Download Document

Can Nature Cope?
As air pollutants are transported from industries and automobiles, as far as
1,000 kilometers by prevailing winds, forming secondary pollutants such as acids
and particles of sulfate and nitrate salts, the communities and ecosystems
several states away are affected. The harmful effects of acid rain are far reaching
and diverse. Some examples include:
 damages statues, buildings, metals and car finishes
 acidifies environmental waters causing death to many fish and other
aquatic species
 contaminates fish in lakes with highly toxic methylmercury – Increased
acidity of lakes converts inorganic mercury compounds in the lake bottom
sediments into the fat-soluble toxin methylmercury.
 damages foliage and weaken trees, especially conifers
 facilitates the release of aluminum from surrounding bedrock which, in
turn, accumulates on the gills of many fish species causing respiratory
difficulties and death for these animals
 makes trees more susceptible to stresses such as cold temperatures,
diseases, insects, drought and fungi that thrive under acidic conditions
 displaces the potassium, calcium, magnesium and ammonium particles in
topsoil with hydrogen ions, thus reducing soil fertility as well as excessive
amounts of ammonium in ecosystems can damage tree roots and kill many
types of fish
 leads to excessive levels of nitrogen in the soil that over stimulate plant
growth and also increase the depletion of other soil nutrients.
 contributes to human respiratory diseases such as bronchitis and asthma
Acid rain is said to have the potential to completely eliminate aquatic life in
lakes, streams and ponds. However, the amount of damage this form of
pollution is capable of causing depends largely upon an area’s soils. As
rainwater trickles through soils or over land surfaces, alkaline soils are able to
neutralize or buffer the rain’s acids. It is interesting to note that the areas in
which acid rain is most damaging are often the areas which have soils
incapable of buffering the incoming acids. These regions include nearly all of
eastern Canada, New England, New York’s Catskill and Adirondack
Mountains, parts of the Appalachians and much of Minnesota, Michigan and
Wisconsin. The Catskills, for instance, commonly have rain water with a pH of
4.28 (Murdoch, USGS/Frost Valley studies, 1991) which the base-poor soils are
unable to neutralize. thus, the effects of acid precipitation are much more
evident in this region’s ecosystems.
To test a soil’s ability to buffer or cope with acid solutions, students can
perform the following experiment with soils from your area.
Materials: small plastic garbage bags, soil samples, large plastic gallon milk jugs,
filter paper, jars, pH paper, vinegar, baking soda, water
Procedures:
1. Begin by having the class investigate your school grounds for different
variety of soils. Using the plastic bags, collect 1 pound samples from a
variety of locations.
2. In the classroom, use gallon jugs with their bottoms cut off to serve as
large funnels. Have the students place a piece of filter paper at the
bottom of each funnel. Next, fill each funnel with a different soil sample.
3. The students then need to mix up an acid solution with a low pH value.
50 mls of vinegar mixed with 150 mls of water will generally give you a
solution with a pH of 4.0 depending on the acidity of your water.
4. The experiment begins when the students pour equal amounts of the
acidic water through the funnels into catching containers. Compare the
resulting pH values for each of the leachates. Determine which soil has
the best buffering capacity.
Variations:


To amplify the alkalinity and thus the buffering capacity of one of the soil
samples, add a tablespoon of baking soda to the soil mixture. Record and
compare the results with the other samples.
To illustrate the effects of the acid solution on soils and metals, set a glass of the
acidic water aside for a week with a penny or marble chip inside. For
comparison, leave a penny or marble chip outside of the solution for the same
length of time. Note the changes in the metal or mineral examples.
Watershed Discussion Questions:
 Why would people in New York City be concerned about the Catskill
soils’ buffering capacities?
 What are some other ways of testing to see if acid rain is affecting
surfaces in your area?
 How do we decrease the amounts of acid deposition in our area?
Source: Adapted from Can the Soil Cope? In Acid Rain: A Teacher’s
Guide, Activities for Grades 4 to 12