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Environmental fate & pathways

Biodegradation in soil

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Endpoint:
biodegradation in soil: simulation testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
September 8, 2017-April 10, 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 307 (Aerobic and Anaerobic Transformation in Soil)
Qualifier:
according to guideline
Guideline:
EPA OPPTS 835.4100 (Aerobic Soil Metabolism)
GLP compliance:
yes
Test type:
laboratory
Radiolabelling:
yes
Oxygen conditions:
aerobic
Soil classification:
USDA (US Department of Agriculture)
Year:
2017
Soil no.:
#1
Soil type:
sandy loam
% Clay:
14
% Silt:
20
% Sand:
66
% Org. C:
1.7
pH:
6.7
CEC:
14 meq/100 g soil d.w.
Bulk density (g/cm³):
1.2
Soil no.:
#2
Soil type:
loam
% Clay:
24
% Silt:
46
% Sand:
30
% Org. C:
1.8
pH:
5.1
CEC:
15.5 meq/100 g soil d.w.
Bulk density (g/cm³):
1.02
Soil no.:
#3
Soil type:
clay loam
% Clay:
34
% Silt:
30
% Sand:
36
% Org. C:
3.5
pH:
7.2
CEC:
25.8 meq/100 g soil d.w.
Bulk density (g/cm³):
0.99
Soil no.:
#4
Soil type:
sandy loam
% Clay:
18
% Silt:
16
% Sand:
66
% Org. C:
2.6
pH:
6.6
CEC:
15.4 meq/100 g soil d.w.
Bulk density (g/cm³):
0.96
Details on soil characteristics:
SOIL COLLECTION AND STORAGE
- Geographic location: #1 42.1095°N, -94.2963°W, #2 38.6944°N, -89.3392°W, #3 47°43.990'N, 97°38.138'W, #4 47°48.145'N, 97°37.237'W
- Pesticide use history at the collection site: no previous application of pesticides
- Sampling depth (cm): Soil #1 20 cm, all others 0-6 cm
- Storage conditions: refrigerated in the dark
- Soil preparation (e.g., 2 mm sieved; air dried etc.): 2 mm sieved

PROPERTIES OF THE SOILS (in addition to defined fields)
- Moisture at 1/3 atm (%): #1 24.0, #2 38.4, #3 42.1, #4 27.9
Soil No.:
#1
Duration:
120 d
Soil No.:
#2
Duration:
120 d
Soil No.:
#3
Duration:
120 d
Soil No.:
#4
Duration:
120 d
Soil No.:
#1
Initial conc.:
4.55 other: uCi/vessel
Based on:
test mat.
Soil No.:
#2
Initial conc.:
4.55 other: uCi/vessel
Based on:
test mat.
Soil No.:
#3
Initial conc.:
4.55 other: uCi/vessel
Based on:
test mat.
Soil No.:
#4
Initial conc.:
4.55 other: uCi/vessel
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
radiochem. meas.
Soil No.:
#1
Temp.:
20 degrees C
Humidity:
pF 2.0
Microbial biomass:
462 ug carbon/g soil
Soil No.:
#2
Temp.:
20 degrees C
Humidity:
pF 2.0
Microbial biomass:
553 ug carbon/g soil
Soil No.:
#3
Temp.:
20 degrees C
Humidity:
pF 2.0
Microbial biomass:
796 ug carbon/g soil
Soil No.:
#4
Temp.:
20 degrees C
Humidity:
pF 2.0
Microbial biomass:
875 ug carbon/g soil
Details on experimental conditions:
EXPERIMENTAL DESIGN
- Soil preincubation conditions (duration, temperature if applicable): 5 days at 20 degrees C in the dark
- Soil condition: fresh
- Soil (g/replicate): 50 g dry weight
- Control conditions, if used (present differences from other treatments, i.e., sterile/non-sterile, experimental conditions): Untreated biomass samples incubated under similar conditions as treatment groups.
- No. of replication controls, if used: 4 per soil
- No. of replication treatments: 20 per soil
- Test apparatus (Type/material/volume): 250 mL amber bottles
- Details of traps for CO2 and organic volatile, if any: two caustic traps with 10% aqueous NaOH were used to trap CO2. A single ethylene glycol trap was used to determine the amount of volatile organics.

Test material application
- Volume of test solution used/treatment: 100 uL in 25 uL aliquots
- Application method (e.g. applied on surface, homogeneous mixing etc.): Aliquots were added using a glass syringe. Bottles were then vortexed.

Experimental conditions (in addition to defined fields)
- Moisture maintenance method: Air was passed through deionized water to the test vessels to provide moisture.
- Continuous darkness: Yes

OXYGEN CONDITIONS (delete elements as appropriate)
- Methods used to create the an/aerobic conditions: Air was passed through deionized water to the test vessels to provide moisture and aeration.

SAMPLING DETAILS
- Sampling intervals: days 0, 2, 7, 14, 30, 62, 120
- Sampling method for soil samples: Duplicate samples of soil were removed and placed in pre-weighed fluorinated 250 mL centrifuge bottles. This was extracted with 100 mL acetonitrile and 0.1 M HCl, shaken for 30 minutes, centrifuged at 3500 rpm for 15 minutes, and the supernatent decanted. This extraction was repeated twice more. The fourth extraction was performed with 100 mL aceetone and shaken for 30 minutes and centrifuged at 3500 rpm for 15 minutes, and then the supernatent was decanted. This was repeated once more. Extracts were then combined. Four 0.5 g samples of the extracts were taken and combusted to determine the amounts of unextracted radiocarbon.
- Method of collection of CO2 and volatile organic compounds: CO2 was collected in NaOH traps and aliquots taken for analysis by LSC. Volatile organics were collected in ethylene glycol traps and aliquots taken for analysis by LSC.
- Sampling intervals/times for: same intervals as above
> Moisture content: moisture content was monitored throughout the study
> Sample storage before analysis: Samples were extracted on day of collection and HPLC analysis performed within 1 day.
Soil No.:
#1
% Recovery:
96.6
St. dev.:
1.3
Soil No.:
#2
% Recovery:
96.8
St. dev.:
2
Soil No.:
#3
% Recovery:
96.3
St. dev.:
2.5
Soil No.:
#4
% Recovery:
97.2
St. dev.:
2.9
Key result
Soil No.:
#1
% Degr.:
42.2
Parameter:
radiochem. meas.
Sampling time:
120 d
Key result
Soil No.:
#2
% Degr.:
63.5
Parameter:
radiochem. meas.
Sampling time:
120 d
Key result
Soil No.:
#3
% Degr.:
61.6
Parameter:
radiochem. meas.
Sampling time:
120 d
Key result
Soil No.:
#4
% Degr.:
48.4
Parameter:
radiochem. meas.
Sampling time:
120 d
Key result
Soil No.:
#1
DT50:
178 d
Type:
other: double first-order in parallel
Temp.:
20 °C
Key result
Soil No.:
#1
DT50:
378 d
Type:
other: double first-order in parallel
Temp.:
12 °C
Remarks on result:
other: Result was temperature adjusted from 20 C using Arrhenius equation
Key result
Soil No.:
#2
DT50:
67 d
Type:
other: double first-order in parallel
Temp.:
20 °C
Key result
Soil No.:
#2
DT50:
142 d
Type:
other: double first-order in parallel
Temp.:
12 °C
Remarks on result:
other: Result was temperature adjusted from 20 C using Arrhenius equation
Key result
Soil No.:
#3
DT50:
23 d
Type:
other: double first-order in parallel
Temp.:
20 °C
Key result
Soil No.:
#3
DT50:
49 d
Type:
other: double first-order in parallel
Temp.:
12 °C
Remarks on result:
other: Result was temperature adjusted from 20 C using Arrhenius equation
Key result
Soil No.:
#4
DT50:
108 d
Type:
other: double first-order in parallel
Temp.:
20 °C
Key result
Soil No.:
#4
DT50:
229 d
Type:
other: double first-order in parallel
Temp.:
12 °C
Remarks on result:
other: Result was temperature adjusted from 20 C using Arrhenius equation
Transformation products:
yes
No.:
#1
Details on transformation products:
- Formation and decline of each transformation product during test: See tables below.
- Pathways for transformation: Pathway not determined
Evaporation of parent compound:
no
Volatile metabolites:
no
Remarks:
Less than =< 0.1% AR of organic volatiles were detected
Residues:
yes
Details on results:
TEST CONDITIONS
- Aerobicity (or anaerobicity), moisture, temperature and other experimental conditions maintained throughout the study: Yes

MAJOR TRANSFORMATION PRODUCTS: CO2
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: 0%, days 0, 2, 7, 14, 30, 62, 120
- Range of maximum concentrations in % of the applied amount at end of study period: 26.0%, 37.2%, 32.2%, 25.6% (120 days)

MINOR TRANSFORMATION PRODUCTS: Bound Residues
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: 0.1-1.1%, days 0, 2, 7, 14, 30, 62, 120
- Range of maximum concentrations in % of the applied amount at end of study period: 12.8%, 20.2%, 21.8%, 15.1% (120 days)

TOTAL UNIDENTIFIED RADIOACTIVITY (RANGE) OF APPLIED AMOUNT: 1.3-4.4%

EXTRACTABLE RESIDUES
- % of applied amount at day 0: 96.0-96.9%
- % of applied amount at end of study period: 54.1%, 33.4%, 34.4%, 48.3% (120 days)

NON-EXTRACTABLE RESIDUES
- % of applied amount at day 0: 0.1-1.1%
- % of applied amount at end of study period: 12.8%, 20.2%, 21.8%, 15.1% (120 days)

MINERALISATION
- % of applied radioactivity present as CO2 at end of study: 26.0%, 37.2%, 32.2%, 25.6% (120 days)

VOLATILIZATION
- % of the applied radioactivity present as volatile organics at end of study: Organic volatiles were not detected.

Soil 1

Day

1,4-Di(2-decanyl)benzene (% AR)

CO2

(% AR)

Bound Residues

(% AR)

Volatile Organics

(% AR)

Other

(% AR)

Day 0

96.3

--

0.1

NA

0

Day 2

93.2

0.3

4.8

0

0

Day 7

84.6

3.2

8.5

0

0

Day 14

78.5

7.1

10.3

0

0

Day 30

65.6

14.7

15.8

0

0

Day 62

66.5

17.2

12.5

0

2.4

Day 120

54.1

26.0

12.8

0

1.3

 

Soil 2

Day

1,4-Di(2-decanyl)benzene (% AR)

CO2

(% AR)

Bound Residues

(% AR)

Volatile Organics

(% AR)

Other

(% AR)

Day 0

96.9

--

0.6

NA

0

Day 2

97.8

0

1.1

0

0

Day 7

77.2

4.5

14.2

0

0.9

Day 14

67.4

10.8

18.6

0

1.8

Day 30

61.4

17.6

18.6

0

0

Day 62

58.6

17.9

14.9

0

3.6

Day 120

33.4

37.2

20.2

0

4.0

 

Soil 3

Day

1,4-Di(2-decanyl)benzene (% AR)

CO2

(% AR)

Bound Residues

(% AR)

Volatile Organics

(% AR)

Other

(% AR)

Day 0

96.0

--

1.1

NA

0

Day 2

83.9

0.6

15.1

0

0

Day 7

67.6

7.2

21.5

0

0

Day 14

55.1

14.2

26.9

0

0

Day 30

49.4

23.1

24.8

0

0

Day 62

31.2

31.4

28.0

0

5.0

Day 120

34.4

32.2

21.8

0

4.4

 

Soil 4

Day

1,4-Di(2-decanyl)benzene (% AR)

CO2

(% AR)

Bound Residues

(% AR)

Volatile Organics

(% AR)

Other

(% AR)

Day 0

96.7

--

0.4

NA

0

Day 2

89.5

0.7

9.5

0

0

Day 7

73.9

7.1

17.6

0

0

Day 14

70.3

10.8

16.4

0.1

0.6

Day 30

61.9

17.2

16.6

0

0

Day 62

49.5

23.7

21.0

0

5.5

Day 120

48.3

25.6

15.1

0

2.8

 

Conclusions:
The test substance degraded moderately in soil in aerobic conditions.
Executive summary:

The biodegradation of the test substance under aerobic conditions was determined in an OECD Guideline 307 test. Radiolabelled test substance was added to four different types of soil, and incubated for 120 days under aerobic conditions. NaOH traps were used to determine the amount of CO2 evolved, and ethylene glycol traps were used to measure the amount of organic volatiles produced. Measurements were taken on days 0, 2, 7, 14, 30, 62, and 120. The amount of CO2 evolved at the end of the 120 days ranged from 25.6 -37.2%. Bound residues ranged from 12.8 -21.8%. No volatile orangics were detected. The test substance degraded moderately in soil in aerobic conditions.

Endpoint:
biodegradation in soil: simulation testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
May 30, 2017 - May 9, 2019
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 307 (Aerobic and Anaerobic Transformation in Soil)
Qualifier:
according to guideline
Guideline:
EPA OPPTS 835.4200 (Anaerobic Soil Metabolism)
GLP compliance:
yes
Test type:
laboratory
Radiolabelling:
yes
Oxygen conditions:
anaerobic
Soil classification:
USDA (US Department of Agriculture)
Year:
2017
Soil no.:
#1
Soil type:
sandy loam
% Clay:
14
% Silt:
20
% Sand:
66
% Org. C:
1.7
pH:
6.7
CEC:
14 meq/100 g soil d.w.
Bulk density (g/cm³):
1.2
Soil no.:
#2
Soil type:
loam
% Clay:
24
% Silt:
46
% Sand:
30
% Org. C:
1.8
pH:
4.8
CEC:
14 meq/100 g soil d.w.
Bulk density (g/cm³):
1.02
Soil no.:
#3
Soil type:
clay loam
% Clay:
34
% Silt:
30
% Sand:
36
% Org. C:
3.5
pH:
7.2
CEC:
25.8 meq/100 g soil d.w.
Bulk density (g/cm³):
0.99
Soil no.:
#4
Soil type:
sandy loam
% Clay:
18
% Silt:
16
% Sand:
66
% Org. C:
2.6
pH:
6.6
CEC:
15.4 meq/100 g soil d.w.
Bulk density (g/cm³):
0.96
Details on soil characteristics:
SOIL COLLECTION AND STORAGE
- Geographic location: #1 42.1095° N, -94.2963° W, #2 38.6944°N, -89.3392°W, #3 47° 43.990'N, 97° 38.138'W, #4 47° 48.145'N, 97° 37.237'W
- Pesticide use history at the collection site: no previous application of pesticides
- Sampling depth (cm): 0-6 cm
- Storage conditions: refrigerated in the dark
- Soil preparation (e.g., 2 mm sieved; air dried etc.): 2 mm sieved

PROPERTIES OF THE SOILS (in addition to defined fields)
- Moisture at 1/3 atm (%): #1 24.0, #2 38.4, #3 42.1, #4 27.9
Soil No.:
#1
Duration:
148 d
Soil No.:
#2
Duration:
148 d
Soil No.:
#3
Duration:
148 d
Soil No.:
#4
Duration:
148 d
Soil No.:
#1
Initial conc.:
5.17 other: uCi/vessel
Soil No.:
#2
Initial conc.:
5.17 other: uCi/vessel
Soil No.:
#3
Initial conc.:
5.17 other: uCi/vessel
Soil No.:
#4
Initial conc.:
5.17 other: uCi/vessel
Parameter followed for biodegradation estimation:
CO2 evolution
radiochem. meas.
Soil No.:
#1
Temp.:
20 degrees C
Humidity:
pF 2.0
Microbial biomass:
391 ug carbon/g soil
Soil No.:
#2
Temp.:
20 degrees C
Humidity:
pF 2.0
Microbial biomass:
470 ug carbon/g soil
Soil No.:
#3
Temp.:
20 degrees C
Humidity:
pF 2.0
Microbial biomass:
682 ug carbon/g soil
Soil No.:
#4
Temp.:
20 degrees C
Humidity:
pF 2.0
Microbial biomass:
997 ug carbon/g soil
Details on experimental conditions:
EXPERIMENTAL DESIGN
- Soil preincubation conditions (duration, temperature if applicable): 20 degrees C in the dark for at least 20 days
- Soil condition: air dried/fresh
- Soil (g/replicate): 50 g
- Control conditions, if used (present differences from other treatments, i.e., sterile/non-sterile, experimental conditions): biomass controls and surrogates to ensure anaerobic conditions
- No. of replication controls, if used: 4 soil
- No. of replication treatments: 20 per soil
- Test apparatus (Type/material/volume): 250 mL amber bottles
- Details of traps for CO2 and organic volatile, if any: Two 10% aqueous NaOH traps were used to collect evolved CO2. An ethylene glycol trap was used to collect organic volatiles.

Test material application
- Volume of test solution used/treatment: 100 uL
- Application method (e.g. applied on surface, homogeneous mixing etc.): Test substance was added using a 100 uL glass syringe. Test substance was placed on the top of the soil in a spiral pattern. The test bottles were then vortexed to mix.

Experimental conditions (in addition to defined fields)
- Moisture maintenance method: After 28 days, the test vessels were flooded with HPLC grade water that had been flushed with nitrogen for 20 minutes. Water was added 60-150 mL at a time until a water layer of 1-3cm was observed.
- Continuous darkness: Yes

Other details, if any:

OXYGEN CONDITIONS (delete elements as appropriate)
- Methods used to create the an/aerobic conditions: Test vessels were incubated for 28 days under aerobic conditions and then flooded to create anaerobic conditions for 120 days.
- Evidence that an/aerobic conditions were maintained during the experiment (e.g. redox potential): Dissolved oxygen and redox potential was measured at each sampling interval.

SAMPLING DETAILS
- Sampling intervals: Pre-flood - days 0 and 28; Post-flood - days 7, 14, 30, 62, 120
- Sampling method for soil samples: Aerobic Phase - Duplicate samples of soil were removed and placed in pre-weighed fluorinated 250 mL centrifuge bottles. This was extracted with 100 mL acetonitrile and 0.1 M HCl, shaken for 30 minutes, centrifuged at 3500 rpm for 15 minutes, and the supernatent decanted. This extraction was repeated twice more. The fourth extraction was performed with 100 mL aceetone, shaken for 30 minutes, centrifuged at 3500 rpm for 15 minutes, and then the supernatent was decanted. This was repeated once more. Extracts were then combined. Four 0.5 g samples of the extracts were taken and combusted to determine the amounts of unextracted radiocarbon.
Anaerobic Phase - Duplicate samples of soil were removed. The pH and ORP in water and soil layers were measured, as was the dissolved oxygen content. 30 mL of ACN was added to a graduated cylinder, and the decant water added. Volume was measured, and then the solution was transferred to a 250 mL FLPE centrifuge bottle. This was centrifuged for 10 minutes at 3500 rpm. Supernatent was placed in a new 250 mL FLPE centrifuge bottle, and three 1 mL aliquots were taken. Soils were placed in pre-weighed fluorinated 250 mL centrifuge bottles. This was extracted with 100 mL acetonitrile and 0.1 M HCl. Shaken for 30 minutes and centrifuged at 3500 rpm for 15 minutes and the supernatent decanted. This extraction was repeated twice more. The fourth extraction was performed with 100 mL aceetone and shaken for 30 minutes and centrifuged at 3500 rpm for 15 minutes, and then the supernatent was decanted. This was repeated once more. Extracts were then combined. Four 0.5 g samples of the extracts were taken and combusted to determine the amounts of unextracted radiocarbon.
- Method of collection of CO2 and volatile organic compounds: CO2 was collected in NaOH traps and aliquots taken for analysis by LSC. volatile organics were collected in ethylene glycol traps and aliquots taken for analysis by LSC
- Sampling intervals/times for: same intervals as above
> Moisture content: Soils were flooded to maintain anaerobicity.
> Redox potential/other: 2 surrogates per soil were set up to ensure anaerobicity was maintained.
> Sample storage before analysis: Samples were extracted on day of collection and HPLC analysis performed within 6 days.
Soil No.:
#1
% Recovery:
97.8
St. dev.:
2.2
Soil No.:
#2
% Recovery:
98.1
St. dev.:
2.5
Soil No.:
#3
% Recovery:
97.2
St. dev.:
1.8
Soil No.:
#4
% Recovery:
97.5
St. dev.:
1.6
Key result
Soil No.:
#1
% Degr.:
10.2
Parameter:
radiochem. meas.
Sampling time:
120 d
Key result
Soil No.:
#2
% Degr.:
19.5
Parameter:
radiochem. meas.
Sampling time:
120 d
Key result
Soil No.:
#3
% Degr.:
21.6
Parameter:
radiochem. meas.
Sampling time:
120 d
Key result
Soil No.:
#4
% Degr.:
19.7
Parameter:
radiochem. meas.
Sampling time:
120 d
Key result
Soil No.:
#1
DT50:
406 000 000 d
Type:
other: single-first order model
Temp.:
20 °C
Key result
Soil No.:
#1
DT50:
860 000 000 d
Type:
other: single-first order model
Temp.:
12 °C
Remarks on result:
other: Result was temperature adjusted from 20 C using Arrhenius equation
Key result
Soil No.:
#2
DT50:
1 114 d
Type:
other: single-first order model
Temp.:
20 °C
Key result
Soil No.:
#2
DT50:
2 365 d
Type:
other: single-first order model
Temp.:
12 °C
Remarks on result:
other: Result was temperature adjusted from 20 C using Arrhenius equation
Key result
Soil No.:
#3
DT50:
1 631 d
Type:
other: single-first order model
Temp.:
20 °C
Key result
Soil No.:
#3
DT50:
3 462.6 d
Type:
other: single-first order model
Temp.:
12 °C
Remarks on result:
other: Result was temperature adjusted from 20 C using Arrhenius equation
Key result
Soil No.:
#4
DT50:
6 320 000 000 d
Type:
other: single-first order model
Temp.:
20 °C
Key result
Soil No.:
#4
DT50:
13 000 000 000 d
Type:
other: single-first order model
Temp.:
12 °C
Remarks on result:
other: Result was temperature adjusted from 20 C using Arrhenius equation
Transformation products:
yes
No.:
#1
Details on transformation products:
- Pathways for transformation: Unknown
Evaporation of parent compound:
no
Volatile metabolites:
no
Residues:
yes
Details on results:
TEST CONDITIONS
- Aerobicity (or anaerobicity), moisture, temperature and other experimental conditions maintained throughout the study: Yes

MAJOR TRANSFORMATION PRODUCTS: CO2
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: 0%, pre-flood days 0 and 28, post-flood days 7, 14, 30, 62, and 128
- Range of maximum concentrations in % of the applied amount at end of study period: 5.1%, 9.0%, 10.7%, 10.5%

MINOR TRANSFORMATION PRODUCTS: Bound residues
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: 0%, pre-flood days 0 and 28, post-flood days 7, 14, 30, 62, and 128
- Range of maximum concentrations in % of the applied amount at end of study period: 4.3%, 9.1%, 7.7%, 6.8%

EXTRACTABLE RESIDUES
- % of applied amount at day 0: 0%
- % of applied amount at end of study period: 0%

NON-EXTRACTABLE RESIDUES
- % of applied amount at day 0: 0.1-0.3%
- % of applied amount at end of study period: 4.3%, 9.1%, 7.7%, 6.8%

MINERALISATION
- % of applied radioactivity present as CO2 at end of study: 5.1%, 9.0%, 10.7%, 10.5%


VOLATILIZATION
- % of the applied radioactivity present as volatile organics at end of study: 0%

Soil 1

Day

1,4-Di(2-decanyl)benzene (% AR)

CO2

(% AR)

Bound Residues

(% AR)

Volatile Organics

(% AR)

Other

(% AR)

Pre-Flood Day 0

98.3

--

0.1

NA

0

Pre-Flood Day 28

91.8

5.0

4.9

0

0

Post-Flood Day 7

84.1

5.7

6.6

0

0

Post-Flood Day 14

82.9

6.3

6.5

0

0

Post-Flood Day 30

85.5

6.4

6.5

0

0

Post-Flood Day 62

82.4

5.6

5.7

0

0

Post-Flood Day 120

88.1

5.1

4.3

0

0

 

Soil 2

Day

1,4-Di(2-decanyl)benzene (% AR)

CO2

(% AR)

Bound Residues

(% AR)

Volatile Organics

(% AR)

Other

(% AR)

Pre-Flood Day 0

98.3

--

0.3

NA

0

Pre-Flood Day 28

82.8

9.5

8.8

0

0

Post-Flood Day 7

84.3

7.3

7.3

0

0

Post-Flood Day 14

79.8

8.3

7.8

0

0

Post-Flood Day 30

78.6

10.0

9.4

0

0

Post-Flood Day 62

73.0

9.8

7.3

0

0

Post-Flood Day 120

78.8

9.0

9.1

0

0

 

Soil 3

Day

1,4-Di(2-decanyl)benzene (% AR)

CO2

(% AR)

Bound Residues

(% AR)

Volatile Organics

(% AR)

Other

(% AR)

Pre-Flood Day 0

98.9

--

0.4

NA

0

Pre-Flood Day 28

83.9

8.0

8.4

0

0

Post-Flood Day 7

79.3

7.7

8.9

0

0

Post-Flood Day 14

76.8

9.1

9.8

0

0

Post-Flood Day 30

77.9

9.8

8.9

0

0

Post-Flood Day 62

76.1

9.2

6.5

0

0

Post-Flood Day 120

77.3

10.7

7.7

0

0

 

Soil 4

Day

1,4-Di(2-decanyl)benzene (% AR)

CO2

(% AR)

Bound Residues

(% AR)

Volatile Organics

(% AR)

Other

(% AR)

Pre-Flood Day 0

99.3

--

0.2

NA

0

Pre-Flood Day 28

78.8

10.0

9.3

0

0

Post-Flood Day 7

77.5

10.5

9.6

0

0

Post-Flood Day 14

73.6

10.1

9.8

0

0

Post-Flood Day 30

76.5

10.0

8.5

0

0

Post-Flood Day 62

73.9

11.5

7.7

0

0

Post-Flood Day 120

79.6

10.5

6.8

0

0

 

Conclusions:
The test substance degraded slowly under aerobic conditions, and even more slowly under anaerobic conditions.
Executive summary:

The anaerobic biodegradation potential of the test substance was determined in an OECD Guideline 307 study. The test substance was radiolabelled and added to four different soils. For the first 28 days, the soils were incubated at 20 degrees C under aerobic conditions. The soils were then flooded, and the soils incubated under anaerobic conditions for an additional 120 days. The redox potential was measured to ensure anaerobic conditions. NaOH traps were used to collect evolved CO2, and ethylene glycol traps were used to collect any organic volatiles produced. Soils were sampled at days 0 and 28 pre-flooding, and days 7, 14, 30, 62, and 120 post-flooding. HPLC and LSC was used to determine the amount biodegraded. The percent degradation ranged from 10.2% to 22.7% at day 120 post-flood. No volatile organics were detected. The bound residues in the soil at day 120 post-flood were 4.3 -9.1%. The major degradation product was CO2 with 5.1 -10.7% evolved. The half-life ranged from 1114 to 6.32E9 days. The test substance degraded slowly under aerobic conditions, and even more slowly under anaerobic conditions.

Description of key information

Key value for chemical safety assessment

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

Additional information

Anaerobic and aerobic biodegradation simulation studies in soil were perfomed using radiolabelled C10 dialkylbenzene, a major category of HAB which comprises 20 -70% of the composition. The testing was perfomed in four different soils with an exposure period of 120 days (in the anaerobic testing, there was a 28 day aerobic exposure period prior to the 120 day anaerobic exposure period). The initial concentration was 5.17 uCi/vessel for the anaerobic test, and 4.55 uCi/vessel for the aerobic test. Half-lives for the substance in the aerobic testing ranged from 23 to 178 days at 20 C. When the results were adjusted for 12 C using the Arrhenius equation, the half-lives ranged from 49 to 378 days. Anaerobic degradation was significantly slower with half-lives ranging from 1114 to 4.6E+08 days and 2365 to 8.6E+08 days at 20 and 12 C, respectively.