Composition of the atmosphere. The air envelope of our planet - atmosphere protects the earth's surface from the harmful effects of ultraviolet radiation from the Sun on living organisms. It also protects the Earth from cosmic particles - dust and meteorites.
The atmosphere consists of a mechanical mixture of gases: 78% of its volume is nitrogen, 21% is oxygen and less than 1% is helium, argon, krypton and other inert gases. The amount of oxygen and nitrogen in the air is practically unchanged, because nitrogen almost does not combine with other substances, and oxygen, which, although very active and spent on respiration, oxidation and combustion, is constantly replenished by plants.
Up to an altitude of approximately 100 km, the percentage of these gases remains virtually unchanged. This is due to the fact that the air is constantly mixed.
In addition to the mentioned gases, the atmosphere contains about 0.03% carbon dioxide, which is usually concentrated close to earth's surface and is distributed unevenly: in cities, industrial centers and areas of volcanic activity, its amount increases.
There is always a certain amount of impurities in the atmosphere - water vapor and dust. The content of water vapor depends on the air temperature: the higher the temperature, the more vapor the air can hold. Due to the presence of vaporous water in the air, atmospheric phenomena such as rainbows, refraction of sunlight, etc. are possible.
Dust enters the atmosphere during volcanic eruptions, sand and dust storms, during incomplete combustion of fuel at thermal power plants, etc.
The structure of the atmosphere. The density of the atmosphere changes with altitude: it is highest at the Earth's surface and decreases as it goes up. Thus, at an altitude of 5.5 km, the density of the atmosphere is 2 times, and at an altitude of 11 km, it is 4 times less than in the surface layer.
Depending on the density, composition and properties of gases, the atmosphere is divided into five concentric layers (Fig. 34).
Rice. 34. Vertical section of the atmosphere (stratification of the atmosphere)
1. The bottom layer is called troposphere. Its upper boundary passes at an altitude of 8-10 km at the poles and 16-18 km at the equator. The troposphere contains up to 80% of the total mass of the atmosphere and almost all water vapor.
The air temperature in the troposphere decreases with height by 0.6 °C every 100 m and at its upper boundary is -45-55 °C.
The air in the troposphere is constantly mixed and moves in different directions. Only here are fogs, rains, snowfalls, thunderstorms, storms and other weather phenomena observed.
2. Above is located stratosphere, which extends to an altitude of 50-55 km. Air density and pressure in the stratosphere are negligible. Thin air consists of the same gases as in the troposphere, but it contains more ozone. The highest concentration of ozone is observed at an altitude of 15-30 km. The temperature in the stratosphere increases with altitude and at its upper boundary reaches 0 °C and above. This is because ozone absorbs short-wave energy from the sun, causing the air to warm up.
3. Lies above the stratosphere mesosphere, extending to an altitude of 80 km. There the temperature drops again and reaches -90 °C. The air density there is 200 times less than at the surface of the Earth.
4. Above the mesosphere is located thermosphere(from 80 to 800 km). The temperature in this layer increases: at an altitude of 150 km to 220 °C; at an altitude of 600 km up to 1500 °C. Atmospheric gases (nitrogen and oxygen) are in an ionized state. Under the influence of short-wave solar radiation, individual electrons are separated from the shells of atoms. As a result, in this layer - ionosphere layers of charged particles appear. Their densest layer is located at an altitude of 300-400 km. Due to the low density, the sun's rays are not scattered there, so the sky is black, stars and planets shine brightly on it.
In the ionosphere there are polar lights, powerful electric currents are generated that cause disturbances magnetic field Earth.
5. Above 800 km is the outer shell - exosphere. The speed of movement of individual particles in the exosphere is approaching critical - 11.2 mm/s, so individual particles can overcome gravity and escape into outer space.
The meaning of atmosphere. The role of the atmosphere in the life of our planet is exceptionally great. Without her, the Earth would be dead. The atmosphere protects the Earth's surface from extreme heating and cooling. Its effect can be likened to the role of glass in greenhouses: allowing the sun's rays to pass through and preventing heat loss.
The atmosphere protects living organisms from short-wave and corpuscular radiation from the Sun. The atmosphere is the environment where weather phenomena occur, with which all human activity is associated. The study of this shell is carried out at meteorological stations. Day and night, in any weather, meteorologists monitor the state of the lower layer of the atmosphere. Four times a day, and at many stations hourly they measure temperature, pressure, air humidity, note cloudiness, wind direction and speed, precipitation, electrical and sound phenomena in the atmosphere. Meteorological stations are located everywhere: in Antarctica and in tropical rainforests, on high mountains and in the vast expanses of the tundra. Observations are also carried out on the oceans from specially built ships.
Since the 30s. XX century observations began in the free atmosphere. They began to launch radiosondes that rise to a height of 25-35 km and, using radio equipment, transmit information about temperature, pressure, air humidity and wind speed to Earth. Nowadays, meteorological rockets and satellites are also widely used. The latter have television installations that transmit images of the earth's surface and clouds.
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5. The air shell of the earth§ 31. Heating of the atmosphere
Composition of the Earth. Air
Air is a mechanical mixture of various gases that make up the Earth's atmosphere. Air is necessary for breathing living organisms, is widely used in industry.
The fact that air is a mixture, and not a homogeneous substance, was proven during the experiments of the Scottish scientist Joseph Black. During one of them, the scientist discovered that when white magnesia (magnesium carbonate) is heated, “bound air” is released, that is, carbon dioxide, and burnt magnesia (magnesium oxide) is formed. When burning limestone, on the contrary, “bound air” is removed. Based on these experiments, the scientist concluded that the difference between carbon dioxide and caustic alkalis is that the former contains carbon dioxide, which is one of the components air. Today we know that in addition to carbon dioxide, the composition of the earth’s air includes:
The ratio of gases in the earth's atmosphere indicated in the table is typical for its lower layers, up to an altitude of 120 km. In these areas lies a well-mixed, homogeneous region called the homosphere. Above the homosphere lies the heterosphere, which is characterized by the decomposition of gas molecules into atoms and ions. The regions are separated from each other by a turbo pause.
The chemical reaction in which molecules are decomposed into atoms under the influence of solar and cosmic radiation is called photodissociation. The decay of molecular oxygen produces atomic oxygen, which is the main gas of the atmosphere at altitudes above 200 km. At altitudes above 1200 km, hydrogen and helium, which are the lightest of the gases, begin to predominate.
Since the bulk of the air is concentrated in the 3 lower atmospheric layers, changes in air composition at altitudes above 100 km do not have a noticeable effect on general composition atmosphere.
Nitrogen is the most common gas, accounting for more than three-quarters of the Earth's air volume. Modern nitrogen was formed by the oxidation of the early ammonia-hydrogen atmosphere by molecular oxygen, which is formed during photosynthesis. Currently, small amounts of nitrogen enter the atmosphere as a result of denitrification - the process of reducing nitrates to nitrites, followed by the formation of gaseous oxides and molecular nitrogen, which is produced by anaerobic prokaryotes. Some nitrogen enters the atmosphere during volcanic eruptions.
In the upper layers of the atmosphere, when exposed to electrical discharges with the participation of ozone, molecular nitrogen is oxidized to nitrogen monoxide:
N 2 + O 2 → 2NO
Under normal conditions, the monoxide immediately reacts with oxygen to form nitrous oxide:
2NO + O 2 → 2N 2 O
Nitrogen is essential chemical element earth's atmosphere. Nitrogen is part of proteins and provides mineral nutrition to plants. It determines the bio speed chemical reactions, plays the role of an oxygen diluent.
The second most common gas in the Earth's atmosphere is oxygen. The formation of this gas is associated with the photosynthetic activity of plants and bacteria. And the more diverse and numerous photosynthetic organisms became, the more significant the process of oxygen content in the atmosphere became. A small amount of heavy oxygen is released during degassing of the mantle.
In the upper layers of the troposphere and stratosphere, under the influence of ultraviolet solar radiation (we denote it as hν), ozone is formed:
O 2 + hν → 2O
As a result of the same ultraviolet radiation, ozone decomposes:
O 3 + hν → O 2 + O
О 3 + O → 2О 2
As a result of the first reaction, atomic oxygen is formed, and as a result of the second, molecular oxygen is formed. All 4 reactions are called the “Chapman mechanism”, named after the British scientist Sidney Chapman who discovered them in 1930.
Oxygen is used for the respiration of living organisms. With its help, oxidation and combustion processes occur.
Ozone serves to protect living organisms from ultraviolet radiation, which causes irreversible mutations. The highest concentration of ozone is observed in the lower stratosphere within the so-called. ozone layer or ozone screen, lying at altitudes of 22-25 km. The ozone content is small: at normal pressure, all the ozone in the earth's atmosphere would occupy a layer only 2.91 mm thick.
The formation of the third most common gas in the atmosphere, argon, as well as neon, helium, krypton and xenon, is associated with volcanic eruptions and the decay of radioactive elements.
In particular, helium is a product of the radioactive decay of uranium, thorium and radium: 238 U → 234 Th + α, 230 Th → 226 Ra + 4 He, 226 Ra → 222 Rn + α (in these reactions the α-particle is the helium nucleus, which in During the process of energy loss, it captures electrons and becomes 4 He).
Argon is formed during the decay of the radioactive isotope of potassium: 40 K → 40 Ar + γ.
Neon escapes from igneous rocks.
Krypton is formed as the end product of the decay of uranium (235 U and 238 U) and thorium Th.
The bulk of atmospheric krypton was formed in the early stages of the Earth's evolution as a result of the decay of transuranic elements with a phenomenally short half-life or came from space, where the krypton content is ten million times higher than on Earth.
Xenon is the result of the fission of uranium, but the bulk of this gas remains from the early stages of the formation of the Earth, from the primordial atmosphere.
Carbon dioxide enters the atmosphere as a result of volcanic eruptions and during the decomposition of organic matter. Its content in the atmosphere of the Earth's mid-latitudes varies greatly depending on the seasons of the year: in winter the amount of CO 2 increases, and in summer it decreases. This fluctuation is associated with the activity of plants that use carbon dioxide in the process of photosynthesis.
Hydrogen is formed as a result of the decomposition of water by solar radiation. But, being the lightest of the gases that make up the atmosphere, it constantly evaporates into outer space, and therefore its content in the atmosphere is very small.
Water vapor is the result of the evaporation of water from the surface of lakes, rivers, seas and land.
The concentration of the main gases in the lower layers of the atmosphere, with the exception of water vapor and carbon dioxide, is constant. In small quantities the atmosphere contains sulfur oxide SO 2, ammonia NH 3, carbon monoxide CO, ozone O 3, hydrogen chloride HCl, hydrogen fluoride HF, nitrogen monoxide NO, hydrocarbons, mercury vapor Hg, iodine I 2 and many others. In the lower atmospheric layer, the troposphere, there is always a large amount of suspended solid and liquid particles.
The sources of particulate matter in the Earth's atmosphere are volcanic eruptions, plant pollen, microorganisms, and Lately and human activities, such as the burning of fossil fuels during production. The smallest particles of dust, which are condensation nuclei, cause the formation of fogs and clouds. Without particulate matter constantly present in the atmosphere, precipitation would not fall on Earth.
The Earth's atmosphere is a shell of air.
The presence of a special ball above the earth's surface was proven by the ancient Greeks, who called the atmosphere a steam or gas ball.
This is one of the geospheres of the planet, without which the existence of all living things would not be possible.
Where is the atmosphere
The atmosphere surrounds the planets with a dense layer of air, starting from the earth's surface. It comes into contact with the hydrosphere, covers the lithosphere, extending far into outer space.
What does the atmosphere consist of?
The air layer of the Earth consists mainly of air, the total mass of which reaches 5.3 * 1018 kilograms. Of these, the diseased part is dry air, and much less is water vapor.
Over the sea, the density of the atmosphere is 1.2 kilograms per cubic meter. The temperature in the atmosphere can reach –140.7 degrees, air dissolves in water at zero temperature.
The atmosphere consists of several layers:
- Troposphere;
- Tropopause;
- Stratosphere and stratopause;
- Mesosphere and mesopause;
- A special line above sea level called the Karman line;
- Thermosphere and thermopause;
- Scattering zone or exosphere.
Each layer has its own characteristics; they are interconnected and ensure the functioning of the planet’s air envelope.
Limits of the atmosphere
The lowest edge of the atmosphere passes through the hydrosphere and the upper layers of the lithosphere. The upper boundary begins in the exosphere, which is located 700 kilometers from the surface of the planet and will reach 1.3 thousand kilometers.
According to some reports, the atmosphere reaches 10 thousand kilometers. Scientists agreed that the upper boundary of the air layer should be the Karman line, since aeronautics is no longer possible here.
Thanks to constant studies in this area, scientists have established that the atmosphere comes into contact with the ionosphere at an altitude of 118 kilometers.
Chemical composition
This layer of the Earth consists of gases and gaseous impurities, which include combustion residues, sea salt, ice, water, and dust. The composition and mass of gases that can be found in the atmosphere almost never changes, only the concentration of water and carbon dioxide changes.
The composition of the water can vary from 0.2 percent to 2.5 percent, depending on latitude. Additional elements are chlorine, nitrogen, sulfur, ammonia, carbon, ozone, hydrocarbons, hydrochloric acid, hydrogen fluoride, hydrogen bromide, hydrogen iodide.
A separate part is occupied by mercury, iodine, bromine, and nitric oxide. In addition, liquid and solid particles called aerosol are found in the troposphere. One of the rarest gases on the planet, radon, is found in the atmosphere.
In terms of chemical composition, nitrogen occupies more than 78% of the atmosphere, oxygen - almost 21%, carbon dioxide - 0.03%, argon - almost 1%, the total amount of the substance is less than 0.01%. This air composition was formed when the planet first emerged and began to develop.
With the advent of man, who gradually moved to production, chemical composition changed. In particular, the amount of carbon dioxide is constantly increasing.
Functions of the atmosphere
Gases in the air layer perform a variety of functions. Firstly, they absorb rays and radiant energy. Secondly, they influence the formation of temperature in the atmosphere and on Earth. Thirdly, it ensures life and its course on Earth.
In addition, this layer provides thermoregulation, which determines the weather and climate, the mode of heat distribution and atmospheric pressure. The troposphere helps regulate the flow of air masses, determine the movement of water, and heat exchange processes.
The atmosphere constantly interacts with the lithosphere and hydrosphere, providing geological processes. The most important function is that it provides protection from dust of meteorite origin, from the influence of space and the sun.
Data
- Oxygen provides the Earth with decomposition organic matter o hard rock, which is very important for emissions, decomposition of rocks, oxidation of organisms.
- Carbon dioxide helps photosynthesis occur, and also contributes to the transmission of short waves of solar radiation and the absorption of long thermal waves. If this does not happen, then the so-called greenhouse effect is observed.
- One of the main problems associated with the atmosphere is pollution, which occurs due to the operation of factories and automobile emissions. Therefore, many countries have introduced special environmental control, and at the international level special mechanisms are being undertaken to regulate emissions and the greenhouse effect.
Every literate person should know not only that the planet is surrounded by an atmosphere made of a mixture of all kinds of gases, but also that there are different layers of the atmosphere that are located at unequal distances from the Earth’s surface.
Observing the sky, we do not see at all its complex structure, its heterogeneous composition, or other things hidden from view. But it is precisely thanks to the complex and multicomponent composition of the air layer that conditions exist around the planet that allowed life to arise here, vegetation to flourish, and everything that has ever been here to appear.
Knowledge about the subject of conversation is given to people already in the 6th grade at school, but some have not yet completed their studies, and some have been there so long ago that they have already forgotten everything. Nevertheless, every educated person should know what the world around him consists of, especially that part of it on which the very possibility of his normal life directly depends.
What is the name of each layer of the atmosphere, at what altitude is it located, and what role does it play? All these issues will be discussed below.
The structure of the Earth's atmosphere
Looking at the sky, especially when it is completely cloudless, it is very difficult to even imagine that it has such a complex and multi-layered structure, that the temperature there at different altitudes is very different, and what exactly is happening there, in the altitude critical processes for all flora and fauna on Earth.
If it were not for such a complex composition of the gas cover of the planet, then there would simply be no life here and even the possibility for its origin.
The first attempts to study this part of the surrounding world were made by the ancient Greeks, but they could not go too far in their conclusions, since they did not have the necessary technical base. They did not see the boundaries of different layers, could not measure their temperature, study their component composition, etc.
Basically, only weather phenomena prompted the most progressive minds to think that the visible sky is not as simple as it seems.
It is believed that the structure of the modern gas shell around the Earth was formed in three stages. First there was a primordial atmosphere of hydrogen and helium captured from outer space.
Then volcanic eruptions filled the air with a mass of other particles, and a secondary atmosphere arose. After passing through all the basic chemical reactions and particle relaxation processes, the current situation arose.
Layers of the atmosphere in order from the surface of the earth and their characteristics
The structure of the gas shell of the planet is quite complex and diverse. Let's look at it in more detail, gradually reaching the highest levels.
Troposphere
Apart from the boundary layer, the troposphere is the lowest layer of the atmosphere. It extends to a height of approximately 8-10 km above the earth's surface in polar regions, 10-12 km in temperate climates, and 16-18 km in tropical parts.
Interesting fact: this distance may vary depending on the time of year - in winter it is slightly less than in summer.
The air of the troposphere contains the main life-giving force for all life on earth. It contains about 80% of all available atmospheric air, more than 90% of water vapor, and it is here that clouds, cyclones and other atmospheric phenomena form.
It is interesting to note the gradual decrease in temperature as you rise from the surface of the planet. Scientists have calculated that for every 100 m of altitude, the temperature decreases by about 0.6-0.7 degrees.
Stratosphere
The next most important layer is the stratosphere. The height of the stratosphere is approximately 45-50 kilometers. It starts at 11 km and negative temperatures already prevail here, reaching as much as -57°C.
Why is this layer important for humans, all animals and plants? It is here, at an altitude of 20-25 kilometers, that the ozone layer is located - it traps ultraviolet rays emanating from the sun and reduces their destructive effect on flora and fauna to an acceptable level.
It is very interesting to note that the stratosphere absorbs many types of radiation that come to the earth from the sun, other stars and outer space. The energy received from these particles is used to ionize the molecules and atoms located here, and various chemical compounds appear.
All this leads to such a famous and colorful phenomenon as the northern lights.
Mesosphere
The mesosphere begins at about 50 and extends to 90 kilometers. The gradient, or temperature difference with changes in altitude, is no longer as large here as in the lower layers. At the upper boundaries of this shell the temperature is about -80°C. The composition of this area includes approximately 80% nitrogen as well as 20% oxygen.
It is important to note that the mesosphere is a kind of dead zone for any flying devices. Airplanes cannot fly here, since the air is too thin, and satellites cannot fly at such a low altitude, since the available air density for them is very high.
Another one interesting characteristic mesosphere – This is where meteorites that strike the planet burn up. The study of such layers distant from the earth occurs with the help of special rockets, but the efficiency of the process is low, so the knowledge of the region leaves much to be desired.
Thermosphere
Immediately after the considered layer comes the thermosphere, whose altitude in kilometers extends for as much as 800 km. In some ways, this is almost outer space. Here there is an aggressive impact of cosmic radiation, radiation, solar radiation.
All this gives rise to such a wonderful and beautiful phenomenon as the aurora.
The lowest layer of the thermosphere is heated to temperatures of approximately 200 K or more. This happens due to elementary processes between atoms and molecules, their recombination and radiation.
The upper layers are heated due to the flowing here magnetic storms, electric currents, which are generated in this case. The temperature of the layer is uneven and can fluctuate very significantly.
Most flights occur in the thermosphere artificial satellites, ballistic bodies, manned stations, etc. Also, launch tests of various types of weapons and missiles are carried out here.
Exosphere
The exosphere, or as it is also called the scattering sphere, is the highest level of our atmosphere, its limit, followed by interplanetary outer space. The exosphere begins at an altitude of approximately 800-1000 kilometers.
The dense layers are left behind and here the air is extremely rarefied; any particles that enter from the outside are simply carried away into space due to the very weak effect of gravity.
This shell ends at an altitude of approximately 3000-3500 km, and there are almost no particles here anymore. This zone is called the near-space vacuum. What predominates here is not individual particles in their normal state, but plasma, most often completely ionized.
The importance of the atmosphere in the life of the Earth
This is what all the main levels of the atmosphere of our planet look like. Its detailed scheme may include other regions, but they are of secondary importance.
It's important to note that The atmosphere plays a decisive role for life on Earth. A lot of ozone in its stratosphere allows flora and fauna to escape from the deadly effects of radiation and radiation from space.
It is also here that the weather is formed, all atmospheric phenomena occur, cyclones and winds arise and die, and this or that pressure is established. All this has a direct impact on the condition of humans, all living organisms and plants.
The nearest layer, the troposphere, gives us the opportunity to breathe, saturates all living things with oxygen and allows them to live. Even small deviations in the structure and component composition of the atmosphere can have the most detrimental effect on all living things.
That is why such a campaign has now been launched against harmful emissions from cars and production, environmentalists are sounding the alarm about the thickness of the ozone layer, the Green Party and others like it are advocating for maximum conservation of nature. This is the only way to prolong normal life on earth and not make it unbearable in terms of climate.
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. 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 highly developed in the troposphere, clouds appear, and cyclones and anticyclones develop. Temperature decreases with increasing altitude with an average vertical gradient of 0.65°/100 m
The following are accepted as “normal conditions” at the Earth’s surface: density 1.2 kg/m3, barometric pressure 101.35 kPa, temperature plus 20 °C and relative humidity 50%. These conditional indicators have purely engineering significance.
Stratosphere
A layer of the atmosphere located at an altitude of 11 to 50 km. Characterized by a slight change in temperature in the 11-25 km layer (lower layer of the stratosphere) and an increase in temperature in the 25-40 km layer from −56.5 to 0.8 ° (upper layer of the stratosphere or inversion region). 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 mesosphere.
Stratopause
The boundary layer of the atmosphere between the stratosphere and mesosphere. In the vertical temperature distribution there is a maximum (about 0 °C).
Mesosphere
Mesopause
Transitional layer between the mesosphere and thermosphere. There is a minimum in the vertical temperature distribution (about -90°C).
Karman Line
The height 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 to high altitudes. Under the influence of ultraviolet and x-ray solar radiation and cosmic radiation, ionization of the air (“ auroras”) occurs - the main regions of the ionosphere lie inside the thermosphere. At altitudes above 300 km, atomic oxygen predominates.
Exosphere (scattering sphere)
Up to an altitude of 100 km, the atmosphere is a homogeneous, well-mixed mixture of gases. In higher layers, the distribution of gases over height depends on their molecular weights, 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 kinetic energy individual particles at altitudes of 200-250 km correspond to a temperature of ~1500°C. Above 200 km, significant fluctuations in temperature and gas density in time and space are observed.
At an altitude of about 2000-3000 km, the exosphere gradually turns into the so-called near space vacuum, which is filled with highly rarefied particles of interplanetary gas, mainly hydrogen atoms. But this gas represents only part of the interplanetary matter. The other part consists of dust particles of cometary and meteoric origin. In addition to extremely rarefied dust 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 - about 20%; mass of the mesosphere - no more than 0.3%, thermosphere - less than 0.05% of total mass atmosphere. Based on the electrical properties in the atmosphere, the neutronosphere 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 the area where gravity affects the separation of gases, since their mixing at such an altitude is negligible. This implies a 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 the 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 air mass is (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). The solubility of air in water at 0°C is 0.036%, at 25°C - 0.22%.
Physiological and other properties of the atmosphere
Already at an altitude of 5 km above sea level, an untrained person begins to experience oxygen starvation and without adaptation, a person’s performance is significantly reduced. The physiological zone of the atmosphere ends here. Human breathing becomes impossible at an altitude of 15 km, although up to approximately 115 km the atmosphere contains oxygen.
The atmosphere supplies us with the oxygen necessary for breathing. However, due to the drop in the total pressure of the atmosphere, as you rise to altitude, the partial pressure of oxygen decreases accordingly.
The human lungs constantly contain about 3 liters of alveolar air. The partial pressure of oxygen in alveolar air at normal atmospheric pressure is 110 mmHg. Art., carbon dioxide pressure - 40 mm Hg. Art., and water vapor - 47 mm Hg. Art. With increasing altitude, oxygen pressure drops, and the total vapor pressure of water and carbon dioxide in the lungs remains almost constant - about 87 mm Hg. Art. The supply of oxygen to the lungs will completely stop when the ambient air pressure 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 altitude, 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 has an intense effect on the body - primary cosmic rays; At altitudes of more than 40 km, the ultraviolet part of the solar spectrum is dangerous for humans.
As we rise to an ever greater height above the Earth's surface, such familiar phenomena observed in the lower layers of the atmosphere as sound propagation, the occurrence of aerodynamic lift and drag, heat transfer by convection, etc., gradually weaken and then completely disappear.
In rarefied layers of air, sound propagation 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 conventional 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 devoid of another remarkable property - the ability to absorb, conduct and transmit thermal energy by convection (i.e. by mixing air). This means that various elements of equipment, orbital equipment space station will not be able to cool outside in the way that is usually done on an airplane - with the help of air jets and air radiators. At this altitude, as in space generally, the only way to transfer heat is thermal radiation.
Atmospheric composition
The Earth's atmosphere consists mainly of gases and various impurities (dust, water droplets, 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).
| Gas | Content by volume,% |
Content by weight,% |
|---|---|---|
| Nitrogen | 78,084 | 75,50 |
| Oxygen | 20,946 | 23,10 |
| Argon | 0,932 | 1,286 |
| Water | 0,5-4 | - |
| Carbon dioxide | 0,032 | 0,046 |
| Neon | 1.818×10 −3 | 1.3×10 −3 |
| Helium | 4.6×10 −4 | 7.2×10 −5 |
| Methane | 1.7×10 −4 | - |
| Krypton | 1.14×10 −4 | 2.9×10 −4 |
| Hydrogen | 5×10 −5 | 7.6×10 −5 |
| Xenon | 8.7×10 −6 | - |
| Nitrous oxide | 5×10 −5 | 7.7×10 −5 |
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. The troposphere constantly contains a large amount of suspended solid and liquid particles (aerosol).
History of atmospheric formation
According to the most common theory, the Earth's atmosphere has had four different compositions over time. Initially, it consisted of light gases (hydrogen and helium) captured from interplanetary space. This is the 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 it was formed secondary atmosphere(about three billion years before the present day). This atmosphere was restorative. Further, the process of atmosphere formation 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 3 billion years ago. N2 is also released into the atmosphere as a result of denitrification of nitrates and other nitrogen-containing compounds. Nitrogen is oxidized by ozone to NO in the upper atmosphere.
Nitrogen N 2 reacts only under specific conditions (for example, during a lightning discharge). The oxidation of molecular nitrogen by ozone during electrical discharges is used in the industrial production of nitrogen fertilizers. Oxidize it with low energy consumption and convert it into biological active form Cyanobacteria (blue-green algae) and nodule bacteria that form rhizobial symbiosis with leguminous plants, the so-called. green manure.
Oxygen
The composition of the atmosphere began to change radically with the appearance 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, ferrous form of iron contained in the oceans, etc. At the end this stage The oxygen content in the atmosphere began to increase. Gradually, a modern atmosphere with oxidizing properties formed. Because it caused major and abrupt changes in many processes occurring in the atmosphere, lithosphere, and biosphere, the event was called the Oxygen Disaster.
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. Organics buried in the ocean, swamps and forests turn into coal, oil and natural gas. (see Geochemical carbon cycle)
Noble gases
Air pollution
Recently, humans have 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 eras. 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 industrial activity. Over the past 100 years, the content of CO 2 in the atmosphere has increased by 10%, with the bulk (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 could lead to global climate change.
Fuel combustion is the main source of polluting gases (CO, SO2). Sulfur dioxide is oxidized by atmospheric oxygen to SO 3 in the upper layers of the atmosphere, which in turn interacts with water and ammonia vapor, and the resulting sulfuric acid (H 2 SO 4) and ammonium sulfate ((NH 4) 2 SO 4) are returned to the surface of the Earth in the form of the so-called. acid rain. Usage
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