In this article we will discuss about ozone and ozone hole
What is Ozone?
Ozone is triatomic form of oxygen(O3) concentrated in the Ozone layer/ Ozonosphere.
What is Ozone layer?
It extends from 20 km to 35 km in the Stratosphere.
How is ozone layer formed?
The conc. of ozone layer is maintained by a reversible process which includes fragmentation, atomisation, and Formation. It’s normal conc. is 400 Dobson.
UV radiation which is a part of electromagnetic radiation released by Sun has identified into three parts on the basis of Wavelength.
1) UV- A – 4000- 3200 Angstrong
2) UV- B – 3200- 2800 Angstrong
3) UV- C – 2800- 2000 Angstrong
UV- A is not absorbed by Ozone Layer. It is responsible for the production of Vitamin D and pigmentation of skin color.
UV- B is absorbed by ozone molecule and ozone itself get fragmentated into Oxygen molecule ( O2) and Oxygen atom (O).
UV- B + O3 fragmentation >O2 + O
UV- C + O2 atomization > O + O
O2 + O Formation > O3
The process of fragmentation, atomization and formation are responsible for absorbtion of harmful UV Radiation. The process of fragmentation and atomization in general is balanced by the formation of ozone molecule and this maintains the conc. of ozone molecules in the ozone layer at 400 Dobson.
What are Ozone Depleting Substances?
Many artificial compounds such as Chloro Fluro Carbons ( CFCs), Hydro Chloro Fluro Carbons ( HCFCs), Carbon Tetra Chloride (CCl4) , Chloroform (CHCl3) etc are Ozone Depleting Substances. These are used in several industries such as Refrigeration, Air Conditioning, Cooling, Foam, Paint, Fire Extinguishers and Sprays.
During their production, use and discarding these substances, they are released into atmosphere. Strong Storms, cyclones, jet streams facilitate their entry into the Stratosphere.
In stratosphere, under the influence of UV Radiations , their bonds are broken to form free Carbon atoms, Chlorine atoms, fluorine atoms and Hydrogen atoms.
These atoms combine with Nascent oxygen [O], Oxygen molecule (O2) , to form mono and di- oxides. This process reduces conc. of ozone molecules in the ozone layer.
What is Ozone Hole?
Declining conc. of Ozone Molecules and resultant thinning of ozone layer due to human interference is called Ozone layer depletion.This depletion creates a large hole in the sheet of ozone.
It indicates decline in the conc. of Ozone below 400 Dobson.
First ozone hole was detected in 1985 above South Pole (Antarctica), now it is visible over north pole also
What are the effects of Ozone Layer Depletion?
As ozone layer depletes and ozone hole becomes larger, more amount of UV- B radiation will be received by earth. This will adversely affect :
1- Human Beings– Incidence of Skin burn and Skin Cancer will increase. UV radiation is harmful for vision and immunity of human beings. Incidence of blindness and Cataract will increase due to persistent exposure to UV radiations.
2- Climate- As ozone layer depletes, amount of energy received by earth in the form of short waves will increase. Process of Photosynthesis will slow down, as a result of which Carbon- di-oxide (CO2 ) Conc will increase, thereby adding to global warming.
3- Ecosystems- Micro organisma are mostly unicellular, and highly sensitive to UV radiations. Increased UV radiations will either kill them or produce harmful mutations in them. Killing of these micro- organisams will adversely affect the process of decomposition and nutrient recycling.
In marine and aquatic ecosystems, phytoplankton and zooplanktons are producers and primary consumers and these are mostly unicellular. Their destruction will adversely affect aquatic and marine life.
Harmful mutations in disease causing viruses, bacteria and protozoans etc will produce new strains of diseases.
4- Agricultural Production and Productivity- UV Radiations deactivates hormones and enzymes and retard the process of Photosynthesis. Food production will decline.