F.3 Geog. notes/3.2 What are the causes of air pollution ?/P.1 of
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Pui Ying College
F.3 Geography
Section 3.2
What are the causes of air
pollution ?
A.
Causes of air pollution
What are the sources of air pollutants ?
natural sources
volcanic eruption
human sources
manufacturing
and hill fires
produce dust and
harmful gases
power
transport/
generation/ heavy traffic
power plants
domestic
activities
farming
activities
e.g. spraying of
pesticides
produce dirty smoke, suspended particulates and waste gases, such as
sulphur dioxide and nitrogen oxides
1.
Air pollutants may come from natural or human sources.
2.
Natural hazards, e.g. volcanic eruptions and hill fires emit a large amount of ashes and
wastes gases into the atmosphere.
3.
Yet, most air pollutants come from human sources.
4.
Human activities, e.g. factories, power plants and heavy traffic produce large amount of
suspended particulates and waste gases, e.g. sulphur dioxide and nitrogen oxides.
B.
Formation of smog
1.
Factories, cars and power plants give out a lot of waste gases, especially nitrogen oxides.
2.
Under calm conditions, the waste gases will build up in the atmosphere.
3.
They will have chemical reaction with sunlight.
4.
A yellow layer of harmful fog-like fumes, called smog (smoke + fog) will be formed.
C.
Relationship between air pollution and urban and industrial activities
1.
Air pollution is more serious in densely populated urban and industrial areas because these
areas are source areas of air pollutants.
2.
Wastes gases may form smog when they react with sunlight. This is common in large cities,
e.g. Los Angeles, and is harmful to people.
3.
Yet, air pollution may be serious in areas which do not produce the pollutants. This is
because air pollutants may be carried by winds to other countries. This results in great
global impact. The spread of acid rain is an example.
4.
Recently, many factories have been relocated to mainland China, especially in cities like
F.3 Geog. notes/3.2 What are the causes of air pollution ?/P.2 of
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Shenzhen and Guangzhou. Pollutants from these regions are blown to Hong Kong and cause
smog on windless days.
D.
Comparison of air quality in inner city and new towns
1.
In inner city areas, streets are narrow and buildings are tall. So, pollutants cannot be
easily blown away by wind.
2.
In new towns in the suburbs, land uses are well-planned. Factories are often carefully
sited. They may be separated from residential land uses by green belts or open space.
Besides, streets are wider and population density is lower. So, pollutants can be blown
away more easily.
Vocabulary
1. natural sources
6. transport
11. sulphur dioxide
2. volcanic eruption
7. domestic activities
12. nitrogen oxides
3. human sources
8. farming activities
13. calm
4. manufacturing
9. spraying of pesticides
14. chemical reaction with sunlight
5. power generation
10. suspended particulates
15. densely populated urban areas