Ozone holes

It is known that the bulk of natural ozone is concentrated in the stratosphere at an altitude of 15 to 50 km above the Earth's surface. The ozone layer begins at altitudes of about 8 km above the poles (or 17 km above the Equator) and extends upward to altitudes of approximately 50 km. However, the density of ozone is very low, and if you compress it to the density that air has at the surface of the earth, the thickness of the ozone layer will not exceed 3.5 mm. Ozone is formed when ultraviolet radiation from the sun bombards oxygen molecules.

Most ozone is in the five-kilometer layer at an altitude of 20 to 25 km, which is called the ozone layer.

Protective role. Ozone absorbs part of the ultraviolet radiation from the Sun: its wide absorption band (wavelength 200-300 nm) also includes radiation that is harmful to all life on Earth.

Causes of the formation of the "ozone hole"

In summer and spring, ozone concentrations increase; over the polar regions it is always higher than over the equatorial ones. In addition, it changes on an 11-year cycle, coinciding with the solar activity cycle. All this was already well known when in the 1980s. Observations have shown that over Antarctica there is a slow but steady decrease in stratospheric ozone concentrations from year to year. This phenomenon was called the “ozone hole” (although, of course, there was no hole in the proper sense of the word) and began to be carefully studied. Later, in the 1990s, a similar decrease began to occur over the Arctic. The phenomenon of the Antarctic “ozone hole” is not yet clear: whether the “hole” arose as a result of anthropogenic pollution of the atmosphere, or whether it is a natural geoastrophysical process.

At first it was assumed that ozone was affected by particles emitted from atomic explosions; tried to explain the change in ozone concentration by the flights of rockets and high-altitude aircraft. In the end, it was clearly established that the cause of the undesirable phenomenon was the reaction of certain substances produced by chemical plants with ozone. These are primarily chlorinated hydrocarbons and especially freons - chlorofluorocarbons, or hydrocarbons in which all or most of the hydrogen atoms are replaced by fluorine and chlorine atoms.

It is assumed that due to the destructive effects of chlorine and similarly acting bromine, by the end of the 1990s. ozone concentration in the stratosphere decreased by 10%.

In 1985, British scientists released data according to which, over the previous eight years, ozone holes had been discovered over the North and South Poles, increasing every spring.

Scientists have proposed three theories to explain the reasons for this phenomenon:

nitrogen oxides - compounds formed naturally in sunlight;

destruction of ozone by chlorine compounds.

The first thing to be clear is that the ozone hole, contrary to its name, is not a hole in the atmosphere. The ozone molecule differs from an ordinary oxygen molecule in that it consists of not two, but three oxygen atoms connected to each other. In the atmosphere, ozone is concentrated in the so-called ozone layer, at an altitude of approximately 30 km within the stratosphere. This layer absorbs ultraviolet rays emitted by the Sun, otherwise solar radiation could cause great harm to life on the surface of the Earth. Therefore, any threat to the ozone layer deserves to be taken very seriously. In 1985, British scientists working at the South Pole discovered that during the Antarctic spring, the level of ozone in the atmosphere there was significantly below normal. Every year at the same time the amount of ozone decreased - sometimes to a greater extent, sometimes to a lesser extent. Similar, but less pronounced ozone holes also appeared over the North Pole during the Arctic spring.

In subsequent years, scientists figured out why the ozone hole appears. When the sun goes down and the long polar night begins, temperatures plummet and high stratospheric clouds containing ice crystals form. The appearance of these crystals causes a series of complex chemical reactions leading to the accumulation of molecular chlorine (a chlorine molecule consists of two joined chlorine atoms). When the sun appears and the Antarctic spring begins, under the influence of ultraviolet rays, intramolecular bonds are broken, and a stream of chlorine atoms rushes into the atmosphere. These atoms act as catalysts for reactions that convert ozone into simple oxygen, proceeding according to the following dual scheme:

Cl + O3 -> ClO + O2 and ClO + O -> Cl + O2

As a result of these reactions, ozone molecules (O3) are converted into oxygen molecules (O2), with the original chlorine atoms remaining in a free state and again participating in this process (each chlorine molecule destroys a million ozone molecules before they are removed from the atmosphere by other chemical reactions). As a result of this chain of transformations, ozone begins to disappear from the atmosphere over Antarctica, forming an ozone hole. However, soon, with warming, the Antarctic vortexes collapse, fresh air (containing new ozone) rushes into the area, and the hole disappears.

In 1987, the Montreal Protocol was adopted, according to which a list of the most dangerous chlorofluorocarbons was determined, and the countries producing chlorofluorocarbons pledged to reduce their production. In June 1990, in London, clarifications were made to the Montreal Protocol: by 1995, reduce the production of freons by half, and by 2000, stop it completely.

It has been established that the ozone content is influenced by nitrogen-containing air pollutants, which appear both as a result of natural processes and as a result of anthropogenic pollution.

Thus, NO is formed in internal combustion engines. Accordingly, the launch of rockets and supersonic aircraft leads to the destruction of the ozone layer.

The source of NO in the stratosphere is also the gas N2O, which is stable in the troposphere, but in the stratosphere it decays under the influence of hard UV radiation.

The ozone layer was first explored 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 journal Nature announced the annual depletion of the ozone layer and the formation of ozone holes.

What is the ozone hole and the reasons for its appearance

Ozone is produced in large quantities in the stratosphere above the tropics, where UV radiation is strongest. It then circulates in the earth's atmosphere towards the poles. The amount of ozone varies depending on location, time of year, and daily climate conditions. The decrease in ozone concentration in the atmosphere, which is observed at the Earth's poles, 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 . Chlorofluorocarbons contained in aerosol cans and refrigerants are released into the atmosphere by human activities. The chemical reactions that occur in the atmosphere destroy ozone molecules. This thins the ozone layer and reduces its ability to absorb ultraviolet light.
• Global 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 pearlescent 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 harmful UV radiation, which is highly reactive.

• When exposed to ultraviolet light, DNA is damaged. This can lead to unwanted mutations in living organisms.
• UV rays even penetrate 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 concentration increases the incidence of skin cancer by 5%).
• Direct contact of ultraviolet radiation with the retina of the eyes provokes the occurrence 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 into the atmosphere of harmful gases 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.

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MINISTRY OF TRANSPORT OF THE RUSSIAN FEDERATION

FSOUVPO ULYANOVSK HIGHER AVIATION SCHOOL

CIVIL AVIATION (INSTITUTE)

FACULTY OF FLIGHT OPERATIONS AND AIR TRAFFIC MANAGEMENT

DEPARTMENT OF PASSOP

ABSTRACT

on the topic of:Ozone holes: causesAndconsequences

Completed by: Bazarov M.A.

Head: Morozova M.M.

Ulyanovsk 2012

Introduction

1. Reasons

2. Consequences

3. Geographical location

4. The role of civil and military aircraft in the formation of ozone holes

5. Ways to solve problems

Conclusion

Introduction

With the emergence of human civilization, a new factor appeared that influenced the fate of living nature. It has achieved enormous power in the current century and especially in recent times. 5 billion of our contemporaries have an impact on nature on the same scale as the people of the Stone Age could have had if their number had been 50 billion people, and the amount of energy released is received by the earth from the sun.

Since the emergence of a highly industrialized society, dangerous human intervention in nature has sharply increased, the scope of this intervention has expanded, it has become more diverse and now threatens to become a global danger to humanity.

The consumption of non-renewable raw materials is increasing, more and more arable land is leaving the economy, as cities and factories are built on it. The Earth's biosphere is currently subject to increasing anthropogenic impact. At the same time, several of the most significant processes can be identified, any of which does not improve the condition of the airspace of our planet.

The accumulation of carbon dioxide in the atmosphere is also progressing. The further development of this process will strengthen the undesirable trend towards an increase in the average annual temperature on the planet.

As a result, a dilemma arose before society: either mindlessly roll towards its inevitable death in an impending ecological catastrophe, or consciously transform the powerful forces of science and technology created by the genius of man from a weapon previously turned against nature and man himself, into a weapon of their protection and prosperity, into a weapon rational environmental management.

A real threat of a global environmental crisis looms over the world, understood by the entire population of the planet, and the real hope for its prevention lies in continuous environmental education and enlightenment of people.

The World Health Organization has determined that human health depends 20% on heredity, 20% on the environment, 50% on lifestyle and 10% on medicine. In a number of regions of Russia, by 2005, the following dynamics of factors influencing human health are expected: the role of ecology will increase to 40%, the effect of the genetic factor will increase to 30%, the ability to maintain health through lifestyle will decrease to 25%, and the role of medicine will decrease to 5%. .

Characterizing the current state of ecology as critical, we can identify the main reasons that lead to environmental disaster: pollution, poisoning of the environment, depletion of the atmosphere in oxygen, ozone holes.

The purpose of this work was to summarize the literature data on the causes and consequences of ozone layer destruction, as well as ways to solve the problem of the formation of “ozone holes”.

ozone layer hole environmental

1. Causes

Ozone hole is a local drop in ozone concentration in the Earth's ozone layer. According to the theory generally accepted in the scientific community, in the second half of the 20th century, the increasing impact of the anthropogenic factor in the form of the release of chlorine- and bromine-containing freons led to a significant thinning of the ozone layer.

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

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: J. Shanklin (English), J. Farman (English), B. Gardiner (English), who published the corresponding article in the journal Nature. Every August it appeared, and in December - January it ceased to exist. Another hole was forming over the Northern Hemisphere in the Arctic, but of a smaller size. At this stage of human development, world scientists have proven that there are a huge number of ozone holes on Earth. But the most dangerous and largest is located above Antarctica.

A combination of factors leads to a decrease in ozone concentration 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 that prevents the penetration of ozone from subpolar latitudes, and the formation polar stratospheric clouds (PSC), the surface of which 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 absence of a continental surface, the temperature is several degrees higher than in the Antarctic, and PSOs are less common and also tend to disintegrate in early autumn. Being chemically active, 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, chlorine, bromine atoms), inorganic (hydrogen chloride, nitrogen monoxide) and organic compounds (methane, fluorochlorine and fluorobromofreons, which release chlorine and bromine atoms). In contrast, for example, to hydrofluorofreons, which decompose to fluorine atoms, which, in turn, quickly react with water to form stable hydrogen fluoride. Thus, fluorine does not participate in ozone decomposition reactions. Iodine also does not destroy stratospheric ozone, since iodine-containing organic substances are almost completely consumed in the troposphere. The main reactions that contribute to the destruction of ozone are given in the article about the ozone layer.

Chlorine “eats” both ozone and atomic oxygen due to fairly rapid reactions:

O3 + Cl = O2 + ClO

СlO + O = Cl + O2

Moreover, the latter reaction leads to the regeneration of active chlorine. Chlorine, therefore, is not even consumed, destroying the ozone layer.

In summer and spring, ozone concentrations increase. It is always higher over the polar regions than over the equatorial ones. In addition, it changes on an 11-year cycle, coinciding with the solar activity cycle. All this was already well known when in the 1980s. Observations have shown that over Antarctica there is a slow but steady decrease in stratospheric ozone concentrations from year to year. This phenomenon was called the “ozone hole” (although, of course, there was no hole in the proper sense of the word).

Later, in the 90s of the last century, the same decrease began to occur over the Arctic. The phenomenon of the Antarctic “ozone hole” is not yet clear: whether the “hole” arose as a result of anthropogenic pollution of the atmosphere, or whether it is a natural geoastrophysical process.

Among the versions of the formation of ozone holes are:

the influence of particles emitted during atomic explosions;

flights of rockets and high-altitude aircraft;

reactions with ozone of certain substances produced by chemical plants. These are primarily chlorinated hydrocarbons and especially freons - chlorofluorocarbons, or hydrocarbons in which all or most of the hydrogen atoms are replaced by fluorine and chlorine atoms.

Chlorofluorocarbons are widely used in modern household and industrial refrigerators (that’s why they are called “freons”), in aerosol cans, as dry cleaning agents, for extinguishing fires in transport, as foaming agents, for the synthesis of polymers. World production of these substances has reached almost 1.5 million tons/year.

Being highly volatile and quite resistant to chemical influences, chlorofluorocarbons enter the atmosphere after use and can remain in it for up to 75 years, reaching the height of the ozone layer. Here, under the influence of sunlight, they decompose, releasing atomic chlorine, which serves as the main “disturber of order” in the ozone layer.

2. Consequences

The ozone hole poses a danger to living organisms because the ozone layer protects the Earth's surface from excessive doses of ultraviolet radiation from the Sun. The weakening of the ozone layer increases the flow of solar radiation onto the earth and causes an increase in the number of skin cancers in people. Plants and animals also suffer from increased levels of radiation.

Ozone in the stratosphere protects the Earth from destructive ultraviolet and solar radiation. Depleting the ozone layer will allow more solar radiation to reach the Earth's surface.

Each percent of stratospheric ozone lost results in a 1.5 to 2 percent increase in exposure to ultraviolet solar radiation, according to the U.S. Environmental Protection Agency. For humans, an increase in the intensity of ultraviolet radiation is primarily dangerous due to the effects of solar radiation on the skin and eyes.

Radiation with wavelengths in the spectrum from 280 to 320 nanometers - UV rays, which are partially blocked by ozone - can cause premature aging and an increase in the number of skin cancers, as well as damage to plants and animals.

Radiation with a wavelength greater than 320 nanometers, the UV spectrum, is practically not absorbed by ozone and is actually necessary for humans to form vitamin D. UV radiation with a wavelength in the spectrum of 200 - 280 nanometers can cause serious consequences for biological organisms. However, radiation from this spectrum is almost completely absorbed by ozone. Thus, the “Achilles heel” of earthly life is the radiation of a rather narrow spectrum of UV waves with a length from 320 to 280 nanometers. As wavelengths shorten, their ability to harm living organisms and DNA increases. Fortunately, ozone's ability to absorb ultraviolet radiation increases as the wavelength of the radiation decreases.

· Increasing incidence of skin cancer.

· Suppression of the human immune system.

· Eye damage.

Ultraviolet radiation can damage the cornea, connective tissue of the eye, lens and retina. Ultraviolet radiation can cause photokeratosis (or snow blindness), similar to a sunburn of the cornea or connective tissue of the eye. Increased exposure to ultraviolet radiation as a result of ozone depletion will lead to an increase in the number of people with cataracts, according to the authors of How to Save Our Skin. Cataracts cover the lens of the eye, reducing visual acuity and can cause blindness.

· Destruction of crops.

3. Geographical location

The thinning of the ozone layer began to be recorded in the 70s. It decreased especially significantly over Antarctica, which led to the emergence of the common expression “ozone hole.” Small holes are also recorded in the northern hemisphere - over the Arctic, in the area of ​​the Plesetsk and Baikonur cosmodromes. In 1974, two scientists from the University of California - Mario Molina and Sherward Rowland - hypothesized that the main factor in ozone destruction was freon gases used in the refrigeration and perfume industries. Less significant ozone depleting factors are the flights of rockets and supersonic aircraft.

The location of the “ozone holes” tends to localize positive global magnetic anomalies. In the Southern Hemisphere this is the Antarctic, and in the Northern Hemisphere it is the East Siberian global magnetic anomaly. Moreover, the power of the Siberian anomaly is growing so strongly that even in Novosibirsk the vertical component of the geomagnetic field is growing annually by 30 gamma (nanotesla).

The loss of the ozone layer over the Arctic basin was so significant this year that for the first time in the history of observations we can talk about the emergence of an “ozone hole” similar to the Antarctic one. At altitudes above 20 km, ozone loss was about 80%. The probable cause of this phenomenon is the unusually long persistence of relatively low temperatures in the stratosphere at these latitudes.

4. The role of civil and military aviation in educationozone holes

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 turbojet engines of high-altitude aircraft. Nitrogen oxides are formed from the nitrogen and oxygen that are found there. The higher the temperature, i.e., the greater the engine power, the greater the rate of formation of nitrogen oxides.

It's not just the power of an airplane's engine that matters, but also the altitude at which it flies and releases ozone-depleting nitrogen oxides. The higher the nitrous oxide or oxide is formed, the more destructive it is to ozone.

The total amount of nitrogen oxide that is emitted 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, the number of which amounts to tens of thousands. They fly primarily at altitudes in the ozone layer.

5. Ways to solve problems

To begin global restoration, it is necessary to reduce the access to the atmosphere of all substances that very quickly destroy ozone and are stored there for a long time.

Also, we - all people - must understand this and help nature start the process of restoring the ozone layer, new forest plantings are needed, stop cutting down forests for other countries that for some reason do not want to cut down theirs, but make money from our forests.

To restore the ozone layer, it needs to be recharged. At first, for this purpose, it was planned to create several ground-based ozone factories and “throw” ozone into the upper layers of the atmosphere on cargo planes. However, this project (probably it was the first project to “treat” the planet) was not implemented.

A different way is proposed by the Russian consortium Interozon: producing ozone directly in the atmosphere. In the near future, together with the German company Daza, it is planned to raise balloons with infrared lasers to a height of 15 km, with the help of which they can produce ozone from diatomic oxygen.

If this experiment turns out to be successful, in the future it is planned to use the experience of the Russian Mir orbital station and create several space platforms with energy sources and lasers at an altitude of 400 km. Laser beams will be directed into the central part of the ozone layer and will constantly replenish it. The energy source can be solar panels. Astronauts on these platforms will only be required for periodic inspections and repairs.

Conclusion

The potential for human impact on nature is constantly growing and has already reached a level where it is possible to cause irreparable damage to the biosphere. This is not the first time that a substance that was long considered completely harmless turns out to be extremely dangerous. Twenty years ago, hardly anyone could have imagined that an ordinary aerosol can could pose a serious threat to the planet as a whole. Unfortunately, it is not always possible to predict in time how this or that compound will affect the biosphere. However, in the case of CFCs there was such a possibility: all the chemical reactions that describe the process of destruction of ozone by CFCs are extremely simple and have been known for quite a long time. But even after the CFC problem was formulated in 1974, the only country that took any measures to reduce CFC production was the United States, and these measures were completely insufficient. It took a strong enough demonstration of the dangers of CFCs for serious action to be taken on a global scale. It should be noted that even after the discovery of the ozone hole, ratification of the Montreal Convention was at one time in jeopardy. Perhaps the CFC problem will teach us to treat with greater attention and caution all substances entering the biosphere as a result of human activity.

The problem of historical and modern climate change has turned out to be very complex and does not find a solution in the schemes of single-factor determinism. Along with the increase in carbon dioxide concentration, changes in the ozonosphere associated with the evolution of the geomagnetic field play an important role. The development and testing of new hypotheses are a necessary condition for understanding the patterns of general atmospheric circulation and other geophysical processes affecting the biosphere.

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One of the most remarkable "green" myths is the claim that the ozone holes above the Earth's poles are caused by emissions of certain substances produced by humans into the atmosphere. Thousands of people still believe in it, even though any schoolchild who hasn’t skipped chemistry and geography classes can debunk this myth.

The myth that human activity is causing the so-called ozone hole to grow is remarkable in many ways. Firstly, it is extremely plausible, that is, it is based on real facts. Such as the presence of the ozone hole itself and the fact that a number of substances produced by humans can destroy ozone. And if so, then a non-specialist has no doubt that it is human activity that is to blame for the depletion of the ozone layer - just look at the graphs of the hole’s growth and the increase in emissions of relevant substances into the atmosphere.

And here another feature of the “ozone” myth emerges. For some reason, those who believe the above-mentioned evidence completely forget that the mere coincidence of two graphs does not mean anything. After all, it may just be an accident. In order to have undeniable evidence of the anthropogenic theory of the origin of ozone holes, it is necessary to study not only the mechanism of ozone destruction by freons and other substances, but also the mechanism of subsequent restoration of the layer.

Well, here comes the fun part. As soon as an interested non-specialist begins to study all these mechanisms (for which you do not need to sit in the library for days - just remember a few paragraphs from school textbooks on chemistry and geography), he immediately understands that this version is nothing more than a myth. And remembering the impact this myth had on the world economy by limiting the production of freons, he immediately understands why it was created. However, let's look at the situation from the very beginning and in order.

We remember from the chemistry course that ozone is an allotropic modification of oxygen. Its molecules contain not two O atoms, but three. Ozone can be formed in different ways, but the most common in nature is this: oxygen absorbs a portion of ultraviolet radiation with a wavelength of 175-200 nm and 280-315 nm and is converted into ozone. This is exactly how the ozone protective layer was formed in ancient times (somewhere 2-1.7 billion years ago), and this is how it continues to form to this day.

By the way, from the above it follows that almost half of the dangerous UV radiation is actually absorbed by oxygen, not ozone. Ozone is only a “by-product” of this process. However, its value lies in the fact that it also absorbs part of the ultraviolet - that whose wavelength is from 200 to 280 nm. But what happens to the ozone itself? That's right - it turns back into oxygen. Thus, in the upper layers of the atmosphere there is a certain cyclic equilibrium process - ultraviolet of one type promotes the conversion of ozone into oxygen, and it, absorbing UV radiation of another type, again turns into O 2.

A simple and logical conclusion follows from all this - in order to completely destroy the ozone layer, we need to deprive our atmosphere of oxygen. After all, no matter how much human-produced freons (hydrocarbons containing chlorine and bromine, used as refrigerants and solvents), methane, hydrogen chloride and nitrogen monoxide destroy ozone molecules, ultraviolet irradiation of oxygen will again restore the ozone layer - after all, these substances are “turned off” unable! As well as reducing the amount of oxygen in the atmosphere, since trees, grasses and algae produce hundreds of thousands of times more of it than humanity - the aforementioned ozone destroyers.

So, as you can see, not a single substance created by people is able to destroy the ozone layer as long as oxygen is present in the Earth’s atmosphere and the Sun emits ultraviolet radiation. But why then do ozone holes occur? I want to say right away that the term “hole” itself is not entirely correct - we are talking only about the thinning of the ozone layer in certain parts of the stratosphere, and not about its complete absence. However, to answer the question, you just need to remember where exactly on the planet the largest and most persistent ozone holes exist.

And here there is nothing to remember: the largest of the stable ozone holes is located directly above Antarctica, and the other, slightly smaller one, is located above the Arctic. All other ozone holes on Earth are unstable; they form quickly, but are “darned” just as quickly. Why does the thinning of the ozone layer persist for quite a long time in the polar regions? Yes, simply because in these places the polar night lasts for six months. And during this time, the atmosphere over the Arctic and Antarctic does not receive enough ultraviolet light to convert oxygen into ozone.

Well, O 3, in turn, left without “replenishment”, begins to quickly collapse - after all, it is a very unstable substance. That is why the ozone layer over the poles is thinning considerably, although the process occurs with some delay - a visible hole appears at the beginning of summer and disappears by mid-winter. However, when the polar day arrives, ozone begins to be produced again and the ozone hole is slowly mended. True, not completely - all the same, the time of intense receipt of UV radiation in these parts is shorter than the period of its deficiency. That's why the ozone hole doesn't disappear.

But why, in this case, was the myth created and replicated? The answer to this question is not only simple, but very simple. The fact is that the presence of a permanent ozone hole over Antarctica was first proven in 1985. And at the end of 1986, specialists from the American company DuPont (that is, DuPont) launched the production of a new class of refrigerants - fluorocarbons that do not contain chlorine. This greatly reduced the cost of production, but the new substance still had to be promoted to the market.

And here DuPont finances the dissemination in the media of a myth about evil freons that spoil the ozone layer, which was created by a group of meteorologists on its order. As a result, a frightened public began to demand that the authorities take action. And these measures were taken at the end of 1987, when a protocol was signed in Montreal to limit the production of substances that deplete the ozone layer. This led to the ruin of many companies that produced freons, and also to the fact that DuPont became a monopolist in the refrigerant market for many years.

By the way, it was precisely the speed with which DuPont management made the decision to use the ozone hole for its own purposes that led to the fact that the myth turned out to be so unfinished that it could be exposed by an ordinary schoolchild who did not skip chemistry and geography classes. If they had more time, you see, they would have composed a more convincing version. Nevertheless, even what the scientists eventually “gave birth” at the request of DuPont was able to convince many people.

Kazan National Research Technological University

Abstract Depletion of the ozone layer

Completed by: student gr.5111-41 Garifullin I.I. Checked by: Fatykhova L.A.

Kazan 2015

1. Introduction

2.Main part:

a) Determination of ozone

b) Causes of “ozone holes”

c) Main hypotheses of ozone layer destruction

d) Environmental and medical-biological consequences of the destruction of the ozone layer

3.Conclusion

4. List of used literature

Introduction.

In the 21st century Among the many global environmental problems of the biosphere, the problem of destruction of the ozone layer and the associated increase in biologically hazardous ultraviolet radiation on the earth's surface remains very relevant. This could further develop into an irreversible catastrophe destructive for humanity. In recent decades, numerous studies have established a steady trend towards a decrease in the ozone content in the atmosphere. According to the World Health Organization (WHO), every 1% decrease in ozone levels in the atmosphere (and corresponding 2% increase in UV radiation) leads to a 5% increase in the number of cancer diseases.

The modern oxygen atmosphere of the Earth is a unique phenomenon among the planets of the solar system, and this feature is associated with the presence of life on our planet.

The environmental problem is undoubtedly the most important for people now. The reality of an environmental catastrophe is indicated by the destruction of the Earth's ozone layer. Ozone is a triatomic form of oxygen, formed in the upper layers of the atmosphere under the influence of hard (short-wave) ultraviolet radiation from the Sun.

Today, ozone worries everyone, even those who previously did not suspect the existence of an ozone layer in the atmosphere, but only believed that the smell of ozone was a sign of fresh air. (It’s not for nothing that ozone means “smell” in Greek.) This interest is understandable - we are talking about the future of the entire biosphere of the Earth, including man himself. Currently, there is a need to make certain decisions that are binding on everyone, which would allow us to preserve the ozone layer. But for these decisions to be correct, we need complete information about those factors that change the amount of ozone in the Earth’s atmosphere, as well as about the properties of ozone, and how exactly it reacts to these factors. Therefore, I consider the topic I have chosen to be relevant and necessary for consideration.

Main part: Ozone determination

It is known that ozone (Oz), a modification of oxygen, has high chemical reactivity and toxicity. Ozone is formed in the atmosphere from oxygen during electrical discharges during thunderstorms and under the influence of ultraviolet radiation from the Sun in the stratosphere. The ozone layer (ozone screen, ozonosphere) is located in the atmosphere at an altitude of 10-15 km with a maximum ozone concentration at an altitude of 20-25 km. The ozone screen delays the penetration of the most severe UV radiation (wavelength 200-320 nm), which is destructive for all living things, to the earth's surface. However, as a result of anthropogenic impacts, the ozone “umbrella” became leaky and ozone holes began to appear in it with a noticeably reduced (up to 50% or more) ozone content.

Causes of ozone holes

Ozone (ozone) holes are only part of the complex environmental problem of the depletion of the Earth's ozone layer. In the early 1980s. a decrease in the total ozone content in the atmosphere was noted over the area of ​​scientific stations in Antarctica. So, in October 1985 There were reports that the ozone concentration in the stratosphere over the English station Halley Bay decreased by 40% from its minimum values, and over the Japanese station - almost 2 times. This phenomenon is what caused the “ozone hole.” Significant ozone holes appeared over Antarctica in the spring of 1987, 1992, 1997, when a decrease in the total content of stratospheric ozone (TO) by 40 - 60% was recorded. In the spring of 1998, the ozone hole over Antarctica reached a record area of ​​26 million square meters. km (3 times the territory of Australia). And at an altitude of 14 - 25 km in the atmosphere, almost complete destruction of ozone occurred.

Similar phenomena were observed in the Arctic (especially since the spring of 1986), but the size of the ozone hole here was almost 2 times smaller than over the Antarctic. In March 1995 The Arctic ozone layer was depleted by about 50%, and “mini-holes” formed over the northern regions of Canada and the Scandinavian Peninsula, the Scottish Islands (UK).

Currently, there are about 120 ozonometric stations in the world, including 40 that have appeared since the 60s. XX century on Russian territory. Observational data from ground stations indicate that in 1997, a calm state of total ozone content was observed over almost the entire controlled territory of Russia.

To clarify the reasons for the emergence of powerful ozone holes precisely in the circumpolar spaces at the end of the twentieth century. Research was carried out (using flying laboratory aircraft) of the ozone layer over Antarctica and the Arctic. It has been established that, in addition to anthropogenic factors (emissions of freons, nitrogen oxides, methyl bromide, etc. into the atmosphere), natural influences play a significant role. Thus, in the spring of 1997, in some areas of the Arctic, a drop in ozone content in the atmosphere of up to 60% was recorded. Moreover, over the course of a number of years, the rate of depletion of the ozonosphere over the Arctic has been increasing even in conditions when the concentration of chlorofluorocarbons (CFCs), or freons, in it remained constant. According to a Norwegian scientist K. Henriksen, over the past decade, an ever-expanding vortex of cold air has formed in the lower layers of the Arctic stratosphere. It created ideal conditions for the destruction of ozone molecules, which occurs mainly at a very low temperature (about -80*C). A similar funnel over Antarctica is the cause of ozone holes. Thus, the cause of the ozone depletion process in high latitudes (Arctic, Antarctica) may be largely due to natural influences.