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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
other: DIN ISO 11266
Principles of method if other than guideline:
Determination of the Biodegradability of Organic Chemicals in Soil under aerobic Conditions
GLP compliance:
not specified
Test type:
laboratory
Radiolabelling:
no
Oxygen conditions:
aerobic
Soil classification:
not specified
Soil no.:
#1
Soil type:
other: LUFA standard soil No 2.2
% Clay:
8.6
% Silt:
16.6
% Sand:
74.8
% Org. C:
1.61
pH:
5.4
CEC:
9.9 meq/100 g soil d.w.
Bulk density (g/cm³):
1.198
Details on soil characteristics:
Nitrogen content: 0.17% ± 0.01%
Suspended solids (< 0.02 mm) : 8.6% ± 1.2%
max water holding capacity: 42.5 ± 3.2 g/100 g dry mass
Soil No.:
#1
Duration:
28 d
Soil No.:
#1
Initial conc.:
739.44 mg/kg soil d.w.
Based on:
test mat.
Soil No.:
#1
Initial conc.:
196 mg/kg soil d.w.
Based on:
TOC
Soil No.:
#1
Initial conc.:
717.8 mg/kg soil d.w.
Based on:
ThCO2
Parameter followed for biodegradation estimation:
CO2 evolution
Details on experimental conditions:
The pre-conditioned soil was adjusted to 50% of its maximal water retaining capacity. Test and control items were homogeneously mixed into the soil by aid of household mixer. Thereafter, aliquots of 180 grams dry matter were weighed into each of two gas washing bottles and then plugged with the respective equipment. Blanks were prepared in the same way where the stock solutions of test and control items were replaced by the respective amount of deionized water. The test treatments were aerated by humidified CO2-free compressed air. The incubation took place in an air conditioned room at 20 +- 1°C. Upon degradation of test and reference items ther carbon content is transformed into CO2 and liberated. This CO2 is trapped in a system of gas washing bottles being filled with bariumhydroxide solution and quatified by titration with hydrochloric acid. Comparing the amount of CO2 produced upon degradation of the test substance with the theoretical amount of CO2 (ThCO2) the percentage of degradation is calculated. The mean value of the blanks is subtracted from those with the test and control items.
Soil No.:
#1
% Degr.:
50
Parameter:
CO2 evolution
Sampling time:
28 d
Soil No.:
#1
% Degr.:
72
Parameter:
CO2 evolution
Sampling time:
63 d
Transformation products:
not measured
Conclusions:
Only the reference item was degraded at a rate >60% within 28 days under the chosen conditions. The mean degradation value of the test item was 50% within 28 days and 72% after 63 days. There was no toxicity towards the bacteria at the concentration used as the toxicitity control exhibited a degradation of 55% after 28 days and 74% after 63 days. Degradation seems not having been complete after 63 days and further degradation is likely.
Executive summary:

Only the reference item was degraded at a rate >60% within 28 days under the chosen conditions. The mean degradation value of the test item was 50% within 28 days and 72% after 63 days. There was no toxicity towards the bacteria at the concentration used as the toxicitity control exhibited a degradation of 55% after 28 days and 74% after 63 days. Degradation seems not having been complete after 63 days and further degradation is likely.

Description of key information

Degradation of the test substance was measured by CO2 evolution during incubation in the standard LUFA 2.2 soil. The mean degradation value of the test item was 50 % within 28d, and 72% after 63 days. There was no toxicity towards the bacteria at the concentration used as the toxicity control exhibited a degradation of 55% after 28d, and 74% after 63 days. Degradation seems not having been complete after 63 days and further degradation is likely.

Key value for chemical safety assessment

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

Additional information