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Understanding ozone depletion

Ozone is a protective layer that surrounds the earth. Due to various forms of man made pollution there are holes forming in the ozone layer. If we do not take preventive action this continent sized hole will grow even bigger and have harmful effects for the planet.

What is the ozone layer?

The ozone layer is not a new discovery. Neither is the reduction in the ozone layer. Two French physicists Charles Fabry and Henri Busson discovered the ozone layer way back in 1913. Ever since 1970’s mankind has known that the ozone layer is depleting. Ozone is chemically represented by the symbol O3. So where do you find this layer? It is located some 10 to 50 kilometres above the surface of the earth. You will find most ozone concentrated between 20 to 40 kilometres above the surface of the earth. The distance of the ozone layer varies across the earth. The ozone layer is closer to you when you stand at the poles, than when you are in the tropical region of our planet.

Ever since 1970’s mankind has known that the ozone layer is depleting.

How is it formed?

The ozone layer is a result of ultraviolet rays striking oxygen molecules. When this happens, the two atoms of oxygen is split which then combines with unbroken molecules of oxygen to form ozone. The molecule of ozone is unstable, so when light hits this ozone it splits it further into molecular oxygen and an atom of atomic oxygen.

Why can’t we live without it?

The ozone layer is important in preventing the sun’s harmful ultraviolet light from affecting the earth. The ozone layer acts like an umbrella blocking out harmful radiations. The ozone layer is so effective that it absorbs 93 – 99% of this radiation. This radiation is harmful to humans. An excessive amount of ultraviolet B rays is known to cause skin cancer and cataracts in both humans and animals. Ozone depletion can also affect the growth of important food crops like rice. Phytoplankton in the sea is also affected by the effects of UV rays.

How is it disappearing?

Certain chemicals called free radical catalysts cause the ozone layer to disappear. These substances are called ozone depleting substances. Examples of such catalysts are nitrous oxide (the largest ozone depleting substance), atomic bromine, hydroxyl and atomic chlorine. These are very powerful chemicals. Just one atom of chlorine can destroy over thousand molecule of ozone.

Just one atom of chlorine can destroy over thousand molecule of ozone.

Why are CFCs bad?

These chemicals were contained in chlorofluorocarbons (CFCs) that were commonly used as aerosols, refrigerants. These substances were widely used because they were stable, non-flammable, not toxic and cheap to produce. When old fridges and air conditioners that used these chlorofluorocarbons were disposed, harmful chemicals were often released these into the environment.

In 1974 scientists discovered the harmful effects of these chemicals. CFCs do not dissolve in rain and there is no natural process that can remove the compounds of CFC from the environment. Due to exposure to strong UV radiation CFC’s release atomic chlorine, which we have already learned has such a harmful effect. Since 1996, there has been a ban on the use of CFCs. This has helped reduce the amount of chlorine present in the atmosphere. However it will take fifty years to heal the ozone layer naturally.

What are we doing about it?

One of the preventive steps taken to reduce the impact on the ozone layer is the signing of the Montreal protocol in 1987. This is an agreement between 191 countries to reduce ozone depleting substances.  This joint approach has lead to a small reduction in the amount of these harmful substances. Today September 16th is recognised as the International Day for the Protection of the Ozone Layer. This was established in 1995 by the United Nations.

Tags :     History and Future     Ozone depletion     Charles Fabry     Henri Busson     Phytoplankton     CFC     aerosols     refrigerants    


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