Shop Windows to the Universe

Arches National Park Geology Tour provides an extensive, visually rich description of the geology of Arches, by Deborah Ragland, Ph.D. See our DVD collection.
Acid rain damages buildings such as this one in Copola, Mexico.
Click on image for full size
Courtesy UCAR

Acid Rain

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.

Last modified February 4, 2008 by Becca Hatheway.

Shop Windows to the Universe Science Store!

Cool It! is the new card game from the Union of Concerned Scientists that teaches kids about the choices we have when it comes to climate change—and how policy and technology decisions made today will matter. Cool It! is available in our online store.

Windows to the Universe Community



You might also be interested in:

Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

Biomes and Ecosystems

Biomes are large regions of the world with similar plants, animals, and other living things that are adapted to the climate and other conditions. Explore the links below to learn more about some of the...more

Air Pollution

What do smog, acid rain, carbon monoxide, fossil fuel exhausts, and tropospheric ozone have in common? They are all examples of air pollution. Air pollution is not new. As far back as the 13 th century,...more

Nitric Acid - HNO3

Nitric acid is a colorless, corrosive liquid and a toxic acid which can cause severe burns. Nitric acid consists of nitrogen, oxygen, and hydrogen atoms. Nitric acid, in its gas phase, is present in very...more

Sulfuric Acid - H2SO4

Sulfuric acid is a viscous, oily liquid and a strong acid which can cause severe burns. Sulfuric acid consists of sulfur, oxygen, and hydrogen atoms. Sulfuric acid is one of the components of acid rain....more


Rain is precipitation that falls to the Earth in drops of 5mm or greater in diameter according to the US National Weather Service. Virga is rain that evaporates before reaching the ground. Raindrops form...more

Atmospheric Chemistry of Earth's Troposphere

Chemistry plays an influential role in the behavior of the lowest layer of Earth's atmosphere, the troposphere. The various gases in the troposphere are constantly mixing with and reacting with each other....more


Nitrogen is a chemical element with an atomic number of 7 (it has seven protons in its nucleus). Molecular nitrogen (N2) is a very common chemical compound in which two nitrogen atoms are tightly bound...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF