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Ozone layer refers to the layer of atmosphere approximately between 10 to 50 kilometers above earth's surface which contain high levels of ozone. Though ozone is present everywhere in the atmosphere, is concentration is highest in this layer.
The ozone in the ozone layer is very effective in absorbing most of the harmful ultra-violet radiations from the sun and thus make the environment of the earth much more suitable for plant and animal life including human life. Unfortunately some substances that are released in atmosphere as a result of our modern life and industrialization, reduce the quantity of ozone in the ozone layer, which in turn leads to degradation of earths environment. The substances that reduce the amount of ozone in the ozone layer and thus make the ozone layer thinner include nitric oxide (NO), hydroxyl (HO), atomic chlorine (Cl) and atomic bromine (Br). Large quantities of Cl and Br are released in made made chemicals such as chlorofluorocarbons (CFC) and bromofluorocarbons used in aerosol sprays and as refrigerants. In an attempt to protect to the ozone layer, many countries producing such chemicals have signed treaties to reduce or totally stop production o such chemicals.
In the outer regions of the atmosphere(stratosphere), the layer of oxygen molecule O3 , called ozone , protects the earth by absorbing the harmful rays belonging to the ultra violet spectra. The ultrra violet rays are harmful for the living beings - plants , animals or hamans. Ozone , after absorbing the ultra violet rays, splits into O2 and O and once again regenerates O3, the ozone. However ,trom the man made chemicals , the free radicals of hyrooxyl and nitric oxide and atomic halogines that escape to the atmosphere react with the atomic oxygen. This cause the regenarion of O3 The Among these , the chloroflourocarbon(CFCl3) , is the major cause, to block the regeneration of the ozone.After use of the chemical, chloroflourocarbon, in refrigerators and air condtioners ,medicine,it escapes to atmosphere . The free chlorine atom has a higher reativity to with free oxygen atom to combine with to form chlorine monoxide:
O3 ---(after absorbing ultra violet rays)-----> O2 + O
CFCl3 ---(ultraviolet ray)---> CFClO2 + Cl
From the above reaction we can see how the atomic halogines(Chlorine, Bromine ) have multi-cycles to prevent regeneration of O3 from O2 ang O atoms .
Presently the thinning of ozone layers and the hole formations observed in the arctic regions. It is a dangerous trend to the health of living beings that the thinning has been gradually increasing over the years since 1970.
Ozone (0 3) is a gas that contains molecules composed of three oxygen atoms. It is located in the upper atmosphere at an altitude over 10-50 km. Experts have estimated that currently there are about 3 billion tones of ozone.
In l985, it was published a report stating that since the '70s, chemicals known as chlorofluorocarbons used for a long time as aerosol sprays are a potential threat to the ozone layer. Released into the atmosphere, these chemicals are decomposed by sunlight; chlorine destroys ozone molecules.
Cosmic rockets and supersonic airplanes are also responsible for this phenomenon. Aircraft gases contain nitrogen oxides, substances that are partially forbidden in the United States.
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