Debromination Of BDE-209 Research Articles

Spatial distribution, source, and ecological risk of polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs) in Jiaozhou Bay, China

Polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs) are commonly found in the environment as components of brominated flame retardants. Due to their potential impact on human health and wildlife, it is imperative to closely monitor and manage their levels in the environment. This study investigated the spatial distribution, sources, and ecological risks of PBDEs and HBCDs in Jiaozhou Bay (JZB), a large bay situated on the eastern coast of China. The results showed that PBDE concentrations ranged from not detected (ND) to 7.93 ng/L in the water and ND to 65.76 ng/g in the sediment, while HBCD concentrations ranged from ND to 0.31 ng/L in the water and ND to 16.63 ng/g in the sediment. Furthermore, we observed significantly higher concentrations of PBDEs and HBCDs in the inner JZB compared to the outer JZB. Our source apportionment analysis showed that PBDEs primarily originated from the production and debromination of BDE-209, as well as the emission of commercial PeBDEs, whereas HBCDs in sediments mostly stemmed from anthropogenic activities and river input. Finally, our eco-logical risk assessment highlighted the need for continuous monitoring of PBDEs in JZB sediments. Overall, our study aims to provide valuable assistance for the environmental management of the JZB bay area, which is characterized by a complex net-work of rivers and a thriving economy.

Decabromodiphenylether trends in the European environment: Bird eggs, sewage sludge and surficial sediments

Concern on relatively high levels and the potential bioaccumulation of decabromodiphenylether (BDE209) has led to a European 8-year monitoring program on trends in BDE209 concentrations in birds, sewage sludge and sediments from seven countries. BDE209 was analysed in four environmental matrices: sparrowhawk eggs (UK), glaucous gull eggs (Bear Island, Norway), sewage sludge (UK, Ireland and the Netherlands) and sediment (France, Germany, the Netherlands, UK and Ireland). BDE209 was detected in most of the glaucous gull and sparrow hawk eggs but neither increasing nor decreasing trends in these BDE209 levels were observed. An indication for debromination of BDE209 in sparrowhawk eggs was found. BDE209 concentrations in sediments ranged from very low ng/g (88 ng/g on an organic carbon (OC) basis) concentrations, in the rivers Elbe, Ems, Seine and the Outer Humber, to high μg/g (120 μg/g OC), in the Western Scheldt, Liverpool Bay and River Mersey. Apart from decreasing values in the Western Scheldt sediment no further decreases in BDE209 concentrations were observed over time, neither in sediment nor in sewage sludge showing that the voluntary emissions control program of the bromine industry only had a local effect. In contrast to the sewage sludge samples from the Netherlands (mean 355 ng/g dry weight (dw) or 1026 ng/g OC), the BDE209 concentrations in the UK increased at all sites from 2006 to 2011 (8092 ng/g dw or 22,367 ng/g OC). The BDE209 levels in several UK sediments and sewage sludge were still very high at the end of the program in 2012, most likely caused by frequent use of BDE209 in the textile industry. This may be indicative of the persistence of BDE209 and the limited degradation into lower brominated congeners in sediment, although it cannot be excluded that ongoing BDE209 emissions have played a role as well.

Polybrominated diphenyl ethers in surface sediments from fishing ports along the coast of Bohai Sea, China

The distribution, congener patterns, possible sources, and ecological risks of polybrominated diphenyl ethers (PBDEs) were investigated in the surface sediments of 20 fishing ports along the coast of Bohai Sea. PBDEs are widespread pollutants in fishing ports, and the total concentrations of 14 PBDEs (∑14PBDEs) are 4.23–20.59 ng/g with a mean value of 12.56 ng/g. BDE-209 was the dominant congener. The fishing ports with high PBDE concentrations were located near Liaohe River, Haihe River, manufacturing plants of BFRs near Laizhou Bay, and tipping areas of marine garbage. BDE-209 and BDE-47 were the most important congeners that discriminate PBDE pollution. The possible sources of PBDEs included the input of commercial mixtures of penta-BDE, octa-BDE, and deca-BDE, the debromination of BDE-209, and the atmospheric transport of the low brominated diphenyl ethers. The ecological risks in surface sediments were attributed to the congeners of tetra-BDE, penta-BDE, and deca-BDE with low or medium levels.

Enhanced remediation of BDE-209 in contaminated mangrove sediment by planting and aquaculture effluent

Toxic and persistent flame retardant (BDE-209) and aquaculture effluent (AE) are ubiquitous in coastal environments, but how their co-existence influences their fate is not yet investigated. This study investigated AE effects on remediation and uptake of BDE-209 by Kandelia obovata (Ko) and Avicennia marina (Am), true and dominant mangrove species. After 12-months, a significant removal of BDE-209 was achieved in planted mangrove sediment and the removal was significantly enhanced by AE addition, possibly due to the enhancement of nitrogen (N) and phosphorous (P) content in sediment. Residual percentages of parent BDE-209 in Ko and Am planted sediments without AE were 61.4% and 70.9%, respectively, but decreased to 46.9% and 48.0% with AE addition after 12-months. A similar trend was found in unplanted sediment, with 86.5% and 65.3% of BDE-209 retained in sediments without and with AE addition, respectively. The results demonstrated that AE addition not only increased the debromination of BDE-209 in all treated sediments with the production of debrominated congeners (de-PBDEs) like di- to nona-BDEs in unplanted and planted sediments, but also enhanced the take up of BDE-209 in Ko root, and de-PBDEs in both Ko and Am, thus enhancing the phytoremediation of BDE-209 in contaminated sediments.

Environmental factors in debromination activity of polybrominated diphenyl ethers by hepatic microsomes of freshwater fish.

Although the debromination of polybrominated diphenyl ethers (PBDEs) in fish species has been studied, environmental factors, such as chemical contamination and habitat temperature, have not been well understood. This study compared debromination of BDE209 by hepatic microsomes of wild and cultured fish. PBDE concentrations in muscle tissue were lower in cultured fish than in wild fish. Debromination activity was high in wild common carp, followed by cultured common carp, moderate in cultured ayu sweetfish, and low in two cultured fish (rainbow trout and cherry salmon) and wild Japanese sea bass. Although common carps have been known as the species which have higher debromination ability, there were differences between wild and cultured common carps. First, wild common carp debrominated much more BDE209 than cultured common carp. Second was debromination of BDE209 lasted 96 h in wild carp but only 24 h in cultured carp. Wild carp were collected from warm wastewater effluent with consistently high concentrations of micropollutants. Cultured carp were collected from colder clean waters. Therefore, environmental factors in debromination include contamination or ambient temperature. To investigate the effects of habitat environment on debromination of PBDEs, we collected wild carp in summer and winter at two different locations with similar PBDE contamination levels. Carp collected from the natural river in winter had the highest BDE99 debromination activity. Although the results indicated seasonal difference of debromination of BDE209, we could not confirm whether habitat temperature or physiological cycle of carp affected to debromination ability. Thus, further investigation such as in vivo experiment is required.

Transportation and degradation of decabrominated diphenyl ether in sequential anoxic and oxic crop rotation

This work evaluated the debromination and uptake of 14C-labeled BDE-209 in rice cultivars grown in anoxic soil for 120 days (d) followed by cultivation of vegetables (peanut, eggplant and pepper) in oxic soil (120 d). Degradation of BDE-209 to lower polybrominated diphenyl ethers (PBDEs) occurred in cultivated soils, and more metabolites were released in oxic soil than in anoxic soil. The crop rotation from anoxic to oxic greatly enhanced the dissipation of BDE-209 in the soil (P < 0.05), in which the dissipation in anoxic soil planted with Huanghuazhan (HHZ, indica) and Yudao 1 (YD1, indica) were 6.8% and 2.4%, respectively, while in oxic soil with peanut and pepper were increased to 25.8% and 21.7%, respectively. The crop rotation also enhanced the degradation of BDE-209 in the soil, the recovered BDE-209 in soil after 120 d anoxic incubation with YD1 was 81.1%, but it decreased to 47.8% and 45.8% after another 120 d oxic incubation. Bioconcentration factors were between 0.23 and 0.36 for rice, eggplant and pepper but reached to 0.5 in peanut, which contains more lipids in the edible portion than the other test crops. The estimated daily intake for vegetables was 0.01–0.07 μg BDE-209-equivalent kg−1 bw day−1, which is at least two orders of magnitude below the maximum acceptable oral dose (7 μg kg−1 bw day−1). Our work confirms that crop rotation from rice to vegetable enhanced the dissipation and debromination of BDE-209 in the soil, and indicate that sequential anoxic-oxic rotation practice is considered to be effective in remediation of environmental pollutants.

Compound-specific carbon isotope analysis for mechanistic characterization of debromination of decabrominated diphenyl ether.

Decabrominated diphenyl ether (BDE-209) is a notorious persistent organic pollutant widely found in the environment. Developing a compound-specific isotope analysis (CSIA) method is much needed in order to trace its transport and degradation processes and to evaluate the effectiveness of the remediation of BDE-209 in the environment. However, the conventional CSIA method, i.e. gas chromatography (GC) combustion isotope ratio mass spectrometry, is not appropriate for BDE-209 because of its high thermal instability and incomplete combustion. We developed a high-performance liquid chromatography (HPLC) method for the separation and purification of BDE-209 that prevents its thermal reactivity as occurred in prior GC-based methods. The δ13 C value of the purified BDE-209 was determined using offline elemental analyzer isotope ratio mass spectrometry (EA/IRMS). This two-step method was applied to determine the δ13 C values of BDE-209 in two commercial samples and to characterize carbon isotope fractionation associated with the debromination of BDE-209 via nanoscale zero-valent iron. The mean values of daily δ13 C analyses of six replicates of a BDE-209 standard varied from -27.66‰ to -27.92‰, with a standard deviation ranging from 0.07‰ to 0.16‰, indicating a good reproducibility of EA/IRMS. The EA/IRMS analysis of the purified BDE-209 standard indicated no obvious isotope fractionation during the sample purification. The impurity content in commercial BDE-209 samples may contribute additional variation of the δ13 C values of BDE-209. The δ13 C values of BDE-209 gradually changed from -27.47 ± 0.37‰ to -24.59 ± 0.19‰ when 74% of the BDE-209 standard was degraded within 36 h. The estimated carbon isotope enrichment factor was -1.72 ± 0.18‰. The two-step method based on HPLC and EA/IRMS avoids the thermal instability of BDE-209 in the traditional CSIA method. It offers a novel approach for elucidating the degradation mechanisms of BDE-209 in the environment and for source identification in contaminated sites.

The toxicity, bioaccumulation and debromination of BDE-47 and BDE-209 in Chlorella sp. under multiple exposure modes

Polybrominated diphenyl ethers (PBDEs) are a series of important persistent organic pollutants (POPs) in marine environments. Microalgae are the start of PBDEs bioaccumulated and bioconcentrated along the marine food web. In order to investigate the variations of PBDEs bioaccumulation by microalgae and its influencing factors, we set up a series of experiments with Chlorella sp. under different BDE-47 or BDE-209 exposure modes to measure their toxicity, bioaccumulation and degradation patterns. The inhibition effect on cell growth was much more obvious in BDE-47 than BDE-209, with the EC50 values at 96 h calculated as 64.7 μg L−1 and 4070 μg L−1, respectively. Microalgal uptake rates showed BDE-209 diffused less into cells than BDE-47, with highest measured uptake rates of 0.145 × 10−7 μg h−1 cell−1 and 0.45 × 10−7 μg h−1 cell−1, respectively. The bioaccumulation amount by unit microalgal cell varied with PBDE concentrations and culture time, which appeared to be related to the changes of extracellular polymeric substances (EPS) and cellular neutral lipids under the toxicity of PBDEs. Finally, we found Chlorella sp. delayed the debromination patterns of BDE-209 compared to seawater. This study linked the toxicity, microalgal bioaccumulation and metabolism of PBDEs, provided new insights in the research of POPs by microalgae and marine food webs.

Pathways and influential factors study on the formation of PBDD/Fs during co-processing BDE-209 in cement kiln simulation system

The thermal processes of cement kilns are sources of polybrominated dibenzofurans and dioxins (PBDD/Fs); however, when co-processing decabromodiphenyl ether (BDE-209) soil in cement kilns, very few reports have investigated the mechanism of PBDD/Fs formation from BDE-209. Therefore, the pathways and factors that influence the formation of PBDD/Fs were investigated using Box-Behnken design (BBD) of the response surface methodology (RSM) at lab-scale. The PBDEs, HBr/Br2 and PBDD/Fs emissions in flue gas from the simulated thermal process were analyzed using gas chromatography/mass spectroscopy (GC/MS), high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS), and ion chromatography (IC). Density functional theory (DFT) was also used to further discuss the formation of PBDD/Fs. The major products of BDE-209 thermal decomposition in flue gas were 97.1% HBr/Br2 (a.v. 26.6%/70.6%) > 2.7% PBDEs >0.2% PBDD/Fs. Formation of precursors were the main pathways for PBDD/Fs, and those precursors were dominated by higher-brominated PBDEs (heptãdeca-BDEs); debromination of BDE-209 was also a crucial pathway for the formation of PBDD/Fs throughout the thermal process. Interestingly, it was easier to form HpBDD/Fs from OBDD/Fs than from PBDEs. The O2 percentage and interaction factors of O2 percentage, temperature, and CaCO3 percentage have the largest influence on PBDD/Fs emissions and formation.

Airborne brominated, chlorinated and organophosphate ester flame retardants inside the buildings of the Indian state of Bihar: Exploration of source and human exposure.

Since many household products used by individuals contain flame retardants (FRs), there is more chance that these chemicals may be present in the various exhibit of the indoor environment. Despite being one of the fastest-growing economies worldwide, the contamination level, sources, products, and pathways of FRs in India, is either not known or limited. This inspired us to investigate the level, profile, spatial distribution, and sources of different classes of FRs in the indoor air. For this purpose, 15 brominated, 2 chlorinated, and 8 organophosphate FRs (OPFRs) were investigated in indoor air samples from urban and suburban sites of an Indian state of Bihar. Additionally, inhalation health risk exposure to children and the adult was estimated to predict the risk of these chemicals. Overall, ∑8OPFRs (median 351pg/m3) was the most prominent in air, followed by novel brominated FR (∑6NBFRs) (median 278pg/m3), polybrominated diphenyl ether (∑9PBDE) (median 5.05pg/m3), and dechlorane plus (∑2DPs) (median 2.52pg/m3), and accounted for 55%, 44%, 0.8% and 0.4% of ∑FRs, respectively. Generally, ∑9PBDEs (median 6.29pg/m3) and ∑8OPFRs (median 355pg/m3) were measured high at sub-urban sites, while urban sites had the highest level of ∑2DPs (median 2.81pg/m3) and ∑6NBFRs (median 740pg/m3). BDE-209 was most abundant among ∑9PBDEs, while syn-DP dominated in ∑2DPs. Likewise, DBDPE was most prevalent in ∑6NBFRs, while TMPP topped among ∑8OPFRs. The principal component analysis revealed contribution from household items, food packaging and paints, hydraulic fluid, a gasoline additive, and de-bromination of BDE-209 as the primary sources of FRs. The estimated daily inhalation exposure (DIE) indicated a relatively high risk to children than the adult. The DIE of individual FR was several folds lower than their corresponding oral reference dose (RfDs), suggesting minimal risk. However, exposure risk, especially to children, may still need attention because other routes of intake may always be significant in the case of Bihar.

Emergent contaminants in sediments and fishes from the Tamsui River (Taiwan): Their spatial-temporal distribution and risk to aquatic ecosystems and human health

The occurrence of emergent contaminants, 24 polybrominated diphenyl ethers (PBDEs), di(2-ethylhexyl)phthalate (DEHP), dibutyl phthalate (DBP), butyl benzyl phthalate (BBP), diethyl phthalate (DEP), dimethyl phthalate (DMP), di-n-octyl phthalate (DnOP), bisphenol A (BPA) and nonylphenol (NP), was investigated in sediments and fishes collected from the Tamsui River system to determine the factors that influence their distribution and their risk to aquatic ecosystems and human health. The concentrations of total PBDEs, DEHP, DBP, BBP, DEP, DMP, DnOP, BPA and NP in sediments were 1–955, ND-23570, <50–411, <50–430, ND-80, ND-<50, ND-<50, 1–144, 3–19624 μg/kg dw, respectively. The spatial-temporal distribution trends of these compounds in sediments could be attributed to urbanization, industrial discharge and effluents from wastewater treatment plants. The PBDE congener distribution patterns (BDE-209 was the dominant congener) in sediments reflected the occurrence of debromination of BDE-209 and the elution of penta-BDE from the treated products. The concentrations of total PBDEs, DEHP, DBP, BBP, DEP, DMP, DnOP, BPA and NP in fish muscles were 2–66, 17–1046, <10–231, <10–66, <30, ND-<30, ND-<30, 0.4–7 and 3–440 μg/kg ww, respectively. The species-specific bioaccumulation of these compounds by fish was found and four species particularly showed high bioaccumulation potential. BDE-47 was the predominant BDE congener in fish muscles, suggesting high bioavailability and bioaccumulation of this compound. The results of biota–sediment accumulation factors showed that BDE-47, 99, 100, 153 and 154 had relatively high bioavailability and bioaccumulation potential for some fish species. The ecological risk assessment showed that the concentrations of BPA and NP in sediments were likely to have adverse effects on aquatic organisms (risk quotients > 1). The human health risk assessment according to hazard quotients (HQs) and carcinogenic risks (CRs) revealed no remarkable risk to human health through consumption of fish contaminated with BDE-47, 99, 100, 154, 209, DEHP, BPA and NP.

Microwave-induced degradation as a novel treatment for destruction of decabromodiphenyl ether sorbed on porous minerals

• Highly hydrophobic BDE-209 sorbed efficiently on the porous minerals evaluated. • Microwave irradiation caused rapid degradation of BDE-209 sorbed on porous minerals. • Surface cations in mineral micropores greatly impacted degradation of sorbed BDE-209. • Full debromination of sorbed BDE-209 occurred under continuous microwave irradiation. • The treatment is promising for full destruction of BDE-209 and other PBDE congeners. Decabromodiphenyl ether (deca-BDE or BDE-209) is a major brominated flame retardant released from plastics in thermal processing of e-waste, and there is a significant need for developing effective technologies for its destruction. This study reports a novel treatment for complete debromination and destruction of BDE-209 by adsorbing it onto porous minerals followed by microwave irradiation. Being highly hydrophobic, BDE-209 could be sorbed efficiently by porous mineral sorbents, with the density and type of surface cations of the sorbents apparently playing little role. Microwave irradiation caused rapid degradation of the BDE-209 sorbed on the porous minerals, and the fastest degradation occurred on the microporous minerals, with the density and type of surface cations present in the mineral micropores had significant impact on the degradation rate. Evolution of the degradation intermediates during the course of microwave irradiation indicates that the sorbed BDE-209 underwent pyrolytic decomposition, involving a series of reactions, including cleavage of the ether bond, debromination, hydroxylation, ring cleavage, and oxidation. Microwave-induced degradation could cause full mineralization of the sorbed BDE-209 without producing lower brominated congeners, which is supported by the results of density functional theory (DFT) calculations and infrared spectra. Together, these findings demonstrate that microporous mineral sorption coupled with microwave irradiation could be a rapid and efficient technology for destruction of BDE-209 and other polybrominated diphenyl ethers (PBDEs).

Effect of light on the transformation of BDE-47 by living and autoclaved cultures of Microcystis flos-aquae and Chlorella vulgaris

Polybrominated diphenyl ethers (PBDEs) are ubiquitous and toxic contaminants found in high concentrations in watercourses, and are not well removed by conventional wastewater treatment facilities. This study aimed to evaluate the removal and transformation of BDE-47, one of the environmentally predominant PBDE congener, by a green alga (Chlorella vulgaris) and a cyanobacterium (Microcystis flos-aquae) under different light conditions. Living and autoclaved cultures were exposed to BDE-47 at a concentration of 10 μg L−1 for 7 days. Both species removed >90% of BDE-47 very shortly after spiking. Light intensity affected the transformation of BDE-47 in living cultures of both species, since 5 to 11 times more debromination products were measured at a light intensity of 100 μmol photons m−2 s−1 than at 20 μmol photons m−2 s−1. Living cultures of M. flos-aquae transformed BDE-47 at a rate of 0.22 day−1 while no transformation was observed in the respective autoclaved cultures. On the contrary, both living and autoclaved cultures of C. vulgaris had similar BDE-47 transformation rates of 0.05–0.06 day−1. Debromination of BDE-47 was a predominant transformation pathway in cultures of C. vulgaris, with two times higher BDE-28 concentrations measured than in M. flos-aquae, while hydroxylation was more dominant with the cyanobacterium. Most BDE-47 and its debromination product BDE-28 were found on the cell surface of both species. These results reveal that different transformation mechanisms were involved in C. vulgaris and M. flos-aquae cultures and confirm the importance of species selection for the removal of PBDEs from contaminated environments.

Flame retardants and plasticizers in a Canadian waste electrical and electronic equipment (WEEE) dismantling facility

Here we report on the concentrations of 79 flame retardants (FRs) and plasticizers, including 34 polybrominated diphenyl ethers or PBDE congeners, 17 “novel” brominated FRs (NBFRs), 15 dechloranes, and 13 organophosphate esters (OPEs) in air (n = 9) and dust (n = 24) samples from an active waste electrical and electronic equipment (WEEE) dismantling facility in Ontario, Canada, collected in February–March 2017. This is the first study of its kind in North America. The facility processes a range of WEEE including monitors, computers, printers, phones, and toys. Of the 79 target compounds, at least 60 were detected at a frequency of at least 50% in both air and dust. Dust and air concentrations were dominated by three compounds: BDE-209 (median 110,000 ng/g and 100 ng/m3, respectively), DBDPE (median 41,000 ng/g and 41 ng/m3), and TPhP (median 42,000 ng/g and 27 ng/m3). Levels of PBDEs, NBFRs, and dechloranes were close to two orders-of-magnitude higher in dust from the dismantling facility than in residential homes, while OPEs were one order-of-magnitude higher. Congener profiles of PBDEs indicated debromination of BDE-209. We calculated that a total mass of 44 ± 1 mg day−1 of 79 target analytes were released to air from WEEE processed in the dismantling hall and a further 270 ± 91 mg day−1 were released to dust. It is clear that WEEE dismantling facilities are a serious concern as a source of emissions for a wide range of FRs at relatively high concentrations to both workers and the immediate environment.

Mechanisms and pathways of debromination of polybrominated diphenyl ethers (PBDEs) in various nano-zerovalent iron-based bimetallic systems

This study investigated the relative significance of electron transfer (e-transfer) and H-atom transfer (H-transfer) in a nanoscale zerovalent iron (n-ZVI) system and six n-ZVI-based bimetallic systems (Fe/Cu, Fe/Ni, Fe/Pd, Fe/Ag, Fe/Pt, and Fe/Au) through a case study of the debromination of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47). The results revealed that the reactivities of these bimetallic particles to BDE-47 decreased in the following order: Fe/Pd>Fe/Ag>Fe/Cu>Fe/Ni>Fe/Au>Fe/Pt≈n-ZVI. Debromination of BDE-47 in metal-H2 systems suggested that Ni, Pd, Pt, Cu and Au can utilize H2 to debrominate BDE-47. In the H-transfer process, BDE-47 preferentially debrominated the para‑bromine substituent to generate BDE-17, whereas in the e-transfer process, BDE-47 preferentially debrominate ortho‑bromine substituent to generate BDE-28. The debromination pathways of BDE-47 in bimetallic and NaBH4-metal systems suggested that Fe/Ni, Fe/Pd and Fe/Pt debrominate polybrominated diphenyl ethers (PBDEs) through a H-transfer dominant mechanism, while Fe/Ag debrominate PBDEs through an e-transfer dominant mechanism. In the cases of Fe/Cu and Fe/Au, the e-transfer and H-transfer may be equally involved in the debromination of PBDEs. These results greatly improve our understanding of the relative significance of e-transfer and H-transfer in the dehalogenation of halogenated aromatic compounds (HACs) in various n-ZVI-based bimetallic systems.

Degradation of decabromodiphenyl ether (BDE-209) in microcosms mimicking sediment environment subjected to comparative bioremediation strategies

The aim of this study was to examine bioremediation strategies for BDE-209 contaminated sediments. Sediment microcosms were established to observe anaerobic debromination of BDE-209 under conditions representing three bioremediation strategies: biostimulation, bioaugmentation and natural attenuation. To simulate biostimulation, a defined mineral medium containing both a carbon source (sodium formate) and electron donor (ethanol) was added into sediments. Bioaugmentation was established by enrichment of the sediments using a culture of Dehalobium chlorocoercia strain DF-1, previously shown to dechlorinate polychlorinated biphenyls, to sediments. No amendments were made to the third set in order to represent natural attenuation. The biostimulation, bioaugmentation and natural attenuation strategies resulted in 55.3%, 40.2% and 30.9% reductions in BDE-209, respectively, after 180 days. Nona- through tri-BDEs were observed as products, with 17 PBDE congeners detected in 25 different proposed debromination pathways. At the end of the 180 day incubation period, the products for bioaugmentation, biostimulation and natural attenuation were tri-BDEs, tetra-BDEs and penta-BDEs, respectively. The proposed pathways revealed that meta- and ortho-Br removal were favored in sediments, and that debromination regiospecificity varied with each bioremediation strategy applied. Lastly, pseudo-first-order rate constants for BDE-209 reduction were calculated as 0.0049 d−1, 0.0028 d−1, 0.0025 d−1 for biostimulation, bioaugmentation and natural attenuation, respectively.

Debromination of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) by synthetic Pd/Fe0 and Cu/Fe0 in different protic solvents

Polybrominated diphenyl ethers (PBDEs) belong to a class of persistent organic pollutants (POPs), with potential toxicity to the liver, reproductive system, and development of mammals. The highly toxic and concentrated congener, 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47), was chosen to investigate debromination mechanisms by the two synthetic iron-based bimetals (Pd/Fe0 and Cu/Fe0) in two protic solvents (water and ethanol). SEM, XPS, and BET analyses showed that the synthetic bimetals Pd/Fe0 and Cu/Fe0 were spherical with diameters of about 100 nm and loaded with ∼1% (wt%) of Pd and Cu, respectively. GC-MS was used for the analysis of degradation products and the chromatograms showed that both Pd/Fe0 and Cu/Fe0 bimetals had effective reducing properties in water solvent. In ethanol solvent, debromination of BDE-47 by Pd/Fe0 showed a similar high activity, but BDE-47 could be hardly degraded by Cu/Fe0. The dominant debromination products of BDE-47 by Pd/Fe0 and Cu/Fe0 were ortho-substituted and para-substituted BDEs, respectively. Active H-atomic transfer was found to play a key role in the debromination of BDE-47 by Pd/Fe0 in both, water and ethanol, with a preference for para-debromination along with the formation of dibenzo-p-furan (DF) as the by-product, mainly in water. In contrast, electron transfer with a preference for ortho-debromination was found to play a predominant role for Cu/Fe0 system in water. More importance should be provided to active H-atomic transfer for its high efficiency. In-depth study on the mechanism of formation of by-product DF would be significant for its higher toxicity, possibility of accumulation and migration in the environment.

Production of more toxic hexa-brominated diphenyl ether from rapid biotransformation of decabromodiphenyl ether in anaerobic granular sludge

Decabromodiphenyl ether (BDE-209) is used widely as a flame retardant and deserves more attention due to its potential danger to environment. Previous studies generally considered that BDE-209 degraded slowly in environment. Herein, a rapid reductive debromination of BDE-209 to BDE-154 was demonstrated with simultaneous stoichiometric bromide recovery (45%) in 10 h driven by the anaerobic granules. Debromination occurred in anaerobic granules when they were spiked with BDE-209 dissolved in the solvent dimethyl sulfoxide (DMSO), which was proved a potential cosubstrate for stimulating PBDE debromination. Moreover, the solvent DMSO enhanced the penetration of BDE-209 across cell membranes and forced the dominant phylum in anaerobic granules to change from Bacteroidetes to Euryarchaeota. Thus, the amended culture could better raise the functional genera Ralstonia and Pseudomonas, accounting for the rapid degradation of BDE-209. This is the first report that BDE-209 could be quickly debrominated to BDE-154 in anaerobic granules. Given the high cytotoxicity of BDE-154 produced from BDE-209, the fate of BDE-209 in the wastewater treatment plants should be paid more attention.

Distribution of polybrominated diphenyl ethers in the atmosphere of the Pearl River Delta region, South China.

Air samples were collected from 26 air-monitoring stations located in the Pearl River Delta (PRD) and two in Shaoguan, South China, to investigate the spatial distribution and temporal changes in polybrominated diphenyl ethers (PBDEs) after the production and use of PBDE commercial formulations was restricted in China and the "dual transfer strategy" implemented by Guangdong Province. The spatial distribution of PBDEs was inhomogeneous in the PRD region, with concentrations ranging from 26.3 to 634pg/m3 and a mean value of 105pg/m3. The PBDE levels in the five western cities (Guangzhou, Foshan, Zhaoqing, Zhongshan, and Jiangmen) were markedly higher than those in the four eastern cities (Dongguan, Huizhou, Shenzhen, and Zhuhai). BDE-209 was the predominant congener, accounting for 57.3-89.8% of the total measured PBDEs in this study. The proportion of penta- and nona-BDE congeners in the four eastern cities was markedly higher than those in five western cities. Principal component analysis showed that this elevation might be related to the debromination of BDE-209 during the thermal treatment process of products when PBDEs are used as flame retardants. Although the PBDE levels found in this study were markedly lower than those reported in previous studies, further efforts are still needed to clarify if there was a decreasing trend for PBDEs in the atmosphere of the PRD, in view of the increasing trends of PBDEs found by other researchers in mangrove sediments from Hong Kong and the Pearl River estuary in 2014 and 2015.

Roles of intrinsic Mn3+ sites and lattice oxygen in mechanochemical debromination and mineralization of decabromodiphenyl ether with manganese dioxide

Commercial β-MnO2 with a chemical formula of approximate Mn0.774+Mn0.233+O1.88 was used for mechanochemical (MC) oxidative degradation of decabromodiphenyl ether (BDE209). The ball milling process initiated the degradation of BDE209 on β-MnO2, yielding a nearly complete degradation and debromination of BDE209 within 2 h. The use of β-MnO2 exhibited much higher MC debromination efficiency than that by using birnessite (δ-MnO2, 40.2%), Bi2O3 (45.6%), CaO (65.3%), and persulfate (81.9%). It was demonstrated that the oxidative degradation of BDE209 was promoted by the redox half reactions of both Mn4+→ Mn3+ and Mn3+→ Mn2+, but naturally existed Mn3+ centers on the surface of β-MnO2 functioned as dominant reactive species at the initial stage of the MC degradation (often before the degradation efficiency of BDE209 achieved 50%). Moreover, the surface lattice oxygen of MnO2, rather than O2, played a key role in the debromination and mineralization of BDE209. The Mn3+ sites on β-MnO2 not only easily accepted the electron of BDE209, but also promoted the mobility of lattice oxygen from the bulk to the surface for mineralizing BDE209. These results firstly highlighted the importance of Mn3+ availability and oxygen mobility on the reactivity of manganese oxide for the MC oxidative degradation of organic pollutants.