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Biodegradation in water and sediment: simulation tests

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Reference
Endpoint:
biodegradation in water: sediment simulation testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
30 Sep 2010 to 19 Jun 2012
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)
Version / remarks:
adopted 24 April 2002
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPPTS 835.4300 (Aerobic Aquatic Metabolism)
Version / remarks:
June 2008
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPPTS 835.4400 (Anaerobic Aquatic Metabolism)
Version / remarks:
June 2008
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Radiolabelling:
yes
Oxygen conditions:
aerobic/anaerobic
Inoculum or test system:
natural water / sediment: freshwater
Details on source and properties of surface water:
The study was conducted using two water-sediment systems, Calwich Abbey and Swiss Lake. The Calwich Abbey and Swiss Lake water-sediment systems were sampled at Calwich, Ashbourne, Derbyshire, England and Chatsworth, Derbyshire, England, respectively. The water was sampled from the lake using a bucket and subsequently transferred into containers. Full details of the sampling dates and the locations are given in Table 1 in 'Any other information on materials and methods incl. tables'. After receipt, the water-sediment systems were stored, waterlogged and routinely maintained at 2 - 8°C. Prior to characterisation and dispensing, the water was passed through 0.212 mm mesh. The key characteristics of the water-sediment systems are summarised in Table 3 in ‘Any other information on materials and methods incl tables’. Test system parameters, including pH (water), dissolved oxygen (water) and redox potential (water and sediment) were measured throughout the study.
Details on source and properties of sediment:
The study was conducted using two water-sediment systems, Calwich Abbey and Swiss Lake. The Calwich Abbey and Swiss Lake water-sediment systems were sampled at Calwich, Ashbourne, Derbyshire, England and Chatsworth, Derbyshire, England, respectively. The sediment was sampled by hand using a scoop and transferred into containers. Full details of the sampling dates and the locations are given in Table 1 in ‘Any other information on materials and methods incl. tables’. After receipt, the water-sediment systems were stored, waterlogged and routinely maintained at 2 - 8°C. Prior to characterisation and dispensing, the sediment was passed through a 2 mm sieve. The key characteristics of the water-sediment systems are summarised in Table 2 in ‘Any other information on materials and methods incl. tables’. Test system parameters, including redox potential (water and sediment) were measured throughout the study.
Details on inoculum:
not applicable
Duration of test (contact time):
100 d
Initial conc.:
0.623 mg/L
Based on:
act. ingr.
Remarks:
based on the registered test substance
Parameter followed for biodegradation estimation:
CO2 evolution
radiochem. meas.
test mat. analysis
Details on study design:
STUDY DESIGN
- The experimental design is summarised in Table 4 in 'Any other information on materials and methods incl. tables'. Anaerobicity, per cited guidelines, exists at a redox potential (Eh) < –100 mV; the dissolved oxygen concentration (DOC) should be at or near 0 mg/L.

PREPARATION OF TEST SYSTEMS
- Aliquots of the appropriate sediment were dispensed into pre-labelled glass cylinder incubation units (10 cm diameter) to a depth of approximately 3 cm. With the minimum of disturbance, the associated surface water was added to a depth of 9 cm above the sediment surface. Ratios of approximately 1:3 (based upon sediment: water depth) were obtained for all samples of both systems. These vessels were numbered sequentially and labelled with the study number and a code representing the incubation group. The dry matter was determined in triplicate for each sediment type at the time of dispensing.

RADIOCHEMICAL PURITY
- An aliquot of each application solution was removed before each application session on the day of use. The aliquots were analysed by high performance liquid chromatography (HPLC) to provide radiochemical purity and stability measurement HPLC method 1.

PREPARATION OF TREATMENT SOLUTIONS
- Prior to each application, solutions of the radiolabelled test item were prepared in water. The actual concentration of the test item in solution at the time of application was measured by the liquid scintillation counting of replicate aliquots, pre and post-dose.

APPLICATION OF 14C-SUBSTANCE
- The 14C-labelled test item, dissolved in water, was added to the water/sediment in each test vessel at an application rate of 0.33 µg/mL Substance ion (equivalent to 0.6227 µg/mL of substance dibromide). Even distribution of the test item was achieved by gentle mixing of the water, with care taken not to disturb the sediment.

INCUBATION, MONITORING AND PARAMETERS MEASUREMENT
- These parameters are given in Table 5 in 'Any other information on materials and methods incl. tables'.

SAMPLING
- The definitive sampling regimes are summarised in Table 6 in 'Any other information on materials and methods incl tables'.

SAMPLE EXTRACTION AND ANALYSIS
- SEPARATION OF WATER AND SEDIMENT PHASES AND EXTRACTION OF SEDIMENT
- Sample Extraction – First day of analysis: The water sample was siphoned to a separate labelled pre-weighed pot ensuring no sediment was transferred in process. Duplicate 1000 µL aliquots were removed and weighed. 4 mL of Ultima Gold XR added to each aliquot, vortex mixed then quantified by LSC. The sediment was transferred into a 2 L round bottomed flask (RBF) with 675 mL of water. A 10 mL homogeneous water sample was centrifuged at 8,500 rpm for 10 minutes. Duplicate 1000 µL aliquots were weighed and 4 mL of Ultima Gold XR added to each aliquot, vortex mixed then quantified by LSC. Approximately 0.4 mL of Octan-2-ol was added to reach RBF. A few anti-bumping granules were added. To each RBF 325 mL of concentrated sulphuric acid (18 M) was slowly added (incubation unit was carefully rinsed with sulphuric acid prior to adding to the RBF to ensure a high recovery). The flasks were wrapped with aluminium foil and placed on heating mantles. The samples were allowed to reflux for 5 hours then allowed to cool to room temperature. The condenser units were carefully rinsed with 30mL of water and rinsings added to the RBFs. The supernatant was carefully extracted off into a separate pre-weighed pot labelled Ext 1 and weight recorded. Duplicate 200 µL aliquots were weighed into 25 mL glass vials and 1 mL of methanol added to each then vortex mixed. 15 mL of Hionic Fluor was added to each vial, vortex mixed then quantified by LSC. Original sediment samples and RBF samples were stored at 20 °C in the dark if they were analysed within three days or stored at -20 °C if longer storage required.
- Sample Extraction – Second day of analysis: The RBF were removed from storage and if necessary allowed to reach room temperature. A second 5 hour reflux was performed after addition of 675 mL of water and 325 mL of concentrated sulphuric acid. The supernatant was carefully extracted off into a separate plastic pot then transferred to a pre-weighed pot labelled Ext 2 and weight recorded. Duplicate 200 µL aliquots were weighed into 25 mL glass vials and 1 mL of methanol added to each then vortex mixed. 15 mL of Hionic Fluor was added to each vial, vortex mixed then quatified by LSC. The RBF was then stoppered and shaken, remaining solution was transferred to pre- weighed plastic pots labelled Residue. This sample was centrifuged at 3,200 rpm and the supernatant transferred into a pre-weighed platic pot labelled Ext 3 and the weight recorded. Duplicate 200 µL aliquots were weighed into 25 mL glass vials and 1 mL of methanol added to each then vortex mixed. 15 mL of Hionic Fluor was added to each vial, vortex mixed then quantified by LSC. Approximately 100 mL of millipore water was added to the Residue pot and the contents shaken to re-suspend pellet. Sample was centrifuged at 3,200 rpm and the supernatant transferred into a pre-weighed platic pot labelled Water Wash and the weight recorded. Duplicate 200 µL aliquots were weighed into 25 mL glass vials and 1 mL of methanol added to each then vortex mixed. 15 mL of Hionic Fluor was added to each vial, vortex mixed then quantified by LSC. Approximately 100 mL of acetone was added to the Residue pot and the contents shaken to re-suspend pellet. Sample was centrifuged at 3,200 rpm and the supernatant transferred into a pre-weighed plastic pot labelled Acetone Wash and the weight recorded. Duplicate 200 µL aliquots were weighed into 25 mL glass vials and 1 mL of methanol added to each then vortex mixed. 20 mL of Hionic Fluor was added to each vial, vortex mixed then quantified by LSC. Ext 2 and Ext 3, Water and Acetone Washes were stored at -20 °C for further analysis.

SPE CLEAN-UP SEDIMENT EXTRACTS
- A ca. 50 mL extract pool (Extract 4) was prepared by combining proportional aliquots of extracts 1, 2 and 3. Extract 4 was taken and pH adjusted to ca 8 - 9 by the dropwise addition of ammonia solution. The pH adjusted extract was centrifuged (3200 rpm, 10 minutes) and supernatant taken (Extract 4a). Extract 4a was loaded onto a pre-conditioned (acetonitrile followed by water) ENVI-carb SPE cartridge and the waste collected as Extract 5. The cartridge was washed with water (5 mL) and the waste combined with Extract 5. The cartridge was eluted with acetonitrile : 250mM ammonium formate : orthophosphoric acid (30:70:1.25, v/v/v) (2 x 5 mL) and the eluant collected as Extract 6. Extract 6 was concentrated under nitrogen at 35 – 40 °C to ca 1 mL and renamed “Extract 7”. Procedural recoveries were generally quantitative for each step of the process, hence the final samples remain representative of the original samples analysed. This is further supported by the consistent chromatographic properties observed between replicate samples.

AIR-DRYING SAMPLES FOR COMBUSTION
- After completion of the Acetone wash, the residual sample was air dried on a labelled tray, Sediment Residue. The sample was spread evenly over the tray breaking down any lumps to aid drying process. If samples had not dried within two days the sample was mixed on the tray to further aid the drying process. Once dry, the sample was homogenised in a mortar and pestle then transferred into a pre-weighed pot labelled Sediment Residue Homogenate and contents thoroughly shaken to ensure homogeneity. Duplicate 250 µg weighed aliquots of Sediment residue homogenate (triplicate 200 µg weighed aliquots of subsample) were prepared for sample combustion.
Compartment:
natural water: freshwater
Sampling date:
2011
% Total extractable:
98.14
% Non extractable:
2.76
% CO2:
0.31
% Recovery:
100
St. dev.:
3.87
Remarks on result:
other: Mean recovery of applied radioactivity in the Calwich Abbey under aerobic conditions
Compartment:
natural water / sediment: freshwater
% Total extractable:
96.31
% Non extractable:
1.44
% CO2:
0.32
% Recovery:
99.76
St. dev.:
4.03
Remarks on result:
other: Mean recovery of applied radioactivity in the Swiss Lake under aerobic conditions
Compartment:
natural water / sediment: freshwater
% Total extractable:
100
% Non extractable:
2.88
% CO2:
0.05
% Recovery:
100
St. dev.:
1.81
Remarks on result:
other: Mean recovery of applied radioactivity in the Calwich Abbey under anaerobic conditions
Compartment:
natural water / sediment: freshwater
% Total extractable:
100
% Non extractable:
1.73
% CO2:
0.05
% Recovery:
100
St. dev.:
2.83
Remarks on result:
other: Mean recovery of applied radioactivity in the Swiss Lake under anaerobic conditions
Parent/product:
parent
Compartment:
total system
Remarks:
Aerobic Calwich Abbey
% Degr.:
5.06
Parameter:
radiochem. meas.
Sampling date:
2011
Sampling time:
100 d
Parent/product:
parent
Compartment:
total system
Remarks:
Aerobic Swiss Lake
% Degr.:
7.14
Parameter:
radiochem. meas.
Sampling date:
2011
Sampling time:
100 d
Parent/product:
parent
Compartment:
total system
Remarks:
Anaerobic Calwich Abbey
% Degr.:
0
Parameter:
radiochem. meas.
Sampling date:
2011
Sampling time:
100 d
Parent/product:
parent
Compartment:
total system
Remarks:
Anaerobic Swiss Lake
% Degr.:
3
Parameter:
radiochem. meas.
Sampling date:
2011
Sampling time:
100 d
Key result
Compartment:
natural water / sediment: freshwater
DT50:
> 1 000 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: in aerobic total system of Calwich Abbey
Key result
Compartment:
natural water / sediment: freshwater
DT50:
> 1 000 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: in aerobic total system of Swiss Lake
Compartment:
natural water: freshwater
DT50:
0.46 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: in aerobic water phase of Calwich Abbey
Compartment:
natural water: freshwater
DT50:
0.36 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: in aerobic water phase of Swiss Lake
Compartment:
natural water: freshwater
DT50:
0.76 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: in anaerobic water phase of Calwich Abbey
Compartment:
natural water: freshwater
DT50:
1.15 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: in anaerobic water phase of Swiss Lake
Compartment:
natural water / sediment: freshwater
DT50:
> 1 000 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: in anaerobic total system of Calwich Abbey
Compartment:
natural water / sediment: freshwater
DT50:
> 1 000 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: in anaerobic total system of Swiss Lake
Transformation products:
no
Evaporation of parent compound:
no
Volatile metabolites:
no
Residues:
yes
Remarks:
Parent compound (Substance) was the main component detected in the sediment in all samples analysed. Full results are presented in Tables 7 and 8 in 'Any other information on results incl tables'.
Details on results:
MICROBIAL BIOMASS
- At the time of treatment, the microbial biomass carbon in the aerobic system was 948.2 and 117.2 mg/kg and after the 100 DAT incubation period, it was 725 and 79.1 mg/kg for Calwich Abbey and Swiss Lake, respectively. This indicated the sediment supported a viable microbial population and that the sediment was suitable for use in a laboratory degradation study.

RADIOCHEMICAL PURITY
- The radiochemical purity, as measured by HPLC with on-line radioactivity detection, in the application solutions for both aerobic and anaerobic phases were greater than 97% on all occasions measured (before application on the day of use).

TREATMENT RATE
- Water sediment samples were treated with 14C-substance dibromide at a rate equivalent to a direct overspray of a 30cm deep water body at a nominal field application of 1000 g ai/ha of Substance ion. Samples were therefore treated with substance at a target application rate of 235 µg of substance ion (440 µg of substance dibromide) per flask. Achieved application rates were 958.6 g ai/ha for aerobic systems (equivalent to 1790.6 g substance dibromide/ha) and 893.4 g ai/ha for anaerobic systems (equivalent to 1668.8 g substance dibromide/ha).
- The final masses applied to Calwich Abbey water-sediment system were 251 and 234 µg of substance ion per flask for the aerobic and anaerobic incubations, which equivalent to 469 and 437 µg of substance dibromide respectively. The final masses applied to Swiss Lake water- sediment system were 232 and 219 µg of substance ion per flask for the aerobic and anaerobic incubations, which equivalent to 434 and 410µg of substance dibromide respectively The radioactivity added to each flask was 0.68 - 0.73 MBq and 0.64 - 0.68 MBq for Calwich Abbey and Swiss Lake, respectively.
- The exact application rate was determined from the LSC quantification of application homogeneity checks taken before and after each application. The application solutions were shown to be homogenous throughout each application, with coefficient of variation for the application checks of 1.4% and 2.7% for the aerobic and anaerobic phases, respectively.

TEST SYSTEM PARAMETERS
- Test system parameters, including pH (water), dissolved oxygen (water) and redox potential (water and sediment) were measured throughout the study and considered to be within acceptable limits for the maintenance of the required conditions.

AEROBIC INCUBATION

MASS BALANCE
- Full mass balance data is presented in Tables 1 and 2 in 'Any other information on results incl. tables'.

VOLATILE DEGRADATION PRODUCTS
- Carbon dioxide was a negligible product of metabolism in aerobic systems reaching a mean maximum 0.32% of the applied dose by the end of the incubation. The extent of volatile degradation can be summarised in Table 1 - Table 3 in 'Any other information on results incl. tables' (mass balance).

DISTRIBUTION OF RADIOACTIVE RESIDUES
- The distribution of radioactive residues can be summarised in Tables 1, 2 and 4 in 'Any other information on results incl. tables' (mass balance).

RADIOACTIVE RESIDUES IN WATER PHASE
- Aliquots of water were analysed directly. Substance was the main component detected in all samples analysed. No other radioactive regions accounted for > 2.15% of applied radioactivity. Full results are presented in Tables 5 and Table 6 in 'Any other information on results incl. tables'.

RADIOACTIVE RESIDUES IN SEDIMENT EXTRACTS
- Procedural recoveries were generally quantitative for each step of the process, hence the final samples remain representative of the original samples analysed. This is further supported by the consistent chromatographic properties observed between replicate samples.
- Parent compound (Substance) was the main component detected in the sediment in all samples analysed. No other radioactive regions accounted for > 1.65% of applied radioactivity. No other components were identified by LC/MS-MS. Full results are presented in Tables 7 and 8 in 'Any other information on results inc.l tables'.

ANAEROBIC INCUBATION

MASS BALANCE
- Full mass balance data is presented in Tables 9 and 10 in 'Any other information on results incl. tables'.

VOLATILE DEGRADATION PRODUCTS
- Carbon dioxide was a negligible product of metabolism in anaerobic systems reaching a mean maximum 0.05% of the applied dose by the end of the incubation. The extent of volatile degradation can be summarised in Table 9 - Table 11 in 'Any other information on results incl. tables' (mass balance).

DISTRIBUTION OF RADIOACTIVE RESIDUES
- The distribution of radioactive residues can be summarised in Tables 9,10 and 12 in 'Any other information on results incl. tables' (mass balance).

RADIOACTIVE RESIDUES IN WATER PHASE
- Aliquots of water were analysed directly. Substance was the main component detected in the majority of samples analysed. A number of minor degradates of Substance were observed in the Swiss Lake water samples at low level (none reached 5%). Full results are presented in Tables 7 and 8 in 'Any other information on results incl. tables'.

RADIOACTIVE RESIDUES IN SEDIMENT EXTRACTS
- Procedural recoveries were generally quantitative for each step of the process, hence the final samples remain representative of the original samples analysed. This is further supported by the consistent chromatographic properties observed between replicate samples.
- Parent compound (Substance) was the main component detected in the sediment in all samples analysed. Full results are presented in Tables 7 and 8 in 'Any other information on results incl. tables'.

STRUCTURAL ASSIGNMENTS
- LC/MS was used to provide qualitative confirmation of the identification of Substance in a selection of representative water samples and sediment extracts. TLC analysis was used but proved to be unsuitable. Substance was confirmed to be present in all water samples and concentrated sediment extracts analysed.

DISSIPATION AND DEGT50 OF SUBSTANCE IN WATER-SEDIMENT SYSTEMS
- The dissipation rate (DT50) and degradation rate (DegT50) of substance was calculated using a single first order kinetic model (SFO, CAKE v1.4). SFO kinetics described the dissipation and degradation of substance very well with a Chi-squared (χ2) value better than 15 (water analysis) or 4 (total system) in all cases. Results have been tabulated in Table 13 in 'Any other information on results incl. tables'.
- Dissipation rates from the water phases were similar in aerobic and anaerobic systems, under the experimental conditions, with DT50 values of 0.36 – 0.46 (aerobic) and 0.76 – 1.15 days (anaerobic). Degradation rates calculated for substance in the total system indicated little degradation of the test compound under the experimental conditions used, with DegT50 values of >1000 days obtained for both sediment systems.

Table 1. Distribution and Recovery of Radioactivity: Calwich Abbey (Aerobic Incubation). All values are % applied radioactivity

Fraction

Replicate

Incubation time (days)

0

0.17

0.33

1

7

30

60

100

Water

A

102.75

73.20

61.28

24.13

0.03*

0.27

0.19

0.11

B

101.48

82.46

60.52

27.78

3.07

0.41

0.13

0.12

Mean

102.12

77.83

60.90

25.96

3.07

0.34

0.16

0.12

Sediment Extraction 1

A

2.11

17.01

19.51

36.31

1.34*

52.93

47.75

44.97

B

1.04

11.32

17.19

35.62

47.29

49.72

45.38

36.53

Mean

1.58

14.17

18.35

35.97

47.29

51.33

46.57

40.75

Sediment Extraction 2

A

1.02

9.88

11.11

24.02

0.32*

34.99

29.48

25.45

B

0.61

6.51

10.70

19.91

27.72

36.50

28.73

27.61

Mean

0.82

8.20

10.91

21.97

27.72

35.75

29.11

26.53

Sediment Extraction 3

A

0.00

4.58

7.86

12.18

0.00*

14.70

15.91

26.23

B

0.00

3.18

6.03

10.75

16.12

14.20

16.63

31.59

Mean

0.00

3.88

6.95

11.47

16.12

14.45

16.27

28.91

Sediment Water Wash

A

0.00

0.28

0.51

0.90

0.11*

1.41

1.02

1.26

B

0.00

0.31

0.43

0.60

0.99

1.47

1.12

1.33

Mean

0.00

0.30

0.47

0.75

0.99

1.44

1.07

1.30

Sediment Acetone Wash

A

0.00

0.18

0.26

0.53

0.20*

0.65

0.41

0.48

B

0.00

0.12

0.23

0.38

0.64

0.63

0.47

0.60

Mean

0.00

0.15

0.25

0.46

0.64

0.64

0.44

0.54

Total Extractables

Mean

104.51

104.52

97.82

96.56

95.83

103.94

93.61

98.14

Sediment Residue

A

0.00

0.48

0.70

1.57

0.00*

1.59

2.74

2.59

B

0.00

0.37

0.62

1.60

2.32

2.42

2.90

2.92

Mean

0.00

0.43

0.66

1.59

2.32

2.01

2.82

2.76

14CO2

A

NC

0.01

0.01

0.01

0.01*

0.08

0.20

0.26

B

NC

0.01

0.01

0.01

0.03

0.12

0.14

0.35

Mean

NA

0.01

0.01

0.01

0.03

0.10

0.17

0.31

TOTAL

A

105.88

105.62

101.24

99.65

2.01*

106.62

97.70

101.35

B

103.13

104.28

95.73

96.65

98.18

105.47

95.50

101.05

Mean

104.51

104.95

98.49

98.15

98.18

106.05

96.60

101.20

Mean ± SD

 

101.20 ± 3.87

NC– Not calculated. No day 0 sample. NA– Not applicable.

*– Excluded from mean. Vessel not dosed inerror.

 

Table 2. Distribution and Recovery of Radioactivity: Swiss Lake (Aerobic Incubation). All values are % applied radioactivity.

Fraction

Replicate

Incubation time (days)

0

0.17

0.33

1

7

30

60

100

Water

A

101.08

62.14

49.71

25.87

5.57

1.95

0.92

1.16

B

102.18

56.63

45.09

24.34

5.80

1.72

0.85

0.62

Mean

101.63

59.39

47.40

25.11

5.69

1.84

0.89

0.89

Sediment Extraction 1

A

1.62

28.87

38.25

55.52

66.50

70.01

64.71

61.47

B

0.93

32.00

35.90

54.13

53.28

71.93

57.09

71.57

Mean

1.28

30.44

37.08

54.83

59.89

70.97

60.90

66.52

Sediment Extraction 2

A

1.57

8.95

10.52

10.21

16.60

26.12

21.14

20.27

B

1.62

10.89

15.21

12.07

26.35

21.35

23.78

15.98

Mean

1.60

9.92

12.87

11.14

21.48

23.74

22.46

18.13

Sediment Extraction 3

A

0.00

2.15

1.34

4.69

5.34

4.46

4.50

10.45

B

0.00

2.14

2.48

4.14

7.20

3.84

8.44

6.54

Mean

0.00

2.15

1.91

4.42

6.27

4.15

6.47

8.50

Sediment Water Wash

A

0.00

0.98

0.44

0.57

0.83

1.04

0.76

1.76

B

0.00

0.87

0.69

0.62

0.98

1.91

0.84

1.55

Mean

0.00

0.93

0.57

0.60

0.91

1.48

0.80

1.66

Sediment Acetone Wash

A

0.00

0.21

0.25

0.19

0.58

0.57

0.49

0.62

B

0.00

0.29

0.40

0.28

0.64

0.60

0.66

0.63

Mean

0.00

0.25

0.33

0.24

0.61

0.59

0.58

0.63

Total Extractables

Mean

104.50

103.06

100.14

96.32

94.84

102.75

92.09

96.31

Sediment Residue

A

0.00

0.45

0.38

0.88

1.23

1.27

1.25

1.06

B

0.00

0.44

0.79

1.23

0.89

1.48

1.47

1.82

Mean

0.00

0.45

0.59

1.06

1.06

1.38

1.36

1.44

14CO2

A

NC

0.01

0.01

0.01

0.06

0.13

0.24

0.31

B

NC

0.01

0.01

0.01

0.07

0.17

0.20

0.33

Mean

NA

0.01

0.01

0.01

0.07

0.15

0.22

0.32

TOTAL

A

104.27

103.76

100.90

97.94

96.71

105.55

94.01

97.10

B

104.73

103.27

100.57

96.82

95.21

103.00

93.33

99.04

Mean

104.50

103.52

100.74

97.38

95.96

104.28

93.67

98.07

Mean ± SD

 

99.76 ± 4.03

NC– Not calculated. No day 0 sample. NA– Not applicable.

 

Table 3. Extent of volatile degradation under aerobic conditions

14CO2

Small amounts of radioactivity were evolved as volatile products throughout the

course of the study.

14CO2evolved at end of study

Calwich Abbey (aerobic): Mean 0.31% Swiss Lake (aerobic): Mean 0.32%

 

Table 4. Summary of distribution of radioactive residues under aerobic conditions

Water residues

Water residues declined with time in all test systems.

Total water residues at 0 DAT

Calwich Abbey (aerobic): Mean 102.12% Swiss Lake (aerobic): Mean 101.63%

Total water residues at end of study

Calwich Abbey (aerobic): Mean 0.12% Swiss Lake (aerobic): Mean 0.89%

Extractable residues

Extractable residues generally declined with time in all test systems.

Total extractable residues at 0 DAT (including radioactivity in water phase)

Calwich Abbey (aerobic): Mean 104.51% Swiss Lake (aerobic): Mean 104.50%

Total extractable residues at end of study (including radioactivity in water phase)

Calwich Abbey (aerobic): Mean 98.14% Swiss Lake (aerobic): Mean 96.31%

Bound residues

Bound residues increased throughout the incubation period.

Bound residues at end of study (100 DAT)

Calwich Abbey (aerobic): Mean 2.76% Swiss Lake (aerobic): Mean 1.44%

 

Table 5. Summary of Characterisation / Identification of Radioactive Residues in Aerobic Calwich Abbey Water-Sediment System.

Radioactive residue in the water-sediment total system

Transformation

products

Rep

Sampling times (days)

0

0.17

0.33

1

7

30

60

100

 

Substance

A

102.90

103.06

98.33

94.13

(i)

102.68

92.05

95.86

B

101.71

102.08

93.22

90.84

93.38

100.16

90.27

94.01

Mean

102.31

102.57

95.78

92.49

90.38(ii)

101.42

91.16

94.94

Unidentified product(s), if any (iv)

A

2.98

1.61

1.43

2.51

(i)

0.21

1.28

0.90

B

1.42

1.39

1.22

3.22

0.82

0.67

0.60

1.84

Mean

2.20

1.50

1.33

2.87

0.82(ii)

0.44

0.94

1.37

 

Volatile organics

A

NS

0.01

0.01

0.01

(i)

0.08

0.20

0.26

B

NS

0.01

0.01

0.01

0.03

0.12

0.14

0.35

Mean

NA

0.01

0.01

0.01

0.03(ii)

0.10

0.17

0.31

Radioactive residue in the waterphase

Transformation

products

Rep

Sampling times (days)

0

0.17

0.33

1

7

30

60

100

 

Substance

A

99.77

71.88

59.99

21.67

(i)

0.27(iii)

0.19(iii)

0.11(iii)

B

100.06

81.31

59.43

24.75

3.07(iii)

0.41(iii)

0.13(iii)

0.12(iii)

Mean

99.92

76.60

59.71

23.21

3.07(iii)

0.34(iii)

0.16(iii)

0.12(iii)

 

Unidentified product(s), if any (iv)

A

2.98

(1.75)

1.32

(0.88)

1.29

(0.98)

2.46

(1.11)

NA

NA

NA

NA

B

1.42

(0.41)

1.15

(1.15)

1.09

(0.42)

3.03

(1.08)

NA

NA

NA

NA

Mean

2.20

1.24

1.19

2.75

NA

NA

NA

NA

Radioactive residue in the sedimentphase

Transformation

products

Rep

Sampling times (days)

0

0.17

0.33

1

7

30

60

100

 

Substance

A

3.13(iii)

31.18

38.34

72.46

(i)

102.41

91.86

95.75

B

1.65(iii)

20.77

33.79

66.09

90.31

99.75

90.14

93.89

Mean

2.39(iii)

25.98

36.07

69.28

90.31(ii)

101.08

91.00

94.82

 

Unidentified product(s), if any (iv)

A

NA

0.29

(0.24)

0.14

(0.07)

0.05

(0.05)

(i)

0.21

(0.10)

1.28

(0.53)

0.90

(0.52)

B

NA

0.24

(0.12)

0.13

(0.06)

0.19

(0.19)

0.82

(0.50)

0.67

(0.33)

0.60

(0.43)

1.84

(1.65)

Mean

NA

0.27

0.14

0.12

0.82(ii)

0.44

0.94

1.37

The amount of the test substance for the total system for Day 0 included the radioactivity found in the sediment extracts, and for Day 7 – Day 100, included the radioactivity found in the water phase, which was assumed to be the test substance

(i) Vessel not dosed in error.

(ii) No mean value for this sample. One replicate only.

(iii) Due to low level, no analysis was carried out. Values quoted from the recovery (assume worst case scenario).

(iv) Total unidentified products contain multiple minor components (largest single minor component)

NA: Not applicable as no analysisperformed

NS: Sample notcollected

All figures are quoted as % of applied radioactivity

 

Table 6. Summary of Characterisation / Identification of Radioactive Residues in Aerobic Swiss Lake Water-Sediment System.

 

Radioactive residue in the water-sediment total system

 

Transformation

products

Rep

Sampling times (days)

 

0

0.17

0.33

1

7

30

60

100

 

 

Substance

A

101.04

97.20

99.21

93.36

93.62

102.04

89.56

92.03

 

B

97.68

100.54

97.02

89.31

92.32

98.32

89.28

93.68

 

Mean

99.36

98.87

98.12

91.34

92.97

100.18

89.42

92.86

 

Unidentified product(s), if any (iv)

A

3.23

4.91

0.61

2.93

0.39

0.50

1.71

1.32

 

B

7.05

1.12

1.66

5.37

0.31

0.52

0.88

1.03

 

Mean

5.14

3.02

1.14

4.15

0.35

0.51

1.30

1.18

 

 

Volatile organics

A

NS

0.01

0.01

0.01

0.06

0.13

0.24

0.31

 

B

NS

0.01

0.01

0.01

0.07

0.17

0.20

0.33

 

Mean

NA

0.01

0.01

0.01

0.07

0.15

0.22

0.32

Radioactive residue in the waterphase

Transformation

products

Rep

Sampling times (days)

0

0.17

0.33

1

7

30

60

100

 

Substance

A

97.85

57.67

49.71(i)

23.80

5.57(iii)

1.95(iii)

0.92(iii)

1.16(iii)

B

95.13

55.78

44.10

19.72

5.80(iii)

1.72(iii)

0.85(iii)

0.62(iii)

Mean

96.49

56.73

46.91

21.76

5.69(iii)

1.84(iii)

0.89(iii)

0.89(iii)

 

Unidentified product(s), if any (iv)

A

3.23

(0.71)

4.47

(1.99)

NA

2.07

(0.62)

NA

NA

NA

NA

B

7.05

(2.15)

0.85

(0.28)

0.99

(0.68)

4.62

(0.73)

NA

NA

NA

NA

Mean

5.14

2.66

0.99(ii)

3.35

NA

NA

NA

NA

Radioactive residue in the sedimentphase

Transformation

products

Rep

Sampling times (days)

0

0.17

0.33

1

7

30

60

 

 

Substance

A

3.19(iii)

39.53

49.50

69.56

88.05

100.09

88.64

90.87

B

2.55(iii)

44.76

52.92

69.59

86.52

96.60

88.43

93.06

Mean

2.87(iii)

42.15

51.21

69.58

87.29

98.35

88.54

91.97

 

Unidentified produc

t(s), if any (iv)

A

NA

0.44

(0.29)

0.61

(0.48)

0.86

(0.37)

0.39

(0.39)

0.50

(0.26)

1.71

(1.45)

1.32

(1.22)

B

NA

0.27

(0.18)

0.67

(0.31)

0.75

(0.35)

0.31

(0.10)

0.52

(0.38)

0.88

(0.46)

1.03

(0.52)

Mean

NA

0.36

0.64

0.81

0.35

0.51

1.30

1.18

The amount of the test substance for the total system for Day 0 included the radioactivity found in the sediment extracts, and for Day 0.33, Rep A and Day 7 – Day 100 included the radioactivity found in the water phase, which was assumed to be the test substance

(i) No chromatography data for this timepoint. Values quoted from recovery (assume worst case scenario)

(ii) No mean value for this sample. One replicate only.

(iii) Due to low level, no analysis was carried out. Values quoted from the recovery (assume worst case scenario).

(iv) Total unidentified products contain multiple minor components (largest single minor component)

NA: Not applicable as no analysisperformed

NS: Sample notcollected

All figures are quoted as % of applied radioactivity

 

Table 7. Summary of Characterisation / Identification of Radioactive Residues in Anaerobic Calwich Abbey Water-Sediment System.

Radioactive residue in the water-sediment total system

 

Transformation

products

Rep

Sampling times (days)

 

0

0.33

1

7

30

60

100

 

 

Substance

A

107.27

106.76

103.88

104.35

101.88

99.35

106.28

 

B

103.45

105.13

102.35

103.31

104.22

99.47

101.56

 

Mean

105.36

105.95

103.12

103.83

103.05

99.41

103.92

 

Unidentified product(s), if any (iii)

A

1.78

1.41

1.86

0.02

0.53

0.80

0.09

 

B

4.88

1.17

0.68

0.06

0.64

0.39

0.46

 

Mean

3.33

1.29

1.27

0.04

0.59

0.60

0.28

 

 

Volatile organics

A

NS

0.01

0.01

0.08

0.02

0.03

0.05

 

B

NS

0.01

0.01

0.01

0.03

0.03

0.04

 

Mean

NA

0.01

0.01

0.05

0.03

0.03

0.05

 

Radioactive residue in the waterphase

 

Transformation

products

Rep

Sampling times (days)

 

0

0.33

1

7

30

60

100

 

 

Substance

A

102.95

87.33

50.25

12.06(i)

2.71(ii)

0.57(ii)

0.86(ii)

 

B

101.20

71.74

28.00

10.41(i)

2.85(ii)

0.89(ii)

0.63(ii)

 

Mean

102.08

79.54

39.13

11.24(i)

2.78(ii)

0.73(ii)

0.75(ii)

 

 

Unidentified product(s), if any (iii)

A

1.78

(0.63)

0.53

(0.53)

1.77

(0.78)

NA

NA

NA

NA

 

B

4.88

(2.02)

1.09

(1.09)

0.37

(0.37)

NA

NA

NA

NA

 

Mean

3.33

0.81

1.07

NA

NA

NA

NA

 

Radioactive residue in the sedimentphase

Transformation

products

Rep

Sampling times (days)

0

0.33

1

7

30

60

100

 

Substance

A

4.32(ii)

19.43

53.63

92.29

99.17

98.78

105.42

B

2.25(ii)

33.39

74.35

92.90

101.37

98.58

100.93

Mean

3.29(ii)

26.41

63.99

92.60

100.27

98.68

103.18

 

Unidentified product(s), if any (iii)

A

NA

0.88

(0.76)

0.09

(0.08)

0.02

(0.02)

0.53

(0.26)

0.80

(0.31)

0.09

(0.09)

B

NA

0.08

(0.07)

0.31

(0.19)

0.06

(0.06)

0.64

(0.41)

0.39

(0.39)

0.46

(0.32)

Mean

NA

0.48

0.20

0.04

0.59

0.60

0.28

The amount of Substance for the total system for Day 0 included the radioactivity found in the sediment extracts, and for Day 7 – Day 100 included the radioactivity found in the water phase, which was assumed to be the test substance

(i) No chromatography data for this timepoint. Values quoted from recovery (assume worst case scenario)

(ii) Due to low level, no analysis was carried out. Values quoted from the recovery (assume worst case scenario).

(iii) Total unidentified products contain multiple minor components (largest single minor component)

NA: Not applicable as no analysis performed

NS: Sample not collected

All figures are quoted as % of applied radioactivity

 

Table 8. Summary of Characterisation / Identification of Radioactive Residues in Anaerobic Swiss Lake Water-Sediment System.

Radioactive residue in the water-sediment total system

Transformation

products

Rep

Sampling times (days)

0

0.33

1

7

30

60

100

 

Substance

A

88.26

103.85

91.44

100.33

89.00

93.09

98.88

B

92.51

101.78

88.01

85.02

92.12

90.78

95.12

Mean

90.39

102.82

89.73

92.68

90.56

91.94

97.00

Unidentified product(s), if any (iv)

A

19.14

5.63

13.39

1.00

18.57

9.74

0.19

B

14.44

8.06

18.09

17.34

14.67

11.78

0.25

Mean

16.79

6.85

15.74

9.17

16.62

10.76

0.22

 

Volatile organics

A

NS

0.01

0.01

0.01

0.03

0.03

0.05

B

NS

0.01

0.01

0.03

0.03

0.03

0.05

Mean

NA

0.01

0.01

0.02

0.03

0.03

0.05

Radioactive residue in the waterphase

Transformation

products

Rep

Sampling times (days)

0

0.33

1

7

30

60

100

 

Substance

A

84.87

79.09

43.79

8.38(i)

9.97

1.29

7.85(i)

B

90.93

80.71

47.93

3.83

3.81

4.38

1.68(iii)

Mean

87.90

79.90

45.86

6.11

6.89

2.84

4.77

 

Unidentified product(s), if any (iv)

A

19.14

(4.47)

4.51

(1.17)

13.38

(3.26)

NA

17.80

(4.42)

9.26

(2.16)

NA

B

14.44

(4.95)

7.98

(1.69)

17.82

(4.34)

16.96

(3.66)

14.18

(3.62)

11.32

(2.42)

NA

Mean

16.79

6.25

15.60

16.96(ii)

15.99

10.29

NA

Radioactive residue in the sedimentphase

Transformation

products

Rep

Sampling times (days)

0

0.33

1

7

30

60

100

 

Substance

A

3.39(i)

24.76

47.65

91.95

79.03

91.80

91.03

B

1.58(i)

21.07

40.08

81.19

88.31

86.40

93.44

Mean

2.49(i)

22.92

43.87

86.57

83.67

89.10

92.24

 

Unidentified product(s), if any (iv)

A

NA

1.12

(0.89)

0.01

(0.01)

1.00

(0.37)

0.77

(0.32)

0.48

(0.32)

0.19

(0.10)

B

NA

0.08

(0.08)

0.27

(0.17)

0.38

(0.38)

0.49

(0.49)

0.46

(0.24)

0.25

(0.25)

Mean

NA

0.60

0.14

0.69

0.63

0.47

0.22

The amount of the test substance for the total system for Day 0 included the radioactivity found in the sediment extracts, and for Day 7, Rep A and Day 100 included the radioactivity found in the water phase, which was assumed to be the test substance

(i) No chromatography data for this timepoint. Values quoted from recovery (assume worst casescenario)

(ii) No mean value for this sample. One replicate only.

(iii) Due to low level, no analysis was carried out. Values quoted from the recovery (assume worst casescenario).

(iv) Total unidentified products contain multiple minor components (largest single minor component)

NA: Not applicable as no analysis performed

NS: Sample not collected

All figures are quoted as % of applied radioactivity

 

Table 9. Distribution and Recovery of Radioactivity: Calwich Abbey (Anaerobic Incubation). All values are % applied radioactivity.

Fraction

Replicate.

Incubation time (days)

0

0.33

1

7

30

60

100

Water

A

104.73

87.86

52.02

12.06

2.71

0.57

0.86

B

106.08

72.83

28.37

10.41

2.85

0.89

0.63

Mean

105.41

80.35

40.20

11.24

2.78

0.73

0.75

Sediment Extraction 1

A

2.23

13.00

28.21

49.41

48.09

50.83

52.32

B

0.92

19.35

33.43

51.15

44.65

44.05

44.73

Mean

1.58

16.18

30.82

50.28

46.37

47.44

48.53

Sediment Extraction 2

A

1.46

5.29

14.94

26.80

31.56

31.60

35.52

B

1.10

9.46

23.82

24.77

31.10

33.87

36.35

Mean

1.28

7.38

19.38

25.79

31.33

32.74

35.94

Sediment Extraction 3

A

0.63

2.02

10.57

16.10

20.05

17.15

17.67

B

0.23

4.66

17.41

17.04

26.26

21.05

20.31

Mean

0.43

3.34

13.99

16.57

23.16

19.10

18.99

Sediment Water Wash

A

0.00

0.20

0.50

1.29

1.47

1.12

1.09

B

0.05

0.42

0.78

1.42

1.58

1.06

1.46

Mean

0.03

0.31

0.64

1.36

1.53

1.09

1.28

Sediment Acetone Wash

A

0.04

0.00

0.22

0.61

0.70

0.53

0.22

B

0.00

0.16

0.34

0.54

0.64

0.65

0.47

Mean

0.02

0.08

0.28

0.58

0.67

0.59

0.35

Total Extractables

Mean

108.74

107.63

105.31

105.80

105.83

101.69

105.82

Sediment Residue

A

0.00

0.38

1.29

2.21

2.60

2.19

3.07

B

0.00

0.65

2.07

1.92

2.73

3.43

2.68

Mean

0.00

0.52

1.68

2.07

2.67

2.81

2.88

14CO2

A

NC

0.01

0.01

0.08

0.02

0.03

0.05

B

NC

0.01

0.01

0.01

0.03

0.03

0.04

Mean

NA

0.01

0.01

0.05

0.03

0.03

0.05

TOTAL

A

109.09

108.76

107.76

108.56

107.20

104.02

110.80

B

108.38

107.54

106.23

107.26

109.84

105.03

106.67

Mean

108.74

108.15

107.00

107.91

108.52

104.53

108.74

Mean ± SD

 

107.65 ± 1.81

NC– Not calculated. No day 0 sample. NA– Not applicable.

 

Table 10. Distribution and Recovery of Radioactivity: Swiss Lake (Anaerobic Incubation). All values are % applied radioactivity.

Fraction

Rep.

Incubation time (days)

0

0.33

1

7

30

60

100

Water

A

104.01

83.60

57.17

8.38

27.77

10.55

7.85

B

105.37

88.69

65.75

20.79

17.99

15.70

1.68

Mean

104.69

86.15

61.46

14.59

22.88

13.13

4.77

Sediment Extraction 1

A

2.04

19.27

34.55

62.68

62.81

68.77

51.74

B

0.91

16.28

25.91

65.58

69.33

64.08

53.16

Mean

1.48

17.78

30.23

64.13

66.07

66.43

52.45

Sediment Extraction 2

A

1.18

5.73

9.75

22.50

11.51

19.10

29.01

B

0.54

4.26

11.49

11.53

14.92

18.11

29.53

Mean

0.86

5.00

10.62

17.02

13.22

18.61

29.27

Sediment Extraction 3

A

0.17

0.88

3.36

7.77

5.48

4.41

10.47

B

0.13

0.61

2.95

4.46

4.55

4.67

11.00

Mean

0.15

0.75

3.16

6.12

5.02

4.54

10.74

Sediment Water Wash

A

0.07

0.20

0.41

1.06

0.59

0.78

1.87

B

0.08

0.16

0.40

0.66

0.73

0.79

3.12

Mean

0.08

0.18

0.41

0.86

0.66

0.79

2.50

Sediment Acetone Wash

A

0.00

0.13

0.28

0.70

0.42

0.42

0.58

B

0.00

0.11

0.21

0.47

0.45

0.45

0.55

Mean

0.00

0.12

0.25

0.59

0.44

0.44

0.57

Total Extractables

Mean

107.25

109.96

106.12

103.29

108.28

103.92

100.28

Sediment Residue

A

0.00

0.21

0.45

1.00

1.44

1.09

1.88

B

0.00

0.17

0.56

0.84

0.85

1.30

1.57

Mean

0.00

0.19

0.51

0.92

1.15

1.20

1.73

14CO2

A

NC

0.01

0.01

0.01

0.03

0.03

0.05

B

NC

0.01

0.01

0.03

0.03

0.03

0.05

Mean

NA

0.01

0.01

0.02

0.03

0.03

0.05

TOTAL

A

107.47

110.03

105.98

104.10

110.05

105.15

103.45

B

107.03

110.29

107.28

104.36

108.85

105.13

100.66

Mean

107.25

110.16

106.63

104.23

109.45

105.14

102.06

Mean ± SD

 

106.42 ± 2.83

NC– Not calculated. No day 0 sample. NA– Not applicable.

 

Table 11. Extent of volatile degradation under anaerobic conditions

14CO2

Small amounts of radioactivity were evolved as volatile products throughout the

course of the study.

14CO2 evolved at end of study

Calwich Abbey (anaerobic): Mean 0.05% Swiss Lake (anaerobic): Mean 0.05%

 

Table 12. Summary of distribution of radioactive residues under anaerobic conditions

Water residues

Water residues declined with time in all test systems.

Total water residues at 0 DAT

Calwich Abbey (anaerobic): Mean 105.41% Swiss Lake (anaerobic): Mean 104.69%

Total water residues at end of study

Calwich Abbey (anaerobic): Mean 0.75% Swiss Lake (anaerobic): Mean 4.77%

Extractable residues

Extractable residues generally declined with time in all test systems.

Total extractable residues at 0 DAT (including radioactivity in water phase)

Calwich Abbey (anaerobic): Mean 108.74% Swiss Lake (anaerobic): Mean 107.25%

Total extractable residues at end of study (including radioactivity in water phase)

Calwich Abbey (anaerobic): Mean 105.82% Swiss Lake (anaerobic): Mean 100.28%

Bound residues

Bound residues increased throughout the incubation period.

Bound residues at end of study (100 DAT)

Calwich Abbey (anaerobic): Mean 2.88% Swiss Lake (anaerobic): Mean 1.73%

 

Table 13. Summary of Dissipation and DegT50 Values for the substance

Water/sediment

SFO

Rate of dissipation of parent from water phase

Rate of dissapation of parent from total system

DT50 [days]

χ2

DegT50 [days]

χ2

Aerobic

Calwich Abbey

0.46

2.95

>1000

3.39

Swiss Lake

0.36

14.46

>1000

2.93

Anaerobic

Calwich Abbey

0.76

10.82

>1000

1.35

Swiss Lake

1.15

11.15

>1000

3.73

 

Validity criteria:
In accordance with OECD TG 308, the recoveries should range from 90% to 110% for labelled chemicals.
Observed value:
99.76% - 107.65%
Validity criteria fulfilled:
yes
Conclusions:
Dissipation of the test substance from the surface water was fast in both water/sediment test systems under aerobic condition with dissipation rate (DT50) of <0.5 days. There was negligible degradation of the test substance in both water/sediment systems in the aerobic and anaerobic incubation observed under the experimental conditions, resulting in calculated DegT50 values of > 1000 days for the total systems. No single radioactive component other than the test substance was observed at > 2.15% of the applied dose for the aerobic incubation. The maximum observed was 2.15% and 1.65% applied radioactivity, for water and sediment respectively. No single radioactive component other than the test substance was observed at > 4.95% of the applied dose for the anaerobic incubation. The maximum observed was 4.95% and 0.89% applied radioactivity, for water and sediment respectively. The test substance was confirmed to be present in all water samples and concentrated sediment extracts analysed. There was limited degradation to volatile products, levels were << 1% AR throughout the incubation period. Unextracted residues remained very low, < 3% throughout the incubation period.
Executive summary:

The rate and route of degradation of 14C-labelled test substance cation was investigated in two different water sediment systems: Calwich Abbey (Site A, silt loam) and Swiss Lake (Site C - sand). 14C-labelled test substance cation was applied to the water at a nominal rate of 0.33 µg/mL (equivalent to 0.6227 µg/mL of the test substance) in the water phase, which is approximately equivalent to direct overspray of 1000 g ai/ha (test substance cation) over a 30 cm depth water body. For each sediment type, one set was maintained under aerobic conditions and one under anaerobic conditions. The systems were incubated in the laboratory and maintained in dark conditions at 20 ± 2 ºC for 100 days. For the aerobic system, duplicate samples were taken for analysis at eight intervals (0, 0.17, 0.33, 7, 14, 30, 60 and 100 days). For the anaerobic system, duplicate samples were taken for analysis at seven intervals (0, 0.33, 7, 14, 30, 60 and 100 days). At each sampling time, complete test systems were removed. The water phase was then separated from the sediment by siphon into another flask, taking care not to disturb the sediment. The resultant sediment was extracted twice in 6M sulphuric acid, refluxed for 5 hours using a condenser system. Extractable 14C-residues were analysed by HPLC and confirmation of the test substance by LC/MS. Any volatile radioactivity was continuously flushed from the vessels, collected in traps and analysed. A mass balance was determined for each sample. Separate microbial biomass and anaerobicity surrogate samples were similarly incubated and analysed appropriately. The mean mass balance from all aerobic water/sediment systems was 101.20% ± 3.87% (range 96.60 – 106.05%) for Calwich Abbey and 99.76% ± 4.03% (range 93.67 – 104.50%) for Swiss Lake. The mean mass balance from all anaerobic water/sediment systems was 107.65% ± 1.81% (range 104.53 – 108.74%) for Calwich Abbey and 106.42% ± 2.83% (range 102.06 – 110.16%) for Swiss Lake. Under aerobic conditions, dissipation of the test substance was fairly rapid from the water phase in both water-sediment systems, with the parent compound representing only <<1% AR (in Calwich Abbey) and 1.84% AR (in Swiss Lake) in the water after 30 days of incubation. Under anaerobic incubation, dissipation of the test substance from the water phase of Calwich Abbey sediment was fairly fast, with the parent compound representing only 2.78% of the applied radioactivity in the water after 30 days of incubation. However, dissipation of the test substance from the water phase of Swiss Lake sediment was slower, with 4.77% AR still remaining after 100 days of incubation. The dissipation rate from water (DT50) and the degradation rate (DegT50) of the parent in the total system was estimated using single first-order (SFO) kinetics.

Under both aerobic and anaerobic conditions, the test substance was essentially stable throughout the time-course of the experiment with no major degredates being observed in either water samples or sediment extracts. The largest value for non-test substance related degradates of 4.95% applied radioactivity was observed in the Swiss Lake anaerobic water sample, replicate B (0 DAT). The maximum degradant in sediment, 1.65% applied radioactivity, was observed in the Calwich Abbey on Day 100, replicate B aerobic sample. Carbon dioxide was a negligible product of metabolism in both aerobic and anaerobic systems reaching a mean maximum 0.32% of the applied dose by the end of the incubation. Under aerobic conditions, unextracted residues generally increased slowly throughout the incubation, reaching a mean maximum of 2.76% and 1.44% of applied radioactivity by the end of the incubation, for Calwich Abbey and Swiss Lake, respectively. Under anaerobic conditions, unextracted residues generally increased slowly throughout the incubation, reaching a mean maximum of 2.88% and 1.73% of applied radioactivity by the end of the incubation, for Calwich Abbey and Swiss Lake, respectively. Dissipation of the test substance from the surface water was fast in both water/sediment systems under aerobic condition with dissipation rate (DT50) of <0.5 days. There was negligible degradation of the test substance in both water/sediment systems in the aerobic and anaerobic incubation observed under the experimental conditions, resulting in calculated DegT50 values of >1000 days for the total systems. No single metabolite was observed at > 2.15% of the applied dose for the aerobic incubation. The maximum observed was 2.15% and 1.65% applied radioactivity, for water and sediment respectively.

Description of key information

Total system (surface freshwater/sediment) DT50 values were both > 1000 days; degradation was considered negligible, OECD TG 308, Ford 2012.

Key value for chemical safety assessment

Half-life in freshwater sediment:
1 000 d
at the temperature of:
20 °C

Whole System

Half-life in whole system:
1 000 d
at the temperature of:
20 °C
Type of system:
fresh water and sediment

Additional information

Biodegradation in sediment


The biodegradation in freshwater sediment was determined in a study performed in accordance to OECD TG 308 and in compliance with GLP criteria. The rate and route of degradation of 14C-labelled test substance cation was investigated in two different water sediment systems: Calwich Abbey (Site A, silt loam) and Swiss Lake (Site C - sand). 14C-labelled test substance cation was applied to the water at a nominal rate of 0.33 µg/mL (equivalent to 0.6227 µg/mL of the test substance) in the water phase, which is approximately equivalent to direct overspray of 1000 g ai/ha (test substance cation) over a 30 cm deep water body. For each sediment type, one set was maintained under aerobic conditions and one under anaerobic conditions. The systems were incubated in the laboratory and maintained in dark conditions at 20 ± 2 ºC for 100 days. For the aerobic system, duplicate samples were taken for analysis at eight intervals (0, 0.17, 0.33, 7, 14, 30, 60 and 100 days). For the anaerobic system, duplicate samples were taken for analysis at seven intervals (0, 0.33, 7, 14, 30, 60 and 100 days). At each sampling time, complete test systems were removed. The water phase was then separated from the sediment by siphon into another flask, taking care not to disturb the sediment. The resultant sediment was extracted twice in 6M sulphuric acid and refluxed for 5 hours using a condenser system. Extractable 14C-residues were analysed by HPLC and confirmation of the test substance occurred by LC/MS. Any volatile radioactivity was continuously flushed from the vessels, collected in traps and analysed. A mass balance was determined for each sample. Separate microbial biomass and anaerobicity surrogate samples were similarly incubated and analysed appropriately.


 


The mean mass balance from all aerobic water/sediment systems was 101.20% ± 3.87% (range 96.60 – 106.05%) for Calwich Abbey and 99.76% ± 4.03% (range 93.67 – 104.50%) for Swiss Lake. The mean mass balance from all anaerobic water/sediment systems was 107.65% ± 1.81% (range 104.53 – 108.74%) for Calwich Abbey and 106.42% ± 2.83% (range 102.06 – 110.16%) for Swiss Lake.


Under aerobic conditions, dissipation of the test substance was fairly rapid from the water phase in both water-sediment systems, with the parent compound representing only <<1% AR (in Calwich Abbey) and 1.84% AR (in Swiss Lake) in the water after 30 days of incubation.


Under anaerobic incubation, dissipation of the test substance from the water phase of Calwich Abbey sediment was fairly fast, with the parent compound representing only 2.78% of the applied radioactivity in the water after 30 days of incubation. However, dissipation of the test substance from the water phase of Swiss Lake sediment was slower, with 4.77% AR still remaining after 100 days of incubation.


The dissipation rate from water (DT50) and the degradation rate (DegT50) of the parent in the total system was estimated using single first-order (SFO) kinetics. Under both aerobic and anaerobic conditions, the test substance was essentially stable throughout the time-course of the experiment with no major degradation products being observed in either water samples or sediment extracts. The largest value for non-test substance related degradation products of 4.95% applied radioactivity was observed in the Swiss Lake anaerobic water sample, replicate B (0 DAT). The maximum degradant in sediment, 1.65% applied radioactivity, was observed in the Calwich Abbey on Day 100, replicate B aerobic sample. Carbon dioxide was a negligible product of metabolism in both aerobic and anaerobic systems reaching a mean maximum of 0.32% applied radioactivity by the end of the incubation.


Under aerobic conditions, unextracted residues generally increased slowly throughout the incubation, reaching a mean maximum of 2.76% and 1.44% of applied radioactivity by the end of the incubation, for Calwich Abbey and Swiss Lake, respectively.


Under anaerobic conditions, unextracted residues generally increased slowly throughout the incubation, reaching a mean maximum of 2.88% and 1.73% of applied radioactivity by the end of the incubation, for Calwich Abbey and Swiss Lake, respectively.


Dissipation of the test substance from the surface water was fast in both water/sediment systems under aerobic condition with dissipation rate (DT50) of < 0.5 days. There was negligible degradation of the test substance in both water/sediment systems in the aerobic and anaerobic incubation observed under the experimental conditions, resulting in calculated DegT50 values of > 1000 days for the total systems. No single metabolite was observed at > 2.15% of the applied dose for the aerobic incubation. The maximum observed was 2.15% and 1.65% applied radioactivity, for water and sediment respectively.


 


Biodegradation in surface water


As reported in the OECD TG 308 study above (Ford, 2012) the test substance rapidly dissipates from surface water and is adsorbed to sediment. This is also indicated by the test substance log Koc > 4. Thus, in an OECD 309 experiment the test substance will most likely distribute in sediment rather than surface water. For this reason, an OECD 309 study on biodegradation simulation in surface water is not deemed necessary and technically not feasible due to the high adsorption capacity of the test substance cation.