Ozone, O3, is mostly found high in the atmosphere, between 10 to 450km high. The ozone in the stratosphere is about 90% of the world’s ozone. Ozone is created from a reaction with oxygen, O2, and the ultraviolet light given off by the sun. The ultraviolet light strikes the oxygen and splits them up into the oxygen atoms. The oxygen atoms then join with the unbroken O2 to form O3, ozone. The oxygen atom can also join with other molecules to form other compounds.<p>
Ozone can also be found at ground level and is mostly produced by city traffic. The ozone created by city traffic is a result of a photochemical reaction where oxides of nitrate and volatile organic compounds in the presents of sunlight. Ozone is harmful to animals and plants even at low concentrations. It can cause eye irritation or discomfort to subjects suffering breathing disorders.<p>
Ozone can also be artificially made for industrial uses. Ozone is used in the treatment of air and water purifications and is made by an ozone generator. Ultraviolet light produces ozone on a small scale so to harvest large quantities of it a negative corona discharge, a type of electrical discharge, needs to be used to create the ozone. The corona discharge creates free radicals and ions. Normal air supplied by an air compressor or bottled oxygen is then pumped into a chamber with the discharge and ozone is formed. The transformation from 3O2 → 2O3 generates a lot of heat so it is more efficient if the generator is cooled. The following is a simple diagram of an ozone generator.<p>
The ozone located in the stratosphere is called the ozone layer. The ozone is very important to the earth because it absorbs harmful ultraviolet radiation, which causes skin cancers, given of by the sun. The amount of molecules at this level is very small, in fact if they were to be brought down to ground level they would form a layer of gas no more then 3mm thick. It is because of this thin thickness that it can easily be disrupted. O3 doesn’t just react with ultraviolet radiation but with chlorine and chlorine compounds. The compounds that are most destructive to the ozone layer are known as CFC’s, chlorofluorocarbons. CFC’s are used commercially in cleaning products, propellants and refrigerates. When CFC’s reach the ozone layer the ultraviolet radiation breaks them down and releasing the chlorine atoms. The chlorine atom known as a ‘free radical’ then breaks up the ozone resulting in O2 and Chlorine. The chlorine given off can then break up more ozone. A single chlorine atom can last for four to ten years in the upper atmosphere.<p>
The use of CFC’s and the destruction of the ozone layer have resulted in a hole in the ozone layer. The hole is located over Antarctica and in 2003 was 28 million square kilometers. This means that because of the lack of ozone in this area ultraviolet radiation is stronger then most other places on the earth which contributes to issues such as global warming.<p>
Different laws and legislation have been brought in overseas to prevent the use of CFC’s to reduce the size of the hole in the ozone layer. The first ban on CFC’s was in the US state of Oregon in 1975.In 1978 the US and several European nations banned the use of CFC’s but the biggest law to come into effect specifically to stop CFC emissions was the Montreal Protocol. The international treaty was designed to phase out the use of any substance which destroyed the ozone layer. It was opened for signing on the 16th of September 1987 and enforced January 1st, 1989. Since then it has undergone five revisions. At present 189 countries are members of the protocol. Funding has been set up to help developing nations to reduce and stop use of CFC’s and it is planned that by 2010 that there should be no use of CFC’s anywhere in the world.
Replacements for CFC’s are used. HCFC, hydrochlorofluorocarbons, are not as harmful to ozone because the C-H bond makes them more reactive with the atmosphere therefore many don’t reach the stratosphere. Common HCFC’s used include chlorodifluoromethane, 1-chloro-1,1-difluoroethane, 1,1-difluoroethane and are used in fridges, airconditioners and aerosols.<p>
Australia is a member of the Montreal Protocol which means CFC’s can not be used. As far as national laws, Australia has in place legislation to stop the use of products which destruct the ozone layer. The Environmental protection Authority, EPA, established in 1997 the Ozone protection Regulation. “This Regulation imposes controls on the sale, purchase and use of certain ozone-depleting substances.” (anon. 2006, 1). Heavy penalties and jail time are given to persons who knowingly disobey this regulation.<p>
This regulation also prevents the use of HCFC’s which means other substitutes in Australia have to be used. An example of a substitute which is legal in Australia is Perfluorocarbons. The use of CFC’s and the destruction of ozone can be seen as a long or short term problem depending on the definition of these. Ozone has been around for nearly a billion years and the use of CFC’s and the destruction of ozone has only been happening since the 50s meaning in regards to the age of the destruction compared to the age of ozone this is a short term problem. The early discovery of the destruction means that the effects can be easily reversed. The main problem is money. The cost for companies being fined outweighs the cost for the companies using CFC alternates. As for developing counties, the set up of funding by the Montreal Protocol means more incentive for them not to use CFC’s. This means that the plan for total elimination of CFC’s by 2010 is not optimistic but very realistic. Since the discovery in the 80s of the hole and the reduction of the use of CFC’s, the size of the hole has also reduced. And with the chlorine only ‘living’ four to ten years at the high altitude the hole can only reduce and eventually disappear.
Ozone and the destruction of
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2 June 2006
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