Acid Rain | ||||||||
| By Steve Flynn | ||||||||
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What is Acid Rain? Acid rain isn�t what it sounds like. Acid rain isn�t purr acid falling out of the sky. It is rainfall that has been mixed with elements and gases that have caused the moisture to become more acidic than normal. Pure water has a pH of a little less than 7, which is neutral. Acid rain, however, has a pH of 5 � 5.5 and even 4 in the Northeastern United States where there is a lot of industry. What Causes Acid Rain? Acid rain is caused by the burning of coal and oil by power production companies and industries that release sulfur into the air. The sulfur combines with oxygen in the air to form sulfur dioxide. Exhausts from automobiles cause formation of nitrogen oxides in he air. From these gases, airborne sulfuric acid and nitric acid can be formed and dissolved in the water vapor in the air. Dry Deposition Acid rain doesn�t account for all of the acidity that falls back to earth from pollutants. About half the acidity in the atmosphere falls back to the earth through dry deposition as gases and dry particles. The wind blows these acidic particles and gases onto buildings, cars, homes, and trees. In some examples, these gases and particles can eat away the things on which they settle. Dry deposition gases and particles are sometimes washed from trees and other surfaces by rainstorms. When that happens, the runoff water adds those acids to the acid rain, making the combination more acidic than falling rain alone. The combination of acid rain plus dry deposition is called acid deposition. What are the Effects of Acid Rain? Our environment can usually adapt to a certain amount of acid rain. Soil is often basic, due to limestone, which has a pH greater than 7. Since bases counteract acids, these soils can balance out some of the acid rain�s acidity. In areas such as the Rocky Mountains, limestone doesn�t naturally appear in soil. Here acid rain harms the environment. Some fish and animals have a difficult time adapting to an environment. Many plants are damaged by acid rain and acid fog. The Black Forest of Germany has been affected by acid rain. Much of this forest is black because the green pine needles have been destroyed, leaving only black trunks and limbs. Acid rain can also eat away at the stone in city buildings. Acid Rain is a Problem That Can Travel The chemical reactions that change air pollution to acid rain can take from several hours to several days. Years ago, when smokestacks were only a few stories high, pollution from smokestacks usually stayed near the ground and settled on land nearby. This caused unhealthy conditions for plants and animals near the smokestacks. To reduce this pollution, the government passed a law permitting the construction of very tall smokestacks. At that time, people thought that if the pollution were sent high into the air it would no longer be a problem. Scientists now know that this is incorrect. Sending pollution high into the sky increases the time that pollution stays in the air. The longer the pollution is in the air, the chances that the pollutants will form acid rain are greater. In addition, the wind can carry these pollutants for hundreds of miles before they become joined with water droplets to form acid rain. For that reason, acid rain is can also be a problem in areas far from the polluting smokestacks. Dry deposition is usually more sufficient near the cities and industrial areas where the pollutants are released. What Can Be Done About Acid Rain? To reduce this problem of acid rain, something must be done about the companies that release sulfur in the atmosphere. We also must reduce the amount of automobiles used each day. Acid rain is a problem that is killing out trees and animals in some areas. One way that you can help is to try and carpool if you travel alone and try not to waste fossil fuels. | |||||||
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