Alkaline soil cadmium (Cd) contamination in wheat fields seriously threatens grain safety. While the soil microbiome shows both positive and negative influences on Cd accumulation in wheat. This study aims to verify the feasibility of harnessing native soil microbes for reducing Cd uptake and improving grain quality. This research constructed a pot experiment under rhizosphere microbiome engineering (via benomyl application or fungus Rhizopus, Alternaria inoculation) versus native microbiota in weakly alkaline Cd-contaminated soil (1.63 mg kg−1) to systematically examine Cd, aflatoxin accumulation, and nutritional profiles in wheat (Triticum aestivum L.). Soil application of fungicide benomyl (50 mg kg⁻1) or seed born Cd resistant fungus Alternaria (100 spores kg⁻1) most effectively improved the qualities of wheat grains with reduced Cd (31.7–33.0

The Qinghai-Tibet Plateau (QTP), acclaimed as the "Third Pole"," is an ecologically vulnerable region pivotal to global biogeochemical cycles. However, our knowledge of edaphic antibiotic resistance genes (ARGs) across its heterogeneous land-use regimes remains limited. Here, we systematically characterized the patterns, potential risks, and driving mechanisms of ARGs by analyzing soil samples encompassing anthropogenically disturbed soils (ADS) and pristine alpine meadows on the QTP, coupled with comparative analysis of national cropland metagenomic datasets. Metagenomic analysis identified 897 ARG subtypes, with ADS harboring significantly higher ARG abundance, diversity, and horizontal transfer potential compared to pristine alpine meadows. Source tracking analysis confirmed yak feces as the predominant source of soil ARGs, contributing 31.35%-38.33% across different land-use types. At the national scale, QTP croplands exhibited a distinct resistome profile containing 158 unique ARG subtypes, and the abundance of ARG-carrying pathogens was 1.4-fold higher than the national average, with human pathogens being the most prevalent. Non-dominant ARGs were pinpointed as pivotal biomarkers for differentiating land-use types and geographic regions. Rare microorganisms were critical drivers shaping ARG distribution, whereas mobile genetic elements and virulence factors augmented ARG transmissibility and pathogenicity. This study presents the first comprehensive characterization of the soil resistome on the QTP, highlighting that anthropogenic activities have triggered non-negligible ARG contamination in this ecologically vulnerable ecosystem. These findings underscore the urgency of implementing "One Health" strategies to mitigate the spread of antibiotic resistance in high-altitude regions, with far-reaching implications for global public health and ecological security.

Returning plant residue to farmland maintains or enhances the fertility and the investigation of how residue management strategies affect soil organic carbon (SOC) and labile organic carbon (LOC) fractions is crucial for addressing concerns related to agricultural sustainability. However, knowledge gaps remain about how these C fractions change in deep soil (>40 cm) under different strategies. A 10-year field experiment (2012-2021) in Northeast China compared three strategies: residue covered on the surface (RC), residue incorporated into 0-20 cm soil (RI), and residue removed (CK). In 2021, the vertical distribution (0-90 cm) of SOC and five LOC fractions (microbial biomass carbon [MBC], dissolved organic carbon [DOC], particulate organic carbon [POC], easily oxidizable carbon [EOC], and light fraction organic carbon [LFOC]) was analyzed. The results showed that SOC and LOC fractions generally decreased with increasing soil depth, except for the RI treatment in the 0-20 cm layer. The largest treatment differences occurred in the 0-5 cm layer, where RC had significantly higher SOC and LOC concentrations than RI. RI resulted in the highest SOC and LOC contents in the 5-20 cm layer, while RC exceeded RI and CK below 20 cm. Below 40 cm, the highest SOC content was mostly observed in RC, but no significant differences among the three treatments were detected in the 20-40 cm layer. POC proportions in the 0-90 cm profile ranged from 30.06% to 5.34% (RC), 26.60% to 4.76% (RI), and 21.75% to 4.78% (CK). Pearson correlation analysis and principal component analysis revealed that SOC changes were primarily driven by POC, EOC, and LFOC, while MBC and DOC played a secondary role due to their high lability. This study highlights that overlooking deep subsoil carbon dynamics masks key opportunities for SOC sequestration and may lead to incomplete conclusions about the impact of residue management on long-term carbon storage in Mollisols of Northeast China.

Nanoplastics (NPs) have emerged as ubiquitous environmental contaminants, raising increasing concerns over their ecological impacts and potential risks to human health. However, accurate quantification of NPs in aquatic environments remain analytically challenging due to the lack of effective enrichment techniques capable of operating at trace concentrations. Herein, we developed a robust, rapid, and organic-free flocculation-based preconcentration strategy for NP quantification in water samples. Utilizing polymerized ferrous sulfate (PFS) as an flocculant, diverse NPs, including polystyrene (PS), poly(methyl methacrylate) (PMMA), poly(vinyl chloride) (PVC), polypropylene (PP), and poly(ethylene terephthalate) (PET), were efficiently coprecipitated with ferrihydrite (FeOOH) and subsequently isolated by centrifugation. The enriched NPs were analyzed by pyrolysis gas chromatography/mass spectrometry (Py-GC/MS), achieving high recoveries (≥92.8%) and low detection limits (0.01-0.02 μg/L). Field application revealed PS NP concentrations ranging from 0.11 to 0.36 μg/L, while recovery experiments in representative natural waters yielded consistent results (81.3-97.3%), confirming the method's accuracy and matrix tolerance. Compared with conventional extraction approaches (e.g., cloud point extraction), this protocol avoids the introduction of organic additives that may interfere with pyrolysis, thereby improving analytical sensitivity and reducing background complexity. Overall, the proposed method provides a reliable and practical platform for monitoring NP pollution in diverse aquatic systems.

Cadmium (Cd) accumulation in rice poses a significant threat to food safety and human health. Plant growth-promoting endophytes (PGPEs) offer a promising strategy to mitigate Cd stress. Yet, the mechanisms underlying microbe-mediated reduction of Cd uptake, particularly through specific plant-microbe interactions, remain poorly understood. Here, we demonstrate that the root endophyte Bacillus sp. RE35, a Cd-tolerant and high-IAA producer isolated from rice, established an effective apoplastic niche and significantly enhanced Cd retention in roots through a multi-level mechanism. Successful colonisation of RE35 in the root apoplast, confirmed by the red fluorescent protein labelling, strain-specific gene quantification and colonisation-related genes analysis, promoted extensive root morphological remodelling via both de novo and salvage pathways of IAA biosynthesis under Cd stress. Notably, RE35 inoculation drastically reshaped Cd distribution, increasing cell wall-bound Cd by 64.7% while reducing shoot Cd accumulation by 24.1%-49.7%. This enhanced apoplastic trapping of Cd was attributed to a comprehensive cell wall remodelling program, activated through RE35-induced expression of plant receptor kinases (e.g., LRR-RLKs, LysM-RLKs) and the upregulation of key genes involved in the biosynthesis of pectin, hemicellulose and lignin. In parallel, RE35 modulated host Cd transport by downregulating influx transporter genes (OsNRAMP5, OsZIP5/9) and upregulating the vacuolar sequestration gene OsHMA3. Our findings reveal a Cd-responsive regulatory network where endophytes enhance apoplastic immobilisation by coordinating auxin signalling, receptor kinase activation and cell wall remodelling, providing a mechanistic basis for sustainable agriculture in contaminated environments.

Aquatic ecosystems are increasingly at risk of exposure to silver sulfide nanoparticles (Ag2S NPs) through anthropogenic waste streams, with these particles traditionally considered less toxic due to their low solubility. However, emerging evidence suggests that the oxidative dissolution of Ag2S NPs can lead to the release of silver ions (Ag+), raising questions about whether Ag2S NP-induced toxicity can be explained by Ag+ release in aquatic environments. Herein, we assess the immunotoxicity of Ag2S NPs and Ag+ in freshwater clams (Corbicula fluminea) through an immunometabolic framework. Environmental concentrations of Ag2S NPs caused substantial inflammation, broad activation of the innate immune system, and a pronounced oxidative burst, while Ag+ at equivalent silver mass mainly caused cytotoxic and did not induce immune activation. Metabolomic and transcriptomic profiling revealed distinct features of Ag2S NPs compared with Ag⁺, characterized by tissue-level glucose metabolic responses involving PPP-related features and upregulated proinflammatory signaling genes. These findings provide an immunometabolic perspective for understanding the Ag2S NP-induced toxicity, suggesting that the observed toxicity cannot be fully explained by Ag+ release during aqueous exposure and highlighting the potential ecological risk of metal sulfide nanoparticles to benthic communities. Our results suggest that Ag2S NPs pose a greater environmental hazard than previously thought, warranting further consideration in nanoparticle risk assessments.

Liming offers unique benefits for reducing cadmium (Cd) uptake in crops by lowering soil Cd bioavailability. However, its effectiveness in reducing Cd accumulation in wheat grains is often insufficient, and the underlying mechanisms remain unclear. This study employed rhizobag pot experiments to systematically evaluate the self-limiting factors of liming on Cd uptake in wheat, focusing on micronutrient dynamics, rhizosphere organic acid secretion, and Cd transporter gene expression. Lime addition (0.5–4.0 g·kg−1) significantly increased soil pH and reduced Cd availability by up to 95.4

Exogenous organic carbon (EOC) input is a key management measure for enhancing soil carbon sink function, yet the global patterns and regulatory mechanisms by which it promotes carbon sequestration through microbial necromass accumulation remain unclear. To address this, we conducted a meta-analysis based on 380 observations from 74 peer-reviewed studies worldwide, systematically examining the effects of EOC input on soil microbial necromass carbon (MNC) accumulation and its driving factors. EOC-amended soils had on average 29.4% higher soil organic carbon (SOC) and 38.7% higher MNC contents; the proportion of MNC in SOC was also 5.2% higher in these soils. The universal regulatory pathway underlying this positive effect is that EOC input provides additional carbon substrates that directly stimulate microbial growth and biomass turnover, and the subsequent MNC accumulation contributes to the SOC pool. However, the efficiency of this process is critically modulated by both the quality (C/N) and quantity (carbon input rate) of applied organic materials. Low-C/N materials improve soil carbon and nitrogen synergy, promoting carbon flow toward biomass synthesis and necromass formation, while carbon input rate directly stimulates microbial biomass accumulation, but with a threshold beyond which the contribution of MNC to SOC declines. This study demonstrates that improving the stoichiometric balance and application rates of exogenous organic materials is an effective strategy for enhancing the function of the microbial carbon pump and increasing soil carbon sink potential.

Dietary intake is a predominant pathway of human exposure to environmental Cadmium (Cd), but wheat (Triticum aestivum L.) has not received enough concerns for its risk of Cd contamination. A field survey of Cdcontaminated rice-wheat rotation farmlands in China provided detailed comparison of Cd accumulation capacity by rice and wheat grains. The results indicated that Cd-BCF of wheat grains (median values 0.42) were obviously higher than those of rice grains (median values 0.12) under wide soil Cd levels and pH ranges. Soil Cd levels rather than pH played a vital role on Cd accumulation by wheat grains, and high wheat grain Cd concentrations (0.12-0.13 mg kg-1) were even observed in mildly alkaline soil that normally have low Cd mobility. Dietary Cd exposure risks were assessed by the crop Cd exposure models considering different soil Cd content, pH and dietary structures of residents. The results indicated that the intake of wheat grains contributed 56.1-86.5% of total crop Cd exposure, with an increase in its contribution with the increase of soil pH. Residents favoring wheat would have a significant Cd exposure risk if consuming crops from soils with Cd levels above 0.41 mg kg-1, which was considerably lower than the current soil Cd risk screening value for alkaline soils (0.6 mg kg-1). Our findings indicate a high Cd accumulation capacity of wheat grains and consequent risk of dietary Cd exposure, which deserves further exploration on the correlation among soil Cd screening value, grain Cd limit value and its dietary exposure risk.

Foliar zinc (Zn) application offers a promising strategy for cadmium (Cd) mitigation and Zn biofortification in wheat, while the poor leaf adhesion of conventional Zn formulations limits their effectiveness. This study utilized hydroxyapatite nanoparticles (nHAP) as a nanocarrier and prepared the nHAP-Zn complex through simple reactions. The complex exhibited superior leaf adhesion compared to ZnSO4 solution. Foliar application of nHAP-Zn increased grain Zn concentration by 38.8 % in the low-Cd-accumulating wheat cultivar Ningmai-11 (NM11) and 31.6 % in the high-Cd-accumulating cultivar Zhengmai-10 (ZM10), surpassing the effects of ZnSO4. Notably, nHAP-Zn decreased grain Cd concentration by 31.5 % in NM11 and 32.9 % in ZM10. Mechanistically, nHAP-Zn suppressed Cd uptake by downregulating the expression of TaNramp5, TaIRT1, and TaZIP5 genes in the roots, and inhibited Cd translocation from node Ito the grain by reducing xylem-to-phloem Cd transfer-related gene expression (i.e., TaHMA2, TaZIP3, and TaZIP7 in NM11, and TaHMA2, TaLCT1, TaZIP5, and TaZIP7 in ZM10). Furthermore, nHAP-Zn application did not compromise plant growth characteristics such as plant biomass and height. These findings highlight nHAP-Zn as a highly efficient foliar fertilizer for enhancing Zn biofortification while mitigating Cd accumulation in wheat cultivated in Cd-contaminated regions. This study presents a novel approach to improving wheat safety and nutritional quality.

Biochar is a popular amendment in Cd polluted soil. However, the performance of bulk biochar is still less than satisfactory, so effective modification is very important to improve its capacity to adsorb Cd. In the present study, biochar derived from reed straw was modified by ball milling with the addition of either potassium hydroxide (KOH) alone (QK) or combined with attapulgite (QKA). Both batch experiments and pot cultivation were conducted to elucidate the adsorption mechanisms of Cd by modified biochar and their effects on Cd passivation and plant uptake in Cd polluted soil. The results showed that QK and QKA could provide higher pH values, and more oxygen-containing functional groups and minerals compared with bulk biochar (YC), promoting the complexation, ion exchange and precipitation of biochar to cadmium (Cd). The modified biochar was more inclined to multi-layer, non-ideal surface and chemical adsorption, which was an endothermic process. Compared to non-biochar addition (CK), the application of QK or QKA significantly promoted the values of pH, EC, CEC, available potassium and organic matter in soil. The addition of QK, QKA and YC decreased the availability of Cd by 22.61%, 22.32% and 14.16%, accompanied by the increase of residual Cd by 47.96%, 47.60% and 37.27%, respectively, indicating the more effective passivation of the modified biochar (QK and QKA). Compared to CK, biochar applications could significantly improve Chinese cabbage growth, and decrease Cd content in the aerial/edible part of plants by 42.97, 18.16 and 7.29%, respectively, for QK, QKA and YC. With the application of QK, Cd concentrations in the aerial/edible part of Chinese cabbage were reduced to 0.15 mg kg−1 (lower than 0.2 mg/kg, the leafy vegetables national safety standard). Generally, the performance of QK on the remediation effects and vegetable production was better than that of QKA, indicating the potential of QK for the remediation of Cd-contaminated soil and the safe production of vegetables.

Cadmium (Cd) pollution in farmland soil leads to excessive Cd in vegetables, which can be transferred to humans through the food chain, posing a significant threat to human health, and requires urgent measures to combat it. Modified biochar may have the potential to remediate Cd pollution in farmland soils. In this experiment, bulk biochar (YC) derived from reed straw or modified biochar by ball milling (Q) either alone or combined with a combination of several passivation agents {potassium hydroxide (K), attapulgite (A), calcium magnesium phosphate fertilizer (M), and polyacrylamide (P)} was applied to soils polluted with Cd, to investigate the growth, yield, and quality of pakchoi (Brassica chinensis L.). The results showed that bulk biochar (YC) provided pakchoi with plenty of nitrogen, phosphorus, and potassium, while passivation agents enhance macronutrient accumulation. Compared to YC, modified biochar improved pakchoi yields and nutritional quality. Among them, concentrations of nitrates in pakchoi significantly decreased by 51.8% and 51.0%, while vitamin C levels increased by 29.6% and 19.0%, respectively, in QKAMP and QKAM treatments. The contents of Cd in pakchoi significantly decreased by 21.6% and 18.6%, respectively, in QKAMP and QKAM treatments. The implementation of QKAMP led to the cadmium contents in edible vegetables being lower than the maximum stipulated content as defined by the national standard, but QKAM failed to accomplish it. In conclusion, QKAMP effectively reduced the bioavailability of Cd in the middle to slightly Cd-polluted alkaline soils, making it a suitable soil amendment to improve the yield and quality and mitigate Cd accumulation in vegetables.

Soil salinity and cadmium (Cd) contamination pose significant threats to agricultural productivity and food security, particularly in rice-growing regions. This study investigates the synergistic effects of plant growth-promoting rhizobacteria (PGPRs) (Pseudomonas koreensis, Bacillus coagulans, and Pseudomonas stutzeri) and selenium nanoparticles (SeNPs) in remediating saline Cdcontaminated soils and enhancing rice (Oryza sativa L.) performance. Over two consecutive growing seasons (2022-2023), the combined application of PGPRs and SeNPs significantly improved soil health, reducing soil pH from 8.50 to 8.02 and electrical conductivity (ECe) from 5.97 to 4.01 dS m-1 , while increasing soil organic matter (SOM) by 6.5 % and cation exchange capacity (CEC) by 25.6 %. The treatment also reduced soil Cd content by 34.6 %, from 0.81 to 0.53 mg kg-1 , and decreased Cd accumulation in rice roots, shoots, and seeds by 56.7 %, 65.0 %, and 50.0 %, respectively, ensuring safer rice grain production. Furthermore, SeNPs significantly enhanced selenium (Se) content in rice shoots and seeds, with Se levels increasing from 0.55 to 1.47 mu g g-1 in shoots and from 0.01 to 0.51 mu g g-1 in seeds, highlighting their role in improving rice nutritional quality. Physiological analyses revealed enhanced photosynthetic pigment concentrations, with chlorophyll a increasing by 112.3 % and carotenoids by 213.6 %, alongside a 101.9 % increase in superoxide dismutase (SOD) activity under the combined treatment. These improvements translated into a 25.0 % increase in grain yield, from 5.76 to 7.24 ton ha-1 , and a 21.4 % increase in 1000-grain weight. The findings highlight the efficacy of PGPRs and SeNPs in mitigating oxidative stress, improving nutrient uptake, reducing Cd toxicity, and enhancing rice productivity under combined salinity and Cd stress. This study provides a novel, eco-friendly

The biogeochemical cycling of carbon (C) and its associated enzyme activities are vital for maintaining crop productivity and play a crucial role in soil C sequestration. However, distinguishing the specific effects on the rhizosphere and bulk soils soil organic C (SOC), labile organic C (LOC) and enzyme activities presents a significant knowledge gap that needs to be addressed. The objective of this study is to explore the effects of various tillage management practices on soil C fractions and enzyme activities, while examining their interrelationships in both the rhizosphere and bulk soil. We measured SOC and LOC fractions, including microbial biomass C (MBC), dissolved organic C (DOC), particulate organic C (POC), easily oxidizable C (EOC) and light-fraction organic C (LFOC), as well as soil enzyme activities, including cellobiohydrolase (CBH), beta-glucosidase (BG) and xylosidase (BXYL) after 10 years of different tillage management practice. The tillage management included no-tillage with straw return (NTS), mouldboard ploughing with straw incorporated into the 0-20 cm soil layer (MPS) and conventional tillage practice (CT). The results demonstrated that NTS and MPS significantly increased both rhizosphere and bulk SOC contents, LOC fractions and enzyme activities compared to the CT treatment. Moreover, the rhizosphere exhibited higher SOC, LOC and enzyme activity levels than the bulk soil. Redundancy (RDA) analysis unveiled that tillage practices boost soil enzyme activities through the modulation of SOC and LOC levels. RDA analysis also indicated significant impacts of tillage management techniques and soil type on SOC, LOC components (including MBC, DOC, POC, EOC, LFOC) and C-cycle enzyme activities (CBH, BG, BXYL). Notably, soil CBH activity exhibited positive associations with MBC, DOC and LFOC, while no significant correlations were observed between CBH and SOC, POC or EOC. Furthermore, it highlights the differential responses of SOC, LOC and enzyme activity to tillage management in both the rhizosphere and bulk soil. These findings contribute to a deeper understanding of the interactions between the rhizosphere and tillage management, offering valuable implications for assessing the ecological dynamics of rhizosphere soil. Such insights can guide the development of plant-focused strategies aimed at enhancing productivity and promoting sustainability within agroecosystems.

Nanoplastics (NPs) are prevalent in the environment, posing risks to ecosystems and human health. While research into their effects on bacterial activity has increased, the mechanisms underlying NP-bacteria interactions─specifically whether NPs penetrate cells or adhere to the cell surface─remain poorly understood. This knowledge gap largely stems from the absence of quantitative analytical methods. Herein, we developed a novel approach combining lysozyme treatment with pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) to differentiate between intracellular and cell wall-bound NPs in Escherichia coli (E. coli) quantitatively. The method involves selective removal of the bacterial cell wall using lysozyme, protein corona-induced extraction to enrich cell wall-bound NPs, and hydrogen peroxide digestion to eliminate protoplast interference before Py-GC/MS analysis. Validation with europium (Eu)-labeled NPs, quantified by inductively coupled plasma mass spectrometry (ICP-MS), confirmed the method's accuracy and reliability. Using this approach, we found that after NP exposure, only a small fraction (9.6-10.5%) of NPs penetrated E. coli cells, while the majority (36.9-63.8%) adhered to the cell surface. Transmission electron microscopy further corroborated these findings. Consequently, this work provides a robust tool for the quantification of NP uptake and biodistribution in bacterial systems, advancing our understanding of NP-microorganism interactions and their environmental implications.

The extensive use of cadmium sulfide nanoparticles (CdS-NPs), along with their natural formation through the complex biogeochemical transformation of anthropogenic cadmium ions (Cd2+), poses substantial risks to ecosystems and human health. Despite this, the mechanisms underlying the toxicity of CdS-NPs remain unclear. A key question is whether their toxicity arises from the nanoparticulate form of cadmium (Cd) or from the release of Cd2+. To explore this, we exposed freshwater clams (Corbicula fluminea) to environmentally relevant concentrations (0.01-1 mg/L) of CdS-NPs or Cd2+ for 10 days. Hematoxylin and eosin (HE) staining revealed significant damage to the digestive gland in both cases. Although CdS-NPs released some Cd2+ (≤10.4%), transcriptomic and quantitative reverse transcription polymerase chain reaction (qRT-PCR) analyses indicated different toxicity mechanisms. CdS-NPs primarily induce ferroptosis, triggered by lysosomal dysfunction that releases Fe2+ into the cytoplasm, disrupting the cellular iron metabolism. In contrast, Cd2+ primarily induces an autophagic response, as evidenced by the upregulation of autophagy-related markers and activation of apoptosis pathways linked to mitochondrial membrane permeabilization. Overall, our findings suggest that the toxicity of CdS-NPs is not solely derived from Cd2+, highlighting the need to evaluate the risks posed by metal sulfide nanoparticles to benthic ecosystems.

This study explores the impact of microplastics (MPs) and nanoplastics (NPs) on hepatic lipid metabolism in pearl gentian grouper (Epinephelus fuscoguttatus female x Epinephelus lanceolatus male) during overwintering and elucidates the underlying mechanisms. Fish were exposed to polystyrene (PS) MPs and NPs of varying sizes (5 mu m, 500 nm, and 50 nm) for a 15-day exposure period. Histopathological analysis, oxidative stress assessment, and gene expression profiling related to lipid metabolism revealed significant toxic effects on the liver. Results showed that NPs preferentially accumulated in the liver, causing hepatocyte swelling, inflammation, and lipid metabolism disorders. Smaller particle sizes intensified oxidative stress, reduced triglyceride (TG) content, and elevated low-density lipoprotein cholesterol (LDL-C) and total cholesterol (T-CHO) levels. Transcriptomic analysis indicated that MPs and NPs altered the expression of lipid metabolism genes, particularly those in glyceride metabolism and lipolysis pathways, with significant upregulation of PNPLA2 and LIPG (p < 0.05) under cold stress. This led to excessive energy reserve depletion and hepatic lipid metabolism dysfunction. This study establishes a "environmental stress-gene-metabolism" response model and provides novel insights into the molecular mechanisms by which NPs disrupt lipid homeostasis in aquatic organisms, offering a theoretical basis for understanding the toxicological effects of emerging contaminants.

An iron anode electrolytic biochar biofilter with distributed effluents was constructed to explore the roles of iron anode electrolysis and biochar substrate in phosphorus (P) removal. The results showed that iron anode electrolysis is the primary factor driving P removal. Subsequently, the released iron ions were effectively adsorbed by biochar, which is another pathway for enhanced P removal. At a voltage as low as 5 V, the average removal rate of PO43--P was 98.37 ± 1.01 %. Under power-off conditions, the average removal rate of PO43--P by iron-loaded biochar was as high as 95.92 ± 2.61 %. Biochar substrate can effectively adsorb Fe(II) or Fe(III) produced by the iron anode, with an iron loading of 4.3 ± 0.62 mg/g biochar. X-ray powder diffractometer (XRD) analysis found that the principal crystalline iron oxides loaded on biochar were FeOOH and Fe3O4. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) showed that iron-loaded biochar exhibits strong electron-exchangeability and effectively reduces charge-transfer resistance. 16S rRNA analysis showed that biochar can serve as a carrier for microorganisms, and iron electrolysis enriched the microbial community structure of the biochar substrate, as the Fe(II)/Fe(III) electron pairs generated by iron anode electrolysis enriched the electron donors or acceptors of microbes. Due to its redox functional groups and graphite-like structure, biochar can shuttle electrons. It facilitates the extracellular electron transfer of iron-reducing bacteria and indirectly promotes the Fe(II)/Fe(III) cycle, thereby influencing the iron-binding and adsorption capacity of PO43--P. The phosphorus adsorbed by iron-loaded biochar was mainly composed of NaOH-P and BD-P, indicating that biochar-loaded iron enhances phosphate fixation and improves P resource utilization during adsorption.

Conservation tillage offers a viable solution for restoring degraded cropland and maintaining ecological function of agricultural systems (Busari et al. 2015; Chimsah et al. 2020), especially long-term conservation tillage providing great potential for reducing N fertilization owing to its benefit of improving soil N pools (Chen et al. 2022). To align with modern agricultural development goals, it has been suggested that the environmental impacts should be taken into consideration for optimizing N management (Cai et al. 2023). However, most studies have primarily focused on comparing crop yield, resource utilization and GHG emissions (Su et al. 2014; Lv et al. 2019), lacking the systematic assessment of crop production and environmental impact. The TOPSIS approach offered a robust solution to this gap (Wang et al. 2019). As a ranking method, TOPSIS operates on the principle of measuring the proximity between a finite set of evaluation objects and an idealized target. It systematically assesses the relative merits and drawbacks of existing objects, enabling effective multi-criteria and multi-objective decision analysis. In the context of agricultural production, adopting TOPSIS thus provides a holistic perspective on the comprehensive performance of different N fertilization levels. This, in turn, facilitates evidence-based decision-making, allowing for more precise identification of the most efficient and sustainable N management strategies.