Persistence of three bisphenols and other trace organics of concern in anaerobic sludge under methanogenic conditions.

The degradation and distribution of bisphenol A (BPA), bisphenol S (BPS) and bisphenol AF (BPAF) were evaluated in dilute anaerobic sludge slurries amended with a single bisphenol or a mixture of all three and maintained under methanogenic conditions over a 28-d period. No significant degradation of the bisphenols was observed in methane-generating microcosms. Rapid sorption to sludge particles was the primary removal process with sorption observed: BPAF > BPA > BPS. Several other trace organic chemicals of concern in the sludge were detected using quadrupole time of flight mass spectrometry. Of those detected, triclosan and triclocarban had sufficiently high intensities to quantify changes over the 28-d period in the bisphenol-amended microcosms. Similar to the bisphenols, triclosan and triclocarban concentrations also did not significantly change over the 28-d period with concentrations quantified at 2021 ± 627 and 1864 ± 769 µg/kg dry weight, respectively. Findings exemplify that methane-generating microcosms do not appear conducive to significant degradation of trace organics of concern in anaerobic sludge digesters.

Time series analysis of water use and indirect reuse within a HUC-4 basin (Wabash) over a nine year period.

Anthropogenic water use and reuse represent major components of the water cycle. In the context of climate change, water reuse and recycling are considered necessary components for an integrated water management approach. Unplanned, or de facto, indirect water reuse occurs in most of the U.S. river systems, however, there is little real-time documentation of it. Despite the fact that there are national and state agencies that systematically collect data on water withdrawals and wastewater discharges, their databases are organized and managed in a way that makes it challenging to use them for water resource management analysis. The ability to combine reported water data to perform large scale analysis about water use and reuse is severely limited. In this paper, we apply a simple but effective methodology to complete a time series watershed-scale analysis of water use and unplanned indirect reuse for the Wabash River Watershed. Results document the occurrence of indirect water reuse, ranging from 3% to 134%, in a water-rich area of the U.S. The time series analysis shows that reported data effectively describe the water use trends through nine years, from 2009 to 2017, clearly reflecting both anthropogenic and natural events in the watershed, such as the retirement of thermoelectric power plants, and the occurrence of an extreme drought in 2012. We demonstrate the feasibility and significance of using available water datasets to perform large scale water use analysis, describe limitations encountered in the process, and highlight areas for improvement in water data management.

Impacts of molybdenum-, nickel-, and lithium- oxide nanomaterials on soil activity and microbial community structure.

The nano forms of the metals molybdenum oxide (MoO3), nickel oxide (NiO) and lithium oxide (Li2O) are finding wide application in advanced technologies including batteries and fuel cells. We evaluated soil responses to nanoMoO3, nanoNiO, and nanoLi2O as some environmental release of the materials, either directly or following the land application of biosolids, is expected. Using Drummer soil (Fine-silty, mixed, superactive, mesic Typic Endoaquolls), we evaluated the impacts of the three nanometals on soil gas (N2O, CH4, and CO2) emissions, enzyme activities (ß-glucosidase and urease), and microbial community structure (bacterial, archaeal, and eukaryal) in a 60 day microcosms incubation. Soil treated with nanoLi2O at 474 µg Li/g soil, released 3.45 times more CO2 with respect to the control. Additionally, ß-glucosidase activity was decreased while urease activity increased following nanoLi2O treatment. While no clear patterns were observed for gas emissions in soils exposed to nanoMoO3 and nanoNiO, we observed a temporary suppression of ß-glucosidase activity in soil treated with either metal. All three domains of microbial community were affected by increasing metal concentrations. This is the first evaluation of soil responses to nanoMoO3, nanoNiO, or nanoLi2O.

Influence of fullerene (C60) on soil bacterial communities: aqueous aggregate size and solvent co-introduction effects.

Fullerene C60 nanoparticles are being used in broad range of applications. It is important to assess their potential impacts in the environment. We evaluated the effects of C60 introduced as aqueous suspensions of nC60 aggregates of different particle size or via organic solvents on soils with different organic matter contents in this study. Impacts of the application were evaluated by measuring total microbial biomass, metabolic activity and bacterial community structure. Results show that nC60 aggregates, introduced as an aqueous suspension, had size-dependent effects on soil bacterial community composition in the low organic matter system, but induced minimal change in the microbial biomass and metabolic activity in soils with both high and low organic matter contents. Fullerene C60, co-introduced via an organic solvent, did not influence the response of soil microbes to the organic solvents. Our results suggest that nC60 aggregates of smaller size may have negative impact on soil biota and soil organic matter may play a key role in modulating the environmental effect of nanomaterials.

The assessment of water use and reuse through reported data: A US case study.

Increasing demands for freshwater make it necessary to find innovative ways to extend the life of our water resources, and to manage them in a sustainable way. Indirect water reuse plays a role in meeting freshwater demands but there is limited documentation of it. There is a need to analyze its current status for water resources planning and conservation, and for understanding how it potentially impacts human health. However, the fact that data are archived in discrete uncoordinated databases by different state and federal entities, limits the capacity to complete holistic analysis of critical resources at large watershed scales. Humans alter the water cycle for food production, manufacturing, energy production, provision of potable water and recreation. Ecosystems services are affected at watershed scales but there are also global scale impacts from greenhouse gas emissions enabled by access to cooling, processing and irrigation water. To better document these issues and to demonstrate the utility of such an analysis, we studied the Wabash River Watershed located in the U.S. Midwest. Data for water extraction, use, discharge, and river flow were collected, curated and reorganized in order to characterize the water use and reuse within the basin. Indirect water reuse was estimated by comparing treated wastewater discharges with stream flows at selected points within the watershed. Results show that during the low flow months of July-October, wastewater discharges into the Wabash River basin contributed 82 to 121% of the stream flow, demonstrating that the level of water use and unplanned reuse is significant. These results suggest that intentional water reuse for consumptive purposes such as landscape or agricultural irrigation could have substantial ecological impacts by diminishing stream flow during vulnerable low flow periods.

Microbial transformation of 8:2 fluorotelomer acrylate and methacrylate in aerobic soils.

Biotransformation of fluorotelomer (FT) compounds, such as 8:2 FT alcohol (FTOH) is now recognized to be a source of perfluorooctanoic acid (PFOA) as well as other perfluoroalkyl acids. In this study, microbially mediated hydrolysis of FT industrial intermediates 8:2 FT acrylate (8:2 FTAC) and 8:2 FT methacrylate (8:2 FTMAC) was evaluated in aerobic soils for up to 105d. At designated times, triplicate microcosms were sacrificed by sampling the headspace for volatile FTOHs followed by sequential extraction of soil for the parent monomers as well as transient and terminal degradation products. Both FTAC and FTMAC were hydrolyzed at the ester linkage as evidenced by 8:2 FTOH production. 8:2 FTAC and FTMAC degraded rapidly with half-lives ⩽5d and 15d, respectively. Maximum 8:2 FTOH levels were 6-13mol% within 3-6d. Consistent with the known biotransformation pathway of 8:2 FTOH, FT carboxylic acids and perfluoroalkyl carboxylic acids were subsequently generated including up to 10.3mol% of PFOA (105d). A total mass balance (parent plus metabolites) of 50-75mol% was observed on the last sampling day. 7:2 sFTOH, a direct precursor to PFOA, unexpectedly increased throughout the incubation period. The likely, but unconfirmed, concomitant production of acrylic acids was proposed as altering expected degradation patterns. Biotransformation of 8:2 FTAC, 8:2 FTMAC, and previously reported 8:2 FT-stearate for the same soils revealed the effect of the non-fluorinated terminus group linked to the FT chain on the electronic differences that affect microbially-mediated ester cleavage rates.

Transformation of 17α-estradiol, 17ß-estradiol, and estrone in sediments under nitrate- and sulfate-reducing conditions.

The natural manure-borne hormones, 17α-estradiol (17α-E2), 17ß-estradiol (17ß-E2), and estrone (E1), are routinely detected in surface water near agricultural land and wastewater treatment facilities. Once in the stream network, hormones may enter the sediment bed where they are subject to anaerobic conditions. This study focuses on the difference in anaerobic transformation rates and formation of metabolites from 17α-E2, 17ß-E2, and E1 (applied at ∼3.66 µmol kg(-1) of sediment on a dry weight basis) under nitrate- and sulfate-reducing conditions. Sediment extracts were analyzed using negative electrospray ionization tandem mass spectrometry. Under both redox conditions, degradation was stereospecific and followed similar trends in half-lives, 17ß-E2 < 17α-E2 < E1, with degradation considerably slower under sulfate-reducing conditions. Both E2 isomers were predominantly converted to E1; however, isomeric conversion also occurred with peak concentrations of ∼1.7 mol % of 17ß-E2 formed in 17α-E2 amended sediments and peak concentrations of ∼2.4 mol % of 17α-E2 formed from 17ß-E2. In E1-amended systems, E1 transformed to E2 with preferential formation of the more potent 17ß isomer up to ∼30 mol % suggesting that isomer interconversion is through E1. Sediments, therefore, may serve as both a sink and a source of the more estrogenic compound E2. Transformation of amended hormones in autoclaved sediments was markedly slower than in nonautoclaved sediments. Results support the inclusion of isomer-specific behavior and the potential for reversible transformation and interconversion in anaerobic sediments in modeling fate in stream networks and developing risk management strategies.

Linking performance with microbial community characteristics in an anaerobic baffled reactor.

The performance and microbial community characteristics of a laboratory scale anaerobic baffled reactor (ABR) with four compartments (C1-C4) treating sugar refinery wastewater were investigated. The COD removal was 94.8 % with a CH4 yield of 0.21 L g(-1) CODremoved at total organic loading rate (OLR) of 5.33 kg COD/m(-3) day(-1). Fermentative bacteria were dominant in C1 and C2, while syntrophic acetogens and methanogens were dominant in C3 and C4. Some acid-tolerant methanogens were enriched in acidogenic phase. The present of the acid-tolerant methanogens could improve the efficiency and stability of the ABR as the most of the methanogens are vulnerable to low pH. In addition, high functional redundancy of the fermentative bacteria implicated that the microbial communities in acidogenic phase were stable functionally and allowed the ABR to balance perturbation. It was also found that syntrophic acetogenesis might be a weakness in the ABR as syntrophic acetogens were poor as compared with fermentative bacteria and methanogens.

Aerobic biodegradation of 8:2 fluorotelomer stearate monoester and 8:2 fluorotelomer citrate triester in forest soil.

Aerobic biodegradation of 8:2 fluorotelomer stearate (FTS) and 8:2 fluorotelomer citrate triester (TBC) was evaluated in a forest soil in closed bottle microcosms. Loss of parent, production of 8:2 fluorotelomer alcohol (8:2 FTOH), which is released along with stearic acid (SA) by microbial ester linkage, and subsequent metabolites from FTOH degradation were monitored for up to 7months. Soil microcosms were extracted with ethyl acetate followed by two heated 90/10 v/v acetonitrile/200mM NaOH extractions. Cleavage of the ester linkage in the 8:2 FTS occurred (t1/2∼28d), producing 8:2 FTOH and various levels of subsequent metabolites. Quantifying the generation of SA from ester cleavage in FTS was complicated by the natural production and degradation of SA in soil, which was probed in an additional FTS and SA study with the same soil that had been stored at 4°C for 12months. In the latter study, FTS degraded faster (t1/2∼5d) such that SA production well above soil background levels was clearly observed along with rapid subsequent SA degradation. Cold storage was hypothesized to enrich fungal enzymes, which are known to be effective at hydrolytic cleavage. 8:2 TBC biotransformation was slow, but evident with the production of PFOA well above levels expected from known FTOH residuals. Slower degradation of TBC compared to FTS is likely due to steric hindrances arising from the close proximity of three 8:2 FT chains on the citrate backbone limiting the enzyme access.

Response of soil microorganisms to As-produced and functionalized single-wall carbon nanotubes (SWNTs).

The use of single-wall carbon nanotubes (SWNTs) in manufacturing and biomedical applications is increasing at a rapid rate; however data on the effects of a potential environmental release of the materials remain sparse. In this study, soils with either low or high organic matter contents as well as pure cultures of E. coli are challenged with either raw as-produced SWNTs (AP-SWNTs) or SWNTs functionalized with either polyethyleneglycol (PEG-SWNTs) or m-polyaminobenzene sulfonic acid (PABS-SWNTs). To mimic chronic exposure, the soil systems were challenged weekly for six weeks; microbial activities and community structures for both the prokaryote and eukaryote community were evaluated. Results show that repeated applications of AP-SWNTs can affect microbial community structures and induce minor changes in soil metabolic activity in the low organic matter systems. Toxicity of the three types of SWNTs was also assessed in liquid cultures using a bioluminescent E. coli-O157:H7 strain. Although decreases in light were detected in all treated samples, low light recovery following glucose addition in AP-SWNTs treatment and light absorption property of SWNTs particles suggest that AP-SWNTs suppressed metabolic activity of the E. coli, whereas the two functionalized SWNTs are less toxic. The metals released from the raw forms of SWNTs would not play a role in the effects seen in soil or the pure culture. We suggest that sorption to soil organic matter plays a controlling role in the soil microbiological responses to these nanomaterials.

The effects of silver nanoparticles on fathead minnow (Pimephales promelas) embryos.

Nanoparticles are being used in many commercial applications. We describe the toxicity of two commercial silver (Ag) nanoparticle (NP) products, NanoAmor and Sigma on Pimephales promelas embryos. Embryos were exposed to varying concentrations of either sonicated or stirred NP solutions for 96 h. LC(50) values for NanoAmor and Sigma Ag NPs were 9.4 and 10.6 mg/L for stirred and 1.25 and 1.36 mg/L for sonicated NPs, respectively. Uptake of Ag NPs into the embryos was observed after 24 h using Transmission Electron Microscopy and Ag NPs induced a concentration-dependent increase in larval abnormalities, mostly edema. Dissolved Ag released from Ag NPs was measured using Inductively Coupled-Mass Spectrometry and the effects tested were found to be three times less toxic when compared to Ag nitrate (AgNO(3)). The percentage of dissolved Ag released was inversely proportional to the concentration of Ag NPs with the lowest (0.625 mg/L) and highest (20 mg/L) concentrations tested releasing 3.7 and 0.45% dissolved Ag, respectively and percent release was similar regardless if concentrations were stirred or sonicated. Thus increased toxicity after sonication cannot be solely explained by dissolved Ag. We conclude that both dissolved and particulate forms of Ag elicited toxicity to fish embryos.

Quantification of aromatic oxygenase genes to evaluate enhanced bioremediation by oxygen releasing materials at a gasoline-contaminated site.

Subsurface injection of oxygen-releasing materials (ORMs) is frequently performed at petroleum-contaminated sites to stimulate aerobic bioremediation of benzene, toluene, ethylbenzene, and xylenes (BTEX). In this study, qPCR enumeration of aromatic oxygenase genes and PCR-DGGE profiles of bacterial 16S rRNA genes were combined with groundwater monitoring to determine the impact of ORM injection on BTEX bioremediation at a gasoline-contaminated site. Prior to injection, BTEX concentrations were greater than 3 mg/L and DO levels were typically lessthan 2 mg/L, butphenol hydroxylase (PHE) and ring-hydroxylating toluene monooxygenase (RMO) genes were detected in impacted wells indicating the potential for aerobic BTEX biodegradation. Following injection, DO increased, BTEX concentrations decreased substantially, and PHE and RMO genes copies increased by 1-3 orders of magnitude. In addition, naphthalene dioxygenase (NAH) and xylene monooxygenase (TOL) genes were intermittently detected during periods of increased DO. Following depletion of the ORM, DO decreased, BTEX concentrations rebounded, and oxygenase genes were no longer detected. Temporal changes in PCR-DGGE microbial community profiles reflected the dynamic changes in subsurface conditions. Overall, the combination of chemical and geochemical analyses with quantification of aromatic oxygenase genes demonstrated that injection stimulated BTEX biodegradation until the ORM was depleted.

Enumeration of aromatic oxygenase genes to evaluate biodegradation during multi-phase extraction at a gasoline-contaminated site.

Multi-phase extraction (MPE) is commonly used at petroleum-contaminated sites to volatilize and recover hydrocarbons from the vadose and saturated zones in contaminant source areas. Although primarily a physical treatment technology, the induced subsurface air flow can potentially increase oxygen supply and promote aerobic biodegradation of benzene, toluene, ethylbenzene, and xylenes (BTEX), the contaminants of concern at gasoline-contaminated sites. In this study, real-time PCR enumeration of aromatic oxygenase genes and PCR-DGGE profiles were used to elucidate the impact of MPE operation on the aquifer microbial community structure and function at a gasoline-contaminated site. Prior to system activation, ring-hydroxylating toluene monooxygenase (RMO) and naphthalene dioxygenase (NAH) gene copies were on the order of 10(6) to 10(10)copies L(-1) in groundwater samples obtained from BTEX-impacted wells. Aromatic oxygenase genes were not detected in groundwater samples obtained during continuous MPE indicating decreased populations of BTEX-utilizing bacteria. During periods of pulsed MPE, total aromatic oxygenase gene copies were not significantly different than prior to system activation, however, shifts in aromatic catabolic genotypes were noted. The consistent detection of RMO, NAH, and phenol hydroxylase (PHE), which catabolizes further oxidation of hydroxylated BTEX metabolites indicated the potential for aerobic biodegradation of dissolved BTEX during pulsed MPE.

Assessing the impact of nanomaterials on anaerobic microbial communities.

As the technological benefits of nanotechnology begin to rapidly move from laboratory to large-scale industrial application, release of nanomaterials to the environment is inevitable. Little is known about the fate and effects of nanomaterials in nature. Major environmental receptors of nanomaterials will be soil, sediment, and biosolids from wastewater treatment. Analysis of anaerobic microbial activity and communities provides needed information about the effects of nanoparticles in certain environments. In this study, biosolids from anaerobic wastewater treatment sludge were exposed to fullerene (C60) in order to model an environmentally relevant discharge scenario. Activity was assessed by monitoring production of CO2 and CH4. Changes in community structure were monitored by denaturing gradient gel electrophoresis (DGGE), using primer sets targeting the small subunit rRNA genes of Bacteria, Archaea, and Eukarya. Findings suggest that C60 fullerenes have no significant effect on the anaerobic community over an exposure period of a few months. This conclusion is based on the absence of toxicity indicated by no change in methanogenesis relative to untreated reference samples. DGGE results show no evidence of substantial community shifts due to treatment with C60, in any subset of the microbial community.

Reductive debromination of polybrominated diphenyl ethers in anaerobic sediment and a biomimetic system.

Because of the bioaccumulation of penta- and tetrapolybrominated diphenyl ether (PBDE) flame retardants in biota,the environmental biotransformation of decabromodiphenyl ether (BDE-209) is of interest. BDE-209 accounts for more than 80% by mass of PBDE production and is the dominant PBDE in sediments. Most sediments are anaerobic and reports of microbial reductive dehalogenation of hydrophobic persistent organohalogen pollutants are numerous. Reductive debromination of BDE-209 in the environment could provide a significant source of lesser-brominated PBDEs to biota. Moreover, a recent study showed that BDE-209 debrominates in sewage sludge, and another demonstrated that some halorespiring bacteria will debrominate BDE-209. To determine whether reductive debromination of BDE-209 occurs in sediments, parallel experiments were conducted using anaerobic sediment microcosms and a cosolvent-enhanced biomimetic system. In the biomimetic system, reductive debromination occurred at rates corresponding to bromine substitution levels with a BDE-209 half-life of only 18 s compared with a halflife of almost 60 days for 2,2',4,4'-tetrabromodiphenyl ether. In sediment, the measured debromination half-life of BDE-209 was well over a decade and was in good agreement with the predicted value obtained from the biomimetic experiment. Product congeners were predominantly double para-substituted. BDE-209 debrominated in sediment with a corresponding increase in nona-, octa-, hepta-, and hexa-PBDEs. Nine new PBDE congeners appeared in sediment from reductive debromination. Given the very large BDE-209 burden already in sediments globally, it is important to determine whether this transformation is a significant source of lesser-brominated PBDEs to the environment.

Enumeration of aromatic oxygenase genes to evaluate monitored natural attenuation at gasoline-contaminated sites.

Monitoring groundwater benzene, toluene, ethylbenzene, and xylene (BTEX) concentrations is the typical method to assess monitored natural attenuation (MNA) and bioremediation as corrective actions at gasoline-contaminated sites. Conclusive demonstration of bioremediation, however, relies on converging lines of chemical and biological evidence to support a decision. In this study, real-time PCR quantification of aromatic oxygenase genes was used to evaluate the feasibility of MNA at two gasoline-impacted sites. Phenol hydroxylase (PHE), ring-hydroxylating toluene monooxygenase (RMO), naphthalene dioxygenase (NAH), toluene monooxygenase (TOL), toluene dioxygenase (TOD), and biphenyl dioxygenase (BPH4) genes were routinely detected in BTEX-impacted wells. Aromatic oxygenase genes were not detected in sentinel wells outside the plume indicating that elevated levels of oxygenase genes corresponded to petroleum hydrocarbon contamination. Total aromatic oxygenase gene copy numbers detected in impacted wells were on the order of 10(6)-10(9)copies L(-1). PHE, RMO, NAH, TOD, and BPH4 gene copies positively correlated to total BTEX concentration. Mann-Kendall analysis of benzene concentrations was used to evaluate the status of the dissolved BTEX plume. The combination of trend analysis of contaminant concentrations with quantification of aromatic oxygenase genes was used to assess the feasibility of MNA as corrective measures at both sites.

Impact of fullerene (C60) on a soil microbial community.

The nascent state of the nanoproduct industry calls for important early assessment of environmental impacts before significant releases have occurred. Clearly, the impact of manufactured nanomaterials on key soil processes must be addressed so that an unbiased discussion concerning the environmental consequences of nanotechnology can take place. In this study, soils were treated with either 1 microg C60 g(-1) soil in aqueous suspension (nC60) or 1000 microg C60 g(-1) soil in granularform, a control containing equivalent tetrahydrofuran residues as generated during nC60 formation process or water and incubated for up to 180 days. Treatment effects on soil respiration, both basal and glucose-induced, were evaluated. The effects on the soil microbial community size was evaluated using total phospholipid derived phosphate. The impact on community structure was evaluated using both fatty acid profiles and following extraction of total genomic DNA, by DGGE after PCR amplification of total genomic DNA using bacterial variable V3 region targeted primers. In addition, treatment affects on soil enzymatic activities for beta-glucosidase, acid-phosphatase, dehydrogenase, and urease were followed. Our observations show that the introduction of fullerene, as either C60 or nC60, has little impact on the structure and function of the soil microbial community and microbial processes.

Biotransformation of 8:2 fluorotelomer alcohol in soil and by soil bacteria isolates.

The microbial transformation of 8:2 fluorotelomer alcohol (FTOH) to perfluorocarboxylic acids, including the globally detected perfluorooctanoic acid (PFOA), has recently been confirmed to occur in mixed bacteria cultures, activated sludge, and soil. However, little is known to date about the microbes involved in the transformation. In the present study, the effect of three carrier solvents (ethanol, octanol, and 1,4-dioxane), which may serve as carbon sources, on the aerobic degradation rate of 8:2 FTOH and metabolite distribution was evaluated both in a clay loam soil and in two pure soil bacterial cultures. Biodegradation pathways appeared similar regardless of the solvent; however, significant differences in 8:2 FTOH degradation rates were observed: 1,4-dioxane > ethanol > octanol. In the presence of 1,4-dioxane, which is not easily biodegraded, 8:2 FTOH degradation was the fastest With octanol, which is a structural analogue of 8:2 FTOH, the transformation was inhibited, but upon depletion of octanol, 8:2 FTOH was biodegraded. In the pure culture study, two soil bacterial strains, Pseudomonas species OCY4 and OCW4, enriched from soil using octanol as a sole carbon source, also transformed 8:2 FTOH without prior exposure or acclimation to 8:2 FTOH. Increased biomass resulting from octanol metabolism did increase 8:2 FTOH transformation rates; however, 8:2 FTOH could not support bacterial growth, indicating the transformation by pure cultures was via cometabolic processes.

Birnessite mediated debromination of decabromodiphenyl ether.

Decabromodiphenyl ether (BDE-209) is a major component of a commercial flame retardant formulation; however, there is limited information on the fate of BDE-209 in the environment, including metal oxide mediated degradation. Laboratory experiments were conducted to investigate the birnessite (delta-MnO(2))-promoted debromination of BDE-209 in tetrahydrofuran (THF)-water systems as well as catechol solutions. Up to 100% (0.1044 micromol initial charge) of BDE-209 disappeared upon reaction with birnessite in THF/H(2)O (4:6-9:1). The formation of aqueous Br(-) from BDE-209 reduction was determined and up to 16 mole% of initial bromine was released over the course of the reaction indicating approximately 1.7 Br-C bonds were reduced per BDE-209 molecule. The distribution of debrominated congeners, however, indicated a much greater extent of debromination for some products than what was inferred from an average bromine mass balance. The produced congeners varied from tetra- to nona-bromodiphenyl ether, including BDE-47 and -99, during the 24 h reaction. Experiments with deuterated water indicated that water was not the major hydrogen donor in the reduction but rather THF provided the reducing power. This conclusion was supported by the presence of succinic acid, which was produced from oxidation of THF. The reactions with aqueous catechol, rather than THF-water mixtures, were performed to assess the possible role that compounds found in natural environments, such a tannin-like phenols, might have on the chemistry. These experiments indicated that birnessite mediated debromination of BDE-209 might occur in natural settings.

Photodegradation of decabromodiphenyl ether adsorbed onto clay minerals, metal oxides, and sediment.

The photodebromination of decabromodiphenyl ether (BDE-209) adsorbed onto six different solid matrixes was investigated in sunlight and by irradiation with 350 +/- 50 nm lamps (four lamps at 24 W each). After 14 days of lamp irradiation, BDE-209 degraded with a half-life of 36 and 44 days, respectively, on montmorillonite or kaolinite, with much slower degradation occurring when sorbed on organic carbon-rich natural sediment (t1/2 = 150 days). In late summer and fall sunlight (40.5 degrees N, elevation 600 ft), the half-lives of BDE-209 sorbed on montmorillonite and kaolinite were 261 and 408 days, respectively. Under both irradiation schemes, no significant loss of BDE-209 occurred when sorbed to aluminum hydroxide, iron oxide (ferrihydrite), or manganese dioxide (birnessite). Upon exposure to both lamp and solar light and in the presence of montmorillonite and kaolinite, numerous lesser brominated congeners (tri- to nonabromodiphenyl ethers) were produced. Nearly identical product distribution was evident on montmorillonite and kaolinite. Dark control experiments for each mineral showed no disappearance of BDE-209 or appearance of degradation products. These results suggest that photodegradation of BDE-209 on mineral aerosols during long-range atmospheric transport may be an important fate process for BDE-209 in the environment.