The removal of emerging micropollutants remains a major challenge for current water environment, thereby driving the development of efficient and recyclable photocatalysts. However, the sustainability and reusability of powder photocatalysts in the treatment of real wastewater is unsatisfactory. In this work, a Z-scheme Mn-HTCC/ BiOBr (20-MHB) heterojunction modified polyvinylidene fluoride (PVDF) floating membrane was successfully fabricated by a simple hydrothermal method and phase transformation technique to effectively boost the photocatalytic degradation performance. Under visible light irradiation, 20-MHB heterojunction achieved efficient removal of ciprofloxacin (CIP), tetracycline (TC), and sulfamethoxazole (SMZ), with efficiencies of 94.2%, 96.5%, and 71.6%, respectively. Furthermore, the 20-MHB@PVDF photocatalytic membrane solved the problem of photocatalyst recycling and maintained an excellent degradation efficiency of CIP (93.2%) under natural sunlight. Experimental and density functional theory (DFT) calculations reveal that 20-MHB heterojunction inhibits the electron-hole (e--h+) pair recombination, thereby promoting the generation of superoxide radicals (center dot O2-) and hydroxyl radicals (center dot OH). The formation of this unique heterojunction expands light absorption in the visible region, facilitates the separation and transfer of photogenerated carriers, and enhances the photocatalytic redox capacity, thereby improving degradation efficiency of micropollutants. This study provides reference values for the design of Z-scheme heterojunction modified PVDF membranes, which have significant potential to degrade emerging micropollutants in practical wastewater.

Enrofloxacin (ENR), as a widely used antimicrobial agent in aquaculture, poses potential risks to ecosystems and human health due to its environmental persistence. Therefore, it is of great significance to explore efficient methods for removing ENR from aquaculture wastewater. In this study, a series of shrimp shell-derived aerogel (MBC300-MBC700) were fabricated from Litopenaeus vannamei shells through chemical modification followed by pyrolysis at 300-700 °C, and their adsorption performance and mechanisms toward ENR were systematically investigated. The modified porous materials exhibited a well-developed micro-mesoporous structure, high specific surface area, and abundant surface functional groups. Meanwhile, MBC400 demonstrated the highest adsorption capacity for ENR, reaching 14.56 mg/g, with a corresponding specific surface area of 77.71 m2/g. The adsorption kinetics followed the pseudo-second-order model, and the isothermal data were better fitted by the Freundlich model, indicating a chemisorption-dominated, heterogeneous multilayer adsorption process. Thermodynamic analysis revealed that the adsorption was spontaneous (ΔG < 0) and endothermic (ΔH > 0). In regeneration experiments, 30% ethanol solution achieved the best desorption efficiency for MBC400, with adsorption efficiency remaining above 75% after three cycles. Based on the characterization and adsorption results, adsorption mechanism of ENR on MBC400 was elucidated as a synergistic effect of hydrogen bonding, π-π stacking, electrostatic interaction, and surface complexation. This study provides a novel strategy and theoretical basis for the high-value utilization of shrimp shell waste and for the efficient removal of fluoroquinolone antibiotics from aquaculture effluents.

The inherent "trade-off" effect between salt rejection and water permeability, together with poor chlorine resistance, remains a major challenge for reverse osmosis (RO) membranes. To overcome these limitations, a modified polyamide (PA) membrane was developed using a "chain terminator" strategy, in which cyclohexanecarboxylic acid chloride (CAC) was introduced as a chain-terminating agent during interfacial polymerization. As a kind of monofunctional acyl chloride, CAC effectively terminates polymer chain growth, resulting in reduced cross-linking density and membrane thickness, and thereby forming a thinner and moderately loosened PA selective layer that facilitates water transport. In addition, structural modifications reduced the water contact angle and surface zeta potential of the membrane. These changes significantly enhanced the water transport pathways and led to a substantial increase in water flux. Compared to conventional trimesoyl chloride (TMC) -based membranes, when c(TMC):c(CAC) = 1:1, the optimized membrane exhibits a 125.50% increase in water flux while maintaining a high NaCl rejection of 99.10%, with only a marginal decrease compared to the pristine membrane. Moreover, adjustment of the co-monomer ratio enables regulation of the membrane separation behavior, suggesting a possible transition from dense RO-type separation toward looser ion-selective separation at higher CAC contents. In addition, CAC incorporation enhanced the chlorine tolerance of the PA layer. The alicyclic segments introduced by CAC reduce the susceptibility of the PA network to electrophilic aromatic chlorination, while the monofunctional acyl chloride structure partially caps residual amine terminals and mitigates chlorine-induced degradation. After 24 h of static chlorination at 1000 ppm (pH = 4), the TFCO-1:1 membrane exhibited only a 2.64% decrease in NaCl rejection, demonstrating improved chlorine tolerance compared with the pristine TFC membrane.

Geological CO2 storage may pose environmental risks if leaked CO2 migrates into near-surface soils. To evaluate early surface-soil responses to low-concentration CO2 exposure, a 42-day aerated soil microcosm experiment was conducted using a control group and two CO2 treatment levels of 2000 and 10,000 ppm. Soil physicochemical properties, dissolved cations, metal fractions, enzyme activities, bacterial community composition, and metagenomic functional profiles were analyzed. Sustained CO2 exposure increased electrical conductivity and HCO3- concentrations, whereas soil pH remained within a narrow weakly alkaline range. Sequential extraction showed limited redistribution of selected metals among operationally defined fractions, but no evidence of extensive metal mobilization was observed. Among microbial indicators, FDA hydrolase activity responded significantly to CO2 exposure, whereas microbial community structure, alpha diversity, and overall KEGG and CAZy functional profiles remained largely stable. Representative carbon- and nitrogen-cycling genes were influenced mainly by incubation time rather than CO2 concentration. Under the tested short-term, low-concentration, aerated microcosm conditions, the soil system exhibited considerable buffering capacity and resistance to CO2 exposure. The observed effects were mainly expressed as minor changes in soil solution chemistry and selected functional indicators rather than pronounced geochemical deterioration or microbial community restructuring. These findings provide experimental evidence and insights into the geochemical buffering capacity and microbial response mechanisms of surface soil systems under potential leakage scenarios of underground CO2 storage. The findings offer scientific references for environmental risk assessment of CO2 geological sequestration and the selection and interpretation of sensitive monitoring indicators.

Conventional membrane separation technologies are constrained by their inherent sequential operating mode, making it difficult to synchronously and efficiently purify emulsions. This study breaks the norm and proposes a new strategy for synchronous separation and parallel treatment of opposing emulsion using heterogeneous wetting membranes. Here the membrane features spatially distributed hydrophilic/hydrophobic regions, combined with a bidirectional gradient contraction channel module, enabling a single device to synchronously and continuously separate opposing emulsion, such as oil-in-water (O/W) and water-in-oil (W/O) emulsions. The non-uniform shear field of the gradient contraction channel destabilizes emulsion droplets and enables gradual demulsification at the membrane interface. Membrane with patterned wettability guides the dispersion to migrate in the opposite direction, coupled with shear demulsification and directional phase transport. The two-phase separation efficiency of this mechanism exceeds 99.9%, and its anti-fouling performance and long-term stability have been notably enhanced. This work establishes a new paradigm for synchronous separation and parallel processing of opposite emulsions, paving the way for efficient integrated oil–water separation technology. A heterogeneous wetting membrane integrated with bidirectional gradient contraction channels enables the synchronous and continuous separation and parallel processing of opposing oil-in-water and water-in-oil emulsions with over 99.9% efficiency while delivering enhanced anti-fouling performance and long-term operational stability.

Abstract Oil spills pose severe threats to marine ecosystems. Insufficient attention has been paid to the hydrocarbon components and sulfur, nitrogen, silicon, and metal elements in these oil spills, despite the significant environmental risks. This study investigated the weathering behavior of these elements in Omani crude oil, gasoline with a research octane number of 95 (GB 17930; hereafter 95 RON gasoline), and China Grade 0 automotive diesel fuel (GB 19147; hereafter grade 0 diesel) using inductively coupled plasma optical emission spectrometry (ICP-OES), while concurrently evaluating the stability ratio of the non-aromatics to total aromatics (NA/TA) via high-performance liquid chromatography (HPLC) combined with normalization. The results demonstrated that the density increased across all three oils during weathering, with 95 RON gasoline showing the largest increase (12.44% with artificial seawater by day 7), followed by Omani crude oil (4.94%), and grade 0 diesel (0.34%). The presence of artificial seawater significantly accelerated the density changes through emulsification effects. The sulfur content in Omani crude oil increased by 35.59% in the presence of artificial seawater, whereas that of 95 RON gasoline decreased by 32.99% without seawater but showed complex fluctuations with seawater. In contrast, grade 0 diesel remained stable throughout weathering (6.45% increase with seawater), attributed to the predominance of heavy sulfur compounds. The nitrogen content of Omani crude oil increased by 15.74% with artificial seawater, compared to a substantial increase of 131.91% for 95 RON gasoline. The nitrogen content of grade 0 diesel fluctuated minimally owing to the stable carbazole compounds. The NA/TA ratio indicated weathering stability for crude oil (1.82–2.03) and gasoline (0.12–0.20 after day 3), establishing this metric as a reliable diagnostic indicator for identifying the type of oil spill, with a simpler sample preparation and shorter analysis time compared to traditional gas chromatography-mass spectrometry (GC/MS) methods. Among the other elements, the content of the metalloid silicon decreased rapidly on day 1 and stabilized thereafter. Calcium was detected at the highest concentration, and its relative concentration gradually increased with weathering. The concentration of vanadium in gasoline and diesel increased with the weathering time, whereas the chromium content of gasoline decreased, contrasting with the patterns for crude oil, owing to the refining processes. Correlation analysis revealed that the calcium content was positively correlated with the density, Sulfur (S), Nitrogen (N), NA/TA, and multiple metal elements in crude oil, whereas the vanadium content was negatively correlated with the density and several metals. These findings provide critical data for environmental remediation strategies and for enhancing oil spill traceability identification systems by incorporating non-hydrocarbon components as complementary diagnostic indicators.

Geological CO2 sequestration, while pivotal for climate mitigation, carries the inherent risk of leakage into surface ecosystems. To evaluate the potential impacts of CO2 leakage on changes in surface soil geochemical parameters and microbial processes, this study employed laboratory cultivation experiments. A control group and two CO2 treatment groups were established and continuously cultivated for 42 days. Sustained CO2 infusion induced a subtle yet discernible acidification, driving the soil pH into a narrow weakly alkaline range while promoting HCO3- accumulation. Under these conditions, the dynamic changes in various metal ions reflected the combined regulation of multiple transient adsorption and rebalancing processes at the solid-liquid interface. Metals such as Fe, Al, and Zn primarily redistributed among different non-residual forms, with no evidence of significant dissolution-release or reduction-migration processes. Microbial responses indicated that despite adjustments in some enzyme activities and metabolic processes, microbial community structure, diversity, and macro-functional pools (KEGG and CAZy) remained largely stable. Collectively, under the temporal scale and CO2 concentration conditions of this experiment, CO2 leakage primarily induces subtle responses in element migration and microbial metabolism by regulating soil solution chemistry and interfacial reactions. However, these effects are insufficient to cause significant restructuring of soil system structure and function. Our findings provide experimental evidence and insights into the geochemical buffering capacity and microbial response mechanisms of surface soil systems under potential leakage scenarios of underground CO2 storage. The findings offer scientific references for environmental risk assessment of CO2 geological sequestration and the selection and interpretation of long-term monitoring indicators.

Partially hydrolyzed polyacrylamide (HPAM), an ultrahigh-molecular-weight polymer widely present in enhanced oil recovery (EOR) wastewater, is highly resistant to conventional oxidation due to its chemically robust C–C backbone and extended chain architecture. In this study, we present a carbon-modified molybdenum disulfide (C-MoS2)-assisted Fe3 +/peroxymonosulfate (PMS) Fenton-like system specifically designed for the efficient oxidative degradation of HPAM. Structural characterization indicates that carbon modification partially converts 2H-MoS2 to the 1 T phase, increasing defect density and interfacial electron mobility. Compared with PMS alone or the Fe3+/PMS binary system, the C-MoS2/ Fe3+/PMS ternary system exhibits significantly enhanced activity, achieving rapid cleavage of both main and side chains of HPAM. Mechanistic studies using quenching experiments and electron paramagnetic resonance reveal that singlet oxygen (1O2) is the dominant reactive species, with SO₄•–, •OH, and •O2– contributing synergistically. The polymeric nature of HPAM dictates structure-dependent reactivity, resulting in degradation pathways distinct from those of small-molecule contaminants. The enhanced performance arises from the synergistic interplay between the carbon-modified electronic structure and catalytically active Mo centers, which accelerate PMS activation via the Fe3+/Fe2+ redox cycle and facilitate electron transfer along polymer chains. This work elucidates the challenges and mechanisms associated with high-molecular-weight polymer oxidation and provides a promising catalytic strategy for the effective abatement of polymeric organic pollutants in industrial wastewater.

Frequent oil spills necessitate advanced materials for complex oily wastewater remediation. Although wettability-engineered materials effectively remediate surface oil, single-wettability designs remain suboptimal in handling complex oil-water systems containing multi-component crude oil and surfactant-stabilized emulsions, primarily due to their functional inflexibility under dynamic and heterogeneous environments. Inversely inspired by the water-harvesting mechanism of the desert beetle, we designed a bioinspired oil-absorbing felt featuring hydrophilic-hydrophobic patterned surfaces that utilize hydrophilic sites on a hydrophobic matrix to selectively capture surfactant-coated oil droplets with hydrophilic shells from complex mixtures. This heterogeneous-wettability surface is constructed through the synergistic assembly of ZnO nanorod arrays and hydrophobic Zr-MOFs, followed by strategic UV irradiation to create spatially controlled wettability patterns. The obtained UV-MZβZ@PP demonstrates accelerated capture kinetics and superior oil retention toward multi-component crude oils, with enhanced adsorption capacity for common oils reaching 11.24–25.82 g/g. Notably, it exhibits remarkable performance in deconstructing surfactant-stabilized emulsions, achieving 66–76% total organic carbon (TOC) removal for oil-in-water types and a separation flux of 741.37 L·m−2·h−1·bar−1 with 99.42% efficiency for water-in-oil counterparts. This superiority stems from the patterned architecture, which overcomes diffusion barriers via synergistic capillary pressure gradients, enabling the interlaced hydrophilic-hydrophobic sites to function as selective traps that facilitate synergistic sequestration and accelerated interfacial coalescence of multifaceted droplets. Furthermore, the felt possesses the mechanical robustness, UV resistance, and thermal stability essential for rigorous field deployment. By extending separation capabilities from layered mixtures to complex emulsions, this work provides an efficient and innovative approach to oil spill remediation and industrial wastewater treatment.

Phase-selective organogelators (PSOGs) can selectively gel the oil phase in oil/water biphasic systems, demonstrating significant research value in organic solvent leakage and oil spill emergency response. In this study, N-cinnamoyl-6-dodecanoyl chitosan (L1.75C1CS) oil gelling agent was successfully prepared using natural biopolymer chitosan as the backbone through a two-step grafting modification process. The gelling mechanism of L1.75C1CS to form gels in solvents was investigated via UV-vis, FT-IR, and XRD. The experimental results showed that the formation of gel mainly depended on the synergistic effect of intermolecular hydrogen bonding, π-π stacking, and van der Waals force. At room temperature, L1.75C1CS exhibited critical gel concentrations ranging from 0.09 to 0.18 g/g in various oils and rapidly solidified high-viscosity crude oil within 2 min. It also exhibited excellent gelling performance at low temperatures, achieving over 80% of its optimal value. Meanwhile, the gel exhibited a maximum strain of 8.09%, which enabled it to effectively withstand a certain degree of environmental disturbance and created favorable conditions for the physical recovery of oil spills. To sum up, the powdered oil gelling agent preparation process developed in this work was energy-efficient, simple, and low-cost. The material has excellent phase selectivity and wide substrate applicability, demonstrating significant application potential in the field of marine oil spill emergency response.

River estuary interfaces are hotspots of terrestrial pollutant input and dynamic physicochemical gradient that can disrupt microbial-driven biogeochemical processes. This study uses multi-site (19 surface water sites and 2 sediment sites), seasonal 16S rRNA sequencing combined with comprehensive environmental monitoring to identify the key drivers and mechanisms by microbial community composition and functions restructure. Microbial alpha diversity in surface water and sediments was significantly higher (Student's t test, p < 0.05) in summer than in winter. Physical factors mainly influenced microbial communities in surface water during the winter, while chemical factors exerted a stronger impact during the summer. Proteobacteria was the dominant phylum in surface water during the winter, whereas Bacteroidota abundance increased prominently during the summer. In the case of sediment, the dominant bacteria included photosynthetic autotrophs such as Cyanobacteria and Chloroflexi during the winter, while heterotrophic degraders, including Bacteroidota and Actinobacteriota were more prevalent during the summer. Microbial communities in surface water and sediments during the winter tended to be photosynthetic or chemoautotrophic and perform basic organic mineralization functions. Microbes were characterized by chemical heterotrophy, denitrification, and sulfur cycle activities during the summer. Microbes synergistically degraded organic pollutants during the winter and participated in nitrogen removal during the summer. This study provides systematic data and analysis frameworks for revealing microbial ecological processes and biogeochemical cycling mechanisms in river estuary ecosystems.

Traditional chlorine-based disinfectants used in industrial circulating water systems, such as sodium hypochlorite (NaClO), suffer from poor stability, strong corrosiveness, weak biofilm removal capability and generate toxic environmental byproducts, creating an urgent need for more sustainable and environmentally compatible antimicrobial alternatives. Herein, chitosan quaternary ammonium salt/rhamnolipid composite nanoparticles (HACC/RL-NPs) were prepared via ionic cross-linking, representing a new strategy that combines the cationic antibacterial activity and good water solubility of HACC with the membrane-disruptive effect of RL. By optimizing the mass ratio between HACC and RL, the formulation denoted as H/R-2 exhibited the optimal comprehensive performance. Against Staphylococcus aureus and Escherichia coli, at MIC levels, H/R-2 achieved antibacterial rates exceeding 98% and biofilm inhibition rates up to 83.83% and 86.06%, significantly outperforming H-NPs. Its inhibitory activity against S. aureus and its antibiofilm performance against both strains were superior to those of NaClO. Dynamic light scattering revealed that RL incorporation reduced particle size and improved colloidal stability, indicating enhanced physicochemical properties of the composite. Furthermore, acute zebrafish toxicity tests confirmed that H/R-2 exhibited lower acute toxicity than NaClO. This work provides a novel, efficient and more sustainable HACC/RL composite antibacterial material for biofouling control in industrial water treatment and related applications.

Rapid expansion of carbon capture, utilization, and storage (CCUS) is increasing the need for publicly accessible environmental evidence that can support monitoring design, storage assurance, permitting, and post-closure oversight across diverse storage settings. Public records remain dispersed among controlled-release experiments, operating projects, natural analogues, incident datasets, project databases, and regulatory documents, and their combined suitability for cross-setting assessment has not been evaluated at global scale. We assembled 23 evidence modules, 223 events, 464 extracted metrics, and 1,110 project records to assess topical breadth, cross-module support, geographic public-evidence availability, and deployment-weighted monitoring and disclosure demand. The 16 × 99 module-dimension matrix contained 111 positive cells; 95 of 99 dimensions occurred at least once, but 80 were represented by only one module. Related terms were organized into 42 parent concepts, of which 13 depended on a single substantive module. Country-level demand was strongly associated with deployment pressure (Spearman ρ = 0.939), confirming that the index represents scale-dependent monitoring and disclosure workload rather than leakage probability or project safety. Public CCUS environmental evidence is broad in topic but uneven in cross-module support, analytical comparability, geographic availability, and transferability. The greatest gains for monitoring and storage assurance would come from comparable measurements across contrasting settings, longer public time series, and reporting that preserves site context, baseline and recovery information, analytical quality, and data-access conditions.

Hydrolyzed polyacrylamide stabilized oil-in-water emulsions are highly persistent because the polymer strengthens both continuous-phase rheology and the oil-water interfacial film, making demulsification difficult in polymer-flooding produced liquids. Here, an hydrolyzed polyacrylamide degrading bacterium, Delftia lacustris EPDB-8, was isolated, and its ability to destabilize hydrolyzed polyacrylamide-containing emulsions was investigated from molecular, bulk rheological, and interfacial perspectives. EPDB-8 effectively degraded HPAM, causing marked reductions in total organic carbon, total nitrogen, absolute zeta potential, and polymer molecular weight, with an approximately 63-fold decrease after 7 days. SEM, FT-IR, and GPC analyses showed that biodegradation proceeded through deamidation and random chain scission, collapsing the polymer network and generating low-molecular-weight fragments. Driven by bacterial hydrolyzed polyacrylamide degradation, these structural alterations disrupted the viscoelastic composite interfacial film formed by hydrolyzed polyacrylamide and indigenous surface-active species, directly causing emulsion stabilization to shift from polymer-assisted viscous and steric protection to a less effective asphaltene-dominated interfacial structure and thereby accelerating droplet aggregation, coalescence, and phase separation. Although bacterial cells exerted a transient particle-assisted interfacial effect, long-term emulsion stability remained governed by polymer integrity. This study establishes a mechanistic link between hydrolyzed polyacrylamide biodegradation and the rheological and interfacial evolution governing emulsion breakdown, providing a cost-effective and environmentally benign biological strategy for demulsification and treatment of polymer-flooding produced water. These findings offer practical guidance for the design of microbial-based produced-water treatment systems and contribute to the sustainable management of oilfield wastewater generated during enhanced oil recovery operations.

Oil-adsorbing materials with photothermal conversion serves as an important strategy for viscous crude oil spill cleanup, yet the application of conventional photothermal adsorbents is greatly limited by the instability of natural light irradiation. In this study, a novel type of aerogel-based adsorbent with efficient photothermal conversion and energy storage ability (Paraffin@PDMS/Fe/GCA) was fabricated through simple ambient drying strategy. Paraffin@PDMS/Fe/GCA was constructed by natural graphite flakes and cellulose nanofibrils (CNF), and then paraffin was encapsulated as phase change materials (PCM) to realize the energy storge and release. The complexation between Fe3+ ions and the surface groups of CNF (-OH and -COOH) contributes to the stability of the 3D structure, which not only enables effective PCM encapsulation, but also resists capillary forces during the ambient drying process. This study achieves the preparation of aerogel-based phase change composites through simple ambient drying. The resulting Paraffin@PDMS/Fe/GCA exhibits remarkable photothermal performance, reaching a steady-state temperature of 77 degrees C under 100 mW/cm2 irradiation, and demonstrates a high adsorption capacity for viscous crude oil. Importantly, by releasing the stored heat by paraffin, it can clean up crude oil spills on the low temperature seawater surface (near 0 degrees C) or under conditions of intermittent sunlight. The crude oil recovery rate of Paraffin@PDMS/Fe/GCA was 1.61 times higher than that of PDMS/Fe/GCA after two cycles of turning on and off the lights. This novel photothermal adsorbent can be produced on a large scale, and avoid the use of expensive photothermal materials, demonstrating unique advantages in the remediation of crude oil spills.

Partially hydrolyzed polyacrylamide (HPAM), an ultrahigh-molecular-weight polymer widely present in enhanced oil recovery (EOR) wastewater, is highly resistant to conventional oxidation due to its chemically robust C–C backbone and extended chain architecture. In this study, we present a carbon-doped molybdenum disulfide (C-MoS2)-assisted Fe3+/peroxymonosulfate (PMS) Fenton-like system specifically designed for the efficient oxidative degradation of HPAM. Structural characterization indicates that carbon doping partially converts 2H-MoS2 to the 1T phase, increasing defect density and interfacial electron mobility. Compared with PMS alone or the Fe3+/PMS binary system, the C-MoS2/ Fe3+/PMS ternary system exhibits significantly enhanced activity, achieving rapid cleavage of both main and side chains of HPAM. Mechanistic studies using quenching experiments and electron paramagnetic resonance reveal that singlet oxygen (1O2) is the dominant reactive species, with SO₄•–, •OH, and O2– contributing synergistically. The polymeric nature of HPAM dictates structure-dependent reactivity, resulting in degradation pathways distinct from those of small-molecule contaminants. The enhanced performance arises from the synergistic interplay between the carbon-modified electronic structure and catalytically active Mo centers, which accelerate PMS activation via the Fe3+/Fe2+ redox cycle and facilitate electron transfer along polymer chains. This work elucidates the challenges and mechanisms associated with high-molecular-weight polymer oxidation and provides a promising catalytic strategy for the effective abatement of polymeric organic pollutants in industrial wastewater.

Rhamnolipids are attractive biosurfactants for enhanced oil recovery, but the commonly used producing strains may raise biosafety concerns. In this study, a rhamnolipid-producing isolate, designated Bacillus sp. DQ-4, was obtained from oily sludge and cultivated in a glucose-based fermentation medium. The purified product, DQ-Rha, was characterized by TLC, FTIR, MALDI-TOF MS, and 1D/2D NMR (1H, 13C, 1H-1H COSY, 1H-13C HSQC, and HMBC). The combined spectroscopic results were consistent with a rhamnolipid structure, and no obvious conflicting signals were detected. DQ-Rha reduced the surface tension to 33.4 mN/m, and the DQ-4 supernatant showed an oil-spreading diameter of 89.3 mm and an emulsification index of 72.3% against diesel. In oil-displacement-related evaluations, DQ-Rha gave an oil-washing efficiency of 54.62%. In etched micromodel experiments, the total recovery factor reached 60.06%, which was comparable to that of commercial rhamnolipid (59.53%). In core flooding experiments at 85°C, injection of DQ-Rha after primary water flooding further increased the recovery factor by 10.56%, again showing performance comparable to commercial rhamnolipid. Acute oral toxicity testing in ICR mice showed no mortality or obvious toxic symptoms at 5040.6 mg/kg, and the acute oral LD50 was greater than 5000 mg/kg under the test conditions. These results suggested that DQ-Rha was a rhamnolipid biosurfactant with favorable oil-displacement-related performance and low acute oral toxicity.

Methane released from the subseafloor is significantly attenuated during upward migration, yet the preservation of methane-derived organic carbon (OC) in global deep-sea sediments remains poorly understood. Here, we measured carbon isotopes coupled with temperature-ramped analyses on various methane seepage sediments. Our results reveal a correlation between the radiocarbon (14C) content in deep-sea surface sediments and sulfate-methane transition depth. Notably, our findings suggest that a substantial amount of 14C-depleted OC may originate from deep-seated methane and is efficiently preserved in surface seepage sediments. We propose that the efficient OC preservation is related to microbial-mediated aggregate formation at the seawater-sediment interface, where physical occlusion within coarse-grained matrices reduces oxygen availability and enhances OC stability. We estimate that at least 6 Tg C of methane-derived OC are preserved annually in surface sediments of the global continental slopes. This process may play a non-negligible role in OC preservation in sediments, reducing methane emission into the atmosphere.