Atmospheric content. An excerpt characterizing the Earth's atmosphere. Physical properties of different atmospheric layers

Together with the Earth, the gaseous shell of our planet, called the atmosphere, also rotates. The processes that take place in it determine the weather on our planet, it is also the atmosphere that protects the animal and plant world from the harmful effects of ultraviolet rays, ensures optimal temperature, and so on. , is not so easy to determine, and here's why.

Atmosphere of the earth km

The atmosphere is a gaseous space. Its upper limit is not clearly expressed, since the gases, the higher, the more rarefied and gradually pass into outer space. If we talk about the approximate diameter of the earth's atmosphere, then scientists call the figure about 2-3 thousand kilometers.

The Earth's atmosphere is of four layers, which also smoothly transition from one to another. This is:

• troposphere;
• stratosphere;
• mesosphere;
• ionosphere (thermosphere).

By the way, an interesting fact: the planet earth without an atmosphere would be as quiet as the moon, since sound is vibrations of air particles. And the fact that the sky is blue light is explained by the specifics of the decomposition of the sun's rays passing through the atmosphere.

Features of each layer of the atmosphere

The thickness of the troposphere is from eight to ten kilometers (in temperate latitudes - up to 12, and above the equator - up to 18 kilometers). The air in this layer is heated by land and water, so the more radius of the earth's atmosphere, the lower the temperature. 80 percent of the entire mass of the atmosphere is concentrated here and water vapor is concentrated, thunderstorms, storms, clouds, precipitation are formed, air moves in vertical and horizontal directions.

The stratosphere is located from the troposphere at an altitude of eight to 50 kilometers. The air here is rarefied, so the sun's rays do not scatter, and the color of the sky becomes purple. This layer absorbs ultraviolet radiation due to ozone.

The mesosphere is located even higher - at an altitude of 50-80 kilometers. Here already the sky seems black, and the temperature of the layer is up to minus ninety degrees. Next comes the thermosphere, here the temperature already rises sharply and then stops at an altitude of 600 km at around 240 degrees.

The most rarefied layer is the ionosphere, it is characterized by high electrification, and it also reflects radio waves of different lengths, like a mirror. This is where the northern lights are formed.

Updated: March 31, 2016 by: Anna Volosovets

The structure of the Earth's atmosphere

The atmosphere is the gaseous shell of the Earth with aerosol particles contained in it, moving together with the Earth in world space as a whole and at the same time taking part in the rotation of the Earth. At the bottom of the atmosphere, most of our lives take place.

Almost all the planets in our solar system have their own atmospheres, but only Earth's atmosphere can support life.

When our planet formed 4.5 billion years ago, it was apparently devoid of an atmosphere. The atmosphere was formed as a result of volcanic emissions of water vapor mixed with carbon dioxide, nitrogen and other chemicals from the depths of the young planet. But the atmosphere can only contain a limited amount of moisture, so the excess moisture through condensation gave rise to the oceans. But then the atmosphere was devoid of oxygen. The first living organisms that originated and developed in the ocean, as a result of the photosynthesis reaction (H 2 O + CO 2 = CH 2 O + O 2), began to release small portions of oxygen, which began to enter the atmosphere.

The formation of oxygen in the Earth's atmosphere led to the formation of the ozone layer at altitudes of about 8 - 30 km. And, thus, our planet has acquired protection from the harmful effects of ultraviolet study. This circumstance served as an impetus for the further evolution of life forms on Earth, since. as a result of increased photosynthesis, the amount of oxygen in the atmosphere began to grow rapidly, which contributed to the formation and maintenance of life forms, including on land.

Today our atmosphere is 78.1% nitrogen, 21% oxygen, 0.9% argon, 0.04% carbon dioxide. Very small fractions compared to the main gases are neon, helium, methane, krypton.

The particles of gas contained in the atmosphere are affected by the force of gravity of the Earth. And, given that air is compressible, its density gradually decreases with height, passing into outer space without a clear boundary. Half of the entire mass of the earth's atmosphere is concentrated in the lower 5 km, three-quarters - in the lower 10 km, nine-tenths - in the lower 20 km. 99% of the mass of the Earth's atmosphere is concentrated below a height of 30 km, and this is only 0.5% of the equatorial radius of our planet.

At sea level, the number of atoms and molecules per cubic centimeter of air is about 2 * 10 19 , at an altitude of 600 km it is only 2 * 10 7 . At sea level, an atom or molecule travels about 7 * 10 -6 cm before colliding with another particle. At an altitude of 600 km, this distance is about 10 km. And at sea level, about 7 * 10 9 such collisions occur every second, at an altitude of 600 km - only about one per minute!

But not only pressure changes with altitude. The temperature also changes. So, for example, at the foot of a high mountain it can be quite hot, while the top of the mountain is covered with snow and the temperature there is at the same time below zero. And it is worth taking an airplane to a height of about 10-11 km, as you can hear a message that it is -50 degrees overboard, while at the surface of the earth it is 60-70 degrees warmer ...

Initially, scientists assumed that the temperature decreases with height until it reaches absolute zero (-273.16 ° C). But it's not.

The Earth's atmosphere consists of four layers: troposphere, stratosphere, mesosphere, ionosphere (thermosphere). Such a division into layers is taken on the basis of data on temperature changes with height. The lowest layer, where air temperature drops with height, is called the troposphere. The layer above the troposphere, where the temperature drop stops, is replaced by isotherm and, finally, the temperature begins to rise, is called the stratosphere. The layer above the stratosphere where the temperature drops rapidly again is the mesosphere. And, finally, the layer where the temperature rise again begins, called the ionosphere or thermosphere.

The troposphere extends on average in the lower 12 km. This is where our weather is formed. The highest clouds (cirrus) form in the uppermost layers of the troposphere. The temperature in the troposphere decreases adiabatically with height, i.e. The change in temperature is due to the decrease in pressure with height. The temperature profile of the troposphere is largely determined by the solar radiation reaching the Earth's surface. As a result of the heating of the Earth's surface by the Sun, upward convective and turbulent flows are formed, which form the weather. It is worth noting that the influence of the underlying surface on the lower layers of the troposphere extends to a height of approximately 1.5 km. Of course, excluding mountainous areas.

The upper boundary of the troposphere is the tropopause, the isothermal layer. Recall the characteristic appearance of thunderclouds, the top of which is an "ejection" of cirrus clouds, called "anvil." This "anvil" just "spreads" under the tropopause, because due to isotherm, the ascending air currents are significantly weakened, and the cloud ceases to develop vertically. But in special, rare cases, the tops of cumulonimbus clouds can invade the lower layers of the stratosphere, overcoming the tropopause.

The height of the tropopause depends on the geographic latitude. So, at the equator, it is at an altitude of about 16 km, and its temperature is about -80 ° C. At the poles, the tropopause is located lower - approximately at an altitude of 8 km. Its temperature here is -40°C in summer and -60°C in winter. Thus, despite higher temperatures near the Earth's surface, the tropical tropopause is much colder than at the poles.

The atmosphere is what makes life possible on Earth. We get the very first information and facts about the atmosphere in elementary school. In high school, we are already more familiar with this concept in geography lessons.

The concept of the earth's atmosphere

The atmosphere is present not only in the Earth, but also in other celestial bodies. This is the name of the gaseous shell surrounding the planets. The composition of this gas layer of different planets is significantly different. Let's look at the basic information and facts about otherwise called air.

Its most important component is oxygen. Some mistakenly think that the earth's atmosphere is made entirely of oxygen, but air is actually a mixture of gases. It contains 78% nitrogen and 21% oxygen. The remaining one percent includes ozone, argon, carbon dioxide, water vapor. Let the percentage of these gases be small, but they perform an important function - they absorb a significant part of the solar radiant energy, thereby preventing the luminary from turning all life on our planet into ashes. The properties of the atmosphere change with altitude. For example, at an altitude of 65 km, nitrogen is 86% and oxygen is 19%.

The composition of the Earth's atmosphere

• Carbon dioxide essential for plant nutrition. In the atmosphere, it appears as a result of the process of respiration of living organisms, rotting, burning. The absence of it in the composition of the atmosphere would make it impossible for any plants to exist.
• Oxygen is a vital component of the atmosphere for humans. Its presence is a condition for the existence of all living organisms. It makes up about 20% of the total volume of atmospheric gases.
• Ozone It is a natural absorber of solar ultraviolet radiation, which adversely affects living organisms. Most of it forms a separate layer of the atmosphere - the ozone screen. Recently, human activity has led to the fact that it begins to gradually collapse, but since it is of great importance, active work is underway to preserve and restore it.
• water vapor determines the humidity of the air. Its content may vary depending on various factors: air temperature, geographical location, season. At low temperatures, there is very little water vapor in the air, maybe less than one percent, and at high temperatures, its amount reaches 4%.
• In addition to all of the above, in the composition of the earth's atmosphere there is always a certain percentage solid and liquid impurities. These are soot, ash, sea salt, dust, water drops, microorganisms. They can get into the air both naturally and by anthropogenic means.

Layers of the atmosphere

And the temperature, and density, and the qualitative composition of the air is not the same at different heights. Because of this, it is customary to distinguish different layers of the atmosphere. Each of them has its own characteristic. Let's find out which layers of the atmosphere are distinguished:

• The troposphere is the layer of the atmosphere closest to the Earth's surface. Its height is 8-10 km above the poles and 16-18 km in the tropics. Here is 90% of all water vapor that is available in the atmosphere, so there is an active formation of clouds. Also in this layer there are such processes as the movement of air (wind), turbulence, convection. The temperature ranges from +45 degrees at noon in the warm season in the tropics to -65 degrees at the poles.
• The stratosphere is the second furthest layer from the atmosphere. It is located at an altitude of 11 to 50 km. In the lower layer of the stratosphere, the temperature is approximately -55, towards the distance from the Earth it rises to +1˚С. This region is called the inversion and is the boundary between the stratosphere and the mesosphere.
• The mesosphere is located at an altitude of 50 to 90 km. The temperature at its lower boundary is about 0, at the upper it reaches -80...-90 ˚С. Meteorites entering the Earth's atmosphere burn out completely in the mesosphere, which causes airglows to occur here.
• The thermosphere is about 700 km thick. The northern lights appear in this layer of the atmosphere. They appear due to the action of cosmic radiation and radiation emanating from the Sun.
• The exosphere is a zone of air dispersion. Here, the concentration of gases is small and their gradual escape into interplanetary space takes place.

The boundary between the earth's atmosphere and outer space is considered to be a line of 100 km. This line is called the Karman line.

atmospheric pressure

Listening to the weather forecast, we often hear barometric pressure readings. But what does atmospheric pressure mean, and how might it affect us?

We figured out that air consists of gases and impurities. Each of these components has its own weight, which means that the atmosphere is not weightless, as was believed until the 17th century. Atmospheric pressure is the force with which all layers of the atmosphere press on the surface of the Earth and on all objects.

Scientists conducted complex calculations and proved that the atmosphere presses on one square meter of area with a force of 10,333 kg. This means that the human body is subject to air pressure, the weight of which is 12-15 tons. Why don't we feel it? It saves us its internal pressure, which balances the external one. You can feel the pressure of the atmosphere while in an airplane or high in the mountains, since the atmospheric pressure at altitude is much less. In this case, physical discomfort, stuffy ears, dizziness are possible.

A lot can be said about the atmosphere around. We know a lot of interesting facts about her, and some of them may seem surprising:

• The weight of the earth's atmosphere is 5,300,000,000,000,000 tons.
• It contributes to the transmission of sound. At an altitude of more than 100 km, this property disappears due to changes in the composition of the atmosphere.
• The movement of the atmosphere is provoked by uneven heating of the Earth's surface.
• A thermometer is used to measure air temperature, and a barometer is used to measure atmospheric pressure.
• The presence of an atmosphere saves our planet from 100 tons of meteorites daily.
• The composition of the air was fixed for several hundred million years, but began to change with the onset of rapid industrial activity.
• It is believed that the atmosphere extends upwards to an altitude of 3000 km.

The value of the atmosphere for humans

The physiological zone of the atmosphere is 5 km. At an altitude of 5000 m above sea level, a person begins to experience oxygen starvation, which is expressed in a decrease in his working capacity and a deterioration in well-being. This shows that a person cannot survive in a space where this amazing mixture of gases does not exist.

All information and facts about the atmosphere only confirm its importance for people. Thanks to its presence, the possibility of the development of life on Earth appeared. Already today, having assessed the extent of the harm that mankind is capable of inflicting with its actions on the life-giving air, we should think about further measures to preserve and restore the atmosphere.

He is invisible, and yet we cannot live without him.

Each of us understands how much air is necessary for life. The expression "It is necessary as air" can be heard when talking about something very important for a person's life. Since childhood, we know that living and breathing are practically the same thing.

Do you know how long a person can live without air?

Not all people know how much air they inhale. It turns out that during the day, making about 20,000 breaths, a person passes 15 kg of air through the lungs, while he absorbs only about 1.5 kg of food, and 2-3 kg of water. At the same time, air is a matter of course for us, like the sunrise every morning. Unfortunately, we only feel it when there is not enough of it, or when it is polluted. We forget that all life on Earth, developing over millions of years, has adapted to life in an atmosphere of a certain natural composition.

Let's see what air is made of.

And let's conclude: Air is a mixture of gases. Oxygen in it is about 21% (approximately 1/5 by volume), nitrogen accounts for about 78%. The remaining mandatory components are inert gases (primarily argon), carbon dioxide, and other chemical compounds.

The study of the composition of air began in the 18th century, when chemists learned to collect gases and conduct experiments with them. If you are interested in the history of science, watch a short film about the history of the discovery of air.

The oxygen contained in the air is required for the respiration of living organisms. What is the essence of the breathing process? As you know, in the process of breathing, the body consumes oxygen from the air. Air oxygen is required for numerous chemical reactions that continuously occur in all cells, tissues and organs of living organisms. In the process of these reactions, with the participation of oxygen, those substances that come with food slowly “burn out” with the formation of carbon dioxide. At the same time, the energy contained in them is released. Due to this energy, the body exists, using it for all functions - the synthesis of substances, muscle contraction, the work of all organs, etc.

In nature, there are also some microorganisms that can use nitrogen in the process of life. Due to the carbon dioxide contained in the air, the process of photosynthesis takes place, the biosphere of the Earth as a whole lives.

As you know, the air shell of the Earth is called the atmosphere. The atmosphere extends for about 1000 km from the Earth - it is a kind of barrier between the Earth and space. According to the nature of temperature changes in the atmosphere, there are several layers:

Atmosphere is a kind of barrier between the Earth and space. It softens the effect of cosmic radiation and provides conditions on Earth for the development and existence of life. It is the atmosphere of the first of the earth's shells that meets the sun's rays and absorbs the hard ultraviolet radiation of the Sun, which has a detrimental effect on all living organisms.

Another "merit" of the atmosphere is related to the fact that it almost completely absorbs the Earth's own invisible thermal (infrared) radiation and returns most of it back. That is, the atmosphere, transparent in relation to the sun's rays, at the same time is an air "blanket" that does not allow the Earth to cool down. Thus, on our planet, the temperature that is optimal for the life of various living beings is maintained.

The composition of the modern atmosphere is unique, the only one in our planetary system.

The Earth's primary atmosphere consisted of methane, ammonia, and other gases. Along with the development of the planet, the atmosphere changed significantly. Living organisms played a leading role in the formation of the composition of atmospheric air, which arose and is maintained with their participation at the present time. You can see in more detail the history of the formation of the atmosphere on Earth.

Natural processes, both consumption and formation of atmospheric components, approximately balance each other, that is, provide a constant composition of the gases that make up the atmosphere.

Without human economic activity, nature copes with such phenomena as the entry into the atmosphere of volcanic gases, smoke from natural fires, dust from natural dust storms. These emissions dissipate in the atmosphere, settle or fall on the Earth's surface with precipitation. Soil microorganisms are taken for them, and in the end they are processed into carbon dioxide, sulfur and nitrogen compounds of the soil, that is, into the “ordinary” components of air and soil. This is the reason why atmospheric air has a constant composition on average. With the advent of man on Earth, at first gradually, then rapidly and now threateningly, the process of changing the gas composition of the air and destroying the natural stability of the atmosphere began.About 10,000 years ago people learned to use fire. Combustion products of various types of fuel have been added to natural sources of pollution. Initially, it was wood and other types of plant material.

At present, the most harmful to the atmosphere is caused by artificially produced fuel - petroleum products (gasoline, kerosene, solar oil, fuel oil) and synthetic fuel. When burned, they form nitrogen and sulfur oxides, carbon monoxide, heavy metals and other toxic substances of non-natural origin (pollutants).

Considering the huge scale of the use of technology today, one can imagine how many engines of cars, aircraft, ships and other equipment every second the atmosphere was killed Aleksashina I.Yu., Kosmodamiansky A.V., Oreshchenko N.I. Natural science: A textbook for the 6th grade of educational institutions. - St. Petersburg: SpecLit, 2001. - 239 p. .

Why are trolleybuses and trams considered environmentally friendly modes of transport compared to buses?

Especially dangerous for all living things are those stable aerosol systems that are formed in the atmosphere along with acid and many other gaseous waste products. Europe is one of the most densely populated and industrialized parts of the world. A powerful transport system, large-scale industry, high consumption of fossil fuels and minerals lead to a noticeable increase in the concentrations of pollutants in the air. In almost all major European cities, there is smog Smog is an aerosol consisting of smoke, fog and dust, one of the types of air pollution in large cities and industrial centers. For more information see: http://en.wikipedia.org/wiki/Smog and an increased content in the air of such dangerous pollutants as nitrogen and sulfur oxides, carbon monoxide, benzene, phenols, fine dust, etc. is regularly recorded.

There is no doubt that the increase in the content of harmful substances in the atmosphere is directly related to the growth of allergic and respiratory diseases, as well as a number of other diseases.

Serious measures are needed in connection with the increase in the number of cars in cities, the development of industry planned in a number of Russian cities, which will inevitably increase the amount of pollutant emissions into the atmosphere.

See how the problems of cleanliness of atmospheric air are being solved in the "green capital of Europe" - Stockholm.

A set of measures to improve air quality must necessarily include improving the environmental performance of cars; construction of a gas cleaning system at industrial enterprises; the use of natural gas, not coal, as a fuel in energy enterprises. Now in every developed country there is a service for monitoring the state of air purity in cities and industrial centers, which somewhat improved the current bad situation. Thus, in St. Petersburg there is an automated system for monitoring the atmospheric air of St. Petersburg (ASM). Thanks to it, not only state authorities and local self-government, but also city residents can learn about the state of atmospheric air.

The health of residents of St. Petersburg - a metropolis with a developed network of transport routes - is affected, first of all, by the main pollutants: carbon monoxide, nitrogen oxide, nitrogen dioxide, suspended solids (dust), sulfur dioxide, which enter the atmospheric air of the city from emissions from thermal power plants, industry, and from transport. Currently, the share of emissions from motor vehicles is 80% of the total emissions of major pollutants. (According to expert estimates, in more than 150 cities of Russia, the predominant influence on air pollution is exerted by motor vehicles).

How are things in your city? What do you think can and should be done to make the air in our cities cleaner?

The information about the level of atmospheric air pollution in the areas where AFM stations are located in St. Petersburg has been posted.

It must be said that in St. Petersburg there is a tendency to reduce emissions of pollutants into the atmosphere, but the reasons for this phenomenon are mainly associated with a decrease in the number of operating enterprises. It is clear that from an economic point of view this is not the best way to reduce pollution.

Let's draw conclusions.

The air shell of the Earth - the atmosphere - is necessary for the existence of life. The gases that make up the air are involved in such important processes as respiration, photosynthesis. The atmosphere reflects and absorbs solar radiation and thus protects living organisms from harmful X-rays and ultraviolet rays. Carbon dioxide keeps the thermal radiation of the earth's surface. Earth's atmosphere is unique! Our health and life depend on it.

Man thoughtlessly accumulates waste products of his activities in the atmosphere, which causes serious environmental problems. We all need to not only be aware of our responsibility for the state of the atmosphere, but also, to the best of our ability, do what we can to preserve the purity of the air, the basis of our life.

Its upper limit is at an altitude of 8-10 km in polar, 10-12 km in temperate and 16-18 km in tropical latitudes; lower in winter than in summer. The lower, main layer of the atmosphere. It contains more than 80% of the total mass of atmospheric air and about 90% of all water vapor present in the atmosphere. Turbulence and convection are strongly developed in the troposphere, clouds appear, cyclones and anticyclones develop. Temperature decreases with altitude with an average vertical gradient of 0.65°/100 m

For "normal conditions" at the Earth's surface are taken: density 1.2 kg/m3, barometric pressure 101.35 kPa, temperature plus 20 °C and relative humidity 50%. These conditional indicators have a purely engineering value.

Stratosphere

The layer of the atmosphere located at an altitude of 11 to 50 km. A slight change in temperature in the 11-25 km layer (lower layer of the stratosphere) and its increase in the 25-40 km layer from −56.5 to 0.8 ° (upper stratosphere or inversion region) are characteristic. Having reached a value of about 273 K (almost 0 ° C) at an altitude of about 40 km, the temperature remains constant up to an altitude of about 55 km. This region of constant temperature is called the stratopause and is the boundary between the stratosphere and the mesosphere.

Stratopause

The boundary layer of the atmosphere between the stratosphere and the mesosphere. There is a maximum in the vertical temperature distribution (about 0 °C).

Mesosphere

mesopause

Transitional layer between mesosphere and thermosphere. There is a minimum in the vertical temperature distribution (about -90°C).

Karman Line

Altitude above sea level, which is conventionally accepted as the boundary between the Earth's atmosphere and space.

Thermosphere

The upper limit is about 800 km. The temperature rises to altitudes of 200-300 km, where it reaches values ​​of the order of 1500 K, after which it remains almost constant up to high altitudes. Under the influence of ultraviolet and x-ray solar radiation and cosmic radiation, air is ionized ("polar lights") - the main regions of the ionosphere lie inside the thermosphere. At altitudes above 300 km, atomic oxygen predominates.

Exosphere (scattering sphere)

Up to a height of 100 km, the atmosphere is a homogeneous, well-mixed mixture of gases. In higher layers, the distribution of gases in height depends on their molecular masses, the concentration of heavier gases decreases faster with distance from the Earth's surface. Due to the decrease in gas density, the temperature drops from 0 °C in the stratosphere to -110 °C in the mesosphere. However, the kinetic energy of individual particles at altitudes of 200–250 km corresponds to a temperature of ~1500°C. Above 200 km, significant fluctuations in temperature and gas density are observed in time and space.

At an altitude of about 2000-3000 km, the exosphere gradually passes into the so-called near space vacuum, which is filled with highly rarefied particles of interplanetary gas, mainly hydrogen atoms. But this gas is only part of the interplanetary matter. The other part is composed of dust-like particles of cometary and meteoric origin. In addition to extremely rarefied dust-like particles, electromagnetic and corpuscular radiation of solar and galactic origin penetrates into this space.

The troposphere accounts for about 80% of the mass of the atmosphere, the stratosphere accounts for about 20%; the mass of the mesosphere is no more than 0.3%, the thermosphere is less than 0.05% of the total mass of the atmosphere. Based on the electrical properties in the atmosphere, the neutrosphere and ionosphere are distinguished. It is currently believed that the atmosphere extends to an altitude of 2000-3000 km.

Depending on the composition of the gas in the atmosphere, they emit homosphere and heterosphere. heterosphere- this is an area where gravity affects the separation of gases, since their mixing at such a height is negligible. Hence follows the variable composition of the heterosphere. Below it lies a well-mixed, homogeneous part of the atmosphere, called the homosphere. The boundary between these layers is called turbopause, it lies at an altitude of about 120 km.

Physical properties

The thickness of the atmosphere is approximately 2000 - 3000 km from the Earth's surface. The total mass of air - (5.1-5.3)? 10 18 kg. The molar mass of clean dry air is 28.966. Pressure at 0 °C at sea level 101.325 kPa; critical temperature ?140.7 °C; critical pressure 3.7 MPa; C p 1.0048?10? J / (kg K) (at 0 °C), C v 0.7159 10? J/(kg K) (at 0 °C). Solubility of air in water at 0°С - 0.036%, at 25°С - 0.22%.

Physiological and other properties of the atmosphere

Already at an altitude of 5 km above sea level, an untrained person develops oxygen starvation and, without adaptation, a person's performance is significantly reduced. This is where the physiological zone of the atmosphere ends. Human breathing becomes impossible at an altitude of 15 km, although up to about 115 km the atmosphere contains oxygen.

The atmosphere provides us with the oxygen we need to breathe. However, due to the decrease in the total pressure of the atmosphere, as one rises to a height, the partial pressure of oxygen also decreases accordingly.

The human lungs constantly contain about 3 liters of alveolar air. The partial pressure of oxygen in the alveolar air at normal atmospheric pressure is 110 mm Hg. Art., pressure of carbon dioxide - 40 mm Hg. Art., and water vapor - 47 mm Hg. Art. With increasing altitude, the oxygen pressure drops, and the total pressure of water vapor and carbon dioxide in the lungs remains almost constant - about 87 mm Hg. Art. The flow of oxygen into the lungs will completely stop when the pressure of the surrounding air becomes equal to this value.

At an altitude of about 19-20 km, the atmospheric pressure drops to 47 mm Hg. Art. Therefore, at this height, water and interstitial fluid begin to boil in the human body. Outside the pressurized cabin at these altitudes, death occurs almost instantly. Thus, from the point of view of human physiology, "space" begins already at an altitude of 15-19 km.

Dense layers of air - the troposphere and stratosphere - protect us from the damaging effects of radiation. With sufficient rarefaction of air, at altitudes of more than 36 km, ionizing radiation, primary cosmic rays, has an intense effect on the body; at altitudes of more than 40 km, the ultraviolet part of the solar spectrum, which is dangerous for humans, operates.

As we rise to an ever greater height above the Earth's surface, such phenomena that are familiar to us observed in the lower layers of the atmosphere, such as the propagation of sound, the emergence of aerodynamic lift and drag, heat transfer by convection, etc., gradually weaken, and then completely disappear.

In rarefied layers of air, the propagation of sound is impossible. Up to altitudes of 60-90 km, it is still possible to use air resistance and lift for controlled aerodynamic flight. But starting from altitudes of 100-130 km, the concepts of the M number and the sound barrier familiar to every pilot lose their meaning, there passes the conditional Karman Line, beyond which the sphere of purely ballistic flight begins, which can only be controlled using reactive forces.

At altitudes above 100 km, the atmosphere is also deprived of another remarkable property - the ability to absorb, conduct and transfer thermal energy by convection (i.e., by means of air mixing). This means that various elements of equipment, equipment of the orbital space station will not be able to be cooled from the outside in the way it is usually done on an airplane - with the help of air jets and air radiators. At such a height, as in space in general, the only way to transfer heat is thermal radiation.

Composition of the atmosphere

The Earth's atmosphere consists mainly of gases and various impurities (dust, water drops, ice crystals, sea salts, combustion products).

The concentration of gases that make up the atmosphere is almost constant, with the exception of water (H 2 O) and carbon dioxide (CO 2).

In addition to the gases indicated in the table, the atmosphere contains SO 2, NH 3, CO, ozone, hydrocarbons, HCl, vapors, I 2, as well as many other gases in small quantities. In the troposphere there is constantly a large amount of suspended solid and liquid particles (aerosol).

History of the formation of the atmosphere

According to the most common theory, the Earth's atmosphere has been in four different compositions over time. Initially, it consisted of light gases (hydrogen and helium) captured from interplanetary space. This so-called primary atmosphere(about four billion years ago). At the next stage, active volcanic activity led to the saturation of the atmosphere with gases other than hydrogen (carbon dioxide, ammonia, water vapor). This is how secondary atmosphere(about three billion years before our days). This atmosphere was restorative. Further, the process of formation of the atmosphere was determined by the following factors:

• leakage of light gases (hydrogen and helium) into interplanetary space;
• chemical reactions occurring in the atmosphere under the influence of ultraviolet radiation, lightning discharges and some other factors.

Gradually, these factors led to the formation tertiary atmosphere, characterized by a much lower content of hydrogen and a much higher content of nitrogen and carbon dioxide (formed as a result of chemical reactions from ammonia and hydrocarbons).

Nitrogen

The formation of a large amount of N 2 is due to the oxidation of the ammonia-hydrogen atmosphere by molecular O 2, which began to come from the surface of the planet as a result of photosynthesis, starting from 3 billion years ago. N 2 is also released into the atmosphere as a result of the denitrification of nitrates and other nitrogen-containing compounds. Nitrogen is oxidized by ozone to NO in the upper atmosphere.

Nitrogen N 2 enters into reactions only under specific conditions (for example, during a lightning discharge). Oxidation of molecular nitrogen by ozone during electrical discharges is used in the industrial production of nitrogen fertilizers. It can be oxidized with low energy consumption and converted into a biologically active form by cyanobacteria (blue-green algae) and nodule bacteria that form rhizobial symbiosis with legumes, the so-called. green manure.

Oxygen

The composition of the atmosphere began to change radically with the advent of living organisms on Earth, as a result of photosynthesis, accompanied by the release of oxygen and the absorption of carbon dioxide. Initially, oxygen was spent on the oxidation of reduced compounds - ammonia, hydrocarbons, the ferrous form of iron contained in the oceans, etc. At the end of this stage, the oxygen content in the atmosphere began to grow. Gradually, a modern atmosphere with oxidizing properties formed. Since this caused serious and abrupt changes in many processes occurring in the atmosphere, lithosphere and biosphere, this event was called the Oxygen Catastrophe.

Carbon dioxide

The content of CO 2 in the atmosphere depends on volcanic activity and chemical processes in the earth's shells, but most of all - on the intensity of biosynthesis and decomposition of organic matter in the Earth's biosphere. Almost the entire current biomass of the planet (about 2.4 × 10 12 tons) is formed due to carbon dioxide, nitrogen and water vapor contained in the atmospheric air. Buried in the ocean , swamps and forests , organic matter turns into coal , oil and natural gas . (see Geochemical carbon cycle)

noble gases

Air pollution

Recently, man has begun to influence the evolution of the atmosphere. The result of his activities was a constant significant increase in the content of carbon dioxide in the atmosphere due to the combustion of hydrocarbon fuels accumulated in previous geological epochs. Huge amounts of CO 2 are consumed during photosynthesis and absorbed by the world's oceans. This gas enters the atmosphere due to the decomposition of carbonate rocks and organic substances of plant and animal origin, as well as due to volcanism and human production activities. Over the past 100 years, the content of CO 2 in the atmosphere has increased by 10%, with the main part (360 billion tons) coming from fuel combustion. If the growth rate of fuel combustion continues, then in the next 50 - 60 years the amount of CO 2 in the atmosphere will double and may lead to global climate change.

Fuel combustion is the main source of polluting gases (СО,, SO 2). Sulfur dioxide is oxidized by atmospheric oxygen to SO 3 in the upper atmosphere, which in turn interacts with water vapor and ammonia, and the resulting sulfuric acid (H 2 SO 4) and ammonium sulfate ((NH 4) 2 SO 4) return to the surface of the Earth in the form of a so-called. acid rain. The use of internal combustion engines leads to significant air pollution with nitrogen oxides, hydrocarbons and lead compounds (tetraethyl lead Pb (CH 3 CH 2) 4)).

Aerosol pollution of the atmosphere is caused both by natural causes (volcanic eruption, dust storms, entrainment of sea water droplets and plant pollen, etc.) and by human economic activity (mining of ores and building materials, fuel combustion, cement production, etc.). Intense large-scale removal of solid particles into the atmosphere is one of the possible causes of climate change on the planet.

Literature

1. V. V. Parin, F. P. Kosmolinsky, B. A. Dushkov "Space biology and medicine" (2nd edition, revised and enlarged), M.: "Prosveshchenie", 1975, 223 pages.
2. N. V. Gusakova "Chemistry of the environment", Rostov-on-Don: Phoenix, 2004, 192 s ISBN 5-222-05386-5
3. Sokolov V. A. Geochemistry of natural gases, M., 1971;
4. McEwen M., Phillips L.. Atmospheric Chemistry, M., 1978;
5. Wark K., Warner S., Air pollution. Sources and control, trans. from English, M.. 1980;
6. Monitoring of background pollution of natural environments. in. 1, L., 1982.

see also

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