Presentation on theme: "Acid rain, smog and global warming"— Presentation transcript:
1Acid rain, smog and global warming Unit 8 Acid rain, smog and global warmingUnit 8Acid rain, smog and global warming
2Are there acids in the air? Unit 8 Acid rain, smog and global warmingAre 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 dioxideH2OSulphuric acidNitrogen oxides are emitted from both stationary and transportation-related sources.Nitrogen oxidesH2ONitric acid
3Are there acids in the air? Unit 8 Acid rain, smog and global warmingAre 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 RAINBattery acidAcidicBasicPure rain (5.6)Distilled waterAmmoniaNeutral
4Areas most affected by acid rain Unit 8 Acid rain, smog and global warmingAreas most affected by acid rainkmAreas most affected by acid rainIndian OceanPacific OceanAtlantic OceanArctic OceanAustralasiaAsiaEuropeAfricaNorth AmericaSouth AmericaN
5How acid rain is formed? Sulphur dioxide Unit 8 Acid rain, smog and global warmingHow acid rain is formed?Sulphur dioxideNitrogen oxidesPower stationFactoryMotor vehicleAcid rainMoisture + sulphur dioxide + nitrogen oxides
6Are there acids in the air? Unit 8 Acid rain, smog and global warmingAre there acids in the air?Acid rain affects industrial areas and the neighbouring regions around them.Buildings and statues are damaged
7Are there acids in the air? Unit 8 Acid rain, smog and global warmingAre 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.
8Effects of acid rain Unit 8 Acid rain, smog and global warming Air pollution usually forms high in the cloudsAir pollution creates acid rainStreams are polluted by acid rainAnimals and fishes are seriously affected
9Unit 8 Acid rain, smog and global warming Acid rain in China40% 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.
10Unit 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.SmogPollutants such as hydrocarbons, dust, smoke, nitrogen dioxide and ozone react with sunlight to give air a hazy appearance.
11Unit 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.
12How smog is formed? Sunlight Ozone Still air Gases, dust, smoke Gases Unit 8 Acid rain, smog and global warmingHow smog is formed?SunlightGases, dust, smokeGasesMotor vehicleStill airOzonePower stationFactory
13Unit 8 Acid rain, smog and global warming What is smog?Los Angeles on the western coast of USA is seriously affected by smog.
14Unit 8 Acid rain, smog and global warming What is smog?SydneySantiagoNew York City on the eastern coast of USA and other big cities are also affected by smog.
15Unit 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.
16Unit 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.SunlightOzoneNitrogen dioxide It is formed when nitrogen dioxide reacts with sunlight.LightningOxygenOzone
17The major greenhouse gases Unit 8 Acid rain, smog and global warmingWhat is global warming?Carbon dioxide 60%Water vapour 8%CFCs 12%5%Nitrogen oxidesMethane 15%The major greenhouse gasesGreenhouse gasesThere 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.
18Methane is produced in rice farming and cattle rearing. Unit 8 Acid rain, smog and global warmingGreenhouse gasesCarbon dioxide and nitrogen oxides are produced in the burning of fossil fuels.Methane is produced in rice farming and cattle rearing.
19Things that give off CFCs Unit 8 Acid rain, smog and global warmingThings that give off CFCsCFCs are used as coolants in air-conditioners, refrigerators and as aerosol propellants.Air-conditionerComputerSpray canRefrigeratorMotor vehicleFast food plastic foam container
20Unit 8 Acid rain, smog and global warming What is global warming?SunSunlightEarth surfaceHeat reflected back to Earth’s surfaceWater vapour, carbon dioxide, methane, nitrogen oxides, CFCsGreenhouse gases trap heatThe heat-trapping process the “greenhouse effect” has resulted in a rise in world temperature -- global warming.
21What is global warming? Ozone hole Unit 8 Acid rain, smog and global warmingWhat 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.
22The “hole” in the Antarctic Unit 8 Acid rain, smog and global warmingThe “hole” in the AntarcticSince 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.
23Unit 8 Acid rain, smog and global warming Terms to learnAcid 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.