NiFe2O4-based magnetic covalent organic framework nanocomposites for the efficient adsorption of brominated flame retardants from water.

A new kind of NiFe2O4-based magnetic covalent organic framework nanocomposites (NiFe2O4@COFs) was fabricated through facile synthesis approach under room temperature. The NiFe2O4@COFs exhibited higher adsorption capacity for brominated flame retardants than carbon nanotube material based on hydrophobic interactions, π-π stacking interaction, and van der Waals forces. In addition, the adsorption isotherm and the kinetic model were more suitable for Langmuir and pseudo-second-order model, respectively. NiFe2O4-based magnetic covalent organic framework nanocomposites combined with HPLC-UV (absorption wavelength: 214 nm) technology has excellent adsorption performance, which exhibited low detection limits (0.03-1.9 µg L-1), wide linear range (0.11-1000 µg L-1), good recoveries (91.5-102%) with a relative standard deviation of less than 2.9%. Finally, the prepared magnetic material was successfully used asadsorbents of magnetic solid-phase extraction and applied to the determination of five BFRs from the real water samples. The adsorption and removal of BFRs by NiFe2O4@COFs from water samples.

High throughput extraction strategy for simultaneous analysis of 19 tetrabromobisphenol A and halogenated carbazole analogs in seafood.

Tetrabromobisphenol A (TBBPA), halogenated carbazole (HCZ), and their analogs are the emerging pollutants invading the marine environment. So far, a few methods have been reported for the simultaneous analysis of these pollutants due to their large polarity difference. In this study, an effective extraction and cleanup strategy was developed for the simultaneous determination of 19 TBBPA and HCZ congeners in seafood. The 19 analytes could be directly analyzed through high performance liquid chromatography after ultrasonic extraction (methanol, duplicate ethyl acetate-acetone (1:1, v/v)) and gel permeation chromatography cleanup. The acceptable spike-recoveries were within 65.7-118.3%; the precision was intra-/inter-day RSDs: 0.0-6.7%/0.0-8.5%; and the matrix effects were between -14.1% and 12.4%. The detection limits and quantification limits were 0.002-0.014 and 0.020-0.200 µg g-1 dw, respectively. Additionally, this method successfully analyzed the seafood samples and the concentrations of these analytes were in range of nd-5.4 µg g-1 dw.

Isocadiolides A-H: Polybrominated Aromatics from a Synoicum sp. Ascidian.

Isocadiolides A-H (1-8) and cadiolide N (9), new polybrominated aromatic compounds, were isolated from a Korean Synoicum sp. ascidian. On the basis of the results of extensive spectroscopic analyses, these compounds possessed tris-bromohydroxyphenyl moieties as a common structural motif, while their cores varied [cyclopentenedione (1-5), dihydrofuran (6 and 7), pyranone (8), and furanone (9)], reflecting different extents of rearrangement and oxidation. Several of these compounds exhibited weak antibacterial activities and moderate abilities to inhibit the microbial enzymes sortase A and isocitrate lyase.

A clean-up method for determination of multi-classes of persistent organic pollutants in sediment and biota samples with an aliquot sample.

In the present study, we developed a novel method to simultaneously detect eight classes of persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs), polybrominated diphenyl ethers (PBDEs), polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs), polychlorinated naphthalenes (PCNs), organochlorine pesticides (OCPs), short-chain chlorinated paraffins (SCCPs) and Dechlorane Plus (DP), in sediment and fish tissue samples. The samples were extracted by accelerated solvent extraction (ASE) system, and the extracts were purified and fractionated into fraction1 and fraction2 with multi-layer silica gel column, followed by further fractionation using a basic alumina column (fraction1) and a Florisil column (fraction2), respectively. Finally, fractions were analyzed with different chromatographic columns and different detectors according to the properties of a chemical compound. The limit of detection for eight classes of POPs ranged from 1 to 30 pg/gdw in fish tissue samples, and from 1 to 33 pg/gdw in sediment samples, except for SCCPs (from 5.6 to 7.6 ng/g in fish tissue samples, and from 1.2 to 8.3 ng/gdw in sediment samples). The recoveries of eight classes of POPs spiked in fish tissue and sediment samples ranged from 43% to 120%, and from 45% to 115%, respectively. The relative standard deviation (RSD) was less than 25%. The accuracy of method was satisfactorily demonstrated by analysis of standard reference materials NIST SRM 1649b and WMF-01. In addition, the newly developed method was successfully applied for analysis of sediment and fish samples collected from the Baiyangdian Lake.

Changes in microbial community during removal of BDE-153 in four types of aquatic sediments.

Indigenous microorganisms in sediments could degrade polybrominated diphenyl ethers (PBDEs), but how the microbial communities respond to PBDEs was seldom reported. The effect of BDE-153, a common congener in aquatic environments, on the microbial communities in four types of aquatic sediments was evaluated during the 150days' incubation under an anaerobic condition. The intrinsic potential to remove BDE-153 varied significantly among four sediment types, and the removal rates of mangrove, mudflat, marine and freshwater sediments were 0.013, 0.013, 0.011, and 0.009day-1, respectively. The observed microbial species, Simpson, Shannon, and Chao1 indices in all sediments were rather stable and were not changed significantly by BDE-153 amendment. However, BDE-153 amendment altered the microbial community compositions in three saline sediments at the end of the incubation period. Distance-based multivariate multiple regression analysis revealed that salinity, total organic carbon (TOC) and BDE-52, the major debromination product of BDE-153, were the three main factors explaining the variations in microbial community compositions in BDE-treated sediments; whereas salinity, TOC and pH were the main contributing factors in control sediments without BDE-153. The daughter congeners generated during anaerobic debromination process need more attention, especially their effect on the microbial communities in aquatic sediments.

Investigation of nanoscale zerovalent iron-based magnetic and thermal dual-responsive composite materials for the removal and detection of phenols.

In this study, well-defined magnetic and thermal dual-responsive nanomaterials were synthesized, which contained ultrafine core-shell Fe@SiO2 nanoparticles as magnetic core and poly(N-isopropylacrylamide) (PNIPAM) as thermosensitive outer shell. The fabricated nanoparticles were characterized and investigated for the adsorption of four phenolic compounds, including bisphenol A (BPA), tetrabromobisphenol A (TBBPA), 4-tert-octylphenol (4-OP) and 4-n-nonylphenol (4-NP). The experimental results demonstrated that the excellent adsorption rates were attributed to hydrophobic effect, hydrogen-bonding interaction, and electrostatic attraction. The adsorption process followed pseudo-second-order kinetics model and nonlinear isotherms, indicating heterogeneous adsorption process. The adsorption efficiency of 4-NP using Fe@SiO2@PNIPAM was more than 90% under optimized condition within 2 h. The determined maximum adsorption amounts of BPA, TBBPA, 4-OP and 4-NP were 2.43, 6.83, 24.75, and 49.34 mg g-1, respectively. Meanwhile, a magnetic solid phase extraction (MSPE) method with Fe@SiO2@PNIPAM was established to determine these four compounds simultaneously. Under the optimal conditions, the linearity ranges were in the range of 2-200, 2-300, 2-100 and 2-100 µg L-1 for BPA, 4-OP, TBBPA, and 4-NP, respectively, and the detection limits were in the range of 0.58-0.76 µg L-1, respectively. The applicability of the proposed method was evaluated by analyzing three fresh water samples, and satisfactory spiked recoveries in the range 70.9-119.9% were achieved. It was proved that these adsorbents could be easily collected and recycled owing to the appropriate magnetism. The results also demonstrated that the as-prepared adsorbents had promising potential in the enrichment and analysis of detrimental organic pollutants from water.

Rapid Removal of Tetrabromobisphenol A by Ozonation in Water: Oxidation Products, Reaction Pathways and Toxicity Assessment.

Tetrabromobisphenol A (TBBPA) is one of the most widely used brominated flame retardants and has attracted more and more attention. In this work, the parent TBBPA with an initial concentration of 100 mg/L was completely removed after 6 min of ozonation at pH 8.0, and alkaline conditions favored a more rapid removal than acidic and neutral conditions. The presence of typical anions and humic acid did not significantly affect the degradation of TBBPA. The quenching test using isopropanol indicated that direct ozone oxidation played a dominant role during this process. Seventeen reaction intermediates and products were identified using an electrospray time-of-flight mass spectrometer. Notably, the generation of 2,4,6-tribromophenol was first observed in the degradation process of TBBPA. The evolution of reaction products showed that ozonation is an efficient treatment for removal of both TBBPA and intermediates. Sequential transformation of organic bromine to bromide and bromate was confirmed by ion chromatography analysis. Two primary reaction pathways that involve cleavage of central carbon atom and benzene ring cleavage concomitant with debromination were thus proposed and further justified by calculations of frontier electron densities. Furthermore, the total organic carbon data suggested a low mineralization rate, even after the complete removal of TBBPA. Meanwhile, the acute aqueous toxicity of reaction solutions to Photobacterium Phosphoreum and Daphnia magna was rapidly decreased during ozonation. In addition, no obvious difference in the attenuation of TBBPA was found by ozone oxidation using different water matrices, and the effectiveness in natural waters further demonstrates that ozonation can be adopted as a promising technique to treat TBBPA-contaminated waters.

Quantification of Hydroxylated Polybrominated Diphenyl Ethers (OH-BDEs), Triclosan, and Related Compounds in Freshwater and Coastal Systems.

Hydroxylated polybrominated diphenyl ethers (OH-BDEs) are a new class of contaminants of emerging concern, but the relative roles of natural and anthropogenic sources remain uncertain. Polybrominated diphenyl ethers (PBDEs) are used as brominated flame retardants, and they are a potential source of OH-BDEs via oxidative transformations. OH-BDEs are also natural products in marine systems. In this study, OH-BDEs were measured in water and sediment of freshwater and coastal systems along with the anthropogenic wastewater-marker compound triclosan and its photoproduct dioxin, 2,8-dichlorodibenzo-p-dioxin. The 6-OH-BDE 47 congener and its brominated dioxin (1,3,7-tribromodibenzo-p-dioxin) photoproduct were the only OH-BDE and brominated dioxin detected in surface sediments from San Francisco Bay, the anthropogenically impacted coastal site, where levels increased along a north-south gradient. Triclosan, 6-OH-BDE 47, 6-OH-BDE 90, 6-OH-BDE 99, and (only once) 6'-OH-BDE 100 were detected in two sediment cores from San Francisco Bay. The occurrence of 6-OH-BDE 47 and 1,3,7-tribromodibenzo-p-dioxin sediments in Point Reyes National Seashore, a marine system with limited anthropogenic impact, was generally lower than in San Francisco Bay surface sediments. OH-BDEs were not detected in freshwater lakes. The spatial and temporal trends of triclosan, 2,8-dichlorodibenzo-p-dioxin, OH-BDEs, and brominated dioxins observed in this study suggest that the dominant source of OH-BDEs in these systems is likely natural production, but their occurrence may be enhanced in San Francisco Bay by anthropogenic activities.

Simultaneous enhanced removal of Cu, PCBs, and PBDEs by corn from e-waste-contaminated soil using the biodegradable chelant EDDS.

We evaluated the influence of the biodegradable chelant ethylenediamine disuccinic acid (EDDS) on plant uptake of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and Cu by corn from electronic waste (e-waste)-contaminated soil. The highest concentration and highest total uptake of Cu in corn were observed in the treatment with 5 mM EDDS, which resulted in a 4-fold increase of the Cu translocation factor (C(shoot)/C(root)) compared to the control. The concentrations of PCBs and PBDEs in shoots and roots increased with increasing application rates of EDDS, and 1.58- and 1.32-fold average increases in the concentrations of PCBs and PBDEs, respectively, were observed in shoots in the EDDS treatments. A significant positive correlation was observed between shoot Cu and shoot PCBs and PBDEs. We speculate that PCBs and PBDEs were activated by the EDDS-triggered dissolved organic carbon (DOC) and then indiscriminately taken up by roots and translocated to shoots following damage to the roots mainly by the increased extractable Cu resulting from the EDDS application.

Physicochemical Changes of Few-Layer Graphene in Peroxidase-Catalyzed Reactions: Characterization and Potential Ecological Effects.

The environmental implications of graphene have received much attention, however, little is known about how graphene affects or may be affected by the enzymatic reactions that are critically involved in natural organic matter transformation processes. We conducted experiments to examine the role of few-layer graphene (FLG) in the reaction system of tetrabromobisphenol A (TBBPA) mediated by horseradish peroxidase (HRP). We found that TBBPA was transformed by HRP into two products that were likely formed from coupling of two TBBPA radicals via interaction of an oxygen atom on one radical and a propyl-substituted aromatic carbon atom on the other. Presence of FLG greatly increased the reaction rate by protecting HRP from inactivation. Direct reactions between TBBPA radicals and FLG were unequivocally evidenced using (14)C labeling and the characteristic photoelectron response of bromine contained in TBBPA. The thickness, size, and aggregation profile of FLG was modified by the reaction as shown by multiple characterization tools. Assessment using Daphnia magna revealed a substantial decrease in the bioaccumulation and toxicity of the FLG after being modified. The data provides the first evidence that FLG can be modified in HRP-mediated reactions and indicates that such modifications may have strong implications in its ecological effects.

Evaluation of a Fast and Simple Sample Preparation Method for Polybrominated Diphenyl Ether (PBDE) Flame Retardants and Dichlorodiphenyltrichloroethane (DDT) Pesticides in Fish for Analysis by ELISA Compared with GC-MS/MS.

A simple, fast, and cost-effective sample preparation method, previously developed and validated for the analysis of organic contaminants in fish using low-pressure gas chromatography-tandem mass spectrometry (LPGC-MS/MS), was evaluated for the analysis of polybrominated diphenyl ethers (PBDEs) and dichlorodiphenyltrichloroethane (DDT) pesticides using enzyme-linked immunosorbent assay (ELISA). The sample preparation technique was based on the quick, easy, cheap, rugged, effective, and safe (QuEChERS) approach with filter-vial dispersive solid phase extraction (d-SPE). Incurred PBDEs and DDTs were analyzed in three types of fish with 3-10% lipid content: Pacific croaker, salmon, and National Institute of Standards and Technology (NIST) Standard Reference Material 1947 (Lake Michigan fish tissue). LPGC-MS/MS and ELISA results were in agreement: 108-111 and 65-82% accuracy ELISA versus LPGC-MS/MS results for PBDEs and DDTs, respectively. Similar detection limits were achieved for ELISA and LPGC-MS/MS. Matrix effects (MEs) were significant (e.g., -60%) for PBDE measurement in ELISA, but not a factor in the case of DDT pesticides. This study demonstrated that the sample preparation method can be adopted for semiquantitative screening analysis of fish samples by commercial kits for PBDEs and DDTs.

Rapid determination of tetrabromobisphenol A and its main derivatives in aqueous samples by ultrasound-dispersive liquid-liquid microextraction combined with high-performance liquid chromatography.

A method of ultrasound-dispersive liquid-liquid microextraction (US-DLLME) combined with high-performance liquid chromatography/variable wavelength detection (HPLC-VWD) has been developed for rapid measuring tetrabromobisphenol A and its five derivatives in water. Parameters affecting the extraction efficiency including the extraction solvents and dispersive solvents and their volume, ionic strength of the sample, and ultrasound time were optimized, and further validated by orthogonal array design (OAD). The optimized conditions provided enrichment factors for analytes of 74-490. Most analytes had linear responses between 2 and 500 µg L(-1), with correlation coefficients (r(2)) of 0.9923-0.9994. Limits of detection were 0.13-0.63 µg L(-1). Relative standard deviations (RSDs) for five replicates ranged from 2.6% to 4.5% for all analytes. When applied to spiked samples of real water, the method provided recoveries of 88.6-106.3% for tap water, 87.8-108.5% for Mi River water, 82.7-113.5% for chemical wastewater, 45.5-115.3% for urine, and 46.4-126.2% for fruit juice, with RSDs (n=5) less than 4%, 6%, 8%, 10%, and 9% respectively.

Concurrent extraction, clean-up, and analysis of polybrominated diphenyl ethers, hexabromocyclododecane isomers, and tetrabromobisphenol A in human milk and serum.

A method has been developed and validated for the concurrent extraction, clean-up, and analysis of polybrominated diphenyl ethers (PBDEs), α-, ß-, and γ-hexabromocyclododecane (HBCD), and tetrabromobisphenol A (TBBPA) in human milk and serum. Milk and serum samples were extracted using accelerated solvent extraction with acetone/hexane 1:1, v/v and liquid-liquid extraction with methyl-tert-butyl ether/hexane 1:1, v/v, respectively. The removal of co-extracted biogenic materials was achieved by gel permeation chromatography followed by sulfuric acid treatment. The fractionation of the PBDEs and HBCD/TBBPA was performed using a Supelco LC-Si SPE cartridge. The detection of the PBDEs was then performed by GC-MS and that of the HBCDs and the TBBPA was performed using UPLC-MS/MS. The pretreatment procedure was optimized, and the characteristic ions and fragmentation of the analytes were studied by MS or MS/MS. A recovery test was performed using a matrix spiking test at concentrations of 0.05-10 ng/g. The recoveries ranged from 78.6-108.8% with RSDs equal to or lower than 14.04%. The LODs were 1.8-60 pg/g. The usefulness of the developed method was tested by the analysis of real human samples, and several brominated flame retardants in different samples were detected and analyzed.

[Research on removal of tetrabromobisphenol A from synthetic wastewater by nanoscale zero valent iron supported on organobentonite].

The removal of tetrabromobisphenol A (TBBPA) in methanol aqueous solutions by nanoscale zero valent iron supported on organobentonite (NZVI-CMT) was studied. The effects of temperature, initial concentration of TBBPA and the dose of NZVI-CMT on the degradation and debromination of TBBPA were investigated. The removal rate by NZVI-CMT reached 97.5% within 12 hours at 25 degrees C, when the initial concentration of TBBPA was 10 mg x L(-1). And the removal rate of NZVI-CMT was higher than those of two simple materials, namely organobentonite (CMT) and nanoscale zero valent iron (NZVI), as well as the sum of those two simple materials. In addition, NZVI-CMT exhibited a better reusable attribute, and the rate of the materials remained above 90% after being used for 3 times. Based on the identification of degradation products and analysis of the TBBPA removal by NZVI-CMT, the main reaction mechanism was suggested as adsorption and debromination, and higher reaction temperature was preferable for debromination.

Reductive debromination of tetrabromobisphenol A by Pd/Fe bimetallic catalysts.

The bimetallic catalysts of micron sizes were synthesized and the rates of tetrabromobisphenol A (TBBPA) transformation were measured under various conditions using a batch reactor system. The results showed that TBBPA was rapidly debrominated to tri-, di- and mono-bromobisphenol A and to bisphenol A (BPA). The pseudo-first-order rate constants normalized to the specific surface area of the catalysts were found to increase as functions of the Pd coverage on the Fe particles and the dosages of the catalysts and the mass of Pd within the reactors. The rate constants were also decreasing as the solution pH increased. At pH 4.2, Pd coverage of 0.022wt% and catalyst dosage of 4gL(-1), 99% of TBBPA was transformed within 2min, and tri-, di-, and mono-bromobisphenol A were detected as the major intermediate products. After reaction for 45min, BPA was the only compound found in this specific system. Meanwhile, the rate constants measured at constant solution pH correlated linearly with the Pd mass introduced to the reactors, regardless of Pd/Fe catalyst dosage or Pd surface coverage. The study suggested that Pd/Fe catalysts could be used for efficiently treating brominated flame retardants extracted from e-wastes.

A humin-dependent Dehalobacter species is involved in reductive debromination of tetrabromobisphenol A.

Tetrabromobisphenol A (TBBPA) is the most widely used brominated flame retardant on the market. It has been detected in various environmental samples, and a growing body of evidence has demonstrated its toxic effects on living organisms. In this study, we report the enrichment and phylogenetic identification of bacteria that debrominate TBBPA to bisphenol A in the presence of humin. Incubation experiments indicated that humin was required for this debromination activity. Of the five compounds examined for inclusion in the TBBPA-debrominating culture, formate was the optimal electron donor. A 16S rRNA gene library showed that the culture was dominated by three known dehalogenator genera: Dehalobacter, Geobacter, and Sulfurospirillum. Further investigation indicated that Dehalobacter was responsible for the debromination of TBBPA. PCR-denaturing gradient gel electrophoresis analysis showed that Dehalobacter grew in the culture by utilizing TBBPA. Moreover, the copy number of the Dehalobacter 16S rRNA genes increased by about two orders of magnitude in the cultures without the addition of TBBPA, whereas it increased by approximately four orders of magnitude when TBBPA was present. The incubation experiments showed that Dehalobacter was reliant on humin for its debromination activity, indicating a new type of metabolism in Dehalobacter that is linked to humin respiration.

Transformation and removal of tetrabromobisphenol A from water in the presence of natural organic matter via laccase-catalyzed reactions: reaction rates, products, and pathways.

The widespread occurrence of the brominated flame retardant tetrabromobisphenol A (TBBPA) makes it a possible source of concern. Our experiments suggest that TBBPA can be effectively transformed by the naturally occurring laccase enzyme from Trametes versicolor. These reactions follow second-order kinetics, whereby apparent removal rate is a function of both substrate and enzyme concentrations. For reactions at different initial concentrations and with or without natural organic matter (NOM), reaction products are identified using liquid or gas chromatography with mass spectrometry. Detailed reaction pathways are proposed. It is postulated that two TBBPA radicals resulting from a laccase-mediated reaction are coupled together via interaction of an oxygen atom on one radical and a propyl-substituted aromatic carbon atom on the other. A 2,6-dibromo-4-isopropylphenol carbocation is then eliminated from the radical dimer. All but one of the detected products arise from either substitution or proton elimination of the 2,6-dibromo-4-isopropylphenol carbocation. Three additional products are identified for reactions in the presence of NOM, which suggests that reaction occurs between NOM and TBBPA radical. Data from acute immobilization tests with Daphnia confirm that TBBPA toxicity is effectively eliminated by laccase-catalyzed TBBPA removal. These findings are useful for understanding laccase-mediated TBBPA reactions and could eventually lead to development of novel methods to control TBBPA contamination.

Sequential reduction-oxidation for photocatalytic degradation of tetrabromobisphenol A: kinetics and intermediates.

C-Br bond cleavage is considered as a key step to reduce their toxicities and increase degradation rates for most brominated organic pollutants. Here a sequential reduction/oxidation strategy (i.e. debromination followed by photocatalytic oxidation) for photocatalytic degradation of tetrabromobisphenol A (TBBPA), one of the most frequently used brominated flame retardants, was proposed on the basis of kinetic analysis and intermediates identification. The results demonstrated that the rates of debromination and even photodegradation of TBBPA strongly depended on the atmospheres, initial TBBPA concentrations, pH of the reaction solution, hydrogen donors, and electron acceptors. These kinetic data and byproducts identification obtained by GC-MS measurement indicated that reductive debromination reaction by photo-induced electrons dominated under N(2)-saturated condition, while oxidation reaction by photoexcited holes or hydroxyl radicals played a leading role when air was saturated. It also suggested that the reaction might be further optimized for pretreatment of TBBPA-contaminated wastewater by a two-stage reductive debromination/subsequent oxidative decomposition process in the UV-TiO(2) system by changing the reaction atmospheres.

Newly discovered methoxylated polybrominated diphenoxybenzenes have been contaminants in the Great Lakes herring gull eggs for thirty years.

We recently reported the discovery and identification of novel methoxylated polybrominated diphenoxybenzenes (MeO-PBDPBs) in herring gulls eggs from the Laurentian Great Lakes of North America. We presently investigated the temporal changes (1982-2010) in MeO-PBDPB concentrations and congener patterns, as well as chemical tracers of diet (ratios of carbon and nitrogen stable isotopes), in egg pool homogenates from five selected colony sites across the Great Lakes. Egg pool homogenates from the Channel-Shelter (C-S) Island (Lake Huron) contained ∑MeO-PBDPB concentrations orders of magnitude greater than those from other colonies, suggesting potential point contamination sources nearby. In the C-S Island egg pools, concentrations increased from the initial study year (31 ng/g wet weight) and peaked around the late 1990s, followed by a general decline until 2010. Over the period, concentrations generally increased in eggs from Fighting Island (Lake Erie), Toronto Harbour (Lake Ontario) and Big Sister Island (Lake Michigan) colonies, whereas the levels in Agawa Rock (Lake Superior) declined. Although other factors likely exist, changes over time in the carbon and nitrogen isotope tracers reflected a shift of the gull diet from aquatic to more terrestrial origins, and suggested this diet shift partially accounted for the temporal changes of ∑MeO-PBDPB levels in eggs from most colonies. The ratio of Br(6)- to Br(5)-MeO-PBDPB congeners generally decreased over time in the colonies at Channel-Shelter Island, Fighting Island and Agawa Rock. This suggested that Br(5)- versus Br(6)-MeO-PBDPB congeners and/or possibly their nonmethoxylated and higher brominated precursors may have been more abundant in diets of terrestrial origin. Notably, these MeO-PBDPB congeners are not "emerging" brominated substances, but rather "recently discovered" contaminants since, as of 2011, ∑MeO-PBDPB concentrations have been constantly in the range of 30-100 ng/g ww for at least the last 30 years.

[Microbial degradation of 2, 2', 4, 4'-tetrabrominated diphenyl ether under anaerobic condition].

Polybrominated diphenyl ethers are emerging contaminants in the environment, among which 2, 2' 4, 4'-tetrabrominated diphenyl ether (BDE-47) is one of the most frequently detected and the most toxic to organisms. Using BDE-47 as the object, this study investigated the degradation of BDE-47 by six enriched cultures containing Dehalococcoides species. The purpose is to understand the microbial degradation of BDE-47 under anaerobic condition and its kinetics. Serum bottles of 100 mL were used to construct the microcosms and enrich the anaerobic microorganisms. For each culture, two treatments were performed. One used BDE-47 as the only energy source with the designed concentration of 200 microg x L(-1), and the other used both BDE-47 and trichloroethene (TCE) as the energy source with the designed concentrations being 200 microg x L(-1) and 13 mg x L(-1), respectively. After three months of experiment, two enriched cultures (6M6B and T2) could obviously degrade BDE-47, producing BDE-17 and BDE-4 (and small amount of DE). The presence of TCE inhibited the degradation of BDE-47 by 6M6B and T2 cultures to a certain degree. The PCR-DGGE assay was performed to compare the microbial community structure of various enrichments and it was found that Acetobacterium sp. had good correlation with the degradation of BDE-47. Under three different initial BDE-47 concentrations (50 microg x L(-1), 250 microg x L(-1) and 500 microg x L(-1)), the degradation rates of BDE-47 were 0.003 3, 0.001 4 and 0.001 0 d(-1), respectively. This study demonstrated that BDE-47 could be reductively degraded by bacteria under anaerobic condition, producing BDE-17 and BDE-4. Acetobacterium sp. might play an important role in the degradation of BDE-47. High concentration of BDE-47 might inhibit the activity of the BDE-47 degrading bacteria to a certain degree.