Posted on June 26, 2007 in Latest News
The ozone layer is a part of the stratosphere , the atmosphere around the earth extending from ten to fifty kilometres above its surface.It contains ozone that helps absorb harmful ultraviolet(UV) radiation from the sun.Two French physicists Charles Fabry and Henri Buisson discovered the ozone layer in 1913. The British scientist G M B Dobson created a simple spectrophotometer to measure the amount of ozone from the Earth’s surface. He set up several ozone monitoring stations around the world that are still operational.
Creation of the ozone layer
When ultraviolet light hits oxygen molecules in the stratosphere , it splits them in to separate oxygen atoms. This combines with an unbroken oxygen molecule to form ozone.Again this ozone molecule is unstable and splits in to atomic oxygen and a molecule of oxygen. This oxygen-ozone cycle continues and creates an ozone layer in the stratosphere. The maximum concentration of ozone is between fifteen to forty kilometres. Some ozone is also found in the troposphere where it comes from the stratosphere and through other mechanisms.
Importance of the ozone layer
Solar radiation consists of harmful ultraviolet rays namely UV A, UV B, UV C. The ozone layer completely blocks out UV C rays at 35 kms above the earth’s surface. UV B rays that can cause skin cancer , sunburn and genetic problems are aslo screened by the ozone layer, though some of it does reach the Earth’s surface. UV A rays are least harmful and most of this radiation reaches the earth’s surface. In the past two decades there has been a significant depletion in the ozone layer and this is a cause for concern .This implies more harmful UV rays are reaching the earth’s surface and they can cause genetic problems in all living organisms.
Concentration of the ozone layer in the stratosphere
The concentration of the ozone layer depends on a number of factors . It is smaller near the equator and denser towards the poles. It is thicker in spring and thinner in autumn. The different concentrations are due to different solar intensity and complicated circulatory patterns termed Brewer Dobson patterns. The greatest ozone concentration is over the Arctic regions between March and April and the lowest ozone concentration is over the Antarctic between September to October, due to the hole in the ozone layer in the Southern hemisphere over Antarctica.
Depletion in the ozone layer
Increased use of chloroflurocarbons has lead to a depletion of the ozone layer. These compounds contain Chlorine and Bromine that are broken in to free radicals by ultraviolet light in the stratosphere. These free radicals can then break down more than ten thousand ozone molecules. Scientists have observed a more than four percent drop in the ozone levels every decade around the poles and this is termed as the hole in the ozone layer. Other factors that deplete the ozone layer include volcanic activity, greenhouse gases and sunspot cycles.
Controlling the depletion of the ozone layer
When scientists discovered the ozone hole over the Antarctic in 1985, several countries around the globe joined hands under the Montreal Protocol in 1987 to stop the total use of chloroflurocarbons over the next decade. Countries like Sweden, the US and Canada have taken positive steps to curb the use of chloroflurocarbons. Research is underway to find eco-friendly compounds that will not affect the ozone layer, to replace chloroflurocarbons. A study by the American Geophysical Unioin in 2003, confirmed a slowdown in the ozone depletion as a result of these global efforts.
Hence it is important to save the ozone layer in order for mankind to survive in to the next century.
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