Ozone (O3) is a form of the element oxygen (O) which has three atoms in each molecule instead of the two of normal oxygen molecules (O2). It is formed in the stratosphere by the action of solar radiation on oxygen molecules in a process called photolysis; O2 molecules are broken down to yield atomic oxygen, which in turn combines with molecular oxygen to produce ozone.
Ozone is destroyed naturally through a series of catalytic cycles involving oxygen, nitrogen, chlorine, bromine and hydrogen. The stratosphere (10-50km above the earth's surface) contains 90% of all ozone in the atmosphere. Looking up through the atmosphere, the ozone column has its maximum partial pressure in the lower stratosphere at a level of 19-23km above the Earth.
The ozone layer is going decomposed by several chemicals. Without the ozone layer it is impossible for living beings tobe on earth.Ozone is located in the whole atmosphere but in the stratosphere is located most of this gas.Ozone prevents earth from uv-radiation (UV-B). Increasing UV-radiating effects more cases of skin-cancer and eye-affections (cataracts). There are also consequences for flora and fauna: Decrease of fertility and less yield from culture plants. Scientists like Crutzen, Molina and Rowland have shown that chemicals in the upper atmosphere destroy ozone. These chemicals - especially fluorchlorine hydrocarbon (FCKW) - were used in indusry and trade.At this time the production of these substances in industrial countries isn´t allowed anymore. The timescale from full recovering is in the order of 30 to 40 years. This chemical prozess take it´s course mainly above Antarctica. Between 12 and 25 kilometers the whole ozone vanished for weeks, in the whole atmosphere it decreases for 70 percent. Such a phenomenon is also possible above Arctica but depends on temperature and airflow. Depletion of ozone won´t be stopped until long-living FCKWs and other substances which destroy ozone disappear from atmosphere.
Crutzen, a famous scientist, was the first who found out the chemistry in the ozone layer-destroying. 1970 he found out the reaction of nitrogen oxides (NOand NO2) in the upper atmospheric layer, the stratosphere, with ozone (O3).In this reaction the three-atomic molecules get dismantled.These nitrogen oxides originate from microbic destruction in soil.
These science-results were the basis to discover biologic-geochemical circulation more intensiv.Crutzens results got down the plans in the USA to build a fleet of supersonic aircrafts.Such aircrafts would have eject many of these nitrogen combines 20 kilometers above earth - right in the middle of the stratosphere.1974 the Mexican Mario Molina and the American Sherwood Rowland found out the connections between chlorine-chemistry and destroying of ozone layer.
Crutzen, Molina and Rowland got the Nobel prize in 1995 for their researches.
(transkription and translation by Silke Seiler, student vet.med.-vienna)
1) UV-light splits Oxygen molecules (O2) into two single oxygen atoms (O).
2) Free oxygen atoms combine with further O2 molecules and a further atom to form ozone (O3).
3) Ozone atoms also disintegrate naturally under the action of UV, but in the absence of anthropogenic compounds this process is well balanced with ozone fomation.
4) Free clorine atoms released from CFC molecules (through reservoir molecules CIONO2 and HCI) react with ozone, forming CIO and O2.
5) CIO is short lived, it reacts with free O atom to form a further O2 molecule, releasing the free Cl atom ready to decompose another ozone molecule.