ozone layer
TRANSCRIPT
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DEPLETION OF OZONE LAYER IN THE ATMOSPHERE AND ITS
EFFECTS
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ContentsSr.no Topic Pg.No
1. Ozone Layer 32. Formation of ozone layer 43. Depletion of ozone layer 54. Causes of depletion 75. Process of depletion 86. Effects of ozone depletion 107. Preventions 138. Steps taken by India for
protection of ozone layer14
9. Analysis of ozone hole with graph
15
10. Top 5 facts about ozone 1611. Steps taken by NASA 17
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What is Ozone Layer?• Ozone was discovered by Christian Friedrich Schonbein in 1840.• The ozone layer is a layer in 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 the earth’s surface.• It’s thickness varies seasonally and geographically.• This layer absorbs UV-radiations from the sunlight and prevent it from reaching the earth surface.
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Formation Of Ozone layer• The ozone layer or ozone forms by conversion of atmospheric oxygen(O2) into ozone (O3), this process is called as
“Chapman Cycle”
The oxygen get photolyzed by U.V.rays to form oxygen radical.
U.V.Light 2 O2 O
The oxygen radical then react with molecular oxygen and forms ozone molecule.
+ O O2 O3 At the same time ozone gets reduce to oxygen by reacting with oxygen radical.
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+O3 O O2
So, ozone is constantly get created and destroyed by “Chapman cycle” , which is a natural process.
Depletion of ozone layerDecrease in concentration of ozone and thinning of ozone layer is called Ozone Depletion.
Ozone layer depletion is 8th most serious environmental problem from top 10 environmental problems faced by earth.
It is also a prime reason which is leading to global warming.
From the 1970s the depletion of the ozone layer started to capture the attention of the scientists,environmentalists,and the world community at large.
It is observed that around 40 to 50% depletion of ozone layer occurs in the south polar region.Such a large reduction is called “Ozone Hole”.
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Such ozone holes where later noticed in the North Polar regions.
Comparison of holes in ozone layer with year
Holes in Antarctica
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Causes of depletion of ozone layer The main things that lead to the destruction of the ozone gas in the ozone layer are:1. Low temperatures2. Increase in the level of chlorine3. Increase in the level of bromine gas in the upper stratosphere
But the one and the most important reason for ozone layer depletion is the production and the emission of chlorofluorocarbons(CFCs), Hydro chlorofluorocarbons (HCFC’s), halogens, etc. This is what which leads to almost 80 percent of the total ozone layer depletion, as it contains or produce Chlorine(Cl)atom
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All these ozone depleting substance remains stable in the lower atmospheric region , but as they reach the stratosphere , they get exposed to the ultra violet rays.
This leads to their breakdown and releasing of free chlorine atoms which reacts with the ozone gas
Process of ozone layer depletion
Due to the solar radiations i.e. U.V. Rays CFC’s,HCFC’s breaks and form Cl atom which react with ozone molecule and forms Chlorine monoxide(ClO).
+
Cl O3 ClO O2
ClO than reacts with oxygen free radical to form Chlorine atom and molecular oxygen.
U.V.Light
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+ +
ClO O Cl O2
Net Reaction:-
O3 O O2
As Cl atom acts as a catalyst , one Cl atom can destroy 100000 molecules of ozone.
+
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Effects Of Ozone Depletion As U.V Rays coming directly from sun to the earth is consisted of U.V Ray A and U.V RayB it effects all the
organisms on the earth.
U.V A
U.V BEarthSUN
OZONE
1.Effects on Plants:-• UVB radiation affects the physiological and developmental
processes of plants.• Sometimes we see the small spots on the plants which are
also due to the U.V rays .• Plants growth is affected due to UVB rays.• These changes can have important implications for plant
competitive balance, herbivore, plant diseases , and biogeochemical cycles.
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2. Effects on Marine Ecosystem:-• Phytoplankton which forms the foundation of the aquatic food webs, it is affected due to the UVB rays due to
which aquatic organisms survival is not possible.• UVB rays has been found to cause damage to early development stages of fish , crab and other marine
animals.• The most severe effect is decreased reproductive capacity.
3.Effects on Human Health:-• Ozone layer depletion increases the amount of UVB that
reaches the earth surface.• Laboratory studies demonstrate that the UVB causes non-
melanoma skin cancer and plays a major role in malignant melanoma development.
• UVB has linked to the development of cataracts , a clouding of the eye’s lens.
• Certain skin cancer are also caused due to these harmful U.V Rays
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4.Effects on materials:-
• Synthetic polymers , naturally occurring biopolymers are adversely affected by the UVB radiations.
• Today the materials are somewhat protected by special additives.• If the amount of UVB increases than UVB levels will accelerate their breakdown.
5. Effects on climate:-
• Global Warming• Green house effect• Acidic Rain• Melting of snow
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Preventions• Limit private vehicles driving to decrease vehicle emissions.• Use public transport system to decrease pollution and global warming.• 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.• Grow more and more trees.• Excess use of air conditioners must be prevented.
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Steps taken by India to protect the ozone layer• India signed and ratified the Vienna Convention for the protection of the Ozone Layer in 1991.• Also signed Montreal Protocol on substances that deplete the ozone layer in 1992.• Since 1993 India has spend US $40 million in multilateral fund projects .• India has banned a production of many substances which produce a large amount of CFC’s.• In the place of carbon tetrachloride many countries including India have started using tetrachloroethene in
manufacturing of the steel which is less harmful.• UNDP is supporting India in phasing out(HCFC’s) by 2030,as a part of country’s commitment to Montreal
protocol
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Analysis of ozone hole size with Year from(1978-96)
• According to graph we can conclude that:-
1. From year 1978-79 no ozone holes were there.2. From 1979-81 holes started in ozone layer and its
size was approximately 1 Million square km.3. From year 1981-85 it increases continuously but
decreases from 14-10 million square km from year 1985-86.
4. The decrease was max from year 1987-88 i.e., from 18-8 million square km .
5. From year 1988 hole size continuously increases.
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Top 5 facts about ozone To make people aware about the protection of ozone layer in year 1995 , United Nations
declared16th September as a “World Ozone Day”. Ozone is a pungent smelling blue gas. A molecule of ozone is consists of 3 oxygen atoms. Scientist named it after the Greek for ‘to smell’ which is ‘ozein’. Industrial use of ozone include disinfection and the sanitising of swimming pool water. The ozone layer is 12-20 miles above the earth’s surface and contains most of our ozone.
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• This a package of instruments about to be launched on a weather balloon into the skies over southeast India by NASA Langley’s Jean-Paul Vernier.
• Vernier and colleague Tobias Wegner travelled to Godanki, Indiain 2014 , to study an atmospheric feature called the Asian Tropopause Aerosol Layer or ATAL. Photo by NASA.
Steps taken by NASA
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Conclusions• The problem of ozone depletion deserves extensive research and
attention.• The decision to ban CFCs completely is not decided by US or even UN.• The entire world must be unite to expel this problem forever.• If each human will be willing to make a small sacrifice for the greater
good, the future of our ozone will undoubtly be secure.
“Save Ozone, Save Earth and Save Ourselves”
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THANK YOU.