The document discusses the ozone layer, how it is formed through the Chapman cycle, and how it is depleted. The ozone layer is a layer in the stratosphere that contains 90% of atmospheric ozone and protects the Earth from harmful UV rays. It is formed through a process called the Chapman cycle where oxygen is converted to ozone. Ozone depletion occurs when gases like CFCs and halons react with ozone due to UV light, destroying the ozone molecules. This depletion leads to the formation of the ozone hole over Antarctica and increased UV radiation reaching the Earth's surface, harming human health, aquatic life, and contributing to global warming.

1. Prof. Anju Chaudhary
B.ed, M.sc , Phd

2. OZONE LAYER
The ozone layer is a layer is a layer in the earth’s atmosphere
which contains 90% of atmospheric ozone (O3). The ozone layer is found
in the lower portion of the stratosphere from about 20 to 30 km above
earth’s surface. It’s thickness varies seasonly and geographically.

3. FORMATION OF OZONE LAYER
The ozone layer or the ozone forms by conversion
of atmospheric oxygen(O2) into ozone (O3), this process
is called as Chapman cycle . The oxygen gets
photolyzed by U.V.rays to form Free oxygen radicals.
U.V. Light
O2
2
O

4. The oxygen radical then react with molecular oxygen and forms
ozone molecule (O3).
At the same time ozone gets reduce to oxygen by reacting with oxygen
radical
O3
O2
2
O
O3
O2O
So, ozone is constantly get created and destroyed by Chapman cycle, which is a
natural process.

5. OZONE DEPLETION
Decrease in concentration of ozone and thinning of ozone layer is
called Ozone depletion.
From industries and our day to day life many gases like
Chlorofluorocarbons (CFC’s) , Hydro- chlorofluorocarbons
(HCFC’s) , halons, halogens, etc. get evolved in atmosphere
which are mainly responsible for ozone depletion, as it contains or
produce Chlorine (Cl) atom.
let’s take look at the process of ozone depletion---

6. PROCESS OF OZONE DEPLETION
Due to solar radiation i.e. U.V. Rays CFC’s , HCFC’s breaks and form
Cl atom which react with ozone molecule and forms Chlorine monoxide (ClO).
Chlorine monoxide then reacts with oxygen radical to form Chlorine atom and
molecular oxygen.
O3
U.V. Light
O2
O O2

7. NET REACTION :
O3
O2
2
U.V. Light
O
As Cl atom acts as a catalyst , one single
Cl atom can destroy large amount of ozone
molecules.

8. OZONE HOLE
As a result of ozone depletion, over Antarctica
the ozone hole is formed. This ozone hole leads to
melting of ice of Antarctica, increase in sea level and
other harmful effects on it’s environment.

9. OZONE DEPLETING SUBSTANCES
Ozone depleting substances are
mainly CFC’s, HCFC’s, Halons, etc. which
are found in Refrigerators, Cleaning agents,
sprays, Pesticides, Air conditioners, car
emissions, etc.

10. EFFECT OF OZONE DEPLETION
• Due to ozone depletion harmful U. V. Rays such
as UV-B Radiation reaches to earth which leads to
harmful effects on animals, plants, aquatic life as well
as on humans also.
1. Effect on Aquatic System: Affects
phytoplankton, fish, larval crabs. Decrease in amount
of phytoplankton increase the CO2 in atmosphere
which contribute the global warming.
2. Effect on Materials: Degradation of paints and
plastics.
3. Effect on Climate: Global Warming (Increasing
the Average temperature of the Earth’s surface).

11. 4. Effect on Human Health:
Damage genetic materials in the cells.
Leads to more people suffering from Cataracts.
Causes cancer, allergies and some other infectious disease.
10% depletion in ozone layer results in 30% increase in skin
cancer infection.

12. PREVENTIONS
• Limit private vehicle driving to decrease vehicle emissions.
• By using Eco-friendly household or other cleaning agents.
• Avoid excess use of pesticides. Replacing CFC’s by other
material which are less damaging.
• Manufacturing and using of ozone depleting chemicals must
be stopped, etc.

13. P.A.C 2015