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Write the adverse effects of depletion in Ozone and how it can be controlled?

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Ozone is a gas and its symbol is O3. It gives a smell of rotten fish. The concentration of the ozone is measured at the surface of earth with the help of dobsonmeter. The unit of measurement is dobson unit (DU) and 1DU is equal to 27 million ozone molecules per cm³.90% of atmospheric ozone is situated in the stratosphere at a height from 15 to 30 km. [12 to 35 km. range] but at the poles the height is only 8 km. The concentration of ozone in the ozone layer is found to be 300 DU.

In the nature, ozone is formed as follows (Given by Sydney Chapman (1930).


The ozone absorbs cosmic rays and U-V rays, and protect the Earth’s life (animals, human beings, plants etc.) from the harmful effects of radiation.

Depletion of Ozone :
There is depletion in the ozone at many places due to increase in environmental pollution. For example, depletion in the ozone concentration is observed over Scandinavian countries (Sweden, Denmark, Norway and Northern part of Finland).

Forman, Gardiner and Shanklin reported, in Nature of May, 1985, a 70% depletion in Ozone over the Antartica. It is named as Ozone hole. In this region, the Ozone concentration is reduced to 117 DU from 300 DU. The diameter of the Ozone hole varies from 83 to 100 lakh Square Mile.

The most affected country because of to ozone hole is Australia. The increase in the radiation due to Ozone hole resulted in skin cancer, cataract and a significant decrease in the production of rice, as UVB killed Cyano-bacteria found in the roots of paddy plants as symboiont. During winters PSC (Polar Stratospheric Clouds) are formed over the Antartica and the sunlight fail to reach upto the pole. As a result winters at Antartica is total dark and the temperature is droped upto -80°C. In this conditions, PSC develops Ice particles containing NAT (Nitric Acid Trihydrate). These ice particles provide surface for the chemical reactions and NAT reacts with CFC to release Chlorine radicles. These chlorine radicles destroy ozone and resulted in the formation of ozone hole.

Factors responsible for Ozone depletions :
The main factor that cause Ozone depletion are as follows

  1. CFC (Chloro Floro Carbon), CBC (Chloro Bromo Carbon) and BFC (Bromo Floro Carbon). These compounds are collectively called as Freon and they are highly voltile organic compounds. They are used in refrigeration industries, Aerosols, formation of foam, cleaning of many industrial machines etc. The CFC compounds release Chlorine radicals which remain active for about two years and destroy 1 lakh molecules of Ozone by chain reaction.

2. Nitrogen Oxides (NO—Nitric Oxide. N3O—Nitrous oxide)- They are released mainly by the chemical fertilizers and they destroy the Ozone.

3. Jet Aeroplanes – Most of the jet aeroplanes prefer to fly in/close to the stratosphere. The jet of air and other pollutants released by them harm the Ozone.

4. Nuclear blasts also harm the Ozone.

5. Deforestation is also a major cause of Ozone depletion.

6. Sulphur oxides (SO3. SO3) and Hydrochloric acid (HCl).

Adverse Effects of Ozone Depletion :

  • Increase in skin cancer and cataract in the eyes.
  • Depletion in paddy and other cereals production.
  • Disturbance in the marine food chains.

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