Radiation Environment of Kazakhstan's Aktobe Region Territory
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Article-84 Eco. Env. & Cons. 23 (4) : 2017; pp. (582-588) Copyright@ EM International ISSN 0971–765X Radiation environment of Kazakhstan’s aktobe region territory Kozy Kibatayev1*, Gulnur Urgushbayeva2, Dina Yegizbayeva2, Kulyan Shayakhmetova2, Gulnura Kalbagayeva2, Alima Kashkinbayeva2, Yuliya Zame2 and Gulshara Abasheva2 1Technopark “Zerek” of S. Baishev Aktobe University, Aktobe, Republic of Kazakhstan 2West Kazakhstan Marat Ospanov State Medical University, Aktobe, Republic of Kazakhstan (Received 20 September, 2017; accepted 5 November, 2017) ABSTRACT This paper presents theresults of soil investigations conducted in the Aktobe region to determine the radionuclide content, radon concentration and gamma exposure dose rate. The study shows no excess of health-based exposure limits. However, the excess of radonconcentrationwas registered at the site of land allocation for average global construction, and the radionuclide content (226Ra, 232Th, 40Ê) in the soil of some regions was higher than the worldwide background (percentage abundance) and multi-year average data for the Russian Federation and Kazakhstan. Key words : Exposure dose rate, Radon exhalation, Radionuclide soil contamination, Radionuclide specific activity, Soil type, Natural and artificial radionuclides Introduction places where the levels of radiation are much higher than the average value (0.3-0.6 mSv/year). People get the element part of exposure to natural The dose of radiation also depends on human radiation sources. Natural radiation background lifestyle. The deployment of some constructional consists of cosmic ray terrestrial radiation. Accord- materials, the use of gas for cooking, open coal fry- ing to the data of U.Ya.Margulisand Yu.I. Bregadze ing pans, the sealing of rooms and even flights on (2000), the effective dose of radiation created by cos- airplanes increase the level of radiation due to natu- mic radiation at sea level is 0.32 mSv. According to ral radiation sources (Kayukov, Fedorov and the data of A.M. Lyutsko, I.V. Rolevich and V.I. Efremov, 2002; Sivintsev, 1991; Kibatayev, 2009). Ternov (1990), the average annual dose is 0.3 mSv, The radionuclides preserved in the earth’s crust but the overwhelming majority of Kazakhstan’s and having a long half-life (Ò1/2) include K-40 (Ò1/2= population receives the dose of 0.38 mSv/year, as 1.3 billion years), U-238 (Ò1/2= 4.5 billion years), U- far as this territory is fixed at an altitudeof 300-400 235 (Ò1/2 = 0.7 billion years), Th-232 (Ò1/2 = 14 billion m above sea level (Kayukov, Fedorov and Efremov, years). U-238, U-235 and Th-232 are the ancestors of 2002). radioactive families that make up a chain of radio- In addition to cosmic radiation, man receives ra- nuclides. diation from radioactive elements scattered in ter- Human exposure is due to external influence and restrial rocks. In this case, the dose of radiation de- the intake of radionuclides inside (with food and pends on the place of residence, forasmuch as the water and from the air in the process of breathing). level of radiation depends on the concentration of It is very important to determine the radioactive their occurrence in radioactive rocks. There are emanations of Rn-222 and Rn-220, which create KIBATAYEV ET AL 583 about 50% of the total dose received from natural Chasnikov, 1998) to 12 nuclear explosions produced sources (Kayukov, Fedorov and Efremov, 2002; in the Aktobe region (Faizov, Raimzhanov and Kibatayev, 2009). Alimbekov, 2003). Of great importance for the formation of radia- In addition,there are oil and gas production en- tion background is soil contamination with the ra- terprises in the Aktobe region, which causesurface 137 dioisotope of Cesium-137 ( Cs), with a half-life (T1/ contaminationby Ra-226, Ra-228 and Th-232 2) of 30.2 years, which has a high migration ability (Kayukov, Fedorov and Efremov, 2002; and toxicity. The radioisotopes of cesium are formed Urgushbayeva, Kibatayev, and Mamyrbayev, 2015). during the fission of heavy elements atomic nuclei The migration of radioactive substances upon (in nuclear explosions and in nuclear reactors) and their release to the soil depends on a number of con- through the use of charged-particles accelerator. ditions: physicochemical isotope properties; physi- Nuclear explosions and major radiation accidents at cochemical soil characteristics (soil type); nature of nuclearenterprises have become the main source of ground water movement; environment acidity; cli- radioactive contamination of the environment. The matic parameters; residence time of radionuclides in contribution of the USSR and the USA to radioactive soil, etc. Different soils have different radionuclide contamination is approximately the same –40%, the absorption capacities. High absorption capacity is remaining 20% fall on England, France and China possessed by chernozem andclayed soils, their (Vasilenko and Vasilenko, 2001). sorptivity is due to the presence of humus. The ab- The intensive development of major uranium sorption capacity of sod-podzolic and sandy soils is deposits in Kazakhstan (according to various esti- much more limited. mates, its reserves in the country correspond to 25- According to the data of V.I. Baranov and N.G. 30% of the world figures) and the forty-year testing Morozova (1966), the greatest natural radioactivity of nuclear facilities at the Semipalatinsk Nuclear is possessed by acid eruptions of the rock. This is Test Site (SNTS) and other facilities created a huge explained by a higher content of uranium and other mass of radioactive waste of various activities, scat- natural radionuclides in acidic eruptive rocks. The tered throughout most of the country. radioactivity of sedimentary clays and silts is rela- In addition to the widely known Semipalatinsk tively high. The radioactivity of precipitation and Test Site, the Azgir Nuclear Test Site was located on biogenic deposits is low. the territory of Western Kazakhstan. There were The accumulation of radioactive compounds in also a whole series of test sites at which the explo- hydromorphic, gley, meadow-sod, alluvial soils is sions of nuclear charges were made: Taysoyghan, observed in the soil cover. Thepresence of radium Urda, Zhanakala, etc. (Urgushbayeva,Kibatayev and thorium in the soil leads to the appearance of andMamyrbayev, 2015). The distribution of cesium- radioactive gases (radon, thoron) in the soil air. Ra- 137 in the top soil of nuclear sites had a certain regu- dioactive emanations are more pronounced in hu- larity: the greatest shareof cesium-137 (25.2% - mus soils (for example, in chernozem) (Kovda,1985; 40.7%) was found in medium and small soil suites, Aktobe region. Kazakhstan. National encyclope- which is a risk factor for environmental contamina- dia,2004). tion during the wind erosion of the soil The Aktobe region is located in West Kazakhstan (Kozhakhmetov,2007;Toguzbayeva,Kozhakhmetov between 51 and 45 degrees north latitude and 49 andFilin, 2003). and 64 degrees east longitude. The length of the ter- One of the test sites where a nuclear explosion ritory from west to east is about 800 km, from north was made on 3 October 1987 (Batolit-2) for the pur- to south – about 700 km. pose of seismic sounding, with a capacity of 8.5 kt, at The Aktobe region is located between the a depth of 1,002 m, 320 km south-west of Aktobe Caspian Depression in the west, the UstyurtPlateau City, is the village of Kaldaybek, Bayganin District in the south, the TuranDepression in the southeast of the Aktoberegion, located on the coast of the and the southern spurs of the Urals in the north. Emba River.Such explosions are called produced for Most of the region is a plain, divided by river val- peaceful (economic) purposes. There were more leys, 100-200 m high. In the middle part there are than 30 of such “peaceful” explosions on the terri- Mugodzhar Hills (the highest point is Big tory of Kazakhstan. According to various data, from Baktybaimountain, 657 m). In the west of the Aktobe 1957 to 1962there were from 10 (Chasnikov, 1992; region there is the Sub-Ural Plateau, which in the 584 Eco. Env. & Cons. 23 (4) : 2017 southwest passes into the Caspian Depression; in and in the most dissected parts of the gully network the southeast – arrays of hilly sands – the Aral are replaced by sandy loam and medium loamy de- Karakum Desert and the Big and Small Barsuki. In posits representing ancient alluvial-talus deposits the northeast of theAktobe region there is the (Novikova et al., 1968; GOST R 54038-2010,2012). Turgay Plateau. Taking into account the above, we believe that According to the nature of the soil cover, three monitoring the regional radiation situation is essen- soil zones are distinguished on the territory of the tial, since the irradiation of the population is pos- region: chernozem, chestnut and brown. sible both with external and internal irradiation (en- Each zone is divided into subzones, different in a try into the body during breathing, ingestion of food variety of soil, vegetation and economic use. In the and water). chernozem zone, a subzone of southern chernozems The research objective is to study the radiation is distinguished; in the zone of chestnut soils – dark issue in the Aktobe region. chestnut, chestnut and light chestnut; in the zone of brown soils – a subzone of brown as such and grey Materials and Methods brown soils. Dark chestnut carbonate solonetzic soils lie to- The research data of the radiological laboratory of gether with dark chestnut calcareous soils and are the Republican State Enterprise on the Right of Eco- distributed throughout the north.In the eastern part nomic Use “National Centre of Expert Review” of of the subzone there are widespread heavy loam the Committee for the Protection of Consumer and clayey low-humus medium-thick chernozems Rights of the Ministry of National Economy of the confined to flat areas.In the southern part of the re- Republic of Kazakhstan for the Aktobe region for gion, dark chestnut soils are formed on the territory 2013-2016 were analyzed.