Integrated transcriptomics and metabolomics analyses reveal the aerobic biodegradation and molecular mechanisms of 2,3',4,4',5-pentachlorodiphenyl (PCB 118) in Methylorubrum sp. ZY-1.

2,3',4,4',5-pentachlorodiphenyl (PCB 118), a highly representative PCB congener, has been frequently detected in various environments, garnering much attention across the scientific community. The degradation of highly chlorinated PCBs by aerobic microorganisms is challenging due to their hydrophobicity and persistence. Herein, the biodegradation and adaptation mechanisms of Methylorubrum sp. ZY-1 to PCB 118 were comprehensively investigated using an integrative approach that combined degradation performance, product identification, metabolomic and transcriptomic analyses. The results indicated that the highest degradation efficiency of 0.5 mg L-1 PCB 118 reached 75.66% after seven days of inoculation when the bacteria dosage was 1.0 g L-1 at pH 7.0. A total of eleven products were identified during the degradation process, including low chlorinated PCBs, hydroxylated PCBs, and ring-opening products, suggesting that strain ZY-1 degraded PCB 118 through dechlorination, hydroxylation, and ring-opening pathways. Metabolomic analysis demonstrated that the energy supply and redox metabolism of strain ZY-1 was disturbed with exposure to PCB 118. To counteract this environmental stress, strain ZY-1 adjusted both the fatty acid synthesis and purine metabolism. The analysis of transcriptomics disclosed that multiple intracellular and extracellular oxidoreductases (e.g., monooxygenase, alpha/beta hydrolase and cytochrome P450) participated in the degradation of PCB 118. Besides, active efflux of PCB 118 and its degradation intermediates mediated by multiple transporters (e.g., MFS transporter and ABC transporter ATP-binding protein) might enhance bacterial resistance against these substances. These discoveries provided the inaugural insights into the biotransformation of strain ZY-1 to PCB 118 stress, illustrating its potential in the remediation of contaminated environments.

Unravelling the removal mechanisms of trivalent arsenic by sulfidated nanoscale zero-valent iron: The crucial role of reactive oxygen species and the multiple effects of citric acid.

The remediation of arsenic-contaminated groundwater by sulfidated nanoscale zero-valent iron (S-nZVI) has raised considerable attention. However, the role of trivalent arsenic (As(III)) oxidation by S-nZVI in oxic conditions (S-nZVI/O2) remains controversial, and the comprehensive effect of citric acid (CA) prevalent in groundwater on As(III) removal by S-nZVI remains unclear. Herein, the mechanisms of reactive oxygen species (ROS) generation and multiple effects of CA on As(III) removal by S-nZVI/O2 were systematically explored. Results indicated that the removal efficiency of As(III) by S-nZVI/O2 (97.81 %) was prominently higher than that by S-nZVI (66.71 %), resulting from the significant production of ROS (mainly H2O2 and OH) under oxic conditions, which played a crucial role in promoting the As(III) oxidation. Additionally, CA had multiple effects on As(III) removal by S-nZVI/O2 system: (i) CA impeded the diffusion of As(III) towards S-nZVI and increased the secondary risk of immobilized As(III) re-releasing into the environment due to the Fe dissolution from S-nZVI; (ii) CA could significantly enhance the yields of OH from 25.29 to 133.00 µM via accelerating the redox cycle of Fe(II)/Fe(III) and increasing the oriented conversion rate of H2O2 to OH; (iii) CA could also enrich the types of ROS (such as O2- and 1O2) in favor of further As(III) oxidation. This study contributed novel findings regarding the control of As(III) contaminated groundwater using S-nZVI technologies.

Bioremediation of PBDEs and heavy metals co-contaminated soil in e-waste dismantling sites by Pseudomonas plecoglossicida assisted with biochar.

Biochar-assisted microbial remediation has been proposed as a promising strategy to eliminate environmental pollutants. However, studies on this strategy used in the remediation of persistent organic pollutants and heavy metals co-contaminated soil are lacking, and the effect of the combined incorporation of biochar and inoculant on the assembly, functions, and microbial interactions of soil microbiomes are unclear. Here, we studied 2,2',4,4'-tetrabrominated diphenyl ether (BDE-47) degradation and heavy metal immobilization by and biochar-based bacterial inoculant (BC/PP) in an e-waste contaminated soil, and corresponding microbial regulation mechanisms. Results showed that BC/PP addition was more effective in reducing Cu and Pb availability and degrading BDE-47 than inoculant alone. Notably, BC/PP facilitated bound-residue formation of BDE-47, reducing the ecological risk of residual BDE-47. Meanwhile, microbial carbon metabolism and enzyme activities (related to C-, N-, and P- cycles) were enhanced in soil amended with BC/PP. Importantly, biochar played a crucial role in inoculant colonization, community assembly processes, and microbiome multifunction. In the presence of biochar, positive interactions in co-occurrence networks of the bacterial community were more frequent, and higher network stability and more keystone taxa were observed (including potential degraders). These findings provide a promising strategy for decontaminating complex-polluted environments and recovering soil ecological functions.

Interaction between Phthalate Ester and Rice Plants: Novel Transformation Pathways and Metabolic-Network Perturbations.

Our understanding is limited concerning the interaction mechanism between widespread phthalate esters and staple crops, which have strong implications for human exposure. Therefore, this study was aimed at illuminating the transformation pathways of di-n-butyl phthalate (DnBP) in rice using an untargeted screening method. UPLC-QTOF-MS identified 16 intermediate transformation products formed through hydroxylation, hydrolysis, and oxidation in phase I metabolism and further by conjugation with amino acids, glutathione, and carbohydrates in phase II metabolism. Mono-2-hydroxy-n-butyl phthalate-l-aspartic acid (MHBP-asp) and mono-2-hydroxy-n-butyl phthalate-d-alanyl-ß-d-glucoside (MHBP-ala-glu) products were observed for the first time. The proteomic analysis demonstrated that DnBP upregulated the expression of rice proteins associated with transporter activity, antioxidant synthesis, and oxidative stress response and downregulated that of proteins involved in photosynthesis, photorespiration, chlorophyll binding, and mono-oxygenase activity. Molecular docking revealed that DnBP can affect protein molecular activity via pi-sigma, pi-alkyl, and pi-pi interactions or by forming carbon-hydrogen bonds. The metabolomic analysis showed that key metabolic pathways including citrate cycle, biosynthesis of aminoacyl-tRNA, and metabolism of amino acids, sphingolipids, carbohydrates, nucleotides, and glutathione were activated in rice plants exposed to DnBP and its primary metabolite mono-n-butyl phthalate (MnBP). Furthermore, exposure to 80 ng/mL MnBP significantly perturbed the metabolic profile and molecular function in plants, with downregulation of the levels of beta-alanine (0.56-fold), cytosine (0.48-fold), thymine (0.62-fold), uracil (0.48-fold), glucose (0.59-fold), and glucose-1-phosphate (0.33-fold), as well as upregulation of the levels of l-glutamic acid (2.97-fold), l-cystine (2.69-fold), and phytosphingosine (38.38-fold). Therefore, the degradation intermediates of DnBP pose a potentially risk to plant metabolism and raise concerns for crop safety related to plasticizer pollution.

Methanol promotes the biodegradation of 2,2',3,4,4',5,5'-heptachlorobiphenyl (PCB 180) by the microbial consortium QY2: Metabolic pathways, toxicity evaluation and community response.

As one of the most frequently detected PCB congeners in human adipose tissue, 2,2',3,4,4',5,5'-heptachlorobiphenyl (PCB 180) has attracted much attention. However, PCB 180 is difficult to be directly utilized by microorganisms due to its hydrophobicity and obstinacy. Herein, methanol (5 mM) as a co-metabolic carbon source significantly stimulated the degradation performance of microbial consortium QY2 for PCB 180 (51.9% higher than that without methanol addition). Six metabolic products including low-chlorinated PCBs and chlorobenzoic acid were identified during co-metabolic degradation, denoting that PCB 180 was metabolized via dechlorination, hydroxylation and ring-opening pathways. The oxidative stress and apoptosis induced by PCB 180 were dose-dependent, but the addition of methanol effectively promoted the tolerance of consortium QY2 to resist unfavorable environmental stress. Additionally, the significant reduction of intracellular reactive oxygen species (ROS) and enhancement of cell viability during methanol co-metabolic degradation proved that the degradation was a detoxification process. The microbial community and network analyses suggested that the potential PCB 180 degrading bacteria in the community (e.g., Achromobacter, Cupriavidus, Methylobacterium and Sphingomonas) and functional abundance of metabolic pathways were selectively enriched by methanol, and the synergies among species whose richness increased after methanol addition might dominate the degradation process. These findings provide new insights into the biodegradation of PCB 180 by microbial consortium.

Deciphering the distinct successional patterns and potential roles of abundant and rare microbial taxa of urban riverine plastisphere.

Microbial colonization on microplastics has provoked global concern; however, many studies have not considered the successional patterns and potential roles of abundant and rare taxa of the plastisphere during colonization. Hence, we investigate the taxonomic composition, assembly, interaction and function of abundant and rare taxa in the riverine plastisphere by conducting microcosm experiments. Results showed that rare taxa occupied significantly high community diversity and niche breadth than the abundant taxa, which implies that rare taxa are essential components in maintaining the community stability of the plastisphere. However, the abundant taxa played a major role in driving the succession of plastisphere communities during colonization. Both stochastic and deterministic processes signally affected the plastisphere community assemblies; while, the deterministic patterns (heterogeneous selection) were especially pronounced for rare biospheres. Plastisphere microbial networks were shaped by the enhancement of network modularity and reinforcement of positive interactions. Rare taxa played critical roles in shaping stable plastisphere by occupying the key status in microbial networks. The strong interaction of rare and non-rare taxa suggested that multi-species collaboration might be conducive to the formation and stability of the plastisphere. Both abundant and rare taxa were enriched with plentiful functional genes related to carbon, nitrogen, phosphorus and sulfur cycling; however, their potential metabolic functions were significantly discrepant, implying that the abundant and rare microbes may play different roles in ecosystems. Overall, this study strengthens our comprehending of the mechanisms regarding the formation and maintenance of the plastisphere.

Photocatalysis of carbamazepine via activating bisulfite by ultraviolet: Performance, transformation mechanism, and residual toxicity assessment of intermediates products.

Carbamazepine (CBZ) as an extensively distributed emerging pollutant has menaced ecological security. The degradation performance of CBZ by UV driven bisulfite process was investigated in this work. The kinetics results indicated that CBZ was high-efficiently degraded by UV/bisulfite following a pseudo first-order kinetic model (Kobs = 0.0925 min-1). SO4•- and •OH were verified as the reactive oxidants by EPR test and the radicals scavenging experiment using MeOH and TBA. SO4•- played a dominant role for CBZ degradation. The Density functional theory (DFT) and LC-qTOF-MS/MS clarified that hydroxylation, ketonation, ring opening reaction, and ring contraction were main transformation patterns of CBZ. As to influence factors, CBZ degradation was significantly hindered in presence of CO32-, HPO42- and NOM. Toxicological analysis derived from metabonomics suggested that the remarkable alteration of metabolic profile was triggered by exposure to intermediates mixture. CBZ intermediates interfered in several key metabolic pathways, including pentose phosphate, amino acids, lysine degradation, glycerophospholipid, glutathione, nucleotides and carbohydrate, which was alleviated after UV/bisulfite treatment. This work provided a meaningful support to potential risk of CBZ intermediates products, which shed light on the future application in eliminating drugs using UV /bisulfite.

Remediation performance and mechanisms of Cu and Cd contaminated water and soil using Mn/Al-layered double oxide-loaded biochar.

The combined pollution of heavy metals is ubiquitous worldwide. Mn/Al-layered double oxide-loaded crab shells biochar (LDO/BC) was prepared, so as to remediate the combined pollution of Cd and Cu in soil and water. The pristine and used LDO/BC were characterized and the results revealed that the layered double oxide was successfully loaded on crab shells biochar (BC) and metal element Ca in crab shells was beneficial to the formation of more regular layered and flake structure. The maximal adsorption capacity (Qm) of LDO/BC for aqueous Cu2+ and Cd2+ was 66.23 and 73.47 mg/g, respectively. LDO/BC and BC were used to remediate e-waste-contaminated soil for the first time and exhibited highly efficient performance. The extraction amount of Cu and Cd in the contaminated soil by diethylene triamine penta-acetic acid (DTPA) after treating with 5% LDO/BC was significantly reduced from 819.84 to 205.95 mg/kg (with passivation rate 74.8%) and 8.46 to 4.16 mg/kg (with passivation rate 50.8%), respectively, inferring that the bioavailability of heavy metals declined remarkably. The experimental result also suggested that after remediation by LDO/BC the exchangeable and weak acid soluble Cu and Cd in soil translated to reducible, residual and oxidizable fraction which are more stable state. Precipitation, complexation and ion exchange were proposed as the possible mechanisms for Cd and Cu removal. In general, these experiment results indicate that LDO/BC can be a potentially effective reagent for remediation of heavy metal contaminated water and soil.

Progress in symmetry preserving robot perception and control through geometry and learning.

This article reports on recent progress in robot perception and control methods developed by taking the symmetry of the problem into account. Inspired by existing mathematical tools for studying the symmetry structures of geometric spaces, geometric sensor registration, state estimator, and control methods provide indispensable insights into the problem formulations and generalization of robotics algorithms to challenging unknown environments. When combined with computational methods for learning hard-to-measure quantities, symmetry-preserving methods unleash tremendous performance. The article supports this claim by showcasing experimental results of robot perception, state estimation, and control in real-world scenarios.

Mechanisms and influencing factors for electron transfer complex in metal-biochar nanocomposites activated peroxydisulfate.

The mechanisms and influencing factors for electron transfer complex need to be further studied by comparing radical and nonradical pathways. Herein, metal-biochar (BC) nanocomposites including CuO/BC, Fe3O4/BC and ZnO/BC were prepared to activate peroxydisulfate (PDS) for bisphenol A (BPA) degradation. The existence of electron transfer complex in CuO/BC-PDS system were directly demonstrated. Whereas radical pathway was dominant in Fe3O4/BC- and ZnO/BC-PDS systems for BPA degradation. There was a relationship between PDS adsorption and catalytic reaction. The rate-limiting step for BPA degradation in nonradical pathway was PDS adsorption, but in radical pathway was BPA degradation. Interestingly, among metal-BC, CuO/BC had the most effective performance in transformation of adsorbed PDS to electron transfer complex via out-sphere complexation. After pretreatment by PDS solutions, the separated CuO/BC achieved an efficiency of 60% in ensuing BPA degradation without re-addition of PDS. In addition, the activity of electron transfer complex in BPA degradation (kobs > 0.0480 min-1) was not affected by water matrix (e.g., Cl-, HCO3-, natural organic matter (NOM) and actual water bodies), but affected by solution property (i.e., dissolved oxygen and conductivity) and oxidant species. Moreover, in BPA degradation process, nonradical pathway exhibited lower ecotoxicity instead of radical pathway.

Promotion of the biodegradation of phenanthrene adsorbed on microplastics by the functional bacterial consortium QY1 in the presence of humic acid: Bioavailability and toxicity evaluation.

The adsorption of hydrophobic organic compounds (HOCs) by microplastics (MPs) has attracted great attention in recent years. However, the ultimate environmental fate of the HOCs sorbed on MPs (HOCs-MPs) is poorly understood. In this work, we investigated the potential influence of the biotransformation process on the environmental fate of phenanthrene (PHE, a model HOC) sorbed on MPs (PHE-MPs) under the existence of humic acid (HA, the main ingredient of dissolved organic matter (DOM)) in the aquatic environment. The results indicated that the adsorption behavior of PHE on MPs decreased its bioavailability and thus inhibited its biotransformation efficiency. However, HA significantly promoted the biodegradation rate and percentage of PHE-MPs. This was probably because HA improved the desorption of PHE from MPs, which promoted the acquisition of PHE by bacteria from the aqueous phase. Further, HA dramatically increased the bacterial community diversity and richness and altered the community composition. The richness of some PHE-degrading bacteria, such as Methylobacillus and Sphingomonas, significantly increased, which may also be an important factor for promoting PHE biodegradation. Molecular ecological network analysis implied that HA enhanced the modularity and complexity of bacterial interaction networks, which was beneficial to maintaining the functional stability of the consortium QY1. Besides, HA decreased the cytotoxicity of functional microbes induced by HOCs-MPs. This work broadens our knowledge of the environmental fate of HOCs-MPs and interactions of MPs, HOCs, DOMs and functional microbial consortiums in aqueous environments.

Understanding the role of biochar in affecting BDE-47 biodegradation by Pseudomonas plecoglossicida: An integrated analysis using chemical, biological, and metabolomic approaches.

Biochar-assisted microbial degradation technology is considered as an important strategy to eliminate organic pollutants, but the mechanism of biochar in affecting biodegradation has not been systematically studied. To address this knowledge gap, the effect of various biochars on biodegradation of different initial concentrations of BDE-47 by Pseudomonas plecoglossicida was investigated. The results showed that biochar exhibited significant promotion to the biodegradation of BDE-47, especially at concentrations of BDE-47 above 100 µg/L. The promotion effect was negatively influenced by the aromaticity and micropore volume of biochar. Biochar alleviated the cytotoxicity of BDE-47 to P. plecoglossicida and promoted cell proliferation based on toxicity assays. Additionally, biochar acted as shelter and stimulated the secretion of extracellular polymeric substances, which might support P. plecoglossicida to struggle with extreme conditions. Metabolomic analysis indicated that biochar resulted in upregulation expression of 38 metabolites in P. plecoglossicida. These upregulated metabolites were mainly related to glyoxylate and dicarboxylate metabolism, citrate cycle, and serial amino acid metabolism, suggesting that biochar could improve the BDE-47 biodegradation via enhancing oxidative metabolism and energy supply of the bacterial cells. This work elucidates how biochar can affect BDE-47 biodegradation and provides insights for the application prospect of biochar-assisted microbial degradation technology in the environment.

Discrepancy strategies of sediment abundant and rare microbial communities in response to floating microplastic disturbances: Study using a microcosmic experiment.

Floating microplastics (FMPs) in surface water have been extensively studied, but their influence on sedimentary microbial ecosystems is poorly understood. Here, we investigated response patterns of abundant and rare sedimentary microbes to FMP disturbances by performing microcosmic experiments using fluvial sediment with polyethylene (PE), polylactic acid (PLA), polystyrene (PS) and polyvinyl chloride (PVC) MPs. The results indicated that FMPs altered sediment microbial community diversity and composition. Some organic-degrading, nitrifying and denitrifying bacteria significantly decreased in response to FMP disturbances, which may affect the sediment carbon and nitrogen cycles. Rare taxa persisted under FMP disturbances, whereas abundant taxa were more susceptible to FMP disturbances, suggesting a higher sensitivity of abundant taxa to FMP disturbances. Although stochastic processes governed the assembly of the overall microbial communities, the assembly mechanisms of abundant and rare populations have significantly different responses to FMP interference. The relative contribution of deterministic processes was reinforced by enhanced homogenous selection in abundant populations, while it markedly decreased in rare populations under FMP disturbances. Furthermore, FMPs substantially decreased the network complexity, loosened the coexistence relationships, and increased the negative correlations. Rare species play an important role in reshaping complex microbial interactions and coexistence networks in response to FMP disturbances. This research broadens our perspectives for comprehensively evaluating the ecological effects of FMPs in the aquatic environment to formulate further policy controls.

Shifts of bacterial community and molecular ecological network in activated sludge system under ibuprofen stress.

The major objectives of this study were to explore the long-term effects of ibuprofen (IBP) on nutrient removal, community compositions, and microbial interactions of the activated sludge system. The results showed that 1 mg/L IBP had no inhibitory effects on the removal of organic matters and nutrients. IBP significantly reduced the microbial diversity and changed the bacterial community structure. Some denitrifiers (Denitratisoma and Hyphomicrobium) increased significantly, while NOB (Nitrospira) significantly decreased under IBP stress (P < 0.05). Furthermore, molecular ecological network analysis indicated that IBP reduced the overall network size and links, but led to a closer network with more efficient communication, which might be the strategy of microbes to survive under the stress of IBP and further maintain the performance stability. Different phylogenetic populations had different responses to IBP, as a closer subnetwork with more synergistic relations was observed in Chloroflexi and a looser subnetwork with more competitive relationships was detected in Proteobacteria. The topological roles of nodes significantly changed, and the putative keystone species decreased under the stress of IBP. This study broadens our knowledge of the long-term effects of IBP on the microbial community structure and the interactions between species in the activated sludge system.

MgO-loaded nitrogen and phosphorus self-doped biochar: High-efficient adsorption of aquatic Cu2+, Cd2+, and Pb2+ and its remediation efficiency on heavy metal contaminated soil.

In this study, the MgO-loaded fish scale biochar (MgO-FB) was synthesized by impregnation of MgCl2 using fish scales as precursor, and the modified biochar was applied for the adsorption of aquatic Cu2+, Cd2+, and Pb2+, and the immobilization of heavy metals in soils. The maximum adsorption capacities of MgO-FB for Cu2+, Cd2+, and Pb2+ were 505.8, 327.2, and 661.2 mg/g, respectively. In addition, MgO-FB can keep the excellent adsorption capacity under various environmental disturbances including pH, humic acid, and high ionic strength. Multiple characterizations and comparative experiments have demonstrated that the hydroxyapatite components and the MgO micro-nanoparticles on MgO-FB enhanced the adsorption capacity for Cu2+, Cd2+, and Pb2+ through ion-exchange and precipitation process. The metal-π electron coordination and complexation with oxygen-, nitrogen-, and phosphorus-containing groups were also responsible for the removal of heavy metal ions. Besides, MgO-FB also performed excellently for the immobilization of Cu, Cd, and Pb in soils, and the contents of available Cu, Cd, and Pb were reduced by 84.2%, 74.2%, and 53.7% respectively with the addition of MgO-FB. In general, these results show that waste fish scales co-pyrolysis with MgCl2 impregnation can be considered as a promising and efficient material for the remediation of heavy metal contaminated waters and soils.

Synergistic removal of Cr(VI) by S-nZVI and organic acids: The enhanced electron selectivity and pH-dependent promotion mechanisms.

The effects of organic acids on hexavalent chromium (Cr(VI)) removal by reduced iron-based materials have been extensively studied. Nevertheless, the promotion mechanism from the perspective of the electron transfer process is still unclear. Herein, sulfidated nanoscale zero-valent iron (S-nZVI) and the selected organic acids, citric acid (containing both -OH and -COOH groups) and oxalic acid (containing only -COOH groups), showed significant synergistic promotion effects in Cr(VI) removal. The FeS and FeS2 on S-nZVI surface could enhance the Cr(VI) reduction as the reductive entity and electron conductor. Furthermore, even though the reactivity of FeS with Cr(VI) is higher than that with FeS2, the Cr(VI) removal efficiency by FeS2 was much higher than that by FeS with organic acids. Under neutral and alkaline conditions (pH 6.0-8.0), organic acids promoted the diffusion, adsorption and complexation of Cr(VI) on S-nZVI surface, thus enhancing the electron selectivity towards Cr(VI). However, when the solution pH changed to acidic conditions (pH 4.0), organic acids facilitated the dissolution of Fe(II) ions from S-nZVI and enhanced the electron utilization towards Cr(VI) via the fast Fe(III) reduction process. This study provided a new insight into the Cr(VI) removal, which was beneficial to understand the application boundaries of S-nZVI for Cr(VI) remediation.

Environmental contamination and human exposure of polychlorinated biphenyls (PCBs) in China: A review.

Polychlorinated biphenyls (PCBs), together with 11 other organic compounds, were initially listed as persistent organic pollutants (POPs) by the Stockholm Convention because of their potential threat to ecosystems and humans. In China, many monitoring studies have been undertaken to reveal the level of PCBs in environment since 2005 due to the introduced stricter environmental regulations. However, there are still significant gaps in understanding the overall spatial and temporal distributions of PCBs in China. This review systematically discusses the occurrence and distribution of PCBs in environmental matrices, organisms, and humans in China. Results showed that PCB contamination in northern and southern China was not significantly different, but the PCB levels in East China were commonly higher than those in West China, which might have been due to the widespread consumption of PCBs and intensive human activities in East China. Serious PCB contamination was found in e-waste disassembling areas (e.g., Taizhou of Zhejiang Province and Qingyuan and Guiyu of Guangdong Province). Higher PCB concentrations were also chronicled in megalopolises and industrial clusters. The unintentionally produced PCBs (UP-PCBs) formed during industrial thermal processes may play an increasingly significant role in PCB pollution in China. Low PCB levels were recorded in rural and underdeveloped districts, particularly in remote and high-altitude localities such as the Tibetan Plateau and the South China Sea. However, these data are limited. Human exposure to PCBs is closely related to the characteristics of environmental pollution. This review also discusses existing issues and future research prospects on PCBs in China. For instance, the accumulation characteristics and migration regularities of PCBs in food webs should be further studied. More investigations should be undertaken to assess the quantitative relationship between external and internal exposure to PCBs. For example, bioaccessibility and bioavailability studies should be supplemented to evaluate human health risks more accurately.

Degradation of organophosphorus flame retardants in heterogeneous photo-Fenton system driven by Fe(III)-based metal organic framework: Intermediates and their potential interference on bacterial metabolism.

Organophosphorus flame retardants (OPFRs) have been regarded as one of the most rebarbative classes of emerging contaminants due to their persistence and toxicity. In the current study, Fe-based metal organic framework (MIL-88A) was synthesized and employed as photo-Fenton catalyst for the degradation of tris-(2-chloroisopropyl) phosphate (TCPP), a typical representative of OPFRs. The observations indicated that visible light could boost the reduction of ≡FeIII to ≡FeII in Fe-O clusters of MIL-88A during the photo-Fenton system and consequently induce the transformation of H2O2 to OH, which realized efficient degradation of TCPP. Due to the excellent function of MIL-88A, the effective pH application range of photo-Fenton system was extended in comparison with traditional Fenton system. The degradation efficiency of TCPP was visibly influenced in presence of humic acid (HA). MIL-88A exhibited a commendable reusability and stability after 3 times cycle. As the photo-Fenton reaction proceeded, TCPP was disintegrated to several kinds of carboxylated, dechlorinated and hydroxylated products. The observations of metabolomics endorsed that the interference of intermediate products mixture on E. coli weakened to a certain extent. In conclusion, carboxylation, dechlorination, hydroxylation and oxidation of TCPP were likewise effective for its detoxification, revealing that heterogeneous photo-Fenton system driven by Fe-based metal organic framework will be an attractive and safe treatment technique for OPFRs control.

Amino-functionalized MIL-88B as heterogeneous photo-Fenton catalysts for enhancing tris-(2-chloroisopropyl) phosphate (TCPP) degradation: Dual excitation pathways accelerate the conversion of FeIII to FeII under visible light irradiation.

In this work, the amino-functionalized metal-organic frameworks (MIL-88B-NH2) was synthesized, characterized and used as heterogeneous photo-Fenton catalyst for tris-(2-chloroisopropyl) phosphate (TCPP) degradation. The photo-Fenton activity of MIL-88B-NH2 was investigated on the basis of influence factors, such as initial pH and TCPP concentration, and coexisting impurities. The results revealed that MIL-88B-NH2+H2O2+Vis system exhibited a satisfactory degradation efficiency of TCPP (almost 100%) within 60 min accompanied by a good reusability. Noticeably, the degradation kinetics constant of TCPP by MIL-88B-NH2+H2O2+Vis system was 0.086 min-1, which was visibly higher than that of MIL-88B+H2O2+Vis system (0.021 min-1) since the addition of amino-functionalized organic linker inhibiting the recombination rate of the photo-generated electron-hole pairs and improving the visible light response. Combined with the characterization, the conversion of FeIII to FeII could be accelerated by the photo-generated electron from the excitation of Fe-O clusters and NH2 functionalities, which strengthened the decomposition of H2O2 and formed plenty •OH. Simultaneously, six steady products were validated and potential degradation pathways of TCPP were proposed. It was anticipated that MIL-88B-NH2 could be considered as a desirable and alternative candidate in the application of heterogeneous photo-Fenton reaction to control the environmental risks caused by organophosphate flame retardants (OPFRs).

[Degradation 2,2',4,4'-Tetrabromodiphenyl Ether by Activated Peroxymonosulfate Using Magnetic Biochar Supported α-MnO2].

Polybrominated diphenyl ethers(PBDEs) are potentially harmful to human health and the ecological environment. It is, therefore, of great significance to develop efficient, economic, and environmentally-friendly advanced oxidation systems for their effective degradation. Here, a magnetic biochar supported manganese dioxide composite(α-MnO2/MWB) synthesized by hydrothermal methods was used as a catalyst to activate peroxymonosulfate(PMS) in the degradation of 2, 2', 4, 4'-tetrabrominated diphenyl ether(BDE-47). The prepared materials were characterized by SEM, XRD, FT-IR, and BET. The results showed that α-MnO2/MWB had the best catalytic performance, and the highest degradation efficiency reached 94% under optimal conditions(α-MnO2/MWB mass ratio=1:2, catalyst dosage=0.05 g·L-1, PMS concentration=5 mmol·L-1, BDE-47 concentration=1 mg·L-1). The effect of initial pH on the system was not distinct, while chloride ions(Cl-) and humic acid(HA) inhibited the degradation of BDE-47. In comparison, nitrate ions(NO3-) and bicarbonate ions(HCO3-) had no notable effect on the degradation. SO4-· and·OH were the key free radicals in the degradation of BDE-47 in this system, with SO4-· being dominant. As showed by the XPS characterization of the materials before and after the reaction, a change in the valence states of Mn and Fe was the main reason for the activation of PMS. It was also revealed that α-MnO2/MWB composites maintained high catalytic performance after being reused up to four times.