Accidental releases and legacy contamination of hexavalent chromium [Cr(VI)] in soils pose severe risks to environmental protection and process safety of soil utilization. Conventional solidifiers for Cr(VI)-contaminated soil are plagued by inadequate early-age strength, substantial carbon footprint, and inefficient leaching control. Herein, a novel solidifier was synthesized from waste-derived alkali-activated cementitious material (AACM) and combined with D(+)-Glucose (GLU) as a reductant for effective and sustainable in-situ solidification of Cr(VI)contaminated soils. The optimized AACM composition achieved a strength of 1026 kPa and a permeability coefficient of 6.33 & times; 10-8 cm/s within 24 h. The incorporation of GLU substantially enhanced Cr(VI) leaching control, with solidification efficiencies exceeding 99.37% and Cr(VI) and 98.90% total Cr solidification efficiencies under various pH environment, achieving criteria for subgrade materials. Multi-scale characterization revealed that the Cr(VI) was converted to Cr(III) by GLU and S2-and subsequently locked into C-A-S-H/N-A-S-H gels through precipitation, isomorphic substitution, and electrostatic adsorption. Under the influence of these mechanisms, Cr leaching was diffusion-controlled, indicating stability of solidified bodies. A carbon emissions assessment revealed a 61.13% reduction in CO2 emissions compared with ordinary solidifiers, with a negative CO2 abatement cost. This work develops an efficient and environmentally friendly strategy for large-scale Cr(VI)contaminated soils solidification and the utilization of solid waste resources.

This study systematically investigated how trace divalent metal cations (M(II): Cu2 +, Zn2+, Cd2+, and Ni2+) affect the precipitation, stability, and phase transformation of hydrous ferric arsenate (HFA) as well as the mechanisms governing As(V) and M(II) mobilization in acidic systems. Natural crystalline ferric arsenate (scorodite) samples from Guangxi, China, validated the environmental relevance of the findings. The results showed that coexisting M(II) slightly inhibited the precipitation of Fe(III)-As(V), and the addition of M(II) promoted the partial dissolution of pre-formed HFA. Density functional theory (DFT) calculations attributed these effects to the site-selective incorporation of M(II) into the HFA chain (Fe1-As1-Fe2-As2) via substitution at the Fe1 site. Aging experiment results (70 °C) revealed that the doping level of M(II) in HFA and secondary scorodite is controlled by a combination of thermodynamics and kinetics. DFT and extended X-ray absorption spectroscopy (EXAFS) results confirmed that the scorodite lattice exerts a thermodynamic screening effect on incorporated M(II). Both Zn2+ and Cd2+ displayed favorable formation energies, whereas Cu2+ and Ni2+ tended toward remobilization. The resulting M(II) incorporation capacities in scorodite follow the order: Zn2+ (15.2 g/kg) > Cu2+ (12.6 g/kg) > Ni2+ (8.3 g/kg) > Cd2+ (3.4 g/kg). This study proposes a kinetic entrapment-thermodynamic screening mechanism for M(II)-As(V) co-immobilization that provides atomic-scale insights into As and M(II) in multi-M(II) acidic waste streams.

Biological ion channels realize exceptional selectivity for transition metal ions through the synergistic effects of angstrom-scale confinement and highly specific ligand-ion coordination. Inspired by this molecular recognition principle, we develop mercaptosuccinic acid (MSA) functionalized Ti3C2Tx MXene biomimetic nanochannel membranes that operate under a coordination-dominated ion transport pattern. The introduction of MSA induces chemically regulated angstrom-scale nanochannels with stabilized hydrated spacing, thereby effectively suppressing structural swelling in aqueous environments. In this system, highly selective separation of Cd2+ or Ni2+ is achieved mainly through specific coordination between thiol-carboxyl functional groups and transition metal ions, with K+/Cd2+ and K+/Ni2+ selectivity reaching ∼103. By contrast, the K+/Mg2+ selectivity is much lower. Theoretical calculations reveal that strong coordination interactions between transition metal ions and MSA functional groups impose significantly elevated translocation energy barriers, effectively immobilizing Cd2+ and Ni2+ within the confined channels, while K+ and Mg2+ experience weaker interactions and retain facile transport pathways. The selective accumulation of divalent ions at channel entrances reflects the combined effects of strong ligand-ion interactions and high dehydration barriers. This work establishes a thiol-carboxyl coordination-dominated transition metal ion recognition pattern in angstrom-confined two-dimensional nanochannels and provides a theoretical basis for the rational design of artificial ion channels with programmable selectivity.

Marine microalgae, as the primary producers in ocean ecosystems, play a critical role in global carbon cycling and are efficient accumulators of arsenic (As) from seawater, raising concerns about its trophic transfer through marine food webs. Rising terrestrial nutrient inputs, particularly excess nitrogen, have elevated nitrogen-to-phosphorus (N/P) ratios, representing a widespread ecological concern that alters marine biogeochemical cycles and threatens the survival of marine microalgae. A deeper understanding of how arsenic uptake and transformation biogeochemistry in marine microalgae respond to intensifying N/P ratios is thus crucial to predict the response of marine ecosystems and their contribution to global climate change. Despite these concurrent trends, the impact of altered nutrient dynamics on the arsenic biogeochemistry in marine microalgae remains largely unexplored. Here, we show that appropriately increased N/P ratios markedly enhance arsenic accumulation and promote the intracellular conversion of inorganic As to organic species. Transcriptome data further demonstrate that marine microalgae could significantly upregulate gene expressions associated with arsenic transport-related genes to cope with increased N/P ratios. Metabolomic flux analysis revealed that elevated N/P ratios promoted photosynthetic carbon fixation, ATP synthesis, and carbohydrate metabolism, while the amino acid metabolism was suppressed in marine microalgae, and the redirected energy flow may facilitate arsenic metabolism. Collectively, the reallocation of metabolic energy under high N/P conditions contributed to increased arsenic uptake and biotransformation in marine microalgae. An analysis of the Tara Oceans database confirmed these patterns and showed that arsenic metabolism-related genes are widely distributed across global surface oceans. Continuous nitrogen inputs and rising N/P ratios may alter arsenic speciation and mobility, benefiting cellular detoxification in the short term but potentially increasing organic arsenic accumulation, trophic transfer, and associated ecological and human health risks over longer time scales.

The antibiotic florfenicol (FF) represents a persistent environmental threat owing to its high chemical stability and ubiquitous presence in aquatic ecosystems. While non-thermal plasma technology exhibited significant degradation potential, the complex non-linear coupling among its operating parameters rendered the simultaneous achievement of high efficiency and low energy consumption exceptionally challenging. To address this, this study developed a high precision predictive framework capable of multi-objective synergistic optimization and inverse parameter identification, integrating an artificial neural network (ANN) with a genetic algorithm (GA). Within this ANN-GA framework, degradation kinetics and energy yield were effectively decoupled, and three operating regimes with distinct reactive species supply levels were established under a fixed energy yield constraint. Experimental verification confirmed that hydroxyl radical (center dot OH) was the predominant oxidant, and the reaction pathways were systematically elucidated. Crucially, density functional theory calculations integrated with ecotoxicity assessments revealed that a high flux of center dot OH could effectively surmount critical rate limiting energy barriers, thereby preventing the accumulation of toxic intermediates. Under the optimized kinetic regime, 10 mg/L of FF achieved 100% removal in 8 min. This precise regulation strategy reconciled high degradation efficiency, minimized energy consumption, and thorough detoxification, providing a novel paradigm for the sustainable remediation of antibiotic pollutants.

ABSTRACT Sustainable bioprocesses for selenite [Se(IV)] remediation and selenium (Se) recovery are constrained by the limited tolerance of most reported microorganisms for elevated Se(IV) concentrations. Here, we identified Paenibacillus polymyxa P10, isolated from estuarine sediment, as a highly tolerant and efficient Se(IV)-reducing bacterium. Strain P10 completely reduced 5 mM Se(IV) to Se nanoparticles (SeNPs) within 48 h and retained measurable Se(IV)-reducing activity up to 1,000 mM Se(IV). It also maintained activity over a wide range of pH (5–10), temperature (20–45°C), and salinity (1%–3.5%) conditions. In addition, P10 maintained high Se(IV) reduction performance over five repeated-batch cycles. Transcriptomic and enzymatic analyses showed that Se(IV) exposure triggered coordinated metabolic responses, including carbohydrate metabolism, oxidative phosphorylation, and nitrogen metabolism, which together supported energy generation and reductive transformation. Nitrite reductase-associated activity was linked to Se(IV) reduction. These findings establish strain P10 as a robust biocatalyst for Se(IV) detoxification and SeNP recovery, and provide mechanistic insight into microbial selenite reduction relevant to the development of scalable Se-containing wastewater treatment processes. IMPORTANCE Selenite [Se(IV)] is among the most problematic selenium (Se) species in wastewater due to its high toxicity and mobility. Although microbial Se(IV) reduction is an attractive strategy for Se detoxification and recovery, its practical use is limited by the poor tolerance and weak environmental robustness of most known microorganisms. This study identifies a highly tolerant Se(IV)-reducing bacterium with broad adaptability to pH, temperature, and salinity stress, extending the known ecological and functional potential of microbial Se reducers. These findings strengthen the basis for developing more reliable bioprocesses for Se-contaminated wastewater treatment and Se resource recovery.

Selenium (Se) is an essential trace element that plays a dual role in environmental and biological systems, acting as both a nutrient and a potential toxin depending on its chemical form and concentration. Microalgae serve as critical mediators in aquatic Se cycling by assimilating inorganic Se species and transforming them into bioavailable organic and volatile compounds. However, the molecular basis of Se uptake and biotransformation in marine microalgae remains poorly understood. In this study, we systematically examined the effects of Se concentration, chemical speciation, and competing anions on the uptake and transformation of selenite and selenate in two representative marine microalgae, Dunaliella salina and Phaeodactylum tricornutum. Under competitive anion conditions, D. salina exhibited nearly fourfold higher Se accumulation than P. tricornutum, indicating species-specific uptake strategies. The presence of sulfate and phosphate further enhanced the conversion of inorganic Se into bioavailable organic forms. Integrated transcriptomic and metabolomic analyses identified key transmembrane transporters involved in Se uptake, including members of the ABC, PIT, MFS, and SIT families, and revealed a putative metabolic pathway encompassing reduction, methylation, and incorporation into selenocysteine and selenoproteins. The findings of this study provide mechanistic insights into selenium bioavailability and metabolic transformation in marine microalgae and establish a foundation for their application as sustainable biocatalysts in selenium removal, resource recovery, and ecological remediation within aquatic environments.

Reduction of arsenite (As(III)) to elemental arsenic As(0) is an immerging approach for the removal of arsenic from nonferrous smelting waste acids. However, previously established photo-/electrocatalytical As reduction technologies suffer from low efficiency, high energy consumption, and heavy reliance on sacrificial agents or toxic by-products (e.g., AsH3), limiting their practical application. To address these issues, we prepared a photoelectrode with Z-type heterostructure and N/O bivacancies, MoOx/g-C3N4@CF. XRD, XPS, EPR, and photoelectrochemical measurements unveiled that N/O-bivacancies enhance performance by extending the light absorption range and supplying abundant active sites for As(III) adsorption and reduction. The Z-type heterostructure further accelerated electron transfer and inhibits carrier recombination, synergistically improving the photo-electrocatalytic activity. In the photo-enhanced electrocatalytic reduction of As(III), the optimal 2.0-MoOx/g-C3N4@CF achieved 97.0% As(III) removal within 1.5 h under -1.25 V (vs Hg/Hg2SO4) in 0.4 M H2SO4, which was nearly twice as fast as pristine CF. Additionally, the toxic by-product AsH3 yield was reduced from 17 ppm to similar to 3 ppm, and the Faraday efficiency for As(0) formation (FE(As(0))) was increased from 13.7% to 21.7%. When treating the actual waste acid (2.1 g/L As(III)), it achieved 93.3% arsenic removal in 2 h, outperforming pristine CF by about 1 h. This work provided a green and efficient strategy for the removal and resource recovery of As(III) from strongly acidic wastewater, with significant environmental and industrial application value.

The production of ordinary Portland cement remains one of the largest anthropogenic sources of CO2 emissions, motivating the search for carbon-negative alternatives. Herein, a biochar-MgO co-milled activator was developed to prepare biochar-coupled MgO-activated slag system with enhanced hydration and carbonation resistance. Ball-milling of MgO with corn-stalk-derived biochar significantly increased the MgO reactivity, thereby accelerating the formation of calcium silicate hydrate and layered double hydroxide phases. The resulting biocharcoupled MgO-activated slag system exhibited 75 % higher compressive strength and 45 % lower porosity than conventional MgO-activated slag. Under accelerated carbonation (20 vol% CO2), biochar-coupled MgO-activated slag system mitigated decalcification and converted calcium silicate hydrate into well-crystallized calcite while preserving matrix integrity through adsorption and buffering by layered double hydroxide phases. Thermodynamic modeling further confirmed the synergistic role of biochar on phase evolution during hydration and carbonation. Life-cycle assessment indicated a 63 % reduction in cradle-to-gate CO2 emissions relative to ordinary Portland cement, attributable to both biochar's carbon-negative nature and improved CO2 fixation efficiency. This study demonstrates a synergistic biochar-MgO strategy for producing durable, low-carbon binders through controlled hydration and mineral carbonation, providing a scalable pathway toward carbon-neutral construction materials.

Understanding and predicting the reactivity of organic pollutants toward reactive species is crucial for designing efficient and targeted degradation strategies for advanced oxidation processes. However, the structural complexity and chemical diversity of pollutants pose challenges for developing interpretable and high-throughput predictive frameworks. Here, a machine-learning-based approach that integrates quantum chemical descriptors and molecular fingerprints descriptors to predict pollutant reactivity toward sulfate radicals is presented. By combining RDKit and conceptual density functional theory (CDFT) descriptors, key structure-activity features, including EHOMO(N), electron-donating capacity, ring structures, branching, and molecular surface areas, are identified, and their quantitative reactivity thresholds are established. Additionally, the quantitative read-across structure-activity relationship model incorporating intermolecular similarity expands the applicability domain (AD) to 74.3% across 12 pollutant classes, a 2.1-fold increase in the AD over quantitative structure-activity relationship (QSAR) approaches. Experimental validations across structurally diverse compounds demonstrate strong predictive performance (R2 = 0.811). This work provides a transparent and high-throughput predictive framework for reactivity prediction of organic pollutants, facilitating the bottom-up design of an advanced oxidation process tailored to specific pollutant profiles.

Riverine suspended particulate matter (SPM) inputs play a crucial role in regulating phytoplankton sedimentation and stability in estuarine ecosystems, thereby mediating organic matter cycling. However, our understanding of how the physicochemical properties of SPM influence the short-term response mechanisms of phytoplankton remains insufficient. This study focuses on the sedimentation phase following SPM input and employs a controlled microcosm experimental system. Through short-term sedimentation experiments, it thoroughly investigates the effects of SPM particle size and surface charge on the sedimentation behavior and community composition of marine phytoplankton. The results show that SPM sedimentation substantially decreased phytoplankton biomass in seawater, with sedimentation rates increasing significantly as SPM particle size decreased. Surface charge also strongly enhanced phytoplankton sedimentation. In terms of community composition, SPM markedly altered phytoplankton structure by significantly reducing the relative abundance of Bacillariophyta and Dinophyta while increasing that of Heterokontophyta. Among the examined factors, SPM particle size emerged as a primary driver of these changes. Additionally, SPM inputs increased the relative abundance of microalgae-associated symbiotic bacteria, and combined with the changes in community composition and the results of co-occurrence network analysis, it is hypothesized that the enriched microalgae-associated bacteria may form potential ecological associations with phytoplankton under SPM disturbance conditions. Overall, this study provides new insights into the short-term responses of marine phytoplankton to riverine SPM input during the initial sedimentation phase, and offers preliminary mechanistic references for understanding particulate matter-driven plankton dynamics in estuarine systems.

Bentonite-based hydraulic barriers are prone to performance degradation under high-concentration contaminant attack. Research on solid-waste-based barrier materials with high bentonite contents remains limited. To achieve low carbon footprint, high strength, and low permeability, this study proposes an in situ gel-growth strategy: under sodium hexametaphosphate (SHMP)-mediated electrostatic-hydration coupling, a montmorillonite-C-(A)-S-H intergrown framework is constructed within a high-loading (72 wt%: bentonite accounts for 72 % of the total dry powder raw materials.) Ca-bentonite/industrial solid-waste composite (BM@GF). Multivariate optimization and response surface analysis show that BM@GF attains a minimum permeability coefficient (PC) of 7.03 × 10-12 m·s-1 and an unconfined compressive strength (UCS) of 4.22 MPa, corresponding to 438-fold and 19-fold improvements, respectively, over a conventional soil-bentonite (S-B) barrier. During rapid setting (24 h) under aggressive media (strong acids/alkalis; 10-100 mmol·L-1 Pb2+ and Cr3+), the chemical-compatibility (CC) retention exceeds 95 %. Life-cycle assessment indicates a 75.3 % reduction in carbon footprint and a 25 % decrease in production cost relative to Portland-cement-based materials, while leaching tests verify immobilization of hazardous metals below regulatory thresholds. SHMP-mediated construction of the montmorillonite-C-(A)-S-H intergrown architecture provides a new pathway for the sustainable valorization of industrial solid wastes in barrier applications.

Trace metal(loid) contamination in paddy soils derived from either geogenic sources or mining activities is widely occurring in mid-south to south China and south to south east Asia. Due to their toxicities, these trace metal(loid)s may influence microbial community assembly and carbon/nitrogen (C/N) cycling. However, how metal(loid) contamination reshapes community composition, functional potential, and genomic traits of key functional microorganisms remains unclear. Here, we collected paddy soil samples from mid-south to south China and classified them into low- and high-contamination groups based on the Nemerow index. The associations among contamination level, microbial community composition, C/N-cycling potential, and genomic traits of key functional microorganisms were examined by combining soil physicochemical characterization, 16S rRNA gene amplicon sequencing, metagenomics, and metagenome-assembled genome (MAG) reconstruction. Bacterial and archaeal richness did not differ significantly between contamination levels, whereas community composition varied markedly. Methane oxidation genes were enriched in high-contamination soils, whereas methanogenesis genes were more abundant in low-contamination soils. Denitrification- and dissimilatory nitrate reduction to ammonium (DNRA)-related genes increased under heavy contamination, whereas several nitrogen fixation genes declined. Environmental association analyses identified As, Cd, Pb, Cr, and Zn as key variables associated with C/N cycling genes. Several MAGs carried both elemental cycling genes and metal(loid)-response or transformation genes, suggesting potential multifunctionality in contaminated paddy soils. Overall, metal(loid) contamination, together with associated edaphic variation, reorganized microbial communities and redistributed C/N cycling potential. This work provides a genomic basis for identifying microorganisms that could serve as bioindicators or functional targets in contaminated paddy soils.

Coastal ecosystems currently face significant challenges due to nutrient enrichment and trace metal contamination. However, the effects of arsenic (As) and other trace metals (copper, lead, zinc, cadmium, mercury) on denitrification processes and nitrous oxide (N2O) emissions in estuarine sediments remain poorly understood. Here, we examined the influence of As and other trace metals on denitrification and N2O emissions in a single denitrifying strain, Marinobacter sp. MSD-1, isolated from metal-contaminated estuarine sediments based on its As(III)-oxidizing and denitrifying abilities and functional microbial composition. The results showed that As did not significantly affect the denitrification or N2O emission of MSD-1. However, Cd(II) at concentrations of 5-10 mg/L significantly induced the accumulation of N2O, while not significantly affecting the reduction of nitrate (NO3-) and nitrite (NO2-). The presence of As(III) further inhibited the N2O reduction under Cd exposure, but it had no significant effect on the N2O reduction after exposure to other trace metals. A negative correlation was observed between N2O reductase (NO2R) activity and N2O emissions, indicating that Cd(II) inhibits the reduction process of N2O mainly by suppressing the activity of NO2R. This study highlights the detrimental effects of cadmium on microbial denitrification and subsequent emissions of the greenhouse gas N2O, thereby improving our understanding of how estuarine and coastal ecosystems respond and adapt to trace metal pollution.

Arsenic-calcium residue (ACR) is a hazardous solid waste generated by the metallurgical industry, posing a significant environmental risk. However, the stability and transformation behavior of ACR in sulfidic conditions remains unclear. Herein, we have investigated the stability and speciation evolution of arsenic (As), sulfur (S), and trace metals during the exposure of ACR to diverse S(-II) concentrations under anoxic conditions at pH of 6 and 11. Our results indicate that environmentally relevant levels of S(-II) (i.e., 1, 10, and 50 mM) significantly enhance the mobilization of As(III) and Cd2+ from ACR, with greater release at pH 6. The main mechanism for the release of As(III) and trace metals from ACR is the reductive dissolution of Ca-arsenate/arsenite and As-trace metals-gypsum. The reductive dissolution of As-trace metals-gypsum leads to the formation of S2O32 & horbar; and SO32 & horbar;. XRD, FE-SEM, FTIR, XPS, and HRTEM analyses reveal that gypsum serves as the host phase for As fixation at pH 6, while calcium-arsenate/arsenite phases predominate at pH 11. Secondary As2S3, CdS, CuS, and symplesite are generated at pH 6, whereas parasymplesite, CdS, and CuS are predominant at pH 11. These results enhance our understanding of the environmental behavior of As, S, and trace metals associated with ACR.

Nano zero-valent iron (nZVI) exhibits remarkable effectiveness in degrading recalcitrant organochlorine pollutants, yet its practical application is hindered by rapid passivation and insufficient electron utilization efficiency. This study developed a biochar-supported sulfidated nZVI (S-nZVI@BC) with a distinctive core-shell structure to synergistically enhance the degradation efficiency of lindane (gamma-HCH). Systematic characterization revealed that modulating the S/Fe molar ratio (optimal at 0.077) precisely controlled sulfur speciation distribution between core and shell regions, optimized surface hydrophobicity, and improved electron transfer efficiency, achieving nearly complete removal of 5 mg/L gamma-HCH within 24 h. Unlike conventional supports, biochar demonstrated dual functionality: its electron shuttle effect increased Fe0 utilization compared to unsupported counterparts, while its conductive aromatic structures facilitated long-range electron transfer, significantly enhancing dechlorination performance. Mechanistic investigations revealed that core properties rather than shell characteristics dominated the material's reactivity, challenging conventional surface-centric theories. The synergistic mechanism involves sulfur doping suppressing hydrogen recombination side reactions to strengthen atomic hydrogen-mediated reduction, while biochar simultaneously inhibits nZVI agglomeration through physical dispersion and optimizes reaction kinetics as an electron conductor. These findings provide a theoretical framework for designing high-performance engineered carbon-iron materials for organochlorine-contaminated site remediation and highlight critical considerations for field-scale implementation.

Ferrihydrite sulfidation is an important process influencing the environmental behavior of co-existent arsenate (As(V)) and cadmium (Cd(II)) pollutants in mining-impacted environments. However, the mineral evolution of ferrihydrite and the coupled mobilization behavior of co-existent As(V) and Cd(II) remain unclear. In this study, we have investigated As(V)-Cd(II)-bearing ferrihydrite conversion behavior induced by environmentally relevant concentrations of S(-II) (1 and 5 mM). PXRD, HR-TEM, and XAS results demonstrate that the co-existent As(V) and Cd(II) inhibit the conversion of ferrihydrite to secondary lepidocrocite (gamma-FeO(OH)) and subsequently to goethite (alpha-FeO(OH)) at different S(-II) concentrations. Elevated As(V) and Cd(II) levels promote the formation of amorphous mackinawite (FeS) and pyrite (FeS2). Lepidocrocite and greenockite (CdS) are the predominant secondary phases at 1 mM S(-II) but lepidocrocite and pyrite are dominant at 5 mM S(-II) when the As(V) and Cd (II) levels are low. These sulfidation transformation pathways reduce the mobilization of the co-existent As(V) and Cd(II). Cs-TEM and chemical extraction results reveal that substantial portions of Cd(II) and As(V) are incorporated into secondary pyrite and lepidocrocite, in addition to surface adsorption and greenockite precipitation. These findings not only enhance our understanding of the geochemical cycling of Fe(III), As(V), and Cd(II) in natural anoxic sulfidic environments but also may provide guidelines for developing effective remediation methods for As-Cd co-contaminated settings.

Soil contamination with heavy metal(loid)s (HMs) threatens soil ecosystem health and function. However, how cross-regional HM contamination influences the structure and function of soil fungal communities remains understudied. We conducted a large-scale soil survey in southern China, using the Nemerow synthetic Pollution Index to assess contamination levels of seven metals (copper, lead, cadmium, arsenic, nickel, zinc and chromium). Soils were classified as low, medium, and high contamination (LC/MC/HC) to examine HM biogeographic patterns and their ecological impacts on soil fungi along the gradient. Cd was the most prevalent contaminant, followed by As in all the studied soils. The combined soil pollution significantly altered fungal community structure, with Cd and Pb identified as key drivers of structural and evenness changes, respectively. Fungal diversity and evenness declined with pollution, accompanied by reduced Staphylotrichum (-0.45 %) and Saitozyma (-1.5 %). Homogeneous selection dominated the assembly processes of soil fungal communities across all contamination levels (contributing 55.8-64.9 %). The most enriched characteristic species included Eurotiomycetes (LC), Sordariales (MC), and Coniochaeta (HC). Pollution-induced habitat heterogeneity enhanced the complexity and stability of fungal symbiotic networks, with 10.0 % more synergistic interactions in highly contaminated soils. The abundance of potential pathogenic fungi increased by 3.0-5.8 % in highly polluted soils compared to low- and moderately polluted soils, indicating possible negative implications for ecosystem health. Our findings provide novel and comprehensive insights into the ecological response of soil fungal communities to HM contamination.

Understanding iron mineral-mediated dissolved organic matter (DOM) transformation is key to predicting the carbon cycle in aquatic environment. However, the catalytic roles of iron (oxyhydr)oxides in mediating molecular transformations and chemodiversity of algal-derived dissolved organic matter (ADOM) remain poorly understood. This study systematically investigates ferrihydrite (FH), goethite (GOE), and hematite (HEM) under dark and irradiated conditions. Three-dimensional fluorescence analyses revealed that all three iron oxides accelerated ADOM transformation, with crystalline phases (HEM and GOE) inducing a distinct fluorescent component (excitation/emission: 250(340)/434 nm), particularly under HEM exposure. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) data demonstrated preferential adsorption of aromatic and carboxylic acid compounds by iron oxides, forming ADOM molecules characterized by low unsaturation. Light irradiation enhanced molecular chemodiversity, reducing aromaticity by 32.7 % while increasing unsaturated and oxygen-rich compounds by 13.1 % and 22.8 %, respectively. Electron paramagnetic resonance spectroscopy identified reactive oxygen species (ROS) generation via surface electron transfer. Specifically, singlet oxygen (1O2) and hydroxyl radicals (•OH) produced by GOE and HEM induced aromatic ring cleavage and structural reorganization. This oxidative transformation significantly increased the DOM lability index (MLB) 32.7 % in the GOE system and 41.2 % in the HEM system. Mechanistically, iron (oxyhydr)oxides function as dual agents, acting as electron transfer mediators and radical catalysts, which collectively regulate DOM composition and lability. These findings provide critical insights into iron-driven biogeochemical cycling of organic matter in aquatic systems.

Rapid pollutant containment in contaminated sites requires cutoff materials with fast setting, early strength, high impermeability, and chemical resistance. This study develops a Sulfur-aluminum-ferric (SAF) binder synthesized from industrial solid wastes and modified with biochar (BC). The potential of this material as a soil-cement pollution cutoff wall was evaluated through strength experiments, microstructure analysis, permeability modeling, pollution cutoff validation, and life cycle assessment (LCA). The material attained a final setting time <1 h and met the 28-day unconfined compressive strength (UCS) requirement specified for cutoff walls as early as 16 h. BC accelerated hydration by promoting calcium silicate hydrate (C-S-H) and ettringite (AFt) formation, refined the pore structure, and improved interfacial transition zones (ITZ), resulting in ∼70 % lower intrinsic permeability. The visualization simulation of absolute permeability showed that the modified material has lower internal absolute permeability, effective porosity, and total flow rate, as well as higher tortuosity, pressure gradient, and more uniform internal pressure field. Sparse streamline distribution implied poor fluid transport capacity. Samples maintained stable performance in an acidic, alkaline, salt, and VOCs containing environments. BC also reduced the leaching concentration of heavy metals from the waste. Pilot-scale experiments confirmed the material's ability to prevent contaminant migration in actual contaminated sites. LCA revealed a 63.9 % reduction in global warming potential, along with significant decreases in ecotoxicity, acidification, and human carcinogenic toxicity relative to Portland cement. The integration of industrial solid waste and BC enhances engineering performance and environmental resilience, providing a potential material for pollution cutoff wall.