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Acid Precipitation
Environmental Science
Spring 2010
What is Acid Precipitation?

Rain, sleet, or snow that
contains a high
concentration of acid
because of pollution in
the atmosphere

SO2 and NO2 combine
with water in the
atmosphere to create
acid precipitation
How is acidity measured?

pH is a number that indicates the acidity of a solution

A pH of 7 is neutral, a pH of less than 7 is acidic, and
a pH of greater than 7 is basic.
How is acidity measured?

Normal precipitation is slightly acidic because
atmospheric carbon dioxide dissolves into the
precipitation and forms carbonic acid.

Precipitation is considered acid precipitation if
it has a pH of less than 5.0
How acid precipitation effects plants
and soil

Acid precipitation can cause a drop in the pH in soil
or water – called acidification

Nutrients in the soil are dissolved and wash away

Aluminum and other toxic metals are more easily
absorbed by plants – causes root damage

SO2 in water vapor can clog openings in plant leaves
Acid Precipitation and Aquatic
Ecosystems

If the water’s pH changes, it can kill aquatic
organisms

Acid precipitation also can cause aluminum to
leach out of the soil and into a lake.

The aluminum accumulates in the gills of fish
and interferes with oxygen and salt exchange
so the fish slowly suffocate.
Acid Precipitation and Aquatic
Ecosystems

Acid shock – when large amounts of highly
acidic run off enters an aquatic ecosystem



Most often happens when snow melts in the spring
or heavy rains after a drought
Causes fish to die and those that don’t die lay
fewer eggs and most of the eggs don’t hatch
The offspring that do hatch often have birth
defects and cannot reproduce
Acid Precipitation and Humans

Acid Precipitation releases aluminum and
toxic metals into the soil that gets into crops,
water and fish.

Research also indicates a relationship between
large amounts of acid precipitation and
respiratory problems in children
International Cooperation

One problem in controlling acid precipitation
is that pollutants can be release in one place
and fall hundreds of miles away


It can be especially difficult to solve on an
international level
Canada and the United States signed the
Canada-U.S. Air Quality Agreement in 1991.