Notes of chapter: Pollution of Air and Water are presented below. Indepth notes along with worksheets and NCERT Solutions for Class 8.
(1) Air pollution-
When harmful substances like gases ( oxides of nitrogen and sulphur), particles, etc. enter into air in large quantities and have harmful effect on living organisms and non- living things, is referred as air pollution.
(i) Air pollutants-
The substances that contaminate the air are called air pollutants.
(ii) Causes of air pollution-
Air pollution causes from two sources.
(a) When quantity of pollutants increase in air by natural sources are called natural cause of air pollution.
Eg:- Volcano eruption, forest fire etc.
(b) When quantity of air pollutant increases in the air by manmade sources are called artificial causes of air pollution.
Eg:- Pollutants from power plants, fire wood, dung cakes, etc.
Artificial causes to increase air pollution-
(a) Automobiles or vehicles produce high level of pollutants like carbon mono oxide and smoke. Carbon mono oxide is a very dangerous gas which is produced from the incomplete burning of the fuels like petrol and diesel. Carbon mono oxide reduces the oxygen carrying capacity of the blood.
(b) The smog is a thick fog like layer that is made up from a combination of oxides of nitrogen with air pollutants and fog.
(c) Many industries like petroleum refineries are responsible for producing air pollutant like sulphur dioxide and nitrogen dioxide. Sulphur dioxide is produced by combustion of fuels like coal in power plant.
(d) Refrigerators, air conditioners and aerosol sprays are producing air pollutants chlorofluorocarbons (CFCs) which damage the ozone layer. The ozone layer protects us from the harmful ultraviolet rays of the sun.
(e) When diesel and petrol burns in automobiles, it produces tiny pollutant of nitrogen and sulphur particles that remain suspended in the air for long time period. Such particles are produced in steel making and mining. Power plants give out tiny ash particles which also pollute the atmosphere.
(f) Greenhouse effect is a natural process in which radiation from the sun rays fall on the atmosphere of the Earth and a part of it is radiated back to space as heat by atmosphere. But, other part is absorbed by the earth’s surface. Now, earth heats up and released back radiation into atmosphere and space. The greenhouse gases which are present in the atmosphere absorbed reflected back radiation (heat). Less part of it emitted back to space and large part is absorbed by the greenhouse gases. These gases do not allow the absorbed heat to go back in space. The trapped radiation or absorbed radiation is good for human life because it keeps earth warm and makes possible life on the earth. Hence, the trapping of radiations by the Earth’s atmosphere is known as greenhouse effect. It is very necessary for life on the Earth.
(g) The temperature of earth‘s atmosphere is gradually increasing, this is called global warming. It happens because of the increase of co2 in the atmosphere. The co2 is released by the humans in breathing, burning coal and other fuels. Plants used carbon dioxide in photosynthesis. But co2 is increasing in atmosphere because of deforestation.
Effects of global warming-
(a) It can cause sea levels to rise.
(b) Glaciers are melting because of the global warming.
Case study – The Taj Mahal
The Taj Mahal is a non- living object. But it is also affected by the air pollutants produced by the industries located in and around Agra like rubber processing, automobile, chemicals and Mathura oil refinery. These are producing pollutants like sulphur dioxide and nitrogen dioxide. These gases react with the water vapour present in the atmosphere to form sulphuric acid and nitric acid. The acid is drop down with rain. This process is known as acidic rain. This acidic rain corrodes marble.
Now, CNG and LPG are using as fuel in the industries around the Taj. Automobiles are also operating on CNG or lead free petrol.
Effects of the air pollution-
(a)Pollutants like carbon mono oxide reduce the oxygen – carrying capacity of the blood.
(b)The smog causes breathing difficulties such as asthma, cough and wheezing in children.
(c) Combustion of fuels causes respiratory problems, including lung damage.
(d) Tiny pollutant particles produced at the time of fuel burning remain suspended in the air for long time period. They reduce visibility.
Steps to control air pollution-
(i) Use CNG or unleaded petrol for vehicles.
(ii) The solar energy, hydropower and wind energy should be used in place of fossil fuel.
(iii) More plants should be planted to lower the carbon dioxide in the atmosphere.
(2) Water Pollution-
When harmful substances such as sewage, toxic chemicals, silt etc. mixed with water and effect living organism adversely, is referred as water pollution.
(ii) The substance that pollute water is called water pollutant.
Eg:- Sewage, toxic chemicals etc.
(iii) Ganga – A case study-
The World Wide Fund for Nature (WWF) found that Ganga is one of the ten most endangered rivers in the world. Ganga action plan was launched in 1985 to clean the river.
Reasons for the pollution in the river Ganga-
(a) Throwing garbage in to the river Ganga.
(b) Throwing dead bodies in to the Ganga.
(c) Untreated sewage directly flow in the ganga.
(d) Industries discharge also goes into the river. Examples are oil refineries, paper factories, textiles and sugar mills, etc. These industries contaminate water by releasing arsenic, lead and fluorides which are very harmful for living organisms
(e) Pesticides and the weedicides are used for the protection of the crops. These chemicals dissolve in water and washed into water bodies from the fields. They also seep into the ground to pollute ground water.
(f) A lot of algae grow in ponds it is caused by the excessive quantities of chemicals which get washed from the fields.
The chemicals used in the fields and washed into ponds or water bodies from the fields are nutrients for the algae grow in water bodies. A lot of oxygen in the water body gets used by algae. It results in a decrease in the oxygen level which may kill aquatic organisms.
(g) Hot water from the industries raises the temperature of the water and adversely affects the animals and plants living in water bodies.
(iv) Potable water is suitable for drinking purposes.
How to get safe drinking water-
(a) Water can be filtered to remove impurities. A popular household filter is a candle type filter.
(b) Boiling of water kills germs of water and we get safe drinking water.
(c) Chlorination is a commonly used chemical method for purifying water. It is done by adding Chlorine tablets or bleaching powder to the water.
Steps should be taken to purify water-
(a) Laws should be implement strictly for the dispose off industrial water.
(b) Water treatment plant should be installed in all industrial areas.
(c) We should save water. Reduce, Reuse and recycle should be our Mantra.