No 3 (2025)

The morphology of soil profiles during their summer and winter period was studied as well as the microstructure and major physic chemical properties of permafrost-affected loamy tundra soils. Studied objects were the initial (zero-moment) soils and the same profiles after 7 and 23 years up to the fully developed soil profiles of Middle and Early Holocene age. The leading role of the cryogenic processes in formation of morphology and properties and structure organization at different stages of development was determined. This effect realizes through the thermal yield ability and ice segregation. The difference of summer and winter structural organization was obtained. The instability of morphological features formed by cryogenic processes was also determined. These features may change and disappear due to the changes in hydrothermal regime, freezing-thawing processes, ice segregation forms. The stability of soil structure is determined by the formation of soil-aggregate chemical complexes. It was also shown that the structural morphological features in soil diagnostic horizons form before the significant differences of chemical properties appear. The cryogenic effect on soil formation is mainly realized through the microturbations of the uppermost horizons at the initial stages of soil formation. Later on, the horizontal and vertical migration of organogenic material may affect the structure and properties of the middle and lowermost soil horizons. One of the leading processes in permafrost-affected soils’ formation is the physical (cryogenic) disintegration of plant litter and forming of detritus in the upper parts of the profiles and coarse humus enrichment of the middle and lowermost soil horizons due to the cryoturbation.

This study is dedicated to the soils of one of the least studied mountainous regions of Europe – the Polar Urals, which develop on carbonate rocks under mountain tundra and meadow communities. The objective of this study was to examine the structural and functional parameters of humic acids isolated from different types of carbonate soils in the Polar Urals region and to elucidating their relationship with the environmental conditions that influence soil formation. The molecular composition of humic acids was investigated using modern physicochemical methods of analysis, including ¹³C NMR spectroscopy, exclusion liquid gel chromatography and gas chromatography. The impact of soil formation on the accumulation of humus and the variation of structural and functional parameters of humic acids in the organogenic and humus horizons of the studied soils has been established. The humic acid content was estimated to range from 0.03 to 6.27% and was found to be related to the aboveground biomass stock. It was demonstrated that humic acid molecules are predominantly formed by aliphatic fragments, which determine the number-average molecular mass. It has been identified that the least condensed structures correspond to humic acids of organogenic horizons of soils formed under shrubby-moss and shrubby-moss communities. This is likely to be related to the deficiency of lignin in the composition of humification precursors. This group of soils corresponds to the highest ratio of carbohydrates to unoxidized aliphatic fragments, indicating a low degree of humification and stability of organic matter.

This paper presents the results of a study on the stratigraphy, morphology, micromorphology, chemical, and physicochemical characteristics of the cultural layer in the residential area of the early medieval town of Dzhankent (Eastern Aral Sea region, Kazakhstan). The town is located in an arid paleo-deltaic landscape with a dynamic water supply. Sets of diagnostically significant micromorphological features are described, including: 1) features resulting from anthropogenic input and redistribution of matter (plant detritus, phytoliths, bone fragments, etc.); 2) pedofeatures resulting from the transformation of human-introduced material by anthropogenic processes (pyrogenic forms of carbonates, organic and phosphate-organic pedofeatures); 3) pedofeatures consisting of carbonates, gypsum, and iron oxides, mainly associated with natural processes. Stratigraphic units of the cultural layer, along with the processes and conditions of their formation, were defined, and the archaeological context was interpreted for each lithostratigraphic unit based on their morphological and analytical characteristics. The upper stratigraphic unit consists of the destruction products of adobe materials, with ash interlayers, some of which are stratigraphically traceable and likely correspond to fire events. The middle unit comprises residential and domestic sediments, including a series of living surfaces, and contains an ash layer possibly resulting from a fire event. The lower unit is composed of alluvial-delta deposits slightly impacted by residential activities and periodically affected by fluctuating groundwater. The distribution of organic carbon and phosphorus in the cultural layer corresponds well with the observed organic substrates at the macro-stratigraphic level, being significantly higher in loose layers rich in plant detritus, charcoal, ash, and bone material. However, the analytical characteristics of the cultural layer (pH, electroconductivity, contents of organic carbon, phosphorus, carbonates, gypsum), determined from homogenized samples of the stratigraphic units, do not always align with the composition observed at the micromorphological level (abundance of micro-artifacts, anthropogenic, and soil microfeatures). These discrepancies are primarily due to the extremely high lateral and microstratigraphic heterogeneity of the cultural layer.

The results of a study of ¹³⁷Cs migration in leached chernozems at slopes and soils in hollows of erosive agricultural landscapes of the Tula region are presented. A study has revealed that there was an active redistribution and differentiation of ¹³⁷Cs fluxes entering erosive agricultural landscapes due to the Chernobyl accident. The distribution of ¹³⁷Cs in soils across various parts of slope landscapes is influenced by factors such as the exposure, length, steepness, and shape of the slopes, along with the presence of microrelief features. Radionuclide removal zones are at the top of slopes, transit zones are in the middle, and the main accumulation occurs at the bottom of the slopes. A notable feature of the distribution of ¹³⁷Cs in diluvial deposits at the toes and bottoms of slopes is the increase in ¹³⁷Cs reserves with depth. This increase reaches a peak at a depth of 10–40 cm, depending on the thickness of the deposits. Following this, depending on the presence of geochemical barriers, there is a sharp or moderately gradual decrease in ¹³⁷Cs reserves in the lower layers of the soil profile. The contamination density of ¹³⁷Cs increases moving from the upper part to the lower line of the greatest slope and, conversely, decreases closer to the watershed. The ratio of ¹³⁷Cs contamination densities between the watershed sections and gulch bottoms is typically 1.0:(1.2–1.5), and between the upper and lower sections relative to the bottoms, it is 1.0:(2.0–1.5). The maximum differences between these indicators are typical for the steep, longitudinally straight southern slopes, as well as longitudinally concave southwestern slopes. The minimum values were observed in the gentler slopes of the eastern and western exposures. The highest ¹³⁷Cs densities were recorded at feet and bottoms of short slopes. On slopes of medium length, there has been a notable increase in soil surface contamination by ¹³⁷Cs, primarily concentrated in the central areas of these slopes. The extent of soil contamination by ¹³⁷Cs is affected by the steepness of the slopes. Steeper slopes have a 1.3 times higher contamination density compared to the upper parts of the slopes. On gentler slopes, the contamination density decreases to 1.1 times. Understanding these factors and the migration patterns of ¹³⁷Cs is important for accurately predicting how radionuclides will spread in different types of land. This knowledge helps in developing effective measures to enhance soil fertility and reduce the build-up of radionuclides in agricultural products.