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The article shows the fundamental role of mineral fertilizers in solving the problems of global food security. Due to a number of reasons, primarily the increase in the cost of fertilizers and restrictions on their supply, as well as sanctions restrictions on the supply of raw materials, techniques for more efficient use of fertilizers are given. The role of precision agriculture is characterized, including issues of increasing the efficiency of fertilizer use. The results of agrochemical experiments with various crops and in various soil and environmental conditions are presented, their agronomic and economic efficiency is shown. Further directions of work on the evaluation of the effectiveness of the use of fertilizers, in particular nitrogen, are given. The risk assessment and management measures are also noted.

It is shown that in order to ensure food security on a global scale, it is necessary to focus on the interaction of genetics × environment × management (G × E × M), where management means, first of all, the use of a sufficient amount of mineral fertilizers in precision agriculture. This opens up the potential to feed 9 billion people. The current state of production and application of mineral fertilizers is described, and it is shown that at the same time it is necessary to invest in methane chemistry. The possible role of RES in fertilizer production is also considered. The article presents data showing that the increase in actual yield depends on mineral fertilizers, in the production of which it is necessary to use methane — a source of carbon dioxide and hydrogen, as well as an energy source.

We assessed biomass variability and uptake of major and trace elements in different plant families of steppe landscapes under conditions of the geochemical properties of soils and the climatic parameters variability. The data obtained will contribute to a better understanding of the geochemical function of plants in steppes, which is crucial for predicting the response of landscapes to climate change. Plant and soil samples were taken in different types of dry steppes (southeast of Russia) along a climatic gradient. In the obtained samples, the contents of Ca, K, Al, S, Mg, P, Cl, Fe, Ti, Zn, Mn, Cr, Sr, Ba and Rb were determined. Soil grain size, pH, carbonates (CaCO3) and soil organic carbon (SOC) were determined. Increased mean annual precipitation and decreased temperatures contributed to the predominance of graminoid species, thus facilitating the accumulation of the studied major and trace elements in the upper soil horizons. Climate desiccation promoted the growth of wormwood and goosefoot in the ground cover, increased the alkalisation of the upper soil horizons and contributed to the accumulation of Ca, K, P, S and Cl by these plants. The contribution of plants to the total contents of Rb, Ti, Fe, Ca, P, Mg and S in the soil was higher in arid landscapes, where the ground cover was dominated by Asteraceae and Amaranthaceae, which may promote the accumulation of those elements in the upper soil horizons under the increasing trend of desiccation. Our data confirm that the biodiversity of steppe vegetation, that is mainly determined bythe ratio of heat and moisture, affects the chemical properties of soils. This should be taken into account when assessing the environmental effects of further climate warming, given that desiccation will cause an increase in the contents of Ca, K, P, S and Cl in plants and soils.

In the modern scientific literature, there are many reports about the successful application of neural network technologies for solving complex applied problems, in particular, for modeling the urban real estate market. There are neural network models that can perform mass assessment of real estate objects taking into account their construction and operational characteristics. However, these models are static because they do not take into account the changing economic situation over time. Therefore, they quickly become outdated and need frequent updates. In addition, if they are designed for a specific city, they are not suitable for other cities. On the other hand, there are several dynamic models taking into account the overall state of the economy and designed to predict and study the overall price situation in real estate markets. Such dynamic models are not intended for mass real estate appraisals. The aim of this article is to develop a methodology and create a complex model that has the properties of both static and dynamic models. Moreover, our comprehensive model should be suitable for evaluating real estate in many cities at once. This aim is achieved since our model is based on a neural network trained on examples considering both construction and operational characteristics, as well as geographical and environmental characteristics, along with time-changing macroeconomic parameters that describe the economic state of a specific region, country, and the world. A set of examples for training and testing the neural network were formed on the basis of statistical data of real estate markets in a number of Russian cities for the period from 2006 to 2020. Thus, many examples included the data relating to the periods of the economic calm for Russia, along with the periods of crisis, recovery, and growth of the Russian and global economy. Due to this, the model remains relevant with the changes of the international economic situation and it takes into account the specifics of regions. The model proved to be suitable for solving the following tasks: industrial economic analysis, company strategic and operational management, analytical and consulting support of investment, and construction activities of professional market participants. The model can also be used by government agencies authorized to conduct public cadastral assessment for calculating property taxes.

The Middle Longcraig Limestone (late Visean) at Catcraig, Scotland, is densely covered with large (about 1 m in diameter) hollows, which are surrounded by numerous fossilized roots. The latter represent the positions of tree-sized plants belonging to a fossil forest. This paper aims to reconstruct its ecology based on paleosol properties, size and spatial distribution of root-casts, rooting system morphology and characteristics of coalified plant remnants. The obtained data are consistent with the supposition that the Visean peat wetland forest of Catcraig represents a Cordaitalean dominated community composed of mono-sized, most probably, even-aged giant trees. The peaty paleosol (Histosol) contains pyrite and siderite, indicating reducing and acidic conditions, whilst the abundant presence of gypsum testifies periods of elevated salinity. The adaptation of trees to such conditions is supported by morphologically evident large root mass (typically more than 1000 individual roots per cast). Good preservation of plant tissues in peat, in addition to other paleosol and rooting system characteristics allow us to conclude that the trees occupied seacoast settings or lagoons, which were not permanently flooded.

The glass crystallization regime plays a crucial role in the fabrication of glass ceramics: it affects both phase composition and microstructure, and thus the properties of the final product. In the search for new glass-ceramic materials, the development of a proper heat-treatment schedule involves the utilization of numerous glass samples that need to be thermally treated and then investigated to determine the values of the target characteristics. In this study, we evaluated the effect of crystallization temperature on the glass structure, phase composition, and hardness of glass ceramics in the ZnO-MgO-Al2O3-SiO2 system containing TiO2 and ZrO2 as nucleators. To maximize the number of heat treatments, we performed polythermal crystallization of the glass in a wide temperature range with the help of a gradient furnace. Using X-ray diffraction, Raman spectroscopy, and transmission electron microscopy, we showed the precipitation of gahnite nanocrystals as the main phase in the bulk of a single glass sample and observed a gradual change in its microstructure, transparency, and hardness. The dependence of Vickers hardness values on heat treatment temperature was found to follow a non-linear trend, revealing the optimal thermal range for glass crystallization.

The results of the study of paleosols of different ages buried under kurgan mounds allowed specific features of soil evolution to be determined, and a reconstruction of the climate dynamics in the steppe zone of Eastern Europe over the second half of the Holocene. It has been shown that over the past 6000 years, this area has undergone repeated changes in climatic conditions, causing variations in the boundaries of soil-geographical zones. Humid conditions of the Atlantic period of the Holocene existed until the end of the 4th millennium BC; after that, a trend towards a gradual increase in aridity and soil salinization began. The maximum aridity was at the turn of the 2nd millennium BC. This was followed by several periods of increasing humidity and soil desalinization in the 18th–15th and the 5th–4th centuries BC, interrupted by stages of aridization, erosion, carbonate accumulation, and salinization.

Information about the past evolutionary changes in the soil cover is essential as a retrospective basis for long-term forecasts of soil development under the changing climatic conditions, and also for understanding the present-day problems of desertification and land degradation in the south of the East European Plain. The principal task of the present study was to estimate quantitatively the shift of the boundary between the steppe and desert-steppe zones in this region during the late Holocene under the impact of global climate variations. The properties of about 100 paleosols of archaeological sites widely represented in the region were used for quantitative reconstruction of paleoprecipitation, paleotemperature, and climate aridity. To obtain regional calibrations, the dependences of the magnetic properties of modern soils on climatic parameters in the south of the East European Plain were analyzed in detail. Samples of 35 soil profiles along the 1500-km-long Voronezh–Volgograd–Astrakhan–Elista–Voronezh transect were used. This transect crosses several natural climatic zones with gradients in the annual precipitation of about 500 mm/yr and in the annual temperatures of about 3°C, which allowed us to obtain reliable relationships between the climatic parameters and the properties of recent soils. Limitations for paleoclimate reconstructions based on the magnetic properties of soils in the range of mean annual precipitation

The article discusses the time frame and the role of the anthropogenic factor in the solonetz process in soils of the desert–steppe zone of the southeastern Russian Plain. Based on the study of soils of different ages buried under the mounds of the Bronze and Middle Ages (6200–700 years ago) within the Salsko–Manych ridge, it was established that the soils of the region did not bear signs of the solonetz process at the macro level before the beginning of the 3rd millennium BC. The first solonetzes in the region began to form 4800–4700 years ago. Their appearance chronologically coincided with the beginning of increased climate aridization. During this period, desert steppes began to be actively inhabited by ancient cattle breeders specializing in breeding small cattle, which resulted in a sharp increase in the load on the soils and ecosystems of the steppe. The article considers the possible cause-effect relationships in the system “climate–economic model–solonetz process.”

We have studied magnetotransport of a degenerate two-dimensional electron gas in a Hall sample in the Knudsen regime, when the mean free paths of electrons with respect to their collisions with each other and with impurities are much larger than the width of the sample. In contrast to the usually considered symmetric sample, whose both its edges reflect electrons diffusely, we considered an asymmetric sample, one edge of which reflects them diffusely, while the other specularly. It is shown that in such structure in low magnetic fields the Hall coefficient is parametrically large in comparison with its standard value. Also the situation is discussed when all types of scattering can be neglected except for scattering at the edges of the sample.

Climatic conditions are an important factor affecting mineralogical and chemical compositions of soils and paleosols with the formation of paleosol archives that reflect major stages of the evolution of biogeosphere systems in the Quaternary period. In the steppe zone of the south of the East European Plain, two types of the “time capsules” storing information on paleoecosystems and paleoclimate of the Quaternary period are found. First, these are loess/paleosol complexes in coastal zone of the Sea of Azov and in the North Caucasus; their environmental records extend back into the Pleistocene for about 800 ka. Second, these are Holocene paleosols of archeological sites; they are buried under kurgans constructed in different periods of the Middle and Late Holocene. The completeness and reliability of paleoenvironmental reconstructions depend on the chosen study objects. For quantitative reconstruction of the environmental parameters in the past, independent methods based on the assessment and interpretation of soil solid-phase properties—magnetic. mineralogical, geochemical, isotopic, etc.—are to be applied. Detailed mineralogical study of paleosols coupled with the analysis of their organomineral complexes and variations in the concentrations of biophile and lithophile elements significantly increase the reliability of soil indicators of the paleoclimatic conditions. The sets of soil indicators obtained from the study of Holocene paleosols and loess/paleosol sequences in the Sea of Azov region allow us to estimate parameters of the paleoenvironment: paleotemperature, paleoprecipitation, and aridity of the climate.

The results of studies of the regularities of evolution of soils and the environment in the steppe zone of the East European Plain are presented. Different culture-based chronological stages of the Bronze Age, Iron Age, and Middle Ages (3rd millennium BC–2nd millennium AD) are considered on the basis of buried soils at archeological monuments (burial mounds).

Developed method for the quantitative determination of 5-[2-(3-tret-butylamino-2-hydroxypropoxy) phenoxymethyl]-3-methyl-1,2,4-oxadiazole hydrochloride in polymer drug films by UV-spectrometry. The method was validated by indicators such as accuracy, specificity, analytical area, the linearity and convergence. The method can be used for the quantitative determination of 5-[2-(3-tret-butylamino-2-hydroxypropoxy)phenoxymethyl]-3-methyl-1,2,4-oxadiazole hydrochloride in polymer drug films.

The loess-paleosol sequence exposed in the Beregovoye section (southwest of the Crimean Peninsula) has been thoroughly studied. Detailed analysis of the paleosol morphology, physical properties and chemical composition, micromorphology and other characteristics made it possible to identify types of paleosols formed in the Pliocene and Pleistocene. The results obtained gave us an insight into the climate and environments of the past. According to them, the climate of the Pliocene optimum was extremely hot and wet, and the soil zonality was hardly pronounced practically over entire Central and Eastern Europe. At the final phase of the Pliocene the climate became drier, though the rainfall amount was still greater than in the Holocene. During the Early Pleistocene the soil development followed the Mediterranean type, the climate being still warm, though less humid than in the Pliocene. There are two peaks of catastrophic changes in the evolution of the climate and environments distinctly traceable in the Beregovoye section: first – corresponding to the global change recorded between the Pliocene and Pleistocene and second, falling on the initial phase of the modern (Holocene) soil formation.

A chronosequence of five Visean (Aleksinian–Venevian interval, C1v, 326–336 Mya) paleosols on the territory of Moscow calcareous sedimentary basin (Brontsy quarry, Kaluga region) was studied in detail. Two lowermost paleosols are coastal peat-bearing paleosols developed under mangrove vegetation. Three upper paleosols develop pedocomplexes, in which the lower part is the marine limestone altered to different degrees by weathering/pedogenesis with the formation of eroded Rendzina-type soil. It is overlain by paleosols developed from terrigenous sediments of playa origin. They are characterized by elevated concentrations of Fe, Mg, Ti, Ga, and some other elements; the formation of secondary micritic carbonates, iron oxides, and smectites; and increased values of geochemical indexes (such as CIA-K). Smectite (low-charged beidellite) predominates in these paleosols. Iron oxides are represented by goethite and lepidocrocite attesting to the predominance of oxygenic environments. Pedocomplex at the Mikhaylovian/Venevian boundary is overlain by non-marine palustrine deposits known as “black rhizoidal limestone.” The paleoclimate reconstruction based on the chemical composition data attests to its polycyclic character. The Mikhaylovian time was most humid was (~1000 mm/yr). Later, starting from Venevian, gradual aridization of the climate began and annual precipitation decreased to 750 mm/yr and less.

A soil catena was studied on the Ergeni Upland; the soils and plants were sampled in five dependent points. The contents of macro- and microelements in them were determined. It was found that the radial (vertical) geochemical migration predominates in the eluvial positions of the catena, and the lateral geochemical migration predominates in the transeluvial and transeluvial–accumulative positions. Plants of the Poa L. genus intensely accumulated elements within the eluvial part of the catena, whereas plants of the Artemisia genus were element accumulators within the trans-superaquatic position. Plants of the Artemisia genus were generally characterized by a higher coefficient of the biological uptake of elements in all parts of the catena, except for the eluvial position, where this parameter was higher for plants from the Poa L genus. A rise in the magnetic susceptibility of the soil profile relative to the parent material was the highest in the eluvial position and the lowest in the trans-superaquatic position. A comparative analysis of geochemical ratios for modern soils showed that they are determined by the topographic position of the given point. However, the gradient of variations for surface soils is much smaller in comparison with that for buried soils indicative of the climatic fluctuations. The obtained geochemical indicators can be used for comparative analysis of buried soils found not only on the divides but also in the subordinate landscape positions.

A 700 km long soil transect in the southern Russian plain was studied. The difference in the average annual precipitation within the transect was 240 mm/year, and the average annual temperature was 3 °C. The objective of this study was to understand the behaviour of chemical elements and features of chemical weathering in semi-arid soils that developed on loesses and loess-like sediments. It was found that the semi-arid soils of the Russian plain are characterized by a low intensity of present chemical weathering. In an alkaline environment with a low amount of precipitation, the rate and direction of silicate weathering are determined not by the climate, but by the geochemical environment of the soil formation, which had already taken shape by the beginning of the Holocene. The alkaline oxidative environment hinders the hydrolysis and prevents the migration of chemical elements in ionic form. As a result, the removal of chemical elements from primary silicate minerals to soil solutions is not a determining process for vertical geochemical migration. The degree of weathering of present soils is mostly inherited from the parent materials of the Quaternary. Conditions for acid hydrolysis occur only in the upper horizons during increased biochemical activity and lower pH values. However, soil processes (carbonatization, salinization, illitization, and loessivage) make the behaviour of alkali (Na2O, K2O) and alkaline-earth (MgO, CaO, Sr) metals more complex, involving them in recycling in the upper soil horizons, and hinder the quantitative characterization of weathering of silicate minerals. Therefore, the use of CIA geochemical indicator as a quantitative measure of chemical weathering for semiarid soils formed in the Holocene becomes problematic. This study will improve the understanding of the geochemical processes that took place in modern soils in semi-arid regions and clarify the possibility of using geochemical weathering ratios in saline sediments.

The article presents a new methodology for the complex assessment of factors that restrict working conditions, which is based on matrix mechanisms of complex assessment, allowing to take into account heterogeneous complexity factors. As criteria for determining the cramped working conditions, the following are used: the mass and dimensions of the inventory, their number and the complexity of work to prepare the workplace for construction and installation work. The presented approach is able to take into account any factors‘ combination, which makes it possible to abandon the existing fixed number of coefficients. Illustrated examples are shown and that clearly demonstrates the methodology for assessing the complexity of construction and installation work. The proposed method can be used in the management of construction projects, to adjust the cost of work, etc. The screen forms of the software module created specifically to provide a comprehensive assessment of complexity factors are demonstrated.

The experimental results of the sorption properties and the capillary-vesicular structure of wild-growing seed grass are given in this study. This data can be applied to refining the drying process parameters. Methods for improvement of drying plants used for heat treatment of wild-growing seed grass, as well as for technical plant varieties are proposed.

Numerous pedogenically altered subaerial exposure surfaces within Middle–Late Mississippian (Visean–Serpukhovian) shallow carbonates in the Moscow Basin attest to sea-level fluctuations and climate change. In total, fifteen palaeosols at seven stratigraphical levels from five open pits were described and studied in detail. They show both stratigraphic and lateral soil type variability. The factors of major influence are substrate type, time of exposure (tectonics and relief), and climate. All palaeosols are polycyclic and consist of at least two parts. The lower unit (substrate), consisting mainly of limestone, with siliciclastic deltaic and palustrine beds, was altered to different degrees by weathering/pedogenesis. Depending on climate, the limestone was transformed into calcrete or caliche. The substrate is capped by a terrigeneous topclay which represents an individual palaeosol developed prior to subsequent marine flooding. Indications of gley conditions, as well as the presence of coal, sphaerosiderite and framboidal pyrite, indicate a wet peat–swamp environment that was, however, periodically dry. The calculated mean annual precipitation (MAP) based on a CIA-K proxy of siliciclastic units shows that the climate was characterized by alternating periods of aridity and humidity, with the most humid conditions (~ 1250 mm) during the middle Visean. The same proxy applied to Late Mississippian sediments of the Appalachian Basin shows a similar MAP range. High-amplitude sea-level fluctuations at the Mikhailovian–Venevian boundary followed by prolonged exposure resulted in the development of a laterally extensive deep karst capped by a pedocomplex and then by a palustrine bed. The structure and scale of this unconformity are comparable to those of the Florida Everglades environment, which represents a modern marsh landscape. The majority of topclays are smectitic, except for the most humid and most arid environments, which are dominated by kaolinite and palygorskite, respectively. Besides mineralogy, we also provide data regarding geochemistry, carbon isotopic composition of carbonate, organic matter characteristics including solid state 13C NMR and δ13C data, and evidence of vegetation types based on field observations and SEM images.

The biogeochemical technology of recultivation of disturbed tundra soils includes the joint application of local peat and its potassium humate from the Taz peninsula (the Yamalo-Nenets Autonomous Okrug). At the same time the potassium humate is produced from humic acids of local peat by consecutive decalcifying, extraction, sedimentation and clarification. Efficiency of application of peat and potassium humate to the disturbed soils in doses depending from their granulometric composition is estimated on a basis of biomass of grown grass-cereals plants. The given technology is forwarded to increasing the efficiency of recultivation of the disturbed soils.

The aim of the study was to investigate the transformations of clay minerals at the laboratory experiments under the growth and fossilization of alkaline cyanobacteria. The clays incubation with cyanobacteria resulted in different trends of their transformations. The direction and intensity of transformation depends on type of clay mineral. The observed processes were fast and completed within the first 10–60 days of experiments. Cyanobacteria most actively influenced the processes of mineral dissolution and the transformations during the stage of their photosynthesis. Formation of carbonate in the experiments with palygorskite, bentonite, and kaolinite was observed at the stage of cyanobacteria fossilization.

The changes in the material composition of the buried soils and loesses in relation to the dynamics of the climate and sediment accumulation were studied for revealing the pedogenetic features and assessing the natural conditions in the steppe zone of the southern Russian Plain. A comparative analysis of the chemical compositions of the different-aged Pleistocene loess-soil complexes (the Otkaznoe, Port-Katon, and Shabel’skoe profiles) on the Terek-Kuma Plain and the Azov-Kuban’ Lowland was performed. An increase in the concentrations of Fe and Mn, which are intensively involved in the biological cycle, and Rb, which is accumulated due to the activation of weathering processes, was observed in the paleosols that developed in interglacial periods of activation of pedogenesis. Increased coefficients of weathering (chemical index of alteration (CIA)) = [Al/(Al + Ca + Na + K)] 100, Al/(Al + Ca + Na + Mg), Rb/Sr, and Mn/Sr), leaching (Ba/Sr), and biological activity and bioproductivity (Mn/Fe, Mn/Al) were also noted for the paleosol horizons as compared with the loess horizons. It is argued that geochemical coefficients can be used as an efficient tool in the soil and paleogeographic studies aimed at the reconstruction and refinement of the schemes of changes in the bioclimatic conditions during the Pleistocene.

We consider the typical features of application of the laser Doppler method for determination of blood flow rate in hemodialysis machines. We have analyzed the scattering characteristics of blood and blood flow in the blood tubing. We have obtained estimates of the basic parameters of the Doppler signal and we present the optical layout of the flowmeter.

Modern solonetzes and paleosolonetzes buried under steppe kurgans 3800–600 years ago were studied in the Lower Volga region. Overall, 28 quantitative parameters used in the description of the solonetzic process were examined. These parameters included the textural (the clay content, the ratio of the clay (

Late Paleozoic strata commonly include lithologic cycles (“cyclothems”), driven by sea-level fluctuations that repeatedly flooded and exposed broad expanses of epeiric shelves. Such successions, commonly with multiple unconformities, are well documented in Permo-Pennsylvanian sedimentary successions, but remain less understood in the East European Craton (EEC), part of the Euramerican continental shelf rim. This study documents unconformities and paleosols from the Podolskian to Myachkovian (middle Pennsylvanian) epeiric-carbonate succession of the EEC and explores the non-actualistic soil types, landscapes, and the character and density of vegetation in this Pennsylvanian calcimagnesian dryland environment. Thin (mostly < 1 m) paleosols developed at seven successive unconformities consist of an upper terrestrial clay layer or “topclay”, a crust of beta calcrete beneath the topclay, and a weakly karsted substrate limestone with rare rhizocretions. Solution pits and small (< 3 m deep) karst sinkholes are rare. Nontruncated topclays commonly consist of two layers: in situ clayey epipedons and resedimented terrestrial clays. The latter are interpreted as playa sediments. The Myachkovian unconformities of the northernmost localities studied, near Arkhangelsk, lack beta calcrete and root traces, and the limestone beneath these unconformities is sepiolitized. In Podolskian paleosols of the southern Moscow Basin, the topclays are predominantly palygorskitic. The Myachkovian paleosol clays are smectitic–illitic with occasional chlorite admixture. The majority of late Moscovian paleosols surveyed formally conform to lithic (rendollic) haplocalcids within the aridisol class or rendzic calcic leptosols. A detailed study of a representative Podolskian paleo-pedon reveals development of shallow soil carbonate, low alumina/bases and Ba/Sr ratios, enhanced Mn and Sr, presence of soil gypsum and opal, and a characteristic peak in magnetic susceptibility, all suggesting a semiarid to arid pedogenic environment. The palygorskite clay of this paleo-pedon retains 1.1–1.5% of connate organic matter in the form of covalently bound organomineral complexes, and is fulvate-dominated resembling organic matter from extant dryland soils. The palygorskitic composition of Podolskian topclays and shallow (< 30 cm) pedogenic carbonates is interpreted to reflect hot, well-drained semidesert conditions with precipitation less than 300 mm/yr. The transition from palygorskitic to smectitic soil clays across the Podolskian–Myachkovian boundary, apparently deeper soil carbonate, and an increase in the degree of karstification record a general increase in humidity such that annual precipitation may have exceeded 300–400 mm. The available data reconstruct the “great calcimagnesian plain” landscapes formed during low sea level, supposedly glacial phases, across tens of thousands of square kilometers of the EEC. This non-actualistic system apparently lacked a fluvial network and was covered by uniform soils and playas. The primary productivity of this early (310–305 Ma old) dryland ecosystem inferred from high TOC and rhizogenic beta calcretes was not markedly different from present-day steppe or savanna grasslands and semideserts. In the northernmost outcrops surveyed, near Arkhangelsk, drier conditions probably limited colonization by higher plants. The available data open a “hidden chapter” in the Paleozoic evolution of terrestrial ecosystems which is not recorded by paleobotany and urges modifications in the concept of low-productivity character of pre-Miocene dry landscapes.

Transformation of clay minerals (smectite-zeolite, illite, kaolinite, and bentonite) and admixtures of iron oxides (hydroxides) under the action of an alkaline cyanobacterial community was studied. The results demonstrate that the processes of transformation of clay minerals such as intensification of removal of exchange bases and dissolution of silicates and iron oxides occurred in the presence of the alkaliphilic cyanobacterial community. The main factor that determines resistance of a mineral to biochemical weathering is its composition. Transformations of clay minerals in the course of active cyanobacterial photosynthesis (up to 14 days) and at decomposition of organic matter (OM) (28–60 days) are different. For smectite-zeolite and illite, these processes are dissolution of silicates and oxides (removal of Si and Fe) and removal of exchange bases (K), which were observed at both the of biomass production and OM destruction stages. For two other clays, the processes of neosynthesis are more typical: formation of carbonates (most probably siderite for bentonite clay and Mg-calcite for kaolin clay) and transformation of ferrihydrite into the more thermodynamically stable goethite.

Water-stable aggregates isolated from three subtropical and one tropical soil (Western Georgia and China) were studied for their organic carbon, cation exchange capacity (CEC), specific surface area, magnetic susceptibility, and total chemical elements. The soils were also studied for their particle-size distribution, mineralogy, and nonsilicate Fe and Al oxides. Describe the water stability, three indices have been used: the content of water-stable macroaggregates (>0.25 mm), the mean weighted diameter of the aggregates, and the numerical aggregation index. The yellow-cinnamonic soil (China) was neutral, and the three other soils were acid. The soils were degraded with a low content of organic matter. The yellow-cinnamonic soil was characterized by the lowest water stability due to the predominantly vermiculite composition of the clay. The high water stability of the Oxisol structure was determined by the kaolinites and high content of oxides. In three out of the four soils studied, the hierarchical levels of the soil structure organization were defined; they were identified by the content of organic matter and the Ca + Mg (in Oxisols). Iron oxides mainly participated in the formation of micro-aggregates; Al and Mn contributed to the formation of macroaggregates. The water-stable aggregates acted as sorption geochemical barriers and accumulated Pb, Zn, Cd, Cs, and other trace elements up to concentrations exceeding their levels in the soil by 5 times and more. The highest correlations were obtained with CEC, Mn, and P rather than with organic carbon and Fe.