First set the composition of the air. Let's now define what oxygen is.

The air of the hot, sunny south and the harsh, cold north contain the same amount of oxygen.

One liter of air always contains 210 cubic centimeters of oxygen, which is 21 percent by volume.

Most of all, nitrogen is in the air - it is contained in a liter of 780 cubic centimeters, or 78 percent by volume. There is also a small amount of inert gases in the air. These gases are called inert because they almost never combine with other elements.

Of the inert gases in the air, argon is the most - it is about 9 cubic centimeters per liter. Neon is found in much smaller quantities in the air: there are 0.02 cubic centimeters in a liter of air. Even less helium - it is only 0.005 cubic centimeters. Krypton is 5 times less than helium - 0.001 cubic centimeters, and very little xenon - 0.00008 cubic centimeters.

The composition of the air also includes gaseous chemical compounds, for example, carbon dioxide, or carbon dioxide (CO 2). The amount of carbon dioxide in the air ranges from 0.3 to 0.4 cubic centimeters per liter. The content of water vapor in the air is also variable. In dry and hot weather, they are less, and in rainy weather - more.

The composition of air can also be expressed in weight percent. Knowing the weight of 1 liter of air and the specific gravity of each gas included in its composition, it is easy to switch from volumetric values ​​to weight values. Nitrogen in the air contains about 75.5, oxygen - 23.1, argon - 1.3 and carbon dioxide (carbon dioxide) - 0.04 weight percent.

The difference between weight and volume percentages is explained by the different specific gravities of nitrogen, oxygen, argon, and carbon dioxide.

Oxygen, for example, readily oxidizes copper at high temperatures. Therefore, if you pass air through a tube filled with hot copper shavings, then when it leaves the tube it will not contain oxygen. Phosphorus can also remove oxygen from the air. During combustion, phosphorus eagerly combines with oxygen, forming phosphoric anhydride (P 2 O 5).

The composition of air was determined in 1775 by Lavoisier.

By heating a small amount of metallic mercury in a glass retort, Lavoisier brought the narrow end of the retort under a glass cap, which was tipped over into a vessel filled with mercury. This experience lasted twelve days. The mercury in the retort, heated almost to a boil, became more and more covered with red oxide. At the same time, the level of mercury in the overturned cap began to rise noticeably above the level of mercury in the vessel containing the cap. The mercury in the retort, being oxidized, took more and more oxygen from the air, the pressure in the retort and the cap dropped, and instead of the oxygen consumed, mercury was sucked into the cap.

When all the oxygen was used up and the oxidation of mercury stopped, the suction of mercury into the bell also stopped. The volume of mercury in the cap was measured. It turned out that it was V 5 part of the total volume of the cap and retort.

The gas remaining in the cap and retort did not support combustion and life. This part of the air, which occupied almost 4/6 of the volume, was called nitrogen.

More accurate experiments at the end of the 18th century showed that air contains 21 percent oxygen and 79 percent nitrogen by volume.

And only at the end of the 19th century it became known that argon, helium and other inert gases are part of the air.

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.

Let's make a reservation right away, nitrogen in the air occupies a large part, however, the chemical composition of the remaining share is very interesting and diverse. In short, the list of main elements is as follows.

However, we will also give some explanations on the functions of these chemical elements.

1. Nitrogen

The content of nitrogen in the air is 78% by volume and 75% by mass, that is, this element dominates in the atmosphere, has the title of one of the most common on Earth, and, in addition, is found outside the human habitation zone - on Uranus, Neptune and in interstellar spaces. So, how much nitrogen is in the air, we have already figured out, the question remains about its function. Nitrogen is necessary for the existence of living beings, it is part of:

• proteins;
• amino acids;
• nucleic acids;
• chlorophyll;
• hemoglobin, etc.

On average, about 2% of a living cell is just nitrogen atoms, which explains why there is so much nitrogen in the air as a percentage of volume and mass.
Nitrogen is also one of the inert gases extracted from atmospheric air. Ammonia is synthesized from it, used for cooling and for other purposes.

2. Oxygen

The oxygen content in the air is one of the most popular questions. Keeping the intrigue, let's digress to one funny fact: oxygen was discovered twice - in 1771 and 1774, however, due to the difference in the publications of the discovery, the credit for the discovery of the element went to the English chemist Joseph Priestley, who actually isolated oxygen second. So, the proportion of oxygen in the air fluctuates around 21% by volume and 23% by mass. Together with nitrogen, these two gases form 99% of the earth's air. However, the percentage of oxygen in the air is less than nitrogen, and yet we do not experience breathing problems. The fact is that the amount of oxygen in the air is optimally calculated specifically for normal breathing, in its pure form this gas acts on the body like a poison, leads to difficulties in the functioning of the nervous system, respiratory failure and blood circulation. At the same time, the lack of oxygen also negatively affects health, causing oxygen starvation and all the unpleasant symptoms associated with it. Therefore, how much oxygen is contained in the air, so much is needed for healthy full breathing.

3. Argon

Argon in the air takes the third place, it has no smell, color and taste. A significant biological role of this gas has not been identified, but it has a narcotic effect and is even considered doping. Argon extracted from the atmosphere is used in industry, medicine, for creating an artificial atmosphere, chemical synthesis, fire fighting, creating lasers, etc.

4. Carbon dioxide

Carbon dioxide makes up the atmosphere of Venus and Mars, its percentage in the earth's air is much lower. At the same time, a huge amount of carbon dioxide is contained in the ocean, it is regularly supplied by all breathing organisms, and is emitted due to the work of industry. In human life, carbon dioxide is used in fire fighting, the food industry as a gas and as a food additive E290 - a preservative and baking powder. In solid form, carbon dioxide is one of the most well-known dry ice refrigerants.

5. Neon

The same mysterious light of disco lanterns, bright signs and modern headlights use the fifth most common chemical element, which is also inhaled by a person - neon. Like many inert gases, neon has a narcotic effect on a person at a certain pressure, but it is this gas that is used in the preparation of divers and other people working at elevated pressure. Also, neon-helium mixtures are used in medicine for respiratory disorders, neon itself is used for cooling, in the production of signal lights and those same neon lamps. However, contrary to the stereotype, neon light is not blue, but red. All other colors give lamps with other gases.

6. Methane

Methane and air have a very ancient history: in the primary atmosphere, even before the appearance of man, methane was in much greater quantities. Now this gas, extracted and used as a fuel and raw material in production, is not so widely distributed in the atmosphere, but is still emitted from the Earth. Modern research establishes the role of methane in the respiration and life of the human body, but there are no authoritative data on this subject yet.

7. Helium

Looking at how much helium is in the air, anyone will understand that this gas is not one of the most important in importance. Indeed, it is difficult to determine the biological significance of this gas. Not counting the funny distortion of the voice when inhaling helium from a balloon 🙂 However, helium is widely used in industry: in metallurgy, the food industry, for filling balloons and meteorological probes, in lasers, nuclear reactors, etc.

8. Krypton

We are not talking about the birthplace of Superman 🙂 Krypton is an inert gas that is three times heavier than air, chemically inert, extracted from air, used in incandescent lamps, lasers and is still being actively studied. Of the interesting properties of krypton, it is worth noting that at a pressure of 3.5 atmospheres it has a narcotic effect on a person, and at 6 atmospheres it acquires a pungent odor.

9. Hydrogen

Hydrogen in the air occupies 0.00005% by volume and 0.00008% by mass, but at the same time it is the most abundant element in the universe. It is quite possible to write a separate article about its history, production and application, so now we will limit ourselves to a small list of industries: chemical, fuel, food industries, aviation, meteorology, electric power industry.

10. Xenon

The latter is in the composition of air, which was originally considered to be only an admixture to krypton. Its name translates as "alien", and the percentage of content both on Earth and beyond is minimal, which led to its high cost. Now xenon is essential: the production of powerful and pulsed light sources, diagnostics and anesthesia in medicine, spacecraft engines, rocket fuel. In addition, when inhaled, xenon significantly lowers the voice (the opposite effect of helium), and more recently, inhalation of this gas has been added to the doping list.

The chemical composition of the air is of great hygienic importance, since it plays a decisive role in the implementation of 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. one.

Oxygen (O 2) - 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 dramatically and can reach 4.5/5 liters or more in 1 minute. Fluctuations in the oxygen content in the atmospheric air are small and do not exceed, as a rule, 0.5%.

In residential, public and sports premises, significant changes in the oxygen content are not observed, since outside air penetrates into them. Under the most unfavorable hygienic conditions in the room, a decrease in the oxygen content by 1% was noted. Such fluctuations do not have a noticeable effect on the body.

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

In sports practice, in order to increase the efficiency and intensity of recovery processes, oxygen inhalation is used.

Carbon dioxide (CO 2), or carbon dioxide, is a colorless, odorless gas formed during the breathing of people and animals, decay and decomposition of organic substances, fuel combustion, etc. In the atmospheric air outside settlements, the carbon dioxide content averages 0.04%, and in industrial centers its concentration rises to 0.05-0.06%. In residential and public buildings, when there are a large number of people in them, the content of carbon dioxide can increase up to 0.6-0.8%. Under the worst hygienic conditions in the room (large crowds, 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 with a content of 1 - 1.5% carbon dioxide, a deterioration in health is noted, and at 2-2.5%, pathological changes are detected. Significant disturbances in body functions and a decrease in efficiency occur when the carbon dioxide content is 4-5%. At a content of 8-10%, loss of consciousness and death occurs. A significant increase in the content of carbon dioxide in the air can occur in emergency situations in confined spaces (mines, mines, submarines, bomb shelters, etc.) or in places where there is an intensive decomposition of organic matter.

Determination of carbon dioxide content in residential, public and sports facilities can serve as an indirect indicator of air pollution by human waste products. As already noted, carbon dioxide itself in these cases does not harm 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 disturbed, foul-smelling gases appear). Indoor air is considered poor quality if the carbon dioxide content in it exceeds 0.1%. This value is taken as a calculated one when designing and installing ventilation in rooms.

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.