SECTION 5: ENVIRONMENTAL EFFECTS OF PARTICULATE
MATTER
This section with the environmental effects of particulate matter. We begin by recapitulating
some basic information regarding particulate matter composition and then define the scope of
this review. The main environmental effects of PM are expected to be those from acid deposition, impaired visibility, and ozone. Reduction of fine PM levels quantifiably improves visibility
and reduces ozone levels, but the effects on levels of acid deposition are unclear. Paradoxically,
the effects of acid deposition are the most well-studied. In addition, the effects of acid deposition
are widespread, affecting urban area, rural landscapes and natural ecosystems, while problems
associated with visibility and ozone are more likely to be localized. The difficulty in assessing
the economic costs and benefits to the environment of reducing particulate matter concentrations
lies in the uncertainty of dose-response pathways as well as the difficulty of assigning economic
value to ecological systems, services and processes.
5.1 Introduction
The history of air quality management includes many examples of society’s responses to pollution. During the Middle Ages in London the ever-present cloud of dust and soot and its effects on
human health led to prohibition on coal burning. During the Industrial Revolution, air pollution
was generally considered a municipal problem rather than a public health issue and was managed
on a local level, which continued well into the 20th century. The emergence of air pollution as a
public health issue in the 1950s led to the development of federally funded research programs,
culminating in the Clean Air Act and establishment of the EPA in 1970.
Around the world, countries were developing institutional responses to combat the air pollution
threat to human health. The effect of air pollution on ecology, however, was not yet considered a
serious issue. Having been first documented in England at the end of the 19th century, acid rain
and its ecological effects became regional issues in northwestern Europe and in the northeastern
United States in the late 1960s. The mounting anecdotal evidence of its harmful effects on
aquatic and terrestrial ecosystems launched acid rain as perhaps the first air pollution threat to
the environment to the environment to receive international attention.
Before we continue, we would like to define two basic terms. In the literature, there is often
some confusion over the use and meaning of environmental versus ecological effects. Generally,
environment refers to all aspects of one’s surroundings, both living and non-living. Ecological
effects are strictly limited to living organisms and the interactions between them. In this section,
we use environment to include urban landscapes as well as agricultural, rural and natural areas.
Our discussion of ecological effects refers only to “natural areas”, e.g. non-urban, nonagricultural systems.
As reviewed in Section 1, there are two major categories of particulate matter (PM), PM 10 and
PM2.5. Particulate matter is composed of a mixture of particles directly emitted into the air and
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particles formed in the air from the chemical transformation of gaseous pollutants (secondary
particles). The principle types of directly emitted particles are soil-related particles and organic
and elemental carbon particles from the combustion of fossil fuels and biomass materials. Secondary particles are primarily ammonium sulfate and nitrate formed in the air from gaseous
emissions of sulfur dioxide (SO2) and oxides of nitrogen (NOx) reacting with ammonia (NH3)
(EPA, 1997a). In eastern urban areas, almost 50% of ambient PM2.5 levels can be composed of
sulfate, and another 10 to 15% of nitrate. Soil-related particles make up only 5% of ambient
PM2.5 levels, with combustion-related particles making up the remaining 35%. This is markedly
different from the composition of fine particulate matter (PM2.5) in other areas of the continental
US, where most PM2.5 comes from combustion-related sources. The composition of PM10 (coarse
particulate matter) in eastern urban areas differs from the composition of PM2.5 especially in the
proportion of soil-related particles (31% of ambient measurements), with correspondingly lower
proportions of PM10 from combustion-related activities (26%) and sulfate (34%).
Like most environmental problems, the effects of particulate matter are complex. In addition to
the effects of the principle components (the already-mentioned directly emitted and secondary
compounds) themselves, some compounds react with other particles to form reaction products
with important effects. One of these important reaction products is trophospheric ozone.
The very different chemical natures of the major components of PM2.5 have very different effects
on the human environment. We have identified the major effects of fine particulate matter as
being changes in visibility, acid deposition, and ozone. In the following sections, we consider
each of those effects separately. We begin by reviewing the contribution of fine PM to each of
the effects, and then discuss those effects for urban, agricultural and ecological systems. Since
the effects of acid deposition are the most acute and well-studied, we concentrate a large part of
this section to its effects in natural ecosystems, focussing on New Jersey’s most sensitive and
unique ecosystems, freshwater, estuarine and coastal waterways, and the Pine Barrens.
5.2 Acid Deposition
The fine particulate matter and acid deposition issues are closely linked in the eastern United
States. Both share the same dominance of large sulfate fraction in the chemical composition of
collected. Samples. Sulfates are a significant component of fine particles in the East and have
been directly linked to ecosystem damage. Both direct emissions of particulate matter and secondary particle formation caused by oxidation of sulfur dioxide, nitrogen dioxide and aerosol organic carbon species contribute to overall levels of airborne particles. In urban environments this
greatly affects many construction materials and paints, while its effects in agricultural and natural ecosystems range from reduced productivity to disruption of nutrient cycles to the massive
summer fish kills of Chesapeake Bay and Long Island Sound observed through the last two decades.
5.2.1 Urban environment: materials
The deposition of airborne particles on the surface of building materials and culturally important
articles can cause damage and soiling, thus reducing the life usefulness and aesthetic appeal of
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such structures (National Research Council, 1979). Furthermore, the presence of particles on surfaces may also exacerbate the physical and chemical degradation of materials that normally occur when these materials are exposed to factors such as sun, wind, temperature fluctuations and
moisture. Beyond these effects, particles, whether suspended in the atmosphere, or already deposited on a surface, also adsorb or absorb acidic gases from other pollutants like sulfur dioxide
(SO2) and nitrogen dioxide (NO2), thus serving as nucleation sites for these gases. The deposition
of “acidified” particles on a susceptible material surface is capable of accelerating chemical degradation of the material. Therefore, concerns about effects of particles on materials are related
both to impacts on aesthetic appeal and physical damage to material surfaces, both of which may
have serious economic consequences. Insufficient data are available regarding perceptions
thresholds with respect to pollutant concentration, particle size, and chemical composition to determine the relative roles these factors play in contributing to materials damage.
This section briefly discusses the effects of particle exposure on the aesthetic appeal and physical
damage to different types of building materials: metals, paints, stone and cement, and then summarizes these effects and their possible economic relevance. For more detailed discussion of the
effects of acid gases on materials, see the 1991 National Acid Precipitation Assessment Program
report (Baedecker et al., 1991).
Available information supports the fact that exposure to acid-forming aerosols promotes the corrosion of metals beyond the corrosion rates expected from exposure to natural environmental
elements (see Box H). Metals undergo corrosion in the absence of pollutant exposure through a
series of physical chemical and biological interactions involving moisture, temperature, oxygen
and various types of biological agents. In addition to these environmental factors, atmospheric
pollutant exposure may accelerate the corrosion process. The rate of corrosion is dependent on
deposition rate and the nature of the pollutant, the variability in electrochemical reactions, the
amount of moisture present, the presence and concentration of other surface electrolytes and the
orientation of the metal surface.
Acid-forming aerosols have been found to limit the life expectancy of paints by causing discolorations, loss of gloss, and loss of thickness of the paint film layer. Various building stones and
cement products are damaged from exposure to acid-forming aerosols. However, the extent of
damage to building stones and cement products produced by pollutants, beyond that expected as
part of the natural weathering process, is uncertain.
A significant detrimental effect of particle pollution is the soiling of painted surfaces and other
building materials. Soiling is defined as a degradation mechanism that can be remedied by
cleaning or washing, and depending on the soiled surface, repainting. Available data on pollution
exposure indicates that particles can result in increased cleaning frequency of the exposed surface, and may reduce the life usefulness of the material soiled. Data on the effects of particulate
matter on other surfaces are not as well understood.
Several types of economic losses result from materials damage and soiling. Financial or out-ofpocket losses include the reduction in service life of a material, decreased utility, substitution of
a more expensive material, losses due to an inferior substitute, protection of susceptible materials, and additional required maintenance, including cleaning. Economic losses from pollutant
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exposure can be estimated using a damage function approach or using direct economic methods.
It is, however, difficult to estimate fully the financial losses because reliable information is not
available on many economically important materials. Another major problem is the inability to
separate pollutant effects from natural weathering processes. Attempts have been made to quantify the pollutants exposure levels at which materials damage and soiling have been perceived.
However, to date, insufficient data are available to advance our knowledge regarding perception
thresholds with respect to pollutant concentrations, particle size and chemical composition.
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BOX H: THE EFFECT OF ACID DEPOSITION ON MATERIALS
Iron, steel and steel alloys. The rate of corrosion is related to the amount of SO2 in the atmosphere. The rate of corrosion
was also found to depend on the deposition rate of SO2. A separate study (Butlin et al., 1992a) showed that corrosion of
steel samples under natural meteorological conditions was highly correlated with long-term SO2 concentrations and only
minimally related to nitrogen oxides. Stainless steels, incorporating chromium, molybdenum and nickel, are highly corrosion resistant because of the protective properties of the oxide corrosive film.
Aluminum. Aluminum is generally considered corrosion-resistant.
Copper and copper patinas. A study in the New York area on the chemical composition of patinas concluded that longterm corrosion of copper was not controlled by deposition of pollutants, but rather, it was likely controlled by availability
of copper to react with deposited pollutants (Graedel et al., 1987). The patina, that is mostly basic sulfate, is not readily
dissolved by acids and thus provides significant protection for the substrate metal. However, this patina can take as long
as 5 years to form and varies with meteorological conditions. In bronze, as with many metals, dry deposition between rain
events was concluded to dominate soluble corrosion. For copper and copper alloys, though, if the patina color has aesthetic value, and SO2 accelerates the formation, then the presence of SO2 may be beneficial.
The effects of dust alone. Only limited information is available on the effects of particles alone on metals. Barton (1958)
found that dust contributed to the early stages of metal corrosion. The effect of dust was lessened as the rust layer was
formed. Other studies report that particles, by forming nuclei for the concentration of active ionic species, increase the
corrosion rate of SO2. A laboratory study of the synergistic effects of different types of particles and SOx on the corrosion
of aluminum, iron and zinc showed that four most aggressive species of particles were salt and salt/sand from marine and
de-iced locations, ash from iron smelters, ash from municipal incinerators and coal mine dusts.
Paints. Paints, opaque film coatings, are by far the dominant class of manmade materials exposed to air pollutants in both
indoor and outdoor environments. Paints are used as decorative coverings and protective coatings against environmental
elements on a variety of finished including woods, metals, cement and asphalt. Paints primarily consist of two components: the film forming component and the pigments. Paints undergo natural weathering processes from exposure to environmental factors such as sunlight, moisture, fungi and varying temperatures. Evidence exists that pollutants affect the
durability of paint (National Resources Council, 1979). Paint films permeable to water are also susceptible to penetration
by SO2 and SO42- aerosols (PM). Unpigmented polymer films have a large range of permeabilities but polymers used in
paint formulations do not generally form barriers to SO2 either in the gaseous state or in solution as sulfurous acid. There
appears to be little degradation to the polymer itself from SO2 at low concentrations. A controlled exposure study was
conducted to determine the effects of gaseous pollutants on four classes of exterior paints: oil-base house paint, vinylacrylic house paint, and vinyl and acrylic coatings for metals (Spence et al., 1975). SO2 and relative humidity markedly
affect the erosion of oil-based house paint. The presence of NO2 increased the weight of the paint film. Blisters formed on
acrylic latex house paint at high SO2 levels. The vinyl and acrylic coating are resistant to SO2. In addition, the weathering
of wood prior to painting decreases paint adhesion.
Automobile finishes. Reports indicate that particles can cause damage to automobile finishes. The formulation of the
paint will affect the paint’s durability under exposure to varying environmental factors and pollution. However, failure of
the paint system results in the need for more frequent repainting and additional cost. The New York area, which includes
northeastern New Jersey, with California, has the highest costs associated with paint soiling.
Stone and cement. In general, stone containing lime is especially susceptible to the effects of acid deposition. There can
be facilitating effects between different constituents of particulate matter. For instance, marble in cemeteries in the Los
Angeles basin showed that SO2 is more reactive with the calcium in marble under high NO2 conditions.
Soiling. An additional, significant and detrimental effect of particle pollution is the soiling of man-made surfaces. The
black crust found in the protected areas of buildings is formed from a hard crust of gypsum mixed with dust, aerosols and
carbonaceous particles. Increased frequency of cleaning, washing or repainting over soiled surfaces becomes an economic
burden and can reduce the life usefulness of the material soiled. A study of repainting frequency and particulate concentration found that houses in Steubenville, OH, where PM concentrations average 235 µm per year, needed to be repainted
every year. Fairfax, VA, on the other hand, had a mean annual PM concentration of 60 µm/m3; the time between repainting was generally 4 years.
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5.2.2 Acid deposition and natural ecosystems in New Jersey
New Jersey consists of 19% wetlands and 42% forest area. Its five physiological regions (Figure
5-1) sustain a wildlife abundance and diversity that is exceeded only by a few states. Within the
course of a year over 430 bird species can be sighted, ranking the state species list as fourth in
the nation, surpassed only by the much larger states of Texas, California, and Florida. New Jersey has more than 75 mammal species and over 40 species of reptiles and amphibians. Because
of its latitude, the state has an extraordinary blend of northern and southern animal and plant
species that reach their limit of the ranges here. Because New Jersey is the fourth smallest and
most densely populated state in the nation, many environmental problems surface and need to be
solved here first (Kane et al, 1992).
Today, air pollution is a major global environmental problem. In Europe about half the air pollution crosses borders and kills fish, trees and corrodes buildings and monuments. Governments in
Europe have responded to this problem by collaborating within the Long-Range Transboundary
Air Pollution (LRTAP) Convention, as well as by taking measures within the European Community and at the national level (Levy, 1993). Central to the work plan is the idea to use critical
loads as the basis of LRTAP protocols in order to manage transborder pollutants. A critical load
is defined as “a quantitative estimate of exposure to one or more pollutants below which significant harmful effects on specified sensitive elements of the environment do not occur according to
the present knowledge”. Critical loads focus negotiators’ attention on scientific issues. Using
dose-response data on soils, vegetation and freshwaters, national focal centers are preparing
critical load maps for sulfur nitrogen and total acidity. Critical loads vary a great deal across
Europe because ecological sensitivity is highly dependent on geology and weather conditions.
Therefore in order to determine the critical load, each country focuses on its most sensitive ecosystem. We apply this idea to the ecosystems of New Jersey and focus on what we think are the
most sensitive ecosystems in the state: aquatic ecosystems and the Pine Barrens.
The effects of deposition on sensitive receptors can range from days to centuries. Ecosystems are
complex systems that are simultaneously responding to a variety of inputs, such as climate, landuse patterns and other pollutants besides sulfur and nitrogen oxides. These multiple stressors can
result in chemical changes within the ecosystem, which can exhibit long lag times before manifesting a response. Therefore, in many effect areas, responses to current reductions will not be
expected for many years. Monitoring the changes in the effects areas over time will be necessary
to determine whether the expected benefits are realized.
5.2.3 Aquatic ecosystems
The following section describes the basic chemical principles behind how acid deposition produces the observed effects in aquatic systems. Due to the different chemical properties of fresh
and salt water, the major observed effects of acid deposition in freshwater and saltwater systems
are fairly different and are treated under separate subheadings.
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Figure 5-1. Physiographic Regions of New Jersey
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If there is a change in the concentration of an anion contributed by acid deposition (e.g., sulfate
or nitrate), then other anions and/or cation concentrations must also change, such that the total
concentration of anions always equals the total concentration of cations in the surface water. This
is called the principle of electroneutrality, whereby positive and negative ions are found in equal
amounts. Thus, if acid deposition causes sulfate and nitrate concentrations to increase, then some
or all of the following changes will also occur:
•
Bicarbonate anion decreases, which causes a reduction in acid neutralizing capacity
•
Base cations (calcium, magnesium, sodium, potassium) increase, which prevent or
minimize acidification of drainage waters, but may deplete soil reserves and affect
forest growth
•
Hydrogen cation increases (decrease pH), which can adversely affect aquatic biota
•
Aluminum cation increases which can negatively affect aquatic biota
If a reduction in acid deposition causes sulfate and nitrate concentrations to decrease, the
changes opposite to those enumerated above will also occur. An increase in the concentration of
base cations in drainage waters as a consequence of acid deposition has both positive and negative connotations. Removal of base cations from soils to balance sulfate or nitrate from acid
deposition minimizes the extent of surface water acidification. Over time, however, base cation
reserves in the soils can become depleted if they are lost from the soils faster than they are supplied from atmospheric inputs and weathering. This can delay acidification recovery (NAPAP,
1998).
Although it is too early to detect specific changes in aquatic systems from emission reductions
under Title IV, significant progress has been made since 1990 in refining understanding of the
acidification process and quantifying dose-response relationships. This information improves
model forecasts of anticipated change in aquatic systems due to reduced emissions. Particular
areas include naturally occurring organic acidity, the depletion of base cation reserves from soils,
nitrogen dynamics in forest and alpine ecosystems, interactions between acid deposition and land
use, and the role of aluminum in fisheries response.
Rivers, streams and lakes
The concentration of sulfate in surface waters has decreased in many lakes and streams over the
past 10-20 years. This decrease has been caused by reductions in emissions and subsequent decreases in atmospheric deposition of sulfur on a regional basis in the United States during that
period. In parts of the northeastern United States, approximate reductions of 15% in sulfate concentrations of lakes and streams have been measured in recent years (NAPAP, 1998) . Sulfate
concentrations are expected to continue to decline in the Northeast. Exactly how that will affect
surface water acidity and biological recovery is uncertain and will require continued monitoring.
On the other hand, lakes in New England do appear to show statistically significant recovery in
acid-neutralizing capability as a result of sulfate reductions. However, the majority of Adirondack lakes have remained fairly constant, while the sensitive Adirondack lakes continue to acidify (Bulger et al., 1998).
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Concurrent changes in the concentrations of other chemical parameters have been generally less
clear and less consistent than for sulfate and base cations. There other parameters are more
strongly influenced by factors other than atmospheric deposition. Concentrations of key chemical
parameters often vary per season by more than can be accounted for by acid deposition. Seasonal
variability is particularly problematic in determining long-term trends. Continued monthly
monitoring of different types of lakes and streams located in sensitive regions will provide much
needed data on seasonal variability.
Adverse effects on fish populations and communities of chronically acidified streams comes
from Shenandoah National Park (Virginia). Fish species richness, population density, condition
factor, age distribution, size and bioassay survival were all reduced in streams with low acidneutralizing capacity, as compared to those with intermediate and high acid neutralizing capabilities (Bulger et al., 1998).
A study of 13 streams in the Adirondack and Catskill Mountains showed long-term adverse episodic effects on fish populations. Streams with suitable chemistry during low flow, but low pH
and high aluminum levels during high flow, had substantially lower numbers and biomass of
brook trout than were found in nonacidic streams. Streams having acidic episodes showed significant fish mortality. A study of coastal plain streams indicated that larval mortality of river
herring due to episodic acidification may be substantial during wet years, which exhibit more
frequent and severe episodes. Episodic acidification may also be relevant to certain kinds of
lakes, depending on the magnitude and duration of the spring snowmelt period. Rainbow trout
are sensitive to acidification not because of acidity itself, but because of elevated aluminum concentrations due to low pH levels (lower than 5.0). Aluminum accumulates on gills and disrupts
gill ion transport and respiratory function (NAPAP, 1998).
Estuaries and near-coastal waters
It is now obvious that ammonium and nitrate deposition are central concerns to the health of
coastal ecosystems. Although these species are major contributors to acid deposition, their main
environmental consequence is eutrophication of coastal waters. The problem is not just deposition to the water bodies themselves, but the transport of airborne nitrogen species through surrounding watersheds, streams, ground water into the water bodies that become overenriched with
nutrients. Depending on the water body in question, atmospheric deposition is likely to account
for as much as 30-40% of the total nutrient loading received.
Nitrogen is the limiting nutrient for the growth of algae in many estuaries and near-coastal systems, rather than phosphorus, which typically limits algal growth in freshwater systems. Chesapeake Bay is the nation’s largest estuarine system, with a watershed of almost 64,000 square
miles, encompassing one-sixth of the Eastern Seaboard. The Bay has an important fish and shellfish industry and serves as a nursery for marine commercial and sport fish. There has been considerable research and monitoring on the effects of nitrogen and phosphorus loading to Chesapeake Bay. New Jersey’s southern shore borders Delaware Bay, which has experienced many
problems similar to those of the Chesapeake. Changes in atmospheric nitrogen deposition can
have significant impacts on aquatic biology. Excess nitrogen entering the Bay produces algal
blooms that block sunlight needed for submerged aquatic grasses, and the decomposition of excess algae depletes life-sustaining oxygen needed by invertebrates inhabiting bottom waters. The
best estimates of atmospheric nitrogen loads to Chesapeake Bay and other estuaries along the
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Atlantic and gulf Coasts range from 10% to 45% of the total nitrogen inputs from all sources.
Additional research is needed to quantify the current effects and the expected benefits from reducing nitrogen deposition on estuary systems.
5.2.4 New Jersey Pine Barrens
The Pine Barrens of New Jersey are unique and of global interest. The Pine Barrens region, or
Pinelands, is a large, mostly forested region that harbors many unique plant and animal species.
Ecologically, it consists of some 2000 to 2250 square miles of generally flat, sandy, acidic, and
sterile soils which constitute a major part of the Outer Coastal Plain section of the Atlantic
Coastal Plain in New Jersey (Boyd, 1991). For a detailed description of this ecosystem see Forman (1979). In addition to agriculture, some of the principle uses of the Pine Barrens are recreational: camping, canoeing, hiking and hunting. Another important use is valuable scientific research.
The possible impacts of acid deposition on the vegetation of the Pine Barrens, and upon plant
and animal life in its streams are currently under study by the Division of Pinelands Research at
Rutgers University. The nature and source of acid rain is changing the type of acidity in Pine
Barrens streams from organic to mineral. This is shown by increased levels of sulfate in the water and decreased concentrations of dissolved organic matter. The acidity characteristic of soils in
the Pine Barrens is created when decaying vegetation produces an organic acid that washes down
through and is absorbed by sandy soils. These organic acids leach out aluminum found in Pineland soils, making it harmless in Pine Barren waters. However, the sulfuric acids in acid rain do
not bond with aluminum, so this mineral is washed, in its pure form, into streams (Morgan,
1984). It is concluded that the pollution caused by these increased sulfates, nitrates, and aluminum may be toxic to aquatic life, but long-term effects of this pollution are unknown at this time
(Section 5.4.3.1 discusses the toxic effects of aluminum on fish in freshwater streams). Acid
deposition has also been shown to increase levels of mercury and nitrate in pine needles and
other vegetation. Animals eating this vegetation will tend to concentrate those toxic compounds
in their body tissues, possibly increasing mortality. While the physiological pathways for increased plant adsorption of these toxins are well-known, the mechanism by which they accumulate in animals and the effects on morbidity and mortality have not been rigorously demonstrated
and await further scientific evidence.
Significant impacts of acid deposition on forest health have not been detected in the southern
pine and pine-hardwood region, to which the New Jersey Pine Barrens are similar. However,
acid deposition is a major contributor to the depletion of base cations in many poorly buffered
soils supporting southern pines and will, most likely, over the long term (decades), impede productivity. Short-term positive effects on growth are expected for some nitrogen-deficient soils,
while negative effects are expected to be limited to the most acidic, base-depleted soils.
A synthesis of studies that originated as part of a NAPAP to evaluate the sensitivity of southern
pines to acid deposition and ozone has now been completed. In chamber studies, saplings of the
three principle commercial pine species (loblolly, shortleaf, and slash pine) were exposed to
simulated acid rainfall and ozone. Maximum annual growth reductions in saplings due to due to
ambient ozone were quite small (2-5%), but the yield could be significantly reduced over the
longer time frames. Growth rates of saplings typically responded positively to ambient levels
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acid rainfall. However, longer-term exposures are expected to have cumulative negative effects
on soil nutrition. While these impacts will most likely have negative long-term consequences, the
inputs of atmospheric sources of nitrogen to many soils with low nitrogen reserves should have
small cumulative positive effects on productivity for as long as decades (NAPAP, 1998).
5.2.5 Trends in acid deposition
Title IV of the 1990 Clean Air Act Amendments (CAAA) requires the reduction of acid rain precursors—namely, emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) from electric
utilities. Emissions of SO2 in the United States have decreased significantly since the enactment
of Title IV of the Clean Air Act, from 26 million tons per year in 1980 to18 million tons in 1995.
Most, if not all, of those reductions in SO2 emissions have come from reductions in the emissions of Phase I utilities, especially electric utilities. Seasonal trends in fine-particulate sulfur
show increases for the summer months and slight decreases during the winter in Great Smokey
Mountains and Shenandoah National Parks from 1982 to 1994. Total Sulfur Ambient Air Concentrations from 1989 to 1995 have decreased an average of 30% (NAPAP, 1998). While annual
mean pH of precipitation in New Jersey continues to be very low (4.3), the total annual deposition of sulfate ions (kg/ha) is below the threshold considered to be detrimental to natural ecosystems (20 kg/ha).
Analysis of the 1995 wet deposition monitoring data demonstrates that the 1995 reduction in
SO2 emissions in the Midwestern and northeastern United States resulted in a substantial reduction of the acidity and sulfate concentration of precipitation in those regions. Unlike sulfate and
hydrogen ions, nitrate concentrations in 1995 were greater than estimated concentrations at most
of the sites in the eastern and western regions of the country. This is not unexpected, since implementation of Title IV NOx reductions only began in January 1996.
In 1995, dry deposition rates of sulfur at State College, Pennsylvania, decreased to their lowest
rates since 1986. Deposition rates of nitrogen have slowly increased. Current capabilities for understanding the processes controlling dry deposition are still exploratory. Work conducted in the
United States on dry deposition of SO2 indicates that the historic evaluation of dry deposition of
gaseous sulfur may underestimate actual rates, perhaps as much as 15-20%, depending on the
site.
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5.3 Visibility
The National Research Council’s Committee on Haze in National Parks and Wilderness Areas
said, “Visibility is the degree to which the atmosphere is transparent to visible light.” Section
169A of the 1977 Clean Air Act (CAA) Amendments (42 U.S.C. 7491) and the 1979 Report to
Congress (U.S. Environmental Protection Agency, 1979) define visibility impairment as a reduction in visual range and atmospheric discoloration. Equating visibility to the visual range is
consistent with historical visibility measurements at airports, where human observers recorded
the greatest distance at which one of a number of pre-selected targets could be perceived.
Visibility may also be defined as the clarity (transparency) and color fidelity of the atmosphere.
Transparency can be quantified by the contrast transmittance of the atmosphere. This definition
of visibility is consistent with both (1) the historical records based on human observation of the
perceptibility of targets, which include both the longest duration and most widespread records
now available, and (2) the definition of visibility recommended by the National Research Council.
5.3.1 Air pollution and visibility
Air pollution can also alter the colors of the atmosphere and the perceived colors of objects
viewed through the atmosphere. A complete quantification of visibility should include a measure
of the color changes caused by the atmosphere. Such measures have been included in plume
visibility models, but there is no consensus on the best parameter to quantify color changes
caused by air pollution from many sources.
The perception of color depends on illumination and setting. For example, when there is a brilliant sunset, a white picket fence will appear to be white, but will be distinctly yellow in a photograph. A nitrogen dioxide-containing plume appears to be yellow against a blue sky even when a
photograph or spectral measurement shows that the plume is blue, but less blue than the surrounding sky. The eye correctly perceives that a yellow gas is present in the plume. These properties of human vision have been explored elsewhere (EPA, 1997d).
One way to measure the effect of particulate matter on visibility is to measure the light scattering
efficiency of particles. The higher the light scattering efficiency, the less light from any given
object reaches an observer’s eyes, decreasing visibility. The light-scattering efficiency differs
considerably for fine and coarse particles, ranging from 2.4 to 3.1 m2/g for fine particles and 0.2
to 0.4 m2/g for coarse particles (EPA, 1997f). Larger light-scattering efficiencies for fine particles have been observed when significant numbers of the particles are in the 0.5 to 1.0 µm size
range. The great majority of light absorption by particles is caused by elemental carbon. Determinations of the mass-specific light-absorption emission of elemental carbon give values in the
range of 9 to 10 m2/g. Great reductions in visibility occur when water condenses to form fog or
clouds. Water is also present in all ambient particles, even on relatively clear days. The increase
in the amount of water in particle phase that occurs at high relative humidity (RH) has a significant effect on visibility. Light-scattering efficiency of fine particles also increase with high RH,
and ammonium sulfate particles are an aerosol component that contributes to the absorption of
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water at high RH. Thus, fine particles cause more visibility problems than coarse particles, and
on hot, humid days exasperate conditions that lower visibility.
Particulate sulfate found in the atmosphere by the conversion of SO2 is responsible for 40-65%
of the haze in the eastern United States, based on a combination of measurements and calculations. Nitrates contribute 6-14% of the haze on an annual average basis, with much lower contributions in summer (less than 5%) than in winter (almost 30%). Nitrate concentrations in urban
areas are generally higher than in surrounding rural areas as a result of the influence of urban
transportation sources.
Economic studies have estimated values for two types of visibility effects potentially related to
particulate matter and NOx: (1) use and non-use values for preventing the types of plumes caused
by power plant emissions, visible from recreation areas in the southwestern United States; and
(2) use values of local residents for reducing or preventing increases in urban haze in several different locations.
In the eastern United States, the accepted value for natural visibility is between 60 and 80 miles.
From 9 to 12% of visibility reduction in these states comes from natural vegetation; 60 to 70% of
anthropogenically-induced visibility impairment is estimated to come from sulfates, while carbon-based compounds contribute roughly 20%. In urban areas, nitrates are thought to be more
important than in rural areas (Anon, 1994). While visibility is lower during the summer months,
the relative contribution of different particle species does not vary with season.
In the long-term, mean visibility has steadily decreased in the eastern states for all seasons since
1970. Visibility during the summer months is significantly affected, with mean visibility less
than 10 miles for all states east of the Mississippi (Anon, 1994).
5.3.2 Haze in protected natural areas
In August 1977, Congress amended the Clean Air Act (CAA) to establish as a national goal “the
prevention of any future and remedying of any existing impairment of visibility in mandatory
Class I Federal areas, which impairment results from man-made air pollution” (Title I Part C
Section 169A; 42 U.S.C. 7491). Class I areas include many national parks and wilderness areas,
including Brigantine Federal Wildlife Refuge in Southern New Jersey. The mandate to protect
visibility in national parks and wilderness areas led to the development of the Interagency
Monitoring of Protected Visual Environments (IMPROVE), a cooperative visibility monitoring
network managed and operated by federal land management agencies, the U.S. EPA and State air
quality organizations.
In National Park Service (NPS) studies during the summers of 1983, 1984, and 1985, visitors at
Grand Canyon, Mesa Verde, Mount Rainier, Great Smoky Mountains, and Everglades National
Parks were given a list of park features and asked how important each one was to their recreational experience. At each of the five parks, "clean, clear air" was ranked among the top 4 features. For example, 82 percent of the 638 respondents at Grand Canyon rated "clean, clear air" as
"very important" or "extremely important" to their recreational experience.
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The Grand Canyon Visibility Transport Commission is currently conducting a comprehensive
study on the economic impact of visibility impairment on national parks and wilderness areas
and the cost of controls. Several studies have estimates on-site values for preventing an airpollution plume visible from recreation areas in the southwestern United States. The estimated
on-site use values for the prevention or elimination of the plume ranged from $3 to $6 (1989
dollars) per day per visitor-party at the park. A potential problem common to all studies is the
use of daily entrance fees as a payment vehicle.
That people notice changes in visibility conditions, and that visibility conditions affect the wellbeing of individuals, has been verified in scenic and visual air quality rating studies, through observation that individuals spend less time at scenic vistas on days with lower visibility and
through use of attitudinal surveys (Ross, 1988; EPA, 1997f). In New Jersey, this probably affects
revenue from tourism, especially for sites such as Barnegut Lighthouse in Cape May County and
Liberty Island State Park in Jersey City.
Edwin B. Forsythe Federal Wildlife Refuge (FWR), formerly known as the Brigantine FWR, is
one of few IMPROVE sites in the eastern United States and the only such site in New Jersey.
Unfortunately, visibility data from the monitors is not currently available. New Jersey’s Department of Environmental Protection does take smoke shade information, which shows that visibility problems are concentrated in the northeast of the state (Figure 5-2). However, the correlation
of this data with fine particulate matter levels is unclear. Section 4.6, Effects and Benefits, presents trends observed in the eastern United States and relates them to CAAA effects.
5.3.3 Urban haze
Interest in protecting visibility in urban areas has a long history and is strong in today’s society.
Smoke in European cities, especially London, has been a concern for centuries. Many of the
modern advances in the understanding of fine particles were made during the 1969 Pasadena
Smog Experiment (Whitby et al., 1992). The continuing interest in urban visibility is indicated in
the list of short-term intensive visibility and aerosol studies summarized by the National Acid
Precipitation Assessment Program (NAPAP) Report on Visibility (Trijonis et al., 1991). Visibility, while an important aesthetic aspect of urban environments, could be an important factor in
air traffic problems.
A study based on answers to direct willingness to pay questions in Eastern cities (Chicago, Atlanta, Boston, Washington, D.C., Miami and Cincinnati) showed that households were willing to
pay $8 to $51 (average $18) a month for 14% average improvement in visibility alone (Tolley et
al., 1986).
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Figure 5-2. State of New Jersey Average Smoke Shade, 1996
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5.3 Ozone
At ground level, ozone is created by a chemical reaction between oxides of nitrogen (NOx), and
volatile organic compounds (VOC) in the presence of sunlight. Ozone is a gas that forms in the
atmosphere when 3 atoms of oxygen are combined (O3). Ozone has the same chemical structure
whether it occurs high above the earth or at ground level and can be "good" or "bad," depending
on its location in the atmosphere.
Ozone occurs in two layers of the atmosphere. The layer surrounding the earth’s surface is the
troposphere. Here, ground level or "bad" ozone is an air pollutant that damages human health,
vegetation, and many common materials. It is a key ingredient of urban smog. The troposphere
extends to a level about 10 miles up, where it meets the second layer, the stratosphere. The
stratospheric or "good" ozone layer extends upward from about 10 to 30 miles and protects life
on earth from the sun's harmful ultraviolet rays (UV-B).
Motor vehicle exhaust and industrial emissions, gasoline vapors, and chemical solvents are some
of the major sources of NOx and VOC, also known as ozone precursors, and significant components of fine PM. Strong sunlight and hot weather cause ground-level ozone to form in harmful
concentrations in the air. Many urban areas tend to have high levels of ground-level ozone, but
other areas are also subject to high ozone levels as winds carry NOx emissions hundreds of miles
away from their original sources.
Ozone concentrations can vary from year to year. Changing weather patterns (especially the
number of hot, sunny days), periods of air stagnation, and other factors that contribute to ozone
formation make long-term predictions difficult.
5.4.1 Effects of ozone on ecosystems
Ground-level ozone interferes with the ability of plants to produce and store food, so that growth,
reproduction and overall plant health are compromised. By weakening sensitive vegetation,
ozone makes plants more susceptible to disease, pests, and environmental stresses. Ground-level
ozone has been shown to reduce agricultural yields for many economically important crops (e.g.,
soybeans, kidney beans, wheat, and cotton). In the United States, this is worth an estimated 500
million dollars in reduced crop yield each year. The effects of ground-level ozone on long-lived
species such as trees are believed to add up over many years so that whole forests or ecosystems
can be affected. For example, ozone can adversely impact ecological functions such as water
movement, mineral nutrient cycling, and habitats for various animal and plant species. Groundlevel ozone can kill or damage leaves so that they fall off the plants too soon or become spotted
or brown. These effects can significantly decrease the natural beauty of an area, such as in national parks and recreation areas.
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5.4.2 Trends in ozone
Between 1980 and 1997, between 6 and 60 days per year have exceed the ozone limit New Jersey, although that number of days has decreased steadily in that time period. This is largely due
to ozone-related summertime nitrogen oxide controls.
Nitrogen oxides and volatile organic compounds are the primary precursors of trophospheric
ozone. As a result of oxidation reactions in the atmosphere, these compounds form ozone. These
same oxidation reactions convert sulfur oxides and nitrogen dioxides to their sulfate and nitrate
forms, leading to acid deposition. Research contributing to the understanding of ozone chemistry, transport and fate will be critical in interpreting the results of sulfur dioxide and nitrogen
oxide controls to reduce acid deposition. It will be important to know how controls of these
compounds have interacted to produce beneficial results in environmentally sensitive regions,
and to be able to distinguish between their relative contributions. Trophospheric ozone and acid
deposition both have nitrogen oxides in common. Understanding their sources and sinks will be
important in resolving those issues. An important question to address in the future will be the
degree to which ozone-related nitrogen-oxide controls also mitigate acid deposition and coastal
eutrophication problems.
5.5 Effects and benefits
Economic methods for valuing the effects of pollution on marketed goods and services have been
available for many years. The ability to estimate benefits for these effects is limited by the availability of economic and scientific data. In contrast, methods for estimating the non-market values
and passive-use values have only recently become widely used and accepted.
Market goods and services in this case include agriculture and commercial forests and materials.
Non-market goods and services are those associated with aquatic and forest recreation and visibility. By nonuse values we mean ecosystem health and cultural resources.
5.5.1 A general overview
The 1998 NAPAP Biennial Report to Congress analyzes benefits associated with each sector and
the expected effects of further reductions to each sector. In general, quantifiable benefits are
relatively large in the areas of health and visibility. The main problem in both materials and cultural resources valuation is the lack of a complete information in all areas: an inventory of affected assets, economic lives of assets, change in associated human behavioral responses to damage. Ecosystem changes associated with Title IV reductions in emissions cannot yet be determined. The science-to-economics links for fishing, boating and swimming are not yet welldeveloped, but are better for the northeastern United States than in the rest of the country. There
is ample evidence of the effects of sulfur, nitrogen and ozone on forests. A key concern is the
decline of forest resources. However, the link between primary pollutants and the effects that
people may care about most, such as foliage intensity and range, is not established. A variety of
confounding factors, such as drought and introduced pests, has made it difficult for forest re-
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searchers to quantify the relationship between air pollution levels and forest decline. Susceptibility to these factors may well be associated with forest health. Of all air pollutants, ambient ozone
is likely to cause the most significant crop damage. Dose-response functions for ozone are available for most major agronomic crops and some specialty crops. NOx reductions are believed to
decrease the creation of ozone and damage to agriculture (NAPAP, 1998).
As a result of emission reduction, potentially significant benefits may be achieved in the areas of
visibility and materials. As preliminary evidence discussed earlier indicates, reasonable estimates
of benefits to materials and cultural resources are not available. With regard to visibility, in one
study standard visual range with and without Title IV was compared to assess the economic
benefits of improvements in visibility. Drawing on several previous survey studies to value
changes in visibility, substantial monetary benefits were obtained for residential areas in 31 eastern states and for national parks in the southeastern United States. Benefits to this region were
estimated to be $3.4 billion (1994 dollars) in 2010, or about $377 per ton of SO2 emission reduction. Alternative scenarios predict median visibility benefits for improvements at $118 to $224
per ton of SO2 reduction. Visibility changes vary in a nonlinear fashion with emission changes,
resulting in the variation in benefits per ton. Benefits at residential sites were found to be of substantial magnitude.
Reasonable estimates of potential ecosystem (non-use) benefits are not available at this time.
Ecosystem health benefits are expected to be large in part because they encompass broad
changes that affect many environmental end points, perhaps to a small degree, but that taken together could alter large-scale systems. Aquatic and terrestrial effects are likely to have significant
benefits through non-use values, but uncertainties around those values remain the largest.
5.5.2 Effects for New Jersey
What do these figures mean for New Jersey? In this section we have reviewed the basic mechanisms of how problems associated with fine particulate matter have complex effects in the
natural environment, differentiating between the urban areas of northeastern and central-west
New Jersey, and rural areas, especially southern New Jersey. The major effects of air pollution
are not just limited to the effects of primary particles, but also to secondary products of airborne
compounds that form particulate matter. As we have stressed throughout the section, the very
different chemical natures of the components of PM2.5 mean that their effects in natural systems
also differ greatly. We identify three major effects of particulate matter:
•
•
•
acid deposition
changes in visibility
ozone
We also stress that the lack of scientific information and long-term data (which is in the process
of being collected) makes it extremely difficult to make exact predictions and economic arguments regarding the effects of particulate matter, and on the possible effects of changing their
regulation standards. However, just to highlight the possible magnitude of these impacts, it may
be useful to consider the industries that are affected by the effects of particulate matter.
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Increased visibility is the most well-understood and predictable effect of changing particulate
matter standards. Changes in visibility have been hypothesized to affect airport operations. Based
on a study conducted by the U.S. EPA (1985), the percentage of the visibility impairment incidents sufficient to affect air traffic activity might be attributable in part to man-made air pollutants (possibly 2 to 12% in the summer for the eastern United States). Lowered visibility was seen
to lower the amount of time and the amount of money that tourists spend in the Grand Canyon.
This result probably similar at some New Jersey tourist destinations, for instance, Liberty State
Park in Jersey City. Jersey City is also the site in New Jersey with the highest average annual
Coefficient of Haze. Liberty State Park is one of the most visited tourist sites in New Jersey.
Since New Jersey Smoke Shade measures (Coefficient of Haze) are not comparable to the Grand
Canyon “deciview” units of visibility, we cannot directly attribute economic benefits to increasing visibility at these sites.
Tourism in New Jersey is worth slightly more than $25 billion dollars annually. New Jersey is a
well-known birding site, being a major stop on the eastern seaboard migration route, especially
for seabirds and neotropical migrants (among which include several endangered species). This
sector of tourism would be affected severely by ecosystem degradation, due to acid deposition
and ozone damage. We have shown that acid deposition affects materials, increasing maintenance and replacement costs.
Ecosystem degradation would also affect the agriculture and fisheries sectors. New Jersey is
home to some of the largest commercial and recreational fishing ports on the Eastern Coast. In
1995, New Jersey commercial fisherman harvested over 177 million pounds of fish and seafood
valued at over $96 million. The state’s fledgling aquaculture industry contributed an additional
farmgate value of $4 million. It is estimated that the commercial and seafood industries contributed approximately $624 million to the economy of the Garden State in 1995 with an additional
$762.2 million generated by the recreational fishing industry. Signs of decline already exist, and
show signs of improvement with stringent monitoring and clean-up efforts over the last 40 years.
After dramatic crashes in fish populations in the early 80s, the Delaware River and Estuary has
shown increases in the abundance of several major fisheries in recent years, including striped
bass, weakfish, and American Shad. However, even these current levels for fish abundances are
still significantly lower than those a century ago, some times as much as two orders of magnitude
in the case of the Atlantic sturgeon.
Cash receipts from farms totaled $773 million in New Jersey in 1997. The largest part of this
figure comes from the nursery/greenhouse/sod industry ($257 million), followed by vegetables
($169 million). Other important sectors were equine ($115 million), fruit ($86 million), field
crops ($60 million), dairy ($42 million) and poultry and eggs ($36 million). While an estimate of
agricultural losses due to air pollution and fine particulate matter is impossible at this time, we
might begin by looking at the effects of ozone on agricultural production. The effects of ozone
on production are well documented for many agricultural crops. Since the precursors to ozone
are the same particles that contribute to particulate matter, we feel that this may provide a good
estimate for the order of magnitude for agricultural losses due to air pollution. Agriculture in the
United States produced a little over $86 billion in agricultural crops alone in 1997. Ozone damage is estimated to cause losses of $500 million to agricultural crops alone, which works out to
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0.5% of agricultural crop production. Assuming that ozone decreased the production of only agricultural field crops and not vegetables, fruits and nuts, or any other agricultural and farm product, and extrapolating from national figures for agricultural losses, this implies a loss of a $350
thousand per year. If this were to include all principal crops then losses for New Jersey could be
on the order of $1.6 million per annum. All of the above estimates are upper bounds on the possible economic effects of particulate matter. However, as we have seen above, the effects of particulate matter in ecosystems are not simple relationships, and biological and ecological pathways often magnify and accumulate pollutants and their effects such that results are only observable after long time delays. The following paragraphs address this concern.
In order to examine the question of “threshold” effects in ecosystems and the possible effects of
the new fine PM standards, we outline the possible effects of reduced nitrogen and sulfur deposition in surface water, soils and forests (NAPAP, 1998). Since biological responses to changes
in acid-base chemistry are along a continuum, there is not a single value or set of chemical concentrations that represent a threshold for significant adverse biological effects. We therefore have
a difficult task in determining the level of acceptable risk.
Adverse ecological effects are any injury (i.e. loss of chemical or physical quality or viability) to
any ecological or ecosystem component, up to and including at the regional level, over both long
and short terms. Using this working definition we are interested in looking at a dose-response
relationship along a continuum of ecological effects.
The main question of interest therefore is: as the dose of air pollution (specifically sulfur and nitrogen emissions and its subsequent formation of acid deposition) is reduced, how do aquatic and
terrestrial ecosystems respond?
We know that both nitrogen and sulfur deposition are important contributors to chronic and episodic acidification of surface waters. Further reductions in nitrogen as well as sulfur deposition
may be necessary to fully protect targeted sensitive systems.
The literature search for this project has shown us that there is still much research to be done if
we are to protect sensitive ecosystems appropriately. It is this lack of knowledge that has limited
the EPA’s ability to recommend specific deposition standards.
The Nitrogen Bounding Study (Van Sickle & Church, 1995) illustrates the modeled results of
scenarios of potential future nitrogen and sulfur deposition rates and different watershed nitrogen
retention conditions and their combined effects on surface water chemistry at regional scales.
The main results suggest that sulfur deposition is likely to remain the primary acidification
problem in the most sensitive areas of eastern North America. Additionally sulfur and nitrogen
are projected to have approximately equal roles in surface water acidification. For most areas
where current or near-term needs for additional controls are projected, and where watershed nitrogen saturation is not likely imminent, the greatest potential benefits will come primarily from
control of sulfur emissions and deposition. In regions where nitrogen deposition is now or would
likely become a more direct cause of chronically acidic conditions in sensitive waters, with potential effects of sulfur and nitrogen deposition becoming approximately equal and directly addi-
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tive, further limits on nitrogen deposition could produce a twofold impact by both reducing acid
deposition rates and lengthening average times to watershed nitrogen saturation.
Scientific uncertainties regarding varying regional rates and differences in processes affecting
watershed assimilation of acid-forming sulfur and nitrogen compounds preclude quantifying the
reduction in deposition of either chemical below which there would be no significant adverse
impact. Available information indicates that additional decreases in deposition would reduce regional proportions of chronically acidic surface waters or proportions of surface water most sensitive to episodic effects. The magnitude of these potential benefits to each group of surface waters varies considerably by region. Deposition reductions could benefit 20% or more of the acidic
or sensitive waters. However, even a few percentage points may mean that many lakes or miles
of stream reaches are benefiting.
The acid-base chemistry of the soils and the water draining forest soils will depend on the characteristics and sensitivity of the soils. A recent study has shown that New Jersey’s soils have a
high probability of experiencing a delayed or future response to acidic deposition (Turner et al.,
1986). In general, decreasing the input of sulfur and nitrogen from deposition will decrease sulfate and nitrate levels in soils and soil water. The timing of this decrease in soil and soil water
sulfate depends on the amount of sulfur stored. Soils high in sulfur will most likely experience a
slower decrease in soil water sulfate, as the soil slowly releases stored sulfur. For nitrogen, the
timing of the decrease will depend on the amount of nitrogen stored and the growth needs of the
forest. A forest that has high demand for nitrogen, relative to the nitrogen storage and throughput, will experience smaller decreases in nitrogen in soil water in response to decreased nitrogen
deposition compared to a forest that has a low demand for nitrogen. A forest’s need for nitrogen
is strongly dependent upon the age of the forest. Thus, young actively growing forests are far less
likely to experience nitrogen saturation than older stands that have reached the steady-state equilibrium.
5.6 Conclusions
The main components of fine particulate matter (PM2.5) are soil-related particles, sulfur oxides
(SO2), nitrogen oxides (NOx), and volatile organic compounds (VOC). These components can
combine in a variety of ways that noticeably affect urban, agricultural and natural systems. We
discuss the effects of acid deposition, reduced visibility and ozone in urban environments, on agriculture, and on what we consider to be New Jersey’s most sensitive ecosystems: aquatic systems and the Pine Barrens. Table 5-1 lists the contribution of the components of fine PM to these
secondary effects. Sulfates and nitrates in the atmosphere nucleate around fine dust particles or
react with other compounds to form secondary fine PM. They can be washed out of the atmosphere by rain (wet acid deposition), or directly deposited (dry acid deposition) onto buildings,
trees or whatever else intercepts these particles. Reduced visibility is caused by the physical
scattering of light by PM in the atmosphere. Fine PM scatters light more efficiently than coarse
PM, and is a major cause of the haze that characterizes summertime urban areas and that reduces
visibility at important national monuments like Grand Canyon National Park and Liberty Island
State Park. Ozone is formed as a product of reactions between nitrates and volatile organic compounds, also components of fine PM. To the extent that regulations lower ambient levels of fine
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PM, they also lower the formation of secondary products and reduce the problems associated
with acid deposition, reduced visibility and ground-level ozone formation.
Table 5-1: Contributions of PM2.5 particles to environmental effects
Particle type
soil
organic carbon compounds
sulfates
nitrates
Contributes to
reduced visibility
ozone
reduced visibility
acid deposition
reduced visibility
acid deposition
ozone
Table 5-2 summarizes the major environmental and ecological effects of acid deposition, reduced visibility and ozone, the possible economic ramifications of those effects and the sectors
that would be most likely impacted by changes in ambient fine PM levels. Acid deposition is the
most widespread problem, that affects urban areas as much as natural ecosystems. Its effects are
also among the most well-studied In urban areas acid deposition contributes to corrosion of
building materials, increasing maintenance and repair costs. For instance, repainting frequency
for houses in Virginia increased from once every four years in areas of low acid deposition to
once every one or two years for areas with high acid deposition. Acid deposition contributes to
nitrification and eutrophication of surface waters. High levels of nitrates in water are toxic to
animals and humans, lower levels affect drinking water quality and can change the dynamics and
composition of aquatic plant communities by encouraging the growth of “weedy” species. Accelerated plant growth and death overloads the bottom communities responsible for decomposition, depletes oxygen levels and can cause deaths that cascade up the food chain, resulting in the
massive fishkills observed in the last two decades throughout the Northeastern United States.
These same conditions cause beach closings and can be expected to significantly affect recreational activities. Acidic conditions can increase the concentrations of certain heavy metals such
as aluminum, nickel, cadmium and mercury in runoff which ends up in streams. This can poison
fish and shellfish that are important in human consumption. In terrestrial systems, acid deposition, especially of nitrates, can interrupt nutrient cycling. It can also increase plant uptake of
heavy metals and nitrates, which in turn increases the morbidity and possibly mortality of animals eating them.
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Table 5-2. Environmental and ecological consequences of acid deposition,
reduced visibility and ozone, and their economic and social ramifications
Problem and scope
Acid deposition
(Urban, widespread)
(Freshwater and coastal
waters)
(Terrestrial ecosystems)
Reduced visibility
(Local)
Ozone
(Local)
Economic/social
ramifications
Consequences
Damage to materials
Nitrification and eutrophication of surface waters
Increased runoff of toxic
minerals
Changes in nutrient cycling
Increased maintenance
and repair costs
Increased fishkills
Sectors affected
Many or all
Fisheries
Foul odors and unpalatable tastes Drinking Water
in drinking water
Increased morbidity and mortality
Agriculture
of wildlife and livestock
Loss of ecosystem services,
Loss of sensitive species
Recreation
like aluminum buffering
from ecosystem
Reduced visibility
Decreased income from tourism
Recreation
Increased risk of air traffic accidents
Industry
Reduced visibility
Decreased income from tourism to
Recreation
parks and reserves
Decreased productivity of
Lowered agricultural productivity
Agriculture
plants
Toxicity to animals
Increased morbidity and
mortality of wildlife
Reductions in fine PM levels can be expected to have noticeable effects on visibility and ozone
However, the effects on acid deposition are unclear. Because the causes of acid deposition are
multiple and complex, and because responses and reactions of ecosystems can take years and
decades to register, we do not know what the effects of reducing fine PM will be on levels of
acid deposition, nor what the effects of reducing acid deposition would mean for terrestrial ecosystems such as the Pine Barrens. For aquatic systems, the reduction of acid deposition is an important step in reducing the causes of nitrification and eutrophication of surface waters. However, without concurrent reductions in other sources of nitrates and other pollutants, few noticeable short-term improvements in aquatic system health would be expected.
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