Ozone layer depletion

Global Issues: Ozone Depletion,
Global Warming and Acid Rain
About ozone depletion
Causes of ozone depletion
Effects of ozone depletion
Solutions in tackling ozone depletion
About global warming
About greenhouse effect
Sources of greenhouse gases
Effects of global warming
Discussion of controversial views
Solutions in tackling global warming
About acid rain
Causes of acid rain
Effects of acid rain
Solutions in tackling acid rain
Air pollution is exerting increasing impact on the
environment. Humans have been altering the
chemistry of the atmosphere on a global scale.
These changes may:
• Modify the global climate
• Threaten the health of human beings
• Create many environmental problems such as
– Acid rain
– Depletion of ozone layer
– Global warming
• Seriously upset the global ecosystem
What is ozone depletion?
• Ozone is a highly reactive gas comprising triatomic
• Ozone layer in the stratosphere protects the Earth’s
surface from UV light
• Ozone depletion refers to a lowered concentration of
ozone in the upper atmosphere
• “Holes” are formed
• More UV radiation is reaching the Earth’s surface
October ozone levels over Antarctica since the late 1950s.
What are the causes of ozone
• Presence of chlorofluorocarbons (CFCs)
• Presence of oxides of nitrogen
• Presence of halogens
• Presence of bromine
The radicals would speed up the loss of
ozone because they constantly re-emerge
to trigger another reaction
What are the effects of ozone
• UV radiation is absorbed by DNA and modifies
them, affecting the expression of genetic
• A higher incidence of skin cancer,lung diseases
and cataract
• Reduce the yields of crops
• Disruption of the ecological balance in the ocean
• A higher incidence of photochemical smog
What can we do to solve the
problems of ozone depletion?
• Reduce emissions of ozone-depleting
• Reduce the uses of aerosol sprays
• Use the aerosol sprays that are free of
CFC compounds instead
What is global warming?
• Global warming refers to the gradual increase
in the average temperature in the atmosphere
• Increase in concentration of greenhouse gases
in the atmosphere
• The heat loss from the Earth to the Space is
slowed down
• An enhancement of the greenhouse effect
leads to global warming
• Greenhouse gases include carbon dioxide,
chlorofluorocarbons, methane, nitrous oxides,
ozone, water vapour, etc
What is greenhouse effect?
• Most of the incoming solar
radiation is in the visible part of
the spectrum
• Most visible light passes
through the atmosphere
without being absorbed
• The earth radiates heat back
out towards space when
warmed up
• Much of the radiation does not
escape into space
• Most is trapped by certain
gases in the atmosphere,
carbon dioxide and particular
water vapour
What are the sources of
greenhouse gases?
• Greenhouse gases are generated by
varies human activities, because of
• burning of fossil fuels
• deforestation
• extensive rearing of livestock
• extensive use of cooling agents, blowing
agents, insulating and packaging materials,
aerosol sprays and solvents
What are the effects of global
Thermal expansion of the oceans, melting of glacial ice
Low-lying cities would be submerged
Global climate would be affected due to the removal of
Distribution of the climatic regions and ocean currents
would be changed
Increase in frequency and severity of weather extremes
Increase in temperature of marine
Alter disease pattern, thus, increase the spread of
Pests could become more active and grow faster
The trend of global warming is
• It is believed that an increase in atmospheric
temperature would lead to faster growth of
plants and phytoplankton on land and aquatic
environments. This would increase the
consumption of carbon dioxide in
photosynthesis, bringing a re-balance of carbon
dioxide in the atmosphere. Plants would
transpire faster in the warmer air. The
atmosphere would thus become more humid
and more advantageous to plant growth.
What can we do to solve the
problems of global warming?
Use “cleaner energy”
Smart transportation and land use
Watch less TV
Use less air conditioner
Turn off the light when leaving the room
Take public transport
Use less microwave oven
What is acid rain?
• Acid rain refers to precipitation in the form
of dilute acid solutions
• Not a single phenomenon
• The pollutants involved are sulphur dioxide,
oxides of nitrogen, ammonia, ozone and
various volatile organic vapours
• Acid rain typically has a pH from 4.0 to 5.4
What are the causes of acid
• Sulpur dioxide reacts with oxygen in air, forming
sulphur trioxide
• Sulphur trioxide dissolved in rain water to form a
dilute solution of sulphuric acid
• Sulphur dioxide can also dissolves in rain water
• Nitrogen dioxide is formed by combining
nitrogen monoxide with oxygen
• Nitrogen dioxide reacts with water and oxygen to
form nitric acid
What are the effects of
acid rain?
Damage the buildings, statues
Corrode marble and metals
Causes human respiratory diseases
Increases the acidity of soil
Induce the release of aluminium ions from
soil particles
• Acidify lakes
What can we do to solve the
problems brought by acid rain?
For individuals:
Individuals can contribute directly by conserving energy, since
energy production causes the largest portion of the acid
deposition problem.
• Turn off lights, computers, and other appliances
when you're not using them
• Use energy efficient appliances: lighting, air
conditioners, heaters, refrigerators, washing
machines, etc.
• Only use electric appliances when you need
• Carpool, use public transportation, or better yet,
walk or bicycle whenever possible
• Buy vehicles with low NOx emissions, and
maintain all vehicles well.
For society:
• Understand acid deposition's causes and
• Clean up smokestacks and exhaust pipes
• Use alternative energy sources
• Restore a damaged environment
• Look to the future
• http://www.epa.gov/ozone/
• http://www.beyonddiscovery.org/content/vi
• http://www.ucsusa.org/global_environment
• http://www.cln.org/themes/ozone.html
• http://www.epa.gov/acidrain/site_students/i
• http://globalwarming.enviroweb.org/
The End
6B Cheung Yee Lin (4), Ching Yi Yan (5)