Density Functional Theory Study of Marine Polybrominated Diphenyl Ethers in Anaerobic Degradation

Polybrominated diphenyl ethers(PBDEs)are a kind of serious pollutants in the ocean.Biodegradation is considered as an economical and safe way for PBDEs removal and reductive debromination dominates the initial pathway of anaerobic degradation.On the basis of experimental study,Octa-BDE 197,Hepta-BDE 183,Hexa-BDE 153,Penta-BDE 99 and Tetra-BDE 47 were selected as the initial degradation objects,and their debromination degradation were studied using density functional theory.The structures were optimized by Gaussian 09 program.Furthermore,the molecular orbitals and charge distribution were analyzed.All C-Br bond dissociation energies at different positions including ortho,meta and para bromine atoms were calculated and the sequence of debromination was obtained.There is a close relationship between molecular structure,charge,molecular orbital and C-Br bond.All PBDEs exhibited similar debromination pathways with preferential removal of meta and para bromines.

Ecotoxicological effects of mixed pollutants resulted from e-wastes recycling and bioaccumulation of polybrominated diphenyl ethers in Chinese loach(Misgurnus anguillicaudatus)

To understand potential ecotoxicological effects of electrical and electronic equipment waste （e-waste） recycling and polybrominated diphenyl ethers （PBDEs） bioaccumulation in loaches, a semi-field experiment using Chinese loach （Misgurnus anguiUicaudatus） as experimental fish was performed. Larval loaches were kept in net-cage for three months in an e-wastes recycling site and a reference site in Southeastern China. There was significant difference of the survival rate between the loaches from the e-wastes recycling site （27%, 19/70） and from reference site （70%, 49/70）. Histopathological responses were also found in all the livers examined in loaches from the e-wastes recycling site. These results showed that mixed pollutants resulted from e-wastes recycling led to ecotoxicological effects on loaches. The bioaccumulation of polybrominated diphenyl ethers （PBDEs）, the main pollutants in e-waste, in loaches was also studied, the mean concentration of total PBDEs in sediment was 6726.17 ng/g wet weight and in water samples was 4.08 ng/L （dissolved phase）. BDE 209 was the dominant congener in sediment and with relatively high concentration in water. Relatively low concentration of BDE 209 （less than 0.01% of total PBDEs） and high concentration of BDE47 （up to 39.34% of total PBDEs） were detected in loaches.

Occurrence of polybrominated diphenyl ethers in fish and shellfish downstream from electronic-waste recycling plants

We measured 39 polybrominated diphenyl ethers （PBDEs） in the muscle tissue of three species of fish （Sciaenops ocellatus,Sparus macrocephalus,and Lateolabrax japonicus） and four species of shellfish （Tegillarca granosa,Cyclina sinensis,Sinonovacula constricta,and Ostrea cucullata） that were collected downstream of electronic-waste recycling plants in Taizhou,China.A total of 24 PBDE congeners （PBDE 24） in the samples were detected.The PBDE 24 （total PBDE） ranged from 545.4 to 1688.7 ng/kg ww （wet weight）.The mean PBDE 24 concentration was 1382.6 ng/kg ww in fish and 858.1 ng/kg ww in shellfish.The lower brominated congeners were detected at relatively high concentrations in all species.The penta-products,produced from e-waste,were found at relatively low levels.A principal component analysis suggested a significant correlation among di-,tri-,tetra-,and hepta-BDEs for the three species of fish.Similarly,we found a significant correlation between mono-and tri-BDEs in the shellfish.Our results suggested that the processes of PBDE metabolism and elimination were similar in both fish and shellfish.In addition,the primary source of PBDEs appeared to be from the debromination of high brominated PBDEs.

Prediction of Aqueous Solubility for 209 Polychlorinated Diphenyl Ethers from Molecular Structural Parameters by DFT Method

Optimized calculations of 209 polychlorinated diphenyl ethers （PCDEs） and diphenyl ethers were carried out at the B3LYP/6-31G^＊ level with the Gaussian 98 program. Based on the theoretical linear solvation energy relationship （TLSER） model, the obtained structural parameters were taken as theoretical descriptors to establish the novel QSPR model for predicting aqueous solubility （-lgSw） of PCDEs. The model obtained in this work contains two variables： mean molecular polarizability （a） and the most positive partial charge on a hydrogen atom （qH^＋）, of which RE = 0.9606 and SD = 0.32. And the results of cross-validation test also show that the model exhibits optimum stability and better predictive power. Moreover, the predictive power of the new model is better than that of MCIs method.

Identification of the metabolites of polybrominated diphenyl ether 99 and its related cytochrome P450s

Objective：To investigate the metabolites of polybrominated diphenyl ether 99（BDE-99）and its related cytochrome P450s in an in vitro system.Methods：Rat primary hepatocytes were isolated and treated with BDE-99 for 24-72 h.Metabolites were then extracted from the hepatocytes and media,and detected by GC/MS.Several mRNAs of metabolic enzymes were also extracted from the same cells and the gene expression levels were determined using quantitative real-time PCR.In addition,selected recombinant cytochrome P450s（CYPs） were expressed in a bacurovirus/sf9 system,and these were further used to explore the metabolism of BDE-99 in vitro.The parent depletion approach was used for screening the ability of CYPs to eliminate BDE-99.Results： A reductively debrominated metabolite,BDE-47,and three oxidative metabolites,2,4,5-tribromophenol,5-OH-BDE-47,and 5＇-OH-BDE-99,were identified from the BDE-99-treated rat hepatocytes,whereas no MeO metabolite was detected in the system.RT-PCR analysis showed that CYP 3A23/3A1,1A2,and 2B1/2 were induced by BDE-99.Furthermore,using the heterological expressed CYP proteins in in vitro BDE-99 metabolism experiments we found that CYP1A2 and CYP3A4 showed the highest metabolic efficiency for BDE-99,with the metabolic clearance rates of CYP1A2 and CYP3A4 being 30.3%and 27.7%,respectively.CYP1A1 and CYP2A6 displayed relatively low clearance rates,while CYP2E1 seemed not to be associated with the BDE-99 metabolism.Conclusions：In our in vitro rat primary hepatocyte metabolism system,four metabolites of BDE-99 were identified,and CYP3A4 and CYP1A2 were demonstrated to be involved in the BDE-99 metabolism.

Predicting the Relative Retention Time (RRT) of Polybrominated Diphenyl Ethers (PBDEs)

Using the molecular electronegativity distance vector descriptors derived directly from the molecular topological structures, the relative retention time （RRT） of polybrominated diphenyl ethers （PBDEs） were predicted. A four-variable regression model （M30） with the correlation coefficient of 0.9816 and the root mean square errors of 0.061 was developed using a training set including 30 PBDEs. The correlation coefficient of 0.9841 and the root mean square errors of 0.054 between the values of RRT predicted by M30 and the RRT observed for 16 external PBDEs show a good predictive potential of M30. The descriptors included in the M30 represent four interactions between four pairs of atom types, i.e., atom -C= and -C=, -C= and 〉C=, 〉C= and 〉C=, -C= and -Br.

Polybrominated Diphenyl Ethers in Surface Sediment from Songhua River Basin,Northeast of China

Sixty sediment samples were collected from the main Songhua River in three years. Twelve polybrominated diphenyl ether( PBDE) congeners( BDE17,28,47,66,99,100,153,154,138,183,and BDE-209) were detected to state the pollution situation. The results showed that the total concentration of total PBDEs ranges from 0. 424 to 23. 0 ng / g dry weight,with the mean of 3. 02 ng / g,and the total PBDEs concentration is at relative low level compared with those worldwide. The congener profile showed that BDE-209 is the dominant congener that accounts for more than 80. 1% of total PBDEs in sediments,followed by BDE-47 and BDE-99. These profiles are consistent with a high consumption of Deca-BDEs for the brominated flame retardant market in China. The results of spatial and seasonal observations indicated that local sources,temperature variation, and hydrologic conditions are significant factors on PBDEs concentrations. Hazard quotients suggested that PBDEs pose no potential risk to benthic organisms in detected area at present.

Synthesis and antibacterial activity of brominated 2′(4′)-nitro-3-hydroxy diphenyl ethers

Eight new brominated 2＇（4＇）-nitro-3-hydroxy diphenyl ethers have been designed and synthesized. The structures of new compounds were confirmed by ^1H NMR, IR and HRMS. The bioactivity tests showed that these compounds possessed antibacterial activities against the tested bacteria. These new compounds cannot be transformed into dioxins when they were manufactured and used.

Concentrations of Polybrominated Diphenyl Ethers in Maternal Blood,Placental Size,and Risk for Fetal Growth Restriction:A Nested Case-control Study

Objective To explore the effects of prenatal exposure to polybrominated diphenyl ethers(PBDEs)on placental size and birth outcomes.Methods Based on the perspective Wenzhou Birth Cohort,this nested case-control study included 101 fetal growth restriction(FGR)and 101 healthy newborns.Maternal serum samples were collected during the third trimester and measured for PBDEs by gas chromatography tandem mass spectrometry.The basic information of mother-newborn pairs was collected from questionnaires,whereas the placental size and birth outcomes of newborns were obtained from hospital records.Results A total of 19 brominated diphenyle ether(BDE)congeners were detected in maternal serum samples.Higher concentrations of BDE-207,-208,-209,and∑19PBDEs were detected in FGR cases than in controls.Increased BDE-207,-208,-209,and∑19PBDEs levels in maternal serum were related to decreased placental length,breadth,surface area,birth weight,birth length,gestational age,and Quetelet index of newborns.After adjusting for confounders,BDE-207 and∑19PBDE concentrations in maternal serum were significantly associated with an increased risk of FGR.Conclusion A negative association was found between PBDE levels in maternal serum and placental size and birth outcomes.Prenatal PBDE exposure may be associated with elevated risk of the incidence of FGR birth.

Non-Halogenated Solvent-Processed High-Efficiency Polymer Solar Cells:the Role of Diphenyl Ether in Morphology,Light-Trapping,Transport Properties

There is an urgent need to use green non-halogenated solvents to prepare polymer solar cells(PSCs) for industrialization.It is time-consuming but necessary to find a suitable non-halogenated solvent/additive combination for a given donor:acceptor materials system.In this research,we report a non-halogenated binary solvent system toluene/diphenyl ether(DPE) for the PBDTT-DTffBT:PC_(71)BM and PM6:Y6 blending systems that exhibit comparable power conversion efficiency(PCE) to that of devices prepared with halogenated solvents.The nano scale morphology indicates that blending film processed solely with toluene has poor phase segregation and a rough surface,which hinders charge separation and interfacial contact.Besides,the total absorption spectra revealed significant light-trapping losses in the toluene-processed solar cells,resulting in low photocurrent generation.DPE incorporation addresses these issues and significantly improves the short-circuit current density and fill factor.Moreover,non-halogen solvent-processed devices exhibit high hole mobility and low transporting impedance properties.The present study enriches the families of eco-friendly,high-efficiency PSCs fabricated using nonhalogenated solvents.

Determination of brominated diphenyl ethers in atmospheric particulate matter using selective pressurized liquid extraction and gas chromatography–mass spectrometry with a negative chemical ionization

This study describes the development and validation of a sensitive and reliable method for determination of polybrominated diphenyl ethers(PBDEs)in atmospheric particulate matter using selective pressurized liquid extraction(SPLE)and gas chromatography–mass spectrometry with a negative chemical ionization(GC-NCI-MS).Extraction and clean-up were performed using PLE with 2 g florisil and 3 g silica placed in the extraction cells.Under optimal conditions,14 PBDEs were extracted at 70°C using hexane/dichloromethane(50:50,v/v)as solvent.Validation of SPLE returned excellent recoveries for most analytes,with relative standard deviations mostly below20%.Method detection limits ranged from 0.13 to15.38 ngám L^(-1)for the GC-MS analyses.The method was successfully applied to atmospheric particulate matter of Beijing,where analytes were detected in the range of182.79 to 468.99 pgám^(-3).

Variation of Bioaccumulation Ability of 2,2',4,4'-Tetrabromodiphenyl Ether by Marine Diatom Skeletonema costatum Under Different N:P Ratios

The growth, biochemical content and bioaccumulation quantity of 2,2',4,4'-tetrabromodiphenyl ether(BDE-47) in Skeletonema costatum were studied under different N:P ratios(1, 4, 16, 64 and 128). All cellular biochemical contents of S. costatum presented decreasing trend over cultivation time. At early stage of cultivation, the cellular protein, carbohydrate and lipid in S. costatum presented higher values in treatments of N:P=4 and 16. However, they were lower in these treatments at the late stage, but higher in treatments N:P=1 and 128. Similarly, BDE-47 levels per cell of S. costatum were higher in treatments of N:P=4 and 16 at early stage of cultivation, which were 3.8 and 3.7 ng(106 cells)-1, respectively. At the middle stage of cultivation, the BDE-47 level per S. costatum cell lowered; and it further reduced in the treatments of N:P=4 and 16 at the late stage with the values 0.6 and 0.5 ng(106 cells)-1, respectively. However, it rose in N:P=128, reaching up to 2.3 ng(106 cells)-1. Compared with BDE-47 per cell, BDE-47 per algal volume under different N:P ratios did not present obvious difference. The quantity BDE-47 accumulated per cell of S. costatum was positively correlated with protein, carbohydrate and lipid per cell; meanwhile, the BDE-47 per volume had a positive correlation with biochemical content per volume. The variation of bioaccumulation ability of BDE-47 in S. costatum can be explained by biochemical changes due to N:P ratios.

A study on hydrogen uptake and release of a eutectic mixture of biphenyl and diphenyl ether

Hydrogen storage in Liquid Organic Hydrogen Carrier(LOHC)systems is appealing for the safe storage and distribution of excess renewable energy via existing gasoline infrastructures to end-users.We present the eutectic mixture of biphenyl and diphenyl ether of its first use as a LOHC material.The material is hydrogenated with 99%selectivity without the cleavage of C–O bond,with commercial heterogeneous catalysts,which is confirmed by nuclear magnetic spectroscopy and gas chromatography-mass spectrometry.Equilibrium concentration,dehydrogenation enthalpy,and thermo-neutral temperature are calculated using a density functional theory.The results indicate that O-atom-containing material exhibits more favorable dehydrogenation thermodynamics than that of the hydrocarbon analogue.The H2-rich material contains6.8 wt%of gravimetric hydrogen storage capacity.A preliminary study of catalytic dehydrogenation on a continuous reactor is presented to demonstrate a reversibility of this material.

A Validated Liquid Chromatography-Mass Spectrometry Method for the Detection and Quantification of Oxidative Metabolites of 2,2',4,4'-Tetrabromodiphenyl Ether in Rat Hepatic Microsomes

In the present study, we developed and validated an analytical method using ultra performance liquid chromatography-mass spectrometry (UPLC/MS) for the quantitative determination of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) metabolism by rat hepatic microsomes. BDE-47 is a brominated flame retardant that was widely used in a variety of consumer products and has subsequently been identified as a ubiquitous environmental contaminant. Hydroxy-bromodiphenyl ethers (OH-BDEs) were isolated from rat hepatic microsomes by liquid-liquid extraction. Chromatographic separation was achieved by UPLC on a C18 column with gradient elution using a mobile phase consisting of methanol and water, each containing 0.1% formic acid, at a flow rate of 0.2 mL/min. Detection and quantification were performed using a mass spectrometer in single ion recording mode with negative electrospray ionization. The UPLC/MS method was validated for linearity, limit of quantification (LOQ), accuracy, precision and recovery. The weighted calibration curves (1/X2) were linear over a concentration range of 5 - 250 nM with LOQ values between 5 nM and 50 nM for the individual OH-BDEs. Intra- and inter- day accuracy (%DEV) and precision (%RSD) values ranged from –11.7% to 9.5% and 5.9% to 16.5%, respectively. Recovery values of 70% to 90% were obtained for all OH-BDEs. The validated method allowed us to successfully analyze metabolite formation following incubation of BDE-47 with hepatic microsomes prepared from phenobarbital-treated rats. Results demonstrate that the UPLC/MS method has sufficient sensitivity and reproducibility to fully characterize the in vitro metabolism of BDE-47 and possibly other PBDEs.

Dose-dependent effects of pentabrominated diphenyl ethers on sexual hormone and histology of male reproductive system in rats

Polybrominated diphenyl ethers (PBDEs) used as flame retardants are widely used in a variety of consumer products, like textiles, foam and building materials. They are persistent in the environment, and increasing levels of PBDEs have been found both biota and human tissue samples. In the present study we examined the dose-dependent effects of pentabrominated diphenyl ether (PBDE-99) on the serum hormone and histology of reproductive system in male rats. 40 health 4-week-old SD rats were divided into 4 groups randomly. The treated rats were orally administered with BDE-99 at the dose of 60,120 or 180 mg/kg, while controls received equal volume of corn oil. We examined the changes of serum hormone levels, histopathology, and PCNA after 30 days exposure to BDE-99. With increasing doses of BDE-99, testis organ coefficient increased, serum hormone levels lower, PCNA positive expression reduced, and the degeneration of seminiferous epithelium were revealed in treated group. These indicators with significant dose-effect relationship showed that BDE-99 can reduce the serum sex hormone levels and cause severe degeneration of seminiferous epithelium.

Bioaccumulative Characteristics of Polybrominated Diphenyl Ethers in Channel Catfish and Fish Feeds from China

PBDEs are widely used brominated flame retardant, which are increasingly reported in the environment. Concentrations of thirteen PBDEs in a large number of channel catfish and fish feeds collected from Hubei province of China were investigated in this study. A fast isotopic dilution GC-MS method was firstly developed to simultaneously determine thirteen PBDEs in channel catfish and fish feeds in this study, and especially for the first time PBDEs in fish feeds. Pressurized liquid extraction and multi-layer silica gel column chromatography cleanup were used, some important steps and crucial parameters were modified and intensified compared with other literatures, and GC and MS conditions were optimized. The limits of quantitation values of 0.25 - 5 μg·kg-1 wet weight in channel catfish were calculated for PBDEs;so did 1 - 20 μg·kg-1 wet weight in fish feeds. In addition, good repeatability and accuracy of the whole method were achieved. The established methods were therefore suitable for the simultaneous determinations of thirteen PBDEs in these samples at trace contamination levels. Using the established methods, PBDEs emerged in 10 of 180 channel catfish and 13 of 115 fish feeds, and the dominant PBDEs homologues were PBDE-28, PBDE-47, PBDE-100, PBDE-99, PBDE-154, PBDE-153 and PBDE-183. The detection rates of seven PBDEs congeners were in turn respectively 1.74%, 7.83%, 4.35%, 5.22%, 3.48%, 2.61% and 2.61% in fish feeds, and detection rates of seven PBDEs congeners were in turn respectively 1.11%, 3.89%, 2.22%, 1.67%, 1.11%, 1.11% and 1.11% in channel catfish. There was significant correlation in PBDEs between matching channel catfish and fish feeds (R2 = 0.742, P < 0.001, n = 30), suggesting that fish feeds contaminated with PBDEs possibly resulted in PBDEs residual in channel catfish through biological transfer.

Colloid-facilitated release of polybrominated diphenyl ethers at an e-waste recycling site: evidence from undisturbed soil core leaching experiments

Polybrominated diphenyl ethers (PBDEs), a class of persistent organic pollutants, have been frequently detected in soil at e-waste recycling sites. However, the key factors controlling the transport of PBDEs from surface soil to the vadose zone and groundwater are unclear. Here, colloid-enhanced leaching of PBDEs from undisturbed soil cores collected at an e-waste recycling site in Tianjin, China, is reported. Spatially heterogeneous release of colloids and PBDEs was observed in all the tested soil cores under chemical and hydrodynamic perturbations, indicating the presence of preferential flow paths. Colloid concentration in the effluent significantly increased as ionic strength decreased (from 10 to 0.01 mmol/L), probably due to the stronger electrostatic repulsion between colloidal particles and the soil matrix at lower ionic strength. In contrast, colloid mobilization was not significantly affected by the changes in pH of the influent (from 4.0 to 10.0) and flow rate (from a Darcy velocity of 1.5 to 6.0 cm/h). The concentrations of 2,2′,3,3′,4,4′,5,5′,6,6′-decabromodiphenyl ether (BDE-209), the predominant PBDE congener at the site, detected in the leachate (ranging from 1.09 to 3.43 ng/L) were much lower than previously reported results from packed column leaching tests, and were positively correlated with colloid concentrations. This indicates that remobilization of colloids at e-waste recycling sites can promote the leaching and downward migration of PBDEs from surface soil. The findings highlight the potential risk of surface soil PBDE contamination to groundwater quality and call for further understanding of colloid-facilitated transport for predicting the fate of PBDEs at e-waste recycling sites.

Efficient removal of polybrominated diphenyl ethers from soil washing effluent by dummy molecular imprinted adsorbents: Selectivity and mechanisms

Surfactant enhanced elution is an effective method for removing hydrophobic organic pollutants from soils.The key to the development of leaching technology is selective removal of targeted pollutants in soil washing effluent and recycling of surfactant solutions.In this study,a molecular imprinting technique was applied to selectively sorb polybrominated diphenyl ethers(PBDEs)in soil washing effluent.The novel molecular imprinted polymers(MIPs)using different template molecules were synthesized by precipitation polymerization.Adsorption behaviors andmechanisms ofMIPs were studied through experiments and theoretical calculations.The results show that 4-bromo-4'-hydroxybiphenyl and toluene can be effective imprinting molecule for MIPs synthesis.The maximal adsorption capacity of selected dummy molecular imprinted polymer(D1-MIP)was 1032.36μmol/g,and that of part molecular imprinted polymer(P-MIP)was 981.13μmol/g.Their imprinting factors in 5 PBDEs adsorption ranged from 2.13 to 5.88,the recovery percentage of Triton X-100 can reach 99.09%,confirming the feasibility of reusing surfactant.Various PBDEs could be removed by MIPs,and Quantitative Structure Property Relationship analysis revealed that PBDEs’molecular volume,planarity,polarity,and hydrophobicity have major influences on their adsorption performance.DFT calculation revealed that Van derWaals force and hydrogen bonding played important roles during selective adsorption.These results can provide effective theoretical guidance for surfactant enhanced soil elution in practical engineering applications.

The interaction mechanisms of co-existing polybrominated diphenyl ethers and engineered nanoparticles in environmental waters: A critical review

This review focuses on the occurrence and interactions of engineered nanoparticles(ENPs)and brominated flame retardants(BFRs)such as polybrominated diphenyl ethers(PBDEs)in water systems and the generation of highly complex compounds in the environment.The release of ENPs and BFRs(e.g.PBDEs)to aquatic environments during their usage and disposal are summarised together with their key interaction mechanisms.The major interaction mechanisms including electrostatic,van derWaals,hydrophobic,molecular bridging and steric,hydrogen andπ-bonding,cation bridging and ligand exchange were identified.The presence of ENPs could influence the fate and behaviour of PBDEs through the interactions as well as induced reactions under certain conditions which increases the formation of complex compounds.The interaction leads to alteration of behaviour for PBDEs and their toxic effects to ecological receptors.The intermingled compound(ENPs-BFRs)would show different behaviour from the parental ENPs or BFRs,which are currently lack of investigation.This review provided insights on the interactions of ENPs and BFRs in artificial,environmental water systems and wastewater treatment plants(WWTPs),which are important for a comprehensive risk assessment.

Chemical reductive technologies for the debromination of polybrominated diphenyl ethers: A review

Polybrominated diphenyl ethers(PBDEs)are widely used as brominated flame retardants,which had attracted amounts of attention due to their harmful characteristics of high toxicity,environmental persistence and potential bioaccumulation.Many chemical reductive debromination technologies have been developed for the debromination of PBDEs,including photolysis,photocatalysis,electrocatalysis,zero-valent metal reduction,chemically catalytic reduction and mechanochemical method.This review aims to provide information about the degradation thermodynamics and kinetics of PBDEs and summarize the degradation mechanisms in various systems.According to the comparative analysis,the rapid debromination to generate bromine-free products in an electron-transfer process,of which photocatalysis is a representative one,is found to be relatively difficult,because the degradation rate of PBDEs depended on the Br-rich phenyl ring with the lowest unoccupied molecular orbital(LUMO)localization.On the contrary,the complete debromination occurs easily in other systems with active hydrogen atoms as the main reactive species,such as chemically catalytic reduction systems.The review provides the knowledge on the chemical reductive technique of PBDEs,which would greatly help not only clarify the degradation mechanism but also design the more efficient system for the rapid and deep debromination of PBDEs in the future.