Selina Concise Solutions for ICSE Class 9 Geography Chapter 17 Sources of Pollution

Exercises

I. Short Answer Questions

Question 1. Name any three air pollutants and the sources of each of them.
Answer:
Pollutant :
1. Carbon Monoxide (\( CO \)) :
2. Nitrogen Oxides (\( NO_x \)) :
3. Sulphur Oxides (\( SO_x \)) :
Sources :
1. Gasoline fuel, motor vehicles fuel, burning of wood and coal, solid waste disposal, Industrial processes.
2. Primary sources are motor vehicles and power generation stations, combustion of organic matters, furnace stacks, incinerators.
3. Mainly due to burning of coal, smelting operations, refineries, chemical plants, open burning of garbage and municipal incinerators.
In simple words: Major air pollutants like carbon monoxide and sulphur oxides come from burning things. This includes gasoline in our cars, coal in factories, and even when people burn wood or trash at home.

📝 Teacher's Note: Use a simple chart to link each gas to a daily activity, like connecting \( CO \) to car exhausts, to help students visualize where these invisible gases come from.

🎯 Exam Tip: To score full marks, list the chemical symbol alongside the name, such as Carbon Monoxide (\( CO \)), and provide at least two sources for each.

Question 2. What are natural sources of air pollution ?
Answer: Natural sources are volcanic eruptions, sand, dust, forest fires etc.
In simple words: Pollution doesn't just come from humans; nature can create it too. Smoke from big forest fires and ash from volcanoes are ways the Earth naturally adds "junk" to the air.

📝 Teacher's Note: Explain that while these sources are natural, human-caused climate change is making things like forest fires much more frequent and severe.

🎯 Exam Tip: "Volcanic eruptions" and "Forest fires" are the strongest keywords to use for natural sources of pollution.

Question 3. Name one industry which pollutes the atmosphere with gaseous as well as with particulate matter.
Answer: Automobile industry.
In simple words: The industry that makes cars and trucks is a major polluter. It releases both harmful invisible gases and tiny solid bits of "dust" called particulate matter into the air.

📝 Teacher's Note: Differentiate between "gaseous" (invisible gases) and "particulate matter" (tiny solid or liquid droplets like soot) so students understand the two types of pollution.

🎯 Exam Tip: Ensure you mention the "Automobile industry" specifically, as it is the primary answer expected for this combination of pollutants.

Question 4. What is known as smog ? What harm is done by smog especially in winter ?
Answer: Smog means smoke + fog. In winter season smog is responsible for many accidents due to the obstacle in visibility.
In simple words: Smog is a thick, dirty mixture of smoke and natural fog. In the winter, it can become so thick that drivers can't see the road, leading to many dangerous traffic accidents.

📝 Teacher's Note: Use the word equation "Smoke + Fog = Smog" as an easy mnemonic for the class to remember the definition.

🎯 Exam Tip: Always mention "visibility" as the main problem caused by smog to get full marks on the "harm" part of the question.

Question 5. Name three gases emitted during burning of garbage.
Answer: These are Carbon dioxide, Sulphur dioxide, Nitrogen oxides.
In simple words: When trash is set on fire, it releases a cocktail of toxic gases. The three most common ones are carbon dioxide, sulphur dioxide, and nitrogen oxides.

📝 Teacher's Note: Explain that burning plastic and chemicals in garbage makes these gases much more dangerous than just burning dry leaves.

🎯 Exam Tip: Memorize these three specific gases: \( CO_2 \), \( SO_2 \), and \( NO_x \), as they are the standard trio for combustion-based pollution questions.

Question 6. Mention any two sources of water pollution.
Answer: Two sources of water pollution are :
- household detergents and sewage,
- oil spills
In simple words: Water gets dirty from things we use at home, like soaps and toilet waste. It also gets polluted by big accidents in the ocean called oil spills.

📝 Teacher's Note: Mention that detergents contain phosphates which can cause algae to grow too fast, choking the life out of ponds and lakes.

🎯 Exam Tip: If the question asks for two sources, picking one "domestic" (sewage) and one "industrial/accidental" (oil spills) shows a well-rounded understanding.

Question 7. Name two heavy metals from industries that pollute water.
Answer: Heavy metals are Lead and Mercury.
In simple words: Some factories release dangerous metals into our rivers. Lead and Mercury are particularly bad because they can make fish and humans very sick if they get into our water.

📝 Teacher's Note: Discuss the "Minamata disease" briefly as a real-world example of how mercury pollution in water can devastate a community.

🎯 Exam Tip: Lead and Mercury are the "gold standard" examples for heavy metal pollution; always keep these two at the top of your list.

Question 8. Mention any four sources of soil pollution.
Answer: These are industrial wastes, domestic waste, chemical fertilizers and pesticides.
In simple words: The ground gets poisoned by factory trash and the garbage we throw away at home. Farmers also accidentally pollute the soil by using too many chemicals to kill bugs or make plants grow faster.

📝 Teacher's Note: Highlight the irony that chemical fertilizers are meant to help plants but can actually ruin the soil's health in the long run.

🎯 Exam Tip: Ensure you include "pesticides" and "chemical fertilizers" as they are key agricultural sources of soil degradation.

Question 9. Why are radioactive pollutants very dangerous ?
Answer: The emission of radioactive minerals Uranium 235 Plutonium 239, make the whole surroundings radioactive after fission and carried away by wind to long distances. These are dangerous to health, as these remain as it is for a long time.
In simple words: Radioactive materials like Uranium stay dangerous for hundreds or even thousands of years. They emit invisible rays that can travel far with the wind and cause very serious illnesses like cancer.

📝 Teacher's Note: Use the analogy of a "permanent invisible fire" to explain why radioactivity is so much harder to manage than regular smoke or trash.

🎯 Exam Tip: Use keywords like "fission," "long distances," and "long time" to explain why these pollutants are uniquely hazardous.

Question 10. What kind of solid and liquid pollutants does the offshore drilling produce ?
Answer: Drilling produces dust, stones etc and crude oil spills pollute largely the oceanic water and disturb marine life.
In simple words: When we dig for oil in the ocean, it creates a lot of solid waste like crushed rocks. Even worse, if the oil leaks (spills), it coats the water and kills fish and seabirds.

📝 Teacher's Note: Clarify that "offshore" means drilling in the sea, which is why the pollution directly affects "marine life."

🎯 Exam Tip: Distinguish your answer into "Solid" (dust, stones) and "Liquid" (crude oil spills) to address both parts of the question.

Question 11. What are primary pollutants ?
Answer: The pollutants that are directly emitted from the sources and are found in the atmosphere in the form in which they are emitted are known as primary pollutants, e.g., ash, radioactive compounds, oxides of sulphur and nitrogen etc.
In simple words: Primary pollutants are "fresh" from the source. They come out of a car or factory and stay in that same form while they float in the air.

📝 Teacher's Note: Think of these as the "raw ingredients" of pollution. They haven't changed or mixed with anything else yet.

🎯 Exam Tip: Use the phrase "directly emitted" in your definition to clearly distinguish them from secondary pollutants.

Question 12. With an example, state what are secondary pollutants?
Answer: The pollutants that are formed in the atmosphere by chemical interactions between primary pollutants and atmospheric constituents are known as secondary pollutants. Examples of secondary pollutants are Sulphur trioxide, Ozone, Peroxyacetyl Nitrate (PAN), Ketones etc.
In simple words: Secondary pollutants are like a "chemical recipe" that happens in the sky. They are created when primary pollutants mix together and react with the air to form something new and often more toxic.

📝 Teacher's Note: A classic example is Acid Rain. \( SO_2 \) (primary) mixes with water vapor to form Sulphuric Acid (secondary).

🎯 Exam Tip: "Ozone" (at ground level) and "PAN" are excellent high-level examples to include for secondary pollutants.

Question 13. What is the connection between urbanisation and air pollution ?
Answer: The major connection between urbanisation and air pollution are automobiles, industries, burning of garbage and brick kilns. These sources release pollutants such as oxides of carbon, oxides of sulphur, oxides of nitrogen, and hydrocarbons, ozone, chlorofluoromethanes, etc.
In simple words: As cities grow (urbanisation), we get more cars, more factories, and more trash. All these activities release a lot of different harmful gases that ruin the air quality for everyone living in the city.

📝 Teacher's Note: Help students connect the word "Urban" to "City." More people in cities means more demand for electricity (industries) and travel (automobiles).

🎯 Exam Tip: When discussing urbanisation, focus on the "concentration" of sources like automobiles and industries in a small area.

Question 14. How much are the automobiles responsible for air pollution ?
Answer: Automobiles are mainly responsible for \( 80\% \) air pollution, emitting Carbon monoxide, Hydrocarbons, Nitrogen monoxide etc.
In simple words: In many cities, cars and bikes are the biggest culprits, causing almost \( 80\% \) of all the air pollution. They pump out dangerous gases every time we drive.

📝 Teacher's Note: This massive percentage (\( 80\% \)) shows why switching to electric vehicles or public transport is so important for city health.

🎯 Exam Tip: The number "\( 80\% \)" is the key data point here. Don't forget to list at least two gases they emit.

Question 15. How are brick kilns a source of gases and particulate matter that cause air pollution ?
Answer: Brick kilns produce huge amount of Carbon oxides, smoke and dust etc.
In simple words: Brick kilns use huge fires to bake clay into bricks. These fires release massive clouds of black smoke and thick dust that settle on everything nearby.

📝 Teacher's Note: Explain that kilns often use low-quality fuel like coal or even old tires, which makes their smoke particularly thick and dirty.

🎯 Exam Tip: Mention both "gases" (Carbon oxides) and "particulate matter" (smoke and dust) to fully answer the question.

II. Long Answer Questions :

Question 1. With reference to noise pollution, answer the following:
1. How does traffic contribute to noise pollution ?
2. Why are the construction sites considered as worse than factories in their contribution to noise pollution ?
3. How do the airplanes cause noise pollution ?
Answer:
1. The increasing number of vehicles on the roads are a big source of noise pollution. Increasing traffic jams in congested areas lead to repeated hooting of horns by impatient drivers causing noise pollution.
2. Noise from construction sites is generally far worse than noise originating from factories. This is because whatever construction takes place noise emissions levels are higher as well as the equipment is inherently noisy.
3. Noise pollution caused by airplanes has been increasing steadily during recent years, especially in the areas close to international airports. This problem has mainly arisen because of the widespread use of heavy long-range jet aircraft. Noise made by jet planes is more disturbing than that of the old propeller driven aircraft because it is of far higher pitch. Jet noise is caused by the violent mixing of the jet of gases from the engine with the surrounding air. It is at maximum level during take-off when the engine delivers maximum thrust, and falls away rapidly as the aircraft climbs. During landing, the main source of high-frequency noise is the sound made by the air compressor and turbine blades. Aircraft pass close to the ground for quite a distance during the landing operation and this noise often constitutes a more sustained environmental nuisance than the intense noise of shorter duration produced during take-off.
In simple words: Traffic causes noise through constant honking, especially during jams. Construction sites are louder than factories because their machines are naturally noisier. Airplanes, especially big jets, create a high-pitched roar that is most annoying when they are taking off or landing near houses.

📝 Teacher's Note: Explain that noise is measured in "decibels" and that prolonged exposure to high decibel levels (like at a construction site) can cause permanent hearing loss.

🎯 Exam Tip: For the airplane section, mention that "take-off" is the loudest point due to "maximum thrust" to show technical understanding.

Question 2. Air pollution is the contamination of air by pollutants. In this context answer the following :
(i) How does the use of automobiles cause air pollution ?
(ii) Write short notes on industrial air pollution.
(iii) What special kind of air pollution do the brick kilns produce?
Answer:
(i) Automobiles produce large amount of \( CO \), hydrocarbons, oxides and suspended particulate matter and cause air pollution.
(ii) Industrial pollution cannot be avoided, as without it development is not possible. So it is an unavoidable problem faced by urban industrial areas, because harmful gases, garbage etc. is emitted by industrial activities, e.g. Industries release \( CO \), oxides of Sulphur and Nitrogen, smoke, dust etc. to the air.
(iii) Dust and smoke are the main elements produced by the brick kilns to pollute the air.
In simple words: Cars pollute by burning fuel and releasing chemicals. Industries are necessary for development but they release dangerous gases and dust as a side effect. Brick kilns specifically add a lot of heavy dust and thick smoke to the sky.

📝 Teacher's Note: Discuss the concept of "Sustainable Development"—finding ways to have industries and cars that don't destroy our air quality.

🎯 Exam Tip: When writing a note on industrial pollution, categorize the pollutants into "gases" and "particulates" (smoke/dust) for a more structured answer.

Question 3. With reference to the sources of water pollutants answer the following questions:
(i) Why is it harmful to dispose of household detergents in water bodies ?
(ii) In what way does the industrial waste pollute water?
(iii) How do the radioactive wastes get into the water bodies?
(iv) How is the thermal pollution of water caused ? What are its effects ?
Answer:
(i) Detergents contain some phosphates which are helpful to 1 produce algae and aquatic weeds which pollute the water.
(ii) Many harmful wastes are produced by the industries which ; pollute water, e.g. Kanpur leather works continuously are polluting water of Ganga river creating a big problem. Industrial wastes mixed with water make it poisonous and unhygenic and may result in various diseases.
(iii) Wastes produced by nuclear power stations nuclear weapons / testing, research laboratories, and hospitals, are the main radioactive wastes which pollute the water bodies.
(iv) The thermal power plants located near the rivers use water for cooling purposes. They release the recycled hot water into the rivers leading to thermal pollution. The hot water makes the temperature of aquatic environment rise which endangers the aquatic ecosystem.
In simple words: Soap in water makes weeds grow too fast, which takes away oxygen from fish. Factories dump poisonous chemicals into rivers like the Ganga. Radioactive waste comes from nuclear plants and hospitals, while "thermal pollution" is just hot water that is too warm for fish to survive in.

📝 Teacher's Note: Help students understand that even "clean" hot water is a pollutant (Thermal) because it can kill aquatic life that isn't used to high temperatures.

🎯 Exam Tip: For "Thermal pollution," the effect is "endangering the aquatic ecosystem"—make sure to use this phrase.

Question 4. Write short notes on soil pollution by
(a) Pesticides
(b) Biomedical waste.
Answer:
(a) Pesticide waste mixed with the soil make it harmful for natural composition of soil and natural plants which cannot be taken in food material due to toxic material and the soil is contaminated for a long time.
(b) Biomedical waste Hospital wastes contain organic materials, chemicals, metal, needles, plastics contaminate the soil and make it unfit for growth of plants etc. Third world countries are facing this problem deeply.
In simple words: Pesticides stay in the ground for years and can get into our food, making it toxic. Hospital waste like needles and chemicals is dangerous because it stops anything healthy from growing in that soil.

📝 Teacher's Note: Explain that biomedical waste is especially dangerous because it can also carry infectious diseases if not disposed of correctly.

🎯 Exam Tip: Use the term "contaminated for a long time" to describe the lasting impact of pesticide use on soil.

Question 5. What are the sources of radioactive pollution ? Describe each of them.
Answer: These are natural sources from cosmic rays, man-made sources by use of \( X \)-rays, nuclear weapons, Atomic reactors and fuel, radioactive isotopes in research laboratories are the main reasons to pollute rivers, streams and lakes etc. through sewers.
In simple words: We get radiation naturally from space (cosmic rays). But most pollution comes from humans using \( X \)-rays, testing nuclear bombs, or running nuclear power plants. These wastes often end up in our water through sewers.

📝 Teacher's Note: Remind students that while \( X \)-rays are helpful in medicine, the materials used to create them must be handled as dangerous waste afterward.

🎯 Exam Tip: Categorize your answer into "Natural" and "Man-made" sources to show a clear and logical breakdown.

Question 6. What are the man-made sources of air pollution ?
Answer: Man-made sources are human activities, e.g., industries, factories, urban settlement, aircraft, nuclear experiments, automobiles, agricultural and power plants etc. are the sources of air pollution.
In simple words: Almost everything humans do to live in cities pollutes the air. This includes our cars, the factories that make our clothes, the airplanes we fly in, and even the power plants that give us electricity.

📝 Teacher's Note: Ask students to count how many "man-made sources" they see on their way to school, like cars or construction sites, to bring the lesson to life.

🎯 Exam Tip: Provide a diverse list of examples, including "automobiles," "industries," and "agricultural activities" to ensure a comprehensive answer.