FATE OF DDT AND NITRATE
IN GROUND WATER
U. S. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
ROBERT S. KERR WATER RESEARCH CENTER
ADA, OKLAHOMA
US. DEPARTMENT OF AGRICULTURE
SOIL AND WATER CONSERVATION DIVISION
AGRICULTURAL RESEARCH SERVICE
SOUTHWESTERN GREAT PLAINS RESEARCH CENTER
BUSHLAND, TEXAS
APRIL 1968
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FATE OF DDT AND NITRATE IN GROUND WATER
by
Marion R. Scalf,- Victor L, .Hauser,- Leslie G^McMillion,-
William J. Dunlap,- and Jack W. Keeley-
-^Research Sanitary Engineer, Robert S. Kerr Water Research Center,
Federal Water Pollution Control Administration, U. S. Department
of the Interior, Ada, Oklahoma.
-^Research Agricultural Engineer, Southwestern Great Plains Research
Center, Agricultural Research Service, U. S. Department of
Agriculture, Bushland, Texas.
-^Head, Pollution Fate Section, Ground Water Research Program, Robert S.
Kerr Water Research Center, Federal Water Pollution Control Adminis-
tration, U. S. Department of the Interior, Ada, Oklahoma.
-/Research Chemist, Robert S. Kerr Water Research Center, Federal Water
Pollution Control Administration, U. S. Department of the Interior,
Ada, Oklahoma.
-Chief, Ground Water Research Program, Robert S. Kerr Water Research
Center, Federal Water Pollution Control Administration, U. S.
Department of the Interior, Ada, Oklahoma.
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PREFACE
The intelligent management of water resources in the United States
is necessarily based on considerations of both quantity and quality.
An attractive possibility for the conservation of areal water
exists in the Southern High Plains of northwestern Texas and eastern
New Mexico where surface runoff is collected in natural basins called
playas. To prevent extensive losses by evaporation, this runoff water
could be injected into the Ogallala Aquifer, the area's major water
supply.
Although most of the ground water pumped in this area is used for
irrigation of agricultural lands, many cities and towns and thousands
of farmers also pump water from the same aquifer for household use.
The water supply available for recharge is mostly runoff water from
agricultural lands and may contain chemicals harmful to man or animals.
There is justifiable concern over the safety of drinking water supplies
exposed to these chemicals and other pollutants. However, there is a
notable lack of reliable data and facts concerning the movement,
degradation, and disappearance of toxic materials which are used on
watersheds and may enter ground waters by ground-water recharge. This
report is intended to illuminate part of the darkness now surrounding
the subject.
This project was unique from a standpoint other than its concern
with ground-water quality and the corresponding hydraulics of recharge
operations—the United States Departments of the Interior and of
Agriculture combined their diverse facilities and human competencies.
Under formal agreement, personnel of the Robert S. Kerr Water
Research Center, U. S. Department of the Interior, and of the South-
western Great Plains Research Center, U. S. Department of Agriculture,
worked together on field and laboratory phases of this project as well
as report preparation.
This cooperation paid off in a number of ways. The area of
research was of mutual concern and, since each agency contributed
certain facilities and services that were not readily available to
the other, the project moved with greater efficiency, at reduced cost,
and produced highly satisfactory results. This union of resources
demonstrated the research economy and professional compatibility
needed in practical resources conservation and management.
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PROJECT DESCRIPTION
The objectives of this project were as follows:
1. To determine the distance and manner in which DDT and nitrate
move from a well that is being recharged;
2. To determine the degree to which the aquifer will adsorb DDT
and nitrate;
3. To study the manner in which DDT and nitrate are released
from an aquifer by pumping a well which has been recharged
for a specified time with water containing measured concen-
trations of these substances; and
4. To perform these tests under conditions where recharge rates,
discharge rates, water-level fluctuations, and the physical
and hydraulic characteristics of the aquifer are described
and recorded sufficiently so as to extend results of this
project to other ground-water situations.
s
The field facilities of the Southwestern Great Plains Research
Center at Bushland, Texas were selected as the site for conduct of
this project. This site offered the following conditions and advan-
tages:
1. It contained a large-capacity well that could be used for
recharging the Ogallala Formation and could also be pumped
at high rates.
2. There were several very well constructed observation wells
at varying distances from the recharge well where water
samples could be collected during the test. Only one
additional observation well was considered to be needed.
3. An irrigation well capable of providing adequate water for the
recharge phase was present. This well was far enough from the
recharge well that the influence of its pumping would not
affect conditions resulting from recharge operations.
4. Thorough and accurate geologic and hydraulic, information on
the aquifer had already been obtained by personnel at the
Southwestern Great Plains Research Center.
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5. Aquifer conditions at this site were believed to be fairly
representative of many of the heavily pumped areas of the
Ogallala, particularly of those where playa water is
available for recharge,
6. The point at which recharge water would enter the receiving
formation was so far removed from any domestic or stock wells
and so distant from any privately-owned lands that the tests
would pose no pollutional hazards.
iii
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ACKNOWLEDGEMENTS
In projects of this nature, it is important that a full measure
of appreciation be extended to those who contributed significantly
to the project's successful completion.
These people are:
From the Robert S. Kerr Water Research Center:
Bert E. Bledsoe, Chemist
Michael L. Cook, Physical Science Technician
Roger L. Cosby, Chemist
Billy L. DePrater, Research Chemist
Montie H. Fraser, Engineering Technician
Bruce W. Maxwell* Research Geologist
James F. McNabb, Microbiologist
Leon H. Myers, Research Chemist
Bobby D, Newport, Physical Science Technician
Tommy N. Redman, Engineering Aid
From the Southwestern Great Plains Research Center:
Ordie R. Jones, Hydraulic Engineering Technician
Oliver R. Lehman, Agricultural Research Technician
Donald C. Signor, Agricultural Engineer
Robert 0. Toland, Core Drill Operator
iv
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TABLE OF CONTENTS
Chapter Page
PREFACE i
PROJECT DESCRIPTION ... ii
ACKNOWLEDGEMENTS iv
LIST OF FIGURES vii
LIST OF TABLES ix
I. INTRODUCTION 1
General Extent and Cause of Problem 1
DDT in Ground Water 1
Nitrates in Ground Water 4
Areal Description of the Ogallala Formation ... 5
II. FIELD INSTRUMENTATION AND PROCEDURES 8
Physical Description 8
Instrumentation 9
Well Construction 10
Injection and Pumping Procedures 11
III. HYDRAULICS AND GEOLOGY 13
Hydrogeology of the Field Site 13
Hydraulics 14
IV. POLLUTIONAL PARAMETERS 18
Recharge of Pollutants 18
Methods of Sampling 19
Methods of Analysis 21
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Chapter
V. RESULTS OF ANALYSES ................ 26
O £
Tracer Recovery ..................
Nitrate Recovery
DDT Recovery
VI. SUMMARY AND CONCLUSIONS .............. 40
VII. BIBLIOGRAPHY .................... 43
vi
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Figure
No. Title
LIST OF FIGURES
Follows
Page
6
1-1 Southern Ogallala Formation
II-l Southwestern Great Plains Research Center 8
Facilities
II-2 Location Map of Field Site 8
II-3 Chemical Feed System °
II-4 Cross Section of Mixing Chamber 9
II-5 Cross Section of Recharge-Pumping Well 9
II-6 Slot-Type Sand Sampler 10
H-7 Recharge Rate of Recharge-Pumping Well 12
HI-1 Particle Size Distribution 13
III-2 Electric and Gamma Logs ^
III-3 Storage and Transmissibility by Modified 15
Theis Formula
Of)
IV-1 Portable Pump System ^u
IV-2 Mobile Laboratory and Gas Chromatograph 21
IV-3 AutoAnalyzer and Liquid Scintillation System 21
IV-4 Gas Chromatogram Obtained in Analysis of 23
Recharge Water
IV-5 Structural Formula of Principal DDT Isomers 24*
V-l Tracer Dispersion During Recharge 26
*0n page 24.
vii
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Figure Follows
No. Title Page
V-2 Determination of Detention Time Using 27
Tritiated Water
V-3 Determination of Detention Time 27
V-4 Tracer Recovery While Pumping Well No. 1 27
V-5 Nitrate Behavior—Well No. 1 28
V-6 Nitrate Behavior—Well No. 2 28
V-7 Nitrate Behavior—Well No. 3 28
V-8 Comparison of Nitrate and Tritiated Water 29
Transport
V-9 DDT Recharge Concentration 32
V-10 DDT Concentration After Pumping Begins 33
V-ll DDT Concentration After Pumping Begins 33
V-12 Analysis of DDT Adsorption on Ogallala 36
Sand
V-13 Rate of Sand Production After Pumping 37
Begins
viii
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LIST OF TABLES
Table Follows
No. Title page
III-l Wet and Dry Sieve Comparison 14
III-2 Core Analyses of Ogallala 14
V-l Rate of DDT Recovery on Sand After Pumping 37*
Began
*0n page 37.
ix
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I. INTRODUCTION
General Extent and Cause of Problem
Increasing demands on the water resources of the High Plains area
of West Texas and Eastern New Mexico have given rise to the very real
possibility of storing water underground. This would be accomplished
by recharging the Ogallala Aquifer—the area's major source of water.
Water storage in aquifers is highly desirable because large storage
volumes are available, water is available wherever the aquifer exists,
little or no water is lost from aquifers by evaporation, ground-water
quality is usually good, ground waters are not easily polluted, and
often there is no other feasible storage site.
Artificial recharge practices give rise to concern that ground
water may be contaminated by undesirable substances introduced with
the recharge water.
Pesticides and nitrates are of particular importance in future
recharge programs because of their association with agricultural
practices in the High Plains area.
This report presents findings concerned with the fate of DDT and
nitrate under actual recharge conditions in the Ogallala Aquifer.
DDT in Ground Water
The extent of ground-water pollution with pesticides is not known
at this time; however, they are used in every section of the country
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and, hence, are potential pollutants in all states. Artificial
recharge is carried out to some extent in all sections of the country
and as water use increases will become more important and widespread,
creating increased opportunity for pollution of ground water.
The movement of pesticides through an aquifer from a recharge
well and the concentration of these compounds in water subsequently
pumped from the aquifer will obviously be greatly affected by the degree
of adsorption of the pesticides by aquifer solids. The adsorption of
pesticides on aquifer particles is a complex phenomenon involving many
variables. Little work has been done concerning pesticide adsorption
and saturated ground-water flow in aquifers, but there is considerable
literature dealing with the behavior of pesticides in soils and surface
waters/1'2'3'4'"
Extrapolation of soil research to aquifers indicates that the mineral
composition of particles constituting an aquifer will strongly affect
adsorption. Increasing proportions of clays, particularly the mont-
morillionites, would be expected to result in greater adsorption
because of the ionic nature and large surface areas of these substances.
Aquifers generally, however, have a low clay content and high percentages
of sand or coarser material likely to be of lesser adsorptive capacity.
Amorphous and crystalline hydroxides and oxides of aluminum, iron, and
silica, which have large surface areas, would likewise be expected to
increase adsorption capacities of aquifer particles. Such compounds
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are present in minor, but possibly important, amounts in the aquifer
material of the Ogallala. Also, the presence of organic matter will
greatly increase adsorption, but organic matter is very low in the
Ogallala.
Pore size and pore concentration in an aquifer will affect the
adsorption characteristics because of their influence on adsorbate-
adsorbent distances and their influence on the rate of flow past any
given particle. It would appear from a mass action and solubility
standpoint that the greater the volume of water moving past a point
in a given unit of time, the greater will be the desorption.
Temperature and pH are also likely to be of importance in the
adsorption of pesticides in an aquifer. Generally, such adsorption
would be expected to increase with decreases in both temperature and
pH.
Finally, the nature of the ads orb ate will obviously be a primary
factor in determining the degree of adsorption. Different pesticides
will be adsorbed to different degrees on identical adsorbents because
of differences in the chemical structures of pesticide molecules and
the resulting variations in affinities for adsorbent and solute. It
seems probable that within a given family of pesticides the adsorption
will be inversely proportional to water solubility.
DDT was chosen as a representative pesticide for use in this
study because of its relatively low toxicity, its persistence, and
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its membership in the family of chlorinated hydrocarbons which are
widely used. If the factors likely to affect adsorption of pesticides
are carefully considered, it is believed that results obtained in this
investigation may be employed as a guideline in considering the possible
fate of other chlorinated hydrocarbons such as dieldrin and endrin under
similar conditions.
Nitrates in Ground Water
Nitrates were incorporated in this study because of the health
aspects in regard to both humans and animals.
The cause of infant cyanosis (methemoglobinemia) or blue babies
has long been attributed to nitrates in water supplies. ' In this
case, nitrate is first converted to nitrite in the intestinal tract;
the nitrite is then absorbed into the blood stream where it combines
with hemoglobin, thus depriving the organs and tissues of needed
oxygen.
In addition, there is evidence that high nitrate water can
produce intestinal pathological conditions resulting in chemical
fo\
diarrhea.
For human consumption, the U. S. Public Health Service has
established drinking water limits of 45 mg/1 nitrates. There is,
however, increasing evidence that even this limit can significantly
affect both animals and humans, and some reports show harmful effect
,. (9,10)
with concentrations as low as 5 mg/l.
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Nitrates occur in almost all natural waters. Concentrations
range up to hundreds of mg/1; but, except when contamination is present,
they seldom exceed 20 mg/1, with 10 mg/1 or greater often regarded as
a probable indication of sewage contamination.
The use of nitrogen fertilizers accounts for 30% of our food
production. ' Such widespread use has caused some speculation
as to possible pollution of surface and ground water from the
application or over-application of nitrogen fertilizers. '
The nitrate ion does not readily adsorb but, rather, moves freely
through the aquifer. Although movement is not completely free, inhi-
bition by the aquifer material is minute. The presence of anaerobic
bacteria can convert nitrates to nitrites so that less nitrate will be
recovered from a system than is added to it. It is generally believed
that these bacteria are not normally active in aquifers, especially at
depths characteristic of the Ogallala, and would be expected to have
little effect on the nitrate content of the water.
Areal Description of jhe Ogallala Formation
The Ogallala Formation is truly one of the large ground-water
reservoirs of the world. Paralleling the eastern front of the Rocky
Mountains, it extends from southern South Dakota to southwest Texas,
a distance of some 825 miles. East to west, it averages about 190
miles in width. Its total area of about 158,000 square miles covers
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parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South
Dakota, Wyoming, and Texas. This total area is about the size of the
state of California.
Although these figures of geographic expanse are highly impressive,
the formation is also of great economic importance to its region in
that it is the principal source of fresh water and because much of
its surface exposure is comprised of rich, level soils highly suited
to irrigated agriculture. Because of this combination of water and
soils, in recent years the region has been developed into one of the
largest and more productive irrigation areas in the nation.
Since current data on overall development and use of ground water
from the Ogallala Formation are not readily available, the situation
in the High Plains of Texas, south of the Canadian River, will be
discussed briefly to illustrate the economic significance of the
Formation. The Ogallala covers 24,800 square miles in this area as
shown in Figure 1-1. Rayner in 1965 reported that about 45,000
irrigation wells, 650 municipal wells and 400 industrial water supply
wells are developed in this part of the Ogallala, and about four
million acre-feet of water per year is pumped from these wells—an
amount four times the total annual use for the state of Oklahoma.
Water-yielding characteristics of the Ogallala are adequate for
development of large-capacity wells throughout its geographic extent
except in those areas where river valleys dissect the formation and
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COLORADO
KANSAS
NEW MEXICO
OKLAHOMA
SPRING
Fine Textured Soils
Sondy Soils
Little Or No Water
In Ogallola Formation
Sand Dunes
MILES
100
FATE OF DDT AND NITRATE IN GROUND WATER
SOUTHERN OGALLALA FORMATION
U.S. DEPARTMENT OF AGRICULTURE
AGRICULTURAL RESEARCH SERVICE
SOUTHWESTERN GREAT PLAINS
RESEARCH CENTER
BUSHLAND.TEX AS
US. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION
CONTROL ADMINISTRATION
ROBERT S. KERR
WATER RESEARCH CENTER
ADA, OKLAHOMA
FIGURE I-l
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in certain localities where water-saturated thickness of the formation
is thin or nonexistent. The formation consists of river-deposited
clay, silt, sand, and gravel. Even though continuity of layering is
difficult to trace for more than a few miles, the physical appearance
of the formation from one locality to another is surprisingly similar.
For example, the outcrop near Ogallala, Nebraska, where the formation
was officially first described and from which town its name is derived,
very much resembles formation outcrops in the eastern escarpment of
the High Plains east of Lubbock, Texas.
However, hydraulic characteristics of the formation may vary
greatly from one locality to another. Such variations often result
from differences in saturated thickness, but more often result from
the presence of beds of well sorted coarse materials such as sand
and gravel.
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II. FIELD INSTRUMENTATION AND PROCEDURES
Physical Description
This research was conducted at the Southwestern Great Plains
Research Center at Bushland, Texas. Recharge and observation wells
were located in a large play a depression near the edge of a dry
playa lake as shown in Figures II-l and II-2. The bottom of this
lake consists of an impermeable clay layer which varies in thickness
from 4 to 30 feet and prevents or greatly inhibits vertical percola-
tion into the soil and ground water.
The recharge water was supplied by an irrigation well located
2,280 feet northeast of the recharge area. Water from this source
well was transported by irrigation pipe through two parallel sand
traps, two propeller meters, and into the recharge well. The sand
filters collected several hundred pounds of sand from the recharge
water, preventing possible filling of the recharge well.
A constant head of 5 psi at the point of injection was main-
tained in the injection pipes at the ground surface by an overflow
pipe located near the sand traps.
Two chemical mixing tanks were alternately connected to a
piston-type chemical feed pump which delivered about three gallons
per hour of nitrate, DDT, tritium and water mixture to the recharge
pipe as shown in Figure II-3. A mixing chamber containing an auger
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•1-40 8 U.S. 66
Underground
Concrete —••
Pipeline
Recharge Area—*
Aluminum Pipeline
On Surf
Irrigation
Well
K
m
L
c
C
500
Scale In Feet
tooo
FATE OF DDT AND NITRATE IN GROUND WATER
SOUTHWESTERN GREAT PLAINS
RESEARCH CENTER FACILITIES
U.S. DEPARTMENT OF AGRICULTURE
AGRICULTURAL RESEARCH SERVICE
SOUTHWESTERN
RESEARCH
GREAT PLAINS
CENTER
BUSHLAND, TEXAS
U.S. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION
CONTROL ADMINISTRATION
ROBERT S. KERR
WATER RESEARCH CENTER
ADA, OKLAHOMA
FIGURE II-I
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Overflow And
Constant Head
Control
Basin- Used only for
waste water
Mixing Tank 8 Injection Point
pp RPP f
" *—*—*&
Fi£in$r-i—"®i
Sand Sampler
pp— Propeller Flow Meter
RPP-Recording Propeller Row Meter
—Recharge Well
Observation Well
FATE OF DDT AND NITRATE IN GROUND WATER
LOCATION MAP OF FIELD SITE
U.S. DEPARTMENT OF AGRICULTURE
AGRICULTURAL RESEARCH SERVICE
U.S. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION
CONTROL ADMINISTRATION
ROBERT S. KERR
WATER RESEARCH CENTER
ADA, OKLAHOMA
BUSHLAND, TEXAS
FIGURE II-2
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FATE OF DDT AND NITRATE IN GROUND WATER
CHEMICAL FEED SYSTEM
U.S. DEPARTMENT OF AGRICULTURE
AGRICULTURAL RESEARCH SERVICE
SOUTHWESTERN
RESEARCH
GREAT PLAINS
CENTER
U.S. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION
CONTROL ADMINISTRATION
ROBERT S KERR
WATER RESEARCH CENTER
ADA, OKLAHCMA
FIGURE
-3
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system shown in Figure II-4, immediately provided turbulence for
mixing the pollutants and tracer with the recharge water before
injection into the recharge well.
Recharge of the well was through two 2-inch pipes connected to
the mixing chamber and terminating 145 feet below the ground surface.
During recharge operations, the ends of both pipes were submerged
in the well at all times. Figure II-5 presents a cross section of
the recharge well and injection pipes. To prevent air entrainment
difficulties, it was necessary to maintain a positive pressure at
all points in the injection system. A streamlined plug was suspended
on a cable from the end of each pipe, and the plug was positioned
so as to maintain this positive pressure.
The recharge-pumping well was equipped with a water-lubricated
deep-well turbine pump powered by a V8 internal combustion engine.
This system had a pumping capacity of more than 1,000 gpm for
prolonged periods of time.
Ins trumentation
Two propeller-type meters were used to measure the flow rate of
the recharge water. One of the meters was connected to a recording
rate meter which maintained a continuous record of the flow throughout
the 22-day recharge-pumping period. A third meter was also used in
measuring the flow rate during the pumping phase of the experiment.
The differences in measurements between the different meters were
within the factory specified plus or minus 2 percent precision for
the meters.
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ro
20"Auger
Left Rot.
Pressure.
Gage
*1
•Flow Straightening
Vanes
20" Auger Right Rotation
Chemica
Inlet
SECTION A-A
.Chemical Injection
Point
FATE OF DDT AND NITRATE IN GROUND WATER
CROSS-SECTION OF MIXING CHAMBER
U.& DEPARTMENT OF AGRICULTURE
AGRICULTURAL RESEARCH SERVICE
SOUTHWESTERN GREAT PLAINS
RESEARCH CENTER
BUSHL AN D.TEXAS
US. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION
CONTROL ADMINISTRATION
ROBERT S. KERR
WATER RESEARCH CENTER
ADA, OKLAHOMA
FIGURE II-4
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Recharge Water
Inlet
Flange
Pump Base
Stuffing
Box
2 X,Pipe
I !
16 Well
Casing
2" Steel Pipe
'/e" Cable
Plug
8 Pump
Column
FATE OF DDT AND NITRATE IN GROUND WATER
CROSS-SECTION OF RECHARGE - PUMPING WELL
U.S. DEPARTMENT OF AGRICULTURE
AGRICULTURAL RESEARCH SERVICE
SOUTHWESTERN GREAT PLAINS
RESEARCH CENTER
BUSHLAND, TEXAS
U.S. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION
CONTROL ADMINISTRATION
ROBERT S, KERR
WATER RESEARCH CENTER
ADA, OKLAHOMA
FIGURE II-5
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10
Float-operated water level recorders were used continuously in
Wells No. 5 and 7 and four others located between 250 and 1,000 feet
from the recharge well. Water levels were measured in Wells No. 3, 4,
and 6 several times each day with an electric well sounder. This
method was also used on five other wells in the test area. Air-
operated bubbler-gauge recorders were used to record water levels in
Well No. 1 and in a 2-inch well located 90 feet south.
To measure the sand produced by Well No. 1 during the pumping
phase of the experiment, the flow was diverted through a "T11 and
into a slot type sampler shown in Figure II-6.
Well Construction
Well No. 1, the re charge-pump ing well, was drilled 28 inches in
diameter and 269 feet in depth by conventional hydraulic rotary
drilling methods. The well screen and 1/4-inch casing were 16 inches
in outside diameter. Continuously wound galvanized steel wire screen
spanned 90 feet of the well from 161 to 253 feet below the ground
surface, terminating above the clay layer. Gravel pack, designed to
hold the formation in place during pumping or recharge, filled the
annulus around the well screen. Concrete filled 16 feet of the
casing below the screen and extended into the clay layer. Concrete
was also placed between the casing and the drilled hole from the
surface to a depth of 92 feet.
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FATE OF DDT AND NITRATE IN GROUND WATER
SLOT TYPE SAND SAMPLER
U.S. DEPARTMENT OF AGRICULTURE
AGRICULTURAL RESEARCH SERVICE
SOJThWESTERri GREAT PLAINS
RESEARCH CENTER
,TEXAS
U.S. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION
CONTROL ADMINISTRATION
ROBERT S KERS
WATER RESEARCH CENTER
ADA, OKLAHOMA
FIGURE 11-6
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11
Observation Wells No. 2 through 7 were drilled by conventional
hydraulic rotary drilling methods to depths ranging from 270 to 354
feet and were lined with 6-inch casings. All casings except Well
No. 4 were slotted by acetylene cutting torch from about 100 feet
below the surface to depths ranging from 265 to 354 feet and surrounded
by gravel pack. Well No. 4 had special factory made casing slots,
from 160 to 260 feet below the surface, designed to hold back formation
sand without gravel pack.
Wells No. 1, 3, and 5 had been used in previous experiments by
USDA for recharge of playa lake water. ' Following these
operations, bailing of the wells produced several cubic yards of
sand. Cavities created outside Wells No. 3 and 5 were later filled
with gravel.
Several 2-inch wells in the vicinity of the recharge well were
used for water level measurements. These wells were developed by
air-lift pumping and consisted of a 2-inch pipe and 2-inch by 2-foot
well points installed inside a 4 1/2-inch drilled hole. Water level
response was the same as that in the 6-inch wells which fully
penetrated the aquifer.
Infection and Pumping Procedures
On the day before the project started, water was recharged into
the injection well for a few hours to adjust all the flow control
equipment and minimize start-up adjustments.
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12
Recharge started at 9:15 a.m. on October 31, 1967, and addition
of pollutants started at 10:00 a.m. of the same day. Recharge continued
at a 10-day average rate of 348 gpm, with fluctuations within plus or
minus 2 percent (Figure II-7), until 9:58 a.m. on November 10, 1967.
Following the 10 days of recharge, the well was allowed to sit
idle for 3 hours; pumping started at 1:00 p.m. on November 10. Water
was pumped continuously from the recharge well at an average rate of
504 gpm, plus or minus 2 percent, until 1:00 p.m. on November 22, 1967.
The pumped water was transported by pipeline to a clay bottomed
reservoir and allowed to evaporate.
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in
o>
o
b
I
^
w
O
cn
360
355
6 350
a
a:
ui
345
340
10
a>
o
O
f
O
tn
a.
o
55
Average Flow (Recharge)
Rate 348.0
7
I
I
Oct. 31 Nov. I
456
TIME (NOVEMBER 1967)
10
FATE OF DDT AND NITRATE IN GROUND WATER
RECHARGE RATE OF RECHARGE-PUMPING WELL
U.S. DEPARTMENT OF AGRICULTURE
AGRICULTURAL RESEARCH SERVICE
SOUTHWESTERN GREAT PUAINS
RESEARCH CENTER
BUSHLAND.TEXAS
US. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION
CONTROL ADMINISTRATION
ROBERT S. KERR
WATER RESEARCH CENTER
ADA, OKLAHOMA
FIGURE II-7
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III. HYDRAULICS AND GEOLOGY
Hydrogeology of the Field Site
The Ogallala Aquifer at the test location is bounded on the top
by caprock at a mean sea level (MSL) elevation of 3,768.3 feet. The
sandstone caprock, cemented primarily with calcium carbonate, is about
two feet thick over all the area influenced by this experiment. In
October 1967, the water table stood at a MSL elevation of 3,635.3 feet,
leaving 133 feet—or more than one-half of the Ogallala—unsaturated.
The bottom of the aquifer at the test site consists of a dense clay
layer of extremely low permeability. This clay layer has been found to
be at least three feet thick in all test wells within 1,500 feet of the
recharge well. Although the top of clay is not horizontal, the elevation
varies less than five feet within a 500-foot radius of the recharge well.
The aquifer in the test area is comprised primarily of fine sand.
There are numerous thin layers and nodules of sand cemented with
calcium carbonate and other acid-soluble cementing agents. Figure III-l
presents the particle-size distribution of undisturbed core samples
from below the present water table in a test hole 66 feet southwest of
Well No. 1. The distributions shown were obtained without crushing so
as to retain cemented nodules in their original size and shape.
These nodules vary in size from two sand grains up to one or two
feet in diameter and have been observed in undisturbed cores and in
-------
O
0
'
> F
o
L/> — CJ
O £* PI
ll M
•x m
o 3>
I z
r w
| 3
w <
O
l
O rn
i; :.
I I* ? ^
o o rn tO-o H
" H(3 I
3Jr m
= II 3
5 m
'
-
r
i
CD
m
98
95
90
80
70
o 60
Z 50
% 40
£ 30
* 20
10
5
TTT
I T
172-173
• I
0.1
0.5 1-0
^^^^
99* %« 0.5 mm
200
0.1 0.5 1.0
SIEVE SIZE-MM
I I
// 227-229*
' / / __-A-
•ta. ^J I *~~
0.1
0.5 1.0
-------
14
places in the walls of shafts down to 95 feet below the ground surface.
Particle sizes were determined from one set of core samples by two
different methods. The first group was wet-sieved to preserve cemented
nodules in their natural state while the second group of samples was
dried and crushed with a rubber roller in a steel pan. Table III-l
presents the difference in percent by weight larger than 0.841 millimeter
in diameter.
Laboratory permeability, particle size distribution, and carbonate
content from representative core samples are presented in Table III-2.
All of more than 100 core samples analyzed from the test aquifer
contained more than one percent by weight of clay. Permeability
determined from cores, electric and gamma ray well logs, and driller's
logs indicates a highly stratified aquifer with a greatly variable
permeability over short vertical distances. Figure III-2 presents
electric and gamma logs from the test well 66 feet southwest of
Well No. 1.
Hydraulics
Investigations of ground-water hydraulics necessarily involve
the parameters of permeability, transmissibility, and storage.
1. Coefficient of permeability (p) is defined as the number
of gallons per day flowing through an area of 1 square foot
under a hydraulic gradient of unity (1 ft/ft) and maintains
2
units of gallons per day per foot .
-------
Table III-l
Wet and Dry Sieve Comparison
Percent Larger Than 0.841 mm
Depth
(ft.)
150-152
160-162
172-173
180-182
190-192
200-201
227-229
240-242
250-252
Wet Sieve*
(%)
4.2
<0.9
2.2
<0,75
<0.27
4.0
4.2
10.3
<1.3
Dry Sieve
(crushed)
0.2
0.0
0.6
0.0
0.0
1.3
0.4
0.2
0.2
*Wet sieve had minimum disturbance; the sample was washed through
sieves larger than 0.5 mm, and the portion smaller than 0.5 mm
was sieved dry.
**Dry sieve samples were crushed before dry sieving by a rubber
roller on a steel surface. Quartz sand grains were not crushed.
-------
Table III-2
Core Analyses of Ogallala
Mean Sea
Level
Elevation
(ft.)
3639.2
to
3637.2
3618.2
to
3616.2
3595.7
to
3595.2
Sand
K* >50u
(cm/day) (%)
1,401 feet
87
155
75
93
11
83
30 95
Silt
2-50y
(%)
Clay
>2y C00
fo/\ f°/*\
v™/ \™/
' Comments'
south of recharge well
5
4
2
2
2
1,049 feet west-southwest
3599.9
to
3597.9
3570.4
to
3568.4
0.8 92
29 85
3
4
1.4 6.6
1.4 19.6
2.0 3.0
2.3 12.7
1.2 1.8
of recharge well
2.7 2.3
2.4 8.6
Top
Bottom
Top
Bottom
*Permeability, cm/day.
**Indicates top or bottom of core; permeability is average
for entire core.
-------
i .
__ _3vj.vlvj.-^----:
GAMMA RAY
SELF POTENTIAL
SINGLE POINT
SIX-FT. LATERAL
SURFACE SOIL
CAP ROCK
OGALLALA
1963
WATER TABLE
1967
LOOSE SAND WITH ROCK
- 300"-
SAND AND ROCK
CLAY
SAND AND CLAY
FATE OF DDT AND NITRATE IN GROUND WATER
ELECTRIC AND GAMMA LOGS
U.S. DEPARTMENT OF AGRICULTURE
AGRICULTURAL RESEARCH SERVICE
SOUTHWESTERN GREAT PLAINS
RESEARCH CENTER
BUSHLAND, TEXAS
U.S. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION
CONTROL ADMINISTRATION
ROBERT S. KERR
WATER RESEARCH CENTER
ADA. OKLAHOMA
FIGURE JJE - 2
-------
15
2. Coefficient of transmissibility (T) is defined as the number
of gallons per day flowing through a vertical section of the
aquifer 1 foot wide under a unit hydraulic gradient (1 ft/
ft). It is therefore the product of the permeability
coefficient and the aquifer's saturated depth in feet.
The units are gallons per day per foot.
3. Coefficient of storage (S ) is defined as the volume of
C*
water removed from a 1 square foot column of the aquifer
when the water table is lowered 1 foot.
These coefficients were determined by the modified Theis
formula from the recharge portion of this project using water
level observations at the recharge well and four selected observation
wells. Storage coefficients calculated by this method varied from
0.05 at Well No. 2 to 0.13 at Well No. 7, and transmissibility
coefficients ranged from 10,266 gpd/ft using water levels at the
recharge well to 22,000 gpd/ft using levels at Well No. 7.
Solution of the Theis formula at Well No. 7, which most nearly
satisfies necessary assumptions, is shown in Figure III-3. Storage
and transmissibility coefficients compare favorably with those
determined in previous recharge experiments at Bushland and with
those reported by Moulder and Frazor.
-------
m
OJ
SB
c c
•3, X
? 53
a "«
*ai
» 3
o a 11
Si
w ~; PI
^ >
m
31
s
j>
X
e
to
m
1
o
m
1
»;
-•5
x>
.
> 5
S!
z -n
8
"
2m
m
fc
J
3: 2
ac
N
t0= 1.74 Days
Z =
Theoretical Curve
where T
WELL NO. 7
Q=348 gpm
r = 300 ft.
o
I
S.= (.3)(22,000)(1.74) . n 13
(300)2 ,
I
500
1000 5000
RECHARGE TIME (Min.)
10000
-------
16
There was wide variation in calculated coefficients at Bushland
because observations failed to fit the theoretical formulations used.
This departure has been reported by others, including Moulder and
(21)
Frazor who performed recharge tests on the Ogallala Aquifer nine
miles east of the Bushland site. These authors attribute theoretical
departures to slow filling of the aquifer during recharge and to the
magnitude of the water level rise in relation to the aquifer's
saturated depth. They concluded that conformance to theoretical
consideration was more closely achieved after longer recharge periods
and at greater distances from the recharge well. This conformance
would only be realized at some time greater than that used in this
project.
Moulder and Frazor best pointed out the possible inadequacies in
using this approach to describe this aquifer's characteristics:
Conditions during the tests departed markedly from
the conditions set forth in the derivation of the
analytical equations; therefore, the determinations
of aquifer coefficients are subject to considerable
error. For example, slow drainage or slow filling
of sediments with water made the data collected
early in the tests unusable for analysis by the
nonequilibrium method. Conformance to theoretical
conditions takes longer times at greater distances
from the pumping or recharging well. Adjustments
to the basic data may be made to correct or compensate
for such things as regional water-level trends and
changes in saturated thickness of the aquifer, but
the success of these adjustments in determining the
true aquifer coefficients is dependent largely upon
the agreement between field conditions and the
conditions assumed by the adjustments.(2°)
At Bushlandt another method was employed to calculate the
storage coefficients. Using detention times calculated from tracer
-------
17
studies described in Section V of this report, storage coefficients
of 0.23 and 0.20 were calculated from the detention times of
tritium and nitrates, respectively, between recharge and observation
wells. These values are believed to be reliable since the method
of calculation is relatively insensitive to reasonable variations
in detention time and aquifer depth. Also, these values are not
subject to the numerous assumptions required for the pump test
method and which are not usually met in practice. In addition,
these higher values agree with storage coefficients found by the
USDA at Bush land in laboratory studies of 100 undisturbed cores
of the aquifer.
-------
IV. POLLUTIONAL PARAMETERS
Recharge of Pollutants
Artificial recharge operations in the High Plains normally
employ, as a source of recharge water, rainfall collected in playa
lakes common to this area. Because suspended matter often causes
clogging of the recharge wells, clarification is sometimes needed
before these waters can be recharged. In addition, other pollutants
may be present in various and significant concentrations.
To avoid this problem and because the supply of playa lake
water at Bushland, Texas was limited, an irrigation well was used
as the only source of recharge water for this project.
The recharge rate was maintained at 348 gallons per minute for
the full 10-day period. This rate is representative of recharge
practices in the High Plains. Nitrate was added to the recharge
water at a weighted average rate of 24.4 mg/1, including the 7.7
mg/1 background from the supply well, and p,p'-DDT was added at an
average rate of 74 parts per billion (ppb). Over the total recharge
period, this concentration amounted to 1,028 and 3.11 pounds of
nitrates and DDT, respectively. In addition, four curies of
tritiated water were added as a tracer at a rate of 210 micromicro-
curies per milliliter (yyc/ml).
-------
19
Tracer, nitrate, and DDT were received in the form of tritiated
water, industrial grade sodium nitrate, and commercial grade 50
percent wettable DDT powder, respectively. Suitable quantities of
all three were added daily to one of two mixing barrels and diluted
to about 80 gallons. An electric motor was used to power a mixing
paddle in each barrel in order to maintain the DDT in suspension.
The contents of each barrel were agitated overnight and during a
subsequent feed period of about 24 hours.
Methods of Sampling
Sampling was confined primarily to Well No. 1, the recharge
well, and Observation Wells No. 2, 3, and 4 located at radial
distances of 33, 66, and 150 feet, respectively, from the point of
recharge. Occasionally, samples were taken from wells at greater
distances. These wells included the domestic water supply for the
agricultural experiment station at Bushland. Samples taken from
distances greater than 150 feet were collected primarily for back-
ground information and as a safety precaution and were generally
analyzed only for tracer concentrations.
During the 10-day recharge period, samples designated Well
No. 1 represented recharge water after mixing with the pollutants
and tracer and were taken from the top of the recharge well through
a manometer tube. During the pumping period, Well No. 1 samples
were taken immediately on the effluent side of the pump.
-------
20
Observation wells were sampled with the portable pump system
O~\ \
shown in Figure IV-1. The system consisted of a submersible
pump which was lowered or raised in an observation well, using a
hose on an electric winch and spool assembly. The sampling depth
was about 190 feet below the ground surface (approximately 30 feet
below static water level) in all the observation wells. Before each
sampling, the well was purged for 30 minutes by pumping at 10 gallons
per minute. This time was sufficient to withdraw about three times
the volume of water in the well and was believed to provide a
representative sample of the aquifer at that location.
To reduce the quantity of sand and other particulate matter in
the aqueous samples during collection, the sample stream was passed
through a Tyler equivalent mesh No. 270 (53 microns or 0.0021 inches)
standard eight-inch brass sieve. The sample stream was directed at
the side of the sieve so that the water moved across the screen rather
than directly through it; this reduced forcing of particulate matter
through the sieve by hydrostatic pressure.
Samples were collected in one-quart glass jars with teflon-lined
lids. These jars and teflon liners were previously washed thoroughly
with dichromate cleaning solution, tap water, and distilled water.
Great care was exercised during sampling to prevent contamination
of samples with substances which would interfere with DDT analysis.
Sand samples for the determination of adsorbed DDT were taken
from the pumped stream in the cleansed one-quart jars. They were
-------
FATE OF DDT AND NITRATE IN GROUND WATER
PORTABLE PUMP SYSTEM
U.S. DEPARTMENT OF AGRICULTURE
AGRICULTURAL RESEARCH SERVICE
SOUTHWESTERN
RESEARCH
GREAT PLAINS
C£C»TER
, TEXAS
U.S. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION
CONTROL ADMINISTRATION
KOBEKT S KER1?
WATER RESEARCH CENTER
ADA, OKLAHOMA
FIGURE IV-I
-------
21
obtained simply by collecting the unfiltered stream and decanting
after the particulate matter had settled.
Methods of Analyses
Analyses for tritium, nitrates, and DDT were conducted in a
mobile laboratory (Figures IV-2 and IV-3) of the Robert S. Kerr
Water Research Center.
Nitrite and nitrate nitrogen were determined by use of a
(22}
Technicon AutoAnalyzerv ' following the automated technique
(23)
described by Kamphake, Hannah, and Cohen, All samples were
analyzed immediately after collection to reduce any errors arising
from changes in the nitrogen balance. Standards were analyzed
before and during each day's run for accuracy. At intervals,
duplicate samples were compared for reproducibility of results.
All samples were analyzed for tritium with a Beckman Model
LS-150 Liquid Scintillation Spectrometer.
The methods employed for quantitative analysis of DDT in the
various water samples were essentially those described by
Breidenbach et al,(24) with some modification. Samples of 600 to
800 ml of water were extracted twice consecutively by stirring for
30 minutes each time with 35 ml portions of hexane. Extractions
were conducted in the original quart sample bottles with teflon-lined
lids, using two-inch teflon-coated magnetic stirring bars. After
each extraction, the hexane and water phases were separated in one
-------
Outside View Of Mobile Laboratory
GAS CHROMATOGRAPH SYSTEM- Used For DDT Analyses
FATE OF DDT AND NITRATE IN GROUND WATER
MOBILE LABORATORY AND
GAS CHROMATOGRAPH
U.S. DEPARTMENT OF AGRICULTURE
AGRICULTURAL RESEARCH SERVICE
SOUTHWESTERN GREAT PLAINS
RESEARCH CENTER
BUSHLAND, TEXAS
U.S. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION
CONTROL ADMINISTRATION
ROBERT S, KERR
WATER RESEARCH CENTER
ADA, OKLAHOMA
FIGURE IV-2
-------
AUTO ANALYZER- Used For Nitrate And
Nitrite Determination
LIQUID SCINTILLATION SYSTEM-Used For Tritium
Measurements
FATE OF DDT AND NITRATE IN GROUND WATER
AUTO ANALYZER AND LIQUID
SCINTILLATION SYSTEM
U.S. DEPARTMENT OF AGRICULTURE
AGRICULTURAL RESEARCH SERVICE
SOUTHWESTERN GREAT PLAINS
RESEARCH CENTER
BUSHLAND, TEXAS
U.S. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION
CONTROL ADMINISTRATION
ROBERT S. KERR
WATER RESEARCH CENTER
ADA,OKLAHOMA
FIGURE IV-3
-------
22
liter separatory funnels and the combined hexane extracts were dried
by passing through 2" x 7/8" columns of anhydrous sodium sulfate.
Extracts of samples from recharge stream and pumped water, in which
DDT concentrations were relatively high, were adjusted to appropriate
volumes and subjected to analysis by electron capture gas chromatography
without further treatment. Extracts of samples from observation wells
which contained low levels of DDT were subjected to thin-layer chroma-
tography before quantitation of DDT in order to minimize interference
by other extract components during the gas chromatography step. In
this procedure, the extracts were evaporated to 2 to 8 ml volume,
transferred to 15 ml centrifuge tubes, and further evaporated carefully
to dryness under a gentle stream of air or nitrogen in a water bath
at 40 C. The residues were dissolved in 100 yl of pure hexane; and
50 yl aliquots, together with standard DDT samples, were chromatographed
on thin-layers of Adsorbosil 1 (Applied Science Laboratories, State
College, Pennsylvania) with carbon tetrachloride as developing solvent.
After locating zones containing DDT by spraying the standards with
Rhodamine B, these zones were removed from the thin-layers by means of
(25)
a microvacuum cleaner apparatus, and the DDT was eluted directly
into 15 ml conical centrifuge tubes with 5 to 6 ml of petroleum ether-
diethyl ether mixture (1:1). The solvent was gently evaporated from
these eluates, and the residues were dissolved in appropriate quantities
(usually 100 to 500 yl) of pure hexane and subjected to gas chromatography.
-------
23
For gas chromatography, a Varian-Aerograph Model 204B gas
chromatograph equipped with tritium-foil electron capture detector
and Minneapolis-Honeywell Model 16 recorder with Disc integrator
was employed. A 5f x 1/8" stainless steel column packed with 5.4%
DC-200 on 80/100 mesh Gas Chrom Q (Applied Science Laboratories,
State College, Pennsylvania) was used for most analyses. In order
to confirm identity of peaks, a 5' x 1/8" glass column packed with
5% QF-1 on 100/120 Aeropak 30 (Varian-Aerograph, Walnut Creek,
California) was employed for analysis of a few samples. Essential
operating parameters were: column temperature, 205°; injection
port temperature, 235 ; detector temperature, 211°; carrier gas,
N_; flow rate, 40 ml/min. Figure IV-4 shows a typical chromatogram
obtained in analysis of recharge water. This chromatogram reveals
the presence of the two principal isomeric forms of dichlorodiphenyl-
trichloroethane, p,p'-DDT [1,1,1 - trichloro - 2,2 - bis (p-chlorophenyl)
ethane] and o,p~DDT [1,1,1 - trichloro - 2-o - chlorophenyl - 2 - p -
chlorophenyl ethane]. These are shown structurally in Figure IV-5.
In this research, only p,p'-DDT, which comprised approximately 80% of
the total DDT isomers of the recharge stream, was determined routinely;
and the term DDT as used in this report refers to the p,p' isomer only
unless otherwise noted.
-------
p.p'-DDT
o.p-DDT^
FATE OF DDT AND NITRATE IN GROUND WATER
GAS CHROMATOGRAM OBTAINED IN
ANALYSIS OF RECHARGE WATER
US. DEPARTMENT OF AGRICULTURE
AGRICULTURAL RESEARCH SERVICE
SOUTHWESTERN GREAT PLAINS
RESEARCH CENTER
BUSHLAND, TEXAS
U.S. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION
CONTROL ADMINISTRATION
ROBERT 3. KERR
WATER RESEARCH CENTER
ADA, OKLAHOMA
FIGURE IV-4
-------
24
Figure IV-5
Structural Formula of Principal DDT Isomers
H " Cl
o — c — ci ci— c — ci
Cl Cl
p,p'-DDT o,p-DDT
Highly purified solvents were employed throughout the DDT
analysis, and extensive precautions were taken to prevent contam-
ination during the analytical procedures. Standard p,p'-DDT
samples were routinely carried through the procedure with the
unknowns to check recovery of DDT, which was found to vary from
70 to 98%. Correction of obtained DDT values to compensate for
recovery efficiencies was not attempted,
For analysis of DDT adsorbed on sand samples, excess water
was first decanted from the sample. The remaining aqueous sand
slurry was then poured into a 22 mm diameter column equipped with
fritted glass disc. The sand was washed with 350 to 500 ml of
distilled water to remove all nonsorbed DDT and then was washed
successively with two 100 ml portions of pure acetone and two 100 ml
portions of pure hexane. The solvent was carefully evaporated from
the acetone washings, and the residues were dissolved in pure hexane
and dried with sodium sulfate. The resulting solutions and the
-------
25
original hexane washings were adjusted to appropriate volumes and
analyzed by electron capture gas chromatography, as previously
described. The washed sand was dried and weighed to determine DDT
adsorbed per unit weight of sand. This washing procedure appeared
to be quite effective in removing adsorbed DDT from the sand since
extraction of the previously washed sand in a Soxhlet extractor with
acetone for 10 hours yielded no significant additional quantities
of DDT. Essentially all of the adsorbed DDT was found to be removed
from the sand by the first acetone wash.
-------
V. RESULTS OF ANALYSES
Tracer Recovery
Due to expected mixing and dilution of recharge water with
water native to the aquifer, a tracer was necessary to determine
the magnitude of these effects. The recharge water was tagged
with tritiated water to determine the degree of dilution, the
rate of movement of the recharge water, and the amount of recharge
water recovered during pumping operations. Tritiated water was
selected because its behavior is essentially chemically and
physically identical to the water being studied.
By comparing tracer concentrations in observation wells with
concentrations in the recharge water, it was possible to calculate
the pollutant concentrations expected in the absence of breakdown,
adsorption, or other losses in the aquifer.
Tritium was added to 348 gpm of recharge water at an average
rate of 210 micromicrocuries per milliliter (yyc/ml) for 10 days
as shown in Figure V-l. This injection rate resulted in a total
of 4.0 curies being added to the ground water.
Tracer was recovered at Observation Wells No. 2 and 3 located
33 feet and 66 feet, respectively, from the recharge well. The
native water in the aquifer between Well No. 2 and the recharge
well was totally displaced after about three days of injection.
-------
WEIGHTED AVERAGE _J
INPUT CONCENTRATION
CONCENTRATIONS AT
WEL NO. 2
CONCENTRATIONS AT
WEL NO. 3
72 96 120 144
TIME AFTER RECHARGE BEGAN (Hours)
-------
27
The native water in the aquifer between Well No. 3 and the recharge
well was not completely displaced during this experiment as shown by
the failure of the tritium concentration to reach the average recharge
concentration. Part of this failure may be attributed to the low
recharge concentrations noted on the fourth through sixth days as
shown in Figure V-l. Tritium was not detected at all in Well No. 4
which was located 150 feet from the recharge well.
Detention times between the recharge well and observation wells
were determined for use in calculation of aquifer storage coefficient
mentioned in Section III and again in nitrate recovery.
The increase in tracer concentration at Wells No. 2 and 3 follow
the normal ess-shaped curvature expected in these types of phenomena.
The flow-through time, detention time, or geometric mean observation
time to each of these wells is equal to the inflection point of their
respective dispersion curves or to the second derivative of the
formulation of these curves equated to zero.
Detention times were determined graphically in Figure V-2 by
plotting the summation of tracer which had passed a radius, r, in
time, t. This process involves two linear functions. The intersection
of the two straight lines describes the flow-through or roughly the
(26)
detention times.
A more commonly used graphical solution is shown in Figure V-3
where the data are plotted on logarithmitic probability paper. A
straight line fitted to the data intersects the 50 percentile concen-
tration at the geometric mean observation time.
-------
3.0 -
I
5
•
.
-
I
=• I
S3 1
rn .4
t* in
s i
> P
wi<"
8 g
o
> 3 >
H O O
, x 2
r c/> O
> m c
2 33
* a
3
.
5™
mm »;
s^S
III
5 SS H
S §
3) ijt
m
H
m
> O
H m
m H
o rn
i|
m z
i
:
•
25
50
75 IOO 125 150
TIME AFTER RECHARGE BEGAN (Hours)
175
200
-------
300
o
I
200
o
i^
QQ
UJ
cs
CK
100
I
o
UJ 90
°= 80
cc
UJ 70
£ 60
£ 50
E
o
I
OJ
ro
Well No. 3
J L
I 1 1
10
20 30 40 50 60 70 80 90
PERCENT OF RECHARGE CONCENTRATION
FATE OF DDT AND NITRATE IN GROUND WATER
DETERMINATION OF DETENTION TIME
U.S.DEPARTMENT OF AGRICULTURE
AGRICULTURAL RESEARCH SERVICE
SOUTHWESTERN GREAT PLAINS
RESEARCH CENTER
BUSHLAND, TEXAS
U.S. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION
CONTROL ADMINISTRATION
ROBERT S. KERR
WATER RESEARCH CENTER
ADA,OKLAHOMA
FIGURE V-3
-------
28
Detention times at the recharge rate of 348 gpm were 1.7 and
5.4 days to Wells No. 2 and 3, respectively. Using the saturated
volume calculated from observed water levels, a storage coefficient
of 0.23 was calculated.
Following the 10-day recharge period, pumping the recharge well
at 504 gpm for 10 days yielded 3.75 curies or 94 percent of the
injected tritiated water. Tracer recovery during pumping is shown
in Figure V-4. If no losses occurred due to adsorption, breakdown,
denitrification, etc., then a similar recovery could be expected for
nitrates and DDT. This high recovery of tracer adds to the reliability
of tritium as a tracer for determining flow and dispersion character-
istics of underground formations.
The recharge well was pumped for 12 days with samples taken each
day from Well No. 1. The observation wells were sampled for the first
four days and again on the eleventh day when tracer concentrations in
all wells had returned to background.
Nitrate Recovery
Nitrate was added to recharge waters with a weighted average
concentration of 24.46 mg/1 as shown in Figure V-5. Over the 10-day
recharge period, this addition amounts to 1,028 pounds of N03- The
background N03 concentration of the supply well was 7.74 mg/1 which
accounted for 325 pounds in the recharge water, leaving 703 pounds
artificially added.
-------
o
c
33
m
i
250
1 21
2 !H 5
i ^1 -^
w m
m ">
> 2
r~ m
33 3
m •
CO Q
2 J
o
S ^g
& mm
- 05 rn
o nij
:* J>
3?
^x
m
83
zm
H5
33>
Or
m
€ S
i o!
2 mi;
J> Z3I
H
m
x
§3
I"
COT)
IE
m
O
m
m
o
m
'
m
» "
WELL NO. I
216
240
264
288
TIME AFTER PUMPING BEGAN (Hours)
-------
O
'
o
m
i
01
25
-20
"> =
O O
c c
=" i
CD m *
c co m
w m W
I b H
i- 3) m
| Si
r m
i
m
m
33
I
I
111
DO
m
:
:
-
-
m
•
•
m
'
o
i'6
Q
L
'
>
UJ
•
n
I
7
WEIGHTED
AVERAGE
INPUT
n,
L
SUPPLY WELL
BACKGROUND WELL NO. I
MIDNIGHT
OCT. 30
NOV.
17
-------
29
Figure V-5 also depicts the rate at which NO., concentrations
were reduced after pumping began. The area under the curve during
pumping operations can be equated to pounds of NO,, produced.
The background of Well No. 1 was 5.00 mg/1 which amounts to
360 pounds of the recovered NO™, leaving 660 pounds recovered of
that which was artificially added. This amounts to a nitrate
recovery of 94 percent.
Figures V-6 and V-7 show the behavior of nitrates at Wells
No. 2 and 3, both under recharge and pumping conditions. As shown,
the nitrates in these wells were reduced to near background by the
end of the pumping period.
By recovering 94 percent of the nitrate artificially injected,
it is apparent that no significant losses were encountered during
the test. Although minor concentrations of nitrite (NO^ were
measured at Well No. 2 after pumping began, there was no evidence
of extensive denitrification.
Although a high percentage of N03 was recovered, it is important
to compare its movement with that of the tritiated water. Figure V-8
shows how both the tritium and N03 concentrations were evidenced at
Wells No. 2 and 3. It is evident that although no significant
denitrification occurs, care must be taken in using nitrate as a
tracer in ground-water studies.
From Figure V-8, it appears that the nitrates may move somewhat
faster than tritium through the aquifer. Undoubtedly, most of the
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30
difference between the two curves is due to the higher relative
(27)
background of NOo in the recharge area. However, Kaufman and Orlob
noted that the chloride ion passed through a natural soil medium
faster than tritium and the difference was correlated to clay content
of the soil. It was believed that tritiated water molecules passed
through the free pore water as did the chloride ion, but the tritiated
water also exchanged with the water adsorbed on the clay minerals and
with the water of hydration in cations associated with these minerals.
Therefore, tritium-labeled water and unlabeled water would be
expected to displace almost all of the water in the aquifer. Nitrates
could be expected to react in a similar manner to chloride. The
clay content of the formation studied at Bushland was low; and, if the
effect of background was removed, NO- and tritium dispersion curves
would be more similar.
A comparison of the use of such tracers can be gained, as an
( 28)
example, in the determination of the aquifer storage coefficient.
Using the nitrate dispersion curves, detention or displacement
times between the recharge well and Wells No. 2 and 3 were determined
to be 1.3 and 4.4 days, respectively. These detention times with a
recharge rate of 348 gpm and a saturated volume calculated from
observed water levels yield a storage coefficient of 0.20. This
value corresponds to a value of 0.23 obtained by using tritiated
water as the tracer.
As shown in Figure V-7, a peak was reached in both N03 and
tritium concentrations shortly after recharge began. This peak
-------
31
indicates that some portion of the recharged water moved more
rapidly to the observation wells than did other portions. These
differences in rates of movement appear to be related to differences
in horizontal permeability of the layers comprising the formation.
Examination of well logs and laboratory analyses of formation
cores revealed that a stratum only a few feet in thickness and lying
immediately above the static water table (water level in the wells
before recharging began) is considerably more permeable than other
strata that transmitted water during the recharge test. For this
reason, it is postulated that recharged water moving in this stratum
reached the observation wells before any other recharged water;
however, as the test proceeded, water from underlying strata entered
this stratum as water pressures equalized throughout the saturated
part of the formation. Mixing of water from the underlying strata
with the recharged water in the layer of higher horizontal permea-
bility resulted in a reduction in concentrations of nitrate and
tritium since waters from the underlying strata were at this time
largely of native, unaltered quality. This concentration reduction
is reflected in curves shown in Figure V-8.
As recharged water began reaching the observation wells from
the other strata, concentrations of nitrate and tritium began to
gradually increase and the curves took on a shape that would be
expected for a situation involving an aquifer having fairly uniform
horizontal permeability.
-------
32
DDT Recovery
Project plans called for the addition of DDT during recharge
at a rate of 100 ppb (parts per billion) or 100,000 ng/1 (1 nanogram =
10~9 grams). Difficulties in controlling the chemical feed rate
reduced this to about 90 ppb total DDT, or 74 ppb p,p'-DDT, the
principal DDT isomer which was routinely determined in this work.
With a recharge rate of 348 gpm, the actual input of p,p'-DDT
amounted to 3.11 pounds during the 10-day recharge period. The
input concentration of p,p'-DDT, as measured in the recharge stream,
is shown in Figure V-9.
Analyses of water samples from Well No. 2, 33 feet from the
recharge well, indicates a probable slight increase in DDT in this
well during the recharge period. However, the concentration of about
0.4 ppb DDT in water from this well after 10 days of recharge was
much more comparable with the background concentration of 0.1 ppb
DDT at the beginning of recharge than with the concentration of
74 ppb DDT in the recharge water, and it would appear that no
significant breakthrough of DDT to Well No. 2 occurred during the
period of this study. No increase in DDT in Wells No. 3 and 4, 66
and 150 feet respectively from the recharge well, was noted during
the recharge period. The DDT entering the aquifer with the recharge
water must, therefore, have been largely adsorbed onto the aquifer
material near the recharge well.
-------
120
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WEIGHTED AVERAGE '
INPUT CONCENTRATION
1
MIDNIGHT
OCT. 30
NOV. I
NOV. 10
FATE OF DDT AND NITRATE IN GROUND WATER
DDT RECHARGE CONCENTRATION
U.S.DEPARTMENT OF AGRICULTURE
AGRICULTURAL RESEARCH SERVICE
SOUTHWESTERN GREAT PLAINS
RESEARCH CENTER
BUSHLAND, TEXAS
U.S. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION
CONTROL ADMINISTRATION
ROBERT S. KERR
WATER RESEARCH CENTER
ADA,OKLAHOMA
FIGURE V-9
-------
33
Recharge ended at 10:00 a.m., November 10, 1967; and, after
three hours of inactivity, pumping of the recharge well began at
1:00 p.m. The pumped stream was sampled in order to determine:
(1) the amount of DDT in the water, both in solution and suspension;
(2) the DDT adsorbed per gram of produced sand; and (3) the amount
of sand produced on a temporal basis. (The term DDT as employed
herein refers to p,p'-DDT only.)
Figures V-10 and V-ll show the concentration of DDT in the
pumped water. (Figure V-ll uses arithmetic scales and provides
a better picture of the relative times involved.) Although the
well was recharged with 74 ppb DDT, the first sample—collected
one minute after pumping began—showed a DDT concentration of 1,204
ppb. Hence, the initial concentration of produced water was over
16 times that of the recharge water. On the basis of reported
(29 30 31 32)
studies of the solubility of DDT in water, ' ' ' it is
evident that much of this DDT was not in true solution, but probably
occurred as minute, undissolved particles in suspension or was
adsorbed to colloidal soil particles suspended in the water.
Although the initial DDT concentration of the pumped water was
very high, it decreased rapidly during the early period of pumping
and was reduced by two orders of magnitude after only 10 hours of
pumping at 504 gpm.
There are two significant portions of the DDT recovery curve
shown in Figures V-10 and V-ll. Throughout the first two days of
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34
pumping the measured DDT concentration continued to decrease at
decreasing rate with time, following the relationship shown in
Equation V-l with a correlation coefficient of 0.941.
C = 53,7 t-°-723 Eq. V-l.
where C = concentration of DDT.in produced water (ppb)
t = time after pumping began (hours)
Hence, after pumping for 27.5 hours, the DDT concentration of the
produced water had declined to 4.8 ppb by actual measurement and
to a calculated value of 4.9 ppb by Equation V-l; similarly determined
and calculated values after 43.5 hours were 4.6 and 3.5 ppb,
respectively. During the third day of pumping, however, determined
DDT concentrations of pumped water began to differ significantly
from values calculated by means of Equation V-l. For the remainder
of the pumping period DDT concentrations considerably exceeded those
predicted by Equation V-l and were often quite erratic. On three
occasions—the fourth, seventh, and eighth days—measured DDT
concentrations were relatively high, approaching or exceeding the
recharge concentration. That rapid fluctuation of DDT concentration
of produced water may have been occurring during this period was
indicated by an almost twofold difference (121.0 and 67.7 ppb) in
DDT concentrations of samples collected in immediate succession on
the fourth day of pumping. Unfortunately, samples were not collected
with sufficient frequency after the fourth day to permit confirmation
of this apparent phenomenon.
-------
35
The observed recovery of DDT in produced water becomes more
understandable if concurrent production of sand during pumping of
the well is considered. For the first two days, when DDT concen-
trations were declining regularly, sand produced by pumping the well
was decreasing or relatively constant at a low level, following an
initial heavy production during the first two or three hours of
pumping. During the third and fourth days of pumping, however, when
DDT concentrations became erratic and higher than expected, there
was a sudden and sporadic increase in sand production; and for the
remainder of the pumping period sand production gradually increased,
although never attaining a very high level relative to production
during the early hours of pumping. This increased sand production
almost certainly indicated major disturbances, possibly cave-ins, in
the aquifer material near the well casing. Such disturbances would
be likely to expose fresh surfaces of particulate matter which
constitutes the aquifer. Water flowing at high velocity over these
newly exposed surfaces might result in more rapid removal of adsorbed
DDT and higher DDT concentrations in produced water. Also, such
disturbances would likely result in increased and nonuniform release
of colloidal soil particles high in adsorbed DDT, as well as colloidal
particles of DDT which might be lodged in the interstitial areas of
the aquifer material. Although all samples were screened during
collection, as previously described, such colloidal particles would
-------
36
not be removed and would greatly increase DDT content of samples
receiving them. It is quite plausible, therefore, that the increased
and variable DDT concentrations of samples of water produced after the
second day of pumping were manifestations of disturbances in aquifer
structure.
Integration of Equation V-l from 0 to 48 hours, the period during
which DDT content of produced water was decreasing regularly with time,
indicates that only 0.142 pound of DDT was recovered in produced water
during the first two days of pumping the recharge well. Quantitative
estimation of DDT recovered in produced water during the remaining
ten days of pumping cannot be made, however, because of the indicated
variability of DDT concentration in pumped water and the relative
infrequency of sampling during this period.
Another means by which DDT can be removed from the formation
after a recharge operation is by the production of sand in the
pumped stream. Analysis of produced sand in this study indicated a
considerable capacity of the Ogallala sand for adsorption of DDT;
this is consistent with a recent report of relatively high adsorption
(33)
of DDT from aqueous medium onto fine sand in laboratory studies.
During the early hours of pumping, the amount of DDT adsorbed
per unit weight of produced sand was found to decrease regularly
with time as shown in Figure V-12 and according to Equation V-2
with a correlation coefficient of 0.987
-------
10000
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8000
7000
6000
C"
Q
< 5000
19
:
a
x
o
V.
Q
4
Q
C
4000
30OO
2000
D=( 11,000) |0-°'625f
CORRELATION COEFFICIENT = 0.987
1
J
0.5 1-0
TIME AFTER PUMPING BEGAN (Hours)
FATE OF DDT AND NITRATE IN GROUND WATER
ANALYSIS OF DDT ADSORPTION ON OGALLALA SAND
U.S.DEPARTMENT OF AGRICULTURE
AGRICULTURAL RESEARCH SERVICE
SOUTHWESTERN GREAT PLAINS
RESEARCH CENTER
BUSHLAND,TEXAS
U.S. DEPARTMENT OFTHE INTERIOR
FEDERAL WATER POLLUTION
CONTROL ADMINISTRATION
ROBERT Si KERR
WATER RESEARCH CENTER
ADA, OKLAHOMA
FIGURE V-12
-------
37
,-0.625t
D = (11,000) 10 "'""- Eq. V-2.
where D = DDT adsorbed per gram of sand (ng/g)
t = time after pumping began (hours)
The amount of sand recovered during early phases of pumping
is shown on a temporal basis in Figure V-13. These data can be
formulated as shown by Equation V-3 with a correlation coefficient
of 0.956.
W = (268,500) Hf1*611* Eq. V-3
where W = rate of produced sand (grams/hour)
t = time after pumping began (hours)
By integrating Equations V-2 and V-3 the quantity of DDT
recovered on produced sand during the early phases of pumping can
be calculated. Because of rapid decrease with time of sand produced
and DDT adsorbed per unit weight of sand, the rate of DDT recovery
on sand was most rapid during the first few minutes after pumping
began as shown in Table V-l.
Table V-l
Rate of DDT Recovery on Sand
After Pumping Began
Time After Pumping Began
(Minutes)
5
10
15
20
25
30
35
40
45
60
Total Weight of DDT Recovered
(Grams)
0.20
0.33
0.40
0.45
0.51
0.53
0.54
0.55
0.56
0.57
-------
W= (268,500) IO"1'6"
CORRELATION COEFFICIENT: 0.956
100,000 —
I Hour
TIME AFTER PUMPING BEGAN (Hours)
FATE OF DDT AND NITRATE IN GROUND WATER
RATE OF SAND PRODUCTION
BEGINS
AFTER PUMPING
U.S. DEPARTMENT OF AGRICULTURE
AGRICULTURAL RESEARCH SERVICE
SOUTHWESTERN GREAT PLAINS
RESEARCH CENTER
BUSHLAND, TEXAS
U.S. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION
CONTROL ADMINISTRATION
ROBERT S. KERR
WATER RESEARCH CENTER
ADA, OKLAHOMA
FIGURE V-13
-------
38
Hence, almost all of the adsorbed DDT which was recovered by sand
production during the first two days of pumping was recovered within
the first hour after pumping began. It appears that most of the sand
which contributed significantly to DDT recovery during this period was
probably either in the well casing when pumping began or moved from
the aquifer very quickly.
As previously noted, sand production sporadically increased during
the third and fourth days of pumping and gradually increased thereafter
until the end of this investigation. It seems unlikely that significant
DDT was recovered adsorbed to produced sand during this period, however,
because the magnitude of sand production, was not sufficient to contribute
much DDT at observed levels of adsorption.
It should be noted that the sand collected for DDT adsorption
characteristics in this study did not reflect all of the fines because
of sampling procedure. Since the fine particles, particularly those
high in clay, present with the aquifer solids are likely to adsorb
significant quantities of DDT, the indicated recoveries of DDT adsorbed
on sand in this investigation may be low. Nevertheless, it appears a
valid conclusion that the quantity of DDT recovered by production of
sand in this study was probably small compared with the amount recovered
in produced water.
Summation of the DDT recovered in the produced water and adsorbed
on the produced sand during the first two days of pumping indicates
that less than 5% of the total system input was recovered during this
period of pumping the recharge well.
-------
39
Although the data obtained in this study are not sufficient to
permit quantitative estimation of DDT recovered during the full 12-
day pumping period, they do indicate that a major proportion of the
DDT introduced into the aquifer during recharge remained adsorbed in
the aquifer following termination of pumping.
-------
VI. SUMMARY AND CONCLUSIONS
This project was a cooperative venture between the Robert S.
Kerr Water Research Center of the U. S. Department of the Interior
and the Southwestern Great Plains Research Center of the U. S.
Department of Agriculture. The work was done at Bushland, Texas.
The Ogallala Aquifer was recharged at 348 gpm for a period
of 10 days with water taken from an irrigation well 2,280 feet
from the recharge point.
Tritiated water, nitrate, and p,p'-DDT were injected into the
recharge stream at concentrations of 210 uuc/ml, 24.46 mg/1, and
74 ppb, respectively.
The system was monitored by chemical analyses of samples taken
at several observation wells with principal interest in those
located at 33, 66, and 150 feet from the injection well. Water
levels were monitored continuously at 16 points located up to 1,000
feet from the recharge well.
At the end of the recharge period, the system was allowed to
stabilize for three hours before pumping began at a rate of 504 gpm.
The well was pumped at that rate for 12 days with the system continuing
to be monitored for chemical and hydraulic parameters.
o
Tritiated water (H.O) can be used satisfactorily in ground-
water studies to define the movement of water and at the same time
-------
41
describe the aquifer's characteristics such as storage coefficient.
This is evidenced by its physical and chemical characteristics and
a demonstrated recovery of 94 percent. At the end of the 12-day
pumping period, the tritiated water had been removed from the aquifer.
With a recovery of 94 percent, there was not evidence of nitrate
loss due to denitrification; however, the behavioral pattern at the
observation wells was not the same as that of the tritiated water.
This was due mainly to the difficulties in accountability to the
aquifer's nitrate background. After the end of pumping, the aquifer
had returned to near its original nitrate background.
There was no significant breakthrough of DDT to the first
observation well 33 feet from the recharge well. Apparently, the
injected DDT was largely adsorbed to the aquifer material near the
recharge-pumping well.
The DDT concentration in the pumped water was over 16 times the
recharge concentration at initiation of pumping but decreased to below
the recharge concentration in about one hour and continued to decrease
at a decreasing rate during the first two days of pumping. DDT concen-
trations then became erratic and on three occasions approached or
slightly exceeded recharge concentration, apparently as a result of
disturbances in the aquifer structure.
The amount of DDT recovered adsorbed on sand was relatively
small, but a considerable capacity of Ogallala Aquifer material for
adsorption of DDT was shown.
-------
42
Apparently, a major proportion of the DDT introduced into the
aquifer during recharge was not recovered during pumping but remained
in the aquifer.
The three most important points resulting from this study are:
1. When present, nitrate pollution of the Ogallala is probably
of more immediate concern than DDT because of its ability to
move through the aquifer.
2. A well, used for domestic purposes, should not be recharged
with water in which DDT is suspected because of the possible
release of DDT contaminated aquifer material into water
subsequently pumped from the well.
3. Considerable caution must be used in extending this work to
other pesticides because of the myriad of solubilities and
the obviously varied adsorption characteristics encountered.
-------
VIII. BIBLIOGRAPHY
1. Bailey, George W. and White, Joe L., "Review of Adsorption and
Desorption of Organic Pesticides by Soil Colloids, with Implications
Concerning Pesticide Bioactivity." Agricultural and Food Chemistry
21:324-332. July-August 1964.
2. Pesticides and Their Effects on Soils and Water. ASA Special
Publication No. 8. Madison, Soil Science Society of America,
Inc., November 1966. 127 p.
3. Bailey, George W. and White, Joe L., "Adsorption of Organic
Herbicides by Montmorillionite: Role of pH and Chemical
Character of Adsorbate." Presented at American Society of
Agronomy National Meeting, Columbus, Ohio, November 1, 1965.
13 p.
4. Nash, Ralph G. and Woolson, Edwin A., "Persistence of Chlo-
rinated Hydrocarbon Insecticides in Soils." Science, 157:
924-927.
5, Knutson, Herbert, "Relationships Between Pesticidal
Application and Water Contamination Under Irrigation in
the Great Plains." Grant Proposal from Department of
Entomology of Kansas State University, March 1966.
12 p.
6. Smith, George E., "Nitrate Problems in Plants and Water
Supplies in Missouri." Presented at Second Annual Symposium
on the Relation of Geology and Trace Elements to Nutrition,
92nd Annual Meeting American Public Health Association,
New York City, October 7, 1964. 21 p., 9 tables, 8 figures.
(Missouri Agricultural Experiment Station Journal Series
No. 2830)
7. Larson, T. E. and Henley, Laurel, "Occurrence of Nitrate
in Well Waters." University of Illinois Water Resources
Center, Final Report Project 65-05G, June 1966. 8 p.,
5 tables, 2 figures.
-------
44
8. Hanway, J. J., et al, "The Nitrate Problem." Iowa State
University of Science and Technology Special Report No. 34,
August 1963. 20 p.
9. Keller, W. D. and Smith, George E., "Ground-Water Contamina-
tion by Dissolved Nitrate." Presented at 1964 Meeting of
Geological Society of America, Miami, Florida. 27 p.
10. Case, A. A., et al, "Nature and History of the Nitrate
Problem." Science and Technology Guide, August 1964.
2 p.
11. Lenain, August F., "The impact °f Nitrates on Water Use."
Jour. AWWA. August 1967. p. 1049-1054.
12. Smith, George E., "Nitrate Problems in Plants and Water
Supplies in Missouri." Presented at Second Annual
Symposium on the Relation of Geology and Trace Elements
to Nutrition, 92nd Annual Meeting American Public Health
Association, New York City, October 7, 1964. 21 p.,
9 tables, 8 figures. (Missouri Agricultural Experiment
Station Journal Series No. 2830)
13. Allison, Franklin E., "The Fate of Nitrogen Applies to
Soils." Advances in Agronomy 18:219-258. 1966.
14. Stewart, et al, "Nitrate Pollution under Feed Lots and
Agricultural Lands." Agricultural Research Service,
U. S. Department of Agriculture, ARS 41-134. 1967.
15. White, A. W., Barnett, A. P. and Jackson, W. A., "Nitrogen
Fertilizer Loss in Runoff." Crops and Soils 19:4. January
1967.
16. Rayner, Frank A., "The Ground-Water Supplies of the Southern
High Plains of Texas." Proceedings of the Third West Texas
Water Conference, February 5, 1965. pp. 20-42.
17. Hauser, V. L., and Lotspeich, F. B., "Artificial Ground-
Water Recharge Through Wells." J. Soil and Water Conserv.
22:1. 1967.
18. Rebhum, M. and Hauser, V. L., "Clarification of Turbid Water
with Polyelectrolytes for Recharge Through Wells." Proceedings
Symposium on Artificial Recharge and Management of Aquifers,
Haifa, International Association for Science Hydrology,
Publication No. 72, pp. 218-228. 1967.
-------
45
19. Jacob, C. E., "Drawdown Test to Determine Effective Radius of
Artesian Well." Trans. ASCE 112;1047-1070. 1947.
20. Texas Board of Water Engineers, "Artificial-Recharge Experiments
at McDonald Well Field, Amarillo, Texas." Bulletin 5701, 34 p.
January 1957.
21. McMillion, Leslie G. and Keeley , Jack W., " Sampling Equipment
for Ground-Water Investigations." Ground Water Research
Program, Robert S. Kerr Water Research Center, Ada, Oklahoma,
December 1967. 3 p., 2 figures.
22. Technicon Corporation, Ardsley, New York.
23. Kamphake, L. J., Hannah, S. A., and Cohen, J. M., "Automated
Analysis for Nitrate by Hydrazine Reduction." USDI, Robert A.
Taft Sanitary Engineering Center, Cincinnati, Ohio.
24. Breidenbach, A. W., et al, "The Identification and Measurement
of Chlorinated Hydrocarbon Pesticides in Surface Waters."
USDI, FWPCA, WP-22, November 1966. 70 p.
25. Hagen, R. E., et al, "A Chromatographic-Fluorometric Method
for Determination of Naringin, Naringenin Rutinoside, and
Related Flaranone Glycosides in Grapefruit Juice and Juice
Sacs." Analytical Biochemistry 12:472. 1965.
26. U, S. Geological Survey, Double Mass Curves, Manual of
Hydrology: Part 1 General Surface Water Techniques.
Washington, U. S. Government Printing Office. 1960.
(Geological Survey Water Supply Paper 1541-B)
27. Kaufman, W. J. and Orlob, G. T., "Measuring Ground-Water
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