The ongoing anthropogenic impact on the Russian Arctic river ecosystems leads to an anthropogenic transformation of their ecological state, which makes it necessary to assess the anthropogenic load and compare it with the degree of water pollution in the Arctic river mouth areas. The scientific practice uses various approaches to assess the anthropogenic pressure on water bodies. The main approach is to develop a methodology for ecological standardization and determination of critical levels of pressure on aquatic ecosystems. The study deals with the assessment of the level of anthropogenic load on river mouth sections using runoff rates of chemical substances, namely readily oxidizable organic matter, ammonia nitrogen and oil products, which are integral indicators of the quality of the aquatic environment.

The paper presents the results of assessing the anthropogenic load on river mouth sections and water quality data for the Russia Arctic rivers for the periods from 1980 to 1999 and from 2000 to 2018. The objects of research are large rivers, such as Pechora, Ob, Pur, Taz, Yenisei, Anabar, Lena, Yana, Indigirka and Kolyma.

In the process of comparative analysis of the anthropogenic load in terms of the runoff rates of ammonia nitrogen, organic matter, and oil products significant differences were revealed. The rivers of the Pechora River basin and Western Siberia showed higher level of anthropogenic pressure, while the Eastern Siberia rivers are characterized by the lowest total anthropogenic load. The anthropogenic load demonstrates the decreasing dynamics according to most of the estimated indicators for most of the studied large rivers of the Russia Arctic zone. At the same time, water quality of the rivers of the European and East Siberian parts of the Russia Arctic zone varies in between the 3rd and 4th quality classes, while in the West Siberian part in the range of the 4th and 5th classes. Generally, multidirectional tendencies of water quality changes were revealed for the studied rivers. The trend of improving water quality for the studied tributaries of the Pechora River and mouth sections of the Yenisei, Anabar, Indigirka and Kolyma rivers was statistically confirmed based on the correlation analysis.

The results of the study could be useful for the elaboration of environmentally-sound water protection measures to increase the environmental safety in fragile mouth areas of the Arctic rivers.

A review and analysis of the published data on migration links and the nature of the transformation of polyarenes in the soil-natural water-atmosphere system that have appeared over the past two decades show that the direction and intensity of these phenomena depend on a combination of many factors, namely climatic conditions, physical and chemical properties of the environment, the characteristics and activity of microbiota, the nature of vegetation cover, as well as on the sources, characteristics and composition of polyarenes themselves. Volatilization of PAHs, their deposition, leaching, sorption, and photo- and biodegradation are the primary processes in which PAHs are involved in soils, natural waters, and the atmosphere. The intensity of these processes is different in each of these environments and during the interaction between them. At the same time, the levels of knowledge about the migration and transformation of polyarenes in three environments are also different. The analysis shows that the accumulation of new knowledge on the topic is very intensive and new approaches to research and modern methods of obtaining data are being formed. However, there are still ‟blank spots” in the study of some issues, some scientific assessments are unambiguous, and the conclusions are sometimes contradictory.

The paper discusses regional protection of phytodiversity within well-developed mining area of the Arctic zone of Russia (case study of the Khibiny Mts and surrounding plain). A large industrial hub with mining and processing enterprises is situated there, and the resident population is over 80 000 people. The Khibiny Mts and their piedmont plain are characterized by an exceptional variety of landscapes and vegetation and also high biodiversity. Information on rare and endangered species of plants and lichens was collected through floristic and geobotanic surveying in 2010-2020s and the analysis of herbaria and published data. About 20% of the total number of rare and endangered species of the Murmansk Region was found in the Khibiny Mts and the adjacent plain, mainly within 11 special protected areas (SPA), which cover 123 220 ha. Some rare plants inhabit the anthropogenically transformed areas. The most critical factors of biodiversity loss in the Khibiny Mts are the expansion of mining industry, deforestation and fires. Organization of small SPA near mining areas and cities is very important because they essentially contribute to the conservation of regional biodiversity. The existence and evolution of a polarized landscape requires nature protection in the form of a large SPA, otherwise it is anthropogenically transformed and fragmented even in its remote areas, and loses its biodiversity. At present the existent system of SPAs makes the region a successful model of territorial conservation of biodiversity, which combines local and extensive areal protection of rare and endangered species and plant communities.

The paper shows the prospects of using the unmanned aerial vehicles (UAVs) for the monitoring of reservoir shores particularly in the absence of observation points of the state monitoring network of water bodies. The abrasion activity consequences, such as the retreat of cliff edge and the reduction of land area, were assessed for several sections of the Tsimlyansk reserve shores, applying the mutual linkage of aerial photos by reference points and successive interval parallel consideration of heterochronous orthophotomaps.

The first method, providing observation accuracy within 10 cm, made it possible to identify periods of cliff edge retreat by 5-30 cm resulting in land loss of 2.8 to 22 thou. m² and stabilization periods when the position of the cliff edge changed little if at all.

The second method allowed the reliable identification of time intervals with active exogenous geological processes resulting in the cliff edge retreat by a meter or more.

It is shown that the most considerable changes in the shore slope configuration took place in the region of Ovchinnikov and Vesyoly farmsteads and Nagavskaya stanitsa as the result of the storm in May 2018 under N.W.L. (Normal Water Level). At the same period, the retreat of shores by 5-10 m probably occurred at some locations in the region of "Vinzavod” Garden Partnership and at the shore section from the eastern cape of Zhukovsky Bay to the Baklanovskaya village.

It is found that the coastline stabilization coincides with the periods of the reservoir water level at 1-2 m below N.W.L. and the absence of heavy precipitation. During these periods, the intensity of exogenous geological processes decreases noticeably. The main forms of their manifestation are the ruptures at the distance up to first meters from the cliff edge; failures of small blocks of rocks; forming of small swellings.

Spatial disintegration is understood in the study as a process of disruption and destruction of system-forming connections between territorial units of a state. Based on previous studies carried out by other authors, seven factors of spatial disintegration are identified, namely historical, socio-economic, electoral, ethno-cultural, transport, military-strategic and foreign-political. To quantify the risks of spatial disintegration, a calculation method has been developed that allows for a comparative analysis of the danger of disintegration for particular countries as integral systems, and for their administrative-territorial units.

The risks of spatial disintegration are calculated for three Latin American countries, i. e. Venezuela, Mexico and Chile, which are quite different in socio-economic, ethno-cultural and political-administrative terms. The greatest risk of spatial disintegration is characteristic of Venezuela. The most significant risks of spatial disintegration at the subnational level are typical for the Tachira state in Venezuela; for the Baja California and Tamaulipas states in Mexico; and for the Arica y Parinacota and Araucania regions in Chile.

The correlation analysis between the parameters showing the effect of various disintegration factors is carried out. The following correlations are significant for Mexico: positive between socio-economic and foreign policy factors and negative between socio-economic and ethno-cultural, socio-economic and transport factors. The correlation between socio-economic and ethno-cultural factors is positive in Venezuela, as well as between foreign policy and electoral factors, and negative between socio-economic and electoral factors. Only two significant correlations were found for Chile: between socio-economic and military-strategic factors, and socio-economic and foreign policy factors.

The principal components method made it possible to identify two leading components in the Latin American countries under study. The first one is frontier regions with a high level of human development, which at the same time are less integrated into economic and transport links with their internal neighbors. The second one is "implant” regions, which differ from the main regions of the country by racial composition and in which the power control of the mother state is strengthened.

Spatial interpolation methods for generation of a digital terrain model were compared for the forested areas of the "Nizhnyaya Kama” National Park (Republic of Tatarstan, Russia). The available topographic maps of the park territory at a scale of 1 : 100 000 were used. The interpolation methods, namely the inverse distance weighting with different power parameters p (IDW1, IDW2, IDW3, IDW4), ordinary kriging with Matern (OKMat) and spherical (OKSph) variogram models, multilevel b-splines (MBS) and thin plate splines (TPS), were evaluated in terms of vertical accuracy and hydrological precision. The hydrological precision was calculated based on the distance of the channel network identified on the basis of interpolated terrain models from their actual location. The results of the assessment based on the nodes of isolines and characteristic points of the terrain showed that the method of inverse weighted distances produces the greatest error when creating a digital elevation model. Geostatistical and spline methods had similar accuracies. According to the precision of the channel network positioning, all methods were arranged in the following order: IDW1 - IDW3 - MBS -IDW4 - IDW2 - OKSph - TPS - OKMat. The general conclusion is that TPS and ordinary kriging methods allow obtaining the most realistic representation of relief for the tasks requiring a hydrologically correct terrain model. In particular, the ordinary kriging method with the Matern variogram model was the most correct interpolator for the surveyed territory of the "Nizhnyaya Kama” National Park.

The article deals with the analysis of economic development of the Don River catchment area using statistical materials, remote sensing data and geoinformation technologies. The data sources include official national statistics, information products of the Global Land Cover types with a resolution of 30 m and a CCI Land Cover product of the European Space Agency with a resolution of 250 m. The authors elaborated a sectoral geoinformation system, which contains information about the main types of underlying surface, cultivated areas, gross harvests and crop yields in the basin for 43 design water-resource areas, 8 enlarged water-resource regions, 276 municipal districts, 15 entities of the Russian Federation and 3 regions of Ukraine. It has been established that the growth of cultivated areas and gross harvests of agricultural crops leads to increasing consumption of soil moisture for transpiration. The northwestern part of the basin is characterized by decreasing surface runoff and increasing underground runoff and a significant predominance of spring crops over winter ones (approximately 60% versus 40%) is observed there. Winter plowing before sowing spring crops reduces the surface runoff and enhances the filtration. The development of agriculture in the basin is oriented towards the expansion of cultivated areas, higher application of mineral and organic fertilizers and the growth in gross yields of basic crops (primarily grain, sugar beets and potatoes). According to the official data, cultivated areas in the Russian part of the basin amount to about 17 million hectares, while according to the remote sensing data they cover 30-34 million hectares. The area of forests in the basin is about 2.8 million hectares, and the area of urbanized territories is 1.4 million hectares, or 3.2%. Up-to-date data on the land cover should be used for modeling and analysis of water balance within the catchment areas of the Don River and its tributaries.

The work deals with the assessment of possible changes in the level regime of a largest water body in Central Asia. The anthropogenic Aidar-Arnasay lake system is formed by the inflow of drainage waters from the eastward-situated irrigated lands. In the past periodic discharges of fresh water from the Shardara reservoir led to water level transgression in the lake system. The damming of the Arnasai lakes and the projected absence of fresh water inflow put a task of assessing water level change in the remaining Aidarkul-Tuzkan system, taking into account various options for the volume of drainage water inflow. The problem was solved on the basis of simulation modeling of the water balance stochastic equation for the lake system. If the current volume of the annual inflow is maintained, the future equilibrium water level will drop from the current level of 245 m abs to about 239 m abs. Under the increase of average inflow by 0.5 km³/year the level will fluctuate near the equilibrium level of 243 m abs. Under the same decrease in the average inflow the equilibrium level will drop to 236 m abs.

The purpose of the work is to discuss and identify the reasons of 2015-2019 rise of the upper boundary of the hydrogen sulfide zone above the edge of the Black Sea shelf. The position of the boundary is particularly important for the hydrochemistry of the Black Sea, since its rise to the surface could create a threat of the ecological catastrophe. Taking into account the intensive inter-basin water exchange, this may affect the state of the ecosystems of the Eastern Mediterranean and the Sea of Azov.

The paper discusses the position of the top boundary of hydrogen sulfide, identified by the 3 μM isosulfide, above the edge of the Crimean shelf, according to the data of 2015-2019 expeditionary studies of the Marine Hydrophysical Institute of the Russian Academy of Sciences. The position of the hydrogen sulfide boundary over the edge is of particular importance for the western shelf of Crimea, which is part of the northwestern shelf of the Black Sea (NWS). Probable leakage of hydrogen sulfide from the deeper part of the sea to the northwestern shelf can further aggravate the already less favorable ecological state of the shelf bottom waters, in which hypoxia regularly occurs in the warm season, sometimes culminating in fish kills.

Comparison of the averaged profiles of hydrogen sulfide concentration in terms of the scale of conditional density (σ_t) shows that the profiles over the southern shelf of the Crimea (to the east of the Khersones Cape) differ just slightly from those for the deeper part of the sea; the hydrogen sulfide zone appears on the isopycnic surface of σ_t = 16.15 kg/m³ in these areas. On the NWS of the Black Sea its occurrence is somewhat higher, i. e. at σ_t = 16.06-16.09 kg/m³. Among the profiles of 21 stations surveyed in 2015-2019 on the NWS, three stations were identified at which hydrogen sulfide appeared unexpectedly high at a depth of 85-90 m. The rise is exclusively related to water dynamics in early December 2017, since the stations were not distinguished in any way on the density scale. Their profiles were located side by side and intersected with the average profile along the NWS; like at most other offshore stations, their 3 μM isosulfide was located on the isopycnic surface of σ_t = 16.06-16.09 kg/m³. Five stations above the shelf edge were also identified, where the hydrogen sulfide occurred above the isopycnic surface of σ_t = 16.0 kg/m³. The analysis of hydrological situation showed that these stations were located on the periphery of anticyclonic eddies, which in all cases contributed to the ascent of the hydrogen sulfide-containing bottom water.

To assess the influence of salinity and chemical composition of readily soluble salts on the partitioning of heavy metals in soils of the Baraba forest-steppe, the vertical distribution of Co, Ni, Cu, Zn and Pb mobile fractions extracted by acetate-ammonium buffer and 1n HNO₃ and the total Co, Ni, Cu, Zn and Pb content were studied in associated Salic Mollic Gleyic Solonetz, Gleyic Chernozems, Calcic Oxygleyic Mollic Gleysols (Protosalic) with different salinity and Calcic Mollic Gleyic Solonchaks within two key sites. The amount of toxic salts varied from <0.1% (no salinization) in Gleyic Chernozems to 3% (very strong salinization) in So-lonchak topsoils. Some Gleyic Chernozems show the signs of alkalinization. Salinization of A and O horizons of Gleysols and Solonchaks by Na₂SO₄, NaCl and NaNO₃ increases the mobility of Co, Ni, Cu and Pb and supports their removal from topsoil horizons by radial and lateral flows. Mixed Na₂SO₄ and NaHCO₃ salinization of Solonetz and Gleysols leads to heavy metals accumulation on the alkaline-sorption barrier in Bn and Bk horizons. The distribution of Zn mobile fractions in the investigated soils is primarily determined by its biogenic accumulation due to the sorption and precipitation mechanisms.

The village of Palana is situated on the north-eastern coast of the Sea of Okhotsk at the mouth of the same-name river. Palana is an important fishing center of the Kamchatka region. The river mouth is blocked by an accumulative barrier bar, the morphodynamics of which makes the navigation rather difficult. The article deals with possible improvements of navigable conditions in the estuary. The work is based on the analysis of archive and published materials, space images, the results of our fieldwork and modeling. Three types of morphodynamic evolution were identified, namely: 1) consecutive elongation of the spit to the south-south-west at 100‒150 m/year on the average; 2) spit increase in the same direction by 400‒600 m and more per year; and 3) relative stability of the spit. Elongation of the spit to the south-south-west is a natural phenomenon. The maximum length of the spit was 2.8 km. On rare occasions (several times in a century) the estuary spit was broken and the channel straightened due to natural reasons, most likely, a significant increase in river runoff during seasonal floods. In addition, the mouth of the Palana River was artificially straightened several times. After natural or anthropogenic breaking of the spit the development cycle in the river mouth restarts. Sediments for the elongation of the spit come from the underwater coastal slope and the active cliffs on the abrasion segment of the coast to the north of the river mouth; the role of river sediment is insignificant. When the tip of the spit gets closer to rocks and stones to the south of the river mouth it threatens the local navigation. The only way to settle the problem is to control the length of the spit. For the purpose, recommendations were developed, with due account of material and technical resources available in the settlement and the practical experience. We specified the prerequisites for hydrotechnical measures, the most favorable time for their implementation and the method of constructing a new breach.

The results of the study of pure tree stands growth within 33‒36-year-old 2‒4-row forest belts in the south of Western Siberia are presented. The response of the current increase in height and diameter of Ulmus laevis PALL., Betula pendula ROTH, and Pinus silvestris L. model trees to the fluctuations in the amount of atmospheric precipitation for a hydrological year, cold and warm seasons were analyzed, as well as the density and age of tree stands. It was found that the growth and longevity of trees in sparse forest belts is highly dependent on the regime of atmospheric moisture and other factors that determine their moisture supply. Solid precipitations are of great importance for their water supply which increases with the density and age of the stands. Snowy winters delay the beginning of the growing season, slow down the growth of deciduous trees, and, on the contrary, accelerate the pine growth. Forest belts with proximate rows and higher number of the rows impairs their growth and makes them more dependent on the state of soil cover within the adjacent fields. By contrast, the fringe rows of shrubs increase the volume of trapped snow and spring reserves of soil moisture, and reduce the effect of weather conditions during the growing season, the adjacent fields and the age of tree stands.

Two-three-row belts with row spacing about 3 m wide and density of 1‒2 thousand of middle-aged trees per 1 ha have relatively stable growth, and are, therefore, more durable on the chestnut soils of Western Siberia. Pure planting of Pinus silvestris L. and Ulmus laevis PALL. and forest belts with edge rows of low shrubs should be used more widely in field-protective afforestation in the south of the region. Agrotechnical reclamation should be applied during their creating, and timely thinning should be carried out in young and middle-aged stands.

Specific features of the thermal regime of a cooling reservoir are considered using the example of the Desnogorsk reservoir. The results of hydrological surveys of the reservoir in different seasons were analyzed to describe the structure of water column and its intra-annual transformation in the area affected by the heat sink from the Smolensk nuclear power plant (SNPP). The reasons of the absence of reverse winter stratification in the most mixed part of heat-affected area are discussed. It was found that the direct stratification of water column could continue in winter in the parts of water area adjacent to the point of heat discharge. The process of formation of a long-lasting autumn-winter-spring homothermy and its transition to spring-summer direct stratification is described for thermally altered part of the reservoir. Its interaction with not-affected water mass of the reservoir is considered. It is noted that the spring transition to direct stratification is significantly accelerated due to the influence of the density (cold) flow at the bottom and the heat one at the surface.