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Environmental fate & pathways

Biodegradation in soil

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Reference
Endpoint:
biodegradation in soil: simulation testing
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
1994
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study without detailed documentation
Justification for type of information:
Refer to the Quaternary ammonium salts (QAS) category or section 13 of IUCLID for details on the category justification.
Principles of method if other than guideline:
The aerobic biodegradation of the substance in loamy soil (at 10 mg carbon per 50 g soil) was determined using a closed bottle test for 28 days according to the US FDA Environmental Assessment Handbook, Technical Assistance Document 3.12 (1987).
GLP compliance:
no
Test type:
laboratory
Oxygen conditions:
aerobic
Soil classification:
other: loam
Details on soil characteristics:
COMPOSITION OF SOIL:
- %OM: 2.4
- % sand: 35.4
- % silt: 49.3
- % clay: 15.3
- CEC: 13.1 meq/100 g
- Additional substrate: No
- Test temperature: 22  3 degree C
- pH: 7.6
- Aeration of dilution water: No
Duration:
70 d
Initial conc.:
10 other: mg C per 50 g soil
Based on:
other: carbon
Parameter followed for biodegradation estimation:
CO2 evolution
Details on experimental conditions:
TEST SYSTEM:
- Culturing apparatus: Slightly modified biometers described by Bartha and Pramer. Both the Erlenmeyer and the side tube were closed with Mininert valves to enable direct sampling from the side tube and to provide pure oxygen in the Erlenmeyer. The Erlenmeyer and the side tube were fused together with an air- tight coupling so that the side tube and the Erlenmeyer could be weighed separately
- Number of culture flasks/concentration: 3
- Measuring equipment: Dohrmann DC-190 NPOC apparatus
- Test performed in closed vessels due to significant volatility of TS: No

INOCULUM:
- Nature: Loam
- Source: Heino, The Netherlands
- Sampling site: The soil was collected from below the litter layer
- Laboratory culture: No
- Preparation of inoculum for exposure: Stones and plant fragments were removed by hand. After collection the soil was air dried for approximately 2 days and sieved through a 2 mm sieve
- Pretreatment: No pretreatment, the soil was stored at room temperature in polyethylene bags until use in the experiment

SAMPLING: Once a week

STATISTICS:
The theoretical CO2 production of the test substance was calculated from the carbon content of the test substance. The amount of carbon dioxide produced by the test substance was calculated by subtracting the mean carbon dioxide production level in the control blank. The biodegradation was calculated as the ratio of experimental dioxide production to the theoretical carbon dioxide production (ThCO2P).


Key result
% Degr.:
64
Parameter:
CO2 evolution
Sampling time:
70 d
Key result
DT50:
40 d
Remarks on result:
other: DT50
Transformation products:
no
Details on results:
The test substance was biodegraded in loam. The percentage reached at Day 70 was 64. This percentage of the theoretical carbon dioxide production presumes complete mineralisation. The DT50 was estimated to be 40d.

No validity criteria are available for this test, but the test was performed according to a standard guideline and therefore considered to be valid without restrictions.

Conclusions:
Under the study conditions, there was 64% degradation of the read across substance after 70 days. This percentage of the theoretical carbon dioxide production presumes complete mineralization. The DT50 was estimated to be 40 days
Executive summary:

A study was conducted to determine the aerobic biodegradation of the read across substance, C12-16 ADBAC (50% active in water) in loamy soil, using a closed bottle test for 28 days according to the US FDA Environmental Assessment Handbook, Technical Assistance Document 3.12 (1987). The study comprised two treatments: test and chemical blank control group, each with three replicates. The read across substance was added into biometers at a concentration of 10 mg carbon per 50 g soil using appropriate amount of deionised water required for bringing the soils to 50-70% of the moisture capacity. Loam was added to the biometers after the test solutions to facilitate uniform moistening of the soils by capillary action. The test was then incubated at 22 ± 3°C and run for approximately 90 d. The side tube of the biometer contained 20 mL 0.2 M KOH for absorbing carbon dioxide produced by the microorganisms. The theoretical CO2 production of the read across substance was calculated from its carbon content. The amounts of carbon dioxide were calculated by subtracting the mean carbon dioxide production in the test systems containing the read across substance and the mean carbon dioxide production level in the control blank. Biodegradation was calculated as the ratio of experimental carbon dioxide production to theoretical carbon dioxide production [ThCO2P]. Under the study conditions, there was 64% degradation of the read across substance after 70 days. This percentage of the theoretical carbon dioxide production presumes complete mineralization. The DT50 was estimated to be 40 days (van Ginkel, 1994). Based on the results of the read across study, similar degradation potential in soil can be expected for the test substance.

Description of key information

Based on the results of the read across study, the test substance can also expected to undergo 64% degradation in 70 days, with DT50 value of 40 days.

Key value for chemical safety assessment

Half-life in soil:
40 d
at the temperature of:
20 °C

Additional information

A study was conducted to determine the aerobic biodegradation of the read across substance, C12-16 ADBAC (50% active in water) in loamy soil, using a closed bottle test for 28 days according to the US FDA Environmental Assessment Handbook, Technical Assistance Document 3.12 (1987). The study comprised two treatments: test and chemical blank control group, each with three replicates. The read across substance was added into biometers at a concentration of 10 mg carbon per 50 g soil using appropriate amount of deionised water required for bringing the soils to 50-70% of the moisture capacity. Loam was added to the biometers after the test solutions to facilitate uniform moistening of the soils by capillary action. The test was then incubated at 22 ± 3°C and run for approximately 90 d. The side tube of the biometer contained 20 mL 0.2 M KOH for absorbing carbon dioxide produced by the microorganisms. The theoretical CO2 production of the read across substance was calculated from its carbon content. The amounts of carbon dioxide were calculated by subtracting the mean carbon dioxide production in the test systems containing the read across substance and the mean carbon dioxide production level in the control blank. Biodegradation was calculated as the ratio of experimental carbon dioxide production to theoretical carbon dioxide production [ThCO2P]. Under the study conditions, there was 64% degradation of the read across substance after 70 days. This percentage of the theoretical carbon dioxide production presumes complete mineralization. The DT50 was estimated to be 40 days (van Ginkel, 1994). Based on the results of the read across study, similar degradation potential and half-life is considered for the test substance.