Gas is one of the aggregate states of matter. Gases are present not only in the air on Earth, but also in space. They are associated with lightness, weightlessness, volatility. The lightest is hydrogen. What is the heaviest gas? Let's find this out.

Heaviest gases

The word "gas" comes from the ancient Greek word for "chaos". Its particles are mobile and weakly connected to each other. They move chaotically, filling all the space available to them. A gas can be a simple element and consist of atoms of one substance, or it can be a combination of several.

The simplest heavy gas (at room temperature) is radon, its molar mass is 222 g / mol. It is radioactive and completely colorless. After it, xenon is considered the heaviest, the atomic mass of which is 131 g / mol. The rest of the heavy gases are compounds.

Among inorganic compounds, the heaviest gas at a temperature of +20 ° C is tungsten (VI) fluoride. Its molar mass is 297.84 g / mol and its density is 12.9 g / l. Under normal conditions, it is a colorless gas; in humid air, it smokes and turns blue. Tungsten hexafluoride is very active, it easily turns into a liquid when cooled.

Radon

The discovery of the gas occurred during the period of research on the study of radioactivity. In the course of the decay of some elements, scientists have repeatedly noted some substance emitted along with other particles. E. Rutherford called it emanation.

So the emanation of thorium - thoron, radium - radon, actinium - actinon was discovered. Later it was found that all these emanations are isotopes of the same element - an inert gas. Robert Gray and William Ramsay first isolated it in its purest form and measured its properties.

In the periodic table, radon is an element of the 18th group with atomic number 86. It is located between astatine and francium. Under normal conditions, the substance is a gas, tasteless, odorless and colorless.

Gas is 7.5 times denser than air. It dissolves in water better than other noble gases. In solvents, this indicator increases even more. Of all inert gases, it is the most active, easily interacting with fluorine and oxygen.

Radioactive gas radon

One of the properties of the element is radioactivity. The element has about thirty isotopes: four are natural, the rest are artificial. All of them are unstable and subject to radioactive decay. radon, more precisely, its most stable isotope, is 3.8 days.

Due to its high radioactivity, the gas is fluorescent. In the gaseous and liquid state, the substance is highlighted in blue. Solid radon changes its palette from yellow to red when cooled to a nitrogen temperature of about -160 o C.

Radon can be very toxic to humans. As a result of its decay, heavy non-volatile products are formed, for example, polonium, lead, bismuth. They are extremely poorly excreted from the body. By settling and accumulating, these substances poison the body. After smoking, radon is the second most common cause of lung cancer.

Location and use of radon

The heaviest gas is one of the rarest elements in the earth's crust. In nature, radon is part of ores containing uranium-238, thorium-232, uranium-235. When they decay, it is released, falling into the hydrosphere and atmosphere of the Earth.

Radon accumulates in river and sea waters, in plants and soil, in building materials. In the atmosphere, its content increases with the activity of volcanoes and earthquakes, with the extraction of phosphates and the operation of geothermal power plants.

With the help of this gas, tectonic faults, thorium and uranium deposits are found. It is used in agriculture to activate pet food. Radon is used in metallurgy, in the study of groundwater in hydrology, in medicine, radon baths are popular.

Many people do not even know how many dangers the air they breathe can be fraught with. It may contain a variety of elements - some are completely harmless to the human body, others are causative agents of the most serious and dangerous diseases. For example, many people know about the danger that is fraught with radiation, but not everyone realizes that an increased share can be easily obtained in everyday life. Some people mistake symptoms from exposure to elevated levels of radioactivity for signs of other illnesses. A general deterioration in well-being, dizziness, body aches - a person is used to associating them with completely different root causes. But this is very dangerous because radiation can lead to very serious consequences, and a person spends time fighting contrived illnesses. The mistake of many people is that they do not believe in the possibility of receiving radiation doses in their daily life.

What is radon?

Many people believe that they are sufficiently protected, since they live far enough from the workers of nuclear power plants, do not visit warships powered by nuclear fuel on excursions, and they have heard about Chernobyl only from films, books, news and games. Unfortunately, this is not so! Radiation is present around us everywhere - it is important to be where its quantity is within acceptable standards.

So what can the normal air around us hide? Do not know? We will simplify your task by giving a leading question, and immediately the answer to it:

- Radioactive gas 5 letters?

- Radon.

The first prerequisites for the discovery of this element were made at the end of the nineteenth century by the legendary Pierre and Marie Curie. Subsequently, other famous scientists became interested in their research, who were able to identify radon in its pure form in 1908, and also describe some of its characteristics. During its history of official existence, this gas changed many names, and only in 1923 did the ode become known as radon- 86th element in the periodic table of Mendeleev.

How does radon gas get into premises?

Radon... It is this element that can imperceptibly surround a person in his house, apartment, office. Gradually lead to a deterioration in the state of health of people cause very serious illness. But avoiding danger is very difficult - one of the dangers that is fraught with radon gas, lies in the fact that it cannot be determined by color or smell. Radon does not emit anything from the surrounding air, therefore it can unnoticeably irradiate a person for a very long time.

But how can this gas appear in ordinary buildings where people live and work?

Where and most importantly how can it be detected radon?

Quite logical questions. One of the sources of radon is the soil layers that are located under buildings. There are many substances that secrete this gas... For example, ordinary granite. That is, a material that is actively used in construction work (for example, as an additive to asphalt, concrete) or is found in large quantities directly in the Earth. To the surface gas can take out groundwater, especially during heavy rains, do not forget about deep-water wells, from where many people draw invaluable liquid. Another source of this radioactive gas is food - in agriculture, radon is used to activate feed.

The main trouble is that a person can settle in an ecologically clean place, but this will not give him a full guarantee of protection from the harmful effects of radon. Gas can penetrate into his abode with food, tap water, as fumes after rain, from the surrounding elements of the decoration of the building and the materials from which it was erected. Every time a person orders or buys something will not be interested in radiation level at the place of manufacture of the purchased products?

Bottom line - radon gas can concentrate in dangerous quantities in rooms where people live and work. Therefore, it is important to know the answer to the second question posed above.

Rooms at risk

Radon is significantly heavier than air. That is, when it enters the air, its main volume is concentrated in the lower layers of the air. Therefore, apartments in multi-storey buildings on the ground floors, private households, basements and semi-basements are considered potentially dangerous places. Effective way of getting rid from this threat is the constant ventilation of the premises and the detection of the source of radon intake. In the first case, you can avoid the dangerous concentration of radon, which could appear in the structure at random. In the second - to destroy the source of its constant occurrence. Naturally, most people do not think much about some of the characteristics of the building materials used, and in the cold season they do not always ventilate the premises. Many basements do not have a natural or forced ventilation system at all, and therefore become a source of concentration of a dangerous amount of this radioactive gas.

87. The radioactive gas radon and the rules of protection from its effects.

Harmful effects of radon gas and methods of protection

Radon gas provides the greatest contribution to the collective radiation dose of Russians.

Radon is an inert heavy gas (7.5 times heavier than air) that is released from the soil everywhere or released from some building materials (for example, granite, pumice, red clay bricks). Radon has no smell or color, which means that it cannot be detected without special radiometer devices. This gas and its decay products emit very dangerous (α-particles that destroy living cells. Adhering to microscopic dust particles, (α-particles create a radioactive aerosol. We inhale it - this is how the cells of the respiratory organs are irradiated. Significant doses can provoke lung cancer or leukemia.

Regional programs are being developed that provide for radiation examination of construction sites, children's institutions, residential and industrial buildings, and control over the radon content in the air. As part of the program, firstly, the radon content in the city's atmosphere is constantly measured.

Houses should be well insulated from radon penetration. During the construction of the foundation, anti-radon protection is necessarily performed - for example, bitumen is laid between the slabs. And the radon content in such premises requires constant monitoring.

Exposure dose

The measure of air ionization as a result of the action of photons on it, equal to the ratio of the total electric charge dQ of ions of the same sign, formed by ionizing radiation absorbed in a certain mass of air, to the mass dM

Dexp = dQ / dM

Measurement unit (non-systemic) - X-ray (R). At Dexp = 1 P in 1 cm3 of air at 0o C and 760 mm Hg (dM = 0. 001293 g) 2.08.109 pairs of ions are formed, carrying a charge dQ = 1 electrostatic unit of the amount of electricity of each sign. This corresponds to an energy absorption of 0.113 erg / cm3 or 87.3 erg / g; for photon radiation Dexp = 1 P corresponds to 0.873 rad in air and about 0.96 rad in biological tissue.

89. Dose absorbed

The ratio of the total energy of ionizing radiation dE absorbed by the substance to the mass of the substance dM

Dab = dE / dM

The unit of measurement (SI) is Gray (Gy), which corresponds to the absorption of 1 J of ionizing radiation energy by 1 kg of a substance. The off-system unit is rad, corresponding to the absorption of 100 egr of the energy of the substance (1 rad = 0.01 Gy).

90. Equivalent dose:

Deq = kDabs

where k is the so-called radiation quality factor (dimensionless), which is a criterion of relative biological effectiveness in chronic irradiation of living organisms. The larger k, the more dangerous the irradiation at the same absorbed dose. For monoenergetic electrons, positrons, beta particles and gamma quanta k = 1; for neutrons with energy E< 20 кэВ k = 3; для нейтронов с энергией 0, 1 < E <10 МэB и протонов с E < 20 кэB k = 10; для альфа-частиц и тяжелых ядер отдачи k = 20. Единица измерения эквивалентной дозы (СИ) - зиверт (Зв), внесистемная единица - бэр (1 бэр = 0, 01 Зв) .

Sanitary protection zone of the enterprise.

Environmental assessment of industries and enterprises. Environmental Impact Assessment (EIA).

91. The fight against radioactive contamination of the environment can only be of a preventive nature, since there are no methods of biological decomposition and other mechanisms to neutralize this type of contamination of the natural environment. The greatest danger is posed by radioactive substances with a half-life from several weeks to several years: this time is sufficient for the penetration of such substances into the organism of plants and animals.

storage of nuclear waste seems to be the most acute problem of protecting the environment from radioactive atomic energy.

92.Biological pollution of the environment - bringing into the ecosystem and reproduction of alien species of organisms. Microbial contamination is also called bacteriological or microbiological contamination.

Biologist. loading- 1-biotic (biogenic) and 2- microbiological (microbial)

1.distribution in the environment of biogenic substances - emissions from enterprises, production, certain types of food (meat processing plants, dairies, breweries), enterprises producing antibiotics, as well as contamination with animal corpses. B.Z. leads to disruption of the processes of self-purification of water and soil. 2. arises as a result of the masses. size of microorganisms in environments changed in the course of economic activities of people.

93.environmental monitoring -an information system for observing, assessing and forecasting changes in the state of the environment, created with the aim of highlighting the anthropogenic component of these changes against the background of natural processes.

94. The territorial bodies of the State Committee for Ecology of Russia, together with the executive authorities of the constituent entities of the Russian Federation, carried out an inventory of storage and disposal sites for production and consumption waste in more than 30 constituent entities of the Russian Federation. The results of the inventory make it possible to systematize information about the places of storage, storage and disposal of waste, to assess the degree of filling the availability of free volumes in places of storage and disposal of waste, to determine the types of waste accumulated in these places, including by hazard classes, to assess the conditions and condition of the places disposal of waste and the degree of their impact on the environment, as well as to make proposals on the implementation of certain measures to prevent environmental pollution by production and consumption waste.

95. One of the main problems of our time is the disposal and processing of solid waste - solid household waste . It is still difficult to talk about fundamental changes in this area in our country. As for European countries and the United States, there people have long come to the conclusion that the resource potential of solid waste should not be destroyed, but used. You cannot approach the problem of solid waste as a fight against waste, setting the task to get rid of it at any cost.

But in Russia, technological lines have already been created, where secondary raw materials are washed, crushed, dried, fused and turned into granules. Using the revived polymer as a binder, it is possible to produce, among other things, from the most tonnage and inconvenient for processing waste - phosphogypsum and lignin, fine bricks, paving slabs, tiles, decorative fences, curbs, benches, various household goods and construction materials ...

As the first months of operation have shown, the quality of the "reanimated" polymer is no worse than the primary one, and it can even be used in its "pure" form. This significantly expands the scope of its application.

96. Pesticides. Pesticides are a group of artificially created substances used to control pests and plant diseases. Pesticides are divided into the following groups: insecticides - to fight harmful insects, fungicides and bactericides - to fight bacterial plant diseases, herbicides - against weeds. It was found that pesticides, destroying pests, harm many beneficial organisms and undermine the health of biocenoses. Agriculture has long faced the problem of transition from chemical (polluting) to biological (environmentally friendly) methods of pest control. Currently, more than 5 million tons. pesticides are supplied to the world market. About 1.5 million tons of these substances have already entered the composition of terrestrial and marine ecosystems by ash and water. The industrial production of pesticides is accompanied by the appearance of a large number of by-products that pollute wastewater. In the aquatic environment, representatives of insecticides, fungicides and herbicides are more common than others. The synthesized insecticides are divided into three main groups: organochlorine, organophosphorus and carbonates. Organochlorine insecticides are obtained by chlorination of aromatic and heterocyclic liquid hydrocarbons. These include DDT and its derivatives, in the molecules of which the stability of aliphatic and aromatic groups in the joint presence increases, all kinds of chlorinated chlorodiene derivatives (eldrin). These substances have a half-life of up to several tens of years and are very resistant to biodegradation. In the aquatic environment, polychlorinated biphenyls are often found - derivatives of DDT without an aliphatic part, numbering 210 homologues and isomers. Over the past 40 years, more than 1.2 million tons have been used. polychlorinated biphenyls in the production of plastics, dyes, transformers, capacitors. Polychlorinated biphenyls (PCBs) are released into the environment from industrial wastewater discharges and from the incineration of solid

waste in landfills. The latter source supplies PBX to the atmosphere, from where they fall out with atmospheric precipitation in all regions of the globe. Thus, in snow samples taken in Antarctica, the content of PBQ was 0.03 - 1.2 kg / l.

97. Nitrates - salts of nitric acid, for example NaNO 3, KNO 3, NH 4 NO 3, Mg (NO 3) 2. They are normal metabolic products of nitrogenous substances of any living organism - plant and animal, therefore there are no "nitrate-free" products in nature. Even in the human body, 100 mg or more of nitrates are formed and used in metabolic processes per day. Of the nitrates that daily enter the body of an adult, 70% comes with vegetables, 20% - with water and 6% - with meat and canned foods. When consumed in increased quantities, nitrates in the digestive tract are partially reduced to nitrites (more toxic compounds), and the latter, when entering the bloodstream, can cause methemoglobinemia. In addition, N-nitrosamines, which have carcinogenic activity (promote the formation of cancerous tumors), can be formed from nitrites in the presence of amines. When taking high doses of nitrates with drinking water or food, nausea, shortness of breath, blue skin and mucous membranes, and diarrhea appear after 4–6 hours. All this is accompanied by general weakness, dizziness, pain in the occipital region, palpitations. First aid - abundant gastric lavage, intake of activated charcoal, saline laxatives, fresh air. The permissible daily intake of nitrates for an adult is 325 mg per day. As you know, the presence of nitrates up to 45 mg / l is allowed in drinking water.

Radon in your apartment

People who are interested in their health often find such a phrase "Radioactive gas-Radon" in the list of environmental hazards in the premises. What is it? And is he really that dangerous?

Determination of radon in a room is of paramount importance, since it is this radionuclide that provides more than half of the entire dose load on the human body. Radon is an inert gas, colorless and odorless, 7.5 times heavier than air. It enters the human body together with the inhaled air (for reference: ventilation of the lungs in a healthy person reaches 5-9 liters per minute).

Radon isotopes are members of natural radioactive series (there are three of them). Radon is an alpha emitter (decays with the formation of a daughter element and an alpha particle) with a half-life of 3.82 days. Among the daughter products of radioactive decay (DPR) of radon, there are both alpha and beta emitters.

Sometimes alpha and beta decay accompanies gamma radiation. Alpha radiation cannot penetrate the human skin, therefore, in case of external influence, it does not pose a health hazard. The radioactive gas enters the body through the respiratory tract and irradiates it from the inside. Since radon is a potential carcinogen, lung cancer is the most frequent consequence of its chronic effects on humans and animals.

The main source of radon-222 and its isotopes in indoor air is their release from the earth's crust (up to 90% on the first floors) and from building materials (~ 10%). A certain contribution can be made by the intake of radon from tap water (when using artesian water with a high content of radon) and from natural gas burned for heating rooms and cooking. The highest levels of radon are observed in one-story village houses with an underground floor, where there is practically no protection against the penetration of radioactive gas released from the soil into the room. The lack of ventilation and careful sealing of premises, which is typical for regions with a cold climate, lead to an increase in the concentration of radon.

Among building materials, the most dangerous are rocks of volcanic origin (granite, pumice, tuff), and the least dangerous - wood, limestone, marble, natural gypsum.

Radon is almost completely removed from tap water by settling and boiling. But in the bathroom air when a hot shower is on, its concentration can reach high values.

All of the above has led to the need to standardize radon concentrations in rooms (standards "NRB-99"). In accordance with these sanitary standards, when designing new residential and public buildings, it should be provided that the average annual equivalent volumetric activity of radon isotopes in indoor air (АRn + 4.6ATh) does not exceed 100 Bq / m3. The total effective dose due to natural radionuclides in drinking water should not exceed 0.2 mSv / year.

Maksimova O.A.
candidate of geological and mineralogical sciences