The only way to reduce acid rain is to reduce the amount of acidic oxides in the air.

Dealing with
Acid Rain

Acid rain is a major environment problem to the whole world, from rivers and lakes to forests and buildings, nothing ever escapes acid rain. There are both short and long-term ways of reducing acid rain.

How can we reduce acid rain?

SHORT TERM METHOD

Liming (calcium hydroxide) is one of the very few ways to reduce the effects of acid rain.

Thousands of lakes in Sweden were made unsuitable for any organisms to live in it by acid rain. Slaked lime is emptied into the lakes to neutralize the acid so that plants and other marine life can return to their habitats again.

However, this can only be a short-term method as liming requires to be done regularly and that will prove to be very costly. The only way to stop acid rain is to reduce the amount of acidic oxides released into the air.

LONG TERM METHODS

1. Reducing the use of fossil fuels by using more public transport and practicing carpooling and using less of cars but more of walking and bicycles.

2. Using fossil fuels of low sulphur contents

3. Extracting sulphur from the existing fossil fuels before using them. However, this method might not be very feasible, as it is very costly to do so, especially at a large scale.

4. Using pollution control equipment such as catalytic converters in vehicles and scrubbers in factories and power stations and also using the method of desulphurisation.

How do catalytic converters work?

The catalytic converter is attached to the exhaust system of a car. It contains the catalysts platinum and rhodium. When hot exhaust gases pass over the catalysts, redox reactions occur.
(See how a catalytic converter works.)

2NO(g) + 2CO(g) ~~> N₂ (g) + 2CO₂(g)

2C₈H₁₈(g) + 25CO₂(g) ~~> 16CO₂(g) + 18H₂O(g)

As you can see, carbon monoxide is oxidized to carbon dioxide, oxides of nitrogen are reduced to nitrogen, and unburnt hydrocarbons are oxidized to water and carbon dioxide. Therefore, all the gases released will be rather harmless to the environment.

How does desulphurisation work?

The removal of sulphur dioxide from the waste gases or flue gases is called desulphurisation.
(See the desulphurisation process.)

As sulphur dioxide passes through the plant, it reacts with an aqueous suspension of calcium carbonate to form solid calcium sulphite:

CaCO₃ (aq) + SO₂ (g) ~~> CaSO₃(s) + CO₂ (g)

The calcium sulphite is further oxidized to calcium sulphate by atmospheric oxygen:

2CaSO₃(s) + O₂ (g) ~~> 2CaSO₄(s)

Besides calcium carbonate, calcium oxide can also be used for desulphurisation:

CaO(s) + SO₂ (g) ~~> CaSO₃(s)