Articles

Thermal properties of the upper arable horizon of urban soil sampled on the territory of the Experimental soil station of Moscow State University, birch biochar, and their mixtures were studied. Soil from the Ap horizon was sieved through a 1 mm sieve and then mixed with biochar in various proportions; the biochar content in the mixtures ranged from 1 to 15% by dry weight. Plastic cylinders 5.1 cm high and 7.7 cm in diameter were filled with soil, biochar, and their mixtures. The bulk density of the samples varied from 1.34 g·cm–3 for the Ap horizon to 0.28 g·cm–3 for biochar. Thermal properties were measured with a probe method using a TEMPOS device with an SH-3 probe; the distance between the probe needles was 0,6 cm. A series of measurements were performed for each of the six samples with a stepwise change in sample moisture content from the maximum one after capillary saturation to the minimum one in an air-dry state. At each moisture content for each sample, the thermal properties were measured in tenfold repetition, successively placing the probe in different positions within the central zone of the sample. The heat capacity, thermal conductivity, and thermal diffusivity of the substrates consistently decreased with increasing biochar content over the entire moisture content range; the highest values of all thermal properties were obtained for the Ap horizon, and the lowest for biochar. All samples demonstrated a linear growth of volumetric heat capacity with moisture content, and the slopes of the obtained curves were quite similar. The specific heat capacity of soil moisture calculated from the experimental data was equal to 3406.8 J·kg–1·K–1, which confirms the concept that the heat capacity of water in the soil is less than the heat capacity of free water. The thermal conductivity of biochar increased almost linearly with moisture content. The thermal conductivity of soil and mixtures increased rapidly with moisture content in the range of 0.03–0.20 cm3·cm–3, then the growth slowed down, and with an increase in moisture above 0.45 cm3·cm–3, the thermal conductivity decreased. The thermal diffusivity of biochar was very low and almost constant over the entire moisture range. The thermal diffusivity vs. moisture content dependences for soil and mixtures were similar to the curves for thermal conductivity, but had two weakly expressed maxima, the first of which was observed at moisture content below 0.20 cm3·cm–3. It is concluded that the introduction of biochar into loamy soil reduces its thermal diffusivity and thereby stabilizes the soil temperature regime, reducing the range of diurnal temperature fluctuations and slowing down seasonal warming. For urban conditions with high summer temperatures, this effect can be regarded as positive; for regions with low heat supply, the introduction of biochar into the soil is rather undesirable, at least in the context of soil temperature regime.

The patterns of transformation of n-alkanes as biomarkers were studied to assess the transformation of petroleum products (NP) in oil-contaminated soils of the chestnut range (Stavropol region) in dynamics. The patterns of hydrocarbons conversion in oil-contaminated soils are revealed, and the possibility of launching self-purification processes based on the results of an assessment of the composition of NP was shown. Medium-molecular n-alkanes were dominated in the oil composition. The absence of high-molecular weight n-alkanes (heavy fractions) and the presence of liquid ones (a part of the kerosene fraction) were the main feature of the hydrocarbon state in background uncontaminated soils. This indicated the existing regional background in the content of NP in soils. Homologous series of n-alkanes of freshly oil-contaminated soil samples included compounds with a number of carbon atoms from C11 to C40, which contain markers of organic matter of hydrobiont genesis (C15, C17, C19), markers of organic matter of bacterial genesis (C20–C25) and markers of terrigenous humic organic matter (C27, C29, C31). Normal alkanes with the long carbon chain C20–C25 and C26–C40 were represented in almost equal proportions with a slight predominance of the latter. It was shown that after 4 months from the moment of crude oil contamination, the results of soil self-purification were recorded, leading to a change in the composition of n-alkanes. The biodegradation of n-alkanes in soils was confirmed by an increase in the carbon of microbial biomass in oil-contaminated soils relative to background analogues. The nature of the distribution of even and odd homologues of n-alkanes, the amount of the sum of odd n-alkanes (ΣC27, C29, C31) are advisable to evaluate along with the total content of NP, when choosing background analogues of soils.

Magnetic susceptibility methods are widely used as effective and sensitive express methods for establishing genesis, evolution of soils, and their diagnostics. At the same time, there is absolutely no information on the magnetic properties of soils in the Southern Cis-Baikal region. The paper considers the magnetic susceptibility of gray metamorphic soil and clay-illuvial chernozem (on hummocks) located in the conditions of paleocryogenic hummocky-depression complex with gray- and dark-humus stratozems (in depressions). It is established that the values of specific magnetic susceptibility confirm the weak textural differentiation of the gray metamorphic soil profile associated with the attenuation of the podzolic process. Low values of magnetic susceptibility in clay-illuvial chernozem and their sharp drop with depth are caused, primarily by a decrease in humus content, a decrease in the acidity level and an increase in the amount of carbonates in the parent rock. Under conditions of paleocryogenic microrelief, magnetic susceptibility was noticeably higher in the buried humus horizon of the forest landscape depression soil compared to the modern horizon, which indicates a clear change in soil formation conditions and processes. On the contrary, no such changes were found in dark humus stratozem: magnetic susceptibility values showed the same values in the modern and buried humus horizons. The dependences of this indicator on such soil properties as specific electrical resistance, soil acidity, humus and exchangeable cation content, carbonates, silt and physical clay, total iron, as well as soil age were revealed.

The article considers changes of paleoenvironment on the western edge of continental Europe using the example of the Nantua section deposits, the formation period of which falls on the Middle Pleistocene cryochron corresponding to MIS 6 and, possibly, the transition to MIS 5e. The approach used is based on a set of characteristics of specific carbonaceous (humus) substances contained in the deposits, including its most reflective component – humic acids (HA). It is shown that the correlation coefficients of the indicator parameters of the composition and properties of modern humic acids in soils, obtained using different methods for studying their molecular features, are within 0.78–0.90. Based on the changes in the characteristics of the humus component of the deposits, it was established that the latter were formed in changing conditions, when, against the background of general coldness of the climate, there were five relative warmings of varying severity, which caused the appearance of clear signs of pedogenesis and primitive paleosols formation. A trend towards increasing moisture conditions was revealed, which is manifested in an increase in the proportion of fulvic acids relative to humic acids and a decrease in the absolute values of Cha:Cfa. Preliminary calculations of the average long-term air temperatures and the duration of the biological activity period (BAP) showed that their possible limits, respectively, lay between minus 5.9°C and –7.8°C and 52–80 days. The terms “humus” and “humus substance system” are used as synonyms in this paper.

The article aims to test the scanning electron microscopy (SEM) technique for studying earthen archaeological sites of the steppe zone of Russia. The earthen material of the Maikop culture kurgan (the 4th-3th millennia BC) in the Western Caucasus and two “black platforms” of the Sintashta culture (the 19th-18th centuries BC) in the Southern Pre-Urals are examined using a JEOL JSM 6060 A SEM with an EX-2300 BU energy-dispersive spectrometer (JEOL, Japan). The elemental composition of the surface was determined in each instance, and variations in the structure of earthen buildings were exposed based on their visibility during SEM investigations. The samples from earthen constructions are unique because nearly all of their interior surfaces are covered with a clay film of various thicknesses. The earthen “cement” used by the Maikop people to hold the stoneworks on the kurgan's slopes and the cromlech at its base was characterized by especially smoothed clay forms, consolidated structure, and a comparatively high content of Al and a low content of Si in the clay film. In contrast, the material inside the kurgan has a higher Si content, a looser structure, and a fragmented clay coating. The structure of the two “black platforms” of the Suntashta culture was found to differ; one was looser, while the other was consolidated and essentially monolithic (“stone-like”), and the elemental makeup of its substance showed an increase in Al and Fe concentration. In terms of building technology, the SEM studies enabled us to assume that the sedimentation process contributed to the smooth (clay-based) surfaces of the earthen structure fragments in the Maikop kurgan, and that the application of specific compaction techniques produced an artificial stone-like body of the black platform of the Sintashta culture.

This article compares the earthen kurgan constructions and building technologies of seven kurgans of the Bronze Age Yamnaya culture in the Orenburg region. We conducted a comprehensive analysis to determine the source materials for kurgan construction and the primary earthen building techniques used to create kurgans, focusing on macro-, meso-, and micromorphological properties. It made it possible to prove that ancient people did not simply pile up earthen materials in a chaotic manner but always used specific building plans, skills, and technologies available. We have noted the similarities and differences in the structure of earthen constructions, using the results of studying the kurgans of the Yamnaya culture from the beginning of the developed stage A to the end of the developed stage B (3300–2600 cal BC). Some of the identified differences are because of even slight changes in environmental conditions and, consequently, in the available raw materials that affect construction materials and technologies. Based on the analysis of all the kurgans, the primary way of their building has been identified — the creation of a “pestrotsvet” (patchy-colored material) and the techniques used for this — kneading, tamping, and inclusion of artificially introduced material. Local soils formed the primary material, to which various inclusions were added (river silt, bones, coals, etc.). Kurgan size, the original material's particle-size pattern, and its resulting cementing properties determined whether the material was extensively kneaded and tamped, or if a more complex design was employed.

The paper focuses on the preliminary description of the paleosol profile (microprofile) of Late Proterozoic (Vendian) age. The profile was found on the left bank of the Kosva River downstream of the Shirokovskoe water reservoir (Gubakha District of the Perm region). The upper part of this profile (genetic horizons of B and BC) is dissected by vertical tracks of desiccation. The lower part of the profile (siltstone of the horizon C) contains fossils of soft-bodied metazoan organisms including pinnate forms (Petalonamae), bilateral movable benthic forms (Proarticulata), medusoids and cyano-bacterial films. A model of organization of the studied facial and paleoecological loci is proposed. The paleosuccession is reconstructed on the basis of the sections studied and discussed. The matrix containing the paleosol profile formed in conditions of near-coast shallow-water basin. The siltstones of the matrix with the lumpy structure and small spherical concretions were exposed in aerial conditions, what influenced on structure of initial sediment from stratificated layer to lumpy soil matrix in a result of vertical cracking of the initial sandy-clayey matrix. After that, the conditions of shallow-water marine or lagoon basin came back, and the biota of soft-bodied organisms had developed there. Then, after shallowing of the basin, the deposited sediments exposed in aerial conditions again, perhaps in zone of wave dropping near the littoral. Presence of water let the bacterial-algal community to develop. Atmospheric agents together with insolation led to cracking of upper surface of the forming soil microprofile FPS-Sh1.

Paleopedological studies were conducted on the territory of the Kostenkovsko-Borshchevsky district. The K12 ancient human site is a reference section for regional studies of paleopedology, paleoecology, geological and cultural sequences. K12 contains a complete series of cultural layers related to the first part of MIS-3 in the range of 53–42 thousand years BP. This study is a continuation of previously conducted work on the K1 site, located on the opposite side of the “Pokrovsky Log” balka. In excavation K12, 16 lithological layers were identified, differing in structure, composition and properties. The material composition of the sediments is represented by chalk eluvium, which forms the sides of the balka, and loess-like loams of the watershed. Deposits with different proportions of chalk and loam were formed in the aqueous and aerial phases of sedimentation. In the excavation, about 5 m deep, three buried soils were found. The age of the lower one is about 50 thousand years BP. Cultural layers are confined to paleosols. Paleosols are an indicator of breaks in sedimentation. Four soil-sedimentary complexes were identified in the excavation. A description of the processes and the chronological sequence of their formation is given. The conducted research opens up new aspects in the study of buried soils of gully sedimentary complexes.

The discovery of Pleistocene paleosols, including a level corresponding to the previous interglacial (MIS 5e), in the north of Western Siberia is of fundamental importance for Quaternary stratigraphy and paleoecology. This paper presents, for the first time, the results of a study of a pedocomplex found in the Belaya Gora section (Valley of the Vakh River). The period of its formation, established through uranium-thorium dating and taking into account paleobotanical and paleontological data, spans from the end of MIS 6 to MIS 4 inclusive. Morphogenetic analysis at the macro-, meso-, and micro-levels, as well as data on granulometry, mineralogy, and humus composition — including the humic acid/fulvic acid ratio and the proportions of the main structure-forming elements (C, H, N) in humic acids — made it possible to reconstruct the succession of pedogenetic, sedimentary, and cryogenic processes. Based on the obtained comprehensive geological record and considering previously published paleontological data, a paleoecological reconstruction was carried out, along with the chronostratigraphic attribution of all pedocomplex levels. A paleosol subprofile corresponding to the warmest substage of MIS 5e — the Kazantsev thermochron was identified. At the same time, it was shown that the permafrost-gley (cryohydromorphic) stage, which marks the end of the formation of each paleosol level and took place during the cold substages of MIS5, exerts a dominant influence on paleosol morphology and masks the features of preceding, warmer phases. An unexpected finding of neoformed gypsum crystals in combination with ferruginous nodules was explained by the oxidation of previously formed pyrite and was also attributed to the cryohydromorphic phase of paleopedogenesis. An interregional correlation of the studied profile with pedostratigraphic schemes of the loess formation in adjacent regions — the East European Plain and the south of West Siberia — was carried out. For most elements of the studied pedocomplex and the overlying sedimentary and cryogenic units, correlative levels in loess-paleosol sequences were identified, with the exception of the paleosols from the end of MIS 6 — the Taz cryochron, indicating a gap in the South Siberian loess-paleosol record.