Acid Rain

Acid rain forms when sulfur and nitrogen dioxides combine with moisture in the
atmosphere to produce rain, snow, or another kind of precipitation. This kind of pollution may also
be suspended in fog or deposited in a dry form. Acid rain is most common in North America and
Europe. Acid rain has also been detected in other areas of the world such as tropical rain forests
of Africa. Canada has placed limitations on the sulfur emissions. The United States has not, so
the emissions may still drift into Canada.
The acid rain cycle begins with hundreds of power plants burning millions of tons of coal.
Burning coal produces electricity for us. Coal is made of carbon, but the coal that we mine is not
pure carbon. It is mixed with other minerals. Two of these are sulfur and nitrogen. Then the coal
is burned some of the sulfur changes into sulfur dioxide and nitrogen changes into nitrogen oxide.
These escape in to the air as poisonous gases. Some smokestacks release chemicals like
mercury, arsenic, and aluminum. Some of these minerals are changed in to gases and others
become tiny specks of ash. As these chemicals drift, they may change again. They may react
with other chemicals in the air. When sulfur dioxide combines with water, the result is sulfuric acid.
When nitrogen oxide gas combines with water, the result is also another acid. When the clouds
releases rain or other precipitation, the acid goes with it. This is called acid rain.
The level of acid is measured in pH levels. The pH scale begins at 0 and ends with 14. A
reading lower than 7 is called acidic, and a reading higher than 7 is called basic. Seven is neutral.
Normal rain is slightly acidic with a pH level of about 6.5. Rain with a pH of 5.5 is then times more
acidic than normal rain and rain with pH of 4.5 is a hundred times more acidic than normal rain.
In parts of the country, rain with pH levels of 4.5 to 5.0 is common.
An English scientist named Robert Angus Smith discovered acid rain in 1872, but no
other scientist continued this study. Then in 1961 the Sweden wanted to know why the fish in their
lakes were dying. Svante Odén discovered that the reason was acid rain. After Odén's discovery,
other scientist began to study acid rain too.
Acid rain has destroyed plant and animal life in lakes, damaged forests and crops. It has
also endangered marine life in coastal waters, eroded structures, and contaminated drinking water.
It can kill fish, frogs, and insects in lakes. Acid rain can also be harmful to humans. It can hurt
their lungs and make it harder for them to breath. Acid fog can be particularly harmful to people
with respiratory problems. Acid rain can corrode stones and some metals. Higher acid levels can
be dangerous to our drinking water. Some water pipes are made of lead, and when the water is
acidic, it can dissolve the metal. Then the metals end up in the water we drink.