The application of passivators represents a typical remediation strategy for soil heavy metal pollution， a process that not only affects heavy metal bioavailability but also modifies nitrogen transformation processes. However， the influence of passivators on the structure of functional microbial communities governing nitrogen transformation in cadmium （Cd）-contaminated soils remains poorly understood. In this study， typical passivators （lime and biochar） were applied in a pot experiment with rapeseed cultivated in Cd-contaminated soil. High-throughput sequencing and complementary methodologies were employed to investigate shifts in gene abundance and community characteristics of soil nitrogen-fixing bacteria and ammonia-oxidizing microorganisms， along with their driving factors. The results revealed that lime application significantly reduced the Shannon index of nitrogen-fixing bacteria， ammonia-oxidizing archaea （AOA）， and ammonia-oxidizing bacteria （AOB） by 8.62%， 9.11%， and 82.80%， respectively， while increasing their Simpson index by 22.78%， 3.56%， and 55.86%. In contrast， biochar application exclusively reduced the Shannon index of AOB by 80.13% and increased its Simpson index by 71.63%. Lime significantly enhanced AOA amoA gene abundance but reduced AOB amoA gene abundance， whereas biochar induced no significant changes in amoA genes. Lime markedly altered the β-diversity of nitrogen-fixing bacteria， AOA， and AOB， while biochar only significantly affected AOA β-diversity. These findings demonstrate that passivators can restructure soil microbial communities involved in nitrogen transformation， with lime exerting more substantial effects than biochar. Additionally， both passivators significantly modified the relative abundance of dominant microbial groups （e.g.， Proteobacteria and Crenarchaeota） within functional communities. Changes in key nitrogen-transforming microbial communities showed strong correlations with soil physicochemical properties： Nitrogen-fixing bacteria were primarily governed by pH and available Cd （ACd）； AOA by ACd and pH； and AOB by soil organic matter （SOM）， pH， and ACd. Within nitrogen-fixing bacteria， Geobacter exhibited significant positive correlations with ACd， NH4+， and NO3- but a negative correlation with pH， while Azohydromonas displayed inverse responses. Among AOA， Crenarchaeota and Thaumarchaeota positively correlated with pH but negatively with ACd， whereas Nitrososphaera showed negative correlations with pH but positive associations with soil total nitrogen （STN）. For AOB， taxa such as β-Proteobacteria demonstrated positive correlations with ACd， NH4+， and NO3- but negative correlations with pH. By elucidating how passivators （particularly lime） significantly restructure key microbial consortia involved in soil nitrogen transformation， this study provides a theoretical foundation for understanding the mechanisms through which passivators influence nitrogen cycling processes in Cd-contaminated soils.

Metastable amorphous ferrihydrite (Fh), ubiquitous in redox-dynamic environments, regulates associated trace metal (Cd, As) fate. Nevertheless, how the co-presence of Cd and As influences the phase transformation of Fh and the mobility of coexisting Cd and As remains elusive. Herein, we incubated Fh nanoparticles with Cd/As at pH 6.0 under 25 °C and 75 °C for 60 days. Solution concentrations were monitored, and transformed solids were extracted with P/Ca at pH 4.0/8.0. We showed that aging enhanced Cd and As adsorption in binary/ternary systems, with As co-presence significantly promoting Cd sorption. However, 75 °C aging caused partial Cd and As release after 60 days. The assessment of sorption stability following incubation indicated that Cd and As exhibited distinct behaviors during the extraction by P and Ca. This phenomenon arises from electrostatic interactions between adsorbates and extractant and variations in sorption affinity between Cd and As towards Fh. Elevated temperatures altered the Fh surface structure, enhancing As immobilization but reducing Cd retention. Notably, Cd-As co-presence mutually enhanced release due to ternary complex instability. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and fourier transform infrared spectroscopy (FTIR) results showed that mixed mineral phases (goethite, hematite, and Fh) were detected at relatively lower Cd and As concentrations. Further extraction experiments revealed that the non-extractable state (structurally incorporated or pore blocked) of Cd and As increased to 42.8 % and 89.7 %, respectively, at lower Cd-As concentrations. Overall, the aging process induces alterations in Fh surface properties (specific surface area, reactive sites, mixed phases, etc.), diminishing Cd/As stability and facilitating its release with competitive ions.

Due to the relatively weak iron absorption capacity of general biomass, it is difficult to prepare nZVI-biochar with high loading and encapsulation performance. In this study, waste black fungus with strong water absorption capacity facilitated the adsorption of iron ions was employed to prepare composite material with high loading and high encapsulation of nZVI with biochar (AG/Fe0-800). The results shown that AG/Fe0-800 can achieve a removal rate of 98.20 % for hexavalent chromium (Cr(VI)) in water within 30 min, and it also maintains extremely low iron leaching in complex water environments. Adsorption and reduction are the main intrinsic mechanisms by which AG/Fe0-800 reduces Cr(VI). Encapsulated nZVI removes Cr(VI) through direct reduction and indirect reduction. This study has developed a new type of highly efficient remediation material with nZVI encapsulation and environmental-friendly, providing an innovative solution for the remediation of heavy metal pollution.

The escalation of industrial and agricultural activities has intensified heavy metal co-contamination, particularly Cd2+-Pb2+ complexes in aquatic systems. This study engineered manganese ferrite-modified hydrochar (FM/HC) through integrated hydrothermal carbonization (200 °C, 8 h) and liquid-phase precipitation with optimized Fe/Mn atomic ratio (2:1). The FM/HC had a surface area that was 117.36

Covalent bond-containing (CBC) catalysts exhibit remarkable chemical stability and exceptional structural properties, rendering them promising compounds for efficient catalysis in various chemical reactions. These catalysts are synthesized through the unique orientation and saturation characteristics of covalent bonds, which feature a chemically bond-driven tunable interaction between metal atoms and non-metal elements. This tunable interaction provides a platform to selectively lower the activation energy required for specific chemical reactions, thereby enabling catalytic processes to accelerate or decelerate reaction rates. Our review presents the fundamental theories and advancements related to covalent bonding and catalysts. We classify the two constituent forms of covalent bonds (metal-nonmetal covalent bonds and nonmetal covalent bonds) to explore their respective property characteristics and discuss experimental strategies for catalyst construction. Furthermore, we propose strategies to optimize the utilization of covalent bonds within catalyst structures, encompassing three key performance characteristics. Subsequently, we summarize the applications of CBC catalysts in catalytic oxidation, hydrogenation, dehydrogenation, cracking, and dehydration. Finally, we delved into the structure and applications of CBC catalysts at the molecular and atomic scales, providing guidance on current challenges and future research directions.

In paddy fields, the co-occurrence of arsenic (As) and cadmium (Cd) poses a significant challenge to food security. This study elucidates a key mechanism: phosphorus (P) gradients direct the partitioning of As and Cd in rice by modulating the crystallinity of root-surface iron plaque (IP). Through hydroponic experiments, we found that low-P conditions fostered amorphous IP, which exhibited a remarkable selectivity for As adsorption (2366.53 mg·kg− 1) while impeding Cd fixation (45.59 mg·kg− 1). Conversely, high-P accelerated IP crystallization, enhancing Cd adsorption (105.69 mg·kg− 1) but drastically reducing As capture (264.87 mg·kg− 1). This morphological shift dictated metal fate: under low-P, 75

Under environmental stress, the migration and accumulation of heavy metals in soil profoundly affect ecosystem dynamics and environmental risks. This study applied CiteSpace bibliometric methods to visually analyze 1,768 publications from 2000 to 2024, based on the Web of Science Core Collection. The analysis included publication trends, keyword frequencies, international collaboration, core authors, and institutions. Results show a shift in focus from pollution identification and mechanisms to health risk assessment and material-based remediation. Notably, increasing attention has been given to lignocellulose-derived amendments such as humic acid and biochar for their potential in stabilizing soils under compound environmental stressors. Leading institutions such as the Chinese Academy of Sciences and U.S. research bodies have played prominent roles, while high-impact journals, including the Journal of Biogeography, reflect strong academic output. Keyword clustering and burst analysis highlight emerging cores like “speciation,” “health risk,” and “biochar,” showing a phase-based evolution of research themes. The field’s short citation half-life, frequent keyword bursts, and multidisciplinary integration confirm its status as a research frontier. This study provides a comprehensive knowledge map and valuable insight into the dynamic behavior of soil heavy metals under environmental stress.

Heavy metal or antibiotic contamination significantly affects microbial community structure and soil function. However, the effects of combined heavy metal and antibiotic contamination on soil microbial communities and their metabolic characteristics remain unclear. Hence, this study investigated microbial community responses to sulfamethoxazole (SMX) gradients (0, 1, 10, and 50 mg kg-1) in arsenic (As)-contaminated soils using 16S rRNA sequencing and biochemical analyses. The results showed that bacteria, fungi, and archaea in As-contaminated soils developed distinct adaptation mechanisms to SMX stress. The complexity and connectivity of bacterial networks in As-contaminated soils increased after SMX exposure, while fungal and archaeal networks decreased. Antibiotic-resistant bacteria displaced fungi/archaea as keystone taxa in network hubs due to SMX-driven competitive advantages. SMX stress also increased microbial carbon limitation by 16.6-25.0 % in Ascontaminated soils, attributed to heightened As toxicity and fungal metabolic compensation. Conversely, bacterial community restructuring reduced microbial phosphorus limitation by 4.37-11.4 %. These findings reveal microbial metabolic adaptation mechanisms under combined contamination and offer critical perspectives for soil nutrient management in combined contaminated ecosystems.

As an emerging contaminant, tungsten (W) displays unexpectedly high mobility in soil despite its extremely low solubility, challenging current scientific understanding. This paradox underscores the limited knowledge regarding the specific W species responsible for its high mobility. In this study, a series of field and incubation experiments were conducted across multiple soil types to investigate the distribution and speciation of W in soil porewater, widely known as '' the most mobile fraction ''. Ultrafiltration analysis revealed that W in soil porewater predominantly existed in colloidal-size (5 kDa-0.45 mu m) phases rather than the '' truly-dissolved '' phase (<5 kDa). Especially in deeper soil layers approaching shallow groundwater, colloidal W content exceeded 93 %. XANES spectra showed that colloidal W was mainly in the hexavalent state (W-VI), and insoluble W metal (W-0) entering the soil could rapidly oxidize into W-VI through biotic or abiotic processes. Advanced characterizations, including STEM-EDS-SAED, SEM-EDS, and SR-XRF, identified aluminosilicate mineral colloids as the primary carrier for W in soil porewater. Within these W-bearing aluminosilicate mineral colloids, W was primarily present as Al-2(WO4)(3) precipitates with a W-Al distance of similar to 3.64 & Aring;, as confirmed by EXAFS. Additionally, a minor fraction of silicotungstates was also detected in the colloidal fraction using XAS and STEM-EDS-SAED. These two species were further substantiated through geochemical modeling and density functional theory (DFT) analysis. Importantly, this study hypothesizes that the associations of W with aluminosilicate mineral colloids and silicotungstates are widespread across different soil types. The finding suggests that colloid-associated W mobility is a dominant yet previously overlooked process, helping to explain why W, despite its low solubility, exhibits exceptionally high mobility in soils.

This study investigated the accumulation and distribution of cadmium (Cd) in the Soil-Lilium system and researched the effects and mechanisms of applying oyster shell powder (OSP) and organic fertilizer (OF) on reducing Cd accumulation and enhancing Lilium yield. The results showed that the total Cd content in soils across different planting regions was below 0.3 mg·kg−1, while the Cd content in Lilium bulbs ranged from 0.44 mg·kg−1 to 1.35 mg·kg−1, indicating a consistent trend of Cd accumulation in Lilium bulbs. Cd contents were highest in the leaves and lowest in the bulbs, suggesting a strong translocation of Cd from the roots to the aerial parts. Both OSP and OF treatments improved Lilium growth and reduced Cd accumulation in the bulbs. OF significantly increased bulb yield by 62.5%, while OSP effectively reduced Cd content in the bulbs to 0.30 mg·kg−1, below the regulatory safety threshold. OSP mitigated Cd accumulation by decreasing the availability of Cd in the soil and by competing with Cd for root uptake via its abundant Ca2+ ions. OF reduced Cd accumulation in the bulb by enhancing Cd sequestration in the fibrous roots and promoting its translocation away from the bulb. This study provides new insights into Cd dynamics in the Soil-Lilium system and offers practical strategies for producing Lilium safely.

In this study, the preparation of a new adsorbent, manganese dioxide-loaded volcanic rock (termed 3VRM), to improve the copper adsorption capacity of volcanic rocks (VRs) is reported. The effects of the loading ratio, 3VRM dosage, pH, and ionic strength on the Cu(II) adsorption capacity of 3VRM were determined. The samples were characterized by scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). SEM analysis revealed that spherical nanoscale manganese dioxide with a plum pattern was attached to the surface of VR, effectively increasing the specific surface area and number of reactive sites on the adsorbent. The main components of volcanic rocks are schistose and foshagite; manganese dioxide also exists in an amorphous form. Manganese dioxide is stable in the form of Mn4+ before and after adsorption. The results revealed that 3VRM had the greatest effect on Cu(II) adsorption at a loading ratio of 3 : 1, dosage of 2.5 g/L, and pH of 4–6. The Cu(II) adsorption capacity of 3VRM was shown to fit well with the pseudo-first-order kinetic model and the Freundlich model. The reaction equilibrium time was 10 min, and the theoretical maximum adsorption amount reached 434.7 mg/g. The acidity of the solution had less effect on the 3VRM, so it could be used in a wide pH range of 3–6. Studies of ion exchange and surface complexation have shown that the material demonstrated high efficiency in removing copper ions. Owing to its good adsorption performance and high efficiency, it is expected to be used for copper-containing wastewater treatment in the future.

Previous studies have shown that the traditional copyrolysis method for the preparation of carbon-based Fe0 composite materials leads to a significant increase in the surface free energy of the metal, which inevitably leads to the coexistence of iron atoms and iron clusters, and thus affects the reduction and degradation performance of pollutants. In this study, we prepared a carbon-embedded reducing agent material, referred to as NC/Fe, which incorporates both iron atoms and iron clusters. This composite effectively mitigates the pollution caused by chloramphenicol (CAP) antibiotics, which are prevalent contaminants in wastewater that pose a serious threat to global freshwater resources. The maximum degradation efficiency of CAP achieved by NC/Fe reached 98.05 % within 20 minutes, whereas the maximum dechlorination efficiency attained was 70.19 % within 8 hours. Compared with the NC/Fe material, NC/Fe-SAC-comprising only iron atoms-exhibited slightly reduced performance regarding CAP degradation; notably, the existence of iron clusters did not further influence the activity of these iron atoms. Additionally, H* is formed by the electron transfer of the encapsulated Fe0, and H* is then briefly adsorbed by the shell of the packaging material, thereby inhibiting the hydrogen evolution reaction. This study elucidates the reduction mechanism associated with Fe0 composite materials and offers novel insights into their application for environmental remediation efforts.

Amorphous Fe(III) (hydr)oxides ubiquitously interact with organic matter, forming organic-inorganic assemblages in natural environments. Yet, how their hetero-aggregation with pyrogenic organic matter influences coexisting pollutants remains unclear. Herein, we simulated two associations of rice straw-derived black carbon (RBC) with Fe(III) oxide, by employing different formation scenarios (sorption and coprecipitation) across various Fe/C ratios. Batch experiments and microscopic characterization techniques (e.g. XRD, XPS, FTIR, BET) were used to evaluate the effects of hetero-aggregation between RBC and Fe(III) oxides on the fate of the co-presence of As(III) and As(V). We showed that iron minerals and RBC mainly through-COOH and Si-O bonds formed different Fe/C associations, and RBC greatly modified the surface properties of iron minerals (e.g. zeta potential, pore structure). Batch experiments demonstrated that RBC significantly improved the retention of As (III) and As(V) on iron minerals, with a pronounced effect on As(V). Our multi-mechanistic study, utilizing non-local density functional theory, radical quenching, and electrostatic interactions, demonstrated that the heteroaggregation of RBC/Fe(III) oxides resulted in the formation of more characteristic pores across various mineral systems, significantly enhancing the pore diffusion of As(III) and As(V) within the bulk mineral matrix. We identified distinct electrostatic interactions between As(III)/As(V) and various mineral end-members, with As(V) promoting the aggregation of iron oxides and decreasing pore width, whereas As(III) exhibited minimal impact on the pore structures of iron oxides. Interestingly, RBC enhanced the resistibility of the pore structure against negative potential, thereby facilitating the extensive diffusion of As(III) and As(V). Furthermore, we identified that RBC-mediated radical reaction also contributed to the immobilization of As(III). Our findings help better understand how arsenic behaves under black carbon-rich geological settings where iron-carbon coupled reactions prevail.

The co-contamination of micro-/nanoplastics (MNPs) and ketoprofen (KTF) threatens agricultural ecosystems and crop health. This study examines the physiological and biochemical responses of Chinese cabbage (Brassica rapa L.) to 100 nm polyethylene (PE) and polypropylene (PP) nano-particles, individually and with KTF. Results show that NPs and KTF significantly reduce chlorophyll, biomass, and photosynthetic efficiency, with PP exhibiting greater toxicity than PE. Exposure triggers oxidative stress, increasing reactive oxygen species (ROS), hydrogen peroxide (H2O2), and malondialdehyde (MDA), alongside elevated antioxidant enzyme (SOD, CAT) activities. PE accumulates in roots, causing localized damage, while PP translocates to aerial parts, inducing widespread stress. The interaction between NPs and KTF intensifies toxicity, driven by adsorption of KTF on NPs. The mechanism involves NP polarity: PE's polar nature restricts it to roots, while PP's non-polarity enables aerial translocation. These findings highlight the role of NP polarity and pollutant interactions in ecological risk assessment, providing insights into the mechanisms of NP-KTF co-contamination and its impact on crop health and food safety.

Soil amendment application has been proposed as an effective approach to remediate Cd contamination and improve soil nutrient status. Most previous studies have emphasized Cd immobilization, whereas few studies have evaluated the influences of amendments on P transformations in Cd-contaminated agricultural soil that are often P-limited. In this study, different soil amendments (i.e. control, 0.3

Tungsten (W), a widely used yet understudied emerging contaminant, forms oxyanions in aqueous environments, distinguishing it from conventional heavy metals. While dissolved organic matter (DOM) demonstrates considerable potential for W binding, DOM-W interactions remain largely unexplored. Of particular significance, yet frequently overlooked, are the conformational changes in DOM during W binding processes. This study proposes a novel theoretical framework integrating superposition and charge transfer models to elucidate the complexity of these interactions. By combining spectroscopic techniques and photophysical models, we revealed that aromatic compounds containing 1-3 rings, especially monocyclic aromatic protein-like components, exhibit high affinity for W (logK=3.74-4.00). Phenolic hydroxyls served as primary binding sites for W, with aromatic rings facilitating binding through it interactions. Importantly, W binding to aromatic compounds induced conformational changes in DOM, transitioning from a loosely aggregated state to a more compact configuration. These changes facilitated W encapsulation within DOM through the synergistic effects of hydrophobic interactions, hydrogen/it-hydrogen bonding and it-stacking, potentially leading to stable trapping of W. Two-dimensional correlation spectroscopy analysis elucidated the sequential encapsulation process, involving phenolic, aromatic carboxylic/aliphatic carboxylic, polysaccharides, and aliphatics. The intricate behavior of DOM-W binding profoundly reshapes DOM's conformation, subtly yet significantly orchestrating W's binding affinity, environ- mental transport, and bioavailability in aquatic ecosystems.

Tungsten (W) contamination presents emerging environmental challenges, necessitating the need to establish soil screening levels (SSLs), especially for residential soils. This study assessed the health exposure risk and derived national and regional residential SSLs for W in Chinese residential soils, incorporating machine-learning prediction of in-vitro soil W bioaccessibility. We analyzed 204 residential soil samples collected across 24 provinces, recording a wide range of W concentrations (0.01-3063.2 mg/kg). Synchrotron-based X-ray fluorescence spectroscopy, chemical extractions, and random forest modeling indicated that the key determinants of soil W bioaccessibility were soil pH, cation exchange capacity, organic matter, and clay contents. Monte Carlo simulations demonstrated that soil W contamination predominantly results in noncarcinogenic health risks to residents via oral exposure, especially in mining-affected regions. A national residential SSL (NRSSL) of 35.5 mg/kg and regional residential SSLs (RRSSLs) of 34.5-49.2 mg/kg were established. Incorporating predicted bioaccessibility increased the NRSSL to 73.8 mg/kg and the RRSSLs to 69.8-112.5 mg/kg. Southern China, which is rich in W ore, exhibited lower RRSSLs, underscoring a need for enhanced safety management. Our framework and findings provide a robust scientific foundation for future soil contamination risk assessment studies, and we present customized SSLs that can guide targeted W risk control strategies.

Cadmium (Cd) and arsenic (As) generally exhibit mutually beneficial co-sorption behavior on iron oxyhydroxides through multiple mechanisms, including surface precipitation, ternary surface complexes, and electrostatic interactions. However, the numerous factors that control the immobilization of Cd and As in turn complicated the processes and mechanisms involved in their co-desorption from iron minerals, which hindered the full understanding of their geochemical behaviors. Here, the simultaneous release of Cd(II) and As(V) from newly precipitated ferrihydrite nanoparticles by either Ca or P was investigated through kinetics and isothermal desorption experiments. We showed that the Cd(II) and As(V) present two-phase desorption processes (rapid desorption and slow desorption) in both binary (Fe-Cd or Fe-As alone) and ternary systems (Fe-Cd-As co-presence). Compared to their binary counterparts, Cd(II) and As(V) in the ternary systems are more prone to detachment from ferrihydrite. Further desorption of Cd(II) and As(V) at different co-presence scenarios (different initial concentrations) demonstrated mutual promotion behaviour towards their counterparts; the co-presence of Cd(II) facilitates the desorption of As(V), while the co-presence of As(V) also promotes the desorption of Cd(II). XPS and FTIR results demonstrated that either Ca or P showed minor effects on the binding environment of Cd and As. Further results from the in-situ ATR-FTIR experiment and second derivative peak fitting analysis indicate that the enhanced detachment of Cd(II) and As(V) from the ternary system may be due to the synergistic desorption of the ternary surface complexes and other surface complex species. Our results provide new insights into the prediction of the environmental behaviour of the coexistence of Cd(II) and As(V) in iron-rich geological settings. The potential environmental risks of iron-based remediation methods should be considered due to the enhanced bioavailability of Cd(II) and As(V) in co-presence circumstances.

The passivation and agglomeration issues of ZVI were effectively addressed through the preparation of a carbon- coated material (ZVI/BC-0.8-800) containing embedded iron atoms and nZVI,which exhibits excellent reducing properties towards Cr(VI). Our results demonstrate that ZVI/BC-0.8-800 possesses iron atoms and nZVI, achieving a remarkable removal rate of 99.8 % for Cr(VI) within 20 minutes, surpassing that achieved by commercial nZVI. Moreover, nearly all Cr(VI) is reduced to Cr(III). After ageing different water bodies or in the air for 15 days, the removal rate of ZVI/BC-0.8-800 remains at approximately 70 % when placed in water reaches up to 95 % in air. This efficient and stable removal is due to the protective effect of carbon materials, and the presence of iron atoms and nZVI as the double reduction center in the Cr(VI) removal process, which enhances the reduction effect. The respective contribution rates from iron atoms and nZVI are 29.13 % and 50.32 % respectively. Overall, this multi-form composite with double reduction centers consisting primarily of nZVI embedded within a carbon material holds great promise for in-situ groundwater remediation applications.