Acid rain is caused by sulfur and nitrogen oxides reacting with water in the atmosphere. It is formed primarily from emissions from coal-burning power plants and vehicle exhaust. Acid rain harms buildings, statues, trees and aquatic ecosystems, damaging soils, leaves and disrupting the nutrient balance in affected waters. Some of the areas most impacted include northeastern North America, Central Europe and parts of Asia. Control measures have included emissions standards, scrubbers on smokestacks and converting to cleaner burning fuels.

1. The Acid Rain

2. I. What is Acid Rain? Acid rain is rainfall that has been acidified. Rain is acidified by oxides of sulfur and nitrogen. Acid rain usually has a pH of less than 5.6. Acid rain is formed when pollutants called oxides of sulfur and nitrogen, contained in power plant smoke, factory smoke, and car exhaust, react with the moisture in the atmosphere. Dry deposition, such as soot and ash, sleet, hail, snow, smog and low level ozone are forms that acid rain can take, despite its name.

3. II. Causes Acid rain can be caused by many things. Industrial emissions from factories and power plants that burn fuels such as natural gas, coal or oil, emit smoke that gives off oxides of sulfur and nitrogen is one cause. Another cause is vehicles (e.g. cars, buses) that burn gasoline and diesel. The exhaust emitted by burning these fuels contains sulfur dioxide, an oxide of sulfur. Also, vehicles that have gas engines will produce oxides of nitrogen, another cause of acid rain. One other cause is home fires giving off smoke that contains sulfur dioxide. Some fairly minor causes are natural causes which are volcanoes, swamps and rotting plants giving off sulfur dioxide. Natural causes only account for 10% of the pollution causing acid rain.

4. III. Effects and Problems There are many problems and effects caused by acid rain. Acid rain can cause buildings, statues and bridges to deteriorate faster than usual. Another problem is it harms thousands of lakes, rivers, and streams worldwide. It disrupts lake ecosystems and kill wildlife in affected lakes, rivers and streams. Acid rain also damages soil and the tree roots in it. When soil is acidified, tree roots are damaged, leaving them not able to draw in enough nutrients to support the tree. When acid rain falls on trees, it makes their leaves turn brownish-yellow and the tree can no longer carry out photosynthesis properly. Another problem is it will harm people when they breathe in smog, acid rain in one of its many forms. Acid rain can also harm people indirectly. This happens when people eat fish caught in affected lakes or rivers. Also, if the water source is acidic enough, it will react with copper or lead pipes to harm humans. It also washes aluminum into the water supply. Birds can be harmed if they live in affected waters or feed on fish living in affected waters.

5. IV. Areas Affected There are several places around the world affected by acid rain and here are the main ones. The Northeastern section of the United States where acid rain is caused by high numbers of factories and power plants is one affected area. Also in that same region, the Southeastern section of Canada is affected and the main cause is factories in the Toronto-Hamilton area and possibly large numbers of automobiles. Central Europe (Black Triangle of Lower Silesia in Poland, Southern Saxony in Germany and Northern Bohemia in Czech Republic) and Scandinavia (Sweden, Norway and Finland) are also affected, here being the British and other European factories doing the damage. One more main area that is affected is parts of Asia, specifically India and China, where acid rain is caused by large numbers of factories.

6. V. The History of the Acid Rain Problem Here is a little bit on the history of the acid rain problem. The problem of acid rain probably originated during the 1730's, at the height of the industrial revolution. It was discovered in the 1950's and started being noticed in the 1960's. Since the 1960's, the problem has gotten worse in rural areas because the tall chimneys on factories allow the wind to transport pollutants far away from their sources. In 1984 it was reported that almost half of the trees in the famous black forest in Germany had been damaged by acid rain. In 1988, as part of the United Nations-sponsored Long Range Transboundary Air Pollution Agreement, the U.S.A. and 24 other nations agreed to some rules limiting nitrogen oxide emissions to 1987 levels.1990 changes to the Clean Air Act set rules to cut down the release of sulfur dioxide from power plants down to 10 million tonnes by January 1, 2000.

7. VI. What Acid Rain Has Done There are many bad things that have happened because of acid rain and here are some. In Sweden, drinking water once contained enough water to make people's hair turn green. In the Czech Republic, many trees lost all their leaves as a result of acid rain. The Taj Mahal in India, one of the ten wonders of the world, is being constantly threatened by acid rain. Some famous statues, such as the Lincoln Memorial and Michaelangelo's statue of Marcus Aurelius, have started deteriorating because of acid rain. In London in 1952, very thick acid smog killed 4,000 people.

8. VII. Possible Solutions There are many possible solutions to the acid rain problem. One is to use fuels that burn more cleanly. Another solution is to burn coal more efficiently. Power plant and factory chimneys can be fitted with scrubbers that release 90-95% sulfur free smoke and also produces sludge from which gypsum, a building material, can be produced. This problem can also be solved by enforcing tight emission standards on vehicles that burn gas and diesel. One other solution is fitting devices such as a catalytic converter into car exhaust pipes to minimize the amount of sulfur dioxide in car exhaust.

9. VIII. What We Can Do? We can do things to help solve the acid rain problem. We can cut back on car use by walking, cycling, using public transit or carpooling. We can also help by turning off electrical devices not in use such as lights and computers. Avoid burning fires. Recycle and reuse as much as possible.