Almidon

Students
What is Acid Rain?

Additional Resources
* Clean Air Status and Trends Network (CASTNET) – CASTNET provides atmospheric data on the dry deposition component of total acid deposition, ground-level ozone and other forms of atmospheric pollution.
* National Atmospheric Deposition Program (NADP) – NADP is a network of over 100 federal, state and local government agencies, andprivate sector entities that collect data on acid deposition, as well as mercury deposition.
* EPA Clean Air Markets Data and Maps – Provides access to a variety of data associated with emissions trading programs, including trends in emissions and heat input, environmental assessment maps, data sets and reports on acid deposition, facility attributes and contacts, and other file downloads
"Acidrain" is a broad term referring to a mixture of wet and dry deposition (deposited material) from the atmosphere containing higher than normal amounts of nitric and sulfuric acids. The precursors, or chemical forerunners, of acid rain formation result from both natural sources, such as volcanoes and decaying vegetation, and man-made sources, primarily emissions of sulfur dioxide (SO2) and nitrogenoxides (NOx) resulting from fossil fuel combustion. In the United States, roughly 2/3 of all SO2 and 1/4 of all NOx come from electric power generation that relies on burning fossil fuels, like coal.  Acid rain occurs when these gases react in the atmosphere with water, oxygen, and other chemicals to form various acidic compounds. The result is a mild solution of sulfuric acid and nitric acid. Whensulfur dioxide and nitrogen oxides are released from power plants and other sources, prevailing winds blow these compounds across state and national borders, sometimes over hundreds of miles.

Wet Deposition
Wet deposition refers to acidic rain, fog, and snow. If the acid chemicals in the air are blown into areas where the weather is wet, the acids can fall to the ground in the form of rain,snow, fog, or mist. As this acidic water flows over and through the ground, it affects a variety of plants and animals. The strength of the effects depends on several factors, including how acidic the water is; the chemistry and buffering capacity of the soils involved; and the types of fish, trees, and other living things that rely on the water.
Dry Deposition
In areas where the weather is dry,the acid chemicals may become incorporated into dust or smoke and fall to the ground through dry deposition, sticking to the ground, buildings, homes, cars, and trees. Dry deposited gases and particles can be washed from these surfaces by rainstorms, leading to increased runoff. This runoff water makes the resulting mixture more acidic. About half of the acidity in the atmosphere falls back toearth through dry deposition.
Effects of Acid Rain

Acid rain causes acidification of lakes and streams and contributes to the damage of trees at high elevations (for example, red spruce trees above 2,000 feet) and many sensitive forest soils. In addition, acid rain accelerates the decay of building materials and paints, including irreplaceable buildings, statues, and sculptures that are part ofour nation's cultural heritage. Prior to falling to the earth, sulfur dioxide (SO2) and nitrogen oxide (NOx) gases and their particulate matter derivatives—sulfates and nitrates—contribute to visibility degradation and harm public health.
The links below provide more detailed information on each of these effects:
* Surface waters (lakes and streams) and aquatic animals
* Forests
*Automotive coatings
* Materials
* Visibility
* Human health
* Measuring Acid Rain
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* For Students
* To learn more about measuring the pH of water and soil, visit the Science Experiments page. This page includes information on how to measure pH, how to make a natural pH indicator, and more.
* Acid rain is measured using a scale called “pH.” The lower a substance's...