In light of the rapid development of science and technology, experts are concerned about the lack of promotion of radiation hygiene among the population. Experts predict that in the next decade, "radiological ignorance" could become a real threat to the security of society and the planet.
The invisible killer
In the 15th century, European physicians were perplexed by the abnormally high mortality from lung diseases among workers in mines that extract iron, polymetals and silver. A mysterious illness, called "mountain sickness", struck miners fifty times more often than the average layman. Only at the beginning of the 20th century, after the discovery of radon, it was he who was recognized as the reason for stimulating the development of lung cancer among miners in Germany and the Czech Republic.
What is radon? Does it only have a negative effect on the human body? To answer these questions, one should remember the history of the discovery and study of this mysterious element.
Emanation means "outflow"
The discoverer of radon acceptedconsider the English physicist E. Rutherford. It was he who in 1899 noticed that thorium-based preparations, in addition to heavy α-particles, emit a colorless gas, leading to an increase in the level of radioactivity in the environment. The researcher called the alleged substance an emanation of thorium (from emanation (lat.) - expiration) and assigned it the letter Em. Similar emanations are also characteristic of radium preparations. In the first case, the emitted gas was called thoron, in the second - radon.
Later it was possible to prove that gases are radionuclides of a new element. The Scottish chemist, Nobel laureate (1904) William Ramsay (together with Whitlow Gray) in 1908 managed to isolate it in its pure form for the first time. Five years later, the name radon and the symbol Rn were finally assigned to the element.
What is radon?
In the periodic table of chemical elements of D. I. Mendeleev, radon is in the 18th group. Has atomic number z=86.
All existing isotopes of radon (more than 35, with mass numbers from 195 to 230) are radioactive and pose a certain danger to humans. In nature, there are four types of atoms of the element. All of them are part of the natural radioactive series of actinouranium, thorium and uranium - radium. Some isotopes have their own names and, according to historical tradition, they are called emanations:
- anemone - actinon 219Rn;
- thorium - thoron 220Rn;
- radium - radon 222Rn.
The last one is differentthe greatest stability. The half-life of radon 222Rn is 91.2 hours (3.82 days). The steady state time of the remaining isotopes is calculated in seconds and milliseconds. During decay with radiation of α-particles, isotopes of polonium are formed. By the way, it was during the study of radon that scientists first encountered numerous varieties of atoms of the same element, which they later called isotopes (from the Greek "equal", "same").
Physical and chemical properties
Under normal conditions, radon is a colorless and odorless gas, the presence of which can only be detected with special instruments. Density - 9, 81 g/l. It is the heaviest (air is 7.5 times lighter), the rarest and most expensive of all gases known on our planet.
We will well dissolve in water (460 ml/l), but in organic compounds the solubility of radon is an order of magnitude higher. It has a fluorescence effect caused by high intrinsic radioactivity. For the gaseous and liquid state (at temperatures below -62˚С) a blue glow is characteristic, for the crystalline (below -71˚С) - yellow or orange-red.
The chemical characteristic of radon is due to its belonging to the group of inert ("noble") gases. It is characterized by chemical reactions with oxygen, fluorine and some other halogens.
On the other hand, the unstable core of an element is a source of high-energy particles that affect many substances. Exposure to radon stains glass and porcelain, decomposes water into oxygen,hydrogen and ozone, destroys paraffin and vaseline, etc.
Getting radon
To isolate radon isotopes, it is enough to pass a jet of air over a substance containing radium in one form or another. The gas concentration in the jet will depend on many physical factors (humidity, temperature), on the crystal structure of the substance, its composition, porosity, homogeneity and can vary from small fractions to 100%. Usually, solutions of bromide or radium chloride in hydrochloric acid are used. Solid porous substances are used much less often, although radon is released more pure.
The resulting gas mixture is purified from water vapor, oxygen and hydrogen, passing it through a hot copper grid. The remainder (1/25000 of the original volume) is condensed with liquid air, and impurities of nitrogen, helium and inert gases are removed from the condensate.
Note: only a few tens of cubic centimeters of the chemical element radon are produced worldwide per year.
Spread in nature
Radium nuclei, the fission product of which is radon, in turn are formed during the decay of uranium. Thus, the main source of radon is soils and minerals containing uranium and thorium. The highest concentration of these elements is found in igneous, sedimentary, metamorphic rocks, dark-colored shales. Due to its inertness, radon gas easily leaves the crystal lattices of minerals and easily spreads over long distances through voids and cracks in the earth's crust, escaping into the atmosphere.
Besides, ground interlayer waters, washing such rocks, are easily saturated with radon. Radon water and its specific properties have been used by man long before the discovery of the element itself.
Friend or foe?
Despite thousands of scientific and popular science articles written about this radioactive gas, it is unequivocal to answer the question: "What is radon and what is its significance for mankind?" seems difficult. Modern researchers face at least two problems. The first is that in the sphere of the impact of radon radiation on living matter, it is both a harmful and useful element. The second is the lack of reliable means of registration and monitoring. The existing radon detectors in the atmosphere, even the most modern and sensitive ones, can give results that differ by several times when measurements are repeated.
Beware of radon
The main dose of radiation (more than 70%) in the process of life a person receives due to natural radionuclides, among which the leading positions belong to the colorless gas radon. Depending on the geographical location of the residential building, its "contribution" can range from 30 to 60%. A constant amount of unstable isotopes of a dangerous element in the atmosphere is maintained by a continuous supply from the earth's rocks. Radon has the unpleasant property of accumulating inside residential and public buildings, where its concentration can increase tens or hundreds of times. For good he althhuman danger is not so much the radioactive gas itself, but the chemically active isotopes of polonium 214Po and 218Po, formed as a result of its decay. They are firmly held in the body, having a detrimental effect on living tissue with internal α-radiation.
In addition to asthmatic attacks of suffocation and depression, dizziness and migraine, this is fraught with the development of lung cancer. The risk group includes workers of uranium mines and mining and processing plants, volcanologists, radon therapists, the population of unfavorable areas with a high content of radon derivatives in the earth's crust and artesian waters, and radon resorts. To identify such areas, maps of radon hazard are compiled using geological and radiation-hygienic methods.
For a note: it is believed that it was radon exposure that provoked the death from lung cancer in 1916 by the Scottish researcher of this element, William Ramsay.
Methods of protection
In the last decade, following the example of Western neighbors, the necessary anti-radon measures began to spread in the countries of the former CIS. Regulatory documents appeared (SanPin 2.6.1., SP 2.6.1.) with clear requirements for ensuring the radiation safety of the population.
The main measures to protect against soil gases and natural radiation sources include:
- Arrangement on the earth underground of wooden floors of a monolithic concrete slab with a crushed stone base and reliable waterproofing.
- Providing enhanced ventilationbasement and basement space, ventilation of residential buildings.
- Water entering kitchens and bathrooms must be subjected to special filtration, and the rooms themselves are equipped with forced exhaust devices.
Radiomedicine
What is radon, our ancestors did not know, but even the glorious horsemen of Genghis Khan healed their wounds with the waters of the sources of Belokurikha (Altai), saturated with this gas. The fact is that in microdoses, radon has a positive effect on the vital organs of a person and the central nervous system. Exposure to radon water accelerates metabolic processes, due to which damaged tissues are restored much faster, the work of the heart and circulatory system normalizes, and the walls of blood vessels are strengthened.
Resorts in the mountainous regions of the Caucasus (Essentuki, Pyatigorsk, Kislovodsk), Austria (Gastein), Czech Republic (Yakhimov, Karlovy Vary), Germany (Baden-Baden), Japan (Misasa) have long enjoyed well-deserved fame and popularity. Modern medicine, in addition to radon baths, offers treatment in the form of irrigation, inhalation under the strict supervision of an appropriate specialist.
In the service of humanity
The scope of radon gas is not limited to medicine alone. The ability of isotopes of an element to adsorb is actively used in materials science to measure the degree of heterogeneity of metal surfaces and decoration. In the production of steel and glass, radon is used to control the flow of technological processes. With his helpcheck gas masks and chemical protection equipment for tightness.
In geophysics and geology, many methods of searching for and detecting deposits of minerals and radioactive ores are based on the use of radon surveys. The concentration of radon isotopes in the soil can be used to judge the gas permeability and density of rock formations. Monitoring of the radon situation looks promising in terms of predicting upcoming earthquakes.
It remains to be hoped that humanity will still cope with the negative effects of radon and the radioactive element will only benefit the population of the planet.
