18 POLLUTION OF AIR 18 AND WATER TEXTBOOK QUESTIONS AND THEIR ANSWERS Q.1. What are the different ways in which water gets contaminated? Ans. The different ways in which water gets contaminated are : (a) Sewage getting disposed off in rivers. (b) Industries throwing chemical wastes into the water resources. (c) Breeding of micro-organisms in water. (d) Harmful agricultural wastes getting mixed up with ground water. Q.2. At an individual level, how can you help to reduce air pollution? Ans. At an individual level, we can help to reduce air pollution in the following ways: 1
(a) We can plant trees to reduce the level of carbon dioxide. (b) We can get our vehicles serviced at proper time to reduce incomplete consumption of fuels. (c) We can say no to crackers during Diwali to reduce the addition of harmful gases to air. Q.3. Clear, transparent water is always fit for drinking. Comment. Ans. Water which is clear and transparent is fit for consumption as it is free from pollutants assuming no micro-organisms and dust particles are present in it. Q.4. You are a member of the municipal body of your town. Make list of measures that would help your town to ensure the supply of clean water to all its residents. Ans. If I am a member of municipal body of our town. I will take these measures that would help my town to ensure the supply of clean water to all its residents : (a) Ensure water reaching every home is treated water. (b) Industries should be instructed by strict laws to not put chemical wastes in water. 2
(c) Open defecation in water resources by slum dwellers should be strictly prohibited. (d) Chlorine tablets should be distributed for purification of water during rainy season. (e) People should be made aware to keep water resources clean. Q.5. Explain circumstances leading to acid rain. How does acid rain affect us? Ans. When the industries release poisonous gases like sulphur dioxide and nitrogen dioxide, these gases react with moisture present in air and form nitric and sulphuric acid. These acids fall on the earth with rain making rain water acidic and harmful. This is called acid rain. Acid rain causes the corrosion of buildings. Acid rain makes fruits, vegetables and food grains, unfit for consumption. Q.6. Which of the following is not a greenhouse gas? (a) Carbon dioxide (c) Methane (b) Sulphur dioxide (d) Nitrogen Ans. (b) 3
Q.7. Describe the Green House Effect in your own words. Ans. Sun s rays warm the earth s surface. A part of radiation falling on the earth is absorbed by it and a part is reflected back into space. A part of reflected radiation is trapped by the atmosphere. The trapped radiation further warms the earth. This trapping of radiation is called greenhouse effect. CO 2 is one of the gases responsible for this effect. Deforestation leads to an increase in the amount of CO 2 in the air. There is excess of CO 2 in the air and acts as a pollutant. Q.8. Prepare a brief speech on global warming that you have to make in your class. Ans. Continuous increase in average temperature of earth s atmosphere caused due to pollution of air, excessive heat trapped by greenhouse gases, is called global warming. Global warming can cause varying effects on rainfall patterns, agriculture, forests, plants and animals. It can also cause a rise in sea level. Global warming is a threatening phenomenon, if not handled carefully at present, may lead to many harmful consequences in future. Q.9. Describe the threat to the beauty of the Taj Mahal. 4
Ans. Excessive poisonous gases and smoke due to increased air pollution has led to discolouring of white marble of the Taj Mahal. Acid rains have also started to corrode the marble, thus making the Taj Mahal loose its beauty and charm. Q.10. Why does the increased level of nutrients in the water affect the survival of aquatic organisms? Ans. Addition of nutrients in water flourishes the growth of microorganisms like algae. When these micro-organisms die, they become food for bacteria. When these bacteria become active, they consume a lot of oxygen present in water. Decrease in oxygen in water leads to death of certain aquatic animals because of insufficient amount of oxygen to breathe. Q.11. Does acid rain affect the soil and plants also? Ans. Yes, acid rain spoils the soil and the plants. Q.12. How does CO 2 content rise in the atmosphere and become excessive? Ans. CO 2 content rises in the atmosphere because of air pollution caused by harmful gases added to air from industries, burning of garbage, etc. On the other hand, forest area is decreasing due to urbanisation. The plants which helps in decreasing CO 2 5
in air by utilising it in the process of photosynthesis, are also decreasing. Thus, deforestation and pollution both contribute to CO 2 content rise in the atmosphere. Q.13. What are the factors responsible for pollution of the river? Ans. The factors responsible for pollution of the river are as follows : (a) Throwing large quantities of garbage. (b) Disposing harmful and toxic chemicals by the industries. (c) Human activities like washing, bathing, defecating in the river water. (d) Throwing flowers, idols of God and Goddesse and nonbiodegradable polythene bags into rivers. (e) Disposing of untreated sewage. Q.14. What steps can be taken to restore the river Ganga to its past glory? Ans. The step that should be taken to restore the river Ganga to its past glory are the following: (a) Sewage from homes should not be disposed in it. 6
(b) Industrial wastes should not be disposed in it. (c) Throwing of garbage, flowers, polythene bags and idols of God should be highly prohibited. (d) Bathing, washing of clothes, defecating and throwing of dead bodies in the river should be strictly stopped. Q.15. How would the disposal of garbage, etc. affect the living organisms in the river? Ans. The disposal of garbage etc. increases the pollution level of the rivers and hence, the toxicity so caused in the river waters affect the living organisms living in it. Q.16. Have you seen ponds which look green from a distance because they have a lot of algae growing in them? Give reason. Ans. Yes, we have seen ponds which look green from a distance because they have a lot of algae growing in them. This is caused by excessive quantity of chemicals which get washed from crop fields. These act as nutrients for algae to flourish. Q.17. Can ground water get polluted by sewage? How? 7
Ans. Pesticides and weedicides used for protection of crops get dissolved in water during agricultural practices and are washed into water bodies from the fields. This agricultural sewage from our crop fields also seeps into the soil and makes the ground water polluted. Q.18. How can you save water? Ans. There are the following methods to save water: (a) Industries should treat the waste produced before disposing it to the river. (b) We can reuse the water for washing and for other household works. (c) Do not leave the tap open when you are not using the water. (d) Agricultural sewage should also be treated before throwing it to a water body. 8