Articles

The contribution of organic matter content to the hydrosorption properties of soils is demonstrated. Hydrosorption properties have been studied for soils of different genesis and degree of technogenic loading. Among the technogenic soils, urban and arable soils are considered. Natural soils are represented by Albic Stagnic Retisol (Siltic) on varved clays, Luvic Greyzemic Phaeozem (Clayic, Humic) and Luvic Chernozem (Clayic, Humic) on brown clays. The sorption isotherms constructed using the BET method and the specifi c surface areas of the initial samples and samples after organic matter destruction were compared. The destruction of organic matter was carried out in a laboratory experiment using hydrogen peroxide. It was found that treatment with H2O2 resulted in a significant decrease in the sorption capacity of soils and a change in hysteresis phenomena. At the same time, the sorption capacity of the soils decreased in different ways. The specific surface area decreased from 1.9 to 2.8 times. Statistical analysis showed no correlation between the degree of reduction in specific surface area and the degree of reduction in organic matter content. However, a close correlation was found between the degree of reduction in specific surface area and the initial organic matter content. The higher the initial organic matter content of the soil, the greater the reduction in specific surface area as a result of the treatment. Treatment with H2O2 was found to have the most significant effect on equilibrium water contents during the capillary condensation interval. The sorption capacity of the urban soils was lower than that of their natural and arable counterparts. With a relatively high organic carbon content in the urban soils, the effect of its destruction on the specific surface was less than for the other soils, which allows us to consider it in relation to the qualitative composition of the organic matter.

The article presents a new methodological approach to modeling the soil water retention curve (WRC), based entirely on the Deryagin phenomenon of wedging pressure of water films in relation to the soil physical system. It operates with a variable mass fraction of the liquid phase (soil solution) with the parameters of the concentration and charge of electrolyte ions, the specific surface area of the solid phase, as well as limitations by porosity and the standard potential of a conditionally zero water content in the soil. The new model, validated according to the author’s and independent literature data for soils of various genesis and granulometric composition from sands to clays, showed good agreement with experimental data and a more adequate description of water retention with normalized root-mean-square errors 5–10 times smaller compared with the most common empirical van Genuchten model for describing the WRC. Along with an adequate description of WRC in the entire range from the state of water saturation to conditionally zero water content, the new model makes it possible to analytically calculate pore size distributions, estimate the generalized Hammaker constant for interphase molecular interactions of liquid and solid phases of soil, the Debye thickness of the double electric layer and the specific surface area of the solid phase of soil, alternatively to the standard BET method.

The paper presents the results of experiments to study changes in hydrological properties of soil substrates composing profiles of artificial soils (construktozems) 1-4 years aft er their creation. Constructozems are represented by two variants - layered soils including Ap horizon, lowland peat and quarry sand of the same thickness, and a mixture of these substrates in an identical amount by weight, as for layered constructozems. Water retention curves obtained by capillarimetric method on samples of undisturbed structure were compared. A decrease in the water-holding capacity of the peat layer and an increase in the mixture samples were found a year after their functioning as part of the artificial soils. Laboratory and field experiments showed a statistically significant difference in water filtration rates of the layered constructozems and the mixture. Sharp boundaries between soil horizons contrasting in their properties reduce water migration rates down to zero values. Obtaining breakthrough curves of potassium ions allowed us to establish that the formation of continuous paths of rapid movement of water and dissolved substances is observed after four years of functioning of artificial soils and is most pronounced in constructions with homogeneous soil profile structure.

The problems of determination and classification of soils by granulometric composition from the point of view of domestic and international soil science are considered. The development of methods and devices for granulometric analysis of soils was largely promoted by the works of the Department of Soil Physics and Reclamation, on the basis of which the necessity of two stages of granulometric analysis was shown, the all-Russian method of sedimentation analysis of particles by pipette method was founded, with the development of the classification of N.A. Kachinsky and names of soils by granulometry, which are fundamentally different from those generally accepted in the world practice. At present, at the first stage the method of pretreatment with 4% sodium pyrophosphate is widespread, at the second stage — measurement of granulometric composition two approaches are used — sedimentation method and laser diffractometry, which have different physical bases. The difference of final results on granulometric composition of soils is usually associated with different shape and density of solid phase of organic and mineral particles. This paper presents the studies of granulometric composition of agrodernovo-podzolic sandy loam soil (Tver region, VNIIMZ experimental site) with low content of organic matter in comparison of three methods of granulometric composition determination: laser diffractometer, sedimentometric methods of suspension pressure estimation on Pario - ISP+ (Integral Suspension Pressure) device and classical pipette method. Th e laser diffractometer for fine fractions showed systematically underestimated data with the same pretreatment procedure compared to ISP and pipette method. The ISP+ method compared to the classical pipette method gives similar results.

The purpose of this work was to study the absorption capacity of degraded soils of agricultural land (using the ex- ample of agricultural farms in the southern part of the Shakhtersky district of the Donetsk People’s Republic). The main objectives of the research included studying the amount of exchangeable bases, exchangeable calcium and exchangeable magnesium. To study the soil cover of agricultural lands, model sites of varying degrees of degradation were selected. When choosing them, factors such as the prevalence of the type of disturbance within the study site, the degree of anthropogenic transformation, and the type of cultivated crop were taken into account. Soil sampling was carried out in September 2023. It was found that the most significant decrease in the amount of exchangeable bases was recorded in areas left fallow after growing a number of crops — sunflower, corn and wheat. The values of the sum of exchangeable bases were reduced compared to the control by 56–85%. The indicators of exchangeable calcium in the soils of the studied agrocenoses varied fr om 5,5 to 38,08 mEq×100 g-1 of soil, which depended on the position of the site in the landscape, the link in the crop rotation system, and the type of crop being cultivated. The lack of a proper soil care system in the studied areas affected the content of exchangeable calcium, reducing its content by an average of 42,7–84,8%. The percentage of magnesium from the total exchangeable bases ranged from 14,3 to 20,6%. The most significant decrease in the content of exchangeable calcium and magnesium in relation to the control was recorded in sites after sunflower cultivation, as well as in areas left fallow, wh ere the combined effect of a number of unfavorable factors (sloping surface, predecessor crop with an increased level of removal of mineral nutrition elements) influenced the change this indicator.

Dry steppe chestnut soils (Kastanozems) of the Tamsagbulag oil field are subject to intensive technogenic impact of oil production facilities. It has been established that the technogenic impact on chestnut soil during oil production is manifested in the discreteness of physical-chemical parameters in the surface horizon. The value of the miner- alization of the aqueous extract ranged from 32.5 to 325.0 mg∙L-1, the specific electrical conductivity from 65.4 to
647.0 μS∙cm-1. The concentration of hydrocarbons (HC) varied from 7 to 647 mg∙kg-1 and, with rare exceptions, was at the level of background values (100 mg/kg) established for oil production areas. The proportion of HC from the organic carbon content Corg varied widely, from 0.01 to 6.20%. Gas-chromatographic analysis of the molecular weight distribution of n-alkanes in the composition of HC showed that high-molecular homologues C27–C39 dominate in the surface horizon of the soil, with a sufficiently high degree of transformation of individual odd n-alkanes. The proportion of average molecular weight homologues ∑C22–C25 did not exceed 8% of the sum of n-alkanes. In the microbial community, heterotrophic bacteria dominated among the ecological-trophic groups of microorganisms (unicellular bacteria, actinomycetes, micromycetes), in their composition the proportion of oil-oxidizing bacteria was 9.1–39.3%. The process of destruction of petroleum HC was accompanied by the formation of a wide range of volatile organic compounds. It is shown that the quantitative and qualitative composition of oil components in the surface horizon of soils is determined by two processes — vertical migration and transformation of hydrocarbons, which compensate for the accumulation of oil.

The article presents the results of measuring the toxicity of soils with a specific activity of 137Cs in the range of 3,3∙102–1,3∙106 Bq∙kg-1, the flux density of β-particles and the dose rate of γ radiation on the surface of a bulk sample of 5,4-192,7 imp∙sec-1∙cm-2 and 0,2-2,7 μSv∙h-1, respectively. The forms of toxicity were detected in a solid-phase biotest with Allium cepa L., simulating the situation of external irradiation of dividing cells in contact with soil. The toxic effect was assessed relative to the control as mitotoxicity by reducing the mitotic index and as genotoxicity by inducing chromosomal aberrations, taking into account the contribution of the clastogenic effect. The value of the mitotic index in a series of biotests with contaminated soil decreased to values of 8,6±1,1–14,6±2,3% compared with the control proliferation level of 14,9±1,2%. At the same time, the frequency of chromosomal aberrations increased conjugately from 4,7±0,3 to 18,2±3,3%, with a control level of 3,9±0,5%, with an increase to 68% of the proportion of pathologies associated with clastogenic effects on chromosomes. A number of significant correlations between the values of toxicity indexes and indicators of radioactive contamination of soils have been revealed.

Water erosion is one of the most extensive processes of soil and land degradation. This process significantly deteri- orates the quality of ecosystem services provided. Studying the mechanism and consequences of this phenomenon will help develop strategies to mitigate its impact on the environment. One of the challenges in studying water erosion is the high cost of conducting field research over large areas. Another challenge is the limitation of existing models, which are often developed for specific regions. Our research aims to address these problems by adapting the widely used RUSLE2 model to local conditions. Beijing was chosen as the study area due to its rich information resources and extensive results from field measurements of soil water erosion. Calculations were performed using a raster data model, which included a slope angle model, slope length, soil erodibility, rainfall erosion potential factors from precipitation and snowmelt, land use types, and vegetation cover management factors. All data were taken from open sources. The average soil erosion in the studied area was 25 t·ha–¹ per year. The discrepancy with other studies was less than 1%. The modified RUSLE2 model showed good results, correlating with other studies in this area.

Erosion-accumulation processes are realized through paragenetic processes of soil destruction, transport, redepo- sition and accumulation of pedosediments enriched in organic carbon. A promising approach in modern methods for substantiating permissible erosion losses of soils is the integration of assessments of the quality of soil resources, the rate of erosion and soil formation, including calculations of the balance of organic carbon in soils of agroeco- systems. The range of research tasks included: analysis of current integrated approaches to justify the permissible erosion losses of soils that are the most promising from the point of view of the completeness of reflection of ag- ropedogenesis; assessment of the effectiveness of the process of regeneration of the humus horizon under primary, recent and postagrogenic variants of soil reproduction; identification of patterns of formation of natural soil cover on dated and full Holocene erosional pedotopocatena; determination of the effectiveness of erosion-accumulation processes in the formation of pedosediments enriched with organic carbon in the thalwegs of runoff depressions during an extreme hydrological event and in accumulative elements of the landscape over a centuries-long period. The main objects of the study were soils of different ages in a state of renaturation, which were selected in anthropo- genically disturbed geosystems of the European forest-steppe. In addition, soil-geomorphological features within different-aged erosional pedotopocatenes and processes of accumulation of pedosediments at different scale levels were studied.
The results of mathematical modeling of the soil-forming process over time, based on an extensive database of soil-chronological data, show significant differences in the rate of formation of the humus horizon at the initial and quasi-final stages of pedogenesis, as well as the relationship between the ontogenetic maturity of the humus profile and the rate of pedogenesis, which must be taken into account when justifying acceptable erosion losses. Long-term studies of the processes of renaturation of disturbed soils in the forest-steppe zone have identified a special type of reproduction in Agroabrozems, when functional rehabilitation of the residual humus horizon occurs, which differs from primary pedogenesis during the formation of a humus profile on parent rocks. Depending on the erosional transformation of the predecessor soil profile, the average rates of formation of the postagrogenic humus horizon in forest-steppe Chernozems range from 3,6 to 6,0 mm·year–1. As shown by the results of studying different-age and full-Holocene pedotopocatenes, the natural soil cover, which reflects the processes of erosion-accumulation and landscape slope microzonality, and soil-geomorphological relationships can be adequately formalized by improving the formula for calculating the relief function in erosion models through the introduction of a variable power value for the slope length index.