&EPA
United States
Environmental Protection
Agency
Office of
Public Affairs (A-107)
Washington DC 20460
OPA-86-009
September 1986
ACID RAIN
An EPA Journal
Special Supplement
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Acid rain . . .
Few environmental problems have caused so much
controversy— and so much confusion . . .
People have been worrying about acid rain for decades . . .
Now countries in several parts of the world are working
together to control it ...
Research into many different aspects of acid rain is
advancing . . .
And so is the technology to reduce it.
In this special supplement, the EPA JOURNAL takes a look at
what we know about acid rain—-and what we don't know:
• The Acid Rain Phenomenon
• An Acid Rain Chronology
• An International Perspective
• Acid Rain Research
• Control Technologies
• Implementation Issues
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The Acid Rain Phenomenon
All rainfall is by nature somewhat
acidic. Decomposing organic matter,
the movement of the sea, and volcanic
eruptions all contribute to the
accumulation of acidic chemicals in the
atmosphere, but the principal factor is
atmospheric carbon dioxide, which
causes a slightly acidic rainfall (pH of
5.6) even in the most pristine of
environments. (See box for an
explanation of pH.)
In some parts of the world, the acidity
of rainfall has fallen well below 5.6. In
the northeastern United States, for
example, the average pH of rainfall is
4.6, and it is not unusual to have
rainfall with a pH of 4.0—which is 1000
times more acidic than distilled water.
Although precipitation in the western
United States tends to be less acidic
than in the East, incidents of fog with a
pH of less than 3.0 have been
documented in southern California.
There is no doubt that man-made
pollutants accelerate the acidification of
rainfall. We know that man-made
emissions of sulfur dioxide SO2 and
nitrogen oxides (NOJ
transformed into acids in the
atmosphere, where they often travel
hundreds of miles before falling as
acidic rain, snow, dust, or gas. All these
wet and dry forms of acid deposition
are known loosely as "acid rain," which
is now recognized as a potentially
serious long-term air pollution problem
for many industrialized nations.
Emissions
and Deposition
Before the Clean Air Act was passed in
1970, U.S. SO2 and NOX emissions were
increasing dramatically. (See Table 1.)
Between 1940 and 1970, annual SO2
emissions had increased by more than
55 percent. Over the same period, NOX
emissions had almost tripled.
TABLE 1
Historic U.S. SO2 and NOX Emissions
(In Millions of Tons)
1940 1950 1960 1970 1980 1984
S02 19.8 22.4 22.0 31.1 25.6 23.6
NOX 7.5 10.3 14.1 20.0 22.5 21.7
The Clean Air Act helped to curb the
growth of these emissions. By 1984,
annual SO2 emissions had declined by
24 percent, and NOX emissions had
increased by only 9 percent. These
reductions in historical growth rates
took place despite the fact that the U.S.
economy and the combustion of fossil
fuels grew substantially over the same
period.
Acid-forming emissions are not
spread evenly over the United States.
Ten states in the central and upper
Midwest—Missouri, Illinois, Indiana,
Tennessee, Kentucky, Michigan, Ohio,
Pennsylvania, New York, and West
Virginia—produce 53 percent of total
U.S. SO2 and 30 percent of total U.S.
NO*.
Table 2 lists the top ten SO2 and NOX
emitting states. SO2 emissions are
concentrated along the Ohio River
Valley in Ohio, Indiana, Pennsylvania,
Illinois, and West Virginia. These five
states, along with Missouri and
Tennessee, produce 44 percent of all
SO2 in the United States.
U.S. NOX emissions tend to be more
evenly distributed, but again, states
along the Ohio River are especially high
producers. Four of the five highest
SO2-producing states—Ohio, Indiana,
Pennsylvania, and Illinois—are also
among the top ten NOx-producing states.
Thus, the Ohio River Valley and the
states immediately adjacent to it lead
the U.S. in emissions of both major
components of acid rain.
TABLE 2
Top Ten SO2 and NOx Producing
States in 1984 (In Millions of Tons)
S02 NOX
1.
2.
3.
4.
5,
6.
7.
8.
0.
10,
Ohio 2.58
Indiana 1.67
Pennsylvania 1.60
Illinois 1.38
Texas 1.24
Missouri 1.18
West Virginia 1.02
Florida 0.99
Georgia 0.93
Tennessee 0.92
Texas 3.25
California 1.17
Ohio 1.14
Illinois 0.99
Pennsylvania 0.92
Indiana 0.83
Florida 0.70
Michigan 0.69
Louisiana 0.68
New York 0.62
How "Acid" Is Acid Rain?
Lemon
V Vinegar /
\ / /
"Pure" Rain (5.6]
Distilled Water
/ ^Baking Soda
1 1 1 1
ACID RAIN
1 1 1 1
1 2 3 4 5 6 7 8 9 10 11 12 13 14
ACIDIC NEUTRAL BASIC
The pH scale ranges from 0 to 14. A value of
7.0 is neutral. Readings below 7.0 are acidic;
readings above 7.0 are alkaline. The more pH
decreases bolow 7.0, the more acidity
increases.
Because the pH scale is logarithmic, there is
a tenfold difference between one number and
the one next to it. Therefore, a drop in pH
from 6.0 to 5.0 represents a tenfold increase
in acidity, while a drop from 6.0 to 4.0
represents a hundredfold increase.
All rain is slightly acidic. Only rain with a
pH below 5.6 is considered "acid rain."
Acid Rain Precursors
44%
34%
Transportation Electrical
Utilities
NITROGEN OXIDES [NOX)
19.7 million metric tons.NO,,
18%
1%
Industrial
Processes
and Fuel
Combustion
Commercial/
Industrial/
Residential
Other
EPA JOURNAL
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Although we can't be certain of
long-term trends in acid deposition, it is
possible to draw conclusions about
current patterns. A comparison of the
pH of U.S. rainfall with the states
producing the greatest SO2 and NOX
emissions clearly shows the solid link
between acidic emissions and acidic
deposition. Data collected by several
different monitoring networks show that
the areas of the U.S. receiving the most
acid rainfall are downwind and
northeast of those states with the
highest SO2 and NOX emissions.
Effects
of Acid Rain
The environmental effects of acid rain
are usually classified into four general
categories: aquatic, terrestrial, materials,
and human health. Although there is
evidence that acid rain can cause
certain effects in each category, the
extent of those effects is very uncertain.
The risks these effects may pose to
public health and welfare are also
unclear and very difficult to quantify.
The extent of damage caused by acid
rain depends on the total acidity
deposited in a particular area and the
sensitivity of the area receiving it. Areas
with acid-neutralizing compounds in
the soil, for example, can experience
years of acid deposition without
problems. Soils like this are common
throughout the midwestern United
States. On the other hand, the thin soils
of the mountainous Northeast have very
little acid-buffering capacity, making
them vulnerable to damage from acid
rain.
Aquatic Effects
The adverse effects of acid rain are seen
most clearly in aquatic ecosystems. The
most common impact appears to be on
reproductive cycles. When exposed to
acidic water, female fish, frogs,
salamanders, etc., may fail to produce
eggs or produce eggs that fail to develop
normally.
Low pH levels also impair the health
of fully developed organisms. Some
scientists believe that acidic water can
kill fish and amphibian reptiles by
altering their metabolism, but we have
little evidence that this is happening
now.
We do know, however, that acid rain
plays a role in what scientists call the
"mobilization" of toxic metals. These
metals remain inert in the soil until acid
rain moves through the ground. The
acidity of this precipitation is capable of
dissolving and "mobilizing" metals such
as aluminum, manganese, and mercury.
Transported by acid rain, these toxic
metals can then accumulate in lakes and
streams, where they may threaten
aquatic organisms.
Some lakes in areas of high acid
deposition and low buffering capacity
have been found to be both highly
acidic and lifeless. Yet other lakes in
similarly sensitive areas have not.
Different lakes vary in the time it takes
to reach an acidic condition, and rates
of recovery from acidification also seem
to vary.
Scientists are using field studies,
long-term water quality data, studies of
fish population declines, and lake
sediment studies to analyze the
acidification of various lakes. However,
both the data and the theoretical models
currently available are unproven in their
ability to make an accurate prediction of
the effects of continued acidic
emissions.
Terrestrial Effects
We know less about acid rain's effects
on forests and crops than we do about
effects on aquatic systems. The most
extreme form of damage some have
attributed to acid rain is the
phenomenon known as "dieback."
Dieback is a term applied to the
unexplained death of whole sections of
a once-thriving forest. At this time,
however, we have little direct evidence
linking acid rain to forest dieback.
Scientists do agree that acid rain can
lead to other, less extreme effects on
soil and forest systems. It can leach
nutrients from soil and foliage while
inhibiting photosynthesis. Acid rain can
also kill certain essential
microogranisms. The toxic metals it
mobilizes when passing through soil
can be harmful not just to aquatic life
but to trees and crops as well. But,
again, we have little evidence that such
damage is occurring now because of
acid rain.
Some experts even point to data
indicating that acid deposition may
actually benefit certain trees and crops.
For example, some pitch pine seedlings
SULFUR DIOXIDE (SO2)
21.4 million metric tons SO2
Transportation
Electrical
Utilities
Industrial
Processes
and Fuel
Combustion
Commercial/
Industrial/
Residential
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have grown better when treated with
increasingly acidic water, and exposure
to combinations of acid rain and mist
has stimulated red spruce growth. It is
possible that nitrates derived from the
nitrogen oxides in acid rain confer some
nutritional benefits on trees and plants.
Materials Effects
Acid rain can also damage man-made
materials, such as those used in
construction and sculpture. We are all
familiar with photographs of statues that
are losing their features and shape, with
acid rain often cited as the culprit.
The problem is far more than
aesthetic. Building materials, too, can be
degraded by acidity. For example,
limestone, marble, carbonate-based
paints, and galvanized steel all can be
eroded and weakened by the kind of
dilute acids found in acid deposition.
Since materials naturally deteriorate
with time, it is difficult to differentiate
the effects of acid rain from damage
caused by normal weathering. It is also
hard to identify the specific damage
caused by specific pollutants or
combinations of pollutants. As a result,
the particular role played by acid rain
in the deterioration of materials is still a
major unknown.
Human Health Effects
So far, we don't know of any human
health problems resulting from direct
contact with acid rain. Inhaling acidic
particles in acid fog may possibly carry
some health risk, but more research is
needed to confirm whether this
constitutes a real risk.
Acid rain may also indirectly affect
human health when it mobilizes toxic
trace metals such as aluminum and
mercury. When dissolved in acidic
water, these metals can be ingested by
fish and animals, building up in the
human food chain. Acidic water could
also leach lead out of pipe solder and
into drinking water supplies.
But these are only possibilities. No
one has established that current
emissions of SC>2 and NOX are actually
causing such damage, or that such
damage will continue or increase in the
future if SC>2 and NOX emissions are not
reduced.
An Acid Rain Chronology
A lead chamber
constructed by
19th century
English scientist
Robert Angus Smith
as part of
his experimental
research
into air quality.
1661-2: English investigators John
Evelyn and John Graunt publish
separate studies speculating on the
adverse influence of industrial
emissions on the health of plants and
people. They mention the problem of
transboundary exchange of pollutants
between England and France. They also
recommend remedial measures such as
locating industry outside of towns and
using taller chimneys to spread "smoke"
into "distant parts."
1734: Swedish scientist C.V. Linne
describes a 500-year-old smelter at
Falun, Sweden: ". . . we felt a strong
smell of sulphur . . . rising to the west
of the city ... a poisonous, pungent
sulphur smoke, poisoning the air wide
around . . . corroding the earth so that
no herbs can grow around it."
1872: English scientist Robert Angus
Smith coins the term "acid rain" in a
book called Air and Rain: The
Beginnings of a Chemical Climatology.
Smith is the first to note acid rain
damage to plants and materials. He
proposes detailed procedures for the
collection and chemical analysis of
precipitation.
1911: English scientists C. Crowther and
H.G. Ruston demonstrate that acidity of
precipitation decreases the further one
moves from the center of Leeds,
England. They associate these levels of
acidity with coal combustion at Leeds
factories.
1923: American scientists W.H.
Maclntyre and I.E. Young conduct the
first detailed study of precipitation
chemistry in the United States. The
focus of their work is the importance of
airborne nutrients to crop growth.
1948: Swedish scientist Hans Egner,
working in the same vein of agricultural
science as Maclntyre and Young, sets up
the first large-scale precipitation
chemistry network in Europe. Acidity of
precipitation is one of the parameters
tested.
EPA JOURNAL
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An In
:tive
1954 : Swedish scientists Carl Gustav
Rossby and Erik Eriksson help to
expand Egner's regional network into
the continent-wide European Air
Chemistry Network. Their pioneering
work in atmospheric chemistry
generates new insights into the
long-distance dispersal of air pollutants.
1972: Two Canadian scientists, R.J.
Beamish and H.H. Harvey, report
declines in fish populations due to
acidification of Canadian lake waters.
1975: Scientists gather at Ohio State
University for the First International
Symposium on Acid Precipitation and
the Forest Ecosystem.
1977: The U.N. Economic Commission for
Europe (ECE) sets up a Cooperative
Programme for Monitoring and
Evaluating the Long-Range Transmission
of Air Pollutants in Europe.
1979: The U.N.'s World Health
Organization establishes acceptable
ambient levels for SO2 and NOX.
Thirty-one industrialized nations sign
the Convention on Long-Range
Transboundary Air Pollution under the
aegis of the ECE.
1980: The U.S. Congress passes an Acid
Deposition Act providing for a 10-year
acid rain research program under the
direction of the National Acid
Precipitation Assessment Program.
1980: The U.S. and Canada sign a
Memorandum of Intent to develop a
bilateral agreement on transboundary air
pollution, including "the already serious
problem of acid rain."
1985: The ECE sets 1993 as the target
date to reduce SO2 emissions or their
transboundary fluxes by at least 30
percent from 1980 levels.
1986: On January 8, the Canadian and
U.S. Special Envoys on Acid Rain
present a joint report to their respective
governments calling for a $5 billion
control technology demonstration
program.
1986: In March, President Ronald
Reagan and Prime Minister Brian
Mulroney of Canada endorse the Report
of the Special Envoys and agree to
continue to work together to solve the
acid rain problem.
Principal source: Ellis B. Cowling,
"Acid Precipitation in Historical
Perspective," Environmental Science
and Technology, Volume 16, Number 2,
1982.
Aid rain is not considered a threat to
the global environment. Large parts
of the earth are not now, and probably
never will be, at risk from the effects of
man-made acidity. But concern about
acid rain is definitely growing.
Although acid rain comes from the
burning of fossil fuels in industrial
areas, its effects can be felt on rural
ecosystems hundreds of miles
downwind. And, if the affected area is
in a different country, the economic
interests of different nations can come
into conflict.
Such international disputes can be
especially difficult to resolve because
we do not yet know how to pinpoint the
sources in one country that are
contributing to environmental damage
in another.
Concerns about acid rain tend to be
raised whenever large-scale sources of
acidic emissions are located upwind of
international borders. Japan, for
example, has not yet suffered any
environmental damage due to acid rain,
but the Japanese are worried about the
potential downwind effects of China's
rapidly increasing industrialization. A
similar problem has risen on the
U.S.-Mexican border, where some
people are worried that Mexico's new
copper smelter at Nacozari could cause
acid rain on the pristine peaks of the
Rocky Mountains. Besides scattered
instances such as these, acid rain has
emerged as a serious international issue
only in two places: western Europe and
northeastern North America.
Europe
Diplomatic problems related to
cross-boundary air pollution first
surfaced in Europe in the l!)50s, when
the Scandinavian countries began to
complain about industrial emissions
traveling across the North Sea from
Great Britain. Since then, acid
deposition has been linked to ecological
damage in Norway, Sweden, and West
Germany, and low-pH rainfall has been
measured in a number of other
European countries. (See map on this
page for the average pH of rainfall over
Europe in 1980.)
The political and scientific
controversies over acid rain an:
multiplied in Europe because so many
countries are involved. Table 3 lists the
SO2 emissions of 21 European nations
in 1980.
A comparison of the pH map with
Table 3 reveals that some countries
producing very low amounts of S()2 are
nevertheless experiencing low-pH
rainfall and high rates of acid
deposition. Norway, for example.
produced approximately 137,000 metric
tons of SO2 in 1980. yet receded
depositions of about 300,000 metric:
tons. Clearly, Norway, like a number of
other European nations, is being
subjected to acid deposition that
originates outside its borders.
Sweden pioneered the development of
extensive and consistent monitoring for
acid precipitation in the late 1940s. In
1954, the Swedish monitoring program
TABLE 3
European S().; Emissions in 1980
(In Thousands of Metric Tons)
Austria
Belgium
Bulgaria
Czechoslovakia
Denmark
Finland
France
Federal Republic
of Germany
Greece
Hungary
Italy
Netherlands
Norway
Poland
Portugal
Romania
Sweden
Switzerland
United Kingdom
USSR
Yugoslavia
441)
809
1 .000
3,100
399
600
3,270
3,580
700
1.663
3.HOO
487
137
2,755
149
200
450
119
4,680
25,500
;t.ooo
(Figures from U.S. Department of State)
-------
was expanded to include other
European countries. The results of this
monitoring revealed the high acidity of
rainfall over much of western Europe.
Prompted by these findings, the U.N.
Conference on the Human Environment
recommended a study of the impact of
acid rain, and in July 1972, the U.N.
Organization for Economic Cooperation
and Development (OECD) began an
inquiry into "the question of acidity in
atmospheric precipitation." In 1979, a
U.N. Economic Commission for Europe
(ECE) conference in Stockholm
approved a multi-national "Convention"
for addressing the problem of long-range
transboundary air pollution. Both the
United States and Canada joined the
European signatories. Since then, a
number of European countries,
including France, West Germany,
Czechoslovakia, and all the
Scandinavian countries, have agreed to
reduce their 1993 SO2 emissions by at
least 30 percent from 1980 levels.
More recently, ECE members decided
in 1985 to broaden their goals to
include the control of nitrogen oxides,
which have been gaining recognition as
important acid rain precursors.
Workshops are now underway to
determine the nature and extent of NOX
pollution in various countries, as well
as possible approaches for controlling it.
North America
The United States and Canada share the
longest undefended border in the world
and billions of dollars in trade every
year. We also share a number of
environmental problems, foremost
among them the problem of acid rain.
In both countries, acidic emissions are
concentrated relatively close to our
mutual border. Canadian emissions
originate primarily in southern Ontario
and Quebec, while a majority of U.S.
emissions originate along the Ohio River
Valley. Each country is contributing to
acid rain in the other. But because of
prevailing wind patterns and the greater
quantities of U.S. emissions, the United
States sends much more acidity to
Canada than Canada sends to us. In
1980, for example, the U.S. produced
over 23 million metric tons of SO', and
over 20 million metric tons of NOX;
Canada produced 4.6 million metric
tons of SO2 and 1.7 million tons of NOX.
In the early 1970s, Canadian scientists
began to report on the adverse
environmental effects of acidity in lake
water, and to link fish kills in acidic
lakes and streams in eastern Canada to
U.S. emissions. By the late 1970s, acid
rain had become a serious diplomatic
issue affecting the relationship of the
two countries.
In 1980, we took our first joint step
towards resolving the issue with a
Memorandum of Intent that called for
shared research and other bilateral
efforts to analyze and control acid rain.
One of the most spectacular projects
was a high-altitude experiment called
"CAPTEX." Trace elements of various
chemicals were inserted into SO2
plumes from coal-fired power plants in
the Midwest. Their dispersion was
monitored along a path extending across
the northeastern United States to
Canada. These and other experiments
have helped scientists gain new data on
the formation and distribution of acid
rain.
When Brian Mulroney became Prime
Minister of Canada in 1984, he pressed
for more than research; he wanted
bilateral action to control acid rain. At
the first "Shamrock Summit" in March
1985, Mulroney and President Reagan
agreed that Canada and the United
States would each appoint a high-level
Special Envoy to study acid rain. The
Special Envoys would be charged with
recommending a plan to alleviate both
the environmental and the political
damage caused by acid rain.
William Davis, former Premier of
Ontario, and Drew Lewis, former U.S.
Secretary of Transportation, were named
Special Envoys. In January 1986, the
two men presented their joint
recommendations for U.S.-Canadian
action. They proposed a $5 billion U.S.
technology demonstration program,
ongoing bilateral consultations at the
highest diplomatic levels, and
cooperative research projects.
Western Europe and North America
are highly industrialized, and it is likely
that acid rain will continue to be a
serious concern in both areas for the
foreseeable future. But the nations
involved are coming to terms with their
common problem. In Europe, several
nations have already taken steps to
reduce transboundary air pollution.
In North America, the President of the
United States has endorsed the proposal
to invest $5 billion to demonstrate
innovative technologies that can be used
to reduce transboundary air pollution.
And in both Europe and North America,
the diplomatic groundwork for
long-term cooperative activities has
been established.
EPA JOURNAL
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Acid Rain Research
Despite intensive research into most
aspects of acid rain, scientists still
have many areas of uncertainty and
disagreement. That is why the United
States emphasizes the importance of
further research into acid rain.
Scientific research into acid rain has
accelerated significantly in the 1980s. In
1982, the federal agencies (see box)
involved in the National Acid
Precipitation Assessment Program
(NAPAP) budgeted $14.4 million for
acid rain research. For 1987, the
President is requesting $85 million for
acid rain research: a more than fivefold
increase in as many years.
The increased funding has shown
results. Scientists today have a much
greater understanding of the chemistry
of acid rain than they did in 1980. But
they are still seeking a better grasp of
the effects of acid rain on lakes, streams,
forests, and construction materials.
National
Surface Water Survey
The National Surface Water Survey is
EPA's primary source of data on the
impact of acid rain on America's lakes
and streams. Plans for the project began
in 1983, with the first of three planned
phases completed by the fall of 1984.
The goal of Phase I was to measure
the acidity of U.S. lakes and streams. It
was not feasible to sample all the lakes
and streams in potentially susceptible
areas, so methods of statistical sampling
The National Acid
Precipitation Assessment
Program
With a dozen federal agencies
involved, acid rain research can be
complicated organizationally as
well as scientifically. To prevent
duplication of effort and foster
creative cooperation among the
agencies, the National Acid
Precipitation Assessment Program
(NAPAP) was set up in 1980.
NAPAP is chaired jointly by
EPA, the President's Council on
Environmental Quality, the
National Oceanic and Atmospheric
Administration, and the
Departments of Agriculture,
Energy, and Interior.
EPA plays a major role in
several of NAPAP's key research
initiatives:
• Expansion of the National
Trends Network, which gathers
definitive acid rain data at
monitoring stations throughout the
nation. This network currently
monitors wet deposition at 150
locations around the country, and
it is being extended to include 100
dry deposition monitoring stations.
• Investigations into
"source-receptor relationships,"
the relation between changes in
emissions and changes in
deposition levels at distant
locations. EPA's Atmospheric
Processes Program is developing
an ambitious Regional Acid
Deposition Model that will enable
scientists to predict the amounts of
acid rain resulting from given
levels of emissions. With the
model's predictive powers,
policy-makers will be able to weigh
the benefits and drawbacks of
different regulatory scenarios.
• The Delayed/Direct Response
Project, which is working to
determine the rate at which lakes
acidify and to identify factors that
hasten or retard that process, such
as the acid-neutralizing capacity of
surrounding soil. A "delayed"
response is one that takes 10 years
or longer. A "direct" response is
acidification occurring in fewer
than 10 years. Under this program,
EPA has sampled 145 watersheds
in New England with the help of
the Soil Conservation Service.
as li.
rent'
brought ;
were used to make the final selection.
Phase I data collection was divided
into three components: Eastern Lakes,
Western Lakes, and Eastern Streams.
Preliminary findings from the Eastern
Lakes Survey were made public in
August 1985.
Many people expected that more
acidic lakes would be found in the
Northeast than in other parts of the
United States. They based this
expectation on the fact that Northeast
states are downwind of the major
generators of acid rain precursors in the
Ohio River Valley.
Eastern Lake Survey teams took
samples at 763 northeast lakes. On the
basis of those samples, EPA scientists
estimated that only 3.4 percent of the
lakes sampled in the Northeast had pH
values of 5.0 or less. The comparable
figure for the Upper Midwest was also
low: 1.5 percent.
Surprisingly, Florida—far to the south
of industrial sources of acid rain—had a
much higher percentage of acidic lakes
than the Northeast and the Upper
Midwest. Over 12 percent of lakes
sampled in Florida had pH levels of 5.0
or less.
EPA believes that it is too early to
attribute this high Florida figure to the
impact of acid rain. Natural processes or
land use practices may also contribute
substantially to the acidity of many
Florida lakes.
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It took a lot of hard work to gather the
data that formed the basis of these
findings. Scientists on the helicopter
sampling crews had to cope with the
pressure of weeks of constant travel as
well as the hazards posed by erratic
weather conditions. At all times and
under all conditions, scientists had to
observe rigid test procedures to protect
the validity of their data.
Nature didn't help, either. Survey
work had to be completed in the fall,
because chemical variations within
lakes were lowest then. But during the
Western Lake Survey, premature winter
weather froze many lakes in the Rockies
and the Sierra Nevada, and snow and
high winds whipped Wyoming and
Colorado. Helicopter teams had to
curtail their flying schedules to avoid
treacherous afternoon wind storms. And
some ground teams were trapped in
blizzards and had to be rescued.
Ground teams were needed for the
Western Lake Survey because many of
the 757 lakes sampled in that part of the
country were in areas protected by the
Wilderness Act. Because the Act forbids
any mechanized means of transport in
wilderness areas, the U.S. Forest Service
would not permit EPA's flotation
helicopters to land there. Instead, Forest
Service teams had to hike to remote
lakes to complete their sampling.
The Forest Service did permit EPA to
sample 50 wilderness lakes with both
helicopter and ground-access crews,
enabling the Agency to check samples
obtained by ground crews against those
obtained by helicopter teams.
Expertise gained during Phase I of the
National Surface Water Survey is
already proving useful in Phase II,
which was initiated in the Northeast at
the end of 1985. Phase II researchers are
looking for variations in surface water
chemistry from region to region and
from season to season. They are also
planning to calculate the fish
population at selected lakes and streams
surveyed in Phase I. This data will be
valuable as scientists try to evaluate the
impact of acid rain on aquatic life.
For Phase III, EPA plans to modify a
long-term monitoring project already in
progress. The goal of Phase III will be to
identify trends in surface water
chemistry using long-term monitoring
data. The work, which is planned to
continue indefinitely, is being designed
to be adaptable to other surface water
pollution problems as well as acid
rain.
Materials Effects
Research
Scientists who specialize in the
materials effects of acid rain still don't
know how wet and dry acid deposition
affects the natural processes of decay.
One way to answer this question is to
measure tombstones. EPA recently
sponsored research into the rates of
deterioration of headstones at 18
A Day in the Life of a
National Surface Water
Survey Helicopter Team
Helicopter teams involved in
Phase I of the National Surface
Water Survey faced demanding
schedules. With nearly 1600 lakes
to sample within a few weeks in
the fall of 1984, they had to stay
on the go constantly.
When flying conditions were
good, the teams had daily
itineraries that could include as
many as six lakes within a
hundred-mile radius. Poor weather
conditions, on the other hand,
could force cancellation of an
entire day of sampling.
Just verifying the identities of
the lakes to be sampled was a big
job. Map coordinates used by the
helicopter's navigation system had
to be double-checked against U.S.
Geological Survey maps, and the
lakes had to be photographed to
further verify their identities. Once
landed on the lake surface, the
helicopters had to maintain stable
positions in the water while the
scientists took samples and
measured lake waters for depth.
pH, conductivity, temperature, and
transparency. The completed
samples were then rushed back to
mobile field laboratories, usually
by 6 or 7 p.m. The helicopter
teams could then relax for the
evening, although their usually
isolated base stations rarely offered
much in the way of recreational
activities.
But for the chemists in the field
lab trailer, the night was just
beginning. Procedures for the
survey required that the samples
be processed and filtered
immediately after their delivery to
the base station. Work in the
lab trailer often stretched long past
midnight. Chemists had to put in
extra hours to make sure the
samples were ready by daybreak
for the flight to a cooperating
laboratory, where they were
further analyzed for 20 chemical
variables.
By morning, yesterday's samples
were on their way to the lab.
Meanwhile, at another set of lakes,
the helicopter teams were
gathering additional samples. And
so the process was repeated until
1592 lakes in four areas east of the
Mississippi had been sampled. The
thousands of samples collected
during Phase I of the Surface
Water Survey will help
scientists understand much more
clearly the effects of acid rain on
aquatic ecosystems.
EPA JOURNAL
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Veterans Administration cemeteries.
Two of the cemeteries provided
particularly valuable data. One was
located in an industrial area close to
New York City, while the other was in a
semi-rural area of Long Island. New
York University had previously traced
changes in the thickness of tombstones
at both cemeteries, as well as the depth
of their emblem inscriptions. Using
these data to calculate weathering rates
at the two cemeteries, scientists
compared them with estimates of rates
of increase in SO2 in New York City
from 1880 to 1980. They found what is
known as a "linear" relation between
the two rates. In other words, increased
SO2 concentrations were directly
proportional to increased weathering
rates.
This correlation enabled scientists to
develop a formula for calculating the
damage caused to materials in the New
York area by SO2: 10 millimeters of fine
grain marble will be worn away every
century for every part per million of
SO2 in the air.
This study was the first statistically
significant proof of damage to stone
from an acid rain precursor. It would be
difficult to carry out other experiments
of this kind, because historical data on
air pollution levels are extremely rare.
But it is clear that decay accelerated by
acid deposition has ramifications far
beyond the graveyard.
Some acid rain concerns are primarily
cultural. For example, the rapid
deterioration of the Acropolis in modern
times prompted EPA to join a recently
completed NATO pilot study on the
conservation and restoration of
monuments. Scientists from 10
countries monitored acid rain damage to
monuments, developed formats and
procedures for documenting acid rain
damage, and evaluated various means of
conserving and restoring damaged
monuments.
But acid rain threatens more than
cultural artifacts. Though experts cannot
yet fix an exact dollar value to the
materials damage caused by acid rain,
they agree that it damages homes,
commercial buildings, highways,
bridges, and other structures vital to our
everyday lives. EPA is now working
with the U.S. Army Corps of Engineers
to develop a list of materials subject to
acid rain damage. This inventory will
draw together the data needed to assess
the magnitude of acid rain-induced
materials damage. Estimates should be
ready by 1990,
Forest Response Program
In the early 1980s, experts began to see
unexplained growth reductions and
foliage damage in U.S. forests. The
evidence was first spotted in New York
and New England, but similar problems
have now been detected in the
Appalachians and the Carolinas. Even
worse forest deterioration has occurred
in Europe, where whole stands of
European trees, especially on mountain
peaks, have gone into an unprecedented
decline.
Scientists are still uncertain of acid
rain's role in such instances. Many
factors other than acid rain could be
responsible for forest damage. Changes
in soil or climate could play a role, as
could changes in insect or pathogen
activity. For these reasons, among
others, the evidence for acid rain
damage to forests is thought to be
weaker than corresponding evidence of
damage to aquatic systems.
To clarify the effects of acid rain on
trees and other vegetation, EPA began
the Forest Response Project (FRP) in
1985. FRP scientists are studying the
role of acid rain and other pollutants in
causing or contributing to forest damage
in the United States, They are also
trying to determine the mechanisms
causing the damage, and the
relationship between various "doses" of
acid deposition and the "responses"
they are suspected of causing,
Initial research is studying two types
of U.S. forests that have experienced
damage or decline. The first type of
forest, common to New England and
New York, contains spruce and fir. The
second, known as "Southern
commercial," includes several species of
pines valuable to the economy of the
southeastern United States. At two sites
in New England and three sites in the
Southeast, tree's are being classified and
checked for height and radial growth.
Scientists are also conducting field
experiments to compare the growth of
trees in open-top chambers with those
in rain-exclusion chambers. Control
chambers in laboratories permit
comparable experiments with seedlings,
although it is still difficult to
extrapolate from seedlings to mature
trees.
EPA is also setting up a "Mountain
Cloud" data-gathering network to study
the effects of various acid rain patterns
on forests at differing elevations.
"Mountain Cloud" sites will be
co-located with biological stations that
measure plant growth and productivity,
as well as soil chemistry.
This work and other studies planned
for eastern hardwood forests and
western conifers should begin to give us
a clearer idea of the kind of threat acid
rain poses to the $38.5 billion forest
products industry.
The Future
Many challenges confront acid rain
scientists. There is still a need to
increase scientific understanding of the
effects of acid rain, and the rate at
which those effects occur. As yet,
scientists lack reliable methods of
extrapolating on a regional level what is
known about the effects of acid rain in
small-scale environments. They also
need to determine the level of acid
deposition that is realistically
compatible with protecting our valuable
resources. As these and other questions
are answered, we will have a much
clearer understanding of the type of
control program needed to protect all
the resources at risk from acid rain.
A videotape documentary entitled "The
National Lake Survey" is available for
loan from the Audio-Visual Division of
the EPA Office of Public Affairs (A-107),
Room 2435, 401 M Street SW,
Washington DC 20460. Phone (202J
382-2044. This 15-minute overview of
the lakes portion of the National
Surface Water Survey offers a first-hand
look at acid rain sampling in action.
-------
Control Technologies
Over the last few years, the U.S.
Gongress has considered several
pieces of legislation proposing acid rain
control programs. Most of them have
called for SO2 and NOX reductions of 8
to 10 million tons a year.
To achieve that level of control, many
existing sources of SO2 and
NOX—especially utility and industrial
coal-fired boilers—would have to be
retrofitted with control equipment. But
the availability, cost, and technical
complexity of existing retrofit controls
leave much to be desired.
Existing
Control Options
A number of different methods of
equipping new boilers with NOX
controls have been developed and
tested. But, overall, NOX control
technologies have not been
commercially retrofitted on existing
boilers as extensively as SO2 controls.
At present, there are three techniques
available for reducing the amount of
SO2 emitted from existing coal-fired
boilers: coal-switching, coal-cleaning,
and flue gas desulfurization.
Unfortunately, each of these techniques
Ohio ;
ivhf
' u LIMB ui'r pollution
has drawbacks that limit their ability to
reduce SO2 emissions by 8 to 10 million
tons per year.
A coal-burning facility could cut
down on SO2 emissions by switching
from a high-sulfur to a low-sulfur coal.
However, this fuel shift could damage
some kinds of boiler equipment. It
could also generate regional hostility by
causing shifts in existing coal markets.
A second option is for sulfur to be
cleaned from coal before it is burned.
Physical coal-cleaning technologies are
available commercially today. A
substantial amount of coal already is
being cleaned because of the savings
that result from lower shipping costs,
lower boiler-maintenance costs, and the
higher energy content of the cleaned
coal. However, coal is cleaned primarily
to rid it of ash and other
non-combustibles. Not enough SO2
could be cleaned from coal to hit the
emissions reduction target of a
large-scale acid rain control program.
Currently, there is only one
technology available that could reduce
SO2 emissions to the extent required by
an ambitious acid rain control program:
flue gas desulfurization (FGD), a process
better known as "scrubbing." FGD uses
"sorbents" such as limestone to soak up
(or "scrub") SO2 from exhaust gases.
This technology, which is capable of
reducing SO2 emissions by up to 95
percent, can be added to existing
coal-fired boilers.
FGD does have several drawbacks.
The control equipment is very
expensive and very bulky. Smaller
facilities do not always have the capital
or the space needed for FGD equipment.
Even some larger power plants would
find it technically very difficult to
retrofit FGD systems on older cramped
facilities.
Expanding Our
Control Options
The Report of the Special Envoys on
Acid Rain, presented to President
Reagan on January 8, 1986, recognized
the political and economic problems
that stem from having only a limited
menu of pollution control options. The
report stated: "The availability of
cheaper, more efficient control
technologies would improve our ability
to formulate a national response that is
politically and economically
acceptable." The Special Envoys went
on to recommend a $5 billion U.S.
program to fund the commercial
demonstration of control technologies
that promise greater emissions
reductions, lower costs, or applicability
to a wider range of existing sources.
They also recommended that special
consideration be given to projects that
have the potential to reduce SO2
emissions from existing facilities that
burn high-sulfur coal.
Over the past several years, millions
of dollars have been spent researching a
variety of innovative approaches to the
control of SO2 and NOX emissions from
existing coal-fired utility and industrial
boilers. Major federal research programs
are being funded by the Environmental
Protection Agency, the Department of
Energy, the national laboratories
(Argonne, Brookhaven, Lawrence
Berkeley, and Oak Ridge) and the
Tennessee Valley Authority. In addition,
the Electric Power Research Institute is
cooperating with different electric
utilities to improve the control of utility
boilers. This research and testing have
already generated a number of attractive
candidates for the kind of commercial
demonstrations recommended in the
Report of the Special Envoys.
The four technologies described here
represent just a few of the wide range of
potential candidates for funding as
commercial demonstration projects. The
EPA JOURNAL
-------
purpose of these projects will be to
determine whether technologies such as
these can be proven to work in existing
commercial facilities.
LIMB
The Limestone Injection Multistage
Burner (LIMB) is an emerging control
technology that can be retrofitted on a
large portion of existing coal-fired
boilers, both utility and industrial. Its
broad applicability makes it an
attractive candidate for funding under
the proposed commercial demonstration
program.
In a LIMB system, an SO2 sorbent
(e.g., limestone) is injected into a boiler
equipped with low NOX burners. The
sorbent absorbs the SO2, and the
low NOX burners limit the amount of
NOX formed. Thus, LIMB is capable of
reducing both SO2 and NOX by about 50
to 60 percent.
LIMB technology will not be applied
widely until a number of technical
problems are solved. The sorbent
injected into the boiler tends to increase
slagging and fouling, which in turn
increase operation and maintenance
costs. Because boilers retrofitted with
LIMB tend to produce more particulates
of smaller sizes, particulate control
becomes more difficult. Furthermore,
technical questions remain as to what
sorbents are most effective in a LIMB
system, and how and where to inject the
sorbents.
EPA has a major research and
development program in progress to
improve LIMB technology. A full-scale
demonstration of LIMB is underway on
a utility boiler in Lorain, OH. The
retrofitted boiler will be started up in
the spring of 1987, and the results of
early tests will help determine whether
LIMB technology is a suitable candidate
for funding under the proposed
commercial demonstration program.
In-Duct Spraying
LIMB controls SO2 and NOX emissions
during the combustion process itself. It
is also possible to control SO2 after
combustion by cleaning it out of the
exhaust gases. The scrubbers now in use
apply this kind of post-combustion
technology. If ways could be found to
reduce the technical complexity and
economic costs of scrubbing,
post-combustion controls would become
a more attractive method of reducing
SO2 emissions.
EPA, DOE, and private industry are
involved in efforts to improve flue gas
desulfurization (FGD) technology. Much
of the research focuses on the
development of more effective sorbent
materials. In addition, the possibility of
injecting a sorbent directly into existing
exhaust ductwork is being investigated.
An in-duct spray drying FGD system
would improve on traditional scrubbers
in several ways. Current scrubbers
require the construction of very large
reaction vessels where the exhaust gases
and sorbent can mix to extract the SO2.
These vessels are very expensive, and
sometimes the space they demand
simply isn't available at existing
facilities.
If, however, the sorbent could be
injected into existing ductwork, the cost
of the reaction vessel could be
eliminated, and it would be much easier
to retrofit controls on a wider range of
sources. Space constraints would no
longer be a limiting factor.
In order to test and improve in-duct
scrubbing techniques, a demonstration
control system is in the process of being
tested at a utility in Beverly, OH. The
Department of Energy plans to fund
another demonstration project in the
near future. Even if this research is
successful, it is unlikely that in-duct
FGD systems will achieve an SO2
control rate of much more than 50 to 60
percent. But if they can be retrofitted
widely and at relatively low cost,
in-duct FBC systems could join LIMB as
an attractive candidate for a commercial
demonstration program.
Reburning
Another relatively new technology
known as reburning, or fuel staging, is
capable of reducing NOX emissions in
existing boilers. In a coal-fired boiler,
reburning is accomplished by
substituting 15 to 20 percent of the coal
with natural gas or low sulfur oil and
burning it at a location downstream of
the primary combustion zone of the
boiler. Oxides of nitrogen formed in the
primary zone are reduced to nitrogen
and water vapor as they pass through
the reburn zone. Additional air is
injected downstream of the reburn zone
to complete the combustion process at a
lower temperature.
In general, NOX reductions of 50
percent or more are achievable by
reburning. When combined with other
low NOX technologies, such as low NOX
burners, NOX reductions of up to 90
percent may be achievable.
Reburning tests have been performed
by EPA on gas-, oil-, and coal-fired
research combustion systems. EPA and
the Gas Research Institute are preparing
to co-sponsor reburning tests at a large
industrial or utility coal- or oil-fired
boiler.
Fluidized Bed Combustion
Fluidized bed combustion (FBC) is an
innovative approach to SO2 and NOX
control in both utility and industrial
boilers. In an FBC boiler, pulverized
coal is burned while suspended over a
turbulent cushion of injected air. This
technique is promising from an
economic perspective, because FBC
boilers allow improved combustion
efficiencies and reduced boiler fouling
and corrosion. Such boilers also are
capable of burning different kinds of
low-grade fuels like refuse, wood bark,
and sewage sludge.
In addition, FBC offers a number of
environmental advantages. If the coal is
mixed with limestone or some other
sorbent material during combustion, the
SO2 is captured and retained in the ash.
FBC boilers have another
environmental advantage over typical
coal-fired boilers: they have the
potential to control NOX as well as SO2.
FBC boilers must operate within a
narrow temperature range (1500-1600
degrees Fahrenheit) that is substantially
lower than typical boiler temperatures.
Lower combustion temperatures
inherently limit the formation of NOX.
Thus, FBC boilers may be able to
control NOX by 50 to 75 percent at the
same time as they control SO2 by up to
90 percent.
An FBC system does have one major
drawback: it requires the construction of
a new boiler. Thus, it is more of a
replacement technology than a retrofit.
The number of existing boilers that
could be replaced with FBC boilers at
reasonable cost is limited, and its
promise is more likely to be realized on
new sources.
A Less Limited Future
Limestone injection multistage burners,
in-duct sprayers, reburners, and
fluidized bed combustion systems: these
and several other technologies are
capable of expanding the current rather
limited "menu" of acid rain control
options. If they can be proven to work
on existing commercial facilities, state
and federal lawmakers will have much
more latitude as they frame legislation
for controlling acid rain.
Clearly, it would be inefficient and
ineffective to try to implement a major
acid rain control program before
technically viable and economically
affordable technologies are available.
Thus, the proposed five-year, $5 billion
program for commercial demonstration
of acid rain control technologies fills a
very real need.
-------
Implementation Issues
Solving problems can sometimes
create problems. Take, for example,
the implementation of a major new
regulatory program. Enacted to control
one problem, it can generate many
problems of its own. If the undertaking
is complicated, expensive, and
time-consuming, it can catch state
governments unprepared.
What would happen if the U.S.
Congress passed a law controlling acid
rain? Under several bills now being
considered, experts foresee the
following difficulties:
• New reductions would probably be
required in a shorter time—and at
greater marginal cost—than those
already achieved under the Clean Air
Act.
• Requirements for control of acid rain
precursors (SO2 and NOX) could
generate conflict and confusion as to
which sources should be controlled.
Who would make these choices, and on
what grounds?
• It would be hard to develop a
convincing rationale, in terms of local
costs incurred, for an acid rain control
program because most of the
environmental benefits would accrue in
another state. Existing air pollution
programs did not face this problem,
because they tended to impose costs in
the same areas where environmental
quality was improved. Acid rain
controls, on the other hand, would be
intended to protect whole regions, but
the costs would not be spread evenly
over the region.
However, some of the cost of
controlling acid rain would be felt on a
regional scale. Controls imposed on a
utility in one state would, to varying
degrees, affect utility rates in
neighboring states, because electric
power is often generated in one state and
sold in another. There would also be
shifts in the cost of high- and low-sulfur
coal, in the cost of manufactured goods,
and in employment. These shifts would
be felt in the economies of whole
regions, not just states.
Policy-makers must consider all these
factors as they design a major acid rain
control program. They must also
recognize that a control effort will have
significant impacts on many sectors:
electric utilities as well as other
industries, public utility commissions as
well as state executive and legislative
offices. Therefore, the concerns of these
and other parties must be incorporated
into the decision-making process.
State Acid Rain Programs
To help prepare for the complexity of
implementing a major acid rain control
program, EPA has committed to work
with the states on these kinds of issues.
With a special Congressional
appropriation EPA established the State
Acid Rain (STAR) program to identify
and resolve potential problems. It is
now funding studies in 36 states on
such implementation questions as:
• How should control obligations be
allocated to individual pollution sources
so that statewide emissions reduction
targets can be met?
• What techniques are available to
control each source, and what are their
economic and social costs?
• How can the gains secured for the
environment be maintained in the
future without impeding economic
growth?
Projects in Progress
Different states and regions are using
their STAR grants in different ways.
Wisconsin, for example, has substantial
SO2 emissions in excess of the
quantitative limitation incorporated in
many acid rain control proposals.
Therefore, Wisconsin is faced with the
possibility of a very substantial
emissions reduction requirement. To
prepare for whatever may come, the
state's air pollution control officials
decided to develop complete model
programs for hypothetical statewide
emissions reductions of 30, 50, and 70
percent. The broad issues of data base,
available control techniques, control
strategy, and maintenance of achieved
emissions reductions are all being
studied.
Wisconsin's air officials, together with
those of Minnesota and Michigan, are
also studying possible tri-state
emissions reduction plans. In
recognition of the crucial role that
existing regulation of utility rates will
play in acid rain control, they are also
bringing together environmental officials
and utility regulatory officials of the
midwestern states to pool their
knowledge and coordinate their
planning.
A group of eight northeastern states
decided to look in greater depth at the
technologies available for controlling
their specific acid rain sources. They
wanted to be ready in case they needed
to prepare state or regional strategies for
controlling acid rain. They are also
beginning the essential task of
coordinating the ideas, plans, and
policies of their environmental agencies
with those of their public utility
commissions.
These northeastern states are also
studying various ways of maintaining
environmental goals while permitting
economic growth. One approach
recommends an initial period of
over-control to build up a margin of
compliance that permits later economic
growth. Another suggests offsetting
emissions from new sources with new
controls on older sources.
Another noteworthy STAR program is
being conducted by the states of
Tennessee, Kentucky, and Alabama, in
conjunction with the Tennessee Valley
Authority. This project is examining
alternative emission reduction strategies
for a multistate utility system.
State Acid Rain (or STAR) projects are
enabling environmental professionals to
study the interrelated problems that an
acid rain control program is likely to
raise, and to search for equitable and
efficient solutions. The states involved
in the STAR program have very
different views of the policy questions
raised by acid rain. Their citizens have
very different, and very large, interests
at stake. Nevertheless, the air pollution
professionals in the states and at EPA
have agreed to put any policy
disagreements to one side while they
seek answers to the questions that will
have to be resolved if any acid rain
control program is to be successfully
implemented, n
If you have any further questions about
acid rain, contact the Department of
Environment in your state or EPA's
Office of Air and Radiation, either in
Washington DC (202/382-7407) or in the
EPA regional office that serves your
community (Show map of EPA regions).
EPA JOURNAL
-------
This small pilot scale LIMB combuster,
designed to reduce both sulfur dioxide
and nitrogen oxides emissions from
coaJ-burning facilities, is being tested
with funds from EPA's Air and Energy
Engineering Research Laboratory.
-------
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