Type Of Metal Research Articles

Modulation of Sulfur Vacancies in ZnIn2S4/MXene Schottky Heterojunction Photocatalyst Promotes Hydrogen Evolution

AbstractThe sustainable production of hydrogen utilizing solar energy is a pivotal strategy for reducing reliance on fossil fuels. ZnIn2S4 (ZIS), as a typical metal sulfide semiconductor, has received extensive attention in photocatalysis. Although the introduction of sulfur (S) vacancies in ZIS to enhance photocatalytic hydrogen production by creating defect energy levels has been explored, detailed studies on the control and modulation of S‐vacancies in ZIS are sparce. This study demonstrates that while moderate levels of S‐vacancies can enhance hydrogen evolution, excessive vacancies may hinder the process, underscoring the importance of S‐vacancy modulation. Guided by theoretical calculations, We have designed and synthesized ZIS with modulated S‐vacancies to realize favorable hydrogen adsorption‐free energy and integrated in a Schottky‐heterojunction with MXene co‐catalysts for enhanced hydrogen evolution. The optimized hydrogen evolution performance of ZnIn2S4/MXene (ZMX) reaches 14.82 mmol g−1 h−1 under visible light irradiation, surpassing many reported ZnIn2S4‐based photocatalysts. The enhanced performance is ascribed to widened light absorption and enhanced carrier transportation realized by S‐vacancy modulation and the co‐catalytic effect. Femtosecond ultrafast absorption (fs‐TA) spectra and other in‐situ/ex‐situ characterizations further prove an efficient separation and transfer in an as‐prepared ZMX catalyst. These findings open up new perspectives for designing catalysts with vacancy modulation.

Embryo growth alteration and oxidative stress responses in germinating Cucurbita pepo seeds exposed to cadmium and copper toxicity

This study investigated the influence of cadmium (Cd) and copper (Cu) heavy metals on germination, metabolism, and growth of zucchini seedlings (Cucurbita pepo L.). Zucchini seeds were subjected to two concentrations (100 and 200 μM) of CdCl2 and CuCl2. Germination parameters, biochemical and phytochemical attributes of embryonic axes were assessed. Results revealed that germination rate remained unaffected by heavy metals (Cd, Cu). However, seed vigor index (SVI) notably decreased under Cd and Cu exposure. Embryonic axis length and dry weight exhibited significant reductions, with variations depending on the type of metal used. Malondialdehyde and H2O2 content, as well as catalase activity, did not show a significant increase at the tested Cd and Cu concentrations. Superoxide dismutase activity decreased in embryonic axis tissues. Glutathione S-transferase activity significantly rose with 200 μM CdCl2, while glutathione content declined with increasing Cd and Cu concentrations. Total phenol content and antioxidant activity increased at 200 μM CuCl2. In conclusion, Cd and Cu heavy metals impede zucchini seed germination efficiency and trigger metabolic shifts in embryonic tissue cells. Response to metal stress is metal-specific and concentration-dependent. These findings contribute to understanding the intricate interactions between heavy metals and plant physiology, aiding strategies for mitigating their detrimental effects on plants.

Highly efficient field-free switching of perpendicular yttrium iron garnet with collinear spin current

Yttrium iron garnet, a material possessing ultralow magnetic damping and extraordinarily long magnon diffusion length, is the most widely studied magnetic insulator in spintronics and magnonics. Field-free electrical control of perpendicular yttrium iron garnet magnetization with considerable efficiency is highly desired for excellent device performance. Here, we demonstrate such an accomplishment with a collinear spin current, whose spin polarization and propagation direction are both perpendicular to the interface. Remarkably, the field-free magnetization switching is achieved not only with a heavy-metal-free material, Permalloy, but also with a higher efficiency as compared with a typical heavy metal, Pt. Combined with the direct and inverse effect measurements, we ascribe the collinear spin current to the anomalous spin Hall effect in Permalloy. Our findings provide a new insight into spin current generation in Permalloy and open an avenue in spintronic devices.

Breaking Barriers in Eco-Friendly Synthesis of Plant-Mediated Metal/Metal Oxide/Bimetallic Nanoparticles: Antibacterial, Anticancer, Mechanism Elucidation, and Versatile Utilizations

Nanotechnology has emerged as a promising field in pharmaceutical research, involving producing unique nanoscale materials with sizes up to 100 nm via physiochemical and biological approaches. Nowadays more emphasis has been given to eco-friendly techniques for developing nanomaterials to enhance their biological applications and minimize health and environmental risks. With the help of green nanotechnology, a wide range of green metal, metal oxide, and bimetallic nanoparticles with distinct chemical compositions, sizes, and morphologies have been manufactured which are safe, economical, and environment friendly. Due to their biocompatibility and vast potential in biomedical (antibacterial, anticancer, antiviral, analgesic, anticoagulant, biofilm inhibitory activity) and in other fields such as (nanofertilizers, fermentative, food, and bioethanol production, construction field), green metal nanoparticles have garnered significant interest worldwide. The metal precursors combined with natural extracts such as plants, algae, fungi, and bacteria to get potent novel metal, metal oxide, and bimetallic nanoparticles such as Ag, Au, Co, Cu, Fe, Zr, Zn, Ni, Pt, Mg, Ti, Pd, Cd, Bi2O3, CeO2, Co3O4, CoFe2O4, CuO, Fe2O3, MgO, NiO, TiO2, ZnO, ZrO2, Ag-Au, Ag-Cr, Ag-Cu, Ag-Zn, Ag-CeO2, Ag-CuO, Ag-SeO2, Ag-TiO2, Ag-ZnO, Cu-Ag, Cu-Mg, Cu-Ni, Pd-Pt, Pt-Ag, ZnO-CuO, ZnO-SeO, ZnO-Se, Se-Zr, and Co-Bi2O3. These plant-mediated green nanoparticles possess excellent antibacterial and anticancer activity when tested against several microorganisms and cancer cell lines. Plants contain essential phytoconstituents (polyphenols, flavonoids, terpenoids, glycosides, alkaloids, etc.) compared to other natural sources (bacteria, fungi, and algae) in higher concentration that play a vital role in the development of green metal, metal oxide, and bimetallic nanoparticles because these plant-phytoconstituents act as a reducing, stabilizing, and capping agent and helps in the development of green nanoparticles. After concluding all these findings, this review has been designed for the first time in such a way that it imparts satisfactory knowledge about the antibacterial and anticancer activity of plant-mediated green metal, metal oxide, and bimetallic nanoparticles together, along with antibacterial and anticancer mechanisms. Additionally, it provides information about characterization techniques (UV–vis, FT-IR, DLS, XRD, SEM, TEM, BET, AFM) employed for plant-mediated nanoparticles, biomedical applications, and their role in other industries. Hence, this review provides information about the antibacterial and anticancer activity of various types of plant-mediated green metal, metal oxide, and bimetallic nanoparticles and their versatile application in diverse fields which is not covered in other pieces of literature.

Activation of ERK/NF-kB Pathways Contributes to the Inflammatory Response in Epithelial Cells and Macrophages Following Manganese Exposure.

Different types of metals, including manganese (Mn), are constantly encountered in various environmental matrices due to natural and anthropogenic activities. They induce a sustained inflammatory response in various organs, which is considered to be an important priming event in the pathogenesis of several diseases. Mn-induced neuroinflammation and subsequent neurodegeneration are well recognized. However, emerging data suggest that occupationally and environmentally relevant levels may affect various organs, including the lungs. Therefore, the present study was carried out to investigate the effects of Mn (as Mn2+) exposure on the inflammatory response in human normal bronchial (BEAS-2B) and adenocarcinoma alveolar basal (A549) epithelial cells, as well as in murine macrophages (J774). Mn2+ exposure significantly induced mRNA and protein expression of various pro-inflammatory mediators (cytokines and chemokines) in all cells compared to corresponding vehicle controls. Furthermore, Mn2+ treatment also led to increased phosphorylation of extracellular-signal-regulated kinase (ERK)1/2 and nuclear factor-kappa B (NF-kB) p65 in both epithelial cells and macrophages. As expected, cells treated with inhibitors of ERK1/2 (PD98059) and NF-kB p65 (IMD0354) effectively mitigated the expression of various pro-inflammatory mediators induced by Mn2+, suggesting that ERK/NF-kB pathways have a critical role in the Mn2+-induced inflammatory response. Further, in vivo studies are required to confirm these in vitro findings to support clinical translation.

Selective recovery of palladium from wastewater by modified PVC waste pipe

Green, efficient, and cost effective methods of recycling palladium (Pd) from wastewater have attracted increasing attention. In the present study, polyvinyl chloride (PVC) was utilized as a backbone for N-(3-aminopropyl)-imidazole to graft onto and yield an adsorbent suited for selective Pd recovery from wastewater by chlorine coordination. Batch experiments showed that the self-synthesized adsorbent had a Pd(II) adsorption rate of >99% at pH 1.0–3.0 and >93% in 4 min. The selectivity of the adsorbent in a complex mixed system containing high concentrations of typical base metals (CCu(II):CZn(II):CPd(II) = 66:33:1) was investigated, and the adsorbent demonstrated much higher selectivity for Pd (97.59%) than for Cu (0.52%) and Zn (2.96%). The adsorbent can also be reused as the adsorption rate remained above 99% after five cycles. Furthermore, waste PVC pipes also could be used as the synthetic raw material. The adsorbent demonstrated a high adsorption rate even when synthesized from discarded PVC pipes and the adsorption rate reached over 93% in 2 h and reached 95.15% at equilibrium in 4 h. Scanning electron microscopy and energy-dispersive spectrometry, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy were used to analyze the adsorption mechanism, which was attributed to electrostatic interaction and intermolecular interaction. The self-synthesized adsorbent is potentially applicable to the green recovery of Pd from wastewater owing to its high adsorption rate and selectivity.

Detecting changes in industrial pollution by analyzing heavy metal concentrations in tree-ring wood from Romanian conifer forests

The impact of air pollution on forests, especially in urban areas, has been increasingly discussed recently. Many pollutants, including heavy metals, are released into the atmosphere from various sources, such as mining, non-ferrous metal processing plants, and fossil fuel combustion. These pollutants can adversely affect not only tree growth but also other species, including humans.This study compared the concentrations of several elements in tree-ring wood from two conifer species (Silver fir, Abies alba; Norway spruce, Picea abies) growing in polluted and unpolluted areas. Two regions in northern Romania (Bicaz and Tarnița) that were subjected to historical pollution changes were selected. Two chemical analyses were used: inductively coupled plasma mass spectrometry (ICP-MS) and X-ray fluorescence spectrometry (XRF).The silver fir trees from the intensively polluted area in the Tarnița region were negatively impacted by industrial pollution: the Mn concentrations were, on average, three times higher in polluted areas than in unpolluted areas (ca. 30 vs. 10 mg kg−1). This finding was consistent for both ICP-MS and XRF analyses. However, in Norway spruce, this difference was found only in the XRF data, which detected Mn concentrations seven times higher in trees from polluted areas than those from unpolluted areas (ca. 700 vs. 100 mg kg−1). In the Tarnița region, Norway spruce accumulated more heavy metals than silver fir, but the most pronounced differences between polluted and unpolluted areas were found in silver fir.The two analytical methods are commonly used to determine metal concentrations in wood, and they complement each other, with ICP-MS having a low detection limit for some elements and XRF having higher detection limits and better accuracy. Each method has its advantages and disadvantages, and the optimal method depends on many factors, such as the type of heavy metal analyzed, its concentration in wood, sample type, cost, analysis time, and sample preparation.

Study on the turbulent Prandtl number model for liquid metal flow and heat transfer in a narrow rectangular channel

In order to improve the core power density of liquid metal reactors, plate-type fuel assemblies are typically used, which have obvious advantages in heat transfer capacity. For the low Prandtl number fluid, the RANS turbulence model-based CFD method needs to be modified by inserting the turbulent Prandtl number model. This paper investigated the turbulent Prandtl number model for the turbulent heat transfer of liquid metal flow in a narrow rectangular channel. First, the existing turbulent Prandtl number models were summarized and classified as the local turbulence Prandtl number model and the global turbulence Prandtl number model. They were evaluated based on the experimental data. The results showed that the prediction results of each model are not ideal. Then, a typical numerical example was used to analyze the temperature field and flow field in the narrow gap of a narrow rectangular channel. It was shown that the entire flow region only includes the near-wall region and the transition region, and the transition region accounts for the main proportion. A semi-empirical local turbulence Prandtl number model was obtained by solving the turbulent transport equation, and the unknown coefficients were determined iteratively with the experimental data. The error was controlled within ±20%. Finally, the applicability of the newly proposed turbulent Prandtl number model was explored, and the results showed that it has good applicability for the different runner sizes and different liquid metal types. This study can provide a reference for the numerical simulation of turbulent heat transfer of metal liquid in the narrow rectangular channel.

The Hund-metal path to strong electronic correlations

A new type of metal has taken the scientific community by surprise. Classic concepts from atomic physics—the electrons’ orbitals and spin alignment—are key to understanding it.

The Effect of Welding Current on Shear Test and Microstructure TIG Brazing of Cemented Carbide and Steel

The need for good welding results as knowledge in the process of welding different types of materials is needed in the community, and this res- earch is to determine the effect of variations in welding currents of different types of metals on cemented carbide and carbon steel using the TIG brazing method. For the base metal, YG6 cemented carbide and SS400 carbon steel with CuSi filler metal are used. The sample method is made by connecting different types of materials with the welding process using variations in current of 60 ampere; 80 ampere, and 100 ampere. The mechanical properties of this material connection were tested using the Hydraulic Universal Testing Machine, while for the microstructure examination, a microstructure test tool with a magnification of 100 x was used. The results of the tests revealed that the highest average compressive strength was 22.2 kN at a welding current variation of 60 A, and the lowest average value was 10.2 kN at a welding current variation of 100 A. Furthermore, for the average value of shear stress, the highest value at 60 A variation is 148 N/mm2 and the lowes t value is at 100 A welding current, which is 67 N/mm2. The res ults of testing the microstructure of the connection area s how that the higher the current strength, the more enriched the Cu content and will affect the size and spacing of Si grains.

Application of metal–organic frameworks in stomatology

Metal–organic frameworks (MOFs), a new class of porous organic–organic hybrid materials controlled by self-assembly of metal atoms and organic pillars, are attracting considerable interest because of their specific properties. More recently, the advantages of different types of nanoscale metal–organic frameworks for the use of MOF nanoparticles in stomatology have been reported in the literature. This article covers the treatment of oral cancer, surface modification of implants, antibacterial dressings, and treatment of periodontitis and periodontal regeneration. It presents recent applications, future challenges, and prospects for MOFs in stomatology in four areas. It provides an overview of recent advances in the design and application of MOFs in stomatology from their intrinsic properties to different syntheses and their use as smart drug delivery systems or a combination of these.

Supramolecular Coordination Complexes for Synergistic Cancer Therapy.

Supramolecular coordination complexes (SCCs) are predictable and size-tunable supramolecular self-assemblies constructed through directional coordination bonds between readily available organic ligands and metallic receptors. Based on planar and 3D structures, SCCs can be mainly divided into two categories: metallacycles (e.g., rhomboidal, triangular, rectangular, and hexagonal) and metallacages (e.g., tetrahedral, hexahedral, and dodecahedral). The directional coordination bonds enable the efficient formation of metallacycles and metallacages with well-defined architectures and geometries. SCCs exhibit several advantages, including good directionality, strong interaction force, tunable modularity, and good solution processability, making them highly attractive for biomedical applications, especially in cellular imaging and cancer therapy. Compared with their molecular precursors, SCCs demonstrate enhanced cellular uptake and a strengthened tumor accumulation effect, owing to their inherently charged structures. These properties and the chemotherapeutic potential inherent to organic platinum complexes have promoted their widespread application in antitumor therapy. Furthermore, the defined structures of SCCs, achieved via the design modification of assembly elements and introduction of different functional groups, enable them to combat malignant tumors through multipronged treatment modalities. Because the development of cancer-treatment methodologies integrated in clinics has evolved from single-modality chemotherapy to synergistic multimodal therapy, the development of functional SCCs for synergistic cancer therapy is crucial. While some pioneering reviews have explored the bioapplications of SCCs, often categorized by a specific function or focusing on the specific metal or ligand types, a comprehensive exploration of their synergistic multifunctionality is a critical gap in the current literature.In this Account, we focus on platinum-based SCCs and their applications in cancer therapy. While other metals, such as Pd-, Rh-, Ru-, and Ir-based SCCs, have been explored for cancer therapy by Therrien and Casini et al., platinum-based SCCs have garnered significant interest, owing to their unique advantages in antitumor therapy. These platinum-based SCCs, which enhance antitumor efficacy, are considered prominent candidates for cancer therapies owing to their desirable properties, such as potent antitumor activity, exceptionally low systemic toxicity, active tumor-targeting ability, and enhanced cellular uptake. Furthermore, diverse diagnostic and therapeutic modalities (e.g., chemotherapy, photothermal therapy, and photodynamic therapy) can be integrated into a single platform based on platinum-based SCCs for cancer therapy. Consequently, herein, we summarize our recent research on platinum-based SCCs for synergistic cancer therapy with particular emphasis on the cooperative interplay between different therapeutic methods. In the Conclusions section, we present the key advancements achieved on the basis of our research findings and propose future directions that may significantly impact the field.

SOIL QUALITY INDEX AT PASIR GUDANG INDUSTRIAL AREA

Soil Quality Index (SQI) is a very useful and efficient method for assessing the quality of soil. It is a useful tool for obtaining information on overall quality of soil. Five soil attributes namely acidity (pH), Organic Matter (OM), Phosphorus (P), Potassium (K), and Electrical Conductivity (EC), have been combined to construct an index to represent the soil quality. Location characteristics were observed during the time of sampling, and it was categorized according to industrial, riverside residential and educational area. From the determination of heavy metals concentration, certain area especially nearby Pasir Gudang industry has recorded heavy metal concentration exceeded the world average value for a few types of heavy metal. Soil quality index at Sg Kim Kim recorded poor quality index whereas the other locations indicated good to average soil quality index.

Recent Advances in Anti-Urease Activity of Schiff Bases and their Metal Complexes

The urease enzyme, found in plants, fungi and bacteria, plays a crucial role in catalyzing the hydrolysis of urea, a process integral to microbial metabolism. Its ureolytic activities have garnered significant attention for their impact on agriculture and the health of living organisms. Notably, urease activity in the human stomach, urinary tract and animal cells can lead to pathogenic outcomes. Schiff bases, characterized by their carbonyl-type imine or azomethine linkage, are recognized for their diverse biological effects, including anti-urease activity. Additionally, the metal complexes derived from the Schiff bases demonstrate controlled urease inhibition activity, influenced by factors such as the type of metal, its oxidation state and the coordination environment. This inhibition occurs through the interaction of the Schiff base ligand with the nickel containing active site of urease or the protein sphere surrounding the metal, disrupting the ureolytic mechanism. In this review, the utilization of Schiff bases and their metal complexes in urease inhibition is highlighted as explored by various research groups.

Distribution, occurrence, and leachability of typical heavy metals in coal gasification slag

Coal gasification slag (CGS) contains variable amounts of heavy metals, which can negatively impact the environment. The mineral composition, element distribution, occurrence, and leaching characteristics of heavy metals in coal gasification coarse slag (CGCS) and coal gasification fine slag (CGFS) are studied to explain the leaching behavior of heavy metals in CGS. The movable components of heavy metals in CGFS (0.06 %–63.03 %) are significantly higher than those in CGCS (0 %–18.72 %). Leaching Environmental Assessment Framework 1313 data shows that heavy metals Zn, Cr, Cd, As, Pb, Ni, and Cu exhibit high leaching rates at low pH conditions, with Zn leaching concentrations as high as 2.11 mg/L at pH 2. Zn, Cr, and As exhibit obvious amphoteric leaching characteristics, and the leaching concentration of As at high pH (1.34 mg/L) even exceeds that at low pH (1.31 mg/L). Except for Cu, all heavy metals in CGS exceed the class III groundwater standard in some cases. Therefore, evaluation is needed before resource utilization of CGS due to potential leaching of some heavy metals.

Self-powered sodium borohydride alkaline fuel cell for efficient removal of lead(II) and copper(II)

Heavy metals in industrial wastewater cause serious environmental pollution and they are easy to accumulate and difficult to degrade. Copper and lead are two typical heavy metals, and it is of great significance to remove them at the same time. This work shows a strategy of reducing and removing Pb(II) and Cu(II) by self-powered non-biological fuel cell (SP-nBFC) with dual-chamber reactor. Therein, sodium borohydride in alkaline solution as fuel (electron donor) was electrooxidized on nicke1 foam (NF) at anode and Pb(II) and Cu(II) ions (electron acceptors) in strong acidic solution were electro-reduced at Bi/MXene/GP cathode (bismuth nanoparticles and MXene modified graphite paper (GP)).Additionally, a proton exchange membrane, Nafion, was introduced into form complete circuit by offering ions channel. The results showed that Cu(II) and Pb(II) were reduced to Cu and Pb, and the SP-nBFC could produce electricity in this process without external energy consumption. The Bi/MXene/GP cathode could increase significantly removal efficiencies of Cu(II) and Pb(II), which were higher than about 37.0 %, 22.5 % for Cu(II) and 25.7 %, 16.3 % for Pb(II) than those of GP and MXene/GP cathode. This system could obtain a high Cu(II) removal efficiency (RE, 99.3 %) and moderate Pb(II) RE of 56.8 %, and acquire Cu and Pb sediments in cathode chamber. Furthermore, the proposed system could generate 923 mV of maximum potential and 1420 mW/m2 of maximum power density in 48 h. Thus, this SP-nBFC system provides a viable method for treatment of Cu(II) and Pb(II) pollution and generating electricity simultaneously, and also has prospective approach for other heavy metals remediation.

Molecular dynamics simulation study of void collapse mechanisms in cubic metals under shock compression

Molecular dynamics simulations have revealed the collapse mechanism of a void in cubic metals under shock compression along [100] direction. The results show that the void collapse is caused by emitting dislocations from its surface. The type of cubic metal plays a decisive role in the subsequent microstructural evolution around the void. Void in face-centered-cubic metals collapses by emitting Shockley dislocations from its surface when piston velocity exceeds the threshold; while void in body-centered-cubic metals collapses by emitting prismatic dislocation loops, which are formed by the reaction of edge dislocations. Simulation results also reveal that the type of dislocation that induces void collapse is independent of void size. Finally, based on the elastic theory, we find that the maximum resolved shear stress along the slip direction determines the types of dislocation emitted from the voids.

Semi-supervised segmentation of metal-artifact contaminated industrial CT images using improved CycleGAN.

Accurate segmentation of industrial CT images is of great significance in industrial fields such as quality inspection and defect analysis. However, reconstruction of industrial CT images often suffers from typical metal artifacts caused by factors like beam hardening, scattering, statistical noise, and partial volume effects. Traditional segmentation methods are difficult to achieve precise segmentation of CT images mainly due to the presence of these metal artifacts. Furthermore, acquiring paired CT image data required by fully supervised networks proves to be extremely challenging. To address these issues, this paper introduces an improved CycleGAN approach for achieving semi-supervised segmentation of industrial CT images. This method not only eliminates the need for removing metal artifacts and noise, but also enables the direct conversion of metal artifact-contaminated images into segmented images without the requirement of paired data. The average values of quantitative assessment of image segmentation performance can reach 0.96645 for Dice Similarity Coefficient(Dice) and 0.93718 for Intersection over Union(IoU). In comparison to traditional segmentation methods, it presents significant improvements in both quantitative metrics and visual quality, provides valuable insights for further research.

Sensitivity Improvements for Picosecond Ultrasonic Thickness Measurements in Gold and Tungsten Nanoscale Films

Picosecond ultrasonics, as a nondestructive and noncontact method, can be employed for nanoscale metallic film thickness measurements. The sensitivity of the system, which determines the measurement precision and practicability of this technique, is often limited by the weak intensity of the ultrasonic signal. To solve this problem, we investigate the distinct mechanisms involved in picosecond ultrasonic thickness measurement for two types of metals, namely tungsten (W) and gold (Au). For thickness measurement in W films, theory and simulation show that optimizing the pump and probe laser wavelengths, which determine the intensity and shape of the ultrasonic signal, is critical to improving measurement sensitivity, while for Au film measurements, where acoustic-induced beam distortion is dominant, the signal intensity can be optimized by selecting an appropriate aperture size and sample position. The above approaches are validated in experiments. A dual-wavelength pump–probe system is constructed based on a passively mode-locked ytterbium-doped fiber laser. The smoothing method and multipeak Gaussian fitting are employed for the extraction of ultrasonic time-of-flight. Subnanometer measurement precision is achieved in a series of W and Au films with thicknesses of 43–750 nm. This work can be applied to various high-precision, noncontact measurements of metal film thickness in the semiconductor industry.

Characterization of dissolved organic matter in rivers impacted by acid mine drainage: Components and complexation with metals

Dissolved organic matter (DOM), a ubiquitous and active ingredient, is extensively involved in the transformation and migration of environmental pollutants in aquatic ecosystems. However, its chemical composition in acid mine drainage (AMD)-impacted rivers remains poorly characterized, hindering our understanding of its role in the biogeochemistry of key elements in contaminated fluvial environments. Here, we investigated the concentration of dissolved organic carbon (DOC) and spectroscopic and molecular characteristics of DOM in a headwater river contaminated with polymetallic mine-derived AMD in southern China. Terrestrial humic-like (C1) and typically groundwater-supplied aromatic protein/tyrosine-like (C2) substances which were partially from AMD, were identified as the predominant fluorescent components in the river water. Notably, tryptophan-like (C3) substances originating from tailings pond spills were only occasionally detected in the river. Although DOM biogeochemical transformations and degradation occurred in the lateral soil-water riparian interface and longitudinal in-stream transport processes, the molecular compositions identified by FT-ICR MS showed a core set of molecular formulae in the lignin/saturated compound/tannin region of the van Krevelen diagram of the water samples across the rivers. The complexation of DOM with typical metals in AMD was investigated using fluorescence quenching experiments. The results showed that the highest binding ability of Fe(III) to C2 followed by C1, with both detected in the experimental water samples. Mg(II) and Ca(II) strengthened the binding of DOM-Fe(III) when the ferric/DOM ratio was low, while Cu(II) weakened the binding of DOM-Fe(III) due to competition. Ca(II) inhibited the binding of Fe(III) to C1 but promoted the binding of the complex to C2 when both Cu(II) and Mg(II) were present. Since DOM-Fe(III) complexation was associated with the cotransport of AMD-derived metals/metalloids in diverse aqueous environments with multiple co-existing ions (typically Ca(II) input for remediation), our study on the composition of DOM and its complexation with metals can contribute to managing and remediating AMD-impacted rivers.