McWane Science Center

In this activity, the effects that varying pH levels have on plants are tested as a way to see the importance of clean, fresh water to living things. This activity will also demonstrate that water pollution is not just a local issue, but rather a global issue. Explanation: Acid rain is a prime example of how activities in one area can have a serious effect on conditions of a global scale. Acid rain primarily results from the transformation of industrial pollutants such as sulphur dioxide (SO2) and nitrogen oxides into other compounds such as sulphuric acid (H2SO4), and nitric acid (HNO3). This transformation occurs as these pollutants are transported in the atmosphere over distances of hundreds to thousands of kilometers. For example, sulfur dioxide emissions from industrial processes and the burning of fossil fuels have resulted in extensive acid rain and accompanying water pollution problems in southeastern Canada and the northeastern US. These emissions have global implications: more than half of the acid deposition in eastern Canada originates from emissions in the United States. Even slight changes in the pH of lakes and rivers can cause the loss of fish and invertebrates which are important links in the food chain. Acid rain is also responsible for extensive loss of forest cover in that region.

For this activity, stream table models are utilized. Students introduce pollutants into the sediment in the stream table. Then they introduce water into the stream table and observe the sediment and “downstream” waterway. This demonstration shows how ground pollution and upstream water pollution can be carried downstream to other bodies of water and land. The “ground” in the stream table model has been polluted with green food coloring (before the water is added). As the water passes over the polluted area, the pollution contaminates the stream, surrounding land and the larger body of water at the end of the steam. After polluted water has entered into larger bodies of water (seas, gulfs and oceans), it can be spread to other areas by the Coriolis effect. The Coriolis effect is caused by the rotation of the Earth. The effect deflects objects moving along the surface of the Earth to the right in the Northern hemisphere and to the left in the Southern hemisphere. The resulting movements can cause pollution to spread far beyond its source and affect other parts of the world.