AIR POLLUTION
Chapter 2: Air pollution
What is air pollution?
Air pollution is the presence of harmful materials in the atmosphere.
These substances can be released into the atmosphere because of human
activity or natural processes.
This means that harmful substances, like chemicals, are released into
the atmosphere. These substances can be very harmful to the
environment and to humans, who breathe air.
The three main causes of air pollution in Europe are:
 motor vehicles
 factories
 power stations.
Pollution from motor vehicles
Motor vehicle exhausts put harmful chemicals
into the atmosphere, causing air pollution.
These chemicals include sulphur dioxide,
nitrogen oxide and carbon monoxide. These
chemicals are proven to cause severe damage
to the environment and to humans.
Pollution from factories and power stations
Factories and power stations also give out harmful
chemicals, such as sulphur dioxide and nitrogen
oxide, through the burning of fossil fuels for
energy.
Sulphur dioxide and nitrogen oxide lead to acid
rain.
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AIR POLLUTION
Acid rain
Acid rain occurs when air pollution mixes with precipitation (all
types of rain, hail, sleet, snow) and returns back to earth. Sulphur
dioxide and nitrogen oxide mix with the moisture in the air to form
acid, which can be carried long distances before it falls as acid rain.
Figure 2: Causes of acid rain
Pollution from
industry
Pollution from
motor vehicles
Activity 5
Look at the diagram above. Describe the causes of acid rain.
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Is all of Europe affected by acid rain?
Urban areas (towns and cities) where there are more people, cars and
industry are likely to have higher levels of pollutants and acid in the
air than rural areas (countryside).
Why there are differences across Europe
Different areas of Europe are affected by acid rain. This is because of
the prevailing wind. This means that because of the direction the wind
blows across Europe, countries in the east are more affected than those
in the west. For example, high levels of acid rain in Sweden and
Norway are blamed on pollution from the UK.
The diagram below shows the effect of the prevailing wind on the
distribution of acid rain.
Figure 3: The effect of the prevailing wind
Source: SQA
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Activity 6
Use the instructions below and the key to colour in the areas on the map
(Figure 4) with different levels of acidity.
HIGH – Red
MEDIUM – Brown
LOW – Orange
VERY LOW - Yellow
Discuss with your teacher what the map shows.
Figure 4: Distribution of acid rain in Europe
Prevailing wind
Source: SQA
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Activity 7
Using Figure 4, answer the following questions.
1.
Name one country with high levels of acidity in its atmosphere .
2.
Can you think of any reasons why this particular country has high
levels of acidity?
3.
Why is the distribution of acid rain affected by the prevailing
wind?
4.
Some areas on the map have very low levels of acidity in the
atmosphere. Identify one and give a reason why this is.
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AIR POLLUTION
Effects of acid rain
Acid rain is harmful to the human and physical environment.
Water in lakes and streams
Acid rain can affect the acidity in lakes and streams. As the acidity in
the water increases, the more harm it causes to the plant and wildlife
species that live there. Plant and animal life decreases as acidity
increases. Insects, salmon and trout are some of the wildlife affected.
Trees
When acid rain falls it is washed through the soil. Trees need nutrients
from the soil to be able to grow. The acidity in the rainfall can wash
away the important nutrients trees need to grow. This means that trees
will be damaged. They start to lose their leaves and needles and may
not grow as well as they should.
Wildlife
Apart from wildlife living in lakes and other freshwater environments,
acid rain can also affect animals that live in the soils for example,
earthworms. This in turn has an effect on the birds that eat the worms.
Also, animals that depend on fish for food, such as otters and birds, can
be affected.
Buildings
Buildings naturally wear away due to a process called weathering.
This means that weather (rain and wind) wear away the stone that
buildings are made of. Acid rain speeds up the process of weathering
of buildings made of sandstone. Limestone and marble have all been
damaged by the high levels of acidity in rainfall.
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Activity 8
Design a poster to show the impact of acid rain. You can work in pairs
or a group. Use the following pieces of information to label your
poster.
Acid rain is caused by chemicals released into
the atmosphere combining with moisture –
mainly sulphur dioxide and nitrogen oxide.
Sulphur dioxide is released into the
atmosphere through the burning of
fossil fuels for energy.
Most nitrogen oxide released into the
atmosphere comes from motor vehicle
exhaust fumes.
Acid rain can cause damage to trees by
taking all the important nutrients that
trees need to grow out of the soil.
Acid rain can harm wildlife in lakes and
streams by increasing the acidity in the water
and causing plant and animal life to die.
Acid rain can be very harmful to
wildlife, especially earthworms and
other insects that live in the soil.
Wildlife that eat earthworms and
fish will be affected as they may
not have enough food to eat.
Buildings can be worn away by the acid in
the rain – especially buildings made from
limestone, sandstone and marble.
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AIR POLLUTION
The greenhouse effect and global warming
Greenhouse gases are found in the atmosphere. They keep our planet
warm because they trap warm air from the sun in our atmosphere – just
like a greenhouse!
The levels of greenhouse gases in our atmosphere are increasing. This
is because of increased levels of greenhouse gases being released into
the atmosphere through the burning of fossil fuels for energy.
Factories, power stations and motor vehicles all release carbon dioxide
into the atmosphere when coal, oil or gas is burned to create energy.
Carbon dioxide is a greenhouse gas that absorbs heat from th e earth.
As more and more carbon dioxide builds up in the atmosphere, the more
heat it absorbs. This means that the temperature of the world rises.
This is global warming.
Figure 5: The greenhouse effect
Sun
Some heat escapes into space
Atmosphere
Some heat trapped
by greenhouse gases
travels back to Earth
The sun’s
rays warm
the earth
Earth
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Global warming can cause many environmental problems. One problem
is a rise in sea levels. This happens because:
 When global temperatures rise, the polar ice caps melt. This means
that lots of freshwater melts into the sea causing levels to rise .
 When water heats up, it expands: it takes up more room causing sea
levels to rise.
If sea levels rise then many areas of Europe could be under threat of
flooding. We will look at one of these areas as a case study later in this
unit.
What can be done to prevent acid rain
and global warming?
Governments have been working to try to cut
down on the amount of harmful pollutants being
released into the atmosphere.
The European Union
 We know that nitrogen oxide and carbon dioxide are released into the
atmosphere through exhaust fumes from our cars. Countries of the
European Union (EU) have agreed to reduce the amounts of harmful
nitrogen oxide, carbon dioxide and sulphur dioxide into the atmosphere.
For example, the UK has agreed to reduce emissions of sulphur dioxide
by 85% and emissions of nitrogen oxide by 49% by the year 2010.
This can be done by fitting all cars with catalytic converters. This is
something built into the car that reduces the amount of harmful gas
released into the atmosphere. All new cars sold in Britain since 1993
have catalytic converters fitted as standard.
 The level of sulphur dioxide emissions has been reduced in recent
years due to the introduction of cleaner technology. This means that
harmful sulphur is taken out before the coal and oil are burned. This
means that when they are burned the harmful gases will not be
released into the atmosphere.
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AIR POLLUTION
These measures have proven to be successful and we have seen the
levels of sulphur dioxide and nitrogen oxide in the atmosphere get
lower.
What can we do?
 We can use cars less and use public transport more. Or even better,
walk or ride a bike to get to our destination. This would mean that
there would be fewer cars on the road and therefore less harmful
gases released into the atmosphere.
 We can use less energy in our homes. Make sure that lights are not
left on in rooms that are not being used, turn the temperature down
on the central heating and the washing machine. Every little thing
helps!
Look at the Scottish Environmental Protection Agency’s website to see
how Scotland is trying to cut pollution: www.sepa.org.uk
There are many websites about acid rain and global warming; one of
these is the Encyclopaedia of the Atmospheric Environment
(www.ace.mmu.ac.uk/eae/english.html).
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Activity 9
Hidden in the word search are ways that we can help to reduce acid rain
and global warming. Use the word bank below to help you to find
them.
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Word bank
catalytic converter
cleaner technology
turn out lights
turn down temperatures
use less energy
use public transport
remove sulphur
walk more
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AIR POLLUTION
Look at the figures given in Table 1, which shows sulphur dioxide
emissions in the UK from 1970 to 2000.
Table 1: Sulphur emissions in the UK since 1970
Year
Amount of sulphur (million tonnes)
1970
1980
1990
2000
6.4
4.8
3.9
1.2
Source: DEFRA
Activity 10
Amount of sulphur (million tonnes)
Complete the line graph below to show the change in sulphur dioxide
levels in the UK from 1970 to 2000.
1970
1980
1990
Years
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