High Concentrations Of Cr Research Articles

Risk assessment of aluminum, chromium and nickel exposure through ingestion of Arabica and Robusta coffee infusions prepared in aluminum and steel moka pots

The study investigates Al, Cr and Ni contents in coffee beans and infusions. The aim was to show the effect of the material from which the moka pot is made on the quality of infusions and assessing the risk connected with increased consumption of these metals based on hazard quotients calculation. Arabica and Robusta coffee samples of different origin (America, Africa, Asia) and type of processing were tested. The highest concentrations of Cr and Ni were obtained using a steel moka pot, 9.8µgL-1 and 66.8µgL-1, respectively. Drinking 3 cups of coffee per day brewed in this pot, the consumer will be exposed to a daily dose of 4.75·10-5 and 3.23·10-4mgkg-1 day-1 of Cr and Ni, respectively. On the other hand, brewing coffee in an aluminum moka pot results in a concentration of Al up to above 1mgL-1, therefore the migration of this element is significantly higher than that of Cr and Ni. Such a concentration will result in a daily dose of 5.36·10-3mgkg-1 day-1. However, the increased concentration of heavy metals due to the use of an aluminum or steel moka pot does not result in exceeding the maximum permissible dose.

Modular hydrogel selectively adsorbs phosphates and hexavalent chromium while enabling phosphate recovery

Electroplating wastewater containing high concentrations of phosphates and hexavalent chromium Cr(VI) poses serious environmental pollution. Moreover, phosphorus, as a non-renewable resource, necessitates its recovery to meet sustainable development goals. To address this issue, this study used sodium alginate as the scaffold module, synthesized lanthanum carbonate in situ within a chitosan module to serve as the phosphate adsorption module, and employed polyethyleneimine (PEI) modules to enhance the adsorption capacity for Cr(VI), successfully fabricating a modular hydrogel (LC-CSP). LC-CSP exhibits a complex porous structure and surface morphology, forming an ultra-low-density fiber network with good strength and elasticity, ensuring uniform distribution and exposure of active sites. Under optimal conditions for single-component adsorption, LC-CSP achieved adsorption capacities of 232.02 mg/g for phosphates and 474.61 mg/g for Cr(VI). Additionally, LC-CSP demonstrated excellent reusability, retaining over 83 % of its performance after five cycles. In simulated electroplating wastewater experiments with various interfering substances, LC-CSP maintained high removal efficiencies (>90.72 %) for phosphates and Cr(VI). Post-experiment, enriched water after phosphate desorption was further treated to recover phosphorus resources in complex water environments. Multiple characterization techniques elucidated the adsorption mechanisms of LC-CSP: phosphate adsorption primarily involved ligand exchange, electrostatic interactions, and hydrogen bonding, while Cr(VI) adsorption included electrostatic interactions, hydrogen bonding, and reduction reactions. Finally, fixed-bed simulated wastewater adsorption experiments validated the technical potential of LC-CSP for practical electroplating wastewater management.

Enhanced compressive strength by Ti[sbnd]Cr coating on cBN particle surface using vacuum vapor deposition

In order to enhance compressive strength of the coating on cBN particles, this study proposes using vacuum vapor deposition to achieve a Titanium-Chromium (TiCr) co-deposited coating on the surface of cBN particles. Base on deposition process of the TiCr coating using vacuum vapor deposition technology, it proposed a simulation model by an Angular Coefficient Method(ACM), and conducts compressive strength experiments on the TiCr coating of cBN particles. Using the simulation and analysis model, the effect of temperature on the formation of TiCr coating during the reaction process was systematically analyzed, the molecular flow, the change of film thickness, and the deposition rate at different temperature stages was got, and verify the simulation results through experiments. The formation mechanism of TiCr co-deposited coatings was derived by SEM, XRD characterization and reaction thermodynamic analysis. Experiments show that TiCr co-deposited coatings are effective in increasing compressive strength, and the experimental results can be a guidance in controlling Ti/Cr amount in the coatings. In addition, it was found in experiments that by using vacuum vapor deposition technique, Ti/Cr powder mixing ratio of 1:1 provided the best compressive strength, and the compressive strength increased with higher Cr content in the coating after heating. This achievement is of significant importance for the formation of alloyed coatings on superhard materials, enhancing the wettability between the surfaces of superhard materials and their substrates under high-temperature conditions.

Highly efficient reduction of Cr(VI) from industries sewage using novel biomass-driven carbon dots modified TiO2 under sunlight

Hexavalent chromium (Cr(VI)) pollution poses a significant global environmental challenge, with current photocatalysts exhibiting limited efficiencies under natural sunlight, especially in neutral to alkaline conditions or at high Cr(VI) concentrations. In this study, amine-rich biomass-derived carbon dots (CDs) were synthesized from peanut shells and ethylenediamine via a hydrothermal method, combined with titanium dioxide (TiO2) to form a composite with a narrower band gap. This enhanced the electrostatic interactions with Cr(VI), thus improving photocatalytic performance. The composite (1 % CDs) effectively reduced 50 mg/L of Cr(VI) within 60 min under sunlight irradiation, demonstrating stable performance across various pH levels (3, 5, 7, and 9) and Cr(VI) concentrations (10 to 60 mg/L). Even after five cycles, the reduction efficiency remained high at 96.83 %. The composite also achieved reduction rates of 90.09 % and 89.01 % for domestic and electroplating wastewater, respectively, while exhibiting antibacterial properties. Free-radical scavenging experiments confirmed that electrons and holes were the primary active species driving the reduction. This work highlights the potential of the composites for efficient and stable Cr(VI) reduction in real-world water treatment applications.

Sintering behaviours of different ladle filler sands with high-chromium stainless steel

In order to investigate the sintering behaviours of different types of filler sands (chromite-based, zircon-based, and silica-based) with high-chromium stainless steel grades ( w[Cr] = 11.70% and 16.26%), laboratory experiments were carried out at 1600°C in an inert atmosphere. It is found that the high content of Cr in stainless steel promotes the formation of Cr2O3 in the liquid phase of these sintered filler sands, thereby significantly affecting the sintering of the filler sands. Compared with the elements of Mn and Al in conventional steel grades, the Cr element in stainless steel shows a different impact on the sintering of filler sands. The sintering of chromite-based sands is restricted by the rise of Cr content in stainless steel, whereas the dissolved Cr in the steels enhances the sintering of zircon-based and silica-based filler sands. Chromite-based filler sands are recommended for stainless steel. Because the melting point of the liquid phase is significantly influenced by the content of (Cr2O3 + Al2O3), the contents of Al2O3 and Cr2O3 in chromite-based sands should be accordingly adjusted for stainless steel.

Origin of the Oligocene–Miocene Sailipu ultrapotassic volcanic rocks in southern Tibet: Melting of Asian mantle pyroxenites triggered by eastward tearing of the subducting Indian continental slab

Widely distributed Oligocene−Miocene ultrapotassic volcanic rocks in the Lhasa terrane of southern Tibet have been associated with the melting of the lithospheric mantle, plateau uplift, and porphyry Cu-Au mineralization. This study presents the mineral chemistry of olivine and clinopyroxene phenocrysts, whole-rock major and trace element data, and zircon U-Pb geochronological and Hf isotopic data for the Sailipu primitive ultrapotassic volcanic rocks. The Sailipu volcanic rocks exhibit high MgO (5.6−11.4 wt%), Cr (386−981 ppm), Co (22−43 ppm), and Ni (95−423 ppm) concentrations and have highly fractionated rare earth elements [REEs; (La/Yb)N = 23−73] and high-Fo (89.1−90.8) olivine phenocrysts containing elevated NiO (up to 0.59 wt%), which suggests a pyroxenitic mantle source that partially melted in the garnet stability field. Their high K2O contents (4.8−8.0 wt%) and global subduction sediment-like trace element patterns suggest that the metasomatic agents, which reacted with mantle peridotites to form phlogopite-bearing pyroxenites, were dominantly derived from the melting of subducted continental sediments. Their high whole-rock Ba/La and Th/Nd ratios are consistent with this hypothesis. The Sailipu ultrapotassic volcanic rocks also exhibit low initial 176Hf/177Hf ratios that resemble those of Himalayan leucogranites, and high Ca contents in olivine phenocrysts, which is consistent with contributions from the subducted carbonate-rich sedimentary strata on top of the thinned Greater Indian continental crust. The zircon U-Pb chronological data yielded concordant ages of 24.33 ± 0.19 Ma, 21.20 ± 0.62 Ma, and 17.05 ± 0.31 Ma for different exposures of the Sailipu volcanic rocks, which establishes a maximum age of ca. 24 Ma for these rocks. The northwest−southeast spatial distribution and the southeastward decrease in age (80°E−90°E) suggest west-to-east tearing of the thinned Greater Indian slab, which caused asthenospheric upwelling and melting of the Tibetan lithospheric mantle. Geothermometric calculations show relatively high primary magma temperatures (∼1250 °C) that are consistent with asthenospheric upwelling. We propose a mechanism that could genetically link the coeval Cu-Au ore-forming granitoids with the ultrapotassic magmatism of the Gangdese belt. The ultrapotassic rocks supply a large-volume of external magmatic volatiles, particularly H2O, which could trigger melting of the Tibetan lower crust and lead to the generation of the ore-forming granitoids and the establishment of oxidizing conditions for porphyry deposits. The oxygen fugacity (log ƒO2 values of ΔFMQ) of the primitive Sailipu ultrapotassic volcanic rocks (ΔFMQ = 0.48 ± 0.51 based on the Dol/melt V oxybarometer and ΔFMQ = 0.33 ± 1.19 according to the magmatic zircon U-Ce-Ti oxybarometer) is slightly lower than that of porphyry Cu-Au ore-forming granitoids in the eastern Gangdese (ΔFMQ = +0.8 to +2.9), which suggests that the direct injection of ultrapotassic melts into ore-forming granitoids played a limited role in changing oxygen fugacity, but more oxidized fluids/volatiles exsolved from these ultrapotassic melts may have facilitated the remelting of sulfide-bearing lower crust and/or directly scavenged sulfides from the mush-state reservoirs of the ore-forming granitoids in the middle−upper crust.

Investigation of softening in hardfaced layers during welding

Hardfacing is a widely used technique to create wear-resistant layer on the base material to ensure good durability and performance under harsh operating conditions. However, despite its effectiveness in improving wear resistance, hardfaced layers can sometimes exhibit softening phenomena during welding, compromising their mechanical properties and overall performance. In this research, the effect of heat input was investigated in case of Fe-based hardfacing material with high Cr content. 4 different heat inputs were applied with gas metal arc welding and significant differences were determined in hardnesses, which can be influential to the lifetime of hardfaced parts. Hardness drop happens in the heat-affected zones between the hardfaced layers and the highest heat input causing the most significant softening (20% hardness drop).

The electronic and magnetic properties of Cr-doped ZnO monolayer at higher percentage by first principles calculations

The crystal structure, structural stability, electronic band structures and magnetization of Cr-doped ZnO monolayer (ML) have been investigated by GGA+U method using first principles calculations in this work. The stability of these systems is confirmed by the negative formation energies at different Cr concentrations. The calculated band gaps with and without the Hubbard U correction aligned well with other computational results. With the increase of Cr concentration, the band gap of Cr-doped ZnO monolayer decreases for the spin-up configuration. However, in the spin-down configuration, the band gap increases first and then decreases and the maximum band gap is obtained at 22.22% Cr concentrations. At 33.33% Cr concentration, the ZnO ML exhibits metallic behavior. The density of states (DOS) analysis reveals an asymmetric nature, indicating ferromagnetism in Cr-doped ZnO MLs at various concentrations, with a magnetic moment per Cr atom of approximately 3.99 μB. The total magnetic moment rises with increasing Cr concentration. Charge density difference analysis shows increased magnetization with higher Cr concentration. At 22.22% Cr concentration, the ZnO ML exhibits ferromagnetism and semiconducting properties, suggesting significant potential for spintronic applications as a diluted magnetic semiconductor.

Unraveling the Subsurface Damage and Material Removal Mechanism of Multi-Principal-Element Alloy FeCrNi Coatings During the Scratching Process

Multi-principal-element alloys (MPEAs) exhibit superior strength and good ductility. However, tribological properties of FeCrNi MPEAs remain unknown at nanoscale and complex environments. Here, we investigate the effects of scratching speed, depth, and temperature on microstructural and tribological characteristics of FeCrNi using molecular dynamics simulations combined with an elevated temperature tribological experiment. The scratching force experiences the increase stage, the undulated stage, and the stable stage due to chip formation. Compared to traditional alloy coatings, low force enhances the useful life. With increased speed, the friction coefficient decreases, agreeing with previous work. High speed impacting includes severe local plastic deformation, from dislocation to amorphization. As the scratching depth increases, the average scratch force and friction coefficient increases owing to material accumulation in front of the abrasive particles. The surface morphology and dislocation behavior are significantly different during the scratching process. In addition, we revealed a temperature-dependent friction mechanism. FeCrNi MPEAs have excellent wear resistance at an intermediate temperature, which is attributed to the high Cr content promoting the formation of the compact oxide layer. This work provides atomic-scale mechanistic insights into the tribological behavior of FeCrNi, and would be applied to the design of MPEAs with high performance.

Efficient extraction of refractory Cr from stainless steel dust by sodium persulfate oxidation roasting

Stainless steel dust (SSD) contains a high content of Cr and is listed as hazardous solid waste. However, SSD is mainly stockpiled in legacy waste sites due to its complexity and lack of investigation. Herein we comprehensively investigates the microscopic interaction between heavy metals and coexisting phases of SSD from the electric arc furnace (EAF). Furthermore, a new approach for extracting Cr from SSD was developed for the first time. It was found that SSD is enriched with Cr, Ni, Mn, and Zn. Most of these heavy metals are bound to stable spinel (e.g., FeCr2O4) and encapsulated by silicate. Using Na2S2O8 as the flux (1–24 mmol), under roasting at 350–750 °C in the air for 0.25–6 h, efficient heavy metal extraction can be achieved (Cr-80 %, Ni-86 %, Mn-93 %, Zn-94 %) at 650 °C for 1h. During the roasting processes, the silicate shell was broken, which facilitated the mass transfer of the oxidant. Fe(II) was oxidized to Fe(III) and collapsed the spinel structure, releasing the heavy metals during the following acid leaching. The total mass of SSD is reduced by 90–95 %, and detoxification of SSD is achieved after processing. In conclusion, efficient extraction refractory metals in SSD by Na2S2O8 roasting and the mechanism was elucidated for the first time. This method might also be applied for the treatment of other slags/ash waste that have a stable spinel structure and are encapsulated by silicate.

Arsenic, cadmium, and chromium concentrations in contrasting phosphate fertilizers and their bioaccumulation by crops: Towards a green label?

Potentially toxic elements such as arsenic (As), cadmium (Cd), and chromium (Cr) are severely regulated in fertilizers and deserve continuous investigation. Phosphate-derived Cd has been a stepping-stone toward achieving sustainable and safe worldwide food production, especially after a new regulation aiming for reduced limits of Cd in P fertilizers (EU, 2019/1009). Three pot experiments were conducted to assess the variability of As, Cd, and Cr concentrations - with a particular focus on Cd - from monoammonium phosphates (MAP 1, MAP 2, and MAP 3 from different geographic origins) and their accumulation in limed and unlimed soils, and contrasting crops, representing staple food and significant sources of these elements for humans (i.e., potato, tobacco, and rice). A diverse array of sensitive techniques for trace elements determination were used to reveal the highest level of Cd of MAP 3 (20.71 mg kg−1 MAP), which loaded the highest amounts of this element to the soil matrix and solution, plant shoots, and xylem sap, contrasting with results for MAP 1 (0.87 mg kg−1 MAP), which has almost ten times less Cd than that required for low-Cd labeling of P fertilizers (≤20 mg Cd kg−1 P2O5). MAP 3 also had the highest Cr concentration (139.3 mg kg−1 MAP). Among crops, rice accumulated 16-fold less Cd than potato plants. Liming decreased Cd in tobacco and potato shoots up to 35%. Moreover, reductions of about 20% were also observed for Cd accumulation in tubers and sap. Conversely, Cd from MAP 3 was always much more accumulated in soil solution, achieving up to 20 μg L−1, while values < 5 μg L−1 (i.e., a groundwater limit) were obtained from MAP 1. Our findings may be used as a reference in developing green labels for fertilizers in scenarios where Cd accumulation represents a potential risk for soil and human health.

Used in Urban Area for Landscape Planning and Design Spatial and Temporal Variations in Chromium (Cr) Concentrations in Picea orientalis L.

This study investigates the spatial and temporal variations in chromium (Cr) concentrations in Picea orientalis L., across different directions (north, east, south, and west) and plant organs (outer bark, inner bark, and wood) in a forested region. The research, conducted over eight age periods spanning 1980 to 2020, aimed to assess the effectiveness of Picea orientalis L. as a biomonitor for Cr pollution. The highest Cr concentrations were observed in the east direction, particularly in the inner bark and wood, while the lowest levels were found in the west. The study was conducted in an urban area near the industrial zone and highway, as well as in forested regions. A total of 100 trees were selected for the study, with samples collected from three different organs: outer bark (OB), inner bark (IB), and wood. Samples were taken from each organ at breast height (approximately 1.3 meters above the ground) to ensure consistency. The sampling covered various age periods, specifically 1980–2020, to analyze temporal changes in Cr concentrations. Statistical analysis revealed significant variations in Cr concentrations across most directions and periods, with notable increases during certain periods, especially in the west direction. These variations can be attributed to several factors, including the proximity to industrial sources of pollution, which typically release higher levels of chromium into the environment. The eastern direction likely experiences greater exposure to these emissions due to prevailing wind patterns and urban runoff, leading to increased accumulation in Picea orientalis L. Additionally, seasonal changes, temperature fluctuations, and soil characteristics may influence the bioavailability of chromium, affecting its uptake by the tree. The results suggest that Picea orientalis L. can effectively reflect Cr pollution levels, with significant directional and temporal variations that highlight the influence of these environmental factors on Cr accumulation. This study underscores the potential of Picea orientalis L. as a valuable tool for monitoring and managing Cr pollution in forested environments.

Risk factors for postoperative hepatic dysfunction in overweight patients with acute type A aortic dissection

BackgroundAcute hepatic dysfunction (AHD) is a common postoperative complication in patients with acute type A aortic dissection. The aim of this study was to identify risk factors for acute hepatic dysfunction after surgery for acute type A aortic dissection.MethodsWe performed a retrospective study from March 1, 2019, to February 28, 2021. The primary endpoints of this study were morbidity due to AHD and risk factors for incidence. Univariate analysis and multivariate logistic regression analysis were used to analyse the related factors, and receiver operating characteristic (ROC) curves were plotted to evaluate their predictive value.ResultsAmong 147 patients, 29 (19.73%) developed postoperative acute hepatic dysfunction, and 9 (6.12%) died. Univariate analysis revealed that the ALT (P = 0.042), Cr (P < 0.001), and BUN (P = 0.008) levels were significantly different between the two groups. Multivariate logistic regression analysis revealed that Cr (OR = 1.013, 95% CI = 1.003–1.023, P = 0.008) was an independent risk factor for postoperative hepatic dysfunction in overweight (BMI > 24) patients with ATAAD. The area under the ROC curve (AUC) for Cr was 0.745 > 0.7, indicating good predictive value.ConclusionA high Cr concentration is an independent risk factor for postoperative AHD in overweight (BMI > 24) patients with ATAAD.

A study on microstructure evolution of MCrAlY coatings after thermal aging in Te environment

The effects of thermal exposure on tellurium (Te) diffusion behavior in MCrAlY coatings were investigated at 800 °C in Te vapor. The results showed that the diffusion depth of Te in MCrAlY coatings gradually increased with the exposure time, and the dense Cr3Te4 layer formed on the coating surface in the initial stage was no longer continuous, especially under aging conditions with higher Te concentration. The high Cr content of the coating promoted the solid phase transition of the surface reaction product from Cr3Te4 to Cr7Te8, and resulting in the formation of large α-Cr phase either within or beneath the reaction layer during long aging processes. As a result of this phase transition, excess Te atoms were released from Cr3Te4 and continued to diffuse into the coating. Te did not exhibit obvious intergranular diffusion characteristics within the coating. When it encountered Y, it was captured by Y and formed a YTe phase. After aging for 3000 h, Te was distributed throughout the coating, and numerous voids were formed at the interface between the coating and the substrate. These two factors deteriorated the plasticity and adhesion of the coating. Results from molten salt corrosion tests indicated that the high content of Cr and Al in the coating, as well as high densities of grain boundaries providing diffusion pathways, reduced the corrosion resistance of the coating to molten salt.

Unraveling the Protolith Origin of Serpentinite Rocks from the Tengnoupal Area, Manipur Ophiolite Complex, Indo-Myanmar Range

Objective: This article mainly focuses on investigating the protolith origin of serpentinite rocks in and around Tengnoupal, within the Manipur Ophiolite Complex (MOC), using a combined petrographic and geochemical approach. Methods: During fieldwork, samples were collected and cut into thin sections to reveal their mineralogical and textural relationships. Major oxides and trace elements were determined by XRF, and rare earth elements analysis was carried out by ICP-MS to determine the nature and origin of the rocks. Findings: The studied rock samples exhibit varying degrees of serpentinization, ranging from partial to complete, and exhibit a pseudomorphic texture including mesh and hour structures replacing the original olivine and bastite texture replacing pyroxene. Geochemically, the analyzed rock types exhibit komatiitic affinity and are characterized by high magnesium numbers (Mg# average 84.4). The studied serpentinite rocks have lower Al/Si ratios (Average=0.05) and higher Mg/Si ratios (average= 0.95) in bulk rock compositions indicating a refractory abyssal mantle peridotite protolith when compared to the primitive mantle. The high Ti (range 300-480 ppm) and Cr (628-3186 ppm) contents indicate a subduction environment. In addition, the rock samples exhibit slight depletion chondrite-normalized Rare Earth Elements (REE) patterns ((La/Yb) N = average 0.87). The rocks exhibit spoon-shaped normalized Rare Earth Element patterns and primitive mantle are similar to mid-oceanic ridge abyssal mantle rocks. Novelty: The origins of the rocks studied suggest a transitional phase between abyssal and subduction zone-related serpentinites, forming after harzburgite-peridotite. As subduction began, dehydrated orogenic peridotite from the abyssal serpentinites was thrust or obducted, forming the MOC serpentinites. This indicates that the serpentinite rocks in MOC share similarities with those found in mid-oceanic ridge environments, which is characteristic of a supra-subduction zone setting. Keywords: Ultramafic rocks, Serpentinization, Supra­subduction zone, Abyssal, REE

Investigation of microplastics and potentially toxic elements (PTEs) in sediments of two rivers in Southwestern Nigeria.

Microplastics (MPs) are emerging and ubiquitous contaminants, known to accumulate in river sediments. In many developing nations, the absence of policies for managing plastic waste puts the inland river ecosystems at risk of excessive abundance of plastics and MPs. However, only limited studies have reported MPs in river environments in these countries. The current study therefore examined the abundance and nature of MPs and potentially toxic elements (PTEs) in the sediments of the Odo-Ona and Ogun Rivers in Southwest Nigeria. MPs were extracted from the sediments using the density separation method and categorized according to their size, colour and shapes. The range of MP abundances found in the Ogun River sediments was 66.6 ± 12.2 to 311 ± 20.8 particles/kg, while that of the Odo-Ona River ranged from 133 ± 50 to 433 ± 100 particles/kg. The MPs polymer analyses revealed the presence of polyethylene (PE), polypropylene (PP) and polyamide (PA) particles in the sediments. PE was most abundant in the two rivers, constituting 72.8% and 59.7% of MPs (with 0.5 - 5mm size), recovered from the Odo-Ona and Ogun Rivers, respectively. High concentrations of Cr and Pb with ranges of 10.3 - 48.3 and 10.1 - 211mg/kg, respectively, were detected in the sediments and were associated with anthropogenic effects. This study reveals the impact of indiscriminate waste dumping on the water bodies, and calls for strict enforcement of environmental laws in the country.

Geochemistry and conditions of formation of Mesoarchean banded iron formations (BIF-1) from the Kostomuksha Greenstone belt, Karelian Craton

Three variably old groups of banded iron formation (BIF) are known in the Kostomuksha Greenstone belt (KGB) of the Karelian Craton. This paper deals with the earliest of them, Mesoarchean (2.87–2.81 Ga) – BIF-1. BIF-1 occurs among the komatiite-basalt unit of the KGB. BIF-1 consists mainly of quartz and magnetite, with varying amounts of amphibole, biotite, and garnet; they contain 48.3-58.6 SiO2 and 21.34–33.82 wt. %, Fe2O3T, suggesting that the rocks are BIF. BIF-1 of the KGB, as well as most Archean BIFs, contain high Fe2O3T, concentration, display a contrasting positive Eu anomaly, lost of Ce anomaly, the depletion of LREE relative to HREE. However, they stand out among other BIFs with high Al2O3, TiO2, MgO, K2O, Cr, Ni, Zr, Ba, Cu and Zn concentrations. BIF-1 was formed in a marine basin in an anoxic atmosphere due to hydrothermal fluids, the proportion of which varies from 20 to 80 %, and a terrigenous component derived mainly from basalts, komatiites, and dacites in host rocks. Mesoarchean BIF-1 of the KGB s was formed in a small rift within an oceanic volcanic plateau, the formation of which is associated with the influence of a mantle plume on the oceanic lithosphere.

Retrieval of chromium and mercury concentrations in agricultural soils: Using spectral information, environmental covariates, or a fusion of both?

The universal contamination of arable land with potentially toxic elements (PTEs) poses a severe threat to food security and jeopardizes worldwide efforts to meet the United Nations Sustainable Development Goals (SDGs). How to obtain more reliable concentrations of PTEs in regional agricultural soils is a priority problem to be solved. Multispectral satellite remote sensing, with its advantages of high spatial and temporal resolution, broad coverage, and low cost, offers the potential to acquire spatial distribution of PTEs in agricultural soils over large areas. However, owing to the complexity of soil environments and the insufficiency of spectral information, the mechanism for retrieving concentrations of PTEs in agricultural soils via multispectral satellites is not yet clear, and the accuracy needs to be improved. In this study, we aimed to assess whether employing a fusion of spectral information and environmental covariates, results in more accurate retrievals of PTEs, specifically chromium (Cr) and mercury (Hg), in croplands than does employing spectral information alone. Three machine learning algorithms—kernel-based support vector machine (SVM), neural network-based back propagation neural network (BPNN), and tree-based extreme gradient boosting (XGBoost)—were developed to retrieve Cr and Hg concentrations in agricultural soils. The results showed that the fusion of spectral information and environmental covariates combined with the XGBoost model performed best in retrieving both Cr and Hg concentrations in agricultural soils with coefficient of determination (R2) values of 0.73 and 0.74, respectively. Environmental covariates were important variables for determining Cr and Hg concentrations in agricultural soils, but the ability to retrieve these element concentrations by utilizing spectral information alone was limited. High Cr concentrations occurred in central towns and southern hilly mountains. High Hg concentrations were detected in the northwestern region and southern hilly mountains. The potential of fusing spectral information and environmental covariates to precisely retrieve PTE concentrations in agricultural soils can serve as a reference for agricultural soil health information monitoring worldwide.

Chromium contamination affects the fungal community and increases the complexity and stability of the network in long-term contaminated soils

Chromium (Cr) contamination can adversely affect soil ecology, yet our knowledge of how fungi respond to Cr contamination at heavily contaminated field sites remains relatively limited. This study employed high-throughput sequencing technology to analyze fungal community characteristics in soils with varying Cr concentrations. The results showed that Cr contamination significantly influenced soil fungi's relative abundance and structure. Mantel test analysis identified hexavalent chromium (Cr(VI)) as the primary factor affecting the structure of the soil fungal community. In addition, FUNGuild functional prediction analysis exhibited that Cr contamination reduced the relative abundance of Pathotroph and Symbiotroph trophic types. High concentrations of Cr may lead to a drop in the relative abundance of Animal Pathogens. Molecular ecological network analysis showed that Cr contamination increased interactions among soil fungi, thereby enhancing the stability and complexity of the network. Within these networks, specific keystone taxa, such as the genus Phanerochaete, exhibited properties capable of removing or reducing the toxicity of heavy metals. Our studies suggest that Cr contamination can alter indigenous fungal communities in soil systems, potentially impacting soil ecosystem function.

Effect of multi-element synergistic addition on the microstructure evolution and performance enhancement of laser hot-wire cladded Fe-based alloy

To satisfy the requirements of hardness and corrosion resistance for laser additive manufacturing of hydraulic supports, this study applied the synergistic addition of C, B, Cr, Ni, Nb and Mo elements in Fe-based alloys. The multi-phases, martensite + austenite + ferrite were designed. The microstructure, hardness and corrosion resistance of the coatings were analyzed. Increasing the C and B contents could significantly increase the hardness of the coatings, while the corrosion resistance was decreased. The corrosion resistance of the coatings was determined by the Cr contents. However, increasing the Cr contents to 20.0 wt % resulted in the ferrite structure with lower hardness (21 HRC). The coatings with 0.25 wt % C, 1.2 wt % B and 19.0 wt % Cr showed the optimal matching of hardness (56 HRC) and corrosion resistance (survived in neutral salt spray test≥300h). The resulted coatings were mainly consisted of dendritic structure. Fine lath martensite phase was dominant in the dendrite regions. The interdendritic regions were consisted of nano-sized intermetallics with a mixture of σ+Nb + FeNb + Cr2Nb+(Fe,Cr)2B + NbC compounds. These interdendritic regions (14.2 GPa) showed higher hardness than that of the dendritic regions (7.1 GPa). The high Cr contents with finer dendritic structures were the major mechanisms for the excellent combination of hardness and corrosion resistance. The precipitation and growth mechanisms of the interdendritic phases were elaborated. This work provides a valuable reference for laser hot-wire cladding to prepare Fe-based alloys with high hardness and excellent corrosion resistance.