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Acid Deposition Essay, Research Paper


By Jody Prouse


Picture a cancer, eating a human, a sister, a brother, away bit by bit. Destroying every organ, slowing every heart beat, weakening every muscle. Then finally, shutting the body down. Ending it?s existence. Acid deposition is the earth?s cancer. Every rain drop causing massive destruction throughout the world. Every downpour, killing another lake, stream, fish, tree, or human. Every smog, killing it?s inhabitants, weakening it?s life.

Unlike many environmental problems, including CFCs (chlorofluro-carbons), which directly destroys the ozone, it?s effects touch more than just one thing directly. The precipitation, and the dry deposition kill or weaken anything and everything it touches. It can also effect everything indirect, as the chemicals and acids stored in the rain are transferred through leaves and soil to roots and lakes from runoff. This is the silent killing it performs, with obvious effects, and so close to home.

Believe it or not, but Canada receives a lot of the acidic deposition. The Canadian government has even dubbed the problem, the most pressing environmental issue facing the nation. The United States is mainly to blame for this domestic epidemic. The United States creates over 130 million tons of sulfur dioxide (50 to 70% of overall sulfur dioxide emissions in Canada come over the border from the United States) , which is transported through the air to Canada, where it kills our lakes, our rivers, our trees, and our wildlife. Even though emissions have been cut down in Canada by 30%, the US still manages to produce millions of tones of harmful chemicals which end up polluting our nation, our home.

Acidity, the pH scale, and measurements

To understand what makes precipitation acidic, one must understand what an acid is and how it is measured. The acidity or alkalinity of a substance is measured on a potential hydrogen (pH) scale. This measures the amount of hydrogen ions in a substance. The more hydrogen ions, the lower the pH level. A reading below 7 indicates an acid, therefore one above 7 indicates a base. Clean, unpolluted precipitation is naturally acidic, with a pH of 5.6. When precipitation with pH levels lower than 5.6 fall, the number of hydrogen ions in the soils and plants increase, upsetting their natural balance, killing all life. Rain, in Pitlochry, Scotland, has been tested with pH levels as low as 2.4, almost that of lemon juice. The pH levels of acid deposition have been strong enough to wipe out whole lakes of water species.

What is Acid Deposition?

Acid deposition, by definition, is “the transfer of acids from the earth?s atmosphere to its surface.” This is done two ways: acid precipitation and dry deposition. Acid Rain, the most popular form of acid precipitation, attracts most of the attention of the media, and most environmentalist groups, but it isn?t the only form of acid precipitation there is. The acids can be transferred through acid fogs, acid sleets, acid snows, acid hails, acid fogs, and through acid mists. It is the biggest culprit when it comes to the damage caused by acid deposition.

The other form of acid deposition, is very common, yet unknown to many environmentalists. Dry deposition, is the falling action of acidic particles (mainly sulfur dioxide, nitric oxide, and nitrogen oxides) during dry periods. Examples of such would be smog. Both examples contribute equally to the destruction of the earth?s environments and inhabitants.


Acid deposition is the result of smoke emissions from fossil fueled power plants, oil refineries, (such as Inco, Algoma Steel, and Falconbridge). It is also the result of every single person, who drives or rides a vehicle to work everyday. An unfortunate fact being that 90% of the sulfur dioxide and 95% of the nitrogen oxide emissions occurring in eastern North America are of human origin. “The burning of fossil fuels, such as coal and oil are largely to be blamed for half of the emissions of this gas (sulfur dioxide) in the world.” These environmental felons kill life everyday.

Acid deposition is caused by the emissions of nitric oxide (NO), nitrogen oxide (NO2) and sulfur dioxide (SO2) into the atmosphere. These gases are emitted by natural sources such as volcanoes, sea spray, rotting vegetation, and plankton, but the amounts are not substantial enough to cause precipitation with pH levels that low.

Acid precipitation is caused when emissions containing sulfur dioxide, nitric oxide, and nitrogen oxide, combine with moisture in the air to form acid precipitation. When combined with water, they complete a chemical formula, one that represents destruction and devastation.

Dry Deposition is the particles of the chemicals themselves suspended in the air.

Effects on the Environment

All forms of acid precipitation damage all kinds of vegetation. The problems caused by it are numerous and in most cases cause death, whether it be a tree, shrub, lake, stream, or fish. The effects, though, depend on weather conditions, humidity, sunlight , presence of other pollutants, length of time the pollutants have remained in the atmosphere, and buffering capacity . They also depend on contact with:

? Primary receptors – come into direct contact with pollutants (e.g. building, trees, plants, etc.).

? Secondary receptors – come into contact after they?ve come into contact with other materials (e.g. foliage of plants, soil beneath vegetation, etc.).

? Tertiary receptors – indirectly affected (e.g. subsoil, bedrock, watercourses and lakes).

All effects may come in combinations, separately, or all at once.

Effects on crops

Scientists have now received evidence that proves that acid deposition greatly effects agriculture, along with everything else. One some croplands, tomatoes grow to only half their full weight and the leaves of radishes wither. Nitrogen oxide is the culprit responsible for $2 billion to $4.5 billion worth of wheat, corn, soybeans, and peanuts. This decrease can hurt 3rd world countries, and augment the price of food worldwide. Thousands of people could starve due to this new scientific discovery.

Effects on Forests

A young man kills someone with his bare hands, and citizens cry out in rage. They say they will do anything to prevent him from hurting another, killing another. Yet silently, everyday, vegetation is weakened, threatened and killed, far away or close to their homes, and they sit back and watch.

Scientists have known for twenty years now the effects that acid deposition has on the forests. The forests themselves grow thinner, and slower, than their predecessors, due to the damage it has caused. Coniferous tree needles die-back , their growth is stunted, they loose their resistance to disease and drought, and they experience a lack of natural regrowth. Deciduous trees, on the other hand, grow discolored or misshapen leaves, experience early leaf fall, have dead tree tops and/or damaged bark, loose their resistance to drought and disease, and experience a lack of natural regrowth. The loss of feeder roots and smaller tree rings are also effects. Basically, the forests are slowly dying off.

Forests in high mountain regions receive additional acid from the acidic clouds and fog, which are often more acidic than the rainfall. When leaves are frequently bated in this acid fog their protective waxy coating can wear away. The loss of the coating damages the leaves and, and they become unable to produce enough food energy to remain healthy. Once trees are weak, they can be more easily attacked by diseases or insects that ultimately kill them. It seems that damage to plants through short periods of highly concentrated exposure is more are more damaging than prolonged exposure to weak concentrations of acids.

Effects on Humans

Humans don?t exactly react the same way to acid deposition as the rest of nature. They don?t mutate, or fail to reproduce. They don?t yellow from the outside in, or slowly corrode until they vanish. “The links between acid pollution and human illness are generally unclear.” Acid deposition distributes toxic metals into our water systems, and are consumed when eat, or drinking. They have been linked to everything from headaches to cancer, brain damage and senile dementia. Aluminum, which acid deposition releases into the soil, is known to cause Alzheimer?s disease. Sulfuric aerosols have been known to cause bronchitis, tracheitis, respiratory problems, such as asthma, and poor visibility.

Effects on Water

Unlike the changes to the forest, lakes react in a slower fashion. “The effect of acid deposition on lakes is gradual, quiet and insidious.” It takes a large amount of water to change the pH level in a lake or stream, particularly if the water is constantly moving, yet of 200 lakes in the Killarney region, 40 are dead and dying. That means that those lakes have taken a large amount of precipitation. It also means that way too much acid deposition is being produced.

First of all, to understand all the effects, one must learn the concept of a dead lake. When a lake is dead, like every one in five in Norway, it contains no life within. Have you ever noticed why Lake Simcoe, for example, is so clear? It?s because there are no fish, no plants, not even the slightest bacteria in the lake. Why? The pH levels are to high.

Lakes become acidic once the soil surrounding the lake cannot buffer the acid rain enough to neutralize it. When lakes reach a certain pH level, fish dye off, effecting the natural balance within the lake, and thus killing everything within. As you can see in the diagram, certain fish die off at different points, yet they are effected in some way by such a small change in the pH levels. A change like this prevents fish eggs from hatching, and caused serious mutations among the fish. As you can see, murder is not the only crime that acid deposition commits.

Effects on man made materials

As everyone knows, acids corrode metal. This fact works when describing the effects of acid deposition on metals. Building materials, statues, pillars, etc., wear out naturally, over the centuries, due to rain, and wind. Acid deposition speeds up the process. An example of the damage that this issue has caused would be the ancient Mayan ruins in Central America, which have turned black due to the amount of acid deposition it receives. One must remember how precious and irreplaceable these things are. The statue of liberty had to be redone in 1984 due to acid deposition?s dirty deeds. Even cars aren?t immune to the damage. Paint has been known to chip away, or change colour due to the precipitation it receives. This is not a minor problem.


There are no permanent solutions to acid deposition, but there are alternatives. Some countries have forced their domestic industries to install filters on their smokestacks to decrease the amount of toxic pollution released into the atmosphere. Some countries have done so, yet the majority haven?t, due to fear of the companies leaving for somewhere cheaper, where they can pollute if they please.

Scientists have found a way to neutralize the effects of acid deposition through a process known as liming. Lime (crushed limestone) is an alkaline which reacts with the acids in the lakes, streams, or soil, neutralizing them. This process is frequently used, yet is expensive. About 4 tones per hectare are needed to raise the pH level from 5.5 to 6.5. Species and animals quickly return to the lakes thereafter. Liming is repeated in the lakes ever 2 to 5 years to prevent the return of the acids.

Conservation of energy is a key to the prevention of acid deposition. Over 50% of the energy produced today come from fossil fuels; the main contributor to acid deposition. The Canadian government estimates that high standards of living can still be enjoyed if measures were taken to consume 50% less energy. The less energy used means less energy produced. Companies have recently switched from burning coal (which produces high levels of sulfur dioxide) to burning low-sulfur coal. Scrubbers are also used on smokestacks to prevent the release of fly ash (part of dry deposition) and smoke from tormenting the atmosphere. Almost 90% of the sulfur oxides are removed from the emissions, due to the spray of limestone in the scrubbers.

By using unleaded fuel, one can prevent the emissions of hazardous chemicals into the atmosphere, and save a few dollars. Catalytic converters also reduce the pollution caused by cars.

Taking precautions costs a lot of money, and normally takes a large chunk out of the profit margin of large companies. The Department of Commerce Bureau of Economic Analysis estimates the overall cost for air pollution control exceeds $32 billion a year. Scrubbers alone cost millions of dollars for installation, and maintenance. Liming is the cheapest method, at approximately $10 to $15 a square acre, but is only temporary, and must be done often.

Canada has realized that it must take control of it?s environmental state. It was a member of the 30% Club, which was a meeting of 35 different countries from around the world who promised to reduce sulfur dioxide emissions by 30% by the year 1982. The Clean Air Act which proposed a 50% reduction in the same emissions by 1995. It forced companies to choose between scrubbers or clean coal technologies to install in their plants. It also called for a 10% reduction of nitrogen oxides by the same year.

Another alternative would be to use alternate sources of energy. Coal, oil, and natural gas account for 75% of the worlds energy requirements. These are not replaceable sources of energy, and may eventually run out. Renewable sources are a recommended alternate to certain forms of energy production. Hydro-electric, wave and tidal power use the power of water to turn turbines. It produces 25% of the world?s electricity. Geothermal energy is produced using natural heat from inside the earth?s crust. Wind power, from windmills produce the least amount of energy due to the unpredictability of the weather. Nuclear energy is a very efficient source of clean power, yet causes much fear of accidents or disposal of nuclear waste. Hydro-electric is the most effective source of pollution-free energy, that causes little damage to the environment. Scientists and governments should look at more effective ways to produce energy and conserve the environment.



Baines – Acid Rain, ? 1989, Wayland Publishers Ltd., East Sussex, England.

Gay, Kathleen – Acid Rain, ? 1983, Franklin Watts, New York.

Howard, Ross and Perley, Michael – Poisoned Skies, ? 1991, Stoddart Publishing Co. Ltd., Toronto.

Kahan, Archie M. – Acid Rain, ? 1986, Fulcrum, Inc., Golden, Colorado.

McCormick, John – Acid Earth, ? 1989, Earthscan Publications Ltd., London.

Miller, Christina G. and Berry, Louise A. – Acid Rain, ? 1986, Julian Messner, New York.

Patten, J.M. – Acid Rain, ? 1995, The Rourke Book Co., Vero Beach, Fl.

Pawlick, Thomas – A Killing Rain, ? 1984, Douglas and McIntyre, Vancouver.

Pringle, Lawrence – Rain of Troubles, ? 1988, MacMilan Publishing Co., New York.

Ostmann Jr., Robert – Acid Rain, ? 1982, Dillon Press Inc. Minneapolis, Minn.

Weller, Phil, and the Waterloo Public Interest Research Group – Acid Rain, ? 1980, Between the Lines, Kitchener, ON.


The New Encyclopedia Britannica – Vol. 1, 15th Ed. – ? 1997, Encyclopedia Britannica Inc.

The World Book Encyclopedia – Vol. 1 – ? 1992, World Book Inc.


Corbeil, Jean-Claude and Archambault, Ariane – The Colour Visual Dictionary, ? 1992, Stoddart Publishing Co. Ltd., Toronto.

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