The increasing pollution of water sources by microplastics and cyanobacteria has promoted the formation of microplastic–cyanobacteria heteroaggregates, which can enter drinking water treatment plants. This study investigated the effects of these heteroaggregates on filtration and NaClO disinfection processes. The results showed that the interfacial interactions between microplastics and cyanobacteria increased cell membrane permeability by 19.9%–54.8% and augmented the malondialdehyde content of cyanobacteria from 9.8 nmol/mg to 46.5 nmol/mg. These interactions induced the release of intracellular substances and reduced the normalized membrane flux from 1.000 to 0.178 for microplastic–Oscillatoria heteroaggregates and from 1.000 to 0.124 for microplastic–Microcystis aeruginosa heteroaggregates. More severe membrane fouling caused by microplastic–M. aeruginosa heteroaggregates was attributed to the fact that unicellular M. aeruginosa led to more serious membrane pore blockage compared with filamentous Oscillatoria sp. After NaClO disinfection, water pollution caused by microplastic–cyanobacteria heteroaggregates became more severe than that caused by cyanobacteria alone. Specifically, the content of dissolved organic carbon increased from 7.5 mg/L to 25.2 mg/L for M. aeruginosa-containing systems and from 2.9 mg/L to 15.9 mg/L for Oscillatoria-containing systems. Meanwhile, the concentration of microcystins increased from 6.3 μg/L to 11.4 μg/L in M. aeruginosa systems, and the cylindrospermopsin concentration increased from 2.5 μg/L to 11.2 μg/L in Oscillatoria sp. systems. Furthermore, the levels of disinfection by-product formation potentials, especially the trichloronitromethane formation potential, in water containing microplastic–cyanobacteria heteroaggregates were higher than those in microplastic-free algal water. Therefore, drinking water treatment plants must fully consider the impact of microplastic–cyanobacteria heteroaggregates on filtration and disinfection processes.

The CaSO3/Fe(VI) system was demonstrated to efficiently degrade emerging contaminants under alkaline conditions. However, the integrated impacts of pH-driven mechanisms remain to be fully elucidated. The present study investigated the degradation of sulfonamide antibiotics (SAs) in both buffer solution (BS) and deionized water (DW) by conducting comparative experiments under varying pH conditions, evaluating the pH-driven degradation efficiency and mechanisms, and clarifying the integrated impacts of pH variations in the CaSO3/Fe(VI) system. The results indicated that pH significantly influenced the degradation performance and kinetics of the CaSO3/Fe(VI) system toward SAs, identifying neutral pH as the optimum condition. The dynamic increasing in pH in DW enhanced the oxidation capacity under acidic conditions. In neutral and alkaline conditions, Fe(V) was the primary active species, while alkaline conditions favored radical generation. Conversely, acidic conditions favored the formation of Fe(IV) as the predominant species. Furthermore, the active sites of SAs were identified, and degradation pathways were proposed, confirming that the process simultaneously achieves contaminant removal and toxicity reduction. In terms of engineering implications, the CaSO3/Fe(VI) system offers a highly competitive treatment cost of only 0.45 CNY/m3, while also reducing chemical dosage requirements in potential processes such as coagulation and disinfection. Moreover, the end products SO42- and Fe(III) both promote coagulation, demonstrating broad application potential. Such findings underscore the significance of pH in the CaSO3/Fe(VI) system, elucidate the integrated impacts of pH-driven mechanisms, and provide data support for engineering applications.

Nanofiltration (NF) is a key separation technology and reducing the energy consumption while improving the processing efficiency of NF membranes remains a central research objective. Microporous membranes are ideal support materials for NF because of their low mass-transfer resistance and high surface porosity. However, this same high porosity weakens the adhesion between the polyamide separation layer and the support. Under high shear, frequent chemical cleaning, or pressure shocks the interface can fail, compromising the long-term operational stability of the membrane. In this work, polyethyleneimine (PEI) was blended into the microporous support so that its surface-exposed amine groups could participate in the interfacial polymerization reaction and bond the separation layer to the support. The resulting interfacial anchoring, evidenced by an increase in the maximum tolerable back-flush pressure from 15 kPa to 96 kPa, markedly improves the interfacial adhesion and operational stability of the NF membrane. PEI modulates the distribution of piperazine (PIP) molecules in the aqueous phase and regulates the rate of the interfacial polymerization, membranes with a more uniform pore-size distribution were obtained. After optimization of the aqueous-phase composition, a high-performance NF membrane was achieved with a water permeance of 24.3 L m−2 h−1 bar−1, an Na2SO4 rejection of 99.3%, and a Li+/Mg2+ separation factor of 73.2. The as-prepared membrane combines higher salt rejection with a water permeance roughly 1.87 times that of the commercial NF270, which is expected to reduce the specific energy demand of the separation process at a given productivity. The proposed strategy offers a promising route toward high-performance NF membranes.

Most research on antibiotics in the environment disregards chiral antibiotics, such as ofloxacin (OF). In this study, tadpoles of Rana nigromaculata were exposed to 1 µg/L OF and levofloxacin (LVFX, an enantiomer of OF) for 75 d. Compared with dextrofloxacin, LVFX treatment had a greater effect on the inhibition of bodyweight, body length, development stage, and pathological liver damage. Therefore, OF exerts a stereoselective inhibitory effect on both growth and development, which is consistent with the results at the systemic metabolism level. Transcriptomic analysis revealed that the differentially expressed genes between OF and LVFX were mainly immune related. Targeted metabolomics showed that the stereoselective biological effect of OF on R. nigromaculata was caused by differences in contents of PE-O 16:0–22:4, PE 16:0–14:0, TAG 45:0–FA16:0, PE-P 18:0–16:0, PE 16:0–16:0, PC 16:0–22:4 + AcO, PE 18:1–18:3, PC 16:1–18:1 + AcO, and PC 18:1–18:3 + AcO. Furthermore, two enantiomers of OF were selectively bound to enzymes related to lipid metabolism. This study provides both theoretical and practical references for the accurate evaluation and scientific control of the ecological risk of chiral antibiotics.

Natural organic matter (NOM), prevalent in surface water, contributes to severe membrane fouling, which is a critical issue in ultrafiltration (UF) operations. This study proposed the use of ascorbic acid-activated hydrogen peroxide (AA/H2O2) as a pre-treatment strategy for ultrafiltration processes. The experiment assessed the membrane fouling characteristics of humic acid (HA), sodium alginate (SA), and bovine serum albumin (BSA) before and after AA/H2O2 treatment. The results showed that after 1 h of treatment, the final normalized flux of HA, SA, and BSA increased from 0.43, 0.12, and 0.76 to 0.64, 0.67, and 0.81, respectively, with a reduction of irreversible fouling. Interfacial free energy analysis revealed that the pre-treatment enhanced the repulsive interactions between foulants and the membrane, reducing the likelihood of foulants deposition on the membrane surface and delaying the accumulation of the filter cake layer. The oxidation process diminished fluorescent substances and decreased the particle size of foulants, thereby mitigating membrane fouling. The introduction of anions affected the system's oxidative capacity, while the introduction of cations altered the characteristics of the foulants, thereby influencing fouling mitigation efficiency. Additionally, pH was found to affect the system's oxidative capacity, and appropriate pH control improved the treatment effectiveness. Overall, the AA/H2O2 system exhibited an effective and environmentally friendly solution for addressing UF membrane fouling.

Iodinated contrast agents are widely detected in aquatic environments, raising concerns about their persistence, bioaccumulation, and the formation of iodinated disinfection byproducts. This study established a UV222/NaClO system to degrade iopamidol (IPM) as the target pollutant. The advantages and drawbacks of Far-UVC (UV222) in pollutant degradation were evaluated in comparison with low-pressure UV (UV254). Steady-state concentrations of reactive species and their contributions to the pseudo-first-order rate constant (kobs) were determined. Results indicated that the dichlorine radical (Cl2- center dot) played the predominant role in the degradation of IPM, contributing 41.76 % in the UV222/NaClO system, while ozone contributed only 7.72 %. Increasing NaClO concentrations enhanced the steady-state concentrations of reactive chlorine species (RCS) and their contributions to kobs, while neutral pH showed more efficient IPM removal. The presence of Cl- and HCO3- enhanced Cl2- center dot and CO3- center dot formation but inhibited overall degradation efficiency, while natural organic matter (NOM) primarily suppressed ClO center dot activity. Despite similar trends in free radical kinetics and oxidation products in both systems, UV222/NaClO achieved higher RCS conversion and lower acute toxicity to zebrafish, Chlorella, and Photobacterium phosphoreum, alongside reduced energy consumption. These findings demonstrate the potential of UV222/NaClO as an energyefficient alternative for removing iodinated contaminants, offering insights into advanced water treatment strategies.

Developing facile, on-site, and hand-held devices remains challenging for pyrethroids' residual detection in environmental waters and crops. Herein, we synthesized a fluorescent molecule, DTC, to determine pyrethroids via intermolecular interactions. Trifluoromethyl groups in DTC reduced water solubility and promoted dimer formation, and simultaneously diethylamino groups induced a stable twisted intramolecular charge transfer (TICT) state to quench DTC's intrinsic fluorescence. Specific binding between DTC and pyrethroids facilitated the transition from TICT to intramolecular charge transfer (ICT) states, disrupting dimers and recovering quenched fluorescence. Leveraging this, a dual-emitting fluoroprobe combining DTC with a water-soluble Eu-ICP was developed, enabling broad-spectrum and rapid quantification of six pyrethroids (15 s reaction time and detection limits of ∼61 nM). To minimize errors from hardware variations and smartphone-based operations, a fluorescence-visual transverter (FVT) was applied to enable hand-held rapid detection in the field and remote areas. Meanwhile, the environmental friendliness of the detection protocol was confirmed by studying the behavior and morphology of embryonic-larval zebrafish and performing an oxidative damage assessment. Thus, this satisfies the technological requirement for modern "green" analysis in routine environmental and food monitoring.

Chlorella blooms in water bodies caused by eutrophication can pose a potential membrane fouling problem for ultrafiltration. In this study, an innovative combination of far-ultraviolet light (Far-UVC) and permanganate (Mn (VII)) mild pre-oxidation was proposed to mitigate ultrafiltration membrane fouling primarily induced by Chlorella pollutants. With 30 min Far-UVC/Mn(VII) treatment, the final J/J0 surged by 0.65 compared with that of raw water, indicating a good improvement in flux, with Rr and Rir respectively decreased by 98.8 % and 76.8 %. The results of the model fitting showed that membrane fouling changed from complete clogging to the cake filtration stage, and the clogging of membrane pores was significantly reduced. Meanwhile, the increase in interfacial free energy also made it difficult for pollutants to adhere to the membrane surface. Mechanism analysis revealed that HO & sdot; and reactive manganese (RMnS, including Mn(III) and Mn(V)) produced during combined pretreatment fulfilled a vital role in the removal of algal foulants. In addition, in situ formation of MnO2 promoted the aggregation of algal cells, further reducing the fouling load. Under the electrostatic action of MnO2, the zeta potential of flocs declined from-21.1 mV to-4.7 mV, indicating a decrease in electrostatic repulsion, which could promote Chlorella cell aggregation. Simultaneously, the content of fluorescent components was also significantly reduced by the oxidation of HO & sdot; and RMnS. Far-UVC/Mn(VII) pretreatment maintained the integrity of Chlorella cells without causing significant damage, thereby preventing the release of intracellular organic matter and effectively reducing the accumulation of algal-related contaminants on the membrane surface. This work provides an effective way to alleviate membrane fouling induced by Chlorella-laden water and advances the practice of Far-UVC oxidation processes.

Fouling of ultrafiltration (UF) membranes by natural organic matter (NOM) remains a persistent challenge. Herein, far-ultraviolet (Far-UVC) photolysis of chlorine was developed as a pretreatment to solve the membrane fouling problem arising from NOM. The findings demonstrated that Far-UVC/NaClO pretreatment efficiently increased membrane flux while reducing reversible and irreversible fouling resistance by 80.0 % and 47.1 %, individually. Specifically, Cl•, ClO• and HO• were identified by quenching and probing experiments to play key roles in NOM degradation. Interfacial free energy analysis revealed that Far-UVC/NaClO pretreatment markedly enhanced the repulsive force between contaminant and membrane, thus reducing the tendency of membrane pore clogging. Through molecular-level reaction analysis, unsaturated and aromatic compound macromolecules were decomposed into small molecules, thus reducing membrane pore clogging. Mass difference analysis further revealed the degradation pathways of NOM, which mainly included decarboxylation, dealkylation, and oxygen addition reactions. Moreover, chlorine disinfection by-products (Cl-DBPs) such as trichloroacetic acid, dichloroacetic acid, chloral hydrate and trichloromethane were detected following post-chlorination. Subsequent UF process effectively reduced the formation of DBPs by 19.3-34.3 %. This study demonstrates the application potential of Far-UVC-based oxidation technology to mitigate membrane fouling resulting from NOM.

Dynamic membranes (DMs) can effectively mitigate ultrafiltration membrane fouling by forming a dynamic barrier layer. However, DMs still face challenges in balancing separation efficiency, antifouling capacity, and regeneration frequency during practical applications. Herein, we propose a novel catalytic DM synergistically integrated with sepiolite (SEP) and cobalt-copper layered double hydroxide (Co-Cu-LDH). The prepared membrane exhibited a three-dimensional (3D) fibrous SEP network integrated within the substrate membrane, embedding with a Co-Cu-LDH catalyst layer. This structure significantly enhanced peroxymonosulfate (PMS) activation, leading to the generation of hydroxyl radical, superoxide radical, sulfate radical and singlet oxygen species. The LDH-SEP DM/PMS system achieved superior performance in treating secondary effluent, removing 92.3 % of dissolved organic carbon. Due to the synergistic effect of foulant interception and catalytic oxidation, the LDH-SEP DM exhibited excellent antifouling performance. Following three cycles filtration of secondary effluent, the membrane flux dropped by only 10 %, with the flux recovery rate of 99 %. Membrane fouling mechanism has also been changed, and the formation of cake filtration was significantly delayed. Overall, this work not only advances the mechanistic understanding of PMS activation via Co-Cu-LDH, but also provides a scalable strategy for designing multifunctional membranes tailored for high-efficiency, low-maintenance water purification systems.

Silver nanoparticles (AgNPs) are extensively utilized for their antibacterial properties, leading to their release into the environment and subsequent bioaccumulation and biomagnification within the food chain. Polystyrene nanoplastics (PSNPs), as emerging pollutants, act as carriers for contaminants and alter their transformation processes. However, the toxicological effects and underlying mechanisms associated with the coexistence of these pollutants remain largely unexplored. Herein, the hepatotoxic effects and underlying mechanisms of acute combined exposure to PSNPs and AgNPs were explored using zebrafish as a model organism. After exposed to PSNPs and AgNPs, the larvae (120 hours post-fertilization) exhibited lipid metabolism disorders, increased oxidative stress, hepatomegaly, and liver dysfunction, with these effects being more pronounced than those observed with AgNPs exposure alone. This increase in hepatic toxicity may be due to the enhanced accumulation of AgNPs under combined exposure. Mechanistic investigations revealed that co-exposure led to a significant elevation in malondialdehyde and Fe2 + levels, a loss of mitochondrial cristae and a decrease in membrane potential, along with the abnormal expression of ferroptosis-related genes, which are hallmark indicators of ferroptosis. Furthermore, the introduction of the ferroptosis inhibitor deferoxamine alleviated all observed hepatotoxic phenotypes, thereby confirming that PS+AgNPs co-exposure induced liver injury through the ferroptosis pathway.

BACKGROUND:Micro/nanoplastics and silver nanoparticles (AgNPs) are emerging environmental contaminants widely detected in aquatic environments. However, previous research has primarily focused on the interactions between micro/nanoplastics and organic substances or heavy metals, whereas the interactions and combined toxic effects of micro/nanoplastics with AgNPs remain unclear. OBJECTIVE:Our study aimed to investigate the effects and mechanisms of coexposure to AgNPs and polystyrene micro/nanospheres (PS M/NPs) on the nervous system, comparing the toxicity of AgNPs alone and in combination with PS M/NPs in larval zebrafish. METHODS:We investigated the dynamics of AgNPs' (5 nm) adsorption onto PS M/NPs (5μm/100 nm) using inductively coupled plasma-mass spectrometry. Zebrafish larvae were coexposed to PS M/NPs (200μg/L) and AgNPs (10μg/L) from 6 h post fertilization (hpf) to 72 hpf to∼120 hpf to evaluate neuroinflammatory effects from multiple perspectives, including developmental abnormalities, oxidative stress, neurobehavioral differences, vascular development, immune responses, differences in gene expression, and differences upon neuroinflammation inhibitor addition. RESULTS:Adsorption experiments showed PS M/NPs could stably adsorb AgNPs, with higher adsorption in smaller particles. Zebrafish larvae exposed to combined PS M/NPs and AgNPs demonstrated neurodevelopmental abnormalities, including developmental malformations, lower levels of locomotor activity, delayed response, and abnormal neuronal development. In addition, exposed zebrafish also exhibited disrupted neurodevelopmental markers, including vascular and apoptotic indicators, and oxidative stress and neuroimmune responses. Quantitative real-time polymerase chain reaction analysis showed differences in gene expression within neurotoxic pathways in PS M/NPs and AgNPs-exposed zebrafish, focusing on key genes in immunity, apoptosis, vascular, and neural development. Furthermore, these neurotoxic effects induced by combined exposure were alleviated following the introduction of the neuroinflammation inhibitor curcumin. DISCUSSION:Our findings demonstrate that polystyrene nanospheres (PSNPs) intensified AgNPs-induced neurotoxicity in larval zebrafish, whereas polystyrene microspheres (PSMPs) had a lesser effect, indicating distinct gene regulation roles when combined with AgNPs. These findings enhance the assessment of environmental risks in settings with coexisting nanomaterials and microplastics, offering important insights for evaluating combined exposure risks. https://doi.org/10.1289/EHP14873.

Microplastics are prevalent in municipal wastewater, posing risks to health and the environment. When treated by an algal-bacterial consortium, microplastics interact with organic matter and microorganisms to form heteroaggregates, impacting treatment efficacy. In our study, particle size significantly influenced microplastic behavior within the consortium. Smaller microplastics (25PS) caused oxidative cell damage, formed compact heteroaggregates with strong shading effects, inhibited microbial proliferation, and increased effluent organic content due to the release of intracellular substances. In contrast, larger microplastics (100PS) formed weaker heteroaggregates and primarily affected organic matter adsorption, reducing effluent organic content. Notably, 100PS upregulated K01915 expression in Chlorella, enhancing nitrogenous organic matter degradation, while 25PS suppressed K01915 and key carbon metabolism genes (K00626, K00382, K00627, K00058, K00873, K00615), impairing organic carbon hydrolysis. During sludge separation, microplastic heteroaggregates improved sludge settling efficiency, with smaller particles settling faster. However, microplastics, irrespective of size, increased solids in sludge or supernatant, complicating sludge treatment and elevating ecological risks associated with effluent.

Toxic blooms of benthic cyanobacteria greatly threaten freshwater ecological health and drinking water safety. Meanwhile, microplastic pollution is becoming increasingly severe and microplastics accumulate in large quantities at the bottom of lakes and rivers, widely coexisting with algae. However, impacts of microplastics on benthic cyanobacteria are still unknown. This study investigated effects of microplastic polyethylene terephthalate (PET) - which is commonly found at the bottom of lakes and rivers - and its leachate at environmentally relevant concentration (0.3 mg/L) and high exposure concentration (3.0 mg/L) on typical benthic cyanobacteria (Oscillatoria sp. and Pseudanabaena sp.), and clarified the related molecular mechanisms through transcriptomic analysis. Results show that PET or PET leachate (PET-L) can promote benthic cyanobacterial growth and promotive effect of PET-L is more obvious than that of PET system. Promotion effect of PET or PET-L is more significant at environmentally relevant concentration (39-63 % increase compared with the control) compared with high exposure concentration (21-58 % increase compared with the control). In the presence of PET or PET-L, due to an increase in the number of cyanobacterial cells, concentrations of harmful metabolites (cylindrospermopsin, geosmin, and 2-methylisoborneol) in water also increased. Although PET particles may not be conducive to benthic cyanobacterial growth due to shading effect and mechanical damage, photosynthetic efficiency of algae was improved and dysregulated genes related to photosynthesis and extracellular transport of glycolipid were upregulated according to transcriptome analysis. Moreover, PET decomposition components, such as terephthalic acid and ethylene glycol, may be able to serve as carbon sources for cyanobacterial growth. Upregulation of genes associated with glycolysis, oxidative phosphorylation, and translation revealed that PET can promote the growth of benthic cyanobacteria. This study has important value in evaluating the impact of benthic cyanobacteria on aquatic ecological health and drinking water safety with the coexistence of microplastics.

Tannery wastewater presents a significant challenge for biological treatment due to its high concentrations of nitrogen and sulfide. Conventional heterotrophic denitrification is often limited by the requirement for costly organic carbon supplementation. This study demonstrates efficient nitrogen removal from authentic tannery wastewater without external carbon input, achieved under synergistic mixotrophic conditions. Integrated multi-omics analyses revealed sulfur autotrophic denitrification (SADN) as the primary nitrogen removal pathway. Concurrently, endogenous heterotrophs (e.g., Bacteroidota) degraded inherent organic matter, contributing to chemical oxygen demand (COD) removal. By integrating multi-omics analyses (16S rRNA sequencing, metagenomics, and metaproteomics), we uncovered the underlying microbial synergy. The process was facilitated by a succession of functional microorganisms, predominantly Proteobacteria and Bacteroidota, which facilitated simultaneous sulfur oxidation and organic matter degradation. We identified a complete enzymatic electron transfer chain, coupling sulfur oxidation with denitrification, which was strongly supported by the co-expression of key relevant genes and the high abundance of their corresponding core enzymes. This microbial synergy resulted in a substantially enhanced total nitrogen removal rate without any organic carbon input, alongside a notable reduction in chemical oxygen demand and accumulation of sulfate. Furthermore, bioaugmentation with sulfur-metabolizing consortia improved system stability, and the recycling of sulfur fillers significantly reduced operating costs compared to conventional heterotrophic processes. This work establishes SADN as a sustainable and cost-effective strategy for advanced tannery wastewater treatment, with future research directed at elucidating the impact of salinity on the functional microbial community. The revealed synergistic mixotrophic metabolism, where autotrophic denitrifiers and endogenous heterotrophs synergistically remove nitrogen and organic carbon, provides a carbon-efficient treatment strategy that eliminates the need for external carbon input.

Zebrafish are widely used not only as a model in ecotoxicology but also to study the potential impact of chemicals on human health. Typically, zebrafish are exposed to chemicals dissolved in egg water or other defined media, which is the standard routine for ecotoxicology testing. This straightforward exposure method is usually also employed to monitor adverse effects in zebrafish to predict potential hazards and modes of action in humans. Here, we compared different exposure media and studied the impact of salinity and solvents relevant to ecotoxicity testing. For comparison, toxicants also were directly injected into the bloodstream of zebrafish embryos, as this method better simulates the exposure scenario for assessing the adverse effects of drugs administered intravenously to patients. As model compounds we studied platinum-based anticancer drugs, which are known micropollutants, but also lead to severe side effects in humans. Striking differences in sensitivity and phenotypes, i.e. adverse outcomes, were observed dependent on the exposure route and media. The bioavailability of the platinum compounds was significantly altered in the different media and by the commonly used solvent DMSO. These findings highlight the relevance of the exposure route and media as well as of solvents to be considered when interpreting zebrafish studies in the field of ecotoxicology or in cross-species comparisons to predict effects on human health.

A comprehensive monitoring and risk assessment of arsenic (As) pollution concerning surface water and sediment is performed in the Jie River basin, where gold smelting enterprises are concentrated. The study area is divide into six regions, labeled as A, B, C, D, E, and F, from sewage outlets to downstream. Results shows that with far away from the sewage outlets, the total As concentrations in water and sediment gradually decrease from regions A to F. However, in region F, the concentration of bioavailable As significantly increases in the sediment due to the higher pH, leading to the transformation of As(V) into more mobile As(III). In sediment, Paracladius sp. exhibits strong resistance to As pollution in sediment, which can potentially elevate the risk of disease transmission. In water bodies, diatoms and euglena are the main phytoplankton in the Jie River while toxic cyanobacteria exhibits lower resistance to As pollution. Overall, measures should be taken to ecologically remediate the sediment in downstream while implementing appropriate isolation methods to prevent the spread of highly contaminated sediments from regions near sewage outlets.

The immobilization of phosphorus (P) in sediments plays a pivotal role in managing lake eutrophication over the long term. Therefore, key factors that may cause uncertainties in P fixation are of increasing interest to researchers. Calcium‑aluminum composites (CA) can passivate sediment P well; however, the effect of cyanobacterial bloom decline on their sediment P remediation remains unclear. In this study, CA addition significantly reduced P equilibrium concentration as well as augmented P adsorption capacity of sediment characterized as cyanobacterial dominance zone (CDZ). The results of the simulated experiments on cyanobacterial bloom decline indicated that the algae decomposition led to a rapid decrease in dissolved oxygen (DO) level, and to release amounts of P, thus increasing the P concentration in the overlying water. The released algal P into the sediment primarily encouraged the formation of iron-bound phosphorus (Fe-P), followed by calcium-bound phosphorus (Ca-P). The subsequent anaerobic incubation led to a notable release of the newly formed Fe-P, strengthening the anaerobic P release from sediments. Conversely, CA-capping accelerated the adsorption of algal P by sediments, and promoted the formation of Ca-P in sediment from cyanobacterial P, hindering the generation of reactive Fe-P. Moreover, during subsequent anaerobic incubation, the P forms in sediments capped with CA remained stable, showing no obvious P release. These findings suggested that CA capping induced the formation of stable P from algal P and disrupted the positive feedback effect between P contamination in sediments and cyanobacterial blooms, which would provide valuable insights for the remediation of sediments in CDZ.

Microplastic hetero-aggregates are stable forms of microplastics in the aqueous environment. However, when disinfecting water containing microplastic hetero-aggregates, the response of them in water to different oxidizing agents and the effect on water quality have not been reported. Our results showed that Ca(ClO)2, K2S2O8, and sodium percarbonate (SPC) treatment could lead to the disaggregation of microplastic hetero-aggregates as well as a rise in cell membrane permeability, which caused a large amount of organic matter to be released. When the amount of oxidant dosing is insufficient, the oxidant cannot completely degrade the released organic matter, resulting in DOC, DTN, DTP and other indicators being higher than before oxidation, thus causing secondary pollution of the water body. In comparison, K2FeO4 can purify the water body stably without destroying the microplastic hetero-aggregates, but it only weakly inhibits the toxic cyanobacteria Microcystis and Pseudanabaena, which may cause cyanobacterial bloom as well as algal toxin and odorant contamination in practical application. Compared with the other oxidizers, K2S2O8 provides better inhibition of toxic cyanobacteria and has better ecological safety. Therefore, when treating microplastic-containing water bodies, we should consider both water purification and ecological safety, and select appropriate oxidant types and dosages to optimize the water treatment.