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Environmental fate & pathways

Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption: screening
Remarks:
adsorption/desorption
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Acceptable, well-documented publication/study report which meets basic scientific principles (also assessed by OECD)
Qualifier:
according to
Guideline:
other: See below
Principles of method if other than guideline:
Method given in "EPA, Office of solid waste and emergency response, batch type adsorption procedures for estimating soil attenuation of chemicals, draft technical resource document for public comment, 1987"
GLP compliance:
not specified
Type of method:
batch equilibrium method
Media:
soil
Specific details on test material used for the study:
As a solution in ethanol
Radiolabelling:
yes
Test temperature:
20±2°C
Details on study design: HPLC method:
Not applicable
Analytical monitoring:
yes
Details on matrix:
Silty clay - LUFA Speyer clay soil (0.64% organic carbon)
Loamy sand - BBA standard soil 2.2 (2.22% organic carbon)
Silt Loam - Soil Hoefchen (2.60% organic carbon)
Details on test conditions:
Equilibration experiments carried out with 4 different concentrations of TPP, corresponding to 50, 37.5, 25 and 5% of the water solubility. (1; 0.75; 0.5; 0.1 mg TPP/l)
Duration:
48 h
Type:
Koc
Value:
>= 2 514 - <= 3 561 dimensionless
Details on results (HPLC method):
Not applicable
Adsorption and desorption constants:
Adsorption:
Silty clay Kd 16.09, Koc 2514, 1/n=0.9299
Loamy sand Kd 79.05, Koc 3561, 1/n=0.9315
Silt loam Kd 71.67, Koc 2756, 1/n=0.8924

Desorption:
Silty clay Kd 21.52, Koc 3363, 1/n=0.7750
Loamy sand Kd 77.72, Koc 3501, 1/n=8893
Silt loam Kd 67.50, Koc 2596, 1/n=0.8407
Recovery of test material:
Chromatographic examination of the aqueous solutions showed partial degradation of TPP by hydrolysis with the formation of mainly diphenyl phosphate. This was greatest in the silty clay soil.
Transformation products:
yes
Depending on soil properties hydrolysis to diphenyl phosphate was observed 
during the equilibration period, hence the  determined values include TPP 
as well as diphenyl phosphate.



Conclusions:
Koc values for adsorption were between 2514 and 3561 and between 2596 and 3501 for desorption. As diphenyl phosphate was formed during the test these values relate to both TPP and the diphenyl phosphate. The values obtained indicate that TPP is virtually non mobile in soil.
Executive summary:

Koc values were determined according to method given in "EPA, Office of solid waste and emergency response, batch type adsorption procedures for estimating soil attenuation of chemicals, draft technical resource document for public comment, 1987" leading to Koc values for adsorption between 2514 and 3561 and for desorption between 2596 and 3501 depending on the soil used. As diphenyl phosphate was formed during the test these values relate to both TPP and diphenyl phosphate. The values obtained indicate that TPP is virtually non mobile in soil.

Description of key information

Koc values for adsorption were 2514, 2756 and 3561 depending on soil used, leading to a mean Koc of 2944. As diphenyl phosphate was formed during the test these values relate to both TPP and diphenyl phosphate. The values obtained indicate that TPP is virtually non mobile in soil. 

Key value for chemical safety assessment

Koc at 20 °C:
2 944

Additional information

Koc values have been determined both experimentally and by calculation from the water solubility and octanol-water partition coefficient. High Koc values (2514 - 5500) have been determined under experimental conditions and by calculation - all of the results indicate that TPP will be relatively immobile in soil. Determination of the partition between water and sediment indicates that the major concentration of TPP will be present in the sediment.

[LogKoc: 3.47]