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Ozone Layer Depletion its causes and effects - Practice Questions & MCQ

Edited By admin | Updated on Sep 18, 2023 18:34 AM | #NEET

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Ozone Depletion in the Stratosphere is considered one of the most asked concept.

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Ozone Depletion in the Stratosphere

The ozone found in the upper part of the atmosphere called the stratosphere, is called good ozone.
It acts as a shield absorbing ultraviolet radiation from the sun.
UV rays are highly injurious to living organisms since DNA and proteins of living organisms preferentially absorb UV rays, and its high energy breaks the chemical bonds within these molecules.
The thickness of the ozone in a column of air from the ground to the top of the
the atmosphere is measured in terms of Dobson units (DU).
Naturally, ozone gas is continuously formed by the action of UV rays on molecular oxygen, and also degraded into molecular oxygen in the stratosphere.
There should be a balance between production and degradation of ozone in the stratosphere.
Of late, the balance has been disrupted due to enhancement of ozone degradation by chlorofluorocarbons (CFCs).
CFCs find wide use as refrigerants.
CFCs discharged in the lower part of the atmosphere move upward and reach the stratosphere.
In the stratosphere, UV rays act on them, releasing Cl atoms.
Cl degrades ozone releasing molecular oxygen, with these atoms acting merely as catalysts; Cl atoms are not consumed in the reaction.
Hence, whatever CFCs are added to the stratosphere, they have permanent and continuing effects on Ozone.
Although ozone depletion is occurring widely in the stratosphere, the depletion is particularly marked over the Antarctic region.
This has resulted in formation of a large area of thinned ozone layer, commonly called the ozone hole.
UV radiation of wavelengths shorter than UV-B, are almost completely absorbed by Earth’s atmosphere, given that the ozone layer is intact.
But, UV-B damages DNA and mutation may occur.
It causes aging of skin, damage to skin cells and various types of skin cancers.
In the human eye, cornea absorbs UV-B radiation, and a high dose of UV-B causes inflammation of cornea, called snow-blindness cataract, etc.
Such exposure may permanently damage the cornea.
Recognising the deleterious effects of ozone depletion, an international treaty, known as the Montreal Protocol, was signed at Montreal (Canada) in 1987 (effective in 1989) to control the emission of ozone depleting substances.
Subsequently many more efforts have been made and protocols have laid down definite roadmaps, separately for developed and developing countries, for reducing the emission of CFCs and other ozone depleting chemicals.