What does an air molecule consist of? Chemical composition of air and its hygienic importance

Air is the natural mixture of gases, mainly nitrogen and oxygen, that makes up the earth's atmosphere. Air is necessary for the normal existence of the vast majority of terrestrial living organisms: the oxygen contained in the air enters the body's cells during respiration and is used in the oxidation process, which results in the release of energy necessary for life. In industry and in everyday life, atmospheric oxygen is used to burn fuel to produce heat and mechanical energy in internal combustion engines. Noble gases are obtained from air by liquefaction. In accordance with the Federal Law “On the Protection of Atmospheric Air,” atmospheric air is understood as “a vital component of the environment, which is a natural mixture of atmospheric gases located outside residential, industrial and other premises.”

The most important factors determining the suitability of the air environment for human habitation are the chemical composition, degree of ionization, relative humidity, pressure, temperature and speed of movement. Let's consider each of these factors separately.

In 1754, Joseph Black experimentally proved that air is a mixture of gases and not a homogeneous substance.

Normal air composition

*Substance*	*Designation*	*By volume, %*	*By weight,%*
Nitrogen
Oxygen
Argon
Carbon dioxide
Neon		0,001818
Methane			0,000084
Helium		0,000524	0,000073
Krypton		0,000114
Hydrogen
Xenon		0,0000087

Light air ions

Every resident of St. Petersburg feels that the air is heavily polluted. An ever-increasing number of cars, factories and factories emit tons of waste from their activities into the atmosphere. Polluted air contains uncharacteristic physical, chemical and biological substances. The main pollutants in the atmospheric air of a metropolis are: aldehydes, ammonia, atmospheric dust, carbon monoxide, nitrogen oxides, sulfur dioxide, hydrocarbons, heavy metals (lead, copper, zinc, cadmium, chromium).

The most dangerous components of smog are microscopic particles of harmful substances. Approximately 60% are combustion products from automobile engines. It is these particles that we inhale while walking along the streets of our cities and accumulate in our lungs. According to doctors, the lungs of a metropolis resident are very similar in degree of contamination to the lungs of a heavy smoker.

In terms of contribution to air pollution, car exhaust gases are in first place, emissions from thermal power plants are in second place, and the chemical industry is in third place.

Degree of air ionization

High degree of ionization

Atmospheric air is always ionized and contains more or less air ions. The process of ionization of natural air occurs under the influence of a number of factors, the main ones being the radioactivity of soil, rocks, sea and groundwater, cosmic rays, lightning, splashing of water (Lennard effect) in waterfalls, in wave caps, etc., ultraviolet radiation from the Sun, flames from forest fires, some aromatic substances, etc. Under the influence of these factors, both positive and negative air ions are formed. Neutral air molecules instantly settle on the resulting ions, giving rise to the so-called normal and light atmospheric ions. Encountering dust particles suspended in the air, smoke particles, and tiny droplets of water on their way, light ions settle on them and turn into heavy ones. On average, 1 cm 3 above the earth's surface contains up to 1500 ions, among which positively charged ones predominate, which, as will be shown below, is not entirely desirable for human health.

In some regions, air ionization is characterized by more favorable indicators. Areas where the air is especially ionized include the slopes of high mountains, mountain valleys, waterfalls, and the shores of seas and oceans. They are often used to organize recreational facilities and sanatorium-resort treatment.

Thus, air ions are a constantly operating environmental factor, such as temperature, relative humidity and air speed.

A change in the degree of ionization of inhaled air inevitably entails changes in various organs and systems. Hence the natural desire to use ionized air in, on the one hand, and the need to develop apparatus and devices for artificially changing the concentration and ratio of ions in atmospheric air, on the other. Today, using special equipment, it is possible to increase the degree of ionization of air, increasing the number of ions per 1 cm 3 thousands of times.

The sanitary and epidemiological rules and regulations SanPiN 2.2.4.1294-03 provide hygienic requirements for the air ion composition of the air in industrial and public premises. Please note that not only the number of negatively and positively charged air ions is important, but also the ratio of the concentration of positive to the concentration of negative, which is called the unipolarity coefficient (see table below).

In accordance with hygienic requirements, the number of negatively charged air ions must be greater or, in extreme cases, equal to the number of positively charged air ions. If you live in cities and work in office premises, you should use air ionizers in order not to lose concentration and get tired more slowly during the working day.

Microclimate: rel. humidity, temperature, speed, pressure

Microclimate refers to a set of physical environmental parameters that affect human heat exchange and health. The main microclimate parameters are relative humidity, temperature, pressure and air speed. Maintaining all these parameters at normal levels indoors is a key factor determining the comfort of a person’s stay in it.

The normal value of microclimate parameters allows the human body to spend a minimum of energy: to maintain the required level of heat exchange, to obtain the required amount of oxygen; at the same time, a person does not feel either heat, cold, or stuffiness. According to statistics, microclimate violations are the most common among all violations of sanitary and hygienic standards.

The microclimate is determined by the influence of the external environment, the construction features of the building and heating, ventilation and air conditioning systems.

In multi-storey buildings there is a strong difference in air pressure outside the building and inside. This leads to the accumulation of various contaminants in the building, and their concentration will be different on the upper and lower floors, which has a detrimental effect on.

The microclimate features of each specific apartment are formed under the influence of air flows, moisture and heat. The air in the room is constantly in motion. Therefore, one of the key parameters of air is the speed of its movement.

Below is a table that shows the optimal and permissible values of temperature, humidity and air velocity in various rooms in accordance with the current SanPiN 2.1.2.2801-10 “Changes and additions No. 1 to SanPiN 2.1.2.2645-10 “Sanitary and epidemiological requirements for living conditions in residential buildings and premises.”

Air parameters in your home, office or country cottage, you can take appropriate measures to normalize the identified deviations.

Current sanitary rules and air standards

*The name of a room*	*Air temperature, °C*		*Relative humidity, %*		*Air speed, m/s*
*The name of a room*	optim.	permissible	optim.	permissible	optim.	permissible
Cold season
Living room

Air is a natural mixture of gases

When most of us hear the word “air,” a perhaps somewhat naive comparison involuntarily comes to mind: air is what we breathe. Indeed, the etymological dictionary of the Russian language indicates that the word “air” is borrowed from the Church Slavonic language: “to sigh.” From a biological point of view, air is therefore a medium for supporting life through oxygen. The air might not have contained oxygen - life would still have developed in anaerobic forms. But the complete absence of air apparently excludes the possibility of the existence of any organisms.

For physicists, air is primarily the earth’s atmosphere and the gas shell surrounding the earth.

But what is the air itself from a chemical point of view?

It took scientists a lot of effort, labor and patience to uncover this mystery of nature, that air is not an independent substance, as was believed more than 200 years ago, but is a complex mixture of gases. The scientist and artist Leonardo da Vinci (15th century) was the first to speak out about the complex composition of air.

About 4 billion years ago, the Earth's atmosphere consisted mainly of carbon dioxide. Gradually it dissolved in water and reacted with rocks, forming carbonates and bicarbonates of calcium and magnesium. With the advent of green plants, this process began to proceed much faster. By the time humans appeared, carbon dioxide, so necessary for plants, had already become scarce. Its concentration in the air before the start of the industrial revolution was only 0.029%. Over the course of 1.5 billion years, the oxygen content gradually increased.

Chemical composition of air

Components
Components	By volume	By weight
Nitrogen ( N 2)	78,09	75,50
Oxygen (O 2)	20,95	23,10
Noble gases (He, Ne, Ar, Kr, Xe, Rn, mainly argon)	0,94
Carbon monoxide (IV) – carbon dioxide	0,03	0,046

The quantitative composition of air was first established by the French scientist Antoine Laurent Lavoisier. Based on the results of his famous 12-day experiment, he concluded that all air as a whole consists of oxygen, suitable for respiration and combustion, and nitrogen, a non-living gas, in proportions of 1/5 and 4/5 of the volume, respectively. He heated metallic mercury in a retort on a brazier for 12 days. The end of the retort was brought under a bell placed in a vessel with mercury. As a result, the mercury level in the bell rose by about 1/5. An orange substance, mercury oxide, formed on the surface of the mercury in the retort. The gas remaining under the bell was unsuitable for breathing. The scientist suggested renaming “life air” to “oxygen”, since when burned in oxygen, most substances turn into acids, and “suffocating air” into “nitrogen”, because it does not support life, it harms life.

Lavoisier's experiment

The qualitative composition of air can be proven by the following experiment

The main component of air for us is oxygen; it is 21% by volume in the air. Oxygen is diluted with a large amount of nitrogen - 78% of the air volume and a relatively small volume of noble inert gases - about 1%. Air also contains variable components - carbon monoxide (IV) or carbon dioxide and water vapor, the amount of which depends on various reasons. These substances enter the atmosphere naturally. When volcanoes erupt, sulfur dioxide, hydrogen sulfide and elemental sulfur enter the atmosphere. Dust storms contribute to the appearance of dust in the air. Nitrogen oxides also enter the atmosphere during lightning electrical discharges, during which nitrogen and oxygen in the air react with each other, or as a result of the activity of soil bacteria that can release nitrogen oxides from nitrates; Forest fires and peatland burning also contribute to this. The processes of destruction of organic substances are accompanied by the formation of various gaseous sulfur compounds. The water in the air determines its humidity. Other substances have a negative role: they pollute the atmosphere. For example, there is a lot of carbon dioxide in the air of cities devoid of greenery, and water vapor above the surface of oceans and seas. The air contains small amounts of sulfur (IV) oxide or sulfur dioxide, ammonia, methane, nitric oxide (I) or nitrous oxide, and hydrogen. The air near industrial enterprises, gas and oil fields or volcanoes is especially saturated with them. There is another gas in the upper atmosphere - ozone. A variety of dust also flies in the air, which we can easily notice when looking from the side at a thin beam of light falling from behind a curtain into a darkened room.

Permanent components of air gases:

· Oxygen

· Nitrogen

· Noble gases

Variable components of air gases:

· Carbon monoxide (IV)

· Ozone

· Other

Conclusion.

1. Air is a natural mixture of gaseous substances, in which each substance has and retains its physical and chemical properties, so air can be separated.

2. Air is a colorless gaseous solution, density - 1.293 g/l, at temperatures -190 0 C it turns into a liquid state. Liquid air is a bluish liquid.

3. Living organisms are closely related to air substances, which have a certain effect on them. And at the same time, living organisms influence it because they perform certain functions: redox - they oxidize, for example, carbohydrates to carbon dioxide and reduce it to carbohydrates; gas - absorb and release gases.

Thus, living organisms created in the past and maintain the atmosphere of our planet for millions of years.

Air pollution - introduction of new uncharacteristic physical, chemical and biological substances into the atmospheric air or a change in the natural average long-term concentration of these substances in it.

The process of photosynthesis removes carbon dioxide from the atmosphere and returns it through the processes of respiration and decay. The balance established during the evolution of the planet between these two gases began to be disturbed, especially in the second half of the 20th century, when human influence on nature began to increase. For now, nature copes with disturbances in this balance thanks to ocean water and its algae. But will nature have enough strength for long?

Scheme. Air pollution

Main air pollutants in Russia

The number of cars is constantly growing, especially in large cities, and accordingly, the emission of harmful substances into the air is growing. Cars are responsible for 60% of harmful emissions in the city!
Russian thermal power plants emit up to 30% of pollutants into the atmosphere, and another 30% is the contribution of industry (ferrous and non-ferrous metallurgy, oil production and oil refining, chemical industry and production of building materials). The level of air pollution from natural sources is background ( 31–41% ), it changes little over time ( 59–69% ). Currently, the problem of anthropogenic atmospheric pollution has become global. What pollutants that are dangerous to all living things enter the atmosphere? These are cadmium, lead, mercury, arsenic, copper, soot, mercaptans, phenol, chlorine, sulfuric and nitric acids and other substances. We will study some of these substances in the future, find out their physical and chemical properties and talk about the destructive power they contain for our health.

The scale of environmental pollution of the planet, Russia

In which countries of the world is the air most polluted by vehicle exhaust gases?
The greatest danger of air pollution from exhaust gases threatens countries with large vehicle fleets. For example, in the USA, motor vehicles account for approximately 1/2 of all harmful emissions into the atmosphere (up to 50 million tons annually). The car fleet of Western Europe annually emits up to 70 million tons of harmful substances into the air, and in Germany, for example, 30 million cars produce 70% of the total volume of harmful emissions. In Russia, the situation is aggravated by the fact that vehicles in use comply with environmental standards by only 14.5%.
It pollutes the atmosphere and air transport with plumes of exhaust from many thousands of aircraft. According to expert estimates, as a result of the activities of the global vehicle fleet (which is about 500 million engines), 4.5 billion tons of carbon dioxide alone are released into the atmosphere annually.
Why are these pollutants dangerous? Heavy metals - lead, cadmium, mercury - have a harmful effect on the human nervous system, carbon monoxide - on the composition of the blood; Sulfur dioxide, interacting with water from rain and snow, turns into acid and causes acid rain. What is the scale of this pollution? The main regions where acid rain occurs are the USA, Western Europe, and Russia. Recently, these include the industrial regions of Japan, China, Brazil, and India. The spread of acid precipitation is associated with the concept of transboundary nature - the distance between the areas of its formation and the areas of fallout can be hundreds and even thousands of kilometers. For example, the main “culprit” of acid rain in southern Scandinavia is the industrial areas of Great Britain, Belgium, the Netherlands and Germany. In the Canadian provinces of Ontario and Quebec, acid rain is transferred from neighboring areas of the United States. These precipitations are transported to Russian territory from Europe by westerly winds.
An unfavorable environmental situation has developed in the northeast of China, in the Pacific zone of Japan, in the cities of Mexico City, Sao Paulo, and Buenos Aires. In Russia in 1993, in 231 cities with a total population of 64 million people, the content of harmful substances in the air exceeded the norm. In 86 cities, 40 million people live in conditions where pollution exceeds standards by 10 times. Among these cities are Bryansk, Cherepovets, Saratov, Ufa, Chelyabinsk, Omsk, Novosibirsk, Kemerovo, Novokuznetsk, Norilsk, Rostov. The Ural region ranks first in Russia in terms of the amount of harmful emissions. Thus, in the Sverdlovsk region, the state of the atmosphere does not meet the standards in 20 territories, where 60% of the population lives. In the city of Karabash, Chelyabinsk region, a copper smelter annually emits 9 tons of harmful compounds into the atmosphere per inhabitant. The incidence of cancer here is 338 cases per 10 thousand inhabitants.
An alarming situation has also developed in the Volga region, in the south of Western Siberia, and in Central Russia. In Ulyanovsk, more people suffer from upper respiratory tract diseases than the Russian average. The incidence of lung cancer has increased 20-fold since 1970, and the city has one of the highest child mortality rates in Russia.
In the city of Dzerzhinsk, a large number of chemical enterprises are concentrated in a limited area. Over the past 8 years, there have been 60 releases of highly toxic substances into the atmosphere, leading to emergency situations, in some cases resulting in death. In the Volga region, up to 300 thousand tons of soot, ash, soot, and carbon oxides fall on city residents every year. Moscow ranks 15th among Russian cities in terms of total air pollution levels.

The chemical composition of air is of great hygienic importance, since it plays a decisive role in the respiratory function of the body. Atmospheric air is a mixture of oxygen, carbon dioxide, argon and other gases in the ratios given in table. 1.

Oxygen (O 2) is the most important component of air for humans. At rest, a person usually absorbs an average of 0.3 liters of oxygen per minute.

During physical activity, oxygen consumption increases sharply and can reach 4.5/5 liters or more per minute. Fluctuations in the oxygen content in atmospheric air are small and, as a rule, do not exceed 0.5%.

In residential, public and sports premises, no significant changes in oxygen content are observed, since outside air penetrates into them. Under the most unfavorable hygienic conditions in the room, a decrease in oxygen content of 1% was noted. Such fluctuations do not have a noticeable effect on the body.

Typically, physiological changes are observed when the oxygen content decreases to 16-17%. If its content decreases to 11-13% (when rising to a height), pronounced oxygen deficiency appears, a sharp deterioration in well-being and a decrease in performance. Oxygen content up to 7-8% can be fatal.

In sports practice, oxygen inhalation is used to increase performance and intensity of recovery processes.

Carbon dioxide (CO 2), or carbon dioxide, is a colorless, odorless gas formed during the respiration of people and animals, rotting and decomposition of organic substances, fuel combustion, etc. In atmospheric air outside populated areas, the carbon dioxide content averages 0.04%, and in industrial centers its concentration increases to 0.05-0.06%. In residential and public buildings, when there are a large number of people in them, the carbon dioxide content can increase to 0.6-0.8%. Under the worst hygienic conditions in a room (large crowds of people, poor ventilation, etc.), its concentration usually does not exceed 1% due to the penetration of outside air. Such concentrations do not cause negative effects in the body.

With prolonged inhalation of air containing 1-1.5% carbon dioxide, a deterioration in health is noted, and at 2-2.5% pathological changes are detected. Significant disruption of body functions and decreased performance occur when the carbon dioxide content is 4-5%. At levels of 8-10%, loss of consciousness and death occur. A significant increase in the content of carbon dioxide in the air can occur during emergency situations in confined spaces (mines, mines, submarines, bomb shelters, etc.) or in places where intensive decomposition of organic substances occurs.

Determining the carbon dioxide content in residential, public and sports facilities can serve as an indirect indicator of air pollution from human waste products. As already noted, carbon dioxide itself in these cases does not cause harm to the body, however, along with an increase in its content, a deterioration in the physical and chemical properties of the air is observed (temperature and humidity increase, the ionic composition is disrupted, foul-smelling gases appear). Indoor air is considered to be of poor quality if the carbon dioxide content in it exceeds 0.1%. This value is accepted as a calculated value when designing and installing ventilation in rooms.

The structure and composition of the Earth’s atmosphere, it must be said, were not always constant values in one or another period of the development of our planet. Today, the vertical structure of this element, which has a total “thickness” of 1.5-2.0 thousand km, is represented by several main layers, including:

Troposphere.
Tropopause.
Stratosphere.
Stratopause.
Mesosphere and mesopause.
Thermosphere.
Exosphere.

Basic elements of atmosphere

The troposphere is a layer in which strong vertical and horizontal movements are observed; it is here that weather, sedimentary phenomena, and climatic conditions are formed. It extends 7-8 kilometers from the surface of the planet almost everywhere, with the exception of the polar regions (up to 15 km there). In the troposphere, there is a gradual decrease in temperature, approximately by 6.4 ° C with each kilometer of altitude. This indicator may differ for different latitudes and seasons.

The composition of the Earth's atmosphere in this part is represented by the following elements and their percentages:

Nitrogen - about 78 percent;

Oxygen - almost 21 percent;

Argon - about one percent;

Carbon dioxide - less than 0.05%.

Single composition up to an altitude of 90 kilometers

In addition, here you can find dust, water droplets, water vapor, combustion products, ice crystals, sea salts, many aerosol particles, etc. This composition of the Earth’s atmosphere is observed up to approximately ninety kilometers in altitude, so the air is approximately the same in chemical composition, not only in the troposphere, but also in the overlying layers. But there the atmosphere has fundamentally different physical properties. The layer that has a general chemical composition is called the homosphere.

What other elements make up the Earth's atmosphere? In percentage (by volume, in dry air) gases such as krypton (about 1.14 x 10 -4), xenon (8.7 x 10 -7), hydrogen (5.0 x 10 -5), methane (about 1.7 x 10 -5) are represented here. 4), nitrous oxide (5.0 x 10 -5), etc. As a percentage by mass, the most of the listed components are nitrous oxide and hydrogen, followed by helium, krypton, etc.

Physical properties of different atmospheric layers

The physical properties of the troposphere are closely related to its proximity to the surface of the planet. From here, reflected solar heat in the form of infrared rays is directed back upward, involving the processes of conduction and convection. That is why the temperature drops with distance from the earth's surface. This phenomenon is observed up to the height of the stratosphere (11-17 kilometers), then the temperature becomes almost unchanged up to 34-35 km, and then the temperature rises again to altitudes of 50 kilometers (the upper limit of the stratosphere). Between the stratosphere and the troposphere there is a thin intermediate layer of the tropopause (up to 1-2 km), where constant temperatures are observed above the equator - about minus 70 ° C and below. Above the poles, the tropopause “warms up” in summer to minus 45°C; in winter, temperatures here fluctuate around -65°C.

The gas composition of the Earth's atmosphere includes such an important element as ozone. There is relatively little of it at the surface (ten to the minus sixth power of one percent), since the gas is formed under the influence of sunlight from atomic oxygen in the upper parts of the atmosphere. In particular, the most ozone is at an altitude of about 25 km, and the entire “ozone screen” is located in areas from 7-8 km at the poles, from 18 km at the equator and up to fifty kilometers in total above the surface of the planet.

The atmosphere protects from solar radiation

The composition of the air in the Earth's atmosphere plays a very important role in the preservation of life, since individual chemical elements and compositions successfully limit the access of solar radiation to the earth's surface and the people, animals, and plants living on it. For example, water vapor molecules effectively absorb almost all ranges of infrared radiation, with the exception of lengths in the range from 8 to 13 microns. Ozone absorbs ultraviolet radiation up to a wavelength of 3100 A. Without its thin layer (only 3 mm on average if placed on the surface of the planet), only water at a depth of more than 10 meters and underground caves where solar radiation does not reach can be inhabited. .

Zero Celsius at the stratopause

Between the next two levels of the atmosphere, the stratosphere and mesosphere, there is a remarkable layer - the stratopause. It approximately corresponds to the height of ozone maxima and the temperature here is relatively comfortable for humans - about 0°C. Above the stratopause, in the mesosphere (starts somewhere at an altitude of 50 km and ends at an altitude of 80-90 km), a drop in temperature is again observed with increasing distance from the Earth's surface (to minus 70-80 ° C). Meteors usually burn up completely in the mesosphere.

In the thermosphere - plus 2000 K!

The chemical composition of the Earth's atmosphere in the thermosphere (begins after the mesopause from altitudes of about 85-90 to 800 km) determines the possibility of such a phenomenon as gradual heating of layers of very rarefied “air” under the influence of solar radiation. In this part of the “air blanket” of the planet, temperatures range from 200 to 2000 K, which are obtained due to the ionization of oxygen (atomic oxygen is located above 300 km), as well as the recombination of oxygen atoms into molecules, accompanied by the release of a large amount of heat. The thermosphere is where auroras occur.

Above the thermosphere is the exosphere - the outer layer of the atmosphere, from which light and rapidly moving hydrogen atoms can escape into outer space. The chemical composition of the Earth's atmosphere here is represented mostly by individual oxygen atoms in the lower layers, helium atoms in the middle layers, and almost exclusively hydrogen atoms in the upper layers. High temperatures prevail here - about 3000 K and there is no atmospheric pressure.

How was the earth's atmosphere formed?

But, as mentioned above, the planet did not always have such an atmospheric composition. In total, there are three concepts of the origin of this element. The first hypothesis suggests that the atmosphere was taken through the process of accretion from a protoplanetary cloud. However, today this theory is subject to significant criticism, since such a primary atmosphere should have been destroyed by the solar “wind” from a star in our planetary system. In addition, it is assumed that volatile elements could not be retained in the formation zone of terrestrial planets due to too high temperatures.

The composition of the Earth's primary atmosphere, as suggested by the second hypothesis, could have been formed due to the active bombardment of the surface by asteroids and comets that arrived from the vicinity of the Solar system in the early stages of development. It is quite difficult to confirm or refute this concept.

Experiment at IDG RAS

The most plausible seems to be the third hypothesis, which believes that the atmosphere appeared as a result of the release of gases from the mantle of the earth's crust approximately 4 billion years ago. This concept was tested at the Institute of Geography of the Russian Academy of Sciences during an experiment called “Tsarev 2”, when a sample of a substance of meteoric origin was heated in a vacuum. Then the release of gases such as H 2, CH 4, CO, H 2 O, N 2, etc. was recorded. Therefore, scientists rightly assumed that the chemical composition of the Earth’s primary atmosphere included water and carbon dioxide, hydrogen fluoride (HF), carbon monoxide gas (CO), hydrogen sulfide (H 2 S), nitrogen compounds, hydrogen, methane (CH 4), ammonia vapor (NH 3), argon, etc. Water vapor from the primary atmosphere participated in the formation of the hydrosphere, carbon dioxide was to a greater extent in a bound state in organic substances and rocks, nitrogen passed into the composition of modern air, and also again into sedimentary rocks and organic substances.

The composition of the Earth's primary atmosphere would not allow modern people to be in it without breathing apparatus, since there was no oxygen in the required quantities then. This element appeared in significant quantities one and a half billion years ago, believed to be in connection with the development of the process of photosynthesis in blue-green and other algae, which are the oldest inhabitants of our planet.

Minimum oxygen

The fact that the composition of the Earth's atmosphere was initially almost oxygen-free is indicated by the fact that easily oxidized, but not oxidized graphite (carbon) is found in the oldest (Catarchaean) rocks. Subsequently, so-called banded iron ores appeared, which included layers of enriched iron oxides, which means the appearance on the planet of a powerful source of oxygen in molecular form. But these elements were found only periodically (perhaps the same algae or other oxygen producers appeared in small islands in an anoxic desert), while the rest of the world was anaerobic. The latter is supported by the fact that easily oxidized pyrite was found in the form of pebbles processed by flow without traces of chemical reactions. Since flowing waters cannot be poorly aerated, the view has developed that the atmosphere before the Cambrian contained less than one percent of the oxygen composition of today.

Revolutionary change in air composition

Approximately in the middle of the Proterozoic (1.8 billion years ago), an “oxygen revolution” occurred when the world switched to aerobic respiration, during which 38 can be obtained from one molecule of a nutrient (glucose), and not two (as with anaerobic respiration) units of energy. The composition of the Earth's atmosphere, in terms of oxygen, began to exceed one percent of what it is today, and an ozone layer began to appear, protecting organisms from radiation. It was from her that, for example, such ancient animals as trilobites “hid” under thick shells. From then until our time, the content of the main “respiratory” element gradually and slowly increased, ensuring the diversity of development of life forms on the planet.

Oxygen(O2) is the most important component of air for humans. At rest, a person usually absorbs an average of 0.3 liters of oxygen per minute.

In sports practice, oxygen inhalation is used to increase performance and intensity of recovery processes.

Carbon dioxide(CO2), or carbon dioxide, is a colorless, odorless gas formed during the respiration of people and animals, rotting and decomposition of organic substances, fuel combustion, etc. In atmospheric air outside populated areas, the carbon dioxide content averages 0.04%, and in industrial centers its concentration increases to 0.05-0.06%. In residential and public buildings, when there are a large number of people in them, the carbon dioxide content can increase to 0.6-0.8%. Under the worst hygienic conditions in a room (large crowds of people, poor ventilation, etc.), its concentration usually does not exceed 1% due to the penetration of outside air. Such concentrations do not cause negative effects in the body.

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Chemical composition of air is important in the implementation of respiratory function. Atmospheric air is a mixture of gases: oxygen, carbon dioxide, argon, nitrogen, neon, krypton, xenon, hydrogen, ozone, etc. Oxygen is the most important. At rest, a person absorbs 0.3 l/min. During physical activity, oxygen consumption increases and can reach 4.5–8 l/min. Fluctuations in the oxygen content in the atmosphere are small and do not exceed 0.5%. If the oxygen content decreases to 11-13%, symptoms of oxygen deficiency appear.

Oxygen content of 7-8% can lead to death. Carbon dioxide is colorless and odorless, formed during respiration and decay, combustion of fuel. In the atmosphere it is 0.04%, and in industrial zones – 0.05-0.06%. With a large crowd of people it can increase to 0.6 - 0.8%. With prolonged inhalation of air containing 1-1.5% carbon dioxide, a deterioration in health is noted, and with 2-2.5% - pathological changes. At 8-10% loss of consciousness and death, the air has a pressure called atmospheric or barometric. It is measured in millimeters of mercury (mmHg), hectopascals (hPa), millibars (mb). Normal atmospheric pressure is considered to be at sea level at a latitude of 45˚ at an air temperature of 0˚C. It is equal to 760 mmHg. (The air in a room is considered to be of poor quality if it contains 1% carbon dioxide. This value is accepted as a calculated value when designing and installing ventilation in rooms.

Air pollution. Carbon monoxide is a colorless and odorless gas that is formed during incomplete combustion of fuel and enters the atmosphere with industrial emissions and exhaust gases from internal combustion engines. In megacities, its concentration can reach 50-200 mg/m3. When smoking tobacco, carbon monoxide enters the body. Carbon monoxide is a blood and general toxic poison. It blocks hemoglobin, it loses its ability to carry oxygen to tissues. Acute poisoning occurs when the concentration of carbon monoxide in the air is 200-500 mg/m3. In this case, headache, general weakness, nausea, and vomiting are observed. The maximum permissible average daily concentration is 0 1 mg/m3, one-time – 6 mg/m3. The air can be polluted by sulfur dioxide, soot, tarry substances, nitrogen oxides, and carbon disulfide.

Microorganisms. They are always found in small quantities in the air, where they are carried with soil dust. Microbes of infectious diseases entering the atmosphere quickly die. The air in residential premises and sports facilities poses a particular danger in terms of epidemiology. For example, in wrestling halls there is a microbial content of up to 26,000 per 1m3 of air. Aerogenic infections spread very quickly in such air.

Dust It is light dense particles of mineral or organic origin; when dust gets into the lungs, it lingers there and causes various diseases. Industrial dust (lead, chrome) can cause poisoning. In cities, dust should not exceed 0.15 mg/m3. Sports grounds must be regularly watered, have a green area, and carry out wet cleaning. Sanitary protection zones have been established for all enterprises that pollute the atmosphere. In accordance with the hazard class, they have different sizes: for enterprises of class 1 - 1000 m, 2 - 500 m, 3 - 300 m, 4 -100 m, 5 - 50 m. When placing sports facilities near enterprises, it is necessary to take into account the wind rose, sanitary protective zones, degree of air pollution, etc.

One of the important measures to protect the air environment is preventive and ongoing sanitary supervision and systematic monitoring of the state of atmospheric air. It is carried out using an automated monitoring system.

Clean atmospheric air at the surface of the Earth has the following chemical composition: oxygen - 20.93%, carbon dioxide - 0.03-0.04%, nitrogen - 78.1%, argon, helium, krypton 1%.

The exhaled air contains 25% less oxygen and 100 times more carbon dioxide.
Oxygen. The most important component of air. It ensures the flow of redox processes in the body. An adult consumes 12 liters of oxygen at rest, and 10 times more during physical work. In the blood, oxygen is bound to hemoglobin.

Ozone. A chemically unstable gas, it is capable of absorbing solar short-wave ultraviolet radiation, which has a detrimental effect on all living things. Ozone absorbs long-wave infrared radiation emanating from the Earth, and thereby prevents its excessive cooling (the Earth's ozone layer). Under the influence of ultraviolet radiation, ozone decomposes into an oxygen molecule and an atom. Ozone is a bactericidal agent for water disinfection. In nature, it is formed during electrical discharges, during the evaporation of water, during ultraviolet radiation, during a thunderstorm, in the mountains and in coniferous forests.

Carbon dioxide. It is formed as a result of redox processes occurring in the body of people and animals, combustion of fuel, and decay of organic substances. In the air of cities, the concentration of carbon dioxide is increased due to industrial emissions - up to 0.045%, in residential premises - up to 0.6-0.85. An adult at rest emits 22 liters of carbon dioxide per hour, and during physical work - 2-3 times more. Signs of deterioration in a person’s health appear only with prolonged inhalation of air containing 1-1.5% carbon dioxide, pronounced functional changes - at a concentration of 2-2.5% and pronounced symptoms (headache, general weakness, shortness of breath, palpitations, decreased performance) – at 3-4%. The hygienic importance of carbon dioxide lies in the fact that it serves as an indirect indicator of general air pollution. The carbon dioxide standard in gyms is 0.1%.

Nitrogen. An indifferent gas serves as a diluent for other gases. Increased inhalation of nitrogen can have a narcotic effect.

Carbon monoxide. Formed during incomplete combustion of organic substances. It has neither color nor smell. The concentration in the atmosphere depends on the intensity of vehicle traffic. Penetrating through the pulmonary alveoli into the blood, it forms carboxyhemoglobin, as a result of which hemoglobin loses its ability to carry oxygen. The maximum permissible average daily concentration of carbon monoxide is 1 mg/m3. Toxic doses of carbon monoxide in the air are 0.25-0.5 mg/l. With prolonged exposure, headache, fainting, palpitations.

Sulphur dioxide. It enters the atmosphere as a result of burning fuel rich in sulfur (coal). It is formed during the roasting and melting of sulfur ores and during the dyeing of fabrics. It irritates the mucous membranes of the eyes and upper respiratory tract. The sensation threshold is 0.002-0.003 mg/l. The gas has a harmful effect on vegetation, especially coniferous trees.
Mechanical air impurities come in the form of smoke, soot, soot, crushed soil particles and other solids. Air dust content depends on the nature of the soil (sand, clay, asphalt), its sanitary condition (watering, cleaning), air pollution from industrial emissions, and the sanitary condition of the premises.

Dust mechanically irritates the mucous membranes of the upper respiratory tract and eyes. Systematic inhalation of dust causes respiratory diseases. When breathing through the nose, up to 40-50% of dust is retained. Microscopic dust that remains suspended for a long time is the most unfavorable from a hygienic point of view. The electrical charge of dust enhances its ability to penetrate and linger in the lungs. Dust. containing lead, arsenic, chromium and other toxic substances, causes typical poisoning phenomena, and when penetrated not only by inhalation, but also through the skin and gastrointestinal tract. In dusty air, the intensity of solar radiation and air ionization are significantly reduced. To prevent the adverse effects of dust on the body, residential buildings are located on the windward side of air pollutants. Sanitary protection zones with a width of 50-1000 m or more are arranged between them. In residential premises, systematic wet cleaning, ventilation of rooms, change of shoes and outerwear, in open areas the use of dust-free soils and watering.

Air microorganisms. Bacterial pollution of air, as well as other environmental objects (water, soil), poses an epidemiological danger. There are various microorganisms in the air: bacteria, viruses, molds, yeast cells. The most common is airborne transmission of infections: a large number of microbes enter the air and enter the respiratory tract of healthy people when they breathe. For example, during a loud conversation, and even more so when coughing and sneezing, tiny droplets are sprayed over a distance of 1-1.5 m and spread with air over 8-9 m. These droplets can be suspended for 4-5 hours, but in most cases settle in 40-60 minutes. In dust, the influenza virus and diphtheria bacilli remain viable for 120-150 days. There is a well-known relationship: the more dust in indoor air, the more abundant the microflora content in it.

Chemical composition of air

Air is a mixture of gases that form a protective layer around the Earth - the atmosphere. Air is necessary for all living organisms: animals for breathing, and plants for nutrition. In addition, air protects the Earth from the harmful ultraviolet radiation of the Sun. The main components of air are nitrogen and oxygen. The air also contains small admixtures of noble gases, carbon dioxide and a certain amount of solid particles - soot and dust. All animals need air to breathe. About 21% of air is oxygen. An oxygen molecule (O2) consists of two bonded oxygen atoms.

Air composition

The percentage of various gases in the air varies slightly depending on location, time of year and day. Nitrogen and oxygen are the main components of air. One percent of the air consists of noble gases, carbon dioxide, water vapor and pollutants such as nitrogen dioxide. Gases contained in air can be separated by fractional distillation. The air is cooled until the gases become liquid (see the article “Solids, Liquids and Gases”). After this, the liquid mixture is heated. Each liquid has its own boiling point, and the gases formed during boiling can be collected separately. Oxygen, nitrogen and carbon dioxide constantly enter living organisms from the air and return to the air, i.e. a cycle occurs. Animals inhale oxygen from the air and exhale carbon dioxide.

Oxygen

Oxygen is essential for life. Animals breathe it, use it to digest food and get energy. During the day, a process occurs in plants photosynthesis, and plants release oxygen. Oxygen is also necessary for combustion; Without oxygen, nothing can burn. Almost 50% of the compounds in the earth's crust and oceans contain oxygen. Ordinary sand is a compound of silicon and oxygen. Oxygen is used in breathing apparatus for divers and in hospitals. Oxygen is also used in steel production (see article "Iron, steel and other materials") and rocketry (see article "Rockets and spacecraft").

In the upper layers of the atmosphere, oxygen atoms combine in threes to form the ozone molecule (O3). Ozone is an allotropic modification of oxygen. Ozone is a poisonous gas, but in the atmosphere the ozone layer protects our planet by absorbing most of the sun's harmful ultraviolet radiation (more in the article "The Sun's Impact on Earth").

Nitrogen

More than 78% of air is nitrogen. Proteins, from which living organisms are built, also contain nitrogen. The main industrial application of nitrogen is ammonia production needed for fertilizers. To do this, nitrogen is combined with hydrogen. Nitrogen is pumped into packaging for meat or fish, because... upon contact with ordinary air, products oxidize and deteriorate. Human organs intended for transplantation are stored in liquid nitrogen because it is cold and chemically inert. A nitrogen (N2) molecule consists of two bonded nitrogen atoms.

Plants obtain nitrogen from the soil in the form of nitrates and use it to synthesize proteins. Animals eat plants, and nitrogen compounds are returned to the soil through animal excretions and when their dead bodies decompose. In the soil, nitrogen compounds are decomposed by bacteria, releasing ammonia and then free nitrogen. Other bacteria absorb nitrogen from the air and convert it into nitrates for use by plants.

Carbon dioxide

Carbon dioxide is a compound of carbon and oxygen. The air contains about 0.003% carbon dioxide. A carbon dioxide (CO2) molecule consists of two oxygen atoms and one carbon atom. Carbon dioxide is one of the elements of the carbon cycle. Plants absorb it during photosynthesis, and animals exhale it. Carbon dioxide is also produced by the combustion of substances containing carbon, such as wood or gasoline. Because our cars and factories burn so much fuel, the proportion of carbon dioxide in the atmosphere is increasing. Most substances cannot burn in carbonic acid gas, which is why it is used in fire extinguishers. Carbon dioxide is denser than air. It “smothers” the flame, cutting off the access of oxygen. Carbon dioxide dissolves slightly in water, forming a weak solution of carbonic acid. Solid carbon dioxide is called dry ice. When dry ice melts, it turns into gas; it is used to create artificial clouds in the theater.

Air pollution

Soot and poisonous gases - carbon monoxide, nitrogen dioxide, sulfur dioxide - pollute the atmosphere. Carbon monoxide is formed during combustion. Many substances burn so quickly that they do not have time to add enough oxygen and instead of carbon dioxide (CO2), carbon monoxide (CO) is formed. Carbon monoxide is very poisonous; it prevents the animals' blood from carrying oxygen. There is only one oxygen atom in a carbon monoxide molecule. Car exhaust contains carbon monoxide as well as nitrogen dioxide, which causes acid rain. Sulfur dioxide is released when fossil fuels, especially coal, are burned. It is poisonous and makes breathing difficult. In addition, it dissolves in water and causes acid rain. Dust and soot particles emitted into the atmosphere by enterprises also pollute the air; we inhale them, they settle on plants. Lead is added to gasoline for better combustion (however, many cars now run on lead-free gasoline). Lead compounds accumulate in the body and have a detrimental effect on the nervous system. In children they can cause brain damage.

Acid rain

Rainwater always contains a little acid due to dissolved carbon dioxide, but pollutants (sulfur and nitrogen dioxides) increase the acidity of the rain. Acid rain causes corrosion of metals, corrodes stone structures and increases the acidity of fresh water.

Noble gases

Noble gases are 6 elements of group 8 of the periodic table. They are extremely chemically inert. Only they exist in the form of individual atoms that do not form molecules. Because of their passivity, some of them are used to fill lamps. Xenon is practically not used by humans, but argon is pumped into light bulbs, and fluorescent lamps are filled with creep tone. Neon flashes red-orange when electrically charged. It is used in sodium street lamps and neon lamps. Radon is radioactive. It is formed by the decay of the metal radium. No helium compounds are known to science, and helium is considered completely inert. Its density is 7 times less than the density of air, which is why airships are filled with it. Helium-filled balloons are equipped with scientific equipment and launched into the upper atmosphere.

Greenhouse effect

This is the name for the currently observed increase in carbon dioxide content in the atmosphere and the resulting global warming, i.e. increase in average annual temperatures around the world. Carbon dioxide prevents heat from leaving the Earth, just as glass maintains high temperatures inside a greenhouse. As there is more carbon dioxide in the air, more heat is trapped in the atmosphere. Even slight warming causes sea levels to rise, winds to change and some of the ice at the poles to melt. Scientists believe that if the carbon dioxide content increases as quickly, then in 50 years the average temperature could increase by 1.5°C to 4°C.

air is a mixture of gases, and therefore elements. . Nitrogen, oxygen, carbon dioxide. There are other gases in cities...

Percentage of gases.

do you need a graphical representation of an air molecule?

Air in chemistry - NO2

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If you think that air has its own separate formula, you are mistaken; in chemistry it is not designated in any way.

Air is the natural mixture of gases, mainly nitrogen and oxygen, that makes up the earth's atmosphere. Air composition: Nitrogen N2 Oxygen O2 Argon Ar Carbon dioxide CO2 Neon Ne Methane CH4 Helium He Krypton Kr Hydrogen H2 Xenon Xe Water H2O In addition, air always contains water vapor. So, at a temperature of 0 °C, 1 m³ of air can hold a maximum of 5 grams of water, and at a temperature of +10 °C - already 10 grams. In alchemy, air is symbolized as a triangle with a horizontal line.

nitrogen

we inhale the main component. air

Alternative descriptions

Gas that makes metal brittle

A gas that makes up 78% air

Main "air filler"

The main component of the air you inhale, which cannot be breathed in its pure form.

Air Component

Fertilizer in the air

Chemical element - the basis of a number of fertilizers

Chemical element, one of the main plant nutrients

Chemical element, component of air

Nitrogenium

Liquid refrigerant

Chemical element, gas

Magic sword of Paracelsus

In Latin, this gas is called “nitrogenium”, that is, “giving birth to saltpeter”

The name of this gas comes from the Latin word for lifeless.

This gas, a component of air, was practically absent from the Earth's primary atmosphere 4.5 billion years ago.

A gas whose liquid is used to cool ultra-precision instruments

What liquid gas is stored in a Dewar flask?

The gas that froze Terminator II

Gas cooler

What gas extinguishes fire?

Most abundant element in the atmosphere

Base of all nitrates

Chemical element, N

Freezing Gas

Three quarters air

Contains ammonia

Gas from air

Gas number 7

Element from saltpeter

The main gas in the air

The most popular gas

Element from nitrates

Liquid gas from a vessel

No. 1 gas in the atmosphere

Fertilizer in the air

78% air

Gas for cryostat

Almost 80% air

Natural chemical composition of atmospheric air

In terms of chemical composition, pure atmospheric air is a mixture of gases: oxygen, carbon dioxide, nitrogen, as well as a number of inert gases (argon, helium, krypton, etc.). Since air is a physical mixture, and not a chemical compound of its constituent gases, when rising even tens of kilometers, the percentage of these gases practically does not change.

However, with height, as a result of a decrease in atmospheric density, the concentrations and partial pressure of all gases in the air decrease.

At the Earth's surface the atmospheric air contains:

oxygen – 20.93%;

nitrogen – 78.1%;

carbon dioxide – 0.03-0.04%;

inert gases – from 10-3 to 10-6%.

Oxygen (O2)- the most important part of air for life. It is necessary for oxidative processes and is found in the blood, mainly in a bound state - in the form of oxyhemoglobin, which is transported by red blood cells to the cells of the body.

The transition of oxygen from alveolar air to blood occurs due to the difference in partial pressure in alveolar air and venous blood. For the same reason, oxygen flows from arterial blood into the interstitial fluid, and then into the cells.

In nature, oxygen is spent mainly on the oxidation of organic substances contained in air, water, soil and combustion processes. The loss of oxygen is replenished due to its large reserves in the atmosphere, as well as as a result of the activity of phytoplankton in the oceans and land plants. Continuous turbulent flows of air masses equalize the oxygen content in the surface layer of the atmosphere. Therefore, the oxygen level at the Earth's surface fluctuates slightly: from 20.7 to 20.95%. In residential premises and public buildings, the oxygen content also remains virtually unchanged due to its easy diffusion through the pores of building materials, cracks in windows, etc.

In sealed rooms (shelters, submarines, etc.), the oxygen content can decrease significantly. However, a pronounced deterioration in well-being and a decrease in performance in people are observed with a very significant drop in oxygen content - up to 15-17% (at normal - almost 21%). It should be emphasized that in this case we are talking about a reduced oxygen content at normal atmospheric pressure.

When the air temperature increases to 35-40°C and high humidity, the partial pressure of oxygen decreases, which can have a negative effect on patients with hypoxia.

In healthy people, oxygen starvation due to a decrease in the partial pressure of oxygen can be observed when flying (altitude sickness) and when climbing mountains (mountain sickness, which begins at an altitude of about 3 km).

Altitudes of 7-8 km correspond to 8.5-7.5% oxygen in the air at sea level and for untrained people are considered incompatible with life without the use of oxygen devices.

A dosed increase in the partial pressure of oxygen in the air in pressure chambers is used in surgery, therapy and emergency care.

Oxygen in its pure form has a toxic effect. Thus, in experiments on animals it was shown that when breathing pure oxygen, animals exhibit atelectasis in the lungs after 1-2 hours, impaired capillary permeability in the lungs after 3-6 hours, and pulmonary edema after 24 hours.

Hyperoxia develops even faster in an oxygen environment with high pressure - both damage to the lung tissue and damage to the central nervous system is observed.

Carbon dioxide or carbon dioxide, in nature exists in free and bound states. Up to 70% of carbon dioxide is dissolved in the water of the seas and oceans; the composition of some mineral compounds (limestones and dolomites) includes about 22% of the total amount of carbon dioxide. The rest comes from flora and fauna. In nature, continuous processes of release and absorption of carbon dioxide occur. It is released into the atmosphere as a result of human and animal respiration, as well as combustion, rotting, and fermentation. In addition, carbon dioxide is formed during the industrial roasting of limestones and dolomites, and it can be released with volcanic gases. Along with the processes of formation in nature, there are processes of assimilation of carbon dioxide - active absorption by plants during the process of photosynthesis. Carbon dioxide is washed out of the air by precipitation.

An important role in maintaining a constant concentration of carbon dioxide in the atmospheric air is played by its release from the surface of the seas and oceans. Carbon dioxide dissolved in the water of the seas and oceans is in dynamic equilibrium with carbon dioxide in the air and, when the partial pressure in the air increases, dissolves in water, and when the partial pressure decreases, it is released into the atmosphere. The processes of formation and assimilation are interconnected, due to this the content of carbon dioxide in the atmospheric air is relatively constant and amounts to 0.03-0.04%. Recently, the concentration of carbon dioxide in the air of industrial cities has been increasing as a result of intense air pollution by fuel combustion products. The carbon dioxide content in urban air can be higher than in a clean atmosphere, up to 0.05% or more. The role of carbon dioxide in creating the “greenhouse effect”, leading to an increase in the temperature of the surface layer of air, is known.

Carbon dioxide is a physiological stimulant of the respiratory center. Its partial pressure in the blood is ensured by the regulation of acid-base balance. In the body, it is in a bound state in the form of sodium carbonate salts in plasma and red blood cells. When large concentrations of carbon dioxide are inhaled, redox processes are disrupted. The more carbon dioxide in the air we breathe, the less of it the body can release. The accumulation of carbon dioxide in the blood and tissues leads to the development of tissue anoxia. When the carbon dioxide content in the inhaled air increases to 3-4%, symptoms of intoxication are observed; at 8%, severe poisoning occurs and death occurs. The carbon dioxide content is used to judge the cleanliness of air in residential and public buildings. A significant accumulation of this compound in the air of enclosed spaces indicates a sanitary problem in the room (crowding of people, poor ventilation). The maximum permissible concentration of carbon dioxide in the air of medical institutions is 0.07%, in the air of residential and public buildings - 0.1%. The last value is accepted as a calculation value when determining the ventilation efficiency of residential and public buildings.

Nitrogen. Along with oxygen and carbon dioxide, the composition of atmospheric air includes nitrogen, which in terms of quantitative content is the most significant part of atmospheric air.

Nitrogen belongs to the inert gases; it does not support respiration and combustion. Life is impossible in a nitrogen atmosphere. Its cycle occurs in nature. Nitrogen in the air is absorbed by certain types of soil bacteria, as well as blue-green algae. Under the influence of electrical discharges, nitrogen in the air turns into oxides, which, washed out of the atmosphere by precipitation, enrich the soil with salts of nitrous and nitric acids. Under the influence of soil bacteria, nitrous acid salts are converted into nitric acid salts, which in turn are absorbed by plants and serve for protein synthesis. It has been established that 95% of atmospheric air is assimilated by living organisms and only 5% is bound as a result of physical processes in nature. Consequently, the bulk of fixed nitrogen is of biogenic origin. Along with the absorption of nitrogen, it is released into the atmosphere. Free nitrogen is formed during the combustion of wood, coal, and oil; a small amount of free nitrogen is released during the decomposition of organic compounds by denitrifying microorganisms. Thus, in nature there is a continuous nitrogen cycle, as a result of which atmospheric nitrogen is converted into organic compounds. When these compounds decompose, nitrogen is restored and released into the atmosphere, and then it is again bound by biological objects.

Nitrogen is an oxygen diluent, and therefore performs a vital function, since breathing pure oxygen leads to irreversible changes in the body. When studying the effect of various nitrogen concentrations on the body, it was noted that its increased content in the inhaled air contributes to the onset of hypoxia and asphyxia due to a decrease in the partial pressure of oxygen. When the nitrogen content increases to 93%, death occurs. Nitrogen exhibits the most pronounced adverse properties under conditions of high pressure, which is associated with its narcotic effect. The role of nitrogen in the origin of decompression sickness is also known.

Noble gases. Inert gases include argon, neon, helium, krypton, xenon, etc. Chemically, these gases are inert; they dissolve in body fluids depending on the partial pressure. The absolute amount of these gases in the blood and tissues of the body is negligible. Among the inert gases, a special place is occupied by radon, actinon and thoron - decay products of the natural radioactive elements radium, thorium, actinium.

Chemically, these gases are inert, as noted above, and their dangerous effect on the body is associated with their radioactivity. Under natural conditions, they determine the natural radioactivity of the atmosphere.

Air temperature

Atmospheric air is heated mainly from the earth's surface due to the heat it receives from the Sun. About 47% of solar energy reaching the earth is absorbed by the earth's surface and converted into heat. Approximately 34% of the sun's energy is reflected back into space from cloud tops and the Earth's surface, and only a fifth (19%) of the sun's energy directly heats the atmosphere. In this regard, the maximum air temperature occurs between 13 and 14 hours, when the earth's surface is heated to the greatest extent. The heated ground layers of air rise upward, gradually cooling. Therefore, with an increase in altitude above sea level, the air temperature decreases by an average of 0.6 ° C for every 100 meters of rise.

Heating of the atmosphere occurs unevenly and depends, first of all, on geographic latitude: the greater the distance from the equator to the pole, the greater the angle of inclination of the sun's rays to the plane of the earth's surface, the less energy is supplied per unit area and the less it heats it.

The difference in air temperatures depending on the latitude of the area can be very significant and amount to more than 100°C. Thus, the highest air temperatures (up to +60°C) were recorded in equatorial Africa, the minimum (up to –90°C) – in Antarctica.

Daily fluctuations in air temperature are also very significant in a number of equatorial countries, constantly decreasing towards the poles.

Daily and annual fluctuations in air temperature are influenced by a number of natural factors: the intensity of solar radiation, the nature and topography of the area, altitude above sea level, proximity of seas, the nature of sea currents, vegetation cover, etc.

The effect of unfavorable air temperature on the body is most pronounced when people stay or work outdoors, as well as in some industrial premises, where very high or very low air temperatures are possible. This applies to agricultural workers, construction workers, oil workers, fishermen, etc., as well as those working in hot shops, in ultra-deep mines (1-2 km), specialists servicing refrigeration units, etc.

In residential and public premises there are opportunities to ensure the most favorable air temperature (through heating, ventilation, use of air conditioners, etc.).

Atmosphere pressure

On the surface of the globe, fluctuations in atmospheric pressure are associated with weather conditions and during the day, as a rule, do not exceed 4-5 mm Hg.

However, there are special conditions of human life and work in which there are significant deviations from normal atmospheric pressure that can have a pathological effect.