What can be done about it?

All this damage costs money. Replacing rusty motor vehicles and restoring stonework costs money. The Canadian timber industry is suffering as the growth of trees is affected. Tourism is suffering in Canada and Sweden: tourists do not want to fish in “dead” lakes. Sweden has adopted the practice of spraying calcium oxide into acid lakes. Being a base, calcium oxide neutralizes acids.

American companies have started neutralizing sulphur dioxide at its source. They use jets of wet lime (calcium oxide) to bombard the combustion gases before they leave the chimney. This process removes sulphur dioxide, nitrogen dioxide and other acid gases from the exhaust gases. Cleaning the exhaust gases in this way costs money. The product is calcium sulphate. Some of this by-product can be used as hardcore in road-making. The rest must be removed and dumped.

Another method of removing sulphur dioxide is to “scrub” the exhaust gases with ammonia. The end product of this process is ammonium sulphate. It can be sold in large quantities as a fertilizer.

In 1979, 31 European countries signed the Convention on Long Range Transboundary Air Pollution. In this agreement, each nation agreed to reduce the amount of pollution that it allows to sweep across its frontiers. Canada and the USA have signed a similar agreement.

SUMMARY NOTE

The damage caused by acid is costly. European countries have agreed to stop exporting their pollutions. Industries and power stations are trying methods of reducing their emission of acidic gases.

2. Make sure if you remember the meaning of the following words. Consult a dictionary if necessary:

To observe, to crumble, readily, elsewhere, to attribute, gauge, link, chimney, to prevail, to trickle, jet, hardcore, to scrub, to sweep.

3. Answer the questions:

1. What did Robert Smith write about the phenomenon he called “acid rain”?

2. What causes acid rain?

3. What are the consequences of acid rain?

4. What can be done to reduce the effects of acid rain?

4. Look at the diagram below.

* DRY DEPOSITION CAUSING DIRECT DAMAGE Pollutants: Sulphur dioxide Nitrogen oxides Particles of pollutant material fall back to earth and blacken buildings and plants

* Pollutants react chemically in the atmosphere and combine with water vapour; they can be blown hundreds of kilometers by the wind.

* WET DEPOSITION (ACID RAIN) CAUSING INDIRECT DAMAGE Pollutants, now weak sulphuric and nitric acids, fall with rain and snow

a) Write down the names of the two main pollutants which cause “acid rain”.

b) Give two differences between dry deposition and wet deposition.

c) Write down what do you think is the difference between “direct” and “indirect” damage.

4. Do you think “acid rain” is a good term to use to describe what is causing the damage to lakes and trees? Give reasons for your answers. Unit 4 land pollution Text