Polyhydroxybutyrate Plastics Show Rapid Disintegration and More Straightforward Biogeochemical Impacts than Polyethylene under Marine Biofragmentation.

Although massive studies have investigated the spatiotemporally occurring marine plastisphere, a new microbial ecosystem colonizing the surfaces of plastics, the resulting biofragmentation process and impacts of plastics on biogeochemical cycles remain largely unknown. Here, we leverage synchrotron-based Fourier transform infrared spectromicroscopy (FTIR mapping) and metagenomic sequencing to explore independent marine microcosms amended with petroleum-based polyethylene (PE) and biobased polyhydroxybutyrate (PHB) plastic films. FTIR mapping results demonstrate unequal fragmentation scenarios by which the PE plastic rarely releases oxidized fragments while PHB disintegrates quickly, gradually forming fragments composed of extracellular polymeric substances resembling plastic films. Metagenomic analysis shows the critical role of hydrocarbonoclastic lineages in the biodegradation of the two plastics by the fatty acid degradation pathway, where the PE plastics host different microbial trajectories between the plastisphere (dominated by Alcanivorax) and surrounding seawater. In contrast, the PHB addition demonstrates decreased microbial richness and diversity, consistent community composition (dominated by Phaeobacter and Marinobacter), and apparently stimulated sulfur cycle and denitrification pathways in both the plastisphere and surrounding seawater. Our study gives scientific evidence on the marine biotic processes distinguishing petroleum- and biobased plastics, highlighting marine PHB input exerting straightforward impacts on the water phase and deserving critical management practices.

High-speed eye tracking based on a synchronized imaging mechanism by a dual-ring infrared lighting source.

It is a challenge for conventional monocular-camera single-light source eye-tracking methods to achieve high-speed eye tracking. In this work, a dual-ring infrared lighting source was designed to achieve bright and dark pupils in high speed. The eye-tracking method used a dual-ring infrared lighting source and synchronized triggers for the even and odd camera frames to capture bright and dark pupils. A pupillary corneal reflex was calculated by the center coordinates of the Purkinje spot and the pupil. A map function was established to map the relationship between the pupillary corneal reflex and gaze spots. The gaze coordinate was calculated based on the mapping function. The average detection time of each gaze spot was 3.76 ms.

Metagenomic and Metatranscriptomic Responses of Chemical Dispersant Application during a Marine Dilbit Spill.

The global increase in marine transportation of dilbit (diluted bitumen) can increase the risk of spills, and the application of chemical dispersants remains a common response practice in spill events. To reliably evaluate dispersant effects on dilbit biodegradation over time, we set large-scale (1,500 mL) microcosms without nutrient addition using a low dilbit concentration (30 ppm). Shotgun metagenomics and metatranscriptomics were deployed to investigate microbial community responses to naturally and chemically dispersed dilbit. We found that the large-scale microcosms could produce more reproducible community trajectories than small-scale (250 mL) ones based on the 16S rRNA gene amplicon sequencing. In the early-stage large-scale microcosms, multiple genera were involved in the biodegradation of dilbit, while dispersant addition enriched primarily Alteromonas and competed for the utilization of dilbit, causing depressed degradation of aromatics. The metatranscriptomic-based metagenome-assembled genomes (MAG) further elucidated early-stage microbial antioxidation mechanism, which showed that dispersant addition triggered the increased expression of the antioxidation process genes of Alteromonas species. Differently, in the late stage, the microbial communities showed high diversity and richness and similar compositions and metabolic functions regardless of dispersant addition, indicating that the biotransformation of remaining compounds can occur within the post-oil communities. These findings can guide future microcosm studies and the application of chemical dispersants for responding to a marine dilbit spill. IMPORTANCE In this study, we employed microcosms to study the effects of marine dilbit spill and dispersant application on microbial community dynamics over time. We evaluated the impacts of microcosm scale and found that increasing the scale is beneficial for reducing community stochasticity, especially in the late stage of biodegradation. We observed that dispersant application suppressed aromatics biodegradation in the early stage (6 days), whereas exerting insignificant effects in the late stage (50 days), from both substance removal and metagenomic/metatranscriptomic perspectives. We further found that Alteromonas species are vital for the early-stage chemically dispersed oil biodegradation and clarified their degradation and antioxidation mechanisms. These findings help us to better understand microcosm studies and microbial roles for biodegrading dilbit and chemically dispersed dilbit and suggest that dispersant evaluation in large-scale systems and even through field trails would be more realistic after marine oil spill response.

Transcriptomics and metabolomics of engineered Synechococcus elongatus during photomixotrophic growth.

BACKGROUND: Converting carbon dioxide (CO2) into value-added chemicals using engineered cyanobacteria is a promising strategy to tackle the global warming and energy shortage issues. However, most cyanobacteria are autotrophic and use CO2 as a sole carbon source, which makes it hard to compete with heterotrophic hosts in either growth or productivity. One strategy to overcome this bottleneck is to introduce sugar utilization pathways to enable photomixotrophic growth with CO2 and sugar (e.g., glucose and xylose). Advances in engineering mixotrophic cyanobacteria have been obtained, while a systematic interrogation of these engineered strains is missing. This work aimed to fill the gap at omics level. RESULTS: We first constructed two engineered Synechococcus elongatus YQ2-gal and YQ3-xyl capable of utilizing glucose and xylose, respectively. To investigate the metabolic mechanism, transcriptomic and metabolomic analysis were then performed in the engineered photomixotrophic strains YQ2-gal and YQ3-xyl. Transcriptome and metabolome of wild-type S. elongatus were set as baselines. Increased abundance of metabolites in glycolysis or pentose phosphate pathway indicated that efficient sugar utilization significantly enhanced carbon flux in S. elongatus as expected. However, carbon flux was redirected in strain YQ2-gal as more flowed into fatty acids biosynthesis but less into amino acids. In strain YQ3-xyl, more carbon flux was directed into synthesis of sucrose, glucosamine and acetaldehyde, while less into fatty acids and amino acids. Moreover, photosynthesis and bicarbonate transport could be affected by upregulated genes, while nitrogen transport and assimilation were regulated by less transcript abundance of related genes in strain YQ3-xyl with utilization of xylose. CONCLUSIONS: Our work identified metabolic mechanism in engineered S. elongatus during photomixotrophic growth, where regulations of fatty acids metabolism, photosynthesis, bicarbonate transport, nitrogen assimilation and transport are dependent on different sugar utilization. Since photomixotrophic cyanobacteria is regarded as a promising cell factory for bioproduction, this comprehensive understanding of metabolic mechanism of engineered S. elongatus during photomixotrophic growth would shed light on the engineering of more efficient and controllable bioproduction systems based on this potential chassis.

Digital PCR as an Emerging Tool for Monitoring of Microbial Biodegradation.

Biodegradation of contaminants is extremely complicated due to unpredictable microbial behaviors. Monitoring of microbial biodegradation drives us to determine (1) the amounts of specific degrading microbes, (2) the abundance, and (3) expression level of relevant functional genes. To this endeavor, the cultivation independent polymerase chain reaction (PCR)-based monitoring technique develops from endpoint PCR, real-time quantitative PCR, and then into novel digital PCR. In this review, we introduce these three categories of PCR techniques and summarize the timely applications of digital PCR and its superiorities than qPCR for biodegradation monitoring. Digital PCR technique, emerging as the most accurately absolute quantification method, can serve as the most promising and robust tool for monitoring of microbial biodegradation.

Arteriogenesis in murine adipose tissue is contingent on CD68+ /CD206+ macrophages.

OBJECTIVE: The surgical transfer of skin, fat, and/or muscle from a donor site to a recipient site within the same patient is a widely performed procedure in reconstructive surgeries. A surgical pretreatment strategy that is intended to increase perfusion in the flap, termed "flap delay," is a commonly employed technique by plastic surgeons prior to flap transplantation. Here, we explored whether CD68+ /CD206+ macrophages are required for arteriogenesis within the flap by performing gain-of-function and loss-of-function studies in a previously published flap delay murine model. METHODS AND RESULTS: Local injection of M2-polarized macrophages into the flap resulted in an increase in collateral vessel diameter. Application of a thin biomaterial film loaded with a pharmacological agent (FTY720), which has been previously shown to recruit CD68+ /CD206+ macrophages to remodeling tissue, increased CD68+ /CD206+ cell recruitment and collateral vessel enlargement. Conversely, when local macrophage populations were depleted within the inguinal fat pad via clodronate liposome delivery, we observed fewer CD68+ cells accompanied by diminished collateral vessel enlargement. CONCLUSIONS: Our study underscores the importance of macrophages during microvascular adaptations that are induced by flap delay. These studies suggest a mechanism for a translatable therapeutic target that may be used to enhance the clinical flap delay procedure.

Macrophage Recruitment and Polarization During Collateral Vessel Remodeling in Murine Adipose Tissue.

OBJECTIVE: During autologous flap transplantation for reconstructive surgeries, plastic surgeons use a surgical pre-treatment strategy called "flap delay," which entails ligating a feeding artery into an adipose tissue flap 10-14 days prior to transfer. It is believed that this blood flow alteration leads to vascular remodeling in the flap, resulting in better flap survival following transfer; however, the structural changes in the microvascular network are poorly understood. Here, we evaluate microvascular adaptations within adipose tissue in a murine model of flap delay. METHODS AND RESULTS: We used a murine flap delay model in which we ligated an artery supplying the inguinal fat pad. Although the extent of angiogenesis appeared minimal, significant diameter expansion of pre-existing collateral arterioles was observed. There was a 5-fold increase in recruitment of CX3CR1(+) monocytes to ligated tissue, a threefold increase in CD68(+) /CD206(+) macrophages in ligated tissue, a 40% increase in collateral vessel diameters supplying ligated tissue, and a 6-fold increase in the number of proliferating cells in ligated tissue. CONCLUSIONS: Our study describes microvascular adaptations in adipose in response to altered blood flow and underscores the importance of macrophages. Our data supports the development of therapies that target macrophages in order to enhance vascular remodeling in flaps.

Paradoxical Adipose Hyperplasia and Cellular Effects After Cryolipolysis: A Case Report.

Cryolipolysis is a noninvasive technique for the reduction of subcutaneous adipose tissue by controlled, localized cooling, causing adipocyte apoptosis, reportedly without affecting surrounding tissue. Although cryolipolysis has a low incidence of adverse side effects 33 cases of paradoxical adipose hyperplasia (PAH) have been reported and the precise pathogenesis of PAH is poorly understood. This present case study of PAH aims to characterize the pathological changes in the adipose tissue of PAH on a cellular level by using multiple different assays [hematoxy lin and eosin staining, LIVE/DEAD staining, BODIPY(®) 558/568 C12 (4,4-Difluoro-5-(2-Thienyl)-4-Bora-3a,4a-Diaza-s-Indacene-3-dodecanoic acid) staining]. to identify the underlying mechanism of PAH and reduce the prevalence of PAH in the future. Tissue with PAH had fewer viable cells, significantly decreased quantities of interstitial cells (p = 0.04), and fewer vessels per adipose tissue area when compared to the control tissue. Adipocytes from the PAH tissue were on average slightly smaller than the control adipocytes. Adipocytes of PAH tissue had irregularly contoured edges when compared to the smooth, round edges of the control tissue. These findings from a neutral third party are contrary to prior reports from the inventors of this technique regarding effects of cryolipolysis on both the microvasculature and interstitial cells in adipose tissue. Our use of different assays to compare cryolipolysis-treated PAH tissue with untreated adipose tissue in the same patient showed adipose tissue that developed PAH was hypocellular and hypovascular. Contrary to prior reports from the inventors, cryolipolysis may cause vessel loss, which could lead to ischemia and/or hypoxia that further contributes to adipocyte death. LEVEL OF EVIDENCE 5: Risk.

Evaluation of fluorophore-tethered platinum complexes to monitor the fate of cisplatin analogs.

The platinum drugs cisplatin, carboplatin, and oxaliplatin are highly utilized in the clinic and as a consequence have been extensively studied in the laboratory setting, sometimes by generating fluorophore-tagged analogs. Here, we synthesized two Pt(II) complexes containing ethane-1,2-diamine ligands linked to a BODIPY fluorophore, and compared their biological activity with previously reported Pt(II) complexes conjugated to carboxyfluorescein and carboxyfluorescein diacetate. The cytotoxicity and DNA damage capacity of Pt-fluorophore complexes was compared to cisplatin, and the Pt-BODIPY complexes were found to be more cytotoxic with reduced cytotoxicity in cisplatin-resistant cells. Microscopy revealed a predominately cytosolic localization, with nuclear distribution at higher concentrations. Spheroids grown from parent and resistant cells revealed penetration of Pt-BODIPY into spheroids, and retention of the cisplatin-resistant spheroid phenotype. While most activity profiles were retained for the Pt-BODIPY complexes, accumulation in resistant cells was only slightly affected, suggesting that some aspects of Pt-fluorophore cellular pharmacology deviate from cisplatin.

MXene materials in electrochemical energy storage systems.

MXenes, due to their unique geometric structure, rich elemental composition, and intrinsic physicochemical properties, have multi-functional applications. In the field of electrochemical energy storage, MXenes can be used as active components, conductive agents, supports, and catalysts in ion-intercalated batteries, metal-sulfur batteries, and supercapacitors. The electrochemical performance of MXene materials is closely related to their distinctive physical and chemical properties, which depend on their geometry, surface functional groups, and elemental composition. How to regulate MXene materials to optimize electrochemical functions is a key scientific challenge. Herein, we correlated the function of MXene materials with their interlayer structure, surface functional groups, and specific catalytic sites, analyzed the electrochemical function of MXene materials, and showed how to design the electrochemical function of MXene materials based on ion/electron transport. Additionally, this feature article provides an outlook on the opportunities and challenges for MXenes, offering theoretical and technical guidance on using MXene materials in energy storage systems.

Marine biodegradation of plastic films by Alcanivorax under various ambient temperatures: Bacterial enrichment, morphology alteration, and release of degradation products.

The global ocean has been receiving massive amounts of plastic wastes. Marine biodegradation, influenced by global climate, naturally breaks down these wastes. In this study, we systematically compared the biodegradation performance of petroleum- and bio-based plastic films, i.e., low-density polyethylene (LDPE), polylactic acid (PLA), and polyhydroxyalkanoates (PHAs) under three ambient temperatures (4, 15, and 22 °C). We deployed the our previously isolated cold-tolerant plastic-degrading Alcanivorax to simulate the accelerated marine biodegradation process and evaluated the alteration of bacterial growth, plastic films, and released degradation products. Notably, we found that marine biodegradation of PHA films enriched more bacterial amounts, induced more conspicuous morphological damage, and released more microplastics (MPs) and dissolved organic carbon (DOC) under all temperatures compared to LDPE and PLA. Particularly, MPs were released from film edges and cracks with a mean size of 2.8 µm under all temperatures. In addition, the degradation products released by biodegradation of PHA under 22 °C induced the highest acute toxicity to Vibrio fischeri. Our results highlighted that: (1) marine biodegradation of plastics would release millions of MPs per cm2 exposed surface area even in cold environments within 60 days; (2) different marine biodegradation scenarios of these plastics may raise disparate impacts and mitigation-related studies.

Fluorine-Modulated MXene-Derived Catalysts for Multiphase Sulfur Conversion in Lithium-Sulfur Battery.

Fluorine owing to its inherently high electronegativity exhibits charge delocalization and ion dissociation capabilities; as a result, there has been an influx of research studies focused on the utilization of fluorides to optimize solid electrolyte interfaces and provide dynamic protection of electrodes to regulate the reaction and function performance of batteries. Nonetheless, the shuttle effect and the sluggish redox reaction kinetics emphasize the potential bottlenecks of lithium-sulfur batteries. Whether fluorine modulation regulate the reaction process of Li-S chemistry? Here, the TiOF/Ti3C2 MXene nanoribbons with a tailored F distribution were constructed via an NH4F fluorinated method. Relying on in situ characterizations and electrochemical analysis, the F activates the catalysis function of Ti metal atoms in the consecutive redox reaction. The positive charge of Ti metal sites is increased due to the formation of O-Ti-F bonds based on the Lewis acid-base mechanism, which contributes to the adsorption of polysulfides, provides more nucleation sites and promotes the cleavage of S-S bonds. This facilitates the deposition of Li2S at lower overpotentials. Additionally, fluorine has the capacity to capture electrons originating from Li2S dissolution due to charge compensation mechanisms. The fluorine modulation strategy holds the promise of guiding the construction of fluorine-based catalysts and facilitating the seamless integration of multiple consecutive heterogeneous catalytic processes.

Causal prior-embedded physics-informed neural networks and a case study on metformin transport in porous media.

This study introduces a novel approach to transport modelling by integrating experimentally derived causal priors into neural networks. We illustrate this paradigm using a case study of metformin, a ubiquitous pharmaceutical emerging pollutant, and its transport behaviour in sandy media. Specifically, data from metformin's sandy column transport experiment was used to estimate unobservable parameters through a physics-based model Hydrus-1D, followed by a data augmentation to produce a more comprehensive dataset. A causal graph incorporating key variables was constructed, aiding in identifying impactful variables and estimating their causal dynamics or "causal prior." The causal priors extracted from the augmented dataset included underexplored system parameters such as the type-1 sorption fraction F, first-order reaction rate coefficient α, and transport system scale. Their moderate impact on the transport process has been quantitatively evaluated (normalized causal effect 0.0423, -0.1447 and -0.0351, respectively) with adequate confounders considered for the first time. The prior was later embedded into multilayer neural networks via two methods: causal weight initialization and causal prior regularization. Based on the results from AutoML hyperparameter tuning experiments, using two embedding methods simultaneously emerged as a more advantageous practice since our proposed causal weight initialization technique can enhance model stability, particularly when used in conjunction with causal prior regularization. amongst those experiments utilizing both techniques, the R-squared values peaked at 0.881. This study demonstrates a balanced approach between expert knowledge and data-driven methods, providing enhanced interpretability in black-box models such as neural networks for environmental modelling.

Migration and diffusion of unsteady-state flow of volatile organic compounds on activated carbon adsorption beds under reverse ventilation.

Despite increasing attention to the influence of unsteady-state volatile organic compounds (VOCs) on the adsorption of activated carbon, studies in this regard are rare. Therefore, in this study, an investigation into the migration and diffusion of unsteady-state VOCs on activated carbon adsorption beds under reverse ventilation was conducted. Here, reverse clean air was introduced when the activated carbon bed reached the penetration point. The influence of reverse ventilation temperature, reverse superficial gas velocity, activated carbon filling height, and different ventilation modes on the adsorption of unsteady toluene by activated carbon were studied. Our experimental results show that when the reverse ventilation temperature increased from 20 °C to 60 °C, the quasi-first-order desorption rate constant increased from 0.00356 min-1 to 0.00807 min-1, an increase in the reverse superficial gas velocity led to a higher rate constant, and at greater reverse superficial gas velocities, the stripping capacity increased. It was observed that the maximum stripping capacity was achieved at a reverse superficial gas velocity of 0.3 m/s. For different activated carbon filling heights, following reverse ventilation, the stripping capacity of a 5 cm and 30 cm activated carbon bed accounted for 41.43% and 65.85% of the original adsorption capacity, respectively. The study concludes that concentration of toluene first increased and then decreased with time under forward ventilation, whereas the concentration gradually decreased under reverse ventilation.

Exploring the use of sodium caseinate-assisted responsive separation for the treatment of washing effluents in shoreline oil spill response.

The produced effluents after shoreline washing contain a certain number of oil droplets and further treatment is necessary. In this study, the innocuous, widely available, and biodegradable sodium caseinate (NaCas) was deployed to capture oil pollutants from oily wastewater. Oil droplets can be effectively and rapidly captured by NaCas and subsequently removed after pH-triggered separation, producing a clean supernatant with low turbidity. The removal efficiency was enhanced by increasing NaCas concentration and separation time. The salinity inhibited the oil removal by increasing the interfacial tension of NaCas and reducing their sorption sites caused by the large particle size. Humic acid negatively influenced the oil separation performance of NaCas because of the competitive sorption and enhanced repulsion force between oil and NaCas. In addition, the increasing temperature was found to augment the oil removal. Factorial analysis revealed the individual factors and two-factor interactions that had significant effects on oil removal. Biotoxicity experiments proved that NaCas can fully offset the inhibitory effect of oil on the photosynthesis of algae and thus promote algae growth. Two post-treatment methods, namely thermal treatment, and biodegradation, can be used for the post-treatment of NaCas/oil precipitation residues. The use of NaCas-assisted responsive separation in the treatment of washing effluents can help achieve a sustainable shoreline oil spill response.

Insight into the plant-associated bacterial interactions: Role for plant arsenic extraction and carbon fixation.

This study investigated the interactions between rhizosphere and endosphere bacteria during phytoextraction and how the interactions affect arsenic (As) extraction and carbon (C) fixation of plants. Pot experiments, high-throughput sequencing, metabonomics, and network analysis were integrated. Results showed that positive correlations dominated the interconnections within modules (>95 %), among modules (100 %), and among keystone taxa (>72 %) in the bacterial networks of plant rhizosphere, root endosphere, and shoot endosphere. This confirmed that cooperative interactions occurred between bacteria in the rhizosphere and endosphere during phytoextraction. Modules and keystone taxa positively correlating with plant As extraction and C fixation were identified, indicating that modules and keystone taxa promoted plant As extraction and C fixation simultaneously. This is mainly because modules and keystone taxa in plant rhizosphere, root endosphere, and shoot endosphere carried arsenate reduction and C fixation genes. Meanwhile, they up-regulated the significant metabolites related to plant As tolerance. Additionally, shoot C fixation increased peroxidase activity and biomass thereby facilitating plant As extraction was confirmed. This study revealed the mechanisms of plant-associated bacterial interactions contributing to plant As extraction and C fixation. More importantly, this study provided a new angle of view that phytoextraction can be applied to achieve multiple environmental goals, such as simultaneous soil remediation and C neutrality.

Bioherder Generated by Rhodococcus erythropolis as a Marine Oil Spill Treating Agent.

There is an urgent call for contingency planning with effective and eco-friendly oil spill cleanup responses. In situ burning, if properly applied, could greatly mitigate oil in water and minimize the adverse environmental impacts of the spilled oil. Chemical herders have been commonly used along with in situ burning to increase the thickness of spilled oil at sea and facilitate combustion. These chemical surfactant-based agents can be applied to the edges of the oil slick and increase its thickness by reducing the water-oil interfacial tension. Biosurfactants have recently been developed as the next generation of herds with a smaller environmental footprint. In this study, the biosurfactant produced by Rhodococcus erythropolis M25 was evaluated and demonstrated as an effective herding agent. The impact of environmental and operational factors (e.g., temperature, herder dose, spilled oil amount, water salinity, and operation location) on its performance was investigated. A five-factor fractional design was applied to examine the importance of these factors and their impact on herding effectiveness and efficiency. The results of this study showed that higher temperature and a higher dose of herder could result in an increased oil slick thickness changing rate. Differences in water salinity at the same temperature led to the same trend, that is, the herding process effectively goes up with increasing herder-oil ratio (HOR). Further large-scale testing needs to be conducted for evaluating the applicability of the developed bioherder in the field.

Shrimp-waste based dispersant as oil spill treating agent: Biodegradation of dispersant and dispersed oil.

The emerging demand for the enhancement of biodegradation of persistent organic pollutants from marine oil spills using oil-treating agents to minimize the environmental impacts promotes the development of green dispersants. Shrimp waste is a potential raw material to generate green dispersants. The biodegradability of dispersed oil and dispersants themselves are key factors for the national consideration of the approval, stockpile, and usage of dispersants. However, it is unknown whether shrimp-waste-based dispersant (SWD) has high bioavailability or facilitates the biodegradation of dispersed oil. In this study, we tackled the biodegradation of oil dispersed by a purified SWD. Furthermore, the SWD biodegradability was evaluated by exploring the degradation genes via metagenomic sequencing, analyzing the enzymatic activities for dispersant biodegradation by molecular docking, and discussing the SWD toxicity. We discovered that the SWD facilitated the biodegradation of two crude oils (Alaska North Slope and Marine Fuel-No.6). The metagenomic analysis with molecular docking showed that fresh seawater had feasible enzymes to degrade the SWD to safety components. Additionally, the SWD was low toxic and high bioactive. The findings helped confirm that the purified SWD is an effective and eco-sustainable marine oil spill treating agent and tracked the biodegradation of dispersed oil and the SWD.

Machine learning-aided causal inference for unraveling chemical dispersant and salinity effects on crude oil biodegradation.

Chemical dispersants have been widely applied to tackle oil spills, but their effects on oil biodegradation in global aquatic systems with different salinities are not well understood. Here, both experiments and advanced machine learning-aided causal inference analysis were applied to evaluate related processes. A halotolerant oil-degrading and biosurfactant-producing species was selected and characterized within the salinity of 0-70 g/L NaCl. Notably, dispersant addition can relieve the biodegradation barriers caused by high salinities. To navigate the causal relationships behind the experimental data, a structural causal model to quantitatively estimate the strength of causal links among salinity, dispersant addition, cell abundance, biosurfactant productivity and oil biodegradation was built. The estimated causal effects were integrated into a weighted directed acyclic graph, which showed that overall positive effects of dispersant addition on oil biodegradation was mainly through the enrichment of cell abundance. These findings can benefit decision-making prior dispersant application under different saline environments.

Advanced oxidation processes in microreactors for water and wastewater treatment: Development, challenges, and opportunities.

The miniaturization of reaction processes by microreactors offers many significant advantages over the use of larger, conventional reactors. Microreactors' interior structures exhibit comparatively higher surface area-to-volume ratios, which reduce reactant diffusion distances, enable faster and more efficient heat and mass transfer, and better control over process conditions. These advantages can be exploited to significantly enhance the performance of advanced oxidation processes (AOPs) commonly used for the removal of water pollutants. This comprehensive review of the rapidly emerging area of environmental microfluidics describes recent advances in the development and application of microreactors to AOPs for water and wastewater treatment. Consideration is given to the hydrodynamic properties, construction materials, fabrication techniques, designs, process features, and upscaling of microreactors used for AOPs. The use of microreactors for various AOP types, including photocatalytic, electrochemical, Fenton, ozonation, and plasma-phase processes, showcases how microfluidic technology enhances mass transfer, improves treatment efficiency, and decreases the consumption of energy and chemicals. Despite significant advancements of microreactor technology, organic pollutant degradation mechanisms that operate during microscale AOPs remain poorly understood. Moreover, limited throughput capacity of microreactor systems significantly restrains their industrial-scale applicability. Since large microreactor-inspired AOP systems are needed to meet the high-throughput requirements of the water treatment sector, scale-up strategies and recommendations are suggested as priority research opportunities. While microstructured reactor technology remains in an early stage of development, this work offers valuable insight for future research and development of AOPs in microreactors for environmental purposes.