Ozone (O3) layer is present in the stratosphere which acts as a natural sunscreen. It absorbs the harmful Ultra violet (UV) radiations coming from the sun which can cause DNA mutation and Skin cancer. In the absence of Ozone layer the temperature of lower atmosphere will rise.
Formation of Ozone: It is formed in stratosphere by a photochemical reaction
O2 + hv → O + O
The atomic oxygen reacts with the molecular oxygen to form Ozone.
O + O2 + M (Third body) → O3 + M
M is the third body which carry away the excess energy liberated in the reaction and stabilize O3 molecule.
Depletion of Ozone layer: Ozone can be destroyed by a number of free radicals like Nitric oxide (NO), Bromine (Br) and atomic Chlorine (Cl). These elements are found in stable compounds like Chlorofluorocarbons (CFCs) which are used as Refrigerants. The CFCs are mainly responsible for ozone depletion in stratosphere. CFCs are used as coolants in Refrigerators and air conditioners, as cleaning solvents and as propellants. CFCs reached the stratosphere, remain there for many years and deplete the ozone layer. A single molecule of CFC can destroy tens of thousands of ozone molecules.
Ozone layer, depletion, stratosphere, ultra violet, UV, radiations, skin cancer, DNA, nitric oxide, bromine, chlorine, CFCs, refrigerants, propellants