Explore Air

Acid Rain Lesson Plan

Activity 4 – How Acid Rain is Measured and Monitored in the U.S.

Time: 2 hours

Behavioral Objectives


  1. Explain how acid rain is measured.
  2. Explain how acid rain is monitored in the United States.
  3. Compare locally measured pH or rain with that of Great Smoky mountains National Park and national figures as displayed in isopleths (Figure 3) for a specific storm event.


You will need:

  1. Inexpensive pH test kit or comparator kit for water (many scientific supply houses for schools carry these).
  2. Clean wide-mouth glass or plastic container for collecting ain samples.
  3. Data sheet (Figure 6)
  4. Isopleth map (Figure 3)
  5. Accurate rain gauge

Instructions to Teacher

  1. Describe to the students how the NADP measures acid rain. Refer to "Background Information."
  2. Do test for one week or until sufficient rain is collected to run the tests.
  3. Whenever the students work with any type of chemicals (pH kit), they should be under direct supervision.

Instructions to Students

  1. As a group, you will be monitoring the pH of rainfall in your community. This pH test can be run once or many times. You will then be able to compare your local pH with the pH indicated on the isopleth map your teacher has.
  2. Place the collection container in an open area away from buildings or trees that might block the rain.
  3. Use rain gauge to measure rainfall during collecting period.
  4. With the help of your teacher, test the rain sample for H, using the measurement kit.
  5. Record the results of the test on a data sheet provided by your teacher. It will include:
  • Class and teacher's name
  • Date
  • Time information was recorded
  • Total rainfall of test period
  • Average pH of rain

6. The pH test of the sample should be run three times to get an average figure. Calculate the average directly on the data sheet in the space provided.

7. Using the isopleth map, compare your test results with the pH figure on the map for your locality.

Questions to Students

  1. What was the average pH of the rain you tested?
  2. How does your pH compare with that found in step 7 above? Was yours more or less than the isopleth map figure?
  3. Can you think of reasons why your figures may be different from those on the map? How does your figure compare with the average pH figure given for Great Smoky Mountains National Park (pH scale, Figure 1)? Although one test is enough to demonstrate pH testing, repetition will give a more complete picture of pH levels in your area.

updated on 04/20/2006  I   http://www.nature.nps.gov/air/edu/Lessons/Activity4.cfm   I  Email: Webmaster