Anaerobic digestion (AD) is widely applied for its ability to convert organic waste into bioenergy, which helps to optimize the energy structure. However, ammonia inhibition, which is frequently associated with process instability in biogas plants, has significantly limited AD applications. Existing reviews have explored ammonia inhibition from various perspectives but have primarily focused on the methanogenesis process. By contrast,​ the contribution of impaired acetogenesis function to ammonia-induced inhibition has been largely overlooked. This review integrates molecular biological evidence to demonstrate that acetogenesis serves as the key link affecting ammonia-inhibited reactor performance, with a particular focus on the effects of ammonia stress on the dynamic succession, energy harvest, and enzymatic activities involved in acetogenesis. The impaired energy harvest and downregulation of enzymatic activities have been identified as the primary causes of the irreversible ammonia inhibition of acetogens, which then leads to the failure of the acetogenesis process, volatile fatty acid accumulation, and ultimately the irreversible deterioration of reactor performance. Furthermore, building on this new mechanistic insight, this review re-evaluates the efficiency and limitations of ammonia inhibition mitigation strategies. Future efforts should focus on developing innovative multi-data integration analysis strategies—such as combining activated cell sorting with targeted metaproteomics, and stable isotope probing with metabolomics—to overcome current methodological challenges in analyzing​ ammonia inhibition mechanism. These insights provide a new perspective on the ammonia inhibition mechanism and important guidance for the stable operation of fermentation systems.

This study investigates the migration and long-term ecological risks of seven heavy metals (HMs) in an industrial park of the Yangtze River Delta using a Monte Carlo-optimized Level IV fugacity model. By integrating regional parameters and emission inventories, the model quantified fluxes among air-water-soil-sediment compartments, and its performance was validated using Theil's inequality coefficient. Simulated concentrations in soil and sediment closely matched measurements, while aqueous deviations were mainly driven by environmental dynamics. Pb and Hg dominated air-soil exchange; Cr and Ni contributed substantially to soil-water migration; Hg showed the lowest mobility due to organic matter binding. Sediments acted as the ultimate sink, retained approximately 99 % of aqueous fluxes, but released nearly 50 % through resuspension, constituting potential secondary pollution pathways. Risk assessment identified Cd and Hg as the primary threats, with sediment accumulation rates one to three orders of magnitude higher than in soil. Projections suggest sediment Cd will reach high risk by 2025 and extremely high risk by 2036, while soil Hg will reach high risk by 2071. A 20 % emission reduction significantly delayed the projected increase in risk levels. The findings highlight sediments as long-term pollution reservoirs and recommend priority control of Cd and Hg, supported by dynamic risk earlywarning strategies.

Lithium demand is surging to support the global energy transition, raising concerns over the environmental impacts of its production. However, the quantitative contribution of advanced extraction technologies in reducing the environmental impacts of lithium is still unclear. To fill this gap, this study first conducts a comprehensive life cycle assessment (LCA) of 11 environmental impact categories from lithium extraction worldwide, covering diverse sources (brines, spodumene, clays, and geothermal brines) and extraction technologies. Results reveal that producing 1 kg of Li2CO3 generates 2.14-19.11 kg CO2-eq, where the Mg2+/Li+ ratio in brines is a key driver of environmental outcomes, influencing extraction efficiency. We further evaluate emerging Direct Lithium Extraction (DLE) technologies for low-concentration, high Mg2+/Li+ brines, finding that most DLE methods yield ∼4-fold higher impacts than traditional methods due to intensive chemical and energy use. In contrast, four advanced DLE technologies, including adsorption-coupled membrane, solvent extraction, and electrochemical deintercalation/intercalation with LFP/FP or LiMn2O4/λ-MnO2 electrodes, reduce emissions by up to 60% relative to other DLE options. Transitioning to renewable energy enhances DLE viability, potentially lowering impacts below traditional levels. Our findings highlight pathways for sustainable lithium supply through technological advancement and energy decarbonization.

This study investigated how ethanol pretreatment (EP) enhances the resilience of high-solid anaerobic digestion against rapid organic loading shocks. Semi-continuous reactors fed with either untreated or EP-treated food waste were compared, and the underlying mechanisms were elucidated by integrating thermodynamic calculations with metagenomic analyses. At an organic loading rate of 6.0 g VS/(Lˑd), the control group (untreated) collapsed due to the accumulation of propionate and other longer-chain volatile fatty acids (VFAs), resulting in a methane yield decrease exceeding 70%. In contrast, the EP group maintained stability, exhibiting a methane yield decrease of less than 5%, with VFAs dominated by readily degradable acetate. Thermodynamic analysis confirmed that EP significantly lowered the energy barriers for VFA degradation. Metagenomic analysis revealed that both propionate/butyrate activation pathways (with lower energy cost or independence from acetyl-CoA) and syntrophic acetate oxidation were activated in the EP group, thereby avoiding the VFA metabolic stress observed in the control group. Furthermore, higher abundances of conductive type IV pili genes, Complex II, and archaeal V/A-type ATPase were detected in the EP group, suggesting the establishment of direct interspecies electron transfer and enhanced electron flux and energy capture efficiency. Moreover, under high loading conditions, only a few high-abundance metagenome-assembled genomes (MAGs) were detected in the control group, while multiple MAGs carrying identical VFA-degrading enzyme systems were identified in the EP group. The functionally redundant microbiota, unobstructed VFA metabolic pathways, and efficient electron transfer and energy supply collectively sustained the stability of the EP group under loading shocks.

Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) can bioaccumulate in aquatic food webs and pose potential health risks through aquatic product consumption. This study investigated the occurrence, health risks, and dietary management implications of PCBs and PBDEs in 12 commonly consumed freshwater and marine species from Guangdong, China. Concentrations and congener profiles were determined, followed by population-specific carcinogenic and noncarcinogenic risk assessment. A linear programming approach was applied to develop optimized dietary recommendations by integrating nutritional requirements, contaminant exposure, and economic cost. All samples contained detectable levels of PCBs and PBDEs, with higher concentrations in freshwater species than in marine species. PCBs were dominated by tetra- to heptachlorinated congeners (79.2%-99.97% of ΣPCBs), while PBDEs were mainly composed of tri- to penta-brominated congeners and BDE-209 (70.0%-99.9% of ΣPBDEs). Risk assessment showed that regular consumption of several species exceeded the cancer risk (CR) benchmark of 1 × 10-6 (USEPA), primarily driven by dioxin-like polychlorinated biphenyls (dl-PCBs). The optimization framework provides tailored guidance for different groups in Guangdong, balancing protein intake, cost, and contaminant exposure. Low-risk, protein-rich, and affordable options included Scatophagus argus, Turritella bacillum, and Procambarus clarkii. Tailored consumption advice can reduce exposure without compromising nutrition.

Foaming poses a significant threat to the stability of food waste anaerobic digestion (AD) systems. This study elucidates the regulatory mechanisms of quorum sensing (QS) underlying foaming by integrating multi-omics tracking and quorum quenching verification methodologies. The results indicate that an increased organic loading rate leads to the proliferation of core microorganisms (MAG25, MAG57, MAG153) and upregulates QSrelated genes (hdtS, RpfB, DAC, DGC), which drives the accumulation of short-chain acyl-homoserine lactones (AHLs) (C4/C6/C8-HSL), diffusible signal factor (DSF), and cyclic di-nucleotides (c-di-AMP/c-di-GMP), thereby activating the QS network. This network triggers foaming events by activating the transcription factor bapA, coordinating the complete protein (PN) metabolic cascade, and secreting excessive PN in extracellular polymeric substances (EPS), with an increase of 31 % to 1914 +/- 28 mg/L within 5 days. Additionally, vanillin (100 mg/L) was found to concurrently quench signaling molecules, reduce EPS-PN accumulation, decrease foaming, and maintain methane production, thereby confirming the causal relationship between QS and foaming. This study provides the first direct evidence of c-di-AMP in AD foaming and indicates that the QS network (core signals: short-chain AHLs/DSF/c-di-AMP/c-di-GMP) drives the excessive synthesis of EPS-PN as the core mechanism of foaming, offering theoretical support for foam control based on quorum quenching.

Positive matrix factorization (PMF) is widely used for source apportionment in environmental studies. However, its interpretation can be subjective, and integration with emission inventories remains challenging, particularly for emerging pollutants such as phthalate esters (PAEs). To address these limitations, a dMFA-guided PMF interpretation framework was established for six PAEs in surface water of the Chongqing section of the Yangtze River, China. Total PAE concentrations ranged from 326.80 to 868.40 ng/L and were dominated by DEHP and DBP. Concentration data were analyzed via PMF, resolving three factors accounting for 47.5% (mixed urban/ consumer source), 38.4% (industrial emission source), and 14.1% (packaging/agricultural source) of total PAEs. A complementary dMFA life cycle inventory indicated that 96.4% of aquatic emissions originated from in-use stocks, with household (57.5%, DBP&DIBP-dominated) and construction (25.2%, DEHP-dominated) sectors as the principal contributors. Innovatively, this study used the sector-and stage-resolved emission compositions provided by dMFA as independent prior information, which was quantitatively matched with the PMF-derived source profiles, thereby constraining and reconciling the interpretation of PMF profiles. The results demonstrated a high degree of consistency between the PMF-resolved factors and the industrial, packaging, and other consumer-related sectors quantified by dMFA. This framework significantly enhances the reliability of source apportionment, thereby providing actionable sector-specific insights for life cycle interventions in urban aquatic systems.

To address the challenges of slow start-up, poor humification efficiency, and elevated gaseous pollutant emissions during food waste residue composting, this study employed a synergistic strategy combining high-temperature pretreatment (HTP) with the addition of distiller's grains (DG). By monitoring the composting process, humification, gas emissions, and conducting metagenomic analysis, the enhancement potential and underlying mechanisms of this strategy were elucidated. The results indicated that, compared to conventional composting, the synergistic enhancement of HTP and DG significantly shortened the maturity period by 35.7 %, increased the humification index by over 55.0 %, and elevated the total nitrogen, total phosphorus, and total potassium contents of the final product by 28.1 %, 14.3 %, and 17.1 %, respectively, while achieving the highest levels of available nutrients and synergistic reductions in greenhouse gas and odor emissions. Mechanistically, HTP rapidly improved the physical structure of the feedstock, establishing a favorable foundation for microbial activity; DG selectively enriched core functional genera, including Pseudomonas and Marinobacter, and upregulated functional genes associated with N2O reduction (nosZ), sulfur oxidation, and lignocellulose degradation, thereby enhancing humus synthesis and pollutant gas mitigation at the metabolic level. This study elucidates the synergistic mechanism of physical pretreatment and bioaugmentation from a microbial functional perspective, providing not only a feasible 'waste-treats-waste' technical pathway for the resource utilization of food waste residue but also a theoretical basis for the targeted design of efficient and low-emission composting processes.

Potentially toxic element (PTE) pollution in marine sediments has generated global concern due to its ecological risks and health impacts. This study aims to characterize the spatiotemporal distribution, assess the ecological risk, and identify the sources of seven PTEs in Beibu Gulf sediments by leveraging a seasonal sampling campaign in August and December. The mean PTE concentrations (mg/kg) in summer/winter are 82.14/78.79 for Zn, 40.57/39.74 for Cr, 33.94/21.69 for Pb, 15.00/11.93 for Cu, 6.30/7.32 for As, 0.09/0.12 for Hg, 0.09/0.08 for Cd, and follow the order of Zn > Cr > Pb > Cu > As>Hg/Cd across seasons. Marked seasonal fluctuations were observed for Cu, Pb and Hg, while Zn, Cd, Cr and As remained relatively stable. Spatially, the distributions followed a nearshore enrichment pattern. Ecological risk assessment identified Hg as the predominant risk factor throughout the year, with overall pollution levels higher in winter. Combined multivariate statistical and positive matrix factorization (PMF) analyses indicated that the main sources of PTEs were agriculture/aquaculture (summer: 30.3 %; winter: 18.6 %), industrial/traffic emissions (summer: 36.9 %; winter: 32.6 %), natural geological sources (summer: 29.6 %; winter: 43.6 %), and shipping operations (summer: 3.3 %; winter: 5.2 %). This study provides critical scientific data and a quantitative basis for formulating targeted environmental protection and ecological health management strategies in the Beibu Gulf.

Ammonia inhibition represents a significant bottleneck in the anaerobic digestion (AD) of high-nitrogen organic wastes. This study employed a batch reactor system subjected to alternating carbon-sufficient and carbon-limited phases to investigate whether pulsed micro-aeration, with a peak oxidation-reduction potential ranging from -150 to -50 mV, could promote the conversion of total ammonia nitrogen (TAN) to N2 in anaerobic digesters maintained under bulk anaerobic conditions, while simultaneously elucidating the competitive interplay between this nitrogen removal process and methanogenesis. The investigation integrated reactor performance monitoring, 15N stable-isotope tracing, and combined metagenomic and metaproteomic analyses. Compared to the strictly anaerobic control, the pulsed micro-aeration group exhibited a significant decrease in TAN concentration, with a maximum removal rate of 23.41 mg·L-1·d-1. Isotope analysis revealed that approximately 82.49% of the transformed 15NH4+-N was recovered as 15N2, thereby confirming the conversion of TAN to N2. The transient accumulation of NO2- and NH2OH, coupled with the absence of sustained NO3- accumulation and the enhanced expression of Hao, Nir, Nor, and Nos proteins, collectively suggested the involvement of a hydroxylamine/nitrite-associated pathway in conjunction with denitrification within the micro-aerated system. This nitrogen removal process was primarily mediated by native fermentative/facultative heterotrophic bacteria in the AD system, including Ottowia and Comamonas, which exhibited pronounced metabolic flexibility in response to carbon availability. When carbon was abundant, nitrogen removal was predominantly driven by heterotrophic denitrification; under carbon limitation, the system transitioned towards endogenous maintenance modes characterized by potential hydrogen utilization, mobilization of intracellular reserves (such as polyhydroxybutyrate and fatty acids), scavenging of residual organic matter, and the glyoxylate cycle. However, the activation of nitrogen removal through micro-aeration was accompanied by a suppression of methanogenesis, resulting in a methane loss of 1.31-2.77 mL per mg of TAN removed. Consequently, a paradigm of "mainstream methanogenesis-side-stream micro-aerobic nitrogen removal" is proposed, offering a novel strategy for developing robust processes to mitigate ammonia inhibition in AD.

Ammonia inhibition represents a significant bottleneck that constrains the stability and efficiency of anaerobic digestion (AD) processes, particularly for high-nitrogen organic waste. This review synthesizes multi-scale evidence to illustrate that while elevated ammonia levels can alter the overall microbial community structure, process failure is most directly linked to its profound inhibition of two thermodynamically constrained, low-redundancy metabolic steps: syntrophic propionate oxidation and acetoclastic methanogenesis. This selective vulnerability is fundamentally linked to the mechanism by which ammonia stress interferes with core cellular functions related to transcription and translation. To address this bottleneck, existing mitigation strategies can be categorized into those aimed at overcoming ammonia inhibition or those focused on ammonia removal. The former, which includes additive application and bioaugmentation, can alleviate ammonia stress in the short term and may further facilitate the acclimation of microbial communities, thereby supporting relatively stable operations under high-ammonia conditions. However, challenges related to cost, operational complexity, and long-term stability persist. Alternatively, ammonia removal strategies, such as iron-mediated anaerobic ammonium oxidation and vacuum evaporation, offer potential for fundamental mitigation, although techno-economic feasibility remains critical for practical implementation. Notably, the phenomenon of microaeration-driven nitrogen removal, repeatedly reported in recent studies, suggests that AD systems may possess an underappreciated micro-oxygen interface along with potentially unrecognized nitrogen transformation pathways. This observation indicates a potential paradigm shift from strictly anaerobic operation to controllable micro-oxygen regulation, representing a promising frontier for future research. This review aims to provide systematic insights into clarifying the cascading failure mechanisms of ammonia inhibition and developing next-generation, efficient, and economical mitigation strategies.

This study investigates the efficacy and mechanisms of hydrogen/oxygen nano-bubble water (H-2/O-2-NBW) in enhancing anaerobic digestion (AD) performance. Batch experiments demonstrated that H-2-NBW and O-2-NBW significantly increased methane yields by 4.21 % to 16.98 % and 3.37 % to 13.43 %, respectively, compared to the control group (p < 0.05). Partial least squares path modeling and random forest algorithms identified 100 %H-2-NBW and 80 %O-2-NBW as optimal dosages. Under these optimal dosage conditions, semi-continuous tests revealed that methane production rates increased by 4.9-fold for H-2-NBW and 4.1-fold for O-2-NBW at an organic loading rate of 4 g volatile solids (VS)/(Ld) compared to the control group, while maintaining a stable output of 157.01-163.66 mL/gVSd at 5 g VS/(Ld) when the control failed. Mechanistic investigations indicated that O-2-NBW generates hydroxyl radicals that reduce cellulose crystallinity by 39.81 % and upregulate hydrolytic enzymes such as xylanase, cellulase, protease, and alpha-glucosidase, targeting the regulation of hydrolytic and acidogenic bacteria (Sedimentibacter). In contrast, H-2-NBW activates hydrogenotrophic methanogenesis through the stimulation of dehydrogenase, acetokinase, and coenzyme F-420, along with the enrichment of DMER64 and Methanobacterium. Microbial co-occurrence network analysis indicated that the addition of NBW significantly altered microbial interaction patterns. Functional predictions confirmed that H-2/O-2-NBW specifically strengthened the putative metabolic pathways of hydrogenotrophic methanogenesis and hydrolysis-acidogenesis. The synergistic mechanism of physical deconstruction and biological regulation of nanobubble water revealed in this study has opened a new pathway for the development of technologies aimed at enhancing AD performance.

To investigate the potential and mechanisms of bioaugmentation in overcoming ammonia and salt exposure, this study first examined the performance of food waste anaerobic digestion under two sequential batch experiments (R1, R2) exposed to salt (5-15 g/L) and ammonia (3-9 g/L), respectively. R1 and R2 proceed consecutively and under identical operating conditions. Subsequently, domesticated sludge from the highest exposure group was mixed with fresh inoculum (0 %-50 % ratio) and reintroduced into new systems with 9 g/L ammonia and 15 g/L salt exposure to evaluate performance and microbial community responses. The results demonstrated that reactor performance declined with increasing exposure levels in R1. However, under identical exposure levels, R2 consistently outperformed R1, indicating that microbial domestication enhanced reactor resistance to both ammonia and salt exposure within the tested ranges. In bioaugmentation experiments, all test groups exhibited superior digestion performance compared to controls. While salt-exposed groups showed no significant differences across domesticated sludge dosages ( p > 0.05), ammonia-exposed reactors displayed improved performance with the increasing domesticated sludge ratios. Microbial analysis revealed that sequential exposure enriched 7 salt-tolerant and 8 ammonia-tolerant genera. However, only a subset of these resilient genera (4/7 in salt-exposed and 3/8 in ammonia-exposed groups) successfully colonized the bioaugmented systems. Notably, the introduction of domesticated sludge triggered a "microbiological domino effect ", enriching functionally redundant non-dominant microbes, which likely contributed to the enhancement of digestion performance.

The treatment of nitrogen-rich organic waste via high-solid anaerobic digestion (AD) often encounters challenges due to ammonia inhibition, resulting in process instability and reduced methane production. To improve AD efficiency, this study developed a bioelectrochemically assisted anaerobic digestion (BEAD) system. Although such systems have been employed to mitigate inhibition, existing research has primarily concentrated focused on low-solid conditions, neglecting the critical interaction between total solids (TS) and applied voltage. This study systematically investigated the synergistic effects of TS (5 %-15 %) and applied voltage (0-3.0 V) on methane production and nitrogen removal performance during the treatment of cattle manure. The results indicated that the dominant electrochemical metabolic pathways of the system evolved with increasing TS and voltage, with the optimal voltage increasing alongside higher TS levels (5 % TS: 0.6 V; 15 % TS: 3.0 V). Under their respective optimal conditions, the cyclic voltammetry (CV) curves of the low-TS system (5 %) exhibited anodic oxidation peaks consistent with volatile fatty acid (VFAs) oxidation. Methane production increased by 35.9 %, primarily due to the enrichment of hydrolytic-acidogenic bacteria and methanogens. In contrast, the high-TS system (15 %) exhibited characteristic electrochemical signals associated with ammonia oxidation in the CV curves. This was accompanied by the enrichment of methanogens, ammonia-oxidizing bacteria (e.g., Dethiobacter), and heterotrophic nitrifying bacteria (e.g., Bacillus), leading to synergistic improvements in both methane production and nitrogen removal efficiency, which increased by 16.3 % and 21.6 %, respectively. Integrated analyses of electrochemical, physicochemical, microbial community structure, and functional predictions indicated that TS primarily drives the restructuring of functional microbial communities by regulating substrate ammonia nitrogen concentration. Meanwhile, the applied voltage directly enhances key metabolic pathways such as methanogenesis and nitrification/denitrification through electrical stimulation. Structural equation modeling further confirmed this cascading regulatory mechanism of "environmental factors -> microbial community -> system function." This study provides a novel synergistic regulation strategy involving "TS-voltage" to address the persistent challenge of ammonia inhibition in high-solid anaerobic digestion, providing both a theoretical foundation and practical direction for its engineering application.

To evaluate the effect of vanillin, a quorum sensing inhibitor (QSI), on the defoaming potential in food waste anaerobic digestion (AD) systems, various concentrations of vanillin were introduced into different AD reactors. The performance of these systems, along with foaming characteristics, extracellular polymeric substances (EPS) parameters, and microbial community structure and functional genes were monitored. The results show that the addition of vanillin at varying concentrations effectively reduced the foaming potential of the AD system. Specifically, vanillin at low concentrations (50 and 100 mg/L) did not inhibit methane production, whereas higher concentrations (200 and 500 mg/L) significantly inhibited methane production performance (p < 0.05). Optimal methane production and defoaming performance were observed at a vanillin concentration of 100 mg/L, where its methane production rate was not significantly different from that of the control group, but foam stability was significantly reduced by 84.69 % (p < 0.05). The incorporation of vanillin suppressed AHLs-mediated quorum sensing effects, reduced the synthesis and secretion of proteins (PN), decreased the content of PN and hydrophobic PN in EPS, lowered the viscosity of the digestate, reduced the contact angle, and ultimately diminished both foaming potential and stability, thereby achieving effective defoaming.

This study investigated the effect of the partially substituting chemical fertilizers (CF) with digestate-based organic amendment (OA) on the amelioration of red soil and the growth of plant. OA with nitrogen substitution rates ranging from 10 % to 40 % were mixed with CF and applied to red soil in a pot experiment. The results indicated that plant growth was significantly enhanced in the treatment where 20 % of the CF was substituted with the OA (OA20) compared to other treatments (p < 0.05). Specifically, the OA20 treatment increased nutrient use efficiency by 54.76 %-100.42 % compared to the treatment using only CF. Furthermore, all OA treatments improved the quality of red soil, with the nutrient content significantly higher in the OA20 group than in the other treatments (p < 0.05). The parameters of total phosphorus (TP), available nitrogen (AN), available phosphorus (AP), and total potassium (TK) significantly affected the soil quality index and plant growth, serving as reliable indicators of soil quality and plant yield. Microbial analysis revealed that the bacterial Chao index and the abundance of microorganisms involved in C-N nutrient cycling, such as Chryseolinea and norank_f__norank_o__Actinomarinales, were highest in the OA20 group. Significant correlations were observed between soil nutrient content (AN, AP, and TK) and the abundance of norank_f__norank_o__Actinomarinales and Chryseolinea, indicating their close relationship with pakchoi growth. Consequently, digestate-based OA may positively affect plant growth in acidic ecosystems by enhancing soil properties, inducing shifts in microbial community composition, and promoting the enrichment of potentially beneficial bacteria. This study provides valuable insights for the enhancement of low-quality soils and the resource utilization of digestate.

To investigate the potential of high-temperature pretreatment composting of food waste for the amendment of cadmium(Cd)and lead(Pb)-contaminated soil,food waste subjected to high-temperature pretreatment composting(HC),traditional composting(TC),and only high-temperature pretreatment were combined with inorganic passivators(lime/zeolite)for an indoor passivation cultivation experiment.The results indicated that HC combined with the inorganic passivators group(HLZ)exhibited the most effective passivation potential for Cd and Pb in soil,achieving passivation rates of 76.92%and 86.29%,respectively.Additionally,the residual fraction of Cd and Pb in the soil increased by 10.65%and 19.94%compared to that of the control group(CK).Fourier transform infrared spectroscopy analysis revealed that high-temperature pretreatment could facilitate the degradation of organic matter during aerobic composting,thereby improving the humification degree of organic fertilizer.As a result,the produced carboxylic acids and hydroxyl compounds were able to complex with more Cd and Pb ions,reducing their bioavailability and mobility.Moreover,the pH and electrical conductivity(EC)of the soil in the HLZ group significantly increased by 28.23%and 23.80%,respectively(P<0.05).Furthermore,the HLZ group exhibited the highest levels of available nitrogen,phosphorus,and potassium nutrients(1.62,2.94,and 1.34 times higher than in CK),as well as activities of urease,hydrogen peroxide enzyme,sucrase enzyme,and phosphatase enzyme(7.17,2.09,1.83,and 8.36 times higher than in CK).Notably,phosphatase activity was positively correlated with the passivation rates of Cd and Pb(P<0.05).The HLZ group,characterized by high phosphatase activity(23.83 mg·g-1·d-1),exhibited greater potential in passivating heavy metals Cd and Pb and improving soil ecological functions.Redundancy analysis of soil physicochemical indicators and the passivation effect of heavy metals indicated that soil pH,available nitrogen,organic matter,and EC significantly influenced the transformation of Cd and Pb fractions(P<0.01).The soil in the HLZ group possessed high pH,effective nitrogen,organic matter,and EC and particularly significantly higher levels of effective nitrogen content and EC compared to those in other treatment groups(P<0.05),which could be the primary reason for the optimal potential of HLZ in the amendment of Cd and Pb-contaminated soils.This study provides a feasible application of high-temperature pretreatment compost products from food waste and the amendment of heavy metal-contaminated soil.

Food waste digestate (FWD) composting faces significant challenges, including prolonged processing times, high emissions of odorous gases and greenhouse gases (GHGs), and poor compost maturity. To address these issues, this study investigates the effects of high-temperature pretreatment (HTP) on FWD composting by testing various conditions (temperature: 70, 80, 90 degrees C; duration: 2, 4, 6 h; aeration rate: 0, 0.1, 0.2 m3 center dot min- 1 center dot m-3). The results demonstrate that HTP significantly enhances composting efficiency, with the optimal condition (80 degrees C, 2 h, 0.2 m3 center dot min- 1 center dot m-3, referred to as the 822 group) achieving a 33.33 % reduction in composting time, a 30.94 % increase in polymerization degree (DP), and a 4.90 % improvement in total nutrient content compared to the calvinKlein (CK). Gas emission analysis reveals that the 822 group shows significant reductions relative to CK: NH3 (16.90 %), H2S (21.82 %), Me2S (41.18 %), Me2SS (32.79 %), CO2 (20.42 %), CH4 (17.12 %), and N2O (14.54 %). Microbial analysis demonstrates that HTP altered the microbial composition, increasing the abundance of microorganisms that facilitate humification while decreasing the abundance of those positively correlated with odorous gas and greenhouse gas emissions. Network analysis indicated that HTP improved the modularity of the microbial community, promoting the clustering of key functional bacteria and strengthening intra-colony interactions. This study not only identifies optimal HTP parameters for FWD composting but also elucidates the microbial mechanisms underlying its efficacy, providing a scientifically grounded strategy to improve composting efficiency and reduce environmental impacts.

Rice consumption serves as a primary pathway for human dietary exposure to methylmercury (MeHg), a potent neurotoxin predominantly formed in paddy soils. Although soil physicochemical properties exert a strong influence on MeHg production and accumulation, soil heterogeneity has hindered the identification of consistent controlling factors. In this study, a systematic meta-analysis of 22 peer-reviewed datasets was conducted to evaluate environmental regulators of MeHg contamination in paddy soils, with a specific distinction made between sites located within and outside Hg mining areas. The results revealed significantly elevated Hg and MeHg levels in paddy soils associated with Hg mining activity. Across both site types, soil pH, organic matter (OM), and total Hg (THg) were identified as key determinants of MeHg dynamics. MeHg accumulation was highest under weakly alkaline conditions (pH 7.0-8.0), while both low (<10 g/kg) and high OM (>60 g/kg) OM levels were unfavorable for MeHg accumulation. In Hg mining area paddy fields, maximum %MeHg occurred at OM levels of 30-40 g/kg, whereas in ordinary paddy fields, the optimal range was 20-30 g/kg. In addition, rice cultivation significantly absorbs soil MeHg. In acidic paddy soils, modest pH reduction coupled with appropriate OM amendments may suppress MeHg production. These findings offer important insights for the targeted management and remediation of Hg and MeHg in paddy soil.

This study aimed to investigate the effectiveness and mechanism of biochar and modified magnetic biochar addition in improving the anaerobic digestion (AD) efficiency of swine wastewater under ammonia stress. Two batches of serial experiments were carried out with ammonia levels of 3000, 4500, and 6000mg/L. The results indicated that a one-time addition of 15g/L of both types of carbon materials could sustainably optimize the AD performance of swine wastewater at ammonia nitrogen levels of 3000 and 4500mg/L. In the second batch of experiments, at 4500mg/L ammonia, groups with C and FeC additions showed 6.5%, 16.2% higher cumulative methane yield and 45.5%, 60.0% greater maximum gas production rates than controls. However, under the ammonia stress condition of 6000mg/L, the reactor exhibited a mismatch between the carbon material addition and the degree of stress. The maximum methane production rate was intensified only in the first batch, which was 71.8% and 105.1% higher in the C and FeC groups, respectively, than in the control group. The microbiological analysis revealed that biochar optimized the AD performance by enriching the abundance of fermentative bacteria and enhancing the activity of Methanosaeta. In contrast, modified magnetic biochar promoted the enrichment of acetogens and shifted the dominant methanogens from sensitive Methanosaeta to the highly ammonia-tolerant Methanosarcina, thus causing the optimization of AD performance. The findings of this study provided new insights into the mitigation of inhibition and enhancement of efficacy in the anaerobic digestion of swine wastewater.