期刊导航

Totally found 2966 items.

  • [期刊] Efficient sorptive removal of F-53B from water by layered double hydroxides: Performance and mechanisms
    Chlorinated polyfluoroalkyl ether sulfonates (trade name F-53B) has been detected in various environmental matrices, and reported to be equally or more toxic than perfluorooctane sulfonate. Efficient sorptive removal of F-53B from water by two types of layered double hydroxides (LDHs), NO3--LDH and sodium dodecyl sulfate modified NO3--LDH (SDS-LDH), was demonstrated in this study. Both LDHs removed F-53B in several minutes and had sorption capacities of over 860 mg/g. SDS-LDH exhibited a greater F-53B uptake than NO3--LDH under the influence of different solution chemistry, including pH 3-11, or in the presence of competing anions or co-contaminants, primarily due to the higher surface areas and the presence of SDS for SDS-LDH. Batch experiments, structural characterization, molecular dynamics simulations, and density functional theory calculations were combined to explore the sorption mechanisms, which mainly include ion exchange (specifically, O-H center dot center dot center dot O/F hydrogen bond), C-F/Cl center dot center dot center dot H hydrogen bond, and micellar sorption (occurring at high initial F-53B concentrations). Accordingly, we propose to improve the sorption performance of LDHs by increasing their surface areas and modifying LDHs to produce more hydrogen bond sites, as well as exfoliating LDHs into two dimensional nanosheets to eliminate the steric hindrance for the micellar formation of F-53B or other per- and polyfluoroalkyl substances. (C) 2020 Elsevier Ltd. All rights reserved.
  • [期刊] DEHP degradation and dechlorination of polyvinyl chloride waste in subcritical water with alkali and ethanol: A comparative study
    In this study, subcritical water-NaOH (CW-NaOH) and subcritical water-C2H5OH (CW-C2H5OH) processes were developed for diethylhexyl phthalate (DEHP) degradation and dechlorination of polyvinyl chloride (PVC) waste. The introduction of NaOH or C2H5OH in subcritical water had a noticeable influence on the mechanism of DEHP degradation and dechlorination. For both CW-NaOH and CW-C2H5OH treatments, the increase in temperature could increase dechlorination efficiency (DE) of PVC. The DE of CW-NaOH is much higher than that of CW-C2H5OH under the same conditions. The DE of CW-NaOH could exceed 95% at 300 degrees C. Hydroxyl nucleophilic substitution was the main dechlorination mechanism in CW-NaOH, while nucleophilic substitution and direct dehydrochlorination were equally important in CW-C2H5OH. In CW-NaOH treatment, 2-ethyl-1-hexanol, benzaldehyde, and toluene were obtained by hydrolysis and reduction reactions of DEHP. Acetophenone was produced by the further cyclization, dehydrogenation and rearrangement reactions of 2-ethyl-1-hexanol. Transesterification was the main degradation pathway of DEHP in CW-C2H5OH at 300 degrees C. The cyclization and dehydration of 2ethyl-1-hexanol resulted in producing a high level of ethyl-cyclohexane and 1-ethyl-cyclohexene in CW-C2H5OH at 350 degrees C. Furthermore, high concentration of ethyl palmitate and ethyl stearate could be prepared in CW-C2H5OH system by the strong reactivity of C2H5OH with the lubricants in PVC. (C) 2020 Elsevier Ltd. All rights reserved.
  • [期刊] Effects of intermittent mixing mode on solid state anaerobic digestion of agricultural wastes
    This study investigated the effects of three different intermittent mixing modes (top, middle and bottom) on the performance of solid state anaerobic digestion (SS-AD) process of pig manure, corn stover and cucumber residues in a stirred tank reactor (STR). Results showed the cumulative methane yields of reactors had similar values (P> 0.05) except for the unmixed reactor (CK), which had a very low methane production. Reactors of top-mixed (T1) had shortest technical digestion time (T-80) and more stable physicochemical characteristics than the other treatments. These findings indicated the three mixing modes had almost no effect on the cumulative methane yields, but affected the digestion process. The main bacteria in T1 reactor was Clostridium_sensu_stricto_1. However, Caldicoprobacter accounted for a relatively large proportion of the bacteria in middle-mixed (T2) and bottom-mixed (T3) which was consistent with the later methane production than Tl. Methanosarcina was the dominant archaea in T1 reactor. Methanoculleus and Methanosarcina were the main microorganisms in top and bottom area of T2 and T3 reactor. Acidogenic (top area) and methanogenic zones (bottom area) were formed in all reactors respectively, by combining the physicochemical properties and microorganisms. Overall, T1 showed more advantages for methane production during SS-AD. (C) 2020 Elsevier Ltd. All rights reserved.
  • [期刊] Theoretical investigation of AhR binding property with relevant structural requirements for AhR-mediated toxicity of polybrominated diphenyl ethers
    Polybrominated diphenyl ethers (PBDEs) are more frequently suspected with the induction of toxicity via signal transduction pathway of cytosolic aryl hydrocarbon receptor (AhR), the initial binding to which is assumed to be an essential prerequisite during the ligand-dependent activation. However, the AhR binding property and associated toxicity of PBDEs is yet to be clearly known for lacking insights into the structural requirements at molecular level. To understand the AhR binding property of PBDEs, the ligand binding domain (LBD) of AhR was simulatively developed on homologous protein after basic validation of geometrical rationality and the binding interaction profile was visually described using molecular docking approach. For AhR binding, the offset or edge-on pi-pi stackings with aromatic motifs including Phe289, Phe345 and His285 were shown to be structurally required whereas the electrostatic attraction validated for AhR binding to dioxins might be less effective for 2,2',3,4,4'-pentabromodiphenyl ether (BDE-85). Besides the demands of less steric hindrance from alanines and weak formulation of hydrogen bonds, the dispersion force through large contact and polarization of S-pi electrons seemed to be impactful when BDE-85 were closer to Cys327, Met334 or Met342. With theoretical computation of AhR binding energies, the more significant correlativity with bioassays was derived especially for the lowly/moderately brominated congeners, and could be used to predict the AhR binding affinity on certain degree. The informative results would thus not only help well understand the molecular basis of AhR-mediated toxicity but give an approach for accelerative evaluation of AhR binding and toxicity of PBDEs. (C) 2020 Elsevier Ltd. All rights reserved.
  • [期刊] Serum elimination half-lives adjusted for ongoing exposure of tri-to hexabrominated diphenyl ethers: Determined in persons moving from North America to Australia
    The objective of the study was to determine the human serum elimination half-life of polybrominated diphenyl ethers (PBDEs) adjusted for ongoing exposure in subjects moving from a higher exposure region (North America) to a lower exposure region (Australia).The study population was comprised of exchange students and long-term visitors from North America moving to Brisbane, Australia (N = 27) and local residents (N = 23) who were followed by repeated serum sampling every other month. The local residents were sampled to adjust for ongoing exposure in Australia. Only one visitor remained in Australia for a period of time similar to the elimination half-life and had a sufficiently high initial concentration of PBDEs to derive a half-life. This visitor arrived in Australia in March of 2011 and remained in the country for 1.5 years. Since the magnitude of PBDE exposure is lower in Australia than in North America we observed an apparent 1st order elimination curve over time from which we have estimated the serum elimination half-lives for BDE28, BDE47, BDE99, BDE100, and BDE153 to be 0.942, 1.19, 1.03, 2.16, and 4.12 years, respectively. Uncertainty in the estimates were estimated using a Monte Carlo simulation. The human serum elimination half-life adjusted for ongoing exposure can allow us to assess the effectiveness and reduction in exposure in the general population following phase out of commercial penta- and octaBDE in 2004 in the United States. (C) 2020 Published by Elsevier Ltd.
  • [期刊] Detection of high PBDD/Fs levels and dioxin-like activity in toys using a combination of GC-HRMS, rat-based and human-based DR CALUX? reporter gene assays
    Brominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) are increasingly reported at significant levels in various matrices, including consumer goods that are manufactured from plastics containing certain brominated flame retardants. PBDD/Fs are known ligands for the aryl hydrocarbon receptor (AhR) but are not yet considered in the hazard assessment of dioxin mixtures. The aim of the present study was to determine if PBDD/Fs levels present in plastic constituents of toys could pose a threat to children's health. PBDD/Fs, unlike their chlorinated counterparts (PCDD/Fs), have not been officially assigned toxic equivalence factors (TEFs) by the WHO therefore, we determined their relative potency towards AhR activation in both human and rodent cell-based DR CALUX (R) bioassays. This allowed us to compare GC-HRMS PBDD/F congener levels, converted to total Toxic Equivalents (TEQ) by using the PCDD/F TEFs, to CALUX Bioanalytical Equivalents (BEQ) levels present in contaminated plastic constituents from children's toys. Finally, an estimate was made of the daily ingestion of TEQs from PBDD/Fs-contaminated plastic toys by child mouthing habits. It is observed that the daily ingestion of PBDD/Fs from contaminated plastic toys may significantly contribute to the total dioxin daily intake of young children. (C) 2020 The Author(s). Published by Elsevier Ltd.
  • [期刊] Long-term 1-nitropyrene exposure induces endoplasmic reticulum stress and inhibits steroidogenesis in mice testes
    1-Nitropyrene (1-NP) is a representative nitro-polycyclic aromatic hydrocarbon from diesel exhaust. Recently, we found that maternal 1-NP exposure caused fetal growth retardation and disturbed cognitive development in adolescent female offspring. To investigate long-term 1-NP exposure on spermatogenesis and steroidogenesis, male mice were exposed to 1-NP (1.0 mg/kg/day) by gavage for 70 days. There was no significant difference on relative testicular weight, number of testicular apoptotic cells and epididymal sperm count between 1-NP-exposed mice and controls. Although long-term 1-NP exposure did not influence number of Leydig cells, steroidogenic genes and enzymes, including STAR, P450scc, P45017 alpha and 1713-HD, were downregulated in 1-NP-expoed mouse testes. Correspondingly, serum and testicular testosterone (T) levels were reduced in 1-NP-exposed mice. Additional experiment showed that testicular GRP78 mRNA and protein were upregulated by 1-NP. Testicular phospho-IRE1 alpha and sliced xbp-1 mRNA, a downstream molecule of IRE1 alpha, were elevated in 1-NP-exposed mice. Testicular phosphoPERK and phospho-elF2 alpha, a downstream molecule of PERK pathway, were increased in 1-NP-exposed mice. Testicular NOX4, a subunit of NAPDH oxidase, and HO-1, MDA, two oxidative stress markers, were increased in 1-NP-exposed mice. Testicular GSH and GSH/GSSG were decreased in 1-NP-exposed mice. These results suggest that long-term 1-NP exposure induces reactive oxygen species-evoked ER stress and disrupts steroidogenesis in mouse testes. (C) 2020 Elsevier Ltd. All rights reserved.
  • [期刊] Quantum chemical calculations on the mechanism and kinetics of ozone-initiated removal of p-coumaryl alcohol in the atmosphere
    p-Coumaryl alcohol (p-CMA), as the simplest lignin precursor, was determined in the process of lignin polymer degradation and wood smoke. However, its transformation and migration in the atmosphere have not been well clarified. In this work, the gas-phase reaction mechanisms and kinetic parameters of ozone-initiated removal of p-CMA were performed by using quantum chemical calculations. Seven primary addition reaction pathways were summarized. A more comprehensive and detailed reaction routes of the favorable Criegee intermediate (IM9) were presented, including the reactions with small molecules, as well as its own isomerization and decomposition reactions. p-Hydroxybenzaldehyde (P1) is the most dominant product in the further reactions of IM9 and the subsequent ozonolysis mechanisms of P1 also were elucidated. All thermodynamic calculations were investigated on the density functional theory (DFT) method at the M06-2X/6-311 + G (3df, 2p)//M06-2X/6-311 + G (d,p) level. The overall and individual rate constants have estimated by using the KiSThelP under typical atmospheric temperature (198-338 K) and pressure. The total rate constant is 3.37 x 10(-16) cm(3) molecule(-1) s(-1) at 298 K and 1 atm. In addition, the atmospheric lifetime of p-CMA by ozone-determined is 1.18 h under the average ozone concentration of 7 x 10(11) molecules cm(3). The short lifetime indicates that the degradation processes of p-CMA determined by O-3 cannot be ignored, especially in areas where the tip concentration of O-3 molecules is high. The present study provides a synthetical investigation on ozonolysis of p-CMA for the first time and enriches our understanding of atmospheric oxidation processes of other lignin compounds. (C) 2020 Elsevier Ltd. All rights reserved.
  • [期刊] Activation of persulfate and removal of ethyl-parathion from soil: Effect of microwave irradiation
    Advanced persulfate oxidation technology is widely used in organic pollution control of super fund sites. In recent years, microwave radiation has been proven a promising method for persulfate activation. However, most of the prior works were focused on the treatment of polluted water, but there are few reports aiming at contaminated sites, especially the knowledge of using microwave activated persulfate technology to repair pesticide-contaminated sites. In this study, an effective activation/oxidation method for the remediation of pesticide-contaminated soil, i.e., microwave/persulfate, was developed to treat soil containing ethyl-parathion. The concentration of persulfate, reaction temperature, and time were optimised. The results showed that up to 77.32% of ethyl-parathion was removed with the addition of 0.1 mmol.persulfate.g(-1) soil under the microwave temperature of 60 degrees C. In comparison, 19.43% of ethyl-parathion was removed at the same reaction temperature under the condition of water bath activated persulfate. Electron paramagnetic resonance (EPR) spectroscopy combined with spin-trapping technology was used to detect reactive oxidation species, and center dot OH and SO4-center dot were observed in the microwave/persulfate system. Quenching experiments suggested that ethyl-parathion was degraded by the generated center dot OH and SO4-center dot. Paraoxon, phenylphosphoric acid, 4-nitrophenol, dimethyl ester phosphate, and some alkanes were the dominant oxidative products identified by gas chromatography-mass spectrometry (GC-MS) analysis. A possible pathway for ethyl-parathion degradation was proposed in this study. The results obtained serve as the guidance to the development of remediation technologies involving persulfate and microwave for soil contaminated by organic contaminants such as pesticides. (C) 2020 Elsevier Ltd. All rights reserved.
  • [期刊] Levofloxacin and sulfamethoxazole induced alterations of biomolecules in Pseudokirchneriella subcapitata
    Levofloxacin (LEV) and sulfamethoxazole (SMX) are two extensively used antibiotics. Most investigations have been concentrated on the toxic effects of antibiotics on algal species evaluated with traditional ecotoxicological endpoints; however, limited information is available on the alterations in biomolecules induced by antibiotics. Here we investigated alterations in the structure and function of biomolecules to a model species Pseudokirchneriella subcapitata following exposure of LEV and SMX by applying Fourier transform infrared spectroscopy (FTIR). The growth inhibition tests revealed that both LEV and SMX had negative effects on algal growth, while SMX was found to be more toxic to P. subcapitata than LEV. Based on the FTIR analysis, alterations in the structure, composition and function of lipids and proteins were observed on microalgal cells, which were correlated with the dosage of LEV and SMX. As a result of lipid peroxidation induced by LEV and SMX, an increase in the lipid/protein ratio and decrease in the ratios of CH2/lipid, CH3/lipid, carbonyl ester/lipid and olefinic = CH/lipid were observed in all treatment groups with respect to the reference control. Moreover, alterations in the composition and secondary structure of proteins were also observed in accompany with a decrease in the Amide I/Amide II ratio and an increase of the loose beta-sheet structure protein. LEV caused an elevated level of lipid peroxidation, while SMX induced a more obvious protein aggregation. The findings from this study showed that FTIR could reveal the toxic mechanism of these two antibiotics to algae at the biochemical level by linking alterations in biomolecules to biochemical dynamics and function. (C) 2020 Elsevier Ltd. All rights reserved.
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