What do cars emit into the atmosphere? What is in car exhaust? Hydrocarbons and organic oils

A small educational program for lovers to breathe out exhaust pipe.

The exhaust gases of internal combustion engines contain about 200 components. The period of their existence lasts from a few minutes to 4-5 years. According to the chemical composition and properties, as well as the nature of the impact on the human body, they are combined into groups.

First group. It includes non-toxic substances (natural components of atmospheric air

Second group. This group includes only one substance - carbon monoxide, or carbon monoxide (CO). The product of incomplete combustion of petroleum fuels is colorless and odorless, lighter than air. In oxygen and in air, carbon monoxide burns with a bluish flame, releasing a lot of heat and turning into carbon dioxide.

Carbon monoxide has a pronounced toxic effect. It is due to its ability to react with blood hemoglobin, leading to the formation of carboxyhemoglobin, which does not bind oxygen. As a result, gas exchange in the body is disturbed, oxygen starvation appears and there is a violation of the functioning of all body systems.

Car drivers are often exposed to carbon monoxide poisoning. Vehicle when spending the night in the cab with the engine running or when the engine is warming up in a closed garage. The nature of carbon monoxide poisoning depends on its concentration in the air, the duration of exposure and the individual susceptibility of a person. A mild degree of poisoning causes a throbbing in the head, darkening of the eyes, increased heart rate. In severe poisoning, consciousness becomes clouded, drowsiness increases. At very high doses of carbon monoxide (over 1%), loss of consciousness and death occur.

Third group. It contains nitrogen oxides, mainly NO - nitrogen oxide and NO 2 - nitrogen dioxide. These are gases formed in the combustion chamber of an internal combustion engine at a temperature of 2800 ° C and a pressure of about 10 kgf / cm 2. Nitric oxide is a colorless gas, does not interact with water and is slightly soluble in it, does not react with solutions of acids and alkalis.

Easily oxidized by atmospheric oxygen and forms nitrogen dioxide. Under normal atmospheric conditions, NO is completely converted into NO 2 - a brown-colored gas with a characteristic odor. It is heavier than air, therefore it collects in depressions, ditches and is a great danger during vehicle maintenance.

For the human body, nitrogen oxides are even more harmful than carbon monoxide. The general nature of exposure varies depending on the content of various nitrogen oxides. Upon contact of nitrogen dioxide with a wet surface (mucous membranes of the eyes, nose, bronchi), nitric and nitrous acids are formed, which irritate the mucous membranes and affect the alveolar tissue of the lungs. At high concentrations of nitrogen oxides (0.004 - 0.008%), asthmatic manifestations and pulmonary edema occur.

Inhaling air containing nitrogen oxides in high concentrations, a person does not have unpleasant sensations and does not imply negative consequences. With prolonged exposure to nitrogen oxides in concentrations exceeding the norm, people get chronic bronchitis, inflammation of the mucosa of the gastrointestinal tract, suffer from heart failure, and nervous disorders.

A secondary reaction to the effects of nitrogen oxides is manifested in the formation of nitrites in the human body and their absorption into the blood. This causes the conversion of hemoglobin to metahemoglobin, which leads to a violation of cardiac activity.

Nitrogen oxides also have a negative effect on vegetation, forming solutions of nitric and nitrous acids on leaf plates. The same property determines the effect of nitrogen oxides on building materials and metal structures. In addition, they are involved in the photochemical reaction of smog formation.

Fourth group. This most numerous group includes various hydrocarbons, that is, compounds of the C x H y type. The exhaust gases contain hydrocarbons of various homologous series: paraffinic (alkanes), naphthenic (cyclanes) and aromatic (benzene), about 160 components in total. They are formed as a result of incomplete combustion of fuel in the engine.

Unburned hydrocarbons are one of the causes of white or blue smoke. This happens when ignition is delayed. working mixture in the engine or at low temperatures in the combustion chamber.

Hydrocarbons are toxic and have an adverse effect on the human cardiovascular system. Hydrocarbon compounds of exhaust gases, along with toxic properties, have a carcinogenic effect. Carcinogens are substances that contribute to the emergence and development of malignant neoplasms.

The aromatic hydrocarbon benz-a-pyrene C 20 H 12 contained in the exhaust gases is distinguished by a special carcinogenic activity. gasoline engines and diesels. It dissolves well in oils, fats, human blood serum. Accumulating in the human body to dangerous concentrations, benz-a-pyrene stimulates the formation of malignant tumors.

Hydrocarbons under the influence of ultraviolet radiation from the Sun react with nitrogen oxides, resulting in the formation of new toxic products - photooxidants, which are the basis of "smog".

Photooxidants are biologically active, have a harmful effect on living organisms, lead to the growth of pulmonary and bronchial diseases in humans, destroy rubber products, accelerate the corrosion of metals, and worsen visibility conditions.

Fifth group. It is made up of aldehydes. organic compounds containing an aldehyde group -CHO associated with a hydrocarbon radical (CH 3, C 6 H 5 or others).

Exhaust gases contain mainly formaldehyde, acrolein and acetaldehyde. The largest number aldehydes is formed in the modes idle move and small loads when combustion temperatures in the engine are low.

Formaldehyde HCHO is a colorless gas with bad smell, heavier than air, easily soluble in water. It irritates human mucous membranes, respiratory tract, affects the central nervous system. Causes the smell of exhaust gases, especially in diesel engines.

Acrolein CH 2 \u003d CH-CH \u003d O, or acrylic acid aldehyde, - colorless poisonous gas with the smell of burnt fats. It has an effect on the mucous membranes.

Acetic aldehyde CH 3 CHO is a gas with a pungent odor and a toxic effect on the human body.

Sixth group. Soot and other dispersed particles (engine wear products, aerosols, oils, soot, etc.) are released into it. Soot is black solid carbon particles formed during incomplete combustion and thermal decomposition of fuel hydrocarbons. It does not pose an immediate danger to human health, but may irritate the respiratory tract. By creating a smoky plume behind the vehicle, soot impairs visibility on the roads. The greatest harm of soot lies in the adsorption of benzo-a-pyrene on its surface, which in this case has a stronger negative effect on the human body than in its pure form.

Seventh group. It is a sulfur compound - inorganic gases such as sulfur dioxide, hydrogen sulfide, which appear in the exhaust gases of engines if fuel with a high sulfur content is used. Significantly more sulfur is present in diesel fuels compared to other types of fuels used in transport.

Domestic oil fields (especially in the eastern regions) are characterized by a high percentage of the presence of sulfur and sulfur compounds. Therefore, diesel fuel obtained from it using outdated technologies has a heavier fractional composition and, at the same time, is less purified from sulfur and paraffin compounds. According to European standards put into effect in 1996, the sulfur content in diesel fuel should not exceed 0.005 g/l, and according to the Russian standard - 1.7 g/l. The presence of sulfur increases the toxicity of diesel exhaust gases and is the cause of the appearance of harmful sulfur compounds in them.

Sulfur compounds have a pungent odor, are heavier than air, and dissolve in water. They irritate the mucous membranes of the throat, nose, eyes of a person, can lead to a violation of carbohydrate and protein metabolism and inhibition of oxidative processes, at high concentrations (over 0.01%) - to poisoning of the body. Sulfur dioxide also has a detrimental effect on the plant world.

Eighth group. The components of this group - lead and its compounds - are found in exhaust gases. carbureted cars only when using leaded gasoline, which contains an additive that increases octane number. It determines the engine's ability to run without detonation. The higher the octane number, the more resistant the gasoline is to knocking. Detonation combustion of the working mixture proceeds at supersonic speed, which is 100 times faster than normal. The operation of the engine with detonation is dangerous because the engine overheats, its power drops, and the service life is sharply reduced. Increasing the octane number of gasoline helps to reduce the possibility of detonation.

As an additive that increases the octane number, an antiknock agent is used - ethyl liquid R-9. Gasoline with the addition of ethyl liquid becomes leaded. The composition of the ethyl liquid includes the antiknock itself - tetraethyl lead Pb (C 2 H 5) 4, the scavenger - ethyl bromide (BrC 2 H 5) and α-monochloronaphthalene (C 10 H 7 Cl), the filler - B-70 gasoline, the antioxidant - paraoxydiphenylamine and dye. During the combustion of leaded gasoline, the scavenger helps to remove lead and its oxides from the combustion chamber, turning them into a vapor state. They, together with the exhaust gases, are released into the surrounding area and settle near the roads.

In roadside areas, approximately 50% of particulate lead emissions are immediately distributed to the adjacent surface. The rest is in the air in the form of aerosols for several hours, and then is also deposited on the ground near roads. The accumulation of lead in the roadside leads to pollution of ecosystems and makes nearby soils unsuitable for agricultural use.

The addition of R-9 additive to gasoline makes it highly toxic. Different grades of gasoline have different percentages of additives. To distinguish brands of leaded gasoline, they are colored by adding multi-colored dyes to the additive. Unleaded gasoline is supplied uncolored (Table 9).

In the developed world, the use of leaded gasoline is limited or has already been completely discontinued. In Russia, it is still widely used. However, the goal is to stop using it. Large industrial centers and resort areas are switching to the use of unleaded gasoline.

Ecosystems are negatively impacted not only by the considered components of engine exhaust gases, divided into eight groups, but also by hydrocarbon fuels, oils and lubricants themselves. Possessing a great ability to evaporate, especially when the temperature rises, vapors of fuels and oils spread in the air and adversely affect living organisms.

Accidental spills and intentional discharges of used oil directly onto the ground or into bodies of water occur at fuel and oil refueling sites. Vegetation does not grow in place of the oil spot for a long time. Oil products that have fallen into water bodies have a detrimental effect on their flora and fauna.

Now, thanks to the media, the planet is under the close attention of the public, namely its saturation and pollution with car exhaust gases. With particular attention, people monitor and discuss such a by-product of widespread motorization, circulated in the press, as the "greenhouse effect" and harm exhaust gases diesel cars.

However, as exhaust gases are known, exhaust gases are different, despite the fact that they are all dangerous to the human body and other life forms on Earth. So what makes them dangerous? And what makes them different from each other? Let's look under a microscope of what the blue smog flying out of the exhaust pipe consists of. Carbon dioxide, soot, nitric oxide and some other equally dangerous elements.

Scientists note that the environmental situation in many industrialized and developing countries has improved significantly over the past 25 years. This is mainly due to the gradual but inevitable tightening environmental standards, as well as the transfer of production to other continents and other countries, including East Asia. In Russia, Ukraine, and other CIS countries, a large number of enterprises were closed due to political and economic upheavals, which on the one hand created an extremely difficult socio-economic environment, but greatly improved the environmental performance of these countries.

However, according to research scientists, it is cars that pose the greatest danger to our green planet. Even with a gradual tightening of the standards for emissions of harmful substances into the atmosphere, due to an increase in the number of cars, the results of this work, alas, are leveled.

If segmented total weight a variety of vehicles now present on the planet remain the dirtiest, especially dangerous cars with this type of fuel in excess of nitrogen oxide. Despite decades of development and assurances from automakers that they can make diesels cleaner, nitrous oxide and fine soot remain diesel's biggest enemy.

It is in connection with these problems associated with the use diesel engines, major German cities such as Stuttgart and Munich are currently discussing a ban on heavy fuel vehicles.

Here is a comprehensive list of harmful substances in exhaust gases and the harm caused to human health when they are inhaled.

Traffic fumes

Off-gases are gaseous wastes generated during the conversion of liquid hydrocarbon fuel into the energy on which the internal combustion engine runs by combustion.

Benzene

Benzene is found in small amounts in gasoline. Colorless, transparent, easily mobile liquid.

As soon as you fill your car's tank with gasoline, the first thing you'll come into contact with is the benzene that evaporates from the tank. But the most dangerous is benzene during fuel combustion.

Benzene is one of those substances that can cause cancer in humans. However, a decisive reduction in airborne hazardous benzene was achieved many years ago with a three-way catalyst.

Fine dust (solid particles)

This air pollutant is an undefined substance. It is better to say that it is a complex mixture of substances, which may differ in origin, form and chemical composition.

In cars, ultra-fine abrasive is present in all forms of operation, for example, when tires and brake discs wear out. But the greatest danger is soot. Previously, only diesel engines suffered from this unpleasant moment in operation. Thanks to the installation of particulate filters, the situation has improved significantly.

Now a similar problem appeared and petrol models, as they increasingly use direct fuel injection systems, resulting in co-production of even finer particulate matter than diesel engines.

However, according to scientists investigating the nature of the problem, only 15% of the fine dust deposited in the lungs is produced by cars, any human activity can be a source of a dangerous phenomenon, from Agriculture, to laser printers, fireplaces and, of course, cigarettes.

The health of residents of megacities

The actual load on the human body from exhaust gases depends on the volume of traffic and weather conditions. Someone who lives on a busy street is much more exposed to nitrogen oxides or fine dust.

Exhaust fumes are not equally dangerous for all residents. Healthy people will hardly feel a "gas attack" in any way, although the intensity of the load will not decrease from this, but the health of an asthmatic or a person with cardiovascular diseases can deteriorate significantly due to the presence of exhaust gases.

Carbon Dioxide (CO2)

Harmful to the entire climate of the planet, gas inevitably arises from the combustion of fossil fuels such as diesel or gasoline. In terms of CO2, diesel engines are slightly “cleaner” than gasoline engines because they generally consume less fuel.

CO2 is harmless to humans, but not to nature. The greenhouse gas CO2 is responsible for much of global warming. According to the German Federal Ministry for the Environment, in 2015 the share of carbon dioxide in total greenhouse gas emissions was 87.8 percent.

Since 1990, carbon dioxide emissions have been declining almost continuously, with a total decrease of 24.3 percent. However, despite the production of more and more economical engines, the growth of motorization and the increase freight traffic undermines attempts by scientists and engineers to reduce harm. As a result, carbon dioxide emissions remain high.

By the way: all vehicles in, say, Germany are responsible for “only” 18 percent of CO2 emissions. More than twice as much, 37 percent, goes to energy emissions. In the US, the picture is the opposite, where it is cars that cause the most serious damage to nature.

Carbon monoxide (Co, carbon monoxide)

An extremely hazardous by-product of combustion. Carbon monoxide is a colorless, tasteless and odorless gas. The combination of carbon and oxygen occurs during incomplete combustion of carbon-containing substances and is an extremely dangerous poison. Therefore, high-quality ventilation in garages and underground parking lots is essential for the life of their users.

Even a small amount of carbon monoxide causes damage to the body, a few minutes spent in a poorly ventilated garage with a car running can kill a person. Be extremely careful! Do not warm up in closed boxes and rooms without ventilation!

But how dangerous is carbon monoxide on outdoors? An experiment carried out in Bavaria showed that in 2016 the average values ​​shown by the measuring stations were between 0.9-2.4 mg/m 3 , well below the limit values.

Ozone

For the layman, ozone is not some kind of dangerous or toxic gas. However, in reality this is not the case.

When exposed to sunlight, hydrocarbons and nitric oxide are converted into ozone. Through the respiratory tract, ozone enters the body and leads to cell damage. Consequences, effects of ozone: local inflammation of the respiratory tract, cough and shortness of breath. With small volumes of ozone, there will be no problems with the subsequent restoration of body cells, but at high concentrations, this seemingly harmless gas can safely kill a healthy person. It is not for nothing that in Russia this gas is classified as the most high class danger.

With climate change, the risk of high concentrations of ozone is increasing. Scientists believe that by 2050 the ozone load should rise sharply. To solve the problem, nitrogen oxides emitted by transport must be significantly reduced. In addition, there are many factors influencing the spread of ozone, for example, solvents in paints and varnishes also actively contribute to the problem.

Sulfur dioxide (SO2)

This pollutant is produced when sulfur is burned in fuel. It is one of the classic atmospheric pollutants from combustion, power plants and industry. SO2 is one of the main "ingredients" of pollutants that form smog, also called "London smog".

In the atmosphere, sulfur dioxide undergoes a series of conversion processes that can produce sulfuric acid, sulfites and sulfates. SO2 acts primarily on the mucous membranes of the eye and upper respiratory tract. In the environment, sulfur dioxide can damage plants and cause soil acidification.

Nitrogen Oxides (NOx)

Nitrogen oxides are formed mainly during the combustion process in engines internal combustion. Diesel vehicles considered the main source. The introduction of catalysts and particulate filters continues to increase, so that emissions will decrease markedly, but this will happen only in the future.

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The effect of exhaust gases on the atmosphere is an urgent environmental problem. Many people use cars and do not even realize how badly they poison the air. To assess the damage, it is worth studying the composition of exhaust gases and the consequences of their impact on the environment.

What are exhaust gases made of?

Vehicle exhaust gases are produced during engine operation, as well as during incomplete or complete combustion of the fuel used. In total, over two hundred different components are found in them: some exist for only a few minutes, while others decompose for years and hover in the air for a long time.

Classification

All exhausts are divided into several groups according to their properties, constituent components and the degree of impact on the environment and the human body:

1. The first group includes all substances that do not have toxic properties. This includes water vapor, as well as natural and integral components of atmospheric air, which inevitably penetrate car engines. This category also includes emissions of CO2 - carbon dioxide, which is also non-toxic, but reduces the concentration of oxygen in the air.
2. The second group of constituents of automotive exhaust gases includes carbon monoxide, ie carbon monoxide. It is a product of incomplete combustion of fuel and has pronounced toxic and toxic properties. This substance, getting into the human body by inhalation, penetrates into the blood and reacts with hemoglobin. As a result, the oxygen concentration is greatly reduced, hypoxia occurs, and in severe cases, death.
3. The third group covers nitrogen oxides, which have a brownish tint, an unpleasant pungent odor. Such substances are dangerous to humans, as they can irritate mucous membranes and affect the membranes. internal organs, especially the lungs.
4. The fourth group of exhaust gas components is the most numerous and includes hydrocarbons that appear due to incomplete combustion of the fuel used in automotive engines. And it is these substances that form bluish or light white smoke.
5. The fifth group of exhaust components is represented by aldehydes. The highest concentrations of these substances are observed at minimal loads or during the so-called idling, when temperature regime combustion in the engine is characterized by low rates.
6. The sixth group of components of automobile exhaust gases are various dispersed particles, including soot. They are considered wear products of engine parts, and may also include oil particles, aerosols, carbon deposits. Soot itself is not dangerous, but it can settle in the respiratory tract and impair visibility from exhaust gases.
7. The seventh group of substances that make up the exhaust gases are various sulfur compounds formed during the combustion in engines of fuels containing sulfur (primarily diesel). Such components have a sharp characteristic odor, and they can irritate the mucous membranes, as well as disrupt metabolic processes and oxidative reactions.
8. The eighth group is different lead compounds. They appear during operation. carburetor engines subject to the use of leaded gasoline with additives that increase the octane number.

Consequences of exposure to exhaust gases

The impact of exhaust gases on human health, the environment and the atmosphere is extremely detrimental. First of all, the harmful emissions generated during the combustion of fuel in automobile engines greatly pollute the air, forming smog. Some small and light particles are able to rise and reach the atmospheric layers, changing their composition and compacting the structure.

Exhaust gases are one of the reasons greenhouse effect, which is developing at a rapid pace and poses a real threat to the environment and all of humanity. It causes weather anomalies, warming, melting glaciers, rising sea levels.

Another direction of the negative impact of exhaust gases is to contribute to the formation of acid rain. Recently, they began to go more and more often and greatly harm the ecosystem. Precipitation, which is highly acidic, changes the composition of the soil, which can make it unsuitable for growing plants and growing crops.

The flora suffers greatly: the rains literally corrode the foliage and fruits. Also, acid precipitation is harmful and dangerous to humans: they have an irritating and toxic effect on the skin, scalp.

The impact of car exhausts is extremely dangerous for the human body. Gas components almost immediately enter the respiratory system, irritate the mucous membranes of the lungs and bronchi, disrupt and inhibit respiratory function, and also cause a number of chronic diseases, including asthma and bronchitis. But substances from the respiratory tract are absorbed into the blood and change its composition, for example, significantly reduce the concentration of oxygen. Also, compounds penetrate into all tissues and organs, and some are capable of causing degeneration and mutation of cells in the future, their destruction.

How to avoid the serious effects of exhaust emissions

To minimize the dangerous and serious consequences of the negative effects of automotive exhaust gases, a number of measures should be taken:

1. Competent, rational and moderate operation of motor vehicles. Don't let long work idling, avoid driving at high speeds, if possible, abandon the car in favor of using public transport, namely trolleybuses and trams.
2. The most efficient way is to move away from oily fuels and switch to alternative sources energy. In the past few years, scientists have begun to develop cars that run on electricity and even solar panels.
3. Constantly monitor the health of the car, and especially the condition of the engine and all its parts, as well as the operation of the exhaust system.
4. Available modern facilities that reduce the concentration of harmful substances in automobile exhausts. These include the so-called catalytic converters exhaust gases. If you apply them constantly, then the emissions will be less dangerous for the atmosphere and humanity.

Using a car, each owner must take care not only about its serviceability, but also about the impact of transport and emissions on health and the environment. Only in this case will it be possible to avoid sad consequences.

As a result of the operation of the internal combustion engine, which is equipped with each modern car, hydrocarbon fuels are burned, and a huge amount of various chemical compounds. Since the mid-1960s, exhaust emissions have become a concern for many people. From this moment begins the struggle of mankind for the maximum possible reduction of these emissions.

The problem with the greenhouse effect

Climate change at the global level is one of the important features of the 21st century. In many ways, these changes are due to the activities of mankind, in particular, greenhouse gas emissions into the atmosphere have increased significantly in recent decades. The main source of emissions are vehicle exhaust gases, 30% of which are greenhouse gases.

Greenhouse gases exist naturally and are designed to regulate the temperature of our blue planet, but even a slight increase in their amount in the atmosphere can lead to serious global consequences.

The most dangerous greenhouse gas is CO2, or carbon dioxide. It accounts for about 80% of all emissions, most of which is associated with the combustion of fuel in car engines. Carbon dioxide remains active in the atmosphere for a long time, which increases its danger.

The car is the main air pollutant

One of the main sources of carbon dioxide is car exhaust. In addition to CO2, they emit carbon monoxide CO, hydrocarbon residues, nitrogen oxides, sulfur and lead compounds, and particulate matter. All of these compounds enter the air in huge quantities, leading to a global increase in temperature and the emergence of serious diseases in people living in large cities.

Besides, different cars emit exhaust gases of different composition, it all depends on the type of fuel used, such as gasoline or diesel fuel. So, when gasoline is burned, a whole bunch of chemical compounds appear, which consist mainly of carbon monoxide, nitrogen oxides, hydrocarbons and lead compounds. Diesel engine exhaust contains soot, which causes smog, unburned hydrocarbons, nitrogen oxides and sulfuric anhydride.

Thus, the harm of exhaust gases to the environment is undeniable. Work is currently underway to reduce the amount of emissions from each car, as well as replacing the use of gasoline with alternative and more environmentally friendly energy sources, such as solar or wind energy. Much attention is paid hydrogen fuel, the result of combustion of which is ordinary water vapor.

Impact of emissions on human health

The harm that exhaust gases cause to human health can be very serious.

First of all, carbon monoxide is dangerous, which causes loss of consciousness and even death if its concentration in the atmosphere is increased. In addition to it, sulfur oxides and lead compounds are harmful, which fly out in large quantities from the exhaust pipe of a car. Sulfur and lead are known to be highly toxic and can remain in the body for a long time.

Hydrocarbons and soot particles, which also enter the atmosphere as a result of partial combustion of fuel in the engine, can cause severe diseases of the respiratory system, including the development of malignant tumors.

The constant and prolonged effect of exhaust gases on the body leads to a weakening of human immunity, bronchitis. Damage is done to blood vessels and the nervous system.

Vehicle exhaust

Currently, in all countries of the world, cars are subject to mandatory checks for compliance with established standards. environmental standards. In most cases, the following exhaust gases are called, the environmental damage from which is maximum:

• carbon monoxide and carbon dioxide;
• various hydrocarbon residues.

However, modern standards of the developed countries of the world also impose requirements on the level of nitrogen oxides emitted into the atmosphere and on the system for monitoring the process of fuel evaporation from the fuel tank.

Carbon Dioxide (CO)

Of all the environmental pollutants, carbon dioxide is the most dangerous because it has neither color nor smell. Harm to the health of car exhaust gas is significant, for example, its concentration in the air of only 0.5% can cause a person to lose consciousness and subsequent death within 10-15 minutes, and such a concentration as 0.04% leads to a headache.

This product of the internal combustion engine is formed in large quantities when the gasoline mixture is rich in hydrocarbons and poor in oxygen. In this case, incomplete combustion of the fuel occurs and CO is formed. The problem can be solved by properly adjusting the carburetor, replacing or cleaning the dirty air filter, adjustment of valves that inject a combustible mixture, and some other measures.

A large amount of CO is released in the exhaust gases during the warm-up process of the car, because its engine is cold and partially burns the gasoline mixture. Therefore, warming up the car should be carried out in a well-ventilated area or in the open air.

Hydrocarbons and organic oils

Hydrocarbons that do not burn out in the engine, as well as evaporated organic oils, are substances that determine the main environmental damage caused by car exhaust gases. By themselves, these chemical compounds do not pose a danger, however, when they enter the atmosphere, they react with other substances under the influence of sunlight, and the resulting compounds cause pain in the eyes and make it difficult to breathe. In addition, hydrocarbons are the main cause of smog in large cities.

Reducing the amount of hydrocarbons in the exhaust gases is achieved by adjusting the carburetor so that it prepares both a lean and a rich mixture, as well as constant control reliability of compression rings in engine cylinders and adjustment of spark plugs. Complete combustion of hydrocarbons leads to the formation of carbon dioxide and water vapor, which are harmless substances both for the environment and for humans.

nitrogen oxides

About 78% of atmospheric air consists of nitrogen. It is a fairly inert gas, but at fuel combustion temperatures above 1300 ° C, nitrogen splits into individual atoms and reacts with oxygen, forming various types oxides.

The harmful effects of exhaust gases on human health are also associated with these oxides. In particular, the respiratory system suffers the most. At high concentrations and prolonged action, nitric oxides can cause headaches and acute bronchitis. Oxides are also harmful to the environment. Once in the atmosphere, they form smog and destroy the ozone layer.

To reduce emissions of nitrogen oxides, a special gas emission recirculation system is used in cars, the principle of which is to maintain the engine temperature below the threshold for the formation of these oxides.

Fuel evaporation

The mere evaporation of fuel from a tank can be one of the major sources of environmental pollution. In this regard, over the past few decades, special tanks have been manufactured, the design of which is designed to solve this problem.

The fuel tank must also "breathe". Designed for this special system, which lies in the fact that the tank cavity itself is connected by means of hoses to a tank filled with activated carbon. This coal is able to absorb the resulting fuel vapors when the car engine is not running. As soon as the engine is started, the corresponding hole opens and the vapors absorbed by the coal enter the engine for combustion.

The performance of this entire system from the tank and hoses must be constantly monitored, since they may leak fuel vapors that will pollute the environment.

Solving the problem of emissions in large cities

Tens of thousands of factories are concentrated in large modern cities, millions of people live and hundreds of thousands of cars drive along the streets. All this greatly pollutes the atmosphere, which has become the main problem of the 21st century. To solve it, the city authorities introduce a number of administrative and measures.

So, in 2003, a protocol against pollution by road transport of the environment was adopted in London. Under this protocol, drivers who drive through the central areas of the city are charged additional fee in the amount of £10. In 2008, the London authorities approved new law, which began to more effectively regulate the movement freight transport, buses and personal cars in the central part of the city, setting an upper speed threshold for them. These measures led to a reduction in the content of harmful gases in the atmosphere over London by 12%.

Since the 2000s, similar measures have been taken in many million-plus cities. Among them are the following:

• Tokyo;
• Berlin;
• Athens;
• Madrid;
• Paris;
• Stockholm;
• Brussels and others.

The opposite effect of the anti-pollution law

The fight against car exhaust is not an easy task, which is clearly demonstrated by the example of two of the most polluted cities on the planet: Mexico City and Beijing.

Since 1989, the Mexican capital has had a law prohibiting the use of Personal car on certain days of the week. At first, this law began to bring positive results and gas emissions decreased, but after a while, residents began to purchase second used cars, thanks to which they began to travel every day by personal transport, replacing one car with another within a week. This situation worsened the state of the urban atmosphere even more.

A similar situation is observed in the capital of China. According to 2015 data, about 80% of Beijing residents have several cars, allowing them to travel every day on them. In addition, a huge number of violations of the anti-pollution law are recorded in this metropolis.

Exhaust gases (or exhaust gases) - the main source of toxic substances of an internal combustion engine - are a heterogeneous mixture of various gaseous substances with a variety of chemicals and physical properties, consisting of products of complete and incomplete combustion of fuel, excess air, aerosols and various microimpurities (both gaseous and in the form of liquid and solid particles) coming from engine cylinders into its exhaust system. In their composition, they contain about 300 substances, most of which are toxic.

The main regulated toxic components of engine exhaust gases are oxides of carbon, nitrogen and hydrocarbons. In addition, saturated and unsaturated hydrocarbons, aldehydes, carcinogens, soot and other components enter the atmosphere with exhaust gases. Sample composition.

Composition of exhaust gases

Exhaust gas components	Content by volume, %		Toxicity
	Engine
	petrol	diesel
Nitrogen	74,0 - 77,0	76,0 - 78,0	No
Oxygen	0,3 - 8,0	2,0 - 18,0	No
water vapor	3,0 - 5,5	0,5 - 4,0	No
Carbon dioxide	5,0 - 12,0	1,0 - 10,0	No
carbon monoxide	0,1 - 10,0	0,01 - 5,0	Yes
Hydrocarbons are non-carcinogenic	0,2 - 3,0	0,009 - 0,5	Yes
Aldehydes	0 - 0,2	0,001 - 0,009	Yes
Sulfur oxide	0 - 0,002	0 - 0,03	Yes
Soot, g/m3	0 - 0,04	0,01 - 1,1	Yes
Benzopyrene, mg/m3	0,01 - 0,02	up to 0.01	Yes

When the engine is running on leaded gasoline, lead is present in the exhaust gases, and soot is present in engines running on diesel fuel.

Carbon monoxide (CO - carbon monoxide)

Transparent, odorless poisonous gas, slightly lighter than air, poorly soluble in water. Carbon monoxide is a product of incomplete combustion of fuel that burns in air with a blue flame to form carbon dioxide (carbon dioxide). In the combustion chamber of an engine, CO is formed due to poor atomization of the fuel, as a result of cold flame reactions, during the combustion of fuel with a lack of oxygen, and also due to the dissociation of carbon dioxide during high temperatures. During subsequent combustion after ignition (after the top dead center, on the expansion stroke), combustion of carbon monoxide is possible in the presence of oxygen with the formation of dioxide. At the same time, the process of burning CO continues in the exhaust pipeline. It should be noted that during the operation of diesel engines, the concentration of CO in the exhaust gases is low (approximately 0.1 - 0.2%), therefore, as a rule, the concentration of CO is determined for gasoline engines.

Nitrogen oxides (NO, NO2, N2O, N2O3, N2O5, hereinafter NOx)

Nitrogen oxides are among the most toxic components of exhaust gases. Under normal atmospheric conditions, nitrogen is a highly inert gas. At high pressures and especially temperatures, nitrogen actively reacts with oxygen. In the exhaust gases of engines, more than 90% of the total amount of NOx is nitric oxide NO, which is easily oxidized into dioxide (NO2) even in the exhaust system, and then in the atmosphere. Nitrogen oxides irritate the mucous membranes of the eyes, nose, and destroy human lungs, because when moving through the respiratory tract, they interact with the moisture of the upper respiratory tract, forming nitric and nitrous acids. As a rule, poisoning of the human body with NOx does not appear immediately, but gradually, and there are no neutralizing agents.

Nitrous oxide (N2O hemioxide, laughing gas) is a gas with a pleasant odor and is highly soluble in water. Has a narcotic effect.

NO2 (dioxide) is a pale yellow liquid involved in the formation of smog. Nitrogen dioxide is used as an oxidizing agent in rocket fuel. It is believed that for the human body, nitrogen oxides are about 10 times more dangerous than CO, and when secondary transformations are taken into account, 40 times. Nitrogen oxides are dangerous for plant leaves. It has been established that their direct toxic effect on plants manifests itself when the concentration of NOx in the air is in the range of 0.5 - 6.0 mg/m3. Nitric acid is highly corrosive to carbon steels. The temperature in the combustion chamber has a significant effect on the emission of nitrogen oxides. So, with an increase in temperature from 2500 to 2700 K, the reaction rate increases by 2.6 times, and with a decrease from 2500 to 2300 K, it decreases by 8 times, i.e. the higher the temperature, the higher the NOx concentration. Early fuel injection or high pressures compression in the combustion chamber also contributes to the formation of NOx. The higher the oxygen concentration, the higher the concentration of nitrogen oxides.

Hydrocarbons (CnHm ethane, methane, ethylene, benzene, propane, acetylene, etc.)

Hydrocarbons are organic compounds whose molecules are built only from carbon and hydrogen atoms, are toxic substances. Exhaust gases contain more than 200 different CHs, which are divided into aliphatic (open or closed chain) and those containing a benzene or aromatic ring. Aromatic hydrocarbons contain in the molecule one or more cycles of 6 carbon atoms interconnected by single or double bonds (benzene, naphthalene, anthracene, etc.). They have a pleasant smell. The presence of CH in the exhaust gases of engines is explained by the fact that the mixture in the combustion chamber is heterogeneous, therefore, at the walls, in over-enriched zones, the flame is extinguished and chain reactions break. Incompletely burned CH, emitted with exhaust gases and representing a mixture of several hundred chemical compounds, have an unpleasant odor. CH are the cause of many chronic diseases. Gasoline vapors, which are hydrocarbons, are also toxic. Permissible average daily concentration of gasoline vapors is 1.5 mg/m3. The content of CH in the exhaust gases increases with throttling, when the engine is running in forced idle modes (PHX, for example, during engine braking). When the engine is running in these modes, the process of mixture formation (mixing of the air-fuel charge) worsens, the combustion rate decreases, ignition worsens and, as a result, its frequent misfires occur. The release of CH is caused by incomplete combustion near cold walls, if until the end of combustion there are places with a strong local lack of air, insufficient fuel atomization, with insufficient swirl of the air charge and low temperatures(for example, idle mode). Hydrocarbons are formed in overenriched zones where oxygen access is limited, as well as near the relatively cold walls of the combustion chamber. They play an active role in the formation of biologically active substances that cause irritation of the eyes, throat, nose and their disease, and damage the flora and fauna.

Hydrocarbon compounds provide narcotic effect on the central nervous system, can cause chronic diseases, and some aromatic CH have toxic properties. Hydrocarbons (olefins) and nitrogen oxides, under certain meteorological conditions, actively contribute to the formation of smog.

Exhaust smog.

Smog (Smog, from smoke smoke and fog - fog) poisonous fog formed in the lower layer of the atmosphere, polluted harmful substances from industrial enterprises, exhaust gases from vehicles and heat-producing installations under adverse weather conditions. It is an aerosol consisting of smoke, fog, dust, soot particles, liquid droplets (in a humid atmosphere). Occurs in the atmosphere of industrial cities under certain meteorological conditions. Harmful gases entering the atmosphere react with each other and form new, including toxic compounds. At the same time, reactions of photosynthesis, oxidation, reduction, polymerization, condensation, catalysis, etc. take place in the atmosphere. As a result of complex photochemical processes stimulated by the ultraviolet radiation of the Sun, photooxidants (oxidizers) are formed from nitrogen oxides, hydrocarbons, aldehydes and other substances.

Low concentrations of NO2 can create large amounts of atomic oxygen, which in turn forms ozone and reacts again with pollutants. atmospheric air. The presence of formaldehyde, higher aldehydes and other hydrocarbon compounds in the atmosphere also contributes, together with ozone, to the formation of new peroxide compounds. Dissociation products interact with olefins, forming toxic hydroperoxide compounds. When their concentration is more than 0.2 mg/m3, water vapor condenses in the form of tiny mist droplets with toxic properties. Their number depends on the season of the year, time of day and other factors. In hot, dry weather, smog is observed in the form of a yellow veil (the color is given by nitrogen dioxide NO2 present in the air as droplets of a yellow liquid). Smog irritates mucous membranes, especially the eyes, and can cause headache, swelling, hemorrhage, complications of respiratory diseases. It worsens visibility on the roads, thereby increasing the number of traffic accidents. The danger of smog to human life is great. So, for example, the London smog of 1952 is called a disaster, since about 4 thousand people died from smog in 4 days. The presence of chloride, nitrogen, sulfur compounds and water droplets in the atmosphere contributes to the formation of strong toxic compounds and acid vapors, which has a detrimental effect on plants and structures, especially on historical monuments made of limestone. The nature of smog is different. For example, in New York, the formation of smog is promoted by the reaction of fluoride and chloride compounds with water droplets; in London, the presence of fumes of sulfuric and sulphurous acids; in Los Angeles (California or photochemical smog) the presence of nitrogen oxides, hydrocarbons in the atmosphere; in Japan, the presence of soot and dust particles in the atmosphere.