The stratosphere layer of our atmosphere contains considerable amount of ozone which protects us from the harmful ultraviolet rays of the sun, which can cause skin cancer in humans.
What is ozone hole?
Ozone is thermodynamically unstable and decomposes to molecular oxygen. Thus, a dynamic equilibrium exists between production and decomposition of ozone.
In recent years, the main reason for ozone layer depletion is found to be the release of chloro fluoro carbons(CFCs), also known as freons. These compounds are non reactive, non flammable, non toxic organic molecules and therefore used in refrigerators and air conditioners.
Once CFCs are released in to the environment, they mix with other gases and reach stratosphere. In stratosphere, they get broken down by UV rays in to chlorine free radicals. Thus, CFCs are transporting agent for continuosly generating chlorine radicals and thus depleting the ozone layer.
In 1980s, the atmospheric scientists working in Antarctica reported about depletion of ozone layer commonly known as OZONE HOLE over the South Pole.
It was found that a unique sets of conditions were responsible for ozone hole. In summers, nitrogen dioxide and methane react with chlorine monoxide and chlorine atoms to form chlorine sinks preventing ozone layer depletion.
Whereas in winter special types of clouds called polar stratospheric are formed over Antarctica. These polar stratospheric clouds provide surface on which chlorine nitrate formed gets hydrolyzed to form hypochlorous acid. It also reacts with Hydrogen Chloride produced to form molecular chlorine.
When sunlight returns to Antarctica in spring, the sun warmth breaks up the clouds and HOCl and Cl2 are photolyzed by sunlight. The chlorine radicals thus formed initiates the chain reaction.
Harmful effects of ozone depletion
With the depletion of ozone layer, more ultraviolet rays filters in to the troposphere.
UV radiations lead to ageing of skin, cataract, sunburn, skin cancer, killing of many phytoplanktons, damage to fish productivity.
It has also been reported that planet proteins are easily affected by UV rays which leads to harmful mutation of cells.
It also increases evaporation of surface water through the stomata of the leaves and decrease the moisture content of the soil.
Increase in UV rays damage paints and fibres causing them to fade faster.