Pollution Science Notes

Pollution Science Notes

Important Points:

→ Industrialization, increasing population, mining, transportation, indiscriminate use of pesticides and fertilizers, etc. are all man-made causes that is degrading the environment of the earth.
→ Due to all these activities pollution of various kinds is created. This affects all the living organisms including human beings.

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Pollution is the contamination of natural environment causing harmful effects to ecosystems.


Pollutants are the factors that adversely impact natural functions of ecosystem causing harmful effects on abiotic and biotic components of the ecosystem. They are hazardous and cause toxic and hazardous effects depending upon all the living organisms.

→ Two types of pollutants

  • Natural
  • Man-made

The natural pollutants are degraded naturally after certain duration of time. But man-made pollutants persist for a long period of time.

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Air pollution:

Air pollution is the contamination of air by harmful substances like poisonous gases, smoke, particulate matter, microbes, etc.

→ Reasons of air pollution

→ Natural reasons:

Source Pollutants
1. Volcanic eruption Solid, gaseous and liquid materials like Hydrogen sulphide, sulphur dioxide, carbon dioxide, ammonium chloride, hydrogen, vapours, dust
2. Earthquake Poisonous gases and water vapours present in the interior of the earth
3. Cyclones and dust storms Dust, soil, garbage, pollens, microbes
4. Forest fires Carbon dioxide, sulphur dioxide, hydrogen sulphide, smoke
5. Microbes in air Pollens of Parthenium, spores of bacteria, fungi

→ Man-made reasons:

Source Pollutants
Burning of fuel (coal, timber, LPG, kerosene, diesel, petrol) carbon dioxide, carbon monoxide, nitrogen oxide, sulphur dioxide, lead compounds
Burning of solid waste, agricultural waste, etc.
Industrialization sulphur powder, nitrogen oxide, cotton seed powder in air
Atomic energy plants and atomic blasts Uranium, thorium, graphite, plutonium release radiations

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Peeping in the history

Some notorious episodes of air pollution:

→ In London, during 5th to 9th December 1952 and 3rd to 7th December 1962 there was thick smog due to smoke emitted by combustion of coal which mixed with fog forming smog.
→ In 1948 in the city of Petersburg, smoke and soot spread so much that the entire city appeared dark as night during a day time. This city was then called black city.
→ Union carbide company in Bhopal suffered from an accident when the toxic methyl isocyanate gas was leaked killing 8000 people and making few more thousands disabled forever. This incidence happened on the night of 2nd December 1984. This incidence is known as Bhopal Gas tragedy. It is said to be the worst ever industrial accident.

→ Effect of air pollution on plants and animals:

Plants Animals
1. Stomata are choked due to dust particles. 1. Animals cannot respire properly.
2. Rate of photosynthesis declines. 2. Irritation to eyes and throat.
3. Plant growth is retarded.
4. Yellowing of the leaves resulting into their fall.

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Effects of air pollution on atmosphere:

→ Depletion in Ozone layer: Below the stratosphere ozone layer is present. Ozone layer is a protective layer that helps the living world of the earth from ultraviolet rays (UV-B) present in the solar radiation. One of the effects of air pollution is destruction of ozone layer.

→ Greenhouse effect and Global warming: C02 is present in very small quantity in the atmosphere around Earth. It absorbs radiated heat from the solar radiation. Due to C02 there is warmth on the earth’s surface. However, in recent times there has been continuous increase in the amount of C02 due to continuous growth of industrialization and burning of fossil fuels.

→ This C02 is forming an additional covering around the earth along with other gases such as Nitrous oxide, methane and CFC. This layer does not allow the re-radiation of the solar heat but traps the same. This causes warming of the Earth. All of these gases are called greenhouse gases. They bring about greenhouse effect. Greenhouse effect is causing global warming.

Due to greenhouse effect

  • Global warming
  • Climate change
  • Decrease in the agricultural yield.
  • Threat to wildlife
  • Melting of glaciers and icebergs resulting into sea-level rise and coastal land submergence.

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Acid Rain

When timber, coal and fossil fuels are burnt they release oxides of sulphur and nitrogen into atmosphere. These get dissolved in rainwater and turn into acids like sulphuric acid, nitric acid, nitrous acid, etc. When there is rainfall, the acids fall on the ground in the form of acid rain. Sulphur containing air pollutants affect the colours in paints, oil paintings and materials such as nylon, cotton fabrics, leather articles and papers, etc.

→ Effects of acid rain

→ Soil and water bodies become acidic. This causes harm to resident animals and plants. The entire ecosystem is threatened.
→ Due to acid rain, erosion of buildings, bridges, metal idols, busts, historical monuments, wire fences, etc. get rusted.
→ Plants absorb the heavy metals. Heavy metals such as cadmium and mercury indirectly enter the food chain through plants.
→ Water is acidified. It enters the pipes causing leaching of metal and plastic material. This results in serious health problems.

→ Preventive measures of air pollution

→ The exhaust gases from the factories should not be left into the atmosphere without proper treatment. The polluting particulates should be filtered through proper machinery. The arresters and filters should be used for this purpose.
→ Proper management should be done to dispose solid waste material which stinks.
→ The atomic testing, chemical weapons, etc. should be totally banned for the betterment of the earth.
→ CFC should be either controlled or banned to protect the ozone layer.

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Air Quality Index:

The air quality index, proportion of S02, CO, N02, ozone, particulate matter, etc. is measured every day in big cities. This information is displayed on the boards for the citizen for their knowledge. The extent of air pollution in the city is thus known by air quality index.

Water pollution:

When the water becomes unclean and toxic due to mixing of natural or artificial polluting substances, then it is called water pollution. Pollutants cause water to become toxic and unclean. The dissolved oxygen content in water becomes less causing harm to the resident living organisms. Disease causing epidemics break due to pathogens added to the water due to pollution. Physical, chemical, and biological changes in the water are caused due to water pollutants.

Water Pollutants:

Type of water pollutants Particulars
Biological pollutants Algae, bacteria, viruses, parasites
Inorganic pollutants Suspended particles like fine sand, dust, soil, precipitates of salt, mercury, and traces of compounds of arsenic, cadmium, lead, radioactive material
Organic pollutants Weedicides, insecticides, fertilizers, sewage, industrial effluents, etc.

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Causes of water pollution

→ Natural causes and effects

Causes Effects
1. Aquatic weeds 1. Depletion of oxygen levels
2. Change in the natural characters of water.
3. Eutrophication
2. Decomposing matter Decomposing bodies of dead animals or plants.
3. Mud/sludge River current changes due to sludge and this causes diversion of the currents.
4. Soil erosion Due to soil erosion, many biotic and abiotic factors are added to water.
5. Fungi and bacteria On the organic matter the fungal and bacterial growth occurs.
6. Algae Excessive algal growth pollutes water.
7. Nematodes The rainwater carried the soil nematodes in the water.

→ Man-made causes and effects

Causes Effects
1. Domestic sewage Domestic sewage water from villages and cities.
2. Industrial effluent Effluents are from industries which add various pigments, bleaching chemicals, leather pieces, fibres, mercury, lead, etc.
3. Oil spillage 1. During transportation, spillages of crude oil may occur.
2. Cleaning of tankers
3. Accidents occurring at tankers or oil rigs causing oil slicks in water.
4. Use of fertilizers and pesticides 1. Fertilizers containing N, P and K
2. Endrin, chlorine, carbonate containing pesticides, wash off and enter water.
5. Other man­made reasons 1. Pollution by human excreta
2. Washing of clothes
3. Decomposing hemp and flax in water
4. Disposal of ashes
5. Floral offerings to god
6. Warm water from thermal power plant

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→ Effects of water pollution

1. Effects of polluted water on human beings 1. Diseases: hepatitis, typhoid, cholera, skin diseases
2. Ailments of liver, kidneys, brain
3. Deformities in bones, hypertension
2. Effects on ecosystem 1. Retarded plant growth
2. Loss of plant species
3. Increase in salinity of water
4. Decreased content of dissolved oxygen
5. Disturbance in aquatic ecosystem
6. Death of marine and aquatic animals
7. Adverse effects on sea birds

Soil Pollution:

Soil pollution: Physical, biological and chemical properties and the fertility of j soil is decreased due to either natural or man-made cause. Such a condition that results into lesser productivity of the soil is called soil pollution.

→ Effects of soil pollution:

Soil becomes unfertile. The salty, acidic materials from nearby industries when mixed with soil make it unproductive.

Some toxic pollutants can be transferred through the food chain. Insecticides like D.D.T. are accumulated into the bodies of plants and animals. Radioactive substances enter the soil, from soil into crops and then to the nearby water sources and ultimately to human beings.

Some insecticides that are sprayed in the farms and fields are carried to the water sources from the soil by the flowing water. If they are in excess, they leach into the ground water table. In this way the pollutants cause soil pollution and water pollution.

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→ Various pathogens in the soil transmit the diseases.

→ Relationship of soil pollution with air and water pollution:

→ When the wet organic waste is thrown into the water bodies, it gets deteriorated and decomposed. The harmful pathogenic bacteria grow in such garbage. When such waste is mixed in the water, it causes water pollution.
→ Excessive use of chemical fertilizers, insecticides and weedicides cause soil pollution. The sprayed insecticides and weedicides cause air pollution.
→ Overuse of chemical fertilizers cause water pollution as these substances are washed off into water bodies.
→ Soil pollution is also caused by human urine and excreta, animal dung and bird droppings.
→ Such wastes emit foul smelling gases causing stink in the area. These gases when mixed with air cause air pollution. The same waste if mixed with water cause water pollution. Such waste can be pathogenic causing diseases and outbreak of epidemics.

Pollution – Prevention and control:

→ Government of India has made following laws and rules related to the control of pollution. These laws are followed in order to keep the environment pollution- free.

  • Water Pollution and Prevention Act, 1974
  • Air Pollution and Prevention Act, 1981
  • Environmental Protection Act, 1986
  • Biomedical waste (Handling and management) Rules – 1998
  • Hazardous waste (Handling and management) Rules – 1989
  • Noise pollution (Regulation and Control) Rules – 2000
  • E-waste (Handling and Management) Rules – 2011

→ Government statutory bodies like Maharashtra Pollution Control Board and Central Pollution Control Board supervise the industries, industrial areas, local governing bodies like municipalities, district councils, panchayat samiti, gram panchayat, etc. They make sure that all these organizations follow the laws about pollution control.

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