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A comparative study was carried out for the first time of the magnetic susceptibility for two subtypes of Siberian chernozems, depending on the characteristics of their geographical distribution, formation of properties, and composition. A total of 12 soil profilespit were studied, nine of which are represented by ordinary and three by leached long-term frozen and permafrost chernozems of Western, Middle, and Eastern Siberia. The volumetric magnetic susceptibility (χ) of the studied chernozems was determined using a specially developed and patented, precise, express, and reliable method using a small-sized KM-7 cappameter from the Czech manufacturer StatisGeo. The specific magnetic susceptibility (χ) was calculated using the formula: χ = χ/ρ, where ρ is soil density, kg/m3. It is shown that the studied chernozems of Siberia are formed in contrasting landscape and climatic conditions of soil formation and composition of soil-forming rocks, leading to significant differences in their magnetic susceptibility, manifested both at the subtype level and at the level of individual pedons. Close positive correlations have been established between the specific magnetic susceptibility of these chernozems and the content of humus, coarse and medium sand fractions, as well as of fine sand, and negative ones for pHн2o, easily soluble salts, and CaCO3. While ordinary chernozems in the European part of Russia are characterized by a typically accumulative magnetic profile, those in Siberia, subject to prolonged freezing and on permafrost, are characterized by a regressive-accumulative profile. At the same time, ordinary permafrost chernozems differ from long-term frozen soils in their statistically significant values of specific magnetic susceptibility, which, in our opinion, is associated with the processes of cryogenic ferruginization.

The composition of the water-extractable organic matter (WEOM) of sedimented soils, namely, dark-humus water-accumulative stratozems (Fluvic Chernic Phaeozems (Loamic, Pachic)) in the nonplowed bottom of a dry valley is studied and compared to the WEOM composition of arable soils (Haplic Chernozems and Fluvic Chernic Phaeozems (Loamic, Pachic) ) on the adjacent cropland of a small catchment. The WEOM composition of stratozems is examined layer by layer from the surface to the depth of 120 cm with a step of 20 cm. Water extracts are analyzed for organic carbon, nitrogen, and pH. The optical properties of WEOM are analyzed by spectrophotometry and fluorescence spectroscopy and compared in these soil types. The specific features of the changes in the properties of stratozems with the depth are also analyzed. The erosion and accumulation processes are shown to considerably influence the composition of soil WEOM. However, the content of dissolved carbon in WEOM does not significantly differ either between arable chernozems and sediments or down along the vertical profiles of the sediments on dry valley bottom. In turn, the content of nitrogen in the WEOM of arable chernozems is generally higher as compared with that in sediments, where it predictably decreases with depth. Presumably, the decrease in the nitrogen content of WEOM in sediments with depth is associated with its uptake by plant roots and an increase with depth in the share of anaerobic zones, with their activated denitrification processes. The top 0–60-cm soil layer in sediments actively retains the nutrients leached from arable soils, primarily, dissolved nitrogen. This process promotes the carbon accumulation in the underlying layers. An increase in the content of total organic carbon in Fluvic Chernic Phaeozem (Loamic, Pachic) layers below 60 cm is explainable with the accumulation of the dissolved organic matter migrating downward. On the one hand, the dissolved organic matter is sorbed by soil and, on the other hand, is preserved as a result of a decrease in the microbial activity caused by the deficiency in nutrients.

Influence of spring grass fires on the properties of the upper humus horizon of migrational–mycellary chernozem (Haplic Chernozem) has been studied by the example of soils at the Basic Experimental Complex, Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences (Tomsk). A total of 56 samples (5–14 replicates) were collected at the plots burned two months ago, 1, 2, 3, and 11 years ago. A considerably high stability of the controlled soil properties (cation–anion composition of water extract, content of grain-size fractions and mobile compounds of a wide range of elements, total C and N, organic carbon, pH value, basicity of ) under pyrogenic impact of spring grass fires has been found. The content of mobile Ca, Mg and Sr, as well as water-soluble Mg 2+ and basicity of appear to be informative parameters reflecting a significant pyrogenic impact over the past 11 years. Their content is higher in the soils at recently (0–3 years ago) burnt plots as compared to old-burnt (11 years ago) and unburnt plots. Among the studied parameters, the pH value, the content of mobile Ba and Sr, and the content of grain-size fractions 1–5, 5–10, and 10–50 µm show a low variation coefficient (mainly <20% in all studied subsets of samples); whereas the content of water-soluble ammonium and mobile Li and Zn manifest a high variation coefficient (>70%).

This article presents findings on the study of content, profile distribution, and reserves of various carbon forms (organic carbon (TOC) and inorganic carbon (IC)) in Urbic Technosols and Ekranic Technosols within the residential zone of the city, alongside zonal Calcic Chernozems in the recreational zone of Rostov-on-Don, Aksai, and Bataysk. It was revealed that the TOC content in the upper horizons of Urbic Technosols is significantly lower than in the chernozem horizons of fallow areas, registering at 2.59 ± 0.79% and 3.25 ± 0.94%, respectively. IC exhibits an inverse trend, with maximum content observed in the upper horizons of Ekranic Technosols. Down the soil profile, disparities in TOC and IC contents are mitigated. This specificity in TOC accumulation and profile distribution signifies a “bipartite” profile alteration in buried chernozems, affecting solely the upper stratum rather than the entire soil profile. The presence of woody vegetation in the dry-steppe zone positively influences TOC accumulation. Calcic Chernozems beneath woody vegetation showcase the highest TOC reserves within the 30-cm layer (10.61 ± 1.45 kg/m 2 ). Calcic Chernozems of fallow areas under natural steppe vegetation contain 8.94 ± 1.75 kg/m 2 , Technosols of the residential zone 8.44 ± 2.47 kg/m 2 . For Technosols of the residential zone, a weakening of the dependence of TOC and IC content on the depth of the soil horizon is observed.

Background and aims Cover cropping is a strategy to increase soil phosphorus (P) use efficiency in agroecosystems. We investigated adaptations on P acquisition strategies of nine cover crops grown in a calcareous and a non-calcareous chernozem with low available P. Methods Through a 108-day pot experiment using a calcareous and a decalcified chernozem, we evaluated black oat ( Avena strigosa Schreb.), white lupin ( Lupinus albus L.), narrow-leaf lupin ( Lupinus angustifolius L.), phacelia ( Phacelia tanacetifolia Benth.), berseem clover ( Trifolium alexandrinum L.), buckwheat ( Fagopyrum esculentum Moench), linseed ( Linum usitatissimum L.), ramtil ( Guizotia abyssinica [Lf] Cass.) and white mustard ( Sinapis alba L.) for their dry biomass production, tissue P concentration and uptake, and effects on soil pH, phosphatase activity, mycorrhiza infection rate and soil P fractions. Results Cover crops differed in several parameters between the two soils. Dry biomass varied from 3.3 (white lupin) to 41.6 g pot -1 (mustard). Tissue P concentrations ranged from 0.046% (mustard) to 0.24% (clover). Species affected pH of both soils, ranging from − 0.66 to + 0.24. Acid phosphatase activity was higher in the decalcified soil, while alkaline phosphatases were higher in the calcareous soil. Root mycorrhizal infection rates ranged from 0 to > 50%. Most plants explored soil labile P exclusively, with organic P mineralization being more relevant in the calcareous soil. Conclusion We confirm that cover crops favoured distinct strategies to access the predominant soil labile P forms in each soil. Mycorrhizal species were particularly efficient in the decalcified soil, while species with high phosphatase secretion accessed higher Po, especially in the calcareous soil.

The regularities of benzo[α]pyrene (BaP) accumulation and distribution in chernozems (Haplic Chernozems), meadow-chernozemic soils (Haplic Chernozems (Stagnic)), and alluvial soils (Fluvisols) affected by the aerotechnogenic emissions from the Novocherkasskaya Electric Power Station (NEPS) were studied on the basis of long-term (2002–2011) monitoring data. A 5-km-wide zone stretching to the northwest from the electric power station and coinciding with the predominant wind direction was found to be most contaminated, with the maximum accumulation of BaP at about 1.6 km from the source. The coefficients of vertical BaP distribution between the layers of 0–5 and 5–20 cm closely correlated with the contents of physical clay, clay, and humus, and with the cation exchange capacity. The content of BaP in soils was shown to be indicative of the level of technogenic loads related to the combustion products of hydrocarbon fuels.

The content of various chemical elements such as metals, metalloids, and nonmetals in the environment is associated with natural and anthropogenic sources. It is necessary to normalize the content of metals, metalloids, and nonmetals as potentially toxic elements (PTE) in the Haplic Chernozem. The soils of the Southern Russia are of high quality and fertility. However, this type of soil, like Haplic Chernozem, is subject to contamination with a wide range of PTE. The aim of the work was to rank metals, metalloids, and nonmetals by ecotoxicity in Haplic Chernozem. To assess the ecotoxicity of chernozem, data for 15 years (2005–2020) were used. Biological indicators used to assess the ecotoxicity of Haplic Chernozem: catalase activity, cellulolytic activity, number of bacteria, Azotobacter spp. abundance, to change of length of radish’s roots. Based on these biological indicators, an integral indicator of the state of Haplic Chernozem was calculated. The ecotoxicity of 23 metals (Cd, Hg, Pb, Cr, Cu, Zn, Ni, Co, Mo, Mn, Ba, Sr, Sn, V, W, Ag, Bi, Ga, Nb, Sc, Tl, Y, Yb), 5 metalloids (B, As, Ge, Sb, Te) and 2 nonmetals (F, Se) as priority pollutants. It is proposed to distinguish three hazard classes of metals, metalloids, and nonmetals to Haplic Chernozem: I class — Te, Ag, Se, Cr, Bi, Ge, Sn, Tl, Hg, Yb, W, Cd; II class — As, Co, Sc, Sb, Cu, Ni, B, Nb, Pb, Ga; III class — Sr, Y, Mo, Zn, V, Ba, Mn, F. It is advisable to use the results of the study for predictive assessment of the impact of metals, metalloids, and nonmetals on the ecological state of the soil during pollution.

Statistical analysis of 3802 samples of saline soils from different regions of Russia made it possible to substantiate preliminary conclusions about a higher proportion of magnesium in soils containing gypsum in comparison with gypsum-free saline soils. Gypsum is not a toxic salt and its presence does not cause an increase in salinity. Salinization is mainly related to sodium and magnesium salts, with the sodium percentage often exceeding the magnesium percentage. It is statistically substantiated that in the studied saline soils without gypsum, sodium often dominates among cations in the soil water extract (1 : 5) at any degree of salinity, The appearance of gypsum in the soil profile is accompanied by a significant increase in the proportion of magnesium. In slightly or moderately saline horizons with more than 1% of gypsum, the proportion of magnesium in the water extract (1 : 5) often exceeds 50% of the sum of sodium and magnesium according to the median, arithmetic mean, upper quartile, and maximum values. Even in strongly and very strongly saline soil horizons containing gypsum, the proportion of magnesium is significant with the median of 43 and 31%, respectively, which is 5.8–6.7 times higher than the proportion of magnesium in gypsum-free horizons of the same degree of salinity.

Aims Arsenic is a nonessential element for plants; however, high levels of As can inhibit plant growth. The toxicity of As is influenced mainly by its speciation in soil. The objectives of the present study were to determine the fractional composition of As in soil, its accumulation in plants, and its potentially toxic effects on the morphological, anatomical, and ultrastructural levels. Methods In a model experiment, barley ( Hordeum sativum L .) was planted in Haplic Chernozem spiked with three different concentrations of As (20, 50 and 100 mg/kg). The fraction composition of As in the experimental soil was analysed using a method of sequential fractionation. The phytotoxic effects of As were analysed microscopically at the tissue, cellular, and intracellular levels. Results Analysis of the fraction composition of As revealed a higher amount of mobile forms of As that contaminated the generative organs of plants. Oxides of Fe, Al, and Mn became the main soil components to retain As when contamination of As increased. Arsenic toxicity inhibited plant growth by affecting morphological parameters (shape, size, and colour). It caused impairment in the root cells and a reduction in the size of the chlorophyllic parenchyma in the leaves. The ultrastructural analysis found changes in the main cellular organelles (chloroplasts, mitochondria, and peroxisomes). Conclusions The bioconcentration factor (BCF), bioaccumulation factor (BF-soluble), and translocation factor (TF) allowed evaluation of plant protection mechanisms and determination of hazardous concentrations of As in soil. Despite the high buffering capacity of the soil, high As concentration affected morphological and ultrastructural parameters of the H. sativum .

Nanotechnology, especially in the field of photocatalysis, has witnessed rapid advancements, with titanium dioxide being one of the most widely used photocatalysts. As the use of products containing photoactive nanomaterials increases, concerns have arisen regarding their potential release into the environment over time. This release can impact soil, groundwater, and surrounding ecosystems, resulting in nanoparticles being dispersed in water and eventually depleted from the system. This study aimed to investigate how different soil solutions affect the structural, textural properties, and photocatalytic activity of titanium dioxide-based, commercial reference Evonik Aeroxide P25. The Regosol soil solution, characterized by acidic pH, low ionic content, and high organic matter content, induced nanoparticle aggregation and bandgap changes. In addition, the acidic pH hindered the adsorption process, potentially affecting the photocatalytic processes. In contrast, the Chernozem soil solution, with slightly alkaline pH, high ionic content, and low organic matter content, did not significantly alter the morphology or structure of the material. However, various organic compounds were absorbed on the surface, reducing the availability of active sites. The study highlights the importance of understanding the influence of soil solutions on nanomaterials, as it impacts their properties and environmental risks. Results show that the material is still activated, i.e., it can exert its photoactive effect on the environment. This sheds light on the challenges posed by nanoparticles in soil, particularly in terms of their toxicity and consequences for the surrounding ecosystems. The study underlines the need for further research in this area to assess potential risks and optimise the use of nanomaterials in environmental remediation.