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Environmental fate & pathways

Biodegradation in soil

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Administrative data

Endpoint:
biodegradation in soil: simulation testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
no data available
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
2009

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
a defined amount of natural soil was incubated with 14C-labelled test material and 14Clabelled CO2 evolved through exposure period was collected and determined.
GLP compliance:
no
Remarks:
University study, not GLP
Test type:
laboratory

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
14C-EDTA (0.9 mg, 1.85 MBq, Sigma, St. Louis, USA)
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
no data available
Radiolabelling:
yes

Study design

Oxygen conditions:
aerobic
Soil classification:
not specified
Details on soil characteristics:
Two uncontaminated soils from Keith and Booleroo in South Australia and a rice paddy soil from Changsha, China with past contamination from mining were selected for this study. The soils were collected in the field to a depth of 20 cm, air-dried and sieved to <2 mm.
Soil properties (physical and chemical characteristics of the selected soils:

Soil properties Keith Booleroo Changsha
pH (1:5 soil/water) 5.4 7.3 7.9
MWHCa (%) 30.2 40.7 49.4
Moisture (%) 1.3 2.2 1.3
Organic Carbon (%) 0.6 1.0 1.4
Clay (%) 12 23 13
Silt (%) 2 22 38
Sand (%) 40 56 47

Parameter followed for biodegradation estimation:
CO2 evolution
Details on experimental conditions:
The soils were incubated at 50 +/- 5% of their maximum water holding capacity (MWHC) in the dark at 25 °C for 28 d to stimulate microbial activity. Working solutions of 14C-EDTA were prepared by spiking 0.1 mmol/l solutions of EDTA with 14C-EDTA (0.9 mg, 1.85 MBq, Sigma, St. Louis, MO).
After incubation, 0.5 ml of each 14C-labelled working solution was added to plastic vials containing 25 g of each soil by pipette, then mixed throughout the soil using a spatula to obtain spiking rates of 2 mmol/kg for EDTA (corresponding to 584 mg/kg soil) . Each vial was placed in a sealed 250 ml polypropylene jar and incubated at 25 °C in the dark for 20 d. All soil samples amended with different treatments were analysed in triplicate.

Results and discussion

% Degradation
% Degr.:
> 0 - < 20
Parameter:
CO2 evolution
Sampling time:
20 d
Transformation products:
not specified
Details on transformation products:
no data available
Evaporation of parent compound:
not specified
Volatile metabolites:
not specified
Residues:
not specified
Details on results:
on average 14 % of EDTA was readily degraded in all three soils.
Results with reference substance:
no data available

Applicant's summary and conclusion

Conclusions:
on average 14 % of EDTA was degraded after 20 d.
Executive summary:

The rate of EDTA degradation was determined in three natural soils after 20 d of exposure. 14 % of a 2 mmol/kg EDTA treatment (equivalent to 584 mg/kg soil) was readily degraded in the three used soils under test conditions.