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Environmental fate & pathways

Biodegradation in soil

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Reference
Endpoint:
biodegradation in soil: simulation testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
16/10/2017 to 11/04/2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
Guideline study, conducted to GLP and current methodology.
Reason / purpose:
reference to other study
Qualifier:
according to
Guideline:
OECD Guideline 307 (Aerobic and Anaerobic Transformation in Soil)
Deviations:
yes
Remarks:
One amendment concerning the realization of a second test because during the first test samples were frozen and a stability test of soil spiked with the test item showed a decrease of the test item concentration of 25% in 7 days.
GLP compliance:
yes (incl. certificate)
Test type:
laboratory
Specific details on test material used for the study:
No further details specified in the study report.
Radiolabelling:
no
Oxygen conditions:
aerobic/anaerobic
Soil classification:
not specified
Year:
2018
Details on soil characteristics:
Four standard soils (2.2; 2.3, 2.4 and 5M) were supplied by LUFA Speyer.
The four soils were significantly different based on the texture and percentage organic carbon. Soils were sampled and analysed for texture, pH, cation exchange capacity, organic carbon, bulk density, water retention characteristic by a GLP subcontractor (LUFA Speyer, Obere Laggasse 40, D-67346 Speyer).
Duration:
120 d
Initial conc.:
30 other: μg/kg dry weight
Based on:
test mat.
Parameter followed for biodegradation estimation:
test mat. analysis
Soil No.:
#1
Temp.:
12°C
Humidity:
Not specified
Microbial biomass:
115 mg/kg; referenced as soil 2.2
Soil No.:
#2
Temp.:
12°C
Humidity:
Not specified
Microbial biomass:
56.3 mg/kg; referenced as soil 2.3
Soil No.:
#3
Temp.:
12°C
Humidity:
Not specified
Microbial biomass:
85 mg/kg; referenced as soil 2.4
Soil No.:
#4
Temp.:
12°C
Humidity:
Not specified
Microbial biomass:
34.4 mg/kg; referenced as soil 5M
Details on experimental conditions:
Preparation of the soil system
A period of pre-incubation for the soils was performed prior to the beginning of the test, in order to allow germination and removal of seeds and to re-establish equilibrium of microbial metabolism following the change from sampling or storage conditions to incubation conditions. A pre-incubation period between 2 and 28 days approximating the temperature and moisture conditions of the actual test will generally be adequate. Storage and pre-incubation time together should not exceed three months.
Prior to start of the incubation period, the soils of each system were shipped to SADEF Laboratory, for the determination of the microbial biomass using the fumigation-extraction method.

Performing the test
The test was performed in incubators containing at least 50g of soil (dry weight basis).
A stock solution of the test item (C.I. Yellow 124) was prepared in acetone at a concentration of 1 g.L-1. Then, the test solution was prepared by addition of the stock solution in water used to obtain the relevant moisture. The test system was spiked with this solution to obtain a test item quantity of approximately 30 μg in the test system.
Two flasks with test item and one control were prepared, for each sampling time (i.e. 14 flasks containing the test item and 7 control flasks).
An abiotic control was performed with soils sterilized.
The frequency of atmospheric air renewal of the headspace of the flasks in the aerobic test was twice a week in order to compensate the oxygen consumption by the biomass.
The soil moisture content was regurlarly controlled by weighing of the incubation flasks and water losses compensated by adding demineralized water.
A trap with ethylene glycol was used for the trapping of volatile products.
The test was performed under the darkness and at 12°C ± 2.
To establish and maintain anaerobic conditions, one soil treated with the test substance and incubated under aerobic conditions for approximately 5 days was water-logged (1-3 cm water layer) and the incubation system was flushed with an inert gas (nitrogen).
The anaerobic system headspace was renewed regularly with inert gas (nitrogen).
6 samplings have been performed during the test (0, 3, 7, 11, 25 days and final time) for aerobic soil system and 7 samplings (0, 3, 7, 11, 25, 80 days and final time) for anaerobic soil system. For each sampling, two flasks containing the test item and a control flask were sacrificed.
At the final time, the soils were shipped to SADEF laboratory for the determination of microbial biomass.
The test item and identifiable transformation product (with known analytical standards) were measured for each sampling in the soils and water (for anaerobic system).
Mineralization and mass balance have not been performed because the molecules were not radiolabelled.
Soil No.:
#1
% Recovery:
1.6
Remarks on result:
other: Aerobic, Soil 2.2
Remarks:
120 days
Soil No.:
#2
% Recovery:
2.8
Remarks on result:
other: Aerobic, Soil 2.3
Remarks:
120 days
Soil No.:
#3
% Recovery:
2.4
Remarks on result:
other: Aerobic, Soil, 2.4
Remarks:
120 days
Soil No.:
#4
% Recovery:
1.4
Remarks on result:
other: Aerobic, Soil 5M
Remarks:
120 days
Soil No.:
#5
% Recovery:
4.9
Remarks on result:
other: Anaerobic, Soil 2.4
Remarks:
120 days
Key result
Soil No.:
#1
DT50:
4.1 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Remarks on result:
other: FOMC
Remarks:
Soil 2.2 Aerobic
Key result
Soil No.:
#2
DT50:
4.5 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Remarks on result:
other: FOMC / HS
Remarks:
Soil 2.3 Aerobic
Key result
Soil No.:
#3
DT50:
5.4 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Remarks on result:
other: DFOP / FOMC
Remarks:
Soil 2.4 Aerobic
Key result
Soil No.:
#4
DT50:
5.4 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Remarks on result:
other: FMOC / DFOP
Remarks:
Soil 5M Aerobic
Key result
Soil No.:
#5
DT50:
50.5 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Remarks on result:
other: SFO
Remarks:
Soil 2.4 Anaerobic
Transformation products:
no
Details on results:
At the start of incubation, between 22 and 28.5 μg/kg dry weight (corresponding to 74%-94% of the applied dose) of the 30 μg the nominally applied of C.I. Yellow 124 were recovered in the aerobic soil systems.
After 3 days of incubation, the amount of C.I. Yellow 124 decreased to approximately 15 μg/kg dry weight (corresponding to 50% of the applied dose) in the aerobic soil systems.
Subsequently, C.I. Yellow 124 further decreased in the aerobic soil system to approximately 0.5-0.8 μg/kg dry weight at the end of the incubation period.

At the start of incubation, between 22 and 24 μg/kg dry weight (corresponding to 73%-81% of the applied dose) of the 30 μg the nominally applied of C.I. Yellow 124 were recovered in the anaerobic soil system. The soil system was water-logged after 5 days of incubation.
During 22 days after this step, the amount of C.I. Yellow 124 was stable at approximately 15 μg/kg dry weight (corresponding to 50% of the applied dose) in the anaerobic soil system.
Subsequently, C.I. Yellow 124 further decreased in the anaerobic soil system to approximately 1.5 μg/kg dry weight at the end of the incubation period.

Carbon in NaOH traps
In carbon traps, approximately 500 mg.L-1 of inorganic carbon was found in the control and different test systems. No significant production of inorganic carbon was highlighted in test system compared to the control.

Dosage of ethylene glycol traps
No degradation compounds was detected.

Microbial biomass

Soil

Microbial biomass (mg/kg)

2.2

115

2.3

56,3

2.4

85

5M

34,4

 

Measurement of C.I. Yellow 124

Aerobic soil

Yellow 124 (ug/kg) in test system

Days

Test system

0

3

7

11

25

120

Soil 2.2

<LOQ

<LOQ

<LOQ

<LOQ

<LOQ

<LOQ

23.97

13.17

13.40

7.22

2.75

0.38

28.32

14.16

8.96

8.35

2.74

0.56

mean

26.14

13.66

11.18

7.79

2.74

0.47

Soil 2.3

<LOQ

<LOQ

<LOQ

<LOQ

<LOQ

<LOQ

24.83

13.33

11.25

8.86

4.83

0.66

25.48

14.05

11.53

6.75

3.67

1.03

mean

25.16

13.69

11.39

7.81

4.25

0.84

Soil 2.4

<LOQ

<LOQ

<LOQ

<LOQ

<LOQ

<LOQ

22.20

13.80

10.35

6.45

2.85

0.78

23.08

15.27

10.56

6.05

2.58

0.69

mean

22.64

14.53

10.45

6.25

2.72

0.73

Soil 5M

<LOQ

<LOQ

<LOQ

<LOQ

<LOQ

<LOQ

24.32

17.60

9.58

6.90

2.52

0.38

27.06

19.10

11.29

7.07

2.23

0.47

mean

25.69

18.35

10.43

6.98

2.37

0.42

 

% dose applied in test system

Days

Test system

0

3

7

11

25

120

Soil 2.2

79,9

43,9

44,7

24,1

9,2

1,3

94,4

47,2

29,9

27,8

9,1

1,9

mean

87,1

45,5

37,3

26,0

9,1

1,6

Soil 2.3

82,8

44,4

37,5

29,5

16,1

2,2

84,9

46,8

38,4

22,5

12,2

3,4

mean

83,9

45,6

38,0

26,0

14,2

2,8

Soil 2.4

74,0

46,0

34,5

21,5

9,5

2,6

76,9

50,9

35,2

20,2

8,6

2,3

mean

75,5

48,4

34,8

20,8

9,1

2,4

Soil 5M

81,1

58,7

31,9

23,0

8,4

1,3

90,2

63,7

37,6

23,6

7,4

1,6

mean

85,6

61,2

34,8

23,3

7,9

1,4

 

Anaerobic soil

Yellow 124 (ug/kg) in soil

Days

Test system

0

3

7

11

25

80

120

Soil 2.4 Anaerobic

<LOQ

<LOQ

<LOQ

<LOQ

<LOQ

<LOQ

<LOQ

24.24

16.14

14.00

14.96

22.56

3.92

1.52

21.98

15.48

16.40

16.00

15.52

5.20

1.44

mean

23.11

15.81

15.20

15.48

19.04

4.56

1.48

 

Yellow 124 (ug/L) in aqueous phase

Days

Test system

0

3

7

11

25

80

120

Soil 2.4 Anaerobic

0,063

0,02

<LOQ

<LOQ

<LOQ

0,08

0,04

0,02

<LOQ

<LOQ

0,11

0,06

0,04

<LOQ

<LOQ

mean

0,09

0,05

0,03

<LOQ

<LOQ

 

% dose applied in test system

Days

Test system

0

3

7

11

25

80

120

Soil 2.4 Anaerobic

80,8

53,8

46,7

49,9

75,2

13,1

5,1

73,3

51,6

54,7

53,3

51,7

17,3

4,8

mean

77,0

52,7

50,7

51,6

63,5

15,2

4,9

 

DT50and DT90determination

Soil 2.2

Test system

Kinetics

Visual fit

ꭓ2

DT50

(days)

DT90

(days)

Soil 2.2 Aerobic

SFO

moderate

13.66

5.8

19.4

FOMC

moderate

8.34

4.1

38.8

 

Soil 2.3

Test system

Kinetics

Visual fit

ꭓ2

DT50

(days)

DT90

(days)

Soil 2.3 Aerobic

SFO

moderate

14.46

6.6

21.9

FOMC

good

5.21

4.5

32.4

HS

good

5.21

4.5

32.4

 

Soil 2.4

Test system

Kinetics

Visual fit

ꭓ2

DT50

(days)

DT90

(days)

Soil 2.4 Aerobic

SFO

good

7.16

6.2

20.7

FOMC

good

4.3

5.4

30.1

DFOP

good

5.53

5.4

26.8

HS

good

5.73

5.6

24.1

 

Soil 5M

Test system

Kinetics

Visual fit

ꭓ2

DT50

(days)

DT90

(days)

Soil 5M Aerobic

SFO

good

5.18

5.7

18.9

FOMC

good

4.67

5.4

21.8

DFOP

good

4.45

5.4

22.5

HS

good

4.06

5.3

23.8

 

Soil 2.4 Anaerobic

Test system

Kinetics

Visual fit

ꭓ2

DT50

(days)

DT90

(days)

Soil 2.4 Anaerobic

SFO

moderate

18.93

50.5

167.7

 

Conclusions:
At the start of incubation, between 22 and 28.5 μg/kg dry weight (corresponding to 74%-94% of the applied dose) of the 30 μg the nominally applied of C.I. Yellow 124 were recovered in the aerobic soil systems.
After 3 days of incubation, the amount of C.I. Yellow 124 decreased to approximately 15 μg/kg dry weight (corresponding to 50% of the applied dose) in the aerobic soil systems.
Subsequently, C.I. Yellow 124 further decreased in the aerobic soil system to approximately 0.5-0.8 μg/kg dry weight at the end of the incubation period.
At the start of incubation, between 22 and 24 μg/kg dry weight (corresponding to 73%-81% of the applied dose) of the 30 μg the nominally applied of C.I. Yellow 124 were recovered in the anaerobic soil system. The soil system was water-logged after 5 days of incubation.
During 22 days after this step, the amount of C.I. Yellow 124 was stable at approximately 15 μg/kg dry weight (corresponding to 50% of the applied dose) in the anaerobic soil system.
Subsequently, C.I. Yellow 124 further decreased in the anaerobic soil system to approximately 1.5 μg/kg dry weight at the end of the incubation period.
No metabolite was identified through this test. The decrease of C.I. Yellow 124 measured concentration could be due to mineralization (CO2 production) or important adsorption on soil (Non-extractable (bound) residues).
Executive summary:

The objective of this study was to assess the aerobic transformation rate of the test item in soil.

 

The test was performed in the dark in a soil system. As the test item is poorly soluble, the test item was dissolved in acetone to spiked the soils. Concentration of the test item and the transformation products was measured regularly in soil samples. The identification of transformation products was based on comparison with control.

 

The test was performed on four soils under aerobic condition and one soil under anaerobic condition for 120 days at the most.

 

At the start of incubation, between 22 and 28.5 μg/kg dry weight (corresponding to 74%-94% of the applied dose) of the 30 μg the nominally applied of C.I. Yellow 124 were recovered in the aerobic soil systems.

After 3 days of incubation, the amount of C.I. Yellow 124 decreased to approximately 15 μg/kg dry weight (corresponding to 50% of the applied dose) in the aerobic soil systems.

Subsequently, C.I. Yellow 124 further decreased in the aerobic soil system to approximately 0.5-0.8 μg/kg dry weight at the end of the incubation period.

At the start of incubation, between 22 and 24 μg/kg dry weight (corresponding to 73%-81% of the applied dose) of the 30 μg the nominally applied of C.I. Yellow 124 were recovered in the anaerobic soil system. The soil system was water-logged after 5 days of incubation.

During 22 days after this step, the amount of C.I. Yellow 124 was stable at approximately 15 μg/kg dry weight (corresponding to 50% of the applied dose) in the anaerobic soil system.

Subsequently, C.I. Yellow 124 further decreased in the anaerobic soil system to approximately 1.5 μg/kg dry weight at the end of the incubation period.

 

No volatiles was found through this test in ethylene glycol traps. No metabolite was identified through this test. The decrease of C.I. Yellow 124 measured concentration could be due to mineralization (CO2production) or important adsorption on soil (Non-extractable (bound) residues).

 

The DT50and DT90values of C.I. Yellow 124 in soil systems are shown in the table below.

 

Test system

Kinetics

Visual fit

X2

DT50

(days)

DT90

(days)

Soil 2.2 aerobic

FOMC

moderate

8.34

4.1

38.8

Soil 2.3 aerobic

FOMC

good

5.21

4.5

32.4

Soil 2.4 aerobic

FOMC

good

4.3

5.4

30.1

Soil 5M aerobic

HS

good

4.06

5.3

23.8

Soil 2.4 anaerobic

SFO

moderate

18.93

50.5

167.7

 

 

Description of key information

The DT50and DT90values of C.I. Yellow 124 in soil systems are shown in the table below.

 

Test system

Kinetics

Visual fit

X2

DT50

(days)

DT90

(days)

Soil 2.2 aerobic

FOMC

moderate

8.34

4.1

38.8

Soil 2.3 aerobic

FOMC

good

5.21

4.5

32.4

Soil 2.4 aerobic

FOMC

good

4.3

5.4

30.1

Soil 5M aerobic

HS

good

4.06

5.3

23.8

Soil 2.4 anaerobic

SFO

moderate

18.93

50.5

167.7

 

 

Key value for chemical safety assessment

Half-life in soil:
50.5 d
at the temperature of:
12 °C

Additional information

The objective of this study was to assess the aerobic transformation rate of the test item in soil.

The test was performed in the dark in a soil system. As the test item is poorly soluble, the test item was dissolved in acetone to spiked the soils. Concentration of the test item and the transformation products was measured regularly in soil samples. The identification of transformation products was based on comparison with control.

The test was performed on four soils under aerobic condition and one soil under anaerobic condition for 120 days at the most.

 

At the start of incubation, between 22 and 28.5 μg/kg dry weight (corresponding to 74%-94% of the applied dose) of the 30 μg the nominally applied of C.I. Yellow 124 were recovered in the aerobic soil systems.

After 3 days of incubation, the amount of C.I. Yellow 124 decreased to approximately 15 μg/kg dry weight (corresponding to 50% of the applied dose) in the aerobic soil systems.

Subsequently, C.I. Yellow 124 further decreased in the aerobic soil system to approximately 0.5-0.8 μg/kg dry weight at the end of the incubation period.

At the start of incubation, between 22 and 24 μg/kg dry weight (corresponding to 73%-81% of the applied dose) of the 30 μg the nominally applied of C.I. Yellow 124 were recovered in the anaerobic soil system. The soil system was water-logged after 5 days of incubation.

During 22 days after this step, the amount of C.I. Yellow 124 was stable at approximately 15 μg/kg dry weight (corresponding to 50% of the applied dose) in the anaerobic soil system.

Subsequently, C.I. Yellow 124 further decreased in the anaerobic soil system to approximately 1.5 μg/kg dry weight at the end of the incubation period.

No volatiles was found through this test in ethylene glycol traps. No metabolite was identified through this test. The decrease of C.I. Yellow 124 measured concentration could be due to mineralization (CO2production) or important adsorption on soil (Non-extractable (bound) residues).

 

The DT50and DT90values of C.I. Yellow 124 in soil systems are shown in the table below.

 

Test system

Kinetics

Visual fit

X2

DT50

(days)

DT90

(days)

Soil 2.2 aerobic

FOMC

moderate

8.34

4.1

38.8

Soil 2.3 aerobic

FOMC

good

5.21

4.5

32.4

Soil 2.4 aerobic

FOMC

good

4.3

5.4

30.1

Soil 5M aerobic

HS

good

4.06

5.3

23.8

Soil 2.4 anaerobic

SFO

moderate

18.93

50.5

167.7