The constant shortage of fresh water for drinking and municipal use in the Republic of Kalmykia has become critically acute recently. Both natural factors, i.e. increasing climate aridity, limited reserves of fresh surface and groundwater, lack of sufficiently long sections of large rivers with constant flow, and the deterioration of hydraulic structures are the reasons. The exploitation of groundwater in existing deposits has led to their depletion and deterioration, while large deposits of fresh and slightly brackish groundwater in the southern Caspian region cannot be used because the content of pollutants in them is rather high. Recovery of old and construction of new water pipelines from the Volga River requires permanent significant financial investments at the federal level. Therefore, recently a new way to increase the supply of fresh water suitable for drinking purposes, i.e. an artificial groundwater recharge (AGR), has been actively discussed. The article provides an actual assessment of water resources of the little-studied surface runoff of the rivers of Kalmykia, considers the possibility and feasibility of creating infiltration basins to replenish groundwater reserves, and calculates the parameters and operating mode of five planned basins.

The main source of fresh surface water in Kalmykia is the rivers of the Ergeni Upland. The average longterm flow from its eastern slope is estimated at 0,120 km³/year, from the western slope at 0,105 km³/year and from the southern slope at 0,045 km³/year. Trends in modern modification of the hydrological regime of rivers under the influence of climate change have been revealed, namely a decrease in annual runoff and its intraannual redistribution with a reduction of spring floods, a slight increase in winter runoff and a leveling of summer low-water periods. Calculation of the operating mode of planned infiltration basins allowed us to draw the following conclusions: the maximum possible volume of total infiltration will be about 220 thousand m3/year, which is 36 times less than the present-day water intake from the Troitsk and Bayarninsky fields for public water supply; sufficiently efficient operation of pools is only possible with annual cleaning of accumulated silt deposits, otherwise the soil filtration coefficient will come down each year, resulting in the reduction of infiltration supply by dozens times. Thus, the AGR can only be a temporary measure to compensate for the subsidence of groundwater level until the reconstruction and construction of new water pipelines from the Volga River to supply the city of Elista and the surrounding area with drinking water of acceptable quality.

The article suggests a method for calculating emissions from the autonomous heating systems (AHS) of individual residential buildings based on the assessment of the number and area of farmsteads using remote sensing data, the volume and type of fuel and the type of combustion according to population surveys data and data provided by the administrations of municipal districts and settlements. The importance of AHS as a source of atmospheric pollution was evaluated at three spatial levels: the regions of Russia, where the AHS are of the greatest importance, were identified according to the structure of fuel consumption; the emissions from the combustion of residential heating fuel were calculated for the municipalities of the Baikal natural territory (BNT) and the types of territories were identified according to the structure of emission sources; and the role of AHS in air pollution of the residential areas was assessed for settlements. AHS are the dominant air pollution source (over 90%) for most of the BNT territory. Unlike CHPPs and boiler facilities, emissions from individual residential buildings using coal and firewood in most cases significantly affect air quality (up to 4,9 MPC of particulate matter and sulfur dioxide), and the areas of such impact are limited to the residential area of settlements. Strategies to reduce pollution depend on the location of a territory, type of settlement, income levels, the current structure of fuel consumption, the presence of exploited coal deposits and other factors.

The article presents the results of the ecological module of complex recreational monitoring in specially protected natural territories of federal importance. The work was carried out according to the methodological recommendations elaborated in 2021 by a team of authors (V.V. Nepomnyaschy, A.V. Zavadskaya, V.P. Chizhova).

Monitoring of the state of natural complexes under the influence of tourist and recreational activities was carried out in the zone of areal and linear impacts at the Oglakhty site of the Khakass reserve. The main results are presented for the 2022 tourist season. Currently, the entire territory of the Oglakhty site is mainly occupied by quasi-natural complexes. The linear impact is concentrated mainly on patrol roads and manifests itself in the pedestrian movement zone. The areal impact is on the stopover places near information banners and display objects on the routes, as well as in places of the economic activities. Recommendations for the effective development of eco-tourism on the Oglakhty site include the construction of additional flooring on the most popular route, as well as the redistribution of tourist flow to the less attended routes with sufficient capacity, increasing their attractiveness for various target audiences.

The paper presents the results of studying modern alluvial deposits of the Don and Kuban rivers by the pollen analysis method. The study was carried out to clarify methodological issue, including the movement of pollen and spores by flowing waters. The obtained data show that pollen assemblages of river sediments formed in the process of pollen mixing by water and air characterize the composition of the regional vegetation cover rather than local near-river plant groups. According to the results for the subrecent sediments of the Don River the transfer of pollen grains and spores by water was insignificant, which can be clearly seen at the border of the forest-steppe and steppe zones. Pollen assemblages of the forest-steppe zone contain 50% of tree species pollen, while in the steppe zone, including its northern part, tree species make up less than 30–35%. Sporadic forest elements such as Picea pollen, Lycopodium species spores and Sphagnum mosses in alluvial deposits of the steppe section of the Don River, as well as in the subrecent sediments of the Sea of Azov, could be neglected in the palaeoreconstructions. The composition of subrecent pollen assemblages of the Kuban River sediments is less variable from the middle course to the mouth with rather stable ratio of components. Pollen of the Caucasian flora elements (Fagus orientalis, Carpinus caucasica) is poorly dispersed by water from high and midmountain landscapes of the upper reaches of the river. The comparison of pollen assemblages from alluvial and marine (the Sea of Azov) sediments have shown that the distortion of fossil assemblages’ composition due to material input by water is minimal.

Palaeoecoligical reconstructions of pre-delta area of the North Caspian Sea were based on the multidisciplinary study of the core from the Rybachya borehole containing the Holocene deposits. Geochemical, grain size, mollusk fauna, diatom and ostracod analyses were performed, and the radiocarbon dating was carried out. The structure of deposits reflects palaeogeographic events of different scales including the inception of a palaeoincision in the Lower Khvalynian deposits, accompanied by erosion of the Upper Khvalynian deposits; its development during the Mangyshlak regression and gradual filling during the multistage Holocene Neocaspian transgression. The Holocene age of the deposits filling the palaeodepression is confirmed by radiocarbon dates – 8070 ± 110 and 7020 ± 140 cal. BP. The paleontological data indicate the interchange of tranquil and dynamic water regimes and the quasi-cyclical change in the conditions of the water basin, from brackish to freshwater and to marine during the stage of sedimentation, corresponding to the present-day conditions on the North Caspian shelf.

Wildfires are an important environmental factor which determines the carbon cycle intensity in mires. The article presents the assessment of the consequences of pyrogenic transformation and the current state of burntout mires in the taiga and forest-tundra zones of Western Siberia 6–8 years after the wildfire, with regard to their microhabitat heterogeneity. Field studies were conducted in 2022 on three mires (a total of 13 post-pyrogenic and pristine plots) and included a total-station survey of the surface, an assessment of the occurrence of species in the grass-dwarf shrub and moss-lichen tiers, sampling for laboratory analysis of the physical properties and botanical composition of peat. Sphagnum mosses, Polytrichum strictum, lichens and dwarf shrubs were considered as recovery indicator species. As a result of the study, it was found that the intensity of pyrogenic transformation is determined by the initial state of bog ecosystem and increases in a row: the hydro forestation site on the Bakchar raised bog – palsa – the Ust-Bakchar raised bog drained for peat extraction. At most of the studied plots, microdepressions were more susceptible to burnout, while hummocks were preserved or only partially burned out. The transformation of peat deposit properties extends beyond the layer directly exposed to burnout, and manifests itself in a decrease in water content, and an increase in ash content, bulk density and degree of humification. At the first stages of post-pyrogenic successions, similar patterns were revealed for the mires of taiga and forest-tundra zones, i.e. an intensive overgrowth with P. strictum. According to the results of the study, it was concluded that the hydroforestation site in the Bakchar bog could possibly restore the species composition of vegetation cover and resume peat accumulation. Irreversible changes in vegetation cover have occurred in the Ust-Bakchar bog, where the restoration of sphagnum mosses does not occur even 20 years after the fire.

The article presents the results of an extensive study of the bottom topography of the Ob River Gulf in the Kara Sea, which is a follow-up to the long-term studies of the authors. It refines the existing ideas and aims at solving a fundamental problem of reconstructing the conditions for the formation of bottom topography in the shallow bays of the Kara Sea in the Late Pleistocene and Holocene. The work aims to create a regional characteristic of the geomorphologic structure of the Ob River Gulf bottom. The initial data on the bottom topography were taken from marine navigational maps and sounding boards at a scale of 1:50 000 – 1:100 000. We processed and interpreted the collected cartographic material to create a detailed DEM of the bottom and a bathymetric map at a scale of 1:200 000 with an isobaths interval of 1 m. In addition to bathymetric data, the compilation of a geomorphologic map engaged a large amount of literature and stock materials on geomorphology, geology, and geocryology of the region. The original morphogenetic legend was elaborated with due account of current ideas regarding the conditions for the formation of periglacial plains relief at the regressive stage of the Kara Sea shelf evolution. It was found that the relict fluvial relief prevails within the gulf and was partly modified by subaqueous processes during post-LGM transgression and the current epoch. We have indicated the most critical features of the structure and pattern of the flooded pra-valley of the Ob River, as well as the total ancient erosion network. The selected individual forms and relief elements take into account the scale of objects and the degree of their generalization on the map and give an idea of the development of reliefforming processes both at the subaerial stage and under subaqueous conditions, including specific features of modern dynamics of the coastal and bottom relief.

The ecological and geographical differentiation of the bird population at 18 sites of the Urup and Iturup islands was analyzed. The method of route accounting was applied. A total of 109 species were recorded, 62 of them on both islands. The coefficient of faunal commonality between the terrestrial habitats of the islands is 72%, and between the coastal-marine – 71%. The coefficient of similarity of the bird population between the land habitats of the islands is 36%, and between the coastal-marine – 29%. The values of bird population density on the islands are close both between terrestrial (610–757 ind./km²) and coastal-marine (536–607 ind./km²) habitats. The high population density is everywhere due to the abundance of numerically predominant species of the Far Eastern island and the Chinese fauna types. The total population of species of these faunas accounts for more than 50% of the population in terrestrial (282–469 ind./km²) and coastal marine (172–333 ind./km²) habitats. The spatio-temporal dynamics of the bird population is characteristic.

To reveal variations in the isotopic composition of O and H in the atmospheric precipitation in Moscow and the processes influencing the isotope composition, all events of precipitation in 2017–2019 were sampled at the Meteorological Observatory of the Moscow State University: 158 samples in 2017, 119 samples in 2018 and 143 samples in 2019. The study is a prolongation of continuous measurements of the isotope composition of precipitation, started by authors in 2014. The study of the isotope composition of precipitation at the MSU Meteorological Observatory was supported by the IAEA and became a part of the Global Network of Isotopes in Precipitation (GNIP) database. It has been found that the intra–annual variability of the isotope composition of precipitation has a pronounced seasonality. The most isotopically heavy precipitation falls from May to August, and the most isotopically light precipitation at December-February, mainly due to seasonal air temperature variations. The ratio of the average monthly δ¹⁸O values in precipitation and air temperature for the study period varied from 0.34 to 0.39‰/°C, which is consistent with the previously obtained data for precipitation in Moscow. The δ²H–δ¹⁸O ratio in precipitation was close to that of the Global Meteoric Water Line, pointing to the equilibrium conditions during precipitation formation. It was established that in the summer months isotopic composition is significantly influenced by undercloud evaporation. The deuterium excess values in precipitation are not markedly seasonal; however, lower d_exc values (below the 3-year average of 11‰) are typical for the summer months (July–August). It is most likely due to undercloud evaporation in conditions of low relative humidity and high air temperatures. Higher d_exc values (above 11‰) prevailed from October to April.

We consider the potential and limitations of widely accepted remote sensing algorithms for detecting forest areas damaged by fires, which allow the monitoring systems to automatically form data about the fire areas and the areas where death of tree stands is subsequently recorded. The resulting size of the detected areas has a measurement error, which is typically determined on the basis of a one-time survey for a large territory and one forest fire season. Depending on the geographical features of the territory, forest fires have specific spatiotemporal and qualitative characteristics, and are accompanied by specific heterogeneous damage to forests, which affect the accuracy of remote detection of a burnt area or fire-damaged forest. Hence the use of the unified large-area error estimate for local-level surveys could lead to inaccurate results. The analysis of space images of forest fund lands in the Tver region for the period 2007–2022 demonstrated the need to establish regional values of the measurement error for fire-impacted areas. By comparing the medium spatial resolution data with the data of high spatial resolution we identify a regional bias, which is significant given the relatively small size of the detected areas. The study demonstrates the expediency of establishing regional error values for measurements of pyrogenic impact on forest areas. By implementing the suggested changes we could improve the accuracy of remotely-sensed estimates of fire-impacted areas and the amount of associated damage to forests.

The article proposes a method for identifying “reviving” rural settlements (RS). Case studies of the Tver region RS revealed what features of the geographical location determine a settlement opportunities for revitalization. The previous typology, based on the analysis of satellite images, showed a considerable differentiation in the degree of RS degradation, classified according to the 2010 census as “without population”. Further work to determine the leading factors of revitalization was based on the study of those RS where the houses and outbuildings, identified by satellite images, have been preserved to the greatest extent. Nearness to rivers and water bodies, position relative to federal and regional highways, and location near the regional and/or district center were chosen as key features of the geographical location that have an effect on the prospects for revitalization of a territory. The presence of registered residents (according to current records) and demarcated cadastral plots are indicators of the RS revitalization.

The study showed that one third of all RS, which fell into the category “without population” according to 2010 statistics, could now be considered “reviving”. A key factor in the revitalization of rural settlements of the Tver region is their nearness to the river, mainly to the Volga River. Another important factor is the location in the zone of influence of main centers, primarily the city of Tver. The main function is the recreational (dacha) use of such villages.

Volumetric characteristics and renewal time of the Pacific waters (PW) in the Arctic Ocean were calculated based on the data of oceanographic expeditions during the 2007–2008 International Polar Year (617 stations). Isopycnal surfaces of their upper and lower boundaries (25,5 and 27,5 kg/m³, respectively), the thickness between these limits and the equivalent thickness (i. e. the specific thickness of untransformed “pure” water mass) have been determined, as well as the boundaries where the highest concentrations of silicates in the selected density interval disappears. The Pacific waters extend to the north up to the North Pole region (thickness up to 40–50 m), in the west they can be traced up to the northern part of the Laptev Sea (thickness 20–30 m), in the east they are preserved in a minimally transformed form (thickness of more than 100 m) up to the Canadian Arctic Archipelago. The characteristic depths are between 50 and 150 m. The thickest PW exceeding 150 m were found within the Beaufort Gyre. The total volume of “pure” (untransformed) Pacific waters in the Arctic Ocean was estimated at (197 ± 19) · 103 km³ or about 1,1% of the overall volume of the Arctic Ocean. If their mixing with the surrounding waters between selected isopycnic surfaces is taken into account, the volume of Pacific waters is (313 ± 16) · 103 km³, or about 1,7% of the volume of the Arctic Ocean. Taking into account the total inflow of the PW through the Bering Strait, their renewal time in the Arctic basin is estimated to be about 5–6 years.