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EurAsian Journal of BioSciences Eurasia J Biosci 13, 2225-2231 (2019)

Distribution of radionuclides in the system “soil-vegetation-livestock products” on the area near the Semipalatinsk Nuclear Test Site

Assel Murzalimova 1*, Zheken Mamutov 1, Guldana Minzhanova 1, Olga Zubova 1, Amangeldy Zhanadilov 2, Gulnur Kekіlbayeva 3, Nurzhamal Zhylybayeva 4 1 Al-Farabi Kazakh National University, Almaty, KAZAKHSTAN 2 Shakarim State University of Semey, Semey, KAZAKHSTAN 3 S.Seifullin Kazakh Agrotechnical University, Nur-Sultan, KAZAKHSTAN 4 Institute of combustion problems, Almaty, KAZAKHSTAN *Corresponding author: Assel Murzalimova

Abstract This paper presents the results of complex radioecological monitoring in the system “soil-vegetation-livestock products” on the area of winter and summer camps located near the Semipalatinsk Nuclear Test Site. The gamma exposure rate (GER) does not exceed 0.13 μSv/h, beta-particle flux density values are below 10 freq/(min · cm2). The concentration of 241Am and 137Cs not exceeded the permissible levels and varied from 0.4 to 0.6 for 241Am, 0.7 to 1.7 for 137Cs. The high concentration of 3H in mare’s milk was observed in milk and meat samples from the farms located near the Shagan River. The specific activity of 137Cs in the aerial part of vegetation in 90% of all measurements, and in the roots - in 60% are below 23 Bq/kg. For 90Sr content, in 80% of cases in the aerial part, the specific activity is below 25 Bq/kg, in the roots in 70% of cases below 41 Bq/kg. Keywords: Semipalatinsk Nuclear Test Site, radionuclide, soil, vegetation, horse milk, meat, radon Murzalimova A, Mamutov Z, Minzhanova G, Zubova O, Zhanadilov A, Kekіlbayeva G, Zhylybayeva N (2019) Distribution of radionuclides in the system “soil-vegetation-livestock products” on the area near the Semipalatinsk Nuclear Test Site. Eurasia J Biosci 13: 2225-2231. © 2019 Murzalimova et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License.

INTRODUCTION The study of radioactive contamination is the most

important environmental factor that affects biota and poses a hazard to human health. It is necessary to solve the problem of soil contamination with radioactive elements - the maximum possible reduction in the transfer of radionuclides to the vegetation and prevent their accumulation in the organisms of farm animals (Duyssembaev et al. 2014, Murzalimova et al. 2019).

Nuclear tests conducted at Semipalatinsk Test Site (STS) in the period from 1949 to 1989 created a very complex radiation situation at the test site, which evolves over time. The STS territory is located in the north-east of the Republic of Kazakhstan in the zone of the eastern part of the Central Kazakh hillocky area. Administratively, the territory of Semipalatinsk Test Site is located on three regions: East Kazakhstan, Pavlodar and Karaganda, each of which accounts for 54%, 39% and 7%, respectively. The test site area is 18.5 thousand km2. The northern border coincides with the Irtysh River watershed, the southern and southwestern parts are represented by isolated massifs of low mountains (Kakimov et al. 2016, Steinhauzler et al. 2001).

As a result of nuclear explosions on the territory of the former Semipalatinsk test site (STS) and the

surrounding area, a complex radioecological situation has developed, characterized by a motley picture of radionuclide contamination of environment. Several local places where the soil with a high content of artificial radionuclides in a relatively clean area are often observed (Kakimov et al. 2017, Michailov 1996, Sakaguchi et al. 2006).

Currently, the media are discussing the proposal of the National Nuclear Center of Republic of Kazakhstan on the transfer of land of STS for farming. One of such territories is the winter camps Sarapan and Zhanan, which are already actively used by local farmers for grazing livestock and hay. In the summer, several shepherd families with children live on these lands. It is known that no nuclear tests were carried out on the investigated part of the test site, however, the Balapan test site is located close to this territory (Lukashenko 2011).

The aim of this work is to study the degree of radionuclide contamination of the soil-water-plant-livestock production system on the farming areas located near STS.

Received: August 2019 Accepted: October 2019 Printed: December 2019

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MATERIALS AND METHODS The radioecological studies in the system “soil-plant-

livestock production” were performed in 5 farms (winter camps) located on the right bank of the Shagan River, near the “Atomic Lake” and “Balapan” Test Site of STS: “Yubileynaya”, “Zavet Il’icha”, “Berezka”, “Zhanan”, “Sarapan”. All winter camps are located directly on the territory of STS. Soil, water, plants, livestock products (meat and milk) samples were selected for radioecological measurements.

Sampling and Field Measurements Field works consisted of measuring radiation

parameters, sampling of soil, water, vegetation and livestock products and determining geographical coordinates. Based on the previously outlined images from Google earth on the territory of the wintering pastures, field identification of the contours and objects of the area was carried out. Also, a survey of residents of farms was conducted in order to determine the

territory of grazing animals, areas of hay harvesting and water use facilities. The choice of research sites is based on the allocation of areas with the most typical zonal vegetation. As a result, 30 research sites were selected on pastureland (Fig. 1), each of which carried out a geobotanical description (the vegetation families were identified, dominant plant species were established).

In accordance with standard methods, radiation parameters were measured at each research site — β-particle flux density and equivalent dose rate (EDR). Soil samples (n = 18) were taken with a depth of 0-5, 5-10, 10-15, 15-20 cm from all research sites (Duyssembaev et al. 2017).

Detailed measurements of EDR and β-particle flux density on soil surface (3 cm) with 2×2 m step size were made in each of the animal housing enclosures. 10 research points were laid in each enclosure, where samples of animal faeces were taken to a depth of 0-5 cm. Measurements of volumetric activity (VA) and equivalent equilibrium volumetric activity (EEVA) of radon were carried out in living rooms. Radiation parameters were measured in 2×2 m step sizes in the adjacent area. The area of each site was at least 150 m2.

Water samples were taken from water sources on all farms for radionuclide analyses. In addition, in order to study the spatial movement of radionuclides with water, several sampling points were placed on the channel of the Shagan River. The first point is located in front of the reservoir dam, next all - followed by each 1 km. A total of 20 points were placed. In each sampling point the water samples were taken 2 times with the interval of 2 months for radionuclide analyses.

To identify the presence of radionuclides and the dynamics of their content in animal products (meat, milk), the samples were taken in spring, summer and autumn.

Vegetation Samples Preparation for Radionuclide Analyses

Vegetation samples shredded (1-3 cm long), dried at a temperature of 100 ºC, then grinded into powder. The ashing temperature of samples for the determination of 137Сs was – 400 ºС, 90Sr, 241Am – 500 ºС. Sample preparation was carried out according to National Standard GOST R 51419–99 (2000), National Standard GOST R 54040–2010 (2011), Method for analysis of … (2010).

Soil Samples Preparation for Radionuclide Analyses

Soil samples were dried at a temperature of 80–100 °С and sieved through a 1.5 mm mesh. The obtained fractions were scattered on a kraft paper sheet, mixed thoroughly, and then leveled into a layer 1.5–2 cm thick. Weighed portions of the test sample were taken by the quarting method.

Fig. 1. Map, showing the places of the research sites

Fig. 2. Map of the Atomic Lake

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Livestock Products Preparation for Radionuclide Analyses

For gamma spectrometric measurement (137Cs, 241Am) fresh livestock products were sampled. The animal bone tissue ashed (380 °C), after which the ash was measured on a spectrometer with Ge detector gamma-spectrometer CANBERRA (National Standard GOST R 54016–2010, 2011).

The method for determining 90Sr is based on the conversion of strontium isotopes into a solution, the isolation of strontium isotopes in a radiochemically pure form, the accumulation of 90Y for two weeks, and the measurement of its activity.

Sample Preparation for Tritium Determination The content of tritium was determined in the free

water extracted from plants, milk and muscle tissue. The first condensate was removed in the amount of 10 ml, and the next 5-6 ml was taken for analysis. The analytical samples were placed in 20 ml plastic bottles with the addition of a scintillating cocktail in the ratio of 5:15 (ratio - scintillator) (ISO 9698:2010, 2010).

137Cs and 241Am Determination Specific activity of 137Cs and 241Am radionuclides was

determined using a Canberra γ spectrometer with a germanium detector (BE 2020). Measurements were made in accordance with the method of measurements on the γ-spectrometer (MI 2143-91 Activity of radionuclides in bulk samples 1991). The detection limit of 137Cs in bioobjects was 1.0 Bq/kg and 0.3 Bq/kg for 241Am. The measurement error did not exceed 20%.

90Sr Determination Analyses on measurement of specific activity of 90Sr

by a method of radiochemical extraction in samples were carried out according to the standard methodical instructions (Method for analysis of the … 2010). The detection limit for animal samples is 1.0 Bq/kg. Determination of 90Sr in soil and plant samples was carried out using the β-spectrometer “Progress” (Methodology for measuring radionuclide activity using … 2004). The detection limit is 100.0 Bq/kg. The measurement error did not generally exceed 30%.

3Н Determination Measurement of specific activity of 3H was carried

out in the prepared samples by the method of liquid scintillation spectrometry on TriCarb 2900 TR and Quantulus 1220 spectrometers. The measurement time of each sample was 120 minutes. The detection limit of

3H in free water of samples was about 12 Bq/L. The measurement error did not exceed 30%.

RESULTS AND DISCUSSION The radiation doses in the territory of winter and

summer camps were at the level of background values - gamma exposure rate (GER) does not exceed 0.13 μSv / h, beta-particle flux density values are below the detection limit of the measuring device and was <10 freq/(min · cm2). Table 1 presents the measurement results.

The values of equivalent equilibrium volume activity (EEVA) of radon in the air of residential premises were in the range of 40 - 180 Bq/m3 and did not exceed the level specified in the Hygiene Standards of Republic of Kazakhstan “Sanitary and epidemiological requirements for providing radiation safety” for residential premises (200 Bq/m3), which was expected due to frequent ventilation of the premises during the summer period.

The level of volume activity (VA) of radon in water was 30-61 Bq/kg, in two cases (58 and 61 Bq/kg), values were close to maximum level (60 Bq/kg), approved by Hygiene Standards. According to the standards of the Hygiene Standards, the permissible level is not more than 80 mBq/(m²·s).

The data obtained indicate that the radiation situation in the territory of the studied winter camps was at the level of the background of global fallout. According to the radon hazard criterion, the studied territories can be classified as suitable for living and vital activities of the population, under observance of anti-radon measures: regular ventilation of the premises, the presence of ventilation in the premises, preparation of water before use (sedimentation, boiling).

The range of α-particle flux density ranges from <0.5 to 2 freq/ (min * cm2), β-particles from <10 to 30 freq /(min*cm2), GER on the soil surface is in the range from 0.12 up to 0.50 μSv/h.

Analyzing the data of gamma-spectrometric and radiochemical analyzes (Makhonko 1991), it was found that the specific activity of 137Cs and 90Sr in soil samples slightly exceeds the level of global precipitation. The high level of contamination with 137Cs and 90Sr radionuclides (2 times higher than the level of global fallout) was observed in the soil section at research site III, which was apparently due to its closeness to the well 1004.

Table 1. Results of radiological measurement of winter camps Name of the winter camp GER h1м µSv/h

beta-particle flux density, freq/(min · cm2)

Radon concentration in room, Bq/m3 Radon concentration in water (VA), Bq/l EEVA VA

Yubileynaya 0.15 ˂10 47 123 45 Zavet Il’icha 0.15 ˂10 130 423 61 Berezka 0.15 ˂10 60 215 58 Atomic lake 0.15 ˂10 51 316 30 Zhanan-2 0.15 ˂10 40 210 40 Sarapan 0.15 ˂10 40 210 40

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When assessing the quality of livestock products the meat and milk were sampled from the residents of farms located on the territory of STS, which were then transferred to spectrometric measurements. The measurement results are presented in Table 2.

As shown in Table 2, the content of 137Cs, 90Sr radionuclides in meat and milk samples was below the detection of the measuring device. Of course, it may seem strange that in the products sampled from the territories of STS, were very low concentrations of radionuclides. However, it should be realized that the territory of STS has a local or spotty nature of contamination and animals can graze in both “clean” and “contaminated” areas.

Production of mare’s milk is one of the main activity of farmers lived on the territory near STS. The volume of its production in 2010 amounted to more than 900 liters per day. More horse population is concentrated in the southeastern part of the STS, near the Degelen site, where there is a high probability of 3H entering into the animal body.

In this regard, we evaluated the content of 3H in mare’s milk. The results of the study showed that the content of 3H in most cases does not exceed the lower limits of the measurement of equipment. The quantitative values recorded in individual cases are significantly lower than the level of 7600 Bq/kg reported in the Hygiene Standards of Republic of Kazakhstan “Sanitary and epidemiological requirements for providing radiation safety”. 3H concentrations in mare’s milk are shown in Fig. 3.

One of the areas where high concentrations of 3H may enter the animal body is the area adjacent to the Shagan River. An analysis of the results showed that the highest specific activity of 3H radionuclide in agricultural products of animal origin was observed in farms whose animals grazing near the Shagan River with maximum 3H values in the water. With the distance from the Atomic Lake in the direction of the Shagan River, a decrease in the specific activity of 3Н in meat and milk was observed (Fig. 4).

In general, the assessment of the content of radionuclides in livestock products produced in STS showed that the concentration of 3H can reach high

Table 2. Radionuclide concentration in meat and milk samples, Bq/kg Studied sites, places of STS Sample type, number of

samples The specific activity of radionuclides, Bq/kg

241Am 137Cs 90Sr

Near the Shagan River meat – – – milk, (n=2) – 1.7±0.4 0.8±0.2

Southeastern part meat, (n=10) < 0.6 < 0.8 – milk, (n=12) < 0.4 < 0.7 <0.09

South part meat, (n=6) < 0.6 < 0.8 – milk, (n=4) < 0.4 < 0.7 –

Southwest part meat, (n=2) < 0.6 < 0.8 – milk, (n=3) < 0.4 < 0.7 –

Fig. 3. 3H concentration in horse milk

(a)

(b)

Fig. 4. Specific activity of 3H in farm products: a) by location to Atomic Lake; b) by location to the Shagan River

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values, while the content of radionuclides 241Am, 137Cs and 90Sr were very low.

To establish the biogeochemical parameters of 137Cs and 90Sr radionuclides, they were determined in the aerial parts and the roots of the dominant vegetation species of the studied area (Table 3).

As shown by the data of gamma-spectrometric and radiochemical analyzes, the values of specific activity in the aerial part and roots of the vegetation have a wide range of variations. However, in general, the concentration of 137Cs and 90Sr radionuclides among the studied plant species does not exceed the permissible level. So, from the total number of observed values (n = 22), the specific activity of 137Cs in the aerial part in 90% of cases, and in the roots - in 60%, below 23 Bq/kg. For 90Sr content, in 80% of cases in the aerial part, the specific activity is below 25 Bq/kg, in the roots in 70% of cases below 41 Bq/kg. The maximum specific activity of 90Sr observed for tarragon (Artemisia dracunculus) and, most likely due to the high content of this radionuclide in the soil at research site III (Table 4). The concentration of 90Sr in this vegetation reaches ~ 660 Bq/kg in the aerial part and 1000 Bq/kg in the roots. The highest

content of 137Cs in the studied plants is 542 Bq/kg in the aerial part and 406 Bq/kg in the roots.

A significant variety of concentrations of 137Cs and 90Sr radionuclides, both in the aerial part and in the roots, is indicated by the analysis in the total set of species of the studied plants (Table 4).

Different species of the studied plants are characterized by different specific activity of radionuclides. So, in decreasing order of the average radionuclide content, the studied plant species are arranged in the following rows:

by average 137Cs content - wormwood (Artemisia albida) (1)> tarragon (Artemisia dracunculus) (1)> thin wormwood (Artemisia gracilescens) (1)> June grass (Koeleria cristata) (1)> Volga fescue (Festuca valesiaca) (1) > feather grass (Stipa sareptana) (4)> meadowsweet (Spiraea hypericifolia) (2);

by average 90Sr content - tarragon (Artemisia dracunculus) (1)> wormwood (Artemisia albida) (1)> meadowsweet (Spiraea hypericifolia) (2)> thin wormwood (Artemisia gracilescens) (1)> feather grass (Stipa sareptana) (4) > Volga fescue (Festuca valesiaca) (1)> June grass (Koeleria cristata) (1).

Table 3. The specific activity of 137Cs and 90Sr in aerial parts and roots of vegetation Study site Type of vegetation Part of vegetation Specific activity, Bq/kg

137Cs 90Sr

I Wormwood (Artemisia albida)

aerial parts 542 518 roots 406 636

II Meadowsweet (Spiraea hypericifolia) aerial parts 5 2,8 roots 3,6 5,5

III Tarragon (Artemisia dracunculus)

aerial parts 23 659 roots 149 1000

IV Meadowsweet (Spiraea hypericifolia) aerial parts 1,3 25 roots 10 178

V Feather-grass (Stipa sareptana)

aerial parts 4 1,3 roots 16 10

VI Feather-grass (Stipa sareptana)

aerial parts 0,8 2,2 roots 22 22

VII Feather-grass (Stipa sareptana)

aerial parts 2,8 5 roots 9 41

VIII Volga fescue (Festuca valesiaca)

aerial parts 2,6 4,9 roots 21 16

IX Feather-grass (Stipa sareptana)

aerial parts 1,3 2,6 roots 19 5,1

X Thin wormwood (Artemisia gracilescens) aerial parts 16 9,8 roots 148 14

XI June grass (Koeleria cristata)

aerial parts 20 5,9 roots 22 13,3

Permissible levels of radionuclides in vegetation: 137Cs – 74 Bq/kg, 90Sr – 111 Bq/kg (Temporary permissible levels of radionuclides in the objects … n.d.)

Table 4. Concentration of 137Cs and 90Sr in studied vegetation Radionuclide Statistic parameters

n variation, Bq/kg M±m, Bq/kg V, % Aerial parts

137Cs 11 0.8 - 542 541.2 56.3 ± 48.64 286.5

90Sr 11 1.3 - 659 657.7 112.4 ± 71.63 211.4

Roots 137Cs 11 3.6 - 406

402.4 75.1 ± 36.82 162.6

90Sr 11 5.1 - 1000 994.9 176.4 ± 99.85 187.8

Note: M±m – arithmetic mean and arithmetic mean error, V - the coefficient of variation, n – number of samples

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The highest values of the radionuclide content are mainly observed for the studied species of the wormwood genus (Artemisia albida, Artemisia dracunculus, Artemisia gracilescens), which may be associated with their specific features, both at the generic and at the species level.

A noticeable difference in the quantitative content of radionuclides in the studied plants is also observed at the level of the families to which they belong, which can be easily seen in the following series of decrease: for 137Cs - Compositae (3)> Cereals (Gramineae) (6)> Rose Family (Rosaceae) (2); for 90Sr - Compositae (3)> Rose Family (Rosaceae) (2)> Cereals (Gramineae) (6).

A general analysis of data on the radionuclide content in the aerial part and roots showed that in almost all plant samples, the specific activity of radionuclides in the roots exceeds the specific activity of the aerial part. Thus, in the radionuclide transfer in the soil, along with the aboveground part, the root system of plants also played a significant role. Besides the fact that the roots act as a supplier of radionuclides that are readily available to plants, they are also a kind of “reservoir”

where the radionuclides is accumulated and then involved in the biological cycle (Otarov 2003). The diagrams show the fractional distribution of 137Cs and 90Sr radionuclides in the aerial part and the roots of various plant species at research sites (Figs. 5 and 6).

As can be seen from Figs. 5 and 6, 137Cs and 90Sr radionuclides in plants mainly accumulated in the root system, often exceeding even specific activity in the soil (Table 4), regardless of their species and variety of light chestnut soils. An exception is the specific activity of 137Cs at research sites I and II, which in the aerial part of wormwood (Artemisia albida) and meadowsweet (Spiraea hypericifolia) exceeded the values of specific activity in the roots, which to some extent may be associated with a composition of light chestnut sandy loam soils.

The largest accumulation of 137Cs and 90Sr in the root system (~88%) was noted for perennial feather grass. Most likely, this may be due to its well-developed root system of the rhizome type, capable of forming a dense turf, which, in turn, in most cases acts as a cluster of radionuclides.

Fig. 5. The specific activity of 137Cs (values in columns) in the aerial part and the roots of the studied plants depending on the type soils of research sites (I-XI)

Fig. 6. The specific activity of 90Sr (values in columns) in the aerial part and the roots of the studied plants depending on the type soils of research sites (I-XI)

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