Ozone Depletion : A catasrophe in waiting

We humans are greedy animals. In the quest of our never ending needs and desires, we seem to have forgotten our nearest neighbors, to be exact, fauna, flora and the environment. In the present day rat race, we just gobble up all the resources of nature and overlook their replenishment. One such gift is the Ozone layer in the upper reaches of the Earth’s atmosphere.

            The Ozone layer is principally a stratum of the ozone (O_3, an allotrope of oxygen) gas, in upper stratosphere at about 50 kms above ground level, which blocks the hazardous “Ultraviolet (UV) Rays” present in the spectrum of the Sun. The UV rays are very harmful to all life forms on earth as their prolonged and excessive exposure leads to various kinds of dermatological ailments including skin cancer for animals and growth diminishment for plants. Yet we are unconsciously damaging the ozone layer thus jeopardizing our very own survival.

            In the later part of the 19^th century we had discovered the comfort of refrigeration. In the course of events, a group of chemical compounds called “chlorofluorocarbons” (CFCs) were developed which served as coolant in the process. The CFCs gradually found their use in aerosol sprays, domestic fire extinguishers etc., perpetually all kinds of pressurized packs.

Little did we realize that these useful appearing chemicals were silently creating a hole in the ozone layer. Surprisingly, this hole, of the size of U.S.A., was observed to be most prevalent over the frozen continent of Antarctica. Also, CFCs were known to be heavy molecules and chemically inert. Then how could they cause ozone depletion and that too predominantly over the South Pole, this question puzzled scientists for long before the following theory was proved.

            CFCs, once released in the atmosphere, move about near ground level for many years till they reach the equatorial region where due to direct heating by sunrays they rise up into upper atmosphere with the air. Further, due to the phenomenon of “Polar Vortex” (due to pressure variations air from sub polar regions moves to the poles in a clockwise fashion) they move over to the Antarctic region. Here the relatively inert CFC molecule, due to cosmic bombardment, breaks down to give a free chloride ion. This chloride ion breaks down the O₃ molecule into O₂ and chlorine monoxide (ClO). But this isn’t the end. The ClO further reacts with a free oxide ion to give O₂ and another chloride ion, and this chain reaction continues. This explains the massiveness of the damage.

            Another observation was that the ozone levels were found to be very low at the onset of the Antarctic spring. Scientists thought that there must be some catalyst present in the atmosphere at that time to aid the depletion. They found it to be ice crystals formed and suspended in the upper atmosphere during the 3-month long Antarctic winter night. So, even Mother Nature has a role in this deadly play.

            In addition to the earlier mentioned deadly consequences, a hard to swallow fact is that this depletion is also indirectly affecting food chains. One such chain can be visualized as follows:

§         UV rays will destroy microscopic algae “Phytoplankton” growing on the lower surface of polar ice sheets.

§         Another type of microscopic organisms called “Zooplankton” and polar sea creatures, which feed on phytoplankton, would decrease their number along with their predators.

§         When the polar ice sheets melt in summer, they carry the algae with them to the Southern Seas as food to the fish there. Fewer algae would mean lesser fish.

  So, we can see that our one measure for comfort has become a discomfort for us as well as others. To this if we add the problems of pollution due to burning of fossil fuels, Greenhouse effect due to excess amount of CO₂ , …. it’s making me breathless !!!

Shall we ever be able come out of this cloud ? If there is a solution we have to implement it fast, otherwise we all are going to be devoured by this menacing monster.

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Written by :-                         

SAYAK  CHAKRABARTI

Email: sayakch@lycos.com

B.Sc.(Hons) Electronics-II

Andc, Delhi, India.

Article Dated : 12-6-2001

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