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Biodegradation in water and sediment: simulation tests

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Endpoint:
biodegradation in water: simulation testing on ultimate degradation in surface water
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Well documented guideline study
Justification for type of information:
The justification for read across is provided as an attachment in IUCLID Section 13.
Reason / purpose:
read-across: supporting information
Qualifier:
according to
Guideline:
OECD Guideline 306 (Biodegradability in Seawater)
Deviations:
yes
Remarks:
Ammonium chloride was omitted from the medium to prevent oxygen consumption due to nitrification and the oxygen consumption was measured at day 0, 7, 14 and 28 instead of day 5, 15 and 28
GLP compliance:
yes
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
No surrogate or analogue material
Radiolabelling:
no
Oxygen conditions:
aerobic
Inoculum or test system:
natural water
Details on source and properties of surface water:
Seawater was collected from coastal water near the Oosterscheldedam (Banjaard, The Netherlands) at high tide (20-10-2008). The seawater was sampled approximately 10 cm below the water surface. The temperature of the water was 14.3°C. The seawater was aged to reduce the concentration of biodegradable compounds present in the seawater. To this end, the seawater was aerated for 7 days at room temperature in diffused light.
Details on source and properties of sediment:
No sediment
Details on inoculum:
No inoculum: natural population from the seawater
Duration of test (contact time):
28 d
Initial conc.:
1 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: Natural sea water + added nutrients:
KH2PO4 8.5 mg/L
K2HPO4 21.75 mg/L
Na2PO4 . 2H20 33.3 mg/L
MgSO4.7H20 22.5 mg/L
CaCl2 27.5 mg/L
FeCl3.6H2O 0.25 mg/L
Ammonium was omitted from the medium to prevent nitrification.
- Solubilising agent (type and concentration if used): silicone oil AR 20 (1 mL/L test medium)
- Test temperature: 18 +/- 2°C
- pH: 7.6
- pH adjusted: no
- Continuous darkness: yes


TEST SYSTEM
- Culturing apparatus: 0.30 L BOD bottles with glass stoppers
- Number of culture flasks/concentration:
10 bottles containing seawater and silicone oil
10 bottles containig the test substance (1.0 mg/L) in silicone oil and seawater
10 bottles containing sodium acetate (6.7 mg/L) and seawater
10 bottles containing only seawater
- Measuring equipment: see above §"details on analytical methods"
- Test performed in closed vessels due to significant volatility of test substance: yes



SAMPLING
- Sampling frequency: every week (7, 14, 21 and 28 days)
- Sampling method: two duplicate bottles of all series were withdrawn for analyses of the dissolved oxygen concentration at each sampling time
Reference substance:
acetic acid, sodium salt
Remarks:
6.7 mg/l
Test performance:
The validity of the test is demonstrated by an endogenous respiration of 1.0 mg/L at day 28. The blank respiration therefore does not exceed 30% of the oxygen in the test bottles. Sodium acetate was degraded 85% of its ThOD after 28 days. The validity of the test is also shown by oxygen concentrations >0.5 mg/L in all bottles during the test period.
Compartment:
other: water, material (mass) balance
% Recovery:
100
Compartment:
other: sediment, material (mass) balance
% Recovery:
0
% Degr.:
74
Parameter:
O2 consumption
Sampling time:
28 d
Transformation products:
not specified
Details on transformation products:
No details
Details on results:
See § Any other information below.
Results with reference substance:
Biodegradation of the reference substance was 85% at day 28 (see § "Overall remarks" for detailed results).

Table 1. Dissolved oxygen concentrations (mg/L) in the closed bottles.

 

Time (days)

Oxygen concentration (mg/L)

Oco

Ot

Oc

Oa

0

7.1

7.1

7.1

7.1

7.1

7.1

7.1

7.1

Mean (M)

7.1

7.1

7.1

7.1

7

6.9

5.2

6.8

2.7

6.7

4.8

6.9

2.6

Mean (M)

6.8

5.0

6.9

2.7

14

6.5

4.2

6.5

2.0

6.4

4.3

6.4

2.0

Mean (M)

6.5

4.3

6.5

2.0

21

6.1

3.9

6.0

1.5

6.1

3.8

6.1

1.4

Mean (M)

6.1

3.9

6.1

1.5

28

6.0

3.5

6.1

1.5

6.1

3.5

6.1

1.4

Mean (M)

6.1

3.5

6.1

1.5

Oco     =               Seawater (inoculum) with mineral nutrient solution, with 0.3 mL of silicone oil but without test material.

Ot =   Seawater (inoculum) with mineral nutrient solution with test material in silicone oil (1.0 mg/L).

Oc =   Seawater (inoculum) with mineral nutrient solution but without test material and reference substance.

Oa=   Seawater (inoculum) with mineral nutrient solution with sodium acetate (6.7 mg/L).

 

 

Table 2. Oxygen consumption (mg/L) and the percentages biodegradation (BOD/ThOD) of DEV 2008-016 and sodium acetate in the closed bottle test inoculated with seawater

 

Time (days)

Oxygen consumption (mg/L)

Biodegradation (%)

Test

Acetate

Test

Acetate

0

0.0

0.0

0

0

7

1.8

4.2

51

78

14

2.2

4.5

63

83

21

2.2

4.6

63

85

28

2.6

4.6

74

85

 

Validity criteria fulfilled:
yes
Conclusions:
DEV 2008-016 is degraded 74% at 28 days. It is therefore considered readily biodegradable.
Executive summary:

In order to assess the biotic degradation in seawater, a biodegradability test was performed which allows the biodegradability to be measured in seawater. The biodegradability was determined in the Closed Bottle test performed according to slightly modified OECD Test Guidelines, and in compliance with the OECD principles of Good Laboratory Practice.

DEV 2008 -016 did not cause a reduction in the endogenous respiration. The test substance is therefore considered to be non-inhibitory to the inoculum.

DEV 2008 -016 was biodegraded 74% at day 28 in the Closed Bottle test. Hence this substance should be classified as readily biodegradable.

The test is valid as shown by an endogenous respiration of 1.0 mg/L and by the total mineralisation of the reference compound, sodium acetate. Sodium acetate was degraded 85% of its theoretical oxygen demand after 28 days. Finally, the most important criterion was met by oxygen concentrations >0.5 mg/L in all bottles during the test period.

Endpoint:
biodegradation in water: sediment simulation testing
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
the study does not need to be conducted because the substance is readily biodegradable

Description of key information

Biodegradation in seawater

Several studies conducted according to OECD 306 guideline were available and all concluded to the ready biodegradability of C14-20 Aliphatics (≤2% aromatic)i n seawater according to OECD criteria for biodegradability in seawater.

Biodegradation in sediment

C14-20 Aliphatics (≤2% aromatic) are readily biodegradable. Therefore, simulation tests in sediment are not required.

Key value for chemical safety assessment

Additional information