OZONE  DEPLETION AND ITS CONSEQUENCES 
PROF WAQAR HUSSAIN HEAD OF CHEMISTRY DEPARTMENT (14/29-A SAMANABAD LAHORE)03336700587 /04237594038
      Science has progressed astonishingly in the recent years. It has completely mechanized this world and is stepping to hold nature under its thumb, but all these blessings seem to be a Pandora's box; the sidelined complications of various inventions are far more threatening than their rewards. It is rightly said: “In nature there are neither rewards nor punishments, there are only consequences”.
        National Aeronautics and Space Administration (NASA) stated that ozone layer is corroding much quicker than it was estimated by the world scientists. Here are some facts about the ozone layer and its depletion. These will help in starting the campaign against forthcoming peril and to mark World Environment Day 2012; commemorated on every 5th June to create awareness about major environmental hazards and enhance political attention and public action. This year theme is “green economy: does it include you”. Green Economy is that which improve quality of life without sacrificing environment.
      What is ozone? An oxygen molecule comprises of two atoms while ozone has three atoms. Oxygen and ozone are allotropic forms, abbreviated as O2 and O3 respectively. Oxygen is a colourless and odourless while Ozone is a blue coloured, pungent smelling gas. The action of electric discharge converts oxygen to ozone but the former is more stable. Nature has provided a thick layer of ozone in upper atmosphere "stratosphere" enclosing the earth. It blocks the dangerous ultraviolet (UV) radiation (280-315nm) from reaching the earth and acts as a protective shield for the biosphere. Ozone belt is present in atmosphere between 10-30 miles from the earth.
·         The cause of depletion of ozone is due to presence of chlorofluorocarbons (CFCs) in the atmosphere. Chlorine atom which is the part of CFCs disintegrates ozone molecules. How do Chlorine reach the ozone layer? The answer is: CFCs manage their way to the upper part of ozone layer as they remain nonreactive on the earth and lower part of ozone belt.
·         In the upper part of the belt, UV rays interact with CFCs and liberate chlorine which reacts chemically with ozone to form oxygen and chlorine-monoxide:
      ClFC+O3 +U.V. rays--- ClO+ O2
This chlorine-monoxide reacts chemically and releases chlorine again. In this way just one chlorine atom destroys one lakh ozone molecules.
It is evident that ozone layer can be protected if chlorine is stopped from reaching it. Chlorine maneuvers to get as far in the flying saucer of CFCs. We can say ironically that CFC stands for Chlorine's Flying Car. So the use of CFC must be restricted or abolished: there is only Hobson's choice.Other cause is spring time polar tropospheric depletion.
        By 1975, the chlorine concentration was 1.4 parts per billion (ppb) now it is about 3--enough to create holes in the ozone layer. Ozone volume is declining at a rate of 4% per decade. The first hole was discovered above the South Pole and was called the Antarctic Hole with a size equal to that of USA and depth, Mount Everest can sink. In fact,G.M.B.Dobson was first to observe ozone hole in 1956.He was surprised to find 320 DU of ozone, about 150 DU below spring level but his discovery could not get the world attention. The second hole is above the Arctic Ocean.
          Chlorofluorocarbons are used in billions of refrigerators and car air-conditioners of the world. They are widely used in manufacture of plastic, foam, pesticide, perfumes, aerosol spray, etc.
            If countries are grouped according to the use of CFC; the first would contain the USA, former USSR, Japan, European countries etc.The second group comprises Canada,Brazil,Australia,South Africa,Pakistan,China etc.The list of third group is quite long.Once it was reported that the production of CFCs by the USA and European countries was 7,50,000 tones. Former USSR alone had a figure of 60,000 tones. This shows which countries are responsible for hanging the Sword of Damocles over the head of entire world. UNEP estimated that 7000-14000 tones of CFCs are smuggled annually to developing countries.There is 5791000 tones of CFCs in existing items.Approximately one-third of it will be emitted in next decade.
         When 1% ozone layer is depleted, 2% more UV reaches earth. Ultra-violet radiation causes diseases of eyes (e.g. cataract). Some 17 million more cases of cataract are expected in near future. Skin cancers, both benign basal and squamous cell carcinomas and lethal malignant carcinoma, are linked with UV exposure, ozone depletion has increased the incidence of cancer by 2%. With 10% increase of UV, 35% melanoma cases increase. According to an estimate 60 million American born by 2075 will get skin cancer and 1 million will die. UV leads to increase ground level ozone which is toxic due to its oxidant properties. At ground level, UV interacts with vehicle exhaust gases to produce ozone. Scientists took skin biopsies of 150 whales in the Gulf of California and found acute sunburns of skin by excessive UV radiation. UV also enhances incidences of malaria and other infectious diseases; premature signs of old age and weakening of our defense mechanism against diseases.
         These rays kill the plankton so all animals feeding on plankton would also die, so ocean will be hit hard. UV reduces the yield of crops. The low production of crops in Australia and the Argentina is attributed to be the effect of UV rays. Rice production depends on nitrogen fixing cyanobacteria present on their roots. These bacteria are sensitive to UV rays as a result rice crop is affected. Further wind pattern will alter thus climate will suffer a drastic change throughout the world. Unpredicted rains, nasty droughts, furious floods, animals’ migrations—all will hit mankind.  
          The world is striving to save the ozone belt. The advanced countries are planning to manufacture refrigerators and air-conditioners without CFC. The refrigerators already in use will be destroyed after capturing CFC. In this way, CFC will not be able to reach the atmosphere. Many alternatives of CFCs were tried. Hydro fluorocarbon HFCs are now being used in automobile air conditioners. Hydrocarbon refrigerants (a propane/isobutane blend) are used in mobile air conditioner in Australia.
             The US government has enforced a law saying that refrigerators which have ceased to function normally will not be allowed to dispose off without taking possession of CFC first. In 1987, Montreal Protocol called for drastic reduction in the production of CFCs. In 1989,12 countries of European Community agreed to ban the production of CFCs by 2000.In 1990,diplomats in London voted for complete elimination of CFCs by 2000 and in 2010,CFCs should have been completely eliminated from developing countries In 2007, 200 countries agreed to accelerate the elimination of CFCs by 2020.Developing countries were given time until 2030. . Efforts are on but with no significant advancement.
             Scientific analysis reveals that the CFCs already present near the ozone will remain active for a hundred years. It means if we abolish the use of CFC, the escaped CFC will continue to eat up ozone for the next hundred years.
           The question arises whether nature has any arrangement for the production of ozone to compensate this loss. The answer is, yes.
Ozone is produced on the earth by the interaction of sunlight and hydrocarbons. But it has a weak chemical bond and it suddenly transforms into stable oxygen. Even if it doesn't convert into oxygen, it is very difficult for ozone molecules to reach the layer. In the stratosphere, UV of 240nm interacts to produce ozone but in a quantity far less than is being destroyed. Second, UV of 300 nm disintegrates ozone. So net production is almost zero.
        It is imperative to mention that chlorine used to clean water is not dangerous for ozone as it cannot reach the upper atmosphere. These chlorines and chlorides react with water and other elements to form different compounds and remain on the earth.
         There are some precautionary measures which must be adopted to minimize the effect of UV rays.
*During noon time, exposure to sun-rays must be avoided.
*Ears must be covered by a cap or cloth to protect for the sunlight.
*During peak hours of day, sunglasses (or crookes) must be used.
         The abolition of use of CFC, adoption of precautionary steps, patience and perseverance are required to retrieve the lost position and a lesson to learn; “in nature there are neither rewards nor punishments, there are only consequences”.
WAQAR HUSSAIN

Monday, June 4, 2012