Acid precipitation is caused by sulfur dioxide and nitrogen oxide pollutants combining with water in the atmosphere to form acids. It is measured on the pH scale, with below 5.0 considered acidic. Acid precipitation harms plants by acidifying soils and making nutrients and toxic metals more available, and harms aquatic life by changing water pH and releasing aluminum that suffocates fish. International cooperation is needed to address acid precipitation because pollutants can travel long distances across borders.

1. Acid Precipitation Environmental Science

2. What is Acid Precipitation? Rain, sleet, or snow that contains a high concentration of acid because of pollution in the atmosphere SO 2 and NO 2 combine with water in the atmosphere to create acid precipitation

3. How is acidity measured? pH is a number that indicates the acidity of a solution A pH of 7 is neutral, a pH of less than 7 is acidic, and a pH of greater than 7 is basic.

4. How is acidity measured? Normal precipitation is slightly acidic because atmospheric carbon dioxide dissolves into the precipitation and forms carbonic acid. Precipitation is considered acid precipitation if it has a pH of less than 5.0

5. How acid precipitation effects plants and soil Acid precipitation can cause a drop in the pH in soil or water – called acidification Nutrients in the soil are dissolved and wash away Aluminum and other toxic metals are more easily absorbed by plants – causes root damage SO 2 in water vapor can clog openings in plant leaves

6. Acid Precipitation and Aquatic Ecosystems If the water’s pH changes, it can kill aquatic organisms Acid precipitation also can cause aluminum to leach out of the soil and into a lake. The aluminum accumulates in the gills of fish and interferes with oxygen and salt exchange so the fish slowly suffocate.

7. Acid Precipitation and Aquatic Ecosystems Acid shock – when large amounts of highly acidic run off enters an aquatic ecosystem Most often happens when snow melts in the spring or heavy rains after a drought Causes fish to die and those that don’t die lay fewer eggs and most of the eggs don’t hatch The offspring that do hatch often have birth defects and cannot reproduce

8. Acid Precipitation and Humans Acid Precipitation releases aluminum and toxic metals into the soil that gets into crops, water and fish. Research also indicates a relationship between large amounts of acid precipitation and respiratory problems in children

9. International Cooperation One problem in controlling acid precipitation is that pollutants can be release in one place and fall hundreds of miles away It can be especially difficult to solve on an international level Canada and the United States signed the Canada-U.S. Air Quality Agreement in 1991.