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 from military aircraft, which number 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.

These and other recent scientific findings reinforced the conclusion of previous assessments that the body of scientific evidence suggests that the observed loss of ozone at mid and high latitudes is mainly due to anthropogenic chlorine- and bromine-containing compounds.

Original text (English)

These and other recent scientific findings strengthen the conclusion of the previous assessment that the weight of scientific evidence suggests that the observed middle- and high-latitude ozone losses are largely due to anthropogenic chlorine and bromine compounds

According to another hypothesis, the process of formation of "ozone holes" can be largely natural and is not associated solely with the harmful effects of human civilization.

To determine the boundaries of the ozone hole, a minimum level of ozone in the atmosphere of 220 Dobson units was chosen.

The area of ​​the ozone hole over the Antarctic averaged 22.8 million square kilometers in 2018 (in 2010-2017, the average annual values ​​ranged from 17.4 to 25.6 million square kilometers, in 2000-2009 - from 12.0 to 26 .6 million square kilometers, in 1990-1999 - from 18.8 to 25.9 million square kilometers).

Story [ | ]

An ozone hole with a diameter of over 1000 km was first discovered in 1985 in the Southern Hemisphere, over Antarctica, by a group of British scientists: (English), (English), (English), who published a corresponding article in the journal Nature. Every August it appeared, and in December - January it ceased to exist. Numerous mini-ozone holes exist over the Northern Hemisphere in the Arctic in autumn and winter. The area of ​​such a hole does not exceed 2 million km², its lifetime is up to 7 days.

Mechanism of education[ | ]

As a result of the absence of solar radiation, ozone is not formed during the polar nights. No ultraviolet - no ozone. Having a large mass, ozone molecules descend to the Earth's surface and are destroyed, as they are unstable at normal pressure.

Rowland and Molina suggested that chlorine atoms could cause the destruction of large amounts of ozone in the stratosphere. Their findings were based on similar work by Paul Joseph Crutzen and Harold Johnstone, who showed that nitric oxide (II) (NO) can accelerate ozone depletion.

A combination of factors leads to a decrease in the concentration of ozone in the atmosphere, the main of which is the death of ozone molecules in reactions with various substances of anthropogenic and natural origin, the absence of solar radiation during the polar winter, a particularly stable polar vortex, which prevents the penetration of ozone from subpolar latitudes, and the formation polar stratospheric clouds (PSC), whose surface particles catalyze ozone decay reactions. These factors are especially characteristic of the Antarctic, in the Arctic the polar vortex is much weaker due to the lack of a continental surface, the temperature is several degrees higher than in the Antarctic, and PSOs are less common, and they also tend to break up in early autumn. Being reactive, ozone molecules can react with many inorganic and organic compounds. The main substances that contribute to the destruction of ozone molecules are simple substances (hydrogen, oxygen atoms, chlorine, bromine), inorganic (hydrogen chloride, nitrogen monoxide) and organic compounds (methane, fluorochlorine and fluorobromofreons, which emit chlorine and bromine atoms). Unlike, for example, hydrofluorofreons, which decompose to fluorine atoms, which, in turn, quickly react with water, forming stable hydrogen fluoride. Thus, fluorine does not participate in ozone decay reactions. Iodine also does not destroy stratospheric ozone, since iodine-containing organic matter is almost completely consumed even in the troposphere. The main reactions that contribute to the destruction of ozone are given in the article about the ozone layer.

Effects [ | ]

The weakening of the ozone layer increases the flow of ultraviolet solar radiation penetrating into ocean waters, which leads to an increase in mortality among marine animals and plants.

Restoration of the ozone layer[ | ]

Although mankind has taken measures to limit emissions of chlorine- and bromine-containing freons by switching to other substances, such as fluorine-containing freons, the process of restoring the ozone layer will take several decades. First of all, this is due to the huge volume of freons already accumulated in the atmosphere, which have a lifetime of tens and even hundreds of years. Therefore, the tightening of the ozone hole should not be expected before 2048. According to Professor Susan Solomon, between 2000 and 2015, the ozone hole over Antarctica shrank by about the size of India. According to NASA, in 2000 the average annual area of ​​the ozone hole over Antarctica was 24.8 million square kilometers, in 2015 - 25.6 million square kilometers.

Misconceptions about the ozone hole[ | ]

There are several widespread myths about the formation of ozone holes. Despite their unscientific nature, they often appear in the media [ ] - sometimes out of ignorance, sometimes supported by conspiracy theorists. Some of them are listed below.

The ozone hole over Antarctica has been around for a long time[ | ]

Systematic scientific observations of the ozone layer of Antarctica have been carried out since the 20s of the XX century, but only in the second half of the 70s was the formation of a “stable” Antarctic ozone hole discovered, and its rapid development (increase in size and decrease in the average concentration of ozone within the boundaries of the hole ) in the 1980s and 1990s caused panic fears that the point of no return in the degree of destructive anthropogenic impact on the ozone layer had already been passed.

Freons are the main destroyers of ozone.[ | ]

This statement is true for middle and high latitudes. In the rest, the chlorine cycle is responsible for only 15-25% of ozone loss in the stratosphere. At the same time, it should be noted that 80% of chlorine is of anthropogenic origin (for more details about the contribution of various cycles, see the article on the ozone layer). That is, human intervention greatly increases the contribution of the chlorine cycle. And if there was a tendency to increase the production of freons before the entry into force of the Montreal Protocol (10% per year), from 30 to 50% of the total ozone loss in 2050 would be due to exposure to freons. Before human intervention, the processes of ozone formation and its destruction were in equilibrium. But freons emitted by human activity have shifted this balance towards a decrease in ozone concentration. As for the polar ozone holes, the situation is completely different. The mechanism of ozone destruction is fundamentally different from higher latitudes, the key stage is the conversion of inactive forms of halogen-containing substances into oxides, which occurs on the surface of particles of polar stratospheric clouds. And as a result, almost all ozone is destroyed in reactions with halogens, chlorine is responsible for 40-50% and bromine is about 20-40%.

DuPont position[ | ]

DuPont, after the publication of data on the participation of freons in the destruction of stratospheric ozone, took this theory with hostility and spent millions of dollars on a press campaign to protect freons. The DuPont chairman wrote in a July 16, 1975 article in Chemical Week that the ozone depletion theory was science fiction, nonsense that made no sense. In addition to DuPont, a number of companies around the world have produced and continue to produce various types of freons royalty-free.

Freons are too heavy to reach the stratosphere[ | ]

It is sometimes argued that since Freon molecules are much heavier than nitrogen and oxygen, they cannot reach the stratosphere in significant quantities. However, atmospheric gases are mixed completely and not stratified or sorted by weight. Estimates of the required time for diffusional separation of gases in the atmosphere require times of the order of thousands of years. Of course, this is not possible in a dynamic atmosphere. The processes of vertical mass transfer, convection and turbulence completely mix the atmosphere below the turbopause much faster. Therefore, even such heavy gases as inert or freons are evenly distributed in the atmosphere, including reaching the stratosphere. Experimental measurements of their concentrations in the atmosphere confirm this; Measurements also show that it takes about five years for gases released on the Earth's surface to reach the stratosphere, see the second graph on the right. If the gases in the atmosphere did not mix, then such heavy gases from its composition as argon and carbon dioxide would form a layer several tens of meters thick on the Earth's surface, which would make the Earth's surface uninhabitable. But it's not. Both krypton with an atomic mass of 84 and helium with an atomic mass of 4 have the same relative concentration, which is near the surface, which is up to 100 km in height. Of course, all of the above is only true for gases that are relatively stable, like freons or inert gases. Substances that enter into reactions and are also subjected to various physical influences, say, dissolve in water, have a dependence of concentration on height.

The main sources of halogens are natural, not anthropogenic[ | ]

Sources of chlorine in the stratosphere

There is an opinion that natural sources of halogens, such as volcanoes or oceans, are more significant for the process of ozone depletion than those produced by man. Without questioning the contribution of natural sources to the overall balance of halogens, it should be noted that they generally do not reach the stratosphere due to the fact that they are water-soluble (mainly chloride ions and hydrogen chloride) and are washed out of the atmosphere, falling as rain on the ground. Also, natural compounds are less stable than freons, for example, methyl chloride has an atmospheric lifetime of only about a year, compared to tens and hundreds of years for freons. Therefore, their contribution to the destruction of stratospheric ozone is rather small. Even the rare eruption of Mount Pinatubo in June 1991 caused a drop in ozone levels not due to the released halogens, but due to the formation of a large mass of sulfuric acid aerosols, the surface of which catalyzed the reactions of ozone destruction. Fortunately, after three years, almost the entire mass of volcanic aerosols was removed from the atmosphere. Thus, volcanic eruptions are relatively short-term factors affecting the ozone layer, unlike freons, which have lifetimes of tens and hundreds of years.

The ozone hole must be above the freon sources[ | ]

Dynamics of changes in the size of the ozone hole and ozone concentration in Antarctica by years

Many do not understand why the ozone hole is formed in the Antarctic, when the main emissions of freons occur in the Northern Hemisphere. The fact is that freons are well mixed in the troposphere and stratosphere. Due to their low reactivity, they are practically not consumed in the lower layers of the atmosphere and have a lifetime of several years or even decades. Being highly volatile molecular compounds, they reach the upper atmosphere relatively easily.

The Antarctic "ozone hole" itself does not exist year-round. It appears in late winter - early spring (August-September) and manifests itself in a noticeable decrease in the average ozone concentration within a vast geographical area. The reasons why the ozone hole forms in Antarctica are related to the peculiarities of the local climate. The low temperatures of the Antarctic winter lead to the formation of the polar vortex. The air inside this vortex moves mainly along closed paths around the South Pole and weakly mixes with air from other latitudes. At this time, the polar region is not illuminated by the Sun, and in the absence of ultraviolet radiation, ozone is not formed, but, accumulated before, is destroyed (both as a result of interactions with other substances and particles, and spontaneously, since ozone molecules are unstable). With the advent of the polar day, the amount of ozone gradually increases and again reaches the normal level. That is, fluctuations in ozone concentration over the Antarctic are seasonal.

But if we trace the dynamics of changes in the ozone concentration and the size of the ozone hole averaged over each year over the past decades, then there is a pronounced trend towards a decrease in the average ozone concentration within a huge geographical area.

Sources and notes[ | ]

1. Scientific Assessment of Ozone Depletion: 2006(English) . Retrieved December 13, 2007. Archived from the original on February 16, 2012.
2. "Knowledge is power" Science news: 27.12.99 (Russian). Retrieved July 3, 2007. Archived from the original on February 16, 2012.

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 from military aircraft, which number 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 holes - "children" of stratospheric vortices

Although there is not much ozone in the modern atmosphere - no more than one three millionth of the rest of the gases - its role is extremely large: it delays hard ultraviolet radiation (the short-wave part of the solar spectrum), which destroys proteins and nucleic acids. In addition, stratospheric ozone is an important climatic factor that determines short-term and local weather changes.

The rate of ozone destruction reactions depends on catalysts, which can be both natural atmospheric oxides and substances released into the atmosphere as a result of natural disasters (for example, powerful volcanic eruptions). However, in the second half of the last century, it was discovered that substances of industrial origin can also serve as catalysts for ozone destruction reactions, and humanity was seriously worried ...

Ozone (O 3) is a relatively rare molecular form of oxygen, consisting of three atoms. Although there is not much ozone in the modern atmosphere - no more than one three millionth of the rest of the gases - its role is extremely large: it delays hard ultraviolet radiation (the short-wave part of the solar spectrum), which destroys proteins and nucleic acids. Therefore, before the advent of photosynthesis - and, accordingly, free oxygen and the ozone layer in the atmosphere - life could exist only in water.

In addition, stratospheric ozone is an important climatic factor that determines short-term and local weather changes. By absorbing solar radiation and transferring energy to other gases, ozone heats the stratosphere and thereby regulates the nature of planetary thermal and circular processes throughout the atmosphere.

Unstable ozone molecules in natural conditions are formed and decomposed under the influence of various factors of animate and inanimate nature, and in the course of a long evolution this process has come to a certain dynamic equilibrium. The rate of ozone destruction reactions depends on catalysts, which can be both natural atmospheric oxides and substances released into the atmosphere as a result of natural disasters (for example, powerful volcanic eruptions).

However, in the second half of the last century, it was discovered that substances of industrial origin can also serve as catalysts for ozone destruction reactions, and mankind was seriously worried. Public opinion was especially excited by the discovery of the so-called ozone "hole" over Antarctica.

"Hole" over Antarctica

A noticeable decrease in the ozone layer over Antarctica - the ozone hole - was first discovered back in 1957, during the International Geophysical Year. Her real story began 28 years later with an article in the May issue of the magazine Nature, where it was suggested that the reason for the anomalous spring minimum of TO over Antarctica is industrial (including Freons) atmospheric pollution (Farman et al., 1985).

It was found that the ozone hole over Antarctica usually occurs once every two years, lasts about three months, and then disappears. It is not a through hole, as it may seem, but a recess, so it is more correct to speak of "ozone layer sagging". Unfortunately, all further studies of the ozone hole were mainly aimed at proving its anthropogenic origin (Roan, 1989).

Today, there are different hypotheses regarding the chemical and dynamic mechanisms of the formation of ozone holes. However, many known facts do not fit into the chemical anthropogenic theory. For example, the growth of stratospheric ozone in certain geographic regions.

Here is the most "naive" question: why is a hole formed in the southern hemisphere, although freons are produced in the northern, despite the fact that it is not known whether there is air communication between the hemispheres at that time?

None of the existing theories is based on large-scale detailed TO measurements and studies of processes occurring in the stratosphere. To answer the question about the degree of isolation of the polar stratosphere over Antarctica, as well as a number of other questions related to the problem of the formation of ozone holes, it was possible only with the help of a new method for tracking the movements of air flows proposed by V. B. Kashkin (Kashkin, Sukhinin, 2001; Kashkin et al., 2002).

Air flows in the troposphere (up to a height of 10 km) have long been traced by observing the translational and rotational movements of clouds. Ozone, in fact, is also a huge "cloud" over the entire surface of the Earth, and changes in its density can be used to judge the movement of air masses above 10 km, just as we know the direction of the wind by looking at a cloudy sky on an overcast day. For these purposes, the ozone density should be measured at the points of the spatial lattice with a certain time interval, for example, every 24 hours. By following how the ozone field has changed, it is possible to estimate the angle of its rotation per day, the direction and speed of movement.

Using the new method, the dynamics of the ozone layer was studied in 2000, when a record-breaking ozone hole was observed over Antarctica (Kashkin et al., 2002). For this, satellite data on the density of ozone throughout the southern hemisphere, from the equator to the pole, were used. As a result, it was found that the ozone content is minimal in the center of the funnel of the so-called circumpolar vortex, which formed above the pole, which we will discuss in detail below. On the basis of these data, a hypothesis of a natural mechanism for the formation of ozone "holes" was put forward.

Global dynamics of the stratosphere: a hypothesis

Circumpolar vortices are formed during the movement of stratospheric air masses in the meridional and latitudinal directions. How does this happen? The stratosphere is higher at the warm equator and lower at the cold pole. Air streams (together with ozone) roll down from the stratosphere like a hill, and move faster and faster from the equator to the pole. The movement from west to east occurs under the influence of the Coriolis force associated with the rotation of the Earth. As a result, air flows seem to be wound, like threads on a spindle, on the southern and northern hemispheres.

The "spindle" of air masses rotates throughout the year in both hemispheres, but is more pronounced in late winter and early spring, because the height of the stratosphere at the equator almost does not change throughout the year, and at the poles it is higher in summer and lower in winter, when it is especially cold.

The ozone layer in the middle latitudes is created due to a powerful influx from the equator, as well as as a result of photochemical reactions occurring in place. But the ozone in the region of the pole owes its origin mainly to the flow from the equator and from the middle latitudes, and its content there is quite low. Photochemical reactions at the pole, where the sun's rays fall at a low angle, are slow, and a significant part of the ozone coming from the equator has time to be destroyed along the way.

But air masses don't always move like that. In the coldest winters, when the stratosphere over the pole drops very low above the Earth's surface and the "hill" becomes especially steep, the situation changes. Stratospheric currents roll down so fast that there is an effect familiar to anyone who has watched water flow down through a hole in a tub. Having reached a certain speed, the water begins to rotate rapidly, and a characteristic funnel is formed around the hole, created by centrifugal force.

Something similar happens in the global dynamics of stratospheric flows. When the currents of stratospheric air gain a sufficiently high speed, the centrifugal force begins to push them away from the pole towards the middle latitudes. As a result, air masses move from the equator and from the pole towards each other, which leads to the formation of a rapidly rotating "shaft" of the vortex in the middle latitudes.

The exchange of air between the equatorial and polar regions ceases, and ozone from the equator and from the middle latitudes does not reach the pole. In addition, the ozone remaining at the pole, as in a centrifuge, is squeezed out to the middle latitudes by centrifugal force, since it is heavier than air. As a result, the ozone concentration inside the funnel drops sharply - an ozone "hole" is formed above the pole, and in the middle latitudes - an area of ​​high ozone content, corresponding to the "shaft" of the circumpolar vortex.

In spring, the Antarctic stratosphere warms up and rises higher - the funnel disappears. Air communication between middle and high latitudes is being restored, and photochemical reactions of ozone formation are also accelerating. The ozone hole disappears before another particularly cold winter at the South Pole.

What about in the Arctic?

Although the dynamics of stratospheric flows and, accordingly, the ozone layer in the northern and southern hemispheres is generally similar, the ozone hole only occurs from time to time over the South Pole. There are no ozone holes above the North Pole because the winters are milder and the stratosphere never drops low enough for air currents to pick up the speed needed to form a funnel.

There is another important difference. In the southern hemisphere, the circumpolar vortex rotates almost twice as fast as in the northern. And this is not surprising: Antarctica is surrounded by seas and there is a circumpolar sea current around it - in essence, gigantic masses of water and air rotate together. The picture is different in the northern hemisphere: in the middle latitudes there are continents with mountain ranges, and the friction of the air mass against the earth's surface does not allow the circumpolar vortex to gain a sufficiently high speed.

However, small ozone "holes" of a different origin sometimes appear in the middle latitudes of the northern hemisphere. Where do they come from? The movement of air in the mid-latitude stratosphere of the mountainous northern hemisphere resembles the movement of water in a shallow stream with a rocky bottom, when numerous whirlpools form on the surface of the water. In the middle latitudes of the northern hemisphere, the role of the bottom surface relief is played by temperature differences at the border of continents and oceans, mountain ranges and plains.

A sharp change in temperature on the Earth's surface leads to the formation of vertical flows in the troposphere. Stratospheric winds colliding with these currents create eddies that can rotate in both directions with equal probability. Within them, areas with low ozone content appear, that is, ozone holes much smaller in size than at the South Pole. And it should be noted that such vortices with different directions of rotation were discovered at the first attempt.

Thus, the dynamics of stratospheric air flows, which we traced while observing the ozone cloud, allows us to give a plausible explanation for the mechanism of the formation of the ozone hole over Antarctica. Apparently, such changes in the ozone layer, due to aerodynamic phenomena in the stratosphere, took place long before the appearance of man.

All of the above does not mean at all that freons and other gases of industrial origin do not have a destructive effect on the ozone layer. However, scientists have yet to find out what is the ratio of natural and anthropogenic factors influencing the formation of ozone holes - it is unacceptable to draw hasty conclusions on such important issues.

There are many hypotheses trying to explain the decline in ozone concentration. The reasons for its fluctuations in the Earth's atmosphere are related to:

• · with dynamic processes occurring in the Earth's atmosphere (internal gravitational waves, Azores anticyclone, etc.);
• With the influence of the Sun (fluctuations in its activity);
• · with volcanism as a consequence of geological processes (outflow of freons from volcanoes involved in the destruction of the ozone layer, variations in the Earth's magnetic field, etc.);
• · with natural processes occurring in the upper shells of the Earth, including the activity of nitrogen-producing microorganisms, sea currents (the El Niño phenomenon), forest fires, etc.;
• · with the anthropogenic factor associated with human economic activity, when significant volumes of ozone-depleting compounds are produced into the atmosphere.

In recent decades, the effect of anthropogenic factors has increased dramatically, which led to the emergence of environmental problems that were unexpectedly turned into global ones by people themselves: the greenhouse effect, acid rain, deforestation, desertification of territories, pollution of the environment with harmful substances, reduction of the biological diversity of the planet.

Some scientists believe that it was human economic activity that largely increased the share of the halogen pathway of stratospheric ozone decay, which provoked the emergence of ozone holes.

The Montreal Protocol of 1987 banned the production of refrigerants, which in the past half century allowed food to be preserved and thereby not only made life more comfortable for people, but also saved the lives of many millions of people suffering from food shortages. As cheap refrigerants were banned, underdeveloped countries were unable to purchase expensive refrigerators. Therefore, they cannot store their agricultural products. Expensive imported equipment, developed in the countries of the initiators of the "fight against ozone holes", brings them considerable income. The prohibition of refrigerants contributed to the increase in mortality in the poorest countries.

Today we can say with confidence that there is no strictly scientifically proven evidence of the destructive effect of artificially created chlorofluorocarbon molecules on the planet's ozone layer. But in the scientific community, the point of view prevails, according to which, in the second half of the 20th century, the reason for the decrease in the thickness of the ozone layer is the anthropogenic factor, which, in the form of the release of chlorine- and bromine-containing freons, led to a significant thinning of the ozone layer.

Freons are fluorine-containing derivatives of saturated hydrocarbons (mainly methane and ethane) used as refrigerants in refrigerators. In addition to fluorine atoms, freon molecules usually contain chlorine atoms, less often bromine atoms. More than 40 different freons are known. Most of them are produced by the industry.

Freon 22 (Freon 22) - refers to substances of the 4th hazard class. Under the action of temperatures above 400°C, it can decompose with the formation of highly toxic products: tetrafluoroethylene (hazard class 4), hydrogen chloride (hazard class 2), hydrogen fluoride (hazard class 1).

Thus, the obtained data strengthened the conclusion of many (but not all!) researchers that the observed loss of ozone in middle and high latitudes is mainly due to anthropogenic chlorine- and bromine-containing compounds.

But according to other ideas, the formation of "ozone holes" is largely a natural, periodic process, not exclusively associated with the harmful effects of human civilization. Not many people share this point of view today, not only because of their lack of arguments, but because it turned out to be more profitable to follow in the wake of “global utopias”. Many scientists, in the absence of funds for scientific research, have become and are becoming victims of grants to substantiate the ideas of "global environmental chauvinism" and the guilt of progress in this.

As G. Kruchenitsky, A. Khrgian, Russia's leading expert on ozone, points out, he was practically the first to draw attention to the fact that the formation and disappearance of ozone holes in the northern hemisphere correlates with atmospheric-dynamic rather than chemical processes. The ozone content can change by several tens of percent within two to three days. That is, the point is not in ozone-depleting substances, but in the dynamics of the atmosphere itself.

E. Borisenkov, a prominent specialist in the field of atmospheric studies, based on the processing of data from nine Western European stations over twenty-three years, established a correlation between 11-year cycles of solar activity and ozone changes in the Earth's atmosphere.

The causes of ozone holes are mostly associated with anthropogenic sources of compounds penetrating into the stratospheric layer of the Earth's atmosphere. However, there is one catch. It consists in the fact that the main sources of ozone-depleting compounds are not located in the polar (southern and northern) latitudes, but are concentrated closer to the equator and are almost entirely located in the northern hemisphere. While the most frequent phenomena of the occurrence of thinning of the ozone layer (the actual appearance of ozone holes) are observed in Antarctica (southern hemisphere) and less often in the Arctic zone.

That is, the sources of ozone-depleting compounds must be rapidly and well mixed in the Earth's atmosphere. At the same time, they quickly leave the lower layers of the atmosphere, where their reactions with the participation of ozone should also be observed. In fairness, it should be noted that there is much less ozone in the troposphere than in the stratosphere. In addition, the "lifetime" of these compounds can reach several years. Therefore, they can reach the stratosphere under conditions of dominant vertical movements of air masses and heat. But here comes the difficulty. Since the main movements associated with heat and mass transfer (heat + transported air mass) are carried out precisely in the troposphere. And since the air temperature already at an altitude of 11-10 km is constant and is about -50? C, this heat and mass transfer from the tropospheric layer to the stratospheric should be slowed down. And the participation of anthropogenic sources that destroy the ozone layer may not be as significant as it is believed so far.

The next fact that can reduce the role of the anthropogenic factor in the destruction of the Earth's ozone layer is the appearance of ozone holes, mostly in spring or winter. But this, firstly, contradicts the assumption about the possibility of rapid mixing of ozone-depleting compounds in the Earth's atmosphere and their penetration into the stratospheric layer of high ozone concentration. Secondly, the anthropogenic source of ozone-depleting compounds is a permanent one. Consequently, it is difficult to explain the reason for the appearance of ozone holes in spring and winter, and even in polar latitudes, by an anthropogenic cause. On the other hand, the presence of polar winters and the natural decrease in solar radiation in winter satisfactorily explain the natural cause of the occurrence of ozone holes over Antarctica and the Arctic. For example, ozone concentrations in the Earth's atmosphere in summer vary from 0 to 0.07%, and in winter from 0 to 0.02%.

In Antarctica and the Arctic, the mechanism of ozone depletion is fundamentally different from higher latitudes. Here, the conversion of inactive forms of halogen-containing substances into oxides mainly occurs. The reaction takes place on the surface of particles of polar stratospheric clouds. As a result, almost all ozone is destroyed in reactions with halogens. At the same time, chlorine is responsible for 40-50% and bromine is about 20-40%.

With the advent of the polar summer, the amount of ozone increases and again reaches its previous norm. That is, fluctuations in ozone concentration over the Antarctic are seasonal. Everyone recognizes this. But if, nevertheless, earlier supporters of anthropogenic sources of ozone-depleting compounds were inclined to assert that during the year there was a steady decrease in ozone concentration, then later this dynamics turned out to be the opposite. The ozone holes began to shrink. Although, in their opinion, the restoration of the ozone layer should take several decades. Since it was believed that a huge volume of freons from anthropogenic sources had accumulated in the atmosphere, which had a lifetime of tens, and even hundreds of years. Therefore, the tightening of the ozone hole should not be expected before 2048. As you can see, this prediction did not come true. On the other hand, efforts to reduce freon production volumes were made cardinal.

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