Largest Ever Ozone Layer (Picture courtesy of NASA)In recent decades, media tell about a 'hole' in the ozone layer have appeared with regularity. And each year the 'hole' is getting bigger and bigger until it reaches the biggest ever like the one displayed in the photo above. The true fact is maybe around 75% of the ozone over the South Pole (the picture above shows the ozone hole over the South Pole) disappears in the south polar spring when the hole develops but it returns to near normal levels in the autumn.
Now what is exactly ozone? Ozone (O3) is toxic to all life forms at high concentrations, but it is an unavoidable fact that this Oh-Three gas is important in the atmosphere because it acts as a shield to protect the earth from relentless solar radiation. If more ozone layer was depleted, more solar radiation will batter the earth causing a dramatic increase in the incidence of various skin tumours and eye cataracts.
The most contributors of the ozone depletion is the excessive use of chemicals like chlorofluorocarbons or CFCs, this is familiar to many as the Freons used widely in (old) air-conditioners and (old) fridges. Why those CFCs are very popular in use? The asnwer is simple: because they are inexpensive and very stable, yet not toxic, flammable nor corrosive. CFCs are ideal for many applications. They are used in aerosol cans as propellants, as solvents, as refrigerants (like the ones used in old air-conditioners and old fridges), as fire extinguishers and even they are ideal for blowing bubbles into fomaed plastic insulation.
But alas, the stability of the CFCs itself that takes the toll! CFCs do persist in the environment or in the atmosphere, it makes the chemical to slowly find the way to the upper atmosphere where they go through a series of reactions that eventually result in ozone depletion. These series of reactions involve ultraviolet light from the sun which strikes a CFC moelcule. The carbon-chlorine bond is broken, producing a very reactive free radical Cl.. The chlorine free radical then reacts with ozone to produce oxygen and ClO. The chemical reactions that take place is depicted below:
CFCl3 ---------------> CFCl2 + Cl.
Cl. + O3 -----------> ClO. + O2
Recognition of the problem led governments in the world to take action before it's gone too late. And worldwide efforts to reduce the use of CFC began with an international agreement reached in 1987. A total ban of CFCs was reached in 1996 worldwide including in our country, Indonesia.
(Written by Yari NK, simplified from various sources)