The document discusses ozone depletion and the ozone layer. It begins with an overview of the earth's atmosphere and ultraviolet radiation. It then discusses ozone, its physical properties, types (stratospheric and tropospheric), and effects on human health. The document outlines how CFCs and other ozone depleting substances cause ozone layer depletion, leading to formation of the ozone hole over Antarctica. This in turn causes effects like increased skin cancer and damage to marine life. The Montreal Protocol was adopted to phase out ozone depleting substances and protect the ozone layer. Individual actions and use of substitutes can also help mitigate ozone depletion.

1. OZONE LAYER
DEPLITION
Presnted by
Jeemon P Mathew
MSc Chemistry

2. TOPICS TO BEDISCUSSED
What is Ozone?
Types of Ozone.
Effects of Ozone.
Physical and Chemical Properties of Ozone.
Source of Ozone.
Ozone Depletion.
Ozone Hole.
Effects of Ozone Depletion.
How can we protect Ozone?
How can we protect ourselves?

3. Overview of Earth’sAtmosphere
An atmosphere is a layer or layers of gases surrounding a planet
material body of sufficient mass. The earth’s atmosphere is comprised of gases
consisting mostly of nitrogen and oxygen. It also contains lesser amounts of
argon, carbon dioxide, and many other trace gases.
From bottom to top, the layers are:
• The Troposphere
• The Stratosphere
• The Mesosphere
• The Thermosphere
• The Exosphere
The different layers of the atmosphere have contrasting characteristics.

6. Ultraviolet Radiation
• Ultra-violet means “beyond violet” in
Latin since violet is the shortest
wavelength of visible light and UV
light is the next shortest. They are high
energy electromagnetic wave emitted
from the sun. It is made up of
wavelengths ranging from 100nm to
400nm.
• UV radiation include:
iii.
i. UV-A, the least dangerous form of
UV radiation, with a wavelength
range between 315nm to 400nm.
ii. UV-B with a wavelength range
between 280nm to 315nm.
UV-C which is the most dangerous
between 100nm to 280nm. UV-C is
unable to reach Earth’s surface due
to stratospheric ozone’s ability to
absorb it.
• Shorter wavelength meanshigher frequency.
• Higher frequency means higher energy.

7. OZONE
Ozone (O3) is a highly reactive gas composed of
three oxygen atoms. It is both a natural and a
man-made product that occurs in the Earth's
upper atmosphere (the stratosphere) and lower
atmosphere (the troposphere). Depending on
where it is in the atmosphere, ozone affects life
on Earth in either good or bad ways.
Ozone is present in low concentrations
throughout the Earth's atmosphere. In total,
ozone makes up only 0.6 ppm (parts per million)
of the atmosphere.

8. PHYSICAL PROPERTIES
Standard State: Gas
Boling temperature: -111.9 °C
Melting temperature: -195.5 °C
Specific Gravity: 2.144
Color: Colorless OR Pale Blue
Odor: Pungent Smell
• Ozone levels are reported in in Dobson Units (DU)
& 300 DU is an average value.

9. TYPESOF OZONE
Stratospheric Ozone
Stratospheric ozone is formed naturally through the interaction of solar
ultraviolet (UV) radiation with molecular oxygen (O2). The "ozone layer“,
approximately 6 through 30 miles OR 10 through 50 km above the Earth's
surface, reduces the amount of harmful UV radiation reaching the Earth's
surface.

10. TYPESOF OZONE
Tropospheric Ozone
Ozone is also found much nearer the ground, in the troposphere, the lowest level
of Earth’s atmosphere. Unlike the ozone that occurs naturally in the stratosphere,
tropospheric ozone (what webreathe) is man-made.
It is an indirect result of air pollution
created by photochemical reactions
between two major classes of air
pollutants, volatile organic compounds
(VOC) and nitrogen oxides (NOx) which
are present in automobile exhaust and
emissions from factories andpower plants.

11. EFFECTS OF OZONE
Effect of Ozone on Human Health:
1. Stratospheric ozone absorbs UV
light, reducing human exposure to
harmful UV radiation that causes skin
cancer and cataracts.
2. Tropospheric ozone, when inhaled,
reacts chemically with many
biological molecules in the respiratory
tract, leading to a number of adverse
health effects. This makes ozone a
potent respiratory hazard and
pollutant near ground level.

12. STRATOSPHERE OZONE
Ozone Layer
The ozone layer ismainly found in the lower portion of the stratosphere
from approximately 20 to 30 kilometers (12 to 19 miles) above Earth,
though the thickness varies seasonally and geographically. It prevents the
harmful ultraviolet radiations of the sun from reaching the Earth's surface,
and benefits both plants and animals.
The ozone layer can absorb 97–99%of the Sun's medium-frequency
ultraviolet light (from about 200 nm to 315 nm wavelength).

13. Ozone Layer Depletion
• Normal ozone concentration is about 300 to 350 DU
• The term “Ozone hole” is applied over region when stratospheric ozone depletion
is so severe that levels fall below 200 DU.
• Special meteorological conditions and very low air temperatures accelerate and
enhance the destruction of ozone loss by man-made ozone depleting chemicals
(ODCs).
• Ozone loss now occurs every late winter and spring time above Antarctica (South
pole), and to a lesser extent the Arctic (North pole).

15. OZONE DEPLITING SUBSTANCES
CFCs
HCFCs
Haloalkanes
Methyl bromide
Carbon tetra chloride
Methyl chloroform

16. NO+O3
NO2+O
NO2+O2
NO+ O2
Net Reaction: O3+O 2O2

19. Net Reaction: O3 + O 2O2
• One chlorine atom from CFC can destroy up to 100,000 ozone atoms in a
catalytic process.
• As a result, continuous deplition of the ozone in the stratospere created the
hole in ozone layer “OZONE HOLE“
Cl+O3
ClO+O
ClO+O2
Cl+O2

21. OZONE LAYER DEPLITION

23. • Why is an ozone hole formed only above Antarctica and
not over developed countries that emit a lot of CFCs?
CFCs gases takes 6 to 7 years to move up to the stratosphere and the
wind spreads them all around the world. Extreme cold, a freezing
wind, frozen stratospheric clouds and 6-months darkness over Antarctica,
all provides ideal conditions for Chlorine to break from the CFC . The
Chlorine (or Bromine) gasses, then destroy the ozone during spring(Dec)
and causes the formation of ozone holes above Antarctica more than
otherplaces.

24. Effects Of OzoneLayer Depletion
 Harm to humanhealth:
 Skin cancers, sunburns and premature aging of the skin.
 DNA absorbs UV-B radiation and changes its shape. This changes in the DNA results in
mutated cells or the cells die and then cancer.
Note: Scientific evidence suggests that 1%depletion in ozone layer results in 5%increasein skin cancer.

25. Effects OfOzone Layer Depletion
 Cataracts, blindness and other eye diseases.
 Weakening of the human immune system

26. Effects OfOzone Layer Depletion
Damage tomarine life
Inparticular, plankton (tiny organisms in
the surface layer of oceans) are
threatened by increased UV radiation.
Plankton are the first vital step in aquatic
food chains.

27. Effects OfOzone Layer Depletion
 Animals
 In domestic animals, UV overexposure may cause eye and skin cancers. Species
of marine animals in their developmental stage (e.g. young fish, shrimp larvae and
crab larvae) have been threatened in recent years by the increased UV radiation
under the Antarctic ozonehole.
 Materials
 Wood, plastic, rubber, fabrics and many construction materials are degraded by
UV radiation.
 The economic impact of replacing and protecting materials could be
significant.

28. MONTREAL PROTOCOL
• After the discovery of ozone depletion in the late 1970’s, many countries agreed
that something must be done worldwide to stop the production of man-
made,ozone harmful products.
• The international community adopted the Vienna Convention in 1985 followed by
the Montreal Protocol in 1987.
• Protocol on substances that deplete the ozone layer was adopted on
16/09/1987,Governments recognized the need for stronger measures to reduce the
production and consumption of CFCs.
• The latest reports confirm that it has led to the phasing out of about 95% of the
consumption of ozone depleting substances (ODS) listed in the
agreement.Inturn,this has led to the prospect of the ozone layer recovering by 2050
to 2075.

29. PROTECT THEENVIRONMENT
 What You Can Do about Ozone Layer Depletion?
 Established policies that prevent future use of certain
types of chemicals.
 Know the rules: It is illegal to recharge refrigerators,
freezers and home/vehicle air conditioners with CFCs.
 If you have an older refrigerator or an older vehicle with
an air conditioner, have it serviced by a qualified
technician, and make sure the CFC is recaptured and
recycled by technician who is specifically certified to do
this work.
 Don't buy or use portable fire extinguishers that contain
 Halogens
 Chlorofluorocarbons (CFCs)
 Carbon tetrachloride
 Methyl chloroform
 Hydrochlorofluorocarbons (HCFCs)

30. CFC SUBSTITUTES
• As a safeguard against ozone deplition the recommended CFC substitutes are
1.Hydroalkanes
2.HCFC-22, HCFC -142,HFC 134a, HFC-152a
They have low ozone deplition potential,short tropospheric lifetime.

31.  The world started promoting and
adopting products that are ozone
friendly, today we can see that
refrigerators and air conditioners are now
coming with coolant made up of
hydrocarbon and not CFCs. Also in the
aerosol sprays we can find written as
ozone safe, ozone friendly etc
 International Ozone day is celebrated
on September 16 every year.

32. There is no doubt that the problem of ozone depletion exists
and deserves extensive research and attention. With the
release of each and every CFC, our ozone layer takes one small
step towards its destruction. The decision to ban completely
CFCs sooner than later cannot be decided by the United States
or even the United Nations. The entire world must unite in
order to expel this problem forever. What can we do, as concerned
citizens, to ensure that our children have a viable planet to inhabit.
CONCLUSIONCONCLUSION