The percentage of nitrogen in the earth's atmosphere is. The composition of the Earth's atmosphere as a percentage. The chemical composition of the Earth's atmosphere

At least atmospheric, it owes its origin not so much to the Sun as to life processes. There is a striking discrepancy between the content of element No. 7 in the lithosphere (0.01%) and in the atmosphere (75.6% by mass or 78.09% by volume). In general, we live in a nitrogen atmosphere moderately enriched with oxygen.

Meanwhile, neither on other planets of the solar system, nor in the composition of comets or any other cold cosmic objects, free has been found. There are its compounds and radicals - CN*, NH*, NH*2, NH*3, but there is no nitrogen. True, about 2% of nitrogen has been recorded in the atmosphere of Venus, but this figure still needs to be confirmed.

It is believed that there was no element 7 in the Earth's primary atmosphere either. Where, then, is he in the air? Apparently, the atmosphere of our planet initially consisted of volatile substances formed in the earth's interior: H2, H2O, CO2, CH4, NH3. Free if vented as a product of volcanic activity, turn into ammonia. The conditions for this were the most suitable: an excess of hydrogen, elevated temperatures - the Earth's surface has not yet cooled down. So what does it mean that nitrogen was first present in the atmosphere in the form of ammonia? Apparently so. Let's remember this fact.

But then life arose... Vladimir Ivanovich Vernadsky argued that "the earth's gas shell, our air, is the creation of life." It was life that launched the amazing mechanism of photosynthesis. One of the end products of this process - free began to actively combine with ammonia, releasing molecular nitrogen:

Photosynthesis

CO2 + 2H2O → HCO + NaO + O2;

4NH3 + 3O2 → 2N2 + 6H2O

And nitrogen, as is known, does not react with each other under normal conditions, which allowed the earth's air to maintain the "status quo" of the composition. Note that a significant part of the ammonia could have been dissolved in water during the formation of the hydrosphere.

Nowadays, the main source of N2 in the atmosphere is volcanic gases.

If you break the triple bond...

Having destroyed the inexhaustible reserves of bound active nitrogen, living nature confronted the problem of how to bind nitrogen. As we know, it turned out to be very inert in the free, molecular state. The reason for this is its triple molecule: N≡N.

Usually bonds of such multiplicity are unstable. Recall the classic example of acetylene: HC≡ CH. The triple bond of its molecule is very fragile, which explains the incredible chemical activity of this gas. But nitrogen has a clear anomaly here: its triple bond forms the most stable of all known diatomic molecules. It takes a lot of effort to break this connection. For example, the industrial synthesis of ammonia requires a pressure of more than 200 atm and a temperature of more than 500 ° C, and even the obligatory presence of catalysts ... Solving the problem of nitrogen fixation, nature had to establish a continuous production of nitrogen compounds by the thunderstorm method.

Statistics say that more than three billion lightning strikes annually in the atmosphere of our planet. The power of individual discharges reaches 200 million kilowatts, while the air is heated (locally, of course) up to 20 thousand degrees. At such a monstrous temperature, the molecules of oxygen and nitrogen decompose into atoms, which, easily reacting with each other, form fragile nitric oxide:

N2 + O2 → 2NO

Due to rapid cooling (a lightning discharge lasts a ten-thousandth of a second), nitric oxide does not decompose and is freely oxidized by air oxygen to a more stable dioxide

2NO + O2 → 2NO2.

In the presence of atmospheric moisture and raindrops, nitrogen dioxide is converted to nitric acid:

3NO2 + H2O → 2HNO3 + NO

So, having fallen under a fresh thunderstorm rain, we get the opportunity to swim in a weak solution of nitric acid. Penetrating into the soil, atmospheric forms with its substances a variety of natural fertilizers.

Nitrogen is also fixed in the atmosphere by photochemical means: having absorbed a quantum of light, the N2 molecule goes into an excited, activated state and becomes able to combine with oxygen.

The atmosphere is the air envelope of the Earth. Extending up to 3000 km from the earth's surface. Its traces can be traced to a height of up to 10,000 km. A. has an uneven density of 50 5; its masses are concentrated up to 5 km, 75% - up to 10 km, 90% - up to 16 km.

The atmosphere consists of air - a mechanical mixture of several gases.

Nitrogen(78%) in the atmosphere plays the role of an oxygen diluent, regulating the rate of oxidation, and, consequently, the rate and intensity of biological processes. Nitrogen is the main element of the earth's atmosphere, which is continuously exchanged with the living matter of the biosphere, and constituent parts the latter are nitrogen compounds (amino acids, purines, etc.). Extraction of nitrogen from the atmosphere occurs inorganic and biochemical ways, although they are closely interrelated. Inorganic extraction is associated with the formation of its compounds N 2 O, N 2 O 5 , NO 2 , NH 3 . They are found in atmospheric precipitation and are formed in the atmosphere under the action of electrical discharges during thunderstorms or photochemical reactions under the influence of solar radiation.

Biological nitrogen fixation is carried out by some bacteria in symbiosis with higher plants in soils. Nitrogen is also fixed by some plankton microorganisms and algae in the marine environment. In quantitative terms, the biological binding of nitrogen exceeds its inorganic fixation. The exchange of all the nitrogen in the atmosphere takes approximately 10 million years. Nitrogen is found in gases of volcanic origin and in igneous rocks. When various samples of crystalline rocks and meteorites are heated, nitrogen is released in the form of N 2 and NH 3 molecules. However, the main form of the presence of nitrogen, both on Earth and on the planets terrestrial group, is molecular. Ammonia, getting into the upper atmosphere, is rapidly oxidized, releasing nitrogen. In sedimentary rocks, it is buried together with organic matter and is found in an increased amount in bituminous deposits. In the process of regional metamorphism of these rocks, nitrogen in various forms is released into the Earth's atmosphere.

Geochemical nitrogen cycle (

Oxygen(21%) is used by living organisms for respiration, is part of organic matter(proteins fats carbohydrates). Ozone O 3 . blocking life-threatening ultraviolet radiation from the Sun.

Oxygen is the second most abundant gas in the atmosphere, playing an extremely important role in many processes in the biosphere. The dominant form of its existence is O 2 . In the upper layers of the atmosphere, under the influence of ultraviolet radiation, the dissociation of oxygen molecules occurs, and at an altitude of about 200 km, the ratio of atomic oxygen to molecular (O: O 2) becomes equal to 10. When these forms of oxygen interact in the atmosphere (at an altitude of 20-30 km), ozone belt (ozone shield). Ozone (O 3) is necessary for living organisms, delaying most of the solar ultraviolet radiation that is harmful to them.

In the early stages of the Earth's development, free oxygen arose in very small quantities as a result of the photodissociation of carbon dioxide and water molecules in the upper atmosphere. However, these small amounts were quickly consumed in the oxidation of other gases. With the advent of autotrophic photosynthetic organisms in the ocean, the situation has changed significantly. The amount of free oxygen in the atmosphere began to progressively increase, actively oxidizing many components of the biosphere. Thus, the first portions of free oxygen contributed primarily to the transition of ferrous forms of iron into oxide, and sulfides into sulfates.

In the end, the amount of free oxygen in the Earth's atmosphere reached a certain mass and turned out to be balanced in such a way that the amount produced became equal to the amount absorbed. A relative constancy of the content of free oxygen was established in the atmosphere.

Geochemical oxygen cycle (V.A. Vronsky, G.V. Voitkevich)

Carbon dioxide, goes to the formation of living matter, and together with water vapor creates the so-called "greenhouse (greenhouse) effect."

Carbon (carbon dioxide) - most of it in the atmosphere is in the form of CO 2 and much less in the form of CH 4. The significance of the geochemical history of carbon in the biosphere is exceptionally great, since it is a part of all living organisms. Within living organisms, reduced forms of carbon occur, and in environment biospheres are oxidized. Thus, the chemical exchange of the life cycle is established: CO 2 ↔ living matter.

The primary source of carbon dioxide in the biosphere is volcanic activity associated with secular degassing of the mantle and lower horizons of the earth's crust. Part of this carbon dioxide arises from the thermal decomposition of ancient limestones in various metamorphic zones. Migration of CO 2 in the biosphere proceeds in two ways.

The first method is expressed in the absorption of CO 2 in the process of photosynthesis with the formation of organic substances and subsequent burial in favorable reducing conditions in the lithosphere in the form of peat, coal, oil, oil shale. According to the second method, carbon migration leads to the creation of a carbonate system in the hydrosphere, where CO 2 turns into H 2 CO 3, HCO 3 -1, CO 3 -2. Then, with the participation of calcium (less often magnesium and iron), the precipitation of carbonates occurs in a biogenic and abiogenic way. Thick strata of limestones and dolomites appear. According to A.B. Ronov, the ratio of organic carbon (Corg) to carbonate carbon (Ccarb) in the history of the biosphere was 1:4.

Along with the global cycle of carbon, there are a number of its small cycles. So, on land, green plants absorb CO 2 for the process of photosynthesis during the daytime, and at night they release it into the atmosphere. With the death of living organisms on the earth's surface, organic matter is oxidized (with the participation of microorganisms) with the release of CO 2 into the atmosphere. In recent decades, a special place in the carbon cycle has been occupied by the massive combustion of fossil fuels and the increase in its content in the modern atmosphere.

The carbon cycle in geographical envelope(according to F. Ramad, 1981)

Argon- the third most common atmospheric gas, which sharply distinguishes it from the extremely scarcely common other inert gases. However, argon in its geological history shares the fate of these gases, which are characterized by two features:

1. the irreversibility of their accumulation in the atmosphere;
2. close association with the radioactive decay of certain unstable isotopes.

Inert gases are outside the circulation of most cyclic elements in the Earth's biosphere.

All inert gases can be divided into primary and radiogenic. The primary ones are those that were captured by the Earth during its formation. They are extremely rare. The primary part of argon is represented mainly by 36 Ar and 38 Ar isotopes, while atmospheric argon consists entirely of the 40 Ar isotope (99.6%), which is undoubtedly radiogenic. In potassium-containing rocks, radiogenic argon accumulated due to the decay of potassium-40 by electron capture: 40 K + e → 40 Ar.

Therefore, the content of argon in rocks is determined by their age and the amount of potassium. To this extent, the concentration of helium in rocks is a function of their age and the content of thorium and uranium. Argon and helium are released into the atmosphere from the earth's interior during volcanic eruptions, through cracks in earth's crust in the form of gas jets, as well as in the weathering of rocks. According to the calculations performed by P. Dimon and J. Culp, helium and argon in modern era accumulate in the earth's crust and enter the atmosphere in relatively small quantities. The rate of entry of these radiogenic gases is so low that during the geological history of the Earth it could not provide the observed content of them in the modern atmosphere. Therefore, it remains to be assumed that most of the argon of the atmosphere came from the bowels of the Earth at the earliest stages of its development, and a much smaller part was added later in the process of volcanism and during the weathering of potassium-containing rocks.

Thus, during geological time, helium and argon had different processes migrations. There is very little helium in the atmosphere (about 5 * 10 -4%), and the "helium breath" of the Earth was lighter, since it, as the lightest gas, escaped into outer space. And "argon breath" - heavy and argon remained within our planet. Most of the primary inert gases, like neon and xenon, were associated with the primary neon captured by the Earth during its formation, as well as with the release into the atmosphere during degassing of the mantle. The totality of data on the geochemistry of noble gases indicates that the primary atmosphere of the Earth arose at the earliest stages of its development.

The atmosphere contains water vapor And water in liquid and solid state. Water in the atmosphere is an important heat accumulator.

The lower layers of the atmosphere contain a large number of mineral and technogenic dust and aerosols, combustion products, salts, spores and plant pollen, etc.

Up to a height of 100-120 km, due to the complete mixing of air, the composition of the atmosphere is homogeneous. The ratio between nitrogen and oxygen is constant. Above, inert gases, hydrogen, etc. predominate. In the lower layers of the atmosphere there is water vapor. With distance from the earth, its content decreases. Above, the ratio of gases changes, for example, at an altitude of 200-800 km, oxygen prevails over nitrogen by 10-100 times.

Atmosphere(from the Greek atmos - steam and spharia - ball) - the air shell of the Earth, rotating with it. The development of the atmosphere was closely connected with the geological and geochemical processes taking place on our planet, as well as with the activities of living organisms.

The lower boundary of the atmosphere coincides with the surface of the Earth, since air penetrates into the smallest pores in the soil and is dissolved even in water.

The upper limit at an altitude of 2000-3000 km gradually passes into outer space.

Oxygen-rich atmosphere makes life possible on Earth. Atmospheric oxygen is used in the process of breathing by humans, animals, and plants.

If there were no atmosphere, the Earth would be as quiet as the moon. After all, sound is the vibration of air particles. The blue color of the sky is explained by the fact that the sun's rays, passing through the atmosphere, as if through a lens, are decomposed into their component colors. In this case, the rays of blue and blue colors are scattered most of all.

The atmosphere retains most of the ultraviolet radiation from the Sun, which has a detrimental effect on living organisms. It also keeps heat at the surface of the Earth, preventing our planet from cooling.

The structure of the atmosphere

Several layers can be distinguished in the atmosphere, differing in density and density (Fig. 1).

Troposphere

Troposphere- the lowest layer of the atmosphere, whose thickness above the poles is 8-10 km, in temperate latitudes - 10-12 km, and above the equator - 16-18 km.

Rice. 1. The structure of the Earth's atmosphere

The air in the troposphere is heated from the earth's surface, i.e. from land and water. Therefore, the air temperature in this layer decreases with height by an average of 0.6 °C for every 100 m. At the upper boundary of the troposphere, it reaches -55 °C. At the same time, in the region of the equator at the upper boundary of the troposphere, the air temperature is -70 ° C, and in the region North Pole-65 °С.

About 80% of the mass of the atmosphere is concentrated in the troposphere, almost all water vapor is located, thunderstorms, storms, clouds and precipitation occur, and vertical (convection) and horizontal (wind) air movement occurs.

We can say that the weather is mainly formed in the troposphere.

Stratosphere

Stratosphere- the layer of the atmosphere located above the troposphere at an altitude of 8 to 50 km. The color of the sky in this layer appears purple, which is explained by the rarefaction of the air, due to which the sun's rays almost do not scatter.

The stratosphere contains 20% of the mass of the atmosphere. The air in this layer is rarefied, there is practically no water vapor, and therefore clouds and precipitation are almost not formed. However, stable air currents are observed in the stratosphere, the speed of which reaches 300 km / h.

This layer is concentrated ozone(ozone screen, ozonosphere), a layer that absorbs ultraviolet rays, preventing them from passing to the Earth and thereby protecting living organisms on our planet. Due to ozone, the air temperature at the upper boundary of the stratosphere is in the range from -50 to 4-55 °C.

Between the mesosphere and the stratosphere there is a transitional zone - the stratopause.

Mesosphere

Mesosphere- a layer of the atmosphere located at an altitude of 50-80 km. The air density here is 200 times less than at the surface of the Earth. The color of the sky in the mesosphere appears black, stars are visible during the day. The air temperature drops to -75 (-90)°С.

At an altitude of 80 km begins thermosphere. The air temperature in this layer rises sharply to a height of 250 m, and then becomes constant: at a height of 150 km it reaches 220-240 °C; at an altitude of 500-600 km it exceeds 1500 °C.

In the mesosphere and thermosphere, under the action of cosmic rays, gas molecules break up into charged (ionized) particles of atoms, so this part of the atmosphere is called ionosphere- a layer of very rarefied air, located at an altitude of 50 to 1000 km, consisting mainly of ionized oxygen atoms, nitric oxide molecules and free electrons. This layer is characterized by high electrification, and long and medium radio waves are reflected from it, as from a mirror.

In the ionosphere, auroras arise - the glow of rarefied gases under the influence of electrically charged particles flying from the Sun - and sharp fluctuations in the magnetic field are observed.

Exosphere

Exosphere- the outer layer of the atmosphere, located above 1000 km. This layer is also called the scattering sphere, since gas particles move here at high speed and can be scattered into outer space.

Composition of the atmosphere

The atmosphere is a mixture of gases consisting of nitrogen (78.08%), oxygen (20.95%), carbon dioxide (0.03%), argon (0.93%), a small amount of helium, neon, xenon, krypton (0.01%), ozone and other gases, but their content is negligible (Table 1). The modern composition of the Earth's air was established more than a hundred million years ago, but the sharply increased human production activity nevertheless led to its change. Currently, there is an increase in the content of CO 2 by about 10-12%.

The gases that make up the atmosphere perform various functional roles. However, the main significance of these gases is determined primarily by the fact that they very strongly absorb radiant energy and thus have a significant effect on the temperature regime of the Earth's surface and atmosphere.

Table 1. Chemical composition dry atmospheric air near the earth's surface

Nitrogen, the most common gas in the atmosphere, chemically little active.

Oxygen, unlike nitrogen, is a chemically very active element. The specific function of oxygen is the oxidation of organic matter of heterotrophic organisms, rocks, and incompletely oxidized gases emitted into the atmosphere by volcanoes. Without oxygen, there would be no decomposition of dead organic matter.

The role of carbon dioxide in the atmosphere is exceptionally great. It enters the atmosphere as a result of the processes of combustion, respiration of living organisms, decay and is, first of all, the main construction material to create organic matter during photosynthesis. In addition, the property of carbon dioxide to transmit short-wave solar radiation and absorb part of thermal long-wave radiation is of great importance, which will create the so-called greenhouse effect, about which we will talk below.

Influence at atmospheric processes, especially on the thermal regime of the stratosphere, and has ozone. This gas serves as a natural absorber of solar ultraviolet radiation, and the absorption of solar radiation leads to air heating. The average monthly values ​​of the total ozone content in the atmosphere vary depending on the latitude of the area and the season within 0.23-0.52 cm (this is the thickness of the ozone layer at ground pressure and temperature). There is an increase in the ozone content from the equator to the poles and an annual variation with a minimum in autumn and a maximum in spring.

A characteristic property of the atmosphere can be called the fact that the content of the main gases (nitrogen, oxygen, argon) changes slightly with height: at an altitude of 65 km in the atmosphere, the nitrogen content is 86%, oxygen - 19, argon - 0.91, at an altitude of 95 km - nitrogen 77, oxygen - 21.3, argon - 0.82%. The constancy of the composition of atmospheric air vertically and horizontally is maintained by its mixing.

In addition to gases, air contains water vapor And solid particles. The latter can have both natural and artificial (anthropogenic) origin. These are flower pollen, tiny salt crystals, road dust, aerosol impurities. When the sun's rays penetrate the window, they can be seen with the naked eye.

There are especially many particulate matter in the air of cities and large industrial centers, where emissions of harmful gases and their impurities formed during fuel combustion are added to aerosols.

The concentration of aerosols in the atmosphere determines the transparency of the air, which affects the solar radiation reaching the Earth's surface. The largest aerosols are condensation nuclei (from lat. condensatio- compaction, thickening) - contribute to the transformation of water vapor into water droplets.

The value of water vapor is determined primarily by the fact that it delays the long-wave thermal radiation of the earth's surface; represents the main link of large and small moisture cycles; raises the temperature of the air when the water beds condense.

The amount of water vapor in the atmosphere varies over time and space. Thus, the concentration of water vapor near the earth's surface ranges from 3% in the tropics to 2-10 (15)% in Antarctica.

The average content of water vapor in the vertical column of the atmosphere in temperate latitudes is about 1.6-1.7 cm (the layer of condensed water vapor will have such a thickness). Information about water vapor in different layers of the atmosphere is contradictory. It was assumed, for example, that in the altitude range from 20 to 30 km, the specific humidity strongly increases with height. However, subsequent measurements indicate a greater dryness of the stratosphere. Apparently, the specific humidity in the stratosphere depends little on height and amounts to 2–4 mg/kg.

The variability of water vapor content in the troposphere is determined by the interaction of evaporation, condensation, and horizontal transport. As a result of the condensation of water vapor, clouds form and precipitation occurs in the form of rain, hail and snow.

The processes of phase transitions of water proceed mainly in the troposphere, which is why clouds in the stratosphere (at altitudes of 20-30 km) and mesosphere (near the mesopause), called mother-of-pearl and silver, are observed relatively rarely, while tropospheric clouds often cover about 50% of the entire earth surfaces.

The amount of water vapor that can be contained in the air depends on the temperature of the air.

1 m 3 of air at a temperature of -20 ° C can contain no more than 1 g of water; at 0 °C - no more than 5 g; at +10 °С - no more than 9 g; at +30 °С - no more than 30 g of water.

Conclusion: The higher the air temperature, the more water vapor it can contain.

Air can be rich And not saturated steam. So, if at a temperature of +30 ° C 1 m 3 of air contains 15 g of water vapor, the air is not saturated with water vapor; if 30 g - saturated.

Absolute humidity- this is the amount of water vapor contained in 1 m 3 of air. It is expressed in grams. For example, if they say "absolute humidity is 15", then this means that 1 mL contains 15 g of water vapor.

Relative humidity- this is the ratio (in percent) of the actual content of water vapor in 1 m 3 of air to the amount of water vapor that can be contained in 1 m L at a given temperature. For example, if a weather report is broadcast over the radio that the relative humidity is 70%, this means that the air contains 70% of the water vapor that it can hold at a given temperature.

The greater the relative humidity of the air, t. the closer the air is to saturation, the more likely it is to fall.

Always high (up to 90%) relative humidity is observed in the equatorial zone, since there is a high air temperature throughout the year and there is a large evaporation from the surface of the oceans. The same high relative humidity is in the polar regions, but only because at low temperatures even a small amount of water vapor makes the air saturated or close to saturation. In temperate latitudes, relative humidity varies seasonally - it is higher in winter and lower in summer.

The relative humidity of the air is especially low in deserts: 1 m 1 of air there contains two to three times less than the amount of water vapor possible at a given temperature.

To measure relative humidity, a hygrometer is used (from the Greek hygros - wet and metreco - I measure).

When cooled, saturated air cannot retain the same amount of water vapor in itself, it thickens (condenses), turning into droplets of fog. Fog can be observed in the summer on a clear cool night.

Clouds- this is the same fog, only it is formed not at the earth's surface, but at a certain height. As the air rises, it cools and the water vapor in it condenses. formed tiny droplets water and make clouds.

involved in the formation of clouds particulate matter suspended in the troposphere.

Clouds can have a different shape, which depends on the conditions of their formation (Table 14).

The lowest and heaviest clouds are stratus. They are located at an altitude of 2 km from the earth's surface. At an altitude of 2 to 8 km, more picturesque cumulus clouds can be observed. The highest and lightest are cirrus clouds. They are located at an altitude of 8 to 18 km above the earth's surface.

Atmospheric protection

The main source are industrial enterprises and cars. In large cities, the problem of gas contamination of the main transport routes is very acute. That is why in many major cities around the world, including in our country, introduced environmental control of the toxicity of car exhaust gases. Filed by experts, smoke and dust in the air can halve the flow solar energy to the earth's surface, which will lead to a change in natural conditions.

Why is there so much nitrogen in the Earth's atmosphere? and got the best answer

Answer from Marat[guru]
Several reasons can be identified. HOME: Earth is the only planet solar system, where the protein form of life was formed, stabilized and continues to develop. The composition of the Earth's primary atmosphere was simpler: hot water vapor and CO2, the main products of volcanic gases, predominated. After the atmosphere cooled, the processes of photosynthesis and water condensation led to a significant decrease in the proportion of CO2 and the appearance of free oxygen. IMPORTANT point: among the products of protein decomposition (animal and vegetable world) urea (carbamide) and uric acid play an important role. These substances, in turn, gradually undergo irreversible (!) hydrolysis with the formation of ammonia (NH3). IMPORTANT: NH3 is a lighter gas than a mixture of O2, CO2 and water vapor - therefore, it gradually rises to the upper layers of the atmosphere, where, under the influence of ultraviolet rays, it begins to slowly oxidize with molecular oxygen to form free NITROGEN and water: NH3 + O2 => N2 + H2O. Since nitrogen is relatively heavy gas, it is held by the Earth's gravitational field. Finally, do not forget that under NORMAL conditions N2 is a very chemically inert substance; this factor also contributes to the accumulation of molecular nitrogen in the atmosphere of our planet.
Marat
Enlightened
(25806)
Re: "I still don't understand why there is so little nitrogen in the atmospheres of Mars and Venus."
Because there has never been biomass in such quantity as on Earth.
Re: "Probably you want to say that on other planets, nitrogen is mainly represented by ammonia."
I didn't say that 🙂
Re: "Ammonia is light and therefore leaks out of the atmosphere."
Does not leak, but reaches the zone of action of ultraviolet rays.
Re: "But the fact of the matter is that ammonia in the atmospheres of Mars and Venus is even less than helium (helium is a very light gas)"
Agree.
Re "Yes, and there is nothing to form ammonia from there, there is no life, there is no organic matter."
Right, I meant the same.

Answer from Yoergey Zaika[guru]
hello, no, but the giant planets, Jupiter and Saturn, is there no nitrogen there either? Paragraph... Nitrogen itself is chemically neutral and there is so much of it, other gases are more chemically aggressive and react with everything and everything, and that is in a bound state in the form of salts and minerals in rocks.

Answer from Kirill Nikitin[guru]
I'm not sure, but I think this is due to the increased nitrogen cycle under the action of living organisms (proteins)

Answer from Mikhail Levin[guru]
I'll try to think...
Nitrogen is a very common element, so there should be plenty of it everywhere.
The presence of gas in the atmosphere depends on the balance of arrival (from the bowels of the planet) and escape into outer space.
Nitrogen is lighter than CO2, so it leaves faster. Mars, most likely, simply cannot hold it (as the Earth cannot hold hydrogen or helium).
But with Venus - big question. It has 4% nitrogen in the atmosphere, but the atmosphere itself is monstrous, it is not a fact that in absolute numbers it has less nitrogen than the Earth.
Another thing is that the Earth has very little carbon dioxide in the atmosphere (although it is released from the bowels). Here the matter is already in the presence of water and life that binds it.

Answer from ARTYOM.[master]
Atmospheric nitrogen fixation in nature occurs in two main directions - abiogenic and biogenic. The first route involves mainly the reactions of nitrogen with oxygen. Since nitrogen is chemically very inert, large amounts of energy (high temperatures) are required for oxidation. These conditions are achieved during lightning discharges, when the temperature reaches 25,000 °C or more. In this case, the formation of various nitrogen oxides occurs. There is also a possibility that abiotic fixation occurs as a result of photocatalytic reactions on the surfaces of semiconductors or broadband dielectrics (desert sand).
However, the main part of molecular nitrogen (about 1.4 108 t/year) is fixed biotically. For a long time it was believed that only a small number of microorganism species (although widely distributed on the Earth’s surface) can bind molecular nitrogen: bacteria Azotobacter and Clostridium, nodule bacteria of legume plants Rhizobium, cyanobacteria Anabaena, Nostoc, etc. Now it is known that many have this ability. other organisms in water and soil, for example, actinomycetes in tubers of alder and other trees (160 species in total). All of them convert molecular nitrogen into ammonium compounds (NH4+). This process requires a significant amount of energy (to fix 1 g of atmospheric nitrogen, bacteria in legume nodules spend about 167.5 kJ, that is, they oxidize about 10 g of glucose). Thus, the mutual benefit of the symbiosis of plants and nitrogen-fixing bacteria is visible - the former provide the latter with a “place to live” and supply the “fuel” obtained as a result of photosynthesis - glucose, the latter provide the nitrogen necessary for plants in the form they assimilate.
Nitrogen in the form of ammonia and ammonium compounds, obtained in the processes of biogenic nitrogen fixation, is rapidly oxidized to nitrates and nitrites (this process is called nitrification). The latter, not connected by plant tissues (and further along the food chain by herbivores and predators), do not remain in the soil for long. Most nitrates and nitrites are highly soluble, so they are washed off by water and eventually enter the oceans (this flow is estimated at 2.5-8 107 tons / year).
Nitrogen included in the tissues of plants and animals, after their death, undergoes ammonification (the decomposition of complex compounds containing nitrogen with the release of ammonia and ammonium ions) and denitrification, that is, the release of atomic nitrogen, as well as its oxides. These processes are entirely due to the activity of microorganisms in aerobic and anaerobic conditions.
In the absence of human activity, the processes of nitrogen fixation and nitrification are almost completely balanced by opposite reactions of denitrification. Part of the nitrogen enters the atmosphere from the mantle with volcanic eruptions, part is firmly fixed in soils and clay minerals, in addition, nitrogen is constantly leaking from the upper layers of the atmosphere into interplanetary space.

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The role of nitrogen in the Earth's atmosphere.

Nitrogen is the main element of the Earth's atmosphere. Its main role is to regulate the rate of oxidation by diluting oxygen. Thus, nitrogen affects the speed and intensity of biological processes.

There are two interconnected ways to extract nitrogen from the Earth's atmosphere:

• 1) inorganic,
• 2) biochemical.

Figure 1. Geochemical nitrogen cycle (V.A. Vronsky, G.V. Voitkevich)

Inorganic extraction of nitrogen from the Earth's atmosphere.

In the Earth's atmosphere, under the influence of electrical discharges (during a thunderstorm) or in the process of photochemical reactions (solar radiation), nitrogen compounds are formed (N 2 O, N 2 O 5, NO 2, NH 3, etc.). These compounds, dissolving in rainwater, fall to the ground along with precipitation, falling into the soil and water of the oceans.

Biological nitrogen fixation

Biological binding of atmospheric nitrogen is carried out:

• - in the soil - nodule bacteria in symbiosis with higher plants,
• - in water - plankton microorganisms and algae.

The amount of biologically bound nitrogen is much greater than the inorganically fixed one.

How does nitrogen get back into the Earth's atmosphere?

The remains of living organisms decompose as a result of exposure to numerous microorganisms. In the process, nitrogen, which is part of the proteins of organisms, undergoes a series of transformations:

• - in the process of protein decomposition, ammonia and its derivatives are formed, which then enter the air and into ocean water,
• - further ammonia and other nitrogen-containing organic compounds under the influence of bacteria Nitrosomonas and nitrobacteria form various nitrogen oxides (N 2 O, NO, N 2 O 3 and N 2 O 5). This process is called nitrification,
• Nitric acid reacts with metals to form salts. These salts are attacked by denitrifying bacteria,
• - in progress denitrification elemental nitrogen is formed, which returns back to the atmosphere (an example is underground gas jets consisting of pure N 2).

Where is nitrogen found?

Nitrogen enters the Earth's atmosphere through volcanic eruptions in the form of ammonia. Getting into the upper atmosphere, ammonia (NH 3) is oxidized and releases nitrogen (N 2).

Nitrogen is also buried in sedimentary rocks and is contained in large quantities in bituminous deposits. However, this nitrogen also enters the atmosphere during the regional metamorphism of these rocks.

• Thus, the main form of nitrogen presence on the surface of our planet is molecular nitrogen (N 2) in the composition of the Earth's atmosphere.

This was the article Nitrogen in the composition of the Earth's atmosphere - the content in the atmosphere is 78%. ". Read further: « Oxygen in the composition of the Earth's atmosphere - the content in the atmosphere is 21%.«

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