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| NINTH LARGEST OZONE HOLE |
Ozone is an allotrope of
oxygen consisting of three oxygen atoms. It is found in earth’s atmosphere,
mainly in stratosphere located 10-15 km above earth’s surface and is called as
ozone layer. Ozone layer acts as a natural cover and prevents the ultraviolet
rays to reach the earth’s surface by absorbing most of them. This prevents harm
to plant’s and animal’s life, reduce sun burn and cancer as well as reduce the
risk of mutation.
Human activities are the
greatest cause of the upset of delicate ozone balance. Depletion in ozone is
caused by release of ozone depletion substances (ODS). Volcanic eruptions may
eject chemicals such as chlorine and methane gases that react with and break
ozone apart. One of the main ODS is chlorofluorocarbons (CFCs) commonly known
as Freon. Freon is mainly used in refrigerators, propellants, foaming agents,
fire extinguisher agents etc. Oxides of nitrogen also destroy ozone
catalytically. The sources of oxides of nitrogen are mainly thermonuclear explosions.
Another ODS is carbon tetrachloride which is used in dry cleaning sprays, spray
adhesives etc.
Loss of ozone in the
stratosphere was first observed in 1970s by a research group from the British
Antarctica Survey (BAS) who was monitoring the atmosphere over Antarctica from a research station. It has noticed that more
than 50 % of stratospheric ozone is decreasing every year in Antarctica
forming pockets known as ozone hole.
Ozone layer depletion results
in solar UV radiation’s penetration to the earth surface which causes eye
diseases, skin cancer, functioning of immunity system and other infectious
diseases. In plants, UV radiations affect leaf size and reduce crop yields. It
has found to cause damage in early development stages of fish, crabs etc. Ozone
layer depletion is also associated with global warming.
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