Registration Dossier

Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

Currently viewing:

Administrative data

Endpoint:
biodegradation in water: sediment simulation testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
19 April to 28 July 2006
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Guideline study, to GLP, with certain deviations

Data source

Referenceopen allclose all

Reference Type:
study report
Title:
Unnamed
Year:
2007
Report Date:
2007
Reference Type:
secondary source
Title:
Proposal for identification of a substance as a CMR, PBT, vPvB or a substance of an equivalent level of concern.
Author:
UK
Year:
2008
Bibliographic source:
Annex XV Restriction Report.
Report Date:
2008

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 308 (Aerobic and Anaerobic Transformation in Aquatic Sediment Systems)
Deviations:
yes
Remarks:
Both marine and freshwater sediments that were similar in organic content were used and test substances were spiked into the test sediment due to their low aqueous solubility rather than into the overlying water.
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): [14C]-n-decane (C10), 65% chlorinated and [14C]-n-tridecane (C13), 64.9% chlorinated
- Substance type: technical product
- Physical state: viscous liquids
- Analytical purity: >98%
- Impurities (identity and concentrations): no data
- Composition of test material, percentage of components: 65% chlorinated [U-14C] decance and 64.9% chlorinated [U-14C]-tridecane
- Lot/batch No.: 04BLY052
- Radiochemical purity (if radiolabelling): >98%
- Specific activity (if radiolabelling): chlorinated decane: 0.91 mCi/g (33.7 MBq/g); chlorinated tridecane: 1.0 mCi/g (37 MBq/g)
- Locations of the label (if radiolabelling): U-14C-decane and U-14C tridecane
- Expiration date of radiochemical substance (if radiolabelling): no data
- Storage condition of test material: in the dark, a freezer and in containers in which they were received
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
No data
Radiolabelling:
yes

Study design

Oxygen conditions:
aerobic/anaerobic
Inoculum or test system:
other: freshwater and marine water-sediment systems
Details on source and properties of surface water:
- Details on collection (e.g. location, sampling depth, contamination history, procedure): overlying water to the sediment was collected from one marine and one freshwater site, considered relatively remote from sources of significant industrial contamination. Marine water was collected on 22 March 2006 from Black Ness, Dart Estuary, Devon, UK (Grid Reference SX859556) and freshwater on 21 March 2006 from Tidcombe Bridge, Grand Western Canal, Tiverton, Devon, UK (Grid Reference SS973122). Samples were collected in plastic containers.
- Storage conditions: under refrigeration
- Storage length: until required for use
- Temperature (°C) at time of collection: freshwater: 5.1°C ; marine water: 5.6°C
- pH at time of collection: freshwater: 8.6; marine water: 7.8
- Redox potential (mv) initial/final: at sample collection - freshwater: 460 mV Eh; marine water: 356 mV Eh; during test - freshwater aerobic: 514 to 614 mV Eh, anaerobic: -146 to 671 mV Eh; marine water aerobic: 493 to 604 mV Eh, anaerobic: -22 to 614 mV Eh
- Oxygen concentration (mg/l) initial/final: dissolved oxygen (% air saturation) - freshwater: 100; marine water: 98
- Dissolved organic carbon (%): total organic carbon at start of test - freshwater aerobic: 8.3mg/L, anaerobic: 11 mg/L; marine water aerobic: 5.6 mg/L, anaerobic: 5.3 mg/L; at end of test - freshwater aerobic: 6.3mg/L, anaerobic: 10 mg/L; marine water aerobic: 12 mg/L, anaerobic: 13 mg/L
- Water filtered: no
Details on source and properties of sediment:
- Details on collection (e.g. location, sampling depth, contamination history, procedure): sediment was collected from one marine and one freshwater site, considered relatively remote from sources of significant industrial contamination. Marine sediment was collected on 22 March 2006 from Black Ness, Dart Estuary, Devon, UK (Grid Reference SX859556) and freshwater sediment on 21 March 2006 from Tidcombe Bridge, Grand Western Canal, Tiverton, Devon, UK (Grid Reference SS973122). Sediments were collected through the water column using a grab sampler. For the marine sediment, sampler contents were separated into the superficial, aerobic sediment and the subsurface, anaerobic sediment. Such a separation of freshwater sediment was not possible. The sediments were transferred to plastic containers for transport to the laboratory. Sufficient overlying water was added to the containers to ensure the sediments remained water-saturated. For the anaerobic sediment, the containers were sealed to minimise oxygenation of the sediment.
- Storage conditions: under refrigeration
- Storage length: 6 and 7 days for marine and freshwater sediments respectively
- Textural classification (i.e. %sand/silt/clay): freshwater sediment - sandy clay loam: 56% sand, 21% silt, 23% clay; marine sediment aerobic and anaerobic - silty clay: 8% sand, 51% silt, 41% clay
- pH at time of collection: at start of acclimation - freshwater sediment: 7.1, marine sediment aerobic: 7.7, anaerobic: 7.8
- Organic carbon (%): start of acclimation - freshwater sediment: 5.8 % w/w; marine sediment aerobic and anaerobic: 4.4% w/w; at start of test - freshwater sediment aerobic: 4.5% w/w, anaerobic 4.8% w/w; marine sediment aerobic and anaerobic: 4.1% w/w; at end of test - freshwater sediment aerobic: 5.5% w/w, anaerobic 6.5% w/w; marine sediment aerobic 4.2% w/w, anaerobic: 4.3% w/w
- Redox potential (mv) initial/final: at sample collection - freshwater sediment: 231 mV Eh; marine sediment aerobic 279 mV Eh, anaerobic 216 mV Eh; during test - freshwater sediment aerobic: -188 to -31 mV Eh, anaerobic -234 to -216 mV Eh; marine sediment aerobic -161 to 44 mV Eh, anaerobic -172 to 204 mV Eh
- CEC (meq/100 g): start of acclimation - freshwater sediment: 16.5 meq/100g; marine sediment aerobic: 23.5 meq/100g, anaerobic: 23.3 meq/100g
- Biomass (e.g. in mg microbial C/100 mg, CFU or other): at start of acclimation - freshwater sediment: 330 ugC/g; marine sediment aerobic: 520 ug C/g, anaerobic 260 ug C/g; at start of test - freshwater sediment aerobic: 268 ug C/g, anaerobic: 286 ug C/g; marine sediment aerobic: 220 ug C/g, anaerobic 216 ug C/g; at end of test - microbial biomass, control - freshwater sediment aerobic: 400 ug C/g, anaerobic: 380 ug C/g; marine sediment aerobic: 250 ug C/g, anaerobic 160 ug C/g; microbial biomass, chlor-decane - freshwater sediment aerobic: 420 ug C/g, anaerobic: 440 ug C/g; marine sediment aerobic: 280 ug C/g, anaerobic 160 ug C/g; microbial biomass, chlor-tridecane - freshwater sediment aerobic: 400 ug C/g, anaerobic: 400 ug C/g; marine sediment aerobic: 250 ug C/g, anaerobic 160 ug C/g
- Sediment samples sieved: yes - 2 mm
Details on inoculum:
None used
Duration of test (contact time):
>= 86 - <= 100 d
Initial test substance concentrationopen allclose all
Initial conc.:
>= 6.2 - <= 8.2 other: mg chlor-decane/kg dry weight
Based on:
test mat.
Initial conc.:
>= 6.4 - <= 8.7 other: mg chlor-tridecane/kg dry weight
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
other: CO2 or methane evolution; under anaerobic conditions
Details on study design:
Wet sediments were weighed into the test vessels to provide an equivalent dry weight of 65 g (marine) and 75 g (freshwater) of sediment/vessel. 525 ml of the relevant overlying water was added to each vessel and the vessels were acclimatised for 22 days. A proportion of each test sediment was dried at 60 degrees C for >24 h and to constant weight and 5 g aliquots were added to glass vials. 0.5 ml of a stock solution of the test substance in acetone was added to each vial and the spiked sediment aliquots air dried to allow the acetone to evaporate. Control sediment was prepared with acetone only. One spiked dried sediment aliquot was added to each of the test vessels containing the acclimated sediment and overlying water and the spiked and wet sediments mixed by use of a magnetic stirrer. For the anaerobic treatments, the introduction of air to the system was minimised and the systems were flushed with nitrogen after assembly.The test substance concentration of the acetone stock solutions used for the spiking were determined by radiochemical analysis before and after the spiking procedure. After addition of the spiked sediment, each glass vial was washed with scintillation fluid and the washings analysed to determine the quantity of radioactivity remaining in the vial and to calculate the amount of test substance added to each vessel.

16 vessels were spiked for each of the 8 treatments (substance/sediment/aerobicity combination) and a further 28 vessels served as the unspiked controls (7 per sediment/aerobicity combination).

The aerobic test was carried out in a gas flow-through system, consisting of a 1 L glass bottle with a gas-tight lid and an air inlet and outlet. After spiking it contained 70 g dry weight of marine sediment or 80 g dry weight of freshwater sediment, providing 25 +/- 5 mm depth of sediment, and overlayed with 525 mL appropriate water. An air supply was provided above the water surface and supplied air at a rate of 20-30 ml/min. Influent air was drawn into the test vessel by a vacuum pump via a gas trap filled with deionised water to humidify the air and the effluent air was drawn through two tubes to trap volatile organic substances and then through 2 gas traps containing NaOH to collect evolved CO2. Test vessels were maintained, in the dark, at 16 +/- 2 degrees C and the duration of the tests were 98 days. Each upstream gas trap (closest to the test vessel) was removed on days 14, 27, 42, 55, 68, 83 and 98 and analysed in triplicate. On days 0, 14, 35, 56, 77 and 98, duplicate vessel systems from each combination were randomly selected and analysed for the distribution of radioactivity and the mass balance. Overlying water and sediment were analysed separately and in triplicate.

The anaerobic systems were set up as described above except a flow of nitrogen rather than air was used. After addition and mixing of the test substance, the systems were flushed overnight with nitrogen to remove oxygen introduced during the spiking procedure. The vessels were then operated as static closed systems to provide containment of evolved methane. The duration of the tests were 86-100 days. At least 4 control vessels and 16 test vessels (4/test substance/sediment combination) were assessed each week to determine evolution of methane. However, because there was no evidence of significant methane production, anaerobic vessels were only analysed on day 35 and during the final 23 days of the study. Duplicate vessels from each combination were analysed on day 35 for the determination of the distribution of radioactivity and mass balance without analysis for methane. Duplicate vessels from each test combination were also sacrificed on 2 occasions from days 77-85 and 86-100, to assess total evolved CO2 (via evolved methane and CO2, itself) in the whole test system.

Test tempertaure was continuously monitored, redox potential and pH of the water and sediment as well as dissolved oxygen concentration of the water were measured at weekly intervals in the control vessels, and sediment microbial biomass and total organic carbon of the sediment and water were measured in triplicate in comtrol vessels on days 1 and 99 of the test.
Reference substance
Reference substance:
not specified

Results and discussion

Mean total recovery
Compartment:
other: water / sediment, material (mass) balance
Remarks on result:
other: See "any other information on results", Table 1
% Degradationopen allclose all
% Degr.:
3.7
Parameter:
CO2 evolution
Sampling time:
98 d
Remarks on result:
other: C10, 65% Cl, freshwater aerobic system
% Degr.:
13.1
Parameter:
CO2 evolution
Sampling time:
98 d
Remarks on result:
other: C10, 65% Cl, marine water aerobic system
% Degr.:
2.2
Parameter:
CO2 evolution
Sampling time:
98 d
Remarks on result:
other: C13, 65% Cl, freshwater aerobic system
% Degr.:
6.6
Parameter:
CO2 evolution
Sampling time:
98 d
Remarks on result:
other: C10, 65% Cl, marine water aerobic system
% Degr.:
< 0.1
Parameter:
CH4 evolution
Sampling time:
100 d
Remarks on result:
other: C10 and C13, 65% C,l in both marine and freshwater sediments
% Degr.:
<= 1.3
Parameter:
CO2 evolution
Sampling time:
100 d
Remarks on result:
other: C10, 65% Cl, marine water anaerobic system
% Degr.:
< 1
Parameter:
CO2 evolution
Sampling time:
100 d
Remarks on result:
other: C10, 65% Cl, freshwater anaerobic system and both freshwater and marine water anaerobic chlor-tridecane systems
Half-life of parent compound / 50% disappearance time (DT50)open allclose all
Compartment:
sediment
DT50:
1 629 d
Type:
not specified
Remarks on result:
other: 95% CL 1400-1800 d, average of C10 and C13 (65% Cl) data, freshwater aerobic system
Compartment:
sediment
DT50:
453 d
Type:
not specified
Remarks on result:
other: 95% CL 430-480 d, average of C10 and C13 (65% Cl) data, marine water aerobic system
Compartment:
sediment
DT50:
1 341 d
Type:
not specified
Remarks on result:
other: 95% CL 1200-1500 d, C10 (65% Cl), freshwater aerobic system
Compartment:
sediment
DT50:
335 d
Type:
not specified
Remarks on result:
other: 95% CL 320-360 d, C10 (65% Cl), marine water aerobic system
Compartment:
sediment
DT50:
1 786 d
Type:
not specified
Remarks on result:
other: 95% CL 1500-2100 d, C13 (65% Cl), freshwater aerobic system
Compartment:
sediment
DT50:
681 d
Type:
not specified
Remarks on result:
other: 95% CL 630-740 d, C13 (65% Cl), marine water aerobic system
Other kinetic parameters:
first order rate constant
Transformation products:
not specified
Evaporation of parent compound:
not specified
Volatile metabolites:
not specified
Residues:
yes
Details on results:
Under anaerobic conditions, no significant formation of 14C-labelled methane was noted during the test and only a limited amount of 14C-labelled CO2 leading to the conclusion that there was insufficient anaerobic biodegradation to allow the calculation of rate constants.

Sediment-water partition coefficients and oragnic carbon partition coefficients were calculated (see table 2 under "any other information on results" section below).
Results with reference substance:
No data

Any other information on results incl. tables

Analyses of the spiking vials, following addition of the spiked dry sediment aliquots to the test vessels on day 0, revealed that a mean of <0.1% (maximum 0.46%) of the radioactivity remained on the walls of the vials, confirming the values of applied radioactivity.

Table 1

Test substance

Aerobicity

Sediment

% Mass Balance (Mean ± SD)

Chlor-decane

 

Aerobic

Freshwater

100 ± 12

Marine

80 ± 9.5

Chlor-tridecane

Freshwater

98 ± 11

Marine

77 ± 15

Chlor-decane

 

Anaerobic

Freshwater

93 ± 11

Marine

77 ± 17

Chlor-tridecane

Freshwater

89 ± 12

Marine

75 ± 19

 

Table 2

Substance

Aerobicity

System

%OC

Kd

Koc

Log Koc

Chlor-decane

 

Aerobic

Freshwater

5.5

487

8850

3.9

Marine

4.2

103

2450

3.4

Chlor-tridecane

Freshwater

5.5

1021

18600

4.3

Marine

4.2

219

5210

3.7

Chlor-decane

 

Anaerobic

Freshwater

6.5

343

5280

3.7

Marine

4.3

50

1160

3.1

Chlor-tridecane

Freshwater

6.5

786

12100

4.1

Marine

4.3

99

2300

3.4

 Kd = sediment-water partition coefficients

Koc = organic carbon partition coefficients

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
In a GLP study conducted according to OECD Guideline 308, the rate of mineralisation under aerobic conditions of a C10 and a C13 chlorinated paraffin (65% chlorination) was low, with an average half-life of the two substances of around 1630 days in freshwater sediment and around 450 days in marine sediment. Little or no mineralisation was evident under anaerobic conditions in both freshwater and marine sediment over the timeframe of this study.
Executive summary:

In a GLP study conducted according to OECD Guideline 308, a C10 and a C13 chlorinated paraffin (65% chlorination) were assessed for biodegradation in both freshwater and marine sediments. The two radiolabelled test substances were separately spiked into the sediment phase of both systems under both aerobic and anaerobic conditions and aerobic biodegradation was monitored as the evolution of carbon dioxide over a period of 98 days and anaerobic biodegradation monitored as the evolution of methane and carbon dioxide over a period of 86-100 days.

No parent compound analysis was conducted in this study and so the extent of primary degradation was not determined. However, under aerobic conditions, both test substances in both marine and freshwater sediments showed biodegradation to carbon dioxide, the biodegradation in the marine sediment being more rapid than that in the freshwater sediment. In both sediments, the C10 paraffin biodegraded faster than the C13 paraffin. The average half-lives of the two chlorinated paraffins under aerobic conditions were around 1630 days in freshwater sediment and around 450 days in marine sediment. Under anaerobic conditions, there was insufficient mineralisation to methane or carbon dioxide to allow half-life rates to be calculated for either substance in either sediment.