The Neutron Activation Analysis (NAA) technique at the REGATA facility of the IBR-2 reactor is used to meet a range of tasks in ecology, biology, geology, nanotoxicology, materials science and in other fields.

Biomonitoring of air pollution using moss biomonitors

Within the framework of the international programme "Atmospheric deposition of heavy metals in Europe - estimates based on the analysis of biomonitor mosses", SNAAPI carries out work on estimating the state of air in the JINR Member States. In 2020, an atlas of atmospheric deposition of heavy metals "Atmospheric deposition of heavy metals in Europe - estimates based on the analysis of biomonitor mosses" was published in JINR that included results for 36 countries, including 14 JINR Member States: Azerbaijan, Armenia, Belarus, Bulgaria, Vietnam, Georgia, Kazakhstan, Moldova, Mongolia, Poland, Russian Federation, Romania, Slovakia, Ukraine and Czech Republic. The data on the simultaneous accumulation of biomonitor mosses over large areas, presented in the atlas, allowed to estimate both spatial and temporal trends in changes of the concentrations of heavy metals, as well as to identify areas with a high level of pollution as a result of local and transboundary transport of metals.

Figure 1. Left: Atlas of atmospheric deposition of heavy metals. Right: Analytical techniques used to determine metal content in moss samples [1]

In addition to passive biomonitoring, active biomonitoring is widely used in SNAAPI (the technique of moss in bags). Work on estimating air quality in the city of Tula near the Kosogorsky metallurgical plant is given as an example. Mosses Pleurozium schreberi, Sphagnum fallax and Dicranum polysetum were chosen as bioindicators. The values ​​of the relative accumulation factor (RAF) indicated a high degree of contamination of the study area as a result of industrial activities, mainly Mn and Fe (Fig. 2) [2].

Figure 2. Accumulation factor values ​​for a) manganese and b) iron at 7 exposure points of moss bags; Pl- Pleurozium schreberi, Sp- Sphagnum fallax, Dp- Dicranum polysetum. The red line shows RAF value = 1.00 [2]

Water pollution monitoring

The NAA technique is widely used to determine the content of elements in marine biomonitors: mussels, oysters, sponges, algae. A great deal of work on the determination of macro- and microelements in soft tissues and shells of mussels of the species Mytilus galloprovincialis selected in areas with different levels of anthropogenic pressure in the Republic of South Africa, Namibia and Mozambique is carried out in the Sector. Thus, the content of 24 macro- and microelements in soft tissues and 18 elements in the shells of mussels of the species Mytilus galloprovincialis, selected in 8 contaminated and 4 clean zones of Namibia, the western and eastern coasts of South Africa and Mozambique, was determined (Fig. 3). Al, Cr, Fe, Ni, As, and I have been calculated to be hazardous to human health when consumed less than 100 g of mussels/week per person in cities such as Swakopmund, East London, Port Shepstone, Richards Bay, Shai-Shai, Vilanculos and San Sebastian. Higher consumption levels (200g mussels per week) may pose a risk to human health for Zn and Se in Namibia, Saldana Bay (Se), Hout Bay (Se), Port Shepstone (Se) and Mozambique (Se, Vilanculo and Capo San Sebastian). Among the analyzed elements with a high risk to human health: Al, Cr and Fe are presumably of terrigenous origin, while Ni, As and I are of anthropogenic origin. The obtained results and risk levels can be included in the regulatory documents for the studied areas [3].

Figure 3. Left: Sampling map. Right: Risk ratios for Al, Cr, Ni and As in mussels sampled in the study areas [3].

Cleaning of drains

Work on the extraction of metal ions from model solutions and industrial wastewater using biological and inorganic sorbents is carried out in SNAAPI.

Work on the purification of rhenium-containing wastewater (Re, Re-Mo, Re-Cu and Re-Cu-Mo) using the cyanobacterium Spirulina platensis as a battery is implemented. Interest in the recovery of rhenium from wastewater is due to its high cost and wide application in industry. The accumulation of rhenium in spirulina biomass depended on the chemical composition of the model systems and the highest accumulation of 161 mg/kg (1540 times more than the control) was distinguished in the Re-Cu system (Fig. 4). At the same time, it is worth mentioning the high accumulation of other metal ions in the analyzed systems. The addition of rhenium to the spirulina nutrient medium resulted in an increase in biomass productivity, as well as in an increase in the content of proteins, carbohydrates, lipids and pigments. Meanwhile, the occurrence of copper in the nutrient medium caused oxidative stress, expressed as a decrease in biomass productivity, as well as a decrease in the content of proteins and carbohydrates. It should be noted that spirulina is an efficient and environmentally friendly sorbent [4].

Figure 4. Accumulation of Spirulina biomass metals from rhenium containing effluents with different chemical compositions [4].

Geochemistry and bioremediation of soils

Due to the ease of sample preparation for analysis, NAA is widely used to determine the elemental composition of soils and geological samples. So, in SNAAPI, work was carried out to study geochemistry and to estimate the ecological state of soils and bottom sediments in the valley of the Zarafshan River and its tributaries, northwestern Tajikistan. This region is known for rich deposits of Au, Ag, Sb, Hg, W, Sn, Pb, Zn and other minerals that are currently developed. NAA was used to analyze 116 samples of soils and bottom sediments. Analysis of the obtained data showed that the studied samples are mainly felsic rocks and limestones and dolomites were found at several points. The values ​​of the technogenic capacity factor (CF) and pollution load index (PLI) calculated for mercury, arsenic and antimony and at some points for tungsten and vanadium indicate strong or extreme contamination of soils and bottom sediments with these elements (Fig. 5). The lower reaches of the Dzhidzhikrut River can be considered the most polluted. The mining industry is the main source of soil and bottom sediment pollution in the region [5].

Figure 5. CF and PLI values ​​for unaffected soils (A) and bottom sediments (B) and anthropogenic impacted soils (C and D) and bottom sediments (E and F)

Reducing soil pollution is possible by using bioremediation techniques. The storage capacity of millet Echinochloa frumentacea grown on soils with polyelement anomalies selected near metallurgical enterprises and highways in the city of Tula was determined. As a result of the work, the toxic effect of soils with strong polyelement anomalies (multiple excesses of the maximum permissible concentration (MPC) for Cr, Ni, Zn, As, oil products) on biometric indicators and adaptive characteristics of millet was shown. It was found that Echinochloa frumentacea accumulated Mn, Co, As, and Cd from soils with polyelement contamination within the average values. V was accumulated mainly in the root system (transition coefficient from roots to shoots 0.01–0.05), the mechanism of its absorption is rhizofiltration. The removal of Zn by shoots of Echinochloa frumentacea increased on soils where the content of the element exceeded the MPC and amounted to 100–454 mg/kg dry weight (168–508 g/ha). An analysis of the obtained data allows to recommend Echinochloa frumentacea for soil phytoremediation from Cu and Zn at a low level of polyelement pollution [6]. The possibility of using the cynobacteria Nostoc linckia for the remediation of soils with polyelement pollution, where chromium and copper were the main pollutants, was also tested.

Assessment of the quality of food and medicinal plants

The elemental composition of soils, fruit (apples, plums and grapes) from four regions of the Republic of Moldova was determined using NAA. A total of 40 elements were identified in soils and 22 elements - in fruit. The values ​​of the bioaccumulation factor of elements from soil to fruit and the hazard index were calculated. In every analyzed fruit, the highest bioaccumulation factor values ​​were obtained for potassium and rubidium (Fig. 6). Hazard index (HI) values ​​for all elements except antimony in the Cahul and Criulena areas were below 1.0, indicating that they are safe for the consumer. Discriminant analysis allowed to separate fruit by type and place of origin. The main contribution to the division of samples into groups was made by the following elements: Na, Mg, Cl, K, Fe, Cu, Zn, As, and Rb [7].

Figure 6. Bioaccumulation factor values ​​for the soil-fruit system calculated for fruit from four regions of the Republic of Moldova

Particular attention is drawn to the determination of the elemental composition of medicinal plants. The composition of seven herbal teas developed at the scientific centre of the North Ossetian State University named after K.L. Khetagurov, each of which contains from 3 to 8 plant components was analyzed. The content of 37 elements was determined for the first time in herbal teas using NAA and AAS. Elements K, Ca, Mg, Cl, Na, Fe have the highest concentration in all samples, their content exceeds 100 µg/g. The content of the elements Mn, Zn, Ba, Rb, Ti, Sr is less than 100 µg/g and more than 10 µg/g, the content of the elements Br, Ni, Cr is less than 10 µg/g and more than 1 µg/g and the content of such elements as Mo, Se, Co, Ce, V, La, Cs, W, Th, Sc, Sb, Sm, Hf, U, In, Ta, Tb, Au - less than 1 µg/g. All seven herbal teas have a low concentration of elements such as Pb, Cd, As, Cu compared to TLV that indicates their safety for human health [8].

Nanotoxicology

A range of investigations on the effect of metal nanoparticles that came from the mother's body during the prenatal and lactation periods were implemented in SNAAPI. The levels of cognitive functions in young animals exposed to gold nanoparticles and control animals were compared. The gold content in various organs (blood, liver, lungs, kidneys and brain) of females and their offsprings was determined using NAA. According to the data obtained in females, the highest gold content was determined in the kidneys, then in the liver, lungs, brain and blood. In the offsprings, the accumulation of gold in the organs changed in the same order. The average mass content of gold in the brain of females was 0.25 ± 0.10 ng and in the brain of offsprings - 08±0.03 ng (Fig. 7). No significant differences in spatial orientation and memory were found between experimental and control offsprings in the Morris test, but experimental mice showed increased levels of anxiety in the elevated plus maze. Thus, the effect of gold nanoparticles on the emotional state of mice exposed to nanoparticles during prenatal and early postnatal development was found, but not on their cognitive abilities. The data obtained are important for estimating the toxic effect of nanomaterials on the human reproductive system [9]. A review on the effect of metal nanoparticles on the cognitive abilities of animals was also prepared.

Figure 7. Gold content in the brain of females and their offsprings [9].

Investigations on the effect of gold, silver and copper nanoparticles on the growth and biochemical composition of medicinal plants has started.

Objects of extraterrestrial origin

As part of the space experiment “Test”, in order to study the sorption of cosmosol that develops a finely dispersed sedimentary medium on the surface of the ISS, it was proposed to remove and deliver to Earth a cotton bundle of fabric placed by astronauts on the outer surface of the ISS. The studied bundle of tissue was fixed by Yury Lonchakov and American astronaut Michael Fincke on bracket 2312 during the EVA session. It was installed on 10 March, 2009, dismantled by astronauts on 15 May, 2019, placed in a Zip-Lock bag in the atmosphere of a space station and delivered to Earth in September, 2019 (Fig. 8). Thus, the time of its stay in outer space was more than 10 years.

Figure 8. Direction of station movement and positioning of a roll of cotton fabric attached to the outer surface of the ISS

Using NAA, it was possible to determine the content of 39 elements in the contaminated fragment of the tissue fold and 19 elements in the clean fragment. Three main sources of elements deposited on the towel have been identified. One of the important sources can be considered dust particles produced during the fall of meteorites, asteroids or comets. To determine the nature of the elements, the ratios of the elements established for chondrites were compared with the ratios obtained for the contaminated fragment of the roll. Thus, the cosmic origin of magnesium, silicon, iron, uranium and thorium was confirmed.

Since the ISS is mainly constructed from aluminum and the pipelines are manufactured from corrosion-resistant steels and titanium alloys, the station can be considered the basic source of these elements. In addition to cosmic bodies and the ISS itself, particles emitted from the Earth, such as, volcanic ash, can be considered another source of deposition of elements on the roll. Volcanic ash can be considered an important source of Ba, Zr, Re, Sr, Rb and rare earth elements. In the upper part of the ionosphere at the height of the ISS orbit, ionized particles from the composition of gas and dust emissions from fumarole fields of the volcano can get with the ascending branch of the global electrical circuit. This kind of ionospheric lift ensures the slow rise of aerosols in the field of the "Earth-ionosphere" condenser due to a number of coupled mechanisms of turbulent electrothermal diffusion, accompanied by mass transfer of dispersed material [10].

The content of 27 elements (Si, Ti, Cr, Al, Fe, Mn, Mg, Ca, Na, K, V, Sc, Co, Ni, Zn, As, Se, Rb, Mo, Ag, Sb, Cs, Sm, Tm, Ir, Au, U) in a fragment of the Chelyabinsk meteorite was distinguished using NAA. The obtained data were compared to the elemental composition of LL chondrites. The analyzed fragment was enriched in chemical elements Au, Ag, Rb, Tm, U and Zn relative to the chemical composition of LL chondrites [11].

Radioecology

In 2022, work on radioecology started, in particular, work was carried out to determine the natural radionuclides ⁴⁰K, ²³²Th, ²³⁸U, ²³⁵U и ¹³⁷Cs in soils selected in 15 recreational areas of Moscow at a depth of 0-5 and 5-20 cm. Research of the distribution of radionuclides depth showed a uniform distribution of natural radionuclides and a decrease in ¹³⁷Cs activity with increasing depth.

Figure 9. Left: sampling points, right: content of natural radionuclides and 137Cs in the soils of Moscow recreational areas [12].

The average values ​​of the specific activity of radium, the hazard indices of external and internal exposure, the gamma index, the annual efficient dose and the excess lifetime carcinogenic risk did not exceed the recommended values and the average value of the absorbed dose rate of gamma radiation exceeded the value established by the UN Scientific Committee on the Effects of Atomic Radiation. In this regard, it is recommended to monitor the content of radionuclides in the soils of Moscow on an ongoing basis.

SNAAPI Publications 2020-2023.

References

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2. Świsłowski P., Vergel K., Zinicovscaia I., Rajfur M., Wacławek M.,2022, Mosses as a biomonitor to identify elements released into the air as a result of car workshop activities. Ecological Indicators, 138, 108849. https://doi.org/10.1016/j.ecolind.2022.108849
3. Nekhoroshkov P., Zinicovscaia I., Vergel K., Grozdov D., Chaligava O., Kravtsova A., 2022, Macro- and Microelements and Radionuclides in the Mussel Mytilus galloprovincialis from Recreational and Harbor Sites of the Crimean Peninsula (The Black Sea). Hydrobiology, Volume 1, Issue 3, pp 304-316. https://doi.org/10.3390/hydrobiology1030022
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6. Gorelova S.V., Muratova A.Y., Zinicovscaia I., Okina O.I., Kolbas A., 2022, Prospects for the Use of Echinochloa frumentacea for Phytoremediation of Soils with Multielement Anomalies. Soil Syst., 6, 27. https://doi.org/10.3390/soilsystems6010027
7. Zinicovscaia I., Sturza R., Duliu O. G., Grozdov D., Gundorina S., Ghendov-Mosanu A., Duca G., Determination of major and minor elements in Moldavan fruits by neutron activation analysis and assessment of their provenance. International Journal of Environmental Research and Public Health, 2020,17, 7112, doi:10.3390/ijerph17197112
8. Лавриненко Ю.В., Плиева А.М., Христозова Г., Фронтасьева М.В., Зиньковская И., Ткаченко К.Г., Элементный состав травяных чаев, исследованных с помощью инструментального нейтронного активационного анализа и атомной абсорбционной спектрометрии. Химия растительного сырья 3, 305-314, 2020
9. Ivlieva A., Zinicovscaia I., Petritskaya E., Yushin N., Rogatkin D., Peshkova A.,2022, Assessment of Gold Nanoparticles Uptake in Tissues of Female Mice and Their Offspring Using Neutron Activation Analysis. In: Tiginyanu I., Sontea V., Railean S. (eds) 5th International Conference on Nanotechnologies and Biomedical Engineering. ICNBME 2021. IFMBE Proceedings, vol 87. Springer, Cham. https://doi.org/10.1007/978-3-030-92328-0_51
10. Zinicovscaia, D. Grozdov, N. Yushin, A. Safonov, I. Proshin, M. Volkov, A. Pryadka, V. Belyaev, E. Shubralova, O. Tsygankof. Analysis of the rolled cotton cloth fixed on the outer surface of the International Space Station using neutron activation analysis and complementary techniques. Acta Astronautica 189 (2021) 278–282, https://doi.org/10.1016/j.actaastro.2021.08.052
11. Kirillov, D. Grozdov, I. Zinicovscaia, T. Vasilenko. Elemental composition of the Chelyabinsk meteorite determined by neutron activation analysis Journal of Radioanalytical and Nuclear Chemistry, 2021, https://doi.org/10.1007/s10967-021-08078-z.
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