Search Results (49)

Carbonaceous–siliceous–argillaceous rock-type uranium deposits, a major uranium resource in China, pose significant environmental risks due to heavy metal contamination. Geochemical investigations in the former Zoige uranium mine revealed elevated As, Cd, Cr, Cu, Ni, U, and Zn concentrations in soils and sediments, particularly at river confluences and downstream regions, attributed to leachate migration from ore bodies and tailings ponds. Surface samples exhibited high Cd bioavailability. The integrated BCR and mineral analysis reveals that Acid-soluble and reducible fractions of Ni, Cu, Zn, As, and Pb are governed by carbonate dissolution and Fe-Mn oxide dynamics via silicate weathering, while residual and oxidizable fractions show weak mineral-phase dependencies. Positive Matrix Factorization identified natural lithogenic, anthropogenic–natural composite, mining-related sources. Pollution assessments using geo-accumulation index and contamination factor demonstrated severe contamination disparities: soils showed extreme Cd pollution, moderate U, As, Zn contamination, and no Cr, Pb pollution (overall moderate risk); sediments exhibited extreme Cd pollution, moderate Ni, Zn, U levels, and negligible Cr, Pb impacts (overall extreme risk). USEPA health risk models indicated notable non-carcinogenic (higher in adults) and carcinogenic risks (higher in children) for both age groups. Ecological risk assessments categorized As, Cr, Cu, Ni, Pb, and Zn as low risk, contrasting with Cd (extremely high risk) and sediment-bound U (high risk). These findings underscore mining legacy as a critical environmental stressor and highlight the necessity for multi-source pollution mitigation strategies. Full article

Additive manufacturing of metals is limited by a fundamental tradeoff between deposition rates and manufacturability of fine-scale features. To overcome this problem, a laser-ablated bound metal deposition (laBMD) process is demonstrated in which 3D-printed green-state bound metal deposition (BMD) parts are post-processed via laser ablation prior to conventional BMD debinding and sintering. The laBMD process is experimentally characterized via a full-factorial design of experiments to determine the effect of five factors—number of laser passes (one pass, three passes), laser power (25%, 75%), scanning speed (50%, 100%), direction of laser travel (perpendicular, parallel), and laser resolution (600 dpi, 1200 dpi)—on as-sintered ablated depth, surface roughness, width, and angle between ablated and non-ablated regions. The as-sintered ablation depth/pass ranged from 3 to 122 µm/pass, the ablated surface roughness ranged from 3 to 79 µm, the angle between ablated and non-ablated regions ranged from 1° to 68°, and ablated bottom widths ranged from 729 to 1254 µm. This study provides novel insights into as-manufactured ablated geometries and surface finishes produced via laser ablation of polymer–metallic composites. The ability to inexpensively and accurately manufacture fine-scale features with tailorable geometric tolerances and surface finishes is important to a variety of applications, such as manufacturing molds for microfluidic devices. Full article

The Kallintiri area (SW Byala Reka–Kechros Dome, Rhodope) hosts a polymetallic (critical, base, and precious metals) ore deposit, tectonically controlled by the late Eocene–Oligocene, top-to-SW Kallintiri Detachment System. The earliest structure associated with the Kallintiri Detachment is a ductile shear zone at the interface between the high-grade footwall gneisses of the Lower and Intermediate Rhodope Terranes. The detachment zone encompasses the uppermost part of the gneisses and the ultramylonitic Makri Unit marble. The marble is bound by a brittle–ductile shear zone at the base and a knife-sharp, low-angle normal fault at the roof, exhibiting considerable brecciation and ultracataclasite development. The hanging wall includes the Makri Unit phyllites and the overlying mid–late-Eocene–Oligocene supra-detachment sediments, which show syn-depositional slump structures and brittle deformation with low- and high-angle faulting and non-cohesive cataclasites. Extensive hydrothermal fluid circulation along the detachment zone and through NW tension gashes and high-angle faults led to pronounced silicification and ore deposition. Field observations and mineralogical and geochemical analyses revealed two primary types of ore mineralization spatially and temporally associated with different structures. Base and precious metals-rich ores are associated with the detachment, while Sb ore deposition is localized mostly within the NW-trending tension gashes and high-angle faults. Full article

The quality, reproducibility, and reliability of additive-manufactured parts strongly depend on optimizing printing parameters and post-processing treatments. This study evaluates the effects on the microstructure and corrosion resistance properties of solution annealing and aging heat treatments performed on 17-4 PH stainless steel samples fabricated with different build-up orientations using a material extrusion technology: the Bound Metal Deposition^TM. The chemical composition and microstructures were determined using X-ray diffraction, chemical etching, optical microscopy, and scanning electron microscopy. The corrosion resistance properties in neutral sodium chloride electrolytes were investigated through cyclic potentiodynamic polarization and open circuit potential monitoring and analysis. The findings demonstrated that the solution annealing heat treatment remarkably enhanced the overall corrosion resistance properties of the samples. The improvement was attributed to the growth of the ferritic phase along the grain boundaries of the martensitic matrix and a finer dispersion of copper precipitates. The aging heat treatment performed after solution annealing enhanced the ferritic phase development, resulting in a further improvement of the localized corrosion resistance properties. Full article

Bound metal deposition (BMD) additive manufacturing technique was used to fabricate gears of PH 17-4 stainless steel material. The gears were fabricated with different layer heights (namely 150 μm and 50 μm) and also subjected to post-fabrication machining. Each gear was tested against commercially available gear in a high-precision control test rig. The operational temperature and noise level were measured during the test, while the material loss due to wear was evaluated at the end of the test. The 50 μm layer height gear performed the best with the least wear loss, minimum noise generation, and temperature rise. The 150 μm layer height gear, which was mechanically polished, performed very similarly to it (50 μm layer height gear) and cost 33% less to print; thus, it was considered the best performing when cost was incorporated. The conclusions found that post machining of printed parts greatly impacts their performance, and thus, the post-print conditions should be considered just as much as the printing conditions. Full article

Dry riverbeds can transport mining waste during torrential rain events, disseminating pollutants from mining areas to natural ecosystems. This study evaluates the impact of these mine wastes on soils, sediments, and runoff/pore water in the La Carrasquilla dry riverbed (southeastern Spain). An integrated approach utilizing geochemical and mineralogical techniques was employed, analyzing water, soil, and sediment samples from both the headwater and mouth of the riverbed. Soil profiles and pore water were collected at 30 cm, 60 cm, and 90 cm deep, alongside sediment and runoff water samples. The assessment of metal(loid) contamination focused on arsenic, cadmium, chromium, copper, iron, nickel, manganese, zinc, and lead, utilizing sequential extraction to evaluate metal partitioning across soil phases. Various pollution indices, including the contamination factor (Cf), pollution load index (PLI), potential ecological risk index (RI), and metal(loid) evaluation index (MEI), were employed to classify contamination levels. The highest level of contamination was reported in the headwater, which suggested anthropogenic activities linked to the presence of mining residues as the major source of metal(loid)s. However, an active deposition of As, Cd, Cu, Fe, Mn, and Zn was reported in the topsoil at the mouth. In the headwater, a quartz and muscovite-rich zone exhibited the highest Cf for Pb (1022), primarily bound to the soil residual fraction (62.8%). At the headwater and mouth, pore water showed higher concentrations of sulfate, Ca, Na, Cl, Mg, and Mn and higher salinity than acceptable limits for drinking water or irrigation established by the World Health Organization. Runoff-water metal concentrations surpassed established guidelines, with MEI values indicating significant contamination by cadmium (36.1) and manganese (19.0). These findings highlight the considerable ecological risk of Pb and underscore the need for targeted remediation strategies to mitigate environmental impacts in the Mar Menor coastal lagoon. Full article

As challenges in precious and base metal exploration intensify due to the diminishing availability of high-grade ore deposits, rising demand, energy costs, and stricter regulations towards net-zero carbon activities, advanced techniques to enhance exploration efficiency are becoming increasingly critical. This study demonstrates the effectiveness of quantitative X-ray diffraction (QXRD) with Rietveld refinement, coupled with multivariate statistical analysis (including agglomerative hierarchical clustering, principal component analysis, and fuzzy analysis), in characterizing the complex mineralogy of strata-bound volcanic-associated limestone-skarn Zn-Pb-Ag-(Cu-Au)-type sulphide deposits (SVALS). Focusing on 113 coarse rejects from the Gumsberg project located in the Bergslagen mining district in central Sweden, the research identified five distinct mineralogical clusters corresponding to polymetallic base metal sulphide mineralization, its proximal alteration zones, and variably metamorphosed host rocks. The results reveal significant sulphide mineralization, ranging from disseminated to massive occurrences of sphalerite, pyrrhotite, pyrite, and galena, with trace amounts of secondary minerals like anglesite in certain samples indicating weathering processes. The study also identifies rare minerals such as armenite, often overlooked in traditional geological logging. These findings underscore the potential of QXRD to enhance resource estimation, optimize exploration strategies, and contribute to more efficient and sustainable mineral exploration programs. The accuracy of QXRD was cross-validated with geological logs and geochemical data, confirming its reliability as a mineralogical discrimination tool. Full article

Owing to their potential to transform traditional medical diagnostics and health monitoring, wearable biosensors have become an alternative evolutionary technology in the field of medical care. However, it is still necessary to overcome some key technique challenges, such as the selectivity, sensitivity, and stability of biometric identification. Herein, a novel, wearable electrochemical sensor based on a molecularly imprinted polymer (MIP) integrated with a copper benzene-1,3,5-tricarboxylate metal–organic framework (MOF) was designed for the detection of stress through the on-body monitoring of cortisol in sweat. The MOF was used as the substrate for MIP deposition to enhance the stability and sensitivity of the sensor. The sensor consisted of two layers, with a microfluidic layer as the top layer for spontaneous sweating and a modified electrode as the bottom layer for sensing. The sensor measured cortisol levels by detecting the current change that occurred when the target molecules bound to the imprinted cavities, using Prussian blue nanoparticles embedded in the MIP framework as the REDOX probe. The proposed sensor exhibited a linear detection range of 0.01–1000 nM with a detection limit of 0.0027 nM, and favorable specificity over other analogies. This facile anti-body free sensor showed excellent stability, and can be successfully applied for in situ cortisol monitoring. Full article

Exposure to heavy metals (HMs) is often associated with inflammation and cell death, exacerbating respiratory diseases including asthma. Most inhaled particulate HM exposures result in the deposition of HM-bound fine particulate matter, PM_2.5, in pulmonary cell populations. While localized high concentrations of HMs may be a causative factor, existing studies have mostly evaluated the effects of systemic or low-dose chronic HM exposures. This report investigates the impact of local high concentrations of specific HMs (NaAsO₂, MnCl₂, and CdCl₂) on sphingolipid homeostasis and oxidative stress, as both play a role in mediating responses to HM exposure and have been implicated in asthma. Utilizing an in vitro model system and three-dimensional ex vivo human tissue models, we evaluated the expression of enzymatic regulators of the salvage, recycling, and de novo synthesis pathways of sphingolipid metabolism, and observed differential modulation in these enzymes between HM exposures. Sphingolipidomic analyses of specific HM-exposed cells showed increased levels of anti-apoptotic sphingolipids and reduced pro-apoptotic sphingolipids, suggesting activation of the salvage and de novo synthesis pathways. Differential sphingolipid regulation was observed within HM-exposed lung tissues, with CdCl₂ exposure and NaAsO₂ exposure activating the salvage and de novo synthesis pathway, respectively. Additionally, using spatial transcriptomics and quantitative real-time PCR, we identified HM exposure-induced transcriptomic signatures of oxidative stress in epithelial cells and human lung tissues. Full article

Choosing the right metal AM equipment and material is a highly intricate process that forms a crucial part of every manufacturing company’s strategic plan. This study undertakes a comprehensive comparison of the performance and material properties of three Metal Additive Manufacturing (AM) technologies: Powder Bed Fusion (PBF), Metal Filament Deposition Modeling (MFDM), and Bound Metal Deposition (BMD). An automotive nozzle was selected and manufactured using all three technologies and three metallic materials to understand their respective advantages and disadvantages. The samples were then subjected to a series of tests and evaluations, including dimensional accuracy, mechanical properties, microstructure, defects, manufacturability, and cost efficiency. The nozzle combinations were PBF in aluminum, MFDM in stainless steel, and BMD in hard tool steel. The results underscore significant differences in functionality, material characteristics, product quality, lead time, and cost efficiency, all of which are crucial factors in making equipment investment decisions. The conclusions drawn in this paper aim to assist automotive industry equipment experts in making informed decisions about the technology and materials to use for parts with characteristics like these. Future studies will delve into other technologies, automotive components, and materials to further enhance our understanding of the application of metal AM in manufacturing. Full article

Particulate-bound mercury (PBM) has a large dry-deposition rate and removal coefficient, both of which import mercury into terrestrial and marine ecosystems, causing global environmental problems. In order to illustrate the concentration characteristics, main sources, and health risk of PBM in the atmospheric environment during the spring dust storm period in Xi’an in 2022, PM_2.5 samples were collected in Xi’an in March 2022. The concentration of PBM and the PM_2.5 composition, including water-soluble ions and elements, were analyzed. The input of dust caused a significant increase in the concentration of PBM, Ca²⁺, Na⁺, Mg²⁺, SO₄²⁻, and metal elements in the aerosol. The research results revealed that the dust had a strong enrichment influence on the atmospheric PBM in Xi’an. Anthropogenic mercury emissions and long-distance migration in the sand source area promote the rise in PBM concentration and should be included in the mercury inventory. The values of the risk index for a certain metal (E_rⁱ) (572.78–1653.33) and the geo-accumulation index (Igeo) (2.47–4.78) are calculated during this study, showing that atmospheric PBM has a strong pollution level with respect to the ecological environment and that Hg mainly comes from anthropogenic mercury emissions. The non-carcinogenic health risk of atmospheric PBM in children (8.48 × 10⁻²) is greater than that in adults (1.01 × 10⁻²). The results show that we need to pay more attention to children’s health in the process of atmospheric mercury pollution control. This study discusses the distribution characteristics of PBM during spring sandstorms and the effects of atmospheric mercury on residents’ health, providing a basis for studying the sustainable development of environmental health and formulating effective strategies for mercury emission control. Full article

Rhenium is an extremely rare critical metal element in Earth’s continental crust. Owing to its extremely high melting point and heat-stable crystalline structure, rhenium is an essential component of alloy materials used in high-performance aircraft engines. Demand for rhenium resources is therefore growing. Currently, most rhenium is produced as a byproduct of molybdenum mining in porphyry copper–molybdenum deposits. Research has therefore focused on the enrichment characteristics of rhenium in this type of deposit, with little attention paid to rhenium in other types of deposits. This study reports the occurrence state and enrichment mechanism of rhenium in the Qianjiadian sandstone-type uranium deposit in the Songliao Basin, Northeast China. Sequential extraction revealed that the average proportions of different forms of rhenium are as follows: water-soluble (57.86%) > organic-sulfide-bound (13.11%) > residual (12.26%) > Fe/Mn oxide-bound (10.67%) > carbonate-bound (6.10%). Combining mineralogical analysis techniques such as SEM-EDS, EMPA, and XRD, it has been established that rhenium does not occur as a substitute in sulfides (e.g., molybdenite) or uranium minerals in various types of deposits. Instead, it is mainly adsorbed onto clay minerals and Fe-Ti oxides, and in a small number of other minerals (pyrite, organic matter, and pitchblende). Rhenium is similar to redox-sensitive elements such as uranium and vanadium, and it is transported in a water-soluble form by oxidizing groundwater to the redox transition zone for enrichment. However, unlike uranium, which generally forms as uranium minerals, rhenium is mainly adsorbed and enriched onto clay minerals (kaolinite and interlayered illite–smectite). Most of the rhenium in sandstone-type uranium deposits occurs in an ion-adsorption state, and is easily leached and extracted during in-situ leaching mining of uranium ores. This type of deposit demonstrates excellent production potential and will become a crucial recoverable resource for future rhenium supply. Full article

The structural determination and characterization of molecules, namely proteins and enzymes, is crucial to gaining a better understanding of their role in different chemical and biological processes. The continuous technical developments in the experimental and computational resources of X-ray diffraction (XRD) and, more recently, cryogenic Electron Microscopy (cryo-EM) led to an enormous growth in the number of structures deposited in the Protein Data Bank (PDB). Bioinorganic chemistry arose as a relevant discipline in biology and therapeutics, with a massive number of studies reporting the effects of metal complexes on biological systems, with vanadium complexes being one of the relevant systems addressed. In this review, we focus on the interactions of vanadium compounds (VCs) with proteins. Several types of binding are established between VCs and proteins/enzymes. Considering that the V-species that bind may differ from those initially added, the mentioned structural techniques are pivotal to clarifying the nature and variety of interactions of VCs with proteins and to proposing the mechanisms involved either in enzymatic inhibition or catalysis. As such, we provide an account of the available structural information of VCs bound to proteins obtained by both XRD and/or cryo-EM, mainly exploring the more recent structures, particularly those containing organic-based vanadium complexes. Full article

Meromictic lakes of the marine coast, quite widely distributed in the northern hemisphere, are the result of climate changes and glacier retreat. The bottom sediments of these lakes serve as a geological chronicle of the history of marine basin’s development with the geochemical occurrence forms of elements indicate various processes of their accumulation. This paper presents research results concerning the occurrence of forms of heavy metals in lake sediments along the coast of the White Sea. These results are based on a sequential seven step leaching procedure, followed by ICP-MS analysis and subsequent statistical data processing. To determine differences among the examined geochemical parameters, Pearson’s correlation analysis and Ward’s cluster analysis were utilized. The total content of Cr, Mn, Fe, Co, Ni, Zn, V, and Pb in the sediments did not exhibit significant differences based on their degree of isolation from the sea. The major contribution to deposition of these metals in sediments of the meromictic lakes studied is the residual form, encompassing the mineral matrix of the sediment. At the same time, the elevation of mobile forms for all the metals examined corresponds to an increase in the isolation of lakes from the White Sea. In the meromictic lake sediments, concentrations of Cu, Mo, and U demonstrated significant increases in forms tightly bound to organic matter, while Cd exhibited an association with Fe-Mn oxyhydroxides. Notably, a significant difference in the occurrence forms of Cu, Cd, Mo, and U was evident in the reduced sediments of meromictic lakes when compared to those of open sea bays. The meromictic lakes along the White Sea coast, positioned at various stages of isolation, hold promise for investigating the migration of metals in response to environmental changes. Full article

Metal additive manufacturing (AM) technologies can be classified according to the physical process involving the raw material as fusion-based and solid-state processes. The latter includes sintering-based technologies, which are aligned with conventional fabrication techniques, such as metal injection molding (MIM), and take advantage of the freeform fabrication of the initial green part. In the present work, 17-4PH stainless steel samples were fabricated by material extrusion, or rather bound metal deposition (BMD), a solid-state AM technology. The powder-based raw material was characterized together with samples fabricated using different angular infill strategies. By coupling different characterization technologies, it was possible to identify and classify major properties and defects of the raw material and the fabricated samples. In addition, microstructural modifications were found to be linked with the mesostructural defects typical of the BMD solid-state additive manufacturing technology applied to metals. Full article