Bioavailability Of Polybrominated Diphenyl Ethers Research Articles

Reducing plant uptake of a brominated contaminant (2,2′,4,4′‑tetrabrominated diphenyl ether) by incorporation of maize straw into horticultural soil

Application of crop residues is a conventional practice that contributes to crop production through nutrient returns and other benefits to soil health: driving soil physicochemical and biological functions. However, little is known about the impacts of straw residue incorporation on the bioavailability of organic pollutants and associated changes in microbial community structure in contaminated soils. In this study, maize straw was added to a soil contaminated with a model polybrominated diphenyl ether (BDE-47). A pot experiment was conducted and planted with carrot (Daucus carota L.). We found that straw addition greatly reduced the bioavailability of BDE-47, changed the bacterial community structure and affected a range of soil physiochemical properties. Moreover, the amount of BDE-47 that had accumulated in carrot roots and aboveground tissues was significantly reduced. This study may therefore describe an effective agronomic strategy to reduce the bioavailability of polybrominated diphenyl ethers (PBDEs) in a soil used to grow high value vegetable crops. This strategy draws on traditional wisdom and shows promise as a practical method to support horticultural production systems, remediate soils, and help to ensure food safety.

Relationships between the bioavailability of polybrominated diphenyl ethers in soils measured with female C57BL/6 mice and the bioaccessibility determined using five in vitro methods

Several in vitro methods for simulating human gastrointestinal digestion have been validated for predicting the bioavailability of heavy metals, but the methods for successfully predicting the bioavailability of organic pollutants are still limited. In this study, we used an adapted fasting in vitro digestion method (Fa-VDM) from the Simulator of the Human Intestinal Microbial Ecosystem and four other in vitro methods comprising In Vitro Gastrointestinal, a physiologically-based extraction test, the unified BARGE method, and Deutsches Institut für Normung e.V. in order to measure the bioaccessibility of polybrominated diphenyl ethers (PBDEs) in soils from an e-waste dismantling town, China, with a Standard Reference Material (SRM2585) as the control. Furthermore, the bioaccessibility data were compared with the bioavailability measured using female C57BL/6 mice. The bioavailability of PBDEs in the soils and SRM2585 were 1.7% to 38.1% and 3.9% to 48.8%, respectively, and the bioaccessibility determined using Fa-VDM were 1.6–55.4% and 6.7–32.1%. There were negative and parabolic correlations between octanol/water partition coefficient for PBDEs and the bioavailability and bioaccessibility, respectively, whereas the H/C ratios and organic matter contents of the soils did not correlate with them. The bioaccessibility data determined by Fa-VDM were generally higher than those obtained using the other four methods, mainly due to the higher bile concentration and larger liquid to solid ratio in the digestion solution in Fa-VDM. There was a significant linear relationship between the results according to the in vivo and in vitro method of Fa-VDM where the slopes varied from 0.83 to 1.16 (R2 > 0.73) and intercepts from 0.3%–7.7% for BDE47, 99, 100, and 153 measured using Fa-VDM, thereby indicating that the bioaccessibility assessed by this method can potentially be used to predict the bioavailability of moderately brominated congeners in soils.

Sorption, mobility, and bioavailability of PBDEs in the agricultural soils: Roles of co-existing metals, dissolved organic matter, and fertilizers

Polybrominated diphenyl ethers (PBDEs) are common pollutants released from electronic waste (e-waste) dismantling and recycling activities. Our city-wide survey of agricultural soils in Qingyuan (40 sampling sites), where e-waste recycling has been active, observed exceedance of PBDEs above background levels (average of 251.9ngg−1, 87 times the regional baseline concentration) together with elevated levels of metals/metalloids at the contamination hotspots, such as As (180.4mgkg−1), Cu (100.7mgkg−1), Zn (93.4mgkg−1), Pb (37.8mgkg−1), Cr (15.1mgkg−1), and Cd (0.3mgkg−1). Hence, a twenty-cycle batch sorption test on composite soil samples from the e-waste site was conducted to study the fate of BDE-28 (2,4,4′-tribromodiphenyl ether) and BDE-99 (2,2′,4,4′,5-pentabromodiphenyl ether) under the influence of co-existing trace elements (TEs) (Cu, Pb, Zn, and Cd, which exceeded Chinese Environmental Quality Standard for Soils), dissolved organic matter (extracted from local peat), and locally available commercial fertilizer. The results showed that the presence of TEs barely affected the sorption of BDEs, probably because the low concentration of BDEs in the environment resulted in nearly complete sorption onto the soil. In contrast, metals sorption onto soil was promoted by the presence of BDEs. The mobility of BDE-28 was higher than BDE-99 in water leaching tests, while the leaching concentration of BDE-99 was further reduced in simulated acid rain possibly due to protonation of π-accepting sites in soil organic matter. In the freshly spiked soil, BDEs of greater hydrophobicity and larger molecular size exhibited higher bioavailability (due to greater affinity to Tenax extraction), which was contrary to the field contaminated soil. Similarly, the co-occurrence of metals and fertilizer increased the bioavailability of newly sorbed BDE-99 more than BDE-28 in the soil. These results illustrate the need to holistically assess the fate and interactions of co-existing organic and inorganic pollutants in the agricultural soils.

Comparing black carbon types in sequestering polybrominated diphenyl ethers (PBDEs) in sediments

Polybrominated diphenyl ethers (PBDEs) are widely found in sediments, especially congeners from the penta-BDE formula. Due to their strong affinity for black carbon (BC), bioavailability of PBDEs may be decreased in BC-amended sediments. In this study, we used a matrix-SPME method to measure the freely dissolved concentration (Cfree) of PBDEs as a parameter of their potential bioavailability and evaluated the differences among biochar, charcoal, and activated carbon. Activated carbon displayed a substantially greater sequestration capacity than biochar or charcoal. At 1% amendment rate in sediment with low organic carbon (OC) content (0.12%), Cfree of six PBDEs was reduced by 47.5–78.0%, 47.3–77.5%, and 94.1–98.3% with biochar, charcoal, and activated carbon, respectively, while the sequestration was more limited in sediment with high OC content (0.87%). Therefore, it is important to consider the type and properties of the BC and the sediment in BC-based remediation or mitigation.

Bioaccumulation of polybrominated diphenyl ethers and decabromodiphenyl ethane in fish from a river system in a highly industrialized area, South China

Polybrominated diphenyl ethers (PBDEs) and decabromodiphenyl ethane (DBDPE) were determined in water, sediment, and three fish species from the Dongjiang River, a highly polluted river by brominated flame retardants in South China due to the intensive industry activities. The stable isotope analysis was used to compare differences between the feeding ecology of the fish species. The bioaccumulations of PBDEs and DBDPE were evaluated by calculation of bioaccumulation factors (BAFs) and biota-sediment accumulation factors (BSAFs). Two potential debromination products of DBDPE were detected in sediment. The occurrence of these two compounds probably ascribed to the thermal degradation during instrumental analysis but degradation in the environment cannot be ruled out. Three fish species showed two quite different PBDE congener profiles. Two carp species were dominated by BDE47 while plecostomus were dominated by both BDE47 and BDE99. The contributions of higher brominated congeners were higher in plecostomus than in two carp species. This different PBDE congener profile can be attributed to the difference in metabolism and feeding habits among fish species. The calculated BAFs for PBDE congeners follow a bioaccumulation model. The BSAFs for all PBDE congeners except for BDE47 and BDE100 were less than unit, implying that bioavailability of PBDEs in sediments is low. Contrary to expectation, the BAFs value of DBDPE was one order of magnitude higher than that of BDE209 in fish, which can partly attributed to the absence of debromination of DBDPE in fish. The calculated BAFs for DBDPE indicated that this compound can significantly accumulate in fish.

Predicting the bioavailability of sediment-associated polybrominated diphenyl ethers using a 45-d sequential Tenax extraction

A 45-d Tenax extraction was used to evaluate the bioavailability of polybrominated diphenyl ethers (PBDEs) in three spiked sediments. The effect of aging on desorption kinetics of PBDEs was investigated by incubating one of the sediments for 7, 14, 30 and 60d at room temperature. Desorption kinetics were well described by a three-compartment model. The fraction of very slow desorption (Fvs) contributed the most of the desorbed PBDEs from sediments. The total desorption amount of PBDEs decreased with the increase of total organic carbon in the sediments, suggesting that organic matter is an important factor controlling the partition of PBDEs in sediments. The total desorption amount of PBDEs decreased while log [(Fslow+Fvs)/Frap] increased with logKow of PBDE congeners, indicating that the bioavailability of PBDEs in sediment decreases with logKow of the congeners. As the residential time of PBDEs in the sediment increased from 7 to 60d, Frap of individual PBDE congeners decreased gradually with simultaneous increase of Fvs. There was a good positive correlation between Frap and F6/F24, indicating that either 6h or 24h Tenax extraction could be a proxy for Frap and bioavailability. In general, the results in present study suggest that the bioavailability of nona- and deca-BDEs in sediment is very low due to their strong hydrophobicity and large molecular size.

Biodegradation of diphenyl ether and transformation of selected brominated congeners by Sphingomonas sp. PH-07

Polybrominated diphenyl ethers (PBDEs) are common flame-retardant chemicals that are used in diverse commercial products such as textiles, circuit boards, and plastics. Because of the widespread production and improper disposal of materials that contain PBDEs, there has been an increasing accumulation of these compounds in the environment. The toxicity and bioavailability of PBDEs are variable for different congeners, with some congeners showing dioxin-like activities and estrogenicity. The diphenyl ether-utilizing bacterium Sphingomonas sp. PH-07 was enriched from activated sludge of a wastewater treatment plant. In liquid cultures, this strain mineralized 1 g of diphenyl ether per liter completely within 6 days. The metabolites detected and identified by gas chromatography/mass spectrometry (MS) and electrospray ionization/MS analysis corresponded with a feasible degradative pathway. However, the strain PH-07 even catabolized several brominated congeners such as mono-, di-, and tribrominated diphenyl ethers thereby producing the corresponding metabolites.