We all notice every time that after a thunderstorm the air smells pleasantly of freshness. From what does this happen? The fact is that after a thunderstorm, a large amount of a special gas, ozone, appears in the air. It is ozone that has such a gentle pleasant smell of freshness. Many companies involved in the production of household chemicals are trying to create products with the smell of rain, but still no one has succeeded. Everyone's perception of fresh air is different. So, the mechanism of the appearance of ozone in the air after a thunderstorm:

• in the air there are a large number of molecules of various gases;
• many gas molecules contain oxygen in their composition;
• as a result of the impact of a powerful electric charge of lightning on gas molecules, ozone appears in the air - a gas whose formula is represented by a molecule consisting of three oxygen atoms.

The reasons for the short preservation of fresh air after a thunderstorm

In general, unfortunately, this freshness does not last very long. Much depends on how strong and how long the thunderstorm was. We all know that the pleasant freshness of post-storm air fades after a while. This is due to the process of diffusion. The science of physics, and to some extent chemistry, is the study of this process. In simple terms, diffusion means the process of mixing substances, the mutual penetration of atoms of one substance into another. As a result of the diffusion process, the atoms of substances are mutually evenly distributed in a certain space, in a given volume. The ozone molecule is made up of three oxygen atoms. In the process of movement, the molecules of various gases collide and exchange atoms. As a result, molecules of oxygen, carbon dioxide, nitrogen and many other gases reappear.

• in the process of diffusion, gas molecules collide and exchange atoms;
• many different gases arise: nitrogen, oxygen, carbon dioxide and others;
• The concentration of ozone in the area where a thunderstorm occurred gradually decreases due to the even distribution of the available amount of gas in the atmosphere.

It is the process of diffusion that leads to this natural phenomenon.

“I love a thunderstorm at the beginning of May,” the famous poet exclaimed, identifying himself with that half of humanity that admires thunderstorms. The other half is terrified of them.

Which of them is right? By and large, this is not so important. From thunder and lightning, you can hide under the covers, or you can admire the violence of the elements. More important is what happens after the storm. Usually, after a downpour subsides, people pour out into the street and begin to inhale the “smell of a thunderstorm”, “the smell of freshness”, as it is usually called, with full breasts. In fact, at this moment everyone is breathing ordinary ozone, formed from lightning electrical discharges, breathing, breathing and ... causing significant damage to their health.

Ozone plays a dual role in the fate of mankind. On the one hand, he is a protector. If there were no ozone in the stratosphere surrounding our planet, the ultraviolet rays of the Sun would have incinerated all earthlings long ago. This "top" chemical element is sometimes simply referred to as "good" ozone.

A completely different role in the fate of mankind is played by the "lower" ozone, which is located near the earth (the so-called surface). This is "bad" ozone. I do not know who first said that ozone is useful, but this person is an unscrupulous liar, or just an uneducated charlatan. In fact, ozone is a very aggressive chemical compound, the strongest oxidizing agent. It causes very significant harm to the human body. Unfortunately, few people know about this.

The upper respiratory tract is primarily affected by ground-level ozone, since this substance irritates their mucous membrane, reacts sharply to ozone and bronchi, in severe cases, pulmonary edema is possible from the “fresh smell”. Some people who inhale ozone begin to have watery eyes, a sore throat, or a sudden cough, headache, and someone may subsequently develop allergic reactions. But almost no one connects their condition with the "smell of a thunderstorm."

In general, it is absolutely impossible to breathe ozone. On the contrary, during a thunderstorm and after it, doors and windows must be kept tightly closed so that not only some ball lightning does not fly into the house, but also post-storm ozone does not penetrate. Fortunately, this substance is volatile and quickly leaves the level of the human nose - it is enough to sit at home with a book for an hour and you can go outside.

However, a thunderstorm is not the main source of toxic ozone. This natural element does not happen so often, it passes quickly, and you can hide and wait out from thunderstorm ozone. Other malicious sources are much more dangerous. Some of them are not widely known, others are impossible to do...

The second source of dangerous ozone is a hundred-kilometer zone around large cities. That is, where summer cottages, suburban towns and villages are mainly located. During a heat wave, measuring instruments record a significant increase in the level of ground-level ozone here. In addition to specialists, almost no one knows about this, and summer residents do not even realize that they are slowly poisoning their bodies.

I understand that giving advice not to go to the dacha in extreme heat is a hopeless occupation. It is in the heat that everyone strives to go there. Then make your life in the country at least the safest. In the morning, long before the peak heat of the day sets in, close all the windows and doors in the house, make it an oasis of clean air so that you can periodically catch your breath from the ozone. You are on the street for no more than 1-2 hours, and then for the same time (and even more) go into the house. Anyone who has respiratory diseases, especially those diagnosed with bronchial asthma, as well as those suffering from cardiovascular diseases, should not go out at all in the heat. Ventilate the premises with the onset of coolness - in the evenings and at night. And plug again in the morning. And do not forget about the cracks, if they are in your house.

The third source of hazardous ground-level ozone is power lines (TL). Under no circumstances should you breathe “fresh air” under power lines. But with this, everything is simple - do not come, do not walk, do not live nearby.

The fourth generator of harmful ozone - devices for ozonizing the air in the apartment. With these devices, as well as with power lines, everything is also very simple - do not buy, do not use. But if you are fans of ozonation and consider it necessary to “refresh” your apartment, then at least follow the safety measures. While the appliance is working, the window must be open, and all citizens must leave the premises.

The fifth culprit of toxic ozone is the most dangerous, because the invincible, and also widespread, is household and office equipment. Achievements of technical progress every second spit out hefty portions of ozone to the right and left, and the worst thing is indoors, where it accumulates in high concentration.

Copiers and air cleaners are considered the most harmful, although other devices and units are also to some extent guilty. In addition to technical ozone in the premises packed with modern technology, there is a violation of the balance of air ions (charged particles). Devices in such rooms record constantly high rates of positively charged air ions harmful to human health. Together with technical ozone, an explosive mixture is obtained in general! But we can’t do anything about it yet, we won’t run back from progress. So again, you just have to minimize the risk of harm.

I think many, entering the supermarket, feel the specific smell of the same “freshness”. By the way, experts say that the smell of ozone already indicates the excess of safe concentrations of this substance. So do not walk for a long time in such a store, looking at the windows and goods. We made the necessary purchases - and ran from there.

With employees of supermarkets and offices, the situation is more complicated. According to statistics, in every fourth person in such places the body does not withstand the harmful effects. They have headache, dizziness or weakness - constant symptoms. The owners and managers of such enterprises should generally pay their employees extra money for harmfulness and do a shorter working day. But, alas...

I can only advise everyone who has respiratory diseases and, first of all, bronchial asthma, as well as those who constantly feel unwell - DO NOT WORK IN SUPERMARKETS AND OFFICES stuffed with appliances. Take pity on yourself - find another job.

air after a thunderstorm

A colorless gas with a pungent odor used to disinfect water and air

Oxygen option

A gas with a pungent odor, a combination of three oxygen atoms

Thunderstorm gas

A gas consisting of oxygen molecules with a modified structure

Gas used to purify air, water

Symbol of freshness, air after a thunderstorm

triatomic oxygen

Poisonous gas with a pungent odor, formed during electrical discharges from oxygen (O3 molecules)

The smell of freshness

Director of 8 Women

Allotropic modification of oxygen

French composer, director of the film "8 Women"

According to people who were present at nuclear tests, this smell accompanies all atomic explosions, but what does it smell like after an explosion, if this smell is also familiar to you?

What is the name of the gas, discovered in 1839 by the German chemist Christian Schönbein, for its characteristic smell, somewhat similar to the smell of bromine?

Gas in which mankind has made many holes

blue oxygen

Gas, which in Greek means "smelling"

. "leaky" atmospheric gas

Gas, a compound of three oxygen atoms

Directed the film "Eight Women"

Gas after lightning in the sky

Gas with a pungent odor

. "fresh air"

Gaz and Romanian trio

Gas used to purify water

Special form of oxygen

Gas in the atmosphere

Gas in a thunderstorm

Fresh smelling gas

. "leaky" gas

Triple Oxygen

Gas that purifies water

triple oxygen

Blue oxygen

Oxygen from three atoms

. "perforated" gas

Oxygen after lightning discharge

. thunderstorm scent

. "leaky" atmospheric gas

Gas with its holes in the atmosphere

. the "smell" of a thunderstorm

trivalent thunderstorm oxygen

What kind of gas smells like in a thunderstorm?

lightning gas

Oxygen

stormy freshness

Thunderstorm Gas

Gas born from lightning

Directed the film "Pool"

Three oxygen molecules

Inadequate thunderstorm oxygen

Gas perforating our atmosphere

Its layer is perforated in the atmosphere

gas in the atmosphere

Earth shirt

Thunderstorm smell

blue color gas

Gas permeating the atmosphere

odorous gas

Three oxygens at once

blue gas

Gives a scent to the air

. "material" for a hole

Three oxygen atoms

lightning gas

Gas, a compound of three oxygen atoms

A gas consisting of oxygen molecules with a modified structure

Allotropic modification of oxygen, a gas with a pungent odor

French filmmaker ("Raindrops on Hot Stones", "Under the Sand")

The physical properties of ozone are very characteristic: it is an easily exploding blue gas. A liter of ozone weighs approximately 2 grams, while air weighs 1.3 grams. Therefore, ozone is heavier than air. The melting point of ozone is minus 192.7ºС. This "melted" ozone is a dark blue liquid. Ozone "ice" has a dark blue color with a violet tint and becomes opaque at a thickness of more than 1 mm. The boiling point of ozone is minus 112ºС. In the gaseous state, ozone is diamagnetic, i.e. It does not have magnetic properties, and in the liquid state it is weakly paramagnetic. The solubility of ozone in melt water is 15 times greater than that of oxygen and is approximately 1.1 g/l. A liter of acetic acid dissolves 2.5 grams of ozone at room temperature. It also dissolves well in essential oils, turpentine, carbon tetrachloride. The smell of ozone is felt at concentrations above 15 µg/m3 of air. In minimal concentrations, it is perceived as a "smell of freshness", in higher concentrations it acquires a sharp irritating tinge.

Ozone is formed from oxygen according to the following formula: 3O2 + 68 kcal → 2O3. Classical examples of ozone formation: under the action of lightning during a thunderstorm; exposed to sunlight in the upper atmosphere. Ozone can also be formed during any processes accompanied by the release of atomic oxygen, for example, during the decomposition of hydrogen peroxide. The industrial synthesis of ozone is associated with the use of electrical discharges at low temperatures. Technologies for producing ozone may differ from each other. So, to obtain ozone used for medical purposes, only pure (without impurities) medical oxygen is used. The separation of the formed ozone from the oxygen impurity is usually not difficult due to differences in physical properties (ozone liquefies more easily). If certain qualitative and quantitative parameters of the reaction are not required, then obtaining ozone does not present any particular difficulties.

The O3 molecule is unstable and rather quickly turns into O2 with the release of heat. At low concentrations and without foreign impurities, ozone decomposes slowly, at high concentrations - with an explosion. Alcohol on contact with it instantly ignites. Heating and contact of ozone with even negligible amounts of the oxidation substrate (organic substances, some metals or their oxides) sharply accelerates its decomposition. Ozone can be stored for a long time at -78ºС in the presence of a stabilizer (a small amount of HNO3), as well as in vessels made of glass, some plastics or precious metals.

Ozone is the strongest oxidizing agent. The reason for this phenomenon lies in the fact that in the process of decay, atomic oxygen is formed. Such oxygen is much more aggressive than molecular oxygen, because in the oxygen molecule the deficit of electrons at the outer level due to their collective use of the molecular orbital is not so noticeable.

Back in the 18th century, it was noticed that mercury in the presence of ozone loses its luster and sticks to glass; oxidized. And when ozone is passed through an aqueous solution of potassium iodide, gaseous iodine begins to be released. The same "tricks" with pure oxygen did not work. Subsequently, the properties of ozone were discovered, which were immediately adopted by mankind: ozone turned out to be an excellent antiseptic, ozone quickly removed organic substances of any origin from water (perfumes and cosmetics, biological fluids), became widely used in industry and everyday life, and has proven itself in as an alternative to a dental drill.

In the 21st century, the use of ozone in all areas of human life and activity is growing and developing, and therefore we are witnessing its transformation from exotic into a familiar tool for everyday work. OZONE O3, an allotropic form of oxygen.

Obtaining and physical properties of ozone.

Scientists first became aware of the existence of an unknown gas when they began experimenting with electrostatic machines. It happened in the 17th century. But they began to study the new gas only at the end of the next century. In 1785, the Dutch physicist Martin van Marum created ozone by passing electrical sparks through oxygen. The name ozone appeared only in 1840; it was invented by the Swiss chemist Christian Schönbein, deriving it from the Greek ozon, smelling. The chemical composition of this gas did not differ from oxygen, but was much more aggressive. So, he instantly oxidized colorless potassium iodide with the release of brown iodine; Shenbein used this reaction to determine ozone by the degree of blueness of paper impregnated with a solution of potassium iodide and starch. Even mercury and silver, which are inactive at room temperature, oxidize in the presence of ozone.

It turned out that ozone molecules, like oxygen, consist only of oxygen atoms, only not of two, but of three. Oxygen O2 and ozone O3 are the only example of the formation of two gaseous (under normal conditions) simple substances by one chemical element. In the O3 molecule, the atoms are located at an angle, so these molecules are polar. Ozone is produced as a result of “sticking” to O2 molecules of free oxygen atoms, which are formed from oxygen molecules under the action of electrical discharges, ultraviolet rays, gamma rays, fast electrons and other high-energy particles. Ozone always smells near working electric machines, in which brushes “sparkle”, near bactericidal mercury-quartz lamps that emit ultraviolet radiation. Oxygen atoms are also released during some chemical reactions. Ozone is formed in small quantities during the electrolysis of acidified water, during the slow oxidation of wet white phosphorus in air, during the decomposition of compounds with a high oxygen content (KMnO4, K2Cr2O7, etc.), under the action of fluorine on water or on barium peroxide of concentrated sulfuric acid. Oxygen atoms are always present in a flame, so if you direct a stream of compressed air across the flame of an oxygen burner, the characteristic smell of ozone will be found in the air.

The reaction 3O2 → 2O3 is highly endothermic: 142 kJ must be spent to produce 1 mole of ozone. The reverse reaction proceeds with the release of energy and is carried out very easily. Accordingly, ozone is unstable. In the absence of impurities, gaseous ozone decomposes slowly at a temperature of 70°C and quickly above 100°C. The rate of ozone decomposition increases significantly in the presence of catalysts. They can be gases (for example, nitric oxide, chlorine), and many solid substances (even vessel walls). Therefore, pure ozone is difficult to obtain, and working with it is dangerous due to the possibility of an explosion.

It is not surprising that for many decades after the discovery of ozone, even its basic physical constants were unknown: for a long time no one managed to obtain pure ozone. As D.I. Mendeleev wrote in his textbook Fundamentals of Chemistry, “with all methods of preparing gaseous ozone, its content in oxygen is always insignificant, usually only a few tenths of a percent, rarely 2%, and only at very low temperatures does it reach 20%.” Only in 1880, the French scientists J. Gotfeil and P. Chappui obtained ozone from pure oxygen at a temperature of minus 23 ° C. It turned out that in a thick layer ozone has a beautiful blue color. When the cooled ozonated oxygen was slowly compressed, the gas turned dark blue, and after the rapid release of pressure, the temperature dropped even more and dark purple liquid ozone droplets formed. If the gas was not cooled or compressed quickly, then the ozone instantly, with a yellow flash, turned into oxygen.

Later, a convenient method for the synthesis of ozone was developed. If a concentrated solution of perchloric, phosphoric or sulfuric acid is subjected to electrolysis with a cooled anode made of platinum or lead(IV) oxide, then the gas released at the anode will contain up to 50% ozone. The physical constants of ozone were also refined. It liquefies much lighter than oxygen - at a temperature of -112 ° C (oxygen - at -183 ° C). At -192.7 ° C, ozone solidifies. Solid ozone is blue-black in color.

Experiments with ozone are dangerous. Gaseous ozone is capable of exploding if its concentration in the air exceeds 9%. Liquid and solid ozone explode even more easily, especially when in contact with oxidizing substances. Ozone can be stored at low temperatures in the form of solutions in fluorinated hydrocarbons (freons). These solutions are blue in color.

Chemical properties of ozone.

Ozone is characterized by an extremely high reactivity. Ozone is one of the strongest oxidizing agents and is inferior in this respect only to fluorine and oxygen fluoride OF2. The active principle of ozone as an oxidizing agent is atomic oxygen, which is formed during the decay of the ozone molecule. Therefore, acting as an oxidizing agent, the ozone molecule, as a rule, “uses” only one oxygen atom, while the other two are released in the form of free oxygen, for example, 2KI + O3 + H2O → I2 + 2KOH + O2. Many other compounds are oxidized in the same way. However, there are exceptions when the ozone molecule uses all three oxygen atoms it has for oxidation, for example, 3SO2 + O3 → 3SO3; Na2S + O3 → Na2SO3.

A very important difference between ozone and oxygen is that ozone exhibits oxidizing properties even at room temperature. For example, PbS and Pb(OH)2 do not react with oxygen under normal conditions, while in the presence of ozone the sulfide is converted to PbSO4, and the hydroxide to PbO2. If a concentrated solution of ammonia is poured into a vessel with ozone, white smoke will appear - this ozone has oxidized ammonia to form ammonium nitrite NH4NO2. Especially characteristic of ozone is the ability to “blacken” silver items with the formation of AgO and Ag2O3.

By attaching one electron and turning into a negative ion O3-, the ozone molecule becomes more stable. "Ozonate salts" or ozonides containing such anions have been known for a long time - they are formed by all alkali metals except lithium, and the stability of ozonides increases from sodium to cesium. Some ozonides of alkaline earth metals are also known, for example Ca(O3)2. If a stream of gaseous ozone is directed to the surface of a solid dry alkali, an orange-red crust is formed containing ozonides, for example, 4KOH + 4O3 → 4KO3 + O2 + 2H2O. At the same time, solid alkali effectively binds water, which prevents ozonide from immediate hydrolysis. However, with an excess of water, ozonides rapidly decompose: 4KO3 + 2H2O → 4KOH + 5O2. Decomposition also occurs during storage: 2KO3 → 2KO2 + O2. Ozonides are highly soluble in liquid ammonia, which made it possible to isolate them in their pure form and study their properties.

Organic substances that ozone comes into contact with, it usually destroys. So, ozone, unlike chlorine, is able to split the benzene ring. When working with ozone, you can not use rubber tubes and hoses - they will instantly “leak out”. Ozone reacts with organic compounds with the release of a large amount of energy. For example, ether, alcohol, cotton wool moistened with turpentine, methane and many other substances ignite spontaneously when in contact with ozonated air, and mixing ozone with ethylene leads to a strong explosion.

The use of ozone.

Ozone does not always "burn" organic matter; in a number of cases it is possible to carry out specific reactions with highly dilute ozone. For example, ozonation of oleic acid (it is found in large quantities in vegetable oils) produces azelaic acid HOOC(CH2)7COOH, which is used to produce high-quality lubricating oils, synthetic fibers, and plasticizers for plastics. Similarly, adipic acid is obtained, which is used in the synthesis of nylon. In 1855, Schönbein discovered the reaction of unsaturated compounds containing C=C double bonds with ozone, but it was not until 1925 that the German chemist H. Staudinger established the mechanism of this reaction. The ozone molecule joins the double bond with the formation of ozonide - this time organic, and in place of one of the C \u003d C bonds there is an oxygen atom, and in place of the other - the -O-O- group. Although some organic ozonides have been isolated in pure form (for example, ethylene ozonide), this reaction is usually carried out in dilute solution, since ozonides in the free state are very unstable explosives. The ozonation reaction of unsaturated compounds enjoys great respect among organic chemists; problems with this reaction are often offered even at school olympiads. The fact is that when the ozonide is decomposed by water, two molecules of aldehyde or ketone are formed, which are easy to identify and further establish the structure of the original unsaturated compound. Thus, at the beginning of the 20th century, chemists established the structure of many important organic compounds, including natural ones, containing C=C bonds.

An important field of application of ozone is the disinfection of drinking water. Usually the water is chlorinated. However, some impurities in the water under the action of chlorine are converted into compounds with a very unpleasant odor. Therefore, it has long been proposed to replace chlorine with ozone. Ozonated water does not acquire foreign smell or taste; when many organic compounds are completely oxidized with ozone, only carbon dioxide and water are formed. Purify with ozone and waste water. The products of ozone oxidation even of such pollutants as phenols, cyanides, surfactants, sulfites, chloramines are harmless compounds without color and odor. Excess ozone quickly decomposes with the formation of oxygen. However, water ozonation is more expensive than chlorination; in addition, ozone cannot be transported and must be produced on site.

Ozone in the atmosphere.

There is not much ozone in the Earth's atmosphere - 4 billion tons, i.e. on average only 1 mg/m3. The concentration of ozone increases with distance from the Earth's surface and reaches a maximum in the stratosphere, at an altitude of 20-25 km - this is the "ozone layer". If all the ozone from the atmosphere is collected near the Earth's surface at normal pressure, a layer only about 2-3 mm thick will be obtained. And such small amounts of ozone in the air actually provide life on Earth. Ozone creates a "protective screen" that does not allow the harsh ultraviolet rays of the sun to reach the Earth's surface, which are detrimental to all living things.

In recent decades, much attention has been paid to the emergence of so-called "ozone holes" - areas with a significantly reduced content of stratospheric ozone. Through such a "leaky" shield, the harder ultraviolet radiation of the Sun reaches the Earth's surface. Therefore, scientists have been monitoring the ozone in the atmosphere for a long time. In 1930, the English geophysicist S. Chapman proposed a scheme of four reactions to explain the constant concentration of ozone in the stratosphere (these reactions are called the Chapman cycle, in which M means any atom or molecule that carries away excess energy):

O + O + M → O2 + M

O + O3 → 2O2

O3 → O2 + O.

The first and fourth reactions of this cycle are photochemical, they are under the influence of solar radiation. For the decomposition of an oxygen molecule into atoms, radiation with a wavelength of less than 242 nm is required, while ozone decays when light is absorbed in the region of 240-320 nm (the latter reaction just protects us from hard ultraviolet, since oxygen does not absorb in this spectral region) . The remaining two reactions are thermal, i.e. go without the action of light. It is very important that the third reaction leading to the disappearance of ozone has an activation energy; this means that the rate of such a reaction can be increased by the action of catalysts. As it turned out, the main catalyst for ozone decay is nitric oxide NO. It is formed in the upper atmosphere from nitrogen and oxygen under the action of the most severe solar radiation. Once in the ozonosphere, it enters a cycle of two reactions O3 + NO → NO2 + O2, NO2 + O → NO + O2, as a result of which its content in the atmosphere does not change, and the stationary ozone concentration decreases. There are other cycles leading to a decrease in the ozone content in the stratosphere, for example, with the participation of chlorine:

Cl + O3 → ClO + O2

ClO + O → Cl + O2.

Ozone is also destroyed by dust and gases, which in large quantities enter the atmosphere during volcanic eruptions. Recently, it has been suggested that ozone is also effective in destroying hydrogen released from the earth's crust. The totality of all reactions of formation and decay of ozone leads to the fact that the average lifetime of an ozone molecule in the stratosphere is about three hours.

It is assumed that in addition to natural, there are also artificial factors affecting the ozone layer. A well-known example is freons, which are sources of chlorine atoms. Freons are hydrocarbons in which hydrogen atoms are replaced by fluorine and chlorine atoms. They are used in refrigeration and for filling aerosol cans. Ultimately, freons get into the air and slowly rise higher and higher with air currents, finally reaching the ozone layer. Decomposing under the action of solar radiation, freons themselves begin to catalytically decompose ozone. It is not yet known exactly to what extent freons are to blame for the "ozone holes", and, nevertheless, measures have long been taken to limit their use.

Calculations show that in 60-70 years the ozone concentration in the stratosphere can decrease by 25%. And at the same time, the concentration of ozone in the surface layer - the troposphere, will increase, which is also bad, since ozone and the products of its transformations in the air are poisonous. The main source of ozone in the troposphere is the transfer of stratospheric ozone with air masses to the lower layers. Approximately 1.6 billion tons enter the ground layer of ozone annually. The lifetime of an ozone molecule in the lower part of the atmosphere is much longer - more than 100 days, since in the surface layer there is less intensity of ultraviolet solar radiation that destroys ozone. Usually, there is very little ozone in the troposphere: in clean fresh air, its concentration averages only 0.016 μg / l. The concentration of ozone in the air depends not only on altitude, but also on the terrain. Thus, there is always more ozone over the oceans than over land, since ozone decays more slowly there. Measurements in Sochi showed that the air near the sea coast contains 20% more ozone than in the forest 2 km from the coast.

Modern humans breathe much more ozone than their ancestors. The main reason for this is the increase in the amount of methane and nitrogen oxides in the air. Thus, the content of methane in the atmosphere has been constantly growing since the middle of the 19th century, when the use of natural gas began. In an atmosphere polluted with nitrogen oxides, methane enters a complex chain of transformations involving oxygen and water vapor, the result of which can be expressed by the equation CH4 + 4O2 → HCHO + H2O + 2O3. Other hydrocarbons can also act as methane, for example, those contained in the exhaust gases of cars during the incomplete combustion of gasoline. As a result, in the air of large cities over the past decades, the concentration of ozone has increased tenfold.

It has always been believed that during a thunderstorm, the concentration of ozone in the air increases dramatically, since lightning contributes to the conversion of oxygen into ozone. In fact, the increase is insignificant, and it does not occur during a thunderstorm, but several hours before it. During a thunderstorm and for several hours after it, the concentration of ozone decreases. This is explained by the fact that before a thunderstorm there is a strong vertical mixing of air masses, so that an additional amount of ozone comes from the upper layers. In addition, before a thunderstorm, the electric field strength increases, and conditions are created for the formation of a corona discharge at the points of various objects, for example, the tips of branches. It also contributes to the formation of ozone. And then, with the development of a thundercloud, powerful ascending air currents arise under it, which reduce the ozone content directly under the cloud.

An interesting question is about the ozone content in the air of coniferous forests. For example, in the Course of Inorganic Chemistry by G. Remy, one can read that “ozonized air of coniferous forests” is a fiction. Is it so? No plant emits ozone, of course. But plants, especially conifers, emit a lot of volatile organic compounds into the air, including unsaturated hydrocarbons of the terpene class (there are a lot of them in turpentine). So, on a hot day, a pine tree releases 16 micrograms of terpenes per hour for every gram of dry weight of needles. Terpenes are distinguished not only by conifers, but also by some deciduous trees, among which are poplar and eucalyptus. And some tropical trees are able to release 45 micrograms of terpenes per 1 g of dry leaf mass per hour. As a result, one hectare of coniferous forest can release up to 4 kg of organic matter per day, and about 2 kg of deciduous forest. The forested area of ​​the Earth is millions of hectares, and all of them release hundreds of thousands of tons of various hydrocarbons, including terpenes, per year. And hydrocarbons, as was shown in the example of methane, under the influence of solar radiation and in the presence of other impurities contribute to the formation of ozone. Experiments have shown that, under suitable conditions, terpenes are indeed very actively involved in the cycle of atmospheric photochemical reactions with the formation of ozone. So ozone in a coniferous forest is not an invention at all, but an experimental fact.

Ozone and health.

What a pleasure to take a walk after a thunderstorm! The air is clean and fresh, its invigorating jets seem to flow into the lungs without any effort. “It smells like ozone,” they often say in such cases. “Very good for health.” Is it so?

Once upon a time, ozone was certainly considered beneficial to health. But if its concentration exceeds a certain threshold, it can cause a lot of unpleasant consequences. Depending on the concentration and time of inhalation, ozone causes changes in the lungs, irritation of the mucous membranes of the eyes and nose, headache, dizziness, lowering blood pressure; ozone reduces the body's resistance to bacterial infections of the respiratory tract. Its maximum permissible concentration in the air is only 0.1 µg/l, which means that ozone is much more dangerous than chlorine! If you spend several hours indoors with an ozone concentration of only 0.4 μg / l, chest pains, coughing, insomnia may appear, visual acuity decreases. If you breathe in ozone for a long time at a concentration of more than 2 μg / l, the consequences can be more severe - up to stupor and a decline in cardiac activity. With an ozone content of 8-9 µg/l, pulmonary edema occurs after a few hours, which is fraught with death. But such negligible amounts of a substance are usually difficult to analyze by conventional chemical methods. Fortunately, a person feels the presence of ozone already at very low concentrations - about 1 μg / l, at which starch iodine paper is not going to turn blue. To some people, the smell of ozone in small concentrations resembles the smell of chlorine, to others - to sulfur dioxide, to others - to garlic.

It's not just ozone itself that's poisonous. With its participation in the air, for example, peroxyacetyl nitrate (PAN) CH3-CO-OONO2 is formed - a substance that has a strong irritant, including tear, effect that makes breathing difficult, and in higher concentrations causes heart paralysis. PAN is one of the components of the so-called photochemical smog formed in summer in polluted air (this word is derived from the English smoke - smoke and fog - fog). The concentration of ozone in smog can reach 2 μg/l, which is 20 times higher than the maximum allowable. It should also be taken into account that the combined effect of ozone and nitrogen oxides in the air is ten times stronger than each substance separately. Not surprisingly, the consequences of such smog in large cities can be catastrophic, especially if the air above the city is not blown by "drafts" and a stagnant zone forms. So, in London in 1952, more than 4,000 people died from smog within a few days. A smog in New York in 1963 killed 350 people. Similar stories were in Tokyo and other major cities. Not only people suffer from atmospheric ozone. American researchers have shown, for example, that in areas with a high content of ozone in the air, the service life of car tires and other rubber products is significantly reduced.

How to reduce the ozone content in the ground layer? Reducing methane emissions into the atmosphere is hardly realistic. There remains another way - to reduce emissions of nitrogen oxides, without which the cycle of reactions leading to ozone cannot go. This path is also not easy, since nitrogen oxides are emitted not only by cars, but also (mainly) by thermal power plants.

Ozone sources are not only on the street. It is formed in x-ray rooms, in physiotherapy rooms (its source is mercury-quartz lamps), during the operation of copiers (copiers), laser printers (here the reason for its formation is a high-voltage discharge). Ozone is an inevitable companion for the production of perhydrol, argon arc welding. To reduce the harmful effects of ozone, it is necessary to equip the hood with ultraviolet lamps, good ventilation of the room.

And yet, it is hardly correct to consider ozone, of course, harmful to health. It all depends on its concentration. Studies have shown that fresh air glows very weakly in the dark; the cause of the glow is an oxidation reaction involving ozone. Glow was also observed when water was shaken in a flask, into which ozonized oxygen was preliminarily filled. This glow is always associated with the presence of small amounts of organic impurities in the air or water. When mixing fresh air with an exhaled person, the intensity of the glow increased tenfold! And this is not surprising: microimpurities of ethylene, benzene, acetaldehyde, formaldehyde, acetone, and formic acid were found in the exhaled air. They are "highlighted" by ozone. At the same time, "stale", i.e. Completely devoid of ozone, although very clean, the air does not cause a glow, and a person feels it as "stale". Such air can be compared to distilled water: it is very pure, contains practically no impurities, and it is harmful to drink it. So the complete absence of ozone in the air, apparently, is also unfavorable for humans, since it increases the content of microorganisms in it, leads to the accumulation of harmful substances and unpleasant odors, which ozone destroys. Thus, it becomes clear the need for regular and long-term ventilation of the premises, even if there are no people in it: after all, the ozone that has entered the room does not linger in it for a long time - it partially decomposes, and largely settles (adsorbs) on the walls and other surfaces. It is difficult to say how much ozone should be in the room. However, in minimal concentrations, ozone is probably necessary and beneficial.

Thus, ozone is a time bomb. If it is used correctly, it will serve humanity, but as soon as it is used for other purposes, it will instantly lead to a global catastrophe and the Earth will turn into a planet like Mars.