Anion Composition Research Articles

Synthesis and Analysis of Ionic Liquid As Additive for Li-Ion Battery Electrolyte

Lithium ion batteries are promising power sources for various applications such as portable electronics and electrical vehicles, due to their high specific energy density and long cycle life. As one key component of lithium ion battery, the electrolyte should allow lithium ion transport but prevent electron conduction. One big challenge of lithium ion battery is that the high voltage and high current in the charge process can cause self-decomposition of the electrolyte, leading to combustion of the battery. In order to solve the combustion problem in the fast charge process, new electrolyte materials with high ionic conductivity and good chemical stability are urgently needed.Ionic liquid is usually organic salt consisting of anion and cation with low vapor pressure, high boiling point, high ionic conductivity, large specific heat capacity, and non-flammable characteristics. Ionic liquid is aqueous at or near the room temperature. The features of ionic liquid such as the high heat resistance and wide liquid temperature range make it a promising electrolyte material for lithium ion battery.This project aims at tailoring the suitable structure of ionic liquid as the additive for lithium ion battery. Our ionic liquid is a designed composition of anion of TFSI as SEI forming additive and imidazole based cation. A two-step process has been developed for synthesizing ionic liquid. The physical and chemical properties of the ionic liquid were measured to evaluate the feasibility of applying ionic liquid to lithium ion battery.Both the density and the viscosity of the ionic liquid are measured at different temperatures. The density was found to decrease linearly with temperature in both single and binary system. The determined negative excess molar volume of ethyl acetate and ionic liquid system is relative to the interaction between different molecules. The viscosity of the analyzed electrolyte solvent was found to decrease linearly with increasing temperature. Arrhenius-like law was found to be able to fit the measured data well. The fitting parameters were able to predict viscosity at different temperature.The conductivity of the whole electrolyte system and compatibility with the active materials will be tested and discussed in the next study.

Engineering perovskites with anions

Solar Cells The bandgap of the perovskite top layer in tandem silicon solar cells must be tuned to ∼1.7 electron volts. Usually, the cation composition is varied because the bromine-rich anion compositions with wide bandgaps are structurally unstable. Kim et al. show that by using phenethylammonium as a two-dimensional additive, along with iodine and thiocyanate, bromine-rich perovskite films can be stabilized. A tandem silicon cell delivered >26% certified power conversion efficiency, and a perovskite device maintained 80% of its initial power conversion efficiency of >20% after 1000 hours under illumination. Science , this issue p. [155][1] [1]: /lookup/doi/10.1126/science.aba3433

Optical and structural investigations on titanium oxynitride films for visible-UV photocatalytic applications

We report on the epitaxial growth of titanium oxynitride (TiOxNy) films on α-Al2O3 (0001) substrates by using a pulsed-laser deposition technique and their optical properties. Using TiN as a solid source, N content (y) in the films was tuned by changing the partial pressure of O2 gas. The crystalline phase was found to evolve up to y ≈ 0.4 either from rock-salt type or from rutile-type structures. The optical absorption spectra of the films had two distinct components in regions of 0.44–2.4 eV and 2.4–6 eV, which arise from d–d and charge-transfer transitions, respectively. The former transition decreased with decreasing y and vanished at y ≈ 0.26, where a fundamental absorption edge due to the latter transition was found to be 2.4 eV. The results demonstrate a range of anion compositions in the TiOxNy being suitable for visible-light harvesting applications.

Functional Groups of Bacteria and Their Involvement in Geochemical Processes in Microbial Communities of Mineral Sources in Sakhalin Island (Far East, Russia)

The chemical composition of mineral waters as well as the diversity, quantity and distribution peculiarities of different functional groups of bacteria in microbial mats in Sakhalin mineral springs was studied. The prevalence of sodium cations in the composition of bicarbonate anions and chloride ions was noticed. The studied waters were substantially enriched with silicone, iodine, boron, iron and strontium. It was established that the main morphogenic bacteria in the mats of cold springs were the colorless sulfur bacteria Thiotrix sp. The microbial mats formed at the outlets of Sakhalin mineral springs contain a high quantity of different functional bacteria groups that play an important role in the geochemical cycles of carbon, nitrogen, sulfur, iron and manganese. Prevalence of bacteria of sulfur and carbon cycles is a peculiarity of microbial mats in Antonovsky and Nevelsky mineral waters. The important role of sulfur cycle bacteria is confirmed by high quantities of thionic, sulfate-reducing bacteria and colorless sulfur bacteria. The mat of Alexandrovsky thermal spring contains a high amount of bacteria of carbon and nitrogen geochemical cycles; an important role of these microorganisms in mat’s functioning is shown. Pure bacterial cultures were isolated; they mostly include gram-positive, spore-forming motile rods Bacillus sp.

Influence of Nitrogen Content on Persistent Photoconductivity in Zinc Oxynitride Thin Film Transistors

In this work, the influence of anion composition on the photoresponse characteristics of zinc oxynitride thin film transistors is investigated and compared directly to conventional In-Ga-Zn-O TFTs. Increasing the ratio of N to (N+O) led to higher field effect mobility and improved subthreshold swing. The subgap density of states extracted by monochromatic photonic capacitance-voltage measurement indicated that the nitrogen-related defect states, such as nitrogen vacancies, increased with increasing nitrogen gas flow rate. Furthermore, the photoconductivity mechanism of ZnON TFTs is discussed in detail.

Efficient, stable silicon tandem cells enabled by anion-engineered wide-bandgap perovskites.

Maximizing the power conversion efficiency (PCE) of perovskite/silicon tandem solar cells that can exceed the Shockley-Queisser single-cell limit requires a high-performing, stable perovskite top cell with a wide bandgap. We developed a stable perovskite solar cell with a bandgap of ~1.7 electron volts that retained more than 80% of its initial PCE of 20.7% after 1000 hours of continuous illumination. Anion engineering of phenethylammonium-based two-dimensional (2D) additives was critical for controlling the structural and electrical properties of the 2D passivation layers based on a lead iodide framework. The high PCE of 26.7% of a monolithic two-terminal wide-bandgap perovskite/silicon tandem solar cell was made possible by the ideal combination of spectral responses of the top and bottom cells.

The research on riverine hydrochemistry and controlling factors in the Danjiangkou Reservoir

The riverine dissolved solids, indicating the environment information in watersheds, generally originated from rock weathering, soil erosion and anthropogenic inputs etc. The hydro-chemical characteristics of Danjiangkou Reservoir and its influencing factors after the implementation of South-to-North Water Transfer Project were discussed, based on water quality investigation from October 2017 to July 2018. The water in Danjiangkou Reservoir was moderately alkalescent, with pH ranging from 7.02 to 8.58. The dissolved oxygen, oxidation–reduction potential and conductivity had showed obviously seasonal variations. The total dissolved solids average was 176.14 ± 15.98 mg/L, which was much higher than that average of main rivers in the world. The Ca2+ concentration was the highest among cationic composition, accounting for 50% to 70% of total cations. Among the anion composition, $${\text{HCO}}_{3}^{ - }$$ concentrations accounted for more than 70% in most sampling points. Researches showed that carbonates weathering had contributed 70.1% of chemical compositions and mainly controlled the hydro-chemical characteristics. Some riverine ions were affected by silicates weathering. The 17.75% of chemical species were released into rivers by anthropogenic inputs, which proved to be the important factors affecting riverine chemical characteristics, especially in the wet season.

Characteristics and sources of water-soluble ionic associated with PM2.5 particles and cytotoxicity effects using MTT assay in Tehran, Iran

Air pollution with its harmful effects has become the most important environmental problem in Tehran city, Iran. The main aim of the present study was to investigate the physical and chemical characteristics of particulate matters (PM) such as scanning electron microscopy (SEM), coupled with energy dispersive X-ray analysis (SEM-EDX), dynamic light scattering measurement (DLS), and Thermal gravimetric analyses (TGA) analysis and determine the ionic composition of cations (Na+, K+, Mg2+, and Ca2+) and anions (Cl−, SO42−, NO3−, and F−), and principal component analysis (PCA) analysis in different stations, during four types of seasons in 2016. The cell viability of human A549 cells of water-soluble and organic extract from PM2.5 particles was tested using the MTT assay. The results showed that the SEM image of PM2.5 particles was a size range of 1.44–2.03 μm and EDX analysis shows that the presence of Si, Ca, Na, and Mg with a higher amount in the structure of PM2.5 particles. The total concentration of ions in PM2.5 for urban stations during spring, summer, autumn, and winter was 7.01 ± 3.2 μg/m3, 6.86 ± 2.85 μg/m3, 7.46 ± 4.85 μg/m3, 8.49 ± 4.1 μg/m3, respectively. The seasonal concentrations of ionic compounds for urban and traffic stations were higher in winter and autumn than in spring and summer. The highest positive correlation for PM2.5 was identified between ionic species in the traffic station, NO3-SO4 (R = 0.93), Cl-SO4 (R = 0.61), Cl-NO3 (R = 0.67), MgCa (R = 0.67), NaMg (R = 0.68), and KMg (R = 0.57). Toxicity studies showed that a wide range of cytotoxicity values were obtained for organic and water-soluble extractable PM2.5, from 45 to 91% in summer and 36 to 70% in winter, for the three stations.

The Impact of Molecular Oxygen on Anion Composition in a Hazy Archean Earth Atmosphere.

Atmospheric organic hazes are common in planetary bodies in our solar system and likely exoplanet atmospheres as well. In addition, geochemical data support the existence of an organic haze in the early Earth's atmosphere. Much of what is known about organic haze formation derives from studies of Saturn's moon Titan. It is believed that on Titan ions play an important role in haze formation. It is possible, by using Titan as an analog for the Archean Earth, to consider that an Archean haze could have formed by similar processes. Here, we examine the anion chemistry that occurs during laboratory simulations of early Earth haze formation and measure the composition of gaseous anions as a function of O2 mixing ratio. Gaseous anion composition and relative abundances are measured by an atmospheric pressure interface time-of-flight mass spectrometer and are compared to previous photochemical haze mass loading measurements. Numerous anions are observed spanning from mass-to-charge ratio 26 to 246, with a majority of the identified anions containing carbon, hydrogen, nitrogen, and/or oxygen. A shift in the anion composition occurs with increasing the precursor O2 mixing ratio. With 0-20 ppmv O2 in CH4/CO2/N2 mixtures, ions contain mostly organic nitrogen, with CNO- being the most intense ion peak. As the precursor O2 is increased to 200 and 2000 ppmv, inorganic nitrogen ions become the dominant chemical group, with NO3- having the most intense ion signal. The clear shift in the ionic composition could be indicative of a modification to the gas-phase chemistry that occurs in the transition from an anoxic atmosphere to an oxygen-containing atmosphere, with potential astrobiological significance.

Kainotropite, Cu4Fe3+O2(V2O7)(VO4), a new mineral with a complex vanadate anion from fumarolic exhalations of the Tolbachik volcano, Kamchatka, Russia

ABSTRACT The new mineral kainotropite Cu4Fe3+O2(V2O7)(VO4) was found in sublimates of fumaroles related to the Tolbachik volcano, Kamchatka, Russia. The holotype specimen originates from the Yadovitaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption; associated minerals are hematite, langbeinite, calciolangbeinite, tenorite, piypite, lyonsite, rutile, pseudobrookite, sanidine, and lammerite. In paleo-fumarolic deposits of Mountain 1004 kainotropite is associated with diopside and hematite. It forms prismatic crystals up to 0.2 × 0.2 × 0.5 mm3, isolated or combined in clusters up to 0.7 mm across. Kainotropite is iron-black to reddish-black, with semi-metallic luster. Dcalc is 4.10 g/cm3. In reflected light, kainotropite is grey, weakly anisotropic. The reflectance values [Rmax–Rmin,% (λ, nm)] are: 18.3–17.3 (470), 17.3–16.3 (546), 16.9–15.7 (589), 16.3–15.1 (650). The chemical composition of the holotype sample (wt.%, electron microprobe) is: CuO 46.69, Al2O3 1.40, Fe2O3 10.04, TiO2 0.32, V2O5 37.58, As2O5 2.55, MoO3 0.76, total 99.34. The empirical formula, based on 13 O apfu, is: Cu3.96Fe3+0.85Al0.19Ti0.03(V2.78As0.15Mo0.04)Σ2.97O13. Kainotropite is orthorhombic, Pnma, a = 14.139(2), b = 6.7102(7), c = 11.4177(15) Å, V = 1083.3(2) Å3, and Z = 4. The strongest reflections of the powder XRD pattern [d,Å(I)(hkl)] are: 8.89(100)(101), 5.728(33)(002), 3.698(35)(212), 3.357(52)(020,203), 3.034(77)(220), 2.968(60)(303), and 2.655(27)(321,204). The crystal structure was solved from single-crystal XRD data, R = 0.085. Kainotropite represents a novel structure type. Cu2+ polyhedra (distorted tetragonal pyramids and strongly distorted octahedra) and Fe3+ octahedra are connected via common edges to form zigzag ribbons. Adjacent ribbons are connected by both V2O7 and VO4 groups (isolated from each other) to form a heteropolyhedral pseudo-framework. The name kainotropite is derived from the Greek word καινóτρoπoς, unusual, in allusion to its uncommon (for natural vanadates) anionic composition: it is the first mineral containing both pyrovanadate (V2O7)4– and orthovanadate (VO4)3– anions.

Development of Approaches to the Formation of Platinum Sites with Desired Properties Using Layer-Structured Supports

Specific properties of layered double hydroxides (LDHs), directions of their use as supports and support precursors for synthesis of catalysts, and advantages of using such catalysts for various reactions were considered. The possibility to vary the chemical composition of LDHs (cationic layers, interlayer space) without destroying the structure of the material allows tuning their adsorption and acid-base properties and selectively realizing various mechanisms of anchoring the active component precursor toward preparing highly dispersed and stable supported catalysts. Approaches to the formation of supported platinum particles with desired properties through changing the anionic and cationic compositions of LDHs were proposed for the Pt/MgAl(M)-LDH system taken as an example.

Multinary Halogenido Bismuthates beyond the Double Perovskite Motif.

Both lead halide perovskites and bismuth-based double perovskites have generated intense research interest in the past few years. There is, however, a broader class of bismuthates that transcends the double perovskite motif. These multinary halogenido bismuthates remain severely underexplored and offer rich research opportunities with regard to new structure motifs and material properties. In this Forum Article, we want to provide both an overview of the work on this class of compounds that has been done in the last 2 decades and an example of how new compounds can be obtained and which challenges are associated with their synthesis. We present the synthesis and characterization of six new bismuthates, (PBz4)3Bi3Br12 (1) (PBz4)2(MeCN)2Cu2Bi2Br10 (2), (PBz4)Bi2I7 (3), (PBz4)2(MeCN)2Cu2Bi2I10 (4), (PBz4)2AgBi2I9 (5), and (PBz4)3Bi3I12·C4H8O (6), based on the tetrabenzylphosphonium cation PBz4+. 2, 4, and 5 represent new multinary bismuthates, featuring both a familiar anion motif with a new element combination in 2 and a previously unknown anionic chain in 5. We use this series of compounds to further elucidate the influence of the anion composition, nuclearity, and dimensionality on the compounds' onset of absorption and discover that an additional factor, the connectivity between coordination polyhedra, plays a role in copper iodido bismuthates.

Fabrication and Characterization of Polysaccharide Composite Films from Polyion Complex Particles.

Biomaterials made of natural polysaccharides have attracted much attention due to the fact of their excellent properties, such as high biocompatibility and biodegradability, and their specific biological functions based on their chemical structures. This study demonstrates that polysaccharide composite films can be fabricated from polyion complexes (PICs) with their particles used as building components. Dispersion of PIC particles prepared by mixing, centrifugation, and re-dispersion of dilute solutions of cationic and anionic polysaccharides were cast, dried, and formed into films several micrometers thick. These films were homogenous and water insoluble. It was revealed that the component anionic polysaccharides affected the film’s properties such as the swelling behavior and mechanical characteristics. Adhesion of NIH3T3 cells (integrin: high, CD44: lack or weak) and A549 cells (integrin: high, CD44: high) to the composite films were examined. Both NIH3T3 and A549 cells adhered to heparin/chitosan (HEP/CHI) film because HEP has an affinity for integrin through fibronectin. However, A549 cells adhered to chondroitin sulfate (CS)/CHI and hyaluronic acid (HYA)/CHI films, whereas NIH3T3 cells did not, because both CS and HYA have affinity for CD44. These results indicated that the biological functions of anionic polysaccharides were maintained on the surface of the composite films. It was also possible to fabricate films composed of three kinds of polysaccharides: one cationic polysaccharide and two kinds of anionic polysaccharides. These results show that the properties of films composed of three kinds of polysaccharides may be controllable depending on the anionic polysaccharide composition rates.

Membrane Association of the Intrinsically Disordered N-Terminal Region of ChiZ

Multiple proteins including ChiZ that comprise the cell division machinery (divisome) of Mycobacterium tuberculosis (Mtb; causative agent of tuberculosis) contain disordered regions, often enriched in cationic residues. Given the highly anionic lipid composition, membrane association of Mtb divisome proteins may be expected to play important roles in cell division, a process with implications for both pathogenesis and drug resistance. Here we combined NMR spectroscopy and molecular dynamics (MD) simulations to characterize the membrane association of ChiZ. The 165-residue ChiZ consists of a disordered cytoplasmic N-terminal region (NT; residues 1-64), a transmembrane helix (TM; residues 64-86), and a periplasmic LysM domain (residues 114-165). 1H-15N HSQC spectra showed that NT associated only with highly anionic membranes (7:3 POPG/POPE liposomes), with terminal residues remaining dynamic. 13C-13C INEPT and CP experiments further revealed that most residues, but not some arginines, were dynamic when NT was membrane-bound. PRE experiments indicated that arginines strongly interacted with lipids, both in NT and in full-length ChiZ. Extensive MD simulations found that not all arginines interacted with membranes to the same extent. NT was anchored to membranes in the midsection by Arg37, forming on average 0.93 hydrogen bonds (HBs); arginines forming a least 0.5 HBs extended upstream to Arg33 and downstream to Arg49. When tethered to membranes by TM, the above pattern was largely preserved, except now the TM-proximal Arg62 formed 1.47 HBs. Overall, the second half of NT is more adaptive to membrane association, becoming more compact, whereas the first half is more autonomous. This difference is largely attributable to the exclusive occurrence of anionic residues in the first half of the NT sequence. These insights into sequence-conformation-interaction relations have broad significance, as numerous membrane proteins may involve membrane association of disordered regions in their functional processes.

Electrochemical removal of nitrate from high salinity waste stream in a continuous flow reactor

Nitrate contamination of groundwater continues to be a major concern worldwide. Nitrate removal from groundwater by Donnan dialysis generates a purified water stream and a contaminated waste stream of high salinity NaCl or Na2SO4 containing only the anionic composition of the treated groundwater. The objective of this research was to study the electrochemical removal of nitrate from a high salinity Donnan dialysis waste stream in a continuous flow system using Cu-DSA electrodes. The difference between the two high saline solutions were manifested in the nitrate removal efficiencies and ammonia production. Nitrate removal from Donnan dialysis waste, at an optimal 90 min residence time, resulted in a maximum removal of 63 % in high salinity Na2SO4 and 44 % in high salinity NaCl. Ammonia formation was suppressed by NaCl while 70 % of the nitrogen was reduced to ammonia in the high salinity Na2SO4 solution. The anionic composition had no effect of nitrate removal in high salinity Na2SO4. Yet, in high salinity NaCl solution bicarbonate inhibited the nitrate reduction, and sulfate facilitated the removal of the nitrate. Periodic current reversal, applied to overcome cathodic deactivation, resulted in copper dissolution. Higher salinities led to less cathodic dissolution in both high saline solutions. The results of this study render support to the viability of nitrate removal from high salinity stream by a continuous flow electrochemical cell.

Assessment of the influence of additives in concrete by the Raman spectroscopy method

The effect of nano SiC additives with a particle size less than 50 nm, carbon black with a specific surface of about 80 m2/g, SiO2 and Al2O3 zol, AlCl3, FeCl3 solutions on the composition of silicon-oxygen anions in the pure C-S-H phase and hydrated cement was studied. The mixture was pressed at a specific pressure of 100 MPa and tested for compressive strength after 1, 7 and 28 days of normal aging. The Raman spectroscopy method was used to determine the composition of silicon-oxygen anions (SOA) in the C-S-H phase of cement and compared it with the strength of the stone, as well as with the SOA composition in the pure C-S-H phase. It was found that the initial powder of the C-S-H phase mainly contains isolated Q0 and terminal Q1 tetrahedra [SiO4]. Pressing the powder at 100 MPa leads to the advanced formation of chains of cross-linking Q2 and Q3 tetrahedra. The addition of silica to C-S-H promotes maximum chain formation from Q2. The Raman spectrum of C-S-H with silica zol is identical to the spectrum of hydrated cement. Iron chloride prevents the formation of extended chains of silicon-oxygen tetrahedrons. Carbon-containing nano-additives significantly alter the spectrum of C-S-H calcium substructures.

Minerals of the System Stichtite–Pyroaurite–Iowaite–Woodallite from Serpentinites of the Terekta Ridge (Gorny Altai, Russia)

Abstract —Hydrotalcite supergroup minerals stichtite, pyroaurite, iowaite, and woodallite form a complex solid-solution system at the Kyzyl-Uyuk locality (Terekta Ridge, Gorny Altai, Russia). The diversity of these minerals is due to: (1) subdivision by anionic interlayer composition into carbonate (stichtite and pyroaurite) and chloride (iowaite and woodallite) species and (2) isomorphism of M3+ cations, mainly between Cr- (stichtite and woodallite) and Fe3+-dominant species (pyroaurite and iowaite), with a quantitative predominance of stichtite and iowaite. Most of the studied samples correspond to stichtite and woodallite with high Fe3+ contents or pyroaurite and iowaite with high Cr3+ contents. According to vibrational (IR and Raman) spectroscopy data, the interlayer Cl– is partially substituted by OH– rather than CO32- groups. We suppose that the presence/absence of a band in the region 1400–1350 cm–1 in the Raman spectra of stichtite can be explained by the local distortion of triangular CO3 groups. Stichtite and iowaite occur here in polytypic modifications 3R and 2H that are the most widespread for the hydrotalcite supergroup iowaite and stichtite is 2:1. For both minerals, the polytype 3R strongly dominates over 2H. The lowest 3R/2H ratio determined for the Terekta iowaite and stichtite is 2:1. The Altai stichtite is close in 3R/2H to the stichtite from Tasmania (Australia) and differs significantly from that in Transvaal samples (South Africa).

Solubility and diffusivity of CO2 in ionic polyimides with [C(CN)3]x[oAc]1−x anion composition

Recently, mixtures of ionic liquids (ILs) containing acetate [oAc−] and tricyanomethanide [C(CN)3−] anions have demonstrated promising characteristics as solvents and as CO2 adsorbents. The anion composition can be optimized to obtain a significant improvement in the diffusivity while only slightly decreasing the solubility. Here, we explore a similar investigation applied to an ionic polyimide (i-PI) material in order to understand the molecular-level kinetic and thermodynamic characteristics that emerge when a polymeric material is used instead. The i-PI systems studied are part of an emerging class of “high-performance” ionene polymers that hold significant potential for applications in gas separation membranes. Here, neat i-PI systems with the two counter anions, [oAc−] and [C(CN)3−], at varying concentrations are modeled by a combination of molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) simulations. Higher concentrations of [C(CN)3−] are predicted to improve CO2 diffusion, similar to the pure IL performance, while solubility remains relatively unchanged. The structural characteristics of the i-PI systems provide detailed insight into the effect that the anions have on the adsorption properties. The solubility is weakly related to the theoretical surface area, and the diffusivity is moderately correlated to the fractional free volume (FFV). Overall, the combination of different anions is predicted to be a viable strategy for improving the diffusivity throughout i-PI materials, but the behavior of pure ILs cannot be simply extrapolated to ion behavior in membranes.

Who lives in a pine tree well? Community Associations Salvio tomentosae-Pinetum pallasianae Korzh. 1984 on gradients of environmental factors

Goal. To analyze the current state of the Crimean pine forest communities and give a forecast of possible changes in the trend of global climatic changes. Materials and methods. The object of research is phytocenosis (nomenclature description of the association), described in the Yalta Amphitheater at an altitude of 1000 m above sea level. The packing density of species on gradients of environmental factors was calculated using the original Pover program. Unified information on the distribution of plant species along gradients of factor conditions and resource factors (illumination-shading, thermal mode, cryo mode, humidification, moisture variability, substrate acidity, salt regime (anionic composition), carbonate content, nitrogen content, particle size distribution (mechanical) composition (porosity) of the substrate) was obtained from the Ecodata database. Results. The community will become most vulnerable when the cenotic factor “lighting-shading” changes with a significant decrease in the amount of light entering the day surface. Succession rearrangements of phytocenoses can cause an increase in the average July temperature by 2.4 degrees, exceeding the tolerance level for a given phytocenosis. Other environmental factors and resource factors have a significant margin of safety.

The Impact of Fires on the Properties of Steppe Soils in the Trans-Ural Region

The impact of fires that happened in different times (1 week, 1.5 and 2 months, 1 and 2 years ago) on the properties of southern (textural-carbonate) chernozems was studied in the Trans-Ural steppe (Bashkortostan Republic and Chelyabinsk oblast, Russia). The topsoil horizons (0–5, 5–10, and 10–20 cm) were sampled in summer 2018. After the fires, the carbon content in the layer 0–5 cm increased by 8.7–12.0% relative to the initial content, and the contents of major nutrients (nitrogen, phosphorus, and potassium) sharply increased and remained at this level for two years. The pH values in the humus horizon after the fire increased by 1.5 pH units. The contents of exchangeable calcium, potassium, and sodium correlated with pH (r = 0.57, 0.58, and 0.65, respectively, at p < 0.001). The content of exchangeable sodium increased from 0.17 ± 0.01 to 0.23 ± 0.01 cmol(+)/kg of soil. The TDS of water extracts from the soil of background plots averaged 0.11 ± 0.01% increasing to 0.17 ± 0.02% in the soils after fires; on some plots, the soils became slightly or moderately saline with the TDS of up to 0.56%; the composition of major anions remained stable and was characterized by a predominance of sulfates and bicarbonates. The activities of dehydrogenase, urease, and protease in a week after the fire decreased by 8–11%; the activity of invertase decreased by 18%. However, in 1.5 months after the fire, the activities of dehydrogenase, invertase, and protease were even higher than those in the background soil. The urease activity was restored to the background level in a year after the fire. The soil acidity approached the background level after two years. Fires are an important factor of pedogenesis in steppe ecosystems that have positive and negative consequences.