Acid rain is a general term for rain or other precipitation that has been polluted by chemicals called acids. This environmental problem can pollute lakes, rivers, and streams. It can damage metals and other construction materials. And it can even pose a health risk to people.
Acid rain forms when certain pollutants mix with tiny droplets of water vapor in the atmosphere. These pollutants include sulfur oxides and nitrogen oxides. Power plants are the main source of pollutants causing acid rain.
Smoke from factories, exhaust fumes from automobiles and trucks, and
even gases given off by chemical fertilizers also put pollutants into
the air. The pollutants change the clean, fresh water to droplets of acid. These acids fall to the ground as rain, snow, or sleet. Even fog can contain acids.
Rain normally contains some naturally occurring acids. These are not considered a problem. However, sulfuric and nitric acids in rain are a problem. Acid rain soaks the ground and can make soil, lakes, and rivers abnormally acidic. In badly affected regions, plants and many types of aquatic animals are harmed. Entire lakes and some forest trees can be affected. Even buildings and statues can be damaged by acid rain.
Pollution That Causes Acid Rain
Pollutants such as sulfur oxides and nitrogen oxides enter the air when fossil fuels are burned. Fossil fuels include oil, coal, and gas. They are burned in industrial plants or automobile engines.
Nitrogen oxides and other acid-forming chemicals also enter the air from the breakdown of agricultural fertilizers. Hydrochloric acid often comes directly from smokestacks. Carbon monoxide and carbon dioxide are produced by motor vehicles.
Pollutants can travel over hundreds and even thousands of miles. As a result, acid rain often affects areas that are far from power plants and heavy automobile exhaust. Pollutants in smoke enter the air high above the ground through tall smokestacks. And they are carried by winds for great distances. Pollutants from the midwestern United States are regularly carried to New York, New England, and southeastern Canada. Similarly, pollution from Canada is carried by winds into the United States. Norway and Sweden have received acid rain created by pollutants from England, Germany, Italy, France, and Austria.
The Effects of Acid Rain
Millions of tons of acids fall in rain on the United States and Canada each year. The concentrations of these acids are too weak to cause burns. But they do produce other less severe effects.
When acid rain falls on metal objects, the objects can be damaged. Shiny objects become dull. If the process continues for many years, the metal objects can corrode and lose strength or crumble. Acid rain also affects the surfaces of stone statues and stone or brick buildings.
The way in which acid rain reacts with aluminum can cause serious ecological problems. Aluminum is normally present in soil. If acid rain causes soil acidification, the aluminum in the soil may dissolve in water. This aluminum may be absorbed by plants, where it can damage root cells. Animal cells are also very sensitive to aluminum. In lakes and streams, it can kill the eggs of many kinds of fish and the embryos of salamanders and other amphibians. Aluminum affects mature fish by causing the gills to clog with mucus. The fish cannot breathe. Aluminum also disrupts eggshell formation in birds.
Human beings may also be at risk from the effects of acid rain. In moist air, high levels of pollutants from acidic aerosols have been found to affect lung function in experimental studies. People who suffer from asthma, emphysema, and chronic bronchitis are more sensitive to acid environments.
Stopping Acid Rain
In 1990, the United States passed the Clean Air Act Amendments. This was a law that required significant annual reductions in air pollution. One measure to fight acid rain is to remove from the air those sulfur and nitrogen compounds that become acids. Some of these compounds can be taken out of fuel before the fuel is burned. Or the pollutants can be removed from smoke before the smoke enters the air. Each individual can also play a role in reducing air pollution by conserving energy. Individuals can cut back on the use of electricity, carpool, or use public transportation.
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