What is acid rain?
Acid rain is the widespread term used to describe all forms of acid precipitation e.g. rain, snow, hail etc. It first began with the Industrial Revolution when large amounts of fossil fuels were burnt to produce the steam power necessary to drive machinery The term "acid rain" was coined in the nineteenth century by scientist Robert Smith, then working in Manchester. In those days the problem of acid rain was confined to industrial towns and cities but the situation gradually worsened and in the last decades of the twentieth century scientists began to observe widespread environmental damage on a global scale, establishing a clear link between acid rain and fuels that are used in industry
The presence of carbon dioxide in the atmosphere renders rainwater naturally acidic. It has a pH factor close to 5.4. The burning of fossil fuels e.g. coal, oil and gas in power stations releases sulphur dioxide (SO into the atmosphere.
Likewise the burning of oil and petrol in motor vehicles releases nitrogen oxides( NOx). These two gases when mixed with water droplets in the atmosphere create solutions of nitric and sulphuric acid. This is acid rain.
There are two kinds of acid rain:
1. Dry deposition: Dry particles and gases in the atmosphere. These make up about 50% of acid that lands on the Earth.
2. Wet Deposition: This includes rain, snow and fog that are more acid than normal.
The effects of acid rain
It is not always easy to know the exact effects of acid rain around the world as some areas have been studied more than others but scientists do know that the effects are widespread. Acid pollutants do not only affect the countries that produce them, their impact can be felt far and wide depending on the intensity and the type of air pollutant. Winds around the earth mean that these substances move from their source, often being blown across national boundaries, to other areas where they combine with water droplets and fall as acid rain. Many forests in Central Europe have suffered damage by acid rain caused partly by the activities of neighbouring countries and remote regions in Canada experience damage to their environment, caused by industries in the USA.
Acid rain affects all plants but it is often trees that display the first signs of damage after prolonged exposure. Nutrients are washed from the soil so that growth is slowed down. Meanwhile, chemicals present in the soil are taken up by the trees roots. These harmful substances cause the leaves to fall off and without foliage the tree cannot use sunlight to make food. Trees exposed to acid rain may also have difficulty withstanding stresses such as periods of drought, disease, cold weather and infestation by insects.
Many of the world most famous buildings and statues show damage that can be attributed to acid pollutants in the atmosphere. Decorative carvings lose their definition and the erosion of limestone and sandstone is speeded up by the effect of acid rain. This speeding up is also apparent in the corrosion of metal.
Polluted rain also falls/drains into rivers and lakes often washing toxic chemicals into the water. As only 1/50 of the earth is covered by fresh water it is essential that these remain uncontaminated by acid rain. When fish, aquatic insects and amphibians become damaged they are less lightly to breed successfully. The food chain begins to break down and slowly animal life (particularly in lakes) disappears.
A recent study, however, (August 2004) led by Vincent Gauci of the Open University and carried out in Scotland found that acid rain may have positive effects. The study suggests that the sulphur-eating bacteria found in the wetland regions in Moray out compete the methane -emitting microbes. The experiments carried out have revealed that sulphur deposits can reduce methane production in small regions by up to 30% by activating the sulphur-eating bacteria. Richard Betts, a climate systems expert, emphasised the need to look at the interaction between greenhouse gases and the other effects in the biosphere in climate prediction but stressed that acid rain still remains a major environmental problem.
It is debatable whether or not the problem of acid rain can be solved completely and the damage to the environment undone. Much will depend on the will of governments and industry to control SOand NOX by legislation. Since 1993 all new cars manufactured in Europe have been fitted with catalytic converters to reduce nitrogen oxides. Laws to measure and control the amount of harmful gases given out by vehicles have been implemented and an improvement in fuels means that there is less sulphur and so fuel burns more completely.
Power stations have been encouraged to take steps to reduce the emissions of sulphur dioxide. The burning of purer coal eliminates SOfrom the air and the installation of scrubbers and filters in chimneys trap SOfrom waste gases. Some power stations have gone over to natural gas, which produces little sulphur dioxide, but this is a short-term solution as supplies are limited and the way forward seems to be the building of nuclear power stations. These, however, bring their own environmental problems. Non fossil fuels e.g. hydro -electric power, solar power, wind energy etc. which emit no SO are seen as the future for a cleaner and greener environment.
How to help
1. Shop with care, buy articles with only the minimum amount of plastic packaging if possible. Refuse that free carrier bag
2. When buying new white goods for the house or replacing central heating boilers choose the most energy efficient ones or ones that use the cleanest fuel.
3. Walk; don't take the car for short journeys. Walking is good for you.
4. Recycle materials as much as possible. It uses less fossil fuel to recycle materials than to produce new supplies from raw materials.
5. Insulate the house so that it takes less fuel to heat it.
6. Switch off lights and computer screens and turn down the central heating thermostat a degree or two to save energy.
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