Class 10th Science Chapter 13 – Our Environment | Ozone Layer and Ozone Depletion

Our Environment

Ozone Layer and Ozone Depletion

ओजोन परत एवं ओजोन क्षरण

Our Environment | Ozone Layer and Ozone Depletion

1. Introduction | परिचय

The ozone layer is a region of the stratosphere containing relatively higher concentrations of ozone (O₃). It absorbs a large fraction of the Sun's harmful ultraviolet (UV) radiation and therefore plays an important protective role for life on Earth.

ओजोन परत समताप मंडल (Stratosphere) का वह क्षेत्र है जहाँ ओजोन (O₃) की अपेक्षाकृत अधिक मात्रा पाई जाती है। यह सूर्य से आने वाली हानिकारक पराबैंगनी (UV) विकिरण का एक बड़ा भाग अवशोषित करके पृथ्वी पर जीवन की रक्षा करती है।

2. What is Ozone? | ओजोन क्या है?

Ozone is a molecule made up of three oxygen atoms.

Ozone = O₃

Oxygen gas normally exists mainly as O₂, whereas ozone consists of O₃ molecules. Ozone is chemically reactive and has a characteristic sharp smell at relatively high concentrations.

ऑक्सीजन गैस सामान्यतः O₂ के रूप में पाई जाती है, जबकि ओजोन O₃ अणुओं से बनी होती है।

3. Where is the Ozone Layer Found?

The ozone layer is primarily located in the stratosphere, roughly 15–35 km above Earth's surface, with the highest ozone concentrations typically around 20–30 km. The exact concentration varies with location, season and atmospheric conditions.

Atmospheric Region	Approximate Location	Important Point
Troposphere	Surface to ~8–15 km	Weather occurs mainly here
Stratosphere	~15–50 km	Ozone layer mainly occurs here
Mesosphere	~50–85 km	Very cold upper atmospheric region

4. Formation of Ozone | ओजोन का निर्माण

High-energy ultraviolet radiation from the Sun can split oxygen molecules (O₂) into individual oxygen atoms. These oxygen atoms can then combine with O₂ to form ozone.

O₂ + UV → 2O

O + O₂ → O₃

5. Natural Ozone–Oxygen Cycle

Ozone is continuously formed and destroyed naturally in the stratosphere. This dynamic balance is commonly described as the ozone–oxygen cycle.

O₂ + UV → O + O
O + O₂ → O₃
O₃ + UV → O₂ + O

The ozone layer is therefore not a permanent solid layer. It is a region where ozone molecules are continuously formed and broken down.

6. Importance of the Ozone Layer

Function	Importance
UV absorption	Absorbs much of the biologically harmful UV-B and almost all UV-C reaching the upper atmosphere
Protection of organisms	Reduces harmful UV exposure to humans, animals and plants
Protection of ecosystems	Helps protect terrestrial and aquatic organisms from excessive UV radiation
Atmospheric chemistry	Participates in important stratospheric photochemical reactions

7. Ultraviolet Radiation | पराबैंगनी विकिरण

Ultraviolet radiation is electromagnetic radiation with wavelengths shorter than visible violet light.

Type	Approximate Wavelength	Important Point
UVA	315–400 nm	Reaches Earth's surface relatively efficiently
UVB	280–315 nm	Partly absorbed by ozone; can damage biological tissues
UVC	100–280 nm	Strongly absorbed by atmospheric gases, including ozone

For Class 10 level, remember: ozone layer protects living organisms from harmful ultraviolet radiation, especially by absorbing much UV-B and UV-C.

8. What is Ozone Depletion?

Ozone depletion refers to a reduction in stratospheric ozone concentrations. It can be caused by chemical reactions involving human-made ozone-depleting substances that release reactive chlorine or bromine in the stratosphere.

ओजोन क्षरण का अर्थ समताप मंडल में ओजोन की मात्रा में कमी से है। मानव निर्मित कुछ रसायन समताप मंडल में जाकर सक्रिय क्लोरीन या ब्रोमीन उत्पन्न कर सकते हैं, जो ओजोन को नष्ट करने वाली अभिक्रियाओं में भाग लेते हैं।

9. Major Ozone-Depleting Substances

Substance	Example / Use	Problem
CFCs	Historically used in refrigeration, air-conditioning and aerosol applications	Release chlorine in the stratosphere
Halons	Historically used in some fire-suppression systems	Contain bromine that can destroy ozone
Carbon tetrachloride	Industrial solvent / feedstock historically	Ozone-depleting substance
Methyl chloroform	Industrial solvent historically	Ozone-depleting substance
Methyl bromide	Fumigant historically	Releases bromine in the stratosphere

10. CFCs | क्लोरोफ्लोरोकार्बन

CFCs are a group of human-made compounds containing carbon, fluorine and chlorine. They were widely used because they are chemically stable and useful in refrigeration and other applications.

Their chemical stability at Earth's surface becomes a problem because some CFCs can persist long enough to reach the stratosphere, where ultraviolet radiation can break them apart and release chlorine-containing reactive species.

11. How CFCs Damage Ozone

12. Catalytic Ozone Destruction

Reactive chlorine can participate in catalytic cycles. In simplified form:

Cl + O₃ → ClO + O₂

ClO + O → Cl + O₂

Overall: O₃ + O → 2O₂

The chlorine atom is regenerated during the cycle, allowing it to participate in the destruction of many ozone molecules.

13. Ozone Hole | ओजोन छिद्र

The term ozone hole refers to a region of severe seasonal depletion of stratospheric ozone, most prominently observed over Antarctica during the Southern Hemisphere spring.

An "ozone hole" does not mean that the atmosphere has literally become an empty hole. It refers to a substantial reduction in ozone concentration over a large region.

14. Why is Ozone Depletion Strong over Antarctica?

The Antarctic stratosphere becomes extremely cold during winter. Polar stratospheric clouds can form under these conditions. Reactions on the surfaces of these particles convert relatively inactive chlorine compounds into forms that can rapidly participate in ozone destruction when sunlight returns in spring.

Cold polar conditions + Polar Stratospheric Clouds + Sunlight
↓ Activation of chlorine
↓ Rapid ozone destruction

15. Effects of Ozone Depletion

Area	Possible Effect of Increased UV-B Exposure
Human Health	Increased risk of skin damage, skin cancers and cataracts
Immune System	Excess UV exposure can affect immune responses
Plants	Can interfere with growth and physiological processes in sensitive species
Phytoplankton	Can be affected by increased UV exposure, potentially influencing aquatic food webs
Materials	Some plastics, paints and other materials can degrade more rapidly under UV exposure

16. Ozone Depletion and Human Health

Reduced stratospheric ozone can allow more UV-B radiation to reach Earth's surface. Excessive UV-B exposure can damage DNA and increase the risk of certain skin cancers and eye conditions such as cataracts.

Ozone depletion does not mean that every person exposed to sunlight will develop disease. Risk depends on exposure level, duration, location, behaviour and individual factors.

17. Ozone Depletion and Plants

Increased UV-B exposure can affect photosynthesis, growth, reproduction and other physiological processes in some plants. The magnitude of the effect varies among species and environmental conditions.

18. Ozone Depletion and Aquatic Ecosystems

Phytoplankton are microscopic organisms that form an important foundation of many aquatic food webs. Excess UV radiation can affect some phytoplankton and other aquatic organisms, potentially influencing ecosystem productivity and food webs.

19. Ozone Depletion vs Global Warming

Ozone Depletion	Global Warming
Reduction of stratospheric ozone	Long-term rise in average surface temperature
Strongly associated with ozone-depleting substances	Strongly associated with increased greenhouse gas concentrations
Allows more UV-B to reach the surface	Changes Earth's energy balance and climate system
CFCs are major historical ozone-depleting substances	CO₂, CH₄ and N₂O are important greenhouse gases

Exam Trick: Ozone depletion and global warming are related environmental issues but they are not the same phenomenon.

20. Stratospheric Ozone vs Ground-Level Ozone

Stratospheric Ozone	Ground-Level Ozone
Located mainly in the stratosphere	Occurs near Earth's surface
Protective role	Air pollutant at elevated concentrations
Absorbs harmful UV radiation	Can irritate respiratory tissues
Often called "good ozone"	Often called "bad ozone"

21. Montreal Protocol

The Montreal Protocol on Substances that Deplete the Ozone Layer is an international environmental agreement adopted in 1987 to control and phase out the production and consumption of ozone-depleting substances.

The Montreal Protocol is widely regarded as one of the most successful international environmental agreements. Its implementation has substantially reduced the atmospheric abundance of many ozone-depleting substances.

22. Kigali Amendment

The Kigali Amendment to the Montreal Protocol was adopted in 2016 and provides for the phasedown of hydrofluorocarbons (HFCs), which generally do not deplete ozone but can have high global-warming potential.

Important distinction: HFCs are not major ozone-depleting substances, but many have high global-warming potential. The Kigali Amendment addresses their phasedown under the Montreal Protocol framework.

23. Protection of the Ozone Layer

• Phase out ozone-depleting substances.
• Use safer alternatives where technically and economically appropriate.
• Prevent leakage of refrigerants.
• Recover and properly dispose of old refrigerants and equipment.
• Maintain refrigeration and air-conditioning systems properly.
• Follow environmental regulations concerning ozone-depleting substances.
• Support international agreements such as the Montreal Protocol.

24. Animated Concept Flow

25. Important Definitions | महत्वपूर्ण परिभाषाएँ

Term	Definition
Ozone	O₃ molecule containing three oxygen atoms
Ozone Layer	Stratospheric region containing relatively higher ozone concentrations
Ozone Depletion	Reduction in stratospheric ozone concentration
Ozone Hole	Region of severe seasonal stratospheric ozone depletion
CFCs	Human-made chlorofluorocarbon compounds, many of which are ozone-depleting substances
UV Radiation	Electromagnetic radiation with wavelengths shorter than visible violet light
ODS	Ozone-Depleting Substances

🧠 Golden Memory Trick

🛡️ Ozone Layer → Protection from harmful UV

🧪 CFCs → Chlorine → Ozone destruction

☀️ UV → CFC breakdown → Reactive chlorine

🌍 Ozone depletion → More UV-B reaches surface

🧴 ODS → Ozone-Depleting Substances

📜 Montreal Protocol → Protection of ozone layer

🌡️ Kigali Amendment → HFC phasedown

🔑 Good ozone → Stratosphere | Bad ozone → Ground level

26. 30 MCQs | Multiple Choice Questions

1. Ozone is represented by:

A. O₃

B. O₂

C. CO₂

D. H₂O

Answer: A

2. The ozone layer is mainly located in the:

A. Troposphere

B. Stratosphere

C. Mesosphere

D. Thermosphere

Answer: B

3. The major protective role of stratospheric ozone is to absorb:

A. Radio waves

B. Microwaves

C. Harmful ultraviolet radiation

D. Sound waves

Answer: C

4. Which substance has historically been a major ozone-depleting substance?

A. Oxygen

B. Nitrogen

C. Carbon dioxide

D. CFC

Answer: D

5. CFCs can release which reactive element in the stratosphere?

A. Chlorine

B. Sodium

C. Calcium

D. Iron

Answer: A

6. Which radiation helps break oxygen molecules during ozone formation?

A. Infrared

B. Ultraviolet

C. Radio

D. Microwave

Answer: B

7. Ozone depletion can increase exposure to:

A. Visible light only

B. Radio waves

C. UV-B radiation

D. Sound waves

Answer: C

8. The ozone hole is most prominently observed over:

A. Europe

B. Asia

C. Africa

D. Antarctica

Answer: D

9. Which international agreement was adopted in 1987 to protect the ozone layer?

A. Montreal Protocol

B. Kyoto Protocol

C. Paris Agreement

D. Ramsar Convention

Answer: A

10. The Kigali Amendment mainly addresses the phasedown of:

A. CFCs

B. HFCs

C. Oxygen

D. Nitrogen

Answer: B

11. Which type of ozone is generally protective?

A. Ground-level ozone

B. Tropospheric ozone

C. Stratospheric ozone

D. Urban ozone

Answer: C

12. Ground-level ozone is generally considered:

A. A protective UV shield

B. A nutrient

C. A greenhouse-free gas

D. An air pollutant

Answer: D

13. Which can be a health effect of increased UV-B exposure?

A. Increased risk of skin damage

B. Improved eyesight

C. Increased bone length

D. Better hearing

Answer: A

14. Which cells form the basis of many aquatic food webs?

A. Rocks

B. Phytoplankton

C. Plastic particles

D. Sand grains

Answer: B

15. Which compound group contains carbon, fluorine and chlorine?

A. HFCs

B. Nitrates

C. CFCs

D. Sulfates

Answer: C

16. Ozone depletion means:

A. Complete disappearance of oxygen

B. Increase of nitrogen

C. Formation of clouds

D. Reduction of stratospheric ozone

Answer: D

17. Which element is important in catalytic ozone destruction from CFCs?

A. Chlorine

B. Calcium

C. Potassium

D. Magnesium

Answer: A

18. Why can one chlorine atom affect many ozone molecules?

A. It becomes oxygen immediately

B. It can be regenerated in a catalytic cycle

C. It becomes water

D. It disappears permanently after one reaction

Answer: B

19. Which atmospheric layer is directly above most of the troposphere?

A. Mesosphere

B. Thermosphere

C. Stratosphere

D. Exosphere

Answer: C

20. Which is an ozone-depleting substance?

A. Oxygen

B. Nitrogen

C. Water vapour

D. Halon

Answer: D

21. Polar stratospheric clouds are important in Antarctic ozone depletion because they:

A. Help convert chlorine compounds into more reactive forms

B. Produce oxygen gas directly

C. Remove all sunlight

D. Stop atmospheric circulation completely

Answer: A

22. Which UV category has the shortest wavelength?

A. UVA

B. UVC

C. UVB

D. Visible light

Answer: B

23. Which statement is correct?

A. All ozone is harmful

B. All ozone is beneficial

C. Stratospheric ozone is protective while ground-level ozone can be harmful

D. Ozone has no role in atmospheric chemistry

Answer: C

24. Which is NOT a direct purpose of the ozone layer?

A. Absorbing UV radiation

B. Protecting organisms from excessive UV exposure

C. Participating in stratospheric chemistry

D. Producing all atmospheric oxygen

Answer: D

25. Which action helps protect the ozone layer?

A. Preventing release of ozone-depleting substances

B. Increasing CFC emissions

C. Releasing halons

D. Dumping refrigerants into the atmosphere

Answer: A

26. Which substance generally does NOT deplete ozone but can contribute strongly to warming?

A. CFC

B. HFC

C. Halon

D. Methyl bromide

Answer: B

27. Ozone is made of:

A. Two carbon atoms

B. Two oxygen atoms

C. Three oxygen atoms

D. Three hydrogen atoms

Answer: C

28. Ozone depletion can affect plants mainly because:

A. UV radiation can influence plant physiological processes

B. Plants cannot absorb visible light

C. Plants require CFCs

D. Ozone is plant food

Answer: A

29. Which statement about the ozone hole is correct?

A. It is a physical hole in the atmosphere

B. It means complete absence of air

C. It refers to severe seasonal ozone depletion

D. It occurs equally everywhere

Answer: C

30. The Montreal Protocol primarily deals with:

A. Plastic waste

B. Ocean currents

C. Deforestation

D. Substances that deplete the ozone layer

Answer: D

27. 30 Subjective Questions with Answers

2 Marks 1. What is ozone?

Ozone is a molecule made up of three oxygen atoms and is represented by O₃.

2 Marks 2. What is the ozone layer?

It is a region of the stratosphere containing relatively higher concentrations of ozone that absorbs much harmful UV radiation.

2 Marks 3. Where is the ozone layer mainly located?

The ozone layer is mainly located in the stratosphere, approximately 15–35 km above Earth's surface.

2 Marks 4. What is ozone depletion?

Ozone depletion is a reduction in the concentration of ozone in the stratosphere.

2 Marks 5. What are CFCs?

CFCs are chlorofluorocarbon compounds containing carbon, fluorine and chlorine. Many CFCs are ozone-depleting substances.

2 Marks 6. What is an ozone hole?

An ozone hole is a region of severe seasonal depletion of stratospheric ozone, most prominently observed over Antarctica.

3 Marks 7. Write the importance of the ozone layer.

The ozone layer absorbs much harmful UV radiation, reducing UV exposure at Earth's surface and protecting living organisms.

3 Marks 8. Name three ozone-depleting substances.

CFCs, halons and carbon tetrachloride are examples of ozone-depleting substances.

3 Marks 9. What are the three major types of UV radiation?

UVA, UVB and UVC.

3 Marks 10. How is ozone formed naturally?

UV radiation splits O₂ into oxygen atoms. These atoms combine with O₂ molecules to form O₃.

3 Marks 11. Why are CFCs harmful to the ozone layer?

CFCs can reach the stratosphere, where UV radiation breaks them down and releases chlorine-containing reactive species that participate in ozone-destroying reactions.

3 Marks 12. Give three effects of increased UV-B exposure.

It can increase the risk of skin damage and certain skin cancers, contribute to cataracts and affect some plants and aquatic organisms.

4 Marks 13. Explain the formation of ozone.

High-energy UV radiation breaks O₂ molecules into oxygen atoms. The oxygen atoms then combine with O₂ molecules to form ozone (O₃). This occurs mainly in the stratosphere.

4 Marks 14. Explain how CFCs cause ozone depletion.

CFCs are stable in the lower atmosphere and can reach the stratosphere. UV radiation breaks them down, releasing chlorine-containing reactive species. These participate in catalytic cycles that convert ozone into oxygen.

4 Marks 15. Differentiate between stratospheric and ground-level ozone.

Stratospheric ozone protects Earth by absorbing UV radiation. Ground-level ozone is a pollutant formed through atmospheric chemical reactions and can harm respiratory health.

4 Marks 16. What is the ozone hole?

It refers to severe seasonal depletion of stratospheric ozone, particularly over Antarctica. It is caused by complex chemical reactions involving chlorine and bromine under cold polar conditions.

5 Marks 17. Explain the effects of ozone depletion on human beings.

Reduced stratospheric ozone can increase UV-B exposure. Excessive UV-B can damage skin DNA, increase the risk of certain skin cancers, contribute to cataracts and affect immune responses.

5 Marks 18. Explain the effects of ozone depletion on plants.

Increased UV-B exposure can affect photosynthesis, growth, reproduction and other physiological processes in sensitive plant species. The effect varies with species and environmental conditions.

5 Marks 19. Explain the effects of ozone depletion on aquatic ecosystems.

Increased UV exposure can affect phytoplankton and other aquatic organisms. Because phytoplankton form the base of many aquatic food webs, changes in their productivity can influence higher trophic levels.

5 Marks 20. Differentiate between ozone depletion and global warming.

Ozone depletion is the reduction of stratospheric ozone and can increase surface UV-B exposure. Global warming is the long-term rise in Earth's average surface temperature associated mainly with increased greenhouse gas concentrations.

5 Marks 21. Explain the role of the Montreal Protocol.

The Montreal Protocol, adopted in 1987, controls and phases out the production and consumption of many ozone-depleting substances. It has played a major role in reducing emissions of these substances globally.

6 Marks 22. Explain the complete mechanism of ozone depletion by CFCs.

CFCs released at Earth's surface can persist and reach the stratosphere. UV radiation breaks CFC molecules and releases reactive chlorine. Chlorine reacts with ozone to form chlorine monoxide and oxygen. Further reactions regenerate chlorine, allowing catalytic cycles to destroy many ozone molecules.

6 Marks 23. Explain the formation and destruction of ozone in the stratosphere.

UV radiation splits O₂ into oxygen atoms. Oxygen atoms combine with O₂ to form O₃. Ozone can then absorb UV radiation and split back into O₂ and oxygen atoms. This natural cycle maintains a dynamic balance, although human-made ozone-depleting substances can disturb it.

6 Marks 24. Explain why the Antarctic ozone hole develops.

During Antarctic winter, extremely low temperatures allow polar stratospheric clouds to form. Reactions on these particles convert chlorine compounds into reactive forms. When sunlight returns in spring, rapid catalytic reactions destroy ozone, producing severe seasonal depletion.

6 Marks 25. Explain measures for protecting the ozone layer.

Ozone protection requires phasing out ozone-depleting substances, using safer alternatives, preventing refrigerant leakage, properly recovering old refrigerants, maintaining cooling equipment and implementing international agreements such as the Montreal Protocol.

5 Marks 26. Explain the difference between UVA, UVB and UVC.

UVA has wavelengths of about 315–400 nm, UVB about 280–315 nm and UVC about 100–280 nm. Atmospheric gases strongly absorb UVC, while ozone absorbs much UVB. UVA reaches Earth's surface relatively efficiently.

4 Marks 27. Why is stratospheric ozone called good ozone?

Stratospheric ozone absorbs much harmful UV radiation from the Sun and therefore protects living organisms. It is called good ozone because of this protective role.

5 Marks 28. Why is ground-level ozone called bad ozone?

Ground-level ozone is a secondary air pollutant. At elevated concentrations it can irritate the respiratory system and damage vegetation and materials.

6 Marks 29. Explain the relationship between ozone depletion and UV radiation.

Stratospheric ozone absorbs a significant portion of incoming harmful UV radiation. If ozone concentration decreases, less UV-B is absorbed in the stratosphere and more can reach Earth's surface. Increased UV exposure can damage living tissues and affect ecosystems.

6 Marks 30. Explain why ozone protection is an international environmental issue.

Ozone-depleting substances can spread through the global atmosphere regardless of where they are emitted. Their effects therefore cross national boundaries. International cooperation through agreements such as the Montreal Protocol is necessary to control their production, use and release.

28. Assertion–Reason Questions

1. Assertion: The ozone layer protects living organisms from harmful UV radiation.
Reason: Ozone absorbs a significant fraction of ultraviolet radiation.

Answer: Both Assertion and Reason are true, and the Reason correctly explains the Assertion.

2. Assertion: CFCs can contribute to ozone depletion.
Reason: UV radiation can release reactive chlorine from CFCs in the stratosphere.

Answer: Both Assertion and Reason are true, and the Reason correctly explains the Assertion.

3. Assertion: Ground-level ozone is protective like stratospheric ozone.
Reason: Ground-level ozone is an air pollutant at elevated concentrations.

Answer: Assertion is false, but Reason is true.

4. Assertion: The Antarctic ozone hole is a physical empty hole in the atmosphere.
Reason: The term refers to severe seasonal ozone depletion.

Answer: Assertion is false, but Reason is true.

5. Assertion: The Montreal Protocol is associated with protection of the ozone layer.
Reason: It controls and phases out many ozone-depleting substances.

Answer: Both Assertion and Reason are true, and the Reason correctly explains the Assertion.

29. HOTS | Higher Order Thinking

HOTS 1: Why can ozone depletion affect aquatic ecosystems even though the ozone layer is high in the atmosphere?

Ozone depletion can allow more UV-B radiation to reach Earth's surface. Increased UV exposure can affect phytoplankton and other aquatic organisms, potentially influencing aquatic food webs.

HOTS 2: Why is the stability of CFCs at Earth's surface both useful and environmentally problematic?

Their stability made them useful in many applications, but it also allowed some CFCs to persist long enough to reach the stratosphere, where UV radiation can release reactive chlorine.

HOTS 3: Why is the ozone layer not a solid physical layer?

Ozone molecules are distributed within the stratosphere rather than forming a solid sheet. Ozone is continuously formed and destroyed through atmospheric photochemical reactions.

HOTS 4: Why should ozone depletion and global warming be studied separately?

They involve different atmospheric processes and environmental outcomes. Some substances and policies can affect both issues, but ozone depletion concerns stratospheric ozone and UV radiation, whereas global warming concerns Earth's energy balance and climate system.

30. Quick Revision Chart

Topic	Key Point
Ozone	O₃; three oxygen atoms
Ozone Layer	Mainly in stratosphere
Main Function	Absorbs much harmful UV radiation
Ozone Depletion	Reduction of stratospheric ozone
CFCs	Important historical ozone-depleting substances
Reactive Chlorine	Participates in catalytic ozone destruction
Ozone Hole	Severe seasonal depletion, especially Antarctic
UV-B	Can damage living tissues; partly absorbed by ozone
Montreal Protocol	International agreement to control ozone-depleting substances
Kigali Amendment	Phasedown of HFCs

31. One-Minute Revision

🧪 Ozone = O₃

🌍 Ozone layer = mainly Stratosphere

🛡️ Main function = UV protection

❄️ Antarctica = strongest seasonal ozone depletion

🧴 CFCs = important historical ODS

☀️ UV breaks CFCs → reactive chlorine

⚗️ Cl participates in catalytic ozone destruction

🕳️ Ozone hole = severe seasonal ozone depletion

📜 Montreal Protocol = ozone protection

🌡️ Kigali Amendment = HFC phasedown

🟢 Stratospheric ozone = protective

🔴 Ground-level ozone = pollutant

32. Final Summary | अंतिम सारांश

The ozone layer is an important part of the stratosphere that protects life by absorbing much harmful ultraviolet radiation. Ozone is continuously formed and destroyed naturally, creating a dynamic ozone–oxygen cycle. Human-made ozone-depleting substances such as CFCs and halons can release reactive chlorine or bromine in the stratosphere. These substances can participate in catalytic reactions that destroy ozone. Severe seasonal depletion is particularly prominent over Antarctica. Ozone depletion can increase UV-B exposure at Earth's surface and affect human health, plants, aquatic organisms and materials. International cooperation, especially through the Montreal Protocol, has significantly reduced the use of many ozone-depleting substances.

ओजोन परत समताप मंडल का एक महत्वपूर्ण भाग है जो हानिकारक पराबैंगनी विकिरण को अवशोषित करके पृथ्वी पर जीवन की रक्षा करती है। ओजोन का निर्माण और विनाश प्राकृतिक रूप से लगातार होता रहता है। CFCs और halons जैसे ओजोन-क्षयकारी पदार्थ समताप मंडल में सक्रिय क्लोरीन या ब्रोमीन उत्पन्न कर सकते हैं, जो ओजोन के क्षरण में योगदान देते हैं। अंटार्कटिका के ऊपर मौसमी ओजोन क्षरण विशेष रूप से महत्वपूर्ण है। ओजोन क्षरण के कारण पृथ्वी की सतह तक UV-B विकिरण अधिक पहुँच सकता है। इससे मानव स्वास्थ्य, पौधों, जलीय जीवों और कुछ पदार्थों पर प्रभाव पड़ सकता है।

CBSE Exam Key Point:
Ozone layer → Stratosphere → absorbs harmful UV radiation → CFCs/other ODS can cause depletion → reactive chlorine/bromine → catalytic destruction → increased UV-B exposure → health and ecosystem impacts → Montreal Protocol.

Our Environment | Ozone Layer and Ozone Depletion
CBSE Class 10 Science • Foundation • Competitive Preparation