In light of the rapid development of science and technology, experts express concern over the lack of promotion of radiation hygiene among the population. Experts predict that in the next decade, "radiological ignorance" may cause a real threat to the security of society and the planet.
Invisible killer
In the 15th century, European physicians were baffled by the abnormally high mortality from pulmonary diseases among workers in mines that mine iron, polymetals and silver. The mysterious illness, called "mountain sickness", struck miners fifty times more often than the average layman. It was only at the beginning of the 20th century, after the discovery of radon, that it was recognized as the reason for the stimulation of lung cancer in Germany and the Czech Republic.
What is radon? Is it only negatively affecting the human body? To answer these questions, we should recall the history of the discovery and study of this mysterious element.
Emanation means expiration
The pioneer of radon is considered to be 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, which leads to an increase in the level of environmental radioactivity. The researcher called the alleged substance emanation of thorium (from emanation (lat.) - expiration) and assigned it the letter designation Em. Similar emanations are also characteristic of radium preparations. In the first case, the emitted gas is called thoron, in the second - radon.
In the future, it was possible to prove that gases are radionuclides of a new element. The Scottish chemist, the Nobel laureate (1904) William Ramsay (together with Whitlow Gray) in 1908 succeeded in isolating it in its pure form for the first time. Five years later, the name radon and the symbol designation Rn were finally assigned to the element.
What is radon?
In the periodic system of chemical elements of D. I. Mendeleev, radon is in the 18th group. It has an atomic number z = 86.
All existing radon isotopes (more than 35, with mass numbers from 195 to 230) are radioactive and pose a certain danger to humans. In nature, there are four varieties of element atoms. All of them are part of the natural radioactive series of actinouran, thorium and uranium - radium. Some isotopes have their own names and, according to historical tradition, they are called emanations:
- actinium - actinon 219 Rn;
- thorium - thoron 220 Rn;
- radium - radon 222 Rn.
The latter is most stable. The half-life of radon 222 Rn is 91.2 hours (3.82 days). The steady state time of the remaining isotopes is calculated in seconds and milliseconds. During decay with the emission of α particles, polonium isotopes 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", "identical").
Physical and chemical properties
Under normal conditions, radon is a gas without color and odor, the presence of which can be determined only by special instruments. Density - 9.81 g / l. It is the heaviest (the air is 7.5 times lighter), the rarest and most expensive of all known gases on our planet.
It is soluble 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 ° C) a blue glow is characteristic, for crystalline (below -71 ° C) it is yellow or orange-red.
The chemical characterization 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. The effect of radon leads to staining of glass and porcelain, decomposes water into oxygen, hydrogen and ozone, destroys paraffin and petroleum jelly, etc.
Receiving Radon
To isolate radon isotopes, it is enough to let a stream of air over a substance containing radium in one form or another. The concentration of gas in the stream will depend on many physical factors (humidity, temperature), on the crystal structure of the substance, its composition, porosity, uniformity and can range from small fractions to 100%. Usually, solutions of radium bromide or chloride in hydrochloric acid are used. Solid porous substances are used much less frequently, although radon is more pure.
The resulting gas mixture is purified from water vapor, oxygen and hydrogen, passing it through a red-hot copper grid. The remainder (1/25000 of the original volume) is condensed with liquid air and nitrogen, helium and inert gases are removed from the condensate.
For a note: all over the world in a year, only a few tens of cubic centimeters of the chemical element of radon are produced.
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 in igneous, sedimentary, metamorphic rocks, and schist shales. Due to its inertness, gas radon easily leaves the crystal lattices of minerals and easily spreads over voids and cracks in the earth's crust over long distances, releasing into the atmosphere.
In addition, ground interstratal waters, washing such rocks, are easily saturated with radon. Radon water and its specific properties were 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 unambiguous to answer the question: "What is radon and what is its significance for humanity?" seems difficult. Modern researchers face at least two problems. The first is that in the sphere of influence of radon radiation on living matter, it is both a harmful and useful element. The second - in the absence of reliable means of registration and monitoring. Existing radon detectors in the atmosphere, even the most modern and sensitive ones, can repeat the measurements several times when repeated.
Caution 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 position belongs to the colorless gas radon. Depending on the geographical location of the residential building, its “contribution” can be from 30 to 60%. A constant amount of unstable isotopes of a hazardous element in the atmosphere is supported by continuous supply from terrestrial rocks. Radon has the unpleasant property of accumulating inside residential and public buildings, where its concentration can increase tens or hundreds of times. For human health, the danger is not so much the radioactive gas itself as the chemically active isotopes of polonium 214 Po and 218 Po, resulting from its decay. They are firmly held in the body, perniciously affecting 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 employees of uranium mines and mining and processing enterprises, volcanologists, radon therapists, the population of disadvantaged areas with a high content of radon derivatives in the earth's crust and artesian waters, radon resorts. To identify such territories, maps of radon hazard are compiled using geological and radiation-hygienic methods.
To note: it is believed that it was exposure to radon that provoked the death of lung cancer in 1916 by Scottish researcher of this element, William Ramsay.
Protection methods
In the last decade, following the example of its western neighbors, the necessary anti-radar measures have begun 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 radiation safety of the population.
The main measures to protect against soil gases and natural sources of radiation include:
- Arrangement of an earthen underground wooden floors of a monolithic concrete slab with crushed stone base and reliable waterproofing.
- Providing enhanced ventilation of the basement and basement, ventilation of residential buildings.
- The water entering the kitchens and bathrooms must be specially filtered, and the premises themselves are equipped with forced draft 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 springs of Belokurikha (Altai) saturated with this gas. The fact is that in microdoses, radon has a positive effect on the vital organs of the person and the central nervous system. Exposure to radon water accelerates metabolic processes, due to which damaged tissues are restored much faster, the functioning of the heart and circulatory system is normalized, and the walls of blood vessels become stronger.
Resorts in the mountains of the Caucasus (Essentuki, Pyatigorsk, Kislovodsk), Austria (Gastein), Czech Republic (Jachymov, Karlovy Vary), Germany (Baden-Baden), Japan (Misas) have long been deserved fame and popularity. In addition to radon baths, modern medicine 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 element isotopes to adsorption 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 serves to control the flow of technological processes. With its help, gas masks and chemical protective equipment are checked for leaks.
In geophysics and geology, many methods for searching and detecting mineral deposits and radioactive ores are based on the use of radon surveys. By the concentration of radon isotopes in the soil, one can judge the gas permeability and density of rock formations. Monitoring of the radon environment looks promising in terms of forecasting upcoming earthquakes.
It is hoped that the negative effects of radon, mankind still cope and the radioactive element will only bring benefits to the population of the planet.