The Russian Federation, including the Oryol region, is characterized by iodine deficiency in the environment. It’s increased the risk of thyroid diseases (specifically among the rural population), which is intensified by selenium deficiency. The aim of the research is to study the spatial heterogeneity of iodine and selenium in the Oryol region. Samples were collected within 31 settlements in different parts of the region during the summer of 2022. A soil sampling tube sampled the upper 20-cm layer of pasture soils (n = 27). Groundwater samples (n = 52) were taken from centralized water supply and private wells. I and Se concentrations were determined using spectrophotometry and spectrofluorimetry correspondently. The content of iodine and selenium in soils ranged widely both in arable Greyzems (I: 0.21–2.75, Me = 1.10 mg/kg; Se: 0.027–0.419, Me = 0.174 mg/kg) and arable Chernozems (I: 0.48–5.71, Me = 2.44 mg/kg; Se: 0.006–0.502, Me = 0.146 mg/kg), reaching a maximum in the upper 5-cm layer. Iodine content decreases with depth in Chernozems while increasing in Greyzems. An opposite trend was determined for selenium. High heterogeneity of studied elements concentration was detected in groundwater (I: 2.02–33.8, Me = 9.41 μg/l; Se: 0.012–3.704, Me = 0.166 μg/l). Spatial differentiation of the concentrations attributed primarily to the aquifer: higher iodine concentrations are associated with the Cretaceous system (I: 17.4–33.8, Me = 25.7 μg/l; Se: 0.013–0.737, Me = 0.054 μg/l), lower with the Devonian aquifer (I: 2.18–18.5, Me = 4.59 μg/l; Se: 0.086–3.704, Me = 0.210 μg/l). Inverse differentiation of selenium was also found. Concentrations below optimal level were detected in 58

Owing to the importance of drinking water in human nutrition, in this study, we performed a comparative analysis of the chemical composition of drinking water from settlements endemic to Kashin–Beck disease and from territories that are not endemic to Kashin–Beck disease. Our analysis showed that all drinking water samples were weakly alkaline and had a hydrocarbonate–calcium–magnesium composition. There were no considerable differences in mineralization, pH, or concentrations of Mg, Si, F, Se Zn, K, and Na. All waters had weak hardness specific for the waters from the northern territories. The mineral waters from the Urov biogeochemical subregion of the biosphere have elevated concentrations of Ca, Mg, Sr, Si, and Li and lower concentrations of I, Se, and Cu. The maximum Sr content was found in mineral water from the Bazanovo village, i.e., 20 mg/L, with a Ca/Sr ratio of 8 units. Owing to the inconsistency of data on the chemical composition of drinking water from the territories endemic for Kashin–Beck disease, we suggest an indirect role of biogeochemical factors in the disease pathogenesis. Previous pathologies may be important, which have arisen because of hypothermia, common cold, hormonal imbalance, and alimentary factors.

The vertical and lateral distribution of iodine and selenium in the soils on different types of parent material, i. e. loesslike loams and fluvioglacial sands and sandy loams, was studied within associated landscape-geochemical systems of the Titovka River basin (Bryansk region, Russia). It was found that the content of both elements in particular genetic horizons of the studied soils under the contrasting environment varies widely, namely I: 0,22-7,93 mg/kg, n = 93, and Se: 0,001-0,668 mg/kg, n = 93, airdry mass. Gray forest loamy soil on loesslike loams contains 2 times more iodine and almost 4 times more selenium than sodpodzolic sandy loam soil on binary deposits (1,67 / 0,81 mg/kg for I (p < 0,05); 0,453 / 0,120 mg/kg for Se (p < 0,05), respectively).This may be due to both the type of parent material and higher content of organic matter, and the lighter texture of gray forest soils. The content of iodine and selenium in bottom sediments of the Titovka River (0,59 and 0,36 mg/kg of airdry mass) is most comparable with the upper horizon of sodcarbonategley soil sampled a few meters from the sampling site of bottom sediments (I - 0,57 mg/kg; Se - 0,35 mg/kg of airdry mass). At the same time, the elements showed dissimilar differentiation in soil horizons, due to their affinity to geochemical barriers. Iodine is actively fixed on the alkaline-carbonate barrier and is mobile under reducing conditions, while selenium concentrates on the gleyic barrier and is mobile in an oxidizing environment. This should be taken into account when assessing the availability of these biologically significant chemical elements in soils and local food products, particularly in the areas exposed to radioactive isotopes of iodine.

The purpose of this study is to estimate the migration of heavy metals (HMs) and As into the water of the Ardon river, and their content in the soils of the areas adjacent to the Unal Tailings Pond (UTP) caused due to the industrial waste of the Mizur Ore Mining and Processing Enterprise (OMPE) (North Ossetia). The main survey loops for experimental research and collection of biogeochemical materials are located in the Ardon river basin where the major abandoned polymetallic fields of the Republic are located. Soil samples were taken from 20 sites throughout the Ardon river and within the UTP. HMs and As levels in the water, alluvium, soils samples were determined using the atomic-absorption spectroscopy (AAS) in its flame version and/or electrothermal atomisation. We have determined that UTP wastewater discharge into the Ardon river along with Me introduction with waters of the Unaldon river, as well as the dust/pulp coming from UTP followed by the formation of bottom polymetallic anomalies provide a significant contribution to the Me pollution of the Ardon. High Me content in soil and slurry as a result of its deflation and in UTP effluents may lead to Me absorption by plants and other organisms. The data obtained reflect the processes of modern transformation of mountain taxa of the biosphere with a technogenic component and can be used for remediation of contaminated areas.

Biogeochemical studies were carried out in two territories of the Northern Caucasus, including the Unal depression (which is enriched in Zn, Pb, Cu, and Cd) in the basin of the Ardon River in the Republic of North Ossetia–Alania and a profile down the Baksan River (which is characterized by elevated W and Mo concentrations) in the Kabardino–Balkarian Republic. The accumulation of metals was studied in both individual plants and ecogroups and in a lateral profile and a profile across altitudinal belts in the basin of the Ardon River. Selective Zn enrichment was found in the leaves of the birch Betula platyphylla Sukacz., whereas Cd and Zn were detected to be accumulated in the leaves of various willow and aspen types. Correlations were evaluated between the activity of soil enzymes (dehydrogenases, invertase, peroxidase, and catalase) and the concentration levels metals in soils at base-metal and W–Mo of biogeochemical provinces. It was determined that an increase in the totals of the concentrations of all metals in the soils of both areas is inhibited the activity of dehydrogenase. According to the degree of their inhibition by metals, the soil enzymes define the following sequence: dehydrogenases > invertase > (catalase and peroxidase). A change in the activity of soil enzymes at anthropogenic pollution can serve as an additional biogeochemical indicator for exploration operations and in ecological studies.

The assessment of opportunities of various methods of complex ecologo-biogeochemical monitoring of objects of the accumulated environmental damage (tailings dams) in modern biospheric conditions is very significant. Organisms of different levels of the organization are applied: from infusorians to the highest mammals and the human body. In addition to direct determination of levels of toxicants in organism researchers often use their morphometric parameters, in particular - the fluctuating asymmetry. Calculation of this parameter for sheet plate of the birch growing near the Unalsky tailings dam (North Ossetia) was compared to determination of biologically active sulfur-containing components (metallotioneins, glutathione, cysteine) and pigments (a-chlorophyll, b-chlorophyll, carotene). In the technogenic horizons of urbozem and natural soils, leaves and hay crops of plants the content of microelements is found. In soils and urbozem it is revealed: Pb - 10.5-589, Cu - 7.0-891, Zn - 23-4156, Cd - 0.2-91, As - 5-18.8, Se - 0.05-4.6 mg/kg. High positive correlation between the content of Pb in soils and asymmetry of birch leaves (r = 0.89) is established. On other metals correlation was low (r = 0.18-0.21). Floristic inspection found noticeable decrease in phytovariety and biomass on technogenic platforms. Value of the fluctuating asymmetry is moderately correlated with amount of metals in soils and leaves. The same relation is found between its value and content of glutathione and metallotionein in extracts of birch leaves. Correlation with levels of pigments (a-chlorophyll and carotinoids) was not observed. Comparison of the fluctuating asymmetry of leaves of white birch with the total content of metals and the concentration in water extract confirms certain correlation between these parameters. Higher concentration of the sum of metals and sulfur-containing biologically active agents is followed by increase in value of asymmetry.

RedOx processes determine the resistance of the organism to pollutants. The aim of the study was to establish a possible relationship between copper and zinc concentration in the blood of calves and the enzyme activity of superoxide dismutase. The study was conducted in 2019 on 50 calves with a weight of 201-250 kg. The samples of venous blood were taken to estimate the level of hemoglobin, glutathione, metallothioneins, as well as zinc, copper, and superoxide dismutase activity. The obtained average values of these substances concentration were compared between each other. A positive correlation between the activity of superoxide dismutase and the concentration of zinc (r = 0.64) and copper (r = 0.87) in the blood of calves has been established. It may be because both metals are obligatory components of superoxide dismutase. There is also a positive relationship between the levels of copper and zinc (r = 0.68). For the other parameters, no reliable relationship was found. The data obtained indicate a positive relationship between the activity of superoxide dismutase and metal concentrations of copper and zinc in the blood of calves. At the same time, a more significant positive relationship is established for copper.

The comparative assessment of the levels of content and migration parameters of biologically active chemical elements in the biogeochemical food chains of the main localities of the Urov endemic disease in the Eastern Transbaikalia: rocks-soils-plants-animal hair, milk was conducted. The differentiated polyelement microelementosis with an excess of Sr [1], Mn, Cr, Ni, in some cases – P, Ba, As, Zn and deficiency of Se, J, Cu, and Mo is typical in Urov biogeochemical provinces of Eastern Transbaikalia against the background territories. Soil landscapes are not much different in content of selenium, but its migration in plants was reduced in places of spread of Urov disease. Parameters of migration of chemical elements in the soil-plant complex reflected on their content in wheat, hair cover of animals and milk cows. The sources of this imbalance are soil-forming rocks, specific conditions of soil formation (accumulation of organic matter in freezing soils of narrow valleys with a high degree of moisture and low flow, and selective concentration by plants). For floodplain soils with a high level of organic matter is characterized by a high content of micromycetes of the genus Fusarium as their species composition and abundance. The data obtained are consistent with the results of research by Chinese scientists on the assessment of the chemical elemental composition of hair in healthy children and with Urov Kashin-Beck pathology [2] and considered as risk factors in the genesis of this endemic disease. Funding This study was supported by the Russian Foundation for Basic Research, project No. 19-05-00054 References 1. Ermakov V.V., U. A. Gulyaeva, S. F. Tyutikov, T. G. Kuz’mina, and V. A. Safonov. Biogeochemistry of Calcium and Strontium in the Landscapes of Eastern Transbaikalia. Geochemistry International, 2017, 55 (12). P. 1105–1117. https://link.springer.com/article/10.1134%2FS0016702917090026 2. Wang X., Ning Y., Zhang P., Li C., Zhou R., Guo X. Hair multi-bioelement profile of Kashin-Beck disease in the endemic regions of China. J Trace Elem Med Biol., 2019. 54 (July 2019). P. 79-97. https://rareomics.healx.io/disease/kashin-beck-disease.

— Combined ecological and geochemical assessment was performed for the major- and trace-element composition of groundwater of Bryansk oblast used for drinking water supply, and settlements and districts were ranked with respect to the contents of I, Se, and some other chemical elements and their concentrations were compared with the existing hygienic standards. It was shown that the I and Se contents of drinking water is controlled by the geochemical conditions of water formation and do not reach physiological optimum levels (10 mg/L for I and 2.5–3.3 mg/L for Se) in most districts of the oblast, which could intensify the adverse response of the thyroid gland (TG) to the contamination of the region with I-131 during the Chernobyl nuclear accident of 1986. Furthermore, we revealed other unfavorable hydrochemical factors, which may influence the distribution of natural endemic diseases among local inhabitants related to local elevated concentrations of Mn (up to 10 MPC), Fe (up to 26 MPC), Si, and Sr (up to 2 MPC) in drinking waters confined to certain hydrogeologic complexes.

The higher accumulation of Mo, W, Cu and Re by soils and organisms in the Baksan River basin owing to the anthropogenic contamination by the former Tyrnyauz W–Mo industrial complex and migration of the metals with natural waters are discovered during biogeochemical studies of W–Mo mining landscapes of the North Caucasus and background territories. The man-made transformed soils of the Baksan River valley and natural waters are enriched in moderately mobile compounds of Mo and other metals. The competitive relationships are found not only between Mo and Cu, but also between Mo and W while assessing the biogenic migration of metals. An increased content of Mo and W is found in the hair coat, blood and milk of farm animals, which is accompanied by changes in the activity of some enzymes.

The paper presents analysis of the accumulation of toxic and vital chemical elements in discrete links of the food chain under conditions of a biogeochemical province in relation to the accumulation of phytochelatins and metallothioneins in the leaves of white birch (Betula pubescens). Gradients of metal concentrations are determined in the soils with increasing distance from the Unal tailing dump and the effects of these gradients on the concentrations of the elements in birch leaves. Correlations are determined between the concentrations of toxic elements in the pulp and leaves separately for the native sample and water washout. A strong correlation was found between the total dissolved concentration of all metals and the total metallothionein and glutathione concentrations. It is hypothesized that the biochemical system of glutathione is more closely related to the accumulation of metals by plants than the system of metallothioneins. Estimates are made whether it is possible to apply the method of bioindication of the ecological state of a territory by determining the fluctuating asymmetry of birch leaves. This bioindication parameter was evaluated separately for each of the cardinal points. It is demonstrated that a high total concentrations of the metals in soils and birch leaves is correlated with an increase in the fluctuating asymmetry of the leaves and the concentration level of sulfur-bearing biological active compounds. The bioindication technique is however still far from perfect and is difficult to apply and, hence, requires further studies.

Using the methods of selective extraction, atomic absorption, and gas-liquid chromatography, we determined that the river and lake waters in arid and/or humid regions differ in their total and alkylated mercury content indices. Mercury high content levels in waters of arid landscapes (e.g., in Kyrgyzstan) do not activate metal methylation process. The features of the interaction of mercury and humic compounds like fulvic (FA) and humic (HA) acids are discussed. The FA are found to promote mercury dispersion in the biosphere due to the formation of fulvic complexes and abiogenic methylation of mercury resulting in the toxic organomercuric compounds. The HA manifest high sorption capacity levels in relation to mercury ions and serve as sorbents. At a competitive interaction in the system FA-Нg-HA, Кd for mercury drops sharply with an increase in FA concentration and рН system. The metabolism of mercury in the biosphere in terms of its content in the soilplant complex is discussed.

This study was aimed at assessment of strontium and calcium mobility in soils and their accumulation with plants in the areas endemic for Kashin–Beck disease in Eastern Transbaikalia. The strontium and calcium mobility levels were determined using the method of sequential chemical extraction for 7 samples of meadow soils collected from the endemic region and 7 soil samples taken from conditionally control sites. To measure the Ca and Sr levels in the soil and plant samples, XRF analysis and AAS were used. The increased strontium level in the meadow soils of the endemic areas is accompanied by the element’s higher mobility. The highest strontium yield was observed in the course of soil extraction using 1 M ammonium acetate, while the soils taken from the control sites gave lower amounts of the trace element. Furthermore, there is a positive correlation between the amount of the strontium extracted and its content in plants (r = + 0.86 − 0.98). At the sequential chemical extraction of calcium from the soils using the above method, the calcium yield was maximal in the ammonium acetate fraction (background sites) and in ammonium acetate and 6 M HCl fractions (endemic areas). The correlation between the amount of the calcium extracted in 1 M ammonium acetate and the macroelement levels found in plants was + 0.968. In addition, a peculiarly high accumulation of strontium in various willow species as compared to other meadow plants was revealed for the first time ever. Thus, the work introduces new data into the trace element biogeochemistry and environmental monitoring.

Specific responses of plants and animals to changes in the contents of microelements (Pb, Cd, Cu, Zn, As, Se, etc.) in abiotic environmental components of the Ardon River Basin (North Ossetia) were studied by new biogeochemical indication methods. In comparison to background areas, a local increase in the Pb, Cd, Cu, Zn, and As contents in soils and organisms occurs under the impact of natural and technogenic factors. The heavy metal contents in Ardon River water are generally within hygienic norms. Activation of sulfurcontaining synthesis in the leaves of willow, sea buckthorn, and coltsfoot was revealed for the maximum heavy metal content in soils. On plots adjacent to the Unal tailing dump, the contents of pigments and their proportions in leaves of coltsfoot, dandelion, and willow do not differ from those in less contaminated areas. On technogenic plots, the species richness of plants decreases, as well as the mowed biomass and projective cover of herbaceous plants (to 40%); inhibition of plant growth, chlorosis, necrosis, and lamina deformation are observed. A new metallophyte species (Cladochaeta candidissima M. Bieb.) was revealed. The increase in lead and arsenic contents in soils and plants of the Ardon floodplain is accompanied by an increase in their concentrations in the blood and hair of animals.

Ecological–biogeochemical monitoring of a linden avenue on Kosygin Street, Moscow, has revealed that soils at sites regarded as contaminated contain elevated Mn, Fe, Sr, and Se concentrations and lower Zn contents. Linden leaves at the assumed contaminated sites typically contain higher Cu and Fe concentrations and not as much higher Zn, As, and Cr concentrations but much lower Mn and Sr concentrations. Water leachates of soils at sites regarded as background have slightly lower pH and lower Ca, Mg, K, and Na concentrations and total mineralization. Test for phytochelatins in the leaves proved to be rather ineffective, as also were estimates of the fluctuating asymmetry of the leaf laminas. The greatest differences were detected in the degree of leaf pathology and the contents of pigments.