Ozone depletion

Ozone depletion mean two distinct but related observations.First is a slow, steady decline of about 4 percent per decade in the total amount of ozone in Earth's stratosphere since the late 1970s and a much larger but seasonal, decrease in stratospheric ozone over Earth's polar regions during the same period. The latter phenomenon is commonly called as the ozone hole. there are also tropospheric ozone depletion events, which occur near the surface in polar regions during spring.The detailed mechanism by which the polar ozone holes form is different from that for the mid-latitude thinning, but the most important process in both trends is catalytic destruction of ozone by atomic chlorine and bromine.The main source of these halogen atoms in the stratosphere is photodissociation of chlorofluorocarbon (CFC) compounds, commonly called freons, and of bromofluorocarbon compounds known as halons. These compounds are transported into the stratosphere after being emitted at the surface. Both ozone depletion mechanisms strengthened as emissions of CFCs and halons increased.The amount of ozone in the stratosphere is determined by a balance between photochemical production and recombination.Ozone can be destroyed by a number of free radical catalysts.


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