Acid Rain

Ref: GCSE Geography pg 60

The branch on the left is from a tree in the Black Forest in Germany.

Learning objectives

• What is acid rain?• How is it formed?• What effects does it have on people

and the environment?• Where are the effects evident?• How can the effects be reduced?

The Formation of Acid Rain

Burn fossil fuels in

Transport, Industry, Homes, power

stations

The rest reacts with sunlight and ozone in the atmosphere; nitric (HNO3), and sulphuric acid (H2SO4) are produced

Gas, Oil, Coal

Some falls back to Earth close to the source as dry particles, gas and aerosols (NOx and SO2) (dry deposition)

NO2 SO2

It is dissolved in the moisture in the atmosphere making

2H+ and SO42_

and can be carried large distances before falling as rain or snow (wet deposition)

TRANSBOUNDARY POLLUTION

H2O

H+ NO3

_ SO4

2_

The main pollutants which cause acid rain are…

Sulphur dioxide – released from coal fired power stations

Nitrous oxides - released from gas fired and coal fired power stations and car exhaust emissions

Acid Deposition

Acid deposition involves the deposition of both wet and dry acidic components

• The chemical pollutants may become incorporated into dust or smoke and fall to the ground through dry deposition but they combine with any moisture on the surface of buildings, trees etc to form an acid.

Dry Deposition

• The polluting gases react with oxygen in the atmosphere to produce dilute forms of sulphuric acid and nitric acid. These acids are taken into solution by cloud and rain droplets and then move through the hydrological cycle.

• This wet deposition can travel a long way from the source of pollution

Wet Deposition

The effects…

The effects …

Acids activate aluminium from the soil which leaches into water and fish die. Drinking water is contaminated

Acid rain destroys tree roots. The trees are then more likely to suffer from drought and disease

The chemical weathering of buildings, statues and stone objects.

Chemical reactions release toxic metals, particularly aluminium into solution

Soils become more acidic. Unless lime is added the quality of the crops is reduced

Why is acid rain an international issue?

Transboundary deposition

• The countries that are producing the majority of the Pollution that causes acid rain (Britain, Germany, USA) aren’t that badly affected by acid rain.

• Instead, the wind direction means the acid rain falls elsewhere (in Europe this affect Scandinavia; USA affects Canada).

How might the effects of acid rain be reduced?

Burning coal which contains less sulphur

Remove sulphur from coal before it is used

Remove sulphur from waste gases after it is used (Flue gas desulphurisation)

Using unleaded petrol

But …

It costs

Tales a long time to phase out thermal power stations

Impact on coal mining industry as demand falls

International agreements to reduce sulphur dioxide emissions

Add lime to lakes affected by acidification

Switch to alternative energy supplies

Energy conservation methods