Unit 8

1. Unit 8 Acid rain, smog and global warming Unit 8 Acid rain, smog and global warming

2. Sulphur dioxide  H2O Nitrogen oxides  H2O Unit 8 Acid rain, smog and global warming Are there acids in the air? Acid rain is also called “acid precipitation” (snow, rain, fog, and dry particulate acidic depositions). Sulphur dioxide is emitted primarily from stationary sources such as power plants that burn fossil fuels. Sulphuric acid Nitrogen oxides are emitted from both stationary and transportation-related sources. Nitric acid

3. Battery acid Pure rain (5.6) Distilled water Ammonia ACID RAIN Acidic Neutral Basic Unit 8 Acid rain, smog and global warming Are there acids in the air? We use the pH scale to describe the strength of an acid. The scale is a numerical one from 0 to 14. Pure rain has a pH of about 5.6 while distilled water a pH of 7, which is neutral. Acid rain is defined as precipitation which has a pH of below 5.6.

4. N  Arctic Ocean North America Europe Asia Atlantic Ocean Pacific Ocean Africa Indian Ocean South America Australasia Areas most affected by acid rain km Unit 8 Acid rain, smog and global warming Areas most affected by acid rain

5. Sulphur dioxide Moisture + sulphur dioxide + nitrogen oxides Nitrogen oxides Acid rain Motor vehicle Factory Power station Unit 8 Acid rain, smog and global warming How acid rain is formed?

6. Unit 8 Acid rain, smog and global warming Are there acids in the air? Acid rain affects industrial areas and the neighbouring regions around them. Buildings and statues are damaged

7. Trees are particularly sensitive to acid rain. The acid deposition weakens the trees and affects their nutrient uptake. Unit 8 Acid rain, smog and global warming Are there acids in the air? Acid rain affects farming and forested areas.

8. Unit 8 Acid rain, smog and global warming Effects of acid rain Air pollution usually forms high in the clouds Air pollution creates acid rain Streams are polluted by acid rain Animals and fishes are seriously affected

9. Unit 8 Acid rain, smog and global warming Acid rain in China 40% of the area of China is now affected by acid rain. Jiangsu, Zhejiang and five other coastal provinces are the most seriously affected area. These provinces lose about $3.7 billion worth of farm products annually because of acid rain. More than 1.28 million hectares of forest are also affected.

10. Smog Unit 8 Acid rain, smog and global warming What is smog? Smog is a layer of brown haze covering a city caused by pollutants reacting with sunlight. Pollutants such as hydrocarbons, dust, smoke, nitrogen dioxide and ozone react with sunlight to give air a hazy appearance.

11. Unit 8 Acid rain, smog and global warming What is smog? A city with a large population, a lot of factories, thousands of motor vehicles, light winds and plenty sunshine is ideal for the formation of smog.

12. Sunlight Ozone Still air Gases, dust, smoke Gases Motor vehicle Power station Factory Unit 8 Acid rain, smog and global warming How smog is formed?

13. Los Angeles on the western coast of USA is seriously affected by smog. Unit 8 Acid rain, smog and global warming What is smog?

14. Sydney Santiago Unit 8 Acid rain, smog and global warming What is smog? New York City on the eastern coast of USA and other big cities are also affected by smog.

15. Unit 8 Acid rain, smog and global warming What is smog? Exhaust gas from vehicles on a windless day is the main cause of the formation of smog in Hong Kong. China is also seriously affected by smog, especially in those big cities.

16. It is formed when sunlight or lightning strikes oxygen. It is formed when nitrogen dioxide reacts with sunlight. Sunlight Ozone Lightning Nitrogen dioxide Oxygen Ozone Unit 8 Acid rain, smog and global warming What is ozone? Ozone (O3) is a gas made up of oxygen. It is a pollutant gas which has a sharp smell. How ozone is formed?

17. Water vapour 8% CFCs 12% 5% Nitrogen oxides Carbon dioxide 60% Methane 15% The major greenhouse gases Unit 8 Acid rain, smog and global warming What is global warming? Greenhouse gases There are gases in the atmosphere which trap heat and keep the earth’s surface warm. Most of the greenhouse gases have increased rapidly in quantity in the atmosphere except water vapour.

18. Unit 8 Acid rain, smog and global warming Greenhouse gases Carbon dioxide and nitrogen oxides are produced in the burning of fossil fuels. Methane is produced in rice farming and cattle rearing.

19. Spray can Air-conditioner Fast food plastic foam container Computer Motor vehicle Refrigerator Unit 8 Acid rain, smog and global warming Things that give off CFCs CFCs are used as coolants in air-conditioners, refrigerators and as aerosol propellants.

20. Sun Water vapour, carbon dioxide, methane, nitrogen oxides, CFCs Greenhouse gases trap heat Sunlight Heat reflected back to Earth’s surface Earth surface Unit 8 Acid rain, smog and global warming What is global warming? The heat-trapping process the “greenhouse effect” has resulted in a rise in world temperature -- global warming.

21. Unit 8 Acid rain, smog and global warming What is global warming? Ozone hole  The ozone layer protects us from ultraviolet radiation from the sun. Too much ultraviolet radiation causes cancer in people and animals.

22. Unit 8 Acid rain, smog and global warming The “hole” in the Antarctic Since the late 1970s, scientists have found that ozone in the atmosphere above the Antarctic has been decreasing. The layer of ozone above it becomes so thin that a “hole” develops over the continent.  The percentage of ozone in the Antarctic ozone layer is rapidly declining.

23. Unit 8 Acid rain, smog and global warming Terms to learn Acid rain (酸雨)-- rain that is acidic because it has mixed with acidic gases sulphur oxides and nitrogen oxides. It has a pH of below 5.6. Smog (煙霧)-- a layer of brown haze covering a city caused by pollutants reacting with sunlight. Greenhouse effect (溫室效應)-- the process in which greenhouse gases trap sun’s heat, leading to the rise in world temperature. Global warming (全球增溫)-- the rise in world temperature as a result of the greenhouse effect.