Why does acid mine drainage form?

In many areas, acid drainage forms naturally when certain minerals come into contact with water, air and bacteria. This contact and the chemical reactions that take place are part of the weathering process. The weathering of the rocks and minerals in the creek slowly releases the acids, salts, metals and sulfates into creeks, rivers, lakes and wetlands. Weathering is a natural process, but many times human activities interfere and can increase the amounts. When too much of these acids and minerals enter creeks, they become polluted and can no longer support animals.

Tools and things you will need

  • Bottles and containers
  • Coal chunks
  • Gloves
  • Limestone
  • Litmus paper
  • Pieces of ore (Use small pieces; iron, aluminum, or magnesium ores are available at local science and nature supply stores)
  • Rocks and other solid materials
  • Rubber boots
  • Tap water

What to do?

  1. Collect solid materials that are found where you live.
  2. Add tap water to bottles. Measure the pH with litmus paper.
  3. Add one type of solid material to each of the water bottles. You may want to crush the solid materials into small pieces to get better results.
  4. Put water but no solids in one bottle. (This is called your control.)
  5. Measure the pH over time and write down what you see.

What did you see?

  1. What materials lowered the pH of the water?
  2. What materials raised the pH of the water?
  3. How long did it take for acid to form?
  4. What else did you see?

What did you conclude?

  1. What materials in your area do you think can cause acid mine drainage?
  2. How could you prevent acid mine drainage from forming?
  3. What are your conclusions? "Write down what you think."
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