United States

Department of

Agriculture

Forest Service

Pacific Northwest

Research Station

United States

Department of the

Interior

Bureau of Land

Management

General Technical

Report

PNW-GTR-447

July 1999

An Assessment of the Effects

of Human-Caused Air Pollution

on Resources Within the

Interior Columbia River Basin

Anna W. Schoettle, Kathy Tonnessen, John Turk,

John Vimont, and Robert Amundson
Authors

ANNA W. SCHOETTLE is a plant physiologist, U.S. Department of Agriculture, Forest Service,

Rocky Mountain Research Station, 240 W. Prospect Rd., Fort Collins, CO 80526-2098; KATHY

TONNESSEN is an aquatic effects specialist and JOHN VIMONT is a visibility modeler, U.S.

Department of the Interior, National Park Service, P.O. Box 25287, Lakewood, CO 80225-0287;

JOHN TURK is an aquatic effects specialist, U.S. Geological Survey, MS 415 Denver Federal Center,

Denver, CO 80225; ROBERT AMUNDSON is an environmental consultant, Portland, OR 97201;

ANN ACHESON is an air program manager, U.S. Department of Agriculture, Forest Service,

Intermountain Region, P.O. Box 7669, Missoula, MT 59807; and JANICE PETERSON is an air

quality specialist, U.S. Department of Agriculture, Forest Service, Pacific Northwest Region, 21905

64th Ave. W., Mountlake Terrace, WA 98043.

This document was prepared as part of the Interior Columbia Basin Ecosystem Management Project in

cooperation with and under the science leadership of the Pacific Northwest Research Station.
An Assessment of Effects of Human-Caused

Air Pollution on Resources Within the Interior

Columbia River Basin

Anna W. Schoettle, Kathy Tonnessen, John Turk, John Vimont, and

Robert Amundson

Ann Acheson and Janice Peterson, Technical Editors

Interior Columbia Basin Ecosystem Management

Project: Scientific Assessment

Thomas M. Quigley, Editor

U.S. Department of Agriculture

Forest Service

Pacific Northwest Research Station

Portland, Oregon

General Technical Report PNW-GTR-447

July 1999
Abstract

Schoettle, Anna W.; Tonnessen, Kathy; Turk, John; Vimont, John; Amundson, Robert,

authors; Acheson, Ann; Peterson, Janice, tech. eds. 1999. An assessment the effects of

human-caused air pollution on resources within the interior Columbia River basin. Gen. Tech. Rep.

PNW-GTR-447. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest

Research Station. 66 p. (Quigley, Thomas M., ed.; Interior Columbia Ecosystem Management

Project: scientifice assessment).

An assessment of existing and potential impacts to vegetation, aquatics, and visibility within the

Columbia River basin due to air pollution was conducted as part of the Interior Columbia Basin Ecosystem Management Project. This assessment examined the current situation and potential trends due

to pollutants such as ammonium, nitrogen oxides, sulfur oxides, particulates, carbon, and ozone. Ecosystems and resources at risk are identified, including certain forests, lichens, cryptogamic crusts, highelevation lakes and streams, arid lands, and class I areas. Current monitoring data are summarized and

air pollution sources identified. The assessment also includes a summary of data gaps and suggestions

for future research and monitoring related to air pollution and its effects on resources in the interior

Columbia River basin.

Keywords: Atmospheric deposition, acid rain, air pollution, aquatic effects, class I areas, terrestrial

effects, sensitive species, visibility.
Preface

The Interior Columbia Basin Ecosystem Management Project was initiated by the Forest Service and

the Bureau of Land Management to respond to several critical issues including, but not limited to,

forest and rangeland health, anadromous fish concerns, terrestrial species viability concerns, and the

recent decline in traditional commodity flows. The charter given to the project was to develop a

scientifically sound, ecosystem-based strategy for managing the lands of the interior Columbia River

basin administered by the Forest Service and the Bureau of Land Management. The Science Integration Team was organized to develop a framework for ecosystem management, and assessment of the

socioeconomic and biophysical systems in the basin, and an evaluation of alternative management

strategies. This paper is one in a series of papers developed as background material for the framework,

assessment, or evaluation of alternatives. It provides more detail than was possible to disclose directly

in the primary documents.

The Science Integration Team, although organized functionally, worked hard at integrating the approaches, analyses, and conclusions. It is the collective effort of team members that provides depth

and understanding to the work of the project. The Science Integration Team leadership included

deputy team leaders Russel Graham and Sylvia Arbelbide; landscape ecology—Wendel Hann, Paul

Hessburg, and Mark Jensen; aquatic—Jim Sedell, Kris Lee, Danny Lee, Jack Williams, Lynn Decker;

economic—Richard Haynes, Amy Horne, and Nick Reyna; social science—Jim Burchfield, Steve

McCool, and Jon Bumstead; terrestrial—Bruce Marcot, Kurt Nelson, John Lehmkuhl, Richard

Holthausen, and Randy Hickenbottom; spatial analysis—Becky Gravenmier, John Steffenson, and

Andy Wilson.

Thomas M. Quigley

Editor

United States

Department of

Agriculture

Forest Service

United States

Department of

the Interior

Bureau of Land

Management

Interior Columbia

Basin Ecosystem

Management Project
Contents

1 Introduction

1 Data Used to Evaluate Air Quality Condition

5 Atmosphere-Biosphere Interactions

5 Air Pollutants of Concern

11 Deposition of Air Pollutants

12 Monitoring Data

25 Aquatic Ecosystems

25 Predicting Response of Aquatic Ecosystems to Air Pollutants

25 Sources of Historical Data and Background Information

26 Present Status of Aquatic Ecosystems

26 Ability of Aquatic Ecosystems to Respond to Additional Threats

26 Geographic Distribution of Air Pollutant Concentrations

32 Location of Aquatic Ecosystems Affected by or Sensitive to Air Pollutants

32 Information Needed for Assessing Future Risks to Aquatic Ecosystems

32 Terrestrial Ecosystems

33 Sulfur Dioxide Effects on Terrestrial Ecosystems

38 Nitrogen Oxide Effects on Terrestrial Ecosystems

41 Ozone Effects on Terrestrial Ecosystems

43 Fluoride

44 Visibility in the Basin

45 Available Data

45 Discussion

48 Ecosystems and Resources at Risk From Air Pollution

48 Forests

48 High-Elevation Lakes and Streams

50 Arid Lands

50 Class I Areas

50 Research, Development, and Assessment

52 Definitions of Terms Used

52 Conversion Table

54 Literature Cited

61 Appendix 1

Class I Areas Within the Interior Columbia River Basin

63 Appendix 2

Nonattainment Areas Within or Near the Interior Columbia River Basin

65 Appendix 3

Species List
This page has been left blank intentionally.

Document continues on next page.
Introduction

One of the building blocks of any ecosystem, at

any scale, is air and its condition or quality. As

human populations increase, they have an effect

on air quality, which has an effect on ecosystems.

It is appropriate, therefore, to evaluate as part of

the Interior Columbia Basin Ecosystem Management Project (ICBEMP), the current condition

and expected trends in air quality and its effects to

resources within the Columbia River basin (also

referred to as “the basin”).

A team of scientists gathered to conduct such an

evaluation. The team was familiar with the resources within the ICBEMP, and their expertise

encompassed the areas of climate, atmospheric

deposition, aquatic ecosystems, vegetation, and

visibility (visual effects). They focused their work

on assessing the effects of human-caused air pollution on natural resources. This pollution is normally associated with industry and urban lifestyles, such as power plants or traffic emissions,

but can include agricultural and silvicultural practices. The team omitted an evaluation of human

health effects to limit the scope so that a product

could be delivered within the time allotted. A different team performed an extensive analysis of

smoke effects generated from wildland fire. The

climate and meteorology of the interior Columbia

River basin are discussed by Ferguson (1997,

1998).

The evaluation of air quality and its effects within

the basin was conducted through review of existing data (national databases where possible) about

emissions, atmospheric deposition, snow and lake

chemistry, vegetation, and visibility; development

of tools to analyze weather and climate patterns

affecting the basin; literature reviews; and conversations with other experts in the field. A geographic information system (GIS) was used as a

mapping tool to identify areas potentially impacted by air pollution based on a resource’s sensitivity to air pollution, its proximity to emissions

sources, and meteorology. Other politically designated areas sensitive to air pollution, such as

class I or nonattainment areas (table 1, appendices 1 and 2; defined in “Definitions of Terms

Used”), also were mapped (fig. 1). The prevention of significant deterioration of air quality

within class I areas is mandated by the 1977 and

reinforced by the 1990 Clean Air Act amendments

(U.S. Laws, Statutes 1977, Public Law 95-95, and

U.S. Laws, Statutes 1990, Public Law 101-549,

respectively). Federal land managers of class I

areas have an affirmative responsibility to protect

the air-quality-related values of these areas from

adverse effects of air pollution. This report is organized into discussions of atmosphere-biosphere

interactions, aquatic ecosystems, terrestrial ecosystems, and visibility.

Data Used to Evaluate Air Quality

Condition

Emissions and monitoring data from within and

around the basin were used to assess the current

and predicted condition of air quality and its effects on resources. The emissions data for point

and area sources (excluding silvicultural and agricultural burning) were from 1990 and were the

same data compiled for the Grand Canyon Visibility Transport Commission (legislated by Congress to assess visibility and causes of impairment

in national parks and wilderness areas of the

Colorado Plateau). These data have been extensively reviewed and validated by the air regulatory agencies of the affected states. In general,

emissions of air pollutants in the basin are less

than in the Eastern United States or California

(Environmental Protection Agency [EPA] 1994b),

so basin air quality can be assumed to be relatively cleaner; however, long-term air-quality

monitoring data for the basin do not exist (Böhm

1992, Lefohn and Lucier 1991).

This air-quality team focused primarily on the effects of the EPA “criteria” pollutants of particulate matter (PM-10), nitrogen oxides, and sulfur

oxides, but also considered volatile organic compounds, ammonium, and ozone and some hazardous air pollutants. Other pollutants were considered based mainly on their effects to water or

vegetation.

Ambient air monitoring data from national, state,

or local monitoring were obtained through either

the national EPA emissions inventory database or

individual state agencies. The most recent year of

data used was 1991, 1992, or 1993. Specifics of

other monitoring data used in this report are

described later.

1
Table 1—Potential air quality threats to vegetation in class I areas in the interior Columbia River

basin assessment area

Elevation Potential threat

Class I area State Low High Ozone SOx NOx SO2 emissions within 25kma

− −Meters− − Tons per year

Alpine Lakes WA 500 2408 yesb

yes

b <1000

Anaconda Pintlar MT 1597 3290 <1000

Bob Marshall MT 1257 2825 <500

Cabinet Mountains MT 940 2663 <1000

Caribou CA 2000 2553 <1500

Crater Lake

National Park OR 1433 2486 <500

Craters of the Moon

National Monument ID 1625 2356 0

Eagle Cap OR 853 2999 <5500

Flathead MT 768 2762 <5000

Gates of the Mountain MT 1174 2425 yes <21,000c

Gearhart Mountain OR 1798 2528 yesb <500

Glacier National Park MT 975 3190 <28,500

Glacier Peak WA 600 2679 yesb

yes

b <500

Goat Rocks WA 885 2500 yesb

yes

b 0

Grand Teton

National Park WY 1951 4197 0

Hells Canyon ID,OR 244 2863 <2500

Jarbidge NV 2134 3304 0

Lassen Volcanic

National Park CA 1634 2652 <1500

Lava Beds CA 1231 1616 <500

Marble Mountain CA 244 2530 <500

Mission Mountain MT 1409 2799 <2500

Mount Adams WA 1300 3751 yesb

yes

b 0

Mount Hood OR 1250 3424 yesb

yes

b <6000

Mount Rainier

National Park WA 512 4392 yes yes 0

Mount Washington OR 945 2376 yesb

yes

b <1500

2
Table 1—Potential air quality threats to vegetation in class I areas in the interior Columbia River

basin assessment area (continued)

Elevation Potential threat

Class I area State Low High Ozone SOx NOx SO2 emissions within 25kma

− −Meters− − Tons per year

North Cascades

National Park WA 600 2703 yes yes <500

Pasayten WA 366 2721 yesb

yes

b <500

Red Rock Lake MT 2012 3048 0

Sawtooth ID 1219 3353 0

Scapegoat MT 1566 2857 <500

Selway Bitterroot MT 501 3088 <3000

South Warner CA 1402 3015 yesd <1000

Strawberry Mountain OR 1463 2755 <1500

Three Sisters OR 610 3157 yesb

yes

b <4500

Yellowstone

National Park WY, MT 1676 3220 <1000

a Point source SO2 emissions only. b Peterson and others 1992b.

c Nonattainment area.

d Peterson and others 1992a.

3
LEGEND

Class I areasNon attainment areasLandscapecharacterizationboundaryState boundaryCounty boundary

Figure 1—Class I and nonattainment areas within or near the interior Columbia River basin. See appendices 1 and 2 for specificinformation regarding class I and nonattainment areas.

4
Atmosphere-Biosphere

Interactions

Air Pollutants of Concern

The need for abundant and reliable new energy

sources, minerals, timber, and agricultural pro

duction will result in increased atmospheric emissions of pollutants in the basin and other western

areas. To use these resources without damaging

nearby wilderness areas and other Federal lands,

land management decisions need to be based on

an understanding of the present status of the

basin’s resources and the potential risk associated with atmospheric emissions.

Sulfur oxides (SOx)—Sulfur is of concern because of its transformation to secondary pollutants

such as sulfuric acid and sulfate particles, which

affect vegetation, certain lakes and streams, and

visibility. Globally, the major inputs of sulfur to

the atmosphere come from seasalt (42.1 percent),

human emissions (27.2 percent) biogenic gases

(19.0 percent), volcanic emissions (5.8 percent),

and gypsum dust (5.8 percent) (Brimblecombe

and others 1989). Human-caused sulfur emissions are in the form of sulfur dioxide (Charlson

and others 1992, Moller 1984). Charlson and

others (1992) note that sulfur dioxide is converted

to sulfate at a rate of about 1 percent per hour and

that once converted to sulfate, the sulfur generally

returns to Earth’s surface as wet or dry deposition

in about 2 days. Sulfur emissions are viewed as a

regional issue because the sulfur may travel 1000

km1 in a few days. Significant environmental effects are usually apparent within about 4 to 20 km

of the source (Ludwig and others 1980).

Air arriving on the western shore of North America is relatively free of human-caused sulfur after

traveling thousands of kilometers over open

ocean. Human-caused sulfur found in the basin is

probably from the large area and point sources

located both outside and within the assessment

boundary. The largest point sources, emitting

more than 5,000 tons of sulfur per year, are in

the counties of Spokane, WA, Morrow, OR,

Humboldt, NV, Bannock, ID, Caribou, ID, Lewis

and Clark, MT, and Sublette, WY (fig. 2; see fig.

3 for a map of all counties within the basin). Area

sources are aggregated by county. The counties

within the basin having SOx emissions between

1,000 and 5,000 tons per year are associated with

the cities of Boise, Lewiston, and Idaho Falls, ID;

Spokane, WA; and Bend, OR (fig. 4).

Nitrogen oxides (NOx)—Human-caused alterations of N-cycling in managed and unmanaged

ecosystems are of concern because nitrogen often

limits primary productivity (Aber and others

1989, Field and Mooney 1986, Schulze and others

1994), and increased inputs of nitrogen to forest

ecosystems have been associated with changes in

plant community structure (Ellenberg 1988).

Human-caused sources of nitrogen within the basin are associated primarily with combustion of

fossil fuels for energy production and transportation and with changes in land use (agricultural and

forestry practices).

Area sources for NOx are more dispersed than for

SOx but still are associated with urban areas

within the basin and on its western edge (fig. 5).

The areas with the largest NOx emission inventory

are Portland, OR, and Seattle-Tacoma, WA, with

emissions exceeding 20,000 tons per year. It is

likely that most of these emissions are from

vehicles.

The area emissions data available for this assessment did not include emissions of nitrogen oxides

derived from soil microbial activity or fertilized

agricultural land. The actual area emissions of

nitrogen in the basin probably are higher than

reported here.

Ozone (O3)—Ozone is a colorless, odorless gas

that is a secondary pollutant produced when emissions of volatile organic compounds combine with

NOx emissions in the presence of sunlight. Volatile organic compounds (VOCs) are emitted by

both human and natural sources (vegetation for

example). Ozone is formed in the atmosphere

under hot, dry conditions and can be transported

long distances from the source of the precursor

emissions.

Text continues on page 10

1 Units of measure shown in this document may be either

metric or English, depending on the most frequently used

convention for the particular parameter described. See the

“Conversion Table” at the end of the text.

5
LEGEND

Class I areasLandscapecharacterizationboundaryState boundaryCounty boundary

Tons per year

< 500

 500 to 999

 1,000 to 4,999 5,000 to 19,999

20,000 +

Figure 2—Sulfur oxide (SOx) point source emissions within or around the interior Columbia River basin.

6
LEGEND

LandscapecharacterizationboundaryState boundaryCounty boundary

Figure 3—Counties within the interior Columbia River basin.

7
LEGEND

Class I areasLandscapecharacterizationboundaryState boundaryCounty boundary

Tons per year

< 500

 500 to 999

 1,000 to 4,999 5,000 to 19,999

20,000 +

Figure 4—Sulfur oxide (SOx) area source emissions within or around the interior Columbia River basin.

8
LEGEND

Class I areasLandscapecharacterizationboundaryState boundaryCounty boundary

Tons per year

< 500

 500 to 999

 1,000 to 4,999 5,000 to 19,999

20,000 +

Figure 5—Nitrogen oxide (NOx) area source emissions within or around the interior Columbia River basin.

9
Ozone is degraded by reacting with other air contaminants and biotic and abiotic surfaces that it

contacts. Ozone production and destruction therefore can be rapid in urban areas and result in low

ambient concentrations. Conversely, ozone destruction is less in rural areas, which contributes

to the potential of high ambient ozone concentrations in rural locations. Ozone can threaten remote ecosystems and resources far from pollutant

sources.

Ozone is highly phytotoxic to plants and is likely

to affect vegetation in the basin because (1) it is

found globally in elevated concentrations, and

(2) ozone precursors, for example NOx, are increasing within and upwind of the basin. Our

assessment of ozone effects on vegetation was

limited, however, both by inadequate monitoring

data (Böhm 1992, Böhm and others 1995) and

uncertainties in area emission estimates of NOx

within the basin. Ozone does not affect aquatic

resources.

The EPA and state and local air agencies monitor

ozone concentrations in many urban areas. Ozone

concentrations measured near The Dalles, OR,

increase (1 hour maximum, 92 parts per billion

[ppb]) when winds move NOx and ozone from the

Portland area through the Columbia River Gorge.

Unfortunately, ozone monitoring for The Dalles

began only in 1992. More information on ozone

concentrations produced by polluted air masses

moving into the basin from the Vancouver, BC, to

Eugene, OR, urban corridor is needed to assess

the impacts on forests closest to this large source

of ozone and its precursors (Edmonds and Basabe

1989). Ozone concentrations also are elevated

around Spokane, WA (Böhm and others 1995)

and likely are elevated in other basin urban

areas (Boise, ID; and the Richland, Pasco, and

Kennewick, WA vicinity). For a review of ozone

levels found in parts of Oregon, Washington, and

Idaho, refer to Eilers and others (1994).

Particles—Small airborne particles may originate

from road dust, agricultural and silvicultural burning, volcanic eruptions, or atmospheric transformation of NOx and SOx to ammonium nitrate and

ammonium sulfate particles, respectively. In remote areas, particles have potential effects on air

quality-related values such as visibility. Small

particles (0.1- to 1.0-micron category) can reduce

visibility to the point of obscuring views (Malm

1992). Results of a 1990 National Park Service

study of visibility in national parks in the Washington Cascade Range (Malm and others 1994)

indicate that carbon contributes about 60 percent

of the total impairment, with 30 percent from sulfates, 5 percent from nitrates, and 5 percent from

soil-related particles. These parks are on the edge

of the basin, but information on particle composition and source regions should be relevant to that

watershed. (See the “Visibility” section of this

report for more information.)

Radionuclides and hazardous air pollutants—

Two nuclear technology facilities are within the

basin: Hanford Nuclear Reservation in southeastern Washington and Idaho National Engineering Lab in south-central Idaho. At the Hanford

site, extensive air monitoring for both hazardous

air pollutants (HAPs) and radionuclides has led to

the conclusion that air concentrations at the site

perimeter meet all applicable standards (Gray

1995). There will be risk of release of both radionuclides and HAPs to the air during the period of

site cleanup, which is expected to last for the next

30 years or more. The greatest risk of airborne

radionuclides and HAPs from these facilities is

bioaccumulation in aquatic and terrestrial biota,

which might cause physiological effects in top

predators, including humans.

Mercury is the hazardous air pollutant now receiving attention due to its potential for longdistance transport and bioaccumulation, especially in aquatic systems (Watras and Huckabee

1994). Airborne mercury is present in the elemental form; most of the deposited mercury is in

the oxidized form (inorganic or methylmercury).

Human-mediated release of mercury to the air is

through coal combustion, incineration operations,

smelting, and landfill emissions. Microbes convert inorganic mercury to methylmercury, the

compound that can then bioaccumulate in fish

and piscivores, including humans. Methylmercury

is a potent neurotoxin in vertebrates.

Because the transport of mercury via the air pathway is a regional and global phenomena, it is difficult to determine source-receptor relations for

mercury within the interior Columbia River basin.

Because this part of the Northwestern United

States has a relatively low population density and

10
sparse industrial development, it is unlikely that

the region is a significant contributor to mass

fluxes of this toxic air contaminant. The degree to

which the basin is accumulating mercury in soils,

water, and biota is not known at this time. Two

states within the basin (Oregon and Montana)

have issued fish consumption advisories for specific water bodies to warn consumers about

mercury-contaminated fish and shellfish (EPA

1994c). These advisories may be associated with

specific point sources of mercury contamination

rather than long-distance transport of elemental

mercury.

Persistent organic pollutants, which include such

compounds as PCBs (polychlorinated biphenyls),

dioxins (2,3,7,8 TCDD), and chlordane, are included among the 189 hazardous air pollutants

named by the EPA. These byproducts of industrial activities and pesticide applications can

travel via the air pathway and deposit on terrestrial and aquatic surfaces. When these chemicals

make their way into water bodies, they are not

easily degraded and are concentrated in biota,

where they can then accumulate up the food

chain. These toxins may accumulate in lake trout,

salmon and the higher predators, wading birds,

eagles, and humans to levels that can result in deformities, reproductive disruption, and death.

Many of these organic hazardous air pollutants

can be revolatilized from the water bodies and

transported via the air pathway to other sensitive

receptors. Much of what we know about the transport and biomagnification of these chemicals

comes from the Great Waters Program (EPA

1994a, 1994c), required by the Clean Air Act

amendments of 1990 (U.S. Laws, Statutes 1990,

Public Law 101-549).

Little information on sources and receptors of

persistent organic pollutants is available for the

basin. Under the 1990 Clean Air Act amendments, many of the industries emitting hazardous

air pollutants are required to deploy maximum

achievable control technology to prevent toxic

emissions. The technology standards developed

to prevent or ameliorate effects on human health

and ecosystems in the more polluted areas (for

example the Great Lakes basin) therefore will

benefit the Northwestern United States, which

currently does not have as many local sources or

potential for regional transport of hazardous air

pollutants to remote ecosystems.

Deposition of Air Pollutants2

Wet deposition—Wet deposition includes rain,

snow, rime ice, sleet and hail, along with “occult”

deposition (fogwater and cloudwater). Chemical

species of interest in determining the dose to the

ecosystem include sulfate (SO4

-

), nitrate (NO3

-

),

ammonium (NH4

+

), and hydrogen ion (H+).

Acidity in wet deposition can directly affect vegetation by interactions with leaf or needle surfaces, especially as concentrated cloudwater. In

general, acidity in rain and snow can affect soil

fertility and nutrient cycling processes. Soils affected by acids often have high concentrations of

aluminum in soilwater, which in turn affects root

function. Acidity in rain and snow can result in

chronic or episodic acidification of sensitive lakes

and streams.

Dry deposition—Dry deposition is the term used

for the removal of gaseous and particulate species from the atmosphere to terrestrial and aquatic

systems. The species of interest with respect to

“loadings” to natural ecosystems include sulfur dioxide, sulfate particles, sulfuric acid aerosol, nitric

acid aerosol, nitrate ammonium particles, and

nitrogen oxide gas. The uptake of ozone by vegetation also is considered a dry deposition process.

An important anion in acid deposition is nitrate.

Vegetation can be impacted directly by increased

inputs of nitrogen via either wet or dry deposition

(Aber and others 1989, Fenn and Bytnerowicz

1993) or indirectly through NOx mediated increases in ozone (Hogsett and others 1993). Additional indirect effects of NOx on vegetation can

be through changes in climate by increases in the

global warming gas and nitrous oxide (N2O)

(Mooney and others 1987) or through nitric oxide

(NO) destruction of stratospheric ozone, leading

to increased UV-B-mediated mutagenicity

(Davidson 1991). Deposition of excess nitrogen

species (nitrate and ammonium) to both terrestrial

and aquatic systems can result in fertilization or

eutrophication and episodic acidification of

streams and lakes (Stoddard 1994).

2 A thorough discussion of regional wet and dry deposition

and its effects on watersheds and surface waters can be

found in Charles (1991); information on areas containing

sensitive lakes in the Cascade Range and the Rocky Mountains can be found in Nelson (1991) and Turk and Spar

(1991), respectively.

11
The reaction of nitric acid with ammonia gas

emitted from feedlots and fertilized fields results

in ammonium nitrate particles. When this buffered compound reaches soils and surface waters,

the ammonium is preferentially taken up by biota,

thus generating acidity. Most counties within the

basin have some level of ammonia emissions,

primarily less than 500 tons per year (fig. 6). It is

possible, however, for ammonium nitrate transformation and transport to deliver nitrogen species to parks and wilderness areas in the basin,

depending on the pattern of local ammonia emissions relative to the supply of nitric acid vapor.

Monitoring Data

Wet deposition monitoring—Wet deposition is

measured in the United States by a national network of about 200 sites coordinated by the National Atmospheric Deposition Program/National

Trends Network (NADP/NTN). Currently the

only wet deposition network sites operating in the

interior Columbia River basin are NADP/NTN

sites at nine locations in Oregon, Washington,

Idaho, Wyoming, and Montana (fig. 7):

NADP/NTN site Elevation

Meters

Idaho:

Craters of the Moon

National Monument 1807

Reynolds Creek 1198

Smiths Ferry 1442

Oregon:

Silver Lake Ranger Station 1336

Starkey Experimental Forest 1253

Washington:

Palouse Conservation Farm 766

Montana:

Glacier National Park 968

Lost Trail Pass 2414

Wyoming:

Yellowstone National Park 1912

The 1992 NADP/NTN data for the nine interior

Columbia River basin sites are displayed in

figures 8 and 9. The solutes of interest in this data

set include nitrate, sulfate, ammonium, and pH

(or hydrogen ion). The annual precipitationweighted pH of wetfall measured at these nine

sites ranges from 5.3 at Glacier National Park to

6.0 at Reynolds Creek (fig. 8). The pH of wetfall

seems to correlate with annual amounts of precipitation, with the Reynolds Creek site receiving

about 17 cm of wetfall and Glacier National Park

receiving about 70 cm in 1992 (fig. 8). The Lost

Trail site received the highest precipitation

amount in 1992 (78 cm) and is also the highest

elevation site of the nine monitored.

In general, wet deposition samples at these nine

sites showed that nitrate exceeds sulfate and ammonium, with concentration peaks observed in

the summer (fig. 9). The precipitation-weighted

mean concentrations in the basin are lower than

those recorded in the Eastern United States; for

example, the highest annual average nitrate concentration for the two southern Idaho sites is

0.8 mg/l compared to maximum values in 1992

of 1.8 mg/l recorded at sites in Pennsylvania

(fig. 10) (NADP 1993). Comparisons of annual

concentrations of sulfate show a large difference

between Eastern and Western sites, with the

highest annual sulfate concentration of 0.5 mg/l

for southern Idaho contrasted with the maximum

sulfate concentration of 3.2 mg/l at Indiana Dunes

National Lakeshore (fig. 11).

Wet deposition estimates reflect both the concentrations of solutes in wetfall and the total amount

of wet deposition that fell during the year (fig.

12). These values can be used to estimate total

loading of pollutants to ecosystems (kg⋅ha-1⋅yr

-1)

when combined with other sources of inputs,

such as dry deposition and occult deposition. As

with concentration data, the 1992 deposition

values for the nine NADP stations in the basin

show higher loadings for nitrate than sulfate. The

stations with the highest snowfall, Glacier National Park, Yellowstone National Park, and Lost

Trail Pass, have the highest annual loading of

nitrate, all in the range of 2 to 3 kg/ha. This is still

low compared to the highest value of 29 kg/ha in

upstate New York (fig. 13). The annual sulfate

deposition is close to the loadings for nitrate at

two sites (Glacier National Park and Palouse Conservation Farm) in the basin. These values would

be higher but snow deposition is not measured

accurately. The NADP/NTN samplers are poor

collectors of snow due to wind scour, overtopping

the bucket, and mechanical malfunctions.

Text continued on page 21

12
LEGEND

Class I areasLandscapecharacterizationboundaryState boundaryCounty boundary

Tons per year

< 500

 500 to 999

 1,000 to 4,999 5,000 to 19,999

20,000 +

Figure 6—Ammonia (NH3) area source emissions within or around the interior Columbia River basin.

13
Location from which

associated histogramdata was collected

LEGEND

Class I areasLandscapecharacterizationboundaryState boundaryCounty boundary

Figure 7—1992 National Atmospheric Deposition Program (NADP) monitoring sites.

14
Figure 8—National Atmospheric Deposition Program (NADP) seasonal and annual pH and precipitation from sites within the interior Columbia River

basin.

15
Figure 9—National Atmospheric Deposition Program (NADP) seasonal and annual average concentrations from sites within the interior

Columbia River basin.

16
Figure 10—Annual precipitation-weighted mean nitrate ion concentrations for 1992 (milligrams per liter) (NADP 1993).

17
Figure 11—Annual precipitation-weighted mean sulfate ion concentrations for 1992 (milligrams per liter) (NADP 1993).

18
Figure 12—National Atmospheric Deposition Program (NADP) seasonal and annual deposition from sites within the interior Columbia River basin.

19
Figure 13—Estimated nitrate ion deposition for 1992 (kilograms per hectare) (NADP 1993).

20
Additional analysis of wet chemistry data (1980

to 1992) for selected NADP sites throughout the

United States was performed by Lynch and others

(1995) to look for statistically significant trends

in average concentrations. Three sites in the basin

were included in this analysis (Glacier National

Park, Yellowstone National Park, and Craters of

the Moon National Monument; fig. 14). During

these 12 years, sulfate, base cation, and hydrogen

ion concentrations significantly decreased at all

three sites, with a measured increase in nitrate

concentrations at two of the three sites (although

not statistically significant), and no change in ammonium concentrations. This result agrees with

the trends in estimated emissions, with decreasing

SOx emissions and increasing NOx emissions in

the basin.

Dry deposition monitoring—Dry deposition is

measured by monitoring ambient concentrations

of gases and particles and then using models to

infer deposition. Air concentrations have been

measured by the EPA as part of the 50-site

National Dry Deposition Network and by the National Oceanic and Atmospheric Administration

(NOAA) network of filter packs.3 There are three

National Dry Deposition Network sites located

within the basin, two colocated with NADP sites

(fig. 15): Reynolds Creek in Idaho, Glacier National Park in Montana, and Saval Ranch in

Nevada. These sites have operated since 1988 or

1989, with data reported as weekly-average

concentrations of SO2, particulate-sulfate, nitric

acid, particulatenitrate, and ammonia. For details

of sampling protocols, see Clarke and Edgerton

(1992).

The dry deposition estimates for 1990 for the

three National Dry Deposition Network sites for

1990 show that nitric acid had the highest loading of all the dry species at all three sites, with a

range of 1 kg/ha at the Glacier National Park site

to about 2.5 kg/ha at the two more southerly sites

(fig. 16). Deposition of particle nitrate was extremely low at all three sites, with a maximum

value of about 0.2 kg/ha. Because 1990 is one of

the first years of data reporting for these sites, the

variability of dry deposition is unknown.

Only two sites within the interior Columbia River

basin currently monitor ozone, and they both report elevated ozone concentrations. More ozone

monitoring should be done within the basin, particularly near class I areas and sensitive forests.

A more concerted effort to estimate dry deposition

of nitrogen species and ozone in the basin is

needed, particularly near sensitive forests and

watersheds.

Snowpack monitoring—Regional snow deposition along the Continental Divide in Montana,

Wyoming, Colorado, and New Mexico is being

sampled by the U.S. Geological Survey, in cooperation with the U.S. Department of AgricultureForest Service, State of Colorado, and National

Park Service (Turk 1995). An earlier synoptic

snow monitoring project along the Cascade Range

and Sierra Nevada crest is reported in Laird and

others (1986).

Snowpacks in the basin tend to have dilute chemistry. During the survey by Laird and others

(1986) of February through March 1983, the pH

of the snowpack along the Washington, Oregon,

and northern California Cascade Range ranged

from 5.11 to 5.88, nitrate concentrations ranged

from 0.007 to 0.12 mg/l, and sulfate ranged from

0.05 to 0.32 mg/l. The pH of snowpack recorded

in the Rocky Mountains during 1993 was mostly

above 5.0, except for sites in the vicinity of the

Mount Zirkel Wilderness Area, where researchers

have suggested that emissions from power facilities in the Yampa Valley are influencing snow

chemistry (Ingersoll 1995).

Cloudwater and fogwater monitoring—

Cloudwater and fogwater can contribute significantly to total loading of solutes in certain types

of environments. In high-elevation areas of eastern North America, cloudwater impaction can account for as much loading of sulfate and nitrate as

do other forms of wet precipitation (for example

at Noland Divide in Great Smoky Mountains National Park, [Johnson and Lindberg 1992]). Böhm

(1992) summarizes what is known about the contribution of cloudwater to high-elevation areas in

the vicinity of the basin, including the Washington

Cascade Range and Mount Werner in northwest

Colorado. Cloudwater pH ranged from 3.1 to 5.9

in the Washington Cascade Range and from 3.0

to 5.2 at Mount Werner. Cloudwater collected at

these sites had higher concentrations of all ions

3 National Acid Precipitation Assessment Program. 1995.

Draft 1994 report to Congress of the National Acid

Precipitation Assessment Program. Washington, DC.

[pages unknown]. On file with: [unknown].

21
Figure 14—National Atmospheric Deposition Program (NADP) sites included in national precipitation trends analysis (from Lynch and others 1995).

22
Location from which

associated histogramdata was collected

LEGEND

Class I areasLandscapecharacterizationboundaryState boundaryCounty boundary

Figure 15—National Dry Deposition Network (NDDN) monitoring sites within the interior Columbia River basin in 1990.

23
Figure 16—Deposition and average concentrations from National Dry Deposition Network (NDDN) monitoring sites within the interior Columbia River

basin in 1990.

24
than did precipitation. The total loading of such

species of nitrate, sulfate, and ammonium are

likely, however, to be lower owing to the small

volume of water that these samples represent.

Aquatic Ecosystems

Predicting Response of Aquatic

Ecosystems to Air Pollutants

Aquatic ecosystems include the obvious hydrologic components of lakes, streams, and ground

water and the rain, snow, and fog that replenish

them. Other critical components include bedrock

and surficial materials, soils, and terrestrial and

aquatic communities that define much of the ecosystem’s character and the movement of water,

nutrients, and toxic materials through the ecosystem. Unfortunately, consideration of the many

possible complex interactions of all these components with air pollutants would be difficult at best

in intensively studied watersheds and impossible

in the many remote wilderness areas and other

Federal lands in the interior Columbia River

basin. This section presents a regionally oriented

approach to help the reader determine the present

status of aquatic ecosystems and assess the risk

of future threats to aquatic ecosystems from air

pollutants in the basin. Most of this discussion

uses existing data on lakes, snowpack, and rain

plus snow (wetfall). These hydrologic components integrate many of the complex interactions

of their respective ecosystems and allow the

reader to rank the degree of threat and sensitivity

to that threat.

One useful approach to predicting response of

aquatic ecosystems to air pollutants is to consider:

1. Present status of aquatic ecosystems with

respect to critical levels of some measure of

ecosystem health, for example, pH.

2. Ability of aquatic ecosystems to respond to

additional threats to ecosystem health, for

example, acid neutralizing capacity.

3. Present geographic distribution of air pollutant

concentrations.

4. Location of aquatic ecosystems already

affected by air pollutants or having very little

ability to respond to increased air pollutants in

the future.

Aquatic resources at low elevation tend to be less

sensitive to acid rain than high-elevation aquatic

ecosystems; however, aquatic ecosystems at any

elevation could be sensitive to other atmospheric

pollutants owing to the same chemical and biological processes and characteristics that determine

sensitivity to acid rain; for example, low pH and

small acid neutralizing capacity would tend to

make a lake sensitive to many toxic metals whose

solubility is increased at low pH. Further, the

short hydrologic flow paths and thin soils typical

of lakes sensitive to acid rain provide minimal

opportunity to remove inorganic and organic air

pollutants by sorption to soil or by biological uptake or degradation. Thus, knowledge gained from

acid rain studies can be used to select aquatic resources that may be sensitive to other air

pollutants.

Sources of Historical Data and

Background Information

Lakes—Most knowledge of the present status of

aquatic resources of the interior Columbia River

basin and risk from air pollutants has been summarized by Turk and Spahr (1991), Nelson

(1991), and Melack and Stoddard (1991). These

references discuss the 1985 EPA Western Lake

Survey (Landers and others 1987)—the only lake

study including the entire basin—and numerous

smaller studies.

Atmospheric deposition—Current atmospheric

deposition in the basin has been measured by the

National Atmospheric Deposition Program as discussed above in this paper. Atmospheric deposition as characterized by snowpack chemistry was

surveyed during 1983 by the U.S. Geological Survey (USGS) throughout the Cascade Range and

the Sierra Nevada (Laird and others 1986). In

1993, another survey of snowpack chemistry

throughout the Rocky Mountains was conducted

by the USGS (Turk 1995).

Watershed processes—A collaborative effort by

six Federal agencies recently resulted in published

results from the 10-year National Acid Precipitation Assessment Program (NAPAP 1991). Although the NAPAP focus was primarily on the

Eastern United States, much of what we know

about the effects of air pollution on aquatic ecosystems and watershed processes is a result of

NAPAP and related work.

25
Present Status of Aquatic

Ecosystems

The only geographically extensive historical data

are for lakes sampled as part of the Western

Lakes Survey (Landers and others 1987). In the

interior Columbia River basin, most lakes sampled as part of this survey have pH between 6 and

8 and only two have pH less than 6 (fig. 17). The

pH data typically represent conditions during

summer and fall, although lower pH is expected

to occur during snowmelt, for which data are unavailable. Mortality in amphibians common to

lakes and ephemeral pools in alpine areas occurs

at pH values as high as 5 to 6 (Corn and Vertucci

1992, Harte and Hoffman 1989). Thus, pH of

lakes typically is not at a critical level for the

basin during the summer and fall sample period.

Seasonal snowmelt supplies most of the water in

sensitive lakes, ephemeral breeding pools, and

low order streams, all tending to occur in alpine

and subalpine areas of the basin. At times, this

snowmelt may totally or largely displace more

alkaline water that typically would occupy such

systems during periods other than snowmelt.

Thus, surveys conducted during summer and fall,

the case for all lake surveys referenced above,

may provide a poor estimate of worst-case acidification of aquatic systems. The chemical nature

of this snowmelt, and aquatic systems most influenced by it, may be a more appropriate measure of aquatic chemistry than is the chemistry of

lakes reported by the surveys above. It is possible

that areas having lakes with insufficient acid

neutralizing capacity to buffer acidity released

during snowmelt may experience episodic pH

low enough to result in biological damage, but

data are not available to determine whether this

occurs in the basin.

Ability of Aquatic Ecosystems to

Respond to Additional Threats

Lakes are ranked in sensitivity to acidification

based on their acid neutralizing capacity (ANC.)

To be able to buffer atmospheric deposition as

acidic as that commonly observed in the Eastern

United States, and to retain a moderate amount of

acid neutralizing capacity to provide stability in

pH, an acid neutralizing capacity of 200 microequivalents per liter (μeq/L) is often used to

divide sensitive (ANC < 200 μeq/L) and nonsensitive (ANC > 200 μeq/L) lakes (Hendrey and

others 1980, Turk and Adams 1983). Many lakes

in the interior Columbia River basin have acid

neutralizing capacity less than 200 μeq/L, and

numerous clusters of lakes have acid neutralizing

capacity much less than 200 μeq/L (fig. 18); however, no acidic (ANC < 0) lakes have been identified in the basin.

Geographic Distribution of Air

Pollutant Concentrations

Air pollutants can directly enter aquatic ecosystems as solutes in wetfall and from the snowpack.

The present geographic distribution of areas of

greater concentration of air pollutants in snowpack can be seen for pH (fig. 19), nitrate, (fig. 20)

and sulfate (fig. 21). Generally, the smallest concentrations of air pollutants in the snowpack

are in the Cascade Range, the Sierra Nevada,

and in Montana. Concentrations are greatest in

Wyoming and a small area within Montana near

the junction with Idaho and Wyoming. Some of

the largest concentrations of sulfate, nitrate, and

acidity were measured at sites in this area west of

Yellowstone National Park.

The present geographic distribution of areas of

greater concentration of air pollutants in wetfall

can be seen for pH, sulfate, and nitrate (figs. 8

and 9). Generally the wetfall sites near snowpack

sampling sites, shown in figures 19, 20, and 21,

have values comparable to the snowpack values.

Wetfall sites at lower elevation, however, have

somewhat greater concentrations than do the

higher elevation snowpack sites. Much of this

difference is caused by a seasonal pattern with

greatest concentration of air pollutants in the summer and smallest concentration in the winter,

when the snowpack accumulates.

Text continues on page 32

26
LEGEND

Class I areasLandscapecharacterizationboundaryState boundaryCounty boundary

pH

< 6.06.0 to 6.97.0 to 7.98.0 +

Figure 17—Lake pH values from sites within or near the interior Columbia River basin (from Eilers and others 1987).

27
LEGEND

Class I areasLandscapecharacterizationboundaryState boundaryCounty boundary

Microequivalents per liter

0 to 4950 to 99100 to 199200 +

Figure 18—Lake acid neutralizing capacity values from sites within or near the interior Columbia River basin (from Eilers and others1987).

28
LEGEND

Class I areasLandscapecharacterizationboundaryState boundaryCounty boundary

pH

< 5.05.0 to 9.96.0 to 6.97 +

Figure 19—Snowpack pH values from sampling sites within or near the interior Columbia River basin (from Laird and others 1986,Turk 1995).

29
LEGEND

Class I areasLandscapecharacterizationboundaryState boundaryCounty boundary

Microequivalents per liter

0 to 4.95.0 to 9.910.0 to 14.915.0 +

Figure 20—Nitrate (NO3-) values from snow sampling sites within or near the interior Columbia River basin (from Laird and others

1986, Turk 1995).

30
LEGEND

Class I areasLandscapecharacterizationboundaryState boundaryCounty boundary

Microequivalents per liter

0 to 4.95.0 to 9.910.0 to 14.915.0 +

Figure 21—Sulfate (SO4-) values from snow sampling sites within or near the interior Columbia River basin (from Laird and others

1986, Turk 1995).

31