ACID RAIN

Clean air and clean water are basic human rights. These have however become increasingly scarce and expensive commodities in the “Modern world”.
Many poisonous gases and other chemicals are poured into the atmosphere everyday as waste products from power stations, factories and cars. Two of these waste gases are Sulphur dioxide (SO2) and Nitrogen Oxide (NO) which get mixed with the moisture in the air and become Sulphuric Acid (H2SO4) and Nitric Acid (H2NO3) respectively. These acids are absorbed by the rain clouds and the rain which falls is a weak acid. This phenomenon is called Acid Rain. Acid rain is a perfectly normal and essential phenomenon. But we, with our highly industrialized society, have added a great deal more of these gases to the natural system and begun to overload the natural system and its controls.

CAUSES:

1. World wide some 100 million tonnes of Sulphur a year enters the atmosphere as a result of human activities, like:
a) Burning of fossil fuels without adequate treatment of the resultant products.
b) Vehicle exhausts also contribute a significant amount of pollutants which increases the degree of acidification.
c) Untreated sewage- It is often discharged into the sea. This helps stimulate the growth of those algae that generate dimethylsulphide which quickly oxidizes in the atmosphere above the seas to give sulphur dioxide.

2. Modern farming with its heavy inputs of artificial fertilizers plays havoc with natural cycles. Synthetic fertilizers contain high proportion of nitrogen in the form of nitrates or ammonium salts. At least 10% of this evaporates directly into the atmosphere.

3. Poisonous gases like sulphur dioxide and nitrogen oxide from coal-fired power stations and factory chimneys. By building tall chimneys to clean up urban areas, Industry has merely succeeded in dispersing acid rains.

EFFECTS:

Rain clouds are carried over great distance by the wind. This acid rain can fall a long way from the place where the gases first entered the atmosphere. The global environment is thus damaged.
It kills trees and destroys many wildlife habitats. Vast stretches of forest in Europe and the Unites States have been destroyed by acid rain. It has been estimated that the damaging effects of acid rain in Europe causes the loss of timber worth over $20 billion every year.
When Acid Rain falls into lakes, rivers or sea, it harms the fish, plants and other water-life. It can pollute drinking water supply and can directly affect human health.

It can weaken the stonework of structures and buildings.
Acidification also alters the chemistry of soil. Soluble toxic minerals such as lead, aluminium, cadmium, mercury etc. which normally remain harmlessly bound to the particles of the soil, get dissolved in the acids and are available to plants with disastrous effects. Part of it is also washed out into water supply adversely affecting human and marine life.

It damages the crops and makes the soil infertile and acidic.