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The ozone layer that is present in the stratosphere region is a type of protective layer that saves us from harmful ultraviolet rays. The depletion of the ozone layer is mainly caused by the compounds containing chlorofluorocarbons or CFCs as they react with the ozone layer in the presence of UV rays of the sun in order to form oxygen molecules and destroy ozone in the process. Scientists have discovered a hole in the ozone layer above the South Pole. Once the layer is depleted completely, the harmful UV rays from the sun will be able to pass through the troposphere to reach the Earth.
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Key terms: Ozone Layer, Ultraviolet radiations, Stratosphere, Oxygen molecule, sun, chlorofluorocarbons
What is Ozone Layer?
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The ozone layer in the stratosphere absorbs the harmful ultraviolet radiations of the sun and hence protects lives on Earth.
- The ozone layer is found in the upper part of the stratosphere
- The ultraviolet rays break the oxygen molecule into free oxygen atoms.
- These free oxygen atoms combine with the oxygen molecule in order to form ozone.
The ozone layer acts as a shield protecting the earth from harmful ultraviolet radiation. The ultraviolet rays are harmful as -
- The ultraviolet rays lead to aging of the skin and cause various skin problems.
- It can cause skin cancer, cataract, and sunburn in humans as well as animals.
- The phytoplanktons in the water die in the presence of UV rays, therefore resulting in the destruction of aquatic life.
Also Read:
Causes & Effects of Ozone Layer Depletion
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The harmful effects of ozone layer depletion are -
- The increase in the evaporation of water through the stomata in leaves leads to a decrease in the moisture content of the soil.
- The protein cell present in plants undergoes harmful mutations due to the harmful ultraviolet radiation.
- Fibers and paints fade faster due to the damage by the increased exposure to ultraviolet rays.
Chlorofluorocarbons and other halocarbons that are responsible for ozone layer depletion are major greenhouse gases.
- They absorb heat in the atmosphere and increase the temperature of the earth, further causing global warming.
- An increase in the temperature on Earth leads to the melting of the ice caps.
- This in turn increases the water level in seas and oceans.
- Therefore, coastal areas are flooded and the area under land becomes less.
Also Read:
The Ozone Hole
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Scientists in 1980 reported the depletion of the ozone layer in the Antarctica region known as the ozone to hold commonly. The depletion of the ozone layer is caused due to unique climatic conditions. Nitrogen dioxide and methane in the summer react with chlorine atoms and chlorine monoxide in the atmosphere. This causes shrinkage of chlorine and therefore prevents ozone layer depletion.
ClO (g) + NO2 (g) → ClONO2 (g)
Cl (g) + CH4 (g) → CH3 (g) + HCl (g)
In winters, special clouds are formed over the Antarctic region. They provide the surface for the formation of hypochlorous acid by the hydrolysis of chlorine nitrate. Chlorine nitrate also produces molecular chlorine by reacting with Hydrogen Chloride.
ClONO2 (g) + H2O (g) → HOCl (g) + HNO3 (g)
ClONO2 (g) + HCl (g) → Cl2 (g) + HNO3 (g)
In spring, sunlight breaks up the clouds in Antarctica. Photolysis of Cl2 and HOCl form radical chlorine which initiates the depletion of the ozone layer.
Read More: Difference between air pollution and greenhouse gases
Prevention of Depletion of Ozone Layer
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The ozone layer depletion can be prevented by following these measures -
- Using eco-friendly products for domestic purposes.
- Reducing vehicular emissions that result in smog and harm the ozone layer. Therefore, encouraging carpooling and public modes of transport.
- Proper disposal of waste and avoiding burning waste materials such as plastic. Promoting reuse, reduce and recycle.
- Replacing CFCs in refrigerators and air conditioners with Hydrofluorocarbons (HFCs).
- Avoiding the use of pesticides to get rid of weeds and instead promote natural remedies.
Ozone layer is vital for our survival and protection from various kinds of diseases. Taking measures to protect the Earth from harmful ultraviolet rays can reduce the harmful effects of depletion of the ozone layer.
Things to Remember
- The ozone layer in the stratosphere prevents the ultraviolet rays of the sun from reaching the Earth and causing harm.
- Ozone layer depletion refers to the thinning of the ozone layer in the stratosphere region.
- The UV rays can cause various types of skin diseases in humans.
- The cause of depletion of the ozone layer is the ozone-depleting substances such as CFCs, carbon tetrachloride, etc.
- Montreal Protocol is a global agreement proposed in 1987 that focuses on the protection of the ozone layer by minimising the production and consumption of ODS or ozone-depleting substances.
Previous Years Questions
- Which is wrong with respect to our responsibility as a human being to protect our environment? [JEE Mains 2019]
- Ozone is destroyed by CFCs in the upper stratosphere Ozone holes increase the amount of UV…? [JEE Mains 2019]
- BOD stands for? [JEE Mains 2016]
- Biochemical Oxygen Demand (BOD) value can be a measure of water pollution caused by the…? [JEE Mains 2016]
- Addition of phosphate fertilisers to water bodies causes? [JEE Mains 2015]
- A water sample has ppm level concentration of the following metals…? [JEE Mains 2019]
Sample Questions
Ques 1: List the various greenhouse gases that are responsible for global warming. (3 marks)
Ans: The various greenhouse gases are:
- Carbon Dioxide
- Methane
- Nitrous Oxide
- Chlorofluorocarbons
Ques 2: Define good ozone. (2 marks)
Ans: Ozone absorbs ultraviolet rays coming from the sun and thus acts as a shield. Hence, it is known as good ozone. It is present in the upper part of the atmosphere, known as the stratosphere.
Ques 3: What is snow blindness and how is it caused to humans? (1 mark)
Ans: Snow blindness is a temporary pain in the eye of a human being caused by the extreme absorption of UV-B radiation.
Ques 4: What are the causes of the depletion of the ozone layer? Name the effects caused by this on human beings. (3 marks)
Ans: The disruption in the balance of production and the degradation of ozone is caused mainly due to CFCs. The ill effects caused to human beings are:
- The depletion of the ozone layer allows UV rays to penetrate into the atmosphere which increases the mutation and as a result damages DNA.
- It can cause damage to the skin cells and can also result in cancer.
- Snow blindness, cataracts, etc.
Ques 5: How can global warming be controlled? (5 marks)
Ans: It can be controlled by:
- The usage of fossil fuels should be reduced.
- Reducing the cutting down of trees.
- Planting more and more trees
- The efficiency of the usage of energy can be improved.
- Reducing the emission of greenhouse gases into the environment.
Ques 6: List the effects of Deforestation. (5 marks)
Ans: Due to deforestation, the following effects are caused:
- Hydrological cycle is disturbed.
- It can lead to soil erosion.
- Levels of CO2 concentration increase in the atmosphere.
- Deforestation leads to desertification in many cases.
- The habitat is destroyed which leads to the loss of biodiversity.
Ques 7: What are the results of improper resource utilization ? (5 marks)
Ans: The results are:
- Water logging and soil salinity
- Waterlogging in the soil occurs when irrigation is done without adequate drainage.
- It leads to the deposition of more salt on the surface of the land or near the roots of the plants.
- Soil erosion and desertification
- The formation of topsoil is formed over a long period of time.
- The topsoil which is fertile gets removed due to human activities like unrestricted grazing, poor irrigation practices, over-cultivation of land, deforestation, etc.
- Once the topsoil is removed as a result of these activities, the lands with barren patches are left for a long time, resulting in the formation of deserts.
- Due to increased urbanisation, desertification has become a major problem.
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