THE ABSTRACT OF THE DOCTORAL THESIS Air pollution is a phenomenon of increasing the volume of toxins in the air Air quality has a significant impact on human health, especially for low-income and vulnerable groups such as the elderly and children According to the World Health Organization (WHO), air pollution exposure causes 6.5 million early deaths worldwide Nearly 90% of these cases occur in low and medium-income countries and about two-thirds of the Asia Pacific There has been much evidence from epidemiological studies in Asia that air pollution causes many health damages and leaves long-term consequences According to the international IQAir in 2019, Vietnam ranked 15th in the list of countries and territories with the worst air quality globally and ranked second in Southeast Asia after Indonesia in 2019 Hanoi has become the capital with a level of air pollution (PM2.5) ranked 7th in the world, even above Beijing, with an average PM2.5 of 46.9 mg m-3, while the length is according to the KTQG Standard Rules of the air quality around 25 mg.m-3 Without effective response measures, air quality is expected to continue to deteriorate in the future due to the impact of the rapid growth of polluting economic activities To control the air quality in big cities such as Hanoi, Ho Chi Minh City, Hai Phong, Da Nang, many air quality monitoring stations have been installed However, setting up a complete real time air pollution monitoring system requires a lot of equipments and complicated operating procedures and high running cost A traditional method to study heavy metal (HM) pollution in the air is using an air sampling pump HM content in the air pump filters is then analyzed with high sensitivity analytics devices However, this method is also costly and difficult to implement on a wide range for a long time One of the simple, economical methods to address these disadvantages is to use plants as biological only, in which moss is more commonly used This method has been widely deployed to study HM air pollution in many countries worldwide, especially in Europe The particular advantage of moss is: (1) The moss root is a fake root, so it does not absorb nutrients from the soil Nutrients are absorbed only from the air; (2) mosses have no logo like high-level plants, so the ability to absorb metal elements is remarkably high; (3) mosses are well resistant to pollution This means it can build up HM elements with remarkably high content; (4) mosses have a substantial amount of surface space/weight to absorb metals from high air; and (5) moss can be collected self-nature, easy to model, and style Due to the diversity and complexity of air pollution factors and the passing impact between ecosystem systems in the environment, solving the math of air pollution requires the participation of many sectors of science, using various analytical techniques to gather complete information in the analysis sample taken from places of interest representatives Among the analytical techniques applied to the research of air pollution, nuclear techniques such as neutron-activated analytics (INAA) or Particle Induced X-Ray Emission (PIXE) show many advantages outstanding such as (1) multifaceted analysis in a single projection, which can simultaneously determine the content of many elements present in the sample; (2) nuclear analysis is a method of non-destruction of samples; (3) for degree highly sensitive, met the need for analysis of HM elements in moss samples; (4) quick analysis time The thesis was entitled with subject as "Application of nuclear techniques to study heavy metal pollution in the air in Hanoi using biological moss indicators" that focus on the following two main goals: (1) Research, development and application of moss biological indicators and modern nuclear analytical techniques INAA, PIXE in the study of HM pollution in the air around Hanoi City (2) Assess the pollution level and determine the possible source of pollution of HM elements in the air in some areas of Hanoi City In this thesis, two types of moss are Barbula indica and Sphagnum girgensohnii used to study air pollution levels and evaluate HM air pollution by passive and active methods in some selected areas of the region Hanoi city and some surrounding areas Using REGATA activation systems at the Joint Institute for Nuclear Research (Dubna, Russia) and PIXE Analysis System at the Nishina Memorial Cyclotron Center (Japan), through the application of a multifaceted statistical analysis methods of results HM analysis accumulated in moss samples will give the source of HM pollution in the air in Hanoi City The correlation between the volume of HM elements in moss samples and aerosol samples collected by air pumps will also be studied, evaluated In addition to the opening, conclusion, and reference documents, the main content of the thesis is presented in chapters: − Chapter 1: Study overview of HM pollution issues in the air, and air pollution research situation using moss biological indicators, HM analysis methods in moss; − Chapter 2: Presents HM pollution research methods and techniques in air moss use and INAA and PIXE element analysis techniques, HM interval research in moss and aerosol samples, statistical analysis methods a variety of experimental data − Chapter 3: Describes the on-site practice process, collecting, processing air pollution research moss samples We are introducing the REGATA analysis system on the IBR-2M nuclear reactor (Dubna, Russia) and the PIXE analytical system equipped at the NMCC Center (Japan) used to analyze of HM elements from the moss samples collected Experimental procedures and data analysis − Chapter 4: Presents the study results of HM air pollution in some areas of Hanoi City using two types of Barbula indica and Sphagnum girgensohnii mosses Correlation Assessment of heavy metal content in moss samples and aerosol samples using an air pump The results of applying Multivariate Statistical Analysis methods to determine the potential sources of pollution of metal elements in the air in Hanoi City The major results of the thesis: − Developing an experimental procedures to study air pollution using Barbula indica moss as a passive bioindicator and Sphagnum girgensohnii moss as an active bioindicator; − Study and successfully apply two modern nuclear analysis techniques: neutron activation analysis using reactors (INAA) and proton beam X-ray emission analysis (PIXE) using accelerators; − The data on the concentration of heavy metals in the air using Barbula indica moss and INAA analysis; and using moss Sphagnum girgensohnii and PIXE analysis in some areas of Hanoi; − Research results on the correlation of heavy metal concentration in moss samples and aerosol samples at the survey areas of Hanoi; − The results of using statistical analysis methods to assess air pollution in Hanoi and possible pollution emission sources − INAA analysis technique, obtained data shows the average concentration distribution of 33 heavy metal elements identified in 27 samples of Barbula indica moss collected in some areas of Hanoi and its surrounding areas The estimated values of the pollution coefficients of the elements shows that it is possible to classify the level of air pollution in Hanoi and surrounding areas as follows: high pollution with Zn, Ba, and Ta, light pollution Al, Cl, Sc, Ti, V, Cr, Mn, Fe, Ni, Co, As, Cd, Sb, La, Ce, Sm, Gd, Tb, Yb, Hf, Th and U, and can be contaminated with Na, Mg, K, Ca, Se, Br, Sr, and Cs − PIXE analysis technique, the concentration of 27 heavy metal elements was obtained in 45 samples of moss Sphagnum girgensohnii in some areas of Hanoi Statistical analysis results show that the air in Hanoi is heavily polluted by Co; severe V and Se contamination; moderate contamination of Cl, Cr, As, Br, Zr, Nb, Mo, and Hg; light pollution of Mg, Al, Si, K, Ca, Ti, Fe, Cu, Zn, Ga, Rb, Sr, Mo, Ba, W and Pb; and suspected to be contaminated with P, S, and Mn The summary of the new findings of the thesis: − Successfully applying a new research method to Vietnam for monitoring and assessing air pollution using the moss as the biological indicators combined with modern nuclear analysis techniques; − Supply essential data on the distribution of toxic heavy metals in the air in some areas of Hanoi; − Evaluation of severe other air pollution levels in Hanoi and identify possible sources of heavy metals pollution in Hanoi and its surrounding areas; − It has been proven that the data on the average content of heavy metals in mosses reflects the average concentration of these elements in the air Therefore, it is confirmed that moss can be used to study the pollution of heavy metals in the air; − The obtained analytical results show the topicality and urgency of researching air pollution in some cities of Vietnam, especially HCM City and Hanoi; the suitability and efficiency of using moss as a bio-indicator; modernity and high reliability of INAA and PIXE analysis techniques as well as the prospect of using these nuclear analysis techniques in Vietnam Discussion and conclusion: − The obtained research results show that the average concentration of most of the heavy metals in the moss samples in the air of Hanoi has been always higher than in other cities in Europe The results of the multivariate statistical analysis show that the primary potential pollution sources that can be suggested include dust and road dust discharged from traffic, industrial activities, and biomass construction Using coal fuel in daily life and burning rice straw and solid waste are also sources of air pollution in Hanoi − A study on the correlation of heavy metal concentration in moss and aerosol samples was carried out with two methods using hanging moss bags, and direct aerosol sampling using air pumps conducted simultaneously and at a location The results show a correlation between the average concentration of heavy metal elements in moss and the air However, these are just some of the initial results; increasing the reliability of the results, it is necessary to conduct a correlation between many different sample objects (moss samples, air dust samples, rainwater samples, simulation data ) and must be performed on enough population of samples The study is also a trend of research that needs to be continued