Ozone layer serves as a protective umbrella to save the living being on the earth from danger radiations like ultraviolet rays, cosmic rays. Ozone layer is a natural gift for living creatures offered by nature. But it is being destroyed by the production of greenhouse gases like CO₂, CO, NO, NO₂, SO₂, SO₃, CH₄, C₂H₆, CFC, etc due to human activities such as industrialization, deforestation, combustion of coal, diesel, wood and scientific research.

These gases diffuse from earths surface forming a hazy layer to the stratosphere region where they react with ozone and make a hole in the ozone layer. The phenomenon formation of a hole in the ozone layer by destroying it with greenhouse gases like NO₂, SO₂, SO₃, CO₂, CO, NO, NO₂, CH₄, C₂H₆, CFC is known as ozone layer depletion.

In 1958, NASA scientists observed a hole in the ozone layer over Antarctica and it has been found that the ozone layer is depleting at an alarming rate. Although all greenhouse gases are partially responsible for the depletion of the ozone layer, the main culprits are CFCs i.e. chlorofluorocarbon or Freon’s which is extremely stable, non-corrosive and inert compounds. It is thought that one molecule of CFC has capability to destroy one lakh molecules of ozone (O₃).

The probable mechanism of ozone layer depletion is;

         CFCl₃ ————> CFCl₂^˚ + Cl^˚

         Cl^˚   + O₃ ————-> ClO˚ + O₂

             ClO˚ + O ————-> Cl^˚ + O₂

The reaction goes on utill the ability to destroying by ClO˚ ion is ceased.

Effect of Ozone layer depletion      

The effects of ozone layer deflection are

1. The UV rays directly reach to the earth and affect the living being on the earth.
2. It causes global warming due to the heating effect of UV light.
3. It destroys the green plants and small creatures.
4. It can burn skin and causes blindness.
5. It decreases the fertility rate and resists the growth.
6. It destroys fertile land and decreases crop productions.

Controls measures

It can be controlled by

1. CFC producing refrigerator, spray can, air condenser should be prohibited.
2. Combustion of fossil fuel, plastic and diesel should be diminished.
3. Bombarding should be controlled.
4. People should be given the knowledge ozone layer.

CFC(ChlorofluoroCarbon)

At the first time CFCs were considered as a miracle chemicals because of the non-reactive, non-toxic, non-inflammable and stable nature of CFCs. They were used as coolant in the refrigerators, air conditioners, spray can etc for long time.

But later, it has been found that CFCs are the major culprit for the ozone depletion. Therefore, now a day, the use of CFC is replacing by other molecules like ammonia as a coolant. CFCs are released by the operation of such refrigerants, aerosol can, burning of plastics, hydrocarbons and diffuses to the stratosphere. In the stratosphere, CFCs react with ozone molecules.

Since CFCs are extremely stable and nonreactive, they can persist for a long time and diffuse into stratosphere where they get dissociated by ultraviolet radiations.

It is believed that one molecule of CFC can destroy one lakh molecules of O₃ continuous which forms the hole in the ozone layer.

The probable reaction is 

         CFCl₃ ——-> CFCl₂^˚ + Cl^˚

         Cl^˚  + O₃ ———> ClO˚ + O₂

           ClO˚ + O ——-> Cl^˚ + O₂

The reaction goes on till the ability of destroying by ClO˚ ion is ceased

Effects of CFC

1. Depletes the ozone layer due to which UV rays reach the earth.
2. It causes global warming.
3. It invites the destruction of living being due to enter of UV rays.

Controls measures

1. CFCs must not be used in cooler, air condenser
2. Plastic should not be burnt but recycled.
3. CFC producing appliances must be banned.
4. It can be controlled by making awareness about the effect of CFC.

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