United States
Environmental Protection
Agency
Robert S. Kerr Environmental
Research Laboratory
Ada OK 74820
Research and Development
EPA/600/S2-91/064 Jan. 1992
& EPA Project Summary
Identification of Sources of
Ground-Water Salinization Using
Geochemical Techniques
Bernd C. Richtef and Charles W. Kreitler
This report deals with salt-water
sources that commonly mix with and
deteriorate fresh ground water. It re-
views characteristics of salt-water
sources and geochemical techniques
that can be used to Identify these
sources after mixing has occurred.
The report is designed to assist In-
vestigators of salt-water problems In a
step-by-step fashion. Seven major
sources of salt water are distinguished:
(1) natural saline ground water, (2) .ha-
lite solution, (3) sea-water intrusion, (4)
oil- and gas-field brines, (5) agricultural
effluents, (6) saline seep, and (7) road
salting. The geographic distribution of
these sources was mapped individually
and together, Illustrating potential
sources at any given area In the United
States. In separate chapters, each po-
tential source Is then discussed in de-
tail regarding physical and chemical
characteristics, examples of known
techniques for Identification of mixtures
between fresh water and that source,
and known state-by-state occurrences.
Individual geochemlcal parameters that
are used within these techniques are
presented in a separate chapter, fol-
lowed by a discussion concerning where
and how to obtain them. Also provided
Is a description of basic graphical and
statistical methods that are used fre-
quently In salt-water studies. An exten-
sive list of references for further study
concludes this report.
This Project Summary was devel-
oped by EPA's Robert S. .Ken Environ-
mental Research Laboratory, Ada, OK,
to announce key findings of the research
project that Is fully documented In a
separate report of the same title (see
Project Report ordering Information at
back).
Introduction
The purpose of this report is to summa-
rize geochemical techniques that can be
used in studies of salinization of fresh wa-
ter. The report is designed to assist inves-
tigators through detailed discussion of
potentially useful chemical parameters and
techniques, as well as of physical and
geographical characteristics of potential
salinization sources. The topic of salt-wa-
ter contamination has been extensively re-
searched, evidenced by the list of hundreds
of references compiled for this report. No
compendium of the overall topic, however,
has previously been compiled. The pur-
pose of this document is not to develop
new geochemical techniques for identify-
ing sources of ground-water salinity, but to
summarize known approaches for all dif-
ferent sources into a single document to
allow a researcher to have a reference
manual reviewing available work.
Salinization of fresh water is perhaps
the most widespread threat to ground-wa-
ter resources, as saline ground water (total
dissolved solids [TDS]>1,000 ppm) of vari-
able origin underlies approximately two-
thirds of the United States. This document
deals with geochemical characteristics of
major known sources of salinity, and as
such will be helpful to investigators of salt-
water problems. The extent to which this
document will be of help will depend to a
large degree on the investigator's back-
ground knowledge of the problem. To an
experienced researcher in the field of
ground-water quality, this document may
Printed on Recycled Paper
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serve as a summary of and reference to
some of the known techniques that are
being used. To investigators new in this
field, we suggest the following possible
methodology of investigation in combina-
tion with this report.
Step 1:Tha general geographic distribu-
tion of major potential salinization
sources, that is (1) natural saline
ground water, (2) halite solution, (3)
sea-water intrusion, (4) oil- and gas-
field brines, (5) agricultural effluents,
(6) saline seep, and (7) road salt, is
addressed through a series of maps
that show the distribution of each
source as well as the overlap be-
tween these sources. These maps
provide the investigator with a gen-
eral idea about the potential saliniza-
tion source or sources that exist at
her/his local area of interest at any
given area of the country.
Step 2: After potential sources of salt wa-
ter have been identified, the discus-
sion of individual sources should be
consulted. This will provide the re-
searcher with the necessary back-
ground information about the
source(s) of interest. Each of the
seven sources is discussed in de-
tail, including mechanisms of mix-
ing with fresh ground water,
chemical characteristics, geochemi-
cal case studies, recommended
chemical techniques for identifica-
tion of salinization caused by these
sources, and a state-by-state sum-
mary of occurrences.
Step 3: After having selected techniques
that are useful for the particular prob-
lem case, the geochemical param-
eters of interest can be reviewed.
This will give the investigator a gen-
eral overview of parameter charac-
teristics as well as sampling
techniques and likely costs of labora-
tory analyses.
Step 4: Depending on the area of inter-
est, chemical data may or may not
be available to the investigator from
published sources, agency files, or
computerized data banks. Some of
the selected techniques may be ap-
plicable using existing data from state
and federal data bases, but others
may necessitate collection of water
samples for parameters that are not
determined on a regular basis (for
example, Isotopes). Data should be
selected carefully, because existing
data can be helpful but also mislead-
ing. Chemical analyses that may be
representative of potential saliniza-
tion sources can be found in the
referenced literature.
Step 5: Once data have been selected
from existing sources or collected in
the field, evaluation can be accom-
plished using a variety of graphical
and statistical techniques. Hopefully,
the source of salinity can then be
determined.
Background
All natural waters contain some dis-
solved minerals through the interaction with
atmospheric and soil gases, mixing with
other solutions, and/or interaction with the
biosphere and lithosphere. In many cases,
these processes result in natural waters
that contain TDS concentrations above
those recommended for drinking water.
Salinization, that is the increase in TDS, is
the most widespread form of water con-
tamination. The effect of salinization is an
increase in concentrations of specific
chemical constituents as well as in overall
chemical content.
Of the variety of potential sources of
salinity, some are natural and others are
anthropogenic. Precipitation interacts with
atmospheric gases and particles even be-
fore it reaches the earth's surface, as re-
flected in often low pH values in areas of
high sulfur dioxide content in the atmo-
sphere (formation of sulfuric acid "acid
rain"). Strong winds carry mineral matter
and solution droplets (for example, ocean
spray) that can be dissolved and incorpo-
rated into precipitation. Surface runoff dis-
solves mineral matter on its way toward a
surface-water body, where it mixes with
water of different chemical composition.
Water that enters the soil is subject to
additional chemical, physical, and biologi-
cal changes, such as evapotranspiration,
mineral solution and precipitation, solution
of gases, and mixing with other solutions.
Changes in chemical composition continue
in ground water along flow paths from
recharge areas to discharge areas. Water-
rock interaction and mixing are the domi-
nant processes. Mixing of different waters
is often enhanced by human activities. For
example, improper drilling, completion and
final construction of wells may create artifi-
cial connections between fresh-water aqui-
fers and saline-water aquifers. Pumping of
fresh water may change directions of
ground-water flow and may cause en-
croachment of saline water toward the
pumped well. Improper waste-disposal ac-
tivities or techniques may introduce artifi-
cial solutions that contaminate natural
ground water. Some areas of the country
experience very few problems regarding
salinization of fresh-water resources,
whereas in other areas most of the avail-
able ground water is saline, reflecting natu-
ral and human-induced degradation.
Potential Salinization Sources
Many sedimentary basins are known to
contain saline ground water and large de-
posits of rock salt in the form of salt beds
or salt domes. Some of these deposits
occur at great depths, such as those in
southern Florida at greater than 10,000 ft
below land surface. Others occur close to
land surface, such as in parts of Utah.
Shallow occurrences of salt in Texas, Loui-
siana, Alabama, and Mississippi along the
Gulf of Mexico are due to salt diapirism;
the solution of salt and salinization of local
ground waters will occur where ground
water comes into contact with salt domes,
often enhanced by heavy drilling and min-
ing activities.
Where coastal aquifers are intercon-
nected with the open ocean, sea-water
intrusion can occur. The potential of well-
water salinization exists when formation
water has not been flushed out, sea water
has intruded or is intruding coastal aqui-
fers as a result of high sea-water levels, or
pumping induces landward flow of sea
water.
Associated with the exploration of oil
and gas is the creation of avenues for
water migration from great depths into the
shallow subsurface. Subsequent produc-
tion brings huge amounts of brine to land
surface. These drilling activities and the
disposal of these brines are some of the
biggest salinization hazards in the country.
Parts of 25 producing states are potentially
affected by this hazard.
Salinization as a result of agricultural
activities is found nationwide. Irrigation-
return waters pose a potential threat in the
western half of the United States, where
precipitation rates are low and where
evapotranspiration rates and salt contents
in soil are high. Another salinization source
enhanced by agriculture is dryland saline
seep. Terracing of land and destruction of
natural vegetation added to this phenom-
enon in several states results in saliniza-
tion of soil and ground water.
Due to weather conditions, road salting
is concentrated in the northeastern part of
the country. There, millions of tons of salt
are applied to roads each winter, imposing
a salinization threat to soil, plants, and
surface and ground water in the vicinity of
highways.
Mapping of potential salinization
sources is helpful in determining sources
of salinity at any particular area in the
country. By overlaying maps of potential
sources, a variety of combinations between
these sources becomes evident. This large
variety complicates generic approaches to
salt-water studies, because salt-water char-
acteristics change considerably from area
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1
to area depending on the kind of combina-
tion of sources involved. But not only do
the potential salinization sources change
from area to area, the chemical character-
istics of individual sources may also
change, greatly increasing the number of
potential combinations of possible mixing
between fresh-water and salt-water
sources. As the composite map (Figure 1)
of the above-mentioned potential sources
indicates, approximately three-quarters of
the country could possibly be affected by
two or less of the selected sources. In
these areas, identification of an actual salin-
ization source should be easier than in
other areas, where three or more potential
sources exist.
Geochemlcal Parameters
It is important in a salinization study to
know which methods and parameters are
the best to use for the particular problem.
Through the years, a variety of chemical
constituents and constituent ratios have
been used as possible tracers of salinity
sources (Table 1). Parameters used most
often include the major cations, Ca, Mg,
Na, the major anions, HCO3, SO4, Cl, some
minor elements, K, Br, I, Li, and some
isotopes, "O,2H, 3H, 14C.
Natural Saline Ground Water
Most of the salinity sources described
in this report occur naturally at some place
or another where they mix with fresh ground
water. In other cases, mixing of naturally
saline water with fresh water is initiated or
facilitated by anthropogenic activities, such
as heavy pumpage of fresh water, drilling
through fresh-water- and salt-water-bear-
ing zones, or disposal of produced water.
In most instances, chemical characteris-
tics will not differ significantly between natu-
ral mixing of fresh water and salt water and
artificial mixing of the same salt water with
fresh water. Therefore, significant param-
eters for identification of natural saliniza-
tion are the same as those for any individual
source discussed in this report.
Salinization is generally indicated by
an increase in chloride concentration. If
this increase is substantial, occurs sud-
Potential Sources of Salinity:
• Natural Saline Ground Water
• Sea-water Intrusion
. Halite Dissolution
• Oil- and Gas-field Activities
• Irrigation
. Saline Seep
.Road Salt
Legend: Geographic Overlap of Potential Salinity Sources
O None
© Any One Potential Source
© Any Two'Potential Sources
• Any Three Potential Sources
300 600km
Figure 1. Composite map of major potential sources of salinity in the United States.
3
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Ttbto 1. Cfochemhal Parameters Used for Identification of Salinity Sources
Saffl&atibfl Sources Chemical Parameter
Natural saino water
versus others
Ha!i:o-soiutfon brine
versus others
Sea-water Intrusion
versus others
Oil-fold brines
versus others
Agricultural olfluonts
versus others
Salino seep
versus others
Road salt
versus others
Cl, Br, I, S-34,1eO, D, Br/CI, Na/CI, I/CI, I
Mg/CI, K/CI, Ca/CI, (Ca+MgJ/SO*, Sr
K/Na, Br/TDS, (Ca+Mg)/(Na+K), Na/CI,
Ca/CI, Mg/CI, SO4/CI, Br/CI, K/CI,
(Ca+Mg)/SO4, I/CI, "O/D, I/CI, SO4/(Na+K),
S04/TDS,S04/CI
Cl, Major Ions (Piper), "C, 3H, I/CI, B, Ba, I
"O, *H, "C, CaJMg, CI/SO* B/CI, Ba/CI
Br/CI
Cl, Major Ions, Na/CI, Ca/CI, Mg/CI, SO4/CI,
Br/CI, I/CI, Major ion ratios, Cl, Br,
(Na+CiyrDS, LVBr, NaJBr, Na/CI, Br/CI
Cl, NO* CWVOj, K, TDS
SO* Ca/CI, Mg/CI, SO4/CI, NO3
Cl, Major Ion ratios, Br/CI, Dye
donly, and is localized, a nonnatural mecha-
nism and source should be suspected. If,
however, the change is subtle and of re-
gional scale, a natural mechanism or source
may exist. Mixing of fresh water with natu-
rally saline ground water or the evolution
of ground water toward higher salinities
(as opposed to mixing with road-salt solu-
tions, mixing with brine along boreholes, or
disposal of produced oil-field brine) can be
expected to be a relatively stow process
during which the water has time to react
extensively with the aquifer matrix. There-
fore, saline ground water in its natural
environment will reflect conditions of chemi-
cal equilibrium more closely than artificially
Induced mixtures of fresh water and saline
water. This may be used to distinguish
natural mixing or evolution from induced
mixing.
The stable isotopes Oxygen-18 and
deuterium are generally useful in distin-
guishing between local precipitation water
and water that is derived from a nonlocal
source and in identifying evaporation of
local recharge water. Molar ratios of major
chemical constituents, such as Na/CI, Ca/
Cl, and Mg/CI, can be used to differentiate
an evaporation trend (1:1 slope) from a
mixing trend (typically not a 1:1 slope).
Mixing trends can best be evaluated using
the most conservative constituents dis-
solved in ground water, that is, chloride
and bromide. These constituents are often
useful not only to identify the mixing source
of salinity, but also to estimate the mixing
ratio.
Halite Solution, Oil- and Gas-Field
Brines
Halite solution produces some of the
lowest Br/CI ratios found in natural salt
waters. Ratios are typically less than ap-
proximately 10 x 10-* in halite-solution
brines and greater than 10 x 10^ in oil-field
and formation brines. Ratio differences be-
tween these two potential end-members of
mixing with fresh water are generally big
enough to allow differentiation of the re-
spective source in brackish water down to
chloride concentrations of a few hundreds
of milligrams per liter, although identifica-
tion is best at high concentrations. Sea
water also has a much higher Br/CI ratio
than halite-solution brine, which could al-
low differentiation between halite solution
and sea-water intrusion in coastal salt-
dome areas.
The ratio of Na/CI works well to distin-
guish halite-solution brine from oil-field brine
at high chloride' concentrations. Sodium
and chloride occur in halite at equal molar
concentrations '(Na/CI molar = 1, Na/CI
weight = 0.648). Brines that originate from
solution of halite within a shallow ground-
water flow system will exhibit a similar ratio
as long as concentrations are high enough
to keep the Na/CI ratio from being appre-
ciably affected by ion exchange reactions.
In most oil-field brines molar Na/CI ratios
are much less than one. Exchange of cal-
cium and magnesium for sodium on clay
mineral surfaces and alteration of feldspar
may account for the low ratios in formation
and oil-field brines. The Na/CI ratio is also
much smaller in sea water (mNa/mCI =
0.85) than in halite-solution brine.
Ratios of I/CI in halite-solution brines
are typically small and less than oil-field/
deep-basin brines, which allows separa-
tion between these two major sources of
salt water.
Halite deposits are often associated
with abundant beds of gypsum and anhy-
drite. Dissolution of these beds is reflected
in molar (Ca+Mg)/SO4 ratios close lo one,
which is much smaller than the respective
ratio in oil-field brines (»1) or in sea water
(2.3).
Sea-Water Intrusion
The chemical composition of sea water
changes as it intrudes a fresh-water aqui-
fer. Changes occur in response to mixing
and chemical reactions, and are most pro-
nounced within the initial sea-water front
that mixes with fresh water. Subsequent
intrusion deviates little from sea-water com-
position.
Mixing of fresh water and sea. water
occurs within a transition zone and is
characterized by chloride concentrations
somewhat between high background con-
centration values to somewhat below sea-
water concentration. The front part of this
transition zone is characterized by ion ex-
change as discussed below. Behind the
ion-exchange front, simple dilution charac-
terizes the deviation of brackish water from
sea-water composition. This can easily be
identified on trilinear plots in the straight-
line relationship between data points. On
bivariate plots of major cations and anions
versus chloride, data points plot close to
the theoretical mixing line between local
fresh water and sea water.
Clay minerals, especially montmorillo-
nite, have free negative surface charges
that are occupied by cations in proportion
to the abundance of cations in the water
and to the sorption characteristics of the
cations and the minerals. In atypical fresh-
water aquifer, these sites are saturated
mainly with calcium ions, whereas in a
typical salt-water aquifer, the sites are oc-
cupied mainly by sodium ions. Whenever
the relation of calcium to sodium in the
water changes (for example, in response
to sea-water intrusion into a fresh-water
aquifer), ion exchange will occur, sodium
will be taken out of solution, and calcium
will be released from mineral exchange
sites. Magnesium and potassium may also
be exchanged for calcium, but the Na-Ca
exchange is the most significant one. For
example, more than 96 percent of the base
exchange in the Chalk aquifer of east-
central England has been attributed to Na-
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Ca exchange. This exchange is assumed
to be instantaneous. On a Piper diagram,
ion exchange between calcium and so-
dium produces a cluster in the cation tri-
angle, whereas mixing produces a straight
line in the anion triangle as chloride con-
tent increases. The diamond-shaped field
will reflect the slight increase in Ca+Mg,
the matching decrease in Na+K, and the
high increase in CI+SO4 percentages. In-
trusion of fresh water into a salt-water
aquifer will cause the opposite ion ex-
change.
The chloride concentration is not af-
fected by ion exchange, which makes the
Na/CI ratio a potential tracer of intrusion. If
sea water intrudes a fresh-wafer aquifer,
Na/CI ratios will decrease from those often
>1 to those often less than the value in sea
water. In contrast, if fresh water replaces
marine water or washes out marine sedi-
ments, very high Na/CI ratios can result.
No changes in the Na/CI ratio will occur in
water that intrudes behind the front of ion
exchange because all the exchange sites
are already occupied. Therefore, the Na/CI
ratio should approach the ratio of sea wa-
ter (0.85 molar ratio), which differs from
the typical ratio of halite-dissolution brines
(0.64 molar ratio) and from the small ratio
characteristic for many oil-field/deep-basin
brines (<0.50 molar ratio). The degree of
change that occurred because of ion ex-
change may not only indicate the position
within the intruding front, but also the tim-
ing of the intrusion. Recent sea-water in-
trusion would be expected to be associated
with data points predominantly showing
tan exchange, whereas old sea-water in-
trusion would be expected to include many
data points with little or no evidence of ion
exchange.
Mixing of fresh water and sea water,
both saturated with calcium carbonate, can
result in a mixing water that is undersatu-
rated with calcium carbonate. This mixing
water can dissolve carbonates; thus, cal-
cium and bicarbonate concentrations will
increase. Additional calcium carbonate dis-
solution may occur in the presence of sul-
fate reduction of organic-rich sediments
because of the associated change in pH
and CO2 content of the water. Sea water is
relatively high in dissolved sulfate content.
Under reducing conditions in ground-water
systems, and with the presence of com-
pounds that can be oxidized as well as of
reaction catalysts, sulfate will be reduced.
This results in a decrease in sulfate con-
centration relative to the sea-water compo-
sition.
Agricultural Effluents
Degradation of ground-water quality by
agricultural activities can be caused by
solution and transport of chemicals, such
as herbicides, pesticides, and fertilizers,
disposal of animal wastes and waste water
from animal farms, and irrigation-return
flow. With respect to ground-water salinity,
irrigation-return flow is the most important
source of degradation. Evapotranspiration
and leaching of soil minerals accounts for
increases in most chemical components in
drainage waters from irrigated areas. Typi-
cally, chloride and sodium concentrations
show the highest increases, although other
constituents may be high in some areas,
reflecting local conditions. Significant pa-
rameters in irrigation-return flow may
change over time, as original soil minerals
are dissolved in the initial irrigation stage
of an area and minerals brought in by
irrigation water are dissolved in subse-
quent irrigation phases.
A significant parameter that differenti-
ates agricultural-induced contamination
from other salinization sources discussed
in this report is nitrate. In agricultural ar-
eas, nitrate concentrations are often above
background values. Salinization associated
with other sources, such as sea-water in-
trusion or oil-field pollution, in contrast, is
typically associated with increases in chlo-
ride, sodium, calcium, and magnesium con-
centrations and with small NCyCI ratios.
Saline Seep
Saline-seep water chemistry is gov-
erned by evaporation, resulting in an in-
crease of all constituents in the water. The
increase is reflected on constituent plots
as evaporation trends, in contrast to mix-
ing trends toward a saline-water source
observed for the other salinization sources
discussed in this report, with exception of
irrigation-return waters. At low salinities,
this increase is characterized by more or
less constant constituent ratios of major
ions, such as Ca/CI, Mg/CI, or SO4/CI. With
increasing salinity, mineral precipitation will
change these ratios as carbonates and
sutfates begin to form. Precipitation prod-
ucts will vary from area to area depending
on the chemical composition of soil and
water. Where sources of sulfate are abun-
dant, dissolved sulfate concentrations may
by far exceed the concentration of dis-
solved chloride, which distinguishes seep
water from most other saline ground water.
Miscellaneous trace constituents may serve
as good tracers on a local basis, as these
are more concentrated in evaporated
ground waters than in most mixing waters
between fresh ground water and brine at
similar salinities.
Road Salt
By far the most widely used parameter
in identification of street-salt contamination
is the chloride ion. Chloride is a good
tracer because it is the most conservative
tan dissolved in ground water, it is the
most abundant tan in street-salt solutions,
and it is analyzed on a routine basis. Back-
ground chloride concentrations are known
for a vast number of water wells all over
the country. Because contamination from
street salt is a seasonal phenomenon with
high chloride concentrations in spring run-
off and decreasing (dilution) concentration
throughout the remainder of the year, de-
viation of chloride concentrations from back-
ground levels are in most instances a good
measure of the degree of salt contamina-
tion. Accumulation of salt may occur in the
soil and in ground water, which means that
background levels may increase over the
years. When salt-brine runoff infiltrates the
vadose zone and the saturated zone, so-
dium is often absorbed into soil and aqui-
fer material. Therefore, the Na/CI ratio may
be smaller in salt-affected ground water
than in salt-affected surface water.
Because of its conservative nature once
dissolved in ground water, bromide can be
a good tracer of salinity. Expressed as Br/
Cl weight ratios, it can be used to differen-
tiate salinity derived from road salt (halite)
as opposed to oil- and gas-field brines,
deep-formation waters, and sea water, as
halite solution produces some of the low-
est Br/CI ratios measured in naturally sa-
line waters.
On a local basis, high concentrations of
calcium and chloride may be indicative of
road-salt contamination where large
amounts of CaCI2 are added to the salt
mixture. Because road-salt contamination
involves the current production of salt wa-
ter, dye tracers (for example, rhodamine)
may be useful for identifying point sources
of alleged street-salt contaminations.
Graphical and Statistical
Techniques
Evaluation of chemical analyses is of-
ten accomplished with graphical display
and statistical manipulation of physical and
chemical data. Which technique is used
depends largely on the amount of data and
on the type of information that is needed.
In salt-water studies, techniques are used
that maximize the separation of chemical
characteristics between potential salt-wa-
ter sources, and illustrate to which salt-
water source a contaminated water sample
belongs. Graphical techniques are used to
(1) illustrate the chemical character of a
single analysis, (2) compare the character-
istics of several analyses, (3) assist in
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Identifying the relationship that exists be-
tween water samples, and (4) calculate
mixing ratios between fresh water and the
contaminating source. Various approaches
Include analysis of a single parameter, for
example on contour maps, or of multiple
parameters, as on Stiff diagrams, Schoeller
diagrams, PIperdiagrams, orbh/ariate plots.
The application of statistics depends to
a high degree on the number of observa-
tions in the data base and the nature of the
required information. Statistical techniques
are most useful and appropriate when a
large data base of observations is avail-
able. The literature abounds with question-
able applications of statistical procedures.
Statistics should be used as a means to
test and verify theories instead of creating
theories from statistical data. Statistical
approaches vary from simple techniques,
such as maxima, minima, or means, to
complex multivariate analyses, such as
Stepwise Discriminant Analysis.
•U.S. Government Printing Office: 1992— 648-080/60040
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Bomd C. R'tchterand Charles W. Kreitlerare with the University of Texas, Austin, TX
78713-7508.
BertBledsoe !s the EPA Project Officer, (see below).
The complete report, entitled "Identification of Sources of Ground-Water Salinization
UsingGeochemicalTechniques" (OrderNo. PB92-119650/AS;Cost:$35.00, subject
to changs) will be available only from:
National Technkal Information Service
5285 Port Royal Road
SpringfiQld,VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Robert S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
Ada, OK 74820
Untied States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA PERMIT NO. G-35
Official Business
Penalty for Private Use $300
EPA/600/S2-91/064
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