What is the composition of air. Gas composition of atmospheric air

That part of the atmosphere, which is adjacent to the Earth and which, accordingly, a person breathes, is called the troposphere. The troposphere has a height of nine to eleven kilometers and is a mechanical mixture of various gases.

The composition of the air is not constant. Depending on the geographical location, terrain, weather conditions, the air can have a different composition and different properties. The air can be gassed or discharged, fresh or heavy - all this means that it contains certain impurities.

Nitrogen - 78.9 percent;

Oxygen - 20.95 percent;

Carbon dioxide - 0.3 percent.

In addition, other gases are present in the atmosphere (helium, argon, neon, xenon, krypton, hydrogen, radon, ozone), as well as their sum is slightly less than one percent.

It is also worth pointing out the presence in the air of some permanent impurities of natural origin, in particular, some gaseous products that are formed as a result of both biological and chemical processes. Ammonia deserves special mention among them (the composition of air away from populated areas includes about three to five thousandths of a milligram per cubic meter), methane (its level is on average two ten thousandths of a milligram per cubic meter), nitrogen oxides (in the atmosphere their concentration reaches approximately fifteen thousandths of a milligram per cubic meter), hydrogen sulfide and other gaseous products.

In addition to vaporous and gaseous impurities, the chemical composition of the air usually includes dust of cosmic origin, which falls on the Earth's surface in the amount of seven hundred thousandths of a ton per square kilometer during the year, as well as dust particles that come from volcanic eruptions.

However, to the greatest extent (and not for the better) the composition of the air and pollute the troposphere is the so-called ground (vegetable, soil) dust and smoke from forest fires. Especially a lot of such dust in the continental air masses originating in the deserts of Central Asia and Africa. That is why we can say with confidence that an ideally clean air environment simply does not exist, and it is a concept that exists only theoretically.

The composition of the air tends to change constantly, and its natural changes usually play a rather small role, especially in comparison with the possible consequences of its artificial disturbances. Such violations are mainly associated with the production activities of mankind, the use of devices for consumer services, as well as vehicles. These violations can lead, among other things, to air denaturation, that is, to pronounced differences in its composition and properties from the corresponding indicators of the atmosphere.

These and many other types of human activity have led to the fact that the basic composition of the air began to undergo slow and insignificant, but nevertheless absolutely irreversible changes. For example, scientists have calculated that over the past fifty years, mankind has used about the same amount of oxygen as over the previous million years, and in percentage terms - two-tenths of a percent of its total supply in the atmosphere. At the same time, the release into the air increases accordingly. This release, according to the latest data, has reached almost four hundred billion tons over the past hundred years.

Thus, the composition of the air is changing for the worse, and it is difficult to imagine what it will become in a few decades.

The lower layers of the atmosphere are made up of a mixture of gases called air. , in which liquid and solid particles are suspended. The total mass of the latter is insignificant in comparison with the entire mass of the atmosphere.

Atmospheric air is a mixture of gases, the main of which are nitrogen N2, oxygen O2, argon Ar, carbon dioxide CO2 and water vapor. Air without water vapor is called dry air. Near the earth's surface, dry air is 99% nitrogen (78% by volume or 76% by mass) and oxygen (21% by volume or 23% by mass). The remaining 1% falls almost entirely on argon. Only 0.08% remains for carbon dioxide CO2. Numerous other gases are part of the air in thousandths, millionths and even smaller fractions of a percent. These are krypton, xenon, neon, helium, hydrogen, ozone, iodine, radon, methane, ammonia, hydrogen peroxide, nitrous oxide, etc. The composition of dry atmospheric air near the Earth's surface is given in Table. one.

Table 1

The composition of dry atmospheric air near the Earth's surface

	Volume concentration, %	Molecular mass	Density in relation to density dry air
Oxygen (O2)
Carbon dioxide (CO2)
Krypton (Kr)
Hydrogen (H2)
Xenon (Xe)
dry air

The percentage composition of dry air near the earth's surface is very constant and practically the same everywhere. Only the content of carbon dioxide can change significantly. As a result of breathing and combustion processes, its volumetric content in the air of closed, poorly ventilated premises, as well as industrial centers, can increase several times - up to 0.1-0.2%. The percentage of nitrogen and oxygen changes quite insignificantly.

The composition of the real atmosphere includes three important variable components - water vapor, ozone and carbon dioxide. The content of water vapor in the air varies significantly, unlike other components of the air: at the earth's surface, it varies between hundredths of a percent and several percent (from 0.2% in polar latitudes to 2.5% at the equator, and in some cases fluctuates almost from zero to 4%). This is explained by the fact that, under the conditions existing in the atmosphere, water vapor can pass into a liquid and solid state and, conversely, can enter the atmosphere again due to evaporation from the earth's surface.

Water vapor continuously enters the atmosphere by evaporation from water surfaces, from moist soil and by transpiration of plants, while in different places and at different times it enters in different quantities. It spreads upward from the earth's surface, and is carried by air currents from one place on the Earth to another.

Saturation may occur in the atmosphere. In this state, water vapor is contained in the air in an amount that is the maximum possible at a given temperature. Water vapor is called saturating(or saturated), and the air containing it saturated.

The saturation state is usually reached when the air temperature drops. When this state is reached, then with a further decrease in temperature, part of the water vapor becomes redundant and condenses changes to a liquid or solid state. Water droplets and ice crystals of clouds and fogs appear in the air. Clouds can evaporate again; in other cases, droplets and crystals of clouds, becoming larger, can fall on the earth's surface in the form of precipitation. As a result of all this, the content of water vapor in each part of the atmosphere is constantly changing.

The most important weather processes and climate features are associated with water vapor in the air and with its transitions from a gaseous state to a liquid and solid state. The presence of water vapor in the atmosphere significantly affects the thermal conditions of the atmosphere and the earth's surface. Water vapor strongly absorbs long-wave infrared radiation emitted by the earth's surface. In turn, he himself emits infrared radiation, most of which goes to the earth's surface. This reduces the nighttime cooling of the earth's surface and thus also the lower layers of the air.

Large amounts of heat are expended on the evaporation of water from the earth's surface, and when water vapor condenses in the atmosphere, this heat is transferred to the air. Clouds resulting from condensation reflect and absorb solar radiation on its way to the earth's surface. Precipitation from clouds is an essential element of weather and climate. Finally, the presence of water vapor in the atmosphere is essential for physiological processes.

Water vapor, like any gas, has elasticity (pressure). Water vapor pressure e proportional to its density (content per unit volume) and its absolute temperature. It is expressed in the same units as air pressure, i.e. either in millimeters of mercury, either in millibars.

The pressure of water vapor at saturation is called saturation elasticity. This is the maximum pressure of water vapor possible at a given temperature. For example, at a temperature of 0° saturation elasticity is 6.1 mb . For every 10° of temperature, the saturation elasticity approximately doubles.

If the air contains less water vapor than is needed to saturate it at a given temperature, it can be determined how close the air is to saturation. To do this, calculate relative humidity. This is the name of the ratio of actual elasticity e water vapor in the air to saturation elasticity E at the same temperature, expressed as a percentage, i.e.

For example, at a temperature of 20 °, the saturation elasticity is 23.4 mb. If the actual vapor pressure in the air is 11.7 mb, then the relative humidity of the air is

The pressure of water vapor near the earth's surface varies from hundredths of a millibar (at very low temperatures in winter in Antarctica and Yakutia) to 35 mbi more (near the equator). The warmer the air, the more water vapor it can contain without saturation and, therefore, the greater the elasticity of water vapor can be in it.

Relative humidity can take on all values ​​- from zero for completely dry air ( e= 0) to 100% for saturation state (e = E).

Less than 200 years ago, the earth's atmosphere contained 40% oxygen. Today, the air contains only 21% oxygen.

In the city park 20,8%

In the woods 21,6%

By the sea 21,9%

In the apartment and office less 20%

Scientists have proven that a 1% decrease in oxygen leads to a decrease in performance by 30%.

The lack of oxygen is the result of automobiles, industrial emissions and pollution. In the city, oxygen is 1% less than in the forest.

But the biggest culprit in the lack of oxygen is ourselves. Having built warm and hermetic houses, living in apartments with plastic windows, we protected ourselves from fresh air. With each exhalation, reducing the concentration of oxygen and increasing the amount of carbon dioxide. Often the oxygen content in the office is 18%, in the apartment 19%.

The quality of the air necessary to support the life processes of all living organisms on Earth,

determined by its oxygen content.

The dependence of air quality on the percentage of oxygen in it.

The level of comfortable oxygen content in the air

Zone 3-4: limited by the legally mandated minimum indoor oxygen standard (20.5%) and the "reference" fresh air (21%). For urban air, an oxygen content of 20.8% is considered normal.

Favorable levels of oxygen in the air

Zone 1-2: this level of oxygen content is typical for ecologically clean areas, forests. The oxygen content in the air on the ocean can reach 21.9%

Insufficient level of oxygen in the air

Zano 5-6: limited by the minimum allowable level of oxygen when a person can be without a breathing apparatus (18%).

A person's stay in rooms with such air is accompanied by rapid fatigue, drowsiness, decreased mental activity, and headaches.

Prolonged stay in rooms with such an atmosphere is dangerous to health.

Dangerously low oxygen levels in the air

Zone 7 onwards: at oxygen content16% dizziness, rapid breathing,13% - loss of consciousness,12% - irreversible changes in the functioning of the body, 7% - death.

External signs of oxygen starvation (hypoxia)

- deterioration in skin color

- fatigue, decreased mental, physical and sexual activity

- depression, irritability, sleep disturbance

- headaches

Prolonged exposure to a room with insufficient oxygen levels can lead to more serious health problems, because. oxygen is responsible for all metabolic processes of the body, then the consequence of its lack is:

Metabolic disease

Decreased immunity

Properly organized ventilation system of living and working premises can be the key to good health.

The role of oxygen in human health. Oxygen:

Increases mental performance;

Increases the body's resistance to stress and increased nervous stress;

Supports the level of oxygen in the blood;

Improves the coordination of the work of internal organs;

Increases immunity;

Promotes weight loss. Regular oxygen consumption, combined with physical activity, leads to active breakdown of fats;

Sleep normalizes: it becomes deeper and longer, the period of falling asleep and physical activity decreases

Findings:

Oxygen affects our life, and the more it is, the more colorful and diverse our life is.

You can buy an oxygen tank or drop everything and go to live in the forest. If this is not available to you, air your apartment or office every hour. Draft, dust, noise interfere, install ventilation that will supply you with fresh air, clean it from exhaust gases.

Do everything to fresh air in your home and you will see changes in your life.

LECTURE No. 3. Atmospheric air.

Topic: Atmospheric air, its chemical composition and physiological

the meaning of the components.

Atmospheric pollution; their impact on public health.

Lecture plan:

The chemical composition of atmospheric air.

The biological role and physiological significance of its constituents: nitrogen, oxygen, carbon dioxide, ozone, inert gases.

The concept of atmospheric pollution and their sources.

Impact of atmospheric pollution on health (direct impact).

Influence of atmospheric pollution on the living conditions of the population (indirect impact on health).

Questions of protection of atmospheric air from pollution.

The gaseous envelope of the earth is called the atmosphere. The total weight of the earth's atmosphere is 5.13  10 15 tons.

The air that forms the atmosphere is a mixture of various gases. The composition of dry air at sea level is:

Table No. 1

The composition of dry air at a temperature of 0 0 C and

pressure 760 mm Hg. Art.

Components Components	Percentage composition by volume	Concentration in mg/m 3
Oxygen
Carbon dioxide
Nitrous oxide

The composition of the earth's atmosphere remains constant over land, over the sea, in cities and rural areas. It also does not change with height. It should be remembered that we are talking about the percentage of air constituents at different heights. However, this cannot be said about the weight concentration of gases. As we rise upwards, the air density decreases and the number of molecules contained in a unit of space also decreases. As a result, the weight concentration of the gas and its partial pressure decrease.

Let us dwell on the characteristics of the individual components of air.

The main component of the atmosphere is nitrogen. Nitrogen is an inert gas. It does not support breathing and combustion. In a nitrogen atmosphere, life is impossible.

Nitrogen plays an important biological role. Air nitrogen is absorbed by some types of bacteria and algae, which form organic compounds from it.

Under the influence of atmospheric electricity, a small amount of nitrogen ions is formed, which are washed out of the atmosphere by precipitation and enrich the soil with salts of nitrous and nitric acid. Salts of nitrous acid under the influence of soil bacteria turn into nitrites. Nitrites and ammonia salts are absorbed by plants and serve for the synthesis of proteins.

Thus, the transformation of the inert nitrogen of the atmosphere into the living matter of the organic world is carried out.

Due to the lack of nitrogenous fertilizers of natural origin, mankind has learned to obtain them artificially. A nitrogen-fertilizer industry has been created and is developing, which processes atmospheric nitrogen into ammonia and nitrogenous fertilizers.

The biological significance of nitrogen is not limited to its participation in the cycle of nitrogenous substances. It plays an important role as a diluent of atmospheric oxygen, since life is impossible in pure oxygen.

An increase in the nitrogen content in the air causes hypoxia and asphyxia due to a decrease in the partial pressure of oxygen.

With an increase in partial pressure, nitrogen exhibits narcotic properties. However, in an open atmosphere, the narcotic effect of nitrogen does not manifest itself, since fluctuations in its concentration are insignificant.

The most important component of the atmosphere is gaseous oxygen (O 2 ) .

Oxygen in our solar system in a free state is found only on Earth.

Many assumptions have been put forward regarding the evolution (development) of terrestrial oxygen. The most accepted explanation is that the vast majority of the oxygen in the modern atmosphere came from photosynthesis in the biosphere; and only the initial, small amount of oxygen was formed as a result of water photosynthesis.

The biological role of oxygen is extremely high. Life is impossible without oxygen. The earth's atmosphere contains 1.18  10 15 tons of oxygen.

In nature, the processes of oxygen consumption are continuously going on: the respiration of humans and animals, the processes of combustion, oxidation. At the same time, the processes of restoring the oxygen content in the air (photosynthesis) are continuously going on. Plants absorb carbon dioxide, break it down, absorb carbon, and release oxygen into the atmosphere. Plants emit 0.5  10 5 million tons of oxygen into the atmosphere. This is enough to cover the natural loss of oxygen. Therefore, its content in the air is constant and amounts to 20.95%.

The continuous flow of air masses mixes the troposphere, which is why there is no difference in the oxygen content in cities and rural areas. The oxygen concentration fluctuates within a few tenths of a percent. It does not matter. However, in deep pits, wells, caves, the oxygen content can drop, so descending into them is dangerous.

With a drop in the partial pressure of oxygen in humans and animals, oxygen starvation phenomena are observed. Significant changes in the partial pressure of oxygen occur when rising above sea level. The phenomena of oxygen deficiency can be observed when climbing mountains (mountaineering, tourism), during air travel. Climbing to a height of 3000m can cause altitude sickness or altitude sickness.

With long-term living in highlands, people develop an addiction to a lack of oxygen and acclimatization occurs.

A high partial pressure of oxygen is unfavorable for humans. At a partial pressure of more than 600 mm, the vital capacity of the lungs decreases. Inhalation of pure oxygen (partial pressure 760 mm) causes pulmonary edema, pneumonia, convulsions.

Under natural conditions, there is no increased oxygen content in the air.

Ozone is an integral part of the atmosphere. Its mass is 3.5 billion tons. The ozone content in the atmosphere varies with the seasons of the year: in spring it is high, in autumn it is low. The ozone content depends on the latitude of the area: the closer to the equator, the lower it is. The ozone concentration has a diurnal variation: it reaches its maximum by noon.

The ozone concentration is unevenly distributed along the height. Its highest content is observed at an altitude of 20-30 km.

Ozone is continuously produced in the stratosphere. Under the influence of ultraviolet radiation from the sun, oxygen molecules dissociate (break down) to form atomic oxygen. Oxygen atoms recombine (combine) with oxygen molecules and form ozone (O 3). At altitudes above and below 20-30 km, the processes of photosynthesis (formation) of ozone slow down.

The presence of an ozone layer in the atmosphere is of great importance for the existence of life on Earth.

Ozone delays the short-wave part of the solar radiation spectrum, does not transmit waves shorter than 290 nm (nanometers). In the absence of ozone, life on earth would be impossible, due to the destructive effect of short ultraviolet radiation on all living things.

Ozone also absorbs infrared radiation with a wavelength of 9.5 microns (microns). Due to this, ozone traps about 20 percent of the earth's thermal radiation, reducing the loss of its heat. In the absence of ozone, the absolute temperature of the Earth would be lower by 7 0 .

In the lower layer of the atmosphere - the troposphere, ozone is brought from the stratosphere as a result of the mixing of air masses. With weak mixing, the ozone concentration at the earth's surface decreases. An increase in ozone in the air is observed during a thunderstorm as a result of discharges of atmospheric electricity and an increase in turbulence (mixing) of the atmosphere.

At the same time, a significant increase in the concentration of ozone in the air is the result of photochemical oxidation of organic substances that enter the atmosphere with vehicle exhaust gases and industrial emissions. Ozone is one of the toxic substances. Ozone has an irritating effect on the mucous membranes of the eyes, nose, throat at a concentration of 0.2-1 mg/m 3 .

carbon dioxide (CO 2 ) is found in the atmosphere at a concentration of 0.03%. Its total amount is 2330 billion tons. A large amount of carbon dioxide is found in dissolved form in the water of the seas and oceans. In a bound form, it is a part of dolomites and limestones.

The atmosphere is constantly replenished with carbon dioxide as a result of the vital processes of living organisms, the processes of combustion, decay, and fermentation. A person emits 580 liters of carbon dioxide per day. A large amount of carbon dioxide is released during the decomposition of limestone.

Despite the presence of numerous sources of formation, there is no significant accumulation of carbon dioxide in the air. Carbon dioxide is constantly assimilated (assimilated) by plants during photosynthesis.

In addition to plants, the seas and oceans are the regulator of carbon dioxide in the atmosphere. When the partial pressure of carbon dioxide in the air rises, it dissolves in water, and when it decreases, it is released into the atmosphere.

In the surface atmosphere, small fluctuations in the concentration of carbon dioxide are observed: it is lower over the ocean than over land; higher in the forest than in the field; higher in cities than outside the city.

Carbon dioxide plays an important role in the life of animals and humans. It stimulates the respiratory center.

There is some amount in the air inert gases: argon, neon, helium, krypton and xenon. These gases belong to the zero group of the periodic table, do not react with other elements, and are inert in the chemical sense.

Inert gases are narcotic. Their narcotic properties are manifested at high barometric pressure. In an open atmosphere, the narcotic properties of inert gases cannot manifest themselves.

In addition to the constituent parts of the atmosphere, it contains various impurities of natural origin and pollution introduced as a result of human activities.

The impurities that are present in the air besides its natural chemical composition are called atmospheric pollution.

Atmospheric pollution is divided into natural and artificial.

Natural pollution includes impurities that enter the air as a result of natural processes (plant, soil dust, volcanic eruptions, cosmic dust).

Artificial atmospheric pollution is formed as a result of human production activities.

Artificial sources of atmospheric pollution are divided into 4 groups:

transport;

industry;

thermal power engineering;

garbage burning.

Let's take a look at their brief description.

The current situation is characterized by the fact that the volume of road transport emissions exceeds the volume of emissions from industrial enterprises.

One car releases more than 200 chemical compounds into the air. Each car consumes an average of 2 tons of fuel and 30 tons of air per year, and emits 700 kg of carbon monoxide (CO), 230 kg of unburned hydrocarbons, 40 kg of nitrogen oxides (NO 2) and 2-5 kg ​​of solids into the atmosphere.

The modern city is saturated with other modes of transport: rail, water and air. The total amount of emissions into the environment from all modes of transport tends to continuously increase.

Industrial enterprises are second only to transport in terms of environmental damage.

Ferrous and non-ferrous metallurgy enterprises, petrochemical and coke-chemical industries, as well as enterprises for the production of building materials pollute the atmospheric air most intensively. They emit tens of tons of soot, dust, metals and their compounds (copper, zinc, lead, nickel, tin, etc.) into the atmosphere.

Entering the atmosphere, metals pollute the soil, accumulate in it, penetrate into the water of reservoirs.

In areas where industrial enterprises are located, the population is at risk of adverse effects of atmospheric pollution.

In addition to solid particles, industry emits various gases into the air: sulfuric anhydride, carbon monoxide, nitrogen oxides, hydrogen sulfide, hydrocarbons, radioactive gases.

Pollutants can stay in the environment for a long time and have a harmful effect on the human body.

For example, hydrocarbons remain in the environment for up to 16 years, take an active part in photochemical processes in the atmospheric air with the formation of toxic mists.

Massive air pollution is observed during the combustion of solid and liquid fuels at thermal power plants. They are the main sources of air pollution with sulfur and nitrogen oxides, carbon monoxide, soot and dust. These sources are characterized by massive air pollution.

Currently, many facts are known about the adverse effects of atmospheric pollution on human health.

Air pollution has both acute and chronic effects on the human body.

Examples of the acute impact of atmospheric pollution on public health are toxic mists. Concentrations of toxic substances in the air increased under unfavorable meteorological conditions.

The first toxic fog was registered in Belgium in 1930. Several hundred people were injured, 60 people died. Subsequently, similar cases were repeated: in 1948 in the American city of Donora. 6,000 people were affected. In 1952, 4,000 people died from the Great London Fog. In 1962, 750 Londoners died for the same reason. In 1970, 10 thousand people suffered from smog over the Japanese capital (Tokyo), in 1971 - 28 thousand.

In addition to the catastrophes listed above, the analysis of research materials by domestic and foreign authors draws attention to an increase in the general morbidity of the population due to atmospheric pollution.

The studies carried out in this plan allow us to conclude that as a result of the impact of atmospheric pollution in industrial centers, there is an increase in:

overall mortality from cardiovascular and respiratory diseases;

acute nonspecific morbidity of the upper respiratory tract;

chronic bronchitis;

bronchial asthma;

emphysema;

lung cancer;

decrease in life expectancy and creative activity.

In addition, at present, mathematical analysis has revealed a statistically significant correlation between the level of morbidity of the population with diseases of the blood, digestive organs, skin diseases and levels of atmospheric air pollution.

The respiratory organs, the digestive system and the skin are the “entrance gates” for toxic substances and serve as targets for their direct and indirect action.

The impact of atmospheric pollution on living conditions is regarded as an indirect (indirect) impact of atmospheric pollution on the health of the population.

It includes:

decrease in general illumination;

reduction of ultraviolet radiation from the sun;

changing climatic conditions;

deterioration of living conditions;

negative impact on green spaces;

negative impact on animals.

Substances that pollute the atmosphere cause great damage to buildings, structures, building materials.

The total economic damage to the United States from air pollutants, including their impact on human health, building materials, metals, fabrics, leather, paper, paints, rubber and other materials, is $15-20 billion annually.

All of the above indicates that the protection of atmospheric air from pollution is a problem of extreme importance and the object of close attention of specialists in all countries of the world.

All measures for the protection of atmospheric air should be carried out comprehensively in several areas:

Legislative measures. These are laws adopted by the government of the country aimed at protecting the air environment;

Rational placement of industrial and residential areas;

Technological measures aimed at reducing emissions into the atmosphere;

Sanitary measures;

Development of hygienic standards for atmospheric air;

Control over the purity of atmospheric air;

Control over the work of industrial enterprises;

Improvement of populated areas, landscaping, watering, creation of protective gaps between industrial enterprises and residential complexes.

In addition to the listed measures of the intrastate plan, interstate programs for the protection of atmospheric air are currently being developed and widely implemented.

The problem of protecting the air basin is solved in a number of international organizations - WHO, UN, UNESCO and others.

The air that makes up the earth's atmosphere is a mixture of gases. Dry atmospheric air contains: oxygen 20.95%, nitrogen 78.09%, carbon dioxide 0.03%. In addition, atmospheric air contains argon, helium, neon, krypton, hydrogen, xenon and other gases. Ozone, nitric oxide, iodine, methane, and water vapor are present in small amounts in the atmospheric air.

In addition to the constant components of the atmosphere, it contains a variety of pollution introduced into the atmosphere by human production activities.

1. An important component of atmospheric air is oxygen , the amount of which in the earth's atmosphere is 1.18 × 10 15 tons. A constant oxygen content is maintained due to continuous processes of its exchange in nature. On the one hand, oxygen is consumed during the respiration of humans and animals, is spent on maintaining the processes of combustion and oxidation, on the other hand, it enters the atmosphere due to the processes of plant photosynthesis. Land plants and phytoplankton of the oceans fully restore the natural loss of oxygen. With a drop in the partial pressure of oxygen, the phenomena of oxygen starvation can develop, which is observed when ascending to a height. The critical level is the partial pressure of oxygen below 110 mm Hg. Art. Reducing the partial pressure of oxygen to 50-60 mm Hg. Art. usually incompatible with life. Under the influence of short-wave UV radiation with a wavelength of less than 200 nm, oxygen molecules dissociate to form atomic oxygen. The newly formed oxygen atoms are added to the neutral formula of oxygen, forming ozone . Simultaneously with the formation of ozone, its decay occurs. The general biological significance of ozone is great: it absorbs short-wave UV radiation, which has a detrimental effect on biological objects. At the same time, ozone absorbs infrared radiation coming from the Earth, and thus prevents excessive cooling of its surface. Ozone concentrations are unevenly distributed along the height. Its greatest amount is noted at the level of 20-30 km from the Earth's surface.

2. Nitrogen in terms of quantitative content, it is the most significant component of atmospheric air; it belongs to inert gases. Life is impossible in a nitrogen atmosphere. Air nitrogen is assimilated by certain types of soil bacteria (nitrogen-fixing bacteria), as well as by blue-green algae; under the influence of electrical discharges, it turns into nitrogen oxides, which, falling out with atmospheric 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. Along with the assimilation of nitrogen in nature, it is released into the atmosphere. Free nitrogen is formed during the combustion of wood, coal, oil; a small amount of it is formed during the decomposition of organic compounds. Thus, in nature there is a continuous circulation, as a result of which the nitrogen of the atmosphere is converted into organic compounds, restored and enters the atmosphere, then is again bound by biological objects.

Nitrogen is necessary as an oxygen diluent, since breathing pure oxygen leads to irreversible changes in the body.

However, an increased content of nitrogen in the inhaled air contributes to the onset of hypoxia due to a decrease in the partial pressure of oxygen. With an increase in the nitrogen content in the air to 93%, death occurs.

In addition to nitrogen, the inert gases of air include argon, neon, helium, krypton and xenon. 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.

3. An important component of atmospheric air is carbon dioxide (carbon dioxide, carbonic acid). In nature, carbon dioxide is in free and bound states in the amount of 146 billion tons, of which only 1.8% of its total amount is contained in atmospheric air. Most of it (up to 70%) is in a dissolved state in the water of the seas and oceans. Some mineral compounds, limestones and dolomites contain about 22% of the total amount of dioxide and carbon. The rest of the amount falls on the animal and plant world, coal, oil and humus.

Under natural conditions, there are continuous processes of release and absorption of carbon dioxide. It is released into the atmosphere due to the respiration of humans and animals, the processes of combustion, decay and fermentation, during the industrial roasting of limestones and dolomites, etc. At the same time, processes of assimilation of carbon dioxide are going on in nature, which is absorbed by plants in the process of photosynthesis.

Carbon dioxide plays an important role in the life of animals and humans, being a physiological causative agent of the respiratory center.

When high concentrations of carbon dioxide are inhaled, the redox processes in the body are disturbed. With an increase in its content in the inhaled air up to 4%, headaches, tinnitus, palpitations, and an excited state are noted; at 8% death occurs.

From a hygienic point of view, the content of carbon dioxide is an important indicator by which the degree of air purity in residential and public buildings is judged. The accumulation of large amounts of it in indoor air indicates sanitary problems (crowding, poor ventilation).

Under normal conditions, with natural ventilation of the premises and infiltration of outdoor air through the pores of building materials, the content of carbon dioxide in the air of residential premises does not exceed 0.2%. With an increase in its concentration in the room, a deterioration in the well-being of a person, a decrease in working capacity, may be noted. This is explained by the fact that simultaneously with an increase in the amount of carbon dioxide in the air of residential and public buildings, other properties of the air worsen: its temperature and humidity increase, gaseous products of human vital activity appear, the so-called anthropotoxins (mercaptan, indole, hydrogen sulfide, ammonia).

With an increase in the content of CO 2 in the air and the deterioration of meteorological conditions in residential and public buildings, the ionization regime of the air changes (an increase in the number of heavy and a decrease in the number of light ions), which is explained by the absorption of light ions during breathing and contact with the skin, as well as the intake of heavy ions with exhaled air.

The maximum allowable concentration of carbon dioxide in the air of medical institutions should be considered 0.07%, in the air of residential and public buildings - 0.1%. The latter value is taken as a calculated one when determining the efficiency of ventilation in residential and public buildings.

4. In addition to the main components, atmospheric air contains gases released as a result of natural processes occurring on the surface of the Earth and in the atmosphere.

Hydrogen contained in the air in an amount of 0.00005%. It is formed in the high layers of the atmosphere due to the photochemical decomposition of water molecules into oxygen and hydrogen. Hydrogen does not support respiration, in a free state it is not absorbed and is not released by biological objects. In addition to hydrogen, atmospheric air contains a small amount of methane; usually the concentration of methane in the air does not exceed 0.00022%. Methane is released during anaerobic decay of organic compounds. As an integral part, it is part of natural gas and gas from oil wells. When inhaling air containing methane in high concentrations, death from asphyxia is possible.

As a decomposition product of organic substances, small amounts of ammonia. Its concentrations depend on the degree of contamination of the area with sewage and organic emissions. In winter, due to the slowdown in the processes of decay, the concentration of ammonia is somewhat lower than in summer. During anaerobic processes of decomposition of sulfur-containing organic substances, the formation of hydrogen sulfide, which, in low concentrations, gives the air an unpleasant odor. In atmospheric air, iodine and hydrogen peroxide can be found in small concentrations. Iodine enters the atmospheric air due to the presence of the smallest droplets of sea water and seaweed. Due to the interaction of UV rays with air molecules, hydrogen peroxide; together with ozone, it contributes to the oxidation of organic substances in the atmosphere.

In the atmospheric air are suspended matter, which are represented by dust of natural and artificial origin. The composition of natural dust includes cosmic, volcanic, ground, sea dust and dust generated during forest fires.

Natural processes play an important role in the release of the atmosphere from suspended solids. self-cleaning, among which the dilution of pollution by convection air currents near the Earth's surface is of significant importance. An essential element of self-purification of the atmosphere is the precipitation of large particles of dust and soot from the air (sedimentation). As the altitude increases, the amount of dust decreases; at a height of 7 - 8 km from the Earth's surface, there is no dust of terrestrial origin. Significant Precipitation plays a role in self-cleaning processes, increasing the amount of settled soot and dust. The dust content in the atmospheric air is affected by meteorological conditions and aerosol dispersion. Coarse dust with a particle diameter of more than 10 microns falls out quickly, fine dust with a particle diameter of less than 0.1 microns practically does not fall out and is in suspension.