Acid in the Water Cycle
The Source of Acid Rain
Coal-burning plants, metal smelters, and oil refineries provide energy
and valuable materials, but at the same time produce air pollutants that
contain sulfur and nitrogen. The burning of fossil fuels in cars and the
processing of nitrogen fertilizers also produce these pollutants. The
pollutants enter the atmosphere and combine with water droplets to
form acids, as shown in the above figure.
These acidic droplets act like normal water droplets in the water cycle
– they eventually fall as rain or snow. The term acid rain is used to
describe the movement of sulfur- and nitrogen-containing acids from
the atmosphere to the land and water.
Effects of Acid Rain
Acid rain eats away marble, metal, mortar, rubber, and plastics. It kills
fish, microbes in the soil, and both water and land plants.
Some areas are more sensitive than others to acid rain. Soils that have
only a thin layer of rich soil on top of a solid granite base, such as
those in the Muskoka and Haliburton areas of Ontario, can do little to
reduce the impact of the acid before it runs off into streams and lakes.
Deeper soils over limestone can reduce the acidity of the water.
1. Why is acid rain a problem? (4 marks)
2. How do acids enter the water cycle? (4 marks)
3. Offer two suggestions that would reduce acid rain. (4 marks)
4. A lake in northern Ontario was checked in 1925 and again in
1999. Fish were collected and the following data was obtained.
Year pH Level Number of fish
trout whitefish bottom feeders
1925 6.6 22 12 5
1999 4.6 0 0 8
a) What has happened to the acidity of the lake? (2 marks)
b) What conclusions can you draw about the effect of acid rain on
fish? (2 marks)
c) Other research data shows that the lake was murky in 1925 but
clear in 1999. Does this indicate that the water is now better to
drink? Explain. (2 marks)
d) How does the acidity of a lake affect human health and the local
economy? (2 marks)
Nelson Science and Technology 8, 2000, page 286
http://www.jamesglass.org/JGA/2labor/Z_laborIMAGES/00general/0-5_glossary/acid_rain.gif, April 20, 2009
http://www.scienceclarified.com/images/uesc_01_img0005.jpg, April 20, 2009
http://mrsmaineswiki.wikispaces.com/file/view/acid-rain-2a.jpg, April 20, 2009