Oxygen content in the air under normal conditions. Composition and structure of the atmosphere

The ratio of gases in the earth's air indicated in the table is typical for its lower layers, up to an altitude of 120 km. Within these regions lies a beautifully mixed, uniformly composed region called the homosphere. Above the homosphere lies the heterosphere, which is characterized by the decomposition of gas molecules into atoms and ions.

The regions are separated from each other by a turbo pause.

The chemical reaction in which molecules are decomposed into atoms under the influence of solar and cosmic radiation is called photodissociation. The decay of molecular oxygen produces atomic oxygen, which is the main gas in the air at altitudes of more than 200 km. At altitudes above 1200 km, hydrogen and helium, which are the lightest of the gases, begin to predominate.

Because the main mass of air is concentrated in the 3 lower atmospheric layers, transformations in the air composition at altitudes of more than 100 km do not have a noticeable effect on the general air composition.

Nitrogen is the most popular gas, accounting for more than three-quarters of the earth's air. Modern nitrogen appeared from the oxidation of early ammonia-hydrogen air with molecular oxygen, which is formed during photosynthesis.

Currently, a small amount of nitrogen enters the air as a result of denitrification - the process of reducing nitrates to nitrites, followed by the formation of gaseous molecular nitrogen and oxides, which is produced by anaerobic prokaryotes. Some nitrogen enters the air during volcanic eruptions.

In the upper layers of air, under the action of electrical discharges with the participation of ozone, molecular nitrogen is oxidized to nitrogen monoxide:

Under simple conditions, the monoxide immediately reacts with oxygen to form nitrous oxide:

Nitrogen is the most significant chemical element in the earth's atmosphere. Nitrogen is part of proteins and supplies mineral nutrition to plants. It determines the rate of chemical reactions and plays the role of an oxygen diluent.

The second most common gas in the soil air is oxygen. The formation of this gas is associated with the photosynthetic activity of bacteria and plants. And the more diverse and countless photosynthetic organisms became, the greater the process of oxygen content in the air became.

Small amounts of heavy oxygen are released as the mantle degasses.

In the upper layers of the stratosphere and troposphere, under the influence of ultraviolet solar radiation (let's denote it as h?), ozone is formed:

As a result of the same ultraviolet radiation, ozone decomposes:

O3 + h? O2 + O

As a result of the first reaction, atomic oxygen is formed, and as a result of the second, molecular oxygen is formed. All 4 reactions are called the “Chapman mechanism”, named after the English scientist Sidney Chapman who discovered them in the first half of the 30s of the twentieth century.

Oxygen helps living organisms breathe. With its help, combustion and oxidation processes occur.

Ozone helps to protect living organisms from ultraviolet radiation, which leads to irreversible mutations. The largest concentration of ozone is observed in the lower stratosphere within the so-called. ozone layer or ozone screen lying at heights

The formation of the third most common gas in the air, argon, and neon, helium, xenon and krypton, is associated with the decay and volcanic eruptions of radioactive elements.

In particular, helium is a product of the radioactive decay of uranium, radium and thorium: 238 U 234 Th + ?, 230 Th 226 Ra + 4 He, 226 Ra 222 Rn + ? (in these reactions the particle is a helium nucleus, which, during the loss of energy, captures electrons and becomes 4 He).

Argon is formed during the decay of the radioactive isotope of potassium: 40 K 40 Ar + ?.

Neon escapes from igneous rocks.

Krypton is formed as the end product of the decay of uranium (235 U and 238 U) and thorium Th.

The main mass of atmospheric krypton appeared in the early stages of the evolution of the Soil as a consequence of the decay of transuranic elements with a phenomenally short half-life or came from space, the content of krypton in which is ten million times higher than on Earth.

Xenon is the result of the fission of uranium, but the main mass of this gas remained from the early stages of soil formation, from the primary air.

Carbon dioxide enters the air as a result of volcanic eruptions and during the decomposition of organic matter. Its content in the air of mid-latitude soils varies greatly depending on the seasons of the year: in winter the amount of CO2 increases, and in summer it decreases. This fluctuation is associated with the activity of plants, which use carbon dioxide during photosynthesis.

Hydrogen is formed as a result of the decomposition of water by solar radiation. But, being the lightest of the gases that make up the air, it always evaporates into outer space, and therefore its content in the air is very small.

Steam is the result of the evaporation of water from the surface of lakes, rivers, seas and land.

The concentration of the main gases in the lower layers of air, with the exception of water vapor and carbon dioxide, is constant. Sulfur oxide SO2 is found in small quantities in the air. ammonia NH3. Carbon monoxide CO, ozone O3. hydrogen chloride HCl, hydrogen fluoride HF, nitrogen monoxide in what quantity, hydrocarbons, mercury vapor Hg, iodine I2 and many others. In the lower atmospheric layer, the troposphere, there is always a lot of suspended solid and liquid particles.

The sources of hard particles in the air of the soil are volcanic eruptions, plant pollen, microbes, and now human activities, for example, the burning of fossil fuels during production. Small dust particles, which are condensation nuclei, are the cause of the formation of fogs and clouds. Without the hard particles that are invariably present in the air, precipitation would not fall on the Earth.

Atmospheric air is a mixture of various gases. It contains permanent components of the atmosphere (oxygen, nitrogen, carbon dioxide), inert gases (argon, helium, neon, krypton, hydrogen, xenon, radon), small amounts of ozone, nitrous oxide, methane, iodine, water vapor, as well as in variable quantities, various impurities of natural origin and pollution resulting from human production activities.

Oxygen (O2) is the most important part of air for humans. It is necessary for the implementation of oxidative processes in the body. In atmospheric air, the oxygen content is 20.95%, in the air exhaled by a person - 15.4-16%. Reducing it in atmospheric air to 13-15% leads to disruption of physiological functions, and to 7-8% leads to death.

Nitrogen (N) is the main component of atmospheric air. The air inhaled and exhaled by a person contains approximately the same amount of nitrogen - 78.97-79.2%. The biological role of nitrogen is mainly that it is an oxygen diluent, since life is impossible in pure oxygen. When the nitrogen content increases to 93%, death occurs.

Carbon dioxide (carbon dioxide), CO2, is a physiological regulator of respiration. The content in clean air is 0.03%, in human exhalation - 3%.

A decrease in CO2 concentration in the inhaled air does not pose a danger, because its required level in the blood is maintained by regulatory mechanisms due to its release during metabolic processes.

An increase in the carbon dioxide content in the inhaled air to 0.2% causes a person to feel unwell; at 3-4% there is an excited state, headache, tinnitus, palpitations, slow pulse, and at 8% severe poisoning occurs, loss of consciousness and death comes.

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. An increase in CO2 in the atmospheric air leads to the appearance of toxic fogs in cities and the “greenhouse effect” associated with the retention of thermal radiation from the earth by carbon dioxide.

An increase in CO2 content above the established norm indicates a general deterioration in the sanitary condition of the air, since, along with carbon dioxide, other toxic substances can accumulate, the ionization regime may worsen, and dust and microbial contamination may increase.

Ozone (O3). Its main quantity is observed at the level of 20-30 km from the Earth's surface. The surface layers of the atmosphere contain a negligible amount of ozone - no more than 0.000001 mg/l. Ozone protects living organisms on the earth from the harmful effects of short-wave ultraviolet radiation and at the same time absorbs long-wave infrared radiation emanating from the Earth, protecting it from excessive cooling. Ozone has oxidizing properties, so in the polluted air of cities its concentration is lower than in rural areas. In this regard, ozone was considered an indicator of air purity. However, it has recently been established that ozone is formed as a result of photochemical reactions during the formation of smog, therefore the detection of ozone in the atmospheric air of large cities is considered an indicator of its pollution.

Inert gases do not have a pronounced hygienic and physiological significance.

Human economic and production activities are a source of air pollution with various gaseous impurities and suspended particles. The increased content of harmful substances in the atmosphere and indoor air has an adverse effect on the human body. In this regard, the most important hygienic task is to standardize their permissible content in the air.

The sanitary and hygienic state of the air is usually assessed by the maximum permissible concentrations (MPC) of harmful substances in the air of the working area.

The maximum permissible concentration of harmful substances in the air of a working area is a concentration that, during daily 8-hour work, but not more than 41 hours a week, during the entire working period, does not cause diseases or deviations in the health of the present and subsequent generations. The daily average and maximum one-time maximum permissible concentrations are established (valid for up to 30 minutes in the air of the working area). The maximum permissible concentration for the same substance can be different depending on the duration of its exposure to a person.

At food enterprises, the main causes of air pollution with harmful substances are disruptions in the technological process and emergency situations (sewage, ventilation, etc.).

Hygienic hazards in indoor air include carbon monoxide, ammonia, hydrogen sulfide, sulfur dioxide, dust, etc., as well as air pollution by microorganisms.

Carbon monoxide (CO) is an odorless and colorless gas that enters the air as a product of incomplete combustion of liquid and solid fuels. It causes acute poisoning at a concentration in the air of 220-500 mg/m3 and chronic poisoning - with constant inhalation of a concentration of 20-30 mg/m3. The average daily maximum concentration of carbon monoxide in atmospheric air is 1 mg/m3, in the air of the working area - from 20 to 200 mg/m3 (depending on the duration of work).

Sulfur dioxide (S02) is the most common impurity in atmospheric air, since sulfur is contained in various types of fuel. This gas has a general toxic effect and causes respiratory diseases. The irritating effect of the gas is detected when its concentration in the air exceeds 20 mg/m3. In atmospheric air, the average daily maximum concentration of sulfur dioxide is 0.05 mg/m3, in the air of the working area - 10 mg/m3.

Hydrogen sulfide (H2S) - usually enters the atmospheric air with waste from chemical, oil refineries and metallurgical plants, and is also formed and can pollute indoor air as a result of rotting food waste and protein products. Hydrogen sulfide has a general toxic effect and causes discomfort in humans at a concentration of 0.04-0.12 mg/m3, and a concentration of more than 1000 mg/m3 can be fatal. In atmospheric air, the average daily maximum concentration of hydrogen sulfide is 0.008 mg/m3, in the air of the working area - up to 10 mg/m3.

Ammonia (NH3) - accumulates in the air of enclosed spaces during the rotting of protein products, malfunction of refrigeration units with ammonia cooling, during sewerage failures, etc. It is toxic to the body.

Acrolein is a product of fat decomposition during heat treatment and can cause allergic diseases in industrial conditions. MPC in the working area is 0.2 mg/m3.

Polycyclic aromatic hydrocarbons (PAHs) - their connection with the development of malignant neoplasms has been noted. The most common and most active of them is 3-4-benzo(a)pyrene, which is released when fuels are burned: coal, oil, gasoline, gas. The maximum amount of 3-4-benzo(a)pyrene is released when burning coal, the minimum - when burning gas. In food processing plants, a source of PAH air pollution may be the long-term use of overheated fat. The average daily maximum concentration limit of cyclic aromatic hydrocarbons in atmospheric air should not exceed 0.001 mg/m3.

Mechanical impurities - dust, soil particles, smoke, ash, soot. Dust levels increase with insufficient landscaping, poor access roads, disruption of the collection and removal of production waste, as well as violation of the sanitary cleaning regime (dry or irregular wet cleaning, etc.). In addition, dustiness of premises increases with violations in the design and operation of ventilation, planning solutions (for example, with insufficient isolation of the vegetable pantry from production workshops, etc.).

The impact of dust on humans depends on the size of the dust particles and their specific gravity. The most dangerous dust particles for humans are those less than 1 micron in diameter, because... they easily penetrate the lungs and can cause chronic disease (pneumoconiosis). Dust containing admixtures of toxic chemical compounds has a toxic effect on the body.

The maximum permissible concentration for soot and soot is strictly standardized due to the content of carcinogenic hydrocarbons (PAHs): the average daily maximum concentration for soot is 0.05 mg/m3.

In high-power confectionery shops, the air may become dusty with sugar and flour dust. Flour dust in the form of aerosols can cause irritation of the respiratory tract, as well as allergic diseases. The maximum permissible concentration of flour dust in the work area should not exceed 6 mg/m3. Within these limits (2-6 mg/m3), maximum permissible concentrations of other types of plant dust containing no more than 0.2% of silicon compounds are regulated.

Air is natural mixture various gases. Most of all it contains elements such as nitrogen (about 77%) and oxygen, less than 2% are argon, carbon dioxide and other inert gases.

Oxygen, or O2, is the second element of the periodic table and the most important component, without which life on the planet would hardly exist. He participates in various processes, on which the vital activity of all living things depends.

Air composition

O2 performs the function oxidative processes in the human body, which allow you to release energy for normal life. At rest, the human body requires about 350 milliliters of oxygen, with heavy physical activity this value increases three to four times.

What percentage of oxygen is in the air we breathe? The norm is 20,95% . Exhaled air contains less O2 – 15.5-16%. The composition of exhaled air also includes carbon dioxide, nitrogen and other substances. A subsequent decrease in the percentage of oxygen leads to malfunction, and a critical value of 7-8% causes death.

From the table you can understand, for example, that exhaled air contains a lot of nitrogen and additional elements, but O2 only 16.3%. The oxygen content of the inhaled air is approximately 20.95%.

It is important to understand what an element such as oxygen is. O2 – the most common on earth chemical element, which is colorless, odorless and tasteless. It performs the most important function of oxidation in.

Without the eighth element of the periodic table you can't make fire. Dry oxygen improves the electrical and protective properties of films and reduces their volume charge.

This element is contained in the following compounds:

1. Silicates - they contain approximately 48% O2.
2. (sea and fresh) – 89%.
3. Air – 21%.
4. Other compounds in the earth's crust.

Air contains not only gaseous substances, but also vapors and aerosols, as well as various contaminants. This could be dust, dirt, or other various small debris. It contains microbes, which can cause various diseases. Flu, measles, whooping cough, allergens and other diseases are just a small list of negative consequences that appear when air quality deteriorates and the level of pathogenic bacteria increases.

The percentage of air is the amount of all the elements that make up it. It is more convenient to show clearly what air consists of, as well as the percentage of oxygen in the air, on a diagram.

The diagram shows which gas is found more in the air. The values ​​shown on it will be slightly different for inhaled and exhaled air.

Diagram - air ratio.

There are several sources from which oxygen is formed:

1. Plants. It is also known from a school biology course that plants release oxygen when they absorb carbon dioxide.
2. Photochemical decomposition of water vapor. The process is observed under the influence of solar radiation in the upper layer of the atmosphere.
3. Mixing of air flows in the lower atmospheric layers.

Functions of oxygen in the atmosphere and for the body

For a person, the so-called partial pressure, which the gas could produce if it occupied the entire occupied volume of the mixture. The normal partial pressure at 0 meters above sea level is 160 millimeters of mercury. An increase in altitude causes a decrease in partial pressure. This indicator is important, since the supply of oxygen to all important organs and to the body depends on it.

Oxygen is often used for the treatment of various diseases. Oxygen cylinders and inhalers help human organs function normally in the presence of oxygen starvation.

Important! The composition of air is influenced by many factors; accordingly, the percentage of oxygen may change. The negative environmental situation leads to deterioration in air quality. In megacities and large urban settlements, the proportion of carbon dioxide (CO2) will be greater than in small settlements or in forests and protected areas. Altitude also has a big influence - the percentage of oxygen will be lower in the mountains. You can consider the following example - on Mount Everest, which reaches a height of 8.8 km, the oxygen concentration in the air will be 3 times lower than in the lowlands. To stay safely at high mountain peaks, you need to use oxygen masks.

The composition of the air has changed over the years. Evolutionary processes and natural disasters led to changes in, therefore the percentage of oxygen has decreased, necessary for the normal functioning of biological organisms. Several historical stages can be considered:

1. Prehistoric era. At this time, the oxygen concentration in the atmosphere was about 36%.
2. 150 years ago O2 occupied 26% from the total air composition.
3. Currently, the oxygen concentration in the air is just under 21%.

Subsequent development of the surrounding world can lead to further changes in the composition of the air. In the near future, it is unlikely that the O2 concentration could be below 14%, as this would cause disruption of the body's functioning.

What does lack of oxygen lead to?

Low intake is most often observed in stuffy transport, poorly ventilated areas or at altitude . Decreased oxygen levels in the air can cause negative impact on the body. Mechanisms are depleted; the nervous system is most affected. There are several reasons why the body suffers from hypoxia:

1. Blood shortage. Called for carbon monoxide poisoning. This situation reduces the oxygen content of the blood. This is dangerous because the blood stops delivering oxygen to hemoglobin.
2. Circulatory deficiency. It's possible for diabetes, heart failure. In such a situation, blood transport worsens or becomes impossible.
3. Histotoxic factors affecting the body can cause loss of the ability to absorb oxygen. Arises in case of poisoning with poisons or due to exposure to severe...

A number of symptoms indicate that the body requires O2. First of all breathing rate increases. The heart rate also increases. These protective functions are designed to supply oxygen to the lungs and provide them with blood and tissue.

Lack of oxygen causes headaches, increased drowsiness, deterioration in concentration. Isolated cases are not so terrible; they are quite easy to correct. To normalize respiratory failure, the doctor prescribes bronchodilators and other medications. If hypoxia takes severe forms, such as loss of human coordination or even coma, then treatment becomes more complicated.

If symptoms of hypoxia are detected, it is important consult a doctor immediately and do not self-medicate, since the use of a particular drug depends on the causes of the disorder. Helps for mild cases treatment with oxygen masks and pillows, blood hypoxia requires blood transfusion, and correction of circular causes is possible only with surgery on the heart or blood vessels.

The incredible journey of oxygen through our body

Conclusion

Oxygen is the most important air component, without which it is impossible to carry out many processes on Earth. The air composition has changed over tens of thousands of years due to evolutionary processes, but currently the amount of oxygen in the atmosphere has reached in 21%. The quality of the air a person breathes affects his health Therefore, it is necessary to monitor its cleanliness in the room and try to reduce environmental pollution.

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 outline:

Chemical composition of atmospheric air.

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

The concept of atmospheric pollution and its sources.

Impact of atmospheric pollution on health (direct impact).

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

Issues of protecting 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 will be as follows:

Table No. 1

Composition of dry air at a temperature of 0 0 C and

pressure 760 mm Hg. Art.

The composition of the earth's atmosphere remains constant over land, over sea, in cities and in rural areas. It also does not change with height. It should be remembered that we are talking about the percentage of air components at different altitudes. However, the same cannot be said about the weight concentration of gases. As you rise upward, the density of the air 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 or combustion. Life is impossible in a nitrogen atmosphere.

Nitrogen plays an important biological role. Nitrogen in the air is absorbed by certain 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 are converted into nitrites under the influence of soil bacteria. Nitrites and ammonia salts are absorbed by plants and serve for the synthesis of proteins.

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

Due to the lack of nitrogenous fertilizers of natural origin, humanity has learned to obtain them artificially. A nitrogen fertilizer industry has been created and is developing, which processes atmospheric nitrogen into ammonia and nitrogen 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 nitrogen content in the air causes hypoxia and asphyxia due to a decrease in the partial pressure of oxygen.

When partial pressure increases, nitrogen exhibits narcotic properties. However, in open atmosphere conditions 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 is found in a free state only on Earth.

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

The biological role of oxygen is extremely great. Without oxygen, life is impossible. The Earth's atmosphere contains 1.18  10 15 tons of oxygen.

In nature, processes of oxygen consumption continuously occur: the respiration of humans and animals, the processes of combustion, oxidation. At the same time, processes of restoration of oxygen content in the air (photosynthesis) are continuously taking place. Plants absorb carbon dioxide, break it down, metabolize 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 oxygen content in cities and rural areas. The oxygen concentration fluctuates within a few tenths of a percent. It doesn't matter. However, in deep holes, wells, and caves, the oxygen content may drop, so descending into them is dangerous.

When the partial pressure of oxygen drops in humans and animals, phenomena of oxygen starvation are observed. Significant changes in the partial pressure of oxygen occur as you rise above sea level. Phenomena of oxygen deficiency can be observed during mountain climbing (mountain climbing, tourism), and during air travel. Climbing to an altitude of 3000m can cause altitude or mountain sickness.

When living in high mountains for a long time, people become accustomed to the lack of oxygen and acclimatization occurs.

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, and 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: it is high in spring and low in autumn. The ozone content depends on the latitude of the area: the closer to the equator, the lower it is. Ozone concentration has a diurnal variation: it reaches its maximum at noon.

Ozone concentration is unevenly distributed over altitude. 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 apart) to form atomic oxygen. Oxygen atoms recombine (combine) with oxygen molecules and form ozone (O3). 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 blocks the short-wavelength part of the solar radiation spectrum and 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-term ultraviolet radiation on all living things.

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

Ozone is brought into the lower layer of the atmosphere - the troposphere - from the stratosphere as a result of mixing air masses. With weak mixing, the ozone concentration at the earth's surface drops. 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 ozone concentration 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 a toxic substance. Ozone has an irritating effect on the mucous membranes of the eyes, nose, and throat at a concentration of 0.2-1 mg/m3.

Carbon dioxide (CO 2 ) is present in the atmosphere at a concentration of 0.03%. Its total quantity is 2330 billion tons. A large amount of carbon dioxide is found dissolved in the water of the seas and oceans. In bound form, it is 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, rotting, and fermentation. A person emits 580 liters of carbon dioxide per day. Large amounts of carbon dioxide are 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 (absorbed) by plants during the process of photosynthesis.

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

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

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

There is a certain amount in atmospheric 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 manifest themselves at high barometric pressure. In an open atmosphere, the narcotic properties of inert gases cannot manifest themselves.

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

Impurities that are present in the air other than its natural chemical composition are called atmospheric pollution.

Atmospheric pollution is divided into natural and artificial.

Natural pollution includes impurities entering the air as a result of spontaneous natural processes (plant and 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;

burning of garbage.

Let's look at their brief characteristics.

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

One car emits 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: railway, water and air. The total amount of emissions into the environment from all types of transport tends to continuously increase.

Industrial enterprises rank second after transport in terms of the degree of damage to the environment.

The most intensive pollutants of atmospheric air are enterprises of ferrous and non-ferrous metallurgy, petrochemical and coke-chemical industries, as well as enterprises producing building materials. 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, and 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 particulate matter, industry emits various gases into the air: sulfuric anhydride, carbon monoxide, nitrogen oxides, hydrogen sulfide, hydrocarbons, and radioactive gases.

Pollutants can remain 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 and take an active part in photochemical processes in the atmospheric air with the formation of toxic mists.

Massive air pollution is observed when solid and liquid fuels are burned at thermal power plants. They are the main sources of atmospheric 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.

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

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

The first toxic fog was recorded in Belgium in 1930. Several hundred people were injured and 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), and in 1971 – 28 thousand.

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

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

overall mortality rate from cardiovascular and respiratory diseases;

acute nonspecific morbidity of the upper respiratory tract;

chronic bronchitis;

bronchial asthma;

emphysema;

lung cancer;

decreased life expectancy and creative activity.

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

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

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

It includes:

reduction of general illumination;

reduction of ultraviolet radiation from the sun;

changes in climatic conditions;

deterioration of living conditions;

negative impact on green spaces;

negative impact on animals.

Air pollutants cause great damage to buildings, structures, and construction materials.

The total economic cost to the United States from air pollutants, including their impact on human health, building materials, metals, fabrics, leather, paper, paint, 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 to protect atmospheric air must 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;

Monitoring 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 internal state plan, interstate programs for the protection of atmospheric air are currently being developed and widely implemented.

The problem of air protection is being solved in a number of international organizations - WHO, UN, UNESCO and others.

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:

1. The troposphere.
2. Tropopause.
3. Stratosphere.
4. Stratopause.
5. Mesosphere and mesopause.
6. Thermosphere.
7. 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 Institute of Geography 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 most ancient (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 oxygen-free 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.