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Aniaal life

INTERMEDIATE
PRODUCTS OF
‘Se COMPOSITION

INITIAL
PRODUCTS OF
DECOMPOSITION

Animal Vife

DECOMPGSITION
Nitrate aitrogen

(b) anaerobic decomposition

Figure 1. Nitrogen cycle


TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)

7. REPORT NO. 2 [3. RECIPIENT'S ACCESSIONNO.
EPA~660/3-75-030
4. TITLE AND SUBTITLE 5. REPORT DATE

NITROGEN IN THE SUBSURFACE ENVIRONMENT

l6. PERFORMING ORGANIZATION CODE

7. AUTHOR(S) Is. PERFORMING ORGANIZATION REPORT NO.
M. L. Rowe and Susan Stinnett

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. eAOs NO.
: 1BA02
East Central Oklahoma State University

Ada, Oklahoma 74820 71, CONTRACT/GRANT NO.
’ 7
Grant No. R80138]

12, SPONSORING AGENCY NAME AND ADORESS 13. TYPE OF REPORT AND PERIOD COVERED
U, S. Environmental Protection Agency Fina
Robt. S. Kerr Environmental Research Laboratory 14, SPONSORING AGENCY CODE

National Environmental Research Center
P. 0. Box 1198, Ada, Oklahoma 74820

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

a. DESCRIPTORS b.IDENTIFIERS/OPEN ENDED TERMS |c. COSATI Field/Group

Ground Water Nitrates 08/04
Nitrogen Compounds Nitrites

Water Pollution Effects Subsoil
Subsurface Waters
Geochemistry

18, DISTRIBUTION STATEMENT 19. SECURITY CLASS (This Report) 21, NO. OF Hoes
3

20. SECURITY CLASS (This page) 22, PRICE

EPA Form 2220-1 (9-73) U.S. GOVERNMENT PRINTING OFFICE: (975-698-982 19 REGION 10



70.

71.

72.

73.

74.

75.

76.

77.

78.

80.

81.

Kilmer, V. J. and J. C. Barber, Fertilizer Use and Misuse.
(Presented at Symposium on Nitrogen In Soll and Water,
Hespeler, Ontario, 1971.)

Smith, G, E, Fertilizer Nutrients as Contaminants in Water
Supplies. (Presented at American Assoctation for the Advance~
ment of Sctence Meeting, Washington, D. C., December 27, 1966.)

Miller, D. W., F. A. DeLuca, and T. L. Tessier. Ground Water
Contamination in the Northeast States. Environmental Protection
Agency. Washington, D. C. Publication Number EPA-660/2-74-056.
June, 1974, p. 219-272.

National Research Council. Accumulation of Nitrate. Washington,
D. C., National Academy of Sciences, 1972. p. 106,

Hanson, A. M. and G. F. Lee. Forms of Inorganic Nitrogen in
Domestic Wastewater. Journal Water Pollution Control Federation.
43:2271-2279, November, 1971.

Miller, D. W., F. A. DeLuca, and T. L. Tessier. Ground Water
Contamination in the Northeast States. Environmental Protection
Agency, Washington, D. C. Publication Number EPA-660/2-74-056.
June, 1974. p. 171.

Walker, W. H., T. R. Peck, and W. D. Lembke. Farm Ground Water
Nitrate Pollution--A Case Study. (Presented at American Society
of Chemical Engineers Annual and National Environmental Engineer-
ing Meeting. Houston, Texas. October 16-22, 1972.) p. 1516.

Boyle, W. C. and R. K. Ham. Biological Treatability of Landfill
Leachate. Journal Water Pollution Control Federation. 46:806-
872, May, 1974.

Miller, D. W., F. A. DeLuca, and T. L. Tessier. Ground Water
Contamination in the Northeast States. Environmental Protection
Agency, Washington, D. C. Publication Number EPA-660/2-74-056.
June, 1974. p. 22-25.

Schmidt, D. L. Soil Nitrification and Nitrates in Waters.
Public Health Reports. 71(5):497-503, 1956.

Christensen, M. H. and P. Harremoes. Biological Denitrification
in Water Treatment. Department of Sanitary Engineering. Tech-
nical University of Denmark. Report 2-72. 1972.

Broadbent, F. E. and F. Clark. Denitrification. In: Soil

Nitrogen, Agronomy Monograph 10, Bartholomew, W. V. (ed.).
Madison, American Society of Agronomy, 1965. p. 347-362.

31


pH, and soils with high organic contents are less efficient than mineral
soils with similar cationcexchange capacities. The ammonium fon can be

leached, however, through the soil profile If the cation exchange capacity
of the sofl ts satisfled.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 are negatively charged and the movement of
these species through the soi] 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 sotl solutton.!9 The deter-
minants of movement in the profile are the amount of water infiltrated
Tnto the soil, the soil moisture content at the start of the precipita-
tion event, the porosity of the soil, and its permeabl lity.? The nitrate
species is more stable than the nitrite and, therefore, is more commonly
encountered in soll and water systems, although investigations have con-
firmed the presence of the nitrite ion in a number of well water supplies.!1,12
Crabtree's investigation in Wisconsin showed that there was no clearly
defined relationship between the depth of the wel] and high nitrate con-
centration for the area, but a trend did exist between fncreasing nitrite
concentration and wel] depth, The highest incidence of nitrite occurred

most commonly in shallow and dug wells immediately after heavy precipi-
tation.

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 activitles.!! Some microorganisms
are capable of taking nitrogen directly from the air and converting it in-
to usable forms. There are estimates that some 44 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.

The tnorganic 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 jin caves

in close proximity to those streams.28,29,30

Rainfall and dust are two other natural sources of nitrogen which

should not be overJooked, Much nitrogen is added to the soi] by both
of these methods.3!,32,33,34,35 Rainfall, dew, and snow can contain

8


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, evapotranspiration 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 the 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 fung tion nor follows

the same metabolic pathway in all these organisms. 4 However, the

most significant nitrification appears to be accomplished by the autotrophs.

18


CONTENTS

Sectton
t ConcJustons
tt | Recommendat tons
ttt tntroduction
tv Forms and Sources of Nitrogen tn Ground Water

v Movement and Reactions of Nitrogen In the Subsurface
Enyt ronment

Movement of Gases

Movement of Non-Gaseous Nitrogen Compounds
Nitrtftcatton

Denttrificatton

VI Specific Incidents of Nitrogen Contamination in
Ground Water

VIL References

N Fw

13

15

18
20

22

25


48.

49.

50.

51.

52.

53.

54.

55.

56.

57.

Mielke, L. N., J. R. Ellis, N. F. Swanson, J. C. Lorimor, and T. M.
McCalla. Ground Water Quality in Fluctuation in a Shallow Uncon-
fined Aquifer Under a Level Feedlot. In: Relationship of Agri-
culture to Soil and Water Pollution, Proceedings of Cornell Univer-
sity Conference on Agricultural Waste Management. 1970. p. 31-40.

McCalla, T. M. Beef Cattle Feedlot Waste Management Research in
the Great Plains. (Presented at Control of Agriculture-related
Pollution in the Great Plains, Seminar. Lincoln, Nebraska. July
24-25, 1972.)

Lorimor, J. C., L. N. Mielke, L. F. Elliott, and J. R. Ellis. Ni-
trate Concentrations in Groundwater Beneath a Beef Cattle Feedlot.
Water Resources Bulletin. 8(5):999-1005, October, 1972.

Miner, J. R. and T. L. Willrich. Livestock Operations and Field
Spread Manure as Sources of Pollutants. Agricultural Practices and
Water Quality. Ames, lowa State University Press, 1970. p. 231-240.

Stewart, B. A., F. G. Viets, Jr., G. L. Hutchinson, W. D. Kemper,

and F. E. Clark. Distribution of Nitrates and other Water Pollutants
under Fields and Corrals in the Middle South Platte Valley of Colorado.
Agricultural Research Service. Publication Number ARS 41-134. De-
cember, 1967. 206 p.

Battelle Memorial Institute. Inorganic Fertilizer and Phosphate
Mining Industries - Water Pollution and Control. Environmental
Protection Agency. Publication Number 12020 FPD 09/71. September,
1971.

Nelson, L. B. Agricultural Chemicals in Relation to Environmental
Quality: Chemical Fertilizers, Present and Future. Journal of En-
vironmental Quality. 1(1):2-6, January-March, 1972.

Farrell, J. B. Nitrogen in Industry. (Presented at Symposium on
Nitrogen in Soil and Water. Hespeler, Ontario. March 30-31, 1971.)

Commoner, B., G. Shearer, and D. Kohl. Origins of Nitrates in Sur-
face Water, First Year Progress Report for a Study of Certain Eco-
logical, Public Health, and Economic Consequences of the Use of In-
organic Nitrogen Fertilizer. Center for the Biology of Natural

Systems, Washington University, St. Louis, Missouri. May 5, 1972.

Walker, W. H. Ground Water Nitrate Pollution in Rural Areas. Ground
Water. 11(5):19-22, Séptember-October, 1973.

29


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 7.5.36

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.

Ammonium fons, 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 agricultural ly-
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


Many denitrifiers 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, H2N20 or NO2NH2) have been postulated.

The strain of denitrifying organism determines which 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
denitrification is slow in acid but fast in alkaline media: it usually
occurs in soils of pH 6 or above. The relative amounts of N90 and No
produced are affected by temperature, with N20 being predominantly formed
at lower temperatures and Ng 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 N20 in the product,
while a ratio of 0:1 results in the predominance of No.

Conditions conducive to denitrification are commonly found in fine-tex-
tured, water-logged soils with high organic content. Water apparently

has a direct effect on denitrification, as the closer the soil is to sat-
uration, the more denitrification occurs there. Little occurs in soils
less than about 60 percent saturated.8! Because of this dependence on
high water content, it is probable that denitrification 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 in and above saturated zones beneath agricultural areas that

are fertilized with nitrates or irrigated with waters high in nitrate,
stnce nitrate is readily leached from upper soil layers. tn 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 denitrification alone.9/ High organic content is con-
ducive to denitrification, 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 denitrification also occurs
in nature, there is considerable debate over its mechanisms and its ex-
tent. Chemical denitrification 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 denitrification. Nelson and Bremner report that
nitrogen gas forms readily from reactions invglving deomposition of ni-
trite In acidic soils high tn organic matter. 9'

2)


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 fons 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.

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 evapotranspiration rates are reduced.
Denitrification may occur during the leaching process, as indicated in
studies of nitrate concentration beneath an irrigated field. 83

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


58.

60.

61.

62.

63.

64.

65.

66.

67.

68.

69.

Walker, W. H., T. R. Peck, and W. D. Lembke. Farm Ground Water
Nitrate Pollution--A Case Study. (Presented at American Society
of Chemical Engineers Annual and National Environmental Engineer-
ing Meeting. Houston, Texas. October 16-22, 1972.) 25 p.

Nightingale, H. 1. Nitrates in Soll and Ground Water Beneath
Irrigated and Fertilized Crops. Soil Science. 114(4):300,
October, 1972.

Feth, J. H. Nitrogen Compounds tn Natural Waters--A Review.
Water Resources Research. 2(1):41-58, January-February, 1966.

Johnston, W. R., F. Ittihadieh, R. M. Daum, and A. F. Pillsbury.
Nitrogen and Phosphorus in Tile Drainage Effluent. Soil Science
Society of America Proceedings. 29(3):287-289, 1965.

Fitzsimmons, D. W., G. C. Lewis, D. V. Naylor, and J. Busch.
Nitrogen, Phosphorus and other Inorganic Materials in Waters

in a Gravity !trrigated Area. Transactions of the American
Society of Agricultural Engineers. 15(2):292-295, March-April,
1972.

Bower, C. A., and L. V. Wilcox. Nitrate Content of the Upper
Rio Grande as Influenced by Nitrogen Fertilization of Adjacent
Irrigated Lands. Soil Science Society of America Proceedings.
33(6) 971-973, November-December, 1969.

Moe, P. G., J. V. Mannering, and C. B. Johnson. Loss of
Fertilizer Nitrogen in Surface Runoff Water. Soil Science.
104 (6) :389-394, December, 1967.

Aldrich, S. R. The Influence of Cropping Patterns, Soil
Management, and Fertilizer on Nitrates. (Presented at
Proceedings of the 12th Sanitary Engineering Conference

on miprete and Water Supply, Source and Control. February 11-12,
1970.

Pratt, P. F. Nitrate in the Unsaturated Zone under Agricultural
Lands. Environmental Protection Agency. Publication Number
EPA 16060 DOEO#/72. April, 1972. 45 p.

Shaw, E. C. and P. Wiley. Nitrate lon Concentration in Well
Water. California Agriculture. 23:11, May, 1969.

Reinhorn, T. and Y. Avinmelech. Nitrogen Release Associated
with the Decrease in Soil Organic Matter in Newly Cultivated
Soils. Journal of Environmental Quality. 3(2):118-121, April-
June, 1974.

Carter, D. L, J. A. Bondurant, and C. W. Robbins. Water-Soluble
NO3. Nitrogen, P0,-Phosphorus, and Total Salt Balances on a Large
Irrigation Tract. Soil Science Society of America Proceedings,
35(2) :331-335, March-April, 1971.

30


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 abgut 90 percent of this material is disposed of in landfill
sites.16,75 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.!6 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.23
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./8 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


SECTION tII

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 forms.! 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.2 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.


23.

24,

25.

26.

27.

28.

29.

30.

31.

32.

33.

34.

35.

Malo, B. A. and E. R. Purvis. Soil Absorption of Atmospheric Ammonia.
Soll Science. 97:242-274, April, 1964.

Hanawalt, R. B. Environmental Factors Influencing the Sorption of
Atmospheric Ammonia by Soils. Soil Science Society of America Pro-
ceedings. 33(2):231-234, March-April, 1969.

Smith, G. E. Why Nitrates in Water Supplies. Hoard's Dairyman.
110(18) : 1048-1049, September 25, 1965.

Bremner, J. M. Organic Nitrogen in Soils. In: Soil Nitrogen,
Agronomy Monograph 10, Bartholomew, M. V. (ed.). Madison, American
Society of Agronomy, 1965. p. 93-149.

Goldberg, M. C. Sources of Nitrogen in Water Supplies. In: Agri-
cultural Practices and Water Quality. Ames, lowa University Press,
1970. p. 94-124.

Riley, T. M. Our Mineral Resources. New York, John Wiley & Sons,
Inc. 1959. 338 p.

Smith, G. E. Nitrate Pollution of Water Supplies. In: Trace Sub~
stances Environmental Health-3, Proceedings of University of Missouri's
3rd Annual Conference, 1970. p. 273-287.

Hutchinson, G. E. Nitrogen Bio-Geo-Chemistry of the Atmosphere.
Bio-chemistry American Scientist. 32:178-195, 1944.

Olsen, R. J., R. F. Hensler, 0. J. Attoe, J. Osborne, and S. A. Wit-
zel, Comparison of Inorganic Nitrogen Contents of Undisturbed, Cul-
tivated, and Barnyard Soil Profiles in Wisconsin. Soil Science
Society of America Proceedings. 34(4):699-701, July-August, 1970,

Allen, S. E., A. Carlisle, E. J. White and C. C. Evans. Plant Nu-
trtent Content of Rainwater. Journal of Ecology. 56(2):497-504,
1968.

Herman, F. A. and E. Gorham. Total Mineral Activity Acidity, Sul-
fur, and Nitrogen in Rain and Snow at Kentville, Nova Scotia. Tel-
lus (Sweden). 9:180-183, 1957.

Erikson, E. Composition of Atmospheric Precipitation: 1. Nitrogen
Compounds. Tellus(Sweden). 4:215-232, 1952.

Angstrom, A. and L. Hogberg. The Content of Nitrogen (Ammoniacal

Nitrogen and Nitrite Nitrogen) in Atmospheric Precipitation. Tel-
lus(Sweden). 4:31-42, 1952.

27


samples were above 5 mg/l and the highest value was 38 mg/1.17 Another
case of interest in the state of Colorado is a Colorado city of 7,500
people where a shallow aquifer water FapPly had reached nitrate levels
of over 60 mg/1 (as nitrate) by 1962. !0:

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./9 :

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./2 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 aquiffers 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 195] sur-
vey of approximately 20,000 wells showing nitrate-concentrations greater
than 20 mg/l 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.

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.

24


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


ACKNOWLEDGEMENTS

This report was prepared by the staff of the School of Environmenta]
Science, East Central Oklahoma State Untverstty and funds were pro-
vided by the Envfronmental Protection Agency Grant Number R801381,

The authors would Jike to acknowJedge 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
materfals used In the preparation of this report

Linda Merryman and Jeanette Cook deserve special mentton 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


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 mathepatical review of the kinetics of transport is
provided by Garner. 1

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


SECTION I]

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.


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, Srepping practices, season of the year,
and soil treatment 84,85 ,86,87,8 The 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 be medium-
textured, limed soils of the midwestern United States. 't 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.87 The optimum temperature range for nitrifying bacteria has
been reported as 30-35° C, with little nitrification occurring above
4o° c.84 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 45 percent of the dry weight in clays. Apparently,
there is an abrupt reducgion in nitrification as the soil becomes nearly
saturated with moisture.97 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.89 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.
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. tn the United States, for example, nitrite

19


EPA-660/3-75-030
JUNE 1975

Ecological Research Series



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.


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.» 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:!0 Approximately 2000 cases have been reported
in North America and Europe with a fatality rate of 7 to 8 percent.
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 fon.!] 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.11,12 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/l nitrate as nitrogen, for
municipal water supplies.2»!3 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. !2,14
These anions have been shown to inhibit iodine and vitamin A metabolism

in research animals.!5


10.

12.

13.

14,

16.

7.

18.

19.

20.

21.

22.

Smith, G. E. Nitrate Problems in Plants and Water Supplies in
Missouri. (Presented at Second Annual Sympostum on the Relation
of Geology and Trace Elements to Nutrition, 92nd Annual Meeting of
the American Public Health Association. New York City. October 7,
1964.) 21 p.

Keller, W. D. and G. E. Smith. Ground-Water Contamination by Dis-
solved Nitrate. The Geological Society of America. Special Paper
90. 1967. p. 47-56.

Crabtree, K. T. Nitrate and Nitrite Variation in Ground Water.
Department of Natural Resources, Madison, Wisconsin. Technical Bul-
letin No. 58. 1972. p. 2-22.

Abbott, G. A. High Nitrates in Drinking Waters and Their Toxicity

to Infants. In: Annual Proceedings, North Dakota Academy of Science.
1949. p. 51-54.

Case, A. A. Some Aspects of Nitrate Intoxication in Livestock.
Journal of the American Veterinary Medical Association. 130(8):
323-328, 1957.

Grundman, J. E. Nitrates Danger for Humans, Too. Missouri Rural-
ist. p. 24-25. February 27, 1965.

National Research Council. Accumulation of Nitrate. Washington,
D. C., National Academy of Sciences, 1972. p. 5-23.

Stewart, B. A., F. G. Viets, Jr., G. L. Hutchinson, and W. D. Kemper.
Nitrate and other Water Pollutants under Fields and Feedlots. En-
vironmental Science and Technology. 1:736-739, September, 1967.

Coffee, R. C. and W. F. Bartholomew. Some Aspects of Ammonia Sorp-
tion by Soil Surfaces. Soil Science Society of America Proceedings.
28(4) :485-490, July-August, 1964.

Schmidt, K. D. Nitrate in Ground Water of the Fresno-Clovis Metro-
politan Area, California. Ground Water. 10(1)50:61, January-
February, 1972.

Delwiche, C. C. The Nitrogen Cycle. Scientific American. 223(3):
69, September, 1970.

DeRossi, G. LaFisszione del Azote Atmospherico el Terreno. Annali
Della Facolta di Agraria (Milan). 3:140-175, 1945.

Ingham, G. J. Effect of Minerals Absorbed from the Atmosphere in
Maintaining Soil Fertility. Soil Science. 70:205-212, 1950.

26


SECTION VII
REFERENCES

Engberg, R. A. The Nitrate Hazard in Well Water. Nebraska Water
Survey Paper 21. 1967. p. I-Il.

Lenain, A. F. The Impact of Nitrates on Water Use. Journal of the
American Water Works Association. 59:1050-1051, August, 1967.

Dunlap, W. J. and J. F. McNabb. Subsurface Biological Activity in
Relation to Ground Water Pollution. Environmental Protection Agency,
Ada, Oklahoma. Publication Number EPA-660/2-73-014. September,
1973. p. 4-5.

_ Miller, D. W., F. A. DeLuca, and T. L. Tessier. Ground Water Con-

tamination in the Northeast States. Environmental Protection Agency,
Washington, D. C. Publication Number EPA-660/2-74/056. June, 1974.
p. 8-22.

Preul, H. C. and G. S. Schroepfer. Travel of Nitrogen in Soils.
Journal Water Pollution Control Federation. 40:30-48, January, 1968.

Corey, J. C., D. Kirkham, and D. R. Nielsen. The Movement of Chlor-
ide and Nitrate through Certain lowa Soils. lowa Academy of Science.
74:131-141, 1967.

Christy, M., J. R. Brown, and L. S. Murphy. Nitrate in Soils and
Plants Guide. Columbia, University of Missouri Extension Division,
1965. p. 9804-9806.

Winton, E. F., R. G. Tardiff, and L. J. McCabe. Nitrate in Drinking
Water. Journal of the American Water Works Association. 63:93-98,
1971.

Subbotin, F. N. Nitrates in Drinking Water and Their Effect on the

Formation of Methemoglobin. S. M. Kirov Order of Lenin Army Medical
Academy (USSR). 25(2) :63-67, 1961.

25


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 fon 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.


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 soil.

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 ark review of the techniques

used is given by McGarity and Rajaratnam. 2 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 so#l] 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


94.

95.

96.

97.

98.

99.

100.

101.

102.

103.

104.

Jansson, S. L. Use of 15y in Studies of Soil Nitrogen. In: Soil
Biochemistry, Vol. 2, McLaren, A. D. and J. Skujins (ed.). New
York, Marcel Dekker, Inc., 1971. p. 129-162.

Felbeck, G. T., Jr. Chemical and Biological Characterization of
Humic Matter. In: Soil Biochemistry, Vol. 2, McLaren, A. D. and
J. Skujins (ed.). New York, Marcel Dekker, Inc., 1971. p. 36-57.

Schnitzer, M. Characterization of Humic Constitutents by Spectros-~
copy. In: Soil Blochemistry, Vol. 2, McLaren, A. D. and J. Skujins
(ed.). New York, Marcel Dekker, Inc., 1971. p. 60-93.

Kurtz, L. T. The Fate of Applied Nutrients on Soils. Journal of
Agricultural and Food Chemistry. 18(5):773-780, 1970.

Nelson, D. W. and J. M. Bremner. Gaseous Products of Nitrite De-
composition in Soils. Soil Biology and Biochemistry. 2(3):203-
215, 1970,

Baars, J. K. Experiences in the Netherlands with Contamination of
Ground Water. In: Groundwater Contamination, Proceedings of 1961
Symposium held in Cincinnati, Ohio, April 5-7, 1961. Cincinnati,
U. S. Public Health Service, Robert A. Taft Sanitary Engineering
Center, Technical Report W61-5, 1961, p. 56-63.

Ballentine, R. K., S. R. Reznik, and C. W. Hall. Subsurface Pol-
lution Problems in the United States. Environmental Protection
Agency, Washington, D. C. Report TS-00-72-02. May, 1972. p. 14-15.

Walker, W. H. Ground Water Nitrate Pollution in Rural Areas.
Ground Water. 11(5):111-112, September-October, 1973.

Larson, T. E. Occurrence of Nitrate in Well Waters. University
of Illinois Water Resource Center, Urbana, Project 65-05G. June,
1966. p. 5-6.

Woodward, F. L. Ground Water Contamination in the Minneapolis and
St. Paul Suburbs. In: Groundwater Contamination, Proceedings of
1961 Symposium held at Cincinnati, Ohio, April 5-7, 1961. Cin-
cinnatt, U. S. Public Health Service, Robert A. Taft Sanitary Eng-
Ineering Center, Technical Report W61-5, 1961. p. 56-63.

Flynn, J. M. Impact of Suburban Growth of Ground Water Quality in
Suffolk County, New York. In: Groundwater Contamination, Pro-
ceedings of 1961 Symposium held in Cincinnati, Ohio, April 5-7,
1961. Cincinnati, U. S. Public Health Service, Robert A. Taft
Santtary Engtneertng Center, Technical Report W61-5, 1961. p. 56-

33


105.

106.

Winton, E. F. The Health Effects of Nitrates in Water. In: Pro-
ceedings 12th Sanitary Engineering Conference on Nitrate and Water
Supply: Source and Control, University of Illinois, February 11-12,

1970. Urbana, tllinois University, College of Engineering, 1970.
p. 55.

Jones, D. C. An Investigation of the Nitrate Problem in Runnels
County, Texas. Environmental Protection Agency, Washington, D. C.
Publication Number EPA-R2-73-267. June, 1973. p. 1-8.

34


SECTION VI

SPECIFIC INCIDENTS OF NITROGEN CONTAMINATION IN GROUND WATER

The detection of nitrogen contamination in ground-water supplfes Is not
new, as Abbott points out in one of his articles. Data obtained jn the
lowa Water Survey made tn 1935-36 showed that in 200 water samples ana-
lyzed, nitrate values varied from 0-125 mg/] 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.

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 fons 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/] of nitrogen.

Ballentine discusses a survey conducted in the state of I]linois 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. Walker also reports that chemical analysis of ground-
water samples from throughout I]linois indicated that nitrate pollution

in aquifers was widespread, especially in rural parts of the state. In
Washington, County, I1linois, 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, !]linois,
only 3 of 201 samples showed nitrate concentrations greater than 18 mg/l.
Two of these 3 samples showed nitrate values greater than 45 mg/1, 102

tn 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 Ina
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/]
nitrate-nitrogen. 10

22


ABSTRACT

Increased quantittes of yartous forms of nftrogen are being
released to the sot] systems and higher concentrattons of
nftrogeneous compounds are consequently maktng thetr way fnto
subsoil regtons. Knowledge of the behavtor and fate of nitro-
geneous chemtca] spectes tn the subsurface environment fs needed
By those concerned with the preventton and contro] of ground-
water poljutton, This paper presents tnformatton concerning the
nature and orfgin of nttrogeneous substances polJuting ground
water, the probable movement and reaction of nitrogeneous com-
pounds tn the subsurface environment, and spectfic cases of
ground water pollutton by nitrogen-containing compounds,

Thts report was submitted tn fulfi]Iment of Grant Number R80J38]
By the Schoo] of Envtronmental Science, East Central Oklahoma
State University, Ada, Oklahoma, under the sponsorshtp of the
Environmental Protection Agency. The work was completed as of

May, 1975.


various forms of nitrogen, and Walker indicates that the nitrogen
additions by this method may be as much as 7 ki loggams 435 pounds)

of nitrogen per acre per year in some localities.7°??/> 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 ang some can be attributed to salts
formed in the atmosphere. 3 240,41,42,43

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.3/>

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.47,48,49 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 .29991 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.22

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 Song 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.!0 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 feggilizers constitute the
largest share of the fertilizer market. 8, 54,55

This topic has been and will continue to be a controversial issue.
Investigations of nitrogen levels in central !llinois indicate a
correlation between the usage of nitrogen fertilizers and levels of


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 5.4 kilograms

(11.9 pounds) per year, 16 If 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 gallons). 6,75 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 occurs. 16

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 contaminagjon 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. !6,36,74 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./5 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.

VW


EPA-660/3-75-030
JUNE 1975

NITROGEN IN THE SUBSURFACE ENVIRONMENT

By

M, L. Rowe
Susan Stinnett
School of Environmental Sclence
East Central Oklahoma
State University
Ada, Oklahoma 74820

Grant No. R801381
Program Element 1BA024
ROAP 21AKQ/Task 14

Project Officer

Marton R. Scalf
Robert S,. Kerr Environmental Research Laboratory
National Environmental Research Center
P. 0. Box 1198
Ada, Oklahoma 74820

NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
U. S. ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OREGON 97330
7


82.

83.

84,

85.

86.

87.

88.

89.

90.

91.

92.

93.

McGarity, A. W. and J. A. Rajartnam. Apparatus for the Measure-
ment of Losses of Nitrogen as Gas from the Field and Simulated
Field Environments. Soil Biology and Blochemistry. 5(1):131-132,
January, 1973.

Meek, D. D., L. B. Grass, and A. J. Mackenzie. Applied Nitrogen
Losses in Relation to Oxygen Status in Soils. Soil Science Society
of America Proceedings. 33(4):575-578, July-August, 1969.

Alexander, M. Nitrification. In: Soil Nitrogen, Agronomy Mono-
graph 10, Bartholomew, W. V. (ed.). Mad?son, American Society of
Agronomy, 1965. p. 309-346.

Mahendrappa, M. D., R. L. SMith, and A. T, Christiansen. Nitrify-
ing Organisms Affected by Climatic Region in Western United States.
Soil Science Soctety of America Proceedings. 30(1):60-62, January-
February, 1966.

Sabey, B. R. Influence of Soil Moisture Tension on Nitrate Ac-
cumulation in Soils. Soil Science Society of America Proceedings.
33(2) :263-266, March-April, 1969.

Parker, D. T. and W. E. Larson. Nitrification as Affected by Temp-
erature and Moisture Content of Mulched Sofls. Soil Science Society
of America Proceedings. 26(3):238-242, May-June, 1962.

Campbell, C. A., W. A, Ferguson, and F. G. Warder. Winter Changes
in Sof] Nitrate and Exchangeable Ammonium, Canadian Journal of
Sotl Sctence. 50:151~-162, 1970.

McLaren, A. D. and J. Skujins. Trends in the Biochemistry of Ter-
restrial Soils. In: Soil Biochemistry, Vol. 2, McLaren, A. D.
and J. Skujins (ed.). New York, Marcel Dekker, Inc., 1971. p. I-15.

Marshall, K. C. Sorptive Interactions Between Soil Particles and
Microorganisms. In: Soil Biochemistry, Vol. 2, McLaren, A. D. and
ii Skujins (ed.). New York, Marcel Dekker, Inc., 1971. p. 409-

2.

Alexander, M. Microorganisms and Chemical Pollution. Bioscience.
23 (9) :509-515, 1973.

Good, J. M. and R. L. Carter, Nitrification Lag Following Soil
Fumigation. Phytopathology. 55(10):1147-1150, 1965.

Van Dijk, H. Colloid Chemical Properties of Humic Matter. In:
Soil Biochemistry, Vol. 2, McLaren, A. D. and J. Skujins (ed.).
New York, Marcel Dekker, Inc., 1971. p. 16-33.

32


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 fhese 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 jn 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, tf the ammonium con-

centration is not limiting and if conditions are favorable for nitrifi-
cation.

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-(trichloromethy!) pyridine, by steam, or by chem-
ical fumigants such as technical dichloropropengs or a mixture of methyl
bromide, chloropicrin and propargyl bromide. 1,32 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 resistant to biological breakdown, and they remain in stable humus
material. Humus is colloidal in nature, and this may further decrease its
biological reactivity.7°° 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.9. 95,96

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 is Inhibited by oxygen, and it rarely occurs in dry,
well-aerated sofl. .

20


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 envi ronmental
technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in
related fields. The five series are:

Environmental Health Effects Research
Environmental Protection Technology
Ecological Research

« Environmental Monitoring
Socioeconomic Environmental Studies

OPW

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.


36.

37.

38.

39.

40.

AL.

42,

43.

Ah,

45.

46.

47,

Keeney, D. R. and L. W. Walsh. Available Nitrogen In Rural Eco~
systems: Sources and Fate. Hortscience. 7(3) 219-223, June, 1972.

Luebs, R. A., K. R. Davis, and A. E. Lang. Enrichment of the At-
mosphere with Nitrogen Compounds Volatilized from a Large Dairy
Area. Journal of Environmental Quality 2(1):137-141, January-March,
1973.

Dawes, J. H., T. E. Larson, and R. H. Harmeson. Nitrate Pollution
of Water. In: Frontiers in Conservation. Proceedings of the 24th
Annual Meeting of the Sofl Conservation Society of America, August,
1969.- Fort Collins, Colorado State University, 1970. p. 94-102.

Keeney, D. R. and L. W. Walsh. Available Nitrogen in Rural Eco-
systems: Sources and Fate. Hortscience. 7(3):492, June, 1972.

Stevenson, F. J. Origin and Distribution of Nitrogen in Soil, In:
Soil Nitrogen, Agronomy Monograph 10, Bartholomew, W. V. (ed.).
Madison, American Society of Agronomy, 1965. p. 1-42.

Stefanson, R. C. Evolution Patterns of Nitrous Oxide and Nitrogen
in Sealed Soil~Plant Systems. Soil Biology and Biochemistry. 5:
167-170, January, 1973.

Brezonik, P. L. Nitrogen Sources and Cycling in Natural Waters.
Environmental Protection Agency, Gainesville, Florida. Publication
Number EPA~660-3-73-002. 1973.

Hutchinson, G. L. and F. G. Viets, Jr. Nitrogen Enrichment of Sur-
face Water by Absorption of Ammonia Volatilized from Cattle Feed-
lots. Science. 166(3904):514-515, October, 1969.

Lipper, R. I., J. R. Miner, and G. H. Larson, Cattle Feedlot Waste
Problems. (Presented at Oklahoma Cattle Feeders Seminar. Still-
water. February 2-3, 1967.) 9p.

Viets, F. G. and R. H. Hazeman. Factors Affecting the Accumulation
of Nitrate in Soil, Water, and Plants. Agriculture Handbook Num-
ber 413. United States Department of Agriculture. November, 1971.
63 p.

Gillham, R. W. and L. R. Webber. Nitrogen Contamination of Ground~
water by Barnyard Leachates. Journal Water Pollution Control Fed-
eration. 41:1752-1762, October, 1969.

Butchbaker, A. F., J. E. Ganton, G. W. A. Mahoney, and M. D. Paine.
Evaluation of Beef Cattle Feedlot Waste Management Alternatives.
Environmental Protection Agency, Stillwater, Oklahoma. Publication
Number EPA-13040 FX611071. November, 1971. 322 p.

28


A comprehensive study by the Minnesota Department of Health in the
Minneapolis-St. Pau] area consisted of collection of random samples from
63,000 wells which seryed more than 250,000 people.!03 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 1960 of 665,000, About
59 percent of the population obtains water from 90 communal or public
water supplfes. 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 perfod 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/] nitrate-nitrogen. 10!

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. /> 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 sttes.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/l or more throughout the
period, 12 The variations tn nitrate concentration were closely related to
the amount of precipitation and concentratlon was highest during heavy
rainy seasons and Jowest during dry perlods 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/I and only 2 samples contained as much as ]
mg/l. 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


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 ions.16 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
jons to be held in the soil profile by the negatively charged soil
micelles.!8 In general, clay soils hold ammonium ions more efficiently
than sandy soils, soils of low pH more efficiently than those of high

7


nitrate found in the rivers of the area. Walker's work in Illinois
also reveals the close correlation that occurs between fertilizer usage
in Illinois and levels of nitrate in ground water.2/558 Dependency

of the ground-water nitrate levels on the fertilizer management practices
for cropping systems in the California area are indicated.59,60,61,

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. 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.°2 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 fertilizers.64,65

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, 5961 ,66,67
It appears that heavy application on highly permeable soils has conte pbuted
significant amounts of nitrogen to underground water supplies .60, 62,6
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

ggme localities even a major potential source of nitrogen contamination.56,65,
9,70 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.

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, 472,73 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.54 Investigations by Keeney show that the
nitrogen content of urban runoff is sometimes higher than the nitrogen
content of sewage.