Počvovedenie

Geochemical features of organo-accumulative (Eutric Regosols (Laomic, Ochric), Cambic Someric Phaeozems (Loamic)) soils widely distributed in the soil cover of the subtaiga and subtaiga-forest-steppe light coniferous forests forming the lower boundary of the forest belt in the mountain structures of Northern Mongolia are considered. Data on the microelement composition of soil-forming rocks are given. It was found that the paragenetic association of trace elements in them is represented by Pb, Cu, Zn, Co, V, Cr, Ni, Mn, Mo, Ba, Sr, Zr and B. It was found that, compared with the average content in the lithosphere within the subtaiga and subtaiga-forest-steppe forest-growing belt, the residual and re-deposited weathering crusts of igneous rocks are enriched with Zn, Cr, Mo, B, at the same time they contain less Pb, Co, Mn, Ba, Sr, Zr. The residual and re-deposited weathering crusts of carbonate rocks are enriched with Pb, Cu, Zn, V, Cr, Sr, B, they contain little Co, Ni, Mn, Mo, Ba, Zr. Data on the morphological structure of soils, their physico-chemical and chemical properties, as well as on the content of trace elements and their radial distribution in the soils under consideration are discussed. The data obtained indicate the accumulation of most trace elements in the surface organogenic and humus-accumulative horizons of soils, which is associated with both the heterogeneity of soil-forming rocks and the influence of soil processes that cause the accumulative redistribution of elements and their deposition on organo-sorption and carbonate geochemical barriers. It is shown that the studied soils differ not only in the absolute values of trace elements involved in the biological cycle, but also in the intensity of their involvement in biogenic migration.

The involving of organic compounds in accumulation of Ni, Co, Cu, Cr, and Pb by Fe–Mn nodules in agro-dark-humus podbels (Planosols (Aric)) under different types of long-term agrotechnical impact has been studied in the south of Primorskii region. The profile patterns of the level of SOC content in soils and in nodules indicate the active deposition of organic compounds in nodules in the lower parts of soil profiles in the of fallow and phytomeliorative variants of the experiment. Fulvic acids were noted to predominate in the composition of humus in the nodules in these variants. The long-term application of organic fertilizers contributed to the decrease of SOC incorporation into nodules and to the increase of the part of humic acids in nodules. Nodules were characterized by a high accumulation levels of Co and Pb in all variants of the experiment. Accumulation of Ni, Cr, and Cu was recorded in nodules from particular horizons of studied soils. The intensity of elements accumulation in nodules of different variants of the experiment varied. Accumulation of Ni was controlled by the content of Mn-containing compounds. The most active sorption phases of nodules from soils with a longer period of organic matter transformation (fallow variant and long-term addition of manure variant) were Fe-containing and organic compounds.

Cumulative (June–August) soil respiration (R_soil(cum)), obtained based on field measurements and mathematical modeling, increased from wet areas of the oligotrophic bog to drained ones – “Hollow E.”, “Hollow Sh.” (hollows, dominated by Eriophorum vaginatum and Scheuchzeria palustris, respectively), “Open bog” (sphagnum bog with sparse low pine trees), “Ridge” (oligotrophic ridges covered with low pine trees), “Tall ryam” and “Ryam” (forested pine-shrub-sphagnum bog): 135 ± 2.3, 139 ± 2.4, 275 ± 7.8, 279 ± 7.5, 466 ± 16.4, 510 ± 18.5 g C/ (m² season), respectively (mean ± std). An important factor of seasonal and annual variability of R_soil was the water table level (WTL): the extremely low amount of precipitation (6 mm) that fell in July 2022 led to a sharp drop of WTL in August, an increase of the aerated soil zone. As result, total R_soil(cum) over the summer in the studied biotopes increases by 29–54% compared to the same period in 2021. At the same time, the most intensive growth of R_soil during the drop of the WTL was on the edge of the bog (“Tall ryam”, “Ryam” and “Open Bog”), in contrast to its central area.

Microbial biomass, diversity of cultivated bacteria and micromycetes, as well as the number of functional nitrogen cycle genes in the supraglacial systems of the Aldegonde and Bertel glaciers were studied. Biomass of microorganisms varied from 2.54 to 722 µg/g of substrate. It has been shown for the first time that the majority (78.7–99.8%) of the microbial biomass of supraglacial objects is represented by fungi rather than prokaryotes. Main part (from 70 to 90%) of the fungal biomass was mycelium, the length of which varied from 6.70 to 537.51 m/g of substrate. The number of prokaryotes varied from 2.4 × 10⁸ to 1.95 × 10⁹ cells/g of substrate. The length of actinomycete mycelium varied from 2.6 to 62.61 m/g of substrate. The abundance of cultivated bacteria and actinomycetes varied from 3.3 × 10⁴ to 1.2 × 10⁶ CFU/g of substrate, and that of micromycetes varied from 2.2 × 10¹ to 1.7 × 10⁴ CFU/g of substrate. Bacteria of the genera Arthrobacter, Bacillus, Rhodococcus, and Streptomyces, as well as micromycetes of the genera Antarctomyces, Cadophora, Hyphozyma, Teberdinia and Thelebolus dominated. Micromycetes Antarctomyces psychrotrophicus, Hyphozyma variabilis and Teberdinia hygrophila were found in Svalbard for the first time. The number of amoA genes in ammonium-oxidizing bacteria varied from 5.33×10⁶ to 4.86 × 10⁹; nitrogen fixation genes nifH, from 9.89 × 10⁷ to 9.81 × 10¹⁰; nirK denitrification genes, from 4.82 × 10⁷ to 3.34 × 10¹⁰ gene copies/g of substrate. The results obtained indirectly indicate the leading role of fungi in the microbiome of the supraglacial objects of Svalbard and the significant contribution of prokaryotes to the emission of greenhouse gases from them.

The review is devoted to the analysis of the characteristics of salt-tolerant fungi in order to identify the possibility of their use for indicating chemical contamination of highly mineralized soils and the search for potential test species for laboratory mycotesting. A list of representatives of halophilic and halotolerant genera of micromycetes is given, which can serve as indicators of pollution by heavy metals, oil products and other toxicants against the background of increased mineralization of soil substrates. For biotesting of soils with an average level of mineralization, micromycetes belonging to moderate halotolerant species are proposed as promising. The morphological, physiological and molecular mechanisms of adaptation of halophilic and halotolerant fungi to conditions of increased salinity of habitats are analyzed. The effects on fungal communities, which are caused by a combination of salinity with chemical pollution of different nature, are considered. Methodological aspects of the practical use of salt-tolerant fungi for biodiagnostics of the degree of unfavourability of saline soils are considered: the composition of media, cultivation conditions, and test reactions of fungal cultures that are optimal for an adequate assessment of the degree of halotolerance of fungi and ecotoxicity of soil samples.

Current medium- and small-scale estimates of soil erosion in Russia are very few. At the same time, a favorable situation has now developed for assessing the rates and volumes of soil erosion losses. Erosion models have been developed that are adapted to available digital elevation models, various farmland masks and climate databases have been created. The paper studies the accuracy of erosion estimates using various maps of arable land. Two maps are public (ESA WC, GLCLU), the third is the official Ministry of Agriculture (MA) of the Russian Federation, the fourth map is an author’s reference map of Alekseevsky district. It has been established that the map of the MA gives the most average arable land areas among the first three maps. Public access maps showed maximum and minimum estimates of arable land area. Comparison with the standard showed that the accuracy of the map of the MA does not exceed 90%, the remaining maps – 84 and 83%. The area of arable land in the Belgorod region varies slightly (from 1,445 to 1,586 thousand hectares); so the region is favorable for erosion modelling. Deviations from the average rates of soil erosion calculated using different maps of arable land in the region as a whole amounted to 7%, and in some areas reached 27%. Thus, today assessments of soil erosion at the regional level can be carried out with an error of at least 10–15% only as a result of the uncertainty in mapping the boundaries of arable land. In the Russia as a whole, data on the area of arable land varies significantly, from 80 to 132 million hectares. Consequently, the use of existing maps of arable land can lead to significant uncertainties in soil erosion estimates averaged at the level of districts and above.

The pollution of the topsoils of the city of Baikalsk (Irkutsk region) under the influence of industrial emissions and wastes of the Baikal Pulp and Paper Mill (BPPM) was studied. The content of 16 individual PAH structures in samples of urban and background soils taken during the soil geochemical survey in the summer of 2019 was analyzed. Relatively low levels of PAH content were found in the lignin sludge from the BPPM and СHP ash. The concentration of total PAHs in CHP ash reaches 46 mg/ kg with a predominance of low molecular weight compounds (the proportion of naphthalene and its homologues is 24% and 34% of the total PAHs, respectively), among high molecular weight PAHs, 5-nuclear benzo(b)fluoranthene dominates (16%). In lignin sludge, the amount of PAHs is 7.16 mg/kg with the predominance of benzo(b)fluoranthene (83%). In the soils of Baikalsk, the average total content of PAHs (38.4 mg/kg) is 5 times higher than the background content. In urban soils, 4–5-nuclear fluoranthene (61.1%) and benzo(b)fluoranthene (29.4%) prevail. This makes it possible to attribute soil pollution to the fluoranthene type. The soils of the motor transport (total PAH 105 mg/kg) and industrial (59.5 mg/ kg) zones are the most polluted, where the most contrasting PAH anomalies were formed. In descending order of the amount of PAHs, the land use zones of the city form a series: motor transport > industrial > residential one-storey > railway transport > residential multi-storey > recreational zone. Several local anomalies in the amount of PAHs are distinguished, forming two large pollution halos in the western and eastern parts of the city. The leading factors in the accumulation of high molecular weight PAHs in soils are acid-alkaline conditions and soil organic matter, while the accumulation of low molecular weight polyarenes is mainly controlled by pH. The environmental hazard of pollution of Baikalsk soils with polyarenes is due to benzo(b)fluoranthene, its contribution is 83.5%.