No 3 (2024)

The paper highlights the influence of moisture on the soil formation process on loamy deposits during the primary vegetation succession. The study was carried out in the north-eastern part of European Russia (Komi Republic) in the middle taiga subzone. The authors analyzed young soils on the territory of a quarry for extraction of loamy grounds and background soils in the vicinity of it. Planting the Siberian spruce cultures on the territory of the quarry activated formation of the tree layer and thereby accelerated formation of the zonal type soils. The third succession decade in drained conditions saw formation of organic soil horizons (litters), a decrease in soil density in the upper profile part, a tendency to redistribute and differentiate the silty fraction by one-and-a-half oxides, indicating the beginning of selective podzolization. The rise in soil moisture content increased conservation of organic residues (peat formation) and made gley formation active. The quarry soils, like background soils, increased in acidity, carbon and nitrogen reserves along with the soil moisture content increase. In automorphic soil formation conditions, the rate of organic carbon accumulation in the upper 0–20-cm layer is 0.4 t· ha^–1·year¹; the excessive soil moisture content further increased it (1.0–1.2 t·ha^–1·year¹). The reserves of C_org in the upper 20-cm soil layer of young soils are by 2–4 times less than those in background soils.

In world practice, the measurement of the mass fraction of carbon of organic compounds (C_org) in soils containing carbonates is carried out in various ways. An analysis of methods that allow solving this problem was carried out, including the latest approaches: thermogravimetry, differential scanning calorimetry, spectroscopy. It has been shown that the presence of CaCO₃ does not prevent the use of the dichromatometric method (Tyurin, Walkley-Black) for determining C_org. The disadvantages of the method boil down to the laboriousness of the analysis, the need for constant presence of the operator, incomplete oxidation of organic compounds and environmental pollution. The method of measuring soil mass loss-on-ignition (LOI) is economical and rapid, but it gives an overestimated C_org content, which is associated with the inadequacy of the conversion factor of 1.724, the presence of adsorbed and chemically bound water, as well as mineral components decomposing at T = 105–550°С. The most relevant solution for finding C_org in carbonate soils is to use an analyzer and a calcimeter, although the accuracy of Corg measurements in the presence of carbonates is significantly reduced due to the quadratic summation of the errors of the two methods. The high cost of the device, maintenance, verification and repair limit its widespread use in soil laboratories. To measure the content of soil carbonates, it is possible to use both gravimetric (LOI) and volumetric (calcimeter) methods. The use of the latter is preferable for soils with a predominance of CaCO₃ in carbonate composition. Preliminary removal of carbonates from soil samples is labor-intensive and can lead to partial loss of C_org due to acid extraction. The high cost of instruments and the lack of libraries of soil spectra hinder the development of vis-NIR and MIR spectroscopy as an alternative to “wet” chemistry methods. Continuing comparative studies will improve the understanding of the spatial patterns of distribution of carbon in soil organic compounds.

Enzymatic activity of soils is the most important diagnostic indicator of the ecological state of soils under various types of anthropogenic impact. The aim of the study was to evaluate the enzymatic activity of common chernozem (Haplic Chernozem) under Ag, Bi, Te, and Tl contamination. 10 enzymes (catalase, dehydrogenase, peroxidase, polyphenol oxidase, ascorbate oxidase, ferrireductase, protease, phosphatase, invertase and urease) were analyzed. According to the degree of inhibition of enzymes, heavy metals form the following sequence: Tl > Ag > Bi > Te. With an increase in the concentration of heavy metals, the toxic effect on the activity of enzymes increases. The oxidoreductases showed greater sensitivity to Ag, Bi, Te, and Tl contamination than hydrolases. Among oxidoreductases, the highest sensitivity was found for ferrireductase, and the lowest for ascorbate oxidase. According to the activity of enzymes of the hydrolase class, invertase is the most sensitive, and urease is the least sensitive. When contaminated with Ag, Bi, and Te, invertase has the highest informative value, and when contaminated with Tl, urease and polyphenol oxidase are the most informative. Among the enzymes of the oxidoreductase class, the highest informativeness was found in peroxidase, and the lowest in ascorbate oxidase. Among the enzymes of the hydrolase class, invertase is the most sensitive, and phosphatase is the least sensitive. The results of the study can be used to assess the ecological state of soils contaminated with Ag, Bi, Te and Tl.

The study of the structure of peat deposits of the Bolsheberezovskoye and Podkosmovo inundated mires which were formed during the Atlantic – subboreal periods of the Holocene in the valley of the Nepryadva River, in the north-eastern part of the Middle-Russian Upland. The results of the botanical composition of peat deposits showed that the genesis of mires is represented by eutrophic paleocenoses, which accumulated carbon at a rate of 21.8-95 g/m² per year. The formed eutrophic peat was characterized by a high degree of decomposition (45-55%) and a low rate of vertical growth (on average, 0.3-0.6 mm/year), which is due to the seasonal dynamics of the level of occurrence of mire waters. The carbon content in peat by peat deposit profiles is 14% for the Podkosmovo mire and 31% for the Bolsheberezovskoye mire. The differences are due to the peculiarities of the water-mineral nutrition of the mires, which is manifested in the high content of carbonates and ash content of the Podkosmovo mire. Carbon reserves in peat soils of inundated mires vary from 51.5 up to 125 kg/m² for horizons with a capacity of 10 cm. This indicator is determined by the intensity of decomposition of plant residues, which depends on the composition and structure of microbial complexes. On the Bolsheberezovskoye mire the microbial complex is dominated by the fungal component, on the Podkosmovo mire – by the bacterial component. This is the reason for the differences in the microbial biomass of the mires: 222 g/ m² for the Podkosmovo, 898 g/m² for the Bolsheberezovskoye mire. The reason for the differences in inundated mires is the range of variation in the level of mire waters during the growing season, due to the reclamation measures carried out in the Bolsheberezovskoye mire. Nevertheless, inundated mires are important “depots” of atmospheric carbon and the intensity of its accumulation is determined by a complex of factors.

In laboratory model experiments, the ecotoxicity of Tl was assessed by changing the microbiological, biochemical and phytotoxic properties of soils in the South of Russia: ordinary chernozem (Haplic Chernozem (Loamic)), seropesks (Eutric Arenosol) and brown forest slightly unsaturated soil (Eutric Cambisol), differing in granulometric composition, pH and organic matter content. As a rule, there was a direct relationship between the concentration of Tl and the degree of deterioration of the studied soil properties. Tl nitrate showed higher ecotoxicity than oxide. The strongest ecotoxic effect of Tl was manifested on chernozem and seropesks 10 days after contamination, on brown forest soil — 30 days later. Restoration of biological properties of soils was observed for 90 days. Ordinary chernozem showed the greatest resistance to Tl contamination, and seropeski showed the least. The results obtained indicate a high ecotoxicity of Tl.

For the first time, on an example of the Vecherny Oasis, Thala Hills, Enderby Land, data on the content of microplastic particles (less than 5 mm) in the soils of East Antarctica were obtained. Seven samples taken from a depth of 0–15 cm were analyzed. Two soil fractions (less than 1 mm and 1–5 mm) were studied in 3 replicates (42 individual samples). The technique for isolating microplastic particles included soil sieving, density separation in zinc chloride solution, centrifugation, vacuum filtration, and microscopic analysis. For filtration, glass fiber filters with a pore diameter of 1.6 μm were used. Quantification of microplastic particles was carried out using a microscope, digital camera and advisory software. It was found that microplastic particles present in all analyzed samples. Their number varies from 66 to 1933 units/kg of dry soil. In most cases, particles less than 1 mm predominate, accounting from 70 to 100%. In 70% of cases, fibers dominate, in 30% – fragments of irregularly shaped plastics; films occur singly. There is no clearly defined confinement of increased amount of microplastic particles to infrastructure facilities; this may be a consequence of the influence of other factors, including local and long-range transport.