Acid Rain

Objectives:

- to know how acid rain forms
- to recognise that acid rain is an issue of international concern
- to consider what we might do to reduce the impact of human activities in creating acid rain

This is the PowerPoint we used in the lesson. I've had to remove the movies as Slidehsare can't cope with them! However, just so you don't feel you're missing out, I have linked to several YouTube movies below.

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Acid rain is a result of air pollution. When any type of fuel is burnt, lots of different chemicals are produced. The smoke that comes from a fire or the fumes that come out of a car exhaust don't just contain the sooty grey particles that you can see - they also contains lots of invisible gases that can be even more harmful to our environment.

Acid Rain is caused by the burning of fossil fuels. Burning oil, gas and coal in power stations releases Sulphur Dioxide (SO2) into the atmosphere. Burning oil and petrol in motor vehicles puts nitrogen oxides (NOX) into the atmosphere. These gases mix with water droplets in the atmosphere and create weak solutions of nitric and sulphuric acids. These then fall as acid rain.



Acidity is measured using a scale called the pH scale. This scale goes from 0 to 14. 0 is the most acidic and 14 is the most alkaline. Something with a pH value of 7, we call neutral, this means that it is neither acidic nor alkaline. Rain is always slightly acidic because it mixes with naturally occurring oxides in the air. Unpolluted rain would have a pH value of between 5 and 6. When the air becomes more polluted with nitrogen oxides and sulphur dioxide the acidity can increase to a pH value of 4. Some rain has even been recorded as being pH2.



Acid rain increases the acidity levels of rivers, lakes and seas which can kill aquatic life. It also increases the acidity levels of soils which can kill vegetation. Acid rain has been found to destroy the roots and leaves of forests in Germany and Scandinavia have been destroyed as the result of acid rain emissions from the UK.

Acid rain can also erode buildings and monuments (particularly if they are made from limestone like the statue below).

Acid rain can be carried great distances in the atmosphere, not just between countries but also from continent to continent. The acid can also take the form of snow, mists and dry dusts. The rain sometimes falls many miles from the source of pollution but wherever it falls it can have a serious effect on soil, trees, buildings and water.

Thanks to YouTube user Jamie Harris for this movie:

What can be done to prevent acid rain?

The main way of tackling the problem of acid rain is to reduce emissions. We can do this by:

• researching new ways to create energy which don't produce so much pollution

• spending more money on pollution control even if it does mean an increase in the price of electricity

• wash sulphur out of smoke by spraying a mixture of water and powdered limestone into the smokestack

• fit cars with catalytic converters which remove three dangerous chemicals from exhaust gases

• give greater subsidies to public transport encourage people to use public transport rather than always travelling by car

• make an effort to save energy by switching off lights when they are not being used and using energy-saving appliances - when less electricity is being used, pollution from power plants decreases

• walking, cycling and sharing cars all reduce the pollution from vehicles