The paper demonstrates that the instability of straight movement of river flows causes their sinuosity (meandering) or splitting into branches and is reflected in the evolution of any channel pattern type. In a straight unbraided channel the instability is manifested as a sinuosity of the dynamic axis of river flow which bends round side­bars, i. e. elevated parts of channel relief drying out during the low water, or in braided channel reaches, where each branch of the stream forms further bends. In braided channels the sinuosity of the dynamic axis of the flow causes a specific distribution of flow velocities, circulation currents and particular angles of approaching the banks, thus resulting in bank erosion and sediment accumulation near the islands. Therefore, the channel branches look like gentle bends in single braided reaches, while in conjugated braided reaches the sinuosity of main river flow occurs along a series of the islands, and the branches of anabranching and split channels also form meanders. Thus, meandering is a universal process of different channel patterns formation. In braided channels it occurs in line with the distribution of water flow over the branches, which determine the parameters of bends, as well as the rate and direction of their deformation. Meandering channels of large rivers and bends of branches of split channels are, in their turn, complicated by islands in the wings and the top parts of meanders. However, the distribution of water flow into branches is not characteristic for small and medium-size rivers. The patterns discussed in the paper should be taken into account when substantiating the methods of channel processes management for the solution of practical problems.

The paper describes the results of studying the geochemical parameters of snow cover in the city of Tyumen (Western Siberia) during the winter period of 2019–2020. Dust load, concentrations and spatial distribution patterns of major and trace elements in insoluble particulate matters and physical-chemical characteristics of snowmelt water were evaluated for the territory of Tyumen and surrounding background area. The background concentrations of insoluble particles in the snow vary from 4,1 to 10,9 mg/l. The dust load amounted to 5,5 mg/m² per day and was at an average level compared to the unpolluted territories within Tomsk, Omsk and Novosibirsk regions. A significant alcalization (by 1,6 pH units) and higher mineralization of snowmelt water, as well as the increasing average dust load (up to 20 mg/m² per day) are characteristic of the urban territory. The dust load varies from 5,4 to 94 mg/m² per day in Tyumen, the value being lower than in the cities with more intensive industrial activities. Higher Cl and Na concentrations were revealed close to the main roads where the bicarbonate-calcium waters turn into bicarbonate-sodium and chloride­sodium ones under the influence of deicing chemicals. Calculation of concentration coefficients showed that Mn, Ni, Co, W, Sb, Cr, Cd, Pb and Cu form the association of elements-polluters. Higher concentrations of Ni, Co, Mn and W are characteristic of solid deposits along the main roads. The high concentration of Pb (37 times the background value) was recorded in the vicinity of a battery factory. The increased concentration of Cd in the zone of single-storey houses is due to incineration of household wastes and stove heating. Calculation of total pollution and immission values suggests that despite the high concentrations of metals and metalloids in the solid fraction the overall flow of pollutants is rather low due to relatively small dust load.

The integrated hydroecological research is especially relevant and actual for water­stressed regions, such as the Republic of Crimea. The purpose of the study is to use the example of the Maly Salgir River basin to make a comprehensive assessment of the hydroecological situation and develop a list of measures aimed at the rational use of its water resource potential. The studies were carried out in 2017–2019 and included visual observations of water bodies, measuring water discharges, studying chemical composition of water, calculation of water pollution index, assessment of water suitability for irrigation purposes, study of water toxicity and water balance calculation. The main pollutants of water resources are sulphates, phosphates and heavy metals (Cu, Cd, Pb, Zn). The quality of river water according to the WPI (water pollution index) varied from grade II "clean" to grade VI "very dirty", while the quality of channel ponds water was from grade II to grade IV "contaminated". Water balance calculations showed no water scarcity, as well as the possibility of additional water withdrawal for regular irrigation. Among the priority environmental measures there are the need for sewerage of villages located in the river basin, the inclusion of ponds that do not have inventory numbers in the state water register and the accounting of water resources use by the population.

Based on the data of long-term (1970–2009) observations, the spatial distribution of seasonal concentrations of the main biogenic elements (phosphates, nitrates, ammonium nitrogen, silicic acid) were studied and the variability of their content in the surface layer of the northwestern part of the Black Sea (NWBS) was estimated. The seasonal concentrations of nutrients in the northern, western, southwestern and central regions, which differ in the degree of the influence of transformed river waters, were evaluated. It is shown that the seasonal variability of the content of nutrients in the indicated areas of the northwestern part of the Black Sea depends on the variability of the volume of river runoff and the spread of transformed river waters over the shelf, as well as on the regional hydrometeorological conditions and the intensity of the biotic cycle of nitrogen, phosphorus, and silicon. The detailed studies of the seasonal variability of the concentration of phosphates, nitrates and chlorophyll "a" and water salinity were carried out for the spring and summer seasons, which are the most provided with data on the alongshore and latitudinal (45°N) sections of the western region. The relationship between the seasonal values of the Danube runoff volume, water salinity, chlorophyll "a" concentration, phytoplankton biomass, and seasonal nutrient concentrations for the western region of the NWBS was assessed. The calculated multiple coefficients of correlation and determination showed that in the spring and summer periods the input of phosphates, nitrates and silicic acid with transformed river waters provided for about 20%, 36–50% and about 36% of their total dispersion, respectively. The assimilation of these biogenic elements by phytoplankton indicates that phosphates accounted for 10–23%, nitrates for 23–52% and silicic acid for 17–52% of their total dispersion, respectively. The obtained results indicate a relationship between the input of nutrients with transformed river waters and their output associated with the assimilation of nutrients by microplankton (phytoplankton and bacteria). Obviously, these fluxes could be regarded as the main components providing the annual balance of nutrients in the NWВS.

The article deals with the problem of evaluating the effectiveness of forest reclamation of arable land in the areas affected by wind and water erosion, which has recently become a little popular practice in Russia. The method of calculating the parameters of soil protection and environmental impact of the system of protected forest belts has been improved. A quantitative assessment of regional costs and environmental and economic effects depending on the level of protective forest cover of fields and other bioengineering features of forest reclamation models was obtained relative to the soil and climate conditions of the south of the European territory of Russia. Their structure, absolute and relative values are determined. The regularities of the zonal dynamics of the efficiency of capital investments in protective afforestation are described, as well as the influence of natural and forest-cultural factors. It is established that the cost of protective afforestation pays off in the first year of full operation of forest belt systems, i. e. after 7 to 10 years of their growing. About 40 to 80% of the total ecological and economic effect of forest belts falls upon their soil protection influence and more than 10 to 50% upon the forest resource value, environmental and recreational functions. The contribution of the agro­ameliorative effect of windbreak forest belts, i. e. increase in grain crop yield, does not exceed 1%, and flow-regulation effect is about 4 to 12%. Thus, the protective afforestation could be first of all regarded as an important measure for preserving land resources, improving the safety of agricultural production, and as a means of providing low-forested regions with forest resources, improving the quality of the environment and solving social problems.

An integrated model of slope soil erosion is hard to elaborate because of the up to billion-fold difference in scales of the processes involved. Therefore, the elements of the general theory of soil erosion should be developed with due consideration of their scale. The aim of the work was to apply the hydraulic approximation to obtain an analytical solution of the problem of soil aggregate size reduction as a result of attrition during transportation by a steady slope flow. To achieve it, we studied separation, transport, transformation and re-sedimentation of an individual soil particle (aggregate), initially resting on the bottom of a temporary water flow. Unlike empirical approaches and those based on arbitrarily introduced equations and statistical distributions, the study, as in the previous case of wind erosion, was carried out using the methods of multiphase media mechanics at mesoscale. Particle transformation is defined as its attrition due to repeated impact interaction with the bed of a temporary slope water flow. As a result, a novel analytical solution of the problem of soil aggregate size reduction due to attrition during transport by a steady slope flow has been found (in equations format) under the hydraulic approximation. It has been determined, that degree of abrasion, defined as a ratio of an actual soil particle radius to the initial one, depends on its mechanical properties and the relation between the hydraulic parameters of the flow and those of the aggregates. At this soil aggregate mechanical properties are represented by two empirical coefficients of the abrasion equation, while the hydraulic parameters of the flow and the aggregates are represented by the erosion number. As a result of theoretical solution, the physical meaning of the erosion number has been expanded; it appeared to be both a ratio of the vortex lift to the aggregate weight, governing the mode of aggregate motion in the flow, and a coefficient of its maximum abrasion during transportation by a steady water flow. The coefficients representing mechanical properties of aggregates abraded by water flow can be found empirically by experiments in hydraulic flumes, such as we used in our study.

The article deals with the analysis of morphotectonic indices as a principal tool to identify the areas experiencing rapid tectonic deformations, or estimate relative variations of tectonic activity in a specific area. We applied the analysis in the Zeferh fault zone, located within the Urumieh-Dokhtar Volcanic Arc (UDVA) in the Central Iran. The Zefreh fault is a most important fault in the central part of the UDVA. The Zefreh fault stretches for 130 km in NW–SE direction from the Natanz town in the north to the Zefreh village in the south. The Zefreh fault cuts and displaces the UDVA along its whole trace. The dextral strike-slip component confirmed by tectonic features was shown based on the analysis of fault lineations, and interpretation of Landsat satellite images and field data. We calculated morphotectonic indices along the Zefreh fault zone and evaluated the tectonic activity of the area. We used topographic maps, geological maps, satellite images, and field observations for identification and calculation of morphotectonic indices. A digital elevation model (DEM) was obtained by digitizing contour lines from topographic maps. Standard methods in ArcGIS, Global Mapper, and Envi programs were used to calculate indices and identify tectonic features. The coefficients of mountain-front sinuosity (Smf), ratio of the valley floor width to the valley slope height (Vf) and ratio of the valley width to the valley slope height (V) average to 1,17, 0,78 and 6,92 respectively. In addition, the stream length gradient index (SL), the displacement of river valleys, the presence of asymmetric and curved proluvial fans and the increasing rate of vertical erosion, as well as the residual effects of fault movement in Quaternary sediments, indicate that the Zefreh fault is still active.

The paper suggests an original technique for mapping the honey resources of Russia, which has a number of advantages. Firstly, it is based on the actual (specific content of a melliferous plant pollen in the honey) rather than potential (area of growth of melliferous plant, honey production) characteristics of melliferous plants. Secondly, the use of GIS technology and the results of pollen (melissopalinological) analysis made it possible to identify the areas where the melliferous plants are of particular importance for producing monofloral honey and the regions of their subordinate importance. Thirdly, a clear georeferencing to the place of honey harvest (the location of an apiary) makes it possible to describe in detail both zonal and regional features of the honey harvest. Thanks to many years of work, Our long-lasting research covered all natural areas of the European part of Russia with widespread beekeeping, from the forest tundra (Arkhangelsk oblast) to the subtropics (Krasnodar Krai). Pollen analysis of 858 honey samples from 45 regions showed that the main melliferous plants of the studied territory include Tilia spp., Helianthus annuus, Melilotus sp., Amoria repens and A. hybrida, Robinia pseudoacacia, Fagopyrum esculentum and Salix sp. They provide for the production of 75% of monofloral honeys. The basic group also includes Echium vulgare, Linaria vulgaris, Coriandrum sativum, Carduus sp., Brassica napus, Sinapis sp., Castanea sativa, Chamerion angustifolium, Angelica sylvestris and Onobrychis sp. It has been established that in the north (forest­tundra and taiga zones) the honey is gathered from the majority of natural melliferous plants (Salix sp., Rubus idaeus, Chamerion angustifolium, etc.). The areas of honey harvest from Amoria repens and Tilia spp. are further south in the forest zone The principal melliferous plants supplying monofloral honeys in forest-steppes and steppes are fodder and agricultural crops (Helianthus annuus, Fagopyrum esculentum, Sinapis sp., Coriandrum sativum, Onobrychis sp. and Melilotus sp.), as well as weeds (Carduus sp. and Echium vulgare). An exception is Brassica napus, providing for the monofloral honey harvest from the subtaiga to the steppe zone. Productive honey gathering from Robinia pseudoacacia and Castanea stiva is in the southwest. The wide-range melliferous plants are Salix sp., Rubus idaeus, Amoria repens, Melilotus sp., Echium vulgare and Linaria vulgaris; their pollen was found in both northern and southern samples of honey. The evidence obtained substantially supplement the existing ideas about the melliferous zones of the European part of Russia and can be further applied to diagnose the geographical origin of the Russian honey.

A bibliometric analysis of studies related to the Arctic was carried out, based on 1980–2018 publications extracted from the Web of Science Core Collection database. The focus was on the dynamics of the scope of investigations conducted in the world and by country/group of countries, the thematic profiles of research, and indicators of international scientific cooperation. We identified 13 most significant research countries and analyzed for them in more details: the growth rates of research activity and the positions in the area under consideration, the structure and dynamics of their co-authorship network, as well as their contribution to the pool of highly cited publications. The bibliometric indicators were applied to characterize the stages of Arctic research development in Russia (USSR) and their geographical structure, and identify the most efficient scientific organizations. In the recent decade the world research on the Arctic showed a rapid quantitative growth, both by the Arctic countries, and non-Arctic ones, first of all China. Relying on the traditionally strong positions of the Russian academic school and the growing activity of universities, Russia has significantly exceeded the global average growth rate and now ranks third in the world in terms of the scope of Arctic research. "Geosciences multidisciplinary" are more frequently represented in the thematic profile of world studies than other WoS subject categories, followed by "Environmental sciences", "Meteorology and atmospheric sciences". The general growth of scientific cooperation has been noted, as well as the formation of a cohesive core of countries (out of 13 selected), which produce the largest part of highly cited publications. Other countries tend towards cooperation with the core group, which includes the preferred partners of Russia (Germany, Norway and the United States). Nevertheless, Russia conducts a significant part of the research independently. Analysis of the geographic structure of Russian studies made it possible to identify their long-term shift from the center to the eastern regions, where most of the country’s Arctic zone is located.

The ecological-geographical regularities of the spatial differentiation of bird population within the mountain-taiga altitudinal belt of the Putorana plateau are analyzed. The studies were carried out in 1988– 2018 in the northern, southern, western and eastern parts of the region. The survey was carried out as route accounting on transects of unlimited width at the elevations up to 1412 m above sea level. m. The maximum density of bird populations within the forest belt is in estuaries and floodplains of rivers and in the lower parts of mountain slopes; the forests on flat lakeside and river terraces are much sparsely populated. The population density is higher in the forests on the mountain slopes of southern exposure, covered with high-stemmed forests with dense undergrowth. The bird population density is sharply lower in the suppressed and thinned forests on the slopes of northern exposure. The mosaic distribution of many bird species within the Putorana plateau is supported by the mountain-and-basin topography of the area and the tendency of territorial pairs of a number of non-colonial species to form dispersed monospecific settlements. Poly-species territorial settlements consisting of 3 to 5 species of passerines are formed 3 times more often, which probably indicates more active colonization of mountain-subarctic landscapes by the whole communities of birds than by individual species. About 90% of all birds of the forest belt are concentrated in the lower part of the mountain-northern taiga belt. The altitudinal inversion of forest vegetation results in much more even distribution of birds. A number of species, usually nesting in the lower part of the forest belt, sometime form a second "upper echelon" of settlement in its upper part. The formation of the upper zone of settlement is due to the "forest edge effect" and the ecological adaptations of species, as well as the experience of "imprinting" mountain landscapes by young birds during the period of post-nesting vertical migrations.

Heat runoff of the rivers of the White Sea catchment area and its variability are discussed. A representative time span of 1990–2014 has been chosen to estimate the annual variability of water and heat runoff and the water temperature in river mouths of the White Sea catchment area. A standard formula was used for estimating the heat runoff; partial watersheds of individual rivers were determined using the 1:1 000 000 maps and refined using 1:200 000 maps. For the period of 1990–2014 the heat runoff from the White Sea catchment area was 5480.94∙10¹⁵ J. The increase in water temperature in river mouths of the White Sea catchment area is shown for the period of 1956–2015, which was particularly pronounced since 1990. To identify the consequences of heat runoff variability, we used the results of mathematical modeling by the JASMINE software package. Thirteen numerical experiments were carried out; the dates of water temperature transition through 0,2; –0,5 and –1°С in spring and autumn for the Dvina, Onega and Mezen bays were used as markers. The experiments have shown that an increase or decrease in the mean monthly water temperature in rivers by 2°С, as well as the change of their water runoff by 30%, would not lead to a significant change in the timing of ice formation and ice destruction in the White Sea bays, but will only change water temperature during the warm season. The amplitude of temperature fluctuations will not be great, i.e. just several tenths of a degree of Celsius. The shift in model dates of ice formation and ice destruction under changing mean monthly temperature of rivers and their runoff in the catchment area would not exceed several hours. During both warming and cooling, the spring and summer temperatures of the surface sea layer in bays change first of all; such an effect is practically unnoticeable at greater depths. The results of the model studies prove the resistance of thermohydrodynamic system of the White Sea to external thermal effects of the rivers within its catchment area.

Based on hydrobotanical studies carried out in summer 2013 within key areas of the protected water area of the "Coastal-aquatic complex (CAC) near the Dzhangul landslide coast" nature monument, the resource components of macrophytobenthos and dominant algae species were studied. It was revealed that the geological and geomorphologic structure of the coastal zone of the studied area determines certain features of the bottom vegetation distribution, as well as the species composition of macrophytes and their quantitative indicators. Typical sequence of plant communities, associated with just increasing depth and decreasing light and wave intensity, was observed on the abrasive shores of the area. The abrasive-landslide seashores of the upper shoreface slope are characterized by varying steepness and slope exposure. Apart from edificators, the mosaic groups of deep-sea and seasonal-winter algae species are typical for the composition of phytocenoses there. According to the calculated data, the total reserves of macrophytobenthos in the water area from the Maly Kastel Bay to the Dzhangul area are estimated at 866.75 t, of which Cystoseira species account for 596.62 t and Phyllophora for 50.34 t. Characteristically, the resources of bottom vegetation and reserves of Cystoseira species in the area of the Maly Kastel Bay – the Ternovaya gully are respectively 1,3 and 1,2 times higher, and those of Phyllophora crispa 1,1 times lower than the same indicators for the Ternovaya gully – the Dzhangul area, which could be explained by specific features of the geological and geomorphologic structure of these areas. During the period from 1965 to 2013, a decrease in the reserves of bottom vegetation and key algae species was revealed. The most pronounced negative transformation was identified in the lower sublittoral zone, which may be due to the complex impact of both natural factors and increasing trophic capacity of water near the Black Sea coast. Nevertheless, the "CAC near the Dzhangul landslide coast" nature monument is characterized by high values of the resource component of macrophytes and a significant degree of preservation of Cystoseira and Phyllophora phytocenoses. The area is a certain reserve of Phyllophora crispa at the western coast of the Crimean Peninsula, which is included in the Red Books of the Russian Federation and the Crimea.