It is our deepest sorrow to pay tribute to Prof. Badal Kumar Mandal (Born: 19th March 1963 – Death: 6th April 2026), who is well-known as a prominent chemist, academician, and mentor whose contributions have significantly influenced the world of science and technology.

Cadmium (Cd) contamination severely hampers rice (Oryza sativa L.) growth by disrupting root development, nutrient uptake, and exudation processes, posing a major risk to food security. This study investigated the role of silicon nanoparticle (SiNP) on root architecture and root exudation dynamics in rice grown hydroponically under two levels of Cd (10 and 20 mu M). Cadmium markedly impaired root development, as evidenced by significant reductions in root length (8.94 % and 17.93 %), surface area (15 % and 31.42 %), diameter (15.78 % and 28.94 %), volume (8.15 % and 25.54 %), biomass (31.19 % and 40.36 %), and water uptake efficiency (11.94 % and 28.05 %) at 10 and 20 mu M, respectively, while concurrently increasing root branching. Co-application of SiNP mitigated these effects, enhancing root biomass (28.00 % and 32.30 %) and restoring water uptake (14.31 % and 11.91 %) relative to Cd-only treatments. Cadmium stress inhibited antioxidant enzymes (APX, CAT, SOD, POD) and increased oxidative damage (MDA, electrolyte leakage). SiNP co-application substantially mitigated Cd-induced oxidative stress in rice roots by restoring APX 17.8 and 39.4 %, CAT 37.0 and 70 %, SOD by 7.25 and 15.61 % and POD by 14.59 and 38.00 %, respectively, with both levels of Cd stress, while reduced MDA and electrolyte leakage by 27.7 % and 29.6 %, respectively, with the highest levels of Cd stress. Cadmium stress also significantly altered the profile of root exudates, decreasing oxalic acid (Cd10: 22.03 %; Cd20: 32.60 %) and citric acid (Cd10: 38.23 %; Cd20: 49.67 %) while increasing malic acid production (Cd10: 11.48 %; Cd20: 17.84 %). SiNP supplementation reversed these shifts by elevating oxalic (Cd20: 17.43 %) and citric (Cd20: 24.29 %) acids, suppressing malic acid release (Cd10: 21.39 %; Cd20: 26.83 %), and overall enhancing total organic acid secretion, thereby contributing to rhizosphere acidification. Over time, SiNP significantly lowered Cd bioavailability in the nutrient solution, likely via Si-Cd complexation and organic acid-mediated chelation. At the cellular scale, SiNP supplementation reduced Cd accumulation in both the cell wall and symplast, indicating restricted Cd uptake and transport. Moreover, Cd stress substantially increased total organic carbon (TOC) (Cd10: 32.28 % and Cd20: 58.13 %) and total nitrogen (TN) (Cd10: 4.25 % and Cd20: 27.71 %) in rhizosphere exudates, SiNP co-treatment also moderated these elevations and concurrently preserved cellular ultrastructure. Therefore, SiNP mitigated Cd toxicity by improving root architecture, modulating exudation, and reducing Cd bioavailability and uptake. These findings demonstrate the potential of SiNPs as a sustainable nanotechnology-based strategy for reducing Cd accumulation in rice and safeguarding food quality.

The Driver, Pressure, State, Impact, Response (DPSIR) framework was applied to assess microplastic pollution and the risk of secondary contamination from microplastic-laden spent adsorbents. Key driving forces include increasing plastic production, widespread polymer consumption, and growing reliance on adsorption technologies for microplastic remediation. These drivers impose pressures through the continuous release of polystyrene microplastics (PS-MPs) into aquatic systems and the accumulation of spent adsorbents after treatment. The resulting state is characterized by microplastic-contaminated water and spent adsorbents that pose secondary pollution risks if unmanaged. Circular carbon material (CCM), produced via pyrolysis of spent adsorbents at 600 degrees C for 2 h, achieved approximately 60% PS-MP removal and exhibited a surface area of 108-137 m(2)/g and showed a Type II isotherm. The associated impacts include limited recovery efficiency and potential microplastic remobilization. As a response, CCM was upcycled into magnetic circular carbon (MCC) via co-precipitation of iron oxide nanoparticles, improving removal efficiency to similar to 89%, enhancing mesoporosity and producing a Type IV-H3 isotherm (enhanced mesoporosity), and enabling easy magnetic separation. Overall, DPSIR analysis demonstrates that spent-adsorbent upcycling offers a stabilization and risk-mitigation pathway for microplastic-laden residues, reducing their environmental mobility and supporting circular-economy-based microplastic remediation, while highlighting the need for future emissions characterization to fully quantify net environmental benefits.

Excessive Fe3+ contamination in aquatic environments poses significant risks to water quality and ecosystem health, necessitating the development of rapid, low-cost, and sustainable detection platforms. A sustainable solid-state fluorescent sensor was evaluated for Fe3+ detection using carbon quantum dots (CQDs) derived from Syzygium aromaticum embedded within a corn starch biopolymeric film. The clove-derived CQDs, synthesized via a green hydrothermal route, exhibited quasi-spherical morphology with an average particle size of 3.02 nm, excitation-dependent blue fluorescence with a maximum emission at 440 nm under 350 nm excitation, a fluorescence quantum yield of 9.46%, and a high negative zeta potential (-45 mV), indicating excellent colloidal stability. Incorporation of CQDs into the starch matrix significantly enhanced film performance, increasing tensile strength from 21.21 to 27.26 MPa and reducing water vapor permeability from 7.27 to 6.63 × 10-10 g m-1 s-1 Pa-1, while simultaneously increasing surface wettability (contact angle decreased from 72° to 62°), indicating enhanced surface polarity without compromising barrier properties. The CS-CQDs film exhibited strong and selective fluorescence quenching toward Fe3+, with F/F₀ decreasing to ~0.10 at 1 ppm, a Stern-Volmer constant of 3.678 ± 0.256 ppm-1, and excellent linearity (R2 = 0.9887). The detection limit was calculated as 0.163 ppm, below both World Health Organization (0.3 ppm) and Indonesian drinking water standards (0.2 ppm). Accurate Fe3+ quantification in tap and underground water was achieved with recoveries of 94.8-104.0% and RSD values below 1%. This low-cost platform enables portable, real-time water quality monitoring, supporting SDG 6, 14, and 15.

Antibiotic resistance genes (ARGs) in wastewater treatment works (WWTWs) represent a critical pathway for the dissemination of antimicrobial resistance into receiving aquatic environments, yet uncertainties remain regarding their persistence through current treatment stages and the factors influencing their removal. This study investigated selected ARGs' prevalence, removal efficiency, and fate in four WWTWs in the Hunter region of New South Wales, Australia, providing insight into the efficacy of treatment processes under existing operating conditions. Using quantitative PCR (qPCR), we quantified the absolute and relative abundance of five selected ARGs (dfrA1, tetA, qnrS, vanB, and sul1), an integron marker gene (intI1), and bacterial 16S rRNA gene across different wastewater treatment phases. Results revealed that all ARGs were present in influent samples, with tetA and intI1 being the most abundant. The tertiary treatment phase, particularly disinfection, significantly reduced ARG levels, with removal efficiencies ranging from 94.89 % to 99.98 %. However, tetA exhibited lower removal rates than other ARGs, particularly in Morpeth WWTW (83 %), persisting at detectable levels in influent and final effluent. The study further indicated that correlations between ARGs, nutrients, and trace metals were variable and gene-specific within WWTWs. These findings demonstrate the effectiveness of tertiary wastewater treatment in reducing the loads of the selected ARGs, certain resistance determinants can persist and potentially contribute to environmental dissemination. This study advances current understanding by identifying risks and environmental interactions that should be considered in WWTW design, monitoring frameworks, and public health risk assessments related to antimicrobial resistance.

Sexually dimorphic species, such as the semaphore crab Heloecius cordiformis, provide useful models for understanding how environmental contaminants influence behaviour essential for fitness. While lead (Pb) exposure impairs male-male size-based competition, a component of intrasexual selection in this species, its effects on female competitive interactions remain untested. We experimentally examined whether Pb exposure alters female-female competition for burrow ownership and whether chela size predicts contest outcomes. Mature females were exposed for 96 h to 0, 10, or 100 µg/L Pb and then paired in size-matched and size-asymmetric contests for burrow access. Exposed crabs (10 & 100 µg/L) were less successful than control crabs in chela size-matched paired competitive interactions, spending less time in burrows and predominantly losing burrow ownership. While in size-asymmetric contests, female crabs showed no size-based advantage under any exposure condition, and outcomes were instead dominated by resource pre-emption (first entry into burrow) rather than physical contests. Field data across a contamination gradient showed weak, non-significant negative trends between sediment Pb and female chela length, further supporting the absence of selection pressure on chela size in females. Together, these results show that Pb may influence competitive interactions in female semaphore crabs, but its effect is unrelated to size, in contrast to males. This study provides evidence underscoring substantial sex-specific differences in behavioural competitive interactions and evolutionary responses to environmental stressors.

Mangrove ecosystems play a vital role in supporting aquatic organisms by providing food sources, shelter, and spawning grounds. However, microplastic contamination has emerged as a significant environmental threat that may disrupt the ecological functions of these ecosystems. Unfortunately, studies investigating the vertical distribution of plastics and their relationship with sediment grain size in mangrove environments remain limited. Hence, this study aimed to investigate the abundance, vertical distribution, and characteristics of microplastics, as well as their relationship with sediment grain size in the mangrove sediments of Northern Aceh, Indonesia. A total of 40 sediment samples were collected and analyzed from eight mangrove areas across five sediment layers. The results showed that the abundance of microplastics in the sampling areas ranged from 210 to 440 items/kg dry weight. Higher concentrations of microplastics were observed in the upper layer (0–10 cm) (p < 0.05). Particles smaller than 500 μm, predominantly black and fragment-shaped, were most common. Polyethylene and polypropylene were the dominant polymers identified, followed by nylon and polystyrene. Microplastic abundance showed a significant correlation with sediment grain size, particularly with granules, very fine sand, and clay fractions. In contrast, a significant negative correlation was observed between microplastic abundance and the percentage of clay.

Rice (Oryza sativa L.) faces critical challenges, including low yield and arsenic (As) contamination, necessitating sustainable agronomic interventions. This study evaluates the efficacy of double transplantation (DT) in enhancing rice yield and mitigating arsenic accumulation compared to single transplantation (ST). Two rice cultivars, Sambha Mansoori and Kaveri Chintu, were cultivated using both methods in an arsenic-contaminated field in Uttar Pradesh, India. Morphological, biochemical, and molecular parameters were assessed, along with yield and total arsenic and arsenic speciation analysis. Results indicated that DT significantly improved morphological traits such as shoot biomass, tiller number, and spikelet number in both cultivars. DT plants exhibited increased root cell wall components like cellulose, pectin, hemicellulose 1 (HC1), and HC2, indicating enhanced structural integrity. Furthermore, RT-PCR analysis revealed down-regulation of cellulose synthase (CESA) genes in the two rice varieties under DT conditions which were cultivar-specific. The results showed that DT might influence cellular arsenic concentration by altering cell wall composition. Yield analysis demonstrated an increase in grain yield for both cultivars under DT, with Sambha Mansoori showing a more pronounced response. Crucially, DT led to a significant reduction in total arsenic content in grains, especially in Sambha Mansoori. Arsenic speciation analysis revealed a decline in inorganic while an increase in organic arsenic levels in DT-grown Sambha Mansoori. These findings suggest that DT is a promising approach for sustainable rice cultivation, offering benefits such as increased yield, improved plant health, and reduced arsenic accumulation. However, further research is necessary to understand the underlying mechanisms of DT technique and optimize its application for different rice varieties and environmental conditions.

Chromated copper arsenate (CCA) is widely used globally as a waterborne inorganic wood preservative, acting as a fungicide and insecticide to prevent timber damage. Toxic metals (Cr, As, and Cu) can leach into the environment, posing risks, and a thorough understanding of the immobilisation agents used to prevent leaching is lacking. This study systematically investigated the leaching behaviour of As, Cr, and Cu from fresh and weathered CCA-treated timber in block and mulch forms under simulated rainfall conditions. The effectiveness of selected immobilisation agents (iron sulfate, bentonite, iron powder, and steel wool) was evaluated for their ability to lock up and immobilise toxic metal(loid)s from leaching out via a column study. Column experiments were conducted over 15 weeks to quantify metal(loid)s release and treatment performance. Compared with fresh timber, weathered timber exhibited sustained and greater metal(loid)s leaching, with arsenic showing the most significant mobility. Among the immobilisation agents tested, iron powder and steel wool markedly reduced metal(loid)s leaching, resulting in a >99% reduction in As and substantial reductions in Cr and Cu. Speciation, SEM–EDS, and XRD analyses revealed that zero-valent iron promoted the reduction of Cr(VI) to Cr(III) and facilitated adsorption, co-precipitation, and the incorporation of As and Cr into newly formed iron (oxyhydr)oxide and mixed Fe–As–Cr mineral phases, thereby decreasing metal mobility. Notably, steel wool treatment increased both bacterial and fungal diversity in the timber mulch, indicating reduced toxicity following immobilisation. Overall, this study demonstrates that iron-based amendments, particularly steel wool, provide a practical, mechanistically robust approach for immobilising toxic metals in CCA-treated timber, supporting safer, risk-based management and reuse strategies.

Fly ash (FA), a byproduct of coal combustion, poses major environmental disposal challenges. This study aimed to develop a green, one-step hydrothermal strategy to valorize Indonesian FA into zeolite without toxic acid pretreatment, and to evaluate its performance for methylene blue (MB) removal from aqueous solution. The obtained fly ash-derived zeolite (FADZ) was characterized using FTIR, XRD, and SEM, and exhibited a high surface area (226.25 m(2)/g). The adsorption of MB followed pseudo-second-order kinetics with a maximum capacity of 92.44 mg/g (Langmuir model). By utilizing the natural iron oxides in FA as catalytic sites, the material enabled a synergistic adsorption-Fenton-like degradation process, enhancing MB removal efficiency from 34.28% (adsorption only) to 98.11%. Thermodynamic analysis confirmed that the adsorption was endothermic and spontaneous. Reusability tests demonstrated stable performance with > 95% removal efficiency over four cycles. Overall, the study demonstrates that FADZ is a stable, dual-functional, and cost-effective material for sustainable dye-contaminated wastewater treatment.

The indiscriminate and excessive use of pesticides ultimately reaches the aquatic ecosystems and results in detrimental impacts on fish and other aquatic species. The current study focused on elucidating the acute toxic effects of the organophosphate pesticide, profenofos, on various blood biomarkers in banded gourami (Trichogaster fasciata). Fish were subjected to different sub-lethal concentrations (0%, 5%, 10%, 20%, and 40% of the 96-h LC50 = 2972.7 μg/L) of profenofos for 1, 24, and 96 h. Fish exposed to profenofos induced a significant rise (p < 0.05) in glucose, white blood cell levels, mean corpuscular volume, and mean corpuscular hemoglobin and a subsequent decrease in hemoglobin, red blood cell count, and packed cell volume. Furthermore, erythrocytic nuclear abnormalities such as micronucleus, notched nucleus, karyopyknosis, and blebbed nucleus, and erythrocytic cellular abnormalities such as elongated, fusion, spindle, tear-drop, and twin-shaped cells were observed. These abnormalities displayed a dose- and time-dependent increase compared with the control. This study underscores the detrimental impact of the prevalent utilization of profenofos within aquatic environments and highlights the need for interdisciplinary actions to conserve the aquatic environment as well as the aquatic biota.

Microplastic (MP) contamination in aquatic systems poses a significant threat to water quality and ecosystem health, necessitating the development of advanced treatment solutions. This study investigates stearic-acidmodified magnetic biochar (SMBC) for removing polystyrene MPs under varied conditions. This work integrates a greener hydrophobic modification with mechanistic interpretation (wettability-charge-porosity coupling), interpretable machine learning, and an end-of-life upcycling pathway for MP-loaded sorbents. Characterization confirmed that stearic-acid grafting increased surface hydrophobicity and introduced aliphatic-CH domains that favor PS affinity. SMBC achieved up to 94% MP removal, with adsorption kinetics following the pseudo-first-order model (R-2 = 0.987). The Sips model (R-2 = 0.970) best represented the equilibrium data, with n approximate to 1 indicating weak heterogeneity and adsorption behavior approaching Langmuir characteristics. In real water matrices, SMBC retained high performance over five reuse cycles, with a gradual decline after the third cycle. SMBC removed 84% of MPs from rainwater and maintained strong stability over five reuse cycles. Machine-learning models enhanced predictive accuracy and operational optimization; Gradient Boosting and Decision Tree performed best. Shapley Additive Explanations (SHAP) analysis provided interpretable insights, identifying contact time, pH, and adsorbent type as dominant factors, aligning with mechanisms such as hydrophobic interaction, electrostatic attraction, pore filling, and pi-pi stacking. Spent SMBC loaded with MPs was successfully upcycled via pyrolysis and reused for methylene blue removal (similar to 91%), demonstrating circular-economy potential. Overall, SMBC offers a robust, sustainable adsorbent for advanced water treatment targeting MP contamination, integrating mechanistic understanding with data-driven insights.

Plastic pollution has become a critical environmental issue in coastal and estuarine ecosystems, raising concerns about its impact on ecologically and economically important crustaceans such as mud crabs (Scylla spp.). This review synthesizes current research on the occurrence, characteristics, and toxicological effects of plastic contamination in mud crabs. A systematic literature search identified 15 relevant studies published between 2022 and 2025, including 13 that reported the presence of plastics in mud crabs and 2 that examined physiological impacts. Microplastics were the predominant size class, primarily in the gastrointestinal tract, followed by the gills and hepatopancreas. Fragments and fibers were the most common shapes observed, while blue, transparent, and black were the dominant colors. Twelve polymer types have been documented, with polyethylene (PE) and polypropylene (PP) most frequently reported, reflecting their widespread use and prevalence in mangrove and estuarine environments. Plastic abundance varies substantially across regions, species, and tissue types. Toxicological evidence indicates that microplastics tend to accumulate in various fish tissues, particularly in the digestive and respiratory organs, leading to oxidative stress, altered antioxidant enzyme activity, and DNA damage. Despite these emerging findings, substantial knowledge gaps persist, including the absence of data on muscle contamination, limited comparisons between wild and farmed crabs, lack of sex-based assessments, and minimal understanding of impacts on early developmental stages. This review highlights the urgent need for standardized methodologies and comprehensive ecotoxicological studies to improve understanding of plastic exposure pathways, physiological responses, and the broader ecological and food-safety implications for Scylla spp. populations.

This study examined the concentrations, geochemical partitioning, mineralogical controls, and probable mobility of potentially toxic elements (PTEs) in mining impacted surface soils from Anka, Zamfara State, Nigeria. Soil samples (n = 50) were analyzed for physicochemical properties, total elemental burdens, and sequential extraction fractions. The soils ranged from sandy loam to clay loam and showed moderately acidic to near-neutral pH, elevated organic carbon, and high cation exchange capacity, reflecting substantial capacity for metal retention. Total elemental concentrations revealed lead (Pb) in the highest amount (1240.23 ± 92.94 mg kg−1), compared to arsenic (As), zinc (Zn), manganese (Mn), barium (Ba), and iron (Fe). Correlation studies indicated strong associations between Ba-Fe and Mn-Pb, suggesting shared mineralogical or oxide-based controls on distribution. Sequential extraction revealed marked differences in elemental mobility. Lead was primarily bound to reducible Fe-Mn oxides (∼83%), with only ∼13% in the extractable fraction. Arsenic was dominated by residual and oxidizable pools (>90%), indicating minimal mobility. However, Ba and Fe remained primarily in residual and reducible forms. In contrast, Zn was highly labile, with nearly 90% occurring in the extractable fraction displaying mixed extractable and reducible associations and reflecting its redox sensitivity. Mineralogical analyses confirmed quartz-dominant soils containing illite, muscovite, albite, galena, and Pb-As jarosite, with SEM-EDS further verifying PbS (galena), supporting the limited bioavailability of Pb in oxic conditions. Risk Assessment Code (RAC) values placed As in low-risk and Fe in the no-risk category, Ba in medium to high risk, Mn in high risk and Pb in medium risk, and Zn in very high risk (∼90%). Overall ecological risk ranking followed the order Zn > Mn > Ba > Pb > As > Fe. These findings highlight that while total Pb remains elevated, its mobility is restricted by mineralogical sinks, whereas Zn, despite low concentrations, exhibits high mobility and environmental responsiveness. These contrasting behaviours emphasize the need to interpret total elemental concentrations alongside geochemical fractionation when assessing contamination risk in mining-impacted landscapes.

Cigarette butts constitute the most ubiquitous plastic litter worldwide, serving as a persistent source of microplastic fibers and toxic chemical leachates in terrestrial and aquatic ecosystems. Primarily made of cellulose acetate, discarded butts degrade slowly via physicochemical processes, liberating cigarette butt-derived microplastics alongside hazardous additives such as nicotine, heavy metals, and polycyclic aromatic hydrocarbons. This PRISMA-guided narrative review consolidates evidence on the environmental prevalence, transport, and fate of these microplastics, rigorously appraises progress in analytical detection methods, and evaluates their ecotoxicological impacts across food web levels. Studies reveal induction of behavioral changes, elevated mortality, and bioaccumulation in aquatic species, with particles functioning as carriers for persistent organic contaminants and metals. The review also addresses the considerable economic costs of cigarette butt pollution and scrutinizes mitigation options, including cutting-edge removal techniques, extended producer responsibility schemes, and circular-economy pathways such as cellulose acetate reclamation and composite sorbent fabrication. Persistent gaps exist in long-term degradation patterns, realistic exposure limits, and practical remediation efficacy, necessitating focused research to support evidence-based policies and sustainable waste management.

Study area: North-eastern Ethiopia, Lower Awash Basin Study focus: The study aims to investigate the processes influencing groundwater composition and evolution using ionic ratios, chemometrics, and inverse geochemical modeling based on major ion chemistry of 164 groundwater samples that were collected from hand-dug wells, springs, and boreholes New hydrogeological insights: The Results from the Gibbs plot, Ca + Mg vs SO4+HCO3, Ca/Na vs HCO3/Na vs Ca/Na vs Mg/Na, and Chloralkaline indices showed that rock water interaction, silicate weathering, cation exchange, and evaporation are the major geochemical processes that control the groundwater chemistry. Principal component analysis identified three components: PC-I and PC-II reflect geogenic processes, whereas PC-III indicates anthropogenic influences. Hierarchical cluster analysis grouped the groundwater samples in to two main clusters: cluster I represents fresh Ca-Mg-HCO3 type from the recharge zone alongside a mixed water type from transition zone, while cluster II includes mineral-rich samples from the discharge zone (Na-HCO3 and Na-Cl). Inverse geochemical modeling indicated that major geochemical process that affect groundwater chemistry and evolution are dissolution of primarily silicate minerals such as plagioclase, olivine, and pyroxene, along with the precipitation of calcite and clay minerals. This study addresses the gap in conventional hydrochemical approaches in the understanding of hydrogeochemical processes by employing a quantitative approach and contributes in the formulation of policies for sustainable groundwater resource management.

ABSTRACT Cadmium (Cd) is a toxic trace metal that causes severe environmental pollution and alters plants' physiological and biochemical responses. Although commercially synthesised silicon nanoparticles (SiNP) have been reported in alleviating biotic and abiotic stresses, the role of PV (photovoltaic) driven SiNP in modulating plant physio‐biochemical response under Cd stress has not systematically evaluated to strengthen the circular economy framework. A glasshouse experiment was therefore conducted to investigate the effects of solar PV panel‐sourced SiNP on rice's physico‐chemical responses under Cd stress. Three SiNP concentrations (0, 0.5, and 1 mM) and three Cd levels (0, 10, and 20 µM) were used in this hydroponic culture. The results revealed that increases in Cd stress significantly reduced the photosynthetic pigment content, plant growth and biomass. Elevated Cd levels also enhanced the accumulation of hydrogen peroxide (H2O2), electrolyte leakage (EL) and lipid peroxidation (MDA), suppressed antioxidant activity in roots and shoots, which caused severe damage to the roots and leaves. In contrast, SiNP supplementation (0.5 and 1 mM) improved photosynthetic pigments, antioxidant activity, cell membrane stability and overall growth under 20 µM Cd stress. Both SiNP levels significantly downregulated the H2O2, EL and MDA content, thereby minimzing leaf tissue injury under 10 and 20 µM Cd stress. Transmission electron microscopy (TEM) observations confirmed that SiNP supplement substantially alleviated Cd‐induced ultrastructural damage in leaf cells. The study concluded that PV‐derived SiNP application mitigated oxidative stress, promoted rice growth and biomass, improved Cd stress tolerance, and offered a promising strategy for sustainable farming practices in Cd‐prone areas.

Arsenic (As) transfer from contaminated soils to food grains is a major pathway of As entry into humans in paddy growing areas posing a serious risk to human health. This study investigates the effectiveness of irrigation water management combined with phosphate (P) and vermicompost applications, in immobilizing As and blocking its entry to rice grain. Different doses (0, 30 and 60 mg kg–1) of P, vermicompost (C), (0, 2.5 and 5.0 g kg–1) were applied under W1 (submerged) and W2 (alternate wetting and drying, AWD). Total and bioavailable As in soil were 33.8 mg kg–1 and 3.41 mg kg–1, respectively. Under different treatment combinations, As in soil was highest in amorphous hydrous oxides of Fe and Al (F3) fraction whereas least in non-specifically sorbed (F1) fraction. Arsenic content in rice grain decreased from 0.38 (P1-0 mg kg–1) to 0.25 mg kg–1 (P3-60 mg kg–1), whereas in case of vermicompost application the grain As decreased from 0.32 (C1-0 g kg–1) to 0.27 mg kg–1 (C3-5.0 g kg–1). The lowest grain As content was observed under the W2 condition with the combined application of P (P2-30 mg kg–1) and vermicompost (C2-2.5 g kg–1). Both grain and straw As were positively correlated with As associated with F1 and F2 soil fractions, whereas both showed negative correlation with As in F3, dithionite citrate bicarbonate-As, and oxalate-extractable Fe. Overall, the combined application of P (at 30 mg kg–1) and vermicompost (at 2.5 g kg–1) effectively reduced grain As content under W2. These findings suggest that combining AWD with P and vermicompost application can be a viable approach for reducing As toxicity in rice cultivation; however, field-scale validation across different soils and cultivars is required before broader recommendations can be made. Based on the graphical abstract, this study evaluates the effectiveness of irrigation water management combined with phosphate (P) and vermicompost (C) applications in immobilizing arsenic (As) and limiting its transfer to rice grains. Different doses of P and vermicompost were applied under two irrigation regimes: W1 (continuous submergence) and W2 (alternate wetting and drying, AWD). The total and bioavailable As contents in soil were 33.8 mg kg⁻¹ and 3.41 mg kg⁻¹, respectively. Across all treatment combinations, the highest proportion of soil As was associated with the amorphous hydrous oxides of Fe and Al (F3), while the lowest was found in the non-specifically sorbed (F1) fraction. Under W1 conditions, As distribution was higher in labile fractions (F1 = 0.52

Arsenic (As) mobilization in flooded paddy soils poses a critical food-safety risk due to its efficient uptake by rice. This study evaluated iron-modified rice husk biochar (Fe-MRHB) as an amendment for controlling As speciation, mobility, and accumulation across the soil-porewater-root-grain interface in two contrasting paddy soils (neutral pH and acidic). Iron modification increased Fe content and introduced Fe-bearing phases and oxygen-containing functional groups, enhancing redox buffering and sorptive capacity of Fe-MRHB. Fe-MRHB reduced pore-water As by 28–62% and lowered As(III):As(V) ratios, indicating enhanced oxidation of mobile As(III) and reduced As bioavailability. Iron-plaque development on rice roots increased by up to 67%, while plaque-associated As declined by 40–55%. XPS analysis confirmed mixed-valence Fe species with a shift in As speciation toward less mobile forms at root surfaces, while TEM-EDS of root vascular tissue showed reduced As deposition in cell walls and restricted intracellular diffusion. Fe-MRHB substantially altered bacterial community composition in flooded soils. Consequently, rice grains exhibited declines of up to 55% in total As and 47% in inorganic As. Multivariate analyses identified pore-water EC, Eh, and DOC, together with soil EC and S, as dominant drivers of grain As accumulation. Collectively, Fe-MRHB disrupted As mobilization pathways and limited its accumulation in rice grains through coupled changes in pore-water chemistry, bacterial community composition, and root-surface processes. This study provides comprehensive mechanistic evidence supporting Fe-modified biochar as a viable means of mitigating As risks in rice cultivation, thereby contributing to a safer food supply.