IB Environmental Systems and Societies

1. Topic 5
Pollution Management
5.8 Acid Deposition
http://www.youtube.com/watch?v=v09KnqiYi-c

2. Acid Rain
• NOx andSOx may either fall to the ground as
particles, aerosols or gases (dry deposition) or
else forms acid rain (wet deposition)
• The longer they remain suspended in the
air, the more likely they will be oxidised to
HNO3 and H2SO4
• Wet deposition may occur thousands of
kilometres from the pollution source
(especially now that chimney stacks may be
hundreds of metres tall)

3. Effects of Acid Rain
• Lakes
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Reduced biodiversity
Acidity may cause death of fish fry
Decreased turbidity
Growth of white moss on lake beds
Increased concentrations of dissolved metals
(including Cd2+, Cu2+, Al3+, Zn2+, Pb2+) – this
makes them bioavailable to water plants and
also allows them to enter drinking water
• Forests
– Damage to lipids and membranes leading to
plant death
– SOx interferes with photosynthesis especially in
coniferous plants
– Acidity causes conifers to shed needles too
rapidly
– Low soil pH causes damage to root hairs and
and inhibits water and nutrient uptake

4. Distribution of Acid Deposition
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It is a global rather than localised problem, since
deposition may occur thousands of kilometres
from source
There are natural sources of acidity, including
plants which acidify soils (heather and bog
moss), volcanic eruptions and the dissolution of
carbon dioxide in precipitation (carbonic acid)
There also exist natural sources of
buffering, including chalk and limestone
deposits
Conversely, granite deposits are naturally acidic
and have low buffering capacity
The areas most affected by anthropogenic acid
deposition are
Sweden, Norway, Denmark, Scotland, Germany,
The Netherlands, Austria and The East Coast of
the U.S.
This appears to be largely due to prevailing
winds and levels of rainfall
They are also areas rich in lakes and rivers with

5. Management Strategies
• Prevention
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Burn less fossil fuels
Reduce numbers of private vehicles
Increased use of public transport and bikes
Switch to low emission fuels (or electric cars?)
Remove sulphur before combustion or SOx after (scrubbing)
Burn coal with a neutralising agent (such as limestone)
Use chemicals to buffer soil and allow decomposition of
plants to offset the acidification process
– International agreements are necessary since the polluter
and the victim of the pollution may be different countries
(e.g. The Gothenburg Protocol, 1999)

6. Questions
1. Describe how acid rain is caused
2. Describe the effects of acid deposition on
living things
3. Describe and evaluate strategies to control
acid rain