Chapter 10

By Eugene F. Provenzo, Jr. and Cory A. Buxton

Acid Rain

     

     

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Florida Sunshine State Standards Benchmark
SC.A. 1.2.1The properties of materials (in this pH) can be compared and measured.
SC.A. 1.2.5Materials made by chemically combining two or more substances may have properties that differ from the original materials.
SC.G. 2.2.3Changes in the habitat of an organism may be beneficial or harmful.

     
     

   
   
   
       

Acid Rain & pH

       

Water pollution comes in many forms. Some are obvious and highly visible, like an oil spill or trash floating in a lake. Other forms of water pollution can be difficult to detect. Acid rain is not obviously pollution, but can cause great damage to water ecosystems by lowering the pH of the water. Acid rain is rain that has been made acidic by certain pollutants in the air. An acid is a substance that has a very low pH. The scale for measuring pH runs from zero (the most acidic) to 14 (the most basic or least acidic). A substance that has a pH of 7 is neither basic nor acidic and is called “neutral.”

       

       

       

Human activities are the main cause of acid rain. Cars, power plants, and factories release many different chemicals into the air that change the mix of gases in the atmosphere. These pollutants cause acid rain. Acid rain can be extremely harmful to forests. Acid rain that seeps into the ground dissolves nutrients that trees need to be healthy and also make it difficult for tree roots to absorb water. These trees become weaker and more prone to damage from infections, insects, and cold weather. Acid rain is also very harmful to lakes and streams. Most lakes and streams have a natural pH level between 6 and 7.

       

Acid rain, however, has caused many lakes and streams to have much lower pH levels. This increase in acidity can be deadly to aquatic wildlife, including fish, insects, frogs, plankton, and aquatic plants. The chart shows the pH scale, examples of common liquids with different pH levels, and the effect of lowering pH on aquatic life.

       

     

     

Activity: The Effect of Acid Rain on Radish Plants

     

In the following activity you will test the effects of simulated acid rain on growing plants.


     

Materials Needed

     

         
  • a pack of radish seeds
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  • bag of potting soil
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  • three small pots
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  • permanent markers
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  • tap water
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  • vinegar
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  • graduated cylinder
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  • ruler
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  • two clean cups
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  • pH test strips
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  • copy of Acid Rain Activity Worksheet on page 57
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To test the effects of acid rain on radish plants, follow the steps below:

     

         
  1. Fill one clean cup with tap water and the other cup with vinegar.
    2.      
  2. Using the pH strips, measure the pH of each liquid and record on the acid rain data sheet.
    3.      
  3. Label the three pots A, B, and C with the marker.
    4.      
  4. Fill each pot with potting soil and poke several small holes in the bottom for drainage.
    5.      
  5. With your finger, make a hole 4 cm deep in the soil in each cup.
    6.      
  6. Place five radish seeds in each hole and carefully cover the seeds with soil.
    7.      
  7. In Pots A and B, use the graduated cylinder to water the seeds with 50 ml of water.
    8.      
  8. In Pot C, water the seeds with 50 ml of vinegar.
    9.      
  9. Place all three pots in the same growing area.
    10.      
  10. Check the plants each day, using the ruler to measure and record their growth on the data sheet.
    11.      
  11. Add 20 ml of water every other day to Pots A and B.  Add 20 ml of vinegar to Pot C every other day.
    12.      
  12. After one week, continue to water Pot A with 20 ml of water every other day. Water Pots B and C with 20 ml of vinegar every other day. (Note that Pot B has now switched from water to vinegar).
    13.      
  13. Continue measuring and recording plant growth each day for a three-week period.
    14.      
  14. After plants have grown for three weeks, create a bar graph from your data to compare the growth of the plants in the three pots.
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Have students review the following summary questions:

       

             
  1. What can you conclude based on your data?
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  2. What effect did changing Pot B to a vinegar mixture have on the growth of the radish plant?
    3.          
  3. What effect does acid rain have on plant growth?
    4.        

       

       
     
       

       

Exploring One Water

Look at the following clip to see how pollution affects the local environment in Louisiana.

       
       

         

     

     

     
     

       

Consider the Following Poem

       

“There is nothing softer and weaker than water,
And yet there is nothing better for attacking hard and strong things.
For this reason there is no substitute for it.” —Lao-Tzu circa B.C. 550

   
   
     

       

Extension Activities

       

Elementary School Students

       

Review with students the ways fresh water can become polluted. Talk with them about ways they can help prevent certain water pollution. List them on the board.

       
       

         

Multimedia

         

Have students draw pictures of the causes of water pollution in their community.

       

         
       

Middle School Students

       

Review with students the ways fresh water can become polluted. Talk with them about the places where they think water pollution might be going on in their community or in other parts of the country. Have them compile a descriptive list of water pollution sites (local and national).

       
       

         

Multimedia

       

Use the local community list generated by students to go out and document with photographs the sources of water pollution that they can find in their communities. Have them create a bulletin board exhibit or website with their photographs.

       

       
       

Secondary School Students

       

Have students research in their community to find out if there is a site that has serious water pollution. Have them try to discover who is responsible and what can be done about the problem. This activity can culminate in the writing of an action letter to a local government official or representative, or to the newspaper.

       
       

         

Multimedia

         

Have students create a film showing a water pollution problem in their local community. In the film, have them suggest actions that can be taken to solve the problem. Post the film to a website such as YouTube.