There are many chemicals that pollute the air. In cities, the major source of pollution is carbon monoxide. Carbon monoxide is caused most of the time by gasoline-powered motor vehicles. You might have felt some of the effects of air pollution in big cities. If you have ever visited a big city, you might have noticed that your eyes burned or that you had trouble breathing. Air pollution is a problem in big cities because cars, homes, and factories release many kinds of harmful substances, or pollutants, into the air.
Concern about air pollution has recently focused on indoor pollution. Indoor pollutants include tobacco smoke, gases from stoves, car exhaust in attached garages, and chemicals used for cleaning. Of special concern is a radioactive gas called radon. Radon comes from traces of uranium and radium that exist in practically all rocks and soil. Dangerous amounts can build up in homes, especially in basements, as the gas enters through foundation cracks and openings around pipes. Scientists think that as many as 30,000 of the 125,000 annual lung cancer deaths in the U. S. may be attributed to radon.
Sulfur dioxide is one kind of air pollutant. It is released into the air when coal is burned. The sulfur dioxide combines with water in the air, forming sulfuric acid. This weak acid becomes part of rainwater, which falls to the earth. The acid rain harms living things and also damages buildings and other structures.
Some factories that burn coal have taken steps to cut down on acid rain. These factories have placed devices called scrubbers on their smokestacks. The scrubbers remove sulfur dioxide as it is released from burning coal. (An activity to use to show the effect of acid rain can be used at this time.)
Place a few drops of hydrochloric acid on a piece of limestone.
The reaction will cause a fizzing. Tell students that the bubbles
form as carbon dioxide is released from the carbonate minerals
in the rock. Ask students what the acid does over a period of
time. (Dissolves it or wears it away) Tell students this is similar
to the results of acid rain. In a few years, acid rain can have
a disastrous effect on wildlife and eat away at buildings.
Trees are an important wildlife resource that do more than provide
solitude and beauty. They add oxygen and water to the air. They
act as windbreaks and have a cooling effect on temperatures. Their
presence slows the runoff of rainwater, and their root systems
hold the soil. Together, both functions prevent harmful soil erosion.
A major environmental concern of the rural community would be
soil erosion. In the mid 1930''s, several years of drought followed
by dust storms blew hundreds of millions of tons of soil from
farm fields in the Great Plains, leaving them bare. One centimeter
of soil takes 200 to 400 years to form. Yet wind and water erosion
can remove soil from an area in just a few years or even overnight.
To conserve soil, farmers plant crops in rows. Planting crops
in this way prevents water from flowing downhill and washing away
soil. Farmers also plant tall trees along their fields. How do
you think this method helps conserve soil? (response)
Listed below are some class projects for evaluating possible solutions to some environmental problems:
1. Use the latest edition of The World Almanac to find some natural sources of energy and how much they are used. How much energy is produced by these sources. Would more energy be used in a city or in rural area?
2. Natural resources such as air, land, and water can become polluted. Find out about potential pollution sources in your community. Make a list of these sources. Find out how your community helps control pollution. Have the mayor or other appropriate city or county official address the class.
3. List four substances that are sometimes indoor air pollutants and give one possible source for each.
4. Make a list of alternative energy sources. Next to each source write advantages and disadvantages.