What is acid rain? Acid rain is the term for pollution caused
when sulfur and nitrogen dioxides combine with atmospheric
moisture. The term ‘acid rain’ is slightly misleading, and would
be more accurate if deemed ‘enhanced acid rain’, as rain occurs
acidic naturally. Acidity is measured on what is know as the pH
scale. Fourteen is the most basic, seven is the most neutral, and
zero is the most acidic. Pure rain has a pH level of 7, which is
exactly neutral. The acidity of rain is determined by the pH of
pure water in reaction with atmospheric concentrations of
carbon dioxide, resulting in carbonic acid. These particles
partly dissociate to produce hydrogen ions and bicarbonate
ions. A bicarbonate atom is an ion formed by one hydrogen
atom, one carbon at atom, and three oxygen atoms, and is very
effective in natural waters at neutralizing hydrogen ions and
reducing acidity. The dissociation results in the natural acidity
of pure rain, which is moderately acidic at a pH of 5.7. Rain
less than 5.7 is considered ‘acid rain’, meaning it has reacted
with acidic atmospheric gases other than carbon dioxide, such
as sulfur dioxide and nitrogen dioxide. Sulfur dioxide is
produced by electric utilities, industrial, commercial and
residential heating, smelters, diesel engines and marine and rail
transport, which creates sulfuric acid in rain. Nitrogen dioxide
will also react with the rain, caused largely by transportation
(cars, trucks, planes, etc.) and electric utilities, producing
nitric acid. There is a certain degree of naturally occurring
acidity in rain water. This acid is from reaction with alkaline
chemicals, found in soils, lakes and stream, and can occasionally
occur when a volcano erupts as well. Bacterial action in soils
and degasing from oceanic plankton also contribute to the
acidity found in rain. More than 90% of the sulfur and 95% of
the nitrogen emissions which occur in North America are due to
the pollution created by humans.1 How Is Acid Rain Formed?
Acid rain consists mainly of acids formed in the atmosphere. It
consists of the oxides of sulfur, SO2 and SO3, and of nitrogen
NO and NO2. Let us examine the major contributor to acid
rain, sulfur oxides. Natural sources which emit sulfur dioxide
include volcanoes, sea spray, plankton and rotting vegetation.
Despite these natural occurrences, the burning of fossil fuels
(such as coal and oil) can be largely blamed for the emissions.
The chemical reactions begin as energy from sunlight, in the
form of photons, hit ozone molecules (O3) to form free oxygen
(O2), as well as single reactive oxygen atoms (O). The oxygen
atoms react with water molecules (H2O), producing electrically
charged, negative hydroxyl radicals (HO). These hydroxyl
radicals are responsible for oxidizing sulfur dioxide and
nitrogen dioxide, which produces sulfuric acid and nitric acid.
Some particles will settle to the ground (in the form of acid
deposition) or vegetation can absorb some of the SO2 gas
directly from the atmosphere. When sulfur dioxide comes in
contact with the atmosphere, it oxidizes and forms a sulfate
ion. It becomes sulfuric acid as it joins with hydrogen atoms in
the air and falls down to earth. Oxidation occurs most in clouds,
especially in heavily polluted air, where other compounds such
as ammonia and ozone help to catalyze the reaction, increasing
the amount of sulfur dioxide changing to sulfuric acid. Not all
of the sulfur dioxide is converted to sulfuric acid, and it is not
uncommon for a substantial amount to float up into the
atmosphere, move to another area, and return to earth as sulfur
dioxide, unconverted. S (in fossil fuels) + O2 =* SO2 2 SO2 +
O2 =* 2 SO3 Much of the sulfur dioxide is converted to sulfur
trioxide in the atmosphere SO3 + H2O =* H2SO4 The sulfur
trioxide can then dissolve within water to form sulfuric acid
Nitric oxide and nitric dioxide are mainly from power plants
and exhaust fumes. Similar to sulfur dioxide, reactions are
heavily catalyzed in heavily polluted clouds where iron,
manganese, ammonia and hydrogen peroxide are present. Also,
the formation of nitric acid can trigger further reactions which
release new hydroxyl radicals to generate more sulfuric acid.
The following is a typical reaction, which is direct combination
of nitrogen and oxygen at the high temperature inside a car
engine. N2 + O2 + heat =* 2NO 2NO + O2 =* 2NO2 This
nitrogen monoxide immediately reacts with oxygen and forms
nitrogen dioxide in the following reaction 3NO2 + H2O =*
2HNO3 (aq) + NO The nitrogen will then dissolve in water in
the atmosphere and produce nitric acid There are several other
potential contributors to acid rain. These include oxidation by
products of alkene-ozone reactions, oxidation by reactions of
NxOy species and oxidation by peroxy radicals. Each of these
reactions, however prove to be minor contributors and are
rather insignificant. How Is Acid Rain Harmful? Environmental
Hazards Aquatic Ecosystems Acid rain has an effect on
virtually all ecosystems it touches. Perhaps the most prominent,
and equally as troubling is the harmful results it produces when
in contact with lakes, streams and ponds. Scientists studying
the effects of acid rain went to a lake about 135 km away from
the Ontario- Manitoba border called Lake 223. This lake, so
far north acid rain did not reach it, was extremely healthy, and
was a perfect setting to explore the effects of acid rain on
aquatic ecosystems. In 1974, scientists began to add sulfuric
acid into the lake. The acid was added very slowly, and it was
four years later when they saw a major change. The freshwater
shrimp began to die out. Fathead minnows stopped reproducing
and began to vanish. As the scientists continued adding acid to
Lake 223 in low amounts, large algae mats began to form and
crayfish became unhealthy and died. Seven years after the
beginning of the experiment, the lake trout stopped
reproducing, and most of the fish species, leeches, crawfish and
mayflies began to die. In 1984, the scientists stopped adding
the acid. Without the addition of deadly sulfuric acid, the lake
slowly began to recover. Some of the fish species began to
recover, however some of the scientists estimated it would take
one hundred years for the lake to fully recover, even without
the addition of any more acid. Fish can still live in a lake with a
low acid level, however they will get sick and not grow to
proper proportions. Often the fish will not reproduce, and
eventually, as the acid level increases, all the fish will die. The
acid will also ‘leach’ metals from the bottom of the lake. There
are metals contained within the mud and rocks of the lake
bottom, however they remain not dangerous as long as they are
not released. The acid will draw out these harmful metals and
dissolve them in the water, resulting in the deterioration and
disappearance of a species. One of these damaging metals is
aluminum, which will coat and burn the gills of the fish as it
intakes the polluted water. Some fish found in acidic lakes
contain higher levels of mercury in their bodies, which is
harmful to humans, resulting in the government telling society to
limit the amount of fish they eat from certain lakes and rivers.
If the numbers of one species or group of species changes in
response to acidification, the ecosystem of the entire body of
water is likely to be affected through the predator-prey
relationships. Let us examine how acid rain is dangerous to fish.
A freshwater fish’s respiration consists of a ‘trade’ of
hydrogen ions (H+) in their blood for sodium ions (Na+) from
the water around them. If the concentration of hydrogen ions in
the water is increased, which is essentially what happens when
pH falls, there are (proportionally) fewer sodium ions. Fish are
forced to absorb more hydrogen while finding it harder to
obtain sodium. The acidity of their blood increases, while the
salt content drops. An experiment involving brown trout showed
that at a pH of 5.2 or lower, this process was fatal to this
species, and is likely deadly to many other trout species. The
following chart shows the steps typical to freshwater fish as
the acidity increases. (Fig 1-1) ACIDITY LEVEL (pH)
EFFECTS ON AQUATIC LIFE 7 Neutral, H+ and H- are in
balance 6.8 Shells of clams and snails become thinner, due to
lack of hazardous calcium ions in the water 6.6 The viability of
eggs of the fathead minnow is reduced, rain can have and fewer
eggs hatch 6.5 Lake trout begin to have difficulty reproducing,
clams and snails become scarcer, green algae growth increases 6
Several clam and snail species disappear, several trout species
populations decrease, the smooth newt is gone, smallmouth bass,
walleyes and spotted salamanders have difficulty reproducing,
several mayfly species cease to lay eggs 5.8 Copepods (a
critical link of crustaceans in the marine food chain) are gone,
crayfish have trouble regrowing exoskeleton after molting 5.7
Several algae species decrease, while filamentous green algae
increases, plankton decreases 5.5 Rainbow trout, fathead
minnows and smallmouth bass lose considerable population,
walleyes, brook trout, roach, lake trout and shiners don’t
reproduce, leeches and mayfly larvae vanish. 5.4 Crayfish
reproductivity is impaired. 5 Snail and clams are extinct. All
but one species of crayfish are extinct, brook trout, walleyes
and most bullfrogs are gone, most fish species experience
reproduction difficulties, zooplankton population begins to
drop, green and green-blue algae mats have largely spread 4.8
Leopard frog numbers decline 4.5 Mayflies and stoneflies
vanish, a slowing in growth rate and oxygen uptake of bacteria
is notable 4.2 The common toad disappears 4 The oxygen output
of Lobelia plants declines 75% 3.5 Virtually all clams, snails,
frogs, fish and crayfish vanish 2.5 Only a few species of
acid-tolerant midges, bacteria and fungi are alive 2 In
practical terms, the lake is sterile Two hundred and twenty
lakes in Ontario have been found acidified, meaning their pH is
less that 5.1 year round.2 Terrestrial Plant Life It is much
more difficult to solve the mystery of forest destruction
compared to that of a lake. This is partially because trees live
so much longer than fish do, and acid rain damage in trees may
not show up for thirty or forty years. It is also very difficult
to replicate forest conditions in a laboratory, such as insects,
cold winters, pollution, elevation and abrupt changes in rainfall.
Each of these conditions put stress on the trees and can be
considered variables. Many scientists are convinced that
because of the complexity of a forest ecosystem, it is nearly
impossible to prove the death of forests is due to pollution in
the form of acid rain, but deduce from many experiments it is a
main factor in forest destruction. Deciduous trees are like air
filters, and screen particles that pass through the air around
them. These particles collect on the leaves of the tree, and
studies have shown that when these particles contain acid they
can cause damage to the leaves. The leaves are the part of the
tree that help make food, hence any damage to the leaves will
result in harm to the health of the entire tree. Coniferous trees
are vulnerable to the harmful effects of acid rain as well. The
tree’s needles are designed to nourish the tree after they fall
to the ground. Each needle houses whole colonies of microscopic
bacteria and algae that help the tree change nitrogen into food
at the roots. Acid rain will often burn away this material,
thereby reducing adequate food supply, and weakening the
tree’s health. After the damage has been done to leaves and
needles, acid rain harms the trees even more through the soil.
Soil has a level of acid. Acid in the soil can do damage to the
trees by releasing aluminum, which, once in contact with acid,
becomes highly poisonous to forests. The aluminum will enter
the tree’s hairlike roots, choking them, and when these become
clogged, the upper branches are no longer nourished. Even
though there may be plenty of moisture in the soil, the tree can
die of thirst. Scientists have discovered that the aluminum
content in soil has tripled since the 1960s.3 Acid rain also kills
important organisms on the forest floor. The process of
decomposition is interrupted as the acid kills many of the
bacteria and fungi that live on the forest floor. At a pH level
of 4.0, the earthworm dies, further damaging the decomposition
process. Without earthworms and bacteria to decompose the
debris consisting of animal and bird droppings, twigs and dead
leaves, the materials continue to build on the forest floor.
When debris builds up, seedlings from the trees are not able to
survive, because they can not work their way down to the soil
to root. This causes the forest to slowly disappear, as older
trees die, and the forest will not be able to rejuvenate itself.
Acid rain is hardest on trees high up in mountains, because it is
often covered in mist or fog, literally bathing the trees in an
acidic atmosphere. Trees also suffer because of changes in the
soil. Acid rains leach metals (draw metals out of mud and rocks)
in the soil, and the trees in turn intake these harmful metals
through their roots. Figure 1-2 shows the damage that acid rain
can to do a forest Human Health It is known that the earth
contains many metals that are potentially dangerous to humans,
such as lead, mercury, and aluminum. Most of the time these
metals are harmless because they are in the soil, bonded to
other elements. The problem occurs when acid detaches these
metals from the rocks and soils, and can be carried deep into
the ground and make their way to underground streams. These
streams eventually connect to our water sources. Medical
researchers have found these metals can be dangerous, and on
rare occasion, is even fatal. Aluminum has been found to kill
people who have kidney problems, and can also collect in brain
tissue. Some scientists even suspect that aluminum deposits on
the brain cause Alzheimer’s disease. (A disease that results in
memory loss, nervous system problems, and death. Acid rain is
known to irritate the whole respiratory system, beginning with
mucous membranes in the nose and throat, all the way to tissue
in the lungs. Consequently, acid rain has an increased effect on
people with respiratory problems. The U.S. Council on
Environmental Quality estimates health-related problems due
to acid precipitation cost the United States $2 billion per
year.4 In August 1987, over one hundred people were treated
for eye, throat, and mouth irritation when 1.8 metric tonnes of
highly toxic sulfur dioxide gas leaked from an Inco plant near
Sudbury, Ontario. Even Fig 1-2 This picture shows how a
coniferous forest has been virtually destroyed. Acid rain is
blamed for the destruction of terrestrial ecosystems around
the world. without accidents, the sulfur dioxide regularly
emitted from Inco smokestacks has been linked to chronic
bronchitis in Inco employees.5 Drinking Water Acid rain
damages drinking water in various ways. Thus far, amounts of
metals in drinking water have been minimal, however the fact
that metals even leak into the water is troubling to scientists.
Since metals remain in the body once ingested, over time, small
amounts accumulate into large quantities, and it has yet to be
concluded how large an amount will prove to be harmful to
humans. Acid rain causes damage by loosening metals off metal
water pipes. Modern plumbing uses plastic tubing, but older
systems have copper pipes. The copper pipes are held together
by a mixture of tin and lead. Lead is known to be extremely
dangerous to humans, even in small amounts, and will cause
damage to the brain and nervous system. A study that was done
in Ontario found that water sitting in plumbing pipes for ten
days contained hazardous levels of copper and lead. This
discovery could be a widespread danger, since often people will
go on vacation and not shut off the plumbing, allowing water to
sit and absorb these dangerous metals. Acid rain can also
dissolve the reinforcements that occur around large water
pipes. In some parts of the United States, asbestos is used to
reinforce the cement bases that hold water pipes. Asbestos is
not dangerous when bound to the cement, but is highly
dangerous when separated, and has been linked to cancer and
other serious diseases. Many health officials worry that loose
asbestos will find it’s way to the city’s water when acid rain
comes in contact with the cement. Effects On Man Made
Structures Scientists are becoming increasingly concerned with
acid rain’s destruction of the ‘built environment’. There are
objects in our built environment that are irreplaceable.
Historic landmarks and statues, old cathedrals and temples,
paintings and sculpture – all are part of the built environment
and are slowly being damaged. Some of these objects are
practical, making life easier, safer or more comfortable. Many
factors determine how much damage acid rain will do, including
the amount of rain, the location, and direction of wind. All
influence the amount of corrosion done. Areas that have a large
amount fog or humidity tend to suffer more than dry areas,
which is why many steel bridges located over water get rusted
and corroded by acid. When metal is decayed, it cannot take
the same amount of stress of weight as when it was originally
created. Acid rain has been blamed in several collapses of
bridges around the world. Acid rain corrodes the steel track
used on railroads, thus the tracks must be constantly checked.
Metal in air planes can also be eaten away by acid rain. The
United States Air Force spends more that $1 billion every year
to repair or replace damaged parts.6 A study done in Sweden
showed that metal rusts four times faster in areas that receive
a lot of acid rain. This figure is staggering, and yet, metal is
not the only material damaged by acid rain. Houses and
buildings made of brick and stone are affected as well. Acid
rain can dissolve the mortar, which is used in cement to hold
bricks together. When the mortar is worn away, the bricks
crumble more easily, because they shift and cannot stay intact
against the heavy weight of the bricks pressuring from above.
The corrosive effects of acid rain are particularly obvious on
limestone, because it is composed of calcium carbonate, which is
highly reactive with acid rain. Tombstones made of marble
(which is metamorphosed or heated limestone) have been badly
damaged, while older tombstones made of slate remain intact.
Famous buildings such as the Taj Mahal, The United States
Capitol building and the Lincoln Memorial in Washington, are all
being continually damaged by acid rain. Statues made of bronze
and copper are particularly susceptible to corrosion. These
statues turn green naturally, and this covering, called a patina,
acts as a protective shield against the elements. Acid rain eats
away at the patina, and where the acid dissolves the green
covering, it leaves a streaky black coat. This process ruins
statues throughout the world. How Does Acid Rain Affect the
Economy? Canada/American Relations Canada is particularly
susceptible to the effects of acid rain. Its geographical
location places it directly in the path of a large amount of U.S.
emission, and the granite bedrock of the Canadian Shield has a
poor buffering quality. (A buffer is a material that can
chemically weaken acid soil and is less harmful to the
environment, such as lime or baking soda.) The lack of such a
quality renders Eastern Canada highly vulnerable to damage due
to United States pollution. Canada suffers more from acid rain
than the United States does, even though much of the pollution
originates in the United States. Acid rain costs Canadians
hundreds of millions of dollars every year. To try and decrease
the large amounts of money the pollution is costing tax payers,
Canada has passed laws to force its electrical companies to cut
down on harmful emissions. However, no matter what laws are
passed in Canada, it is not possible to stop U.S. power plants
from sending acid in its direction. Figure 1-3 displays amounts
of emissions created by the United States and Canada. The
Gavin power plant is an excellent example of how the United
States sends tonnes of acid to Canada every year. Every hour,
this power plant burns 600 tonnes of coal. The higher the
smokestack, the further the dangerous gases will travel, and the
Gavin smokestack is 1 103 feet tall.7 Obviously, The Gavin can
not be solely blamed for the pollution, but it is power plants
such as these that have caused trouble between the two
countries. It is estimated that about 50% of the sulfate
deposited in Canada derived from American sources.8 Sixty of
the largest plants and thus largest polluters are located in the
Ohio Valley, a short distance away from vulnerable Canadian
land. In 1980, Canada and the United States signed a
Memorandum of Intent, an agreement that both countries would
make acid rain control a priority. They both promised to focus
on developing ideas to cut down the amount of sulfur dioxide
and nitrogen oxide emissions being pumped into the air. In the
past, Canada has presented devastatingly large figures to the
United States, in an attempt to have them change laws and
regulations regarding pollution. Unfortunately, the attempts
thus far have been unsuccessful, as the US government requests
more testing and studies instead of altering laws. In the recent
past, the negotiations between Canada and United States
representatives have been hardly reminiscent of efforts put
forth by Canadian officials. Many U.S. politicians still qualify
acid rain as a ‘minor’ problem, and it is treated as such,
according to Raymond Robinson, chairman of the Canadian
Environmental Ass
Bibliography
What is acid rain? Acid rain is the term for pollution caused
when sulfur and nitrogen dioxides combine with atmospheric
moisture. The term ‘acid rain’ is slightly misleading, and would
be more accurate if deemed ‘enhanced acid rain’, as rain occurs
acidic naturally. Acidity is measured on what is know as the pH
scale. Fourteen is the most basic, seven is the most neutral, and
zero is the most acidic. Pure rain has a pH level of 7, which is
exactly neutral. The acidity of rain is determined by the pH of
pure water in reaction with atmospheric concentrations of
carbon dioxide, resulting in carbonic acid. These particles
partly dissociate to produce hydrogen ions and bicarbonate
ions. A bicarbonate atom is an ion formed by one hydrogen
atom, one carbon at atom, and three oxygen atoms, and is very
effective in natural waters at neutralizing hydrogen ions and
reducing acidity. The dissociation results in the natural acidity
of pure rain, which is moderately acidic at a pH of 5.7. Rain
less than 5.7 is considered ‘acid rain’, meaning it has reacted
with acidic atmospheric gases other than carbon dioxide, such
as sulfur dioxide and nitrogen dioxide. Sulfur dioxide is
produced by electric utilities, industrial, commercial and
residential heating, smelters, diesel engines and marine and rail
transport, which creates sulfuric acid in rain. Nitrogen dioxide
will also react with the rain, caused largely by transportation
(cars, trucks, planes, etc.) and electric utilities, producing
nitric acid. There is a certain degree of naturally occurring
acidity in rain water. This acid is from reaction with alkaline
chemicals, found in soils, lakes and stream, and can occasionally
occur when a volcano erupts as well. Bacterial action in soils
and degasing from oceanic plankton also contribute to the
acidity found in rain. More than 90% of the sulfur and 95% of
the nitrogen emissions which occur in North America are due to
the pollution created by humans.1 How Is Acid Rain Formed?
Acid rain consists mainly of acids formed in the atmosphere. It
consists of the oxides of sulfur, SO2 and SO3, and of nitrogen
NO and NO2. Let us examine the major contributor to acid
rain, sulfur oxides. Natural sources which emit sulfur dioxide
include volcanoes, sea spray, plankton and rotting vegetation.
Despite these natural occurrences, the burning of fossil fuels
(such as coal and oil) can be largely blamed for the emissions.
The chemical reactions begin as energy from sunlight, in the
form of photons, hit ozone molecules (O3) to form free oxygen
(O2), as well as single reactive oxygen atoms (O). The oxygen
atoms react with water molecules (H2O), producing electrically
charged, negative hydroxyl radicals (HO). These hydroxyl
radicals are responsible for oxidizing sulfur dioxide and
nitrogen dioxide, which produces sulfuric acid and nitric acid.
Some particles will settle to the ground (in the form of acid
deposition) or vegetation can absorb some of the SO2 gas
directly from the atmosphere. When sulfur dioxide comes in
contact with the atmosphere, it oxidizes and forms a sulfate
ion. It becomes sulfuric acid as it joins with hydrogen atoms in
the air and falls down to earth. Oxidation occurs most in clouds,
especially in heavily polluted air, where other compounds such
as ammonia and ozone help to catalyze the reaction, increasing
the amount of sulfur dioxide changing to sulfuric acid. Not all
of the sulfur dioxide is converted to sulfuric acid, and it is not
uncommon for a substantial amount to float up into the
atmosphere, move to another area, and return to earth as sulfur
dioxide, unconverted. S (in fossil fuels) + O2 =* SO2 2 SO2 +
O2 =* 2 SO3 Much of the sulfur dioxide is converted to sulfur
trioxide in the atmosphere SO3 + H2O =* H2SO4 The sulfur
trioxide can then dissolve within water to form sulfuric acid
Nitric oxide and nitric dioxide are mainly from power plants
and exhaust fumes. Similar to sulfur dioxide, reactions are
heavily catalyzed in heavily polluted clouds where iron,
manganese, ammonia and hydrogen peroxide are present. Also,
the formation of nitric acid can trigger further reactions which
release new hydroxyl radicals to generate more sulfuric acid.
The following is a typical reaction, which is direct combination
of nitrogen and oxygen at the high temperature inside a car
engine. N2 + O2 + heat =* 2NO 2NO + O2 =* 2NO2 This
nitrogen monoxide immediately reacts with oxygen and forms
nitrogen dioxide in the following reaction 3NO2 + H2O =*
2HNO3 (aq) + NO The nitrogen will then dissolve in water in
the atmosphere and produce nitric acid There are several other
potential contributors to acid rain. These include oxidation by
products of alkene-ozone reactions, oxidation by reactions of
NxOy species and oxidation by peroxy radicals. Each of these
reactions, however prove to be minor contributors and are
rather insignificant. How Is Acid Rain Harmful? Environmental
Hazards Aquatic Ecosystems Acid rain has an effect on
virtually all ecosystems it touches. Perhaps the most prominent,
and equally as troubling is the harmful results it produces when
in contact with lakes, streams and ponds. Scientists studying
the effects of acid rain went to a lake about 135 km away from
the Ontario- Manitoba border called Lake 223. This lake, so
far north acid rain did not reach it, was extremely healthy, and
was a perfect setting to explore the effects of acid rain on
aquatic ecosystems. In 1974, scientists began to add sulfuric
acid into the lake. The acid was added very slowly, and it was
four years later when they saw a major change. The freshwater
shrimp began to die out. Fathead minnows stopped reproducing
and began to vanish. As the scientists continued adding acid to
Lake 223 in low amounts, large algae mats began to form and
crayfish became unhealthy and died. Seven years after the
beginning of the experiment, the lake trout stopped
reproducing, and most of the fish species, leeches, crawfish and
mayflies began to die. In 1984, the scientists stopped adding
the acid. Without the addition of deadly sulfuric acid, the lake
slowly began to recover. Some of the fish species began to
recover, however some of the scientists estimated it would take
one hundred years for the lake to fully recover, even without
the addition of any more acid. Fish can still live in a lake with a
low acid level, however they will get sick and not grow to
proper proportions. Often the fish will not reproduce, and
eventually, as the acid level increases, all the fish will die. The
acid will also ‘leach’ metals from the bottom of the lake. There
are metals contained within the mud and rocks of the lake
bottom, however they remain not dangerous as long as they are
not released. The acid will draw out these harmful metals and
dissolve them in the water, resulting in the deterioration and
disappearance of a species. One of these damaging metals is
aluminum, which will coat and burn the gills of the fish as it
intakes the polluted water. Some fish found in acidic lakes
contain higher levels of mercury in their bodies, which is
harmful to humans, resulting in the government telling society to
limit the amount of fish they eat from certain lakes and rivers.
If the numbers of one species or group of species changes in
response to acidification, the ecosystem of the entire body of
water is likely to be affected through the predator-prey
relationships. Let us examine how acid rain is dangerous to fish.
A freshwater fish’s respiration consists of a ‘trade’ of
hydrogen ions (H+) in their blood for sodium ions (Na+) from
the water around them. If the concentration of hydrogen ions in
the water is increased, which is essentially what happens when
pH falls, there are (proportionally) fewer sodium ions. Fish are
forced to absorb more hydrogen while finding it harder to
obtain sodium. The acidity of their blood increases, while the
salt content drops. An experiment involving brown trout showed
that at a pH of 5.2 or lower, this process was fatal to this
species, and is likely deadly to many other trout species. The
following chart shows the steps typical to freshwater fish as
the acidity increases. (Fig 1-1) ACIDITY LEVEL (pH)
EFFECTS ON AQUATIC LIFE 7 Neutral, H+ and H- are in
balance 6.8 Shells of clams and snails become thinner, due to
lack of hazardous calcium ions in the water 6.6 The viability of
eggs of the fathead minnow is reduced, rain can have and fewer
eggs hatch 6.5 Lake trout begin to have difficulty reproducing,
clams and snails become scarcer, green algae growth increases 6
Several clam and snail species disappear, several trout species
populations decrease, the smooth newt is gone, smallmouth bass,
walleyes and spotted salamanders have difficulty reproducing,
several mayfly species cease to lay eggs 5.8 Copepods (a
critical link of crustaceans in the marine food chain) are gone,
crayfish have trouble regrowing exoskeleton after molting 5.7
Several algae species decrease, while filamentous green algae
increases, plankton decreases 5.5 Rainbow trout, fathead
minnows and smallmouth bass lose considerable population,
walleyes, brook trout, roach, lake trout and shiners don’t
reproduce, leeches and mayfly larvae vanish. 5.4 Crayfish
reproductivity is impaired. 5 Snail and clams are extinct. All
but one species of crayfish are extinct, brook trout, walleyes
and most bullfrogs are gone, most fish species experience
reproduction difficulties, zooplankton population begins to
drop, green and green-blue algae mats have largely spread 4.8
Leopard frog numbers decline 4.5 Mayflies and stoneflies
vanish, a slowing in growth rate and oxygen uptake of bacteria
is notable 4.2 The common toad disappears 4 The oxygen output
of Lobelia plants declines 75% 3.5 Virtually all clams, snails,
frogs, fish and crayfish vanish 2.5 Only a few species of
acid-tolerant midges, bacteria and fungi are alive 2 In
practical terms, the lake is sterile Two hundred and twenty
lakes in Ontario have been found acidified, meaning their pH is
less that 5.1 year round.2 Terrestrial Plant Life It is much
more difficult to solve the mystery of forest destruction
compared to that of a lake. This is partially because trees live
so much longer than fish do, and acid rain damage in trees may
not show up for thirty or forty years. It is also very difficult
to replicate forest conditions in a laboratory, such as insects,
cold winters, pollution, elevation and abrupt changes in rainfall.
Each of these conditions put stress on the trees and can be
considered variables. Many scientists are convinced that
because of the complexity of a forest ecosystem, it is nearly
impossible to prove the death of forests is due to pollution in
the form of acid rain, but deduce from many experiments it is a
main factor in forest destruction. Deciduous trees are like air
filters, and screen particles that pass through the air around
them. These particles collect on the leaves of the tree, and
studies have shown that when these particles contain acid they
can cause damage to the leaves. The leaves are the part of the
tree that help make food, hence any damage to the leaves will
result in harm to the health of the entire tree. Coniferous trees
are vulnerable to the harmful effects of acid rain as well. The
tree’s needles are designed to nourish the tree after they fall
to the ground. Each needle houses whole colonies of microscopic
bacteria and algae that help the tree change nitrogen into food
at the roots. Acid rain will often burn away this material,
thereby reducing adequate food supply, and weakening the
tree’s health. After the damage has been done to leaves and
needles, acid rain harms the trees even more through the soil.
Soil has a level of acid. Acid in the soil can do damage to the
trees by releasing aluminum, which, once in contact with acid,
becomes highly poisonous to forests. The aluminum will enter
the tree’s hairlike roots, choking them, and when these become
clogged, the upper branches are no longer nourished. Even
though there may be plenty of moisture in the soil, the tree can
die of thirst. Scientists have discovered that the aluminum
content in soil has tripled since the 1960s.3 Acid rain also kills
important organisms on the forest floor. The process of
decomposition is interrupted as the acid kills many of the
bacteria and fungi that live on the forest floor. At a pH level
of 4.0, the earthworm dies, further damaging the decomposition
process. Without earthworms and bacteria to decompose the
debris consisting of animal and bird droppings, twigs and dead
leaves, the materials continue to build on the forest floor.
When debris builds up, seedlings from the trees are not able to
survive, because they can not work their way down to the soil
to root. This causes the forest to slowly disappear, as older
trees die, and the forest will not be able to rejuvenate itself.
Acid rain is hardest on trees high up in mountains, because it is
often covered in mist or fog, literally bathing the trees in an
acidic atmosphere. Trees also suffer because of changes in the
soil. Acid rains leach metals (draw metals out of mud and rocks)
in the soil, and the trees in turn intake these harmful metals
through their roots. Figure 1-2 shows the damage that acid rain
can to do a forest Human Health It is known that the earth
contains many metals that are potentially dangerous to humans,
such as lead, mercury, and aluminum. Most of the time these
metals are harmless because they are in the soil, bonded to
other elements. The problem occurs when acid detaches these
metals from the rocks and soils, and can be carried deep into
the ground and make their way to underground streams. These
streams eventually connect to our water sources. Medical
researchers have found these metals can be dangerous, and on
rare occasion, is even fatal. Aluminum has been found to kill
people who have kidney problems, and can also collect in brain
tissue. Some scientists even suspect that aluminum deposits on
the brain cause Alzheimer’s disease. (A disease that results in
memory loss, nervous system problems, and death. Acid rain is
known to irritate the whole respiratory system, beginning with
mucous membranes in the nose and throat, all the way to tissue
in the lungs. Consequently, acid rain has an increased effect on
people with respiratory problems. The U.S. Council on
Environmental Quality estimates health-related problems due
to acid precipitation cost the United States $2 billion per
year.4 In August 1987, over one hundred people were treated
for eye, throat, and mouth irritation when 1.8 metric tonnes of
highly toxic sulfur dioxide gas leaked from an Inco plant near
Sudbury, Ontario. Even Fig 1-2 This picture shows how a
coniferous forest has been virtually destroyed. Acid rain is
blamed for the destruction of terrestrial ecosystems around
the world. without accidents, the sulfur dioxide regularly
emitted from Inco smokestacks has been linked to chronic
bronchitis in Inco employees.5 Drinking Water Acid rain
damages drinking water in various ways. Thus far, amounts of
metals in drinking water have been minimal, however the fact
that metals even leak into the water is troubling to scientists.
Since metals remain in the body once ingested, over time, small
amounts accumulate into large quantities, and it has yet to be
concluded how large an amount will prove to be harmful to
humans. Acid rain causes damage by loosening metals off metal
water pipes. Modern plumbing uses plastic tubing, but older
systems have copper pipes. The copper pipes are held together
by a mixture of tin and lead. Lead is known to be extremely
dangerous to humans, even in small amounts, and will cause
damage to the brain and nervous system. A study that was done
in Ontario found that water sitting in plumbing pipes for ten
days contained hazardous levels of copper and lead. This
discovery could be a widespread danger, since often people will
go on vacation and not shut off the plumbing, allowing water to
sit and absorb these dangerous metals. Acid rain can also
dissolve the reinforcements that occur around large water
pipes. In some parts of the United States, asbestos is used to
reinforce the cement bases that hold water pipes. Asbestos is
not dangerous when bound to the cement, but is highly
dangerous when separated, and has been linked to cancer and
other serious diseases. Many health officials worry that loose
asbestos will find it’s way to the city’s water when acid rain
comes in contact with the cement. Effects On Man Made
Structures Scientists are becoming increasingly concerned with
acid rain’s destruction of the ‘built environment’. There are
objects in our built environment that are irreplaceable.
Historic landmarks and statues, old cathedrals and temples,
paintings and sculpture – all are part of the built environment
and are slowly being damaged. Some of these objects are
practical, making life easier, safer or more comfortable. Many
factors determine how much damage acid rain will do, including
the amount of rain, the location, and direction of wind. All
influence the amount of corrosion done. Areas that have a large
amount fog or humidity tend to suffer more than dry areas,
which is why many steel bridges located over water get rusted
and corroded by acid. When metal is decayed, it cannot take
the same amount of stress of weight as when it was originally
created. Acid rain has been blamed in several collapses of
bridges around the world. Acid rain corrodes the steel track
used on railroads, thus the tracks must be constantly checked.
Metal in air planes can also be eaten away by acid rain. The
United States Air Force spends more that $1 billion every year
to repair or replace damaged parts.6 A study done in Sweden
showed that metal rusts four times faster in areas that receive
a lot of acid rain. This figure is staggering, and yet, metal is
not the only material damaged by acid rain. Houses and
buildings made of brick and stone are affected as well. Acid
rain can dissolve the mortar, which is used in cement to hold
bricks together. When the mortar is worn away, the bricks
crumble more easily, because they shift and cannot stay intact
against the heavy weight of the bricks pressuring from above.
The corrosive effects of acid rain are particularly obvious on
limestone, because it is composed of calcium carbonate, which is
highly reactive with acid rain. Tombstones made of marble
(which is metamorphosed or heated limestone) have been badly
damaged, while older tombstones made of slate remain intact.
Famous buildings such as the Taj Mahal, The United States
Capitol building and the Lincoln Memorial in Washington, are all
being continually damaged by acid rain. Statues made of bronze
and copper are particularly susceptible to corrosion. These
statues turn green naturally, and this covering, called a patina,
acts as a protective shield against the elements. Acid rain eats
away at the patina, and where the acid dissolves the green
covering, it leaves a streaky black coat. This process ruins
statues throughout the world. How Does Acid Rain Affect the
Economy? Canada/American Relations Canada is particularly
susceptible to the effects of acid rain. Its geographical
location places it directly in the path of a large amount of U.S.
emission, and the granite bedrock of the Canadian Shield has a
poor buffering quality. (A buffer is a material that can
chemically weaken acid soil and is less harmful to the
environment, such as lime or baking soda.) The lack of such a
quality renders Eastern Canada highly vulnerable to damage due
to United States pollution. Canada suffers more from acid rain
than the United States does, even though much of the pollution
originates in the United States. Acid rain costs Canadians
hundreds of millions of dollars every year. To try and decrease
the large amounts of money the pollution is costing tax payers,
Canada has passed laws to force its electrical companies to cut
down on harmful emissions. However, no matter what laws are
passed in Canada, it is not possible to stop U.S. power plants
from sending acid in its direction. Figure 1-3 displays amounts
of emissions created by the United States and Canada. The
Gavin power plant is an excellent example of how the United
States sends tonnes of acid to Canada every year. Every hour,
this power plant burns 600 tonnes of coal. The higher the
smokestack, the further the dangerous gases will travel, and the
Gavin smokestack is 1 103 feet tall.7 Obviously, The Gavin can
not be solely blamed for the pollution, but it is power plants
such as these that have caused trouble between the two
countries. It is estimated that about 50% of the sulfate
deposited in Canada derived from American sources.8 Sixty of
the largest plants and thus largest polluters are located in the
Ohio Valley, a short distance away from vulnerable Canadian
land. In 1980, Canada and the United States signed a
Memorandum of Intent, an agreement that both countries would
make acid rain control a priority. They both promised to focus
on developing ideas to cut down the amount of sulfur dioxide
and nitrogen oxide emissions being pumped into the air. In the
past, Canada has presented devastatingly large figures to the
United States, in an attempt to have them change laws and
regulations regarding pollution. Unfortunately, the attempts
thus far have been unsuccessful, as the US government requests
more testing and studies instead of altering laws. In the recent
past, the negotiations between Canada and United States
representatives have been hardly reminiscent of efforts put
forth by Canadian officials. Many U.S. politicians still qualify
acid rain as a ‘minor’ problem, and it is treated as such,
according to Raymond Robinson, chairman of the Canadian
Environmental Ass