NITROGEN

IN THE NATION’S RAIN

NATIONAL ATMOSPHERIC DEPOSITION PROGRAM
HOW TO OBTAIN NADP DATA

Data products are available from the National Atmospheric Deposition

Program (NADP) free of charge. The easiest way to obtain data is by

visiting our Internet site at http://nadp.sws.uiuc.edu

Our products include:

• Weekly and daily precipitation chemistry data

• Monthly, seasonal, and annual precipitation-weighted mean concentrations

• Annual and seasonal deposition totals

• Mercury deposition data

• Daily precipitation totals

• Color isopleth maps of precipitation concentrations and wet deposition

• Site photos and information

• Quality assurance data and other information

For further information, contact:

NADP Program Office

Illinois State Water Survey

2204 Griffith Drive

Champaign, Illinois 61820

E-mail: nadp@sws.uiuc.edu

CREDITS

Contributors: Ellen Porter, U.S. Fish & Wildlife Service; Kathy Tonnessen,

National Park Service; John Sherwell, Maryland Department of Natural

Resources; and Richard Grant, Department of Agronomy, Purdue University

Editors: Eva Kingston, Van Bowersox, and Gayle Zorrilla

Designer: Wheeler Arts

Photography: All uncredited photos are copyrighted by Nova Development

Corporation and its licensors.

Computer Support: Bob Larson and Linda Hascall

4M—2000—99-2975

NADP Brochure 2000-01c (revised) 2M—05-02—02-1802—ek
Nitrogen is essential for all living

things. Nearly 98% of the world’s nitrogen is found in the solid earth within the

chemical structure of rock, soil, and sediment. The remainder moves in a dynamic

cycle involving the atmosphere, oceans,

lakes, streams, plants, and animals. Small

amounts of the nitrogen in soil and sediment also enter this complex cycle. 

Molecular nitrogen (N2) is a colorless

odorless gas that comprises 78% of our

atmosphere. Nearly 8 metric tons of

nitrogen sit atop every square meter of

the earth’s surface. Molecular nitrogen

is stable and converting it to other

chemical compounds requires considerable energy. A lightning bolt provides

sufficient energy to do the job, causing

some nitrogen and oxygen in the air to

form nitrogen oxides. Photosynthetic

energy in plants and chemical energy in

soil microorganisms also can convert

nitrogen to other chemical forms. All of

these natural processes occur in the

cycling of nitrogen in our environment. 

In addition to molecular nitrogen,

trace amounts of nitrogen oxides, nitric

acid vapor, gaseous ammonia, particulate nitrate and ammonium compounds,

and organic nitrogen circulate through

the atmosphere. In the United States,

nitrogen contributions from human

activities rival or exceed contributions

from natural sources for many of these

trace compounds. 

Atmospheric nitrogen compounds

cycle to the land and water through

atmospheric deposition. Wet deposition,

predominantly rain and snow, carries

nitrate and ammonium. Dry deposition

involves complex interactions between

airborne nitrogen compounds and plant,

water, soil, rock, or building surfaces.

Key issues for scientists, policymakers, and the public are the extent to

which human activities are affecting the

form and amount of nitrogen in the air,

the deposition of nitrogen compounds

from the air, and nitrogen cycling in 

the environment.

Nitrogen in the Nation’s Rain 1

NITROGEN IN THE NATION’S RAIN
Atmospheric nitrogen pathways.

Source: Adapted from National Science and Technology Council Committee on Environment and

Natural Resources, Air Quality Research Subcommittee, 1999. 

Which Human Activities

Contribute Nitrogen? 

Combustion provides high temperatures in which nitrogen can be oxidized

to form nitrogen oxides. It’s not surprising, then, that emissions from motor

vehicles, electric utilities, and industrial

boilers are the largest sources of atmospheric nitrogen oxides in the United

States. Human activities now account

for more than 90% of U.S. nitrogen

oxide emissions. According to the U.S.

Environmental Protection Agency, nitrogen oxide emissions fluctuated between

20 and 23 million metric tons since

1972, which is double the 1950 value. 

Atmospheric chemical reactions that

occur when sunlight is present strongly

link nitrogen oxides and other trace

gases with formation of ozone. Depending on atmospheric conditions, these

reactions can occur within several hundred meters of the original nitrogen

oxide source or after the pollutants have

been carried several hundred kilometers

downwind — perhaps crossing state or

national borders. Ultimately, some nitrogen oxides are converted to nitric acid

vapor or particulate nitrates. Precipitation efficiently removes both pollutants

Nitrogen in the Nation’s Rain 2

Prevailing

Winds

Photochemistry

Cloud Processes

Chemical Transformations

Fire

Ground Water

Drinking Water

Aquatic

Ecosystem

Cultural

Resources

Human

Health

Agricultural

 Products

Soils

Visibility

Lightning

Agriculture Industry

Wet Deposition Dry Deposition

Vertical

Mixing

Sources Transport / Transformation Removal

Effects

Forest

 Productivity

Transportation

Estuaries

Runoff

Soils

Dispersion

Sewage

Plants

Nitrate

Samoa Hawaii Alaska Eastern U.S.

milligrams per liter

Nitrate content of precipitation 

in remote and highly populated locations

0

0.2

0.4

0.6

0.8

1.0

1.2

Source: National Atmospheric Deposition Program National Trends Network

(after J.N. Galloway, G.E. Likens, and M.E. Hawley, 1984. Science 226:829).
1998 wet deposition of nitrogen

from nitrate and

ammonium.

Source: National

Atmospheric Deposition Program National

Trends Network.

from the air. As a consequence, nitrates

in precipitation tend to be highest where

the air is most polluted with nitrogen

oxides. These areas are likely to have

high population densities, numerous

motor vehicles, and many power plants

or industrial boilers.

Ammonia and ammonium are other

forms in which nitrogen occurs. Ammonia is a gas that becomes ammonium

when dissolved in water or when present in soils or airborne particles. Unlike

nitrogen oxides that form during combustion, soil microorganisms naturally

form ammonia and ammonium, compounds of nitrogen and hydrogen. Other

processes also form these compounds. 

Today, farmers apply millions of tons

of nitrogen fertilizers to the soil. The

U.S. Environmental Protection Agency

estimates that half a million metric tons

of ammonia were emitted to the atmosphere from fertilizer applications alone

in 1997. More than three times as much

was emitted from livestock waste

(manure and urine). These two sources

account for almost 80% of ammonia

emissions in the United States.

Precipitation readily removes ammonia and ammonium from the air. Wet

deposition of these compounds and

nitrate could be viewed as another

source of fertilizer for agricultural crops

(see sidebar on agriculture). It can also

be an unwanted input of fertilizer to sensitive ecosystems.

The U.S. map below shows the total

inorganic nitrogen deposited in precipitation in 1998. Total inorganic nitrogen

includes the nitrogen from nitrate

ammonium. Wet inorganic nitrogen

deposition was highest in the intensely

cultivated upper Midwest. Parts of eight

states from eastern Nebraska to western

Ohio received 7 kilograms per hectare

(6.2 pounds per acre) or higher. Onehalf to three-quarters of the total inorganic nitrogen deposited in this area is

from ammonium deposition, which

peaks in this same area.

A U.S. Environmental Protection

Agency map shows that atmospheric

ammonia emissions also peak there.

Ammonium-nitrogen dominates the

total inorganic nitrogen deposition in the

upper Midwest, while nitrate-nitrogen

generally dominates in the Northeast.

Areas with the highest nitrogen emissions do not necessarily experience the

greatest deposition effects, which can

occur far from the original nitrogen

source. Scientists have found that some

Nitrogen in the Nation’s Rain 3

Alaska

Puerto Rico

Virgin Islands

N

(kg/ha)

7.0

6.0 - 7.0

5.0 - 6.0

4.0 - 5.0

3.0 - 4.0

2.0 - 3.0

1.0 - 2.0

<– 1.0

>
GRAPHIC COURTESY OF With advances in JOHN DEERE - NAAMC.

satellite, computer,

and electronics,

crop production is

moving into a 

new age.

Nitrogen in the Nation’s Rain 4

The Role of Agriculture 

Persons engaged in the business of agriculture have a multifaceted interest in

nitrogen deposition. Applying nitrogen-based fertilizers has proven very effective in increasing crop yields, but these same fertilizers may be detrimental to the

goal of sustainable agriculture and may raise the amount of nitrogen in ground

water and surface water downstream of the farmland, contributing to the degradation of aquatic ecosystems. Therefore, one of the major challenges facing

environmentally conscious crop producers today is the fertilizer application rates

that will optimize crop yield and profit and minimize potential environmental

damage. Availability of nitrogen for plant growth and crop yield depends on

numerous factors: historical land use, crop type, residual nitrogen from legumes

such as soybeans, soil type and condition, amount of nitrogen released by soil

organic matter, and amount of nitrogen deposited by atmospheric deposition.

Precision farming addresses this complex problem by providing real-time

variable-rate fertilizer application that takes into consideration the crop, soil

type, soil fertility, and other factors within an individual field. This maximizes

the efficiency of fertilizer application, minimizes waste, and reduces surface

water contamination. On a larger scale, the management guidelines of statewide

fertilizer use for a given crop can be adjusted for the spatial variation of plantavailable atmospheric nitrogen deposition. For instance, precipitation over the

Midwest annually contributes 3 to 7 kilograms per hectare of inorganic nitrogen

to the soil, representing less than 5% of the inorganic nitrogen needs of corn and

up to 15% of the nitrogen needs of wheat, depending on the target yield of the

crop and on soil quality. Estimated atmospheric nitrogen deposition for the eastern United States could account for at least 10% of the nitrogen needs of major,

nonnitrogen-fixing crops.

All of us benefit as science and technology continue to work together to optimize farmland crop production and safeguard the water supply and terrestrial

and aquatic ecosystems.
Nitrogen in the Nation’s Rain 5

Bristlecone pines

are among the

oldest living organisms. Increases

in the amount of

nitrogen that

reaches this tree

may reduce its

chances of survival in such a harsh

environment.

PHOTO BY GARY LEAR

ecosystems are more sensitive to added

nitrogen than others: certain high-elevation eastern forests and streams, East

and Gulf Coast estuaries, and western

alpine areas and high-elevation forests.

What Effects 

Are Associated 

with Nitrogen Deposition? 

Depending on the chemical form and

amount in the environment, nitrogen can

serve as a nutrient, enhancing growth

and productivity, or as a toxin, causing

ecological damage or harming human

health. Scientists often refer to nitrogen

as a macronutrient because plants and

animals require it in relatively large proportions compared to other essential

nutrients such as iron or copper. 

Nitrogen needs vary, depending on

the ecosystem and on the plant or animal species. Different life forms within

the same ecosystem do not have the

same nitrogen requirements.

Many ecosystems and crops are limited by the availability of nitrogen.

That’s why the advent of synthetic fertilizers earlier in the 20th century has been

such a boon to agricultural productivity.

That’s also why atmospheric deposition

of nitrogen in some ecosystems may

stimulate unhealthy growth or cause

growth of some plants at the expense 

of others.

Air quality and atmospheric deposition are closely linked. Nitrogen oxides

contribute to the formation of ozone, a

lung irritant. Many studies have shown

that elevated ozone levels also damage

plant leaves and reduce crop yields.

Near urban or industrial air pollution

sources, high nitrogen dioxide concentrations can irritate human lung tissues

and lower resistance to influenza or

other respiratory infections.

Visibility degradation and acidic

deposition are also linked. Too many

fine particles in the air create the

unsightly haze that reduces visibility in

many U.S. cities and even occasionally

shrouds the beautiful vistas in national

park and wilderness areas. These fine

particles contain nitrogen compounds

(nitrate, ammonium, or both) and other

pollutants (sulfate and carbon compounds). Sulfate is often more important

than nitrogen in degrading visibility,

especially in the eastern United States.

When sunlight is present, nitrogen dioxide gas may also contribute to degradation of visibility .

While precipitation cleans the air,

rain and snow contain nitrates and sulfates, making them more acidic. Statues,

monuments, and the exteriors of buildings are all subject to acid rain damage.

Acidic precipitation also affects sensitive streams, lakes, and soils, which are

easily altered by chemical inputs. Acidic

precipitation can disturb the delicate balance in these sensitive ecosystems.
Stream acidification in Shenandoah National

Park has had

effects on some

native species,

such as this

brook trout.

Stream-water

nitrogen often

reaches a peak

during the spring

when snowmelt or

rainstorms can

flush nitrate from

the soils.

Nitrogen deposition also may have a

fertilizer effect. In estuaries and coastal

ecosystems, this can lead to eutrophication, a condition characterized by algae

blooms, low dissolved oxygen, and loss

of invertebrates, fish, and other wildlife.

Effects on Freshwater 

and Terrestrial Systems

Freshwater streams, ponds, and lakes

respond to the water and chemical

inputs from rainstorms and snowmelt.

On rare occasions when the ground is

frozen, some headwater streams carry a

surge of nitrate, sulfate, and acidity provided directly by rain or melting snow.

More typically, precipitation soaks

into the ground adding nitrate and ammonium to the nitrogen cycle, which

also involves soils, decaying plant and

animal matter, microbes, and living

plant roots. Many factors control the

rate at which nitrogen enters and leaves

this complex cycle, including soil type,

temperature, microbial activity, and

plant needs. Precipitation is just one

source of the nitrogen in soils.

Scientists have found that the cumulative effect of years of nitrogen

deposition does increase the amount of

nitrogen carried by streamflow from

some watersheds. Rainstorms and snowmelt can flush accumulated nitrate from

soils into these streams.

Nitrogen deposition, especially in

combination with sulfate, can contribute

to episodic acidification of streams. Not

all aquatic organisms have the same tolerance for these episodes, which can

cause a decline in acid-sensitive fish,

amphibian, and invertebrate populations.

Nitrogen deposition to forest and

alpine soils can affect plant populations

and overall forest health. Decades of

acidic nitrate and sulfate deposition has

depleted the supply of calcium and

mobilized aluminum in some forest

soils. Calcium is essential for tree

growth, but aluminum interferes with

the uptake of this nutrient by tree roots.

Low soil calcium has been linked to

the dieback of sugar maples in some

northeastern forests. Researchers are

studying nitrogen-saturated, high-elevation spruce/fir forests in the Great Smoky Mountains National Park. They find

that as aluminum in soil water increases,

the calcium in spruce trees decreases,

Nitrogen in the Nation’s Rain 6

PHOTO BY KATHY TONNESSEN
possibly making trees more vulnerable

to drought and insect infestations.

Experiments have shown that adding

nitrogen to alpine forest and grass communities alters the species mix. Those

plants that can store and use the added

nitrogen become predominant.

Effects on Estuarine Systems

The numerous estuaries along the

U.S. coastline have great economic, aesthetic, and ecological value. Watersheds

collect water and direct its flow into

estuaries and other water bodies. Atmospheric deposition delivers nitrogen to

estuaries and their watersheds. Nitrogen

from many sources enters an estuary;

only a portion is from atmospheric

deposition (see sidebar on Chesapeake

Bay). Estuary and watershed size are

important in evaluating the atmospheric

contribution to the total nitrogen entering an estuary.

Soils, plants, and animals retain

much of the nitrogen deposited in estuarine watersheds. Much of the remainder leaves these watersheds in runoff to

streams and rivers. Subsurface water

carrying nitrogen can also enter these

waterways, which feed into estuaries.

Nitrogen has unique effects on individual estuaries. Along the East and

Gulf Coasts, nitrogen promotes growth

of algae. These microscopic waterborne

plants cloud water and block sunlight,

which can interfere with aquatic plant

and animal productivity and affect water

temperature and currents. For example,

algae can inhibit growth of sea grasses

that offer habitat for fish and shellfish.

While living algae can degrade habitat, decaying algae also can have effects

as they complete their life cycle, sink to

the bottom, and decompose. Decomposition of algae and other dead matter

removes oxygen from bottom waters

and can lead to hypoxia, a low-oxygen

condition. Hypoxia has negative impacts

on populations of bottom dwellers such

as crabs, oysters, mussels, and clams.

Nitrogen in the Nation’s Rain 7

How is Nitrogen

Deposition Measured?

Nitrogen deposition occurs as both

wet and dry deposition. The National

Atmospheric Deposition Program

(NADP) National Trends Network

(NTN) measures nitrate and ammonium

in one-week rain and snow samples at

nearly 240 regionally representative

sites in 48 states. Nitrate and ammonium

are measured in daily samples at another

10 sites in NADP’s Atmospheric Integrated Research Monitoring Network

(AIRMoN). These two NADP networks

measure the wet deposition of inorganic

nitrogen (see NADP sidebar).

Two networks measure atmospheric

concentrations of gaseous nitric acid and

particulate ammonium and nitrate at

rural locations across the United States.

The U.S. Environmental Protection

Agency Clean Air Status and Trends

Network (CASTNet) operates 84 sites.

The National Oceanic and Atmospheric

Administration operates the 5 sites in

the AIRMoN dry deposition program.

Dry deposition rates are calculated using

PHOTO BY KATHY TONNESSEN Bioassays can

assess the health

of fish.
Nitrogen in the Nation’s Rain 8

Sources of 

nitrogen to the

Chesapeake Bay.

Source: Chesapeake Bay Program,

The State of the

Chesapeake Bay,

CBP/TRS 222/108,

October 1999.

A water quality

analysis of nitrate

as N in the Chesapeake Bay.

Source: Chesapeake

Bay Program.

The Chesapeake Bay 

The Chesapeake Bay, located in coastal Maryland and Virginia, is the largest

of 130 estuaries in the nation. The Bay’s most troubling problem is an overabundance of nutrients. Excess nutrients lead to increased algal production and

organic matter, a process known as eutrophication. Nitrate accumulates in the

Bay during winter and spring. As temperatures rise, this nitrate promotes excessive algal growth. By mid-summer the decay of algae and other dead matter lead

to hypoxia in the bottom waters of the Bay (see “Effects on Estuarine Systems”).

Researchers are using NADP data to compute the amount of nitrogen deposited by precipitation in Chesapeake Bay and its watershed. Scientists are using

computer modeling to simulate the complex cycling of nitrogen through this terrestrial watershed, which has a far greater area than the Bay itself. Chesapeake

Bay Program models were used to estimate the contributions of the primary

sources of nitrogen to the Bay (see pie chart).

The Chesapeake Bay Program seeks ways to reduce the amount of nitrogen entering the Bay (see map). High-quality data from NADP measurements

give cooperating scientists and policymakers the information they need to

meet this goal.

Nitrate as N

Point Sources

Water

Land

Nonpoint Sources

Atmospheric Deposition

N
these concentration data and deposition

velocities simulated by a computer

model. The model uses meteorological

measurements, and information on land

use, vegetation, and surface conditions.

Calculating the dry deposition of inorganic nitrogen requires summing the

individual rates for nitric acid, nitrate,

and ammonium.

The amount of nitrogen deposited by

precipitation can be calculated for locations without NTN or AIRMoN sites.

One approach uses NADP rainfall,

nitrate and ammonium concentration

data, and digital terrain maps. These

maps make it possible to generate plots

that account for terrain effects on wet

deposition. The map generated for the

Chesapeake Bay watershed using this

technique includes important information for planners, policymakers, and the

scientific community about the complex

relationship between the atmosphere

and the ecological health of the nation’s

estuarine systems.

Nitrogen in the Nation’s Rain 9

A headwater

stream.

Summary

Nitrogen is a macronutrient that is

essential for all living things. Fossil

fuel combustion, animal husbandry

practices, nitrogen fertilizer production and application, and other human

activities add substantial amounts of

nitrogen compounds to the atmosphere every year. Higher airborne

nitrate and ammonium concentrations

from these activities increase the wet

and dry deposition rates of nitrogen.

Increased atmospheric deposition can

affect natural and agricultural systems.

Information on nitrogen deposition,

such as that collected by the NADP, is

important to regulators, policymakers,

and land managers responsible for the

protection of air and water quality in

natural and managed ecosystems.

Nitrogen (kg/ha)

Estimated 1997

wet deposition of

nitrogen in the

Chesapeake Bay

watershed. 

Source: J. W. Grimm

and J. A. Lynch,

Pennsylvania State

University. 
Nitrogen in the Nation’s Rain 10

About the National Atmospheric

Deposition Program

Evaluating nitrogen deposition from the atmosphere is a major role of the

National Atmospheric Deposition Program (NADP) — a partnership of State

Agricultural Experiment Stations, federal, state, and local government agencies,

universities, public institutions, Native American organizations, and industries.

Continued commitments by these organizations make it possible for NADP to

provide the only long-term record of precipitation chemistry in the United

States. This information is used by scientists, policymakers, and the public in

addressing the health, environmental, and agricultural issues facing the nation,

including policy decisions related to the Clean Air Act amendments.

NADP was initiated in 1977 to address the problem of atmospheric deposition and its effects on agricultural crops, forests, rangelands, surface waters, and

other natural resources. NADP coordinates approximately 240 sites in the

National Trends Network, which collects weekly precipitation samples for

chemical analysis. Samples are analyzed at the program’s Central Analytical

Laboratory in Champaign, Illinois, to determine the amounts of certain chemicals, including nitrate and ammonium.

Two additional networks joined NADP in the 1990s: the Atmospheric

Integrated Research Monitoring Network (AIRMoN) in 1992 and the Mercury

Deposition Network (MDN) in 1996. The AIRMoN wet deposition program

evaluates the effect of emission changes on precipitation chemistry, combining

measurements with atmospheric models. MDN is investigating the importance

of atmospheric deposition as a source of mercury in lakes and streams.

A number of federal agencies support NADP, including the Tennessee Valley

Authority; U.S. Department of Agriculture (Cooperative State Research, Education, and Extension Service, and Forest Service); U.S. Department of Commerce

(National Oceanic and Atmospheric Administration); U.S. Department of Interior (Bureau of Land Management, National Park Service, U.S. Fish & Wildlife

Service, and U.S. Geological Survey); and U.S. Environmental Protection Agency. Additional support comes from various other federal agencies, State Agricultural Experiment Stations, state and local government agencies, universities,

Native American organizations, and public and private research organizations.

For more information, contact:

NADP Program Office

Illinois State Water Survey

2204 Griffith Drive

Champaign, IL 61820

E-mail: nadp@sws.uiuc.edu 

Internet: http://nadp.sws.uiuc.edu

The Illinois State Water Survey is an Affiliated Agency

of the University of Illinois and a Division of the Illinois

Department of Natural Resources.

NATIONAL ATMOSPHERIC DEPOSITION PROGRAM

A Cooperative Research Support Program of the

State Agricultural Experiment Stations (NRSP-3)

Federal and State Agencies

and Private Research Organizations

NATURAL

RESOURCES

DEPARTMENT OF

ILLINOIS
Nitrogen in the Nation’s Rain 11

Ammonia/Ammonium

Compounds of nitrogen and hydrogen

that readily dissolve in water. In oxygen-rich water, ammonium is easily

transformed to nitrate and in oxygenpoor water to molecular nitrogen. Ammonium and nitrate comprise most of

the inorganic nitrogen in precipitation.

Atmospheric Deposition 

The process whereby airborne particles

and gases are deposited on the earth’s

surface by wet deposition (precipitation)

or by dry deposition (processes such as

settling, impaction, and adsorption). 

Dry Deposition 

Atmospheric deposition that occurs

when particles settle to a surface, collide

with and attach to a surface, or when

gases stick to a surface (adsorption) or

are absorbed.

Estuary 

An arm of the sea at the mouth of a

stream or river where freshwater and

salt water meet.

Eutrophication

A process in which nutrients degrade

water quality due to excessive growth of

microscopic plants and animals. As this

matter dies and decays, it sometimes

removes so much dissolved oxygen

from the water that fish and other organisms cannot survive.

Hypoxia 

A low-oxygen condition whereby

decaying microscopic plants and animals in estuarine waters remove oxygen

to a level below which most aquatic animals can survive. Although fish and

shrimp can migrate from hypoxic zones,

less mobile bottom dwellers cannot.

Nitrate 

A compound of nitrogen and oxygen

that is highly soluble in water. Nitrate is

stable over a wide range of environmental conditions and is readily transported

in surface and ground water.

Nitrogen 

Molecular nitrogen (N2), an extremely

stable gas, comprises 78% of the

atmosphere. Converting this gas to

other chemical compounds requires

lots of energy. Other compounds of

nitrogen include nitrate and ammonia/

ammonium.

Watershed 

A land surface from which water drains

to a lake, stream, river, estuary, or bay.

Wet Deposition 

Atmospheric deposition that occurs

when rain, snow, or fog carry gases and

particles to the earth’s surface.

KEY TERMS
Nitrogen in the Nation’s Rain 12

Fenn, M.E., M.A. Poth, J.D. Aber, J.S. Baron, B.T.

Bormann, D.W. Johnson, A.D. Lemly, S.G. McNulty,

D.F. Ryan, and R. Stottelmeyer. 1998. Nitrogen Excess

in North American Ecosystems: a Review of Geographic Extent, Predisposing Factors, Ecosystem

Responses, and Management Strategies. Ecol. Appl.

8:706-733.

Galloway, J.N., H. Levy III, and P.S. Kasibhatla. 1994.

Year 2020: Consequences of Population Growth and

Development on the Deposition of Oxidized Nitrogen.

Ambio 23:120-123.

National Science and Technology Council Committee

on Environment and Natural Resources Air Quality

Subcommittee. 1999. The Role of Monitoring Networks

in the Management of the Nation’s Air Quality. Washington, D.C.: U.S. Government Printing Office.

(http://www.nnic.noaa.gov/CENR/cenr.html)

Stoddard, J. 1994. Long-term Changes in Watershed

Retention of Nitrogen; Its Causes and Aquatic

Consequences. In Baker, L.A. (ed.). Environmental

Chemistry of Lakes and Reservoirs. Washington, D.C.:

American Chemical Society: pp. 223-284.

Vitousek, P.M., J.D. Aber, R.W. Howarth, G.E. Likens,

P.A. Matson, D.W. Schindler, W.H. Schlesinger, and

D.G. Tilman. 1997. Human Alteration of the Global

Nitrogen Cycle: Sources and Consequences. Ecol.

Appl. 7(3):737-750.

Williams, J.N., J. Baron, R. Caine, R. Sommerfeld, and

J.R. Sanford. 1996. Nitrogen Saturation in the Rocky

Mountains. Environ. Sci. & Tech. 30:640-646.

RESOURCES

Web Site Resources

Chesapeake Bay Program: www.chesapeakebay.net

Ecological Society of America: www.esa.org

National Acid Precipitation Assessment Program:

www.oar.noaa.gov/organization/napap.html

National Atmospheric Deposition Program: nadp.sws.uiuc.edu

National Oceanic and Atmospheric Administration AIRMoN Dry

Deposition Program:

www.arl.noaa.gov/research/projects/airmon_dry.html

National Park Service Air Resources Division: www2.nature.nps.gov/ard

U.S. Environmental Protection Agency

Clean Air Status and Trends Network: www.epa.gov/castnet

Environmental Monitoring and Assessment Program:

www.epa.gov/emap

Gulf of Mexico Program: pelican.gmpo.gov

National Estuary Program: www.epa.gov/nep

Office of Air & Radiation: www.epa.gov/oar

U.S. Geological Survey Acid Rain Program:

bqs.usgs.gov/acidrain/index.htm
NADP COOPERATORS

State Agricultural Experiment Stations

Auburn Univ.-Black Belt Substa.; Auburn Univ.-Sand Mtn. Substa.;

Colorado State Univ.-Central Plains Experimental Range; Cornell Univ.-

Aurora Res. Farm; Iowa State Univ.-McNay Res. & Demonstration Farm;

Kansas State Univ.-Konza Prairie; Louisiana State Univ.-Iberia Res. Sta.;

Louisiana State Univ.-Southeast Res. Sta.; Montana State Univ.-Northern

Ag. Res. Ctr.; North Carolina State Univ.-Finley Farm; North Carolina

State Univ.-Horticultural Crops Res. Sta.; North Carolina State Univ.-

Peanut Belt Res. Sta.; North Carolina State Univ.-Piedmont Res. Sta.;

Ohio State Univ.-Eastern Ohio R&D Ctr.; Ohio State Univ.-Ohio Ag. 

R&D Ctr.; Oklahoma State Univ.-Goodwell Res. Sta.; Oregon State Univ.-

Hyslop Farm; Pennsylvania State Univ.-School of Forest Resources;

Pennsylvania State Univ.-Fruit Res. & Extension Ctr.; Purdue Univ.-

Purdue Ag. Res. Ctr.; Purdue Univ.-Southwest-Purdue Ag. Ctr.; South

Dakota State Univ.-Cottonwood Range Livestock Field Sta.; Texas A&M

Univ.-Texas A&M Ag. Res. Sta.-Beeville; Texas A&M Univ.-Texas A&M

Ag. Res. Sta.-Sonora; Univ. of Arkansas-Ag. Res. & Extension Ctr.; Univ.

of California-Davis; Univ. of California-Hopland Field Sta.; Univ. of

Florida-Bradford Forest; Univ. of Georgia-Coastal Plain Exp. Sta.; Univ.

of Georgia-Georgia Exp. Sta.; Univ. of Illinois-Dixon Springs Ag. Ctr.;

Univ. of Illinois-Northern Illinois Agron. Res. Ctr.; Univ. of IllinoisNorthwestern Illinois Ag. Res. & Demonstration Ctr.; Univ. of MaineGreenville Sta.; Univ. of Maryland-Wye Res. & Education Ctr.; Univ. of

Massachusetts-Suburban Exp. Sta.; Univ. of Michigan-Biological Sta.;

Univ. of Michigan-Kellogg Biological Sta.; Univ. of Minnesota-Southwest

Res. & Outreach Ctr.; Univ. of Missouri-Baskett Wildlife Area; Univ. of

Missouri-Univ. Forest; Univ. of Nebraska-Ag. R&D Ctr.; Univ. of

Nebraska-North Platte Ag. Exp. Sta.; Univ. of Vermont-Proctor Maple Res.

Ctr.; Univ. of Wisconsin-Spooner Ag. Res. Sta.; Utah State Univ.-Utah Ag.

Exp. Sta.; Virginia Polytechnic Inst. & State Univ.-Horton Res. Ctr.;

Washington State Univ.-Palouse Conservation Farm

Universities

Alfred Univ.; Colorado State Univ.; Cornell Univ.; Eastern Kentucky

Univ.; Miami Univ. of Ohio; Murray State Univ.; New Mexico State Univ.;

North Carolina State Univ.-Southern Oxidant Study; Pennsylvania State

Univ.; State Univ. of New York-Albany; State Univ. of New YorkFredonia; State Univ. of New York-Oswego; State Univ. of New YorkSyracuse; Texas A&M Univ.; Univ. of Alaska, Fairbanks-Water &

Environmental Res. Ctr.; Univ. of Arkansas-Monticello; Univ. of

Colorado-Inst. of Arctic & Alpine Res.; Univ. of Delaware; Univ. of

Kentucky-Ctr. for Applied Energy Res.; Univ. of Massachusetts; Univ. of

Michigan-Biological Sta.; Univ. of Minnesota; Univ. of Missouri; Univ. of

New Hampshire; Univ. of Oklahoma; Univ. of Puerto Rico; Univ. of South

Carolina-Baruch Inst. for Marine Biology & Coastal Res.; Univ. of

Vermont; Univ. of Virginia; Washington Univ.-Tyson Res. Ctr.

United States Government Agencies

National Aeronautics & Space Admin.; National Science FoundationLong-Term Ecological Res. Program; Tennessee Valley Authority; U.S.

Dept. of Agriculture (Ag. Res. Service, Cooperative State Res. Education

& Extension Service, Science & Education Admin.); U.S. Dept. of

Agriculture/Forest Service (Wildlife, Fish, Water & Air Res., Bitterroot

Nat’l Forest, Bridger-Teton Nat’l Forest, Coweeta Hydrologic Lab., Forest

Sciences Lab.-Delaware, Ohio, Fremont Nat’l Forest, Gifford Pinchot Inst.

for Conservation Studies, Hiawatha Nat’l Forest, H.J. Andrews

Experimental Forest, Hubbard Brook Experimental Forest, HuronManistee Nat’l Forest, Kane Experimental Forest, Medicine Bow-Routt

Nat’l Forest, North Central Res. Sta., Northeastern Res. Sta., Pacific

Northwest Res. Sta., Pacific Southwest Res. Sta., Rocky Mtn. Res. Sta., San

Juan Nat’l Forest, Shoshone Nat’l Forest, Southern Res. Sta., Superior

Nat’l Forest, White River Nat’l Forest); U.S. Dept. of Commerce/National

Oceanic & Atmospheric Admin. (Air Resources Lab., Atmospheric

Turbulence & Diffusion Div., Nat’l Weather Service); U.S. Dept. of

Defense/U.S. Military Academy; U.S. Dept. of Energy (Argonne Nat’l

Lab., Los Alamos Nat’l Lab., Nat’l Energy Tech. Lab., Oak Ridge Nat’l

Lab.); U.S. Dept. of Interior/Bureau of Land Mgt. (Nat’l Applied Resource

Sciences Ctr., Lander Field Ofc.-Wyoming, Las Vegas Field Ofc.-Nevada,

Little Snake Field Ofc.-Colorado, Safford Field Ofc.-Arizona); U.S. Dept.

of Interior/Bureau of Reclamation; U.S. Dept. of Interior/National Park

Service (Air Resources Div., Acadia Nat’l Park, Allegheny Portage

Railroad Nat’l Historic Site, Assateague Island Nat’l Seashore, Bandelier

Nat’l Monument, Big Bend Nat’l Park, Bryce Canyon Nat’l Park, Buffalo

Nat’l River, Canyonlands Nat’l Park, Cape Cod Nat’l Seashore, Capulin

Volcano Nat’l Monument, Chiricahua Nat’l Monument, Craters of the

Moon Nat’l Monument, Death Valley Nat’l Park, Denali Nat’l Park,

Everglades Nat’l Park, Glacier Nat’l Park, Grand Canyon Nat’l Park,

Great Basin Nat’l Park, Great Smoky Mtns. Nat’l Park, Guadalupe Mtn.

Nat’l Park, Hawaii Volcanoes Nat’l Park, Indiana Dunes Nat’l Lakeshore,

Isle Royale Nat’l Park, Joshua Tree Nat’l Park, Lassen Volcanic Nat’l

Park, Little Big Horn Battlefield Nat’l Monument, Mesa Verde Nat’l Park,

Mt. Rainier Nat’l Park, North Cascades Nat’l Park, Olympic Nat’l Park,

Organ Pipe Cactus Nat’l Monument, Pinnacles Nat’l Monument, Rocky

Mtn. Nat’l Park, Sequoia Nat’l Park, Shenandoah Nat’l Park, Theodore

Roosevelt Nat’l Park, Valley Forge Nat’l Historical Park, Virgin Islands

Nat’l Park, Voyageurs Nat’l Park, Yellowstone Nat’l Park, Yosemite Nat’l

Park); U.S. Dept. of Interior/U.S. Fish & Wildlife Service (Air Quality

Branch, Attwater Prairie Chicken Nat’l Wildlife Refuge, Cape Romain

Nat’l Wildlife Refuge, Chassahowitzka Nat’l Wildlife Refuge, Edwin B.

Forsythe Nat’l Wildlife Refuge, Hatchie Nat’l Wildlife Refuge, Mingo Nat’l

Wildlife Refuge, Muleshoe Nat’l Wildlife Refuge, Okefenokee Nat’l Wildlife

Refuge, Salt Plains Nat’l Wildlife Refuge, Santee Nat’l Wildlife Refuge,

Seney Nat’l Wildlife Refuge); U.S. Dept. of Interior/U.S. Geological

Survey; U.S. Environmental Protection Agency (Ofc. of Air & RadiationClean Air Markets Div., Ofc. of Wetlands, Oceans, and Watersheds, Nat’l

Health & Environmental Effects Res. Lab.-Western Ecology Div.)

State & Local Government Agencies

Alabama Dept. of Environmental Mgt.; Arkansas Dept. of Environmental

Quality; Delaware Dept. of Natural Resources & Environmental

Conservation Trap Pond State Park; Florida Dept. of Environmental

Protection; Fort Worth, Texas, Dept. of Environmental Mgt.; Illinois State

Water Survey; Indiana Dept. of Environmental Mgt.; Iowa Conservation

Commission; Kansas Dept. of Wildlife & Parks; Louisiana Dept. of

Environmental Quality; Maine Dept. of Environmental Protection;

Maryland Dept. of Natural Resources; Massachusetts Dept. of

Environmental Protection; Minnesota Pollution Control Agency; Missouri

Dept. of Natural Resources; New Hampshire Dept. of Environmental

Services; New Jersey Dept. of Environmental Protection; New Mexico

Environment Dept.; North Carolina Dept. of Environment, Health, &

Natural Resources; North Dakota State Parks & Recreation-Icelandic State

Park; Northeast States for Coordinated Air Use Mgt.; Oklahoma

Conservation Commission; Pennsylvania Dept. of Conservation & Natural

Resources; Pennsylvania Dept. of Environmental Resources; Portland,

Oregon, Water Bureau; San Francisco Estuary Inst.; San Jose

Environmental Services Dept.; Siskiyou County, California-Air Pollution

Control Dist.; South Carolina Dept. of Health & Environmental Control;

South Carolina Dept. of Natural Resources; South Florida Water Mgt.

Dist.; St. Johns River Water Mgt. Dist.; Texas Natural Resource

Conservation Commission; Vermont Dept. of Environmental

Conservation; Wisconsin Dept. of Natural Resources

Industry

Advance Tech. Systems, Inc.; Atmospheric Res. & Analysis, Inc.; BP

Amoco; Constellation Energy Group; Dynamac Corp.; Exxon Mobil

Corp.; Florida Power & Light Co.; Frontier Geosciences, Inc.; Harding

ESE, Inc.; Lockheed Martin Energy Res.; SF Phosphates, Ltd.; Southern

Company; Union Camp Corp.; Westinghouse Savannah River Co.

Native American Tribes and Organizations

Fond du Lac Reservation; Fort Peck Tribes; Grand Traverse Band; Lac

Courte Oreilles Tribe; Menominee Indian Tribe; Mille Lacs Band of

Ojibwe; Penobscot Nation; St. Regis Mohawk Tribe

Other Research Organizations

Black Rock Forest Inst.; Electric Power Res. Inst.; Environment CanadaAtmospheric Environment Branch; Environment Canada-Air Quality Res.

Branch; Environment Canada-Environmental Conservation Service;

Environment Canada-Meteorological Service of Canada; Green River

High School, Utah; Huntsman Marine Science Centre, Canada; Ministere

de l’Environnement du Quebec; New Brunswick Dept. of Environment;

North Woods Audubon Nature Ctr., Minnesota; Wolf Ridge Environmental

Learning Ctr., Minnesota

Nitrogen in the Nation’s Rain 13