In the stratosphere ozone is present in small quantity and it is stretched over a distance of 10-35 kilometers from the ground. Under the influence of ultraviolet rays of the son, oxygen CO2 of the atmosphere decomposes to oxygen atoms (O) and one oxygen molecule combines chemically with the oxygen atom to form ozone molecule of three oxygen atoms as show below:
The ozone presence in the ambitious air is harmful to public health. But the stratospheric ozone layer has a specific positive role. Because, this ozone layer strongly absorbs ultraviolet radiation from the sun (295-32 (mm) which is injurious for the life on the earth. Thus, it protects living species on the earth from the ultraviolet rays of the sun by covering the earth as an umbrella. But recent human activities have injected some dangerous chemicals in the stratosphere which consume ozone and reduce its concentration. This is the phenomenon of ozone hole in the stratosphere.
Exhaust gases from Jet aircrafts and artificial satelites discharge nitric oxide (NO) nitrogen dioxide (NO2) etc which immediately react with ozone.
O3 +NO à O2 + NO2
(ozone) (nitric Oxygen (Nitrogen
O3 +NO2 à O2 + NO3
(ozone) (nitrogen oxygen (Nitrogen
In presence of ultraviolet radiation (200 mm) from the sun CFF which is used as coolars in refrigerators and air conditioners, breaks by into chlorine free radical (cl) which readily consume ozone.
Cl– + O2àCIO + O2
ClO– + Oà Cl– + O2
The damage by CFC continues for 100 years.
In 1979 ozone hole was observed in the sky over America. In Montreal Conference 1987, and London conference 1992 it was decided that the developing countries would totally ban CFC production by 2000 and the developing countries by 2000 AD.
Environmental Importance of Ozone hole:
Ozone is a poisonous gas having blue color and fishy smell. But it presents the ultraviolet rays of sun from coming to the earth. But ozone hole, allows passage of ultraviolet tradition to the earth where it causes damages to plants, animals and environment as follows:
Effect on plants:
- Ozone hole causes damage on photosynthesis and germination of seed. The leaf, fruit etc. become day and growth of plants is hampered. As a result a material for food, cloth and shelter becomes scarce.
- The phytoplankton and zoo plankton die in water reservoir. As a result fishes suffer badly for their food and want of fishes, a protein rich animal appears in the country.
Effect on animals:
- Ultraviolet rays are dangerous to living belongs. Particularly VV-B cause’s skin cancer and eye-sight defect.
- The immunity of the skin i.e. preventive capacity of the skin decreases due to the effect of ultraviolet ray’s. As a result, bacteria virus funguses etc. find their place of attacking the skin causing various skin diseases.
- Ultraviolet rays affect the reproductive system of living beings including man.
Effect on Environment:
- The food web in ecosystem is affected by V.V. rays. As a result ecosystem falls in danger.
- The acid in the air increased causing more acid rain.