It is tri atomic oxygen (03) and is a gas found in the troposphere as well as in the stratosphere. Tropospheric ozone is undesirable since it is a pollutant these, causing photochemical smog and greenhouse effect. In the stratosphere, it acts as a protectant since,
(i) It absorbs the dangerous UV-radiations
(ii) It helps to trap the weather pattern within the troposphere, by generating a temperative inversion in the stratosphere.
Tropospheric ozone is increasing due to human activities, while stratospheric Or, is decreasing. This decrease is called Ozone Depletion
Ozone depletion deals with the steady decline in the concentrations of ozone in the stratosphere due to its faster destruction by chemicals released by man into the environment.
Depletion is mainly caused by chlorofluoro carbons (CFCs), halons, methyl chloroform and carbon tetrachloride. There substances contain chlorine or, bromine which, can reach the stratosphere. These elements are capable of catalytically breaking down ozone into oxygen.
Ozone depletion can also be caused by supersonic jet exhausts. They liberate NO which reacts with 03 to form N02 and 02
The area on the earth falling under the ozone hole is unprotected from the destructive UV-radiations, during the ozone whole period. Even with 03 depletion, the global rates of UV-flux is on the increase as we are receiving more UV-radiations on the earth’s surface now than before.
These radiations can cause damage to human health, ecosystems and to the global climate. They can cause skin cancers and catatracts of the eye, as well as decrease the immune reactions, making humans vulnerable to infections, diseases.
They can also kill plankton, thereby destroying the marine ecosystems. Many plants are also unable to tolerate an increase of whole ecosystems, threat to the food security of the world, are some of the other effects. Ozone depletion can also result in a stratospheric cooling and greenhouse effect in the lower layer.