Acid Rain

Acid rain damages buildings such as this one in Copola, Mexico.
Click on image for full size (171 Kb)
Courtesy UCAR

Acid rain is a general term used to describe different kinds of acidic air pollution. Although some acidic air pollutants return directly back to Earth, a lot of it returns in rain, snow, sleet, hail, mist or fog, hence the term acid rain. Most acidic compounds eventually get deposited because they are water soluble and therefore make their way into the water droplets in the atmosphere.

When power plants, factories, houses and cars release pollution into the atmosphere, it contains chemicals known as sulfur dioxide and nitrogen oxides. Sometimes, these chemicals return to the ground. This is known as dry deposition. The rest of the time, they mix with water (moisture) in the air to form acids. Once these acids have formed, they can be transported long distances by the wind before being deposited in rain, snow or hail. This is what we commonly call acid rain.

During the 1970s, scientists in Sweden and Norway began noticing that acid rain was damaging their trees and fresh water. Much of the acid rain was caused by pollution that was transported through the air from other countries, primarily the United Kingdom. After that, acid rain was understood to be an international problem.

Acid rain can have harmful impacts on the ecosystems in the environment. It acidifies the soil and water where it falls, damaging or even killing plants and animals. Surface water acidification can lead to a decline in, and loss of, fish populations and other aquatic species including frogs, snails and crayfish. Acid rain affects trees, usually by weakening them through damage to their leaves. Certain types of building stone, such as limestone and marble, can be gradually dissolved in acid rain.


Atmospheric Chemistry

Pollution Sources

Air Pollution

Pollution Effects

Acid Rain Has Greater Impact on Coastal Ocean Waters

Acid Rain

Acid rain damages buildings such as this one in Copola, Mexico.
Click on image for full size (171 Kb)
Courtesy UCAR

Acid rain is a general term used to describe different kinds of acidic air pollution. Although some acidic air pollutants return directly back to Earth, a lot of it returns in rain, snow, sleet, hail, mist or fog, which is why we call it acid rain.

When power plants, factories, houses and cars release pollution into the atmosphere, it contains chemicals known as sulfur dioxide and nitrogen oxides. Sometimes, these chemicals fall directly back to the ground. This is called dry deposition. The rest of the time, they mix with water (moisture) in the air to form acids. Once these acids have formed, they can be transported long distances by the wind before being deposited in rain, snow or hail. This is what we commonly call acid rain.

During the 1970s, scientists in Sweden and Norway began noticing that acid rain was damaging their trees and fresh water. Much of the acid rain was caused by pollution that was transported through the air from other countries, primarily the United Kingdom. After that, acid rain was understood to be an international problem.

Acid rain can have harmful impacts on the ecosystems in the environment. It acidifies the soil and water where it falls, damaging or killing plants and animals. Surface water acidification can lead to a decline in, and loss of, fish populations and other aquatic species including frogs, snails and crayfish. Acid rain affects trees, usually by weakening them through damage to their leaves. Certain types of building stone, such as limestone and marble, can be slowly dissolved in acid rain.


Atmospheric Chemistry

Pollution Sources

Air Pollution

Pollution Effects

Acid Rain Has Greater Impact on Coastal Ocean Waters

Acid Rain

Acid rain damages buildings such as this one in Copola, Mexico.
Click on image for full size (171 Kb)
Courtesy UCAR

Have you ever heard of acid rain? Acid rain is what happens when some types of air pollution is washed out of the sky by rain. Sometimes, the pollution can be washed out by snow, sleet, hail, mist or fog, but it is still called acid rain.

Power plants, factories, houses and cars all put pollution into the atmosphere. Sometimes these chemicals return directly to the ground. The rest of the time, they mix with water in the air to form acids. Once the acids form, they can be carried a long way by the wind before being washed out of the air by rain, snow or hail. That is why we call it acid rain.

During the 1970s, scientists in Sweden and Norway noticed that acid rain was hurting their trees and fresh water. Most of the acid rain was caused by pollution that came from other countries. After that, scientists knew that acid rain was an international problem.

Acid rain can have harmful impacts on ecosystems. It makes the soil and water where it falls more acidic. This can hurt or kill plants and animals. Making water more acidic can lead to smaller fish populations. Other species that live in the water are also hurt, like frogs, snails and crayfish. Acid rain affects trees, making them weaker by damaging their leaves. Some types of stone, such as limestone and marble, can be slowly dissolved in acid rain. This can damage buildings and statues.


Atmospheric Chemistry

Pollution Sources

Air Pollution

Pollution Effects

Acid Rain Has Greater Impact on Coastal Ocean Waters


Page created January 30, 2006 by Dennis Ward. Last modified February 4, 2008 by Becca Hatheway.
The source of this material is Windows to the Universe, at http://www.windows.ucar.edu/ at the University Corporation for Atmospheric Research (UCAR). © The Regents of the University of Michigan. All Rights Reserved. Site policies and disclaimer