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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:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Principles of method if other than guideline:
Aerobic batch laboratory microcosm experiments using different soils to determine the loss rate of p-cresol
GLP compliance:
not specified
Test type:
laboratory
Oxygen conditions:
aerobic
Soil classification:
other: natural soils
Soil no.:
#1
Soil type:
other: Typic Paleudults
% Clay:
8.6
% Silt:
23.4
% Sand:
68
% Org. C:
0.94
pH:
4.8
CEC:
6.4 meq/100 g soil d.w.
Soil no.:
#2
Soil type:
Mollisol
% Clay:
7.4
% Silt:
31.1
% Sand:
61.5
% Org. C:
3.25
pH:
7.8
CEC:
10.8 meq/100 g soil d.w.
Details on soil characteristics:
Texture of soil no.1 is a sandy loam; Texture of soil no. 2 is a sandy silt loam
Soil No.:
#1
Duration:
64 d
Soil No.:
#2
Duration:
64 d
Soil No.:
#1
Initial conc.:
100 mg/kg soil d.w.
Based on:
test mat.
Soil No.:
#2
Initial conc.:
45 mg/kg soil d.w.
Based on:
test mat.
Parameter followed for biodegradation estimation:
test mat. analysis
Soil No.:
#1
Temp.:
20°C
Humidity:
80% of field capacity
Soil No.:
#2
Temp.:
20°C
Humidity:
80% of field capacity
Key result
Soil No.:
#1
% Degr.:
139
Parameter:
other: rate constant (% per day)
Sampling time:
1 d
Key result
Soil No.:
#1
DT50:
0.5 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: r²=0.93
Key result
Soil No.:
#2
DT50:
> 1 d
Type:
other: substance not detectable after 1 d
Temp.:
20 °C
Transformation products:
not measured

The recovery efficiencies for p-cresol of the soils were 78% and 97%. The chemical concentrations were corrected by the recovery efficiencies.

Conclusions:
The degradation behaviour of p-cresol was investigated in two different soils. The first soil (acidic) was a sandy loam with an organic carbon content of 0.94%. The second was a sandy silt loam with an organic carbon content of 3.25%. The loadings of the soils and the degradation were monitored by an HPLC method. Maintained in the dark at 20°C, p-cresol degraded with half-live times of <1d for the sandy loam and 0.5 d for the sandy silt loam.
Executive summary:

The degradation behaviour of p-cresol was investigated by Loehr et al. (1992) in two different soils. The first soil (acidic) was a sandy loam with an organic carbon content of 0.94%. The second was a sandy silt loam with an organic carbon content of 3.25%. The loadings of the soils and the degradation were monitored by an HPLC method. Maintained in the dark at 20°C, p-cresol degraded with half-live times of <1d for the sandy loam and 0.5 d for the sandy silt loam.

Description of key information

p-Cresol degraded with half-live times of <1 d for the sandy loam (basic soil) and 0.5 d for the sandy silt loam (acidic soil).

Key value for chemical safety assessment

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

Additional information

The substance is readily biodegradable and no biodegradation simulation test has to be performed for soil according to REACH Annex IX column 2.

The degradation behaviour of p-cresol was investigated in two different soils. The first soil (acidic) was a sandy loam with an organic carbon content of 0.94%. The second was a sandy silt loam with an organic carbon content of 3.25%. The loadings of the soils and the degradation were monitored by an HPLC method. Maintained in the dark at 20°C, p-cresol degraded with half-live times of < 1d for the sandy loam and 0.5 d for the sandy silt loam.

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