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OZONE LAYER
DEPLETION
1
WHAT IS OZONE?
 Ozone is a form of oxygen with 3
oxygen atoms (O3).
2
How is ozone produced?
It is formed when oxygen absorbs solar
radiation - O2 +h(<240nm)  O+O
O+ O2  O3
3
4
OZONE LAYER
• Ozone is a triatomic form of oxygen (O3)
found in Earth’s upper and lower
atmosphere.
• The ozone layer, is situated in the
stratosphere about 15 to 30 km above the
earth's surface.
5
6
Ozone (parts per million)
0
20
40
60
80
100
Altitude
(km)
Troposphere
Mesosphere
Thermosphere
Ozone Facts
Altitude
(miles)
10
0
20
30
40
50
60
90% of ozone is in the
stratosphere
0 2 4 6 8
10% of ozone is in the troposphere
7
The amount of ozone within the stratosphere
varies according to altitude
Why is the ozone layer important
• Ozone acts as the Earth’s protective
shield against the Sun’s harmful
Ultraviolet radiation (UV radiation).
• Without the ozone layer, life would not
exist on Earth!
8
Why life would not exist?
Exposure to Ultraviolet rays results into;
• Sunburn (or erythema) is redness of the skin,
which is due to increased blood flow in the skin
caused by dilatation of the superficial blood
vessels in the dermis as a result of exposure to
UV radiation
• Tanning refers to delayed pigmentation of the
skin, or melanin pigmentation. It usually
becomes noticeable one to two days after
exposure to the sun and gradually increases for
several days persisting for weeks or months.
9
Why life would not exist?
• Premature Aging of the Skin
One of the chronic effects resulting from
repeated exposure to UV radiation is premature
aging of the skin, which encompasses a number
of clinical signs that reflect structural changes in
the dermis. These clinical signs include dryness,
wrinkles
10
Why life would not exist?
• Suppression of the Immune System
Suppression of the immune system resulting
from exposure to UV radiation is believed to be
an important contributor to the development of
nonmelanoma skin cancers.
• Damage to the Eyes
UV rays can also damage the eyes as more than
99% of UV radiation is absorbed by the front of
the eyes.
11
Why life would not exist?
Corneal damage, cataracts, and macular
degeneration are all possible chronic effects
from UV exposure and can ultimately lead to
blindness
• Skin Cancer
Skin cancers are the most commonly occurring
cancers in terms of incidence in the world.
12
UV radiation
• UV radiation is emitted from the sun with
wavelength from 200-400 nm
(nanometers)
• UV radiation is divided into three ranges
▫ UV-A, 320 - 400 nm
▫ UV-B, 290 - 320 nm
▫ UV-C, 200 - 290 nm
• The shorter wavelength are more harmful
to biological life.
13
OZONE LAYER DEPLETION
• The Ozone layer depletion is caused by
chemicals called CFCs
(chlorofluorocarbons). CFCs escape
into the atmosphere from refrigeration
and propellant devices and processes,
and they are so stable they last for
decades.
• This long life allows some CFCs to
eventually reach the stratosphere.
14
• The chemicals that make up CFCs,
mainly chlorine and fluorine, float
around the stratosphere, breaking up
ozone molecules.
• One molecule of CFC can destroy more
than 100,000 molecules of
stratospheric ozone.
15
The ozone depletion process
16
Destruction of ozone by chlorine
17
Chemical reactions
• CCl3F + UV Light => CCl2F + Cl
• CCl2F2 + UV Light => CClF2 + Cl
• The chlorine atoms formed in the
above reactions readily depletes ozone
via a chain reaction:
• Cl + O3 => ClO + O2
• ClO + O => Cl + O2
18
The important catalysts for
stratospheric O3 destruction
• Hydroxy radical (OH)
.OH + O3 = HO2
. + O2
HO2
. + O = .OH + O2
Net: O + O3 = 2 O2
• Chlorine and bromine (Cl and Br)
Cl. + O3 = ClO. + O2
ClO. + O = Cl. + O2
Net: O + O3 = 2 O2
• Nitric oxide (NO)
NO + O3 = NO2 + O2
NO2 + O = NO + O2
Net: O + O3 = 2 O2
HOx cycle
ClOx cycle
NOx cycle
19
20
Ozone Depleting Substances
• Chlorofluorocarbons (CFC’s)
▫ Contains: Cl, F, C
▫ Long-lived, non-toxic, non-corrosive,
and non-flammable
▫ In 1960’s used in refrigerators, air
conditioners, spray cans, solvents,
foams
▫ Phased out in 1996 in developed
countries
21
• Hydrochlorofluorocarbons
(HCFCs)
▫ Contains: H, Cl, F, C
▫ First major replacement for CFC
▫ Much less destructive but also ozone
depleting
▫ Reduce HCFC’s by 35% in 2004 in
developed countries
22
• Halons
▫ Contain: Br, Cl (in some but not all),
F, H (in some but not all), C
▫ Br many times more effective in
destroying O3
▫ Halons used in fire extinguishers
▫ Phased out in 1994
23
• Methyl Bromide (CH3Br)
▫ an effective pesticide, used to
fumigate e.g. soil and products
24
Breakdown of Sources
Sterilization
3%
Aerosols
5%
Refrigeration
and Air
Conditioning
30%
Other Products
1
2%
Solvent Cleaning
Products
36%
Foam Products
1
4%
25
Responsibility for ozone damage each
year
26
OZONE HOLE
The ozone hole is a region of
depleted ozone in the stratosphere
over the Antarctic that happens at the
beginning of Southern Hemisphere
spring
27
WHERE IS THE OZONE HOLE?
Ozone hole largely restricted to areas over
Antarctica
Ozone hole may pass over tip of South
America
Ozone hole seldom comes near Australia.
28
Who discovered the Ozone Hole?
• The Antarctic Ozone Hole was
discovered in 1985 by British scientists
Joseph Farman, Brian Gardiner, and
Jonathan Shanklin of the British
Antarctic Survey.
29
September 2006
© NASA
30
Monthly averages for October
31
EFFECT OF OZONE LAYER
32
Why Protect the Ozone Layer?
• Ozone Depletion leads to excessive UV-B
radiation.
• Excessive UV-B radiation leads to:
▫ More skin cancers
▫ Eye cataracts.
▫ Less productivity of plants.
▫ Loss of immunity to diseases.
▫ Adverse effects on plastics.
▫ Damage to ocean eco-ecosystems
33
PROTECTING THE OZONE LAYER
• Ban the use of CFC’s
Have to replace with something
Current replacements are greenhouse
gases and do not eliminate ozone
depletion, just slow it down
• Air Quality Standards
Limit amounts of pollutants that can be
emitted by pollution sources
34
What is being done about ozone
depletion?
 Montreal Protocol (1987): international
agreement designed to protect
the stratospheric ozone layer
by phasing out ozone depleting
chemicals
35
What is the Montreal Protocol?
• The Montreal Protocol says that the
production and consumption of
compounds that deplete ozone in the
stratosphere--chlorofluorocarbons (CFCs),
halons, carbon tetrachloride, and methyl
chloroform--are to be phased out by 2030.
36
37
Montreal Protocol
• Vienna Convention in 1985
▫ framework agreement
• Montreal Protocol in 1987
▫ Phase-out schedules for CFCs and
halons
• London Amendment in 1990
▫ accelerated phase outs; additional
CFC’s, CCl4, CH3CCl3
• Copenhagen Amendment in 1992
▫ added methyl bromide, HBFCs,
HCFCs
• Montreal Amendment in 1997
▫ finalized phase-out schedules for
methyl bromide
38
Efforts Need to Be Continued
• Create reliable models
▫ To gain a better understanding of the
effects ozone depletion has on organisms
living within different ecosystems
• Enforcement of Montreal Protocol
▫ To reduce concentrations of chemicals
responsible for ozone depletion
...
39
• Monitoring chemicals being emitted
• Gain a better overall understanding on just
how ozone depletion is affecting our
planet
40
Montreal Protocol
Summary of Montreal Protocol control measures
Ozone depleting substances Developed countries Developing countries
Chlorofluorocarbons (CFCs) Phased out end of 1995a Total phase out by 2010
Halons Phased out end of 1993 Total phase out by 2010
Carbon tetrachloride Phased out end of 1995a Total phase out by 2010
Methyl chloroform Phased out end of 1995a Total phase out by 2015
Hydrochlorofluorocarbons (HCFCs) Freeze from beginning of 1996b
35% reduction by 2004
75% reduction by 2010
90% reduction by 2015
Total phase out by 2020c
Freeze in 2013 at a base level
calculated as
the average of 2009 and 2010
consumption levels
10% reduction by 2015
35% reduction by 2020
67.5% reduction by 2025
Total phase out by 2030d
Hydrobromofluorocarbons (HBFCs) Phased out end of 1995 Phased out end of 1995
Methyl bromide
(horticultural uses)
Freeze in 1995 at 1991 base levele
25% reduction by 1999
50% reduction by 2001
70% reduction by 2003
Total phase out by 2005
Freeze in 2002 at average 1995-1998
base levele
20% reduction by 2005
Total phase out by 2015
Bromochloromethane (BCM) Phase out by 2002 Phase out by 2002
41
Recovery of Ozone Layer
• Since the adoption and strengthening
of the Montreal Protocol has led to
reductions in the emissions of CFCs,
atmospheric concentrations of the
most significant compounds have
been declining. These substances are
being gradually removed from the
atmosphere.
42
• By 2015, the Antarctic ozone hole
would be reduced by only 1 million
km² out of 25
• Complete recovery of the Antarctic
ozone layer will not occur until the
year 2050 or later.
43
Signs of Recovery???
There have been some signs of recovery
▫ 1997 satellite showed a decline of
several known ozone-depleting
gases
▫ Satellite images show some slowing
down of ozone loss
However recovery is slow….
44
Images of Antarctica Taken Indicate A Slow
Recovery
45

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LECTURE 2 OZONE LAYER DEPLETION.ppt

  • 2. WHAT IS OZONE?  Ozone is a form of oxygen with 3 oxygen atoms (O3). 2
  • 3. How is ozone produced? It is formed when oxygen absorbs solar radiation - O2 +h(<240nm)  O+O O+ O2  O3 3
  • 4. 4
  • 5. OZONE LAYER • Ozone is a triatomic form of oxygen (O3) found in Earth’s upper and lower atmosphere. • The ozone layer, is situated in the stratosphere about 15 to 30 km above the earth's surface. 5
  • 6. 6
  • 7. Ozone (parts per million) 0 20 40 60 80 100 Altitude (km) Troposphere Mesosphere Thermosphere Ozone Facts Altitude (miles) 10 0 20 30 40 50 60 90% of ozone is in the stratosphere 0 2 4 6 8 10% of ozone is in the troposphere 7 The amount of ozone within the stratosphere varies according to altitude
  • 8. Why is the ozone layer important • Ozone acts as the Earth’s protective shield against the Sun’s harmful Ultraviolet radiation (UV radiation). • Without the ozone layer, life would not exist on Earth! 8
  • 9. Why life would not exist? Exposure to Ultraviolet rays results into; • Sunburn (or erythema) is redness of the skin, which is due to increased blood flow in the skin caused by dilatation of the superficial blood vessels in the dermis as a result of exposure to UV radiation • Tanning refers to delayed pigmentation of the skin, or melanin pigmentation. It usually becomes noticeable one to two days after exposure to the sun and gradually increases for several days persisting for weeks or months. 9
  • 10. Why life would not exist? • Premature Aging of the Skin One of the chronic effects resulting from repeated exposure to UV radiation is premature aging of the skin, which encompasses a number of clinical signs that reflect structural changes in the dermis. These clinical signs include dryness, wrinkles 10
  • 11. Why life would not exist? • Suppression of the Immune System Suppression of the immune system resulting from exposure to UV radiation is believed to be an important contributor to the development of nonmelanoma skin cancers. • Damage to the Eyes UV rays can also damage the eyes as more than 99% of UV radiation is absorbed by the front of the eyes. 11
  • 12. Why life would not exist? Corneal damage, cataracts, and macular degeneration are all possible chronic effects from UV exposure and can ultimately lead to blindness • Skin Cancer Skin cancers are the most commonly occurring cancers in terms of incidence in the world. 12
  • 13. UV radiation • UV radiation is emitted from the sun with wavelength from 200-400 nm (nanometers) • UV radiation is divided into three ranges ▫ UV-A, 320 - 400 nm ▫ UV-B, 290 - 320 nm ▫ UV-C, 200 - 290 nm • The shorter wavelength are more harmful to biological life. 13
  • 14. OZONE LAYER DEPLETION • The Ozone layer depletion is caused by chemicals called CFCs (chlorofluorocarbons). CFCs escape into the atmosphere from refrigeration and propellant devices and processes, and they are so stable they last for decades. • This long life allows some CFCs to eventually reach the stratosphere. 14
  • 15. • The chemicals that make up CFCs, mainly chlorine and fluorine, float around the stratosphere, breaking up ozone molecules. • One molecule of CFC can destroy more than 100,000 molecules of stratospheric ozone. 15
  • 16. The ozone depletion process 16
  • 17. Destruction of ozone by chlorine 17
  • 18. Chemical reactions • CCl3F + UV Light => CCl2F + Cl • CCl2F2 + UV Light => CClF2 + Cl • The chlorine atoms formed in the above reactions readily depletes ozone via a chain reaction: • Cl + O3 => ClO + O2 • ClO + O => Cl + O2 18
  • 19. The important catalysts for stratospheric O3 destruction • Hydroxy radical (OH) .OH + O3 = HO2 . + O2 HO2 . + O = .OH + O2 Net: O + O3 = 2 O2 • Chlorine and bromine (Cl and Br) Cl. + O3 = ClO. + O2 ClO. + O = Cl. + O2 Net: O + O3 = 2 O2 • Nitric oxide (NO) NO + O3 = NO2 + O2 NO2 + O = NO + O2 Net: O + O3 = 2 O2 HOx cycle ClOx cycle NOx cycle 19
  • 20. 20
  • 21. Ozone Depleting Substances • Chlorofluorocarbons (CFC’s) ▫ Contains: Cl, F, C ▫ Long-lived, non-toxic, non-corrosive, and non-flammable ▫ In 1960’s used in refrigerators, air conditioners, spray cans, solvents, foams ▫ Phased out in 1996 in developed countries 21
  • 22. • Hydrochlorofluorocarbons (HCFCs) ▫ Contains: H, Cl, F, C ▫ First major replacement for CFC ▫ Much less destructive but also ozone depleting ▫ Reduce HCFC’s by 35% in 2004 in developed countries 22
  • 23. • Halons ▫ Contain: Br, Cl (in some but not all), F, H (in some but not all), C ▫ Br many times more effective in destroying O3 ▫ Halons used in fire extinguishers ▫ Phased out in 1994 23
  • 24. • Methyl Bromide (CH3Br) ▫ an effective pesticide, used to fumigate e.g. soil and products 24
  • 25. Breakdown of Sources Sterilization 3% Aerosols 5% Refrigeration and Air Conditioning 30% Other Products 1 2% Solvent Cleaning Products 36% Foam Products 1 4% 25
  • 26. Responsibility for ozone damage each year 26
  • 27. OZONE HOLE The ozone hole is a region of depleted ozone in the stratosphere over the Antarctic that happens at the beginning of Southern Hemisphere spring 27
  • 28. WHERE IS THE OZONE HOLE? Ozone hole largely restricted to areas over Antarctica Ozone hole may pass over tip of South America Ozone hole seldom comes near Australia. 28
  • 29. Who discovered the Ozone Hole? • The Antarctic Ozone Hole was discovered in 1985 by British scientists Joseph Farman, Brian Gardiner, and Jonathan Shanklin of the British Antarctic Survey. 29
  • 31. Monthly averages for October 31
  • 32. EFFECT OF OZONE LAYER 32
  • 33. Why Protect the Ozone Layer? • Ozone Depletion leads to excessive UV-B radiation. • Excessive UV-B radiation leads to: ▫ More skin cancers ▫ Eye cataracts. ▫ Less productivity of plants. ▫ Loss of immunity to diseases. ▫ Adverse effects on plastics. ▫ Damage to ocean eco-ecosystems 33
  • 34. PROTECTING THE OZONE LAYER • Ban the use of CFC’s Have to replace with something Current replacements are greenhouse gases and do not eliminate ozone depletion, just slow it down • Air Quality Standards Limit amounts of pollutants that can be emitted by pollution sources 34
  • 35. What is being done about ozone depletion?  Montreal Protocol (1987): international agreement designed to protect the stratospheric ozone layer by phasing out ozone depleting chemicals 35
  • 36. What is the Montreal Protocol? • The Montreal Protocol says that the production and consumption of compounds that deplete ozone in the stratosphere--chlorofluorocarbons (CFCs), halons, carbon tetrachloride, and methyl chloroform--are to be phased out by 2030. 36
  • 37. 37 Montreal Protocol • Vienna Convention in 1985 ▫ framework agreement • Montreal Protocol in 1987 ▫ Phase-out schedules for CFCs and halons
  • 38. • London Amendment in 1990 ▫ accelerated phase outs; additional CFC’s, CCl4, CH3CCl3 • Copenhagen Amendment in 1992 ▫ added methyl bromide, HBFCs, HCFCs • Montreal Amendment in 1997 ▫ finalized phase-out schedules for methyl bromide 38
  • 39. Efforts Need to Be Continued • Create reliable models ▫ To gain a better understanding of the effects ozone depletion has on organisms living within different ecosystems • Enforcement of Montreal Protocol ▫ To reduce concentrations of chemicals responsible for ozone depletion ... 39
  • 40. • Monitoring chemicals being emitted • Gain a better overall understanding on just how ozone depletion is affecting our planet 40
  • 41. Montreal Protocol Summary of Montreal Protocol control measures Ozone depleting substances Developed countries Developing countries Chlorofluorocarbons (CFCs) Phased out end of 1995a Total phase out by 2010 Halons Phased out end of 1993 Total phase out by 2010 Carbon tetrachloride Phased out end of 1995a Total phase out by 2010 Methyl chloroform Phased out end of 1995a Total phase out by 2015 Hydrochlorofluorocarbons (HCFCs) Freeze from beginning of 1996b 35% reduction by 2004 75% reduction by 2010 90% reduction by 2015 Total phase out by 2020c Freeze in 2013 at a base level calculated as the average of 2009 and 2010 consumption levels 10% reduction by 2015 35% reduction by 2020 67.5% reduction by 2025 Total phase out by 2030d Hydrobromofluorocarbons (HBFCs) Phased out end of 1995 Phased out end of 1995 Methyl bromide (horticultural uses) Freeze in 1995 at 1991 base levele 25% reduction by 1999 50% reduction by 2001 70% reduction by 2003 Total phase out by 2005 Freeze in 2002 at average 1995-1998 base levele 20% reduction by 2005 Total phase out by 2015 Bromochloromethane (BCM) Phase out by 2002 Phase out by 2002 41
  • 42. Recovery of Ozone Layer • Since the adoption and strengthening of the Montreal Protocol has led to reductions in the emissions of CFCs, atmospheric concentrations of the most significant compounds have been declining. These substances are being gradually removed from the atmosphere. 42
  • 43. • By 2015, the Antarctic ozone hole would be reduced by only 1 million km² out of 25 • Complete recovery of the Antarctic ozone layer will not occur until the year 2050 or later. 43
  • 44. Signs of Recovery??? There have been some signs of recovery ▫ 1997 satellite showed a decline of several known ozone-depleting gases ▫ Satellite images show some slowing down of ozone loss However recovery is slow…. 44
  • 45. Images of Antarctica Taken Indicate A Slow Recovery 45