EPA-660/3-75-030
JUNE 1975
Ecological Research Series
Nitrogen in the Subsurface Environment
National Environmental Research Center
Office of Research and Development
U.S^Environmental Protection Agency
Corvallis, Oregon 97330
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development,
U.S. Environmental Protection Agency, have been grouped into
five series. These five broad categories were established to
facilitate further development and application of environmental
technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in
related fields. The five series are:
1. Envi ronmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ECOLOGICAL RESEARCH STUDIES
series. This series describes research on the effects of pollution
on humans, plant and animal species, and materials. Problems are
assessed for their long- and short-term influences. Investigations
include formation, transport, and pathway studies to determine the
fate of pollutants and their effects. This work provides the technical
basis for setting standards to minimize undesirable changes in living
organisms in the aquatic, terrestrial and atmospheric environments.
EPA REVIEW NOTICE
This report has been reviewed by the Office of Research and
Development, EPA, and approved for publication. Approval does
not signify that the contents necessarily reflect the views and
policies of the Environmental Protection Agency, nor does mention
of trade names or commercial products constitute endorsement or
recommendation for use.
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EPA-660/3-75-030
JUNE 1975
NITROGEN IN THE SUBSURFACE ENVIRONMENT
By
M, L, Rowe
Susan Stinnett
School of Environmental Science
East Central Oklahoma
State University
Ada, Oklahoma 7^820
Grant No. R801381
Program Element 1BA024
ROAP 21AK07Task l*f
Project Officer
Marlon R. Scalf
Robert S. Kerr Environmental Research Laboratory
National Environmental Research Center
P. 0. Box 1198
Ada, Oklahoma 7^820
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
U. S. ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OREGON 97330
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ABSTRACT
Increased quantities of various forms of nitrogen are being
released to the soil systems and hl'gHer concentrations of
nHrogeneous compounds are consequently making their way Into
subsoil regions, Knowledge of the behavior and fate of nitro-
geneous chemical species In the subsurface environment i"s needed
By those concerned with the prevention and control of ground-
water pollution. This paper presents Information concerning tKe
nature and origin of nftrogeneous substances polluting ground
water, the probable movement and reaction of nrtrogeneous com-
pounds In the subsurface environment, and specific cases of
ground water pollution by nitrogen'-containing compounds.
This report was submHted In fulfillment of Grant Number R801381
by the School of Environmental Science, East Central Oklahoma
State University, Ada, Oklahoma, under the sponsorship of the
Environmental Protection Agency. The work was completed as of
May, 1975.
i!
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CONTENTS
Sect Ion Page
I Conclusions 1
II Recommendations 3
III Intreduction 4
IV Forms and Sources of Nitrogen In Ground Water 7
V Movement and Reactions of Nitrogen In the Subsurface 13
Environment
Movement of Gases 15
Movement of Non-Gaseous Nitrogen Compounds 16
Nitrification 18
Denitrification 20
VI Specific incidents of Nitrogen Contamination in 22
Ground Water
Vil References 25
Hi
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ACKNOWLEDGEMENTS
This report was prepared by the staff of the School of Environmental
Science, East Central Oklahoma State University and funds were pro-
vided by the Environmental Protection Agency Grant Number R801381,
The authors would like to acknowledge both Ralph H. Ramsey, former
Director, School of Environmental Science, who assisted with the
preparation of the preliminary draft and Casper Duffer, Librarian,
East Central Oklahoma State University, who secured the reference
materials used in the preparation of this report.
Linda Merryman and Jeanette Cook deserve special mention for their
assistance in organizing and editing the various drafts of this
report and special thanks are also due to Jackie Kifer, Debbie
Keith, and Marsha Hula for their contributions to this effort.
The authors appreciate the patience of Jack W. Keeley and are
grateful to Marion R, Scalf for his assistance In the preparation
of the report.
iv
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SECTION I
CONCLUSIONS
A survey of the literature which is currently available concerning
nitrogen and its compounds in relation to the subsurface environment
leads to the following conclusions:
1. Increased quantities of various forms of nitrogen are
being released to the soil systems and higher concen-
trations of nitrogenous compounds are consequently
making their way into subsoil regions.
2. Knowledge of the behavior and fate of nitrogenous
chemical species in the subsurface environment is
needed by those concerned with the prevention and
control of ground-water pollution.
3. Any nitrogen compounds can be leached if the proper
conditions are satisfied. The rate and amount of
nitrogen leached from soil is dependent on soil
characteristics, climate, biological characteristics,
use of the soil system, and the amount and form of
nitrogen present.
4. Compounds of nitrogen can move through porespaces of
soil as gases or as solutes in aqueous solution. The
distance, direction, and amount of nitrogen transported
varies with time as well as chemical, biological, and
physical properties of the soil. Each soil profile
is unique due to its geology, topography, climate,
and the vegetation that exists at each site.
5. Nitrification and denitrification reactions occur in
the soil systems and these reactions are dependent
on factors such as soil texture, moisture, temperature,
pH, etc.
6. Nitrogen contamination of ground-water supplies can be
attributed to a number of sources such as agricultural
fertilizers, animal wastes, domestic waste, and natural
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sources. Each case of contamination must be examined
individually in order to determine the source of
pollution.
A potential health hazard does exist from the ingestion
of nitrate in water supplies. The most apparent danger
is to those infants less than six months of age, but the
nitrite ion could cause methemoglobinemia in adults if
it is present in sufficient concentrations. The effects
of long term ingestion of low concentrations of nitrate
is not known.
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SECTION II
RECOMMENDATIONS
It is recommended that studies be initiated which would focus attention
on the movement and fate of nitrogen in the subsurface environment.
The various possible reactions of nitrogen compounds in the subsurface
environment and the factors affecting these reactions should be stressed.
This could give valuable information concerning the role that microbial
reactions in the subsurface environment play in relation to ground -
water contamination. As a result of these studies, those individuals
concerned with the protection of ground-water supplies could direct
proper control measures.
It is also recommended that careful attention and planning be given
to the proper agricultural practices involving the use of fertilizers,
irrigation practices, and livestock handling operations. All of
these have been cited as potential sources of ground-water contamination
and careful planning could possibly prevent the further contamination
of underground water supplies.
Since it is realized that nitrogen can be leached after it is added
to the soil, care should be exercised in the way man disposes of the
sewage and solid waste which he generates. Proper means of disposing
of domestic waste and solid waste should be emphasized and research
concerning better means of disposing of these types of waste should
be stressed.
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SECTION III
INTRODUCTION
Nitrogen is a unique element in the ecosphere, comprising approxi-
mately 80 per cent of the earth's atmosphere. Some oxidized forms
of nitrogen are essential for life; however, nitrogen in the elemental
form is relatively inert and is not a suitable source of the element
for most living formsJ The demand for food is continually increasing
throughout the world and the oxidized forms of nitrogen can be a
limiting factor to the amount of food that can be produced in a specific
locality. Some concentrations of the oxides of nitrogen are added to
the soil through natural processes such as lightning, microbiological
oxidation of ammonia known as nitrification, and by man's activities
in urban and rural living.^ But to meet the increasing demand for
food by an expanding population, the oxidized forms of nitrogen have
been introduced to soil systems by new technology rather than the
slow processes of nitrification or symbiotic nitrogen fixation.
Until recently, the main reason for investigations concerning the
oxidized forms of nitrogen in soil systems below the rooting depth of
plants was to evaluate the loss of nitrate to the crop and to estimate
the loss of production. In recent years, attention has been focused
on these oxidized forms of nitrogen as potential pollutant sources
of both ground water and surface water.
Ground water is that water in the saturated zone beneath the earth's
surface, and although less easily polluted than surface waters, potential
for pollution of ground water is increasing. In the United States
there are approximately 13 million septic tanks and numerous lagoons
or leaching ponds employed for disposal of domestic, industrial, and
agricultural wastes. Also there are soil treatment systems, landfill
operations, and agricultural operations, all of which are considered
to be potential sources of nitrogen pollution of ground water.3 In 1970,
the total withdrawal of fresh ground water in the nation was 68 billion
gallons per day, accounting for approximately 20 per cent of the total
quantity of water being used for all purposes in the United States.3,4
With the expected growth in water demands, it is almost certain that
ground-water resources will be increasingly used to satisfy man's
future needs. In order to meet these future needs, the ground-water
resource must be maintained in a form which will not produce adverse
effects on humans and animals.
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The oxidized forms of nitrogen are soluble in water, and the nitrate
and nitrite ions are negatively charged. Therefore, the potential
for these forms of nitrogen to move between negatively charged soil
micelles in the soil system and make their way toward ground-water
zones is great once these ions are in the soil system.5,6,7
Health hazards can exist for humans (especially infants) and domestic
animals if some forms of nitrogen are in water supplies in significant
concentrations. The most apparent danger to humans concerns nitrate
ingestion in those infants less than six months of age.°
Methemoglobinemia is caused by bacterial conversion of nitrate to
nitrite, which chemically combines with the hemoglobin of the blood to
form methemoglobin. The bacteria necessary for the conversion of
nitrate to nitrite are more likely to exist in infants because the pH
of an infant's stomach is more suitable for the growth of nitrate
reducing bacteria. Once the nitrite has combined with the hemoglobin
to form methemoglobin, the oxygen carrying capacity of the blood is
reduced and methemoglobinemia, characterized by asphyxia and possible
death, may result.9,10 Approximately 2000 cases have been reported
in North America and Europe with a fatality rate of 7 to 8 percent.0
Since the condition (methemoglobinemia) is not a reportable disease,
it is conceivable that this number is only a small percentage of
the actual number of cases.
Although most of the public health concern in relation to nitrogen
and ground water has been centered around the nitrate form, it should
be emphasized that the nitrite ion is much more aggressive than the
nitrate ion.'' If the nitrite form is present in water supplies,
methemoglobinemia can be expected to result in the adult population.
Also, it should be noted that nitrite is present in some shallow wells,
probably from percolation through the soil system under waste disposal
systems."*'2 There is also some concern about the concentration of
nitrite which might be formed by biochemical processes in the subsurface
environment, thus making its way into the ground-water system.
The long term effects of exposure to low concentrations of nitrate
and nitrite are unknown. Authorities do not agree on the safe limits of
nitrate or nitrite in water supplies, but as a safeguard for people in
metropolitan areas, the United States Public Health Service has set a
safety limit of 45 mg/1 nitrate or 10 mg/1 nitrate as nitrogen, for
municipal water suppl ies.2J3 This is also the concentration of nitrate
proposed for the National Drinking Water Standards by the Environmental
Protection Agency. Some authorities feel that the tolerance for infants
is even lower than this value. Although no limit has been set specifically
for rural domestic supplies, the potential dangers of nitrate concentrations
greater than 45 mg/1 should be recognized. Domestic animals, including
poultry, have also been shown to be sensitive to nitrates and nitrites.'^,14
These anions have been shown to inhibit iodine and vitamin A metabolism
in research animals.'5
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Because of the importance to agriculture, the movement and reactions
of nitrogen in the topmost layers of the earth's crust, considered
by soil scientists as true soil, have received much attention. The
fate of nitrogenous materials in those regions of the earth's crust
underlying the soil zone has, however, been given relatively little
attention. Since increased quantities of various forms of nitrogen
are being released to the soil and higher concentrations of nitrogenous
compounds are consequently making their way Into subsoil regions,
knowledge of the behavior and fate of these substances in the subsurface
environment is needed by those concerned with the prevention and control
of ground-water pollution. This paper presents information concerning
the nature and origin of nitrogenous substances polluting ground water,
the probable movement and reactions of nitrogenous compounds in the
subsurface environment, and specific cases of ground-water pollution
by nitrogen-containing compounds.
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SECTION IV
FORMS AND SOURCES OF NITROGEN IN GROUND WATER
Nitrogen is a diatomic element existing in the gaseous state and is
the most predominant species in the atmosphere. This element is
capable of exhibiting a number of oxidation states and combining with
a number of other elements to form organic and inorganic compounds.
Nitrogen is an essential nutrient for plants and animals and is found
in all protein materials. Nitrogen exists in a number of other
naturally and synthetically produced organic and inorganic compounds.
The inorganic forms of nitrogen which are common in nature are the
nitrate, nitrite, and ammonium ionsJ6 Nitrate and nitrite are
anionic species which are often found in combination with sodium,
potassium, calcium, magnesium, and other monovalent and divalent
metallic ions. Ammonia readily forms the ammonium cation which is
commonly found in nature with a number of the metallic cations.
The compounds and ionic species of nitrogen have been implicated as
pollutant materials of surface water for a number of years, but in
recent times more attention has been directed toward nitrogen and its
role in the contamination of ground-water supplies. Organic nitrogen
has not received as much attention as the ionic form of nitrogen,
but the presence of organic nitrogen in some underground water supplies
is to be expected. In locales with swamps or marshes having high water
tables, the potential for leaching organic nitrogen could be expected.
Some of these organic compounds could be highly mobile and easily
transported through the soil by percolation. The presence of organic
nitrogen in some water supplies can be expected in close proximity
to landfills, livestock operations, and sewage treatment facilities.
The presence of the ammonium ion in ground-water supplies has not
received as much attention as some other inorganic forms, but investiga-
tions have confirmed its presence in' some locations. One investigator
in Colorado confirmed the presence of the ammonium ion in conjunction
with organic carbon and noted that some samples of ground water even
exhibited offensive odors.'7 An ammonia molecule can readily combine
with an available proton to form an ammonium ion which is positively
charged. It is this positive charge which causes most of the ammonium
ions to be held in the soil profile by the negatively charged soil
micelles.'° In general, clay soils hold ammonium ions more efficiently
than sandy soils, soils of low pH more efficiently than those of high
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pH, and soils with high organic contents are less efficient than mineral
soils with similar cation^exchange capacities. The ammonium ion can be
leached, however, through the soil profile if the cation exchange capacity
of the sofl Is satisfied.18
Most investigations concerning nitrogen and ground water have been di-
rected toward the inorganic anionic species, especially the nitrate ion.
Nitrate and nitrite anions ape negatively charged and the movement of
these species through the soil profile is accelerated because of the
anionic state of most of the soil mineral fractions. Little inhibition
to movement exists for these ions when in soil solution.19 The deter-
minants of movement in the profile are the amount of water infiltrated
into the soil, the soil moisture content at the start of the precipita-
tion event, the porosity of the soil, and its permeability.5 The nitrate
species is more stable than the nitrite and, therefore, is more commonly
encountered in soil and water systems, although investigations have con-
firmed the presence of the nitrite ion in a number of well water supplies.11»12
Crabtree's investigation in Wisconsin showed that there was no clearly
defined relationship between the depth of the well and high nitrate con-
centration for the area, but a trend did exist between increasing nitrite
concentration and well depth. The highest incidence of nitrite occurred
most commonly in shallow and dug wells immediately after heavy precipi-
tation. 12
Nitrogen contamination of ground water can be attributed to a number of
sources. The most widely recognized sources are fertilizers, animal
wastes, and domestic wastes. However, investigations of nitrogen sources
which can account for contamination of ground-water supplies indicate
that much of the contamination can be attributed to natural sources—that
is, those not directly related to man's activities.11 Some microorganisms
are capable of taking nitrogen directly from the air and converting it in-
to usable forms. There are estimates that some kk million metric tons
leave the atmosphere by this procedure annually.20 Some of the nitrogen
from this process can possibly percolate downward to ground water. The
atmosphere is considered to contribute from 0.9 to 2.7 kilograms (2 to
6 pounds) of nitrogen to an acre of land over the period of a year.12,21,22,23,24
The degradation of vegetation—especially old stands of alfalfa—can also
contribute much nitrogen to the soil.25 Soils contain other sources of
organic matter which can be broken down and converted to usable forms.2°
The inorganic forms of nitrogen placed in the soil in this manner are
capable of being leached from the upper soils to underground water supplies.
Some natural soil deposits such as organic rich shale and some deposits of
limestone contain considerable amounts of nitrate which can be leached.12,27,2«
Investigations In Missouri indicate that the potential source of nitrogen
contamination of some streams is probably the bat guano mounds in caves
In close proximity to those streams.28,29,30
Rainfall and dust are two other natural sources of nitrogen which
should not be overlooked. Much nitrogen is added to the soil by both
of these methods.31,32,33,3*»r35 Rainfall, dew, and snow can contain
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various forms of nitrogen, and Walker indicates that the nitrogen
additions by this method may be as much as 7 kilograms (15 pounds)
of nitrogen per acre per year in some local ities.3°»37,3o Very
little information is available concerning the amount of nitrogen
which may reach the soil systems from the settling of dust, but one
investigator feels that as much as 4.5 kilograms (10 pounds) of nitrogen
per acre per year is possible.39 Much of this nitrogen is being
recycled from the soil or barnyard and some can be attributed to salts
formed in the atmosphere.36,40,41,42,43
Animal waste materials contain nitrogenous compounds which are converted
to ammonia during the decomposition process. The ammonia can then be
converted to nitrite and nitrate ions. This process is characteristic
of the waste from all animals, but man's handling of domestic animals
has created a serious threat to water supplies.43,44,45 The practice
of confining large numbers of animals together in restricted areas
creates high concentrations of pollutant materials in a locale.37,46
The present methods of handling the vast accumulation of animal waste,
usually piling, spreading, or lagoon treatment, does not prevent the
nitrogen forms from being a potential pollutant source.^7,48,49 Farm
manure contains about 4.5 kilograms (10 pounds) of nitrogen per ton
of dry matter and poultry waste is even higher.7 Estimates concerning
the amount of nitrogen waste per animal vary but some authorities
attribute about 43 kilograms (95 pounds) of nitrogen per year for each
animal in a beef feedlot operation.'" Investigations reveal that the
nitrate contamination of water supplies is common around dairy operations,
barnyards, and feedlots, with feedlots presenting the most serious
problem in many parts of the country.50,51 One investigator in Missouri
found over 920 kilograms (2022 pounds) of nitrate nitrogen per acre at
a depth of 4.3 meters under a feedlot operation.25 Similar accumulations
have been reported in Colorado under conditions of lower precipitation.52
Another potential source of nitrogen contamination not often recognized
involves the handling of silage. The leachate from silage is rich in
organics and sometimes tremendously high in nitrogen; this leachate
has been shown by some investigators to be a problem in the area of
water contamination.3°
An agricultural practice which has received a great deal of attention
as a potential source of nitrogen contamination is the use of commercial
fertilizers. Fertilizers account for more than 30 per cent of the food
produced in the United States at the present time JO In 1970 the
United States consumption of commercial fertilizers was approximately
36,000,000 short tons, and it is estimated that 70,000,000 short tons
will be used annually by 1980.53 Nitrogen fertilizers constitute the
largest share of the fertilizer market.38,54,55
This topic has been and will continue to be a controversial issue.
Investigations of nitrogen levels in central Illinois indicate a
correlation between the usage of nitrogen fertilizers and levels of
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nitrate found in the rivers of the area.5° Walker's work in Illinois
also reveals the close correlation that occurs between fertilizer usage
in Illinois and levels of nitrate in ground water.57,58 Dependency
of the ground-water nitrate levels on the fertilizer management practices
for cropping systems in the California area are indicated.59,60,61,62
The effects of fertilization on the nitrogen content of surface runoff
and ground water show variations from locale to locale. The nitrate
content of the waters of the upper Rio Grande did not show a significant
increase in nitrate concentrations over a thirty-year period even
though the rate of application of the nitrogen fertilizers increased
from a low level to a high level over the period.°3 However, an
investigation by Stewart in Colorado revealed that nitrate is moving
through the soil and into the ground-water supply under both feedlots
and irrigated fields, excluding alfalfa.52 This study showed that
larger amounts of nitrate are present under feedlots than irrigated
lands, but that irrigated lands are contributing more nitrate to the
ground water since the ratio of irrigated land to that in feedlot for
the study area is 200 to 1. In Missouri, the only waters considered
contaminated by nitrogen fertilizers were located under light sandy
alluvial soils along the Mississippi and Missouri Rivers.29 The
varied results of studies of fertilizer effects on the nitrogen levels
of ground and surface waters emanating from crop production areas imply
that each area and cropping system utilized will have to be examined
for the pollution effects resulting from the use of nitrogen ferti1izers.6^,65
Irrigation practices in conjunction with fertilizer applications have
received some attention, and the increased amount of nitrogen in ground-
water supplies in some regions of California has been attributed to
the liberal uses of fertilizer in conjunction with irrigation.59,61,66,67
It appears that heavy application on highly permeable soils has contributed
significant amounts of nitrogen to underground water supplies.60,62,6o
Since a number of factors, such as improper application practices, soil
conditions, etc., are important, fertilizers should be recognized as
a potential source of contamination of ground-water supplies and in
some localities even a major potential source of nitrogen contamination.56,65,
69,70 Improper handling of fertilizers before they reach crop lands
should also be considered a potential source of contamination due to
accidental spills and leaching from storage sites.71
Runoff from land has been recognized as a source of nitrogen pollution,
but it should be stressed that this source should include runoff from
all land, not just that land under cultivation.36,*H,72,73 Until very
recent times, little attention had been devoted to runoff from urban
land, but recent investigations cite this as a potential pollution
source. Water of this type is known to contain nitrogen from lawn
fertilizers, dust fall, leaves, waste materials from domestic pets,
household wastes, etc.5*f Investigations by Keeney show that the
nitrogen content of urban runoff is sometimes higher than the nitrogen
content of sewage.36
10
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The disposal of human wastes has been recognized as a potential source
of contamination of ground-water supplies, and none of the commonly
used methods of treatment, in rural or urban areas, can eliminate nitrogen
as a potential source of pollution. The average amount of nitrogen
released by each individual is considered to be about 5-** kilograms
(11.9 pounds) per year.16 |f only a small portion of the nitrogen from
human wastes makes its way to the ground water, the impact on these
supplies could be serious.
The nitrogen contamination of a number of wells in urban and rural
areas has been attributed to septic tanks. The septic tank system is
the predominant method of sewage disposal in rural areas and is still
widely used in many urban areas as well. It is estimated that 25 per-
cent of the population of the United States use septic tanks or cess-
pools for the treatment of household wastes. In Nassau County, Long
Island, New York, the daily discharge into septic tank systems is
estimated to be 300 million liters (79 million gal Ions).'°>75 The
waste materials from humans contain a number of nitrogenous materials
which are largely converted to ammonia in septic tank treatment systems.
Much of the ammonia is removed by soil fixing and adsorption, but under
the right conditions, the ammonia can be converted to nitrate and nitrite,
which can readily be leached to ground water. In addition to the
effluent from the septic tanks, the sludge removed from these systems
is high in nitrogen and can be a problem if improper disposal occursJ°
In addition to septic tanks, much of the human wastes in urban and
rural areas is treated by cesspools, privys, and lagoon systems.
With all of these methods of disposal, there is a potential for the
nitrogen in the treated effluents to leach to ground-water supplies
and the contamination problem may persist for years after such systems
are discontinued.'"
Conventional treatment systems are not to be eliminated as potential
sources of nitrogen pollution of ground-water supplies. It is estimated
that about 75 percent of the population in the United States is now
served by sewer systems. Primary treatment removes approximately
5 percent of the nitrogen from sewage and secondary sewage treatment
removes less than one-half.l°»3o»7^ Therefore, the effluent from such
systems contains large amounts of nitrogen, some of which can travel
through soil systems to ground-water supplies. Also, that nitrogen
removed by sewage treatment is retained in sludge and may be leached
into ground water if the sludge is handled by normal land disposal methods.
A recent investigation concerning the contamination of ground-water
supplies in the northeastern United States revealed that sewer lines
are also a source of contamination. In King County, New York, the
nitrate contamination of a water supply was attributed to a broken
sewer line.75 It is a known fact that many of the sewer lines in
the United States are old and contain breaks which allow the leaching
of pollutants to ground-water supplies. It is difficult to estimate
the amount of contamination which occurs from these sources.
11
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Another problem area involving the handling of man's waste is the
practice of solid waste disposal. It is estimated that 2.42 kilograms
(5-3 pounds) of solid waste are generated per person per day and
that about 90 percent of this material is disposed of in landfill
sites.'",75 The nitrogen content of most solid waste material is
about 0.5 percent so about 800,000 metric tons of nitrogen is buried
in this manner each year in the United States.'" A leachate is formed
in the course of aging of the system, and investigations reveal that
this aqueous phase is high in nitrogen.'' The leachate coming from
a landfill may contain high concentrations of nitrogen for several
years after the use of the system is discontinued.
Some industrial operations are known to contribute significant amounts
of nitrogen to soil systems, creating a potential for leaching to
ground-water supplies. Coking processes, petroleum refining, dairy
processing, and meat processing are only a few of the activities known
to produce liquid waste materials high in nitrogen.36 Also, some
attention has been devoted to those industries producing nitrogen
containing compounds such as the fertilizer manufacturing operations.53
These and many other industries sometimes use surface impoundments
for the treatment of materials which cannot be discharged to municipal
treatment systems. In a survey conducted in the northeastern states,
57 cases of ground-water contamination from such industrial surface
impoundments has been noted.78 The majority of these 57 cases of
contamination included nitrogen as one of the pollutant materials.
The contamination of some ground-water supplies in several sections
of the country has been attributed to the draining of wetlands. Marsh
or swamp waters may contain high concentrations of nitrogen. When
the wetlands are drained, anaerobic activity stops, and some of the
nitrogen is oxidized and, therefore, subject to leaching through
the soil systems.36,79
Wastewaters are sometimes purposely disposed of or recharged to the
underground in a number of different ways. These methods of recharge
involve discharging the wastewater to deep wells, shallow wells, pits
or basins, or irrigation plots. These practices have become more
popular in recent years with the increased restrictions on waste
discharge to surface waters. There is not a great deal of information
available about these methods and their effect on the subsurface
environment, but all can serve as potential sources of ground-water
contamination.72
12
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SECTION V
MOVEMENT AND REACTIONS OF NITROGEN IN
THE SUBSURFACE ENVIRONMENT
It is obvious that compounds of nitrogen from a number of sources
may enter ground-water supplies and that nitrates and nitrites are
probably the nitrogenous substances of most significance as pollutants
because of their mobility in soil profiles and their health effects.
Understanding and controlling the pollution of ground water by
nitrogenous substances, however, requires knowledge of the transport
of the substances and the reactions which they may undergo in the
subsurface environment.
Nitrogen may move through the subsurface zones by several modes which
can operate independently or in conjunction. Compounds of nitrogen
can move through the soil porespace as gases or as solutes in aqueous
solution. Nitrogen fixed in insoluble organic matter or in mineralized
form may be transported through the soil profile by organisms (through
excretion or mechanical transport) or by suspension of the particles
in soil water. The distance, direction and amount of nitrogen transported
varies with time and with chemical, biological and physical properties
of the soil.
The soil profile at each geographical location is unique in its nitrogen
transport capability. This uniqueness is the result of the specific
culmination of geology, topography, climate, and vegetation that exist
at each site and each parameter can influence the part played by other
variables. A mathematical review of the kinetics of transport is
provided by Garner."'
The transport of nitrogen in the subsurface environment is, of course,
a function of the types of nitrogenous compounds present and, hence,
dependent on the transformations which these compounds may undergo in
this environment. The simplified nitrogen cycle in Figure 1 describes
dynamically the transformations of nitrogen compounds as they are
known to occur in the surface and shallow subsurface environments. In
considering this figure, it should be noted that the term "cycle" does
not imply that the nitrogen atoms are moving through the cycle from
step to step in an eternal movement. The pathway of nitrogen atoms is
13
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'V/INTEWEDIATE
PRODUCTS OF
KCOIVOSITION
Atronti nitrogen
(a) aerobic decomposition
RESHWOIR OF \0xygen 'or blologlci! g I - \ °
NITROGEK > o«1d»tton - 1 » 1 »
III AIR MD
IV IHTERWOIATE
PRODUaS OF
DECOMPOSITION
(b) anaerobic decomposition
Figure 1. Nitrogen cycle
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not progressive nor continuous, and it is possible for an atom of
nitrogen to stay at one place in the cycle.'"
Microorganisms play an important role in the nitrogen cycle, particularly
in the soil environment. Over 90 percent, of the total nitrogen in
soils is in an unavailable organic form.^ Organic nitrogen in the
soil may be converted by microbial activity to ammonium ion, by the
process called "ammonification". The ammonium ions thus produced can
be held in the soil by negatively charged particles of clay and soil
organic matter, and are therefore resistant to percolation. The
ammonification process is dependent on soil temperature, aeration,
and soil pH among other variables.
"Nitrification" is the process of microbial oxidation of the ammonium
ion to the nitrate form. This occurs most rapidly under well aerated
conditions, with a temperature of 60-85° F and a pH of 6.5 to 7.5-^
Nitrate is available for plant uptake but is also subject to leaching,
the rate depending on soil conditions and properties. Under poor
aeration, nitrate can be reduced by microbes to gaseous nitrogen and
lost to the atmosphere through the process known as "denitrification".
This occurs when oxidizable organic material is present to act as a
source of electrons for nitrate reduction. Denitrification is more
likely to occur in warm soils which have a neutral to alkaline pH.3"
Ammonium ions, amino acids, and nitrate ions (via ammonia) may be
incorporated into the protoplasm of microorganisms. At the death of
the organisms, the organic nitrogen of the protoplasm may again be
converted to available ammonium ions by the process of ammonification.
Most of the available information concerning reactions of nitrogen,
particularly the microbial processes of the nitrogen cycle, as well
as nitrogen transport data, has been developed in agriculturally-
related research pertaining to the topmost, or soil, layer of the
earth's crust. Those regions lying below the soil zone, including
both the unsaturated zone above the water table and saturated ground-
water zones, have received much less investigation in this regard.
Information regarding nitrogen movement and reactions in the soil zone
is important, however, because the fate of nitrogen in this zone
undoubtedly plays a major role in determining the extent and nature
of pollution of ground water by nitrogenous compounds and also
because the processes occurring in this zone provide a basis for
predicting probable movement and fate of nitrogen in the deeper zones
of the earth's crust and for determining research needs pertaining to
nitrogen in these zones. The remainder of this section considers in
more detail available information concerning the movement and reactions
of nitrogen compounds in the subsurface, principally the soil zone.
MOVEMENT OF GASES
Gases move through soil in response to pressure differentials within
15
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the soil porespace. Physical processes affecting pressure differentials
can result from unequal partial pressures of gases making up the soil
atmosphere, differences in atmospheric pressures, temperature gradients
in the soil profile, or displacement of the gas in the soil porespace
by a liquid. Molecular diffusion of gases causes movement through the
profile, depending on such rate-controlling factors as concentration
gradients, gas temperature, molecular structure, and chemical reactivity
of the gas.
Physical processes can be activated by biological processes occurring
in the soil. Decomposers can create gas pressure or concentration
differentials leading to a gas flow through the porespace, and
adsorption of soil water by plant roots induces airflow into the soil
to fill vacated porespaces.
Production of volatile gases, especially nitrous oxide and nitrogen,
occurs when nitrate or nitrite is reduced in biochemical reactions
favored by wet soil conditions, manure, and other organic material.
Such denitrification reactions are inhibited by oxygen, and they
rarely occur in dry, well-aerated soils. Ammonia can also be volatilized
from the soi1.
A constant emission of gases from the soil is improbable since the
conditions favoring nitrogenous gas formation are episodic; however,
the amounts that are emitted may constitute a considerable loss from
the soil. Researchers confront problems in the lack of methodology
and equipment needed to adequately identify and quantify the nitrogenous
gases present in soil. A state of the art review of the techniques
used is given by McGarity and Rajaratnam."* Continued work on the
movement of nitrogenous gases is necessary to determine the importance
of this factor in the nitrogen balance of the subsurface zone.
MOVEMENT OF NON-GASEOUS NITROGEN COMPOUNDS
The movement of water through the soil profile is of major significance
to the nitrogen cycle in the subsurface environment. Displacement of
gas in the sofl by infiltrating water initiates gas movement and
water in the porespace can produce anoxic conditions suitable for
denitrification by facultative and anaerobic bacteria. It also produces
habitat conditions favorable to many organisms because dissolved
organic and inorganic nutrient material is transported by soil water
as it moves in response to complex gradients caused by variations in
pressure and capillarity.
The quantity of nitrogen leached from the soil is a function of many
factors operating in the soil profile. These vary greatly with time,
and their effects on each other complicate any quantitative evaluations
of the rate and amount of nitrogen transfer caused by each. At the
present time, information regarding these factors is qualitative in
nature, but useful in understanding the process or in comparing the
leaching potentials of different situations. Some variables affecting
16
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the rate and amount of nitrogen leached from soils include:
1. Soil characteristics (texture, porosity, structure,
consistency, soil moisture, depth of profile, percolation
rates, etc.)
2. Climate characteristics (amount, frequency, duration
and time of precipitation, rates of evapotranspiration,
and temperature regimen)
3. Biological characteristics (presence or absence of
plant cover, depth of root zone, nitrogen use
characteristics of the vegetation, periods of plant
growth, levels of soil organic matter, microbial
and animal populations)
4. Cultural characteristics (land use patterns and soil
management practices)
5. Nitrogen characteristics (amount and type of fertilizer
application, type of fertilizer applied, amount of
organic matter in the soil)
Interactions of these variables produce a complex, everchanging pattern
of nitrogen distribution in soil profiles. Any nitrogen compound
in the soil can be leached if the proper conditions are satisfied,
but primary concern has been directed to the highly soluble inorganic
forms. Ammonium ions can be leached once the cation exchange capacity
of the soil is satisfied. During saturation periods, when oxygen levels
are low and biological activities are reduced, physical adsorption may
occur. The amount of adsorption decreases with increased concentrations
of potassium cations. Where high concentrations of other cations exist,
especially several hundred milligrams per liter of calcium and magnesium,
they probably interfere with ammonium adsorption.5
The conversion of nitrogen compounds to anionic forms (nitrite and
nitrate) promotes leaching, since most of the mineral fractions of soils
are anionic. Determinants of movement of these compounds include the
amount of water infiltrating the soil, soil moisture content at the
beginning of the precipitation event, and the porosity and permeability
of the soil. Nitrate leaching increases during wet periods, as soil
moisture levels are high and evapotranspirat ion rates are reduced.
Denitrification may occur during the leaching process, as indicated in
studies of nitrate concentration beneath an irrigated field.^3
Leaching of nitrate occurs during or shortly after precipitation events.
The wetting front proceeds through the profile and satisfies the
storage capacity of each successive zone. If the front is dissipated
before passing through the root zone, no nitrates are removed. The
evapotranspiration process causes capillary movement toward the soil
surface. Nitrate salts carried in the water may enter the root hairs
17
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of plants, or they may be deposited as salts in the surface soil as
the water evaporates. During the next precipitation event, the
nitrate salts dissolve and may be assimilated by plants or carried
downward toward the water table.
In periods of active plant growth, evapotranspi.ration rates are
high, plants have a high demand for nitrates and ammonia, and little
leaching occurs. With cooler autumn weather in the temperate regions,
nitrogen begins to accumulate in t'he profile. Winter and early spring
precipitation may then leach the accumulated nitrogen to the ground
water.
Nitrates leach more slowly from a profile containing a high percentage
of clay or colloidal material than from a loamy sand. Water is held
more readily by clay soils, and the dissolved nitrate is held with
it. Ground-water contamination from increased nitrate concentration
is much greater under light, sandy soils because of more rapid movement
of the soil solution through the porous structure.
Organic nitrogen compounds per se are not usually considered a
pollution threat to ground water. Mineralization of these compounds
is of concern, however, since organic forms are generally converted
to inorganic forms before much distance has been traveled from
the originating source. Where water tables are high and respond quickly
to surface water levels, as in swamps and marshes, the potential for
leaching organic nitrogen along with inorganic forms increases.
NITRIFICATION
The process of nitrogen fixation results in the production of the
ammonium ion, a cation which leaches fairly slowly. Classically,
nitrification is a process performed by microbes capable of oxidizing
reduced forms of nitrogen: ammonium is oxidized to nitrite, which
in turn is oxidized to nitrate. Nitrate, a form of nitrogen readily
usable by most plants, is anionic, leaches much more readily than
does ammonium, and is subject ultimately to conversion to atmospheric
nitrogen or nitrous oxide by denitrifiers.
Typical nitrifiers are autotrophic aerobic bacteria: Nitrosomonas
is a common ammonium oxidizer, and Nitrobacter is a common nitrite
oxidizer. While the process is related to the energy relations within
these cells and is therefore essential to their metabolism, several
heterotrophic organisms can also oxidize ammonium under appropriate
conditions. These heterotrophs, which include bacteria, actinomycetes
and fungi, can achieve large populations in soils. They are also capable
of good growth under conditions unfavorable to nitrification, so
apparently the process neither serves the same function nor follows
the same metabolic pathway in all these organisms.°^ However, the
most significant nitrification appears to be accomplished by the autotrophs.
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Nitrifying populations are sensitive to a variety of environmental
conditions. The nitrification capacity of soil has been linked to such
diverse parameters as ammonium content, pH, oxygen content, moisture,
temperature, organic matter, carbon dioxide content, cation exchange
capacity of the soil, depth, cropping practices, season of the year,
and soil treatment.84,85,86,87,88 jhe exact effect of these factors
is being studied in several localities.
Of all these factors, temperature and moisture are probably the
most important ones governing nitrate accumulation in the medium-
textured, limed soils of the midwestern United States.°° It appears
that temperature affects the rate of nitrification but not the total
amount of nitrate produced over a 5~week period within the range of
16-20° C.°7 The optimum temperature range for nitrifying bacteria has
been reported as 30-35° C, with little nitrification occurring above
40° C.81* Nitrification is also minimal at or below 0° C.°& Maximum
accumulation of nitrate occurs at lower moisture tension than field
capacity, the water content of the moist soil layer after capillary
movement of water has become negligible. Most soils reach field
capacity within 2 days or less after a rain or irrigation. Far from
saturation, field capacities range from about 5 percent in very sandy
soil to about k$ percent of the dry weight in clays. Apparently,
there is an abrupt reduction in nitrification as the soil becomes nearly
saturated with moisture.°7 However, as with most microbiological
processes, the optimum conditions for nitrifiers vary with the type
and strain of organism.
Nitrification studies have been performed in soil columns using
known concentrations of ammonium ion added to columns containing
known microbial species, population sizes, and even distribution of
microbes through the soil. Reaction rates for individual stages
in the process can then be calculated. Mathematical analysis of the
kinetics of such experiments are given by McLaren and Skujins.°9 Such
studies are the best available approach currently used to approximate
nitrification under field conditions, and they are useful in making
predictions. However, they are not subject to the variable nature
of ecosystems and the important interactions of mixed and fluctuating
populations, hydrodynamics, diffusion, temperature and soil surfaces.
More studies need to be carried out with single variables although
this will oversimplify the picture.
In the first stage of the classical nitrification pathway, ammonium is
oxidized to nitrite by organisms such as Nitrosomonas. In the second
stage nitrate is oxidized to nitrate by organisms such as Nitrobacter.
The organisms responsible for this oxidation are aerobes and grow best
in well-aerated soils of lightly alkaline pH. The pH for nitrification
rates appears to be slightly higher in soil than in solution cultures.90
Ammonium oxidizers do not proliferate in even slightly acidic soils,
but they seem to be less sensitive to changes of temperature, ammonium
concentration and moisture content than are nitrite oxidizers. When
conditions are not optimum for complete nitrification, nitrite will
accumulate in some soils. In the United States, for example, nitrite
19
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accumulates in southern soils at low temperatures, while in northern
soils it accumulates at high temperatures.85
Several factors have been shown to favor nitrite or nitrate accumulation
following their production by soil microbes. If large amounts of urea,
anhydrous ammonia or ammonium salts are added to soils of high pH, or to
soils whose pH rises as the result of urea hydrolysis, nitrite can build
up significantly. Under these conditions it has been shown to persist
for at least nine months. ^ Nitrite does not persist in acid soils. Ni-
trate is formed during the cold periods, when plant demands are low, and
is more subject to leaching from the root zone in autumn than during the
spring.
Using equations derived from kinetic studies of nitrate accumulations,
one can estimate the nitrate accumulation that should occur in soils sim-
ilar to the loess-derived silt loams common in the midwestern United
States. Such estimates can be made for any temperature between 0° and
25° C, and at any moisture tension from 0.1-15 bars, ff the ammonium con-
centration is not limiting and if conditions are favorable for nitrifi-
cation.86
Anything that inhibits the rate of nitrification results in less conver-
sion of cationic ammonium to anions, and therefore retards the activity
of denitrifiers that depend on nitrate for their activity. Retardation
of nitrification can be accomplished by the additions of pesticides,
particularly 2-chloro-6-(trichloromethyl) pyridine, by steam, or by chem-
ical fumigants such as technical dichloropropenes or a mixture of methyl
bromide, chloropicrin and propargyl bromide.9"»92 Certain plants may al-
so produce inhibitors which may be excreted through the roots.°^
Products of nitrification are subject to a variety of further transform-
ations In completing the nitrogen cycle. These include uptake by plants
and microbes, which incorporate them into organic material, denitrifica-
tion, and chemical fixation by soil organic matter. When organisms de-
compose, an appreciable amount of their organic nitrogen compounds are
fairly resfstant to biological breakdown, and they remain in stable humus
material. Humus is colloidal in nature, and this may further decrease its
biological reactivity.93,9** Humic nitrogen compounds and their resistance
to biological transformations are as yet poorly understood, but they are
being studied in physical, chemical and biological investigations.93,95,So
DENITRIFICATION
A balancing aspect of the nitrogen cycle is, in effect, the reversal of
the processes of nitrogen fixation and nitrification. Denitrification
occurs in anaerobic conditions when performed by microbial agents, al-
though in strictly chemical reactions, it may occur in an environment of
air. In biological systems, nitrate and nitrite are reduced to volatile
gases, especially nitrous oxide and nitrogen, in reactions that are fa-
vored by wet soil condition and the presence of organic material such as
manure. The process ts inhibited by oxygen, and it rarely occurs in dry,
well-aerated soil.
20
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Many denitrffiers are facultative anaerobes. Under anaerobic conditions,
they carry on anaerobic respiration, substituting nitrate or a related
nitrogenous compound for oxygen as the terminal electron acceptor. The
nitrate is thus reduced. The pathway usually described reduces nitrate
to nitrite to nitrous oxide to nitrogen gas, although some intermediates
(such as HNO, ^£0 or N02NH2) have been postulated.
The strain of denitrifying organism determines whi-ch enzymes are present
and what products will be formed. Several other factors determine the
rate of the reactions. The pH of the soil environment is important, since
denitrif ication is slow in acid but fast in alkaline media: it usually
occurs in soils of pH 6 or above. The relative amounts of N£0 and N2
produced are affected by temperature, with N20 being predominantly formed
at lower temperatures and N2 at higher ones. Also, the ratio of ammon-
ium to nitrate in the soil will affect the products formed: a one-to-one
ratio of ammonium to nitrate favors the predominance of ^0 in the product,
while a ratio of 0:1 results in the predominance of N2.^
Conditions conducive to denitrif ication are commonly found in fine-tex-
tured, water-logged soils with high organic content. Water apparently
has a direct effect on denitrif ication, as the closer the soil is to sat-
uration, the more denitrif ication occurs there. Little occurs in soils
less than about 60 percent saturated."' Because of this dependence on
high water content, it is probable that denitrif ication may be quite ex-
tensive in the anaerobic capillary fringe zone just above water tables,
where water is held in soil spaces by capillary action. This is especially
indicated fn and above saturated zones beneath agricultural areas that
are fertilized with nitrates or irrigated with waters high in nitrate,
since nitrate is readily leached from upper soil layers. In considering
the fate of nutrients such as ammonia, urea and nitrate added to soils,
it appears that 10-30 percent of the nitrogen added in fertilizer can
be lost through denitrif ication alone. 97 High organic content is con-
ducive to denitrif ication, since heterotrophic denitrifiers need oxidizable
organic material as a source of carbon for synthesis of protoplasm and
as a source of electrons for the reduction of nitrogenous compounds.
While it is commonly accepted that chemical denitrif ication also occurs
in nature, there is considerable debate over its mechanisms and its ex-
tent. Chemical denitrif ication reactions are known to occur in normal
aerobic soil. Nitrite ions can react with many compounds, including some
ammonium salts, simple amines like urea, non-nitrogenous carbohydrates
and sulfur compounds, to generate nitrogen gas under slightly acid con-
ditions. These reactions probably occur when soil conditions are favor-
able for nitrification reactions, and for the growth of aerobic microbes
and plants, rather than in the anaerobic, neutral to alkaline conditions
that support biological denitrif ication. Nelson and Bremner report that
nitrogen gas forms readily from reactions involving deomposition of ni-
trite in acidic soils high in organic matter. 98
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SECTION VI
SPECIFIC INCIDENTS OF NITROGEN CONTAMINATION IN GROUND WATER
The detection of nitrogen contamination in ground-water supplies is not
new, as Abbott points out in one of his articles. Data obtained in the
Iowa Water Survey made tn 1935-36 showed that in 200 water samples ana-
lyzed, nitrate values varied from 0-125 mg/1 in domestic and municipal
wells. He also discusses a later survey in North Dakota which revealed
that of 151 dug wells sampled in North Dakota, about one-half of them
contained more than 10 mg/1 of nitrate-nitrogen.'3
The problem of ground-water contamination is not one which is unique to
the United States. Holland, which takes about 77 percent of its water
supply from underground sources, detected the presence of nitrate and
nitrite ions in some of its municipal water supplies in a survey in 1960.99
Subbotin also reports that well water around Leningrad, U. S. S. R., con-
tains some nitrates equivalent to about 20-40 mg/1 of nitrogen.9
Ballentine discusses a survey conducted in the state of Illinois in which
30 percent of the wells less than 25 feet in depth showed concentrations
in excess of the 45 mg/1 Public Health Service Drinking Water Standard
recommendations.100 Walker also reports that chemical analysis of ground-
water samples from throughout Illinois indicated that nitrate pollution
in aquifers was widespread, especially in rural parts of the state. In
Washington, County, Illinois, recent analyses of water samples from 263
farm-supply wells showed a median nitrate concentration of 143 mg/1 and
more than the recommended 45 mg/1 level was found in over 73 percent of
the wells sampled.101 Larson reports that in Livingston County, Illinois,
46 wells within a 12 to 13 square mile area were sampled and 26 of these
samples showed nitrate concentrations greater than 15 mg/1. In another
area representing about 25 to 30 square miles in Iroquois County, Illinois,
only 3 of 201 samples showed nitrate concentrations greater than 15 mg/1.
Two of these 3 samples showed nitrate values greater than 45 mg/1.'^
In some counties in Missouri, more than 75 percent of the wells surveyed
were contaminated by the nitrates. Some wells in close proximity to feed-
lot areas showed values of more than 300 mg/1 nitrate-nitrogen.29 In a
more recent survey in the state of Missouri, including 45 counties and
representing more than 5000 wells, about 45 per cent contained over 5 mg/1
n i t rate-n i t rogen.1°
22
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A comprehensive study by the Minnesota Department of Health in the
MinneapolIs-St. Paul area consisted of collection of random samples from
63,000 wells which served more than 250,000 people.'°3 About 46.5 per-
cent of the samples showed evidence of nitrate-nitrogen contamination
and 10.6 percent showed more than 10 mg/1 nitrate-nitrogen.
Suffolk County, New York has been the topic of a number of well publi-
cized investigations and the results of some surveys show the impact of
suburban growth on ground-water quality. This county Includes an area
of about 922 square miles, with a population in I960 of 665,000, About
59 percent of the population obtains water from 90 communal or public
water supplies. In 1958 it became evident to the Suffolk County Health
Department that the quality of the water from private wells was poor and
deteriorating. Townships and municipal suppliers were asked to cooper-
ate in programs leading to the extension of public water supplies to
serve existing residential areas. The first group of these wells was
constructed In August and September of 1958. In February and March of
1961, samples were collected from 47 of these wells. During this 2 1/2
year period of time, a number of the wells had become contaminated with
nitrate ions and free ammonia. Of the 47 wells surveyed, 5 showed greater
than 10 mg/1 nitrate-nitrogen.^^
In the same vicinity, Kings County, Long Island, New York, according to
a recent United States Geological Survey study, leakage from sewers may
be a principal source of the nitrate and total nitrogen in ground-water
supplies.75 Landfill leachate has been blamed for ammonia contamination
of ground water in the same county. This is only one of about 100 cases
of ground-water contamination problems in the northeastern states related
to landfill sites.75
An investigation into the degree of contamination of ground-water supplies
by nitrate-nitrogen in the central Wisconsin farm area of Marathon County
revealed that 55 percent of the wells contained nitrate concentrations
of 45 mg/1 or more. Among 242 wells investigated, 82 private wells were
sampled 2 times per month for a period of 14 months. Nearly 70 percent
of the 82 wells contained nitrate levels of 45 mg/1 or more throughout the
period.'2 -rne variations in nitrate concentration were closely related to
the amount of precipitation and concentration was highest during heavy
rainy seasons and lowest during dry periods for the majority of wells ex-
amined.
Stewart and co-workers have investigated the ground water under irrigated
fields and feedlots in the South Platte River Valley of Colorado. The
average concentration of ammonia-nitrogen of the waters from beneath 28
irrigated fields was 0.2 mg/1 and only 2 samples contained as much as 1
mg/1. Water from beneath 29 feedlots averaged 4.5 mg/1 of nitrogen (as
ammonia) and 15 of those contained more than 1 mg/1. Seven of these
23
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samples were above 5 mg/1 and the highest value was 38 mg/1J7 Another
case of interest in the state of Colorado is a Colorado city of 7,500
people where a shallow aquifer water supply had reached nitrate levels
of over 60 mg/1 (as nitrate) by 1962.105
Concern has also been shown in the state of Nebraska for possible con-
tamination of ground water by nitrate and other nitrogen forms. Some
reports of high nitrate water from several wells in northern Holt County
caused the Lincoln, Nebraska office of the United States Geological Sur-
vey to look into the problem of nitrate contamination. Water samples
were collected from 71 wells and nitrate concentrations ranged from 0.1
to 400 mg/1; The Delaware Geological Survey also reveals that 25 percent
of the shallow wells in the state yield water with nitrate levels above
20 mg/1.75
Leakage of wastewater from surface impoundments has been investigated in
57 cases of ground-water contamination in the northeastern United States.
Many of the samples examined in these investigations showed evidence of.
contamination by ammonia and nitrate-nitrogen.72 Also, in the northeast-
ern United States, 36 cases of ground-water contamination have apparently
been caused by spills and surface discharge. Three of these showed evi-
dence of contamination by nitrate-nitrogen. Shallow disposal wells in
freshwater aquifiers are used in this part of the country for disposal of
a variety of liquid wastes including storm water, sewage, cooling water,
and industrial effluent. Nitrates have been reported in some samples
collected from wells in close proximity to these disposal sites. 2
It would appear that many of the cases involving contamination could be
attributed to man's activities, but natural contamination has been cited
also. Runnels County and some other counties in this area of Texas show
evidence of widespread nitrate contamination as indicated by a 1951 sur-
vey of approximately 20,000 wells showing nitrate-concentrations greater
than 20 mg/1 in approximately 3,000 wells and some concentrations as high
as 1,000 mg/1. Large quantities of natural nitrate are present in the
soil system of this area and the porosity of the soil is low. Changed
climatic conditions have provided sufficient precipitation to raise the
water table, thus resulting in the dissolution of part of the soil ni-
trate. 106
Specific cases of ground-water contamination have been documented in a
number of states as well as some foreign countries. These cases represent
contamination due to natural causes and also those due to the activities
of man. The contaminations cover a wide range of concentrations from low
to very high nitrate-nitrogen values. The situation is one which should
receive attention because the problem is widespread and can be expected
to continue if proper plans for abatement are not Implemented.
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SECTION VII
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-660/3-75-030
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
NITROGEN IN THE SUBSURFACE ENVIRONMENT
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
M. L. Rowe and Susan Stinnett
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORG \NIZATION NAME AND ADDRESS
East Central Oklahoma State University
Ada, Oklahoma 7^820
10. PROGRAM ELEMENT NO.
IBA024
11. CONTRACT/GRANT NO.
Grant No. R801381
12. SPONSORING AGENCY NAME AND ADDRESS
U. S. Environmental Protection Agency
Robt. S. Kerr Environmental Research Laboratory
National Environmental Research Center
P. 0. Box 1198, Ada, Oklahoma 74820
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Increased quantities of various forms of nitrogen are being released to the soil
systems and higher concentrations of nitrogeneous compounds are consequently
making their way into subsoil regions. Knowledge of the behavior and fate of
nitrogeneous chemical species in the subsurface environment is needed by those
concerned with the prevention and control of ground-water pollution. This paper
presents information concerning the nature and origin of nitorgeneous substances
polluting ground water, the probable movement and reaction of nitrogeneous
compounds in the subsurface environment, and specific cases of ground-water
pollution by nitrogen-containing compounds.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Ground Water
Nitrogen Compounds
Water Pollution Effects
Nitrates
Nitrites
Subsoil
Subsurface Waters
Geochemistry
08/04
8. DISTRIBUTION STATEMENT
19. SECURITY CLASS (ThisReport)
21. NO. OF PAGES
20. SECURITY CLASS (Thispage)
22. PRICE
EPA Form 2220-1 (9-73)
U. S. GOVERNMENT PRINTING OFFICE: 1975-698-982 /9 REGION 10
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