2003 Progress Report: Anaerobic Microbial Reductive Debromination of Polybrominated Diphenyl Ethers

EPA Grant Number: R830251
Title: Anaerobic Microbial Reductive Debromination of Polybrominated Diphenyl Ethers
Investigators: Nies, Loring , Filley, Timothy , Tokarz, John A.
Current Investigators: Nies, Loring , Ahn, Mi Youn , Filley, Timothy
Institution: Purdue University
EPA Project Officer: Lasat, Mitch
Project Period: August 12, 2002 through August 13, 2004 (Extended to September 1, 2006)
Project Period Covered by this Report: August 12, 2002 through August 13, 2003
Project Amount: $230,795
RFA: Futures Research in Natural Sciences (2001) RFA Text |  Recipients Lists
Research Category: Land and Waste Management , Ecological Indicators/Assessment/Restoration , Hazardous Waste/Remediation

Objective:

The overall objective of this research project is to determine the extent to which decabromodiphenyl ether (BDE-209) will undergo reductive debromination in anaerobic sediments. Based on data regarding the environmental occurrence of polybrominated diphenyl ethers (PBDEs), as well as knowledge about the reductive dehalogenation of polychlorinated biphenyls, polybrominated biphenyls, and polychlorinated dibenzo-p-dioxins, we postulate that BDE-209 will undergo reductive debromination producing less brominated, more bioavailable and toxic PBDE congeners. To obtain the most complete picture possible of the anaerobic fate of PBDEs, we will conduct sediment microcosm studies and parallel abiotic biomimetic dehalogenation studies on both the highly brominated BDE-209 and the lesser brominated 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and 2,2',4,4',5-pentabromodiphenyl ether (BDE-99). BDE-47 and BDE-99 are two PBDE congeners that are being detected in the biosphere in increasing concentrations.

Progress Summary:

Analytical Methods

Methods have been developed for the quantification of PBDEs using gas chromatography-electron capture detector (GC-ECD) and gas chromatography-mass spectrometry. Analytical standard solutions of 45 of the possible 209 PBDE congeners have been purchased from Cambridge Isotope Laboratories, Inc. (refer to Figure 1 for a chromatogram of a standard suite of PBDEs purchased from Cambridge Isotope Laboratories). Other sources for pure congener standards are Wellington Labs and Accustandard. Retention times of these 45 PBDEs have been documented. The detection limit for BDE-209 on our HP 5890 Series II GC-ECD is consistently 20 picograms.

Sediment extraction and cleanup methods for PBDEs have been developed. We obtain an average extraction efficiency from sediments of 60 percent for BDE-209. We are using octachloronaphthalene (OCN) as an internal recovery standard for the quantification of PBDEs extracted from sediment or buffered aqueous/cosolvent biomimetic systems. We are using 1,2,3,4-tetrachlorobenzene as an absolute recovery standard to monitor GC performance. Our check standard is composed of 39 different PBDE congeners (purchased from Cambridge Isotope Laboratories, Inc.) plus 1,2,3,4-tetrachlorobenzene and OCN. Figure 1 below is a chromatogram of the check standard run on an HP 5890 Series II GC-ECD.

Figure 1. Chromatogram of Check Standard Mixture

Table 1 contains the congener identification corresponding to each peak number (1-40) along with the concentration of each analyte and internal standard. The highlighted rows in Table 1 correspond to coeluting congeners. The peak pairs, which have coeluting congeners, are the following peak numbers: 8, 9, 13, 14, 30, and 33. As new standards become available, they will be added to the check standard. If needed, the GC program will be modified to ensure adequate peak separation.

Table 1. Peak Identification of Check Standard Mixture

Peak # on Chromatogram
Component
BDE #
Retention Time [min.]
Concentration [mg/L]
1
Toluene (Solvent)
N/A
1.13
N/A
2
1,2,3,4-Tetrachlorobenzene (ARS)a
N/A
2.17
0.19
3
2-Monobromodiphenyl ether
1
3.77
0.07
4
3-Monobromodiphenyl ether
2
4.38
0.07
5
4-Monobromodiphenyl ether
3
4.73
0.07
6
2,6-Dibromodiphenyl ether
10
7.50
0.07
7
2,4-Dibromodiphenyl ether
7
8.52
0.07
8
3,3'-Dibromodiphenyl ether
11
9.05
0.07
8
2,4'-Dibromodiphenyl ether
8
9.05
0.07
9
3,4-Dibromodiphenyl ether
12
9.35
0.07
9
3,4'-Dibromodiphenyl ether
13
9.35
0.07
10
4,4'-Dibromodiphenyl ether
15
9.79
0.07
11
2,4,6-Tribromodiphenyl ether
30
11.99
0.07
12
2,4',6-Tribromodiphenyl ether
32
13.46
0.07
13
2,2',4-Tribromodiphenyl ether
17
14.04
0.07
13
2,3',4-Tribromodiphenyl ether
25
14.04
0.07
14
2,4,4'-Tribromodiphenyl ether
28
14.65
0.07
14
2',3,4-Tribromodiphenyl ether
33
14.65
0.07
15
3,3',4-Tribromodiphenyl ether
35
15.12
0.07
16
3,4,4'-Tribromodiphenyl ether
37
15.66
0.07
17
2,4,4',6-Tetrabromodiphenyl ether
75
18.44
0.07
18
2,3',4',6-Tetrabromodiphenyl ether
71
18.89
0.07
19
2,3',4,4'-Tetrabromodiphenyl ether
66
19.06
0.07
20
2,2',4,4'-Tetrabromodiphenyl ether
47
19.69
0.07
21
2,2',4,5'-Tetrabromodiphenyl ether
49
20.39
0.07
22
3,3',4,4'-Tetrabromodiphenyl ether
77
21.49
0.07
23
2,2',4,4',6-Pentabromodiphenyl ether
100
23.42
0.11
24
2,3',4,4',6-Pentabromodiphenyl ether
119
23.79
0.11
25
2,2',4,4',5-Pentabromodiphenyl ether
99
24.51
0.11
26
2,3,4,5,6-Pentabromodiphenyl ether
116
24.83
0.11
27
1,2,3,4,5,6,7,8-Octachloronaphthalene (IRS)b
N/A
24.94
0.04
28
2,3',4,4',5-Pentabromodiphenyl ether
118
25.36
0.11
29
2,2',3,4,4'-Pentabromodiphenyl ether
85
26.36
0.11
30
3,3',4,4',5-Pentabromodiphenyl ether
126
26.69
0.11
30
2,2',4,4',6,6'-Hexabromodiphenyl ether
155
26.69
0.14
31
2,2',4,4',5,6'-Hexabromodiphenyl ether
154
27.47
0.14
32
2,2',4,4',5,5'-Hexabromodiphenyl ether
153
28.91
0.14
33
2,2',3,4,4',5'-Hexabromodiphenyl ether
138
30.78
0.14
33
2,3,4,4',5,6-Hexabromodiphenyl ether
166
30.78
0.14
34
2,2',3,4,4',5',6-Heptabromodiphenyl ether
183
33.04
0.17
35
2,2',3,4,4',5,6-Heptabromodiphenyl ether
181
35.31
0.17
36
2,3,3',4,4',5,6-Heptabromodiphenyl ether
190
35.69
0.17
37
2,2',3,3',4,5,5',6,6'-Nonabromodiphenyl ether
208
49.78
N/A
38
2,2',3,3',4,4',5,6,6'-Nonabromodiphenyl ether
207
51.72
N/A
39
2,2',3,3',4,4',5,5',6-Nonabromodiphenyl ether
206
55.13
N/A
40
1,1',2,2',3,3',4,4',5,5'-Decabromodiphenyl ether
209
77.66
1.04
a: ARS = Absolute Recovery Standard, b: IRS = Internal Recovery Standard

Anaerobic Sediment Microcosms

As proposed in our original experimental plan, three multireplicate sets of sediment microcosms containing BDE-209, BDE-99, or BDE-47 have been set up (see Figure 2). The concentration of PBDE congeners in these sediment microcosms is 5.0 mg/kg. Sets of control microcosms have been autoclaved. They are being monitored for methane production to ensure that the anaerobic microcosms are biologically active and utilizing the organic substrates that are available. These microcosms are sampled and analyzed for PBDE on a monthly basis. Figure 3 is a chromatogram of the BDE-209 sediment microcosm extraction, and Table 2 contains the peak identification of BDE-209 sediment microcosm extraction.

Figure 2. BDE-209 Anaerobic Sediment Microcosms

Figure 3. Chromatogram of a BDE-209 Sediment Microcosm Extraction

Table 2. Peak Identification of BDE-209 Sediment Microcosm Extraction

Peak # on Chromatogram
Component
BDE #
Retention Time [min.]
Concentration [mg/L]
1
Toluene (Solvent)
N/A
1.09
N/A
2
1,2,3,4-Tetrachlorobenzene (ARS)a
N/A
2.16
0.19
3
1,2,3,4,5,6,7,8-Octachloronaphthalene (IRS)b
N/A
24.93
0.06
4
2,2',3,3',4,5,5',6,6'-Nonabromodiphenyl ether
208
50.31
N/A
5
2,2',3,3',4,4',5,6,6'-Nonabromodiphenyl ether
207
51.66
N/A
6
2,2',3,3',4,4',5,5',6-Nonabromodiphenyl ether
206
55.09
N/A
7
1,1',2,2',3,3',4,4',5,5'-Decabromodiphenyl ether
209
77.57
0.85
a: ARS = Absolute Recovery Standard, b: IRS = Internal Recovery Standard

Biomimetic Studies

Initial biomimetic studies have been performed on BDE-209. In these experiments, the PBDEs are dissolved in an aqueous tris-buffer/tetrahydrofuran cosolvent matrix. Vitamin B12 is used as the electron transfer mediator, and titanium citrate (Ti3+) is the reducing agent. All experiments are performed in a COY Laboratory Products, Inc., brand anaerobic chamber (see Figure 4). Under the highly reducing conditions produced by titanium-citrate, the BDE-209 was rapidly, completely and reductively debrominated in a matter of hours. It appears that the debromination of BDE-209 proceeded via multiple pathways. Because of the rapid reaction kinetics, only a few transient debromination products could be identified. Future experiments will be performed under weaker reducing conditions in which the debromination kinetics will be sufficiently reduced to allow for the determination of the major debromination products of BDE-209. Similar experiments will be conducted using BDE-99 and BDE-47 as starting materials.

Figure 4. COY Laboratory Products, Inc., Anaerobic Chamber

Future Activities:

We will continue to sample and analyze the sediment microcosms on a monthly basis. Additional biomimetic experiments will be conducted using varying concentrations of vitamin B12 and titanium-citrate on BDE-209, BDE-99, and BDE-47.

Journal Articles:

No journal articles submitted with this report: View all 6 publications for this project

Supplemental Keywords:

environmental fate, brominated flame retardants, decabromodiphenylether, biomimetic, environmental chemistry., RFA, Scientific Discipline, Waste, Water, Ecosystem Protection/Environmental Exposure & Risk, Contaminated Sediments, Environmental Chemistry, Restoration, Environmental Monitoring, Ecology and Ecosystems, Aquatic Ecosystem Restoration, Exp. Research/future, Futures, reducitve debromination, biodiversity, reductive debromination, contaminated sediment, flame retardants, PBDE, conservation, contaminant uptake, exploratory research, remediation, ecological pollutants, environmental stress, environmental rehabilitation, ecotoxicology, anaerobic biotransformation

Progress and Final Reports:

Original Abstract
  • 2004
  • 2005 Progress Report
  • 2006
  • Final Report