Acid Rain
Acid rain is created when sulfur and nitrogen dioxides (acids) fall to Earth by means of rain, snow, dew or dry particles. This precipitation increases the acidity of the soil and affects water pH levels. The acid pollutants can cause human health problems and regional haze.
As sulfur and nitrogen dioxides are released (generally from fossil fuel plants or combustion but also in limited amounts from natural sources like volcanoes and decaying vegetation) they are absorbed into the atmosphere. In wet areas the acids are absorbed by clouds and return to the ground through precipitation. In drier areas, winds, dust, and smoke blow acid particles causing them to stick to the ground (where they typically leach into runoff waters). Polluted waters greatly damage river and lake ecosystems (often killing fish and aquatic birds). Acid rains also affect trees, leaving them weakened against attacks by insects, disease or adverse temperatures.
After analyzing layers of glacial rock, scientists discovered a sudden increase in the prevalence of acid rain following the Industrial Revolution. Reducing the release of pollutants is the best way to reduce acid rain. In the United States, attempts to reduce toxic emissions have been partially successful, cutting sulfur dioxide emissions by 35 percent compared to 1990 levels.
Sources:
-- “Acid Rain Program 2005 Progress Report,” EPA Web site. Accessed Sept. 5, 2007. http://www.epa.gov/airmarkets/progress/arp05.html
-- “Acid Rain’s Effects Felt Through the Food Chain,” by Brian Handwerk. National Geographic Web site. Accessed Sept. 5, 2007. http://green.nationalgeographic.com/environment/global-warming/acid-rain-overview.html?nav=A-Z
