The ozone layer is a wide atmospheric belt extending from 10 to 50 km above the Earth's surface. Chemically, ozone is a molecule consisting of three oxygen atoms (an oxygen molecule contains two atoms). The concentration of ozone in the atmosphere is very low, and small changes in the amount of ozone lead to large changes in the intensity of ultraviolet reaching the earth's surface. Unlike ordinary oxygen, ozone is unstable, it easily transforms into a diatomic, stable form of oxygen. Ozone is a much stronger oxidizing agent than oxygen, and this makes it capable of killing bacteria and inhibiting plant growth and development. However, due to its low concentration in the surface layers of air under normal conditions, these features of it practically do not affect the state of living systems.
Much more important is its other property, which makes this gas absolutely necessary for all life on land. This property is the ability of ozone to absorb the hard (shortwave) ultraviolet (UV) radiation from the Sun. Quanta of hard UV have energy sufficient to break some chemical bonds, so it is referred to as ionizing radiation. Like other radiation of this kind, X-ray and gamma radiation, it causes numerous disturbances in the cells of living organisms. Ozone is formed under the influence of high-energy solar radiation, which stimulates the reaction between O2 and free oxygen atoms. Under the influence of moderate radiation, it decays, absorbing the energy of this radiation. Thus, this cyclical process "eats" the dangerous ultraviolet.
Ozone molecules, like oxygen, are electrically neutral, i.e. carry no electrical charge. Therefore, the Earth's magnetic field itself does not affect the distribution of ozone in the atmosphere. The upper layer of the atmosphere - the ionosphere, almost coincides with the ozone layer.
In the polar zones, where the lines of force of the Earth's magnetic field are closed on its surface, the distortion of the ionosphere is very significant. The number of ions, including ionized oxygen, in the upper layers of the atmosphere of the polar zones is reduced. But the main reason for the low content of ozone in the region of the poles is the low intensity of solar radiation, which falls even during the polar day at small angles to the horizon, and during the polar night is completely absent. The area of polar "holes" in the ozone layer is a reliable indicator of changes in total atmospheric ozone.
The ozone content in the atmosphere fluctuates due to many natural causes. Periodic fluctuations are associated with cycles of solar activity; many components of volcanic gases are capable of destroying ozone, so an increase in volcanic activity leads to a decrease in its concentration. Ozone-destroying substances are spread over large areas due to high, super-hurricane speeds of air currents in the stratosphere. Not only ozone depleters are transported, but also ozone itself, so ozone concentration disturbances quickly spread over large areas, and local small “holes” in the ozone shield, caused, for example, by a rocket launch, are relatively quickly drawn in. Only in the polar regions is the air inactive, as a result of which the disappearance of ozone there is not compensated by its drift from other latitudes, and the polar "ozone holes", especially at the South Pole, are very stable.
Sources of destruction of the ozone layer. Among the depleters of the ozone layer are:
1) Freons.
Ozone is destroyed under the influence of chlorine compounds known as freons, which, also being destroyed under the influence of solar radiation, release chlorine, which “tear off” the “third” atom from the ozone molecules. Chlorine does not form compounds, but serves as a “rupture” catalyst. Thus, one chlorine atom is able to "destroy" a lot of ozone. It is believed that chlorine compounds are able to remain in the atmosphere from 50 to 1500 years (depending on the composition of the substance) of the Earth. Observations of the planet's ozone layer have been carried out by Antarctic expeditions since the mid-1950s.
The ozone hole over Antarctica, which increases in spring and decreases in autumn, was discovered in 1985. The discovery of meteorologists caused a chain of consequences of an economic nature. The fact is that the existence of a “hole” was blamed on the chemical industry, which produces substances containing freons that contribute to the destruction of ozone (from deodorants to refrigeration units).
There is no consensus on the question of how much a person is guilty of the formation of “ozone holes”.
On the one hand, yes, definitely guilty. The production of ozone-depleting compounds should be minimized or, better yet, stopped altogether. That is, to abandon the whole sector of industry, with a turnover of many billions of dollars. And if you do not refuse, then transfer it to a “safe” track, which also costs money.
The point of view of skeptics: human influence on atmospheric processes, for all its destructiveness on a local level, on a planetary scale is negligible. The anti-freon campaign of the “greens” has a completely transparent economic and political background: with its help, large American corporations (DuPont, for example) stifle their foreign competitors by imposing agreements on “environmental protection” at the state level and forcibly introducing a new technological revolution, which is more economically weak states are not able to withstand.
2) High-altitude aircraft.
The destruction of the ozone layer is facilitated not only by freons released into the atmosphere and entering the stratosphere. Nitrogen oxides, which are formed during nuclear explosions, are also involved in the destruction of the ozone layer. But nitrogen oxides are also formed in the combustion chambers of high-altitude aircraft turbojet engines. Nitrogen oxides are formed from the nitrogen and oxygen that are there. The rate of formation of nitrogen oxides is the greater, the higher the temperature, i.e., the greater the engine power.
Not only is the engine power of an aircraft important, but also the altitude at which it flies and releases ozone-destroying nitrogen oxides. The higher the oxide or nitrous oxide is formed, the more destructive it is for ozone.
The total amount of nitrogen oxide released into the atmosphere per year is estimated at 1 billion tons. About a third of this amount is emitted by aircraft above the average tropopause level (11 km). As for aircraft, the most harmful emissions are military aircraft, the number of which is in the tens of thousands. They fly mainly at the heights of the ozone layer.
3) Mineral fertilizers.
Ozone in the stratosphere can also decrease due to the fact that nitrous oxide N2O enters the stratosphere, which is formed during the denitrification of nitrogen bound by soil bacteria. The same denitrification of bound nitrogen is also carried out by microorganisms in the upper layer of the oceans and seas. The process of denitrification is directly related to the amount of bound nitrogen in the soil. Thus, one can be sure that with an increase in the amount of mineral fertilizers applied to the soil, the amount of nitrous oxide N2O formed will also increase to the same extent. Further, nitrogen oxides are formed from nitrous oxide, which lead to the destruction of stratospheric ozone.
4) Nuclear explosions.
Nuclear explosions release a lot of energy in the form of heat. The temperature equal to 60,000 K is set within a few seconds after a nuclear explosion. This is the energy of the fireball. In a strongly heated atmosphere, such transformations of chemical substances take place, which either do not occur under normal conditions, or proceed very slowly. As for ozone, its disappearance, the most dangerous for it are the oxides of nitrogen formed during these transformations. Thus, during the period from 1952 to 1971, as a result of nuclear explosions, about 3 million tons of nitrogen oxides were formed in the atmosphere. Their further fate is as follows: as a result of the mixing of the atmosphere, they fall to different heights, including into the atmosphere. There they enter into chemical reactions with the participation of ozone, leading to its destruction. ozone hole stratosphere ecosystem
5) Fuel combustion.
Nitrous oxide is also found in flue gases from power plants. Actually, the fact that nitrogen oxide and dioxide are present in combustion products has been known for a long time. But these higher oxides do not affect ozone. They, of course, pollute the atmosphere, contribute to the formation of smog in it, but are quickly removed from the troposphere. Nitrous oxide, as already mentioned, is dangerous for ozone. At low temperatures, it is formed in the following reactions:
N2 + O + M = N2O + M,
2NH3 + 2O2 =N2O = 3H2.
The scale of this phenomenon is very significant. In this way, approximately 3 million tons of nitrous oxide are formed in the atmosphere every year! This figure suggests that this source of ozone depletion is significant.
Ozone hole over Antarctica
A significant decrease in total ozone over Antarctica was first reported in 1985 by the British Antarctic Survey based on analysis of data from the Halle Bay Ozone Station (76 degrees S). Ozone depletion has also been observed by this service in the Argentine Islands (65 degrees S).
From August 28 to September 29, 1987, 13 flights of the laboratory aircraft over the Antarctic were performed. The experiment made it possible to register the origin of the ozone hole. Its dimensions were obtained. Studies have shown that the greatest decrease in the amount of ozone took place at altitudes of 14 - 19 km. Here, the instruments registered the largest amount of aerosols (aerosol layers). It turned out that the more aerosols there are at a given altitude, the less ozone there is. Aircraft - the laboratory registered a decrease in ozone equal to 50%. Below 14 km. ozone changes were insignificant.
Already by the beginning of October 1985, the ozone hole (the minimum amount of ozone) covers pressure levels from 100 to 25 hPa, and in December the range of heights at which it is observed expands.
In many experiments, not only the amount of ozone and other small components of the atmosphere was measured, but also the temperature. The closest relationship was established between the amount of ozone in the stratosphere and the air temperature there. It turned out that the nature of the change in the amount of ozone is closely related to the thermal regime of the stratosphere over Antarctica.
The formation and development of the ozone hole in Antarctica was observed by British scientists in 1987. In the spring, the total ozone content decreased by 25%.
American researchers measured ozone and other small components of the atmosphere (HCl, HF, NO, NO2, HNO3, ClONO2, N2O, CH4) in the Antarctic in winter and early spring of 1987 using a special spectrometer. The data from these measurements made it possible to delineate an area around the South Pole in which the amount of ozone is reduced. It turned out that this region coincides almost exactly with the extreme polar stratospheric vortex. When passing through the edge of the vortex, the amount of not only ozone changed dramatically, but also other small components that affect the destruction of ozone. Within the ozone hole (or, in other words, the polar stratospheric vortex), the concentrations of HCl, NO2, and nitric acid were significantly lower than outside the vortex. This takes place because chlorins during the cold polar night destroy ozone in the corresponding reactions, acting as catalysts in them. It is in the catalytic cycle with the participation of chlorine that the main decrease in the concentration of ozone occurs (at least 80% of this decrease).
These reactions take place on the surface of the particles that make up the polar stratospheric clouds. This means that the larger the area of this surface, i.e., the more particles of stratospheric clouds, and hence the clouds themselves, the faster ozone eventually decays, which means that the ozone hole is formed more efficiently.
Ozone is found in waste gases emitted by businesses and is a hazardous chemical. It is a very active element and can cause corrosion of structural elements of various structures. However, in the atmosphere, ozone is transformed into an invaluable assistant, without which life on Earth could simply not exist.
The stratosphere is called which follows the one in which we live. Its upper part is covered with ozone, its content in this layer is 3 molecules per 10 million other air molecules. Despite the fact that the concentration is very low, ozone performs the most important function - it is able to block the path of ultraviolet rays coming from space at the same time as sunlight. Ultraviolet rays negatively affect the structure of living cells and can cause the development of diseases such as eye cataracts, cancer and other serious ailments.
The basis of protection is the following principle. At the moment when oxygen molecules meet on the path of ultraviolet rays, the reaction of their splitting into 2 oxygen atoms occurs. The resulting atoms combine with non-split molecules, creating ozone molecules consisting of 3 oxygen atoms. When meeting with ozone molecules, the latter destroy them into three oxygen atoms. The moment of splitting of molecules is accompanied by the release of heat, and they no longer reach the surface of the Earth.
Ozone holes
The process of converting oxygen into ozone and vice versa is called the oxygen-ozone cycle. Its mechanism is balanced, however, the dynamism varies depending on the intensity of solar radiation, the season and natural disasters, in particular, the scientists concluded that human activity negatively affects its thickness. The depletion of the ozone layer has been recorded over the past decades in many places. In some cases, it disappeared completely. How to reduce the negative impact of a person on this cycle?
Ozone holes arise due to the fact that the process of destruction of the protective layer is much more intense than its generation. This is due to the fact that in the process of human life the atmosphere is polluted by various ozone-depleting compounds. These are, first of all, chlorine, bromine, fluorine, carbon and hydrogen. Scientists believe that CFCs are the main threat to the ozone layer. They are widely used in refrigeration, industrial solvents, air conditioners and aerosol cans.
Chlorine, reaching the ozone layer, interacts with. The chemical reaction also produces an oxygen molecule. When chlorine oxide meets a free oxygen atom, another interaction occurs, as a result of which chlorine is released, and an oxygen molecule appears. In the future, the chain is repeated, because chlorine is not able to go beyond the boundaries of the atmosphere or sink to the ground. Ozone holes are a consequence of the fact that the concentration of this element decreases due to its accelerated splitting when extraneous foreign components appear in its layer.
Places of localization
The largest ozone holes have been found over Antarctica. Their size practically corresponds to the area of the continent itself. This area is practically uninhabited, but scientists express concern that the gap could spread to other areas of the planet, heavily populated. This is fraught with the death of the Earth.
To prevent the reduction of the ozone layer, it is necessary first of all to reduce the amount of damaging substances emitted into the atmosphere. In 1987, the Montreal Treaty was signed in 180 countries, which provides for the reduction of emissions of substances containing chlorine in a phased manner. Now the ozone holes are already shrinking, and scientists are expressing hope that the situation will completely improve by 2050.
The occurrence of ozone holes in the polar regions is due to the influence of a number of factors. The concentration of ozone decreases as a result of exposure to substances of natural and anthropogenic origin, as well as due to a lack of solar radiation during the polar winter. The main anthropogenic factor causing the occurrence of ozone holes in the polar regions is due to the influence of a number of factors. The concentration of ozone decreases as a result of exposure to substances of natural and anthropogenic origin, as well as due to a lack of solar radiation during the polar winter. The main anthropogenic factor causing a decrease in ozone concentration is the release of chlorine- and bromine-containing freons. In addition, extremely low temperatures in the polar regions cause the formation of so-called polar stratospheric clouds, which, in combination with polar vortices, act as catalysts in the ozone decay reaction, that is, they simply kill ozone.
Sources of destruction
Among the depleters of the ozone layer are:
1) Freons.
Ozone is destroyed under the influence of chlorine compounds known as freons, which, also being destroyed under the influence of solar radiation, release chlorine, which “tear off” the “third” atom from the ozone molecules. Chlorine does not form compounds, but serves as a “rupture” catalyst. Thus, one chlorine atom is able to "destroy" a lot of ozone. It is believed that chlorine compounds are able to remain in the atmosphere from 50 to 1500 years (depending on the composition of the substance) of the Earth. Observations of the planet's ozone layer have been carried out by Antarctic expeditions since the mid-1950s.
The ozone hole over Antarctica, which increases in spring and decreases in autumn, was discovered in 1985. The discovery of meteorologists caused a chain of consequences of an economic nature. The fact is that the existence of a “hole” was blamed on the chemical industry, which produces substances containing freons that contribute to the destruction of ozone (from deodorants to refrigeration units). There is no consensus on the question of how much a person is guilty of the formation of “ozone holes”. On the one hand - yes, of course, guilty. The production of ozone-depleting compounds should be minimized or, better yet, stopped altogether. That is, to abandon the whole sector of industry, with a turnover of many billions of dollars. And if you do not refuse, then transfer it to a “safe” track, which also costs money.
The point of view of skeptics: human influence on atmospheric processes, for all its destructiveness on a local level, on a planetary scale is negligible. The anti-freon campaign of the “greens” has a completely transparent economic and political background: with its help, large American corporations (DuPont, for example) stifle their foreign competitors by imposing agreements on “environmental protection” at the state level and forcibly introducing a new technological revolution, which is more economically weak states are not able to withstand.
2)high-altitude aircraft
The destruction of the ozone layer is facilitated not only by freons released into the atmosphere and entering the stratosphere. Nitrogen oxides, which are formed during nuclear explosions, are also involved in the destruction of the ozone layer. But nitrogen oxides are also formed in the combustion chambers of high-altitude aircraft turbojet engines. Nitrogen oxides are formed from the nitrogen and oxygen that are there. The rate of formation of nitrogen oxides is the greater, the higher the temperature, i.e., the greater the engine power. Not only is the engine power of an aircraft important, but also the altitude at which it flies and releases ozone-destroying nitrogen oxides. The higher the oxide or nitrous oxide is formed, the more destructive it is for ozone. The total amount of nitrogen oxide released into the atmosphere per year is estimated at 1 billion tons. About a third of this amount is emitted by aircraft above the average tropopause level (11 km). As for aircraft, the most harmful emissions are military aircraft, the number of which is in the tens of thousands. They fly mainly at the heights of the ozone layer.
3) Mineral fertilizers
Ozone in the stratosphere can also decrease due to the fact that nitrous oxide N 2 O enters the stratosphere, which is formed during the denitrification of nitrogen bound by soil bacteria. The same denitrification of bound nitrogen is also carried out by microorganisms in the upper layer of the oceans and seas. The process of denitrification is directly related to the amount of bound nitrogen in the soil. Thus, one can be sure that with an increase in the amount of mineral fertilizers applied to the soil, the amount of nitrous oxide N 2 O formed will also increase to the same extent. Further, nitrogen oxides are formed from nitrous oxide, which lead to the destruction of stratospheric ozone.
4) nuclear explosions
Nuclear explosions release a lot of energy in the form of heat. A temperature equal to 6000 0 C is set within a few seconds after a nuclear explosion. This is the energy of the fireball. In a strongly heated atmosphere, such transformations of chemical substances take place, which either do not occur under normal conditions, or proceed very slowly. As for ozone, its disappearance, the most dangerous for it are the oxides of nitrogen formed during these transformations. So, during the period from 1952 to 1971, as a result of nuclear explosions, about 3 million tons of nitrogen oxides were formed in the atmosphere. Their further fate is as follows: as a result of the mixing of the atmosphere, they fall to different heights, including into the atmosphere. There they enter into chemical reactions with the participation of ozone, leading to its destruction.
5) Fuel combustion.
Nitrous oxide is also found in flue gases from power plants. Actually, the fact that nitrogen oxide and dioxide are present in combustion products has been known for a long time. But these higher oxides do not affect ozone. They, of course, pollute the atmosphere, contribute to the formation of smog in it, but are quickly removed from the troposphere. Nitrous oxide, as already mentioned, is dangerous for ozone. At low temperatures, it is formed in the following reactions:
N 2 + O + M \u003d N 2 O + M,
2NH 3 + 2O 2 \u003d N 2 O \u003d 3H 2.
The scale of this phenomenon is very significant. In this way, approximately 3 million tons of nitrous oxide are formed in the atmosphere every year! This figure indicates that it is a source of ozone destruction.
Conclusion: Sources of destruction are: freons, high-altitude aircraft, mineral fertilizers, nuclear explosions, fuel combustion.
The ozone hole is considered to be a local drop in the ozone concentration in the Earth's ozone layer. Initially, experts assumed that the concentration of ozone tends to change due to particles that are emitted during any atomic explosion.
For a long time, high-altitude aircraft and spacecraft flights were considered the culprits for the appearance of ozone holes in the Earth's atmosphere.
However, in the course of numerous studies and experiments, it has been proven that the ozone content can vary qualitatively due to certain natural air pollutants containing nitrogen.
The main reasons for the appearance of ozone holes
It has long been established that the main amount of natural ozone is contained at an altitude of 15 to 50 kilometers above the Earth's surface - in the stratosphere. Ozone brings its greatest benefit by absorbing a significant amount of ultraviolet solar radiation, which would otherwise be detrimental to living organisms on our planet. A decrease in the concentration of ozone in a certain place can be due to two types of air pollution. These include:
- The natural processes by which air pollution occurs.
- Anthropogenic pollution of the Earth's atmosphere.
Degassing processes are constantly carried out in the Earth's mantle, as a result of which a variety of organic compounds are released. Mud volcanoes and hydrothermal springs can generate these types of gases.
In addition, certain gases are located in the earth's crust, which are in a free state. Some of them are able to reach the earth's surface and diffuse into the atmosphere through cracks in the earth's crust. Therefore, surface air over oil and gas basins often contains elevated levels of methane. These types of pollution can be attributed to natural - occurring in connection with natural phenomena.
Anthropogenic air pollution can be caused by launches of space rockets and flights of supersonic jet aircraft. Also, a large number of various chemical compounds are released into the atmosphere during the extraction and processing of numerous minerals from the bowels of the earth.
Large industrial cities, which are a kind of anthropogenic sources, also play a significant role in atmospheric pollution. Air masses in such areas are polluted by the extensive flow of road transport, as well as due to emissions from various industrial enterprises.
The history of the discovery of ozone holes in the atmosphere
The ozone hole was first discovered in 1985 by a group of British scientists led by Joe Farman. The diameter of the hole was more than 1000 kilometers, and it was located above Antarctica - in the Southern Hemisphere. Occurring annually in August, this ozone hole disappeared from December to January.
1992 was marked for scientists by the fact that already over the Northern Hemisphere in Antarctica another ozone hole was formed, with a much smaller diameter. And in 2008, the diameter of the first ozone phenomenon discovered in Antarctica reached its maximum record size - 27 million square kilometers.
Possible consequences of expanding ozone holes
Since the ozone layer is designed to protect the surface of our planet from an excess of ultraviolet solar radiation, ozone holes can be considered a really dangerous phenomenon for living organisms. A decrease in the ozone layer significantly increases the flow of solar radiation, which can affect the sharp increase in the number of skin cancers. No less detrimental is the appearance of ozone holes for plants and animals on Earth.
Thanks to public attention, the Vienna Convention for the Protection of the Ozone Layer was adopted in 1985. Then there was the so-called Montreal Protocol, adopted in 1987 and defining a list of the most dangerous chlorofluorocarbons. At the same time, the producing countries of these atmospheric pollutants pledged to limit their release, and by the year 2000 to stop completely.
Hypotheses about the natural origin of the ozone hole
But Russian scientists have published confirmation of the hypothesis about the natural origin of the Antarctic ozone hole. In 1999, NPO Typhoon published a scientific work at Moscow State University, in which, according to the calculations of geophysicists A.P. Kapitsa and A.A. Gavrilov, the Antarctic ozone hole existed before it was discovered by direct experimental methods in 1982, which, according to Russian scientists, confirms the hypothesis of the natural origin of the ozone hole over Antarctica.
The authors of this scientific work were A.P. Kapitsa (corresponding member of the Russian Academy of Sciences) b A.A. Gavrilov (Moscow State University). The two scientists managed to establish that the number of facts contradicting the anthropogenic hypothesis of the origin of the Antarctic ozone hole is constantly growing, and after proving that the data on abnormally low values of the total ozone in Antarctica in 1957-1959 are correct, it became clear that the cause of the ozone holes is different. from anthropogenic.
The results of research by Kapitsa and Gavrilov were published in Doklady Akademii Nauk, 1999, vol. 366, no. 4, p. 543-546
The ozone layer was first studied by scientists at the British Antarctic Stations in 1957. Ozone has been considered as a possible indicator of long-term changes in the atmosphere. In 1985, the annual depletion of the ozone layer and the formation of ozone holes were announced in the journal Nature.
What is the ozone hole and why does it occur?
Ozone is produced in large quantities in the stratosphere above the tropics, where UV radiation is strongest. Then it circulates in the earth's atmosphere towards the poles. The amount of ozone varies depending on the location, time of year and daily climatic conditions. The decrease in the concentration of ozone in the atmosphere, which is observed at the poles of the Earth, is called the ozone hole.
The thinner the ozone layer becomes, the larger the size of the ozone holes. There are 3 main reasons for their formation:
- Natural redistribution of ozone concentration in the atmosphere. The maximum amount of ozone is found at the equator, decreasing towards the poles, forming areas with a reduced concentration of this element.
- Technogenic factor . CFCs contained in aerosol cans and refrigerants are emitted into the atmosphere by human activities. The resulting chemical reactions in the atmosphere destroy the ozone molecules. This thins the ozone layer and reduces its ability to absorb ultraviolet light.
- Global climate warming. The temperature at the earth's surface is constantly rising, while the upper layers of the stratosphere are cooling. This is accompanied by the formation of mother-of-pearl clouds, in which ozone destruction reactions occur.
Consequences of expanding ozone holes
The existence of life on Earth is possible only due to the presence of the ozone layer. It effectively protects the planet from the penetration of harmful UV radiation, which is highly reactive.
- When exposed to ultraviolet radiation, DNA is damaged. This can lead to unwanted mutations in living organisms.
- UV rays penetrate even through water and cause the death of plant cells and microorganisms that serve as food for more developed animals. As a result, their numbers are decreasing.
- In humans, excess UV radiation can cause skin cancer. (A 1% decrease in ozone increases the incidence of skin cancer by 5%).
- Direct contact of ultraviolet light with the retina of the eye provokes the formation of cataracts. This affects the quality of vision and can cause blindness.
In 1987, an international agreement was drawn up - the Montreal Protocol - to regulate the emission of harmful gases into the atmosphere that destroy ozone molecules. Following the protocol helps to gradually reduce the depletion of the ozone layer in the atmosphere and prevent the expansion of ozone holes.
