Chapter 18 : Pollution of Air and Water - Ncert Solutions for Class 8 Science CBSE
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Chapter 18 - Pollution of Air and Water Excercise 250
(i) Agricultural chemicals: Farmers use excessive amounts of pesticides and fertilizers to increase crop production. These chemicals get carried away to the water bodies due to rains and floods which lead to water pollution.
(ii) Industrial wastes: Industries release harmful chemical wastes into water sources, thereby polluting them.
(iii) Sewage wastes: Waste materials from kitchens, toilets, and laundry sources are also responsible for contaminating water.
(i) By using public transport whenever possible.
(ii) By not using vehicles for short distances.
(iii) By using clean fuels such as LPG and CNG instead of diesel and petrol.
(iv) Always disposing the garbage properly and not burning it.
(v) Controlling the emissions from vehicles and household chimneys.
(i) The main water source must be built in clean surroundings and should be maintained properly.
(ii) Chemical methods such as chlorination must be used for purifying water.
(iii) The area around water pipes must also be clean.
Pure air contains around 78% nitrogen, 21% oxygen, and 0.03% carbon dioxide. Other gases such as argon, methane, ozone, and water vapours are also present in small quantities.
When this composition of air is altered by the addition of harmful substances or gases such as nitrogen dioxide, sulphur dioxide, carbon monoxide, and particulate matter, then the air is said to be polluted.
Effects of acid rain:
(i) Acid rains damage crops.
(ii) Acid rains corrode buildings and structures especially those made of marble such as Taj Mahal.
Chapter 18 - Pollution of Air and Water Excercise 251
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