When the oxygen on earth runs out. oxygen on earth. What is ozone

Only 2.3 billion years ago, the air surrounding the Earth contained no oxygen at all. For the then primitive forms of life, this circumstance was a real gift.

Single-celled bacteria that lived in the primitive ocean did not need oxygen to sustain their life. Then something happened.

How did oxygen appear on Earth?

Scientists believe that as they developed, some bacteria "learned" to extract hydrogen from water. It is known that water is a combination of hydrogen and oxygen, therefore, the by-product of the hydrogen extraction reaction was the formation of oxygen, its release into water, and then into the atmosphere.

Some organisms over time adapted to live in an atmosphere with a new gas. The body has found a way to harness the destructive energy of oxygen and use it to control the breakdown of nutrients, which releases energy that the body uses to sustain itself.

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This way of applying oxygen is called breathing, which we use daily, and sow the day. Breathing is a way to ward off the oxygen threat: it made possible the development on Earth of larger organisms - multicellular ones, which already have a complex structure. After all, it was thanks to the appearance of breath that evolution gave birth to man.

Where did oxygen come from on Earth?

Over the millions of years that have passed, the amount of oxygen on earth has increased from 0.2 percent to the current 21 percent of the atmosphere. But bacteria in the oceans are not the only ones to blame for the increase in oxygen in the atmosphere. Scientists believe that colliding continents were another source of oxygen. In their opinion, during the collision, and then during the subsequent divergence of the continents, large amounts of oxygen were released into the atmosphere.

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How? As a result of collisions and divergences of the continents, huge sedimentary rocks descended to the seabed, entraining a large amount of organic matter. If this did not happen, then more oxygen would be spent on the digestion and oxidation of these organic substances. Since they became inaccessible to oxidation, there was a kind of economy of oxygen, and its volume in the atmosphere became larger.

Escape from oxygen

Some organisms have managed to adapt and even benefit from the presence of oxygen in the atmosphere. However, most of the organisms could not stand the changes in living conditions and died out. Some species of living beings were saved by hiding from oxygen in deep cracks and other secluded places. Many today live happily in the roots of legumes, capturing nitrogen gas from the atmosphere and using it to synthesize amino acids (the building blocks of protein) in plants.

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The botulinum bacterium is another fugitive from oxygen. It is found in meat, fish and plants. If in the process of their preparation, the botulism bacillus is not destroyed by the high temperature during cooking, then it can then multiply intensively in canned food, which are prepared from the listed products.

This is because there is no air in the cans. If you eat food contaminated with botulism sticks, you can become dangerously sick.

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• The oldest creatures on earth...

Oxygen is most commonly associated with the atmosphere. The atmosphere is the spacesuit of the planet Earth. If we compare what is more important for a person for life on Earth, then we can try to compare without what and for how long a person cannot live. So, without food, a person can live for about a month; a person can last a week without water; but without air, a person cannot last even an hour. However, one should not be mistaken about this, since all the components of our monastery are vital for us, and without them not only our development, but life itself is impossible.

Where do we get oxygen from?

The word atmosphere itself is of Greek origin and consists of "atmos" - steam and "sfire" - a ball, it is a space suit for the planet and is a reservoir of oxygen. This chemical element is a necessary component for the occurrence of redox reactions in the body and, in addition, performs a number of protective functions.

The atmosphere is over a thousand kilometers long; yes, even at such a height they detect traces of gases entering the atmosphere. This is not surprising since the action of the Earth's gravitational field extends over 10 Earth radii, which is about 60,000 km.

Recall that the atmosphere consists of five main spheres:

• Troposphere (0-10 km).
• Stratosphere (10-50 km).
• Mesosphere (50-100 km).
• Thermosphere (100-800 km).
• Exosphere (800-1100 km).

However, this division of the atmosphere does not accurately reflect its contents. For example, the name ionosphere is given to the layer of the atmosphere, which is exposed to radiation at an altitude of approximately 80 km and reveals a large number of ions and free electrons.

Throughout its length, the atmosphere is more or less stable because it consists of gaseous products that do not react under normal conditions. This mixture is called air. Air mainly consists of nitrogen (78%), oxygen (21%) and argon (1%). Scientists also estimated that the mass of the atmosphere of our planet is 5 * 1015 tons and, of course, that most of it is located "at the bottom" of the fifth air ocean.

However, the atmosphere is not the only source of air and oxygen in particular. For example, huge water reserves, giving a lot of evaporation every second, cause fluctuations in the composition of the air and, as a result, oxygen. Forests, which are often called the "lungs" of the planet, give a significant mass increase in the oxygen component of the atmosphere. An important role in the formation of the composition of the air and the oxygen content in it is played by the activity of people. The fact that oxygen is present in a wide range of solid and liquid substances does not have much effect on the oxygen content of the atmosphere.

An important fact is also that oxygen was not always in the Earth's atmosphere - it appeared there about 2 billion years ago, along with the appearance of the first chlorophyll organisms. But only in the last 20 million years, the concentration of oxygen in the atmosphere has become approximately the same as now.

Can you run out of oxygen?

Is there a real possibility of complete depletion of oxygen on Earth? Theoretically, such a possibility exists, but there is no reason to panic.

Now the main “consumers” of oxygen are already widely known:

• A car that has traveled a distance of 500 km “eats up” the annual respiratory rate of a person;
• An airplane flying 10 thousand km burns 30-50 tons of oxygen, which is the daily production rate of a forest area of ​​​​15-20 thousand hectares

The level of oxygen consumption on Earth is enormous, but experimental measurements show that the amount of atmospheric oxygen has not decreased over the past 100 years. Losses of oxygen in the atmosphere are compensated by the vegetation of the land and the world's oceans, which are still capable of producing about 320 billion tons of free oxygen. However, it should be remembered that human oxygen consumption is growing, and the population of plants on earth is rapidly declining. These processes are not yet controlled by anyone.

Nevertheless, the growth in oxygen consumption does not pose such a significant threat as the annual emissions into the atmosphere of about a billion tons of chemical compounds, as well as several billion tons of solid particles and various aerosols. In other words, not a lack of oxygen, but an excess of other substances constantly emitted into the atmosphere, is the main threat to the suitability of atmospheric air for breathing.

What is ozone

As already mentioned, the gas composition varies from one layer of the atmosphere to another. Oxygen near the earth's surface exists in the form of diatomic molecules, but in the rarefied layers of the atmosphere it undergoes dissociation into atoms under the action of solar radiation. Thus, somewhere at an altitude of 40 km, the content of atomic oxygen is already significant, and at altitudes of 120–150 km, O2 molecules are practically absent.

At a relatively short distance from the earth's surface - about 20-35 km, atomic oxygen, being quite active, forms triatomic ozone molecules O3 with molecular oxygen. This is the height of the Earth's ozone layer. Its importance is that it protects the Earth's surface by blocking ultraviolet rays. By themselves, ozone molecules are opaque to ultraviolet radiation from the sun and almost completely absorb it. On the other hand, the ozone layer retains about a fifth of the infrared thermal radiation from the Earth's surface, thus providing a stable thermal regime for all living things.

It is noteworthy that the ozone layer appeared about 500-400 million years ago and since then the natural balance of life on Earth has been maintained thanks to it. Ozone is millionths of the total air on the planet, but it is enough to maintain conditions suitable for life.

The main "enemies", or destroyers, of the ozone layer are freons, gaseous pollutants of the refrigeration industry, perfumery production, as well as a number of other branches of human activity. The main producers of freons are:

• Europe - 40%.
• USA - 35%
• Japan - 10%
• CIS - 12%.

The influence of freon near the surface is practically absent, here it is an inert gas. When it evaporates and reaches the ozone layer, it becomes an atomic gas under the influence of solar radiation in the form of ultraviolet radiation, and then reacts with ozone. The chlorine monoxide and molecular oxygen obtained during this reaction do not act as absorbers of ultraviolet rays and they reach the Earth.

People have long known about the existence of "ozone holes" and so far it is difficult to say anything definite about their origin; however, it is reliably known that, for example, in Antarctica, not only is there less than half the amount of ozone in the atmosphere, but the concentration of chlorine monoxide is hundreds of times higher than the norm.

What is being done

The debate on oxygen, and especially on ozone, continues. To date, the achievements of mankind include the signing of a number of protocols: from the 1985 Vienna Convention for the Protection of the Ozone Layer by Freon-producing countries to the recent Kyoto Agreement of 2009. This latest international agreement has been signed by 181 countries worldwide, accounting for over 61% of the world's total air emissions.

With regard to steps to preserve the atmosphere and its ozone layer in particular, we can say that work is being actively carried out to reduce freon emissions into the atmosphere (utilization of used freon, replacement of freon with compressed air in aerosol packages, etc.). On the other hand, there are numerous campaigns to conserve forests and prevent pollution of the world's oceans, which have already acquired international status.

It's no secret how useful phytoplankton is for the environment. It also plays an important role in the atmosphere. After all, it is to him that we owe the release of oxygen into the air. In addition, it is at the base of the food pyramid, and, in fact, feeds the entire sea.

Scientists have calculated that in 80 years oxygen will not completely disappear. Employees of the University of Michigan calculated that in 2100 phytoplankton, the main source of oxygen, will finally cease to exist. The reason for this is global warming.

As a result of numerous analyzes of 130 species of phytoplankton, it was found that phytoplankton reproduces better in the waters of the subpolar region and the seas of temperate zones. Since the temperature there is higher than the average annual, which is typical for its habitat.

Tropical plankton, on the contrary, reproduce well at average annual or even lower temperatures. It turns out that it is tropical phytoplankton that will be more sensitive to global warming.

Until now, scientists around the world are not fully aware of how phytoplankton is distributed in world waters, and how it will behave during global warming.

As a result, in about 80 years, according to experts, tropical phytoplankton, which makes up a significant part of the World Ocean, will be pushed to the poles or will die out altogether. Under both outcomes, the death of phytoplankton will be a big blow to marine ecosystems. However, there is still hope that phytoplankton will somehow manage to adapt to new conditions.

Scientists find it difficult to say why some species of plankton did not have ways to adapt to the new temperature regime, especially since the northern species of phytoplankton should adapt well to harsh conditions. In addition, the researchers do not exclude the possibility that seaweed may have had such an opportunity, but over time it was used up. This still allows us to hope that plankton will still be able to adapt to changing climatic conditions. The task for the near future is precisely to find out how fast phytoplankton will adapt to changes in nature.

The Earth's atmosphere has no clear limits. The outer layers extend up to several thousand kilometers. but 90% of its mass is concentrated in the 16-kilometer surface layer.
Although there are no precise geometric boundaries between the atmosphere and space, this can be defined in terms of physics. The physical boundary of the atmosphere is the height at which the air is still sufficiently dense. to register the order of physical phenomena related to the earth, and her space.

The physical properties of the atmosphere are heterogeneous - not only vertical; but also horizontal. With an increase in height, the composition and number of its other properties and parameters change. There are several divisions in the atmosphere, such as separation temperature.

As a basis, it is customary to take the average change in air temperature with altitude in ascent (r = - dT 1 dg). According to their different signs (change in temperature with height, the composition of the atmosphere and the presence of charged particles) the atmosphere is divided into five main layers called fields. Between each transition has a thin layer called breaks. Their names are based on their location; how is the troposphere above the tropopause, etc.

The air that forms the earth's atmosphere is a mixture of various gases. Gases that do not chemically react with each other are called mechanical mixtures. The composition of the air near the earth's surface is established with greater accuracy. In addition to the main gases - nitrogen, oxygen and argon mixtures, mechanical and other gaseous impurities with much lower concentrations are involved. The composition of the air is not the same at different altitudes.

Up to an altitude of about 800 km, nitrogen and oxygen predominate in the atmosphere. More than 400 km began to increase the content of light gases - helium at the beginning: and then hydrogen. 800 km above the main content in the atmosphere is mainly hydrogen.

A clean plan can be assumed to be up to about 200 km of air; the environment is a thin and uniform coating of their physical characteristics. As the surface density grows higher, the non-uniformity of the density decreases, leading to an uneven distribution of the mass of the atmosphere. About half of the table is in layers up to 5 km above the Earth's surface; at an altitude of 30 km is about 99 percent contained. Above 35 km, the atmospheric mass is less than 1% l. Nevertheless; there are a number of processes and phenomena. that result from direct exposure to solar radiation. Actually it is 1°/l intermediate, responsive to solar radiation and transmit them to the lower atmosphere.

However, to call the pace frightening would be an exaggeration.

By studying air bubbles that have been trapped in the glaciers of Granland for hundreds of thousands of years, scientists have found that during this time there has been less oxygen in the Earth's atmosphere. At the same time, a group of specialists led by Daniel Stolper from Princeton University cannot yet name with certainty the reason why the atmosphere lost more oxygen over 800,000 years than it gained.

The researchers emphasize that the concentration of oxygen in the air is decreasing at a very moderate rate - over hundreds of millennia since the Pleistocene, it has decreased by only 0.7 percent. According to experts, they themselves carried out the measurement, first of all, out of curiosity, and could not predict in advance whether the oxygen content in the air had changed during this time and, if so, in which direction. The measurement showed not the brightest, but absolutely clear trend towards its decrease, the researchers note.

As experts recall, in the distant past, fluctuations in the level of oxygen on our planet were very significant. A couple of billion years ago, as expected, this material was not present at all in the atmosphere, but then cyanobacteria began to release it, thereby forever setting the direction of evolution on the planet. Subsequently, a wide variety of plants began to produce oxygen, and even later it turned out to be necessary to maintain the life of complex animals. Oxygen is not only consumed by living beings, but is also "wasted" during the weathering of silicate rocks. Also, according to scientists, approximately every millennium, all O atoms in the atmosphere have time to visit water molecules and become oxygen again.

Scientists assured that, whatever the true causes of the phenomenon they discovered, in the very near future, oxygen on Earth will definitely not end. Nevertheless, experts tend to consider the results obtained as another reason to think about how exactly human actions affect the planet - today people consume a thousand times more oxygen than before, thereby accelerating the already observed in nature process of reducing its amount.