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More acidic Neutral More basic

More acidic Neutral More basic

Acid Precipitation

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Water vapor condenses on dust particles in the air to form droplets that combine to create clouds. Eventually, the droplets become large enough to fall to the ground as precipitation—mist, rain, snow, sleet, or hail. Air pollutants from the burning of fossil fuels can react with water in the atmosphere to form strong acids. Acidity is measured by a value called pH, as shown in Figure 12. Acid precipitation has a pH below 5.6.

Effects Of Acid Rain Acid precipitation washes nutrients from the soil, which can lead to the death of trees and other plants. Runoff from acid rain that flows into a lake or pond can lower the pH of the water. If algae and microscopic organisms cannot survive in the acidic water, fish and other organisms that depend on them for food also die.

Preventing Acid Rain Sulfur from burning coal and nitrogen oxides from vehicle exhaust are the pollutants primarily responsible for acid rain. Using low-sulfur fuels, such as natural gas or low-sulfur coal, can help reduce acid precipitation. However, these fuels are less plentiful and more expensive than high-sulfur coal. Smokestacks that remove sulfur dioxide before it enters the atmosphere also help. Reducing automobile use and keeping car engines properly tuned can reduce acid rain caused by nitrogen oxide pollution. The use of electric cars, or hybrid-fuel cars that can run on electricity as well as gasoline, also could help.

Measuring Acid Rain

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1. Collect rainwater by placing a clean cup outdoors. Do not collect rainwater that has been in contact with any object or organism.

2. Dip a piece of pH indicator paper into the sample.

3. Compare the color of the paper to the pH chart provided. Record the pH of the rainwater.

4. Use separate pieces of pH paper to test the pH of tap water and distilled water. Record these results.

Analysis

1. Is the rainwater acidic, basic, or neutral?

2. How does the pH of the rainwater compare with the pH of tap water? With the pH of distilled water?

SECTION 2 Pollution E ♦ 103

IIOf^Bte^fks Photo Archive/Fundamental Photographs, (r)Kristen Brochmann/Fundamental Photographs

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Topic: Global Warming

Visit booke.msscience.com for Web links to information about global warming.

Activity Describe three possible impacts of global warming. Provide one fact that supports global warming and one fact that does not.

Carbon Dioxide Levels

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