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•Quantitative analysis is used to evaluate the removal of microplastics in global WWTPs.•The filter-based technologies perform better microplastics removal efficiency.•Mechanisms of ...critical treatment technologies in microplastics removal are summarized.•An average of 7.2 billion day−1 microplastics entered the river from WWTPs.•Specific microplastics shall be highlighted besides the common microplastics.
Wastewater treatment plants (WWTPs) are considered to be the main sources of microplastic contaminants in the aquatic environment, and an in-depth understanding of the behavior of microplastics among the critical treatment technologies in WWTPs is urgently needed. In this paper, the characteristics and removal of microplastics in 38 WWTPs in 11 countries worldwide were reviewed. The abundance of microplastics in the influent, effluent, and sludge was compared. Then, based on existing data, the removal efficiency of microplastics in critical treatment technologies were compared by quantitative analysis. Particularly, detailed mechanisms of critical treatment technologies including primary settling treatment with flocculation, bioreactor system, advanced oxidation and membrane filtration were discussed. Thereafter, the abundance load and ecological hazard of the microplastics discharged from WWTPs into the aquatic and soil environments were summarized. The abundance of microplastics in the influent ranged from 0.28 particles L−1 to 3.14 × 104 particles L−1, while that in the effluent ranged from 0.01 particles L−1 to 2.97 × 102 particles L−1. The microplastic abundance in the sludge within the range of 4.40 × 103–2.40 × 105 particles kg−1. In addition, there are still 5.00 × 105–1.39 × 1010 microplastic particles discharged into the aquatic environment each day Moreover, among the critical treatment technologies, the quantitative analysis revealed that filter-based treatment technologies exhibited the best microplastics removal efficiency. Fibers and microplastics with large particle sizes (0.5–5 mm) were easily separated by primary settling. Polyethene and small-particle size microplastics (<0.5 mm) were easily trapped by bacteria in the activated sludge of bioreactor system. The negative impact of microplastics from wastewater treatment plant was worthy of attention. Moreover, unknown transformation products of microplastics and their corresponding toxicity need in-depth research.
With the increasingly serious water environment problem, the persulfate-based advanced oxidation process (PS-AOP) has attracted considerable attention in water pollution treatment. To date, graphitic ...carbon nitride (g-C3N4) has been greatly favored by researchers in activating PS for its capability and unique superiorities. Though g-C3N4-based PS-AOP exhibits huge development prospects in removing organic pollutants, the review about its research progress has not been reported. Herein, this paper reviews the modification of g-C3N4 on the basis of its applications and properties for PS activation systematically. The activation mechanisms of g-C3N4-based modified materials are analyzed in detail, and the main formation pathways of radicals and non-radicals and their interaction mechanism with pollutants are thoroughly summarized. Finally, the existing challenges and future development directions of the PS-AOP driven by g-C3N4-based materials are critically discussed. The key purpose is to provide a reference for promoting the further popularization of this novel and efficient cooperative AOP in water purification industries, as well as multidisciplinary inspirations for g-C3N4-involved fields.
In this paper, the modification methods and activation mechanisms of g-C3N4 in activating persulfate are reviewed for the first time, and the reaction mechanisms and degradation performance based on radical and non-radical oxidation systems are summarized thoroughly. Display omitted
•The recent progress of g-C3N4-based materials for persulfate activation is reviewed.•The persulfate activation mechanisms of g-C3N4-based materials are analyzed.•The generation pathways of radicals and non-radicals are summarized.•The interaction mechanisms of active species with organic pollutants are discussed.•The challenges and prospects of g-C3N4-based materials for persulfate activation are proposed.
Harmful algal blooms have become increasingly frequent due to the dual pressure of excessive nutrient loading and climate change in recent years. Algal-derived dissolved organic matter (DOM) is a ...potentially large component of the labile organic matter pool, and also climate warming may affect the DOM pool, although the results on the latter so far are equivocal. The question of how eutrophication and climate warming may drive the accumulation of autochthonous DOM is much debated. Here, we analysed published data on DOM world-wide and field data that we collected from 97 lakes and major rivers in China (> 4500 samples) as well as results from the longest running shallow-lake mesocosm climate experiment in the world at a research facility in Denmark. Our results indicated that dissolved organic carbon (DOC) concentrations decreased with increasing temperature and enrichment of δ13C-DOM. A negative relationship was found between latitude and %protein-like fluorescence, which increased significantly with increasing elevation and enrichment of δ13C-DOM. Specific ultraviolet absorbance at 254 nm (SUVA) decreased with increasing elevation and enrichment of δ13C-DOM. Fluorescence intensity of autochthonous microbial humic-like substances increased notably with eutrophication but decreased weakly with warming. DOC, biodegradable DOC, chlorophyll-a, δ13C-DOC and autochthonous substances identified using DOM fluorescence and high resolution mass spectrometry from the mesocosm experiment were notably elevated at the high nutrient levels, while the effect of temperature was insignificant. We conclude that while eutrophication promotes DOM, warming potentially suppresses the accumulation of autochthonous DOM in inland waters.
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The interaction between astrocytes and microglia plays a vital role in the damage and repair of brain lesions due to traumatic brain injury (TBI). Recent studies have shown that exosomes act as ...potent mediators involved in intercellular communication.
In the current study, the expression of inflammatory factors and miR-873a-5p in the lesion area and oedema area was evaluated in 15 patients with traumatic brain injury. Exosomes secreted by astrocytes were detected by immunofluorescence, Western blot and electron microscopy. A mouse model of TBI and an in vitro model of LPS-induced primary microglia were established to study the protective mechanism of exosomes from miR-873a-5p overexpressing in TBI-induced nerve injury.
We discovered that exosomes derived from activated astrocytes promote microglial M2 phenotype transformation following TBI. More than 100 miRNAs were detected in these astrocyte-derived exosomes. miR-873a-5p is a major component that was highly expressed in human traumatic brain tissue. Moreover, miR-873a-5p significantly inhibited LPS-induced microglial M1 phenotype transformation and the subsequent inflammation through decreased phosphorylation of ERK and NF-κB p65. This effect also greatly improved the modified neurological severity score (mNSS) and attenuated brain injury in a strictly controlled cortical impact mouse model.
Taken together, our research indicates that miRNAs in the exosomes derived from activated astrocytes play a key role in the astrocyte-microglia interaction. miR-873a-5p, as one of the main components of these astrocyte-derived exosomes, attenuated microglia-mediated neuroinflammation and improved neurological deficits following TBI by inhibiting the NF-κB signalling pathway. These findings suggest a potential role for miR-873a-5p in treating traumatic brain injury.
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•Mixture of acetaldehyde, acetone and ethyl acetate were adsorbed in a CAR-AC.•Ethyl acetate could easiest adsorb on the defect surface in all of three VOCs.•Interaction energy ...between ethyl acetate and C surfaces was low to −13.41 kcal/mol.•CAR-AC exhibited a good adsorption/desorption performance for mixture VOCs.•This study realizes the recycle use of CAR and the clean production of citric acid.
A considerable amount of volatile organic compounds (VOCs) is emitted, and a vast amount of citric acid residue (CAR) waste is simultaneously produced during citric acid production. Thus, a suitable method realizing the clean production of citric acid must be developed. This study investigated the adsorption of the multicomponent VOCs in a homemade CAR waste-based activated carbon (CAR-AC). A fixed-bed experimental setup was used to explore the adsorption and desorption of single- and multi-component VOCs. Surface adsorption and diffusion molecular models with different defects were built to study the underlying adsorption and diffusion mechanisms of multicomponent VOCs on CAR-AC. The adsorption amount of ethyl acetate in CAR-AC from multicomponent VOCs was 3.04 and 5.91 times higher than those of acetone and acetaldehyde, respectively, and the interaction energy between ethyl acetate and C surfaces was low at −13.41 kcal/mol. During desorption, the most weakly adsorbed acetaldehyde desorbed from the surface of CAR-AC first, followed by acetone and ethyl acetate. The regeneration efficiencies of acetaldehyde, acetone, and ethyl acetate reached 88.77, 85.55, and 91.46 %, respectively, after four adsorption/desorption cycles. We aimed to provide a new strategy to realize the recycle use of CAR and the clean production of citric acid.
In order to make clear the role of intercalated anions in layered double hydroxides (LDHs) for catalytic hydrolysis of carbonyl sulfide (COS), the adsorption and reaction characteristics of COS over ...the simple Mg
2
Al-Cl-LDH model catalyst were studied by both theoretical and experimental methods. Density functional theory (DFT) calculations by CASTEP found that the chloride ions in LDH function as the key Brønsted base sites to activate the adsorbed H
2
O with enlarged bond length and angle, facilitate the dissociative adsorption of intermediates including mono-thiocarbonic acid (MTA) and hydrogen thiocarbonic acid (HTA), and participate in the formation of transient states and subsequent hydrogen transfer process with decreased energy barriers during COS hydrolysis. COS hydrolysis will preferentially go through the dissociated intermediates of mono-thiocarbonates (MT) and hydrogen thiocarbonates (HT) with dramatically decreased energy barriers, and the rate-determining step of COS hydrolysis over Mg
2
Al-Cl-LDH will be the nucleophilic addition of C=O in COS by H
2
O (
Ea
= 1.10 eV). The experimental results further revealed that the apparent activation energy (0.89 eV) of COS hydrolysis over Mg
2
Al-Cl-LDH is close to theoretical value (1.10 eV), and the accumulated intermediates of MT, HT, or carbonate were also observed by FT-IR around 1363 cm
−1
on the used Mg
2
Al-Cl-LDH, which are well in accordance with the theoretical prediction. The demonstrated participation of intercalated chlorine anions in the evolution of intermediates and transient states as Brønsted base sites during COS hydrolysis will give new insight into the basic sites in LDH materials.
Abstract Traumatic brain injury (TBI) initiates inflammatory responses that result in an enduring cascade of secondary neuronal loss and behavioural impairment. Toll-like receptor 4 (TLR4), ...predominantly expressed by microglia, recognizes damage-associated molecular patterns (DAMPs) and regulates inflammatory processes. Interestingly, the switch of microglial M1/M2 phenotypes after TBI is highly important regarding damage and restoration of neurological function. Therefore, we investigated the role and mechanisms of the TLR4 signalling pathway in regulating microglial M1/M2 phenotypes. Using a controlled cortical impact (CCI) model, we found that TLR4 knockout (KO) mice exhibited decreased infarct volumes and improved outcomes in behavioural tests. In addition, mice lacking TLR4 had higher expression of M2 phenotype biomarkers but lower expression of M1 phenotype biomarkers. Compared with microglia derived from wild-type (WT) mice, increased expression of M2 phenotype biomarkers and decreased expression of M1 phenotype biomarkers were also noted in primary cultures of microglia from TLR4 KO mice. In TLR4 KO mice, the expression levels of downstream signalling molecules of TLR4, such as active Rac-1 and phospho-AKT, were higher, while MyD88 and phospho-NF-κB p65 expression levels were lower than in WT mice. Our results demonstrate that the absence of TLR4 induces microglial polarization toward the M2 phenotype and promotes microglial migration and, in turn, alleviates the development of neuroinflammation, which indicates potential neuroprotective effects in the TBI mouse model. Furthermore, up-regulation of IL-4 expression in TLR4 KO mice could contribute to anti-inflammatory functions and promote microglial polarization toward the M2 phenotype, which might be mediated by active Rac-1 expression. Taken together, TLR4 deficiency contributes to regulating microglia to switch to the M2 phenotype, which ameliorates neurological impairment after TBI.
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•Distinct responses of abundant and rare communities to permafrost-derived DOM.•Bacterial diversity decreased with decreasing intensity of more aromatic-like DOM.•Microbial ...degradation of more aromatic-like compounds.•Decreasing DOM metabolic diversities along permafrost thawing gradients.
Dissolved organic matter (DOM) released from permafrost thaw greatly influences the biogeochemical cycles of, among others, downstream carbon, nitrogen and phosphorus cycles; yet, knowledge of the linkages between bacterial communities with permafrost DOM heterogeneity is limited. Here, we aim at unravelling the responses of bacterial diversities and metabolic profiles to DOM quantity and composition across permafrost thawing gradients by coupling an extensive field investigation with bio-incubation experiments. Richness, evenness and dissimilarities of the whole and rare communities decreased from thermokarst pits to headstreams and to downstream rivers. The assemblages of the abundant subcommunities were mainly determined by ecological drift-driven stochastic processes. Both the optical and the molecular composition of DOM were significantly related to the changes of the whole (rare) bacterial communities (Mantel’s correlation > 0.5, p < 0.01). Diversity indices of the whole and rare communities decreased with decreasing relative abundance of tannins, condensed aromatics and more aromatic and oxidized lignins as well as with decreased dissolved organic carbon and intensities of all fluorescence components. Laboratory DOM bio-incubation experiments further confirmed microbial consumption of more aromatic and oxidized compounds as well as decreasing metabolic diversities in terms of microbial degradation and production along permafrost thawing gradients. Our findings suggest that changes in the sources of permafrost-derived DOM induced by global warming can have different influences on the diversity and metabolism of bacterial communities and thus on permafrost carbon climate feedbacks along permafrost thawing gradients.
Solar irradiation in aquatic systems can induce the conversion of substances from the solid to the dissolved phase (photodissolution). Yet, the photochemical release of dissolved organic nitrogen ...(DON) from internal particles in lakes remains largely unknown. In this study, suspensions of algal detritus and sediment particles from a shallow eutrophic lake were exposed to simulated solar irradiation, and the release and compositional changes of dissolved organic matter were explored by measuring their UV–Visible absorption spectroscopy and ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The photochemical release of inorganic nitrogen during the incubations was also investigated. Results showed that light irradiation induced stronger dissolved organic carbon and DON production in the algal detritus suspensions, with release rates of 1.17 mg C L−1 h−1 and 0.14 mg N L−1 h−1, respectively, at an algal detritus concentration of 0.1 dry g L−1. Light irradiation also induced compositional changes of DON in both algal and sediment suspensions. A larger number of DON molecules with lower molecular weight were continuously released in the algal suspensions, e.g., the total number of DON formulas increased from 1349 to 4135 during an 8 h irradiation. In contrast, upon irradiation of sediment suspensions, DON showed decreased molecular diversity and increased aromaticity. The photochemical release of ammonium (photoammonification) was also higher in the algal suspensions with a rate of 0.015 mg N L−1 h−1, which may contribute to the eutrophication of the lake. This study provides new molecular insights into the photochemical release of DON from typical internal particles in eutrophic lakes.
We utilize real-time time-dependent density functional theory and Ehrenfest dynamics scheme to investigate excited-state nonadiabatic dynamics of ligand dissociation of cobalt tricarbonyl nitrosyl, ...Co(CO)
NO, which is a precursor used for cobalt growth in advanced technologies, where the precursor's reaction is enhanced by electronic excitation. Based on the first-principles calculations, we demonstrate two dissociation pathways of the NO ligand on the precursor. Detailed electronic structures are further analyzed to provide an insight into dynamics following the electronic excitations. This study sheds light on computational demonstration and underlying mechanism of the electronic-excitation-induced dissociation, especially in molecules with complex chemical bonds such as the Co(CO)
NO.
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