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

Are there acids in the air? 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. Sulphur dioxide  H2O Sulphuric acid Nitrogen oxides are emitted from both stationary and transportation-related sources. Nitrogen oxides  H2O Nitric acid

Are there acids in the air? 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. ACID RAIN Battery acid Acidic Basic Pure rain (5.6) Distilled water Ammonia Neutral

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

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

Are there acids in the air? 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

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

Effects of acid rain Unit 8 Acid rain, smog and global warming 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

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.

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. Smog Pollutants such as hydrocarbons, dust, smoke, nitrogen dioxide and ozone react with sunlight to give air a hazy appearance.

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.

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

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

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

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.

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?  It is formed when sunlight or lightning strikes oxygen. Sunlight Ozone Nitrogen dioxide  It is formed when nitrogen dioxide reacts with sunlight. Lightning Oxygen Ozone

The major greenhouse gases Unit 8 Acid rain, smog and global warming What is global warming? Carbon dioxide 60% Water vapour 8% CFCs 12% 5% Nitrogen oxides Methane 15% The major greenhouse gases 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.

Methane is produced in rice farming and cattle rearing. 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.

Things that give off CFCs 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. Air-conditioner Computer Spray can Refrigerator Motor vehicle Fast food plastic foam container

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

What is global warming? Ozone hole 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.

The “hole” in the Antarctic 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.

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.