What Is Ozone Depletion?
Ozone can be founded as a concentrated thick layer, at varying heights from 16 km to about 40 Km at different latitudes. In the stratosphere, ozone (O3) is formed naturally when oxygen is dissociated by ultra violet rays of the sun in the eave length region of 80 to 240 nm.
Dissociated ozone molecules react with other oxygen molecules and with some third party molecules (most likely nitrogen of the atmosphere). This third body molecule doesn’t undergo any change during the reaction. This formed ozone, then absorbs UV-B radiations (frequency of 200 to 300 nm) that would otherwise reach to the earth’s surface. This absorbance of UV-B radiations dissociates ozone again into oxygen molecule, but it protects earth’s atmosphere from harmful UV-B radiations. Now, depletion of this protective layer of stratospheric ozone will increase the amount UV-B radiations reaching to the earth’s surface. These UV-B radiations are extremely harmful for the human beings; their exposure increases the chances of skin cancer.
Reasons of ozone depletion
The three main areas, where human activities can influence the ozone cycle, have been the direct emission of the NOx by supersonic transport flying above the tropopause, additional transport of nitrous oxide as a result of increased use of nitrogenous fertilizers, and the formation of atomic chlorine in the stratosphere from chloro-fluro carbons (CFCs- used as industrial solvent, aerosol propellant and refrigerant) released in the troposphere. Halons, are also ozone depleting compounds. These are actually bromo fluro carbons or bromo chloro fluro carbons, which are important components of fire-extinguishers. Release of halones is very less as compared to CFCs, but they are 10 times more harmful then CFCs.
Ozone depletion by NOx
Actually the release of NOx from the supersonic planes causes depletion of the ozone layer in the specific pattern. NO reacts with ozone, to produce oxygen molecule and molecule of nitrogen di oxide. This nitrogen di oxide then react with dissociated oxygen radical to further produce the molecule of NO and oxygen. The net effect of this pattern is the destruction of the ozone molecule. NO recover itself at the end of the reaction, so it acts as a catalyst of the reaction. Therefore it can participate in the reaction for several no. of times.
Ozone depletion by CFCs
CFC molecules are inert in nature, but when they get accumulated in larger amounts at high altitudes, and then they release chlorine molecules under the influence of energy provided by UV radiation. Reaction leads into formation of “chlorine” and “ClO” radicals. Chlorine molecules then react with ozone to dissociate it into “ClO” and oxygen. Free oxygen radicals then react with above produced “ClO” to further produce more chlorine molecules. This cycle goes on and before the final precipitation of chlorine molecules; they destroy thousands of ozone molecules.
Event of ozone depletion was first observed in Antarctic zone. A huge ozone hole was discovered in the zone, this hole is expanding day by day, similar hole can also be observed over some Australian land.
Effects of ozone depletion
Ozone layer is extremely important for existence of life on planet earth. This layer protects plants, humans and animals from harmful UV-B radiations of sun. Earth is the only planet of solar system which is protected by ozone layer. UV-B radiations are able to damage genetic make-up of living beings, they are chiefly responsible for the events of skin-cancer. Their presence also accelerates the events of global warming and non-formation of the important stratospheric winds.
