What is ozone layer?
Ozone layer or ozonosphere is a region found in the upper atmosphere that contains relatively high concentrations of ozone gas (O3) to protect the earth’s environment and its biosphere from harmful ultraviolet electromagnetic 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 lies at a height of 23 km from the distance of earth’s surface.
A steady concentration is maintained in the ozone layer by the formation and depletion of ozone molecules. Lowering the steady concentration or depletion of ozone molecules in the ozone layer causes our health problems and affects our skin, eye, and immune system.
Ozone layer formation
- 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 depletion of the ozone molecule or a steady concentration is maintained in the ozone layer of the upper atmosphere.
- If the ultraviolet electromagnetic radiations reach the earth, it will cause skin cancer and destroy different types of organic molecules necessary for life.
Ozone layer and its importance
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, and chlorocarbons (CFC) is the main source of ozone depletion in the upper atmosphere or stratosphere.
|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
Ozone depletion by 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 found in the stratosphere. Present evidence suggests that the ClOx cycle may be three times more active to the destroyed ozone molecules than the NOx cycle.
Ozone hole caused by nuclear testing
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 found in the upper atmosphere.
Ozone depletion by CFC
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 radiation and get broken down into free atomic chlorine in a cycle process. This atomic chlorine continuously causes to depletion of ozone into oxygen in a cycle to damages the ozone layer.
Protection of Ozone Layer
Scientists are worried about the effects of 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 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.