OZONE LAYER DEPLETION

OZONE DEPLETION IN THE STRATOSPHERE:

  • ‘Bad’ ozone formed in the lower atmosphere (troposphere) that harms plants and animals.
  • There is ‘good’ ozone also; this ozone is found in the upper part of the atmosphere called stratosphere, and it acts as a shield absorbing ultraviolet radiation from the sun.
  • The thickness of ozone layer is measured in terms of  Dobson units (DU)
  • Ozone (O3) gas is continuously formed by the action of UV rays on molecular oxygen, and also degraded into molecular oxygen in the stratosphere.
  • There should be proper balance of formation and degradation of ozone.

Ozone depletion:

  • Balance of ozone in stratosphere is disrupted due to enhancement of ozone degradation by chlorofluorocarbons (CFCs).
  • CFCs find wide use as refrigerants.
  • CFCs discharged in the lower part of atmosphere move upward and reach stratosphere.
  • In stratosphere, UV rays acts on CFCs and release active Cl atoms.
  • Cl degrades ozone releasing molecular oxygen.
  • Cl acts as catalysts and not consumed during reaction.
  • Whatever CFCs are added to the stratosphere, they have permanent and continuing affects one Ozone levels.
  • The depletion is marked particularly over the Antarctic region. This has resulted in formation of a large area of thinned ozone layer, commonly called as the ozone hole.
  •  Cultural or Accelerated Eutrophication:

o    Pollutants from man’s activities like effluents from the industries and homes can radically accelerate the aging process. This phenomenon is called Cultural or Accelerated Eutrophication.

 

Causes:

·         Sewage and agricultural and industrial wastes.

·         Prime contaminants are nitrates and phosphates.

Effects on Environment:

·         Unsightly scum and unpleasant odors.

·         Robbing the dissolved oxygen form water.

·         Pollutant inflow kills the fish.

·         Decomposition of dead fish causes further depletion of DO.

·         Finally a lake can literally choke to death.

 Effects of UV rays:

  • UV radiations shorter than UV-B are almost completely absorbed by Earth’s atmosphere, if the ozone layer is intact.
  • DNA and proteins of living organisms are damaged by UV rays as they potentially absorb it.
  • The high energy of UV rays breaks the chemical bond in these molecules.
  • UV – B damages DNA and mutation may occur.
  • It causes ageing of skin.
  • Damage skin cells and causes skin cancers.
  • In human eye cornea absorb UV – B radiation and high dose of UV – B causes inflammation of cornea called snow-blindness, cataract etc.
  • Such exposes may damage cornea.

Prevention:

  • Montreal Protocol was signed at Montreal (Canada) in 1987 to control emission of ozone depleting substances.
  • Many efforts are being made to reduce emission of ozone depleting substances.

Leave a Reply

Your email address will not be published. Required fields are marked *

Related Articles

GREEN HOUSE EFFECT

Green house effect is a natural process that warms the earth surface from the radiations that are not reflected back to the atmosphere due to the presence of green house gases. Green house effect leads to global warming.

Contact

Feel Free To Email Us .At: