Pollutants may be classified as solid (heavy metals, fertilizers, plastics, fibres, microorganisms); liquid (solvents, oil, pesticides, insecticides, effluents); gaseous (fumes, hydrocarbons, vapours, oxides of nitrogen and sulphur; carbon monoxide and carbon dioxide).
Pollution can be broadly classified into five types:
i. Air pollution
ii. Water pollution
iii. Soil pollution
iv. Noise pollution
v. Radiation pollution
1. Air Pollution:
Air is perhaps the most vital element required for our survival. All living organisms, including human beings, cannot live without air even for a few minutes. Air consists of 78 per cent nitrogen, 21 per cent oxygen and 1 per cent of other gases, out of which carbon dioxide constitutes 0.3 per cent. It is shocking to know that the air we breathe in is full of impurities and is the cause of many diseases and malfunctioning of our system.
An air pollutant is a substance present in the atmosphere in concentrations that disturb the natural equilibrium of the atmosphere and produces undesirable effects on humans and environment. There are several types of air pollutants. Some of them are not very harmful but others can be very dangerous and can have serious effects on man and his environment.
In addition, pollutants can also be in the form of solid particles, liquid droplets or gases. Solids or liquids with size less than 100 microns that remain suspended in the air are called particulate pollutants, for example dust, smoke, fog, mist, bacteria and fumes.
Gases such as CO, NH,, SOz, CO, NO, and H, S are continually released into the atmosphere through natural and chemical activities, are toxic and poisonous.
Another classification of air pollutants can be either primary or secondary. The following are the primary pollutants that are emitted directly into the environment and contribute to more than 90 per cent of global air pollution:
i. Carbon monoxide (CO)
ii. Nitrogen oxides (NOx)
iii. Hydrocarbons (HXCX)
iv. Sulphur oxides (SOx)
Secondary pollutants are not emitted directly. Rather, they are formed as a consequence of interaction with primary pollutants, for example photochemical smog, which is a mixture of smoke and fog, sulphuric acid (acid rain), which forms when sulphur dioxide dissolves in rainwater, and nitric acid which forms when nitrogen dioxide dissolves in rainwater.
2. Water Pollution:
We all know water is essential for life. Water covers 71 per cent of earth’s surface and makes up 65 per cent of our bodies. Hence the quality of water is of vital concern for mankind since it is directly linked with human welfare. If water gets polluted, it disturbs the normal uses of water for survival of man, fishes, other aquatic and wildlife as well as for agriculture and industry. Polluted water is the cause of many waterborne diseases and epidemics, which are prevalent in many developing countries.
Generally speaking, water pollution is defined as the state of deviation from the pure condition, which affects its normal functions and properties such that it becomes harmful if used by man, animals and aquatic life. Water pollution includes pollution of fresh water, marine water and groundwater.
We all are aware of the signs of water pollution such as bad taste of drinking water, offensive odours from water bodies, and decline in number of fishes living in it and oil and grease floating on surface of water.
The major sources of water pollution are domestic waste, which is discharged untreated into natural water bodies. Both organic and inorganic substances present in these wastes contaminate water. Hence the water pollutants are broadly classified as organic, inorganic and biological water pollutants.
However, displacement due to development, as well as forest policies, has put Worlis to a lot of trouble. If, for some reasons, they are forced to leave the forests, all their indigenous knowledge would get lost to the world.
Inorganic pollutants consist of inorganic salts, silt (sediment), mineral acids, finely divided metals and their compounds as well as complexes of metals with organics in natural water. Some large visible items polluting water may be termed as ‘floatables’ which include shipwrecks, marine debris and trash (paper, plastic and food waste).
Biological pollutants include pathogens like bacteria, viruses, protozoa, algae and worms. Water pollution is harmful to both fresh water as well as marine water.
Our major source of fresh water is groundwater. It is needed for drinking purposes, for irrigation and in industry. When rain falls, rainwater passes through different layers of soil. This natural filtration purifies it and makes it fit for human consumption.
Snow-fed rivers, rain-fed lakes and ponds are included as freshwater bodies. Contamination of fresh water is due to the following reasons:
i. Seepage of pesticides and fertilizers into groundwater.
ii. Flow of hazardous chemical paste from industries into streams, rivers and ponds.
iii. Flow of domestic sewage into freshwater bodies.
iv. Thermal power plants and many industries discharge hot water into freshwater bodies. This affects the aquatic organisms and disturbs the aquatic ecosystem.
v. Eutrophication caused by the chemical effluents discharged into the water body.
Marine Water Pollution:
Pollution of seas and rivers is caused by the rivers that dump millions of tonnes of wastes into them. Rivers carry agricultural, industrial and domestic wastes into the seas.
Activities along coasts and at seaport cities also generate industrial waste which is often dumped into the seas. Oil spills and oil leaks are a major cause of marine pollution. Layers of soil on seawater surface destroy aquatic life, as well as bird life that feed on aquatic animals.
3. Soil Pollution:
Soil is the uppermost layer of the earth crust which is formed by weathering of the rocks. The top soil is fertile and is a storehouse of microorganisms (bacteria and fungi) and organic matter (humus).
Soil pollution refers to contamination of soils with materials or chemicals released by spill or underground leakage that makes it unfit for productivity. Soil pollution can also lead to water pollution when toxic chemicals leach into the groundwater and further to other water bodies. It also adds to air pollution by releasing the volatile compounds into the atmosphere.
Both organic and inorganic contaminants contribute to soil pollution. Among them, the most important organic soil contaminants include aromatic and chlorinated hydrocarbons, detergents and pesticides. Inorganic contaminants include heavy metals such as nickel, arsenic, cadmium, chromium, lead, inorganic acids, nitrates and phosphates and radioactive substances from nuclear wastes and radioisotopes.
Pollution of soil is most commonly caused by discharge of industrial and man-made waste materials into the soil, such as non-biodegradable plastics, application of pesticides, dumping of oil and fuel; radioactive fallout and percolation of contaminated water into the soil.
With increasing population, the accumulation of municipal waste has increased tremendously. This waste is dumped in landfills near cities and towns. Along with biodegradable waste such as paper, cloth, vegetable, etc., a great deal of non-biodegradable waste is also dumped into the soil.
These include plastics, polythene bags, glass bottles, hospital wastes such as needles and surgical equipment, tin, cans, etc. The natural decomposers in the soil are not able to decompose large amounts of waste, especially as it includes non-biodegradable items.
4. Radiation Pollution:
Radiation pollution is any form of ionizing and nonionizing radiations that results from human activity. These radioactive pollutants are produced by nuclear explosions, war explosives, nuclear power generation, spent-fuel reprocessing plants, by-products of mining operations and research laboratories.
Radioisotopes are also used for medicines and diagnostic purposes. Radiation pollution can have a long-term effect on the environment and increased exposure to radiation causes skin burns and cancer. It is therefore, essential to control these radioactive emissions into the environment.
5. Noise Pollution:
Unpleasant sound that disrupts the concentration of an individual and leads to irritable behaviour can be termed as noise pollution. Noise today has become an indispensable part of our environment, which is increasing in volume every day.
Industrialization and technological progress are adding to the problem of noise pollution. Vehicular traffic which makes tremendous noise on the roads, machines that make loud noise and blaring loudspeakers are adding to the level of noise in our environment.
Excessive exposure to noise pollution causes hearing problems, hypertension, restlessness, irritability and stress. Major contributors to noise pollution are vehicles, aircraft, railways, machines used for construction and sirens.