Pollution of Air and Water

Pollution is the contamination of air, water or soil by harmful substances called pollutants. In this chapter you will learn that air is polluted by gases such as carbon monoxide, formed by incomplete burning of fuels, nitrogen dioxide and sulphur dioxide from vehicles and factories, and by fine particles and smoke that cause smog and breathing problems. Sulphur dioxide and nitrogen dioxide dissolve in rain to form acid rain, which corrodes the marble of monuments such as the Taj Mahal. Chlorofluorocarbons damage the ozone layer, while carbon dioxide, methane and other greenhouse gases trap heat and cause global warming. The chapter also deals with water pollution by sewage, industrial wastes and fertilisers and pesticides from fields, which make water unfit for use and harm aquatic life. You will learn about the Ganga Action Plan, the meaning of potable water, and simple methods to purify water at home, such as filtration, boiling and chlorination, as well as ways to reduce, reuse and recycle.

Detailed Worksheet: Pollution of Air and Water Section A - Definitions (10 marks) 1. Define pollution and pollutants. Give two examples of air pollutants. (2 marks) 2. What is acid rain? Name the gases responsible for it. (2 marks) 3. What is the greenhouse effect? Name two greenhouse gases. (2 marks) 4. What is potable water? Name two methods of making water safe for drinking at home. (2 marks) 5. What is smog? Why is it more common in winter in big cities? (2 marks) Section B - Calculations and Applications (15 marks) 6. The Air Quality Index (AQI) of a city on five days was 120, 180, 260, 310 and 230. (i) Find the average AQI. (ii) On how many days was the AQI above 200, which is considered poor? (iii) Suggest two actions the city can take on such days. (3 marks) 7. A city has 2,00,000 cars, each releasing about 0.15 kg of carbon monoxide per day. Find the total carbon monoxide released by the cars in a day in kg and in tonnes. Why is carbon monoxide dangerous to human health? (3 marks) 8. A family of 5 uses 135 litres of water per person per day. Find the daily and monthly (30 days) water use. If they save 20% by fixing leaking taps and reusing water, how much water is saved in a month? (3 marks) 9. Classify each of the following as a source of air pollution or water pollution, and name the pollutant: (i) burning of crop stubble (ii) washing of clothes in a river (iii) brick kilns (iv) runoff from fields sprayed with pesticides (v) a leather factory discharging waste into a river (vi) vehicles at a traffic signal. (3 marks) 10. Explain how each of the following purifies water: (i) filtration through a cloth or candle filter (ii) boiling (iii) adding chlorine tablets. Which method kills germs but does not remove dust? (3 marks) Section C - Diagrams (10 marks) 11. Draw a labelled diagram showing the greenhouse effect: sunlight passing through the atmosphere, heat being radiated by the Earth, and part of the heat being trapped by greenhouse gases. (4 marks) 12. Draw a flowchart showing how acid rain is formed from the burning of fuels and how it damages buildings, monuments, soil and lakes. (3 marks) 13. Draw a labelled diagram of a simple home water filter or of the steps in a water treatment plant from a river to the tap. (3 marks) Section D - Analysis and Higher-order Thinking (15 marks) 14. The white marble of the Taj Mahal has been turning yellowish and is being corroded. Explain the causes, including acid rain and suspended particles, and describe the steps taken to protect the monument, such as the Taj Trapezium Zone and the use of cleaner fuels. (5 marks) 15. A river flowing past a city receives untreated sewage and industrial waste, and the water becomes dark and smelly, while fish die. Explain why the fish die, how excess fertilisers in the water lead to the growth of algae and a fall in oxygen, and why the Ganga Action Plan was started. Suggest three steps to clean the river. (5 marks) 16. Explain how global warming may affect glaciers, sea levels, rainfall and agriculture. What is the purpose of international agreements to reduce greenhouse gas emissions? Suggest five things you can do to reduce air pollution. (5 marks) Instructions: Time allowed 2 hours. Attempt all sections. Draw flowcharts and diagrams neatly, and use local examples wherever possible.