Ozone Layer in Atmosphere
Ozone layer or ozonosphere is a region of the upper atmosphere that contains relatively high concentrations of ozone gas molecules (O3) to protect the earth and its biosphere from harmful ultraviolet radiation. The region is lying in the stratosphere or between 20 km to 60 km above the earth’s surface. The thickest layer of ozone exists at a height of 23 km from the surface of the earth’s environment.
In the upper atmosphere, ozone gas is formed by solar uv radiation of very high energy. The ozone molecules absorb moderately high energy uv radiation with a very long wavelength to form oxygen atoms or molecules. An equilibrium is established between the formation and destruction of the ozone molecule or a steady concentration is maintained in the ozone layer of the upper atmosphere. If the ultraviolet electromagnetic radiations reaching the earth, it will cause skin cancer and destroy different types of organic molecules necessary for life.
Ozone Hole in Stratosphere
If the protective ozone layer in the atmosphere completely disappears, then all the harmful ultraviolet radiation coming from the sun would reach the earth’s environment. It would cause skin cancer in humans or animals and damage all life on the green planet. In 1980, scientists showed that there is a hole in the O3 layer. This hole was detected over the region of Antarctica. Due to the presence of ozone holes in the stratosphere, the concentration of ozone gas is reduced day by day. Unfortunately, several human activities permanently damage the ozone balance in the upper atmosphere.
Nitrogen dioxide (NO2) from supersonic aircraft, industrial chemical catalyst, chlorocarbons (CFC) is the main source for ozone depletion in the upper atmosphere or stratosphere. Photochemically nitrogen oxides (NOx) and chlorine atoms are continuously regenerated in the ozone depletion process that causing a permanent dame in the ozone balance.
O3 + NO → NO2 + O2
NO2 + O.. (free radical) → NO + O2
NO2 + O3 → O2 + NO3
NO3 → O2 + NO
CF3Cl → Cl. (free radical) + CF3
Cl. + O3 → ClO. + O2
ClO. + O.. → Cl. + O
Oxides of nitrogen
The oxides of nitrogen present in the atmosphere decompose ozone gas into oxygen gas and continuously regenerate. Therefore, the presence of nitrogen dioxide destroyed the ozone layer in the stratosphere. Present evidence suggests that the ClOx cycle maybe three times more active to the destroyed ozone layer than the NOx cycle.
Different types of nuclear reactions for generating nuclear power or weapons in the world generate high temperatures in the earth’s environment. At high temperatures, atmospheric nitrogen oxidizes to form nitrogen oxides which destroy the ozone layer of the upper atmosphere.
Chlorofluorocarbons are the stable compounds of methane like freon-1 (CFCl3) and freon-12 (CF2Cl2). These are emitted from different types of organic spray aerosol, refrigerants, firefighting reagents, and solvents for cleaning electric components. When they enter the stratosphere, they absorbed ultraviolet radiations and get broken down into free atomic chlorine in a cycle process. This atomic chlorine continuously decomposes ozone into oxygen in a cycle to damage the ozone layer.
Protection of Ozone Layer
Scientists are worried about the gradual destruction or depletion of the ozone layer by the oxides of nitrogen and chlorofluorocarbons (CFC). The air pollution or water pollution or acid rain caused by NO and NO2 can be controlled by reducing these gases to convert ammonia by the reaction with hydrogen in presence of finely divided platinum metal before they enter into the atmosphere. To ozone layer destruction or depletion by chlorofluorocarbons (CFC), the use of such types of substances would be banned, and discovered some new types of substances in aerosol spray or refrigerants that do not react with the O3 layer of the upper atmosphere.