Defense of the dissertation of Bagramova Assel for the degree of Doctor of Philosophy (PhD) in the educational program «8D05305 - Nuclear physics»

At he L.N. Gumilyov Eurasian National University, a dissertation defense for the degree of Doctor of Philosophy (PhD) by Bagramova Assel on the topic «Assessment of the concentration of 210Pb in the air of Akmola region» to the educational program «8D05305 – Nuclear physics».

The dissertation was carried out at the «Nuclear physics, new materials and technologies education department» of L.N. Gumilyov Eurasian National University.

The language of defense is russian

Official reviewers:

Zholdybayev Timur Kadyrzhanovich – Candidate of Physical and Mathematical Sciences, Professor, Head of the Nuclear Physics Department, RSE on the REM “Institute of Nuclear Physics” of the Atomic Energy Agency of the Republic of Kazakhstan (Almaty, Republic of Kazakhstan);

Kairambayev Samat Kapashevich – Candidate of Biological Sciences, Chief Expert of the Department of Environmental Protection, Radiation and Nuclear Safety, Production Safety Department, NAC Kazatomprom JSC (Astana, Republic of Kazakhstan).

Temporary members of the Dissertation Committee:

Tolmachev Sergey Yuryevich– Doctor of Philosophy (PhD), Research Professor and Director, United States Transuranium and Uranium Registries, College of Pharmacy and Pharmaceutical Sciences, Washington State University (Richland, Washington, USA);

Gorlachev Igor Dmitrievich – Candidate of Physical and Mathematical Sciences, Head of Analytical Group, RSE on the REM “Institute of Nuclear Physics” of the Atomic Energy Agency of the Republic of Kazakhstan (Almaty, Republic of Kazakhstan);

Tibor Kovacs – Doctor of Philosophy (PhD), Senior Researcher, Institute of Biophysics, Semmelweis University (Budapest, Hungary).

Scientific advisors:

Zhumadilov Kasym Shaimardanovich – Doctor of Philosophy (PhD), Professor, Head of the Department of Nuclear Physics, New Materials and Technologies, L.N. Gumilyov Eurasian National University (Astana, Republic of Kazakhstan)

Sakaguchi Aya - Doctor of Philosophy (PhD), Professor at the Institute of Pure and Applied Science, University of Tsukuba (Tsukuba City, Ibaraki Prefecture, Japan)

The defense will take place on May 26, 2026, at 12:00 PM in the Dissertation Council for the training direction «8D053 – Physical and chemical sciences» in the educational program «8D05305 – Nuclear physics» of L.N. Gumilyov Eurasian National University. The defense meeting is planned to be held online.

Link: https://clck.ru/3TBfsv 

Address: Astana, Kazhymukan St. 13, room 310. 

Abstract (English): ABSTRACT of the dissertation work of Bagramova Assel Aidosovna on the topic of “Assessment of the concentration of 210Pb in the air of Akmola region”, submitted for the degree of Doctor of Philosophy (PhD) in the specialty: “8D05305 - Nuclear Physics” Relevance of the research topic. Kazakhstan is the world's largest producer of natural uranium, holding 15% of global reserves. A significant portion of the country's uranium resources are concentrated in the North Kazakhstan Uranium Province. The long history of uranium mining and processing in the region has created potential risks of radioactive contamination of the environment. A key facility posing a radiation hazard is the tailings dump containing waste from uranium processing at the Stepnogorsk Hydrometallurgical Chemical Plant (SHCP). The main risk factors at such facilities include soil contamination with dust containing radionuclides due to insufficient moisture on the surface of the tailings dump; emissions of radon and its decay products into the atmosphere; and contamination of surface and groundwater. Previous studies of the settlements of Aksu, Zavodskaya and Kvartsitka, located 3-5 km from the SHCP tailings dump, showed that external gamma radiation levels, uranium concentrations in soil samples, and radon levels both indoors and outdoors exceed international standards. The city of Stepnogorsk, located approximately 20 km from this tailings dump, appears to be the most densely populated area within the potential impact zone of uranium industry facilities. However, unlike the near area, the mechanisms and scale of the impact on the environment and the population at this distance have been insufficiently studied. This necessitates a quantitative assessment of the contribution of the remote impact of the uranium industry, compared to other anthropogenic and natural sources, to the formation of atmospheric radioactivity levels in this large settlement. In this study, the naturally occurring radionuclide lead-210 (210Pb) was chosen as the key indicator for assessing atmospheric transport and impact. It is a decay product of 238U and is formed in the atmosphere as a daughter nuclide of radon-222 (222Rn). 222Rn, being an inert gas, can be released from the soil and then dispersed into the atmosphere. Under anthropogenic loads, such as coal combustion, additional contributions of anthropogenic sources of 210Pb to the atmosphere are possible. Given the low volatility of 222Rn decay products (i.e. 218Po, 218At, 214Bi and 214Pb), 210Pb in the atmosphere is primarily associated with the aerosol phase. Due to its relatively long half-life, 210Pb remains associated to aerosol particles until their removal by deposition. Combined with its well-defined source, these properties make 210Pb an effective tracer for atmospheric studies. Furthermore, 210Pb is important for radiological health assessment, as inhaled aerosols can settle in the respiratory tract and eventually accumulate in the skeleton, where its long effective half-life (22.3 years) poses a long-term risk of internal exposure. Thus, the relevance of this study is determined by the need to study 210Pb in atmospheric aerosols in the city of Stepnogorsk, specifically its concentrations, size distribution, seasonal dynamics, and formation factors. The data obtained will help solve two interrelated problems: assess the radiation risk to the population in the zone affected by uranium activity and identify the key sources and processes determining ground-level air radioactivity in the industrial region. The aim of this dissertation work is to study the activity concentrations of the lead -210 (210Pb) in atmospheric aerosols of the near-surface air layer of the city of Stepnogorsk, located within the North Kazakhstan uranium province, in order to identify its seasonal variability of its concentrations, to determine the influence of various factors on the formation of atmospheric 210Pb levels, and to assess the impact on the human body through inhalation exposure. Research objectives. To achieve this aim, the following objectives were addressed in this study: - Study of the methodology and sampling aerosol particles in the ground-level air of Stepnogorsk using a high-volume air sampler equipped with a 6-stage cascade of impactor; - determining the activity of the lead radioisotope 210Pb in size-fractionated samples of atmospheric aerosols using gamma spectrometry; - simulation of the detection efficiency of a high-purity germanium detector using the PHITS program in order to determine the detection efficiency for calculation of 210Pb activity; - studying the relationships between 210Pb atmospheric activity and meteorological parameters to analyze the seasonal variability of its concentrations; - analyzing the size distribution of 210Pb and its relationships with the ionic composition of atmospheric aerosols to examine potential sources of 210Pb in the atmosphere of Stepnogorsk; - assessment of the radiation dose on the population due to inhalation intake of 210Pb with atmospheric aerosols, and analysis of its potential radiological impact on the human body. Object of the study. The city of Stepnogorsk, located in the Akmola region, is a densely populated area situated near to the tailings storage facility of SHCP. Subject of the study is the activity concentration of 210Pb in air. Research methods. During the course of this dissertation work, atmospheric aerosol sampling and fractionation by aerodynamic diameter were carried out using a high-volume air sampler equipped with a 6-stage cascade impactor. The activity of 210Pb in the samples was determined by gamma spectrometry using an HPGe detector. The detection efficiencies of gamma rays were calculated through detector response simulation using the PHITS program. The ionic composition of the aerosols was analyzed by ion chromatography. The internal radiation dose to the population due to inhalation of 210Pb was performed in accordance with the recommendations of the International Commission on Radiological Protection (ICRP). Main provisions submitted for defense: - For the first time in Kazakhstan, the PHITS program was used to simulate the detection efficiency of an HPGe detector for determination of 210Pb activity in atmospheric aerosols. As a result of the simulation, the geometric parameters of the detector were refined, which allowed calculation of the gamma-ray detection efficiencies of 210Pb in filters collecting aerosol particles of different aerodynamic sizes. - 210Pb concentrations in the near-surface air of Stepnogorsk city were determined for 12 distinct months of observations (excluding the winter period). It was established that the 210Pb activity concentrations varied in the range of 0.46-2.60 mBq/m3 (0.86 mBq/m3), which is comparable to levels previously recorded in megacities such as Beijing and Seoul. The effective internal radiation dose for the population was estimated for five age groups (0.9-2.5 µSv/y), showing that children aged 7-12 years receive higher doses compared to adults. - The seasonal variation and size distribution of 210Pb in atmospheric aerosols were established, revealing a predominant enrichment of the radionuclide in the fine particle fraction and elevated 210Pb levels during the colder months. Based on the analysis of the chemical composition of aerosol particles, which revealed strong correlations between 210Pb and major anions, it was concluded that anthropogenic sources make a non-negligible contribution to the formation of atmospheric 210Pb levels at the study site. The scientific novelty of this research lies in the fact that, for the first time in the city of Stepnogorsk, located within the North Kazakhstan uranium province, a combined investigation of atmospheric 210Pb has been conducted. For the first time in Kazakhstan, the PHITS program was used to simulate the response of a semiconductor gamma detector and to calculate the detection efficiency for 210Pb measurements. For the first time for the city of Stepnogorsk, atmospheric concentrations of 210Pb were determined and an age-dependent assessment of internal radiation doses to the population was carried out. The calculated inhalation dose indicated a potentially higher vulnerability of children when inhaling aerosol particles containing 210Pb. For the first time, patterns of seasonal variability and size distribution of 210Pb in atmospheric aerosols of Stepnogorsk were identified, showing the predominant association of the radionuclide with the fine particle fraction and an increase in concentrations during the cold period. Multivariate data analysis revealed a significant anthropogenic contribution. In particular, the significant role of coal combustion at the Stepnogorsk Thermal Power Plant in the formation of atmospheric 210Pb levels was substantiated for the first time. Scientific and practical value of the work. The theoretical significance of this research lies in the advancement of the fundamental principles of atmospheric radioecology and radiation monitoring methodology. This work contributes to the understanding of the formation and distribution processes of long-lived radon progeny in near-surface air layer of uranium-mining and industrialized regions. The established relationships between 210Pb activity and chemical markers of anthropogenic emissions contribute to the development of knowledge regarding the natural and anthropogenic sources of atmospheric 210Pb. The practical significance of the research results is determined by their direct applicability for solving problems related to radiation safety and environmental protection. The obtained quantitative data on concentrations, particle size distributions, and calculated inhalation doses present a ready information basis for sanitary- epidemiological and environmental regulatory authorities in assessing the radiation situation and health risks for the population at the Stepnogorsk city. The key finding regarding the significant role of coal combustion at the Stepnogorsk Thermal Power Plant in the formation of atmospheric 210Pb highlights the importance of considering energy production sources in environmental monitoring and industrial ecological programs. These results also are important for engineering and environmental organizations in substantiating emissions reduction measures to and improving gas purification systems. The developed methodological approach can be applied to similar studies in other industrial regions of Kazakhstan. In addition, the results of this dissertation are valuable for scientific purposes, particularly in the educational process for training of specialists in radiation ecology and nuclear physics. This research was supported by scientific grants of the Ministry of Science and Higher Education of the Republic of Kazakhstan: Grant No. 189/GF24-26 dated September 9, 2024, entitled "Study of the elemental and radioisotopic composition in atmospheric precipitation and aerosols of the Akmola and Abay regions" and Grant No. 269/23-25 dated August 3, 2023, entitled "Assessment of radon hazard in populated areas near radiation hazardous objects using EPR, TL/OSL and nuclear-tracking detectors". Approbation of work. The main results of this dissertation were presented and discussed at the following international and national conferences: - IX National Scientific and Practical Conference with international participation "Medical, Biological, and Environmental Problems in Uranium Mining Regions" (Astana, September 8-9, 2022); - XIX International Scientific Conference "Science and Education-2024" (Astana, April 12, 2024); - VI International Turkic World Congress on Science and Engineering (Baku, Azerbaijan, December 19-21, 2024); - 68th Symposium of the Japan Society of Radiochemistry (Shizuoka, Japan, September 23-25, 2024); - International Scientific Conference "Science and Education-2025" dedicated to the 25th anniversary of L.N. Gumilyov Eurasian National University (Astana, April 11, 2025); - 7th Asia-Pacific Symposium on Radiochemistry APSORC 2025 (Matsue (Shimane Prefecture), Japan, September 14-19, 2025). Publications and personal contribution of the author. The results of the dissertation were published in 10 scientific works, including 2 papers indexed in the international SCOPUS and Web of Science databases, published in peer-reviewed journals with a non-zero impact factor (Atmospheric Environment - Q1; Journal of Radioanalytical and Nuclear Chemistry - Q2). 2 papers were published in scientific journals recommended by the Committee for Quality Assurance in Science and Higher Education of the Ministry of Science and Higher Education of the Republic of Kazakhstan. One publication was included in the scientific database and assigned a digital object identifier (DOI). In addition, the research results were presented in 5 conference proceedings at international scientific conferences. The author independently completed all stages of the research presented in the dissertation. The author's personal contributions include filter preparation and collection of atmospheric aerosol particles; performance of all experimental measurements using gamma spectrometry and ion chromatography; modeling the detection efficiency of the HPGe detector using the PHITS program; as well as the calculation of 210Pb activity concentrations, ion mass concentrations in the air, and radiation doses to the population. At the stage of dissemination, the author independently prepared and wrote all the scientific articles included in the dissertation, as well as materials for presentations at conferences where the results were presented and discussed. The structure and scope of the thesis. The dissertation includes a title page, table of contents, a list of definitions, notations and abbreviations, introduction, 4 chapters, conclusion, list of references, and appendices. Brief conclusions are provided at the end of chapters 3 and 4. The total volume of the work is 81 pages and contains 31 figures, 11 tables and a bibliography of 156 items. The introduction justifies the relevance of the dissertation research, formulates the aim and main objectives of the study, defines the scientific novelty, theoretical and practical significance of the obtained results, and highlights the propositions submitted for defense. Chapter 1 presents a literature review on atmospheric radioactivity and aerosol particles, examines the features radioactive aerosols formation, and the origin of the natural radionuclide 210Pb in the atmosphere. Global and regional characteristics of atmospheric 210Pb distribution are analyzed, and the research significance of the topic is justified. Special attention is given to the North Kazakhstan uranium ore province, the activities of SHCP, and their potential impact on the environment. Approaches to assessing internal exposure doses from inhalation of radioactive aerosols, taking into account the aerodynamic particle sizes, are also considered. Chapter 2 describes the materials and research methods. The sampling site is characterized in the terms of geographic location, climatic conditions, and environmental features. A methodology for collecting atmospheric aerosols using a high-volume air sampler with a cascade impactor is described in detail. Methods of gamma spectrometric analysis, experimental determination and modeling of detection efficiency using the PHITS program, as well as the methodology for calculating 210Pb activity and concentrations in air, are presented. Procedures for concentration correction, ion chromatography measurements, and approaches for assessing the internal dose to the population are also described. Chapter 3 presents the results of the assessment of 210Pb activity concentrations in the atmospheric air of Stepnogorsk. The results of HPGe detector response modeling using the PHITS program are analyzed, and the detection efficiency of the 210Pb gamma line for aerosol-collecting filters is determined. The main conclusions of the chapter are summarized. Chapter 4 evaluates the radiation doses to the population and considers possible sources of atmospheric 210Pb in Stepnogorsk. Levels of atmospheric 210Pb concentrations are analyzed, and inhalation doses from breathing aerosol particles are calculated. Seasonal dynamics of 210Pb concentrations, its distribution by aerosol size fractions, and the ratio of supported to unsupported (excess) 210Pb are investigated. Fractionated ion composition of atmospheric aerosols is analyzed to identify sources of 210Pb, and the contribution of coal combustion to atmospheric ²¹⁰Pb levels is evaluated. The main conclusions of the chapter are provided. The conclusion summarizes the main results of the dissertation research and formulates conclusions reflecting the scientific novelty and practical significance of the work. Acknowledgments. The author expresses sincere gratitude to her academic advisor, Zhumadilov Kassym, for his scientific guidance, valuable consultations, helpful recommendations, and advice throughout the dissertation process, as well as for the opportunity to participate in research projects and international conferences that contributed to the author's professional and scientific development. The author expresses special gratitude to her foreign academic supervisor, Sakaguchi Aya, for the knowledge and scientific experience shared, for providing full access to laboratory equipment and experimental setups, and for material and comprehensive assistance, including mental support, during her research in Japan. The author also expresses sincere appreciation to co-authors Sakata Kohei, Endo Satoru, Kajimoto Tsuyoshi, Takahashi Junko, and Hoshi Masaharu for their assistance in preparing the scientific publications, as well as valuable comments, recommendations, and corrections that contributed to improving the quality of the research.

Dissertation

List of Scientific Works

Consultant's Review

Foreign Consultant's Review

Conclusion of the Research Ethics Committee