mum
EPA-SAB-73-ooi
December 1973
NITROGENOUS
COMPOUNDS in the
ENVIRONMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
Washington, D.C. 20460
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EPA-SAB-73-001
December 1973
NITROGENOUS COMPOUNDS
IN THE ENVIRONMENT
by the
Hazardous Materials Advisory Committee
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON D.C. 20460
For sole by the Superintendent ot Documents, U.S. Government Printing Office, Washington, D.C. 20402
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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 consti-
tute endorsement or recommendation for use.
ii
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HAZARDOUS MATERIALS ADVISORY COMMITTEE
Dr. Emil M, Mrak, Chairman
Chancellor Emeritus
University of California at Davis
Dr. William J. Darby, Cochairman
President, Nutrition Foundation and
Chairman, Department of Biochemistry
Vanderbilt University, Nashville
Mr. Errett Deck
Chairman, Legislative Committee
Association of American Pesticide
Control Officials
Washington State Department of
Agriculture, Olympia
Dr. Leon Golberg
Scientific Cirector, Research
Professor of Pathology
Institute of Experimental Pathology
and Toxicology
Albany Medical College
Dr. Frank Golley
Executive Director and Professor
of Zoology, Institute of Ecology
University of Georgia at Athens
Dr. Gordon E. Guyer
Chairman, Department of
Entomology
Michigan State University, East Lansing
Mr. Roger P- Hansen
Executive Director
Rocky Mountain Center on
Environment, Denver
Dr. Paul E. Johnson
Executive Secretary, Food and
Nutrition Board
National Academy of Sciences
Washington, D.C.
Dr. Norton Nelson
Director, Institute of
Environmental Medicine
New York University
Medical Center, New York City
Dr. Ruth Patrick
Chairman, Department of
Limnology
Academy of Natural Sciences,
Philadelphia
Dr. William R. Rothenberger
Agricultural Production
Specialist
Rothenberger Farm
Frankfort, Indiana
Dr. Earl Swanson
Professor of Agricultural
Economics
University of Illinois at
Urbana-Champaign
Dr. Wilson K. Talley
Assistant Vice-President
University of California at Berkeley
Dr. W. Leonard Weyl
Chief of Surgery,
Northern Virginia Doctors
Hospital
Arlington, Virginia
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Regular Consultants
Dr. Dale R. Lindsay
Associate Director of Medical
and Allied Health Education
Duke University, Durham
Dr. Caro Luhrs
Medical Advisor to the Secretary
U.S. Department of Agriculture
Washington, D.C.
Dr. Lloyd B. Tepper
Associate Commissioner
for Science
Food and Drug Administration
Washington, D.C.
Mr. James G. Terrill, Jr.
Manager, Environmental
Consulting
Westinghouse Electric, Pittsburgh
Dr. Winfred F. Malone
Staff Science Advisor
Staff
Mr. W. Wade Talbot
Executive Officer
Mrs. Dorothy I. Richards
Administrative Assistant
Environmental Protection Agency, Washington, D.C.
iv
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STUDY: NITROGENOUS COMPOUNDS IN THE ENVIRONMENT
Consultants and Authors
Dr. Earl R. Swanson, STUDY COORDINATOR
Professor of Agricultural Economics
Department of Agricultural Economics
University of Illinois at Urbana-Champaign
Dr. Samuel R. Aldrich
Professor of Soil Fertility Extension
Department of Agronomy
University of Illinois at Urbana-Champaign
Dr. William J. Darby
President, Nutrition Foundation, Inc.
New York City
Dr. William B. Davis
William B. Davis and Associates
Consulting and Analytical Services
Bryan, Texas
Mr. Errett Deck
Chairman, Legislative Committee
Association of American Pesticide Control Officials
Washington State Department of Agriculture, Olympia
Mrs-. Mary Ellis
Office of the Associate Commissioner
for Science
Food and Drug Administration
Rockville, Maryland
Dr. Dale R. Lindsay
Associate Director of Medical and
Allied Health Education
Duke University Medical Center, Durham
Dr. Alan C. Lloyd
Assistant Director
California Air Pollution Control Center, Riverside
Dr. Caro Luhrs
Medical Advisor to the Secretary
Office of the Secretary
U.S. Department of Agriculture
Washington, D.C.
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Dr. Norton Nelson
Director, Institute of Environmental
Medicine
New York University Medical Center
New York City
Dr. John C. Nye
Extension Agricultural Engineer
in Waste Management
Purdue University, Lafayette
Dr. Ruth Patrick
Chairman, Department of Limnology
Academy of Natural Sciences, Philadelphia
Dr. James N. Pitts, Jr.
Director
Statewide Air Pollution Control Center
University of California at Riverside
Dr. William R. Rothenberger
Agricultural Production Specialist
Rothenberg Farm
Frankfort, Indiana
Dr. Joseph Simon
Professor of Veterinary Pathology and Hygiene
College of Veterinary Medicine
University of Illinois at Urbana-Champaign
Mr. James G. Terrill, Jr.
Manager, Environmental Consulting
Westinghouse Electric, Pittsburgh
Dr. Frank B. Viets, Jr.
Chief Soil Scientist
USDA Nitrogen Laboratory
Fort Collins, Colorado
Dr. Harold Wolf
Director, Dallas Water Reclamation
Research Center
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PREFACE
The Hazardous Materials Advisory Committee pro-
vides independent and expert advice to the Admin-
istrator of the Environmental Protection Agency on
scientific and policy matters pertaining to haz-
ardous materials in the environment. Early in
1972, the Committee began a study concerning the
sources and effects of nitrogenous compounds in
the environment.
The principal objective of the study is to
inform the Administration about the nature of the
problem and the perceived needs in terms of moni-
toring, research, and regulation.
Each section of the report was prepared by spe-
cialists in the various areas. Following a review
of the report by members of the Hazardous Materi-
als Advisory Committee in early 1973, Dr. Norton
Nelson prepared the committee statement. It rep-
resents the best judgment of the committee relat-
ing to the possible development of policy regard-
ing this matter.
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TABLE OF CONTENTS
Preface
Table of Contents ix
Statement of Hazardous Materials Advisory Ccmnittee 1
Abstract 13
Sources of Nitrogenous Compounds and Methods of Control
Municipal and Solid Wastes - Harold Wblf 15
Discharges into Atmosphere - James N. Pitts and
Alan C. Lloyd 43
Crop Production - Frank B. Viets, Jr. and
Samuel R. Aldrich 67
Animal Wastes - John C. Nye 95
Major Industrial Processes - William B. Davis 111
Environmental and Health Effects of Nitrogenous Compounds
Aquatic Systems - Ruth Patrick 127
Animal Health - Joseph Simon 141
Human Health - Caro E. Luhrs 159
Analytical Procedures - Mary K. Ellis 175
ix
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COMMITTEE STATEMENT
THE MANY FORMS OF NITROGEN are an integral part of our natural
environment. A number of nitrogenous compounds are essential
parts of all living systems. Partly for this reason, there has
been since life began, an enormous natural nitrogen cycle in
which nitrogen moves through the soil, water, atmosphere, and a
myriad of life forms. These cycles are complex and involve enor-
mous quantities of nitrogen, totalling millions of tons each
year.
In part, it is this integral relationship to life that has pro-
duced local disturbances caused by excessive loads at certain lo-
cations within the nitrogen cycle in many places around the world.
Non-biological factors—erosion, weather, and lightning—also con-
tribute to the nitrogen cycle. The need to use fertilizers to im-
prove agricultural productivity, in order to feed the larger popu-
lations that cluster more and more near urban centers, plays its
part in altering the movement of nitrogen through the environment.
Other sources of disturbances due to excessive enrichment have
arisen through energy production. Combustion processes generally
lead to the formation of nitrogen oxides produced from atmospher-
ic nitrogen. Accordingly, the internal combustion engine, heat-
ing, and power production from fossil fuels are all significant
contributors to alterations in the nitrogen cycle.
The growth in population; the concentration in and around urban
centers; and the need to produce food, to keep warm or cool, to
produce electricity, and to move about in our automobiles are all
capable of adding to the nitrogen load that must be assimilated
by the environment. Most of the manifestations tend to be local-
ized. The significance of these disturbances has begun to be
recognized only recently.
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At present, all known trends appear to be ones that can be man-
aged and kept within control, if appropriate steps are taken now.
In the following sections of this statement, some of these major
responses that are needed will be identified. Each of the papers
in this report should be examined for details on the present
status and on the responses needed, in relation to man's effect
on the movement of nitrogen through the environment.
MUNICIPAL DISCHARGES INTO WATER AND SOLID WASTE
Human wastes constitute a major contribution to the nitrogen
burden in water. For example, the nitrogenous material discharged
from sewage-treatment plants in the United States amounts to 0.45
million metric tons per year. This quantity could raise the
nitrogen content of that third of the total annual precipitation
in the United States which is used by man up to the limit set by
the Public Health Service for nitrogen in drinking water—10 mil-
ligrams per liter.
The problem at present in many areas is the concentration of
several discharges into restricted parts of waterways. The tech-
nology for the denitrification of such discharges is still primi-
tive and inadequate. The recovery of nitrogen for useful purposes
(say, in agriculture) is still not generally economical from the
producer's standpoint.
In monitoring the efficiency of waste-water treatment plants,
the critical problem is the fact that the commonly employed bio-
chemical oxygen demand (BOD) test does not measure nitrogen
reduction.
The undesirable consequences of municipal discharges are:
(1) in some areas, the nitrogen concentration in drinking water
is raised to an unacceptable level; and (2) such discharges can
contribute to increased nutrient levels in natural waters to such
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a degree that this leads to undesirable biological changes, such
as algal blooms.
To improve municipal sewage-treatment systems:
1. Greater consideration should be given to the effectiveness of
the denitrification process in the design and operation of
sewage-treatment plants.
2. Tests for nitrogen species should be conducted in order to
monitor the effectiveness of nitrogen reduction in sewage-
treatment plants.
3. The nitrification effects in the biochemical oxygen demand
(BOD) test should be eliminated.
4. Improved procedures, for denitrification need to be developed.
5. Effective and economical means1 for collecting and converting
nitrogenous wastes in wastewaters and slidge into useful pur-
poses are also needed.
A secondary municipal source of nitrogenous material reaching
ground and other waters is that which is leached from sanitary
landfills. The resolution of this problem will require:
1. More thoughtful planning in determining where landfills can
be located safely, without leading to undesirable nitrogen
discharges into local waters.
2. The development of techniques for inserting covers that are
water-impermeable but are gas-permeable, in order to prevent
the contamination of local water.
NITROGEN DISCHARGES INTO THE ATMOSPHERE
The presence in and movement through the atmosphere of nitrogen
compounds is part of the natural nitrogen cycle. As noted previ-
ously, however, man has altered this cycle, at least locally, in
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a number of ways. Of prime importance is the oxidation of atmo-
spheric nitrogen during combustion processes into the nitrogen
oxides, primarily nitric oxide (NO) and nitrogen dioxide (N02)•
Enormous quantities of these oxides are formed by combustion in
space heating, power production, and the operation of internal
combustion engines.
Nitrogen dioxide is directly toxic to man. At relatively low
concentrations, it can contribute to respiratory disease. In
addition, it is directly involved in the formation of photochemi-
cal smog through a series of complex atmospheric and photochemi-
cal reactions. These can produce nitrous and nitric acids, too;
also, peroxyacetyl nitrate (PAN)—which, like N02, produces plant
damage, but at much lower concentrations. As air pollutants, the
nitrogen oxides have received prominent attention in federal air-
pollution legislation. Major steps aimed at control are now
under way. The technology for such control, however, appears to
be inadequate in terms of efficiency as well as cost. Also, the
data correlating ambient levels of nitrogen oxides, particularly
nitrogen dioxide, with adverse health effects are inconclusive.
These requirements are evident:
1. The human health effects of nitrogen oxides and PAN need fur-
ther study, particularly for long-term exposures to ambient
levels of these pollutants.
2. The synergisms for humans and for plants between these com-
pounds and other air pollutants also need further study.
3. The chemical and physical transformations of these compounds,
as well as nitrous and nitric acid, need further study under
real and simulated atmospheric conditions.
4. More effective and economical control procedures for limiting
the discharge of nitrogen oxides must be sought for combus-
tion processes (power production, space heating, the internal
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combustion engine, and so on).
5. Measures must be taken to insure that the use of control
devices (catalytic converters on automobiles) do not add
additional pollutants (NH3 and N20) to the atmosphere.
DISCHARGES OF NITROGEN INTO THE ENVIRONMENT FROM CROP PRODUCTION
The use of nitrogen-containing fertilizers has been a major
source of the substantial increase in agricultural productiv-
ity over the last century in the United States. Our nation's
food supply would be greatly affected by a drastic curtailment
in the use of nitrogen fertilizer.
On the other hand, our high preference for proteins of animal
origin have led to a considerably greater nitrogen requirement
than would be the case if our national diet were based primarily
on plant proteins. This dietary preference and the population
growth have increased the need for available nitrogen on the farm
by almost 8 million tons since 1940 (NAS-NRC Report on Accumula-
tion of Nitrate, p. 37). That is almost a doubling of the
requirement for the use of such nitrogen during the period.
Although many studies have been conducted in recent years on
the effect of fertilizer use (or misuse) on nitrogen levels in
waterways, the effect is still not well defined. It is appar-
ent that in some regions (depending on agricultural practices-,
soil types, rainfall, and drainage patterns), there can•be sig-
nificant, undesirable nitrogen levels -in both surface and ground
water.
It would be useful, therefore, to:
1. Better define the regional patterns of nitrogen concentration
in water—especially in ground water, which has received lit-
tle attention.
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2. Determine the significant factors contributing to such
concentrations.
3. Study more thoroughly the relative crop-yield efficiency as
well as the nitrogen-contamination potential of different
nitrogen fertilizer compounds, rates, times, and methods of
application.
4. Continue research on the maximum loading of animal and human
wastes on crop land.
5. Determine the patterns of nitrogen use that take into account
the efficiency aspects of food production, the maintenance of
soil productivity for future generations, and the environmen-
tal effects.
6. Develop efficient means of helping producers to reliably
determine the actual nitrogen requirements in a particu-
lar set of circumstances (crop, region, field, and the like)
and make this information conveniently available, so producers
can carefully adjust applications of nitrogen (with chemical
fertilizers, and by using animal and human wastes) to actual
needs.
For a variety of reasons, these objectives cannot be determined
or accomplished all at once. However, a major program is needed.
DISCHARGES INTO THE ENVIRONMENT FROM ANIMAL WASTES
The contribution of nitrogen from animal wastes is substantially
greater than that from human wastes. An estimated 6 million met-
ric tons of nitrogen are produced annually from this source in the
United States. Although the N in livestock waste amounts to many
times more than that arising from human wastes, it is usually dis-
tributed over the land, while human wastes are often discharged
into surface waters with little or no treatment to remove the
nitrogen.
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Our preference for meat and other animal proteins is responsible
for the very high livestock production in this country, which is
proportionedely much greater than that in most of the rest of the
world. The problem has been intensified in recent decades with
the growth of livestock production and with the increasing pat-
tern of concentrating such production in large confinement opera-
tions. This had led to locally high concentrations of nitrogenous
compounds in the water and in the atmosphere.
Additional effort to appropriately manage the problem of animal
wastes will require the:
1. Development of economically acceptable means of recycling
livestock wastes for use in crop production or for conver-
sion into usable protein by bacterial protein production or
by other, still-undefined means.
2. Development of practical means for converting livestock waste
into fuel through anaerobic decomposition oif pyrolysis
(burning).
3. Development of denitrification procedures that are economical
as well as feasible.
INDUSTRIAL DISCHARGES
These discharges of nitrogen compounds can be considered from
several aspects. Such discharges add to the available nitrogen
in aquatic systems, increasing the load being generated from other
sources such as human and animal wastes and fertilizer. The mag-
nitude and the extent of the nitrogen-discharge contribution to
the nutrient source varies dramatically from one industry to
another.
The array of synthetic chemicals, their byproducts, and the
altered forms of these chemicals, which by direct loss in man-
ufacture or disposal, also lead to chemical discharge into the
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environment from industrial processes. The problems presented by
these compounds depend entirely on their specific chemical proper-
ties and on their toxicity to various life forms.
Thus, these nitrogen-containing compounds are simply a sub-
classification of all industrial chemicals. Accordingly, they
require the same scrutiny and control as do other industrial chem-
icals that generally enter the environment. The fact that the
synthetic compounds contain nitrogen does not merit placing them
in any special category.
The proposed legislation on the control of toxic substances
would provide a way of dealing directly with these issues.
Industrial chemicals which contain nitrogen—other than those
which alter the nutrient levels as noted previously—need no
special consideration here.
DETRIMENTAL EFFECTS OF NITROGEN COMPOUNDS IN AQUATIC SYSTEMS
Compared to man, aquatic organisms are in some ways less toler-
ant of alterations in nitrogen concentrations. Although man
seems to be able to readily tolerate 10 mg/1 of nitrogen in
drinking water (the 1962 Public Health Service Standard), such
concentrations can severely affect the balance of life forms in
aquatic systems. Two particularly undesirable results lead to
major shifts in aquatic life and the production of algal blooms.
Avoiding severe disturbances in aquatic life may be the major,
limiting factor in nitrogen control in aquatic systems. This
sensitivity results primarily from an alteration in the nutrient
sources available to aquatic life forms. In addition to this
disturbance in nutrient levels, some forms of nitrogen are toxic
to aquatic life. For example, ammonia can be toxic at quite low
concentrations. On the other hand, little is known about the
toxicity of the nitrite ion. Certain industrial nitrogenous
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chemicals discharged into aquatic systems can also be toxic.
Nitrogen concentrations that are detrimental to many forms of
aquatic life are now occurring in waterways. This may bring
about shifts in the abundance of species that cause nuisance
growths. Some of these, such as certain species of blue-green
algae, produce substances that are toxic to many forms of aquatic
life as well as to terrestrial organisms. If detrimental effects
to aquatic life are to be avoided, a number of requirements
should be considered, depending on the particular situation. In
some instances, the requirements listed here may be too strict
because one cannot universally establish a concentration of N
that will prevent algal blooms in all kinds of water. According-
ly, there is a need to pursue further the study of the toxicity
of selected nitrogen compounds discharged into or present in
aquatic environments.
The following requirements should be given consideration in
making decisions regarding the avoidance of detrimental effects
of nitrogenous compounds to aquatic life.
1. Maintain N as NO3 and/or NH4 at the beginning of the growing
season to less than 0.3 mg/1 in lakes and not more than
1 mg/1 in free-flowing waters, or to carry out Provisional
Algal Assay Procedure .(PAAP) tests to determine what level of
nitrogen is likely to cause eutrophication.
2. Maintain levels of un-ionized ammonia to less than 0.02 mg/1,
unless it can be shown that it is not toxic to aquatic life.
3. Maintain the approximate N;P ratios characteristic of natural
waters in the area.
ANIMAL HEALTH
High levels of nitrate and forage have led to toxicity and
livestock loss. The difficulty arises from the bacterial
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conversion of nitrate in the forage into nitrite in the herbivore.
The nitrite so formed leads to methemoglobinemia, which in severe
cases can be fatal. Such episodes have been sporadic and local-
ized. Both natural soil nitrate and nitrate derived from animal
and human wastes and from fertilizers can contribute to high ni-
trate levels in the plants on which the animals graze. The
nitrate level in the plant tends to increase during times of
drouth, leading to a higher risk of poisoning during such
periods.
Nitrosamines can be formed from the simultaneous ingestion of
nitrite and secondary amines, possibly resulting in the formation
of carcinogenic compounds. The role of these compounds in the
induction of cancer in livestock is unknown.
1. Efforts to inform livestock producers about the risk of high
nitrate levels in feed should be continued and extended.
2. Research should be undertaken to identify the significance of
nitrosamines as possible causes of cancer in livestock.
NITROGEN COMPOUNDS AND HUMAN HEALTH
There are a number of ways in which nitrogenous compounds may
affect human health. The first and best understood way relates
to a poisoning known as methemoglobinemia, which is particular-
ly likely to occur in infants. Another is the possible role of
carcinogenic nitrosamines in the induction of human cancer.
Infants can be uniquely efficient in the conversion of ingested
nitrate to nitrite, which in turn reacts with hemoglobin to form
methemoglobin—thus reducing the oxygen-carrying capacity of the
blood. Infant poisoning has been observed primarily from contam-
inated water supplies, and in a few instances from vegetables
containing high concentrations of nitrate. These have been acute
episodes. Little is known about the possible importance of
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chronic toxicity from lower levels of methemoglobinemia.
Within the last decade, a group of chemicals known as nitrosa-
mines have been shown to be potent carcinogens in animals. The
ingestion of nitrite with certain secondary amines can lead to
the formation of these carcinogenic nitrosamines in animals. In
some foods, they are found preformed in low concentrations. Con-
sequently, concern has increased about the widespread use of
nitrite and nitrate in foods, especially in cured meats (wieners,
ham, bacon, and the like). This usage is primarily to inhibit
the growth of C. botulinum microorganisms. Furthermore, nitrites
impart a red color and cured flavor.
1. The present drinking-water standard of 10 mg/1 of nitrate
nitrogen should not be relaxed, but research should be con-
tinued to establish more precisely the levels that are likely
to result in methemoglobinemia in infants.
2. Educational efforts by pediatricians and public health nurses
about the danger of preparing infant formulas .from contami-
nated water should be continued and extended.
3. Analytical techniques to determine the presence of nitrosa-
mines need to be improved and their application extended,
including the-presence and extent of nitrosamines in
foodstuffs.
4. Studies on the likelihood of nitrosamine formation in humans
from ingested chemicals need to be continued and accelerated.
5. The role, if any, of the contribution of nitrosamines to
human cancer also needs study.
ANALYTICAL PROCEDURES
Despite the long history of concern with nitrogenous compounds
in agriculture, in air and water pollution, in waste treatment,
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and in relation to human health and environmental effects, many
inadequacies and inefficiencies remain in the availability of
analytical techniques to monitor and assess the various facets of
nitrogen and its movement through the environment. These are dis-
cussed herein, and some proposals for the correction of these
defects are made.
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ABSTRACT
THIS REPORT is a series of papers on the sources and methods of control and
the environmental and health effects of nitrogenous compounds. Diverse as-
pects of municipal and industrial sources are discussed—waterborne, atmo-
spheric, agricultural, and industrial processes generating nitrogenous com-
pounds. Attention is given to nitrogenous materials in waste and surface
waters, efficiency of sewage treatment, effectiveness of the conventional BOD
test, and the contribution of urban runoff and landfill leakage to the over-
all nitrogen load in the environment. Concentrations, sources, sinks, the
transformation of nitrogenous materials in the lower atmosphere, control
measures for stationary and mobile sources, retrofit systems for used cars,
and new engine systems are reviewed. Plant nutrients, including fertilizers,
and animal wastes are considered. The growing problems resulting from con-
centrated centralized livestock feedlots and methods of control are pointed
out.
Nitrogen is discussed as a nutrient essential to living organisms and as a
toxicant within the aquatic environment. The carcinogenicity of nitrosamines
and their precursors is described as a potential danger to health.
Individual nitrogenous compounds are appropriately identified throughout
the report. Analytical procedures for the identification and quantification
of nitrogenous compounds are reviewed.
As presented to the Environmental Protection Agency in this report, the
statement of the Hazardous Materials Advisory Committee presents the major
concerns regarding nitrogenous compounds in the environment as these relate
to the following Agency activities: research, monitoring, and regulation.
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Municipal and Solid Wastes
Sources of Nitrogenous Compounds and Methods of Control
HAROLD WOLF
WATER-BORNE NITROGENOUS MATERIALS
FROM MUNICIPAL AREAS
THERE ARE TWO BROAD GROUPS of such nitrogenous materials: those present in
wastewater and those in surface runoff. The concentration of nitrogenous
materials found in wastewater varies considerably less than that in run-
off . Man's knowledge about the relationship of the simpler forms of
nitrogen to the biological-oxidation processes of sewage treatment has a
longer record than his knowledge of the biochemical oxygen demand (BOD) asso-
ciations. Prior to the use of BOD procedures, the oxidation of the ammonia
(NIL) in sewage into nitrate (NO.,) formed the basis for the design and opera-
tion of wastewater treatment plants. Nitrogenous materials in runoff, on the
other hand, have been studied only recently.
This part of this paper deals mainly with the wastewater aspects of nitrog-
enous compounds, aerobic as well as anaerobic. Two types are considered:
the point-source discharges into surface water from sewage treatment plants,
and the smaller and more disperse discharges made through anaerobic processes
into ground water. The nitrogenous portions of urban runoff and sanitary-
landfill leachate and analytical problems are also reviewed.
NITROGENOUS MATERIALS IN SEWAGE
Nitrogen can exist in seven states of valence:
NH3 N2 N20 NO N203 N02 N^
3- 0 1+ 2+ 3+ 4+ 5+
Compounds of nitrogen in the 1+, 2+, and 4+ forms appear to have little sig-
nificance in the biological processes generally used in sewage treatment,
F21
aerobic or anaerobic1 . The analytical procedures commonly used in practice
determine NH--N, organic N, N02-N, and N03-N (see the section of this paper
on analytical problems). Total Kjeldahl nitrogen (TKN) is often used to
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express NH -N plus organic N. Dissolved N_ is practically always ignored,
although it has received some attention recently because of fish kills caused
T31
by the supersaturation with N2 of river waters downstream from dams1 •
Approximately 80 percent of the total nitrogen in domestic wastewater orig-
inates as urea. An adult male excretes about 1,500 milliliters of urine a
day. The nitrogen-containing components expressed in grams include urea, 30;
uric acid, 0.7; creatinine, 1; ammonia, 0.7 ; and undetermined N, 0.9 '
Percentage
of nitrogen
Urea 47
Uric acid 33
Creatinine 37
Nitrogen is also contributed from feces. The daily, per capita excretion
of feces on a dry-weight basis is 25 to 50 grams. Of this, total nitrogen
averages 1.3 grams per day . Correcting for the various molecular weights,
the total nitrogen output for an adult male—both urine and feces—is on the
order of 16 grams per day. This value is supported by figures given in a
recent National Academy of Sciences' publication . The estimate shown was
that 1.1 million metric tons of nitrogen are produced each year by 202 mil-
lion Americans, or about 15 grams per day per person.
If we assume that the average amount of water used per capita in a munici-
[81
pal area is 100 gallons per day , 15 grams of nitrogen would produce a con-
centration of 40 milligrams per liter. By comparison, a 1937 committee
f91
report of the American Society of Civil Engineers cites 35 mg/1 ; Weibel
cites 40 mg/1 ; and Keup and MacKenthun cite 34 milligrans per liter^ .
Weibel's review indicates that in raw wastewater, inorganic N (the sum of
nitrite, nitrate, and ammonia as N) constitutes about three-fourths of the
'total nitrogen . Others suggest that total N is about equally divided
between ammonia and organic N, with negligible nitrite and nitrate
, i [9,12]
levelsL ' J.
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Hanson and Lee^ studied the nitrogen content of the wastewater from two
Wisconsin communities. Total N as used in their paper is equivalent to TKN.
The organic N procedure also includes urea. Their findings:
Percentage distribution by type of nitrogen
NH--N Urea-N Total amino acid-N Sum
Madison .... 60 7.6 12.5 80.1
Cross Plains .60 14.5 7.1 81.6
Thus, approximately 20 percent of the total N in each wastewater was not
identifiable. (Hanson and Lee did not consider inorganic N or nitrates,
nitrites, or dissolved N» as part of total nitrogen.) They speculated that
some of the unaccounted-for N might be heterocyclic nitrogen compounds or
complexes—formed by reaction with phenolic substances, lignins, tannins,
or quinones. Quite obviously, they conclude, other chemical forms of ni-
trogen that are measured by the organic-N procedure remain to be determined.
Total (dissolved plus suspended) alpha amino acid-N ranged from 14 to 44
percent of organic N for Madison, and 15 to 26 percent for Cross Plains. A
few analyses for hexosamine-N revealed insignificant quantities. Alpha-amino
acid-N probably includes mucopeptides and teichoic acids, important constitu-
ents of bacterial cell walls. Mucopeptides, in turn, include amino acid com-
plexes containing an amino sugar and muramic acid—the latter having been de-
tected in wastewater. Some nitrogen may exist as chitin, a polymer of
N-acetyl glucosamine. Other N-containing compounds present in sewage are
the nucleic acids—adenine, guanine, cytosine, thymine, and uracil, as
well as xanthine, hypoxanthine, histamine, indole, and skatole.
Urea.-is readily hydrolyzed into ammonia by the enzyme urease. The relative
quantities of urea and ammonia in the sewage arriving at a sewage treatment
unit may be a function of the travel time. This was offered as an explana-
tion of the lower urea finding for sewage from Madison versus Cross Plains
by Hanson and Lee. However, the lowered urea was not reflected in higher
ammonia concentrations; rather, in a higher amino-acid nitrogen.
17
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The chemical qualities of domestic wastewater can be influenced markedly by
the industrial wastes that are discharged into municipal systems. The Madi-
son plant receives wastes from a meat packer (11 percent of the total flow),
a metal-working plant, and a battery producer. For the last two the organic
contribution is understandably reported as quite low. The Cross Plains plant
receives wastes from a creamery (18 percent of the total flow). The meat
packing plant and the creamery would both add substantial organic loads to
the sewage plants, but the packing plant might be expected to exert greater
influence on the alpha amino-acid N concentrations, which is borne out by the
analyses.
The influences of industrial wastes on the nitrogenous characteristics of
municipal wastewater are such that they are better considered plant-by-plant.
Therefore, these influences are excluded from this part of the paper.
MUNICIPAL SEWAGE TREATMENT PROCESSES
Primary treatment. Once wastewater is in the sewage treatment plant, it is
generally exposed first to the anoxic conditions of grit chambers and primary
settlers. These processes have practically no effect on the ammonia concen-
tration at the near-neutral pH levels that generally exist. If the pH value
were higher, a slight reduction might be observed because of the equilibrium
reaction:
NH^ =r NH3 + H+ (1)
lower pH higher pH
Since ammonia is highly soluble and the surface:volume ratio of primary tanks
is very low, little ammonia will be released. For example, at two plants in
Dallas, Texas, the ammonia gain or loss in primary treatment is quite closely
related to the pH range observed:
NH3 gain (+)
or loss (-)
Year mg/1 pH range
White Rock . . .
White Rock . . .
Dallas .....
Dallas
. . . 1970
. . . 1969
. . . 1Q69
-O 7
-O 1
-Ml 1
n.n
7 1 <-^ Q 1
/ . 1 to o.l
7 1 i-« 8 d
/ . -L CO O.U
6C «._ -1 f
• J tO / . O
fi.R 1-r. 7 fl
18
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Since both plants employ recirculation and also send secondary solids to the
digesters through the primary units, these data would not be applicable to
other primary processes. Although primary sewage treatment has little effect
on ammonia concentrations, it does result in a substantially lowered
organic-N concentration, because of materials that settle-out or float and
which are subsequently removed mechanically to sludge-handling facilities.
For the same Dallas plants, these percentage of organic-N reductions were
observed:
Pet. reduction,
Year organic N
White Rock . .
White Rock . .
Dallas ....
Dallas ....
. 1970
. 1969
. 1970
. 1969
34
29
28
27
Since practically no change in concentrations of reduced (ammonia) or oxi-
dized (nitrite or nitrate) nitrogen forms occurs in primary processes,
little biochemical activity involving N-forms takes place during this phase
of sewage treatment.
Secondary treatment. The next step in the treatment of wastewater is gener-
ally an aerobic biological process. Considerable changes in N forms occur,
with the amount of change varying markedly according to the individual plant
and its operation.
In either aerobic or anaerobic environments, organic N is converted into
. [2]
ammonia :
Protein (organic N) + bacterit NH3 (2)
Under aerobic conditions, nitrite formers can carry out the next reaction:
NH3 + 302 bacteria NO^ + H+ + H20 (3)
A second group of nitrifying bacteria then can complete the nitrification
process:
bacteri (4)
Biological Processes 2, 3, and 4 are carried out to various degrees in sewage
treatment plants. The effectiveness of sewage treatment is conventionally
19
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measured by the BOD test, which may or may not reflect the nitrogenous oxygen
demand of the sample. If nitrifying organisms are absent or if too few of
them happen to be in the sample bottle, the result will not express the
nitrogenous oxygen demand—which can be considerable. A more complete dis-
cussion of the relationships involved may be found in a recent article by
[33]
James C. Young
The nitrification processes are slow in comparison to carbonaceous oxida-
[13]
tion, and are quite susceptible to the effects of heavy metals . The
first manifestation of an influx of toxic metals into a nitrifying sewage
treatment plant is the inhibition of nitrification.
These are some recent observations at the Dallas Water Reclamation Research
Center about the effects of nitrification on various factors:
1. Highly nitrified (NH,N < 1.0 mg/1), activated-sludge effluents display
four times the metals removals (average of .all metals observed) of less-
nitrified (NH3N > 8.0 mg/1) effluents.
2. Carbon adsorption also displays different performance in metals removals—
the higher ammonia effluents resulting in poorer removals for some impor-
tant metals, such as cadmium and lead.
3. Highly nitrified, activated-sludge plant operation decreases the refrac-
tory chemical oxygen demand (that COD which passes through carbon adsorp-
tion processes) by half or two-thirds, compared to non-nitrified
operation.
4. The number of bacterial viruses present in the discharge from a highly
nitrifying activated sludge plant is markedly less than that from a non-
nitrifying plant.
5. The ammonia present in non-nitrified discharges combines with chlorine to
form chloramines; and chloramines—although effective against the coli-
form-indicator organisms—are relatively useless in eliminating viruses.
Nitrification is also dependent on pH and temperature. In some sewage
lagoons during the winter months, NH., concentrations will increase because
the nitrifiers are slowed down. As the temperatures rise, the nitrite-form-
ing bacteria become active and produce more nitrites. The remaining
20
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nitrifiers will become active and complete the reaction. If the warming
occurs rapidly, it is possible for a rather high nitrite concentration to
exist for a few days. In a nitrification process, however, nitrites are
usually present only in concentrations of less than 1 milligram per liter.
Reactions occurring among the nitrogenous materials can be summarized as:
organic N oxidatlo,n N03 + organic N
The residual organic N that carries through the biological treatment process
is called "refactory." Data do not always reflect this terminology, however,
because the more complete the oxidation process is, the smaller the amount of
organic N that will be present in the discharge.
The "nitrogen effectiveness" of different types of sewage treatment pro-
cesses can be illustrated by performances observed in Dallas, Texas. The
Dallas plant is a standard-rate, trickling-filter plant—the most-common type
seen throughout the United States.
Dallas Plant
Pet. reduction Effluent
concentration
NH-j-N Organic-N NO_-N (mg/1)
1970 45 49 3.6
1969 44 45 3.2
The White Rock plant is a two-stage, high-rate plant that is organically
overloaded.
White Rock Plant
1970 ....
1969 ....
Pet.
NH3-N
. . . . 12
. . . . 11
reduction
Organic-N
22
25
Effluent
NO--N (mg/1)
J
1.4
0.9
21
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These results can be compared with those obtained from an activated sludge
process. A pilot unit in Dallas receiving primary effluent from the White
Rock plant and operated so it produces a highly nitrified effluent (the slow
growth rate of nitrifying bacteria requires longer reaction times) gave these
results
Reduction in NI^-N (pet.) 94
Reduction in organic-N (pet.) .... 63
NO,-N in final effluent (mg/1) ... 9.5
When a different bioreactor employing a much shorter reaction time was used,
the following results were obtained, using the same influent:
Reduction in NH -N (pet.) 24
Reduction in organic-N (pet.) .... 25
NO -N in final effluent (mg/1) ... 1.2
There is a considerable nitrogen significance involved in this shorter-
reaction-time operation, a process termed "high-rate treatment." For a lower
cost, the high-rate treatment will achieve a greater percentage removal of
the biodegradable carbonaceous material than older processes, but at the
expense of the nitrogenous material. The additional effectiveness is
achieved through a better separation of the solids. The difference is the
absence of "rising" sludge, which is associated with settling-basin denitri-
fication ' . The increasing application of the high-rate treatment is one
of the reasons why the National Technical Advisory Committee on Public Water
Supplies included the statement, "Greater attention to the design and opera-
tion of waste treatment plants for the oxidation of ammonia and organic
nitrogen is needed to minimize the concentration of these pollution forms in
receiving waters"1 . The Iowa Water Pollution Control Board has recently
adopted a regulation limiting ammonia in discharges .
This overall reaction is involved in sewage treatment:
Org. N — NH3 -— N02 —- NO (6)
Environmental problems exist with respect to this reaction and all chemical
forms of nitrogen. Biodegradable organic N will exert an oxygen demand on a
receiving water. Organic N interferes with the chlorination process, which
22
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is reflected in part of the chlorine demand. The chlorine demand must be
satisfied before efficient bactericidal activity can take place. Hence,
organic N reflects a direct economic penalty. NH- is quite toxic to fish.
It also interferes with the chlorination process by combining with the more
effective disinfectant HOC1 and forming a chloramine that has lesser disin-
fecting properties. Chloramine is also toxic to fish — but so are NH~ and
HOCl! The NH3 discharged into streams will be oxidized by nitrifiers so
that it, too, exerts an oxygen demand. Although N0» still has one more oxi-
dative step to go, the effect of its oxygen demand is much less than that of
The .importance of NO™ is recognized in the preliminary version of the new
Drinking Water Standards to be issued by the Environmental Protection Agen-
cy. N02 is limited to 1 mg/1 of the allowable 10 mg/1 of NO_-N where infants
will be ingesting the water. Finally, the NO- form, which is highly stable
and soluble, serves as a necessary plant and algal nutrient. In the anoxic
environment of the intestinal tract, it can be reduced to NO™ — which is a
mechanism of methemoglobinemia.
ADVANCED WASTE TREATMENT
Unit processes other than those just described can be applied to sewage-
treatment-plant effluents in order to obtain further control. These are gen-
erally spoken of as "advanced waste treatment," or "tertiary systems." Such
systems are not widely employed at this time; however, there is no question
that they will be widely adopted in coming years. Increasingly, the direc-
tion of our program to control water pollution is being oriented toward the
control of specific nutrients, mostly for phosphorus at present.
H
Tertiary treatments use processes that are nonspecific for nitrogenous
materials, as well as ones developed specifically for nitrogen removal. The
former include rapid sand filtration of activated-sludge effluents; chemical
coagulation and precipitation using lime, polymers, or iron or aluminum
salts, or various combinations thereof; activated-carbon adsorption; and non-
specific dimineralization. The nitrogen-removal processes include
23
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ammonia-stripping, ion-exchange, biological nitrification, and breakpoint
chlorination. The results that can be expected from these processes often
vary according to where they are used, their location in the treatment
sequence, and the quality of the water involved.
An effective means of increasing our control of water pollution would be to
filter activated-sludge plant effluents. The utility of this treatment has
been under study in Dallas for several years. Filtering the effluent of a
nitrifying activated-sludge plant through sand and anthrafilt gave the fol-
lowing data for September, 1972:
Nitrogen forms, mg/1
Effluent
Pet. removal . . .
NH3-N
. . . 1.5
. . . 1.3
. . . 13.3
Organic N
3 8
2 9
23.7
NO, and
N03 as N
15.7
16 3
+3.8
A substantial, additional increment of organic N was removed by filtration.
The fact that nitrification was proceeding in the filter was demonstrated by
the increased amount of N02 plus NO., in the effluent, an indication that the
water applied to the filter still contained a substantial amount of dissolved
oxygen and/or little degradable carbon.
It is possible to design and operate an activated-sludge filtration system
for denitrification. The activated-sludge plant would be designed to nitri-
fy; and the filters, to denitrify1 . Such a system was first suggested by
Parkhurst &t a^> as a result of their Pomona studies .
In Dallas, the filtration of trickling-filter effluents was demonstrated to
be impractical. The filters quickly blind due to the nature of the suspended
materials applied. However, this does not necessarily mean that it would be
impractical to filter all trickling-filter effluents. More study is needed
by others in order to evaluate this possibility. In Dallas, it is necessary
to provide chemical pretreatment with coagulants—such as in water treatment
24
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processes'—in order to achieve a filterable water. A number of short runs
utilizing iron salts and lime made on the final effluent at White Rock showed
an average organic N removal of about 30 percent. Chemical treatment togeth-
er with filtration provides for 40-percent removal, down to an effluent con-
centration of 2 to 3 milligrams per liter.
Granular activated carbon can be used to achieve additional removal of
organic nitrogen. In general, this type of treatment removes about half
of the applied organic nitrogen. Granular carbon can be used as a filter.
It will function both as a filter and as an adsorber; consequently, the
removal of organic N would be somewhat higher. However, the carbon must be
periodically regenerated when it loses its sorption capacity, and this regen-
eration process is a comparatively expensive one.
Nonspecific demineralization processes include distillation, electrodialy-
sis, reverse osmosis, freezing, and ion-exchange. "Nonspecific" as used here
means that these processes remove other impurities along with the nitrogenous
materials. The processes just listed all represent another generation in
costs, and are not likely to be applied generally to water discharged into
the environment. Their proper place is in treating water for subsequent
domestic or industrial use. In passing by these processes, it is of interest
to note that ammonia N cannot be removed by the distillation process unless
the feed water is first acidified (see Reaction 1) to maintain the nitrogen
in ammonium form
Ammonia-stripping has been used with varying degrees of success at the
South Lake Tahoe plant . The process is applied to a non-nitrifying,
activated-sludge plant effluent. The pH of the water must first be ele-
vated to about 11 (see Reaction 1). Cold weather sharply curtails the effi-
ciency of the process, even in the absence of freezing. Efficiency is so low
(30 percent) when the ambient temperatures are below freezing that little is
gained. Yet, the process can achieve a 90-percent removal quite easily in
warmer weather.
NOTE: The non-nitrifying operation of an activated-sludge plant allows
about half of the organic N to pass undegraded. The stripping tower itself
25
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has no effect on the organic Nl , but the high pH treatment of the applied
F211
water may result in the hydrolysis of some of the nitrogen forms
A selection ion-exchange process to remove ammonium has been developed by
Batte-lle Northwest, and is being considered for full-scale use at Tahoe
After various nitrogen-removal processes were reviewed by researchers at
the Blue Plains plant for Washington, D. C., they determined that biologi-
cal nitrification-denitrification was the most appropriate one for their
needs. The nitrification aspect has been discussed under secondary treat-
ment. The denitrification operation can be carried out in either suspended-
bed or fixed-bed systems.
The former was selected for Blue Plains, where its operation is under
intensive study. The investigators report periodic difficulty with er-
ratic performance, but hope to achieve a consistent level of 2 mg/1 or
less of total nitrogen in the effluent. This would be a 91-percent re-
F221
moval of nitrogen, the most effective treatment reported , and repre-
sents an approach that will have to be initiated elsewhere.
Granular activated carbon, sand, gravel, and the like can all serve as
fixed-bed denitrifiers under the proper conditions . Such conditions
include enough biodegradable carbon to support the denitrifiers (which gener-
ally means that some has to be added), a low amount of dissolved oxygen, and
nitrogen in an oxidized form. Although a 90-percent removal of an applied
20 mg/1 concentration has been reported with water^ , general data are lim-
f 181
ited concerning sewage
Breakpoint chlorination can be used to eliminate the residual ammonia in an
effluent. This treatment is under consideration at both Blue Plains and
Tahoe, following their N-removal processes. A chlorine dose of more than 8:1
as a weight ratio of C1:NH,-N is required, and the treatment does not remove
F231
the organic nitrogen1 . At Dallas, ozone will be studied for its effective-
ness in removing nitrogen.
26
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ANAEROBIC PROCESSES
Under aerobic or anaerobic conditions, as already stated, bacteria can
convert organic N into ammonia. Septic tank processes are, of course, an-
aerobic processes. They are used for individual-household or for small sew-
age-treatment applications. Most often, the water coming out of septic sys-
tems is leached into the soil, which functions in an aerobic manner. When
such applications are relatively isolated and carefully located with respect
to individual ground-water supplies, little effect is observed. When such
use becomes more concentrated, as has been the case in some suburban-type
developments, the quality of the ground water can be reduced substantially.
This has been observed for coliform concentrations and surfactants, as well
as for nitrates.
Another widely used application of the anaerobic process is the sludge
digestion employed at most sewage treatment plants. Sludge digestion is
properly considered as a solids-handling problem. However, for the pur-
poses of this paper, the contents of the digestion tank are considered in the
water-borne sector, and the discharge of sludge from the tank is included in
the solid-waste category.
Anaerobic biological processes are much more sensitive to quality varia-
tions in the wastewater than are the aerobic processes. Domestic septic
tanks operate on a rather consistent type of household effluent and are not
subject to the discharge of industrial wastes, which must be accommodated by
most municipal plants and their digesters. When materials in concentrations
that are toxic to the digestion process enter the digesters, the operating
[241
problems can be monumental
Nitrogen compounds provide the buffering that is essential for effective
digestion processes. Organic N is converted into ammonia, which with C02 and
H20 forms the buffer^25^:
C02 + H20 + NH3—- NH4HC03 (7)
Because of the sensitivity of the anaerobic process and its comparatively
slower reactions, aerobic sludge-digestion processes are being employed more
27
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and more.
The National Academy of Sciences estimates that 75 percent of the popula-
tion is being served by central sewage-treatment plants . This leaves 25
percent for septic tanks and digestion tanks. If 1.1 million metric tons of
nitrogen a year were produced by the whole population, 0.84 million tons
would be entering sewage treatment plants and 0.28 million tons would be
entering septic-tank or individual systems. Of the 0.84 million tons enter-
ing sewage treatment.plants, secondary treatment leaves about 3 kilograms of
nitrogen per person per year in the discharge. Hence, by subtraction, 390
thousand metric tons of nitrogen would be entering sludge digestion processes
yearly.
Anaerobic digester gases contain mostly CH,, C0~, and H^O, with little
degassing of nitrogen forms. Hence, the point-source discharge of nitro-
gen from sludge digestion tanks can also be estimated at approximately 390
thousand metric tons per year. Since septic tank systems give off the same
gases as digestion tanks, the total output of nitrogen would again be some-
what equivalent to the input, a discharge of about 280 thousand metric tons
per year.
Periodically, it is necessary to dispose of the accumulated sludge in sep-
tic tanks. This is generally accomplished by trucking it to a municipal sew-
age treatment plant, or by some type of controlled or uncontrolled ground
disposal. The amount of nitrogen transferred is not likely to be very sig-
nificant, even though the volume of septic-tank contents can be estimated at
approximately one billion gallons per year (assuming five -persons per septic
tank, an average sludge capacity of 500 gallons per tank, and a cleaning once
each five years).
In summary, the bulk of the nitrogenous materials discharged from septic
tanks is percolated into the soil and ground water. The nitrogenous mate-
rials from municipal digesters enter the solid sphere, as defined herein.
28
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URBAN RUNOFF
It once was acceptable practice to build "combined" sewer systems, ones
that transport sewage to sewage treatment plants during dry weather and also
drain the runoff from storms during wet weather. The excess flow (that which
cannot be accommodated by the sewage treatment plant) of the "combined" sew-
age (sewage plus runoff) is diverted directly into surface water. The
rationale behind this practice is that the increased flow of the streams dur-
ing periods of rainfall could accommodate the oxygen demand due to the added
increment of untreated, diluted sewage. Because of the widespread installa-
tion of combined systems in many major U. S. cities, much of the data in the
literature concern the wastewater in such systems.
The earliest study about the quality of urban runoff pev se reported by
F261
Public Health Service workers was from Moscow, Russia, in 19361 . Ni-
trogen information, however, was not reported. Later studies in the U. S.
concerned catch-basin contents and samples from street gutters during rain-
fall. A 1954 English study noted that the first flush following a long dry
period was particularly polluting; but, again, nitrogen information was lack-
ing. The previously mentioned gutter samples plus studies in Sweden and
South Africa have confirmed the high pollution loads that can be contributed
by urban runoff, with organic N concentrations varying from 3.5 to 9.0 milli-
grams per liter.
Weibel, Anderson, and Woodard conducted a study of runoff from a residen-
tial-commercial area in Cincinnati, Ohio, in 1962-63. The mean N values ex-
pressed in mg/1 observed in these studies were: NHg-N, 0.6; organic N, 1.7;
NO_-N, 0.4; and NO--N, 0.05. Total N was calculated to be 8.9 pounds per
[26]
year per acre
In 1968, a study was conducted in the Detroit and Ann Arbor areas of Michi-
gan . The annual mean values observed given in milligrams per liter were:
NH,-N, 1; organic-N, 1; and NO--N, 1.5. Areal contributions for the three-
month study expressed in pounds per acre were: NHg-N, 0.7; organic N, 0.4; and
NO,-N, 0.8. Summing these and extrapolating on a straight-line basis, the
29
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yearly contribution per acre comes to 7.6 pounds, which is a reasonable check
of the Cincinnati findings1 .
The Detroit-Ann Arbor study compared the quality of separately sewered
storm water with combined sewer overflows on an areal basis. The extrap-
olated nitrogen data show that the combined sewer overflows produced 32
pounds of total nitrogen per acre per year, compared to the figure of 7.6
pounds for storm water alone. The workers observed that (1) the annual mean
values for NH--N were more than ten times those observed in combined sewer
systems; (2) that concentrations of organic N were fairly constant throughout
the year; and (3) that the amount of NO,-N dropped in the fall, which they
[27]
attributed to a lower use of fertilizers at that time of year
DeFilippi and Shih published a study of combined and separate systems in
F281
1971 . They noted that the quality of storm sewage varied from storm to
storm as well as within any single storm, and that this depended on the
intensity and duration of rainfall, antecedent conditions, land use, topogra-
phy, and flushing characteristics—among other factors. For their study of the
District of Columbia, they utilized equipment that collected samples at five-
.or ten-minute intervals during the entire duration of storms. Each sample
was analyzed. The only published information about nitrogen content was for
total N—which ranged from 0.5 to 6.5 mg/1, with a mean of 2.1.
Comparing the means for total N of the three major studies shows:
Mean amt. of
total N (mg/1)
Cincinnati 2.75
Michigan 3.5
Washington, D. C. ... 2.1
Runoff nitrogen discharges directly into waterways. Because of increased
efforts to control water pollution, studies are underway in some areas to
provide primary treatment for runoff waters. Chlorination is normally a
health department requirement for application to such discharges; also,
30
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little is known about the chemical forms of nitrogen generated by the chlori-
nation of organic N. Hence, it appears that much more study would be desira-
ble before such plants come into wide use.
LANDFILL LEACHATE
A highly controlled study of the leachate from sanitary landfill has been
F291
under way by workers at Drexel University for a number of years .A sum-
mary of the first two years of the study shows approximate values for total
N (probably NH~-N plus organic N) on a graph. As observed from that graph
(approximate values only), total N peaked at about 490 mg/1 within the first
20 days and then dropped sharply, varying from 15 to 80 mg/1 for the next 130
days. Thereafter, the concentration ranged from 40 to a high of 210 milli-
grams per liter. An approximation for the two. years might be about 90 milli-
grams per liter.
Very little leachate was produced initially. The first high total-N peak
mentioned was related to the initial squeezing caused by compaction. A sec-
ond peak coincided with the first leachate observed from water percolating
through the fill. Once the system reached a water balance—with the water
added equal to the leachate measured (at about 400 days), the total N al-
so came into balance at about 110 milligrams per liter. Eliminating the
water input decreased leachate production to zero.
A total of 421.5 gallons of water was added per year (according to average
conditions of rainfall in southeastern Pennsylvania) to the landfill lysime-
ter of 36 square feet. The yearly contribution of TKN per square foot of
landfill area averaged approximately 4 grams. This leachate exists in an
anaerobic, hence in a reducing, environment; also, some losses of N« and NH_
can be anticipated in such an environment. The Drexel studies demonstrated
the presence of N? coming from the experimental unit, but the quantity was
not reported. Once nitrogen is in an aerobic environment, oxidation to ni-
trate can be anticipated. The production of 4 grams per square foot per year
of TKN is not unimportant. On an acreage basis, this amounts to 384 pounds
per acre per year, compared to the previous contributions from urban runoff
31
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of 7 to 8 pounds. However, the acreages involved differed greatly.
SOLID WASTES
The two main types of these wastes emanating from the urban environment in
a nonaerosol mode are sewage sludge and municipal refuse. Both have already
been discussed from their water-borne aspects.
The disposal of sludge-digestion residues is usually governed by the eco-
nomics of the individual sites. Some of the techniques being used are barg-
ing to sea (New York), ocean disposal through outfalls (California), dewater-
ing and incineration (South Lake Tahoe), and land application (Chicago).
Others include filling open mine pits, using lagoons, and hauling to sanitary
landfills.
The estimated 390 thousand metric tons of digestion-tank nitrogen compares
to 1.6 million metric tons of fertilizer N consumed in 1957 ; and unless
the sludge is used agriculturally, would appear to represent a considerable
waste of this resource. The value of sludge in agricultural fertilization
has long been known. Economically, however, it cannot compete with chemical
fertilizers. The basic reason for this is the cost of removing the water.
Sewage sludge is about 2 to 5 percent solids (95 to 98 percent water). The
water represents a serious cost factor in terms of transportation.
Proprietary equipment is on the market that will achieve some dewatering.
This equipment includes vacuum filters, centrifuges, and filter presses.
Small sewage treatment plants generally dewater their sludges on drained,
sand-drying beds. Before any wide-scale "solids to the land" program is
undertaken, however, two significant factors must be reckoned with, and both
concern health.
The first factor is that digestion does not destroy all of the potential
pathogens in sewage sludge. Therefore, some means of treatment is needed in
order to render the sludge nonpathogenic. One means could be heat. The sec-
ond factor is the high concentration of heavy metals found in sludge .
32
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Conceiveably, this might impose a severe limitation on the use of sludge. At
the very least, more ought to be known about the ramifications.
An example of the type of effort needed can be illustrated using John, Van
Laerhoven, and Chuah's recently published study about cadmium added to soils,
versus plant uptake and phytotoxicity. They found that the cadmium in the
plant tissue was related more to the amount of exchangeable cadmium in the
soil than to the total amount of cadmium added to the soil. While greater
soil acidity was associated with higher cadmium levels in plants, increased
organic matter in the soil was related to lower plant cadmium. In other
words, the organic matter added a capacity for adsorbing cadmium^ . Since
sewage sludge contains organic detritus, the use of sludge as a soil supple-
ment may prevent the uptake of heavy metals by plants, even though these
metals are present. On the other hand, the situation may be even more
complex than is now apparent.
The movement of nitrogen into the soil from landfill operations can be
stopped after the initial leaching due to compaction by providing a water-
impermeable membrane cover over the landfill. Where.the ground water levels
are high enough to reach the fill, such an application is useless.
ANALYTICAL PROBLEMS
The traditionally important forms of nitrogen are ammonia, organic N,
nitrite, and nitrate. All are customarily reported in terms of N, so values
T21
may be interpreted from one form to another without the use of a factor .
All nitrogen that exists as an ammonium ion or as ammonia is considered to
be NH--N. It can be measured by direct Nesslerization or by distillation.
Since the direct Nesslerization procedure is subject to serious error from
extraneous color and turbidity, the distillation procedure is the one gener-
ally employed with wastewater. Because organic N is progressively ammonified
by bacteria, the analysis is best conducted on a fresh sample. Storage is
permissible if the sample is acidified with 0.8 milliliters of concentrated
H2SO, added to each liter of sample and stored at 4° Centigrade1 J. The
33
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percentage of relative error on six samples analyzed by distillation followed
by a Nessler finish varied from 2 to 10 for up to 44 participating
laboratories.
All- nitrogen present in organic compounds is considered to be organic
nitrogen. Most of the organic N in sewage is in the form of proteins or
[2]
their degradation products: polypeptides and amino acids . As with
ammonia-N, the determination must be made on a freshly collected or specially
preserved sample. The method fails to account for the N in azides, azines,
azo, hydrazones, nitrate, nitrite, nitrile, nitro, nitroso, oximes, and semi-
carbazones. If ammonia is not first .removed from the sample, the results are
called TKN (the sum of NH--N and organic-N). At organic N concentrations of
0.8 and 1.5 mg/1, the percentage of relative error for 16 participating labo-
[311
ratories was 8.7 and 4, respectively . The organic N procedure misses N
compounds that are of considerable health importance.
Nitrite represents an intermediate state in the nitrogen cycle; and in
"healthy" biological systems, its presence is a relatively fleeting one.
Nitrite is sometimes used as a corrosion inhibitor in industrial process
water, and care must be taken to prevent its entry into potable water systems
through cross connections. Situations can be encountered in biological sew-
age-treatment processes in which nitrites will occasionally increase in con-
centration above their usual values. Since samples are subject to change
with biological activity, analyses should be run only on fresh or quickly
frozen samples. Acid preservation is acceptable with refrigeration. Ni-
trogen trichloride interferes, as do certain ions: antimonous, auric, bis-
muth, ferric, lead, mercurous, silver, chloroplatinate, and metavanadate.
The percentage of relative error was 12 for 49 laboratories analyzing a pre-
F311
pared sample containing 0.25 milligrams per liter
F311
Standard Methods offers tentative procedures, but recommends no partic-
ular one for the determination of nitrates in wastewater, which Sawyer indi-
cates is the most difficult work an analyst has to perform in order to obtain
[21
results in which he can be genuinely confident . Each of the procedures
has objectionable interferences, which the analyst must consider in selecting
34
-------
a procedure. All tests must- be run on freshly collected or specifically
preserved samples. A summary of the percentage of relative errors
Procedure
Cadmium reduction . .
Phenoldisulfonic acid
No. of
labs
.... 11
.... 50
.... 46
.... 32
N03
(mg/1)
1 4
50
50
1
50
Pet. of
relative
error (mg/1)
+0 2
47.3
7 6
31 to 38
12.5
As Sawyer saws, "The need is great for a more refined and exact method of
analysis"[2J.
CONCLUSIONS AND SUGGESTIONS
Some 202 million Americans produce an estimated 1.1 million met-
ric tons of nitrogen a year. Of this, an estimated 0.84 million'
tons enter sewage treatment plants. The remaining 0.28 million
tons go into septic tanks or individual systems. Of the 0.84 mil-
lion metric tons entering sewage treatment plants, effluents are
estimated to discharge 3 kilograms of nitrogen per person per
year, or 0.45 million tons. The form of the nitrogen discharged
(the relative mix of ammonia, organic, and nitrate forms of ni-
trogen) differs widely from plant to plant. Each form, howev-
er, produces undesirable environmental effects. Additionally,
all of them will ultimately oxidize to the stable, soluble-
nitrate form in an oxidizing environment.
To obtain some perspective about the enormity of the nitrogen
problem, one needs only to look at its theoretical impact in
terms of drinking water standards. Of the total annual precipi-
tation on the U..S., an estimated 100 million acre-feet are
35
-------
[32]
diverted and consumed1 . The 0.45 million metric tons of nitrogen dis-
charged from sewage treatment plants yearly is sufficient to raise 12 trillion
gallons of water to the limit of 10 mg/1 of nitrate nitrogen specified by
Drinking Water Standards. The result in terms of undesirable nutrient levels
would be even more severe.
The trend in sewage treatment over the past two decades—with the exception
of the application of extended aeration plants and until the adoption of water
quality standards—was to increasingly ignore the nitrogenous aspects of sew-
age treatment, much to the dismay of officials concerned with water supply and
purification. Within the past several years, however, the federal water pol-
lution control program has been oriented more and more toward nutrient
limitations.
Control considerations involve the analytical area. Problems are pro-
nounced in the application of the BOD test in a meaningful way, in deter-
mining nitrates with confidence, in knowing what chemical species comprise the
20 percent of undetermined N of the TKN procedure, and in knowing what chemi-
cal forms of nitrogen are created by chlorinating the undetermined nitrogen.
The following suggestions are given (with explanatory information
inserted):
1. A national policy concerning nitrogen control should be developed, one
that would result in greater nitrogen removals by sewage treatment plants.
2. Research relative to nitrogen removal needs to be greatly expanded.
3. More effort should be directed toward developing an improved nitrate
nitrogen procedure for use on polluted waters, including sewage.
4. The chemical forms of nitrogen that make up the 20 percent of unaccounted-
F21
for N or TKN, as revealed by Hanson and Lee , should be identified.
5. Study of the chemical forms of nitrogen created by chlorinating the unde-
termined N in TKN should be initiated.
6. The BOD test should be modified to reflect only the carbonaceous aspect,
and should be supplemented by the four nitrogen determinations of
36
-------
environmental significance—the ammonia, organic, nitrite, and nitrate
forms of nitrogen—for the routine monitoring of our nation's sewage
treatment plants.
7. Studies should be undertaken to quantify the chemical forms of nitrogen
that are not measured by conventional analysis.
Individual sewage systems discharge into ground water. These systems
process an estimated 0.28 million metric tons of nitrogen yearly. Some of
this nitrogen is taken up by plants. Yet, the magnitude of this discharge
comes into perspective when one realizes that 0.28 million metric tons of
nitrogen is sufficient to raise 7.4 trillion gallons of water to the 10 mg/1
limit specified by Federal Drinking Water Standards. Individual systems mani-
fest problems (other than inherent ones) only when they are improperly located
or when their density is too high. Where problems do appear, several alterna-
tives are available; hence, these suggestions:
8. Regulations should be enacted by all states to limit the density of indi-
vidual sewage-disposal systems.
9. Where ground water is already affected, Federal money should be made
available to the communities or areas involved, in order to speed up
the delivery of an uncontaminated supply.
10. Where alternate sources of water are not available, high priority should
be given to affected communities for the construction of sewers and sew-
age treatment plants.
Urban runoff contributes substantially to environmental nitrogen. It is
not feasible to adopt biological processes to control this problem. Certain-
ly, however, chemical-physical treatment can bring about some improvement;
thus, the next two suggestions:
11. All storm-water treatment plants currently in operation or under construc-
tion should be set up to monitor routinely for nitrogenous materials.
12. The desirability of chlorinating storm-water plant effluents should be
evaluated from the viewpoint of what chlorinated products are formed when
this is done.
37
-------
Landfill leachate imposes massive nitrogen loads calculated at some 384
pounds per acre per year on contiguous ground and surface water. Other than
the initial peak caused by compaction, eliminating the water input through the
fill decreases leachate production to zero; therefore, these suggestions are
also given:
13. Where sanitary landfills are not in continuous contact with ground water,
a water-impermeable membrane should be incorporated in or on top of the
fill.
14. Where landfills must be immersed in ground water, other solid-waste dis-
posal techniques should be employed.
The disposal of sewage sludges is estimated to include 390 thousand metric
tons of nitrogen yearly, a substantial waste when not applied usefully.
Research is needed to achieve more economic dewatering and pathogen destruc-
tion. Additionally, greater knowledge is needed about the mobility of heavy
metals; hence, these three suggestions:
15. The technology of dewatering sewage sludge should be developed further.
16. More research should be devoted to the means of destroying pathogens in
sludge.
17. Studies of the agricultural use of sewage sludge should be expanded, with
a significant increase in the attention paid to heavy metals and to a bet-
ter understanding of their movement and concentration.
REFERENCES
1. Task Group Report, Sources of nitrogen and phosphorus in water supplies.
Jour. Am. Water Works Assn. 59:3, p. 344 (1967).
2. Sawyer, C.N. Chemistry for Sanitary Engineers. McGraw-Hill Book Co.,
Inc., p. 289, New York City (1960).
3. Environmental Protection Agency. Nitrogen Supersaturation in the Colum-
bia and Snake Rivers. Technical Report No. TS 09-70-208-016.1, Office of
Water Programs, Region X, Seattle, Washington (July 1971).
38
-------
4. Carlson, A.J., and Johnson, V. The Machinery of the Body, p. 335. Uni-
versity of Chicago Press (1937).
5. Hanson, A.M., and Lee, G.F. Forms of organic nitrogen in domestic waste-
water. J. Water Pollution Control Fed. 43:11, p. 2,271-79 (November
1971).
6. Fruton, J.S., and Simmonds, S. General Biochemistry, 2nd ed. Wiley and
Sons, Inc. New York City (1961).
7. Committee Report. Accumulation of Nitrate, National Academy of Science's,
Washington, B.C. (1972).
8. Symons, J.M. Urban sources of nitrates. Proceedings, Twelfth Sanitary
Engineering Conference, Nitrate and Water Supply: Source and Control,
University of Illinois at Urbana-Champaign (February 11, 12, 1970).
9. Committee Report. Standard practice in separate sludge digestion. Proa.
Am. Soc. Civ. Engr. 63:39 (1937).
10. Weibel, S.R. Urban drainage as a factor in eutrophication. In Eutrophi-
cation: Causes, Consequences3 Correctives, p. 388. National Academy of
Sciences, Washington, D.C. (1969).
11. Keup, L.E., and Mackenthun, K.M. Lakes-restoration and preservation.
Water and Sewage Works 117, R16, 21 (November 1970).
12. Reeves, T. G. Nitrogen removal: A literature review. Jour. Water Pol-
lution Control Fed. 44:10, p. 1,895-1,908 (October 1972).
13. U.S. Dept. of Health, Education, and Welfare. Interaction of Heavy Met-
als and Biological Sewage Treatment Processes. Public Health Service
Publication 999-WP-22, Cincinnati, Ohio (1965).
14. Busch, A.W. Aerobic Biological Treatment of Waste Waters, p. 170.
Oligodynamics Press, Houston, Texas (1971).
15. U.S. Department of the Interior. Report of the National Technical Adviso-
ry Corrmittee. Federal Water Pollution Control Administration, Washington,
D.C. (April 1, 1968).
16. Water Newsletter. Water Information Center, Inc. 14:21 (November 6,
1972).
17. St. Amant, P.P., and McCarty, P.C. Treatment of high nitrate waters.
Jour. Am. Water Works Assn. 61, p. 659 (December 1969).
18. Parkhurst, J.D., et al. Pomona activated carbon pilot plant. Jour.
Water Pollution Control Fed. 39:10, part 2, R70-R81 (October 1967).
39
-------
19. Summary Report, Jan. 1962—June 19643 Advanced Waste Treatment Research,
AWTR-14, Public Health Service Publication No. 999-WP-24 (April 1965).
20. Gulp, R.L., and Gulp, G.L. Advanced Wastewater Treatment. Van Nostrand
Reinhold Co., New York City (1971).
21. Zuckerman, M.M. , and Molof, A.H. High quality reuse water by chemical-
physical wastewater treatment. Jour. Water Pollution Control Fed. 42,
437 .(March 1970).
22. Bishop, D.F., et al. Advanced waste treatment systems at the Environmen-
tal Protection Agency—District of Columbia pilot plant. Paper presented
at the 68th National Meeting of the American Institute of Chemical Engi-
neers, Houston, Texas (March 1971).
23. Pressley, T.A., Bishop, D.F., and Roan, S.G. Nitrogen removal by break-
point chlorination. Robt. A. Taft Water Research Center, Cincinnati,
Ohio (September 1970).
24. Regan, T.M., and Peters, M.M. Heavy metals in digesters: Failure and
cure. J. Water Pollution Control Fed. 42:10, p. 1832 (October 1970).
25. Mohanrao, G.J., Sastry, C.A., and Mehta, R.S. Fundamentals of anaerobic
digestion. Environmental Health 5:2, p. 169 (April 1963).
26. Weibel, S.R., Anderson, R.D., and Woodward, R.L. Urban land run-off as a
factor in stream pollution. J. Water Pollution Control Fed. 36:7, p. 914
(July 1964).
27. Burm, R.J., Krawczyk, D.F., and Harlow, G.L. Chemical and physical com-
parison of combined and separate sewer discharges. J. Water Pollution
Control Fed. 40:1, p. 112 (Jan. 1968).
28. DeFilippi, J.A. and Shih, C.S. Characteristics of separated storm and
combined sewer flows. J. Water Pollution Control Fed. 43:10 (October,
1971).
29. Fungaroli, A.A., and Steiner, R.L. Laboratory study of the behavior of a
sanitary landfill. J. Water Pollution Control Fed. 43:2, p. 252 (Febru-
ary 1971).
30. John, M.K., Van Laerhoven, C.J., and Chuah, H.H. Factors affecting plant
uptake and phytotoxicity of cadmium added to soils. Environ. Science and
Tech. 6:12, p. 1,005-1,009 (November, 1972).
31. American Public Health Association. Standard Methods for the Examination
of Water and Wastewater, 13th ed. New York City (1971).
32. Office of Science and Technology. A Ten-Year Program of Federal Water
Resources Research, p. 4. Supt. of Documents, U.S. Govt. Print. Office,
40
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Washington, D.C. 20402 (February 1966).
33. Young, James C. Chemical methods for nitrification control. J. Watev
Pollution Control 45:4, p. 637-646 (April 1973).
41
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Discharges into the Atmosphere
Sources of Nitrogenous Compounds and Methods of Control
JAMES N. PITTS, JR. AND ALAN C. LLOYD
FOR KEY NITROGENOUS MATERIALS IN THE LOWER ATMOSPHERE (the troposphere), we
review here the concentrations, sources, sinks, transformations, and the
health and environmental effects. Both natural and anthropogenic sources
are considered, as are those nitrogenous compounds that are known (or
believed) to play significant roles in the natural and polluted troposphere.
Those compounds include the inorganic gases—nitric oxide (NO), nitrogen
dioxide (N02), nitrous oxide (NJD), nitrous and nitric acid (HONO and HN03),
and ammonia (NH,); the inorganic particulates—nitrites (N0?), nitrates
(NO,), and ammonia salts (NH.), and the organic peroxynitrates—such as per-
oxyacetyl nitrate (PAN) and peroxybenzoyl nitrate (PBzN). Others that may
play important roles in photochemical smog such as NO- and N-O- are treated
in detail in the reviews referenced herein, and are beyond the scope of this
paper.
This, is not a literature survey; rather, it is a brief yet critical
examination of existing information. When a number of references ap-
ply to the same data, only the most recent are generally given. Recent,
detailed, and relevant reviews include those of Schuck and Stephens, 1969;
Stephens, 1969; Altshuller and Bufalini, 1971; Air Quality Criteria for
Nitrogen Oxides, 1971; Stern, 1968; Calvert, Demerjian, and Kerr, 1972;
Demerjian, Kerr, and Calvert, 1973; Robinson and Robbins, 1972; Niki, Daby,
and Weinstock, 1972; and Levy, 1973.
ATMOSPHERIC CONCENTRATIONS AND SOURCES
NITRIC OXIDE AND NITROGEN DIOXIDE
Historically, the sum of the concentrations of nitric oxide and nitrogen
dioxide (NO ) has been used in referring to the concentrations of nitrogen
X
oxides in polluted atmospheres. This came about because the Jacobs-Hochheiser
43
-------
analytical method, which employs a colorimetric determination of nitrogen
dioxide as an azo dye, does not give the individual concentrations of ni-
tric oxide and nitrogen dioxide. That is unfortunate because the two species
have vastly different physical, chemical, and biological properties. For ex-
ample, NO is colorless and relatively nontoxic; but NO- is a deep red-brown,
is toxic, and is the major precursor to ozone in smog.
The recent introduction of chemiluminescent analytical methods specific to
nitric oxide will rectify this situation. They are based on the reaction
NO + 03 •* NO* 4- 02 (1)
in which the NO- is an electronically excited state that emits intense visi-
ble light. Reaction is also of great interest in the SST debate. Johnston
(1971) has suggested it as a process that could lead to a serious depletion
of ozone in the stratosphere if large amounts of NO are emitted there by jet
aircraft engines.
Robinson and Robbins (1972) suggest that NO formed by bacterial action, and
subsequently oxidized into N0~, could produce the NO,, levels of about 7 parts
per million measured in rural areas of North Carolina by Ripperton et at.
(1970).
The remaining sources of atmospheric NO are due to man-made pollution
X
resulting from high-temperature combustion process involving air. The reac-
tions are complex, but the overall equilibrium can be represented as
N2 + °2 "*" 2NO; AH = 43 kcal/mole (2)
Since the overall reaction is strongly endothermic, relatively small
increases in the reaction temperature during combustion greatly favor NO
production.
In typical, high-efficiency combustion systems (such as fossil-fuel power
plants and internal-combustion automobile engines) approximately 95 percent
of the N0x is emitted as NO; the remainder, as NO-. In polluted atmospheres,
44
-------
the NO is then oxidized into N0« by two distinct mechanisms. At relatively
high concentrations of NO (1,000 to 2,000 parts per million), it is thermal.
2NO -I- 02 •*• 2N02 (3)
At low ambient levels (0.5 ppm), it is photochemical (see the section on
atmospheric transformations and sinks).
NO + Hydrocarbons + Solar UV -»• NO- + 0, + other compounds (4)
Controls are being installed on automobiles and emissions from stationary
sources are being curtailed; therefore, the contribution of NO from such
X
sources as aircraft and domestic home heaters will become increasingly impor-
tant. Recently, the suggestion has been made that atmospheric nuclear tests
are sources of NO ; but fortunately, these have been relatively isolated oc-
j£
currences (Foley and Ruderman, 1972).
From the data tabulated by Robinson and Robbins (1972) and the measurement
of Ripperton et al. (1970), the levels of NO and NO™ in relatively unpolluted
environments fall within the ranges of about 1 to 3 and 1 to 5 ppb, respec-
tively. In urban air, however, these levels increase significantly. In
smoggy Los Angeles air, for example, the values for NO and N02 are typically
0.1 to 1.5 ppm and 0.05 to 0.3 ppm, respectively.
NITROUS OXIDE
This is the most abundant, naturally occurring oxide of nitrogen. Ambient
concentrations in nonpolluted air are typically between 0.25 and 0.5 ppm
(Cadle and Allen, 1970: Robinson and Robbins, 1972).
The major source of N?0 is evolution from the soil as the result of the
decomposition of nitrogen compounds by soil bacteria. Arnold (1959) veri-
fied this by showing that N~0 was produced by bacterial action on ammonia
and nitrate salts. The possibility that some NJ3 could be produced from the
oceans should not be ruled out (Junge and Hahn, 1971).
45
-------
In terms of anthropogenic sources, there is some evidence that N.,0 may be
a product from certain catalytic devices proposed for use on automobiles to
meet the 1975-76 Federal Emission Standards. It is too soon to realistical-
ly consider the consequences of this possible source, but they could be sig-
nificant in both the upper and the lower atmosphere.
NITROUS AND NITRIC ACIDS
Preliminary measurements indicate that nitric acid is present in trace
amounts (measured in ppb) in ambient photochemical smog (Price and Steph-
ens, 1971). No determination has been made in the normal troposphere, but
Levy (1973) has predicted values as high as 30 parts per billion. The main
formation reaction is generally assumed to be
OH + N02 + M -> HN03 + M (5)
A possible heterogenous path also exists.
N2°5 + H2° "*" 2HN03 (6>
Likewise, nitrous acid may well be formed in the atmosphere by the
reactions
NO + N02 + H20 5 2HONO (7)
OH + NO + M •+• HONO + M (8)
Nitrous acid has not yet been measured in ambient air, although some
researchers think it may play a significant role in the formation of
photochemical smog (Johnston, 1970; Demerjian, Kerr, and Calvert, 1972 and
1973).
It is interesting to note that nitric acid has been detected in the
10 —3
stratosphere at a maximum concentration of '^1 x 10 molecules cm at
M19 + 5) km (Williams et aZ.., 1972; Lazrus et al. , 1972).
46
-------
AMMONIA
The major source of ammonia is the bacterial breakdown of amino acids in
organic waste material (Altshuller, 1958; Junge, 1963; Robinson and Robbins,
1972). However, Junge (1963) states that both the soils and the oceans can
act as sources as well as sinks, depending on conditions.
Anthropogenic sources of ammonia are not as significant as the ones just
given. Yeti when coal and oil are burned, measurable quantities of ammon-
ia are emitted. Further, the catalyst systems proposed for automobiles so
they will meet the 1975-76 Federal Air Quality Standards could become addi-
tional sources of ammonia formed by the reaction below (Klimisch and Taylor,
1973).
5H2 + 2NO -»• 2NH3 + 2H20 (9)
As has been noted, the atmospheric concentration of ammonia depends on
biblogical activity; but the background level is around 6 ppb (Robinson and
Robbins, 1972). Measured concentrations have ranged from about 1 ppb
(Junge, 1963) to over 20 ppb (Lodge and Pate, 1966).
PAN AND PBzN
Very little data are available about the atmospheric concentrations of
these compounds on a global basis. Although peroxybenzoyl nitrate has been
identified in chamber experiments, it has not yet been detected in the atmo-
sphere. The peroxyacyl nitrates are products of photochemical reactions in
polluted atmospheres, involving olefins and N0« as well as other precursors
(Stephens, 1969). No natural sources are known.
The concentrations of peroxyacyl nitrates in ambient smog within the Los
Angeles Basin are between 0.005 and 0.05 parts per million. PAN is a pow-
erful lachrymator, causing damage to susceptible plants at concentrations
of greater than 0.01 ppm; and it may well have more serious and lasting
effects on man.
47
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PARTICULATE NITROGENOUS MATERIAL
Atmospheric nitrogenous aerosols may be formed by the reaction of NO- and
NH, to give compounds containing NO- NO- and NH,. One of the most common
J i , J , ''Hi
compounds identified in aerosol analysis is (NH,)2SO,.
Few data are available on the concentration of nitrate or ammonium in
aerosols; but generally, the particulate ions are more dilute than the gase
ous fractions of NO, and NH- (Robinson and Robbins, 1972). Lodge et al.
(1960) found nitrate concentrations of about 0.015 micrograms per cubic
meter in the mid-Pacific area, while Junge (1956) measured NO- and NH, con-
3 _
centrations of 0.08 and 0.04 yg/m , respectively, for Hawaii and average NO-
3 J
levels of about 0.33 yg/m for Florida.
ATMOSPHERIC TRANSFORMATIONS AND SINKS
NITROGEN OXIDES
There are two major mechanisms for the conversion of NO into NO- in the
troposphere. The thermal reaction
2NO + 02 + 2N02 (3)
is slow in ambient air, because the reaction rate depends on the square of
the nitric oxide concentration. However, the reaction is considerably faster
in such things as the plumes of fossil-fuel power plants, where concentra-
tions of 1,000 ppm and more are often encountered.
In simulated atmospheres containing only NO and air and irradiated with
X
ultraviolet light, the N02 photolyses to produce oxygen atoms which, in turn,
result in the formation of ozone when the NO levels become very small.
N02 + hV (2950 A - 4200 A) -»• NO + 0(3P) (10)
0 + 02 + M ->• 03+M (11)
48
-------
0~ + NO •> 07 + N09 (1)
*3 £* £
The net effect of irradiation on this strictly inoTgani,o system is to set up
a dynamic equilibrium that results in a low overall production of ()„:
\$>
N°2 + °2 "* N0 + °3 (5)
However, when hydrocarbons or oxygenated hydrocarbons are present, which is
the case in polluted atmospheres, this dynamic equilibrium is unbalanced.
The imbalance is particularly rapid if an olefin or an alkylated benzene is
used (both of which are common constituents of gasoline), and the following
events take place:
1. The hydrocarbons are oxidized and disappear.
2. Reaction products, such as aldehydes, nitrates, PAN, and others, are
formed.
3. Nitric oxide (NO) is rapidly converted into nitrogen dioxide (NO,,).
4. When all of the NO has been used up, substantial amounts of 0, begin to
appear. On the other hand, PAN and the aldehydes are formed from the
beginning of the reaction.
The full details of the mechanism are still not known, as pointed out in
recent reviews (Altshuller and Bufalini, 1971; Niki, Daby, and Weinstock,
1972; Demerjian, Kerr, and Calvert, 1973). These reviews adequately cover
the known details of the mechanism. Here, we will concentrate on some of the
more recent developments relating to the oxidation of nitric oxide.
The hydroxyl radical is now thought to be the main chain carrier in
photochemical smog (Demerjian, Kerr, and Calvert, 1972). It is inter-
esting that it was as late as 1969 that OH was first suggested to play
a significant role in the mechanism of photochemical smog formation (West-
berg, Cohen, and Wilson, 1971; Niki, Daby, and Weinstock, 1972; Stedman et
at., 1970; Heicklen, Westberg, and Cohen, 1971; Weinstock, Daby, and Niki,
49
-------
1971):
HO + CO ->• H + C02 (12)
H + 02 + M •> H02 + M (13)
H02 + NO + HO + N02 (14)
Recent data have shown that the oxidation of NO by Reaction 14 is rapid
(Davis et al., 1973).
For almost fifteen years, the general assumption was that Reaction 15,
where R is an alkyl group, was rapid and was a key process in the oxida-
tion of NO into N02 in photochemical smog.
R02 + NO -> N02 + RO (15)
However, Spicer, Villa, Wiebe, and Heicklen (1973), on the basis of their
experiments using methylperoxy radicals, CH.,0~, have stated flatly that this
oxidation does not occur and, consequently, that it should be omitted from
the generally accepted mechanisms for photochemical smog formation. Howev-
er, these results are difficult to reconcile with (1) the fast rate of the
somewhat analogous oxidation with H0», Reaction 14; (2) the 7 kcal/mole
greater exothermicity of Reaction 15 over Reaction 14 for R = CH«; and
(3) the generally accepted necessity of incorporating Reaction 15 into the
development of photochemical smog mechanisms (Altshuller and Bufalini, 1971;
Niki, Daby, and Weinstock, 1972; Demerjian, Kerr, and Calvert, 1973).
Clearly, further studies of this key oxidation step are required.
Other atmospheric transformations include the oxidation of NO by peroxy-
acetyl nitrate (PAN) (Schuck and Stephens, 1969) and by free radical spe-
cies, such as NO- and RO, (Demerjian, Kerr, and Calvert, 1973). Nitrous
acid may also be formed by one of the removal processes for NO :
X
N02 + NO + H20 -»• 2HONO (7)
50
-------
Nitrogen dioxide catalyzes the isomerization of olefins in the gas phase,
although the reaction rates under ambient conditions are probably too small
to make such reactions significant in the chemistry of urban atmospheres
(Sprung, Akimoto, and Pitts, 1971; Akimoto, Sprung, and Pitts, 1972).
NITROUS OXIDE, N20
In typical gas-phase reactions at room temperature, nitrous oxide is
generally considered to be quite inert, chemically. Thus, it has always
been assumed to be of little importance in tropospheric reactions. To date,
there is no experimental evidence that it is significantly involved in
photochemical smog formation. However, this view should be accepted with
some reservation because N^O is, in fact, an excellent source of oxygen
atoms. It may well be an unsuspected oxidant in tropospheric systems,
although this is only an "educated hunch."
Photodissociation of N90 proceeds by two routes — direct photolysis at
wavelengths around 2000 A, Process 16, and mercury photosensitization at
2537 A, Reaction 17:
N20 + hv — - N2 + OD) (16)
N90 + Hg(g) + hV - -~N9 + 0(3P) (17)
^ X=2537 &
Nitrous oxide does react with
N20 + 0(XD) — ^ NO + NO (18)
— - N + 0 (19)
But since the concentration of these electronically excited oxygen atoms is
extremely small in the troposphere (Levy, 1973), Reactions 18 and 19 are not
important loss mechanisms. They assume far more importance in the strato-
sphere, the major sink for N20. Thus, N20 is transported vertically where
it mainly undergoes photodissociation, but also reacts with 0( iD) atoms
51
-------
(McElroy and McConnell, 1971)-, since they are present in much larger concen-
trations in the stratosphere than in the troposphere.
It is interesting to note that Schultz, Junge, et al. (1970) suggest that
the tropospheric lifetime of N«0 may be ten years or less. This is much
smaller than the value of seventy years calculated by Bates and Hays (1967),
and may be indicative of the fact that N.O does undergo tropospheric reac-
tions that have not yet been identified.
NITROUS AND NITRIC ACIDS
There are two main mechanisms for the formation of nitrous acid in the
atmosphere:
NO + N02 + H20 -»• 2HONO (20)
OH + NO + M •> HONO + M (21)
Stuhl and Niki (1972) have studied Reaction 21. They found that at
1 atmosphere, it is in its second-order regime and has a bimolecular rate
9 -1 -1
constant of about 1 x 10 1 mole s . The fast rate could make this a sig-
nificant atmospheric formation reaction for HONO, particularly in the dark,
when the facile photolytic decomposition reaction below does not occur.
HONO 4- hv (X < 4000 A) ->• HO + NO (22)
The latter photolysis is the main sink for nitrous acid, as well as being
the main reason for the observation by Demerjian, Kerr, and Calvert (1972
and 1973) that HNO,, can increase the initial rate of smog-forming reactions.
The major gas-phase formation reaction for nitric acid is
OH + N02 + M -> HN03 + M (23)
This reaction is a rapid one; and under atmospheric conditions, should dis-
play second-order kinetics (Simonaitis and Heicklen, 1972; Anderson and
Kaufman, 1972; Morley and Smith, 1972; Westenberg and de Haas, 1972).
52
-------
Simonaitis and Heicklen reported a second-order rate constant of approxi-
9 -1-1
mately 10 1 mole s in reasonable agreement with the value given by Morley
and Smith.
Nitric acid is formed by the reaction
N,0, + H_0 -*• 2HNO- (24)
*• J £. J
This is believed to occur heterogeneously, since the gas-phase reaction is
very low (Levy, 1973).
The ultraviolet absorption spectrum of nitric acid has been determined by
Johnston and Graham (1973), and has been found to extend significantly into
o
the actinic ultraviolet to about 3,200 A. It is believed to undergo photo-
lysis in the atmosphere to produce the highly reactive species OH, with a
quantum yield as yet undetermined. From the continuous nature of the
absorption spectrum, it would appear to photodissociate with reasonable
efficiency.
HN03 + hV (X < 3,200 S) + OH + N02 (25)
Little information is available on the gas-phase atmospheric reactions of
HNOo. Recent measurements of the reaction
OH + HNO, •»• H,0 + NO (26)
«J ' t~ J
by Morley and Smith (1972) indicate that this reaction could be important in
both the polluted and unpolluted troposphere. The rate constant was given
8 —1 —1
as about 10 1 mole s . Although no measurements have been reported, the
analogous reaction for nitrous acid
OH + HN02 •*• H20 + N02 (27)
could also occur at a significant rate (Demerjian, Kerr, and Calvert, 1973).
Reactions with other radical species could occur for both these compounds,
although the highly reactive hydroxyl radical is almost certainly the most
53
-------
important. Finally, reactions with particulates and wash-out mechanisms are
likely to be significant removal .mechanisms for atmospheric nitric acid.
AMMONIA
Ammonia undergoes a rapid reaction with acid
NH3 + HNO -*• NH4N03 (28)
The reaction probably occurs via a heterogeneous mechanism. The reaction
with ozone is likely to be unimportant (Cadle and Allen, 1970).
Ammonia also reacts with oxygen atoms and with hydroxyl radicals
NH3 + 0 •> NH2 + OH (29)
NH3 + OH •> NH2 + H20 (30)
The respective rate constants are 1 x 10 1 mole s (Wong and Potter,
1963) and about 1 x 108 1 mole~1s~1 (Stuhl and Niki, 1972). The rapid
rate of Reaction 30 suggests that it could be a significant sink for atmo-
spheric ammonia. However, the main sink is likely to be the reactions with
acids already mentioned to produce aerosols.
o
Ammonia does not absorb at wavelengths exceeding 2,200 A and, consequent-
ly, does not undergo direct photolysis or excitation in the troposphere.
PAN AND PBzN
The complete mechanism for the formation of PAN has not been fully
determined, although Stephens (1969) thinks the final step is:
0 0
" I!
CH3COO + N02 -> CH3COON02
However, Hanst (1971) has suggested that a possible alternative or parallel
reaction is
54
-------
0 0
II II
Further work is required in order to fully understand the relative merits of
the two mechanisms.
PAN oxidizes nitric oxide in the gas phase to nitrogen dioxide at a rate
that makes the reaction of potential significance in the conversion of NO
into NO in polluted atmospheres (Schuck and Stephens, 1969; Schuck,
X
Stephens, and Price, 1972).
Although, PBZn has yet to be observed in the atmosphere, it is expected to
also act as an effective oxidizing agent for NO, even though the rate of ox-
idation may be slow because of the very small concentration (1 to 5 ppb) ex-
pected to be present in polluted atmospheres (Stephens, 1972). PAN does not
significantly absorb the solar radiation present in the lower atmosphere,
and it is difficult to obtain actual estimates of the maximum rate of photo-
lysis in ambient air (Stephens, 1969). Decomposition on surfaces or on
aerosol particles could be one of the sinks for PAN in the atmosphere, since
it has a low but erratic stability.
PARTICULATES
This is such a broad and complex area that it cannot be covered adequately
here. Detailed discussions have been given in two recent publications — "Air
Quality Criteria for Particulate Matter" (PHS, National Air Pollution Con-
trol Association, 1969), and "Aerosols and Atmospheric Chemistry" (G.M.
Hidy, Editor, Academic Press, N.Y. , 1972). Only a few examples will be,
given.
Nitrate aerosols represent the final stage in the atmospheric oxidation of
gaseous NO . Thus, according to Hidy and Friedlander (1971), nitrate partic-
X
ulates are formed from the large natural emissions of NO and NO- into the at-
mosphere. Substantial quantities of particulate nitrates are also formed in
all urban areas affected by photochemical smog. Thus, the atmospheric burden
55
-------
of particulate nitrates has become increasingly important since the levels
of NO have increased dramatically in urban regions throughout the U.S. dur-
ing the last few years.
Two mechanisms are suggested by Hidy and Friedlander for the formation of
particulate nitrate in the Los Angeles Basin.
1. The reaction between N02 and NaCl, the latter being present in particu-
late matter originating from the ocean.
2. Photochemical reactions involving NO,., and hydrocarbon vapors.
Particle-gas and particle-particle reactions can occur, but the latter
have received even less study than the former. Particle-particle reactions
are likely to occur in the size range below 1 micron.
The reaction between sulfuric acid and ammonia that produces (NH.)pSO, was
studied by Robbins and Cadle (1958). Their results helped to show some of
the effects of humidity on aerosol production.
The chief removal processes for particulate matter are the:
1. Coagulation of smaller particles to produce fallout.
2. Natural deposition of particles.
3. Washout processes in which the air is "scrubbed," for example, by rain.
In conclusion, the degree of sophistication in modeling the chemistry of
urban atmospheres is far from the stage in which heterogeneous reactions
involving particulates can be incorporated into the mechanisms. Much more
work needs to be carried out, both on the modeling aspects and in the chem-
istry and physics of atmospheric particulate matter.
CONTROL MEASURES
There are two general approaches to controlling the oxides of nitrogen:
(1) modifying the combustion process in such a way as to in s-ltu reduce the
nitric oxide formation; and (2) removing nitrogen oxides in the effluent
56
-------
exhaust gases by physical or chemical methods. These are discussed in detail
in the EPA document on the Control of NO from Stationary Sources, in "Con-
trol Techniques for CO, NO and Hydrocarbon Emissions from Mobile Sources"
X
(NAPCA 1970) and in Stern (1968); also, these approaches have been reviewed
recently by Bagg (1971).
STATIONARY SOURCES
Several means are currently employed to reduce the formation of NO during
X
the combustion process in large-scale burners, such as those associated with
fossil-fuel power plants.
The first involves redesigning the original combustion source and
includes a two-stage combustion process and tangential instead of horizon-
tal firing. Tangential firing might reduce NO levels by as much as 50
X
per cent. Similar and perhaps even more effective controls can be
achieved by two-stage combustion (Bagg, 1971).
The second general in situ approach for NO control in stationary sources
X
involves changing the chemistry of the combustion process by changing the
fuel or by introducing fuel additives. The former is relatively straightfor-
ward approach—the order of decreasing NO emissions being coal, fuel oil,
X
and natural gas. For example, a switch from fuel oil to gas may reduce NO
X
emissions by 50 percent. A major problem is the current and rapidly growing
shortage o.f natural gas in the U.S. The issue clearly involves a complex,
sensitive set of priorities dealing with considerations of ecology versus
economics1, and directly involving the public, legislators, control agencies,
and .industry.
Several techniques are employed to remove NO from exhaust gases following
X
combustion. These include, for example, catalytic reduction and sorption in
solutions or on solids such as molecular sieves or silica gel (NAPCA Control
Document, 1970; Stern, 1968; Bagg, 1971). Sorption techniques, although at-
tractive for small volumes of exhaust gases, are presently uneconomical for
large-scale combustion units. Catalytic conversion is more attractive; and
in the case of removing NO in the tail-gas from nitric acid plants, platinum
X
57
-------
metals have been proven to be quite effective, with up to a 90-percent
removal of NO reported (Anderson et al., 1961).
X
Again, we should note that multiple-point sources such as domestic home
heaters also contribute substantially to the atmospheric NO burden and that
X
control measures for such small individual units may well be necessary in the
not-too-distant future.
MOBILE SOURCES
The major mobile source of NO is the motor^ vehicle, but it is significant
X
that emissions from such jet aircraft engine have risen dramatically as new
and more powerful models have been introduced during the last fifteen years.
This fact, plus the greatly expanding fleets of new jumbo jets and booming
air-traffic business, make jet aircraft engines a potentially serious source
of NO , one that is already significant in all modern cities.
X
Several methods are employed to reduce NO emissions on automobile engines.
X
A summary follows.
Retrofit systems for used oars. These include such alterations as
changing the timing by a "vacuum spark disconnect" device and exhaust-
gas recirculation (EGR). Both devices are accredited for installation
in California cars, 1966 through 1970, which are notoriously high emit-
ters of NO . Unfortunately, the control strategy for CO and hydrocarbons
X
has resulted in combustion conditions more favorable to NO formation.
X
New engine systems. The 1970 Muskie Amendment to the National Clean Air
Act set strict controls for 1975 and 1976 for the emissions of hydrocarbons,
CO and NO . The controls are identical for hydrocarbons and CO for both
X
years, but in 1976 they are very much tighter for NO than in 1975. The
X
chief problem facing the automobile industry is that conventional techniques
used to lower hydrocarbons and carbon monoxide generally result in combustion
conditions favoring substantial increases in NO .
X
58
-------
The entire situation concerning the feasibility of the auto industry
meeting the controls for 1975 and 1976 has recently been reviewed by the
National Academy of Sciences Committee on Motor Vehicle Emissions (NAS, 1973).
In their report to the EPA, they cite four engines that will meet the 1975
standards. These include: (1) modified, conventional internal-combustion
engines with an oxidation catalyst; (2) the Wankel engine, with a thermal
reactor and EGR; (3) the diesel; and (4) the carbureted stratified-charge
engine.
Of these, the most favorable appear to be the stratified-charge engine and
the diesel, both of which operate at substantially less penalties in fuel
consumption and so on than the Wankel or the catalyst systems. Particularly
impressive is the new Honda CVCC stratified-charge 2,000 cc engine. In
official tests, it easily met the 1975 standards, and did so over 50,000
miles. The Honda engine is expected to become commercially available in
Japan in 1974.
For 1976, much stricter NO controls are mandated; and other, more complex
X
systems—including those with multi-catalyst and/or thermal reactors, or pos-
sibly fuel injection—may also be required. Here again, the Honda CVCC looks
promising since it already meets the 1976 standards for NO (National Academy
A
of Sciences, 1973).
NITROGENOUS MATERIALS IN THE ENVIRONMENT
Of all the gaseous nitrogenous compounds presently in the polluted
troposphere, only N02 and PAN have been identified as being both suf-
ficiently toxic and present at high enough levels in ambient air to be of
immediate concern. Other compounds may pose real or potential health hazards
(HNO,, HN02, PBzN, and so on); but to date, their chemical and biological
effects in polluted, ambient air are not known.
EFFECTS ON MAN
Nitrogen dioxide poses at least three major problems: (1) it is toxic to
59
-------
man; (2) it has a deep red-brown color, and thus in the higher levels encoun-
tered in photochemical smog it significantly reduces visibility (although it
can be responsible for some beautiful, smoggy sunsets); and (3) in photochem-
ical smog it is the precursor to ozone and PAN, both of which are highly tox-
ic to man and plants—much more so, in fact, than NO- itself ("Air Quality
Criteria for Photochemical Oxidants" National Air Pollution Control Adminis-
tration, Publication No. AP-53, March, 1970).
Stokinger (1959), in reviewing all environmental hazards except ionizing
radiation, stated:
Airborne pollutants are potentially responsible- for more of our ills
than are water- and food-borne contaminants together.... Many of the con-
ditions attributed to exposure to environmental pollutants are either
accelerations of the aging process or are associated with aging. This is
particularly true of the air pollutants; ozone and photochemical oxidants
merely add to and hasten the oxidative destruction of the lung and other
tissue sites; respiratory irritants hasten the onset of emphysema and
bronchitis and would appear to promote cancer of the respiratory tract.
Both the Environmental Protection Agency and the State of California have
set health-related, air-quality standards for NO . The EPA standard is 0.05
ppm, annual average. The California standard is 0.25 ppm per hour. There is
a current debate over the federal standard. Thus, strong criticism has been
'voiced by General Motors scientists, who claim it is too strict in two ways:
(1) the health-effects data on which the EPA based its value were inaccurate;
and (2) the Jacobs Hochheiser method for measuring N02 in ambient air in the
epidemiology study that formed a major input to the federal standard was
seriously in error (Heuss, Nebel, and Colucci, 1971). The second objection
has proven to be valid. The EPA is now making a major effort to obtain new
air-monitoring and health data, and on that basis to reevaluate its N09
standard.
With the significantly increasing levels of N02 in urban air, the health
considerations become a matter of more and more importance. One point should
be noted: Although NO does not seem to constitute a health hazard in itself,
it is readily converted to N02 at low ambient levels in photochemical smog
and thermally at high levels of NO in exhaust plumes (as pointed out elsewhere
60
-------
in this paper). Thus, for example, a plume from a major fossil-fuel power
plant was invisible when it left the stack; but some ten miles and more down-
wind from the plant, an N02 level of approximately 6 ppm were measured at
2,000 feet altitude. These rather startling data were taken on an air-
monitoring survey utilizing an aircraft instrumented to measure air pollutants
and operated by a joint NASA-Ames University of California, Riverside team
(Gloria, Pitts, Behar, Reinish, and Zafonte, 1973). While there was virtual-
ly no possibility of N02 levels approaching that magnitude reaching the
ground from that particular plume, it is sobering to observe such an effi-
cient atmospheric conversion of nitric oxide into nitrogen dioxide.
To date there is no air-quality standard for PAN. In part, this is because
PAN is presently measured at only one monitoring station in the world, the
University of California Statewide Air Pollution Research Center. PAN is
known to be a powerful lachrymator and to have other highly undesirable
effects on man (Air Quality Criteria for Photochemical Oxidants, 1970); but
such health effects have yet to be clarified and quantified in any detail.
EFFECTS ON PLANTS
Both NO™ and PAN are phytoxicants, although the latter is far more destruc-
tive since it causes damage to certain sensitive agricultural crops and orna-
mental plants at levels as low as 15 to 20 ppb after four hours of exposure
(Taylor and MacLean, 1970). Such plants include the petunia, tomato, dwarf
meadow-grass, and romaine lettuce. An ambient level for PAN of 15 to 20 ppb
is often reached, even exceeded, in areas of high photochemical smog; for
example, maximums of 58 ppb at Riverside California (Taylor, 1958) and 50 ppb
at Salt Lake City (Tingey and Hill, 1967).
For plant damage by NO- to become serious, levels on the order of 5 ppm or
more generally have to be realized (Taylor, 1970). These are factors of at
least five to ten more than those usually encountered in ambient air, even
during heavy smog attacks. Thus, as far as plant damage is concerned, the
critical role of N02 seems to be that of a key precursor to PAN.
61
-------
It is also interesting that the alkyl analogs to PAN, peroxypropionyl
0 0
" ii
nitrate PPN (CJ^r C-OON02) and peroxybutyrl nitrate PEN (C^H? CONO™) are even
more toxic than PAN itself (Taylor, 1970). Thus, although the ambient levels
of these analogs are considerably lower than that of PAN, their increased
toxicity would suggest they may be responsible for. significant damage to
field crops and ornamental plants in regions of high photochemical smog.
REFERENCES
1. E.A. Schuck and E.R. Stephens. Oxides of nitrogen, Advan. Environ. Soi.
Teohnol. 1:73 (1969).
2. E.R. Stephens. The formation, reactions, and properties of peroxyacyl
nitrates (PANS) in photochemical air pollution, Advan. Environ. Soi.
Tectmol. 1:119 (1969).
3. A.P. Altshuller and J.J. Bufalini. Environ. Soi. Teohnol. 5:39 (1971).
4. E. Robinson and R.C. Robbins. Emissions, concentrations, and fate of
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5. H. Levy, II. Photochemistry of the troposphere. Advan. Photoohem. 9
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10. M.A. Price and E.R. Stephens. Private communication (1971).
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12. C.E. Junge. Air Chemistry and Radioactivity, Academic Press, New York
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62
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13. A.P. Altshuller. Tellus 10:479 (1958).
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J.A. Weinman. J. Atmos. Sai. 29, 1376 (1972).
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18. J.P. Lodge, Jr., A.J. MacDonald, and E. Volman. Tellus 12:184 (1960).
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20. M.B. McElroy and J.C. McConnell. J. Atmos. Sci. 28:1,095 (1971).
21. K. Schutz, C. Junge, R. Beck, and B. Albrecht. J. Geophys. Ees. 75:2,230
(1970).
22. D.R. Bates and P.B. Hays. Planet, Space Sci. 15:189 (1967).
23. H.M. Foley and M.A. Ruderman. Stratospheric nitric oxide production
from past nuclear explosions and its reference to projected SST pol-
lution, Institute for Defense Analyses, Washington, B.C. Paper P-894,
AD 751295 (August, 1972).
24. R. Simonaitis and J. Heicklen. Int. J. Chem. Kinetics 4:529 (1972).
25. J.G. Anderson and F. Kaufman. Chem. Phys. Lett. 16:375 (1972).
26. C. Morley and J.W.M. Smith. JCS Faraday II 68:1,016 (1972).
27. A.A. Westenberg and N. DeHaas. J. Chem. Phys. 57:5,375 (1972).
28. M.A. Price and E.R. Stephens. Private communication (1971).
29. H.S. Johnston. Project Clean Air Task Force Assessments, Vol. 4, Task
Force 7, Section 3, Univ. of California (1970).
30. A.C. Stern (ed.). Air Pollution, Academic Press, New York City (1968).
31. K.L. Demerjian, J.A. Kerr, and J.C. Calvert. Environ. Lett. 3:73
(1972).
32. H. Niki, E.E. Daby, and B. Weinstock. Mechanisms of smog reactions, In
Advances in Chemistry Series, 113 (1972).
33. J.L. Sprung, H. Akimoto, and J.N. Pitts, Jr., J. Amer. Chem. Soc. 93:
4,358 (1971).
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34. H. Akimoto, J.L. Sprung, and J.N. Pitts, Jr. J. Amer. Chem. Soo. 94:
4,850 (1972).
35. H. Johnston and R. Graham. J. Phys. Chem. 77:62 (1973)-
36. G.M. Hidy and S. Friedlander. Proceedings, 2nd Int. Clean Air Congress,
Academic Press, New York City, (1971).
37. Air Quality Criteria for Particulate Matter. U.S. Dept. of HEW, Nation-
al Air Pollution Control Administration (January, 1969).
38. H.M. Englund and W.T. Beery. Proceedings, 2nd Int. Clean Air Congress,
Academic Press, New York City (1971).
39. H.R. Gloria, J.N. Pitts, Jr., J.V- Behar, R.F. Reinisch, and L. Zafonte.
Airborne measurements of air pollution chemistry and transport, submitted
to J. Environ. Sci. Technol.
40. J. Heicklen, K. Westberg, and N. Cohen. Pub. 115-69, Center for Air
Environmental Studies, Univ. Park, Pa. (1969).
41. E.A. Schuck, E.R. Stephens, and M.A. Price. Paper presented at the
163rd ACS Meeting, Boston (April 9-14, 1972).
42. C.W. Spicer, A. Villa, H.A. Wiebe, and J. Heicklen. J. Amer. Chem. Soo.
95:13 (1973).
43. D.H. Stedman, E.D. Morris, Jr., E.E. Daby, H. Niki, and B. Weinstock.
Paper, Div. of Water, Air, and Waste Chem., 160th National ACS Meeting,
Chicago (September, 1970).
44. H.E. Stokinger. Amer. Ind. Eyg. J. 30:195 (1969).
45. B. Weinstock, E.E. Daby, and H. Niki. Discussion on a paper presented
by E.R. Stephens, In Chemical Reactions in Urban Atmospheres, C.S. Tues-
day (ed.), Elsevier, N.Y., p. 54-55 (1971).
46. K. Westberg, N. Cohen, and K.W. Wilson. Science 171:1,013 (1971).
47. O.C. Taylor and D.C. Maclean. In Recognition of Air Pollution Injury to
Vegetation: A Pictorial Atlas, Informative Report No. 1, TR-7, Agricul-
tural Committee, Air Pollution Control Assn., Pittsburgh (1970).
48. O.C. Taylor. Effects of oxidant air pollutants, Occupational Med. 10:53-
60 (1968).
49. D.T. Tingey and A.C. Hill. The occurrence of photochemical phytotoxi-
cants in the Salt Lake Valley, Utah Acad. PPOQ. 44:1:387-395 (1967).
50. Control Techniques for CO, NO and Hydrocarbon Emissions from Mobile
Sources. National Air Pollution Control Admin. Pub. AP-66 (1970).
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51. Control Techniques for Nitrogen Oxide Emissions from Stationary Sources.
National Air Pollution Control Admin. Pub. AP-66 (March, 1970).
52. Report to the EPA. Committee on Motor Vehicle Emission, National
Academy of Sciences (February, 1973).
53. Air Quality Criteria for Photochemical Oxidants. National Air Pollution
Control Admin. Pub. AP-63 (March, 1970).
54. F. Stuhl and H. Niki. J. Chen. Physios 57:3,677 (1972).
55. J.M. Heuss, G.J. Nebel, and J.M. Colucci. Air Pollut. Cont. Assoo. J.
21:535 (1971).
56. D.S. Earth, J.C. Romanovsky, J.H. Knelson, A.P. Altshuller, and R.J.M.
Horton. Air Pollut. Cant. Assoo. J. 21:544 (1971).
57. R.C. Robbins and R.D. Cadle. J. Phys. Chem. 62:469 (1958).
58. D.D. Davis, W.A. Payne, and L.J. Stief. Science 179:280 (1973).
59. P.L. Hanst. Air Pollut. Cont. Assoo. J. 21:269 (1971).
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Crop Production
Sources of Nitrogenous Compouncs and Methods of Control
FRANK B. VIETS, JR. AND SAMUEL R. ALDRICH
THE SOURCES OF NITROGEN FOR FOOD AND MEAT PRODUCTION
A RECENT STUDY of the National Research Council—National Academy of Sciences
(Alexander et al., 1972) indicates that the United States needs about 18.5
million tons of available nitrogen on farms annually to produce our needs for
protein and other farm-produced products. These calculations assumed an effi-
ciency of only 3.75 percent in nitrogen use because of a low recovery by
plants (estimated to be 50 per cent) and various items of waste. The nitrogen
needed to produce commercial fish in farm ponds and for our substantial export
of farm produets_was not considered.
A very high proportion of our nitrogen needs comes about because^ of Hour
preferences for meat and other proteins of animal origin, such as eggs, milk,
and cheese. We need about 164 pounds of nitrogen per capita each year to pro-
duce our meat and animal products, and only 10.2 pounds for the plant proteins
that we consume directly. These amounts and relationships are not likely to
change unless we alter our preference for proteins of animal origin. As a
nation, our preference for animal proteins started to go up rapidly in the
early 1940s. Population growth and change in food habits have increased our
needs for available N on farms by almost 8 million tons since 1940.
Another estimate of the nitrogen needed for plant production on farms is
the one made by Stanford et al, (1970) that all harvested crops in 1969 con-
tained 9.5 million tons of nitrogen. Applying the same 50-percent efficien-
cy factor for plant recovery of N used by the NAS Committee, the result is 19
million tons of available N needed on farms, close to the 18.5 million tons
given in the NAS report.
The greatest speculative factor entering in these calculations of the
national need for on-farm nitrogen is the assumption that the plant must
67
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have twice as much nitrogen available to its roots as it actually absorbs. An
average recovery of 50 percent is compatible with the estimate made by Allison
(1966), after an exhaustive survey of the data available. Field experiments
have shown that the recovery of nitrogen by the plant can be as low as 25 and
as high as 85 percent. Recovery is never 100 percent. Although an assumed
recovery value of 50 percent may be satisfactory for a national average in the
absence of better data, it cannot be applied to a given crop, area, or manage-
ment system.
What is the source of nitrogen for crop and animal production? Several
attempts have been made to make national and some state N balance sheets, but
a neat tabulation of them might convey the impression that they are really
more accurate than their highly speculative nature would warrant. The largest
voids in information on the input side are the contributions of nonsymbiotic
free-living bacteria; algae; the root-nodule bacteria of legumes; and the pos-
sibly changing inputs from the atmosphere in rain, dry fallout, and direct
absorption of ammonia resulting from air pollution by various forms of fixed
nitrogen. The largest void on the output side is the loss by bacterial deni-
trification of fixed N that shows up in all precise N-balance-sheet experi-
ments. Little is known about denitrification in the field, except that it is
favored by the low oxygen supply in the soil caused by waterlogging or by
incorporating massive amounts of organic waste. Dehitrification also appears
to occur in oxygen-deficient microenvironments in soils that appear to be
well-aerated, based on the macromeasurements usually made of oxygen in soil.
Rain and snow generally contain 0.7 to 1 ppm of N, as ammonium and nitrate.
Concentrations are generally higher near urban and industrial centers than in
rural areas because of the nitrogen oxides and ammonia produced by burning
fossil fuels. This raises the concentration in surface runoff, which, in
turn, adds enough N in most surface water to support algal growth. Runoff
from forest and grassland areas may have a lower N concentration in inorganic
form because of the ability of these N-starved systems to capture and store
nitrogen, but the loss of inorganic N may be more than made up by the amount
of organic N coming from the washout of dead plant residues and the erosion of
68
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soil organic matter.
Precipitation adds an estimated 1.5 million tons of nitrogen annually to
the harvested, cropland surface of the United States (Stanford et al., 1970).
Alexander et al. (1972) estimated 6.2 million tons for the total U. S. land
area. Information is very poor on whether the concentration is changing. We
have few measurements on N in dry fallout, and none on the absorption of
ammonia as the gas directly from the air by soils, water, and plants. Enough
information is available to indicate that ammonia absorption cannot be ignored
in the vicinity of some industrial plants, cattle feedlots, dairy farms, sew-
age-effluent lagoons, and ammonia stripping towers'at tertiary sewage treat-
ment plants.
Unquestionably in the past, the available N coming from the decomposition
of soil organic matter was the largest single source of nitrogen for crop and
animal production. Even now this is true in most agricultural areas—except
in irrigated deserts, some highly productive sections of the Corn Belt, and
many sandy coastal soils devoted to vegetable production. This is nitrogen
that was stored in the soil when it was in grass and forest. The loss of soil
organic N from grass and soils and from forested-area soils when they are put
into cultivation has been documented extensively.
George Stanford estimated that 1.75 billion tons of organic N has been lost
from the cultivated soils of the United States in the last hundred years of
cultivation. How much of this N was lost by erosion, crop removal, denitrifi-
cation, and the percolation of nitrate into ground water is not known. Viets
and Hageman (1971) and others have suggested that deep percolation of nitrate
from the decomposition of the rich prairie soils in the Midwest was a possible
source of the high nitrates in the well water of many Midwest states, noted in
the 1930s and 1940s and associated at that time with a high incidence of
methemoglobinemia in infants. In certain areas it is likely that surface
runoff or leaching from livestock feeding areas and human privies are the pri-
mary sources of high concentrations of nitrate in well water.
69
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One current estimate of available nitrogen still coming from the exploita-
tion of this stored N pool is 3.4 million tons annually (Alexander et at.,
1972). Little doubt exists in the minds of most soil scientists and agrono-
mists that the continued exploitation of this pool of nitrogen is undesirable,
since that jeopardizes the maintaining of soil physical properties and contin-
ued soil productivity. However, much needs to be learned about the specific
nitrogen-supplying capacities of various soils and how these are affected by
cropping, management, and fertilizer practices.
The most accurate estimate of nitrogen inputs available are those from USDA
tonnage reports for commercial fertilizers. Farm and nonfarm use of commer-
cial fertilizer N has increased from about 0.3 million ton in 1940 to over 8
million tons in 1972. Perhaps as much as 3 million tons of nitrogen were
needed to offset a decrease in symbiotically fixed nitrogen. We do not have
data on the legume acreage planted, but seed production of alfalfa, clovers,
and lespedeza (the main N fixers) declined from 405 million pounds in 1940 to
272 million pounds in 1970.
Another interesting comparison is that the increase in fertilizer nitrogen
used on farms was 6.6 million tons from 1940 and through 1968. This corre-
sponds with the increase of 8 million tons of nitrogen needed on farms in
order to produce our increased protein requirements for the same period, the
latter from the NAS report.
This enormous increase in the use of fertilizer N has been part of the cir-
cumstantial evidence used by those claiming that the use of nitrogen is
destroying the "balance of nature" and is causing an accumulation of nitrate
in lakes and aquifers. On the basis of the cited estimates of the amount of
nitrogen needed on farms, fertilizer N supplies from 30 to 40 percent of our
national nitrogen needs. For corn grown under central-pivot sprinkler systems
on sandy soils in parts of the West, fertilizer N must supply practically all
of the nitrogen. In contrast, for wheat grown in alternate fallow-wheat sys-
tems in some parts of the Great Plains, no fertilizer N used to be needed; but
the situation is changing because of higher-yielding varieties and the deple-
tion of the organic matter in the soil.
70
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Practically all commercial N is now the product of ammonium fixation, using
air and natural gas as the raw materials. Ninety percent of the nitrogen sold
to farmers is anhydrous ammonia, ammonium solutions of salts, and urea. Anhy-
drous and aqua ammonia make up over half of the total. From the standpoint of
potential loss to the environment under most conditions of fertilizer use, the
source makes little difference. Urea quickly hydrolyzes in the soil to form
ammonium ions, regardless of whether that urea came from animal urine or out
of a fertilizer bag. Ammonium ions, whether they come from fertilizers or the
decomposition of soil organic matter, plant residues, or organic wastes, are
quickly nitrified by nitrifying bacteria under favorable moisture and tempera-
ture conditions to form nitrate. Nitrate is free to move downward into the
soil water.
Nitrogen transformations in nature are shown in the simplified N cycle
illustrated in the figure.
Plants use mostly nitrate N.because that is the form that is generally
available in the soil. Most species can use ammonium, as shown by exten-
sive work in solution and sand cultures. Yet, in the field, plants are likely
to use little ammonium from fertilizers and organic sources before nitrifica-
tion takes it away.
Some alternate (but expensive) "slow release" forms of nitrogen are avail-
able. These include organic wastes and manures. Urea-formaldehyde complexes
have been available for more than twenty years, but are too expensive for farm
use. Nitrification inhibitors such as N-serve (a pyridine compound) and
potassium azide are commercially available, but are also expensive and seldom
used. The side effects of using large quantities are unknown. To accomplish
the slow release of N, fertilizer pellets can be encased in plastic or resin-
ous membranes and urea pellets can be coated with sulfur. Such materials are
expensive, and probably will not come into general farm use under present con-
ditions. It is not clear whether slow-release materials would be helpful in
reducing the nitrate content of surface and ground water, because, as pointed
out by Allison (1965), the highest nitrogen recovery rates by crops are
71
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N-oxide gases
ANIMALS
ATMOSPHERE
ORGANIC NITROGEN
Humus, plant residues
itrogen oxide gases
following
dentrification
PLANTS
'INORGANIC NITROGEN'
Nitrate (N0£) Plant
available and potentially
teachable
FIG. I SIMPLIFIED NITROGEN CYCLE
observed after an application of readily available forms of nitrogen and prior
to the period of rapid utilization. Delayed release may result in more
nitrate after crop uptake ceases, and may also increase the possibility of
leaching.
Fertilizers are a diffuse or nonpoint potential source of N pollution,
except for accidental spillage in warehousing or transport. Nitrate can
become concentrated in water by the evaporation of drainage in impoundments,
or in the percolate from soil by the evapotranspiration of plants. In this
respect, the accumulation of nitrate is similar to that of the salts
72
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associated with salinity.
Farm and ranch animals produce about 6.6 million tons of nitrogen in feces
annually (Alexander, 1972). A portion of this N escapes into the air as ammo-
nia; part is lost by denitrification. Much of this waste is deposited direct-
ly on range and farm land. Over half of the total is now produced in concen-
trated areas of intensive feeding operations, and the number of these direct
sources of environmental contamination is growing.
The point here is the extent to which animal wastes can be substituted for
commercial fertilizers. If all of this nitrogen could be saved and the loss
prevented, that would amount to about 33 pounds for each of 400 million culti-
vated acres. Since over half of the N is deposited in diffuse sources, and
probably half is volatilized by denitrification or ammonia escaping from the
other half, only about 8 pounds per acre are left as a substitute for ferti-
lizer N on crop land.
Another estimate reported by Better Crops With Plant Food is the one of
White-Stevens that the nitrogen in the nation's total manure production to-
tals about 2 percent of the N used in fertilizers. The manure spread on 500
million acres of arable land would amount to only 0.5 pound of N per acre.
CAUSES FOR THE INCREASING USE OF NITROGEN FERTILIZER
The use of nitrogen fertilizer has spiraled, for a number of reasons that
are closely interrelated and by no means mutually exclusive.
1. The shift to proteins of animal origin. This was pointed out previously
as one of the causes of our greatly increased fertilizer N needs.
Increase in fertilizer N use closely parallels increased on-farmsite fer-
tilizer N needs.
2. Soil depletion. Our once-enormous reserves of humus N—accumulated
through centuries in land covered with grass or forest (N-storing sys-
tems)—have been depleted in soil fertility in many areas as a result of
73
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soil erosion, crop removal, tile drainage, and other losses associated
with cultivation. As mentioned, one estimate indicates that our crop land
soils have lost 1.75 billion tons of N in the last century. Other esti-
mates place the loss of N in rich Midwest soils at 40 percent. Long-term
plot studies in the United States and Europe show that nonfertilized land
decreases in productivity until it reaches a stable level that is too low
for profitable farming and totally inadequate to meet the needs for food
and natural fibers.
3. Better crop varieties and improved cultural practices. Continued
improvements in crop varieties—through plant breeding; cultural prac-
tices; weed, insect, and disease control; irrigation; and land drainage—
have led to potential yield levels at least twice those of 1940. These
potential levels can be realized only if the N requirements of crops can
be satisfied. Viewed another way, these higher-yielding crops will
respond profitably to higher application rates for nitrogen fertilizer.
4. Declining price of N fertilizer. Since World War Two the cost of ferti-
lizer N to the farmer has declined continuously because of advances in
ammonia fixation technology, transportation (some pipelines), and bulk
handling (to and on the farm). The cost per unit of nitrogen has dropped
to at least half, and in some areas to a fourth of the price immediately
after the war. In some areas, anhydrous ammonia has probably been sold at
a loss because of an oversupply. The price has now leveled off, and will
probably increase steadily because of the scarcity of natural gas.
The declining cost of nitrogen and rising prices of other inputs and farm
products has given the farmer an economic incentive to use N, and to sub-
stitute it for N-fixing legumes and for spreading manure on the fields.
Farmers in semiarid and irrigated areas simply cannot afford to use soil-
or reservoir-stored water for producing N-fixing legumes, unless they have
a competitive cash market for hay or use those legumes in livestock pro-
grams. Although the effect of the lower prices for N on agricultural
practices can be described in general terms, it cannot be separated from
the other economic and technological influences that have occurred since
74
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World War Two.
5. Less cultivated land needed. In another section, we have elaborated on
the positive environmental benefits accruing during the last thirty years
from the reductions in the amount of cultivated land needed to supply our
domestic and foreign markets with agricultural products. The proportion
of total need of the nonleguminous crops for nitrogen supplied by break-
down of soil humus may vary from almost 100 percent where no fertilizer is
\
used to only 5 percent or less on sands with a good water supply. The
gradual increase in the average yield per acre—requiring more total N—
and the shrinkage in the acreage needed for cultivated crops have both
contributed to a reduced role for native soil nitrogen and to a marked
increase in the nitrogen deficit that must be made up with fertilizer,
animal manures, and/or legumes.
6. A decline in the acreage of nitrogen-fixing leguminous crops. Alfalfa,
clovers and lespedeza are capable of converting atmospheric N_ into plant-
available forms, through symbiotic nitrogen fixation in root nodules. The
acreage of these crops affects nitrogen requirements in two ways. First,
the need to supply nitrogen as fertilizer or from other sources is reduced
when leguminous crops replace grass-forage crops which require supplemen-
tal nitrogen. Second, alfalfa, clover, and lespedeza enrich the soil in
nitrogen, thus reducing the need for supplemental N for succeeding crops.
The production of alfalfa, clover, and lespedeza seed totaled 360 million
pounds in 1940 and 516 million in 1950, but declined to 244 million in
1970. Assuming that all of the seed was planted and taking into account
the estimated quantities of atmospheric nitrogen fixed by these legumes,
an additional 1 million tons of fertilizer N would have been needed in
1970 to replace the decline in symbiotically fixed nitrogen compared to
1940, and 3.7 million tons compared to 1950.
The impact of large-seeded legumes that are harvested for seed (dry edible
beans, field beans, and soybeans) is difficult to assess. Though capable
of utilizing atmospheric N, these plants contain more nitrogen in the har-
vested grain than the nodules are capable of fixing. Perhaps 60 to 70
75
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pounds per acre is a realistic expectation of the nitrogen that is fixed
per average acre of field beans and soybeans. Based on the fixation of 60
pounds per acre, the change in soybean acreage (from 4.8 million in 1940
to 13.8 in 1950 and 45.8 in 1972) would have supplied 1.23 million addi-
tional tons of N in 1972 versus 1940. However, approximately 40 percent
of the soybean crop is exported, reducing the N-equivalency figure to
about 0.9 million ton. Theoretically, this amount is available as an off-
set against the 1 to 3.7 million tons of nitrogen lost to the domestic
system as a result of a decline in the acreage of alfalfa, clover, and
lespedeza.
SOME OVERLOOKED ENVIRONMENTAL BENEFITS
FROM FERTILIZER USE
A desirable consequence of the higher yield levels obtained through the
application of modern technology, including the use of fertilizers, is the
substantial reduction in cropland acreage, while still meeting our nation-
al needs for farm products. Although our food needs have grown by about 1
percent a year for the last thirty years, the cultivated acres needed for this
production have decreased at the net rate of some 1.4 million acres a year.
To quote from the NAS study (Alexander, 1972):
The 1968 maize crop was harvested from 55.7 million acres yielding 78.4
bushels per acre, whereas the 1940 crop came from.86.4 million acres
yielding 28.4 bushels per acre. If nitrogen fertilizers were removed from
the present scene, productivity would gradually decline and would eventu-
ally revert to the 1940 levels and even lower. Reserves of native soil
nitrogen would be further depleted. If the productivity of American farms
should return to 1940 levels, 98 million additional harvested acres of
corn would be required to produce the equivalent of the 1968 crop.
The report then discusses wheat in a similar fashion. These consequences of
the restriction of fertilizer use on land needs were previously pointed out by
Viets (1971), Barrens (1971), and Aldrich (1972). Ibach (1966) was ahead of
his time when he projected alternatives for the U. S. in 1981, pointing out
76
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that we could meet our food and natural fiber needs with a low fertility sys-
tem of 8.6 million tons of fertilizer nutrients (N, P2°5» and K2°^ on ^50.8
million acres of cropland, or a high fertility system with 26.6 million tons
of nutrients on 300.5 million acres. In this case, 18 million tons of nutri-
ents would be substituted for 150.3 million acres, or about 8.35 acres per ton
of nutrients.
The environmental significance of reducing the cultivated land ares is that
soil erosion and pollution from farming operations are reduced and more land
is available for areas of natural cover and habitats for wild life, and recre-
ational uses. Having less land in cultivated crops permits more land to be
returned to sod crops, grass, and native cover. The net result is less soil
erosion. The effects of these land shifts on water pollution and erosion, and
whether they were made will vary in different places. In the drier Great
Plains, some former wheatland was planted to grass; in the Corn Belt, soybeans
were substituted mainly for oats, wheat, and hay—increasing the erosion
hazard. There are no reliable estimates about the specific effects of nitro-
gen and consequent land retirement on sediment-carried nutrients, although
there are much experimental data on which such estimates could be based.
With less cultivated land, there is less pollution resulting from the farm
operations that must be performed on land without regard to the yield level.
Examples would include use of herbicides and insecticides; also, tractors that
can pollute the rural air as well as the industrial area where they are manu-
factured. There is also a saving in the consumption of fossil fuels. Another
aspect is that land is freed for natural cover, wildlife habitats, and recrea-
tional uses.
RELATION OF FERTILIZER USE TO WATER AND FOOD QUALITY
There is a dearth of data on the nitrate content of the water in streams—
even more so, concerning underground waters—with which to place the nitrate
problem in perspective. Common deficiencies in the records involve (1) the
lack of long-term, continuous measurements to serve as benchmarks; (2) too few
77
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sampling sites; and (3) inadequate information with which to quantify the con-
tributions from fertilizer, animal wastes, human wastes, and soil organic mat-
ter.
Nevertheless, some important generalizations can be made:
1. The nitrate concentration is increasing in some rivers that drain the
great agricultural section of central U. S. The trend is erratic but
undeniably upward. The increase in nitrate content is far less than is
indicated in some environmental literature.
2. Selected small rivers and creeks in the Midwest sometimes exceed nitrate N
level of 10 parts per million, the present standard set by the U. S. Pub-
lic Health Service. Four factors are probably contributing to the exces-
sive nitrate: the soils are inherently high in nitrogen in the form of
humus; row crops, especially corn and soybeans, are the dominant ones;
relatively large amounts of nitrogen fertilizer are applied; and much of
the area has artificial drainage in the form of drain tiles.
In some municipal water supplies, nitrates exceed the USPHS standard, occa-
sionally; for example, in Decatur, Illinois, and in parts of the San
Joaquin and coastal valleys of California. Nightingale (1970) reported
that the NO., in ground water was increasing as fast under the urban
Fresno-Clovis area as under adjacent agricultural areas. In Illinois, the
likely cause is the aggregate effect of natural conditions plus crop pro-
duction practices. Urban wastes are not a significant source of nitrate
in the upper Sangamon River from which Decatur obtains its water. In Cal-
ifornia, the high nitrate levels are believed to trace mainly to nitrate
deposits from ancient geological periods.
3. Nitrates in many farm wells in the central U. S. range from one to ten
times the standard for drinking water. This is neither a recent nor local
problem. A survey of 732 wells in Iowa in 1939 revealed that 27 percent
of them were above the 10 ppm limit of nitrate N, 9 percent of them were
four times more than the standard, and 1 percent were ten times above it.
Only insignificant amounts of nitrogen had been used prior to that time.
78
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Of 7,000 Illinois wells less than 25 feet deep, about 28 percent exceeded
10 ppm of nitrate N, the USPHS standard, from 1895 to 1966. In 1970, 62
per cent of the dug wells in a southern Illinois county exceeded the
standard, and nearly 4 percent were ten times the standard. Minnesota
experienced 139 cases of methemoglobinemia and 14 deaths, attributed to
high nitrate levels in farm wells from January, 1947, to the summer of
1949—a period prior to significant use of fertilizers in that state.
Early indications are that the sources of nitrates in farm wells are prob-
ably animal wastes, septic-tank fields, privies, and long-term accumula-
tions from mineralization of humus. Fertilizer nitrogen could be an
important source in shallow wells on sandy soils.
The problem of identifying the specific portion of the nitrate in a stream
or in ground water that comes from the application of nitrogen fertilizer has
not been solved. Kohl, Shearer, and Commoner (1971) reported their estimates
of the fertilizer-N input into the Sangamon River, which feeds Lake Decatur
(the Decatur, Illinois water supply). Nitrate N in the Sangamon is occasion-
ally over 10 parts per million.
The method employed makes use of the ratio of the heavy, naturally-occurring
15 14
isotope N to the more abundant isotope N „ This method depends on the
degree of natural enrichment of the nitrate coming from oxidation of soil
organic matter with the heavy isotope and the isotope ratio in N fertilizers,
which is supposed to be abo'ut the same as in the atmosphere.
theory, determining the isotope ratio of nitrate in the drainage or in the
river should give an estimate of nitrate coming from current or past N ferti-
lization. Kohl et dl, concluded that at peak nitrate concentrations in the
spring, 55 to 60 percent of the nitrate came from fertilizers. This conclu-
sion has been challenged (Hauck et dl., 1972) by ten soil scientists experi-
enced in the use of N for tracer-N studies. Various technical grounds are
involved in the challenge, revolving mostly around the adequacy of the sam-
15 14
pling. Tracer research using N /N may help pinpoint sources of nitrates,
but may not prove useful unless alternative means can be found for supplying
79
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nitrogen that will produce adequate food without an equal likelihood of con-
tributing nitrates to water.
Excessive nitrate in plants can be toxic to animals. This has been known
since at least 1895, when Mayo reported the death of cattle in Kansas from
drought-stricken corn. A high nitrate content in plants can produce highly
toxic gases when such plants are ensiled. Deaths of infants fed canned spin-
ach and beets high in nitrate have been reported in Europe, but not in the
United States (Alexander et al., 1972). Under drought conditions, some plant
species accumulate nitrate in the vegetative parts and others do not. The
nitrate content of seeds is never high in proportion to that of the vegeta-
tive parts of plants. Lowe and Hamilton (1967) reported 0 to 4.6 ppm in 90
samples of corn, oats, wheat, barley, and lima beans, and 8.6 to 23.8 ppm in
10 samples of soybeans. These figures contrast with 8,000 ppm in a sample of
beets and 15,000 in corn stalks (also Lowe and Hamilton, 1967). Plants in the
beet family can be notorious accumulators of nitrate. Plant species, drought,
and shade are known to be important factors in nitrate accumulation, in combi-
nation, of course, with an adequate source of nitrogen; but nitrogen fertiliz-
ers generally play a minor role under typical growing conditions.
SERIOUSNESS OF THE NITRATE PROBLEM IN
WATER, FOOD, AND FEED
In spite of the alarms spread by some environmentalists and repeated in the
press, several reviewers of the problem and official groups appointed to evalu-
ate it have, in general, judged that the present situation is not of crisis
proportions, but nevertheless is one that warrants additional research and
surveillance. Viets and Hageman (1971) concluded: "Our evaluation of the
available information on nitrate in soil, water, foods, and feeds is that the
potential for nitrate accumulation does not pose a threat of an environmental
crisis. There is no indication of widespread upward trends of nitrate concen-
tration in foods, feeds, surface or ground water." The Illinois Pollution
Control Board, after extensive hearings, concluded that although an upward
trend in nitrate content of some Illinois streams is apparent, there was no
80
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factual basis for restricting the application of nitrogen fertilizer. This
Board recommended further study by the Illinois Institute for Environmental
Quality, including the validity of the present USPHS standard for nitrate in
potable water. The NAS-NRC committee (Alexander, 1972) concluded: "However,
the Committee finds no evidence of danger to man, animals, or the global envi-
ronment from present patterns of fertilizer use." They strongly recommended
that the present upper limit of 10 ppm of nitrate-N in potable water be main-
tained. An expert panel convened by the Food and Agricultural Organization of
the United Nations concluded in January, 1972: "It became apparent that when
fertilizers are applied correctly their contribution to the nutrient content
of surface waters is small in relation to nutrients derived from other
sources."
Throughout the studies reported, there are words of caution, such as "recom-
mended, proper, correct, and management," that need better definition in terms
of specific crops, localities, watersheds, and basins. There are areas in
which nitrate in surface and ground water is increasing. Twenty percent of
our water supply comes from underground sources. The flow of surface water
can usually reduce nitrate quickly, if the source of nitrate is cut off. How-
ever, underground water may have a residence time of a few months to a few
centuries. Once an "old" body of water becomes polluted with nitrate, there
is no way to reverse the pollution without waiting for a length of time at
least equal to that during which it became polluted.
FUTURE TRENDS
What can be safely predicted for the short-term future in terms of concen-
tration of nitrate in water as a result of crop production? We evaluate
potential changes as follows.
1. The rates of application of nitrogen fertilizer per acre of corn ferti-
lized in selected Corn Belt states are presented in Table 1. Corn
receives more N than any other crop; also, it is grown on such a high pro-
portion of land area in the Midwest that a cumulative effect is possible.
81
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Table 1. NITROGEN FERTILIZER APPLICATION RATES ON CORN,
SELECTED MIDWEST STATES, 1967-72.
Ohio
Indiana
Illinois
Iowa
Missouri
Nebraska
1967
88.1
112.2
108.6
89.5
81.3
120.6
1968
Pounds per
85.1
112.3
112.0
104.3
105.9
148.7
1969
harvested aore
93.1
115.3
120.2
108.1
108.2
143.3
1970
receiving
109.5
126.2
118.2
106.9
117.2
146.1
1971
fertilizer
90.0
112.6
112.8
100.5
125.3
141.3
1972
102.4
125.7
128.4
110.0
115.8
139.4
Sources: Cropping Practices, 1964-70, SRS-17, Statistical Reporting Service,
June 1971; 1973 Fertilizer Situation, FS-3, Economic Research Ser-
vice, USDA, December 1972.
The total use of nitrogen fertilizer by farm production regions is shown in
Table 2. Note that the total use for 1971-72 for the 48 states shows no in-
crease over 1970-71.
USDA data (Economic Research Service) reveal that although the total amount
-of nitrogen fertilizer used continues to increase, the percentage of corn
fields receiving 200 or more pounds of N per acre peaked in 1969 and
declined in 1970 and 1971. Some farmers were swept along beyond the opti-
mum rates indicated by research and by unjustified, over-expectations about
yields. This is of great significance because within a given set of sup-
porting production practices, the higher the rate of nitrogen applied, the
greater the proportion that remains after harvest; and hence, is at least
partially leachable.
The causes for the lower application rates are probably a leveling off of
the marked reduction in the cost of N (from 15 to 20 cents per pound
applied to the land in the 1940s, to 5 cents in some areas by 1970) and the
fact that leading farmers are bumping against a yield ceiling until break-
throughs are made in production practices. The top 5 to 10 percent of the
farmers are moving ever closer to the ultimate limiting factors of natural
82
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Table 2. CHANGE IN NITROGEN FERTILIZER USE,
BY FARM PRODUCTION REGIONS
I
Region
Northeast . . .
Lake States
Corn Belt . . .
Northern Plains
Appalachian . .
Southeast . . .
Delta States .
Southern Plains
Mountain . . .
Pacific ....
Forty-Eight
States . . .
'lant nutrien
IIQP 1QS7— 5Q
average
1,0
152
128
440
158
253
352
229
. 145
107
342
. 2,306
t Change
fvrvm 1 Cm7 — ^Q
to 1968-69
00 tons
71
337
343
485
81
91
51
436
243
76
200
(
Pi
1969-70
4
- 6
9
18
4
0
7
8
2
7
7
Change froi
receding y«
1970-71
Percent
12
34
14
3
9
3
10
0
3
5
9
»•
>ar
1971-72
-11
- 7
- 6
3
- 8
5
17
7
4
10
0
Source: 1973 Fertilizer Situation, FS-3, Economic Research Service USDA,
December 1972.
light energy, available water in the absence of irrigation, and other cli-
matic aspects. We may expect substantial increases in the cost of nitrogen
fertilizers in the near future, as the costs of natural gas increase. High-
er N costs will discourage excessive use, in the same way that lower costs
may have contributed to occasional excessive use in the past.
2. The shift in crops from small grains and forage grasses and legumes to more
row crops, especially soybeans, has nearly run its course. This shift is
likely to have increased the nitrates in the water by accelerating the
release of N from soil organic matter as a result of tillage of the soil,
and by reducing the uptake of nitrates during the late fall and early
spring. The proportion of row crops is now 80 to 90 percent in some areas;
83
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hence, the potential for further increase is small.
The rate of release of nitrogen from soil humus is slowing down now that
approximately 40 percent of the N has been used up, especially the portion
more readily mineralized.
The peak in th6 rate of artificial drainage of prime agricultural land and
of wet lands areas was passed long ago. Drainage increased the nitrates
in surface water by speeding up the release of nitrogen from organic mat-
ter and by intercepting nitrates at two- to four-foot depths and conduct-
ing them to surface water.
Inasmuch as nitrate tends to accumulate under stress conditions, it is
reasonable to expect that the nitrate concentration in leafy vegetables
consumed in the U. S. is trending downward, because modern technological
agriculture is designed to minimize stress in these high-value crops
through irrigation, fertility balance, disease and insect control, and the
like.
On the other side of the ledger, the nitrogen content of plant residues is
increasing. Hence, they will release N more rapidly after being incorpor-
ated into the soil.
Each additional increment of N introduced into the ecosystem beyond that
recovered in harvested crops is slightly more susceptible to movement in-
to nearby water, since it is the amount of N beyond some unknown point of
bdlccnoe that determines the susceptibility to undesirable environmental
effects.
We believe that in light of the available information on probable changes
in cropping systems and fertilizer practices, the main increase in nitro-
gen in major nitrogen-using areas will be reasonably well tailored to the
capacity of crops to efficiently utilize the extra nitrogen. This togeth-
er with evaluation of the six points just discussed led us to predict that
the concentrations of nitrates in water from agriculture will not acceler-
ate in the near future and that the rate of change is likely to deceler-
ate. This suggests to us that a grace period is available3 during whioh
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needed research on the model-ing of nitrogen -in the environment, the effect
of alternate courses of action3 and the potential danger of nitrates can
lie further evaluated.
THE ALTERNATIVES
There are three fundamental objectives that interact to determine the opti-
mum use of nitrogen fertilizer in crop production:
1. An adequate amount of high-quality food to meet human needs at an accepta-
ble price.
2. The preservation of the productive capacity of soils for future
generations.
3. A minimum undesirable effect on the environment. No strategy for food
production is acceptable that fails to consider all three.
Although the focus of this paper is on the nitrate content of plants and
water and on means for controlling them at tolerable levels, we are also
forced to consider whether there are current problems or ones that can be
expected in the future, and whether there are more desirable, viable alterna-
tives to the present system. We shall examine these in some detail. '
We shall also pose what seem to us to be hard choices for society to make in
relation to the use of supplemental nitrogen in food production, and we shall
raise the question of whether food production techniques should be drastically
altered at this time.
Perhaps perspective on the choices available to society will be gained by
stating broad, general alternatives before examining any part of the nitrate
issue in detail.
1. A shift in food habits away from animal products (meat, milk,
eggs) to more direct human consumption of grains. Animals do
not efficiently convert the energy in graint to human food.
Alexander et al. (1972) estimate conversion factors
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for plant protein to animal' protein of 4 (milk, cheese, eggs), 6 (poul-
try), and 9 (meat). A major shift in food habits may be possible in the
long term, but we do not consider it to be a viable alternative for the
short term. Alexander et dl. noted a dramatic shift to livestock products
in the U. S. from 1940 through 1968.
A reduction in food and feed exports. This would involve important
humanitarian considerations as well as adverse effects on the balance of
payments. Exports of farm products amounted to almost $8 billion in 1971-
72, and are estimated at nearly $10 billion for 1972-73. Basically a
reduction in exports would seem to ameliorate local nitrate problems by
transferring them to other areas where the food deficits would of neces-
sity be made up. Within the U. S., Illinois (a surplus grain state) could
reduce production, but the grain-deficit Northeast would be forced to
attempt additional production on less suitable soils, thus increasing
potential nitrates and sediment-associated pollution.
More efficient recovery of nitrate nitrogen, irrespective of source.
There are many known practices and some promising unproven techniques for
increasing the efficiency of nitrate after it is added to or is formed
through biological processes within the soil. Each practice by itself
adds a small or modest improvement, but the aggregate effect of many prac-
tices is substantial. These will be examined in detail, but we stress at
this point that high yields per acre are indispensable to efficient utili-
zation and minimal shift of nitrates into surface and ground water.
A question to be answered is whether the upward trend in nitrate concen-
tration of certain steams is the result of questionable strategies used
in the production of food. Although it would be difficult to document
with available data, it appears to us that the upward trend in either
yields or total crop production is increasing at least as rapidly as the
nitrate content of waters, indicating that the nitrate load per unit of
crop produced is declining (since other sources of nitrate are
increasing).
86
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4. Removal of excessive nitrate from public drinking water and from water
used in food processing. The economic and side effects on the environ-
ment of practices to control nitrate transfer into water may at some
future date be greater than the cost of removing them to protect the
health and the biological integrity of streams and lakes. Nitrate removal
from rivers should not be ruled out.
5. Shielding susceptible individuals from consuming more nitrate than they
can tolerate. The difference in tolerance between infants and older peo-
ple is so great that informational programs to avoid ingestion by infants
(and possibly a few genetically sensitive adults) may be preferred by so-
ciety to more drastic programs designed to avoid or remove nitrate from
water.
PROVEN PRACTICES FOR EFFICIENT RECOVERY
OF NITROGEN ON FARMS
Effect of supporting practices. Since nitrogen recovery is directly
related to crop yields, educating farmers about the best .combination
of supporting practices (date of planting; tillage; control of insects,
diseases and weeds; choice of variety; harvesting to reduce field losses,
and the like) is very effective in minimizing nitrate transfer into
waters. Trends in crop yields during the past three decades show that
educational efforts have borne fruit.
An oft-overlooked factor in increasing yields is the continuing trend
toward concentrating crops in the most suitable geographic regions. Corn
acreage, for example, increased in the Corn Belt from 50 percent in 1940
to more than 80 percent by 1970.
Effect of application rates of nitrogen. Successive increments of nitro-
gen are recovered less efficiently in the harvested crop. In 18 Illinois
experiments on corn, for example, four successive increments of nitrogen
produced yield increases equivalent to recoveries of 79, 36, 10, and 4
percent. The lesson from this is that residual nitrogen potentially
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available for leaching is concentrated near the upper end of the response
curve. The economics of production are such that aiming for 95 to 98 per-
cent rather than 100 percent of the maximum possible yield will have lit-
tle effect on the farmer's profit, but may significantly reduce the poten-
tial for the leaching of nitrate. In the 18 Illinois experiments, the
fourth increment of fertilizer increased grain,yield 3 percent at no net
profit to the farmer, but contributed 35 percent of the residual nitrogen
not harvested in grain.
Producing 95 to 98 percent rather than 100 percent of the maximum possible
yield would probably increase the price of the crop more than enough to
maintain the aggregate gross value of the crop to farmers (Mayer and Har-
grove, 1971). It would raise the cost of food a small amount and it would
reduce the amount available for export to other regions or countries. Im-
proved practices including the use of nitrogen aimed at production levels
of 95 to 98 percent by less efficient farmers would have an even more im-
portant effect on food costs and on the amount of food available for
export.
Planning the nitrogen rate for 95 to 98 percent of the maximum possible
yield is more complicated than planning the production in a factory be-
cause of the unpredictable nature of the weather. If the yield falls sub-
stantially below expectations, there will be unusued nitrogen. If a
nitrogen rate is aimed at 95 to 98 percent of the yield expected for a
typical year and the weather turns out to be unusually favorable, the
yield will be less than if the rate had been based on an expectation of
excellent weather.
Many farmers can and do attempt to improve the likelihood of optimum
nitrogen for the season by delaying part or all of their nitrogen ap-
plication until after crops are planted and they can better evaluate
the crop prospects.
3. Chemical form, time and place of application. Since the leaching of
nitrogen is confined mainly to the nitrate form, the trend in recent years
to ammonia, ammonium compounds, and urea has nearly eliminated the danger
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from direct runoff or leaching of freshly applied nitrogen fertilizers.
The nearer the time that nitrogen can be applied to the time of maximum
crop uptake, the less the possibility of loss. Fall application was
strongly promoted in the Midwest during the 1950s and 1960s, but accounted
for less than 10 percent of the total nitrogen applied in 1970. Because
of greater danger of leaching, farmers have been advised against fall or
early spring application on sandy soils, and the advice has been accepted.
On finer-textured soils, agronomists in northern latitudes have encouraged
fall application of nonleachable ammonium forms only after the soil temper-
ature falls to the point where most of the ammonium would not convert to
nitrate until the following spring. We believe that application too early
is practiced on a relatively small acreage. Information programs could
reduce it close to zero.
Sidedressing nitrogen after the crop is established is an accepted tech-
nique for improving the efficiency of utilization. There is, however,
some risk in being unable to apply nitrogen at all if a farmer delays
application until the latest possible date.
A very small amount of nitrogen fertilizer is applied to frozen, sloping
fields. It is a pollution hazard locally; but since it is also uneconom-
ic, it can be eliminated through information programs.
DIFFICULTIES OF REGULATING NITROGEN RATES
Regulations on nitrogen rates, if simple and enforceable, could not assure a
goal of 95 to 98 percent of maximum yield. To attain this goal, restrictions
on permissible rates would be extremely complex and would need to recognize:
(1) differences among crops; (2) the susceptibility of soils to leaching
and/or denitrification losses; (3) effectiveness of drainage system; (4) dif-
ferences in supporting practices from farm to farm—if this evaluation were
based on previous yields, the farmer would be locked into his previous system
without an opportunity for improvement; (5) the yield outlook at the time of
application—farmers could be held to a modest preplant application followed
by a supplemental treatment at a later date, and this would involve a
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determination by some official and an authorization for additional nitrogen;
(6) differences in the type of residues preceding the crop—amount, and the
carbon:nitrogen ratio; (7) whether animal manure was applied; and (8) the pos-
sible need for adjustment in midseason due to excessive losses by heavy rains.
It is in the best interest of individual farmers to recognize all of these
factors in making their decisions about the amount of nitrogen to apply.
NEEDED RESEARCH
The specific research needed in order to chart a better course in the use of
nitrogen fertilizer includes:
1. The effect on nitrate content of surface and ground water of producing
equivalent amounts of food using alternative sources of nitrogen—fer-
tilizer, leguminous crops, and animal or human wastes. Eventually, the
effects may also have to be confirmed on a watershed basis.
2. The influence of fertilizer rates forms and time of application on the
nitrate content of surface and ground water. This will probably have to
be approached on a watershed basis. Such an effort will present special
cost problems because of the scale involved and the experimental design
that would be required. A start has been made by the North Central Water
Center (see its 1971 report).
3. Activating a network of permanent water-sampling stations in order to
determine water-quality status and trends, including nitrate, to serve as
permanent benchmarks. The sites should be selected so that trends within
the various sources of nitrate can be separated to the extent feasible.
4. Techniques for studying the quality of ground water and identifying
sources of contaminants. In some cases, the effects on the environ-
ment may be far removed in time and distance from the initial source.
5. The validity of the nitrate-nitrogen standard of 10 milligrams per liter
for public drinking and food-processing water. The cost:benefit ratio of
meeting the standard through alternate courses of action needs to be
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determined. Part of this issue may be a comparison between major adjust-
ments in food production in order to control the nitrate content of water
versus the removal of excess nitrate from water used for drinking and food
processing.
6. Techniques for reducing nitrates in the soil in late fall.
a. Quick growing grass cover crops.
b* Early incorporation of carbonaceous residues to tie up nitrate.
7. Understanding the factors that cause changes in the nitrogen status of
soils. The variations among soils in their nitrogen-supplying capacity
should be studied. Mineralizable soil nitrogen may possibly be greatly
affected by future cropping, management, and fertilizer practices. Clear-
ly, the amount of supplemental nitrogen needed will depend on the nitrogen-
supplying capacities of the various soils, as well as on the crops grown.
The .emphasis should be on methods for evaluating residual mineral nitrogen
from prior fertilization and the rapidly oxidizable nitrogen of crop resi-
dues and not on the more resistant humus nitrogen of the soil that should
not be exploited further.
8. Alternating deep-rooted legumes with row crops in order to extract nitrate
from soil zones below rooting depth of corn, cotton, lettuce, and the like.
9. An additional examination of nitrification inhibitors and slow-release
fertilizers.
10. Some far-out techniques should be considered for the long term.
a. Promoting denitrification in situ. Determine in the field the extent
of denitrification in the root zone and in the aerated zone above the
water table and the factors affecting rate of denitrification.
b. Inhibit nitrification in situ if it is shown that crops yield equally
well with ammonium NH, as the main source of nitrogen.
c. Metering a greater portion of the nitrogen to the plant as needed in-
the form of foliar applications. This could be counterproductive,
because the nitrogen that is not retained on leaves will be
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positionally unavailable unless washed into the soil or may volati-
lize (NH-) into the air,
d. Temporarily inhibit tile flow to prevent N07 from reaching streams.
11. A study to determine the incentives needed in order to achieve adequate
constraints on the application of nitrogen fertilizer. It is difficult
to evaluate whether a combination of economic considerations, attitudes
of public responsibility, the threat of restrictions on rates, together
with an awareness by farmers of the results of additional technical re-
search will provide whatever may be determined as the "needed" con-
straints. No assumption should be made a priori that such self-imposed
constraints by informed farmers would be inadequate.
POLICY ON THE NITROGEN USED IN CROP PRODUCTION
The most important step in obtaining factual information on which to make
proper future decisions is to fund and otherwise facilitate needed research.
Problems with excessive nitrates should be recognized as essentially local
ones. Some are new. Many others are of long standing.
In the absence of reliable information about fertilizer applications and
their effect on nitrates in the environment, such applications should not be
regulated.
REFERENCES
Aldrich, S.R. 1972. Some effects of crop-production technology on environ-
mental quality. BioSoienoe 22:90-95.
Alexander, M., et al. 1972. Accumulation of nitrate. National Academy of
Sciences, Washington, D.C., 106 p.
Allison, F.E. 1965. Evaluation of incoming and outgoing processes that
affect soil nitrogen. In W.V. Bartholomew and F.E. Clark (ed.). Soil
Nitrogen. Agronomy 10:573-606. Amer. Soc. of Agron., Madison, Wis.
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Allison, F.E. 1966. The fate of nitrogen applied to soils. Advance. Agron.
18; 219-258.
Ayers, R, S, and R. L. Branson (ed.). Nitrates in the upper Santa Anna River
Basin in relation to groundwater pollution, 1973. California Agricultural
Experiment Station, Bui. 861, 59 p.
Barrens, K.C. 1971. Environmental benefits of intensive crop production.
Agv. Sai. Rev. 9:33-39.
Hauck, R.D., et at, 1972. Use of variation in natural nitrogen isotope abun-
dance for environmental studies: a questionable approach. Science 177:453--
Kohl, D.H. , G.B. Shearer, and B. Commoner. 1971. Fertilizer nitrogen contri-
bution to nitrate in surface waters in a cornbelt watershed. Science 174:
1331-4.
Lowe, R.M. and T.L. Hamilton. 1967. Rapid method for the determination of
nitrate in plant and soil extracts. Jour. Agv. Food Chem. 15:359-361.
Mayer, Leo V., and S.H. Hargrove. 1971. Food costs, farm incomes, and crop
yields. With restrictions on fertilizer use. CAED Rpt. No. 38, Dept. Eco-
nomics, Iowa State Univ., Ames, 76 p.
Stanford, G., C.B. England, and A.W. Taylor. 1970. Fertilizer use and water
quality. USDA-ARS 41-168, 19 p.
Viets, F.G., Jr., and R.H. Hageman. 1971. Factors affecting the accumulation
of nitrate in soil, water and plants. USDA Handbook 413, U.S. Govt. Print-
ing Office, Washington, D.C., 63 p.
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Animal Wastes
Sources of Nitrogenous Compounds and Methods of Control
JOHN C. NYE
MEAT, MILK, AND EGGS are produced by converting animal feedstuffs. The
digestive process of the various types of animals results in the excre-
tion of waste products. The nitrogenous waste of digestion comes basically
from two sources. The first one is through the undigested or partially
digested protein, which passes through the digestive process and leaves the
body as fecal matter. Between 20 and 30 percent of the protein being fed
will pass through the animal in this manner. The second source of nitrogen-
ous waste is from the urine. Oser (1965) states that urea is "the principal
end product of metabolism of protein substances in mammals." He also goes on
to point out that 60 percent of the nitrogen appears in the urine as urea.
With poultry, the principal product of protein metabolism is uric acid.
Briefly, the digestive process as it relates to nitrogenous compounds means
that 20 to 30 percent of the nitrogen ingested by an animal in the form of
proteins will pass through that animal in either undigested or partially
digested proteins, found in the fecal matter; the remaining 70 to 80 percent
of the nitrogen will be digested through protein metabolism, then a part of
that is removed from the body in urine—primarily in the form of urea for
mammals and in the form of uric acid for poultry. Both the urea and uric
acid could easily be broken down into ammonia. Therefore, animal waste will
contain nitrogenous compounds in the form of organic nitrogen, urea or uric
acid, and ammonia.
VOLUME AND SOURCES
The following estimates of nitrogen produced in animal waste are presented
in the recent National Academy of Science report, Accumulation of Nitrate:
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Animal Total nitrogen produced in waste
(million metric tons)
Dairy cattle 1-1
Beef cattle 2.9
Poultry 1-4
Swine ' • 0.4
Sheep 0-2
TOTAL 6.0
Tables 1, 2, and 3 show the number of cattle, hogs, and chickens in various
states. The 1964 Census of Agriculture showed that a majority of the live-
stock was still produced on relatively small-scale farms (again, see Tables
1, 2, and 3). In order to increase efficiency, there is a growing trend
toward raising livestock in confinement, using large-scale livestock produc-
tion facilities. This trend is most pronounced in the cattle feedlots of the
southwest United States.
Wells, Meenaghan, Albin, Coleman, and Grub (1972) reported that the average
number of cattle sold per feedlot per year is 1QO in the Corn Belt, 1,700 in
Texas, and 13,000 in Arizona. Viets (1971) pointed out that there are four
primary areas where cattle feedlots are concentrated: 3 million cattle are
fed in southern California and Arizona; 5 million, in the panhandles of Tex-
as and Oklahoma; 8 million, in the central Corn Belt; and 6 million, in east-
ern Colorado through Nebraska and into North Dakota. He also pointed out the
concentrations in the Southwest—noting that in 1968 there were 36 feedlots
of over 16,000 cattle in the Southwest, while there were no feedlots of that
size in the Corn Belt.
The great majority of the cattle feedlots are uncovered. As a result, they
constitute the major source of pollution through the runoff after rains.
In the poultry industry, Loehr (1971) pointed out a similar trend toward
intensification. He stated that, "If an egg producer does not have anywhere
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Table 1. THE TEN STATES HAVING THE GREATEST
NUMBER OF CATTLE AND CALVES
State
Iowa <
Kansas .......
Oklahoma ......
California . . . . ,
South Dakota . . .
Wisconsin .
u.s ,
Number of Cattle
(1,000 head)
12,829
7,773
6,780
6,757
5,441
5,238
4,775
4,543
4,241
3,998
117,916
Average number of
cattle per farm'5
58
59
91
72
53
138
135
97
43
43
46
aCrop Reporting Board, SRS, USDA, February, 1972.
The Census of Agriculture, U.S. Department of Commerce. The figures are for
those farms reporting cattle.
from 15 to 30 thousand birds under his control, he is not really producing a
significant amount of eggs for the market." Loehr went on to note that in
New York, there are farms with a million birds in confined houses. Since
these houses eliminate runoff, the problem that results from large poultry
operations is the proper application of manure to the soil.
In the swine industry, intensification has resulted in fewer farms producing
more hogs. Muehling (1971) reported that 80 percent of the hogs sold in 1964
were produced in the ten Corn Belt states; also, that in 1966, 50 percent of
the hog farms were using central farrowing houses and about 35 percent were
finishing the hogs in confinement. This trend has continued. Now, very few
large hog enterprises do not have an animal-waste detention facility. As a
result, little of such waste is lost through runoff. The problem becomes one
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Table 2. THE TEN STATES HAVING THE GREATEST
NUMBER OF HOGS AND PIGS
State
Number of Hogs'
(1,000 head)
Average number of
hogs per farmb
Iowa
Illinois
Missouri
Minnesota
Nebraska
Ohio
Kansas
Georgia
North Carolina
u.s
. . 16,322
. . 7,468
. . 5,129
. . 5,120
. . 3,692
. . 3,691
. . 2,838
. . 2,202
. . 2,065
. . 2,031
. . 67 540
129
110
94
61
61
77
63
51
32
14
50
Crop Reporting Board, SRS, USDA, December, 1970.
The 1964 Census of Agriculture, U.S. Department of Commerce. The figures
are for those farms reporting hogs.
of applying the waste to the land so as to avoid the loss of
nutrients.
FATE OF NITROGENOUS COMPOUNDS GENERATED
BY THESE SOURCES
There are three major fates of livestock waste. It may be: (1) washed
away in runoff; (2) applied to land by mechanical means; and (3) assimilated
by the soil in the feedlot (a dirt lot) or lost through volatilization in the
air. The runoff that can carry a sizable amount of livestock waste is the
most critical problem facing the beef producer.
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Table 3. THE TEN STATES HAVING THE GREATEST NUMBER OF CHICKENS
FOUR MONTHS OLD AND OVER
State
California
Georgia
Alabama ......
Pennsylvania ....
Florida
Iowa ........
u.s
g,
Number of Chickens
(1,000 head)
. . . . 54,893
. . . . 39 248
. . . . 23,885
. . . . 22,774
. . . . 19 377
. . . . 18 841
. . . . 18,348
. . . . 17,337
. . . . 17,321
. . . . 16,629
. . . . 441,447
Average number of
chickens per farm^
3,200
690
357
217
281
592
485
219
960
264
282
aCrop Reporting Board, SRS, USDA, April, 1972.
The 1964 Census of Agriculture, U.S. Department ov Commerce. The figures are
for those farms reporting chickens.
Gilbertson, McCalla, Ellis, Cross, and Woods (1970) reported that the
amount of runoff depended primarily on the amount of rain, and not on the
slope of the feedlot or the density of the cattle. The runoff ranged from 0
to 72 percent of the rainfall, with the total annual runoff being 40 percent
of the rainfall on the unsurfaced lots. Gilbertson et at. reported two causes
of runoff, rainfall and the melting of snow. The rainfall runoff contained a
lower total nitrogen content—65 to 555 parts per million—than the winter
snowmelt, which contained 1,429 to 5,763 ppm of nitrogen. In the winter run-
off condition, the density of livestock did influence the amount of nitrogen,
with high-density lots losing 1,056 pounds of nitrogen per acre-inch; the low-
density lots, 436 pounds per acre-inch.
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Miner, Fina, Funk, Lipper, and Larson (1966) reported that "more organic
matter and Kjeldahl nitrogen were found in runoff (a) with low-intensity rain-
fall, (b) with moist conditions preceding rainfall, and (c) during warm
weather." The concentration of Kjeldahl nitrogen in the runoff ranged from 94
to 1,000 mg/1 from concrete lots and from 50 to 540 milligrams per liter from
unsurfaced lots.
Scalf, Duffer, and Kreis (1970) studied runoff from a feedlot housing
12,000 cattle in Oklahoma and found that organic nitrogen concentrations
ranged from 80 to 533 mg/1, with ammonia ranging from 60 to 208 mg/1 as nitro-
gen. The runoff in their study ran through a 12,000-foot ditch before enter-
ing a farm pond. This ditch had no effect on the quality of the runoff, but
the pond did reduce the nitrogen content by 60 to 80 percent. This reduction
was caused by the sedimentation of solid matter and by dilution. •
The results of these studies indicate that from "3 to 6 percent of the
material deposited on a feedlot will be transported in the rainfall runoff,"
according to McCalla, Ellis, Gilbertson and Woods (1972). Even more is lost
during winter snowmelt. When this runoff flows unchecked, it can result in
major pollution, as indicated by fishkills (Scalf, et at., 1970).
The improper application of manure to soils can present another source of
pollution. The nitrogen content of the manure applied to the land can be lost
through runoff, or it can be leached away from the root zone.
The method of applying the waste to the land can influence the quality of
runoff—McCaskey, Rollins, and Little (1971). They studied the quality of run-
off from grassland in Alabama where dairy waste was applied by irrigation,
tank spreader, and a conventional "dry" spreader. The plots used in their
study had a slope of 3.3 percent. The results of their work are summar-
ized in Table 4. Their data seem to indicate that when less than 50 tons of
animal waste is applied to the soil, there is no appreciable increase in the
nitrogen lost through runoff. The method of application does not seem to-
affect the losses.
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Table 4. TOTAL ANNUAL LOSS OF NITROGEN FROM PLOTS
THAT RECEIVED DAIRY CATTLE WASTE
(McCaskey, et at., 1971)
Method of
application
Conventional
Total waste
applied
(Tons /A.)
. . . 51.7
51.7a
34.6
16.4
. . . 32.2
32. 2a
21.5
10.7
. . . 144.5
144. 5a
95.8
48.0
. . . 0.0
Nitrogen
Kjeldahl N
(Ib/A)
13.2
7.8
6.1
7.8
4.0
5.6
5.1
6.0
5.5
15.8
21.3
5.9
5.1-
Lost
Ammonia N
(Ib/A)
5.0
2.5
5.4
3.6
1.5
2.2
2.5
2.9
2.4
6.5
8.6
3.2
1.8
Nitrate N
(Ib/A)
2.2
1.1
1.3
2.0
1.1
3.0
.5
1.1
1.5
8.8
2.7
1.2
1.3
aPlots receiving 0.5 inch of simulated rainfall weekly two days before waste
application.
Another method of application that is becoming more popular is to plow-
down. The injection of manure into the soil eliminates the odor problems
associated with spreading. Redell, Johnson, Lyerly, and Hobgood (1971)
reported results of plowing down beef manure at the rates of 300, 600, and 900
tons per acre at the Texas Agricultural Experiment Station (El Paso and
Pecos). The equipment used in their work consisted of an 18-inch plow, a 27-
inch trencher, a 30-inch plow, and a 50-inch disk. They reported "that the
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greatest opportunity for polluting surface water is by ammonia." The ammonia
content in runoff from plots on which 900 tons of manure had been applied
ranged from 5.04 mg/1 to 140 mg/1. The rate of application is extremely high.
In work at Kansas State University—from Bernard, Denit, and Anderson (1971),
100 tons of manure from a beef feedlot was applied to a corn field. Prior to
the manure application, the nitrogen content in the runoff was 15 mg/1. Dur-
ing the first 60 days after application, the runoff contained between 20 and
40 mg/1 of nitrogen. Again, in this study the application rate is higher than
crop removal capacities.
The fate of the inorganic forms of nitrogen from land-disposed manures from
dairies in the Chino-Corona Basin of California- was studied by Adriano, Pratt,
and Bishop (1971). They concluded that the waste of no more than three cows
should be applied to an acre of pasture or cropland to insure that the NO,
concentration would be less than 10 ppm in soil solutions below the root zone.
In summary, land application is a valid disposal technique when the manure
is applied to nearly level crop land in a quantity not in excess of the crop
removal capacity.
NITROGEN LOSSES
The direct losses of nitrogen from an unsurfaced beef feedlot can be
sizable. Many researchers assume that 50 percent of the nitrogen in the waste
will be lost prior to land application. This loss results from the infiltra-
tion of nutrients into the unsurfaced lot or the volatilization of ammonia.
Gilbertson, et al. (1970) reported a 50- to 100-percent increase in total
nitrogen in the upper two to three feet of an unsurfaced feedlot. Viets
(1971) reported that "65 pounds of nitrogen per acre per year can be absorbed
by a lake 1/4 mile from a large feedlot. Another lake 1 mile from the same
feedlot absorbed about half as much, but that was enough to raise the nitrogen
content .6 ppm. That much nitrogen was regarded as sufficient for eutrophica-
tion if other factors are favorable." He has also reported that amines that
have been identified in the air of confined hog operations represent another
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compound which carries out sizable amounts of nitrogen.
The nitrogen lost via infiltration and volatilization has not been general-
ly recognized as a serious problem, such as the consideration given to runoff.
If a feedlot is located at a sufficient distance, at least a mile, from a
major surface-water supply, ammonia losses should not cause serious problems.
AEROBIC AND ANAEROBIC TREATMENT
The new laws enacted by many states require ,that livestock producers store
the manure and runoff for a period of time, to insure that the waste can be
returned to the land in a proper manner. This trend has encouraged the devel-
opment of partial waste-treatment systems. Most of these systems rely on the
biological breakdown of the waste. These biological waste-treatment facili-
ties can be categorized as anaerobic or as aerobic storage units.
The aerobic storage of livestock waste requires a higher capital investment
in either mechanical aeration equipment or in the larger land areas required
for lagoons. As a result of the cost of the aerobic facilities, the majority
of the storage facilities for runoff and livestock waste operate under anaer-
obic conditions. Such anaerobic manure storage causes the livestock waste to
be converted and decomposed. The nitrogenous compounds in the waste are usu-
ally converted into ammonia. Koelliker, Miner, Beer, and Hazen (1971)
reported a reduction of 49 to 86 percent of the nitrogen when anerobic lagoon
effluent was irrigated onto crop land. Some of the reduction was caused by
the desorption of ammonia after pumping but before infiltration. This ranged
from 15 to 40 percent of the total loss. Most of the reduction in nitrogen
was a result of denitrification.
Under aerobic conditions, Chang, Dale, and Bell (1971) reported that
between 40 and 60 percent of the nitrogen is lost during the first for-
ty days of aeration of dairy cattle manure. Most of this nitrogen loss
comes from the release of ammonia. With the loss of ammonia, there is also an
increase in nitrate and nitrite after approximately the first ten days of aer-
ation. This nitrate and nitrite buildup can go as high as 200 milligrams per
103
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liter, they also found that after nitrification, it was possible to denitrify
the waste and to reduce the nitrogen content by 78 percent.
Verification of the results of Chang et dl. (1971) for poultry waste was
done by Dunn and Robinson (1972). They found a 75-percent and an 81-percent
reduction in the total amount of nitrogen in an oxidation ditch after 137
days, when the dissolved oxygen fell from 4.7 to 0.4 ppm and the oxidation
reduction potential fell from 375 to 10 millivolts.
These studies indicate that both anaerobic and aerobic conditions can be
controlled to encourage nitrogen reductions. Other chemical and physical
treatment methods such as dehydration, incineration, or pyrolysis have not
received the public acceptance of the biological treatment techniques.
There are two basic approaches to the protection of the environment from
nitrogenous compounds in animal waste. First, the nitrogen in the waste can
be considered as a high-value product, making every attempt to utilize this in
the most appropriate manner, or it can be considered as a problem, something
to be removed from the waste.
There are two major ways of taking advantage of the nitrogen in the waste.
First, the nitrogen can be viewed as a fertilizer for soils. This is a tradi-
tional approach, which can allow the livestock producer to reduce the amount
of commercial nitrogen fertilizer he buys. The waste can be stored in a
liquid form and returned to the soil by irrigating, hauling, or hauling and
injecting—all in a manner that provides the greatest benefit to the crop.
The manure can also be stored as a solid and returned to the soil, then uti-
lized as a fertilizer for the crop.
The second method of taking advantage of the nitrogen in the waste is to
utilize it as a source of protein for livestock feed. This can be done in a
manner such as that described by Anthony (1969, 1971). He mixed the waste
with grass and ensiled the product to make a feed that he calls "wastelage."
Chicken manure and broiler litter have been fed to cattle by Bull and Reid
(1971); also, by Fontenot, Webb, Harmon, Tucker, and Moore (1971). Flegal and
Zindel (1971) studied the effect of feeding dried poultry litter to poultry.
104
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There is some promise for refeeding some of the waste, but it is impossible to
feed all of the waste to livestock Without some treatment.
The waste can be fermented or aerobically converted into bacterial cells
and refed to livestock as a high-protein feed material, such as that described
by Holmes, Day, and Pfeffer (1971) and Nye (1971).
Holmes, et al. (1971) evaluated the problems of the residue from an oxida-
tion under a confinement swine building. A continuous-flow centrifuge was
used in this work. The amino acid analysis of their work showed the average
product contained 1.15-percent lysine, 0.51-percent histidine and 1.15=percent
arginine on a dry-weight basis.
In the work of Nye (1971), dairy cattle manure was aerobically treated in a
process involving 24-hour detention and continuous culture. The biomass har-
vested after this treatment contained 30-percent crude protein. This product
was fed to laboratory rats as half and as all of the supplemental protein.
When the biomass product was fed as half of the supplemental protein, in 18
percent of the ration there was no significant effect in the rate of gain or
feed efficiency of the rats.
Calvert, Morgan, and Eby (1971) suggested growing houseflies on chicken
manure and feeding these houseflies to growing chickens. It is not possi-
ble for flies to utilize all of the manure.
The second way of Viewing the nitrogen is as a problem, one that must be
removed from the waste. With this approach, the waste is nitrified and de-
nitrified using a technique such as described by Chang, et al. (1970); or
Koelliker, et al. (1971); or Dunn, et al. (1972). In this technique, the
waste is converted into nitrates and then, under anaerobic conditions, the
nitrate is converted to nitrogen gas. This concept may be the most easily
accomplished method of reducing the potential for nitrogen pollution with
today's technology. Erickson, Tiedje, Ellis, and Hansen (1972) have reported
on a barriered landscape water renovation (BLWR) system that could promote the
denitrification of swine and dairy waste. The Kjeldahl nitrogen was reduced
105
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from 650 to 2 mg/1 for swine waste, and from 300 to 3 mg/1 for dairy waste.
They have reported that mechanical breakdown caused the nitrate nitrogen con-
tent to jump from 10 to 200 milligrams per liter. They suggest that by 1973,
it should be possible to design barriered-landscape, water-renovation systems
for commercial livestock producers.
The conclusion can be drawn that at present, the most effective method of
insuring against nitrogen-related pollution from livestock waste is to apply
that waste to the soil, at a rate at which the crop can remove the nitrogen.
Until further research can be financed and completed on the utilization and/or
reduction of nitrogen, land application will be the safest way of insuring the
conservation of nitrogen in animal waste.
SUGGESTIONS
Even though some form of land application is currently recommended, several
systems appear to be possibilities for utilizing animal waste. The most prom-
ising technique appears to be the biological recovery of nitrogenous waste as
high-protein bacterial cells. However, the most efficient method of growing
of growing micro-organisms is yet to be found. An efficient harvesting process
for removing the organisms from a liquid media must also be found. The com-
plete biological protein recovery system has a broad and far-reaching effect
on all organic-waste-treatment systems. Other techniques of turning animal
waste into a valuable resource should also be evaluated. These processes
included the recovery of fuels from the carbonaceous waste.
The reduction of nitrogen through nitrification and denitrification also
needs to be examined. This biological process can be obtained in controlled
aerobic liquid cultures, but the precise technique for making this a valid
nitrogen-reduction process must be determined by research. The same nitrifi-
cation-denitrification process occurs in soils. The influence of soil-moisture
conditions, cropping practices, nitrogenous-waste application, soil acidity,
and other related factors must be determined. These methods of reducing
nitrogen also have application to other nitrogeneous wastes.
106
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The nitrogen in animal wastes has long been looked on as a valuable source
of plant nutrients, and has supplemented commercial fertilizers on many farms.
The proper application of animal manure has prevented it from becoming a haz-
ardous nitrogeneous waste. The increased concentration of livestock has, in
some cases, eliminated the possibility of applying animal wastes to the land.
Therefore, like other industries, livestock producers need these new techno-
logical advances in the utilization and/or reduction of nitrogen in order to
safeguard the environment.
REFERENCES
Adriano, C.C., Pratt, D.F., and Bishop, S.E. 1971. Fate of inorganic forms
of nitrogen and salt from land disposed manures from dairies, Livestock
Waste Management and Pollution Abatement., Amer. Soc. Agr. Eng., PROC-271,
St. Joseph, Mich.
Anthony, W.B. 1969. Cattle manure: Reuse through wastelage feeding, Animal
Waste Management, Cornell Univer., Ithaca, N.Y.
Anthony, W.B. 1971. Cattle manure as a feed for cattle, Livestock Waste
Management and Pollution Abatement, Amer. Soc. Agr. Eng., PROC-271, St.
Joseph, Mich.
Bernard, H., Denit, J., and Anderson, D. 1971. Effluent discharge guidelines
and animal waste technology, Animal Waste Management, Council of State
Government s, Wash., D.C.
Bull, L.S. and Reid, J.T. 1971. Nutritive value of chicken manure for
cattle, Livestock Waste Management and Pollution Abatement, Amer. Soc.
Agr. Eng., PROC-271, St. Joseph, Mich.
Calvert, C.C., Morgan, N.O., and Eby, H.J. Biodegraded hen manure and adult
house flies: Their nutritional value to the growing chick, Livestock
Waste Management and Pollution Abatement, Amer. Soc. Agr. Eng., PROC-271,
St. Joseph, Mich.
Chang, C.C., Dale, A.C., and Bell, J.M. 1971. Nitrogen transformation during
aerobic digestion and denitrification of dairy cattle waste, Livestock
Waste Management and Pollution Abatement, Amer. Soc. Agr. Eng., PROC-271,
St. Joseph, Mich.
Dunn, G.G. and Robinson, J.B. 1972. Nitrogen losses through denitrification
and other changes in continuously aerated poultry manure, Waste Manage-
ment Research, Cornell Univ., Ithaca, N.Y.
107
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Erikson, A.E., Agtiedje, J.N., Ellis, D.G., and Hansen, C.N. 1972. Initial
observations of several medium-sized barriered landscape water renovation
systems for animal waste, Waste Management Research, Cornell Univ., Ith-
aca, N.Y.
Flegal, C.J. and Zindel, H.C. 1971. Dehydrated poultry waste (DPW) as a
feedstuff in poultry rations, Livestock Waste Management and Pollution
Abatements Amer. Soc. Agr. Eng., PROC-271, St. Joseph, Mich.
Fontenot, J.P., Webb, K.E., Harmon, B.W., Tucker, R.E., and Modre, W.E.C.
1971. Studies of processing, nutritional value and palatability of
broiler litter for ruminants, Livestock Waste Management and Pollution
Abatement, Amer. Soc. Agr. Eng., PROC-271, St. Joseph, Mich.
Gilbertson, C.B., McCalla, P.M., Ellis, J.R., Cross, O.E., and Woods, W.R.
1970. The effect of animal density and surface slope on characteris-
tics of runoff, solid waste, and nitrate movement on unpaved feedlot,
Univ. of Nebraska, College of Agr. and Home Economics, SB508, Lincoln.
Gilbertson, C.B., McCalla, T.M., Ellis, J.R., and Woods, W.R. 1971. Charac-
teristics of manure accumulation removed from outdoor, unpaved beef cat-
tle feedlots, livestock Waste Management and Pollution Abatement, Amer.
Soc. Agr. Eng., PROC-271, St. Joseph, Mich.
Holmes, L.W.J., Day, D.L., and Pfeffer, J.T. 1971. Concentration of protein-
aceous solids from oxidation ditch mixed-liquor, Livestock Waste Manage-
ment and Pollution Abatement, Amer. Soc. Agr. Eng., PROC-271, St. Joseph,
Mich.
Koelliker, J.K., Miner, J.R., Beer, C.E., and Hazen, E.E. 1971. Treatment of
livestock waste—lagoon effluent by soil filtration, Livestock Waste Man-
agement and Pollution Abatement, Amer. Soc. Agr. Eng., PROC-271, St.
Joseph, Mich.
Loehr, R.C. 1971. Poultry waste management, Animal Waste Managements Council
of State Governments, Wash., D.C.
McCaskey, T.A., Rollins, G.H., and Little, J.A. 1971. Water quality of
runoff from grassland applied with liquid, semi-liquid, and dry dairy
waste, Livestock Waste Management and Pollution Abatements Amer. Soc.
Agr. Eng., PROC-271, St. Joseph, Mich.
Miner, J.R., Fiena, L.R., Funk, J.W., Lipper, R.I., and Larson, G.H. 1966.
Storm water runoff from cattle feedlots, Management of Farm Animal Wastet
Amer. Soc. Agr. Eng., SP-0366, St. Joseph, Mich.
Miner, J.R. 1971. Farm Animal Waste Management, North-Central Reg. Pub. 206,
Agr. Exp. Sta., Iowa State Univ., Ames.
Muehling, A.J. 1971. The handling and treatment of swine waste, Animal Waste
Management, Council of State Governments, Wash., D.C.
108
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Nye, J.C. 1971. An evaluation of a recycling waste treatment system for
dairy cattle manure. Unpublished Ph.D. thesis, Purdue Univ., West
Lafayette, Ind.
Oser, Bernard L. 1965. Hawk's Physiological, Chemistry, McGraw-Hill Book Co.,
New York City.
Reddell, D.L., Johnson, W.H., and Lyerly, P.J. 1971. Disposal of beef manure
by deep plowing, Livestock Waste Management and Pollution Abatement,
Amer. Soc. Agr. Eng., PROC-271, St. Joseph, Mich.
Scalf, M.R., Duffer, N.R., and Kreis, R.D. 1970. Characteristics and effects
of cattle feedlot runoff. Purdue Industrial Waste Conference, Purdue
Univ., West Lafayette, Ind.
U.S. Dept. of Commerce, 1964 Census of Agriculture.
Viets, F.G. 1971. Cattle feedlot pollution, Animal Waste Management3 Council
of State Governments, Wash., D.C.
Wells, D.M., Meehaghan, G.F., Albin, R.C., Coleman, E.A., and Grub, W. 1972.
Characteristics of waste from southwest beef cattle feedlots, Waste Man-
agement Research^ Cornell Univ., Ithaca, N.Y.
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Major Industrial Processes
Sources of Nitrogenous Compounds and Methods of Control
WILLIAM B. DAVIS
THE FEDERAL WATER POLLUTION CONTROL ACT, as amended in 1972, was passed
on October 18, 1972 (Public Law 92-500). The Administrator of the Envi-
ronmental Protection Agency was directed by that law to publish a list
of categories of sources of pollutants which, at a minimum, include
those listed in Section 306(b) (1) (A). In January of 1973, the Admin-
istrator established the following list of categories:
Pulp and paper mills
Paperboard, builders paper, and board mills
Meat products and rendering processing
Dairy products processing
Grain mills
Canned and preserved fruits and vegetable processing
Canned and preserved seafood processing
Sugar processing
Textile mills
Cement manufacturing
Feedlots
Electroplating
Organic chemicals manufacturing
Inorganic chemicals manufacturing
Plastic and synthetic materials manufacturing
Soap and detergent manufacturing
Fertilizer manufacturing
Petroleum refining
Iron and steel manufacturing
Nonferrous metals manufacturing
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Phosphate manufacturing
Steam electric power plants
Ferroalloy manufacturing
Leather tanning and finishing
Glass and asbestos manufacturing
Rubber processing
Timber products processing
With the exception of feedlots, all of the categories just listed fall
under the industrial classification.
Looking briefly at the list of categories, it would seem that virtual-
ly all of the sources would be responsible for discharging nitrogen in
one form or another. The magnitude and extent of nitrogen discharge,
however, varies quite dramatically from one industry to the next. By
contrast, the discharge of nitrogen from the manufacture of nitrate or
ammonia is considerably greater than that from steam electric power-
plants, which use hydrazine and amines for oxygen control in the boiler
feed water.
It is not the purpose here to consider the specific unit operations
and processes for each of the sources listed. In fact, a detailed re-
view of the various categories would involve consideration of individ-
ual industries far in excess of the twenty-seven categories defined by
the Administrator. A final review of this type would require coordina-
tion of information contained in the Corps of Engineers Applications
filed under the 1899 Refuse Act, additional data being collected by the
EPA, the various technology transfer manuals either completed or being
prepared by the EPA, and various reports and textbooks on the chemical
process industry (for example, The Chem-Loal Process Industries, by
Shreve) . The intention in this paper is to give a general descrip-
tion of the processes that may be responsible for generating nitrogenous
compounds.
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LOCATION AND NATURE OP SOURCE, POINT OR DIFFUSE
Many nitrogenous compounds are created deliberately or inadvertently
when atmospheric nitrogen is heated with oxygen'' •". The oxides' of ni-
trogen are reactive. Many are absorbed in water to form the fully ox-
idized nitrate ion.
Most nitrogen synthesis' involves the production of ammonia initially.
The raw materials for ammonia production are air, water, and a carbon
source (for the generation of hydrogen). Thus the location of nitrogen-
fixing industries is determined more by factors such as transportation,
marketing, and ultimate use than by the need to be located near to a
source of raw materials. Estimates of the amount of fixed nitrogen
eventually used in agriculture amount to approximately 75 percent of the
[3]
total nitrogen produced .
ronment in a diffuse manner.
[3]
total nitrogen produced1 . Hence, most fixed nitrogen enters the envi-
The most complex nitrogen compounds are involved in industrial
applications, and their discharges are often described as point sources.
In many instances, the discharge from individual unit 'operations and
processes may enter the receiving body of water from, separate effluent
lines. This is particularly true of old plants without facilities.
Rainfall runoff from industries such as those involved in the handling
[4]
of solids are generally contaminated with the product . Therefore,
the discharge of these industries is to some degree diffuse.
Other industries may discharge effluents into the water treated by
municipal systems. In most instances, the municipal system was not
designed to remove nitrogenous compounds. As a result, the industry may
be discharging a point source of nitrogen indirectly through the outfall
of a municipal treatment plant.
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NITROGENOUS DISCHARGES FROM SPECIFIED SOURCES
Unfortunately, and with few notable exceptions, the local, state, and
federal criteria for nitrogen discharges have been limited to the inor-
ganic forms of nitrogen; and these limitations have not been strongly
enforced in relation to industrial discharges. As a result, very little
elimination of nitrogen from industrial discharges has resulted from the
modification of in-plant procedures.
Pressures placed on industry by the Federal Water Pollution Control
Act, as amended in 1972, should result in intensive efforts by indus-
tries to coordinate in-plant modifications with treatment facilities
so that appreciable reductions in total discharges result (between 90
and 95 percent). A review of some preliminary EPA guidelines, however,
suggests strong emphasis on reductions in Biochemical Oxygen Demand and
in suspended solids. As a result, nitrogen removal would be a secondary
consideration and the removal of nitrogenous compounds might be a wel-
comed benefit from other treatment needs, and not the result of inten-
sive efforts to remove these compounds.
FORMS OF NITROGEN INVOLVED
INORGANIC COMPOUNDS
Nitrogenous compounds can be broadly classified as either inorganic or
organic. Most inorganic forms of nitrogen are highly soluble, but may
be associated with particulate matter. Inorganic nitrogen production
accounts for the bulk of nitrogen-fixing manufacture. Ammonia is the
most common form of fixed nitrogen produced. It is used directly as a
fertilizer in agriculture or as the basis for the rest of the nitrogen
chemical industry1 .
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Ammonia is manufactured in a catalytic process by the reaction of
nitrogen derived from the atmosphere together with hydrogen obtained by
the reaction of steam, and finally with a carbon source such as natural
gas. Because the catalysts involved in the reaction of hydrogen and ni-
trogen can be poisoned by carbon oxides, it is necessary to remove these
oxides from the hydrogen stream. This procedure results in an ammonia
product of rather high purity. For 1970, the U.S. Department of Com-
merce reported ammonia production of 13.6 million short tons in 94
establishments (Table 1). Of that 13.6 million short tons, 4.6 million
were consumed in the plant of original manufacture .
A principal industrial use of ammonia is in the manufacture of nitric
acid, which is made by the pressure ammonia oxidation process . In
this process, oxygen is absorbed on a catalyst and placed in reaction
with ammonia to produce an imide radical, NH, which reacts with oxygen
to form nitric oxide and water. The nitric oxide is further oxidized
into nitrogen dioxide, which, in turn, reacts with water to form nitric
acid. Traces of nitric oxide and nitrogen peroxide are contained in the
tail gases from the water-absorbtion towers.
For 1970, nitric acid production in the United States was 6.7 million
short tons in 72 establishments . Most of this nitric acid was then
converted into ammonium nitrate at the location of original manufacture.
Sixty-six establishments produced 5.4 million short tons of ammonium ni-
trate fertilizer "• . This fertilizer manufacture represents the princi-
pal utilization of nitric acid. Some 900 thousand short tons of ammoni-
um nitrate were produced in 1970 for the manufacture of explosives
Nitric acid is the second most-important industrial acid, and its pro-
duct ior
States
duction makes up the sixth largest chemical industry in the United
[8]
Among the inorganic nitrogen compounds, cyanide attracts immediate
attention as a hazardous material. Hydrocyanic acid production was 160
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Table 1. PRIMARY PRODUCTION OF NITROGEN FERTILIZER
AND PHOSPHORIC ACID
Production
Chemical and basis 1971 1970
Thousands of
short tons
Ammonia:
Synthetic, anhydrous (100 percent) 13,719.3 13,569.9
Byproduct liquor (ammonia content)3 11.0 12.0
Ammonium nitrate (100 percent):
Original solution13 6,584.3 6,475.1
Fertilizer use:
Solution produced for sale as such for
direct application 401.2 249.9
Solution produced for consumption in the
manufacture of nitrogen solutions or
other fertilizer materials 1,766.0 1,832.6
Solid 3,390.7 3,315.1
Other usesc 972.2 898.9
Ammonium sulfate:
Synthetic (technical) 529.2
Byproduct, other than coke oven 1,251.8 '
Byproduct (coke oven) 539.0 595.0
Nitrogen solutions, including mixtures containing
urea (100 percent N):
Solutions containing ammonia 694.0 580.4
Solutions not containing ammonia 1,211.4 1,178.5
Nitric acid (100 percent): .... 6,670.6 6,684.6
Urea primary solution (100 percent urea)d . . . 2,820.5 3,089.0
Phosphoric acid (100 percent phosphoric oxide)>
total 6,034.4 5,684.6
By source:
From phosphorus 904.9 Ij040.8
Other 5,129.5 4,643.9
By use:
For fertilizer 4,929.4 (NA)
Other 1,105.0 (NA)
REFERENCE: From Current Industrial Reports, Inorganic Fertilizer
Materials and Related Acids, Summary for 1971, Series
M28B(71)-13, U.S. Bureau of the Census, Wash., D.C.
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(NA) Not available.
a
Collected by or in cooperation with the Bureau of Mines.
Represents the total amount of ammonium nitrate produced, including the
amounts used for fertilizer, explosives, and other uses, as well as the
amounts consumed in manufacturing other products, such as nitrogen
solutions.
«
Includes data for government-owned, contractor-operated plants.
Collected by the U.S. Tariff Commission and published in the U.S.
Tariff Commission monthly report, Synthetic Organic Chemicals, Se-
ries C. Annual data on urea produced for use in feed compounds, liquid
fertilizers, solid fertilizers, and plastics are published in the U.S.
Tariff Commission annual report Synthetic Organic Chemicals, U.S. Pro-
duction and Sales.
117
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thousand short tons in 1970. Of this, 110 thousand short tons were
consumed in the plant of original manufacture, indicating that 50 thou-
sand short tons of HCN are transported annually. Cyanide is widely used
in the electroplating industry. However, the toxic nature of cyanide
has led to increasing concern about the quantity being discharged into
the environment. One result has been a shift away from electroplating
processes requiring cyanide. New methods of removing cyanide are being
[9]
investigated .
ORGANIC COMPOUNDS
Nitrogen is found in many organic compounds. A monograph on Industri-
al Organic Nitrogen Compounds by Melvin J. Astle provides the fol-
lowing categories:
Aliphatic amines
Arylamines
Heterocyclic amines
Hydrazines, azo compounds, diazonium salts
Nitriles, amides, and amino acids
Isocyanates, ureas, and thioureas
Aromatic nitro and nitroso compounds
Aliphatic nitro compounds
A synoptic overview of the organic nitrogen industry in the U.S. has
been provided by the U.S. Tariff Commission . Nitrogen is used ex-
tensively in cyclic intermediates for the production of other sub-
stances. These are some annual production figures for these intermedi-
ates:
Million
pounds
Nitrobenzene 548
Isocyanates 513
Aniline 398
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This same reference source indicates that azo dyes account for 30
percent of the total U.S. dye production in 1970. The total production
of azo dye was 72 million pounds in 1970, with a value of $142 million.
Cationic surface-active agents are almost exclusively compounds
containing nitrogen. They include quaternary ammonium salts and primary
monoamines. Total production for 1970 was 228.5 million pounds, approx-
imately 6 percent of the total production of all surface active
agents . The way surface-active agents are used would indicate that
these compounds enter the environment at many sources. Carboxylic acid
amides are employed as nonionic surface-active agents. Production in
1970 totalled 90 million pounds^U^.
Nitric acid is used in the esterification of alcohols. The most
important products of such esterification are nitroglycerin and ni-
trocellulose. The purification of these products represents a potential
discharge of nitrogen wastes; however, the nitric and sulphuric acids
[121
used in these processes are recycled
Several complex organic nitrogenous compounds are used as photographic
chemicals. Diazonium salts are used almost exclusively in this industry.
Urea is a nitrogen compound made by the reaction of carbon dioxide and
ammonia. Production of urea in primary solution totaled 6.5 billion
pounds in 1970 . Urea is used in feed compounds, 672 million pounds;
liquid fertilizer, 2.8 billion pounds; and solid fertilizer, 2.4 billion
pounds (all 1970). Industrial ureas used in the plastic industry
include urea and melamine resins (746 million pounds) and polyurethane
and diisocyanate resins, excluding foam and elastomers (126 million
pounds) .
Acrylonitrile is also one of the principal organic nitrogen
compounds—U.S. production, 1 billion pounds in 1970 . A study of
the problems associated with its production illustrates the difficulties
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encountered by the nitrogen industry as a whole. Acrylonitrile is used
in the manufacture of synthetic polymers, such as orlon and aeryIon.
Acrylonitrile can be produced by adding hydrogen cyanide to acetylene,
It can also be produced by propylene ammino oxidation or by the propyl-
ene nitric oxide process. However, cyanide is produced as a byproduct;
thus, the production of acrylonitrile represents a potential discharge
of a hazardous material.
According to one study, acrylonitrile has a biochemical treatibility
index of 484, rating it as the most resistant to biological treatment of
the 22 organic chemicals tested "•. Nitriles (organic cyanides) are
considered only slightly toxic to humans; yet, they have a highly varia-
ble toxicity to fish. Lactonitrile (which converts to cyanide) and
[14]
acrylonitrile are among the most toxic of such compounds . In other
uses, the polybutadiene acrylonitrile synthetic rubber production
totaled 149 million pounds in 1970, while acrylonitrile butadiene sty-
rene (ABS) and styrene acrylonitrile (SAN) thermoplastic resin produc-
tion was 568 million pounds during the same year .
Nitrogen compounds are also involved within the chemical industry in
many ways that do not appear in the final product. As an example, the
soda ash industry is based on the Solvay process, which includes ammon-
ia as a reactant. The ammonia from this process is recovered in the
form of ammonium sulfate that is then recycled .
Ammonia is also a byproduct of other processes. The U.S. Bureau of
Mines reports that the 1970 production of byproduct ammonia liquor was
12 thousand short tons (NH3 content). The byproduct production of
ammonium sulfate was 648 thousand short tons in 1969 . The produc-
tion of both of these byproducts, however, has been declining for sever-
al years.
In addition to the thousands of nitrogen compounds that are deliberate-
ly generated as items of manufacture and commerce, it is apparent that
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many undefined compounds enter waste streams as undesired byproducts of
chemical synthesis.
FATE OF NITROGEN COMPOUNDS
Since most fixed nitrogen is employed in agriculture as feed and
fertilizer, its ultimate fate is covered in other portions of this
report (as animal and municipal wastes). Much of this waste or fertiliz-
er will eventually appear in the form of the nitrate ion in surface
water. The eutrophication consequences of nitrate accumulation are gen-
erally understood ' . There are biological processes for converting
nitrate into atmospheric nitrogen, but the present rate of nitrate syn-
thesis probably exceeds these natural conversion processes.
The fate of the organic nitrogen compounds is highly variable. Some,
such as nylon, are biologically inert and are likely to persist indefi-
nitely. Many compounds are slowly biodegradable; and for all practical
purposes, should be considered as nonbiodegradable. These compounds are
likely to be found at low levels in reveiving bodies of water, both in
the overlying water and in the sediment. Because of the association of
some nitrogen compounds with cancer, the full effect of these compounds
[19]
on the aquatic environment and on man should be investigated
Recently, the effect of chloramines on fish life has become an area of
wide concern.
REDUCING THE OUTPUT OF NITROGENOUS COMPOUNDS
Because of the large number of nitrogenous compounds involved and the
differing adverse environmental effects of these compounds or groups of
compounds, a basic list of the most hazardous ones should be prepared.
Specific guidelines for eliminating the discharge of these compounds
should be developed. These guidelines would be expected to encompass
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the following:
Conventional treatment (biological reactors).
Conventional treatment, followed by biological denitrification.
Physical-chemical treatment.
Process modifications.
Changes in raw materials in order to reduce discharge of nitrogenous
compounds.
Segregation of waste streams.
Elimination of product lines.
Intensive considerations must be given to the real hazards associated
with particular nitrogenous compounds before a given solution can be
recommended and enforced.
SUGGESTIONS FOR REGULATION, MONITORING, RESEARCH,
AND INFORMATIONAL PROGRAMS
The regulation of compounds originating from an industry as diverse as
the nitrogen industry will be difficult to achieve. Criteria and priori-
ties must be established. The toxic effects of such chemicals should be
catalogued.
The most hazardous of the nitrogenous materials should be correlated
with the rate of manufacture, as indicated by sources such as "Synthet-
ic Organic Chemicals' in order to pinpoint the industrial processes
needing immediate attention. If the use of Synthetic Organic Chemicals
is precluded by the confidential nature of the reported material, Corps
of Engineer Applications filed under the 1899 Refuse Act might possibly
be used.
The processes involved in the manufacture of organic nitrogen, such as
the nitration reaction, generate a myriad of unclassified byproducts
that are separated from the desired product and treated before
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discharge. Since the specific chemicals discharged from such operations
are likely to be of an unknown composition, a micro and macro bioassay
of the discharges from specific unit operations could prove to be valua-
ble in determining the possible areas needing regulation immediately.
Some of the wastes are so resistant to biological degradation, that
the usual criteria of water quality in terms of BOD have little mean-
ing in determing how much of the waste materials are discharged. In
addition, the presence of toxic organic materials in the waste stream is
likely to inhibit bacterial processes, thus diminishing the effective-
ness of biological treatment processes as well as concealing the true
extent of the organic chemical content of the waste stream. In some
cases, the measurable BOD increases while the stream is being treated,
suggesting that hydrolysis of the waste material is taking place slowly.
In cases in which a particular waste stream is introducing a toxic
material that is inhibiting the effectiveness of the total treatment
process, that stream should be isolated from the process and treated
independently. The identification and isolation of such streams should
considerably enhance the effectiveness of the treatment operations, as
well as improve the biological health of the receiving water.
In some situations, chemical reactions take place beyond the point of
discharge—reactions that alter the nature of the receiving water. Am-
monia has been deliberately used in combination with chlorine to produce
chloramines. These chloramines have bacterial effects that last longer
than those of chlorine alone. Excessive ammonia entering a water-
treatment plant can increase the amount of chlorine required for effec-
tive disinfection. In some circumstances when chlorine is added to a
waste stream containing the right amount of ammonia, chloramines are
produced that decrease the apparent BOD and harm other organisms in the
receiving water.
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In high-volume manufacturing operations, such as the production of
ammonia, nitric acid, and fertilizers, air and water pollution will have
to be considered, in view of their particular detrimental effects on the
region involved. A potential necessity for a trade-off exists in this
area. Air pollution can be reduced by converting the nitrogenous prod-
ucts into nitrates. Yet, these represent a potential source of water
pollution. Alternately, processes exist for removing nitrogen from water
by means of air stripping ammonia from the water in towers at a high pH.
This ammonia can represent an air-pollution problem, as well as a poten-
tial water pollution problem, since such ammonia is readily soluble in
water. Thus, the total effect of any proposed treatment system must be
considered fully.
Low-volume manufacturing operations, such as those involving the
production of photographic chemicals and some dyes, are likely to
involve relatively few points of manufacture. Many of these chemicals
are likely to have only one source. If so, industry-wide standards
will have little meaning. The manufacturers of such chemicals have a
historical reticence concerning their methods of production and disposal.
This need for secrecy and the esoteric nature of the chemicals involved
indicate that effluent guidelines for such industries should be promul-
gated at the earliest opportunity.
REFERENCES
1. Shreve, R.N. The Chemical Process Industries. McGraw-Hill, New
York City (1967).
2. Cornelius, W. and Agnew, W.G. (ed.). Emissions from Continuous
Combustion Systems. Plenum Press, New York City (1972).
3. Slack, A.W. Chemistry and Technology of Fertilizers. Interscience,
New York City (1967).
4. Bingham, E.C. "Air Pollution Problems at a Nitrogen Fertilizer
Plant." In Recent Developments in Pollution Control: Proceedings of
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the Fourth Annual North Eastern Regional Antipollution Conference
Technomlc, Westport, Conn. (1971).
5. Frear, G.L., and R.L. Baber. "Ammonia." Kirk-Othmer Encyclopedia of
Chemical Technology, Vol. 2, 2nd Ed. Interscience, New York City
(1963).
6. "Inorganic Chemicals, 1970." Current Industrial Reports Series
M28A(70)-14, U.S. Bureau of the Census, Washington, D.C. (1972).
7. Chilton, T.H. "The Manufacture of Nitric Acid by the Oxidation of
Ammonia; the Du Pont Pressure Process." Chemical Engineering
Progress Monograph. Series No. 3, Vol. 56, American Institute of
Chemical Engineers, New York City (1960).
8. Powell, R. "Nitric Acid Technology—Recent Developments—1969 "
Chemical Process Review No. 30, Noyes Development Corp., Park Ridge,
N.J. (1969).
9. "Giving Cyanide the Treatment." Chemical Week 110(2): 55,57
(Jan. 12, 1972).
10. Astle, M.J. "Industrial Organic Nitrogen Compounds." American
Chemical Society Monograph Series. Reinhold, New York City (1961).
11. Synthetic Organic Chemicals; U.S. Production and Sales—1970. T.C.
Publication 479, U.S. Tariff Commission, Washington, D.C. (1972).
12. Miles, F.D. Nitric Acid—Manufacture and Uses. Oxford Univ. Pre_ss,
London (1961).
13, Thompson, C.H., et al. "The Biochemical Treatibility Index (BTI)
Concept." Proceedings 24th Industrial Waste Conference. Purdue
Univ., West Lafayette, Ind., 413-435 (1969).
14. Henderson, C., O.K. Pickering, and A.E. Lemke. The Effect of Some
Organic Cyanides (Nitriles) of Fish." Proceedings, 15th Industrial
Waste Conference. Purdue Univ., West Lafayette, Ind. (1960).
15. Jones, H.R. Environmental Control in the Inorganic Chemical
Industry. Noyes Data Corp., Park Ridge, N.J. (1972).
16. "Trends." Pollution Engineering 4(8): 31 (Nov. 1972).
17. Fruh, E.G. "The Overall Picture of Eutrophication." Journal Water
Pollution Control Federation (39): 1,449 (Sept. 1967).
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18. Yulish, J. "Are Phosphates at Fault?" Chemical Engineering (77)
70 (June 1, 1970).
19. Lijinsky, W. and S.S. Epstein. "Nitrosamines as Environmental
Carcinogens." Nature 225: 21-(Jan. 1970).
126
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Aquatic Systems
Environmental and Health Effects of Nitrogenous Compounds
RUTH PATRICK
UNDER NATURAL CONDITIONS, nitrogen enters the aquatic ecosystem by rain or
by the diffusion from the atmosphere of molecular nitrogen, which is then
fixed by aquatic organisms. Nitrogen may also enter by the infiltration
of soil water containing various compounds of nitrogen; also, by debris,
excretions, and the decomposition of terrestrial organisms that enter the
aquatic system.
SOURCES OF NITROGEN IN SURFACE WATER
Man's activities constitute major sources of nitrogen. Municipal waste
water may contain domestic as well as industrial waste in various propor-
tions. According to Babbitt and Bauman (1959), such water contains the
following—expressed in milligrams per liter: total nitrogen, 25 to 86;
organic nitrogen, 10 to 35; free ammonia nitrogen, 15 to 50; nitrite ni-
trogen, 0 to 0.1; and nitrate nitrogen, 0.1 to 0.4.
Different estimates have been given for various types of storm water and
combinations of storm and sewer water. Woodward (1961) reported that con-
stituents of storm water runoff from a 27-acre, residential-like commer-
cial area with separate storm and sanitary sewers were for the storm
water: total nitrogen, 3.1 mg/1; and inorganic nitrogen, 1 mg/1. Sylves-
ter (1959) gave mean values of 2.01 mg/1 for total Kjeldahl nitrogen and
0.53 mg/1 for N as NO, for runoff from urban streets.
The runoff from fertilized fields also contributes nitrogen to the
aquatic environment. Allison (1955) estimated that erosion and leaching
together account for about 65 percent of the losses of nitrogen from fer-
tilizer applied to the soil. Weibel, et al. (1966) stated that there
were 7.8 mg/1 of total nitrogen and 4.1 mg/1 of inorganic nitrogen in the
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runoff from a 1.45-acre cultivated field of winter wheat in Ohio from
March, 1964, to February, 1965.
Livestock wastes are becoming a greater problem because of the increasing
number of concentrated, centralized feedlots. In animal feedlots, drainage
ammonia is a major nitrogen constituent caused by the hydrolysis of urea.
According to Pomeroy and Orlob (1967), typical concentrations of ammonia
may run as high as 150 mg/1 of nitrogen as NHg. High nitrate concentra-
tions in ground water have been traced to contamination from feedlots and
livestock wastes in Missouri, Minnesota, and other areas.
The deforestation of a. watershed may also have a tremendous effect on
the amount of nitrogen entering a stream. Likens, Bormann, and Johnson
carried out some experiments on Hubbard Brook. They found that in the
area which had been deforested, the nitrate concentration changed from 0,9
' . I
mg/1 before the vegetation was removed to 53 mg/1 afterward. This increase
in nitrate mobilization seemed to be caused by an increase in microbial ni"
trification. The result of this increase in the amount of nitrates enter-
ing the stream produced unusual algal blooms (personal communication) that
were not present before deforestation took place (Likens, Bormann, and
Johnson, 1969).
In the natural world, there is a balance between the (1) input of
nitrogen and (2) that which is utilized by the aquatic biosphere, depos-'
ited in sediments, and returned to the atmosphere. The cycling of nitro-
gen in the biosphere is relatively complex. Molecular nitrogen must be
oxidized in the form of ammonium or organic compounds so it can be uti-r
lized by organisms. Molecular nitrogen may be oxidized by lightning in
the atmosphere, or it may be reduced to form ammonia by various bacteria
(azobacteria) and blue-green algae. That second process requires energy
which is derived from the utilization of pyruvic acid (Fogg, 1956, and
Burris, 1969).
A list of the blue-green algae known or believed to be able to carry out
this process is given in Table 1. Ammonia in the aquatic environment may
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Table 1. CAPABILITIES OF VARIOUS BLUE-GREEN
ALGAE FOR NZ FIXATION
Certain Doubtful Nil
Anabaena flos-aquae x
A. airoinalsis x
A. soheremetieV'ii x
Anabaenopsis G-irainalis x
Anabaena spirooides x
Anabaeneesis spec. x
Aphanizemenon flos-aquae x
Gloetriohia eahinulata x
Microaystis qeruginosa x
Osoillatoifia rubesoens x
be taken in by nitrosomas bacteria and changed to nitrites which, in turn,
are taken up by nitrobacteria and changed into N0_ nitrogen. Some anerob-
ic bacteria such as the Pseudomones group utilize NO- as an oxygen donor
and reduce it to N in the process (Martin and Goff, 1972).
Most algae, bacteria, fungi, and other aquatic plants absorb nitrates,
ammonia, or various amino acids from the aquatic environment. A few can
utilize molecular nitrogen (Table 2), Within the cell, however, ammonium
is used in the formation of amino acids. Whether or not a plant uses
ammonia or nitrates as a nitrogen source depends on the plant species
involved and also on the pH of the medium. For example, Soenedesmus quad-
rata, a green alga, will utilize NH, or NO, within a pH range of 7 to 9;
but above 9.5, no growth occurred with NH,, although some growth took
place with N0_ up to a pH of 11 (Hutchinson, 1957).
Nitrate nitrogen is the preferred form of nitrogen for Botvyocoocous
Braunii and for some diatoms (Chti, 1942). Chlovella can utilize ammon-
ium, nitrite, nitrate, acetamine, and other amino acids (Hutchinson,
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Table 2. ABSORPTION CAPABILITY OF VARIOUS AQUATIC PLANTS
Organic N
N(NH3)
N(N03)
Some bacteria and Eumycetes,
Some bacteria and Eumycetes
Most bacteria, Eumycetes,
algae, and higher plants
Some bacteria and blue-green algae. .
X X
X XX
X XXX
1957) . Hutchinson (1967) reported that the flagellates Eugl'ena and Phaaus
prefer ammonia as their nitrogen source.
As stated by North, et al. (1971), low concentrations of amino acid in
water near the shore (about. 1 micromohl per liter) can support the nitro-
gen requirements of Chalmydomonas . Macroscopic algae may also utilize
amino acids. Ulva and Enteromorpha show rapid accumulations of amino
acids in dilute solutions. Other algae which have been shown to utilize
amino acids are the diatoms Skelatonema oostatum3 Cyalotella nana3 Melo-
sira sp., Nitzsohia olosterium, N. ovalis, and Thalassiosira fluviatilis3
and other green algae such as Chlorella sp. , Chaetomorpha, Coditorij Entevo-
morpha, and Ulva. The brown algae are Colpomenia, Egreth-La, Eespevophyous,
Macrocystis, Paohydictyon, Pleetia-, and the red algae are Boss-Leila, Coral-
lina, Endoaladia3 Gelidiwn3 Gigartinea, Graoilaviopsis 3 Lithofhrix, Por-
3 and Weeks-ia.
The kind of nitrogen compound as well as the amount of nitrogen an
aquatic plant will absorb depend on the conditions of the plant and
the concentration in the medium. As pointed out by Fitzgerald (1968), the
condition of the plant — that is, whether or not it is nitrogen-starved —
greatly influences the uptake. Table 3 sets forth the differences in
uptake rates for various algae and other aquatic plants.
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Table 3. UPTAKE BATES: ug/1 Nfy-N ABSORBED/10 mg
DRY WT/HR BY ALGAE
Complete N-limited
Algae medium medium
GREEN ALGAE
Chlamydomonas chlamydoeama ... 0 18
Scenedesmus dimorpha 17 62
Cladophora sp 3 18
Spiroqyra sp 7 30
DIATOMS
BLUE-GREEN ALGAE
M-Lovooystis aevuqinosa
Andbaena ftos-aquae
Aphanizomenon fios-aquae ....
SPERMATOPHYTES
Lerma minor (duckweed)
Ceratophyllwn
«•
16
0
3
4
10
J*»J
36
1
0
18
7
Modified from Fitzgerald (1968).
These studies show that a plant starved for nitrogen will have a much
greater nitrogen uptake rate than one in a medium with sufficient nitro-
gen. Furthermore, the amount of nitrogen that is accumulated within the
plant will vary according to the concentration of nitrogen in the medium.
For example, in the common aquarium plant, El-odea, the increase in
nitrogen in the tissue will be linear with the increase in dry weight
until the nitrogen reaches 1.3 percent of the dry weight. Concentrations
of nitrogen in the tissues may increase beyond this amount, but the
increase in cells will not be linear. In fact, it may be very little.
Gerloff (19.69) has referred to this as "luxury consumption," because it is
an accumulation of nitrogen beyond that necessary for growth. This phe-
nomenon is often found in polluted waters where nitrogen compounds are
excessive.
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Aquatic plants, like terrestrial plants, utilize many chemicals for
food, growth, and reproduction. Under optimum conditions, those chem-
icals are in the correct amounts and ratios for a given species. A shift
in amounts and ratios will bring about a change in the kinds of species or
in the abundance of a species. This often means a shift from species with
high predator pressure to those with the opposite. The result is a large
standing crop, with the accompanying effects of nuisance growths. Thus,
imbalances in nutrients without increases in concentration may develop
nuisance problems.
In natural lakes and streams, the ratio of nitrogen to phosphorus varies
greatly. Part of this variation is due to the chemical and physical condi-
tions of the body of water being studied, but it also depends on whether
one is talking about total nitrogen and phosphorus or soluble nitrogen and
phosphorus. For example, Hutchinson (1957) discusses the phosphorus and
nitrogen in Wisconsin lakes. The average N as ammonia is 307 milligrams
per cubic meter. The average N as N03 is 64 milligrams per cubic meter,
with a total of 371 milligrams per cubic meter of soluble nitrogen. The
mean amount of soluble phosphorus for lakes in northern Wisconsin is
3 milligrams per cubic meter, or an approximate ratio of 127 to 1. Howev-
er, if one considers the total phosphorus (45 mg per cubic meter), then
the ratio of total phosphorus to soluble N is roughly 8 to 1.
Although these ratios are variable, one often finds ranges of N to P
from 50:1 to 1:1, depending on the degree of eutrophication of the
lake. However, in lakes in which phosphorus appears to be limiting,
such as Hutchinson (1967) found on occasions for Linsley Pond, the ra-
tio of inorganic combined N to P was 0 to 220;1. The amounts of nitro-
gen and phosphorus characteristic of lakes with various levels of
eutrophication are given in Table 4, as set forth by Vollenweider
(1968). Sawyer (1947) working on lakes in Wisconsin presented the
hypothesis that an aquatic bloom would develop if the inorganic N is
greater than 300 milligrams per cubic meter and if the phosphorus is
3
greater than 10 mg/m in a lake at the beginning of the growth period
for algae and other plants. Vollenweider (1968) stated that findings
in Europe support this hypothesis.
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Table 4. INORGANIC N CONCENTRATIONS IN LAKE WATER
ASSOCIATED WITH DIFFERENT TROPHIC LEVELS
Increasing levels of Inorganic N
nutrient availability
Ultra-oligotrophic ........... 0.2
Oligo-mesotrophic ........... 0.2 to 0.4
Meso-eutrophic ............. 0.3 to 0.65
Eu-polytrophic ............. 0.5 to 1
Poly trophic .............. 1.5
Source: Vollenweider (1968)
In flowing water, the concentration of nitrogen may be somewhat greater
without producing excessive growths. In White Clay Creek in Eastern Penn-
sylvania (Chester County) , we have found that the nitrogen concentration
may vary from 1 and 2.5 mg/1 without producing excessive algal growths.
The nitrogen is mainly in the form of nitrates, and the amounts of ammonia
or nitrites present are very low. Vollenweider (1968) reported that simi-
lar concentrations are characteristic of streams in Europe, ones that do
not sustain nuisance growths .
The reason rivers can tolerate higher levels of nitrogen, phosphate, and
other nutrient concentrations versus lakes is probably the result of dif-
ferences in the cycling of nutrients. Nutrients that enter a lake are
usually taken up by the growth of phytoplankton and zooplankton organisms,
as well as by benthic species . Upon the death of these organisms or by
excretions from them, the nutrients become absorbed onto sediments and
settle-out in the bottom of the lake.
During the summer, particularly in deep lakes, a stratified anaerobic
zone may develop. This brings into solution the nutrients that former-
ly were precipitated out of solution. During the fall overturn, these
nutrients are recycled and again reach the epilimnion, where they are
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converted into plant and animal organisms. This continual recycling of
nutrients brings about a buildup in concentrations within the lake over
time. The only nutrients that leave the lake are those in the outfall of
water and sediments from the lake and those that leave the lake in the
form of emergent organisms. The lake or pond functions as a sink for the
accumulation of nutrients.
By contrast, the river is a flowing system. Nutrients are always enter-
ing and leaving any given section. They only accumulate temporarily in
the sediment of slack water and in pools, from which they are usually
flushed out by floods occurring sporadically throughout the year. Because
the sediments in the bed of a stream or river are typically in an oxidized
state, they do not produce soluble nitrogen compounds. It is only in deep
pools that anaerobic respiration may take place, thus yielding redissolved
nutrients. It is this continual flushing of nutrients that enables the
flowing-water ecosystem to tolerate higher nitrogen levels without produc-
ing nuisance growths.
In estuaries and in the open sea, nitrogen compounds—particularly
ammonia and nitrates—are often present in very low concentrations; and as
a result, limit the total biomass and determine the types of species it
contains. For example, Sverdrup and Allen (1939) and Sargent and Walker
(1948) related diatom populations to the large-scale eddies and areas of
upwelling water off the coast. These upwelling waters from the deep sea
are rich in nutrients, particularly nitrogen.
Much of the year, the surface water off southern California is depleted
of its plant nutrients, especially nitrogen. Nitrates are undectable at
the surface, and ammonia concentrations are less than one micromohl.
Thus, any increase in nitrogen usually results in a greater algal bloom.
Enriched waters in the open sea usually bring about diatom blooms; whereas
an increase in nitrogen along the shore often brings about blooms of dino-
flagellates, which are referred to as "red tides."
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This difference in the type of bloom is probably partly due to the dif-
ferences in the form of nitrogen in the two areas. In southern California,
nitrate is the major form of nitrogen associated with upwelling. Ammonia
is the principal form of nitrogen found in sewage discharged along the
coast. Phytoplankton appear to utilize both forms of nitrogen equally
well—although the composition of plankton, especially the C-N ratios, may
vary somewhat with the nitrogen source used for growth (Eppley e~t al. ,
1971.).
TOXICITY OF NITROGEN COMPOUNDS TO AQUATIC LIFE
There are two natural forms of nitrogen that are most toxic to aquatic
life. These are nitrogen as a gas dissolved in water and ammonia. The
toxic effect of molecular nitrogen in water occurs when there is a sudden
rise in the temperature of a body of water in which fish ate confined.
This may happen below the dam in a river, a place where fish congregate in
the cold water in the pools. If the flow of water is curtailed for any
reason, the water in the pool can warm up very rapidly, particularly in
the summer. This increase in temperature allows gas bubbles to be
released in the blood of fish and embolism occurs. This is a disease sim-
ilar to "the bends" in humans. Fish kills caused by embolism have been
reported below the dam on the Susquehanna in Pennsylvania and below the dam
in the Roanoke River in Virginia.
The toxicity of ammonia is related to the pH, since only the un-ionized
molecule is toxic. The toxicity may increase rapidly with slight increase
in the pH level (Burrows, 1964). Greater concentrations of dissolved oxy-
gen and carbon dioxide, elevated temperatures, and bicarbonate alkalinity
are also important in increasing ammonia toxicity (Lloyd, 1961). Various
effects of ammonia toxicity have been reported. Burrows (1964) described
major gill damage to juvenile salmon when the un-ionized ammonia concen-
trations were as low as 0.01 milligrams per liter. Data given by Lloyd
and Herbert (1960), Ball (1967), and Lloyd and Orr (1969) indicate toxici-
ties below 1 mg/1 for fish.
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Little is known about the toxicity of nitrites in relation to aquatic
life. Considering its toxicity to warm-blooded invertebrates, this com-
pound deserves further study. Recent investigations by R. Krauss indicate
that N and N0? are lost from the cultures of C'hloTella soToM-niana growth
in nitrate and in urea.
Many other nitrogen compounds have been shown to be toxic to aquatic
life. Some of these are acrylonitrils, nitroamylene, nitrobenzene, ni-
trophenol, chloroamines, diethylamine, dinitrocresol, dynitrophenol,
ethylamine, ethylenediamine, triethylenediamine,, and trinitrophenol.
CONCLUSIONS
Although nitrogen is an essential nutrient chemical for all living
organisms, it is now occurring in concentrations in our waterways that are
hazardous to many forms of aquatic life. These concentrations are helping
to bring about increases in the abundance of species that cause nuisance
growths. Some of these, such as certain species of blue-greens, produce
substances that are toxic to many forms of aquatic life as well as to ter-
restrial organisms. The concentrations of nitrates in some ground and
surface water are high enough to be dangerous to man. For these reasons,
efforts should be made to maintain the levels of N as N0_ or NH, at the
beginning of the growing season to less than 0.3 mg/1 in lakes and not
more than 1 mg/1 in f.ree-flowir.g waters. In some instances, such require-
ments may be too strict because one cannot universally establish a concen-
tration of N that will prevent algal blooms in all kinds of water. There-
fore, it may be necessary to run a laboratory test such as the Provisional
Algal Assay Procedure (1969) to determine what additions of N will produce
algal blooms in the type of water in question. Since un-ionized ammonia
is toxic to many forms of aquatic life, its concentration should be con-
trolled so it does not exceed 0.02 milligrams per liter. Care should also
be taken not to change to any great degree the existing N:P ratio. In
water used for drinking, the level of nitrogen as N-NO., should be less
than 10 milligrams per liter.
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phosphorus as factors in eutrophication. Organization for Economic
Co-operation and Development, Paris. DAS-CSI-68.27-
Weibel, S.R., R.B. Weidner, J.M. Cohen, and A.G. Christiansen. 1966.
Pesticides and other contaminants in rainfall and runoff. Journal of
the American Water works Association, 58:1,075-1,084.
138
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Woodward, L. April, 1961. Ground water contamination in Minneapolis and
St. Paul suburbs. In: proceedings of a 1961 Symposium on Ground Wa-
ter Contamination. Robert A. Taft Engineering Center, Technical
Report W61-5.
139
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Animal Health
Environmental and Health Effects of Nitrogenous Compounds
JOSEPH SIMON
THE IMPORTANCE OF NITROGENOUS COMPOUNDS in animal health and/or disease is
unknown, because of the limited nature of clinical and field observations,
clinical pathologic and necropsy reports, and experimental studies.
r ss i
Historically, the studies of outbreaks of cornstalk poisoning in
[12 3 81
Kansas and oat hay poisoning ' ' J in the High Plains States incrimi-
nated nitrite, obtained from nitrate reduction, as the intoxicant.
Nitrite intoxication is usually categorized as acute and lethal, or as
chronic and sublethal. A diagnosis of acute nitrite intoxication can
usually be made. Diagnosing sublethal or chronic intoxication is diffi-
cult. In all probability, chronic nitrite poisoning has been an "ash can"
diagnosis for diseases of unknown etiology.
Because of a complex digestive system that permits the reduction of
nitrate into nitrite, herbivora, cattle ' * ' and horses are
affected most frequently by nitrite intoxication. An occasional report
r ng 31
suggests that intoxication may be encountered in other species '
NITROGENOUS COMPOUNDS INVOLVED
Although the literature contains reports of nitrate intoxication,
nitrate is essentially innocuous. It is its reduction into nitrite
f £ O OQ "I
that provides the hazard of intoxication ' . In addition to ni-
trite, these other nitrogenous compounds have been incriminated in animal
disease: urea, ammonia, oxides of nitrogen, hydroxylamine, and
nitrosamines.
141
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TYPES OF HAZARD
ACUTE OR LETHAL NITRATE (NITRITE) TOXICITY
Acute nitrite toxicity in animals is characterized by hypoxia, the
r co go 091
result of methemoglobin ' ' formation. Usually, the transfor-
mation of 70 percent of hemoglobin into methemoglobin is believed to
result in death. Basically, nitrite oxidizes iron from the ferrous to the
ferric state, depriving hemoglobin of its ability to transport oxygen.
Experimental studies have shown that in animals fed either nitrate or
F 781
nitrite, the production of methemoglobinemia is contingent on numer-
. [14,98] . ,.,.:, [54,66,85,89]
ous factors—such as the species ; microbial flora ;
ions[85]; Mo, Cu; sex[81]; PH[85]; dietU7]; vitamin C levels[45];
age ' ; pregnancy ' ; disease state, concomitant infections ;
and/or neoplasia.
Nitrite may react with hemoglobin and methemoglobin in the formation of
a reversible complex between excessive free nitrite and ferric heme groups
[79]
of methemoglobin . An analytic problem could result, because this com-
plex in nitrited erythrocytes may result in lower methemoglobin values in
spectrophotometry.
r fo 1
It has been shown in vitro that the addition of nitrite to blood may
result in a compound, nitrosohemoglobin. The amount formed varies with
the animal species and is greatest in actively metabolizing red blood
cells. In vivo, in sublethal nitrite intoxication, and under certain con-
ditions in which nitrite methemoglobin is not formed, nitrosohemoglobin
forms with conversion to nitrosomethemoglobin, which decomposes into
methemoglobin and nitrous oxide. The relative importance of this al-
ternate means of methemoglobin formation is unknown. The age, health
status, and the species involved constitute important variables. Ex-
perimental studies are needed for clarification.
142
-------
Nitrites and organic nitrates are known vasodilators in monogastric ani-
r OQ £-1 -I F21
mals ' . In cattle, limited work suggests that in this respect
they probably are of little importance.
CHRONIC OR SUBLETHAL NITRATE (NITRITE) TOXICITY
Experimental evidence suggests that nitrate and/or nitrite ingestion may
[7 99]
interfere with thyroxine synthesis ' in rats and sheep. The effect is
rg g IT gi 991
transitory ' ' ' ' . Under optimum conditions, ruminant animals do
not develop thyroxine deficiency when fed low levels of nitrate. In cases
of iodine deficiency or the ingestion of other goiterogenic substances,
however, nitrate may augment relative decreases in thyroid secretion
There is considerable confusion about the effect of nitrate (nitrite) in
.„ - A „,.•,. [15,16,27,34,39,40,43,46,72,86,98] . _ ,.
vitamin A metabolism >>»>»>>>>> Apparently, the
formation of nitrite from nitrate requires an almost neutral pH, which
occurs in the rumen. Following formation, the nitrite is reduced or
absorbed so that little will be found in the true ruminant stomach, the
abomasum. Nitrite destroys carotene and/or vitamin A at a pH of 4.
Hence, in the normal runinant, nitrite probably is of little significance
•>, . . v -, • t!6,20,2],32,42,64,80]
in carotene and/or vitamin A metabolism
In some cases, in which carotene or vitamin A losses have occurred in
the processing of feed prior to ruminant ingestion, nitrates or nitrites
[25]
have been blamed for avitaminosis A . Field reports have been made
during the winter months in Illinois of feeder steers fed yellow corn
grown on highly fertilized fields manifesting joint and pectoral edema,
signs reported to be associated with vitamin A deficiency. The adminis-
tration of high dosages of vitamin A has been reported to result in a
cure; admittedly, these comments are empiric
In monogastric animals ' ' , the acid pH of the stomach in associa-
tion with ingested nitrite may affect carotene and/or vitamin A metabo-
lism. In swine with reduced liver stores of vitamin A, the ingestion of
143
-------
water containing 0.08 percent nitrite (240 ppm—NO~-N) has been associ-
F961
ated with reduced weight gain and reduced food intake
Nitrates (nitrites) in rations or water have been incriminated—in
some cases with reduced weight gains ' ' or with decreased milk1
and egg production *'. In general, the palatability of the ration
is thought to be the major consideration. Other studies have revealed no
long-term effects of low level nitrate feeding trials in swine, sheep,
cattle, and poultry.
The role of nitrate (nitrite) in abortions is controversial. Nitrate
(nitrite) intoxication was suspected as the cause of bovine abortion '
in various midwestern states in which cattle consumed forages containing
approximately 1-percent potassium nitrate.
Some experimental studies with cattle have suggested that nitrate
C19 93]
(nitrite) is of little significance ' in the production of abortions
in cattle, sheep, and swine. In contrast to these studies, an investiga-
tion of the lowland abortion syndrome ' ' in Wisconsin suggested
that nitrate (nitrite) does play a role in cattle abortion. Also, rumi-
nants fed balanced rations ' do not respond to the ingestion of
nitrate (nitrite) as do cattle on a marginal or inadequate diet. The dis-
crepancy of the lowland abortion experimental data and other experiments
is attributed to the fact that the experimental animals used in the low-
land abortion study were native cattle on an inadequate diet; hence, their
response differed from cattle on a balanced ration. Unpublished data
revealed that when cattle on a balanced ration were fed levels of nitrate
similar to those given to the cattle in lowland study, they did not abort
and did not manifest placental lesions.
A number of investigators have shown that the long-term ingestion of
sublethal nitrate (nitrite) results in a compensatory polycythemia ' ' •*
as a sequel to abnormal levels of methemoglobin.
144
-------
UREA
[22 231
Blood studies in experimental urea intoxication ' reveal high ammo-
nia levels with clinical signs of respiratory difficulty, excessive sali-
vation, and frothing—presumably the results of severe alkalosis.
AMMONIA
Ammonia constitutes a potential hazard, primarily in the confinement
rearing of swine, Whether NH3 is of importance is currently under in-
vestigation at the Illinois Experiment Station., Preliminary work with
experimental swine housed for four weeks in stainless steel units and sub-
jected to an atmosphere containing 50 ppm of NH, resulted in mild conjunc-
11001
tivitis and blepharitis . In addition, gross pathologic examination
revealed mild inflammation of the turbinates and.trachea. The lungs
appeared to be normal. Histopathologic examination revealed a mild focal,
chronic rhinitis, mild focal chronic tracheitis, and normal lungs.
OXIDES OF NITROGEN
Unconfirmed clinical reports have attributed deaths of cats and
dogs to "yellow gases," apparently derived from recently ensiled corn.
The gases are believed to represent various oxides of nitrogen. Since
necropsy data are not available, the significance of the reports is un-
known. The toxicity of these compounds in animals may be similar to that
of the "silo fillers'^71'88'98-1 disease in man.
HYDROXYLAMINE
Hydroxylamine may represent an intermediate metabolite in the breakdown
F41 931
of nitrite into ammonia. The importance ' J and potential hazard of
this compound has been shown primarily in sheep in which a hemolytic ane-
mia has been produced experimentally. The natural occurrence of this type
of intoxication is unknown.
145
-------
NITROSAMINES
Nitrosamines ' ^ are compounds formed by a reaction between nitrites
and various classes of amines. This reaction can occur in a variety of
foods and biological conditions.
Various N-nitrosamines and N-nitrosoamides have been shown in experimen-
tal laboratory animals to be carcinogenic^ ' ' ' They may also be
[49]
mutagenic and teratogenic. Severe hepatic disease in Norwegian cattle
revealed dimethylnitrosamine (DMN) to be the probable cause. Indirect
evidence suggested that batches of herring meal fed to cattle, sheep ,
and chicks resulted in severe hepatic disease and presumably was the
result of a compound formed between nitrite and another component of the
meal. Subsequent studies in sheep with DMN showed similar hepatic altera-
tions. Hepatic disease has also been observed ii
were fed toxic herring meal which contained DMN.
[50]
tions. Hepatic disease has also been observed in mink and foxes that
MANNER OF DIAGNOSIS OR DETECTION
ACUTE NITRATE (NITRITE) INTOXICATION
A .presumptive diagnosis is based on a history of excessive ingestion of
the compound(s) with concomitant signs of hypoxia, brownish discoloration
of the blood and membranes, and the occurrence of rapid death. Confirma-
tion is usually based on increased methemoglobin ' , nitrate, and ni-
trite blood1 ' ' levels. In addition, the suspect feed and water ^
is analyzed for nitrate (nitrite).
CHRONIC NITRATE (NITRITE) INTOXICATION
A clinical assessment of chronic intoxication poses a diagnostic chal-
lenge and is made after other disease processes are excluded. Addition-
al evidence can be acquired through analyses of blood, milk, urine, water,
[37]
and feed . Methemoglobin values can also be used. However, differ-
F351
ences resulting from delay in the analysis of blood samples and from
146
-------
individual variation may limit such usage.
f o£ TO Q£ Q£*1
Other indirect analyses * ' * that may suggest sublethal or
chronic nitrate (nitrite) intoxication include the carotene and/or vitamin
A level of serum and, if possible, of the liver; hemoglobin concentration;
and the number of erythrocytes, essentially an assessment of polycythemia,
reported as a result of the intoxication.
UREA
Presumptive diagnoses of urea poisoning are based on history *• , clini-
F97]
cal and gross necropsy findings , and blood analyses characterized by
elevated NH, levels and alkalosis.
AMMONIA
Although levels of 50 ppm are irritating to the mucous membranes of man,
limited studies suggest that swine are otherwise essentially unaffected.
The number of diagnoses, if any, of ammonia intoxication in animals is
currently unknown.
OXIDES OF NITROGEN
In a few clinical reports, a presumptive diagnosis was based on a his-
tory of recent silo filling and the subsequent occurrence of a yellow-
colored gas coming from the silo chute. It is believed that affected ani-
mals would probably suffer from extensive respiratory difficulty as a
result of pulmonary edema—similar to that of man in "silo fillers"
disease.
HYDROXYLAMINE
This intermediate compound of nitrate metabolism probably is of minimal
importance as an intoxicant in ruminants, primarily in sheep. Analyses of
rumen contents for this compound, if elevated above control animals under
147
-------
identical conditions, with a concomitant hemolytic anemia could conceiva-
bly have diagnostic significance.
NITROSAMINES
The presence of nitrosainines in various feeds can be confirmed by mass
rQOI F831
spectrometry and chromatography . The fact that nitrosamines are
present in many human foods would suggest by analogy a comparable situa-
tion in animal feeds.
IMPORTANCE OF DAMAGE, AND INDICATIONS OF TRENDS
Acute nitrate (nitrite) intoxication in herbivora is relatively uncommon
under modern methods of animal husbandry.
T581
An outbreak of nitrate (nitrite) intoxication of cattle in Kansas
[14]
and Missouri was associated with drought-affected corn. The utiliza-
tion of nitrogenous fertilizers and herbicides in the Corn Belt, and the
[94]
possibility of drought, present a potential hazard for cattle if they
f 581
consume affected corn stalks . Since relatively few ears of corn would
be produced under extreme drought, the role of either ear or shelled corn
in chronic nitrate (nitrite) intoxication would probably be negligible.
Currently, considerable controversy exists regarding a possible increase
in nitrate (nitrite) in the runoff*• •* from fertilized fields and the crea-
tion of a potential environmental problem. Urea and hydroxylamine are
thought to be of little importance.
The potential role of ammonia, either alone or in association with other
gases emanating from "pits," remains obscure. Empirically, in confinement
swine operations, reproductive problems, marginal weight gains, and respir-
atory disease have been attributed to the various gases, although experi-
mental confirmation is lacking.
148
-------
Perhaps one of the greatest potential hazards is that of the nitro-
samines from the standpoint of carcinogenesis, mutation, and teratoma
formation. Livestock as well as animal products used for human and pet
food would be involved.
POSSIBLE SOURCES OF NITROGENOUS COMPOUNDS
The major source of nitrogenous compounds for herbivora is plants such
as hays and grains. The role of contaminated water remains an enigma.
For swine, NH- derived from wastes constitutes a potential hazard, the
F 951
significance of which remains to be proven. Since nitrosation may
occur under a variety of conditions, the availability of feeds contain-
ing nitrite and various amines poses a potential hazard.
SUGGESTIONS
Current experimental and clinical evidence suggests that nitrate
(nitrite) intoxication in herbivora is of limited occurrence, occurring
primarily during periods of drought. The increased use of readily availa-
ble nitrogenous fertilizers increases the hazard in the event of drought.
The role of nitrate (nitrite) in carotene, vitamin A metabolism, needs
to be delineated more clearly, particularly in relation to cattle, sheep,
and swine. The monitoring of nitrate (nitrite) levels in water should be
expanded, and an assessment of concomitant disease problems in livestock
should be made.
Since the current methodology for nitrosamine detection is laborious and
expensive, better analytic procedures need to be developed. If possible,
the relationship between nitrosamine levels and the induction of neoplasia
should be established. The role and amounts of these compounds as mutagens
and in teratoma formation and in connection with other disease problems al-
so needs to be investigated.
149
-------
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Blakiston Division, McGraw Hill Book Co., New York City.
66. Pfander, W.H., Garner, G.B., Ellis, W.C., and Muhrer, M.E. 1957.
The etiology of nitrate poisoning in sheep. Missouri Agr. Exp. Sta.
Bull. 637-
154
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67. Rath, M.R. and Krantz, J.C., Jr. 1942b. Nitrites. IX. A further
study of the mechanism of action of organic nitrates. J. Pharmaool.
Exp. Ther. 76:33-38.
68. Rein, H., Ristau, 0., Kupfer, E., and Jung, F. 1968. Nitrosohemo-
globinemia in NaNO poisoning. Folia Eaematol. 90:176-181.
69. Ross, J.D. 1963. Deficient activity of DPNH-dependent methemoglobin
diaphorase in cord blood erythrocytes. Blood 21:51-62.
70. Sakshaug, J., Sognen, E., Hansen, M.A., and Koppang, N. 1965.
Dimethylnitrosamine; its hepatotoxic effect in sheep and its occur-
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71. Seaton, V.A. 1957. Pulmonary adenomatosis in cattle produced by
nitrogen dioxide poisoning. N. Amer. Vet. 38:109-111.
72. Seerley, R.W., Emerick, R.J., Embry, L.B., and Olson, O.E. 1965.
Effect of nitrate or nitrite administration continuously in drink-
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73. Sell, J.L. and Roberts, W.K. 1963. Effects of dietary nitrite on
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74. Sell, J.L., Roberts, W.K., and Waddell, D.G. 1963. Methemoglobinem-
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75. Simon, J., Sund, J.M., Douglas, F.D., Wright, M.J., and Kowalczyk, T.
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76. Simon, J., Sund, J.M. , Wright, M.J., Winter, A., and Douglas, F.D.
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135:315-317.
78. Smith, J.E. and Beutler, E. 1966. Methemoglobin formation and
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79. Smith, R.P. 1967. The nitrite methemoglobin complex—Its signifi-
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80. Sokolowski, J.H., Garrigus, U.S., and Hatfield, E.E. 1961. Effects
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81. Stoewsand, G.S. 1970. Influence of sex and dietary ascorbic acid on
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82. Sunderman, F.W., and Sunderman, F.W. 1964. Hemoglobin, Its Precurs-
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83. Telling, G.M., Bryce, T.A., and Althorpe, J. 1971. Use of vacuum
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85. Tillman, A.D., Sheriha, G.M., and Sirny, R.J. 1965. Nitrate reduc-
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100. Personal communication.
157
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Human Health
Environmental and Health Effects of Nitrogenous Compounds
CARO E. LUHRS
METHEMOGLOBINEMIA
NITRATES, NITRITES ARE FOUND in drugs, food, and water. Man is continual-
ly exposed to small amounts of them. Usually, they cause no harm. In
high concentrations and under special circumstances, however, they may
cause illness and even death. Nitrates are generally toxic only by virtue
of their potential for chemical conversion into nitrites.
ACUTE TOXECITY
The major clinical manifestation of acute nitrite toxicity -is cyanosis
(a bluish-purple discoloration of the skin and lips, which generally oc-
curs within 1 to 2 hours after exposure and if unrelieved by oxygen ther-
apy) . There may be nausea, vomiting, and profuse sweating1—in severe
cases, lethargy—progressing to unconsciousness. Blood drawn from a
patient with nitrite-induced cyanosis is a chocolate-brown color. These
manifestations are explained by the oxidation of hemoglobin, the oxygen-
carrying red pigment of blood, into methemoglobin, which is a brown pig-
ment incapable of carrying oxygen. Death from asphyxia may result when
large amounts of methemoglobin are formed and oxygen transport is severely
impeded.
Methemoglobin is normally present in blood, constituting about 1 percent
of the total hemoglobin of a healthy adult and up to some 4 percent of
[391
the total hemoglobin of a healthy newborn infant . Levels above 6 per-
cent have been observed in normal babies with respiratory illness or diar-
T241
rhea . Cyanosis results when roughly 15 percent of the hemoglobin in
blood is converted into methemoglobin. When methemoglobin constitutes 70
159
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percent or more of the total hemoglobin, death may occur . Chemicals
other than nitrites can cause methemoglobinemia. These range from sulfa
drugs and phenacetin to the aniline dyes used in furniture polish, laun-
dry-marking inks, and crayons. The condition may also exist in the
absence of chemicals, as an inherited genetic defect
As indicated previously, nitrates are toxic to man because of their
potential for reduction into nitrites. Such a conversion of nitrates
into nitrites may occur outside the human body (in nitrate-containing
food of water prior to ingestion) or inside the human body (by the ac-
tion of intestinal bacteria on ingested nitrates).
The form of nitrate/nitrite conversion that occurs during digestion
requires very special conditions, ones that are likely to be present only
in infants. The foremost prerequisite is the presence of nitrate-reducing
bacteria in the upper gastrointestinal tract. Such bacteria are not nor-
mally present so high up in the intestinal tract. However, this circum-
stance may occur occasionally in infants, particularly those with gastro-
intestinal infections and a gastric pH insufficiently acid to kill the
bacteria^ .
Several other factors explain why most cases of clinical nitrate-induced
methemoglobinemia occur in infants: (1) the hemoglobin of a very young in-
fant (so-called fetal hemoglobin) is oxidized twice as rapidly by nitrite
to form methemoglobin as the hemoglobin of children and adults; and
(2) the red blood cells of infants are not able to reduce methemoglobin
into hemoglobin as well as that of adults^ .
CHRONIC TOXICITY
In contrast to the relative wealth of acute toxicity data in humans,
reliable data are lacking on the physiologic effects, if any, of chron-
ic nitrate/nitrite toxicity or of mild, non-cyanotic methemoglobinemia.
160
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Studies in animals indicate that nitrates and nitrites may, on occasion,
cause vitamin A deficiency and that nitrate may have an antithyroid effect
f 281
by increasing the requirement for iodine . Thei
to indicate whether such effects can occur in man.
f 281
by increasing the requirement for iodine . There are no data available
Abnormal changes on electroencephalograms have been observed in rats
given 100 to 2,000 ppm of sodium nitrite each day for two weeks . This
obviously raises the question of the effect, if any, of chronically ele-
T321
vated methemoglobin levels on the human brain. One Russian study pur-
ports to show a decreased response to visual and auditory stimuli in
school children with a mean methemoglobin level of 5.3 percent of total
hemoglobin. The study was poorly controlled and the conclusions, there-
fore, must be regarded as potentially unreliable. Patients with hereditary
methemoglobinemia and mental retardation have been reported. However, the
association may be coincidental. Most patients with hereditary methemo-
globinemia do not have mental or neurologic abnormalities J.
SOURCES OF NITRATES AND NITRITES
Drugs. Nitrates (nitroglycerin) and nitrites (amyl nitrite) have been
used for over a hundred years for the relief of pain of angina pectoris.
Methemoglobinemia associated with therapeutic use of cardiac nitrites
(amyl nitrite and sodium nitrite) is rare. It has occurred, however, from
the accidental ingestion of such drugs as in the case of eleven men who
mysteriously turned blue after eating oatmeal that had been seasoned with
[13]
sodium nitrite instead of salt.
Although amyl nitrite and sodium nitrite are still used in the treatment
of cyanide poisoning and in some diagnostic cardiac procedures, angina pec-
toris is more commonly managed by using one of the organic nitrates, such
as nitroglycerin. These compounds allegedly do not cause methemoglobi-
nemia[12J.
Methemoglobinemia has been a rare complication in the use of nitrate-
containing drugs such as bismuth subnitrate (an anti-diarrheal agent),
161
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ammonium nitrate (a diuretic), and silver nitrate (a compound used topic-
ally in the treatment of burns) '
Vegetables. Nitrates and nitrites occur in the human food supply, both
naturally and as additives. Nitrates are natural constituents of plants.
Many fresh vegetables (spinach, kale, beets, radishes, eggplant, broccoli,
lettuce, celery, turnips, carrots, parsley, squash, cabbage, and cauli-
flower) may contain nitrates in high concentrations (over 3,000 ppm of
T191
nitrate) . There may be great variations in nitrate content between
samples of the same vegetable grown in different geographical locations.
This is thought to be a reflection of differences xLn species and also of
the differences in growth conditions, such as water, temperature, sunlight,
and the nitrate content of the soil. In contrast to nitrate, the nitrite
F281
content of fresh vegetables is low . But nitrate may be converted in-
F331
to nitrate during storage by the action of bacteria or of a nitrate-
reducing enzyme. Such an enzyme (nitrate reductase) has been identified
in spinach leaves
Despite the high nitrate content of a number of vegetables and the pos-
sibility for converting nitrate into nitrite during storage, there have
been surprisingly few case reports of vegetable-induced methemoglobinemia
in humans (less than fifty); only two in the United States. All have
involved infants under one year of age. All, save for a single case
r OH]
report implicating commercially packed strained beets , have been
attributed to the ingestion of stored, fresh spinach or carrots.
T44 42 151
In the cases attributable to spinach ' ' , fresh spinach had gener-
ally been pureed and then stored at room temperature or refrigerated for a
day or more before feeding. Home-prepared carrot soup was involved in
sixteen cases that occurred in France, where carrot soup is an apparently
well-known remedy for infant diarrhea. The soup had generally been stored
for a day or more after preparation without refrigeration. In all cases,
the municipal water used in making the soup was free, of excessive concen-
trations of nitrates. The nitrate/nitrite conversion was supposed to have
occurred either as a result of bacterial contamination of the soup or by
162
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virtue of a pre-existing gastroenteritis, which caused nitrate-reducing
bacteria to be present in the infants' upper intestinal tracts . One
case of methemoglobinemia in an infant and attributed to home-prepared
carrot juice has been noted in the United States. One fact of interest is
that the carrots in question were grown without the use of nitrogen-
[181
containing fertilizer
It is important to note that there has been only one case of methemoglo-
binemia attributable to commercially prepared vegetables, that one to
strained beets1 . Industry marketing data1 •* for the year ending in
June, 1972, indicate that 400 thousand jars of canned spinach, 500 thousand
jars of canned beets, and 1.7 million jars of canned carrqts were sold in
the United States. Studies of canned baby-food spinach have shown only
traces of nitrites, even after the jars had been stored open under refrig-
eration for 35 days. By contrast, nitrite accumulation does occur with
r o/1
storage of unprocessed fresh spinach, even under refrigeration
Meat. Nitrates (saltpeter) and salt have been used as additives in the
curing of meat since ancient times. The use of nitrite is comparatively
recent, about 50 years old. It can be traced to the scientific observa-
tion that the typical reddish-pink color of cured meat was not due to
nitrate, rather to the reduction of nitrate into nitrite and the subse-
quent reaction between nitrite and meat pigment to form nitrosylmoglobin,
the characteristic pigment.
At present in the U. S., mixtures of nitrate and/or nitrite and salt are
used in the curing of certain meat and fish products for three distinct
purposes: color-fixation, flavoring, and protection against bacterial
growth; particularly Clostvid-ium botu1inion> In some European countries,
nitrates and/or nitrites are permitted as additives to cheese and flour
as well as to fish and meat.
Cured meat and fish products play a prominent role in the American diet.
They are popular because of their unique taste. Bacon without nitrates
and/or nitrites would not taste like bacon. Cured pork and beef meat
163
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products (ham, bacon, salami, pastrami, corned beef, frankfurters, and the
like) represent about a third of the total meat produced in the United
States^ . Cured fish products (chub, sable, and salmon) represent less
[26]
than 2 percent of the dollar value of all processed fish products
The maximum levels of these compounds permitted in the finished product
are:
Cured Cured
meat fish
ppm
NaN03 1,700 500
NaN02 200 200
Cases of methemoglobinemia have been reported in children and in adults as
the result of an accidental use of excessive nitrate/nitrite in meatL ' .
[43]
and fish products . There have been no case repprts involving usage at
permitted levels.
Water. The most common cause of methemoglobinemia is the consumption
of water containing high levels of nitrates. This has accounted for many
more cases than all other causes combined (nearly 2,000 reported in the
U.S. and Europe). Methemoglobinemia of such etiology has been reported
only in infants. There is one report in the literature of methemoglobi-
nemia resulting from the use of nitrate-contaminated well water for peri-
[31
toneal dialysis in an adult with kidney disease .
In addition to the factors outlined previously that make infants more
susceptible than adults to nitrate-induced methemoglobinemia, an infant's
total fluid intake per unit of body weight is much greater than an
adult's. Thus, an infant consumes proportionately more nitrate than an
adult. Moreover, boiling water for 10 to 15 minutes, which may occur dur-
ing preparation of infant formula, tends to concentrate any nitrate present
in the water.
164
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The critical association between high concentrations of nitrates in the
water used to prepare formula and methemoglobinemia in infants receiving for-
F41
mula was first made in 1945 . Since that time, approximated 2,000 such
cases have been reported for North America and Europe. In the United States,
F521
only one case has been associated with water from a public water supply ;
all the rest (about 300) have been due to well water.
Standards for nitrates in drinking water were set by the U.S. Public Health
Service in 1962 , limiting nitrate to 10 ppm expressed as nitrate/nitrogen
(45 ppm expressed as nitrate). The 10 ppm nitrate/nitrogen level was set be-
cause there had been no reports in this country of infantile methemoglobinem-
ia associated with the ingestion of water containing nitrate at levels below
10 ppm, and because it was a standard that could be met easily by most munici-
pal water supplies.
After the publication of these standards, however, several reviews of the
literature reported from other countries revealed that a small percentage of
cases had occurred where the water nitrate/nitrogen content had been below 10
ppm ' . It is important to note, however, that all these studies were
retrospective—the water was sampled sometime after the infant became ill.
Therefore, there is no certainty about the exact nitrate/nitrogen concen-
tration in the water at the time of illness.
The adequacy of the 1962 standard is now being evaluated in several pros-
pective studies designed to determine more specifically the nitrate levels
in water required to cause elevated levels of methemoglobin and clinical evi-
f53 14 39 541
dence of methemoglobinemia in infants ' ' ' The preliminary results
of these studies indicate that the 1962 standards provide adequate protection
against clinical methemoglobinemia. However, subclinical elevations of
methemoglobin have been found in infants with diarrhea or respiratory dis-
ease, consuming water with a nitrate content below this
[39]
standard
In addition to retrospective and prospective studies, hypothetical calcula-
tions have been made in order to predict potentially toxic levels of
165
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F541
nitrate . Such calculations are based on so many assumptions that they
are of little value. The molar ratio of the nitrate-hemoglobin reaction, the
efficiency of bacterial reduction of nitrate to nitrite and the rate of
reduction of methemoglobin once it is formed are all unknowns that must be
estimated in these hypothetical calculations.
NITROSAMINES
Nitrosamines are formed by the reaction between nitrites and organic com-
pounds containing two, three, or four atoms of nitrogen (the so-called "sec-
ondary," "tertiary," and "quartenary" amines) . Nitrites and/or precursor
nitrates are present in foods, water, drugs and human saliva . Amines
are found in foods, tobacco smoke, beer, tea, wine, toothpaste, and hundreds
[211
of drugs . Certain nitrosamines have been found to be carcinogenic in
animals. Some of these carcinogenic nitrosamines have been detected in food
and tobacco. Concerns about potential hazards for human health arise from
the possibility for (a) contact with preformed carcinogenic nitrosamines and
(b) the formation of carcinogenic nitrosamines within the human body after
exposure to precursor nitrites and amines.
TOXICITY
Nitrosamines have potent biological effects, including acute cellular
injury (primarily involving the liver), carcinogenesis, mutagenesis, and ter-
atogenesis. Approximately a hundred nitrosamines have been tested so far in
animals. The vast majority are carcinogenic. Many species of animals and
many different organs (the liver, esophagus, and kidneys) are susceptible to
F23 291
the cancer-producing effects of these compounds ' . These effects can be
elicited experimentally by various routes of nitrosamine administration
(oral, intravenous, inhalation) by extremely low doses (ppm) of nitrosamines
F221
and, in some instances, after only one exposure .
Studies showing certain nitrosamines to be potent carcinogens in a wide
range of animal species, including the monkey, suggest that the same
166
-------
compounds would also be carcinogenic for man. However, at present, there are
no definitive data confirming this hypothesis.
Two epidemiological studies in Africa have attempted to link a geographic-
ally high incidence of cancer of the esophagus in humans With the ingestion
r 01
of the juice of fruit from a solanaceous bush and alcoholic spirits
[271
derived from fermented maize husks —both purported to contain dimethyl-
nitrosamine, a known carcinogen in animals. However, significant changes in
laboratory methodology for confirming the presence of dimethyInitrosamine
have occurred since these reports were published. Thus, the data are 'open to
some question.
SOURCES OF NITROSAMINES
Food, Two nitrosamines, both known carcinogens in animals, have been
detected in minute (ppb) quantities in some foods: dimethylnitrosamine in
raw fish, smoked fish, nitrate/nitrite-treated smoked fish, cheese, and some
nitrate/nitrite-treated meat products; and nitrosopyrrolidine in cooked
bacon ' . Except for cooked bacon, where nitrosopyrrolidine has been con-
sistently found, nitrosamines are not always present in any given food prod-
uct. Although nitrosamines are more likely to occur in nitrate/nitrite-
treated food products, they may also occur in foods to which no nitrate/
nitrite has been added.
Tobacco smoke. Several carcinogenic nitrosamines, including dimethylni-
trosamine and nitrosopyrrolidine, have been identified in tobacco
smoke * . There are some data to suggest that smoke from tobacco grown
in soil treated with high levels of nitrogen is mote likely to contain
nitrosamines and to contain them in higher concentrations than smoke from
[50]
tobacco grown in fields with a low nitrogen content
Industrial exposure. Nitrosamines are formed in certain industrial pro-
cesses. Important among these is the rocket-propellant industry, in which
dimethylnitrosamine is an intermediate compound in the formation of dimethyl-
[24]
hydrazine • Acute human toxicity to dimethylnitrosamine through its use
167
-------
as a solvent has been reported . Human exposure to mutagenic, teratogen-
ic, and/or carcinogenic nitrosamines occurs in the manufacture of these com-
pounds for research purposes, as well as in their subsequent use by research
workers.
POTENTIAL FOR FORMATION FROM PRECURSORS
Of critical concern is the possible formation of carcinogenic nitrosamines
in the human gut through the combination of ingested nitrites and amines.
[9]
Such reactions have been demonstrated to occur both in vitro and in vivo
F371
(in animals) . Studies in humans fed nitrate and a noncarcinogenic ni-
trosamine precursor amine (diphenylamine) have shown that diphenylnitrosamine
r oc 1
can be formed in the human stomach . Nitrosamine determinations in these
studies were made by thin-layer chromotography, a method now known to give
false positive results. Unfortunately, there has been no confirmation of
these data using the newer techniques of gas-liquid chromatography and mass
spectrophotometry. However, this study raises the possibility that such pre-
cursor reactions may occur in man, leading to the formation of carcinogenic
nitrosamines.
REDUCING HUMAN EXPOSURE TO NITROSAMINES AND TO NITROSAMINE PRECURSORS
As indicated in the part of this report dealing with nitrites and nitrates,
one rationale for the use of these compounds in cured meat products is to
prevent the growth of Clostridiwn botulimm organisms, thus protecting the
consumer against botulism.
A joint research effort by the USDA, the FDA, and the American Meat Insti-
tute Foundation is in progress to determine the minimum levels of nitrate/
nitrite necessary to be added to cured meat products in order to protect
against botulism. If the quantities of nitrates and/or nitrites added to
such good products could be significantly reduced, this might reduce the
chances of nitrosamine formation.
168
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Preliminary data from these studies indicate that, in the case of two cured
meat products (canned ham and bacon), added nitrite, at levels only slightly
below the 200 ppra currently permitted, is absolutely essential in preventing
the formation of botulinus toxin. Nitrate, on the other hand, appears to
have no effect in preventing such toxin formation .
SUGGESTIONS
1. Further prospective studies with infants are needed in order to determine
more precisely the relationship between total daily nitrate/nitrite
intake and levels of methemoglobinemia.
2. Long-term studies are needed to measure the effects, if any, of subclini-
cal methemoglobinemia in humans.
3. The 1962 drinking water standards limiting nitrate to 45 ppm (10 mg/1 of
nitrate nitrogen) should not be relaxed.
4. The use of nitrate and nitrite in cured meat and fish products should be :
limited to those uses that are essential in inhibiting the growth of
Clostridium "botulinim and in obtaining the essential characteristics of
cured meats. The Food and Drug Administration has proposed the banning
of nitrate from most smoked, cured fish products. The U.S. Department of
Agriculture is considering a lowering of the maximum level of nitrate
permitted in cured meat products to 500 ppm and eliminating its use in
those products where it is not essential.
5. Distilled or bottled water with a low nitrate content should be used for
infant feeding in areas where the nitrate content in water is high.
6. The use of fresh vegetables with a potentially high nitrate content
(especially spinach and carrots) should be avoided as much as possi-
ble in infant feeding—particularly when the vegetables have been stored .
prior to feeding or when the infants are less than six months of'age or
have diarrhea.
169
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7. The nitrate content of water used for peritoneal dialysis in patients
with kidney disease should not exceed 45 ppm (10 mg/1 nitrate nitrogen)-
8. The use of nitrate- and/or nitrite-containing drugs known to cause
methemoglobinemia should be avoided where possible.
9. Further studies of the nitrosamine content of foods, beverages, and tobac-
co smoke should be undertaken.
10. Nitrate and nitrite in cured meat and fish products should be limited to
only those uses and those quantities that are essential in inhibiting the
growth of Clostridium botulinum.
REFERENCES
1. American M.eat Institute Foundation/USDA/FDA communication. 1972. Wash-
ington, D.C.
2. Bakshi, S.P. et al. 1967. Sausage cyanosis—acquired methemoglobinemic
nitrite poisoning. NEJM, 277:1,072.
3. Carlson, D.J. et al. 1970. Methemoglobinemia from well water nitrates:
A complication of home dialysis. Ann. Int. Med., 73:75.
4. Comly, H.H. 1945. Cyanosis in infants caused by nitrates in well
water. JAMA, 129:112.
5. Cornblath, M. et al. 1948. Methemoglobinemia in young infants. J.
Pediat., 33:421.
6. Crosby, N.T. et al. 1972. Estimation of steam-volatile N-nitrosamines
in foods at the 1 meg/kg level. Nature, 238:343.
7. DeGraff, H. 1972. Personal communication. American Meat Institute,
Washington, D.C.
8. DuPlessis, L.S. et al. 1969. Carcinogen in a Transkeian Bantu food
additive. Nature, 222:1198.
9. Ender, F. et al. 1971. Conditions and chemical reaction mechanisms by
which nitrosamines may be formed in biological products with reference to
their possible occurrence in food products. Ze-it. Lebsmittel-UnteT.
Forsoh. 133.
170
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10. Fiddler, W. et a . 1972. Formation of N-nitrosodimethylamine from
naturally occurring quaternary ammonium compounds and tertiary amines.
Nature, 236:307.
11. Finch, C.A. 1948. Methemoglobinemia and sulfhemoglobinemia. NEJM,
239:470.
12. Goodman, L.S. and Oilman, A.Z. 1965. The pharmacological basis of
therapeutics, 4th ed. Macmillan Co. New York City.
13. Greenberg, M. et al. 1945. Outbreak of sodium nitrite poisoning. Am.
J. Pub. Health, 35:1217.
14. Gunderson, D.H., et al. 1971. Preliminary Report, Washington County
Nitrate Study—The effect of high dose nitrate on young children. EPA
Office of Water Programs, Cincinnati, Ohio.
15. Holscher, P.M. et al. 1969. Methamoglobinamie bei jungen Sauglingen
durch nitrithaltigen spinat. Dtsch. Med. Wschr., 89:1,751.
16. Hunter, D. The diseases of occupation. Little Brown and Co. Boston,
Mass., p. 593.
17. Jaffe, E.R. et al. 1964. Methemoglobinemia in man. In: Moore, C.V.
and Grown, E.B. (ed.). Progress in Hematology, Vol. 4. Gruen and
Stratton, New York City, p. 48-71.
18. Keating, J. 1972. Personal communication. St. Louis Children's Hos-
pital, St. Louis, Mo.
19. Lee, D.K. 1970. Nitrates, nitrites, and methemoglobinemia. Environ.
Res. 3:48.
20. L'Hirondel, J. et al. 1971. Une cause nouvelle de methemoglobinemia du.
nourrison: La soupe de carottes. Ann. pediatr. (Paris). 18:625.
21. Lijinski, W. 1971. Testimony before hearings, "Regulation of food
additives and mecicated animal feeds," of the Subcommittee of Committee
on Government Operations, House of Representatives. U.S. Govt. Printing
Office, Wash., D.C.
22. Magee, P.N. et al. 1962. J. Path. Bact., 84:19.
23. Magee, P.N. et al. 1967. Adv. Cancer Res., 10:163.
24. Magee, P.N. 1972. Communication to an interdepartmental group on
nitrates, nitrites, and nitrosamines.
25. Marcus, H. et al. 1949. Nitrate methemoglobinemia. NEJM, 240:599.
171
-------
26. Martin, R. 1972. Personal communication. National Fisheries Institute,
Washington, D.C.
27. McGlashan, M.D. et at. 1968. Nitrosamines in African alcoholic spirits
and Oesophageal cancer. Lancet, 2:1,017.
28. National Academy of Sciences. 1972. Accumulation of nitrate, NAS-NRC,
National Academy of Sciences, Washington, D.C., 106 p.
29. Nitrosamines: A jig-saw puzzle 'with missing pieces. 1968. Food Cosmet.
Toxia., 6:647.
30. Orgeron, J.D. et al. 1957. Methemoglobinemia from eating meat with
high nitrite content. Public Health Reports, 72:189.
31. Paneque, A. et al. 1965. Flavin nucleotide nitrate reductase from
spinach. Biochim. Biophys. Acta. 109:79.
32. Petukhov, N.I. et al. 1970. Investigation of certain psychophysiologi-
cal reactions in children suffering from methemoglobinemia due to
nitrates in water. Byg. Sanit., 35:29.
33. Phillips, W.E.J. 1968. Changes in the nitrate and nitrite contents of
fresh and processed spinach during storage. J. Agr. Food Chem. 16:88.
34. Phillips, W.E.J. 1971. Naturally occurring nitrate and nitrite in
foods in relation to infant methaemoglobinaemia. Fd. Cosmet. Toxiool.
9:219.
35. Rhoades, J.W. et al. 1972. N-dimethylnitrosamine in tobacco smoke con-
densate. Nature 236:307.
36. Sander, J. et al. 1969. Bacterial reduction of nitrate in the human
stomach as a cause of nitrosamine formation. Arzheimittelforsahung, 19:
1,031.
37. Sander, J. 1971. Studies on formation of cancerogenic nitroso com-
pounds in the stomach of experimental animals and their significance
for man. Arsheimittelforschung, 21:1,572.
38. Sattelmacher, P.G. 1962. Methamoglobinamie durch nitrate in trinkwas-
ser. Schriftenreiche des Vereins fur Wasser Bodenund Lufthygiene, No.
21.
39. Shearer, L.A. et al. 1972. Methemoglobin levels in infants in an area
with high nitrate water supply. Calif. State Dept. of Public Health
(preprint).
40. Shuval, H.I. et al. 1972. Epidemiological and toxicological aspects of
nitrates and nitrites in the environment. Am. J. Pub. Health* 62:1,045-
1,072.
172
-------
41. Simon, C. et at. 1964. Uber vorkotnmen, pathogenese und moglichkeiten
zur prophylaxe der durch nitrit verusachten methamoglobinamie.
Zeitsahrift fur Kinderheilkundet 91:124.
42. Simon, C. 1966. L'intoxication par les nitrites apres ingestion
d'epinards. Arch. Franaaises de pediatrie 23:231.
43. Singley, T.L. 1962. Secondary methemoglobinemia due to the adultera-
tion of fish with sodium nitrite. Annals of Int. Med., 57:800.
44. Sinios, V.A. et at. 1965. Die spinatvergiftung des sauglings. Dtsah.
Med. tfsehr. 90:1,856.
45. Stewart, R.A. 1972. Personal communication. Gerber Products Co., Fre-
mont, Michigan.
46. Strauch* B. et al. 1969. Successful treatment of methemoglobinemia
secondary to silver nitrate therapy. NEJM, 281:257.
47. Tannenbaum, S.R. 1972. Massachusetts Institute of Technology. Commun-
ication to interdepartment group on nitrates, nitrites, and nitrosamines.
48. Ternberg, J,L. et al. 1968. Methemoglobinemia: A complication of sil-
ver nitrate treatment of burns. Ped. Surgery, 63:328.
49. USDA/FDA. 1972. Communication to an interdepartmental group on
nitrates, nitrites, and nitrosamines.
SO. tiSDA/HEW/British American Tobacco Laboratory, collaborative research.
1972* Personal communication.
51. tf.S. Public Health Service. 1962. Drinking water standards. Public
Service Pub. 956.
52. Vigil, J. et al. 1965. Nitrates in municipal water supplies cause
methemoglobinemia in infants. Public Health Reports, 80:1,119.
53. Winton, E.F. et al. 1969. Preliminary report: Field study on nitrate
in drinking water and infantile methemoglobinemia. U.S. Public Health
Service, Cincinnati.
54. Winton, E*F. et al. 1971. Nitrate in drinking water. J, Amev. Water
Works Assn. 63:95.
173
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Analytical Procedures
MARY K. ELLIS
THE NITROGENOUS COMPOUNDS present in the environment and used as pollutant
indicators are ammonia, nitrate, nitrite, nitrosamines, and other organic com-
pounds (amino acids, polypeptides, and proteins). There are no universal
standard methods for the determination of these compounds. The methods gener-
ally used for water and food are those given in Table 1. For air and soils,
water extracts, except for ammonia in soils, are made from the sample and a
selective method of water analysis is used.
The analysis of nitrogenous compounds, with exception of nitrosamines,
depends on:
1. A color resulting from its reaction with another compound to form a color
complex, or
2. Direct titration of the nitrogen compound employing the use of a color
indicator for an acid-base, end-point reaction.
To identify trace amounts of nitrosamines requires sophisticated and very
expensive instrumentation. The mass spectrometer is, at present, the ultimate
tool in the identification of N-nitroso compounds . The Food and Drug Admin-
istration, the Department of Agriculture, and the Department of the Interior
have this capability but have limited their analyses to fish and meat products,
Of the three methods being used for the detection of ammonia, the Nessler
reagent is the conventional one for low levels in the range of 0.05-2 mg
N'-NH,/!. This depends on the formation of a complex of mercuric ammono-basic
iodide, which is red-brown in color. The intensity of the color caused by
ammonia varies from yellow to brown.
HgI2 + NH3 -^ Hg(NH2)I + 2KI + HI
175
-------
A more recent method involves the development of an Intensely blue compound,
indophenol. Referred to as the phenate or phenolate method, the procedure has
been automated , and requires only two minutes per sample analysis. In this
method, ammonia reacts with hypochlorite and phenol in the presence of a man-
ganous salt catalyst. The sensitivity of this method is in the range of 0.01-
20.0 mg N-NH3 per liter.
The titration method is the choice for samples containing more than 1.0 mg
N-NH,/1 and can be used on samples containing less. The principle is the ti-
tration of the ammonia—collected in a boric-acid solution, with sulfuric acid,
using a color indicator for determining the end-point.
The Nessler method may be performed without prior distillation if the sample
is free of interferences. Ca, Mg, Fe, certain organic compounds, sulfide,
excess alkalinity, excess acidity, color, and turbidity are among the most com-
mon interferences for the detection of ammonia. Distillation will remove most
of the interferences except sulfide, which must be precipitated prior to dis-
tillation. The distillate is collected in boric acid for the Nessler and ti-
trimetric methods, and in sulfuric acid for the phenate method.
The two colorimetric methods require the use of a colorimeter to read the
color intensities, and preparation of standards in the detectable, range is
necessary. In the automated phenolate procedure, a Technicon-autoanalyzer or
its equivalent is also required.
As in the choice of methods for ammonia, the methods for nitrate determina-
tions depend on the concentration of the nitrate in the sample and its matrix.
Samples containing 5 mg of N0~ or less may be tested by direct nitration of
brucine, phenoldisulfonic acid, or chromotropic acid. The choice of method for
waste and saline waters is the alkaloid, brucine. This method is critically
dependent on heat control at 100° ^ ^ for the development of the resulting com-
plex. The interferences that can be eliminated include the color of the sam-
ples due to the high acidity of the reaction, salinity, oxidizing or reducing.
agents, residual chlorine, iron, and manganese. The phenoldisulfonic acid and
chromotropic acid methods are grossly affected by turbidity, and are subject to
176
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Table 1. GENERAL METHODS OF ANALYSIS FOR NITROGENOUS COMPOUNDS
Nitrate-Ammonia (NH,, NH,)
[12 3 41
M^ne.i ^v-j ~0i--s,-mL-1->'Li>-'»^J
Nesslerization
fl 41
Phenolate1 ' J
Titration11'2'3'4!
Nitrogen-Nitrate (N0~)
a. Direct nitration
Brucine[1'3>4l
Phenoldisulfonic acid''1'2'4-'
Chromotropic acid
b. Nitrate reduction
Cd-reductiont:L'2'4]
Hydrazine[4]
[31
Devarda's alloy
[21
Xylenol-reduction
Zn-reduction
c. Direct method
Ultraviolet spectrophotometric
Nitrogen-Nitrite (N0~)
[1234]
Diazotization-coupling (Greiss reaction) ' ' '
[21
KI reduction /
/ N - CH - C
Nitrogen-organic I
\ H R 0
Kjeldahl[1'2>3'4]
[91
Nitrosamines-volatile (R2~N-N02)
177
-------
Table 2. SUMMARY OF METHODS OF ANALYSIS USED
BY ENVIRONMENTAL PROTECTION AGENCY
oo
Nitrogen
form
Ammonia
Organic
total
Method
Distillation
Nesslerization
Titration (H2SO.)
Automated
phenolate
Kjeldahl
Nesslerization
Titration
Semiautomated
(phenolate)
Automated
(phenolate)
Appli- Interferences
cation (c)
A,B,C Ketones,
Aldehydes
Alcohols
Hydrazine
Chloride ion
Mercury,
cyanide
A,C Mercury
Copper
Magnesium
PH
A,B,C None
A,C None
A,B,C Iron, chromium
Copper ions
Sample
size
500 ml
2.90 ml/min
500 ml
2.90 ml/min
For A =
2.50 ml/min
For C =
1.60 ml/min
Sensitivity
(N/l)
.05 to 1 mg
1.0 to 24 mg
.01 to 20 mg
11 mg
1 mg
1 to 10 mg
.05 to 2 mg
Precision
accuracy*
p. 140
p. 145
p. 155
to 156
NA
p. 162
(cont l
-------
Table 2 (cont'd)
Nitrogen^
form
Nitrate
Nitrate -
nitrite
Nitrite
Appli-
Method cation
Brucine A,B,C
Automated A,C
(a) Cd-reduction
(b) Sulfanilamide
reagent
(diazotization-
coupling)
Automated A,B
(a) Hydrazine
reduction
(b) Diazotization
coupling
Diazotization- A,B,C
coupling
Interferences
(c)
Temperature
Dissolved
organics
Salt
Oxidation-
reduction
agents
Chloride ion
Iron
Manganese
NH« , primary
amines
Metal ions
(hg, Cu)
Tolerates high
concentra-
tions of in-
terfering ions
Concentration
l,OOOxN02
PH
Sample Sensitivity Precision
size (N/l) accuracy*
10 ml 0.1 to 2 mg p. 174
1.60 ml/min 0.5 to 10 mg p. 181
to 182
2.90 ml/min 0.5 to 1 mg p. 189
to 190
50 ml 0.5 to 1 mg NA
-------
A—Surface water.
B—Domestic and industrial waste.
C—Saline waters.
(a) N02 + N03 a-b=N03
(b) N02
(c) Most of the interferences are eliminated.
* Reference to pages of the Manual.
NA Not available.
Reference: Methods for Chemical Analysis of Water and Wastes, 1971,
Water Quality Control Laboratory, Water Quality Office,
Environmental Protection Agency, Cincinnati, Ohio, p. 134-
203.
180
-------
Table 3. SUMMARY OF METHODS OF ANALYSIS USED
BY THE DEPARTMENT OF INTERIOR
Nitrogen
form
Method
Appli- Interferences
cation (c)
Sample Sensitivity Precision
size (N/l) accuracy*
Ammonia
Distillation
Natu- Ca, Mg, Fe (a)
ral Sulfide (c)
waters Distilled or-
ganic com-
pounds (e)
500 ml
<2 mg NH3, NA (i)
NH4+/L
Titration Natu- Ca, Mg, Fe (a)
ral Sulfide (c)
waters Distilled or-
ganic com-
pounds (e)
Nitrate Brucine Color- Organic color
le*S NO ~ (b)
waters 2
500 ml >2 mg NH_,
NH4+/L
10 ml <5 mg NO ~/L
NA (i)
.09-. 11
mg/1 (g)
Oxidizing and
reducing
agents
Cl" (f)
Reduction
(Devarda's alloy)
Color- Organic color
less N0~ (b)
waters Oxidizing and
reducing
agents
Cl" (f)
10 ml >30 mg NO /L .09-. 11
mg/1 (g)
(cant 'd)
-------
Table 3 (cont'd)
Nitrogen
form Method
Appli- Interferences
cation (c)
Sample
size
Sensitivity Precision
(N/l)
accuracy*
Nitrite
Diazotiazation
Natu- None
ral
waters
50 ml <4 mg NO, /L
(d) *
CO
Organic Kj eldahl
nitrogen
Natu- Ca, Mg, Fe (a)
ral
waters
500 ml
<2 mg N/L (d)
NA
(a)
(b)
(c)
(d)
Eliminated by distillation.
Eliminated by sulfanilic acid.
Precipitated by lead carbonate.
Higher cmc can be diluted.
(f)
(g)
(h)
(i)
Eliminated by sodium arsenate.
Standard deviation.
Use residue of NH_ nitrogen.
Not available.
(e) Distill sample into H BO- and titrate H2SO,.
Reference: "Methods for Collection and Analysis of Water Samples for Dissolved Minerals and
Gases," Techniques of Water-Resources Investigations of the United States Geolog-
ical Survey3 Book J, Chapter Al, 1970, p. 116-124.
-------
Table 4. SUMMARY OF METHODS OF ANALYSIS USED BY
THE FOOD AND DRUG ADMINISTRATION
oo
CO
Nitrogen
form
Nitrate
(a)
Nitrite
(a)
Nitrite
(b)
Nitrite
(c)
Nitrate
(d)
Nitrite
(e)
Sample
Method Application size Sensitivity Precision
(A) Cd reduction ->• Animal feeds 5 g 10-100 ppm nitrate NA
M>2 N
(B) Sulfanilamide
reagent
[A=N03+N02, B=N02,
A-B=N03]
Diazotization and Flours 2g 0.6 to 1.2 ppm NA
coupling nitrite N
(Sulfanilic acid and
Greiss reagent)
Reduction with KI and Dry curing mix or 50 g 1% NaNO NA
titration with sodi- curing pickle
urn thiosulfate
Nitration of xylenol Meat and meat 5 to 10 g 5 to 500 ppm + 50 ppm*
distillation and products
color development
Modified Greiss Cured meats 5 g NA NA
-------
*Provided by the staff of the USDA Meat and Poultry Laboratory.
NA, Not available.
(a) 7.033-7.039, JAOAC, Jtt, 763 (1968).
(b) 14.037-14.038, JAOC, 34, 273 (1951).
(c) 20.063-20.065, JAOAC, 47, 395 (1964).
(d) 24.011-24.013, JOAC, 18, 459 (1935); 22, 596 (1939).
(e) 24.014-24.015, JOAC, _8, 696 (1925); 315, 344 (1952).
Reference: These methods are contained in the Journal of AOAC, Vol. 48,
No. 5, 1965. The original date of publication is given to
emphasize that the analytical procedures ate not new.
184
-------
A summary of the methods of analysis used by the Environmental Protection
Agency, the Department of the Interior, and the Food and Drug Administration
for nitrogen analysis appears in Tables 2, 3, and 4, respectively, and includes
the sensitivities. The precision'and/or accuracy is either not available or has
been determined by using a limited number of analyses.
The present methods of analyzing nitrogen for the ammonia, nitrate, nitrite,
and organic nitrogen carry with them subjective error within every step of the
procedure. These errors are compounded by the matrix of the sample, the tem-
perature, and time, the preparation of standards, the purity of materials, a
dilution factor, the addition of reagents, recovery, and human error. In addi-
tion, the organic nitrogen method eliminates the detection of amines, hydra-
zones, oximes, carbazones, and other organic nitrogen compounds. One of these
groups, the amines, is a precursor to the formation of the nitrosamines.
The analysis for nitrosamines is restricted to those which are volatile.
But the method is both sensitive and specific.
In consideration of the limitations of present analytical methods, and the
paucity of basic data on the identity and concentration of organic nitrogen
compounds in the environment, the following research projects are suggested for
initiation or continuation:
1. Develop new methods of detection for nitrates and nitrites, and extend the
method development for N-nitrosamines. .These health hazards have now
reached unacceptable levels in one or more phases of our environment.
2. Identify the concentrations of all organic nitrogen compounds in our water
and in the atmosphere.
3. Establish the health hazards presented by the organic nitrogen compounds
found in the water and the atmosphere; also, subsequent method development,
for example, secondary amines as precursors of N-nitrosamines. (Considera-
tion should be given to the clarification of the misnomers "organic-
nitrogen" method and "total organic-nitrogen" method.)
4. Study nitrosamine formation in watersheds, particularly in areas near
slaughter houses and meat-processing plants.
185
-------
5. ri Study the basic amines present in foods, the amines that react with
nitrites to form carcinogenic N-nitrosamines.
REFERENCES
1. Standard Methods for Examination of Water and Waste Water, 13th ed. 1970.
American Public Health Assoc., American Water Works Assoc., Water Pollution
Control Federation.
2. Official Methods of Analysis, Assoc. of Official Analytical Chemists, llth
ed., 1970.
3. Methods of Collection and Analysis of Water Samples for Dissolved Minerals,
Gases, Techniques of Water Resources Investigations of U.S. Geological Sur-
vey, Book 5, Chap. A-l. 1970. p. 116-124.
4. Methods for Chemical Analysis of Water Wastes, 1971. Water Quality Control
Laboratory, Water Quality Office. EPA, Cincinnati, p. 134-203.
5. Report of Subcommittee on Analytical Methods for Nitrosamines. International
Agency for Research on Cancer.
6. Review on the Chemistry and Toxicology of Nitrites, Nitrates and Nitroso
Compounds (Nitrosamines). Aug. 28, 1970. FDA (internal document).
7. Scanlon, R.A. and Libbey, L.M. N-Nitrosamines Not Identified from Heat
Induced D-Glucose/L-Alanine Reactions. J. Agri. Food Chem., Vol. 19, No. 3,
1971, p. 570-571.
8. Fazio, Thomas; Damico, Joseph N.; Howard, John W.; White, Richard H.; and
Watts, James 0. Gas Chromatographic Determination and Mass Spectrometric
Confirmation of N-Nitrosodimethylamine in Smoke-Processed Marine Fish. J.
of Agri. Food Chemistry 19(3): 250-53, March-April 1971.
9. Fazio, Thomas; Howard, John W.; and White, Richard. Multideotion Method for
Analysis of Volatile N'-Nitrosamines in Foods. In Nitroso-compounds, Analy-
sis and Formation. Proceedings of a Conferency, World Health Organization,
International Agency for Research on Cancer, Heidelberg, Germany. Oct. 13-
15, 1971. p. 16-24.
10. Stanford, George, Agri. Res. Serv., Beltsville, Md. (private letter).
11. Kohl, Daniel H.; Shearer, Georgia; and Commoner, Barry. Contribution of
Fertilizer to Nitrogen to Nitrate in Surface Water in a Cornbelt Watershed.
Science 174, Dec. 1971.
12. Dzubay, Thomas. Div. of Chem. and Physics, Air Analytical Methods Branch,
EPA, North Carolina (private communication).
186
-------
13. Jaye, Dr. Frederic, Div..of Chem. and Physics, Source Emission Measurement
Branch, EPA, Research Triangle, N.C. (Private communication.)
14. Hollander, Jack, Lawrence-Berkeley Labs., Berkeley, Calif. (Private
communications).
187
-------
SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
3. Accession No.
4. Title
NITROGENOUS COMPOUNDS IN THE ENVIRONMENT
7. Author(s)
Ma frpr 4 a 1 fl AHv^
9. Organisation
Office of the Principal Science Adviser
Environmental Protection Agency
Sponsoring Organization
15. Supplementary Notes
Environmental Protection Agency Report
Number EPA-SAB-73-001 December 1973
is. Abstract This report is a series of papers on the sources and methods of control and
the environmental and health effects of nitrogenous compounds. Diverse aspects of
municipal and industrial sources are discussed--waterborne, atmospheric, agricultural,
and industrial processes generating nitrogenous compounds. Attention is given to
nitrogenous materials in waste and surface waters, efficiency of sewage treatment,
effectiveness of the conventional BOD test, and the contribution of urban runoff and
landfill leakage to the overall nitrogen load in the environment. Concentrations,
sources, sinks, the transformation of nitrogenous materials in the lower atmosphere,
control measures for stationary and mobile sources, retrofit systems for used cars,
and new engine systems are reviewed. Plant nutrients, including fertilizers, and animal
wastes are considered. The growing problems resulting from concentrated centralized
livestock feedlots and methods of control are pointed out. Nitrogen is discussed as a
nutrient essential to living organisms and as a toxicant within the aquatic environment
The carcinogenicity of nitrosamines and their precursors is described as a potential
danger to health. Individual nitrogenous compounds are appropriately identified
throughout the report. Analytical procedures for the identification and quantification
of nitrogenous compounds are reviewed. Presented are the major concerns regarding
nitrogenous compounds in the environment as these relate to the following Environmental
Protection Agency activities: research, monitoring, and regulation.
17a. Descriptors
Ecology, water pollution, water pollution effects, water pollution
control, groundwater, run-off, urban areas, sewage, industrial wastes, earthfill,
sanitary engineering, air pollution, atmosphere contamination control, amines (and),
nitro compounds, nitrites, methemoglobinemia, nitrogen organic compounds, nitrogen
inorganic compounds, fertilizers (and), wastes, food supply, agricultural wastes
17b. Identifiers
Feedlots, sanitary landfill leachate, nitrosamines
17c. COWRR Field & Group
18. Availability
Government Printing
Office - Unrestricted
•19. Security C 'ass.
(Keport)
20. Security Cltss.
(Page)
Send To:
WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON. O. C. 2O24O
Abstractor VHnfred F. Malone Ph.D.
Institution
Environmental Protection Aencv
188
* U. 8. GOVERNMENT PMNTDJO OFFICE : 1974 731-498/J80
-------
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
March 15, 1974
OFFICE OF
RESEARCH AND DEVELOPMENT
SUBJECT: Nitrogenous Compounds in the Environment
FROM : Acting Staff Director
Science Advisory Board
Attached is a copy of the Hazardous Materials Advisory Committee
report Nitrogenous Compounds in the Environment, December 1973
(EPA-SAB-73-001). We hope you will find it helpful.
Winfred F. Malone, Ph.D.
Attachment
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