unit 8 acid rain, smog and global warming unit 8 acid rain, smog and global warming
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Unit 8Unit 8
Acid rain, smog and global Acid rain, smog and global warmingwarming
Acid rain, smog and global Acid rain, smog and global warmingwarming
Unit 8 Acid rain, smog and global warming
Are there acids in the air?Are there acids in the air?Acid rain is also called “acid precipitation” (snow,
rain, fog, and dry particulate acidic depositions).
Unit 8 Acid rain, smog and global warming
Sulphur dioxide is emitted primarily from stationary sources such as power plants that burn fossil fuels.
Sulphur dioxide H2O Sulphuric acid
Nitrogen oxides H2O Nitric acid
Nitrogen oxides are emitted from both stationary and transportation-related sources.
Are there acids in the air?Are there acids in the air?We use the pH scale to describe the strength of an aci
d. 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.
Unit 8 Acid rain, smog and global warming
ACID RAIN
Battery acid
Acidic Basic
Pure rain (5.6)
Distilled water
Ammonia
Neutral
Areas most affected by acid rainAreas most affected by acid rain
Unit 8 Acid rain, smog and global warming
kmAreas most affected by acid rain
Indian Ocean
Pacific OceanAtlantic Ocean
Arctic Ocean
Australasia
AsiaEurope
Africa
North America
South America
N
How acid rain is formed?How acid rain is formed?Unit 8 Acid rain, smog and global warming
Sulphur dioxideNitrogen oxides
Power station FactoryMotor vehicle
Acid rain
Moisture + sulphur dioxide + nitrogen oxides
Are there acids in the air?Are there acids in the air?Unit 8 Acid rain, smog and global warming
Acid rain affects industrial areas and the neighbouring regions around them.
Acid rain affects industrial areas and the neighbouring regions around them.
Buildings and statues are damaged
Are there acids in the air?Are there acids in the air?Acid rain affects farming and forested areas.
Unit 8 Acid rain, smog and global warming
Trees are particularly sensitive to acid rain.
The acid deposition weakens the trees and affects their nutrient uptake.
Effects of acid rainEffects of acid rainUnit 8 Acid rain, smog and global warming
Air pollution creates acid rain
Air pollution usually forms high in the clouds
Streams are polluted by acid rain
Animals and fishes are seriously affected
Acid rain in ChinaAcid rain in ChinaUnit 8 Acid rain, smog and global warming
These provinces lose about $3.7 billion worth of farm products annually because of acid rain.
40% of the area of China is now affected by acid rain.
More than 1.28 million hectares of forest are also affected.
Jiangsu, Zhejiang and five other coastal provinces are the most seriously affected area.
What is smog?What is smog?Smog is a layer of brown haze covering a city
caused by pollutants reacting with sunlight.
Unit 8 Acid rain, smog and global warming
Pollutants such as hydrocarbons, dust, smoke, nitrogen dioxide and ozone react with sunlight to give air a hazy appearance.
Pollutants such as hydrocarbons, dust, smoke, nitrogen dioxide and ozone react with sunlight to give air a hazy appearance.
Smog
What is smog?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.
Unit 8 Acid rain, smog and global warming
How smog is formed?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?What is smog?Unit 8 Acid rain, smog and global warming
Los Angeles on the western coast of USA is seriously affected by smog.
What is smog?What is smog?Unit 8 Acid rain, smog and global warming
New York City on the eastern coast of USA and other big cities
are also affected by smog. SantiagoSantiago
SydneySydney
Exhaust gas from vehicles on a windless day is the main cause of the formation of smog in Hong Kong.
What is smog?What is smog?Unit 8 Acid rain, smog and global warming
China is also seriously affected by smog, especially in those big cities.
What is ozone?What is ozone?Ozone (O3) is a gas made up of oxygen. It is
a pollutant gas which has a sharp smell.
Unit 8 Acid rain, smog and global warming
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
What is global warming?What is global warming?Unit 8 Acid rain, smog and 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.
Greenhouse gasesGreenhouse gases
Unit 8 Acid rain, smog and global warming
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 CFCsThings that give off CFCs
CFCs are used as coolants in air-conditioners, refrigerators and as aerosol propellants.
Unit 8 Acid rain, smog and global warming
Air-conditioner
Computer
Spray can
RefrigeratorMotor vehicle
Fast food plastic foam container
What is global warming?What is global warming?Unit 8 Acid rain, smog and global warming
Sun
Sunl
ight
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?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.
Unit 8 Acid rain, smog and global warming
The “hole” in the Antarctic 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 learnTerms to learnAcid rainAcid rain ( 酸雨酸雨 ) -- rain that is acidic because it ha
s mixed with acidic gases sulphur oxides and nitrogen oxides. It has a pH of below 5.6.
SmogSmog ( 煙霧煙霧 ) -- a layer of brown haze covering a city caused by pollutants reacting with sunlight.
Greenhouse effectGreenhouse effect ( 溫室效應溫室效應 ) -- the process in which greenhouse gases trap sun’s heat, leading to the rise in world temperature.
Global warmingGlobal warming ( 全球增溫全球增溫 ) -- the rise in world temperature as a result of the greenhouse effect.
Unit 8 Acid rain, smog and global warming