Chromium Research Articles

Trace Elements in Pond Sliders (Trachemys scripta) - Variations Between Sex and Region of Sample Collection in Germany

Abstract Environmental pollution and its effects on organisms are an important aspect of conservation. Pollutants include not only organic substances but also elements such as mercury and arsenic, some of which can accumulate in the food chain and cause considerable damage to the organism. There is little data on pollutants in reptiles, but freshwater turtles in particular are very suitable for monitoring due to their position in the food chain and their long life expectancy. In the present study, we measured the trace elements silver (Ag), arsenic (As), gold (Au), barium (Ba), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), mercury (Hg), magnesium (Mg), manganese (Mn), molybdenum (Mo), nickel (Ni), antimony (Sb), selenium (Se), thallium (Tl), and zinc (Zn) in heparinized blood plasma of 167 healthy pond sliders (Trachemys scripta) kept in different locations in Germany using inductively coupled plasma mass spectrometry (ICP-MS) . The results showed significant (P < 0.05) differences between the sexes for Ag, Au, Ba, Hg, Mg, Mn, Mo, Ni, Sb, Se, and Zn and between the locations for Au, Ba, Cu, Hg, Mg, Tl, Sb, and Zn. A positive correlation with the body weight of the turtles was found for Ba, Hg, Mg, Mn, Mo, Ni, Se, Tl and Zn. These results serve as baseline values and show that both the local environment and the sex of the turtles significantly influence some values. Further studies are needed to show how the animals react to increased and decreased element levels and how blood levels of individual elements differ in animals from polluted regions.

Essential and Nonessential Elements, Lipids and Volatile Compounds in Coffee and Transfer to Coffee Brews: Assessment of the Benefits and Potential Risks for Human Health

ABSTRACTCoffee is a popular beverage with significant commercial and social importance. The study aimed to determine the fatty acids profile, volatile compounds, and concentration of major and trace elements (Na, Mg, K, Ca, P, S, Fe, Mn, Cu, Zn, Cr, Ni, Cd, and Pb) in the two most important varieties of coffee, namely arabica and robusta. The leaching percentages of mineral elements and the effect of boiling time on the transfer of elements to aqueous extracts were also determined. In terms of fatty acids profile, the robusta variety was found to have a higher content of saturated fatty acids (46.68%) compared to the arabica variety (44.38%), whereas arabica contained a higher amount of omega‐6. Regarding the volatile compounds, arabica contained higher amounts of pyrazines (36%), ketones (5.4%), and furans (37.8%). The average contents of the major elements in roasted coffee (arabica and robusta) decreased in the order K > P > S > Mg > Ca > Na, while the trace elements content exhibited a decrease in the order Fe > Mn > B > Cu > Zn > Ni > Pb > Cd ≈ Cr. In coffee brews, the contents of elements have a similar decreasing trend, although variations in leaching percentages were observed. The health risk was assessed considering the concentrations of potentially toxic elements in coffee brews, and no health risks were indicated by the obtained scores. The contribution of coffee brews to the recommended dietary daily intake of essential elements is low. However, it can be significant considering that this beverage is consumed on a daily basis.

High-strength and Low-Thermal-Conductivity Porous Multi-Principal Cation Mullite Ceramic

The secret of porous mullite as a thermal insulation material lies in its excellent mechanical properties and lower thermal conductivity. The optimization of performance often depends on the structure design. Herein, via NH4HCO3 as a sacrificial material to fabricate porous multi-principal cation mullite (MPCM) ceramics that have not been reported for 4 doping elements (Mg, Ti, Zr, and Cr) by a sacrificial template method. The novelties of the present work are: (1) The multiple components cause a serious lattice distortion at the microscopic scale, which increases the mechanical properties of porous MPCM ceramics. (2) Porous MPCM (total porosity ≈ 54%) exhibits superior compressive strength (≈ 93 MPa), and the compressive strength with porosity was well modeled based on the Balshin and Rice equations. (3) As a proof-of-concept, we predict the thermal conductivity of pure mullite (PM) with the same porosity as MPCM ceramics. Here it proved the superiority of MPCM (0.67 W∙m-1∙K-1, 1,000 °C) as a thermal insulation material over conventional PM. Porous MPCM prepared by NH4HCO3 will pave a new path for the design of advanced thermal-insulation materials.

Evaluation of some physicochemical parameters and health risks associated with potentially toxic elements (PTEs) in agricultural soils from the southwest region of Ethiopia

In this study, soil samples collected from Burusa and Bure agricultural sectors were analyzed for their physicochemical parameters and potentially toxic elements (Fe, Mn, Zn, Cu, Co, B, Se, Ni, Cr, Pb, Cd, As, and Hg). Physicochemical parameters were analyzed according to AOAC methods. For quantification of PTEs, the soil samples were digested by using aquaregia (HCl: HNO3; 3:1) and 5 mL of H2O2 (30%) at a digestion temperature of 250°C for 3 hours prior to ICP-OES analysis. The percent recoveries (%R) and relative standard deviation (%RSD) of this method ranged from 83 to 106% and 0.39 to 9.2%, respectively. The LODs and LOQ values were in the range of 4.3 × 10-4-5.3 × 10-2 mg/L and 1.4 × 10-3-1.76 × 10-1 mg/L, respectively. The analyzed mean values of physicochemical parameter including pH, temperature, electrical conductivity, moisture, organic matter and nitrogen content were found in the range of 4.85-6.47, 20.5-21.4°C, 101.6-230.7 µS/cm, 8.67-20.7%, 0.677-1.81% and 5.81-6.85%, respectively. The average amount of potentially toxic elements found in the soil samples were ranged as 57073-81279, 1185-3255, 41.0-72.2, 12.6-29.2, 18.8-50.8, 25.0-40.5, 42.2-60.8, 13.6-34.5, 41.9- 67.2, 25.0-59.4, 9.92-13.3, 0.933-1.12 and 4.97-8.63 in mg/kg for Fe, Mn, Zn, Cu, Co, B, Se, Ni, Cr, Pb, Cd, As and Hg, respectively. The highest concentrations of among the entire PTEs were recorded for Fe, followed by Mn, in the analyzed soil samples. All the studied elements are below the FAO/WHO permissible limit except Fe, Se, Cd, and Hg for all analyzed soil samples and Mn for the Bure soil sample. The target hazard quotient (THQ) and hazard index (HI) values are <1, suggesting an insignificant non-carcinogenic risk of the heavy metals to the adults via ingestion, inhalation, and dermal contact exposure of agricultural soils. Likewise, the individual element incremental lifetime cancer risk (ILCR) occurrence for all studied soil samples is below 1 × 10-4. The total ILCR of potentially toxic heavy metals (Ni, Cr, Pb, Cd and As) resulting from ingestion, inhalation, and dermal contact exposure of agricultural soil by an adult population indicate a slightly higher potential cancer risk (> 1 × 10-4) for soil samples obtained from Bure S1, Bure S2, and Bure S3. Therefore, continuous monitoring of these harmful elements should be made by agricultural sectors and responsible government regulatory authorities are crucial to prevent PTEs related to agricultural soils in Ethiopia.

Metal concentration in bottom sediments for a tropical river, geological or anthropogenic source?

The study analyzes data from a survey of metal concentrations in bottom sediments from both margins (left and right) of the lower main channel of the Orinoco River. This study aims to analyze metal concentrations in the bottom sediments of the lower Orinoco River with different geological settings and anthropological sources. El Almacen (ALM), Las Galderas (G), Los Castillos de Guayana (C), Ciudad Bolivar (CB), and Ciudad Guayana (CG) were the sampling sites. Freshwater physicochemical parameters pH, conductivity, and DO were measured in situ at each sample site. Twenty-four bottom sediment samples were collected with an Eckman grab, dried, and sieved. Trace elements Pb, Cr, Cu, Cd, Ti, and Co were measured in sediments with grain sizes <63μm. Bottom sediment analysis followed EPA method 3050B (digestion with HNO3 + HCl + H2O2). Statistical analyses included the Shapiro-Wilk test, Spearman correlation, Kruskal-Wallis test, and principal component analysis (PCA). Physicochemical parameters highlighted the marked difference between the left and the right river margins, reflecting the cross-channel heterogeneity due to the dissimilar geology and low horizontal mixing. Metal concentrations were generally low, with higher variations associated with urban and industrial sources. Pb, Cr, Cu, Cd, Ba, Ti, and Co concentrations did not generally indicate significant pollution, but potential contamination from sewage and industrial effluents was noted. The differences between the two river margins were common in all the sampling sites, reflecting the sources of water biochemistry related to geochemical origins in the Andes and the Guiana Shield, respectively. The study emphasizes the importance of sampling location within the river channel.

The Expanded Phases Formed in Stainless Steels by Means of Low-Temperature Thermochemical Treatments: A Corrosion Perspective

Surface engineering of stainless steels using thermochemical treatments at low temperatures has been the subject of intensive research for enhancing the surface hardness of these alloys without impairing their corrosion resistance. By using treatment media rich in nitrogen and/or carbon, it is possible to inhibit chromium compound formation and obtain supersaturated solid solutions, known as expanded phases, such as expanded austenite or S-phase in austenitic stainless steels, expanded ferrite in ferritic grades, and expanded martensite in martensitic grades. These low-temperature treatments produce a significant increase in surface hardness, which improves wear and fatigue resistance. However, the corrosion behavior of the modified surface layers remains of paramount importance. In the international literature, many studies on this topic are reported, but the results are not always univocal, and there are still open questions. In this review, the corrosion behavior of the expanded phases and the modified layers in which they are present is critically analyzed and discussed. The relationships between the phase composition and the microstructure of the modified layers and the corrosion resistance are highlighted while also considering the different test conditions. Furthermore, corrosion test methods are discussed, and suggestions are given for improving the measurements. Finally, perspectives on future directions for investigation are suggested for encouraging further research.

Correlation of mechanics degradation and thermal aging damage defects in Z3CN20.09M cast austenitic stainless steels

Microstructural characterization and mechanical testing were performed on 400℃ thermally aged Z3CN20.09M cast austenitic stainless steels. A quantitative mathematical model is introduced for the relationship between aging defects and mechanical properties. Charpy impact energy was used as a characteristic mechanical parameter, and the short-range order of the Cr element segregation that induced by spinodal decomposition was chosen as the characteristic defect parameters. The macroscopic mechanical properties and the microscopic thermal aging defects was quantitatively correlated in this model, which has a great reference significance in safety assessment and lifetime prediction of the reactor structural materials.

A novel layered culture device reveals spatial dynamics of root element uptake and optimal silicon application site for mitigating chromium uptake by rice

Understanding root uptake mechanisms for various elements is crucial for optimizing heavy metal remediation strategies and enhancing plant-nutrient interactions. However, simple and effective methods to differentiate the contributions of specific root segments in element uptake are lacking. Here, we developed a layered culture device consisting of a culture box and a plant suspension mechanism, which isolates different root segments through solid media and waterproof coating. Then, we used the device to investigate the roles of distinct root segments (0–1 cm and 1–2 cm from the tip) in heavy metal chromium (Cr) and beneficial element silicon (Si) uptake in rice. The results indicated that the 0–1 cm root segment contributed approximately 58% of leaf Cr(VI), with higher efflux compared to the 1–2 cm segment. Conversely, the 1–2 cm root segment served as the primary source of leaf Si and Cr(III), accounting for 62% and 54%, respectively. The translocation factors for Cr(VI) were similar for both segments (0.039 and 0.032), while the Cr(III) translocation factor for the 0–1 cm root segment (0.061) was 2.8 times that of the 1–2 cm segment. Notably, Si application to the 0–1 cm segment most effectively alleviated Cr (III) and Cr (VI) stress, boosting shoot length, fresh weight, and chlorophyll concentration and reducing Cr concentrations in roots and leaves by 24.7%–65.7%. In contrast, Si application to the 1–2 cm segment had minimal impact on rice growth or Cr uptake. These results suggest a deep Si application strategy for remediating Cr-contaminated soil. The innovative device provides a scientific foundation for distinguishing element uptake contributions of different root segments and enhancing the utilization efficiency of remediation materials and nutrient management in agriculture.

Characterization of Size Segregated PM10 at a Rural Site in the Eastern Mediterranean

Size-resolved PM10 samples (PM10-2.5 and PM2.5) were collected at a rural site located in the northeastern Mediterranean between August 2010 and April 2013. A total of 461 PM10 aerosol samples were analysed for major and trace elements (Na, Mg, Al, Si, S, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Zn, As, Ba and Pb) and anions (Cl-, NO3- and SO42-). Crustal elements and sea salt particles were found to be mainly associated with the coarse fraction, whereas SO42- and NO3- were predominantly found in the fine mode. Concentrations of most aerosol species exhibited well-defined seasonal variation with higher concentrations in summer than winter. The difference between summer and winter concentrations were not significant for As, Ca, Cr, Pb and NO3-. During the sampling period, 11 specific Saharan dust events were identified.

Investigation of Elemental Composition in White Wine Treated with Varying Doses of Bentonite

Investigation of Elemental Composition in White Wine Treated with Varying Doses of Bentonite

The partitioning of chalcophile and siderophile elements (CSEs) between sulfide liquid and carbonated melt

Carbonated melts play a significant role in mobilizing lithophile and volatile elements in the Earth’s mantle and mantle metasomatism. However, there has been limited investigation into their potential for mobilizing chalcophile and siderophile elements(CSEs). In this study, we experimentally determine the sulfide liquid–carbonated melt partition coefficients of CSEs (DCSESul/C_melt) for a range of elements, including Co, Ni, Cu, Zn, Se, Mo, Ag, Cd, In, Sn, Re, and Pb, at 1300–1600 °C, 1.0–3.0 GPa, andoxygen fugacity (fO2) close to the graphite-CO2 fluid buffer. Furthermore, the DSul/C_melt values for lithophile elements Cr, Mn, Rb, Sr, Y, Zr, Nb, Cs, Ba, Hf, and Ta (DLithoESul/C_melt) are also determined. The obtained DCSESul/C_melt values are 34–1230 for Co, 380–75200 for Ni, 200–14900 for Cu and Ag, 0.5–28 for Zn and Mo, 42–98 for Se, 24–640 for Cd, 5–52 for In and Sn, 650–15200 for Re, and 22–2470 for Pb. The obtained DLithoESul/C_melt values are below 1–10. The variations of DCSESul/C_melt and DLithoESul/C_melt are primarily influenced by the FeOtot content in the carbonated melts. A partitioning model was developed to parameterize DCSESul/C_melt and DLithoESul/C_melt as a multi-function of pressure, temperature, composition of the carbonated melt (mainly the FeOtot content), and composition of the sulfide liquid. Our parameterization can explain the observed large variations of DCSESul/C_melt and DLithoESul/C_melt for most of the trace elements studied. Using our DCSESul/C_melt parameterization, we model the CSE and U–Th contents of low-degree partial melts of carbonated mantle peridotite and slab eclogite with sulfur concentrations ranging from 50 to 500 µg/g. The modeling results can generally explain the trace element patterns observed in natural kimberlites and carbonatites; however, the peridotite- or slab-derived carbonated melts have a low capability in mobilizing CSEs, which can extract less than 3 % of Cu, Ni, Co, Re, and Os, 3–30 % of Mo, Pb, and Se, but up to 30–50 % U and Th from the source lithology. Consequently, the influence of carbonatite metasomatism on the Cu, Ni, Co, Re, and Os systematics of the Earth’s mantle is minimal, although local enrichments of CSEs may occur when sulfides precipitate from carbonated melts. Because of the elevated concentrations of U and Th and the corresponding U/Pb and Th/Pb ratios in the carbonated melts, the mantle lithology that has undergone metasomatism by these melts can become a geochemical reservoir with high 208Pb/206Pb ratios. However, the effect of carbonatite metasomatism on Re–Os isotopic systems of the mantle is minimal due to the low Re concentrations in the carbonated melts. Accordingly, the radiogenic Pb–Os isotopic signatures of HIMU ocean island basalts cannot be explained solely by carbonatite metasomatism in the mantle.

Major and Trace Airborne Elements and Ecological Risk Assessment: Georgia Moss Survey 2019–2023

The study, carried out as part of the International Cooperative Program on Effects of Air Pollution on Natural Vegetation and Crops, involved collecting 95 moss samples across the territory of Georgia during the period from 2019 to 2023. Primarily samples of Hypnum cupressiforme were selected, with supplementary samples of Abietinella abietina, Pleurozium schreberi, and Hylocomium splendens in cases of the former’s absence. The content of 14 elements (Al, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, S, Sr, V, and Zn) was detected using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), while the Hg content was determined using a Direct Mercury Analyzer. To identify any relationships between chemical elements and to depict their sources, multivariate statistics was applied. Principal component analysis identified three main components: PC1 (geogenic, 43.4%), PC2 (anthropogenic, 13.3%), and PC3 (local anomalies, 8.5%). The results were compared with the first moss survey conducted in Georgia in the period from 2014 to 2017, offering insights into temporal trends of air quality. Utilizing GIS, a spatial map illustrating pollution levels across Georgia, based on the Pollution Load Index, was generated. The Potential Environmental Risk Index emphasized significant risks associated with mercury and cadmium at several locations. The study highlights the utility of moss biomonitoring in assessing air pollution and identifying hotspots of contamination. The findings from this study could be beneficial for future biomonitoring research in areas with varying physical and geographical conditions.

Green method for preparation NaVO2 from vanadium-chromium slag based on Na2CO3 roasting and water leaching

An effective and environment-friendly method for preparing NaVO2, which can be used as an energy storage material, from Na2CO3 roasted vanadium-chromium slag was proposed using water as the leaching medium. Vanadium-chromium slag with 30 % Na2CO3 was heated in air and argon atmospheres from 30 °C to 1000 °C, respectively. The results show that vanadium compounds converted to NaVO3 while chromium compounds to Na2CrO4 under air. NaVO3 and Na2CrO4 were water-soluble making the separation of vanadium and chromium complicated. NaVO3 and Na2CrO4 were water-soluble making the separation of vanadium and chromium complicated. Heating vanadium-chromium slag in an argon atmosphere caused Fe2VO4 to react with Na2CO3, forming NaVO2 and NaFeO2 below 1000 °C. However, chromium compounds unreacted in argon. NaFeO2 was insoluble, while NaVO2 was water-soluble with a leaching efficiency exceeding 70 %. Notably, the characteristic peak of V(III) in NaVO2 was first found to be −532.00 ppm by the liquid 51V NMR spectrum. This method represents a novel, green strategy for the resource utilization of vanadium-chromium slag, involving Na2CO3 roasting in an argon atmosphere to produce NaVO2. It offers a promising approach to reduce the cost of NaVO2 battery production and support its commercialization.

Metal Contamination and Human Health Risk Assessment of Soils from Parks of Industrialized Town (Galati, Romania)

The aim of the present study was to evaluate the contamination state of the surface soil from 10 parks from Galati, Romania, and the health hazards of the soil. The soil samples, collected in each site from the playing ground and from the edge of the park, were analyzed by using combined Wavelength- (WDXRF) and Energy-Dispersive (EDXRF) X-ray fluorescence techniques. A total number of 27 chemical elements (Ag, Al, As, Ba, Ca, Cd, Cr, Co, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, P, Pb, Rb, Sb, Sc, Sn, Sr, Ti, V, Zn and Zr) were quantified in the urban soils, and the results were compared to the normal and alert values from Romanian legislation for toxic trace elements, as well as with European and world average values of element concentrations. The mineralogical analyses were performed by Scanning Electron Microscopy with Energy-Dispersive X-ray Analysis (SEM-EDX) and the Attenuated Total Reflectance–Fourier Transform Infrared technique (ATR-FTIR). To assess the soil contamination and the impact on human health of the presence of potential toxic elements and heavy metals in the soil, a series of pollution and health risk indices were used. All the results indicated an unpolluted to moderately polluted soil. The soil samples collected from the edge of the parks presented higher values for the specific pollutants, which originated from heavy traffic, such as Cu, Cr, Zn and Pb. The non-carcinogenic and carcinogenic risk to children was assessed using estimated daily intake (EDI) in relation to the pathways whereby pollutants can enter the human body, such as ingestion, dermal contact, inhalation and vaporization. Using the obtained values for EDI, the hazard quotient and hazard index were determined, which strengthen the formerly issued presumption that soil pollution is moderate and, by itself, does not present any threat to children’s health.

Local structural disorder introduced by Cr in fcc high-/medium-entropy alloys consisting of 3d transition metal elements

High-/medium-entropy alloys (H/MEAs) have attracted attention for their excellent mechanical properties. According to first-principles calculations, the atomic displacements from their lattice points are element-dependent and correlated with the yield strength of H/MEAs. To investigate experimentally the element dependence of the local structure, we measured the extended x-ray absorption fine structure in seven kinds of face-centered cubic H/MEAs consisting of 3d transition metal elements. Our experimental results indicate that the local disorder around chromium (Cr) is larger than that around other elements, which is a common feature in all the measured fcc H/MEAs, aligning with prior theoretical studies indicating larger displacements of Cr in comparison to other elements. We discuss the mechanism underlying the local structural disorder induced by the constituent element Cr.

Evaluating health risks of PM2.5-bound heavy elements in Faridabad, Haryana (India): an industrial perspective.

The present study isfocused on investigating the heavy/toxic metals (Al, Ni, Cr, Pb, Cu, As,Mn, and Zn) of PM2.5 and assessing their associated human health risks. During the study period (July 2022 to July 2023), the PM2.5 samples were collected from two distinct sites in Faridabad (92 samples from site 1 and 85 samples from site 2). In this study, the US EPA's Risk Assessment Guidance for Superfund (RAGS) was followed to evaluate the human health risk associated with PM2.5-bound heavy elements. The annual average of PM2.5 concentrations was 108 ± 16µgm⁻3 at site 1 and 154 ± 11µgm⁻3 at site 2, approximately three to fourtimes higher than the national ambient air quality standards (annual, 40µgm-3). The analysis of enrichment factors (EFs) for the elements Cr, As, Zn, Cu, Mn, Pb, and Ni indicates that the heavy elements associated with PM2.5 primarily originate from anthropogenic sources. The application of the conditional bivariate probability function (CBPF) model for Faridabad revealed local pollution sources contributing to elevated mass concentrations at the receptor site from the southern (S), northwestern (NW), northeastern (NE), southwestern (SW), and southeastern (SE) regions. Furthermore, positive matrix factorization (PMF) analysis identified the predominant sources of PM2.5-bound heavy elements as industrial emissions (41%), vehicular emissions (34%), and combustion processes (25%). After a thorough assessment of health hazards, Cr appeared as a significant carcinogenic risk factor. Children with elevated hazard quotient (HQ) values for Mn and Cr indicated non-carcinogenic health problems. Ultimately, this analysis reinforces the necessity for rigorous monitoring and intervention to safeguard public health from the potentially harmful effects of heavy elements.

Use of spectral transmittance model to improve the detection accuracy of chromium in soil

As a new quantitative analysis method for heavy-metal elements in soil, the main function of the polarization resolution model is to filter out the disturbance of other elements on the spectral signal of target plasma. In order to quantify the mechanism of improving detection performance, the spectral transmittance of plasma intensity in the polarization-resolved optical path has been derived, and the relationship between the intensity of polarization-resolved laser-induced breakdown spectroscopy (PRLIBS) and the characteristic peak wavelength has been defined. Using the spectral data in the wavelength range of 424.50–429.24 nm as the characteristic signal, a quantitative analysis method for detection of the Cr element in soil has been developed. The improvement of spectral intensity stability at the characteristic peak of Cr I 425.7 was analyzed, and the mechanism of enhancing the detection accuracy was elucidated. Research has shown that, based on the polarization characteristics of Cr element plasma, PRLIBS is not affected by the matrix effects of soil and characterizes the amplitude conversion from the reference concentration of Cr element to the plasma spectral intensity. The spectral transmittance of plasma spectra depends not only on the characteristic peak wavelength and complex refractive index of heavy-metal elements but also on the measurement conditions such as spatial geometric angles and reflectivity of the transmission medium.

Effect of bias voltage on high-temperature oxidation resistance and electrical properties of Mn–Co coating with metal interconnects for solid oxide fuel cell

Abstract This study investigated the effects of bias voltage on the microstructure, high-temperature oxidation resistance, electrical conductivity, element diffusion, and barrier of chromium poisoning cathode of Mn–Co coating on the surface of SOFCs metal interconnect SUS441 ferritic stainless steel. A series of Mn–Co coatings were prepared by magnetron sputtering technique at different bias voltages (−10, −50, −90 V) and oxidized at high temperatures for 175 h at 850 °C in an air environment. The results showed that the surface of each coating before oxidation exhibited a cauliflower-like morphology, with the crystallinity of the coating increasing with higher bias voltage. After high-temperature oxidation, especially the Mn–Co coatings prepared at −90 V bias, a dense and stable MnCo2O4 spinel structure was formed, which is crucial in inhibiting the growth of the Cr2O3 oxide layer. In addition, the coating also exhibits excellent electrical conductivity (Ea = 0.35 eV), good high-temperature oxidation resistance (1.182 mg cm−2), and a stronger ability to prevent the diffusion of Cr elements.

Pollution risk assessment and spatial distribution of potentially hazardous elements in selenium-rich soils in the Menyuan Basin of the northeastern Tibetan Plateau

The scientific utilization of selenium (Se)-rich soils necessitates the evaluation of the contents of potentially hazardous elements (PHEs). The Menyuan Basin, a representative Se-rich region located on the northern periphery of the Qinghai–Tibet Plateau, was chosen as the research area. Pollution risk and spatial source analysis was conducted for eight PHEs (As, Cr, Cu, Pb, Zn, Cd, Ni and Hg) using 5297 topsoil samples and 480 deep-soil samples. The results show that more than 50% of the total area has a Se content &gt;0.24 mg kg –1 . According to both single and comprehensive pollution indices, there are extremely few sampling sites with PHEs at risk of contamination. Low ecological risk was seen in 93.34% of the topsoil samples. The results show that although the overall level of surface soil pollution in the study area may be deemed negligible, on the surface or in deeper layers, the concentration centres of As, Cr, Ni, Zn, Pb and other elements show consistency, indicating that underlying parent rocks are the primary source of these elements. The findings presented in this study establish a scientific foundation for the secure development and utilization of Se-rich soils.

Investigation on oxidation behavior and mechanical properties of FeCoNiNbAlCrTa high entropy alloy at 900 °C

In recent years, eutectic high entropy alloys have been found to have excellent mechanical properties and corrosion resistance; however, the simultaneous achievement of these mechanical properties and high-temperature oxidation resistance still constitutes a tough challenge. In this study, Ta and Cr elements are added to (FeCoNiNb)98Al2 high-entropy alloy to improve oxidation resistance, and the changes in microstructure and mechanical properties of (FeCoNiNb)98-2x(TaCr)xAl2 as well as the oxidation behaviors at 900 °C are systematically investigated. The results show that the addition of Ta and Cr elements promotes the increase and growth of the laves phase in the alloy, which improves the oxidation resistance of the alloy and maintains the excellent mechanical properties of (FeCoNiNb)98Al2. The formation of CrTaO4, CrNbO4, and Cr2O3 composite oxide scales can not only prevent the diffusion of O into the alloy, but also inhibit the external diffusion of matrix elements. This result provide experimental data and theoretical support for the optimal design of the high-entropy alloy compositions to improve their antioxidant properties while maintaining excellent mechanical properties.