Ozone Layer & It’s Depletion
What is ozone layer and where it is found?
Ozone (O3) is a form of oxygen (O2) which is colourless and has a very harsh odour. Earth is surrounded by various layers of atmosphere. One layer of ozone (O3) is found at an altitude of about 20-25 kms situated in Stratosphere. 90% of ozone in atmosphere is found here.
How Ozone layer protects us?
The ozone layer is like a sun screen and it is very important because it blocks harmful solar radiation in the form of Ultra Violet Rays (UV Rays).
The UV rays can cause tanning of skin, skin cancer, eye blindness. It also affects all animals and plants. In absence of Ozone layer the existence of life is difficult.
What is ozone hole?
In 1979 scientists observed the hole in the ozone layer over Antartica. This hole was very big which was 10 times bigger that United States (USA) and consequently a smaller hole observed over Artic. The average area of the hole observed since 1991 has been roughly 10 million square miles. Since 1980 the signs of thining observed all over the globe. It was evident from the atmospheic observations taken from Antartica.
Scientists have discovered that the ozone hole over Antarctica started in 1979, and that the ozone layer generally started to get thin in the early 1980s.
Is Ozone layer depleting?
Until 1970s, scientist discovered that ozone level was stable. Since 1979 the severe depletion of ozone started over Antartica. The main cause of depletion is industrial halocarbons which synthetic compounds emiting chlorine and bromine.
Which type of halocarbons affect the ozone layer?
Halocarbons such as Chlorofluorocarbons (CFCs) accounts for 80% of ozone depletion . They are widely used as coolants in refrigeration and air conditioners. Other halocarbons are Methyl Bromide, Carbon tetrachloride.
CFCs are used because they are not poisonous and do not catch fire. Many countries have now stopped using new CFCs.
Why halocarbons destroy ozone?
Halocarbons destroys ozone layer for three reasons:
1) Firstly, halocarbons are not reactive and remain in the atmosphere for long time. Moreover they are neither washed back to Earth by rains nor they are being destroyed in chemical reactions.
2) They act as a catalyst, means they help other natural reactions to destroy zone without affecting itself.
3) They can remain in the atmosphere from 20 to 120 years or more.
What is the chemical process by which ozone is destroyed?
The halocarbons like CFCs once reach the stratosphere, it reacts with UV radiations to form chlorine. Then chlorine speedup ozone depletion. A single atom of chlorine destroy upto 1,00,000 ozone molecules.
