Strontium - a characteristic of properties with a photo, its biological role in the human body, treatment with drugs based on a chemical element. Strontium in the human body

Strontium- an element of the main subgroup of the second group, the fifth period of the periodic system of chemical elements of D. I. Mendeleev, with atomic number 38. It is denoted by the symbol Sr (lat. Strontium). The simple substance strontium is a soft, malleable and ductile alkaline earth metal of a silvery-white color. It has a high chemical activity, in air it quickly reacts with moisture and oxygen, becoming covered with a yellow oxide film.

In 1764, a mineral was found in a lead mine near the Scottish village of Strontian, which they called strontianite. For a long time it was considered a variety of fluorite CaF2 or witherite BaCO3, but in 1790 the English mineralogists Crawford and Cruickshank analyzed this mineral and found that it contained a new "earth", and in the current language, oxide.

Independently of them, the same mineral was studied by another English chemist, Hope. Having come to the same results, he announced that there is a new element in strontianite - the metal strontium.

Apparently, the discovery was already “in the air”, because almost simultaneously the prominent German chemist Klaproth announced the discovery of a new “earth”.

In the same years, the well-known Russian chemist, Academician Toviy Egorovich Lovitz, also came across traces of "strontium earth". He had long been interested in the mineral known as heavy spar. In this mineral (its composition is BaSO4), Karl Scheele discovered in 1774 the oxide of the new element barium. We do not know why Lovitz was not indifferent to heavy spar; it is only known that the scientist, who discovered the adsorption properties of coal and did much more in the field of general and organic chemistry, collected samples of this mineral. But Lovitz was not just a collector, he soon began to systematically study heavy spar and in 1792 came to the conclusion that this mineral contained an unknown impurity. He managed to extract quite a lot from his collection - more than 100 g of new "earth" and continued to explore its properties. The results of the study were published in 1795.

So, almost simultaneously, several researchers in different countries came close to the discovery of strontium. But in its elementary form it was singled out only in 1808.

The outstanding scientist of his time, Humphry Davy, already understood that the element of strontium earth must, apparently, be an alkaline earth metal, and he obtained it by electrolysis, i.e. in the same way as calcium, magnesium, barium. More specifically, the world's first metallic strontium was obtained by electrolysis of its moistened hydroxide. The strontium released at the cathode instantly combined with mercury, forming an amalgam. Decomposing the amalgam by heating, Davy isolated the pure metal.

STRONTIUM (Strontium, Sr) - a chemical element of the periodic system of D. I. Mendeleev, a subgroup of alkaline earth metals. In the human body, S. competes with calcium (see) for inclusion in the crystal lattice of bone oxyapatite (see). 90 Sr, one of the most long-lived radioactive fission products of uranium (see), accumulating in the atmosphere and biosphere during nuclear weapons tests (see), poses a great danger to mankind. S.'s radioactive isotopes are used in medicine for radiation therapy (see), as a radioactive label in diagnostic radiopharmaceuticals (see) in medical biol. research, as well as in atomic electric batteries. S. compounds are used in flaw detectors, in sensitive instruments, and in devices for combating static electricity. In addition, S. is used in radio electronics, pyrotechnics, in the metallurgical and chemical industries, and in the manufacture of ceramic products. S.'s connections are not poisonous. When working with metallic S., one should be guided by the rules for handling alkali metals (see) and alkaline earth metals (see).

S. was discovered as part of a mineral later named SrC03 strontianite in 1787 near the Scottish city of Strontiana.

The serial number of strontium is 38, the atomic weight (mass) is 87.62. The content of S. in the earth's crust averages 4-10 2 wt. %, in sea water - 0.013% (13 mg / l). The minerals strontianite and celestite SrSO 4 are of industrial importance.

The human body contains approx. 0.32 g of strontium, mainly in bone tissue, in the blood, the concentration of S. is normally 0.035 mg / l, in the urine - 0.039 mg / l.

S. is a soft silvery-white metal, t°pl 770°, t°kip 1383°.

According to chem. S.'s properties are similar to calcium and barium (see), in connections strontium valency 4-2, is chemically active, is oxidized under normal conditions by water with formation of Sr(OH) 2, and also by oxygen and other oxidizers.

S. enters the human body hl. arr. with plant foods, as well as with milk. It is absorbed in the small intestine and quickly exchanges with S. contained in the bones. S.'s removal from an organism is strengthened by complexes, amino acids, polyphosphates. The increased content of calcium and fluorine (see) in water interferes with S.'s cumulation in bones. With an increase in the concentration of calcium in the diet by 5 times, S.'s accumulation in the body is halved. Excessive S.'s intake with food and water due to its increased content in the soil of some geochemical. provinces (eg, in some districts of Eastern Siberia) causes an endemic disease - ur disease (see Kashin - Beck disease).

In bones, blood and other biol. S.'s substrates define hl. arr. spectral methods (see Spectroscopy).

radioactive strontium

Natural S. consists of four stable isotopes with mass numbers 84, 86, 87, and 88, of which the latter is the most common (82.56%). Eighteen radioactive isotopes of sulfur are known (with mass numbers 78–83, 85, 89–99) and four isomers of isotopes with mass numbers 79, 83, 85, and 87 (see Isomerism).

In medicine, 90Sr is used for radiation therapy in ophthalmology and dermatology, as well as in radiobiological experiments as a source of β-radiation. 85Sr is produced either by irradiating a strontium target enriched in the 84Sr isotope with neutrons in a nuclear reactor by the reaction 84Sr (11.7) 85Sr, or produced at a cyclotron by irradiating natural rubidium targets with protons or deuterons, for example, by the reaction 85Rb (p, n) 85Sr. The radionuclide 85Sr decays with electron capture, emitting gamma radiation with an energy E gamma equal to 0.513 MeV (99.28%) and 0.868 MeV (< 0,1%).

87mSr can also be obtained by irradiating a strontium target in a reactor by the reaction 86Sr (n, gamma) 87mSr, but the yield of the desired isotope is low, in addition, 85Sr and 89Sr isotopes are formed simultaneously with 87mSr. Therefore, usually 87niSr is obtained using an isotope generator (see Radioactive Isotope Generators) based on the parent isotope of yttrium-87 - 87Y (T1 / 2 = 3.3 days). 87mSr decays with an isomeric transition, emitting gamma radiation with an Egamma energy of 0.388 MeV, and partly with electron capture (0.6%).

89Sr is contained in fission products together with 90Sr; therefore, 89Sr is obtained by irradiating natural sulfur in a reactor. In this case, an 85Sr impurity is also inevitably formed. The 89Sr isotope decays with the emission of P-radiation with an energy of 1.463 MeV (approx. 100%). The spectrum also contains a very weak line of gamma radiation with an energy E gamma equal to 0.95 MeV (0.01%).

90Sr is obtained by isolation from a mixture of uranium fission products (see). This isotope decays with the emission of beta radiation with an energy of E beta equal to 0.546 Meu (100%), without accompanying gamma radiation. The decay of 90Sr leads to the formation of a daughter radionuclide 90Y, which decays (T1 / 2 = 64 hours) with the emission of p-radiation, consisting of two components with Ep equal to 2.27 MeV (99%) and 0.513 MeV (0 .02%). The decay of 90Y also emits very weak gamma radiation with an energy of 1.75 MeV (0.02%).

Radioactive isotopes 89Sr and 90Sr, which are present in the waste of the nuclear industry and are formed during nuclear weapons testing, can enter the human body with food, water, and air when the environment is polluted. Quantification of S.'s migration in the biosphere is usually carried out in comparison with calcium. In most cases, when 90Sr moves from the previous link in the chain to the next, the concentration of 90Sr decreases per 1 g of calcium (the so-called discrimination coefficient), in adults in the body-diet link, this coefficient is 0.25.

Like soluble compounds of other alkaline earth elements, soluble compounds of S. are well absorbed from went. - kish. a path (10-60%), absorption of poorly soluble connections S. (eg, SrTi03) makes less than 1%. The degree of absorption of S.'s radionuclides in the intestine depends on age. With an increase in the calcium content in the diet, S.'s accumulation in the body decreases. Milk promotes increase in S.'s absorption and calcium in intestines. It is believed that this is due to the presence of lactose and lysine in milk.

When inhaled, soluble S. compounds are quickly eliminated from the lungs, while poorly soluble SrTi03 is exchanged in the lungs extremely slowly. Penetration of radionuclide S. through the intact skin makes apprx. one%. Through damaged skin (cut wound, burns, etc.)? as well as from subcutaneous tissue and muscle tissue, S. is absorbed almost completely.

S. is an osteotropic element. Regardless of the route and rhythm of entry into the body, soluble 90Sr compounds selectively accumulate in the bones. Less than 1% of 90Sr is retained in soft tissues.

With intravenous administration, S. is very quickly eliminated from the bloodstream. Soon after administration, the concentration of S. in the bones becomes 100 times or more higher than in soft tissues. Nek-ry distinctions in accumulation 90Sr in separate bodies and fabrics are noted. A relatively higher concentration of 90Sr in experimental animals is found in the kidneys, salivary and thyroid glands, and the lowest - in the skin, bone marrow and adrenal glands. The concentration of 90Sr in the renal cortex is always higher than in the medulla. S. initially lingers on the bone surfaces (periosteum, endosteum), and then is distributed relatively evenly throughout the entire volume of the bone. Nevertheless, the distribution of 90Sr in different parts of the same bone and in different bones turns out to be uneven. During the first time after injection, the concentration of 90Sr in the epiphysis and metaphysis of the bone of experimental animals is approximately 2 times higher than in the diaphysis. From the epiphysis and metaphysis, 90Sr is excreted faster than from the diaphysis: in 2 months. the concentration of 90Sr in the epiphysis and metaphysis of the bone decreases by 4 times, and in the diaphysis almost does not change. Initially 90Sr concentrates in those sites in which there is an active formation of a bone. Abundant blood and lymph circulation in the epimetaphyseal areas of the bone contributes to a more intense deposition of 90Sr in them compared to the diaphysis of the tubular bone. The amount of 90Sr deposition in the bones of animals is not constant. A sharp decrease in 90Sr fixation in bones with age was found in all animal species. Deposition of 90Sr in the skeleton significantly depends on gender, pregnancy, lactation, and the state of the neuroendocrine system. A higher deposition of 90Sr in the skeleton was noted in male rats. In the skeleton of pregnant females, 90Sr accumulates less (up to 25%) than in control animals. Lactation has a significant effect on the accumulation of 90Sr in the skeleton of females. With the introduction of 90Sr 24 hours after birth, 90Sr is retained in the skeleton of rats 1.5-2 times less than in non-lactating females.

The penetration of 90Sr into the tissues of the embryo and fetus depends on the stage of their development, the state of the placenta, and the duration of circulation of the isotope in the mother's blood. Penetration of 90Sr into the fetus is the greater, the longer the gestational age at the time of administration of the radionuclide.

To reduce the damaging effect of strontium radionuclides, it is necessary to limit their accumulation in the body. For this purpose, when the skin is contaminated, it is necessary to quickly decontaminate its open areas (Protection-7 preparation, Era or Astra washing powders, NEDE paste). In case of oral intake of strontium radionuclides, antidotes should be used to bind or absorb the radionuclide. Such antidotes include activated barium sulfate (adso-bar), polysurmin, alginic acid preparations, etc. For example, the drug adsobar, when taken immediately after radionuclides enter the stomach, reduces their absorption by 10-30 times. Adsorbents and antidotes should be prescribed immediately after detection of damage by strontium radionuclides, since delay in this case leads to a sharp decrease in their positive effect. At the same time, it is recommended to prescribe emetics (apomorphine) or to produce abundant gastric lavage, use saline laxatives, cleansing enemas. In case of damage by dust-like preparations, abundant washing of the nose and oral cavity, expectorants (thermopsis with soda), ammonium chloride, injections of calcium preparations, diuretics are necessary. In later periods after the lesion, to reduce the deposition of S.'s radionuclides in the bones, it is recommended to use the so-called. stable strontium (S. lactate or S. gluconate). Large doses of oral calcium or intravenous MofyT replace stable strontium preparations if these are not available. In connection with the good reabsorption of strontium radionuclides in the renal tubules, the use of diuretics is also indicated.

Nek-swarm decrease in accumulation of S.'s radionuclides in an organism can be reached by creation of competitive relations between them and stable isotope S. or calcium, and also creation of deficiency of these elements when S.'s radionuclide was already fixed in a skeleton. However, effective means of decorporation of radioactive strontium from the body have not yet been found.

The minimum significant activity that does not require registration or permission from the State Sanitary Inspection for 85mSr, 85Sr, 89Sr and 90Sr is 3.5*10 -8 , 10 -10 , 2.8*10 -11 and 1.2*10, respectively -12 curies/l.

Bibliography: Borisov V.P. and others. Emergency care for acute radiation exposure, M., 1976; Buldakov L. A. and Moskalev Yu. I. Problems of distribution and experimental estimation of admissible levels of Cs137, Sr90 and Ru106, M., 1968, bibliogr.; Voinar A. I. The biological role of trace elements in the body of animals and humans, p. 46, M., 1960; Ilyin JI. A. and Ivannikov A. T. Radioactive substances and wounds, M., 1979; To and with and in fi-on B. S. and T about r ben to about V. P. Life of a bone tissue, M., 1979; JI e in and V. I N. Obtaining radioactive preparations, M., 1972; Metabolism of strontium, ed. J. M. A. Lenihena and others, trans. from English, M., 1971; Poluektov N. S. and others. Analytical chemistry of strontium, M., 1978; P em and G. Course of inorganic chemistry, trans. from German, vol. 1, M., 1972; Protection of the patient in radionuclide investigations, Oxford, 1969, bibliogr.; Table of isotopes, ed. by C. M. Lederer a. V. S. Shirley, N. Y. a. o., 1978.

A. V. Babkov, Yu. I. Moskalev (rad.).

Strontium is an element of the main subgroup of the second group, the fifth period of the periodic system of chemical elements of D. I. Mendeleev, with atomic number 38. It is designated by the symbol Sr (lat. Strontium). The simple substance strontium is a soft, malleable and ductile alkaline earth metal of a silvery-white color. It has a high chemical activity, in air it quickly reacts with moisture and oxygen, becoming covered with a yellow oxide film.

Atomic number - 38

Atomic mass - 87.62

Density, kg/m³ - 2600

Melting point, ° С - 768

Heat capacity, kJ / (kg ° С) - 0.737

Electronegativity - 1.0

Covalent radius, Å - 1.91

1st ionization potential, ev - 5.69

In 1764, a mineral was found in a lead mine near the Scottish village of Strontian, which they called strontianite. For a long time it was considered a variety of fluorite CaF 2 or witherite BaCO 3, but in 1790 the English mineralogists Crawford and Cruikshank analyzed this mineral and found that it contained a new "earth", and in today's language, oxide.

Independently of them, the same mineral was studied by another English chemist, Hope. Having come to the same results, he announced that there is a new element in strontianite - the metal strontium.

Apparently, the discovery was already “in the air”, because almost simultaneously the prominent German chemist Klaproth announced the discovery of a new “earth”.

In the same years, the well-known Russian chemist, Academician Toviy Egorovich Lovits, also came across traces of "strontium earth". He had long been interested in the mineral known as heavy spar. In this mineral (its composition is BaSO 4), Karl Scheele discovered in 1774 the oxide of the new element barium. We do not know why Lovitz was not indifferent to heavy spar; it is only known that the scientist, who discovered the adsorption properties of coal and did much more in the field of general and organic chemistry, collected samples of this mineral. But Lovitz was not just a collector, he soon began to systematically study heavy spar and in 1792 came to the conclusion that this mineral contained an unknown impurity. He managed to extract quite a lot from his collection - more than 100 g of new "earth" and continued to explore its properties. The results of the study were published in 1795.

So, almost simultaneously, several researchers in different countries came close to the discovery of strontium. But in its elementary form it was singled out only in 1808.

The outstanding scientist of his time, Humphry Davy, already understood that the element of strontium earth must, apparently, be an alkaline earth metal, and he obtained it by electrolysis, i.e. in the same way as calcium, magnesium, barium. More specifically, the world's first metallic strontium was obtained by electrolysis of its moistened hydroxide. The strontium released at the cathode instantly combined with mercury, forming an amalgam. Decomposing the amalgam by heating, Davy isolated the pure metal.

Strontium is found in sea water (0.1 mg/l), in soils (0.035 wt %). By mass, in geochemical processes, it is a satellite of calcium. In igneous rocks, strontium is predominantly in a dispersed form and enters as an isomorphic impurity into the crystal lattice of calcium, potassium, and barium minerals. In the biosphere, Strontium accumulates in carbonate rocks and especially in the sediments of salt lakes and lagoons.

Strontium is an integral part of microorganisms, plants and animals. In marine radiolarians (acantaria), the skeleton consists of strontium sulfate - celestine. Seaweed contains 26-140 mg of Strontium per 100 g of dry matter, terrestrial plants - 2.6, marine animals - 2-50, terrestrial animals - 1.4, bacteria - 0.27-30. Accumulation of Strontium by various organisms depends not only on their species, features, but also on the ratio of Strontium with other elements, mainly Ca and P, in the environment, as well as on the adaptation of organisms to a specific geochemical environment.

In nature, strontium occurs as a mixture of 4 stable isotopes 84Sr (0.56%), 86Sr (9.86%), 87Sr (7.02%), 88Sr (82.56%). Radioactive isotopes with mass numbers from 80 to 97 have been artificially obtained, incl. 90 Sr (T ½ = 27.7 years), formed during the fission of uranium.

There are 3 ways to obtain metallic strontium:

• thermal decomposition of some compounds
• electrolysis of a melt containing 85% SrCl 2 and 15% KCl, however, in this process, the current efficiency is low, and the metal is contaminated with salts, nitride and oxide. In industry, electrolysis with a liquid cathode produces strontium alloys, for example, with tin.
• oxide or chloride reduction

The main raw materials for the production of strontium compounds are concentrates from the enrichment of celestine and strontianite. Strontium metal is obtained by reducing strontium oxide with aluminum at 1100-1150 °C:

4SrO+ 2Al = 3Sr+ SrO Al 2 O 3 .

The process is carried out in electrovacuum apparatuses [at 1 N/m 2 (10 -2 mm Hg)] of periodic action. Vapors of strontium condense on the cooled surface of a condenser inserted into the apparatus; at the end of the reduction, the apparatus is filled with argon and the condensate is melted, which flows into the mold.

The electrolytic production of strontium by electrolysis of a melt of a mixture of SrCl 2 and NaCl has not become widespread due to the low current efficiency and contamination of strontium with impurities.

At room temperature, the lattice of Strontium is face-centered cubic (α-Sr) with a period a = 6.0848Å; at temperatures above 248 °C, it transforms into a hexagonal modification (β-Sr) with lattice periods a = 4.32 Å and c = 7.06 Å; at 614 °C it transforms into a cubic body-centered modification (γ-Sr) with a period a = 4.85Å. Atomic radius 2.15Å, ionic radius Sr 2+ 1.20Å. The density of the α-form is 2.63 g / cm 3 (20 ° C); t pl 770 °C, t kip 1383 °C; specific heat capacity 737.4 kJ/(kg K); electrical resistivity 22.76·10 -6 ohm·cm -1 . Strontium is paramagnetic, the atomic magnetic susceptibility at room temperature is 91.2·10 -6 . Strontium is a soft ductile metal that can be easily cut with a knife.

Polymorphene - three of its modifications are known. Up to 215 o C, the cubic face-centered modification (α-Sr) is stable, between 215 and 605 o C - hexagonal (β-Sr), above 605 o C - cubic body-centered modification (γ-Sr).

Melting point - 768 o C, Boiling point - 1390 o C.

Strontium in its compounds always exhibits a +2 valence. By properties, strontium is close to calcium and barium, occupying an intermediate position between them.

In the electrochemical series of voltages, strontium is among the most active metals (its normal electrode potential is −2.89 V. It reacts vigorously with water, forming hydroxide:

Sr + 2H 2 O \u003d Sr (OH) 2 + H 2

Interacts with acids, displaces heavy metals from their salts. With concentrated acids (H 2 SO 4 , HNO 3) reacts weakly.

Strontium metal rapidly oxidizes in air, forming a yellowish film, in which, in addition to SrO oxide, SrO 2 peroxide and Sr 3 N 2 nitride are always present. When heated in air, it ignites; powdered strontium in air is prone to self-ignition.

Vigorously reacts with non-metals - sulfur, phosphorus, halogens. Interacts with hydrogen (above 200 o C), nitrogen (above 400 o C). Practically does not react with alkalis.

At high temperatures, it reacts with CO 2, forming a carbide:

5Sr + 2CO 2 = SrC 2 + 4SrO

Easily soluble salts of strontium with anions Cl - , I - , NO 3 - . Salts with anions F -, SO 4 2-, CO 3 2-, PO 4 3- are sparingly soluble.

The main areas of application of strontium and its chemical compounds are the radio-electronic industry, pyrotechnics, metallurgy, and the food industry.

Strontium is used for alloying copper and some of its alloys, for introducing into battery lead alloys, for desulfurizing cast iron, copper and steels.

Strontium with a purity of 99.99-99.999% is used to reduce uranium.

Magnetically hard strontium ferrites are widely used as materials for the production of permanent magnets.

Long before the discovery of strontium, its undeciphered compounds were used in pyrotechnics to produce red lights. Until the mid-40s of the 20th century, strontium was, first of all, the metal of fireworks, fun and salutes. The magnesium-strontium alloy has the strongest pyrophoric properties and is used in pyrotechnics for incendiary and signal compositions.

Radioactive 90 Sr (half-life 28.9 years) is used in the production of radioisotope current sources in the form of strontium titanate (density 4.8 g/cm³, energy release about 0.54 W/cm³).

Strontium uranate plays an important role in the production of hydrogen (strontium-uranate cycle, Los Alamos, USA) by the thermochemical method (atomic hydrogen energy), and in particular, methods are being developed for the direct fission of uranium nuclei in the composition of strontium uranate to produce heat during the decomposition of water into hydrogen and oxygen.

Strontium oxide is used as a component of superconducting ceramics.

Strontium fluoride is used as a component of solid-state fluorine batteries with enormous energy capacity and energy density.

Alloys of strontium with tin and lead are used for casting battery down conductors. Strontium-cadmium alloys for anodes of galvanic cells.

The metal is used in glazes and enamels for coating dishes. Strontium glazes are not only harmless, but also affordable (strontium carbonate SrCO 3 is 3.5 times cheaper than red lead). All the positive qualities of lead glazes are also characteristic of them. Moreover, products coated with such glazes acquire additional hardness, heat resistance, and chemical resistance.

Strontium is an active metal. This prevents its wide application in technology. But, on the other hand, the high chemical activity of strontium makes it possible to use it in certain areas of the national economy. In particular, it is used in the smelting of copper and bronze - strontium binds sulfur, phosphorus, carbon and increases the fluidity of the slag. Thus, strontium contributes to the purification of the metal from numerous impurities. In addition, the addition of strontium increases the hardness of copper, almost without reducing its electrical conductivity. Strontium is introduced into electric vacuum tubes to absorb the remaining oxygen and nitrogen, to make the vacuum deeper.

Salts and compounds of strontium have low toxicity; when working with them, one should be guided by the safety regulations with salts of alkali and alkaline earth metals.

One should not confuse the effect on the human body of natural (non-radioactive, low-toxic, and moreover, widely used for the treatment of osteoporosis) and radioactive isotopes of strontium. The strontium isotope 90 Sr is radioactive with a half-life of 28.9 years. 90 Sr undergoes β-decay, turning into radioactive 90 Y (half-life 64 hours). The complete decay of strontium-90 that has entered the environment will occur only after a few hundred years. 90 Sr is formed during nuclear explosions and emissions from nuclear power plants.

Radioactive strontium almost always has a negative effect on the human body:

1. It is deposited in the skeleton (bones), affects the bone tissue and bone marrow, which leads to the development of radiation sickness, tumors of the hematopoietic tissue and bones.

2. Causes leukemia and malignant tumors (cancer) of the bones, as well as damage to the liver and brain.

Strontium accumulates at a high rate in the body of children up to the age of four, when there is an active formation of bone tissue. The exchange of strontium changes in some diseases of the digestive system and the cardiovascular system. Entry routes:

1. water (the maximum permissible concentration of strontium in water in the Russian Federation is 8 mg / l, and in the USA - 4 mg / l)
2. food (tomatoes, beets, dill, parsley, radish, radish, onion, cabbage, barley, rye, wheat)
3. intratracheal intake
4. through the skin (cutaneous)
5. inhalation (through the air)
6. from plants or through animals, strontium-90 can directly pass into the human body.

The influence of non-radioactive strontium is extremely rare and only when exposed to other factors (calcium and vitamin D deficiency, malnutrition, violations of the ratio of trace elements such as barium, molybdenum, selenium, etc.). Then it can cause "strontium rickets" and "uro disease" in children - damage and deformity of the joints, growth retardation and other disorders.

Strontium-90.

Once in the environment, 90 Sr is characterized by the ability to be included (mainly together with Ca) in the metabolic processes of plants, animals, and humans. Therefore, when assessing the pollution of the biosphere with 90 Sr, it is customary to calculate the ratio of 90 Sr/Ca in strontium units (1 s.u. = 1 micron μcurie 90 Sr per 1 g Ca). When 90 Sr and Ca move along biological and food chains, Strontium discrimination occurs, for the quantitative expression of which the “discrimination coefficient” is found, the ratio of 90 Sr / Ca in the next link of the biological or food chain to the same value in the previous link. In the final link of the food chain, the concentration of 90 Sr, as a rule, is much lower than in the initial one.

Plants can receive 90 Sr directly from direct contamination of the leaves or from the soil through the roots. Relatively more 90 Sr is accumulated by leguminous plants, root and tuber crops, less by cereals, including cereals, and flax. Significantly less 90 Sr is accumulated in seeds and fruits than in other organs (for example, 90 Sr is 10 times more in wheat leaves and stems than in grain). In animals (comes mainly with plant foods) and humans (comes mainly with cow's milk and fish), 90 Sr accumulates mainly in the bones. The amount of 90 Sr deposition in the body of animals and humans depends on the age of the individual, the amount of incoming radionuclide, the rate of growth of new bone tissue, and others. 90 Sr poses a great danger to children, in whose body it enters with milk and accumulates in rapidly growing bone tissue.

For humans, the half-life of strontium-90 is 90-154 days.

The conclusion in 1963 in Moscow of the Treaty on the Ban on Tests of Nuclear Weapons in the Atmosphere, Outer Space and Under Water led to the almost complete release of the atmosphere from 90 Sr and a decrease in its mobile forms in the soil.

After the accident at the Chernobyl nuclear power plant, the entire territory with significant contamination with strontium-90 was within a 30-kilometer zone. A large amount of strontium-90 got into water bodies, but its concentration in river water never exceeded the maximum allowable for drinking water (except for the Pripyat River in early May 1986 in its lower reaches).

During the accident at the Chernobyl nuclear power plant, relatively little of it got into the environment - the total release is estimated at 0.22 MKi. Historically, much attention has been paid to this radionuclide in radiation hygiene. There are several reasons for this. Firstly, strontium-90 accounts for a significant part of the activity in the mixture of products of a nuclear explosion: 35% of the total activity immediately after the explosion and 25% after 15-20 years, and secondly, nuclear accidents at the Mayak Production Association in the South Urals in 1957 and 1967, when a significant amount of strontium-90 was released into the environment.

Strontium is an element of the main subgroup of the second group, the fifth period of the periodic system of chemical elements of D. I. Mendeleev, with atomic number 38. It is designated by the symbol Sr (lat. Strontium). The simple substance strontium (CAS number: 7440-24-6) is a soft, malleable and ductile silver-white alkaline earth metal. It has a high chemical activity, in air it quickly reacts with moisture and oxygen, becoming covered with a yellow oxide film.

History and origin of the name

The new element was discovered in the mineral strontianite, found in 1764 in a lead mine near the Scottish village of Stronshian, which later gave the name to the new element. The presence of a new metal oxide in this mineral was established in 1787 by William Cruikshank and Ader Crawford. Isolated in its purest form by Sir Humphry Davy in 1808.

Receipt

There are 3 ways to obtain metallic strontium:
1. thermal decomposition of some compounds
2. electrolysis
3. reduction of oxide or chloride
The main industrial method for obtaining metallic strontium is the thermal reduction of its oxide with aluminum. Further, the resulting strontium is purified by sublimation.
The electrolytic production of strontium by electrolysis of a melt of a mixture of SrCl 2 and NaCl has not become widespread due to the low current efficiency and contamination of strontium with impurities.
During thermal decomposition of strontium hydride or nitride, finely dispersed strontium is formed, which is prone to easy ignition.

Chemical properties

Strontium in its compounds always exhibits a +2 valency. By properties, strontium is close to calcium and barium, occupying an intermediate position between them.
In the electrochemical series of voltages, strontium is among the most active metals (its normal electrode potential is −2.89 V). Reacts vigorously with water to form hydroxide:
Sr + 2H 2 O \u003d Sr (OH) 2 + H 2

Interacts with acids, displaces heavy metals from their salts. With concentrated acids (H 2 SO 4 , HNO 3) reacts weakly.
Strontium metal rapidly oxidizes in air, forming a yellowish film, in which, in addition to SrO oxide, SrO 2 peroxide and Sr 3 N 2 nitride are always present. When heated in air, it ignites; powdered strontium in air is prone to self-ignition.
Vigorously reacts with non-metals - sulfur, phosphorus, halogens. Interacts with hydrogen (above 200°C), nitrogen (above 400°C). Practically does not react with alkalis.
At high temperatures, it reacts with CO 2, forming a carbide:
5Sr + 2CO 2 = SrC 2 + 4SrO

Easily soluble salts of strontium with anions Cl - , I - , NO 3 - . Salts with anions F -, SO 4 2-, CO 3 2-, PO 4 3- are sparingly soluble.

Strontium- alkaline earth metal. It is a substance of a silvery-white color (see photo), very soft and plastic, easily cut even with an ordinary knife. Possesses high activity, burns in the presence of air, enters into chemical interactions with water. Under natural conditions, it is not found in its pure form. It is mainly found in the composition of fossil minerals, usually in combination with calcium.

It was first found in Scotland at the end of the 18th century in a village with the name Stronshian, which gave the name to the found mineral - strontianite. But only 30 years after the discovery, the English scientist H. Davy was able to isolate it in its pure form.

The element's compounds are used in metallurgical production, medicine, and the food industry. Very interesting is its property, when burning, to emit fires of a red hue, which were adopted by pyrotechnics at the beginning of the 20th century.

The action of strontium and its biological role

Many associate the action of a macroelement with high toxicity and radioactivity. But such an opinion is rather erroneous, because. the natural element practically does not possess these qualities and is even present in the tissues of biological organisms, performing an important biological role and some functions as a satellite of calcium. Due to the properties of the substance, it is used for medical purposes.

The main accumulation of strontium in the human body falls on bone tissue. This is due to the fact that the element is similar to calcium in chemical action, and calcium, in turn, is the main component of the "construction" of the skeleton. But the muscles contain only 1% of the total mass of the element in the body.

Also, strontium is present in the deposits of gall and urinary stones, again in the presence of calcium.

By the way, about the harmfulness of strontium - only radioactive isotopes have a devastating effect on health, which in their chemical properties practically do not differ from the natural element. Perhaps this is the reason for this confusion.

Daily rate

The daily norm of a macronutrient is approximately 1 mg. This amount is quite easily replenished with food and drinking water. In total, approximately 320 mg of strontium is distributed in the body.

But it should be borne in mind that our body is able to absorb only 10% of the incoming element, and we get up to 5 mg per day.

Strontium deficiency

The lack of a macronutrient can only theoretically cause some pathologies, but so far this has been shown only in animal experiments. So far, scientists have not identified the negative impact of strontium deficiency on the human body.

At the moment, only some dependences of the assimilation of this macronutrient under the influence of other substances in the body have been identified. For example, this process is facilitated by certain amino acids, the intake of vitamins D and lactose. And drugs based on barium or sodium sulfates, as well as products with a high content of dietary coarse fibers, have an opposite effect.

There is another unpleasant feature - when calcium deficiency occurs, the body begins to accumulate radioactive strontium even from the air (often polluted by industrial enterprises).

Why is strontium dangerous for humans and what is its harm?

Strontium, after all, is capable of exerting a harmful radioactive effect. The element itself does little harm, and a critical dose has not yet been established. But its isotopes can cause diseases and various disorders. Like natural strontium, it accumulates in the skeleton itself, but its action causes damage to the bone marrow and destruction of the very structure of the bones. It can affect the cells of the brain and liver, and thus cause the occurrence of neoplasms and tumors.

But one of the most terrible consequences of exposure to the isotope is radiation sickness. The consequences of the Chernobyl disaster are still being felt in our country, and the accumulated reserves of radioactive strontium make themselves felt in the soil, water and the atmosphere itself. You can also get a large dose by working at enterprises using the element - there is the highest level of diseases of bone sarcoma and leukemia.

But natural strontium can also cause unpleasant consequences. Due to a rather rare set of circumstances such as an inadequate diet, a lack of calcium, vitamin D, and an imbalance in the body of elements such as selenium and molybdenum, specific diseases develop - strontium rickets and uric disease. The latter got its name from the area where local residents suffered from them back in the 19th century. They became disabled due to the curvature of the structure of the skeleton, bones and joints. Moreover, for the most part, those people who grew up in these places from childhood suffered. Only in the 20th century did they find out that the waters of the local river contained an increased amount of the element. And during the period of growth, it is the musculoskeletal system that is most affected.

Contact with strontium oxide on the mucous membranes of the mouth or eyes can cause burns and deep damage. And inhaling it with air can contribute to the development of pathological diseases in the lungs - fibrosis, bronchitis, and heart failure is also possible.

As treatment, drugs based on calcium, magnesium, sodium sulfate or barium are usually used. It is also possible to use complexing agents that bind and remove radioactive toxins from cells.

Getting into the soil, the toxic isotope of strontium is thus able to accumulate in plant fibers, and then in animal organisms. Thus, the human body slowly but surely accumulates toxins by consuming poisoned foods. Heat treatment of products can save the situation a little, which contributes to a fairly significant reduction in the content of harmful toxin in them.

This radionuclide is very difficult to remove from the body, because it may take him almost half a year to get rid of at least half of the accumulated stock.

What food contains?

Indications for treatment with drugs based on this element

There are still indications for the appointment of a macroelement, despite its possible toxicity. And even a radioactive isotope is used for medical purposes. Its radiation in allowed doses can have a therapeutic effect on erosions, tumors on the skin and mucous membranes. With deeper foci, this method is already used.

Also, its compounds serve as drugs for the treatment of epilepsy, nephritis and correction of deformity in childhood by orthopedists. To some extent, it can serve as an antihelminthic agent.