Ozone depletion occurs when chlorofluorocarbons (CFCs) and halons—gases formerly found in aerosol spray cans and refrigerants—are released into the atmosphere (see details below). ... CFCs and halons cause chemical reactions that break down ozone molecules, reducing ozone's ultraviolet radiation-absorbing capacity. The ozone layer that shields life from cancer-causing solar rays is recovering at a rate of one to three percent per decade, reversing years of dangerous depletion caused by the release of harmful chemicals, a U.N. study said on November 5. “The Antarctic ozone hole is recovering, while continuing to occur every year.

1. OZONE LAYER-
GUARDIAN OF OUR PLANET

2. TOPICS TO BE COVERD
 OZONE LAYER
 ITS IMPORTANCE
 ITS DEPLETION
 VARIOUS EFFECTS OF OZONE DEPLETION
 WORLDWIDE MEASURES TO REDUCE OZONE
LAYER DEPLETION

3. OZONE LAYER
 The ozone layer also known as ozone shield.
 The ozone layer region of Earth's stratosphere that absorbs
most of the Sun's ultraviolet radiation. It contains a high
concentration of ozone (O3) in relation to other parts of the
atmosphere.
 Found in the lower portion of the stratosphere, from
approximately 15 to 35 kilometers (9.3 to 21.7 mi) above
Earth, although its thickness varies seasonally and
geographically.
 The ozone layer was discovered in 1913 by the French
physicists Charles Fabry and Henri Buisson. They said
that there is something in our atmosphere which stops the
ultraviolet rays from the sun to strike directly to the earth’s
surface.

4. OZONE LAYER
 It was deduced that the missing radiation was being
absorbed by something in the atmosphere. Eventually
the spectrum of the missing radiation was matched to
only one known chemical, ozone.
 Between 1928 and 1958, Dobson established a
worldwide network of ozone monitoring stations, which
continue to operate to this day. The "Dobson unit", a
convenient measure of the amount of ozone overhead, is
named in his honor.

5. OZONE LAYER
 The ozone layer absorbs 97 to 99 percent of the Sun's
medium-frequency ultraviolet light (from about
200 nm to 315 nm wavelength), which otherwise would
potentially damage exposed life forms near the surface.
KNOWN FACT
 Venus also has a thin ozone layer at an altitude of 100
kilometers above the planet's surface.

6. OZONE LAYER
OZONE-OXYGEN
CYCLE IN
OZONE LAYER

7. OZONE LAYER

8. ITS IMPORTANCE

9. ITS IMPORTANCE
 Absorption of UR and IR radiations.
 Ozone layers blocks harmful UV rays from the sun and
protects biological processes on the earth which are essential
for sustenance of life. If not blocked by Ozone layer, exposure
to ultraviolet radiation can increase the risk of cataracts, skin
cancer and other detrimental effects among humans.
 The ozone layer absorbs 97 to 99 percent of the Sun's medium-
frequency ultraviolet light.
 Necessary for human life.
 Essential for saving earth’s water mass otherwise it will move
out of the earth from the ozone holes.
 Providing less harm to plant life too by reducing UV amount.

10. Atmospheric ozone amt.

11. ITS DEPLETION
 Certain industrial processes and consumer products result in the
emission of ozone-depleting substances (ODSs) to the atmosphere.
 The main ODS are chlorofluorocarbons (CFCs),
hydrochlorofluorocarbons (HCFCs), carbon tetrachloride, methyl
chloroform and halons (brominated fluorocarbons).
 CFCs are the most widely used ODS, accounting for over 80 per cent
of total stratospheric ozone depletion, says a report published in
www.thesangaiexpress.com.
 In 1976, atmospheric research revealed that the ozone layer was
being depleted by chemicals released by industry,
mainly chlorofluorocarbons (CFCs).
 The ozone layer can be depleted by free radical catalysts,
including nitric oxide (NO), nitrous oxide (N2O), hydroxyl (OH),
atomic chlorine (Cl), and atomic bromine (Br).

12. Ozone depletion

13. ITS DEPLETION
 By 2009, nitrous oxide was the largest ozone-depleting
substance (ODS) emitted through human activities.
 Ozone levels have dropped by a worldwide average of about 4
percent since the late 1970s.
 The discovery of the annual depletion of ozone above the
Antarctic was first announced on May 16, 1985.

14. Effects of ozone depletion
 Ozone layer depletion causes increased UV radiation
levels at the Earth's surface, which is damaging to human
health.
 Negative effects include increases in certain types of skin
cancers, eye cataracts and immune deficiency disorders.
UV radiation also affects terrestrial and aquatic
ecosystems, altering growth, food chains and biochemical
cycles. Aquatic life just below the water’s surface, the
basis of the food chain, is particularly adversely affected
by high UV levels. UV rays also affect plant growth,
reducing agricultural productivity.

15. Causes and Effects of depletion

16. Measures to reduce depletion
 Montreal protocol
 In 1987, to address the destruction of the ozone layer, the
international community established the Montreal Protocol on
ozone-depleting substances. It was the first international
treaty to be signed by all countries of the world and is
considered the greatest environmental success story in the
history of the United Nations.
 It’s objective is to cut down the production and consumption
of ozone-depleting substances, in order to reduce their
presence in the atmosphere and thus protect the Earth's ozone
layer.
 Kigali amendment
 The Kigali Amendment requires Parties to put into place an
import and export licensing system for hydrofluorocarbons
(HFCs) by 1st January 2019 (or two years later if required).

17. Montreal protocol

18. Image showing the ozone holes

19. Good news
 The good news about the Ozone layer which had
once begun to deplete is this. The latest Scientific
Assessment of Ozone Depletion completed in 2018,
shows that, as a result, parts of the ozone layer have
recovered at a rate of 1-3% per decade since 2000. At
projected rates, Northern Hemisphere and mid-
latitude ozone will heal completely by the 2030s. The
Southern Hemisphere will follow in the 2050s and
Polar Regions by 2060.

20. OZONE HEALING

21. Conclusion
 Nature is undoubtedly God's greatest gift to the mankind. The
air that we breathe, the food we eat and water we drink, all
these come from nature. Even when we want to escape from
humdrum of daily life, we like going to mountains, forests or in
general closer to nature. The very fact that we using the
expression 'closer to nature' makes it clear that we have over
the years come far from it.
 Technology has definitely changed the way we lead our lives
compared to our ancestors, but it cannot be denied that this
very technology has brought us away from nature, the place
where we truly belong. Surrounded by the concrete jungle, we
often forget that life would not have been possible on earth
without nature which allows biological processes to thrive.

22. References and Sources
 Ozone layer (wikipedia)
link: https://en.wikipedia.org/wiki/Ozone_layer
 One india (website)
link: https://www.oneindia.com/india/how-important-is-the-
ozone-layer-well-the-life-on-earth-depends-on-it-
2948848.html
 Protection of ozone layer
link:
https://ec.europa.eu/clima/policies/ozone_en#:~:text=Ozone
%20layer%20depletion%20causes%20increased,cataracts%20
and%20immune%20deficiency%20disorders.
 Photographs and Pictures
(GOOGLE images)