Accumulation of nitrogen in the atmosphere. Eco Inform - news agency
At least atmospheric, it owes its origin not so much to the Sun as 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, on other planets solar system, neither in the composition of comets or any other cold space 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...
Destroying the inexhaustible reserves of bound active nitrogen, Live nature put herself before the problem: how to bind nitrogen. In a free, molecular state, it, as we know, turned out to be very inert. 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 atmospheric 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 passes into an excited, activated state and becomes able to combine with oxygen.
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The atmosphere is the gaseous shell of our planet that rotates with the Earth. The gas in the atmosphere is called air. The atmosphere is in contact with the hydrosphere and partially covers the lithosphere. But it is difficult to determine the upper bounds. Conventionally, it is assumed that the atmosphere extends upwards for about three thousand kilometers. There it flows smoothly into the airless space.
The chemical composition of the Earth's atmosphere
Formation chemical composition atmosphere began about four billion years ago. Initially, the atmosphere consisted only of light gases - helium and hydrogen. According to scientists, the initial prerequisites for the creation of a gas shell around the Earth were volcanic eruptions, which, together with lava, threw out great amount gases. Subsequently, gas exchange began with water spaces, with living organisms, with the products of their activity. The composition of the air gradually changed and in its present form was fixed several million years ago.
The main components of the atmosphere are nitrogen (about 79%) and oxygen (20%). The remaining percentage (1%) is accounted for by the following gases: argon, neon, helium, methane, carbon dioxide, hydrogen, krypton, xenon, ozone, ammonia, sulfur dioxide and nitrogen, nitrous oxide and carbon monoxide, included in this one percent.
In addition, the air contains water vapor and particulate matter (plant pollen, dust, salt crystals, aerosol impurities).
AT recent times scientists note not a qualitative, but a quantitative change in some air ingredients. And the reason for this is the person and his activity. Only in the last 100 years carbon dioxide has increased significantly! This is fraught with many problems, the most global of which is climate change.
Formation of weather and climate
The atmosphere plays a vital role in shaping the climate and weather on Earth. A lot depends on the amount of sunlight, on the nature of the underlying surface and atmospheric circulation.
Let's look at the factors in order.
1. The atmosphere transmits the heat of the sun's rays and absorbs harmful radiation. The ancient Greeks knew that the rays of the Sun fall on different parts of the Earth at different angles. The very word "climate" in translation from ancient Greek means "slope". So, at the equator, the sun's rays fall almost vertically, because it is very hot here. The closer to the poles, the greater the angle of inclination. And the temperature is dropping.
2. Due to the uneven heating of the Earth, air currents are formed in the atmosphere. They are classified according to their size. The smallest (tens and hundreds of meters) are local winds. This is followed by monsoons and trade winds, cyclones and anticyclones, planetary frontal zones.
All these air masses are constantly moving. Some of them are quite static. For example, the trade winds that blow from the subtropics towards the equator. The movement of others is largely dependent on atmospheric pressure.
3. Atmospheric pressure is another factor influencing climate formation. This is the air pressure on the earth's surface. As you know, air masses move from an area with high atmospheric pressure towards an area where this pressure is lower.
There are 7 zones in total. The equator is a low pressure zone. Further, on both sides of the equator up to the thirtieth latitudes - the region high pressure. From 30° to 60° - again low pressure. And from 60° to the poles - a zone of high pressure. Air masses circulate between these zones. Those that go from the sea to land bring rain and bad weather, and those that blow from the continents bring clear and dry weather. In places where air currents collide, atmospheric front zones are formed, which are characterized by precipitation and inclement, windy weather.
Scientists have proven that even a person's well-being depends on atmospheric pressure. According to international standards, normal atmospheric pressure is 760 mm Hg. column at 0°C. This figure is calculated for those areas of land that are almost flush with sea level. The pressure decreases with altitude. Therefore, for example, for St. Petersburg 760 mm Hg. - is the norm. But for Moscow, which is located higher, the normal pressure is 748 mm Hg.
The pressure changes not only vertically, but also horizontally. This is especially felt during the passage of cyclones.
The structure of the atmosphere
The atmosphere is like a layer cake. And each layer has its own characteristics.
. Troposphere is the layer closest to the Earth. The "thickness" of this layer changes as you move away from the equator. Above the equator, the layer extends upwards for 16-18 km, in temperate zones - for 10-12 km, at the poles - for 8-10 km.
It is here that 80% of the total mass of air and 90% of water vapor are contained. Clouds form here, cyclones and anticyclones arise. The air temperature depends on the altitude of the area. On average, it drops by 0.65°C for every 100 meters.
. tropopause- transitional layer of the atmosphere. Its height is from several hundred meters to 1-2 km. The air temperature in summer is higher than in winter. So, for example, over the poles in winter -65 ° C. And over the equator at any time of the year it is -70 ° C.
. Stratosphere- this is a layer, the upper boundary of which runs at an altitude of 50-55 kilometers. Turbulence is low here, water vapor content in the air is negligible. But a lot of ozone. Its maximum concentration is at an altitude of 20-25 km. In the stratosphere, the air temperature begins to rise and reaches +0.8 ° C. This is due to the fact that ozone layer interacts with ultraviolet radiation.
. Stratopause- a low intermediate layer between the stratosphere and the mesosphere following it.
. Mesosphere- the upper boundary of this layer is 80-85 kilometers. Here complex photochemical processes involving free radicals take place. It is they who provide that gentle blue glow of our planet, which is seen from space.
Most comets and meteorites burn up in the mesosphere.
. Mesopause- the next intermediate layer, the air temperature in which is at least -90 °.
. Thermosphere- the lower boundary begins at an altitude of 80 - 90 km, and the upper boundary of the layer passes approximately at the mark of 800 km. The air temperature is rising. It can vary from +500° C to +1000° C. During the day, temperature fluctuations amount to hundreds of degrees! But the air here is so rarefied that the understanding of the term "temperature" as we imagine it is not appropriate here.
. Ionosphere- unites mesosphere, mesopause and thermosphere. The air here consists mainly of oxygen and nitrogen molecules, as well as quasi-neutral plasma. The sun's rays, falling into the ionosphere, strongly ionize air molecules. In the lower layer (up to 90 km), the degree of ionization is low. The higher, the more ionization. So, at an altitude of 100-110 km, electrons are concentrated. This contributes to the reflection of short and medium radio waves.
The most important layer of the ionosphere is the upper one, which is located at an altitude of 150-400 km. Its peculiarity is that it reflects radio waves, and this contributes to the transmission of radio signals over long distances.
It is in the ionosphere that such a phenomenon as aurora occurs.
. Exosphere- consists of oxygen, helium and hydrogen atoms. The gas in this layer is very rarefied, and often hydrogen atoms escape into outer space. Therefore, this layer is called the "scattering zone".
The first scientist who suggested that our atmosphere has weight was the Italian E. Torricelli. Ostap Bender, for example, in the novel "The Golden Calf" lamented that each person was pressed by an air column weighing 14 kg! But the great strategist was a little mistaken. An adult person experiences pressure of 13-15 tons! But we do not feel this heaviness, because atmospheric pressure is balanced by the internal pressure of a person. The weight of our atmosphere is 5,300,000,000,000,000 tons. The figure is colossal, although it is only a millionth of the weight of our planet.
The atmosphere is the air envelope of the Earth. Extending up to 3000 km from 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. AT quantitatively biological nitrogen fixation 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 atmospheric gas, playing exclusively important role in many processes of the biosphere. The dominant form of its existence is O 2 . In the upper layers of the atmosphere, under the influence of ultraviolet radiation, oxygen molecules dissociate, 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 forms, 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 (rarely 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 special place in the carbon cycle is 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:
- the irreversibility of their accumulation in the atmosphere;
- close relationship with radioactive decay 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-bearing 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 calculations made by P. Dimon and J. Culp, helium and argon accumulate in the earth's crust in the modern era 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 in 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 migration processes. 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 of primary inert gases, like neon and xenon, was associated with 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 amount 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.
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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 when interacting with metals, it gives salts. These salts are attacked by denitrifying bacteria,
- - in the process 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 found 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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