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| Sunday, 19 September 2004 |
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Junior Observer |  |
| News Business Features Editorial
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Be ozone friendly Why is the ozone layer so important?In order to understand this we must first find out what ozone is, which some people think is a refreshing air.The atmosphere consists mainly of three gases: about 78 per cent nitrogen, 21 per cent oxygen and one per cent argon. The remaining ingredients include the carbon dioxide we breath out and the green plants all around us generously absorb, plus traces of helium, hydrogen, krypton, methane, neon, xenon and ozone. Ozone is a poisonous type of oxygen. Each ozone molecule is made up of three oxygen atoms, so its chemical formula is O3. At ground level it makes up less than one part per million of the air. Not a real threat at the moment, but then how come people make such a hue and cry over the protection of the ozone layer? Where exactly is this layer and how does it help us as a life saver? The ozone layer is a thin layer about 24 km (15 miles) above ground level in the stratosphere (the belt 10-50 km above the earth's surface). Up in the stratosphere small amounts of ozone are constantly being made by the action of sunlight on oxygen. The ozone layer is a natural sunblock. It blocks out most of the Sun's burning ultraviolet rays. We know how strong the rays of the sun could be even after this is filtered by the ozone layer. Imagine what the sun's rays would be like if not for the ozone layer? It certainly would kill plants and animals on land if not man.When human activity changes the natural balance of the formation and destruction of ozone in the stratosphere, Earth suffers. More and more ultraviolet radiation enters the earth's surface. Even a one per cent increase in the amount of ozone up there increases the radiation level down here.Unfortunately our bodies cannot detect ultraviolet radiation directly. We can be unaware of the harm it is doing until it is too late! ***** Ozone Formation Ozone Forms a layer in the stratosphere which is thinnest in the tropics (around the equator) and denser towards the poles. **** Ozone and Earth's atmosphere Ozone occurs naturally in the earth's atmosphere composed of several layers. We live in the 'Troposphere' where most of the weather occurs; such as snow, rain and clouds. The 'Stratosphere, is above this.The supersonic jet, the Concorde used to fly in the lower stratosphere whereas subsonic commercial airliners usually fly in the troposphere. The narrow region between these two parts of the atmosphere is called 'Tropopause'. **** Measurement The amount of ozone above a point on the earth's surface is measured in Dobson Units (DU)What is being done to protect the Ozone layer? With the signing of the Montreal Protocol in 1987 agreement has been reached on the control of industrial production of many halocarbons until the year 2030. The signatories agreed not to produce CFCs except for a limited amount for essential uses such as for medical sprays. The countries of the European Community adopted even stricter measures than the Montreal Protocol to protect the ozone layer. ***** Ozone-eaters The synthetic chemicals called chloroflurocarbons (CFCs) are now well-known as environmental 'baddies'. But they are completely non-toxic substances which are useful to us. CFCs which are ozone-depleting substances are naturally occurring compounds and are the most abundant. But they are not the only ozone-killers. How CFCs affect ozone Ozone depleting substances which we release into the atmosphere live long because it takes several years for them to drift up to the stratosphere. When they reach this belt, they are broken apart by exposure to ultraviolet radiation. And, that releases the chlorine atoms - the real ozone killers which react with the ozone to form oxygen and chlorine monoxide. CFCs previously used as refrigerants, foam-blowing agents and propellants in spray cans are now banned in Australia and many other countries. Substances other than CFCs that destroy the ozone layer are methyl bromide used as an insecticide for soil fumigation and carbon tetrachloride used in dry cleaning. *** Hole in the Ozone layer Scientists often refer to the part of the atmosphere where the ozone is most depleted as the 'Ozone hole' but in reality there is no hole. It is only a vast region in the atmosphere where there is less ozone than elsewhere. Antarctica is the worst affected area. Dramatic loss of ozone in the lower stratosphere over Antarctica was first noticed in the 1970s by a research group from British Antarctic Survey (BAS). ***** |
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