The sorption characteristics of sand, peat, the arable layer of Moscow urbanozem and a mixture of these substrates were studied in conjunction with the surface topography of their solid phase, studied by scanning electron microscopy (SEM). The arable layer has the greatest ability to absorb nitrogen, and the peat substrate showed very low values of the sorbed gas. A different picture of the mutual arrangement of substrate sorption isotherms is observed when water vapour is used as a sorbing gas. Peat is distinguished by high values of sorbed moisture in the entire studied range of relative humidity. This leads to differences in the ranking of substrates by specific surface area in descending order of its values. So, the specific surface area by water sorption in the series: peat / arable layer / mixture / sand was: 420 / 72 / 45 / 4 m2/g, respectively. The given surface was ranked according to nitrogen sorption in a different sequence: 8.31 / 2.41 / 1.45 / 0.55 for the series: arable layer, mixture, peat and sand, respectively. The analysis of microstructural characteristics by the SEM method at various magnifications revealed the most developed, rough surface in the arable layer. It turned out to be geometrically the most diverse, even at magnification of ×20 000. The variety and heterogeneity of the relief of the interface of the phases leads to the appearance of hysteresis of the sorption/desorption curves. Its severity in the range of nitrogen vapor concentration in which hysteresis is detected, and in the maximum width of the hysteresis loop, also turned out to be the most significant in the arable layer. The very low nitrogen specific surface of peat, which is close to a sandy substrate, is associated with the presence of organic films draping and leveling the surface of peat particles, which was revealed by analyzing images obtained by scanning electron microscopy. The sorption of water showed their high hydrophilicity, which led to high values of substrate humidity in the entire studied range of relative humidity.

Проведен сравнительный анализ результатов реологических исследований образцов почв методом амплитудной развертки (amplitude sweep test – AST) на модульном реометре MCR 302 (Anton Paar, Австрия). Объектом исследований послужила подзолистая с микропрофилем подзола супесчано-/тяжелосуглинистая почва на покровном суглинке (Folic Albic Retisol (Abruptic, Loamic, Protospodic)) – почва средней тайги (Республика Коми, окрестности г. Сыктывкара). Реологические параметры определялись на образцах нарушенного (растертые и просеянные через сито) и ненарушенного (монолиты) сложения в состоянии капиллярного увлажнения. Это позволило выявить схожий характер реологического поведения и определить специфику отдельных генетических горизонтов. Наиболее устойчив к механическим нагрузкам верхний органогенный горизонт – лесная подстилка (О). Переходный горизонт BEL характеризуется жесткой, но наименее устойчивой структурой с узким диапазоном деформационных возможностей. Ненарушенные образцы имеют прочные и жесткие структурные связи в области вязкоупругого поведения, что обусловлено плотной упаковкой и многоуровневым взаимодействием почвенных частиц, микроагрегированностью и присутствием фрагментов корней. Повышенная жесткость сложения монолитов сочетается с хрупкостью их структуры. Нарушенные образцы при нагрузке характеризовались большей пластичностью по сравнению с монолитами, что обусловлено разрушением агрегатов в процессе растирки и образованием большого количества межчастичных контактов.

Irrigated agricultural lands in arid and semi-arid areas are particularly vulnerable to climate change and subjected to secondary salinization. Detailed maps of the subsurface are necessary to manage and ameliorate salinity but difficult to obtain, as salinity is dynamic and highly spatially variable. Our group tested several on-ground geophysical instruments and geostatistical approaches for studying soil and groundwater salinity around the world for the last 20 years. Here we present an overview for updated methodologies of electrical geophysical methods (galvanic contact and multi-frequency electromagnetic induction) measuring soil electrical conductivity or resistivity in-situ from the surface down to the depth of 10–20 m to estimate soil salinity, water content, and depth to groundwater table in arid and humid environments both in rural and urban settings.

The thermal diffusivity of the upper plow horizon (Ap) of urban soil from the territory of the Experimental soil station of Moscow State University, lowland packed peat, and their mixtures has been studied. The soil from Ap horizon was sieved through a 1-mm sieve and then mixed with peat in various proportions; the content of peat in mixtures ranged from 1 to 80

The results of experiments to study changes in the hydrological properties of soil substrates composing profiles of artificial soils (constructozems) 1–4 years after their creation are presented. Constructozems are represented by two variants, layered soil including Ap horizons, lowland peat and quarry sand of equal thickness, and a mixture of these substrates in an identical amount by weight, as for layered constructozems. Water retention curves obtained by the capillarimetric method on samples with undisturbed structure are compared. A decrease in the water-holding capacity of the peat layer and an increase in the mixture samples are found a year after constructozems had been placed. The laboratory and field experiments have shown a statistically significant difference in moisture filtration rates of the layered constructozem and the mixture. The sharp boundaries between soil horizons contrasting in their properties reduce moisture migration rates to zero values. The obtained breakthrough curves of potassium ions suggest that the continuous pathways of rapid movement of moisture and dissolved substances have formed after 4 years of functioning of artificial soils and are most pronounced in the structures with the homogeneous soil profile.

We have studied mechanical characteristics of soils of Syktyvkar of the same genesis and different land use: agrosoddy–podzolic urban-stratified soil within the city, park postagrozem, and suburban podzolic soil. Their relationship with the organic-matter content and particle-size composition is analyzed. Strength properties are mainly related to the content of coarse fractions (>0.25 mm) in agrosoddy–podzolic urban-stratified soil and to the organic matter content in podzolic soil. Soils are arranged in sequences according to rheological parameters. The strength of structural bonds estimated by the parameter of initial elasticity modulus is the greatest in podzolic soil, and horizons of agrosoddy–podzolic urban-stratified soil are characterized by a wide range of linear viscoelastic status. The starting point of the viscous flow region is the same for postagrozem and podzolic soil.

The dynamics of the physical properties and reserves of humus in saline soils of an arid semi-desert zone is presented. The basis for the research was observational data for 2010-2022. in a typical hilly landscape of the Astrakhan region. A grid of 100 × 100 m was laid. Soil studies were carried out at the grid nodes along the sampling layers. We studied the change in physical properties (soil moisture; salt content according to the amount of dense residue; soil density; filtration coefficient; soil porosity; moisture reserve), humus reserves and salt state of saline soils under desertification. Comparative analysis showed that negative changes have taken place in the study area and it can be stated that the processes of soil degradation and desertification are intensively developing. It has been established that in the soil layer of 0–40 cm there was a significant reduction in soil moisture reserves against the background of an increase in maximum air and soil surface temperatures, as well as changes in the hydrological regime because of the embankment of the territory. Dehumification processes are observed. The most clearly negative trend was revealed for meadow solonchaks. The change in the hydrological regime of the territory because of embankment contributes to an increase in the areas of automorphic soils in the landscape and a reduction in the areas of meadow soils. An increase in the degree of salinity and compaction was recorded for automorphic zonal soils. The physical destruction of the Baer's hills exacerbates the processes of degradation and the development of desertification in such conditions.

The soils of streets, urban parks and suburban areas were examined for yeasts in the summer of 2020 on the territory of the southern cities of Russia and the Republic of Crimea: Krasnodar, Maykop, Sochi and Simferopol. The results of this study are compared with the results of a previous study carried out in these cities in 2019. This study was conducted three months after the lockdown due to the COVID-19 pandemic, which led to a sustained decline in household waste deposition in these areas. The number of tourists visiting these southern cities decreased significantly, and the number of walkers and visitors to urban parks fell sharply. In 2020, after the decline of household waste loads, the yeast abundance was slightly but reliably higher than in 2019. A total of 30 yeast species were observed - 11 ascomycetes and 19 basidiomycetes. This was more than in 2019 and was caused by twice as many autochthonous basidiomycetous yeast species (natural core community), which were found in urban soils only after the reduction in household waste in the environment - Apiotrichum dulcitum, A. laibachii, Saitozyma podzolica Solicoccozyma terricola. And at the same time, the proportion of clinically significant (opportunistic) yeasts, Candida sake and Meyerozyma guilliermondii, was much lower in 2020 than in 2019. Thus, the observed changes in yeast communities in urban soils could be a short-time response of the microbial community to a reduction in household waste.

— Complexes of cultured saprotrophic bacteria and yeasts from different components of soil constructions (humus soil horizon and peat) were studied simultaneously with the assessment of auxin-producing activity (synthesis of 3-indolylacetic acid, IAA), of some bacteria and yeast strains isolated. The study was carried out at the stage of laying two variants of constructions in Syktyvkar, formed from components of local origin (variant 1) and imported components (humus soil horizon, Moscow, Seliger-agro peat, Tver region) (variant 2). The taxonomic structures of microbial complexes isolated from the studied substrates were very similar. At the same time, the components of variant 1 had a greater diversity of cultivated saprotrophic bacteria ( Bacillus ) species resistant to adverse environmental conditions, as well as the presence of the psychrophilic basidiomycete yeast Leucosporidium scottii , which was not found in the components of variant 2. The average IAA production by the yeast strains and saprotrophic bacteria was 647.6 µg/L and 741.3 µg/L, respectively. The highest IAA concentrations were found in the culture liquid of the yeast Tausonia pullulans (strain Y-6, 3362.6 µg/L) isolated from the humus soil layer of variant 1 and the two saprotrophic bacteria Flavobacterium рsychrophilum (strain B-7, 2616.8 µg/L; B-5, 1056.3 µg/L) isolated from the humus soil horizon in variant 1 and from the peat of variant 2. For strains of the yeast Leucosporidium scottii and the cultivated saprotrophic bacteria Flavobacterium psychrophilum, the ability to synthesize IAA was demonstrated for the first time.

Results of the 60-year research on soil physical properties at the large lysimeters of the Experimental Soil Station of Moscow State University are discussed. The main studied issues include the elements of soil water balance, soil evolution, soil temperature regime, and transport of various substances within the soil profile. The long-term changes in soil texture, soil mineralogy, and organic carbon content have been observed. The horizon sequence in the soil profile affects the intensity of drainage flux and its stabilization in the long-term aspect. The amount of the transit transfer of substances in different soil profiles depends on both profile structure and upper boundary conditions.

Urban soils, differing in the intensity of anthropogenic impacts, were studied in several largest (Krasnodar), large (Sochi and Simferopol), and moderately large (Maikop) cities of southern Russia. The obtained data on the diversity of bacterial complexes revealed that urban soils with high anthropogenic load (Sochi, Simferopol, and Krasnodar) undergo considerable transformation of natural bacterial complexes with a sharp increase in representatives of Enterobacteriaceae family. Along with microorganisms indicative of the sanitary status of urban soils ( E. coli and En. faecalis ) the soils also contain bacteria of Klebsiella , Enterobacter , Citrobacter , and Serratia genera; some of their species may cause intestinal and allergic diseases. In the urban soil of Sochi, spores of sulfite-reducing Clostridia , including Clostridium perfringens, have been found. In the urban soil of Maikop with the lowest population density among the studied cities, changes in the structure of natural bacterial complexes are virtually absent. The abundances of sanitary-indicative microorganisms ( Escherichia coli and Enterococcus faecalis ) in urban soils of all the studied cities, except for Maikop, exceeded the normative parameter for sanitary-safe clean soils (<10 CFU/g soil).

Abundance and diversity of cultivated bacteria in saprotrophic soil complexes were monitored for two years on the territory of one of the large industrial cities of the European North of Russia, Syktyvkar. The analysis was carried out before and after quarantine due to the COVID-19 pandemic. The city of Syktyvkar is characterized by a high population and intensive anthropogenic pressure. According to the total indicators of the current state of the environmental components, it should belong to the tense category, by environmental standards. Studies were conducted in 2019–2020. Topsoils (0–10 cm) of urbanozems and horizon A in the park area in the urban space, as well as zonal undisturbed podzolic soil, were analyzed. Comparison of the two-year monitoring results demonstrated a marked increase in the number and diversity of saprotrophic bacterial complexes in 2020 in both urban and control soils (topsoil, 0–10 cm). Due to a sharp and prolonged decrease in the anthropogenic impact on the environment during quarantine measures, content of the bacteria of the families Enterobacteriaceae including sanitary-indicative ( Escherichia coli , Enterococcus faecalis ) and opportunistic and allergenic ( Enterobacter agglomerans , Citrobacter europaeus , Klebsiella oxytoca , Serratia marcescens , etc.) in the urbanozems decreased. This can be considered as a manifestation of the soil’s ability to “self-remediate” during a decrease in anthropogenic impact on the environment.

In a model experiment, the transformation of microbial complexes of cultivated saprotrophic bacteria and yeasts during freezing-thawing was studied in various natural substrates that are used to create soil constructions for urban landscaping and for growing herbaceous plants. The number of saprotrophic bacteria and yeasts depended both on the type of substrate and on temperature changes during freezing-thawing. At the stage of freezing of peat and soil (arable horizon) to 0 and –5°C and at the subsequent stage of thawing to 0°C, a significant increase in yeast number was registered. The maximum number of yeasts in soil and peat was 5.1 log (CFU/g). In contrast to the number of yeasts, number of saprotrophic bacteria in soil and peat was characterized by a sharp decrease when the substrate temperature was negative and peaked at 19–22 and 10°C, respectively. The maximum bacterial number in soil and peat was 7.5 and 8.0 log (CFU/g), respectively. In sand, number of both saprotrophic bacteria and yeasts did not depend on the temperature and was 5.0 log (CFU/g) for bacteria and 3.4 log(CFU/g) for yeasts at all stages of the freezing-thawing cycles. In total, 15 saprotrophic bacterial species and 29 yeast species were isolated from different components of soil constructions. At the maximum temperature of freezing in the cycles (–5°C), three bacterial species with psychrophilic properties (Flavobacterium psychrophilum) and the ability to form endospores resistant to various adverse effects (Bacillus subtilis, B. megaterium) were isolated from soil and peat. Among the yeasts isolated from soil and peat at negative temperature and also having psychrophilic properties were Candida sake, Rhodotorula glutinis, Rh. mucilaginosa, and Solicoccozyma terricola. Bacteria with psychrophilic properties, F. psychrophilum and Pseudomonas fluorescens, as well as two species of bacilli, Bacillus subtilis and B. megaterium were revealed in sand at negative temperatures. Only one yeast species, Debaryomyces hansenii, capable of surviving stress conditions in the form of ascospores, was isolated from sand at –5°C. The effect of short-term temperature drops on the microbial communities’ number and diversity dynamics in soil constructions in a model experiment showed that specialized soil constructions were able to “tolerate” short-term temperature stress drops typical of the spring and autumn period, restoring the number of initial populations after cessation of the negative impacts. This also indicates development of the soil constructions in the process of functioning, rather than their rapid degradation.

Road dust is one of the most significant anthropogenic pollutants in modern urban conditions. Its affect to human health is hard to underestimate because of its composition, including cancerogenic elements, PAHs, PM2.5 particles, etc. But another important aspect of negative influence of urban dust is its influence on the soil properties, such as its wettability. In this work the influence of Moscow road dust on the urban soil's topsoil was studied in a model experiment. The obtained data have shown the high water repellency of road dust and its significant hydrophobization effect on the soil wettability, which have increased from 62.4° in initial topsoil samples to values about 120° in samples with percentage of road dust, equal to 5 and 10-years pollution.

Variation in physical properties of soil depends heavily on freezing process during seasonal changes. Seasonal changes in cold humid regions lead to increasing of soil transformation speed. In the late autumn, soil profile is saturated with water through fallout. During winter, soil solution freezing leads to soil volume increasing due to water transition into the ice. Soil solution freezes in larger pores and the moment water flow stops, water phase transition leads to smaller pores and capillary deformation. Intensity of pore and capillary depletion will define extent of density changes during freezing. Rapidly developing urbanization process requires expansion of urban greening and tree planting, which can be successfully done by sustainable artificial soil implementation for each region, according to its climate conditions and pedogenesis. In order to observe possible porosity and structure changes in artificial soils and change rate due to freeze-thaw phenomenon, we have performed an experiment with a use of artificial soil models and then we have applied X˗Ray computer microtomography method to analyse soil pore space and its composition. As a result, we have seen significant compaction and pore diameter differentiation, as well as geometrical configuration changes.

This study presents new data on structural and hydraulic characteristics of artificially-layered soils and their dynamics in urban environment. Full-profile soils in large lysimeters and short-profile soils at the experimental plots of Moscow University Soil Station were studied. Short-term changes and long-term evolution of soil matrix and soil hydraulic properties are discussed.