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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Endpoint:
biodegradation in water: simulation testing on ultimate degradation in surface water
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2011
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline/GLP-compliant study performed by an experienced contract laboratory
Qualifier:
according to guideline
Guideline:
other: OECD 314C
GLP compliance:
yes
Radiolabelling:
yes
Oxygen conditions:
anaerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Anaerobic digester sludge was collected from the Back River Wastewater Treatment Plant (Baltimore, Maryland) five days prior to start of the test, sieved through a 2 mm screen, purged with nitrogen, and held under anaerobic conditions at 35°C. The total sludge solids were determined by combustion after drying, and adjusted to 4.17% by discarding supernatant after centrifugation. The sludge inoculum was prepared by combining equal volumes of mineral salts solution and the adjusted anaerobic digester sludge. The pH (Orion pH/ISE Meter, model: 520A) and total solids concentration of the test inoculum were 7.6 and 20,820 mg/L, respectively. The test inoculum was held at 35°C under anaerobic conditions until used in the test.
Duration of test (contact time):
63 d
Initial conc.:
0.1 mg/L
Based on:
test mat.
Initial conc.:
12 other: Ci/mL
Based on:
test mat.
Test performance:
The test met the validity criteria specified in the guideline. 14C-volatiles evolved from [14C]d-Glucose positive control chambers (n=2/interval) were quantitated at weekly intervals. By the end of the study, evolved [14C]-volatiles from the [14C]d-Glucose chambers totaled 45.29% and 74.83% of the administered dose, indicating the inocula were viable. The majority of the remaining 14C-activity was detected in the solids (20.0 and 29.3%) with lesser amounts in the aqueous layer (7.8 and 8.7%).
Compartment:
other: water / sediment, material (mass) balance
Remarks on result:
other: see below
% Degr.:
0
Parameter:
CH4 evolution
Sampling time:
63 d
% Degr.:
0
Parameter:
CO2 evolution
Sampling time:
63 d
Transformation products:
no
Details on transformation products:
See below.
Evaporation of parent compound:
no
Volatile metabolites:
no

The entire contents, less three 1 mL aliquots each, of two biotic and two abiotic test chambers treated with [14C]DBDP-Ethane were analyzed on Day 0, 30 and 63 for14C-activity. Results from the biotic and abiotic chambers were similar when compared by day and fraction. On Day 0, the mean total14C-activity from the 4 test chambers (2 biotic, 2 abiotic) was 118.1 ± 15.02%. The mean totals on Days 30 and 63 were lower than on Day 0, but similar to one another, e.g. 78.63 ± 5.12% and 76.65 ± 1.14%, respectively. The majority of14C-activity on all days was associated with the sludge solids. 14C-volatiles and supplemental extraction of test chambers and solids contributed negligible amounts to the total14C-activity recovered on any day. Mineralization was not observed.

With respect to analysis for parent compound and metabolites, results from the biotic and abiotic chambers were again similar on all days. HPLC/β-RAM analysis of sludge extracts detected one peak containing the14C-radiolabel. The peak had a retention time identical to that of the parent compound. 

The mass balance in control and treatment chambers was determined using the triplicate 1 mL samples of Day 0, 30 and 63 sludge and cumulative evolved14C-volatiles. The sludge samples were centrifuged, the solids fraction combusted, and the14C-activity in the supernatant (aqueous) and combustion gases determined on Day 63. The mass balance for the[14C]d-Glucosechambers was similarly determined on Day 63, and was 73.1% and 112.8% of the Day 0 dose (Table 3). Mass balance in the treatment groups were more variable, ranging from 42.1 – 95.1% in the biotic chambers and 36.1 – 155.1% in the abiotic chambers. The greatest variability was observed in the solids fraction, with the lowest value in the biotic Day 63 samples. In contrast, Day 63 solids extraction results (Table 2) were similar in the biotic and abiotic groups and contained a higher percentage of the dose than that of the Day 63 solids measurement, e.g. approximately 76% compared to approximately 42%. The Day 63 solids mass balance in the abiotic chambers (132.8%, 76.0%) was similar to that of the Day 63 solids extraction results (approximately 76%). 

The inability to recover approximately 22% of the anaerobic dose, when using a14C-labelled test material by an experienced laboratory, illustrates the difficulties encountered in working with DBDP-Ethane.  DBDP-Ethane is highly insoluble in water and most organic solvents and has a pronounced tendency to adsorb to surfaces. These properties suggest adherence to glassware during the incubation and extraction steps contributed to lower than expected recovery. Supplemental extraction of the glassware was unable to recover significant amounts of14C-activity, and it was not possible to measure14C-activity on the glassware itself. The majority of the dose was detected in the solids as expected, which raises the possibility that the unaccounted for fraction of the dose was also in this matrix. Incomplete combustion of the sludge solids could have resulted in a lower recovery, however the solids combustion apparatus was routinely tested during the analytical phase and performed properly. Another possible explanation is loss as unrecovered14C-volatiles, however this is highly unlikely.  DBDP-Ethane is not volatile, and mineralization of a substantial fraction of the dose within the timeframe of the study would be exceptional. 

Distribution of14C-activity in anaerobic digester sludge treated with14C-Decabromodipehnyl Ethane.

               

Day

Chamber

14C-Activity (% of Day 0 Dose)

Sludge

Supplemental Extraction

Evolved14C-VOC

Σ

Extracted

Non-extracted+

Sludge

Test Chamber

0

3-Biotic

92.6

22.6

--*

--

--

115.1

4-Biotic

101.7

38.1

--

--

--

139.8

9-Abiotic

99.4

12.3

--

--

--

111.7

10-Abiotic

93.6

12.1

--

--

--

105.6

Mean ± SD

96.83 ± 4.42

21.3 ± 12.2

--

--

--

118.05 ± 15.02

30

5-Biotic

73.9

4.4

--

0.5

0.4

79.2

6-Biotic

69.8

3.5

--

0.5

0.4

74.1

11-Abiotic

77.8

6.7

--

0.8

0.4

85.6

12-Abiotic

71.9

2.5

--

0.8

0.3

75.6

Mean ± SD

73.35 ± 3.41

4.28 ± 1.79

--

0.65 ± 0.17

0.4 ± 0.1

78.63 ± 5.12

63

7-Biotic

73.5

0.9

0.2

0.0

0.8

75.4

8-Biotic

70.6

2.0

0.6

0.2

0.9

74.2

13-Abiotic

72.8

1.9

0.3

0.2

0.8

76.1

14-Abiotic

72.5

2.8

0.1

0.1

1.4

76.9

Mean ± SD

72.35 ± 1.24

1.9 ± 0.78

0.3 ± 0.22

0.13 ± 0.1

0.98 ± 0.29

75.65 ± 1.14

 +Determined by combustion of sludge after extraction.

*Not performed or not measured.

Mass balance expressed as percentage of14C-d-glucose (control) or14C-decabromodiphenyl ethane administered on Day 0. 

Test Day

Chamber

14C-Activity (% of Day 0 Dose)

Solids

Aqueous

Evolved Volatiles

                           

63

1- d-Glucose

20.0

7.8

45.3

73.1

           63

2- d-Glucose

29.3

8.7

74.9

112.8

0

3-Biotic

48.5

1.8

--

50.3

0

4-Biotic

93.5

1.6

--

95.1

30

5-Biotic

71.9

1.5

0.4

73.8

30

6-Biotic

72.5

1.8

0.4

74.7

63

7-Biotic

36.5

5.6

0.8

42.9

63

8-Biotic

37.0

4.2

0.8

42.1

0

9-Abiotic

35.6

0.5

--

36.1

0

10-Abiotic

153.6

1.5

--

155.1

30

11-Abiotic

75.1

6.0

0.4

81.5

30

12-Abiotic

72.7

5.3

0.4

78.4

63

13-Abiotic

126.0

6.0

0.8

132.8

63

14-Abiotic

73.3

1.3

1.4

76.0

Validity criteria fulfilled:
yes
Conclusions:
Evidence for the biodegradation of DBDP-Ethane in anaerobic sewage sludge was not observed over a 63 day period.
Executive summary:

Evidence for the biodegradation of DBDP-Ethane by anaerobic digester sludge was not observed over a 63-d period. Results of the biotic and abiotic chambers were comparable.14C-DBDP-Ethane was used to definitively identify the parent molecule and any degradants.  Only one peak containing the14C-label and having a retention time of DBDP-Ethane was detected in any of the extracts.

Endpoint:
biodegradation in water: sediment simulation testing
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2009
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: Results available as a poster only, but performed by the German UBA in cooperation with the Franunhofer Institute.
Qualifier:
no guideline available
Principles of method if other than guideline:
DBDPEthane dissolved in organic solvents sprayed over the surface of 2 indoor ponds. Concentrations measured in water and sediment at various time points.
GLP compliance:
no
Radiolabelling:
no
Oxygen conditions:
other: water:aerobic; sediment:anaerobic
Inoculum or test system:
natural water / sediment
Duration of test (contact time):
191 d
Initial conc.:
100 other: ng/L
Based on:
test mat.
% Degr.:
0
Parameter:
test mat. analysis
Sampling time:
191 d
Compartment:
water
DT50:
1 - <= 3.8 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: DT90=9-14 d
Compartment:
sediment
DT50:
> 191 d
Type:
other: analysis performed at 191 d
Transformation products:
no

See attached poster.

Validity criteria fulfilled:
not applicable
Conclusions:
After administration to the water surface of 2 indoor ponds, DBDPEthane rapidliy disappeared from water. Degradation in the ponds' anaerobic sediment was not observed 191 d after dosing.
Executive summary:

DBDP-Ethane, dissolved in tetrahydrofurna/toluene/propanol, was applied by spraying onto the water surface of 2 indoor-mesocosm ponds at a dose of 100 ng/L. The ponds' volume ranged from 22 -25 m. DBDP-Ethane's DT50-water ranged from 1 to 3.8 d depending on the kinetic estimation method used. Degradation in anaerobic sediment was not observed over 191 d. BDE 209 also showed no degradation in sediment over 191 d. No formation of lower brominated degradation products of BDE 209 was observed in water or sediment.

Endpoint:
biodegradation in water: sediment simulation testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
November 21, 2013 to February 3, 2015
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 308 (Aerobic and Anaerobic Transformation in Aquatic Sediment Systems)
GLP compliance:
yes
Specific details on test material used for the study:
DBDPEthane was received from PerkinElmer Health Sciences on
February 23, 2010, and assigned Wildlife International identification number 9412. The test substance was
supplied in solid form, and was identified as 1,2-Bis[pentabromophenyl]ethane, [Phenyl-14C[U]];
CUSC72819000MC; lot number 3626190. Information provided by the supplier indicated the
radiochemical purity was 94.5%, the specific activity was 32.4 mCi/mmol, and the molecular weight was
972 mg/mmol. A total of 14.0 mCi was supplied, and no expiration date was provided. A copy of the
certificate of analysis provided by PerkinElmer Health Sciences is available.
Radiolabelling:
yes
Remarks:
14C-ring-labeled DBDPEthane
Oxygen conditions:
aerobic/anaerobic
Inoculum or test system:
natural water / sediment: freshwater
Details on source and properties of surface water:
Collected from Brandywine Creek, Pennsylvania and Choptank River, Maryland.
Details on source and properties of sediment:
Collected from Brandywine Creek, Pennsylvania and Choptank River, Maryland.
Duration of test (contact time):
6 mo
Initial conc.:
10.4 other: uCi per test vessel
Based on:
other:
Remarks:
liquid scintillation count
Parameter followed for biodegradation estimation:
radiochem. meas.
Details on study design:
This study was conducted to assess the potential transformation of DBDPEthane in aerobic and
anaerobic aquatic sediment systems. Both aerobic and anaerobic sediments and their associated waters
were collected from two sites; Brandywine Creek and Choptank River. Test vessels were dosed with
14C-ring labeled DBDPEthane at a nominal concentration of 10.4 μCi per test vessel or 312 μg per test
vessel. Test systems were incubated at approximately 20 ºC for up to 182 days. Aerobic conditions were
maintained by purging the headspace in each vessel with air, while anaerobic conditions were maintained
by purging with nitrogen. Effluent gases were passed through ethylene glycol to trap organic volatiles,
followed by alkali solutions to trap evolved carbon dioxide. Duplicate test chambers of each test system
were sacrificed on months 0, 1, 2, 3, 4, 5 and 6. The overlying water layers were decanted and filtered,
and analyzed for total radioactivity by liquid scintillation counting (LSC). The filtered materials from the
water layers were combined with the sediment layers and extracted once using methanol (MeOH). The
MeOH extracts were analyzed by LSC. The remaining solids were extracted four times using
tetrahydrofuran (THF). The THF extracts were combined and analyzed by LSC. The remaining
sediment solids were analyzed separately for total radioactivity by combustion, followed by LSC.
Reference substance:
not required
Compartment:
natural water / sediment: freshwater
% Recovery:
91
Key result
Compartment:
natural water / sediment: freshwater
DT50:
> 6 mo
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Transformation products:
no
Details on results:

Results from Aerobic Brandywine Creek
The mean material balance results from aerobic Brandywine Creek test systems are presented in
Table 8. Material balance results from individual test vessels
ranged from 86.5% to 102.7% throughout the test. On day 0, the mean percent of dosed
radioactivity in the sediment extracts was 90.8%, and 3.8% was bound to the sediment solids. At the end
of the test, the mean amount in the sediment extracts was 95.2%, and 2.7% was bound to the sediment
solids. During the study, the mean sediment extraction efficiency was 94.5% for all 16 samples. The
mean cumulative amount of 14C gas production over the 6-month test period was <0.1%.
The mean distributions of [14C]DBDPEthane and other products in the sediment extracts are
presented in Table 12. The mean amount of parent
(DBDPEthane) was 93.4% on day 0 and 92.0% on day 182. The mean amounts and concentrations of
DBDPEthane are presented in Table 13. The means were used in regression analyses in an attempt to
determine disappearance rates for DBDPEthane, and did not include the 14C bound to the sediment solids.
The results from a simple first-order (SFO) decay curve model are presented in Table 14. The SFO model did not fit the data well (r2 <0.70), but none of the other models
were a better fit. The amount of DBDPEthane in the sediment extracts never dropped below 87%, so the
DT50 was >6 months.
The mean total amount of other products was 1.3% on day 0, and reached a maximum of 5.2% on
days 62 and 182, but none of the individual other product peaks accounted for >1.5% of the dose. The
amount of impurities in the test substance was 5.5%. The other product peaks observed in the sediment
extracts were attributed to impurities, rather than transformation products.
No further attempts were made to identify the other products.

Results from Aerobic Choptank River
The mean material balance results from aerobic Choptank River test systems are presented in Table
8. Material balance results from individual test vessels ranged from
88.6% to 103.5% throughout the test). On day 0, the mean percent of dosed radioactivity
in the sediment extracts was 96.9%, and 1.1% was bound to the sediment solids. At the end of the test,
the mean amount in the sediment extracts was 98.2%, and 1.7% was bound to the sediment solids.
During the study, the mean sediment extraction efficiency was 97.7% for all 16 samples. The mean
cumulative amount of 14C gas production over the 6-month test period was <0.1%.
The mean distributions of [14C]DBDPEthane and other products in the sediment extracts are
presented in Table 12.. The mean amount of parent
(DBDPEthane) was 94.1% on day 0 and 94.1% on day 182. The mean amounts and concentrations of
DBDPEthane are presented in Table 15. The means were used in regression analyses in an attempt to
determine disappearance rates for DBDPEthane, and did not include the 14C bound to the sediment solids.
The results from a simple first-order (SFO) decay curve model are presented in Table 16. The SFO model did not fit the data well (r2 <0.70), but none of the other models
were a better fit. The amount of DBDPEthane in the sediment extracts never dropped below 86%, so the
DT50 was >6 months.
The mean total amount of other products was 3.7% on day 0, and reached a maximum of 7.9% on
day 32, but none of the individual other product peaks accounted for >2% of the dose. The amount of
impurities in the test substance was 5.5%. The other product peaks observed in the sediment extracts
were attributed to impurities, rather than transformation products.
No further attempts were made to identify the other products.

Results from Anaerobic Brandywine Creek
The mean material balance results from anaerobic Brandywine Creek test systems are presented in
Table 8 .balance results from individual test vessels
ranged from 84.0% to 99.3% throughout the test. On day 0, the mean percent of dosed
radioactivity in the sediment extracts was 87.3%, and 3.8% was bound to the sediment solids. At the end
of the test, the mean amount in the sediment extracts was 93.2%, and 1.8% was bound to the sediment
solids. During the study, the mean sediment extraction efficiency was 94.3% for all 16 samples. The
mean cumulative amount of 14C gas production over the 6-month test period was <0.1%.
The mean distributions of [14C]DBDPEthane and other products in the sediment extracts are
presented in Table 12. The mean amount of parent
(DBDPEthane) was 93.0% on day 0 and 91.7% on day 182. The mean amounts and concentrations of
DBDPEthane are presented in Table 17. The means were used in regression analyses in an attempt to
determine disappearance rates for DBDPEthane, and did not include the 14C bound to the sediment solids.
The results from a simple first-order (SFO) decay curve model are presented in Table 18. The SFO model did not fit the data well (r2 <0.70), but none of the other models
were a better fit. The amount of DBDPEthane in the sediment extracts never dropped below 85%, so the
DT50 was >6 months.
The mean total amount of other products was 1.1% on day 0, and reached a maximum of 6.8% on
day 32, but none of the individual other product peaks accounted for >2.5% of the dose. The amount of
impurities in the test substance was 5.5%. The other product peaks observed in the sediment extracts
were attributed to impurities, rather than transformation products.
No further attempts were made to identify the other products.

Results from Anaerobic Choptank River
The mean material balance results from anaerobic Choptank River test systems are presented in
Table 8. Material balance results from individual test vessels
ranged from 88.0% to 103.4% throughout the test.On day 0, the mean percent of dosed
radioactivity in the sediment extracts was 92.3%, and 0.3% was bound to the sediment solids. At the end
of the test, the mean amount in the sediment extracts was 101.3%, and 1.5% was bound to the sediment
solids. During the study, the mean sediment extraction efficiency was 98.5% for all 16 samples. The
mean cumulative amount of 14C gas production over the 6-month test period was <0.1%.
The mean distributions of [14C]DBDPEthane and other products in the sediment extracts are
presented in Table 12.. The mean amount of parent
(DBDPEthane) was 97.9% on day 0 and 94.2% on day 182. The mean amounts and concentrations of
DBDPEthane are presented in Table 19. The means were used in regression analyses in an attempt to
determine disappearance rates for DBDPEthane, and did not include the 14C bound to the sediment solids.
The results from a simple first-order (SFO) decay curve model are presented in Table 20. The SFO model did not fit the data well (r2 <0.70), but none of the other models
were a better fit. The amount of DBDPEthane in the sediment extracts never dropped below 85%, so the
DT50 was >6 months.
The mean total amount of other products was 1.6% on day 0, and reached a maximum of 9.9% on
day 32, but none of the individual other product peaks accounted for >3% of the dose. The amount of
impurities in the test substance was 5.5%. The other product peaks observed in the sediment extracts
were attributed to impurities, rather than transformation products.No further attempts were made to identify the other products.

Table 1. Properties of Sediments and Waters

Parameters

Aerobic

Brandywine

Creek

Anaerobic

Brandywine

Creek

Aerobic

Choptank

River

Anaerobic

Choptank

River

Date Collected:

Water Temp. (°C)

Water pH

Dissolved Oxygen (mg/O2/L)

Dec. 9, 2013

3.7

7.3

 9.9

Dec. 9, 2013

3.5

57.3

5.5

Nov. 12, 2013

8.3

7.31

11.51

Nov. 12, 2013

8.3

7.35

11.65

USDA Textural Class

% Sand

% Silt

% Clay

% Organic Carbon

% Organic Matter

Bulk Density (disturbed) (g/cc)

pH in 1:1 soil:water ratio

Cation Exchange Capacity (meq/100g)

Moisture Content at 1/3 Bar

Free Iron Oxide (ppm)

 

Silty Clay Loam

10

57

33

7.0

12.0

 0.55

 

5.3

 

9.7

 

 

78.9

 

22120

 

Silty Clay Loam

18

49

33

5.2

9.0

 

0.68

 

5.1

 

9.3

 

 

63.8

 

21420

 

Sand

95

3

2

1.0

1.7

 

1.17

 

6.3

 

4.3

  

6.9

 

19060

 

Sand

93

5

2

1.4

2.5

 

1.08

 

6.3

 

5.5 

 

8.8

 

14920

Moisture Content (Pw)

Bulk Density (g/cm3)

Microbial Biomass (ug/g)

 

118.39%

 

1.2729

 

26.4.7

 

120.06%

 

1.3888

 

99.8

 

72.38%

 

1.6389

 

729.6

 

34.76%

 

1.8626

 

140.6

Table 2. Water Layer Characterization Results

Sample Interval

Parameter

Aerobic

Brandywine

Creek

Aerobic

Choptank

River

Anaerobic

Brandywine

Creek

Anaerobic

Choptank

River

Start of

Acclimation

pH

D.O.

Redox

TOC

6.8

7.8

335.8

3.1

6.9

6.6

376.8

3.9

6.9

3.8

340.1

3.5

6.8

3.6

370.0

3.6

Month 0

(Start of Test)

pH

D.O.

Redox

TOC

7.1

5.1

349.0

3.3

6.9

3.9

325.8

7.1

7.4

0.3

319.9

2.6

7.3

0.2

89.3

4.8

Month 1

pH

D.O.

Redox

7.0

5.0

303.8

7.7

5.2

319.2

7.3

0.2

273.5

7.9

0.3

298.6

Month 2

pH

D.O.

Redox

7.2

5.7

332.4

7.6

5.8

325.7

6.7

0.3

377.1

6.9

0.4

311.7

Month 3

pH

D.O.

Redox

6.7

5.7

272.6

7.7

6.1

278.9

6.3

0.3

293.9

7.6

0.2

265.3

Month 4

pH

D.O.

Redox

6.9

6.4

234.1

7.7

6.2

251.9

6.7

0.3

256.5

7.9

0.1

220.2

Month 5

pH

D.O.

Redox

6.9

4.7

184.6

7.3

4.6

211.6

6.1

0.4

206.7

7.2

0.4

182.9

Month 6

pH

D.O.

Redox

TOC

6.8

5.2

243.8

5.4

7.7

5.4

239.1

13.6

7.0

0.1

235.7

2.8

7.0

0.1

261.9

6.1

D.O.=dissolved oxygen content in overlying water layer (mg O2/L)

RedOx=redox potential of water layer (Eh)

TOC=total organic carbon content in water layer (mg C/L)

Table 3. Sediment Layer Characterization Results

Sample Interval

Parameter

Aerobic

Brandywine

Creek

Aerobic

Choptank

River

Anaerobic

Brandywine

Creek

Anaerobic

Choptank

River

Start of

Acclimation

pH

Redox

TOC

6.2

232.4

6.1

6.8

238.3

1.3

6.4

142.8

4.3

6.7

157.6

0.6

Month 0

(Start of Test)

pH

Redox

TOC

Biomass

7.0

214.0

5.4

44.3

7.0

205.5

1.4

263.2

6.9

-87.4

3.8

0

6.9

-84.5

0.7

83.0

Month 1

pH

Redox

6.7

137.5

7.2

124.5

7.0

-122.5

7.1

-84.6

Month 2

pH

Redox

6.8

141.3

6.9

186.2

6.4

-96.4

6.6

-53.5

Month 3

pH

Redox

6.8

39.3

6.7

81.2

6.4

-76.8

6.9

-51.8

Month 4

pH

Redox

6.7

54.6

6.9

119.1

6.8

-44.2

7.2

-23.6

Month 5

pH

Redox

6.6

51.3

6.7

59.1

6.4

-78.6

6.7

-83.1

Month 6

pH

Redox

TOC

Black Carbon

Biomass

6.9

-20.1

6.2

0.53

56.9

6.9

-27.1

1.4

0.07

180.1

7.0

-152.0

4.1

0.36

6.3

6.8

-177.1

0.6

0.19

41.9

RedOx=redox potential of sediment layer (Eh)

TOC=total organic carbon content in sediment layer (5)

Black carbon-microporous black carbon in sediment layer (%)

Biomass=microbial biomass in sediment layer (ug/g)

Table 4. Sediment RedOx Potentials

Interval

Date

Aerobic

Brandywine

Creek

Aerobic

Choptank

River

Anaerobic

Brandywine

Creek

Anaerobic

Choptank

River

Day-23

Day-22

Day-17

Day-16

Day-15

Day-14

Day-13

Day-10

Day-8

Day-7

Day-6

Day-3

Day-2

Day-1

Day 0

Day 7

Day 14

Day 21

Day 32

Day 47

Day 62

Day 77

Day 92

Day 105

Day 119

Day 137

Day 152

Day 167

Day 182

November 26, 2013

November 27, 2013

December 2, 2013

December 3, 2013

December 4, 2013

December 5, 2013

December 6, 2013

Decmber 9, 2013

December 11, 2013

December 12, 2013

December 13, 2013

December 16, 2013

December 17, 2013

December 18, 2013

December 19, 2013

December 26, 2013

January 2, 2014

January 9, 2014

January 20, 2014

February 4, 2014

February 19, 2014

March 6, 2014

March 21, 2014

April 3, 2014

April 17, 2014

May 5, 2014

May 20, 2014

June 4, 2014

June 19, 2014

NA

NA

NA

NA

NA

NA

NA

NA

131

74

-9

-140

-164

-209

-215

-235

-236

-239

-251

-254

-252

-176

-189

-199

-202

-211

-203

-183

-187

61

59

-153

-193

-253

-246

-247

-256

-235

-255

-254

-237

-258

-255

-257

-238

-247

-254

-248

-258

-255

-229

-228

-228

-225

-226

-228

-230

-230

NA

NA

NA

NA

NA

NA

NA

NA

91

-65

-138

-215

-227

-228

-229

-228

-230

-230

-225

-234

-230

-218

-227

-235

-235

-219

-231

-236

-231

128

-133

-256

-258

-256

-257

-257

-263

-250

-251

-251

-246

-246

-244

-245

-244

-246

-240

-246

-227

-232

-247

-249

-242

-252

-258

-251

-244

-246

Redox potentials given in Eh

Table 5. Viability Results

Test Start

Interval

Anaerobic

Brandywine

Creek

Anaerobic

Choptank

River

Day 0

Day 7

Day 14

Day 21

Day 28

20.1%

40.7%

54.1%

--

13.4%

39.0%

51.4%

--

Day 91

Day 7

Day 14

Day 21

Day 28

22.5%

42.2%

51.0%

--

26.8%

44.6%

53.9%

--

Day 182

Day 7

Day 14

Day 21

Day 28

7.8%

25.4%

40.4%

53.1%

15.9%

41.2%

57.8%

--

Results given in cumulative % of applied14C recovered in gas traps

Table 6. Mean Cumulative Redioactivity in All Transformation Vessel Gas Traps

Test

System

Interval

(Days)

Volatile

14C Gases

Evolved

14CO2

Total

Gases

Aerobic

Brandywine

Creek

32

62

91

119

152

182

0.00%

0.00%

0.00%

0.00%

0.00%

0.00%

0.00%

0.00%

0.01%

0.01%

0.01%

0.02%

0.00%

0.00%

0.01%

0.01%

0.01%

0.02%

Aerobic

Choptank

River

32

62

91

119

152

182

0.00%

0.00%

0.00%

0.00%

0.00%

0.00%

0.00%

0.00%

0.00%

0.00%

0.01%

0.01%

0.00%

0.00%

0.00%

0.01%

0.01%

0.01%

Anaerobic

Brandywine

Creek

32

62

91

119

152

182

0.00%

0.00%

0.00%

0.00%

0.00%

0.00%

0.00%

0.00%

0.00%

0.00%

0.01%

0.01%

0.00%

0.00%

0.00%

0.00%

0.01%

0.01%

Anaerobic

Choptank

River

32

62

91

119

152

182

0.00%

0.00%

0.00%

0.00%

0.00%

0.00%

0.00%

0.00%

0.00%

0.00%

0.01%

0.01%

0.00%

0.00%

0.01%

0.01%

0.01%

0.01%

Table 7. Mean Cumulative Radioactivity in All Mineralization Vessel Gas Traps

Test

System

Interval

(Days)

Evolved

14CO2

Volatile

14C Gases

Total

Gases

Aerobic

Brandywine

Creek

32

62

91

119

152

182

0.01%

0.01%

0.01%

0.01%

0.02%

0.03%

0.00%

0.00%

0.00%

0.01%

0.01%

0.01%

0.01%

0.01%

0.02%

0.02%

0.03%

0.04%

Aerobic

Choptank

River

32

62

91

119

152

182

0.00%

0.00%

0.01%

0.01%

0.02%

0.02%

0.00%

0.00%

0.00%

0.00%

0.01%

0.01%

0.01%

0.01%

0.01%

0.01%

0.02%

0.03%

Anaerobic

Brandywine

Creek

32

62

91

119

152

182

0.00%

0.00%

0.01%

0.01%

0.02%

0.02%

0.00%

0.00%

0.00%

0.00%

0.01%

0.01%

0.00%

0.00%

0.01%

0.01%

0.02%

0.03%

Anaerobic

Choptank

River

32

62

91

119

152

182

0.00%

0.00%

0.01%

0.01%

0.01%

0.02%

0.00%

0.00%

0.00%

0.01%

0.01%

0.01%

0.00%

0.00%

0.01%

0.01%

0.02%

0.03%

Table 8. Mean Distribution of Radioactivity from Test Vessels

Test System

Interval

(Days)

Water

Layers

(%)

MeOH

Extracts

(%)

THF

Extracts

(%)

Combusted

Sediment

Solids (%)

Total

Gases

(%)

Material

Balance

(Recovery)

(%)

Aerobic

Brandywine

Creek

 

 

 

 

Mineral

0

32

62

91

119

152

182

182

0.0

0.5

0.0

0.3

0.1

0.0

0.0

0.1

0.0

0.3

0.2

0.3

0.3

0.2

0.4

0.7

90.8

79.8

85.0

90.8

92.5

90.7

95.2

92.1

3.8

6.0

3.1

5.3

6.0

6.7

2.7

6.0

NA

0.0

0.0

0.0

0.0

0.0

0.0

0.0

94.7

86.6

88.5

96.6

98.9

97.6

98.3

99.0

Aerobic

Choptank

River

 

 

 

 

Mineral

0

32

62

91

119

152

182

182

0.4

0.5

0.0

0.0

0.0

0.0

0.1

0.1

0.0

0.4

0.3

0.2

0.3

0.2

0.3

0.3

96.9

87.9

87.8

95.3

95.6

93.6

98.2

96.5

1.1

2.9

0.7

2.5

2.2

3.0

1.7

3.3

NA

0.0

0.0

0.0

0.0

0.0

0.0

0.0

98.5

91.7

88.9

98.1

98.2

96.7

100.4

100.2

Anaerobic

Brandywine

Creek

 

 

 

 

Mineral

0

32

62

91

119

152

182

182

0.1

0.5

2.1

0.1

0.1

0.1

0.1

0.2

0.0

0.1

0.1

0.1

0.1

0.2

0.1

0.3

87.3

78.7

87.6

89.0

87.2

84.3

93.2

90.8

3.8

5.3

5.2

5.4

4.9

6.5

1.8

6.7

NA

0.0

0.0

0.0

0.0

0.0

0.0

0.0

91.2

84.5

95.1

94.6

92.4

91.2

95.3

97.9

Anaerobic

Choptank

River

 

 

 

 

Mineral

0

32

62

91

119

152

182

182

0.6

0.5

0.1

0.1

0.1

0.2

0.2

0.2

0.0

0.1

0.1

0.1

0.1

0.3

0.1

0.6

92.3

86.1

93.9

96.9

93.9

97.7

101.3

85.0

0.3

1.7

0.9

1.2

1.6

1.6

1.5

2.2

NA

0.0

0.0

0.0

0.0

0.0

0.0

0.0

93.2

88.3

95.1

98.4

95.7

99.9

103.0

88.1

NA - Not Applicable

Table 9. Mean Sediment Extraction Effeciencies

Test

System

Interval

(Days)

Mean

DPM in

Combined

Extracts

Mean

DPM in

Sediment

Solids

Mean

DPM in

Sediment

Layer

Proportion

In/On

Solids

(%)

Mean

Extraction

Efficiency

(%)

Aerobic

Brandywine

Creek

 

 

 

 

Mineral

0

32

62

91

119

152

182

182

13299413

18543761

19754234

21114032

21509622

21131760

22240180

21558256

885152

1401069

722328

1225059

1390706

1554446

637408

1398247

14184565

19944830

20476563

22339091

22900329

22686206

22877589

22956503

6.2

7.0

3.5

5.5

6.1

6.9

2.8

6.1

93.8

93.0

96.5

94.5

93.9

93.1

97.2

93.9

Aerobic

Choptank

River

 

 

 

 

Mineral

0

32

62

91

119

152

182

182

13523627

20505739

20409701

22231525

22289688

21775167

22920625

22539568

259631

669660

170749

575529

505686

685733

400142

759269

13783258

21175399

20580450

22807055

22795373

22460900

23320766

23298837

1.9

3.2

0.8

2.5

2.2

3.1

1.7

3.3

98.1

96.8

99.2

97.5

97.8

96.9

98.3

96.7

Anaerobic

Brandywine

Creek

 

 

 

 

Mineral

0

32

62

91

119

152

182

182

12698410

18285280

20373295

20682796

20314370

19678998

21611489

21184527

883631

1219593

1211298

1249003

1144617

1520042

421070

1553291

13582040

19504872

21584593

21931979

21458987

21199040

22032559

22737818

6.5

6.3

5.6

5.7

5.3

7.2

1.9

6.8

93.5

93.7

94.4

94.3

94.7

92.8

98.1

93.2

Anaerobic

Choptank

River

 

 

 

 

Mineral

0

32

62

91

119

152

182

182

13467277

19970111

21819086

22585282

21876710

22734037

23557981

19908964

69672

385845

207158

285585

376812

370921

346889

508902

13536949

20355955

22026243

22870867

22253522

23104957

23904870

20417867

0.5

1.9

0.9

1.2

1.7

1.6

1.5

2.5

99.5

98.1

99.1

98.8

98.3

98.4

98.5

97.5

Table 10. Mean Chloroform Extraction Results

Test

System

Interval

(Days)

Mean

DPM in

Conc.

Sed. Ext.

Mean

DPM in

Chloroform

Extracts

Mean

DPM in

Aqueous

Fractions

Recovery

(%)

Percent in

Aqueous

Fractions

(%)

Mean

Extraction

Efficiency

(%)

ABC

 

 

 

 

 

 

Mineral

0

32

62

91

119

152

182

182

19094531

17840058

17830256

18757120

18038240

17992983

19824375

20650249

17272897

17535295

17259248

18928896

168879549

18932184

19582525

19922217

327313

74751

166491

139449

705738

85874

119745

37498

93.5

98.7

97.9

101.7

97.5

105.7

99.4

96.7

1.8

0.4

1.0

0.7

4.1

0.5

0.6

0.2

96.8

99.6

99.0

99.3

95.9

99.5

99.4

99.8

ACR

 

 

 

 

 

 

Mineral

0

32

62

91

119

152

182

182

20753958

20574258

17069184

19852672

19537934

19265216

21217780

22103148

19137357

19565473

18555183

20131044

19493621

20467864

20548863

21151433

40570

119196

930

109006

58519

8017

4366

687

93.3

95.7

108.7

102.0

100.1

106.3

96.9

95.7

0.2

0.6

0.0

0.5

0.3

0.0

0.0

0.0

98.8

99.4

100.0

99.5

99.7

100.0

100.0

100.0

NBC

 

 

 

 

 

 

Mineral

0

32

62

91

119

152

182

182

20319883

17774160

18707392

18683719

17552768

17633248

20111576

20692768

17013076

16372907

18961450

16600444

14492776

18003061

19966253

19557828

833139

91107

9735

1165286

766789

45668

806

2970

89.5

92.6

101.4

95.1

86.8

102.3

99.3

94.5

4.5

0.6

0.0

6.6

5.0

0.3

0.0

0.0

93.7

99.4

100.0

93.4

95.0

99.7

100.0

100.0

NCR

 

 

 

 

 

 

Mineral

0

32

62

91

119

152

182

182

21191348

19927923

20771030

20628182

19437952

20761760

22195217

19670792

20084589

17533445

20951175

19943992

19554403

20312021

22015100

18118638

19412

163019

1540

269734

22194

578500

1351

645

95.0

88.8

100.9

98.0

100.7

100.6

99.2

92.1

0.1

0.9

0.0

1.3

0.1

2.8

0.0

0.0

99.8

99.1

100.0

98.7

99.9

97.2

100.0

100.0

Table 11. Mean Procedural Recoveries

Test

System

Interval

(Days)

Mean

Recovery

Combined

Sed. Extract

Concentration

(%)

Mean

Recovery

Chloroform

Extraction

(%)

Mean

Recovery

Chloroform

Extract

Concentration

(%)

Overall

Mean

Procedural

Recovery

(%)

ABC

 

 

 

 

 

 

Mineral

0

32

62

91

119

152

182

182

99.8

103.2

103.2

96.1

97.1

93.3

95.1

103.1

93.5

98.7

97.9

101.7

97.5

105.7

99.4

96.7

106.5

105.9

104.0

104.2

97.6

108.3

106.5

107.8

99.3

107.9

105.0

101.8

92.3

106.8

100.6

107.3

ACR

 

 

 

 

 

 

Mineral

0

32

62

91

119

152

182

182

102.1

107.5

101.0

96.1

97.1

95.3

99.6

104.1

93.3

95.7

108.7

102.0

100.1

106.3

96.9

95.7

109.8

108.0

105.3

105.6

106.2

105.4

106.3

107.4

104.6

111.1

115.6

103.4

103.3

106.7

102.6

107.0

NBC

 

 

 

 

 

 

Mineral

0

32

62

91

119

152

182

182

109.8

106.2

99.7

99.5

98.7

97.9

100.6

105.9

89.5

92.6

101.4

95.1

86.8

102.3

99.3

94.5

104.7

104.5

106.0

102.9

104.6

102.6

104.3

109.7

102.9

102.7

107.1

97.3

898.8

102.7

104.2

109.8

NCR

 

 

 

 

 

 

Mineral

0

32

62

91

119

152

182

182

108.6

105.6

100.7

97.7

98.1

98.4

100.1

106.3

95.0

88.8

100.9

98.0

100.7

100.6

99.2

92.1

105.7

107.7

109.1

111.6

102.4

104.4

108.2

112.8

109.0

101.0

110.8

107.0

101.2

103.3

107.4

110.5

Table 12. Mean Distribution of Parent and Other14C Products in Sediment Extracts

Test

System

Interval

(Days)

Polar

Sample

(%)

Before

(1.0-11.3)

(%)

Parent

(11.3-12.3) (%)

After

(12.3-16.0) (%)

Total

% of

Sample

Total %

Other14C

Products

Aerobic

Brandywine

Creek

 

 

 

 

Mineral

0

32

62

91

119

152

182

182

0.3*

1.2

0.3*

1.3

0.4*

0.6

1.0

1.0

0.3

0.5

2.1

0.9

0.5

0.6

1.3

1.0

93.4

88.3

91.3

90.3

92.7

90.9

92.0

90.7

0.6

2.9

2.8

2.2

0.2

1.0

2.9

1.1

94.7

92.9

96.4

94.6

93.9

93.0

97.2

93.9

1.3

4.6

5.2

4.3

1.1

2.2

5.2

3.2

Aerobic

Choptank

River

 

 

 

 

Mineral

0

32

62

91

119

152

182

182

0.7

1.4

0.4

0.8

0.7

0.2

0.4

0.5

0.5

2.5

0.3

0.3

0.7

0.5

0.8

0.3

94.1

88.9

97.9

94.3

95.1

95.7

94.1

94.5

2.5

4.0

0.5

2.1

1.3

0.6

3.0

1.5

97.8

96.7

99.1

97.4

97.7

96.8

98.3

96.7

3.7

7.9

1.1

3.1

2.7

1.2

4.2

2.2

Anaerobic

Brandywine

Creek

 

 

 

 

Mineral

0

32

62

91

119

152

182

182

0.1*

1.2

2.4

0.2*

0.3*

0.6

0.2

0.5

0.3

0.7

0.9

0.3

1.1

0.9

0.6

0.6

93.0

86.9

89.2

90.8

90.5

89.7

91.7

90.7

0.8

4.9

1.9

3.0

2.8

1.6

5.6

1.4

94.1

93.8

94.4

94.3

94.7

92.8

98.0

93.2

1.1

6.8

5.2

3.5

4.1

3.2

6.3

2.5

Anaerobic

Choptank

River

 

 

 

 

Mineral

0

32

62

91

119

152

182

182

0.7

1.5

0.3

0.2*

0.3

0.6*

0.2

0.9

0.9

0.7

0.0

0.4

0.4

1.0

0.4

0.1

97.9

88.1

96.3

95.6

96.8

93.3

94.2

95.3

0.0

7.8

2.5

2.5

0.8

3.6

3.7

1.1

99.5

98.1

99.0

98.7

98.3

98.4

98.5

97.4

1.6

9.9

2.7

3.1

1.5

5.1

4.3

2.1

Polar Sample = Overlying Water Layer+MeOH Extract+Aqueous Fraction (except*)

*Results from Aqueous Fraction included in HPLC regions

Parent = Parent in Chloroform Extracts+Parent in Aqueous Fractions

Total Other14C Products = Total% of Sample - Parent (DBDPEthane)

Table 13. Disappearance of DBDPEthane from Aerobic Brandywine Creek

Interval

(Days)

Sediment Extracts

%

mg/kg

0

32

62

91

119

152

182

93.4

88.3

91.3

90.3

92.7

90.9

92.0

5.84

5.52

5.70

5.64

5.80

5.68

5.75

Table 14. Regression Analysis of DBDPEthane in Aerobic Brandywine Creek

Simple First-Order Model Statistics

Estimated Values:

Parameter

Value

s

Prob.>t

Lower CI

Upper CI

Parent_O

91.27

1.265

4.838E-09

88.02

94.52

K_Parent

1.766E-12

0.0001268

0.5

-0.0003261

0

s = sigma

Chi-Squared

Parameter

Error %

Degrees of Freedom

All data

1.36

5

Parent

1.36

5

Decay Times:

Compartment

DT50 (Days)

DT90 (Days)

Parent

3.926E+11

1.304E+12

Additonal Statistics:

Parameter

r2(Obs. V. Pred.)

Efficiency

All data

0.00961

6.907E-06

Parent

0.00961

6.907E-06

Parameter Correlation:

 

Parent_O

K_Parent

Parent_O

1

0.8343

K_Parent

0.8343

1

Observed v. Predicted:

Time (Days)

Value

(% of Dose)

Predicted

Value

Residual

0

93.4

91.27

2.129

32

88.3

91.27

-2.971

62

91.3

91.27

0.02851

91

90.3

91.27

-0.9715

119

92.7

91.27

1.428

152

90.9

91.27

-0.3716

182

92

91.27

0.7284

Table 15. Disappearance of DBDPEthane from Aerobic Choptank River

Interval

(Days)

Sediment Extracts

%

mg/kg

0

32

62

91

119

152

182

94.1

88.9

97.9

94.3

95.1

95.7

94.1

4.03

3.80

4.19

4.04

4.07

4.09

4.03

Table 16. Regression Analysis of DBDPEthane in Aerobic Choptank River

Simple First-Order Model Statistics

Estimated Values:

Parameter

Value

s

Prob.>t

Lower CI

Upper CI

Parent_O

94.3

2.052

4.609E-08

89.02

99.58

K_Parent

9.37E-13

0.0001992

0.5

-0.0005121

0.001

 

Chi-Squared:

Parameter

Error %

Degrees of Freedom

All data

2.133

5

Parent

2.133

5

 

Decay Times:

Compartment

DT50 (Days)

DT90 (Days)

Parent

7.391E+11

2.455E+12

 

Additional Statistics:

Parameter

r2(Obs. V. Pred.)

Efficiency

All data

0.09116

1.355E-05

Parent

0.09116

1.355E-05

 

 Parameter Correlation: 

 

Parent_O

K_Parent

Parent_O

1

0.8343

K_Parent

0.8343

1

 

Observed v. Predicted:

Time (Days)

Value

(% of Dose)

Predicted

Value

Residual

0

94.1

94.3

-0.2

32

88.9

94.3

-5.4

62

97.9

94.3

3.6

91

94.3

94.3

-8.581E-05

119

95.1

94.3

0.7999

152

95.7

94.3

1.4

182

94.1

94.3

-0.2002

Table 17. Disappearance of DBDPEthane from Anaerobic Brandywine Creek

Interval

(Days)

Sediment Extracts

%

mg/kg

0

32

62

91

119

152

182

93.0

86.9

89.2

90.8

90.5

89.7

91.7

5.39

5.03

5.17

5.26

5.24

5.19

5.31

Table 18. Regression Analysis of DBDPEthane in Anaerobic Brandywine Creek

Simple First-Order Model Statistics

Estimated Values:

Parameter

Value

s

Prob.>t

Lower CI

Upper CI

Parent_O

90.26

1.459

1.046E-08

86.51

94

K_Parent

2.745E-13

0.000148

0.5

-0.0003805

0

 

Chi-Squared:

Parameter

Error %

Degrees of Freedom

All data

1.585

5

Parent

1.585

5

 

Decay Times:

Compartment

DT50 (Days)

DT90 (Days)

Parent

2.525E+12

8.387E+12

 

Additional Statistics:

Parameter

r2(Obs. V. Pred.)

Efficiency

All data

0.01205

6.629E-06

Parent

0.01205

6.629E-06

 

 Parameter Correlation:

 

 

Parent_O

K_Parent

Parent_O

1

0.8343

K_Parent

0.8343

1

 

Observed v. Predicted:

Time (Days)

Value

(% of Dose)

Predicted

Value

Residual

0

93

90.26

2.743

32

86.9

90.26

-3.357

62

89.2

90.26

-1.057

91

90.8

90.26

0.5428

119

90.5

90.26

0.2427

152

89.7

90.26

-0.5573

182

91.7

90.26

1.443

Table 19. Disappearance of DBDPEthane from Anaerobic Choptank River

Interval

(Days)

Sediment Extracts

%

mg/kg

0

32

62

91

119

152

182

97.9

88.1

96.3

95.6

96.8

93.3

94.2

2.89

2.60

2.84

2.82

2.86

2.75

2.78

Table 20. Regression Analysis of DBDPEthane in Anaerobic Choptank River

Simple First-Order Model Statistics

Estimated Values:

Parameter

Value

s

Prob.>t

Lower CI

Upper CI

Parent_O

94.67

2.448

1.089E-07

88.38

101

K_Parent

8.409E-06

0.0002368

0.4865

-0.0006003

0.001

 

Chi-Squared:

Parameter

Error %

Degrees of Freedom

All data

2.534

5

Parent

2.534

5

 

Decay Times:

Compartment

DT50 (Days)

DT90 (Days)

Parent

8.243E+04

2.738E+05

 

Additional Statistics:

Parameter

r2(Obs. V. Pred.)

Efficiency

All data

0.0002522

0.0002522

Parent

0.0002522

0.0002522

 

Parameter Correlation:

 

Parent_O

K_Parent

Parent_O

1

0.8341

K_Parent

0.8341

1

 

Observed v. Predicted:

Time (Days)

Value

(% of Dose)

Predicted

Value

Residual

0

97.9

94.67

3.228

32

88.1

94.65

-6.547

62

96.3

94.62

1.677

91

95.6

94.6

0.9998

119

96.8

94.58

2.222

152

93.3

94.55

-1.252

182

94.2

94.53

-0.3279

Material Balance                  Water Layers                  Sediment Layer                  

Total Gases

Validity criteria fulfilled:
yes
Conclusions:
DPDPEthane did not appear to degrade in any of the 2 aerobic and 2 anaerobic test systems. The mean percentage of radioactivity recovered as DBDPEthane at the end of the 6-month test was 91% in all sediment extracts. The DT50 values were >6 months for all four test systems.
Executive summary:

This study was conducted to assess the potential transformation of DBDPEthane in aerobic and anaerobic aquatic sediment systems. Both aerobic and anaerobic sediments and their associated waters were collected from two sites; Brandywine Creek and Choptank River. Test vessels were dosed with 14C-ring labeled DBDPEthane at a nominal concentration of 10.4 μCi per test vessel or 312 μg per test vessel. Test systems were incubated at approximately 20 ºC for up to 182 days. Aerobic conditions were maintained by purging the headspace in each vessel with air, while anaerobic conditions were maintained by purging with nitrogen. Effluent gases were passed through ethylene glycol to trap organic volatiles, followed by alkali solutions to trap evolved carbon dioxide. Duplicate test chambers of each test system were sacrificed on months 0, 1, 2, 3, 4, 5 and 6. The overlying water layers were decanted and filtered, and analyzed for total radioactivity by liquid scintillation counting (LSC). The filtered materials from the water layers were combined with the sediment layers and extracted once using methanol (MeOH). The MeOH extracts were analyzed by LSC. The remaining solids were extracted four times using tetrahydrofuran (THF). The THF extracts were combined and analyzed by LSC. The remaining sediment solids were analyzed separately for total radioactivity by combustion, followed by LSC.

The overlying water layers and MeOH extracts contained 4.2% on day 62. No further work was done on these fractions. The THF extracts were analyzed by HPLC for parent test substance and other radio-labeled products.

DBDPEthane did not appear to degrade in any of the four test systems. The mean percentage of radioactivity recovered as DBDPEthane at the end of the 6-month test was >91% in all sediment extracts. There was no clear pattern of decline, and the half-lives were extrapolated well beyond the 6-month test period. The DT50 values were >6 months for all four test systems. Through all test intervals, the mean maximum percentages of radioactivity recovered as other products were 5.2%, 7.9%, 6.8% and 9.9% for the aerobic Brandywine Creek, aerobic Choptank River, anaerobic Brandywine Creek and anaerobic Choptank River test systems, respectively. The other products included the amounts of 14C in the water layers and MeOH extracts, as well as various other peaks observed during HPLC analyses. All of the individual other product peaks represented less than 5% of each sample. The amount of 14C-labeled impurities in the test substance was 5.5%. The other products observed in the sediment extracts were attributed to impurities in the test substance, rather than transformation products. There were no distinct, consistent transformation product peaks observed during the study. The fractions of radiolabeled residues that could not be extracted from the sediments at the end of the test were 2.7%, 1.7%, 1.8% and 1.5% for aerobic Brandywine Creek, aerobic Choptank River, anaerobic Brandywine Creek and anaerobic Choptank River test systems, respectively. The maximum cumulative amount of mineralization or ultimate biodegradation observed was less than 0.1% in all four test systems. Mean material balances (recoveries) ranged from 84.5% to 103.0% throughout the study.

Description of key information

Ready Biodegradation (Kurume Labs, 1991), OECD 301C

EBP was not readily biodegradable by activated sewage sludge over a 28-day period when tested under Japanese MITI/OECD Ready Biodegradability 301C Modified MITI guidelines.  IR spectra indicated the test substance was unchanged.

Anaerobic Digester Sludge (Wildlife, 2011), OECD 314C

Evidence for the biodegradation of EBP by anaerobic digester sludge was not observed over a 63-d period. Results of the biotic and abiotic chambers were comparable.14C-DBDP-Ethane was used to definitively identify the parent molecule and any degradants.  Only one peak containing the14C-label and having a retention time of DBDP-Ethane was detected in any of the extracts.

An evaluation of inherent biodegradability using the CONCAWE test (Wildlife, 2010), OECD 302D:

Inherent biodegradation of EBP by a mixture of pre-exposed sludge and soil bacteria over a 90-day period was not observed. Two methods were used to investigate biodegradation: ThIC and14C-analysis for the parent molecule and metabolites. Because inherent biodegradation tests are designed to assess whether a chemical has any potential for biodegradation (OECD, 2006), the observed results suggest EBPis unlikely to undergo aerobic biodegradation in the environment or in sewage treatment plants. 

EBP: AEROBIC AND ANAEROBIC TRANSFORMATION IN AQUATIC SEDIMENT SYSTEMS (Wildlife, 2015), OECD 308

EBP did not appear to degrade in any of the 2 aerobic and 2 anaerobic test systems. The mean percentage of radioactivity recovered as EBP at the end of the 6-month test was 91% in all sediment extracts. The DT50 values were >6 months for all four test systems. EBP did not appear to degrade in any of the four test systems. The mean percentage of radioactivity recovered as EBP at the end of the 6-month test was >91% in all sediment extracts. There was no clear pattern of decline, and the half-lives were extrapolated well beyond the 6-month test period. The DT50 values were >6 months for all four test systems. Through all test intervals, the mean maximum percentages of radioactivity recovered as other products were 5.2%, 7.9%, 6.8% and 9.9% for the aerobic Brandywine Creek, aerobic Choptank River, anaerobic Brandywine Creek and anaerobic Choptank River test systems, respectively. The other products included the amounts of 14C in the water layers and MeOH extracts, as well as various other peaks observed during HPLC analyses. All of the individual other product peaks represented <5% of each sample. The amount of 14C-labeled impurities in the test substance was 5.5%. The other products observed in the sediment extracts were attributed to impurities in the test substance, rather than transformation products. There were no distinct, consistent transformation product peaks observed during the study. The fractions of radiolabeled residues that could not be extracted from the sediments at the end of the test were 2.7%, 1.7%, 1.8% and 1.5% for aerobic Brandywine Creek, aerobic Choptank River, anaerobic Brandywine Creek and anaerobic Choptank River test systems, respectively. The maximum cumulative amount of mineralization or ultimate biodegradation observed was <0.1% in all four testsystems. Mean material balances (recoveries) ranged from 84.5% to 103.0% throughout the study.

Key value for chemical safety assessment

Additional information