Ozone Layer

The earth’s atmosphere is enveloped by different layers but in the stratosphere it is covered by ozone gas. (Stratosphere extends from 12 km to 30 km above the Earth).

Ozone has three oxygen atoms while oxygen has two. Ozone protects mankind from harmful radiation called ultraviolet (UV) rays from the Sun. The UV light from the Sun causes reaction leading to making and breaking of ozone oxygen. The ozone layer absorbs potentially harmful UV radiation from the Sun (at wavelengths between 240 and 320 nm).

The main destroyers of the ozone are the CFCs (Choloro-fluorohydro-carbons) from air conditioners, refrigerators, aerosols, solvents and in production of some types of packaging) and nitrogen oxides from fertilisers and aircraft emissions occurring high in the troposphere (which rise up into the stratosphere) where they are broken by UV light into chlorine (which has a very devastating effect on the ozone). One atom of chlorine can destroy over 100,000 molecules of ozone. Depletion of the ozone layer will allow UV light of the undesirable wavelengths of penetrate the atmosphere and reach Earth’s surface. This causes skin cancer, severe sunburns and damage vegetation, among other things.

Every August, a hole in the ozone layer forms over Antarctica and closes in December. Since it was discovered in the 1980s, it has doubled to about the size of North America. Sometimes it extends over S.Chile and Argentina. During such time people in the city of Punta Arenas, Chile, don’t go out or limit their exposure to Sun for only 20 minutes per day.

Most countries no longer produce CFCs but it can remain in the atmosphere for many years-destroying the ozone layer and adding to the greenhouse effect. CFCs are being replaced by HFCs (Hydrofluorocarbons) but the latter again is a powerful green house gas-1200 times as powerful as carbon-dioxide. The move is now to replace the HFCs with hydrocarbons (HCs)-like isobutene or propane.