Acid Rain : The Causes, History, and Effects of Acid Rain

What Is Acid Rain?

Acid rain is made up of water droplets that are unusually acidic because of atmospheric pollution, most notably the excessive amounts of sulfur and nitrogen released by cars and industrial processes. Acid rain is also called acid deposition because this term includes other forms of acidic precipitation such as snow.

Acidic deposition occurs in two ways: wet and dry. Wet deposition is any form of precipitation that removes acids from the atmosphere and deposits them on the Earth’s surface.

Dry deposition polluting particles and gases stick to the ground via dust and smoke in the absence of precipitation. This form of deposition is dangerous, however, because precipitation can eventually wash pollutants into streams, lakes, and rivers.

Acidity itself is determined based on the pH level of the water droplets. PH is the scale measuring the amount of acid in the water and liquid. The pH scale ranges from 0 to 14 with a lower pH being more acidic while a high pH is alkaline; seven is neutral. Normal rain water is slightly acidic and has a pH range of 5.3-6.0. Acid deposition is anything below that range. It is also important to note that the pH scale is logarithmic and each whole number on the scale represents a 10-fold change.

Today, acid deposition is present in the northeastern United States, southeastern Canada, and much of Europe including portions of Sweden, Norway, and Germany.

In addition, parts of South Asia, South Africa, Sri Lanka, and Southern India are all in danger of being impacted by acid deposition in the future.

Causes and History of Acid Rain

Acid deposition can be causes by natural sources like volcanoes, but it is mainly caused by the release of sulfur dioxide and nitrogen oxide during fossil fuel combustion.

When these gases are discharged into the atmosphere, they react with the water, oxygen, and other gases already present there to form sulfuric acid, ammonium nitrate, and nitric acid. These acids then disperse over large areas because of wind patterns and fall back to the ground as acid rain or other forms of precipitation.

The gases most responsible for acid deposition are a byproduct of electric power generation and the burning of coal. As such, man-made acid deposition began becoming a significant issue during the Industrial Revolution and was first discovered by a Scottish chemist, Robert Angus Smith, in 1852. In that year, he discovered the relationship between acid rain and atmospheric pollution in Manchester, England.

Although it was discovered in the 1800s, acid deposition did not gain significant public attention until the 1960s, and the term acid rain was coined in 1972. Public attention further increased in the 1970s when the New York Times published reports about problems occurring in the Hubbard Brook Experimental Forest in New Hampshire.

Effects of Acid Rain

After studying the Hubbard Brook Forest and other areas, researchers have found several important impacts of acid deposition on both natural and man-made environments.

Aquatic settings are the most clearly impacted by acid deposition though because acidic precipitation falls directly into them. Both dry and wet deposition also runs off of forests, fields, and roads and flows into lakes, rivers, and streams.

As this acidic liquid flows into larger bodies of water, it is diluted, but over time, acids can accrue and lower the overall pH of the body of water. Acid deposition also causes clay soils to release aluminum and magnesium further lowering the pH in some areas. If the pH of a lake drops below 4.8, its plants and animals risk death. It is estimated that around 50,000 lakes in the United States and Canada have a pH below normal (about 5.3 for water). Several hundred of these have a pH too low to support any aquatic life.

Aside from aquatic bodies, acid deposition can significantly impact forests.

As acid rain falls on trees, it can make them lose their leaves, damage their bark, and stunt their growth. By damaging these parts of the tree, it makes them vulnerable to disease, extreme weather, and insects. Acid falling on a forest’s soil is also harmful because it disrupts soil nutrients, kills microorganisms in the soil, and can sometimes cause a calcium deficiency. Trees at high altitudes are also susceptible to problems induced by acidic cloud cover as the moisture in the clouds blankets them.

Damage to forests by acid rain is seen all over the world, but the most advanced cases are in Eastern Europe. It’s estimated that in Germany and Poland, half of the forests are damaged, while 30% in Switzerland have been affected.

Finally, acid deposition also has an impact on architecture and art because of its ability to corrode certain materials. As acid lands on buildings (especially those constructed with limestone) it reacts with minerals in the stones sometimes causing them to disintegrate and wash away. Acid deposition can also cause concrete to deteriorate, and it can corrode modern buildings, cars, railroad tracks, airplanes, steel bridges, and pipes above and below ground.

What's Being Done?

Because of these problems and the adverse effects air pollution has on human health, a number of steps are being taken to reduce sulfur and nitrogen emissions. Most notably, many governments are now requiring energy producers to clean smoke stacks by using scrubbers which trap pollutants before they are released into the atmosphere and catalytic converters in cars to reduce their emissions. Additionally, alternative energy sources are gaining more prominence today, and funding is being given to the restoration of ecosystems damaged by acid rain worldwide.

Acid Rain: Scourge of the Past or Trend of the Present?

Acid rain. It was a problem that largely affected U.S. eastern states. It began in the 1950s when Midwest coal plants spewed sulfur dioxide and nitrogen oxides into the air, turning clouds--and rainfall--acidic.

As acid rain fell, it affected everything it touched, leaching calcium from soils and robbing plants of important nutrients. New England's sugar maples were among the trees left high and dry.

Acid rain also poisoned lakes in places like New York's Adirondack Mountains, turning them into a witches' brew of low pH waters that killed fish and brought numbers of fish-eating birds like loons to the brink.

Then in 1970, the U.S. Congress imposed acid emission regulations through the Clean Air Act, strengthened two decades later in 1990. By the 2000s, sulfate and nitrate in precipitation had decreased by some 40 percent.

Has acid rain now blown over? Or is there a new dark cloud on the horizon?

In findings recently published in the journal Water Resources Research, Charles Driscoll of Syracuse University and the National Science Foundation's (NSF) Hubbard Brook Long Term Ecological Research (LTER) site in New Hampshire reports that the reign of acid rain is far from over.

It's simply "shape-shifted" into a different form.

Hubbard Brook is one of 26 NSF LTER sites across the nation and around the world in ecosystems from deserts to coral reefs to coastal estuaries.

Co-authors of the paper are Afshin Pourmokhtarian of Syracuse University, John Campbell of the U.S. Forest Service in Durham, N.H., and Katharine Hayhoe of Texas Tech University. Pourmokhtarian is the lead author.

Acid rain was first identified in North America at Hubbard Brook in the mid-1960s, and later shown to result from long-range transport of sulfur dioxide and nitrogen oxides from power plants.

Hubbard Brook research influenced national and international acid rain policies, including the 1990 Clean Air Act amendments.

Researchers at Hubbard Brook have continued to study the effects of acid rain on forest growth and on soil and stream chemistry.

Long-term biogeochemical measurements, for example, have documented a decline in calcium levels in soils and plants over the past 40 years. Calcium is leaching from soils that nourish trees such as maples. The loss is primarily related to the effects of acid rain (and acid snow).

Now, Hubbard Brook LTER scientists have discovered that a combination of today's higher atmospheric carbon dioxide (CO₂) level and its atmospheric fallout is altering the hydrology and water quality of forested watersheds--in much the same way as acid rain.

"It's taken years for New England forests, lakes and streams to recover from the acidification caused by atmospheric pollution," says Saran Twombly, NSF program director for long-term ecological research.

"It appears that these forests and streams are under threat again. Climate change will likely return them to an acidified state. The implications for these environments, and for humans depending on them, are severe."

Climate projections indicate that over the 21st century, average air temperature will increase at the Hubbard Brook site by 1.7 to 6.5 degrees Celsius, with increases in annual precipitation ranging from 4 to 32 centimeters above the average from 1970-2000.

Hubbard Brook scientists turned to a biogeochemical model known as PnET-BGC to look at the effects of changes in temperature, precipitation, solar radiation and atmospheric CO₂ on major elements such as nitrogen in forests.

The model is used to evaluate the effects of climate change, atmospheric deposition and land disturbance on soil and surface waters in northern forest ecosystems.

It was created by linking the forest-soil-water model PnET-CN with a biogeochemical sub-model, enabling the incorporation of major elements like calcium, nitrogen, potassium and others.

The results show that under a scenario of future climate change, snowfall at Hubbard Brook will begin later in winter, snowmelt will happen earlier in spring, and soil and stream waters will become acidified, altering the quality of water draining from forested watersheds.

"The combination of all these factors makes it difficult to assess the effects of climate change on forest ecosystems," says Driscoll.

"The issue is especially challenging in small mountain watersheds because they're strongly influenced by local weather patterns."

The Hubbard Brook LTER site has short, cool summers and long, cold winters. Its forests are made up of northern hardwood trees like sugar maples, American beeches and yellow birches. Conifers--mostly balsam firs and red spruces--are more abundant at higher elevations.

The model was run for Watershed 6 at Hubbard Brook. "This area has one of the longest continuous records of meteorology, hydrology and biogeochemistry research in the U.S.," says Pourmokhtarian.

The watershed was logged extensively from 1910 to 1917; it survived a hurricane in 1938 and an ice storm in 1998.

It may have more to weather in the decades ahead.

The model showed that in forest watersheds, the legacy of an accumulation of nitrogen, a result of acid rain, could have long-term effects on soil and on surface waters like streams.

Changes in climate may also alter the composition of forests, says Driscoll. "That might be very pronounced in places like Hubbard Brook. They're in a transition forest zone between northern hardwoods and coniferous red spruces and balsam firs."

The model is sensitive to climate that is changing now--and climate changes expected to occur in the future. 

In scenarios that result in water stress, such as decreases in summer soil moisture due to shifts in hydrology, the end result is further acidification of soil and water.

Gardens: The Surprising Benefits of Acid Rain

Showing the ecological devastation that sulphuric acid raining down from the sky had on forests and waterways across the world. Yet the decline over the past 30 years in the emissions of toxic sulphur dioxide in air pollution that once caused this phenomenon has had an enduring impact on British soils, with far-reaching effects on agriculture and even our gardens — and not always a positive one.

Sulphur is a key plant nutrient vital to healthy growth, but UK soils are naturally deficient in this essential mineral. Back in the 1980s this was of little concern to growers as these levels were continually topped up by “atmospheric deposition”, ie acid rain.

Fast forward to 2016 and this is increasingly worthy of attention. One small survey conducted over 2014 and 2015, for example, found that only 13% of the crops sampled showed sulphur levels in the “normal” range, with the rest registering as low or slightly low. This is a concern as inadequate sulphur levels have been shown to slash farm yields of some (but admittedly not all) crops by as much as 50%. Surprising as it may seem, even acid rain clouds can have a silver lining.

As many plants also use sulphur pulled up from the soil to generate defence compounds to help ward off pests and diseases, this deficiency can also result in weak, vulnerable crops that require higher pesticide applications. These defence compounds also happen to be the exact same chemicals that give vegetables, like onions, garlic, broccoli and sprouts, their characteristic flavour and associated health benefits. Heard about the antioxidants in broccoli and garlic? It’s the sulphur chemicals, derived from the soil, that are doing the work.

While this effect is likely to be greater in agricultural soils, where crops are constantly taking sulphur from the soil only to be harvested and removed from the site, this can be an issue even in garden soils. Take lawns for example: years of continual mowing and disposal of the grass clippings essentially mimics that of agriculture – acting like a pump on a conveyor belt to suck up the sulphur.

If you suspect your soil is sulphur-deficient, there is a simple solution that offers all of the benefits without the damaging acidity: Epsom salts. This naturally occurring mineral combines both sulphur and another essential plant nutrient, magnesium, in a double whammy and can be bought for minimal cost at any garden centre. Simply sprinkle over the ground according to package directions for higher yields of tastier and more nutritious crops.

Acid Deposition : Acid Rain, Mist and Fog

Acid deposition is a general name for a number of phenomena, namely acid rain, acid fog and acid mist. This means it can imply both wet and dry (gaseous) precipitation. Acid deposition is a rather well known environmental problem, for example acid fog killed several thousand people in London in 1952.

Acid deposition is concerned with long-range rather than local effects. Pollutants are mixed in the atmosphere and therefore usually cannot be attributed to any local source. Pollutants are generally more dispersed and of lower concentrations than local ground level pollutants.

Acid deposition typically has a pH below 4, but this may be as low as 1.5 under seriously acidic conditions. It primarily consists of two types of compounds, namely sulphuric acid (H₂SO₄) and nitric acid (HNO₃).

Sulphuric acid is formed by conversion of sulphur dioxide emitted from power stations, melting processes, home fires, car exhausts and other sources. It contributes about 70% to the overall acidity of deposition.

Reaction mechanism: SO₃ + H₂O -> H₂SO₄

Nitric acid is formed from nitrogen oxide (NO_x) emissions from fossil fuel combustion. It contributes about 30% to the overall acidity of deposition.

Reaction mechanism: NO₂ + OH^- -> HNO₃

Acid rain has various environmental and health effects, for example:

- Chocking plant leave pores (forest loss)

- Corroding stone and brick walls of buildings and monuments

- Corroding paper and rubber objects

- Altering soil chemistry (soil acidification, loss of plant nutrients)

- Altering the chemical balance of lakes and streams

- Disrupting fish gill operation (fish deaths)

- Deteriorating human breathing disorder (asthma, bronchitis, lung oedema)

When people die of acid deposition it is usually caused by access mucous production in the bronchi, leading to chocking from a lack of oxygen, or a heart attack.

Acid deposition in various countries

Acid deposition is a transboundary environmental problem. This basically means that emissions in one country may affect forests and structures in a neighbouring country. Therefore, international agreements were made, such as the Sulphur emissions Reduction Protocol (1979) and the Convention on Long-Range Transboundary Air Pollution (1983).

Some examples of countries that experience(d) acid deposition, either from their own sources or from transboundary air pollution:

- Britain: smog episodes around London, particularly in 1952

- Germany: acid mists in central Germany and the Black Forest area, acid cold smog from Poland and former Czechoslovakia in 1985

- Greece: intense industrialization in the Athens area causes deterioration of ancient monuments such as the Parthenon by acid deposition

- Italy: damage to Venice structures from acid deposition

- Scandinavia: 15% of acid rain caused by Great-Britain

- Scotland: episodes of black acid snow in the Cairngorm mountains in 1984

- The Netherlands: corrosion of bells of the Utrecht Dom tower since 1951

- United States: acid rains disrupts forest ecosystems and pollutes surface waters, industrial fossil fuel combustion processes are adapted to prevent sulphur dioxide emissions.

Positive and Negative Impact of Acid Rain on Humans and the Environment.

Why acid rain is harmful to humans and the environment.

1) Acid rain can contribute to respiratory diseases and exacerbate existing medical conditions. For example, the nitrogen oxide in acid rain leads to the creation of ground-level ozone, which in turn can contribute to respiratory diseases such as pneumonia and bronchitis.

2) Acid rain can increase levels of aluminum in the soil, which prevents trees from taking up adequate water. What is even more troubling is that the higher levels of aluminum can eventually end up in streams and rivers. This in turn can prove fatal to aquatic as well as forest wild-life.

3) Acid rain has contributed to lower pH levels in streams and rivers across the United States, especially in the Northeast region. Most bodies of water have pH levels of about 6.5. Lower pH levels mean that the water is more acidic rather than alkaline. The Environmental Protection Agency recommends that pH levels of water be between 6.5 to 8.5 for drinking purposes. Bodies of water with lower pH levels may have higher iron and sulfur deposits, which in turn can prove harmful to the health of wildlife and humans. Sensitive species of wildlife may experience higher than normal mortality rates if the pH levels of water move away from the optimum range.

The advantages of acid rain.

It has recently come to the attention of the science community that acid rain may have a positive impact on humans and the environment.

As a rule, carbon dioxide and methane contribute significantly to what is considered global warming. However, the sulfur dioxide in acid rain suppresses some portion of methane production in the atmosphere. Methane results from bacteria breaking down organic compounds, and the sulfur in acid rain appears to suppress up to 30 or 40% of methane production in wetlands areas. For example, tests by NASA's Goddard Space Flight Center show that the sulfur in acid rain will continue to suppress methane production until at least 2030.

Other studies have shown that a rise in temperature, along with greater concentrations of nitrogen in the atmosphere, can contribute to higher growth in forests. For example, the nitrogen in acid rain allows the trees to store more carbon. This process is called carbon sequestration and is quite beneficial: higher carbon reserves allow a tree to produce the optimum level of sugars and carbohydrates necessary for growth. The National Institute for Climatic Change Research's Midwestern Regional Center has performed studies concluding that acid rain can contribute to forest growth.

Effects of Acid Rain on the Environment

The effects of acid rain

Acid rain can be carried great distances in the atmosphere, not just between countries but also from continent to continent. The acid can also take the form of snow, mists and dry dusts. The dry dust can cause respiratory illnesses in animals and humans such as asthma.  The rain sometimes falls many miles from the source of pollution but wherever it falls it can have a serious effect on soil, trees, buildings and water. 

In the 1970s the effects of acid rain were at their worst.  Forests all over the world were dying and in Scandinavia the fish were dying; lakes looked crystal clear but contained no living creatures or plant life. Many of Britain's freshwater fish were threatened;  their eggs were damaged and deformed fish were hatched. This in turn affected fish-eating birds and animals.  Animals belong to a food chain and often if one link in a food chain is taken away it can have devastating effects.

Forests

It is thought that acid rain causes trees to grow slower or even to die but scientists have found that the same amount of acid rain seems to have more effect in some areas than it does in others.

As acid rain falls on a forest it trickles through the leaves of the trees and runs down into the soil below. Some of it finds its way into streams and then into rivers and lakes. Some types of soil can help to neutralise the acid - they have what is called a "buffering capacity". Other soils are already slightly acidic so these are particularly susceptible to the effects of acid rain.

Acid rain can effect trees in several different ways, it may:

dissolve and wash away the nutrients and minerals in the soilwhich help the trees to grow such as potassium, calcium and magnesium

cause the release of harmful substances such as aluminium into the soil and waterways which further affects wildlife.

wear away the waxy protective coating of leaves, damaging themand preventing them from being able to photosynthesise properly.

A combination of these effects weakens the trees which means that they can be easily attacked by diseases and insects or injured by bad weather. It is not just trees that are affected by acid rain, other plants may also suffer.

Lakes and rivers

It is in aquatic habitats that the effects of acid rain are most obvious. Acid rain runs off the land and ends up in streams, lakes and marshes - the rain also falls directly on these areas.

As the acidity of a lake increases, the water becomes clearer and the numbers of fish and other water animals decline. Some species of plant and animal are better able to survive in acidic water than others. Freshwater shrimps, snails, mussels are the most quickly affected by acidification followed by fish such as minnows, salmon and roach. The roe and fry (eggs and young) of the fish are the worst affected as the acidity of the water can prevent eggs from hatching properly, can cause deformity in young fish which also struggle to take in oxygen.

The acidity of the water does not just affect species directly, it also causes toxic substances such as aluminium to be released into the water from the soil, harming fish and other aquatic animals.

Lakes, rivers and marshes each have their own fragile ecosystem with many different species of plants and animals all depending on each other to survive. If a species of fish disappears, the animals which feed on it will gradually disappear too. If the extinct fish used to feed on a particular species of large insect, that insect population will start to grow, which in turn will affect the smaller insects or plankton on which the larger insect feeds.

Buildings

Every type of material will become eroded sooner or later by the effects of the climate. Water, wind, ice and snow all help in the erosion process but unfortunately, acid rain can help to make this natural process even quicker. Statues, buildings, vehicles, pipes and cables can all suffer. The worst affected are things made from limestone or sandstone as these types of rock are particularly susceptible and can be affected by air pollution in gaseous form as well as by acid rain.

Reduce emissions:

Burning fossil fuels is still one of the cheapest ways to produce electricity so people are now researching new ways to burn fuel which don't produce so much pollution.

Governments need to spend more money on pollution control even if it does mean an increase in the price of electricity.

Sulphur can also be 'washed' out of smoke by spraying a mixture of water and powdered limestone into the smokestack.

Cars are now fitted with catalytic converters which remove three dangerous chemicals from exhaust gases.

Find alternative sources of energy:

Governments need to invest in researching different ways to produce energy.

Two other sources that are currently used are hydroelectric and nuclear power. These are 'clean' as far as acid rain goes but what other impact do they have on our environment?

Other sources could be solar energy or windmills but how reliable would these be in places where it is not very windy or sunny?

All energy sources have different benefits and costs and all theses have to be weighed up before any government decides which of them it is going to use.

Conserving resources:

Greater subsidies of public transport by the government to encourage people to use public transport rather than always travelling by car.

Every individual can make an effort to save energy by switching off lights when they are not being used and using energy-saving appliances - when less electricity is being used, pollution from power plants decreases.

Walking, cycling and sharing cars all reduce the pollution from vehicles.

What are the effects of acid rain on rocks?

Explore the effects of acid rain on rocks and minerals.

What you need

Chalk

Vinegar

Clear container

Measuring cup

Safety First!

Be careful not to rub your eyes when handling vinegar. Wash your hands immediately after finishing this experiment.

What to do

Break chalk into approximately 1/2 cm pieces.

Crush each 1/2 cm piece of chalk into smaller pieces, keeping each crushed 1/2 cm portion separate from each other.

Pour 100mL of vinegar into a container.

Add one crushed 1/2 cm piece of chalk to the container and observe the changes that take place.

Record what you see happening.

Add another piece of chalk to the container. Record what you see happening.

Continue to add chalk until you do not see any more changes taking place.

Discovery

What’s happening?

When the chalk (which is made of a base called calcium carbonate) is added to an acid like vinegar, a chemical reaction occurs. This reaction is called a neutralization reaction and occurs when an acid (pH less than 7) and a base (pH more than 7) are combined. During the reaction a gas and a neutral solution (pH equal to 7) are formed.

The gas produced in this activity is carbon dioxide and can be seen as bubbles in the vinegar. When the chalk is crushed before being added to the vinegar, the reaction will take place faster. If you keep adding more caulk, eventually you will notice that the bubbles stop forming. This shows that all the acid in the vinegar has been used up and the remaining liquid is now neutralized, meaning no further reaction is taking place. The solid chalk seems to disappear because it has been changed into another substance that has dissolved in the remaining liquid.

This neutralization reaction occurs naturally in the environment when weak acids in rain react with limestone and other rocks, resulting erosion (the wearing away of rock). This reaction occurs very slowly and the effects are not normally seen for hundreds or even thousands of years.

Acid rain is formed when certain pollutants dissolve in rain creating stronger acids. Acid rain is one factor that can increase the rate of erosion, with effects that can be seen in just a few decades. Limestone and marble are composed calcium carbonate, the same material as chalk, and are commonly used for constructing buildings and statues. Rain that is too acidic will “eat away” at these structures very quickly, the same way the vinegar ate away at the chalk.

Why does it matter?

Acid rain erosion of limestone and marble can result in a loss of artwork (outdoor statues, monuments, plaques, etc) that cannot be recovered. This increases the cost of maintaining buildings. Destruction of ecosystems like lakes and rivers can occur when they become too acidic, which can result in fish and other water-dwelling creatures not surviving, and no longer being a food source for birds and other animals.

On the positive side, regions where the bedrock or soil contain large amounts of limestone are less likely to have polluted water due to acid rain than areas with igneous bedrock. This is because the limestone (which is a base) is able to neutralize acid rain before it gets into the lakes and rivers, in much the same way the chalk in our experiment neutralized the vinegar. This means that damage due to acid rain depends on both the pH (amount of acid in a substance) of the rain and the type of soil/bedrock.

Acid Rain Facts

Rain or other types of precipitation that contain elevated hydrogen ion levels, making it acidic, are referred to as acid rain. Elevated levels of hydrogen ions cause the rain to have a low pH, making it damaging to aquatic animals and plants and it can cause paint to peel and corrode steel buildings, bridges and stone sculptures. Acid rain develops when sulfur dioxide and nitrogen oxide emissions react with atmospheric water molecules and produce acid. Although the effects of pollution on structures were noted in the 1600s, the relationship between atmospheric pollution and the acid rain it produces was first brought to attention in 1852 in Manchester, England. Governments have been working since the 1970s to reduce these emissions and their efforts have had very positive results.

Interesting Acid Rain Facts:

1. Acid rain can also be produced from volcanic eruptions, burning coal and even rotting plant life.
2. Acid rain cannot rot your skin. It usually doesn't taste or smell any different than normal rain.
3. The sulfur dioxide and nitrogen oxide that creates acid rain can cause diseases such as cancer, asthma and even heart disease. It's a concern in the air, but not in the rain itself.
4. The acid in acid rain can damage a car's paint job, but it won't melt the car.
5. Acid rain can actually kill a forest. The acid rain can kill the leaves on the trees by cutting off their light and nutrient supply. It also changes the acidity in the soil, making it impossible for trees and other plant life to grow. It also poisons the soil and plant life.
6. When acid rain lands in the water such as streams, lakes and rivers, it changes the pH and makes the water toxic to the fish and other life in the water.
7. Entire lakes have been declared dead because of acid rain.
8. Acid rain has a pH of 4.3 while pure water is perfectly balanced at 7.
9. Acid rain has the same approximate pH as vinegar and orange juice.
10. Rain is not the only type of precipitation that can be called acid rain. Snow, fog, and even dust can contain the same damaging toxins as acid rain.
11. Acid rain can be neutralized the same way as acid can be. In some environments acid rain is more problematic. For instance, Eastern Canada lacks a natural alkalinity. Lime is able to neutralize acid, but there is no lime in the ground in some areas and because of this the acid rain is able to do more damage.
12. Sulphur dioxide, which is a major contributor to acid rain, is produced by burning fossil fuels and it is a by-product of many industrial processes.
13. A large amount of the acid rain that reaches Canada is the result of emissions in the United States.
14. Nitrogen oxide, a major contributor to acid rain, is produced by the exhaust from vehicles, from furnaces and other equipment. A large amount of Canada's nitrogen oxide emissions originate in the United States.
15. Despite major efforts to decrease acid rain, it is still killing lakes and aquatic life. 95,000 lakes in North America have been damaged by acid rain.

Reduce Pollution

What are S02, NOx, and CO2? How do they contribute to pollution?

    CO2: Carbon Dioxide is the principle "greenhouse gas" implicated in global warming. CO2 is released into the atmosphere as a result of burning fossil fuels such as coal, oil and natural gas. Coal is particularly dirty, producing about twice as much CO2 for the same amount of power as natural gas. CO2 is also generated in smaller amounts by forest clearing and cement production.

    NOx: Nitrogen oxides cause smog, irritate the lungs and lower resistance to respiratory infections such as influenza. Smog is formed when nitrogen oxides, which are emitted by burning fossil fuels at electric power plants and in automobiles, mix with other chemicals in the air, sunlight, and heat. The two largest sources of smog-forming pollution are motor vehicles (30%) and power plants (26%).

    The effects of short-term exposure to nitrogen oxides are still unclear, but continued or frequent exposure to concentrations higher than normal may cause increased incidence of acute respiratory disease in children. Nitrogen oxides are an important precursor to both ozone and acidic acid rain and can affect both land and water ecosystems.

    SO2: Sulfur dioxide comes from the combustion of fuel containing sulfur, mostly coal and oil. It is also produced during metal smelting and other industrial processes. The major health concerns associated with exposure to high concentrations of SO2 include effects on breathing, respiratory illness, alterations in the lungs' defenses, and aggravation of existing cardiovascular disease. While everybody is adversely impacted by SO2 to some degree, people that are particularly at risk include asthmatics and individuals with cardiovascular disease or chronic lung disease, as well as children and the elderly.

What is Global warming and why are greenhouse gas emissions raising the earth's temperature?

    Increases in concentrations of carbon dioxide and other pollutants contribute to global warming, which is predicted to raise average temperatures, alter precipitation patterns, and raise sea levels. These changes may negatively impact our quality of life, including increases in infectious diseases, respiratory illness, and weather-related deaths. Global warming may also decrease crop yields, water quality, and regional forest health and productivity. Atmospheric concentrations of CO2 have been increasing at a rate of about 0.5% per year and are now about 30% above pre-industrial levels.

How does SO2 create acid rain?

    Scientists have confirmed that sulfur dioxide (SO2) and nitrogen oxides (NOx) are the primary causes of acid rain. Acid rain occurs when these gases react in the atmosphere with water, oxygen, and other chemicals to form various acidic compounds. Sunlight increases the rate of most of these reactions. The result is a mild solution of sulfuric acid and nitric acid.

How much CO2 is removed by planting trees in the Michoacan forest of Mexico?

    Every tree planted in the monarch forest will remove an additional .29 tons of atmospheric CO2 over the next 42 years. This is calculated by dividing the net carbon increase of a 42 year-old mature forest (157 tons/hectare) by the average number of trees (2000) which equals .0785 tons C per seedling. Because it takes several tons of CO2 to make a ton of carbon, we converted C to CO2 by multiplying the carbon by 3.667: (3.667 x .0785 = .29 tons CO2).

Air Quality Issues of Electricity Production

What is acid rain?

The term "acid rain" is used to describe rain, mist or snow that is unusually acidic. A pH value is the measure of acidic or alkaline material. The lower the pH, the higher the acid reading. Rain and snow are naturally slightly acidic due to naturally occurring chemical reactions in the atmosphere. Compared to normal rainwater with a pH readings of 5.6, the Eastern U.S. suffers from some of the most severe acid rain, with levels typically reading at 4.4, though some locations in the west also face severe impacts.

The burning of fossil fuels generates air pollution that scientists have determined is the major cause of acid rain. Power plants, along with factories and vehicles that also burn fossil fuels, all emit sulfur dioxide (SO2) and oxides of nitrogen (NOx). When combined with moisture in the atmosphere, these pollutants are returned to the earth as acids. This process is known as "deposition" and occurs when it rains or snows, but it can also occur when dust settles out of the atmosphere during dry periods.

Acid precursors can be carried in the atmosphere for several days and travel several hundred miles downwind of the power plant stack before being deposited on the earth's surface. Because of prevailing winds, the northeastern United States and Canada receive significant quantities of acid precursors from coal-fired power plants in states stretching from Missouri to the west and Pennsylvania to the east.

What are the consequences of acid rain?

Acid rain is linked to a range of negative impacts on the natural world as well as human environments:

Aquatic impacts Scientists

believe that acid rain is responsible for the dramatic disappearance of brook trout and other fish species from pristine lakes and streams. These treasured water bodies receive acid directly from the atmosphere and from runoff from the surrounding watershed. Of the lakes and streams studied in a National Surface Water Survey conducted by the US Environmental Protection Agency, acid rain was determined to cause acidity in 75 percent of the acidic lakes and 50 percent of the acidic streams analyzed. Some lakes are particularly susceptible to acid rain since the underlying soil has limited ability to neutralize, or "buffer," the acids. Lakes suffering from chronic acidity can be found in several regions of the United States and Canada, including the Adirondacks, the mid-Appalachian highlands, the upper Midwest and the high elevation West.

Aquatic species vary in their tolerance to elevated levels of acidity. The acid interferes with reproduction much sooner in some especially sensitive species than with others. Generally speaking, acid rain fosters a shift in fish population from acid-sensitive to acid-tolerant fish and other aquatic plant and animal species.

Forest impacts

Acid rain may render intense impacts on the health of forest ecosystems. According to the National Assessment Precipitation Assessment Program's 1998 Biennial Report to Congress, the current mortality and decline of high elevation red spruce populations in the Northeast, and decline in growth rates for Appalachian red spruce, "are the only cases of significant forest damage for which there is strong scientific evidence that acid deposition is a primary cause." Nonetheless, several recent studies conducted by the United States Geological Survey and others point to acid rain as contributing to long-range damage to forests by depleting calcium, a nutrient vital to plant growth.

Materials

Acid rain affects many types of materials, from objects of particular historical artistic or cultural value -- buildings and monuments -- to more ordinary objects such as cars and trucks. Acid rain, especially in the "dry" form, corrodes metal, and accelerates the deterioration of stone and paint.

Visibility

Sulfur dioxide emissions reduce visibility when they form sulfate particles in the atmosphere. Visibility reductions are most pronounced in the eastern part of the United States, particularly in and around national parks. How does electricity production contribute to acid rain? Electricity generation accounts for the lion's share of air pollutants that spawn acid rain. Every year, the nation's fossil fuel power plants spew roughly 70 percent of SO2 emissions and 30 percent of NOx emissions that are critical ingredients in making acid rain.

Of course, not all power plants generate the same level of air pollutants contributing to acid rain. Emissions rates vary widely depending upon factors as the precise fossil fuel type used, the nature of the combustion process, pre- and post-combustion air emission controls, as well as vintage of the power plant. Older coal plants exempt from modern clean air standards under "grandfathering" provisions of the Clean Air Act (especially those designed to burn high sulfur content coal) are at one extreme and are the most significant source of acid rain pollutants. These power plants are highly concentrated in the Ohio Valley and Midwest. Given the prevailing winds, these older, largely uncontrolled pollution sources exacerbate the acid rain experienced in the Northeast.

On the other end of the spectrum are new natural gas-fired generation fitted with best available control technology. They release a fraction of the SO2 produced by coal-fired power plants. However, the performance of natural gas plants is decidedly more mixed in the area of NOx emissions, the other major precursor of acid rain. Although possible to mitigate NOx emissions using advanced technologies, many gas-fired power plants now in service use older, more polluting technologies.

How can consumer electricity choice address acid rain?

Competition in the electricity industry offers consumers for the first time the opportunity to directly influence the environmental footprint of electric power production. In several states, suppliers are assembling electricity resource portfolios that are significantly cleaner than the status quo. By selecting one of these resource portfolios, which boost the amount of renewable energy sources in the fuel mix, consumers can help ensure that the emissions of pollutants that cause acid rain are reduced. Consumers can send a powerful signal to electricity suppliers that they demand their supply not include power from older coal power plants exempt from the nation's federal air quality standards. These dirty power plants have increased their power production recently in response to wholesale competition. Between 1995 and 1995  a single Midwestern utility increased coal-fired generation by 10 percent, which increased its share of NOx emissions by over 50,000 tons. That increase in NOx emissions from a single utility surpasses the total NOx emissions from all fossil power plants operating in Massachusetts and New Hampshire combined.