Search Results (144)

The increasing accumulation of microplastics (MPs) in soils necessitates a better understanding of their effects on soil chemistry and trace element behavior. This study examined the influence of three MPs—low-density poly(ethylene) (LDPE), polypropylene (PP), and poly(ethylene terephthalate) (PET)—on cadmium (Cd) and copper (Cu) mobility in four clayey–sandy soils with similar organic matter content but differing pH, representing acidic and alkaline terrestrial matrices. Soils were incubated with 1% (w/w) MPs at 60% water-holding capacity for 30 and 90 days. Total Cd and Cu concentrations remained largely unaffected; however, time-dependent changes in metal availability and distribution were observed. Extractability (CaCl₂ and DTPA), sequential BCR fractionation, and environmental risk indices (CF, Igeo, RAC, MF, and PLI) indicated slight increases in Cd availability after 30 days, which became more pronounced after 90 days, particularly in acidic soils (pH 5.5). The magnitude of the MP effect followed the trend PET > PP > LDPE in all cases. Among the two target metals, Cd exhibited substantially higher mobility than Cu, as reflected by RAC and MF values. Specifically, Cd RAC (6–35%) and Cd MF (28–63%) values were considerably higher than those of Cu (1.1–3.8% and 15–28%, respectively). Overall, although the general pollution indices remained relatively stable, MPs altered the extractability and geochemical partitioning of the examined heavy metals—particularly Cd—indicating their potential role as vectors in soil environments. These results demonstrate that incubation time, polymer type, and soil pH jointly regulate MP-induced change in Cd and Cu mobility, with important implications for soil ecosystem risk. Full article

A Cu-containing FeCrMnNiAl multi-principal element alloy was processed by laser-based and electron beam-based powder bed fusion (PBF-LB/M and PBF-EB/M) to investigate processing–microstructure–property relationships. In focus were alloy variants with a relatively high Cu content. Two PBF-LB/M scan strategies, employing a Gaussian beam with and without a re-scan with a laser featuring a flat-top profile, were compared to PBF-EB/M processing, followed by heat-treatments between 300 °C and 1000 °C. The phase constitution, elemental partitioning and grain boundary characteristics were analyzed by X-ray diffraction, electron backscatter diffraction and energy-dispersive X-ray spectroscopy. Mechanical behavior was assessed by hardness and tensile testing. Both manufacturing routes promoted the evolution of stable multi-phase microstructures composed of face-centered-cubic (FCC)- and body-centered-cubic (BCC)-type phases across all heat-treatment conditions. PBF-LB/M processing resulted in finer, dendritic microstructures and suppressed formation of a Cu-rich FCC phase due to higher cooling rates, whereas PBF-EB/M promoted the evolution of Cu-rich FCC segregates and equiaxed grain morphologies. Heat-treatment above 700 °C led to recrystallization, accompanied by an increase of the FCC phase fraction, grain coarsening, and recovery. At lower heat-treatment temperatures, the changes in microstructure are different. Here, it is assumed that small, non-clustered Cu-rich precipitates formed at the grain and sub-grain boundaries, although this assumption is only based on the assessment of the mechanical properties. The size of these precipitates is below the resolution limit of the techniques applied for analysis in the present work. Additional structures seen within the Cu-rich areas of PBF-EB/M-manufactured samples treated at lower temperatures also seem to have an influence on the hardness and yield strength. All of the conditions investigated exhibited pronounced brittleness, limiting reliable tensile property evaluation and indicating the need for further optimization of processing strategies and microstructural control for high-Cu-fraction-containing multi-principal element alloys. Full article

This study examines the effect of vanadium addition on the microstructure and mechanical properties of low-cost powder metallurgy Ti-4Al-2Fe-3Cu alloys. Alloys with and without 6 wt.% V were fabricated by hot extrusion of blended elemental powders followed by vacuum heat treatment. Microstructural analysis revealed that the base alloy exhibits a coarse lamellar α/β structure, while vanadium addition promotes a refined basketweave morphology with a significantly higher β-phase fraction, increasing from 28.1% to 46.2%. Energy-dispersive spectroscopy confirmed preferential partitioning of Fe, Cu, and V into the β phase. Mechanical testing showed that the addition of 6 wt.% V markedly enhances strength, increasing yield strength and ultimate tensile strength from 1122 MPa and 1214 MPa to 1291 MPa and 1349 MPa, respectively, while maintaining comparable tensile ductility (~3.5%). The strength improvement is attributed to α-plate refinement, increased β-phase fraction, and solid-solution strengthening of the β phase. These results demonstrate that vanadium addition is an effective approach for improving the strength of low-cost PM titanium alloys without compromising ductility. Full article

Trace metal contamination in lotic freshwater systems exhibits pronounced heterogeneity arising from coupled hydrological connectivity, geochemical partitioning, and anthropogenic forcing, complicating exposure characterization in urban and peri-urban catchments. Addressing this complexity requires integrative analytical approaches capable of deciphering system-level controls, prompting an investigation of the environmental structuring and governing controls of dissolved trace metal signatures in a human-impacted stream using a system-oriented computational framework. To capture temporal variability associated with seasonal hydrological contrasts and heterogeneous pollution inputs, a station-based, season-resolved sampling strategy was implemented during the wet and dry seasons. Physicochemical gradients (pH, temperature, dissolved oxygen, and electrical conductivity), inorganic nitrogen species (NH₃, NO₂⁻, and NO₃⁻), and phosphorus fractions (total phosphorus, TP; total orthophosphate, TOP; soluble reactive P, SRP) were jointly analyzed with dissolved concentrations of chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), cadmium (Cd), mercury (Hg), and arsenic (As). Regression-based machine learning models were used to quantify element-specific sensitivities to hydrochemical drivers under wet–dry periods and to identify optimal predictive configurations. Predictive performance was consistently high for trace metals (R² generally >0.95), with Random Forest providing the best accuracy for Cr, Ni, Pb, Cd, As, and Hg, whereas Cu was most reliably captured by an XGBoost tree ensemble (R² = 0.994). Explainability analyses revealed heterogeneous, metal-specific control regimes: Cr was primarily driven by temperature, Ni by NO₂⁻ and redox-sensitive conditions, Cd by NH₃ and temperature, and As by Hg in combination with phosphorus-related and redox-linked proxies, while Pb showed comparatively lower predictability relative to other metals. Trace metal distributions are therefore structured primarily by differential environmental sensitivity rather than uniform source-driven inputs, reinforcing the need for integrative computational frameworks when interpreting freshwater contamination under intensifying anthropogenic and climatic pressures. Full article

The coupling of physical transport and phase-transfer processes represents a fundamental mechanism governing metal cycling in estuarine systems under tidal oscillations. Taking Quanzhou Bay as a model system, we conducted continuous observations and sample collection at the river channel (Q1), the turbidity maximum zone (Q2), and the outer bay channel (Q3). The metals (Al, Ti, Ba, Cu, Mn, and Zn) were measured by ICP-MS to systematically investigate the distribution, transport, and inter-media transfer across multiple water layers under varying estuarine processes. Our findings demonstrate that particulate metal concentrations in Quanzhou Bay exhibit strong synchrony with suspended sediment concentrations (SSC) over tidal cycles, displaying a distinct sediment-following pattern controlled by alternating end members. Particulate metal fluxes during flood and ebb-tides generally followed the hierarchy Q1 > Q2 >> Q3. Notably, stations Q1 and Q2 were dominated by flood-tide fluxes with net transport directed landward, whereas Q3 was characterized by ebb tide dominance with net flux directed seaward—revealing a spatial division of labor between “inner bay retention/reallocation” and “outer bay channel export”. In contrast, dissolved metals exhibited marked element-specific responses to tidal forcing: Al and Ti increased during flood tides at stations Q1 and Q2, while Ba and Cu showed opposite trends, and Mn and Zn displayed more conservative behavior. Concurrently, solid/liquid partition coefficient (logKd) values for Al, Ti and Ba, Cu exhibited inverse patterns over tidal cycles, suggesting divergent adsorption–desorption regulation under identical hydrodynamic conditions that drives differential phase-transfer dynamics. These disparities likely reflect intrinsic chemical properties and source variations among the elements. This study elucidates, at the tidal timescale, the coupled processes of “alternating end-member control—estuarine filter modulation—concurrent channelized export and inner bay retention” in Quanzhou Bay, providing critical process-level insights for metal flux quantification and bay pollution remediation initiatives in an ecological restoration project. Full article

Successful establishment of resource-efficient perennial crops that can thrive and produce economically viable yields under metal stress conditions requires a clear understanding of macronutrient uptake and metal detoxification regulation mechanisms particularly during crop establishment period. Therefore, this study aimed to evaluate the partitioning of macronutrients and metals in miscanthus and switchgrass grown on metal-contaminated soils, and to evaluate the effect of biostimulant treatments on early crop establishment and biomass productivity. Field trials were conducted with two perennial C₄ grasses, miscanthus (Miscanthus lutarioriparius) and switchgrass (Panicum virgatum L.), under three treatments: control (CK), humic acid (HA), and humic acid combined with microbial inoculants (HAM). At final growth stages, agronomic traits, biomass quality, and macronutrient (N, P, K) and metal (Cd, Cr, Pb, Cu, Zn) contents were analyzed. To investigate metal and macronutrient partitioning dynamics, samples were collected from October to December. The HAM treatment significantly enhanced biomass yield and morphological parameters in both species, particularly in miscanthus. Both HA and HAM improved cellulose and hemicellulose while reducing the lignin content, thereby improving biomass quality. For both crops, roots served as the primary organ for metal accumulation across growth stages. In miscanthus roots from October to December, the proportions of Cd, Cr, and Pb increased (10.5%, 10.8%, 13.6%), while Zn and Cu decreased (6.5%, 11.6%). Over the same period, Pb increased slightly (4.4%), but Cd, Cr, and Cu declined (26%, 1.9%, 12.9%) in switchgrass roots. Coupling and principal component analyses revealed weak macronutrient–metal synchronization in both miscanthus and switchgrass across growth stages. Full article

This study investigates the effects of polypropylene microplastics (PP-MPs) and copper (Cu), applied individually and in combination, on the growth (root and shoot length, fresh and dry biomass), peroxidase (POD) activity, and Cu accumulation of rice seedlings. A hydroponic experiment was conducted with four treatments: control (CK), PP, Cu, and PP+Cu. Exposure to PP-MPs slightly promoted seedling growth, whereas Cu markedly inhibited growth and induced chlorosis. Compared with Cu alone, co-exposure to PP-MPs and Cu (PP+Cu) partially improved shoot growth and alleviated Cu-induced suppression of shoot POD activity. In contrast, root POD activity showed the strongest reduction under PP+Cu (91.7% decrease), revealing a pronounced root–shoot divergence in antioxidant responses. Moreover, total Cu accumulation in seedlings increased by 12.3% in PP+Cu relative to Cu alone, implying that PP-MPs may influence Cu bioavailability and/or internal partitioning. However, Cu speciation and subcellular distribution were not quantified in this study and should be examined in future work. Overall, PP-MPs may simultaneously enhance Cu uptake while partially mitigating shoot-level toxicity, underscoring the complexity of microplastic–metal co-contamination in rice seedling systems. Full article

To investigate the distribution, sources, and partitioning of heavy metals at the sediment–water interface in the northern Jiangsu coastal waters, seawater and sediment samples were collected from 24 stations east of Yanwei Port in April 2021. The concentrations of seven heavy metals (Cu, Pb, Zn, Cd, Cr, Hg, and As) and environmental parameters were determined. Methods including principal component analysis (PCA), random forest (RF), positive matrix factorization (PMF), the partition coefficient (Kp), and the source-specific partition coefficient (S-Kp) were applied. The results showed the following: (1) The overall concentration order was Zn > Cu > As > Pb > Cd > Hg in seawater and Zn > Cr > Cu > Pb > As > Hg > Cd in sediments, with Cd and Pb characterized by high spatial variability. (2) PCA and RF indicated that dissolved heavy metals were mainly influenced by dissolved oxygen, petroleum, phosphate, and dissolved inorganic nitrogen, with DIN playing a common dominant role. PMF revealed three main sources for sediment metals: agricultural (contributing notably to Cu and Zn), traffic and industrial exhaust (dominating Pb, Cr, and Hg inputs), and industrial (primarily affecting Cd, Cr, and Pb). (3) Kp analysis suggested that Pb, As, and Cu were readily adsorbed by sediments, while Cd, Hg, and Zn tended to remain dissolved. Critically, S-Kp demonstrated source dependent partitioning: Pb derived from industrial sources was almost entirely associated with sediments, while Cu and Zn originating from traffic and industrial exhaust emissions were predominantly present in the aqueous phase, and Cu and Pb derived from agricultural sources were largely deposited in sediments. These findings provide a scientific basis for heavy metal pollution control in the region. Full article

Polymetallic nodules enriched in Mn, Ni, Cu, Co, and other metals may be one of the first seabed mineral resources to be exploited. Although optical imagery is crucial for resource evaluation, semi-buried nodules are frequently overlooked. To address this, we propose a framework that integrates the elliptic approximation method (EAM) and the contour interweaving method (CIM) to reconstruct three types of semi-buried nodules segmented by U-Net: edge-buried, partition-buried, and almost-completely-buried. This strategy introduced a decision-making mechanism based on category fusion, which significantly enhanced the robustness and practicality of the reconstruction. Performance was assessed using four metrics: area ratio, absolute percentage change, intersection-over-union, and Chamfer distance. Among 1785 samples, the EAM recovered up to 41.8% of lost area, which substantially improved the minimum values of area ratio and intersection-over-union, and it performed well on almost-completely-buried nodules. The CIM achieved median area ratio and intersection-over-union values of 99.37% and 93.36%, respectively, and excelled in edge-buried and partition-buried types. Fusion experiments demonstrated the complementary strengths of both approaches: 23.96% of buried area was recovered in large-scale imagery recognized by U-Net. The proposed framework balances accuracy, adaptability, and computational efficiency, which enables real-time nodule identification on platforms with limited resources such as autonomous underwater vehicles. This could provide more direct support for resource evaluation and mining applications. Full article

The Sichuan–Yunnan–Guizhou Pb-Zn metallogenic belt (SYG metallogenic belt), a crucial metallogenic unit on the southwestern margin of the Yangtze Block, is a key part of the South China low-temperature metallogenic domain. The incorporation mechanisms and distribution of trace elements (e.g., Ge, Ga, Cd) widely enriched in Pb-Zn sulfides throughout this region remain poorly understood. This study investigates main-ore-stage sulfides (sphalerite and pyrite) from the Maoping Pb-Zn deposit using in situ laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses and mapping to systematically elucidate the partitioning and occurrence of these trace elements. The key findings are as follows: (1) Sulfides show distinct elemental partitioning: sphalerite preferentially concentrates Cd, Ag, Ge, Ga, and Se, whereas pyrite is significantly enriched in Mn, Ni, As, and Co. (2) Sphalerite is the primary host for many trace elements. Cadmium, Ge, Mn, Cu, and Ag mainly enter the sphalerite lattice by substituting for Zn²⁺. Coupled substitution mechanisms, such as Zn²⁺ ↔ Cd²⁺, 2Zn²⁺ ↔ Ge²⁺ + Cu²⁺, and 2Zn²⁺ ↔ Ga³⁺ + Cu⁺, facilitate the incorporation of Ge and Ga. (3) The sphalerite exhibits a trace element assemblage of high Cd-Ge and low Fe-Mn, which is geochemically similar to typical Mississippi Valley-type (MVT) deposits and differs significantly from sedimentary exhalative (SEDEX) and magmatic–hydrothermal deposits, indicating a medium- to low-temperature metallogenic environment. Based on these geochemical signatures and epigenetic textures, we confirm that the Maoping Pb-Zn deposit exhibits similarities with MVT deposits. Nevertheless, distinct differences in the tectonic setting and metal grades suggest it is a unique SYG-type Pb-Zn deposit. Full article

The liquidus and solidus temperatures, the initial temperature of the solidification of binary eutectics, and the partition ratios of the solid solution at the Al corner of the ternary eutectic-type Al-Si-Cu alloy system were calculated using the thermodynamically based ESTPHAD method. It is shown that these data can be calculated from the liquidus and solidus data of the two binary equilibrium phase diagrams (first estimation), the binary phase diagram and the eutectic valleys in the ternary system (second estimation), as well as the binary phase diagram, the eutectic valleys, and one (third estimation) and more (fourth estimation) liquidus and solidus temperatures of the ternary equilibrium phase diagram with varying precisions. A database calculated with Thermo-Calc software (version 4.1.0.4995), was used for the calculations. Full article

The simultaneous challenges of cadmium (Cd) contamination and mineral nutrient imbalance in paddy systems necessitate the development of effective agronomic strategies. This study systematically investigated the coordinated effects of different nitrogen fertilizer forms on the accumulation and translocation of Cd and mineral elements in rice. A hydroponic experiment was conducted using four N sources, including urea (U), nitrate-N (N), ammonium-N (AN), and a mixed ammonium-nitrate source (NN), which were applied at two concentrations (2.9 and 5.8 mM L⁻¹). We evaluated Cd accumulation, mineral element uptake, and translocation in rice seedlings under Cd stress. The results indicated that both the form and level of nitrogen markedly affected Cd accumulation. The AN treatment exhibited a strong Cd-reduction effect, especially at the higher nitrogen level, where it significantly reduced Cd concentration in roots and shoots by 68.75% and 26.81%, respectively. In contrast, the N treatment increased Cd accumulation in roots. Nitrogen fertilization also differentially influenced the accumulation of mineral elements, resulting in notable alterations in root Ca, Mg, Cu, and Zn concentrations, while shoot mineral concentrations remained relatively stable. Correlation and random forest analyses revealed a highly significant positive correlation between root Cd concentration and Mg and Cu concentrations, a significant negative correlation with Zn concentration, and a synergistic relationship between the translocation of Cd and that of Ca, Mg, and Cu. Analysis of ion channel tolerance rates further indicated that the AN treatment suppressed Cd uptake by reducing the permeability of root trace element channels to Cd. These findings demonstrate that nitrogen forms modulate Cd accumulation and partitioning by regulating competitive ion uptake and coordinated translocation. In particular, the AN treatment shows promising potential for reducing Cd accumulation while maintaining mineral nutrient balance, thereby providing a theoretical foundation for precise nitrogen management in Cd-contaminated paddy fields. Full article

A novel heavy metal-resistant bacterium with significant bioremediation capabilities, Sinirhodobacter sp. 1C5-22 was isolated from moderately polluted Shenzhen Futian mangrove rhizosphere sediments. This strain showed exceptional tolerance (MIC ≥ 600 mg/L for Cu/Zn; > 500 mg/L for Ni). Analyses revealed distinct metal-specific distribution strategies: Cd and Ni were predominantly bound extracellularly (>80%); Cu was bound intracellularly (~60%); and Zn exhibited balanced partitioning. Integrated omics analysis identified a molecular defense mechanism coordinated by the CreB transcriptional regulator. This Adsorption–Sequestration–Efflux (ASE) system integrates extracellular polymer binding, periplasmic sequestration via stable metal-binding proteins, and efflux pump activity, resolving the apparent adsorption-tolerance paradox at elevated concentrations. For bioremediation applications, we developed a polyvinyl alcohol–sodium alginate immobilized consortium (PVA-SA 1C5-22). The engineered agent displayed significantly enhanced biosorption capacity compared to free cells and effectively mitigated heavy metal-induced oxidative damage, evidenced by stabilized malondialdehyde levels. It demonstrated robust reusability, maintaining high metal enrichment across five adsorption–desorption cycles in multi-metal wastewater with efficient HCl-driven desorption (55–70%). Critically, it achieved stable nickel removal performance (~20% adsorption, >50% desorption) from authentic electroplating wastewater (1850 mg/L Ni²⁺) through successive multiple cycles. Our integrated approach bridges microbial ecology and environmental biotechnology, establishing this immobilized system as a highly sustainable strategy for complex industrial effluent remediation. Full article

In this study, both trivalent and hexavalent forms of chromium were examined in urban and agricultural Mediterranean soils. Chromium partitioning in different soil fractions was studied. Pot experiments included contamination of soil samples using Cr solutions, as well as a further study regarding Cr distribution in naturally contaminated soils. The soils were subjected to quantitative determination of both the available and total Cr concentration, as well as Cu and Zn, which were naturally present in the soil samples. Metal concentrations in the soil fractions were quantified after the application of the BCR fractional extraction method. The numbers of both trivalent and hexavalent Cr ions in each extract were determined. Considerable discrepancies were noticed regarding the Cr content of each soil fraction in both municipal and cultivated soils, indicating the possible origin of the pollution. The increasing impact of pollution is a significant parameter for the availability of chromium ions in both agricultural and urban soils. Increased pollution durations resulted in a significant increase in the non-available fraction of toxic Cr (VI), mainly in urban soil. Variations were also observed in the chromium species, as changes in soil parameters and in the conditions of the experiment seem to affect the conversion of the less harmful trivalent chromium to the toxic hexavalent chromium. In urban soils, the amount of toxic Cr (VI) bound to iron and manganese oxides exceeds 37.8%, while in agricultural soils, the amount of Cr (VI) associated with soil organic matter reaches 35%. Knowing the mechanisms and variables influencing Cr availability in agricultural and urban Mediterranean soils is desirable, as safe living in ecologically acceptable fields and producing safe goods in healthy soil systems are paramount goals. Full article

As a new generation 3D video coding standard, 3D-HEVC offers highly efficient compression. However, its recursive quadtree partitioning mechanism and frequent rate-distortion optimization (RDO) computations lead to a significant increase in coding complexity. Particularly, intra-frame coding in depth maps, which incorporates tools like depth modeling modes (DMMs), substantially prolongs the decision-making process for coding unit (CU) partitioning, becoming a critical bottleneck in compression encoding time. To address this issue, this paper proposes a fast CU partitioning framework based on hierarchical feature fusion convolutional neural networks (HFF-CNNs). It aims to significantly accelerate the overall encoding process while ensuring excellent encoding quality by optimizing depth map CU partitioning decisions. This framework synergistically captures CU’s global structure and local details through multi-scale feature extraction and channel attention mechanisms (SE module). It introduces the wavelet energy ratio designed for quantifying the texture complexity of depth map CU and the quantization parameter (QP) that reflects the encoding quality as external features, enhancing the dynamic perception ability of the model from different dimensions. Ultimately, it outputs depth-corresponding partitioning predictions through three fully connected layers, strictly adhering to HEVC’s quad-tree recursive segmentation mechanism. Experimental results demonstrate that, across eight standard test sequences, the proposed method achieves an average encoding time reduction of 48.43%, significantly lowering intra-frame encoding complexity with a BDBR increment of only 0.35%. The model exhibits outstanding lightweight characteristics with minimal inference time overhead. Compared with the representative methods under comparison, this method achieves a better balance between cross-resolution adaptability and computational efficiency, providing a feasible optimization path for real-time 3D-HEVC applications. Full article