Ozone layer

What is the ozone hole

The phenomenon of the ozone hole was first observed in the 1980s over the Antarctic. The ozone hole is the ozone depletion in the upper layer of the Earth's atmosphere, so-called stratosphere. It is said that the ozone loss is about 50% due to the emission of compounds which cause a ozone depletion - particularly CFC - the protective ozone layer was damaged at the height of 10 to 50 kilometers.

Research demonstrated that during the last several years the concentration of ozone in the atmosphere fell by 0,2% per annum. The phenomenon is called the ozone hole extension. What is worse, it appears not only over the Antarctic but also over other areas on the Earth.

How is the ozone hole created

The ozone hole - the ozone depletion in the upper layers of the atmosphere is partly a natural process; however, owing to the emission of substances which come from human activity, the process intensified and, at one point, became a huge threat.

The process of the ozone layer appearance and disappearance in the stratosphere looks as follows: ultraviolet radiation interacts with the oxygen contained in the air and causes the appearance of ozone molecules which, in turn, disintegrate reacting with chlorine which is released as CFC disintegrates and which is accumulated in the atmosphere all the time.

Ultraviolet radiation generated by the Sun is decisive in the process of ozone production. For a longer period of time polar areas are hardly lit. Although the production of ozone decreases significantly then, both the natural depletion and the depletion under the influence of chlorine coming from pollution do not stop - these moments cause ozone deficit which leads to the extension of the ozone hole.

To a large extent it was human activity that contributed to the ozone hole. Especially when refrigerating industry (fridges, refrigerating machines, freezers), chemical industry (varnish production), cosmetology (deodorants) and medicine (aerosols) started using chemical compounds such as CFC and derivatives of methane and ethane.

These compounds accumulate in the atmosphere, they do not disintegrate in the upper layers and when they reach the ozonosphere, as a result of ultraviolet radiation, they decompose into carbon, fluorine and chlorine. Fluorine becomes neutral spontaneously (fluorine atoms join), carbon burns and chlorine, unfortunately, speeds up ozone decomposition into the compounds of simple oxygen.

The effects of the ozone hole

The ozone hole threatens life on the Earth. The protective ozone layer is salutary for life on our planet as it absorbs harmful solar ultraviolet radiation. This radiation is so strong that it has a destructive influence on the organic matter.

Furthermore, apart from the protection, the processes which occur in the ozonosphere regulate air exchange in the upper layers of the atmosphere and accordingly they influence indirectly the climate on the surface of the Earth.

And how do ultraviolet rays destroy living organisms? First of all they cause irreparable damage in DNA (destruction of chains, mutations) and their destructive influence depends, to some extent, on the individual organisms' resistance. In water ecosystems the excess of radiation damages chiefly plankton, the consequence of which is the lack of food for other inhabitants of waters and, indirectly, disturbances in the whole food chain. Also plants, including cultivated plants, are characterized by low resistance to the harmful influence of UV radiation which, accordingly, may be the reason for the decrease in agricultural production. As far as people are concerned - for some time we have been sensitized to the harmful effect of this type of radiation - radiation weakens the immunological system, it destroys skin cells, speeds up ageing process and causes malignant cancer. It also has negative impact on sight organ - it irritates conjunctivas and causes cataract. Therefore, the ozone hole is one of the greatest threat to humankind.

Prevention of the ozone layer depletion and the ozone hole extension

The phenomenon of the ozone layer was observed relatively late but immediately people became aware of the significance of the problem and they took protective and preventive actions. In 1987 international Montreal Protocol was signed in which the countries obliged to reduce the production of CFC by 50% until 2000 (in relation to the production in 1986). The protocol indeed resulted in the decrease in the amount of this gas in the atmosphere. Furthermore, in 1990 another international act, the Vienna Convention, was signed and its aim was to protect the ozonosphere. It introduced a ban on the production of CFCs and the import of devices which work on the basis of these gases. Cosmetic industry decided not to use aerosols with CFC a long time ago and cooling devices which are being produced nowadays (fridges, refrigerating machines, freezers) are not also based on these gases.

According to the latest calculations of scientists, as a result of the ban on using CFCs, the gases which have been already emitted ought to be neutralized and removed from the atmosphere within 50 years. Provided that no unforeseeable events happen, the ozone layer should not change and the amount of the ozone in the atmosphere will become even and stabilize until the ozone layer will disappear entirely about in 2065.

It is quite difficult to asses it as even during one year the ozone layer can change, which depends on the amount of solar radiation which reaches strategic, polar areas.

The role of the ozone layer and the phenomenon of the ozone hole

Ozone is one of the forms of oxygen. Oxygen which we breathe consists of two atoms whereas ozone consists of three atoms. Ozone is characterized by lower permanence, it is more subject to chemical reactions - the processes of appearance and disintegration; this characteristic of ozone is connected with the harmful effect of this gas on organisms (human, animals, plants). When an organism comes into contact with three-atom oxygen, its tissues are damaged. It is particularly dangerous in so-called ozone smog (high concentration of the gas which appears in some areas of the ground layer of the atmosphere). It easily penetrates into the respiratory system causing irritations and damage to the tissues of respiratory organs.

On one hand ozone is necessary since it protects us from harmful ultraviolet radiation which reaches us as a result of the processes occurring in the Sun; on the other hand, as mentioned above, in the atmosphere near ground the influence of ozone may be harmful and sometimes even drastically dangerous for health.

Of course the protective function of the gas is of the utmost importance and thus people reacted so quickly to the ozone depletion, which was called the ozone layer, over Antarctica.

It is safe to say that during several years, i.e. from the time when the ozonosphere was observed in the 70s, people were so motivated that they managed to exclude the production of all compounds which have had a destructive influence on the ozone layer and the extension of the ozone hole. This is probably the first notable case of such ecological activation on a global scale. What is more, the activation ended with success.