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The USGS has been at the forefront of studying the impacts of acid rain for decades. How does acid rain form? What does it do to the landscape? Can it burn you like battery acid? Keep reading to find out more...
Acid rain is the term commonly used by scientists to describe rain that is abnormally acidic. What does that mean? Well, plain distilled water, like that used in laboratories, is neutral (not acidic or basic). Since rain naturally has things dissolved in it, it will always be slightly acidic. However, when rain reacts with certain air pollutants, such as sulfur or nitrogen oxides, the water vapor converts into very diluted forms of sulfuric or nitric acids. The acidity of this rain is on par with that of grapefruit juice, which may not seem like much, but is much more caustic than plain water.
The main sources of pollutants that trigger acid rain are vehicles and industrial and power-generating plants. The areas of greatest acidity are in the northeastern United States. This pattern of high acidity is caused by the large number of cities, the dense population, and the concentration of power and industrial plants in the Northeast. In addition, the prevailing wind direction brings storms and pollution to the Northeast from the Midwest.
IMPACT OF ACID RAIN ON FORESTS
Acid rain can dissolve certain more soluble elements from the soil, like aluminum. The dissolved aluminum begins to accumulate and can reach toxic levels as it enters local streams and wetlands. Acid rain also removes important nutrients from the soil, such as calcium, potassium, and magnesium. The lack of nutrients can negatively affect the health of plants and animals. Lastly, the combination of reduced calcium and excessive aluminum can make forests more susceptible to pests, disease, and injury from freezing and drought, as a proper balance of these nutrients is vital to forest health.
WHAT USGS AND OTHERS DOING ABOUT ACID RAIN?
Scientists from many disciplines study acid rain and its impact. The National Acid Precipitation Assessment Program (NAPAP), a Federal program involving representatives from more than a dozen Federal agencies, has sponsored studies on how acid rain forms and how it affects lakes, crops, forests, and materials. Because buildings and monuments cannot adapt to changes in the environment, as plants and animals can, historic structures may be particularly affected by acid precipitation. Scientists are studying effective control technologies to limit the emissions from power plants and automobiles that cause acid rain. The impact and usefulness of regulations that would require limits on air pollution are also being studied. Finally, scientists are examining the processes of deterioration to find effective ways to protect and repair our historic buildings and monuments. Agencies like the National Park Service, which are charged with protecting and preserving our national heritage, are particularly concerned not only about the impact of acid rain but also about making the best choices for maintaining and preserving our historic buildings and monuments.
RELATED USGS RESEARCH
The USGS investigates the chemistry, source, fate, and transport of airborne pollutants and their affect on the landscape.
National Atmospheric Deposition Program
U.S. Environmental Protection Agency
Examples of research USGS conducts on acid rain.
The USGS produces many types of multimedia products. Use the links below to browse our offerings of photographs, podcasts and sound files, and videos related to acid rain.
The USGS reports on the occurence, magnitude, and impacts of acid rain across the country. Here are a few useful publications that showcase USGS acid rain science.
The USGS newsroom distributes media alerts, press releases, and technical memos that highlight new and relevant research.
Below are frequently asked questions associated with acid rain.
When sulfurous, sulfuric, and nitric acids in polluted air and rain react with the calcite in marble and limestone, the calcite dissolves. In exposed areas of buildings and statues, we see roughened surfaces, removal of material, and loss of carved details. Stone surface material may be lost all over or only in spots that are more reactive.You might expect that sheltered areas of stone buildings...