Molybdenum Content Research Articles

Biological nitrogen fixation, diversity and community structure of diazotrophs in two mosses in 25 temperate forests.

Many moss species are associated with nitrogen (N)-fixing bacteria (diazotrophs) that support the N supply of mosses. Our knowledge relates primarily to pristine ecosystems with low atmospheric N input, but knowledge of biological N fixation (BNF) and diazotrophic communities in mosses in temperate forests with high N deposition is limited. We measured BNF rates using the direct stable isotope method and studied the total and potentially active diazotrophic communities in two abundant mosses, Brachythecium rutabulum and Hypnum cupressiforme, both growing on lying deadwood trunks in 25 temperate forest sites. BNF rates in both mosses were similar to those observed in moss species of pristine ecosystems. H. cupressiforme fixed three times more N2 and exhibited lower diazotrophic richness than B. rutabulum. Frankia was the most prominent diazotroph followed by cyanobacteria Nostoc. Manganese, iron, and molybdenum contents in mosses were positively correlated with BNF and diazotrophic communities. Frankia maintained high BNF rates in H. cupressiforme and B. rutabulum even under high chronic N deposition in Central European forests. Moss N concentration and 15 N abundance indicate a rather minor contribution of BNF to the N nutrition of these mosses.

Study of the Elemental Composition of Pectoral Species No. 2 and Its Components

INTRODUCTION. The influence of anthropogenic factors on the content of toxic elements in plants increases the need for monitoring the content of toxic elements in medicinal plant raw materials and the corresponding herbal medicinal products. In addition, studying the elemental composition of herbal medicinal products will help determine their potential in the treatment of elemental metabolism disorders (macroand micro-elementoses).AIM. This study aimed to determine the elemental composition and the heavy metal content in Pectoral Species No. 2 and its components.MATERIALS AND METHODS. The study used Pectoral Species No. 2 and its components, including common coltsfoot (Tussilago farfara L.) leaf, greater plantain (Plantago major L.) leaf, and liquorice (Glycyrrhiza glabra L., G. uralensis Fisch.) root. The samples were manufactured by Krasnogorskleksredstva JSC and purchased at Moscow pharmacies. To determine the elemental composition, the study samples were digested with concentrated nitric acid and analysed by inductively coupled plasma mass spectrometry (ICP-MS). The calibration involved using concentrations ranging from 0.5 to 1.5 times the maximum permissible concentration for each element.RESULTS. This study identified and quantified 26 elements in Pectoral Species No. 2 and its components. The content of heavy metals was within the permissible concentrations. The study established the predominant macronutrients (potassium, calcium, and magnesium), micronutrients (iron, aluminium, and strontium), and ultramicronutrients (barium, nickel, and chromium) in Pectoral Species No. 2. The authors evaluated the contributions of each herbal drug to the total element content in the medicinal product.CONCLUSIONS. Coltsfoot leaf exerts the greatest influence on the content of macro-, micro-, and ultramicronutrients in Pectoral Species No. 2. Greater plantain leaf contributes the most to the zinc, silver, and nickel content. Liquorice root has the highest strontium and molybdenum content.

Alloy Design Optimization of Stainless Steel's Performance and Environmental Impact Through Taguchi‐Based Grey Relational Analysis

The current work presents an optimization approach for improving stainless steel's performance and environmental impact. A Taguchi‐based grey relational analysis is used to determine the optimal alloy design of six stainless steels (304, 316L, 904L, 2304, 2205, 2507). The alloy design of a multivariable system (C, Mn, Cr, Ni, N, Mo, and Cu) is initially formulated based on the Taguchi orthogonal array. It combines the multiperformances (pitting corrosion resistance, proof strength, tensile strength, and greenhouse gas emissions) to determine a numerical score and suggests the optimal combination of alloy contents. The results are further analyzed using a range analysis to detect the significance of each alloy parameter and its level. The results show that nitrogen plays the most important role in determining the stainless steel's combined performance. Besides, the optimum alloy design consists of a high content of nitrogen, chromium, molybdenum, and copper combined with a low content of nickel. The study has a focus on proposing the systematic approach, Taguchi‐based grey relational analysis, to optimize the stainless steel's different mechanical properties with respect to environmental impact.

Boosting oxidative desulfurization from liquid fuels with CuO-MgO assisted by MgMoO4 co-catalyst

Developing a highly efficient catalyst is one of the important topics in the field of oxidative desulfurization from liquid fuels. In this study, the composite metal oxide catalysts (CuO-MgO) with co-catalyst MgMoO4 were prepared by co-precipitation method with simple process, high efficiency and good performance and their structures characterized. An efficient extractive catalytic oxidative desulfurization (ECODS) system for liquid fuel was successfully developed on the basis of as-prepared CuO-MgO-MgMoO4 (CuMgMo) as the catalyst, sodium hypochlorite (NaClO) as the oxidant, and acetonitrile as the extractant. Taking the n-decane and n-tetradecane containing dibenzothiophene (DBT) as the test model oil sample, the main parameters influencing desulfurization performance were examined in detail, such as the molybdenum content, the dosage of CuMgMo, the reaction temperature, the initial S-concentration, the different extractants, the volume ratio of extractant to oil, the different oxidants, and the molar ratio of NaClO to DBT. Based on optimized desulfurization reaction conditions, the model oil containing different sulfur compounds (benzothiophene, 4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene) and the real oil (straight-run gasoline, straight-run kerosene, and straight-run diesel) were further tested. Based on the free radical trapping experiments and the calculation of density functional theory, the reaction mechanism was deeply explored. The results showed that the de-electron reaction of DBT was mainly catalyzed by MgMoO4 and the reaction of HClO obtaining electron was mainly catalyzed by CuO. MgMoO4 plays an assisting role in improving the catalytic reaction rate. This work will provide a useful reference for the construction of efficient ECODS system using composite metal oxides.

Optimizing water electrolysis activity in Mo-doped Sr2FeCoO6-δ perovskites by balancing oxygen vacancies and structural stability

Perovskite-based solid oxide electrolysis cells (SOECs) are promising for efficacious hydrogen production. This work explored how varying molybdenum (Mo) content impacts the structure and performance of Sr2FeCo1-xMoxO6-δ (SFCMx) perovskites for SOEC water electrolysis. SFCMx (x = 0.1–0.5) were synthesized via sol-gel method and incorporated into symmetrical cells. Electrolysis testing showed SFCM0.3 had the highest activity, achieving 2.09 A cm−2 at 2.0 V and 800 °C, compared to 0.964 and 0.847 A cm−2 for SFCM0.1 and SFCM0.5 respectively. This optimal performance with 0.3 Mo doping was put down to simultaneous variations in oxygen vacancy concentration and crystalline structure stability. Lower Mo doping accelerated charge transfer but destabilized the structure, while higher doping stabilized the cubic perovskite structure but reduced vacancies and electrocatalytic activity. This work demonstrates that balancing activity and stability by optimizing dopant concentration is critical to maximize SOEC performance. This provides new insights for enhancing water electrolysis through controlled doping and tuning of the perovskite structure.

Non‐oxidative Methane Activation over Molybdenum and Tungsten Nitride Catalysts

AbstractIn this study, molybdenum (Mo), tungsten (W), and mixed metal oxide and ‐nitride catalysts are synthesized via incipient wetness impregnation on silica support (SBA‐15) with a total target metal loading of 4 wt %. The effect of the Mo : W ratio on the non‐oxidative methane conversion, product selectivity, and coke formation is evaluated. The reduced Mo/SBA‐15 and MoW/SBA‐15 catalysts show higher CH4 conversion activity to benzene (selectivity of ~75.5 %) than for ethylene (selectivity of ~9.5 %) with a rather fast coke formation rate of 19–24 mgCoke gCat−1 h−1 without a clear influence of the Mo : W ratio. In contrast, the metal nitrides have a much smaller coke formation rate. The smallest rate of 0.45 mgCoke gCat−1 h−1 is achieved for the WN/SBA‐15 sample, which increases with the molybdenum content to 4.7 and 8.6 mgCoke gCat−1 h−1 for the MoWN(5 : 1) and MoN/SBA‐15 catalysts, respectively. There seems to be a yet unknown but negative correlation between the coke formation rate and the number of silanamine functional groups formed during the catalyst nitridation (Si−OH→≡Si−NH2→≡Si−NH−Si≡). The C2H4 selectivity is significantly increased with the relative amount of tungsten, with the highest C2H4 selectivity of 63 % for mixed‐metal nitride catalyst containing Mo : W ratio of 1 : 5. While the Mo/SBA‐15 the MoN/SBA‐15 achieve a C2H4 selectivity of less than 10 %.

Magnetic properties of Sr1.5La0.5FeMoO6-δ depending on the phase composition of the reaction mixture

This paper presents investigations of phase transformations during the crystallization of Sr1.5La0.5FeMoO6-δ by the solid-phase technique from a stoichiometric mixture of oxides MoO3, La2O3 and Fe2O3 and SrCO3 and precursors Sr0.5La0.5FeO3 and SrMoO4. Using XRD and thermogravimetric analyses, the influence of synthesis modes on the chemical processes occurring during the formation of double perovskite was studied. It has been established that the synthesis of lanthanum-strontium ferromolybdate in a mixture of oxides proceeds through a number of series-parallel stages. At the initial stage of interaction, the resulting lanthanum-strontium ferromolybdate is enriched with iron and its composition changes during the reaction towards an increase in the molybdenum content. As the temperature increases, the content of double perovskite increases, and the concentration of the secondary phase SrMoO4 does not disappear to zero until the synthesis temperature, which indicates that solid-phase reactions with the formation of a solid solution Sr1.5La0.5FeMoO6-δ from oxides are difficult to occur. It was determined that to minimize the influence of intermediate reaction products it is necessary to use precursors Sr0.5La0.5FeO3 and SrMoO4. Based on the results of studying the temperature dependences of the degree of phase transformations during the crystallization of double perovskite, combined heating modes were optimized. The use of optimized synthesis modes made it possible to obtain single-phase Sr1.5La0.5FeMoO6-δ powder with the superstructural ordering (82%), the Curie temperature of 450 K and a magnetization value of 40.9 A · m2 · kg-1 at T = 77 K in a magnetic field with induction B ≥ 0.86 T.

Yield, nutritional and flavor quality of Chinese cabbage under different rates of chicken manure substituted for chemical fertilizer

Combination of livestock manure (LM) with chemical fertilizer (CF) holds promise for obtaining high productivity. However, there is a relative lack of research on the impact of vegetable quality and its associated influences in the pursuit of high yields. The study aimed to investigate the effects of substituting chicken manure (CM) for CF on growth and quality (nutrition and flavor) of Chinese cabbage (Brassica rapa ssp. pekinensis) under the same nitrogen level. In general, CM substitution for CF recorded higher soil nutrients contents, head yield and phosphorus and molybdenum concentrations than sole application of CF. However, the concentrations of zinc, calcium, nickel, and lead decreased with CM application. Additionally, N concentration decreased by 47.1 % with sole CM application. Treatments had no significant effect on the concentrations of potassium, magnesium, iron, manganese, copper, boron, sodium, chromium, cobalt, arsenic, selenium, cadmium and on nutritional quality. We identified 454 volatiles, the primary percentages were esters (22.1 %), acids (14.3 %), and ketones (14.3 %). CM application inhibited the contents of total volatile and esters (especially isothiocyanates). When CM replaced CF at a rate of 2/3 and 3/3, the richness of volatiles dramatically increased. Furthermore, the Mantel test confirmed a strong correlation between volatile compound contents (VOCs) and soil C/N ratio, total nitrogen (TN), and available phosphorus (AP). Five volatiles (methanethiol, dimethyl disulphide (DMDS), 2-methyl-5-(1-methylethyl)-phenol, 1-propanethiol and dimethyl trisulfide) were collected as aroma compounds. With the CM application DMDS contents increased by 2.0–4.3-fold. Random forest model revealed a negative correlation between DMDS concentration and Ca level, possibly attributed to the decrease in allyl isothiocyanate content and the inhibition of TRPA1 transient receptor potential ion channel. In conclusion, precise adjustment of CM to CF substitution rates is essential for preserving Chinese cabbage yield and quality. This study could offer valuable insights for both nutraceutical and flavor purposes.

Effect of the Molybdenum Content on Wear and Corrosion Behavior of Fe-B-Based Surface-Alloyed Layer

In this study, Fe-Mo-B-based hardfacing electrodes containing different amounts of Mo were coated on an AISI 1020 steel substrate using the electric arc welding method. The findings show that molybdenum is highly effective on the microstructure and minor changes in the coating composition affect the phases and morphological properties. In the hardness tests, an increase of 73% was achieved in the Fe14Mo2B4-based hardfacing coating, compared to the base material, and a 30% increase was achieved, compared to the Fe16B4-based coating. The highest hardness value was measured as 56.4 HRC and the highest phase hardness was measured as 3228 HV in the FeMo2B4 phase. The lowest wear rate was measured in the Fe14Mo2B4-based coating. The wear rate of the Fe14Mo2B4-based coating was 8.1 times lower than that of the substrate material and 4.7 times lower than that of the Fe16B4-based coating. According to corrosion test results, the highest corrosion resistance was obtained in the Fe16B4-based coating. The current density value of the Fe16B4-based coating was measured to be 13.6 times lower than that of the substrate material.

The Influence of Selected Transition Elements on Cell Metabolism

Abstract The elements are present in the environment. Moreover, they are used in pharmacy and the production of new materials used in medical applications. They are often as environmental pollutants. They can accumulate in organisms and induce toxic effects on the cellular level. HepG2, L929 and Caco-2 cell lines were exposed to known concentrations of chromium chloride, iron chloride, nickel chloride, molybdenum trioxide and cobalt chloride (200 or 1000 μ M used alone and in combinations). Concentrations of chromium, iron, nickel, molybdenum and cobalt in the cell lysate and the culture medium were determined by ICP-MS. Moreover, sodium, potassium, calcium and magnesium concentrations were also measured. What is more, cells were observed under light and scanning electron microscope. The dose-dependent increase in the concentration of chromium, iron, nickel, molybdenum and cobalt in all cell lines after incubation with elements was observed. Potassium concentration decreases while sodium calcium and magnesium increase after incubation of cells with of mentioned elements. The incubation of cells with microelements induces cell morphology changes. The presented study shows the crucial role of tested microelements in the induction of cell death as a result of an imbalance of sodium, potassium, calcium and magnesium concentration inside the cell.

Advances in Corrosion Mitigation for Waste-to-Energy Systems: Evaluating Coatings and Application Techniques

Waste-to-Energy (WTE) systems, utilizing post-recycled municipal solid waste (MSW) and other biomass materials, are proven alternatives to landfilling for sustainable waste management. These processes offer benefits such as reduced landfill space, decreased methane emissions, and minimized waste volume. However, operational challenges, specifically high-temperature corrosion (HTC) of superheater tubes, hinder their efficiency due to the presence of chlorine, alkaline salts, and sulfates. To address this issue, a range of coating techniques have been developed, with thermal spray techniques, particularly high velocity oxy-fuel (HVOF) spray, proving the most effective for protecting superheater tubes. A comparative analysis of experimental data from multiple studies indicates that coatings with Alloy 625, Alloy C-276, Colmonoy 88, FeCr, IN625, NiCr, NiCrTi, and A625 offer high corrosion resistance at relatively low material costs, with corrosion rates below 1 mm/year. High chromium, nickel, and molybdenum content coatings perform exceptionally well under high-temperature and high-chlorine conditions. Notably, T92 and P91, due to their low cost and high corrosion resistance, are strong candidates for superheater tubes operating at 550°C. While A625 demonstrates excellent corrosion resistance, its high cost limits its practicality. Ultimately, the selection of suitable coatings depends on the specific WTE plant design and operating experience. The additional cost of applying these coatings is a minor fraction of the overall financial gains, as it extends the superheater tubes' lifetime and reduces plant downtime for tube repair or replacement.

Influence of Mo Content on the Precipitation Behavior of 13Ni Maraging Ultra-High Strength Steels

This study offers valuable insights into the precipitation behavior of 13Ni maraging steels, emphasizing the role of molybdenum content in their microstructure, strengthening, and precipitate evolution. Precipitate morphology and crystallography were examined using a combination of high-resolution transmission electron microscopy and selected area electron diffraction. Strengthening mechanisms were assessed through Vickers hardness measurements. All the examined samples exhibited a lath martensite microstructure and displayed an increasing hardness over the aging time. The molybdenum content not only influenced the presence of retained austenite in the initial microstructure but also affected the type of precipitates formed during the early aging stages. Initially, Ni3Mo precipitates were formed, succeeded by the formation of more stable Fe2(Mo,Ti) Laves precipitates. The ultra-high strength of 13Ni maraging steels arises from the combination of the precipitate type and size distribution. The base composition of 13Ni maraging steels achieved a peak hardness of 798 HV1 through the precipitation of Laves Fe2(Mo,Ti) phases ranging from 3 to 14 nm in diameter.

Properties of high-strength complex-alloy steel for casing pipes in cold-resistant and corrosion-resistant versions

The influence of alloying on the properties of high-tempered steels used for the production of casing pipes has been studied. It has been shown that an increase of molybdenum content from 0.15 to 0.53% provides a noticeable increase of the mechanical characteristics in chromium-molybdenum steels after tempering at 600‒690 °C. Alloying with vanadium and niobium contributes to an additional increase in strength properties. The influence of vanadium on the highly viscoplastic properties of steels is shown. It has been established that the greatest strengthening of steel with 0.32% molybdenum in a highly tempered state is provided by complex alloying with niobium and vanadium. The influence of austenitization and tempering temperature on the structure and properties, including resistance to cracking in an environment saturated with hydrogen sulfide, of chromium-molybdenum steel grade 26CrMoVNb-2 with micro-alloying additives of vanadium and niobium was determined. Alloying with molybdenum, vanadium and niobium makes it possible to obtain steels for high-strength casing pipes that are resistant to brittle fracture and sulfide stress corrosion cracking, subject to comprehensive consideration of the main factors such as austenitization temperature, tempering temperature and duration, dispersion and homogeneity of microstructure

Research and assessment of the molybdenum oxide (VI) nanoparticles toxiсity under inhalation in WISTAR line rats in comparison with the micro-sized chemical analog

Introduction. Molybdenum (VI) oxide nanoparticles (MoO3 NPs) are being actively introduced into practical use as part of catalysts, optics, plastics, textiles, coatings, and lubricants, gas sensors, and crude oil refining processes. MoO3 NPs are known to exhibit toxic properties when interacting with living systems. Atmospheric air pollution with potentially dangerous MoO3 NPs can contribute to the inhalation exposure in the population and, as a result, the development of health disorders caused by the toxic effect of the nanomaterial. In this regard, the study of the adverse effects caused by MoO3 NPs entering the body during aerogenic exposure is particularly relevant.
 
 The aim of the study. Investigation and evaluation of subacute toxicity of MoO3 NPs by the inhalation route of entry into the body in comparison with a microsized chemical analogue.
 
 Materials and methods. The physical properties of MoO3 NPs were studied in comparison with microparticles (MPs). In an experiment on Wistar rats, a comparative analysis was performed and a characteristic of the pathogenetic features of the toxic effect of particles during subacute inhalation exposure at a concentration of 1.84 mg/m3 was given.
 
 Results. According to the totality of physical properties, the MoO3 sample under study is a nanomaterial with an average particle size of 58.8 nm, constituting 84.2% of the total number of particles. MoO3 NPs accumulate in the heart, lungs, kidneys, and brain. The concentration of molybdenum is by 2.50–15.85 times higher than the control levels. The highest content of the studied element was found in the lungs. Bioaccumulation of MP MoO3 was noted only in the lungs, while the concentration of molybdenum is by 3.00 times less in comparison with the exposure to NPs. When exposed to MoO3 NPs, more pronounced changes in biochemical (an increase in the activity of alkaline phosphatase, LDH, the concentration of total bilirubin and creatinine by 1.29–2.11 times) and hematological parameters (a decrease in the number of platelets and thrombocrit by 1.2 times) of blood were noted relative to the impact of a microscale analogue. Under the influence of NPs and MPs of MoO3, pathomorphological changes develop in the lungs, brain, and liver tissues. When exposed to NPs, compensatory lung emphysema, focal microvesicular steatosis in hepatocytes, and acute plethora in the liver were found, which were not detected during exposure to NPs.
 
 Limitations. The study was performed only with subacute inhalation exposure to NPs and MPs of MoO3 in Wistar rats.
 
 Conclusion. MoO3 NPs have a higher degree of bioaccumulation and toxicity relative to MPs. The results of the study make it possible to expand theoretical concepts and gain new knowledge in the field of nanotoxicology about the features of the toxic effect of nano-sized MoO3 with multiple inhalation routes of entry into the body at a concentration of 1.84 mg/m3.
 
 Compliance with ethical standards. The study was carried out in accordance with the European Convention for the Protection of Vertebrate Animals used for Experimental or other Scientific Purposes (ETS No. 123) and the requirements of the Ethics Committee of the Federal Scientific Center for Medical and Preventive Technologies for Public Health Risk Management (protocol No. 6 of 20.01 .2021).

Evaluation of drinking and irrigation water quality, and potential risks indices in the Dera Ismail Khan district, Pakistan

This study sought to asses drinking and irrigation water quality in the Dera Ismail (DI) Khan District, Pakistan with the aid of using drinking water quality index (WQI) and irrigation water quality indices (IWQI). Seventy two water samples were collected from various water sources such as tube wells, dug wells, hand pumps, streams, and springs throughout the DI Khan district. The investigated physicochemical parameters include pH, TDS, EC, turbidity, total hardness, major cations (Na, K, Ca, Mg), anions (Cl, HCO3, SO4), and heavy metals (Fe, Mo, Cr, Ni, Cu, and Zn). IWQI used in the study includes Kelly's ratio (KR), permeability index (PI), sodium percent (Na%), Magnesium Hazard (MH), potential salinity (PS), residual sodium carbonate (RSC), and sodium adsorption ratio (SAR). With the mean value of 63, WQI revealed that most samples are placed in the good category, with a smaller fraction in the excellent and poor classes. On the other hand, a health risk assessment of the data pointed out that the molybdenum (Mo) and chromium (Cr) concentrations in drinking water could pose health risks to children of the concerned population. Rock weathering appears to be the dominant hydro-geochemical pathway controlling water chemistry, Ca–Mg–HCO3 being the dominant facies, followed by Na–HCO3. Kelly's ratio (KR), sodium percent (Na%), sodium adsorption ratio (SAR), and residual sodium carbonate (RSC) had values higher than the recommended threshold. The use of water for irrigation of agricultural fields may raise relevant ecological concerns in the studied district.

Metal levels in waste pickers in Brasilia, Brazil: hair and nail as exposure matrices

ABSTRACT The aim of this cross-sectional study was to compare workplace conditions and metal exposures in 431 waste pickers who worked nearby at the Estrutural Dump in Brasilia utilizing hair (n = 310) and nail (n = 355) as matrices of exposure. Waste pickers were grouped according to their workplace (open waste dump: G1 and sorting plants: G2). Hair and nail samples were collected and analyzed using ICP-MS. The work duration in the facilities was significantly different between the groups with averages of 16.46 (8.48) yrs and 9.26 (6.28) yrs for hair donors in G1 and G2, and 15.92 (7.72) yrs and 8.55 (5.77) yrs for toenail donors in G1 and G2, respectively. The arithmetic means (μg/g) of cadmium, copper, lead, and manganese in hair were significantly higher in G2 (0.076 ± 0.133; 19.61 ± 18.16; 2.27 ± .56 and 3.87 ± 5.59, respectively) compared to G1 (0.069 ± 0.235; 15.72 ± 15.18; 1.72 ± 4.04 and 3.65 ± 5.5, respectively). Concentrations of arsenic, barium, cadmium, copper, cobalt, lead, manganese, and molybdenum in nail were significantly higher in G2 (0.57 ± 0.39; 22.74 ± 42.06; 0.1 ± 0.08; 22.7 ± 51.60; 0.48 ± 0.45; 4.69 ± 9.43; 19.07 ± 20.75; 1.80 ± 1.76, respectively) compared to G1 (0.40 ± 0.28; 15.32 ± 22.31; 0.08 ± 0.11; 11.91 ± 16.25; 0.37 ± 0.37; 3.94 ± 15.04; 13.01 ± 19.08; 1.16 ± 1.80, respective. Our findings suggest that the studied population was exposed to toxic metals and indicates the need for chemical exposure prevention policies to monitor chemical risk exposures in waste pickers.

Trace Element Geochemistry in North Pacific Red Clay Sediment Porewaters and Implications for Water‐Column Studies

AbstractGeochemical analyses of trace elements in the ocean water column have suggested that pelagic clay‐rich sediments are a major source of various elements to bottom‐waters. However, corresponding high‐quality measurements of trace element concentrations in porewaters of pelagic clay‐rich sediments are scarce, making it difficult to evaluate the contributions from benthic processes to global oceanic cycles of trace elements. To bridge this gap, we analyzed porewater and bulk sediment concentrations of vanadium, chromium, cobalt, nickel, copper, arsenic, molybdenum, barium and uranium, as well as concentrations of the major oxidants nitrate, manganese, iron, and sulfate in the top 30 cm of cores collected along a transect from Hawaii to Alaska. The data show large increases in porewater concentrations of vanadium, manganese, cobalt, nickel, copper, and arsenic within the top cm of the sediment, consistent with the release of these elements from remineralized organic matter. The sediments are a sink for sulfate, uranium, and molybdenum, even though conditions within the sampled top 30 cm remain aerobic. Porewater chromium concentrations generally increase with depth due to release from sediment particles. Extrapolated to the global aerial extent of pelagic clay sediment, the benthic fluxes in mol yr−1 are Ba 3.9 ± 3.6 × 109, Mn 3.4 ± 3.5 × 108, Co 2.6 ± 1.3 × 107, Ni 9.6 ± 8.6 × 108, Cu 4.6 ± 2.4 × 109, Cr 1.7 ± 1.1 × 108, As 6.1 ± 7.0 × 108, V 6.0 ± 2.5 × 109. With the exception of vanadium, calculated fluxes across the sediment–water interface are consistent with the variability in bottom‐water concentrations and ocean residence time of the studied elements.

Rational Application of Coal Fly Ash Enhances Plant Growth and Improves Phosphorus Nutrition of Erect Milkvetch Grown on a Loess Soil

ABSTRACT Application of coal fly ash (CFA) as a soil amendment has produced great agronomic benefits. However, there are potential risks of using CFA for soil amelioration, due to the abundance of some elements, both essential and non-essential in plants, which can cause phytotoxicity and it even may cause health problems for humans through the food chain. A pot experiment was conducted to investigate the effects of various CFA application rates (5%, 10%, 20%, 40%, and 80%) on plant growth, accumulation of essential nutrient elements and potentially toxic trace elements in erect milkvetch grown on a loess soil. The results showed that plant growth was significantly enhanced by the 5%, 10%, and 20% CFA treatments, while a CFA application rate ≥ 40% did not benefit plant growth, or even considerably inhibited plant growth. Plant phosphorus nutrition was improved by CFA application, but concentrations of potassium, copper, and zinc in plants declined when CFA was applied. Concentrations of molybdenum, boron, and selenium in plants generally increased with CFA application rate. A 5% CFA application rate is appropriate for the loess soil, a higher rate will cause phytotoxicity in erect milkvetch. CFA is a promising source of nutrients such as phosphorus, rational application of CFA to soil can enhance plant growth and improve plant phosphorus nutrition.

Agro-ecological processes under conditions of biogeochemical imbalance of molybdenum in agrolandscapes of the Forest-Step zone

A special place in the theory and practice of landscape geochemistry belongs to biogeochemical zoning. Biogenic migration of substances and chemical elements can rightfully be considered one of the criteria for the typological classification of geochemical landscapes, which is the basis for building a map of geochemical landscapes of Ukraine. The scientific result of zoning is the recognition of spatial boundaries and areas of the territory consisting of connected components with uniform conditions of geochemical migration of chemical elements. With a long-term violation of the ratio between microelements, various diseases appear, which are called endemic, and the phenomenon itself — biogeochemical endemics. The latter most often occur due to a lack or excess of some threshold value of the concentration of microelements or a violation of the ratio of other micro­elements associated with it. On the basis of landscape-geochemical analysis and zoning, the authors defined the territory of the biogeochemical provinces of the Forest Steppe, where a lack of molybdenum content in the soil for normal plant development was found. In addition, the features of the molybdenum province are determined by low biogenic accumulation and intensive physicochemical dispersion of essential trace elements, increased mobility of most toxic trace elements in natural waters, and the absence of conditions for the formation of barriers of hydroamphoteric elements, including Mo2+. Also, in the territories of biogeochemical provinces, there is a high probability of the development of certain endemic phytopathologies and microelement diseases due to the imbalance of biogeochemical food chains.

Mechanism of Mo content on improving the high-temperature corrosion performance of APS sprayed Ni-clad Al coatings in simulated biomass corrosion condition

The study examined the impact of varying molybdenum content (0 %, 5 %, and 10 % wt) on the high-temperature corrosion resistance of APS-sprayed Ni-clad Al coatings. The coatings were exposed to a simulated biomass-firing environment with pure KCl deposition at 600 °C for 168 h, and a mixed gas containing 15 % water vapor was passed through. The findings revealed that increasing Mo content improved the coating's high-temperature corrosion resistance. The coating with 10 % Mo displayed a continuous layer of Ni and Al oxides on its surface, while KCl was concentrated in the Mo region. Based on the experimental results, a mechanism for how the presence of Mo element contributes to the high-temperature corrosion resistance of NiAl coatings was proposed.