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OCR for page 12
Introduction
During the past 25 years in Europe and the past 10 years
in North America, scientific evidence has accumulated
suggesting that air pollution resulting from emissions of
hydrocarbons and oxides of sulfur and nitrogen may have
significant adverse effects on ecosystems even when the
pollutants or their reaction products are deposited from
the air in locations remote from the major sources of the
pollution (National Research Council 1981, Environment
'82 Committee 1982). Some constituents of air pollution
are acids or become acidic when they reach the Earth's
surface and interact with water, soil, or plant life.
Several studies have documented the potentially harmful
effects of the deposition of acids on ecosystems (NRC
1981, National Research Council of Canada 1981, Overrein
et al. 1980, Drablos and Tollen 1980). Although the
pollutants may be deposited in dry form or in rain, snow,
or fog, the deposition phenomenon is often called acid
rain or acid precipitation. In this report we use the
term acid deposition to encompass both wet and dry
processes.
DEPOSITION ACIDITY
An acid is a chemical substance that, in water, provides
an excess of hydrogen ions (H+) to the solution. In
solutions, the electrical charges of positively charged
ions (cations) balance those of negatively charged ions
(anions). In acid precipitation, excess hydrogen ions
are usually balanced by sulfate (SO4), nitrate
(N05), and to a lesser extent chloride (C1-) ions.
There may, in general, be other cations in addition to H+
present in precipitation. Organic acids, for example, are
12
OCR for page 13
13
found in all areas, but they are important as donors of
hydrogen ions only in remote areas where concentrations of
sulfate and nitrate are lower (Galloway et al. 1982). Acid
deposition in dry form consists of gases such as sulfur
dioxide (SO2), nitrogen oxides (NOX), and nitric acid
vapor (HNO3) as well as particles containing sulfates,
nitrates, and chlorides.
Acids occur naturally in the atmosphere because, for
example, of the dissolution of carbon dioxide (CO2) in
water or the oxidation of naturally occurring compounds of
sulfur and nitrogen. The "natural" acidity of rainwater,
measured as pH, 2 is often assumed to be pH 5.6, which is
an idealized value calculated for pure water in equilibrium
with atmospheric concentrations of CO2. However, the
presence of other naturally occurring species, such as
Sol , ammonia, organic compounds, and windblown dust, can
lead to "natural" values of pH between 4.9 and 6.5
(Charlson and Rodhe 1982, Galloway et al. 1982).
The presence of compounds of sulfur and nitrogen of
anthropogenic origin tends to increase the acidity (lower
the pH) of precipitation. More than half the acidity of
precipitation averaged over the globe may be due to natural
sources, but anthropogenic sources may dominate in some
regions. For example, in eastern North America (i.e., east
of the Mississippi River) 90 to 95 percent of precipitation
acidity may be the result of human activities, although
natural sources may also be important at times in specific
locations (U.S./Canada Work Group #2 1982).
Figure 1.1 shows the mean value of pH in precipitation
weighted by the amount of precipitation in the United
States and Canada in 1980. There are no known natural
causes that can account for either the distribution or the
value of acidity in eastern North America. The region of
highest acidity does, however, correspond to the regions of
heavy industrialization and urbanization along the Ohio
River Valley and the Eastern Seaboard, where anthropogenic
emissions of sulfur dioxide (Figure 1.2), nitrogen oxides
(Figure 1.3), and hydrocarbons are high. Figures 1.4 and
1.5 indicate the spatial distributions of sulfate and
nitrate, respectively, weighted by the amount of precipi-
tation that was deposited in North America in 1980. The
data were obtained from several monitoring networks in the
United States and Canada.
Trends in acid deposition in North America have been
difficult to discern, and data with which to assess them
are sparse. Comparisons of historical data (for example,
Cogbill and Likens 1974) have been questioned because of
OCR for page 14
14
/
~ ;
ant-- ''l:
;.7~/'
i.. ~ 4~:,~
lo.
_~__J I
FIGURE 1.1 Annual mean value of pH in precipitation weighted by the amount of
precipitation in the United States and Canada for 1980. SOURCE: U.S./Canada Work
Group #2 (1982~.
difficulties associated with comparing data obtained by
means of different experimental methods of uncertain
comparability at different sites at different times and
because of difficulties in taking into account the
influence of neutralizing substances on the data (Hanson
and Hidy 1982, Stensland and Semonin 1982). A long-term
(18-year) record of reasonably reliable data on deposition
chemistry is available at only one site in North America
(see Chapter 4).
The relationship between emissions and deposition in
North America is complicated by changes that are not
reflected in data on aggregate emissions. For example,
OCR for page 15
53.
tHI)
15
because of concern about urban air pollution in the 1960s,
there has been a tendency since then to build large new
facilities away from urban centers and to use tall stacks
to eject emissions at higher altitudes, hence promoting
dispersal and dilution of the pollutants. Pollution
control equipment installed during this period also changed
the chemical and physical characteristics of the emissions,
substantially reducing direct emissions of sulfates and
neutralizing substances in fly ash. Thus, while total
emissions of SO2 in the United States increased between
1960 and 1970, urban concentrations of SO2 decreased
(Altshuller 1980). Almost all available data on air
quality reflect urban conditions. Only recently have
extensive networks of monitors been established in rural
areas.
so2
~-
~ 220
\\ 193 I'm!
( ~ ,
Sit
~3
~ 247 ~ ~
/ ~
J 55
OCR for page 16
16
NOx
\~\'~ ~
~ 174
~ 113
231 -___
'I L _ >_ _ _ _ l_ _
76 1
131
251
_ ~_ _
~W] - .D
o
FIGURE 1.3 Representative values of NOX emmissions in the United States and
Canada in 1980 (thousands of metric tonnes). SOURCE: U.S./Canada Work Group
x3B (1982~.
ENVIRONMENTAL EFFECTS
Atmospheric deposition involves three components:
emissions, deposition, and effects on receptors. Certain
aspects of the effects of atmospheric deposition are of
particular importance for the development of effective
policies for emission control. They concern the sig-
nificance for receptors of (1) physical and chemical states
of deposited materials and (2) rates and reversibility of
acidification.
In discussing these issues, it is helpful to distinguish
between primary, secondary, and tertiary receptors accord-
ing to their proximity to the initially deposited
material. Primary receptors experience direct contact with
atmospheric pollutants. Examples are the surfaces of
OCR for page 17
1/
. A ~
.
_~ _ :.4
3-44~
, ~
.7.89-06' I ·5.
I ~
~ ·10 1
i~ ; -~z'~--~.2~'',e,~//
J ~- ~I
1~66-3 ·5.2-
l 1 4 ~ Of - - - - 1
t- - - 7_
t_ _ ~
- 1
4.8 ( \ I V L _ ~ .__-~ l-
5.3 \ ~+ ·2.2
\~_ \ rV 1 -
~ ?
~3.7
\ ~52.7
~°: it'\
1 m mole/m2 = 0.961 kg/ha
FIGURE 1.4 Spatial distribution of mean annual wet deposition of sulfate weighted
by the amount of precipitation in North America in 1980 (mmoles/m2~. SOURCE:
U.S./Canada Work Group #2 (19823.
structures and materials, the outer foliage of vegetative
canopies, and the surfaces of soils that are not protected
by vegetative canopies. Secondary receptors are subject to
wet and dry deposition indirectly and only after the pol-
lutants have been in contact with other materials. Examples
include the inner foliage of vegetative canopies, soil
underneath vegetation, and subsurface layers of exposed
soils. Tertiary receptors are even further removed from
the point of initial contact with deposition. Examples are
subsoil, underlying rock formations, streams and lakes that
receive most of their water from runoff from the watershed,
and lake and stream sediments. The rates of transfer and
mixing of materials are affected by the proximity of the
receptors to the point of initial deposition and by their
mass and other physical and chemical properties.
OCR for page 18
18
~ ~0.5
\` 4.3 · / _ 1 d _ - ~7~ ~ ~(
. 0.91 ~I_ - --- ~\
a/ ~ 3.5 ~
/ i4.~m
~ 0~
// · \~N
8.9
~w I" is
r
/.- 4-5 ·7.5 ~
(4,4- ~\~ 4. -_
it- 7- - -1_
5 . .
~N ~
F___
_ _ _1
~ _ _
T ~-- at_
14.3 ·8.7 -
1 · 7.2 1
:; _~__J
1 m mole/m2= 0.62 kg/ha
;' ;,,::
·2-0~"^": LO
14-~
_~e d~^
19. w_
~ it" b0
/
FIGURE 1.5 Spatial distribution of mean annual wet deposition of nitrate weighted
by the amount of precipitation in North America in 1980 (mmoles/m2 ). SOURCE:
U.S./Canada Work Group #2 (1982~.
Physical and Chemical States
of Deposited Materials
The effects of atmospheric deposition on primary receptors
depend on the physical state (solid, liquid, or gaseous)
and the chemical state (e.g., sulfur or nitrogen species)
of the deposited materials (NRC 1981). The physical form
of deposited material determines its availability for
reaction, whereas its chemical form determines its reac-
tivity. Tertiary receptors are less responsive to the
physical and chemical form of atmospheric deposition than
primary and secondary receptors because of dilution. The
effects of acid and acidifying ions (hydrogen, sulfate,
nitrate, and ammonium) are dependent in part on the
accompanying rates of deposition of neutralizing cations
OCR for page 19
19
(calcium). Hydrogen ions are harmful to the extent that
the receptors cannot prevent or compensate for changes in
acidity or the consequences of acidification.
Many chemical compounds of both sulfur and nitrogen are
naturally present in soils and are involved in chemical and
biological transformations in soils and vegetation. Sulfur
and nitrogen are essential nutrients required for plant
growth. There are many differences in the properties and
biological action of the compounds of the two elements, and
there are differences in the types of transformations they
undergo in the environment. Biological processes (e.g.,
metabolic action, decomposition) have a great influence on
nitrogen transformations, while both geological processes
(e.g., weathering) and microbial transformations strongly
affect the sulfur cycle. There is a larger pool of
endogenous nitrogen than of sulfur in organisms, and larger
amounts of nitrogen than sulfur are required for plant
growth. The two nutrients are closely related, so that
addition of one element to an ecosystem allows greater
biological utilization of the other (Turner and Lambert
1980). The optimum molar ratio of sulfur to nitrogen in
terrestrial ecosystems is approximately 0.03.
Nitrogen usually is efficiently metabolized in
undisturbed ecosystems (Likens et al. 1977), while sulfur
frequently is not retained by forest soils (Abrahamsen
1980). For aquatic ecosystems, therefore, sulfur is more
important for acidification than nitrogen. Alkaline as
well as acidic cations accompany the movement of sulfate
from soils to aquatic systems; consequently, acidification
of soil is more likely to occur from excessive sulfate
deposition than from excessive nitrate deposition. The
spring flush of acids into aquatic systems may, however, be
closely associated with the accumulation of nitrate and
sulfate in snowpack (Galloway and Dillon 1982, McLean 1981).
One of the important effects of acidification is the
potential mobilization of elements from soils due to
increased Volubility and subsequent uptake by vegetation or
movement to aquatic systems. Aluminum is present in bound
form in many soils, and it can be dissolved and become
available for accumulation by organisms to which it can be
toxic. Dissolution of aluminum or other metals depends on
the amount of water passing over a surface; solubility
generally is enhanced in an acidic solution. Thus heavy
rainfall exceeding surface evaporation--even with low acid
content--can mobilize ions over time. This mobilization
from the soil may be enhanced when acid-forming materials
also are deposited from the atmosphere and washed away.
OCR for page 20
20
However, insufficient understanding of the interactions
between soils and groundwater currently precludes
estimation of the rate of mobilization of metals.
Major factors determining effects of atmospheric
pollutants on forests are (1) the chemical nature and
loading of deposited elements, (2) the ion exchange
characteristics of soils, (3) the residence times and
hydrological pathways of water through the watershed, (4)
the nature and extent of existing vegetation, and (5) the
geochemical activity of bedrock and soils (Evans et al.
1981, Zinke 1980). All forest ecosystems are not expected
to respond to acid deposition in the same way.
Effects are
likely to be site-specific and dependent on the relative
contributions of external and internal sources of acidity.
Major factors determining effects of atmospheric pol-
lutants on lakes and streams are (1) the total loadings of
particular compounds, (2) hydrological pathways through the
terrestrial systems upstream of the water body, (3) the
ion-exchange characteristics of soils in terrestrial
systems upstream, (4) the residence times of water in the
terrestrial systems, and (5) the geochemical reactivity of
the bedrock and soils of the terrestrial systems.
Reversibility and Irreversibility
Ecosystems are repeatedly stressed by natural disasters,
extreme climatic and meteorological events, and human
influences such as changes in land use and pollution.
Responses may be reversible or irreversible, depending on
the stress, the receptor, and the time span of interest.
For example, a river may carve a new channel after a flood,
an effect that may be considered irreversible except by
human intervention. Over a period of hundreds of years,
however, the channel may fill with silt, so even this
effect can be "reversed." A lake may become turbid with
sediment and organic matter after a heavy rain, an effect
that usually is reversed rather rapidly by natural
processes. So the consequences of extreme events often are
reversed by natural processes over time; as a result,
considerations of the reversibility or irreversibility of
effects of acid deposition should take account of the time
span of interest.
The most common effect of stress on an ecosystem, such
as may be caused by exposure to pollutants, is retrogression
to conditions typical of an earlier stage of ecological
succession. Reduction in species diversity and simplifica
OCR for page 21
21
tion of ecosystem structure are typical responses to
pollutants (Whittaker 1975). These changes often are
accompanied by alterations in productivity. When exposures
to pollutants are reduced or eliminated, natural processes
may return systems either to their previous pathways of
succession or to different successional pathways.
The extent to which effects of acid deposition are
reversible~depends on the receptor and the type of effect.
Although there have been no clear demonstrations of effects
on terrestrial systems to date, it is reasonable to believe
that adverse effects on primary receptors are more readily
reversed than those on tertiary receptors. For example,
the yield of one annual crop might be reduced by the contact
of acidic deposition with foliage or flowers, but a sub-
sequent crop may be less severely affected if less acid is
deposited. Damage to trees and perennial plants, particu-
larly those that retain foliage for several years (most
conifers), may be less easily reversed because of the long
period required for regeneration and recovery of most woody
plants. When both the aquatic and the terrestrial eco-
systems are acidified in an area in which rates of mineral-
ization and decomposition of organic matter are low,
reversibility is unlikely.
Acid deposition results in net accumulations of certain
elements and net losses of others in ecosystems over long
time scales; the identity of the elements in each category
and their rates of change vary with the ecosystem and rates
of deposition. The effects of slow but persistent changes
may not be apparent for many generations. Signs of these
changes may be observed, but the time scales for occurrence
of irreversible changes are difficult to predict, because
the processes that produce and consume hydrogen ions and
the reactions that affect the accumulation and loss of
elements are complex and poorly understood. Extensive
regions of North America (Figure 1.6) and northern Europe
have little geochemical acid-neutralizing capacity. Perhaps
only in retrospect will we know with certainty that systems
have changed, and the reversibility of these effects by
natural processes might require far more time than the
period initially required to cause the changes due to
anthropogenic acidification.
OTHER RELATED REGIONAL AIR POLLUTION PHENOMENA
In addition to the atmospheric processes affecting acid
deposition, there are other regional air pollution
OCR for page 22
22
~R4~
art\ /' ~ ~-'Q
W! I'
FIGURE 1.6 Regions of North America with low geochemical capacity for neutral-
izing acid deposition. SOURCE: Galloway and Cowling (1978).
phenomena of consequence for environmental quality that are
related to acid deposition in that they are the result of
similar chemical and physical processes acting on the same
pollutants.
One is the occurrence of elevated concentrations of
ozone (03) in polluted air masses extending over several
hundred to a thousand kilometers (Vukovich et al. 1977,
Wolff et al. 1977). Episodes of elevated ozone occur in
summer under conditions that also lead to high atmospheric
concentrations of sulfate aerosol, which is eventually
removed by precipitation. The events are believed to be
associated with increased concentrations of precursor
gases, such as nitrogen oxides and hydrocarbons, that
undergo reactions to form oxidants under conditions of
largerscale atmospheric stagnation.
OCR for page 23
23
A second related phenomenon is the impairment of
visibility by optically dense haze extending over large
geographic areas (Trijonis and Shapland 1979). The
phenomenon, which has been recognized in the eastern United
States for some time, occurs during episodes of high
relative humidity. Degradation of visibility has also been
observed in the West (Macias et al. 1981, Trijonis 1979)
and in the Arctic (Rahn and McCaffrey 1980). Although the
optical characteristics of the atmosphere are linked to
natural climatic factors, such as relative humidity, Husar
and Patterson (1980) found an apparent association in the
historical record of changes in visibility with changes in
the combustion of fossil fuels. There seems little doubt
that sulfate aerosols and other fine particles play a
significant role in regional haze (NRC 1980). Haze in the
Arctic in winter has been attributed to long-range trans-
port of air masses polluted with sulfates and particulate
carbon from sources in northern Europe (Rahn and McCaffrey
1980).
PURPOSE OF THE STUDY
The question of what, if anything, to do about acid
deposition is a complex one, involving~generation and
interpretation of scientific evidence, assessment of risks,
costs, and benefits, and both domestic and international
political considerations.
This report deals with a small
but important part of the analysis that is currently being
conducted to answer the question--the scientific evidence
concerning the relationships between emissions of precursor
gases and deposition of potentially harmful pollutants.
Our purpose is to assess the current state of scientific
information that can be marshaled to describe those
relationships in the hope that our assessment will be
useful to decisionmakers in government and in the private
sector.
The impetus for our work has been proposals for the
adoption of policies to control emissions of sulfur dioxide
and nitrogen oxides (beyond current limitations on
emissions from new facilities) as a means of reducing acid
deposition and hence alleviating reported and anticipated
damage from that deposition. The operators of sources of
the pollution (mostly electric utilities, industrial
boilers, and motor vehicles) reasonably wish to ensure that
the costs they--and their customers--would bear as a result
of control policies are commensurate with any benefits to
OCR for page 24
maintaining the status quo.
porate uniform reductions (rollback)
24
be obtained. A critical link in the evaluation of benefits
is the estimation of the reduction in the deposition of
acids that would accompany a reduction in emissions. A
recent report by the National Research Council (NRC 1981)
concluded that current rates of deposition of hydrogen ions
should be reduced by about 50 percent (corresponding to an
increase in pa of 0.3 unit) if sensitive regions of eastern
North America are to be protected from adverse effects of
the deposition. If this goal were adopted, by how much
would emissions have to be reduced? Conversely, by how
much would deposition rates be reduced if there were
specific reductions in emission rates?
Our committee was organized to assess current scientific
understanding about atmospheric processes that might be
applied to answering these questions. Our objective was to
determine what conclusions can be drawn from the state of
knowledge late in 1982 about the relationships between
emissions and deposition. Essential facts we faced in our
work are that the subject under study is complex, the
scientific evidence is evolving, and uncertainties in
current understanding remain.
Nevertheless, our goal
required that we take account of both the theoretical
understanding and observational evidence that are available
today and make our best scientific judgment about their
meaning.
If national policy on acid deposition is to be made on
the basis of the scientific information currently avail-
able, that policy could take several forms, including
Other policies might incor
in emissions, might be
designed to achieve the maximum possible environmental
benefit, or might be carefully engineered to bring risks,
costs, and benefits into optimal balance. The different
options require scientific and technical information in
different degrees of detail. In addition, they all, to one
degree or another, must account for uncertainties in
understanding. Decisions on almost all issues of public
policy--including military affairs, the economy, and social
welfare no less than environmental issues--are routinely
made in light of uncertainties in knowledge. Provided
uncertainties are taken into account, sufficient informa-
tion is avail able for deciding what, if anything, to do
about acid deposition.
Recognizing that uncertainties in scientific under-
standing about acid deposition currently exist and that
uncertainties are likely to exist to some degree into the
future, we believe that, whatever the near-term decision on
OCR for page 25
25
acid-deposition policy, research and development should
proceed with the goal of supporting more advanced and
sophisticated future policies. Laboratory and field
research on atmospheric processes will be extremely
important in this effort. In the meantime, it seems
prudent to adopt policies that are flexible and adaptable
to the changing base of scientific understanding. As
research continues, it can be hoped that our ability to
design carefully constructed optimal strategies will
continually improve.
ORGANI ZATION OF THE REPORT
This report describes the state of knowledge as of the end
of 1982 regarding the atmospheric processes relating
emissions of precursor gases and acid deposition. It does
not include a detailed examination of the effects of acidic
or acidifying substances on ecosystems once deposited. For
such a treatment, see NRC (1981).
Chapter 2 is a general review of the current theoretical
understanding of the major atmospheric processes involved
in acid deposition: transport and dispersion, chemical
transformation, and deposition. More complete reviews are
contained in the appendixes. Chapter 3 is a general review
of the theoretical models currently used or proposed for
assessing the relationships between sources and receptors.
Chapter 4 reviews and analyzes field data on deposition in
order to develop a phenomenological understanding of acid
deposition in North America. Needed research is described
in Chapter 5. The focus of the report is on conditions in
portions of eastern North America, for which more informa-
tion is available than for regions elsewhere on the
continent.
NOTES
1. More precisely, acidity in aqueous solutions is a
function of the concentration of the hydrated hydrogen ion
.
For
convenience, we adopt the conventional notation, referring
to H3O+ as H+. In solutions, the product of the molar
concentration of HE with that of the hydroxide ion (OH-)
is approximately constant (about 10 14 at 25°C). As acid
is added to water, the concentration of H+ increases and
that of OH- decreases so that the product remains
(BOO ), which is also called the hYdronium ion.
OCR for page 26
26
constant. By an excess concentration of H+, we mea n
that the concentration of H+ is greater than that of
OH .
2. The acidity or alkalinity of a solution is
measured on the pH scale. A solution that is neutra 1
(neither acidic or alkaline) has pH 7.0. Decreasing pH
indicates increasing acidity. The pH scale is logarithm)
(pH equals the negative logarithm to the base 10 of the
hydrogen ion concentration), so a solution of pH 4.0 is
10 times more acidic than one of pH 5.0.
REFERENCES
Abrahamsen, F. 1980. Acid precipitation, plant nutrients
and forest growth. Pp. 58-63 in Proceedings of the
International Conference on Ecological Impact of Acid
Precipitation, D. Drablos and A. Tollan, eds. Oslo:
SNSF Project. Norwegian Council for Scientific and
Industrial Research.
Altshuller, A.P. 1980. Seasonal and episodic trends in
sulfate concentrations (1963-1978) in the easter n
United States. Environ. Sci. Technol. 14:1337-1348.
Charlson, R.J., and H. Rodhe. 1982. Factors controlling
the acidity of natural rainwater, Nature 295:683-685.
Cogbill, C.V., and G.E. Likens. 1974. Acid precipitation
in the northeastern United States. Water Resources
Res. 10:1133-1137.
Cronan, C.S. 1980. Consequences of sulfuric acid inputs
to a forest soil. Pp. 336-343 in Atmospheric Sulfur
Deposition: Envirorunent Impact and Health Effects,
D.S. Shriner, C.R. Richard, and S.E. Lindberg, eds.
Ann Arbor, Mich.: Ann Arbor Science Publishers.
Drablos, D., and A. Tollan, eds. 1980. Proceedings of the
International Conference on Ecological Impact of Acid
Precipitation, Sandefjord, Norway, March 11-14, 1980.
Oslo: SNSF Project. Norwegian Council for Scientific
and Industrial Research.
Environment '82 Committee. 1982. Acidification Today and
Tomorrow. Translated by S. Harper. Stockholm: Swedish
Ministry of Agriculture.
Evans, L.S., G.R. Hendry, D.J. Stensland, D.W. Johnson,
and A.J. Francis. 1980. Acid precipitation:
considerations for an air quality standard. Water,
Air, Soil Pollut. 16:469-509.
Galloway, J.N., and E.B. Cowling. 1978. The effects of
precipitation on aquatic and terrestrial ecosystems:
c
OCR for page 27
27
a proposed precipitation chemistry network. J. Air
Poll. Control Assoc. 28:229-235.
Galloway, J.N., and P.J. Dillon. 1982. Effects of acidic
deposition: the importance of nitrogen. Stockholm
Conference on Acidification of the Environment.
Stockholm: Swedish Ministry of Agriculture.
Galloway, J.N., G.E. Likens, W.C. Keene, and J.M. Miller
1982. The composition of precipitation in remote areas
of the world. J. Geophys. Res. 11:8771-8786.
Hansen, D.A., and G.M. Hidy. 1982. Review of questions
regarding rain acidity data. Atmos. Environ.
15:1597-1604.
Husar, R.B., and D.E. Patterson. 1980. Regional scale air
pollution: source and effects. Ann. N.Y. Acad. Sci.
338:399-417.
Last, F.T., G.E. Likens, B. Ulrich, and L. Walloe. 1980.
Acid precipitation--progress and problems. Pp. 10-12
in Proceedings of the International Conference on
Ecological Impact of Acid Precipitation, D. Drablos
and A. Tollan, eds. Oslo: SNSF Project. Norwegian
Council for Scientific Research.
Likens, G.E., F.H. Bormann, R.S. Pierce, J.S. Eaton, and
N.M. Johnson. 1977. Biogeochemistry of a Forested
Ecosystem. New York: Springer-Verlag.
Macias, E., J. Zwicker, and W.W. White. 1981. Regional
haze case studies in the southwestern U.S. II. Source
contributions. Atmos. Environ. 15:1987-1999.
McLean, R.A.N. 1981. The relative contribution of
sulfuric and nitric acids in acid rain to the
acidification of the ecosystem: implications for
control strategies. J. Air Pollut. Control Assoc.
31:1184-1187.
National Research Council. 1980. Controlling Airborne
.
Particles. Washington, D.C.: National Academy Press.
National Research Council. 1981. Atmosphere-Biosphere
Interactions: Toward a Better Understanding of the
Ecological Consequences of Fossil Fuel Combustion.
Washington, D.C.: National Academy Press.
National Research Council of Canada. 1981. Acidification
in the Canadian aquatic environment: scientific
criteria for assessing the effects of acid deposition
on aquatic ecosystems. NRCC No. 18475. Ottawa:
National Research Council of Canada.
Overrein, L.H., N.M. Seip, and A. Tollan. 1980. Acid
Precipitation--Effects on Forest and Fish. Final
report of the SNSF Project 1972-1980. Oslo: Norwegian
Council for Scientific and Industrial Research.
OCR for page 28
28
Rahn, R., and R. McCaffrey. 1980. On the origin and
transport of the winter arctic aerosol. Ann. N.Y.
Acad. Sci. 338:486-S03.
Stensland, G.J., and R.G. Semonin. 1982. Another
interpretation of the pH trend in the United States.
Bull. Am. Meteorol. Soc. 63:1277-1284.
Trijonis, J. 1979. Visibility in the Southwest--an
explanation of the historical data base. Atmos.
Environ. 13:833-844.
Trijonis, J., and R. Shapland. 1979. Existing Visibility
in the U.S. Report EPA 450/5-79-010. Research Triangle
Park, N.C.: U.S. Environmental Protection Agency.
Turner, J., and M.J. Lambert. 1980. Sulfur nutrition of
forests. Pp. 321-333 in Atmospheric Sulfur
Deposition: Environment Impact and Health Effects,
D.S. Shriner, C.R. Richard, and S.E. Lindberg, eds.
Ann Arbor, Mich.: Ann Arbor Science Publishers.
U.S./Canada Work Group #2. 1982. Atmospheric Science and
Analysis. Final Report. H.L. Ferguson and L. Machta,
cochairmen. Washington, D.C.: U.S. Environmental
Protection Agency.
U.S./Canada Work Group #3B. 1982. Emissions, Costs and
Engineering Assessment. Final Report. M.E. Rivers and
K.W. Riegel, cochairmen. Washington, D.C.: U.S.
Environmental Protection Agency.
Ulrich, B. 1980. Production and consumption of hydrogen
ions in the ecosphere. Pp. 225-282 in Effects of Acid
Precipitation on Terrestrial Ecosystems, T.C.
Hutchinson and M. Havas, eds. New York: Plenum Press.
Vukovich, F.M., W. Bach, B. Crissman, and W. King. 1977.
On the relationship between high ozone in the rural
surface layer and high pressure systems. Atmos.
Environ. 11:967-984.
Whittaker, R.H. 1975. Communities and Ecosystems. 2nd ed.
New York: Macmillan Publishing Company.
Wolff, G., P.J. Lioy, G. Wright, R. Meyers, and R.
Cederwall. 1977. An investigation of long range
transport of ozone across the midwestern and eastern
U.S. Atmos. Environ. 11:709-802.
Zinke, P.J. 1980. Influence of chronic air pollution on
mineral cycling in forests. Pp. 88-99 in Proceedings
of the Symposium on Effects of Air Pollutants on
Mediterranean and Temperate Forest Ecosystems.
General Technical Report PSW-43. Pacific Southwest
Forest and Range Experiment Station, U.S. Forest
Service. Washington, D.C.: U.S. Department of
Agriculture.
Representative terms from entire chapter:
acid precipitation
