Alpine snowpacks provide valuable archives of atmospheric deposition, yet the southern slopes of the Greater Caucasus remain underrepresented in high-altitude geochemical monitoring networks. This study investigated the hydrochemical composition of fresh snow, annual snowpack, and perennial snowfields across an altitudinal transect from 1838 to 2857 m a.s.l. within the Caucasian State Nature Biosphere Reserve to characterize depositional sources and evaluate how snow archive type and landscape structure influence geochemical signal preservation. Major ions were determined by titrimetric and turbidimetric methods, while trace elements and rare earth elements were quantified by ICP-AES and ICP-MS. Complementary soil and vegetation samples assessed landscape controls on elemental accumulation. Marine-associated ions, including Na, Mg, Cl, and Sr, remained detectable across the transect at sites approximately 50 km inland from the Black Sea, indicating orographic transport and scavenging of maritime aerosols during south-westerly circulation. Forest canopy interception reduced sub-canopy snowpack elemental concentrations by approximately 70 to 80 percent relative to open alpine environments, establishing montane forest sites as the most conservative local deposition baseline. Rare earth element concentrations exceeded upper crustal Clarke values by factors of 2 to 5 and corresponded to REE-enriched Paleogene volcanic lithologies of the Mzymta basin, supporting their use as robust lithogenic tracers. Because fresh snow, annual snowpack, and perennial snowfields preserve atmospheric chemistry over fundamentally different temporal scales, they cannot be treated as interchangeable monitoring archives. A spatially distributed annual snowpack sampling design anchored by montane forest reference sites is recommended for integrated seasonal atmospheric monitoring in topographically complex mountain terrain.

This study investigates the elemental composition of seawater and macroalgae (red, green, and brown species) in the Russian Black Sea coastal zone following an M-100 fuel oil spill in December 2024. Our findings indicate a limited transfer of chemical elements from the fuel oil into the dissolved phase of the ambient marine environment. Conversely, the sorption and subsequent bioaccumulation of chemical elements by macrophytes proved significantly more pronounced. The most substantial accumulation was consistently noted in the brown alga Ectocarpus siliculosus. The clear and measurable differentiation between spill-affected and unaffected areas, based on the algal elemental signature, facilitated the development of a novel geochemical indicator of fuel oil pollution (GIP). The GIP is defined as the ratio of the sum of the elements concentration coefficients (Сc – multiplicity of elements' contents excess relative to the background) associated with fuel oil pollution (Mn, Co, and rare earth elements) to the sum for elements characteristic of standard shipping-related pollution (Cd, Zn, V, Ni). A GIP value exceeding one signifies the presence of fuel oil contaminants in the water column and associated biota, enabling a clear distinction from pre-existing background anthropogenic inputs.

The analysis of elemental composition (by ICP method for 70 elements) of Calcic chernozems of the Rostov region in a wide spectrum including rare and scattered chemical elements, the content of most of which was established for these soils for the first time, allowed to reveal geochemical features of these soils. In particular, they are characterized by a rich elemental composition. The mostly studied chemical elements have contents exceeding clarks for soils (clark - average contents for soils of continents). The group of stable excess elements includes: As, Ni, Co, Tl, Sc, Th, as well as rare earth elements (REE). The studied territory is characterized by the ubiquity of carbonate rocks, which are poor in elemental composition among all sedimentary rocks. Thus, the content of soils should be associated with general favorable natural-climatic conditions for soil formation processes and soil with fertile humus, which contributes to good accumulation of chemical elements. REE activity in soils reflects geochemical specialization of regional rocks. The performed traditional ranking of these elements in relation to North American shales allowed us to show the specificity of their regional fractionation, manifested in the predominance of the subgroup of medium and light REEs. It is known that REEs with similar chemical properties are recognized indicators of changing conditions, including anthropogenic activity. Such a pattern can be considered as a background baseline, which makes it possible to identify anthropogenic sources that caused these changes when REE distribution changes. Keywords: RARE EARTH ELEMENTS, SOILS, ANTHROPOGENESIS, FRACTIONATION

By the example of studying the Early Holocene paleoalluvial soil (ancient man's site in Akhtsu Grotto, an overflow terrace of the middle reaches of the Mzymta River, Sochi Black Sea region), the efficiency of using a set of microbiological methods revealing the conditions of formation of the ancient paleoobject and the genesis of the geomorphology of the river valley was shown. The study of morphology and mesomorphology of the palaeo-soil allowed to assume its possible formation under the conditions significantly more hydromorphic in comparison with the modern ones. It is probable that earlier, at the beginning of the Holocene, this area was not a terrace, but a near-terrace, over-watered part of the river floodplain. Microbiological characteristics confirmed this assumption. The composition of the microbial community was identified from the isolated soil DNA of prokaryotic microorganisms (bacteria and archaea) by DNA metabarcoding. Groups and species of microorganisms-indicators reflecting the specificity of genesis of the studied soils were identified. Microbiological indicators of overwatered conditions were representatives of the phylum Planctomycetes of Phycisphaerae and Planctomycetia classes dominant in the microbiome (more than 1% of total DNA) and cyanobacteria of Chloroplast class of Streptophyta, Stramenopiles and Pseudanabaenale orders, as well as archaea (0.5% of total DNA) of Euryarchaeota phylum; Thermoplasmata class; Methanomassiliicoccaceae family, capable of methanogenesis. This species was not found in the microbial complex of the modern background soil. Indicator microorganisms identified as part of the prokaryotic community of palaeo-soils may potentially have useful applicable properties.

Macroalgae have long served as bioindicators of pollution in coastal marine environments. However, conventional pollution assessment methods often take a compartmentalized approach, either focusing on macrophyte biological parameters or independently analyzing heavy metal and oil product bioaccumulation within them. This study establishes connections between: (1) the characteristics of chemical pollution in brown, green, and red macroalgae, (2) organic pollution in the nutrient medium, and (3) the resulting changes in phytocenosis composition and macrophyte morphological characteristics. The research was conducted in the coastal zone near the Sochi River mouth on the Black Sea coast of Russia, encompassing the urban center of the Sochi metropolitan area. Inductively Coupled Plasma (ICP) analysis quantified the accumulation levels of 60 chemical elements within macrophyte algae. The novel aspect of this study is the development of a quantitative metric for assessing the overall chemical pollution impacting the ecologically crucial macroalgae Cystoseira. This systematic approach represents a significant advancement in the comprehensive evaluation and management of coastal water quality. The study identified two contrasting accumulation patterns: (1) pollution-tolerant annual algae exhibited an exclusion mechanism for chemical elements, while (2) Cystoseira displayed a non-exclusion accumulation pattern, potentially explaining its absence in the most heavily polluted zone. This approach paves the way for establishing a standardized scale for algal chemical pollution, reflecting a range from permissible to highly hazardous levels in seawater. This will enable rapid acquisition of both qualitative and quantitative pollution data, streamline monitoring efforts, and expedite the implementation of control measures.

The structural and functional state of microbial communities of different-aged buried ancient soloids (soil-like bodies lacking genetically distinct horizons) have been comprehensively assessed in open archaeological pits of ancient human sites in the middle reaches of the Mzymta River on the Sochi Black Sea coast in the Akhtsu grotto and Akhshtyrskaya cave. A number of changes in the functional biodiversity of ancient soloids as compared with the background soils (alluvial soils formed immediately near the studied soloids with similar mesomorphological properties) are observed. They include a 1.2-fold decrease in the specific metabolic activity of microbial communities assessed by multisubstrate testing and an increased instability of paleomicrobial systems according to the coefficient of rank distribution of the range of substrate consumption d > 1, which is typical of irreversibly damaged systems. The microbial community of ancient soloids has undergone a number of changes associated with anthropogenic activity. According to the analysis of the main range of consumed substrates (multisubstrate testing), the microbial community of the Akhtsu grotto soloid displays a more intensive consumption of alcohols and amino acids, which suggests the supply of the organic matter of an animal origin to the cultural layer of ancient human site. Lactococci and bifidobacteria are identified in the Akhshtyrskaya cave soloid; they are extremely rare in soil and develop under conditions of excess carbohydrates on rich complex media, such as fermented meat and plant residues. In addition, an increased content of keratinolytic fungi capable of decomposing the keratin of hair, wool, feathers, and so on has been found in the cultural layer of the cave site. A comparative analysis of the prokaryotic taxonomy demonstrates the prevalence of the members of the Thermoleophilia class, family Gaiellaceae, order Solirubrobacterales in all the studied soils and soloids. These microorganisms require only positive temperatures for their development, suggesting a mild climate during the soil formation. The Akhtsu grotto paleosols are a promising source of bacteria (genera Janthinobacterium, Lysobacter, and Chitinophaga ) that may possess biotechnological potential and useful properties.

Seawater intrusion, characterized by the infiltration of a seawater wedge into deep coastal freshwater aquifers, poses a significant threat to water quality. Despite extensive research on this hydrogeological phenomenon, monitoring remains challenging, often requiring deep drilling that exacerbates aquifer contamination. This study proposes a novel approach for monitoring seawater intrusion based on hydrogeochemical indicators, specifically focusing on secondary contamination observed in river and spring waters along the Black Sea coast of Russia. Using mass spectrometry, we analyzed the abundance and concentrations of 71 elements, identifying key indicators of secondary contamination influenced by the low hypsometric altitudes of the region. In total, 30 river and spring water samples were analyzed. Notable findings include a positive correlation between excess trace elements and Cl- and SO42-, characteristic of seawater. River waters exhibited lower mineralization compared to spring waters, with consistently higher Mn/Br, Cs/Br, and ∑ rare earth element/Br ratios, serving as reliable indicators of secondary contamination. This study allowed us to propose a geochemical indicator (GIM) GIM = ∑ Mn Cs REE/Br which reflects the secondary contamination intensity. The decrease in GMI dynamics indicates an increase in the impact of the secondary contamination process on surface and spring waters. This innovative approach minimizes the reliance on extensive drilling, providing valuable insights for the study and monitoring of seawater intrusion in coastal aquifers.

A comprehensive assessment of the structural and functional state of microbial communities of multi-temporal buried ancient soloids (a soil-like formation similar to soil but without genetically formed horizons) in open archaeological pits of ancient human sites located in the middle reaches of the Mzymta River on the Sochi Black Sea coast in the Akhtsu Grotto and Akhshtyrskaya Cave was carried out. Changes in the functional biodiversity of ancient soloids compared to the background (alluvial soils that form in close proximity to the studied soloids and have similar mesomorphological properties) are noted: a decrease in the specific metabolic work (W) of microbial communities by 1.2 times according to the method of multisubstrate testing and an increase in the instability of paleomicrobial systems according to the index of the rank distribution of the spectra of consumption of substrates d 1, which is typical for irreversibly damaged systems. The microbial community of ancient soloids has undergone a number of changes associated with anthropogenic activity. The analysis of the main absorption spectrum of substrates (MST method) showed that the microbial community of the soloid of the Akhtsu Grotto is oriented towards more intensive consumption of alcohols and amino acids, which suggests that organic matter of animal origin entered the cultural layer of the ancient human site. In the microbiome of the soloid of the Akhshtyrskaya cave the presence of lactotococci and bifidobacteria was found, which are extremely rare in soil and develop in conditions of excess carbohydrates on rich complex media, such as fermented meat and plant residues. Also, an increase in the content of keratinolytic fungi capable of decomposing keratin of hair, wool, feathers, etc. was found in the cultural layer of the cave site. Prokaryotic taxonomy in all the studied soils, with or without anthropogenic impact, was characterized by the predominance of the members of the Thermoleophilia clade and the families Gaiellaceae and Solirubrobacterales. Considering that these species require positive temperatures to develop, it suggests that the soils were formed in a mild climate. The Akhtsu grotto paleosols are a promising source of bacteria (genera Janthinobacterium, Lysobacter, Chitinophaga) that may have biotechnological potential.

Assessing local air quality using traditional methods, such as analyzing precipitation composition, is often difficult due to the complex data, which is influenced by a variety of chemical elements from distant atmospheric sources and cyclone formation areas. This study presents a new approach to overcome these challenges: a multi-elevation sampling method that improves the accuracy of local air quality measurements. By collecting precipitation samples at different ground elevations, the technique takes advantage of the natural process where raindrops and snowflakes collect more elements as they fall through the air. This method helps to distinguish local air quality from background levels found at higher, non-industrial elevations. The primary goal was to isolate and identify the elemental fingerprints of marine influences, while excluding contributions from cyclones. In February 2023, 51 meltwater samples were collected from 17 observation points in the city of Sochi under southeast wind conditions. These samples revealed a spectrum of chemical elements, predominantly of marine origin (Mg > Na > Sr > Ca > K > Ce > Mn). The results showed significant differences in elemental concentrations between upland and coastal areas. The Geochemical Indicator of Marine Origin (GIM) ranged from 22 to 3235, confirming the strong influence of marine aerosols in the area. These findings demonstrate the effectiveness of the multi-elevation sampling method in providing robust environmental assessments. This approach, combined with the GIM index, offers valuable insights for improving environmental policies and public health, particularly in coastal regions affected by marine aerosols.

Background concentrations of trace elements in soil, that is, the natural abundances of metals and metalloids in soil, have been the subject of much scientific discussion. (The International Union of Pure and Applied Chemistry no longer endorses the term “heavy metal,” so we will not use it. In addition, for the sake of brevity, from now on, the term “metal” will include metalloids (e.g., arsenic). We have attempted to clarify the concept, particularly from the perspective of environmental toxicology and chemistry. In the context of soil contamination assessment, knowledge of background concentrations of metals allows scientists to distinguish between the natural abundances of metals in the environment and the concentrations of the same elements that occur as a result of anthropogenic impacts. Given the controversy surrounding the definition of “background concentration,” we decided to follow the International Organization for Standardization guidance 19258 (2018), which defines “background concentration” as “the concentration of an element or substance characteristic of a soil type in an area or region, arising from both natural sources and anthropogenic diffuse sources such as atmospheric deposition.” The protocol also defines “background value” as a statistical property of the background concentration, such as mean, median, range, or percentile. Elevated concentrations of potentially toxic elements in soils are not always due to anthropogenic sources, but may be related to the natural occurrence of the elements in the environment (McLaughlin & Smolders, 2001). Given that the lithology of the soil parent material determines the background metal concentrations in the soil (Novoselov et al., 2022), background concentrations established in one area are not applicable in areas that differ lithologically. Therefore, Clarke numbers (elemental abundances in the Earth's crust) are of limited use for soil contamination assessment, and useful knowledge of background concentrations of metals in soil must be obtained separately in each watershed (Novoselov et al., 2022). It is known that geochemical data on element concentrations do not follow a normal or lognormal distribution, but rather a skewed distribution with statistical outliers (Reimann & Filzmoser, 2000). Given this fact, we disagree with the procedure in Matschullat et al. (2000), which is widely used to derive background concentrations of elements. In that procedure, statistical outliers are removed from the data set by excluding those values that fall outside the range of two or four standard deviations (hereafter termed 2σ- and 4σ-outlier removal). To demonstrate the shortcomings of that procedure, we used our database of total copper and zinc concentrations in 30 soil samples collected in a pristine area free of anthropogenic influence (Litvinenko & Zakharikhina, 2022). The Kolgorov–Smirnov test showed that the data did not in fact follow the normal distribution, whereas the Grubbs test showed that the data did in fact contain statistical outliers (Table 1), consistent with Reimann and Filzmoser (2000). The presence of outliers in the data set can be explained by the sulfide mineralization shown on the geological maps of the area. After removing 2σ- and 4σ-outliers, the maximum values are significantly lower than in the original data set (Table 1). Following the procedure in Matschullat et al. (2000), this outlier-free data correspond to background values. Let us assume that this outlier-free data are used to determine the background concentrations of metals. Let us also assume that the latter background concentrations were applied to the original data set (with outliers) to determine the occurrence of soil contamination. Taking these assumptions at face value would lead to the erroneous conclusion that some of the soils in the original data set were contaminated by anthropogenic influences. This conclusion would be all the more unreasonable given that the original data came from a pristine area in a national nature reserve where some of the sampling points could only be reached by helicopter. Furthermore, we would like to critically analyze the method of Galuszka (2007), one of the most widely used methods for estimating soil metal contamination in anthropogenically affected areas. Galuszka (2007) eliminates statistical outliers from the data set by iterative 2σ-outlier removal. Under this approach, outlier-free data would reflect background conditions, whereas elevated metal concentrations would signal anthropogenic contamination. However, this procedure is clearly flawed because geochemical data on element concentrations usually contain statistical outliers (Reimann & Filzmoser, 2000), as our own database from an area without anthropogenic activity shows (Table 1). Applying the Galuszka (2007) procedure to our data would therefore lead to the erroneous conclusion that some soils are contaminated with metals due to anthropogenic activity. Moreover, we would like to emphasize that removing outliers from the data has not transformed them into a normal distribution (Table 1). Meanwhile, it is important to note that the procedure for calculating statistical properties (e.g., percentiles) does not require producing a normal distribution of the data or any transformation of the data at all. Background values for metals in soil can be established simply by calculating a given statistical property using the original values of metal concentrations in soil from areas without anthropogenic activities. The difficulty is to find such areas in the upper river valleys of a given study site. Finally, our considerations on background concentrations of metals in soil can be extended to other media and other types of contaminants of interest to environmental toxicology and chemistry. For instance, there are currently no guidelines on how to derive background concentrations at contaminated sediment sites, leading to significant variability, uncertainty, and disagreement on the methodology for deriving representative background concentrations of chemicals of concern at these sites (Geiselbrecht et al., 2019). The argument of the present study aims to help in understanding why removal of outliers is an unsound computational procedure for estimating background concentrations of chemicals in environmental media. Removal of outliers can cause biased and inaccurate results when estimating background concentrations of contaminants. The conceptual flaw of the procedure is that it is based on the false assumption that there are no statistical outliers in the data on contaminant concentrations in the unpolluted environment. A. Neaman and P. Peñaloza wrote the manuscript with the support of the Chilean National Fund for Scientific and Technological Development 1200048 project (awarded to A. Neaman). L.V. Zakharikhina's field and laboratory work was supported by Federal Grant 0492-2021-0016 (awarded to the Subtropical Scientific Center of the Russian Academy of Sciences). Elvira A. Dovletyarova drafted the manuscript with the support of the RUDN University Strategic Academic Leadership Program. The authors thank A. Tchourakov for proofreading the English and for his helpful comments. Alexander Neaman: Conceptualization; Funding acquisition; Methodology; Writing—original draft and review & editing. Lalita V. Zakharikhina: Investigation; Resources; Validation. Claudia Navarro-Villarroel: Data curation; Formal analysis; Resources; Software; Validation. Patricia Peñaloza: Conceptualization; Methodology; Project administration; Validation; Writing—review & editing. Elvira A. Dovletyarova: Conceptualization; Funding acquisition; Methodology; Writing—review & editing. This is a point of reference article. No data were generated.

The peculiarities of the fractionation of rare earth elements (REE) were studied in three genetically similar types of soils in the territory of the humid subtropics of Russia. REE contents were determined by inductively coupled plasma mass spectrometry with full acid decomposition of samples. The following soils were studied: burozems formed on mudstones in the Mzymta river valley; burozems transformed to the state of abrozems formed on similar rocks in Sochi; and brown soils on carbonate rocks in the territory of the Utrish Reserve. Burozems formed in natural conditions on mudstones are characterized by REE fractionation with the predominance of their middle subgroup. In urban soils similar in genesis, an increase in the content of elements of the light subgroup is observed. These changes are due to their transformation as a result of urban load. Over the past 100 years, the soils of the city have undergone significant alkalinization, the index of pH in them increased by 2 units. The relationship between REE fractionation and soil acidity is confirmed by the REE distribution curve for the soils of the Utrish Reserve. The latter are distinguished by an even greater predominance of the light REE subgroup, due to the increased alkalinity of soils caused by the formation of soils on carbonate rocks.

This study examines the regional geochemical anomalies in the soil of the Mzymta River valley in Russia, which was affected by large-scale construction works for the 2014 Winter Olympics.The study found that the elemental composition of soils not affected by human activity is influenced by the chemically rich parent rock and the presence of mineralized zones.The abundance and concentrations of excess and deficient elements in the soil were determined using mass spectrometry for 61 elements, and factor analysis was used to identify the causes of the variations observed.The study identified geochemical indicators that can predict soil-forming factors and revealed both natural and anthropogenic sources of chemical elements in the valley soils.Natural sources include geochemically rich rocks that contributed most significantly to the soil chemistry.The anthropogenic sources of elemental variation in the soil were a result of the construction of Olympic transit infrastructure using local geochemically rich materials.The heavy crushing and subsequent intense weathering of this material resulted in an increase in the concentration of excess elements in the soil compared to the parent rock or mineralized zones.This indicates a significant alteration of the soil's elemental composition due to construction activities in the area.The findings of this study can be applied to predict potential soil contamination in similar river valleys that are experiencing both natural and anthropogenic pressures.

The chemical composition of the waters of 31 springs located in the basins of the Mzymta and Sochi rivers on the southern slope of the Caucasus Range was studied. Both water-bearing fractured carbonate rocks and water-resistant mudstones and igneous rocks are developed here. In addition, the region is characterized by the development of mineralization zones and deposits of thermal hydrogen sulfide waters. Four types of waters have been identified: I) hydrocarbonate calcium, II) hydrocarbonate-sulfate calcium-magnesium, III) hydrocarbonate-sulfate calcium-sodium, IV) hydrocarbonate-chloride-sulfate calcium waters. Due to the geochemical features of regional rocks, all types of waters are characterized by high contents of Se and rare earth elements (REE) and low concentrations of Tl, Zr, Th, and Fe. The first type of waters is associated with fractured carbonate rocks, and due to their good solubility and water permeability, it differs from other types of waters by increased concentrations of Se and REE by factors of 2.3 and 2.6, respectively. The second type, distributed mainly in argillites, is distinguished by relatively low contents of Se, REE and other elements, which is due to the lower water permeability and solubility of argillites compared to carbonate rocks. The third type is characterized by the additional presence of excess elements Ba, Li, Rb and B in the composition, which is associated with the influence of a deposit of hydrothermal mineral waters. Igneous rocks, being the least permeable and less rich in chemical elements than mudstones, influence the formation of groundwater with the lowest concentrations of elements. The low permeability of igneous rocks is confirmed by the analysis performed using the hydrogeochemical Gibbs diagram, indicating that the precipitation factor is superimposed on the formation of these waters. REE for all types of waters are characterized by similar fractionation inherited from the rocks of the region (medium REE heavy REE light REE). The total amount of rare earth elements and their fractionation patterns can be used as a reliable criterion for the interpretation and typification of fresh groundwater.

Показаны особенности формирования химического состава поверхностных вод рек Мацеста и Бзугу, берущих свое начало в средне- и низкогорной зоне Сочинского Причерноморья, при взаимозависимом влиянии на них двух факторов: естественного и техногенного. Река Мацеста в сравнении с рекой Бзугу, за счет большей водности и менее существенной техногенной нагрузки, в меньшей степени загрязнена и в верхнем течении по-прежнему отражает состав контрастных горных пород водосбора своего верховья.

This study examined the chemical pollution of macroalgae and mussels in the coastal region of the Black Sea, near the mouths of the Sochi and Mzymta rivers. A comprehensive analysis was conducted to establish a correlation between the chemical composition of these organisms and the components of the terrestrial ecosystem, with a specific emphasis on the behavior of rare earth elements (REEs). The study revealed that the fractionation pattern of REEs in the terrestrial ecosystem was duplicated in both algae and mussels. However, a less pronounced fractionation was observed in organisms that were not significantly impacted by contaminated river waters. The findings demonstrate that algae serve as a robust absorbent of chemical elements and are highly sensitive indicators of pollution, capable of detecting contamination at greater distances from the shore than mussels. Conversely, mussels, as more complex organisms, display a greater degree of selectivity in their accumulation of chemical elements.

In anthropogenic soils of Sochi (the Black Sea coast, humid subtropical zone of Russia), the acid-alkali properties are transformed in comparison with natural soils (Haplic Acrisols (Clayic)). The pH-water index shifted from 5.8 to 7.5 (average values for the genetic horizons of soils), alkali saturation increased 1.3 times in the upper horizon (from 72.9 to 97.7%) and 1.5 times (from 64.8 to 97.3 %) in the middle clay argic horizon. Assessment of chemical elements contents (61 elements analyzed) in the soils of different landscapes of Sochi in comparison with their concentrations in natural soils revealed the following. Pollutants, the contents of which must be controlled when monitoring urban soils, are: Cu, Ni, Cd and, additionally, on low relief elements: Cs, Ga, Be, Rb, V, Li, as well as 9 rare-earth elements (REE): Dy, Tb, Sm, Ho, Eu, Gd, Sc, Y, Er. The total pollution index (total above-background content of chemical elements) for urban soils is not large. According to the most typical urban relief elements, in the watershed - slope - sea coastline system, the index is distributed as follows - permissible pollution on the slope, moderately hazardous pollution on the flat surface adjacent to the slope, and dangerous pollution in the coastal zone on the territory of sanatoriums. Sochi coastal sanatorium zone requires detailed monitoring in order to identify areas with extremely dangerous contamination of the soil that needs to be recultivated.

For the first time in international practice, agricultural experiments were carried out to introduce volcanic ash from the Kamchatka Peninsula in combination with conventional mineral fertilizers into ocherous volcanic soils (Andosols Acroxic).According to various variables of field experiment, yield increases were obtained relative to the background: for potatoes (Solanum tuberosum) by 31-63% in 2014, by 7-19% in 2017 and by 14-31% in 2018; on timothy (Phleum pretense) by 21-50% in 2015.Production experience in the cultivation of annual forage grasses in 2016 showed an increase in yield by 32%.In addition, the crude protein in forage grasses and the content of starch potato tubers also increase, and potatoes have better resistance to potato diseases.

This paper reports on the radioecological properties of environmental components in the Mzymta and Sochi River valleys on the Russian Black Sea coast. The environmental components covered are river sediments, alluvial soils, mosses, and fluvial water. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used to determine the distribution patterns of Th and U stemming from two geochemical alkaline barriers present in the river valleys. One is a calcium barrier resulting from the metamorphic transition from neutral mudstones to alkaline carbonate rocks. The other is a sodium barrier formed in estuaries under the influence of Na-rich tidal seawater. The sodium barrier was responsible for an increase in Th and U concentrations in river water, a slight decrease in soil and sediments, and strong sorption on mosses. The calcium barrier reduced Th and U concentrations in river water, but increased them in soil and mosses. In the Sochi River valley, the content of calcium in the components of the natural environment is higher compared to the Mzymta River valley and, on average, 4 times higher in the river water. This factor determines the relatively high Th and U content in the natural environment of the Sochi River valley, as these radionuclides are easily extracted from the mineral component of river water by carbonate solutions. On the whole, the radioecological status of the river valleys was recognized as favourable. Gamma radiation exposure dose rate near the surface (20-27 mu R/h or less in mountainous areas and 9-17 mu R/h in the lowlands) was below the natural level typical for open mountainous areas of central Russia. River sediments in both valleys had low radionuclide concentrations based on the specific activities of naturally occurring radionuclides Ra-226, Ra-228, Ra-224, Th-232, and K-40. In similar river basins that may be targeted for future development, accumulation of Th and U in soil and mosses on calcium barriers and elevated concentrations in river water on sodium barriers should be expected.