ACTIVITY CONCENTRATIONS OF NATURAL AND ARTIFICIAL RADIONUCLIDES IN THE SOIL–VEGETATION COVER OF THE ARID ZONE OF KAZAKHSTAN

An assessment was made of the activity concentrations of natural and artificial radionuclides in the soil–vegetation cover of the arid zone of Kazakhstan along the 65th and 75th meridians. The mean activity concentrations in soils were 580.7 Bq/ kg for ⁴⁰K, 34.8 Bq/kg for ²³²Th, 23.0 Bq/kg for ²²⁶Ra, and 16.9 Bq/kg for ¹³⁷Cs. In plants, the mean activity concentrations calculated from the quantitatively determined values were 489.2 Bq/kg for ⁴⁰K, 2.5 Bq/kg for ²³²Th, 14.3 Bq/kg for ²²⁶Ra, and 1.2 Bq/kg for ¹³⁷Cs. The activity concentration of ²⁴¹Am could not be quantified. The highest variability in concentration ratio (CR) values was observed for ¹³⁷Cs, whereas relatively greater uptake by plants was observed for ⁴⁰K and ²²⁶Ra. The estimated absorbed dose rate to plants ranged from 1.6 to 8.9 µGy/day along the 65th meridian and from 3.7 to 15.0 µGy/day along the 75th meridian. These values were substantially below the levels at which radiation effects in reference species are expected. The results obtained can be used as baseline characteristics for radiation monitoring, assessment of radionuclide dynamics, and radiation dose burdens on biota, as well as for subsequent monitoring of the radiological status of the study area.

1. Saibekov, T.S., Abylaev, Zh.A. Radiation Situation in the Territory of the Republic of Kazakhstan from 1954 to 1994. Semipalatinsk Region. Atlas. Vol. 16. Almaty: Ministry of Ecology and Bioresources of the Republic of Kazakhstan, 1997. 400 p.

2. Study of Baseline Characteristics of Radionuclide Contamination of Soil and Air: Final Research Report for 2020. Institute of Radiation Safety and Ecology, National Nuclear Center of the Republic of Kazakhstan (IRSE NNC RK); A.M. Kabdyrakova, project manager. Kurchatov, 2020. 98 p. State Registration No. 0118RK01139. Inventory No. 0220RK00163.

3. Instructions and Methodological Guidelines for Ground-Based Survey of the Radiation Situation in Contaminated Areas. Approved by the Interdepartmental Commission for Radiation Monitoring of the Natural Environment under the USSR State Committee for Hydrometeorology. Moscow, 1989.

4. Radionuclide Activity in Bulk Samples. Measurement Procedure Using a Gamma-Ray Spectrometer. MI 2143-91. Effective from 2 June 1998. Registration No. 5.06.001.98. Moscow: NPO VNIIFTRI, 1991. 17 p.

5. Methodological Recommendations R 52.18.820-2015. Assessment of Radiation and Environmental Impact on Environmental Components Based on Radiation Monitoring Data. Obninsk, 2015. 60 p.

6. ICRP. Environmental Protection: The Concept and Use of Reference Animals and Plants. ICRP Publication 108. Annals of the ICRP, Vol. 38. 2008. 242 p.

7. Training and Methodological Guide on Radioecology and Radioactive Waste Management for the Conditions of Kazakhstan. Project K-112 (ISTC). Almaty: OAO Volkovgeologia, 2002. 304 p.

8. Lukashenko, S.N. (ed.). Radioecological Status of the “Northern” Part of the Semipalatinsk Test Site. 2nd ed. In: Current Issues in Radioecology of Kazakhstan. Institute of Radiation Safety and Ecology, National Nuclear Center of the Republic of Kazakhstan. Pavlodar: Dom Pechati LLP, 2010. Issue 1. 294 p. Illustrations. Bibliography: pp. 281–290; 115 references. 500 copies. ISBN 978-601-7112-38-7 (Russian, English, Kazakh).

9. IAEA. Quantification of Radionuclide Transfer in Terrestrial and Freshwater Environments for Radiological Assessments. IAEA-TECDOC-1616. Vienna: International Atomic Energy Agency, 2009. 163 p.

10. Kryshev, I.I., Sazykina, T.G. Radiation Safety of the Environment: The Need to Harmonise Russian and International Regulatory and Methodological Documents in Light of Federal Legislation Requirements and the New International Basic Safety Standards (BSS-2011). Radiation and Risk, 2013, Vol. 22, No. 1, pp. 47–61.