Ozone layer depletion is one of the major environmental issues which is getting thinner day by day as a result of increasing pollution.

1. OZONE DEPLETION
SUBMITTED BY:
KESHAV KUMAR
M.SC.(F.)
SUBMTTED TO :-
DEPT. OF EES
CDLU SIRSA

2. UNIT OUTLINE
• Definition of Ozone
• Generation of Ozone
• Ozone Layer
• UV radiation
• Ozone Hole
• Effects of ozone depletion
•
Effects on plants
• Effects on the aquatic ecosystem
• Control of ozone depletion
• Efforts to protect the ozone layer depletion
• Vienna Conference
• Helsinki conference
• Efforts to protect the ozone layer depletion

3. DEFINITION OF OZONE
To know the facts of ozone, there are some general, physical and
chemical properties that are given below that gives a whole idea
about ozone
Characteristics General properties of ozone
Discoverer Charles Fabrey and Henry Buisson
in 1913
Location Stratosphere of the atmosphere
Distance 16-40km from the earth surface

4. Characteristics Physical properties of ozone
Physical state Gaseous form
Colour Blue coloured gas
Odour Pungent smell
Characteristics Chemical properties of ozone
Chemical formula O3
Structure Bent
Polarity It is a polar molecule
Solubility More soluble in non-polar molecules like
O2, CO2, CFCS etc. and less soluble in
polar molecule like water
Dipole moment 0.53D
Bond angle 1.272Å
Magnetic property Diamagnetic

5. A high concentration of ozone is found in the
stratosphere region and some concentration is found in
the troposphere of the atmosphere.
• O3 in the stratospheric zone considers being good as
it protects us from the harmful UV rays and refers as
“Good stratosphere ozone”.
• Whereas, O3 found in the troposphere region
considers being bad. It acts as atmospheric pollutants
that can cause many effects like respiratory hazards
(asthma, bronchitis etc.), lungs damage, headaches,
burning eyes etc. and it refers as “Bad troposphere
(low level) ozone“.

6. GENERATION OF OZONE
O3 is continuously generated and dissociated in the stratosphere,
the phenomena known as “Chapman cycle”.
Formation of ozone: It involves the following steps:
1. Firstly, dissociation of the oxygen molecule takes place under
the presence of UV-light of wavelength (80-240nm).
2. After that, the dissociated O-atom combines with the oxygen
molecule to produce ozone in the stratosphere.

7. Dissociation of ozone: It involves the following steps:
Here, ozone absorbs UV-C photon of wavelength (200-300nm)
and dissociates.

8. OZONE LAYER
It refers to “Ozonosphere”. The ozone layer is a thin layer that
acts as a protecting shield by absorbing harmful UV- radiations. It
is situated in the lower portion of the stratosphere region. The
ozone layer is present about 20-30km above the earth surface.
It absorbs up to 97-99% of UV-light less than the wavelength of
290nm. It contains a high concentration of ozone about 300-350
D.O. The level of ozone is measured by the Dobson unit that is
named after the scientist G.M.B. Dobson. He first devised the
instrument which he named “Dobson meter” (a simple
spectrophotometer) to know the amount of ozone that overheads
from the ground.

9. The thickness of the ozone varies, but generally;
Near equator: It is thinner
Near pole: It is thicker

10. UV RADIATION
It is non-ionizing radiation and is the part of electromagnetic rays
whose wavelength ranges from 100-400nm.
UV radiation produces naturally by the sun in the form of solar
energy. It can also be produced artificially by the mercury and
tanning lamp. It was first discovered by Johann Wilhelm Ritter in
the year 1801. The UV radiation is present between the X-rays
and Visible light.
UV-light has wavelength more than X-ray but less than the visible
light.

11. Classification:
On the basis of penetration property, UV light is of three types
Types of UV-
radiation
Wavelength (in nm) Ozone absorption Effects
UV-A 315-400 50% Cause skin aging,
wrinkles, DNA-
damage leads to skin
cancer.
UV-B 280-315 70-90% Cause skin tanning,
eye cataract etc.
UV-C 100-280 100% This is blocked by the
ozone therefore it
does not show any
effect

13. OZONE HOLE
It was first seen in Antarctica continent in the year 1987. During
that year, the ozone hole was observed between 12-24km
altitudes. Later, it was investigated that the occurrence of ozone
hole occurs annually during mid of August and September in the
Antarctic continent.
Cause of Ozone Depletion
The depletion of ozone in the stratosphere by the number of
gaseous pollutants like nitric oxide (NO), nitrous oxide (N2O),
chlorine (Cl), chlorofluorocarbons (CFCs) etc.

14. Nitrogen system: It causes 60% of ozone destruction.
Example: Nitrogen system can be explained by taking an example of
nitrous oxide (N2O). Nitrous oxide produces in the soil and ocean first
enters the atmosphere by the microbial activities and then to the
stratosphere.
1. In the stratosphere, N2O first reacts with the nascent oxygen in
the presence of UV- light to form nitric oxide (NO).
2. Then this nitric oxide reacts with the ozone to produce oxygen
and acts as a powerful destroyer of ozone.

15. Hydrogen system: It causes 10% of ozone destruction.
Example: It can be explained by taking an example of hydroxyl
(OH) group that is derived from the water molecule.
Firstly, the water molecule reacts with the nascent oxygen to form
a hydroxyl group.
Later this hydroxyl group reacts with the ozone and produce
oxygen and water.

16. Chlorine systems: It causes about 15-20% of ozone destruction.
Example: It can be explained by taking the example of CFCs
1. Firstly, CFCl2 in the presence of UV light dissociates to form
chlorine (Cl2).
2. Then Cl2 reacts with the ozone to produce oxygen

17. Other systems: There are several other compounds that deplete
ozone is primarily halons. Halons are the chemical compounds that
are widely used in the fire extinguishers.
Examples of halons , Bromoflourocarbons, Bromochloroflouro
carbons etc.

18. EFFECTS OF OZONE DEPLETION
It is a serious issue that can cause a number of effects to the
living organisms which categorizes into:
Effects on human health
• Skin cancer (sometimes refers as “malignant melanoma”).
• Eye cataract by direct exposure.
• Skin ageing
• The weakening of the immune system
• Skin infections
• tanning of skin

19. EFFECTS ON PLANTS
The depletion of ozone affects the growth and development of the
plant such as:
• Reduced growth of a plant
• Reduction in the efficiency of photosynthesis
• Production of smaller leaves
• Premature death
• Discoloration of leaves

20. EFFECTS ON THE AQUATIC
ECOSYSTEM
• Decrease the photosynthetic efficiency of phytoplankton
• Effect development stages of fish, shrimp and other aquatic
forms.
• Unbalance the marine ecosystem
• Interferes with the marine food chain indirectly

21. CONTROL OF OZONE DEPLETION
• Spread awareness about the ozone depletion.
• There should be restricted use of CFCs.
• Atomic nuclear explosions should be banned as they emit nitric
oxide.
• The eco-friendly household cleansing product must be used.
• Rocket flight and high altitude aircraft should minimize.
• Unleaded gasoline should be used in the vehicles.
• Vehicles should be equipped with a catalytic converter.
• CFCs should be replaced with HCFC’s.

22. EFFORTS TO PROTECT THE
OZONE LAYER DEPLETION
Vienna Conference:
• It took in Vienna ,Austria in 1985.
• The ozone hole first discovered during this time.
• It was singed for the protection of ozone layer.
• It does not include legally binding reduction goal.
Helsinki conference
• It took place in may 1986.
• It revise the Montreal protocol , Helsinki conference
happened.
• There was an agreement to eliminate CFCs.

23. THE MONTREAL PROTOCOL
• The treaty was opened for signature on September 16, 1987,
and entered into force on January 1, 1989, followed by a first
meeting in Helsinki, May 1989. Since then, it has undergone
seven revisions, in 1990 London, 1991 Nairobi, 1992
Copenhagen, 1993 Bangkok, 1995 Vienna, 1997 Montreal,
and 1999 Beijing.
• It is believed that if the international agreement is adhered to,
the ozone layer is expected to recover by 2050.
• Developed and developing countries have different phase out
schedules .