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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
Study period:
1981
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 307 (Aerobic and Anaerobic Transformation in Soil)
Deviations:
not applicable
GLP compliance:
no
Test type:
laboratory
Radiolabelling:
no
Oxygen conditions:
aerobic
Soil classification:
not specified
Soil no.:
#1
Soil type:
sandy loam
% Clay:
10
% Silt:
20
% Sand:
70
% Org. C:
2.16
pH:
4.8
Details on soil characteristics:
See table on soil properties.
Soil No.:
#1
Duration:
30 d
Soil No.:
#1
Initial conc.:
25 mg/kg soil d.w.
Based on:
test mat.
Soil No.:
#1
Temp.:
25°C
Humidity:
Not specified
Microbial biomass:
Not specified
Details on experimental conditions:
The soil used was a sandy loam. The soil sample was air dried, sieved through a 2 mm screen and stored at 10-15°C until needed. Soil pH was determined by glass electrode using 1:1 ratio of soil and water, soil texture by the hydrometer method, and organic content by the modified Scholenberger method. Ten grams of soil were dispensed into test tubes. Each soil tube received 25 µg test item per gram of soil. Sufficient distilled water was added to the tube to obtain moisture content at filed capacity. The soil tubes were incubated in the dark at 30°C and analyzed for nitrite and residual nitrosodiphenylamine at 0, 5, 10, 15, 20 and 30 days incubation.
Soil No.:
#1
Remarks on result:
not measured/tested
Key result
Soil No.:
#1
DT50:
30 d
Type:
(pseudo-)first order (= half-life)
Temp.:
30 °C
Key result
Soil No.:
#1
DT50:
45 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Remarks on result:
other: See remarks
Remarks:
Derived from Arrhenius equation according to the recommendations of ECHA's guidance on information requirements and chemical safety assessment R7b (v4.0; June 2017; p.222)
Transformation products:
not measured
Details on transformation products:
None.
Evaporation of parent compound:
no
Remarks:
The subtance is not volatile, nor has a Henry's constant which would suggest plausible volatilization from water.
Volatile metabolites:
not measured
Residues:
not measured
Details on results:
Nitrosodiphenylamine degradation half-life in soil is 30 days at 30°C.
Results with reference substance:
None.
Conclusions:
Nitrosodiphenylamine has an estimated half-life of 30 days at 30°C (i.e., around 45 days at 12°C according to Arrhenius equation with Ea = 65.4 kJ/mol). Nitrosodiphenylamine degradation half-life in soil is far less than 120 days at 12°C. Therefore, the substance is not considered P/vP according to the criteria of annex XIII REACh regulation EC 1907/2006. However, a substance may be considered rapidly biodegradable according to regulation EC 1272/2008 if degradation half-life in soil is less than 16 days at 12°C. Therefore, nitrosodiphenylamine should not be considered rapidly biodegradable and hence not readily biodegradable either.
Executive summary:

The degradation of nitrosodiphenylamine was investigated in a soil simulation study. The soil used was a sandy loam. The soil sample was a sandy loam (70% sand, 20% silt, 10% clay, 2.2% organic matter). Ten grams of soil were dispensed into test tubes. Each soil tube received 25 µg test item per gram of soil. Sufficient distilled water was added to the tube to obtain moisture content at field capacity. The soil tubes were incubated in the dark at 30°C and analyzed for residual nitrosodiphenylamine at 0, 5, 10, 15, 20 and 30 days incubation. After 20 days, residual nitrosodiphenylamine was around 14 µg/gram of soil. After 30 days, residual nitrosodiphenylamine was around 9 µg per gram of soil. Since no half-life was calculated, a worst-case half-life of 30 days at 30°C was considered. Thus, nitrosodiphenylamine has an estimated half-life of 30 days at 30°C (i.e., around 45 days at 12°C according to Arrhenius equation with Ea = 65.4 kJ/mol). Nitrosodiphenylamine degradation half-life in soil is far less than 120 days at 12°C. Therefore, the substance is not considered P/vP according to the criteria of annex XIII REACh regulation EC 1907/2006.  However, a substance may be considered rapidly biodegradable according to regulation EC 1272/2008 if degradation half-life in soil is less than 16 days at 12°C. Therefore, nitrosodiphenylamine should not be considered rapidly biodegradable and hence not readily biodegradable either.

Description of key information

Degradation half-life of nitrosodiphenylamine is estimated at 45 days at 12°C.

Key value for chemical safety assessment

Half-life in soil:
45 d

Additional information