The evaluation of energy efficiency in wastewater treatment plants (WWTPs) is essential for improving operational management, reducing energy consumption, and mitigating emissions. In this study, the energy efficiency of WWTPs in Jiangsu Province, China, was assessed using three-stage data envelopment analysis (DEA), and the results were compared with those from other provinces. Tobit regression analysis was also performed to explore the key factors affecting energy efficiency. The results revealed that energy efficiency in Jiangsu’s WWTPs was generally at a low level (< 0.26), with only two plants achieving an efficiency score of 1. Scale efficiency was at a relatively high level (> 0.69), but technical efficiency was at a lower level (> 0.33), contributing to the low level of overall efficiency. Compared with the other provinces, Jiangsu (0.241) exhibited moderate performance, with Zhejiang (0.403) and Shanghai (0.387) ranking higher, while Yunnan had the lowest (0.208). Factors influencing efficiency included technology type, treatment volume, plant age, and pollutant removal rate. Anaerobic–anoxic–oxic technology had a moderate level of efficiency but was less effective than were rotating biological contactors and anaerobic–oxic technologies. Energy efficiency levels decreased with increasing treatment scale and plant age but improved with increasing pollutant removal rates in plants meeting the Class I-B standard. This study provides a novel application of three-stage DEA in evaluating the energy efficiency of WWTPs and offers valuable insights to support more energy-efficient operational and management practices.

Anaerobic digestion (AD) is widely considered an effective approach for the treatment of food waste (FW). However, the diversity of antibiotic resistance genes (ARGs) in FW, together with ARG dynamics and their interactions with prokaryotes and DNA viruses during AD, remain insufficiently explored. This study performed metagenomic analyses of FW and digestate samples collected from 9 centralized biogas plants. The results showed that FW served as an important reservoir of ARGs. Although the distribution patterns of ARGs in FW and digestate differed, MLS, multidrug, tetracycline, aminoglycoside, and bacitracin were the five most abundant ARG types in both FW and digestate. While AD reduced the overall quantity of ARGs, its capacity to markedly decrease ARG abundance was limited. Procrustes analysis revealed associations between ARGs and prokaryotes and DNA viruses. Among the reconstructed prokaryotic metagenome-assembled genomes (180), 130 were identified as carrying ARGs. DNA viruses showed close associations with antibiotic-resistant bacteria (ARB), with viral-host relationships detected between 181 DNA viruses and 77 ARBs. Most of these viruses were temperate DNA viruses, which may indirectly influence ARG distribution by regulating ARB populations. Nevertheless, the contribution of DNA viruses to ARG dissemination appeared limited, given the small number of detected ARG-carrying viruses and the lack of high-risk ARGs.

Achieving carbon peak at the city level is crucial for China in the context of its carbon peaking and carbon neutrality goals. Here we established a framework based on MRIO and SDA to investigate the stages, pathways, and key driving factors associated with carbon peaking processes in four Chinese megacities from 2007 to 2017. Our result reveals three-stage evolutionary pathways for urban carbon peaking. In the early stage, declining energy intensity is the main driver of emission reductions, while energy structure changes have limited effects. From 2012 to 2017, lower energy intensity cut emissions by 35.2 Mt in Beijing, 89.4 Mt in Tianjin, 97.5 Mt in Shanghai, and 72.9 Mt in Chongqing. As efficiency gains diminished, accelerating energy structure adjustment toward cleaner energy became crucial, further reducing emissions by 8.2 Mt in Beijing, 5.3 Mt in Tianjin, and 2.9 Mt in Chongqing. The second stage is characterized by industrial transfer, revealing three interregional transfer patterns: emissions-only shifts, simultaneous shifts of emissions and economic benefits, and limited outsourcing. However, this spatial redistribution alone fails to address carbon challenges fundamentally. Consequently, transferring regions must pursue industrial upgrading, marking the third stage, which is dominated by the structural transformation of industries. The transition from traditional manufacturing to strategic emerging manufacturing and services not only reduces total carbon emissions but also enhances economic benefits and job opportunities. The three-stage pathway identified in this study provides valuable guidance for achieving carbon peak at both city and national levels in China.

High molecular weight disinfection byproducts (HMW DBPs, MW > 500 Da) significantly contribute to drinking water toxicity yet remain inadequately characterized. This study provides a comprehensive perspective on HMW DBPs through a systematically optimized size exclusion chromatography with diode array detection, fluorescence detection and organic carbon (SEC-DAD-FLD-OCD) approach, enabling a holistic mapping of their multi-dimensional evolution. Results showed chlorination induced oxidative fragmentation of humic substances (HS, 1.2–5 kDa) into building blocks (BB, 0.45–1.2 kDa) and low molecular weight substances (LMWS, < 0.45 kDa). In real drinking water samples, distinct protein-like fluorescence indicated nitrogenous or microbial precursors absent in simulated samples. Parallel factor analysis (PARAFAC) of SEC-DAD chromatograms identified four components: C1 (100–800 Da) correlated with fast-forming LMWS/BB; C2 (800–1200 Da) as BB intermediates; C3 (1.2–4 kDa) and C4 (2–5 kDa) representing persistent HS precursors. Two-dimensional correlation spectroscopy (2D-COS) revealed the relative formation rates followed the order: fulvic-like acids > LMWS > 0 > humic-like acids > BB. Integrated chromatographic peak areas demonstrated rapid HS degradation (52.7% reduction) and LMWS accumulation (117% increase), alongside significant protein-like material accumulation (450%) after 72 h chlorination. This work established SEC-DAD-FLD-OCD as a robust platform for characterizing HMW DBPs, supporting improved water treatment strategies.

As a vital atmospheric halogen, gaseous hydrochloric acid (HCl) exerts a key influence on various physicochemical processes, particularly in coastal regions. Sea-Land Breeze (SLB) is a common local mesoscale circulation in coastal area that alters local weather conditions and further affects the diffusion and transport of air pollutants. However, the fate of HCl under SLB circulation remains poorly understood, which hinders a comprehensive understanding of coastal halogen chemistry and its associated atmospheric impacts. Here, a measurement campaign conducted in Xiamen, China, during winter 2023 revealed substantial levels of gaseous HCl, with concentrations ranging from 3.9 ppt to 290.4 ppt. Average HCl concentrations were 102.2 ppt and 71.4 ppt under SLB and non-SLB (NSLB) conditions, respectively. The integration of field observations and machine learning methods indicated that gas-particle partitioning could be a key driver of elevated HCl levels. In addition, high RH and abundant particulate nitrate concentrations on SLB days were the dominant factors affecting the HCl formation and reactions between HCl and OH radicals generated atomic chlorine at significant rates, up to 3.6×10³ molecules/(cm³·s). The potential adverse health effects from chlorine-containing oxygenated organic molecules (Cl-OOMs) were greater under SLB conditions than on NSLB days. The observed elevation in HCl concentrations through sea-land air exchange can indicate an important chlorine cycling pathway in the coastal urban environment, further explaining the potential influence of chlorine chemistry on atmospheric oxidizing capacity and health effects in coastal cities.

Small marine trash fish are widely consumed and used in aquaculture feed in Bangladesh. However, microplastic (MP) contamination in these species remains poorly quantified, limiting understanding of risks to food safety and aquaculture sustainability. This study aimed to quantify MPs in 10 prevalent trash fish from the eastern coast of Bangladesh, assess exposure risks to human health, and infer their potential role in transferring MPs to aquaculture via fishmeal. In this study, MP abundance was highest in Cynoglossus arel (muscle: 2.00 ± 0.25 MPs/g; gastrointestinal tract (GIT): 5.00 ± 0.29 MPs/g) and lowest in Escualosa thoracata (muscle: 0.33 ± 0.14 MPs/g; GIT: 0.20 ± 0.06 MPs/g). Fibers dominated across all species, accounting for 76.91%–100% in muscle and 100% in several GIT samples, with most particles < 0.5 mm. The predominant polymers were PE (32%), PET (24%), and PP (18%), largely originating from textiles, packaging, and fishing gear, with species-specific patterns. Risk assessment using the Contamination Factor (CF), Pollution Load Index (PLI), and Polymer Hazard Index (PHI) indicated moderate environmental contamination (PLI: 1.32–1.84). Polymer-associated risks were moderate to high (PHI: 122.6–187.3; Potential Risk Index: 268.5–402.1), with the highest PHI recorded in species dominated by PET and polystyrene. Notably, Eupleurogrammus muticus and Otolithoides pama present considerable ecological and health risks to humans. Direct consumption of these fishes or use in fishmeal production may facilitate the transfer of MP into seafood chain. Dietary exposure estimates were highest for children (3.12 items/kg bw/day) versus adults (1.08 items/kg bw/day), highlighting increased vulnerability in younger populations.

Propionate is a key intermediate in anaerobic digestion (AD), and its accumulation may lead to over-acidification and process failure. This study assessed methanogenic tolerance to increased propionate concentrations. The specific methane yield ranged from 238.0 to 277.3 mL/g COD at the initial propionate concentration of 2 to 10 g COD/L, and slightly decreased to 260.6 and 233.3 mL/g COD at 13 and 16 g COD/L, respectively. Kinetic analysis indicates lower inoculum-to-substrate ratio primarily negatively affected digestion time rather than accumulated methane yield. No clear inhibition occurred, even at 16 g COD/L, indicating a substantial propionate tolerance in AD. 16S rRNA gene analysis revealed that Desulfobacterota, particularly the family Syntrophobacteraceae was positively associated with propionate degradation, showing a linear correlation (p < 0.01) with both initial propionate concentration and digestion duration. Genome-centric metagenomic analysis further identified Bin.002 (Syntrophobacteraceae JABUEY01) and Bin.012 (Syntrophobacteraceae sp.) as dominant syntrophic populations, exhibiting high RPKM abundance and encoding the complete methylmalonyl-CoA (mmc) pathway. A metabolically diverse methanogenic community was also enriched, including aceticlastic Methanosarcina mazei (Bin.006), Methanothrix spp. (Bin.009 and Bin.014), and hydrogenotrophic Methanobacterium spp. (Bin.011 and Bin.026), which rapidly consumed metabolic intermediates, thereby avoiding inhibition at high propionate concentrations. Overall, the batch experiments demonstrated strong propionate tolerance under stable anaerobic conditions, supporting the conclusion that propionate accumulation is more likely a consequence rather than a primary cause of anaerobic reactor imbalance.

Biochar amendment has been proposed to enhance thermophilic anaerobic digestion (AD), yet the influence of biochar physicochemical properties on co-digestion performance and microbial restructuring remains unknown. In this study, three biochars derived from bamboo, hog manure, and hickory shell were evaluated during thermophilic (55 °C) co-digestion of food waste and waste activated sludge. Compared with the control (310.5 ± 7.6 mL CH₄ /g volatile solids), biochar supplementation significantly increased cumulative methane yield, with hickory shell biochar achieving the highest production (393.4 ± 9.8 mL CH₄ /g volatile solids), corresponding to a 26.7% increase. Kinetic analysis showed that biochar increased the maximum methane production rate by up to 34.6% and shortened the lag phase by approximately one-third. Propionate accumulation was suppressed with hickory shell biochar, accompanied by enhanced soluble chemical oxygen demand removal and improved pH buffering. Biochar particle-size variation at the millimeter scale had a negligible effect. Microbial analysis revealed enrichment of hydrolytic Clostridium_sensu_stricto_1 and versatile methanogens such as Methanosarcina and Methanoculleus in biochar-amended systems. Functional prediction indicated an increase in carbohydrate metabolism, acetate conversion (ackA, pta), and methanogenesis genes (mcrA/B/G). Overall, biochar enhanced thermophilic AD through coordinated improvements in hydrolysis, syntrophic metabolism, and methanogenic activity.

Reactive oxygen species (ROS) play a critical role in pollutant degradation. However, achieving efficient and sustainable catalytic systems for ROS generation remains a considerable challenge. In this study, we designed a crystalline-amorphous hybrid material (a-FeOOH-Cu⁰) for water decontamination via molecular oxygen activation. Characterization results indicated that a-FeOOH-Cu⁰ contained abundant low-valent copper species and exhibited electronic redistribution. These properties facilitated the direct cleavage of O−O bonds while bypassing the formation of *OOH intermediates, ultimately leading to a 1.44-fold and 2.91-fold increase in the concentrations of •OH and ¹O₂, respectively, compared to bulk Cu⁰. The abundant ROS significantly enhanced the removal of various organic contaminants (i.e., oxytetracycline, rhodamine B, bisphenol A). Further investigations identified ¹O₂ as the dominant ROS responsible for oxytetracycline degradation, with low-valent copper species serving as crucial active sites. Moreover, the a-FeOOH-Cu⁰ composite demonstrated high stability, good reusability, and strong resistance to matrix interference. This study highlights the potential of crystalline-amorphous hybrid materials in enhancing ROS production and provides a promising strategy for aquatic environmental remediation.

The high antibiotic levels in antibiotic fermentation residues (AFR) impede their disposal or resource recovery due to their recalcitrance and toxicity, limiting organic matter degradation and methane production efficiency. This study has investigated the effects of varying-valence iron nanoparticles (Fe NPs) on the anaerobic Co-digestion (Co-AD) process of AFR and waste activated sludge (WAS), focusing on methane production, resistance gene expression, virulence factors, and microbial community interactions. The incorporation of varying-valence Fe NPs enhanced methane yield, with Fe³⁺ NPs increasing it by approximately 1.46-fold, effectively improving the biodegradation of recalcitrant bacterial residue. Fe³⁺ NPs facilitated microbial Fe(III) reduction under anaerobic conditions, thereby supporting enhanced electron transfer, redox activity, and methanogenic metabolism in the Co-AD system as evidenced by a 40.2% increase in cytochrome C. Microbiological analysis revealed that Fe³⁺ NPs upregulate genes associated with methanogenesis (frh, pta, mtr, and fwd), improving electron transfer between Paraclostridium and Methanobacterium. Additionally, Fe NPs induced enrichment of resistance genes and virulence factors, indicating microbial stress from oxidative and membrane perturbations, whereas Fe³⁺ NPs showed markedly weaker effects, superior biocompatibility, and the highest methane production. Fe NPs also promoted microbial metabolic activity and biofilm formation, optimizing Co-AD efficiency. Importantly, Fe³⁺ NPs exhibited better biocompatibility, with lower lactate dehydrogenase (LDH) and superoxide dismutase (SOD) activities. By overcoming the limitations of conventional antibiotic fermentation residue treatment, this study highlights the potential of Fe NPs, particularly Fe³⁺ NPs, in enhancing anaerobic organics bio-methanation and provides new insights into energy-efficient recalcitrant and toxic organic waste treatment strategies.

Global water scarcity and the persistent threat of emerging organic contaminants demand advanced solutions for wastewater treatment. Metal-organic frameworks (MOFs), particularly water-stable zirconium-based metal organic frameworks (Zr-MOFs), offer exceptional promise due to their high surface areas, tunable pore architectures, and catalytic potential. Herein, we systematically investigate three representative Zr-MOFs, UiO-66, NH₂-UiO-66, and PCN-222, for the adsorption and solar-driven photocatalytic degradation of multiple high-risk pharmaceuticals and personal care products (PPCPs), especially towards halogenated organic compounds. Notably, porphyrinic ones demonstrate superior performance, attributed to their hierarchical mesoporous structure and unique porphyrinic linker. Comprehensive characterization was conducted to explore the reaction mechanism. Upon light irradiation, an efficient ligand-to-cluster charge transfer (LCCT) mechanism within PCN-222 facilitates spatial separation of electron-hole pairs and the generation of reactive oxygen species (¹O₂), driving efficient oxidative degradation of the adsorbed pollutants. This work provides an integrated adsorption–photocatalysis strategy using a series of robust Zr-MOFs for the effective removal of organic micropollutants in water.

The combined pollution of heavy metals and organics in agricultural soils has become a global environmental issue, threatening ecosystem health and agricultural product safety. Our previous study evidenced that exposure to combined pollutants of cadmium and neonicotinoid insecticides (Cd-NIs) can influence Cd accumulation in rice tissues through chelation interactions. However, their combined toxicity to rice metabolism and the underlying molecular mechanisms remain poorly understood. The field experiments demonstrated that three representative NIs, including imidacloprid, thiamethoxam, and clothianidin, significantly reduced the Cd accumulation in rice (Oryza sativa L.) grains (> 3.50% of single Cd) while increased NIs accumulation in leaves (up to 136.08 mg/kg). The increased NIs accumulation inhibited flavonoid metabolism in rice, leading to a significant decrease in flavonoid content (4.01%–9.67%), consequently weakening the antioxidant capacity of rice (4.44%–35.32%). Proteomics and RT-qPCR confirmed that Cd-NIs downregulated the expression of glutathione S-transferase (GST), multidrug and toxin extrusion (MATE), and ATP-binding cassette (ABC) transporters involved in flavonoid transport, with the most pronounced downregulation in ABC transporters. Phylogenetic analysis revealed that the differentially expressed ABC transporters were mainly enriched in the ABCG, ABCI, and ABCB subfamilies, with ABCG containing the most members (6) and the greatest downregulation (> 40%). Molecular simulation suggested that Cd-NIs may compete with flavonoids for binding to ABCG34, potentially diminishing flavonoid accumulation, thereby blocking flavonoid-mediated antioxidant pathways. This study revealed ABCG transporter competition as a novel mechanistic target mediating Cd-NIs-induced disruption of flavonoid metabolism, providing a critical theoretical basis for environmental risk assessment of combined pollutants.

Elucidating the spatiotemporal distribution of phytoplankton in reservoirs is crucial for both water supply security and the protection of riverine ecosystems. In this study, the spatiotemporal characteristics of phytoplankton community diversity in a typical deep, channel-type reservoir were investigated to quantify the contributions of top-down and bottom-up phytoplankton inputs to adjacent water layers and to identify key factors influencing diversity. The Shannon–Wiener and Margalef indices gradually increased from the main channel flowing into the reservoir to the surface water and then decreased toward deeper layers. The Fast Expectation–Maximization Microbial Source Tracking (FEAST) model was applied to quantify contributions from upstream phytoplankton to downstream communities and among different vertical layers within the reservoir. The results revealed that the bottom-up contribution rates of the phytoplankton communities in July, August, and January were significantly higher than the top-down contribution rates, which were driven primarily by increasing numbers of cyanobacteria, whereas the top-down contribution rates were associated with water column overturning. Significant distance-decay patterns of phytoplankton community similarity were observed in summer and autumn in the horizontal dimension and in all seasons except spring in the vertical dimension. Variation partitioning analysis revealed that spatial position exerted a substantially stronger influence on phytoplankton community diversity than nutrient concentration. Overall, this study highlights the source–sink dynamics of phytoplankton and indicates that spatial position is the primary driver of diversity, outweighing local environmental factors such as nutrient availability.

Water ecological environmental protection is undergoing a significant paradigm shift, moving beyond traditional pollution control to a more integrated approach that emphasizes the health of aquatic ecosystems. This process of orderly adaptation in response to uncertain stressors, termed authigenesis, represents a key scientific issue in the field. In this paper, the underlying processes of authigenesis, i.e., self-adaptation, self-balance, and self-recovery, which sustain the resilience of aquatic ecosystems, are explored. This study introduces the innovative concept of “emissions-accommodation synergy” and aims to achieve authigenesis by constructing a dynamic equilibrium between pollutant inputs and the capacity of water bodies to accommodate the pollutants. For the first time, this paper proposes a practical framework for achieving emission-accommodation synergy, focusing on four essential aspects: understanding the mechanisms of emission-accommodation cooperation, developing a multidimensional monitoring and assessment system, advancing innovative technologies for ecosystem management, and establishing intelligent management and control pathways. The study systematically explores water ecology authigenesis from the perspective of synergistic emission-accommodation, providing scientific pathways for ecological water restoration and offering a comprehensive and scientifically grounded approach for sustainable protection and restoration.