Introduction
→ The layer of air present around the earth is called atmosphere.
→ Atmosphere is composed of 78% of nitrogen, 21% of oxygen, and 1% percent other gases such as carbon dioxide, ozone, water vapour, methane, etc.
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Air pollution
→ The phenomenon of contamination of air with unwanted substances so that it becomes harmful for living organisms and non-living substances is known as air pollution.
→ The substances, which cause air pollution, are called air pollutants.
Sources of air pollution
(i) Power plants
(ii) Factories
(iii) Automobiles
(iv) Burning of firewood
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Types of air pollutants
(i) Carbon monoxide
→ It is a colourless poisonous gas.
→ It is produced from incomplete burning of fossil fuels.
(ii) Smog
→ It is made up of smoke and fog.
(iii) Sulphur dioxide
→ It is produced from combustion of fuels.
(iv) Nitrogen dioxide
→ It is produced from incomplete burning of fuels.
(v) Chlorofluorocarbons (CFCs)
→ They are released from refrigerators, air conditioners, and aerosol sprays.
→ They cause damage to the ozone layer resulting in the formation of ozone hole.
(vi) Suspended particulate matter
→ It comprises of tiny particles, which remain suspended in air for a long time.
→ They are produced during burning of fossil fuels in power plants, mining, steel making, and other industrial processes.
→ They reduce visibility and cause haze.
→ They cause respiratory diseases on inhalation.
→ Soot released from Mathura refinery has caused yellowing of the marble of Taj Mahal.
Prevention of air pollution
→ Use of clear fuels such as CNG, LPG, and unleaded petrol in public and private transport.
→ Use of renewable sources of energy such as solar, wind, and hydel energy.
→ Planting more and more trees to prevent pollution.
→ Prevent burning of dry leaves and use them in composting.
→ Kyoto protocol is an agreement between various countries for reducing green house emission.
Acid rain
→ It is formed when sulphur dioxide and nitrogen dioxide present in air react with water droplets to form nitric and sulphuric acid.
→ When it rains, it brings these acids along with it, which causes damage to plants, animals, and monuments.
→ Acid rain has caused corrosion of the marble of Taj Mahal
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Water pollution
→ The addition of harmful substances to water, as a result of which its physical, chemical, and
biological properties get altered, is called water pollution.
→ Substances that pollute water are called water pollutants.
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Sources of water pollution in Ganga river
→ Untreated discharges from textile, paper and sugar mills, and oil refineries.
→ Disposal of agricultural discharge from near-by fields, which are rich in pesticides and weedicides, into the river.
→ Flow of untreated domestic sewage into the river.
→ Cremation of dead bodies into the river.
→ Immersion of idols of gods and goddesses, flowers, garbage, and polythene bags into the river.
→ Ganga Action Plan aimed to reduce the pollution levels in the river.
Types of water pollutants
→ Domestic sewage
→ It is composed of food wastes, detergents, and disease-causing pathogens.
→ The bacteria present in faecal matter of mammals indicate the pollution levels in a river and if such water is consumed, it may cause various diseases.
Industrial waste
→ It is rich in toxic chemicals such as arsenic, fluorides, and lead.
→ It causes toxicity in plants and animals.
→ It affects the soil by causing changes in acidity and growth of worms.
Agricultural waste
→ It is rich in agricultural pesticides and weedicides.
→ It causes ground water pollution.
→ It causes an increase in the population of algae in water.
→ When these algae die, they are acted upon by decomposers, which use lots of oxygen dissolved in water for this purpose.
→ This results in the death of fishes and other aquatic organisms.
Release of Superheated Water
→ The release of superheated water from some industries and nuclear power plants causes thermal pollution of the water bodies.
→ The abrupt change in the temperature of water body can kill the fish and other organisms adapted to particular temperature range.
Methods of preventing water pollution
→ Industrial waste must be chemically treated to remove harmful substances before dumping into the water bodies.
→ Disposal of human and animal excreta into water should be avoided.
→ Sewage water must be treated before releasing into the rivers.
Conservation of water
→ Reusing the waste water from the kitchen (water that has been used to wash vegetables, etc.) to water the plants in the garden.
→ Turning the tap off while brushing or shaving.
→ Checking for leaky taps and fixing them up.
Rainwater harvesting
→ Using improved farming and irrigation techniques
→ Preventing pollution of water
→ Conserving and replenishing ground water
→ Proper removal of silt from water bodies
→ Preventing cutting of trees
→ Prevention of water pollution
→ Proper treatment of industrial waste and domestic waste before their disposal into rivers.
→ Strict implementation of environmental laws in industrial units.
→ Reusing water used in kitchens (such as to wash vegetables) for watering plants.
→ Getting the leaky taps checked and preventing wastage of water.
Potable water
→ Water that is fit for drinking is called potable water.
Methods of obtaining potable water
(i) Physical methods
→ Boiling of water
→ Use of domestic filters such as candle type filter
(ii) Chemical method
→ Use of chlorine tablets
Greenhouse effect
→ Trapping of heat by gases (CO2 ) in the atmosphere.
→ Gases that cause the greenhouse effect are responsible for increasing the temperature of the Earth and thus contributing to the phenomenon called global warming.
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Causes of Green house effect
→ A part of solar radiations cause warming of the earth’s surface.
→ A part of solar radiation is reflected back, which is trapped by the earth’s atmosphere.
→ This phenomenon is called green house effect.
Green house gases
→ These are the gases, which trap the solar radiations, and in this way, are responsible for the increase in the temperature of Earth.
→ The examples include carbon dioxide, methane, nitrous oxide, and water vapours.
Global warming
→ The CO2 level in atmosphere is increasing due to various human activities such as deforestation and burning of fossil fuels.
→ Build up of CO2 in the atmosphere will result in a rise in the average temperature of earth’s atmosphere, leading to global warming.
→ Global warming will lead to melting of glaciers and increase in the sea level.