Kotelnikova, Anna D

Kotelnikova A., Matveeva N., Borisochkina T., Rogova O., Volkov D.S., Savichev A.

Mineral fertilizers are one of the main important sources of elements in agricultural soils. The elements that enter the soil are involved in the transformation of soil organomineral compounds. Elemental analysis of soil granulo-densitometric fractions can be used to characterize these changes in detail. The study analyzes changes in macro- and microelement content in the organomineral fractions of soils under different cultivation. The clay-associated fraction with particle size LF > RF (As, B, Ba, Cr, Fe, Li, V, Zn, P, Mg, K, Na). The second group includes elements with the maximum concentration in the LF: LF > CF > RF (Co, Cu, Mn, Ni, Pb, Sr, Ca). It is shown that the application of mineral fertilizers leads to a redistribution of elements in the soil organomineral fractions, there is an imbalance in the contents and ratios of elements, which can be the cause of chemical degradation of agrocenosis. The main changes are related to the redistribution of trace elements: the elements added with fertilizers are more confined to the organic and transformed mineral components. This may contribute to an increase in the intensity of the mass flux of chemical elements in the soils of highly cultivated farmland. Changes in the "after-effect" group are smoother, indicating that the balance of elements in the soil is restored when fertilization ceases.

Rogova O.B., Shishkin M.A., Kolchanova K.A., Kotelnikova A.D.

Phosphate fertilizers actively used in agriculture can serve as a source of various impurities in the soil, which can have a negative impact on environmental components. In this work, the content of rare earth elements (REEs) in phosphate fertilizers marketed in Russia was evaluated. REEs are a group of elements that are actively studied due to possible negative and positive effects on living organisms. Currently, there are no standards for the content of REEs in soil and fertilizers. Also, in the literature there are no data on REEs content in phosphate fertilizers marketed on the territory of Russia and assessment of the significance of fertilizer application as a factor of REEs input into agricultural soils. Using the method of optical emission spectrometry with inductively coupled plasma, we obtained data on the REEs content in samples of phosphate rock, single and double superphosphate (22 samples). It is shown that phosphate fertilizers can differ significantly in REEs content, high REEs content (over 1000 mg/kg) was observed in some samples of single and double superphosphate. The group of phosphate rock samples is the most homogeneous in terms of REE content in the samples. Light REEs predominate over heavy REEs in the composition of fertilizers. According to the results of the study, it can be concluded that there is potentially no significant effect of the application of the studied phosphate fertilizers on the REEs content in the soil. However, the high REEs content in some fertilizer samples requires monitoring of REEs content in soils of agrocenoses, as well as the development of standards for REE content in mineral fertilizers. Funding. This work was supported by Russian Science Foundation grant No. 22-74-00003, https://rscf.ru/project/22-74-00003/.

Kotelnikova A.D., Borisochkina T.I., Kolchanova K.A., Shishkin M.A., Egorov F.S., Okorkov V.V., Rogova O.B.

The paper analyzes the elemental composition of soils and plants of agrocenosis on the gray forest soil of Vladimir opolye under long-term application of mineral and organic fertilizers. The content of total and mobile forms of Ni, Cu, Zn, Co, Mn, Fe and the content of these elements in aboveground plant organs, as well as changes in the main agrochemical characteristics that can affect the availability of elements to plants were evaluated. It is shown that the application of mineral fertilizers contributes to soil acidification, increase in the content of organic carbon, mobile forms of phosphorus. At the same time, the variants with joint application of mineral and organic fertilizers are subject to less change of these characteristics, which may be due to the increased buffering capacity of the soil with respect to the components coming with mineral salts, due to the applied organic matter. Introduction of Ni, Cu, Zn, Co, Mn, Fe into agrocenosis with fertilizers (organic and mineral) did not affect the gross content of metals in soil. There was a change in the content of mobile forms of metals in the soil due to changes in agrochemical parameters of soils. Changes in the content of trace elements in plant products were recorded. The reduction of Zn, Cu content in plants on the variants with more intensive use of fertilizers (and with higher yield) is explained by "dilution effect". The low content of Co in the soil and its insufficient supply to the plants must be controlled. The joint use of data on changes in the elemental composition of soils and plants allows better differentiation of experimental variants in the space of principal components when analyzed by this method and is promising for monitoring the consequences of agrogenic load of different degrees. The results obtained can be taken into account in the formation of criteria for assessing the mineral nutrition of plants and fertilizer application rates.  

Kotelnikova A.D., Borisochkina T.I., Kolchanova K.A., Shishkin M.A., Egorov F.S., Okorkov V.V., Rogova O.B.

Long-term application of organic and mineral fertilizers can lead to changes in the elemental composition of agroecosystem components. Both the levels of nutrients and potentially toxic elements can change, as can the potential for these elements to be available to plants through changes in soil properties. Soil and plant samples of two species (pea Pisum sativum L. and oat Avena sativa L.) were collected from plots of a long-term field experiment on the application of mineral and organic fertilizers and their combinations to gray forest soils in the Vladimir region, Russia. Soil samples from the 0-20 and 20-40 cm layers were subjected to acid digestion to determine total element content. Mobile forms of elements were extracted from topsoil samples using acetate-ammonium buffer (pH 4.8). Sample preparation of pea and oat plant organs (stems, leaves, pods/ears) included sample digestion in a microwave sample digestion system ETHOS EASY (Milestone, Italy). The elemental composition of the samples was determined by inductively coupled plasma optical emission spectrometry (ICP-OES) using Agilent 5800 ICP-OES (Agilent Technologies, USA). The dataset includes concentration data for 34 elements, including rare earth elements, in these samples collected in 2021. The dataset also contains general agrochemical characteristics of soils of the experimental groups: pH of water and salt suspension, organic carbon content, mobile forms of phosphorus. The data can be valuable to researchers developing fertilizer application systems and modeling changes in the elemental composition of agroecosystems.

Borisochkina T.I., Kotelnikova A.D., Rogova O.B.

The analysis of publications on the mass transfer of chemical elements in agrocenosis in the soil – plant system was carried out. Methods for estimating the content of mobile forms of chemical compounds coming from the soil into plants are considered. The phenomena of antagonism and synergism are characterized, and the necessity to consider them while planning fertilizer application is indicated. It is shown that the phenomena of synergism and antagonism of elements can be used in agriculture to regulate the flow of heavy metals or radionuclides into agricultural products. A balance model for mass transfer of chemical elements in agrocenosis is analyzed. It is shown that the introduction of organic fertilizers in soil mostly leads to a positive balance of microelements in the agrosystem. To characterize the efficiency of fertilizer use an assessment of the balance of nutrients in the agrosystem is required. The removal of trace elements by agricultural crops increases with the use of mineral fertilizers in doses that are optimal for the cultivation of crops in the region. In some cases, the input of heavy metals with technogenic fallout may exceed the removal of metals by plants from the soil. It may cause the accumulation of metals in the system. In uncontaminated background areas, the levels of microelement intake from fertilizers and atmospheric fallout in agrocenoses are comparable.

Kotelnikova A., Rogova O., Volkov D.S.

Lanthanides, including La, Ce, and Nd, as members of the rare-earth elements (REE) group, continue to attract the attention of researchers. Particularly lacking is data on REE toxicity in soil, which may affect specific soil types differently depending on their properties. Toxicity studies on REE-contaminated soil are therefore needed to assess the likely effects of anthropogenic impacts and to set safe content limits. In this study, we assess the potential toxicity of soil samples with a high organic matter content — chernozem — spiked with La, Ce, and Nd. The toxicity of soil samples was assessed using the Allium test on three basic indicators — root length of bulbs germinated on the samples, mitotic activity of cells in the apical meristem (mitotic index (MI)), and the frequency of aberrant cells (FAC). Allium cepa L. bulbs were germinated on soil samples with extraneous lanthanide concentrations from 0 (control) to 200 mg/kg. It was difficult to identify a single pattern for La, Ce, and Nd in their influence on onion root length when a range of concentrations are added to chernozem samples. The significant decrease in MI in the experimental groups of 20 and 100 mg/kg La compared with the control and the significant increase in FAC in the experimental group of 100 and 200 mg/kg Ce compared with the group of 10 mg/kg were shown. The properties of chernozem can largely limit the potential toxicity of La, Ce, and Nd introduced into soil samples in the form of chlorides. The results of REE toxicity assessment studies allow us to place them in an appropriate row, in which the potential toxicity decreases: Ce > Nd > La.

Kotelnikova A.D., Rogova O.B., Karpukhina E.A., Solopov A.B., Levin I.S., Levkina V.V., Proskurnin M.A., Volkov D.S.

Coal combustion byproducts—fly ash (FA), bottom ash (BA), and ash and slag waste (ASW)—are of considerable interest for the development of their application as soil ameliorants since these harmful wastes are produced in large quantities and need to be utilized or processed. Moreover, if FA is studied quite well in this respect, much less data exists on the BA and ASW, with fewer opportunities for their other economically justified use. Thus, this research focused on the possibility of FA and BA (ASW) application as soil ameliorants. Ash samples from power plants in European Russia were selected since they are not studied in detail before. To estimate the impact of ash application, changes in key indicators reflecting the soil quality, its suitability for growing safe products were assessed: particle size distribution , acidity, nutrient, and potentially toxic elements (PTEs; heavy metals and metalloids) concentration, and their potential availability for plants. The application of ash samples to soddy-podzolic soil contributed to pH normalization, confirming the possibility of using these wastes as a stabilizer of soil acidity at the optimum ratio of ash to the soil of 1:2 or 1:5. ASW samples can aggregate with soil particles, contributing to agrophysically valuable aggregates 250–2000 μm. Despite the contents of PTEs, ASW can be considered a safe material as the legislatively established standards are not exceeded.

Grechishcheva N.Y., Yaroslavtsev N.V., Kotelnikova A.D., Ostakh O.S., Kholodov V.A., Zavorotny V.L., Balaba V.I.

The experiments on mobilization of soil organic matter during soil washing with ultrafresh water against the background of salinity pulsing were designed and performed. Unpolluted soil and the soil artificially polluted with copper(II) were used in experiments, namely, clay loamy typical chernozem (Haplic Chernozem) of the Alekhin Central Chernozemic Nature Reserve (Kursk oblast, Russia; 51°34.207 N, 36°05.444 E) and sandy loamy soddy-podzolic soil (Albic Glossic Retisol (Loamic, Cutanic, Ochric)) from the Domodedovo district of Moscow oblast, Russia (55°17.683 N, 37°50.045 E). Soil samples were taken from the upper humus-accumulative (A1) horizon (5–15 cm). A drastic change in the composition of washing solution from fresh water to 0.1 M NaCl solution and back led to destruction of soil aggregates under the impact of osmotic pressure. Soddy-podzolic soil proved to be more resistant to destruction as compared with typical chernozem. Copper(II) was leached off from artificially contaminated samples of soddy-podzolic soil with the flow of dissolved organic matter, whereas copper leaching from typical chernozem was associated with the destruction of aggregates and release of intraaggregate organic matter. It is argued that copper (II) migration models should take into account the amount of dissolved organic matter for soddy-podzolic soil and the content of aromatic fragments in the organic matter for typical chernozem. A conceptual model of the Cu(II) leaching from contaminated soddy-podzolic soil and typical chernozem in the course of soil washing with fresh water against the background of salinity pulsing and the destruction of soil structure is constructed.

Kotelnikova A., Prudnikova E., Grubina P., Savin I., Rogova O., Gorlov A., Chinilin A.

<p>Phosphogypsum (PG) is a by-product of phosphoric acid production, a valuable raw material for reclamation of acidic soils, for remediation of soils contaminated with oil products, a source of rare-earth elements (REE). The use of PG has a positive effect on the development of plants, on the value and quality of yield. Most of the PG produced at the present time is stored in phosphogypsum dumps (PGD), which are a source of pollution of the environment, since the dust particles from dumps can be transported over significant distances. To assess the impact of PGD on the environment and agricultural production it is necessary to identify zones of priority distribution of dust particles and their accumulation in the soils of the surrounding areas. In recent years, geoinformation modeling (GM) have been used to analyze dusting of different types of dumps. There are very few studies on the possibility of using such technologies for modeling the dusting of PGD.</p><p>We carried out GM of dust emissions in the impact area of phosphate fertilizer production factory in Balakovo (Russian Federation).</p><p>The chemical composition of PG samples was determined for whole samples and fractions most susceptible to dusting – <100 µm. The determination of the total REE composition was carried out by ICP-OES method. REEs content in samples of PG is 30-60 times higher than the Clark values for soils. The predominant indicator elements are La, Ce and Nd, the content of which reaches 500-3000 µg/g. The distribution of microparticles in the fine fractions was analyzed using a laser particle size analyzer from ultrasound-stabilized suspensions. In the aqueous suspension PG aggregates disperse to particles <1 µm, forming in turn several size groups. Local maximum contents form particles with sizes 0.03, 0.14 and 0.67 µm.</p><p>The data allowed using the GM to allocate zones of priority distribution of dust particles and their accumulation in the soils surrounding the PGD area. Dusting simulations were performed for particle sizes 8-1, 1-0.1, 0.1-0.05, 0.05-0.03, 0.03-0.01 and <0.01 mm. The results of spatial modeling of the weighted sum of the relative concentration of dust particles indicate that particles up to 0.1 mm predominantly move in northeast, north and southwest directions, particles 0.1-1 mm predominantly fall in northeast direction, particles 1-8 mm - in north direction.</p><p>Correlation analysis showed that the results of dusting modeling are in good agreement with the spatial distribution of REE. The greatest correlation between the weighted sum of the relative concentration of particles of the analyzed size is noted for the content of La and Ce (correlation coefficients 0.74 and 0.68 respectively). Validation of the model was carried out in a field. Joint analysis of the constructed maps and field data showed that the map of the weighted sum of the relative concentrations of analyzed particles well reflects the spatial variability in the soil content of La and Ce.</p><p>The results of modeling can be used to assess the impact of PGD on the surrounding area and its soil cover.</p><p>The reported study was funded by RFBR, project number 19-05-50016.</p>

Kotelnikova A.D., Rogova O.B., Stolbova V.V.

Lanthanides as a separate group of metals geochemically belong to rare earth elements (REEs). For a long time, they have not received proper attention of researchers, whose interest was focused on other harmful environmental pollutants. However, the importance of REEs for modern technologies along with significant gaps in the knowledge about their effects on living organisms has changed the situation. Thanks to the active interest of researchers, a fairly large body of data on REEs in various areas has been accumulated, including their chemical and physical properties, their potential in engineering and instrumentation, their content in various natural objects, effects on human health, and interaction with other living organisms at the cellular level. This review analyzes and generalizes the new information about REEs as a relevant ecological factor with a special focus on the sources of REEs, specific features in their behavior in the soil, the effects of their interaction with plants, their manifestation, and putative mechanisms at the cellular level. The economic importance of plants to humans as well as their role for the entire biosphere as primary producers and their ability to be among the first ecosystem components that respond to negative changes requires focusing on these issues. The purpose of this review is to emphasize the research aspects that need a deeper insight, in particular, the soil–plant interaction and the effect of REEs on plant cell division.

Kotelnikova A., Fastovets I., Rogova O., Volkov D.S.

Rare earth elements (REEs) have received enormous attention in recent years. However, there are many gaps in the understanding of their behavior in the soil-plant system. The aim of this study is to investigate the behavior of three most common REEs (La, Ce, Nd) in the soil-plant system directly on soil samples using barley (Hordeum vulgare L.) in a vegetation experiment. We attribute the absence of significant changes in plant biomass and photosynthetic pigment content to the reduced availability of REEs in soil samples. The concentration of water-soluble forms of La, Ce and Nd didn't exceed 1 mg/kg, while the concentration of exchangeable forms varied and decreased in a row La > Ce > Nd. The transfer factor (TF) from soil to above-ground biomass was low for all three elements (

Stolbova V.V., Mamikhin S.V., Kotelnikova A.D., Prohorova S.A., Zaitseva M.V.

Examples of the use of different types of chromosome aberrations as diagnostic indicators to solve the practical problems of radioecology were considered. The classifications of the chromosome aberrations used to estimate the clastogenic effect of factors of radiation and chemical nature according to the results of cytogenetic studies with uniform staining of the chromosomes were analyzed. Some terminological inconsistency and ambiguity when designating various types and categories of chromosome aberrations, reflecting the clastogenic effect, was detected. It was demonstrated that this inconsistency can complicate the use of such cytogenetic indices in radioecological practice. According to the results of the Allium test using a digital imaging system, original microimages demonstrating the configurations of aberrant chromosomes used in classifications were obtained.

Kotelnikova A., Fastovets I., Rogova O., Volkov D.S., Stolbova V.

Lanthanum (La) and cerium (Ce) are one of the most abundant rare earth elements (REEs). In spite of quite extensive studying of the effects of these lanthanides on biota, some contradictions remain in the results. Also little is known about the effect of lanthanum and cerium on plant cells and their mitotic cycle, especially in soils. In this study, the effects of La and Ce in solutions and soil samples on root growth, mitotic index (MI) and frequency of aberrant cells (FAC) were assayed using one of the most convenient objects for testing of cytotoxicity - onion Allium cepa L. Bulbs were germinated on media containing La and Ce in concentrations 0-200 mg/l and 0-50 mg/l respectively for solutions and 0-200 mg/kg for soil samples. After 5 days of germination in solutions, a significant decrease in root elongation and MI in apical meristem cells are shown. We have also observed an increase in the number of cells with aberrations at 50 mg/l La and Ce concentration. The number of observed stickiness and disturbed metaphase has increased significantly. Soil samples turned out to be less toxic compared to the solutions probably due to the decreased availability of REEs. In spite of this, significant cytotoxicity of soil samples containing the highest concentration of La and Ce (200 mg/kg) is observed. The latter may indicate the importance of considering the cytotoxicity of soils containing high lanthanides concentrations - in extraction and production areas and actively fertilized fields.

Stolbova V.V., Agapkina G.I., Kotelnikova A.D., Dogadova A.V., Abalymova A.A.

A design of a short-term experiment for determining the indices of the cyto- and genotoxicity of soils with hydrophobic organic pollutants has been developed using the Allium test and soil-plate method. A procedure of soil sample preparation, biotester material pretreatment, and the 120-h solid-phase phytotest procedure itself, as well as instrumentation for calculating the results of cytogenetic analysis, have been proposed. The technique has been tested for assessing the cyto(geno)toxicity of urbanozem containing persistent organic pollutants, as well as for the toxicometry of brown forest soil of oil production area.

Yudina A.V., Fomin D.S., Kotelnikova A.D., Milanovskii E.Y.

A review of approaches to particle-size and microaggregate-size distribution analyses applied in soil science is given. The concepts of the structural organization of soils, primary soil particles, elementary soil particles, and soil microaggregates are considered. Methodological problems, such as the preparation of soil samples for the analyses and interpretation and comparison of the results obtained by different methods, are discussed. The authors suggest the theoretical substantiation of differences between the notions of primary soil particles (soil building units) and elementary soil particles. Primary soil particles are individual mineral particles. Elementary soil particles are solid-phase products of pedogenesis represented by fragments of rocks and minerals and by organomineral and organic particles, all the components of which participate in chemical and physicochemical interactions. Special attention is paid to the existing classifications of soils according to their textures. It is suggested that the upper boundary of the clay fraction in the Russian classification should be shifted from 1 to 2 µm.

Xia Y., Gao T., Liu Y., Qi M., Zhu J., Tong H., Lv Y., Liu C.

Coal power plants annually generate quantities of byproducts that release environmentally hazardous heavy metals like Cd and Pb. Understanding the behavior and spatiotemporal impacts on soils of these releases is crucial for pollution control. This study investigated the concentrations and isotope ratios of Cd/Pb in combustion byproducts, depositions and soils collected from a coal-fired power plant or its surrounding area. The pulverized fuel ash (PFA) and desulfurized gypsum (DG) exhibited heavier Cd isotopes with Δ114Cd values of 0.304‰ and 0.269‰, respectively, while bottom ash (BA) showed lighter Cd isotopes (Δ114CdBA-coal = –0.078‰), compared to feed coal. We proposed a two-stage condensation process that governs the distribution of Cd/Pb, including accumulation on PFA and DG within electrostatic precipitators and desulfurization unit, as well as condensation onto fine particles upon release from the stack. Emissions from combustion and large-scale transport make a significant contribution to deposition, while the dispersion of Cd/Pb in deposition is primarily influenced by the prevailing wind patterns. However, the distribution of Cd/Pb in soils not only exhibit predominant wind control but is also potentially influenced by the resuspension of long-term storage byproducts. The power plant significantly contributes to soil in the NW–N–NE directions, even at a considerable distance (66%–79%), demonstrating its pervasive impact on remote regions along these orientations. Additionally, based on the vertical behavior in the profile, we have identified that Cd tends to migrate downward through leaching, while variations in Pb respond to the historical progression of dust removal.

Yu L., He A., Tian R., Liu X., Li H.

Li G., Zheng X., Zhang X., Zhu Y., Guo L., Mei J., Ge X., Li Z.

Jiang Y., Zhang D., Zhang S., Li T., Wang G., Xu X., Pu Y., Nengzi L.

The extensive mining of bastnasite (CeFCO3) has caused severe pollution of lanthanum (La), cerium (Ce), and fluorine (F) in the surrounding farmland soil, threatening the safety of the soil-plant system. However, the stress effects of the interaction among these three elements on the tolerance and accumulation traits of Brassica chinensis L. (B. chinensis) are unclear. In this study, the interaction mechanisms of these three pollutants regulating the growth characteristics, antioxidant capacity, and accumulation characteristics of B. chinensis was explored using pot experiments of La-Ce (LC), Ce-F (CF), La-F (LF), and La-Ce-F (LCF) interactions. The LC interaction pollution treatments at the element concentrations higher than those of LC3 showed significant impact (P < 0.05) on the plant growth. The order of tolerance in B. chinensis under four interaction treatments was La-F > Ce-F > La-Ce-F > La-Ce, which was supported by the integrated biomarker response (IBR) analysis. The synergistic effect of La and Ce in La-Ce experiment promoted these two elements in the plants, whereas the presence of F in CF, LF, and LCF combined pollution treatments inhibited the absorption of La and Ce. Moreover, under the interaction among three elements, the synergistic effect of La and Ce in LC treatment enhanced the biotranslocation factor (BTF) of both elements, reaching the highest levels of 0.36 and 0.40, respectively. The addition of F in CF (BTF of 0.3 and 0.15, respectively), LF (BTF of 0.25 and 0.15, respectively), and LCF (BTF of 0.21, 0.24, and 0.15, respectively) treatments reduced the BTF of La and Ce in the plants due to the formation of insoluble precipitates between F with La or Ce. In conclusion, the interaction between La and Ce could reduce the tolerance of B. chinensis, while the presence of F could enhance the plant resistance to both La and Ce.

Santos J., Neca I., Capitão A., Nogueira J., Santos J.A., Pinto E., Barreto A., Daniel-da-Silva A.L., Maria V.L.

Song A., Si Z., Xu D., Wei B., Wang E., Chong F., Fan F.

Loginova E., Proskurnin M.A., Schollbach K., Brouwers H.J.

The water-based cooldown process (quenching) of Municipal Solid Waste Incineration Bottom Ash (MSWI BA) after incineration may adversely affect its leaching by forming a highly contaminated quench layer on BA particles. A model is proposed to rapidly estimate the leaching of potentially toxic elements from this MSWI BA quench layer. The semi-empirical model is based on calculating the quench-layer-to-core ratio for size fractions for the particle size range from < 63 µm to > 22.4 mm and building leaching profiles for each element. A particle core and quench layer get assigned contribution values based on only two experimental points: leaching data for the largest (the minimum role of the quench layer) and smallest (quench layer domination) fractions of the test sample. The calculated leaching profiles for major anions, alkali and alkaline-earth metals, and copper for a set of 18 narrow fractions demonstrate good leaching prediction, the underestimation error is –(10–20)%. For Ba, Sr, and Sb, the model provides a satisfactory error of 30% mainly due to contribution of core leaching; for Ni, Mn, and Zn, > 50%. Adequate modelling for most elements shows that, despite MSWI BA complexity, a simple semi-empirical model can predict the leaching behavior using a limited experimental dataset and supports the assumption of quench layer contribution to the total MSWI BA leaching.

Jiang Y., Zhang D., Zhang S., Li T., Wang G., Xu X., Pu Y., Nengzi L.

The extensive mining of bastnasite (CeFCO3) has caused pollution of lanthanum (La), cerium (Ce), and fuorine (F) in the surrounding farmland soil, severely threatening the safety of the soil ecosystem. However, the interaction effects of various chemical fractions of La, Ce, and F on the composition of microbial communities are unclear. In our study, high-throughput sequencing was performed based on the pot experiments of four types of combined pollution soils, i.e., La + Ce (LC), Ce + F (CF), La + F (LF), and La + Ce + F (LCF), and the pollution concentration ranges of these three elements of 20–240, 40–450, and 150–900 mg kg–1, respectively. The improved Tessier method was used to investigate the interaction effects of chemical fractions of these elements on the variations in the soil microbial compositions. The result showed the residual form of La (La_RES) displayed restraint on Abditibacteriota, leading to its undetected level in the highest concentration of LC-polluted soils, whereas promoted relative abundance of microbes (Planctomycetota, Elusimicrobiota, Gemmatimonadota, and Rozellomycota) by more than 80%; the exchangeable and organic-bound forms of Ce and F as well as the iron-manganese-bound and residual forms of F were identified as the stress factors for the sensitive bacteria (e.g., WS4, Elusimicrobiota, RCP2-54, and Monoblepharomycota) in CF-polluted soils; in LF-polluted soils, the water-soluble form of La showed the most toxic effect on RCP2-54, Nitrospirota, and FCPU426, leading to decreased relative abundance by more than 80%; while La_RES and iron-manganese-bound form of F were identified as the stress factors for the relative abundance of Nitrospirota, Elusimicrobiota, and GAL15, showing decline of more than 80% in LCF-polluted soils. Our study revealed both inhibition and promotion effects of the element interaction on the growth of microbial communities, providing a certain experimental evidence to support further exploration of the treatment of environmental pollution caused by these elements.

Zamulina I.V., Minkina T.M., Konstantinova E.Y., Nevidomskaya D.G., Litvinov Y.A., Mandzhieva S.S., Bauer T.V.

The physical, chemical, and physicochemical properties of soils and technogenic surface formations (TSFs) in coal dumps in the southeastern part of the Donetsk ridge within the Grushevsko-Nesvetaevskaya syncline (Rostov oblast), which differ in age, the lithological properties of overburden and host rocks composing them, and pyrogenic dynamics, have been studied. The main chemical, physical, and physicochemical characteristics of the soil properties of the studied areas have been established to assess the geoecological situation and patterns of the spread of potentially toxic substances and develop projects for the restoration of the areas. An unequal effect of soil formation factors has been revealed, which is expressed in a high variability and contrast of soil properties. Electron microscopic studies of technogenic samples have shown that the coarse microstructure was formed as a result of the impact of current compaction, cementation, and sintering processes on the rock. The wide range of pH variation (4.4–8.9) and salinity (up to 1.9% of solid residue) make the rocks unsuitable for biological reclamation.

Kastori R., Putnik-Delić M., Maksimović I.

Summary Rare earth elements (REEs) are a group of trace metals relatively abundant in the Earth’s crust. REEs are widely dispersed in small concentrations throughout the environment. These elements demonstrate similar physical and chemical properties. REEs have been widely used in various areas of industry, agriculture and medicine. China was the first country to commercially apply REE products as micro-fertilizers or growth simulators in agriculture. Although REEs are not essential for living organisms, they can influence their life processes. Results of recent investigations demonstrate that hormesis commonly occurs in a variety of plants and microorganisms in response to REEs. REEs affect the growth, reproduction and metabolism of microorganisms. Microorganisms are involved in all geochemical cycles of metals. They can produce various organic acids and other substances capable of mobilizing REEs in the soil, thereby promoting their uptake by plants. Metals can be bound by microorganisms through bioadsorption, bioaccumulation, and interactions with metabolic products, which may help in reducing metal leaching and increase their availability to plants. As a result, microorganisms can be used for the revitalization of habitats polluted by metals, primarily water. It was found that REEs can directly and indirectly affect several types of plant pathogens. REEs can control some phytopathogens directly by reducing their growth and virulence in host plants, while also eliciting disease resistance response in plants. The mechanisms by which REEs act against plant diseases result from complex interactions of many biotic and abiotic factors, which indicates the multifaceted nature of this phenomenon. Current evidence confirms that REEs can control pathogens under certain conditions. However, further studies investigating the mechanisms by which REEs control pathogens and performance of individual elements are necessary for their further application.

Kukowska S., Szewczuk-Karpisz K.

Abstract Purpose Both biochars (BCs) and zeolites (Zs) are defined as soil conditioners affecting various parameters of soil environment. In most cases, BCs and Zs are characterized by well-developed specific surface area, high porosity, and excellent sorption properties, which is highly helpful in soil reclamation or conditioning. This literature review compares impact of BCs and Zs on the physicochemical properties of various soils as well as economic aspects of their synthesis. Materials and methods The review was prepared based on the articles published in the last 5 years (2018–2023). The articles were selected from the ScienceDirect® database using the keywords: ‘biochar/zeolite impact on soil physicochemical properties’, ‘biochar/zeolite impact on water retention of soil’ and ‘biochar/zeolite economic aspects’. Results and discussion Based on the available data, it can be stated that both BCs and Zs have good sorptive properties, which usually contributes to better growth of crops. Comparing them and choosing which one is more promising depends on the specific purpose and type of soil to which they are to be applied. BCs usage contributes mainly to providing organic matter and improving soil structure, while Zs enhance soil water retention. The profitability of BCs/Zs production depends largely on the precursor as well as the synthesis method. Conclusions Due to the fact that impact of synthetic Zs on the soil environment is much less frequently investigated than that of BCs, the research using Zs and various soil types is especially needed. In some cases, it is advisable to apply biochar (BC) and zeolite (Z) simultaneously. Combinations of these materials may provide benefits in soil structure, water retention, and fertility. Such mixed techniques should be investigated in the near future.

Wang M., Wang Y., Wang L., Dai L., Zhang H., Liang T.

Gorniak L., Bucka S.L., Nasr B., Cao J., Hellmann S., Schäfer T., Westermann M., Bechwar J., Wegner C.

ABSTRACT Pseudomonas alloputida KT2440 is a ubiquitous, soil-dwelling bacterium that metabolizes recalcitrant and volatile carbon sources. The latter is utilized by two redundant, Ca- and lanthanide (Ln)-dependent, pyrroloquinoline quinone-dependent alcohol dehydrogenases (PQQ ADH), PedE and PedH, whose expression is regulated by Ln availability. P. alloputida KT2440 is the best-studied non-methylotroph in the context of Ln-utilization. Combined with microfluidic cultivation and single-cell elemental analysis, we studied the impact of light and heavy Ln on transcriptome-wide gene expression when growing P. alloputida KT2440 with 2-phenylethanol as the carbon and energy source. Light Ln (La, Ce, and Nd) and a mixture of light and heavy Ln (La, Ce, Nd, Dy, Ho, Er, and Yb) had a positive effect on growth, whereas supplementation with heavy Ln (Dy, Ho, Er, and Yb) exerted fitness costs. These were likely a consequence of mismetallation and non-utilizable Ln interfering with Ln sensing and signaling. The measured amounts of cell-associated Ln varied between elements. Gene expression analysis suggested that the Ln sensing and signaling machinery, the two-component system PedS2R2 and PedH, responds differently to (non-)utilizable Ln. We expanded our understanding of the lanthanide (Ln) switch in P. alloputida KT2440, demonstrating that it adjusts the levels of pedE and pedH transcripts based on the availability of Ln. We propose that the usability of Ln influences the bacterium’s response to different Ln elements. IMPORTANCE The Ln switch, the inverse regulation of Ca- and Ln-dependent PQQ ADH in response to Ln availability in organisms featuring both, is central to our understanding of Ln utilization. Although the preference of bacteria for light Ln is well known, the effect of different Ln, light and heavy, on growth and gene expression has rarely been studied. We provide evidence for a fine-tuning mechanism of Ca- and Ln-dependent PQQ ADH in P. alloputida KT2440 on the transcriptome level. The response to (non-)utilizable Ln differs depending on the element. Ln commonly co-occur in nature. Our findings underline that Ln-utilizing microbes must be able to discriminate between Ln to use them effectively. Considering the prevalence of Ln-dependent proteins in many microbial taxa, more work addressing Ln sensing and signaling is needed. Ln availability likely necessitates different adaptations regarding Ln utilization.

Kotelnikova A., Matveeva N., Borisochkina T., Rogova O., Volkov D.S., Savichev A.

Mineral fertilizers are one of the main important sources of elements in agricultural soils. The elements that enter the soil are involved in the transformation of soil organomineral compounds. Elemental analysis of soil granulo-densitometric fractions can be used to characterize these changes in detail. The study analyzes changes in macro- and microelement content in the organomineral fractions of soils under different cultivation. The clay-associated fraction with particle size LF > RF (As, B, Ba, Cr, Fe, Li, V, Zn, P, Mg, K, Na). The second group includes elements with the maximum concentration in the LF: LF > CF > RF (Co, Cu, Mn, Ni, Pb, Sr, Ca). It is shown that the application of mineral fertilizers leads to a redistribution of elements in the soil organomineral fractions, there is an imbalance in the contents and ratios of elements, which can be the cause of chemical degradation of agrocenosis. The main changes are related to the redistribution of trace elements: the elements added with fertilizers are more confined to the organic and transformed mineral components. This may contribute to an increase in the intensity of the mass flux of chemical elements in the soils of highly cultivated farmland. Changes in the "after-effect" group are smoother, indicating that the balance of elements in the soil is restored when fertilization ceases.

Ponomarev K.O., Dryagina A.A., Filimonenko E.A., Dimitryuk I.D.

To solve environmental problems and reduce economic costs, it is necessary to improve mineral fertilizer application systems by developing and introducing new technologies, including the use of biochars. Due to the lack of effective monitoring of soil changes, it is difficult to adjust fertilizer application rates. This determines the importance of information on the elemental composition of biochar ameliorants used to reduce the mobility of heavy metals in the soil. The use of biochar for remediation of contaminated soils is based on its ability to immobilize heavy metals and organic pollutants. In this work biochars were used, obtained by slow pyrolysis of organic materials of different types: pine sawdust, cattle manure, wheat straw, pine nut shells and brewer's grains. The effect of biochars (biochar application at a dose of 10 t ha−1) on the concentration of 13 elements (C, N, K, P, Mg, Ca, Fe, Mn, Pb, Ni, Cr, Cd, Co) in the soil was analyzed. The data collected after growing of spring wheat (Triticum aestivum L.) on the sod-podzolic soils were analyzed. It has been established that the heavy metals concentrations in the studied soils reclaimed with biochars are significantly lower than the maximum allowable concentrations for soils (MAC). The content of lead (Pb) in soils treated with biochars is 9 or more times lower than the MAC level, and biochar, produced from manure, significantly reduces the concentration of this metal in the soil.

Chebotarev N.T., Brovarova O.V.

In a long-term stationary field experiment on sod-podzolic soil, the effectiveness of organic and mineral fertilizers and their effect on soil properties, yield and quality of perennial grasses in the feed six-field crop rotation was established. It was determined that the combined use of fertilizers most effectively affected the increase in soil fertility and the productivity of the clover-timothy mixture. The content of humus increased by 0.4–0.6%, mobile phosphorus by 70–150 mg/kg, metabolic and hydrolytic acidity decreased. The complex application of fertilizers, especially in high doses, most significantly increased the yield and quality of perennial grasses.

Hua K., Wang T., Guo Z., Zhan L., He C., Wang D.

There are few assessments and predictions of the accumulation of potentially toxic elements (PTEs) under long-term application of different organic amendments. A 37-year fertilization experiment was conducted with mineral fertilizers alone or with wheat straw, pig and cattle manure to evaluate soil Cu, Zn, Cd and Pb pollution risks. Compared with mineral fertilizers, livestock manure application significantly (p < 0.05) increased soil total or available Cu, Zn and Cd accumulation rates and activities, thereby increasing soil Cu, Zn and Cd accumulation risk. Pig manure had a high risk of soil Cu and Zn pollution, whereas cattle manure had a high soil Cd pollution risk and high comprehensive pollution and potential ecological risk indexes. The recommended safe maximum values for pig and cattle manure application to guarantee 100 years of clean production are 6.2 and 40.4 t ha−1 year−1, respectively. Livestock manure should be applied long term in an appropriate amount to improve soil fertility and maintain soil health simultaneously. Crop straw incorporation is recommended as a clean practice maintaining crop yield without compromising soil health. In future, a Gaussian process regression model should be given priority to simulate and predict the PTE pollution risk after organic amendments are returned to croplands.

Semenov M.V., Ksenofontova N.A., Nikitin D.A., Tkhakakhova A.K., Lukin S.M.

Regular application of mineral and organic fertilizers is one of the essential components of agricultural intensification. The application of fertilizers leads to the artificial enrichment of the soil with readily available substrates and biophilic elements, which can have a significant impact on the soil and rhizosphere microbiome. We studied the impact of different fertilizer systems on the quantitative parameters of various microbial groups in a soddy-podzolic soil (Umbric Albic Retisol) and the rhizosphere of potatoes and barley. The study was carried out on a long-term field experiment, in which mineral (NPK), organic (manure), and mixed (NPK + manure) fertilizer systems had been applied since 1968. The application of organic fertilizers increased the microbial biomass carbon (Cmic) in the bulk soil and the rhizosphere by 25–100% compared to the soil without fertilizers, while the use of mineral fertilizers, on the contrary, decreased the microbial biomass by 10–30%. Basal respiration and metabolic quotient (qСО2) increased in the following order: without fertilizers < NPK < NPK + manure < manure. The gene copy numbers of bacteria, archaea, and fungi significantly increased (by 1.5–2.5 times) under organic fertilizers and decreased (2–2.5 times) under NPK. The fungi/bacteria ratios varied from 32 to 100 and from 0.10 to 0.92 according to luminescent microscopy and quantitative PCR methods, respectively. The lowest ratios were revealed for variants with NPK, and the highest fungi/bacteria ratios were in variants with manure. Thus, the applied doses of mineral fertilizers should be compensated by the addition of fresh organic matter in order to maintain the stability of the soil—microorganisms—plant system.

Borisochkina T.I., Kotelnikova A.D., Rogova O.B.

The analysis of publications on the mass transfer of chemical elements in agrocenosis in the soil – plant system was carried out. Methods for estimating the content of mobile forms of chemical compounds coming from the soil into plants are considered. The phenomena of antagonism and synergism are characterized, and the necessity to consider them while planning fertilizer application is indicated. It is shown that the phenomena of synergism and antagonism of elements can be used in agriculture to regulate the flow of heavy metals or radionuclides into agricultural products. A balance model for mass transfer of chemical elements in agrocenosis is analyzed. It is shown that the introduction of organic fertilizers in soil mostly leads to a positive balance of microelements in the agrosystem. To characterize the efficiency of fertilizer use an assessment of the balance of nutrients in the agrosystem is required. The removal of trace elements by agricultural crops increases with the use of mineral fertilizers in doses that are optimal for the cultivation of crops in the region. In some cases, the input of heavy metals with technogenic fallout may exceed the removal of metals by plants from the soil. It may cause the accumulation of metals in the system. In uncontaminated background areas, the levels of microelement intake from fertilizers and atmospheric fallout in agrocenoses are comparable.

Rogova O.B., Fedotov P.S., Dzhenloda R.K., Karandashev V.K.

Industrial and agricultural activities lead to the release of rare earth elements (REEs) in wastewater and aquatic ecosystems, and their accumulation in soils. However, the behavior of REEs in soils remains somewhat unclear. In the present work the fractionation and fixation of REEs in soddy-podzolic and chernozem soils spiked with La, Ce, and Nd chlorides were studied using dynamic (continuous flow) extraction, which allows natural conditions to be mimicked and artefacts to be minimised. The eluents applied are aimed to dissolve exchangeable, specifically sorbed, bound to Mn oxides, bound to metal–organic complexes, and bound to amorphous and poorly ordered Fe/Al oxides fractions extractable by 0.05 mol/L Ca(NO 3 ) 2 , 0.43 mol/L CH 3 COOH, 0.1 mol/L NH 2 OH·HCl, 0.1 mol/L K 4 P 2 O 7 at pH 11, and 0.1 mol/L (NH 4 ) 2 C 2 O 4 at pH 3.2, respectively. It is found that the fixations of added La, Ce, and Nd in the form of metal–organic complexes is predominant for both types of soils: 35%–38% in soddy-podzolic soil and 50%–79% in chernozem. The fixation of added elements in the first three fractions (exchangeable, specifically sorbed, and bound to Mn oxides) is significant for soddy-podzolic soil (5%–25%). For chernozem, the relative contents of added Ce and Nd in these fractions are nearly negligible. Only the content of exchangeable La is notable, about 5%. Adding any of three elements (La, Ce, or Nd) at the level of 100 mg/kg to an initial sample results in changing the fractionation and bioaccessibility of other REEs present in soil. Their contents increase in the first three fractions and decrease in fifth (oxalate extractable) fraction for both soddy-podzolic soil and chernozem. The main difference is the behavior of REEs in pyrophosphate extractable fraction. For soddy-podzolic soil, adding La, Ce, or Nd results in decreasing the contents of other REEs associated with organic matter. For chernozem, on the contrary, the contents of REEs in the form of metal–organic complexes slightly increase. These processes may be attributed to competitive binding of elements and soil properties; they must be taken into account when assessing the environmental risks of soil pollution with REEs. Adding of La, Ce or Nd results in changing of the fractionation and bioaccessibility of other REEs. • Dynamic extraction is applied to fractionation of rare earth elements (REEs) in soils. • Soddy-podzolic and chernozem soils spiked with La, Ce, and Nd chlorides are studied. • Fixations of added elements as metal–organic complexes is predominant for both soils. • Adding La, Ce, or Nd results in changing the fractionation of other REEs in soil.

Matveeva N.V., Milanovsky E.Y., Rogova O.B.

Soil samples and granulodensimetric fractions isolated from them ((silt particle size less than 1 µm, light fraction (LF) with a density of less than 2 g/cm3 and a fraction of the residues) of ordinary chernozem from experimental fields of the Kamennaya Steppe agricultural landscape of the Voronezh region were studied. The main differences between the variants of the experiment are introducing or stopping mineral fertilizers, and in the aftereffect of irrigation (13 years). There is an increase in the content of LF when using mineral fertilizers, as well as a change in the composition of sizedensity fractionations, expressed in different content of C and N and hydrophobic-hydrophilic components of humus substances (HS) of soils, silt and LF. The irrigation had practically no effect on the hydrophobichydrophilic composition of the initial soils, while the relative content of the hydrophilic components of the silt fraction of the soil increased, and the hydrophilic composition of HS LF decreased. The use of mineral fertilizers led to a significant variation in the degree of hydrophilicity of HS in silt and LF with a smaller change of this indicator for the HS of the soil as a whole. The abolition of fertilizers application, on the contrary, affected the hydrophobichydrophilic composition of the soil as a whole, and the composition of the soil silt and LF. The increase in the proportion of hydrophilic components in the composition of soil HS, as well as in the composition of HS silt and LF occurred simultaneously with an increase in the hydrophobicity of the surface of the solid phase of soil and with an increase in the carbon content in the soil, which indicates the stability of the system as a whole. Since the physical fractions of soils reacted more intensively to changes in the agrogenic load, compared with native soil samples, and changes in their qualitative composition were traced in two versions of the experiment, monitoring of hydrophobic-hydrophilic components of soil and soil granulodensimetric fractions is advisable to monitor and diagnose soil changes during agricultural use.

Lavrishchev A., Litvinovich A.V., Pavlova O.Y., Bure V.M., Schindler U., Saljnikov E.

This chapter presents the results of a long-term study on the dynamics of calcium and strontium in soil and plants when liming with chalk-containing strontium. The ameliorant used was a conversion chalk obtained as a by-product of the production of complex fertilisers and contained 1.5% stable strontium. Four experiments were conducted to study the behaviour of Ca and Sr in the soil–plant system on acid sod-podzolic soils (Umbric Albeluvisol Abruptic). The specific goal was to trace the entire pathway of Sr from the dissolution of the ameliorant, fixation of Sr in the soil-absorbing complex, migration along the profile and finally accumulation in plants of various biological families and in various plant organs. The results showed that the 1.5% Sr contained in the conversion chalk has a high chemical activity. The complete dissolution of high doses of the chalk was achieved in 3–4 years. The migratory mobility of strontium was determined in a series of column experiments. The amount of leached Sr was found to depend on its initial content in the soils, the humus content (HA1 fraction) and the volume of washing water. It was found that the first fraction of humic acids plays a leading role in the fixation of Sr in non-limed soil, which contained about 50% of the total soil strontium. The addition of the Sr-containing chalk increased the leaching of strontium, but Sr was not completely removed from soil after multiple washings. The results showed that the accumulation of Sr in the generative and vegetative organs of plant was controlled by the barrier and barrier-free mechanisms. Strontium-free conversion chalk can be a highly effective ameliorant for reducing waste dumps generated when processing raw phosphate rocks.

Romero-Freire A., González V., Groenenberg J.E., Qiu H., Auffan M., Cotelle S., Giamberini L.

A comprehensive study of the toxicity of lanthanides (LN) in relation to the media composition will enhance the prediction of their potential adverse effects for living organisms. Here we examined the effect of different media on the V. faba root elongation and on the cytotoxic (mitotic index) and the genotoxic (micronucleated cell number) effects from toxicity tests with Ce, Gd and Lu (100, 800 and 6400 μg L −1 ). Three different exposure media were selected: the standard Hoagland media (SH); an alternative SH, without phosphates (SH-P); and distilled water (DW). In the SH no cyto-genotoxic effects were observed and even, for low LN content, potential root elongation stimulation was reported. The absence of toxic effects was explained by a drastic decrease of the total dissolved LN concentration due to the presence of phosphates causing LN precipitation. In SH-P, LN remained largely soluble and inhibition of root elongation was observed mainly for the highest treatments. While in the tests done in DW, toxic effects were obtained for all treatments. Our results showed that in absence of phosphorous, LN appear mainly as free form and complexed in carbonates and sulphates, and can cause toxic effects, whereas toxicity is not expected when phosphorous is available in aquatic media. The highest LN root contents were observed for the tests using distilled water, possibly due to the absence of competition by Ca 2+ for uptake. The present work demonstrated that media composition has a great impact in assessing the ecotoxicology of lanthanides. • Lanthanide toxic effects are not expected when phosphorous is present in media. • In test solution without P, LN showed genotoxicity effects in V. faba roots. • Chemical speciation calculations are needed to predict realistic LN toxic effects. • LN has high affinity to complex with PO 4 , sulphates and carbonates.

Shtangeeva I., Niemelä M., Perämäki P.

Information about biological significance and possible phytotoxicity of many trace elements is still scarce. Bromine and neodymium are among the poorly investigated trace elements. In the research, greenhouse experiment was conducted to study the effects of bromide of neodymium on wheat seedlings grown in soil and water. The wheat seedlings were capable of accumulating large amounts of both Br and Nd. Compared to the soil-grown plants, the water-grown plants accumulated higher concentrations of the trace elements. The bioaccumulation of Br and Nd resulted in statistically significant variations in the concentrations of several elements. The concentrations of P, Cl, and Ca in roots and Cl in leaves of the plants grown in the contaminated water and the concentration of I in roots of the soil-grown plants decreased. In the water-grown seedlings, the concentrations of Na and P were higher and concentrations of Mg and K were lower than those in the seedlings grown in soil. In leaves of the plants grown in water, the concentration of Cl was lower than that in leaves of the soil-grown plants. In roots of the water-grown plants, the concentration of Zn was higher, and in leaves, it was lower compared with Zn content in roots and leaves of the plants grown in soil. The K/Na ratios were 4 (leaves) and 20 (roots) times higher in the soil-grown plants, while the Ca/Mg ratios were 8 – 19 times higher in the water-grown plants. Marked distinctions were also observed in relationships between different elements in the soil-grown and water-grown plants.

Bengtsson G.

Objectives: Anthropogenic exposures to rare earth elements are poorly known and there is limited information on their toxicity and ecotoxicity. At the same time, world production of rare earth elements has doubled every 15 years over the last half-century, and high environmental concentrations of gadolinium and lanthanum have already been found. The current review aims to give some estimates of overall exposures and an initial in-depth appraisal of thresholds for effects on agricultural soil. The results are envisaged to be used in initial assessments of agricultural soil where the natural concentrations have been anthropogenically enhanced. Methods: An extensive review has been made of available scientific literature. Criteria have been established for the selection and analysis of eligible research. For instance, only effects on soils with vegetation have been included in the assessment of biological effects. A species sensitivity distribution based on 25% inhibition of organism functions has been used to establish thresholds for effects on soil organisms. Results: Around the year 2000, mean anthropogenic contributions of lanthanides in European soil regions were at most a few per cent of the total soil content. Since then, they should have increased considerably. The proposed hypothetical threshold for agricultural soils is 1125 mg total rare earth element per kg of soil. This threshold is about 8 times the natural soil concentration. Conclusions: If this result holds up to scrutiny, it implies that general anthropogenic pollution by rare earth elements will not be a threat to agricultural sustainability for the coming generation. A preliminary assessment suggests that this threshold would also protect humans from adverse effects due to secondary exposure.

Xie K., Cakmak I., Wang S., Zhang F., Guo S.

Magnesium (Mg) affects various critical physiological and biochemical processes in higher plants, and its deficiency impedes plant growth and development. Although potassium (K)-induced Mg deficiency in agricultural production is widespread, the specific relationship of K with Mg and especially its competitive nature is poorly understood. This review summarizes current knowledge on the interactions between K and Mg with respect to their root uptake, root-to-shoot translocation and distribution in plants. Their synergistic effects on certain physiological functions are also described. The antagonistic effect of K on Mg is stronger than that of Mg on K in root absorption and transport within plants, indicating that the balanced use of K and Mg fertilizers is necessary for sustaining high plant-available Mg and alleviating K-induced Mg deficiency, especially in plant species with high K demand or in high-available-K soil. The relationship between Mg and K in plant tissues may be antagonistic or synergistic depending on plant species, cell type, leaf age, source- and sink organs. There are synergistic effects of K and Mg on photosynthesis, carbohydrate transport and allocation, nitrogen metabolism, and turgor regulation. Definition of optimal K/Mg ratios for soils and plant tissues is desirable for maintaining proper nutritional status in plants, leading to a physiological state supporting crop production. Future research should concentrate on identifying the physiological and molecular mechanisms underlying the interactions between K and Mg in a given physiological function.

Matveeva N.V., Milanovsky E.Y., Rogova O.B.

Soil samples and physical size-density fractions isolated from them (silt particle size less than 1 µm, light fraction (LF) with a density of less than 2 g/cm3 and a fraction of the residue) of ordinary chernozem were studied in three contrasting variants of the experimental fields of the Kamennaya Steppe agrolandscape of the Voronezh region: mowed steppe, long-term permanent bare fallow and permanent corn – the main differences of which are in tillage (cultivated and not cultivated lands) and in the supply/absence of plant residues and root secretions. The LF content changes in the series: “mowed steppe” > “permanent corn” > “permanent bare fallow”, which corresponds to the direction of changes in the total carbon content of the soil and a decrease in the value of the contact angle of wetting (CA) of the surface of the solid phase of the studied chernozems. The determination of the total C and N content revealed the change in the qualitative and quantitative composition of the size-density fractions for different land use cases. Chromatographic fractionation of alkaline extractions of humus substances (HS) of chernozem samples and size-density fractions revealed an increase in the degree of hydrophilicity of HS while simultaneously increasing the hydrophobicity of the solid phase surface and the carbon content in the soil. HS of LF of the “mowed steppe” turned out to be by 63% more hydrophilic than HS of LF of “permanent bare fallow” and by 47% more hydrophilic than HS of LF of “permanent corn”. While the hydrophilicity of the HS silt differed by 16 and 27%, respectively. The hydrophilicity of the HS of the original soil in the plot of the “mowed steppe” was by 41% higher than the hydrophilicity of the HS in the soil in the plot of “permanent bare fallow” and by 24% higher than in the soil of the plot of “permanent corn”. In addition, changes in the hydrophilicity of HS of size-density fractions are more intense than the HS of the soil, so the change in the degree of hydrophilicity of HS of size-density fractions is an indicator of soil degradation under different agrogenic pressue.

Hu X., Huang X., Zhao H., Liu F., Wang L., Zhao X., Gao P., Li X., Ji P.

New modified fly ash is an excellent amendment for stabilising soil heavy metals. In this study, new modified fly ash and an organic fertilizer were employed for soil heavy metal remediation. The applications of the organic fertilizer to the soil can lead to buffering of the alkalinity of new modified fly ash. The results of mixture treatments were better than those of the application of only new modified fly ash for free heavy metal reduction. Among them, the treatment of 0.4% organic fertilizer and 4% new modified fly ash led to a reduction in the Mehlich-3 extractable cadmium (Cd), copper (Cu), and lead (Pb) of 49.0%, 53.5%, 67.83%, respectively, but the treatment of 4% new modified fly ash led to the reduction of 47.6%, 48.09%, and 62.73%, respectively. By the end of the experiment, the urease and alkaline phosphatase activities in the soil had considerably improved, and those activities in the soil treated with 0.4% organic fertilizer and 4% new modified fly ash increased by 2.21 and 3.2 times, respectively, compared with that in the control treatment soil. Similarly, organic matter and available N, P, and K considerably improved with the addition of the organic fertilizer. This study demonstrated the importance of the application of organic fertilizers and new modified fly ash mixture for the remediation of HM-contaminated soils and the improvement of soil quality.

Li Y., Padoan E., Ajmone-Marsan F.

In the last decade, extensive studies have been conducted to quantify the influence of different factors on potentially toxic elements (PTE) bioaccessibility in soil; one of the most important is soil size fraction. However, there is no agreement about the size fraction and the methods to investigate bioaccessibility, as very few review articles are available on soil PTE bioaccessibility and none addressed the influence of particle size on PTE bioaccessibility. This study provides a review of the relations between PTE bioaccessibility and soil particle size fractions. The available research indicates that PTE bioaccessibility distribution across different size fractions varies widely in soil, but a general trend of higher bioaccessibility in finer size fraction was found. The different elements may exhibit different relationships between bioaccessibility and soil size fraction and, in some cases, their bioaccessibility seems to be more related to the source and to the chemico-physical form of PTE in soil. Often, soil pollution and related health risk are assessed based on PTE total concentration rather than their bioaccessible fraction, but from the available studies it appears that consensus must be pursued on the methods to determine PTE bioaccessibility in the fine soil size fractions to achieve a more accurate human health risk assessment. ● Evidence indicates the importance of soil size fractions in PTE bioaccessibility. ● Pollutant bioaccessibility on a given soil size fraction is PTE dependent. ● A trend of higher PTE bioaccessibility in finer than in coarser fractions was found. ● Contaminant source and its physico-chemical form appear as very important factors. ● Further studies should pay attention to soil size fractions and related health risk.