ENVIRONMENTAL ISSUES

ENVIRONMENTAL ISSUES

Human population size has grown enormously over the

last hundred years. This means increase in demand for

food, water, home, electricity, roads, automobiles and

numerous other commodities. These demands are exerting

tremendous pressure on our natural resources, and are

also contributing to pollution of air, water and soil. The

need of the hour is to check the degradation and depletion

of our precious natural resources and pollution without

halting the process of development.

Pollution is any undesirable change in physical,

chemical or biological characteristics of air, land, water or

soil. Agents that bring about such an undesirable change

are called as pollutants. In order to control environmental

pollution, the Government of India has passed the

Environment (Protection) Act, 1986 to protect

and improve the quality of our environment (air, water

and soil).

16.1 AIR POLLUTION AND ITS CONTROL

We are dependent on air for our respiratory needs. Air

pollutants cause injury to all living organisms. They

reduce growth and yield of crops and cause premature

death of plants. Air pollutants also deleteriously affect the

respiratory system of humans and of animals. Harmfuleffects depend on the concentration of pollutants, duration of exposure

and the organism.

Smokestacks of thermal power plants, smelters and other industries

release particulate and gaseous air pollutants together with harmless

gases, such as nitrogen, oxygen, etc. These pollutants must be separated/

filtered out before releasing the harmless gases into the atmosphere.

There are several ways of removing particulate matter; the most widely

used of which is the electrostatic precipitator (Figure 16.1), which can

remove over 99 per cent particulate matter present in the exhaust from a

thermal power plant. It has electrode wires that are maintained at several

thousand volts, which produce a corona that releases electrons. These

electrons attach to dust particles giving them a net negative charge. The

collecting plates are grounded and attract the charged dust particles.

The velocity of air between the plates must be low enough to allow the

dust to fall. A scrubber (Figure 16.1) can remove gases like sulphur

dioxide. In a scrubber, the exhaust is passed through a spray of water or

lime. Recently we have realised the dangers of particulate matter that are

very very small and are not removed by these precipitators. According to

Central Pollution Control Board (CPCB), particulate size 2.5 micrometers

or less in diameter (PM 2.5) are responsible for causing the greatest harm

to human health. These fine particulates can be inhaled deep into the

lungs and can cause breathing and respiratory symptoms, irritation,

inflammations and damage to the lungs and premature deaths.

Automobiles are a major cause for atmospheric pollution atleast in

the metro cities. As the number of vehicles increase on the streets, this

problem is now shifting to the other cities too. Proper maintenance of

automobiles along with use of lead-free petrol or diesel can reduce the

pollutants they emit. Catalytic converters, having expensive metals namely

platinum-palladium and rhodium as the catalysts, are fitted into

automobiles for reducing emission of poisonous gases. As the exhaust

passes through the catalytic converter, unburnt hydrocarbons are

converted into carbon dioxide and water, and carbon monoxide and nitric

oxide are changed to carbon dioxide and nitrogen gas, respectively. Motor

vehicles equipped with catalytic converter should use unleaded petrol

because lead in the petrol inactivates the catalyst.