This image shows the pH of rainwater collected across the country in 1994. A pH value of 7 represents a completely neutral substance that is neither acidic nor basic. Lower values indicate acid rain, with the lowest values being the most acidic. Rainwater is naturally somewhat acidic. Rainwater in areas that are not downwind from sources of pollution generally has a pH value of 5.0 or higher.

  !   Click the image to see an animation of rainwater pH for 1994 through 1999. Play the animation several times to get a general idea of the acidity of rainfall in different locations across the country.

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2. Which parts of the country experience the lowest pH values? Which part experiences the highest pH values?

3. Over the six year period, did the acid rain problem increase or decrease? Explain your answer.

4. Describe the acid rain situation for your own area. How has it changed over the six years?