Saturday, 2 April 2016

Ozone Layer Depletion

Ozone :

·  Ozone is a form of oxygen that has three atoms (O3) rather than the more common two atoms (O2).
·  Ozne constitutes only less than 0.002 percent of the volume of the atmosphere.

 ozone layer :

·  It is created in the upper atmosphere by the action of solar radiation on oxygen molecules.
·  As far as its position is concerned, it is found in the form of a thin layer in the stratosphere between 15 to 48 kilometre.
·  Ozne constitutes only less than 0.002 percent of the volume of the atmosphere.
·  About 90% of all atmospheric ozone is found in this layer.
·  It strongly absorbs ultraviolet radiation from the sun.
·  Ultraviolet radiation is biologically destructive in many ways.
·  It causes skin cancer and cataracts, suppresses the human immune system, dimimshes the yield of many crops, disrupts the acquatic food chain by killing micro-organisms on the ocean surface and many other negative effects which is still undiscovered.
·  This is happening due to certain recent human activities which have injected certain chemicals in the stratosphere which consume ozone and reduce its concentration.
·  Depletion is mainly caused by chlorofluorocarbons (CFCs), halons, methyl chloroform and carbon tetrachlorides.
·  These chemical substances are mainly either chlorine or bromine which can reach the stratosphere and catalytically break down ozone into oxygen.
·  CFCs are odourless, non-flamable, non-corosive and nontoxic.
·  For this reason, scientist originally believed CFCs could not possibly have any effect on the environment.
·  That is why it is widely used in refrigeration and air conditioning, in foam and plastic manufacturing and in aerosol sprays.
·  Not only is the ozone layer thinning, in some places it has temporarily disappeared.
·  A hole in the layer has developed over Antarctic since 1979 and that hole has persisted for a longer and longer time every year.
·  In 1988, an ozone hole was found over the Arctic for the first time and it too has lasted longer and longer each year since then.

Prevention :

Montreal Protocol of 1987 and London Conference of 1992 :
·  In both these conferences it was decided that the developed countries would totally ban CFC production by 2000 and the developing countries by 2010AD.
·  Even if it is sincerely followed and strictly implemented by all the 150
countries including India, who are signatory to Montreal Protocol even then the chlorofluorocarbon and chlorine shall continue their influance for another 100 years.

·  Therefore, all over the world research efforts are continuing for development of substitutes of CFC as coolants for refrigerators and air conditioners.