Ozone: Ozone O₃, a form of oxygen with 3 molecules, is a gas that is blue in colour. Ozone has a characteristic pungent smell. It occurs throughout the atmosphere but in small quantities.
It forms a shield above the earth in the atmosphere amounting only to 3 mm thickness. Under average conditions, at ground level, each cm of air contains around 10 1⁹ molecules of all gases of which ozone constitute only about 0.1ppm. 90% of ozone lies in the stratosphere which is located in between 15 to 50 km above the surface of the earth. It acts as a filter around the earth and it shields harmful rays such as ultra violet (UV) rays reaching the earth and it protects the earth.
Due to release of gases such as NO, NO₂, Cl, they easily react with ozone. Because of this the amount of Ozone in the atmosphere is decreased and it is known as Ozone Depletion.
Effects of Ozone Depletion:
Increase in UV radiation in the earth
UV rays induces change in DNA and creates skin cancer
It affects Immune System
Quality and quantity of crops will be affected due to change in aquatic and terrestrial ecosystem
It affects quality of air, splitting of O₃ and production of hydrogen peroxide H₂O₂, which results in the damage of human health, terrestrial plants and other creatures.
It affects the growth of early stage of fishes, crab, amphibians and other animals.
Ozone Hole is nothing but the Ozone depletion extending over the entire Antarctic continent forming a hole in the Ozone layer. As a result the biologically active part of Ultra Violet rays called UV-B. This penetrates the ground and it causes health hazards in human, animals and wetland plants.
If UV-B is not filtered by the Ozone shield, it causes, skin cancer, changes in melanin pigmentation, seriously reduces ours body’s immune system, causes damage to eyes resulting in cataracts, increase infectious diseases. In plants , the photosynthesis rate falls down, resulting in poor seeds and fruits and its quality and quantity.
Ozone Hole can be controlled by avoiding the usage of CFC, Halogens Carbon tetrachloride, Methanol, Chloroform and by controlling overall pollution.