). The alternation of collection of "A" and "B" fractions is thought to aid in achieving agreement between "A" and liB" fractions in that it reduces the possibility of one fraction being disproportionately influenced by factors such as drawdown in a small well. 2. Prior to water collection, tracer-carrier solutions are prepared in the laboratory so that a predetermined amount of U-232 spike and iron carrier may be equilibrated with each ----1bo--o"'rtTe--or s amp 0 f c 0 The tracer-carrier solution consists of: A) U-232 spike of known specific activity and in an amount approximately equal to the expected natural uranium activity of the sample. U-232 is a nonnaturally occurring nuclide which was provided under a loan agreement by the U.S. Atomic Energy facility at Oak Ridge. B) Fe+++ carrier (13 mg Fe+++ per liter of sample in the form of Fe(N03)3H20). C) 25 ml 16 N HN03 (sufficient to cause a pH of 1 or less in 3.5 liters of sample). 3. Samples are placed in a water bath and taken to boiling temperature for one hour to aid in removing dissolved gases, especially CO2 which in subsequent chemical processing could possibly form sufficient (NH4)2C03 to act as a holdback carrier by complexing with U to form highly soluble carbonate-uranyl complexes. 4. While still hot, the sample is stirred; and the U is almost quantitatively coprecipitated with ferric hydroxide formed by the addition of sufficient NH40H to attain a pH of 9. 55

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The high temperature of the solution aids in the coagulation of the gelatinous ferric hydroxide precipitate. 5. The precipitate is allowed to settle overnight and is then decanted, centrifuged, dissolved in BCl, evaporated, and redissolved in 8N BCl. It was found that one-gallon disposable plastic bottles, such as milk is sold in, were well suited to heating in the water bath and facilitated decanting by puncturing the bottle well above the precipitate level. 6. The large amount of iron contained in the 8N BCl solution is mostly removed by solvent extraction with an equal volume of isopropyl ether equilibrated for 30 seconds in a separatory funnel. 7. The sample is heated to remove traces of ether and then is evaporated with 5 drops of BCI04 to remove any remaining organics. 8 The sample is redissolved in ION BCl for ion exchange. Ion Exchange .----1. The resin used is Dowex l-X8, mesh, ionic form Cl-, an anion exchange resin. 2. The ion exchange columns consist of a resin bed of approximately 1 cm x 14 cm topped by a 50 ml reservoir and constricted and plugged at the bottom with glass wool. 3. The resin is pretreated in the column by washing the resin with acids in the reverse order that the acids are used in the exchange process. 4. Add the sample to the column in ION BCl; after the sample has passed through the column, the column is washed with 20 ml ION BCl. 5. Elute uranium from column with 30 ml O.lN BCl, evaporate with drops BCI04 and redissolve sample in 7N BN03 6. To a pretreated new column, add the sample in 7N BN0 3 ; after the sample has passed through the column, the column is washed with 20 ml 7N BN03. 7. Elute uranium from column with 30 ml O.lN BCl and evaporate with 5 drops BCI04 for electrodeposition. 56

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Step 3 & 4 Th Ra Ac Ca etc. FLOW CHART First Column Step 1 & 2 I Second Icolumn r .. --, Step 6 Step 7 Fe u Electrodeposition 1. -The sample is dissolved in5ml (pR2.5), in a deposition cell consisting of a 1.5 cm chimney and 3 cm stainless steel planchet, and deposited for 30 minutes at 12 volts and 1 amp. 2. While the current is still flowing, a few drops of concentrated NH40H are added and the solution discarded. 3. The cell is disassembled and the planchet heated over a burner to volatilize any NH4Cl, harden the uranium deposit, and provide a thin source for alpha particle spectrometry. Counting The planchets are counted in a vacuum chamber with a Technical Measurements Corporation Diffused Passivated Detector, 50 KEv resolution and 300 mm active area. This is coupled to a 100-channel TMC pulse height analyzer with a scale expander which facilitates excellent resolution of the alpha particle spectrum. Three peaks of greatest interest are U-238 -4.2 Mev, U-234 -4.75 Mev, and U-232 5.3 Mev. However, peaks such as U-235 4.35 Mev, differing in energy by 0.15 Mev from the nearest principal peak, may be resolved. 57

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General Remarks The average chemical yield of uranium for water samples was 35%, for rocks 38%. With each series of samples, a duplicate set of blanks were run using the same amount of reagents and tracers from the same batch as used in processing the samples. These blanks are necessary to provide a correction factor for background as well as any contaminants introduced in the chemical processing. 58

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APPENDIX B: TREATMENT OF URANIUM DATA Sources of Error Systematic Errors Systematic errors arising from malfunctioning of counting equipment are difficult to detect in low-level radioactive determination. The only practical way of ascertaining that the counting equipment is giving a statistically valid response is by periodic counting of calibration standards and by multiple counting of samples and inspection of the data for an unwarranted variation. In this respect, the counting equipment used was found to be very reliable and little rejection of data due to this type of error was necessary. A second source of systematic error is in calibration of the U-232 spike. To reduce this error to a minimum, the U-232 spike used was calibrated against a uranyl nitrate solution whose activity was calculated from gravimetric and volumetric de-terminations. as welLas determined by _Goun_ting.. As _an additional the U-232 spike was calibrated in a 2TI windowless proportional counter against a uranium oxide standard of % accuracy prepared by the National Bureau of Standards. Random Err ors The possible sources of random errors are: 1. Contaminants introduced in the sampling procedure. 2. Contamination from chemical reagents and glassware used. 3. Failure to achieve equilibration of spike with sample. 4. Variations in counter background. 5. Statistical counting errors. Analyzing samples in duplicate, along with appropriate blanks, greatly reduces the possibility of the first three types of error going undetected and provides a basis for rejection or correction of the results. Background variations were found to be negligible, and only a slight increase in background with time was noted. Of the various random errors, the only one that can be expressed quantitatively is the 59

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counting error arlslng from the random nature of the radioactive disintegration process. Data Handling 1. The recorded including the three uranium peaks were inspected for inconsistencies and graphicallychecke
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Fortran IV Computer Program A Fortran IV computer program was used to treat the raw data. The program performs the stripping of the blank and background contributions from the sample and calculates the desired uranium concentrations, activity ratios and errors. For purposes of calculation, the following errors are assigned: weight or volume %, spike %, 44.6 U-238 %. In K is given so that allealculated errors represent the 0.05 level of significance. 61

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APPENDIX C: REPORTS AND PUBLICATIONS. Research on naturally occurring radioisotopes in the Floridan aquifer supported by Office of Water Resources Research Title I Grants A-005-FLA and A-011-FLA. Rydell, H. S. and M. I. Kaufman Isotopic uranium studies of the Floridan Aquifer and related natural waters (abstract). Program, Geological S-ociety 01' Kmerlca-S-:E:-Secrrof1Meet:tng;Ta-lIah-as-g-ee; Florida. Pages 52-53. 1967. A-005-FLA. Kaufman, M. I., H. S. Rydell and J. K. Osmond U-234/U-238 Disequilibrium as an aid to hydrologic study of the Floridan Aquifer (abstract). Transactions, American Geophysical Union, Vol. 49, No.1. Page 165. 1968. A-005-FLA. Kaufman, M. I. Uranium isotope investigation of the Floridan Aquifer and related natural waters of North Florida. M.S. Thesis. Florida State University. 1968. A-005-FLA. ________ Edward I. Tritium hydrology of the Tallahassee, Florida area with analysis by liquid scintillation counting without isotopic enrichment. M.S. Thesis. Florida State University. 1969. A-011-FLA. Osmond, J. K., H. S. Rydell and M. I. Kaufman Uranium disequilibrium in groundwater: An isotope dilution approach in hydrologic investigations. Science, Volume 162. Pages 997-999. 1968. A-011-FLA. Rydell, H. S. The implications of uranium isotope distributions associated with the Floridan aquifer of North Florida. Ph.D. dissertation. Florida State University, Tallahassee, Florida. 1969. A-011-FLA. Kaufman, M. I., H. S. Rydell and J. K. Osmond U-234/U-238 Disequilibrium as an aid to hydrologic study of the Floridan aquifer. Journal of Hydrology, Volume 9, Number 4. Pages 374-386. 1969. A-011-FLA. Wallick, Edward I. and George A. Knauer A modification of the benzene synthesis method for tritium analysis. Water Resources Research, Volume 6. Pages 986-988. 1970. A-011-FLA. 62

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LITERATURE CITED Adams, J. A. S., J. K. Osmond, and J. J. W. Rogers. 1959. The geochemistry of thorium and uranium, p. 298-348 in Ahrens, L. H., and others, Editors, Physics and chemistry of the Earth, V. 3: London, Pergamon Press, 464 p. Chalov, P. I. 1959. Isotopic ratio of U-234/U-238 in some -------------------, --s-e-e-e-n-ti-a-ry-----mi-n-e pa-ls:-Ge o-e-ae-m-i-s-t-F-y--,-----NQ--.-------Z--,-----p .----Chalov, P. I., T. V. Tuzova, and Ya. A. Musin. 1964. Isotopic ratio U-234/U-238 in natural waters and its use for nuclear geochronology: Geochemistry Internatl., No.3, p. 402-408. Chalov, P. I., and K. I. Merkulova. 1966. Comparative oxidation rates of U-234 and U-238 atoms in certain minerals: -Doklady Akad. Nauk SSSR, V. 167, p. 146-148. Cherdyntsev, V. V., P. I. Chalov, and G. Z. Khaidarov. 1955. Transactions of the third session of the committee for the determination of absolute ages of geological formations: Idv. Akad. Nauk SSSR, p. 175. Cherdyntsev, V. V., I. V. Kazachevskii, and E. A. Kuzmina. 1963. Isotopic composition of uranium and thorium in the supergene zone: Geochemistry, No.3, p. 271-283. Dooley, J. R., Jr., H. C. Granger, and J. N. Rosholt. 1966. Uranium-234 fractionation in the sandstone-type uranium deposits of the Ambrosia Lake District, New Mexico: Econ. Geol., V. 61, p. 1362-1382. Faulkner, Glen L. 1970. Geohydrology of the Cross-Florida Barge Canal area with special reference of the Ocala vicinity, U.S. Geological Survey, Water Resources Division, open file report. Garrels, R. M., and C. L. Christ. 1965. Solutions, minerals, and equilibria: New York, Harper and Row, 450 p. Gremillion, Louis Ray. 1965. The origin of attapulgite in the miocen strata of Florida and Georgia, unpublished Ph.D. Thesis, Florida State University. Healy, H. G. 1962. Piezometric surface and areas of artesian flow of the Floridan Aquifer in Florida, July 6-17, 1961: Florida Geological Survey, Map Series, No.4. 63

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Hendry, C. W., Jr., and C. R. Sproul. 1966. Geology and groundwater resources of Leon County, Florida: Fla. Geol. Survey, Bull 47, 178 p. Isabaev, E. A., E. P. Usatov, and V. V. Cherdyntsev. 1960. Isotopic composition of uranium in natural samples: Radiochemistry. Kaufman, M. I. 1968. Uranium isotope investigation of the Floridan aquif-er and related-naturaTwatersof north Florida: unpublished Master's Thesis, Florida State University, 65 p. Koide, M., and E. D. Goldberg. 1965. U-234/u-238 ratios in sea water, p. 173-177 in Sears, M., Editor, Progress in Oceanography, V. 3: London, Pergamon Press, 409 p. Krauskopf, K. B. 1967. Introduction to Geochemistry: New York, McGraw-Hill, Inc., 721 p. Moore, W. E. 1955. Geology of Jackson County, Florida: Fla. Geol. Survey Bull. 37, 89 p. Noakes, J .--E. ,So M. Kim_, and J._ J. _Stipp-" 1965. __ Chemical and counting advances in liquid scintillation age dating, in Proceedings of the Sixth International Conference on Radiocarbon and Tritium Dating, At. Energy Comm. Publ. CONF-650652, 68-92. Olds, T. S. 1961. Occasional rapid decline and draining of Lake Bradford, Tallahassee, Florida: unpublished Master's Thesis, Florida State University, 64 p. Osmond, J. K. 1964. The distribution of the heavy radioelements in the rocks and waters of Florida, p. 153-159 in Adams, J. A. S., and W. M. Lowder, Editors, The natural radiation environment: Chicago, Ill., UniverSity of Chicago Press, 1069 p. Osmond, J. K., H. S. Rydell, and M. I. Kaufman. 1968. Uranium disequilibrium in groundwater: An isotope dilution approach in hydrologic investigations: Science, V. 162, p. 997-999. Rosholt, J. N. 1958. Radioactive disequilibrium studies as an aid in understanding the natural migration of uranium and its decay products: Proceedings of the Second United Nations International Conference on the Peaceful Uses of Atomic Energy, V. 2, Geneva, p. 230-236. 64

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Rosholt, J. N., W. R. Shields, and E. L. Garner. 1963. Isotopic fractionation of uranium in sandstone: Science, V. 13, p. 224-236. Rosholt, J. N., A. P. Butler, E. L. Garner, and W. R. Shields. 1965. Isotopic fractionation of uranium in sandstone, Powder River Basin, Wyoming, and Slick Rock District, Colorado: Econ. Geol., 60, p. 199-213. -fie>s110lt-,-3;N-.-,B.R-.-Dee,--aooM-.':Pa:tsumete-. -----------Evolution of the isotopic composition of uranium and thorium in soil profiles: Geol. Soc. Amer. Bull., V. 77, No.9, p. 987-1004. Rydell, H. S. Implications of uranium isotope distributions associated with the Floridan aquifer of North Florida, Ph.D. Dissertation, Florida State University, 1969, 119 p. Scott, R. C., and F. B. Barker. 1958. Uranium and radium in the groundwater of the Llano Estacado, Texas and New Mexico: Transactions, Amer. Geophys. Union, V. 39, No.3, p. 459-466. Sellards, E. ana Aucilla Rivers in Florida: Fla. Geol. Survey, Ninth Annual Report, p. 85-139. Serebryakova, M. B. 1964. Application of physicochemical methods to the determination of the mode of occurrence of uranium in groundwaters: Geochemistry Internatl., No.5, p. 898-907. Sever, C. W. 1964. The Chattahoochee Anticline in Georgia: Georgia Geol. Survey Mineral Newsletter, V. 17, p. 39-43. 1966. Miocene structural movements in Thomas County, Georgia: U.S. Geol. Survey Prof. Paper 550-C, p. 12-16. Stringfield, V. T. 1966. Artesian water in Tertiary limestone in the southeastern states: U.S. Geol. Survey Prof. Paper 517, 226 p. Stewart, G. S., and R. K. Farnsworth. 1968. United States tritium rainout and its hydrologic implications: Water Resources Research, V. 4, p. 273. Tamers, M. A., R. Bibron, and G. Delibrias. 1961. A new method for measuring low level tritium using a benzene liquid scintillator in Tritium in the Physical and Biological Sciences, Vol. 1, p. 95, International Atomic Energy Agency, Vienna. 65

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Tamers, M. A., and R. Bibron. 1963. Benzene method measures tritium in rain without isotope enrichment, Nucleonics, 21(6), 90. Tamers, M. A. 1964. Liquid scintillation counting of low level tritium, Packard Tech. Bull. 12. Thurber, D. L. 1962. Anomalous U-234/U-238 in nature: Jour. Geophys. Research, V. 67, p. 4518-4520. U.S. Geological Survey. 1966. Water resources data for Florida: Washington, D. C., U. S. Government Printing Office, V. 1, p. 213. Wait, R. L. 1960. Source and quality of groundwater in southwestern Georgia: Ga. Geol. Survey, Inf. Circ. 18, 74 p. 66