1,1'-(ethane-1,2-diyl)bis[pentabromobenzene]

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption

Remarks:

other: Estimated Koc

Type of information:

(Q)SAR

Remarks:

Migrated phrase: estimated by calculation

Adequacy of study:

supporting study

Study period:

March 31, 2009

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The US EPA's estimation software, EPIwin, is recommened for use by the REACH Guidance. The PCKOC module is recommended to estimate the Koc.

Principles of method if other than guideline:

Estimated using EPI v3.20. February 2007. Estimation Programs Interface. U.S. Environmental Protection Agency Office of Pollution Prevention and Toxic Substances. Syracuse Research Corporation. DBDPEthane's structure was the basis for the estimation.

GLP compliance:

no

Type of method:

other: EPI v 3.20

Radiolabelling:

no

Computational methods:

Adsorption coefficient per organic carbon (Koc) using EPI v3.20 (February 2007. Estimation Programs Interface. U.S. Environmental Protection Agency Office of Pollution Prevention and Toxic Substances. Syracuse Research Corporation).

Type:

Koc

Value:

33 000 000

Validity criteria fulfilled:

yes

Conclusions:

DBDPEthane's estimated Koc is 3,312,000.

Executive summary:

DBDPEthane's estimated Koc is 3,312,000. This is consistent with the substance's known propensity to bind to surfaces.

Reference 2

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2013-2015

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)

GLP compliance:

yes

Type of method:

batch equilibrium method

Media:

soil/sewage sludge

Specific details on test material used for the study:

Name: 1,2-Bis[pentabromophenyl]ethane, [Phenyl- 14C[U]]
Lot/Batch number: 3626190
Specific activity: 32.4 mCi/mmol (determined by weight assay of the precursor
Bibenzyl, [Phenyl-14C[U]])
Formula weight: 972
Radiochemical purity: 94.5%

Radiolabelling:

yes

Test temperature:

All tests were conducted in a temperature-controlled laboratory room at ambient room temperature.
The temperature was monitored by min/max thermometer and was recorded every working day. During the tests
the temperatures ranged from 18.3 to 21.3 oC.

Details on study design: HPLC method:

Known amounts of the test substance were added to the soils, sediments, and activated sludge solids
samples of known dry weight that had been pre-equilibrated with aqueous 0.01 M CaCl2 background solution. The mixtures were agitated for an appropriate time. Then, the solids were separated from the liquids by centrifugation and the aqueous phases were analyzed. The amount of the test substance adsorbed by the soil, sediment or activated sludge solids was assessed either as the difference between the amount of test substance initially added and the amount remaining in the solution after equilibration (indirect method) or determined directly after extraction and decomposition (combustion) of the solid.

Preliminary tests were performed to evaluate adsorption of the test substance to the walls of the test
vessels and membrane filters, as well as its stability. Adsorption kinetics test was performed to estimate the time to reach adsorption equilibrium (quasi-equilibrium) of DBDPEthane in these systems and the distribution coefficient under the test conditions (Kd). Distribution coefficients were calculated based on adsorbed and solution concentrations of this material.

Analytical monitoring:

yes

Details on sampling:

The adsorption kinetics test was performed using the serial method suggested in OECD Guideline 106 with two treated and one untreated (control) test vessels (Wheaton bottle) for each of the solids. The procedure was as follows: each vessel was weighed; a sample (approximately 3 g) of the solid was added, and the vessel with the solid weighed once again. Aliquot 300 mL of aqueous 0.01 M CaCl2 solution (to provide a solid:solution ratio of approximately 1: 100) was added, the test vessel with solid plus solution was weighed, and placed on a shaker for pre-equilibration for at least 12 hours. After pre-equilibration period, each vessel was dosed with the test substance and placed on a shaker. At each sampling interval (2, 4, 10, 24, and 48 hours of equilibration), a 20-mL sample of suspension (solution) was taken from each test vessel using a disposable 25-mL pipette and transferred in a Pyrex® glass tube, and the test vessel was returned to the shaker for further equilibration.

The tubes with the samples were centrifuged for 10 minutes at a RCF of approximately 480 g, triplicate
5-mL sub-samples of the supernatants were withdrawn using serological glass pipettes, and analyzed with LSC. At the final equilibration interval (48 hours), the suspension remaining in each test vessel was transferred into Pyrex glass tubes and centrifuged. Subsamples (5 mL) of the supernatants were withdrawn with glass serological pipettes and analyzed with LSC. The pH was measured in a supernatant in a single vessel for each soil, sediment, and activated sludge solid, as well as in the controls. The remaining supernatants were discarded, the solids were extracted with THF, and combusted with subsequent LSC analysis to determine remaining amount of radioactivity.

Matrix no.:

#1

Matrix type:

silt loam

% Clay:

24.9

% Silt:

54.2

% Sand:

20.9

% Org. carbon:

4.2

pH:

7.1

CEC:

24.1

Matrix no.:

#2

Matrix type:

sand

% Clay:

2

% Silt:

10

% Sand:

88

% Org. carbon:

0.76

pH:

5.4

CEC:

4.3

Matrix no.:

#3

Matrix type:

sandy loam

% Clay:

8.1

% Silt:

39.8

% Sand:

52.1

% Org. carbon:

0.33

pH:

6

Matrix no.:

#4

Matrix type:

sand

% Clay:

0

% Silt:

3.1

% Sand:

96.9

% Org. carbon:

0.59

pH:

6.2

Matrix no.:

#5

Matrix type:

other: activated sludge solids

% Org. carbon:

32.26

pH:

5.7

Matrix no.:

#6

Matrix type:

other: activated sludge solids

% Org. carbon:

29.72

pH:

6.2

Details on matrix:

Matrices 1 & 2 are soils. Matrices 3 & 4 are sediments. Matrices 5 & 6 are activated sludge solids.

Two representative soils of varying texture (USDA Soil Textural Classification) were used. One of the
soils, silt loam (TB-PF), was collected by Agvise Laboratories (Northwood, North Dakota, USA). The second
soil, sandy (Speyer # 2.1), was collected by LUFA Speyer (Landwirtschaftliche Untersuchungs- und
Forschungsanstalt), Germany.

Two representative sediments were used. The sediments were collected from Brandywine Creek
(Chadds Ford, Pennsylvania, USA) and Choptank River (Denton, Maryland, USA). The coordinates of
sediment sampling sites and detailed information on sediment collection are presented in Table 3. The
Brandywine Creek sediment has a fine texture while the Choptank River sediment has a coarse texture. Both
sediments were collected by Wildlife International and characterized by Agvise Laboratories (Northwood,
North Dakota, USA).

Activated sludge solids (ASS) samples were collected from Cambridge Wastewater Treatment facility,
Cambridge, MD, USA and Denton Wastewater Treatment facility, Denton, MD, USA (Table 4).

Details on test conditions:

All tests were conducted in a temperature-controlled laboratory room at ambient room temperature.
The temperature was monitored by min/max thermometer and was recorded every working day. During the tests
the temperatures ranged from 18.3 to 21.3 oC.

Sample No.:

#1

Duration:

48 h

Initial conc. measured:

0.006 other: ug/L aqueous phase

pH:

5.8

Temp.:

20 °C

Sample No.:

#2

Duration:

48 h

Initial conc. measured:

0.014 other: ug/L aqueous phase

pH:

6.6

Temp.:

20 °C

Sample No.:

#3

Duration:

48 h

Initial conc. measured:

0.004 other: ug/L aqueous phase

pH:

7.2

Temp.:

20 °C

Sample No.:

#4

Duration:

48 h

Initial conc. measured:

0.01 other: ug/L aqueous phase

pH:

6.4

Temp.:

20 °C

Sample No.:

#5

Duration:

48 h

Initial conc. measured:

0.106 other: ug/L aqueous phase

pH:

6.3

Temp.:

20 °C

Sample No.:

#6

Duration:

48 h

Initial conc. measured:

0.077 other: ug/L aqueous phase

pH:

6.4

Temp.:

20 °C

Computational methods:

The percentage of the test substance adsorbed at each sampling interval (Kd ) in the test vessels and in
the controls was calculated from the material balance, i.e., the amount of [14C]-radioactivity added into the test vessel and the amount detected in the aqueous phase. The material balance was verified at the final (48-hour) sampling interval based on the amounts of the radioactivity found in the aqueous phase, extracts of the solids, and non-extractable residues assessed by combustion of the solids after extraction.

Key result

Sample No.:

#1

Type:

Kd

Value:

8 830 L/kg

pH:

6.4

Temp.:

20 °C

Matrix:

Silt Loam Soil

% Org. carbon:

4.2

Remarks on result:

not measured/tested

Remarks:

Organic carbon was measured prior to the experiment

Key result

Sample No.:

#2

Type:

Kd

Value:

4 170 L/kg

pH:

6.6

Temp.:

20 °C

Matrix:

Sandy Soil

% Org. carbon:

0.76

Remarks on result:

not measured/tested

Remarks:

Organic carbon was measured prior to the experiment

Key result

Sample No.:

#3

Type:

Kd

Value:

23 700 L/kg

pH:

7.2

Temp.:

20 °C

Matrix:

Sand Loam Sediment

% Org. carbon:

0.33

Remarks on result:

not measured/tested

Remarks:

Organic carbon was measured prior to the experiment

Key result

Sample No.:

#4

Type:

Kd

Value:

5 890 L/kg

pH:

6.4

Temp.:

20 °C

Matrix:

Sandy Sediment

% Org. carbon:

0.59

Remarks on result:

not measured/tested

Remarks:

Organic carbon was measured prior to the experiment

Key result

Sample No.:

#5

Type:

Kd

Value:

428 L/kg

pH:

6.3

Temp.:

20 °C

Matrix:

Cambridge WWTP ASS

% Org. carbon:

33.26

Remarks on result:

not measured/tested

Remarks:

Organic carbon was measured prior to the experiment

Key result

Sample No.:

#6

Type:

Kd

Value:

620 L/kg

pH:

6.4

Temp.:

20

Matrix:

Denton WWTP ASS

% Org. carbon:

29.72

Remarks on result:

not measured/tested

Remarks:

Organic carbon was measured prior to the experiment

Transformation products:

not measured

Selected Properties of the Soils, Sediments, and Activated Sludge Solids

A summary of soil properties is presented in Table 5. Soil analytical reports received from Agvise

Laboratories are shown in Appendix 6. Moisture content in a silt loam soil was 3.83 g /100 g and in a sandy soil

it was 0.35 g/100 g (Table 8). The pH of silt loam (TB-PF) and sandy (Speyer # 2.1) soils (in 0.01 M CaCl2, at

soil: solution ratio 1:2) was 7.1 and 5.4 and soil organic carbon content was 4.2% and 0.76%, respectively

(Table 5). These properties were consistent with the requirements for the soils No. 2 and No. 5 of the OECD

106 study guideline [4], respectively.

Summary of sediment properties is presented in Table 6. Brandywine Creek sediment used in the study contained 52.1%

sand and 0.33% organic carbon, while Choptank River sediment contained 96.9% sand and 0.59% organic

carbon (Table 6). Thus, the samples represented sediments with two different textures. The pH of the sediments

(in 0.01 M CaCl2 at sediment: solution ratio 1:2) was 6.0 and 6.2, respectively. The pH in pore water was not

determined due to insufficient amount of water obtained by centrifugation of these sediments. Brandywine

Creek and Choptank River sediment samples contained 40.34 g/100 g and 28.12 g/100 g of moisture,

respectively (Table 9).

Tier 1. Preliminary Test

Adsorption of the Test Substance to the Test Vessels and to the Filters

Test Vessels

After 24-hour equilibration of [14C] DBDPEthane in aqueous 0.01 M CaCl2 solution in various types of

vessels, the recovery of radioactivity in the aqueous phase was 0.8% to 26.3% of applied radioactivity (AR)

(Table 10). Thus, DBDPEthane was adsorbed by the walls of all tested vessels. Wheaton bottles were selected for use in the subsequent testing due to no alternative vessel providing better recoveries.

Retention by Filters and Centrifuge Tubes

Filtration through Whatman Nylon 0.2 μm pore size 25-mm diameter filters resulted in the recovery of

only 5.6% to 16.1% of that present in the unfiltered solutions at both pH levels (Table 12). Thus, [14C]

DBDPEthane was strongly retained by the materials of the filters and filtration was not applicable to remove

particulate matter in this project. After centrifugation in Pyrex glass 25-mL tubes, the recovery of [14C]

DBDPEthane was 41.9 to 57.8% of the amount in the aqueous layer prior to centrifugation (Table 12).

Centrifugation was selected for separation of aqueous and solid phases.

Distribution between Aqueous Phase and Wheaton Bottle Surfaces

After 24-hour equilibration, total amount of radioactivity recovered in the aqueous phase plus bottle

extraction was 64.6% to 91.1% of AR (Table 13). The bottle extracts generally contained the higher proportion

of AR than the aqueous phases.

Tier 2. Adsorption Kinetics Test

Solution concentration of [14C] DBDPEthane decreased with period of equilibration in the controls and

in all test systems (Tables 14 to 20). After 48 hours of equilibration, concentration of DBDPEthane was 0.006 to 0.015 μg/L in the soil test systems, 0.004 to 0.019 μg/L in sediment systems, and 0.077 to 0.127 μg/L in activated sludge solids systems. In Control test vessels concentration of DBDPEthane decreased to 0.011 - 0.025 μg/L.

 

In soil and sediment test systems 93.3% to 98.8% of applied radioactivity (AR) was adsorbed after

2 hours of equilibration and 96.9% to 99.4% of AR after 48 hours (Tables 15 to 18). In activated sludge solids test systems, the adsorption was 55.3% to 77.5% of AR after 2 hours and 79.2% to 87.6% of AR after 48 hours of equilibration (Tables 19-20). Steady state was apparent in all test systems by the end of the study.

 

Material balance (balance of radioactivity) in the test systems with solids after 48 hours of equilibration

was within 90.1% to 125% (Table 21). Some portion of the solids (clay particles) could be retained on the walls of the test vessels after removal of the solids. In this event, the amounts of radioactivity extracted from the test vessels may include additional radioactivity from these clay particles, e.g., in case of silt loam (TB-PF) soil. One outlier (one replicate of sandy soil Speyer 2.1) was considered related to inhomogeneity of this soil. The sandy soil Speyer 2.1 contained mainly sand (88%) and only 10% of silt fraction. When solids were transferred from the test vessel into glass tubes for centrifugation, mainly the lighter silt fraction was removed while the heavier particles (sand) remained in the test vessel. If the concentration of adsorbed radioactivity in silt fraction was higher than in the sand fraction, this would result in higher-than-expected radioactivity after extraction and combustion of the solids.

 

Total recoveries of radioactivity in replicate control vessels were 82.6% and 105% of AR, respectively.

Adsorption distribution coefficients ( ads d K ) after achievement of equilibrium (quasi-equilibrium) in the systems (48 hours of equilibration) were 8.83×103 L/kg for Silt Loam (TB-PF) soil and 4.17×103 L/kg for Sandy (Speyer 2.1) soil (average values of two replicates) (Table 22). The average value of ads

d K for Brandywine Creek sediment was slightly higher than those observed for the soils (2.37×104 L/kg) and for Choptank River sediment it was similar to that observed for sandy soil (5.89×103 L/kg).

The average values of ads d K calculated for activated sludge solids test systems were lower than for the

soils and the sediments. They were similar for both activated sludge solids (4.28×102 L/kg for Cambridge

WWTP and 6.20×102 L/kg for Denton WWTP) (Table 22).

 

Average organic carbon normalized adsorption coefficient ( ads OC K ) were similar for both soils (2.10×105 L/kg for Silt Loam (TB-PF) soil and 5.49×105 L/kg for Sandy (Speyer 2.1) soil) (Table 22). The values were higher for the sediments (7.17×106 L/kg for Brandywine Creek sediment and 9.98×105 L/kg for Choptank River sediment). For activated sludge solids, the ads OC K values were lower than for the soils and the sediments, 1.29×103 L/kg for Cambridge WWTP and 2.09×103 L/kg for Denton WWTP.

Relatively low solubility of DBDPEthane in aqueous solutions, strong sorption of this compound by

all tested solids as well as by the walls of all types of the test vessels resulted in very low concentration of the test substance in the aqueous phase (Tables 15 to 21). Concentrations of [14C] DBDPEthane in solutions evenat adsorption equilibrium (quasi-equilibrium) were very low and performing a desorption kinetics test, where solution concentrations should be lower than in the adsorption test, was impractical. Similar reasons precluded obtaining complete adsorption and desorprtion isotherms.

Table 5. Selected properties of the soils

Soil Label	Texture class	OC %	Sand	Silt	Clay	CEC mmolc/100 g (meq/100 g	pH	CaCO3 %	Free Iron Oxide mg/kg
			%
TB-PF-010506   Speyer #2.1	Silt Loam   Sand	4.2     0.76	20.9     88	54.2     10	24.9     2	24.1     4.3	7.1     5.4	4.8     ND	9670     5110

Table 6. Selected properties of the sediments

Soil Label	Texture class	OC %	Sand	Silt	Clay	CEC mmolc/100 g (meq/100 g	pH	CaCO3 %	Free Iron Oxide mg/kg
			%
TB-PF-010506   Speyer #2.1	Silt Loam   Sand	4.2     0.76	20.9     88	54.2     10	24.9     2	24.1     4.3	7.1     5.4	4.8     ND	9670     5110

Table 7. Selected properties of the activated sludge solids.

Sample OC % pH AS-043013 – Cambridge WWTP   AS-050613 – Denton WWTP 33.26   29.72 5.7   6.2

Table 8. Soil moisture content

Soil	Moisture Content (g/100 g) (Average of 3 replicates)
Silt Loam (TB-PF)   Sandy (Speyer #2.1)	3.83   0.35

Table 9. Sediment moisture content

Sediment	Moisture Content (g/100 g) (Average of 3 replicates)
Brandywine Creek (BC-082113)   Choptank River (CR-082113)	40.34   28.12

Table 10. Recovery of radioactivity in the aqueous phase after 24 -hr equilibration of [¹⁴C]DBDPEthane in aqueous 0.01 M CaCl₂ solutions in the test vessels

Test Vessel	Recovery (% of applied radioactivity
Fisherbrand polypropylene tube (50 mL) Teflon Oak Ridge tube (20 mL) Stainless Steel Vessel (500 mL) Erlenmeyer Flask (250 mL) Pyrex flass tube ( 25 mm X 150 mm) Glass Wheaton bottle (500 mL)	0.8 0.8 1.7 3.5 9.9 26.3

 

  Table 11. Recovery of radioactivity in the aqueous phase after equilibration of 14C DBDPEthane in Aqueous 0.01M CaCl2 in Wheaton glass 500 mL bottles

Test Vessel Identification (471E-109-)	pH	Recovery %
		Period of equilibration
		4 hrs	24 hrs
25 26 27 28	5.4 5.4 7.1 7.1	24.2 27.5 20.0 26.7	34.8 15.7 13.1 18.0

Table 12. Effect of processing on the recovery of [¹⁴C] DBDPEthane dissolved in aqueous 0.01M CaCl₂

Test Vessel ID (471E-109-)	pH	Recovery (%) of found before each kind of processing
		Centrifugation	Filtration
25 26 27 28	5.4 5.4 7.1 7.1	57.8 48.2 41.9 43.8	5.6 16.1 15.1 7.8

Table 13. Distribution of radioactivity after equilibration of [¹⁴C] DBDPEthane in aqueous 0.01 M CaCl₂ solutions in 500 mL glass Wheaton bottles.

Test Vessel ID (471E-109-)	pH	Recovery (%) of Applied Radioactivity (AR)
		Aqueous Solution	Extract	Total Recovery
25 26 27 28	5.4 5.4 7.1 7.1	34.8 15.7 13.1 18.0	29.8 66.0 78.0 62.5	64.6 81.7 91.1 80.5

Table 14. Recovery of radioactivity in the aqueous phase of the controls in adsorption kinetics test.

Equilibration (hrs)	[^14C] DBDPEthane concentration in the aqueous phase (ug/L)	Recovery of radioactivity in the aqueous phase (% of applied radioactivity)	pH
2 2 4 4 10 10 24 24 48 48	0.238 0.287 0.100 0.150 0.032 0.059 0.018 0.034 0.011 0.025	39.1 46.7 16.4 24.4 5.3 9.6 3.0 5.6 1.8 4.1	NA NA NA NA NA NA NA NA NA NA

Table 15. Apparent kinetics of DBDPEthane adsorption by silt loam (TB-PF) soil.

Equilibration (hrs)	[^14C] DBDPEthane concentration in the Aqueous phase (ug/L)	Apparent adsorption (% of applied radioactivity	pH
2 2 4 4 10 10 24 24 48 48	0.0388 0.0271 0.0361 0.0171 0.0117 0.0325 0.0036 0.0108 0.0063 0.0081	93.7 95.5 94.1 97.2 98.1 94.7 99.4 98.2 99.0 98.7	NA NA NA NA NA NA NA NA 6.4 NA

Table 16. Apparent kinetics of DBDPEthane adsorption by sandy (Speyer #2.1) soil.

Equilibration (hrs)	[^14C] DBDPEthane concentration in the Aqueous phase (ug/L)	Apparent adsorption (% of applied radioactivity	pH
2 2 4 4 10 10 24 24 48 48	0.027 0.013 0.014 0.006 0.023 0.032 0.000 0.010 0.014 0.015	95.6 97.9 97.8 99.0 96.2 94.8 ND 98.4 97.8 97.5	NA NA NA NA NA NA NA NA 6.6 NA

Table 17. Apparent kinetics of DBDPEthane adsorption by sandy loam (Brandywine River) sediment.

Equilibration (hrs)	[^14C] DBDPEthane concentration in the Aqueous phase (ug/L)	Apparent adsorption (% of applied radioactivity	pH
2 2 4 4 10 10 24 24 48 48	0.0072 0.0144 0.0045 0.0009 0.0108 0.0081 0.0009 0.0027 0.0036 0.0036	98.8 97.6 99.3 99.9 98.2 98.7 99.9 99.6 99.4 99.4	NA NA NA NA NA NA NA NA 7.2 NA

Table 18.

Apparent kinetics of DBDPEthane adsorption by sandy (Choptank River) sediment.

Equilibration (hrs)	[^14C] DBDPEthane concentration in the Aqueous phase (ug/L)	Apparent adsorption (% of applied radioactivity	pH
2 2 4 4 10 10 24 24 48 48	0.025 0.041 0.014 0.015 0.028 0.009 0.005 0.014 0.010 0.019	95.9 93.3 97.6 97.5 95.4 98.5 99.1 97.7 98.4 96.9	NA NA NA NA NA NA NA NA 6.4 NA

Table 19. Apparent kinetics of DBDPEthane adsorption by Cambridge WWTP activated sludge solids.

Equilibration (hrs)	[^14C] DBDPEthane concentration in the Aqueous phase (ug/L)	Apparent adsorption (% of applied radioactivity	pH
2 2 4 4 10 10 24 24 48 48	0.274 0.270 0.203 0.198 0.124 0.124 0.068 0.063 0.106 0.127	55.3 55.9 66.9 67.9 79.9 79.8 89.0 89.7 82.6 79.2	NA NA NA NA NA NA NA NA 6.3 NA

Table 20. Apparent kinetics of DBDPEthane adsorption by Denton WWTP activated sludge solids.

Equilibration (hrs)	[14C] DBDPEthane concentration in the Aqueous phase (ug/L)	Apparent adsorption (% of applied radioactivity	pH
2 2 4 4 10 10 24 24 48 48	0.139 0.181 0.065 0.106 0.073 0.113 0.026 0.061 0.077 0.096	77.5 70.6 89.5 82.9 88.1 81.7 95.8 90.0 87.6 84.5	NA NA NA NA NA NA NA NA 6.4 NA

Table 21. Distribution of radioactivity in the test systems after 48 hrs of equilibrium.

Test System	Test Vessels ID (471E-109-)	Recovery (% of applied amount)*
		Aqueous phase	Solids	Vessel Extract	Total
Soils Silt loam (TB-PF)   Sand (Speyer 2.1)   Sediments Sandy loam (Brandywine Creek)   Sandy (Choptank River)   Activated sludge solids Cambridge WWTP   Denton WWTP	53 54 56 57   59   60 62 63   65 66 68 69	1.7 2.0 2.6 2.9   0.7   0.7 2.2 3.6   22.2 25.4 14.5 18.7	77.4 76.8 171** 108   102   121 104 92.1   81.7 68.6 73.9 97.1	21.7 16.3 8.6 3.6   1.9   2.2 4.8 4.4   1.3 2.5 1.4 9.3	101 95.0 182** 115   105   124 111 100   105 96.5 89.8 125
Control	50 51	4.9 8.3	NA NA	77.7 97.1	82.6 105
*calculated based on radioactivity **outlier

Table 22. Apparent adsorption distribution coefficients of DBDPEthane after 48 hr equilibrium.

Test system	Test vessels ID (471E-109-)	Apparent Kd (L/kg)	Apparent Koc ()L/kg)	Average Apparent Kd (L/kg)	Average Apparent Koc (L/kg)
Soils Silt loam (TB-PF)   Sand (Speyer 2.1)   Sediments Sandy loam (Brandywine Creek) Sandy (Choptank River)   Activated sludgesolids Cambridge WWPT   Denton WWTP	53 54 56 57   59 60 62 63       65 66 68 69	9943 7717 4435 3906   23678 23645 7765 4009       475 381 699 541	2.37E+5 1.84E+5 5.84E+5 5.14E+5   7.18E+6 7.17E+7 1.32E+6 6.79E+5       1.43E+3 1.15E+3 2.35E+3 1.82E+3	8.83E+3   4.17E+3     2.37E+4   5.89E+3         4.28E+2   6.20E+2	2.10E+5   5.49E+5     7.17E+6   9.98E+5         1.29E+3   2.09E+3

Validity criteria fulfilled:

yes

Conclusions:

Preliminary work was performed to investigate suitability of six types of test vessels and two types of
separation processes (filtration and centrifugation) for use in the definitive study. Pyrex® glass tubes,
Erlenmeyer glass flasks, Teflon Oak Ridge tubes, Fisherbrand® polypropylene centrifuge tubes, Wheaton
glass 500-mL bottles, and stainless steel vessels were screened for adsorption of [14C] DBDPEthane.
Losses of [14C] DBDPEthane from the aqueous phase occurred with all six vessel types. The highest
recoveries (26.3% of applied radioactivity) were observed in Wheaton glass 500-mL bottles and this kind
of vessels was selected for the definitive study. Filtration of solutions through 0.2-μm pore size membrane filter resulted in losses of 84% to 94% of [14C] DBDPEthane. Centrifugation was selected as the method for separation of solids from the liquid phase in the test systems.

Equilibration of [14C] DBDPEthane with each soil, sediment, and activated sludge solid resulted in a rapid decrease of the test substance concentration in the aqueous phase and an increase in the calculated adsorption. From 93.3% to 98.8% of applied radioactivity (AR) was adsorbed by the soils and sediments after 2 hours of equilibration and 96.9% to 99.4% of AR after 48 hours. Activated sludge solids adsorbed 55.3% to 77.5% of AR after 2 hours and 79.2% to 87.6% of AR after 48 hours. Steady state (quasiequilibrium plateau) was observed in all test systems by the end of the study.

Adsorption distribution coefficients (Kd , L/kg) were calculated based on concentrations of the test
substance in the aqueous and solid phases at equilibrium (quasi-equilibrium). Average (of two replicates) Kd were 8.83×103 for Silt Loam soil, 4.17×103 for Sandy soil, 2.37×104 for sandy loam (Brandywine Creek) sediment, and 5.89×103 for sandy (Choptank River) sediment. Testing with activated sludge solids (ASS) provided the Kd values 4.28×102 for Cambridge WWTP ASS and 6.20×102 for Denton WWTP ASS.

Average Koc (L/kg) values were 2.10×105 and 5.49×105 for the soils, 7.17×106 and 9.98×105 for the sediments, and 1.29×103 and 2.09×103 for the activated sludge solids.

Low solubility of DBDPEthane in the aqueous phase and strong sorption of this compound by all tested solids as well as by the test vessel walls resulted in very low concentrations of the test substance in the aqueous phase. Performing a desorption kinetics test of DBDPEthane was not practical. Similar reasons precluded complete adsorption and desorprtion isotherms in this project. Therefore, the above Kd and Koc values can be taken as appropriate estimates of the adsorption properties of this test substance.

Executive summary:

Adsorption characteristics of 1,2-Bis[pentabromophenyl]ethane, [Phenyl- 14C[U]] ([14C]-decabromodiphenyl ethane (DBDPEthane) were determined on two representative soils, two sediments, and two activated sludge solids. Concentrations of the test substance were determined based on radioactivity by liquid scintillation counting (LSC).

 

Preliminary work was conducted to assess adsorption of the test substance to six types of test vessels as

well as applicability of a filtration/centrifugation separation processes of potential use in the definitive

adsorption study. Pyrex® glass tubes, Erlenmeyer glass flasks, Teflon Oak Ridge tubes, Fisherbrand®

polypropylene centrifuge tubes, Wheaton 500-mL glass bottles, and stainless steel vessels were screened for adsorption of [14C] DBDPEthane. Losses of [14C] DBDPEthane from the aqueous phase occurred in all vessel types. The highest recoveries were observed in Wheaton 500-mL glass bottles, which were selected for the definitive study. Filtration of solutions through 0.2-μm pore size membrane filter resulted in losses of 84% to 94% of [14C] DBDPEthane. Centrifugation was selected as the method for separation of the solids from the liquid phase in the definitive test.

 

The definitive adsorption kinetic test was performed with a silt loam soil, a sandy soil, sediments derived

from two waterways, and activated sludge solids derived from two wastewater treatment plants. The test was performed at a solids to liquid ratio of 1:100. Equilibration of [14C] DBDPEthane with each soil, sediment, and activated sludge solid resulted in a rapid decrease of test material concentration in the aqueous phase and an increase in the calculated adsorption. From 93.3% to 98.8% of applied radioactivity (AR) was adsorbed by the soils and sediments after 2 hours of equilibration and 96.9% to 99.4% of AR after 48 hours. Activated sludge solids adsorbed 55.3% to 77.5% of AR after 2 hours and 79.2% to 87.6% of AR after 48 hours. Steady state (quasi-equilibrium plateau) was observed in all test systems by the end of the study.

 

Adsorption distribution coefficients (Kd ) were calculated based on concentrations of the test substance in the aqueous and solid phases at equilibrium (quasi-equilibrium). Average (of two replicates) Kd were 8.83E+3 10for Silt Loam soil, 4.17E+3 for Sandy soil, 2.37E+4 for sandy loam (Brandywine Creek) sediment, and 5.89E+3 for sandy (Choptank River) sediment. Testing with activated sludge solids (ASS) provided the Kd values 4.28E+2 for Cambridge WWTP ASS and 6.20E+2for Denton WWTP ASS.

 

Average Koc (L/kg) values were 2.10E+5 and 5.49E+5 for the soils, 7.17E+6 and 9.98E+5 for the sediments, and 1.29E+3 and 2.09E+3 for the activated sludge solids.

 

Low solubility of DBDPEthane in the aqueous phase and strong adsorption of this compound by all tested solids as well as by the test vessel walls resulted in very low concentrations of the test substance in the aqueous phase. Performing a desorption kinetics test of DBDPEthane was not practical. Similar reasons precluded complete adsorption and desorprtion isotherms in this project. Therefore, the above Kd and Koc values can be taken as appropriate estimates of the adsorption properties of this test substance.

Description of key information

An Estimated value based on chemical structure was reported to be : 3.3E7.

The key study revealed adsorption coefficients to soil between 428 and 23700 L/kg. The absorption coefficient was strongly related to the organic carbon content and decreased with increasing organic C. A Value od 23.700 is adequate for a low organic carbon content of the soil.

Key value for chemical safety assessment

Koc at 20 °C:

23 700

Additional information

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